.net（c#）版RSA加密算法，拿走不谢

今天有同学对接一个支付平台，涉及到RSA的签名和验签。由于对方是java的sdk，翻成c#语言时，搞了半天也没搞定。网上搜的东西都是各种copy还不解决问题。 碰巧，我之前对接过连连银通的网银支付和代付。连连那边提供了c#版的RSA加密算法，立即破了这位同学的难题。在这里也分享出来，以便大家日后备用。

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

/// <summary>
/// 类名：RSAFromPkcs8
/// 功能：RSA解密、签名、验签
/// 详细：该类对Java生成的密钥进行解密和签名以及验签专用类，不需要修改
/// 版本：1.0
/// 日期：2013-09-30
/// 说明：
/// 以下代码只是为了方便商户测试而提供的样例代码，商户可以根据自己网站的需要，按照技术文档编写,并非一定要使用该代码。
/// </summary>
public sealed class RSAFromPkcs8
{
    /// <summary>
    /// 签名
    /// </summary>
    /// <param name="content">待签名字符串</param>
    /// <param name="privateKey">私钥</param>
    /// <param name="input_charset">编码格式</param>
    /// <returns>签名后字符串</returns>
    public static string sign(string content, string privateKey, string input_charset = "utf-8")
    {
        byte[] Data = Encoding.GetEncoding(input_charset).GetBytes(content);
        RSACryptoServiceProvider rsa = DecodePemPrivateKey(privateKey);
        //SHA1 crypto = new SHA1CryptoServiceProvider();
        MD5 crypto = new MD5CryptoServiceProvider();
        byte[] signData = rsa.SignData(Data, crypto);
        return Convert.ToBase64String(signData);
    }

    /// <summary>
    /// 验签
    /// </summary>
    /// <param name="content">待验签字符串</param>
    /// <param name="signedString">签名</param>
    /// <param name="publicKey">公钥</param>
    /// <param name="input_charset">编码格式</param>
    /// <returns>true(通过)，false(不通过)</returns>
    public static bool verify(string content, string signedString, string publicKey, string input_charset = "utf-8")
    {
        bool result = false;
        byte[] Data = Encoding.GetEncoding(input_charset).GetBytes(content);
        byte[] data = Convert.FromBase64String(signedString);
        RSAParameters paraPub = ConvertFromPublicKey(publicKey);
        RSACryptoServiceProvider rsaPub = new RSACryptoServiceProvider();                
        rsaPub.ImportParameters(paraPub);
        //SHA1 crypto = new SHA1CryptoServiceProvider();
        MD5 crypto = new MD5CryptoServiceProvider();
        result = rsaPub.VerifyData(Data, crypto, data);
        return result;
    }

    /// <summary>
    /// 解密
    /// </summary>
    /// <param name="resData">加密字符串</param>
    /// <param name="privateKey">私钥</param>
    /// <param name="input_charset">编码格式</param>
    /// <returns>明文</returns>
    public static string decryptData(string resData, string privateKey, string input_charset)
    {
        byte[] DataToDecrypt = Convert.FromBase64String(resData);
        List<byte> result = new List<byte>();
        for (int j = 0; j < DataToDecrypt.Length / 128; j++)
        {
            byte[] buf = new byte[128];
            for (int i = 0; i < 128; i++)
            {
                buf[i] = DataToDecrypt[i + 128 * j];
            }
            result.AddRange(decrypt(buf, privateKey, input_charset));
        }
        byte[] source = result.ToArray();
        char[] asciiChars = new char[Encoding.GetEncoding(input_charset).GetCharCount(source, 0, source.Length)];
        Encoding.GetEncoding(input_charset).GetChars(source, 0, source.Length, asciiChars, 0);
        return new string(asciiChars);
    }

