From 3e0b689ac2ea72a8dee81f8ae3a349610ac1fb0c Mon Sep 17 00:00:00 2001
From: nulltoken <emeric.fermas@gmail.com>
Date: Fri, 6 Jul 2018 22:00:25 +0200
Subject: [PATCH] Ensure ClientHandler properly honors Host header (#1483) Fix
 #1481

---
 .../ClientHandler.cs                          | 20 ++++++++++------
 .../TestServerTests.cs                        | 24 +++++++++++++++++++
 2 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/src/Microsoft.AspNetCore.TestHost/ClientHandler.cs b/src/Microsoft.AspNetCore.TestHost/ClientHandler.cs
index 2109809d1a..5471e23d19 100644
--- a/src/Microsoft.AspNetCore.TestHost/ClientHandler.cs
+++ b/src/Microsoft.AspNetCore.TestHost/ClientHandler.cs
@@ -72,10 +72,20 @@ namespace Microsoft.AspNetCore.TestHost
                 req.Method = request.Method.ToString();
 
                 req.Scheme = request.RequestUri.Scheme;
-                req.Host = HostString.FromUriComponent(request.RequestUri);
-                if (request.RequestUri.IsDefaultPort)
+
+                foreach (var header in request.Headers)
                 {
-                    req.Host = new HostString(req.Host.Host);
+                    req.Headers.Append(header.Key, header.Value.ToArray());
+                }
+
+                if (req.Host == null || !req.Host.HasValue)
+                {
+                    // If Host wasn't explicitly set as a header, let's infer it from the Uri
+                    req.Host = HostString.FromUriComponent(request.RequestUri);
+                    if (request.RequestUri.IsDefaultPort)
+                    {
+                        req.Host = new HostString(req.Host.Host);
+                    }
                 }
 
                 req.Path = PathString.FromUriComponent(request.RequestUri);
@@ -87,10 +97,6 @@ namespace Microsoft.AspNetCore.TestHost
                 }
                 req.QueryString = QueryString.FromUriComponent(request.RequestUri);
 
-                foreach (var header in request.Headers)
-                {
-                    req.Headers.Append(header.Key, header.Value.ToArray());
-                }
                 if (requestContent != null)
                 {
                     foreach (var header in requestContent.Headers)
diff --git a/test/Microsoft.AspNetCore.TestHost.Tests/TestServerTests.cs b/test/Microsoft.AspNetCore.TestHost.Tests/TestServerTests.cs
index b1eee1fd94..a4175a75cb 100644
--- a/test/Microsoft.AspNetCore.TestHost.Tests/TestServerTests.cs
+++ b/test/Microsoft.AspNetCore.TestHost.Tests/TestServerTests.cs
@@ -16,6 +16,7 @@ using Microsoft.AspNetCore.Testing.xunit;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DiagnosticAdapter;
 using Microsoft.Extensions.Logging;
+using Microsoft.Net.Http.Headers;
 using Xunit;
 
 namespace Microsoft.AspNetCore.TestHost
@@ -576,6 +577,29 @@ namespace Microsoft.AspNetCore.TestHost
             Assert.NotNull(listener.UnhandledException?.Exception);
         }
 
+        [Theory]
+        [InlineData("http://localhost:12345")]
+        [InlineData("http://localhost:12345/")]
+        [InlineData("http://localhost:12345/hellohellohello")]
+        [InlineData("/isthereanybodyinthere?")]
+        public async Task ManuallySetHostWinsOverInferredHostFromRequestUri(string uri)
+        {
+            RequestDelegate appDelegate = ctx =>
+                ctx.Response.WriteAsync(ctx.Request.Headers[HeaderNames.Host]);
+
+            var builder = new WebHostBuilder().Configure(app => app.Run(appDelegate));
+            var server = new TestServer(builder);
+            var client = server.CreateClient();
+
+            var request = new HttpRequestMessage(HttpMethod.Get, uri);
+            request.Headers.Host = "otherhost:5678";
+
+            var response = await client.SendAsync(request);
+            var responseBody = await response.Content.ReadAsStringAsync();
+
+            Assert.Equal("otherhost:5678", responseBody);
+        }
+
         public class TestDiagnosticListener
         {
             public class OnBeginRequestEventData