Configure ALPN for callback scenarios

src/Servers/Kestrel/Core/src/ListenOptionsHttpsExtensions.cs

@@ -288,6 +288,8 @@ public static ListenOptions UseHttps(this ListenOptions listenOptions, TlsHandsh
             listenOptions.IsTls = true;
             listenOptions.Use(next =>
             {
+                // Set the list of protocols from listen options
+                callbackOptions.HttpProtocols = listenOptions.Protocols;
                 var middleware = new HttpsConnectionMiddleware(next, callbackOptions, loggerFactory);
                 return middleware.OnConnectionAsync;
             });

src/Servers/Kestrel/Core/src/Middleware/HttpsConnectionMiddleware.cs

@@ -46,6 +46,7 @@ internal class HttpsConnectionMiddleware
         // The following fields are only set by TlsHandshakeCallbackOptions ctor.
         private readonly Func<TlsHandshakeCallbackContext, ValueTask<SslServerAuthenticationOptions>>? _tlsCallbackOptions;
         private readonly object? _tlsCallbackOptionsState;
+        private readonly HttpProtocols _httpProtocols;
 
         // Pool for cancellation tokens that cancel the handshake
         private readonly CancellationTokenSourcePool _ctsPool = new();
@@ -127,6 +128,7 @@ internal HttpsConnectionMiddleware(
 
             _tlsCallbackOptions = tlsCallbackOptions.OnConnection;
             _tlsCallbackOptionsState = tlsCallbackOptions.OnConnectionState;
+            _httpProtocols = ValidateAndNormalizeHttpProtocols(tlsCallbackOptions.HttpProtocols, _logger);
             _sslStreamFactory = s => new SslStream(s);
         }
 
@@ -434,6 +436,11 @@ private static async ValueTask<SslServerAuthenticationOptions> ServerOptionsCall
             var sslOptions = await middleware._tlsCallbackOptions!(callbackContext);
             feature.AllowDelayedClientCertificateNegotation = callbackContext.AllowDelayedClientCertificateNegotation;
 
+            // The callback didn't set ALPN so we will.
+            if (sslOptions.ApplicationProtocols == null)
+            {
+                ConfigureAlpn(sslOptions, middleware._httpProtocols);
+            }
             KestrelEventSource.Log.TlsHandshakeStart(context, sslOptions);
 
             return sslOptions;

src/Servers/Kestrel/Core/src/TlsHandshakeCallbackOptions.cs

@@ -42,5 +42,8 @@ public TimeSpan HandshakeTimeout
                 _handshakeTimeout = value != Timeout.InfiniteTimeSpan ? value : TimeSpan.MaxValue;
             }
         }
+
+        // Copied from the ListenOptions to enable ALPN
+        internal HttpProtocols HttpProtocols { get; set; }
     }
 }

src/Servers/Kestrel/test/InMemory.FunctionalTests/HttpsConnectionMiddlewareTests.cs

@@ -793,6 +793,65 @@ void ConfigureListenOptions(ListenOptions listenOptions)
             await AssertConnectionResult(stream, true, expectedBody);
         }
 
+        [ConditionalFact]
+        [OSSkipCondition(OperatingSystems.MacOSX, SkipReason = "ALPN not supported")]
+        public async Task ServerOptionsSelectionCallback_SetsALPN()
+        {
+            static void ConfigureListenOptions(ListenOptions listenOptions)
+            {
+                listenOptions.UseHttps((_, _, _, _) =>
+                    ValueTask.FromResult(new SslServerAuthenticationOptions()
+                    {
+                        ServerCertificate = _x509Certificate2,
+                    }), state: null);
+            }
+
+            await using var server = new TestServer(context => Task.CompletedTask,
+                new TestServiceContext(LoggerFactory), ConfigureListenOptions);
+
+            using var connection = server.CreateConnection();
+            var stream = OpenSslStream(connection.Stream);
+            await stream.AuthenticateAsClientAsync(new SslClientAuthenticationOptions()
+            {
+                // Use a random host name to avoid the TLS session resumption cache.
+                TargetHost = Guid.NewGuid().ToString(),
+                ApplicationProtocols = new() { SslApplicationProtocol.Http2, SslApplicationProtocol.Http11, },
+            });
+            Assert.Equal(SslApplicationProtocol.Http2, stream.NegotiatedApplicationProtocol);
+        }
+
+        [ConditionalFact]
+        [OSSkipCondition(OperatingSystems.MacOSX, SkipReason = "ALPN not supported")]
+        public async Task TlsHandshakeCallbackOptionsOverload_SetsALPN()
+        {
+            static void ConfigureListenOptions(ListenOptions listenOptions)
+            {
+                listenOptions.UseHttps(new TlsHandshakeCallbackOptions()
+                {
+                    OnConnection = context =>
+                    {
+                        return ValueTask.FromResult(new SslServerAuthenticationOptions()
+                        {
+                            ServerCertificate = _x509Certificate2,
+                        });
+                    }
+                });
+            }
+
+            await using var server = new TestServer(context => Task.CompletedTask,
+                new TestServiceContext(LoggerFactory), ConfigureListenOptions);
+
+            using var connection = server.CreateConnection();
+            var stream = OpenSslStream(connection.Stream);
+            await stream.AuthenticateAsClientAsync(new SslClientAuthenticationOptions()
+            {
+                // Use a random host name to avoid the TLS session resumption cache.
+                TargetHost = Guid.NewGuid().ToString(),
+                ApplicationProtocols = new() { SslApplicationProtocol.Http2, SslApplicationProtocol.Http11, },
+            });
+            Assert.Equal(SslApplicationProtocol.Http2, stream.NegotiatedApplicationProtocol);
+        }
+
         [ConditionalFact]
         [OSSkipCondition(OperatingSystems.MacOSX | OperatingSystems.Linux, SkipReason = "Not supported yet.")]
         public async Task CanRenegotiateForClientCertificateOnPostIfDrained()