OpenWrt – Rev 1
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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#define IMG_SIZE 0x3e0000
#define KERNEL_START 0x020000
#define KERNEL_SIZE 0x0b0000
#define ROOTFS_START 0x0d0000
#define ROOTFS_SIZE 0x30ffb2
char* app_name;
void print_usage(void)
{
fprintf(stderr, "usage: dgfirmware [<opts>] <img>\n");
fprintf(stderr, " <img> firmware image filename\n");
fprintf(stderr, " <opts> -h print this message\n");
fprintf(stderr, " -f fix the checksum\n");
fprintf(stderr, " -x <file> extract the rootfs file to <file>\n");
fprintf(stderr, " -xk <file> extract the kernel to <file>\n");
fprintf(stderr, " -m <file> merge in rootfs fil\e from <file>\n");
fprintf(stderr, " -k <file> merge in kernel from <file>\n");
fprintf(stderr, " -w <file> write back the modified firmware\n");
}
unsigned char* read_img(const char *fname)
{
FILE *fp;
int size;
unsigned char *img;
fp = fopen(fname, "rb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
fseek(fp, 0, SEEK_END);
size = ftell(fp);
if (size != IMG_SIZE) {
fprintf(stderr, "%s: image file has wrong size\n", app_name);
fclose(fp);
exit(-1);
}
rewind(fp);
img = malloc(IMG_SIZE);
if (img == NULL) {
perror(app_name);
fclose(fp);
exit(-1);
}
if (fread(img, 1, IMG_SIZE, fp) != IMG_SIZE) {
fprintf(stderr, "%s: can't read image file\n", app_name);
fclose(fp);
exit(-1);
}
fclose(fp);
return img;
}
void write_img(unsigned char* img, const char *fname)
{
FILE *fp;
fp = fopen(fname, "wb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
if (fwrite(img, 1, IMG_SIZE, fp) != IMG_SIZE) {
fprintf(stderr, "%s: can't write image file\n", app_name);
fclose(fp);
exit(-1);
}
}
void write_rootfs(unsigned char* img, const char *fname)
{
FILE *fp;
fp = fopen(fname, "wb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
if (fwrite(img+ROOTFS_START, 1, ROOTFS_SIZE, fp) != ROOTFS_SIZE) {
fprintf(stderr, "%s: can't write image file\n", app_name);
fclose(fp);
exit(-1);
}
}
void write_kernel(unsigned char* img, const char *fname)
{
FILE *fp;
fp = fopen(fname, "wb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
if (fwrite(img+KERNEL_START, 1, KERNEL_SIZE, fp) != KERNEL_SIZE) {
fprintf(stderr, "%s: can't write kernel file\n", app_name);
fclose(fp);
exit(-1);
}
}
unsigned char* read_rootfs(unsigned char* img, const char *fname)
{
FILE *fp;
int size;
int i;
for (i=ROOTFS_START; i<ROOTFS_START+ROOTFS_SIZE; i++)
img[i] = 0xff;
fp = fopen(fname, "rb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
fseek(fp, 0, SEEK_END);
size = ftell(fp);
if (size > ROOTFS_SIZE) {
fprintf(stderr, "%s: rootfs image file is too big\n", app_name);
fclose(fp);
exit(-1);
}
rewind(fp);
if (fread(img+ROOTFS_START, 1, size, fp) != size) {
fprintf(stderr, "%s: can't read rootfs image file\n", app_name);
fclose(fp);
exit(-1);
}
fclose(fp);
return img;
}
unsigned char* read_kernel(unsigned char* img, const char *fname)
{
FILE *fp;
int size;
int i;
for (i=KERNEL_START; i<KERNEL_START+KERNEL_SIZE; i++)
img[i] = 0xff;
fp = fopen(fname, "rb");
if (fp == NULL) {
perror(app_name);
exit(-1);
}
fseek(fp, 0, SEEK_END);
size = ftell(fp);
if (size > KERNEL_SIZE) {
fprintf(stderr, "%s: kernel binary file is too big\n", app_name);
fclose(fp);
exit(-1);
}
rewind(fp);
