mirror of
https://mau.dev/maunium/synapse.git
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441 lines
17 KiB
Python
441 lines
17 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2015, 2016 OpenMarket Ltd
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# Copyright 2019 The Matrix.org Foundation C.I.C.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import hashlib
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import logging
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import os
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import attr
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import jsonschema
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from signedjson.key import (
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NACL_ED25519,
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decode_signing_key_base64,
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decode_verify_key_bytes,
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generate_signing_key,
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is_signing_algorithm_supported,
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read_signing_keys,
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write_signing_keys,
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)
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from unpaddedbase64 import decode_base64
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from synapse.util.stringutils import random_string, random_string_with_symbols
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from ._base import Config, ConfigError
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INSECURE_NOTARY_ERROR = """\
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Your server is configured to accept key server responses without signature
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validation or TLS certificate validation. This is likely to be very insecure. If
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you are *sure* you want to do this, set 'accept_keys_insecurely' on the
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keyserver configuration."""
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RELYING_ON_MATRIX_KEY_ERROR = """\
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Your server is configured to accept key server responses without TLS certificate
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validation, and which are only signed by the old (possibly compromised)
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matrix.org signing key 'ed25519:auto'. This likely isn't what you want to do,
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and you should enable 'federation_verify_certificates' in your configuration.
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If you are *sure* you want to do this, set 'accept_keys_insecurely' on the
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trusted_key_server configuration."""
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TRUSTED_KEY_SERVER_NOT_CONFIGURED_WARN = """\
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Synapse requires that a list of trusted key servers are specified in order to
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provide signing keys for other servers in the federation.
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This homeserver does not have a trusted key server configured in
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homeserver.yaml and will fall back to the default of 'matrix.org'.
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Trusted key servers should be long-lived and stable which makes matrix.org a
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good choice for many admins, but some admins may wish to choose another. To
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suppress this warning, the admin should set 'trusted_key_servers' in
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homeserver.yaml to their desired key server and 'suppress_key_server_warning'
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to 'true'.
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In a future release the software-defined default will be removed entirely and
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the trusted key server will be defined exclusively by the value of
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'trusted_key_servers'.
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--------------------------------------------------------------------------------"""
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TRUSTED_KEY_SERVER_CONFIGURED_AS_M_ORG_WARN = """\
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This server is configured to use 'matrix.org' as its trusted key server via the
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'trusted_key_servers' config option. 'matrix.org' is a good choice for a key
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server since it is long-lived, stable and trusted. However, some admins may
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wish to use another server for this purpose.
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To suppress this warning and continue using 'matrix.org', admins should set
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'suppress_key_server_warning' to 'true' in homeserver.yaml.
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--------------------------------------------------------------------------------"""
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logger = logging.getLogger(__name__)
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@attr.s
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class TrustedKeyServer(object):
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# string: name of the server.
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server_name = attr.ib()
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# dict[str,VerifyKey]|None: map from key id to key object, or None to disable
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# signature verification.
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verify_keys = attr.ib(default=None)
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class KeyConfig(Config):
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def read_config(self, config, config_dir_path, **kwargs):
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# the signing key can be specified inline or in a separate file
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if "signing_key" in config:
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self.signing_key = read_signing_keys([config["signing_key"]])
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else:
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signing_key_path = config.get("signing_key_path")
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if signing_key_path is None:
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signing_key_path = os.path.join(
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config_dir_path, config["server_name"] + ".signing.key"
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)
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self.signing_key = self.read_signing_keys(signing_key_path, "signing_key")
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self.old_signing_keys = self.read_old_signing_keys(
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config.get("old_signing_keys", {})
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)
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self.key_refresh_interval = self.parse_duration(
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config.get("key_refresh_interval", "1d")
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)
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suppress_key_server_warning = config.get("suppress_key_server_warning", False)
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key_server_signing_keys_path = config.get("key_server_signing_keys_path")
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if key_server_signing_keys_path:
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self.key_server_signing_keys = self.read_signing_keys(
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key_server_signing_keys_path, "key_server_signing_keys_path"
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)
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else:
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self.key_server_signing_keys = list(self.signing_key)
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# if neither trusted_key_servers nor perspectives are given, use the default.
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if "perspectives" not in config and "trusted_key_servers" not in config:
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logger.warn(TRUSTED_KEY_SERVER_NOT_CONFIGURED_WARN)
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key_servers = [{"server_name": "matrix.org"}]
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else:
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key_servers = config.get("trusted_key_servers", [])
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if not isinstance(key_servers, list):
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raise ConfigError(
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"trusted_key_servers, if given, must be a list, not a %s"
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% (type(key_servers).__name__,)
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)
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# merge the 'perspectives' config into the 'trusted_key_servers' config.
