3a50a8a91a
The functions RAND_add() and RAND_seed() provide a legacy API which enables the application to seed the CSPRNG. But NIST SP-800-90A clearly mandates that entropy *shall not* be provided by the consuming application, neither for instantiation, nor for reseeding. The provided random data will be mixed into the DRBG state as additional data only, and no entropy will accounted for it. Reviewed-by: Paul Dale <paul.dale@oracle.com> (Merged from https://github.com/openssl/openssl/pull/8722)
110 lines
3.9 KiB
Text
110 lines
3.9 KiB
Text
=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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Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
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B<OPENSSL_API_COMPAT> with a suitable version value, see
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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<RAND_DRBG(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 non-zero 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.
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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<RAND_DRBG(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 2000-2019 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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