=head1 NAME
-RAND_add, RAND_seed, RAND_status, RAND_event, RAND_screen - add
-randomness to the PRNG
+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
#include <openssl/rand.h>
- void RAND_seed(const void *buf, int num);
+ int RAND_status(void);
+ int RAND_poll();
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);
- int RAND_status(void);
+Deprecated:
#if OPENSSL_API_COMPAT < 0x10100000L
- int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
+ int RAND_event(UINT iMsg, WPARAM wParam, LPARAM lParam);
void RAND_screen(void);
#endif
=head1 DESCRIPTION
-RAND_add() mixes the B<num> bytes at B<buf> into the PRNG state. Thus,
-if the data at B<buf> are unpredictable to an adversary, this
-increases the uncertainty about the state and makes the PRNG output
-less predictable. Suitable input comes from user interaction (random
-key presses, mouse movements) and certain hardware events. The
-B<randomness> argument is an estimate of how much randomness is contained in
+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 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 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,
+see L<RAND(7)> for more details.
+
+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 IETF RFC 4086.
-
-RAND_add() may be called with sensitive data such as user entered
-passwords. The seed values cannot be recovered from the PRNG output.
-
-OpenSSL makes sure that the PRNG state is unique for each thread. On
-systems that provide C</dev/urandom>, the randomness device is used
-to seed the PRNG transparently. However, on all other systems, the
-application is responsible for seeding the PRNG by calling RAND_add(),
-L<RAND_egd(3)>
-or 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 deprecated and should not be called.
+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 PRNG has been seeded
+RAND_status() returns 1 if the random generator has been seeded
with enough data, 0 otherwise.
-RAND_event() calls RAND_poll() and returns RAND_status().
+RAND_poll() returns 1 if it generated seed data, 0 otherwise.
-RAND_screen calls RAND_poll().
+RAND_event() returns RAND_status().
The other functions do not return values.
=head1 HISTORY
-RAND_event() and RAND_screen() are deprecated since OpenSSL
-1.1.0. Use the functions described above instead.
+RAND_event() and RAND_screen() were deprecated in OpenSSL 1.1.0 and should
+not be used.
=head1 SEE ALSO
-L<RAND_bytes(3)>, L<RAND_egd(3)>,
-L<RAND_load_file(3)>, L<RAND_cleanup(3)>
+L<RAND_bytes(3)>,
+L<RAND_egd(3)>,
+L<RAND_load_file(3)>,
+L<RAND(7)>
=head1 COPYRIGHT
-Copyright 2000-2016 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