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key_servers.extend(_perspectives_to_key_servers(config))
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if not suppress_key_server_warning and "matrix.org" in (
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s["server_name"] for s in key_servers
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):
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logger.warning(TRUSTED_KEY_SERVER_CONFIGURED_AS_M_ORG_WARN)
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# list of TrustedKeyServer objects
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self.key_servers = list(
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_parse_key_servers(key_servers, self.federation_verify_certificates)
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)
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self.macaroon_secret_key = config.get(
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"macaroon_secret_key", self.registration_shared_secret
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)
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if not self.macaroon_secret_key:
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# Unfortunately, there are people out there that don't have this
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# set. Lets just be "nice" and derive one from their secret key.
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logger.warn("Config is missing macaroon_secret_key")
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seed = bytes(self.signing_key[0])
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self.macaroon_secret_key = hashlib.sha256(seed).digest()
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# a secret which is used to calculate HMACs for form values, to stop
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# falsification of values
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self.form_secret = config.get("form_secret", None)
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def generate_config_section(
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self, config_dir_path, server_name, generate_secrets=False, **kwargs
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):
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base_key_name = os.path.join(config_dir_path, server_name)
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if generate_secrets:
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macaroon_secret_key = 'macaroon_secret_key: "%s"' % (
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random_string_with_symbols(50),
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)
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form_secret = 'form_secret: "%s"' % random_string_with_symbols(50)
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else:
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macaroon_secret_key = "# macaroon_secret_key: <PRIVATE STRING>"
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form_secret = "# form_secret: <PRIVATE STRING>"
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return (
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"""\
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# a secret which is used to sign access tokens. If none is specified,
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# the registration_shared_secret is used, if one is given; otherwise,
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# a secret key is derived from the signing key.
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#
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%(macaroon_secret_key)s
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# a secret which is used to calculate HMACs for form values, to stop
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# falsification of values. Must be specified for the User Consent
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# forms to work.
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#
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%(form_secret)s
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## Signing Keys ##
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# Path to the signing key to sign messages with
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#
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signing_key_path: "%(base_key_name)s.signing.key"
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# The keys that the server used to sign messages with but won't use
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# to sign new messages. E.g. it has lost its private key
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#
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#old_signing_keys:
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# "ed25519:auto":
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# # Base64 encoded public key
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# key: "The public part of your old signing key."
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# # Millisecond POSIX timestamp when the key expired.
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# expired_ts: 123456789123
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# How long key response published by this server is valid for.
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# Used to set the valid_until_ts in /key/v2 APIs.
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# Determines how quickly servers will query to check which keys
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# are still valid.
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#
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#key_refresh_interval: 1d
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# The trusted servers to download signing keys from.
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#
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# When we need to fetch a signing key, each server is tried in parallel.
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#
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# Normally, the connection to the key server is validated via TLS certificates.
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# Additional security can be provided by configuring a `verify key`, which
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# will make synapse check that the response is signed by that key.
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#
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# This setting supercedes an older setting named `perspectives`. The old format
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# is still supported for backwards-compatibility, but it is deprecated.
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#
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# 'trusted_key_servers' defaults to matrix.org, but using it will generate a
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# warning on start-up. To suppress this warning, set
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# 'suppress_key_server_warning' to true.
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#
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# Options for each entry in the list include:
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#
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# server_name: the name of the server. required.
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#
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# verify_keys: an optional map from key id to base64-encoded public key.
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# If specified, we will check that the response is signed by at least
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# one of the given keys.
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#
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# accept_keys_insecurely: a boolean. Normally, if `verify_keys` is unset,
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# and federation_verify_certificates is not `true`, synapse will refuse
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# to start, because this would allow anyone who can spoof DNS responses
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# to masquerade as the trusted key server. If you know what you are doing
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# and are sure that your network environment provides a secure connection
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# to the key server, you can set this to `true` to override this
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# behaviour.
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#
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# An example configuration might look like:
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#
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#trusted_key_servers:
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# - server_name: "my_trusted_server.example.com"
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# verify_keys:
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# "ed25519:auto": "abcdefghijklmnopqrstuvwxyzabcdefghijklmopqr"
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# - server_name: "my_other_trusted_server.example.com"
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#
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trusted_key_servers:
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- server_name: "matrix.org"
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# Uncomment the following to disable the warning that is emitted when the
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# trusted_key_servers include 'matrix.org'. See above.
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#
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#suppress_key_server_warning: true
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# The signing keys to use when acting as a trusted key server. If not specified
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# defaults to the server signing key.
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#
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# Can contain multiple keys, one per line.
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#
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#key_server_signing_keys_path: "key_server_signing_keys.key"
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"""
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% locals()
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)
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def read_signing_keys(self, signing_key_path, name):
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"""Read the signing keys in the given path.
