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Implement v2 key lookup
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Mark Haines committed Apr 20, 2015
1 parent a429515 commit 2f9157b
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Showing 2 changed files with 254 additions and 18 deletions.
268 changes: 251 additions & 17 deletions synapse/crypto/keyring.py
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,8 @@ class Keyring(object):
def __init__(self, hs):
self.store = hs.get_datastore()
self.clock = hs.get_clock()
self.client = hs.get_http_client()
self.perspective_servers = {}
self.hs = hs

@defer.inlineCallbacks
Expand Down Expand Up @@ -85,19 +87,26 @@ def verify_json_for_server(self, server_name, json_object):
@defer.inlineCallbacks
def get_server_verify_key(self, server_name, key_ids):
"""Finds a verification key for the server with one of the key ids.
Trys to fetch the key from a trusted perspective server first.
Args:
server_name (str): The name of the server to fetch a key for.
server_name(str): The name of the server to fetch a key for.
keys_ids (list of str): The key_ids to check for.
"""

# Check the datastore to see if we have one cached.
cached = yield self.store.get_server_verify_keys(server_name, key_ids)

if cached:
defer.returnValue(cached[0])
return

# Try to fetch the key from the remote server.
keys = None
for perspective_name, perspective_keys in self.perspective_servers.items():
try:
keys = yield self.get_server_verify_key_v2_indirect(
server_name, key_ids, perspective_name, perspective_keys
)
break
except:
pass

limiter = yield get_retry_limiter(
server_name,
Expand All @@ -106,10 +115,221 @@ def get_server_verify_key(self, server_name, key_ids):
)

with limiter:
(response, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_context_factory
if keys is None:
try:
keys = yield self.get_server_verify_key_v2_direct(
server_name, key_ids
)
except:
pass

keys = yield self.get_server_verify_key_v1_direct(
server_name, key_ids
)


for key_id in key_ids:
if key_id in keys:
defer.returnValue(keys[key_id])
return
raise ValueError("No verification key found for given key ids")

@defer.inlineCallbacks
def get_server_verify_key_v2_indirect(self, server_name, key_ids,
perspective_name,
perspective_keys):
limiter = yield get_retry_limiter(
perspective_name, self.clock, self.store
)

responses = yield self.client.post_json(
destination=perspective_name,
path=b"/_matrix/key/v2/query",
data={u"server_keys": {server_name: list(key_ids)}},
)

keys = dict()

for response in responses:
if (u"signatures" not in response
or perspective_name not in response[u"signatures"]):
raise ValueError(
"Key response not signed by perspective server"
" %r" % (perspective_name,)
)

verified = False
for key_id in response[u"signatures"][perspective_name]:
if key_id in perspective_keys:
verify_signed_json(
response,
perspective_name,
perspective_keys[key_id]
)
verified = True

if not verified:
logging.info(
"Response from perspective server %r not signed with a"
" known key, signed with: %r, known keys: %r",
perspective_name,
list(response[u"signatures"][perspective_name]),
list(perspective_keys)
)
raise ValueError(
"Response not signed with a known key for perspective"
" server %r" % (perspective_name,)
)

response_keys = process_v2_response(self, server_name, key_ids)

keys.update(response_keys)

yield self.store_keys(
server_name=server_name,
from_server=perspective_name,
verify_keys=keys,
)

defer.returnValue(keys)

@defer.inlineCallbacks
def get_server_verify_key_v2_direct(self, server_name, key_ids):

keys = {}

for requested_key_id in key_ids:
if requested_key_id in keys:
continue

(response_json, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_context_factory,
path="/_matrix/key/v2/server/%s" % (
urllib.quote(requested_key_id),
),
)

if (u"signatures" not in response
or server_name not in response[u"signatures"]):
raise ValueError("Key response not signed by remote server")

if "tls_fingerprints" not in response:
raise ValueError("Key response missing TLS fingerprints")

certificate_bytes = crypto.dump_certificate(
crypto.FILETYPE_ASN1, tls_certificate
)
sha256_fingerprint = hashlib.sha256(certificate_bytes).digest()
sha256_fingerprint_b64 = encode_base64(sha256_fingerprint)

response_sha256_fingerprints = set()
for fingerprint in response_json[u"tls_fingerprints"]:
if u"sha256" in fingerprint:
response_sha256_fingerprints.add(fingerprint[u"sha256"])

if sha256_fingerprint not in response_sha256_fingerprints:
raise ValueError("TLS certificate not allowed by fingerprints")

response_keys = yield self.process_v2_response(
server_name=server_name,
from_server=server_name,
response_json=response_json,
)

keys.update(response_keys)

yield self.store_keys(
server_name=server_name,
from_server=server_name,
verify_keys=keys,
)

for key_id in key_ids:
if key_id in verify_keys:
defer.returnValue(verify_keys[key_id])
return

raise ValueError("No verification key found for given key ids")

