/usr/lib/python3/dist-packages/axolotl/sessionbuilder.py is in python3-axolotl 0.1.39-3.
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import logging
from .ecc.curve import Curve
from .ratchet.aliceaxolotlparameters import AliceAxolotlParameters
from .ratchet.bobaxolotlparamaters import BobAxolotlParameters
from .ratchet.symmetricaxolotlparameters import SymmetricAxolotlParameters
from .ratchet.ratchetingsession import RatchetingSession
from .invalidkeyexception import InvalidKeyException
from .invalidkeyidexception import InvalidKeyIdException
from .untrustedidentityexception import UntrustedIdentityException
from .protocol.keyexchangemessage import KeyExchangeMessage
from .protocol.ciphertextmessage import CiphertextMessage
from .statekeyexchangeexception import StaleKeyExchangeException
from .util.medium import Medium
from .util.keyhelper import KeyHelper
logger = logging.getLogger(__name__)
class SessionBuilder:
def __init__(self, sessionStore, preKeyStore, signedPreKeyStore, identityKeyStore, recepientId, deviceId):
self.sessionStore = sessionStore
self.preKeyStore = preKeyStore
self.signedPreKeyStore = signedPreKeyStore
self.identityKeyStore = identityKeyStore
self.recipientId = recepientId
self.deviceId = deviceId
def process(self, sessionRecord, message):
"""
:param sessionRecord:
:param message:
:type message: PreKeyWhisperMessage
"""
messageVersion = message.getMessageVersion()
theirIdentityKey = message.getIdentityKey()
unsignedPreKeyId = None
if not self.identityKeyStore.isTrustedIdentity(self.recipientId, theirIdentityKey):
raise UntrustedIdentityException(self.recipientId, theirIdentityKey)
if messageVersion == 2:
unsignedPreKeyId = self.processV2(sessionRecord, message)
elif messageVersion == 3:
unsignedPreKeyId = self.processV3(sessionRecord, message)
else:
raise AssertionError("Unkown version %s" % messageVersion)
self.identityKeyStore.saveIdentity(self.recipientId, theirIdentityKey)
return unsignedPreKeyId
def processV2(self, sessionRecord, message):
"""
:type sessionRecord: SessionRecord
:type message: PreKeyWhisperMessage
"""
if message.getPreKeyId() is None:
raise InvalidKeyIdException("V2 message requires one time prekey id!")
if not self.preKeyStore.containsPreKey(message.getPreKeyId()) and \
self.sessionStore.containsSession(self.recipientId, self.deviceId):
logging.warn("We've already processed the prekey part of this V2 session, "
"letting bundled message fall through...")
return None
ourPreKey = self.preKeyStore.loadPreKey(message.getPreKeyId()).getKeyPair()
parameters = BobAxolotlParameters.newBuilder()
parameters.setOurIdentityKey(self.identityKeyStore.getIdentityKeyPair())\
.setOurSignedPreKey(ourPreKey)\
.setOurRatchetKey(ourPreKey)\
.setOurOneTimePreKey(None)\
.setTheirIdentityKey(message.getIdentityKey())\
.setTheirBaseKey(message.getBaseKey())
if not sessionRecord.isFresh():
sessionRecord.archiveCurrentState()
RatchetingSession.initializeSessionAsBob(sessionRecord.getSessionState(),
message.getMessageVersion(),
parameters.create())
sessionRecord.getSessionState().setLocalRegistrationId(self.identityKeyStore.getLocalRegistrationId())
sessionRecord.getSessionState().setRemoteRegistrationId(message.getRegistrationId())
sessionRecord.getSessionState().setAliceBaseKey(message.getBaseKey().serialize())
if message.getPreKeyId() != Medium.MAX_VALUE:
return message.getPreKeyId()
else:
return None
def processV3(self, sessionRecord, message):
"""
:param sessionRecord:
:param message:
:type message: PreKeyWhisperMessage
:return:
"""
if sessionRecord.hasSessionState(message.getMessageVersion(), message.getBaseKey().serialize()):
logger.warn("We've already setup a session for this V3 message, letting bundled message fall through...")
