Merge pull request #129 from matrix-org/key_distribution

Key distribution v2

1 files changed, 283 insertions, 18 deletions

diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 2b4faee4c1..8709394b97 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -15,7 +15,9 @@
 
 from synapse.crypto.keyclient import fetch_server_key
 from twisted.internet import defer
-from syutil.crypto.jsonsign import verify_signed_json, signature_ids
+from syutil.crypto.jsonsign import (
+    verify_signed_json, signature_ids, sign_json, encode_canonical_json
+)
 from syutil.crypto.signing_key import (
     is_signing_algorithm_supported, decode_verify_key_bytes
 )
@@ -28,6 +30,8 @@ from synapse.util.async import create_observer
 
 from OpenSSL import crypto
 
+import urllib
+import hashlib
 import logging
 
 
@@ -38,6 +42,9 @@ class Keyring(object):
     def __init__(self, hs):
         self.store = hs.get_datastore()
         self.clock = hs.get_clock()
+        self.client = hs.get_http_client()
+        self.config = hs.get_config()
+        self.perspective_servers = self.config.perspectives
         self.hs = hs
 
         self.key_downloads = {}
@@ -89,12 +96,11 @@ class Keyring(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:
@@ -117,7 +123,29 @@ class Keyring(object):
 
     @defer.inlineCallbacks
     def _get_server_verify_key_impl(self, server_name, key_ids):
-        # Try to fetch the key from the remote server.
+        keys = None
+
+        perspective_results = []
+        for perspective_name, perspective_keys in self.perspective_servers.items():
+            @defer.inlineCallbacks
+            def get_key():
+                try:
+                    result = yield self.get_server_verify_key_v2_indirect(
+                        server_name, key_ids, perspective_name, perspective_keys
+                    )
+                    defer.returnValue(result)
+                except:
+                    logging.info(
+                        "Unable to getting key %r for %r from %r",
+                        key_ids, server_name, perspective_name,
+                    )
+            perspective_results.append(get_key())
+
+        perspective_results = yield defer.gatherResults(perspective_results)
+
+        for results in perspective_results:
+            if results is not None:
+                keys = results
 
         limiter = yield get_retry_limiter(
             server_name,
@@ -126,10 +154,234 @@ class Keyring(object):
         )
 
         with limiter:
+            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
+        )
+
+        with limiter:
+            # TODO(mark): Set the minimum_valid_until_ts to that needed by
+            # the events being validated or the current time if validating
+            # an incoming request.
+            responses = yield self.client.post_json(
+                destination=perspective_name,
+                path=b"/_matrix/key/v2/query",
+                data={
+                    u"server_keys": {
+                        server_name: {
+                            key_id: {
+                                u"minimum_valid_until_ts": 0
+                            } for key_id in key_ids
+                        }
+                    }
+                },
+            )
+
+        keys = {}
+
+        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 = yield self.process_v2_response(
+                server_name, perspective_name, response
+            )
+
+            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, tls_certificate) = yield fetch_server_key(
-                server_name, self.hs.tls_context_factory
+                server_name, self.hs.tls_context_factory,
+                path=(b"/_matrix/key/v2/server/%s" % (
+                    urllib.quote(requested_key_id),
+                )).encode("ascii"),
+            )
+
+            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[u"tls_fingerprints"]:
+                if u"sha256" in fingerprint:
+                    response_sha256_fingerprints.add(fingerprint[u"sha256"])
+
+            if sha256_fingerprint_b64 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,
+                requested_id=requested_key_id,
+                response_json=response,
+            )
+
+            keys.update(response_keys)
+
+        yield self.store_keys(
+            server_name=server_name,
+            from_server=server_name,
+            verify_keys=keys,
+        )
+
+        defer.returnValue(keys)
+
+    @defer.inlineCallbacks
+    def process_v2_response(self, server_name, from_server, response_json,
+                            requested_id=None):
+        time_now_ms = self.clock.time_msec()
+        response_keys = {}
+        verify_keys = {}
+        for key_id, key_data in response_json["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.time_added = time_now_ms
+                verify_keys[key_id] = verify_key
+
+        old_verify_keys = {}
+        for key_id, key_data in response_json["old_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_ts"]
+                verify_key.time_added = time_now_ms
+                old_verify_keys[key_id] = verify_key
+
+        for key_id in response_json["signatures"][server_name]:
+            if key_id not in response_json["verify_keys"]:
+                raise ValueError(
+                    "Key response must include verification keys for all"
+                    " signatures"
+                )
+            if key_id in verify_keys:
+                verify_signed_json(
+                    response_json,
+                    server_name,
+                    verify_keys[key_id]
+                )
+
+        signed_key_json = sign_json(
+            response_json,
+            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_ts"]
+
+        updated_key_ids = set()
+        if requested_id is not None:
+            updated_key_ids.add(requested_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=time_now_ms,
+                ts_expires_ms=ts_valid_until_ms,
+                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(
@@ -148,11 +400,16 @@ class Keyring(object):
         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]:
@@ -168,10 +425,6 @@ class Keyring(object):
                     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,
             server_name,
@@ -179,14 +432,26 @@ class Keyring(object):
             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")