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author | Nicolai Stange <nstange@suse.de> | 2022-06-02 23:22:29 +0300 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-06-06 09:42:42 +0300 |
commit | b2bef5500e0d2000c40c361720b0788db2abca5e (patch) | |
tree | 5681add6eb2488af360e061a45c061cd5bc35729 /crypto/drbg.c | |
parent | 630192aa45233acfe3d17952862ca215f6d31f09 (diff) | |
download | linux-b2bef5500e0d2000c40c361720b0788db2abca5e.tar.xz |
crypto: drbg - prepare for more fine-grained tracking of seeding state
commit ce8ce31b2c5c8b18667784b8c515650c65d57b4e upstream.
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>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'crypto/drbg.c')
-rw-r--r-- | crypto/drbg.c | 19 |
1 files changed, 10 insertions, 9 deletions
diff --git a/crypto/drbg.c b/crypto/drbg.c index 19ea8d6628ff..87f97da5d0ba 100644 --- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1042,7 +1042,7 @@ 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; @@ -1087,14 +1087,14 @@ 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: @@ -1385,13 +1385,14 @@ 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) @@ -1576,7 +1577,7 @@ 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); |