Fix error handling in RAND_DRBG_set
[openssl.git] / crypto / rand / drbg_lib.c
index 0da4d48..f518ce5 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright 2011-2017 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2011-2018 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
 #include <openssl/err.h>
 #include <openssl/rand.h>
 #include "rand_lcl.h"
+#include "internal/thread_once.h"
+#include "internal/rand_int.h"
+#include "internal/cryptlib_int.h"
 
 /*
- * Support framework for NIST SP 800-90A DRBG, AES-CTR mode.
- * The RAND_DRBG is OpenSSL's pointer to an instance of the DRBG.
+ * Support framework for NIST SP 800-90A DRBG
+ *
+ * See manual page RAND_DRBG(7) for a general overview.
  *
  * The OpenSSL model is to have new and free functions, and that new
  * does all initialization.  That is not the NIST model, which has
  */
 
 /*
- * Set/initialize |drbg| to be of type |nid|, with optional |flags|.
- * Return -2 if the type is not supported, 1 on success and -1 on
- * failure.
+ * The three shared DRBG instances
+ *
+ * There are three shared DRBG instances: <master>, <public>, and <private>.
+ */
+
+/*
+ * The <master> DRBG
+ *
+ * Not used directly by the application, only for reseeding the two other
+ * DRBGs. It reseeds itself by pulling either randomness from os entropy
+ * sources or by consuming randomness which was added by RAND_add().
+ *
+ * The <master> DRBG is a global instance which is accessed concurrently by
+ * all threads. The necessary locking is managed automatically by its child
+ * DRBG instances during reseeding.
+ */
+static RAND_DRBG *master_drbg;
+/*
+ * The <public> DRBG
+ *
+ * Used by default for generating random bytes using RAND_bytes().
+ *
+ * The <public> DRBG is thread-local, i.e., there is one instance per thread.
+ */
+static CRYPTO_THREAD_LOCAL public_drbg;
+/*
+ * The <private> DRBG
+ *
+ * Used by default for generating private keys using RAND_priv_bytes()
+ *
+ * The <private> DRBG is thread-local, i.e., there is one instance per thread.
+ */
+static CRYPTO_THREAD_LOCAL private_drbg;
+
+
+
+/* NIST SP 800-90A DRBG recommends the use of a personalization string. */
+static const char ossl_pers_string[] = "OpenSSL NIST SP 800-90A DRBG";
+
+static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;
+
+
+#define RAND_DRBG_TYPE_FLAGS    ( \
+    RAND_DRBG_FLAG_MASTER | RAND_DRBG_FLAG_PUBLIC | RAND_DRBG_FLAG_PRIVATE )
+
+#define RAND_DRBG_TYPE_MASTER                     0
+#define RAND_DRBG_TYPE_PUBLIC                     1
+#define RAND_DRBG_TYPE_PRIVATE                    2
+
+/* Defaults */
+static int rand_drbg_type[3] = {
+    RAND_DRBG_TYPE, /* Master */
+    RAND_DRBG_TYPE, /* Public */
+    RAND_DRBG_TYPE  /* Private */
+};
+static unsigned int rand_drbg_flags[3] = {
+    RAND_DRBG_FLAGS | RAND_DRBG_FLAG_MASTER, /* Master */
+    RAND_DRBG_FLAGS | RAND_DRBG_FLAG_PUBLIC, /* Public */
+    RAND_DRBG_FLAGS | RAND_DRBG_FLAG_PRIVATE /* Private */
+};
+
+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;
+
+/* A logical OR of all used DRBG flag bits (currently there is only one) */
+static const unsigned int rand_drbg_used_flags =
+    RAND_DRBG_FLAG_CTR_NO_DF | RAND_DRBG_FLAG_HMAC | RAND_DRBG_TYPE_FLAGS;
+
+
+static RAND_DRBG *drbg_setup(RAND_DRBG *parent, int drbg_type);
+
+static RAND_DRBG *rand_drbg_new(int secure,
+                                int type,
+                                unsigned int flags,
+                                RAND_DRBG *parent);
+
+static int is_ctr(int type)
+{
+    switch (type) {
+    case NID_aes_128_ctr:
+    case NID_aes_192_ctr:
+    case NID_aes_256_ctr:
+        return 1;
+    default:
+        return 0;
+    }
+}
+
+static int is_digest(int type)
+{
+    switch (type) {
+    case NID_sha1:
+    case NID_sha224:
+    case NID_sha256:
+    case NID_sha384:
+    case NID_sha512:
+    case NID_sha512_224:
+    case NID_sha512_256:
+    case NID_sha3_224:
+    case NID_sha3_256:
+    case NID_sha3_384:
+    case NID_sha3_512:
+        return 1;
+    default:
+        return 0;
+    }
+}
+
+/*
+ * Set/initialize |drbg| to be of type |type|, with optional |flags|.
+ *
+ * If |type| and |flags| are zero, use the defaults
+ *
+ * Returns 1 on success, 0 on failure.
  */
-int RAND_DRBG_set(RAND_DRBG *drbg, int nid, unsigned int flags)
+int RAND_DRBG_set(RAND_DRBG *drbg, int type, unsigned int flags)
 {
     int ret = 1;
 
+    if (type == 0 && flags == 0) {
+        type = rand_drbg_type[RAND_DRBG_TYPE_MASTER];
+        flags = rand_drbg_flags[RAND_DRBG_TYPE_MASTER];
+    }
+
+    /* If set is called multiple times - clear the old one */
+    if (drbg->type != 0 && (type != drbg->type || flags != drbg->flags)) {
+        drbg->meth->uninstantiate(drbg);
+        rand_pool_free(drbg->adin_pool);
+        drbg->adin_pool = NULL;
+    }
+
     drbg->state = DRBG_UNINITIALISED;
     drbg->flags = flags;
-    drbg->nid = nid;
+    drbg->type = type;
 
