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BIP15x.py
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BIP15x.py
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################################################################################
# #
# Copyright (C) 2020-2021, goatpig. #
# Distributed under the MIT license #
# See LICENSE-MIT or https://opensource.org/licenses/MIT #
# #
################################################################################
BIP15X_UNINITIALIZED = "uninitialized"
BIP15X_ERROR = "error"
BIP15X_ENCRYPTED = "encrypted"
BIP15X_READY = "ready"
#CHACHA20POLY1305MAXBYTESSENT = 1000000000
CHACHA20POLY1305MAXBYTESSENT = 1200
CHACHA20POLY1305MAXPACKETSIZE = 1024 * 1024 * 1024 #1MB
import sys
sys.path.insert(1, './c20p1305_cffi')
from c20p1305 import lib, ffi
AEAD_THRESHOLD_BEGIN = 100,
AEAD_START = 101,
AEAD_PRESENTPUBKEY = 102,
AEAD_PRESENTPUBKEYCHILD = 103, #unused
AEAD_THRESHOLD_ENC = 110,
AEAD_ENCINIT = 111,
AEAD_ENCACK = 112,
AEAD_REKEY = 113,
AEAD_THRESHOLD_AUTH = 130,
AEAD_CHALLENGE = 131,
AEAD_REPLY = 132,
AEAD_PROPOSE = 133,
AEAD_THRESHOLD_END = 150
################################################################################
class AEAD_Error(Exception):
pass
################################################################################
class BIP15xChannel(object):
def __init__(self, incoming):
self.incoming = incoming
#generate a private key for shared secret setup
self.channel = lib.bip151_channel_makenew()
self.bytesOnKey = 0
#############################################################################
def __del__(self):
lib.freeBuffer(self.channel)
self.channel = None
#############################################################################
def getEncInit(self):
encinit = lib.bip151_channel_getencinit(self.channel)
pyencinit = ffi.buffer(encinit, 34)
pyencinit = bytes(AEAD_ENCINIT) + pyencinit
lib.freeBuffer(encinit)
return pyencinit
#############################################################################
def getEncAck(self):
encack = lib.bip151_channel_getencack(self.channel)
pyencack = ffi.buffer(encack, 33)
pyencack = bytes(AEAD_ENCACK) + pyencack
lib.freeBuffer(encack)
return pyencack
#############################################################################
def processEncInit(self, counterparty):
if lib.bip151_channel_processencinit(\
self.channel, counterparty, len(counterparty)) == False:
raise AEAD_Error("failed to generate shared secret")
#############################################################################
def processEncAck(self, counterparty):
if lib.bip151_channel_processencack(\
self.channel, counterparty, len(counterparty)) == False:
raise AEAD_Error("failed to generate shared secret")
################################################################################
class BIP15xConnection(object):
def __init__(self, sendToBridgeLbd):
self.state = BIP15X_UNINITIALIZED
self.step = 0
self.macLen = lib.bip15x_init_lib()
self.inSession = BIP15xChannel(True)
self.outSession = BIP15xChannel(False)
self.sendToBridgeLbd = sendToBridgeLbd
self.notifyReadyLbd = None
self.privkey = lib.generate_random(32)
self.pubkey = lib.compute_pubkey(self.privkey)
#############################################################################
def getPubkeyHex(self):
pubkeyPy = ffi.buffer(self.pubkey, 33)
return bytes(pubkeyPy).hex()
#############################################################################
def __del__(self):
print ("bip15x cleanup")
lib.freeBuffer(self.privkey)
lib.freeBuffer(self.pubkey)
self.privkey = None
self.pubkey = None
self.inSession = None
self.outSession = None
#############################################################################
def setNotifyReadyLbd(self, notifyReadyLbd):
self.notifyReadyLbd = notifyReadyLbd
#############################################################################
def getRandomBytes(self, count):
val = lib.generate_random(count)
valPy = bytes(ffi.buffer(val, count))
return valPy
#############################################################################
def getMacLen(self):
return self.macLen
#############################################################################
def encrypted(self):
return self.state == BIP15X_ENCRYPTED or self.state == BIP15X_READY
#############################################################################
def ready(self):
return self.state == BIP15X_READY
#############################################################################
def serverStartHandshake(self):
#load client cookie
with open("./client_cookie", "rb") as cookieFile:
fileData = cookieFile.read()
self.clientPubkey = bytes(fileData[0:33])
#get EncInit packet
self.step = AEAD_START
encInitPacket = self.outSession.getEncInit()
#send to client
self.sendToBridgeLbd(encInitPacket)
#############################################################################
def getAEADPacketSize(self, header):
if header == AEAD_ENCACK[0]:
return 33
