URL rewrites inside HTML content?

[marcosimioni]

Hello,
I love teleport and it has a lot of cool features, but I'm struggling now with one specific application.

This application renders in its responses a bunch of hrefs having an hardcoded url, let's say application.example.com:443.
I'm using teleport to expose my application with the public URI application.teleport.example.com:8443 (notice the domain and also the port number) and some areas work fine.
However, Teleport is not rewriting those hrefs values, so other features are not working because the browser of my end-user is trying to retrieve those assets via application.example.com:443, which of course does not work (remember? the application is exposed via application.teleport.example.com:8443).

The expected behavior would be that all references to application.example.com:443 contained in the application responses should be rewritten to application.teleport.example.com:8443, or in other words what is described for instance here https://docs.microsoft.com/en-us/iis/extensions/url-rewrite-module/reverse-proxy-with-url-rewrite-v2-and-application-request-routing (In addition, if internal application inserts links into its response HTML that link to elsewhere in those applications, those links should be modified before the response is returned to the client. For example, a page from http://webmail/default.aspx might contain a link like this:).

Is there a way to enable such URL rewriting in Teleport? Or is teleport only able to rewrite URLs on HTTP forwards?

Thanks!

[marcosimioni]

I believe my issue is related to #4716, but the proposed solution seems to work fine for HTTP 302 responses, but not for URLs located inside the HTML Content.

I'll investigate further, but if anybody has any pointer it would be more than welcome.

[webvictim]

I was the person who opened that issue as I had it too. I've just checked and it seems like my router software now uses whatever the URL in the browser is (i.e. window.href or similar) so it probably wasn't fixed in Teleport itself - it was just a coincidence.

I've reopened that issue and will try to investigate further. Teleport's reverse proxy support is unfortunately not as full-featured as that of other servers like nginx yet.

[marcosimioni]

Thanks a lot @webvictim for getting back to me. After looking at the source code, I realised the functionality is just missing.
I am working on a stub of functionality and it seems to be working ok.
I'll submit a PR soon, hopefully it will be merged at some stage.

[marcosimioni]

@webvictim I have submitted the PR (#11769). Can you have a look at it by any chance, or is there someone else you know who could look into it?

I have no idea if I have forked from the right branch, nor if I have followed the process that Gravitational would like to be followed for contributions.

Thank you!

[webvictim]

Hey @marcosimioni, thanks for your work. Unfortunately it looks like we probably won't be accepting the PR upstream as-is, but hopefully we'll get to this when we look at plugin support for app access in future. For now, if the code changes work for you then I'm happy :)