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qemu/crypto/block-luks.c

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/*
* QEMU Crypto block device encryption LUKS format
*
* Copyright (c) 2015-2016 Red Hat, Inc.
*
* This library 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 of the License, or (at your option) any later version.
*
* This library 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 library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "qemu/bswap.h"
#include "block-luks.h"
#include "crypto/hash.h"
#include "crypto/afsplit.h"
#include "crypto/pbkdf.h"
#include "crypto/secret.h"
#include "crypto/random.h"
#include "qemu/uuid.h"
#include "qemu/coroutine.h"
/*
* Reference for the LUKS format implemented here is
*
* docs/on-disk-format.pdf
*
* in 'cryptsetup' package source code
*
* This file implements the 1.2.1 specification, dated
* Oct 16, 2011.
*/
typedef struct QCryptoBlockLUKS QCryptoBlockLUKS;
typedef struct QCryptoBlockLUKSHeader QCryptoBlockLUKSHeader;
typedef struct QCryptoBlockLUKSKeySlot QCryptoBlockLUKSKeySlot;
/* The following constants are all defined by the LUKS spec */
#define QCRYPTO_BLOCK_LUKS_VERSION 1
#define QCRYPTO_BLOCK_LUKS_MAGIC_LEN 6
#define QCRYPTO_BLOCK_LUKS_CIPHER_NAME_LEN 32
#define QCRYPTO_BLOCK_LUKS_CIPHER_MODE_LEN 32
#define QCRYPTO_BLOCK_LUKS_HASH_SPEC_LEN 32
#define QCRYPTO_BLOCK_LUKS_DIGEST_LEN 20
#define QCRYPTO_BLOCK_LUKS_SALT_LEN 32
#define QCRYPTO_BLOCK_LUKS_UUID_LEN 40
#define QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS 8
#define QCRYPTO_BLOCK_LUKS_STRIPES 4000
#define QCRYPTO_BLOCK_LUKS_MIN_SLOT_KEY_ITERS 1000
#define QCRYPTO_BLOCK_LUKS_MIN_MASTER_KEY_ITERS 1000
#define QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET 4096
#define QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED 0x0000DEAD
#define QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED 0x00AC71F3
#define QCRYPTO_BLOCK_LUKS_SECTOR_SIZE 512LL
static const char qcrypto_block_luks_magic[QCRYPTO_BLOCK_LUKS_MAGIC_LEN] = {
'L', 'U', 'K', 'S', 0xBA, 0xBE
};
typedef struct QCryptoBlockLUKSNameMap QCryptoBlockLUKSNameMap;
struct QCryptoBlockLUKSNameMap {
const char *name;
int id;
};
typedef struct QCryptoBlockLUKSCipherSizeMap QCryptoBlockLUKSCipherSizeMap;
struct QCryptoBlockLUKSCipherSizeMap {
uint32_t key_bytes;
int id;
};
typedef struct QCryptoBlockLUKSCipherNameMap QCryptoBlockLUKSCipherNameMap;
struct QCryptoBlockLUKSCipherNameMap {
const char *name;
const QCryptoBlockLUKSCipherSizeMap *sizes;
};
static const QCryptoBlockLUKSCipherSizeMap
qcrypto_block_luks_cipher_size_map_aes[] = {
{ 16, QCRYPTO_CIPHER_ALG_AES_128 },
{ 24, QCRYPTO_CIPHER_ALG_AES_192 },
{ 32, QCRYPTO_CIPHER_ALG_AES_256 },
{ 0, 0 },
};
static const QCryptoBlockLUKSCipherSizeMap
qcrypto_block_luks_cipher_size_map_cast5[] = {
{ 16, QCRYPTO_CIPHER_ALG_CAST5_128 },
{ 0, 0 },
};
static const QCryptoBlockLUKSCipherSizeMap
qcrypto_block_luks_cipher_size_map_serpent[] = {
{ 16, QCRYPTO_CIPHER_ALG_SERPENT_128 },
{ 24, QCRYPTO_CIPHER_ALG_SERPENT_192 },
{ 32, QCRYPTO_CIPHER_ALG_SERPENT_256 },
{ 0, 0 },
};
static const QCryptoBlockLUKSCipherSizeMap
qcrypto_block_luks_cipher_size_map_twofish[] = {
{ 16, QCRYPTO_CIPHER_ALG_TWOFISH_128 },
{ 24, QCRYPTO_CIPHER_ALG_TWOFISH_192 },
{ 32, QCRYPTO_CIPHER_ALG_TWOFISH_256 },
{ 0, 0 },
};
static const QCryptoBlockLUKSCipherNameMap
qcrypto_block_luks_cipher_name_map[] = {
{ "aes", qcrypto_block_luks_cipher_size_map_aes },
{ "cast5", qcrypto_block_luks_cipher_size_map_cast5 },
{ "serpent", qcrypto_block_luks_cipher_size_map_serpent },
{ "twofish", qcrypto_block_luks_cipher_size_map_twofish },
};
/*
* This struct is written to disk in big-endian format,
* but operated upon in native-endian format.
*/
struct QCryptoBlockLUKSKeySlot {
/* state of keyslot, enabled/disable */
uint32_t active;
/* iterations for PBKDF2 */
uint32_t iterations;
/* salt for PBKDF2 */
uint8_t salt[QCRYPTO_BLOCK_LUKS_SALT_LEN];
/* start sector of key material */
uint32_t key_offset;
/* number of anti-forensic stripes */
uint32_t stripes;
} QEMU_PACKED;
QEMU_BUILD_BUG_ON(sizeof(struct QCryptoBlockLUKSKeySlot) != 48);
/*
* This struct is written to disk in big-endian format,
* but operated upon in native-endian format.
