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dm: add verity target

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This device-mapper target creates a read-only device that transparently
validates the data on one underlying device against a pre-generated tree
of cryptographic checksums stored on a second device.

Two checksum device formats are supported: version 0 which is already
shipping in Chromium OS and version 1 which incorporates some
improvements.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Signed-off-by: Will Drewry <wad@chromium.org>
Signed-off-by: Elly Jones <ellyjones@chromium.org>
Cc: Milan Broz <mbroz@redhat.com>
Cc: Olof Johansson <olofj@chromium.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Mikulas Patocka 2012-03-28 18:43:38 +01:00 committed by Alasdair G Kergon
parent a66cc28f53
commit a4ffc15219
4 changed files with 1128 additions and 0 deletions
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194
Documentation/device-mapper/verity.txt Normal file
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@ -0,0 +1,194 @@
dm-verity
==========
Device-Mapper's "verity" target provides transparent integrity checking of
block devices using a cryptographic digest provided by the kernel crypto API.
This target is read-only.
Construction Parameters
=======================
<version> <dev> <hash_dev> <hash_start>
<data_block_size> <hash_block_size>
<num_data_blocks> <hash_start_block>
<algorithm> <digest> <salt>
<version>
This is the version number of the on-disk format.
0 is the original format used in the Chromium OS.
The salt is appended when hashing, digests are stored continuously and
the rest of the block is padded with zeros.
1 is the current format that should be used for new devices.
The salt is prepended when hashing and each digest is
padded with zeros to the power of two.
<dev>
This is the device containing the data the integrity of which needs to be
checked. It may be specified as a path, like /dev/sdaX, or a device number,
<major>:<minor>.
<hash_dev>
This is the device that that supplies the hash tree data. It may be
specified similarly to the device path and may be the same device. If the
same device is used, the hash_start should be outside of the dm-verity
configured device size.
<data_block_size>
The block size on a data device. Each block corresponds to one digest on
the hash device.
<hash_block_size>
The size of a hash block.
<num_data_blocks>
The number of data blocks on the data device. Additional blocks are
inaccessible. You can place hashes to the same partition as data, in this
case hashes are placed after <num_data_blocks>.
<hash_start_block>
This is the offset, in <hash_block_size>-blocks, from the start of hash_dev
to the root block of the hash tree.
<algorithm>
The cryptographic hash algorithm used for this device. This should
be the name of the algorithm, like "sha1".
<digest>
The hexadecimal encoding of the cryptographic hash of the root hash block
and the salt. This hash should be trusted as there is no other authenticity
beyond this point.
<salt>
The hexadecimal encoding of the salt value.
Theory of operation
===================
dm-verity is meant to be setup as part of a verified boot path. This
may be anything ranging from a boot using tboot or trustedgrub to just
booting from a known-good device (like a USB drive or CD).
When a dm-verity device is configured, it is expected that the caller
has been authenticated in some way (cryptographic signatures, etc).
After instantiation, all hashes will be verified on-demand during
disk access. If they cannot be verified up to the root node of the
tree, the root hash, then the I/O will fail. This should identify
tampering with any data on the device and the hash data.
Cryptographic hashes are used to assert the integrity of the device on a
per-block basis. This allows for a lightweight hash computation on first read
into the page cache. Block hashes are stored linearly-aligned to the nearest
block the size of a page.
Hash Tree
---------
Each node in the tree is a cryptographic hash. If it is a leaf node, the hash
is of some block data on disk. If it is an intermediary node, then the hash is
of a number of child nodes.
Each entry in the tree is a collection of neighboring nodes that fit in one
block. The number is determined based on block_size and the size of the
selected cryptographic digest algorithm. The hashes are linearly-ordered in
this entry and any unaligned trailing space is ignored but included when
calculating the parent node.
The tree looks something like:
alg = sha256, num_blocks = 32768, block_size = 4096
[ root ]
/ . . . \
[entry_0] [entry_1]
/ . . . \ . . . \
[entry_0_0] . . . [entry_0_127] . . . . [entry_1_127]
/ ... \ / . . . \ / \
blk_0 ... blk_127 blk_16256 blk_16383 blk_32640 . . . blk_32767
On-disk format
==============
Below is the recommended on-disk format. The verity kernel code does not
read the on-disk header. It only reads the hash blocks which directly
follow the header. It is expected that a user-space tool will verify the
integrity of the verity_header and then call dmsetup with the correct
parameters. Alternatively, the header can be omitted and the dmsetup
parameters can be passed via the kernel command-line in a rooted chain
of trust where the command-line is verified.
