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 42static uint32_t crc32[1<<BPB]; 43static char *magic = "3700"; 44 45static 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 60static 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 69struct header { 70 unsigned char magic[WNDR3700_MAGIC_LEN]; 71 uint32_t crc; 72 unsigned char stuff[56]; 73}; 74 75static void usage(const char *) __attribute__ (( __noreturn__ )); 76 77static 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 85int 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} 151