OpenWrt – Rev 1
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/*
* --- ZyXEL header format ---
* Original Version by Benjamin Berg <benjamin@sipsolutions.net>
* C implementation based on generation-script by Christian Lamparter <chunkeey@gmail.com>
*
* The firmware image prefixed with a header (which is written into the MTD device).
* The header is one erase block (~64KiB) in size, but the checksum only convers the
* first 2KiB. Padding is 0xff. All integers are in big-endian.
*
* The checksum is always a 16-Bit System V checksum (sum -s) stored in a 32-Bit integer.
*
* 4 bytes: checksum of the rootfs image
* 4 bytes: length of the contained rootfs image file (big endian)
* 32 bytes: Firmware Version string (NUL terminated, 0xff padded)
* 4 bytes: checksum over the header partition (big endian - see below)
* 64 bytes: Model (e.g. "NBG6617", NUL termiated, 0xff padded)
* 4 bytes: checksum of the kernel partition
* 4 bytes: length of the contained kernel image file (big endian)
* rest: 0xff padding (To erase block size)
*
* The kernel partition checksum and length is not used for every device.
* If it's notused, pad those 8 bytes with 0xFF.
*
* The checksums are calculated by adding up all bytes and if a 16bit
* overflow occurs, one is added and the sum is masked to 16 bit:
* csum = csum + databyte; if (csum > 0xffff) { csum += 1; csum &= 0xffff };
* Should the file have an odd number of bytes then the byte len-0x800 is
* used additionally.
*
* The checksum for the header is calculated over the first 2048 bytes with
* the rootfs image checksum as the placeholder during calculation.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation.
*
*/
#include <fcntl.h>
#include <getopt.h>
#include <libgen.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#define VERSION_STRING_LEN 31
#define ROOTFS_HEADER_LEN 40
#define KERNEL_HEADER_LEN 8
#define BOARD_NAME_LEN 64
#define BOARD_HEADER_LEN 68
#define HEADER_PARTITION_CALC_LENGTH 2048
#define HEADER_PARTITION_LENGTH 0x10000
struct file_info {
char *name; /* name of the file */
char *data; /* file content */
size_t size; /* length of the file */
};
static char *progname;
static char *board_name = 0;
static char *version_name = 0;
static unsigned int rootfs_size = 0;
static struct file_info kernel = { NULL, NULL, 0 };
static struct file_info rootfs = { NULL, NULL, 0 };
static struct file_info rootfs_out = { NULL, NULL, 0 };
static struct file_info out = { NULL, NULL, 0 };
#define ERR(fmt, ...) do { \
fprintf(stderr, "[%s] *** error: " fmt "\n", \
progname, ## __VA_ARGS__ ); \
} while (0)
void map_file(struct file_info *finfo)
{
struct stat file_stat = {0};
int fd;
fd = open(finfo->name, O_RDONLY, (mode_t)0600);
if (fd == -1) {
ERR("Error while opening file %s.", finfo->name);
exit(EXIT_FAILURE);
}
if (fstat(fd, &file_stat) == -1) {
ERR("Error getting file size for %s.", finfo->name);
exit(EXIT_FAILURE);
}
finfo->size = file_stat.st_size;
finfo->data = mmap(0, finfo->size, PROT_READ, MAP_SHARED, fd, 0);
if (finfo->data == MAP_FAILED) {
ERR("Error mapping file %s.", finfo->name);
exit(EXIT_FAILURE);
}
close(fd);
}
void unmap_file(struct file_info *finfo)
{
if(munmap(finfo->data, finfo->size) == -1) {
ERR("Error unmapping file %s.", finfo->name);
exit(EXIT_FAILURE);
}
}
void write_file(struct file_info *finfo)
{
FILE *fout = fopen(finfo->name, "w");
fwrite(finfo->data, finfo->size, 1, fout);
if (ferror(fout)) {
ERR("Wanted to write, but something went wrong.");
exit(EXIT_FAILURE);
}
fclose(fout);
}
void usage(int status)
{
FILE *stream = (status != EXIT_SUCCESS) ? stderr : stdout;
fprintf(stream, "Usage: %s [OPTIONS...]\n", progname);
fprintf(stream,
"\n"
"Options:\n"
" -k <kernel> path for kernel image\n"
" -r <rootfs> path for rootfs image\n"
" -s <rfssize> size of output rootfs\n"
" -v <version> version string\n"
" -b <boardname> name of board to generate image for\n"
" -o <out_name> name of output image\n"
" -h show this screen\n"
);
exit(status);
}
static int sysv_chksm(const unsigned char *data, int size)
{
int r;
int checksum;
unsigned int s = 0; /* The sum of all the input bytes, modulo (UINT_MAX + 1). */
for (int i = 0; i < size; i++) {
s += data[i];
}
