Now need help setting up a reverse proxy in IIS

You can find the original over on serverfault but I'm pasting the question in here as well just in case.

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So the scenario we have in mind is as follows.

We have an IFRAME. Said IFRAME wants to point to a resource on https://trees.com. It might be, for example, https://trees.com/ficus/macrophylla. However, despite all our requests to trees.com, they refuse to allow us to link directly to their site, blocking the cross-origin request.

So we decide we want to set up a reverse-proxy. We've heard about nginx and apache but we've got a corporate commitment to Microsoft's technology, for better or worse, so decide in favour of IIS.

Using one of our Azure servers, we create a website, let's call it https://figs.wild.com.au. We configure the IFRAMEs so that a request to https://trees.com/ficus/macrophylla actually goes to https://figs.wild.com.au/trees/ficus/macrophylla.

At this point we go slightly insane.

Is it actually possible for the request https://figs.wild.com.au/trees/ficus/macrophylla to be converted, on the figs.wild.com.au server, to a request for https://trees.com/ficus/macrophylla and for the response to that to be fed back to the originator of the IFRAME request?

We've done a lot of searching and we keep finding things that almost work. What actually does work? Is IIS's Url Rewrite the thing to use, and if so, what should the rule/s look like? Or should we be using some C#-y thing instead?

Comments

[radioActive DROID]

Have you tried a url rewrite wildcard with source specified like domain.com/{R:0} and ensure TLS 1.3 is fully supported.

I think it's bizarre that there'll be so much issues with it although I don't know the whole issues.

[Bruce Axtens]

This is, by the way, me trying to find an IIS-based approach. We got a contractor to figure out how to do it in nginx but he only got as far as the server-to-third-party part and couldn't tell us how to do the browser-to-server part. This serverfault posting is me trying to find out what to do next. I got given a pointer but it assumed more knowledge than I actually have.

[Bruce Axtens]

I have tried a number of things like that, but without good results. I'm having a I-just-don't-get-it moment which I'm hoping will pass soon. I finally understood outbound rules this morning. I'm hoping for that understanding of inbound rules will follow soon.

For example a (redacted) error

Requested URL      http://our.server:80/third/third/third/third/third/third/third/third/third/third/third/third/au/mz
Physical Path      C:\web\projects\third\third\third\third\third\third\third\third\third\third\third\third\au\mz

I don't want it to resolve to a physical path. I want it to resolve to a third party site. And what's with all the third repeats? The original request was http://our.server:80/third/au/mx which I want to resolve to http://thirdparty.com/au/mx

And then there's all the links to the thirdparty that will need to get rewritten as links to our.server ... but that's another story.