2 files changed, 114 insertions, 4 deletions
diff --git a/synapse/crypto/event_signing.py b/synapse/crypto/event_signing.py
new file mode 100644
index 0000000000..4dff2c0ec2
--- /dev/null
+++ b/synapse/crypto/event_signing.py
@@ -0,0 +1,108 @@
+# -*- coding: utf-8 -*-
+
+# Copyright 2014 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 synapse.api.events.utils import prune_event
+from syutil.jsonutil import encode_canonical_json
+from syutil.base64util import encode_base64, decode_base64
+from syutil.crypto.jsonsign import sign_json
+from synapse.api.errors import SynapseError, Codes
+
+import hashlib
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+def check_event_content_hash(event, hash_algorithm=hashlib.sha256):
+    """Check whether the hash for this PDU matches the contents"""
+    computed_hash = _compute_content_hash(event, hash_algorithm)
+    logging.debug("Expecting hash: %s", encode_base64(computed_hash.digest()))
+    if computed_hash.name not in event.hashes:
+        raise SynapseError(
+            400,
+            "Algorithm %s not in hashes %s" % (
+                computed_hash.name, list(event.hashes),
+            ),
+            Codes.UNAUTHORIZED,
+        )
+    message_hash_base64 = event.hashes[computed_hash.name]
+    try:
+        message_hash_bytes = decode_base64(message_hash_base64)
+    except:
+        raise SynapseError(
+            400,
+            "Invalid base64: %s" % (message_hash_base64,),
+            Codes.UNAUTHORIZED,
+        )
+    return message_hash_bytes == computed_hash.digest()
+
+
+def _compute_content_hash(event, hash_algorithm):
+    event_json = event.get_pdu_json()
+    event_json.pop("age_ts", None)
+    event_json.pop("unsigned", None)
+    event_json.pop("signatures", None)
+    event_json.pop("hashes", None)
+    event_json.pop("outlier", None)
+    event_json.pop("destinations", None)
+    event_json_bytes = encode_canonical_json(event_json)
+    return hash_algorithm(event_json_bytes)
+
+
+def compute_event_reference_hash(event, hash_algorithm=hashlib.sha256):
+    tmp_event = prune_event(event)
+    event_json = tmp_event.get_pdu_json()
+    event_json.pop("signatures", None)
+    event_json.pop("age_ts", None)
+    event_json.pop("unsigned", None)
+    event_json_bytes = encode_canonical_json(event_json)
+    hashed = hash_algorithm(event_json_bytes)
+    return (hashed.name, hashed.digest())
+
+
+def compute_event_signature(event, signature_name, signing_key):
+    tmp_event = prune_event(event)
+    redact_json = tmp_event.get_pdu_json()
+    redact_json.pop("age_ts", None)
+    redact_json.pop("unsigned", None)
+    logger.debug("Signing event: %s", redact_json)
+    redact_json = sign_json(redact_json, signature_name, signing_key)
+    return redact_json["signatures"]
+
+
+def add_hashes_and_signatures(event, signature_name, signing_key,
+                              hash_algorithm=hashlib.sha256):
+    if hasattr(event, "old_state_events"):
+        state_json_bytes = encode_canonical_json(
+            [e.event_id for e in event.old_state_events.values()]
+        )
+        hashed = hash_algorithm(state_json_bytes)
+        event.state_hash = {
+            hashed.name: encode_base64(hashed.digest())
+        }
+
+    hashed = _compute_content_hash(event, hash_algorithm=hash_algorithm)
+
+    if not hasattr(event, "hashes"):
+        event.hashes = {}
+    event.hashes[hashed.name] = encode_base64(hashed.digest())
+
+    event.signatures = compute_event_signature(
+        event,
+        signature_name=signature_name,
+        signing_key=signing_key,
+    )
diff --git a/synapse/crypto/keyclient.py b/synapse/crypto/keyclient.py
index 5191be4570..bb1f400b54 100644
--- a/synapse/crypto/keyclient.py
+++ b/synapse/crypto/keyclient.py
@@ -18,6 +18,7 @@ from twisted.web.http import HTTPClient
 from twisted.internet.protocol import Factory
 from twisted.internet import defer, reactor
 from synapse.http.endpoint import matrix_endpoint
+from synapse.util.logcontext import PreserveLoggingContext
 import json
 import logging
 
@@ -36,10 +37,11 @@ def fetch_server_key(server_name, ssl_context_factory):
 
     for i in range(5):
         try:
-            protocol = yield endpoint.connect(factory)
-            server_response, server_certificate = yield protocol.remote_key
-            defer.returnValue((server_response, server_certificate))
-            return
+            with PreserveLoggingContext():
+                protocol = yield endpoint.connect(factory)
+                server_response, server_certificate = yield protocol.remote_key
+                defer.returnValue((server_response, server_certificate))
+                return
         except Exception as e:
             logger.exception(e)
     raise IOError("Cannot get key for %s" % server_name)