377 lines
14 KiB
Python
377 lines
14 KiB
Python
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# =============================================================================
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# 企微IT智能服务台 — 企微消息 AES 加解密工具
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# =============================================================================
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# 说明：实现企微回调消息的加解密和签名验证
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# 参考企微官方加解密库逻辑，使用 Python cryptography 库重写
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# 加密模式：AES-CBC-256，PKCS7 填充
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# 签名算法：SHA1(sort(token, timestamp, nonce, encrypt))
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# =============================================================================
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import base64
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import hashlib
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import json
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import logging
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import secrets
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import string
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import struct
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import time
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import xml.etree.ElementTree as ET
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from typing import Dict, Optional, Tuple
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from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
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from cryptography.hazmat.backends import default_backend
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logger = logging.getLogger(__name__)
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class WecomCrypto:
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"""企微消息加解密工具类。
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实现企微回调消息的完整加解密流程：
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1. 签名验证：SHA1(sort(token, timestamp, nonce, encrypt))
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2. AES 解密：CBC 模式，PKCS7 去填充
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3. AES 加密：CBC 模式，PKCS7 填充
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Attributes:
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token: 企微回调配置的 Token
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aes_key: 解码后的 AES 密钥（32 字节）
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corp_id: 企业ID
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"""
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def __init__(self, token: str, encoding_aes_key: str, corp_id: str):
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"""初始化加解密工具。
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Args:
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token: 企微回调配置的 Token（用于签名验证）
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encoding_aes_key: 企微回调配置的 EncodingAESKey（43 位 Base64 字符串）
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corp_id: 企业ID（用于消息体中的校验）
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"""
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self.token = token
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# EncodingAESKey 是 43 位 Base64 编码字符串
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# 解码时需要先补上 1 个 "=" 使其成为合法的 Base64 字符串
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# 解码后得到 32 字节的 AES 密钥（AES-256）
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self.aes_key = base64.b64decode(encoding_aes_key + "=")
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# AES CBC 模式的 IV（初始化向量）取密钥的前 16 字节
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self.iv = self.aes_key[:16]
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self.corp_id = corp_id
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# --------------------------------------------------------------------------
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# 签名验证
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# --------------------------------------------------------------------------
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def verify_signature(
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self, signature: str, timestamp: str, nonce: str, encrypt: str
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) -> bool:
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"""验证企微回调签名。
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企微的签名算法：SHA1(sort([token, timestamp, nonce, encrypt]))
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将 token、timestamp、nonce、encrypt 四个字符串字典序排列后拼接，计算 SHA1。
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Args:
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signature: 企微传来的签名（msg_signature 参数）
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timestamp: 时间戳
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nonce: 随机数
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encrypt: 加密的消息内容
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Returns:
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bool: 签名是否验证通过
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"""
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# 将四个参数按字典序排列
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sort_list = sorted([self.token, timestamp, nonce, encrypt])
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# 拼接为一个字符串
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concat_str = "".join(sort_list)
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# 计算 SHA1 哈希值
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computed = hashlib.sha1(concat_str.encode("utf-8")).hexdigest()
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# 与传入的签名比较
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is_valid = computed == signature
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if not is_valid:
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logger.warning(
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f"签名验证失败: computed={computed}, received={signature}"
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)
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return is_valid
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def generate_signature(
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self, timestamp: str, nonce: str, encrypt: str
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) -> str:
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"""生成签名（用于加密响应消息时）。
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Args:
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timestamp: 时间戳
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nonce: 随机数
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encrypt: 加密后的消息内容
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Returns:
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str: SHA1 签名字符串
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"""
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sort_list = sorted([self.token, timestamp, nonce, encrypt])
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concat_str = "".join(sort_list)
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return hashlib.sha1(concat_str.encode("utf-8")).hexdigest()
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# --------------------------------------------------------------------------
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# AES 解密
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# --------------------------------------------------------------------------
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def decrypt(self, encrypted_text: str) -> str:
