tools/firmware-utils/src/wndr3700.c

   1 /*
   2  * wndr3700.c - partially based on OpenWrt's add_header.c
   3  *
   4  * Copyright (C) 2009 Anael Orlinski  <naouel@naouel.org>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License,
   8  * version 2 as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  18  */
  19
  20 /*
  21  * The add_header utility used by various vendors preprends the buf
  22  * image with a header containing a CRC32 value which is generated for the
  23  * model id + reserved space for CRC32 + buf, then replaces the reserved
  24  * area with the actual CRC32. This replacement tool mimics this behavior.
  25  */
  26
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <stddef.h>
  30 #include <unistd.h>
  31 #include <errno.h>
  32 #include <fcntl.h>
  33 #include <sys/mman.h>
  34 #include <string.h>
  35 #include <netinet/in.h>
  36 #include <inttypes.h>
  37
  38 #define BPB 8 /* bits/byte */
  39
  40 #define WNDR3700_MAGIC_LEN      4
  41
  42 static uint32_t crc32[1<<BPB];
  43 static char *magic = "3700";
  44
  45 static void init_crc32()
  46 {
  47         const uint32_t poly = ntohl(0x2083b8ed);
  48         int n;
  49
  50         for (n = 0; n < 1<<BPB; n++) {
  51                 uint32_t crc = n;
  52                 int bit;
  53
  54                 for (bit = 0; bit < BPB; bit++)
  55                         crc = (crc & 1) ? (poly ^ (crc >> 1)) : (crc >> 1);
  56                 crc32[n] = crc;
  57         }
  58 }
  59
  60 static uint32_t crc32buf(unsigned char *buf, size_t len)
  61 {
  62         uint32_t crc = 0xFFFFFFFF;
  63
  64         for (; len; len--, buf++)
  65                 crc = crc32[(uint8_t)crc ^ *buf] ^ (crc >> BPB);
  66         return ~crc;
  67 }
  68
  69 struct header {
  70     unsigned char magic[WNDR3700_MAGIC_LEN];
  71     uint32_t crc;
  72     unsigned char stuff[56];
  73 };
  74
  75 static void usage(const char *) __attribute__ (( __noreturn__ ));
  76
  77 static void usage(const char *mess)
  78 {
  79         fprintf(stderr, "Error: %s\n", mess);
  80         fprintf(stderr, "Usage: wndr3700 input_file output_file [magic]\n");
  81         fprintf(stderr, "\n");
  82         exit(1);
  83 }
  84
  85 int main(int argc, char **argv)
  86 {
  87         off_t len;                      // of original buf
  88         off_t buflen;                   // of the output file
  89         int fd;
  90         void *input_file;               // pointer to the input file (mmmapped)
  91         struct header header;
  92         unsigned char *buf;     // pointer to prefix + copy of original buf
  93
  94         // verify parameters
  95
  96         if (argc < 3)
  97                 usage("wrong number of arguments");
  98
  99         if (argc > 3)
 100                 magic = argv[3];
 101
 102         if (strlen(magic) != WNDR3700_MAGIC_LEN) {
 103                 fprintf(stderr, "Invalid magic: '%s'\n", magic);
 104                 exit(1);
 105         }
 106
 107         // mmap input_file
 108         if ((fd = open(argv[1], O_RDONLY))  < 0
 109         || (len = lseek(fd, 0, SEEK_END)) < 0
 110         || (input_file = mmap(0, len, PROT_READ, MAP_SHARED, fd, 0)) == (void *) (-1)
 111         || close(fd) < 0)
 112         {
 113                 fprintf(stderr, "Error loading file %s: %s\n", argv[1], strerror(errno));
 114                 exit(1);
 115         }
 116
 117         buflen = len;
 118
 119         init_crc32();
 120
 121         // preload header
 122         memcpy(&header, input_file, sizeof(header));
 123
 124         memcpy(header.magic, magic, WNDR3700_MAGIC_LEN);
 125         header.crc = 0;
 126
 127         // create a firmware image in memory and copy the input_file to it
 128         buf = malloc(buflen);
 129         memcpy(buf, input_file, len);
 130
 131         // CRC of temporary header
 132         header.crc = htonl(crc32buf((unsigned char*)&header, sizeof(header)));
 133
 134         memcpy(buf, &header, sizeof(header));
 135
 136         // write the buf
 137         if ((fd = open(argv[2], O_CREAT|O_WRONLY|O_TRUNC,0644)) < 0
 138         || write(fd, buf, buflen) != buflen
 139         || close(fd) < 0)
 140         {
 141                 fprintf(stderr, "Error storing file %s: %s\n", argv[2], strerror(errno));
 142                 exit(2);
 143         }
 144
 145         free(buf);
 146
 147         munmap(input_file,len);
 148
 149         return 0;
 150 }