使用Rijndael的跨平台(php到C#.NET)加密/解密

Question

我目前在解密由php mcrypt加密的邮件方面遇到了一些问题.php代码如下:

<?php
  //$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
  $iv = "45287112549354892144548565456541";
  $key = "anjueolkdiwpoida";
  $text = "This is my encrypted message";
  $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CBC, $iv);
  $crypttext = urlencode($crypttext);
  $crypttext64=base64_encode($crypttext);
  print($crypttext64) . "\n<br/>";
?>

然后将加密的消息发送到ASP.NET平台(C#).但是,我在保留解密顺序(base64解码到urldecode)时遇到问题.我在ASP.NET中的代码如下(iv和key与php中的相同):

public string Decode(string str)
{
    byte[] decbuff = Convert.FromBase64String(str);
    return System.Text.Encoding.UTF8.GetString(decbuff);
}

static public String DecryptRJ256(string cypher, string KeyString, string IVString)
{

    string sRet = "";
    RijndaelManaged rj = new RijndaelManaged();
    UTF8Encoding encoding = new UTF8Encoding();


    try
    {
        //byte[] message = Convert.FromBase64String(cypher);
        byte[] message = encoding.GetBytes(cypher);

        byte[] Key = encoding.GetBytes(KeyString);
        byte[] IV = encoding.GetBytes(IVString);

        rj.Padding = PaddingMode.Zeros;
        rj.Mode = CipherMode.CBC;
        rj.KeySize = 256;
        rj.BlockSize = 256;
        rj.Key = Key;
        rj.IV = IV;
        MemoryStream ms = new MemoryStream(message);

        using (CryptoStream cs = new CryptoStream(ms, rj.CreateDecryptor(Key, IV), CryptoStreamMode.Read))
        {
            using (StreamReader sr = new StreamReader(cs))
            {
                sRet = sr.ReadToEnd();
            }
        }

    }
    finally
    {
        rj.Clear();
    }

    return sRet;


}

string temp = DecryptRJ256(Server.UrlDecode(Decode(cypher)), keyString, ivString);

时遇到的问题是,我收到从PHP加密的消息后,我将其转换成字节[],然后转换回UTF8编码的字符串,所以我可以urldecode它.然后我将结果提供给函数,在那里我将字符串转换回byte []并在解密过程中运行它.但是,我无法得到理想的结果......任何想法？

提前致谢.

Answer 1

在这里,我可以看到双方的问题.

请记住,编码时得到的不是字符串,而是字节数组.所以在PHP中你不需要urlencode cyphertext.

你只需要base64编码.当你打开base64_encode帮助时,你会看到

base64_encode使用base64对给定数据进行编码.此编码旨在使二进制数据在传输中幸存

还有一件事 - 要使用正确的长度在.net中解码您的消息,您必须手动使用填充字符附加它.RijndaelManaged的默认填充模式是PKCS7,让我们坚持下去.您必须将源字符串扩展为偶数块,其字符代码等于填充字节数.

<?php
  $iv = "45287112549354892144548565456541";
  $key = "anjueolkdiwpoida";
  $text = "This is my encrypted message";

  // to append string with trailing characters as for PKCS7 padding scheme
  $block = mcrypt_get_block_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_CBC);
  $padding = $block - (strlen($text) % $block);
  $text .= str_repeat(chr($padding), $padding);

  $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CBC, $iv);

  // this is not needed here            
  //$crypttext = urlencode($crypttext);

  $crypttext64=base64_encode($crypttext);
  print($crypttext64) . "\n<br/>";
?>

在C#端,你可以从base64到byte []到string到byte [].您必须仅执行从base64到byte []的第一次转换.请记住,base64保存的是包含二进制数据的加密文本,而不是字符串.另请注意,RijndaelManaged是IDisposable,所以我将它包装在using()构造中.调用Close()是必要的,但不如MSDN中所述.

public byte[] Decode(string str)
{
    var decbuff = Convert.FromBase64String(str);
    return decbuff;
}

static public String DecryptRJ256(byte[] cypher, string KeyString, string IVString)
{
    var sRet = "";

    var encoding = new UTF8Encoding();
    var Key = encoding.GetBytes(KeyString);
    var IV = encoding.GetBytes(IVString);

    using (var rj = new RijndaelManaged())
    {
        try
        {
            rj.Padding = PaddingMode.PKCS7;
            rj.Mode = CipherMode.CBC;
            rj.KeySize = 256;
            rj.BlockSize = 256;
            rj.Key = Key;
            rj.IV = IV;
            var ms = new MemoryStream(cypher);

            using (var cs = new CryptoStream(ms, rj.CreateDecryptor(Key, IV), CryptoStreamMode.Read))
            {
                using (var sr = new StreamReader(cs))
                {
                    sRet = sr.ReadLine();
                }
            }
        }
        finally
        {
            rj.Clear();
        }
    }

    return sRet;
}

因此,在C#中使用以下代码将返回初始字符串:

var iv = "45287112549354892144548565456541";
var key = "anjueolkdiwpoida";
var cypher = "u+rIlHB/2rrT/u/qFInnlEkg2unhizsNzGVb9O54sP8=";

var temp = DecryptRJ256(Decode(cypher), key, iv);