From 074bcd4000e0d812bc253f86fedc40f81ed59ccc Mon Sep 17 00:00:00 2001 From: Nicolai Stange Date: Mon, 15 Nov 2021 15:18:07 +0100 Subject: crypto: drbg - make reseeding from get_random_bytes() synchronous get_random_bytes() usually hasn't full entropy available by the time DRBG instances are first getting seeded from it during boot. Thus, the DRBG implementation registers random_ready_callbacks which would in turn schedule some work for reseeding the DRBGs once get_random_bytes() has sufficient entropy available. For reference, the relevant history around handling DRBG (re)seeding in the context of a not yet fully seeded get_random_bytes() is: commit 16b369a91d0d ("random: Blocking API for accessing nonblocking_pool") commit 4c7879907edd ("crypto: drbg - add async seeding operation") commit 205a525c3342 ("random: Add callback API for random pool readiness") commit 57225e679788 ("crypto: drbg - Use callback API for random readiness") commit c2719503f5e1 ("random: Remove kernel blocking API") However, some time later, the initialization state of get_random_bytes() has been made queryable via rng_is_initialized() introduced with commit 9a47249d444d ("random: Make crng state queryable"). This primitive now allows for streamlining the DRBG reseeding from get_random_bytes() by replacing that aforementioned asynchronous work scheduling from random_ready_callbacks with some simpler, synchronous code in drbg_generate() next to the related logic already present therein. Apart from improving overall code readability, this change will also enable DRBG users to rely on wait_for_random_bytes() for ensuring that the initial seeding has completed, if desired. The previous patches already laid the grounds by making drbg_seed() to record at each DRBG instance whether it was being seeded at a time when rng_is_initialized() still had been false as indicated by ->seeded == DRBG_SEED_STATE_PARTIAL. All that remains to be done now is to make drbg_generate() check for this condition, determine whether rng_is_initialized() has flipped to true in the meanwhile and invoke a reseed from get_random_bytes() if so. Make this move: - rename the former drbg_async_seed() work handler, i.e. the one in charge of reseeding a DRBG instance from get_random_bytes(), to "drbg_seed_from_random()", - change its signature as appropriate, i.e. make it take a struct drbg_state rather than a work_struct and change its return type from "void" to "int" in order to allow for passing error information from e.g. its __drbg_seed() invocation onwards to callers, - make drbg_generate() invoke this drbg_seed_from_random() once it encounters a DRBG instance with ->seeded == DRBG_SEED_STATE_PARTIAL by the time rng_is_initialized() has flipped to true and - prune everything related to the former, random_ready_callback based mechanism. As drbg_seed_from_random() is now getting invoked from drbg_generate() with the ->drbg_mutex being held, it must not attempt to recursively grab it once again. Remove the corresponding mutex operations from what is now drbg_seed_from_random(). Furthermore, as drbg_seed_from_random() can now report errors directly to its caller, there's no need for it to temporarily switch the DRBG's ->seeded state to DRBG_SEED_STATE_UNSEEDED so that a failure of the subsequently invoked __drbg_seed() will get signaled to drbg_generate(). Don't do it then. Signed-off-by: Nicolai Stange Signed-off-by: Herbert Xu --- include/crypto/drbg.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/crypto') diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h index 3ebdb1effe74..a6c3b8e7deb6 100644 --- a/include/crypto/drbg.h +++ b/include/crypto/drbg.h @@ -137,12 +137,10 @@ struct drbg_state { bool pr; /* Prediction resistance enabled? */ bool fips_primed; /* Continuous test primed? */ unsigned char *prev; /* FIPS 140-2 continuous test value */ - struct work_struct seed_work; /* asynchronous seeding support */ struct crypto_rng *jent; const struct drbg_state_ops *d_ops; const struct drbg_core *core; struct drbg_string test_data; - struct random_ready_callback random_ready; }; static inline __u8 drbg_statelen(struct drbg_state *drbg) -- cgit v1.2.3