path: root/mkgpt.c

/* SPDX-License-Identifier: MIT */

/* Copyright (C) 2014 by John Cronin
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:

 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "crc32.h"
#include "guid.h"
#include "part.h"
#include "part_ids.h"

#include <errno.h>
#include <limits.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void
dump_help(char *fname);
static int
check_parts();
static int
parse_opts(int argc, char **argv);
static void
write_output();

static size_t sect_size = 512;
static long image_sects = 0;
static long min_image_sects = 2048;
static PART *first_part = NULL;
static PART *last_part = NULL;
static FILE *output = NULL;
static GUID disk_guid;
static int part_count;
static int header_sectors;
static int first_usable_sector;
static int secondary_headers_sect;
static int secondary_gpt_sect;

int
main(int argc, char **argv)
{
	random_guid(&disk_guid);

	if (parse_opts(argc, argv) != 0)
		return -1;

	if (output == NULL) {
		fprintf(stderr, "no output file specifed\n");
		dump_help(argv[0]);
		return -1;
	}
	if (first_part == NULL) {
		fprintf(stderr, "no partitions specified\n");
		dump_help(argv[0]);
		return -1;
	}

	if (check_parts() != 0)
		return -1;

	write_output();
	fclose(output);

	return 0;
}

static int
parse_opts(int argc, char **argv)
{
	int i = 1;
	int cur_part_id = 0;
	PART *cur_part = NULL;

	/* First, parse global options */
	while (i < argc) {
		if (!strcmp(argv[i], "--output") || !strcmp(argv[i], "-o")) {
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr, "no output file specified\n");
				return -1;
			}

			output = fopen(argv[i], "w+");
			if (output == NULL) {
				fprintf(stderr,
					"unable to open %s for writing (%s)\n",
					argv[i], strerror(errno));
				return -1;
			}
			i++;
		} else if (!strcmp(argv[i], "--disk-guid")) {
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"no disk guid file specified\n");
				return -1;
			}

			if (parse_guid(argv[i], &disk_guid) != 0) {
				fprintf(stderr, "invalid disk uuid (%s)\n",
					argv[i]);
				return -1;
			}

			i++;
		} else if (!strcmp(argv[i], "--help") ||
			   !strcmp(argv[i], "-h")) {
			dump_help(argv[0]);
			return -1;
		} else if (!strcmp(argv[i], "--sector-size")) {
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr, "sector size not specified\n");
				return -1;
			}

			sect_size = atoi(argv[i]);

			if (sect_size < 512 || sect_size > 4096 ||
				sect_size % 512) {
				fprintf(stderr,
					"invalid sector size (%zu) - must be "
					">= 512 and <= 4096 and "
					"a multiple of 512",
					sect_size);
				return -1;
			}
			i++;
		} else if (!strcmp(argv[i], "--minimum-image-size") ||
			   !strcmp(argv[i], "-s")) {
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"minimum image size not specified\n");
				return -1;
			}

			min_image_sects = atoi(argv[i]);

			if (min_image_sects < 2048) {
				fprintf(stderr, "minimum image size must be at "
						"least 2048 sectors\n");
				return -1;
			}

			i++;
		} else if (!strcmp(argv[i], "--image-size")) {
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr, "image size not specified\n");
				return -1;
			}

			image_sects = atoi(argv[i]);

			i++;
		} else if (!strcmp(argv[i], "--part") || !strcmp(argv[i], "-p"))
			break;
		else {
			fprintf(stderr, "unknown argument - %s\n", argv[i]);
			dump_help(argv[0]);
			return i;
		}
	}

	/* Now parse partitions */
	while (i < argc) {
		if (!strcmp(argv[i], "--part") || !strcmp(argv[i], "-p")) {
			/* Store the current partition data if there is one */
			if (cur_part != NULL) {
				if (last_part == NULL) {
					first_part = last_part = cur_part;
					cur_part->next = NULL;
				} else {
					last_part->next = cur_part;
					last_part = cur_part;
					cur_part->next = NULL;
				}
			}

