magic-wormhole/src/txwormhole/transit.py

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from __future__ import print_function
import re, sys, time, socket, collections
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from binascii import hexlify, unhexlify
from zope.interface import implementer
from twisted.python.runtime import platformType
from twisted.internet import (reactor, interfaces, defer, protocol,
endpoints, task, address, error)
from twisted.internet.defer import inlineCallbacks, returnValue
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from twisted.protocols import policies
from nacl.secret import SecretBox
from wormhole.hkdf import HKDF
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from wormhole.errors import UsageError
from wormhole.timing import DebugTiming
from . import ipaddrs
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def debug(msg):
if False:
print(msg)
def since(start):
return time.time() - start
class TransitError(Exception):
pass
class BadHandshake(Exception):
pass
class TransitClosed(TransitError):
pass
class BadNonce(TransitError):
pass
# The beginning of each TCP connection consists of the following handshake
# messages. The sender transmits the same text regardless of whether it is on
# the initiating/connecting end of the TCP connection, or on the
# listening/accepting side. Same for the receiver.
#
# sender -> receiver: transit sender TXID_HEX ready\n\n
# receiver -> sender: transit receiver RXID_HEX ready\n\n
#
# Any deviations from this result in the socket being closed. The handshake
# messages are designed to provoke an invalid response from other sorts of
# servers (HTTP, SMTP, echo).
#
# If the sender is satisfied with the handshake, and this is the first socket
# to complete negotiation, the sender does:
#
# sender -> receiver: go\n
#
# and the next byte on the wire will be from the application.
#
# If this is not the first socket, the sender does:
#
# sender -> receiver: nevermind\n
#
# and closes the socket.
# So the receiver looks for "transit sender TXID_HEX ready\n\ngo\n" and hangs
# up upon the first wrong byte. The sender lookgs for "transit receiver
# RXID_HEX ready\n\n" and then makes a first/not-first decision about sending
# "go\n" or "nevermind\n"+close().
def build_receiver_handshake(key):
hexid = HKDF(key, 32, CTXinfo=b"transit_receiver")
return b"transit receiver "+hexlify(hexid)+b" ready\n\n"
def build_sender_handshake(key):
hexid = HKDF(key, 32, CTXinfo=b"transit_sender")
return b"transit sender "+hexlify(hexid)+b" ready\n\n"
def build_relay_handshake(key):
token = HKDF(key, 32, CTXinfo=b"transit_relay_token")
return b"please relay "+hexlify(token)+b"\n"
