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Query missing cross-signing keys on local sig upload (#7289)

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This commit is contained in:
Andrew Morgan 2020-04-22 12:29:36 +01:00 committed by GitHub
parent 556566f0b8
commit f89ad3b6df
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
3 changed files with 181 additions and 19 deletions
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1
changelog.d/7289.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug with cross-signing devices belonging to remote users who did not share a room with any user on the local homeserver.

49
synapse/federation/transport/client.py
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@ -399,20 +399,30 @@ class TransportLayerClient(object):
{
"device_keys": {
"<user_id>": ["<device_id>"]
} }
}
}
Response:
{
"device_keys": {
"<user_id>": {
"<device_id>": {...}
} } }
}
},
"master_key": {
"<user_id>": {...}
}
},
"self_signing_key": {
"<user_id>": {...}
}
}
Args:
destination(str): The server to query.
query_content(dict): The user ids to query.
Returns:
A dict containg the device keys.
A dict containing device and cross-signing keys.
"""
path = _create_v1_path("/user/keys/query")
@ -429,14 +439,30 @@ class TransportLayerClient(object):
Response:
{
"stream_id": "...",
"devices": [ { ... } ]
"devices": [ { ... } ],
"master_key": {
"user_id": "<user_id>",
"usage": [...],
"keys": {...},
"signatures": {
"<user_id>": {...}
}
},
"self_signing_key": {
"user_id": "<user_id>",
"usage": [...],
"keys": {...},
"signatures": {
"<user_id>": {...}
}
}
}
Args:
destination(str): The server to query.
query_content(dict): The user ids to query.
Returns:
A dict containg the device keys.
A dict containing device and cross-signing keys.
"""
path = _create_v1_path("/user/devices/%s", user_id)
@ -454,8 +480,10 @@ class TransportLayerClient(object):
{
"one_time_keys": {
"<user_id>": {
"<device_id>": "<algorithm>"
} } }
"<device_id>": "<algorithm>"
}
}
}
Response:
{
@ -463,13 +491,16 @@ class TransportLayerClient(object):
"<user_id>": {
"<device_id>": {
"<algorithm>:<key_id>": "<key_base64>"
} } } }
}
}
}
}
Args:
destination(str): The server to query.
query_content(dict): The user ids to query.
Returns:
A dict containg the one-time keys.
A dict containing the one-time keys.
"""
path = _create_v1_path("/user/keys/claim")