    #region 内部方法 

    private static byte[] decrypt(byte[] data, string privateKey, string input_charset)
    {
        RSACryptoServiceProvider rsa = DecodePemPrivateKey(privateKey);
        //SHA1 sh = new SHA1CryptoServiceProvider();
        return rsa.Decrypt(data, false);
    }

    private static RSACryptoServiceProvider DecodePemPrivateKey(String pemstr)
    {
        byte[] pkcs8privatekey;
        pkcs8privatekey = Convert.FromBase64String(pemstr);
        if (pkcs8privatekey != null)
        {
            RSACryptoServiceProvider rsa = DecodePrivateKeyInfo(pkcs8privatekey);
            return rsa;
        }
        else
            return null;
    }

    private static RSACryptoServiceProvider DecodePrivateKeyInfo(byte[] pkcs8)
    {
        byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
        byte[] seq = new byte[15];

        MemoryStream mem = new MemoryStream(pkcs8);
        int lenstream = (int)mem.Length;
        BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
        byte bt = 0;
        ushort twobytes = 0;

        try
        {
            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8130)    //data read as little endian order (actual data order for Sequence is 30 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8230)
                binr.ReadInt16();    //advance 2 bytes
            else
                return null;

            bt = binr.ReadByte();
            if (bt != 0x02)
                return null;

            twobytes = binr.ReadUInt16();

            if (twobytes != 0x0001)
                return null;

            seq = binr.ReadBytes(15);        //read the Sequence OID
            if (!CompareBytearrays(seq, SeqOID))    //make sure Sequence for OID is correct
                return null;

            bt = binr.ReadByte();
            if (bt != 0x04)    //expect an Octet string 
                return null;

            bt = binr.ReadByte();        //read next byte, or next 2 bytes is  0x81 or 0x82; otherwise bt is the byte count
            if (bt == 0x81)
                binr.ReadByte();
            else
                if (bt == 0x82)
                    binr.ReadUInt16();
            //------ at this stage, the remaining sequence should be the RSA private key

            byte[] rsaprivkey = binr.ReadBytes((int)(lenstream - mem.Position));
            RSACryptoServiceProvider rsacsp = DecodeRSAPrivateKey(rsaprivkey);
            return rsacsp;
        }

        catch (Exception)
        {
            return null;
        }

        finally { binr.Close(); }

    }

    private static bool CompareBytearrays(byte[] a, byte[] b)
    {
        if (a.Length != b.Length)
            return false;
        int i = 0;
        foreach (byte c in a)
        {
            if (c != b[i])
                return false;
            i++;
        }
        return true;
    }

    private static RSACryptoServiceProvider DecodeRSAPrivateKey(byte[] privkey)
    {
        byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;

        // ---------  Set up stream to decode the asn.1 encoded RSA private key  ------
        MemoryStream mem = new MemoryStream(privkey);
        BinaryReader binr = new BinaryReader(mem);    //wrap Memory Stream with BinaryReader for easy reading
        byte bt = 0;
        ushort twobytes = 0;
        int elems = 0;
        try
        {
            twobytes = binr.ReadUInt16();
            if (twobytes == 0x8130)    //data read as little endian order (actual data order for Sequence is 30 81)
                binr.ReadByte();    //advance 1 byte
            else if (twobytes == 0x8230)
                binr.ReadInt16();    //advance 2 bytes
            else
                return null;

            twobytes = binr.ReadUInt16();
            if (twobytes != 0x0102)    //version number
                return null;
            bt = binr.ReadByte();
            if (bt != 0x00)
                return null;


            //------  all private key components are Integer sequences ----
            elems = GetIntegerSize(binr);
            MODULUS = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            E = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            D = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            P = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            Q = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            DP = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            DQ = binr.ReadBytes(elems);

            elems = GetIntegerSize(binr);
            IQ = binr.ReadBytes(elems);

