text: /*
   * Copyright 2011-2020 The OpenSSL Project Authors. All Rights Reserved.
   *
   * Licensed under the Apache License 2.0 (the "License").  You may not use
   * this file except in compliance with the License.  You can obtain a copy
   * in the file LICENSE in the source distribution or at
   * https://www.openssl.org/source/license.html
   */
  
  #include <string.h>
  #include <openssl/crypto.h>
  #include <openssl/err.h>
  #include <openssl/rand.h>
  #include "rand_local.h"
  #include "internal/thread_once.h"
  #include "crypto/rand.h"
  #include "crypto/cryptlib.h"
  
  /*
   * 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
   * instantiation and un-instantiate, and re-use within a new/free
   * lifecycle.  (No doubt this comes from the desire to support hardware
   * DRBG, where allocation of resources on something like an HSM is
   * a much bigger deal than just re-setting an allocated resource.)
   */
  
  
  typedef struct drbg_global_st {
      /*
       * 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.
       */
      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.
       */
      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.
       */
      CRYPTO_THREAD_LOCAL private_drbg;
  } DRBG_GLOBAL;
  
  typedef struct drbg_nonce_global_st {
      CRYPTO_RWLOCK *rand_nonce_lock;
      int rand_nonce_count;
  } DRBG_NONCE_GLOBAL;
  
  /* NIST SP 800-90A DRBG recommends the use of a personalization string. */
  static const char ossl_pers_string[] = DRBG_DEFAULT_PERS_STRING;
  
  #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(OPENSSL_CTX *ctx, RAND_DRBG *parent, int drbg_type);
  
  static RAND_DRBG *rand_drbg_new(OPENSSL_CTX *ctx,
                                  int secure,
                                  int type,
                                  unsigned int flags,
                                  RAND_DRBG *parent);
  
  static int rand_drbg_set(RAND_DRBG *drbg, int type, unsigned int flags);
  static int rand_drbg_init_method(RAND_DRBG *drbg);
  
  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;
      }
  }
  
  /*
   * Initialize the OPENSSL_CTX global DRBGs on first use.
   * Returns the allocated global data on success or NULL on failure.
   */
  static void *drbg_ossl_ctx_new(OPENSSL_CTX *libctx)
  {
      DRBG_GLOBAL *dgbl = OPENSSL_zalloc(sizeof(*dgbl));
  
      if (dgbl == NULL)
          return NULL;
  
  #ifndef FIPS_MODULE
      /*
       * We need to ensure that base libcrypto thread handling has been
       * initialised.
       */
       OPENSSL_init_crypto(0, NULL);
  #endif
  
      if (!CRYPTO_THREAD_init_local(&dgbl->private_drbg, NULL))
          goto err1;
  
      if (!CRYPTO_THREAD_init_local(&dgbl->public_drbg, NULL))
          goto err2;
  
      dgbl->master_drbg = drbg_setup(libctx, NULL, RAND_DRBG_TYPE_MASTER);
      if (dgbl->master_drbg == NULL)
          goto err3;
  
      return dgbl;
  
   err3:
      CRYPTO_THREAD_cleanup_local(&dgbl->public_drbg);
   err2:
      CRYPTO_THREAD_cleanup_local(&dgbl->private_drbg);
   err1:
      OPENSSL_free(dgbl);
      return NULL;
  }
  
  static void drbg_ossl_ctx_free(void *vdgbl)
  {
      DRBG_GLOBAL *dgbl = vdgbl;
  
      if (dgbl == NULL)
          return;
  
      RAND_DRBG_free(dgbl->master_drbg);
      CRYPTO_THREAD_cleanup_local(&dgbl->private_drbg);
      CRYPTO_THREAD_cleanup_local(&dgbl->public_drbg);
  
      OPENSSL_free(dgbl);
  }
  
  static const OPENSSL_CTX_METHOD drbg_ossl_ctx_method = {
      drbg_ossl_ctx_new,
      drbg_ossl_ctx_free,
  };
  