The on-disk format is especially useful in cases where the hash blocks
are on a separate partition. The magic number allows easy identification
of the partition contents. Alternatively, the hash blocks can be stored
in the same partition as the data to be verified. In such a configuration
the filesystem on the partition would be sized a little smaller than
the full-partition, leaving room for the hash blocks.
struct superblock {
uint8_t signature[8]
"verity\0\0";
uint8_t version;
1 - current format
uint8_t data_block_bits;
log2(data block size)
uint8_t hash_block_bits;
log2(hash block size)
uint8_t pad1[1];
zero padding
uint16_t salt_size;
big-endian salt size
uint8_t pad2[2];
zero padding
uint32_t data_blocks_hi;
big-endian high 32 bits of the 64-bit number of data blocks
uint32_t data_blocks_lo;
big-endian low 32 bits of the 64-bit number of data blocks
uint8_t algorithm[16];
cryptographic algorithm
uint8_t salt[384];
salt (the salt size is specified above)
uint8_t pad3[88];
zero padding to 512-byte boundary
}
Directly following the header (and with sector number padded to the next hash
block boundary) are the hash blocks which are stored a depth at a time
(starting from the root), sorted in order of increasing index.
Status
======
V (for Valid) is returned if every check performed so far was valid.
If any check failed, C (for Corruption) is returned.
Example
=======
Setup a device:
dmsetup create vroot --table \
"0 2097152 "\
"verity 1 /dev/sda1 /dev/sda2 4096 4096 2097152 1 "\
"4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 "\
"1234000000000000000000000000000000000000000000000000000000000000"
A command line tool veritysetup is available to compute or verify
the hash tree or activate the kernel driver. This is available from
the LVM2 upstream repository and may be supplied as a package called
device-mapper-verity-tools:
git://sources.redhat.com/git/lvm2
http://sourceware.org/git/?p=lvm2.git
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/verity?cvsroot=lvm2
veritysetup -a vroot /dev/sda1 /dev/sda2 \
4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076

20
drivers/md/Kconfig
View File

@ -370,4 +370,24 @@ config DM_FLAKEY
---help---
A target that intermittently fails I/O for debugging purposes.
config DM_VERITY
tristate "Verity target support (EXPERIMENTAL)"
depends on BLK_DEV_DM && EXPERIMENTAL
select CRYPTO
select CRYPTO_HASH
select DM_BUFIO
---help---
This device-mapper target creates a read-only device that
transparently validates the data on one underlying device against
a pre-generated tree of cryptographic checksums stored on a second
device.
You'll need to activate the digests you're going to use in the
cryptoapi configuration.
To compile this code as a module, choose M here: the module will
be called dm-verity.
If unsure, say N.
endif # MD

1
drivers/md/Makefile
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@ -42,6 +42,7 @@ obj-$(CONFIG_DM_LOG_USERSPACE) += dm-log-userspace.o
obj-$(CONFIG_DM_ZERO) += dm-zero.o
obj-$(CONFIG_DM_RAID) += dm-raid.o
obj-$(CONFIG_DM_THIN_PROVISIONING) += dm-thin-pool.o
obj-$(CONFIG_DM_VERITY) += dm-verity.o
ifeq ($(CONFIG_DM_UEVENT),y)
dm-mod-objs += dm-uevent.o

913
drivers/md/dm-verity.c Normal file
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@ -0,0 +1,913 @@
/*
* Copyright (C) 2012 Red Hat, Inc.
*
* Author: Mikulas Patocka <mpatocka@redhat.com>
*
* Based on Chromium dm-verity driver (C) 2011 The Chromium OS Authors
*
* This file is released under the GPLv2.
*
* In the file "/sys/module/dm_verity/parameters/prefetch_cluster" you can set
* default prefetch value. Data are read in "prefetch_cluster" chunks from the
* hash device. Setting this greatly improves performance when data and hash
* are on the same disk on different partitions on devices with poor random
* access behavior.
