Securing headers in Apache2 when using it as a reverse proxy

[Peter Schober]

* Nils Kattenbeck <nilskemail+shibboleth at gmail.com> [2021-09-23 00:04]:
> To my knowledge the only way to archive this is to pass the
> information using HTTP headers (as neither localhost:... nor
> unix://... support setting environment variables).

FWIW, passing environment variables from Apache httpd to PHP-FPM via a
Unix socket works just fine, e.g.:

  SetHandler "proxy:unix:/run/php/php7.3-fpm.sock|fcgi://localhost"

or similarly using another method and another server process (uWSGI)
and protocol (httpd also loading mod_uwsgi):

  ProxyPass / unix:/run/uwsgi/some_app.socket|uwsgi://localhost/

> Written in Python using the ASGI standard. This is required as we
> have multiple async features like Websockets and async communication
> with another server.

The only thing I could easily find for ASGI (which I haven't used
myself so far) with the uWSGI server seems to be stale/abandoned,
https://github.com/tovmeod/uwsgi-asgi

-peter