Passing Authorization Basic Headers Along in Proxy

I am currently trying to get a reverse/forward proxy to pass along the authorization headers to the target server. How would I go abou this? I have already looked at the below sources, and one of the comments states that this only works for Proxy-Auth headers. However the proxy has no authenication backend. It looks like the below

User -> Proxy(No Auth Req) -> Backend(HTTP AUTH HERE)

https://stackoverflow.com/questions/6213028/setting-up-mod-proxy-to-pass-http-authentication-to-server

Solution 1:

It was a mod rewrite thing

RewriteRule ^ - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]

The above rule needs to be applied at the proxy.