Message-ID: <Pine.LNX.4.64.1203232346020.6653@file.rdu.redhat.com>
Date:	Fri, 23 Mar 2012 23:48:51 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Mandeep Singh Baines <msb@...omium.org>
cc:	device-mapper development <dm-devel@...hat.com>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Will Drewry <wad@...omium.org>, linux-kernel@...r.kernel.org,
	Elly Jones <ellyjones@...omium.org>,
	Olof Johansson <olofj@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alasdair G Kergon <agk@...hat.com>,
	Milan Broz <mbroz@...hat.com>, taysom@...omium.org
Subject: Re: [dm-devel] [PATCH] dm: remake of the verity target



On Thu, 22 Mar 2012, Mandeep Singh Baines wrote:

> Mikulas Patocka (mpatocka@...hat.com) wrote:
> > 
> > 
> > On Thu, 22 Mar 2012, Mandeep Singh Baines wrote:
> > 
> > > Mikulas Patocka (mpatocka@...hat.com) wrote:
> > > > 
> > > > This is improved patch that supports both the old format and the new 
> > > > format. I checked that it is interoperable with with the old Google 
> > > > userspace tool and with the original Google kernel driver.
> > > > 
> > > 
> > > Thanks much for doing this:)
> > > 
> > > This looks good but would a prepend/append flag be better?
> > 
> > It does more than changing prepend/append salt. I changed alignment in the 
> > new format so that it doesn't have to use a multiply instruction.
> > 
> > In the old format, if digest size is not a power of two, all digests are 
> > placed first and the rest of the block is padded with zeros. In the new 
> > format, each digest is padded with zeros to a power of two.
> > 
> > For example, when using sha1, the old format padding looks like this:
> > aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbbbb
> > bbbbbbbbbbbbbbbbccccccccccccccccccccccccccccccccccccccccdddddddd
> > dddddddddddddddddddddddddddddddd00000000000000000000000000000000
> > 0000000000000000000000000000000000000000000000000000000000000000
> > 
> > ... and the new format padding looks like this:
> > aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa000000000000000000000000
> > bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb000000000000000000000000
> > cccccccccccccccccccccccccccccccccccccccc000000000000000000000000
> > dddddddddddddddddddddddddddddddddddddddd000000000000000000000000
> > 
> > The version "0" (first argument in the target line) actually means the old 
> > style padding and the salt is hashed after the data. The version "1" means 
> > new style padding and the salt is hashed before the data. If someone comes 
> > with another format, we can use version "2" for it, etc.
> > 
> 
> +cc taysom
> 
> Makes sense.
> 
> Signed-off-by: Mandeep Singh Baines <msb@...omium.org>
> 
> Speaking of V2, one idea a colleague of mine (taysom) just had was to
> drop the power of 2 alignment. For SHA-1, this shrinks the tree by 37.5 %.
> You have to replace the shifts with divides but the reduction in I/O
> more than makes up. For the different levels, you could pre-calculate
> the divisor.
> 
> Regards,
> Mandeep
> 
> > Mikulas
> 

BTW. here I'm sending you the new veritysetup tool. The old one that I 
sent before has a bug that it stores zero as the device size in the 
superblock (and ignores it when reading it back), so don't use that old 
tool, use this instead.

It is already integrated in lvm2 cvs.

Mikulas

---

/*
 * veritysetup
 *
 * (C) 2012 Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License v.2.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 * Compile flags to use a specific crypto library:
 * openssl: -lpopt -DCRYPT_OPENSSL -lcrypto
 * nss: -lpopt -DCRYPT_NSS -I/usr/include/nspr/ -I/usr/include/nss -lnss3
 * gcrypt: -lpopt -DCRYPT_GCRYPT -lgcrypt -lgpg-error
 */

#define _FILE_OFFSET_BITS	64

#ifdef HAVE_CONFIG_H
#include "configure.h"
#endif

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdarg.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/mount.h>
#include <arpa/inet.h>
#include <popt.h>
#ifdef CRYPT_OPENSSL
#include <openssl/evp.h>
#include <openssl/rand.h>
#endif
#ifdef CRYPT_GCRYPT
#include <gcrypt.h>
#endif
#ifdef CRYPT_NSS
#include <nss.h>
#include <sechash.h>
#include <pk11pub.h>
#endif

#if !defined(CRYPT_OPENSSL) && !defined(CRYPT_GCRYPT) && !defined(CRYPT_NSS)
#error No crypto engine specified
#endif

