I am having trouble dropping privileges on a system which allows membership to multiple groups at once. I have tried numerous approaches -- setting $) and $(, POSIX::setgid(), and Proc::UID -- and in all situations after I change to 'nogroup' I continue to have membership in root, bin, daemon, etc. Nothing I have found addresses setgid in multi-group systems.

Here is the code and result that I have used to test this. I am running Slackware 10.2 and a 2.4.31 kernel. Any suggestions? Is this a potential bug in Perl? 

mgrimes@pip$ cat priv.pl 
#!/usr/bin/perl

use strict;
use warnings;

print `id`;
my ($login,$pass,$uid,$gid) = getpwnam('nobody');
($<,$>) = ($uid,$uid);
($),$() = ($gid,$gid);
print "Dropped privilege\n";
print `id`;
print `cat priv_file`;


mgrimes@pip$ ll priv_file 
-rw-r-----  1 root root 11 2006-09-08 15:15 priv_file


root@pip$ ./priv.pl 
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm)
Dropped privilege
uid=99(nobody) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(ad
+m)
Privileged - you shouldn't see this!

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In reply to Dropping Privileges by markg

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