# The hint format is: TYPE,VALUE= /^([a-zA-Z0-9]+):(.*)$/ . VALUE depends
# upon TYPE, and it can have more colons in it. For TYPE=tcp (the only one
# currently defined), ADDR,PORT = /^(.*):(\d+)$/ , so ADDR can have colons.
# ADDR can be a hostname, ipv4 dotted-quad, or ipv6 colon-hex. If the hint
# publisher wants anonymity, their only hint's ADDR will end in .onion .
def parse_hint_tcp(hint):
assert isinstance(hint, type(u""))
# return tuple or None for an unparseable hint
mo = re.search(r'^([a-zA-Z0-9]+):(.*)$', hint)
if not mo:
print("unparseable hint '%s'" % (hint,))
return None
hint_type = mo.group(1)
if hint_type != "tcp":
print("unknown hint type '%s' in '%s'" % (hint_type, hint))
return None
hint_value = mo.group(2)
mo = re.search(r'^(.*):(\d+)$', hint_value)
if not mo:
print("unparseable TCP hint '%s'" % (hint,))
return None
hint_host = mo.group(1)
try:
hint_port = int(mo.group(2))
except ValueError:
print("non-numeric port in TCP hint '%s'" % (hint,))
return None
return hint_host, hint_port
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TIMEOUT=15
@implementer(interfaces.IProducer, interfaces.IConsumer)
class Connection(protocol.Protocol, policies.TimeoutMixin):
def __init__(self, owner, relay_handshake, start, description):
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self.state = "too-early"
self.buf = b""
self.owner = owner
self.relay_handshake = relay_handshake
self.start = start
self._description = description
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self._negotiation_d = defer.Deferred(self._cancel)
self._error = None
self._consumer = None
self._consumer_bytes_written = 0
self._consumer_bytes_expected = None
self._consumer_deferred = None
self._inbound_records = collections.deque()
self._waiting_reads = collections.deque()
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def connectionMade(self):
debug("handle %r" % (self.transport,))
self.setTimeout(TIMEOUT) # does timeoutConnection() when it expires
self.factory.connectionWasMade(self)
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def startNegotiation(self):
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if self.relay_handshake is not None:
self.transport.write(self.relay_handshake)
self.state = "relay"
else:
self.state = "start"
self.dataReceived(b"") # cycle the state machine
return self._negotiation_d
def _cancel(self, d):
self.state = "hung up" # stop reacting to anything further
self._error = defer.CancelledError()
self.transport.loseConnection()
# if connectionLost isn't called synchronously, then our
# self._negotiation_d will have been errbacked by Deferred.cancel
# (which is our caller). So if it's still around, clobber it
if self._negotiation_d:
self._negotiation_d = None
def dataReceived(self, data):
try:
self._dataReceived(data)
except Exception as e:
self.setTimeout(None)
self._error = e
self.transport.loseConnection()
self.state = "hung up"
if not isinstance(e, BadHandshake):
raise
def _check_and_remove(self, expected):
# any divergence is a handshake error
if not self.buf.startswith(expected[:len(self.buf)]):
raise BadHandshake("got %r want %r" % (self.buf, expected))
if len(self.buf) < len(expected):
return False # keep waiting
self.buf = self.buf[len(expected):]
return True
def _dataReceived(self, data):
# protocol is:
# (maybe: send relay handshake, wait for ok)
# send (send|receive)_handshake
# wait for (receive|send)_handshake
# sender: decide, send "go" or hang up
# receiver: wait for "go"
self.buf += data
assert self.state != "too-early"
if self.state == "relay":
if not self._check_and_remove(b"ok\n"):
return
self.state = "start"
if self.state == "start":
self.transport.write(self.owner._send_this())
self.state = "handshake"
if self.state == "handshake":
if not self._check_and_remove(self.owner._expect_this()):
return
self.state = self.owner.connection_ready(self)
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# If we're the receiver, we'll be moved to state