#define DEFAULT_BLOCK_SIZE	4096
#define DM_VERITY_MAX_LEVELS	63

#define DEFAULT_SALT_SIZE	32
#define MAX_SALT_SIZE		384

#define MODE_VERIFY	0
#define MODE_CREATE	1
#define MODE_ACTIVATE	2

#define MAX_FORMAT_VERSION	1

static int mode = -1;
static int use_superblock = 1;

static const char *dm_device;
static const char *data_device;
static const char *hash_device;
static const char *hash_algorithm = NULL;
static const char *root_hash;

static int version = -1;
static int data_block_size = 0;
static int hash_block_size = 0;
static char *data_blocks_string = NULL;
static long long data_blocks = 0;
static char *hash_start_string = NULL;
static long long hash_start = 0;
static const char *salt_string = NULL;

static FILE *data_file;
static FILE *hash_file;

static off_t data_file_blocks;
static off_t hash_file_blocks;
static off_t used_hash_blocks;

static unsigned char *root_hash_bytes;
static unsigned char *calculated_digest;

static unsigned char *salt_bytes;
static unsigned salt_size;

static unsigned digest_size;
static unsigned char digest_size_bits;
static unsigned char levels;
static unsigned char hash_per_block_bits;

static off_t hash_level_block[DM_VERITY_MAX_LEVELS];
static off_t hash_level_size[DM_VERITY_MAX_LEVELS];

static off_t superblock_position;

static int retval = 0;

struct superblock {
	uint8_t signature[8];
	uint8_t version;
	uint8_t data_block_bits;
	uint8_t hash_block_bits;
	uint8_t pad1[1];
	uint16_t salt_size;
	uint8_t pad2[2];
	uint32_t data_blocks_hi;
	uint32_t data_blocks_lo;
	uint8_t algorithm[16];
	uint8_t salt[MAX_SALT_SIZE];
	uint8_t pad3[88];
};

#define DM_VERITY_SIGNATURE	"verity\0\0"
#define DM_VERITY_VERSION	0

#if defined(__GNUC__) && __GNUC__ >= 2
	__attribute__((__noreturn__))
#endif
static void help(poptContext popt_context,
		enum poptCallbackReason reason,
		struct poptOption *key,
		const char *arg,
		void *data)
{
	if (!strcmp(key->longName, "help")) {
		poptPrintHelp(popt_context, stdout, 0);
	} else {
		printf("veritysetup");
#ifdef DM_LIB_VERSION
		printf(", device mapper version %s", DM_LIB_VERSION);
#endif
		printf("\n");
	}
	exit(0);
}

static struct poptOption popt_help_options[] = {
	{ NULL,			0,	POPT_ARG_CALLBACK, help, 0, NULL, NULL },
	{ "help",		'h',	POPT_ARG_NONE, NULL, 0, "Show help", NULL },
	{ "version",		0,	POPT_ARG_NONE, NULL, 0, "Show version", NULL },
	POPT_TABLEEND
};

static struct poptOption popt_options[] = {
	{ NULL,			'\0', POPT_ARG_INCLUDE_TABLE, popt_help_options, 0, NULL, NULL },
	{ "create",		'c',	POPT_ARG_VAL, &mode, MODE_CREATE, "Create hash", NULL },
	{ "verify",		'v',	POPT_ARG_VAL, &mode, MODE_VERIFY, "Verify integrity", NULL },
	{ "activate",		'a',	POPT_ARG_VAL, &mode, MODE_ACTIVATE, "Activate the device", NULL },
	{ "no-superblock",	0,	POPT_ARG_VAL, &use_superblock, 0, "Do not create/use superblock" },
	{ "format",		0,	POPT_ARG_INT, &version, 0, "Format version (0 - original Google code, 1 - new format)", "number" },
	{ "data-block-size",	0, 	POPT_ARG_INT, &data_block_size, 0, "Block size on the data device", "bytes" },
	{ "hash-block-size",	0, 	POPT_ARG_INT, &hash_block_size, 0, "Block size on the hash device", "bytes" },
	{ "data-blocks",	0,	POPT_ARG_STRING, &data_blocks_string, 0, "The number of blocks in the data file", "blocks" },
	{ "hash-start",		0,	POPT_ARG_STRING, &hash_start_string, 0, "Starting block on the hash device", "512-byte sectors" },
	{ "algorithm",		0,	POPT_ARG_STRING, &hash_algorithm, 0, "Hash algorithm (default sha256)", "string" },
	{ "salt",		0,	POPT_ARG_STRING, &salt_string, 0, "Salt", "hex string" },
	POPT_TABLEEND
};