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"""AES-CBC 解密企微加密消息。
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解密流程：
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1. Base64 解码得到密文
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2. AES-CBC 解密
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3. 去除 PKCS7 填充
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4. 提取明文内容（格式：random(16) + msg_len(4) + msg + corp_id）
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Args:
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encrypted_text: Base64 编码的加密消息
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Returns:
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str: 解密后的明文 XML 字符串
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Raises:
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ValueError: 解密失败时抛出
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"""
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try:
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# 1. Base64 解码得到密文字节
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encrypted_data = base64.b64decode(encrypted_text)
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# 2. AES-CBC 解密
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cipher = Cipher(
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algorithms.AES(self.aes_key),
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modes.CBC(self.iv),
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backend=default_backend(),
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)
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decryptor = cipher.decryptor()
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decrypted_data = decryptor.update(encrypted_data) + decryptor.finalize()
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# 3. 去除 PKCS7 填充
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# PKCS7: 填充字节的值等于填充的字节数
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# 例如填充了 5 个字节，则每个字节的值都是 0x05
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pad_len = decrypted_data[-1]
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# 校验填充是否合法（填充值应等于填充长度）
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if pad_len < 1 or pad_len > 32:
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raise ValueError(f"无效的 PKCS7 填充值: {pad_len}")
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# 检查所有填充字节是否一致
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for i in range(pad_len):
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if decrypted_data[-(i + 1)] != pad_len:
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raise ValueError("PKCS7 填充校验失败")
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# 去除填充部分
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plaintext_data = decrypted_data[:-pad_len]
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# 4. 提取明文内容
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# 企微加密格式：random(16字节) + msg_len(4字节网络序) + msg + corp_id
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# 跳过前 16 字节随机串
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msg_len = struct.unpack("!I", plaintext_data[16:20])[0]
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msg_content = plaintext_data[20 : 20 + msg_len].decode("utf-8")
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from_corp_id = plaintext_data[20 + msg_len :].decode("utf-8")
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# 5. 校验 corp_id 是否匹配
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if from_corp_id != self.corp_id:
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raise ValueError(
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f"corp_id 不匹配: expected={self.corp_id}, got={from_corp_id}"
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)
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logger.debug(f"AES 解密成功, 明文长度: {len(msg_content)}")
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return msg_content
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except Exception as e:
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logger.error(f"AES 解密失败: {e}")
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raise ValueError(f"消息解密失败: {e}") from e
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# --------------------------------------------------------------------------
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# AES 加密
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# --------------------------------------------------------------------------
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def encrypt(self, plaintext: str) -> str:
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"""AES-CBC 加密消息（用于被动回复）。
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加密流程：
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1. 构造明文：random(16) + msg_len(4) + msg + corp_id
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2. PKCS7 填充
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3. AES-CBC 加密
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4. Base64 编码
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Args:
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plaintext: 要加密的明文字符串
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Returns:
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str: Base64 编码的加密结果
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"""
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try:
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# 1. 构造明文字节
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# 16 字节随机串（增加密文随机性，防止相同明文产生相同密文）
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random_str = secrets.token_bytes(16)
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# 消息内容字节
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msg_bytes = plaintext.encode("utf-8")
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# 消息长度（4 字节网络序，大端）
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msg_len = struct.pack("!I", len(msg_bytes))
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# corp_id 字节
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corp_id_bytes = self.corp_id.encode("utf-8")
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# 拼接
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plaintext_data = random_str + msg_len + msg_bytes + corp_id_bytes
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# 2. PKCS7 填充
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# 块大小为 32 字节（AES-256 的块大小实际是 16 字节，
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# 但企微官方实现使用 32 字节块做 PKCS7 填充）
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block_size = 32
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pad_len = block_size - (len(plaintext_data) % block_size)
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# 填充字节的值等于填充的字节数
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plaintext_data += bytes([pad_len] * pad_len)
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# 3. AES-CBC 加密
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cipher = Cipher(
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algorithms.AES(self.aes_key),
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modes.CBC(self.iv),
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backend=default_backend(),
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)
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encryptor = cipher.encryptor()
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encrypted_data = encryptor.update(plaintext_data) + encryptor.finalize()
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# 4. Base64 编码
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result = base64.b64encode(encrypted_data).decode("utf-8")
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logger.debug(f"AES 加密成功, 密文长度: {len(result)}")