*/
struct QCryptoBlockLUKSHeader {
/* 'L', 'U', 'K', 'S', '0xBA', '0xBE' */
char magic[QCRYPTO_BLOCK_LUKS_MAGIC_LEN];
/* LUKS version, currently 1 */
uint16_t version;
/* cipher name specification (aes, etc) */
char cipher_name[QCRYPTO_BLOCK_LUKS_CIPHER_NAME_LEN];
/* cipher mode specification (cbc-plain, xts-essiv:sha256, etc) */
char cipher_mode[QCRYPTO_BLOCK_LUKS_CIPHER_MODE_LEN];
/* hash specification (sha256, etc) */
char hash_spec[QCRYPTO_BLOCK_LUKS_HASH_SPEC_LEN];
/* start offset of the volume data (in 512 byte sectors) */
uint32_t payload_offset;
/* Number of key bytes */
uint32_t key_bytes;
/* master key checksum after PBKDF2 */
uint8_t master_key_digest[QCRYPTO_BLOCK_LUKS_DIGEST_LEN];
/* salt for master key PBKDF2 */
uint8_t master_key_salt[QCRYPTO_BLOCK_LUKS_SALT_LEN];
/* iterations for master key PBKDF2 */
uint32_t master_key_iterations;
/* UUID of the partition in standard ASCII representation */
uint8_t uuid[QCRYPTO_BLOCK_LUKS_UUID_LEN];
/* key slots */
QCryptoBlockLUKSKeySlot key_slots[QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS];
} QEMU_PACKED;
QEMU_BUILD_BUG_ON(sizeof(struct QCryptoBlockLUKSHeader) != 592);
struct QCryptoBlockLUKS {
QCryptoBlockLUKSHeader header;
/* Cache parsed versions of what's in header fields,
* as we can't rely on QCryptoBlock.cipher being
* non-NULL */
QCryptoCipherAlgorithm cipher_alg;
QCryptoCipherMode cipher_mode;
QCryptoIVGenAlgorithm ivgen_alg;
QCryptoHashAlgorithm ivgen_hash_alg;
QCryptoHashAlgorithm hash_alg;
};
static int qcrypto_block_luks_cipher_name_lookup(const char *name,
QCryptoCipherMode mode,
uint32_t key_bytes,
Error **errp)
{
const QCryptoBlockLUKSCipherNameMap *map =
qcrypto_block_luks_cipher_name_map;
size_t maplen = G_N_ELEMENTS(qcrypto_block_luks_cipher_name_map);
size_t i, j;
if (mode == QCRYPTO_CIPHER_MODE_XTS) {
key_bytes /= 2;
}
for (i = 0; i < maplen; i++) {
if (!g_str_equal(map[i].name, name)) {
continue;
}
for (j = 0; j < map[i].sizes[j].key_bytes; j++) {
if (map[i].sizes[j].key_bytes == key_bytes) {
return map[i].sizes[j].id;
}
}
}
error_setg(errp, "Algorithm %s with key size %d bytes not supported",
name, key_bytes);
return 0;
}
static const char *
qcrypto_block_luks_cipher_alg_lookup(QCryptoCipherAlgorithm alg,
Error **errp)
{
const QCryptoBlockLUKSCipherNameMap *map =
qcrypto_block_luks_cipher_name_map;
size_t maplen = G_N_ELEMENTS(qcrypto_block_luks_cipher_name_map);
size_t i, j;
for (i = 0; i < maplen; i++) {
for (j = 0; j < map[i].sizes[j].key_bytes; j++) {
if (map[i].sizes[j].id == alg) {
return map[i].name;
}
}
}
error_setg(errp, "Algorithm '%s' not supported",
QCryptoCipherAlgorithm_str(alg));
return NULL;
}
/* XXX replace with qapi_enum_parse() in future, when we can
* make that function emit a more friendly error message */
static int qcrypto_block_luks_name_lookup(const char *name,
const QEnumLookup *map,
const char *type,
Error **errp)
{
int ret = qapi_enum_parse(map, name, -1, NULL);
if (ret < 0) {
error_setg(errp, "%s %s not supported", type, name);
return 0;
}
return ret;
}
#define qcrypto_block_luks_cipher_mode_lookup(name, errp) \
qcrypto_block_luks_name_lookup(name, \
&QCryptoCipherMode_lookup, \
"Cipher mode", \
errp)
#define qcrypto_block_luks_hash_name_lookup(name, errp) \
qcrypto_block_luks_name_lookup(name, \
&QCryptoHashAlgorithm_lookup, \
"Hash algorithm", \
errp)
#define qcrypto_block_luks_ivgen_name_lookup(name, errp) \
qcrypto_block_luks_name_lookup(name, \
&QCryptoIVGenAlgorithm_lookup, \
"IV generator", \
errp)
static bool
qcrypto_block_luks_has_format(const uint8_t *buf,
size_t buf_size)
{
const QCryptoBlockLUKSHeader *luks_header = (const void *)buf;
if (buf_size >= offsetof(QCryptoBlockLUKSHeader, cipher_name) &&
memcmp(luks_header->magic, qcrypto_block_luks_magic,
QCRYPTO_BLOCK_LUKS_MAGIC_LEN) == 0 &&
be16_to_cpu(luks_header->version) == QCRYPTO_BLOCK_LUKS_VERSION) {
return true;
} else {
return false;
}
}
/**
* Deal with a quirk of dm-crypt usage of ESSIV.