#if defined(__GNUC__) && __GNUC__ >= 2
	__attribute__((__format__(__printf__, 1, 2), __noreturn__))
#endif
static void exit_err(const char *msg, ...)
{
	va_list args;
	va_start(args, msg);
	vfprintf(stderr, msg, args);
	va_end(args);
	fputc('\n', stderr);
	exit(2);
}

#if defined(__GNUC__) && __GNUC__ >= 2
	__attribute__((__noreturn__))
#endif
static void stream_err(FILE *f, const char *msg)
{
	if (ferror(f)) {
		perror(msg);
		exit(2);
	} else if (feof(f)) {
		exit_err("eof on %s", msg);
	} else {
		exit_err("unknown error on %s", msg);
	}
}

static void *xmalloc(size_t s)
{
	void *ptr = malloc(!s ? 1 : s);
	if (!ptr) exit_err("out of memory");
	return ptr;
}

static char *xstrdup(const char *str)
{
	return strcpy(xmalloc(strlen(str) + 1), str);
}

static char *xprint(unsigned long long num)
{
	size_t s = snprintf(NULL, 0, "%llu", num);
	char *p = xmalloc(s + 1);
	snprintf(p, s + 1, "%llu", num);
	return p;
}

static char *xhexprint(unsigned char *bytes, size_t len)
{
	size_t i;
	char *p = xmalloc(len * 2 + 1);
	p[0] = 0;
	for (i = 0; i < len; i++)
		snprintf(p + i * 2, 3, "%02x", bytes[i]);
	return p;
}

static off_t get_size(FILE *f, const char *name)
{
	struct stat st;
	int h = fileno(f);
	if (h < 0) {
		perror("fileno");
		exit(2);
	}
	if (fstat(h, &st)) {
		perror("fstat");
		exit(2);
	}
	if (S_ISREG(st.st_mode)) {
		return st.st_size;
	} else if (S_ISBLK(st.st_mode)) {
		unsigned long long size64;
		unsigned long sizeul;
		if (!ioctl(h, BLKGETSIZE64, &size64)) {
			return_size64:
			if ((off_t)size64 < 0 || (off_t)size64 != size64) {
				size_overflow:
				exit_err("%s: device size overflow", name);
			}
			return size64;
		}
		if (!ioctl(h, BLKGETSIZE, &sizeul)) {
			size64 = (unsigned long long)sizeul * 512;
			if (size64 / 512 != sizeul) goto size_overflow;
			goto return_size64;
		}
		perror("BLKGETSIZE");
		exit(2);
	} else {
		exit_err("%s is not a file or a block device", name);
	}
	return -1;	/* never reached, shut up warning */
}

static void block_fseek(FILE *f, off_t block, int block_size)
{
	unsigned long long pos = (unsigned long long)block * block_size;
	if (pos / block_size != block ||
	    (off_t)pos < 0 ||
	    (off_t)pos != pos)
		exit_err("seek position overflow");
	if (fseeko(f, pos, SEEK_SET)) {
		perror("fseek");
		exit(2);
	}
}


#ifdef CRYPT_OPENSSL

static const EVP_MD *evp;

static int hash_init(const char *name)
{
	OpenSSL_add_all_digests();
	evp = EVP_get_digestbyname(name);
	if (!evp) return 0;
	return EVP_MD_size(evp);
}

typedef EVP_MD_CTX hash_context;

static void hash_context_init(hash_context *ctx)
{
	EVP_MD_CTX_init(ctx);
}

static void hash_context_reset(hash_context *ctx)
{
	if (EVP_DigestInit_ex(ctx, evp, NULL) != 1)
		exit_err("EVP_DigestInit_ex failed");
}

static void hash_context_update(hash_context *ctx, unsigned char *data, size_t len)
{
	if (EVP_DigestUpdate(ctx, data, len) != 1)
		exit_err("EVP_DigestUpdate failed");
}

static void hash_context_final(hash_context *ctx, unsigned char *digest)
{
	if (EVP_DigestFinal_ex(ctx, digest, NULL) != 1)
		exit_err("EVP_DigestFinal_ex failed");
}

static void hash_context_destroy(hash_context *ctx)
{
	if (EVP_MD_CTX_cleanup(ctx) != 1)
		exit_err("EVP_MD_CTX_cleanup failed");
}

static void crypto_rand_bytes(unsigned char *data, size_t len)
{
	if (RAND_bytes(data, len) != 1)
		exit_err("RAND_bytes failed");
}

