Merge branch 'develop' of github.com:matrix-org/synapse into matrix-org-hotfixes

43 files changed, 5008 insertions, 94 deletions

diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index b276171a32..33780f7c2c 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -40,6 +40,7 @@ from synapse.replication.slave.storage.push_rule import SlavedPushRuleStore
 from synapse.replication.slave.storage.receipts import SlavedReceiptsStore
 from synapse.replication.slave.storage.registration import SlavedRegistrationStore
 from synapse.replication.slave.storage.room import RoomStore
+from synapse.replication.slave.storage.groups import SlavedGroupServerStore
 from synapse.replication.tcp.client import ReplicationClientHandler
 from synapse.rest.client.v1 import events
 from synapse.rest.client.v1.initial_sync import InitialSyncRestServlet
@@ -69,6 +70,7 @@ class SynchrotronSlavedStore(
     SlavedRegistrationStore,
     SlavedFilteringStore,
     SlavedPresenceStore,
+    SlavedGroupServerStore,
     SlavedDeviceInboxStore,
     SlavedDeviceStore,
     SlavedClientIpStore,
@@ -404,6 +406,10 @@ class SyncReplicationHandler(ReplicationClientHandler):
             )
         elif stream_name == "presence":
             yield self.presence_handler.process_replication_rows(token, rows)
+        elif stream_name == "receipts":
+            self.notifier.on_new_event(
+                "groups_key", token, users=[row.user_id for row in rows],
+            )
 
 
 def start(config_options):
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index fa4ec2ad3c..f00d59e701 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -12,14 +12,12 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-
 from twisted.internet import defer
 
 from .federation_base import FederationBase
 from .units import Transaction, Edu
 
-from synapse.util.async import Linearizer
+from synapse.util import async
 from synapse.util.logutils import log_function
 from synapse.util.caches.response_cache import ResponseCache
 from synapse.events import FrozenEvent
@@ -33,6 +31,9 @@ from synapse.crypto.event_signing import compute_event_signature
 import simplejson as json
 import logging
 
+# when processing incoming transactions, we try to handle multiple rooms in
+# parallel, up to this limit.
+TRANSACTION_CONCURRENCY_LIMIT = 10
 
 logger = logging.getLogger(__name__)
 
@@ -52,7 +53,8 @@ class FederationServer(FederationBase):
 
         self.auth = hs.get_auth()
 
-        self._server_linearizer = Linearizer("fed_server")
+        self._server_linearizer = async.Linearizer("fed_server")
+        self._transaction_linearizer = async.Linearizer("fed_txn_handler")
 
         # We cache responses to state queries, as they take a while and often
         # come in waves.
@@ -111,12 +113,39 @@ class FederationServer(FederationBase):
     def on_incoming_transaction(self, transaction_data):
         # keep this as early as possible to make the calculated origin ts as
         # accurate as possible.
-        request_time = int(self._clock.time_msec())
+        request_time = self._clock.time_msec()
 
         transaction = Transaction(**transaction_data)
 
+        if not transaction.transaction_id:
+            raise Exception("Transaction missing transaction_id")
+        if not transaction.origin:
+            raise Exception("Transaction missing origin")
+
         logger.debug("[%s] Got transaction", transaction.transaction_id)
 
+        # use a linearizer to ensure that we don't process the same transaction
+        # multiple times in parallel.
+        with (yield self._transaction_linearizer.queue(
+                (transaction.origin, transaction.transaction_id),
+        )):
+            result = yield self._handle_incoming_transaction(
+                transaction, request_time,
+            )
+
+        defer.returnValue(result)
+
+    @defer.inlineCallbacks
+    def _handle_incoming_transaction(self, transaction, request_time):
+        """ Process an incoming transaction and return the HTTP response
+
+        Args:
+            transaction (Transaction): incoming transaction
+            request_time (int): timestamp that the HTTP request arrived at
+
+        Returns:
+            Deferred[(int, object)]: http response code and body
+        """
         response = yield self.transaction_actions.have_responded(transaction)
 
         if response:
@@ -131,7 +160,7 @@ class FederationServer(FederationBase):
 
         received_pdus_counter.inc_by(len(transaction.pdus))
 
-        pdu_list = []
+        pdus_by_room = {}
 
         for p in transaction.pdus:
             if "unsigned" in p:
@@ -143,22 +172,36 @@ class FederationServer(FederationBase):
                 del p["age"]
 
             event = self.event_from_pdu_json(p)
-            pdu_list.append(event)
+            room_id = event.room_id
+            pdus_by_room.setdefault(room_id, []).append(event)
 
         pdu_results = {}
 
-        for pdu in pdu_list:
-            event_id = pdu.event_id
-            try:
-                yield self._handle_received_pdu(transaction.origin, pdu)
-                pdu_results[event_id] = {}
-            except FederationError as e:
-                logger.warn("Error handling PDU %s: %s", event_id, e)
-                self.send_failure(e, transaction.origin)
-                pdu_results[event_id] = {"error": str(e)}
-            except Exception as e:
-                pdu_results[event_id] = {"error": str(e)}
-                logger.exception("Failed to handle PDU")
+        # we can process different rooms in parallel (which is useful if they
+        # require callouts to other servers to fetch missing events), but
+        # impose a limit to avoid going too crazy with ram/cpu.
+        @defer.inlineCallbacks
+        def process_pdus_for_room(room_id):
+            logger.debug("Processing PDUs for %s", room_id)
+            for pdu in pdus_by_room[room_id]:
+                event_id = pdu.event_id
+                try:
+                    yield self._handle_received_pdu(
+                        transaction.origin, pdu
+                    )
+                    pdu_results[event_id] = {}
+                except FederationError as e:
+                    logger.warn("Error handling PDU %s: %s", event_id, e)
+                    self.send_failure(e, transaction.origin)
+                    pdu_results[event_id] = {"error": str(e)}
+                except Exception as e:
+                    pdu_results[event_id] = {"error": str(e)}
+                    logger.exception("Failed to handle PDU %s", event_id)
+
+        yield async.concurrently_execute(
+            process_pdus_for_room, pdus_by_room.keys(),
+            TRANSACTION_CONCURRENCY_LIMIT,
+        )
 
         if hasattr(transaction, "edus"):
             for edu in (Edu(**x) for x in transaction.edus):
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index 52b2a717d2..36f6eb75e9 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -471,3 +471,371 @@ class TransportLayerClient(object):
         )
 
         defer.returnValue(content)
+
+    @log_function
+    def get_group_profile(self, destination, group_id, requester_user_id):
+        """Get a group profile
+        """
+        path = PREFIX + "/groups/%s/profile" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_group_summary(self, destination, group_id, requester_user_id):
+        """Get a group summary
+        """
+        path = PREFIX + "/groups/%s/summary" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_rooms_in_group(self, destination, group_id, requester_user_id):
+        """Get all rooms in a group
+        """
+        path = PREFIX + "/groups/%s/rooms" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    def add_room_to_group(self, destination, group_id, requester_user_id, room_id,
+                          content):
+        """Add a room to a group
+        """
+        path = PREFIX + "/groups/%s/room/%s" % (group_id, room_id,)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    def remove_room_from_group(self, destination, group_id, requester_user_id, room_id):
+        """Remove a room from a group
+        """
+        path = PREFIX + "/groups/%s/room/%s" % (group_id, room_id,)
+
+        return self.client.delete_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_users_in_group(self, destination, group_id, requester_user_id):
+        """Get users in a group
+        """
+        path = PREFIX + "/groups/%s/users" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def accept_group_invite(self, destination, group_id, user_id, content):
+        """Accept a group invite
+        """
+        path = PREFIX + "/groups/%s/users/%s/accept_invite" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def invite_to_group(self, destination, group_id, user_id, requester_user_id, content):
+        """Invite a user to a group
+        """
+        path = PREFIX + "/groups/%s/users/%s/invite" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args=requester_user_id,
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def invite_to_group_notification(self, destination, group_id, user_id, content):
+        """Sent by group server to inform a user's server that they have been
+        invited.
+        """
+
+        path = PREFIX + "/groups/local/%s/users/%s/invite" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def remove_user_from_group(self, destination, group_id, requester_user_id,
+                               user_id, content):
+        """Remove a user fron a group
+        """
+        path = PREFIX + "/groups/%s/users/%s/remove" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def remove_user_from_group_notification(self, destination, group_id, user_id,
+                                            content):
+        """Sent by group server to inform a user's server that they have been
+        kicked from the group.
+        """
+
+        path = PREFIX + "/groups/local/%s/users/%s/remove" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def renew_group_attestation(self, destination, group_id, user_id, content):
+        """Sent by either a group server or a user's server to periodically update
+        the attestations
+        """
+
+        path = PREFIX + "/groups/%s/renew_attestation/%s" % (group_id, user_id)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def update_group_summary_room(self, destination, group_id, user_id, room_id,
+                                  category_id, content):
+        """Update a room entry in a group summary
+        """
+        if category_id:
+            path = PREFIX + "/groups/%s/summary/categories/%s/rooms/%s" % (
+                group_id, category_id, room_id,
+            )
+        else:
+            path = PREFIX + "/groups/%s/summary/rooms/%s" % (group_id, room_id,)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def delete_group_summary_room(self, destination, group_id, user_id, room_id,
+                                  category_id):
+        """Delete a room entry in a group summary
+        """
+        if category_id:
+            path = PREFIX + "/groups/%s/summary/categories/%s/rooms/%s" % (
+                group_id, category_id, room_id,
+            )
+        else:
+            path = PREFIX + "/groups/%s/summary/rooms/%s" % (group_id, room_id,)
+
+        return self.client.delete_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_group_categories(self, destination, group_id, requester_user_id):
+        """Get all categories in a group
+        """
+        path = PREFIX + "/groups/%s/categories" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_group_category(self, destination, group_id, requester_user_id, category_id):
+        """Get category info in a group
+        """
+        path = PREFIX + "/groups/%s/categories/%s" % (group_id, category_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def update_group_category(self, destination, group_id, requester_user_id, category_id,
+                              content):
+        """Update a category in a group
+        """
+        path = PREFIX + "/groups/%s/categories/%s" % (group_id, category_id,)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def delete_group_category(self, destination, group_id, requester_user_id,
+                              category_id):
+        """Delete a category in a group
+        """
+        path = PREFIX + "/groups/%s/categories/%s" % (group_id, category_id,)
+
+        return self.client.delete_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_group_roles(self, destination, group_id, requester_user_id):
+        """Get all roles in a group
+        """
+        path = PREFIX + "/groups/%s/roles" % (group_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def get_group_role(self, destination, group_id, requester_user_id, role_id):
+        """Get a roles info
+        """
+        path = PREFIX + "/groups/%s/roles/%s" % (group_id, role_id,)
+
+        return self.client.get_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def update_group_role(self, destination, group_id, requester_user_id, role_id,
+                          content):
+        """Update a role in a group
+        """
+        path = PREFIX + "/groups/%s/roles/%s" % (group_id, role_id,)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def delete_group_role(self, destination, group_id, requester_user_id, role_id):
+        """Delete a role in a group
+        """
+        path = PREFIX + "/groups/%s/roles/%s" % (group_id, role_id,)
+
+        return self.client.delete_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def update_group_summary_user(self, destination, group_id, requester_user_id,
+                                  user_id, role_id, content):
+        """Update a users entry in a group
+        """
+        if role_id:
+            path = PREFIX + "/groups/%s/summary/roles/%s/users/%s" % (
+                group_id, role_id, user_id,
+            )
+        else:
+            path = PREFIX + "/groups/%s/summary/users/%s" % (group_id, user_id,)
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            data=content,
+            ignore_backoff=True,
+        )
+
+    @log_function
+    def delete_group_summary_user(self, destination, group_id, requester_user_id,
+                                  user_id, role_id):
+        """Delete a users entry in a group
+        """
+        if role_id:
+            path = PREFIX + "/groups/%s/summary/roles/%s/users/%s" % (
+                group_id, role_id, user_id,
+            )
+        else:
+            path = PREFIX + "/groups/%s/summary/users/%s" % (group_id, user_id,)
+
+        return self.client.delete_json(
+            destination=destination,
+            path=path,
+            args={"requester_user_id": requester_user_id},
+            ignore_backoff=True,
+        )
+
+    def bulk_get_publicised_groups(self, destination, user_ids):
+        """Get the groups a list of users are publicising
+        """
+
+        path = PREFIX + "/get_groups_publicised"
+
+        content = {"user_ids": user_ids}
+
+        return self.client.post_json(
+            destination=destination,
+            path=path,
+            data=content,
+            ignore_backoff=True,
+        )
diff --git a/synapse/federation/transport/server.py b/synapse/federation/transport/server.py
index a78f01e442..c7565e0737 100644
--- a/synapse/federation/transport/server.py
+++ b/synapse/federation/transport/server.py
@@ -25,7 +25,7 @@ from synapse.http.servlet import (
 from synapse.util.ratelimitutils import FederationRateLimiter
 from synapse.util.versionstring import get_version_string
 from synapse.util.logcontext import preserve_fn
-from synapse.types import ThirdPartyInstanceID
+from synapse.types import ThirdPartyInstanceID, get_domain_from_id
 
 import functools
 import logging
@@ -609,6 +609,475 @@ class FederationVersionServlet(BaseFederationServlet):
         }))
 
 
+class FederationGroupsProfileServlet(BaseFederationServlet):
+    """Get the basic profile of a group on behalf of a user
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/profile$"
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.get_group_profile(
+            group_id, requester_user_id
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsSummaryServlet(BaseFederationServlet):
+    PATH = "/groups/(?P<group_id>[^/]*)/summary$"
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.get_group_summary(
+            group_id, requester_user_id
+        )
+
+        defer.returnValue((200, new_content))
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.update_group_profile(
+            group_id, requester_user_id, content
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsRoomsServlet(BaseFederationServlet):
+    """Get the rooms in a group on behalf of a user
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/rooms$"
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.get_rooms_in_group(
+            group_id, requester_user_id
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsAddRoomsServlet(BaseFederationServlet):
+    """Add/remove room from group
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/room/(?<room_id>)$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, room_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.add_room_to_group(
+            group_id, requester_user_id, room_id, content
+        )
+
+        defer.returnValue((200, new_content))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, origin, content, query, group_id, room_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.remove_room_from_group(
+            group_id, requester_user_id, room_id,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsUsersServlet(BaseFederationServlet):
+    """Get the users in a group on behalf of a user
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/users$"
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.get_users_in_group(
+            group_id, requester_user_id
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsInviteServlet(BaseFederationServlet):
+    """Ask a group server to invite someone to the group
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/users/(?P<user_id>[^/]*)/invite$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.invite_to_group(
+            group_id, user_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsAcceptInviteServlet(BaseFederationServlet):
+    """Accept an invitation from the group server
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/users/(?P<user_id>[^/]*)/accept_invite$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        if get_domain_from_id(user_id) != origin:
+            raise SynapseError(403, "user_id doesn't match origin")
+
+        new_content = yield self.handler.accept_invite(
+            group_id, user_id, content,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsRemoveUserServlet(BaseFederationServlet):
+    """Leave or kick a user from the group
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/users/(?P<user_id>[^/]*)/remove$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        new_content = yield self.handler.remove_user_from_group(
+            group_id, user_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsLocalInviteServlet(BaseFederationServlet):
+    """A group server has invited a local user
+    """
+    PATH = "/groups/local/(?P<group_id>[^/]*)/users/(?P<user_id>[^/]*)/invite$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        if get_domain_from_id(group_id) != origin:
+            raise SynapseError(403, "group_id doesn't match origin")
+
+        new_content = yield self.handler.on_invite(
+            group_id, user_id, content,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsRemoveLocalUserServlet(BaseFederationServlet):
+    """A group server has removed a local user
+    """
+    PATH = "/groups/local/(?P<group_id>[^/]*)/users/(?P<user_id>[^/]*)/remove$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        if get_domain_from_id(group_id) != origin:
+            raise SynapseError(403, "user_id doesn't match origin")
+
+        new_content = yield self.handler.user_removed_from_group(
+            group_id, user_id, content,
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsRenewAttestaionServlet(BaseFederationServlet):
+    """A group or user's server renews their attestation
+    """
+    PATH = "/groups/(?P<group_id>[^/]*)/renew_attestation/(?P<user_id>[^/]*)$"
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, user_id):
+        # We don't need to check auth here as we check the attestation signatures
+
+        new_content = yield self.handler.on_renew_group_attestation(
+            origin, content, group_id, user_id
+        )
+
+        defer.returnValue((200, new_content))
+
+
+class FederationGroupsSummaryRoomsServlet(BaseFederationServlet):
+    """Add/remove a room from the group summary, with optional category.
+
+    Matches both:
+        - /groups/:group/summary/rooms/:room_id
+        - /groups/:group/summary/categories/:category/rooms/:room_id
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/summary"
+        "(/categories/(?P<category_id>[^/]+))?"
+        "/rooms/(?P<room_id>[^/]*)$"
+    )
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, category_id, room_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if category_id == "":
+            raise SynapseError(400, "category_id cannot be empty string")
+
+        resp = yield self.handler.update_group_summary_room(
+            group_id, requester_user_id,
+            room_id=room_id,
+            category_id=category_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, origin, content, query, group_id, category_id, room_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if category_id == "":
+            raise SynapseError(400, "category_id cannot be empty string")
+
+        resp = yield self.handler.delete_group_summary_room(
+            group_id, requester_user_id,
+            room_id=room_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsCategoriesServlet(BaseFederationServlet):
+    """Get all categories for a group
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/categories/$"
+    )
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        resp = yield self.handler.get_group_categories(
+            group_id, requester_user_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsCategoryServlet(BaseFederationServlet):
+    """Add/remove/get a category in a group
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/categories/(?P<category_id>[^/]+)$"
+    )
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id, category_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        resp = yield self.handler.get_group_category(
+            group_id, requester_user_id, category_id
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, category_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if category_id == "":
+            raise SynapseError(400, "category_id cannot be empty string")
+
+        resp = yield self.handler.upsert_group_category(
+            group_id, requester_user_id, category_id, content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, origin, content, query, group_id, category_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if category_id == "":
+            raise SynapseError(400, "category_id cannot be empty string")
+
+        resp = yield self.handler.delete_group_category(
+            group_id, requester_user_id, category_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsRolesServlet(BaseFederationServlet):
+    """Get roles in a group
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/roles/$"
+    )
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        resp = yield self.handler.get_group_roles(
+            group_id, requester_user_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsRoleServlet(BaseFederationServlet):
+    """Add/remove/get a role in a group
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/roles/(?P<role_id>[^/]+)$"
+    )
+
+    @defer.inlineCallbacks
+    def on_GET(self, origin, content, query, group_id, role_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        resp = yield self.handler.get_group_role(
+            group_id, requester_user_id, role_id
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, role_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if role_id == "":
+            raise SynapseError(400, "role_id cannot be empty string")
+
+        resp = yield self.handler.update_group_role(
+            group_id, requester_user_id, role_id, content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, origin, content, query, group_id, role_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if role_id == "":
+            raise SynapseError(400, "role_id cannot be empty string")
+
+        resp = yield self.handler.delete_group_role(
+            group_id, requester_user_id, role_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsSummaryUsersServlet(BaseFederationServlet):
+    """Add/remove a user from the group summary, with optional role.
+
+    Matches both:
+        - /groups/:group/summary/users/:user_id
+        - /groups/:group/summary/roles/:role/users/:user_id
+    """
+    PATH = (
+        "/groups/(?P<group_id>[^/]*)/summary"
+        "(/roles/(?P<role_id>[^/]+))?"
+        "/users/(?P<user_id>[^/]*)$"
+    )
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query, group_id, role_id, user_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if role_id == "":
+            raise SynapseError(400, "role_id cannot be empty string")
+
+        resp = yield self.handler.update_group_summary_user(
+            group_id, requester_user_id,
+            user_id=user_id,
+            role_id=role_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, origin, content, query, group_id, role_id, user_id):
+        requester_user_id = parse_string_from_args(query, "requester_user_id")
+        if get_domain_from_id(requester_user_id) != origin:
+            raise SynapseError(403, "requester_user_id doesn't match origin")
+
+        if role_id == "":
+            raise SynapseError(400, "role_id cannot be empty string")
+
+        resp = yield self.handler.delete_group_summary_user(
+            group_id, requester_user_id,
+            user_id=user_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class FederationGroupsBulkPublicisedServlet(BaseFederationServlet):
+    """Get roles in a group
+    """
+    PATH = (
+        "/get_groups_publicised$"
+    )
+
+    @defer.inlineCallbacks
+    def on_POST(self, origin, content, query):
+        resp = yield self.handler.bulk_get_publicised_groups(
+            content["user_ids"], proxy=False,
+        )
+
+        defer.returnValue((200, resp))
+
+
 FEDERATION_SERVLET_CLASSES = (
     FederationSendServlet,
     FederationPullServlet,
@@ -635,11 +1104,41 @@ FEDERATION_SERVLET_CLASSES = (
     FederationVersionServlet,
 )
 