*
* When calculating ESSIV IVs, the cipher length used by ESSIV
* may be different from the cipher length used for the block
* encryption, becauses dm-crypt uses the hash digest length
* as the key size. ie, if you have AES 128 as the block cipher
* and SHA 256 as ESSIV hash, then ESSIV will use AES 256 as
* the cipher since that gets a key length matching the digest
* size, not AES 128 with truncated digest as might be imagined
*/
static QCryptoCipherAlgorithm
qcrypto_block_luks_essiv_cipher(QCryptoCipherAlgorithm cipher,
QCryptoHashAlgorithm hash,
Error **errp)
{
size_t digestlen = qcrypto_hash_digest_len(hash);
size_t keylen = qcrypto_cipher_get_key_len(cipher);
if (digestlen == keylen) {
return cipher;
}
switch (cipher) {
case QCRYPTO_CIPHER_ALG_AES_128:
case QCRYPTO_CIPHER_ALG_AES_192:
case QCRYPTO_CIPHER_ALG_AES_256:
if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_AES_128)) {
return QCRYPTO_CIPHER_ALG_AES_128;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_AES_192)) {
return QCRYPTO_CIPHER_ALG_AES_192;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_AES_256)) {
return QCRYPTO_CIPHER_ALG_AES_256;
} else {
error_setg(errp, "No AES cipher with key size %zu available",
digestlen);
return 0;
}
break;
case QCRYPTO_CIPHER_ALG_SERPENT_128:
case QCRYPTO_CIPHER_ALG_SERPENT_192:
case QCRYPTO_CIPHER_ALG_SERPENT_256:
if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_SERPENT_128)) {
return QCRYPTO_CIPHER_ALG_SERPENT_128;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_SERPENT_192)) {
return QCRYPTO_CIPHER_ALG_SERPENT_192;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_SERPENT_256)) {
return QCRYPTO_CIPHER_ALG_SERPENT_256;
} else {
error_setg(errp, "No Serpent cipher with key size %zu available",
digestlen);
return 0;
}
break;
case QCRYPTO_CIPHER_ALG_TWOFISH_128:
case QCRYPTO_CIPHER_ALG_TWOFISH_192:
case QCRYPTO_CIPHER_ALG_TWOFISH_256:
if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_TWOFISH_128)) {
return QCRYPTO_CIPHER_ALG_TWOFISH_128;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_TWOFISH_192)) {
return QCRYPTO_CIPHER_ALG_TWOFISH_192;
} else if (digestlen == qcrypto_cipher_get_key_len(
QCRYPTO_CIPHER_ALG_TWOFISH_256)) {
return QCRYPTO_CIPHER_ALG_TWOFISH_256;
} else {
error_setg(errp, "No Twofish cipher with key size %zu available",
digestlen);
return 0;
}
break;
default:
error_setg(errp, "Cipher %s not supported with essiv",
QCryptoCipherAlgorithm_str(cipher));
return 0;
}
}
/*
* Given a key slot, and user password, this will attempt to unlock
* the master encryption key from the key slot.
*
* Returns:
* 0 if the key slot is disabled, or key could not be decrypted
* with the provided password
* 1 if the key slot is enabled, and key decrypted successfully
* with the provided password
* -1 if a fatal error occurred loading the key
*/
static int
qcrypto_block_luks_load_key(QCryptoBlock *block,
QCryptoBlockLUKSKeySlot *slot,
const char *password,
QCryptoCipherAlgorithm cipheralg,
QCryptoCipherMode ciphermode,
QCryptoHashAlgorithm hash,
QCryptoIVGenAlgorithm ivalg,
QCryptoCipherAlgorithm ivcipheralg,
QCryptoHashAlgorithm ivhash,
uint8_t *masterkey,
size_t masterkeylen,
QCryptoBlockReadFunc readfunc,
void *opaque,
Error **errp)
{
QCryptoBlockLUKS *luks = block->opaque;
uint8_t *splitkey;
size_t splitkeylen;
uint8_t *possiblekey;
int ret = -1;
ssize_t rv;
QCryptoCipher *cipher = NULL;
uint8_t keydigest[QCRYPTO_BLOCK_LUKS_DIGEST_LEN];
QCryptoIVGen *ivgen = NULL;
size_t niv;
if (slot->active != QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED) {
return 0;
}
splitkeylen = masterkeylen * slot->stripes;
splitkey = g_new0(uint8_t, splitkeylen);
possiblekey = g_new0(uint8_t, masterkeylen);
/*
* The user password is used to generate a (possible)
* decryption key. This may or may not successfully
* decrypt the master key - we just blindly assume
* the key is correct and validate the results of
* decryption later.
*/
if (qcrypto_pbkdf2(hash,
(const uint8_t *)password, strlen(password),
slot->salt, QCRYPTO_BLOCK_LUKS_SALT_LEN,
slot->iterations,
possiblekey, masterkeylen,
errp) < 0) {
goto cleanup;
}
/*
* We need to read the master key material from the
* LUKS key material header. What we're reading is
* not the raw master key, but rather the data after
* it has been passed through AFSplit and the result
* then encrypted.
*/
rv = readfunc(block,
slot->key_offset * QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
splitkey, splitkeylen,
opaque,
errp);
if (rv < 0) {
goto cleanup;
}
/* Setup the cipher/ivgen that we'll use to try to decrypt
* the split master key material */
cipher = qcrypto_cipher_new(cipheralg, ciphermode,
possiblekey, masterkeylen,
errp);
if (!cipher) {
goto cleanup;
}
niv = qcrypto_cipher_get_iv_len(cipheralg,
ciphermode);
ivgen = qcrypto_ivgen_new(ivalg,
ivcipheralg,
ivhash,
possiblekey, masterkeylen,
errp);
if (!ivgen) {
goto cleanup;
}
/*
* The master key needs to be decrypted in the same
* way that the block device payload will be decrypted
* later. In particular we'll be using the IV generator
* to reset the encryption cipher every time the master
* key crosses a sector boundary.
