RsaSsaPkcsSha256.cs

using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
using Waher.Content;
 
namespace Waher.Security.JWS
{
    public class RsaSsaPkcsSha256 : JwsAlgorithm
    {
        private RSA rsa;
        private SHA256 sha;
        private KeyValuePair<string, object>[] jwk;
 
        public RsaSsaPkcsSha256()
            : this(4096)
        {
        }
 
        public RsaSsaPkcsSha256(int KeySize)
        {
            try
            {
                this.rsa = RSA.Create();
                this.rsa.KeySize = KeySize;
            }
            catch (CryptographicException ex)
            {
                throw new CryptographicException("Unable to get access to cryptographic key. Was application initially run using another user?", ex);
            }
 
            this.Init();
        }
 
        public RsaSsaPkcsSha256(RSA RSA)
        {
            this.rsa = RSA;
            this.Init();
        }
 
        public RsaSsaPkcsSha256(RSAParameters Parameters)
        {
            this.rsa = RSA.Create();
            this.RSA.ImportParameters(Parameters);
 
            this.Init();
        }
 
        public void ImportKey(RSA RSA)
        {
            RSAParameters P = RSA.ExportParameters(true);
            this.rsa.ImportParameters(P);
            this.jwk = GetJwk(this.rsa, false);
        }
 
        public RSA RSA => this.rsa;
 
        private void Init()
        {
            this.jwk = GetJwk(this.rsa, false);
            this.sha = SHA256.Create();
        }
 
        public static KeyValuePair<string, object>[] GetJwk(RSA RSA, bool IncludePrivate)
        {
            RSAParameters Parameters = RSA.ExportParameters(IncludePrivate);
 
            if (IncludePrivate)
            {
                return new KeyValuePair<string, object>[]
                {
                    new KeyValuePair<string, object>("kty", "RSA"),
                    new KeyValuePair<string, object>("n", Base64Url.Encode(Parameters.Modulus)),
                    new KeyValuePair<string, object>("e", Base64Url.Encode(Parameters.Exponent)),
                    new KeyValuePair<string, object>("d", Base64Url.Encode(Parameters.D)),
                    new KeyValuePair<string, object>("p", Base64Url.Encode(Parameters.P)),
                    new KeyValuePair<string, object>("q", Base64Url.Encode(Parameters.Q)),
                    new KeyValuePair<string, object>("dp", Base64Url.Encode(Parameters.DP)),
                    new KeyValuePair<string, object>("dq", Base64Url.Encode(Parameters.DQ)),
                    new KeyValuePair<string, object>("qi", Base64Url.Encode(Parameters.InverseQ))
                };
            }
            else
            {
                return new KeyValuePair<string, object>[]
                {
                    new KeyValuePair<string, object>("kty", "RSA"),
                    new KeyValuePair<string, object>("n", Base64Url.Encode(Parameters.Modulus)),
                    new KeyValuePair<string, object>("e", Base64Url.Encode(Parameters.Exponent))
                };
            }
        }
 
        public override void Dispose()
        {
            if (!(this.rsa is null))
            {
                this.rsa.Dispose();
                this.rsa = null;
            }
 
            if (!(this.sha is null))
            {
                this.sha.Dispose();
                this.sha = null;
            }
        }
 
        public override string Name => "RS256";
 
        public override bool HasPublicWebKey => true;
 
        public override IEnumerable<KeyValuePair<string, object>> PublicWebKey => this.jwk;
 
        public override string Sign(string HeaderEncoded, string PayloadEncoded)
        {
            byte[] SignatureBin;
            string Token = HeaderEncoded + "." + PayloadEncoded;
            byte[] TokenBin = Encoding.ASCII.GetBytes(Token);
 
            lock (this.rsa)
            {
                SignatureBin = this.rsa.SignHash(this.sha.ComputeHash(TokenBin), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
            }
 
            return Base64Url.Encode(SignatureBin);
        }
    }
}