diff options
| -rw-r--r-- | changelog.d/5374.feature | 1 | ||||
| -rw-r--r-- | docs/sample_config.yaml | 43 | ||||
| -rw-r--r-- | synapse/config/key.py | 228 | ||||
| -rw-r--r-- | synapse/crypto/keyring.py | 72 | ||||
| -rw-r--r-- | tests/crypto/test_keyring.py | 43 | ||||
| -rw-r--r-- | tests/http/federation/test_matrix_federation_agent.py | 1 |
6 files changed, 293 insertions, 95 deletions
diff --git a/changelog.d/5374.feature b/changelog.d/5374.feature new file mode 100644 index 0000000000..17937637ab --- /dev/null +++ b/changelog.d/5374.feature @@ -0,0 +1 @@ +Replace the `perspectives` configuration section with `trusted_key_servers`, and make validating the signatures on responses optional (since TLS will do this job for us). diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml index 2f37e71601..a2e815ea52 100644 --- a/docs/sample_config.yaml +++ b/docs/sample_config.yaml @@ -952,12 +952,43 @@ signing_key_path: "CONFDIR/SERVERNAME.signing.key" # The trusted servers to download signing keys from. # -#perspectives: -# servers: -# "matrix.org": -# verify_keys: -# "ed25519:auto": -# key: "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw" +# When we need to fetch a signing key, each server is tried in parallel. +# +# Normally, the connection to the key server is validated via TLS certificates. +# Additional security can be provided by configuring a `verify key`, which +# will make synapse check that the response is signed by that key. +# +# This setting supercedes an older setting named `perspectives`. The old format +# is still supported for backwards-compatibility, but it is deprecated. +# +# Options for each entry in the list include: +# +# server_name: the name of the server. required. +# +# verify_keys: an optional map from key id to base64-encoded public key. +# If specified, we will check that the response is signed by at least +# one of the given keys. +# +# accept_keys_insecurely: a boolean. Normally, if `verify_keys` is unset, +# and federation_verify_certificates is not `true`, synapse will refuse +# to start, because this would allow anyone who can spoof DNS responses +# to masquerade as the trusted key server. If you know what you are doing +# and are sure that your network environment provides a secure connection +# to the key server, you can set this to `true` to override this +# behaviour. +# +# An example configuration might look like: +# +#trusted_key_servers: +# - server_name: "my_trusted_server.example.com" +# verify_keys: +# "ed25519:auto": "abcdefghijklmnopqrstuvwxyzabcdefghijklmopqr" +# - server_name: "my_other_trusted_server.example.com" +# +# The default configuration is: +# +#trusted_key_servers: +# - server_name: "matrix.org" # Enable SAML2 for registration and login. Uses pysaml2. diff --git a/synapse/config/key.py b/synapse/config/key.py index eb10259818..aba7092ccd 100644 --- a/synapse/config/key.py +++ b/synapse/config/key.py @@ -1,5 +1,6 @@ # -*- coding: utf-8 -*- # Copyright 2015, 2016 OpenMarket Ltd +# Copyright 2019 The Matrix.org Foundation C.I.C. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. @@ -17,6 +18,8 @@ import hashlib import logging import os +import attr +import jsonschema from signedjson.key import ( NACL_ED25519, decode_signing_key_base64, @@ -32,11 +35,27 @@ from synapse.util.stringutils import random_string, random_string_with_symbols from ._base import Config, ConfigError +INSECURE_NOTARY_ERROR = """\ +Your server is configured to accept key server responses without signature +validation or TLS certificate validation. This is likely to be very insecure. If +you are *sure* you want to do this, set 'accept_keys_insecurely' on the +keyserver configuration.""" + + logger = logging.getLogger(__name__) -class KeyConfig(Config): +@attr.s +class TrustedKeyServer(object): + # string: name of the server. + server_name = attr.ib() + # dict[str,VerifyKey]|None: map from key id to key object, or None to disable + # signature verification. + verify_keys = attr.ib(default=None) + + +class KeyConfig(Config): def read_config(self, config): # the signing key can be specified inline or in a separate file if "signing_key" in config: @@ -49,16 +68,27 @@ class KeyConfig(Config): config.get("old_signing_keys", {}) ) self.key_refresh_interval = self.parse_duration( - config.get("key_refresh_interval", "1d"), + config.get("key_refresh_interval", "1d") ) - self.perspectives = self.read_perspectives( - config.get("perspectives", {}).get("servers", { - "matrix.org": {"verify_keys": { - "ed25519:auto": { - "key": "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw", - } - }} - }) + + # if neither trusted_key_servers nor perspectives are given, use the default. + if "perspectives" not in config and "trusted_key_servers" not in config: + key_servers = [{"server_name": "matrix.org"}] + else: + key_servers = config.get("trusted_key_servers", []) + + if not isinstance(key_servers, list): + raise ConfigError( + "trusted_key_servers, if given, must be a list, not a %s" + % (type(key_servers).__name__,) + ) + + # merge the 'perspectives' config into the 'trusted_key_servers' config. + key_servers.extend(_perspectives_to_key_servers(config)) + + # list of TrustedKeyServer objects + self.key_servers = list( + _parse_key_servers(key_servers, self.federation_verify_certificates) ) self.macaroon_secret_key = config.get( @@ -78,8 +108,9 @@ class KeyConfig(Config): # falsification of values self.form_secret = config.get("form_secret", None) - def default_config(self, config_dir_path, server_name, generate_secrets=False, - **kwargs): + def default_config( + self, config_dir_path, server_name, generate_secrets=False, **kwargs + ): base_key_name = os.path.join(config_dir_path, server_name) if generate_secrets: @@ -91,7 +122,8 @@ class KeyConfig(Config): macaroon_secret_key = "# macaroon_secret_key: <PRIVATE STRING>" form_secret = "# form_secret: <PRIVATE STRING>" - return """\ + return ( + """\ # a secret which is used to sign access tokens. If none is specified, # the registration_shared_secret is used, if one is given; otherwise, # a secret key is derived from the signing key. @@ -133,33 +165,53 @@ class KeyConfig(Config): # The trusted servers to download signing keys from. # - #perspectives: - # servers: - # "matrix.org": - # verify_keys: - # "ed25519:auto": - # key: "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw" - """ % locals() - - def read_perspectives(self, perspectives_servers): - servers = {} - for server_name, server_config in perspectives_servers.items(): - for key_id, key_data in server_config["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) - servers.setdefault(server_name, {})[key_id] = verify_key - return servers + # When we need to fetch a signing key, each server is tried in parallel. + # + # Normally, the connection to the key server is validated via TLS certificates. + # Additional security can be provided by configuring a `verify key`, which + # will make synapse check that the response is signed by that key. + # + # This setting supercedes an older setting named `perspectives`. The old format + # is still supported for backwards-compatibility, but it is deprecated. + # + # Options for each entry in the list include: + # + # server_name: the name of the server. required. + # + # verify_keys: an optional map from key id to base64-encoded public key. + # If specified, we will check that the response is signed by at least + # one of the given keys. + # + # accept_keys_insecurely: a boolean. Normally, if `verify_keys` is unset, + # and federation_verify_certificates is not `true`, synapse will refuse + # to start, because this would allow anyone who can spoof DNS responses + # to masquerade as the trusted key server. If you know what you are doing + # and are sure that your network environment provides a secure connection + # to the key server, you can set this to `true` to override this + # behaviour. + # + # An example configuration might look like: + # + #trusted_key_servers: + # - server_name: "my_trusted_server.example.com" + # verify_keys: + # "ed25519:auto": "abcdefghijklmnopqrstuvwxyzabcdefghijklmopqr" + # - server_name: "my_other_trusted_server.example.com" + # + # The default configuration is: + # + #trusted_key_servers: + # - server_name: "matrix.org" + """ + % locals() + ) def