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return result
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except Exception as e:
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logger.error(f"AES 加密失败: {e}")
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raise ValueError(f"消息加密失败: {e}") from e
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# --------------------------------------------------------------------------
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# 解密回调消息（完整流程）
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# --------------------------------------------------------------------------
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def decrypt_message(
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self,
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xml_body: str,
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msg_signature: str,
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timestamp: str,
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nonce: str,
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) -> Dict[str, str]:
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"""解密企微回调消息的完整流程。
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流程：
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1. 从 XML 中提取 Encrypt 字段
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2. 验证签名
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3. AES 解密
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4. 解析明文 XML，返回消息内容字典
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Args:
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xml_body: 企微 POST 的 XML 请求体
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msg_signature: 企微传来的签名
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timestamp: 时间戳
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nonce: 随机数
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Returns:
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Dict[str, str]: 解密后的消息内容，包含 from_user_name, content, msg_type 等
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Raises:
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ValueError: 签名验证失败或解密失败
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"""
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# 1. 解析 XML，提取 Encrypt 字段
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try:
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root = ET.fromstring(xml_body)
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encrypt_node = root.find("Encrypt")
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if encrypt_node is None:
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raise ValueError("XML 中未找到 Encrypt 字段")
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encrypt = encrypt_node.text or ""
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except ET.ParseError as e:
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raise ValueError(f"XML 解析失败: {e}") from e
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# 2. 验证签名
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if not self.verify_signature(msg_signature, timestamp, nonce, encrypt):
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raise ValueError("签名验证失败")
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# 3. AES 解密
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plaintext_xml = self.decrypt(encrypt)
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# 4. 解析明文 XML
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try:
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plain_root = ET.fromstring(plaintext_xml)
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result = {}
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# 提取常见字段
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for child in plain_root:
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result[child.tag] = child.text or ""
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logger.info(f"消息解密成功: from={result.get('FromUserName', 'unknown')}")
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return result
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except ET.ParseError as e:
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raise ValueError(f"明文 XML 解析失败: {e}") from e
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# --------------------------------------------------------------------------
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# 加密响应消息（完整流程）
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# --------------------------------------------------------------------------
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def encrypt_message(
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self, reply_content: str, nonce: Optional[str] = None
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) -> str:
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"""加密响应消息的完整流程（用于被动回复）。
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流程：
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1. AES 加密消息内容
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2. 生成签名
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3. 构造响应 XML
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Args:
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reply_content: 要回复的消息内容
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nonce: 随机数（可选，默认自动生成）
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Returns:
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str: 加密后的 XML 响应字符串
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"""
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# 生成时间戳和随机数
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timestamp = str(int(time.time()))
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if nonce is None:
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nonce = "".join(
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secrets.choice(string.ascii_letters + string.digits)
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for _ in range(10)
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)
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# AES 加密
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encrypt = self.encrypt(reply_content)
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|
|
|||
|
|
# 生成签名
|
|||
|
|
signature = self.generate_signature(timestamp, nonce, encrypt)
|
|||
|
|
|
|||
|
|
# 构造响应 XML
|
|||
|
|
response_xml = (
|
|||
|
|
f"<xml>"
|
|||
|
|
f"<Encrypt><![CDATA[{encrypt}]]></Encrypt>"
|
|||
|
|
f"<MsgSignature><![CDATA[{signature}]]></MsgSignature>"
|
|||
|
|
f"<TimeStamp>{timestamp}</TimeStamp>"
|
|||
|
|
f"<Nonce><![CDATA[{nonce}]]></Nonce>"
|
|||
|
|
f"</xml>"
|
|||
|
|
)
|
|||
|
|
|
|||
|
|
logger.debug("响应消息加密完成")
|
|||
|
|
return response_xml
|
|||
|
|
|
|||
|
|
# --------------------------------------------------------------------------
|
|||
|
|
# 验证 URL 有效性（GET 请求解密 echostr）
|
|||
|
|
# --------------------------------------------------------------------------
|
|||
|
|
def decrypt_echostr(
|
|||
|
|
self,
|
|||
|
|
msg_signature: str,
|
|||
|
|
timestamp: str,
|
|||
|
|
nonce: str,
|
|||
|
|
echostr: str,
|
|||
|
|
) -> str:
|
|||
|
|
"""解密企微回调验证的 echostr。
|
|||
|
|
|
|||
|
|
企微配置回调 URL 时会发送 GET 请求，需要：
|
|||
|
|
1. 验证签名
|
|||
|
|
2. 解密 echostr
|
|||
|
|
3. 返回明文 echostr
|
|||
|
|
|
|||
|
|
Args:
|
|||
|
|
msg_signature: 企微传来的签名
|
|||
|
|
timestamp: 时间戳
|
|||
|
|
nonce: 随机数
|
|||
|
|
echostr: 加密的验证字符串
|
|||
|
|
|
|||
|
|
Returns:
|
|||
|
|
str: 解密后的 echostr 明文
|
|||
|
|
|
|||
|
|
Raises:
|
|||
|
|
ValueError: 签名验证失败或解密失败
|
|||
|
|
"""
|
|||
|
|
# 验证签名
|
|||
|
|
if not self.verify_signature(msg_signature, timestamp, nonce, echostr):
|
|||
|
|
raise ValueError("回调URL验证签名失败")
|
|||
|
|
|
|||
|
|
# 解密 echostr
|
|||
|
|
plaintext = self.decrypt(echostr)
|
|||
|
|
logger.info("回调URL验证成功，echostr 解密完成")
|
|||
|
|
return plaintext
|