# -*- coding: utf-8 -*-
import base64
import string
import random
import struct
import socket
import six
from Crypto.Cipher import AES
from wechat_sdk.lib.crypto.pkcs7 import PKCS7Encoder
from wechat_sdk.lib.crypto.exceptions import EncryptAESError, DecryptAESError, IllegalBuffer, ValidateAppIDError
from wechat_sdk.utils import to_text, to_binary
class BaseCrypto(object):
"""提供接收和推送给公众平台消息的加解密接口"""
def __init__(self, key):
# self.key = base64.b64decode(key+"=")
self.key = key
# 设置加解密模式为AES的CBC模式
self.mode = AES.MODE_CBC
def encrypt(self, text, appid):
"""对明文进行加密
@param text: 需要加密的明文
@return: 加密得到的字符串
"""
# 16位随机字符串添加到明文开头
text = self.get_random_str() + struct.pack("I", socket.htonl(len(text))) + to_binary(text) + appid
# 使用自定义的填充方式对明文进行补位填充
pkcs7 = PKCS7Encoder()
text = pkcs7.encode(text)
# 加密
cryptor = AES.new(self.key, self.mode, self.key[:16])
try:
ciphertext = cryptor.encrypt(text)
# 使用BASE64对加密后的字符串进行编码
return base64.b64encode(ciphertext)
except Exception as e:
raise EncryptAESError(e)
def decrypt(self, text, appid):
"""对解密后的明文进行补位删除
@param text: 密文
@return: 删除填充补位后的明文
"""
try:
cryptor = AES.new(self.key, self.mode, self.key[:16])
# 使用BASE64对密文进行解码，然后AES-CBC解密
plain_text = cryptor.decrypt(base64.b64decode(text))
except Exception as e:
raise DecryptAESError(e)
try:
if six.PY2:
pad = ord(plain_text[-1])
else:
pad = plain_text[-1]
# 去掉补位字符串
# pkcs7 = PKCS7Encoder()
# plain_text = pkcs7.encode(plain_text)
# 去除16位随机字符串
content = plain_text[16:-pad]
xml_len = socket.ntohl(struct.unpack("I", content[: 4])[0])
xml_content = content[4: xml_len + 4]
from_appid = content[xml_len + 4:]
except Exception as e:
raise IllegalBuffer(e)
if from_appid != appid:
raise ValidateAppIDError()
return xml_content
def get_random_str(self):
""" 随机生成16位字符串
@return: 16位字符串
"""
rule = string.ascii_letters + string.digits
return "".join(random.sample(rule, 16))