-    switch (nid) {
-    default:
-        RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
-        return -2;
-    case 0:
+    if (type == 0) {
         /* Uninitialized; that's okay. */
+        drbg->meth = NULL;
         return 1;
-    case NID_aes_128_ctr:
-    case NID_aes_192_ctr:
-    case NID_aes_256_ctr:
-        ret = ctr_init(drbg);
-        break;
+    } else if (is_ctr(type)) {
+        ret = drbg_ctr_init(drbg);
+    } else if (is_digest(type)) {
+        if (flags & RAND_DRBG_FLAG_HMAC)
+            ret = drbg_hmac_init(drbg);
+        else
+            ret = drbg_hash_init(drbg);
+    } else {
+        drbg->type = 0;
+        drbg->flags = 0;
+        drbg->meth = NULL;
+        RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
+        return 0;
     }
 
-    if (ret < 0)
+    if (ret == 0) {
+        drbg->state = DRBG_ERROR;
         RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_ERROR_INITIALISING_DRBG);
+    }
     return ret;
 }
 
 /*
- * Allocate memory and initialize a new DRBG.  The |parent|, if not
- * NULL, will be used to auto-seed this RAND_DRBG as needed.
+ * Set/initialize default |type| and |flag| for new drbg instances.
+ *
+ * Returns 1 on success, 0 on failure.
  */
-RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
+int RAND_DRBG_set_defaults(int type, unsigned int flags)
 {
-    RAND_DRBG *drbg = OPENSSL_zalloc(sizeof(*drbg));
-    unsigned char *ucp = OPENSSL_zalloc(RANDOMNESS_NEEDED);
+    int all;
+    if (!(is_digest(type) || is_ctr(type))) {
+        RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_TYPE);
+        return 0;
+    }
+
+    if ((flags & ~rand_drbg_used_flags) != 0) {
+        RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_FLAGS);
+        return 0;
+    }
+
+    all = ((flags & RAND_DRBG_TYPE_FLAGS) == 0);
+    if (all || (flags & RAND_DRBG_FLAG_MASTER) != 0) {
+        rand_drbg_type[RAND_DRBG_TYPE_MASTER] = type;
+        rand_drbg_flags[RAND_DRBG_TYPE_MASTER] = flags | RAND_DRBG_FLAG_MASTER;
+    }
+    if (all || (flags & RAND_DRBG_FLAG_PUBLIC) != 0) {
+        rand_drbg_type[RAND_DRBG_TYPE_PUBLIC]  = type;
+        rand_drbg_flags[RAND_DRBG_TYPE_PUBLIC] = flags | RAND_DRBG_FLAG_PUBLIC;
+    }
+    if (all || (flags & RAND_DRBG_FLAG_PRIVATE) != 0) {
+        rand_drbg_type[RAND_DRBG_TYPE_PRIVATE] = type;
+        rand_drbg_flags[RAND_DRBG_TYPE_PRIVATE] = flags | RAND_DRBG_FLAG_PRIVATE;
+    }
+    return 1;
+}
 
-    if (drbg == NULL || ucp == NULL) {
+
+/*
+ * Allocate memory and initialize a new DRBG. The DRBG is allocated on
+ * the secure heap if |secure| is nonzero and the secure heap is enabled.
+ * The |parent|, if not NULL, will be used as random source for reseeding.
+ *
+ * Returns a pointer to the new DRBG instance on success, NULL on failure.
+ */
+static RAND_DRBG *rand_drbg_new(int secure,
+                                int type,
+                                unsigned int flags,
+                                RAND_DRBG *parent)
+{
+    RAND_DRBG *drbg = secure ?
+        OPENSSL_secure_zalloc(sizeof(*drbg)) : OPENSSL_zalloc(sizeof(*drbg));
+
+    if (drbg == NULL) {
         RANDerr(RAND_F_RAND_DRBG_NEW, ERR_R_MALLOC_FAILURE);
-        goto err;
+        return NULL;
     }
-    drbg->size = RANDOMNESS_NEEDED;
-    drbg->randomness = ucp;
+
+    drbg->secure = secure && CRYPTO_secure_allocated(drbg);
     drbg->fork_count = rand_fork_count;
     drbg->parent = parent;
-    if (RAND_DRBG_set(drbg, type, flags) < 0)
+
+    if (parent == NULL) {
+        drbg->get_entropy = rand_drbg_get_entropy;
+        drbg->cleanup_entropy = rand_drbg_cleanup_entropy;
+#ifndef RAND_DRBG_GET_RANDOM_NONCE
+        drbg->get_nonce = rand_drbg_get_nonce;
+        drbg->cleanup_nonce = rand_drbg_cleanup_nonce;
+#endif
+
+        drbg->reseed_interval = master_reseed_interval;
+        drbg->reseed_time_interval = master_reseed_time_interval;
+    } else {
+        drbg->get_entropy = rand_drbg_get_entropy;
+        drbg->cleanup_entropy = rand_drbg_cleanup_entropy;
+        /*
+         * Do not provide nonce callbacks, the child DRBGs will
+         * obtain their nonce using random bits from the parent.
+         */
+
+        drbg->reseed_interval = slave_reseed_interval;
+        drbg->reseed_time_interval = slave_reseed_time_interval;
+    }
+
+    if (RAND_DRBG_set(drbg, type, flags) == 0)
         goto err;
 