+
 ROOM_LIST_CLASSES = (
     PublicRoomList,
 )
 
 
+GROUP_SERVER_SERVLET_CLASSES = (
+    FederationGroupsProfileServlet,
+    FederationGroupsSummaryServlet,
+    FederationGroupsRoomsServlet,
+    FederationGroupsUsersServlet,
+    FederationGroupsInviteServlet,
+    FederationGroupsAcceptInviteServlet,
+    FederationGroupsRemoveUserServlet,
+    FederationGroupsSummaryRoomsServlet,
+    FederationGroupsCategoriesServlet,
+    FederationGroupsCategoryServlet,
+    FederationGroupsRolesServlet,
+    FederationGroupsRoleServlet,
+    FederationGroupsSummaryUsersServlet,
+)
+
+
+GROUP_LOCAL_SERVLET_CLASSES = (
+    FederationGroupsLocalInviteServlet,
+    FederationGroupsRemoveLocalUserServlet,
+    FederationGroupsBulkPublicisedServlet,
+)
+
+
+GROUP_ATTESTATION_SERVLET_CLASSES = (
+    FederationGroupsRenewAttestaionServlet,
+)
+
+
 def register_servlets(hs, resource, authenticator, ratelimiter):
     for servletclass in FEDERATION_SERVLET_CLASSES:
         servletclass(
@@ -656,3 +1155,27 @@ def register_servlets(hs, resource, authenticator, ratelimiter):
             ratelimiter=ratelimiter,
             server_name=hs.hostname,
         ).register(resource)
+
+    for servletclass in GROUP_SERVER_SERVLET_CLASSES:
+        servletclass(
+            handler=hs.get_groups_server_handler(),
+            authenticator=authenticator,
+            ratelimiter=ratelimiter,
+            server_name=hs.hostname,
+        ).register(resource)
+
+    for servletclass in GROUP_LOCAL_SERVLET_CLASSES:
+        servletclass(
+            handler=hs.get_groups_local_handler(),
+            authenticator=authenticator,
+            ratelimiter=ratelimiter,
+            server_name=hs.hostname,
+        ).register(resource)
+
+    for servletclass in GROUP_ATTESTATION_SERVLET_CLASSES:
+        servletclass(
+            handler=hs.get_groups_attestation_renewer(),
+            authenticator=authenticator,
+            ratelimiter=ratelimiter,
+            server_name=hs.hostname,
+        ).register(resource)
diff --git a/synapse/groups/__init__.py b/synapse/groups/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/synapse/groups/__init__.py
diff --git a/synapse/groups/attestations.py b/synapse/groups/attestations.py
new file mode 100644
index 0000000000..5ef7a12cb7
--- /dev/null
+++ b/synapse/groups/attestations.py
@@ -0,0 +1,150 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.api.errors import SynapseError
+from synapse.types import get_domain_from_id
+from synapse.util.logcontext import preserve_fn
+
+from signedjson.sign import sign_json
+
+
+# Default validity duration for new attestations we create
+DEFAULT_ATTESTATION_LENGTH_MS = 3 * 24 * 60 * 60 * 1000
+
+# Start trying to update our attestations when they come this close to expiring
+UPDATE_ATTESTATION_TIME_MS = 1 * 24 * 60 * 60 * 1000
+
+
+class GroupAttestationSigning(object):
+    """Creates and verifies group attestations.
+    """
+    def __init__(self, hs):
+        self.keyring = hs.get_keyring()
+        self.clock = hs.get_clock()
+        self.server_name = hs.hostname
+        self.signing_key = hs.config.signing_key[0]
+
+    @defer.inlineCallbacks
+    def verify_attestation(self, attestation, group_id, user_id, server_name=None):
+        """Verifies that the given attestation matches the given parameters.
+
+        An optional server_name can be supplied to explicitly set which server's
+        signature is expected. Otherwise assumes that either the group_id or user_id
+        is local and uses the other's server as the one to check.
+        """
+
+        if not server_name:
+            if get_domain_from_id(group_id) == self.server_name:
+                server_name = get_domain_from_id(user_id)
+            elif get_domain_from_id(user_id) == self.server_name:
+                server_name = get_domain_from_id(group_id)
+            else:
+                raise Exception("Expected either group_id or user_id to be local")
+
+        if user_id != attestation["user_id"]:
+            raise SynapseError(400, "Attestation has incorrect user_id")
+
+        if group_id != attestation["group_id"]:
+            raise SynapseError(400, "Attestation has incorrect group_id")
+        valid_until_ms = attestation["valid_until_ms"]
+
+        # TODO: We also want to check that *new* attestations that people give
+        # us to store are valid for at least a little while.
+        if valid_until_ms < self.clock.time_msec():
+            raise SynapseError(400, "Attestation expired")
+
+        yield self.keyring.verify_json_for_server(server_name, attestation)
+
+    def create_attestation(self, group_id, user_id):
+        """Create an attestation for the group_id and user_id with default
+        validity length.
+        """
+        return sign_json({
+            "group_id": group_id,
+            "user_id": user_id,
+            "valid_until_ms": self.clock.time_msec() + DEFAULT_ATTESTATION_LENGTH_MS,
+        }, self.server_name, self.signing_key)
+
+
+class GroupAttestionRenewer(object):
+    """Responsible for sending and receiving attestation updates.
+    """
+
+    def __init__(self, hs):
+        self.clock = hs.get_clock()
+        self.store = hs.get_datastore()
+        self.assestations = hs.get_groups_attestation_signing()
+        self.transport_client = hs.get_federation_transport_client()
+        self.is_mine_id = hs.is_mine_id
+
+        self._renew_attestations_loop = self.clock.looping_call(
+            self._renew_attestations, 30 * 60 * 1000,
+        )
+
+    @defer.inlineCallbacks
+    def on_renew_attestation(self, group_id, user_id, content):
+        """When a remote updates an attestation
+        """
+        attestation = content["attestation"]
+
+        if not self.is_mine_id(group_id) and not self.is_mine_id(user_id):
+            raise SynapseError(400, "Neither user not group are on this server")
+
+        yield self.attestations.verify_attestation(
+            attestation,
+            user_id=user_id,
+            group_id=group_id,
+        )
+
+        yield self.store.update_remote_attestion(group_id, user_id, attestation)
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def _renew_attestations(self):
+        """Called periodically to check if we need to update any of our attestations
+        """
+
+        now = self.clock.time_msec()
+
+        rows = yield self.store.get_attestations_need_renewals(
+            now + UPDATE_ATTESTATION_TIME_MS
+        )
+
+        @defer.inlineCallbacks
+        def _renew_attestation(self, group_id, user_id):
+            attestation = self.attestations.create_attestation(group_id, user_id)
+
+            if self.hs.is_mine_id(group_id):
+                destination = get_domain_from_id(user_id)
+            else:
+                destination = get_domain_from_id(group_id)
+
+            yield self.transport_client.renew_group_attestation(
+                destination, group_id, user_id,
+                content={"attestation": attestation},
+            )
+
+            yield self.store.update_attestation_renewal(
+                group_id, user_id, attestation
+            )
+
+        for row in rows:
+            group_id = row["group_id"]
+            user_id = row["user_id"]
+
+            preserve_fn(_renew_attestation)(group_id, user_id)
diff --git a/synapse/groups/groups_server.py b/synapse/groups/groups_server.py
new file mode 100644
index 0000000000..6a85908dd6
--- /dev/null
+++ b/synapse/groups/groups_server.py
@@ -0,0 +1,741 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.api.errors import SynapseError
+from synapse.types import UserID, get_domain_from_id, RoomID
+
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+# TODO: Allow users to "knock" or simpkly join depending on rules
+# TODO: Federation admin APIs
+# TODO: is_priveged flag to users and is_public to users and rooms
+# TODO: Audit log for admins (profile updates, membership changes, users who tried
+#       to join but were rejected, etc)
+# TODO: Flairs
+
+
+class GroupsServerHandler(object):
+    def __init__(self, hs):
+        self.hs = hs
+        self.store = hs.get_datastore()
+        self.room_list_handler = hs.get_room_list_handler()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.keyring = hs.get_keyring()
+        self.is_mine_id = hs.is_mine_id
+        self.signing_key = hs.config.signing_key[0]
+        self.server_name = hs.hostname
+        self.attestations = hs.get_groups_attestation_signing()
+        self.transport_client = hs.get_federation_transport_client()
+        self.profile_handler = hs.get_profile_handler()
+
+        # Ensure attestations get renewed
+        hs.get_groups_attestation_renewer()
+
+    @defer.inlineCallbacks
+    def check_group_is_ours(self, group_id, and_exists=False, and_is_admin=None):
+        """Check that the group is ours, and optionally if it exists.
+
+        If group does exist then return group.
+
+        Args:
+            group_id (str)
+            and_exists (bool): whether to also check if group exists
+            and_is_admin (str): whether to also check if given str is a user_id
+                that is an admin
+        """
+        if not self.is_mine_id(group_id):
+            raise SynapseError(400, "Group not on this server")
+
+        group = yield self.store.get_group(group_id)
+        if and_exists and not group:
+            raise SynapseError(404, "Unknown group")
+
+        if and_is_admin:
+            is_admin = yield self.store.is_user_admin_in_group(group_id, and_is_admin)
+            if not is_admin:
+                raise SynapseError(403, "User is not admin in group")
+
+        defer.returnValue(group)
+
+    @defer.inlineCallbacks
+    def get_group_summary(self, group_id, requester_user_id):
+        """Get the summary for a group as seen by requester_user_id.
+
+        The group summary consists of the profile of the room, and a curated
+        list of users and rooms. These list *may* be organised by role/category.
+        The roles/categories are ordered, and so are the users/rooms within them.
+
+        A user/room may appear in multiple roles/categories.
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        is_user_in_group = yield self.store.is_user_in_group(requester_user_id, group_id)
+
+        profile = yield self.get_group_profile(group_id, requester_user_id)
+
+        users, roles = yield self.store.get_users_for_summary_by_role(
+            group_id, include_private=is_user_in_group,
+        )
+
+        # TODO: Add profiles to users
+
+        rooms, categories = yield self.store.get_rooms_for_summary_by_category(
+            group_id, include_private=is_user_in_group,
+        )
+
+        for room_entry in rooms:
+            room_id = room_entry["room_id"]
+            joined_users = yield self.store.get_users_in_room(room_id)
+            entry = yield self.room_list_handler.generate_room_entry(
+                room_id, len(joined_users),
+                with_alias=False, allow_private=True,
+            )
+            entry = dict(entry)  # so we don't change whats cached
+            entry.pop("room_id", None)
+
+            room_entry["profile"] = entry
+
+        rooms.sort(key=lambda e: e.get("order", 0))
+
+        for entry in users:
+            user_id = entry["user_id"]
+
+            if not self.is_mine_id(requester_user_id):
+                attestation = yield self.store.get_remote_attestation(group_id, user_id)
+                if not attestation:
+                    continue
+
+                entry["attestation"] = attestation
+            else:
+                entry["attestation"] = self.attestations.create_attestation(
+                    group_id, user_id,
+                )
+
+            user_profile = yield self.profile_handler.get_profile_from_cache(user_id)
+            entry.update(user_profile)
+
+        users.sort(key=lambda e: e.get("order", 0))
+
+        membership_info = yield self.store.get_users_membership_info_in_group(
+            group_id, requester_user_id,
+        )
+
+        defer.returnValue({
+            "profile": profile,
+            "users_section": {
+                "users": users,
+                "roles": roles,
+                "total_user_count_estimate": 0,  # TODO
+            },
+            "rooms_section": {
+                "rooms": rooms,
+                "categories": categories,
+                "total_room_count_estimate": 0,  # TODO
+            },
+            "user": membership_info,
+        })
+
+    @defer.inlineCallbacks
+    def update_group_summary_room(self, group_id, user_id, room_id, category_id, content):
+        """Add/update a room to the group summary
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        RoomID.from_string(room_id)  # Ensure valid room id
+
+        order = content.get("order", None)
+
+        is_public = _parse_visibility_from_contents(content)
+
+        yield self.store.add_room_to_summary(
+            group_id=group_id,
+            room_id=room_id,
+            category_id=category_id,
+            order=order,
+            is_public=is_public,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def delete_group_summary_room(self, group_id, user_id, room_id, category_id):
+        """Remove a room from the summary
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        yield self.store.remove_room_from_summary(
+            group_id=group_id,
+            room_id=room_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def get_group_categories(self, group_id, user_id):
+        """Get all categories in a group (as seen by user)
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        categories = yield self.store.get_group_categories(
+            group_id=group_id,
+        )
+        defer.returnValue({"categories": categories})
+
+    @defer.inlineCallbacks
+    def get_group_category(self, group_id, user_id, category_id):
+        """Get a specific category in a group (as seen by user)
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        res = yield self.store.get_group_category(
+            group_id=group_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def update_group_category(self, group_id, user_id, category_id, content):
+        """Add/Update a group category
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        is_public = _parse_visibility_from_contents(content)
+        profile = content.get("profile")
+
+        yield self.store.upsert_group_category(
+            group_id=group_id,
+            category_id=category_id,
+            is_public=is_public,
+            profile=profile,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def delete_group_category(self, group_id, user_id, category_id):
+        """Delete a group category
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        yield self.store.remove_group_category(
+            group_id=group_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def get_group_roles(self, group_id, user_id):
+        """Get all roles in a group (as seen by user)
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        roles = yield self.store.get_group_roles(
+            group_id=group_id,
+        )
+        defer.returnValue({"roles": roles})
+
+    @defer.inlineCallbacks
+    def get_group_role(self, group_id, user_id, role_id):
+        """Get a specific role in a group (as seen by user)
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        res = yield self.store.get_group_role(
+            group_id=group_id,
+            role_id=role_id,
+        )
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def update_group_role(self, group_id, user_id, role_id, content):
+        """Add/update a role in a group
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        is_public = _parse_visibility_from_contents(content)
+
+        profile = content.get("profile")
+
+        yield self.store.upsert_group_role(
+            group_id=group_id,
+            role_id=role_id,
+            is_public=is_public,
+            profile=profile,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def delete_group_role(self, group_id, user_id, role_id):
+        """Remove role from group
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True, and_is_admin=user_id)
+
+        yield self.store.remove_group_role(
+            group_id=group_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def update_group_summary_user(self, group_id, requester_user_id, user_id, role_id,
+                                  content):
+        """Add/update a users entry in the group summary
+        """
+        yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id,
+        )
+
+        order = content.get("order", None)
+
+        is_public = _parse_visibility_from_contents(content)
+
+        yield self.store.add_user_to_summary(
+            group_id=group_id,
+            user_id=user_id,
+            role_id=role_id,
+            order=order,
+            is_public=is_public,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def delete_group_summary_user(self, group_id, requester_user_id, user_id, role_id):
+        """Remove a user from the group summary
+        """
+        yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id,
+        )
+
+        yield self.store.remove_user_from_summary(
+            group_id=group_id,
+            user_id=user_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def get_group_profile(self, group_id, requester_user_id):
+        """Get the group profile as seen by requester_user_id
+        """
+
+        yield self.check_group_is_ours(group_id)
+
+        group_description = yield self.store.get_group(group_id)
+
+        if group_description:
+            defer.returnValue(group_description)
+        else:
+            raise SynapseError(404, "Unknown group")
+
+    @defer.inlineCallbacks
+    def update_group_profile(self, group_id, requester_user_id, content):
+        """Update the group profile
+        """
+        yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id,
+        )
+
+        profile = {}
+        for keyname in ("name", "avatar_url", "short_description",
+                        "long_description"):
+            if keyname in content:
+                value = content[keyname]
+                if not isinstance(value, basestring):
+                    raise SynapseError(400, "%r value is not a string" % (keyname,))
+                profile[keyname] = value
+
+        yield self.store.update_group_profile(group_id, profile)
+
+    @defer.inlineCallbacks
+    def get_users_in_group(self, group_id, requester_user_id):
+        """Get the users in group as seen by requester_user_id.
+
+        The ordering is arbitrary at the moment
+        """
+
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        is_user_in_group = yield self.store.is_user_in_group(requester_user_id, group_id)
+
+        user_results = yield self.store.get_users_in_group(
+            group_id, include_private=is_user_in_group,
+        )
+
+        chunk = []
+        for user_result in user_results:
+            g_user_id = user_result["user_id"]
+            is_public = user_result["is_public"]
+
+            entry = {"user_id": g_user_id}
+
+            profile = yield self.profile_handler.get_profile_from_cache(g_user_id)
+            entry.update(profile)
+
+            if not is_public:
+                entry["is_public"] = False
+
+            if not self.is_mine_id(requester_user_id):
+                attestation = yield self.store.get_remote_attestation(group_id, g_user_id)
+                if not attestation:
+                    continue
+
+                entry["attestation"] = attestation
+            else:
+                entry["attestation"] = self.attestations.create_attestation(
+                    group_id, g_user_id,
+                )
+
+            chunk.append(entry)
+
+        # TODO: If admin add lists of users whose attestations have timed out
+
+        defer.returnValue({
+            "chunk": chunk,
+            "total_user_count_estimate": len(user_results),
+        })
+
+    @defer.inlineCallbacks
+    def get_rooms_in_group(self, group_id, requester_user_id):
+        """Get the rooms in group as seen by requester_user_id
+
+        This returns rooms in order of decreasing number of joined users
+        """
+
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        is_user_in_group = yield self.store.is_user_in_group(requester_user_id, group_id)
+
+        room_results = yield self.store.get_rooms_in_group(
+            group_id, include_private=is_user_in_group,
+        )
+
+        chunk = []
+        for room_result in room_results:
+            room_id = room_result["room_id"]
+            is_public = room_result["is_public"]
+
+            joined_users = yield self.store.get_users_in_room(room_id)
+            entry = yield self.room_list_handler.generate_room_entry(
+                room_id, len(joined_users),
+                with_alias=False, allow_private=True,
+            )
+
+            if not entry:
+                continue
+
+            if not is_public:
+                entry["is_public"] = False
+
+            chunk.append(entry)
+
+        chunk.sort(key=lambda e: -e["num_joined_members"])
+
+        defer.returnValue({
+            "chunk": chunk,
+            "total_room_count_estimate": len(room_results),
+        })
+
+    @defer.inlineCallbacks
+    def add_room_to_group(self, group_id, requester_user_id, room_id, content):
+        """Add room to group
+        """
+        RoomID.from_string(room_id)  # Ensure valid room id
+
+        yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id
+        )
+
+        is_public = _parse_visibility_from_contents(content)
+
+        yield self.store.add_room_to_group(group_id, room_id, is_public=is_public)
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def remove_room_from_group(self, group_id, requester_user_id, room_id):
+        """Remove room from group
+        """
+        yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id
+        )
+
+        yield self.store.remove_room_from_group(group_id, room_id)
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def invite_to_group(self, group_id, user_id, requester_user_id, content):
+        """Invite user to group
+        """
+
+        group = yield self.check_group_is_ours(
+            group_id, and_exists=True, and_is_admin=requester_user_id
+        )
+
+        # TODO: Check if user knocked
+        # TODO: Check if user is already invited
+
+        content = {
+            "profile": {
+                "name": group["name"],
+                "avatar_url": group["avatar_url"],
+            },
+            "inviter": requester_user_id,
+        }
+
+        if self.hs.is_mine_id(user_id):
+            groups_local = self.hs.get_groups_local_handler()
+            res = yield groups_local.on_invite(group_id, user_id, content)
+            local_attestation = None
+        else:
+            local_attestation = self.attestations.create_attestation(group_id, user_id)
+            content.update({
+                "attestation": local_attestation,
+            })
+
+            res = yield self.transport_client.invite_to_group_notification(
+                get_domain_from_id(user_id), group_id, user_id, content
+            )
+
+            user_profile = res.get("user_profile", {})
+            yield self.store.add_remote_profile_cache(
+                user_id,
+                displayname=user_profile.get("displayname"),
+                avatar_url=user_profile.get("avatar_url"),
+            )
+
+        if res["state"] == "join":
+            if not self.hs.is_mine_id(user_id):
+                remote_attestation = res["attestation"]
+
+                yield self.attestations.verify_attestation(
+                    remote_attestation,
+                    user_id=user_id,
+                    group_id=group_id,
+                )
+            else:
+                remote_attestation = None
+
+            yield self.store.add_user_to_group(
+                group_id, user_id,
+                is_admin=False,
+                is_public=False,  # TODO
+                local_attestation=local_attestation,
+                remote_attestation=remote_attestation,
+            )
+        elif res["state"] == "invite":
+            yield self.store.add_group_invite(
+                group_id, user_id,
+            )
+            defer.returnValue({
+                "state": "invite"
+            })
+        elif res["state"] == "reject":
+            defer.returnValue({
+                "state": "reject"
+            })
+        else:
+            raise SynapseError(502, "Unknown state returned by HS")
+
+    @defer.inlineCallbacks
+    def accept_invite(self, group_id, user_id, content):
+        """User tries to accept an invite to the group.
+
+        This is different from them asking to join, and so should error if no
+        invite exists (and they're not a member of the group)
+        """
+
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        if not self.store.is_user_invited_to_local_group(group_id, user_id):
+            raise SynapseError(403, "User not invited to group")
+
+        if not self.hs.is_mine_id(user_id):
+            remote_attestation = content["attestation"]
+
+            yield self.attestations.verify_attestation(
+                remote_attestation,
+                user_id=user_id,
+                group_id=group_id,
+            )
+        else:
+            remote_attestation = None
+
+        local_attestation = self.attestations.create_attestation(group_id, user_id)
+
+        is_public = _parse_visibility_from_contents(content)
+
+        yield self.store.add_user_to_group(
+            group_id, user_id,
+            is_admin=False,
+            is_public=is_public,
+            local_attestation=local_attestation,
+            remote_attestation=remote_attestation,
+        )
+
+        defer.returnValue({
+            "state": "join",
+            "attestation": local_attestation,
+        })
+
+    @defer.inlineCallbacks
+    def knock(self, group_id, user_id, content):
+        """A user requests becoming a member of the group
+        """
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        raise NotImplementedError()
+
+    @defer.inlineCallbacks
+    def accept_knock(self, group_id, user_id, content):
+        """Accept a users knock to the room.
+
+        Errors if the user hasn't knocked, rather than inviting them.
+        """
+
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        raise NotImplementedError()
+
+    @defer.inlineCallbacks
+    def remove_user_from_group(self, group_id, user_id, requester_user_id, content):
+        """Remove a user from the group; either a user is leaving or and admin
+        kicked htem.
+        """
+
+        yield self.check_group_is_ours(group_id, and_exists=True)
+
+        is_kick = False
+        if requester_user_id != user_id:
+            is_admin = yield self.store.is_user_admin_in_group(
+                group_id, requester_user_id
+            )
+            if not is_admin:
+                raise SynapseError(403, "User is not admin in group")
+
+            is_kick = True
+
+        yield self.store.remove_user_from_group(
+            group_id, user_id,
+        )
+
+        if is_kick:
+            if self.hs.is_mine_id(user_id):
+                groups_local = self.hs.get_groups_local_handler()
+                yield groups_local.user_removed_from_group(group_id, user_id, {})
+            else:
+                yield self.transport_client.remove_user_from_group_notification(
+                    get_domain_from_id(user_id), group_id, user_id, {}
+                )
+
+        if not self.hs.is_mine_id(user_id):
+            yield self.store.maybe_delete_remote_profile_cache(user_id)
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def create_group(self, group_id, user_id, content):
+        group = yield self.check_group_is_ours(group_id)
+
+        logger.info("Attempting to create group with ID: %r", group_id)
+        if group:
+            raise SynapseError(400, "Group already exists")
+
+        # TODO: Add config to enforce that only server admins can create rooms
+        is_admin = yield self.auth.is_server_admin(UserID.from_string(user_id))
+        if not is_admin:
+            raise SynapseError(403, "Only server admin can create group on this server")
+
+        profile = content.get("profile", {})
+        name = profile.get("name")
+        avatar_url = profile.get("avatar_url")
+        short_description = profile.get("short_description")
+        long_description = profile.get("long_description")
+        user_profile = content.get("user_profile", {})
+
+        yield self.store.create_group(
+            group_id,
+            user_id,
+            name=name,
+            avatar_url=avatar_url,
+            short_description=short_description,
+            long_description=long_description,
+        )
+
+        if not self.hs.is_mine_id(user_id):
+            remote_attestation = content["attestation"]
+
+            yield self.attestations.verify_attestation(
+                remote_attestation,
+                user_id=user_id,
+                group_id=group_id,
+            )
+
+            local_attestation = self.attestations.create_attestation(group_id, user_id)
+        else:
+            local_attestation = None
+            remote_attestation = None
+
+        yield self.store.add_user_to_group(
+            group_id, user_id,
+            is_admin=True,
+            is_public=True,  # TODO
+            local_attestation=local_attestation,
+            remote_attestation=remote_attestation,
+        )
+
+        if not self.hs.is_mine_id(user_id):
+            yield self.store.add_remote_profile_cache(
+                user_id,
+                displayname=user_profile.get("displayname"),
+                avatar_url=user_profile.get("avatar_url"),
+            )
+
+        defer.returnValue({
+            "group_id": group_id,
+        })
+
+
+def _parse_visibility_from_contents(content):
+    """Given a content for a request parse out whether the entity should be
+    public or not
+    """
+
+    visibility = content.get("visibility")
+    if visibility:
+        vis_type = visibility["type"]
+        if vis_type not in ("public", "private"):
+            raise SynapseError(
+                400, "Synapse only supports 'public'/'private' visibility"
+            )
+        is_public = vis_type == "public"
+    else:
+        is_public = True
+
+    return is_public
diff --git a/synapse/handlers/__init__.py b/synapse/handlers/__init__.py
index 5ad408f549..53213cdccf 100644
--- a/synapse/handlers/__init__.py
+++ b/synapse/handlers/__init__.py
@@ -20,7 +20,6 @@ from .room import (
 from .room_member import RoomMemberHandler
 from .message import MessageHandler
 from .federation import FederationHandler
-from .profile import ProfileHandler
 from .directory import DirectoryHandler
 from .admin import AdminHandler
 from .identity import IdentityHandler
@@ -52,7 +51,6 @@ class Handlers(object):
         self.room_creation_handler = RoomCreationHandler(hs)
         self.room_member_handler = RoomMemberHandler(hs)
         self.federation_handler = FederationHandler(hs)
-        self.profile_handler = ProfileHandler(hs)
         self.directory_handler = DirectoryHandler(hs)
         self.admin_handler = AdminHandler(hs)
         self.identity_handler = IdentityHandler(hs)
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 63c56a4a32..7711cded01 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -122,6 +122,28 @@ class FederationHandler(BaseHandler):
             self.room_queues[pdu.room_id].append((pdu, origin))
             return
 
