.net core 中使用 openssl 公钥私钥进行加解密

这篇博文分享的是 C#中使用OpenSSL的公钥加密/私钥解密 一文中的解决方法在 .net core 中的改进。之前的博文针对的是 .NET Framework ，加解密用的是 RSACryptoServiceProvider 。虽然在 corefx(.NET Core Framework) 中也有 RSACryptoServiceProvider ，但它目前只支持 Windows ，不能跨平台。

之前的 new RSACryptoServiceProvider(); 代码在 mac 上运行，会报下面的错误：

System.PlatformNotSupportedException: Operation is not supported on this platform.
at System.Security.Cryptography.RSACryptoServiceProvider..ctor()

要解决这个问题，需要改用  System.Security.Cryptography.RSA.Create() 工厂方法，使用它之后，在 Windows 上创建的是 System.Security.Cryptography.RSACng 的实例，在 Mac 与 Linux 上创建的是 System.Security.Cryptography.RSAOpenSsl 的实例，它们都继承自 System.Security.Cryptography.RSA 抽象类。

使用了 RSA.Create() 之后，带来了一个问题，RSA 中没有 RSACryptoServiceProvider 中的以下2个签名的加解密方法。

public byte[] Encrypt(byte[] rgb, bool fOAEP);
public byte[] Decrypt(byte[] rgb, bool fOAEP);

只有

public abstract byte[] Encrypt(byte[] data, RSAEncryptionPadding padding);
public abstract byte[] Decrypt(byte[] data, RSAEncryptionPadding padding);

调用时它们时需要传递 RSAEncryptionPadding 类型的参数值：

但对于 openssl 生成的公钥私钥不知道选择哪种 RSAEncryptionPadding ，只能采取笨方法 —— 一个一个试试，试出来的结果是 RSAEncryptionPadding.Pkcs1 。

openssl 的公钥与私钥是在 Mac 上通过下面的2个命令生成的：

openssl genrsa -out rsa_1024_priv.pem 102
openssl rsa -pubout -in rsa_1024_priv.pem -out rsa_1024_pub.pem

（注：一定要用 openssl 命令，用 ssh-keygen -t rsa 命令生成的公钥私钥是不行的）

修改这两个地方（RSA.Create 与 RSAEncryptionPadding.Pkcs1）之后，就可以在 .net core 上使用 openssl 的公钥私钥进行加解密了，以下是测试时所用的完整代码（.net core控制台程序）。经测试，在 Windows，macOS，Linux Ubuntu 上都能成功进行加解密。

Program.cs

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

namespace TryRsa
{
    public class Program
    {
        //openssl genrsa -out rsa_1024_priv.pem 1024
        private static readonly string _privateKey = @"MIICXgIBAAKBgQC0xP5HcfThSQr43bAMoopbzcCyZWE0xfUeTA4Nx4PrXEfDvybJ
EIjbU/rgANAty1yp7g20J7+wVMPCusxftl/d0rPQiCLjeZ3HtlRKld+9htAZtHFZ
osV29h/hNE9JkxzGXstaSeXIUIWquMZQ8XyscIHhqoOmjXaCv58CSRAlAQIDAQAB
AoGBAJtDgCwZYv2FYVk0ABw6F6CWbuZLUVykks69AG0xasti7Xjh3AximUnZLefs
iuJqg2KpRzfv1CM+Cw5cp2GmIVvRqq0GlRZGxJ38AqH9oyUa2m3TojxWapY47zye
PYEjWwRTGlxUBkdujdcYj6/dojNkm4azsDXl9W5YaXiPfbgJAkEA4rlhSPXlohDk
FoyfX0v2OIdaTOcVpinv1jjbSzZ8KZACggjiNUVrSFV3Y4oWom93K5JLXf2mV0Sy
80mPR5jOdwJBAMwciAk8xyQKpMUGNhFX2jKboAYY1SJCfuUnyXHAPWeHp5xCL2UH
tjryJp/Vx8TgsFTGyWSyIE9R8hSup+32rkcCQBe+EAkC7yQ0np4Z5cql+sfarMMm
4+Z9t8b4N0a+EuyLTyfs5Dtt5JkzkggTeuFRyOoALPJP0K6M3CyMBHwb7WsCQQCi
TM2fCsUO06fRQu8bO1A1janhLz3K0DU24jw8RzCMckHE7pvhKhCtLn+n+MWwtzl/
L9JUT4+BgxeLepXtkolhAkEA2V7er7fnEuL0+kKIjmOm5F3kvMIDh9YC1JwLGSvu
1fnzxK34QwSdxgQRF1dfIKJw73lClQpHZfQxL/2XRG8IoA==".Replace("
", "");