r = (s & 0xffff) + ((s & 0xffffffff) >> 16);
checksum = (r & 0xffff) + (r >> 16);
return checksum;
}
static int zyxel_chksm(const unsigned char *data, int size)
{
return htonl(sysv_chksm(data, size));
}
char *generate_rootfs_header(struct file_info filesystem, char *version)
{
size_t version_string_length;
unsigned int chksm, size;
char *rootfs_header;
size_t ptr = 0;
rootfs_header = malloc(ROOTFS_HEADER_LEN);
if (!rootfs_header) {
ERR("Couldn't allocate memory for rootfs header!");
exit(EXIT_FAILURE);
}
/* Prepare padding for firmware-version string here */
memset(rootfs_header, 0xff, ROOTFS_HEADER_LEN);
chksm = zyxel_chksm((const unsigned char *)filesystem.data, filesystem.size);
size = htonl(filesystem.size);
/* 4 bytes: checksum of the rootfs image */
memcpy(rootfs_header + ptr, &chksm, 4);
ptr += 4;
/* 4 bytes: length of the contained rootfs image file (big endian) */
memcpy(rootfs_header + ptr, &size, 4);
ptr += 4;
/* 32 bytes: Firmware Version string (NUL terminated, 0xff padded) */
version_string_length = strlen(version) <= VERSION_STRING_LEN ? strlen(version) : VERSION_STRING_LEN;
memcpy(rootfs_header + ptr, version, version_string_length);
ptr += version_string_length;
/* Add null-terminator */
rootfs_header[ptr] = 0x0;
return rootfs_header;
}
char *generate_kernel_header(struct file_info kernel)
{
unsigned int chksm, size;
char *kernel_header;
size_t ptr = 0;
kernel_header = malloc(KERNEL_HEADER_LEN);
if (!kernel_header) {
ERR("Couldn't allocate memory for kernel header!");
exit(EXIT_FAILURE);
}
chksm = zyxel_chksm((const unsigned char *)kernel.data, kernel.size);
size = htonl(kernel.size);
/* 4 bytes: checksum of the kernel image */
memcpy(kernel_header + ptr, &chksm, 4);
ptr += 4;
/* 4 bytes: length of the contained kernel image file (big endian) */
memcpy(kernel_header + ptr, &size, 4);
return kernel_header;
}
unsigned int generate_board_header_checksum(char *kernel_hdr, char *rootfs_hdr, char *boardname)
{
char *board_hdr_tmp;
unsigned int sum;
size_t ptr = 0;
/*
* The checksum of the board header is calculated over the first 2048 bytes of
* the header partition with the rootfs checksum used as a placeholder for then
* board checksum we calculate in this step. The checksum gained from this step
* is then used for the final board header partition.
*/
board_hdr_tmp = malloc(HEADER_PARTITION_CALC_LENGTH);
if (!board_hdr_tmp) {
ERR("Couldn't allocate memory for temporary board header!");
exit(EXIT_FAILURE);
}
memset(board_hdr_tmp, 0xff, HEADER_PARTITION_CALC_LENGTH);
/* 40 bytes: RootFS header */
memcpy(board_hdr_tmp, rootfs_hdr, ROOTFS_HEADER_LEN);
ptr += ROOTFS_HEADER_LEN;
/* 4 bytes: RootFS checksum (BE) as placeholder for board-header checksum */
memcpy(board_hdr_tmp + ptr, rootfs_hdr, 4);
ptr += 4;
/* 32 bytes: Model (e.g. "NBG6617", NUL termiated, 0xff padded) */
memcpy(board_hdr_tmp + ptr, boardname, strlen(boardname));
ptr += strlen(boardname);
/* Add null-terminator */
board_hdr_tmp[ptr] = 0x0;
ptr = ROOTFS_HEADER_LEN + 4 + BOARD_NAME_LEN;
/* 8 bytes: Kernel header */
if (kernel_hdr)
memcpy(board_hdr_tmp + ptr, kernel_hdr, 8);
/* Calculate the checksum over the first 2048 bytes */
sum = zyxel_chksm((const unsigned char *)board_hdr_tmp, HEADER_PARTITION_CALC_LENGTH);
free(board_hdr_tmp);
return sum;
}
char *generate_board_header(char *kernel_hdr, char *rootfs_hdr, char *boardname)
{
unsigned int board_checksum;
char *board_hdr;
board_hdr = malloc(BOARD_HEADER_LEN);
if (!board_hdr) {
ERR("Couldn't allocate memory for board header!");
exit(EXIT_FAILURE);
}
memset(board_hdr, 0xff, BOARD_HEADER_LEN);
/* 4 bytes: checksum over the header partition (big endian) */
board_checksum = generate_board_header_checksum(kernel_hdr, rootfs_hdr, boardname);
memcpy(board_hdr, &board_checksum, 4);
/* 32 bytes: Model (e.g. "NBG6617", NUL termiated, 0xff padded) */
memcpy(board_hdr + 4, boardname, strlen(boardname));
board_hdr[4 + strlen(boardname)] = 0x0;
return board_hdr;
}
int build_image()
{
char *rootfs_header = NULL;
char *kernel_header = NULL;
char *board_header = NULL;
size_t ptr;
/* Load files */
if (kernel.name)
map_file(&kernel);
map_file(&rootfs);
/*
* Allocate memory and copy input rootfs for temporary output rootfs.
