I found no ready-to-use function for this in BouncyCastle. So, the workaround is to use PemReader
and then format the result. The result will be available as PublicSSH
property:
using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.Generators;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Math;
using Org.BouncyCastle.OpenSsl;
using Org.BouncyCastle.Security;
using System;
using System.IO;
using System.Text;
namespace Deploy4Me.Common.Utils
{
public class RSAKey
{
public string PublicPEM { get; set; }
public string PrivatePEM { get; set; }
public string PublicSSH { get; set; }
}
public static class RSA
{
public static RSAKey Generate()
{
try
{
RSAKey result = new RSAKey();
IAsymmetricCipherKeyPairGenerator gen;
KeyGenerationParameters param;
gen = new RsaKeyPairGenerator();
param = new RsaKeyGenerationParameters(
BigInteger.ValueOf(3L),
new SecureRandom(),
2048,
80
);
gen.Init(param);
AsymmetricCipherKeyPair pair = gen.GenerateKeyPair();
using(TextWriter textWriter = new StringWriter())
{
PemWriter wr = new PemWriter(textWriter);
wr.WriteObject(pair.Private);
wr.Writer.Flush();
result.PrivatePEM = textWriter.ToString();
}
using (TextWriter textWriter = new StringWriter())
{
PemWriter wr = new PemWriter(textWriter);
wr.WriteObject(pair.Public);
wr.Writer.Flush();
result.PublicPEM = textWriter.ToString();
}
using (StringReader sr = new StringReader(result.PublicPEM))
{
PemReader reader = new PemReader(sr);
RsaKeyParameters r = (RsaKeyParameters)reader.ReadObject();
byte[] sshrsa_bytes = Encoding.Default.GetBytes("ssh-rsa");
byte[] n = r.Modulus.ToByteArray();
byte[] e = r.Exponent.ToByteArray();
string buffer64;
using(MemoryStream ms = new MemoryStream()){
ms.Write(ToBytes(sshrsa_bytes.Length), 0, 4);
ms.Write(sshrsa_bytes, 0, sshrsa_bytes.Length);
ms.Write(ToBytes(e.Length), 0, 4);
ms.Write(e, 0, e.Length);
ms.Write(ToBytes(n.Length), 0, 4);
ms.Write(n, 0, n.Length);
ms.Flush();
buffer64 = Convert.ToBase64String(ms.ToArray());
}
result.PublicSSH = string.Format("ssh-rsa {0} generated-key", buffer64);
}
return result;
}
catch (Org.BouncyCastle.Crypto.CryptoException ex)
{
throw ex;
}
}
private static byte[] ToBytes(int i)
{
byte[] bts = BitConverter.GetBytes(i);
if (BitConverter.IsLittleEndian)
{
Array.Reverse(bts);
}
return bts;
}
}
}