     if (parent != NULL) {
-        if (parent->state == DRBG_UNINITIALISED
-                && RAND_DRBG_instantiate(parent, NULL, 0) == 0)
-            goto err;
-        if (!RAND_DRBG_set_callbacks(drbg, drbg_entropy_from_parent,
-                                     drbg_release_entropy,
-                                     NULL, NULL)
-                /*
-                 * Add in our address.  Note we are adding the pointer
-                 * itself, not its contents!
-                 */
-                || !RAND_DRBG_instantiate(drbg,
-                                          (unsigned char*)&drbg, sizeof(drbg)))
+        rand_drbg_lock(parent);
+        if (drbg->strength > parent->strength) {
+            /*
+             * We currently don't support the algorithm from NIST SP 800-90C
+             * 10.1.2 to use a weaker DRBG as source
+             */
+            rand_drbg_unlock(parent);
+            RANDerr(RAND_F_RAND_DRBG_NEW, RAND_R_PARENT_STRENGTH_TOO_WEAK);
             goto err;
+        }
+        rand_drbg_unlock(parent);
     }
 
     return drbg;
 
-err:
-    OPENSSL_free(ucp);
-    OPENSSL_free(drbg);
+ err:
+    if (drbg->secure)
+        OPENSSL_secure_free(drbg);
+    else
+        OPENSSL_free(drbg);
+
     return NULL;
 }
 
-RAND_DRBG *RAND_DRBG_get0_global(void)
+RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
+{
+    return rand_drbg_new(0, type, flags, parent);
+}
+
+RAND_DRBG *RAND_DRBG_secure_new(int type, unsigned int flags, RAND_DRBG *parent)
 {
-    return &rand_drbg;
+    return rand_drbg_new(1, type, flags, parent);
 }
 
 /*
@@ -111,32 +318,50 @@ RAND_DRBG *RAND_DRBG_get0_global(void)
  */
 void RAND_DRBG_free(RAND_DRBG *drbg)
 {
-    /* The global DRBG is free'd by rand_cleanup_int() */
-    if (drbg == NULL || drbg == &rand_drbg)
+    if (drbg == NULL)
         return;
 
-    ctr_uninstantiate(drbg);
-    OPENSSL_cleanse(drbg->randomness, drbg->size);
-    OPENSSL_free(drbg->randomness);
+    if (drbg->meth != NULL)
+        drbg->meth->uninstantiate(drbg);
+    rand_pool_free(drbg->adin_pool);
+    CRYPTO_THREAD_lock_free(drbg->lock);
     CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);
-    OPENSSL_clear_free(drbg, sizeof(*drbg));
+
+    if (drbg->secure)
+        OPENSSL_secure_clear_free(drbg, sizeof(*drbg));
+    else
+        OPENSSL_clear_free(drbg, sizeof(*drbg));
 }
 
 /*
  * Instantiate |drbg|, after it has been initialized.  Use |pers| and
  * |perslen| as prediction-resistance input.
+ *
+ * Requires that drbg->lock is already locked for write, if non-null.
+ *
+ * Returns 1 on success, 0 on failure.
  */
 int RAND_DRBG_instantiate(RAND_DRBG *drbg,
                           const unsigned char *pers, size_t perslen)
 {
     unsigned char *nonce = NULL, *entropy = NULL;
-    size_t noncelen = 0, entlen = 0;
+    size_t noncelen = 0, entropylen = 0;
+    size_t min_entropy = drbg->strength;
+    size_t min_entropylen = drbg->min_entropylen;
+    size_t max_entropylen = drbg->max_entropylen;
 
-    if (perslen > drbg->max_pers) {
+    if (perslen > drbg->max_perslen) {
         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
                 RAND_R_PERSONALISATION_STRING_TOO_LONG);
         goto end;
     }
+
+    if (drbg->meth == NULL) {
+        RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
+                RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
+        goto end;
+    }
+
     if (drbg->state != DRBG_UNINITIALISED) {
         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
                 drbg->state == DRBG_ERROR ? RAND_R_IN_ERROR_STATE
@@ -145,37 +370,60 @@ int RAND_DRBG_instantiate(RAND_DRBG *drbg,
     }
 
     drbg->state = DRBG_ERROR;
+
+    /*
+     * NIST SP800-90Ar1 section 9.1 says you can combine getting the entropy
+     * and nonce in 1 call by increasing the entropy with 50% and increasing
+     * the minimum length to accomadate the length of the nonce.
+     * We do this in case a nonce is require and get_nonce is NULL.
+     */
+    if (drbg->min_noncelen > 0 && drbg->get_nonce == NULL) {
+        min_entropy += drbg->strength / 2;
+        min_entropylen += drbg->min_noncelen;
+        max_entropylen += drbg->max_noncelen;
+    }
+
+    drbg->reseed_next_counter = tsan_load(&drbg->reseed_prop_counter);
+    if (drbg->reseed_next_counter) {
+        drbg->reseed_next_counter++;
+        if(!drbg->reseed_next_counter)
+            drbg->reseed_next_counter = 1;
+    }
+
     if (drbg->get_entropy != NULL)
-        entlen = drbg->get_entropy(drbg, &entropy, drbg->strength,
-                                   drbg->min_entropy, drbg->max_entropy);
-    if (entlen < drbg->min_entropy || entlen > drbg->max_entropy) {
+        entropylen = drbg->get_entropy(drbg, &entropy, min_entropy,
+                                       min_entropylen, max_entropylen, 0);
+    if (entropylen < min_entropylen
+            || entropylen > max_entropylen) {
         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_ENTROPY);
         goto end;
     }
 
-    if (drbg->max_nonce > 0 && drbg->get_nonce != NULL) {
+    if (drbg->min_noncelen > 0 && drbg->get_nonce != NULL) {
         noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
-                                   drbg->min_nonce, drbg->max_nonce);
-        if (noncelen < drbg->min_nonce || noncelen > drbg->max_nonce) {
+                                   drbg->min_noncelen, drbg->max_noncelen);
+        if (noncelen < drbg->min_noncelen || noncelen > drbg->max_noncelen) {
             RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_RETRIEVING_NONCE);
             goto end;
         }
     }
 
