Add support for setting up bypass rules and proxy localhost traffic

examples/Titanium.Web.Proxy.Examples.Wpf/MainWindow.xaml.cs

@@ -105,7 +105,10 @@ public MainWindow()
             };
             proxyServer.Start();
 
-            proxyServer.SetAsSystemProxy(explicitEndPoint, ProxyProtocolType.AllHttp);
+            var proxyLocalhostTraffic = new SystemProxyBypassRuleSet()
+                .SubtractImplicitBypassRules();
+
+            proxyServer.SetAsSystemProxy(explicitEndPoint, ProxyProtocolType.AllHttp, proxyLocalhostTraffic);
 
             InitializeComponent();
         }

src/Titanium.Web.Proxy/Helpers/SystemProxy.cs

@@ -84,7 +84,8 @@ public SystemProxyManager()
     /// <param name="hostname"></param>
     /// <param name="port"></param>
     /// <param name="protocolType"></param>
-    internal void SetProxy(string hostname, int port, ProxyProtocolType protocolType)
+    /// <param name="bypassRules"></param>
+    internal void SetProxy(string hostname, int port, ProxyProtocolType protocolType, string bypassRules)
     {
         using (var reg = OpenInternetSettingsKey())
         {
@@ -106,6 +107,7 @@ internal void SetProxy(string hostname, int port, ProxyProtocolType protocolType
             reg.SetValue(RegProxyEnable, 1);
             reg.SetValue(RegProxyServer,
                 string.Join(";", existingSystemProxyValues.Select(x => x.ToString()).ToArray()));
+            reg.SetValue(RegProxyOverride, bypassRules);
 
             Refresh();
         }

src/Titanium.Web.Proxy/ProxyServer.cs

@@ -452,6 +452,16 @@ public void SetAsSystemHttpProxy(ExplicitProxyEndPoint endPoint)
         SetAsSystemProxy(endPoint, ProxyProtocolType.Http);
     }
 
+    /// <summary>
+    ///     Set the given explicit end point as the default proxy server for current machine.
+    /// </summary>
+    /// <param name="endPoint">The explicit endpoint.</param>
+    /// <param name="bypassRules">The system proxy bypass rules.</param>
+    public void SetAsSystemHttpProxy(ExplicitProxyEndPoint endPoint, SystemProxyBypassRuleSet bypassRules)
+    {
+        SetAsSystemProxy(endPoint, ProxyProtocolType.Http, bypassRules);
+    }
+
     /// <summary>
     ///     Set the given explicit end point as the default proxy server for current machine.
     /// </summary>
@@ -461,12 +471,33 @@ public void SetAsSystemHttpsProxy(ExplicitProxyEndPoint endPoint)
         SetAsSystemProxy(endPoint, ProxyProtocolType.Https);
     }
 
+    /// <summary>
+    ///     Set the given explicit end point as the default proxy server for current machine.
+    /// </summary>
+    /// <param name="endPoint">The explicit endpoint.</param>
+    /// <param name="bypassRules">The system proxy bypass rules.</param>
+    public void SetAsSystemHttpsProxy(ExplicitProxyEndPoint endPoint, SystemProxyBypassRuleSet bypassRules)
+    {
+        SetAsSystemProxy(endPoint, ProxyProtocolType.Https, bypassRules);
+    }
+
     /// <summary>
     ///     Set the given explicit end point as the default proxy server for current machine.
     /// </summary>
     /// <param name="endPoint">The explicit endpoint.</param>
     /// <param name="protocolType">The proxy protocol type.</param>
     public void SetAsSystemProxy(ExplicitProxyEndPoint endPoint, ProxyProtocolType protocolType)
+    {
+        SetAsSystemProxy(endPoint, protocolType, new SystemProxyBypassRuleSet());
+    }
+
+    /// <summary>
+    ///     Set the given explicit end point as the default proxy server for current machine.
+    /// </summary>
+    /// <param name="endPoint">The explicit endpoint.</param>
+    /// <param name="protocolType">The proxy protocol type.</param>
+    /// <param name="bypassRules">The system proxy bypass rules.</param>
+    public void SetAsSystemProxy(ExplicitProxyEndPoint endPoint, ProxyProtocolType protocolType, SystemProxyBypassRuleSet bypassRules)
     {
         if (SystemProxySettingsManager == null)
             throw new NotSupportedException(@"Setting system proxy settings are only supported in Windows.
@@ -500,7 +531,8 @@ public void SetAsSystemProxy(ExplicitProxyEndPoint endPoint, ProxyProtocolType p
                 ? "localhost"
                 : endPoint.IpAddress.ToString(),
             endPoint.Port,
-            protocolType);
+            protocolType,
+            bypassRules?.ToString() ?? string.Empty);
 
