| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | RAND_add, RAND_poll, RAND_seed, RAND_status, RAND_event, RAND_screen,
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| 6 | RAND_keep_random_devices_open
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| 7 | - add randomness to the PRNG or get its status
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| 8 |
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| 9 | =head1 SYNOPSIS
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| 10 |
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| 11 | #include <openssl/rand.h>
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| 12 |
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| 13 | int RAND_status(void);
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| 14 | int RAND_poll();
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| 15 |
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| 16 | void RAND_add(const void *buf, int num, double randomness);
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| 17 | void RAND_seed(const void *buf, int num);
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| 18 |
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| 19 | void RAND_keep_random_devices_open(int keep);
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| 20 |
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| 21 | Deprecated:
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| 22 |
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| 23 | #if OPENSSL_API_COMPAT < 0x10100000L
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| 24 | int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
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| 25 | void RAND_screen(void);
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| 26 | #endif
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| 27 |
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| 28 | =head1 DESCRIPTION
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| 29 |
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| 30 | These functions can be used to seed the random generator and to check its
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| 31 | seeded state.
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| 32 | In general, manual (re-)seeding of the default OpenSSL random generator
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| 33 | (L<RAND_OpenSSL(3)>) is not necessary (but allowed), since it does (re-)seed
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| 34 | itself automatically using trusted system entropy sources.
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| 35 | This holds unless the default RAND_METHOD has been replaced or OpenSSL was
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| 36 | built with automatic reseeding disabled, see L<RAND(7)> for more details.
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| 37 |
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| 38 | RAND_status() indicates whether or not the random generator has been sufficiently
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| 39 | seeded. If not, functions such as L<RAND_bytes(3)> will fail.
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| 40 |
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| 41 | RAND_poll() uses the system's capabilities to seed the random generator using
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| 42 | random input obtained from polling various trusted entropy sources.
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| 43 | The default choice of the entropy source can be modified at build time,
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| 44 | see L<RAND(7)> for more details.
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| 45 |
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| 46 | RAND_add() mixes the B<num> bytes at B<buf> into the internal state
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| 47 | of the random generator.
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| 48 | This function will not normally be needed, as mentioned above.
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| 49 | The B<randomness> argument is an estimate of how much randomness is
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| 50 | contained in
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| 51 | B<buf>, in bytes, and should be a number between zero and B<num>.
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| 52 | Details about sources of randomness and how to estimate their randomness
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| 53 | can be found in the literature; for example [NIST SP 800-90B].
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| 54 | The content of B<buf> cannot be recovered from subsequent random generator output.
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| 55 | Applications that intend to save and restore random state in an external file
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| 56 | should consider using L<RAND_load_file(3)> instead.
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| 57 |
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| 58 | RAND_seed() is equivalent to RAND_add() with B<randomness> set to B<num>.
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| 59 |
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| 60 | RAND_keep_random_devices_open() is used to control file descriptor
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| 61 | usage by the random seed sources. Some seed sources maintain open file
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| 62 | descriptors by default, which allows such sources to operate in a
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| 63 | chroot(2) jail without the associated device nodes being available. When
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| 64 | the B<keep> argument is zero, this call disables the retention of file
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| 65 | descriptors. Conversely, a nonzero argument enables the retention of
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| 66 | file descriptors. This function is usually called during initialization
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| 67 | and it takes effect immediately.
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| 68 |
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| 69 | RAND_event() and RAND_screen() are equivalent to RAND_poll() and exist
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| 70 | for compatibility reasons only. See HISTORY section below.
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| 71 |
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| 72 | =head1 RETURN VALUES
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| 73 |
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| 74 | RAND_status() returns 1 if the random generator has been seeded
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| 75 | with enough data, 0 otherwise.
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| 76 |
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| 77 | RAND_poll() returns 1 if it generated seed data, 0 otherwise.
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| 78 |
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| 79 | RAND_event() returns RAND_status().
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| 80 |
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| 81 | The other functions do not return values.
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| 82 |
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| 83 | =head1 SEE ALSO
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| 84 |
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| 85 | L<RAND_bytes(3)>,
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| 86 | L<RAND_egd(3)>,
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| 87 | L<RAND_load_file(3)>,
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| 88 | L<RAND(7)>
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| 89 |
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| 90 | =head1 HISTORY
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| 91 |
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| 92 | RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
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| 93 | not be used.
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| 94 |
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| 95 | =head1 COPYRIGHT
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| 96 |
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| 97 | Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
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| 98 |
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| 99 | Licensed under the OpenSSL license (the "License"). You may not use
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| 100 | this file except in compliance with the License. You can obtain a copy
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| 101 | in the file LICENSE in the source distribution or at
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| 102 | L<https://www.openssl.org/source/license.html>.
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| 103 |
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| 104 | =cut
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