def handshake(self, circuit):
"""This function is invoked after a circuit was established. The server
generates a time-lock puzzle and sends it to the client. The client
does nothing during the handshake."""
log.debug("Entering handshake().")
if self.circuit == None:
self.circuit = circuit
# Only the server is generating and transmitting a puzzle.
if self.weAreServer:
# Generate master key and derive client -and server key.
masterKey = mycrypto.strong_random(const.MASTER_KEY_SIZE)
self._deriveSecrets(masterKey)
# Append random padding to obfuscate length and transmit blurb.
padding = mycrypto.weak_random(random.randint(0, \
const.MAX_PADDING_LENGTH))
log.debug("Sending puzzle with %d-byte of padding." % len(padding))
puzzle, nonce = timelock.encryptPuzzle( \
timelock.generateRawPuzzle(masterKey))
circuit.downstream.write(nonce + puzzle + padding)
log.debug("Switching to state ST_WAIT_FOR_TICKET.")
self.state = const.ST_WAIT_FOR_TICKET
# Send a session ticket to the server (if we have one).
elif self.weAreClient:
stop = False
try:
with open(const.DATA_DIRECTORY + const.TICKET_FILE,
"rb") as fd:
masterKey = fd.read(const.MASTER_KEY_SIZE)
ticket = fd.read(const.TICKET_LENGTH)
fd.close()
except IOError as e:
log.error("Could not read session ticket from \"%s\"." % \
(const.DATA_DIRECTORY + const.TICKET_FILE))
stop = True
if not stop:
log.debug("Trying to redeem session ticket: 0x%s..." % \
ticket.encode('hex')[:10])
self._deriveSecrets(masterKey)
padding = mycrypto.weak_random(random.randint(0, \
const.MAX_PADDING_LENGTH))
circuit.downstream.write(ticket + padding)
self.redeemedTicket = True
# Now start transmitting cover traffic.
self.stopCoverTraffic = False
reactor.callLater(0, self._sendCoverTraffic, circuit)
def handshake(self, circuit):
"""This function is invoked after a circuit was established. The server
generates a time-lock puzzle and sends it to the client. The client
does nothing during the handshake."""
log.debug("Entering handshake().")
if self.circuit == None:
self.circuit = circuit
# Only the server is generating and transmitting a puzzle.
if self.weAreServer:
# Generate master key and derive client -and server key.
masterKey = mycrypto.strong_random(const.MASTER_KEY_SIZE)
self._deriveSecrets(masterKey)
# Append random padding to obfuscate length and transmit blurb.
padding = mycrypto.weak_random(random.randint(0, const.MAX_PADDING_LENGTH))
log.debug("Sending puzzle with %d-byte of padding." % len(padding))
puzzle, nonce = timelock.encryptPuzzle(timelock.generateRawPuzzle(masterKey))
circuit.downstream.write(nonce + puzzle + padding)
log.debug("Switching to state ST_WAIT_FOR_TICKET.")
self.state = const.ST_WAIT_FOR_TICKET
# Send a session ticket to the server (if we have one).
elif self.weAreClient:
stop = False
try:
with open(const.DATA_DIRECTORY + const.TICKET_FILE, "rb") as fd:
masterKey = fd.read(const.MASTER_KEY_SIZE)
ticket = fd.read(const.TICKET_LENGTH)
fd.close()
except IOError as e:
log.error('Could not read session ticket from "%s".' % (const.DATA_DIRECTORY + const.TICKET_FILE))
stop = True
if not stop:
log.debug("Trying to redeem session ticket: 0x%s..." % ticket.encode("hex")[:10])
self._deriveSecrets(masterKey)
padding = mycrypto.weak_random(random.randint(0, const.MAX_PADDING_LENGTH))
circuit.downstream.write(ticket + padding)
self.redeemedTicket = True
# Now start transmitting cover traffic.
self.stopCoverTraffic = False
reactor.callLater(0, self._sendCoverTraffic, circuit)
def decryptedPuzzleCallback(self, masterKey):
"""This method is invoked as soon as the puzzle is unlocked. The
argument `masterKey' is the content of the unlocked puzzle."""
log.debug("Callback invoked after solved puzzle.")
