#884 Allow explicitly setting PAC file for determining upstream proxy

Author: Gil Mirmovitch

src/Titanium.Web.Proxy/Helpers/WinHttp/WinHttpWebProxyFinder.cs

@@ -144,6 +144,16 @@ public void LoadFromIE()
             proxy = new WebProxy(new Uri("http://localhost"), BypassOnLocal, pi.BypassList);
         }
 
+        internal void UsePacFile(Uri upstreamProxyConfigurationScript)
+        {
+            AutomaticallyDetectSettings = true;
+            AutomaticConfigurationScript = upstreamProxyConfigurationScript;
+            BypassLoopback = true;
+            BypassOnLocal = false;
+            proxy = new WebProxy(new Uri("http://localhost"), BypassOnLocal);
+        }
+
+
         private ProxyInfo getProxyInfo()
         {
             var proxyConfig = new NativeMethods.WinHttp.WINHTTP_CURRENT_USER_IE_PROXY_CONFIG();

src/Titanium.Web.Proxy/ProxyServer.cs

@@ -136,6 +136,11 @@ public ProxyServer(string? rootCertificateName, string? rootCertificateIssuerNam
         /// </summary>
         public bool ForwardToUpstreamGateway { get; set; }
 
+        /// <summary>
+        /// If set, the upstream proxy will be detected by a script that will be loaded from the provided Uri
+        /// </summary>
+        public Uri UpstreamProxyConfigurationScript { get; set; }
+
         /// <summary>
         ///     Enable disable Windows Authentication (NTLM/Kerberos).
         ///     Note: NTLM/Kerberos will always send local credentials of current user
@@ -628,9 +633,17 @@ public void Start(bool changeSystemProxySettings = true)
 
             if (ForwardToUpstreamGateway && GetCustomUpStreamProxyFunc == null && systemProxySettingsManager != null)
             {
-                // Use WinHttp to handle PAC/WAPD scripts.
                 systemProxyResolver = new WinHttpWebProxyFinder();
-                systemProxyResolver.LoadFromIE();
+                if (UpstreamProxyConfigurationScript != null)
+                {
+                    //Use the provided proxy configuration script
+                    systemProxyResolver.UsePacFile(UpstreamProxyConfigurationScript);
+                }
+                else
+                {
+                    // Use WinHttp to handle PAC/WAPD scripts.
+                    systemProxyResolver.LoadFromIE();
+                }
 
                 GetCustomUpStreamProxyFunc = getSystemUpStreamProxy;
             }