  /*
   * drbg_ossl_ctx_new() calls drgb_setup() which calls rand_drbg_get_nonce()
   * which needs to get the rand_nonce_lock out of the OPENSSL_CTX...but since
   * drbg_ossl_ctx_new() hasn't finished running yet we need the rand_nonce_lock
   * to be in a different global data object. Otherwise we will go into an
   * infinite recursion loop.
   */
  static void *drbg_nonce_ossl_ctx_new(OPENSSL_CTX *libctx)
  {
      DRBG_NONCE_GLOBAL *dngbl = OPENSSL_zalloc(sizeof(*dngbl));
  
      if (dngbl == NULL)
          return NULL;
  
      dngbl->rand_nonce_lock = CRYPTO_THREAD_lock_new();
      if (dngbl->rand_nonce_lock == NULL) {
          OPENSSL_free(dngbl);
          return NULL;
      }
  
      return dngbl;
  }
  
  static void drbg_nonce_ossl_ctx_free(void *vdngbl)
  {
      DRBG_NONCE_GLOBAL *dngbl = vdngbl;
  
      if (dngbl == NULL)
          return;
  
      CRYPTO_THREAD_lock_free(dngbl->rand_nonce_lock);
  
      OPENSSL_free(dngbl);
  }
  
  static const OPENSSL_CTX_METHOD drbg_nonce_ossl_ctx_method = {
      drbg_nonce_ossl_ctx_new,
      drbg_nonce_ossl_ctx_free,
  };
  
  static DRBG_GLOBAL *drbg_get_global(OPENSSL_CTX *libctx)
  {
      return openssl_ctx_get_data(libctx, OPENSSL_CTX_DRBG_INDEX,
                                  &drbg_ossl_ctx_method);
  }
  
  /* Implements the get_nonce() callback (see RAND_DRBG_set_callbacks()) */
  size_t rand_drbg_get_nonce(RAND_DRBG *drbg,
                             unsigned char **pout,
                             int entropy, size_t min_len, size_t max_len)
  {
      size_t ret = 0;
      RAND_POOL *pool;
      DRBG_NONCE_GLOBAL *dngbl
          = openssl_ctx_get_data(drbg->libctx, OPENSSL_CTX_DRBG_NONCE_INDEX,
                                 &drbg_nonce_ossl_ctx_method);
      struct {
          void *instance;
          int count;
      } data;
  
      if (dngbl == NULL)
          return 0;
  
      memset(&data, 0, sizeof(data));
      pool = rand_pool_new(0, 0, min_len, max_len);
      if (pool == NULL)
          return 0;
  
      if (rand_pool_add_nonce_data(pool) == 0)
          goto err;
  
      data.instance = drbg;
      CRYPTO_atomic_add(&dngbl->rand_nonce_count, 1, &data.count,
                        dngbl->rand_nonce_lock);
  
      if (rand_pool_add(pool, (unsigned char *)&data, sizeof(data), 0) == 0)
          goto err;
  
      ret   = rand_pool_length(pool);
      *pout = rand_pool_detach(pool);
  
   err:
      rand_pool_free(pool);
  
      return ret;
  }
  
  /*
   * Implements the cleanup_nonce() callback (see RAND_DRBG_set_callbacks())
   *
   */
  void rand_drbg_cleanup_nonce(RAND_DRBG *drbg,
                               unsigned char *out, size_t outlen)
  {
      OPENSSL_clear_free(out, outlen);
  }
  
  /*
   * Set the |drbg|'s callback data pointer for the entropy and nonce callbacks
   *
   * The ownership of the context data remains with the caller,
   * i.e., it is the caller's responsibility to keep it available as long
   * as it is need by the callbacks and free it after use.
   *
   * Setting the callback data 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_callback_data(RAND_DRBG *drbg, void *data)
  {
      if (drbg->state != DRBG_UNINITIALISED
          || drbg->parent != NULL)
          return 0;
  
      drbg->callback_data = data;
      return 1;
  }
  
  /* Retrieve the callback data pointer */
  void *RAND_DRBG_get_callback_data(RAND_DRBG *drbg)
  {
      return drbg->callback_data;
  }
  
  /*
   * 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 type, unsigned int flags)
  {
      return rand_drbg_set(drbg, type, flags) && rand_drbg_init_method(drbg);
  }
  
  static int rand_drbg_set(RAND_DRBG *drbg, int type, unsigned int flags)
  {
      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)) {
          if (drbg->meth != NULL)
              drbg->meth->uninstantiate(drbg);
          rand_pool_free(drbg->adin_pool);
          drbg->adin_pool = NULL;
      }
  
      drbg->state = DRBG_UNINITIALISED;
      drbg->flags = flags;
      drbg->type = type;
      drbg->meth = NULL;
  
      if (type == 0 || is_ctr(type) || is_digest(type))
          return 1;
  
      drbg->type = 0;
      drbg->flags = 0;
      RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);
  
