410 lines
14 KiB
Python
410 lines
14 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright 2014-2016 OpenMarket Ltd
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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 socket
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from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
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from twisted.internet import defer, reactor
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from twisted.internet.error import ConnectError
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from twisted.names import client, dns
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from twisted.names.error import DNSNameError, DomainError
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import collections
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import logging
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import random
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import time
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logger = logging.getLogger(__name__)
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SERVER_CACHE = {}
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# our record of an individual server which can be tried to reach a destination.
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#
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# "host" is actually a dotted-quad or ipv6 address string. Except when there's
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# no SRV record, in which case it is the original hostname.
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_Server = collections.namedtuple(
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"_Server", "priority weight host port expires"
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)
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def matrix_federation_endpoint(reactor, destination, ssl_context_factory=None,
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timeout=None):
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"""Construct an endpoint for the given matrix destination.
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Args:
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reactor: Twisted reactor.
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destination (bytes): The name of the server to connect to.
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ssl_context_factory (twisted.internet.ssl.ContextFactory): Factory
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which generates SSL contexts to use for TLS.
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timeout (int): connection timeout in seconds
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"""
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domain_port = destination.split(":")
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domain = domain_port[0]
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port = int(domain_port[1]) if domain_port[1:] else None
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endpoint_kw_args = {}
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if timeout is not None:
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endpoint_kw_args.update(timeout=timeout)
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if ssl_context_factory is None:
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transport_endpoint = HostnameEndpoint
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default_port = 8008
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else:
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def transport_endpoint(reactor, host, port, timeout):
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return wrapClientTLS(
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ssl_context_factory,
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HostnameEndpoint(reactor, host, port, timeout=timeout))
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default_port = 8448
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if port is None:
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return _WrappingEndpointFac(SRVClientEndpoint(
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reactor, "matrix", domain, protocol="tcp",
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default_port=default_port, endpoint=transport_endpoint,
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endpoint_kw_args=endpoint_kw_args
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))
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else:
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return _WrappingEndpointFac(transport_endpoint(
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reactor, domain, port, **endpoint_kw_args
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))
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class _WrappingEndpointFac(object):
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def __init__(self, endpoint_fac):
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self.endpoint_fac = endpoint_fac
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@defer.inlineCallbacks
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def connect(self, protocolFactory):
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conn = yield self.endpoint_fac.connect(protocolFactory)
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conn = _WrappedConnection(conn)
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defer.returnValue(conn)
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class _WrappedConnection(object):
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"""Wraps a connection and calls abort on it if it hasn't seen any action
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for 2.5-3 minutes.
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"""
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__slots__ = ["conn", "last_request"]
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def __init__(self, conn):
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object.__setattr__(self, "conn", conn)
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object.__setattr__(self, "last_request", time.time())
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def __getattr__(self, name):
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return getattr(self.conn, name)
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def __setattr__(self, name, value):
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setattr(self.conn, name, value)
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def _time_things_out_maybe(self):
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# We use a slightly shorter timeout here just in case the callLater is
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# triggered early. Paranoia ftw.
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# TODO: Cancel the previous callLater rather than comparing time.time()?
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if time.time() - self.last_request >= 2.5 * 60:
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self.abort()
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# Abort the underlying TLS connection. The abort() method calls
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# loseConnection() on the underlying TLS connection which tries to
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# shutdown the connection cleanly. We call abortConnection()
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# since that will promptly close the underlying TCP connection.
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self.transport.abortConnection()
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def request(self, request):
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self.last_request = time.time()
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# Time this connection out if we haven't send a request in the last
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# N minutes
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# TODO: Cancel the previous callLater?
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reactor.callLater(3 * 60, self._time_things_out_maybe)
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d = self.conn.request(request)
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def update_request_time(res):
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self.last_request = time.time()
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# TODO: Cancel the previous callLater?
