*
* AUTOMATIC RESEEDING
*
- * Before satisfying a generate request, a DRBG reseeds itself automatically
- * if the number of generate requests since the last reseeding exceeds a
- * certain threshold, the so called |reseed_interval|. This automatic
- * reseeding can be disabled by setting the |reseed_interval| to 0.
+ * Before satisfying a generate request, a DRBG reseeds itself automatically,
+ * if one of the following two conditions holds:
+ *
+ * - the number of generate requests since the last reseeding exceeds a
+ * certain threshold, the so called |reseed_interval|. This behaviour
+ * can be disabled by setting the |reseed_interval| to 0.
+ *
+ * - the time elapsed since the last reseeding exceeds a certain time
+ * interval, the so called |reseed_time_interval|. This behaviour
+ * can be disabled by setting the |reseed_time_interval| to 0.
*
* MANUAL RESEEDING
*
- * For the three shared DRBGs (and only for these) there is a way to reseed
- * them manually by calling RAND_seed() (or RAND_add() with a positive
+ * For the three shared DRBGs (and only for these) there is another way to
+ * reseed them manually by calling RAND_seed() (or RAND_add() with a positive
* |randomness| argument). This will immediately reseed the <master> DRBG.
- * Its immediate children (<public> and <private> DRBG) will detect this
- * on their next generate call and reseed, pulling randomness from <master>.
+ * The <public> and <private> DRBG will detect this on their next generate
+ * call and reseed, pulling randomness from <master>.
*/
drbg->state = DRBG_READY;
drbg->generate_counter = 0;
-
+ drbg->reseed_time = time(NULL);
if (drbg->reseed_counter > 0) {
if (drbg->parent == NULL)
drbg->reseed_counter++;
drbg->state = DRBG_READY;
drbg->generate_counter = 0;
-
+ drbg->reseed_time = time(NULL);
if (drbg->reseed_counter > 0) {
if (drbg->parent == NULL)
drbg->reseed_counter++;
if (drbg->generate_counter >= drbg->reseed_interval)
reseed_required = 1;
}
-
+ if (drbg->reseed_time_interval > 0) {
+ time_t now = time(NULL);
+ if (now < drbg->reseed_time
+ || now - drbg->reseed_time >= drbg->reseed_time_interval)
+ reseed_required = 1;
+ }
if (drbg->reseed_counter > 0 && drbg->parent != NULL) {
if (drbg->reseed_counter != drbg->parent->reseed_counter)
reseed_required = 1;
*
* The drbg will reseed automatically whenever the number of generate
* requests exceeds the given reseed interval. If the reseed interval
- * is 0, then this automatic reseeding is disabled.
+ * is 0, then this feature is disabled.
*
* Returns 1 on success, 0 on failure.
*/
return 1;
}
+/*
+ * Set the reseed time interval.
+ *
+ * The drbg will reseed automatically whenever the time elapsed since
+ * the last reseeding exceeds the given reseed time interval. For safety,
+ * a reseeding will also occur if the clock has been reset to a smaller
+ * value.
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
+{
+ if (interval > MAX_RESEED_TIME_INTERVAL)
+ return 0;
+ drbg->reseed_time_interval = interval;
+ return 1;
+}
+
/*
* Get and set the EXDATA
*/
ret &= RAND_DRBG_set_callbacks(drbg, rand_drbg_get_entropy,
rand_drbg_cleanup_entropy, NULL, NULL) == 1;
- if (parent == NULL)
+ if (parent == NULL) {
drbg->reseed_interval = MASTER_RESEED_INTERVAL;
- else {
+ drbg->reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
+ } else {
drbg->parent = parent;
drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
+ drbg->reseed_time_interval = SLAVE_RESEED_TIME_INTERVAL;
}
/* enable seed propagation */
/* How many times to read the TSC as a randomness source. */
# define TSC_READ_COUNT 4
-/* Maximum reseed interval */
+/* Maximum reseed intervals */
# define MAX_RESEED_INTERVAL (1 << 24)
+# define MAX_RESEED_TIME_INTERVAL (1 << 20) /* approx. 12 days */
/* Default reseed intervals */
# define MASTER_RESEED_INTERVAL (1 << 8)
# define SLAVE_RESEED_INTERVAL (1 << 16)
+# define MASTER_RESEED_TIME_INTERVAL (60*60) /* 1 hour */
+# define SLAVE_RESEED_TIME_INTERVAL (7*60) /* 7 minutes */
+
+
/* Max size of additional input and personalization string. */
# define DRBG_MAX_LENGTH 4096
* This value is ignored if it is zero.
*/
unsigned int reseed_interval;
+ /* Stores the time when the last reseeding occurred */
+ time_t reseed_time;
+ /*
+ * Specifies the maximum time interval (in seconds) between reseeds.
+ * This value is ignored if it is zero.
+ */
+ time_t reseed_time_interval;
/*
* Counts the number of reseeds since instantiation.
* This value is ignored if it is zero.
)
{
unsigned char buf[32];
+ time_t before_reseed, after_reseed;
int expected_state = (expect_success ? DRBG_READY : DRBG_ERROR);
/*
*/
/* Generate random output from the public and private DRBG */
+ before_reseed = expect_master_reseed == 1 ? time(NULL) : 0;
if (!TEST_int_eq(RAND_bytes(buf, sizeof(buf)), expect_success)
|| !TEST_int_eq(RAND_priv_bytes(buf, sizeof(buf)), expect_success))
return 0;
+ after_reseed = time(NULL);
/*
if (!TEST_int_eq(public->reseed_counter, master->reseed_counter)
|| !TEST_int_eq(private->reseed_counter, master->reseed_counter))
return 0;
+
+ /* Test whether reseed time of master DRBG is set correctly */
+ if (!TEST_time_t_le(before_reseed, master->reseed_time)
+ || !TEST_time_t_le(master->reseed_time, after_reseed))
+ return 0;
+
+ /* Test whether reseed times of child DRBGs are synchronized with master */
+ if (!TEST_time_t_ge(public->reseed_time, master->reseed_time)
+ || !TEST_time_t_ge(private->reseed_time, master->reseed_time))
+ return 0;
} else {
ERR_clear_error();
}
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