/usr/lib/python2.7/dist-packages/axolotl/sessioncipher.py is in python-axolotl 0.1.39-3.
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import sys
import Crypto.Cipher.AES as AES
from Crypto.Util import Counter
from .ecc.curve import Curve
from .sessionbuilder import SessionBuilder
from .util.byteutil import ByteUtil
from .state.sessionstate import SessionState
from .protocol.whispermessage import WhisperMessage
from .protocol.prekeywhispermessage import PreKeyWhisperMessage
from .nosessionexception import NoSessionException
from .invalidmessageexception import InvalidMessageException
from .duplicatemessagexception import DuplicateMessageException
if sys.version_info >= (3, 0):
unicode = str
import logging
logger = logging.getLogger(__name__)
class SessionCipher:
def __init__(self, sessionStore, preKeyStore, signedPreKeyStore, identityKeyStore, recepientId, deviceId):
self.sessionStore = sessionStore
self.preKeyStore = preKeyStore
self.recipientId = recepientId
self.deviceId = deviceId
self.sessionBuilder = SessionBuilder(sessionStore, preKeyStore, signedPreKeyStore,
identityKeyStore, recepientId, deviceId)
def encrypt(self, paddedMessage):
"""
:type paddedMessage: str
"""
# TODO: make this less ugly and python 2 and 3 compatible
# paddedMessage = bytearray(paddedMessage.encode() if (sys.version_info >= (3, 0) and not type(paddedMessage) in (bytes, bytearray)) or type(paddedMessage) is unicode else paddedMessage)
if (sys.version_info >= (3, 0) and
not type(paddedMessage) in (bytes, bytearray)) or type(paddedMessage) is unicode:
paddedMessage = bytearray(paddedMessage.encode())
else:
paddedMessage = bytearray(paddedMessage)
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
sessionState = sessionRecord.getSessionState()
chainKey = sessionState.getSenderChainKey()
messageKeys = chainKey.getMessageKeys()
senderEphemeral = sessionState.getSenderRatchetKey()
previousCounter = sessionState.getPreviousCounter()
sessionVersion = sessionState.getSessionVersion()
ciphertextBody = self.getCiphertext(sessionVersion, messageKeys, paddedMessage)
ciphertextMessage = WhisperMessage(sessionVersion, messageKeys.getMacKey(),
senderEphemeral, chainKey.getIndex(),
previousCounter, ciphertextBody,
sessionState.getLocalIdentityKey(),
sessionState.getRemoteIdentityKey())
if sessionState.hasUnacknowledgedPreKeyMessage():
items = sessionState.getUnacknowledgedPreKeyMessageItems()
localRegistrationid = sessionState.getLocalRegistrationId()
ciphertextMessage = PreKeyWhisperMessage(sessionVersion, localRegistrationid, items.getPreKeyId(),
items.getSignedPreKeyId(), items.getBaseKey(),
sessionState.getLocalIdentityKey(),
ciphertextMessage)
sessionState.setSenderChainKey(chainKey.getNextChainKey())
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
return ciphertextMessage
def decryptMsg(self, ciphertext, textMsg=True):
"""
:type ciphertext: WhisperMessage
:type textMsg: Bool set this to False if you are decrypting bytes
instead of string
"""
if not self.sessionStore.containsSession(self.recipientId, self.deviceId):
raise NoSessionException("No session for: %s, %s" % (self.recipientId, self.deviceId))
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
plaintext = self.decryptWithSessionRecord(sessionRecord, ciphertext)
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
return plaintext
def decryptPkmsg(self, ciphertext, textMsg=True):
"""
:type ciphertext: PreKeyWhisperMessage
"""
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
unsignedPreKeyId = self.sessionBuilder.process(sessionRecord, ciphertext)
plaintext = self.decryptWithSessionRecord(sessionRecord, ciphertext.getWhisperMessage())
# callback.handlePlaintext(plaintext)
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
if unsignedPreKeyId is not None:
self.preKeyStore.removePreKey(unsignedPreKeyId)
return plaintext
def decryptWithSessionRecord(self, sessionRecord, cipherText):
"""
:type sessionRecord: SessionRecord
:type cipherText: WhisperMessage
"""
previousStates = sessionRecord.getPreviousSessionStates()
exceptions = []
try:
sessionState = SessionState(sessionRecord.getSessionState())
plaintext = self.decryptWithSessionState(sessionState, cipherText)
sessionRecord.setState(sessionState)
return plaintext
except InvalidMessageException as e:
exceptions.append(e)
for i in range(0, len(previousStates)):
previousState = previousStates[i]
try:
promotedState = SessionState(previousState)
plaintext = self.decryptWithSessionState(promotedState, cipherText)
previousStates.pop(i)
sessionRecord.promoteState(promotedState)
return plaintext
except InvalidMessageException as e:
exceptions.append(e)
raise InvalidMessageException("No valid sessions", exceptions)
def decryptWithSessionState(self, sessionState, ciphertextMessage):
if not sessionState.hasSenderChain():
raise InvalidMessageException("Uninitialized session!")
