path: root/lib/verity/verity_hash.c

/*
 * dm-verity volume handling
 *
 * Copyright (C) 2012-2021 Red Hat, Inc. All rights reserved.
 *
 * This file is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This file is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this file; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>

#include "verity.h"
#include "internal.h"

#define VERITY_MAX_LEVELS	63

static unsigned get_bits_up(size_t u)
{
	unsigned i = 0;
	while ((1U << i) < u)
		i++;
	return i;
}

static unsigned get_bits_down(size_t u)
{
	unsigned i = 0;
	while ((u >> i) > 1U)
		i++;
	return i;
}

static int verify_zero(struct crypt_device *cd, FILE *wr, size_t bytes)
{
	char block[bytes];
	size_t i;

	if (fread(block, bytes, 1, wr) != 1) {
		log_dbg(cd, "EIO while reading spare area.");
		return -EIO;
	}
	for (i = 0; i < bytes; i++)
		if (block[i]) {
			log_err(cd, _("Spare area is not zeroed at position %" PRIu64 "."),
				ftello(wr) - bytes);
			return -EPERM;
		}
	return 0;
}

static int verify_hash_block(const char *hash_name, int version,
			      char *hash, size_t hash_size,
			      const char *data, size_t data_size,
			      const char *salt, size_t salt_size)
{
	struct crypt_hash *ctx = NULL;
	int r;

	if (crypt_hash_init(&ctx, hash_name))
		return -EINVAL;

	if (version == 1 && (r = crypt_hash_write(ctx, salt, salt_size)))
		goto out;

	if ((r = crypt_hash_write(ctx, data, data_size)))
		goto out;

	if (version == 0 && (r = crypt_hash_write(ctx, salt, salt_size)))
		goto out;

	r = crypt_hash_final(ctx, hash, hash_size);
out:
	crypt_hash_destroy(ctx);
	return r;
}

static int hash_levels(size_t hash_block_size, size_t digest_size,
		       uint64_t data_file_blocks, uint64_t *hash_position, int *levels,
		       uint64_t *hash_level_block, uint64_t *hash_level_size)
{
	size_t hash_per_block_bits;
	uint64_t s, s_shift;
	int i;

	if (!digest_size)
		return -EINVAL;

	hash_per_block_bits = get_bits_down(hash_block_size / digest_size);
	if (!hash_per_block_bits)
		return -EINVAL;

	*levels = 0;
	while (hash_per_block_bits * *levels < 64 &&
	       (data_file_blocks - 1) >> (hash_per_block_bits * *levels))
		(*levels)++;

	if (*levels > VERITY_MAX_LEVELS)
		return -EINVAL;

	for (i = *levels - 1; i >= 0; i--) {
		if (hash_level_block)
			hash_level_block[i] = *hash_position;
		// verity position of block data_file_blocks at level i
		s_shift = (i + 1) * hash_per_block_bits;
		if (s_shift > 63)
			return -EINVAL;
		s = (data_file_blocks + ((uint64_t)1 << s_shift) - 1) >> ((i + 1) * hash_per_block_bits);
		if (hash_level_size)
			hash_level_size[i] = s;
		if ((*hash_position + s) < *hash_position)
			return -EINVAL;
		*hash_position += s;
	}

	return 0;
}

static int create_or_verify(struct crypt_device *cd, FILE *rd, FILE *wr,
				   uint64_t data_block, size_t data_block_size,
				   uint64_t hash_block, size_t hash_block_size,
				   uint64_t blocks, int version,
				   const char *hash_name, int verify,
				   char *calculated_digest, size_t digest_size,
				   const char *salt, size_t salt_size)
{
	char left_block[hash_block_size];
	char data_buffer[data_block_size];
	char read_digest[digest_size];
	size_t hash_per_block = 1 << get_bits_down(hash_block_size / digest_size);
	size_t digest_size_full = 1 << get_bits_up(digest_size);
	uint64_t blocks_to_write = (blocks + hash_per_block - 1) / hash_per_block;
	uint64_t seek_rd, seek_wr;
	size_t left_bytes;
	unsigned i;
	int r;

	if (uint64_mult_overflow(&seek_rd, data_block, data_block_size) ||
	    uint64_mult_overflow(&seek_wr, hash_block, hash_block_size)) {
		log_err(cd, _("Device offset overflow."));
		return -EINVAL;
	}

	if (fseeko(rd, seek_rd, SEEK_SET)) {
		log_dbg(cd, "Cannot seek to requested position in data device.");
		return -EIO;
	}