150
synapse/handlers/e2e_keys.py
View file

@ -174,8 +174,8 @@ class E2eKeysHandler(object):
"""This is called when we are querying the device list of a user on
a remote homeserver and their device list is not in the device list
cache. If we share a room with this user and we're not querying for
specific user we will update the cache
with their device list."""
specific user we will update the cache with their device list.
"""
destination_query = remote_queries_not_in_cache[destination]
@ -961,13 +961,19 @@ class E2eKeysHandler(object):
return signature_list, failures
@defer.inlineCallbacks
def _get_e2e_cross_signing_verify_key(self, user_id, key_type, from_user_id=None):
"""Fetch the cross-signing public key from storage and interpret it.
def _get_e2e_cross_signing_verify_key(
self, user_id: str, key_type: str, from_user_id: str = None
):
"""Fetch locally or remotely query for a cross-signing public key.
First, attempt to fetch the cross-signing public key from storage.
If that fails, query the keys from the homeserver they belong to
and update our local copy.
Args:
user_id (str): the user whose key should be fetched
key_type (str): the type of key to fetch
from_user_id (str): the user that we are fetching the keys for.
user_id: the user whose key should be fetched
key_type: the type of key to fetch
from_user_id: the user that we are fetching the keys for.
This affects what signatures are fetched.
Returns:
@ -976,16 +982,140 @@ class E2eKeysHandler(object):
Raises:
NotFoundError: if the key is not found
SynapseError: if `user_id` is invalid
"""
user = UserID.from_string(user_id)
key = yield self.store.get_e2e_cross_signing_key(
user_id, key_type, from_user_id
)
if key is None:
logger.debug("no %s key found for %s", key_type, user_id)
if key:
# We found a copy of this key in our database. Decode and return it
key_id, verify_key = get_verify_key_from_cross_signing_key(key)
return key, key_id, verify_key
# If we couldn't find the key locally, and we're looking for keys of
# another user then attempt to fetch the missing key from the remote
# user's server.
#
# We may run into this in possible edge cases where a user tries to
# cross-sign a remote user, but does not share any rooms with them yet.
# Thus, we would not have their key list yet. We instead fetch the key,
# store it and notify clients of new, associated device IDs.
if self.is_mine(user) or key_type not in ["master", "self_signing"]:
# Note that master and self_signing keys are the only cross-signing keys we
# can request over federation
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
key_id, verify_key = get_verify_key_from_cross_signing_key(key)
(
key,
key_id,
verify_key,
) = yield self._retrieve_cross_signing_keys_for_remote_user(user, key_type)
if key is None:
raise NotFoundError("No %s key found for %s" % (key_type, user_id))
return key, key_id, verify_key
@defer.inlineCallbacks
def _retrieve_cross_signing_keys_for_remote_user(
self, user: UserID, desired_key_type: str,
):
"""Queries cross-signing keys for a remote user and saves them to the database
Only the key specified by `key_type` will be returned, while all retrieved keys
will be saved regardless
Args:
user: The user to query remote keys for
desired_key_type: The type of key to receive. One of "master", "self_signing"
Returns:
Deferred[Tuple[Optional[Dict], Optional[str], Optional[VerifyKey]]]: A tuple
of the retrieved key content, the key's ID and the matching VerifyKey.
If the key cannot be retrieved, all values in the tuple will instead be None.
"""
try:
remote_result = yield self.federation.query_user_devices(
user.domain, user.to_string()
)
except Exception as e:
logger.warning(
"Unable to query %s for cross-signing keys of user %s: %s %s",
user.domain,
user.to_string(),
type(e),
e,
)
return None, None, None
# Process each of the retrieved cross-signing keys
desired_key = None
desired_key_id = None
desired_verify_key = None
retrieved_device_ids = []
for key_type in ["master", "self_signing"]:
key_content = remote_result.get(key_type + "_key")
if not key_content:
continue
# Ensure these keys belong to the correct user
if "user_id" not in key_content:
logger.warning(
"Invalid %s key retrieved, missing user_id field: %s",
key_type,
key_content,
)
continue
if user.to_string() != key_content["user_id"]:
logger.warning(
"Found %s key of user %s when querying for keys of user %s",
key_type,
key_content["user_id"],
user.to_string(),
)
continue
# Validate the key contents
try:
# verify_key is a VerifyKey from signedjson, which uses
# .version to denote the portion of the key ID after the
# algorithm and colon, which is the device ID
key_id, verify_key = get_verify_key_from_cross_signing_key(key_content)
except ValueError as e:
logger.warning(
"Invalid %s key retrieved: %s - %s %s",
key_type,
key_content,
type(e),
e,
)
continue
# Note down the device ID attached to this key
retrieved_device_ids.append(verify_key.version)
# If this is the desired key type, save it and its ID/VerifyKey
if key_type == desired_key_type:
desired_key = key_content
desired_verify_key = verify_key
desired_key_id = key_id
# At the same time, store this key in the db for subsequent queries
yield self.store.set_e2e_cross_signing_key(
user.to_string(), key_type, key_content
)
# Notify clients that new devices for this user have been discovered
if retrieved_device_ids:
# XXX is this necessary?
yield self.device_handler.notify_device_update(
user.to_string(), retrieved_device_ids
)
return desired_key, desired_key_id, desired_verify_key
def _check_cross_signing_key(key, user_id, key_type, signing_key=None):
"""Check a cross-signing key uploaded by a user. Performs some basic sanity