mirror of
https://github.com/openssl/openssl.git
synced 2024-12-27 06:21:43 +08:00
e587bccdf9
Reviewed-by: Tomas Mraz <tomas@openssl.org> (Merged from https://github.com/openssl/openssl/pull/15513)
112 lines
3.7 KiB
Plaintext
112 lines
3.7 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
RAND_bytes, RAND_priv_bytes, RAND_bytes_ex, RAND_priv_bytes_ex,
|
|
RAND_pseudo_bytes - generate random data
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/rand.h>
|
|
|
|
int RAND_bytes(unsigned char *buf, int num);
|
|
int RAND_priv_bytes(unsigned char *buf, int num);
|
|
|
|
int RAND_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, int num,
|
|
unsigned int strength);
|
|
int RAND_priv_bytes_ex(OSSL_LIB_CTX *ctx, unsigned char *buf, int num,
|
|
unsigned int strength);
|
|
|
|
Deprecated since OpenSSL 1.1.0, can be hidden entirely by defining
|
|
B<OPENSSL_API_COMPAT> with a suitable version value, see
|
|
L<openssl_user_macros(7)>:
|
|
|
|
int RAND_pseudo_bytes(unsigned char *buf, int num);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
RAND_bytes() generates B<num> random bytes using a cryptographically
|
|
secure pseudo random generator (CSPRNG) and stores them in B<buf>.
|
|
|
|
RAND_priv_bytes() has the same semantics as RAND_bytes(). It is intended to
|
|
be used for generating values that should remain private. If using the
|
|
default RAND_METHOD, this function uses a separate "private" PRNG
|
|
instance so that a compromise of the "public" PRNG instance will not
|
|
affect the secrecy of these private values, as described in L<RAND(7)>
|
|
and L<EVP_RAND(7)>.
|
|
|
|
RAND_bytes_ex() and RAND_priv_bytes_ex() are the same as RAND_bytes() and
|
|
RAND_priv_bytes() except that they both take additional I<strength> and
|
|
I<ctx> parameters. The bytes genreated will have a security strength of at
|
|
least I<strength> bits.
|
|
The DRBG used for the operation is the public or private DRBG associated with
|
|
the specified I<ctx>. The parameter can be NULL, in which case
|
|
the default library context is used (see L<OSSL_LIB_CTX(3)>.
|
|
If the default RAND_METHOD has been changed then for compatibility reasons the
|
|
RAND_METHOD will be used in preference and the DRBG of the library context
|
|
ignored.
|
|
|
|
=head1 NOTES
|
|
|
|
By default, the OpenSSL CSPRNG supports a security level of 256 bits, provided it
|
|
was able to seed itself from a trusted entropy source.
|
|
On all major platforms supported by OpenSSL (including the Unix-like platforms
|
|
and Windows), OpenSSL is configured to automatically seed the CSPRNG on first use
|
|
using the operating systems's random generator.
|
|
|
|
If the entropy source fails or is not available, the CSPRNG will enter an
|
|
error state and refuse to generate random bytes. For that reason, it is important
|
|
to always check the error return value of RAND_bytes() and RAND_priv_bytes() and
|
|
not take randomness for granted.
|
|
|
|
On other platforms, there might not be a trusted entropy source available
|
|
or OpenSSL might have been explicitly configured to use different entropy sources.
|
|
If you are in doubt about the quality of the entropy source, don't hesitate to ask
|
|
your operating system vendor or post a question on GitHub or the openssl-users
|
|
mailing list.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
RAND_bytes() and RAND_priv_bytes()
|
|
return 1 on success, -1 if not supported by the current
|
|
RAND method, or 0 on other failure. The error code can be
|
|
obtained by L<ERR_get_error(3)>.
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<RAND_add(3)>,
|
|
L<RAND_bytes(3)>,
|
|
L<RAND_priv_bytes(3)>,
|
|
L<ERR_get_error(3)>,
|
|
L<RAND(7)>,
|
|
L<EVP_RAND(7)>
|
|
|
|
=head1 HISTORY
|
|
|
|
=over 2
|
|
|
|
=item *
|
|
|
|
RAND_pseudo_bytes() was deprecated in OpenSSL 1.1.0; use RAND_bytes() instead.
|
|
|
|
=item *
|
|
|
|
The RAND_priv_bytes() function was added in OpenSSL 1.1.1.
|
|
|
|
=item *
|
|
|
|
The RAND_bytes_ex() and RAND_priv_bytes_ex() functions were added in OpenSSL 3.0
|
|
|
|
=back
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2000-2020 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
|