def __init__(self, replay=OtrReplay()): self.replay=replay self.dh_keys = OtrDH(replay=replay) self.dsa_keys = OtrDSA(replay=replay) self.message_state = self.msd["MSGSTATE_PLAINTEXT"] self.auth_state = self.asd["AUTHSTATE_NONE"] self.authing = True
class OtrAuth:
# SOME OTR VARS, defined in the spec
msd = {
"MSGSTATE_PLAINTEXT" : 0,
"MSGSTATE_ENCRYPTED" : 1,
"MSGSTATE_FINISHED" : 2
}
asd = {
"AUTHSTATE_NONE" : 0,
"AUTHSTATE_AWAITING_DHKEY" : 1,
"AUTHSTATE_AWAITING_REVEALSIG" : 2,
"AUTHSTATE_AWAITING_SIG" : 3,
"AUTHSTATE_V1_SETUP" : 4
}
def __init__(self, replay=OtrReplay()):
self.replay=replay
self.dh_keys = OtrDH(replay=replay)
self.dsa_keys = OtrDSA(replay=replay)
self.message_state = self.msd["MSGSTATE_PLAINTEXT"]
self.auth_state = self.asd["AUTHSTATE_NONE"]
self.authing = True
def set_message_state(self, mst):
self.message_state = self.msd[mst]
#print "SETTING MESSAGE STATE: "+mst
#r = raw_input()
def message_state_is(self, mst):
return self.message_state == self.msd[mst]
def set_auth_state(self, ast):
self.auth_state = self.asd[ast]
#print "SETTING AUTH STATE: "+ast
#r = raw_input()
def auth_state_is(self, ast):
return self.auth_state == self.asd[ast]
def compute_my_M_and_X_values(self, usePrimes=False):
my_dh_keyid = self.dh_keys.get_my_cur_keyid()
if usePrimes:
cKey = self.dh_keys.cprime
m1Key = self.dh_keys.m1prime
else:
cKey = self.dh_keys.c
m1Key = self.dh_keys.m1
# Compute the 32-byte value MB to be the SHA256-HMAC of the following data, using the key m1:
mbytes = []
# gx (MPI)
mbytes.extend( self.dh_keys.my_public_factor_to_mpi(my_dh_keyid) )
# gy (MPI)
mbytes.extend( self.dh_keys.their_public_factor_to_mpi() )
# pubB (PUBKEY)
mbytes.extend( OtrDSA.format_key(self.dsa_keys.my_public_key) )
# keyidB (INT)
keyid = _OT.zero_pad(_OT.int_to_bytes(my_dh_keyid), 4)
mbytes.extend( keyid )
self.replay.check('M', mbytes)
my_M = OtrCrypt.get_sha256_hmac(m1Key, mbytes)
self.replay.check('hash_M', my_M)
# Let XB be the following structure:
xbytes = []
# pubB (PUBKEY)
xbytes.extend( OtrDSA.format_key(self.dsa_keys.my_public_key) )
# keyidB (INT)
xbytes.extend( keyid )
# sigB(MB) (SIG)
# This is the signature, using the private part of the key pubB, of the 32-byte MB
# (which does not need to be hashed again to produce the signature).
xbytes.extend( self.dsa_keys.sign( my_M ) )
my_X = xbytes
self.replay.check('X', my_X)
# Encrypt XB using AES128-CTR with key c and initial counter value 0.
self.my_enc_sig = OtrCrypt.aes_zero_ctr_crypt(cKey, my_X)
self.replay.check('enc_X', self.my_enc_sig)
def get_enc_sig(self):
return _OT.bytes_to_data(self.my_enc_sig)
def get_enc_sig_mac(self, usePrimes=False):
if usePrimes:
m2Key = self.dh_keys.m2prime
else:
m2Key = self.dh_keys.m2
enc_sig_mac = OtrCrypt.get_sha256_hmac_160(m2Key, _OT.bytes_to_data(self.my_enc_sig))
self.replay.check('hash_enc_X', enc_sig_mac)
return enc_sig_mac
def compute_their_M_factor(self, usePrimes=False):
my_dh_keyid = self.dh_keys.get_my_cur_keyid()
their_dh_keyid = self.dh_keys.get_their_cur_keyid()
if usePrimes:
m1PrimeKey = self.dh_keys.m1prime
else:
m1PrimeKey = self.dh_keys.m1
# Compute the 32-byte value MA to be the SHA256-HMAC of the following data, using the key m1':
mbytes = []
# gy (MPI)
mbytes.extend( self.dh_keys.their_public_factor_to_mpi(their_dh_keyid) )
# gx (MPI)
mbytes.extend( self.dh_keys.my_public_factor_to_mpi(my_dh_keyid) )
# pubA (PUBKEY)
mbytes.extend( OtrDSA.format_key(self.dsa_keys.their_public_key) )
# keyidA (INT)
keyid = _OT.zero_pad(_OT.int_to_bytes(their_dh_keyid), 4)
mbytes.extend( keyid )
self.their_M = OtrCrypt.get_sha256_hmac(m1PrimeKey, mbytes)
def check_their_sig(self, enc_sig, sig_mac, usePrimes=False):
my_dh_key = self.dh_keys.get_my_cur_keyid()
if usePrimes:
cKey = self.dh_keys.cprime
m1Key = self.dh_keys.m1prime
m2Key = self.dh_keys.m2prime
else:
cKey = self.dh_keys.c
m1Key = self.dh_keys.m1
m2Key = self.dh_keys.m2
sig = OtrCrypt.aes_zero_ctr_crypt(cKey, enc_sig)
#print sig
byte_reader = ByteStreamReader(sig)
their_dsa_key = byte_reader.get_pubkey()
if their_dsa_key["cipher_code"] != list(OtrConstants["dsa_code_bytes"]):
return False
# now keyid
their_dh_keyid = _OT.bytes_to_int(byte_reader.get_int())
self.dh_keys.associate_their_keyid(their_dh_keyid)
# load their DSA public key - (y,g,p,q)
their_dsa_key_tup = (
_OT.mpi_to_int(their_dsa_key["y_mpi"]),
_OT.mpi_to_int(their_dsa_key["g_mpi"]),
_OT.mpi_to_int(their_dsa_key["p_mpi"]),
_OT.mpi_to_int(their_dsa_key["q_mpi"])
)
self.dsa_keys.load_their_key(their_dsa_key_tup)
# compute their M factor
self.compute_their_M_factor(usePrimes=usePrimes)
# now load their signed M factor
q_len = their_dsa_key["q_len"]
M_sig_r_factor = _OT.bytes_to_int(byte_reader.get_n_bytes(q_len))
M_sig_s_factor = _OT.bytes_to_int(byte_reader.get_n_bytes(q_len))
assert (byte_reader.consumed_all())
if not OtrDSA.verify(self.dsa_keys.their_public_key, self.their_M,
M_sig_r_factor, M_sig_s_factor):
logging.debug("DID NOT VERIFY")
return False
# now check their MAC
calc_sig_mac = OtrCrypt.get_sha256_hmac_160(m2Key, _OT.bytes_to_data(enc_sig))
if calc_sig_mac != sig_mac:
logging.debug( "MAC INCORRECT" )
#print enc_sig
#print calc_sig_mac
#print sig_mac
return False
# alright, looks like everything checks out
return True