Merge pull request #47 from matrix-org/signature_failures

Federation fixes.

3 files changed, 160 insertions, 114 deletions

diff --git a/synapse/federation/federation_base.py b/synapse/federation/federation_base.py
new file mode 100644
index 0000000000..a990aec4fd
--- /dev/null
+++ b/synapse/federation/federation_base.py
@@ -0,0 +1,118 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 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 twisted.internet import defer
+
+from synapse.events.utils import prune_event
+
+from syutil.jsonutil import encode_canonical_json
+
+from synapse.crypto.event_signing import check_event_content_hash
+
+from synapse.api.errors import SynapseError
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+
+
+class FederationBase(object):
+    @defer.inlineCallbacks
+    def _check_sigs_and_hash_and_fetch(self, origin, pdus, outlier=False):
+        """Takes a list of PDUs and checks the signatures and hashs of each
+        one. If a PDU fails its signature check then we check if we have it in
+        the database and if not then request if from the originating server of
+        that PDU.
+
+        If a PDU fails its content hash check then it is redacted.
+
+        The given list of PDUs are not modified, instead the function returns
+        a new list.
+
+        Args:
+            pdu (list)
+            outlier (bool)
+
+        Returns:
+            Deferred : A list of PDUs that have valid signatures and hashes.
+        """
+        signed_pdus = []
+        for pdu in pdus:
+            try:
+                new_pdu = yield self._check_sigs_and_hash(pdu)
+                signed_pdus.append(new_pdu)
+            except SynapseError:
+                # FIXME: We should handle signature failures more gracefully.
+
+                # Check local db.
+                new_pdu = yield self.store.get_event(
+                    pdu.event_id,
+                    allow_rejected=True
+                )
+                if new_pdu:
+                    signed_pdus.append(new_pdu)
+                    continue
+
+                # Check pdu.origin
+                if pdu.origin != origin:
+                    new_pdu = yield self.get_pdu(
+                        destinations=[pdu.origin],
+                        event_id=pdu.event_id,
+                        outlier=outlier,
+                    )
+
+                    if new_pdu:
+                        signed_pdus.append(new_pdu)
+                        continue
+
+                logger.warn("Failed to find copy of %s with valid signature")
+
+        defer.returnValue(signed_pdus)
+
+    @defer.inlineCallbacks
+    def _check_sigs_and_hash(self, pdu):
+        """Throws a SynapseError if the PDU does not have the correct
+        signatures.
+
+        Returns:
+            FrozenEvent: Either the given event or it redacted if it failed the
+            content hash check.
+        """
+        # Check signatures are correct.
+        redacted_event = prune_event(pdu)
+        redacted_pdu_json = redacted_event.get_pdu_json()
+
+        try:
+            yield self.keyring.verify_json_for_server(
+                pdu.origin, redacted_pdu_json
+            )
+        except SynapseError:
+            logger.warn(
+                "Signature check failed for %s redacted to %s",
+                encode_canonical_json(pdu.get_pdu_json()),
+                encode_canonical_json(redacted_pdu_json),
+            )
+            raise
+
+        if not check_event_content_hash(pdu):
+            logger.warn(
+                "Event content has been tampered, redacting %s, %s",
+                pdu.event_id, encode_canonical_json(pdu.get_dict())
+            )
+            defer.returnValue(redacted_event)
+
+        defer.returnValue(pdu)
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index e1539bd0e0..5fac629709 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -16,17 +16,11 @@
 
 from twisted.internet import defer
 
+from .federation_base import FederationBase
 from .units import Edu
 
 from synapse.util.logutils import log_function
 from synapse.events import FrozenEvent
-from synapse.events.utils import prune_event
-
-from syutil.jsonutil import encode_canonical_json
-
-from synapse.crypto.event_signing import check_event_content_hash
-
-from synapse.api.errors import SynapseError
 
 import logging
 
@@ -34,7 +28,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-class FederationClient(object):
+class FederationClient(FederationBase):
     @log_function
     def send_pdu(self, pdu, destinations):
         """Informs the replication layer about a new PDU generated within the
@@ -224,17 +218,17 @@ class FederationClient(object):
             for p in result.get("auth_chain", [])
         ]
 
