Rename OSSL_SERIALIZER / OSSL_DESERIALIZER to OSSL_ENCODE / OSSL_DECODE

[openssl.git] / doc / man3 / RAND_bytes.pod

diff --git a/doc/man3/RAND_bytes.pod b/doc/man3/RAND_bytes.pod
index 80f75aefe1243fd07f0d6d195ccb543db1a5414b..0673f1b8393805a56e3250a88fdfcaf895fc9b1e 100644 (file)
--- a/doc/man3/RAND_bytes.pod
+++ b/doc/man3/RAND_bytes.pod
@@ -2,46 +2,104 @@
 
 =head1 NAME
 
-RAND_bytes, RAND_pseudo_bytes - generate random data
+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);
 
-Deprecated:
+ int RAND_bytes_ex(OPENSSL_CTX *ctx, unsigned char *buf, int num);
+ int RAND_priv_bytes_ex(OPENSSL_CTX *ctx, unsigned char *buf, int num);
+
+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)>:
 
- #if OPENSSL_API_COMPAT < 0x10100000L
  int RAND_pseudo_bytes(unsigned char *buf, int num);
- #endif
 
 =head1 DESCRIPTION
 
-RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes
-into B<buf>. An error occurs if the PRNG has not been seeded with
-enough randomness to ensure an unpredictable byte sequence.
+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 an additional I<ctx> parameter.
+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<OPENSSL_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() returns 1 on success, -1 if not supported by the current
+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.
 
-=head1 SEE ALSO
+=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
 
-L<RAND_bytes(3)>, L<ERR_get_error(3)>,
-L<RAND_add(3)>
+=back
 
 =head1 COPYRIGHT
 
-Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
 
-Licensed under the OpenSSL license (the "License").  You may not use
+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>.