翻墙代理的加密部分
就是怎么在 PHP/mcrypt 和 PyCrypto 之间 DES(或其他加密算法，比如3DES/RSA/..) 通信的问题，我这里还额外考察了下 .NET 平台的算法
网上询问相关问题的还挺多，尤其是 PHP 和 .NET 之间的 DES 转换。主要是 PHP/mcrypt 隐藏了 padding 的细节，且只保留了 ZERO_PADDING 模式，所以不明白cyrpto原理的不太容易找到症结所在。我的传输方案统一用 pkcs#7 padding.
首先是给服务器端增加的 PKCS#7 PADDING 函数，来自PHP官方函数手册上某人的注释
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function padding_pkcs7($crypto, $mode, $dat)
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{
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$block = mcrypt_get_block_size($crypto, $mode);
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$len = strlen($dat);
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$padding = $block - ($len % $block);
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$dat .= str_repeat(chr($padding),$padding);
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return $dat;
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}
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function strip_pkcs7($crypto, $mode, $text)
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{
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$block = mcrypt_get_block_size($crypto, $mode);
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$packing = ord($text{strlen($text) - 1});
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if($packing and ($packing < $block)){
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for($P = strlen($text) - 1; $P >= strlen($text) - $packing; $P--){
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if(ord($text{$P}) != $packing){
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$packing = 0;
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}
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}
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}
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return substr($text,0,strlen($text) - $packing);
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}
本地端 .NET 平台的 descrypto 封装
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# -*- coding: utf-8 -*-
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# ipcrypto.py
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from System import Array, Byte
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from System.Security.Cryptography import DESCryptoServiceProvider, CryptoStream, CryptoStreamMode, PaddingMode
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from System.IO import MemoryStream, StreamWriter, StreamReader
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from hashlib import md5
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def s2ab(s):
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return Array[Byte](tuple(Byte(ord(c)) for c in s))
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def ab2s(ab, len=0):
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if len == 0: len = ab.Length
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return ''.join([chr(ab[i]) for i in range(len)])
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class descrypto():
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def __init__(self, password):
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pwmd5 = md5(password).digest()
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self.key = s2ab(pwmd5[:8])
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self.iv = s2ab(pwmd5[8:])
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self.des = DESCryptoServiceProvider() # 缺省 des.Mode = CipherMode.CBC
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def enc(self, input):
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ms = MemoryStream()
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encStream = CryptoStream(ms, self.des.CreateEncryptor(self.key, self.iv), CryptoStreamMode.Write)
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sw = StreamWriter(encStream)
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sw.Write(input)
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sw.Flush()
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encStream.FlushFinalBlock()
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return ab2s(ms.GetBuffer(), ms.Length)
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def dec(self, input):
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ms = MemoryStream(s2ab(input))
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length = len(input)
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decStream = CryptoStream(ms, self.des.CreateDecryptor(self.key, self.iv), CryptoStreamMode.Read)
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byteArray = Array.CreateInstance(Byte, length)
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length = decStream.Read(byteArray, 0, length)
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return ab2s(byteArray, length)
本地端 PyCrypto 的封装
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# -*- coding: utf-8 -*-
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# pycrypto.py
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from hashlib import md5
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from Crypto.Cipher import DES
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class descrypto():
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def __init__(self, password):
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pwmd5 = md5(password).digest()
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self.key = pwmd5[:8]
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self.iv = pwmd5[8:]
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def enc(self, input):
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des = DES.new(self.key, DES.MODE_CBC, self.iv)
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lastblock = len(input) % 8
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if lastblock > 0:
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padding = 8 - lastblock
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input += padding * chr(padding)
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return des.encrypt(input)
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def dec(self, input):
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des = DES.new(self.key, DES.MODE_CBC, self.iv)
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ret = des.decrypt(input)
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padding = ord(ret[-1])
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for i in range(padding):
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if ord(ret[-1 - i]) != padding:
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padding = 0
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break
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if padding > 0:
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ret = ret[:-padding]
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return ret
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