+        # If we're no longer in the room just ditch the event entirely. This
+        # is probably an old server that has come back and thinks we're still
+        # in the room (or we've been rejoined to the room by a state reset).
+        #
+        # If we were never in the room then maybe our database got vaped and
+        # we should check if we *are* in fact in the room. If we are then we
+        # can magically rejoin the room.
+        is_in_room = yield self.auth.check_host_in_room(
+            pdu.room_id,
+            self.server_name
+        )
+        if not is_in_room:
+            was_in_room = yield self.store.was_host_joined(
+                pdu.room_id, self.server_name,
+            )
+            if was_in_room:
+                logger.info(
+                    "Ignoring PDU %s for room %s from %s as we've left the room!",
+                    pdu.event_id, pdu.room_id, origin,
+                )
+                return
+
         state = None
 
         auth_chain = []
diff --git a/synapse/handlers/groups_local.py b/synapse/handlers/groups_local.py
new file mode 100644
index 0000000000..a2bacbfc38
--- /dev/null
+++ b/synapse/handlers/groups_local.py
@@ -0,0 +1,402 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.api.errors import SynapseError
+from synapse.types import get_domain_from_id
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+def _create_rerouter(func_name):
+    """Returns a function that looks at the group id and calls the function
+    on federation or the local group server if the group is local
+    """
+    def f(self, group_id, *args, **kwargs):
+        if self.is_mine_id(group_id):
+            return getattr(self.groups_server_handler, func_name)(
+                group_id, *args, **kwargs
+            )
+        else:
+            destination = get_domain_from_id(group_id)
+            return getattr(self.transport_client, func_name)(
+                destination, group_id, *args, **kwargs
+            )
+    return f
+
+
+class GroupsLocalHandler(object):
+    def __init__(self, hs):
+        self.hs = hs
+        self.store = hs.get_datastore()
+        self.room_list_handler = hs.get_room_list_handler()
+        self.groups_server_handler = hs.get_groups_server_handler()
+        self.transport_client = hs.get_federation_transport_client()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.keyring = hs.get_keyring()
+        self.is_mine_id = hs.is_mine_id
+        self.signing_key = hs.config.signing_key[0]
+        self.server_name = hs.hostname
+        self.notifier = hs.get_notifier()
+        self.attestations = hs.get_groups_attestation_signing()
+
+        self.profile_handler = hs.get_profile_handler()
+
+        # Ensure attestations get renewed
+        hs.get_groups_attestation_renewer()
+
+    # The following functions merely route the query to the local groups server
+    # or federation depending on if the group is local or remote
+
+    get_group_profile = _create_rerouter("get_group_profile")
+    update_group_profile = _create_rerouter("update_group_profile")
+    get_rooms_in_group = _create_rerouter("get_rooms_in_group")
+
+    add_room_to_group = _create_rerouter("add_room_to_group")
+    remove_room_from_group = _create_rerouter("remove_room_from_group")
+
+    update_group_summary_room = _create_rerouter("update_group_summary_room")
+    delete_group_summary_room = _create_rerouter("delete_group_summary_room")
+
+    update_group_category = _create_rerouter("update_group_category")
+    delete_group_category = _create_rerouter("delete_group_category")
+    get_group_category = _create_rerouter("get_group_category")
+    get_group_categories = _create_rerouter("get_group_categories")
+
+    update_group_summary_user = _create_rerouter("update_group_summary_user")
+    delete_group_summary_user = _create_rerouter("delete_group_summary_user")
+
+    update_group_role = _create_rerouter("update_group_role")
+    delete_group_role = _create_rerouter("delete_group_role")
+    get_group_role = _create_rerouter("get_group_role")
+    get_group_roles = _create_rerouter("get_group_roles")
+
+    @defer.inlineCallbacks
+    def get_group_summary(self, group_id, requester_user_id):
+        """Get the group summary for a group.
+
+        If the group is remote we check that the users have valid attestations.
+        """
+        if self.is_mine_id(group_id):
+            res = yield self.groups_server_handler.get_group_summary(
+                group_id, requester_user_id
+            )
+        else:
+            res = yield self.transport_client.get_group_summary(
+                get_domain_from_id(group_id), group_id, requester_user_id,
+            )
+
+            # Loop through the users and validate the attestations.
+            chunk = res["users_section"]["users"]
+            valid_users = []
+            for entry in chunk:
+                g_user_id = entry["user_id"]
+                attestation = entry.pop("attestation")
+                try:
+                    yield self.attestations.verify_attestation(
+                        attestation,
+                        group_id=group_id,
+                        user_id=g_user_id,
+                    )
+                    valid_users.append(entry)
+                except Exception as e:
+                    logger.info("Failed to verify user is in group: %s", e)
+
+            res["users_section"]["users"] = valid_users
+
+            res["users_section"]["users"].sort(key=lambda e: e.get("order", 0))
+            res["rooms_section"]["rooms"].sort(key=lambda e: e.get("order", 0))
+
+        # Add `is_publicised` flag to indicate whether the user has publicised their
+        # membership of the group on their profile
+        result = yield self.store.get_publicised_groups_for_user(requester_user_id)
+        is_publicised = group_id in result
+
+        res.setdefault("user", {})["is_publicised"] = is_publicised
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def create_group(self, group_id, user_id, content):
+        """Create a group
+        """
+
+        logger.info("Asking to create group with ID: %r", group_id)
+
+        if self.is_mine_id(group_id):
+            res = yield self.groups_server_handler.create_group(
+                group_id, user_id, content
+            )
+            local_attestation = None
+            remote_attestation = None
+        else:
+            local_attestation = self.attestations.create_attestation(group_id, user_id)
+            content["attestation"] = local_attestation
+
+            content["user_profile"] = yield self.profile_handler.get_profile(user_id)
+
+            res = yield self.transport_client.create_group(
+                get_domain_from_id(group_id), group_id, user_id, content,
+            )
+
+            remote_attestation = res["attestation"]
+            yield self.attestations.verify_attestation(
+                remote_attestation,
+                group_id=group_id,
+                user_id=user_id,
+            )
+
+        is_publicised = content.get("publicise", False)
+        token = yield self.store.register_user_group_membership(
+            group_id, user_id,
+            membership="join",
+            is_admin=True,
+            local_attestation=local_attestation,
+            remote_attestation=remote_attestation,
+            is_publicised=is_publicised,
+        )
+        self.notifier.on_new_event(
+            "groups_key", token, users=[user_id],
+        )
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def get_users_in_group(self, group_id, requester_user_id):
+        """Get users in a group
+        """
+        if self.is_mine_id(group_id):
+            res = yield self.groups_server_handler.get_users_in_group(
+                group_id, requester_user_id
+            )
+            defer.returnValue(res)
+
+        res = yield self.transport_client.get_users_in_group(
+            get_domain_from_id(group_id), group_id, requester_user_id,
+        )
+
+        chunk = res["chunk"]
+        valid_entries = []
+        for entry in chunk:
+            g_user_id = entry["user_id"]
+            attestation = entry.pop("attestation")
+            try:
+                yield self.attestations.verify_attestation(
+                    attestation,
+                    group_id=group_id,
+                    user_id=g_user_id,
+                )
+                valid_entries.append(entry)
+            except Exception as e:
+                logger.info("Failed to verify user is in group: %s", e)
+
+        res["chunk"] = valid_entries
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def join_group(self, group_id, user_id, content):
+        """Request to join a group
+        """
+        raise NotImplementedError()  # TODO
+
+    @defer.inlineCallbacks
+    def accept_invite(self, group_id, user_id, content):
+        """Accept an invite to a group
+        """
+        if self.is_mine_id(group_id):
+            yield self.groups_server_handler.accept_invite(
+                group_id, user_id, content
+            )
+            local_attestation = None
+            remote_attestation = None
+        else:
+            local_attestation = self.attestations.create_attestation(group_id, user_id)
+            content["attestation"] = local_attestation
+
+            res = yield self.transport_client.accept_group_invite(
+                get_domain_from_id(group_id), group_id, user_id, content,
+            )
+
+            remote_attestation = res["attestation"]
+
+            yield self.attestations.verify_attestation(
+                remote_attestation,
+                group_id=group_id,
+                user_id=user_id,
+            )
+
+        # TODO: Check that the group is public and we're being added publically
+        is_publicised = content.get("publicise", False)
+
+        token = yield self.store.register_user_group_membership(
+            group_id, user_id,
+            membership="join",
+            is_admin=False,
+            local_attestation=local_attestation,
+            remote_attestation=remote_attestation,
+            is_publicised=is_publicised,
+        )
+        self.notifier.on_new_event(
+            "groups_key", token, users=[user_id],
+        )
+
+        defer.returnValue({})
+
+    @defer.inlineCallbacks
+    def invite(self, group_id, user_id, requester_user_id, config):
+        """Invite a user to a group
+        """
+        content = {
+            "requester_user_id": requester_user_id,
+            "config": config,
+        }
+        if self.is_mine_id(group_id):
+            res = yield self.groups_server_handler.invite_to_group(
+                group_id, user_id, requester_user_id, content,
+            )
+        else:
+            res = yield self.transport_client.invite_to_group(
+                get_domain_from_id(group_id), group_id, user_id, requester_user_id,
+                content,
+            )
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def on_invite(self, group_id, user_id, content):
+        """One of our users were invited to a group
+        """
+        # TODO: Support auto join and rejection
+
+        if not self.is_mine_id(user_id):
+            raise SynapseError(400, "User not on this server")
+
+        local_profile = {}
+        if "profile" in content:
+            if "name" in content["profile"]:
+                local_profile["name"] = content["profile"]["name"]
+            if "avatar_url" in content["profile"]:
+                local_profile["avatar_url"] = content["profile"]["avatar_url"]
+
+        token = yield self.store.register_user_group_membership(
+            group_id, user_id,
+            membership="invite",
+            content={"profile": local_profile, "inviter": content["inviter"]},
+        )
+        self.notifier.on_new_event(
+            "groups_key", token, users=[user_id],
+        )
+
+        user_profile = yield self.profile_handler.get_profile(user_id)
+
+        defer.returnValue({"state": "invite", "user_profile": user_profile})
+
+    @defer.inlineCallbacks
+    def remove_user_from_group(self, group_id, user_id, requester_user_id, content):
+        """Remove a user from a group
+        """
+        if user_id == requester_user_id:
+            token = yield self.store.register_user_group_membership(
+                group_id, user_id,
+                membership="leave",
+            )
+            self.notifier.on_new_event(
+                "groups_key", token, users=[user_id],
+            )
+
+            # TODO: Should probably remember that we tried to leave so that we can
+            # retry if the group server is currently down.
+
+        if self.is_mine_id(group_id):
+            res = yield self.groups_server_handler.remove_user_from_group(
+                group_id, user_id, requester_user_id, content,
+            )
+        else:
+            content["requester_user_id"] = requester_user_id
+            res = yield self.transport_client.remove_user_from_group(
+                get_domain_from_id(group_id), group_id, requester_user_id,
+                user_id, content,
+            )
+
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def user_removed_from_group(self, group_id, user_id, content):
+        """One of our users was removed/kicked from a group
+        """
+        # TODO: Check if user in group
+        token = yield self.store.register_user_group_membership(
+            group_id, user_id,
+            membership="leave",
+        )
+        self.notifier.on_new_event(
+            "groups_key", token, users=[user_id],
+        )
+
+    @defer.inlineCallbacks
+    def get_joined_groups(self, user_id):
+        group_ids = yield self.store.get_joined_groups(user_id)
+        defer.returnValue({"groups": group_ids})
+
+    @defer.inlineCallbacks
+    def get_publicised_groups_for_user(self, user_id):
+        if self.hs.is_mine_id(user_id):
+            result = yield self.store.get_publicised_groups_for_user(user_id)
+            defer.returnValue({"groups": result})
+        else:
+            result = yield self.transport_client.get_publicised_groups_for_user(
+                get_domain_from_id(user_id), user_id
+            )
+            # TODO: Verify attestations
+            defer.returnValue(result)
+
+    @defer.inlineCallbacks
+    def bulk_get_publicised_groups(self, user_ids, proxy=True):
+        destinations = {}
+        local_users = set()
+
+        for user_id in user_ids:
+            if self.hs.is_mine_id(user_id):
+                local_users.add(user_id)
+            else:
+                destinations.setdefault(
+                    get_domain_from_id(user_id), set()
+                ).add(user_id)
+
+        if not proxy and destinations:
+            raise SynapseError(400, "Some user_ids are not local")
+
+        results = {}
+        failed_results = []
+        for destination, dest_user_ids in destinations.iteritems():
+            try:
+                r = yield self.transport_client.bulk_get_publicised_groups(
+                    destination, list(dest_user_ids),
+                )
+                results.update(r["users"])
+            except Exception:
+                failed_results.extend(dest_user_ids)
+
+        for uid in local_users:
+            results[uid] = yield self.store.get_publicised_groups_for_user(
+                uid
+            )
+
+        defer.returnValue({"users": results})
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index ca8c6c55bb..fbf88b46ef 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -25,6 +25,7 @@ from synapse.types import (
 from synapse.util.async import run_on_reactor, ReadWriteLock, Limiter
 from synapse.util.logcontext import preserve_fn
 from synapse.util.metrics import measure_func
+from synapse.util.frozenutils import unfreeze
 from synapse.visibility import filter_events_for_client
 
 from ._base import BaseHandler
@@ -46,6 +47,7 @@ class MessageHandler(BaseHandler):
         self.state = hs.get_state_handler()
         self.clock = hs.get_clock()
         self.validator = EventValidator()
+        self.profile_handler = hs.get_profile_handler()
 
         self.pagination_lock = ReadWriteLock()
 
