For years, mod_rpaf has been the standard module for running Apache behind a reverse proxy. Fortunately, it's not the only one and there are alternatives.
- mod_extract_forwarded which is available in EPEL, so it's available for CentOS systems without compling
- mod_remoteip which is built into Apache 2.4 (but good luck finding a production server running 2.4)
- mod_rpaf modified to support X-Forwarded-Proto/X-Forwarded-HTTPS/X-HTTPS
