blob: e8e9b72d30c5d437fef604e0925a029aba6a4e88 [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2017 Google, Inc.
*/
#include <linux/blk-crypto.h>
#include <linux/device-mapper.h>
#include <linux/module.h>
#define DM_MSG_PREFIX "default-key"
#define DM_DEFAULT_KEY_MAX_WRAPPED_KEY_SIZE 128
static const struct dm_default_key_cipher {
const char *name;
enum blk_crypto_mode_num mode_num;
int key_size;
} dm_default_key_ciphers[] = {
{
.name = "aes-xts-plain64",
.mode_num = BLK_ENCRYPTION_MODE_AES_256_XTS,
.key_size = 64,
}, {
.name = "xchacha12,aes-adiantum-plain64",
.mode_num = BLK_ENCRYPTION_MODE_ADIANTUM,
.key_size = 32,
},
};
/**
* struct dm_default_c - private data of a default-key target
* @dev: the underlying device
* @start: starting sector of the range of @dev which this target actually maps.
* For this purpose a "sector" is 512 bytes.
* @cipher_string: the name of the encryption algorithm being used
* @iv_offset: starting offset for IVs. IVs are generated as if the target were
* preceded by @iv_offset 512-byte sectors.
* @sector_size: crypto sector size in bytes (usually 4096)
* @sector_bits: log2(sector_size)
* @key: the encryption key to use
* @max_dun: the maximum DUN that may be used (computed from other params)
*/
struct default_key_c {
struct dm_dev *dev;
sector_t start;
const char *cipher_string;
u64 iv_offset;
unsigned int sector_size;
unsigned int sector_bits;
struct blk_crypto_key key;
bool is_hw_wrapped;
u64 max_dun;
};
static const struct dm_default_key_cipher *
lookup_cipher(const char *cipher_string)
{
int i;
for (i = 0; i < ARRAY_SIZE(dm_default_key_ciphers); i++) {
if (strcmp(cipher_string, dm_default_key_ciphers[i].name) == 0)
return &dm_default_key_ciphers[i];
}
return NULL;
}
static void default_key_dtr(struct dm_target *ti)
{
struct default_key_c *dkc = ti->private;
int err;
if (dkc->dev) {
err = blk_crypto_evict_key(bdev_get_queue(dkc->dev->bdev),
&dkc->key);
if (err && err != -ENOKEY)
DMWARN("Failed to evict crypto key: %d", err);
dm_put_device(ti, dkc->dev);
}
kfree_sensitive(dkc->cipher_string);
kfree_sensitive(dkc);
}
static int default_key_ctr_optional(struct dm_target *ti,
unsigned int argc, char **argv)
{
struct default_key_c *dkc = ti->private;
struct dm_arg_set as;
static const struct dm_arg _args[] = {
{0, 4, "Invalid number of feature args"},
};
unsigned int opt_params;
const char *opt_string;
bool iv_large_sectors = false;
char dummy;
int err;
as.argc = argc;
as.argv = argv;
err = dm_read_arg_group(_args, &as, &opt_params, &ti->error);
if (err)
return err;
while (opt_params--) {
opt_string = dm_shift_arg(&as);
if (!opt_string) {
ti->error = "Not enough feature arguments";
return -EINVAL;
}
if (!strcmp(opt_string, "allow_discards")) {
ti->num_discard_bios = 1;
} else if (sscanf(opt_string, "sector_size:%u%c",
&dkc->sector_size, &dummy) == 1) {
if (dkc->sector_size < SECTOR_SIZE ||
dkc->sector_size > 4096 ||
!is_power_of_2(dkc->sector_size)) {
ti->error = "Invalid sector_size";
return -EINVAL;
}
} else if (!strcmp(opt_string, "iv_large_sectors")) {
iv_large_sectors = true;
} else if (!strcmp(opt_string, "wrappedkey_v0")) {
dkc->is_hw_wrapped = true;
} else {
ti->error = "Invalid feature arguments";
return -EINVAL;
}
}
/* dm-default-key doesn't implement iv_large_sectors=false. */
if (dkc->sector_size != SECTOR_SIZE && !iv_large_sectors) {
ti->error = "iv_large_sectors must be specified";
return -EINVAL;
}
return 0;
}
/*
* Construct a default-key mapping:
* <cipher> <key> <iv_offset> <dev_path> <start>
*
* This syntax matches dm-crypt's, but lots of unneeded functionality has been
* removed. Also, dm-default-key requires that the "iv_large_sectors" option be
* given whenever a non-default sector size is used.
