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ANDROID: dm: Add wrapped key support in dm-default-key

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To prevent keys from being compromised if an attacker acquires read
access to kernel memory, some inline encryption hardware supports
protecting the keys in hardware without software having access to or the
ability to set the plaintext keys.  Instead, software only sees "wrapped
keys", which may differ on every boot.  The keys can be initially
generated either by software (in which case they need to be imported to
hardware to be wrapped), or directly by the hardware.

Add support for this type of hardware by allowing keys to be flagged as
hardware-wrapped. When used, dm-default-key will pass the wrapped key
to the inline encryption hardware to encryption metadata. The hardware
will internally unwrap the key and derive the metadata encryption key.

Bug: 147209885

Test: Validate metadata encryption & FBE with wrapped keys.

Change-Id: I8078b116dab9e04d7f3f15f29f11823185ea5d50
Signed-off-by: Barani Muthukumaran <bmuthuku@codeaurora.org>
This commit is contained in:
Barani Muthukumaran 2020-02-06 18:01:33 -08:00 committed by Todd Kjos
parent a1423568e2
commit 0dccdc03e0
1 changed files with 20 additions and 8 deletions
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28
drivers/md/dm-default-key.c
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@ -9,7 +9,7 @@
#define DM_MSG_PREFIX "default-key"
#define DM_DEFAULT_KEY_MAX_KEY_SIZE 64
#define DM_DEFAULT_KEY_MAX_WRAPPED_KEY_SIZE 128
static const struct dm_default_key_cipher {
const char *name;
@ -47,6 +47,7 @@ struct default_key_c {
unsigned int sector_size;
unsigned int sector_bits;
struct blk_crypto_key key;
bool is_hw_wrapped;
};
static const struct dm_default_key_cipher *
@ -82,7 +83,7 @@ static int default_key_ctr_optional(struct dm_target *ti,
struct default_key_c *dkc = ti->private;
struct dm_arg_set as;
static const struct dm_arg _args[] = {
{0, 3, "Invalid number of feature args"},
{0, 4, "Invalid number of feature args"},
};
unsigned int opt_params;
const char *opt_string;
@ -115,6 +116,8 @@ static int default_key_ctr_optional(struct dm_target *ti,
}
} 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;
@ -142,7 +145,8 @@ 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_KEY_SIZE];
u8 raw_key[DM_DEFAULT_KEY_MAX_WRAPPED_KEY_SIZE];
unsigned int raw_key_size;
unsigned long long tmpll;
char dummy;
int err;
@ -174,12 +178,15 @@ static int default_key_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}
/* <key> */
if (strlen(argv[1]) != 2 * cipher->key_size) {
ti->error = "Incorrect key size for cipher";
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;
}
if (hex2bin(raw_key, argv[1], cipher->key_size) != 0) {
raw_key_size /= 2;
if (hex2bin(raw_key, argv[1], raw_key_size) != 0) {
ti->error = "Malformed key string";
err = -EINVAL;
goto bad;
@ -224,7 +231,8 @@ static int default_key_ctr(struct dm_target *ti, unsigned int argc, char **argv)
}
err = blk_crypto_init_key(&dkc->key, raw_key, cipher->key_size,
false, cipher->mode_num, dkc->sector_size);
dkc->is_hw_wrapped, cipher->mode_num,
dkc->sector_size);
if (err) {
ti->error = "Error initializing blk-crypto key";
goto bad;
@ -317,6 +325,8 @@ static void default_key_status(struct dm_target *ti, status_type_t type,
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)
@ -325,6 +335,8 @@ static void default_key_status(struct dm_target *ti, status_type_t type,
DMEMIT(" sector_size:%u", dkc->sector_size);
DMEMIT(" iv_large_sectors");
}
if (dkc->is_hw_wrapped)
DMEMIT(" wrappedkey_v0");
}
break;
}
@ -369,7 +381,7 @@ static void default_key_io_hints(struct dm_target *ti,
static struct target_type default_key_target = {
.name = "default-key",
.version = {2, 0, 0},
.version = {2, 1, 0},
.module = THIS_MODULE,
.ctr = default_key_ctr,
.dtr = default_key_dtr,