#endif


#ifdef CRYPT_GCRYPT

static int gcrypt_id;

static int hash_init(const char *name)
{
	retry:
	gcrypt_id = gcry_md_map_name(name);
	if (!gcrypt_id) {
		if (!strcmp(name, "wp512")) {
			name = "whirlpool";
			goto retry;
		}
		if (!strcmp(name, "rmd160")) {
			name = "ripemd160";
			goto retry;
		}
		return 0;
	}
	return gcry_md_get_algo_dlen(gcrypt_id);
}

typedef gcry_md_hd_t hash_context;

static void hash_context_init(hash_context *ctx)
{
	if (gcry_md_open(ctx, gcrypt_id, 0))
		exit_err("gcry_md_open failed");
}

static void hash_context_reset(hash_context *ctx)
{
	gcry_md_reset(*ctx);
}

static void hash_context_update(hash_context *ctx, unsigned char *data, size_t len)
{
	gcry_md_write(*ctx, data, len);
}

static void hash_context_final(hash_context *ctx, unsigned char *digest)
{
	unsigned char *p = gcry_md_read(*ctx, gcrypt_id);
	memcpy(digest, p, gcry_md_get_algo_dlen(gcrypt_id));
}

static void hash_context_destroy(hash_context *ctx)
{
	gcry_md_close(*ctx);
}

static void crypto_rand_bytes(unsigned char *data, size_t len)
{
	gcry_randomize(data, len, GCRY_STRONG_RANDOM);
}

#endif


#ifdef CRYPT_NSS

static HASH_HashType nss_alg;

static int hash_init(const char *name)
{
	if (NSS_NoDB_Init(NULL) != SECSuccess)
		exit_err("NSS_Init failed");
	if (!strcmp(name, "md2")) nss_alg = HASH_AlgMD2;
	else if (!strcmp(name, "md5")) nss_alg = HASH_AlgMD5;
	else if (!strcmp(name, "sha1")) nss_alg = HASH_AlgSHA1;
	else if (!strcmp(name, "sha256")) nss_alg = HASH_AlgSHA256;
	else if (!strcmp(name, "sha384")) nss_alg = HASH_AlgSHA384;
	else if (!strcmp(name, "sha512")) nss_alg = HASH_AlgSHA512;
	else return 0;
	return HASH_ResultLen(nss_alg);
}

typedef HASHContext *hash_context;

static void hash_context_init(hash_context *ctx)
{
	*ctx = HASH_Create(nss_alg);
	if (!*ctx) exit_err("HASH_Create failed");
}

static void hash_context_reset(hash_context *ctx)
{
	HASH_Begin(*ctx);
}

static void hash_context_update(hash_context *ctx, unsigned char *data, size_t len)
{
	HASH_Update(*ctx, data, len);
}

static void hash_context_final(hash_context *ctx, unsigned char *digest)
{
	unsigned result_len;
	HASH_End(*ctx, digest, &result_len, HASH_ResultLen(nss_alg));
}

static void hash_context_destroy(hash_context *ctx)
{
	HASH_Destroy(*ctx);
}

static void crypto_rand_bytes(unsigned char *data, size_t len)
{
	if (PK11_GenerateRandom(data, len) != SECSuccess)
		exit_err("PK11_GenerateRandom failed");
}

#endif


static off_t verity_position_at_level(off_t block, int level)
{
	return block >> (level * hash_per_block_bits);
}

static void calculate_positions(void)
{
	unsigned long long hash_position;
	int i;

	digest_size_bits = 0;
	while (1 << digest_size_bits < digest_size)
		digest_size_bits++;
	hash_per_block_bits = 0;
	while (((hash_block_size / digest_size) >> hash_per_block_bits) > 1)
		hash_per_block_bits++;
	if (!hash_per_block_bits)
		exit_err("at least two hashes must fit in a hash file block");
	levels = 0;

	if (data_file_blocks) {
		while (hash_per_block_bits * levels < 64 &&
		       (unsigned long long)(data_file_blocks - 1) >>
		       (hash_per_block_bits * levels))
			levels++;
	}

	if (levels > DM_VERITY_MAX_LEVELS) exit_err("too many tree levels");

	hash_position = hash_start * 512 / hash_block_size;
	for (i = levels - 1; i >= 0; i--) {
		off_t s;
		hash_level_block[i] = hash_position;
		s = verity_position_at_level(data_file_blocks, i);
		s = (s >> hash_per_block_bits) +
		    !!(s & ((1 << hash_per_block_bits) - 1));
		hash_level_size[i] = s;
		if (hash_position + s < hash_position ||
		    (off_t)(hash_position + s) < 0 ||
		    (off_t)(hash_position + s) != hash_position + s)
			exit_err("hash device offset overflow");
		hash_position += s;
	}
	used_hash_blocks = hash_position;
}

