如何使用信号协议加密/解密?

Question

我在逆向工程WhatsApp网站。我用python创建了一个自定义客户端，用websocket连接到WhatsApp，生成QR码，并将登录凭据保存到文件中。当我尝试使用它时，我意识到WhatsApp的端到端加密是真实的。我使用这个python模块生成了2个信号协议密钥:pre_key_pair = curve.KeyPair.generate()，我将公钥与生成的QR码一起发送到我手机上的WhatsApp。

#!/usr/bin/python3
import websockets as WSocket
import asyncio, json, requests
import base64, random
import qrcode
from io import BytesIO
from tkinter import *
import signal_protocol
wsurl = "wss://web.whatsapp.com/ws"
async def whatsapp(uri):
async with WSocket.connect(uri, extra_headers={"Origin": "https://web.whatsapp.com"}) as ws:
keys = signal_protocol.curve.KeyPair.generate()
pubkey = base64.b64encode(keys.public_key().serialize()[1:]).decode()
#   ^ I removed the first byte, bc it is every time x05
#   (it is the key type)
browserid = "8TDLL9cktZvZvMiicMrubw=="

await ws.send('1633259071.--1,["admin","init",[2,2138,13],["Python","-","x86_64"],"{}",true]'.format(browserid))
data = await ws.recv()
print(data)
lst = data.split(',')
idk = lst[0]
del lst[0]
parsed = json.loads(','.join(lst))
auth = parsed["ref"]

qrtext = '{},{},{}'.format(auth, pubkey, browserid)
print(qrtext)
#await ws.send('1633276651.--1,["admin","Conn","reref"]') #retry

code = qrcode.make(qrtext) #.show()
root = Tk()
w, h = root.winfo_screenwidth(), root.winfo_screenheight()
m = min(w, h) // 2
root.resizable(False, False)
root.geometry(f'{m}x{m}+{w//2-m//2}+{h//2-m//2}')
buffer = BytesIO()
code.resize((m, m)).save(buffer, format="png")
buffer.seek(0)
img = PhotoImage(data=buffer.read())
lable = Button(root, image=img).place(x=0, y=0)
root.attributes('-topmost', True)
root.overrideredirect(True)
root.update()

res = await ws.recv()
print(res)
with open("token", "wt") as o:
o.write(res)
o.write('n')
o.write(browserid)
o.write(',')
o.write(base64.b64encode(keys.private_key().serialize()).decode())
o.close()
root.destroy()
if __name__ == '__main__':
asyncio.run(whatsapp(wsurl))

我的问题是，我如何解密发送给我WhatsApp的密文。这是我的客户:

#!/usr/bin/python3
import websockets as WSocket
import asyncio, json, requests
import base64, random, hmac, hashlib
import signal_protocol
wsurl = "wss://web.whatsapp.com/ws"
def parse(token):
lines = token.strip().split('n')
chunks = lines[0].strip().split(',')
del chunks[0]
jdata = json.loads(','.join(chunks))
print(jdata[0])
plus = lines[1].strip().split(',')
jdata[1]["browserID"] = plus[0]
jdata[1]["key"] = signal_protocol.curve.PrivateKey.deserialize(base64.b64decode(plus[1]))
return jdata[1]
def processdata(data):
print(data)
async def whatsapp(uri, token):
async with WSocket.connect(uri, extra_headers={"Origin": "https://web.whatsapp.com"}) as ws:
print("Logging in...")
await ws.send('1633521509.--0,["admin","init",[2,2138,13],["Python","-","x86_64"],"{}",true]'.format(token["browserID"]))
print(await ws.recv())
await ws.send('1633521518.--1,["admin","login","{}","{}","{}","takeover"]'.format(token["clientToken"],
                    token["serverToken"],
                    token["browserID"])
)
data = await ws.recv()
print(data)
chunks = data.split(',')
del chunks[0]
jdata = json.loads(','.join(chunks))
if type(jdata) == list and jdata[0] == "Cmd" and jdata[1]["type"] == "challenge":
print("Solve challange...")
await ws.send('1633521518.--1,["admin","login","{}","{}","{}","takeover"]'.format(token["clientToken"],
                        token["serverToken"],
                        token["browserID"])
)
#print(jdata)
resolve = base64.b64encode(hmac.new(token["key"].serialize(), base64.b64decode(jdata[1]["challenge"]), hashlib.sha256).digest())
ready = '1633521544.--2,["admin","challenge","{}","{}","{}"]'.format(resolve.decode(), token["serverToken"], token["browserID"])
print(ready)
await ws.send(ready)
elif type(jdata) == list and jdata[0] == "Conn" or jdata["status"] == 200:
print("OK")
else:
raise ValueError("Invalid token")

processdata(data)

