DocumentService/DocumentService.Infrastructure.Crypt/Services/Pkcs11ExternalSigner.cs

using DocumentService.Application.Common.Configuration;
using DevExpress.Office.DigitalSignatures;
using DevExpress.Pdf;

namespace DocumentService.Infrastructure.Crypt.Services;

internal sealed class Pkcs11ExternalSigner(Pkcs11Options options) : Pkcs7SignerBase
{
    private readonly Pkcs11PdfSigningRsa rsa = new(options);
    private readonly DigestCalculator digestCalculator = new(HashAlgorithmType.SHA256);
    private readonly IReadOnlyList<byte[]> certificates = [ReadCertificateBytesWithFallback(options)];

    protected override IDigestCalculator DigestCalculator => digestCalculator;

    protected override string SigningAlgorithmOID => "1.2.840.113549.1.1.1";

    protected override IEnumerable<byte[]> GetCertificates() => certificates;

    protected override byte[] SignDigest(byte[] digest)
    {
        return rsa.SignHash(digest, System.Security.Cryptography.HashAlgorithmName.SHA256, System.Security.Cryptography.RSASignaturePadding.Pkcs1);
    }

    private static byte[] ReadCertificateBytesWithFallback(Pkcs11Options options)
    {
        try
        {
            return Pkcs11SessionRunner.Run(options, session =>
            {
                var attrs = new List<Net.Pkcs11Interop.HighLevelAPI.IObjectAttribute>
                {
                    session.Factories.ObjectAttributeFactory.Create(Net.Pkcs11Interop.Common.CKA.CKA_CLASS, Net.Pkcs11Interop.Common.CKO.CKO_CERTIFICATE),
                    session.Factories.ObjectAttributeFactory.Create(Net.Pkcs11Interop.Common.CKA.CKA_LABEL, options.CertificateLabel)
                };

                var handles = session.FindAllObjects(attrs);
                if (handles.Count == 0)
                    throw new InvalidOperationException($"Certificate '{options.CertificateLabel}' not found in token.");

                var values = session.GetAttributeValue(handles[0], new List<Net.Pkcs11Interop.Common.CKA> { Net.Pkcs11Interop.Common.CKA.CKA_VALUE });
                return values[0].GetValueAsByteArray();
            });
        }
        catch when (Pkcs11ToolBridge.IsAvailable(options))
        {
            return Pkcs11ToolBridge.ReadCertificateBytes(options);
        }
    }
}