*/
if (qcrypto_block_decrypt_helper(cipher,
niv,
ivgen,
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
0,
splitkey,
splitkeylen,
errp) < 0) {
goto cleanup;
}
/*
* Now we've decrypted the split master key, join
* it back together to get the actual master key.
*/
if (qcrypto_afsplit_decode(hash,
masterkeylen,
slot->stripes,
splitkey,
masterkey,
errp) < 0) {
goto cleanup;
}
/*
* We still don't know that the masterkey we got is valid,
* because we just blindly assumed the user's password
* was correct. This is where we now verify it. We are
* creating a hash of the master key using PBKDF and
* then comparing that to the hash stored in the key slot
* header
*/
if (qcrypto_pbkdf2(hash,
masterkey, masterkeylen,
luks->header.master_key_salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
luks->header.master_key_iterations,
keydigest, G_N_ELEMENTS(keydigest),
errp) < 0) {
goto cleanup;
}
if (memcmp(keydigest, luks->header.master_key_digest,
QCRYPTO_BLOCK_LUKS_DIGEST_LEN) == 0) {
/* Success, we got the right master key */
ret = 1;
goto cleanup;
}
/* Fail, user's password was not valid for this key slot,
* tell caller to try another slot */
ret = 0;
cleanup:
qcrypto_ivgen_free(ivgen);
qcrypto_cipher_free(cipher);
g_free(splitkey);
g_free(possiblekey);
return ret;
}
/*
* Given a user password, this will iterate over all key
* slots and try to unlock each active key slot using the
* password until it successfully obtains a master key.
*
* Returns 0 if a key was loaded, -1 if no keys could be loaded
*/
static int
qcrypto_block_luks_find_key(QCryptoBlock *block,
const char *password,
QCryptoCipherAlgorithm cipheralg,
QCryptoCipherMode ciphermode,
QCryptoHashAlgorithm hash,
QCryptoIVGenAlgorithm ivalg,
QCryptoCipherAlgorithm ivcipheralg,
QCryptoHashAlgorithm ivhash,
uint8_t **masterkey,
size_t *masterkeylen,
QCryptoBlockReadFunc readfunc,
void *opaque,
Error **errp)
{
QCryptoBlockLUKS *luks = block->opaque;
size_t i;
int rv;
*masterkey = g_new0(uint8_t, luks->header.key_bytes);
*masterkeylen = luks->header.key_bytes;
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
rv = qcrypto_block_luks_load_key(block,
&luks->header.key_slots[i],
password,
cipheralg,
ciphermode,
hash,
ivalg,
ivcipheralg,
ivhash,
*masterkey,
*masterkeylen,
readfunc,
opaque,
errp);
if (rv < 0) {
goto error;
}
if (rv == 1) {
return 0;
}
}
error_setg(errp, "Invalid password, cannot unlock any keyslot");
error:
g_free(*masterkey);
*masterkey = NULL;
*masterkeylen = 0;
return -1;
}
static int
qcrypto_block_luks_open(QCryptoBlock *block,
QCryptoBlockOpenOptions *options,
const char *optprefix,
QCryptoBlockReadFunc readfunc,
void *opaque,
unsigned int flags,
Error **errp)
{
QCryptoBlockLUKS *luks;
Error *local_err = NULL;
int ret = 0;
size_t i;
ssize_t rv;
uint8_t *masterkey = NULL;
size_t masterkeylen;
char *ivgen_name, *ivhash_name;
QCryptoCipherMode ciphermode;
QCryptoCipherAlgorithm cipheralg;
QCryptoIVGenAlgorithm ivalg;
QCryptoCipherAlgorithm ivcipheralg;
QCryptoHashAlgorithm hash;
QCryptoHashAlgorithm ivhash;
char *password = NULL;
if (!(flags & QCRYPTO_BLOCK_OPEN_NO_IO)) {
if (!options->u.luks.key_secret) {
error_setg(errp, "Parameter '%skey-secret' is required for cipher",
optprefix ? optprefix : "");
return -1;
}
password = qcrypto_secret_lookup_as_utf8(
options->u.luks.key_secret, errp);
if (!password) {
return -1;
}
}
luks = g_new0(QCryptoBlockLUKS, 1);
block->opaque = luks;
/* Read the entire LUKS header, minus the key material from
* the underlying device */
rv = readfunc(block, 0,
(uint8_t *)&luks->header,
sizeof(luks->header),
opaque,
errp);
if (rv < 0) {
ret = rv;
goto fail;
}
/* The header is always stored in big-endian format, so
* convert everything to native */
be16_to_cpus(&luks->header.version);
be32_to_cpus(&luks->header.payload_offset);
be32_to_cpus(&luks->header.key_bytes);
be32_to_cpus(&luks->header.master_key_iterations);
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
be32_to_cpus(&luks->header.key_slots[i].active);
be32_to_cpus(&luks->header.key_slots[i].iterations);
be32_to_cpus(&luks->header.key_slots[i].key_offset);
be32_to_cpus(&luks->header.key_slots[i].stripes);
}
if (memcmp(luks->header.magic, qcrypto_block_luks_magic,
QCRYPTO_BLOCK_LUKS_MAGIC_LEN) != 0) {
error_setg(errp, "Volume is not in LUKS format");
ret = -EINVAL;
goto fail;
}
if (luks->header.version != QCRYPTO_BLOCK_LUKS_VERSION) {
error_setg(errp, "LUKS version %" PRIu32 " is not supported",
luks->header.version);
ret = -ENOTSUP;
goto fail;
}
/*
* The cipher_mode header contains a string that we have
* to further parse, of the format
*
* <cipher-mode>-<iv-generator>[:<iv-hash>]
*
* eg cbc-essiv:sha256, cbc-plain64
*/
ivgen_name = strchr(luks->header.cipher_mode, '-');
if (!ivgen_name) {
