# Conditional Reverse Proxy to Localhost

**URL:** <https://discourse.mitmproxy.org/t/conditional-reverse-proxy-to-localhost/919>\
**Category:** help\
**Created:** [March 15, 2018, 11:52pm UTC](https://discourse.mitmproxy.org/t/conditional-reverse-proxy-to-localhost/919 "2018-03-15T23:52:06Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![JBarna](https://avatars.discourse-cdn.com/v4/letter/j/c57346/32.png) [@JBarna](https://discourse.mitmproxy.org/u/JBarna)\
**Post date:** [March 15, 2018, 11:52pm UTC](https://discourse.mitmproxy.org/t/conditional-reverse-proxy-to-localhost/919/1 "2018-03-15T23:52:06Z")

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It’s possible I’m going to win an award for being the #1 scrub here on the mitmproxy forums but here I go.

**Environment**  
I set up mitmproxy on my mac, installed the certificate, and used the system proxy settings to route all http and https traffic through the mitmproxy port on regular mode.

I want to intercept **https** requests of a singular host and depending on the path, either serve the response from a local file, or pass it on to the regular server. I don’t think I can use a reverse proxy here because I don’t want all of the requests from the host to be served locally, only some of them.

I wrote a simple redirect script and plugged it into mitmproxy and hit my host with postman to test.

```
from mitmproxy import http
def request(flow: http.HTTPFlow) -> None:
    if flow.pretty_host == "js.mywebsite.com" and "redirect" in flow.path:
        flow.host = "localhost"
        flow.port = 9999
        flow.scheme = "http"

```

I have a simple python server on port 9999 serving local files.

Anyway, so if I make a postman request to [http://js.mywebsite.com/redirect](http://js.mywebsite.com/redirect), everything is fine.

But if I make that same request as https, I see that my python file server is hit and returns the correct data, and even in the mitmproxy terminal i see a response that has the data from the file. But the initial request from postman just craps the bed.

I think that I’m missing some vital piece of information about security principles in general, so I’m sorry if I’m trying to do the impossible. But I thought that mitmproxy would create a certificate for [js.mywebsite.com](http://js.mywebsite.com) and return the local data over https and everything would work fine. Guess I’m missing something.

Any help would be appreciated, thanks for reading.

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**Author:** ![mhils](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mitmproxy.org/mhils/32/7_2.png) [@mhils](https://discourse.mitmproxy.org/u/mhils)\
**Post date:** [March 16, 2018, 10:58pm UTC](https://discourse.mitmproxy.org/t/conditional-reverse-proxy-to-localhost/919/2 "2018-03-16T22:58:13Z")

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> [@JBarna](#):
>
> But if I make that same request as https, I see that my python file server is hit and returns the correct data, and even in the mitmproxy terminal i see a response that has the data from the file. But the initial request from postman just craps the bed.

Hm… this particular combination (you see a request and a response in mitmproxy, but your client seems to fail) is quite unusual and may as well be a bug. Is there anything in mitmproxy’s event log? Does the client display any specific error? The only thing you change is HTTP → HTTPS between client and mitmproxy and it doesn’t work anymore?

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**Author:** ![JBarna](https://avatars.discourse-cdn.com/v4/letter/j/c57346/32.png) [@JBarna](https://discourse.mitmproxy.org/u/JBarna)\
**Post date:** [March 17, 2018, 2:46am UTC](https://discourse.mitmproxy.org/t/conditional-reverse-proxy-to-localhost/919/3 "2018-03-17T02:46:10Z")

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Well, I change **https** -\> **http** through the proxy. The request coming into [js.example.com](http://js.example.com) is of https scheme, and my local server that is just hosting files is http. So depending on the path (in my example, if it has ‘redirect’ in the path), then I serve from the local server over http.

I can try to get a giphy of my experience