-    if (!ctr_instantiate(drbg, entropy, entlen,
+    if (!drbg->meth->instantiate(drbg, entropy, entropylen,
                          nonce, noncelen, pers, perslen)) {
         RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ERROR_INSTANTIATING_DRBG);
         goto end;
     }
 
     drbg->state = DRBG_READY;
-    drbg->reseed_counter = 1;
+    drbg->reseed_gen_counter = 1;
+    drbg->reseed_time = time(NULL);
+    tsan_store(&drbg->reseed_prop_counter, drbg->reseed_next_counter);
 
-end:
+ end:
     if (entropy != NULL && drbg->cleanup_entropy != NULL)
-        drbg->cleanup_entropy(drbg, entropy);
-    if (nonce != NULL && drbg->cleanup_nonce!= NULL )
-        drbg->cleanup_nonce(drbg, nonce);
+        drbg->cleanup_entropy(drbg, entropy, entropylen);
+    if (nonce != NULL && drbg->cleanup_nonce != NULL)
+        drbg->cleanup_nonce(drbg, nonce, noncelen);
     if (drbg->state == DRBG_READY)
         return 1;
     return 0;
@@ -183,24 +431,57 @@ end:
 
 /*
  * Uninstantiate |drbg|. Must be instantiated before it can be used.
+ *
+ * Requires that drbg->lock is already locked for write, if non-null.
+ *
+ * Returns 1 on success, 0 on failure.
  */
 int RAND_DRBG_uninstantiate(RAND_DRBG *drbg)
 {
-    int ret = ctr_uninstantiate(drbg);
+    int index = -1, type, flags;
+    if (drbg->meth == NULL) {
+        RANDerr(RAND_F_RAND_DRBG_UNINSTANTIATE,
+                RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
+        return 0;
+    }
 
-    OPENSSL_cleanse(&drbg->ctr, sizeof(drbg->ctr));
-    drbg->state = DRBG_UNINITIALISED;
-    return ret;
+    /* Clear the entire drbg->ctr struct, then reset some important
+     * members of the drbg->ctr struct (e.g. keysize, df_ks) to their
+     * initial values.
+     */
+    drbg->meth->uninstantiate(drbg);
+
+    /* The reset uses the default values for type and flags */
+    if (drbg->flags & RAND_DRBG_FLAG_MASTER)
+        index = RAND_DRBG_TYPE_MASTER;
+    else if (drbg->flags & RAND_DRBG_FLAG_PRIVATE)
+        index = RAND_DRBG_TYPE_PRIVATE;
+    else if (drbg->flags & RAND_DRBG_FLAG_PUBLIC)
+        index = RAND_DRBG_TYPE_PUBLIC;
+
+    if (index != -1) {
+        flags = rand_drbg_flags[index];
+        type = rand_drbg_type[index];
+    } else {
+        flags = drbg->flags;
+        type = drbg->type;
+    }
+    return RAND_DRBG_set(drbg, type, flags);
 }
 
 /*
- * Mix in the specified data to reseed |drbg|.
+ * Reseed |drbg|, mixing in the specified data
+ *
+ * Requires that drbg->lock is already locked for write, if non-null.
+ *
+ * Returns 1 on success, 0 on failure.
  */
 int RAND_DRBG_reseed(RAND_DRBG *drbg,
-                     const unsigned char *adin, size_t adinlen)
+                     const unsigned char *adin, size_t adinlen,
+                     int prediction_resistance)
 {
     unsigned char *entropy = NULL;
-    size_t entlen = 0;
+    size_t entropylen = 0;
 
     if (drbg->state == DRBG_ERROR) {
         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
@@ -211,71 +492,214 @@ int RAND_DRBG_reseed(RAND_DRBG *drbg,
         return 0;
     }
 
-    if (adin == NULL)
+    if (adin == NULL) {
         adinlen = 0;
-    else if (adinlen > drbg->max_adin) {
+    } else if (adinlen > drbg->max_adinlen) {
         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
         return 0;
     }
 
     drbg->state = DRBG_ERROR;
+
+    drbg->reseed_next_counter = tsan_load(&drbg->reseed_prop_counter);
+    if (drbg->reseed_next_counter) {
+        drbg->reseed_next_counter++;
+        if(!drbg->reseed_next_counter)
+            drbg->reseed_next_counter = 1;
+    }
+
     if (drbg->get_entropy != NULL)
-        entlen = drbg->get_entropy(drbg, &entropy, drbg->strength,
-                                   drbg->min_entropy, drbg->max_entropy);
-    if (entlen < drbg->min_entropy || entlen > drbg->max_entropy) {
+        entropylen = drbg->get_entropy(drbg, &entropy, drbg->strength,
+                                       drbg->min_entropylen,
+                                       drbg->max_entropylen,
+                                       prediction_resistance);
+    if (entropylen < drbg->min_entropylen
+            || entropylen > drbg->max_entropylen) {
         RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_ERROR_RETRIEVING_ENTROPY);
         goto end;
     }
 
-    if (!ctr_reseed(drbg, entropy, entlen, adin, adinlen))
+    if (!drbg->meth->reseed(drbg, entropy, entropylen, adin, adinlen))
         goto end;
+
     drbg->state = DRBG_READY;
-    drbg->reseed_counter = 1;
+    drbg->reseed_gen_counter = 1;
+    drbg->reseed_time = time(NULL);
+    tsan_store(&drbg->reseed_prop_counter, drbg->reseed_next_counter);
 