# "wait-for-decision", which means we're waiting for the other
# side (the sender) to make a decision. If we're the sender,
# we'll either be moved to state "go" (send GO and move directly
# to state "records") or state "nevermind" (send NEVERMIND and
# hang up).
if self.state == "wait-for-decision":
if not self._check_and_remove(b"go\n"):
return
self._negotiationSuccessful()
if self.state == "go":
GO = b"go\n"
self.transport.write(GO)
self._negotiationSuccessful()
if self.state == "nevermind":
self.transport.write(b"nevermind\n")
raise BadHandshake("abandoned")
if self.state == "records":
return self.dataReceivedRECORDS()
if isinstance(self.state, Exception): # for tests
raise self.state
def _negotiationSuccessful(self):
self.state = "records"
self.setTimeout(None)
send_key = self.owner._sender_record_key()
self.send_box = SecretBox(send_key)
self.send_nonce = 0
receive_key = self.owner._receiver_record_key()
self.receive_box = SecretBox(receive_key)
self.next_receive_nonce = 0
d, self._negotiation_d = self._negotiation_d, None
d.callback(self)
def dataReceivedRECORDS(self):
while True:
if len(self.buf) < 4:
return
length = int(hexlify(self.buf[:4]), 16)
if len(self.buf) < 4+length:
return
encrypted, self.buf = self.buf[4:4+length], self.buf[4+length:]
record = self._decrypt_record(encrypted)
self.recordReceived(record)
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def _decrypt_record(self, encrypted):
nonce_buf = encrypted[:SecretBox.NONCE_SIZE] # assume it's prepended
nonce = int(hexlify(nonce_buf), 16)
if nonce != self.next_receive_nonce:
raise BadNonce("received out-of-order record: got %d, expected %d"
% (nonce, self.next_receive_nonce))
self.next_receive_nonce += 1
record = self.receive_box.decrypt(encrypted)
return record
def describe(self):
return self._description
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def send_record(self, record):
if not isinstance(record, type(b"")): raise UsageError
assert SecretBox.NONCE_SIZE == 24
assert self.send_nonce < 2**(8*24)
assert len(record) < 2**(8*4)
nonce = unhexlify("%048x" % self.send_nonce) # big-endian
self.send_nonce += 1
encrypted = self.send_box.encrypt(record, nonce)
length = unhexlify("%08x" % len(encrypted)) # always 4 bytes long
self.transport.write(length)
self.transport.write(encrypted)
def recordReceived(self, record):
if self._consumer:
self._writeToConsumer(record)
return
self._inbound_records.append(record)
self._deliverRecords()
def receive_record(self):
d = defer.Deferred()
self._waiting_reads.append(d)
self._deliverRecords()
return d
def _deliverRecords(self):
while self._inbound_records and self._waiting_reads:
r = self._inbound_records.popleft()
d = self._waiting_reads.popleft()
d.callback(r)
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def close(self):
self.transport.loseConnection()
while self._waiting_reads:
d = self._waiting_reads.popleft()
d.errback(error.ConnectionClosed())
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def timeoutConnection(self):
self._error = BadHandshake("timeout")
self.transport.loseConnection()
def connectionLost(self, reason=None):
self.setTimeout(None)
d, self._negotiation_d = self._negotiation_d, None
# the Deferred is only relevant until negotiation finishes, so skip
# this if it's alredy been fired
if d:
# Each call to loseConnection() sets self._error first, so we can
# deliver useful information to the Factory that's waiting on
# this (although they'll generally ignore the specific error,
# except for logging unexpected ones). The possible cases are:
#
# cancel: defer.CancelledError
# far-end disconnect: BadHandshake("connection lost")
# handshake error (something we didn't like): BadHandshake(what)
# other error: some other Exception
# timeout: BadHandshake("timeout")
d.errback(self._error or BadHandshake("connection lost"))
if self._consumer_deferred:
self._consumer_deferred.errback(error.ConnectionClosed())
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# IConsumer methods, for outbound flow-control. We pass these through to
# the transport. The 'producer' is something like a t.p.basic.FileSender
def registerProducer(self, producer, streaming):
assert interfaces.IConsumer.providedBy(self.transport)
self.transport.registerProducer(producer, streaming)
def unregisterProducer(self):
self.transport.unregisterProducer()
def write(self, data):
self.send_record(data)
# IProducer methods, for inbound flow-control. We pass these through to
# the transport.
def stopProducing(self):
self.transport.stopProducing()
def pauseProducing(self):
self.transport.pauseProducing()
def resumeProducing(self):
self.transport.resumeProducing()
# Helper methods
def connectConsumer(self, consumer, expected=None):
"""Helper method to glue an instance of e.g. t.p.ftp.FileConsumer to
us. Inbound records will be written as bytes to the consumer.
Set 'expected' to an integer to automatically disconnect when at
least that number of bytes have been written. This function will then
return a Deferred (that fires with the number of bytes actually
received). If the connection is lost while this Deferred is
outstanding, it will errback.