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Args:
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signing_key_path (str)
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name (str): Associated config key name
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Returns:
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list[SigningKey]
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"""
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signing_keys = self.read_file(signing_key_path, name)
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try:
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return read_signing_keys(signing_keys.splitlines(True))
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except Exception as e:
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raise ConfigError("Error reading %s: %s" % (name, str(e)))
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def read_old_signing_keys(self, old_signing_keys):
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keys = {}
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for key_id, key_data in old_signing_keys.items():
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if is_signing_algorithm_supported(key_id):
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key_base64 = key_data["key"]
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key_bytes = decode_base64(key_base64)
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verify_key = decode_verify_key_bytes(key_id, key_bytes)
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verify_key.expired_ts = key_data["expired_ts"]
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keys[key_id] = verify_key
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else:
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raise ConfigError(
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"Unsupported signing algorithm for old key: %r" % (key_id,)
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)
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return keys
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def generate_files(self, config, config_dir_path):
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if "signing_key" in config:
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return
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signing_key_path = config.get("signing_key_path")
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if signing_key_path is None:
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signing_key_path = os.path.join(
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config_dir_path, config["server_name"] + ".signing.key"
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)
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if not self.path_exists(signing_key_path):
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print("Generating signing key file %s" % (signing_key_path,))
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with open(signing_key_path, "w") as signing_key_file:
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key_id = "a_" + random_string(4)
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write_signing_keys(signing_key_file, (generate_signing_key(key_id),))
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else:
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signing_keys = self.read_file(signing_key_path, "signing_key")
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if len(signing_keys.split("\n")[0].split()) == 1:
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# handle keys in the old format.
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key_id = "a_" + random_string(4)
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key = decode_signing_key_base64(
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NACL_ED25519, key_id, signing_keys.split("\n")[0]
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)
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with open(signing_key_path, "w") as signing_key_file:
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write_signing_keys(signing_key_file, (key,))
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def _perspectives_to_key_servers(config):
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"""Convert old-style 'perspectives' configs into new-style 'trusted_key_servers'
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Returns an iterable of entries to add to trusted_key_servers.
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"""
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# 'perspectives' looks like:
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#
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# {
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# "servers": {
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# "matrix.org": {
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# "verify_keys": {
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# "ed25519:auto": {
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# "key": "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw"
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# }
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# }
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# }
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# }
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# }
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#
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# 'trusted_keys' looks like:
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#
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# [
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# {
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# "server_name": "matrix.org",
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# "verify_keys": {
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# "ed25519:auto": "Noi6WqcDj0QmPxCNQqgezwTlBKrfqehY1u2FyWP9uYw",
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# }
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# }
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# ]
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perspectives_servers = config.get("perspectives", {}).get("servers", {})
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for server_name, server_opts in perspectives_servers.items():
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trusted_key_server_entry = {"server_name": server_name}
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verify_keys = server_opts.get("verify_keys")
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if verify_keys is not None:
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trusted_key_server_entry["verify_keys"] = {
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key_id: key_data["key"] for key_id, key_data in verify_keys.items()
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}
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yield trusted_key_server_entry
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TRUSTED_KEY_SERVERS_SCHEMA = {
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"$schema": "http://json-schema.org/draft-04/schema#",
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"description": "schema for the trusted_key_servers setting",
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"type": "array",
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"items": {
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"type": "object",
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"properties": {
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"server_name": {"type": "string"},
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"verify_keys": {
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"type": "object",
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# each key must be a base64 string
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"additionalProperties": {"type": "string"},
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},
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},
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"required": ["server_name"],
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},
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}
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def _parse_key_servers(key_servers, federation_verify_certificates):
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try:
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jsonschema.validate(key_servers, TRUSTED_KEY_SERVERS_SCHEMA)
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except jsonschema.ValidationError as e:
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raise ConfigError("Unable to parse 'trusted_key_servers': " + e.message)
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for server in key_servers:
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server_name = server["server_name"]
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result = TrustedKeyServer(server_name=server_name)
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verify_keys = server.get("verify_keys")
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if verify_keys is not None:
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result.verify_keys = {}
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for key_id, key_base64 in verify_keys.items():
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if not is_signing_algorithm_supported(key_id):
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raise ConfigError(
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"Unsupported signing algorithm on key %s for server %s in "
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"trusted_key_servers" % (key_id, server_name)
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)
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try:
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key_bytes = decode_base64(key_base64)
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verify_key = decode_verify_key_bytes(key_id, key_bytes)
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except Exception as e:
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raise ConfigError(
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"Unable to parse key %s for server %s in "
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"trusted_key_servers: %s" % (key_id, server_name, e)
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)
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result.verify_keys[key_id] = verify_key
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if not federation_verify_certificates and not server.get(
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"accept_keys_insecurely"
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):
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_assert_keyserver_has_verify_keys(result)
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yield result
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def _assert_keyserver_has_verify_keys(trusted_key_server):
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if not trusted_key_server.verify_keys:
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raise ConfigError(INSECURE_NOTARY_ERROR)
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# also check that they are not blindly checking the old matrix.org key
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if trusted_key_server.server_name == "matrix.org" and any(
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key_id == "ed25519:auto" for key_id in trusted_key_server.verify_keys
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):
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raise ConfigError(RELYING_ON_MATRIX_KEY_ERROR)
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