sure, i can give you an example. but the best examples are in perlsec. you're running AS ROOT, and not checking your variables for taintedness. if i can get you to your web page, i can do VERY EVIL THINGS to your system. of course, i'd never do that ;-)

use -T as well as strict and warnings. don't use the PATH environment, unless you've cleaned it. when you execute a system call, use the full path to the executable, and pass an array, so the shell is bypassed. these and many other good practices can be learned by reading the perlsec documentation. i highly recommend reading Ovid's "Web Programming Using Perl" Course as well. it's helped me tremendously.

here's some code...

#!/usr/bin/perl -wT
use strict;
use CGI;

# clean your environment
BEGIN { $ENV{PATH} = '/usr/bin:/usr/local/bin'; }

my $useradd = '/full/path/to/useradd';
my( $site_count, $username ); # and so on...

# get input, which will be tainted...
# my $username = $CGI->param('username');

# untaint input
#   for instance, username is 1 to 12 word characters
if( $username =~ /^(\w{1,12})$/ ) { $username = $1 }
# and so on...

# now call system, with list of arguments to bypass shell
system( 
  $useradd, 
  qq|-c "fullname"|,
  qq|-d /home/sites/site$site_count/users/$username|,
  qq|-g site$site_count|,
  qq|and so on...|,
) and error( "oh, i didn't expect that! $!" );

[download]

~Particle *accelerates*

In reply to Re^3: Using doublequotes in a system call by particle
in thread Using doublequotes in a system call by rguyer

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