ret = -EINVAL;
error_setg(errp, "Unexpected cipher mode string format %s",
luks->header.cipher_mode);
goto fail;
}
*ivgen_name = '\0';
ivgen_name++;
ivhash_name = strchr(ivgen_name, ':');
if (!ivhash_name) {
ivhash = 0;
} else {
*ivhash_name = '\0';
ivhash_name++;
ivhash = qcrypto_block_luks_hash_name_lookup(ivhash_name,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
}
ciphermode = qcrypto_block_luks_cipher_mode_lookup(luks->header.cipher_mode,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
cipheralg = qcrypto_block_luks_cipher_name_lookup(luks->header.cipher_name,
ciphermode,
luks->header.key_bytes,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
hash = qcrypto_block_luks_hash_name_lookup(luks->header.hash_spec,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
ivalg = qcrypto_block_luks_ivgen_name_lookup(ivgen_name,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
if (ivalg == QCRYPTO_IVGEN_ALG_ESSIV) {
if (!ivhash_name) {
ret = -EINVAL;
error_setg(errp, "Missing IV generator hash specification");
goto fail;
}
ivcipheralg = qcrypto_block_luks_essiv_cipher(cipheralg,
ivhash,
&local_err);
if (local_err) {
ret = -ENOTSUP;
error_propagate(errp, local_err);
goto fail;
}
} else {
/* Note we parsed the ivhash_name earlier in the cipher_mode
* spec string even with plain/plain64 ivgens, but we
* will ignore it, since it is irrelevant for these ivgens.
* This is for compat with dm-crypt which will silently
* ignore hash names with these ivgens rather than report
* an error about the invalid usage
*/
ivcipheralg = cipheralg;
}
if (!(flags & QCRYPTO_BLOCK_OPEN_NO_IO)) {
/* Try to find which key slot our password is valid for
* and unlock the master key from that slot.
*/
if (qcrypto_block_luks_find_key(block,
password,
cipheralg, ciphermode,
hash,
ivalg,
ivcipheralg,
ivhash,
&masterkey, &masterkeylen,
readfunc, opaque,
errp) < 0) {
ret = -EACCES;
goto fail;
}
/* We have a valid master key now, so can setup the
* block device payload decryption objects
*/
block->kdfhash = hash;
block->niv = qcrypto_cipher_get_iv_len(cipheralg,
ciphermode);
block->ivgen = qcrypto_ivgen_new(ivalg,
ivcipheralg,
ivhash,
masterkey, masterkeylen,
errp);
if (!block->ivgen) {
ret = -ENOTSUP;
goto fail;
}
block->cipher = qcrypto_cipher_new(cipheralg,
ciphermode,
masterkey, masterkeylen,
errp);
if (!block->cipher) {
ret = -ENOTSUP;
goto fail;
}
}
block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
block->payload_offset = luks->header.payload_offset *
block->sector_size;
luks->cipher_alg = cipheralg;
luks->cipher_mode = ciphermode;
luks->ivgen_alg = ivalg;
luks->ivgen_hash_alg = ivhash;
luks->hash_alg = hash;
g_free(masterkey);
g_free(password);
return 0;
fail:
g_free(masterkey);
qcrypto_cipher_free(block->cipher);
qcrypto_ivgen_free(block->ivgen);
g_free(luks);
g_free(password);
return ret;
}
static void
qcrypto_block_luks_uuid_gen(uint8_t *uuidstr)
{
QemuUUID uuid;
qemu_uuid_generate(&uuid);
qemu_uuid_unparse(&uuid, (char *)uuidstr);
}
static int
qcrypto_block_luks_create(QCryptoBlock *block,
QCryptoBlockCreateOptions *options,
const char *optprefix,
QCryptoBlockInitFunc initfunc,
QCryptoBlockWriteFunc writefunc,
void *opaque,
Error **errp)
{
QCryptoBlockLUKS *luks;
QCryptoBlockCreateOptionsLUKS luks_opts;
Error *local_err = NULL;
uint8_t *masterkey = NULL;
uint8_t *slotkey = NULL;
uint8_t *splitkey = NULL;
size_t splitkeylen = 0;
size_t i;
QCryptoCipher *cipher = NULL;
QCryptoIVGen *ivgen = NULL;
char *password;
const char *cipher_alg;
const char *cipher_mode;
const char *ivgen_alg;
const char *ivgen_hash_alg = NULL;
const char *hash_alg;
char *cipher_mode_spec = NULL;
QCryptoCipherAlgorithm ivcipheralg = 0;
uint64_t iters;
memcpy(&luks_opts, &options->u.luks, sizeof(luks_opts));
if (!luks_opts.has_iter_time) {
luks_opts.iter_time = 2000;
}
if (!luks_opts.has_cipher_alg) {
luks_opts.cipher_alg = QCRYPTO_CIPHER_ALG_AES_256;
}
if (!luks_opts.has_cipher_mode) {
luks_opts.cipher_mode = QCRYPTO_CIPHER_MODE_XTS;
}
if (!luks_opts.has_ivgen_alg) {
luks_opts.ivgen_alg = QCRYPTO_IVGEN_ALG_PLAIN64;
}
if (!luks_opts.has_hash_alg) {
luks_opts.hash_alg = QCRYPTO_HASH_ALG_SHA256;
}
if (luks_opts.ivgen_alg == QCRYPTO_IVGEN_ALG_ESSIV) {
if (!luks_opts.has_ivgen_hash_alg) {
luks_opts.ivgen_hash_alg = QCRYPTO_HASH_ALG_SHA256;
luks_opts.has_ivgen_hash_alg = true;
}
}
/* Note we're allowing ivgen_hash_alg to be set even for
* non-essiv iv generators that don't need a hash. It will
* be silently ignored, for compatibility with dm-crypt */
if (!options->u.luks.key_secret) {
error_setg(errp, "Parameter '%skey-secret' is required for cipher",
optprefix ? optprefix : "");
return -1;
}
password = qcrypto_secret_lookup_as_utf8(luks_opts.key_secret, errp);
if (!password) {