-        for i, pdu in enumerate(pdus):
-            pdus[i] = yield self._check_sigs_and_hash(pdu)
-
-            # FIXME: We should handle signature failures more gracefully.
+        signed_pdus = yield self._check_sigs_and_hash_and_fetch(
+            destination, pdus, outlier=True
+        )
 
-        for i, pdu in enumerate(auth_chain):
-            auth_chain[i] = yield self._check_sigs_and_hash(pdu)
+        signed_auth = yield self._check_sigs_and_hash_and_fetch(
+            destination, auth_chain, outlier=True
+        )
 
-            # FIXME: We should handle signature failures more gracefully.
+        signed_auth.sort(key=lambda e: e.depth)
 
-        defer.returnValue((pdus, auth_chain))
+        defer.returnValue((signed_pdus, signed_auth))
 
     @defer.inlineCallbacks
     @log_function
@@ -248,14 +242,13 @@ class FederationClient(object):
             for p in res["auth_chain"]
         ]
 
-        for i, pdu in enumerate(auth_chain):
-            auth_chain[i] = yield self._check_sigs_and_hash(pdu)
-
-            # FIXME: We should handle signature failures more gracefully.
+        signed_auth = yield self._check_sigs_and_hash_and_fetch(
+            destination, auth_chain, outlier=True
+        )
 
-        auth_chain.sort(key=lambda e: e.depth)
+        signed_auth.sort(key=lambda e: e.depth)
 
-        defer.returnValue(auth_chain)
+        defer.returnValue(signed_auth)
 
     @defer.inlineCallbacks
     def make_join(self, destination, room_id, user_id):
@@ -291,21 +284,19 @@ class FederationClient(object):
             for p in content.get("auth_chain", [])
         ]
 
-        for i, pdu in enumerate(state):
-            state[i] = yield self._check_sigs_and_hash(pdu)
-
-            # FIXME: We should handle signature failures more gracefully.
-
-        for i, pdu in enumerate(auth_chain):
-            auth_chain[i] = yield self._check_sigs_and_hash(pdu)
+        signed_state = yield self._check_sigs_and_hash_and_fetch(
+            destination, state, outlier=True
+        )
 
-            # FIXME: We should handle signature failures more gracefully.
+        signed_auth = yield self._check_sigs_and_hash_and_fetch(
+            destination, auth_chain, outlier=True
+        )
 
         auth_chain.sort(key=lambda e: e.depth)
 
         defer.returnValue({
-            "state": state,
-            "auth_chain": auth_chain,
+            "state": signed_state,
+            "auth_chain": signed_auth,
         })
 
     @defer.inlineCallbacks
@@ -353,12 +344,18 @@ class FederationClient(object):
         )
 
         auth_chain = [
-            (yield self._check_sigs_and_hash(self.event_from_pdu_json(e)))
+            self.event_from_pdu_json(e)
             for e in content["auth_chain"]
         ]
 
+        signed_auth = yield self._check_sigs_and_hash_and_fetch(
+            destination, auth_chain, outlier=True
+        )
+
+        signed_auth.sort(key=lambda e: e.depth)
+
         ret = {
-            "auth_chain": auth_chain,
+            "auth_chain": signed_auth,
             "rejects": content.get("rejects", []),
             "missing": content.get("missing", []),
         }
@@ -373,37 +370,3 @@ class FederationClient(object):
         event.internal_metadata.outlier = outlier
 