*/
#include "dm-bufio.h"
#include <linux/module.h>
#include <linux/device-mapper.h>
#include <crypto/hash.h>
#define DM_MSG_PREFIX "verity"
#define DM_VERITY_IO_VEC_INLINE 16
#define DM_VERITY_MEMPOOL_SIZE 4
#define DM_VERITY_DEFAULT_PREFETCH_SIZE 262144
#define DM_VERITY_MAX_LEVELS 63
static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
struct dm_verity {
struct dm_dev *data_dev;
struct dm_dev *hash_dev;
struct dm_target *ti;
struct dm_bufio_client *bufio;
char *alg_name;
struct crypto_shash *tfm;
u8 *root_digest; /* digest of the root block */
u8 *salt; /* salt: its size is salt_size */
unsigned salt_size;
sector_t data_start; /* data offset in 512-byte sectors */
sector_t hash_start; /* hash start in blocks */
sector_t data_blocks; /* the number of data blocks */
sector_t hash_blocks; /* the number of hash blocks */
unsigned char data_dev_block_bits; /* log2(data blocksize) */
unsigned char hash_dev_block_bits; /* log2(hash blocksize) */
unsigned char hash_per_block_bits; /* log2(hashes in hash block) */
unsigned char levels; /* the number of tree levels */
unsigned char version;
unsigned digest_size; /* digest size for the current hash algorithm */
unsigned shash_descsize;/* the size of temporary space for crypto */
int hash_failed; /* set to 1 if hash of any block failed */
mempool_t *io_mempool; /* mempool of struct dm_verity_io */
mempool_t *vec_mempool; /* mempool of bio vector */
struct workqueue_struct *verify_wq;
/* starting blocks for each tree level. 0 is the lowest level. */
sector_t hash_level_block[DM_VERITY_MAX_LEVELS];
};
struct dm_verity_io {
struct dm_verity *v;
struct bio *bio;
/* original values of bio->bi_end_io and bio->bi_private */
bio_end_io_t *orig_bi_end_io;
void *orig_bi_private;
sector_t block;
unsigned n_blocks;
/* saved bio vector */
struct bio_vec *io_vec;
unsigned io_vec_size;
struct work_struct work;
/* A space for short vectors; longer vectors are allocated separately. */
struct bio_vec io_vec_inline[DM_VERITY_IO_VEC_INLINE];
/*
* Three variably-size fields follow this struct:
*
* u8 hash_desc[v->shash_descsize];
* u8 real_digest[v->digest_size];
* u8 want_digest[v->digest_size];
*
* To access them use: io_hash_desc(), io_real_digest() and io_want_digest().
*/
};
static struct shash_desc *io_hash_desc(struct dm_verity *v, struct dm_verity_io *io)
{
return (struct shash_desc *)(io + 1);
}
static u8 *io_real_digest(struct dm_verity *v, struct dm_verity_io *io)
{
return (u8 *)(io + 1) + v->shash_descsize;
}
static u8 *io_want_digest(struct dm_verity *v, struct dm_verity_io *io)
{
return (u8 *)(io + 1) + v->shash_descsize + v->digest_size;
}
/*
* Auxiliary structure appended to each dm-bufio buffer. If the value
* hash_verified is nonzero, hash of the block has been verified.
*
* The variable hash_verified is set to 0 when allocating the buffer, then
* it can be changed to 1 and it is never reset to 0 again.
*
* There is no lock around this value, a race condition can at worst cause
* that multiple processes verify the hash of the same buffer simultaneously
* and write 1 to hash_verified simultaneously.
* This condition is harmless, so we don't need locking.
*/
struct buffer_aux {
int hash_verified;
};
/*
* Initialize struct buffer_aux for a freshly created buffer.
*/
static void dm_bufio_alloc_callback(struct dm_buffer *buf)
{
struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
aux->hash_verified = 0;
}
/*
* Translate input sector number to the sector number on the target device.
*/
static sector_t verity_map_sector(struct dm_verity *v, sector_t bi_sector)
{
return v->data_start + dm_target_offset(v->ti, bi_sector);
}
/*
* Return hash position of a specified block at a specified tree level
* (0 is the lowest level).
* The lowest "hash_per_block_bits"-bits of the result denote hash position
* inside a hash block. The remaining bits denote location of the hash block.
