1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
# -*- coding: utf-8 -*-
import sys
from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import padding
from .ecc.curve import Curve
from .sessionbuilder import SessionBuilder
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
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: bytes
"""
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 = self.getCipher(messageKeys.getCipherKey(), messageKeys.getIv())
return cipher.encrypt(plainText)
def getPlaintext(self, version, messageKeys, cipherText):
cipher = self.getCipher(messageKeys.getCipherKey(), messageKeys.getIv())
return cipher.decrypt(cipherText)
def getCipher(self, key, iv):
return AESCipher(key, iv)
class AESCipher:
def __init__(self, key, iv):
self.key = key
self.iv = iv
self.cipher = Cipher(algorithms.AES(key), modes.CBC(iv), backend=default_backend())
def encrypt(self, raw):
padder = padding.PKCS7(128).padder()
rawPadded = padder.update(raw) + padder.finalize()
encryptor = self.cipher.encryptor()
try:
return encryptor.update(rawPadded) + encryptor.finalize()
except ValueError:
raise
def decrypt(self, enc):
decryptor = self.cipher.decryptor()
decrypted = decryptor.update(enc) + decryptor.finalize()
unpadder = padding.PKCS7(128).unpadder()
return unpadder.update(decrypted) + unpadder.finalize()
|
