How to follow HTTP redirects inside nginx?

Question

I have an nginx-based HTTP proxy and I would like to process all HTTP redirects inside it so that clients get only the last response in the redirect chain.

The basic code looks like:

location /proxy {
    rewrite ^/proxy/([^/]+) $1 break;

    proxy_pass http://$uri/;
}

My attempt at following 1 level redirects is this:

error_page 301 302 307 =200 @redir;

... and having this named location:

location @redir {
    proxy_pass $proxy_location;
}

Only there's no $proxy_location variable and I failed to find a way of creating it. It should contain the value of Location: header received from upstream.

Any thoughts?

Answer 1

I believe you want the variable $upstream_http_location.

Variables that begin with $proxy* control what goes from nginx to the upstream. The $upstream* series of variables contains information about the response that nginx itself receives. You can get any aribitrary HTTP header received from an upstream server with $upstream_http_headername.

Note that these $upstream variables cannot be anything but null until the response is received from the upstream server, so there are some limitations on their use.

Answer 2

Here is the full example of what worked for me:

server {
    ...

    location / {
        proxy_pass http://backend;
        # You may need to uncomment the following line if your redirects are relative, e.g. /foo/bar
        #proxy_redirect / /;
        proxy_intercept_errors on;
        error_page 301 302 307 = @handle_redirect;
    }

    location @handle_redirect {
        set $saved_redirect_location '$upstream_http_location';
        proxy_pass $saved_redirect_location;
    }
}

Answer 3

I had a similar issue while trying to proxy the images from https://picsum.photos website. They return a 302 redirect to a HMAC-signed URL when requesting a particular picture.

The working solution for me is:

server {
    listen 80;
    server_name dog.localhost.direct;
    location / {
        proxy_ssl_server_name on;
        proxy_intercept_errors on;
        error_page 301 302 307 = @handle_redirect;
        proxy_pass https://picsum.photos/id/237/536/354;
    }
    location @handle_redirect {
        set $saved_redirect_location '$upstream_http_location';
        resolver 8.8.8.8;
        proxy_pass $saved_redirect_location;
    }
}

Hope this will help somebody.