*/
static sector_t verity_position_at_level(struct dm_verity *v, sector_t block,
int level)
{
return block >> (level * v->hash_per_block_bits);
}
static void verity_hash_at_level(struct dm_verity *v, sector_t block, int level,
sector_t *hash_block, unsigned *offset)
{
sector_t position = verity_position_at_level(v, block, level);
unsigned idx;
*hash_block = v->hash_level_block[level] + (position >> v->hash_per_block_bits);
if (!offset)
return;
idx = position & ((1 << v->hash_per_block_bits) - 1);
if (!v->version)
*offset = idx * v->digest_size;
else
*offset = idx << (v->hash_dev_block_bits - v->hash_per_block_bits);
}
/*
* Verify hash of a metadata block pertaining to the specified data block
* ("block" argument) at a specified level ("level" argument).
*
* On successful return, io_want_digest(v, io) contains the hash value for
* a lower tree level or for the data block (if we're at the lowest leve).
*
* If "skip_unverified" is true, unverified buffer is skipped and 1 is returned.
* If "skip_unverified" is false, unverified buffer is hashed and verified
* against current value of io_want_digest(v, io).
*/
static int verity_verify_level(struct dm_verity_io *io, sector_t block,
int level, bool skip_unverified)
{
struct dm_verity *v = io->v;
struct dm_buffer *buf;
struct buffer_aux *aux;
u8 *data;
int r;
sector_t hash_block;
unsigned offset;
verity_hash_at_level(v, block, level, &hash_block, &offset);
data = dm_bufio_read(v->bufio, hash_block, &buf);
if (unlikely(IS_ERR(data)))
return PTR_ERR(data);
aux = dm_bufio_get_aux_data(buf);
if (!aux->hash_verified) {
struct shash_desc *desc;
u8 *result;
if (skip_unverified) {
r = 1;
goto release_ret_r;
}
desc = io_hash_desc(v, io);
desc->tfm = v->tfm;
desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
r = crypto_shash_init(desc);
if (r < 0) {
DMERR("crypto_shash_init failed: %d", r);
goto release_ret_r;
}
if (likely(v->version >= 1)) {
r = crypto_shash_update(desc, v->salt, v->salt_size);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
goto release_ret_r;
}
}
r = crypto_shash_update(desc, data, 1 << v->hash_dev_block_bits);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
goto release_ret_r;
}
if (!v->version) {
r = crypto_shash_update(desc, v->salt, v->salt_size);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
goto release_ret_r;
}
}
result = io_real_digest(v, io);
r = crypto_shash_final(desc, result);
if (r < 0) {
DMERR("crypto_shash_final failed: %d", r);
goto release_ret_r;
}
if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
DMERR_LIMIT("metadata block %llu is corrupted",
(unsigned long long)hash_block);
v->hash_failed = 1;
r = -EIO;
goto release_ret_r;
} else
aux->hash_verified = 1;
}
data += offset;
memcpy(io_want_digest(v, io), data, v->digest_size);
dm_bufio_release(buf);
return 0;
release_ret_r:
dm_bufio_release(buf);
return r;
}
/*
* Verify one "dm_verity_io" structure.
*/
static int verity_verify_io(struct dm_verity_io *io)
{
struct dm_verity *v = io->v;
unsigned b;
int i;
unsigned vector = 0, offset = 0;
for (b = 0; b < io->n_blocks; b++) {
struct shash_desc *desc;
u8 *result;
int r;
unsigned todo;
if (likely(v->levels)) {
/*
* First, we try to get the requested hash for
* the current block. If the hash block itself is
* verified, zero is returned. If it isn't, this
* function returns 0 and we fall back to whole
* chain verification.
