Given the following situation:
/This means that the application will redirect to /login and serve assets as /style.css, but from the Internet those resources are to be accessed as /customprefix/login and /customprefix/style.css.
SSL is terminated at the reverse proxy, which is also expected to strip the prefix. With Nginx or Apache that wouldn't be a problem (e.g. ProxyPass with Nginx). However, I want to use Traefik as reverse proxy and I can't find the right combination of middlewares to make this happen:
Traefik's StripPrefix correctly maps /customprefix/... to /... but that is for requests only. The response of the backend is left untouched, all paths pointing to / instead of being rewritten as /customprefix.
How can I get Traefik to re-write the response as well for...?:
Converting my comments into an answer:
How would you solve this with nginx or apache? Making this work requires filtering HTML from the backend to rewrite links (e.g. something like mod_proxy_html, and even in that case generally fails when links are generated dynamically using Javascript (because this is running in the client browser so your proxy pipeline has no opportunity to make changes to the result).
I would say that either the backend needs to be aware of the prefix, or it needs to use a relatively small, well known set of paths so that you can create appropriate redirections for all of them on the frontend.
If you have the option, you can use host-based rather than path-based rules to direct traffic to the backend, in which case you can redirect all paths as appropriate.