/* Copyright 2015 The ChromiumOS Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 *
 * This utility wraps around "cgpt" execution to work with NAND. If the target
 * device is an MTD device, this utility will read the GPT structures from
 * FMAP, invokes "cgpt" on that, and writes the result back to NOR flash. */

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <limits.h>
#if !defined(__FreeBSD__)
#include <linux/major.h>
#endif
#include <stdbool.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#if !defined(__FreeBSD__)
#include <sys/sysmacros.h>
#endif
#include <sys/types.h>
#include <unistd.h>

#include "2common.h"
#include "2sha.h"
#include "2sysincludes.h"
#include "cgpt.h"
#include "cgpt_nor.h"
#include "file_keys.h"

// Check if cmdline |argv| has "-D". "-D" signifies that GPT structs are stored
// off device, and hence we should not wrap around cgpt.
static bool has_dash_D(int argc, const char *const argv[])
{
	int i;
	// We go from 2, because the second arg is a cgpt command such as "create".
	for (i = 2; i < argc; ++i) {
		if (strcmp("-D", argv[i]) == 0) {
			return true;
		}
	}
	return false;
}

// Check if |device_path| is an MTD device based on its major number being 90.
static bool is_mtd(const char *device_path)
{
	struct stat stat;
	if (lstat(device_path, &stat) != 0) {
		return false;
	}

#if !defined(__FreeBSD__)
	if (major(stat.st_rdev) == MTD_CHAR_MAJOR) {
		return true;
	}
#endif
	return false;
}

// Return the element in |argv| that is an MTD device.
static const char *find_mtd_device(int argc, const char *const argv[])
{
	int i;
	for (i = 2; i < argc; ++i) {
		if (is_mtd(argv[i])) {
			return argv[i];
		}
	}
	return NULL;
}

static int wrap_cgpt(int argc, const char *const argv[], const char *mtd_device)
{
	uint8_t original_hash[VB2_SHA1_DIGEST_SIZE];
	uint8_t modified_hash[VB2_SHA1_DIGEST_SIZE];
	int ret = 0;

	// Create a temp dir to work in.
	ret++;
	char temp_dir[] = VBOOT_TMP_DIR "/cgpt_wrapper.XXXXXX";
	if (mkdtemp(temp_dir_template) == NULL) {
		Error("Cannot create a temporary directory.\n");
		return ret;
	}
	if (ReadNorFlash(temp_dir) != 0) {
		goto cleanup;
	}
	char rw_gpt_path[PATH_MAX];
	if (snprintf(rw_gpt_path, sizeof(rw_gpt_path), "%s/rw_gpt", temp_dir) < 0) {
		goto cleanup;
	}
	if (VB2_SUCCESS !=
	    DigestFile(rw_gpt_path, VB2_HASH_SHA1, original_hash, sizeof(original_hash))) {
		Error("Cannot compute original GPT digest.\n");
		goto cleanup;
	}

	// Obtain the MTD size.
	ret++;
	uint64_t drive_size = 0;
	if (GetMtdSize(mtd_device, &drive_size) != 0) {
		Error("Cannot get the size of %s.\n", mtd_device);
		goto cleanup;
	}

	// Launch cgpt on "rw_gpt" with -D size.
	ret++;
	const char **my_argv = calloc(argc + 2 + 1, sizeof(char *));
	if (my_argv == NULL) {
		errno = ENOMEM;
		goto cleanup;
	}
	memcpy(my_argv, argv, sizeof(char *) * argc);
	char *real_cgpt;
	if (asprintf(&real_cgpt, "%s.bin", argv[0]) == -1) {
		free(my_argv);
		goto cleanup;
	}
	my_argv[0] = real_cgpt;

	int i;
	for (i = 2; i < argc; ++i) {
		if (strcmp(my_argv[i], mtd_device) == 0) {
			my_argv[i] = rw_gpt_path;
		}
	}
	my_argv[argc] = "-D";
	char size[32];
	snprintf(size, sizeof(size), "%" PRIu64, drive_size);
	my_argv[argc + 1] = size;
	i = ForkExecV(NULL, my_argv);
	free(real_cgpt);
	free(my_argv);
	if (i != 0) {
		Error("Cannot exec cgpt to modify rw_gpt.\n");
		goto cleanup;
	}

	// Write back "rw_gpt" to NOR flash in two chunks.
	ret++;
	if (VB2_SUCCESS ==
	    DigestFile(rw_gpt_path, VB2_HASH_SHA1, modified_hash, sizeof(modified_hash))) {
		if (memcmp(original_hash, modified_hash, VB2_SHA1_DIGEST_SIZE) != 0) {
			ret = WriteNorFlash(temp_dir);
		} else {
			ret = 0;
		}
	}

cleanup:
	RemoveDir(temp_dir);
	return ret;
}

int main(int argc, const char *argv[])
{
	char resolved_cgpt[PATH_MAX];
	pid_t pid = getpid();
	char exe_link[40];
	int retval = 0;

	if (argc < 1) {
		return -1;
	}

	const char *orig_argv0 = argv[0];

	snprintf(exe_link, sizeof(exe_link), "/proc/%d/exe", pid);
	memset(resolved_cgpt, 0, sizeof(resolved_cgpt));
	if (readlink(exe_link, resolved_cgpt, sizeof(resolved_cgpt) - 1) == -1) {
		perror("readlink");
		return -1;
	}

	argv[0] = resolved_cgpt;

	if (argc > 2 && !has_dash_D(argc, argv)) {
		const char *mtd_device = find_mtd_device(argc, argv);
		if (mtd_device) {
			retval = wrap_cgpt(argc, argv, mtd_device);
			goto cleanup;
		}
	}

	// Forward to cgpt as-is. Real cgpt has been renamed cgpt.bin.
	char *real_cgpt;
	if (asprintf(&real_cgpt, "%s.bin", argv[0]) == -1) {
		retval = -1;
		goto cleanup;
	}
	argv[0] = real_cgpt;
	if (execv(argv[0], (char *const *)argv) == -1) {
		err(-2, "execv(%s) failed", real_cgpt);
	}
	free(real_cgpt);
	retval = -2;

cleanup:
	argv[0] = orig_argv0;
	return retval;
}
