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#!/bin/bash
#
#    fwcrack.sh - script to use a brute force method to determine the
#    contents of a binary firmware upgrade file for an embedded linux
#    system (such as a router, internet radio etc.)
#
#    The script first scans through the firmware file to find a mountable 
#    filesystem.
#    I'll decide what to do when that works...
#
#
#    23Aug2009  GJ  ORIGINAL VERSION
#
###########################################################################
#
#    Copyright (C) 2009  Graham Jones
#
#    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 3 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, see <http://www.gnu.org/licenses/>.
#

tmpmnt=tmpmnt
tstimg=test.img

mnttypes="ext2 ext3 msdos reiserfs vfat squashfs cramfs rootfs"

fs_start=0
fs_end=0

case $# in
    1)
	fname=$1
	echo "fwcrack: Using specified file name: "$host
	;;
    *)
	echo 'Usage fwcrack.sh filename'
	exit -1
	;;
esac

if [ ! -d $tmpmnt ]; then
    echo "creating directory "$tmpmnt
    mkdir $tmpmnt
fi

filesize=$(du --apparent-size --block-size=1 $1 | cut -f 1)
echo "filesize="$filesize


#start=786000
start=0
found=0
while [ $found -eq 0 ]
do
    echo start=$start
#    dd "if=$fname" "of=$tstimg" bs=1 skip=$start
#    ls -la $tstimg
    for mnt in $mnttypes
    do
	mount -o loop,offset=$start -t $mnt $tstimg $tmpmnt 2> /dev/null
	retval=$?
#	echo "mount "$mnt" ="$retval
	if [ $retval -eq 32 ]; then
	    umount $tmpmnt 2> /dev/null
	else
	    echo "*********MOUNT WORKED - Start=$start, mnt=$mnt ********"
	    echo "mounted using mount -o loop,offset=$start -t $mnt $tstimg $tmpmnt"
	    found=1
	    exit
	fi
    done

    if [ $start -eq $filesize ]; then
	echo "*************got to end********************"
	found=1
    fi
    start=$[ $start + 1 ]
done