			/* Allocate a new partition structure */
			cur_part = calloc(1, sizeof(*cur_part));
			if (cur_part == NULL) {
				fprintf(stderr, "out of memory allocating "
						"partition structure\n");
				return -1;
			}
			cur_part_id++;
			cur_part->id = cur_part_id;

			/* Get the filename of the partition image */
			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"no partition image specified for "
					"partition %i\n",
					cur_part_id);
				return -1;
			}
			cur_part->src = fopen(argv[i], "r");
			if (cur_part->src == NULL) {
				fprintf(stderr,
					"unable to open partition image (%s) "
					"for partition (%i) - %s\n",
					argv[i], cur_part_id, strerror(errno));
				return -1;
			}

			i++;
		} else if (!strcmp(argv[i], "--name") ||
			   !strcmp(argv[i], "-n")) {
			if (cur_part == NULL) {
				fprintf(stderr, "--part must be specified "
						"before --name argument\n");
				return -1;
			}

			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"partition name not specified %i\n",
					cur_part_id);
				return -1;
			}

			cur_part->name = argv[i];

			i++;
		} else if (!strcmp(argv[i], "--type") ||
			   (!strcmp(argv[i], "-t"))) {
			if (cur_part == NULL) {
				fprintf(stderr, "--part must be specifed "
						"before --type argument\n");
				return -1;
			}

			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"partition type not specified %i\n",
					cur_part_id);
				return -1;
			}

			if (parse_guid(argv[i], &cur_part->type) != 0) {
				fprintf(stderr,
					"invalid partition type (%s) for "
					"partition %i\n",
					argv[i], cur_part_id);
				return -1;
			}

			i++;
		} else if (!strcmp(argv[i], "--uuid") ||
			   (!strcmp(argv[i], "-u"))) {
			if (cur_part == NULL) {
				fprintf(stderr, "--part must be specifed "
						"before --uuid argument\n");
				return -1;
			}

			i++;
			if (i == argc || argv[i][0] == '-') {
				fprintf(stderr,
					"partition uuid not specified %i\n",
					cur_part_id);
				return -1;
			}

			if (parse_guid(argv[i], &cur_part->uuid) != 0) {
				fprintf(stderr,
					"invalid partition uuid (%s) for "
					"partition %i\n",
					argv[i], cur_part_id);
				return -1;
			}

			i++;
		} else {
			fprintf(stderr, "unknown argument - %s\n", argv[i]);
			dump_help(argv[0]);
			return i;
		}
	}

	if (cur_part != NULL) {
		if (last_part == NULL) {
			first_part = last_part = cur_part;
			cur_part->next = NULL;
		} else {
			last_part->next = cur_part;
			last_part = cur_part;
			cur_part->next = NULL;
		}
	}

	return 0;
}

static void
dump_help(char *fname)
{
	printf("Usage: %s -o <output_file> [-h] [--disk-guid GUID] "
	       "[--sector-size sect_size] [-s min_image_size] "
	       "[partition def 0] [part def 1] ... [part def n]\n"
	       "  Partition definition: --part <image_file> --type <type> "
	       "[--uuid uuid] [--name name]\n"
	       "  Please see the README file for further information\n",
		fname);
}

static int
check_parts()
{
	/* Iterate through the partitions, checking validity */
	int cur_part_id = 0;
	int cur_sect;
	PART *cur_part;
	int header_length;
	int needed_file_length;

	/* Count partitions */
	cur_part = first_part;
	part_count = 0;
	while (cur_part) {
		part_count++;
		cur_part = cur_part->next;
	}

	/* Determine the sectors needed for MBR, GPT header and partition
	 * entries */
	cur_sect = 2; /* MBR + GPT header */
	header_length = part_count * 128;
	header_sectors = header_length / sect_size;
	if (header_length % sect_size)
		header_sectors++;

