399 lines
13 KiB
Python
399 lines
13 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 collections
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import logging
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import random
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import re
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import time
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from twisted.internet import defer
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from twisted.internet.endpoints import HostnameEndpoint, wrapClientTLS
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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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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 the hostname acquired from the SRV record. 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 parse_server_name(server_name):
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"""Split a server name into host/port parts.
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Args:
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server_name (str): server name to parse
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Returns:
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Tuple[str, int|None]: host/port parts.
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Raises:
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ValueError if the server name could not be parsed.
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"""
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try:
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if server_name[-1] == ']':
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# ipv6 literal, hopefully
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return server_name, None
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domain_port = server_name.rsplit(":", 1)
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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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return domain, port
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except Exception:
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raise ValueError("Invalid server name '%s'" % server_name)
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VALID_HOST_REGEX = re.compile(
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"\\A[0-9a-zA-Z.-]+\\Z",
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)
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def parse_and_validate_server_name(server_name):
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"""Split a server name into host/port parts and do some basic validation.
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Args:
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server_name (str): server name to parse
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Returns:
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Tuple[str, int|None]: host/port parts.
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Raises:
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ValueError if the server name could not be parsed.
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"""
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host, port = parse_server_name(server_name)
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# these tests don't need to be bulletproof as we'll find out soon enough
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# if somebody is giving us invalid data. What we *do* need is to be sure
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# that nobody is sneaking IP literals in that look like hostnames, etc.
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# look for ipv6 literals
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if host[0] == '[':
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if host[-1] != ']':
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raise ValueError("Mismatched [...] in server name '%s'" % (
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server_name,
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))
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return host, port
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# otherwise it should only be alphanumerics.
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if not VALID_HOST_REGEX.match(host):
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raise ValueError("Server name '%s' contains invalid characters" % (
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server_name,
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))
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return host, port
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def matrix_federation_endpoint(reactor, destination, tls_client_options_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 (unicode): The name of the server to connect to.
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tls_client_options_factory
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(synapse.crypto.context_factory.ClientTLSOptionsFactory):
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Factory which generates TLS options for client connections.
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timeout (int): connection timeout in seconds
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"""
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domain, port = parse_server_name(destination)
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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 tls_client_options_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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# the SNI string should be the same as the Host header, minus the port.
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# as per https://github.com/matrix-org/synapse/issues/2525#issuecomment-336896777,
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# the Host header and SNI should therefore be the server_name of the remote
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# server.
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tls_options = tls_client_options_factory.get_options(domain)
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def transport_endpoint(reactor, host, port, timeout):
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return wrapClientTLS(
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tls_options,
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HostnameEndpoint(reactor, host, port, timeout=timeout),
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)
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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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), reactor)
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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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), reactor)
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class _WrappingEndpointFac(object):
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def __init__(self, endpoint_fac, reactor):
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self.endpoint_fac = endpoint_fac
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self.reactor = reactor
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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, self.reactor)
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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, reactor):
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object.__setattr__(self, "conn", conn)
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object.__setattr__(self, "last_request", time.time())
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self._reactor = reactor
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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 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 TLS connection.
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#
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# In Twisted >18.4; the TLS connection will be None if it has closed
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# which will make abortConnection() throw. Check that the TLS connection
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# is not None before trying to close it.
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if self.transport.getHandle() is not None:
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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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self._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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self._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(b'.')):
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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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servers.append(_Server(
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host=str(payload.target),
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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()) + answer.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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