mirror of https://github.com/openssl/openssl.git
112 lines
4.0 KiB
Plaintext
112 lines
4.0 KiB
Plaintext
=pod
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=head1 NAME
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RAND_add, RAND_poll, RAND_seed, RAND_status, RAND_event, RAND_screen,
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RAND_keep_random_devices_open
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- add randomness to the PRNG or get its status
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=head1 SYNOPSIS
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#include <openssl/rand.h>
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int RAND_status(void);
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int RAND_poll();
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void RAND_add(const void *buf, int num, double randomness);
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void RAND_seed(const void *buf, int num);
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void RAND_keep_random_devices_open(int keep);
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The following functions have been deprecated since OpenSSL 1.1.0, and can be
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hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
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see L<openssl_user_macros(7)>:
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int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
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void RAND_screen(void);
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=head1 DESCRIPTION
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These functions can be used to seed the random generator and to check its
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seeded state.
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In general, manual (re-)seeding of the default OpenSSL random generator
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(L<RAND_OpenSSL(3)>) is not necessary (but allowed), since it does (re-)seed
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itself automatically using trusted system entropy sources.
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This holds unless the default RAND_METHOD has been replaced or OpenSSL was
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built with automatic reseeding disabled, see L<RAND(7)> for more details.
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RAND_status() indicates whether or not the random generator has been sufficiently
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seeded. If not, functions such as L<RAND_bytes(3)> will fail.
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RAND_poll() uses the system's capabilities to seed the random generator using
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random input obtained from polling various trusted entropy sources.
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The default choice of the entropy source can be modified at build time,
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see L<RAND(7)> for more details.
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RAND_add() mixes the B<num> bytes at B<buf> into the internal state
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of the random generator.
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This function will not normally be needed, as mentioned above.
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The B<randomness> argument is an estimate of how much randomness is
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contained in
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B<buf>, in bytes, and should be a number between zero and B<num>.
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Details about sources of randomness and how to estimate their randomness
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can be found in the literature; for example [NIST SP 800-90B].
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The content of B<buf> cannot be recovered from subsequent random generator output.
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Applications that intend to save and restore random state in an external file
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should consider using L<RAND_load_file(3)> instead.
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NOTE: In FIPS mode, random data provided by the application is not considered to
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be a trusted entropy source. It is mixed into the internal state of the RNG as
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additional data only and this does not count as a full reseed.
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For more details, see L<EVP_RAND(7)>.
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RAND_seed() is equivalent to RAND_add() with B<randomness> set to B<num>.
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RAND_keep_random_devices_open() is used to control file descriptor
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usage by the random seed sources. Some seed sources maintain open file
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descriptors by default, which allows such sources to operate in a
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chroot(2) jail without the associated device nodes being available. When
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the B<keep> argument is zero, this call disables the retention of file
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descriptors. Conversely, a nonzero argument enables the retention of
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file descriptors. This function is usually called during initialization
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and it takes effect immediately. This capability only applies to the default
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provider.
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RAND_event() and RAND_screen() are equivalent to RAND_poll() and exist
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for compatibility reasons only. See HISTORY section below.
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=head1 RETURN VALUES
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RAND_status() returns 1 if the random generator has been seeded
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with enough data, 0 otherwise.
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RAND_poll() returns 1 if it generated seed data, 0 otherwise.
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RAND_event() returns RAND_status().
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The other functions do not return values.
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=head1 SEE ALSO
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L<RAND_bytes(3)>,
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L<RAND_egd(3)>,
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L<RAND_load_file(3)>,
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L<RAND(7)>
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L<EVP_RAND(7)>
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=head1 HISTORY
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RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
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not be used.
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=head1 COPYRIGHT
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Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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