From 8d043cc4ddf585261b86fafbee52625be9a38f04 Mon Sep 17 00:00:00 2001
From: Akhil <Akaranth@grubhub.com>
Date: Mon, 15 Aug 2016 13:22:15 -0400
Subject: [PATCH] Do not return Access-Control-Allow-Headers on Non-Preflight
 Cors requests

Motivation:

The CorsHandler currently returns the Access-Control-Allow-Headers
header as on a Non-Preflight CORS request (Simple request).
As per the CORS specification the Access-Control-Allow-Headers header
should only be returned on Preflight requests. (not on simple requests).

https://www.w3.org/TR/2014/REC-cors-20140116/#access-control-allow-headers-response-header

http://www.html5rocks.com/static/images/cors_server_flowchart.png

Modifications:

Modified CorsHandler.java to not add the Access-Control-Allow-Headers
header when responding to Non-preflight CORS request.

Result:

Access-Control-Allow-Headers header will not be returned on a Simple
request (Non-preflight CORS request).
---
 .../java/io/netty/handler/codec/http/cors/CorsHandler.java  | 1 -
 .../io/netty/handler/codec/http/cors/CorsHandlerTest.java   | 6 ++++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java b/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
index d4a43fcaa2..b3bda3d004 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java
@@ -196,7 +196,6 @@ public class CorsHandler extends ChannelDuplexHandler {
             final HttpResponse response = (HttpResponse) msg;
             if (setOrigin(response)) {
                 setAllowCredentials(response);
-                setAllowHeaders(response);
                 setExposeHeaders(response);
             }
         }
diff --git a/codec-http/src/test/java/io/netty/handler/codec/http/cors/CorsHandlerTest.java b/codec-http/src/test/java/io/netty/handler/codec/http/cors/CorsHandlerTest.java
index df075e7fdb..9e170326b9 100644
--- a/codec-http/src/test/java/io/netty/handler/codec/http/cors/CorsHandlerTest.java
+++ b/codec-http/src/test/java/io/netty/handler/codec/http/cors/CorsHandlerTest.java
@@ -68,6 +68,7 @@ public class CorsHandlerTest {
     public void simpleRequestWithAnyOrigin() {
         final HttpResponse response = simpleRequest(forAnyOrigin().build(), "http://localhost:7777");
         assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is("*"));
+        assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
     }
 
     @Test
@@ -77,6 +78,7 @@ public class CorsHandlerTest {
                 .build(), "null");
         assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is("null"));
         assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_CREDENTIALS), is(equalTo("true")));
+        assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
     }
 
     @Test
@@ -84,6 +86,7 @@ public class CorsHandlerTest {
         final String origin = "http://localhost:8888";
         final HttpResponse response = simpleRequest(forOrigin(origin).build(), origin);
         assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is(origin));
+        assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
     }
 
     @Test
@@ -93,8 +96,10 @@ public class CorsHandlerTest {
         final String[] origins = {origin1, origin2};
         final HttpResponse response1 = simpleRequest(forOrigins(origins).build(), origin1);
         assertThat(response1.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is(origin1));
+        assertThat(response1.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
         final HttpResponse response2 = simpleRequest(forOrigins(origins).build(), origin2);
         assertThat(response2.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is(origin2));
+        assertThat(response2.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
     }
 
     @Test
@@ -103,6 +108,7 @@ public class CorsHandlerTest {
         final HttpResponse response = simpleRequest(
                 forOrigins("https://localhost:8888").build(), origin);
         assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_ORIGIN), is(nullValue()));
+        assertThat(response.headers().get(ACCESS_CONTROL_ALLOW_HEADERS), is(nullValue()));
     }
 
     @Test