How to access Apache Basic Authentication user in Flask

I eventually found it, it's available as:

request.environ.get('REMOTE_USER')

Not knowing this wasn't my only problem however, in case it's useful for anyone, here's the story:

Firstly I tried to find out if WSGI was passing the authentication info through to flask. This answer to a different question was very helpful (it shows you how to see everything WSGI is providing before it gets to flask):

https://stackoverflow.com/a/1151129/1956954

When I list the WSGI info as per that answer, it didn't have the user information. But that turned out to be because the setup for apache basic authentication in the relevant sites-enabled apache config file was configured for the document root (a htdocs folder). Since I'm using WSGI to redirect the relevant requests to a folder outside of the document route, I didn't actually have authentication turned on for my page. (And I didn't notice that because I had accessed some pages under htdocs, been forced to authenticate, and assumed that I wasn't being asked to authenticate when I went to my flask pages because the authentication had been cached). Creating another section in the relevant apache sites-enabled file setting up authentication for my flask directories enabled authentication

You can find authentication information in Flask from the request object.

from flask import request

def my_view():
    auth = request.authentication
    username = auth.username
    password = auth.password
    ...

Note however that if you're using apache mod_wsgi, you'll need to turn on the WSGIPassAuthorization directive in your virtualhost config. Otherwise apache will consume the authentication header and won't pass it to the WSGI layers.

<virtualhost *:443>
    ...

    WSGIPassAuthorization On

    ...
</virtualhost>

more info here and here.