Allow customising ProxyAddHeaders

[nbarrientos]

When the Apache instance configured by this module is not dealing with user requests directly because there's another proxy in front, it's undesirable that the "local" Apache resets headers like X-Forwarded-Host. When it does, it could happen that links created using Rails _url helpers do not contain the Host initially sent by the client leading to broken links (as they point to backend nodes not reachable by the user).

This patch makes this setting customisable by the administrator by exposing it as parameter.

Fixes #952

[ekohl]

For what it's worth, you don't need to open an issue for a PR. A PR with a good description is sufficient.

[nbarrientos]

Thanks, next time I'll just send a MR. It used to be mandatory to have an issue for any code contribution to Foreman itself, that's why :)

[ekohl]

I was reading more documentation and wanted to capture it. There's ProxyPreserveHost:

When enabled, this option will pass the Host: line from the incoming request to the proxied host, instead of the hostname specified in the ProxyPass line.

This option should normally be turned Off. It is mostly useful in special configurations like proxied mass name-based virtual hosting, where the original Host header needs to be evaluated by the backend server.

Perhaps this is what you're looking for?

Another is mod_remoteip which may also be useful.

[nbarrientos]

Thanks! Not (re-)setting any X-Forwarded-* header at all (by setting ProxyAddHeaders to Off) on the second Apache is just enough for us, this way Foreman also sees for instance X-Forwarded-For which is I believe consumed by the audit logs.