RsaSecurityKeyExtensions.cs

using System.Security.Cryptography;
using JwkGenerator.Enums;
using Microsoft.IdentityModel.Tokens;

namespace JwkGenerator;

internal static class RsaSecurityKeyExtensions
{
    /// <summary>
    /// Get the JsonWebKey representation of the RSA key
    /// </summary>
    /// <param name="includePrivateKey">Include private key in JsonWebKey (if the current key contains the private key)</param>
    /// <param name="algorithm">Signature or encryption algorithm for which this key will be used for</param>
    /// <returns></returns>
    public static JsonWebKey ToJwk(this RsaSecurityKey key, RsaAlgorithm algorithm, bool includePrivateKey = true)
    {
        RSAParameters parameters;

        if (key.Rsa != null)
            parameters = key.Rsa.ExportParameters(includePrivateKey);
        else
            parameters = key.Parameters;

        var algorithmInfo = algorithm.GetJsonWebAlgorithm();
        var result = new JsonWebKey()
        {
            Kty = JsonWebAlgorithmsKeyTypes.RSA,
            Kid = key.KeyId,
            Use = algorithmInfo?.PublicKeyUse,
            Alg = algorithmInfo?.Name,
            N = parameters.Modulus == null ? null : Base64UrlEncoder.Encode(parameters.Modulus),
            E = parameters.Exponent == null ? null : Base64UrlEncoder.Encode(parameters.Exponent)
        };

        if (includePrivateKey)
        {
            result.P = parameters.P == null ? null : Base64UrlEncoder.Encode(parameters.P);
            result.Q = parameters.Q == null ? null : Base64UrlEncoder.Encode(parameters.Q);
            result.D = parameters.D == null ? null : Base64UrlEncoder.Encode(parameters.D);
            result.DQ = parameters.DQ == null ? null : Base64UrlEncoder.Encode(parameters.DQ);
            result.DP = parameters.DP == null ? null : Base64UrlEncoder.Encode(parameters.DP);
            result.QI = parameters.InverseQ == null ? null : Base64UrlEncoder.Encode(parameters.InverseQ);
        }
        return result;
    }
}