[PATCH v6 3/5] crypto: drbg - add async seeding operation

Stephan Mueller
2015-05-13T19:58:00Z

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 | 25 +++++++++++++++++++++++++
include/crypto/drbg.h | 2 ++
2 files changed, 27 insertions(+)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 36dfece..2b2738e 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1056,6 +1056,24 @@ static inline int __drbg_seed(struct drbg_state *drbg, struct list_head *seed,
return ret;
}

+static void drbg_async_seed(struct work_struct *work)
+{
+ struct drbg_string data;
+ LIST_HEAD(seedlist);
+ struct drbg_state *drbg = container_of(work, struct drbg_state,
+ seed_work);
+ int ret = 0;
+
+ get_blocking_random_bytes(drbg->seed_buf, drbg->seed_buf_len);
+
+ drbg_string_fill(&data, drbg->seed_buf, drbg->seed_buf_len);
+ list_add_tail(&data.list, &seedlist);
+ mutex_lock(&drbg->drbg_mutex);
+ ret = __drbg_seed(drbg, &seedlist, true);
+ memzero_explicit(drbg->seed_buf, drbg->seed_buf_len);
+ mutex_unlock(&drbg->drbg_mutex);
+}
+
/*
* Seeding or reseeding of the DRBG
*
@@ -1125,6 +1143,10 @@ 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))
+ schedule_work(&drbg->seed_work);
+
out:
return ret;
}
@@ -1134,6 +1156,7 @@ static inline void drbg_dealloc_state(struct drbg_state *drbg)
{
if (!drbg)
return;
+ cancel_work_sync(&drbg->seed_work);
kzfree(drbg->V);
drbg->V = NULL;
kzfree(drbg->C);
@@ -1231,6 +1254,8 @@ static inline int drbg_alloc_state(struct drbg_state *drbg)
if (!drbg->seed_buf)
goto err;

+ INIT_WORK(&drbg->seed_work, drbg_async_seed);
+
return 0;

err:
diff --git a/include/crypto/drbg.h b/include/crypto/drbg.h
index b052698..46994b2 100644
--- a/include/crypto/drbg.h
+++ b/include/crypto/drbg.h
@@ -51,6 +51,7 @@
#include <linux/fips.h>
#include <linux/mutex.h>
#include <linux/list.h>
+#include <linux/workqueue.h>

/*
* Concatenation Helper and string operation helper
@@ -119,6 +120,7 @@ struct drbg_state {
bool fips_primed; /* Continuous test primed? */
unsigned char *prev; /* FIPS 140-2 continuous test value */
#endif
+ struct work_struct 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