         if (isHttp) endPoint.IsSystemHttpProxy = true;
 

src/Titanium.Web.Proxy/SystemProxyBypassRuleSet.cs

@@ -0,0 +1,72 @@
+using System.Collections.Generic;
+namespace Titanium.Web.Proxy;
+
+/// <inheritdoc />
+/// <summary>
+///     This class is used to control when system should skip or use (in case of implicitly ignored addresses) system proxy.
+///     By default for secutiry reasons proxy is ignored on local networks considered as trusted, you can disable it by using <see cref="SubtractImplicitBypassRules"/>.
+///     Be aware that rules are check in order they are added, it's important when they are contradicting.
+/// </summary>
+public class SystemProxyBypassRuleSet
+{
+    private const string IgnoreImplicitBypassRules = "<-loopback>";
+    private const string BypassSimpleHostnamesRule = "<local>";
+
+    private readonly List<string> _bypassRules;
+
+    /// <summary>
+    ///     Initialize new system proxy rule set.
+    /// </summary>
+    public SystemProxyBypassRuleSet()
+    {
+        _bypassRules = new List<string>();
+    }
+
+    /// <summary>
+    /// Adds user defined rule to bypass system proxy.
+    /// </summary>
+    /// <param name="rule">Rule specifying which urls should not go though system proxy.</param>
+    /// <returns>Itself.</returns>
+    /// <example>
+    /// <code>
+    /// var ruleSet = 
+    ///     new SystemProxyBypassRuleSet()
+    ///         .AddRule("https://x.*.y.com:99")
+    ///         .AddRule("*foobar.com")
+    ///         .AddRule("*.org:443")
+    ///         .AddRule("192.168.1.1/16");
+    /// </code>
+    /// </example>
+    public SystemProxyBypassRuleSet AddRule(string rule)
+    {
+        _bypassRules.Add(rule);
+        return this;
+    }
+
+    /// <summary>
+    /// Adds rule for bypassing hostnames without a period in them, and that are not IP literals.
+    /// </summary>
+    /// <returns>Itself.</returns>
+    public SystemProxyBypassRuleSet AddSimpleHostnames()
+    {
+        _bypassRules.Add(BypassSimpleHostnamesRule);
+        return this;
+    }
+
+    /// <summary>
+    /// Subtracts the implicit proxy bypass rules (localhost and link local addresses).
+    /// This is generally only needed for test setups. Beware of the security implications to proxying localhost.
+    /// Ordering may matter when using a subtractive rule, as rules will be evaluated in a left-to-right order.
+    /// </summary>
+    /// <returns>Itself.</returns>
+    public SystemProxyBypassRuleSet SubtractImplicitBypassRules()
+    {
+        _bypassRules.Add(IgnoreImplicitBypassRules);
+        return this;
+    }
+
+    public override string ToString()
+    {
+        return string.Join(";", _bypassRules);
+    }
+}

src/Titanium.Web.Proxy/Titanium.Web.Proxy.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net461;net60</TargetFrameworks>
+    <TargetFrameworks>net48;net60</TargetFrameworks>
     <RootNamespace>Titanium.Web.Proxy</RootNamespace>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <SignAssembly>True</SignAssembly>

tests/Titanium.Web.Proxy.UnitTests/SystemProxyTest.cs

@@ -19,13 +19,13 @@ public void CompareProxyAddressReturnedByWebProxyAndWinHttpProxyResolver()
             {
                 CompareUrls();
 
-                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.Http);
+                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.Http, string.Empty);
                 CompareUrls();
 
-                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.Https);
+                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.Https, string.Empty);
                 CompareUrls();
 
-                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.AllHttp);
+                proxyManager.SetProxy("127.0.0.1", 8000, ProxyProtocolType.AllHttp, string.Empty);
                 CompareUrls();
 
                 // for this test you need to add a proxy.pac file to a local webserver