NAME
   Unix::SavedIDs - interface to unix saved id commands: getresuid(),
   getresgid(), setresuid() and setresgid()

SYNOPSIS
       use Unix::SavedIDs;

           my($ruid,$euid,$suid) = getresuid();
           setresuid(10,10,10);

STATUS
   This is alpha code. I'm going to be using it a lot in production and
   once I'm comfortable that it's working well I'll up the version number
   to 1.0 and call it a production release.

DESCRIPTION
   This module is a simple interface to the c routines with the same names.

   If you want to drop root privileges, see Unix::SetUser. This provides a
   simple interface, uses Unix::SavedIDs to handle saved ids, handles
   supplemental groups and generally makes dropping root privileges easy
   and secure.

   If you want to drop root privileges, use Unix::SetUser or this module,
   Unix::SavedIDs. Seriously.

   $<, $>, $(, $) and the POSIX setuid(),seteuid etc... functions give you
   access to the real uid/gid (ruid/rgid) and effective uid/gid
   (*euid*/*egid*), but there was no way to get or set the saved uid/gid
   (*suid*/*sgid*).

WHY THIS MATTERS
           # start as root
           die if $> != 0;
           # I think this should drop root
           $( = 50;
           $) = "50 50";
           $> = 50;
           $< = 50;
           # Make sure I dropped root
           print "\$< = $<\n";
           print "\$> = $>\n";
           # I really dropped root, right?
           # So, I can't possibly switch back.
           $< = 0;
           $> = 0;
           print "\$< = $<\n";
           print "\$> = $>\n";
           # oh crap....

   The effective user id changed back to root. If someone cracks your
   script, they can get root.

FUNCTIONS
 getresuid()
   returns a list of 3 elements, the current *ruid*, *euid* and *suid* or
   croaks on failure.

 getresgid()
   returns a list of 3 elements, the current *rgid*, *egid* and *sgid* or
   croaks on failure.

 setresuid(*ruid*,*euid*,*suid*)
   Sets the current *ruid*, *euid* and *suid* or croaks on failure.

   Any arguments which are unset,undef or -1 tells setresuid to leave that
   value unchanged. E.G.

     setresuid(500);
     setresuid(500,undef,undef);
     setresuid(500,-1,-1);

   ... all will set the *ruid* to 500 and leave the *euid* and *suid* alone
   and:

     setresuid(undef,undef,500)

   ... will set your *suid* to 500 and leave your *ruid* and *euid*
   unchanged.

   setresgid behaves in the same way.

 setresgid(*rgid*,*egid*,*sgid*)
   Sets the current *rgid*, *egid* and *sgid* or croaks on failure.

   Please see setresuid() above to see how to leave an id unchanged.

ACKNOWLEDGMENTS
   I recently discovered Proc::UID by Paul Fenwick. It does everything that
   this module does plus more. Sadly, its unmaintained since 2004 and the
   author specifically states that it is not for production code.

BUGS AND LIMITATIONS
   Installer doesn't check directly for saved ids. Instead it assumes
   anything non posix won't do saved ids. That isn't necessarily true.

   I only have Linux and OpenBSD systems to test on, so I have no idea how
   it might work on other operating systems. If you run a different OS,
   please let me know how this module works in your environment.

   Please report any bugs or feature requests to
   "[email protected]", or through the web interface at
   <http://rt.cpan.org>.

AUTHOR
   Dylan Martin "<[email protected]>"

LICENSE AND COPYRIGHT
   Copyright (c) 2008, Dylan Martin & Seattle Central Community College
   "<[email protected]>".

   Permission to use, copy, modify, and distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
   copyright notice and this permission notice appear in all copies.

DISCLAIMER
   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
   MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
   ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
   WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
   ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
   OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

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