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Under GNU General Public License
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PROVIDER-RAND(7SSL) OpenSSL PROVIDER-RAND(7SSL)
NAME
provider-rand - The random number generation library <-> provider functions
SYNOPSIS
#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
/*
* None of these are actual functions, but are displayed like this for
* the function signatures for functions that are offered as function
* pointers in OSSL_DISPATCH arrays.
*/
/* Context management */
void *OSSL_FUNC_rand_newctx(void *provctx, void *parent,
const OSSL_DISPATCH *parent_calls);
void OSSL_FUNC_rand_freectx(void *ctx);
/* Random number generator functions: NIST */
int OSSL_FUNC_rand_instantiate(void *ctx, unsigned int strength,
int prediction_resistance,
const unsigned char *pstr, size_t pstr_len,
const OSSL_PARAM params[]);
int OSSL_FUNC_rand_uninstantiate(void *ctx);
int OSSL_FUNC_rand_generate(void *ctx, unsigned char *out, size_t outlen,
unsigned int strength, int prediction_resistance,
const unsigned char *addin, size_t addin_len);
int OSSL_FUNC_rand_reseed(void *ctx, int prediction_resistance,
const unsigned char *ent, size_t ent_len,
const unsigned char *addin, size_t addin_len);
/* Random number generator functions: additional */
size_t OSSL_FUNC_rand_nonce(void *ctx, unsigned char *out, size_t outlen,
int strength, size_t min_noncelen,
size_t max_noncelen);
size_t OSSL_FUNC_rand_get_seed(void *ctx, unsigned char **buffer,
int entropy, size_t min_len, size_t max_len,
int prediction_resistance,
const unsigned char *adin, size_t adin_len);
void OSSL_FUNC_rand_clear_seed(void *ctx, unsigned char *buffer, size_t b_len);
int OSSL_FUNC_rand_verify_zeroization(void *ctx);
/* Context Locking */
int OSSL_FUNC_rand_enable_locking(void *ctx);
int OSSL_FUNC_rand_lock(void *ctx);
void OSSL_FUNC_rand_unlock(void *ctx);
/* RAND parameter descriptors */
const OSSL_PARAM *OSSL_FUNC_rand_gettable_params(void *provctx);
const OSSL_PARAM *OSSL_FUNC_rand_gettable_ctx_params(void *ctx, void *provctx);
const OSSL_PARAM *OSSL_FUNC_rand_settable_ctx_params(void *ctx, void *provctx);
/* RAND parameters */
int OSSL_FUNC_rand_get_params(OSSL_PARAM params[]);
int OSSL_FUNC_rand_get_ctx_params(void *ctx, OSSL_PARAM params[]);
int OSSL_FUNC_rand_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
DESCRIPTION
This documentation is primarily aimed at provider authors. See provider(7) for further
information.
The RAND operation enables providers to implement random number generation algorithms and
random number sources and make them available to applications via the API function
EVP_RAND(3).
Context Management Functions
OSSL_FUNC_rand_newctx() should create and return a pointer to a provider side structure
for holding context information during a rand operation. A pointer to this context will
be passed back in a number of the other rand operation function calls. The parameter
provctx is the provider context generated during provider initialisation (see
provider(7)). The parameter parent specifies another rand instance to be used for seeding
purposes. If NULL and the specific instance supports it, the operating system will be
used for seeding. The parameter parent_calls points to the dispatch table for parent.
Thus, the parent need not be from the same provider as the new instance.
OSSL_FUNC_rand_freectx() is passed a pointer to the provider side rand context in the mctx
parameter. If it receives NULL as ctx value, it should not do anything other than return.
This function should free any resources associated with that context.
Random Number Generator Functions: NIST
These functions correspond to those defined in NIST SP 800-90A and SP 800-90C.
OSSL_FUNC_rand_instantiate() is used to instantiate the DRBG ctx at a requested security
strength. In addition, prediction_resistance can be requested. Additional input addin of
length addin_len bytes can optionally be provided. The parameters specified in params
configure the DRBG and these should be processed before instantiation.
OSSL_FUNC_rand_uninstantiate() is used to uninstantiate the DRBG ctx. After being
uninstantiated, a DRBG is unable to produce output until it is instantiated anew.
OSSL_FUNC_rand_generate() is used to generate random bytes from the DRBG ctx. It will
generate outlen bytes placing them into the buffer pointed to by out. The generated bytes
will meet the specified security strength and, if prediction_resistance is true, the bytes
will be produced after reseeding from a live entropy source. Additional input addin of
length addin_len bytes can optionally be provided.
Random Number Generator Functions: Additional
OSSL_FUNC_rand_nonce() is used to generate a nonce of the given strength with a length
from min_noncelen to max_noncelen. If the output buffer out is NULL, the length of the
nonce should be returned.
OSSL_FUNC_rand_get_seed() is used by deterministic generators to obtain their seeding
material from their parent. The seed bytes will meet the specified security level of
entropy bits and there will be between min_len and max_len inclusive bytes in total. If
prediction_resistance is true, the bytes will be produced from a live entropy source.
Additional input addin of length addin_len bytes can optionally be provided. A pointer to
the seed material is returned in *buffer and this must be freed by a later call to
OSSL_FUNC_rand_clear_seed().
