Do not inherit socket handles #2789

Author: Tratcher

src/Kestrel.Transport.Sockets/Internal/NativeMethods.cs

@@ -0,0 +1,31 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets.Internal
+{
+    internal static class NativeMethods
+    {
+        [DllImport("kernel32.dll", SetLastError = true)]
+        private static extern bool SetHandleInformation(IntPtr hObject, HANDLE_FLAGS dwMask, HANDLE_FLAGS dwFlags);
+
+        [Flags]
+        private enum HANDLE_FLAGS : uint
+        {
+            None = 0,
+            INHERIT = 1,
+            PROTECT_FROM_CLOSE = 2
+        }
+
+        internal static void DisableHandleInheritance(Socket socket)
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                SetHandleInformation(socket.Handle, HANDLE_FLAGS.INHERIT, 0);
+            }
+        }
+    }
+}

src/Kestrel.Transport.Sockets/SocketTransport.cs

@@ -80,6 +80,7 @@ public Task BindAsync()
             IPEndPoint endPoint = _endPointInformation.IPEndPoint;
 
             var listenSocket = new Socket(endPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
+            NativeMethods.DisableHandleInheritance(listenSocket);
 
             // Kestrel expects IPv6Any to bind to both IPv6 and IPv4
             if (endPoint.Address == IPAddress.IPv6Any)

test/Kestrel.Transport.FunctionalTests/HandleInheritanceTests.cs

@@ -0,0 +1,60 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Diagnostics;
+using System.Net.Sockets;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Testing;
+using Microsoft.AspNetCore.Testing.xunit;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Server.Kestrel.FunctionalTests
+{
+    public class HandleInheritanceTests : TestApplicationErrorLoggerLoggedTest
+    {
+        [ConditionalFact]
+        [OSSkipCondition(OperatingSystems.MacOSX, SkipReason = "No fix available for Mac https://github.com/aspnet/KestrelHttpServer/pull/2944#issuecomment-426397600")]
+        public async Task SpawnChildProcess_DoesNotInheritListenHandle()
+        {
+            var hostBuilder = TransportSelector.GetWebHostBuilder()
+                .UseKestrel()
+                .ConfigureServices(AddTestLogging)
+                .UseUrls("http://127.0.0.1:0")
+                .Configure(app =>
+                {
+                    app.Run(context =>
+                    {
+                        return context.Response.WriteAsync("Hello World");
+                    });
+                });
+
+            using (var host = hostBuilder.Build())
+            {
+                await host.StartAsync();
+
+                var processInfo = new ProcessStartInfo
+                {
+                    FileName = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "cmd.exe" : "vi",
+                    CreateNoWindow = true,
+                };
+                using (var process = Process.Start(processInfo))
+                {
+                    var port = host.GetPort();
+                    await host.StopAsync();
+
+                    // We should not be able to connect if the handle was correctly closed and not inherited by the child process.
+                    using (var client = new TcpClient())
+                    {
+                        await Assert.ThrowsAnyAsync<SocketException>(() => client.ConnectAsync("127.0.0.1", port));
+                    }
+
+                    process.Kill();
+                }
+            }
+        }
+    }
+}