return -1;
}
luks = g_new0(QCryptoBlockLUKS, 1);
block->opaque = luks;
memcpy(luks->header.magic, qcrypto_block_luks_magic,
QCRYPTO_BLOCK_LUKS_MAGIC_LEN);
/* We populate the header in native endianness initially and
* then convert everything to big endian just before writing
* it out to disk
*/
luks->header.version = QCRYPTO_BLOCK_LUKS_VERSION;
qcrypto_block_luks_uuid_gen(luks->header.uuid);
cipher_alg = qcrypto_block_luks_cipher_alg_lookup(luks_opts.cipher_alg,
errp);
if (!cipher_alg) {
goto error;
}
cipher_mode = QCryptoCipherMode_str(luks_opts.cipher_mode);
ivgen_alg = QCryptoIVGenAlgorithm_str(luks_opts.ivgen_alg);
if (luks_opts.has_ivgen_hash_alg) {
ivgen_hash_alg = QCryptoHashAlgorithm_str(luks_opts.ivgen_hash_alg);
cipher_mode_spec = g_strdup_printf("%s-%s:%s", cipher_mode, ivgen_alg,
ivgen_hash_alg);
} else {
cipher_mode_spec = g_strdup_printf("%s-%s", cipher_mode, ivgen_alg);
}
hash_alg = QCryptoHashAlgorithm_str(luks_opts.hash_alg);
if (strlen(cipher_alg) >= QCRYPTO_BLOCK_LUKS_CIPHER_NAME_LEN) {
error_setg(errp, "Cipher name '%s' is too long for LUKS header",
cipher_alg);
goto error;
}
if (strlen(cipher_mode_spec) >= QCRYPTO_BLOCK_LUKS_CIPHER_MODE_LEN) {
error_setg(errp, "Cipher mode '%s' is too long for LUKS header",
cipher_mode_spec);
goto error;
}
if (strlen(hash_alg) >= QCRYPTO_BLOCK_LUKS_HASH_SPEC_LEN) {
error_setg(errp, "Hash name '%s' is too long for LUKS header",
hash_alg);
goto error;
}
if (luks_opts.ivgen_alg == QCRYPTO_IVGEN_ALG_ESSIV) {
ivcipheralg = qcrypto_block_luks_essiv_cipher(luks_opts.cipher_alg,
luks_opts.ivgen_hash_alg,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
goto error;
}
} else {
ivcipheralg = luks_opts.cipher_alg;
}
strcpy(luks->header.cipher_name, cipher_alg);
strcpy(luks->header.cipher_mode, cipher_mode_spec);
strcpy(luks->header.hash_spec, hash_alg);
luks->header.key_bytes = qcrypto_cipher_get_key_len(luks_opts.cipher_alg);
if (luks_opts.cipher_mode == QCRYPTO_CIPHER_MODE_XTS) {
luks->header.key_bytes *= 2;
}
/* Generate the salt used for hashing the master key
* with PBKDF later
*/
if (qcrypto_random_bytes(luks->header.master_key_salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
errp) < 0) {
goto error;
}
/* Generate random master key */
masterkey = g_new0(uint8_t, luks->header.key_bytes);
if (qcrypto_random_bytes(masterkey,
luks->header.key_bytes, errp) < 0) {
goto error;
}
/* Setup the block device payload encryption objects */
block->cipher = qcrypto_cipher_new(luks_opts.cipher_alg,
luks_opts.cipher_mode,
masterkey, luks->header.key_bytes,
errp);
if (!block->cipher) {
goto error;
}
block->kdfhash = luks_opts.hash_alg;
block->niv = qcrypto_cipher_get_iv_len(luks_opts.cipher_alg,
luks_opts.cipher_mode);
block->ivgen = qcrypto_ivgen_new(luks_opts.ivgen_alg,
ivcipheralg,
luks_opts.ivgen_hash_alg,
masterkey, luks->header.key_bytes,
errp);
if (!block->ivgen) {
goto error;
}
/* Determine how many iterations we need to hash the master
* key, in order to have 1 second of compute time used
*/
iters = qcrypto_pbkdf2_count_iters(luks_opts.hash_alg,
masterkey, luks->header.key_bytes,
luks->header.master_key_salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
QCRYPTO_BLOCK_LUKS_DIGEST_LEN,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
goto error;
}
if (iters > (ULLONG_MAX / luks_opts.iter_time)) {
error_setg_errno(errp, ERANGE,
"PBKDF iterations %llu too large to scale",
(unsigned long long)iters);
goto error;
}
/* iter_time was in millis, but count_iters reported for secs */
iters = iters * luks_opts.iter_time / 1000;
/* Why /= 8 ? That matches cryptsetup, but there's no
* explanation why they chose /= 8... Probably so that
* if all 8 keyslots are active we only spend 1 second
* in total time to check all keys */
iters /= 8;
if (iters > UINT32_MAX) {
error_setg_errno(errp, ERANGE,
"PBKDF iterations %llu larger than %u",
(unsigned long long)iters, UINT32_MAX);
goto error;
}
iters = MAX(iters, QCRYPTO_BLOCK_LUKS_MIN_MASTER_KEY_ITERS);
luks->header.master_key_iterations = iters;
/* Hash the master key, saving the result in the LUKS
* header. This hash is used when opening the encrypted
* device to verify that the user password unlocked a
* valid master key
*/
if (qcrypto_pbkdf2(luks_opts.hash_alg,
masterkey, luks->header.key_bytes,
luks->header.master_key_salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
luks->header.master_key_iterations,
luks->header.master_key_digest,
QCRYPTO_BLOCK_LUKS_DIGEST_LEN,
errp) < 0) {
goto error;
}
/* Although LUKS has multiple key slots, we're just going
* to use the first key slot */
splitkeylen = luks->header.key_bytes * QCRYPTO_BLOCK_LUKS_STRIPES;
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
luks->header.key_slots[i].active = i == 0 ?
QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED :
QCRYPTO_BLOCK_LUKS_KEY_SLOT_DISABLED;
luks->header.key_slots[i].stripes = QCRYPTO_BLOCK_LUKS_STRIPES;
/* This calculation doesn't match that shown in the spec,
* but instead follows the cryptsetup implementation.
*/
luks->header.key_slots[i].key_offset =
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE) +
(ROUND_UP(DIV_ROUND_UP(splitkeylen, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE),
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) * i);
}
if (qcrypto_random_bytes(luks->header.key_slots[0].salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
errp) < 0) {
goto error;
}
/* Again we determine how many iterations are required to
* hash the user password while consuming 1 second of compute
* time */
iters = qcrypto_pbkdf2_count_iters(luks_opts.hash_alg,
(uint8_t *)password, strlen(password),
luks->header.key_slots[0].salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
luks->header.key_bytes,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
goto error;
}
if (iters > (ULLONG_MAX / luks_opts.iter_time)) {
error_setg_errno(errp, ERANGE,
"PBKDF iterations %llu too large to scale",
(unsigned long long)iters);
goto error;
}
/* iter_time was in millis, but count_iters reported for secs */
iters = iters * luks_opts.iter_time / 1000;
if (iters > UINT32_MAX) {
error_setg_errno(errp, ERANGE,
"PBKDF iterations %llu larger than %u",
(unsigned long long)iters, UINT32_MAX);
goto error;
}
luks->header.key_slots[0].iterations =
MAX(iters, QCRYPTO_BLOCK_LUKS_MIN_SLOT_KEY_ITERS);
/* Generate a key that we'll use to encrypt the master
* key, from the user's password
*/
slotkey = g_new0(uint8_t, luks->header.key_bytes);
if (qcrypto_pbkdf2(luks_opts.hash_alg,
(uint8_t *)password, strlen(password),
luks->header.key_slots[0].salt,
QCRYPTO_BLOCK_LUKS_SALT_LEN,
luks->header.key_slots[0].iterations,
slotkey, luks->header.key_bytes,
errp) < 0) {
goto error;
}
/* Setup the encryption objects needed to encrypt the
* master key material
*/
cipher = qcrypto_cipher_new(luks_opts.cipher_alg,
luks_opts.cipher_mode,
slotkey, luks->header.key_bytes,
errp);
if (!cipher) {
goto error;
}
ivgen = qcrypto_ivgen_new(luks_opts.ivgen_alg,
ivcipheralg,
luks_opts.ivgen_hash_alg,
slotkey, luks->header.key_bytes,
errp);
if (!ivgen) {
goto error;
}
/* Before storing the master key, we need to vastly
* increase its size, as protection against forensic
* disk data recovery */
splitkey = g_new0(uint8_t, splitkeylen);
if (qcrypto_afsplit_encode(luks_opts.hash_alg,
luks->header.key_bytes,
luks->header.key_slots[0].stripes,
masterkey,
splitkey,
errp) < 0) {
goto error;
}
/* Now we encrypt the split master key with the key generated
* from the user's password, before storing it */
if (qcrypto_block_encrypt_helper(cipher, block->niv, ivgen,
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
0,
splitkey,
splitkeylen,
errp) < 0) {
goto error;
}
/* The total size of the LUKS headers is the partition header + key
* slot headers, rounded up to the nearest sector, combined with
* the size of each master key material region, also rounded up
* to the nearest sector */
luks->header.payload_offset =
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE) +
(ROUND_UP(DIV_ROUND_UP(splitkeylen, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE),
(QCRYPTO_BLOCK_LUKS_KEY_SLOT_OFFSET /
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE)) *
QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS);
block->sector_size = QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
block->payload_offset = luks->header.payload_offset *
block->sector_size;
/* Reserve header space to match payload offset */
initfunc(block, block->payload_offset, opaque, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto error;
}
/* Everything on disk uses Big Endian, so flip header fields
* before writing them */
cpu_to_be16s(&luks->header.version);
cpu_to_be32s(&luks->header.payload_offset);
cpu_to_be32s(&luks->header.key_bytes);
cpu_to_be32s(&luks->header.master_key_iterations);
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
cpu_to_be32s(&luks->header.key_slots[i].active);
cpu_to_be32s(&luks->header.key_slots[i].iterations);
cpu_to_be32s(&luks->header.key_slots[i].key_offset);
cpu_to_be32s(&luks->header.key_slots[i].stripes);
}
/* Write out the partition header and key slot headers */
