Bug 46644

It's sometimes desirable to have a suexec-ed CGI script read a custom environment variable to find out what it is supposed to do.  I described my scenario, where a CGI script needed to know which of three RewriteRules called it, at:

http://marc.info/?l=apache-httpd-users&m=123166031312092&w=2

The problem is that, for good security reasons, suexec strips out all environment variables except for a whitelist consisting of standard ones set by the Web server.  I would like a safe, supported convention for passing custom environment variables.  (I can stuff them in the HTTP_ namespace, but that's a hack.)  Furthermore, internal redirects should not break the convention.

The obvious solution is to allocate a new namespace.  I previously suggested CGI_, but now I'm thinking SUEXEC_ may be better.  REDIRECT_SUEXEC_ vars could either be passed through or renamed to SUEXEC_REDIRECT_ .  An interesting additional possibility would be to prepend SUEXEC_ to unsafe variables instead of dropping them; this way, the entire environment would be available to suexec-ed CGI scripts (but not in a form that could subvert them) without any extra work on the Apache side.