read_signing_key(self, signing_key_path): signing_keys = self.read_file(signing_key_path, "signing_key") try: return read_signing_keys(signing_keys.splitlines(True)) except Exception as e: - raise ConfigError( - "Error reading signing_key: %s" % (str(e)) - ) + raise ConfigError("Error reading signing_key: %s" % (str(e))) def read_old_signing_keys(self, old_signing_keys): keys = {} @@ -182,9 +234,7 @@ class KeyConfig(Config): if not self.path_exists(signing_key_path): with open(signing_key_path, "w") as signing_key_file: key_id = "a_" + random_string(4) - write_signing_keys( - signing_key_file, (generate_signing_key(key_id),), - ) + write_signing_keys(signing_key_file, (generate_signing_key(key_id),)) else: signing_keys = self.read_file(signing_key_path, "signing_key") if len(signing_keys.split("\n")[0].split()) == 1: @@ -194,6 +244,106 @@ class KeyConfig(Config): NACL_ED25519, key_id, signing_keys.split("\n")[0] ) with open(signing_key_path, "w") as signing_key_file: - write_signing_keys( - signing_key_file, (key,), + write_signing_keys(signing_key_file, (key,)) + + +def _perspectives_to_key_servers(config): + """Convert old-style 'perspectives' configs into new-style 'trusted_key_servers' + + Returns an iterable of entries to add to trusted_key_servers. + """ + + # 'perspectives' looks like: + # + # { + # "servers": { + # "matrix.org": { + # "verify_keys": { + # "ed25519:auto": { + # "key": "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw" + # } + # } + # } + # } + # } + # + # 'trusted_keys' looks like: + # + # [ + # { + # "server_name": "matrix.org", + # "verify_keys": { + # "ed25519:auto": "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw", + # } + # } + # ] + + perspectives_servers = config.get("perspectives", {}).get("servers", {}) + + for server_name, server_opts in perspectives_servers.items(): + trusted_key_server_entry = {"server_name": server_name} + verify_keys = server_opts.get("verify_keys") + if verify_keys is not None: + trusted_key_server_entry["verify_keys"] = { + key_id: key_data["key"] for key_id, key_data in verify_keys.items() + } + yield trusted_key_server_entry + + +TRUSTED_KEY_SERVERS_SCHEMA = { + "$schema": "http://json-schema.org/draft-04/schema#", + "description": "schema for the trusted_key_servers setting", + "type": "array", + "items": { + "type": "object", + "properties": { + "server_name": {"type": "string"}, + "verify_keys": { + "type": "object", + # each key must be a base64 string + "additionalProperties": {"type": "string"}, + }, + }, + "required": ["server_name"], + }, +} + + +def _parse_key_servers(key_servers, federation_verify_certificates): + try: + jsonschema.validate(key_servers, TRUSTED_KEY_SERVERS_SCHEMA) + except jsonschema.ValidationError as e: + raise ConfigError("Unable to parse 'trusted_key_servers': " + e.message) + + for server in key_servers: + server_name = server["server_name"] + result = TrustedKeyServer(server_name=server_name) + + verify_keys = server.get("verify_keys") + if verify_keys is not None: + result.verify_keys = {} + for key_id, key_base64 in verify_keys.items(): + if not is_signing_algorithm_supported(key_id): + raise ConfigError( + "Unsupported signing algorithm on key %s for server %s in " + "trusted_key_servers" % (key_id, server_name) ) + try: + key_bytes = decode_base64(key_base64) + verify_key = decode_verify_key_bytes(key_id, key_bytes) + except Exception as e: + raise ConfigError( + "Unable to parse key %s for server %s in " + "trusted_key_servers: %s" % (key_id, server_name, e) + ) + + result.verify_keys[key_id] = verify_key + + if ( + not verify_keys + and not server.get("accept_keys_insecurely") + and not federation_verify_certificates + ): + raise ConfigError(INSECURE_NOTARY_ERROR) + + yield result diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py index 2b6b5913bc..96964b0d50 100644 --- a/synapse/crypto/keyring.py +++ b/synapse/crypto/keyring.py @@ -585,25 +585,27 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): super(PerspectivesKeyFetcher, self).