	/* The GPT entry array must be a minimum of 16,384 bytes (reports
	 * wikipedia and testdisk, but not the UEFI spec)
	 */
	if (header_sectors < (int)(16384 / sect_size))
		header_sectors = (int)(16384 / sect_size);

	cur_sect += header_sectors;
	first_usable_sector = cur_sect;

	cur_part = first_part;
	while (cur_part) {
		long cur_part_file_len;

		cur_part_id++;

		if (guid_is_zero(&cur_part->type)) {
			fprintf(stderr,
				"partition type not specified for partition "
				"%i\n",
				cur_part_id);
			return -1;
		}

		if (guid_is_zero(&cur_part->uuid))
			random_guid(&cur_part->uuid);

		if (cur_part->sect_start == 0)
			cur_part->sect_start = cur_sect;
		else if (cur_part->sect_start < cur_sect) {
			fprintf(stderr,
				"unable to start partition %i at sector %i "
				"(would conflict with other data)\n",
				cur_part_id, cur_part->sect_start);
			return -1;
		}

		if (cur_part->name == NULL) {
			cur_part->name = malloc(128);
			sprintf(cur_part->name, "part%i", cur_part_id);
		}

		fseek(cur_part->src, 0, SEEK_END);
		cur_part_file_len = ftell(cur_part->src);
		fseek(cur_part->src, 0, SEEK_SET);

		if (cur_part->sect_length == 0) {
			cur_part->sect_length = cur_part_file_len / sect_size;
			if (cur_part_file_len % sect_size)
				cur_part->sect_length++;
		}
		cur_sect = cur_part->sect_start + cur_part->sect_length;

		cur_part = cur_part->next;
	}

	/* Add space for the secondary GPT */
	needed_file_length = cur_sect + 1 + header_sectors;

	if (image_sects == 0) {
		if (needed_file_length > min_image_sects)
			image_sects = needed_file_length;
		else
			image_sects = min_image_sects;
	} else if (image_sects < needed_file_length) {
		fprintf(stderr,
			"requested image size (%zu) is too small to hold the "
			"partitions\n",
			image_sects * sect_size);
		return -1;
	}

	secondary_headers_sect = image_sects - 1 - header_sectors;
	secondary_gpt_sect = image_sects - 1;

	return 0;
}

static void
panic(const char *msg)
{
	fprintf(stderr, "panic: %s", msg);
	exit(EXIT_FAILURE);
}

static void
write_output()
{
	int i;
	uint8_t *mbr, *gpt, *gpt2, *parts, *image_buf;
	PART *cur_part;

	/* Write MBR */
	mbr = calloc(1, sect_size);
	if (mbr == NULL) {
		panic("calloc failed");
	}

	*(uint32_t *)&mbr[446] =
		0x00020000; /* boot indicator = 0, start CHS = 0x000200 */
	mbr[446 + 4] = 0xee; /* OSType = GPT Protective */
	mbr[446 + 5] = 0xff;
	mbr[446 + 6] = 0xff;
	mbr[446 + 7] = 0xff; /* EndingCHS = 0xffffff */
	*(uint32_t *)&mbr[446 + 8] = 0x1; /* StartingLBA = 1 */

	if (image_sects > 0xffffffff)
		*(uint32_t *)&mbr[446 + 12] = 0xffffffff;
	else
		*(uint32_t *)&mbr[446 + 12] = (uint32_t)image_sects - 1;

	mbr[510] = 0x55;
	mbr[511] = 0xaa; /* Signature */

	if (fwrite(mbr, 1, sect_size, output) != sect_size) {
		panic("fwrite failed");
	}

	/* Define GPT headers */
	gpt = calloc(1, sect_size);
	if (gpt == NULL) {
		panic("calloc failed");
	}
	gpt2 = calloc(1, sect_size);
	if (gpt2 == NULL) {
		panic("calloc failed");
	}

	*(uint64_t *)&gpt[0] = 0x5452415020494645ULL; /* Signature */
	*(uint32_t *)&gpt[8] = 0x00010000UL; /* Revision */
	*(uint32_t *)&gpt[12] = 96; /* HeaderSize */
	*(uint32_t *)&gpt[16] = 0; /* HeaderCRC32 */
	*(uint32_t *)&gpt[20] = 0; /* Reserved */
	*(uint64_t *)&gpt[24] = 0x1; /* MyLBA */
	*(uint64_t *)&gpt[32] = secondary_gpt_sect; /* AlternateLBA */
	*(uint64_t *)&gpt[40] = first_usable_sector; /* FirstUsableLBA */
	*(uint64_t *)&gpt[48] = secondary_headers_sect - 1; /* LastUsableLBA */
	guid_to_bytestring(&gpt[56], &disk_guid); /* DiskGUID */
	*(uint64_t *)&gpt[72] = 0x2; /* PartitionEntryLBA */
	*(uint32_t *)&gpt[80] = part_count; /* NumberOfPartitionEntries */
	*(uint32_t *)&gpt[84] = 128; /* SizeOfPartitionEntry */
	*(uint32_t *)&gpt[88] = 0; /* PartitionEntryArrayCRC32 */