return None
ourSignedPreKey = self.signedPreKeyStore.loadSignedPreKey(message.getSignedPreKeyId()).getKeyPair()
parameters = BobAxolotlParameters.newBuilder()
parameters.setTheirBaseKey(message.getBaseKey())\
.setTheirIdentityKey(message.getIdentityKey())\
.setOurIdentityKey(self.identityKeyStore.getIdentityKeyPair())\
.setOurSignedPreKey(ourSignedPreKey)\
.setOurRatchetKey(ourSignedPreKey)
if message.getPreKeyId() is not None:
parameters.setOurOneTimePreKey(self.preKeyStore.loadPreKey(message.getPreKeyId()).getKeyPair())
else:
parameters.setOurOneTimePreKey(None)
if not sessionRecord.isFresh():
sessionRecord.archiveCurrentState()
RatchetingSession.initializeSessionAsBob(sessionRecord.getSessionState(),
message.getMessageVersion(),
parameters.create())
sessionRecord.getSessionState().setLocalRegistrationId(self.identityKeyStore.getLocalRegistrationId())
sessionRecord.getSessionState().setRemoteRegistrationId(message.getRegistrationId())
sessionRecord.getSessionState().setAliceBaseKey(message.getBaseKey().serialize())
if message.getPreKeyId() is not None and message.getPreKeyId() != Medium.MAX_VALUE:
return message.getPreKeyId()
else:
return None
def processPreKeyBundle(self, preKey):
"""
:type preKey: PreKeyBundle
"""
if not self.identityKeyStore.isTrustedIdentity(self.recipientId, preKey.getIdentityKey()):
raise UntrustedIdentityException(self.recipientId, preKey.getIdentityKey())
if preKey.getSignedPreKey() is not None and\
not Curve.verifySignature(preKey.getIdentityKey().getPublicKey(),
preKey.getSignedPreKey().serialize(),
preKey.getSignedPreKeySignature()):
raise InvalidKeyException("Invalid signature on device key!")
if preKey.getSignedPreKey() is None and preKey.getPreKey() is None:
raise InvalidKeyException("Both signed and unsigned prekeys are absent!")
supportsV3 = preKey.getSignedPreKey() is not None
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
ourBaseKey = Curve.generateKeyPair()
theirSignedPreKey = preKey.getSignedPreKey() if supportsV3 else preKey.getPreKey()
theirOneTimePreKey = preKey.getPreKey()
theirOneTimePreKeyId = preKey.getPreKeyId() if theirOneTimePreKey is not None else None
parameters = AliceAxolotlParameters.newBuilder()
parameters.setOurBaseKey(ourBaseKey)\
.setOurIdentityKey(self.identityKeyStore.getIdentityKeyPair())\
.setTheirIdentityKey(preKey.getIdentityKey())\
.setTheirSignedPreKey(theirSignedPreKey)\
.setTheirRatchetKey(theirSignedPreKey)\
.setTheirOneTimePreKey(theirOneTimePreKey if supportsV3 else None)
if not sessionRecord.isFresh():
sessionRecord.archiveCurrentState()
RatchetingSession.initializeSessionAsAlice(sessionRecord.getSessionState(),
3 if supportsV3 else 2,
parameters.create())
sessionRecord.getSessionState().setUnacknowledgedPreKeyMessage(theirOneTimePreKeyId,
preKey.getSignedPreKeyId(),
ourBaseKey.getPublicKey())
sessionRecord.getSessionState().setLocalRegistrationId(self.identityKeyStore.getLocalRegistrationId())
sessionRecord.getSessionState().setRemoteRegistrationId(preKey.getRegistrationId())
sessionRecord.getSessionState().setAliceBaseKey(ourBaseKey.getPublicKey().serialize())
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
self.identityKeyStore.saveIdentity(self.recipientId, preKey.getIdentityKey())
def processKeyExchangeMessage(self, keyExchangeMessage):
if not self.identityKeyStore.isTrustedIdentity(self.recipientId, keyExchangeMessage.getIdentityKey()):
raise UntrustedIdentityException(self.recipientId, keyExchangeMessage.getIdentityKey())
responseMessage = None
if keyExchangeMessage.isInitiate():
responseMessage = self.processInitiate(keyExchangeMessage)
else:
self.processResponse(keyExchangeMessage)
return responseMessage
def processInitiate(self, keyExchangeMessage):
flags = KeyExchangeMessage.RESPONSE_FLAG
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
if keyExchangeMessage.getVersion() >= 3 and not Curve.verifySignature(
keyExchangeMessage.getIdentityKey().getPublicKey(),
keyExchangeMessage.getBaseKey().serialize(),
keyExchangeMessage.getBaseKeySignature()):
raise InvalidKeyException("Bad signature!")
