Chrome Skip DNS Trust Proxy Setup Guide

Chrome Skip DNS Trust Proxy Setup Guide

In some cases, you may want to use a proxy server for specific domains, while allowing direct access for all other domains. This guide will walk you through setting up a proxy.pac script to achieve this goal, focusing on the issue of Chrome failing to resolve specific domains (such as example.com) with the error DNS\_PROBE\_FINISHED\_NXDOMAIN, while Firefox works fine.

Understanding Proxy Auto-Configuration (PAC) Files

A Proxy Auto-Configuration (PAC) file is a script that contains functions and rules to determine whether web traffic should go directly to the internet or be sent through a proxy server. PAC files are useful in scenarios where you want to apply different proxy settings for various domains.

Creating a PAC File for Skipping DNS Trust Proxy Setup

To create a PAC file that works around the Chrome issue and skips the proxy for a specific domain (example.com), follow these steps:

1. Create a new text file and name it proxy.pac.
2. Open the file in a text editor and paste the following JavaScript code:
   function FindProxyForURL(url, host) { if (shExpMatch(host, "example.com")) { return "DIRECT"; } return "PROXY proxy-server.example.org:8080"; }

   Replace proxy-server.example.org:8080 with the address and port of your proxy server.

   Applying the PAC File to Your Browser

   After creating the PAC file, you need to apply it to your browser. The process varies by operating system.

   Windows

   1. Open Internet Options by searching for it in the Start menu.
   2. Navigate to the Connections tab and click LAN settings.
   3. Check the "Use automatic configuration script" option and enter the path to your PAC file (e.g., C:\path\to\proxy.pac).
   4. Click OK to save the changes and close the windows.

   macOS

   1. Open System Preferences and click on Network.
   2. Select the network interface (e.g., Ethernet or Wi-Fi) and click Advanced.
   3. Go to the Proxies tab and select "Automatic Proxy Configuration".
   4. Enter the path to your PAC file (e.g., file:///path/to/proxy.pac).
   5. Click OK to save the changes and close the windows.

   Linux (e.g., Ubuntu)

   Linux distributions handle PAC files differently. For this guide, we will focus on configuring Firefox on Linux. For other Linux browsers or distributions, consult their respective documentation.

   1. Open Firefox and go to the Preferences panel.
   2. Search for "proxy" in the search bar and click on Settings under Network Settings.
   3. Select "Automatic proxy configuration URL" and enter the path to your PAC file.
   4. Click OK to save the changes.
   • Key Concept: Proxy Auto-Configuration (PAC) files help manage proxy settings for different domains.
   • Solution: Create a PAC file that skips the proxy for a specific domain, addressing the Chrome DNS\_PROBE\_FINISHED\_NXDOMAIN issue.
   • Application: Apply the PAC file to your browser using the appropriate method for your operating system.

   References

   • JavaScript Networking, O'Reilly

   • "How to configure a PAC file" iandd.com

   • "Proxy Auto-Configuration (PAC)" Wikipedia