55 lines
1.8 KiB
Python
55 lines
1.8 KiB
Python
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import base64
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import hashlib
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import os
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import socket
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import struct
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from Crypto.Cipher import AES
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class WeChatCrypto:
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BLOCK_SIZE = 32
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def __init__(self, token: str, encoding_aes_key: str, app_id: str):
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self.token = token
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self.app_id = app_id
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self.aes_key = base64.b64decode(encoding_aes_key + "=")
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def verify_signature(
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self,
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signature: str,
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timestamp: str,
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nonce: str,
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msg_encrypt: str = "",
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) -> bool:
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computed = self.compute_signature(timestamp, nonce, msg_encrypt)
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return computed == signature
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def compute_signature(self, timestamp: str, nonce: str, msg_encrypt: str = "") -> str:
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params = sorted([self.token, timestamp, nonce, msg_encrypt])
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return hashlib.sha1("".join(params).encode()).hexdigest()
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def decrypt(self, msg_encrypt: str) -> tuple[str, str]:
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cipher = AES.new(self.aes_key, AES.MODE_CBC, iv=self.aes_key[:16])
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raw = base64.b64decode(msg_encrypt)
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decrypted = cipher.decrypt(raw)
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pad = decrypted[-1]
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content = decrypted[:-pad]
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msg_len = socket.ntohl(struct.unpack("I", content[16:20])[0])
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xml = content[20:20 + msg_len].decode("utf-8")
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receiver_app_id = content[20 + msg_len:].decode("utf-8")
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return xml, receiver_app_id
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def encrypt(self, msg: str) -> str:
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random_bytes = os.urandom(16)
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msg_bytes = msg.encode("utf-8")
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msg_len = socket.htonl(len(msg_bytes))
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raw = random_bytes + struct.pack("I", msg_len) + msg_bytes + self.app_id.encode("utf-8")
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pad_len = self.BLOCK_SIZE - (len(raw) % self.BLOCK_SIZE)
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raw = raw + bytes([pad_len]) * pad_len
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cipher = AES.new(self.aes_key, AES.MODE_CBC, iv=self.aes_key[:16])
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return base64.b64encode(cipher.encrypt(raw)).decode()
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