If 'expected' is None, then this function returns None instead of a
Deferred, and you must call disconnectConsumer() when you are done."""
if self._consumer:
raise RuntimeError("A consumer is already attached: %r" %
self._consumer)
# be aware of an ordering hazard: when we call the consumer's
# .registerProducer method, they are likely to immediately call
# self.resumeProducing, which we'll deliver to self.transport, which
# might call our .dataReceived, which may cause more records to be
# available. By waiting to set self._consumer until *after* we drain
# any pending records, we avoid delivering records out of order,
# which would be bad.
consumer.registerProducer(self, True)
# There might be enough data queued to exceed 'expected' before we
# leave this function. We must be sure to register the producer
# before it gets unregistered.
self._consumer = consumer
self._consumer_bytes_written = 0
self._consumer_bytes_expected = expected
d = None
if expected is not None:
d = defer.Deferred()
self._consumer_deferred = d
# drain any pending records
while self._consumer and self._inbound_records:
r = self._inbound_records.popleft()
self._writeToConsumer(r)
return d
def _writeToConsumer(self, record):
self._consumer.write(record)
self._consumer_bytes_written += len(record)
if self._consumer_bytes_expected is not None:
if self._consumer_bytes_written >= self._consumer_bytes_expected:
d = self._consumer_deferred
self.disconnectConsumer()
d.callback(self._consumer_bytes_written)
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def disconnectConsumer(self):
self._consumer.unregisterProducer()
self._consumer = None
self._consumer_bytes_expected = None
self._consumer_deferred = None
# Helper method to write a known number of bytes to a file. This has no
# flow control: the filehandle cannot push back. 'progress' is an
# optional callable which will be called frequently with the number of
# bytes transferred so far. Returns a Deferred that fires (with the
# number of bytes written) when the count is reached or the RecordPipe is
# closed.
def writeToFile(self, f, expected, progress=None):
progress = progress or (lambda n: None)
fc = FileConsumer(f, expected, progress)
return self.connectConsumer(fc, expected)
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class OutboundConnectionFactory(protocol.ClientFactory):
protocol = Connection
def __init__(self, owner, relay_handshake, description):
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self.owner = owner
self.relay_handshake = relay_handshake
self._description = description
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self.start = time.time()
def buildProtocol(self, addr):
p = self.protocol(self.owner, self.relay_handshake, self.start,
self._description)
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p.factory = self
return p
def connectionWasMade(self, p):
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# outbound connections are handled via the endpoint
pass
class InboundConnectionFactory(protocol.ClientFactory):
protocol = Connection
def __init__(self, owner):
self.owner = owner
self.start = time.time()
self._inbound_d = defer.Deferred(self._cancel)
self._pending_connections = set()
def whenDone(self):
return self._inbound_d
def _cancel(self, inbound_d):
self._shutdown()
# our _inbound_d will be errbacked by Deferred.cancel()
def _shutdown(self):
for d in list(self._pending_connections):
d.cancel() # that fires _remove and _proto_failed
def _describePeer(self, addr):
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if isinstance(addr, address.HostnameAddress):
return "<-%s:%d" % (addr.hostname, addr.port)
elif isinstance(addr, (address.IPv4Address, address.IPv6Address)):
return "<-%s:%d" % (addr.host, addr.port)
return "<-%r" % addr
def buildProtocol(self, addr):
p = self.protocol(self.owner, None, self.start,
self._describePeer(addr))
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p.factory = self
return p
def connectionWasMade(self, p):
d = p.startNegotiation()
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self._pending_connections.add(d)
d.addBoth(self._remove, d)
d.addCallbacks(self._proto_succeeded, self._proto_failed)
def _remove(self, res, d):
self._pending_connections.remove(d)
return res
def _proto_succeeded(self, p):
self._shutdown()
self._inbound_d.callback(p)
def _proto_failed(self, f):
# ignore these two, let Twisted log everything else
f.trap(BadHandshake, defer.CancelledError)
pass
def allocate_tcp_port():
"""Return an (integer) available TCP port on localhost. This briefly
listens on the port in question, then closes it right away."""