OSSL_FUNC_rand_clear_seed() frees a seed buffer of length b_len bytes which was previously
allocated by OSSL_FUNC_rand_get_seed().
OSSL_FUNC_rand_verify_zeroization() is used to determine if the internal state of the DRBG
is zero. This capability is mandated by NIST as part of the self tests, it is unlikely to
be useful in other circumstances.
Context Locking
When DRBGs are used by multiple threads, there must be locking employed to ensure their
proper operation. Because locking introduces an overhead, it is disabled by default.
OSSL_FUNC_rand_enable_locking() allows locking to be turned on for a DRBG and all of its
parent DRBGs. From this call onwards, the DRBG can be used in a thread safe manner.
OSSL_FUNC_rand_lock() is used to lock a DRBG. Once locked, exclusive access is
guaranteed.
OSSL_FUNC_rand_unlock() is used to unlock a DRBG.
Rand Parameters
See OSSL_PARAM(3) for further details on the parameters structure used by these functions.
OSSL_FUNC_rand_get_params() gets details of parameter values associated with the provider
algorithm and stores them in params.
OSSL_FUNC_rand_set_ctx_params() sets rand parameters associated with the given provider
side rand context ctx to params. Any parameter settings are additional to any that were
previously set. Passing NULL for params should return true.
OSSL_FUNC_rand_get_ctx_params() gets details of currently set parameter values associated
with the given provider side rand context ctx and stores them in params. Passing NULL for
params should return true.
OSSL_FUNC_rand_gettable_params(), OSSL_FUNC_rand_gettable_ctx_params(), and
OSSL_FUNC_rand_settable_ctx_params() all return constant OSSL_PARAM arrays as descriptors
of the parameters that OSSL_FUNC_rand_get_params(), OSSL_FUNC_rand_get_ctx_params(), and
OSSL_FUNC_rand_set_ctx_params() can handle, respectively.
OSSL_FUNC_rand_gettable_ctx_params() and OSSL_FUNC_rand_settable_ctx_params() will return
the parameters associated with the provider side context ctx in its current state if it is
not NULL. Otherwise, they return the parameters associated with the provider side
algorithm provctx.
Parameters currently recognised by built-in rands are as follows. Not all parameters are
relevant to, or are understood by all rands:
"state" (OSSL_RAND_PARAM_STATE) <integer>
Returns the state of the random number generator.
"strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>
Returns the bit strength of the random number generator.
For rands that are also deterministic random bit generators (DRBGs), these additional
parameters are recognised. Not all parameters are relevant to, or are understood by all
DRBG rands:
"reseed_requests" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>
Reads or set the number of generate requests before reseeding the associated RAND ctx.
"reseed_time_interval" (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>
Reads or set the number of elapsed seconds before reseeding the associated RAND ctx.
"max_request" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>
Specifies the maximum number of bytes that can be generated in a single call to
OSSL_FUNC_rand_generate.
"min_entropylen" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer>
"max_entropylen" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer>
Specify the minimum and maximum number of bytes of random material that can be used to
seed the DRBG.
"min_noncelen" (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer>
"max_noncelen" (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer>
Specify the minimum and maximum number of bytes of nonce that can be used to
instantiate the DRBG.
"max_perslen" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer>
"max_adinlen" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer>
Specify the minimum and maximum number of bytes of personalisation string that can be
used with the DRBG.
"reseed_counter" (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer>
Specifies the number of times the DRBG has been seeded or reseeded.
"digest" (OSSL_DRBG_PARAM_DIGEST) <UTF8 string>
"cipher" (OSSL_DRBG_PARAM_CIPHER) <UTF8 string>
"mac" (OSSL_DRBG_PARAM_MAC) <UTF8 string>
Sets the name of the underlying cipher, digest or MAC to be used. It must name a
suitable algorithm for the DRBG that's being used.
"properties" (OSSL_DRBG_PARAM_PROPERTIES) <UTF8 string>
Sets the properties to be queried when trying to fetch an underlying algorithm. This
must be given together with the algorithm naming parameter to be considered valid.
RETURN VALUES
OSSL_FUNC_rand_newctx() should return the newly created provider side rand context, or
NULL on failure.
OSSL_FUNC_rand_gettable_params(), OSSL_FUNC_rand_gettable_ctx_params() and
OSSL_FUNC_rand_settable_ctx_params() should return a constant OSSL_PARAM array, or NULL if
none is offered.
OSSL_FUNC_rand_nonce() returns the size of the generated nonce, or 0 on error.
OSSL_FUNC_rand_get_seed() returns the size of the generated seed, or 0 on error.
All of the remaining functions should return 1 for success or 0 on error.
NOTES
The RAND life-cycle is described in life_cycle-rand(7). Providers should ensure that the
various transitions listed there are supported. At some point the EVP layer will begin
enforcing the listed transitions.
SEE ALSO
provider(7), RAND(7), EVP_RAND(7), life_cycle-rand(7), EVP_RAND(3)
HISTORY
The provider RAND interface was introduced in OpenSSL 3.0.
COPYRIGHT
Copyright 2020-2021 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>.
3.0.2 2025-09-18 PROVIDER-RAND(7SSL)
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On Apache
Under GNU General Public License
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