PHP、OpenSSL与C#的AES加密互操作性问题求助

现有一段固定不可修改的PHP脚本，通过openssl_encrypt实现AES-256-CBC加密。需要找到对应的OpenSSL CLI命令和C#代码，解密该脚本输出的加密字符串。目前尝试的OpenSSL命令无法得到匹配的加密/解密结果。

PHP加密脚本 #

<?php

function bad_crypt($string, $action = 'e') {
    if (empty($string)) {
        return "";
    }

    $encrypt_method = "AES-256-CBC";
    $key = "3d13b07f244861f2d323d1734d773ce4bd079e2c17deb5695911e1387e0b579a";
    $iv = "d9ec53dadaf1e968"; // bad practice, but this is just a test

    echo "key:";
    echo "<br>";
    echo $key;
    echo "<br>";

    echo "iv:";
    echo "<br>";
    echo $iv;
    echo "<br>";

    if ($action == 'e') {
        $output = base64_encode(openssl_encrypt($string, $encrypt_method, $key, 0, $iv));
    } else if ($action == 'd') {
        $output = openssl_decrypt(base64_decode($string), $encrypt_method, $key, 0, $iv);
    }

    return $output;
}

$info = "mysecret";
$encInfo = bad_crypt($info);

echo "encrypted:";
echo "<br>";
echo $encInfo;

echo "<br>";
echo "<br>";
echo "<br>";

$t = bad_crypt($encInfo, "d");

echo "decrypted:";
echo "<br>";
echo $t;
?>

PHP脚本输出 #

key:
3d13b07f244861f2d323d1734d773ce4bd079e2c17deb5695911e1387e0b579a
iv:
d9ec53dadaf1e968
encrypted:
QVBBaDcrdkRUdVFqZDV5cGFMNHJCdz09


key:
3d13b07f244861f2d323d1734d773ce4bd079e2c17deb5695911e1387e0b579a
iv:
d9ec53dadaf1e968
decrypted:
mysecret

问题原因 #

之前尝试的OpenSSL命令（如下）无法匹配结果，核心原因是参数解析规则差异：

openssl.exe enc -e -aes-256-cbc -a -K 3d13b07f244861f2d323d1734d773ce4bd079e2c17deb5695911e1387e0b579a -iv d9ec53dadaf1e968 -in mysecret.txt

• PHP的openssl_encrypt直接将密钥/IV的每个字符ASCII字节作为加密密钥/IV
• OpenSSL CLI的-K/-iv参数默认将传入字符串当作十六进制字节值解析，而非ASCII字节序列

需要将PHP中的密钥和IV字符串转换为对应ASCII字节的十六进制表示，再传入OpenSSL CLI。

解决方案 #

一、OpenSSL CLI 解密命令 #

先转换密钥和IV的ASCII字节为十六进制：

• 密钥ASCII字节十六进制：33643133623037663234343836316632643332336431373334643737336365346264303739653263313764656235363935393131653133383765306235373961
• IV ASCII字节十六进制：64396563353364616461663165393638

解密命令

echo "QVBBaDcrdkRUdVFqZDV5cGFMNHJCdz09" | openssl enc -d -aes-256-cbc -a -K 33643133623037663234343836316632643332336431373334643737336365346264303739653263313764656235363935393131653133383765306235373961 -iv 64396563353364616461663165393638

执行后输出：mysecret

加密验证命令（复现PHP结果）

echo -n "mysecret" | openssl enc -e -aes-256-cbc -a -K 33643133623037663234343836316632643332336431373334643737336365346264303739653263313764656235363935393131653133383765306235373961 -iv 64396563353364616461663165393638

执行后输出：QVBBaDcrdkRUdVFqZDV5cGFMNHJCdz09，与PHP输出一致。

二、C# 解密代码 #

C#中需将密钥和IV字符串转换为ASCII字节数组，使用Aes类完成解密：

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

class Program
{
    static void Main()
    {
        string encryptedBase64 = "QVBBaDcrdkRUdVFqZDV5cGFMNHJCdz09";
        string key = "3d13b07f244861f2d323d1734d773ce4bd079e2c17deb5695911e1387e0b579a";
        string iv = "d9ec53dadaf1e968";

        byte[] keyBytes = Encoding.ASCII.GetBytes(key);
        byte[] ivBytes = Encoding.ASCII.GetBytes(iv);
        byte[] encryptedBytes = Convert.FromBase64String(encryptedBase64);

        string decryptedText;

        using (Aes aesAlg = Aes.Create())
        {
            aesAlg.Key = keyBytes;
            aesAlg.IV = ivBytes;
            aesAlg.Mode = CipherMode.CBC;
            aesAlg.Padding = PaddingMode.PKCS7; // PHP默认使用PKCS7填充

            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

            using (MemoryStream msDecrypt = new MemoryStream(encryptedBytes))
            {
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                {
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    {
                        decryptedText = srDecrypt.ReadToEnd();
                    }
                }
            }
        }

        Console.WriteLine("解密结果：" + decryptedText); // 输出 mysecret
    }
}

内容的提问来源于stack exchange，提问作者Quentin A. Miller