# We want to bind() the socket but not listen(). Twisted (in
# tcp.Port.createInternetSocket) would do several other things:
# non-blocking, close-on-exec, and SO_REUSEADDR. We don't need
# non-blocking because we never listen on it, and we don't need
# close-on-exec because we close it right away. So just add SO_REUSEADDR.
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
if platformType == "posix" and sys.platform != "cygwin":
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind(("127.0.0.1", 0))
port = s.getsockname()[1]
s.close()
return port
class _ThereCanBeOnlyOne:
"""Accept a list of contender Deferreds, and return a summary Deferred.
When the first contender fires successfully, cancel the rest and fire the
summary with the winning contender's result. If all error, errback the
summary.
status_cb=?
"""
def __init__(self, contenders):
self._remaining = set(contenders)
self._winner_d = defer.Deferred(self._cancel)
self._first_success = None
self._first_failure = None
self._have_winner = False
self._fired = False
def _cancel(self, _):
for d in list(self._remaining):
d.cancel()
# since that will errback everything in _remaining, we'll have hit
# _maybe_done() and fired self._winner_d by this point
def run(self):
for d in list(self._remaining):
d.addBoth(self._remove, d)
d.addCallbacks(self._succeeded, self._failed)
d.addCallback(self._maybe_done)
return self._winner_d
def _remove(self, res, d):
self._remaining.remove(d)
return res
def _succeeded(self, res):
self._have_winner = True
self._first_success = res
for d in list(self._remaining):
d.cancel()
def _failed(self, f):
if self._first_failure is None:
self._first_failure = f
def _maybe_done(self, _):
if self._remaining:
return
if self._fired:
return
self._fired = True
if self._have_winner:
self._winner_d.callback(self._first_success)
else:
self._winner_d.errback(self._first_failure)
def there_can_be_only_one(contenders):
return _ThereCanBeOnlyOne(contenders).run()
class Common:
RELAY_DELAY = 2.0
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def __init__(self, transit_relay, no_listen=False, tor_manager=None,
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reactor=reactor, timing=None):
if transit_relay:
if not isinstance(transit_relay, type(u"")):
raise UsageError
self._transit_relays = [transit_relay]
else:
self._transit_relays = []
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self._tor_manager = tor_manager
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self._transit_key = None
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self._no_listen = no_listen
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self._waiting_for_transit_key = []
self._listener = None
self._winner = None
self._reactor = reactor
self._timing = timing or DebugTiming()
self._timing_started = self._timing.add_event("transit")
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def _build_listener(self):
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if self._no_listen or self._tor_manager:
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return ([], None)
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portnum = allocate_tcp_port()
direct_hints = [u"tcp:%s:%d" % (addr, portnum)
for addr in ipaddrs.find_addresses()]
ep = endpoints.serverFromString(reactor, "tcp:%d" % portnum)
return direct_hints, ep
def get_direct_hints(self):
if self._listener:
return defer.succeed(self._my_direct_hints)
# there is a slight race here: if someone calls get_direct_hints() a
# second time, before the listener has actually started listening,
# then they'll get a Deferred that fires (with the hints) before the
# listener starts listening. But most applications won't call this
# multiple times, and the race is between 1: the parent Wormhole
# protocol getting the connection hints to the other end, and 2: the
# listener being ready for connections, and I'm confident that the
# listener will win.
self._my_direct_hints, self._listener = self._build_listener()
if self._listener is None: # don't listen
self._listener_d = None
return defer.succeed(self._my_direct_hints) # empty
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# Start the server, so it will be running by the time anyone tries to
# connect to the direct hints we return.
f = InboundConnectionFactory(self)
self._listener_f = f # for tests # XX move to __init__ ?
