Resolving SNI Issues When Configuring Multiple SSL Reverse Proxies with Nginx

Описание: Learn how to troubleshoot and fix SNI issues in Nginx when configuring multiple SSL reverse proxies for different applications.
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This video is based on the question https://stackoverflow.com/q/64301631/ asked by the user 'Stuck' ( https://stackoverflow.com/u/386201/ ) and on the answer https://stackoverflow.com/a/64304171/ provided by the user 'Stuck' ( https://stackoverflow.com/u/386201/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving SNI Issues When Configuring Multiple SSL Reverse Proxies with Nginx

When setting up multiple reverse proxies with SSL using Nginx, you might encounter a common problem where both subdomains direct traffic to the same application instead of the expected ones. If you've found yourself facing this issue, you're not alone. In this post, we'll take a deep dive into the problem and provide a step-by-step guide on how to resolve it.

Understanding the Problem

In our scenario, we are trying to configure two subdomains:

https://api.example.com - http://app:8080

https://pg.example.com - http://pgadmin:80

Despite setting up the Nginx configuration, there was an issue when accessing https://pg.example.com, as it redirected to app instead of pgadmin. The underlying cause of this behavior is often linked to Server Name Indication (SNI) configuration in Nginx or mismatching server names in the configuration files.

The Nginx Configuration

Our client’s original configuration includes three server blocks. Here's a brief overview of these blocks:

HTTP to HTTPS Redirect

[[See Video to Reveal this Text or Code Snippet]]

SSL Configuration for API

[[See Video to Reveal this Text or Code Snippet]]

SSL Configuration for PGAdmin

[[See Video to Reveal this Text or Code Snippet]]

Observations

The server_name for api.example.com is set correctly.

The server_name for pg.example.com must also match, and any typos or incorrect configurations will lead to unexpected redirections.

Debugging the Issue

After a thorough review of the configuration, the source of the problem was traced to a misspelling in the server_name directive for the pg.example.com server block. Here’s how it was resolved:

Identifying the Typo: After replacing the server block for api.example.com with a default catch-all (using server_name _;), the issue was apparent; requests meant for pg.example.com were not matched correctly.

Adding a Default Server Block: By adding a default configuration at the beginning, you ensure that Nginx catches requests accurately, only redirecting to specific handlers when there is a perfect match.

Correcting the Spelling: Correct the misspelled server_name on the pg.example.com block from sever_name to server_name. This small change resolved the misroutes in a single alteration.

Conclusion

Setting up multiple SSL reverse proxies in Nginx can be daunting, especially when it comes to ensuring that the server names are interpreted correctly. Always double-check for typos in configuration files, as they can lead to unexpected behavior.

If you follow these solutions, you should be able to successfully configure multiple reverse proxies without encountering the SNI issues previously experienced. This allows you to route traffic appropriately, maintaining a seamless experience for your application users.

By tackling this problem head-on, you’ve taken an important step towards mastering Nginx and improving your web server’s efficiency!