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##############################################################################
# The Faq-O-Matic is Copyright 1997 by Jon Howell, all rights reserved. #
# #
# This program is free software; you can redistribute it and/or #
# modify it under the terms of the GNU General Public License #
# as published by the Free Software Foundation; either version 2 #
# of the License, or (at your option) any later version. #
# #
# This program is distributed in the hope that it will be useful, #
# but WITHOUT ANY WARRANTY; without even the implied warranty of #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #
# GNU General Public License for more details. #
# #
# You should have received a copy of the GNU General Public License #
# along with this program; if not, write to the Free Software #
# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.#
# #
# Jon Howell can be contacted at: #
# 6211 Sudikoff Lab, Dartmouth College #
# Hanover, NH 03755-3510 #
# jonh@cs.dartmouth.edu #
# #
# An electronic copy of the GPL is available at: #
# http://www.gnu.org/copyleft/gpl.html #
# #
##############################################################################
use strict;
###
### Entropy looks around for some entropy for better password/nonce
### generation. Uses /dev/random if you've got it.
###
package FAQ::OMatic::Entropy;
use Digest::MD5 qw(md5_hex);
# generate a temporary password
# THANKS to Matej Vela <vela@debian.org> for pointing out that my crappy
# first cut ( crypt(rand(time)) ) was very easily attackable with an offline
# attack: so if your fom file becomes world-readable and your config
# goes away, an attacker could easily compute the attack offline, then
# log in and control the config page: that's a lot of power. He can
# specify executables to run there. Yikes!
# Just for kicks, a google search for "temporaryCryptedPassword" found
# four publically-readable passwords. They weren't vulnerable because the
# sites config files are set up correctly ... for now! Scary.
#
# So, to be a little safer, let's use a less-attackable hash (which will
# require admins to install Digest::MD5), and collect entropy wherever
# we can find it.
# (Perhaps we could fancy-up crypt to give more like 112 bits of hash
# quality by tweaking it to essentially do 3DES, but I doubt it, and I
# don't want my crypto sloppiness to expose your machine to attack.)
#
sub gatherRandomString {
my $entropy = '';
$entropy .= $$;
$entropy .= time();
# if you've got real random bits, let's take 128 of them.
# Too bad there's not a standard way to fetch real entropy on all platforms
if (-r "/dev/random") {
my $buf;
open (RANDFH, "/dev/random");
sysread(RANDFH, $buf, 16);
close (RANDFH);
$entropy .= $buf;
}
# grab some more sources for those poor slobs who don't have /dev/random
$entropy .= `uptime`;
$entropy .= `uname -a`;
# hash it all up into a secret password
return md5_hex($entropy);
}
1;
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