*/
int r = verity_verify_level(io, io->block + b, 0, true);
if (likely(!r))
goto test_block_hash;
if (r < 0)
return r;
}
memcpy(io_want_digest(v, io), v->root_digest, v->digest_size);
for (i = v->levels - 1; i >= 0; i--) {
int r = verity_verify_level(io, io->block + b, i, false);
if (unlikely(r))
return r;
}
test_block_hash:
desc = io_hash_desc(v, io);
desc->tfm = v->tfm;
desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
r = crypto_shash_init(desc);
if (r < 0) {
DMERR("crypto_shash_init failed: %d", r);
return r;
}
if (likely(v->version >= 1)) {
r = crypto_shash_update(desc, v->salt, v->salt_size);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
return r;
}
}
todo = 1 << v->data_dev_block_bits;
do {
struct bio_vec *bv;
u8 *page;
unsigned len;
BUG_ON(vector >= io->io_vec_size);
bv = &io->io_vec[vector];
page = kmap_atomic(bv->bv_page);
len = bv->bv_len - offset;
if (likely(len >= todo))
len = todo;
r = crypto_shash_update(desc,
page + bv->bv_offset + offset, len);
kunmap_atomic(page);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
return r;
}
offset += len;
if (likely(offset == bv->bv_len)) {
offset = 0;
vector++;
}
todo -= len;
} while (todo);
if (!v->version) {
r = crypto_shash_update(desc, v->salt, v->salt_size);
if (r < 0) {
DMERR("crypto_shash_update failed: %d", r);
return r;
}
}
result = io_real_digest(v, io);
r = crypto_shash_final(desc, result);
if (r < 0) {
DMERR("crypto_shash_final failed: %d", r);
return r;
}
if (unlikely(memcmp(result, io_want_digest(v, io), v->digest_size))) {
DMERR_LIMIT("data block %llu is corrupted",
(unsigned long long)(io->block + b));
v->hash_failed = 1;
return -EIO;
}
}
BUG_ON(vector != io->io_vec_size);
BUG_ON(offset);
return 0;
}
/*
* End one "io" structure with a given error.
*/
static void verity_finish_io(struct dm_verity_io *io, int error)
{
struct bio *bio = io->bio;
struct dm_verity *v = io->v;
bio->bi_end_io = io->orig_bi_end_io;
bio->bi_private = io->orig_bi_private;
if (io->io_vec != io->io_vec_inline)
mempool_free(io->io_vec, v->vec_mempool);
mempool_free(io, v->io_mempool);
bio_endio(bio, error);
}
static void verity_work(struct work_struct *w)
{
struct dm_verity_io *io = container_of(w, struct dm_verity_io, work);
verity_finish_io(io, verity_verify_io(io));
}
static void verity_end_io(struct bio *bio, int error)
{
struct dm_verity_io *io = bio->bi_private;
if (error) {
verity_finish_io(io, error);
return;
}
INIT_WORK(&io->work, verity_work);
queue_work(io->v->verify_wq, &io->work);
}
/*
* Prefetch buffers for the specified io.
* The root buffer is not prefetched, it is assumed that it will be cached
* all the time.
*/
static void verity_prefetch_io(struct dm_verity *v, struct dm_verity_io *io)
{
int i;
for (i = v->levels - 2; i >= 0; i--) {
sector_t hash_block_start;
sector_t hash_block_end;
verity_hash_at_level(v, io->block, i, &hash_block_start, NULL);
verity_hash_at_level(v, io->block + io->n_blocks - 1, i, &hash_block_end, NULL);
if (!i) {
unsigned cluster = *(volatile unsigned *)&dm_verity_prefetch_cluster;
cluster >>= v->data_dev_block_bits;
if (unlikely(!cluster))
goto no_prefetch_cluster;
if (unlikely(cluster & (cluster - 1)))
cluster = 1 << (fls(cluster) - 1);
hash_block_start &= ~(sector_t)(cluster - 1);
hash_block_end |= cluster - 1;
if (unlikely(hash_block_end >= v->hash_blocks))
hash_block_end = v->hash_blocks - 1;
}
no_prefetch_cluster:
dm_bufio_prefetch(v->bufio, hash_block_start,
hash_block_end - hash_block_start + 1);
}
}
/*
* Bio map function. It allocates dm_verity_io structure and bio vector and
* fills them. Then it issues prefetches and the I/O.
*/
static int verity_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct dm_verity *v = ti->private;
struct dm_verity_io *io;
bio->bi_bdev = v->data_dev->bdev;
bio->bi_sector = verity_map_sector(v, bio->bi_sector);
if (((unsigned)bio->bi_sector | bio_sectors(bio)) &
((1 << (v->data_dev_block_bits - SECTOR_SHIFT)) - 1)) {
DMERR_LIMIT("unaligned io");
return -EIO;
}
if ((bio->bi_sector + bio_sectors(bio)) >>
(v->data_dev_block_bits - SECTOR_SHIFT) > v->data_blocks) {
DMERR_LIMIT("io out of range");
return -EIO;
}
if (bio_data_dir(bio) == WRITE)
return -EIO;
io = mempool_alloc(v->io_mempool, GFP_NOIO);
io->v = v;
io->bio = bio;
io->orig_bi_end_io = bio->bi_end_io;
io->orig_bi_private = bio->bi_private;
io->block = bio->bi_sector >> (v->data_dev_block_bits - SECTOR_SHIFT);
io->n_blocks = bio->bi_size >> v->data_dev_block_bits;
bio->bi_end_io = verity_end_io;
bio->bi_private = io;
io->io_vec_size = bio->bi_vcnt - bio->bi_idx;
if (io->io_vec_size < DM_VERITY_IO_VEC_INLINE)
io->io_vec = io->io_vec_inline;
else
io->io_vec = mempool_alloc(v->vec_mempool, GFP_NOIO);
memcpy(io->io_vec, bio_iovec(bio),
io->io_vec_size * sizeof(struct bio_vec));
verity_prefetch_io(v, io);
generic_make_request(bio);
return DM_MAPIO_SUBMITTED;
}
/*
* Status: V (valid) or C (corruption found)
*/
static int verity_status(struct dm_target *ti, status_type_t type,
char *result, unsigned maxlen)
{
struct dm_verity *v = ti->private;
unsigned sz = 0;
unsigned x;
switch (type) {
case STATUSTYPE_INFO:
DMEMIT("%c", v->hash_failed ? 'C' : 'V');
break;
case STATUSTYPE_TABLE:
DMEMIT("%u %s %s %u %u %llu %llu %s ",
v->version,
v->data_dev->name,
v->hash_dev->name,
1 << v->data_dev_block_bits,
1 << v->hash_dev_block_bits,
(unsigned long long)v->data_blocks,
(unsigned long long)v->hash_start,
v->alg_name
);
for (x = 0; x < v->digest_size; x++)
DMEMIT("%02x", v->root_digest[x]);
DMEMIT(" ");
if (!v->salt_size)
DMEMIT("-");
else
for (x = 0; x < v->salt_size; x++)
DMEMIT("%02x", v->salt[x]);
break;
}
return 0;
}
static int verity_ioctl(struct dm_target *ti, unsigned cmd,
unsigned long arg)
{
struct dm_verity *v = ti->private;
int r = 0;
if (v->data_start ||
ti->len != i_size_read(v->data_dev->bdev->bd_inode) >> SECTOR_SHIFT)
r = scsi_verify_blk_ioctl(NULL, cmd);
return r ? : __blkdev_driver_ioctl(v->data_dev->bdev, v->data_dev->mode,
cmd, arg);
}
static int verity_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
struct bio_vec *biovec, int max_size)
{
struct dm_verity *v = ti->private;
struct request_queue *q = bdev_get_queue(v->data_dev->bdev);
if (!q->merge_bvec_fn)
return max_size;
bvm->bi_bdev = v->data_dev->bdev;
bvm->bi_sector = verity_map_sector(v, bvm->bi_sector);
return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
}
static int verity_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn, void *data)
{
struct dm_verity *v = ti->private;
return fn(ti, v->data_dev, v->data_start, ti->len, data);
}
static void verity_io_hints(struct dm_target *ti, struct queue_limits *limits)
{
struct dm_verity *v = ti->private;
if (limits->logical_block_size < 1 << v->data_dev_block_bits)
limits->logical_block_size = 1 << v->data_dev_block_bits;
if (limits->physical_block_size < 1 << v->data_dev_block_bits)
limits->physical_block_size = 1 << v->data_dev_block_bits;
blk_limits_io_min(limits, limits->logical_block_size);
}
static void verity_dtr(struct dm_target *ti)
{
struct dm_verity *v = ti->private;
if (v->verify_wq)
destroy_workqueue(v->verify_wq);
if (v->vec_mempool)
mempool_destroy(v->vec_mempool);
if (v->io_mempool)
mempool_destroy(v->io_mempool);
if (v->bufio)
dm_bufio_client_destroy(v->bufio);
kfree(v->salt);
kfree(v->root_digest);
if (v->tfm)
crypto_free_shash(v->tfm);
kfree(v->alg_name);
if (v->hash_dev)
dm_put_device(ti, v->hash_dev);
if (v->data_dev)
dm_put_device(ti, v->data_dev);
kfree(v);
}
/*
* Target parameters:
* <version> The current format is version 1.