static void create_or_verify_zero(FILE *wr, unsigned char *left_block, unsigned left_bytes)
{
	if (left_bytes) {
		if (mode != MODE_CREATE) {
			unsigned x;
			if (fread(left_block, left_bytes, 1, wr) != 1)
				stream_err(wr, "read");
			for (x = 0; x < left_bytes; x++) if (left_block[x]) {
				retval = 1;
				fprintf(stderr, "spare area is not zeroed at position %lld\n", (long long)ftello(wr) - left_bytes);
			}
		} else {
			if (fwrite(left_block, left_bytes, 1, wr) != 1)
				stream_err(wr, "write");
		}
	}
}

static void create_or_verify_stream(FILE *rd, FILE *wr, int block_size, off_t blocks)
{
	unsigned char *left_block = xmalloc(hash_block_size);
	unsigned char *data_buffer = xmalloc(block_size);
	unsigned char *read_digest = mode != MODE_CREATE ? xmalloc(digest_size) : NULL;
	off_t blocks_to_write = (blocks >> hash_per_block_bits) +
				!!(blocks & ((1 << hash_per_block_bits) - 1));
	hash_context ctx;
	hash_context_init(&ctx);
	memset(left_block, 0, hash_block_size);
	while (blocks_to_write--) {
		unsigned x;
		unsigned left_bytes = hash_block_size;
		for (x = 0; x < 1 << hash_per_block_bits; x++) {
			if (!blocks)
				break;
			blocks--;
			if (fread(data_buffer, block_size, 1, rd) != 1)
				stream_err(rd, "read");
			hash_context_reset(&ctx);
			if (version >= 1) {
				hash_context_update(&ctx, salt_bytes, salt_size);
			}
			hash_context_update(&ctx, data_buffer, block_size);
			if (!version) {
				hash_context_update(&ctx, salt_bytes, salt_size);
			}
			hash_context_final(&ctx, calculated_digest);
			if (!wr)
				break;
			if (mode != MODE_CREATE) {
				if (fread(read_digest, digest_size, 1, wr) != 1)
					stream_err(wr, "read");
				if (memcmp(read_digest, calculated_digest, digest_size)) {
					retval = 1;
					fprintf(stderr, "verification failed at position %lld in %s file\n", (long long)ftello(rd) - block_size, rd == data_file ? "data" : "metadata");
				}
			} else {
				if (fwrite(calculated_digest, digest_size, 1, wr) != 1)
					stream_err(wr, "write");
			}
			if (!version) {
				left_bytes -= digest_size;
			} else {
				create_or_verify_zero(wr, left_block, (1 << digest_size_bits) - digest_size);
				left_bytes -= 1 << digest_size_bits;
			}
		}
		if (wr)
			create_or_verify_zero(wr, left_block, left_bytes);
	}
	if (mode == MODE_CREATE && wr) {
		if (fflush(wr)) {
			perror("fflush");
			exit(1);
		}
		if (ferror(wr)) {
			stream_err(wr, "write");
		}
	}
	hash_context_destroy(&ctx);
	free(left_block);
	free(data_buffer);
	if (mode != MODE_CREATE) free(read_digest);
}

static char **make_target_line(void)
{
	const int line_elements = 14;
	char **line = xmalloc(line_elements * sizeof(char *));
	int i = 0;
	char *algorithm_copy = xstrdup(hash_algorithm);
		/* transform ripemdXXX to rmdXXX */
	if (!strncmp(algorithm_copy, "ripemd", 6))
		memmove(algorithm_copy + 1, algorithm_copy + 4, strlen(algorithm_copy + 4) + 1);
	if (!strcmp(algorithm_copy, "whirlpool"))
		strcpy(algorithm_copy, "wp512");
	line[i++] = xstrdup("0");
	line[i++] = xprint((unsigned long long)data_file_blocks * data_block_size / 512);
	line[i++] = xstrdup("verity");
	line[i++] = xprint(version);
	line[i++] = xstrdup(data_device);
	line[i++] = xstrdup(hash_device);
	line[i++] = xprint(data_block_size);
	line[i++] = xprint(hash_block_size);
	line[i++] = xprint(data_file_blocks);
	line[i++] = xprint(hash_start * 512 / hash_block_size);
	line[i++] = algorithm_copy;
	line[i++] = xhexprint(calculated_digest, digest_size);
	line[i++] = !salt_size ? xstrdup("-") : xhexprint(salt_bytes, salt_size);
	line[i++] = NULL;
	if (i > line_elements) exit_err("INTERNAL ERROR: insufficient array size");
	return line;
}

