From df65e3ab0db8fd55a6a02b8c067565abc926136f Mon Sep 17 00:00:00 2001
From: ConfusedPolarBear <33811686+ConfusedPolarBear@users.noreply.github.com>
Date: Sat, 2 May 2020 15:29:05 -0500
Subject: [PATCH 1/3] Add Access-Control-Allow-Origin header to exceptions

Fixes #1794
---
 Emby.Server.Implementations/HttpServer/HttpListenerHost.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
index 211a0c1d99..77878eacc9 100644
--- a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
+++ b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
@@ -542,6 +542,11 @@ namespace Emby.Server.Implementations.HttpServer
                     var requestInnerEx = GetActualException(requestEx);
                     var statusCode = GetStatusCode(requestInnerEx);
 
+                    if (!httpRes.Headers.ContainsKey("Access-Control-Allow-Origin"))
+                    {
+                        httpRes.Headers.Add("Access-Control-Allow-Origin", "*");
+                    }
+
                     // Do not handle 500 server exceptions manually when in development mode
                     // The framework-defined development exception page will be returned instead
                     if (statusCode == 500 && _hostEnvironment.IsDevelopment())

From 85f04af04c7d33477df5486ae80b6fa9a2a2bfd7 Mon Sep 17 00:00:00 2001
From: ConfusedPolarBear <33811686+ConfusedPolarBear@users.noreply.github.com>
Date: Mon, 18 May 2020 14:30:23 -0500
Subject: [PATCH 2/3] Reuse existing CORS function

---
 Emby.Server.Implementations/HttpServer/HttpListenerHost.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
index 9554b9f462..9a4e858a51 100644
--- a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
+++ b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
@@ -497,9 +497,9 @@ namespace Emby.Server.Implementations.HttpServer
                     var requestInnerEx = GetActualException(requestEx);
                     var statusCode = GetStatusCode(requestInnerEx);
 
-                    if (!httpRes.Headers.ContainsKey("Access-Control-Allow-Origin"))
+                    foreach (var (key, value) in GetDefaultCorsHeaders(httpReq))
                     {
-                        httpRes.Headers.Add("Access-Control-Allow-Origin", "*");
+                        httpRes.Headers.Add(key, value);
                     }
 
                     bool ignoreStackTrace =

From 949e4d3e64a73102d0a87c8b34918397a2cec303 Mon Sep 17 00:00:00 2001
From: ConfusedPolarBear <33811686+ConfusedPolarBear@users.noreply.github.com>
Date: Mon, 18 May 2020 16:54:36 -0500
Subject: [PATCH 3/3] Apply suggestions from code review

---
 Emby.Server.Implementations/HttpServer/HttpListenerHost.cs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
index 9a4e858a51..7de4f168c1 100644
--- a/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
+++ b/Emby.Server.Implementations/HttpServer/HttpListenerHost.cs
@@ -499,7 +499,10 @@ namespace Emby.Server.Implementations.HttpServer
 
                     foreach (var (key, value) in GetDefaultCorsHeaders(httpReq))
                     {
-                        httpRes.Headers.Add(key, value);
+                        if (!httpRes.Headers.ContainsKey(key))
+                        {
+                            httpRes.Headers.Add(key, value);
+                        }
                     }
 
                     bool ignoreStackTrace =