150 lines
3.6 KiB
C
150 lines
3.6 KiB
C
/*
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* wndr3700.c - partially based on OpenWrt's add_header.c
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*
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* Copyright (C) 2009 Anael Orlinski <naouel@naouel.org>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License,
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* version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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/*
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* The add_header utility used by various vendors preprends the buf
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* image with a header containing a CRC32 value which is generated for the
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* model id + reserved space for CRC32 + buf, then replaces the reserved
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* area with the actual CRC32. This replacement tool mimics this behavior.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stddef.h>
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#include <unistd.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <sys/mman.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <inttypes.h>
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#define BPB 8 /* bits/byte */
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#define WNDR3700_MAGIC_LEN 4
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static uint32_t crc32[1<<BPB];
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static char *magic = "3700";
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static void init_crc32()
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{
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const uint32_t poly = ntohl(0x2083b8ed);
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int n;
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for (n = 0; n < 1<<BPB; n++) {
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uint32_t crc = n;
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int bit;
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for (bit = 0; bit < BPB; bit++)
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crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
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crc32[n] = crc;
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}
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}
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static uint32_t crc32buf(unsigned char *buf, size_t len)
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{
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uint32_t crc = 0xFFFFFFFF;
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for (; len; len--, buf++)
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crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
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return ~crc;
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}
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struct header {
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unsigned char magic[WNDR3700_MAGIC_LEN];
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uint32_t crc;
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unsigned char stuff[56];
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};
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static void usage(const char *) __attribute__ (( __noreturn__ ));
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static void usage(const char *mess)
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{
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fprintf(stderr, "Error: %s\n", mess);
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fprintf(stderr, "Usage: wndr3700 input_file output_file [magic]\n");
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fprintf(stderr, "\n");
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exit(1);
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}
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int main(int argc, char **argv)
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{
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off_t len; // of original buf
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off_t buflen; // of the output file
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int fd;
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void *input_file; // pointer to the input file (mmmapped)
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struct header header;
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unsigned char *buf; // pointer to prefix + copy of original buf
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// verify parameters
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if (argc < 3)
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usage("wrong number of arguments");
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if (argc > 3)
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magic = argv[3];
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if (strlen(magic) != WNDR3700_MAGIC_LEN) {
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fprintf(stderr, "Invalid magic: '%s'\n", magic);
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exit(1);
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}
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// mmap input_file
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if ((fd = open(argv[1], O_RDONLY)) < 0
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|| (len = lseek(fd, 0, SEEK_END)) < 0
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|| (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
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|| close(fd) < 0)
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{
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fprintf(stderr, "Error loading file %s: %s\n", argv[1], strerror(errno));
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exit(1);
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}
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buflen = len;
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init_crc32();
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// preload header
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memcpy(&header, input_file, sizeof(header));
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memcpy(header.magic, magic, WNDR3700_MAGIC_LEN);
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header.crc = 0;
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// create a firmware image in memory and copy the input_file to it
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buf = malloc(buflen);
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memcpy(buf, input_file, len);
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// CRC of temporary header
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header.crc = htonl(crc32buf((unsigned char*)&header, sizeof(header)));
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memcpy(buf, &header, sizeof(header));
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// write the buf
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if ((fd = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
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|| write(fd, buf, buflen) != buflen
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|| close(fd) < 0)
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{
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fprintf(stderr, "Error storing file %s: %s\n", argv[2], strerror(errno));
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exit(2);
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}
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free(buf);
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munmap(input_file,len);
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return 0;
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}
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