* This is important as we have to generate the rootfs checksum over the
* entire rootfs partition. As we might have to pad the partition to allow
* for flashing via ZyXEL's Web-GUI, we prepare the rootfs partition for the
* output image here (and also use it for calculating the rootfs checksum).
*
* The roofs padding has to be done with 0x00.
*/
rootfs_out.data = calloc(rootfs_out.size, sizeof(char));
memcpy(rootfs_out.data, rootfs.data, rootfs.size);
/* Prepare headers */
rootfs_header = generate_rootfs_header(rootfs_out, version_name);
if (kernel.name)
kernel_header = generate_kernel_header(kernel);
board_header = generate_board_header(kernel_header, rootfs_header, board_name);
/* Prepare output file */
out.size = HEADER_PARTITION_LENGTH + rootfs_out.size;
if (kernel.name)
out.size += kernel.size;
out.data = malloc(out.size);
memset(out.data, 0xFF, out.size);
/* Build output image */
memcpy(out.data, rootfs_header, ROOTFS_HEADER_LEN);
memcpy(out.data + ROOTFS_HEADER_LEN, board_header, BOARD_HEADER_LEN);
if (kernel.name)
memcpy(out.data + ROOTFS_HEADER_LEN + BOARD_HEADER_LEN, kernel_header, KERNEL_HEADER_LEN);
ptr = HEADER_PARTITION_LENGTH;
memcpy(out.data + ptr, rootfs_out.data, rootfs_out.size);
ptr += rootfs_out.size;
if (kernel.name)
memcpy(out.data + ptr, kernel.data, kernel.size);
/* Write back output image */
write_file(&out);
/* Free allocated memory */
if (kernel.name)
unmap_file(&kernel);
unmap_file(&rootfs);
free(out.data);
free(rootfs_out.data);
free(rootfs_header);
if (kernel.name)
free(kernel_header);
free(board_header);
return 0;
}
int check_options()
{
if (!rootfs.name) {
ERR("No rootfs filename supplied");
return -2;
}
if (!out.name) {
ERR("No output filename supplied");
return -3;
}
if (!board_name) {
ERR("No board-name supplied");
return -4;
}
if (!version_name) {
ERR("No version supplied");
return -5;
}
if (rootfs_size <= 0) {
ERR("Invalid rootfs size supplied");
return -6;
}
if (strlen(board_name) > 31) {
ERR("Board name is to long");
return -7;
}
return 0;
}
int main(int argc, char *argv[])
{
int ret;
progname = basename(argv[0]);
while (1) {
int c;
c = getopt(argc, argv, "b:k:o:r:s:v:h");
if (c == -1)
break;
switch (c) {
case 'b':
board_name = optarg;
break;
case 'h':
usage(EXIT_SUCCESS);
break;
case 'k':
kernel.name = optarg;
break;
case 'o':
out.name = optarg;
break;
case 'r':
rootfs.name = optarg;
break;
case 's':
sscanf(optarg, "%u", &rootfs_size);
break;
case 'v':
version_name = optarg;
break;
default:
usage(EXIT_FAILURE);
break;
}
}
ret = check_options();
if (ret)
usage(EXIT_FAILURE);
/* As ZyXEL Web-GUI only accept images with a rootfs equal or larger than the first firmware shipped
* for the device, we need to pad rootfs partition to this size. To perform further calculations, we
* decide the size of this part here. In case the rootfs we want to integrate in our image is larger,
* take it's size, otherwise the supplied size.
*
* Be careful! We rely on assertion of correct size to be performed beforehand. It is unknown if images
* with a to large rootfs are accepted or not.
*/
rootfs_out.size = rootfs_size < rootfs.size ? rootfs.size : rootfs_size;
return build_image();
}