	if (wr && fseeko(wr, seek_wr, SEEK_SET)) {
		log_dbg(cd, "Cannot seek to requested position in hash device.");
		return -EIO;
	}

	memset(left_block, 0, hash_block_size);
	while (blocks_to_write--) {
		left_bytes = hash_block_size;
		for (i = 0; i < hash_per_block; i++) {
			if (!blocks)
				break;
			blocks--;
			if (fread(data_buffer, data_block_size, 1, rd) != 1) {
				log_dbg(cd, "Cannot read data device block.");
				return -EIO;
			}

			if (verify_hash_block(hash_name, version,
					calculated_digest, digest_size,
					data_buffer, data_block_size,
					salt, salt_size))
				return -EINVAL;

			if (!wr)
				break;
			if (verify) {
				if (fread(read_digest, digest_size, 1, wr) != 1) {
					log_dbg(cd, "Cannot read digest form hash device.");
					return -EIO;
				}
				if (memcmp(read_digest, calculated_digest, digest_size)) {
					log_err(cd, _("Verification failed at position %" PRIu64 "."),
						ftello(rd) - data_block_size);
					return -EPERM;
				}
			} else {
				if (fwrite(calculated_digest, digest_size, 1, wr) != 1) {
					log_dbg(cd, "Cannot write digest to hash device.");
					return -EIO;
				}
			}
			if (version == 0) {
				left_bytes -= digest_size;
			} else {
				if (digest_size_full - digest_size) {
					if (verify) {
						r = verify_zero(cd, wr, digest_size_full - digest_size);
						if (r)
							return r;
					} else if (fwrite(left_block, digest_size_full - digest_size, 1, wr) != 1) {
						log_dbg(cd, "Cannot write spare area to hash device.");
						return -EIO;
					}
				}
				left_bytes -= digest_size_full;
			}
		}
		if (wr && left_bytes) {
			if (verify) {
				r = verify_zero(cd , wr, left_bytes);
				if (r)
					return r;
			} else if (fwrite(left_block, left_bytes, 1, wr) != 1) {
				log_dbg(cd, "Cannot write remaining spare area to hash device.");
				return -EIO;
			}
		}
	}

	return 0;
}

static int VERITY_create_or_verify_hash(struct crypt_device *cd, bool verify,
	struct crypt_params_verity *params,
	char *root_hash, size_t digest_size)
{
	char calculated_digest[digest_size];
	FILE *data_file = NULL;
	FILE *hash_file = NULL, *hash_file_2;
	uint64_t hash_level_block[VERITY_MAX_LEVELS];
	uint64_t hash_level_size[VERITY_MAX_LEVELS];
	uint64_t data_file_blocks;
	uint64_t data_device_offset_max = 0, hash_device_offset_max = 0;
	uint64_t hash_position = VERITY_hash_offset_block(params);
	uint64_t dev_size;
	int levels, i, r;

	log_dbg(cd, "Hash %s %s, data device %s, data blocks %" PRIu64
		", hash_device %s, offset %" PRIu64 ".",
		verify ? "verification" : "creation", params->hash_name,
		device_path(crypt_data_device(cd)), params->data_size,
		device_path(crypt_metadata_device(cd)), hash_position);

	if (!params->data_size) {
		r = device_size(crypt_data_device(cd), &dev_size);
		if (r < 0)
			return r;

		data_file_blocks = dev_size / params->data_block_size;
	} else
		data_file_blocks = params->data_size;

	if (uint64_mult_overflow(&data_device_offset_max, params->data_size, params->data_block_size)) {
		log_err(cd, _("Device offset overflow."));
		return -EINVAL;
	}
	log_dbg(cd, "Data device size required: %" PRIu64 " bytes.", data_device_offset_max);

	if (hash_levels(params->hash_block_size, digest_size, data_file_blocks, &hash_position,
		&levels, &hash_level_block[0], &hash_level_size[0])) {
		log_err(cd, _("Hash area overflow."));
		return -EINVAL;
	}
	if (uint64_mult_overflow(&hash_device_offset_max, hash_position, params->hash_block_size)) {
		log_err(cd, _("Device offset overflow."));
		return -EINVAL;
	}
	log_dbg(cd, "Hash device size required: %" PRIu64 " bytes.",
		hash_device_offset_max - params->hash_area_offset);
	log_dbg(cd, "Using %d hash levels.", levels);