builder = SymmetricAxolotlParameters.newBuilder()
if not sessionRecord.getSessionState().hasPendingKeyExchange():
builder.setOurIdentityKey(self.identityKeyStore.getIdentityKeyPair())\
.setOurBaseKey(Curve.generateKeyPair())\
.setOurRatchetKey(Curve.generateKeyPair())
else:
builder.setOurIdentityKey(sessionRecord.getSessionState().getPendingKeyExchangeIdentityKey())\
.setOurBaseKey(sessionRecord.getSessionState().getPendingKeyExchangeBaseKey())\
.setOurRatchetKey(sessionRecord.getSessionState().getPendingKeyExchangeRatchetKey())
flags |= KeyExchangeMessage.SIMULTAENOUS_INITIATE_FLAG
builder.setTheirBaseKey(keyExchangeMessage.getBaseKey())\
.setTheirRatchetKey(keyExchangeMessage.getRatchetKey())\
.setTheirIdentityKey(keyExchangeMessage.getIdentityKey())
parameters = builder.create()
if not sessionRecord.isFresh():
sessionRecord.archiveCurrentState()
RatchetingSession.initializeSession(sessionRecord.getSessionState(),
min(keyExchangeMessage.getMaxVersion(), CiphertextMessage.CURRENT_VERSION),
parameters)
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
self.identityKeyStore.saveIdentity(self.recipientId, keyExchangeMessage.getIdentityKey())
baseKeySignature = Curve.calculateSignature(parameters.getOurIdentityKey().getPrivateKey(),
parameters.getOurBaseKey().getPublicKey().serialize())
return KeyExchangeMessage(sessionRecord.getSessionState().getSessionVersion(),
keyExchangeMessage.getSequence(), flags,
parameters.getOurBaseKey().getPublicKey(),
baseKeySignature, parameters.getOurRatchetKey().getPublicKey(),
parameters.getOurIdentityKey().getPublicKey())
def processResponse(self, keyExchangeMessage):
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
sessionState = sessionRecord.getSessionState()
hasPendingKeyExchange = sessionState.hasPendingKeyExchange()
isSimultaneousInitiateResponse = keyExchangeMessage.isResponseForSimultaneousInitiate()
if not hasPendingKeyExchange \
or sessionState.getPendingKeyExchangeSequence() != keyExchangeMessage.getSequence():
logger.warn("No matching sequence for response. "
"Is simultaneous initiate response: %s" % isSimultaneousInitiateResponse)
if not isSimultaneousInitiateResponse:
raise StaleKeyExchangeException()
else:
return
parameters = SymmetricAxolotlParameters.newBuilder()
parameters.setOurBaseKey(sessionRecord.getSessionState().getPendingKeyExchangeBaseKey())\
.setOurRatchetKey(sessionRecord.getSessionState().getPendingKeyExchangeRatchetKey())\
.setOurIdentityKey(sessionRecord.getSessionState().getPendingKeyExchangeIdentityKey())\
.setTheirBaseKey(keyExchangeMessage.getBaseKey())\
.setTheirRatchetKey(keyExchangeMessage.getRatchetKey())\
.setTheirIdentityKey(keyExchangeMessage.getIdentityKey())
if not sessionRecord.isFresh():
sessionRecord.archiveCurrentState()
RatchetingSession.initializeSession(sessionRecord.getSessionState(),
min(keyExchangeMessage.getMaxVersion(), CiphertextMessage.CURRENT_VERSION),
parameters.create())
if sessionRecord.getSessionState().getSessionVersion() >= 3 and not Curve.verifySignature(
keyExchangeMessage.getIdentityKey().getPublicKey(),
keyExchangeMessage.getBaseKey().serialize(),
keyExchangeMessage.getBaseKeySignature()):
raise InvalidKeyException("Base key signature doesn't match!")
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
self.identityKeyStore.saveIdentity(self.recipientId, keyExchangeMessage.getIdentityKey())
def processInitKeyExchangeMessage(self):
try:
sequence = KeyHelper.getRandomSequence(65534) + 1
flags = KeyExchangeMessage.INITIATE_FLAG
baseKey = Curve.generateKeyPair()
ratchetKey = Curve.generateKeyPair()
identityKey = self.identityKeyStore.getIdentityKeyPair()
baseKeySignature = Curve.calculateSignature(identityKey.getPrivateKey(), baseKey.getPublicKey().serialize())
sessionRecord = self.sessionStore.loadSession(self.recipientId, self.deviceId)
sessionRecord.getSessionState().setPendingKeyExchange(sequence, baseKey, ratchetKey, identityKey)
self.sessionStore.storeSession(self.recipientId, self.deviceId, sessionRecord)
return KeyExchangeMessage(2, sequence, flags, baseKey.getPublicKey(), baseKeySignature,
ratchetKey.getPublicKey(), identityKey.getPublicKey())
except InvalidKeyException as e:
raise AssertionError(e)
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