# 1633415961.--2,["admin","challenge","nJOSG/8l6ee33hVSyqhWwGTlEnGDxiSXwGGK9+zAB+w=","1@LV3dAbOqdpPZPnitEw1xI67X7fBTFHUnINQ8ZUdzpmUPWm0pKkJIN/sgxRSog1jqIt+f3AfePp5k1A==","8TDLL9cktZvZvMiicMrubw=="]
# 1633415954.--1,["admin","login","u5a7azVDJzsr7Vpmpkga4sf5LbSpRW7jqdx6/j9GBGs=","1@LV3dAbOqdpPZPnitEw1xI67X7fBTFHUnINQ8ZUdzpmUPWm0pKkJIN/sgxRSog1jqIt+f3AfePp5k1A==","8TDLL9cktZvZvMiicMrubw==","takeover"]
while True:
data = await ws.recv()
processdata(data)
if __name__ == '__main__':
with open("token", "rt") as o:
token = o.read()
o.close()
asyncio.run(whatsapp(wsurl, parse(token)))

Answer 1

我有一个开源项目，正是这样做的，但现在不幸的是whatsapp强制更新，改变了很多，不再支持。

项目如下:WhatsApp Web逆向工程

编辑:

所以我的信号协议是错误的，因为whatsapp使用了curve25519。

当接收到_login(源)生成私钥，并从私钥中获取公钥:

self.loginInfo["privateKey"] = curve25519.Private();
self.loginInfo["publicKey"] = self.loginInfo["privateKey"].get_public();

当接收到Conn(源)时获取"secret";从接收到的json对象，并从接收到的秘密和您的私钥生成共享秘密:

self.connInfo["secret"] = base64.b64decode(jsonObj[1]["secret"]);
self.connInfo["sharedSecret"] = self.loginInfo["privateKey"].get_shared_key(curve25519.Public(self.connInfo["secret"][:32]), lambda a: a);
sse = self.connInfo["sharedSecretExpanded"] = HKDF(self.connInfo["sharedSecret"], 80);

其中HKDF为(源):

def HmacSha256(key, sign):
return hmac.new(key, sign, hashlib.sha256).digest();
def HKDF(key, length, appInfo=""):                      # implements RFC 5869, some parts from https://github.com/MirkoDziadzka/pyhkdf
key = HmacSha256(""*32, key);
keyStream = "";
keyBlock = "";
blockIndex = 1;
while len(keyStream) < length:
keyBlock = hmac.new(key, msg=keyBlock+appInfo+chr(blockIndex), digestmod=hashlib.sha256).digest();
blockIndex += 1;
keyStream += keyBlock;
return keyStream[:length];

然后使用这个获得另外2个密钥(来源):

keysEncrypted = sse[64:] + self.connInfo["secret"][64:];
keysDecrypted = AESDecrypt(sse[:32], keysEncrypted);
self.loginInfo["key"]["encKey"] = keysDecrypted[:32];
self.loginInfo["key"]["macKey"] = keysDecrypted[32:64];

其中AESDecrypt为(源):

def AESUnpad(s):
return s[:-ord(s[len(s)-1:])];
def AESDecrypt(key, ciphertext):                        # from https://stackoverflow.com/a/20868265
iv = ciphertext[:AES.block_size];
cipher = AES.new(key, AES.MODE_CBC, iv);
plaintext = cipher.decrypt(ciphertext[AES.block_size:]);
return AESUnpad(plaintext);

当收到加密消息(源)时，使用self.loginInfo["key"]["encKey"]解密:

decryptedMessage = AESDecrypt(self.loginInfo["key"]["encKey"], messageContent[32:]);