Add option to decrypt Quic traffic in debug builds

src/libraries/System.Net.Quic/src/System.Net.Quic.csproj

@@ -32,6 +32,7 @@
     <Compile Include="$(CommonPath)System\Net\IPAddressParserStatics.cs" Link="Common\System\Net\IPAddressParserStatics.cs" />
     <Compile Include="$(CommonPath)System\Net\Internals\IPEndPointExtensions.cs" Link="Common\System\Net\Internals\IPEndPointExtensions.cs" />
     <Compile Include="$(CommonPath)System\Net\Security\TlsAlertMessage.cs" Link="Common\System\Net\Security\TlsAlertMessage.cs" />
+    <Compile Include="$(CommonPath)System\HexConverter.cs" Link="Common\System\HexConverter.cs" />
     <Compile Include="$(CommonPath)System\Net\Security\TargetHostNameHelper.cs" Link="Common\System\Net\Security\TargetHostNameHelper.cs" />
     <!-- IP parser -->
     <Compile Include="$(CommonPath)System\Net\IPv4AddressHelper.Common.cs" Link="System\Net\IPv4AddressHelper.Common.cs" />

src/libraries/System.Net.Quic/src/System/Net/Quic/Internal/MsQuicSafeHandle.cs

@@ -92,6 +92,23 @@ internal sealed class MsQuicContextSafeHandle : MsQuicSafeHandle
     /// </summary>
     private readonly MsQuicSafeHandle? _parent;
 
+#if DEBUG
+    /// <summary>
+    /// Native memory to hold TLS secrets. It needs to live same cycle as the underlying connection.
+    /// </summary>
+    private unsafe QUIC_TLS_SECRETS* _tlsSecrets;
+
+    public unsafe QUIC_TLS_SECRETS* GetSecretsBuffer()
+    {
+        if (_tlsSecrets == null)
+        {
+            _tlsSecrets = (QUIC_TLS_SECRETS*)NativeMemory.Alloc((nuint)sizeof(QUIC_TLS_SECRETS));
+        }
+
+        return _tlsSecrets;
+    }
+#endif
+
     public unsafe MsQuicContextSafeHandle(QUIC_HANDLE* handle, GCHandle context, SafeHandleType safeHandleType, MsQuicSafeHandle? parent = null)
         : base(handle, safeHandleType)
     {
@@ -108,7 +125,7 @@ public unsafe MsQuicContextSafeHandle(QUIC_HANDLE* handle, GCHandle context, Saf
         }
     }
 
-    protected override bool ReleaseHandle()
+    protected override unsafe bool ReleaseHandle()
     {
         base.ReleaseHandle();
         if (_context.IsAllocated)
@@ -123,6 +140,13 @@ protected override bool ReleaseHandle()
                 NetEventSource.Info(this, $"{this} {_parent} ref count decremented");
             }
         }
+#if DEBUG
+        if (_tlsSecrets != null)
+        {
+            NativeMemory.Clear(_tlsSecrets, (nuint)sizeof(QUIC_TLS_SECRETS));
+            NativeMemory.Free(_tlsSecrets);
+        }
+#endif
         return true;
     }
 }

