HttpWebRequest allow returning redirect response (#34560)

* HttpWebRequest allow returning redirect response

Throw WebException for 3xx responses only when `AllowAutoRedirect = true`

Fixes #1074

* Simplify status code check

Author: centreboard

src/libraries/System.Net.Requests/src/System/Net/HttpWebRequest.cs

@@ -1200,7 +1200,8 @@ private async Task<WebResponse> SendRequest()
 
                 HttpWebResponse response = new HttpWebResponse(responseMessage, _requestUri, _cookieContainer);
 
-                if (!responseMessage.IsSuccessStatusCode)
+                int maxSuccessStatusCode = AllowAutoRedirect ? 299 : 399;
+                if ((int)response.StatusCode > maxSuccessStatusCode || (int)response.StatusCode < 200)
                 {
                     throw new WebException(
                         SR.Format(SR.net_servererror, (int)response.StatusCode, response.StatusDescription),

src/libraries/System.Net.Requests/tests/HttpWebRequestTest.cs

@@ -1197,6 +1197,46 @@ public void BeginGetResponse_CreatePostRequestThenAbort_ThrowsWebException(Uri r
             Assert.Equal(WebExceptionStatus.RequestCanceled, ex.Status);
         }
 
+        [Fact]
+        public async Task GetResponseAsync_AllowAutoRedirectTrueWithTooManyRedirects_ThrowsWebException()
+        {
+            await LoopbackServer.CreateClientAndServerAsync(async uri =>
+            {
+                HttpWebRequest request = WebRequest.CreateHttp(uri);
+                request.AllowAutoRedirect = true;
+                request.MaximumAutomaticRedirections = 1;
+                WebException ex = await Assert.ThrowsAsync<WebException>(async () => await request.GetResponseAsync());
+                Assert.Equal(WebExceptionStatus.ProtocolError, ex.Status);
+            }, server => server.HandleRequestAsync(HttpStatusCode.Redirect));
+        }
+
+        [Fact]
+        public async Task GetResponseAsync_AllowAutoRedirectFalseWithRedirect_ReturnsRedirectResponse()
+        {
+            await LoopbackServer.CreateClientAndServerAsync(async uri =>
+            {
+                HttpWebRequest request = WebRequest.CreateHttp(uri);
+                request.AllowAutoRedirect = false;
+                using (WebResponse response = await request.GetResponseAsync())
+                {
+                    HttpWebResponse httpResponse = Assert.IsType<HttpWebResponse>(response);
+                    Assert.Equal(HttpStatusCode.Redirect, httpResponse.StatusCode);
+                }
+            }, server => server.HandleRequestAsync(HttpStatusCode.Redirect));
+        }
+
+        [Fact]
+        public async Task GetResponseAsync_AllowAutoRedirectFalseWithBadRequest_ThrowsWebException()
+        {
+            await LoopbackServer.CreateClientAndServerAsync(async uri =>
+            {
+                HttpWebRequest request = WebRequest.CreateHttp(uri);
+                request.AllowAutoRedirect = false;
+                WebException ex = await Assert.ThrowsAsync<WebException>(async () => await request.GetResponseAsync());
+                Assert.Equal(WebExceptionStatus.ProtocolError, ex.Status);
+            }, server => server.HandleRequestAsync(HttpStatusCode.BadRequest));
+        }
+
         [Fact]
         public async Task GetRequestStreamAsync_WriteAndDisposeRequestStreamThenOpenRequestStream_ThrowsArgumentException()
         {