MatrixSynapse/synapse/crypto/keyclient.py

# -*- coding: utf-8 -*-
# Copyright 2014-2016 OpenMarket Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import logging

from canonicaljson import json

from twisted.internet import defer, reactor
from twisted.internet.error import ConnectError
from twisted.internet.protocol import Factory
from twisted.names.error import DomainError
from twisted.web.http import HTTPClient

from synapse.http.endpoint import matrix_federation_endpoint
from synapse.util import logcontext

logger = logging.getLogger(__name__)

KEY_API_V1 = b"/_matrix/key/v1/"


@defer.inlineCallbacks
def fetch_server_key(server_name, tls_client_options_factory, path=KEY_API_V1):
    """Fetch the keys for a remote server."""

    factory = SynapseKeyClientFactory()
    factory.path = path
    factory.host = server_name
    endpoint = matrix_federation_endpoint(
        reactor, server_name, tls_client_options_factory, timeout=30
    )

    for i in range(5):
        try:
            with logcontext.PreserveLoggingContext():
                protocol = yield endpoint.connect(factory)
                server_response, server_certificate = yield protocol.remote_key
                defer.returnValue((server_response, server_certificate))
        except SynapseKeyClientError as e:
            logger.warn("Error getting key for %r: %s", server_name, e)
            if e.status.startswith(b"4"):
                # Don't retry for 4xx responses.
                raise IOError("Cannot get key for %r" % server_name)
        except (ConnectError, DomainError) as e:
            logger.warn("Error getting key for %r: %s", server_name, e)
        except Exception:
            logger.exception("Error getting key for %r", server_name)
    raise IOError("Cannot get key for %r" % server_name)


class SynapseKeyClientError(Exception):
    """The key wasn't retrieved from the remote server."""
    status = None
    pass


class SynapseKeyClientProtocol(HTTPClient):
    """Low level HTTPS client which retrieves an application/json response from
    the server and extracts the X.509 certificate for the remote peer from the
    SSL connection."""

    timeout = 30

    def __init__(self):
        self.remote_key = defer.Deferred()
        self.host = None
        self._peer = None

    def connectionMade(self):
        self._peer = self.transport.getPeer()
        logger.debug("Connected to %s", self._peer)

        if not isinstance(self.path, bytes):
            self.path = self.path.encode('ascii')

        if not isinstance(self.host, bytes):
            self.host = self.host.encode('ascii')

        self.sendCommand(b"GET", self.path)
        if self.host:
            self.sendHeader(b"Host", self.host)
        self.endHeaders()
        self.timer = reactor.callLater(
            self.timeout,
            self.on_timeout
        )

    def errback(self, error):
        if not self.remote_key.called:
            self.remote_key.errback(error)

    def callback(self, result):
        if not self.remote_key.called:
            self.remote_key.callback(result)

    def handleStatus(self, version, status, message):
        if status != b"200":
            # logger.info("Non-200 response from %s: %s %s",
            #            self.transport.getHost(), status, message)
            error = SynapseKeyClientError(
                "Non-200 response %r from %r" % (status, self.host)
            )
            error.status = status
            self.errback(error)
            self.transport.abortConnection()

    def handleResponse(self, response_body_bytes):
        try:
            json_response = json.loads(response_body_bytes)
        except ValueError:
            # logger.info("Invalid JSON response from %s",
            #            self.transport.getHost())
            self.transport.abortConnection()
            return

        certificate = self.transport.getPeerCertificate()
        self.callback((json_response, certificate))
        self.transport.abortConnection()
        self.timer.cancel()

    def on_timeout(self):
        logger.debug(
            "Timeout waiting for response from %s: %s",
            self.host, self._peer,
        )
        self.errback(IOError("Timeout waiting for response"))
        self.transport.abortConnection()


class SynapseKeyClientFactory(Factory):
    def protocol(self):
        protocol = SynapseKeyClientProtocol()
        protocol.path = self.path
        protocol.host = self.host
        return protocol