*/
static int default_key_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
struct default_key_c *dkc;
const struct dm_default_key_cipher *cipher;
u8 raw_key[DM_DEFAULT_KEY_MAX_WRAPPED_KEY_SIZE];
unsigned int raw_key_size;
unsigned int dun_bytes;
unsigned long long tmpll;
char dummy;
int err;
if (argc < 5) {
ti->error = "Not enough arguments";
return -EINVAL;
}
dkc = kzalloc(sizeof(*dkc), GFP_KERNEL);
if (!dkc) {
ti->error = "Out of memory";
return -ENOMEM;
}
ti->private = dkc;
/* <cipher> */
dkc->cipher_string = kstrdup(argv[0], GFP_KERNEL);
if (!dkc->cipher_string) {
ti->error = "Out of memory";
err = -ENOMEM;
goto bad;
}
cipher = lookup_cipher(dkc->cipher_string);
if (!cipher) {
ti->error = "Unsupported cipher";
err = -EINVAL;
goto bad;
}
/* <key> */
raw_key_size = strlen(argv[1]);
if (raw_key_size > 2 * DM_DEFAULT_KEY_MAX_WRAPPED_KEY_SIZE ||
raw_key_size % 2) {
ti->error = "Invalid keysize";
err = -EINVAL;
goto bad;
}
raw_key_size /= 2;
if (hex2bin(raw_key, argv[1], raw_key_size) != 0) {
ti->error = "Malformed key string";
err = -EINVAL;
goto bad;
}
/* <iv_offset> */
if (sscanf(argv[2], "%llu%c", &dkc->iv_offset, &dummy) != 1) {
ti->error = "Invalid iv_offset sector";
err = -EINVAL;
goto bad;
}
/* <dev_path> */
err = dm_get_device(ti, argv[3], dm_table_get_mode(ti->table),
&dkc->dev);
if (err) {
ti->error = "Device lookup failed";
goto bad;
}
/* <start> */
if (sscanf(argv[4], "%llu%c", &tmpll, &dummy) != 1 ||
tmpll != (sector_t)tmpll) {
ti->error = "Invalid start sector";
err = -EINVAL;
goto bad;
}
dkc->start = tmpll;
/* optional arguments */
dkc->sector_size = SECTOR_SIZE;
if (argc > 5) {
err = default_key_ctr_optional(ti, argc - 5, &argv[5]);
if (err)
goto bad;
}
dkc->sector_bits = ilog2(dkc->sector_size);
if (ti->len & ((dkc->sector_size >> SECTOR_SHIFT) - 1)) {
ti->error = "Device size is not a multiple of sector_size";
err = -EINVAL;
goto bad;
}
dkc->max_dun = (dkc->iv_offset + ti->len - 1) >>
(dkc->sector_bits - SECTOR_SHIFT);
dun_bytes = DIV_ROUND_UP(fls64(dkc->max_dun), 8);
err = blk_crypto_init_key(&dkc->key, raw_key, raw_key_size,
dkc->is_hw_wrapped, cipher->mode_num,
dun_bytes, dkc->sector_size);
if (err) {
ti->error = "Error initializing blk-crypto key";
goto bad;
}
err = blk_crypto_start_using_key(&dkc->key,
bdev_get_queue(dkc->dev->bdev));
if (err) {
ti->error = "Error starting to use blk-crypto";
goto bad;
}
ti->num_flush_bios = 1;
err = 0;
goto out;
bad:
default_key_dtr(ti);
out:
memzero_explicit(raw_key, sizeof(raw_key));
return err;
}
static int default_key_map(struct dm_target *ti, struct bio *bio)
{
const struct default_key_c *dkc = ti->private;
sector_t sector_in_target;
u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE] = { 0 };
bio_set_dev(bio, dkc->dev->bdev);
/*
* If the bio is a device-level request which doesn't target a specific
* sector, there's nothing more to do.
*/
if (bio_sectors(bio) == 0)
return DM_MAPIO_REMAPPED;
/* Map the bio's sector to the underlying device. (512-byte sectors) */
sector_in_target = dm_target_offset(ti, bio->bi_iter.bi_sector);
bio->bi_iter.bi_sector = dkc->start + sector_in_target;
/*
* If the bio should skip dm-default-key (i.e. if it's for an encrypted
* file's contents), or if it doesn't have any data (e.g. if it's a
* DISCARD request), there's nothing more to do.
