Use the v2 Identity Service API for lookups (MSC2134 + MSC2140) (#5976)

This is a redo of https://github.com/matrix-org/synapse/pull/5897 but with `id_access_token` accepted.

Implements [MSC2134](https://github.com/matrix-org/matrix-doc/pull/2134) plus Identity Service v2 authentication ala [MSC2140](https://github.com/matrix-org/matrix-doc/pull/2140).

Identity lookup-related functions were also moved from `RoomMemberHandler` to `IdentityHandler`.

1 files changed, 166 insertions, 12 deletions

diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index a3a3d4d143..43d10a5308 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -29,9 +29,11 @@ from twisted.internet import defer
 from synapse import types
 from synapse.api.constants import EventTypes, Membership
 from synapse.api.errors import AuthError, Codes, HttpResponseException, SynapseError
+from synapse.handlers.identity import LookupAlgorithm, create_id_access_token_header
 from synapse.types import RoomID, UserID
 from synapse.util.async_helpers import Linearizer
 from synapse.util.distributor import user_joined_room, user_left_room
+from synapse.util.hash import sha256_and_url_safe_base64
 
 from ._base import BaseHandler
 
@@ -626,7 +628,7 @@ class RoomMemberHandler(object):
             servers.remove(room_alias.domain)
         servers.insert(0, room_alias.domain)
 
-        return (RoomID.from_string(room_id), servers)
+        return RoomID.from_string(room_id), servers
 
     @defer.inlineCallbacks
     def _get_inviter(self, user_id, room_id):
@@ -638,7 +640,15 @@ class RoomMemberHandler(object):
 
     @defer.inlineCallbacks
     def do_3pid_invite(
-        self, room_id, inviter, medium, address, id_server, requester, txn_id
+        self,
+        room_id,
+        inviter,
+        medium,
+        address,
+        id_server,
+        requester,
+        txn_id,
+        id_access_token=None,
     ):
         if self.config.block_non_admin_invites:
             is_requester_admin = yield self.auth.is_server_admin(requester.user)
@@ -661,7 +671,12 @@ class RoomMemberHandler(object):
                 Codes.FORBIDDEN,
             )
 
-        invitee = yield self._lookup_3pid(id_server, medium, address)
+        if not self._enable_lookup:
+            raise SynapseError(
+                403, "Looking up third-party identifiers is denied from this server"
+            )
+
+        invitee = yield self._lookup_3pid(id_server, medium, address, id_access_token)
 
         if invitee:
             yield self.update_membership(
@@ -673,7 +688,7 @@ class RoomMemberHandler(object):
             )
 
     @defer.inlineCallbacks
-    def _lookup_3pid(self, id_server, medium, address):
+    def _lookup_3pid(self, id_server, medium, address, id_access_token=None):
         """Looks up a 3pid in the passed identity server.
 
         Args:
@@ -681,14 +696,48 @@ class RoomMemberHandler(object):
                 of the identity server to use.
             medium (str): The type of the third party identifier (e.g. "email").
             address (str): The third party identifier (e.g. "foo@example.com").
+            id_access_token (str|None): The access token to authenticate to the identity
+                server with
+
+        Returns:
+            str|None: the matrix ID of the 3pid, or None if it is not recognized.
+        """
+        if id_access_token is not None:
+            try:
+                results = yield self._lookup_3pid_v2(
+                    id_server, id_access_token, medium, address
+                )
+                return results
+
+            except Exception as e:
+                # Catch HttpResponseExcept for a non-200 response code
+                # Check if this identity server does not know about v2 lookups
+                if isinstance(e, HttpResponseException) and e.code == 404:
+                    # This is an old identity server that does not yet support v2 lookups
+                    logger.warning(
+                        "Attempted v2 lookup on v1 identity server %s. Falling "
+                        "back to v1",
+                        id_server,
+                    )
+                else:
+                    logger.warning("Error when looking up hashing details: %s", e)
+                    return None
+
+        return (yield self._lookup_3pid_v1(id_server, medium, address))
+
+    @defer.inlineCallbacks
+    def _lookup_3pid_v1(self, id_server, medium, address):
+        """Looks up a 3pid in the passed identity server using v1 lookup.
+
+        Args:
+            id_server (str): The server name (including port, if required)
+                of the identity server to use.
+            medium (str): The type of the third party identifier (e.g. "email").
+            address (str): The third party identifier (e.g. "foo@example.com").
 