@defer.inlineCallbacks
def process_v2_response(self, server_name, from_server, json_response):
time_now_ms = clock.time_msec()
response_keys = {}
verify_keys = {}
for key_id, key_data in response["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_base64 = key_data["key"]
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_keys[key_id] = verify_key

old_verify_keys = {}
for key_id, key_data in response["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_base64 = key_data["key"]
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_key.expired = key_data["expired"]
verify_key.time_added = time_now_ms
old_verify_keys[key_id] = verify_key

for key_id in response["signatures"][server_name]:
if key_id not in response["verify_keys"]:
raise ValueError(
"Key response must include verification keys for all"
" signatures"
)
if key_id in verify_keys:
verify_signed_json(
response,
server_name,
verify_keys[key_id]
)

signed_key_json = sign_json(
response,
self.config.server_name,
self.config.signing_key[0],
)

signed_key_json_bytes = encode_canonical_json(signed_key_json)
ts_valid_until_ms = signed_key_json[u"valid_until"]

updated_key_ids = set([requested_key_id])
updated_key_ids.update(verify_keys)
updated_key_ids.update(old_verify_keys)

response_keys.update(verify_keys)
response_keys.update(old_verify_keys)

for key_id in updated_key_ids:
yield self.store.store_server_keys_json(
server_name=server_name,
key_id=key_id,
from_server=server_name,
ts_now_ms=ts_now_ms,
ts_valid_until_ms=valid_until,
key_json_bytes=signed_key_json_bytes,
)

defer.returnValue(response_keys)

raise ValueError("No verification key found for given key ids")

@defer.inlineCallbacks
def get_server_verify_key_v1_direct(self, server_name, key_ids):
"""Finds a verification key for the server with one of the key ids.
Args:
server_name (str): The name of the server to fetch a key for.
keys_ids (list of str): The key_ids to check for.
"""

# Try to fetch the key from the remote server.

(response, tls_certificate) = yield fetch_server_key(
server_name, self.hs.tls_context_factory
)

# Check the response.

x509_certificate_bytes = crypto.dump_certificate(
Expand All @@ -128,11 +348,16 @@ def get_server_verify_key(self, server_name, key_ids):
if encode_base64(x509_certificate_bytes) != tls_certificate_b64:
raise ValueError("TLS certificate doesn't match")

# Cache the result in the datastore.

time_now_ms = self.clock.time_msec()

verify_keys = {}
for key_id, key_base64 in response["verify_keys"].items():
if is_signing_algorithm_supported(key_id):
key_bytes = decode_base64(key_base64)
verify_key = decode_verify_key_bytes(key_id, key_bytes)
verify_key.time_added = time_now_ms
verify_keys[key_id] = verify_key

for key_id in response["signatures"][server_name]:
Expand All @@ -148,9 +373,6 @@ def get_server_verify_key(self, server_name, key_ids):
verify_keys[key_id]
)

# Cache the result in the datastore.

time_now_ms = self.clock.time_msec()

yield self.store.store_server_certificate(
server_name,
Expand All @@ -159,14 +381,26 @@ def get_server_verify_key(self, server_name, key_ids):
tls_certificate,
)

yield self.store_keys(
server_name=server_name,
from_server=server_name,
verify_keys=verify_keys,
)

defer.returnValue(verify_keys)

@defer.inlineCallbacks
def store_keys(self, server_name, from_server, verify_keys):
"""Store a collection of verify keys for a given server
Args:
server_name(str): The name of the server the keys are for.
from_server(str): The server the keys were downloaded from.
verify_keys(dict): A mapping of key_id to VerifyKey.
Returns:
A deferred that completes when the keys are stored.
"""
for key_id, key in verify_keys.items():
# TODO(markjh): Store whether the keys have expired.
yield self.store.store_server_verify_key(
server_name, server_name, time_now_ms, key
server_name, server_name, key.time_added, key
)

for key_id in key_ids:
if key_id in verify_keys:
defer.returnValue(verify_keys[key_id])
return

raise ValueError("No verification key found for given key ids")
4 changes: 3 additions & 1 deletion synapse/rest/key/v2/local_key_resource.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,9 @@ def response_json_object(self):
for key in self.config.signing_key:
verify_key_bytes = key.verify_key.encode()
key_id = "%s:%s" % (key.alg, key.version)
verify_keys[key_id] = encode_base64(verify_key_bytes)
verify_keys[key_id] = {
u"key": encode_base64(verify_key_bytes)
}

old_verify_keys = {}
for key in self.config.old_signing_keys:
Expand Down

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