      return 0;
  }
  
  static int rand_drbg_init_method(RAND_DRBG *drbg)
  {
      int ret;
  
      if (drbg->meth != NULL)
          return 1;
  
      if (is_ctr(drbg->type)) {
          ret = drbg_ctr_init(drbg);
      } else if (is_digest(drbg->type)) {
          if (drbg->flags & RAND_DRBG_FLAG_HMAC)
              ret = drbg_hmac_init(drbg);
          else
              ret = drbg_hash_init(drbg);
      } else {
          /* other cases should already be excluded */
          RANDerr(RAND_F_RAND_DRBG_INIT_METHOD, ERR_R_INTERNAL_ERROR);
          drbg->type = 0;
          drbg->flags = 0;
          return 0;
      }
  
      if (ret == 0) {
          drbg->state = DRBG_ERROR;
          RANDerr(RAND_F_RAND_DRBG_INIT_METHOD, RAND_R_ERROR_INITIALISING_DRBG);
      }
      return ret;
  }
  
  /*
   * Set/initialize default |type| and |flag| for new drbg instances.
   *
   * Returns 1 on success, 0 on failure.
   */
  int RAND_DRBG_set_defaults(int type, unsigned int flags)
  {
      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;
  }
  
  
  /*
   * 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(OPENSSL_CTX *ctx,
                                  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);
          return NULL;
      }
  
      drbg->libctx = ctx;
      drbg->secure = secure && CRYPTO_secure_allocated(drbg);
      drbg->fork_id = openssl_get_fork_id();
      drbg->parent = parent;
  
      if (parent == NULL) {
  #ifdef FIPS_MODULE
          drbg->get_entropy = rand_crngt_get_entropy;
          drbg->cleanup_entropy = rand_crngt_cleanup_entropy;
  #else
          drbg->get_entropy = rand_drbg_get_entropy;
          drbg->cleanup_entropy = rand_drbg_cleanup_entropy;
  #endif
  #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) {
          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:
      RAND_DRBG_free(drbg);
  
      return NULL;
  }
  
  RAND_DRBG *RAND_DRBG_new_ex(OPENSSL_CTX *ctx, int type, unsigned int flags,
                              RAND_DRBG *parent)
  {
      return rand_drbg_new(ctx, 0, type, flags, parent);
  }
  
  RAND_DRBG *RAND_DRBG_new(int type, unsigned int flags, RAND_DRBG *parent)
  {
      return RAND_DRBG_new_ex(NULL, type, flags, parent);
  }
  
  RAND_DRBG *RAND_DRBG_secure_new_ex(OPENSSL_CTX *ctx, int type,
                                     unsigned int flags, RAND_DRBG *parent)
  {
      return rand_drbg_new(ctx, 1, type, flags, parent);
  }
  
  RAND_DRBG *RAND_DRBG_secure_new(int type, unsigned int flags, RAND_DRBG *parent)
  {
      return RAND_DRBG_secure_new_ex(NULL, type, flags, parent);
  }
  /*
   * Uninstantiate |drbg| and free all memory.
   */
  void RAND_DRBG_free(RAND_DRBG *drbg)
  {
      if (drbg == NULL)
          return;
  
      if (drbg->meth != NULL)
          drbg->meth->uninstantiate(drbg);
      rand_pool_free(drbg->adin_pool);
      CRYPTO_THREAD_lock_free(drbg->lock);
  #ifndef FIPS_MODULE
      CRYPTO_free_ex_data(CRYPTO_EX_INDEX_RAND_DRBG, drbg, &drbg->ex_data);
  #endif
  
      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, entropylen = 0;
      size_t min_entropy, min_entropylen, max_entropylen;
  
      if (drbg->meth == NULL && !rand_drbg_init_method(drbg)) {
          RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
                  RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);
          goto end;
      }
  
      min_entropy = drbg->strength;
      min_entropylen = drbg->min_entropylen;
      max_entropylen = drbg->max_entropylen;
  
      if (perslen > drbg->max_perslen) {
          RANDerr(RAND_F_RAND_DRBG_INSTANTIATE,
                  RAND_R_PERSONALISATION_STRING_TOO_LONG);
          goto end;
      }
  
      if (drbg->state != DRBG_UNINITIALISED) {
          if (drbg->state == DRBG_ERROR)
              RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_IN_ERROR_STATE);
          else
              RANDerr(RAND_F_RAND_DRBG_INSTANTIATE, RAND_R_ALREADY_INSTANTIATED);
          goto end;
      }
  