static void free_target_line(char **line)
{
	int i;
	for (i = 0; line[i]; i++)
		free(line[i]);
	free(line);
}

static void create_or_verify(void)
{
	int i;
	memset(calculated_digest, 0, digest_size);
	if (mode != MODE_ACTIVATE) for (i = 0; i < levels; i++) {
		block_fseek(hash_file, hash_level_block[i], hash_block_size);
		if (!i) {
			block_fseek(data_file, 0, data_block_size);
			create_or_verify_stream(data_file, hash_file, data_block_size, data_file_blocks);
		} else {
			FILE *hash_file_2 = fopen(hash_device, "r");
			if (!hash_file_2) {
				perror(hash_device);
				exit(2);
			}
			block_fseek(hash_file_2, hash_level_block[i - 1], hash_block_size);
			create_or_verify_stream(hash_file_2, hash_file, hash_block_size, hash_level_size[i - 1]);
			fclose(hash_file_2);
		}
	}

	if (levels) {
		block_fseek(hash_file, hash_level_block[levels - 1], hash_block_size);
		create_or_verify_stream(hash_file, NULL, hash_block_size, 1);
	} else {
		block_fseek(data_file, 0, data_block_size);
		create_or_verify_stream(data_file, NULL, data_block_size, data_file_blocks);
	}

	if (mode != MODE_CREATE) {
		if (memcmp(calculated_digest, root_hash_bytes, digest_size)) {
			fprintf(stderr, "verification failed in the root block\n");
			retval = 1;
		}
		if (!retval && mode == MODE_VERIFY)
			fprintf(stderr, "hash successfully verified\n");
	} else {
		char **target_line;
		char *p;
		if (fsync(fileno(hash_file))) {
			perror("fsync");
			exit(1);
		}
		printf("hash device size: %llu\n", (unsigned long long)used_hash_blocks * hash_block_size);
		printf("data block size %u, hash block size %u, %u tree levels\n", data_block_size, hash_block_size, levels);
		if (salt_size) p = xhexprint(salt_bytes, salt_size);
		else p = xstrdup("-");
		printf("salt: %s\n", p);
		free(p);
		p = xhexprint(calculated_digest, digest_size);
		printf("root hash: %s\n", p);
		free(p);
		printf("target line:");
		target_line = make_target_line();
		for (i = 0; target_line[i]; i++)
			printf(" %s", target_line[i]);
		free_target_line(target_line);
		printf("\n");
	}
}

#if defined(__GNUC__) && __GNUC__ >= 2
	__attribute__((__noreturn__))
#endif
static void activate(void)
{
	int i;
	size_t len = 1;
	char *table_arg;
	char **target_line = make_target_line();
	for (i = 0; target_line[i]; i++) {
		if (i) len++;
		len += strlen(target_line[i]);
	}
	table_arg = xmalloc(len);
	table_arg[0] = 0;
	for (i = 0; target_line[i]; i++) {
		if (i) strcat(table_arg, " ");
		strcat(table_arg, target_line[i]);
	}
	free_target_line(target_line);
	execlp("dmsetup", "dmsetup", "-r", "create", dm_device, "--table", table_arg, NULL);
	perror("dmsetup");
	exit(2);
}

static void get_hex(const char *string, unsigned char **result, size_t len, const char *description)
{
	size_t rl = strlen(string);
	unsigned u;
	if (strspn(string, "0123456789ABCDEFabcdef") != rl)
		exit_err("invalid %s", description);
	if (rl != len * 2)
		exit_err("invalid length of %s", description);
	*result = xmalloc(len);
	memset(*result, 0, len);
	for (u = 0; u < rl; u++) {
		unsigned char c = (string[u] & 15) + (string[u] > '9' ? 9 : 0);
		(*result)[u / 2] |= c << (((u & 1) ^ 1) << 2);
	}
}

static struct superblock superblock;

static void load_superblock(void)
{
	long long sb_data_blocks;

	block_fseek(hash_file, superblock_position, 1);
	if (fread(&superblock, sizeof(struct superblock), 1, hash_file) != 1)
		stream_err(hash_file, "read");
	if (memcmp(superblock.signature, DM_VERITY_SIGNATURE, sizeof(superblock.signature)))
		exit_err("superblock not found on the hash device");
	if (superblock.version > MAX_FORMAT_VERSION)
		exit_err("unknown version");
	if (superblock.data_block_bits < 9 || superblock.data_block_bits >= 31)
		exit_err("invalid data_block_bits in the superblock");
	if (superblock.hash_block_bits < 9 || superblock.hash_block_bits >= 31)
		exit_err("invalid data_block_bits in the superblock");
	sb_data_blocks = ((unsigned long long)ntohl(superblock.data_blocks_hi) << 31 << 1) | ntohl(superblock.data_blocks_lo);
	if (sb_data_blocks < 0 || (off_t)sb_data_blocks < 0 || (off_t)sb_data_blocks != sb_data_blocks)
		exit_err("invalid data blocks in the superblock");
	if (!memchr(superblock.algorithm, 0, sizeof(superblock.algorithm)))
		exit_err("invalid hash algorithm in the superblock");
	if (ntohs(superblock.salt_size) > MAX_SALT_SIZE)
		exit_err("invalid salt_size in the superblock");

