RAND_DRBG: add a function for setting the reseeding defaults

The introduction of thread local public and private DRBG instances (#5547)
makes it very cumbersome to change the reseeding (time) intervals for
those instances. This commit provides a function to set the default
values for all subsequently created DRBG instances.

 int RAND_DRBG_set_reseed_defaults(
                                   unsigned int master_reseed_interval,
                                   unsigned int slave_reseed_interval,
                                   time_t master_reseed_time_interval,
                                   time_t slave_reseed_time_interval
                                   );

The function is intended only to be used during application initialization,
before any threads are created and before any random bytes are generated.
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5576)

crypto/rand/drbg_ctr.c

@@ -366,6 +366,6 @@ int drbg_ctr_init(RAND_DRBG *drbg)
     }
 
     drbg->max_request = 1 << 16;
-    drbg->reseed_interval = MAX_RESEED_INTERVAL;
+
     return 1;
 }

crypto/rand/drbg_lib.c

@@ -113,6 +113,12 @@ static const char ossl_pers_string[] = "OpenSSL NIST SP 800-90A DRBG";
 
 static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;
 
+static unsigned int master_reseed_interval = MASTER_RESEED_INTERVAL;
+static unsigned int slave_reseed_interval  = SLAVE_RESEED_INTERVAL;
+
+static time_t master_reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
+static time_t slave_reseed_time_interval  = SLAVE_RESEED_TIME_INTERVAL;
+
 static RAND_DRBG *drbg_setup(RAND_DRBG *parent);
 
 static RAND_DRBG *rand_drbg_new(int secure,
@@ -175,6 +181,15 @@ static RAND_DRBG *rand_drbg_new(int secure,
     drbg->secure = secure && CRYPTO_secure_allocated(drbg);
     drbg->fork_count = rand_fork_count;
     drbg->parent = parent;
+
+    if (parent == NULL) {
+        drbg->reseed_interval = master_reseed_interval;
+        drbg->reseed_time_interval = master_reseed_time_interval;
+    } else {
+        drbg->reseed_interval = slave_reseed_interval;
+        drbg->reseed_time_interval = slave_reseed_time_interval;
+    }
+
     if (RAND_DRBG_set(drbg, type, flags) == 0)
         goto err;
 
@@ -710,6 +725,38 @@ int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval)
     return 1;
 }
 
+/*
+ * Set the default values for reseed (time) intervals of new DRBG instances
+ *
+ * The default values can be set independently for master DRBG instances
+ * (without a parent) and slave DRBG instances (with parent).
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+
+int RAND_DRBG_set_reseed_defaults(
+                                  unsigned int _master_reseed_interval,
+                                  unsigned int _slave_reseed_interval,
+                                  time_t _master_reseed_time_interval,
+                                  time_t _slave_reseed_time_interval
+                                  )
+{
+    if (_master_reseed_interval > MAX_RESEED_INTERVAL
+        || _slave_reseed_interval > MAX_RESEED_INTERVAL)
+        return 0;
+
+    if (_master_reseed_time_interval > MAX_RESEED_TIME_INTERVAL
+        || _slave_reseed_time_interval > MAX_RESEED_TIME_INTERVAL)
+        return 0;
+
+    master_reseed_interval = _master_reseed_interval;
+    slave_reseed_interval = _slave_reseed_interval;
+
+    master_reseed_time_interval = _master_reseed_time_interval;
+    slave_reseed_time_interval = _slave_reseed_time_interval;
+
+    return 1;
+}
 
 /*
  * Locks the given drbg. Locking a drbg which does not have locking
@@ -809,14 +856,6 @@ static RAND_DRBG *drbg_setup(RAND_DRBG *parent)
     if (rand_drbg_enable_locking(drbg) == 0)
         goto err;
 
-    if (parent == NULL) {
-        drbg->reseed_interval = MASTER_RESEED_INTERVAL;
-        drbg->reseed_time_interval = MASTER_RESEED_TIME_INTERVAL;
-    } else {
-        drbg->reseed_interval = SLAVE_RESEED_INTERVAL;
-        drbg->reseed_time_interval = SLAVE_RESEED_TIME_INTERVAL;
-    }
-
     /* enable seed propagation */
     drbg->reseed_counter = 1;
 

include/internal/rand.h

@@ -56,6 +56,13 @@ int RAND_DRBG_bytes(RAND_DRBG *drbg, unsigned char *out, size_t outlen);
 int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval);
 int RAND_DRBG_set_reseed_time_interval(RAND_DRBG *drbg, time_t interval);
 
+int RAND_DRBG_set_reseed_defaults(
+                                  unsigned int master_reseed_interval,
+                                  unsigned int slave_reseed_interval,
+                                  time_t master_reseed_time_interval,
+                                  time_t slave_reseed_time_interval
+                                  );
+
 RAND_DRBG *RAND_DRBG_get0_master(void);
 RAND_DRBG *RAND_DRBG_get0_public(void);
 RAND_DRBG *RAND_DRBG_get0_private(void);

util/libcrypto.num

@@ -4521,3 +4521,4 @@ OSSL_STORE_SEARCH_by_alias              4462	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_LOADER_set_find              4463	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_SEARCH_free                  4464	1_1_1	EXIST::FUNCTION:
 OSSL_STORE_SEARCH_get0_digest           4465	1_1_1	EXIST::FUNCTION:
+RAND_DRBG_set_reseed_defaults           4466	1_1_1	EXIST::FUNCTION: