Troubleshooting Slow Nginx Basic Authentication

Recently, I encountered an unusual problem: sites using basic authentication were loading extremely slowly, but only in Chrome. Other browsers? No issues whatsoever.

This post details my investigation into this Chrome-specific slowdown, the troubleshooting steps I took, and the solutions I discovered along the way.

Let's dive in and unravel this mystery together.

The Initial Symptoms

When I first noticed the issue, it was perplexing. Pages protected by basic authentication were taking an unusually long time to load (more than 5 minutes), but only in Chrome. The login prompt would appear after a significant delay, and after entering credentials, the page load time were back to normal speed (in my case extremely fast because I'm using a beefy server).

For those of you who don't know what basic http auth is, here's a quick summary:

Basic HTTP Authentication is a simple method for protecting web resources. When you try to access a protected page, your browser shows a login prompt.

You enter a username and password, which the browser sends to the server encoded (but not encrypted) in the request header. The server checks these credentials against its records and grants access if they're valid.

These are mostly used when you don't want your site to be public. In my case I'm using it for my self hosted OpenWeb UI that's running on docker.

Your browser then remembers these credentials for future requests to the same site. While it's straightforward and widely supported, it's best used over HTTPS for security. The login prompt is provided by the browser itself, so it looks the same across all websites using basic auth.

Ruling Out Server-Side Issues

My first instinct was to check server-side configurations. I actually spend half a day configuring the server on what might be the problem

1. Nginx Configuration: I reviewed and optimized the Nginx settings, ensuring that gzip compression was enabled and that there were no misconfigured location blocks.
2. SSL/TLS Settings: I double-checked the SSL configuration, making sure OCSP stapling was enabled and session tickets were properly configured.
3. Backend Application: I monitored the application logs and database queries to ensure there weren't any slow queries or application-level bottlenecks.

Despite these efforts, the issue persisted in Chrome while other browsers performed normally.

Chrome-Specific Troubleshooting

Realizing this was a Chrome-specific issue, I turned my attention to the browser itself:

1. Incognito Mode Test: The site actually also loaded slow in Incognito mode, so I initially assume that it's not a browser issue. Only when I tried to access it on my phone's browser that I realized that it might be a browser issue.
2. Clearing Cache and Cookies: Another thing I tried was clearing Chrome's cache and cookies, but the problem didn't go away.
3. Disabling Hardware Acceleration: I also tried a bunch of config to chrome's advanced settings and experimental features like disabling hardware acceleration in Chrome's advanced settings, but it didn't resolve the issue.

The Eureka Moment: WebShare Proxy Extension

After methodically disabling extensions one by one, I discovered that the WebShare Proxy extension was the culprit. As soon as I disabled this extension, the basic auth pages loaded instantly, just like in other browsers.

Why WebShare Proxy Caused the Slowdown

The WebShare Proxy extension was causing this issue due to how it interacts with Chrome's network stack, particularly for authenticated requests:

1. Request Interception: The extension intercepts all outgoing requests to check if they should be routed through the proxy.
2. Authentication Handling: For basic auth requests, the extension attempts to modify the request headers, including the authentication information.
3. Proxy Routing Decision: The extension evaluates whether the request should be routed through its proxy based on its configuration.
4. Race Condition: This process creates a race condition between the extension's logic and Chrome's native basic auth handling.
5. Timeout and Retry: When the extension's processing takes too long, Chrome may timeout the initial request and retry, leading to the observed delays.
6. Caching Issues: The extension may also interfere with Chrome's caching mechanisms for authenticated resources, forcing re-authentication more frequently than necessary.

The complexity of this process, combined with potential inefficiencies in the extension's code, resulted in the significant delays we experienced. Essentially, the extension was trying to "help" manage the authentication process but ended up hindering it instead.

The Solution

The immediate solution was simple: disable the WebShare Proxy extension when accessing sites with basic authentication. For a long-term fix, you have a few options:

Remember, when facing browser-specific issues, always consider the role of extensions in your troubleshooting process.