How To Forward Query String Parameters Through Nginx Proxy

Published July 23, 2024

Problem: Forwarding Query String Parameters in Nginx

When using Nginx as a reverse proxy, passing query string parameters from the original request to the backend server can be difficult. This issue often occurs when setting up the proxy_pass directive, as the default behavior may not always keep these parameters.

Implementing Query String Forwarding in Nginx Proxy_Pass

Method 1: Using a Simple Location Block

The location block approach offers a way to forward query string parameters in Nginx. This method uses a location directive with a trailing slash in the proxy_pass statement.

Configuration steps:

Open your Nginx configuration file.
Add or modify the location block:

location /service/ {
    proxy_pass http://apache/;
}

The trailing slash in proxy_pass http://apache/; tells Nginx to replace /service/ with / when passing the request.
This configuration forwards query string parameters without extra modifications.

Tip: Testing Query String Forwarding

To test if query string forwarding is working correctly, you can use a tool like curl or your browser's developer tools. Try accessing a URL with query parameters, such as: http://your-domain.com/service/page?param1=value1&param2=value2. Check if these parameters are correctly forwarded to your backend server.

Method 2: Using Regular Expressions with Query Parameters

For complex scenarios, using regular expressions with query parameters provides more flexibility.

Configuration steps:

Open your Nginx configuration file.
Add or modify the location block using a regex:

location ~* ^/service/(.*) {
    proxy_pass http://apache/$1$is_args$args;
}

The ~* indicates a case-insensitive regular expression match.
^/service/(.*) captures everything after /service/ in the URL.
$1 in the proxy_pass refers to the captured group.
$is_args$args adds the query string to the proxied URL.

This method allows for more control over URL rewriting while keeping query string parameters.

Additional Considerations for Nginx Proxy_Pass Setup

Preserving Original Request Information

When using proxy_pass, it's important to keep the original request intact. Here are some ways to do this:

Use proxy_set_header directives:

proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;

These headers send the original client's information to the backend server.

Enable proxy_buffering:
```
proxy_buffering on;
```
This lets Nginx buffer responses from the backend server, improving performance.
Set timeouts:
```
proxy_connect_timeout 60s;
proxy_send_timeout 60s;
proxy_read_timeout 60s;
```
These settings manage connection times between Nginx and the backend server.

Tip: Preserve URL Path

To keep the original URL path when proxying requests, use the $request_uri variable:

location /api/ {
    proxy_pass http://backend$request_uri;
}

This ensures that the full path after /api/ is sent to the backend server.

Handling SSL/TLS in Proxy Configurations

For secure proxy_pass setups, consider these practices:

Use SSL/TLS for backend connections:

server {
listen 443 ssl;
server_name example.com;

ssl_certificate /path/to/cert.pem;
ssl_certificate_key /path/to/key.pem;

location / {
    proxy_pass https://backend;
    proxy_ssl_verify on;
    proxy_ssl_trusted_certificate /path/to/trusted_ca_cert.pem;
}
}

This config uses HTTPS for the proxy_pass connection and checks the backend server's certificate.

Set SSL protocols and ciphers:
```
ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers HIGH:!aNULL:!MD5;
```
These settings limit the SSL/TLS protocols and ciphers to secure options.
Enable HSTS (HTTP Strict Transport Security):
```
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always;
```
This header tells browsers to always use HTTPS for your domain.

How To Forward Query String Parameters Through Nginx Proxy_Pass?