@@ -1047,6 +1047,27 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
/* 10.1.1.2 / 10.1.1.3 step 5 */
drbg->reseed_ctr = 1;
+ switch (drbg->seeded) {
+ case DRBG_SEED_STATE_UNSEEDED:
+ /* Impossible, but handle it to silence compiler warnings. */
+ fallthrough;
+ case DRBG_SEED_STATE_PARTIAL:
+ /*
+ * Require frequent reseeds until the seed source is
+ * fully initialized.
+ */
+ drbg->reseed_threshold = 50;
+ break;
+
+ case DRBG_SEED_STATE_FULL:
+ /*
+ * Seed source has become fully initialized, frequent
+ * reseeds no longer required.
+ */
+ drbg->reseed_threshold = drbg_max_requests(drbg);
+ break;
+ }
+
return ret;
}
@@ -1095,9 +1116,6 @@ static void drbg_async_seed(struct work_struct *work)
__drbg_seed(drbg, &seedlist, true, DRBG_SEED_STATE_FULL);
- if (drbg->seeded == DRBG_SEED_STATE_FULL)
- drbg->reseed_threshold = drbg_max_requests(drbg);
-
unlock:
mutex_unlock(&drbg->drbg_mutex);
@@ -1534,12 +1552,6 @@ static int drbg_prepare_hrng(struct drbg_state *drbg)
return err;
}
- /*
- * Require frequent reseeds until the seed source is fully
- * initialized.
- */
- drbg->reseed_threshold = 50;
-
return err;
}
Since commit 42ea507fae1a ("crypto: drbg - reseed often if seedsource is degraded"), the maximum seed lifetime represented by ->reseed_threshold gets temporarily lowered if the get_random_bytes() source cannot provide sufficient entropy yet, as is common during boot, and restored back to the original value again once that has changed. More specifically, if the add_random_ready_callback() invoked from drbg_prepare_hrng() in the course of DRBG instantiation does not return -EALREADY, that is, if get_random_bytes() has not been fully initialized at this point yet, drbg_prepare_hrng() will lower ->reseed_threshold to a value of 50. The drbg_async_seed() scheduled from said random_ready_callback will eventually restore the original value. A future patch will replace the random_ready_callback based notification mechanism and thus, there will be no add_random_ready_callback() return value anymore which could get compared to -EALREADY. However, there's __drbg_seed() which gets invoked in the course of both, the DRBG instantiation as well as the eventual reseeding from get_random_bytes() in aforementioned drbg_async_seed(), if any. Moreover, it knows about the get_random_bytes() initialization state by the time the seed data had been obtained from it: the new_seed_state argument introduced with the previous patch would get set to DRBG_SEED_STATE_PARTIAL in case get_random_bytes() had not been fully initialized yet and to DRBG_SEED_STATE_FULL otherwise. Thus, __drbg_seed() provides a convenient alternative for managing that ->reseed_threshold lowering and restoring at a central place. Move all ->reseed_threshold adjustment code from drbg_prepare_hrng() and drbg_async_seed() respectively to __drbg_seed(). Make __drbg_seed() lower the ->reseed_threshold to 50 in case its new_seed_state argument equals DRBG_SEED_STATE_PARTIAL and let it restore the original value otherwise. There is no change in behaviour. Signed-off-by: Nicolai Stange <nstange@suse.de> Reviewed-by: Stephan Müller <smueller@chronox.de> --- crypto/drbg.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-)