Message-ID: <Pine.LNX.4.64.1203202054490.23255@file.rdu.redhat.com>
Date:	Tue, 20 Mar 2012 21:10:54 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Mandeep Singh Baines <msb@...omium.org>
cc:	linux-kernel@...r.kernel.org, dm-devel@...hat.com,
	Alasdair G Kergon <agk@...hat.com>,
	Will Drewry <wad@...omium.org>,
	Elly Jones <ellyjones@...omium.org>,
	Milan Broz <mbroz@...hat.com>,
	Olof Johansson <olofj@...omium.org>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] dm: remake of the verity target

Hi

Here I'm sending the new userspace tool:

Changes since the last version:

* Format is changed to be compatible with the current kernel code (i.e. 
hash salt before the data)

* If no salt is specified, random salt is generated

* Switch -a is used to activate the device (it executes dmsetup with 
the correct parameters)

* There is a superblock that can be used to identify verity hash 
partition. Most arguments are stored in the superblock, so they don't have 
to be specified when verifying or activating. Superblock stores all the 
options except: device names, --hash-start, root block hash.

* The superblock is read or written only by the userspace tool, it is not 
read by the kernel code.


Example use:

# create some filesystem on /dev/sdc2, fill it with data and unmount it
... 
# read /dev/sdc2 and create appropriate hashes on /dev/sdc3
./veritysetup -c /dev/sdc2 /dev/sdc3
# verify the hashes (supply the real hash as reported by ./veritysetup -c)
./veritysetup -v /dev/sdc2 /dev/sdc3 3f1fe1c1ff7f229f1ff113c2b4b76ce4bcd9f455dd7f990673b3e71f6a406e38
# activate the kernel driver with device mapper name "v"
./veritysetup -a v /dev/sdc2 /dev/sdc3 3f1fe1c1ff7f229f1ff113c2b4b76ce4bcd9f455dd7f990673b3e71f6a406e38
# mount the activated filesystem
mount -o ro /dev/mapper/v /mnt/test

---

/* link with -lpopt -lcrypto */

#define _FILE_OFFSET_BITS	64

#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>
#include <openssl/evp.h>
#include <openssl/rand.h>

#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

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 data_block_size = 0;
static int hash_block_size = 0;
static long long hash_start = 0;
static long long data_blocks = 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 const EVP_MD *evp;

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

static void help(poptContext popt_context,
		enum poptCallbackReason reason,
		struct poptOption *key,
		const char *arg,
		void *data)
{
	poptPrintHelp(popt_context, stdout, 0);
	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 },
	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 },
	{ "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_LONGLONG, &data_blocks, 0, "The number of blocks in the data file", "blocks" },
	{ "hash-start",		0,	POPT_ARG_LONGLONG, &hash_start, 0, "Starting block on the hash device", "512-byte sectors" },
	{ "salt",		0,	POPT_ARG_STRING, &salt_string, 0, "Salt", "hex string" },
	{ "algorithm",		0,	POPT_ARG_STRING, &hash_algorithm, 0, "Hash algorithm (default sha256)", "string" },
	{ "no-superblock",	0,	POPT_ARG_VAL, &use_superblock, 0, "Do not create/use superblock" },
	POPT_TABLEEND
};

#if defined(__GNUC__) && __GNUC__ >= 2
	__attribute__((__format__(__printf__, 1, 2)))
#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);
}

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);
	}
}

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));
	EVP_MD_CTX ctx;
	EVP_MD_CTX_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");
			if (EVP_DigestInit_ex(&ctx, evp, NULL) != 1)
				exit_err("EVP_DigestInit_ex failed");
			if (EVP_DigestUpdate(&ctx, salt_bytes, salt_size) != 1)
				exit_err("EVP_DigestUpdate failed");
			if (EVP_DigestUpdate(&ctx, data_buffer, block_size) != 1)
				exit_err("EVP_DigestUpdate failed");
			if (EVP_DigestFinal_ex(&ctx, calculated_digest, NULL) != 1)
				exit_err("EVP_DigestFinal_ex failed");
			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");
			}
			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");
		}
	}
	if (EVP_MD_CTX_cleanup(&ctx) != 1)
		exit_err("EVP_MD_CTX_cleanup failed");
	free(left_block);
	free(data_buffer);
	if (mode != MODE_CREATE) free(read_digest);
}

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);
	line[i++] = xstrdup("0");
	line[i++] = xprint((unsigned long long)data_file_blocks * data_block_size / 512);
	line[i++] = xstrdup("verity");
	line[i++] = xstrdup("0");
	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;
}

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;
	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");
	}
}

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 != 0)
		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 (!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) {
		data_blocks = sb_data_blocks;
	} 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 = 0;
	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_blocks >> 31 >> 1);
	superblock.data_blocks_lo = htonl(data_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;

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

	OpenSSL_add_all_digests();

	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");
	}

	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 (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 (!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) {
		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");
	evp = EVP_get_digestbyname(hash_algorithm);
	if (!evp) exit_err("hash algorithm %s not found", hash_algorithm);
	digest_size = EVP_MD_size(evp);

	if (!salt_bytes) {
		salt_size = DEFAULT_SALT_SIZE;
		salt_bytes = xmalloc(salt_size);
		if (RAND_bytes(salt_bytes, salt_size) != 1)
			exit_err("RAND_bytes failed");
	}

	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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