+
+/*
+ * Locks the given drbg. Locking a drbg which does not have locking
+ * enabled is considered a successful no-op.
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+int rand_drbg_lock(RAND_DRBG *drbg)
+{
+ if (drbg->lock != NULL)
+ return CRYPTO_THREAD_write_lock(drbg->lock);
+
+ return 1;
+}
+
+/*
+ * Unlocks the given drbg. Unlocking a drbg which does not have locking
+ * enabled is considered a successful no-op.
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+int rand_drbg_unlock(RAND_DRBG *drbg)
+{
+ if (drbg->lock != NULL)
+ return CRYPTO_THREAD_unlock(drbg->lock);
+
+ return 1;
+}
+
+/*
+ * Enables locking for the given drbg
+ *
+ * Locking can only be enabled if the random generator
+ * is in the uninitialized state.
+ *
+ * Returns 1 on success, 0 on failure.
+ */
+int rand_drbg_enable_locking(RAND_DRBG *drbg)
+{
+ if (drbg->state != DRBG_UNINITIALISED) {
+ RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
+ RAND_R_DRBG_ALREADY_INITIALIZED);
+ return 0;
+ }
+
+ if (drbg->lock == NULL) {
+ if (drbg->parent != NULL && drbg->parent->lock == NULL) {
+ RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
+ RAND_R_PARENT_LOCKING_NOT_ENABLED);
+ return 0;
+ }
+
+ drbg->lock = CRYPTO_THREAD_lock_new();
+ if (drbg->lock == NULL) {
+ RANDerr(RAND_F_RAND_DRBG_ENABLE_LOCKING,
+ RAND_R_FAILED_TO_CREATE_LOCK);
+ return 0;
+ }
+ }
+
+ return 1;
+}
+