*/
if (bio_should_skip_dm_default_key(bio) || !bio_has_data(bio))
return DM_MAPIO_REMAPPED;
/*
* Else, dm-default-key needs to set this bio's encryption context.
* It must not already have one.
*/
if (WARN_ON_ONCE(bio_has_crypt_ctx(bio)))
return DM_MAPIO_KILL;
/* Calculate the DUN and enforce data-unit (crypto sector) alignment. */
dun[0] = dkc->iv_offset + sector_in_target; /* 512-byte sectors */
if (dun[0] & ((dkc->sector_size >> SECTOR_SHIFT) - 1))
return DM_MAPIO_KILL;
dun[0] >>= dkc->sector_bits - SECTOR_SHIFT; /* crypto sectors */
/*
* This check isn't necessary as we should have calculated max_dun
* correctly, but be safe.
*/
if (WARN_ON_ONCE(dun[0] > dkc->max_dun))
return DM_MAPIO_KILL;
bio_crypt_set_ctx(bio, &dkc->key, dun, GFP_NOIO);
return DM_MAPIO_REMAPPED;
}
static void default_key_status(struct dm_target *ti, status_type_t type,
unsigned int status_flags, char *result,
unsigned int maxlen)
{
const struct default_key_c *dkc = ti->private;
unsigned int sz = 0;
int num_feature_args = 0;
switch (type) {
case STATUSTYPE_INFO:
result[0] = '\0';
break;
case STATUSTYPE_TABLE:
/* Omit the key for now. */
DMEMIT("%s - %llu %s %llu", dkc->cipher_string, dkc->iv_offset,
dkc->dev->name, (unsigned long long)dkc->start);
num_feature_args += !!ti->num_discard_bios;
if (dkc->sector_size != SECTOR_SIZE)
num_feature_args += 2;
if (dkc->is_hw_wrapped)
num_feature_args += 1;
if (num_feature_args != 0) {
DMEMIT(" %d", num_feature_args);
if (ti->num_discard_bios)
DMEMIT(" allow_discards");
if (dkc->sector_size != SECTOR_SIZE) {
DMEMIT(" sector_size:%u", dkc->sector_size);
DMEMIT(" iv_large_sectors");
}
if (dkc->is_hw_wrapped)
DMEMIT(" wrappedkey_v0");
}
break;
}
}
static int default_key_prepare_ioctl(struct dm_target *ti,
struct block_device **bdev)
{
const struct default_key_c *dkc = ti->private;
const struct dm_dev *dev = dkc->dev;
*bdev = dev->bdev;
/* Only pass ioctls through if the device sizes match exactly. */
if (dkc->start != 0 ||
ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
return 1;
return 0;
}
static int default_key_iterate_devices(struct dm_target *ti,
iterate_devices_callout_fn fn,
void *data)
{
const struct default_key_c *dkc = ti->private;
return fn(ti, dkc->dev, dkc->start, ti->len, data);
}
static void default_key_io_hints(struct dm_target *ti,
struct queue_limits *limits)
{
const struct default_key_c *dkc = ti->private;
const unsigned int sector_size = dkc->sector_size;
limits->logical_block_size =
max_t(unsigned int, limits->logical_block_size, sector_size);
limits->physical_block_size =
max_t(unsigned int, limits->physical_block_size, sector_size);
limits->io_min = max_t(unsigned int, limits->io_min, sector_size);
}
static struct target_type default_key_target = {
.name = "default-key",
.version = {2, 1, 0},
.features = DM_TARGET_PASSES_CRYPTO,
.module = THIS_MODULE,
.ctr = default_key_ctr,
.dtr = default_key_dtr,
.map = default_key_map,
.status = default_key_status,
.prepare_ioctl = default_key_prepare_ioctl,
.iterate_devices = default_key_iterate_devices,
.io_hints = default_key_io_hints,
};
static int __init dm_default_key_init(void)
{
return dm_register_target(&default_key_target);
}
static void __exit dm_default_key_exit(void)
{
dm_unregister_target(&default_key_target);
}
module_init(dm_default_key_init);
module_exit(dm_default_key_exit);
MODULE_AUTHOR("Paul Lawrence <paullawrence@google.com>");
MODULE_AUTHOR("Paul Crowley <paulcrowley@google.com>");
MODULE_AUTHOR("Eric Biggers <ebiggers@google.com>");
MODULE_DESCRIPTION(DM_NAME " target for encrypting filesystem metadata");
MODULE_LICENSE("GPL");