python实现openssl的EVP_BytesToKey及AES_256_CBC加解密算法

python实现openssl

EVP_BytesToKey(EVP_aes_256_cbc(), EVP_md5(), NULL, pass, passlen, 1, key, iv);

并实现AES 256 CBC加解密.

python 复制代码

# encoding:utf-8

import base64
from Crypto.Cipher import AES
from Crypto import Random
from hashlib import md5


def EVP_BytesToKey(password, salt, key_len, iv_len):
    """
    实现openssl
    EVP_BytesToKey(EVP_aes_256_cbc(), EVP_md5(), NULL, pass, passlen, 1, key, iv);
    """
    pass_salt = (password + salt).encode(encoding='utf-8') #传给hashlib.md5前要先转成bytes
    dtot = md5(pass_salt).digest() # 返回bytes,不要转成十六进制字符串
    d = [ dtot ]

    while len(dtot) != (key_len + iv_len):
        d.append(md5(d[-1] + pass_salt).digest()) # 在一维列表中，下标为-1表示该元素为列表的最后一项
        dtot += d[-1]
    return dtot[:key_len], dtot[key_len:key_len+iv_len]


def encryt(string, key, iv):
    """
    加密文本
    :param string: 待加密文本
    :param key: 密钥
    :param iv: 偏移量/初始向量
    :return: 密文
    """
    cipher = AES.new(key, AES.MODE_CBC, iv)
    x = AES.block_size - (len(string) % AES.block_size)
    # 长度不整除16时,需要进行补全, 比如少了3个,就填充3个3
    if x != 0:
        string = string + chr(x)*x
    msg = cipher.encrypt(string.encode('utf-8'))

    return msg


def decrypt(en_str, key, iv):
    """
    解密文本
    :param en_str: 待解密文本
    :param key: 密钥
    :param iv: 偏移量/初始向量
    :return: 解密后的文本
    """
    cipher = AES.new(key, AES.MODE_CBC, iv)
    msg = cipher.decrypt(en_str)
    padding_len = msg[len(msg)-1]
    return msg[0:-padding_len]


if __name__ == '__main__':
    with open('res.json', 'r') as fp:
        content = fp.readlines() #list
        text_16str = ''.join(content) # list to str
        text_byte = bytes.fromhex(text_16str) #get bytes

        password = "%^%xxxxxx"
        key, iv = EVP_BytesToKey(password, '', 32, 16)
        
        #out = encryt('world', key, iv)
        print(out.hex())

        out = decrypt(text_byte, key, iv)
        print(out.decode('utf-8'))

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