	data_file = fopen(device_path(crypt_data_device(cd)), "r");
	if (!data_file) {
		log_err(cd, _("Cannot open device %s."),
			device_path(crypt_data_device(cd))
		);
		r = -EIO;
		goto out;
	}

	hash_file = fopen(device_path(crypt_metadata_device(cd)), verify ? "r" : "r+");
	if (!hash_file) {
		log_err(cd, _("Cannot open device %s."),
			device_path(crypt_metadata_device(cd)));
		r = -EIO;
		goto out;
	}

	memset(calculated_digest, 0, digest_size);

	for (i = 0; i < levels; i++) {
		if (!i) {
			r = create_or_verify(cd, data_file, hash_file,
						    0, params->data_block_size,
						    hash_level_block[i], params->hash_block_size,
						    data_file_blocks, params->hash_type, params->hash_name, verify,
						    calculated_digest, digest_size, params->salt, params->salt_size);
			if (r)
				goto out;
		} else {
			hash_file_2 = fopen(device_path(crypt_metadata_device(cd)), "r");
			if (!hash_file_2) {
				log_err(cd, _("Cannot open device %s."),
					device_path(crypt_metadata_device(cd)));
				r = -EIO;
				goto out;
			}
			r = create_or_verify(cd, hash_file_2, hash_file,
						    hash_level_block[i - 1], params->hash_block_size,
						    hash_level_block[i], params->hash_block_size,
						    hash_level_size[i - 1], params->hash_type, params->hash_name, verify,
						    calculated_digest, digest_size, params->salt, params->salt_size);
			fclose(hash_file_2);
			if (r)
				goto out;
		}
	}

	if (levels)
		r = create_or_verify(cd, hash_file, NULL,
					    hash_level_block[levels - 1], params->hash_block_size,
					    0, params->hash_block_size,
					    1, params->hash_type, params->hash_name, verify,
					    calculated_digest, digest_size, params->salt, params->salt_size);
	else
		r = create_or_verify(cd, data_file, NULL,
					    0, params->data_block_size,
					    0, params->hash_block_size,
					    data_file_blocks, params->hash_type, params->hash_name, verify,
					    calculated_digest, digest_size, params->salt, params->salt_size);
out:
	if (verify) {
		if (r)
			log_err(cd, _("Verification of data area failed."));
		else {
			log_dbg(cd, "Verification of data area succeeded.");
			r = memcmp(root_hash, calculated_digest, digest_size) ? -EFAULT : 0;
			if (r)
				log_err(cd, _("Verification of root hash failed."));
			else
				log_dbg(cd, "Verification of root hash succeeded.");
		}
	} else {
		if (r == -EIO)
			log_err(cd, _("Input/output error while creating hash area."));
		else if (r)
			log_err(cd, _("Creation of hash area failed."));
		else {
			fsync(fileno(hash_file));
			memcpy(root_hash, calculated_digest, digest_size);
		}
	}

	if (data_file)
		fclose(data_file);
	if (hash_file)
		fclose(hash_file);
	return r;
}

/* Verify verity device using userspace crypto backend */
int VERITY_verify(struct crypt_device *cd,
		  struct crypt_params_verity *verity_hdr,
		  const char *root_hash,
		  size_t root_hash_size)
{
	return VERITY_create_or_verify_hash(cd, 1, verity_hdr, CONST_CAST(char*)root_hash, root_hash_size);
}

/* Create verity hash */
int VERITY_create(struct crypt_device *cd,
		  struct crypt_params_verity *verity_hdr,
		  const char *root_hash,
		  size_t root_hash_size)
{
	unsigned pgsize = (unsigned)crypt_getpagesize();

	if (verity_hdr->salt_size > 256)
		return -EINVAL;

	if (verity_hdr->data_block_size > pgsize)
		log_err(cd, _("WARNING: Kernel cannot activate device if data "
			      "block size exceeds page size (%u)."), pgsize);

	return VERITY_create_or_verify_hash(cd, 0, verity_hdr, CONST_CAST(char*)root_hash, root_hash_size);
}

uint64_t VERITY_hash_blocks(struct crypt_device *cd, struct crypt_params_verity *params)
{
	uint64_t hash_position = 0;
	int levels = 0;

	if (hash_levels(params->hash_block_size, crypt_get_volume_key_size(cd),
		params->data_size, &hash_position, &levels, NULL, NULL))
		return 0;

	return (uint64_t)hash_position;
}