=head1 NAME
-RAND_add, RAND_poll, RAND_seed, RAND_status, RAND_event, RAND_screen
+RAND_add, RAND_poll, RAND_seed, RAND_status, RAND_event, RAND_screen,
+RAND_keep_random_devices_open
- add randomness to the PRNG or get its status
=head1 SYNOPSIS
void RAND_add(const void *buf, int num, double randomness);
void RAND_seed(const void *buf, int num);
+ void RAND_keep_random_devices_open(int keep);
+
Deprecated:
#if OPENSSL_API_COMPAT < 0x10100000L
=head1 DESCRIPTION
-Random numbers are a vital part of cryptography, including key generation,
-creating salts, etc., and software-based
-generators must be "seeded" with external randomness before they can be
-used as a cryptographically-secure pseudo-random number generator (CSPRNG).
-The availability of common hardware with special instructions and
-modern operating systems, which may use items such as interrupt jitter
-and network packet timings, can be reasonable sources of seeding material.
+These functions can be used to seed the random generator and to check its
+seeded state.
+In general, manual (re-)seeding of the default OpenSSL random generator
+(L<RAND_OpenSSL(3)>) is not necessary (but allowed), since it does (re-)seed
+itself automatically using trusted system entropy sources.
+This holds unless the default RAND_METHOD has been replaced or OpenSSL was
+built with automatic reseeding disabled, see L<RAND(7)> for more details.
-RAND_status() indicates whether or not the CSPRNG has been sufficiently
-seeded. If not, functions such as RAND_bytes(3) will fail.
+RAND_status() indicates whether or not the random generator has been sufficiently
+seeded. If not, functions such as L<RAND_bytes(3)> will fail.
-RAND_poll() uses the system's capabilities to seed the CSPRNG using
+RAND_poll() uses the system's capabilities to seed the random generator using
random input obtained from polling various trusted entropy sources.
-The default choice of the entropy source can be modified at build time
-using the --with-rand-seed configure option, see also the B<NOTES> section.
-A summary of the configure options can be displayed with the OpenSSL
-L<version(1)> command.
+The default choice of the entropy source can be modified at build time,
+see L<RAND(7)> for more details.
-RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state.
+RAND_add() mixes the B<num> bytes at B<buf> into the internal state
+of the random generator.
+This function will not normally be needed, as mentioned above.
The B<randomness> argument is an estimate of how much randomness is
contained in
B<buf>, in bytes, and should be a number between zero and B<num>.
Details about sources of randomness and how to estimate their randomness
-can be found in the literature; for example NIST SP 800-90B.
-The content of B<buf> cannot be recovered from subsequent CSPRNG output.
-This function will not normally be needed, as RAND_poll() should have been
-configured to do the appropriate seeding for the local platform.
-Applications that need to keep random state in an external file should
-use L<RAND_load_file(3)>.
+can be found in the literature; for example [NIST SP 800-90B].
+The content of B<buf> cannot be recovered from subsequent random generator output.
+Applications that intend to save and restore random state in an external file
+should consider using L<RAND_load_file(3)> instead.
RAND_seed() is equivalent to RAND_add() with B<randomness> set to B<num>.
-RAND_event() and RAND_screen() are equivalent to RAND_poll().
+RAND_keep_random_devices_open() is used to control file descriptor
+usage by the random seed sources. Some seed sources maintain open file
+descriptors by default, which allows such sources to operate in a
+chroot(2) jail without the associated device nodes being available. When
+the B<keep> argument is zero, this call disables the retention of file
+descriptors. Conversely, a non-zero argument enables the retention of
+file descriptors. This function is usually called during initialization
+and it takes effect immediately.
+
+RAND_event() and RAND_screen() are equivalent to RAND_poll() and exist
+for compatibility reasons only. See HISTORY section below.
=head1 RETURN VALUES
-RAND_status() returns 1 if the CSPRNG has been seeded
+RAND_status() returns 1 if the random generator has been seeded
with enough data, 0 otherwise.
RAND_poll() returns 1 if it generated seed data, 0 otherwise.
The other functions do not return values.
-=head1 NOTES
-
-The new OpenSSL DRBG has some peculiarities which need to be taken
-into account when it is selected as the default OpenSSL CSPRNG, i.e.,
-when RAND_get_rand_method() == RAND_OpenSSL().
-This applies in particular to the way reseeding is done by the DRBG:
-
-=over 2
-
-=item *
-
-The DRBG seeds itself automatically, pulling random input from trusted
-entropy sources.
-Automatic reseeding occurs after a predefined number of generate requests.
-The selection of the trusted entropy sources is configured at build
-time using the --with-rand-seed option.
-
-=item *
-
-The DRBG distinguishes two different types of random input:
-'entropy', which comes from a trusted source, and 'additional input',
-which can optionally be added by the user and is considered untrusted.
-
-=back
-
-Automatic seeding can be disabled using the --with-rand-seed=none option.
-
-=head2 DRBG with automatic seeding enabled
-
-Calling RAND_poll() or RAND_add() is not necessary, because the DRBG
-polls the entropy source automatically.
-However, both calls are permitted, and do reseed the RNG.
-
-RAND_add() can be used to add both kinds of random input, depending on the
-value of the B<randomness> argument:
-
-=over 4
-
-=item randomness == 0:
-
-The random bytes are mixed as additional input into the current state of
-the DRBG.
-Mixing in additional input is not considered a full reseeding, hence the
-reseed counter is not reset.
-
-
-=item randomness > 0:
-
-The random bytes are used as entropy input for a full reseeding
-(resp. reinstantiation) if the DRBG is instantiated
-(resp. uninstantiated or in an error state).
-A reseeding requires 16 bytes (128 bits) of randomness.
-It is possible to provide less randomness than required.
-In this case the missing randomness will be obtained by pulling random input
-from the trusted entropy sources.
-
-=back
-
-=head2 DRBG with automatic seeding disabled (--with-rand-seed=none)
-
-Calling RAND_poll() will always fail.
-
-RAND_add() needs to be called for initial seeding and periodic reseeding.
-At least 16 bytes (128 bits) of randomness have to be provided, otherwise
-the (re-)seeding of the DRBG will fail.
-
=head1 HISTORY
RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
=head1 SEE ALSO
-L<RAND_bytes(3)>, L<RAND_egd(3)>,
-L<RAND_load_file(3)>
+L<RAND_bytes(3)>,
+L<RAND_egd(3)>,
+L<RAND_load_file(3)>,
+L<RAND(7)>
=head1 COPYRIGHT
-Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
projects / openssl.git / blobdiff