Apache forward REMOTE_USER to X-Forwarded-User

apache-2.2x-forwarded-for

I would like to pass the environment variable REMOTE_USER set by apache when HTTP basic authentication is correct to a backend. This would provide authentication to the backend server as well.

Here is my apache2 configuration file:

<Directory />
  AuthType basic
  AuthUserFile $my_file
  require valid-user
  RewriteEngine on
  RewriteCond %{REMOTE_USER} (.+)
  RequestHeader set X-Forwarded-User %{REMOTE_USER}e
</Directory>

Authentication by apache2 goes well, as I am properly redirected to the backend server, but then, backend server does not receive the REMOTE_USER as the X-Forwarded-User variable does not appear in tcpdump trace.

What may I have forgotten/misconfigured which does not let this REMOTE_USER variable being forwarded to backend as X-Forwarded-User?

Best Answer

REMOTE_USER is not actually an environment variable inside Apache, but is instead set by Apache when running things like CGI or PHP handlers.

The actual value is embedded in a structure within Apache. See Apache documentation on Environment Variables

Perhaps you need to be ENV: as a prefix. 

<Directory />
  AuthType basic
  AuthUserFile $my_file
  require valid-user
  RewriteEngine on
  RewriteCond %{ENV:REMOTE_USER} (.+)
  RequestHeader set X-Forwarded-User %{ENV:REMOTE_USER}e
</Directory>
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