        //openssl rsa -pubout -in rsa_1024_priv.pem -out rsa_1024_pub.pem
        private static readonly string _publicKey = @"MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC0xP5HcfThSQr43bAMoopbzcCy
ZWE0xfUeTA4Nx4PrXEfDvybJEIjbU/rgANAty1yp7g20J7+wVMPCusxftl/d0rPQ
iCLjeZ3HtlRKld+9htAZtHFZosV29h/hNE9JkxzGXstaSeXIUIWquMZQ8XyscIHh
qoOmjXaCv58CSRAlAQIDAQAB".Replace("
", "");

        public static void Main(string[] args)
        {
            var plainText = "cnblogs.com";

            //Encrypt
            RSA rsa = CreateRsaFromPublicKey(_publicKey);                       
            var plainTextBytes = Encoding.UTF8.GetBytes(plainText);
            var cipherBytes = rsa.Encrypt(plainTextBytes, RSAEncryptionPadding.Pkcs1);
            var cipher = Convert.ToBase64String(cipherBytes);
            Console.WriteLine($"{nameof(cipher)}:{cipher}");

            //Decrypt
            rsa = CreateRsaFromPrivateKey(_privateKey);            
            cipherBytes = System.Convert.FromBase64String(cipher);
            plainTextBytes = rsa.Decrypt(cipherBytes, RSAEncryptionPadding.Pkcs1);
            plainText = Encoding.UTF8.GetString(plainTextBytes);
            Console.WriteLine($"{nameof(plainText)}:{plainText}");
        }        private static RSA CreateRsaFromPrivateKey(string privateKey)
        {
            var privateKeyBits = System.Convert.FromBase64String(privateKey);
            var rsa = RSA.Create();
            var RSAparams = new RSAParameters();

            using (var binr = new BinaryReader(new MemoryStream(privateKeyBits)))
            {
                byte bt = 0;
                ushort twobytes = 0;
                twobytes = binr.ReadUInt16();
                if (twobytes == 0x8130)
                    binr.ReadByte();
                else if (twobytes == 0x8230)
                    binr.ReadInt16();
                else
                    throw new Exception("Unexpected value read binr.ReadUInt16()");

                twobytes = binr.ReadUInt16();
                if (twobytes != 0x0102)
                    throw new Exception("Unexpected version");

                bt = binr.ReadByte();
                if (bt != 0x00)
                    throw new Exception("Unexpected value read binr.ReadByte()");

                RSAparams.Modulus = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.Exponent = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.D = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.P = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.Q = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.DP = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.DQ = binr.ReadBytes(GetIntegerSize(binr));
                RSAparams.InverseQ = binr.ReadBytes(GetIntegerSize(binr));
            }

            rsa.ImportParameters(RSAparams);
            return rsa;
        }

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

            if (bt == 0x81)
                count = binr.ReadByte();
            else
                if (bt == 0x82)
            {
                highbyte = binr.ReadByte();
                lowbyte = binr.ReadByte();
                byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
                count = BitConverter.ToInt32(modint, 0);
            }
            else
            {
                count = bt;
            }

            while (binr.ReadByte() == 0x00)
            {
                count -= 1;
            }
            binr.BaseStream.Seek(-1, SeekOrigin.Current);
            return count;
        }