__init__(hs) self.clock = hs.get_clock() self.client = hs.get_http_client() - self.perspective_servers = self.config.perspectives + self.key_servers = self.config.key_servers @defer.inlineCallbacks def get_keys(self, keys_to_fetch): """see KeyFetcher.get_keys""" @defer.inlineCallbacks - def get_key(perspective_name, perspective_keys): + def get_key(key_server): try: result = yield self.get_server_verify_key_v2_indirect( - keys_to_fetch, perspective_name, perspective_keys + keys_to_fetch, key_server ) defer.returnValue(result) except KeyLookupError as e: - logger.warning("Key lookup failed from %r: %s", perspective_name, e) + logger.warning( + "Key lookup failed from %r: %s", key_server.server_name, e + ) except Exception as e: logger.exception( "Unable to get key from %r: %s %s", - perspective_name, + key_server.server_name, type(e).__name__, str(e), ) @@ -613,8 +615,8 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): results = yield logcontext.make_deferred_yieldable( defer.gatherResults( [ - run_in_background(get_key, p_name, p_keys) - for p_name, p_keys in self.perspective_servers.items() + run_in_background(get_key, server) + for server in self.key_servers ], consumeErrors=True, ).addErrback(unwrapFirstError) @@ -629,17 +631,15 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): @defer.inlineCallbacks def get_server_verify_key_v2_indirect( - self, keys_to_fetch, perspective_name, perspective_keys + self, keys_to_fetch, key_server ): """ Args: keys_to_fetch (dict[str, dict[str, int]]): the keys to be fetched. server_name -> key_id -> min_valid_ts - perspective_name (str): name of the notary server to query for the keys - - perspective_keys (dict[str, VerifyKey]): map of key_id->key for the - notary server + key_server (synapse.config.key.TrustedKeyServer): notary server to query for + the keys Returns: Deferred[dict[str, dict[str, synapse.storage.keys.FetchKeyResult]]]: map @@ -649,6 +649,7 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): KeyLookupError if there was an error processing the entire response from the server """ + perspective_name = key_server.server_name logger.info( "Requesting keys %s from notary server %s", keys_to_fetch.items(), @@ -689,11 +690,13 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): ) try: - processed_response = yield self._process_perspectives_response( - perspective_name, - perspective_keys, + self._validate_perspectives_response( + key_server, response, - time_added_ms=time_now_ms, + ) + + processed_response = yield self.process_v2_response( + perspective_name, response, time_added_ms=time_now_ms ) except KeyLookupError as e: logger.warning( @@ -717,28 +720,24 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): defer.returnValue(keys) - def _process_perspectives_response( - self, perspective_name, perspective_keys, response, time_added_ms + def _validate_perspectives_response( + self, key_server, response, ): - """Parse a 'Server Keys' structure from the result of a /key/query request - - Checks that the entry is correctly signed by the perspectives server, and then - passes over to process_v2_response + """Optionally check the signature on the result of a /key/query request Args: - perspective_name (str): the name of the notary server that produced this - result - - perspective_keys (dict[str, VerifyKey]): map of key_id->key for the - notary server + key_server (synapse.config.key.TrustedKeyServer): the notary server that + produced this result response (dict): the json-decoded Server Keys response object + """ + perspective_name = key_server.server_name + perspective_keys = key_server.verify_keys - time_added_ms (int): the timestamp to record in server_keys_json + if perspective_keys is None: + # signature checking is disabled on this server + return - Returns: - Deferred[dict[str, FetchKeyResult]]: map from key_id to result object - """ if ( u"signatures" not in response or perspective_name not in response[u"signatures"] @@ -751,6 +750,13 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): verify_signed_json(response, perspective_name, perspective_keys[key_id]) verified = True + if perspective_name == "matrix.org" and key_id == "ed25519:auto": + logger.warning( + "Trusting trusted_key_server responses signed by the " + "compromised matrix.org signing key 