      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 accommodate 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)
          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->min_noncelen > 0 && drbg->get_nonce != NULL) {
          noncelen = drbg->get_nonce(drbg, &nonce, drbg->strength / 2,
                                     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 (!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_gen_counter = 1;
      drbg->reseed_time = time(NULL);
      tsan_store(&drbg->reseed_prop_counter, drbg->reseed_next_counter);
  
   end:
      if (entropy != NULL && drbg->cleanup_entropy != NULL)
          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;
  }
  
  /*
   * 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 index = -1, type, flags;
      if (drbg->meth != NULL) {
          drbg->meth->uninstantiate(drbg);
          drbg->meth = NULL;
      }
  
      /* 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);
  }
  
  /*
   * 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,
                       int prediction_resistance)
  {
      unsigned char *entropy = NULL;
      size_t entropylen = 0;
  
      if (drbg->state == DRBG_ERROR) {
          RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_IN_ERROR_STATE);
          return 0;
      }
      if (drbg->state == DRBG_UNINITIALISED) {
          RANDerr(RAND_F_RAND_DRBG_RESEED, RAND_R_NOT_INSTANTIATED);
          return 0;
      }
  
      if (adin == NULL) {
          adinlen = 0;
      } 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)
          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 (!drbg->meth->reseed(drbg, entropy, entropylen, adin, adinlen))
          goto end;
  
      drbg->state = DRBG_READY;
      drbg->reseed_gen_counter = 1;
      drbg->reseed_time = time(NULL);
      tsan_store(&drbg->reseed_prop_counter, drbg->reseed_next_counter);
  
   end:
      if (entropy != NULL && drbg->cleanup_entropy != NULL)
          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->seed_pool != NULL) {
          RANDerr(RAND_F_RAND_DRBG_RESTART, ERR_R_INTERNAL_ERROR);
          drbg->state = DRBG_ERROR;
          rand_pool_free(drbg->seed_pool);
          drbg->seed_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->seed_pool = rand_pool_attach(buffer, len, entropy);
              if (drbg->seed_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->seed_pool);
      drbg->seed_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)
  {
      int fork_id;
      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_adinlen) {
          RANDerr(RAND_F_RAND_DRBG_GENERATE, RAND_R_ADDITIONAL_INPUT_TOO_LONG);
          return 0;
      }
  
      fork_id = openssl_get_fork_id();
  
      if (drbg->fork_id != fork_id) {
          drbg->fork_id = fork_id;
          reseed_required = 1;
      }
  
      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 (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;
          }
          adin = NULL;
          adinlen = 0;
      }
  
      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;
      }
  
      drbg->reseed_gen_counter++;
  
      return 1;
  }
  
  /*
   * 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, 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 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
              || drbg->parent != NULL)
          return 0;
      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, unsigned int interval)
  {
      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;
  }
  
  #ifndef FIPS_MODULE
  /*
   * Get and set the EXDATA
   */
  int RAND_DRBG_set_ex_data(RAND_DRBG *drbg, int idx, void *arg)
  {
      return CRYPTO_set_ex_data(&drbg->ex_data, idx, arg);
  }
  
  void *RAND_DRBG_get_ex_data(const RAND_DRBG *drbg, int idx)
  {
      return CRYPTO_get_ex_data(&drbg->ex_data, idx);
  }
  #endif
  
  /*
   * The following functions provide a RAND_METHOD that works on the
   * global DRBG.  They lock.
   */
  
  /*
   * 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(OPENSSL_CTX *ctx, RAND_DRBG *parent, int drbg_type)
  {
      RAND_DRBG *drbg;
  
      drbg = RAND_DRBG_secure_new_ex(ctx, 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;
  
      /* 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:
      RAND_DRBG_free(drbg);
      return NULL;
  }
  
  static void drbg_delete_thread_state(void *arg)
  {
      OPENSSL_CTX *ctx = arg;
      DRBG_GLOBAL *dgbl = drbg_get_global(ctx);
      RAND_DRBG *drbg;
  
      if (dgbl == NULL)
          return;
      drbg = CRYPTO_THREAD_get_local(&dgbl->public_drbg);
      CRYPTO_THREAD_set_local(&dgbl->public_drbg, NULL);
      RAND_DRBG_free(drbg);
  
      drbg = CRYPTO_THREAD_get_local(&dgbl->private_drbg);
      CRYPTO_THREAD_set_local(&dgbl->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.
   */
  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)
  {
      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;
  
      rand_drbg_lock(drbg);
      seedlen = rand_drbg_seedlen(drbg);
  
      buflen = (size_t)num;
  
