mirror of https://github.com/hak5/openwrt.git
197 lines
5.1 KiB
Bash
Executable File
197 lines
5.1 KiB
Bash
Executable File
#!/usr/bin/env bash
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#
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# --- ZyXEL header format ---
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# Original Version by Benjamin Berg <benjamin@sipsolutions.net>
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#
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# The firmware image prefixed with a header (which is written into the MTD device).
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# The header is one erase block (~64KiB) in size, but the checksum only convers the
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# first 2KiB. Padding is 0xff. All integers are in big-endian.
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#
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# The checksum is always a 16-Bit System V checksum (sum -s) stored in a 32-Bit integer.
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#
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# 4 bytes: checksum of the rootfs image
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# 4 bytes: length of the contained rootfs image file (big endian)
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# 32 bytes: Firmware Version string (NUL terminated, 0xff padded)
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# 4 bytes: checksum over the header partition (big endian - see below)
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# 32 bytes: Model (e.g. "NBG6617", NUL termiated, 0xff padded)
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# 4 bytes: checksum of the kernel partition
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# 4 bytes: length of the contained kernel image file (big endian)
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# rest: 0xff padding
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#
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# The checksums are calculated by adding up all bytes and if a 16bit
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# overflow occurs, one is added and the sum is masked to 16 bit:
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# csum = csum + databyte; if (csum > 0xffff) { csum += 1; csum &= 0xffff };
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# Should the file have an odd number of bytes then the byte len-0x800 is
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# used additionally.
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#
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# The checksum for the header is calculated over the first 2048 bytes with
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# the rootfs image checksum as the placeholder during calculation.
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#
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# The header is padded with 0xff to the erase block size of the device.
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#
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board=""
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version=""
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kernel=""
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rootfs=""
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outfile=""
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err=""
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while [ "$1" ]; do
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case "$1" in
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"--board")
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board="$2"
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shift
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shift
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continue
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;;
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"--version")
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version="$2"
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shift
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shift
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continue
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;;
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"--kernel")
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kernel="$2"
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shift
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shift
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continue
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;;
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"--rootfs")
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rootfs="$2"
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shift
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shift
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continue
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;;
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"--rootfssize")
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rootfssize="$2"
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shift
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shift
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continue
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;;
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*)
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if [ ! "$outfile" ]; then
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outfile=$1
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shift
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continue
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fi
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;;
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esac
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done
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if [ ! -n "$board" -o ! -n "$version" -o ! -r "$kernel" -o ! -r "$rootfs" -o ! "$rootfssize" -o ! "$outfile" ]; then
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echo "syntax: $0 [--board ras-boardname] [--version ras-version] [--kernel kernelimage] [--rootfs rootfs] out"
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exit 1
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fi
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rootfs_len=$(wc -c < "$rootfs")
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if [ "$rootfs_len" -lt "$rootfssize" ]; then
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dd if=$rootfs of=$rootfs.new bs=$rootfssize conv=sync
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mv $rootfs.new $rootfs
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fi
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if [ ${#version} -ge 28 ]; then
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echo "version: '$version' is too long"
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exit 1
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fi
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tmpdir="$( mktemp -d 2> /dev/null )"
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if [ -z "$tmpdir" ]; then
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# try OSX signature
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tmpdir="$( mktemp -t 'ubitmp' -d )"
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fi
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if [ -z "$tmpdir" ]; then
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exit 1
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fi
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to_be() {
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local val="$1"
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local size="$2"
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case "$size" in
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4)
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echo $(( "$val" >> 24 | ("$val" & 0xff0000) >> 8 | ("$val" & 0xff00) << 8 | ("$val" & 0xff) << 24 ))
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;;
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2)
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echo $(( "$val" >> 8 | ("$val" & 0xff) << 8))
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;;
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esac
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}
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checksum_file() {
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local file=$1
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# ZyXEL seems to use System V sum mode... Now this is classy, who would have thought?!
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echo $(sum -s ${file} | cut -f1 -d" ")
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}
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append_bin() {
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local val=$1
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local size=$2
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local file=$3
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while [ "$size" -ne 0 ]; do
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printf \\$(printf %o $(("$val" & 0xff))) >> "$file"
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val=$(($val >> 8))
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let size-=1
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done
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return
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}
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tf=${tmpdir}/out
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pad=$(printf '%0.1s' $(printf "\xff"){1..64})
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rootfs_header_file="$tmpdir/rootfs_header"
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rootfs_chksum=$(to_be $(checksum_file ${rootfs}) 4)
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rootfs_len=$(to_be $(wc -c < "$rootfs") 4)
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versionpadlen=$(( 32 - ( ${#version} + 1) ))
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# 4 bytes: checksum of the rootfs image
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append_bin "$rootfs_chksum" 4 "$rootfs_header_file"
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# 4 bytes: length of the contained rootfs image file (big endian)
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append_bin "$rootfs_len" 4 "$rootfs_header_file"
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# 32 bytes: Firmware Version string (NUL terminated, 0xff padded)
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printf "%s\x00%.*s" "$version" "$versionpadlen" "$pad" >> "$rootfs_header_file"
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kernel_header_file="$tmpdir/kernel_header"
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kernel_chksum=$(to_be $(checksum_file ${kernel}) 4)
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kernel_len=$(to_be $(wc -c < "$kernel") 4)
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# 4 bytes: checksum of the kernel image
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append_bin "$kernel_chksum" 4 "$kernel_header_file"
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# 4 bytes: length of the contained kernel image file (big endian)
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append_bin "$kernel_len" 4 "$kernel_header_file"
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board_header_file="$tmpdir/board_header"
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board_file="$tmpdir/board"
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boardpadlen=$(( 64 - ( ${#board} + 1) ))
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# 32 bytes: Model (e.g. "NBG6617", NUL termiated, 0xff padded)
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printf "%s\x00%.*s" "$board" "$boardpadlen" "$pad" > "$board_file"
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cat "$kernel_header_file" >> "$board_file"
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printf "%.12s" "$pad" >> "$board_file"
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# rest: 0xff padding
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for i in {1..511}; do
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printf "%s%s" "$pad" "$pad" >> "$board_file"
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done
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tmp_board_file="$tmpdir/tmp_board_file"
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cat "$rootfs_header_file" > "$tmp_board_file"
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# The checksum for the header is calculated over the first 2048 bytes with
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# the rootfs image checksum as the placeholder during calculation.
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append_bin "$rootfs_chksum" 4 "$tmp_board_file"
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cat "$board_file" >> "$tmp_board_file"
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truncate -s 2048 $tmp_board_file
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board_chksum=$(to_be $(checksum_file ${tmp_board_file}) 4)
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# 4 bytes: checksum over the header partition (big endian)
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append_bin "$board_chksum" 4 "$board_header_file"
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cat "$board_file" >> "$board_header_file"
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cat "$rootfs_header_file" "$board_header_file" "$rootfs" "$kernel" > "$outfile"
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rm -rf "$tmpdir"
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