Add support for ГОСТ Р 34.10 digital signatures

- Implemented the GostKeyValue class for handling public key parameters in ГОСТ Р 34.10 digital signatures.
- Created the GostSignedXml class to manage XML signatures using ГОСТ 34.10, including methods for computing and checking signatures.
- Developed the GostSignedXmlImpl class to encapsulate the signature computation logic and public key retrieval.
- Added specific key value classes for ГОСТ Р 34.10-2001, ГОСТ Р 34.10-2012/256, and ГОСТ Р 34.10-2012/512 to support different signature algorithms.
- Ensured compatibility with existing XML signature standards while integrating ГОСТ cryptography.

src/__Libraries/__Tests/StellaOps.Cryptography.Tests/CryptoProGostSignerTests.cs

@@ -0,0 +1,41 @@
+#if STELLAOPS_CRYPTO_PRO
+using System;
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using Microsoft.IdentityModel.Tokens;
+using StellaOps.Cryptography;
+using StellaOps.Cryptography.Plugin.CryptoPro;
+using Xunit;
+
+namespace StellaOps.Cryptography.Tests;
+
+public class CryptoProGostSignerTests
+{
+    [Fact]
+    public void ExportPublicJsonWebKey_ContainsCertificateChain()
+    {
+        using var ecdsa = ECDsa.Create(ECCurve.NamedCurves.nistP256);
+        var request = new CertificateRequest("CN=stellaops.test", ecdsa, HashAlgorithmName.SHA256);
+        using var cert = request.CreateSelfSigned(DateTimeOffset.UtcNow.AddDays(-1), DateTimeOffset.UtcNow.AddDays(1));
+
+        var entry = new CryptoProGostKeyEntry(
+            "test-key",
+            SignatureAlgorithms.GostR3410_2012_256,
+            cert,
+            "provider",
+            containerName: null,
+            useMachineKeyStore: false,
+            signatureFormat: GostSignatureFormat.Der);
+
+        var signer = new CryptoProGostSigner(entry);
+
+        var jwk = signer.ExportPublicJsonWebKey();
+
+        Assert.Equal("test-key", jwk.Kid);
+        Assert.Equal(SignatureAlgorithms.GostR3410_2012_256, jwk.Alg);
+        Assert.Equal(JsonWebKeyUseNames.Sig, jwk.Use);
+        Assert.Single(jwk.X5c);
+        Assert.Equal("EC", jwk.Kty);
+    }
+}
+#endif

src/__Libraries/__Tests/StellaOps.Cryptography.Tests/GostSignatureEncodingTests.cs

@@ -0,0 +1,42 @@
+#if STELLAOPS_CRYPTO_PRO
+using System;
+using System.Linq;
+using System.Security.Cryptography;
+using StellaOps.Cryptography.Plugin.CryptoPro;
+using Xunit;
+
+namespace StellaOps.Cryptography.Tests;
+
+public class GostSignatureEncodingTests
+{
+    [Theory]
+    [InlineData(32)]
+    [InlineData(64)]
+    public void RawAndDer_RoundTrip(int coordinateLength)
+    {
+        var raw = Enumerable.Range(1, coordinateLength * 2)
+            .Select(i => (byte)(i & 0xFF))
+            .ToArray();
+
+        var der = GostSignatureEncoding.ToDer(raw, coordinateLength);
+        Assert.True(GostSignatureEncoding.IsDer(der));
+
+        var roundTrip = GostSignatureEncoding.ToRaw(der, coordinateLength);
+        Assert.Equal(raw, roundTrip);
+    }
+
+    [Fact]
+    public void ToDer_Throws_When_Length_Invalid()
+    {
+        var raw = new byte[10];
+        Assert.Throws<CryptographicException>(() => GostSignatureEncoding.ToDer(raw, coordinateLength: 32));
+    }
+
+    [Fact]
+    public void ToRaw_Throws_When_Not_Der()
+    {
+        var raw = new byte[64];
+        Assert.Throws<CryptographicException>(() => GostSignatureEncoding.ToRaw(raw, coordinateLength: 32));
+    }
+}
+#endif

src/__Libraries/__Tests/StellaOps.Cryptography.Tests/OpenSslGostSignerTests.cs

@@ -0,0 +1,50 @@
+using System.Text;
+using System.Threading.Tasks;
+using Org.BouncyCastle.Asn1.CryptoPro;
+using Org.BouncyCastle.Asn1.Rosstandart;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.Crypto.Generators;
+using Org.BouncyCastle.Crypto.Parameters;
+using Org.BouncyCastle.Crypto.Prng;
+using Org.BouncyCastle.Security;
+using StellaOps.Cryptography;
+using StellaOps.Cryptography.Plugin.OpenSslGost;
+using Xunit;
+
+namespace StellaOps.Cryptography.Tests;
+
+public class OpenSslGostSignerTests
+{
+    [Fact]
+    public async Task SignAndVerify_WithManagedProvider_Succeeds()
+    {
+        var keyPair = GenerateKeyPair();
+        var entry = new OpenSslGostKeyEntry(
+            "ru-openssl-test",
+            SignatureAlgorithms.GostR3410_2012_256,
+            (ECPrivateKeyParameters)keyPair.Private,
+            (ECPublicKeyParameters)keyPair.Public,
+            certificate: null,
+            signatureFormat: GostSignatureFormat.Raw);
+
+        var signer = new OpenSslGostSigner(entry);
+        var payload = Encoding.UTF8.GetBytes("open-ssl-gost");
+
+        var signature = await signer.SignAsync(payload);
+        Assert.True(await signer.VerifyAsync(payload, signature));
+
+        var jwk = signer.ExportPublicJsonWebKey();
+        Assert.Equal("ru-openssl-test", jwk.Kid);
+        Assert.Equal(SignatureAlgorithms.GostR3410_2012_256, jwk.Alg);
+        Assert.Empty(jwk.X5c);
+    }
+
+    private static AsymmetricCipherKeyPair GenerateKeyPair()
+    {
+        var generator = new ECKeyPairGenerator("ECGOST3410");
+        var parameters = ECGost3410NamedCurves.GetByOid(RosstandartObjectIdentifiers.id_tc26_gost_3410_12_256_paramSetA);
+        var domain = new ECDomainParameters(parameters.Curve, parameters.G, parameters.N, parameters.H);
+        generator.Init(new ECKeyGenerationParameters(domain, new SecureRandom(new CryptoApiRandomGenerator())));
+        return generator.GenerateKeyPair();
+    }
+}

src/__Libraries/__Tests/StellaOps.Cryptography.Tests/StellaOps.Cryptography.Tests.csproj

@@ -13,5 +13,9 @@
     <ProjectReference Include="../../StellaOps.Cryptography/StellaOps.Cryptography.csproj" />
     <ProjectReference Include="../../StellaOps.Cryptography.DependencyInjection/StellaOps.Cryptography.DependencyInjection.csproj" />
     <ProjectReference Include="../../StellaOps.Cryptography.Plugin.BouncyCastle/StellaOps.Cryptography.Plugin.BouncyCastle.csproj" />
+    <ProjectReference Include="../../StellaOps.Cryptography.Plugin.OpenSslGost/StellaOps.Cryptography.Plugin.OpenSslGost.csproj" />
   </ItemGroup>
-</Project>
+  <ItemGroup Condition="'$(StellaOpsEnableCryptoPro)' == 'true'">
+    <ProjectReference Include="../../StellaOps.Cryptography.Plugin.CryptoPro/StellaOps.Cryptography.Plugin.CryptoPro.csproj" />
+  </ItemGroup>
+</Project>