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/*
* wndr3700.c - partially based on OpenWrt's add_header.c
*
* Copyright (C) 2009 Anael Orlinski <naouel@naouel.org>
*
* 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.
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/*
* The add_header utility used by various vendors preprends the buf
* image with a header containing a CRC32 value which is generated for the
* model id + reserved space for CRC32 + buf, then replaces the reserved
* area with the actual CRC32. This replacement tool mimics this behavior.
*/
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
#include <netinet/in.h>
#include <inttypes.h>
#define BPB 8 /* bits/byte */
#define WNDR3700_MAGIC_LEN 4
static uint32_t crc32[1<<BPB];
static char *magic = "3700";
static void init_crc32()
{
const uint32_t poly = ntohl(0x2083b8ed);
int n;
for (n = 0; n < 1<<BPB; n++) {
uint32_t crc = n;
int bit;
for (bit = 0; bit < BPB; bit++)
crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
crc32[n] = crc;
}
}
static uint32_t crc32buf(unsigned char *buf, size_t len)
{
uint32_t crc = 0xFFFFFFFF;
for (; len; len--, buf++)
crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
return ~crc;
}
struct header {
unsigned char magic[WNDR3700_MAGIC_LEN];
uint32_t crc;
unsigned char stuff[56];
};
static void usage(const char *) __attribute__ (( __noreturn__ ));
static void usage(const char *mess)
{
fprintf(stderr, "Error: %s\n", mess);
fprintf(stderr, "Usage: wndr3700 input_file output_file [magic]\n");
fprintf(stderr, "\n");
exit(1);
}
int main(int argc, char **argv)
{
off_t len; // of original buf
off_t buflen; // of the output file
int fd;
void *input_file; // pointer to the input file (mmmapped)
struct header header;
unsigned char *buf; // pointer to prefix + copy of original buf
// verify parameters
if (argc < 3)
usage("wrong number of arguments");
if (argc > 3)
magic = argv[3];
if (strlen(magic) != WNDR3700_MAGIC_LEN) {
fprintf(stderr, "Invalid magic: '%s'\n", magic);
exit(1);
}
// mmap input_file
if ((fd = open(argv[1], O_RDONLY)) < 0
|| (len = lseek(fd, 0, SEEK_END)) < 0
|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
|| close(fd) < 0)
{
fprintf(stderr, "Error loading file %s: %s\n", argv[1], strerror(errno));
exit(1);
}
buflen = len;
init_crc32();
// preload header
memcpy(&header, input_file, sizeof(header));
memcpy(header.magic, magic, WNDR3700_MAGIC_LEN);
header.crc = 0;
// create a firmware image in memory and copy the input_file to it
buf = malloc(buflen);
memcpy(buf, input_file, len);
// CRC of temporary header
header.crc = htonl(crc32buf((unsigned char*)&header, sizeof(header)));
memcpy(buf, &header, sizeof(header));
// write the buf
if ((fd = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
|| write(fd, buf, buflen) != buflen
|| close(fd) < 0)
{
fprintf(stderr, "Error storing file %s: %s\n", argv[2], strerror(errno));
exit(2);
}
free(buf);
munmap(input_file,len);
return 0;
}
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