@@ -211,7 +213,7 @@ class MessageHandler(BaseHandler):
 
                 if membership in {Membership.JOIN, Membership.INVITE}:
                     # If event doesn't include a display name, add one.
-                    profile = self.hs.get_handlers().profile_handler
+                    profile = self.profile_handler
                     content = builder.content
 
                     try:
@@ -555,7 +557,7 @@ class MessageHandler(BaseHandler):
 
         # Ensure that we can round trip before trying to persist in db
         try:
-            dump = ujson.dumps(event.content)
+            dump = ujson.dumps(unfreeze(event.content))
             ujson.loads(dump)
         except:
             logger.exception("Failed to encode content: %r", event.content)
diff --git a/synapse/handlers/profile.py b/synapse/handlers/profile.py
index 7abee98dea..e56e0a52bf 100644
--- a/synapse/handlers/profile.py
+++ b/synapse/handlers/profile.py
@@ -19,14 +19,15 @@ from twisted.internet import defer
 
 import synapse.types
 from synapse.api.errors import SynapseError, AuthError, CodeMessageException
-from synapse.types import UserID
+from synapse.types import UserID, get_domain_from_id
 from ._base import BaseHandler
 
-
 logger = logging.getLogger(__name__)
 
 
 class ProfileHandler(BaseHandler):
+    PROFILE_UPDATE_MS = 60 * 1000
+    PROFILE_UPDATE_EVERY_MS = 24 * 60 * 60 * 1000
 
     def __init__(self, hs):
         super(ProfileHandler, self).__init__(hs)
@@ -36,6 +37,63 @@ class ProfileHandler(BaseHandler):
             "profile", self.on_profile_query
         )
 
+        self.clock.looping_call(self._update_remote_profile_cache, self.PROFILE_UPDATE_MS)
+
+    @defer.inlineCallbacks
+    def get_profile(self, user_id):
+        target_user = UserID.from_string(user_id)
+        if self.hs.is_mine(target_user):
+            displayname = yield self.store.get_profile_displayname(
+                target_user.localpart
+            )
+            avatar_url = yield self.store.get_profile_avatar_url(
+                target_user.localpart
+            )
+
+            defer.returnValue({
+                "displayname": displayname,
+                "avatar_url": avatar_url,
+            })
+        else:
+            try:
+                result = yield self.federation.make_query(
+                    destination=target_user.domain,
+                    query_type="profile",
+                    args={
+                        "user_id": user_id,
+                    },
+                    ignore_backoff=True,
+                )
+                defer.returnValue(result)
+            except CodeMessageException as e:
+                if e.code != 404:
+                    logger.exception("Failed to get displayname")
+
+                raise
+
+    @defer.inlineCallbacks
+    def get_profile_from_cache(self, user_id):
+        """Get the profile information from our local cache. If the user is
+        ours then the profile information will always be corect. Otherwise,
+        it may be out of date/missing.
+        """
+        target_user = UserID.from_string(user_id)
+        if self.hs.is_mine(target_user):
+            displayname = yield self.store.get_profile_displayname(
+                target_user.localpart
+            )
+            avatar_url = yield self.store.get_profile_avatar_url(
+                target_user.localpart
+            )
+
+            defer.returnValue({
+                "displayname": displayname,
+                "avatar_url": avatar_url,
+            })
+        else:
+            profile = yield self.store.get_from_remote_profile_cache(user_id)
+            defer.returnValue(profile or {})
+
     @defer.inlineCallbacks
     def get_displayname(self, target_user):
         if self.hs.is_mine(target_user):
@@ -182,3 +240,44 @@ class ProfileHandler(BaseHandler):
                     "Failed to update join event for room %s - %s",
                     room_id, str(e.message)
                 )
+
+    def _update_remote_profile_cache(self):
+        """Called periodically to check profiles of remote users we haven't
+        checked in a while.
+        """
+        entries = yield self.store.get_remote_profile_cache_entries_that_expire(
+            last_checked=self.clock.time_msec() - self.PROFILE_UPDATE_EVERY_MS
+        )
+
+        for user_id, displayname, avatar_url in entries:
+            is_subscribed = yield self.store.is_subscribed_remote_profile_for_user(
+                user_id,
+            )
+            if not is_subscribed:
+                yield self.store.maybe_delete_remote_profile_cache(user_id)
+                continue
+
+            try:
+                profile = yield self.federation.make_query(
+                    destination=get_domain_from_id(user_id),
+                    query_type="profile",
+                    args={
+                        "user_id": user_id,
+                    },
+                    ignore_backoff=True,
+                )
+            except:
+                logger.exception("Failed to get avatar_url")
+
+                yield self.store.update_remote_profile_cache(
+                    user_id, displayname, avatar_url
+                )
+                continue
+
+            new_name = profile.get("displayname")
+            new_avatar = profile.get("avatar_url")
+
+            # We always hit update to update the last_check timestamp
+            yield self.store.update_remote_profile_cache(
+                user_id, new_name, new_avatar
+            )
diff --git a/synapse/handlers/register.py b/synapse/handlers/register.py
index ee3a2269a8..560fb36254 100644
--- a/synapse/handlers/register.py
+++ b/synapse/handlers/register.py
@@ -36,6 +36,7 @@ class RegistrationHandler(BaseHandler):
         super(RegistrationHandler, self).__init__(hs)
 
         self.auth = hs.get_auth()
+        self.profile_handler = hs.get_profile_handler()
         self.captcha_client = CaptchaServerHttpClient(hs)
 
         self._next_generated_user_id = None
@@ -423,8 +424,7 @@ class RegistrationHandler(BaseHandler):
 
         if displayname is not None:
             logger.info("setting user display name: %s -> %s", user_id, displayname)
-            profile_handler = self.hs.get_handlers().profile_handler
-            yield profile_handler.set_displayname(
+            yield self.profile_handler.set_displayname(
                 user, requester, displayname, by_admin=True,
             )
 
diff --git a/synapse/handlers/room_list.py b/synapse/handlers/room_list.py
index 31ae4613c1..62f2d807b8 100644
--- a/synapse/handlers/room_list.py
+++ b/synapse/handlers/room_list.py
@@ -276,13 +276,14 @@ class RoomListHandler(BaseHandler):
             # We've already got enough, so lets just drop it.
             return
 
-        result = yield self._generate_room_entry(room_id, num_joined_users)
+        result = yield self.generate_room_entry(room_id, num_joined_users)
 
         if result and _matches_room_entry(result, search_filter):
             chunk.append(result)
 
     @cachedInlineCallbacks(num_args=1, cache_context=True)
-    def _generate_room_entry(self, room_id, num_joined_users, cache_context):
+    def generate_room_entry(self, room_id, num_joined_users, cache_context,
+                            with_alias=True, allow_private=False):
         """Returns the entry for a room
         """
         result = {
@@ -316,14 +317,15 @@ class RoomListHandler(BaseHandler):
         join_rules_event = current_state.get((EventTypes.JoinRules, ""))
         if join_rules_event:
             join_rule = join_rules_event.content.get("join_rule", None)
-            if join_rule and join_rule != JoinRules.PUBLIC:
+            if not allow_private and join_rule and join_rule != JoinRules.PUBLIC:
                 defer.returnValue(None)
 
-        aliases = yield self.store.get_aliases_for_room(
-            room_id, on_invalidate=cache_context.invalidate
-        )
-        if aliases:
-            result["aliases"] = aliases
+        if with_alias:
+            aliases = yield self.store.get_aliases_for_room(
+                room_id, on_invalidate=cache_context.invalidate
+            )
+            if aliases:
+                result["aliases"] = aliases
 
         name_event = yield current_state.get((EventTypes.Name, ""))
         if name_event:
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index e30f092c3b..dc92b3026b 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -45,6 +45,8 @@ class RoomMemberHandler(BaseHandler):
     def __init__(self, hs):
         super(RoomMemberHandler, self).__init__(hs)
 
+        self.profile_handler = hs.get_profile_handler()
+
         self.member_linearizer = Linearizer(name="member")
         self.member_limiter = Limiter(3)
 
@@ -288,7 +290,7 @@ class RoomMemberHandler(BaseHandler):
 
                 content["membership"] = Membership.JOIN
 
-                profile = self.hs.get_handlers().profile_handler
+                profile = self.profile_handler
                 if not content_specified:
                     content["displayname"] = yield profile.get_displayname(target)
                     content["avatar_url"] = yield profile.get_avatar_url(target)
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index c3baac6a21..ad6b680231 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -108,6 +108,17 @@ class InvitedSyncResult(collections.namedtuple("InvitedSyncResult", [
         return True
 
 
+class GroupsSyncResult(collections.namedtuple("GroupsSyncResult", [
+    "join",
+    "invite",
+    "leave",
+])):
+    __slots__ = []
+
+    def __nonzero__(self):
+        return bool(self.join or self.invite or self.leave)
+
+
 class DeviceLists(collections.namedtuple("DeviceLists", [
     "changed",   # list of user_ids whose devices may have changed
     "left",      # list of user_ids whose devices we no longer track
@@ -129,6 +140,7 @@ class SyncResult(collections.namedtuple("SyncResult", [
     "device_lists",  # List of user_ids whose devices have chanegd
     "device_one_time_keys_count",  # Dict of algorithm to count for one time keys
                                    # for this device
+    "groups",
 ])):
     __slots__ = []
 
@@ -144,7 +156,8 @@ class SyncResult(collections.namedtuple("SyncResult", [
             self.archived or
             self.account_data or
             self.to_device or
-            self.device_lists
+            self.device_lists or
+            self.groups
         )
 
 
@@ -595,6 +608,8 @@ class SyncHandler(object):
                 user_id, device_id
             )
 
+        yield self._generate_sync_entry_for_groups(sync_result_builder)
+
         defer.returnValue(SyncResult(
             presence=sync_result_builder.presence,
             account_data=sync_result_builder.account_data,
@@ -603,10 +618,57 @@ class SyncHandler(object):
             archived=sync_result_builder.archived,
             to_device=sync_result_builder.to_device,
             device_lists=device_lists,
+            groups=sync_result_builder.groups,
             device_one_time_keys_count=one_time_key_counts,
             next_batch=sync_result_builder.now_token,
         ))
 
+    @measure_func("_generate_sync_entry_for_groups")
+    @defer.inlineCallbacks
+    def _generate_sync_entry_for_groups(self, sync_result_builder):
+        user_id = sync_result_builder.sync_config.user.to_string()
+        since_token = sync_result_builder.since_token
+        now_token = sync_result_builder.now_token
+
+        if since_token and since_token.groups_key:
+            results = yield self.store.get_groups_changes_for_user(
+                user_id, since_token.groups_key, now_token.groups_key,
+            )
+        else:
+            results = yield self.store.get_all_groups_for_user(
+                user_id, now_token.groups_key,
+            )
+
+        invited = {}
+        joined = {}
+        left = {}
+        for result in results:
+            membership = result["membership"]
+            group_id = result["group_id"]
+            gtype = result["type"]
+            content = result["content"]
+
+            if membership == "join":
+                if gtype == "membership":
+                    # TODO: Add profile
+                    content.pop("membership", None)
+                    joined[group_id] = content["content"]
+                else:
+                    joined.setdefault(group_id, {})[gtype] = content
+            elif membership == "invite":
+                if gtype == "membership":
+                    content.pop("membership", None)
+                    invited[group_id] = content["content"]
+            else:
+                if gtype == "membership":
+                    left[group_id] = content["content"]
+
+        sync_result_builder.groups = GroupsSyncResult(
+            join=joined,
+            invite=invited,
+            leave=left,
+        )
+
     @measure_func("_generate_sync_entry_for_device_list")
     @defer.inlineCallbacks
     def _generate_sync_entry_for_device_list(self, sync_result_builder,
@@ -1368,6 +1430,7 @@ class SyncResultBuilder(object):
         self.invited = []
         self.archived = []
         self.device = []
+        self.groups = None
         self.to_device = []
 
 
diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index 6fc3a41c29..8c8b7fa656 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -344,7 +344,7 @@ class MatrixFederationHttpClient(object):
 
     @defer.inlineCallbacks
     def post_json(self, destination, path, data={}, long_retries=False,
-                  timeout=None, ignore_backoff=False):
+                  timeout=None, ignore_backoff=False, args={}):
         """ Sends the specifed json data using POST
 
         Args:
@@ -380,6 +380,7 @@ class MatrixFederationHttpClient(object):
             destination,
             "POST",
             path,
+            query_bytes=encode_query_args(args),
             body_callback=body_callback,
             headers_dict={"Content-Type": ["application/json"]},
             long_retries=long_retries,
@@ -424,13 +425,6 @@ class MatrixFederationHttpClient(object):
         """
         logger.debug("get_json args: %s", args)
 
-        encoded_args = {}
-        for k, vs in args.items():
-            if isinstance(vs, basestring):
-                vs = [vs]
-            encoded_args[k] = [v.encode("UTF-8") for v in vs]
-
-        query_bytes = urllib.urlencode(encoded_args, True)
         logger.debug("Query bytes: %s Retry DNS: %s", args, retry_on_dns_fail)
 
         def body_callback(method, url_bytes, headers_dict):
@@ -441,7 +435,7 @@ class MatrixFederationHttpClient(object):
             destination,
             "GET",
             path,
-            query_bytes=query_bytes,
+            query_bytes=encode_query_args(args),
             body_callback=body_callback,
             retry_on_dns_fail=retry_on_dns_fail,
             timeout=timeout,
@@ -458,6 +452,52 @@ class MatrixFederationHttpClient(object):
         defer.returnValue(json.loads(body))
 
     @defer.inlineCallbacks
+    def delete_json(self, destination, path, long_retries=False,
+                    timeout=None, ignore_backoff=False, args={}):
+        """Send a DELETE request to the remote expecting some json response
+
+        Args:
+            destination (str): The remote server to send the HTTP request
+                to.
+            path (str): The HTTP path.
+            long_retries (bool): A boolean that indicates whether we should
+                retry for a short or long time.
+            timeout(int): How long to try (in ms) the destination for before
+                giving up. None indicates no timeout.
+            ignore_backoff (bool): true to ignore the historical backoff data and
+                try the request anyway.
+        Returns:
+            Deferred: Succeeds when we get a 2xx HTTP response. The result
+            will be the decoded JSON body.
+
+            Fails with ``HTTPRequestException`` if we get an HTTP response
+            code >= 300.
+
+            Fails with ``NotRetryingDestination`` if we are not yet ready
+            to retry this server.
+        """
+
+        response = yield self._request(
+            destination,
+            "DELETE",
+            path,
+            query_bytes=encode_query_args(args),
+            headers_dict={"Content-Type": ["application/json"]},
+            long_retries=long_retries,
+            timeout=timeout,
+            ignore_backoff=ignore_backoff,
+        )
+
+        if 200 <= response.code < 300:
+            # We need to update the transactions table to say it was sent?
+            check_content_type_is_json(response.headers)
+
+        with logcontext.PreserveLoggingContext():
+            body = yield readBody(response)
+
+        defer.returnValue(json.loads(body))
+
+    @defer.inlineCallbacks
     def get_file(self, destination, path, output_stream, args={},
                  retry_on_dns_fail=True, max_size=None,
                  ignore_backoff=False):
@@ -609,3 +649,15 @@ def check_content_type_is_json(headers):
         raise RuntimeError(
             "Content-Type not application/json: was '%s'" % c_type
         )
+
+
+def encode_query_args(args):
+    encoded_args = {}
+    for k, vs in args.items():
+        if isinstance(vs, basestring):
+            vs = [vs]
+        encoded_args[k] = [v.encode("UTF-8") for v in vs]
+
+    query_bytes = urllib.urlencode(encoded_args, True)
+
+    return query_bytes
diff --git a/synapse/http/server.py b/synapse/http/server.py
index 7ef3d526b1..8a27e3b422 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -145,7 +145,9 @@ def wrap_request_handler(request_handler, include_metrics=False):
                                 "error": "Internal server error",
                                 "errcode": Codes.UNKNOWN,
                             },
-                            send_cors=True
+                            send_cors=True,
+                            pretty_print=_request_user_agent_is_curl(request),
+                            version_string=self.version_string,
                         )
                     finally:
                         try:
diff --git a/synapse/push/baserules.py b/synapse/push/baserules.py
index 85effdfa46..9dce99ebec 100644
--- a/synapse/push/baserules.py
+++ b/synapse/push/baserules.py
@@ -1,4 +1,5 @@
 # Copyright 2015, 2016 OpenMarket Ltd
+# Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -238,6 +239,28 @@ BASE_APPEND_OVERRIDE_RULES = [
             }
         ]
     },
+    {
+        'rule_id': 'global/override/.m.rule.roomnotif',
+        'conditions': [
+            {
+                'kind': 'event_match',
+                'key': 'content.body',
+                'pattern': '*@room*',
+                '_id': '_roomnotif_content',
+            },
+            {
+                'kind': 'sender_notification_permission',
+                'key': 'room',
+                '_id': '_roomnotif_pl',
+            },
+        ],
+        'actions': [
+            'notify', {
+                'set_tweak': 'highlight',
+                'value': True,
+            }
+        ]
+    }
 ]
 
 
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index b0d64aa6c4..425a017bdf 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2015 OpenMarket Ltd
+# Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -19,11 +20,13 @@ from twisted.internet import defer
 
 from .push_rule_evaluator import PushRuleEvaluatorForEvent
 
+from synapse.event_auth import get_user_power_level
 from synapse.api.constants import EventTypes, Membership
 from synapse.metrics import get_metrics_for
 from synapse.util.caches import metrics as cache_metrics
 from synapse.util.caches.descriptors import cached
 from synapse.util.async import Linearizer
+from synapse.state import POWER_KEY
 
 from collections import namedtuple
 
@@ -59,6 +62,7 @@ class BulkPushRuleEvaluator(object):
     def __init__(self, hs):
         self.hs = hs
         self.store = hs.get_datastore()
+        self.auth = hs.get_auth()
 
         self.room_push_rule_cache_metrics = cache_metrics.register_cache(
             "cache",
@@ -109,6 +113,29 @@ class BulkPushRuleEvaluator(object):
         )
 
