c# - from - rsacryptoserviceprovider load private key

C#Exportar clave RSA privada/pública de RSACryptoServiceProvider a la cadena PEM

Question

Tengo una instancia de System.Security.Cryptography.RSACryptoServiceProvider, necesito exportar su clave a una cadena PEM, como esta:

-----BEGIN RSA PRIVATE KEY-----
MIICXAIBAAKBgQDUNPB6Lvx+tlP5QhSikADl71AjZf9KN31qrDpXNDNHEI0OTVJ1
OaP2l56bSKNo8trFne1NK/B4JzCuNP8x6oGCAG+7bFgkbTMzV2PCoDCRjNH957Q4
Gxgx1VoS6PjD3OigZnx5b9Hebbp3OrTuqNZaK/oLPGr5swxHILFVeHKupQIDAQAB
AoGAQk3MOZEGyZy0fjQ8eFKgRTfSBU1wR8Mwx6zKicbAotq0CBz2v7Pj3D+higlX
LYp7+rUOmUc6WoB8QGJEvlb0YZVxUg1yDLMWYPE7ddsHsOkBIs7zIyS6cqhn0yZD
VTRFjVST/EduvpUOL5hbyLSwuq+rbv0iPwGW5hkCHNEhx2ECQQDfLS5549wjiFXF
gcio8g715eMT+20we3YmgMJDcviMGwN/mArvnBgBQsFtCTsMoOxm68SfIrBYlKYy
BsFxn+19AkEA82q83pmcbGJRJ3ZMC/Pv+/+/XNFOvMkfT9qbuA6Lv69Z1yk7I1ie
FTH6tOmPUu4WsIOFtDuYbfV2pvpqx7GuSQJAK3SnvRIyNjUAxoF76fGgGh9WNPjb
DPqtSdf+e5Wycc18w+Z+EqPpRK2T7kBC4DWhcnTsBzSA8+6V4d3Q4ugKHQJATRhw
a3xxm65kD8CbA2omh0UQQgCVFJwKy8rsaRZKUtLh/JC1h1No9kOXKTeUSmrYSt3N
OjFp7OHCy84ihc8T6QJBANe+9xkN9hJYNK1pL1kSwXNuebzcgk3AMwHh7ThvjLgO
jruxbM2NyMM5tl9NZCgh1vKc2v5VaonqM1NBQPDeTTw=
-----END RSA PRIVATE KEY-----

Pero no hay tal opción de acuerdo con la documentación de MSDN, solo hay algún tipo de exportación XML. No puedo usar ninguna biblioteca de terceros como BouncyCastle. ¿Hay alguna manera de generar esta cadena?

Answer 1

Para cualquier otra persona que se opuso a la aparente complejidad de la respuesta original (lo cual es muy útil, no me malinterprete), pensé en publicar mi solución, que es un poco más directa de la OMI (pero basada en la respuesta original):

public class RsaCsp2DerConverter {
   private const int MaximumLineLength = 64;

   // Based roughly on: http://.com/a/23739932/1254575

   public RsaCsp2DerConverter() {

   }

   public byte[] ExportPrivateKey(String cspBase64Blob) {
      if (String.IsNullOrEmpty(cspBase64Blob) == true)
         throw new ArgumentNullException(nameof(cspBase64Blob));

      var csp = new RSACryptoServiceProvider();

      csp.ImportCspBlob(Convert.FromBase64String(cspBase64Blob));

      if (csp.PublicOnly)
         throw new ArgumentException("CSP does not contain a private key!", nameof(csp));

      var parameters = csp.ExportParameters(true);

      var list = new List<byte[]> {
         new byte[] {0x00},
         parameters.Modulus,
         parameters.Exponent,
         parameters.D,
         parameters.P,
         parameters.Q,
         parameters.DP,
         parameters.DQ,
         parameters.InverseQ
      };

      return SerializeList(list);
   }

   private byte[] Encode(byte[] inBytes, bool useTypeOctet = true) {
      int length = inBytes.Length;
      var bytes = new List<byte>();

      if (useTypeOctet == true)
         bytes.Add(0x02); // INTEGER

      bytes.Add(0x84); // Long format, 4 bytes
      bytes.AddRange(BitConverter.GetBytes(length).Reverse());
      bytes.AddRange(inBytes);

      return bytes.ToArray();
   }

   public String PemEncode(byte[] bytes) {
      if (bytes == null)
         throw new ArgumentNullException(nameof(bytes));

      var base64 = Convert.ToBase64String(bytes);

