I have an old Apache server that’s serving as a reverse proxy for my webcam. I swapped webcams out and unfortunately the new one requires authentication. I had to figure out how to get Apache to reverse proxy with the proper authentication. The best information I found was given by user ThR37 at superuser.com

Essentially you have to use an Apache module called headers to add an HTTP header to the request. On my Debian system this was not enabled, so I had to install it (thanks to Andy over at serverfault)

sudo a2enmod headers
#if you're on ubuntu then it's mod_headers

I then needed to generate the basic authentication hash for the header to pass. This was done via a simple python script:

#replace USERNAME:PASSWORD below with your credentials
import base64
hash = base64.b64encode(b'USERNAME:PASSWORD')
print hash

Save the above script into a file hash.py and then run it by typing

python hash.py

With headers enabled and hash acquired I just needed to tweak my config by adding a RequestHeader line:

RequestHeader set Authorization "Basic <HASH>"
#Replace <HASH> with hash acquired above

After adding that one line and restarting apache, it worked!