openssl/doc/man3/RAND_get0_primary.pod
Pauli 7d615e2178 rand_drbg: remove RAND_DRBG.
The RAND_DRBG API did not fit well into the new provider concept as
implemented by EVP_RAND and EVP_RAND_CTX. The main reason is that the
RAND_DRBG API is a mixture of 'front end' and 'back end' API calls
and some of its API calls are rather low-level. This holds in particular
for the callback mechanism (RAND_DRBG_set_callbacks()) and the RAND_DRBG
type changing mechanism (RAND_DRBG_set()).

Adding a compatibility layer to continue supporting the RAND_DRBG API as
a legacy API for a regular deprecation period turned out to come at the
price of complicating the new provider API unnecessarily. Since the
RAND_DRBG API exists only since version 1.1.1, it was decided by the OMC
to drop it entirely.

Other related changes:

Use RNG instead of DRBG in EVP_RAND documentation.  The documentation was
using DRBG in places where it should have been RNG or CSRNG.

Move the RAND_DRBG(7) documentation to EVP_RAND(7).

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/12509)
2020-08-07 14:16:47 +10:00

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=pod
=head1 NAME
RAND_get0_primary,
RAND_get0_public,
RAND_get0_private
- get access to the global EVP_RAND_CTX instances
=head1 SYNOPSIS
#include <openssl/rand.h>
EVP_RAND_CTX *RAND_get0_primary(OPENSSL_CTX *ctx);
EVP_RAND_CTX *RAND_get0_public(OPENSSL_CTX *ctx);
EVP_RAND_CTX *RAND_get0_private(OPENSSL_CTX *ctx);
=head1 DESCRIPTION
The default RAND API implementation (RAND_OpenSSL()) utilizes three
shared DRBG instances which are accessed via the RAND API:
The I<public> and I<private> DRBG are thread-local instances, which are used
by RAND_bytes() and RAND_priv_bytes(), respectively.
The I<primary> DRBG is a global instance, which is not intended to be used
directly, but is used internally to reseed the other two instances.
These functions here provide access to the shared DRBG instances.
=head1 RETURN VALUES
RAND_get0_primary() returns a pointer to the I<primary> DRBG instance
for the given OPENSSL_CTX B<ctx>.
RAND_get0_public() returns a pointer to the I<public> DRBG instance
for the given OPENSSL_CTX B<ctx>.
RAND_get0_private() returns a pointer to the I<private> DRBG instance
for the given OPENSSL_CTX B<ctx>.
In all the above cases the B<ctx> parameter can
be NULL in which case the default OPENSSL_CTX is used.
=head1 NOTES
It is not thread-safe to access the I<primary> DRBG instance.
The I<public> and I<private> DRBG instance can be accessed safely, because
they are thread-local. Note however, that changes to these two instances
apply only to the current thread.
For that reason it is recommended not to change the settings of these
three instances directly.
Instead, an application should change the default settings for new DRBG instances
at initialization time, before creating additional threads.
During initialization, it is possible to change the reseed interval
and reseed time interval.
It is also possible to exchange the reseeding callbacks entirely.
=head1 SEE ALSO
L<EVP_RAND(3)>
=head1 HISTORY
These functions were added in OpenSSL 3.0.
=head1 COPYRIGHT
Copyright 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
L<https://www.openssl.org/source/license.html>.
=cut