      StringBuilder b = new StringBuilder();
      b.Append("-----BEGIN RSA PRIVATE KEY-----/n");

      for (int i = 0; i < base64.Length; i += MaximumLineLength)
         b.Append($"{ base64.Substring(i, Math.Min(MaximumLineLength, base64.Length - i)) }/n");

      b.Append("-----END RSA PRIVATE KEY-----/n");

      return b.ToString();
   }

   private byte[] SerializeList(List<byte[]> list) {
      if (list == null)
         throw new ArgumentNullException(nameof(list));

      var keyBytes = list.Select(e => Encode(e)).SelectMany(e => e).ToArray();

      var binaryWriter = new BinaryWriter(new MemoryStream());
      binaryWriter.Write((byte) 0x30); // SEQUENCE
      binaryWriter.Write(Encode(keyBytes, false));
      binaryWriter.Flush();

      var result = ((MemoryStream) binaryWriter.BaseStream).ToArray();

      binaryWriter.BaseStream.Dispose();
      binaryWriter.Dispose();

      return result;
   }
}

Answer 2

Para exportar PublicKey usa este código:

public static String ExportPublicKeyToPEMFormat(RSACryptoServiceProvider csp)
{
    TextWriter outputStream = new StringWriter();

    var parameters = csp.ExportParameters(false);
    using (var stream = new MemoryStream())
    {
        var writer = new BinaryWriter(stream);
        writer.Write((byte)0x30); // SEQUENCE
        using (var innerStream = new MemoryStream())
        {
            var innerWriter = new BinaryWriter(innerStream);
            EncodeIntegerBigEndian(innerWriter, new byte[] { 0x00 }); // Version
            EncodeIntegerBigEndian(innerWriter, parameters.Modulus);
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent);

            //All Parameter Must Have Value so Set Other Parameter Value Whit Invalid Data  (for keeping Key Structure  use "parameters.Exponent" value for invalid data)
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.D
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.P
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.Q
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.DP
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.DQ
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent); // instead of parameters.InverseQ

            var length = (int)innerStream.Length;
            EncodeLength(writer, length);
            writer.Write(innerStream.GetBuffer(), 0, length);
        }

        var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length).ToCharArray();
        outputStream.WriteLine("-----BEGIN PUBLIC KEY-----");
        // Output as Base64 with lines chopped at 64 characters
        for (var i = 0; i < base64.Length; i += 64)
        {
            outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i));
        }
        outputStream.WriteLine("-----END PUBLIC KEY-----");

        return outputStream.ToString();

    }
}

private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true)
{
    stream.Write((byte)0x02); // INTEGER
    var prefixZeros = 0;
    for (var i = 0; i < value.Length; i++)
    {
        if (value[i] != 0) break;
        prefixZeros++;
    }
    if (value.Length - prefixZeros == 0)
    {
        EncodeLength(stream, 1);
        stream.Write((byte)0);
    }
    else
    {
        if (forceUnsigned && value[prefixZeros] > 0x7f)
        {
            // Add a prefix zero to force unsigned if the MSB is 1
            EncodeLength(stream, value.Length - prefixZeros + 1);
            stream.Write((byte)0);
        }
        else
        {
            EncodeLength(stream, value.Length - prefixZeros);
        }
        for (var i = prefixZeros; i < value.Length; i++)
        {
            stream.Write(value[i]);
        }
    }
}

private static void EncodeLength(BinaryWriter stream, int length)
{
    if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
    if (length < 0x80)
    {
        // Short form
        stream.Write((byte)length);
    }
    else
    {
        // Long form
        var temp = length;
        var bytesRequired = 0;
        while (temp > 0)
        {
            temp >>= 8;
            bytesRequired++;
        }
        stream.Write((byte)(bytesRequired | 0x80));
        for (var i = bytesRequired - 1; i >= 0; i--)
        {
            stream.Write((byte)(length >> (8 * i) & 0xff));
        }
    }
}

Answer 3

Tenga en cuenta: El código a continuación es para exportar una clave privada . Si desea exportar la clave pública , consulte mi respuesta here .

