Am Montag, 25. Oktober 2021, 11:25:20 CEST schrieb Nicolai Stange: Hi Nicolai, > 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@xxxxxxx> Reviewed-by: Stephan Müller <smueller@xxxxxxxxxx> Ciao Stephan