     @defer.inlineCallbacks
+    def _get_power_levels_and_sender_level(self, event, context):
+        pl_event_id = context.prev_state_ids.get(POWER_KEY)
+        if pl_event_id:
+            # fastpath: if there's a power level event, that's all we need, and
+            # not having a power level event is an extreme edge case
+            pl_event = yield self.store.get_event(pl_event_id)
+            auth_events = {POWER_KEY: pl_event}
+        else:
+            auth_events_ids = yield self.auth.compute_auth_events(
+                event, context.prev_state_ids, for_verification=False,
+            )
+            auth_events = yield self.store.get_events(auth_events_ids)
+            auth_events = {
+                (e.type, e.state_key): e for e in auth_events.itervalues()
+            }
+
+        sender_level = get_user_power_level(event.sender, auth_events)
+
+        pl_event = auth_events.get(POWER_KEY)
+
+        defer.returnValue((pl_event.content if pl_event else {}, sender_level))
+
+    @defer.inlineCallbacks
     def action_for_event_by_user(self, event, context):
         """Given an event and context, evaluate the push rules and return
         the results
@@ -123,7 +150,13 @@ class BulkPushRuleEvaluator(object):
             event, context
         )
 
-        evaluator = PushRuleEvaluatorForEvent(event, len(room_members))
+        (power_levels, sender_power_level) = (
+            yield self._get_power_levels_and_sender_level(event, context)
+        )
+
+        evaluator = PushRuleEvaluatorForEvent(
+            event, len(room_members), sender_power_level, power_levels,
+        )
 
         condition_cache = {}
 
diff --git a/synapse/push/push_rule_evaluator.py b/synapse/push/push_rule_evaluator.py
index 65f9a63fd8..3601f2d365 100644
--- a/synapse/push/push_rule_evaluator.py
+++ b/synapse/push/push_rule_evaluator.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2015, 2016 OpenMarket Ltd
+# Copyright 2017 New Vector Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -29,6 +30,21 @@ INEQUALITY_EXPR = re.compile("^([=<>]*)([0-9]*)$")
 
 
 def _room_member_count(ev, condition, room_member_count):
+    return _test_ineq_condition(condition, room_member_count)
+
+
+def _sender_notification_permission(ev, condition, sender_power_level, power_levels):
+    notif_level_key = condition.get('key')
+    if notif_level_key is None:
+        return False
+
+    notif_levels = power_levels.get('notifications', {})
+    room_notif_level = notif_levels.get(notif_level_key, 50)
+
+    return sender_power_level >= room_notif_level
+
+
+def _test_ineq_condition(condition, number):
     if 'is' not in condition:
         return False
     m = INEQUALITY_EXPR.match(condition['is'])
@@ -41,15 +57,15 @@ def _room_member_count(ev, condition, room_member_count):
     rhs = int(rhs)
 
     if ineq == '' or ineq == '==':
-        return room_member_count == rhs
+        return number == rhs
     elif ineq == '<':
-        return room_member_count < rhs
+        return number < rhs
     elif ineq == '>':
-        return room_member_count > rhs
+        return number > rhs
     elif ineq == '>=':
-        return room_member_count >= rhs
+        return number >= rhs
     elif ineq == '<=':
-        return room_member_count <= rhs
+        return number <= rhs
     else:
         return False
 
@@ -65,9 +81,11 @@ def tweaks_for_actions(actions):
 
 
 class PushRuleEvaluatorForEvent(object):
-    def __init__(self, event, room_member_count):
+    def __init__(self, event, room_member_count, sender_power_level, power_levels):
         self._event = event
         self._room_member_count = room_member_count
+        self._sender_power_level = sender_power_level
+        self._power_levels = power_levels
 
         # Maps strings of e.g. 'content.body' -> event["content"]["body"]
         self._value_cache = _flatten_dict(event)
@@ -81,6 +99,10 @@ class PushRuleEvaluatorForEvent(object):
             return _room_member_count(
                 self._event, condition, self._room_member_count
             )
+        elif condition['kind'] == 'sender_notification_permission':
+            return _sender_notification_permission(
+                self._event, condition, self._sender_power_level, self._power_levels,
+            )
         else:
             return True
 
diff --git a/synapse/replication/slave/storage/groups.py b/synapse/replication/slave/storage/groups.py
new file mode 100644
index 0000000000..0bc4bce5b0
--- /dev/null
+++ b/synapse/replication/slave/storage/groups.py
@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+# Copyright 2016 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ._base import BaseSlavedStore
+from ._slaved_id_tracker import SlavedIdTracker
+from synapse.storage import DataStore
+from synapse.util.caches.stream_change_cache import StreamChangeCache
+
+
+class SlavedGroupServerStore(BaseSlavedStore):
+    def __init__(self, db_conn, hs):
+        super(SlavedGroupServerStore, self).__init__(db_conn, hs)
+
+        self.hs = hs
+
+        self._group_updates_id_gen = SlavedIdTracker(
+            db_conn, "local_group_updates", "stream_id",
+        )
+        self._group_updates_stream_cache = StreamChangeCache(
+            "_group_updates_stream_cache", self._group_updates_id_gen.get_current_token(),
+        )
+
+    get_groups_changes_for_user = DataStore.get_groups_changes_for_user.__func__
+    get_group_stream_token = DataStore.get_group_stream_token.__func__
+    get_all_groups_for_user = DataStore.get_all_groups_for_user.__func__
+
+    def stream_positions(self):
+        result = super(SlavedGroupServerStore, self).stream_positions()
+        result["groups"] = self._group_updates_id_gen.get_current_token()
+        return result
+
+    def process_replication_rows(self, stream_name, token, rows):
+        if stream_name == "groups":
+            self._group_updates_id_gen.advance(token)
+            for row in rows:
+                self._group_updates_stream_cache.entity_has_changed(
+                    row.user_id, token
+                )
+
+        return super(SlavedGroupServerStore, self).process_replication_rows(
+            stream_name, token, rows
+        )
diff --git a/synapse/replication/tcp/streams.py b/synapse/replication/tcp/streams.py
index 701e2af2e2..07d99dd63c 100644
--- a/synapse/replication/tcp/streams.py
+++ b/synapse/replication/tcp/streams.py
@@ -118,6 +118,12 @@ CurrentStateDeltaStreamRow = namedtuple("CurrentStateDeltaStream", (
     "state_key",  # str
     "event_id",  # str, optional
 ))
+GroupsStreamRow = namedtuple("GroupsStreamRow", (
+    "group_id",  # str
+    "user_id",  # str
+    "type",  # str
+    "content",  # dict
+))
 
 
 class Stream(object):
@@ -464,6 +470,19 @@ class CurrentStateDeltaStream(Stream):
         super(CurrentStateDeltaStream, self).__init__(hs)
 
 
+class GroupServerStream(Stream):
+    NAME = "groups"
+    ROW_TYPE = GroupsStreamRow
+
+    def __init__(self, hs):
+        store = hs.get_datastore()
+
+        self.current_token = store.get_group_stream_token
+        self.update_function = store.get_all_groups_changes
+
+        super(GroupServerStream, self).__init__(hs)
+
+
 STREAMS_MAP = {
     stream.NAME: stream
     for stream in (
@@ -482,5 +501,6 @@ STREAMS_MAP = {
         TagAccountDataStream,
         AccountDataStream,
         CurrentStateDeltaStream,
+        GroupServerStream,
     )
 }
diff --git a/synapse/rest/__init__.py b/synapse/rest/__init__.py
index 3d809d181b..16f5a73b95 100644
--- a/synapse/rest/__init__.py
+++ b/synapse/rest/__init__.py
@@ -52,6 +52,7 @@ from synapse.rest.client.v2_alpha import (
     thirdparty,
     sendtodevice,
     user_directory,
+    groups,
 )
 
 from synapse.http.server import JsonResource
@@ -102,3 +103,4 @@ class ClientRestResource(JsonResource):
         thirdparty.register_servlets(hs, client_resource)
         sendtodevice.register_servlets(hs, client_resource)
         user_directory.register_servlets(hs, client_resource)
+        groups.register_servlets(hs, client_resource)
diff --git a/synapse/rest/client/v1/profile.py b/synapse/rest/client/v1/profile.py
index 1a5045c9ec..d7edc34245 100644
--- a/synapse/rest/client/v1/profile.py
+++ b/synapse/rest/client/v1/profile.py
@@ -26,13 +26,13 @@ class ProfileDisplaynameRestServlet(ClientV1RestServlet):
 
     def __init__(self, hs):
         super(ProfileDisplaynameRestServlet, self).__init__(hs)
-        self.handlers = hs.get_handlers()
+        self.profile_handler = hs.get_profile_handler()
 
     @defer.inlineCallbacks
     def on_GET(self, request, user_id):
         user = UserID.from_string(user_id)
 
-        displayname = yield self.handlers.profile_handler.get_displayname(
+        displayname = yield self.profile_handler.get_displayname(
             user,
         )
 
@@ -55,7 +55,7 @@ class ProfileDisplaynameRestServlet(ClientV1RestServlet):
         except:
             defer.returnValue((400, "Unable to parse name"))
 
-        yield self.handlers.profile_handler.set_displayname(
+        yield self.profile_handler.set_displayname(
             user, requester, new_name, is_admin)
 
         defer.returnValue((200, {}))
@@ -69,13 +69,13 @@ class ProfileAvatarURLRestServlet(ClientV1RestServlet):
 
     def __init__(self, hs):
         super(ProfileAvatarURLRestServlet, self).__init__(hs)
-        self.handlers = hs.get_handlers()
+        self.profile_handler = hs.get_profile_handler()
 
     @defer.inlineCallbacks
     def on_GET(self, request, user_id):
         user = UserID.from_string(user_id)
 
-        avatar_url = yield self.handlers.profile_handler.get_avatar_url(
+        avatar_url = yield self.profile_handler.get_avatar_url(
             user,
         )
 
@@ -97,7 +97,7 @@ class ProfileAvatarURLRestServlet(ClientV1RestServlet):
         except:
             defer.returnValue((400, "Unable to parse name"))
 
-        yield self.handlers.profile_handler.set_avatar_url(
+        yield self.profile_handler.set_avatar_url(
             user, requester, new_name, is_admin)
 
         defer.returnValue((200, {}))
@@ -111,16 +111,16 @@ class ProfileRestServlet(ClientV1RestServlet):
 
     def __init__(self, hs):
         super(ProfileRestServlet, self).__init__(hs)
-        self.handlers = hs.get_handlers()
+        self.profile_handler = hs.get_profile_handler()
 
     @defer.inlineCallbacks
     def on_GET(self, request, user_id):
         user = UserID.from_string(user_id)
 
-        displayname = yield self.handlers.profile_handler.get_displayname(
+        displayname = yield self.profile_handler.get_displayname(
             user,
         )
-        avatar_url = yield self.handlers.profile_handler.get_avatar_url(
+        avatar_url = yield self.profile_handler.get_avatar_url(
             user,
         )
 
diff --git a/synapse/rest/client/v2_alpha/groups.py b/synapse/rest/client/v2_alpha/groups.py
new file mode 100644
index 0000000000..8f3ce15b02
--- /dev/null
+++ b/synapse/rest/client/v2_alpha/groups.py
@@ -0,0 +1,695 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.http.servlet import RestServlet, parse_json_object_from_request
+from synapse.types import GroupID
+
+from ._base import client_v2_patterns
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class GroupServlet(RestServlet):
+    """Get the group profile
+    """
+    PATTERNS = client_v2_patterns("/groups/(?P<group_id>[^/]*)/profile$")
+
+    def __init__(self, hs):
+        super(GroupServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        group_description = yield self.groups_handler.get_group_profile(group_id, user_id)
+
+        defer.returnValue((200, group_description))
+
+    @defer.inlineCallbacks
+    def on_POST(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        yield self.groups_handler.update_group_profile(
+            group_id, user_id, content,
+        )
+
+        defer.returnValue((200, {}))
+
+
+class GroupSummaryServlet(RestServlet):
+    """Get the full group summary
+    """
+    PATTERNS = client_v2_patterns("/groups/(?P<group_id>[^/]*)/summary$")
+
+    def __init__(self, hs):
+        super(GroupSummaryServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        get_group_summary = yield self.groups_handler.get_group_summary(group_id, user_id)
+
+        defer.returnValue((200, get_group_summary))
+
+
+class GroupSummaryRoomsCatServlet(RestServlet):
+    """Update/delete a rooms entry in the summary.
+
+    Matches both:
+        - /groups/:group/summary/rooms/:room_id
+        - /groups/:group/summary/categories/:category/rooms/:room_id
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/summary"
+        "(/categories/(?P<category_id>[^/]+))?"
+        "/rooms/(?P<room_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSummaryRoomsCatServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, category_id, room_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        resp = yield self.groups_handler.update_group_summary_room(
+            group_id, user_id,
+            room_id=room_id,
+            category_id=category_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, group_id, category_id, room_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        resp = yield self.groups_handler.delete_group_summary_room(
+            group_id, user_id,
+            room_id=room_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class GroupCategoryServlet(RestServlet):
+    """Get/add/update/delete a group category
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/categories/(?P<category_id>[^/]+)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupCategoryServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id, category_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        category = yield self.groups_handler.get_group_category(
+            group_id, user_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue((200, category))
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, category_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        resp = yield self.groups_handler.update_group_category(
+            group_id, user_id,
+            category_id=category_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, group_id, category_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        resp = yield self.groups_handler.delete_group_category(
+            group_id, user_id,
+            category_id=category_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class GroupCategoriesServlet(RestServlet):
+    """Get all group categories
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/categories/$"
+    )
+
+    def __init__(self, hs):
+        super(GroupCategoriesServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        category = yield self.groups_handler.get_group_categories(
+            group_id, user_id,
+        )
+
+        defer.returnValue((200, category))
+
+
+class GroupRoleServlet(RestServlet):
+    """Get/add/update/delete a group role
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/roles/(?P<role_id>[^/]+)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupRoleServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id, role_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        category = yield self.groups_handler.get_group_role(
+            group_id, user_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue((200, category))
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, role_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        resp = yield self.groups_handler.update_group_role(
+            group_id, user_id,
+            role_id=role_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, group_id, role_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        resp = yield self.groups_handler.delete_group_role(
+            group_id, user_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class GroupRolesServlet(RestServlet):
+    """Get all group roles
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/roles/$"
+    )
+
+    def __init__(self, hs):
+        super(GroupRolesServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        category = yield self.groups_handler.get_group_roles(
+            group_id, user_id,
+        )
+
+        defer.returnValue((200, category))
+
+
+class GroupSummaryUsersRoleServlet(RestServlet):
+    """Update/delete a user's entry in the summary.
+
+    Matches both:
+        - /groups/:group/summary/users/:room_id
+        - /groups/:group/summary/roles/:role/users/:user_id
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/summary"
+        "(/roles/(?P<role_id>[^/]+))?"
+        "/users/(?P<user_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSummaryUsersRoleServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, role_id, user_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        resp = yield self.groups_handler.update_group_summary_user(
+            group_id, requester_user_id,
+            user_id=user_id,
+            role_id=role_id,
+            content=content,
+        )
+
+        defer.returnValue((200, resp))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, group_id, role_id, user_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        resp = yield self.groups_handler.delete_group_summary_user(
+            group_id, requester_user_id,
+            user_id=user_id,
+            role_id=role_id,
+        )
+
+        defer.returnValue((200, resp))
+
+
+class GroupRoomServlet(RestServlet):
+    """Get all rooms in a group
+    """
+    PATTERNS = client_v2_patterns("/groups/(?P<group_id>[^/]*)/rooms$")
+
+    def __init__(self, hs):
+        super(GroupRoomServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        result = yield self.groups_handler.get_rooms_in_group(group_id, user_id)
+
+        defer.returnValue((200, result))
+
+
+class GroupUsersServlet(RestServlet):
+    """Get all users in a group
+    """
+    PATTERNS = client_v2_patterns("/groups/(?P<group_id>[^/]*)/users$")
+
+    def __init__(self, hs):
+        super(GroupUsersServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        result = yield self.groups_handler.get_users_in_group(group_id, user_id)
+
+        defer.returnValue((200, result))
+
+
+class GroupCreateServlet(RestServlet):
+    """Create a group
+    """
+    PATTERNS = client_v2_patterns("/create_group$")
+
+    def __init__(self, hs):
+        super(GroupCreateServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+        self.server_name = hs.hostname
+
+    @defer.inlineCallbacks
+    def on_POST(self, request):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        # TODO: Create group on remote server
+        content = parse_json_object_from_request(request)
+        localpart = content.pop("localpart")
+        group_id = GroupID.create(localpart, self.server_name).to_string()
+
+        result = yield self.groups_handler.create_group(group_id, user_id, content)
+
+        defer.returnValue((200, result))
+
+
+class GroupAdminRoomsServlet(RestServlet):
+    """Add a room to the group
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/admin/rooms/(?P<room_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupAdminRoomsServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, room_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        result = yield self.groups_handler.add_room_to_group(
+            group_id, user_id, room_id, content,
+        )
+
+        defer.returnValue((200, result))
+
+    @defer.inlineCallbacks
+    def on_DELETE(self, request, group_id, room_id):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        result = yield self.groups_handler.remove_room_from_group(
+            group_id, user_id, room_id,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupAdminUsersInviteServlet(RestServlet):
+    """Invite a user to the group
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/admin/users/invite/(?P<user_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupAdminUsersInviteServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+        self.store = hs.get_datastore()
+        self.is_mine_id = hs.is_mine_id
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, user_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        config = content.get("config", {})
+        result = yield self.groups_handler.invite(
+            group_id, user_id, requester_user_id, config,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupAdminUsersKickServlet(RestServlet):
+    """Kick a user from the group
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/admin/users/remove/(?P<user_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(GroupAdminUsersKickServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id, user_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        result = yield self.groups_handler.remove_user_from_group(
+            group_id, user_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupSelfLeaveServlet(RestServlet):
+    """Leave a joined group
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/self/leave$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSelfLeaveServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        result = yield self.groups_handler.remove_user_from_group(
+            group_id, requester_user_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupSelfJoinServlet(RestServlet):
+    """Attempt to join a group, or knock
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/self/join$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSelfJoinServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        result = yield self.groups_handler.join_group(
+            group_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupSelfAcceptInviteServlet(RestServlet):
+    """Accept a group invite
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/self/accept_invite$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSelfAcceptInviteServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        result = yield self.groups_handler.accept_invite(
+            group_id, requester_user_id, content,
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupSelfUpdatePublicityServlet(RestServlet):
+    """Update whether we publicise a users membership of a group
+    """
+    PATTERNS = client_v2_patterns(
+        "/groups/(?P<group_id>[^/]*)/self/update_publicity$"
+    )
+
+    def __init__(self, hs):
+        super(GroupSelfUpdatePublicityServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def on_PUT(self, request, group_id):
+        requester = yield self.auth.get_user_by_req(request)
+        requester_user_id = requester.user.to_string()
+
+        content = parse_json_object_from_request(request)
+        publicise = content["publicise"]
+        yield self.store.update_group_publicity(
+            group_id, requester_user_id, publicise,
+        )
+
+        defer.returnValue((200, {}))
+
+
+class PublicisedGroupsForUserServlet(RestServlet):
+    """Get the list of groups a user is advertising
+    """
+    PATTERNS = client_v2_patterns(
+        "/publicised_groups/(?P<user_id>[^/]*)$"
+    )
+
+    def __init__(self, hs):
+        super(PublicisedGroupsForUserServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.store = hs.get_datastore()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request, user_id):
+        yield self.auth.get_user_by_req(request)
+
+        result = yield self.groups_handler.get_publicised_groups_for_user(
+            user_id
+        )
+
+        defer.returnValue((200, result))
+
+
+class PublicisedGroupsForUsersServlet(RestServlet):
+    """Get the list of groups a user is advertising
+    """
+    PATTERNS = client_v2_patterns(
+        "/publicised_groups$"
+    )
+
+    def __init__(self, hs):
+        super(PublicisedGroupsForUsersServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.store = hs.get_datastore()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_POST(self, request):
+        yield self.auth.get_user_by_req(request)
+
+        content = parse_json_object_from_request(request)
+        user_ids = content["user_ids"]
+
+        result = yield self.groups_handler.bulk_get_publicised_groups(
+            user_ids
+        )
+
+        defer.returnValue((200, result))
+
+
+class GroupsForUserServlet(RestServlet):
+    """Get all groups the logged in user is joined to
+    """
+    PATTERNS = client_v2_patterns(
+        "/joined_groups$"
+    )
+
+    def __init__(self, hs):
+        super(GroupsForUserServlet, self).__init__()
+        self.auth = hs.get_auth()
+        self.clock = hs.get_clock()
+        self.groups_handler = hs.get_groups_local_handler()
+
+    @defer.inlineCallbacks
+    def on_GET(self, request):
+        requester = yield self.auth.get_user_by_req(request)
+        user_id = requester.user.to_string()
+
+        result = yield self.groups_handler.get_joined_groups(user_id)
+
+        defer.returnValue((200, result))
+
+
+def register_servlets(hs, http_server):
+    GroupServlet(hs).register(http_server)
+    GroupSummaryServlet(hs).register(http_server)
+    GroupUsersServlet(hs).register(http_server)
+    GroupRoomServlet(hs).register(http_server)
+    GroupCreateServlet(hs).register(http_server)
+    GroupAdminRoomsServlet(hs).register(http_server)
+    GroupAdminUsersInviteServlet(hs).register(http_server)
+    GroupAdminUsersKickServlet(hs).register(http_server)
+    GroupSelfLeaveServlet(hs).register(http_server)
+    GroupSelfJoinServlet(hs).register(http_server)
+    GroupSelfAcceptInviteServlet(hs).register(http_server)
+    GroupsForUserServlet(hs).register(http_server)
+    GroupCategoryServlet(hs).register(http_server)
+    GroupCategoriesServlet(hs).register(http_server)
+    GroupSummaryRoomsCatServlet(hs).register(http_server)
+    GroupRoleServlet(hs).register(http_server)
+    GroupRolesServlet(hs).register(http_server)
+    GroupSelfUpdatePublicityServlet(hs).register(http_server)
+    GroupSummaryUsersRoleServlet(hs).register(http_server)
+    PublicisedGroupsForUserServlet(hs).register(http_server)
+    PublicisedGroupsForUsersServlet(hs).register(http_server)
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index 978af9c280..a1e0e53b33 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -200,6 +200,11 @@ class SyncRestServlet(RestServlet):
                 "invite": invited,
                 "leave": archived,
             },
+            "groups": {
+                "join": sync_result.groups.join,
+                "invite": sync_result.groups.invite,
+                "leave": sync_result.groups.leave,
+            },
             "device_one_time_keys_count": sync_result.device_one_time_keys_count,
             "next_batch": sync_result.next_batch.to_string(),
         }
diff --git a/synapse/server.py b/synapse/server.py
index 4d44af745e..10e3e9a4f1 100644
--- a/synapse/server.py
+++ b/synapse/server.py
@@ -51,6 +51,10 @@ from synapse.handlers.initial_sync import InitialSyncHandler
 from synapse.handlers.receipts import ReceiptsHandler
 from synapse.handlers.read_marker import ReadMarkerHandler
 from synapse.handlers.user_directory import UserDirectoyHandler
+from synapse.handlers.groups_local import GroupsLocalHandler
+from synapse.handlers.profile import ProfileHandler
+from synapse.groups.groups_server import GroupsServerHandler
+from synapse.groups.attestations import GroupAttestionRenewer, GroupAttestationSigning
 from synapse.http.client import SimpleHttpClient, InsecureInterceptableContextFactory
 from synapse.http.matrixfederationclient import MatrixFederationHttpClient
 from synapse.notifier import Notifier
@@ -112,6 +116,7 @@ class HomeServer(object):
         'application_service_scheduler',
         'application_service_handler',
         'device_message_handler',
+        'profile_handler',
         'notifier',
         'distributor',
         'client_resource',
@@ -140,6 +145,10 @@ class HomeServer(object):
         'read_marker_handler',
         'action_generator',
         'user_directory_handler',
+        'groups_local_handler',
+        'groups_server_handler',
+        'groups_attestation_signing',
+        'groups_attestation_renewer',
         'spam_checker',
     ]
 
