Mitmproxy: Can't get the WSGI example to work

[beth92]

Problem Description

I was running code very similar to that in the wsgi_flask_app.py example in my project, hoping to serve a basic flask app under a test domain when the proxy is running. Couldn't get it working in my project so after some experimenting I tried to repro the simple example, using mitmproxy 5.0.1 docker image as a base, but I'm still having trouble.
Basically mitmdump doesn't seem to be able to resolve the magic "proxapp.local" domain - when I make requests to it on port 80, the mitmdump logs the request but says:

GET http://proxapp.local/
<< Server connection to ('proxapp.local', 80) failed: Error connecting to "proxapp.local": [Errno -2] Name does not resolve

Steps to reproduce the behavior:

1. This is my Dockerfile

FROM mitmproxy/mitmproxy:5.0.1

RUN pip install flask==1.1.1

COPY proxy.py proxy.py

CMD ["mitmdump", "-s", "proxy.py"]

1. The contents of proxy.py is just copy pasted from: https://github.com/mitmproxy/mitmproxy/blob/v5.0.1/examples/simple/wsgi_flask_app.py
2. I'm running it with:

docker build -t tpr .
docker run --network="host" --rm -it -v ~/.mitmproxy:/home/mitmproxy/.mitmproxy tpr

1. Making requests via the browser (set up to proxy via localhost:8080) to http://proxapp.local gives a 502

My understanding was that I should get back the test "Hello World!" response. Have I missed something?

Also, at some point during my experimentation I uncommented the line at the bottom of the example :
mitmproxy.ctx.master.apps.add(app, "example.com", 443)
but got some error about how apps is not defined on ctx.master, is that information still applicable to v5.0.1?

System Information

Paste the output of "mitmproxy --version" here.
(Running from a shell inside the running container):

Mitmproxy: 5.0.1
Python:    3.6.9
OpenSSL:   OpenSSL 1.0.2u  20 Dec 2019
Platform:  Linux-4.15.0-72-generic-x86_64-with

[mhils]

Thanks for the super detailed repro instructions (which make us look at things right away)! ❤️

It looks like our example is indeed broken. Instead of using the load function, we probably need to specify the addon top-level in the script. Does adding

addons = [
    wsgiapp.WSGIApp(app, "proxapp.local", 80)
]

fix things for you?

[beth92]

Indeed it does - thank you so much for the speedy response! :)

[mhils]

Thanks! You did the majority of the work here, do you want to open a pull request that fixes the example? 😃

[shmuelhertz]

I can't get the SSL version of the app to work.
When I uncomment this line.
# mitmproxy.ctx.master.apps.add(app, "example.com", 443)
I get this error:
in script simple\wsgi_flask_app.py:41 invalid syntax (wsgi_flask_app.py, line 41)

System Information

Mitmproxy: 5.1.1 binary
Python:    3.7.6
OpenSSL:   OpenSSL 1.1.1f  31 Mar 2020
Platform:  Windows-10-10.0.18362-SP0