crypto: drbg - add async seeding operation

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>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 36dfece45e88968737d984f5785e81850bf9710f..aca86847ea49b49d15cb7790c9feab8bb48d9a2d 100644 (file)
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -1056,6 +1056,23 @@ 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);
+
+       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);
+       __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 +1142,10 @@ 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) && !reseed)
+               schedule_work(&drbg->seed_work);
+
 out:
        return ret;
 }
@@ -1231,6 +1252,8 @@ 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:
@@ -1487,6 +1510,7 @@ unlock:
  */
 static int drbg_uninstantiate(struct drbg_state *drbg)
 {
+       cancel_work_sync(&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 b0526981aa85dc896fe2774ec824d9965915cf4d..46994b25dc859d6cb853ac27600fbbacfe0582e0 100644 (file)
--- 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;