'ed25519:auto'. " + "This is a placebo." + ) + if not verified: raise KeyLookupError( "Response not signed with a known key: signed with: %r, known keys: %r" @@ -760,10 +766,6 @@ class PerspectivesKeyFetcher(BaseV2KeyFetcher): ) ) - return self.process_v2_response( - perspective_name, response, time_added_ms=time_added_ms - ) - class ServerKeyFetcher(BaseV2KeyFetcher): """KeyFetcher impl which fetches keys from the origin servers""" diff --git a/tests/crypto/test_keyring.py b/tests/crypto/test_keyring.py index 18121f4f6c..4b1901ce31 100644 --- a/tests/crypto/test_keyring.py +++ b/tests/crypto/test_keyring.py @@ -19,7 +19,7 @@ from mock import Mock import canonicaljson import signedjson.key import signedjson.sign -from signedjson.key import get_verify_key +from signedjson.key import encode_verify_key_base64, get_verify_key from twisted.internet import defer @@ -40,7 +40,7 @@ class MockPerspectiveServer(object): def get_verify_keys(self): vk = signedjson.key.get_verify_key(self.key) - return {"%s:%s" % (vk.alg, vk.version): vk} + return {"%s:%s" % (vk.alg, vk.version): encode_verify_key_base64(vk)} def get_signed_key(self, server_name, verify_key): key_id = "%s:%s" % (verify_key.alg, verify_key.version) @@ -48,9 +48,7 @@ class MockPerspectiveServer(object): "server_name": server_name, "old_verify_keys": {}, "valid_until_ts": time.time() * 1000 + 3600, - "verify_keys": { - key_id: {"key": signedjson.key.encode_verify_key_base64(verify_key)} - }, + "verify_keys": {key_id: {"key": encode_verify_key_base64(verify_key)}}, } self.sign_response(res) return res @@ -63,10 +61,18 @@ class KeyringTestCase(unittest.HomeserverTestCase): def make_homeserver(self, reactor, clock): self.mock_perspective_server = MockPerspectiveServer() self.http_client = Mock() - hs = self.setup_test_homeserver(handlers=None, http_client=self.http_client) - keys = self.mock_perspective_server.get_verify_keys() - hs.config.perspectives = {self.mock_perspective_server.server_name: keys} - return hs + + config = self.default_config() + config["trusted_key_servers"] = [ + { + "server_name": self.mock_perspective_server.server_name, + "verify_keys": self.mock_perspective_server.get_verify_keys(), + } + ] + + return self.setup_test_homeserver( + handlers=None, http_client=self.http_client, config=config + ) def check_context(self, _, expected): self.assertEquals( @@ -371,10 +377,18 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase): def make_homeserver(self, reactor, clock): self.mock_perspective_server = MockPerspectiveServer() self.http_client = Mock() - hs = self.setup_test_homeserver(handlers=None, http_client=self.http_client) - keys = self.mock_perspective_server.get_verify_keys() - hs.config.perspectives = {self.mock_perspective_server.server_name: keys} - return hs + + config = self.default_config() + config["trusted_key_servers"] = [ + { + "server_name": self.mock_perspective_server.server_name, + "verify_keys": self.mock_perspective_server.get_verify_keys(), + } + ] + + return self.setup_test_homeserver( + handlers=None, http_client=self.http_client, config=config + ) def test_get_keys_from_perspectives(self): # arbitrarily advance the clock a bit @@ -439,8 +453,7 @@ class PerspectivesKeyFetcherTestCase(unittest.HomeserverTestCase): self.assertEqual(res["ts_valid_until_ms"], VALID_UNTIL_TS) self.assertEqual( - bytes(res["key_json"]), - canonicaljson.encode_canonical_json(response), + bytes(res["key_json"]), canonicaljson.encode_canonical_json(response) ) def test_invalid_perspectives_responses(self): diff --git a/tests/http/federation/test_matrix_federation_agent.py b/tests/http/federation/test_matrix_federation_agent.py index 4153da4da7..05880a1048 100644 --- a/tests/http/federation/test_matrix_federation_agent.py +++ b/tests/http/federation/test_matrix_federation_agent.py @@ -57,6 +57,7 @@ class MatrixFederationAgentTests(TestCase): # present will not be trusted. We should do better here, though. config_dict = default_config("test", parse=False) config_dict["federation_verify_certificates"] = False + config_dict["trusted_key_servers"] = [] config = HomeServerConfig() config.parse_config_dict(config_dict) |