DigitalData.Core/DigitalData.Core.Security/Cryptographer/RSAFactory.cs

using DigitalData.Core.Abstractions.Security;
using DigitalData.Core.Security.Config;
using Microsoft.Extensions.Options;
using System.Security.Cryptography;

namespace DigitalData.Core.Security.Cryptographer
{
    public class RSAFactory<TRSAFactoryParams> : IRSAFactory<TRSAFactoryParams> where TRSAFactoryParams : RSAFactoryParams
    {
        private static readonly Lazy<RSAFactory<RSAFactoryParams>> LazyInstance = new(() => new(Options.Create<RSAFactoryParams>(new())));

        public static RSAFactory<RSAFactoryParams> Static => LazyInstance.Value;

        protected readonly TRSAFactoryParams _params;

        public RSAFactory(IOptions<TRSAFactoryParams> options) => _params = options.Value;

        public string CreateRSAPrivateKeyPem(int? keySizeInBits = null)
            => RSA.Create(keySizeInBits ?? _params.KeySizeInBits).ExportRSAPrivateKeyPem();

        public string CreateEncryptedPrivateKeyPem(
            int? keySizeInBits = null,
            string? password = null,
            PbeEncryptionAlgorithm? pbeEncryptionAlgorithm = null,
            HashAlgorithmName? hashAlgorithmName = null,
            int? iterationCount = null)
        {
            password ??= _params.PbePassword;

            var pbeParameters = pbeEncryptionAlgorithm is null && hashAlgorithmName is null && iterationCount is null
                ? new PbeParameters(
                    pbeEncryptionAlgorithm ?? _params.PbeEncryptionAlgorithm,
                    hashAlgorithmName ?? _params.PbeHashAlgorithmName,
                    iterationCount ?? _params.PbeIterationCount)
                : _params.PbeParameters;

            var encryptedPrivateKey = RSA.Create(keySizeInBits ?? _params.KeySizeInBits).ExportEncryptedPkcs8PrivateKey(password.AsSpan(), pbeParameters);

            var pemChars = PemEncoding.Write(_params.EncryptedPrivateKeyPemLabel, encryptedPrivateKey);

            return new string(pemChars);
        }
    }
}