#!/bin/bash
# Converts little endian 4-byte unsigned integer given as spaced hex string
# into decimal number (e.g. "00 D0 4C 00" -> 5033984)
hex2dec()
{
# ATTENTION, 'strtonum' is gawk-specific, other awk versions like mawk
# probably do not know it.
echo "$1" | gawk '{ printf "%d\n", strtonum("0x" $4 $3 $2 $1) }'
}
extract_exe_start()
{
echo -e "Extracting executabel first part ..."
exe_length=$kernel_start_at
 #echo "exe_length:$exe_length"
output_file="$output_dir/exe_start"
echo " exe_start, start @ 0, length: $exe_length"
dd if="$input_file" of="$output_file" ibs=$exe_length obs=8192 count=1 2> /dev/null
}
extract_exe_end()
{
echo -e "Extracting executabel end part ..."
act_size=`ls -l "$input_file" | sed -e 's/[^0-9]/#/g' | sed -e 's/#\+[0-9]\+#\+\([0-9]\+\).*/\1/'`
offs=$((bootloder_start_at + bsize))
esize=$((act_size - offs))
output_file="$output_dir/exe_end"
echo " exe_end, start @ $offs, length: $esize, end @ $act_size"
( dd of="/dev/null" ibs=$offs obs=8192 count=1 2> /dev/null && dd of="$output_file" ibs=$esize obs=8192 count=1 2> /dev/null ) < "$input_file"
}
extract_bootloader()
{
echo -e "Extracting bootloader (urlader.image) ..."
output_file="$output_dir/urlader.image"
act_end=$((bootloder_start_at + bsize))
echo " urlader.image, start @ $bootloder_start_at, length: $bsize, end @ $act_end"
( dd of="/dev/null" ibs=$bootloder_start_at obs=8192 count=1 2> /dev/null && dd of="$output_file" ibs=$bsize obs=8192 count=1 2> /dev/null ) < "$input_file"
grep -iq 'entering passive mode' "$output_file" \
&& grep -iq 'ftp server ready' "$output_file" \
&& echo " file is a possible bootloader candidate" 
}
extract_kernel_plus_mid()
{
echo -e "Extracting root kernel (kernel.image) ..."
dd_count=$((kernel_end - kernel_start_at))
output_file="$output_dir/kernel.image"
echo " kernel.image, start @ ${kernel_start_at}, length: $dd_count, end @ $kernel_end"
( dd of="/dev/null" ibs=$kernel_start_at obs=8192 count=1 2> /dev/null && dd of="$output_file" ibs=$dd_count obs=8192 count=1 2> /dev/null ) < "$input_file"
output_file="$output_dir/exe_mid"
echo " exe_mid, start @ $kernel_end, length: $psize, end @ $bootloder_start_at "
( dd of="/dev/null" ibs=$kernel_end obs=8192 count=1 2> /dev/null && dd of="$output_file" ibs=$psize obs=8192 count=1 2> /dev/null ) < "$input_file"
#dd if="$output_file" bs=1 count=16  2> /dev/null | tr -d '[:alpha:]' | sed 's/-\.//' | sed 's/-//' 
OldRversion="$(dd if=$output_dir/exe_mid bs=1 count=32  2> /dev/null)" #get it directly
OldRversion="$(echo $OldRversion | sed 's/\(.*[0-9][0-9]\.[0-9][0-9]\.[0-9][0-9]\).*/\1/')"
echo "Firmware version: $OldRversion"
}
# Extracts kernel.image candidates from input file, based on kernel and
# SquashFS magic strings.
# calculated from assumed length header field is close enough to subsequent
# SquashFS start offset.
# firmwares, but currently no other image types.
## did not work correctly, looks like it works again but is 6 byte shorter
extract_kernel_image()
{
echo -e "Extracting kernel.image ..."
kernel_lines="$(tools/hexgrep "$KERNEL_MAGIC" "$input_file")"
 #echo "kernel magic line: $kernel_lines"
kernel_offs=($(echo "$kernel_lines" | sed 's/:.*//'))
 #echo "kernel offset: $kernel_offs"
squashfs_lines="$(tools/hexgrep "$SQUASHFS_MAGIC" "$input_file")"
 #echo "squashfs magic line: $squashfs_lines"
squashfs_offs=($(echo "$squashfs_lines" | sed 's/:.*//'))
 #echo "squashfs offset: $squashfs_offs"
 #echo -n "squashfs length in hex: "
 #echo "$squashfs_lines" | sed -r 's/^[0-9]+:.{24}(.*)/\1/'
squashfs_length=($(hex2dec "$(echo "$squashfs_lines" | sed -r 's/^[0-9]+:.{24}(.*)/\1/')"))
 #echo "squashfs length in decimal: $squashfs_length"
 #ls -l "$input_file"
act_size=`ls -l "$input_file" | sed -e 's/[^0-9]/#/g' | sed -e 's/#\+[0-9]\+#\+\([0-9]\+\).*/\1/'`
 #echo "File sizes: $act_size"
dd_count=$((squashfs_offs - kernel_offs + squashfs_length))
 ##older firmwaews used to have zerro bytes added
 #dd_count=$((((squashfs_offs - kernel_offs + squashfs_length) | 0xFFF)+1))
 #echo "File sizes: $dd_count"
output_file="$output_dir/kernel.image"
echo " kernel.image, start @ ${kernel_offs}, SquashFS @ ${squashfs_offs}, length: $dd_count, end @ $act_size"
( dd of="/dev/null" ibs=$kernel_offs obs=8192 count=1 2> /dev/null && dd of="$output_file" ibs=$dd_count obs=8192 count=1 2> /dev/null ) < "$input_file"
}
# No exit 0 is used as incudefile