-end:
+ end:
     if (entropy != NULL && drbg->cleanup_entropy != NULL)
-        drbg->cleanup_entropy(drbg, entropy);
+        drbg->cleanup_entropy(drbg, entropy, entropylen);
     if (drbg->state == DRBG_READY)
         return 1;
     return 0;
 }
 
+/*
+ * Restart |drbg|, using the specified entropy or additional input
+ *
+ * Tries its best to get the drbg instantiated by all means,
+ * regardless of its current state.
+ *
+ * Optionally, a |buffer| of |len| random bytes can be passed,
+ * which is assumed to contain at least |entropy| bits of entropy.
+ *
+ * If |entropy| > 0, the buffer content is used as entropy input.
+ *
+ * If |entropy| == 0, the buffer content is used as additional input
+ *
+ * Returns 1 on success, 0 on failure.
+ *
+ * This function is used internally only.
+ */
+int rand_drbg_restart(RAND_DRBG *drbg,
+                      const unsigned char *buffer, size_t len, size_t entropy)
+{
+    int reseeded = 0;
+    const unsigned char *adin = NULL;
+    size_t adinlen = 0;
+
+    if (drbg->pool != NULL) {
+        RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
+        drbg->state = DRBG_ERROR;
+        rand_pool_free(drbg->pool);
+        drbg->pool = NULL;
+        return 0;
+    }
+
+    if (buffer != NULL) {
+        if (entropy > 0) {
+            if (drbg->max_entropylen < len) {
+                RANDerr(RAND_F_RAND_DRBG_RESTART,
+                    RAND_R_ENTROPY_INPUT_TOO_LONG);
+                drbg->state = DRBG_ERROR;
+                return 0;
+            }
+
+            if (entropy > 8 * len) {
+                RANDerr(RAND_F_RAND_DRBG_RESTART, RAND_R_ENTROPY_OUT_OF_RANGE);
+                drbg->state = DRBG_ERROR;
+                return 0;
+            }
+
+            /* will be picked up by the rand_drbg_get_entropy() callback */
+            drbg->pool = rand_pool_attach(buffer, len, entropy);
+            if (drbg->pool == NULL)
+                return 0;
+        } else {
+            if (drbg->max_adinlen < len) {
+                RANDerr(RAND_F_RAND_DRBG_RESTART,
+                        RAND_R_ADDITIONAL_INPUT_TOO_LONG);
+                drbg->state = DRBG_ERROR;
+                return 0;
+            }
+            adin = buffer;
+            adinlen = len;
+        }
+    }
+
+    /* repair error state */
+    if (drbg->state == DRBG_ERROR)
+        RAND_DRBG_uninstantiate(drbg);
+
+    /* repair uninitialized state */
+    if (drbg->state == DRBG_UNINITIALISED) {
+        /* reinstantiate drbg */
+        RAND_DRBG_instantiate(drbg,
+                              (const unsigned char *) ossl_pers_string,
+                              sizeof(ossl_pers_string) - 1);
+        /* already reseeded. prevent second reseeding below */
+        reseeded = (drbg->state == DRBG_READY);
+    }
+
+    /* refresh current state if entropy or additional input has been provided */
+    if (drbg->state == DRBG_READY) {
+        if (adin != NULL) {
+            /*
+             * mix in additional input without reseeding
+             *
+             * Similar to RAND_DRBG_reseed(), but the provided additional
+             * data |adin| is mixed into the current state without pulling
+             * entropy from the trusted entropy source using get_entropy().
+             * This is not a reseeding in the strict sense of NIST SP 800-90A.
+             */
+            drbg->meth->reseed(drbg, adin, adinlen, NULL, 0);
+        } else if (reseeded == 0) {
+            /* do a full reseeding if it has not been done yet above */
+            RAND_DRBG_reseed(drbg, NULL, 0, 0);
+        }
+    }
+
+    rand_pool_free(drbg->pool);
+    drbg->pool = NULL;
+
+    return drbg->state == DRBG_READY;
+}
+
 /*
  * Generate |outlen| bytes into the buffer at |out|.  Reseed if we need
  * to or if |prediction_resistance| is set.  Additional input can be
  * sent in |adin| and |adinlen|.
+ *
+ * Requires that drbg->lock is already locked for write, if non-null.
+ *
+ * Returns 1 on success, 0 on failure.
+ *
  */
 int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
                        int prediction_resistance,
                        const unsigned char *adin, size_t adinlen)
 {
-    if (drbg->state == DRBG_ERROR) {
-        RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
-        return 0;
-    }
-    if (drbg->state == DRBG_UNINITIALISED) {
-        RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
-        return 0;
+    int reseed_required = 0;
+
+    if (drbg->state != DRBG_READY) {
+        /* try to recover from previous errors */
+        rand_drbg_restart(drbg, NULL, 0, 0);
+
+        if (drbg->state == DRBG_ERROR) {
+            RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_IN_ERROR_STATE);
+            return 0;
+        }
+        if (drbg->state == DRBG_UNINITIALISED) {
+            RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_NOT_INSTANTIATED);
+            return 0;
+        }
     }
+
     if (outlen > drbg->max_request) {
         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_REQUEST_TOO_LARGE_FOR_DRBG);
         return 0;
     }
-    if (adinlen > drbg->max_adin) {
+    if (adinlen > drbg->max_adinlen) {
         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
         return 0;
     }
 
     if (drbg->fork_count != rand_fork_count) {
         drbg->fork_count = rand_fork_count;
-        drbg->state = DRBG_RESEED;
+        reseed_required = 1;
     }
 
