Re: [dm-devel] [PATCH] dm: remake of the verity target

From: Mikulas Patocka
Date: Wed Mar 21 2012 - 13:18:33 EST

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On Wed, 21 Mar 2012, Mikulas Patocka wrote:

>
>
> On Tue, 20 Mar 2012, Mandeep Singh Baines wrote:
>
> > > I can introduce a switch to make it accept the old format. Do you want to?
> > >
> >
> > We can carry that as an out-of-tree patch until we migrate.
> >
> > On the other hand, it might be nice to support prepend or append.
> >
> > I don't too strong feelings but it might be nice to have
> > prepend/append flag. Would definitely make our life easier.
>
> 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.
>
> Mikulas

This is the new userspace tool that supports both formats.

Mikulas

---

/* 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

#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 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" },
{ "format", 0, POPT_ARG_INT, &version, 0, "Format version (0 - original Google code, 1 - new format)", "number" },
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 (version >= 1) {
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 (!version) {
if (EVP_DigestUpdate(&ctx, salt_bytes, salt_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");
}
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");
}
}
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++] = 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;
}

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 > 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) {
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 = 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_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 (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) {
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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