/*

 * Copyright 2011-2020 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

 * 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.)

 */

/*

 * 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[] = DRBG_DEFAULT_PERS_STRING;

static CRYPTO_ONCE rand_drbg_init = CRYPTO_ONCE_STATIC_INIT;

static int rand_drbg_type = RAND_DRBG_TYPE;

static unsigned int rand_drbg_flags = RAND_DRBG_FLAGS;

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;

static RAND_DRBG *drbg_setup(RAND_DRBG *parent);

static RAND_DRBG *rand_drbg_new(int secure,

                                int type,

                                unsigned int flags,

                                RAND_DRBG *parent);

/*

 * 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)

{

    int ret = 1;

    if (type == 0 && flags == 0) {

        type = rand_drbg_type;

        flags = rand_drbg_flags;

    }

    /* 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->type = type;

    switch (type) {

    default:

        drbg->type = 0;

        drbg->flags = 0;

        drbg->meth = NULL;

        RANDerr(RAND_F_RAND_DRBG_SET, RAND_R_UNSUPPORTED_DRBG_TYPE);

        return 0;

    case 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 = drbg_ctr_init(drbg);

        break;

    }

    if (ret == 0) {

        drbg->state = DRBG_ERROR;

        RANDerr(RAND_F_RAND_DRBG_SET, 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 ret = 1;

    switch (type) {

    default:

        RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_TYPE);

        return 0;

    case NID_aes_128_ctr:

    case NID_aes_192_ctr:

    case NID_aes_256_ctr:

        break;

    }

    if ((flags & ~rand_drbg_used_flags) != 0) {

        RANDerr(RAND_F_RAND_DRBG_SET_DEFAULTS, RAND_R_UNSUPPORTED_DRBG_FLAGS);

        return 0;

    }

    rand_drbg_type  = type;

    rand_drbg_flags = flags;

    return ret;

}

/*

 * 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);

        return NULL;

    }

    drbg->secure = secure && CRYPTO_secure_allocated(drbg);

    drbg->fork_id = openssl_get_fork_id();

    drbg->parent = parent;

    if (parent == NULL) {

#ifdef OPENSSL_FIPS

        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(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_new(1, 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);

    CRYPTO_free_ex_data(CRYPTO_EX_INDEX_DRBG, drbg, &drbg->ex_data);

    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 = drbg->strength;

    size_t min_entropylen = drbg->min_entropylen;

    size_t 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->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

                                          : 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)

{

    if (drbg->meth == NULL) {

        drbg->state = DRBG_ERROR;

        RANDerr(RAND_F_RAND_DRBG_UNINSTANTIATE,

                RAND_R_NO_DRBG_IMPLEMENTATION_SELECTED);

        return 0;

    }

    /* 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);

    return RAND_DRBG_set(drbg, drbg->type, drbg->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;

}

/*

 * 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);

}

/*

 * 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(RAND_DRBG *parent)

{