-    if (drbg->reseed_counter >= drbg->reseed_interval)
-        drbg->state = DRBG_RESEED;
+    if (drbg->reseed_interval > 0) {
+        if (drbg->reseed_gen_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->parent != NULL) {
+        unsigned int reseed_counter = tsan_load(&drbg->reseed_prop_counter);
+        if (reseed_counter > 0
+                && tsan_load(&drbg->parent->reseed_prop_counter)
+                   != reseed_counter)
+            reseed_required = 1;
+    }
 
-    if (drbg->state == DRBG_RESEED || prediction_resistance) {
-        if (!RAND_DRBG_reseed(drbg, adin, adinlen)) {
+    if (reseed_required || prediction_resistance) {
+        if (!RAND_DRBG_reseed(drbg, adin, adinlen, prediction_resistance)) {
             RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_RESEED_ERROR);
             return 0;
         }
@@ -283,49 +707,214 @@ int RAND_DRBG_generate(RAND_DRBG *drbg, unsigned char *out, size_t outlen,
         adinlen = 0;
     }
 
-    if (!ctr_generate(drbg, out, outlen, adin, adinlen)) {
+    if (!drbg->meth->generate(drbg, out, outlen, adin, adinlen)) {
         drbg->state = DRBG_ERROR;
         RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_GENERATE_ERROR);
         return 0;
     }
 
-    if (drbg->reseed_counter >= drbg->reseed_interval)
-        drbg->state = DRBG_RESEED;
-    else
-        drbg->reseed_counter++;
+    drbg->reseed_gen_counter++;
+
     return 1;
 }
 
 /*
- * Set the callbacks for entropy and nonce.  We currently don't use
- * the nonce; that's mainly for the KATs
+ * Generates |outlen| random bytes and stores them in |out|. It will
+ * using the given |drbg| to generate the bytes.
+ *
+ * Requires that drbg->lock is already locked for write, if non-null.
+ *
+ * Returns 1 on success 0 on failure.
+ */
+int RAND_DRBG_bytes(RAND_DRBG *drbg, unsigned char *out, size_t outlen)
+{
+    unsigned char *additional = NULL;
+    size_t additional_len;
+    size_t chunk;
+    size_t ret = 0;
+
+    if (drbg->adin_pool == NULL) {
+        if (drbg->type == 0)
+            goto err;
+        drbg->adin_pool = rand_pool_new(0, 0, drbg->max_adinlen);
+        if (drbg->adin_pool == NULL)
+            goto err;
+    }
+
+    additional_len = rand_drbg_get_additional_data(drbg->adin_pool,
+                                                   &additional);
+
+    for ( ; outlen > 0; outlen -= chunk, out += chunk) {
+        chunk = outlen;
+        if (chunk > drbg->max_request)
+            chunk = drbg->max_request;
+        ret = RAND_DRBG_generate(drbg, out, chunk, 0, additional, additional_len);
+        if (!ret)
+            goto err;
+    }
+    ret = 1;
+
+ err:
+    if (additional != NULL)
+        rand_drbg_cleanup_additional_data(drbg->adin_pool, additional);
+
+    return ret;
+}
+
+/*
+ * Set the RAND_DRBG callbacks for obtaining entropy and nonce.
+ *
+ * Setting the callbacks is allowed only if the drbg has not been
+ * initialized yet. Otherwise, the operation will fail.
+ *
+ * Returns 1 on success, 0 on failure.
  */
 int RAND_DRBG_set_callbacks(RAND_DRBG *drbg,
-                            RAND_DRBG_get_entropy_fn cb_get_entropy,
-                            RAND_DRBG_cleanup_entropy_fn cb_cleanup_entropy,
-                            RAND_DRBG_get_nonce_fn cb_get_nonce,
-                            RAND_DRBG_cleanup_nonce_fn cb_cleanup_nonce)
+                            RAND_DRBG_get_entropy_fn get_entropy,
+                            RAND_DRBG_cleanup_entropy_fn cleanup_entropy,
+                            RAND_DRBG_get_nonce_fn get_nonce,
+                            RAND_DRBG_cleanup_nonce_fn cleanup_nonce)
 {
-    if (drbg->state != DRBG_UNINITIALISED)
+    if (drbg->state != DRBG_UNINITIALISED
+            || drbg->parent != NULL)
         return 0;
-    drbg->get_entropy = cb_get_entropy;
-    drbg->cleanup_entropy = cb_cleanup_entropy;
-    drbg->get_nonce = cb_get_nonce;
-    drbg->cleanup_nonce = cb_cleanup_nonce;
+    drbg->get_entropy = get_entropy;
+    drbg->cleanup_entropy = cleanup_entropy;
+    drbg->get_nonce = get_nonce;
+    drbg->cleanup_nonce = cleanup_nonce;
     return 1;
 }
 
 /*
  * Set the reseed interval.
+ *
+ * The drbg will reseed automatically whenever the number of generate
+ * requests exceeds the given reseed interval. If the reseed interval
+ * is 0, then this feature is disabled.
+ *
+ * Returns 1 on success, 0 on failure.
  */
-int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, int interval)
+int RAND_DRBG_set_reseed_interval(RAND_DRBG *drbg, unsigned int interval)
 {
-    if (interval < 0 || interval > MAX_RESEED)
+    if (interval > MAX_RESEED_INTERVAL)
         return 0;
     drbg->reseed_interval = interval;
     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;
+}
+
+/*
+ * 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
+ * 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;
+}
+
 /*
  * Get and set the EXDATA
  */
@@ -345,73 +934,292 @@ void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
  * global DRBG.  They lock.
  */
 