	/* Define GPT partition entries */
	parts = calloc(header_sectors, sect_size);
	if (parts == NULL) {
		panic("calloc failed");
	}

	cur_part = first_part;
	i = 0;
	while (cur_part) {
		int char_id;

		guid_to_bytestring(&parts[i * 128],
			&cur_part->type); /* PartitionTypeGUID */
		guid_to_bytestring(&parts[i * 128 + 16],
			&cur_part->uuid); /* UniquePartitionGUID */
		*(uint64_t *)&parts[i * 128 + 32] =
			cur_part->sect_start; /* StartingLBA */
		*(uint64_t *)&parts[i * 128 + 40] = cur_part->sect_start +
						    cur_part->sect_length -
						    1; /* EndingLBA */
		*(uint64_t *)&parts[i * 128 + 48] =
			cur_part->attrs; /* Attributes */

		for (char_id = 0;
			char_id < (int)strlen(cur_part->name) && char_id < 35;
			char_id++)
			*(uint16_t *)&parts[i * 128 + 56 + char_id * 2] =
				(uint16_t)cur_part->name[char_id];

		i++;
		cur_part = cur_part->next;
	}

	/* Do CRC calculations on the partition table entries and GPT headers */
	CalculateCrc32(parts, part_count * 128, (uint32_t *)&gpt[88]);
	CalculateCrc32(gpt, 96, (uint32_t *)&gpt[16]);

	memcpy(gpt2, gpt, 96);
	*(uint32_t *)&gpt2[16] = 0; /* HeaderCRC32 */
	*(uint64_t *)&gpt2[24] = secondary_gpt_sect; /* MyLBA */
	*(uint64_t *)&gpt2[32] = 0x1; /* AlternateLBA */
	*(uint64_t *)&gpt2[72] = secondary_headers_sect; /* PartitionEntryLBA */
	CalculateCrc32(gpt2, 96, (uint32_t *)&gpt2[16]);

	/* Write primary GPT and headers */
	if (fwrite(gpt, 1, sect_size, output) != sect_size) {
		panic("fwrite failed");
	}
	if (fwrite(parts, 1, header_sectors * sect_size, output) !=
		header_sectors * sect_size) {
		panic("fwrite failed");
	}

	/* Write partitions */
	cur_part = first_part;
	image_buf = malloc(sect_size);
	while (cur_part) {
		size_t bytes_read;
		size_t bytes_written = 0;

		fseek(output, cur_part->sect_start * sect_size, SEEK_SET);
		while ((bytes_read = fread(
				image_buf, 1, sect_size, cur_part->src)) > 0) {
			size_t bytes_to_write = bytes_read;

			/* Determine how much to write */
			if ((bytes_written + bytes_to_write) >
				(size_t)(cur_part->sect_length * sect_size))
				bytes_to_write =
					cur_part->sect_length * sect_size -
					bytes_written;

			if (fwrite(image_buf, 1, bytes_to_write, output) !=
				bytes_to_write) {
				panic("fwrite failed");
			}

			bytes_written += bytes_to_write;
		}

		cur_part = cur_part->next;
	}

	/* Write secondary GPT partition headers and header */
	fseek(output, secondary_headers_sect * sect_size, SEEK_SET);
	if (fwrite(parts, 1, header_sectors * sect_size, output) !=
		header_sectors * sect_size) {
		panic("fwrite failed");
	}
	fseek(output, secondary_gpt_sect * sect_size, SEEK_SET);
	if (fwrite(gpt2, 1, sect_size, output) != sect_size) {
		panic("fwrite failed");
	}
}