C# RSACryptoService with openssl rsa key

RSACryptoService.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace CMCloud.SaaS
{
    public class RSACryptoService
    {
        private RSACryptoServiceProvider _privateKeyRsaProvider;
        private RSACryptoServiceProvider _publicKeyRsaProvider;

        /// <summary>
        /// RSA解密
        /// </summary>
        /// <param name="cipherText"></param>
        /// <returns></returns>
        public string Decrypt(string cipherText)
        {
            if (_privateKeyRsaProvider == null)
            {
                throw new Exception("_privateKeyRsaProvider is null");
            }
            return Decrypt2(cipherText);
        }
        /// <summary>
        /// RSA加密
        /// </summary>
        /// <param name="text"></param>
        /// <returns></returns>
        public string Encrypt(string text)
        {
            if (_publicKeyRsaProvider == null)
            {
                throw new Exception("_publicKeyRsaProvider is null");
            }
            return Encrypt2(text);
            //return Convert.ToBase64String(_publicKeyRsaProvider.Encrypt(Encoding.UTF8.GetBytes(text), false));

        }
        private string Encrypt2(string text)
        {


            Byte[] PlaintextData = Encoding.UTF8.GetBytes(text);
            int MaxBlockSize = _publicKeyRsaProvider.KeySize / 8 - 11;//加密块最大长度限制

            if (PlaintextData.Length <= MaxBlockSize)
            {
                return Convert.ToBase64String(_publicKeyRsaProvider.Encrypt(PlaintextData, false));
            }
            else
            {
                using (MemoryStream PlaiStream = new MemoryStream(PlaintextData))
                using (MemoryStream CrypStream = new MemoryStream())
                {
                    Byte[] Buffer = new Byte[MaxBlockSize];
                    int BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);

                    while (BlockSize > 0)
                    {
                        Byte[] ToEncrypt = new Byte[BlockSize];
                        Array.Copy(Buffer, 0, ToEncrypt, 0, BlockSize);

                        Byte[] Cryptograph = _publicKeyRsaProvider.Encrypt(ToEncrypt, false);
                        CrypStream.Write(Cryptograph, 0, Cryptograph.Length);

                        BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);
                    }

                    return Convert.ToBase64String(CrypStream.ToArray(), Base64FormattingOptions.None);
                }
            }




        }

        private string Decrypt2(string ciphertext)
        {


            Byte[] CiphertextData = Convert.FromBase64String(ciphertext);
            int MaxBlockSize = _privateKeyRsaProvider.KeySize / 8;    //解密块最大长度限制

            if (CiphertextData.Length <= MaxBlockSize)
                return System.Text.Encoding.UTF8.GetString(_privateKeyRsaProvider.Decrypt(CiphertextData, false));

            using (MemoryStream CrypStream = new MemoryStream(CiphertextData))
            using (MemoryStream PlaiStream = new MemoryStream())
            {
                Byte[] Buffer = new Byte[MaxBlockSize];
                int BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);

                while (BlockSize > 0)
                {
                    Byte[] ToDecrypt = new Byte[BlockSize];
                    Array.Copy(Buffer, 0, ToDecrypt, 0, BlockSize);

                    Byte[] Plaintext = _privateKeyRsaProvider.Decrypt(ToDecrypt, false);
                    PlaiStream.Write(Plaintext, 0, Plaintext.Length);

                    BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);
                }

                return System.Text.Encoding.UTF8.GetString(PlaiStream.ToArray());
            }
        }
        public RSACryptoService(string privateKey, string publicKey = null)
        {
            if (!string.IsNullOrEmpty(privateKey))
            {
                _privateKeyRsaProvider = CreateRsaProviderFromPrivateKey(privateKey);
            }

            if (!string.IsNullOrEmpty(publicKey))
            {
                _publicKeyRsaProvider = CreateRsaProviderFromPublicKey(publicKey);
            }
        }