if ciphertextMessage.getMessageVersion() != sessionState.getSessionVersion():
raise InvalidMessageException("Message version %s, but session version %s" % (ciphertextMessage.getMessageVersion, sessionState.getSessionVersion()))
messageVersion = ciphertextMessage.getMessageVersion()
theirEphemeral = ciphertextMessage.getSenderRatchetKey()
counter = ciphertextMessage.getCounter()
chainKey = self.getOrCreateChainKey(sessionState, theirEphemeral)
messageKeys = self.getOrCreateMessageKeys(sessionState, theirEphemeral, chainKey, counter)
ciphertextMessage.verifyMac(messageVersion,
sessionState.getRemoteIdentityKey(),
sessionState.getLocalIdentityKey(),
messageKeys.getMacKey())
plaintext = self.getPlaintext(messageVersion, messageKeys, ciphertextMessage.getBody())
sessionState.clearUnacknowledgedPreKeyMessage()
return plaintext
def getOrCreateChainKey(self, sessionState, ECPublickKey_theirEphemeral):
theirEphemeral = ECPublickKey_theirEphemeral
if sessionState.hasReceiverChain(theirEphemeral):
return sessionState.getReceiverChainKey(theirEphemeral)
else:
rootKey = sessionState.getRootKey()
ourEphemeral = sessionState.getSenderRatchetKeyPair()
receiverChain = rootKey.createChain(theirEphemeral, ourEphemeral)
ourNewEphemeral = Curve.generateKeyPair()
senderChain = receiverChain[0].createChain(theirEphemeral, ourNewEphemeral)
sessionState.setRootKey(senderChain[0])
sessionState.addReceiverChain(theirEphemeral, receiverChain[1])
sessionState.setPreviousCounter(max(sessionState.getSenderChainKey().getIndex() - 1, 0))
sessionState.setSenderChain(ourNewEphemeral, senderChain[1])
return receiverChain[1]
def getOrCreateMessageKeys(self, sessionState, ECPublicKey_theirEphemeral, chainKey, counter):
theirEphemeral = ECPublicKey_theirEphemeral
if chainKey.getIndex() > counter:
if sessionState.hasMessageKeys(theirEphemeral, counter):
return sessionState.removeMessageKeys(theirEphemeral, counter)
else:
raise DuplicateMessageException("Received message with old counter: %s, %s" % (chainKey.getIndex(),
counter))
if counter - chainKey.getIndex() > 2000:
raise InvalidMessageException("Over 2000 messages into the future!")
while chainKey.getIndex() < counter:
messageKeys = chainKey.getMessageKeys()
sessionState.setMessageKeys(theirEphemeral, messageKeys)
chainKey = chainKey.getNextChainKey()
sessionState.setReceiverChainKey(theirEphemeral, chainKey.getNextChainKey())
return chainKey.getMessageKeys()
def getCiphertext(self, version, messageKeys, plainText):
"""
:type version: int
:type messageKeys: MessageKeys
:type plainText: bytearray
"""
cipher = None
if version >= 3:
cipher = self.getCipher(messageKeys.getCipherKey(), messageKeys.getIv())
else:
cipher = self.getCipher_v2(messageKeys.getCipherKey(), messageKeys.getCounter())
return cipher.encrypt(bytes(plainText))
def getPlaintext(self, version, messageKeys, cipherText):
cipher = None
if version >= 3:
cipher = self.getCipher(messageKeys.getCipherKey(), messageKeys.getIv())
else:
cipher = self.getCipher_v2(messageKeys.getCipherKey(), messageKeys.getCounter())
return cipher.decrypt(cipherText)
def getCipher(self, key, iv):
# Cipher.getInstance("AES/CBC/PKCS5Padding");
# cipher = AES.new(key, AES.MODE_CBC, IV = iv)
# return cipher
return AESCipher(key, iv)
def getCipher_v2(self, key, counter):
# AES/CTR/NoPadding
# counterbytes = struct.pack('>L', counter) + (b'\x00' * 12)
# counterint = struct.unpack(">L", counterbytes)[0]
# counterint = int.from_bytes(counterbytes, byteorder='big')
ctr = Counter.new(128, initial_value=counter)
cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
return cipher
BS = 16
if sys.version_info >= (3, 0):
pad = lambda s: s + ((BS - len(s) % BS) * chr(BS - len(s) % BS)).encode()
unpad = lambda s : s[0:-s[-1]]
else:
pad = lambda s: s + (BS - len(s) % BS) * chr(BS - len(s) % BS)
unpad = lambda s : s[0:-ord(s[-1])]
class AESCipher:
def __init__(self, key, iv):
self.key = key
self.iv = iv
self.cipher = AES.new(key, AES.MODE_CBC, IV = iv)
def unpad(self, data):
unpadLength = data[-1]
if type(unpadLength) is int:
cmp = bytes([data[-unpadLength]] * unpadLength)
else:
unpadLength = ord(unpadLength)
cmp = data[-unpadLength] * unpadLength
if data[-unpadLength:] != cmp:
raise ValueError("Data not properly padded \n %s" % data)
return data[0:-unpadLength]
def encrypt(self, raw):
# if sys.version_info >= (3,0):
# rawPadded = pad(raw.decode()).encode()
# else:
rawPadded = pad(raw)
try:
return self.cipher.encrypt(rawPadded)
except ValueError:
raise
def decrypt(self, enc):
return self.unpad(self.cipher.decrypt(enc))
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