Nginx - Intercept only 404 from backend and show custom error page

Question

I have some problems with a specific setup that I want to achieve:

Summary:

• Nginx acts as a reverse-proxy
• Backend running at http://localhost:8080/
• Nginx may return HTTP 403 ($block_access = true), in that case I want to show a custom error page (/errors/403.html)
• Backend may return HTTP 404, in that case I also want to show a custom error page (/errors/404.html)

Problems:

• Custom HTTP 403 page does not work, the default Nginx 403 page gets served instead
• Custom HTTP 404 page for the backend works
• If I remove proxy_intercept_errors from the location block, the custom 403 page works for Nginx but the custom 404 page for the proxy obviously doesn't work anymore

Configuration:

server { listen 443 ssl http2; server_name mydomain.com; # Reverse proxy configuration location / { # Let Nginx handle basic blocking behavior if ($block_access) { return 403; } # Proxy request to backend proxy_pass http://localhost:8080/; proxy_buffering off; proxy_http_version 1.1; proxy_set_header Upgrade $http_upgrade; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Connection $http_connection; # Only intercept 404 errors from the backend proxy_intercept_errors on; error_page 404 /errors/404.html; # Serve custom 404 error page location = /errors/404.html { root /var/www/html; internal; } } # Serve custom 403 error page for blocked access ($block_access = true) error_page 403 /errors/403.html; location = /errors/403.html { root /var/www/html; internal; } location /errors/ { root /var/www/html; try_files $uri $uri/ =404; } } 

I am more or less at a complete loss with the search for a solution...

Answer 1

https://nginx.org/r/error_page

These directives are inherited from the previous configuration level if and only if there are no error_page directives defined on the current level.

So you have to repeat directive for 403.

location / { proxy_pass http://localhost:8080/; proxy_intercept_errors on; # ... error_page 403 /errors/403.html; error_page 404 /errors/404.html; } 

UPD: if you want to separate 403 from upstream you could use “fake” error code in your check and replace it to real code in error_page directive.

location / { if ($block_access) { return 453; } # ... error_page 453 =403 /errors/403.html; error_page 404 /errors/404.html; } error_page 453 =403 /errors/403.html; # ...