         return event
-
-    @defer.inlineCallbacks
-    def _check_sigs_and_hash(self, pdu):
-        """Throws a SynapseError if the PDU does not have the correct
-        signatures.
-
-        Returns:
-            FrozenEvent: Either the given event or it redacted if it failed the
-            content hash check.
-        """
-        # Check signatures are correct.
-        redacted_event = prune_event(pdu)
-        redacted_pdu_json = redacted_event.get_pdu_json()
-
-        try:
-            yield self.keyring.verify_json_for_server(
-                pdu.origin, redacted_pdu_json
-            )
-        except SynapseError:
-            logger.warn(
-                "Signature check failed for %s redacted to %s",
-                encode_canonical_json(pdu.get_pdu_json()),
-                encode_canonical_json(redacted_pdu_json),
-            )
-            raise
-
-        if not check_event_content_hash(pdu):
-            logger.warn(
-                "Event content has been tampered, redacting %s, %s",
-                pdu.event_id, encode_canonical_json(pdu.get_dict())
-            )
-            defer.returnValue(redacted_event)
-
-        defer.returnValue(pdu)
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index 5fbd8b19de..4742ca9390 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -16,16 +16,12 @@
 
 from twisted.internet import defer
 
+from .federation_base import FederationBase
 from .units import Transaction, Edu
 
 from synapse.util.logutils import log_function
 from synapse.util.logcontext import PreserveLoggingContext
 from synapse.events import FrozenEvent
-from synapse.events.utils import prune_event
-
-from syutil.jsonutil import encode_canonical_json
-
-from synapse.crypto.event_signing import check_event_content_hash
 
 from synapse.api.errors import FederationError, SynapseError
 
@@ -35,7 +31,7 @@ import logging
 logger = logging.getLogger(__name__)
 
 
-class FederationServer(object):
+class FederationServer(FederationBase):
     def set_handler(self, handler):
         """Sets the handler that the replication layer will use to communicate
         receipt of new PDUs from other home servers. The required methods are
@@ -251,17 +247,20 @@ class FederationServer(object):
             Deferred: Results in `dict` with the same format as `content`
         """
         auth_chain = [
-            (yield self._check_sigs_and_hash(self.event_from_pdu_json(e)))
+            self.event_from_pdu_json(e)
             for e in content["auth_chain"]
         ]
 
-        missing = [
-            (yield self._check_sigs_and_hash(self.event_from_pdu_json(e)))
-            for e in content.get("missing", [])
-        ]
+        signed_auth = yield self._check_sigs_and_hash_and_fetch(
+            origin, auth_chain, outlier=True
+        )
 
         ret = yield self.handler.on_query_auth(
-            origin, event_id, auth_chain, content.get("rejects", []), missing
+            origin,
+            event_id,
+            signed_auth,
+            content.get("rejects", []),
+            content.get("missing", []),
         )
 
         time_now = self._clock.time_msec()
@@ -426,37 +425,3 @@ class FederationServer(object):
         event.internal_metadata.outlier = outlier
 
         return event
-
-    @defer.inlineCallbacks
-    def _check_sigs_and_hash(self, pdu):
-        """Throws a SynapseError if the PDU does not have the correct
-        signatures.
-
-        Returns:
-            FrozenEvent: Either the given event or it redacted if it failed the
-            content hash check.
-        """
-        # Check signatures are correct.
-        redacted_event = prune_event(pdu)
-        redacted_pdu_json = redacted_event.get_pdu_json()
-
-        try:
-            yield self.keyring.verify_json_for_server(
-                pdu.origin, redacted_pdu_json
-            )
-        except SynapseError:
-            logger.warn(
-                "Signature check failed for %s redacted to %s",
-                encode_canonical_json(pdu.get_pdu_json()),
-                encode_canonical_json(redacted_pdu_json),
-            )
-            raise
-
-        if not check_event_content_hash(pdu):
-            logger.warn(
-                "Event content has been tampered, redacting %s, %s",
-                pdu.event_id, encode_canonical_json(pdu.get_dict())
-            )
-            defer.returnValue(redacted_event)
-
-        defer.returnValue(pdu)