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Subject[PATCH v5 3/5] crypto: drbg - add async seeding operation
Date
The async seeding operation is triggered during initalization right
after the first non-blocking seeding is completed. As required by the
asynchronous operation of random.c, a callback function is provided that
is triggered by random.c once entropy is available. That callback
function performs the actual seeding of the DRBG.

CC: Andreas Steffen <andreas.steffen@strongswan.org>
CC: Theodore Ts'o <tytso@mit.edu>
CC: Sandy Harris <sandyinchina@gmail.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
---
crypto/drbg.c | 41 +++++++++++++++++++++++++++++++++++++++++
include/crypto/drbg.h | 1 +
2 files changed, 42 insertions(+)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 36dfece..693dac4 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1056,6 +1056,40 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
return ret;
}

+/* DRBG callback for obtaining data from the async Linux RNG */
+static void drbg_async_seed_cb(void *buf, ssize_t buflen, void *private)
+{
+ struct drbg_string data;
+ LIST_HEAD(seedlist);
+ struct drbg_state *drbg = (struct drbg_state *)private;
+ int ret = 0;
+
+ if (buflen <= 0 || !buf)
+ return;
+
+ drbg_string_fill(&data, buf, buflen);
+ list_add_tail(&data.list, &seedlist);
+ /* sanity check to verify that there is still a DRBG instance */
+ if (!drbg)
+ return;
+ mutex_lock(&drbg->drbg_mutex);
+ /* sanity check to verify that the DRBG instance is valid */
+ if (!drbg->V) {
+ mutex_unlock(&drbg->drbg_mutex);
+ return;
+ }
+ ret = __drbg_seed(drbg, &seedlist, true);
+ memzero_explicit(buf, buflen);
+ mutex_unlock(&drbg->drbg_mutex);
+}
+
+/* Cancel any outstanding async operation and wait for their completion */
+static inline void drbg_async_work_cancel(struct random_work *work)
+{
+ get_blocking_random_bytes_cancel(work);
+ cancel_work_sync(&work->rw_work);
+}
+
/*
* Seeding or reseeding of the DRBG
*
@@ -1125,6 +1159,12 @@ static int drbg_seed(struct drbg_state *drbg, struct drbg_string *pers,
if (!reseed)
drbg->seed_buf_len = drbg->seed_buf_len / 3 * 2;

+ /* Invoke asynchronous seeding unless DRBG is in test mode. */
+ if (!list_empty(&drbg->test_data.list))
+ get_blocking_random_bytes_cb(NULL, &drbg->seed_work,
+ drbg->seed_buf, drbg->seed_buf_len,
+ drbg, drbg_async_seed_cb);
+
out:
return ret;
}
@@ -1487,6 +1527,7 @@ unlock:
*/
static int drbg_uninstantiate(struct drbg_state *drbg)
{
+ drbg_async_work_cancel(&drbg->seed_work);
if (drbg->d_ops)
drbg->d_ops->crypto_fini(drbg);
drbg_dealloc_state(drbg);
diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index b052698..e4980a1 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -119,6 +119,7 @@ struct drbg_state {
bool fips_primed; /* Continuous test primed? */
unsigned char *prev; /* FIPS 140-2 continuous test value */
#endif
+ struct random_work seed_work; /* asynchronous seeding support */
u8 *seed_buf; /* buffer holding the seed */
size_t seed_buf_len;
const struct drbg_state_ops *d_ops;
--
2.1.0



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