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Require sig from origin server on perspectives responses

This commit is contained in:
Richard van der Hoff 2019-04-09 13:03:56 +01:00
parent ec24108cc2
commit 753b1270da
2 changed files with 91 additions and 23 deletions
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28
synapse/crypto/keyring.py
View File

@ -394,8 +394,7 @@ class BaseV2KeyFetcher(object):
POST /_matrix/key/v2/query.
Checks that each signature in the response that claims to come from the origin
server is valid. (Does not check that there actually is such a signature, for
some reason.)
server is valid, and that there is at least one such signature.
Stores the json in server_keys_json so that it can be used for future responses
to /_matrix/key/v2/query.
@ -430,16 +429,25 @@ class BaseV2KeyFetcher(object):
verify_key=verify_key, valid_until_ts=ts_valid_until_ms
)
# TODO: improve this signature checking
server_name = response_json["server_name"]
verified = False
for key_id in response_json["signatures"].get(server_name, {}):
if key_id not in verify_keys:
# each of the keys used for the signature must be present in the response
# json.
key = verify_keys.get(key_id)
if not key:
raise KeyLookupError(
"Key response must include verification keys for all signatures"
"Key response is signed by key id %s:%s but that key is not "
"present in the response" % (server_name, key_id)
)
verify_signed_json(
response_json, server_name, verify_keys[key_id].verify_key
verify_signed_json(response_json, server_name, key.verify_key)
verified = True
if not verified:
raise KeyLookupError(
"Key response for %s is not signed by the origin server"
% (server_name,)
)
for key_id, key_data in response_json["old_verify_keys"].items():
@ -677,12 +685,6 @@ class ServerKeyFetcher(BaseV2KeyFetcher):
except HttpResponseException as e:
raise_from(KeyLookupError("Remote server returned an error"), e)
if (
u"signatures" not in response
or server_name not in response[u"signatures"]
):
raise KeyLookupError("Key response not signed by remote server")
if response["server_name"] != server_name:
raise KeyLookupError(
"Expected a response for server %r not %r"

86
tests/crypto/test_keyring.py
View File

@ -55,12 +55,12 @@ class MockPerspectiveServer(object):
key_id: {"key": signedjson.key.encode_verify_key_base64(verify_key)}
},
}
return self.get_signed_response(res)
def get_signed_response(self, res):
signedjson.sign.sign_json(res, self.server_name, self.key)
self.sign_response(res)
return res
def sign_response(self, res):
signedjson.sign.sign_json(res, self.server_name, self.key)
class KeyringTestCase(unittest.HomeserverTestCase):
def make_homeserver(self, reactor, clock):
@ -238,7 +238,7 @@ class ServerKeyFetcherTestCase(unittest.HomeserverTestCase):
testkey = signedjson.key.generate_signing_key("ver1")
testverifykey = signedjson.key.get_verify_key(testkey)
testverifykey_id = "ed25519:ver1"
VALID_UNTIL_TS = 1000
VALID_UNTIL_TS = 200 * 1000
# valid response
response = {
@ -326,9 +326,10 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):
},
}
persp_resp = {
"server_keys": [self.mock_perspective_server.get_signed_response(response)]
}
# the response must be signed by both the origin server and the perspectives
# server.
signedjson.sign.sign_json(response, SERVER_NAME, testkey)
self.mock_perspective_server.sign_response(response)
def post_json(destination, path, data, **kwargs):
self.assertEqual(destination, self.mock_perspective_server.server_name)
@ -337,7 +338,7 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):
# check that the request is for the expected key
q = data["server_keys"]
self.assertEqual(list(q[SERVER_NAME].keys()), ["key1"])
return persp_resp
return {"server_keys": [response]}
self.http_client.post_json.side_effect = post_json
@ -365,9 +366,74 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase):
self.assertEqual(
bytes(res["key_json"]),
canonicaljson.encode_canonical_json(persp_resp["server_keys"][0]),
canonicaljson.encode_canonical_json(response),
)
def test_invalid_perspectives_responses(self):
"""Check that invalid responses from the perspectives server are rejected"""
# arbitrarily advance the clock a bit
self.reactor.advance(100)
SERVER_NAME = "server2"
testkey = signedjson.key.generate_signing_key("ver1")
testverifykey = signedjson.key.get_verify_key(testkey)
testverifykey_id = "ed25519:ver1"
VALID_UNTIL_TS = 200 * 1000
def build_response():
# valid response
response = {
"server_name": SERVER_NAME,
"old_verify_keys": {},
"valid_until_ts": VALID_UNTIL_TS,
"verify_keys": {
testverifykey_id: {
"key": signedjson.key.encode_verify_key_base64(testverifykey)
}
},
}
# the response must be signed by both the origin server and the perspectives
# server.
signedjson.sign.sign_json(response, SERVER_NAME, testkey)
self.mock_perspective_server.sign_response(response)
return response
def get_key_from_perspectives(response):
fetcher = PerspectivesKeyFetcher(self.hs)
server_name_and_key_ids = [(SERVER_NAME, ("key1",))]
def post_json(destination, path, data, **kwargs):
self.assertEqual(destination, self.mock_perspective_server.server_name)
self.assertEqual(path, "/_matrix/key/v2/query")
return {"server_keys": [response]}
self.http_client.post_json.side_effect = post_json
return self.get_success(
fetcher.get_keys(server_name_and_key_ids)
)
# start with a valid response so we can check we are testing the right thing
response = build_response()
keys = get_key_from_perspectives(response)
k = keys[SERVER_NAME][testverifykey_id]
self.assertEqual(k.verify_key, testverifykey)
# remove the perspectives server's signature
response = build_response()
del response["signatures"][self.mock_perspective_server.server_name]
self.http_client.post_json.return_value = {"server_keys": [response]}
keys = get_key_from_perspectives(response)
self.assertEqual(keys, {}, "Expected empty dict with missing persp server sig")
# remove the origin server's signature
response = build_response()
del response["signatures"][SERVER_NAME]
self.http_client.post_json.return_value = {"server_keys": [response]}
keys = get_key_from_perspectives(response)
self.assertEqual(keys, {}, "Expected empty dict with missing origin server sig")
@defer.inlineCallbacks
def run_in_context(f, *args, **kwargs):