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reactor.callLater(3 * 60, self._time_things_out_maybe)
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return res
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d.addCallback(update_request_time)
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return d
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class SpiderEndpoint(object):
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"""An endpoint which refuses to connect to blacklisted IP addresses
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Implements twisted.internet.interfaces.IStreamClientEndpoint.
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"""
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def __init__(self, reactor, host, port, blacklist, whitelist,
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endpoint=HostnameEndpoint, endpoint_kw_args={}):
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self.reactor = reactor
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self.host = host
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self.port = port
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self.blacklist = blacklist
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self.whitelist = whitelist
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self.endpoint = endpoint
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self.endpoint_kw_args = endpoint_kw_args
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@defer.inlineCallbacks
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def connect(self, protocolFactory):
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address = yield self.reactor.resolve(self.host)
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from netaddr import IPAddress
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ip_address = IPAddress(address)
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if ip_address in self.blacklist:
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if self.whitelist is None or ip_address not in self.whitelist:
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raise ConnectError(
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"Refusing to spider blacklisted IP address %s" % address
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)
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logger.info("Connecting to %s:%s", address, self.port)
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endpoint = self.endpoint(
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self.reactor, address, self.port, **self.endpoint_kw_args
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)
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connection = yield endpoint.connect(protocolFactory)
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defer.returnValue(connection)
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class SRVClientEndpoint(object):
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"""An endpoint which looks up SRV records for a service.
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Cycles through the list of servers starting with each call to connect
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picking the next server.
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Implements twisted.internet.interfaces.IStreamClientEndpoint.
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"""
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def __init__(self, reactor, service, domain, protocol="tcp",
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default_port=None, endpoint=HostnameEndpoint,
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endpoint_kw_args={}):
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self.reactor = reactor
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self.service_name = "_%s._%s.%s" % (service, protocol, domain)
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if default_port is not None:
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self.default_server = _Server(
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host=domain,
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port=default_port,
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priority=0,
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weight=0,
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expires=0,
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)
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else:
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self.default_server = None
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self.endpoint = endpoint
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self.endpoint_kw_args = endpoint_kw_args
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self.servers = None
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self.used_servers = None
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@defer.inlineCallbacks
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def fetch_servers(self):
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self.used_servers = []
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self.servers = yield resolve_service(self.service_name)
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def pick_server(self):
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if not self.servers:
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if self.used_servers:
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self.servers = self.used_servers
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self.used_servers = []
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self.servers.sort()
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elif self.default_server:
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return self.default_server
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else:
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raise ConnectError(
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"No server available for %s" % self.service_name
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)
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# look for all servers with the same priority
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min_priority = self.servers[0].priority
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weight_indexes = list(
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(index, server.weight + 1)
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for index, server in enumerate(self.servers)
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if server.priority == min_priority
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)
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total_weight = sum(weight for index, weight in weight_indexes)
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target_weight = random.randint(0, total_weight)
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for index, weight in weight_indexes:
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target_weight -= weight
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if target_weight <= 0:
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server = self.servers[index]
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# XXX: this looks totally dubious:
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#
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# (a) we never reuse a server until we have been through
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# all of the servers at the same priority, so if the
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# weights are A: 100, B:1, we always do ABABAB instead of
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# AAAA...AAAB (approximately).
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#
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# (b) After using all the servers at the lowest priority,
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# we move onto the next priority. We should only use the
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# second priority if servers at the top priority are
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# unreachable.
