Will do that, thank you :-)
But how you mean it stops me? It somehow check my perl script and if it founds it not secure proof it denies the execution of it or displays warnings? | [reply] |
While your script is running, it will mark variables that come from outside the program as tainted. If you try to perform an unsafe operation with a tainted variable, the program will be killed instead of executing that operation.
However, it actually looks like Perl doesn't consider opening a file readonly to be an unsafe operation, which is surprising to me. So it wouldn't have solved your security problem, but it would help with something like this (which opens a file for append):
#!/usr/bin/perl -T
use warnings;
use strict;
use Scalar::Util qw(tainted);
use CGI qw(:standard);
BEGIN {
if ($ENV{REQUEST_METHOD}) {
eval 'use CGI::Carp qw(fatalsToBrowser)';
}
}
use constant EOL => $ENV{REQUEST_METHOD} ? "<br>\n" : "\n";
if ($ENV{REQUEST_METHOD}) {
start_html();
}
my $file = param('file')
or die "No filename given";
# The next 3 lines will untaint the variable.
$file =~ /^(\w+)$/
or die "illegal filename\n";
$file = $1;
printf "\$file is%s tainted.".EOL,tainted($file)?"":"n't";
open(F,">> /tmp/$file")
or die "Couldn't open file";
print F "Wrote.\n";
close(F);
print "OK".EOL;
if ($ENV{REQUEST_METHOD}) {
end_html();
}
Update: This version should work from the command-line or CGI.
| [reply]
[d/l] |
Thanks but to me it doesnt run at all!
| [reply] |
$ perl -lTe'system;print "RTFM"'
Insecure $ENV{PATH} while running with -T switch at -e line 1.
$ perl -le'system;print "RTFM"'
RTFM
| [reply]
[d/l] |