        private static RSA CreateRsaFromPublicKey(string publicKeyString)
        {
            byte[] SeqOID = { 0x30, 0x0D, 0x06, 0x09, 0x2A, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x01, 0x01, 0x01, 0x05, 0x00 };
            byte[] x509key;
            byte[] seq = new byte[15];
            int x509size;

            x509key = Convert.FromBase64String(publicKeyString);
            x509size = x509key.Length;

            using (var mem = new MemoryStream(x509key))
            {
                using (var binr = new BinaryReader(mem))
                {
                    byte bt = 0;
                    ushort twobytes = 0;

                    twobytes = binr.ReadUInt16();
                    if (twobytes == 0x8130)
                        binr.ReadByte();
                    else if (twobytes == 0x8230)
                        binr.ReadInt16();
                    else
                        return null;

                    seq = binr.ReadBytes(15);
                    if (!CompareBytearrays(seq, SeqOID))
                        return null;

                    twobytes = binr.ReadUInt16();
                    if (twobytes == 0x8103)
                        binr.ReadByte();
                    else if (twobytes == 0x8203)
                        binr.ReadInt16();
                    else
                        return null;

                    bt = binr.ReadByte();
                    if (bt != 0x00)
                        return null;

                    twobytes = binr.ReadUInt16();
                    if (twobytes == 0x8130)
                        binr.ReadByte();
                    else if (twobytes == 0x8230)
                        binr.ReadInt16();
                    else
                        return null;

                    twobytes = binr.ReadUInt16();
                    byte lowbyte = 0x00;
                    byte highbyte = 0x00;

                    if (twobytes == 0x8102)
                        lowbyte = binr.ReadByte();
                    else if (twobytes == 0x8202)
                    {
                        highbyte = binr.ReadByte();
                        lowbyte = binr.ReadByte();
                    }
                    else
                        return null;
                    byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
                    int modsize = BitConverter.ToInt32(modint, 0);

                    int firstbyte = binr.PeekChar();
                    if (firstbyte == 0x00)
                    {
                        binr.ReadByte();
                        modsize -= 1;
                    }

                    byte[] modulus = binr.ReadBytes(modsize);

                    if (binr.ReadByte() != 0x02)
                        return null;
                    int expbytes = (int)binr.ReadByte();
                    byte[] exponent = binr.ReadBytes(expbytes);

                    var rsa = RSA.Create();
                    var rsaKeyInfo = new RSAParameters
                    {
                        Modulus = modulus,
                        Exponent = exponent
                    };
                    rsa.ImportParameters(rsaKeyInfo);
                    return rsa;
                }

            }
        }

        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;
        }
    }
}

project.json

{
  "version": "1.0.0-*",
  "buildOptions": {
    "emitEntryPoint": true
  },

  "dependencies": {
    "Microsoft.NETCore.App": {
        "type": "platform",
        "version": "1.1.0-preview1-001100-00"
    },
    "System.Security.Cryptography.Algorithms": "4.3.0-preview1-24530-04"
  },

  "frameworks": {
    "netcoreapp1.1": {
      "imports": "dnxcore50"
    }
  }
}

相关链接

• ASP.NET Core RSA加密或解密

【更新】

如果遇到解密时遇到"Bad Data"的问题：

System.Security.Cryptography.CryptographicException: Bad Data.

可以使用下面的方法（同事实现的代码）：

public string Decrypt(string cipher)
{
    return Encoding.UTF8.GetString(_rsa.Decrypt(Convert.FromBase64String(cipher), RSAEncryptionPadding.Pkcs1));
    var cipherLength = _rsa.KeySize / 8;
    var cipherBytes = Convert.FromBase64String(cipher);
    if (cipherBytes.Length < cipherLength)
    {
        var delta = cipherLength - cipherBytes.Length;
        var newBytes = new byte[cipherLength];
        Array.Copy(cipherBytes, 0, newBytes, delta, cipherBytes.Length);
        cipherBytes = newBytes;
    }

    return Encoding.UTF8.GetString(_rsa.Decrypt(cipherBytes, RSAEncryptionPadding.Pkcs1));
}