解决PHP RSA私钥解密填充检查失败：密文传输的十六进制编码策略

<?php

class RSA
{
    protected $private;

    public function __construct()
    {
        // 实际应用中，私钥文件路径应通过配置或参数传入，并进行错误处理
        $this->private = @file_get_contents("private.pem");
        if (!$this->private) {
            throw new RuntimeException('Failed to load private key.');
        }
    }

    /**
     * 将字符串转换为十六进制表示
     * @param string $string 待转换字符串
     * @return string 十六进制字符串
     */
    public function toHex($string)
    {
        $hex = '';
        for ($i = 0; $i < strlen($string); $i++) {
            $hex .= dechex(ord($string[$i]));
        }
        return $hex;
    }

    /**
     * 将十六进制字符串还原为原始字符串
     * @param string $hex 待还原的十六进制字符串
     * @return string 原始字符串
     */
    public function toStr($hex)
    {
        $string = '';
        for ($i = 0; $i < strlen($hex) - 1; $i += 2) {
            $string .= chr(hexdec($hex[$i] . $hex[$i + 1]));
        }
        return $string;
    }

    /**
     * 使用私钥解密数据
     * @param string $data 经过十六进制编码的密文数据
     * @return string 解密后的原始数据
     * @throws RuntimeException 如果数据无效或私钥未设置
     * @throws Exception 如果解密失败
     */
    public function decrypt($data)
    {
        if (is_null($data) || empty($data) || is_string($data) === false) {
            throw new RuntimeException('Invalid data for decryption.');
        } elseif (is_null($this->private) || empty($this->private)) {
            throw new RuntimeException('Private key is not set.');
        }

        $key = openssl_get_privatekey($this->private);
        if (!$key) {
            throw new RuntimeException('Failed to load private key resource.');
        }

        // 核心改动：先将十六进制编码的$data还原，再进行Base64解码，最后进行RSA私钥解密
        $decoded_hex_string = $this->toStr($data);
        $base64_decoded_data = base64_decode($decoded_hex_string);

        if ($base64_decoded_data === false) {
            throw new RuntimeException('Base64 decoding failed after hex decoding.');
        }

        if (!openssl_private_decrypt($base64_decoded_data, $result, $key)) {
            // 获取并抛出OpenSSL错误信息
            throw new Exception("RSA decryption failed: " . openssl_error_string());
        }
        return $result;
    }
}

// ... (在decrypt方法内部)
$decoded_hex_string = $this->toStr($data); // 将十六进制字符串还原
$base64_decoded_data = base64_decode($decoded_hex_string); // Base64解码

if (!openssl_private_decrypt($base64_decoded_data, $result, $key)) {
    throw new Exception("RSA decryption failed: " . openssl_error_string());
}
return $result;

using System;
using System.Text;
using System.Linq;

public static class HexConverter
{
    /// <summary>
    /// 将字符串转换为十六进制表示
    /// </summary>
    /// <param name="str">待转换字符串</param>
    /// <returns>十六进制字符串</returns>
    public static string ToHex(string str)
    {
        var sb = new StringBuilder();
        var bytes = Encoding.UTF8.GetBytes(str); // 假设原始字符串是UTF-8编码
        foreach (var t in bytes)
        {
            sb.Append(t.ToString("X2")); // "X2" 格式化为两位十六进制数
        }
        return sb.ToString();
    }

    /// <summary>
    /// 将十六进制字符串还原为原始字符串
    /// </summary>
    /// <param name="hexString">待还原的十六进制字符串</param>
    /// <returns>原始字符串</returns>
    public static string FromHexString(string hexString)
    {
        if (string.IsNullOrEmpty(hexString) || hexString.Length % 2 != 0)
        {
            throw new ArgumentException("Hex string cannot be null, empty, or have an odd length.");
        }

        var bytes = new byte[hexString.Length / 2];
        for (var i = 0; i < bytes.Length; i++)
        {
            bytes[i] = Convert.ToByte(hexString.Substring(i * 2, 2), 16);
        }
        return Encoding.UTF8.GetString(bytes); // 假设原始字符串是UTF-8编码
    }
}