  #ifdef FIPS_MODULE
      /*
       * NIST SP-800-90A mandates that entropy *shall not* be provided
       * by the consuming application. By setting the randomness to zero,
       * we ensure that the buffer contents will be added to the internal
       * state of the DRBG only as additional data.
       *
       * (NIST SP-800-90Ar1, Sections 9.1 and 9.2)
       */
      randomness = 0.0;
  #endif
      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 available then we declare the buffer content
           * as additional data by setting randomness to zero and trigger a regular
           * reseeding.
           */
          randomness = 0.0;
  #endif
      }
  
      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;
  
      rand_drbg_lock(drbg);
      ret = drbg->state == DRBG_READY ? 1 : 0;
      rand_drbg_unlock(drbg);
      return ret;
  }
  
  /*
   * Get the master DRBG.
   * Returns pointer to the DRBG on success, NULL on failure.
   *
   */
  RAND_DRBG *OPENSSL_CTX_get0_master_drbg(OPENSSL_CTX *ctx)
  {
      DRBG_GLOBAL *dgbl = drbg_get_global(ctx);
  
      if (dgbl == NULL)
          return NULL;
  
      return dgbl->master_drbg;
  }
  
  RAND_DRBG *RAND_DRBG_get0_master(void)
  {
      return OPENSSL_CTX_get0_master_drbg(NULL);
  }
  
  /*
   * Get the public DRBG.
   * Returns pointer to the DRBG on success, NULL on failure.
   */
  RAND_DRBG *OPENSSL_CTX_get0_public_drbg(OPENSSL_CTX *ctx)
  {
      DRBG_GLOBAL *dgbl = drbg_get_global(ctx);
      RAND_DRBG *drbg;
  
      if (dgbl == NULL)
          return NULL;
  
      drbg = CRYPTO_THREAD_get_local(&dgbl->public_drbg);
      if (drbg == NULL) {
          ctx = openssl_ctx_get_concrete(ctx);
          /*
           * If the private_drbg is also NULL then this is the first time we've
           * used this thread.
           */
          if (CRYPTO_THREAD_get_local(&dgbl->private_drbg) == NULL
                  && !ossl_init_thread_start(NULL, ctx, drbg_delete_thread_state))
              return NULL;
          drbg = drbg_setup(ctx, dgbl->master_drbg, RAND_DRBG_TYPE_PUBLIC);
          CRYPTO_THREAD_set_local(&dgbl->public_drbg, drbg);
      }
      return drbg;
  }
  
  RAND_DRBG *RAND_DRBG_get0_public(void)
  {
      return OPENSSL_CTX_get0_public_drbg(NULL);
  }
  
  /*
   * Get the private DRBG.
   * Returns pointer to the DRBG on success, NULL on failure.
   */
  RAND_DRBG *OPENSSL_CTX_get0_private_drbg(OPENSSL_CTX *ctx)
  {
      DRBG_GLOBAL *dgbl = drbg_get_global(ctx);
      RAND_DRBG *drbg;
  
      if (dgbl == NULL)
          return NULL;
  
      drbg = CRYPTO_THREAD_get_local(&dgbl->private_drbg);
      if (drbg == NULL) {
          ctx = openssl_ctx_get_concrete(ctx);
          /*
           * If the public_drbg is also NULL then this is the first time we've
           * used this thread.
           */
          if (CRYPTO_THREAD_get_local(&dgbl->public_drbg) == NULL
                  && !ossl_init_thread_start(NULL, ctx, drbg_delete_thread_state))
              return NULL;
          drbg = drbg_setup(ctx, dgbl->master_drbg, RAND_DRBG_TYPE_PRIVATE);
          CRYPTO_THREAD_set_local(&dgbl->private_drbg, drbg);
      }
      return drbg;
  }
  
  RAND_DRBG *RAND_DRBG_get0_private(void)
  {
      return OPENSSL_CTX_get0_private_drbg(NULL);
  }
  
  RAND_METHOD rand_meth = {
      drbg_seed,
      drbg_bytes,
      NULL,
      drbg_add,
      drbg_bytes,
      drbg_status
  };
  
  RAND_METHOD *RAND_OpenSSL(void)
  {
  #ifndef FIPS_MODULE
      return &rand_meth;
  #else
      return NULL;
  #endif
  }
  