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authorNicolai Stange <nstange@suse.de>2021-11-15 15:18:04 +0100
committerHerbert Xu <herbert@gondor.apana.org.au>2021-11-26 16:16:49 +1100
commitce8ce31b2c5c8b18667784b8c515650c65d57b4e (patch)
treed9300e19b40d0452c7676885a5ff3d93a74b9460 /crypto
parent370a40ee228340b5141e5d89dee3186452d9f5fb (diff)
crypto: drbg - prepare for more fine-grained tracking of seeding state
There are two different randomness sources the DRBGs are getting seeded from, namely the jitterentropy source (if enabled) and get_random_bytes(). At initial DRBG seeding time during boot, the latter might not have collected sufficient entropy for seeding itself yet and thus, the DRBG implementation schedules a reseed work from a random_ready_callback once that has happened. This is particularly important for the !->pr DRBG instances, for which (almost) no further reseeds are getting triggered during their lifetime. Because collecting data from the jitterentropy source is a rather expensive operation, the aforementioned asynchronously scheduled reseed work restricts itself to get_random_bytes() only. That is, it in some sense amends the initial DRBG seed derived from jitterentropy output at full (estimated) entropy with fresh randomness obtained from get_random_bytes() once that has been seeded with sufficient entropy itself. With the advent of rng_is_initialized(), there is no real need for doing the reseed operation from an asynchronously scheduled work anymore and a subsequent patch will make it synchronous by moving it next to related logic already present in drbg_generate(). However, for tracking whether a full reseed including the jitterentropy source is required or a "partial" reseed involving only get_random_bytes() would be sufficient already, the boolean struct drbg_state's ->seeded member must become a tristate value. Prepare for this by introducing the new enum drbg_seed_state and change struct drbg_state's ->seeded member's type from bool to that type. For facilitating review, enum drbg_seed_state is made to only contain two members corresponding to the former ->seeded values of false and true resp. at this point: DRBG_SEED_STATE_UNSEEDED and DRBG_SEED_STATE_FULL. A third one for tracking the intermediate state of "seeded from jitterentropy only" will be introduced with a subsequent patch. There is no change in behaviour at this point. 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>
Diffstat (limited to 'crypto')
-rw-r--r--crypto/drbg.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/crypto/drbg.c b/crypto/drbg.c
index f72f340a1321..6329c70e5bbb 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1043,7 +1043,7 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
if (ret)
return ret;
- drbg->seeded = true;
+ drbg->seeded = DRBG_SEED_STATE_FULL;
/* 10.1.1.2 / 10.1.1.3 step 5 */
drbg->reseed_ctr = 1;
@@ -1088,14 +1088,14 @@ static void drbg_async_seed(struct work_struct *work)
if (ret)
goto unlock;
- /* Set seeded to false so that if __drbg_seed fails the
- * next generate call will trigger a reseed.
+ /* Reset ->seeded so that if __drbg_seed fails the next
+ * generate call will trigger a reseed.
*/
- drbg->seeded = false;
+ drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
__drbg_seed(drbg, &seedlist, true);
- if (drbg->seeded)
+ if (drbg->seeded == DRBG_SEED_STATE_FULL)
drbg->reseed_threshold = drbg_max_requests(drbg);
unlock:
@@ -1386,13 +1386,14 @@ static int drbg_generate(struct drbg_state *drbg,
* here. The spec is a bit convoluted here, we make it simpler.
*/
if (drbg->reseed_threshold < drbg->reseed_ctr)
- drbg->seeded = false;
+ drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
- if (drbg->pr || !drbg->seeded) {
+ if (drbg->pr || drbg->seeded == DRBG_SEED_STATE_UNSEEDED) {
pr_devel("DRBG: reseeding before generation (prediction "
"resistance: %s, state %s)\n",
drbg->pr ? "true" : "false",
- drbg->seeded ? "seeded" : "unseeded");
+ (drbg->seeded == DRBG_SEED_STATE_FULL ?
+ "seeded" : "unseeded"));
/* 9.3.1 steps 7.1 through 7.3 */
len = drbg_seed(drbg, addtl, true);
if (len)
@@ -1578,7 +1579,7 @@ static int drbg_instantiate(struct drbg_state *drbg, struct drbg_string *pers,
if (!drbg->core) {
drbg->core = &drbg_cores[coreref];
drbg->pr = pr;
- drbg->seeded = false;
+ drbg->seeded = DRBG_SEED_STATE_UNSEEDED;
drbg->reseed_threshold = drbg_max_requests(drbg);
ret = drbg_alloc_state(drbg);