/*
 * Thanks to Vassily Galinsky for this tool
*****************************************************************************
AIRLINK AR525W firmware image structure
  -8:-5  Extended (httpd) header checksum  -       sum2
  -4:-1  Extended (httpd) header magic     -       "ARRN" - 0x4e525241
   0: 3  Standard (tftpd) header magic     -       "GMTK" - 0x4b544d47
   4: 7  Standard (tftpd) header checksum  -       sum1
   8: b  0
   c: f  Size of compressed linux kernel
  10:13  Size of firmware image file with standard header
  14:17  Product code                      -       0x5
  18:1b  Bootloader checksum               -       sum0
  1c:1f  0
  20:    Compressed linux kernel
  -      Squashfs or jffs2 file system - kernel dependent - either 32 bytes or sector aligned 
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <netinet/in.h>

typedef unsigned long u32;
typedef unsigned char uchar;

u32 crctab[257] = {
	0x00000000, 0x77073096, 0xee0e612c, 0x990951ba,
	0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
	0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
	0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
	0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
	0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
	0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
	0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
	0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
	0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
	0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940,
	0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
	0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116,
	0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
	0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
	0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
	0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a,
	0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
	0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818,
	0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
	0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
	0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
	0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c,
	0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
	0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
	0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
	0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
	0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
	0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086,
	0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
	0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4,
	0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
	0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
	0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
	0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
	0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
	0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe,
	0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
	0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
	0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
	0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252,
	0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
	0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60,
	0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
	0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
	0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
	0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04,
	0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
	0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
	0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
	0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
	0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
	0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e,
	0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
	0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
	0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
	0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
	0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
	0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0,
	0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
	0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6,
	0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
	0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
	0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
	0
};

u32 header[] = {
	0x00000000, 0x4e525241,
	0x4b544d47, 0x00000000, 0x00000000, 0x000afd4a,
	0x00000000, 0x00000005, 0x00000000, 0x00000000
};

static int JFFS2 = 0;

int generate_image(char *kname, char *fsname, char *fname, int EHDR)
{
	int i;
	u32 lenk, lens;
	uchar *bk, *bs;
	int fkd, ffd, fsd;
	fkd = open(kname, O_RDONLY);
	ffd = creat(fname, 0x644);
	if ((fkd < 0) || (ffd < 0))
		return -1;
	if (fsname) {
		fsd = open(fsname, O_RDONLY);
		if (fsd < 0)
			return -1;
	}
	lenk = lseek(fkd, 0, SEEK_END);
	header[5] = lenk;
	bk = (uchar *) mmap(NULL, lenk, PROT_READ, MAP_SHARED, fkd, 0);
	if (bk == MAP_FAILED)
		return -1;
	if (fsname) {
		lens = lseek(fsd, 0, SEEK_END);
		bs = (uchar *) mmap(NULL, lens, PROT_READ, MAP_SHARED, fsd,
				    0);
		if (bs == MAP_FAILED)
			return -1;
	}
	if (EHDR)
		write(ffd, header, 0x28);
	else
		write(ffd, header + 2, 0x20);
	write(ffd, bk, lenk);
	if (!JFFS2) JFFS2 = 0x20;
	printf("Padding header+kernel - 0x%x +  0x%x = 0x%x\n",
	       lenk, ((lenk - 1 + JFFS2) / JFFS2) * JFFS2 - lenk,
	       ((lenk - 1 + JFFS2) / JFFS2) * JFFS2);
	for (i = 0; i < ((lenk - 1 + JFFS2) / JFFS2) * JFFS2 - lenk; i++)
		write(ffd, header, 1);
	if (fsname) {
		write(ffd, bs, lens);
		close(fsd);
	}
	close(ffd);
	close(fkd);
	return 0;
}

