From: Nicolai Stange nstange@suse.de
commit 2bcd25443868aa8863779a6ebc6c9319633025d2 upstream.
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 Signed-off-by: Jason A. Donenfeld Jason@zx2c4.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- crypto/drbg.c | 12 ++++++++---- include/crypto/drbg.h | 1 + 2 files changed, 9 insertions(+), 4 deletions(-)
--- a/crypto/drbg.c +++ b/crypto/drbg.c @@ -1035,14 +1035,14 @@ static const struct drbg_state_ops drbg_ ******************************************************************/
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;
@@ -1092,7 +1092,7 @@ static void drbg_async_seed(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); @@ -1122,6 +1122,7 @@ static int drbg_seed(struct drbg_state * 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))) { @@ -1149,6 +1150,9 @@ static int drbg_seed(struct drbg_state * 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; @@ -1205,7 +1209,7 @@ static int drbg_seed(struct drbg_state * 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); --- 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, };