Use BCL MLKem

.github/workflows/build.yml

@@ -107,6 +107,11 @@ jobs:
     name: Windows Integration Tests .NET Framework
     runs-on: windows-2025
     steps:
+    - name: Print Windows Version
+      shell: pwsh
+      run: |
+        Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion"
+
     - name: Checkout
       uses: actions/checkout@v5
       with:
@@ -149,6 +154,11 @@ jobs:
     name: Windows Integration Tests .NET
     runs-on: windows-2025
     steps:
+    - name: Print Windows Version
+      shell: pwsh
+      run: |
+        Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion"
+
     - name: Checkout
       uses: actions/checkout@v5
       with:
@@ -178,7 +188,7 @@ jobs:
           --logger GitHubActions `
           -p:CollectCoverage=true `
           -p:CoverletOutputFormat=cobertura `
-          -p:CoverletOutput=..\..\coverlet\windows_integration_test_net_9_coverage.xml `
+          -p:CoverletOutput=..\..\coverlet\windows_integration_test_net_10_coverage.xml `
           test\Renci.SshNet.IntegrationTests\
 
     - name: Archive Coverlet Results

src/Renci.SshNet/Renci.SshNet.csproj

@@ -49,14 +49,10 @@
     </PackageReference>
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'net462' ">
+  <ItemGroup Condition=" !$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net10.0')) ">
     <PackageReference Include="Microsoft.Bcl.Cryptography" />
   </ItemGroup>
 
-  <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="System.Formats.Asn1" />
-  </ItemGroup>
-
   <ItemGroup>
     <None Include="..\..\images\logo\png\SS-NET-icon-h500.png">
       <Pack>True</Pack>

src/Renci.SshNet/Security/KeyExchangeMLKem768X25519Sha256.BclImpl.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Security.Cryptography;
+
+namespace Renci.SshNet.Security
+{
+    internal sealed partial class KeyExchangeMLKem768X25519Sha256
+    {
+        private sealed class MLKemBclImpl : Impl
+        {
+            private MLKem _mlkem;
+
+            public override byte[] GenerateClientPublicKey()
+            {
+                _mlkem = MLKem.GenerateKey(MLKemAlgorithm.MLKem768);
+                return _mlkem.ExportEncapsulationKey();
+            }
+
+            public override byte[] CalculateAgreement(byte[] serverPublicKey)
+            {
+                var mlkemSecret = new byte[MLKemAlgorithm.MLKem768.SharedSecretSizeInBytes];
+                _mlkem.Decapsulate(serverPublicKey.AsSpan(0, MLKemAlgorithm.MLKem768.CiphertextSizeInBytes), mlkemSecret);
+                return mlkemSecret;
+            }
+
+            protected override void Dispose(bool disposing)
+            {
+                if (disposing)
+                {
+                    _mlkem?.Dispose();
+                }
+
+                base.Dispose(disposing);
+            }
+        }
+    }
+}

src/Renci.SshNet/Security/KeyExchangeMLKem768X25519Sha256.BouncyCastleImpl.cs

@@ -0,0 +1,36 @@
+using Org.BouncyCastle.Crypto.Generators;
+using Org.BouncyCastle.Crypto.Kems;
+using Org.BouncyCastle.Crypto.Parameters;
+
+using Renci.SshNet.Abstractions;
+
+namespace Renci.SshNet.Security
+{
+    internal sealed partial class KeyExchangeMLKem768X25519Sha256
+    {
+        private sealed class MLKemBouncyCastleImpl : Impl
+        {
+            private MLKemDecapsulator _mlkemDecapsulator;
+
+            public override byte[] GenerateClientPublicKey()
+            {
+                var mlkem768KeyPairGenerator = new MLKemKeyPairGenerator();
+                mlkem768KeyPairGenerator.Init(new MLKemKeyGenerationParameters(CryptoAbstraction.SecureRandom, MLKemParameters.ml_kem_768));
+                var mlkem768KeyPair = mlkem768KeyPairGenerator.GenerateKeyPair();
+
+                _mlkemDecapsulator = new MLKemDecapsulator(MLKemParameters.ml_kem_768);
+                _mlkemDecapsulator.Init(mlkem768KeyPair.Private);
+
+                return ((MLKemPublicKeyParameters)mlkem768KeyPair.Public).GetEncoded();
+            }
+
+            public override byte[] CalculateAgreement(byte[] serverPublicKey)
+            {
+                var mlkemSecret = new byte[_mlkemDecapsulator.SecretLength];
+                _mlkemDecapsulator.Decapsulate(serverPublicKey, 0, _mlkemDecapsulator.EncapsulationLength, mlkemSecret, 0, _mlkemDecapsulator.SecretLength);
+
+                return mlkemSecret;
+            }
+        }
+    }
+}

src/Renci.SshNet/Security/KeyExchangeMLKem768X25519Sha256.cs

@@ -2,19 +2,16 @@
 using System.Linq;
 using System.Security.Cryptography;
 