u32 crc32(uchar * buf, u32 len)
{
	register int i;
	u32 sum;
	register u32 s0;
	s0 = ~0;
	for (i = 0; i < len; i++) {
		s0 = (s0 >> 8) ^ crctab[(uchar) (s0 & 0xFF) ^ buf[i]];
	}
	sum = ~s0;
	return sum;
}

void usage(char *prog)
{
	printf("Usage: %s [-b 0/1] image_filename \n", prog);
	printf("       update checksums for firmware file\n");
	printf
	    ("Usage: %s [-b 0/1] [-j erasesize_in_kibytes] [-e] kernel filesystem image_filename \n",
	     prog);
	printf("       generate firmware file and update checksums\n");
	printf("--------------------------------------------------\n");
	printf("       -e - generate header for web upload\n");
	printf("       -b 0/1 - clear/update bootloader checksum\n");
	printf("       -j erasesize_in_kibytes - generate header for jffs2 filesystem\n");
}

int main(int argc, char **argv)
{
	uchar b[0x400];
	char EHDR = 0;
	char BHDR = 0;
	int c, fd;
	extern char *optarg;
	extern int optind, optopt;

	while ((c = getopt(argc, argv, "b:ej:")) != -1) {
		switch (c) {
		case 'b':
			if (optarg[0] == '1')
				BHDR = 1;
			break;
		case 'e':
			EHDR = 1;
			break;
		case 'j':
			sscanf(optarg, "%i", &JFFS2);
			JFFS2 *= 1024;
			break;
		case '?':
			fprintf(stderr, "\nError: unknown arg %c\n\n\n",
				optopt);
			usage(argv[0]);
			exit(-1);
		}
	}
	if (((argc - optind) < 1) && ((argc - optind) > 3)) {
		usage(argv[0]);
		exit(-1);
	}
	if ((argc - optind) == 3)
		if (generate_image
		    (argv[optind], argv[optind + 1], argv[optind + 2],
		     EHDR)) {
			fprintf(stderr,
				"\nError generating image file %s\n\n\n",
				argv[argc - 1]);
			usage(argv[0]);
			exit(-1);
		}
	if ((argc - optind) == 2)
		if (generate_image
		    (argv[optind], NULL, argv[optind + 1], EHDR)) {
			fprintf(stderr,
				"\nError generating image file %s\n\n\n",
				argv[argc - 1]);
			usage(argv[0]);
			exit(-1);
		}

