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authorNicolai Stange <nstange@suse.de>2021-11-15 15:18:05 +0100
committerHerbert Xu <herbert@gondor.apana.org.au>2021-11-26 16:16:49 +1100
commit2bcd25443868aa8863779a6ebc6c9319633025d2 (patch)
treec9f65e70e7b43b51ae03abe6a44598fa9eb469b6
parentce8ce31b2c5c8b18667784b8c515650c65d57b4e (diff)
crypto: drbg - track whether DRBG was seeded with !rng_is_initialized()
Currently, the DRBG implementation schedules asynchronous works from random_ready_callbacks for reseeding the DRBG instances with output from get_random_bytes() once the latter has sufficient entropy available. However, as the get_random_bytes() initialization state can get queried by means of rng_is_initialized() now, there is no real need for this asynchronous reseeding logic anymore and it's better to keep things simple by doing it synchronously when needed instead, i.e. from drbg_generate() once rng_is_initialized() has flipped to true. Of course, for this to work, drbg_generate() would need some means by which it can tell whether or not rng_is_initialized() has flipped to true since the last seeding from get_random_bytes(). Or equivalently, whether or not the last seed from get_random_bytes() has happened when rng_is_initialized() was still evaluating to false. As it currently stands, enum drbg_seed_state allows for the representation of two different DRBG seeding states: DRBG_SEED_STATE_UNSEEDED and DRBG_SEED_STATE_FULL. The former makes drbg_generate() to invoke a full reseeding operation involving both, the rather expensive jitterentropy as well as the get_random_bytes() randomness sources. The DRBG_SEED_STATE_FULL state on the other hand implies that no reseeding at all is required for a !->pr DRBG variant. Introduce the new DRBG_SEED_STATE_PARTIAL state to enum drbg_seed_state for representing the condition that a DRBG was being seeded when rng_is_initialized() had still been false. In particular, this new state implies that - the given DRBG instance has been fully seeded from the jitterentropy source (if enabled) - and drbg_generate() is supposed to reseed from get_random_bytes() *only* once rng_is_initialized() turns to true. Up to now, the __drbg_seed() helper used to set the given DRBG instance's ->seeded state to constant DRBG_SEED_STATE_FULL. Introduce a new argument allowing for the specification of the to be written ->seeded value instead. Make the first of its two callers, drbg_seed(), determine the appropriate value based on rng_is_initialized(). The remaining caller, drbg_async_seed(), is known to get invoked only once rng_is_initialized() is true, hence let it pass constant DRBG_SEED_STATE_FULL for the new argument to __drbg_seed(). There is no change in behaviour, except for that the pr_devel() in drbg_generate() would now report "unseeded" for ->pr DRBG instances which had last been seeded when rng_is_initialized() was still evaluating to false. Signed-off-by: Nicolai Stange <nstange@suse.de> Reviewed-by: Stephan Müller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
-rw-r--r--crypto/drbg.c12
-rw-r--r--include/crypto/drbg.h1
2 files changed, 9 insertions, 4 deletions
diff --git a/crypto/drbg.c b/crypto/drbg.c
index 6329c70e5bbb..d71c704d0cd2 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1036,14 +1036,14 @@ static const struct drbg_state_ops drbg_hash_ops = {
******************************************************************/
static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
- int reseed)
+ int reseed, enum drbg_seed_state new_seed_state)
{
int ret = drbg->d_ops->update(drbg, seed, reseed);
if (ret)
return ret;
- drbg->seeded = DRBG_SEED_STATE_FULL;
+ drbg->seeded = new_seed_state;
/* 10.1.1.2 / 10.1.1.3 step 5 */
drbg->reseed_ctr = 1;
@@ -1093,7 +1093,7 @@ static void drbg_async_seed(struct work_struct *work)
*/
drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
- __drbg_seed(drbg, &seedlist, true);
+ __drbg_seed(drbg, &seedlist, true, DRBG_SEED_STATE_FULL);
if (drbg->seeded == DRBG_SEED_STATE_FULL)
drbg->reseed_threshold = drbg_max_requests(drbg);
@@ -1123,6 +1123,7 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
unsigned int entropylen = drbg_sec_strength(drbg->core->flags);
struct drbg_string data1;
LIST_HEAD(seedlist);
+ enum drbg_seed_state new_seed_state = DRBG_SEED_STATE_FULL;
/* 9.1 / 9.2 / 9.3.1 step 3 */
if (pers && pers->len > (drbg_max_addtl(drbg))) {
@@ -1150,6 +1151,9 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
BUG_ON((entropylen * 2) > sizeof(entropy));
/* Get seed from in-kernel /dev/urandom */
+ if (!rng_is_initialized())
+ new_seed_state = DRBG_SEED_STATE_PARTIAL;
+
ret = drbg_get_random_bytes(drbg, entropy, entropylen);
if (ret)
goto out;
@@ -1206,7 +1210,7 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
memset(drbg->C, 0, drbg_statelen(drbg));
}
- ret = __drbg_seed(drbg, &seedlist, reseed);
+ ret = __drbg_seed(drbg, &seedlist, reseed, new_seed_state);
out:
memzero_explicit(entropy, entropylen * 2);
diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index 92a87b23ad2f..3ebdb1effe74 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -107,6 +107,7 @@ struct drbg_test_data {
enum drbg_seed_state {
DRBG_SEED_STATE_UNSEEDED,
+ DRBG_SEED_STATE_PARTIAL, /* Seeded with !rng_is_initialized() */
DRBG_SEED_STATE_FULL,
};