	if (version == -1) {
		version = superblock.version;
	} else {
		if (version != superblock.version)
			exit_err("version (%d) does not match superblock value (%d)", version, superblock.version);
	}

	if (!data_block_size) {
		data_block_size = 1 << superblock.data_block_bits;
	} else {
		if (data_block_size != 1 << superblock.data_block_bits)
			exit_err("data block size (%d) does not match superblock value (%d)", data_block_size, 1 << superblock.data_block_bits);
	}

	if (!hash_block_size) {
		hash_block_size = 1 << superblock.hash_block_bits;
	} else {
		if (hash_block_size != 1 << superblock.hash_block_bits)
			exit_err("hash block size (%d) does not match superblock value (%d)", hash_block_size, 1 << superblock.hash_block_bits);
	}

	if (!data_blocks_string) {
		data_blocks = sb_data_blocks;
		data_blocks_string = (char *)"";
	} else {
		if (data_blocks != sb_data_blocks)
			exit_err("data blocks (%lld) does not match superblock value (%lld)", data_blocks, sb_data_blocks);
	}

	if (!hash_algorithm) {
		hash_algorithm = (char *)superblock.algorithm;
	} else {
		if (strcmp(hash_algorithm, (char *)superblock.algorithm))
			exit_err("hash algorithm (%s) does not match superblock value (%s)", hash_algorithm, superblock.algorithm);
	}

	if (!salt_bytes) {
		salt_size = ntohs(superblock.salt_size);
		salt_bytes = xmalloc(salt_size);
		memcpy(salt_bytes, superblock.salt, salt_size);
	} else {
		if (salt_size != ntohs(superblock.salt_size) ||
		    memcmp(salt_bytes, superblock.salt, salt_size))
			exit_err("salt does not match superblock value");
	}
}

static void save_superblock(void)
{
	memset(&superblock, 0, sizeof(struct superblock));

	memcpy(&superblock.signature, DM_VERITY_SIGNATURE, sizeof(superblock.signature));
	superblock.version = version;
	superblock.data_block_bits = ffs(data_block_size) - 1;
	superblock.hash_block_bits = ffs(hash_block_size) - 1;
	superblock.salt_size = htons(salt_size);
	superblock.data_blocks_hi = htonl(data_file_blocks >> 31 >> 1);
	superblock.data_blocks_lo = htonl(data_file_blocks & 0xFFFFFFFF);
	strncpy((char *)superblock.algorithm, hash_algorithm, sizeof superblock.algorithm);
	memcpy(superblock.salt, salt_bytes, salt_size);

	block_fseek(hash_file, superblock_position, 1);
	if (fwrite(&superblock, sizeof(struct superblock), 1, hash_file) != 1)
		stream_err(hash_file, "write");
}

int main(int argc, const char **argv)
{
	poptContext popt_context;
	int r;
	const char *s;
	char *end;

	if (sizeof(struct superblock) != 512)
		exit_err("INTERNAL ERROR: bad superblock size %ld", (long)sizeof(struct superblock));

	popt_context = poptGetContext("verity", argc, argv, popt_options, 0);

	poptSetOtherOptionHelp(popt_context, "[-c | -v | -a] [<device name> if activating] <data device> <hash device> [<root hash> if activating or verifying] [OPTION...]");

	if (argc <= 1) {
		poptPrintHelp(popt_context, stdout, 0);
		exit(1);
	}

	r = poptGetNextOpt(popt_context);
	if (r < -1) exit_err("bad option %s", poptBadOption(popt_context, 0));

	if (mode < 0) exit_err("verify, create or activate mode not specified");

	if (mode == MODE_ACTIVATE) {
		dm_device = poptGetArg(popt_context);
		if (!dm_device) exit_err("device name is missing");
		if (!*dm_device || strchr(dm_device, '/')) exit_err("invalid device name to activate");
	}

	data_device = poptGetArg(popt_context);
	if (!data_device) exit_err("data device is missing");

