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author | 2021-11-15 15:18:05 +0100 | |
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committer | 2021-11-26 16:16:49 +1100 | |
commit | 2bcd25443868aa8863779a6ebc6c9319633025d2 (patch) | |
tree | c9f65e70e7b43b51ae03abe6a44598fa9eb469b6 /include | |
parent | crypto: drbg - prepare for more fine-grained tracking of seeding state (diff) | |
download | linux-2bcd25443868aa8863779a6ebc6c9319633025d2.tar.gz linux-2bcd25443868aa8863779a6ebc6c9319633025d2.tar.bz2 linux-2bcd25443868aa8863779a6ebc6c9319633025d2.zip |
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>
Diffstat (limited to 'include')
-rw-r--r-- | include/crypto/drbg.h | 1 |
1 files changed, 1 insertions, 0 deletions
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, }; |