        

        private RSACryptoServiceProvider CreateRsaProviderFromPrivateKey(string privateKey)
        {
            var privateKeyBits = System.Convert.FromBase64String(privateKey);

            var RSA = new RSACryptoServiceProvider();
            var RSAparams = new RSAParameters();

            using (BinaryReader 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 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 RSACryptoServiceProvider CreateRsaProviderFromPublicKey(string publicKeyString)
        {
            // encoded OID sequence for  PKCS #1 rsaEncryption szOID_RSA_RSA = "1.2.840.113549.1.1.1"
            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;

            // ---------  Set up stream to read the asn.1 encoded SubjectPublicKeyInfo blob  ------
            using (MemoryStream mem = new MemoryStream(x509key))
            {
                using (BinaryReader binr = new BinaryReader(mem))  //wrap Memory Stream with BinaryReader for easy reading
                {
                    byte bt = 0;
                    ushort twobytes = 0;

                    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;

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

                    twobytes = binr.ReadUInt16();
                    if (twobytes == 0x8103) //data read as little endian order (actual data order for Bit String is 03 81)
                        binr.ReadByte();    //advance 1 byte
                    else if (twobytes == 0x8203)
                        binr.ReadInt16();   //advance 2 bytes
                    else
                        return null;

                    bt = binr.ReadByte();
                    if (bt != 0x00)     //expect null byte next
                        return null;

                    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();
                    byte lowbyte = 0x00;
                    byte highbyte = 0x00;

                    if (twobytes == 0x8102) //data read as little endian order (actual data order for Integer is 02 81)
                        lowbyte = binr.ReadByte();  // read next bytes which is bytes in modulus
                    else if (twobytes == 0x8202)
                    {
                        highbyte = binr.ReadByte(); //advance 2 bytes
                        lowbyte = binr.ReadByte();
                    }
                    else
                        return null;
                    byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };   //reverse byte order since asn.1 key uses big endian order
                    int modsize = BitConverter.ToInt32(modint, 0);

                    int firstbyte = binr.PeekChar();
                    if (firstbyte == 0x00)
                    {   //if first byte (highest order) of modulus is zero, don't include it
                        binr.ReadByte();    //skip this null byte
                        modsize -= 1;   //reduce modulus buffer size by 1
                    }

                    byte[] modulus = binr.ReadBytes(modsize);   //read the modulus bytes

                    if (binr.ReadByte() != 0x02)            //expect an Integer for the exponent data
                        return null;
                    int expbytes = (int)binr.ReadByte();        // should only need one byte for actual exponent data (for all useful values)
                    byte[] exponent = binr.ReadBytes(expbytes);

                    // ------- create RSACryptoServiceProvider instance and initialize with public key -----
                    RSACryptoServiceProvider RSA = new RSACryptoServiceProvider();
                    RSAParameters RSAKeyInfo = new RSAParameters();
                    RSAKeyInfo.Modulus = modulus;
                    RSAKeyInfo.Exponent = exponent;
                    RSA.ImportParameters(RSAKeyInfo);

                    return RSA;
                }

            }
        }

        private 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;
        }
    }
}

Is it returning error: Bad Length from "CreateRsaProviderFromPrivateKey" (line 165: RSA.ImportParameters(RSAparams);)

Please check your key, the code above is tested many years ago.

Getting error: Timeouts are not supported on this stream. ???

Getting error: Timeouts are not supported on this stream. ???

If you have any problems, please provide more information about:

• the runtime version you are using (.net or mono, or .net core)
• how did you generate the key with openssl
• how did you use with the code above

(1) .net framework 4.6.1 (VS 2017)
(2) The key is provided by customer
(3) use the above code for signdata with SHA256

My problem is to Import RSA private key RSA.ImportParameters(RSAparams), try it many times but doesn't work.

Any help would be appreciate.

How did your customer generate the key, and make sure it's a vaid rsa key

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));

Why all these parameters get byte[0] or null values while running your code? I am confused.

While running the following statement:

MemoryStream mem = new MemoryStream(privkey);

Get the below error:

•   ReadTimeout	'mem.ReadTimeout' threw an exception of type 'System.InvalidOperationException'	int {System.InvalidOperationException}
  

•   WriteTimeout	'mem.WriteTimeout' threw an exception of type 'System.InvalidOperationException'	int {System.InvalidOperationException}
  

Therefore the mem variable doesn't get any value.

Could you please help? Thank you.