* Vsn 0 is compatible with original Chromium OS releases.
* <data device>
* <hash device>
* <data block size>
* <hash block size>
* <the number of data blocks>
* <hash start block>
* <algorithm>
* <digest>
* <salt> Hex string or "-" if no salt.
*/
static int verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
{
struct dm_verity *v;
unsigned num;
unsigned long long num_ll;
int r;
int i;
sector_t hash_position;
char dummy;
v = kzalloc(sizeof(struct dm_verity), GFP_KERNEL);
if (!v) {
ti->error = "Cannot allocate verity structure";
return -ENOMEM;
}
ti->private = v;
v->ti = ti;
if ((dm_table_get_mode(ti->table) & ~FMODE_READ)) {
ti->error = "Device must be readonly";
r = -EINVAL;
goto bad;
}
if (argc != 10) {
ti->error = "Invalid argument count: exactly 10 arguments required";
r = -EINVAL;
goto bad;
}
if (sscanf(argv[0], "%d%c", &num, &dummy) != 1 ||
num < 0 || num > 1) {
ti->error = "Invalid version";
r = -EINVAL;
goto bad;
}
v->version = num;
r = dm_get_device(ti, argv[1], FMODE_READ, &v->data_dev);
if (r) {
ti->error = "Data device lookup failed";
goto bad;
}
r = dm_get_device(ti, argv[2], FMODE_READ, &v->hash_dev);
if (r) {
ti->error = "Data device lookup failed";
goto bad;
}
if (sscanf(argv[3], "%u%c", &num, &dummy) != 1 ||
!num || (num & (num - 1)) ||
num < bdev_logical_block_size(v->data_dev->bdev) ||
num > PAGE_SIZE) {
ti->error = "Invalid data device block size";
r = -EINVAL;
goto bad;
}
v->data_dev_block_bits = ffs(num) - 1;
if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
!num || (num & (num - 1)) ||
num < bdev_logical_block_size(v->hash_dev->bdev) ||
num > INT_MAX) {
ti->error = "Invalid hash device block size";
r = -EINVAL;
goto bad;
}
v->hash_dev_block_bits = ffs(num) - 1;
if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
num_ll << (v->data_dev_block_bits - SECTOR_SHIFT) !=
(sector_t)num_ll << (v->data_dev_block_bits - SECTOR_SHIFT)) {
ti->error = "Invalid data blocks";
r = -EINVAL;
goto bad;
}
v->data_blocks = num_ll;
if (ti->len > (v->data_blocks << (v->data_dev_block_bits - SECTOR_SHIFT))) {
ti->error = "Data device is too small";
r = -EINVAL;
goto bad;
}
if (sscanf(argv[6], "%llu%c", &num_ll, &dummy) != 1 ||
num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT) !=
(sector_t)num_ll << (v->hash_dev_block_bits - SECTOR_SHIFT)) {
ti->error = "Invalid hash start";
r = -EINVAL;
goto bad;
}
v->hash_start = num_ll;
v->alg_name = kstrdup(argv[7], GFP_KERNEL);
if (!v->alg_name) {
ti->error = "Cannot allocate algorithm name";
r = -ENOMEM;
goto bad;
}
v->tfm = crypto_alloc_shash(v->alg_name, 0, 0);
if (IS_ERR(v->tfm)) {
ti->error = "Cannot initialize hash function";
r = PTR_ERR(v->tfm);
v->tfm = NULL;
goto bad;
}
v->digest_size = crypto_shash_digestsize(v->tfm);
if ((1 << v->hash_dev_block_bits) < v->digest_size * 2) {
ti->error = "Digest size too big";
r = -EINVAL;
goto bad;
}
v->shash_descsize =
sizeof(struct shash_desc) + crypto_shash_descsize(v->tfm);
v->root_digest = kmalloc(v->digest_size, GFP_KERNEL);
if (!v->root_digest) {
ti->error = "Cannot allocate root digest";
r = -ENOMEM;
goto bad;
}
if (strlen(argv[8]) != v->digest_size * 2 ||
hex2bin(v->root_digest, argv[8], v->digest_size)) {
