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PROVIDER-RAND(7ossl)		    OpenSSL		  PROVIDER-RAND(7ossl)

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>.

3.0.0-beta1+quic		  2021-06-19		  PROVIDER-RAND(7ossl)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | NOTES | SEE ALSO | HISTORY | COPYRIGHT

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