	fd = open(argv[argc - 1], O_RDWR);
	if (fd < 0) {
		fprintf(stderr, "\nImage file not found %s\n\n\n",
			argv[argc - 1]);
		usage(argv[0]);
		exit(-1);
	}
	long i, len = lseek(fd, 0, SEEK_END);
	lseek(fd, 0, SEEK_SET);
	uchar *buf = malloc(len);
	read(fd, buf, len);
	u32 sum, l0;
	u32 MagicS = 0x474d544b;
	u32 MagicE = 0x4152524e;
	if (htonl(*((u32 *) buf)) == MagicS) {
		fprintf(stderr,
			"Image without extra 8 bytes - Standard header\n");
		buf[0x10] = len & 0xff;
		buf[0x11] = (len >> 8) & 0xff;
		buf[0x12] = (len >> 16) & 0xff;
		buf[0x13] = (len >> 24) & 0xff;
		lseek(fd, 0x10, SEEK_SET);
		write(fd, buf + 0x10, 0x4);
		EHDR = 0;
	} else if ((htonl(*((u32 *) (buf + 0x8))) == MagicS)
		   && ((htonl(*((u32 *) (buf + 0x4))) == MagicE))) {
		fprintf(stderr,
			"Image with extra 8 bytes - Extended header\n");
		*((u32 *) (buf + 0x18)) = len - 8;
		buf[0x18] = (len - 8) & 0xff;
		buf[0x19] = ((len - 8) >> 8) & 0xff;
		buf[0x1a] = ((len - 8) >> 16) & 0xff;
		buf[0x1b] = ((len - 8) >> 24) & 0xff;
		lseek(fd, 0x18, SEEK_SET);
		write(fd, buf + 0x18, 0x4);
		buf += 8;
		EHDR = 1;
	} else if (len == buf[0x10] | ((u32)buf[0x11] << 8) | ((u32)buf[0x12] << 16) | ((u32)buf[0x13] << 24)) {
		fprintf(stderr,
			"Image without extra 8 bytes - Standard header\n");
		EHDR = 0;
	} else if (len == (buf[0x18] | ((u32)buf[0x19] << 8) | ((u32)buf[0x1a] << 16) | ((u32)buf[0x1b] << 24)) + 8) {
		fprintf(stderr,
			"Image with extra 8 bytes - Extended header\n");
		buf += 8;
		EHDR = 1;
	} else {
		fprintf(stderr, "ERROR: Wrong image size\n");
		exit(-1);
	}
	l0 = buf[0x10] | ((u32)buf[0x11] << 8) | ((u32)buf[0x12] << 16) | ((u32)buf[0x13] << 24);
	if (!BHDR)
		*((u32 *) & buf[0x18]) = 0;
	unsigned long sum0 = buf[0x18] | ((u32)buf[0x19] << 8) | ((u32)buf[0x1a] << 16) | ((u32)buf[0x1b] << 24);
	unsigned long sum1 = buf[0x4] | ((u32)buf[0x5] << 8) | ((u32)buf[0x6] << 16) | ((u32)buf[0x7] << 24);
	*((u32 *) & buf[0x4]) = 0x0L;
	memcpy(b, buf, 0x100);
	memcpy(b + 0x100, buf + ((l0 >> 1) - ((l0 & 0x6) >> 1)), 0x100);
	memcpy(b + 0x200, buf + (l0 - 0x200), 0x200);
	*((u32 *) & b[0x18]) = 0x0L;

	sum = crc32(b, 0x400);
	printf("CRC32 sum0 - (%x, %x, %x)\n", sum, sum0, 0x400);
	if (EHDR)
		lseek(fd, 0x20, SEEK_SET);
	else
		lseek(fd, 0x18, SEEK_SET);
	buf[0x18] = (BHDR ? sum : sum0) & 0xff;
	buf[0x19] = ((BHDR ? sum : sum0) >> 8) & 0xff;
	buf[0x1a] = ((BHDR ? sum : sum0) >> 16) & 0xff;
	buf[0x1b] = ((BHDR ? sum : sum0) >> 24) & 0xff;
	write(fd, &buf[0x18], 0x4);

	sum = crc32(buf, l0);
	printf("CRC32 sum1 - (%x, %x, %x)\n", sum, sum1, l0);
	if (EHDR)
		lseek(fd, 0xC, SEEK_SET);
	else
		lseek(fd, 0x4, SEEK_SET);
	buf[0x4] = sum & 0xff;
	buf[0x5] = (sum >> 8) & 0xff;
	buf[0x6] = (sum >> 16) & 0xff;
	buf[0x7] = (sum >> 24) & 0xff;
	write(fd, &buf[0x4], 0x4);
	if (EHDR) {
		unsigned long sum2 = buf[-0x8] | ((u32)buf[-0x7] << 8) | ((u32)buf[-0x6] << 16) | ((u32)buf[-0x5] << 24);
		*((u32 *) & buf[-0x8]) = 0L;
		sum = crc32(buf - 0x4, len - 0x4);
		sum = htonl(sum);
		printf("CRC32 sum2 - (%x, %x, %x)\n", sum, sum2,
		       len - 0x4);
		lseek(fd, 0, SEEK_SET);
		buf[-0x8] = sum & 0xff;
		buf[-0x7] = (sum >> 8) & 0xff;
		buf[-0x6] = (sum >> 16) & 0xff;
		buf[-0x5] = (sum >> 24) & 0xff;
		write(fd, &buf[-0x8], 0x4);
		buf -= 8;
	}
	close(fd);
	free(buf);
	return 0;
}