def __init__( self ):
"""
Initialise a ScrambleSuitTransport object.
"""
log.error("\n\n################################################\n"
"Do NOT rely on ScrambleSuit for strong security!\n"
"################################################\n")
log.debug("Initialising %s." % const.TRANSPORT_NAME)
super(ScrambleSuitTransport, self).__init__()
# Load the server's persistent state from file.
if self.weAreServer:
self.srvState = state.load()
# Initialise the protocol's state machine.
log.debug("Switching to state ST_WAIT_FOR_AUTH.")
self.protoState = const.ST_WAIT_FOR_AUTH
# Buffer for outgoing data.
self.sendBuf = ""
# Buffer for inter-arrival time obfuscation.
self.choppingBuf = fifobuf.Buffer()
# AES instances to decrypt incoming and encrypt outgoing data.
self.sendCrypter = mycrypto.PayloadCrypter()
self.recvCrypter = mycrypto.PayloadCrypter()
# Packet morpher to modify the protocol's packet length distribution.
self.pktMorpher = packetmorpher.new(self.srvState.pktDist
if self.weAreServer else None)
# Inter-arrival time morpher to obfuscate inter arrival times.
self.iatMorpher = self.srvState.iatDist if self.weAreServer else \
probdist.new(lambda: random.random() %
const.MAX_PACKET_DELAY)
# Used to extract protocol messages from encrypted data.
self.protoMsg = message.MessageExtractor()
# Used by the server-side: `True' if the ticket is already
# decrypted but not yet authenticated.
self.decryptedTicket = False
# If we are in external mode we should already have a shared
# secret set up because of validate_external_mode_cli().
if self.weAreExternal:
assert(self.uniformDHSecret)
if self.weAreClient and not self.weAreExternal:
# As a client in managed mode, we get the shared secret
# from callback `handle_socks_args()' per-connection. Set
# the shared secret to None for now.
self.uniformDHSecret = None
self.uniformdh = uniformdh.new(self.uniformDHSecret, self.weAreServer)
def handle_socks_args(self, args):
"""
Receive arguments `args' passed over a SOCKS connection.
The SOCKS authentication mechanism is (ab)used to pass arguments to
pluggable transports. This method receives these arguments and parses
them. As argument, we only expect a UniformDH shared secret.
"""
log.debug("Received the following arguments over SOCKS: %s." % args)
if len(args) != 1:
raise base.SOCKSArgsError("Too many SOCKS arguments "
"(expected 1 but got %d)." % len(args))
# The ScrambleSuit specification defines that the shared secret is
# called "password".
if not args[0].startswith("password="******"The SOCKS argument must start with "
"`password='******'=')[1].strip()))
except TypeError as error:
log.error(error.message)
raise base.PluggableTransportError("Given password '%s' is not " \
"valid Base32! Run 'generate_password.py' to generate " \
"a good password." % args[0].split('=')[1].strip())
rawLength = len(self.uniformDHSecret)
if rawLength != const.SHARED_SECRET_LENGTH:
raise base.PluggableTransportError(
"The UniformDH password "
"must be %d bytes in length but %d bytes are given." %
(const.SHARED_SECRET_LENGTH, rawLength))
self.uniformdh = uniformdh.new(self.uniformDHSecret, self.weAreServer)
def handle_socks_args(self, args):
"""
Receive arguments `args' passed over a SOCKS connection.
The SOCKS authentication mechanism is (ab)used to pass arguments to
pluggable transports. This method receives these arguments and parses
them. As argument, we only expect a UniformDH shared secret.
"""
log.debug("Received the following arguments over SOCKS: %s." % args)
if len(args) != 1:
raise base.SOCKSArgsError("Too many SOCKS arguments " "(expected 1 but got %d)." % len(args))
# The ScrambleSuit specification defines that the shared secret is
# called "password".
if not args[0].startswith("password="******"The SOCKS argument must start with " "`password='******'%s' is not "
"valid Base32! Run 'generate_password.py' to generate "
"a good password." % args[0].split("=")[1].strip()
)
rawLength = len(self.uniformDHSecret)
if rawLength != const.SHARED_SECRET_LENGTH:
raise base.PluggableTransportError(
"The UniformDH password "
"must be %d bytes in length but %d bytes are given." % (const.SHARED_SECRET_LENGTH, rawLength)
)
self.uniformdh = uniformdh.new(self.uniformDHSecret, self.weAreServer)
def test4_extractPublicKey( self ):
# Create UniformDH authentication message.
sharedSecret = "A" * const.SHARED_SECRET_LENGTH
realEpoch = util.getEpoch
# Try three valid and one invalid epoch value.
for epoch in util.expandedEpoch() + ["000000"]:
udh = uniformdh.new(sharedSecret, True)
util.getEpoch = lambda: epoch
authMsg = udh.createHandshake()
util.getEpoch = realEpoch
buf = obfs_buf.Buffer()
buf.write(authMsg)
if epoch == "000000":
self.assertFalse(udh.extractPublicKey(buf))
else:
self.assertTrue(udh.extractPublicKey(buf))
def setUp( self ):
weAreServer = True
self.udh = uniformdh.new("A" * const.SHARED_SECRET_LENGTH, weAreServer)
def __init__( self, transportConfig ):
"""
Initialise a ScrambleSuitTransport object.
"""
log.error("\n\n################################################\n"
"Do NOT rely on ScrambleSuit for strong security!\n"
"################################################\n")
log.debug("Initialising %s." % const.TRANSPORT_NAME)
util.setStateLocation(transportConfig.getStateLocation())
# Load the server's persistent state from file.
if self.weAreServer:
self.srvState = state.load()
# Initialise the protocol's state machine.
log.debug("Switching to state ST_WAIT_FOR_AUTH.")
self.protoState = const.ST_WAIT_FOR_AUTH
# Buffers for incoming and outgoing data.
self.sendBuf = self.recvBuf = ""
# Buffer for inter-arrival time obfuscation.
self.choppingBuf = ""
# AES instances to decrypt incoming and encrypt outgoing data.
self.sendCrypter = mycrypto.PayloadCrypter()
self.recvCrypter = mycrypto.PayloadCrypter()
# Packet morpher to modify the protocol's packet length distribution.
self.pktMorpher = packetmorpher.new(self.srvState.pktDist
if self.weAreServer else None)
# Inter-arrival time morpher to obfuscate inter arrival times.
self.iatMorpher = self.srvState.iatDist if self.weAreServer else \
probdist.new(lambda: random.random() %
const.MAX_PACKET_DELAY)
if self.weAreServer:
# `True' if the ticket is already decrypted but not yet
# authenticated.
self.decryptedTicket = False
if not hasattr(self, 'uniformDHSecret'):
# As the server, we get the shared secret from the constructor.
cfg = transportConfig.getServerTransportOptions()
self.uniformDHSecret = base64.b32decode(cfg["password"])
self.uniformDHSecret = self.uniformDHSecret.strip()
else:
# As the client, we get the shared secret from obfsproxy calling
# `handle_socks_args()'.
if not hasattr(self, 'uniformDHSecret'):
self.uniformDHSecret = None
self.uniformdh = uniformdh.new(self.uniformDHSecret, self.weAreServer)
# Variables used to unpack protocol messages.
self.totalLen = self.payloadLen = self.flags = None