#!/usr/bin/perl -w
# $Id: cisco-decrypt.pl,v 1.1.1.1 2002/09/02 16:37:35 marck Exp $
#
# Credits for orginal code and description hobbit@avian.org,
# SPHiXe, .mudge et al. and for John Bashinski <jbash@cisco.com>
# for Cisco IOS password encryption facts.
#
# Use for any malice or illegal purposes strictly prohibited!
#

@xlat = ( 0x64, 0x73, 0x66, 0x64, 0x3b, 0x6b, 0x66, 0x6f, 0x41,
          0x2c, 0x2e, 0x69, 0x79, 0x65, 0x77, 0x72, 0x6b, 0x6c,
          0x64, 0x4a, 0x4b, 0x44, 0x48, 0x53 , 0x55, 0x42 );

while (<>) {
        if (/(password|md5)\s+7\s+([\da-f]+)/io) {
            if (!(length($2) & 1)) {
                $ep = $2; $dp = "";
                ($s, $e) = ($2 =~ /^(..)(.+)/o);
                for ($i = 0; $i < length($e); $i+=2) {
                    $dp .= sprintf "%c",hex(substr($e,$i,2))^$xlat[$s++];
                }
                s/7\s+$ep/$dp/;
            }
        }
        print;
}