         Returns:
             str: the matrix ID of the 3pid, or None if it is not recognized.
         """
-        if not self._enable_lookup:
-            raise SynapseError(
-                403, "Looking up third-party identifiers is denied from this server"
-            )
         try:
             data = yield self.simple_http_client.get_json(
                 "%s%s/_matrix/identity/api/v1/lookup" % (id_server_scheme, id_server),
@@ -702,9 +751,116 @@ class RoomMemberHandler(object):
                 return data["mxid"]
 
         except IOError as e:
-            logger.warn("Error from identity server lookup: %s" % (e,))
+            logger.warning("Error from v1 identity server lookup: %s" % (e,))
+
+        return None
+
+    @defer.inlineCallbacks
+    def _lookup_3pid_v2(self, id_server, id_access_token, medium, address):
+        """Looks up a 3pid in the passed identity server using v2 lookup.
+
+        Args:
+            id_server (str): The server name (including port, if required)
+                of the identity server to use.
+            id_access_token (str): The access token to authenticate to the identity server with
+            medium (str): The type of the third party identifier (e.g. "email").
+            address (str): The third party identifier (e.g. "foo@example.com").
+
+        Returns:
+            Deferred[str|None]: the matrix ID of the 3pid, or None if it is not recognised.
+        """
+        # Check what hashing details are supported by this identity server
+        hash_details = yield self.simple_http_client.get_json(
+            "%s%s/_matrix/identity/v2/hash_details" % (id_server_scheme, id_server),
+            {"access_token": id_access_token},
+        )
+
+        if not isinstance(hash_details, dict):
+            logger.warning(
+                "Got non-dict object when checking hash details of %s%s: %s",
+                id_server_scheme,
+                id_server,
+                hash_details,
+            )
+            raise SynapseError(
+                400,
+                "Non-dict object from %s%s during v2 hash_details request: %s"
+                % (id_server_scheme, id_server, hash_details),
+            )
+
+        # Extract information from hash_details
+        supported_lookup_algorithms = hash_details.get("algorithms")
+        lookup_pepper = hash_details.get("lookup_pepper")
+        if (
+            not supported_lookup_algorithms
+            or not isinstance(supported_lookup_algorithms, list)
+            or not lookup_pepper
+            or not isinstance(lookup_pepper, str)
+        ):
+            raise SynapseError(
+                400,
+                "Invalid hash details received from identity server %s%s: %s"
+                % (id_server_scheme, id_server, hash_details),
+            )
+
+        # Check if any of the supported lookup algorithms are present
+        if LookupAlgorithm.SHA256 in supported_lookup_algorithms:
+            # Perform a hashed lookup
+            lookup_algorithm = LookupAlgorithm.SHA256
+
+            # Hash address, medium and the pepper with sha256
+            to_hash = "%s %s %s" % (address, medium, lookup_pepper)
+            lookup_value = sha256_and_url_safe_base64(to_hash)
+
+        elif LookupAlgorithm.NONE in supported_lookup_algorithms:
+            # Perform a non-hashed lookup
+            lookup_algorithm = LookupAlgorithm.NONE
+
+            # Combine together plaintext address and medium
+            lookup_value = "%s %s" % (address, medium)
+
+        else:
+            logger.warning(
+                "None of the provided lookup algorithms of %s are supported: %s",
+                id_server,
+                supported_lookup_algorithms,
+            )
+            raise SynapseError(
+                400,
+                "Provided identity server does not support any v2 lookup "
+                "algorithms that this homeserver supports.",
+            )
+
+        # Authenticate with identity server given the access token from the client
+        headers = {"Authorization": create_id_access_token_header(id_access_token)}
+
+        try:
+            lookup_results = yield self.simple_http_client.post_json_get_json(
+                "%s%s/_matrix/identity/v2/lookup" % (id_server_scheme, id_server),
+                {
+                    "addresses": [lookup_value],
+                    "algorithm": lookup_algorithm,
+                    "pepper": lookup_pepper,
+                },
+                headers=headers,
+            )
+        except Exception as e:
+            logger.warning("Error when performing a v2 3pid lookup: %s", e)
+            raise SynapseError(
+                500, "Unknown error occurred during identity server lookup"
+            )
+
+        # Check for a mapping from what we looked up to an MXID
+        if "mappings" not in lookup_results or not isinstance(
+            lookup_results["mappings"], dict
+        ):
+            logger.warning("No results from 3pid lookup")
             return None
 
+        # Return the MXID if it's available, or None otherwise
+        mxid = lookup_results["mappings"].get(lookup_value)
+        return mxid
+
     @defer.inlineCallbacks
     def _verify_any_signature(self, data, server_hostname):
         if server_hostname not in data["signatures"]:
@@ -844,7 +1000,6 @@ class RoomMemberHandler(object):
                 display_name (str): A user-friendly name to represent the invited
                     user.
         """
-
         is_url = "%s%s/_matrix/identity/api/v1/store-invite" % (
             id_server_scheme,
             id_server,
@@ -862,7 +1017,6 @@ class RoomMemberHandler(object):
             "sender_display_name": inviter_display_name,
             "sender_avatar_url": inviter_avatar_url,
         }
-
         try:
             data = yield self.simple_http_client.post_json_get_json(
                 is_url, invite_config
@@ -1049,7 +1203,7 @@ class RoomMemberMasterHandler(RoomMemberHandler):
             # The 'except' clause is very broad, but we need to
             # capture everything from DNS failures upwards
             #
-            logger.warn("Failed to reject invite: %s", e)
+            logger.warning("Failed to reject invite: %s", e)
 
             yield self.store.locally_reject_invite(target.to_string(), room_id)
             return {}