ti->error = "Invalid root digest";
r = -EINVAL;
goto bad;
}
if (strcmp(argv[9], "-")) {
v->salt_size = strlen(argv[9]) / 2;
v->salt = kmalloc(v->salt_size, GFP_KERNEL);
if (!v->salt) {
ti->error = "Cannot allocate salt";
r = -ENOMEM;
goto bad;
}
if (strlen(argv[9]) != v->salt_size * 2 ||
hex2bin(v->salt, argv[9], v->salt_size)) {
ti->error = "Invalid salt";
r = -EINVAL;
goto bad;
}
}
v->hash_per_block_bits =
fls((1 << v->hash_dev_block_bits) / v->digest_size) - 1;
v->levels = 0;
if (v->data_blocks)
while (v->hash_per_block_bits * v->levels < 64 &&
(unsigned long long)(v->data_blocks - 1) >>
(v->hash_per_block_bits * v->levels))
v->levels++;
if (v->levels > DM_VERITY_MAX_LEVELS) {
ti->error = "Too many tree levels";
r = -E2BIG;
goto bad;
}
hash_position = v->hash_start;
for (i = v->levels - 1; i >= 0; i--) {
sector_t s;
v->hash_level_block[i] = hash_position;
s = verity_position_at_level(v, v->data_blocks, i);
s = (s >> v->hash_per_block_bits) +
!!(s & ((1 << v->hash_per_block_bits) - 1));
if (hash_position + s < hash_position) {
ti->error = "Hash device offset overflow";
r = -E2BIG;
goto bad;
}
hash_position += s;
}
v->hash_blocks = hash_position;
v->bufio = dm_bufio_client_create(v->hash_dev->bdev,
1 << v->hash_dev_block_bits, 1, sizeof(struct buffer_aux),
dm_bufio_alloc_callback, NULL);
if (IS_ERR(v->bufio)) {
ti->error = "Cannot initialize dm-bufio";
r = PTR_ERR(v->bufio);
v->bufio = NULL;
goto bad;
}
if (dm_bufio_get_device_size(v->bufio) < v->hash_blocks) {
ti->error = "Hash device is too small";
r = -E2BIG;
goto bad;
}
v->io_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
sizeof(struct dm_verity_io) + v->shash_descsize + v->digest_size * 2);
if (!v->io_mempool) {
ti->error = "Cannot allocate io mempool";
r = -ENOMEM;
goto bad;
}
v->vec_mempool = mempool_create_kmalloc_pool(DM_VERITY_MEMPOOL_SIZE,
BIO_MAX_PAGES * sizeof(struct bio_vec));
if (!v->vec_mempool) {
ti->error = "Cannot allocate vector mempool";
r = -ENOMEM;
goto bad;
}
/* WQ_UNBOUND greatly improves performance when running on ramdisk */
v->verify_wq = alloc_workqueue("kverityd", WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM | WQ_UNBOUND, num_online_cpus());
if (!v->verify_wq) {
ti->error = "Cannot allocate workqueue";
r = -ENOMEM;
goto bad;
}
return 0;
bad:
verity_dtr(ti);
return r;
}
static struct target_type verity_target = {
.name = "verity",
.version = {1, 0, 0},
.module = THIS_MODULE,
.ctr = verity_ctr,
.dtr = verity_dtr,
.map = verity_map,
.status = verity_status,
.ioctl = verity_ioctl,
.merge = verity_merge,
.iterate_devices = verity_iterate_devices,
.io_hints = verity_io_hints,
};
static int __init dm_verity_init(void)
{
int r;
r = dm_register_target(&verity_target);
if (r < 0)
DMERR("register failed %d", r);
return r;
}
static void __exit dm_verity_exit(void)
{
dm_unregister_target(&verity_target);
}
module_init(dm_verity_init);
module_exit(dm_verity_exit);
MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
MODULE_AUTHOR("Mandeep Baines <msb@chromium.org>");
MODULE_AUTHOR("Will Drewry <wad@chromium.org>");
MODULE_DESCRIPTION(DM_NAME " target for transparent disk integrity checking");
MODULE_LICENSE("GPL");