1 files changed, 57 insertions, 13 deletions
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index c2b38d72a9..9d994a8f71 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -288,19 +288,8 @@ class E2eKeysHandler(object):
 
         one_time_keys = keys.get("one_time_keys", None)
         if one_time_keys:
-            logger.info(
-                "Adding %d one_time_keys for device %r for user %r at %d",
-                len(one_time_keys), device_id, user_id, time_now
-            )
-            key_list = []
-            for key_id, key_json in one_time_keys.items():
-                algorithm, key_id = key_id.split(":")
-                key_list.append((
-                    algorithm, key_id, encode_canonical_json(key_json)
-                ))
-
-            yield self.store.add_e2e_one_time_keys(
-                user_id, device_id, time_now, key_list
+            yield self._upload_one_time_keys_for_user(
+                user_id, device_id, time_now, one_time_keys,
             )
 
         # the device should have been registered already, but it may have been
@@ -313,3 +302,58 @@ class E2eKeysHandler(object):
         result = yield self.store.count_e2e_one_time_keys(user_id, device_id)
 
         defer.returnValue({"one_time_key_counts": result})
+
+    @defer.inlineCallbacks
+    def _upload_one_time_keys_for_user(self, user_id, device_id, time_now,
+                                       one_time_keys):
+        logger.info(
+            "Adding one_time_keys %r for device %r for user %r at %d",
+            one_time_keys.keys(), device_id, user_id, time_now,
+        )
+
+        # make a list of (alg, id, key) tuples
+        key_list = []
+        for key_id, key_obj in one_time_keys.items():
+            algorithm, key_id = key_id.split(":")
+            key_list.append((
+                algorithm, key_id, key_obj
+            ))
+
+        # First we check if we have already persisted any of the keys.
+        existing_key_map = yield self.store.get_e2e_one_time_keys(
+            user_id, device_id, [k_id for _, k_id, _ in key_list]
+        )
+
+        new_keys = []  # Keys that we need to insert. (alg, id, json) tuples.
+        for algorithm, key_id, key in key_list:
+            ex_json = existing_key_map.get((algorithm, key_id), None)
+            if ex_json:
+                if not _one_time_keys_match(ex_json, key):
+                    raise SynapseError(
+                        400,
+                        ("One time key %s:%s already exists. "
+                         "Old key: %s; new key: %r") %
+                        (algorithm, key_id, ex_json, key)
+                    )
+            else:
+                new_keys.append((algorithm, key_id, encode_canonical_json(key)))
+
+        yield self.store.add_e2e_one_time_keys(
+            user_id, device_id, time_now, new_keys
+        )
+
+
+def _one_time_keys_match(old_key_json, new_key):
+    old_key = json.loads(old_key_json)
+
+    # if either is a string rather than an object, they must match exactly
+    if not isinstance(old_key, dict) or not isinstance(new_key, dict):
+        return old_key == new_key
+
+    # otherwise, we strip off the 'signatures' if any, because it's legitimate
+    # for different upload attempts to have different signatures.
+    old_key.pop("signatures", None)
+    new_key_copy = dict(new_key)
+    new_key_copy.pop("signatures", None)
+
+    return old_key == new_key_copy