elif header == AEAD_ENCINIT[0]:
return 34
elif header == AEAD_CHALLENGE[0]:
return 32
elif header == AEAD_PROPOSE[0]:
return 32
elif header == AEAD_REPLY[0]:
return 64
elif header == AEAD_REKEY[0]:
return 33
raise AEAD_Error("unknown AEAD header byte")
#############################################################################
def serverHandshake(self, header, payload):
if header == AEAD_ENCACK[0]:
#sanity check & status update
if self.step != AEAD_START:
raise AEAD_Error("invalid state")
self.step = AEAD_ENCACK
#generate outgoing channel shared secret
self.outSession.processEncAck(payload)
elif header == AEAD_ENCINIT[0]:
#sanity check & status update
if self.step != AEAD_ENCACK:
raise AEAD_Error("invalid state")
self.step = AEAD_ENCINIT
#generate incoming channel secret
self.inSession.processEncInit(payload)
#grab the public key
encAck = self.inSession.getEncAck()
#channel is now encrypted
self.state = BIP15X_ENCRYPTED
#send pubkey to client
self.sendToBridgeLbd(encAck)
elif header == AEAD_CHALLENGE[0]:
#sanity check & status update
if self.step != AEAD_ENCINIT or self.state != BIP15X_ENCRYPTED:
raise AEAD_Error("invalid state")
self.step = AEAD_CHALLENGE
#check challenge
if not lib.bip150_check_authchallenge(\
payload, len(payload), \
self.inSession.channel, self.pubkey):
raise AEAD_Error("invalid challenge")
#get auth reply
authReply = lib.bip150_get_authreply(\
self.outSession.channel, self.privkey)
#sanity check
if lib.isNull(authReply):
raise AEAD_Error("auth reply failure")
#append header
authReplyPy = ffi.buffer(authReply, 64)
authReplyPy = bytes(AEAD_REPLY) + bytes(authReplyPy)
#cleanup C buffer
lib.freeBuffer(authReply)
#encrypt & send to client
encrPayload = self.encrypt(authReplyPy, 65)
self.sendToBridgeLbd(encrPayload)
elif header == AEAD_PROPOSE[0]:
if self.step != AEAD_CHALLENGE or self.state != BIP15X_ENCRYPTED:
raise AEAD_Error("invalid state")
self.step = AEAD_PROPOSE
#check propose
if not lib.bip150_check_authpropose(\
payload, len(payload), \
self.inSession.channel, self.clientPubkey):
raise AEAD_Error("invalid propose")
#return auth challenge
authChallenge = lib.bip150_get_authchallenge(\
self.outSession.channel, self.clientPubkey)
#sanity check
if lib.isNull(authChallenge):
raise AEAD_Error("auth reply failure")
#append header
authChallengePy = ffi.buffer(authChallenge, 32)
authChallengePy = bytes(AEAD_CHALLENGE) + bytes(authChallengePy)
#cleanup C buffer
lib.freeBuffer(authChallenge)
#encrypt & send to client
encrPayload = self.encrypt(authChallengePy, 33)
self.sendToBridgeLbd(encrPayload)
elif header == AEAD_REPLY[0]:
if self.step != AEAD_PROPOSE or self.state != BIP15X_ENCRYPTED:
raise AEAD_Error("invalid state")
self.step = AEAD_REPLY
#check reply
if not lib.bip150_check_authreply(\
payload, len(payload), \
self.inSession.channel, self.clientPubkey):
raise AEAD_Error("invalid auth reply")
#rekey
lib.bip151_channel_initial_rekey(\
self.inSession.channel, self.outSession.channel, \
self.pubkey, self.clientPubkey)
self.outSession.bytesOnKey = 0
#mark connection as ready
self.state = BIP15X_READY
self.notifyReadyLbd()
elif header == AEAD_REKEY[0]:
if self.state != BIP15X_READY:
raise AEAD_Error("invalid rekey request")
if not lib.bip151_isrekeymsg(payload, len(payload)):
raise AEAD_Error("invalid rekey message")
lib.bip151_channel_rekey(self.inSession.channel)
else:
raise AEAD_Error("invalid handshake header")
#############################################################################
def decodeSize(self, payload):
return lib.bip15x_get_length(self.inSession.channel, payload)
#############################################################################
def decrypt(self, payload, payloadSize):
clearText = ffi.new("uint8_t[" + str(payloadSize + 4) + "]")
decryptionResult = lib.bip15x_decrypt(\
self.inSession.channel, payload, payloadSize, clearText)
if decryptionResult != 0:
raise AEAD_Error("failed to decrypt payload: " + str(decryptionResult))
return bytes(clearText)[4:]
#############################################################################
def encrypt(self, payload, payloadSize):
packetSize = payloadSize + 4 + self.macLen
cipherText = ffi.new("uint8_t[" + str(packetSize) + "]")
if lib.bip15x_encrypt(self.outSession.channel, \
payload, payloadSize, cipherText) == False:
raise AEAD_Error("failed to encrypt packet")
self.outSession.bytesOnKey += payloadSize + 4
return bytes(cipherText)
#############################################################################
def needsRekey(self, packetSize):
return self.outSession.bytesOnKey + packetSize + 4 + self.macLen >= \
CHACHA20POLY1305MAXBYTESSENT
#############################################################################
def getRekeyPayload(self):
rekeyPayload = bytes(AEAD_REKEY) + bytearray(33)
encryptedPayload = self.encrypt(rekeyPayload, 34)
#rekey the channel
lib.bip151_channel_rekey(self.outSession.channel)
self.outSession.bytesOnKey = 0
return encryptedPayload