@@ -253,6 +262,9 @@ class HomeServer(object):
     def build_initial_sync_handler(self):
         return InitialSyncHandler(self)
 
+    def build_profile_handler(self):
+        return ProfileHandler(self)
+
     def build_event_sources(self):
         return EventSources(self)
 
@@ -311,6 +323,18 @@ class HomeServer(object):
     def build_user_directory_handler(self):
         return UserDirectoyHandler(self)
 
+    def build_groups_local_handler(self):
+        return GroupsLocalHandler(self)
+
+    def build_groups_server_handler(self):
+        return GroupsServerHandler(self)
+
+    def build_groups_attestation_signing(self):
+        return GroupAttestationSigning(self)
+
+    def build_groups_attestation_renewer(self):
+        return GroupAttestionRenewer(self)
+
     def build_spam_checker(self):
         return SpamChecker(self)
 
diff --git a/synapse/storage/__init__.py b/synapse/storage/__init__.py
index b92472df33..594566eb38 100644
--- a/synapse/storage/__init__.py
+++ b/synapse/storage/__init__.py
@@ -37,7 +37,7 @@ from .media_repository import MediaRepositoryStore
 from .rejections import RejectionsStore
 from .event_push_actions import EventPushActionsStore
 from .deviceinbox import DeviceInboxStore
-
+from .group_server import GroupServerStore
 from .state import StateStore
 from .signatures import SignatureStore
 from .filtering import FilteringStore
@@ -88,6 +88,7 @@ class DataStore(RoomMemberStore, RoomStore,
                 DeviceStore,
                 DeviceInboxStore,
                 UserDirectoryStore,
+                GroupServerStore,
                 ):
 
     def __init__(self, db_conn, hs):
@@ -135,6 +136,9 @@ class DataStore(RoomMemberStore, RoomStore,
             db_conn, "pushers", "id",
             extra_tables=[("deleted_pushers", "stream_id")],
         )
+        self._group_updates_id_gen = StreamIdGenerator(
+            db_conn, "local_group_updates", "stream_id",
+        )
 
         if isinstance(self.database_engine, PostgresEngine):
             self._cache_id_gen = StreamIdGenerator(
@@ -235,6 +239,18 @@ class DataStore(RoomMemberStore, RoomStore,
             prefilled_cache=curr_state_delta_prefill,
         )
 
+        _group_updates_prefill, min_group_updates_id = self._get_cache_dict(
+            db_conn, "local_group_updates",
+            entity_column="user_id",
+            stream_column="stream_id",
+            max_value=self._group_updates_id_gen.get_current_token(),
+            limit=1000,
+        )
+        self._group_updates_stream_cache = StreamChangeCache(
+            "_group_updates_stream_cache", min_group_updates_id,
+            prefilled_cache=_group_updates_prefill,
+        )
+
         cur = LoggingTransaction(
             db_conn.cursor(),
             name="_find_stream_orderings_for_times_txn",
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index b4fc9bf90a..a7db8b6c4a 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -743,6 +743,33 @@ class SQLBaseStore(object):
         txn.execute(sql, values)
         return cls.cursor_to_dict(txn)
 
+    def _simple_update(self, table, keyvalues, updatevalues, desc):
+        return self.runInteraction(
+            desc,
+            self._simple_update_txn,
+            table, keyvalues, updatevalues,
+        )
+
+    @staticmethod
+    def _simple_update_txn(txn, table, keyvalues, updatevalues):
+        if keyvalues:
+            where = "WHERE %s" % " AND ".join("%s = ?" % k for k in keyvalues.iterkeys())
+        else:
+            where = ""
+
+        update_sql = "UPDATE %s SET %s %s" % (
+            table,
+            ", ".join("%s = ?" % (k,) for k in updatevalues),
+            where,
+        )
+
+        txn.execute(
+            update_sql,
+            updatevalues.values() + keyvalues.values()
+        )
+
+        return txn.rowcount
+
     def _simple_update_one(self, table, keyvalues, updatevalues,
                            desc="_simple_update_one"):
         """Executes an UPDATE query on the named table, setting new values for
@@ -768,27 +795,13 @@ class SQLBaseStore(object):
             table, keyvalues, updatevalues,
         )
 
-    @staticmethod
-    def _simple_update_one_txn(txn, table, keyvalues, updatevalues):
-        if keyvalues:
-            where = "WHERE %s" % " AND ".join("%s = ?" % k for k in keyvalues.iterkeys())
-        else:
-            where = ""
-
-        update_sql = "UPDATE %s SET %s %s" % (
-            table,
-            ", ".join("%s = ?" % (k,) for k in updatevalues),
-            where,
-        )
-
-        txn.execute(
-            update_sql,
-            updatevalues.values() + keyvalues.values()
-        )
+    @classmethod
+    def _simple_update_one_txn(cls, txn, table, keyvalues, updatevalues):
+        rowcount = cls._simple_update_txn(txn, table, keyvalues, updatevalues)
 
-        if txn.rowcount == 0:
+        if rowcount == 0:
             raise StoreError(404, "No row found")
-        if txn.rowcount > 1:
+        if rowcount > 1:
             raise StoreError(500, "More than one row matched")
 
     @staticmethod
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 46c5132a75..752f172058 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -784,6 +784,9 @@ class EventsStore(SQLBaseStore):
                     self._invalidate_cache_and_stream(
                         txn, self.is_host_joined, (room_id, host)
                     )
+                    self._invalidate_cache_and_stream(
+                        txn, self.was_host_joined, (room_id, host)
+                    )
 