if (fread(img+KERNEL_START, 1, size, fp) != size) {
fprintf(stderr, "%s: can't read kernel file\n", app_name);
fclose(fp);
exit(-1);
}
fclose(fp);
return img;
}
int get_checksum(unsigned char* img)
{
short unsigned s;
s = img[0x3dfffc] + (img[0x3dfffd]<<8);
return s;
}
void set_checksum(unsigned char*img, unsigned short sum)
{
img[0x3dfffc] = sum & 0xff;
img[0x3dfffd] = (sum>>8) & 0xff;
}
int compute_checksum(unsigned char* img)
{
int i;
short s=0;
for (i=0; i<0x3dfffc; i++)
s += img[i];
return s;
}
int main(int argc, char* argv[])
{
char *img_fname = NULL;
char *rootfs_fname = NULL;
char *kernel_fname = NULL;
char *new_img_fname = NULL;
int do_fix_checksum = 0;
int do_write = 0;
int do_write_rootfs = 0;
int do_read_rootfs = 0;
int do_write_kernel = 0;
int do_read_kernel = 0;
int i;
unsigned char *img;
unsigned short img_checksum;
unsigned short real_checksum;
app_name = argv[0];
for (i=1; i<argc; i++) {
if (!strcmp(argv[i], "-h")) {
print_usage();
return 0;
}
else if (!strcmp(argv[i], "-f")) {
do_fix_checksum = 1;
}
else if (!strcmp(argv[i], "-x")) {
if (i+1 >= argc) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
do_write_rootfs = 1;
rootfs_fname = argv[i+1];
i++;
}
else if (!strcmp(argv[i], "-xk")) {
if (i+1 >= argc) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
do_write_kernel = 1;
kernel_fname = argv[i+1];
i++;
}
else if (!strcmp(argv[i], "-m")) {
if (i+1 >= argc) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
do_read_rootfs = 1;
rootfs_fname = argv[i+1];
i++;
}
else if (!strcmp(argv[i], "-k")) {
if (i+1 >= argc) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
do_read_kernel = 1;
kernel_fname = argv[i+1];
i++;
}
else if (!strcmp(argv[i], "-w")) {
if (i+1 >= argc) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
do_write = 1;
new_img_fname = argv[i+1];
i++;
}
else if (img_fname != 0) {
fprintf(stderr, "%s: too many arguments\n", app_name);
return -1;
}
else {
img_fname = argv[i];
}
}
if (img_fname == NULL) {
fprintf(stderr, "%s: missing argument\n", app_name);
return -1;
}
if ((do_read_rootfs && do_write_rootfs) ||
(do_read_kernel && do_write_kernel)) {
fprintf(stderr, "%s: conflictuous options\n", app_name);
return -1;
}
printf ("** Read firmware file\n");
img = read_img(img_fname);
printf ("Firmware product: %s\n", img+0x3dffbd);
printf ("Firmware version: 1.%02d.%02d\n", (img[0x3dffeb] & 0x7f), img[0x3dffec]);
if (do_write_rootfs) {
printf ("** Write rootfs file\n");
write_rootfs(img, rootfs_fname);
}
if (do_write_kernel) {
printf ("** Write kernel file\n");
write_kernel(img, kernel_fname);
}
if (do_read_rootfs) {
printf ("** Read rootfs file\n");
read_rootfs(img, rootfs_fname);
do_fix_checksum = 1;
}
if (do_read_kernel) {
printf ("** Read kernel file\n");
read_kernel(img, kernel_fname);
do_fix_checksum = 1;
}
img_checksum = get_checksum(img);
real_checksum = compute_checksum(img);
printf ("image checksum = %04x\n", img_checksum);
printf ("real checksum = %04x\n", real_checksum);
if (do_fix_checksum) {
if (img_checksum != real_checksum) {
printf ("** Bad Checksum, fix it\n");
set_checksum(img, real_checksum);
}
else {
printf ("** Checksum is correct, good\n");
}
}
if (do_write) {
printf ("** Write image file\n");
write_img(img, new_img_fname);
}
free(img);
return 0;
}