# Sanity check to verify that we solved a real puzzle.
if not const.MASTER_KEY_PREFIX in masterKey:
log.critical("No MASTER_KEY_PREFIX in puzzle. What did we just " "solve?")
return
masterKey = masterKey[len(const.MASTER_KEY_PREFIX) :]
assert len(masterKey) == const.MASTER_KEY_SIZE
self._deriveSecrets(masterKey)
log.debug("Stopping cover traffic generation.")
self.stopCoverTraffic = True
# Send bridge randomness || magic value.
log.debug("Sending magic value to server.")
assert self.circuit
self.circuit.downstream.write(
mycrypto.weak_random(random.randint(0, const.MAX_PADDING_LENGTH)) + self.sendMagic
)
log.debug("Switching to state ST_WAIT_FOR_MAGIC.")
self.state = const.ST_WAIT_FOR_MAGIC
def decryptedPuzzleCallback(self, masterKey):
"""This method is invoked as soon as the puzzle is unlocked. The
argument `masterKey' is the content of the unlocked puzzle."""
log.debug("Callback invoked after solved puzzle.")
# Sanity check to verify that we solved a real puzzle.
if not const.MASTER_KEY_PREFIX in masterKey:
log.critical("No MASTER_KEY_PREFIX in puzzle. What did we just " \
"solve?")
return
masterKey = masterKey[len(const.MASTER_KEY_PREFIX):]
assert len(masterKey) == const.MASTER_KEY_SIZE
self._deriveSecrets(masterKey)
log.debug("Stopping cover traffic generation.")
self.stopCoverTraffic = True
# Send bridge randomness || magic value.
log.debug("Sending magic value to server.")
assert self.circuit
self.circuit.downstream.write(
mycrypto.weak_random(random.randint(0, const.MAX_PADDING_LENGTH)) +
self.sendMagic)
log.debug("Switching to state ST_WAIT_FOR_MAGIC.")
self.state = const.ST_WAIT_FOR_MAGIC
def _sendMagicValue(self, circuit, magic):
"""Sends the given `magic' to the remote machine using `circuit'. Before
that, the cover traffic generator is stopped."""
log.debug("Stopping cover traffic generation.")
self.stopCoverTraffic = True
# FIXME - Use packet morpher oracle for padding.
circuit.downstream.write(mycrypto.weak_random(random.randint(0, const.MAX_PADDING_LENGTH)) + magic)
def _sendMagicValue(self, circuit, magic):
"""Sends the given `magic' to the remote machine using `circuit'. Before
that, the cover traffic generator is stopped."""
log.debug("Stopping cover traffic generation.")
self.stopCoverTraffic = True
# FIXME - Use packet morpher oracle for padding.
circuit.downstream.write(mycrypto.weak_random(random.randint(0, \
const.MAX_PADDING_LENGTH)) + magic)
def _sendCoverTraffic(self, circuit):
"""Send random cover traffic using `circuit'. This is done to make DPI
boxes believe that we are communicating when in fact the client is busy
solving the puzzle."""
if self.stopCoverTraffic == True:
return
coverTraffic = mycrypto.weak_random(self.pktMorpher.randomSample())
log.debug("Sending %d bytes of cover traffic." % len(coverTraffic))
circuit.downstream.write(coverTraffic)
# When should we send the next chunk of bytes?
if random.random() > 0.3:
delay = self.iatMorpher.randomSample()
else:
delay = random.random() * 5
reactor.callLater(delay, self._sendCoverTraffic, circuit)
def _sendCoverTraffic(self, circuit):
"""Send random cover traffic using `circuit'. This is done to make DPI
boxes believe that we are communicating when in fact the client is busy
solving the puzzle."""
if self.stopCoverTraffic == True:
return
coverTraffic = mycrypto.weak_random(self.pktMorpher.randomSample())
log.debug("Sending %d bytes of cover traffic." % len(coverTraffic))
circuit.downstream.write(coverTraffic)
# When should we send the next chunk of bytes?
if random.random() > 0.3:
delay = self.iatMorpher.randomSample()
else:
delay = random.random() * 5
reactor.callLater(delay, self._sendCoverTraffic, circuit)
