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Edit File: random.h

/* * Copyright (C) Internet Systems Consortium, Inc. ("ISC") * * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, you can obtain one at https://mozilla.org/MPL/2.0/. * * See the COPYRIGHT file distributed with this work for additional * information regarding copyright ownership. */ #ifndef ISC_RANDOM_H #define ISC_RANDOM_H 1 #include <isc/lang.h> #include <isc/types.h> #include <isc/entropy.h> #include <isc/mem.h> #include <isc/mutex.h> /*! \file isc/random.h * \brief Implements pseudo random number generators. * * Two pseudo-random number generators are implemented, in isc_random_* * and isc_rng_*. Neither one is very strong; they should not be used * in cryptography functions. * * isc_random_* is based on arc4random if it is available on the system. * Otherwise it is based on the posix srand() and rand() functions. * It is useful for jittering values a bit here and there, such as * timeouts, etc, but should not be relied upon to generate * unpredictable sequences (for example, when choosing transaction IDs). * * isc_rng_* is based on ChaCha20, and is seeded and stirred from the * system entropy source. It is stronger than isc_random_* and can * be used for generating unpredictable sequences. It is still not as * good as using system entropy directly (see entropy.h) and should not * be used for cryptographic functions such as key generation. */ ISC_LANG_BEGINDECLS typedef struct isc_rng isc_rng_t; /*%< * Opaque type */ void isc_random_seed(uint32_t seed); /*%< * Set the initial seed of the random state. */ void isc_random_get(uint32_t *val); /*%< * Get a random value. * * Requires: * val != NULL. */ uint32_t isc_random_jitter(uint32_t max, uint32_t jitter); /*%< * Get a random value between (max - jitter) and (max). * This is useful for jittering timer values. */ isc_result_t isc_rng_create(isc_mem_t *mctx, isc_entropy_t *entropy, isc_rng_t **rngp); /*%< * Creates and initializes a pseudo random number generator. The * returned RNG can be used to generate pseudo random numbers. * * The reference count of the returned RNG is set to 1. * * Requires: * \li mctx is a pointer to a valid memory context. * \li entropy is an optional entopy source (can be NULL) * \li rngp != NULL && *rngp == NULL is where a pointer to the RNG is * returned. * * Ensures: *\li If result is ISC_R_SUCCESS: * *rngp points to a valid RNG. * *\li If result is failure: * *rngp does not point to a valid RNG. * * Returns: *\li #ISC_R_SUCCESS Success *\li #ISC_R_NOMEMORY Resource limit: Out of Memory */ void isc_rng_attach(isc_rng_t *source, isc_rng_t **targetp); /*%< * Increments a reference count on the passed RNG. * * Requires: * \li source the RNG struct to attach to (is refcount is incremented) * \li targetp != NULL && *targetp == NULL where a pointer to the * reference incremented RNG is returned. */ void isc_rng_detach(isc_rng_t **rngp); /*%< * Decrements a reference count on the passed RNG. If the reference * count reaches 0, the RNG is destroyed. * * Requires: * \li rngp != NULL the RNG struct to decrement reference for */ uint16_t isc_rng_random(isc_rng_t *rngctx); /*%< * Returns a pseudo random 16-bit unsigned integer. */ uint16_t isc_rng_uniformrandom(isc_rng_t *rngctx, uint16_t upper_bound); /*%< * Returns a uniformly distributed pseudo-random 16-bit unsigned integer * less than 'upper_bound'. */ ISC_LANG_ENDDECLS #endif /* ISC_RANDOM_H */