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#
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del self.servers[index]
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self.used_servers.append(server)
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return server
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@defer.inlineCallbacks
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def connect(self, protocolFactory):
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if self.servers is None:
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yield self.fetch_servers()
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server = self.pick_server()
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logger.info("Connecting to %s:%s", server.host, server.port)
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endpoint = self.endpoint(
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self.reactor, server.host, server.port, **self.endpoint_kw_args
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)
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connection = yield endpoint.connect(protocolFactory)
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defer.returnValue(connection)
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@defer.inlineCallbacks
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def resolve_service(service_name, dns_client=client, cache=SERVER_CACHE, clock=time):
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cache_entry = cache.get(service_name, None)
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if cache_entry:
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if all(s.expires > int(clock.time()) for s in cache_entry):
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servers = list(cache_entry)
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defer.returnValue(servers)
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servers = []
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try:
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try:
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answers, _, _ = yield dns_client.lookupService(service_name)
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except DNSNameError:
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defer.returnValue([])
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if (len(answers) == 1
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and answers[0].type == dns.SRV
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and answers[0].payload
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and answers[0].payload.target == dns.Name('.')):
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raise ConnectError("Service %s unavailable" % service_name)
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for answer in answers:
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if answer.type != dns.SRV or not answer.payload:
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continue
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payload = answer.payload
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hosts = yield _get_hosts_for_srv_record(
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dns_client, str(payload.target)
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)
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for (ip, ttl) in hosts:
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host_ttl = min(answer.ttl, ttl)
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servers.append(_Server(
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host=ip,
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port=int(payload.port),
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priority=int(payload.priority),
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weight=int(payload.weight),
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expires=int(clock.time()) + host_ttl,
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))
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servers.sort()
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cache[service_name] = list(servers)
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except DomainError as e:
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# We failed to resolve the name (other than a NameError)
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# Try something in the cache, else rereaise
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cache_entry = cache.get(service_name, None)
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if cache_entry:
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logger.warn(
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"Failed to resolve %r, falling back to cache. %r",
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service_name, e
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)
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servers = list(cache_entry)
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else:
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raise e
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defer.returnValue(servers)
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@defer.inlineCallbacks
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def _get_hosts_for_srv_record(dns_client, host):
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"""Look up each of the hosts in a SRV record
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Args:
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dns_client (twisted.names.dns.IResolver):
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host (basestring): host to look up
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Returns:
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Deferred[list[(str, int)]]: a list of (host, ttl) pairs
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"""
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ip4_servers = []
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ip6_servers = []
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def cb(res):
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# lookupAddress and lookupIP6Address return a three-tuple
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# giving the answer, authority, and additional sections of the
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# response.
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#
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# we only care about the answers.
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return res[0]
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def eb(res, record_type):
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if res.check(DNSNameError):
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return []
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logger.warn("Error looking up %s for %s: %s",
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record_type, host, res, res.value)
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return res
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# no logcontexts here, so we can safely fire these off and gatherResults
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d1 = dns_client.lookupAddress(host).addCallbacks(
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cb, eb, errbackArgs=("A", ))
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d2 = dns_client.lookupIPV6Address(host).addCallbacks(
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cb, eb, errbackArgs=("AAAA", ))
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results = yield defer.DeferredList(
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[d1, d2], consumeErrors=True)
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# if all of the lookups failed, raise an exception rather than blowing out
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# the cache with an empty result.
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if results and all(s == defer.FAILURE for (s, _) in results):
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defer.returnValue(results[0][1])
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for (success, result) in results:
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if success == defer.FAILURE:
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continue
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for answer in result:
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if not answer.payload:
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continue
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try:
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if answer.type == dns.A:
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ip = answer.payload.dottedQuad()
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ip4_servers.append((ip, answer.ttl))
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elif answer.type == dns.AAAA:
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ip = socket.inet_ntop(
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socket.AF_INET6, answer.payload.address,
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)
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ip6_servers.append((ip, answer.ttl))
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else:
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# the most likely candidate here is a CNAME record.
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# rfc2782 says srvs may not point to aliases.
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logger.warn(
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"Ignoring unexpected DNS record type %s for %s",
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answer.type, host,
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)
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continue
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except Exception as e:
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logger.warn("Ignoring invalid DNS response for %s: %s",
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host, e)
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continue
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# keep the ipv4 results before the ipv6 results, mostly to match historical
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# behaviour.
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defer.returnValue(ip4_servers + ip6_servers)
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