PHP RSA私钥解密中的“填充检查失败”问题及基于十六进制编码的解决方案

class RSAUtil
{
    protected $privateKey;

    public function __construct($privateKeyPath)
    {
        $this->privateKey = @file_get_contents($privateKeyPath);
        if (empty($this->privateKey)) {
            throw new RuntimeException('Failed to load private key from ' . $privateKeyPath);
        }
    }

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

    /**
     * 将十六进制字符串转换回原始字符串
     * @param string $hex 十六进制字符串
     * @return string 原始字符串
     * @throws InvalidArgumentException 如果十六进制字符串长度为奇数
     */
    public function toStr($hex)
    {
        $string = '';
        // 确保十六进制字符串长度为偶数
        if (strlen($hex) % 2 !== 0) {
            throw new InvalidArgumentException('Hex string must have an even length.');
        }
        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 $data 经过十六进制编码的加密数据
     * @return string 解密后的原始数据
     * @throws RuntimeException 如果数据无效或私钥未设置
     * @throws Exception 如果解密失败
     */
    public function decrypt($data)
    {
        if (is_null($data) || empty($data) || !is_string($data)) {
            throw new RuntimeException('Decryption data is invalid.');
        } elseif (is_null($this->privateKey) || empty($this->privateKey)) {
            throw new RuntimeException('You need to set the private key.');
        }

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

        // 1. 将十六进制字符串转换回原始的Base64字符串
        $base64EncodedData = $this->toStr($data);
        // 2. Base64解码
        $decodedData = base64_decode($base64EncodedData);

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

// 假设 'private.pem' 是您的私钥文件路径
$rsaUtil = new RSAUtil('private.pem');

// 假设 $receivedHexData 是从请求中接收到的十六进制编码的加密数据
// 例如，加密后的数据经过 Base64 编码后是 "SGVsbG8gV29ybGQ=", 再转换为十六进制就是 "48656c6c6f20576f726c64"
$receivedHexData = '...'; // 从GET/POST参数中获取

try {
    $decryptedData = $rsaUtil->decrypt($receivedHexData);
    echo "Decrypted Data: " . $decryptedData;
} catch (Exception $e) {
    echo "Error: " . $e->getMessage();
}

using System;
using System.Text;

public static class HexConverter
{
    /// <summary>
    /// 将字符串转换为十六进制表示
    /// </summary>
    /// <param name="str">待转换的字符串</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); // 确保使用与PHP相同的编码
        foreach (var t in bytes)
        {
            sb.Append(t.ToString("X2")); // "X2" 格式化为两位大写十六进制
        }
        return sb.ToString();
    }

    /// <summary>
    /// 将十六进制字符串转换回原始字符串
    /// </summary>
    /// <param name="hexString">十六进制字符串</param>
    /// <returns>原始字符串</returns>
    public static string FromHexString(string hexString)
    {
        if (hexString.Length % 2 != 0)
        {
            throw new ArgumentException("Hex string must have an even 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); // 确保使用与PHP相同的编码
    }
}