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/*
* Copyright (C) 2015 Thomas Hebb <tommyhebb@gmail.com>
*
* The format of the header this tool generates was first documented by
* Chris Blake <chrisrblake93 (at) gmail.com> in a shell script of the
* same purpose. I have created this reimplementation at his request. The
* original script can be found at:
* <https://github.com/riptidewave93/meraki-partbuilder>
*
* 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.
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <libgen.h>
#include <getopt.h>
#include <errno.h>
#include <arpa/inet.h>
#include "sha1.h"
#define PADDING_BYTE 0xff
#define HDR_LENGTH 0x00000400
#define HDR_OFF_MAGIC1 0
#define HDR_OFF_HDRLEN 4
#define HDR_OFF_IMAGELEN 8
#define HDR_OFF_CHECKSUM 12
#define HDR_OFF_MAGIC2 32
#define HDR_OFF_FILLER 36
#define HDR_OFF_STATICHASH 40
struct board_info {
uint32_t magic;
uint32_t imagelen;
unsigned char statichash[20];
char *id;
char *description;
};
/*
* Globals
*/
static char *progname;
static char *board_id;
static const struct board_info *board;
static const struct board_info boards[] = {
{
.id = "mr18",
.description = "Meraki MR18 Access Point",
.magic = 0x8e73ed8a,
.imagelen = 0x00800000,
.statichash = {0xda, 0x39, 0xa3, 0xee, 0x5e,
0x6b, 0x4b, 0x0d, 0x32, 0x55,
0xbf, 0xef, 0x95, 0x60, 0x18,
0x90, 0xaf, 0xd8, 0x07, 0x09},
}, {
/* terminating entry */
}
};
/*
* Message macros
*/
#define ERR(fmt, ...) do { \
fflush(0); \
fprintf(stderr, "[%s] *** error: " fmt "\n", \
progname, ## __VA_ARGS__); \
} while (0)
#define ERRS(fmt, ...) do { \
int save = errno; \
fflush(0); \
fprintf(stderr, "[%s] *** error: " fmt "\n", \
progname, ## __VA_ARGS__, strerror(save)); \
} while (0)
static const struct board_info *find_board(const char *id)
{
const struct board_info *ret;
const struct board_info *board;
ret = NULL;
for (board = boards; board->id != NULL; board++) {
if (strcasecmp(id, board->id) == 0) {
ret = board;
break;
}
}
return ret;
}
static void usage(int status)
{
FILE *stream = (status != EXIT_SUCCESS) ? stderr : stdout;
const struct board_info *board;
fprintf(stream, "Usage: %s [OPTIONS...]\n", progname);
fprintf(stream,
"\n"
"Options:\n"
" -B <board> create image for the board specified with <board>\n"
" -i <file> read kernel image from the file <file>\n"
" -o <file> write output to the file <file>\n"
" -s strip padding from the end of the image\n"
" -h show this screen\n"
);
fprintf(stream, "\nBoards:\n");
for (board = boards; board->id != NULL; board++)
fprintf(stream, " %-16s%s\n", board->id, board->description);
exit(status);
}
void writel(unsigned char *buf, size_t offset, uint32_t value)
{
value = htonl(value);
memcpy(buf + offset, &value, sizeof(uint32_t));
}
int main(int argc, char *argv[])
{
int ret = EXIT_FAILURE;
long klen;
size_t kspace;
unsigned char *kernel;
size_t buflen;
unsigned char *buf;
bool strip_padding = false;
char *ofname = NULL, *ifname = NULL;
FILE *out, *in;
progname = basename(argv[0]);
while (1) {
int c;
c = getopt(argc, argv, "B:i:o:sh");
if (c == -1)
break;
switch (c) {
case 'B':
board_id = optarg;
break;
case 'i':
ifname = optarg;
break;
case 'o':
ofname = optarg;
break;
case 's':
strip_padding = true;
break;
case 'h':
usage(EXIT_SUCCESS);
break;
default:
usage(EXIT_FAILURE);
break;
}
}
if (board_id == NULL) {
ERR("no board specified");
goto err;
}
board = find_board(board_id);
if (board == NULL) {
ERR("unknown board \"%s\"", board_id);
goto err;
}
if (ifname == NULL) {
ERR("no input file specified");
goto err;
}
if (ofname == NULL) {
ERR("no output file specified");
goto err;
}
in = fopen(ifname, "r");
if (in == NULL) {
ERRS("could not open \"%s\" for reading: %s", ifname);
goto err;
}
buflen = board->imagelen;
kspace = buflen - HDR_LENGTH;
/* Get kernel length */
fseek(in, 0, SEEK_END);
klen = ftell(in);
rewind(in);
if (klen > kspace) {
ERR("file \"%s\" is too big - max size: 0x%08lX\n",
ifname, kspace);
goto err_close_in;
}
/* If requested, resize buffer to remove padding */
if (strip_padding)
buflen = klen + HDR_LENGTH;
/* Allocate and initialize buffer for final image */
buf = malloc(buflen);
if (buf == NULL) {
ERRS("no memory for buffer: %s\n");
goto err_close_in;
}
memset(buf, PADDING_BYTE, buflen);
/* Load kernel */
kernel = buf + HDR_LENGTH;
fread(kernel, klen, 1, in);
/* Write magic values and filler */
writel(buf, HDR_OFF_MAGIC1, board->magic);
writel(buf, HDR_OFF_MAGIC2, board->magic);
writel(buf, HDR_OFF_FILLER, 0);
/* Write header and image length */
writel(buf, HDR_OFF_HDRLEN, HDR_LENGTH);
writel(buf, HDR_OFF_IMAGELEN, klen);
/* Write checksum and static hash */
sha1_csum(kernel, klen, buf + HDR_OFF_CHECKSUM);
memcpy(buf + HDR_OFF_STATICHASH, board->statichash, 20);
/* Save finished image */
out = fopen(ofname, "w");
if (out == NULL) {
ERRS("could not open \"%s\" for writing: %s", ofname);
goto err_free;
}
fwrite(buf, buflen, 1, out);
ret = EXIT_SUCCESS;
fclose(out);
err_free:
free(buf);
err_close_in:
fclose(in);
err:
return ret;
}
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