-static int drbg_bytes(unsigned char *out, int count)
+/*
+ * Allocates a new global DRBG on the secure heap (if enabled) and
+ * initializes it with default settings.
+ *
+ * Returns a pointer to the new DRBG instance on success, NULL on failure.
+ */
+static RAND_DRBG *drbg_setup(RAND_DRBG *parent, int drbg_type)
 {
-    int ret = 0;
-    size_t chunk;
+    RAND_DRBG *drbg;
 
-    CRYPTO_THREAD_write_lock(rand_drbg.lock);
-    if (rand_drbg.state == DRBG_UNINITIALISED
-            && RAND_DRBG_instantiate(&rand_drbg, NULL, 0) == 0)
+    drbg = RAND_DRBG_secure_new(rand_drbg_type[drbg_type],
+                                rand_drbg_flags[drbg_type], parent);
+    if (drbg == NULL)
+        return NULL;
+
+    /* Only the master DRBG needs to have a lock */
+    if (parent == NULL && rand_drbg_enable_locking(drbg) == 0)
         goto err;
 
-    for ( ; count > 0; count -= chunk, out += chunk) {
-        chunk = count;
-        if (chunk > rand_drbg.max_request)
-            chunk = rand_drbg.max_request;
-        ret = RAND_DRBG_generate(&rand_drbg, out, chunk, 0, NULL, 0);
-        if (!ret)
-            goto err;
-    }
-    ret = 1;
+    /* enable seed propagation */
+    tsan_store(&drbg->reseed_prop_counter, 1);
+
+    /*
+     * Ignore instantiation error to support just-in-time instantiation.
+     *
+     * The state of the drbg will be checked in RAND_DRBG_generate() and
+     * an automatic recovery is attempted.
+     */
+    (void)RAND_DRBG_instantiate(drbg,
+                                (const unsigned char *) ossl_pers_string,
+                                sizeof(ossl_pers_string) - 1);
+    return drbg;
 
 err:
-    CRYPTO_THREAD_unlock(rand_drbg.lock);
+    RAND_DRBG_free(drbg);
+    return NULL;
+}
+
+/*
+ * Initialize the global DRBGs on first use.
+ * Returns 1 on success, 0 on failure.
+ */
+DEFINE_RUN_ONCE_STATIC(do_rand_drbg_init)
+{
+    /*
+     * ensure that libcrypto is initialized, otherwise the
+     * DRBG locks are not cleaned up properly
+     */
+    if (!OPENSSL_init_crypto(0, NULL))
+        return 0;
+
+    if (!CRYPTO_THREAD_init_local(&private_drbg, NULL))
+        return 0;
+
+    if (!CRYPTO_THREAD_init_local(&public_drbg, NULL))
+        goto err1;
+
+    master_drbg = drbg_setup(NULL, RAND_DRBG_TYPE_MASTER);
+    if (master_drbg == NULL)
+        goto err2;
+
+    return 1;
+
+err2:
+    CRYPTO_THREAD_cleanup_local(&public_drbg);
+err1:
+    CRYPTO_THREAD_cleanup_local(&private_drbg);
+    return 0;
+}
+
+/* Clean up the global DRBGs before exit */
+void rand_drbg_cleanup_int(void)
+{
+    if (master_drbg != NULL) {
+        RAND_DRBG_free(master_drbg);
+        master_drbg = NULL;
+
+        CRYPTO_THREAD_cleanup_local(&private_drbg);
+        CRYPTO_THREAD_cleanup_local(&public_drbg);
+    }
+}
+
+void drbg_delete_thread_state(void)
+{
+    RAND_DRBG *drbg;
+
+    drbg = CRYPTO_THREAD_get_local(&public_drbg);
+    CRYPTO_THREAD_set_local(&public_drbg, NULL);
+    RAND_DRBG_free(drbg);
+
+    drbg = CRYPTO_THREAD_get_local(&private_drbg);
+    CRYPTO_THREAD_set_local(&private_drbg, NULL);
+    RAND_DRBG_free(drbg);
+}
+
+/* Implements the default OpenSSL RAND_bytes() method */
+static int drbg_bytes(unsigned char *out, int count)
+{
+    int ret;
+    RAND_DRBG *drbg = RAND_DRBG_get0_public();
+
+    if (drbg == NULL)
+        return 0;
+
+    ret = RAND_DRBG_bytes(drbg, out, count);
+
     return ret;
 }
 
+/*
+ * Calculates the minimum length of a full entropy buffer
+ * which is necessary to seed (i.e. instantiate) the DRBG
+ * successfully.
+ *
+ * NOTE: There is a copy of this function in drbgtest.c.
+ *       If you change anything here, you need to update
+ *       the copy accordingly.
+ */
+static size_t rand_drbg_seedlen(RAND_DRBG *drbg)
+{
+    /*
+     * If no os entropy source is available then RAND_seed(buffer, bufsize)
+     * is expected to succeed if and only if the buffer length satisfies
+     * the following requirements, which follow from the calculations
+     * in RAND_DRBG_instantiate().
+     */
+    size_t min_entropy = drbg->strength;
+    size_t min_entropylen = drbg->min_entropylen;
+
+    /*
+     * Extra entropy for the random nonce in the absence of a
+     * get_nonce callback, see comment in RAND_DRBG_instantiate().
+     */
+    if (drbg->min_noncelen > 0 && drbg->get_nonce == NULL) {
+        min_entropy += drbg->strength / 2;
+        min_entropylen += drbg->min_noncelen;
+    }
+
+    /*
+     * Convert entropy requirement from bits to bytes
+     * (dividing by 8 without rounding upwards, because
+     * all entropy requirements are divisible by 8).
+     */
+    min_entropy >>= 3;
+
+    /* Return a value that satisfies both requirements */
+    return min_entropy > min_entropylen ? min_entropy : min_entropylen;
+}
+
+/* Implements the default OpenSSL RAND_add() method */
 static int drbg_add(const void *buf, int num, double randomness)
 {
-    unsigned char *in = (unsigned char *)buf;
-    unsigned char *out, *end;
+    int ret = 0;
+    RAND_DRBG *drbg = RAND_DRBG_get0_master();
+    size_t buflen;
+    size_t seedlen;
+
+    if (drbg == NULL)
+        return 0;
+
+    if (num < 0 || randomness < 0.0)
+        return 0;
 