src/libraries/System.Net.Quic/src/System/Net/Quic/Internal/MsQuicTlsSecret.cs

@@ -0,0 +1,109 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+#if DEBUG
+using System.Collections.Generic;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading;
+using Microsoft.Quic;
+using static Microsoft.Quic.MsQuic;
+
+namespace System.Net.Quic;
+
+internal sealed class MsQuicTlsSecret : IDisposable
+{
+    private static readonly string? s_keyLogFile = Environment.GetEnvironmentVariable("SSLKEYLOGFILE");
+    private static readonly FileStream? s_fileStream = s_keyLogFile != null ? File.Open(s_keyLogFile, FileMode.Append, FileAccess.Write) : null;
+
+    private unsafe QUIC_TLS_SECRETS* _tlsSecrets;
+
+    public static unsafe MsQuicTlsSecret? Create(MsQuicContextSafeHandle handle)
+    {
+        if (s_fileStream != null)
+        {
+            try
+            {
+                QUIC_TLS_SECRETS* ptr = handle.GetSecretsBuffer();
+                if (ptr != null)
+                {
+                    int status = MsQuicApi.Api.SetParam(handle, QUIC_PARAM_CONN_TLS_SECRETS, (uint)sizeof(QUIC_TLS_SECRETS), ptr);
+
+                    if (StatusSucceeded(status))
+                    {
+                        return new MsQuicTlsSecret(ptr);
+                    }
+                    else
+                    {
+                        if (NetEventSource.Log.IsEnabled())
+                        {
+                            NetEventSource.Error(handle, "Failed to set native memory for TLS secret.");
+                        }
+                    }
+                }
+            }
+            catch { };
+        }
+
+        return null;
+    }
+
+    private unsafe MsQuicTlsSecret(QUIC_TLS_SECRETS* memory)
+    {
+        _tlsSecrets = memory;
+    }
+
+    public void WriteSecret() => WriteSecret(s_fileStream);
+    public unsafe void WriteSecret(FileStream? stream)
+    {
+        if (stream != null && _tlsSecrets != null)
+        {
+            lock (stream)
+            {
+                string clientRandom = string.Empty;
+
+                if (_tlsSecrets->IsSet.ClientRandom != 0)
+                {
+                    clientRandom = HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ClientRandom, 32));
+                }
+
+                if (_tlsSecrets->IsSet.ClientHandshakeTrafficSecret != 0)
+                {
+                    stream.Write(Encoding.ASCII.GetBytes($"CLIENT_HANDSHAKE_TRAFFIC_SECRET {clientRandom} {HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ClientHandshakeTrafficSecret, _tlsSecrets->SecretLength))}\n"));
+                }
+
+                if (_tlsSecrets->IsSet.ServerHandshakeTrafficSecret != 0)
+                {
+                    stream.Write(Encoding.ASCII.GetBytes($"SERVER_HANDSHAKE_TRAFFIC_SECRET {clientRandom} {HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ServerHandshakeTrafficSecret, _tlsSecrets->SecretLength))}\n"));
+                }
+
+                if (_tlsSecrets->IsSet.ClientTrafficSecret0 != 0)
+                {
+                    stream.Write(Encoding.ASCII.GetBytes($"CLIENT_TRAFFIC_SECRET_0 {clientRandom} {HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ClientTrafficSecret0, _tlsSecrets->SecretLength))}\n"));
+                }
+
+                if (_tlsSecrets->IsSet.ServerTrafficSecret0 != 0)
+                {
+                    stream.Write(Encoding.ASCII.GetBytes($"SERVER_TRAFFIC_SECRET_0 {clientRandom} {HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ServerTrafficSecret0, _tlsSecrets->SecretLength))}\n"));
+                }
+
+                if (_tlsSecrets->IsSet.ClientEarlyTrafficSecret != 0)
+                {
+                    stream.Write(Encoding.ASCII.GetBytes($"CLIENT_EARLY_TRAFFIC_SECRET {clientRandom} {HexConverter.ToString(new ReadOnlySpan<byte>(_tlsSecrets->ClientEarlyTrafficSecret, _tlsSecrets->SecretLength))}\n"));
+                }
+
+                stream.Flush();
+            }
+        }
+    }
+
+    public unsafe void Dispose()
+    {
+        if (_tlsSecrets != null)
+        {
+            NativeMemory.Clear(_tlsSecrets, (nuint)sizeof(QUIC_TLS_SECRETS));
+        }
+    }
+}
+#endif

src/libraries/System.Net.Quic/src/System/Net/Quic/QuicConnection.cs

@@ -38,6 +38,13 @@ namespace System.Net.Quic;
 /// </remarks>
 public sealed partial class QuicConnection : IAsyncDisposable
 {
+#if DEBUG
+    /// <summary>
+    /// The actual secret structure wrapper passed to MsQuic.
+    /// </summary>
+    private MsQuicTlsSecret? _tlsSecret;
+#endif
+
     /// <summary>
     /// Returns <c>true</c> if QUIC is supported on the current machine and can be used; otherwise, <c>false</c>.
     /// </summary>
@@ -145,7 +152,6 @@ static async ValueTask<QuicConnection> StartConnectAsync(QuicClientConnectionOpt
     /// Set when CONNECTED is received.
     /// </summary>
     private SslApplicationProtocol _negotiatedApplicationProtocol;
-
     /// <summary>
     /// The remote endpoint used for this connection.
     /// </summary>
@@ -204,6 +210,10 @@ private unsafe QuicConnection()
             context.Free();
             throw;
         }
+
+#if DEBUG
+        _tlsSecret = MsQuicTlsSecret.Create(_handle);
+#endif
     }
 
     /// <summary>
@@ -231,6 +241,9 @@ internal unsafe QuicConnection(QUIC_HANDLE* handle, QUIC_NEW_CONNECTION_INFO* in
 
         _remoteEndPoint = info->RemoteAddress->ToIPEndPoint();
         _localEndPoint = info->LocalAddress->ToIPEndPoint();
+#if DEBUG
+        _tlsSecret = MsQuicTlsSecret.Create(_handle);
+#endif
     }
 
     private async ValueTask FinishConnectAsync(QuicClientConnectionOptions options, CancellationToken cancellationToken = default)
@@ -600,6 +613,9 @@ public async ValueTask DisposeAsync()
             return;
         }
 
+#if DEBUG
+        _tlsSecret?.Dispose();
+#endif
         // Check if the connection has been shut down and if not, shut it down.
         if (_shutdownTcs.TryInitialize(out ValueTask valueTask, this))
         {