                 self._invalidate_cache_and_stream(
                     txn, self.get_users_in_room, (room_id,)
diff --git a/synapse/storage/group_server.py b/synapse/storage/group_server.py
new file mode 100644
index 0000000000..4fe9172adc
--- /dev/null
+++ b/synapse/storage/group_server.py
@@ -0,0 +1,1187 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 Vector Creations Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from twisted.internet import defer
+
+from synapse.api.errors import SynapseError
+
+from ._base import SQLBaseStore
+
+import ujson as json
+
+
+# The category ID for the "default" category. We don't store as null in the
+# database to avoid the fun of null != null
+_DEFAULT_CATEGORY_ID = ""
+_DEFAULT_ROLE_ID = ""
+
+
+class GroupServerStore(SQLBaseStore):
+    def get_group(self, group_id):
+        return self._simple_select_one(
+            table="groups",
+            keyvalues={
+                "group_id": group_id,
+            },
+            retcols=("name", "short_description", "long_description", "avatar_url",),
+            allow_none=True,
+            desc="is_user_in_group",
+        )
+
+    def get_users_in_group(self, group_id, include_private=False):
+        # TODO: Pagination
+
+        keyvalues = {
+            "group_id": group_id,
+        }
+        if not include_private:
+            keyvalues["is_public"] = True
+
+        return self._simple_select_list(
+            table="group_users",
+            keyvalues=keyvalues,
+            retcols=("user_id", "is_public",),
+            desc="get_users_in_group",
+        )
+
+    def get_rooms_in_group(self, group_id, include_private=False):
+        # TODO: Pagination
+
+        keyvalues = {
+            "group_id": group_id,
+        }
+        if not include_private:
+            keyvalues["is_public"] = True
+
+        return self._simple_select_list(
+            table="group_rooms",
+            keyvalues=keyvalues,
+            retcols=("room_id", "is_public",),
+            desc="get_rooms_in_group",
+        )
+
+    def get_rooms_for_summary_by_category(self, group_id, include_private=False):
+        """Get the rooms and categories that should be included in a summary request
+
+        Returns ([rooms], [categories])
+        """
+        def _get_rooms_for_summary_txn(txn):
+            keyvalues = {
+                "group_id": group_id,
+            }
+            if not include_private:
+                keyvalues["is_public"] = True
+
+            sql = """
+                SELECT room_id, is_public, category_id, room_order
+                FROM group_summary_rooms
+                WHERE group_id = ?
+            """
+
+            if not include_private:
+                sql += " AND is_public = ?"
+                txn.execute(sql, (group_id, True))
+            else:
+                txn.execute(sql, (group_id,))
+
+            rooms = [
+                {
+                    "room_id": row[0],
+                    "is_public": row[1],
+                    "category_id": row[2] if row[2] != _DEFAULT_CATEGORY_ID else None,
+                    "order": row[3],
+                }
+                for row in txn
+            ]
+
+            sql = """
+                SELECT category_id, is_public, profile, cat_order
+                FROM group_summary_room_categories
+                INNER JOIN group_room_categories USING (group_id, category_id)
+                WHERE group_id = ?
+            """
+
+            if not include_private:
+                sql += " AND is_public = ?"
+                txn.execute(sql, (group_id, True))
+            else:
+                txn.execute(sql, (group_id,))
+
+            categories = {
+                row[0]: {
+                    "is_public": row[1],
+                    "profile": json.loads(row[2]),
+                    "order": row[3],
+                }
+                for row in txn
+            }
+
+            return rooms, categories
+        return self.runInteraction(
+            "get_rooms_for_summary", _get_rooms_for_summary_txn
+        )
+
+    def add_room_to_summary(self, group_id, room_id, category_id, order, is_public):
+        return self.runInteraction(
+            "add_room_to_summary", self._add_room_to_summary_txn,
+            group_id, room_id, category_id, order, is_public,
+        )
+
+    def _add_room_to_summary_txn(self, txn, group_id, room_id, category_id, order,
+                                 is_public):
+        """Add (or update) room's entry in summary.
+
+        Args:
+            group_id (str)
+            room_id (str)
+            category_id (str): If not None then adds the category to the end of
+                the summary if its not already there. [Optional]
+            order (int): If not None inserts the room at that position, e.g.
+                an order of 1 will put the room first. Otherwise, the room gets
+                added to the end.
+        """
+        room_in_group = self._simple_select_one_onecol_txn(
+            txn,
+            table="group_rooms",
+            keyvalues={
+                "group_id": group_id,
+                "room_id": room_id,
+            },
+            retcol="room_id",
+            allow_none=True,
+        )
+        if not room_in_group:
+            raise SynapseError(400, "room not in group")
+
+        if category_id is None:
+            category_id = _DEFAULT_CATEGORY_ID
+        else:
+            cat_exists = self._simple_select_one_onecol_txn(
+                txn,
+                table="group_room_categories",
+                keyvalues={
+                    "group_id": group_id,
+                    "category_id": category_id,
+                },
+                retcol="group_id",
+                allow_none=True,
+            )
+            if not cat_exists:
+                raise SynapseError(400, "Category doesn't exist")
+
+            # TODO: Check category is part of summary already
+            cat_exists = self._simple_select_one_onecol_txn(
+                txn,
+                table="group_summary_room_categories",
+                keyvalues={
+                    "group_id": group_id,
+                    "category_id": category_id,
+                },
+                retcol="group_id",
+                allow_none=True,
+            )
+            if not cat_exists:
+                # If not, add it with an order larger than all others
+                txn.execute("""
+                    INSERT INTO group_summary_room_categories
+                    (group_id, category_id, cat_order)
+                    SELECT ?, ?, COALESCE(MAX(cat_order), 0) + 1
+                    FROM group_summary_room_categories
+                    WHERE group_id = ? AND category_id = ?
+                """, (group_id, category_id, group_id, category_id))
+
+        existing = self._simple_select_one_txn(
+            txn,
+            table="group_summary_rooms",
+            keyvalues={
+                "group_id": group_id,
+                "room_id": room_id,
+                "category_id": category_id,
+            },
+            retcols=("room_order", "is_public",),
+            allow_none=True,
+        )
+
+        if order is not None:
+            # Shuffle other room orders that come after the given order
+            sql = """
+                UPDATE group_summary_rooms SET room_order = room_order + 1
+                WHERE group_id = ? AND category_id = ? AND room_order >= ?
+            """
+            txn.execute(sql, (group_id, category_id, order,))
+        elif not existing:
+            sql = """
+                SELECT COALESCE(MAX(room_order), 0) + 1 FROM group_summary_rooms
+                WHERE group_id = ? AND category_id = ?
+            """
+            txn.execute(sql, (group_id, category_id,))
+            order, = txn.fetchone()
+
+        if existing:
+            to_update = {}
+            if order is not None:
+                to_update["room_order"] = order
+            if is_public is not None:
+                to_update["is_public"] = is_public
+            self._simple_update_txn(
+                txn,
+                table="group_summary_rooms",
+                keyvalues={
+                    "group_id": group_id,
+                    "category_id": category_id,
+                    "room_id": room_id,
+                },
+                values=to_update,
+            )
+        else:
+            if is_public is None:
+                is_public = True
+
+            self._simple_insert_txn(
+                txn,
+                table="group_summary_rooms",
+                values={
+                    "group_id": group_id,
+                    "category_id": category_id,
+                    "room_id": room_id,
+                    "room_order": order,
+                    "is_public": is_public,
+                },
+            )
+
+    def remove_room_from_summary(self, group_id, room_id, category_id):
+        if category_id is None:
+            category_id = _DEFAULT_CATEGORY_ID
+
+        return self._simple_delete(
+            table="group_summary_rooms",
+            keyvalues={
+                "group_id": group_id,
+                "category_id": category_id,
+                "room_id": room_id,
+            },
+            desc="remove_room_from_summary",
+        )
+
+    @defer.inlineCallbacks
+    def get_group_categories(self, group_id):
+        rows = yield self._simple_select_list(
+            table="group_room_categories",
+            keyvalues={
+                "group_id": group_id,
+            },
+            retcols=("category_id", "is_public", "profile"),
+            desc="get_group_categories",
+        )
+
+        defer.returnValue({
+            row["category_id"]: {
+                "is_public": row["is_public"],
+                "profile": json.loads(row["profile"]),
+            }
+            for row in rows
+        })
+
+    @defer.inlineCallbacks
+    def get_group_category(self, group_id, category_id):
+        category = yield self._simple_select_one(
+            table="group_room_categories",
+            keyvalues={
+                "group_id": group_id,
+                "category_id": category_id,
+            },
+            retcols=("is_public", "profile"),
+            desc="get_group_category",
+        )
+
+        category["profile"] = json.loads(category["profile"])
+
+        defer.returnValue(category)
+
+    def upsert_group_category(self, group_id, category_id, profile, is_public):
+        """Add/update room category for group
+        """
+        insertion_values = {}
+        update_values = {"category_id": category_id}  # This cannot be empty
+
+        if profile is None:
+            insertion_values["profile"] = "{}"
+        else:
+            update_values["profile"] = json.dumps(profile)
+
+        if is_public is None:
+            insertion_values["is_public"] = True
+        else:
+            update_values["is_public"] = is_public
+
+        return self._simple_upsert(
+            table="group_room_categories",
+            keyvalues={
+                "group_id": group_id,
+                "category_id": category_id,
+            },
+            values=update_values,
+            insertion_values=insertion_values,
+            desc="upsert_group_category",
+        )
+
+    def remove_group_category(self, group_id, category_id):
+        return self._simple_delete(
+            table="group_room_categories",
+            keyvalues={
+                "group_id": group_id,
+                "category_id": category_id,
+            },
+            desc="remove_group_category",
+        )
+
+    @defer.inlineCallbacks
+    def get_group_roles(self, group_id):
+        rows = yield self._simple_select_list(
+            table="group_roles",
+            keyvalues={
+                "group_id": group_id,
+            },
+            retcols=("role_id", "is_public", "profile"),
+            desc="get_group_roles",
+        )
+
+        defer.returnValue({
+            row["role_id"]: {
+                "is_public": row["is_public"],
+                "profile": json.loads(row["profile"]),
+            }
+            for row in rows
+        })
+
+    @defer.inlineCallbacks
+    def get_group_role(self, group_id, role_id):
+        role = yield self._simple_select_one(
+            table="group_roles",
+            keyvalues={
+                "group_id": group_id,
+                "role_id": role_id,
+            },
+            retcols=("is_public", "profile"),
+            desc="get_group_role",
+        )
+
+        role["profile"] = json.loads(role["profile"])
+
+        defer.returnValue(role)
+
+    def upsert_group_role(self, group_id, role_id, profile, is_public):
+        """Add/remove user role
+        """
+        insertion_values = {}
+        update_values = {"role_id": role_id}  # This cannot be empty
+
+        if profile is None:
+            insertion_values["profile"] = "{}"
+        else:
+            update_values["profile"] = json.dumps(profile)
+
+        if is_public is None:
+            insertion_values["is_public"] = True
+        else:
+            update_values["is_public"] = is_public
+
+        return self._simple_upsert(
+            table="group_roles",
+            keyvalues={
+                "group_id": group_id,
+                "role_id": role_id,
+            },
+            values=update_values,
+            insertion_values=insertion_values,
+            desc="upsert_group_role",
+        )
+
+    def remove_group_role(self, group_id, role_id):
+        return self._simple_delete(
+            table="group_roles",
+            keyvalues={
+                "group_id": group_id,
+                "role_id": role_id,
+            },
+            desc="remove_group_role",
+        )
+
+    def add_user_to_summary(self, group_id, user_id, role_id, order, is_public):
+        return self.runInteraction(
+            "add_user_to_summary", self._add_user_to_summary_txn,
+            group_id, user_id, role_id, order, is_public,
+        )
+
+    def _add_user_to_summary_txn(self, txn, group_id, user_id, role_id, order,
+                                 is_public):
+        """Add (or update) user's entry in summary.
+
+        Args:
+            group_id (str)
+            user_id (str)
+            role_id (str): If not None then adds the role to the end of
+                the summary if its not already there. [Optional]
+            order (int): If not None inserts the user at that position, e.g.
+                an order of 1 will put the user first. Otherwise, the user gets
+                added to the end.
+        """
+        user_in_group = self._simple_select_one_onecol_txn(
+            txn,
+            table="group_users",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            retcol="user_id",
+            allow_none=True,
+        )
+        if not user_in_group:
+            raise SynapseError(400, "user not in group")
+
+        if role_id is None:
+            role_id = _DEFAULT_ROLE_ID
+        else:
+            role_exists = self._simple_select_one_onecol_txn(
+                txn,
+                table="group_roles",
+                keyvalues={
+                    "group_id": group_id,
+                    "role_id": role_id,
+                },
+                retcol="group_id",
+                allow_none=True,
+            )
+            if not role_exists:
+                raise SynapseError(400, "Role doesn't exist")
+
+            # TODO: Check role is part of the summary already
+            role_exists = self._simple_select_one_onecol_txn(
+                txn,
+                table="group_summary_roles",
+                keyvalues={
+                    "group_id": group_id,
+                    "role_id": role_id,
+                },
+                retcol="group_id",
+                allow_none=True,
+            )
+            if not role_exists:
+                # If not, add it with an order larger than all others
+                txn.execute("""
+                    INSERT INTO group_summary_roles
+                    (group_id, role_id, role_order)
+                    SELECT ?, ?, COALESCE(MAX(role_order), 0) + 1
+                    FROM group_summary_roles
+                    WHERE group_id = ? AND role_id = ?
+                """, (group_id, role_id, group_id, role_id))
+
+        existing = self._simple_select_one_txn(
+            txn,
+            table="group_summary_users",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+                "role_id": role_id,
+            },
+            retcols=("user_order", "is_public",),
+            allow_none=True,
+        )
+
+        if order is not None:
+            # Shuffle other users orders that come after the given order
+            sql = """
+                UPDATE group_summary_users SET user_order = user_order + 1
+                WHERE group_id = ? AND role_id = ? AND user_order >= ?
+            """
+            txn.execute(sql, (group_id, role_id, order,))
+        elif not existing:
+            sql = """
+                SELECT COALESCE(MAX(user_order), 0) + 1 FROM group_summary_users
+                WHERE group_id = ? AND role_id = ?
+            """
+            txn.execute(sql, (group_id, role_id,))
+            order, = txn.fetchone()
+
+        if existing:
+            to_update = {}
+            if order is not None:
+                to_update["user_order"] = order
+            if is_public is not None:
+                to_update["is_public"] = is_public
+            self._simple_update_txn(
+                txn,
+                table="group_summary_users",
+                keyvalues={
+                    "group_id": group_id,
+                    "role_id": role_id,
+                    "user_id": user_id,
+                },
+                values=to_update,
+            )
+        else:
+            if is_public is None:
+                is_public = True
+
+            self._simple_insert_txn(
+                txn,
+                table="group_summary_users",
+                values={
+                    "group_id": group_id,
+                    "role_id": role_id,
+                    "user_id": user_id,
+                    "user_order": order,
+                    "is_public": is_public,
+                },
+            )
+
+    def remove_user_from_summary(self, group_id, user_id, role_id):
+        if role_id is None:
+            role_id = _DEFAULT_ROLE_ID
+
+        return self._simple_delete(
+            table="group_summary_users",
+            keyvalues={
+                "group_id": group_id,
+                "role_id": role_id,
+                "user_id": user_id,
+            },
+            desc="remove_user_from_summary",
+        )
+
+    def get_users_for_summary_by_role(self, group_id, include_private=False):
+        """Get the users and roles that should be included in a summary request
+
+        Returns ([users], [roles])
+        """
+        def _get_users_for_summary_txn(txn):
+            keyvalues = {
+                "group_id": group_id,
+            }
+            if not include_private:
+                keyvalues["is_public"] = True
+
+            sql = """
+                SELECT user_id, is_public, role_id, user_order
+                FROM group_summary_users
+                WHERE group_id = ?
+            """
+
+            if not include_private:
+                sql += " AND is_public = ?"
+                txn.execute(sql, (group_id, True))
+            else:
+                txn.execute(sql, (group_id,))
+
+            users = [
+                {
+                    "user_id": row[0],
+                    "is_public": row[1],
+                    "role_id": row[2] if row[2] != _DEFAULT_ROLE_ID else None,
+                    "order": row[3],
+                }
+                for row in txn
+            ]
+
+            sql = """
+                SELECT role_id, is_public, profile, role_order
+                FROM group_summary_roles
+                INNER JOIN group_roles USING (group_id, role_id)
+                WHERE group_id = ?
+            """
+
+            if not include_private:
+                sql += " AND is_public = ?"
+                txn.execute(sql, (group_id, True))
+            else:
+                txn.execute(sql, (group_id,))
+
+            roles = {
+                row[0]: {
+                    "is_public": row[1],
+                    "profile": json.loads(row[2]),
+                    "order": row[3],
+                }
+                for row in txn
+            }
+
+            return users, roles
+        return self.runInteraction(
+            "get_users_for_summary_by_role", _get_users_for_summary_txn
+        )
+
+    def is_user_in_group(self, user_id, group_id):
+        return self._simple_select_one_onecol(
+            table="group_users",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            retcol="user_id",
+            allow_none=True,
+            desc="is_user_in_group",
+        ).addCallback(lambda r: bool(r))
+
+    def is_user_admin_in_group(self, group_id, user_id):
+        return self._simple_select_one_onecol(
+            table="group_users",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            retcol="is_admin",
+            allow_none=True,
+            desc="is_user_admin_in_group",
+        )
+
+    def add_group_invite(self, group_id, user_id):
+        """Record that the group server has invited a user
+        """
+        return self._simple_insert(
+            table="group_invites",
+            values={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            desc="add_group_invite",
+        )
+
+    def is_user_invited_to_local_group(self, group_id, user_id):
+        """Has the group server invited a user?
+        """
+        return self._simple_select_one_onecol(
+            table="group_invites",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            retcol="user_id",
+            desc="is_user_invited_to_local_group",
+            allow_none=True,
+        )
+
+    def get_users_membership_info_in_group(self, group_id, user_id):
+        """Get a dict describing the membership of a user in a group.
+
+        Example if joined:
+
+            {
+                "membership": "join",
+                "is_public": True,
+                "is_privileged": False,
+            }
+
+        Returns an empty dict if the user is not join/invite/etc
+        """
+        def _get_users_membership_in_group_txn(txn):
+            row = self._simple_select_one_txn(
+                txn,
+                table="group_users",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+                retcols=("is_admin", "is_public"),
+                allow_none=True,
+            )
+
+            if row:
+                return {
+                    "membership": "join",
+                    "is_public": row["is_public"],
+                    "is_privileged": row["is_admin"],
+                }
+
+            row = self._simple_select_one_onecol_txn(
+                txn,
+                table="group_invites",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+                retcol="user_id",
+                allow_none=True,
+            )
+
+            if row:
+                return {
+                    "membership": "invite",
+                }
+
+            return {}
+
+        return self.runInteraction(
+            "get_users_membership_info_in_group", _get_users_membership_in_group_txn,
+        )
+
+    def add_user_to_group(self, group_id, user_id, is_admin=False, is_public=True,
+                          local_attestation=None, remote_attestation=None):
+        """Add a user to the group server.
+
+        Args:
+            group_id (str)
+            user_id (str)
+            is_admin (bool)
+            is_public (bool)
+            local_attestation (dict): The attestation the GS created to give
+                to the remote server. Optional if the user and group are on the
+                same server
+            remote_attestation (dict): The attestation given to GS by remote
+                server. Optional if the user and group are on the same server
+        """
+        def _add_user_to_group_txn(txn):
+            self._simple_insert_txn(
+                txn,
+                table="group_users",
+                values={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                    "is_admin": is_admin,
+                    "is_public": is_public,
+                },
+            )
+
+            self._simple_delete_txn(
+                txn,
+                table="group_invites",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+
+            if local_attestation:
+                self._simple_insert_txn(
+                    txn,
+                    table="group_attestations_renewals",
+                    values={
+                        "group_id": group_id,
+                        "user_id": user_id,
+                        "valid_until_ms": local_attestation["valid_until_ms"],
+                    },
+                )
+            if remote_attestation:
+                self._simple_insert_txn(
+                    txn,
+                    table="group_attestations_remote",
+                    values={
+                        "group_id": group_id,
+                        "user_id": user_id,
+                        "valid_until_ms": remote_attestation["valid_until_ms"],
+                        "attestation_json": json.dumps(remote_attestation),
+                    },
+                )
+
+        return self.runInteraction(
+            "add_user_to_group", _add_user_to_group_txn
+        )
+
+    def remove_user_from_group(self, group_id, user_id):
+        def _remove_user_from_group_txn(txn):
+            self._simple_delete_txn(
+                txn,
+                table="group_users",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+            self._simple_delete_txn(
+                txn,
+                table="group_invites",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+            self._simple_delete_txn(
+                txn,
+                table="group_attestations_renewals",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+            self._simple_delete_txn(
+                txn,
+                table="group_attestations_remote",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+            self._simple_delete_txn(
+                txn,
+                table="group_summary_users",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+        return self.runInteraction("remove_user_from_group", _remove_user_from_group_txn)
+
+    def add_room_to_group(self, group_id, room_id, is_public):
+        return self._simple_insert(
+            table="group_rooms",
+            values={
+                "group_id": group_id,
+                "room_id": room_id,
+                "is_public": is_public,
+            },
+            desc="add_room_to_group",
+        )
+
+    def remove_room_from_group(self, group_id, room_id):
+        def _remove_room_from_group_txn(txn):
+            self._simple_delete_txn(
+                txn,
+                table="group_rooms",
+                keyvalues={
+                    "group_id": group_id,
+                    "room_id": room_id,
+                },
+            )
+
+            self._simple_delete_txn(
+                txn,
+                table="group_summary_rooms",
+                keyvalues={
+                    "group_id": group_id,
+                    "room_id": room_id,
+                },
+            )
+        return self.runInteraction(
+            "remove_room_from_group", _remove_room_from_group_txn,
+        )
+
+    def get_publicised_groups_for_user(self, user_id):
+        """Get all groups a user is publicising
+        """
+        return self._simple_select_onecol(
+            table="local_group_membership",
+            keyvalues={
+                "user_id": user_id,
+                "membership": "join",
+                "is_publicised": True,
+            },
+            retcol="group_id",
+            desc="get_publicised_groups_for_user",
+        )
+
+    def update_group_publicity(self, group_id, user_id, publicise):
+        """Update whether the user is publicising their membership of the group
+        """
+        return self._simple_update_one(
+            table="local_group_membership",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            updatevalues={
+                "is_publicised": publicise,
+            },
+            desc="update_group_publicity"
+        )
+
+    @defer.inlineCallbacks
+    def register_user_group_membership(self, group_id, user_id, membership,
+                                       is_admin=False, content={},
+                                       local_attestation=None,
+                                       remote_attestation=None,
+                                       is_publicised=False,
+                                       ):
+        """Registers that a local user is a member of a (local or remote) group.
+
+        Args:
+            group_id (str)
+            user_id (str)
+            membership (str)
+            is_admin (bool)
+            content (dict): Content of the membership, e.g. includes the inviter
+                if the user has been invited.
+            local_attestation (dict): If remote group then store the fact that we
+                have given out an attestation, else None.
+            remote_attestation (dict): If remote group then store the remote
+                attestation from the group, else None.
+        """
+        def _register_user_group_membership_txn(txn, next_id):
+            # TODO: Upsert?
+            self._simple_delete_txn(
+                txn,
+                table="local_group_membership",
+                keyvalues={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                },
+            )
+            self._simple_insert_txn(
+                txn,
+                table="local_group_membership",
+                values={
+                    "group_id": group_id,
+                    "user_id": user_id,
+                    "is_admin": is_admin,
+                    "membership": membership,
+                    "is_publicised": is_publicised,
+                    "content": json.dumps(content),
+                },
+            )
+
+            self._simple_insert_txn(
+                txn,
+                table="local_group_updates",
+                values={
+                    "stream_id": next_id,
+                    "group_id": group_id,
+                    "user_id": user_id,
+                    "type": "membership",
+                    "content": json.dumps({"membership": membership, "content": content}),
+                }
+            )
+            self._group_updates_stream_cache.entity_has_changed(user_id, next_id)
+
+            # TODO: Insert profile to ensure it comes down stream if its a join.
+
+            if membership == "join":
+                if local_attestation:
+                    self._simple_insert_txn(
+                        txn,
+                        table="group_attestations_renewals",
+                        values={
+                            "group_id": group_id,
+                            "user_id": user_id,
+                            "valid_until_ms": local_attestation["valid_until_ms"],
+                        }
+                    )
+                if remote_attestation:
+                    self._simple_insert_txn(
+                        txn,
+                        table="group_attestations_remote",
+                        values={
+                            "group_id": group_id,
+                            "user_id": user_id,
+                            "valid_until_ms": remote_attestation["valid_until_ms"],
+                            "attestation_json": json.dumps(remote_attestation),
+                        }
+                    )
+            else:
+                self._simple_delete_txn(
+                    txn,
+                    table="group_attestations_renewals",
+                    keyvalues={
+                        "group_id": group_id,
+                        "user_id": user_id,
+                    },
+                )
+                self._simple_delete_txn(
+                    txn,
+                    table="group_attestations_remote",
+                    keyvalues={
+                        "group_id": group_id,
+                        "user_id": user_id,
+                    },
+                )
+
+            return next_id
+
+        with self._group_updates_id_gen.get_next() as next_id:
+            res = yield self.runInteraction(
+                "register_user_group_membership",
+                _register_user_group_membership_txn, next_id,
+            )
+        defer.returnValue(res)
+
+    @defer.inlineCallbacks
+    def create_group(self, group_id, user_id, name, avatar_url, short_description,
+                     long_description,):
+        yield self._simple_insert(
+            table="groups",
+            values={
+                "group_id": group_id,
+                "name": name,
+                "avatar_url": avatar_url,
+                "short_description": short_description,
+                "long_description": long_description,
+            },
+            desc="create_group",
+        )
+
+    @defer.inlineCallbacks
+    def update_group_profile(self, group_id, profile,):
+        yield self._simple_update_one(
+            table="groups",
+            keyvalues={
+                "group_id": group_id,
+            },
+            updatevalues=profile,
+            desc="update_group_profile",
+        )
+
+    def get_attestations_need_renewals(self, valid_until_ms):
+        """Get all attestations that need to be renewed until givent time
+        """
+        def _get_attestations_need_renewals_txn(txn):
+            sql = """
+                SELECT group_id, user_id FROM group_attestations_renewals
+                WHERE valid_until_ms <= ?
+            """
+            txn.execute(sql, (valid_until_ms,))
+            return self.cursor_to_dict(txn)
+        return self.runInteraction(
+            "get_attestations_need_renewals", _get_attestations_need_renewals_txn
+        )
+
+    def update_attestation_renewal(self, group_id, user_id, attestation):
+        """Update an attestation that we have renewed
+        """
+        return self._simple_update_one(
+            table="group_attestations_renewals",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            updatevalues={
+                "valid_until_ms": attestation["valid_until_ms"],
+            },
+            desc="update_attestation_renewal",
+        )
+
+    def update_remote_attestion(self, group_id, user_id, attestation):
+        """Update an attestation that a remote has renewed
+        """
+        return self._simple_update_one(
+            table="group_attestations_remote",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            updatevalues={
+                "valid_until_ms": attestation["valid_until_ms"],
+                "attestation_json": json.dumps(attestation)
+            },
+            desc="update_remote_attestion",
+        )
+
+    @defer.inlineCallbacks
+    def get_remote_attestation(self, group_id, user_id):
+        """Get the attestation that proves the remote agrees that the user is
+        in the group.
+        """
+        row = yield self._simple_select_one(
+            table="group_attestations_remote",
+            keyvalues={
+                "group_id": group_id,
+                "user_id": user_id,
+            },
+            retcols=("valid_until_ms", "attestation_json"),
+            desc="get_remote_attestation",
+            allow_none=True,
+        )
+
+        now = int(self._clock.time_msec())
+        if row and now < row["valid_until_ms"]:
+            defer.returnValue(json.loads(row["attestation_json"]))
+
+        defer.returnValue(None)
+
+    def get_joined_groups(self, user_id):
+        return self._simple_select_onecol(
+            table="local_group_membership",
+            keyvalues={
+                "user_id": user_id,
+                "membership": "join",
+            },
+            retcol="group_id",
+            desc="get_joined_groups",
+        )
+
+    def get_all_groups_for_user(self, user_id, now_token):
+        def _get_all_groups_for_user_txn(txn):
+            sql = """
+                SELECT group_id, type, membership, u.content
+                FROM local_group_updates AS u
+                INNER JOIN local_group_membership USING (group_id, user_id)
+                WHERE user_id = ? AND membership != 'leave'
+                    AND stream_id <= ?
+            """
+            txn.execute(sql, (user_id, now_token,))
+            return [
+                {
+                    "group_id": row[0],
+                    "type": row[1],
+                    "membership": row[2],
+                    "content": json.loads(row[3]),
+                }
+                for row in txn
+            ]
+        return self.runInteraction(
+            "get_all_groups_for_user", _get_all_groups_for_user_txn,
+        )
+
+    def get_groups_changes_for_user(self, user_id, from_token, to_token):
+        from_token = int(from_token)
+        has_changed = self._group_updates_stream_cache.has_entity_changed(
+            user_id, from_token,
+        )
+        if not has_changed:
+            return []
+
+        def _get_groups_changes_for_user_txn(txn):
+            sql = """
+                SELECT group_id, membership, type, u.content
+                FROM local_group_updates AS u
+                INNER JOIN local_group_membership USING (group_id, user_id)
+                WHERE user_id = ? AND ? < stream_id AND stream_id <= ?
+            """
+            txn.execute(sql, (user_id, from_token, to_token,))
+            return [{
+                "group_id": group_id,
+                "membership": membership,
+                "type": gtype,
+                "content": json.loads(content_json),
+            } for group_id, membership, gtype, content_json in txn]
+        return self.runInteraction(
+            "get_groups_changes_for_user", _get_groups_changes_for_user_txn,
+        )
+
+    def get_all_groups_changes(self, from_token, to_token, limit):
+        from_token = int(from_token)
+        has_changed = self._group_updates_stream_cache.has_any_entity_changed(
+            from_token,
+        )
+        if not has_changed:
+            return []
+
+        def _get_all_groups_changes_txn(txn):
+            sql = """
+                SELECT stream_id, group_id, user_id, type, content
+                FROM local_group_updates
+                WHERE ? < stream_id AND stream_id <= ?
+                LIMIT ?
+            """
+            txn.execute(sql, (from_token, to_token, limit,))
+            return [{
+                "stream_id": stream_id,
+                "group_id": group_id,
+                "user_id": user_id,
+                "type": gtype,
+                "content": json.loads(content_json),
+            } for stream_id, group_id, user_id, gtype, content_json in txn]
+        return self.runInteraction(
+            "get_all_groups_changes", _get_all_groups_changes_txn,
+        )
+
+    def get_group_stream_token(self):
+        return self._group_updates_id_gen.get_current_token()
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index a0af8456f5..ccaaabcfa0 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -25,7 +25,7 @@ logger = logging.getLogger(__name__)
 