-using Org.BouncyCastle.Crypto.Generators;
-using Org.BouncyCastle.Crypto.Kems;
 using Org.BouncyCastle.Crypto.Parameters;
 
-using Renci.SshNet.Abstractions;
 using Renci.SshNet.Common;
 using Renci.SshNet.Messages.Transport;
 
 namespace Renci.SshNet.Security
 {
-    internal sealed class KeyExchangeMLKem768X25519Sha256 : KeyExchangeECCurve25519
+    internal sealed partial class KeyExchangeMLKem768X25519Sha256 : KeyExchangeECCurve25519
     {
-        private MLKemDecapsulator _mlkemDecapsulator;
+        private Impl _mlkemImpl;
 
         /// <summary>
         /// Gets algorithm name.
@@ -42,14 +39,16 @@ protected override void StartImpl()
 
             Session.KeyExchangeHybridReplyMessageReceived += Session_KeyExchangeHybridReplyMessageReceived;
 
-            var mlkem768KeyPairGenerator = new MLKemKeyPairGenerator();
-            mlkem768KeyPairGenerator.Init(new MLKemKeyGenerationParameters(CryptoAbstraction.SecureRandom, MLKemParameters.ml_kem_768));
-            var mlkem768KeyPair = mlkem768KeyPairGenerator.GenerateKeyPair();
-
-            _mlkemDecapsulator = new MLKemDecapsulator(MLKemParameters.ml_kem_768);
-            _mlkemDecapsulator.Init(mlkem768KeyPair.Private);
+            if (MLKem.IsSupported)
+            {
+                _mlkemImpl = new MLKemBclImpl();
+            }
+            else
+            {
+                _mlkemImpl = new MLKemBouncyCastleImpl();
+            }
 
-            var mlkem768PublicKey = ((MLKemPublicKeyParameters)mlkem768KeyPair.Public).GetEncoded();
+            var mlkem768PublicKey = _mlkemImpl.GenerateClientPublicKey();
 
             var x25519PublicKey = _impl.GenerateClientPublicKey();
 
@@ -101,20 +100,28 @@ private void HandleServerHybridReply(byte[] hostKey, byte[] serverExchangeValue,
             _hostKey = hostKey;
             _signature = signature;
 
-            if (serverExchangeValue.Length != _mlkemDecapsulator.EncapsulationLength + X25519PublicKeyParameters.KeySize)
+            if (serverExchangeValue.Length != MLKemAlgorithm.MLKem768.CiphertextSizeInBytes + X25519PublicKeyParameters.KeySize)
             {
                 throw new SshConnectionException(
                     string.Format(CultureInfo.CurrentCulture, "Bad S_Reply length: {0}.", serverExchangeValue.Length),
                     DisconnectReason.KeyExchangeFailed);
             }
 
-            var mlkemSecret = new byte[_mlkemDecapsulator.SecretLength];
-
-            _mlkemDecapsulator.Decapsulate(serverExchangeValue, 0, _mlkemDecapsulator.EncapsulationLength, mlkemSecret, 0, _mlkemDecapsulator.SecretLength);
+            var mlkemSecret = _mlkemImpl.CalculateAgreement(serverExchangeValue);
 
-            var x25519Agreement = _impl.CalculateAgreement(serverExchangeValue.Take(_mlkemDecapsulator.EncapsulationLength, X25519PublicKeyParameters.KeySize));
+            var x25519Agreement = _impl.CalculateAgreement(serverExchangeValue.Take(MLKemAlgorithm.MLKem768.CiphertextSizeInBytes, X25519PublicKeyParameters.KeySize));
 
             SharedKey = SHA256.HashData(mlkemSecret.Concat(x25519Agreement));
         }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _mlkemImpl?.Dispose();
+            }
+
+            base.Dispose(disposing);
+        }
     }
 }