	hash_device = poptGetArg(popt_context);
	if (!hash_device) exit_err("metadata device is missing");

	if (mode != MODE_CREATE) {
		root_hash = poptGetArg(popt_context);
		if (!root_hash) exit_err("root hash not specified");
	}

	s = poptGetArg(popt_context);
	if (s) exit_err("extra argument %s", s);

	data_file = fopen(data_device, "r");
	if (!data_file) {
		perror(data_device);
		exit(2);
	}

	hash_file = fopen(hash_device, mode != MODE_CREATE ? "r" : "r+");
	if (!hash_file && errno == ENOENT && mode == MODE_CREATE)
		hash_file = fopen(hash_device, "w+");
	if (!hash_file) {
		perror(hash_device);
		exit(2);
	}

	if (data_blocks_string) {
		data_blocks = strtoll(data_blocks_string, &end, 10);
		if (!*data_blocks_string || *end)
			exit_err("invalid data blocks");
	}

	if (hash_start_string) {
		hash_start = strtoll(hash_start_string, &end, 10);
		if (!*hash_start_string || *end)
			exit_err("invalid hash start");
	}

	if (hash_start < 0 ||
	   (unsigned long long)hash_start * 512 / 512 != hash_start ||
	   (off_t)(hash_start * 512) < 0 ||
	   (off_t)(hash_start * 512) != hash_start * 512) exit_err("invalid hash start");

	if (salt_string || !use_superblock) {
		if (!salt_string || !strcmp(salt_string, "-"))
			salt_string = "";
		salt_size = strlen(salt_string) / 2;
		if (salt_size > MAX_SALT_SIZE)
			exit_err("too long salt (max %d bytes)", MAX_SALT_SIZE);
		get_hex(salt_string, &salt_bytes, salt_size, "salt");
	}

	if (use_superblock) {
		superblock_position = hash_start * 512;
		if (mode != MODE_CREATE)
			load_superblock();
	}

	if (version == -1) version = MAX_FORMAT_VERSION;
	if (version < 0 || version > MAX_FORMAT_VERSION)
		exit_err("invalid format version");

	if (!data_block_size) data_block_size = DEFAULT_BLOCK_SIZE;
	if (!hash_block_size) hash_block_size = data_block_size;

	if (data_block_size < 512 || (data_block_size & (data_block_size - 1)) || data_block_size >= 1U << 31)
		exit_err("invalid data block size");

	if (hash_block_size < 512 || (hash_block_size & (hash_block_size - 1)) || hash_block_size >= 1U << 31)
		exit_err("invalid hash block size");

	if (data_blocks < 0 || (off_t)data_blocks < 0 || (off_t)data_blocks != data_blocks) exit_err("invalid number of data blocks");

	data_file_blocks = get_size(data_file, data_device) / data_block_size;
	hash_file_blocks = get_size(hash_file, hash_device) / hash_block_size;

	if (data_file_blocks < data_blocks) exit_err("data file is too small");
	if (data_blocks_string) {
		data_file_blocks = data_blocks;
	}

	if (use_superblock) {
		hash_start = hash_start + (sizeof(struct superblock) + 511) / 512;
		hash_start = (hash_start + (hash_block_size / 512 - 1)) & ~(long long)(hash_block_size / 512 - 1);
	}

	if ((unsigned long long)hash_start * 512 % hash_block_size) exit_err("hash start not aligned on block size");

	if (!hash_algorithm)
		hash_algorithm = "sha256";
	if (strlen(hash_algorithm) >= sizeof(superblock.algorithm) && use_superblock)
		exit_err("hash algorithm name is too long");

	digest_size = hash_init(hash_algorithm);
	if (!digest_size) exit_err("hash algorithm %s not found", hash_algorithm);

	if (!salt_bytes) {
		salt_size = DEFAULT_SALT_SIZE;
		salt_bytes = xmalloc(salt_size);
		crypto_rand_bytes(salt_bytes, salt_size);
	}

	calculated_digest = xmalloc(digest_size);

 	if (mode != MODE_CREATE) {
		get_hex(root_hash, &root_hash_bytes, digest_size, "root_hash");
	}

	calculate_positions();

	create_or_verify();

	if (use_superblock) {
		if (mode == MODE_CREATE)
			save_superblock();
	}

	fclose(data_file);
	fclose(hash_file);

	if (mode == MODE_ACTIVATE && !retval)
		activate();

	free(salt_bytes);
	free(calculated_digest);
	if (mode != MODE_CREATE)
		free(root_hash_bytes);
	poptFreeContext(popt_context);

	return retval;
}
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