writefunc(block, 0,
(const uint8_t *)&luks->header,
sizeof(luks->header),
opaque,
&local_err);
/* Delay checking local_err until we've byte-swapped */
/* Byte swap the header back to native, in case we need
* to read it again later */
be16_to_cpus(&luks->header.version);
be32_to_cpus(&luks->header.payload_offset);
be32_to_cpus(&luks->header.key_bytes);
be32_to_cpus(&luks->header.master_key_iterations);
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
be32_to_cpus(&luks->header.key_slots[i].active);
be32_to_cpus(&luks->header.key_slots[i].iterations);
be32_to_cpus(&luks->header.key_slots[i].key_offset);
be32_to_cpus(&luks->header.key_slots[i].stripes);
}
if (local_err) {
error_propagate(errp, local_err);
goto error;
}
/* Write out the master key material, starting at the
* sector immediately following the partition header. */
if (writefunc(block,
luks->header.key_slots[0].key_offset *
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
splitkey, splitkeylen,
opaque,
errp) != splitkeylen) {
goto error;
}
luks->cipher_alg = luks_opts.cipher_alg;
luks->cipher_mode = luks_opts.cipher_mode;
luks->ivgen_alg = luks_opts.ivgen_alg;
luks->ivgen_hash_alg = luks_opts.ivgen_hash_alg;
luks->hash_alg = luks_opts.hash_alg;
memset(masterkey, 0, luks->header.key_bytes);
g_free(masterkey);
memset(slotkey, 0, luks->header.key_bytes);
g_free(slotkey);
g_free(splitkey);
g_free(password);
g_free(cipher_mode_spec);
qcrypto_ivgen_free(ivgen);
qcrypto_cipher_free(cipher);
return 0;
error:
if (masterkey) {
memset(masterkey, 0, luks->header.key_bytes);
}
g_free(masterkey);
if (slotkey) {
memset(slotkey, 0, luks->header.key_bytes);
}
g_free(slotkey);
g_free(splitkey);
g_free(password);
g_free(cipher_mode_spec);
qcrypto_ivgen_free(ivgen);
qcrypto_cipher_free(cipher);
g_free(luks);
return -1;
}
static int qcrypto_block_luks_get_info(QCryptoBlock *block,
QCryptoBlockInfo *info,
Error **errp)
{
QCryptoBlockLUKS *luks = block->opaque;
QCryptoBlockInfoLUKSSlot *slot;
QCryptoBlockInfoLUKSSlotList *slots = NULL, **prev = &info->u.luks.slots;
size_t i;
info->u.luks.cipher_alg = luks->cipher_alg;
info->u.luks.cipher_mode = luks->cipher_mode;
info->u.luks.ivgen_alg = luks->ivgen_alg;
if (info->u.luks.ivgen_alg == QCRYPTO_IVGEN_ALG_ESSIV) {
info->u.luks.has_ivgen_hash_alg = true;
info->u.luks.ivgen_hash_alg = luks->ivgen_hash_alg;
}
info->u.luks.hash_alg = luks->hash_alg;
info->u.luks.payload_offset = block->payload_offset;
info->u.luks.master_key_iters = luks->header.master_key_iterations;
info->u.luks.uuid = g_strndup((const char *)luks->header.uuid,
sizeof(luks->header.uuid));
for (i = 0; i < QCRYPTO_BLOCK_LUKS_NUM_KEY_SLOTS; i++) {
slots = g_new0(QCryptoBlockInfoLUKSSlotList, 1);
*prev = slots;
slots->value = slot = g_new0(QCryptoBlockInfoLUKSSlot, 1);
slot->active = luks->header.key_slots[i].active ==
QCRYPTO_BLOCK_LUKS_KEY_SLOT_ENABLED;
slot->key_offset = luks->header.key_slots[i].key_offset
* QCRYPTO_BLOCK_LUKS_SECTOR_SIZE;
if (slot->active) {
slot->has_iters = true;
slot->iters = luks->header.key_slots[i].iterations;
slot->has_stripes = true;
slot->stripes = luks->header.key_slots[i].stripes;
}
prev = &slots->next;
}
return 0;
}
static void qcrypto_block_luks_cleanup(QCryptoBlock *block)
{
g_free(block->opaque);
}
static int
qcrypto_block_luks_decrypt(QCryptoBlock *block,
uint64_t offset,
uint8_t *buf,
size_t len,
Error **errp)
{
assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
return qcrypto_block_decrypt_helper(block->cipher,
block->niv, block->ivgen,
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
offset, buf, len, errp);
}
static int
qcrypto_block_luks_encrypt(QCryptoBlock *block,
uint64_t offset,
uint8_t *buf,
size_t len,
Error **errp)
{
assert(QEMU_IS_ALIGNED(offset, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
assert(QEMU_IS_ALIGNED(len, QCRYPTO_BLOCK_LUKS_SECTOR_SIZE));
return qcrypto_block_encrypt_helper(block->cipher,
block->niv, block->ivgen,
QCRYPTO_BLOCK_LUKS_SECTOR_SIZE,
offset, buf, len, errp);
}
const QCryptoBlockDriver qcrypto_block_driver_luks = {
.open = qcrypto_block_luks_open,
.create = qcrypto_block_luks_create,
.get_info = qcrypto_block_luks_get_info,
.cleanup = qcrypto_block_luks_cleanup,
.decrypt = qcrypto_block_luks_decrypt,
.encrypt = qcrypto_block_luks_encrypt,
.has_format = qcrypto_block_luks_has_format,
};
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