 # Remember to update this number every time a change is made to database
 # schema files, so the users will be informed on server restarts.
-SCHEMA_VERSION = 44
+SCHEMA_VERSION = 45
 
 dir_path = os.path.abspath(os.path.dirname(__file__))
 
diff --git a/synapse/storage/profile.py b/synapse/storage/profile.py
index 26a40905ae..beea3102fc 100644
--- a/synapse/storage/profile.py
+++ b/synapse/storage/profile.py
@@ -13,6 +13,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from twisted.internet import defer
+
 from ._base import SQLBaseStore
 
 
@@ -55,3 +57,99 @@ class ProfileStore(SQLBaseStore):
             updatevalues={"avatar_url": new_avatar_url},
             desc="set_profile_avatar_url",
         )
+
+    def get_from_remote_profile_cache(self, user_id):
+        return self._simple_select_one(
+            table="remote_profile_cache",
+            keyvalues={"user_id": user_id},
+            retcols=("displayname", "avatar_url",),
+            allow_none=True,
+            desc="get_from_remote_profile_cache",
+        )
+
+    def add_remote_profile_cache(self, user_id, displayname, avatar_url):
+        """Ensure we are caching the remote user's profiles.
+
+        This should only be called when `is_subscribed_remote_profile_for_user`
+        would return true for the user.
+        """
+        return self._simple_upsert(
+            table="remote_profile_cache",
+            keyvalues={"user_id": user_id},
+            values={
+                "displayname": displayname,
+                "avatar_url": avatar_url,
+                "last_check": self._clock.time_msec(),
+            },
+            desc="add_remote_profile_cache",
+        )
+
+    def update_remote_profile_cache(self, user_id, displayname, avatar_url):
+        return self._simple_update(
+            table="remote_profile_cache",
+            keyvalues={"user_id": user_id},
+            values={
+                "displayname": displayname,
+                "avatar_url": avatar_url,
+                "last_check": self._clock.time_msec(),
+            },
+            desc="update_remote_profile_cache",
+        )
+
+    @defer.inlineCallbacks
+    def maybe_delete_remote_profile_cache(self, user_id):
+        """Check if we still care about the remote user's profile, and if we
+        don't then remove their profile from the cache
+        """
+        subscribed = yield self.is_subscribed_remote_profile_for_user(user_id)
+        if not subscribed:
+            yield self._simple_delete(
+                table="remote_profile_cache",
+                keyvalues={"user_id": user_id},
+                desc="delete_remote_profile_cache",
+            )
+
+    def get_remote_profile_cache_entries_that_expire(self, last_checked):
+        """Get all users who haven't been checked since `last_checked`
+        """
+        def _get_remote_profile_cache_entries_that_expire_txn(txn):
+            sql = """
+                SELECT user_id, displayname, avatar_url
+                FROM remote_profile_cache
+                WHERE last_check < ?
+            """
+
+            txn.execute(sql, (last_checked,))
+
+            return self.cursor_to_dict(txn)
+
+        return self.runInteraction(
+            "get_remote_profile_cache_entries_that_expire",
+            _get_remote_profile_cache_entries_that_expire_txn,
+        )
+
+    @defer.inlineCallbacks
+    def is_subscribed_remote_profile_for_user(self, user_id):
+        """Check whether we are interested in a remote user's profile.
+        """
+        res = yield self._simple_select_one_onecol(
+            table="group_users",
+            keyvalues={"user_id": user_id},
+            retcol="user_id",
+            allow_none=True,
+            desc="should_update_remote_profile_cache_for_user",
+        )
+
+        if res:
+            defer.returnValue(True)
+
+        res = yield self._simple_select_one_onecol(
+            table="group_invites",
+            keyvalues={"user_id": user_id},
+            retcol="user_id",
+            allow_none=True,
+            desc="should_update_remote_profile_cache_for_user",
+        )
+
+        if res:
+            defer.returnValue(True)
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 3e868159d4..544813eebb 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -533,6 +533,46 @@ class RoomMemberStore(SQLBaseStore):
 
         defer.returnValue(True)
 
+    @cachedInlineCallbacks()
+    def was_host_joined(self, room_id, host):
+        """Check whether the server is or ever was in the room.
+
+        Args:
+            room_id (str)
+            host (str)
+
+        Returns:
+            Deferred: Resolves to True if the host is/was in the room, otherwise
+            False.
+        """
+        if '%' in host or '_' in host:
+            raise Exception("Invalid host name")
+
+        sql = """
+            SELECT user_id FROM room_memberships
+            WHERE room_id = ?
+                AND user_id LIKE ?
+                AND membership = 'join'
+            LIMIT 1
+        """
+
+        # We do need to be careful to ensure that host doesn't have any wild cards
+        # in it, but we checked above for known ones and we'll check below that
+        # the returned user actually has the correct domain.
+        like_clause = "%:" + host
+
+        rows = yield self._execute("was_host_joined", None, sql, room_id, like_clause)
+
+        if not rows:
+            defer.returnValue(False)
+
+        user_id = rows[0][0]
+        if get_domain_from_id(user_id) != host:
+            # This can only happen if the host name has something funky in it
+            raise Exception("Invalid host name")
+
+        defer.returnValue(True)
+
     def get_joined_hosts(self, room_id, state_entry):
         state_group = state_entry.state_group
         if not state_group:
diff --git a/synapse/storage/schema/delta/45/group_server.sql b/synapse/storage/schema/delta/45/group_server.sql
new file mode 100644
index 0000000000..b2333848a0
--- /dev/null
+++ b/synapse/storage/schema/delta/45/group_server.sql
@@ -0,0 +1,167 @@
+/* Copyright 2017 Vector Creations Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+CREATE TABLE groups (
+    group_id TEXT NOT NULL,
+    name TEXT,  -- the display name of the room
+    avatar_url TEXT,
+    short_description TEXT,
+    long_description TEXT
+);
+
+CREATE UNIQUE INDEX groups_idx ON groups(group_id);
+
+
+-- list of users the group server thinks are joined
+CREATE TABLE group_users (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    is_admin BOOLEAN NOT NULL,
+    is_public BOOLEAN NOT NULL  -- whether the users membership can be seen by everyone
+);
+
+
+CREATE INDEX groups_users_g_idx ON group_users(group_id, user_id);
+CREATE INDEX groups_users_u_idx ON group_users(user_id);
+
+-- list of users the group server thinks are invited
+CREATE TABLE group_invites (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL
+);
+
+CREATE INDEX groups_invites_g_idx ON group_invites(group_id, user_id);
+CREATE INDEX groups_invites_u_idx ON group_invites(user_id);
+
+
+CREATE TABLE group_rooms (
+    group_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    is_public BOOLEAN NOT NULL  -- whether the room can be seen by everyone
+);
+
+CREATE UNIQUE INDEX groups_rooms_g_idx ON group_rooms(group_id, room_id);
+CREATE INDEX groups_rooms_r_idx ON group_rooms(room_id);
+
+
+-- Rooms to include in the summary
+CREATE TABLE group_summary_rooms (
+    group_id TEXT NOT NULL,
+    room_id TEXT NOT NULL,
+    category_id TEXT NOT NULL,
+    room_order BIGINT NOT NULL,
+    is_public BOOLEAN NOT NULL, -- whether the room should be show to everyone
+    UNIQUE (group_id, category_id, room_id, room_order),
+    CHECK (room_order > 0)
+);
+
+CREATE UNIQUE INDEX group_summary_rooms_g_idx ON group_summary_rooms(group_id, room_id, category_id);
+
+
+-- Categories to include in the summary
+CREATE TABLE group_summary_room_categories (
+    group_id TEXT NOT NULL,
+    category_id TEXT NOT NULL,
+    cat_order BIGINT NOT NULL,
+    UNIQUE (group_id, category_id, cat_order),
+    CHECK (cat_order > 0)
+);
+
+-- The categories in the group
+CREATE TABLE group_room_categories (
+    group_id TEXT NOT NULL,
+    category_id TEXT NOT NULL,
+    profile TEXT NOT NULL,
+    is_public BOOLEAN NOT NULL, -- whether the category should be show to everyone
+    UNIQUE (group_id, category_id)
+);
+
+-- The users to include in the group summary
+CREATE TABLE group_summary_users (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    role_id TEXT NOT NULL,
+    user_order BIGINT NOT NULL,
+    is_public BOOLEAN NOT NULL  -- whether the user should be show to everyone
+);
+
+CREATE INDEX group_summary_users_g_idx ON group_summary_users(group_id);
+
+-- The roles to include in the group summary
+CREATE TABLE group_summary_roles (
+    group_id TEXT NOT NULL,
+    role_id TEXT NOT NULL,
+    role_order BIGINT NOT NULL,
+    UNIQUE (group_id, role_id, role_order),
+    CHECK (role_order > 0)
+);
+
+
+-- The roles in a groups
+CREATE TABLE group_roles (
+    group_id TEXT NOT NULL,
+    role_id TEXT NOT NULL,
+    profile TEXT NOT NULL,
+    is_public BOOLEAN NOT NULL,  -- whether the role should be show to everyone
+    UNIQUE (group_id, role_id)
+);
+
+
+-- List of  attestations we've given out and need to renew
+CREATE TABLE group_attestations_renewals (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    valid_until_ms BIGINT NOT NULL
+);
+
+CREATE INDEX group_attestations_renewals_g_idx ON group_attestations_renewals(group_id, user_id);
+CREATE INDEX group_attestations_renewals_u_idx ON group_attestations_renewals(user_id);
+CREATE INDEX group_attestations_renewals_v_idx ON group_attestations_renewals(valid_until_ms);
+
+
+-- List of attestations we've received from remotes and are interested in.
+CREATE TABLE group_attestations_remote (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    valid_until_ms BIGINT NOT NULL,
+    attestation_json TEXT NOT NULL
+);
+
+CREATE INDEX group_attestations_remote_g_idx ON group_attestations_remote(group_id, user_id);
+CREATE INDEX group_attestations_remote_u_idx ON group_attestations_remote(user_id);
+CREATE INDEX group_attestations_remote_v_idx ON group_attestations_remote(valid_until_ms);
+
+
+-- The group membership for the HS's users
+CREATE TABLE local_group_membership (
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    is_admin BOOLEAN NOT NULL,
+    membership TEXT NOT NULL,
+    is_publicised BOOLEAN NOT NULL,  -- if the user is publicising their membership
+    content TEXT NOT NULL
+);
+
+CREATE INDEX local_group_membership_u_idx ON local_group_membership(user_id, group_id);
+CREATE INDEX local_group_membership_g_idx ON local_group_membership(group_id);
+
+
+CREATE TABLE local_group_updates (
+    stream_id BIGINT NOT NULL,
+    group_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    type TEXT NOT NULL,
+    content TEXT NOT NULL
+);
diff --git a/synapse/storage/schema/delta/45/profile_cache.sql b/synapse/storage/schema/delta/45/profile_cache.sql
new file mode 100644
index 0000000000..e5ddc84df0
--- /dev/null
+++ b/synapse/storage/schema/delta/45/profile_cache.sql
@@ -0,0 +1,28 @@
+/* Copyright 2017 New Vector Ltd
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+-- A subset of remote users whose profiles we have cached.
+-- Whether a user is in this table or not is defined by the storage function
+-- `is_subscribed_remote_profile_for_user`
+CREATE TABLE remote_profile_cache (
+    user_id TEXT NOT NULL,
+    displayname TEXT,
+    avatar_url TEXT,
+    last_check BIGINT NOT NULL
+);
+
+CREATE UNIQUE INDEX remote_profile_cache_user_id ON remote_profile_cache(user_id);
+CREATE INDEX remote_profile_cache_time ON remote_profile_cache(last_check);
diff --git a/synapse/streams/events.py b/synapse/streams/events.py
index 91a59b0bae..f03ad99118 100644
--- a/synapse/streams/events.py
+++ b/synapse/streams/events.py
@@ -45,6 +45,7 @@ class EventSources(object):
         push_rules_key, _ = self.store.get_push_rules_stream_token()
         to_device_key = self.store.get_to_device_stream_token()
         device_list_key = self.store.get_device_stream_token()
+        groups_key = self.store.get_group_stream_token()
 
         token = StreamToken(
             room_key=(
@@ -65,6 +66,7 @@ class EventSources(object):
             push_rules_key=push_rules_key,
             to_device_key=to_device_key,
             device_list_key=device_list_key,
+            groups_key=groups_key,
         )
         defer.returnValue(token)
 
@@ -73,6 +75,7 @@ class EventSources(object):
         push_rules_key, _ = self.store.get_push_rules_stream_token()
         to_device_key = self.store.get_to_device_stream_token()
         device_list_key = self.store.get_device_stream_token()
+        groups_key = self.store.get_group_stream_token()
 
         token = StreamToken(
             room_key=(
@@ -93,5 +96,6 @@ class EventSources(object):
             push_rules_key=push_rules_key,
             to_device_key=to_device_key,
             device_list_key=device_list_key,
+            groups_key=groups_key,
         )
         defer.returnValue(token)
diff --git a/synapse/types.py b/synapse/types.py
index 111948540d..37d5fa7f9f 100644
--- a/synapse/types.py
+++ b/synapse/types.py
@@ -156,6 +156,11 @@ class EventID(DomainSpecificString):
     SIGIL = "$"
 
 
+class GroupID(DomainSpecificString):
+    """Structure representing a group ID."""
+    SIGIL = "+"
+
+
 class StreamToken(
     namedtuple("Token", (
         "room_key",
@@ -166,6 +171,7 @@ class StreamToken(
         "push_rules_key",
         "to_device_key",
         "device_list_key",
+        "groups_key",
     ))
 ):
     _SEPARATOR = "_"
@@ -204,6 +210,7 @@ class StreamToken(
             or (int(other.push_rules_key) < int(self.push_rules_key))
             or (int(other.to_device_key) < int(self.to_device_key))
             or (int(other.device_list_key) < int(self.device_list_key))
+            or (int(other.groups_key) < int(self.groups_key))
         )
 
     def copy_and_advance(self, key, new_value):
diff --git a/tests/handlers/test_profile.py b/tests/handlers/test_profile.py
index 2a203129ca..a5f47181d7 100644
--- a/tests/handlers/test_profile.py
+++ b/tests/handlers/test_profile.py
@@ -62,8 +62,6 @@ class ProfileTestCase(unittest.TestCase):
         self.ratelimiter = hs.get_ratelimiter()
         self.ratelimiter.send_message.return_value = (True, 0)
 
-        hs.handlers = ProfileHandlers(hs)
-
         self.store = hs.get_datastore()
 
         self.frank = UserID.from_string("@1234ABCD:test")
@@ -72,7 +70,7 @@ class ProfileTestCase(unittest.TestCase):
 
         yield self.store.create_profile(self.frank.localpart)
 
-        self.handler = hs.get_handlers().profile_handler
+        self.handler = hs.get_profile_handler()
 
     @defer.inlineCallbacks
     def test_get_my_name(self):
diff --git a/tests/handlers/test_register.py b/tests/handlers/test_register.py
index c8cf9a63ec..e990e45220 100644
--- a/tests/handlers/test_register.py
+++ b/tests/handlers/test_register.py
@@ -40,13 +40,14 @@ class RegistrationTestCase(unittest.TestCase):
         self.hs = yield setup_test_homeserver(
             handlers=None,
             http_client=None,
-            expire_access_token=True)
+            expire_access_token=True,
+            profile_handler=Mock(),
+        )
         self.macaroon_generator = Mock(
             generate_access_token=Mock(return_value='secret'))
         self.hs.get_macaroon_generator = Mock(return_value=self.macaroon_generator)
         self.hs.handlers = RegistrationHandlers(self.hs)
         self.handler = self.hs.get_handlers().registration_handler
-        self.hs.get_handlers().profile_handler = Mock()
 
     @defer.inlineCallbacks
     def test_user_is_created_and_logged_in_if_doesnt_exist(self):
diff --git a/tests/rest/client/v1/test_profile.py b/tests/rest/client/v1/test_profile.py
index 1e95e97538..dddcf51b69 100644
--- a/tests/rest/client/v1/test_profile.py
+++ b/tests/rest/client/v1/test_profile.py
@@ -46,6 +46,7 @@ class ProfileTestCase(unittest.TestCase):
             resource_for_client=self.mock_resource,
             federation=Mock(),
             replication_layer=Mock(),
+            profile_handler=self.mock_handler
         )
 
         def _get_user_by_req(request=None, allow_guest=False):
@@ -53,8 +54,6 @@ class ProfileTestCase(unittest.TestCase):
 
         hs.get_v1auth().get_user_by_req = _get_user_by_req
 
-        hs.get_handlers().profile_handler = self.mock_handler
-
         profile.register_servlets(hs, self.mock_resource)
 
     @defer.inlineCallbacks
diff --git a/tests/rest/client/v1/test_rooms.py b/tests/rest/client/v1/test_rooms.py
index d746ea8568..de376fb514 100644
--- a/tests/rest/client/v1/test_rooms.py
+++ b/tests/rest/client/v1/test_rooms.py
@@ -1032,7 +1032,7 @@ class RoomMessageListTestCase(RestTestCase):
 
     @defer.inlineCallbacks
     def test_topo_token_is_accepted(self):
-        token = "t1-0_0_0_0_0_0_0_0"
+        token = "t1-0_0_0_0_0_0_0_0_0"
         (code, response) = yield self.mock_resource.trigger_get(
             "/rooms/%s/messages?access_token=x&from=%s" %
             (self.room_id, token))
@@ -1044,7 +1044,7 @@ class RoomMessageListTestCase(RestTestCase):
 
     @defer.inlineCallbacks
     def test_stream_token_is_accepted_for_fwd_pagianation(self):
-        token = "s0_0_0_0_0_0_0_0"
+        token = "s0_0_0_0_0_0_0_0_0"
         (code, response) = yield self.mock_resource.trigger_get(
             "/rooms/%s/messages?access_token=x&from=%s" %
             (self.room_id, token))