-    CRYPTO_THREAD_write_lock(rand_bytes.lock);
-    out = &rand_bytes.buff[rand_bytes.curr];
-    end = &rand_bytes.buff[rand_bytes.size];
+    rand_drbg_lock(drbg);
+    seedlen = rand_drbg_seedlen(drbg);
 
-    /* Copy whatever fits into the end of the buffer. */
-    for ( ; --num >= 0 && out < end; rand_bytes.curr++)
-        *out++ = *in++;
+    buflen = (size_t)num;
 
-    /* XOR any the leftover. */
-    while (num > 0) {
-        for (out = rand_bytes.buff; --num >= 0 && out < end; )
-            *out++ ^= *in++;
+    if (buflen < seedlen || randomness < (double) seedlen) {
+#if defined(OPENSSL_RAND_SEED_NONE)
+        /*
+         * If no os entropy source is available, a reseeding will fail
+         * inevitably. So we use a trick to mix the buffer contents into
+         * the DRBG state without forcing a reseeding: we generate a
+         * dummy random byte, using the buffer content as additional data.
+         * Note: This won't work with RAND_DRBG_FLAG_CTR_NO_DF.
+         */
+        unsigned char dummy[1];
+
+        ret = RAND_DRBG_generate(drbg, dummy, sizeof(dummy), 0, buf, buflen);
+        rand_drbg_unlock(drbg);
+        return ret;
+#else
+        /*
+         * If an os entropy source is avaible then we declare the buffer content
+         * as additional data by setting randomness to zero and trigger a regular
+         * reseeding.
+         */
+        randomness = 0.0;
+#endif
     }
 
-    CRYPTO_THREAD_unlock(rand_bytes.lock);
-    return 1;
+
+    if (randomness > (double)seedlen) {
+        /*
+         * The purpose of this check is to bound |randomness| by a
+         * relatively small value in order to prevent an integer
+         * overflow when multiplying by 8 in the rand_drbg_restart()
+         * call below. Note that randomness is measured in bytes,
+         * not bits, so this value corresponds to eight times the
+         * security strength.
+         */
+        randomness = (double)seedlen;
+    }
+
+    ret = rand_drbg_restart(drbg, buf, buflen, (size_t)(8 * randomness));
+    rand_drbg_unlock(drbg);
+
+    return ret;
 }
 
+/* Implements the default OpenSSL RAND_seed() method */
 static int drbg_seed(const void *buf, int num)
 {
     return drbg_add(buf, num, num);
 }
 
+/* Implements the default OpenSSL RAND_status() method */
 static int drbg_status(void)
 {
     int ret;
+    RAND_DRBG *drbg = RAND_DRBG_get0_master();
+
+    if (drbg == NULL)
+        return 0;
 
-    CRYPTO_THREAD_write_lock(rand_drbg.lock);
-    if (rand_drbg.state == DRBG_UNINITIALISED)
-        RAND_DRBG_instantiate(&rand_drbg, NULL, 0);
-    ret = rand_drbg.state == DRBG_READY ? 1 : 0;
-    CRYPTO_THREAD_unlock(rand_drbg.lock);
+    rand_drbg_lock(drbg);
+    ret = drbg->state == DRBG_READY ? 1 : 0;
+    rand_drbg_unlock(drbg);
     return ret;
 }
 
-RAND_DRBG rand_drbg; /* The default global DRBG. */
-RAND_DRBG priv_drbg; /* The global private-key DRBG. */
+/*
+ * Get the master DRBG.
+ * Returns pointer to the DRBG on success, NULL on failure.
+ *
+ */
+RAND_DRBG *RAND_DRBG_get0_master(void)
+{
+    if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
+        return NULL;
+
+    return master_drbg;
+}
+
+/*
+ * Get the public DRBG.
+ * Returns pointer to the DRBG on success, NULL on failure.
+ */
+RAND_DRBG *RAND_DRBG_get0_public(void)
+{
+    RAND_DRBG *drbg;
+
+    if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
+        return NULL;
+
+    drbg = CRYPTO_THREAD_get_local(&public_drbg);
+    if (drbg == NULL) {
+        if (!ossl_init_thread_start(OPENSSL_INIT_THREAD_RAND))
+            return NULL;
+        drbg = drbg_setup(master_drbg, RAND_DRBG_TYPE_PUBLIC);
+        CRYPTO_THREAD_set_local(&public_drbg, drbg);
+    }
+    return drbg;
+}
+
+/*
+ * Get the private DRBG.
+ * Returns pointer to the DRBG on success, NULL on failure.
+ */
+RAND_DRBG *RAND_DRBG_get0_private(void)
+{
+    RAND_DRBG *drbg;
+
+    if (!RUN_ONCE(&rand_drbg_init, do_rand_drbg_init))
+        return NULL;
+
+    drbg = CRYPTO_THREAD_get_local(&private_drbg);
+    if (drbg == NULL) {
+        if (!ossl_init_thread_start(OPENSSL_INIT_THREAD_RAND))
+            return NULL;
+        drbg = drbg_setup(master_drbg, RAND_DRBG_TYPE_PRIVATE);
+        CRYPTO_THREAD_set_local(&private_drbg, drbg);
+    }
+    return drbg;
+}
 
 RAND_METHOD rand_meth = {
     drbg_seed,