self._listener_d = f.whenDone()
d = self._listener.listen(f)
def _listening(lp):
# lp is an IListeningPort
#self._listener_port = lp # for tests
def _stop_listening(res):
lp.stopListening()
return res
self._listener_d.addBoth(_stop_listening)
return self._my_direct_hints
d.addCallback(_listening)
return d
def _stop_listening(self):
# this is for unit tests. The usual control flow (via connect())
# wires the listener's Deferred into a there_can_be_only_one(), which
# eats the errback. If we don't ever call connect(), we must catch it
# ourselves.
self._listener_d.addErrback(lambda f: None)
self._listener_d.cancel()
def get_relay_hints(self):
return self._transit_relays
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def add_their_direct_hints(self, hints):
for h in hints:
if not isinstance(h, type(u"")):
raise TypeError("hint '%r' should be unicode, not %s"
% (h, type(h)))
self._their_direct_hints = set(hints)
def add_their_relay_hints(self, hints):
for h in hints:
if not isinstance(h, type(u"")):
raise TypeError("hint '%r' should be unicode, not %s"
% (h, type(h)))
self._their_relay_hints = set(hints)
def _send_this(self):
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assert self._transit_key
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if self.is_sender:
return build_sender_handshake(self._transit_key)
else:
return build_receiver_handshake(self._transit_key)
def _expect_this(self):
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assert self._transit_key
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if self.is_sender:
return build_receiver_handshake(self._transit_key)
else:
return build_sender_handshake(self._transit_key)# + b"go\n"
def _sender_record_key(self):
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assert self._transit_key
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if self.is_sender:
return HKDF(self._transit_key, SecretBox.KEY_SIZE,
CTXinfo=b"transit_record_sender_key")
else:
return HKDF(self._transit_key, SecretBox.KEY_SIZE,
CTXinfo=b"transit_record_receiver_key")
def _receiver_record_key(self):
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assert self._transit_key
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if self.is_sender:
return HKDF(self._transit_key, SecretBox.KEY_SIZE,
CTXinfo=b"transit_record_receiver_key")
else:
return HKDF(self._transit_key, SecretBox.KEY_SIZE,
CTXinfo=b"transit_record_sender_key")
def set_transit_key(self, key):
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assert isinstance(key, type(b"")), type(key)
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# We use pubsub to protect against the race where the sender knows
# the hints and the key, and connects to the receiver's transit
# socket before the receiver gets the relay message (and thus the
# key).
self._transit_key = key
waiters = self._waiting_for_transit_key
del self._waiting_for_transit_key
for d in waiters:
# We don't need eventual-send here. It's safer in general, but
# set_transit_key() is only called once, and _get_transit_key()
# won't touch the subscribers list once the key is set.
d.callback(key)
def _get_transit_key(self):
if self._transit_key:
return defer.succeed(self._transit_key)
d = defer.Deferred()
self._waiting_for_transit_key.append(d)
return d
@inlineCallbacks
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def connect(self):
_start = self._timing.add_event("transit connect")
yield self._get_transit_key()
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# we want to have the transit key before starting any outbound
# connections, so those connections will know what to say when they
# connect
winner = yield self._connect()
self._timing.finish_event(_start)
returnValue(winner)
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def _connect(self):
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# It might be nice to wire this so that a failure in the direct hints
# causes the relay hints to be used right away (fast failover). But
# none of our current use cases would take advantage of that: if we
# have any viable direct hints, then they're either going to succeed
# quickly or hang for a long time.
contenders = []
if self._listener_d:
contenders.append(self._listener_d)
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relay_delay = 0
for hint in self._their_direct_hints:
# Check the hint type to see if we can support it (e.g. skip
# onion hints on a non-Tor client). Do not increase relay_delay
# unless we have at least one viable hint.
ep = self._endpoint_from_hint(hint)
if not ep:
continue
description = "->%s" % (hint,)
d = self._start_connector(ep, description)
contenders.append(d)
relay_delay = self.RELAY_DELAY
# Start trying the relay a few seconds after we start to try the
# direct hints. The idea is to prefer direct connections, but not be
# afraid of using the relay when we have direct hints that don't
# resolve quickly. Many direct hints will be to unused local-network
# IP addresses, which won't answer, and would take the full TCP
# timeout (30s or more) to fail.
for hint in self._their_relay_hints:
ep = self._endpoint_from_hint(hint)
if not ep:
continue
description = "->relay:%s" % (hint,)
d = task.deferLater(self._reactor, relay_delay,
self._start_connector, ep, description,
is_relay=True)
contenders.append(d)
winner = there_can_be_only_one(contenders)
return self._not_forever(2*TIMEOUT, winner)
def _not_forever(self, timeout, d):
"""If the timer fires first, cancel the deferred. If the deferred fires
first, cancel the timer."""
t = self._reactor.callLater(timeout, d.cancel)
def _done(res):
if t.active():
t.cancel()
return res
d.addBoth(_done)
return d
def _start_connector(self, ep, description, is_relay=False):
relay_handshake = None
if is_relay:
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assert self._transit_key
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relay_handshake = build_relay_handshake(self._transit_key)
f = OutboundConnectionFactory(self, relay_handshake, description)
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d = ep.connect(f)
# fires with protocol, or ConnectError
d.addCallback(lambda p: p.startNegotiation())
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return d
def _endpoint_from_hint(self, hint):
# TODO: use parse_hint_tcp
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if ":" not in hint:
return None
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pieces = hint.split(":")
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hint_type = hint.split(":")[0]
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if hint_type == "tor" and self._tor_manager:
return self._tor_manager.get_endpoint_for(pieces[1], int(pieces[2]))
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if hint_type != "tcp":
return None
pieces = hint.split(":")
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if self._tor_manager:
# our TorManager will return None for non-public IPv4 addresses
# and any IPv6 address
return self._tor_manager.get_endpoint_for(pieces[1], int(pieces[2]))
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return endpoints.HostnameEndpoint(self._reactor, pieces[1],
int(pieces[2]))
def connection_ready(self, p):
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# inbound/outbound Connection protocols call this when they finish
# negotiation. The first one wins and gets a "go". Any subsequent
# ones lose and get a "nevermind" before being closed.
if not self.is_sender:
return "wait-for-decision"
if self._winner:
# we already have a winner, so this one loses
return "nevermind"
# this one wins!
self._winner = p
return "go"
class TransitSender(Common):
is_sender = True
class TransitReceiver(Common):
is_sender = False
# based on twisted.protocols.ftp.FileConsumer, but:
# - call a progress-tracking function
# - don't close the filehandle when done
@implementer(interfaces.IConsumer)
class FileConsumer:
def __init__(self, f, xfersize, progress_f):
self._f = f
self._xfersize = xfersize
self._received = 0
self._progress_f = progress_f
self._producer = None
self._progress_f(0)
def registerProducer(self, producer, streaming):
assert not self._producer
self._producer = producer
assert streaming
def write(self, bytes):
self._f.write(bytes)
self._received += len(bytes)
self._progress_f(self._received)
def unregisterProducer(self):
assert self._producer
self._producer = None
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# the TransitSender/Receiver.connect() yields a Connection, on which you can
# do send_record(), but what should the receive API be? set a callback for
# inbound records? get a Deferred for the next record? The producer/consumer
# API is enough for file transfer, but what would other applications want?
# how should the Listener be managed? we want to shut it down when the
# connect() Deferred is cancelled, as well as terminating any negotiations in
# progress.
#
# the factory should return/manage a deferred, which fires iff an inbound
# connection completes negotiation successfully, can be cancelled (which
# stops the listener and drops all pending connections), but will never
# timeout, and only errbacks if cancelled.
# write unit test for _ThereCanBeOnlyOne
# check start/finish time-gathering instrumentation
# add progress API
# relay URLs are probably mishandled: both sides probably send their URL,
# then connect to the *other* side's URL, when they really should connect to
# both their own and the other side's. The current implementation probably
# only works if the two URLs are the same.