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3dbf824380
There was recently an instance where a user was confused by the deprecation warnings in the docs. They believed the warning applied to the immediately preceding function declarations, when it fact it applied to the following function declarations. https://mta.openssl.org/pipermail/openssl-users/2021-December/014665.html We clarify the wording to make it clear that the warning applies to the following functions. Reviewed-by: Paul Dale <pauli@openssl.org> Reviewed-by: Tomas Mraz <tomas@openssl.org> Reviewed-by: Richard Levitte <levitte@openssl.org> (Merged from https://github.com/openssl/openssl/pull/17180)
112 lines
3.7 KiB
Plaintext
112 lines
3.7 KiB
Plaintext
=pod
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=head1 NAME
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RAND_bytes, RAND_priv_bytes, RAND_bytes_ex, RAND_priv_bytes_ex,
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RAND_pseudo_bytes - generate random data
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=head1 SYNOPSIS
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#include <openssl/rand.h>
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int RAND_bytes(unsigned char *buf, int num);
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int RAND_priv_bytes(unsigned char *buf, int num);
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int RAND_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, size_t num,
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unsigned int strength);
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int RAND_priv_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, size_t num,
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unsigned int strength);
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The following function has 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_pseudo_bytes(unsigned char *buf, int num);
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=head1 DESCRIPTION
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RAND_bytes() generates B<num> random bytes using a cryptographically
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secure pseudo random generator (CSPRNG) and stores them in B<buf>.
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RAND_priv_bytes() has the same semantics as RAND_bytes(). It is intended to
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be used for generating values that should remain private. If using the
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default RAND_METHOD, this function uses a separate "private" PRNG
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instance so that a compromise of the "public" PRNG instance will not
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affect the secrecy of these private values, as described in L<RAND(7)>
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and L<EVP_RAND(7)>.
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RAND_bytes_ex() and RAND_priv_bytes_ex() are the same as RAND_bytes() and
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RAND_priv_bytes() except that they both take additional I<strength> and
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I<ctx> parameters. The bytes genreated will have a security strength of at
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least I<strength> bits.
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The DRBG used for the operation is the public or private DRBG associated with
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the specified I<ctx>. The parameter can be NULL, in which case
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the default library context is used (see L<OSSL_LIB_CTX(3)>.
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If the default RAND_METHOD has been changed then for compatibility reasons the
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RAND_METHOD will be used in preference and the DRBG of the library context
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ignored.
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=head1 NOTES
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By default, the OpenSSL CSPRNG supports a security level of 256 bits, provided it
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was able to seed itself from a trusted entropy source.
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On all major platforms supported by OpenSSL (including the Unix-like platforms
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and Windows), OpenSSL is configured to automatically seed the CSPRNG on first use
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using the operating systems's random generator.
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If the entropy source fails or is not available, the CSPRNG will enter an
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error state and refuse to generate random bytes. For that reason, it is important
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to always check the error return value of RAND_bytes() and RAND_priv_bytes() and
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not take randomness for granted.
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On other platforms, there might not be a trusted entropy source available
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or OpenSSL might have been explicitly configured to use different entropy sources.
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If you are in doubt about the quality of the entropy source, don't hesitate to ask
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your operating system vendor or post a question on GitHub or the openssl-users
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mailing list.
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=head1 RETURN VALUES
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RAND_bytes() and RAND_priv_bytes()
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return 1 on success, -1 if not supported by the current
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RAND method, or 0 on other failure. The error code can be
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obtained by L<ERR_get_error(3)>.
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=head1 SEE ALSO
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND_priv_bytes(3)>,
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L<ERR_get_error(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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=over 2
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=item *
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RAND_pseudo_bytes() was deprecated in OpenSSL 1.1.0; use RAND_bytes() instead.
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=item *
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The RAND_priv_bytes() function was added in OpenSSL 1.1.1.
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=item *
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The RAND_bytes_ex() and RAND_priv_bytes_ex() functions were added in OpenSSL 3.0
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=back
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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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