El formato PEM es simplemente la codificación ASN.1 DER de la clave (por PKCS#1 ) convertida a Base64. Dado el número limitado de campos necesarios para representar la clave, es bastante sencillo crear un codificador DER rápido y sucio para generar el formato adecuado y luego Base64 codificarlo. Como tal, el código que sigue no es particularmente elegante, pero hace el trabajo:

private static void ExportPrivateKey(RSACryptoServiceProvider csp, TextWriter outputStream)
{
    if (csp.PublicOnly) throw new ArgumentException("CSP does not contain a private key", "csp");
    var parameters = csp.ExportParameters(true);
    using (var stream = new MemoryStream())
    {
        var writer = new BinaryWriter(stream);
        writer.Write((byte)0x30); // SEQUENCE
        using (var innerStream = new MemoryStream())
        {
            var innerWriter = new BinaryWriter(innerStream);
            EncodeIntegerBigEndian(innerWriter, new byte[] { 0x00 }); // Version
            EncodeIntegerBigEndian(innerWriter, parameters.Modulus);
            EncodeIntegerBigEndian(innerWriter, parameters.Exponent);
            EncodeIntegerBigEndian(innerWriter, parameters.D);
            EncodeIntegerBigEndian(innerWriter, parameters.P);
            EncodeIntegerBigEndian(innerWriter, parameters.Q);
            EncodeIntegerBigEndian(innerWriter, parameters.DP);
            EncodeIntegerBigEndian(innerWriter, parameters.DQ);
            EncodeIntegerBigEndian(innerWriter, parameters.InverseQ);
            var length = (int)innerStream.Length;
            EncodeLength(writer, length);
            writer.Write(innerStream.GetBuffer(), 0, length);
        }

        var base64 = Convert.ToBase64String(stream.GetBuffer(), 0, (int)stream.Length).ToCharArray();
        outputStream.WriteLine("-----BEGIN RSA PRIVATE KEY-----");
        // Output as Base64 with lines chopped at 64 characters
        for (var i = 0; i < base64.Length; i += 64)
        {
            outputStream.WriteLine(base64, i, Math.Min(64, base64.Length - i));
        }
        outputStream.WriteLine("-----END RSA PRIVATE KEY-----");
    }
}

private static void EncodeLength(BinaryWriter stream, int length)
{
    if (length < 0) throw new ArgumentOutOfRangeException("length", "Length must be non-negative");
    if (length < 0x80)
    {
        // Short form
        stream.Write((byte)length);
    }
    else
    {
        // Long form
        var temp = length;
        var bytesRequired = 0;
        while (temp > 0)
        {
            temp >>= 8;
            bytesRequired++;
        }
        stream.Write((byte)(bytesRequired | 0x80));
        for (var i = bytesRequired - 1; i >= 0; i--)
        {
            stream.Write((byte)(length >> (8 * i) & 0xff));
        }
    }
}

private static void EncodeIntegerBigEndian(BinaryWriter stream, byte[] value, bool forceUnsigned = true)
{
    stream.Write((byte)0x02); // INTEGER
    var prefixZeros = 0;
    for (var i = 0; i < value.Length; i++)
    {
        if (value[i] != 0) break;
        prefixZeros++;
    }
    if (value.Length - prefixZeros == 0)
    {
        EncodeLength(stream, 1);
        stream.Write((byte)0);
    }
    else
    {
        if (forceUnsigned && value[prefixZeros] > 0x7f)
        {
            // Add a prefix zero to force unsigned if the MSB is 1
            EncodeLength(stream, value.Length - prefixZeros + 1);
            stream.Write((byte)0);
        }
        else
        {
            EncodeLength(stream, value.Length - prefixZeros);
        }
        for (var i = prefixZeros; i < value.Length; i++)
        {
            stream.Write(value[i]);
        }
    }
}

Answer 4

 public static Func<string, string> ToBase64PemFromKeyXMLString= (xmlPrivateKey) =>
        {
            if (string.IsNullOrEmpty(xmlPrivateKey))
                throw new ArgumentNullException("RSA key must contains value!");
            var keyContent = new PemReader(new StringReader(xmlPrivateKey));
            if (keyContent == null)
                throw new ArgumentNullException("private key is not valid!");
            var ciphrPrivateKey = (AsymmetricCipherKeyPair)keyContent.ReadObject();
            var asymmetricKey = new AsymmetricKeyEntry(ciphrPrivateKey.Private);

            PrivateKeyInfo privateKeyInfo = PrivateKeyInfoFactory.CreatePrivateKeyInfo(asymmetricKey.Key);
            var serializedPrivateKey = privateKeyInfo.ToAsn1Object().GetDerEncoded();
            return Convert.ToBase64String(serializedPrivateKey);
        };