Fix SendAsync from impersonated context with default credentials

src/libraries/Common/tests/System/Net/Http/LoopbackServer.cs

@@ -866,6 +866,12 @@ public override async Task<Byte[]> ReadRequestBodyAsync()
                 return buffer;
             }
 
+            public void CompleteRequestProcessing()
+            {
+                _contentLength = 0;
+                _bodyRead = false;
+            }
+
             public override async Task SendResponseAsync(HttpStatusCode statusCode = HttpStatusCode.OK, IList<HttpHeaderData> headers = null, string content = "", bool isFinal = true, int requestId = 0)
             {
                 MemoryStream headerBytes = new MemoryStream();

src/libraries/Common/tests/TestUtilities/System/WindowsIdentityFixture.cs

@@ -0,0 +1,141 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.ComponentModel;
+using System.Linq;
+using System.Net;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using System.Security.Principal;
+using System.Threading.Tasks;
+using Microsoft.Win32.SafeHandles;
+
+namespace System
+{
+    public class WindowsIdentityFixture : IDisposable
+    {
+        public WindowsTestAccount TestAccount { get; private set; }
+
+        public WindowsIdentityFixture()
+        {
+            TestAccount = new WindowsTestAccount("CorFxTstWiIde01kiu");
+        }
+
+        public void Dispose()
+        {
+            TestAccount.Dispose();
+        }
+    }
+
+    public sealed class WindowsTestAccount : IDisposable
+    {
+        private readonly string _userName;
+        private SafeAccessTokenHandle _accountTokenHandle;
+        public SafeAccessTokenHandle AccountTokenHandle => _accountTokenHandle;
+        public string AccountName { get; private set; }
+
+        public WindowsTestAccount(string userName)
+        {
+            _userName = userName;
+            CreateUser();
+        }
+
+        private void CreateUser()
+        {
+            string testAccountPassword;
+            using (RandomNumberGenerator rng = RandomNumberGenerator.Create())
+            {
+                byte[] randomBytes = new byte[33];
+                rng.GetBytes(randomBytes);
+
+                // Add special chars to ensure it satisfies password requirements.
+                testAccountPassword = Convert.ToBase64String(randomBytes) + "_-As@!%*(1)4#2";
+
+                USER_INFO_1 userInfo = new USER_INFO_1
+                {
+                    usri1_name = _userName,
+                    usri1_password = testAccountPassword,
+                    usri1_priv = 1
+                };
+
+                // Create user and remove/create if already exists
+                uint result = NetUserAdd(null, 1, ref userInfo, out uint param_err);
+
+                // error codes https://docs.microsoft.com/en-us/windows/desktop/netmgmt/network-management-error-codes
+                // 0 == NERR_Success
+                if (result == 2224) // NERR_UserExists
+                {
+                    result = NetUserDel(null, userInfo.usri1_name);
+                    if (result != 0)
+                    {
+                        throw new Win32Exception((int)result);
+                    }
+                    result = NetUserAdd(null, 1, ref userInfo, out param_err);
+                    if (result != 0)
+                    {
+                        throw new Win32Exception((int)result);
+                    }
+                }
+
+                const int LOGON32_PROVIDER_DEFAULT = 0;
+                const int LOGON32_LOGON_INTERACTIVE = 2;
+
+                if (!LogonUser(_userName, ".", testAccountPassword, LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT, out _accountTokenHandle))
+                {
+                    _accountTokenHandle = null;
+                    throw new Exception($"Failed to get SafeAccessTokenHandle for test account {_userName}", new Win32Exception());
+                }
+
+                bool gotRef = false;
+                try
+                {
+                    _accountTokenHandle.DangerousAddRef(ref gotRef);
+                    IntPtr logonToken = _accountTokenHandle.DangerousGetHandle();
+                    AccountName = new WindowsIdentity(logonToken).Name;
+                }
+                finally
+                {
+                    if (gotRef)
+                        _accountTokenHandle.DangerousRelease();
+                }
+            }
+        }
+
+        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern bool LogonUser(string userName, string domain, string password, int logonType, int logonProvider, out SafeAccessTokenHandle safeAccessTokenHandle);
+
+        [DllImport("netapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
+        internal static extern uint NetUserAdd([MarshalAs(UnmanagedType.LPWStr)]string servername, uint level, ref USER_INFO_1 buf, out uint parm_err);
+
+        [DllImport("netapi32.dll")]
+        internal static extern uint NetUserDel([MarshalAs(UnmanagedType.LPWStr)]string servername, [MarshalAs(UnmanagedType.LPWStr)]string username);
+
+        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+        internal struct USER_INFO_1
+        {
+            public string usri1_name;
+            public string usri1_password;
+            public uint usri1_password_age;
+            public uint usri1_priv;
+            public string usri1_home_dir;
+            public string usri1_comment;
+            public uint usri1_flags;
+            public string usri1_script_path;
+        }
+
+        public void Dispose()
+        {
+            _accountTokenHandle?.Dispose();
+
+            uint result = NetUserDel(null, _userName);
+
+            // 2221= NERR_UserNotFound
+            if (result != 0 && result != 2221)
+            {
+                throw new Win32Exception((int)result);
+            }
+        }
+    }
+ }
+

src/libraries/Common/tests/TestUtilities/TestUtilities.csproj

@@ -33,6 +33,7 @@
     <Compile Include="System\PlatformDetection.cs" />
     <Compile Include="System\PlatformDetection.Unix.cs" />
     <Compile Include="System\PlatformDetection.Windows.cs" />
+    <Compile Include="System\WindowsIdentityFixture.cs" />
     <!--
       Interop.Library is not designed to support runtime checks therefore we are picking the Windows
       variant from the Common folder and adding the missing members manually.

src/libraries/System.Net.Http/src/System/Net/Http/SocketsHttpHandler/HttpConnectionSettings.cs

@@ -96,8 +96,6 @@ public HttpConnectionSettings CloneAndNormalize()
                 _connectTimeout = _connectTimeout,
                 _credentials = _credentials,
                 _defaultProxyCredentials = _defaultProxyCredentials,
-                _defaultCredentialsUsedForProxy = _defaultCredentialsUsedForProxy,
-                _defaultCredentialsUsedForServer = _defaultCredentialsUsedForServer,
                 _expect100ContinueTimeout = _expect100ContinueTimeout,
                 _maxAutomaticRedirections = _maxAutomaticRedirections,
                 _maxConnectionsPerServer = _maxConnectionsPerServer,
@@ -123,6 +121,8 @@ public HttpConnectionSettings CloneAndNormalize()
                 _plaintextStreamFilter = _plaintextStreamFilter,
                 _initialHttp2StreamWindowSize = _initialHttp2StreamWindowSize,
                 _activityHeadersPropagator = _activityHeadersPropagator,
+                _defaultCredentialsUsedForProxy = _proxy != null && (_proxy.Credentials == CredentialCache.DefaultCredentials || _defaultProxyCredentials == CredentialCache.DefaultCredentials),
+                _defaultCredentialsUsedForServer = _credentials == CredentialCache.DefaultCredentials,
             };
 
             // TODO: Remove if/when QuicImplementationProvider is removed from System.Net.Quic.