            // ------- create RSACryptoServiceProvider instance and initialize with public key -----
            RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
            RSAParameters RSAparams = new RSAParameters();
            RSAparams.Modulus = MODULUS;
            RSAparams.Exponent = E;
            RSAparams.D = D;
            RSAparams.P = P;
            RSAparams.Q = Q;
            RSAparams.DP = DP;
            RSAparams.DQ = DQ;
            RSAparams.InverseQ = IQ;
            RSA.ImportParameters(RSAparams);
            return RSA;
        }
        catch (Exception)
        {
            return null;
        }
        finally { binr.Close(); }
    }

    private static int GetIntegerSize(BinaryReader binr)
    {
        byte bt = 0;
        byte lowbyte = 0x00;
        byte highbyte = 0x00;
        int count = 0;
        bt = binr.ReadByte();
        if (bt != 0x02)        //expect integer
            return 0;
        bt = binr.ReadByte();

        if (bt == 0x81)
            count = binr.ReadByte();    // data size in next byte
        else
            if (bt == 0x82)
            {
                highbyte = binr.ReadByte();    // data size in next 2 bytes
                lowbyte = binr.ReadByte();
                byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
                count = BitConverter.ToInt32(modint, 0);
            }
            else
            {
                count = bt;        // we already have the data size
            }



        while (binr.ReadByte() == 0x00)
        {    //remove high order zeros in data
            count -= 1;
        }
        binr.BaseStream.Seek(-1, SeekOrigin.Current);        //last ReadByte wasn't a removed zero, so back up a byte
        return count;
    }

    #endregion

    #region 解析.net 生成的Pem
    private static RSAParameters ConvertFromPublicKey(string pemFileConent)
    {

        byte[] keyData = Convert.FromBase64String(pemFileConent);
        if (keyData.Length < 162)
        {
            throw new ArgumentException("pem file content is incorrect.");
        }
        byte[] pemModulus = new byte[128];
        byte[] pemPublicExponent = new byte[3];
        Array.Copy(keyData, 29, pemModulus, 0, 128);
        Array.Copy(keyData, 159, pemPublicExponent, 0, 3);
        RSAParameters para = new RSAParameters();
        para.Modulus = pemModulus;
        para.Exponent = pemPublicExponent;
        return para;
    }

    private static RSAParameters ConvertFromPrivateKey(string pemFileConent)
    {
        byte[] keyData = Convert.FromBase64String(pemFileConent);
        if (keyData.Length < 609)
        {
            throw new ArgumentException("pem file content is incorrect.");
        }

        int index = 11;
        byte[] pemModulus = new byte[128];
        Array.Copy(keyData, index, pemModulus, 0, 128);

        index += 128;
        index += 2;//141
        byte[] pemPublicExponent = new byte[3];
        Array.Copy(keyData, index, pemPublicExponent, 0, 3);

        index += 3;
        index += 4;//148
        byte[] pemPrivateExponent = new byte[128];
        Array.Copy(keyData, index, pemPrivateExponent, 0, 128);

        index += 128;
        index += ((int)keyData[index + 1] == 64 ? 2 : 3);//279
        byte[] pemPrime1 = new byte[64];
        Array.Copy(keyData, index, pemPrime1, 0, 64);

        index += 64;
        index += ((int)keyData[index + 1] == 64 ? 2 : 3);//346
        byte[] pemPrime2 = new byte[64];
        Array.Copy(keyData, index, pemPrime2, 0, 64);

        index += 64;
        index += ((int)keyData[index + 1] == 64 ? 2 : 3);//412/413
        byte[] pemExponent1 = new byte[64];
        Array.Copy(keyData, index, pemExponent1, 0, 64);

        index += 64;
        index += ((int)keyData[index + 1] == 64 ? 2 : 3);//479/480
        byte[] pemExponent2 = new byte[64];
        Array.Copy(keyData, index, pemExponent2, 0, 64);

        index += 64;
        index += ((int)keyData[index + 1] == 64 ? 2 : 3);//545/546
        byte[] pemCoefficient = new byte[64];
        Array.Copy(keyData, index, pemCoefficient, 0, 64);

        RSAParameters para = new RSAParameters();
        para.Modulus = pemModulus;
        para.Exponent = pemPublicExponent;
        para.D = pemPrivateExponent;
        para.P = pemPrime1;
        para.Q = pemPrime2;
        para.DP = pemExponent1;
        para.DQ = pemExponent2;
        para.InverseQ = pemCoefficient;
        return para;
    }
    #endregion

}