Fix & update documentation about RAND_priv_bytes()

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Ben Kaduk <kaduk@mit.edu>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/6514)

1 files changed, 37 insertions, 8 deletions

diff --git a/doc/man3/BN_rand.pod b/doc/man3/BN_rand.pod
index 099dda47e9..eb0a6b1386 100644
--- a/doc/man3/BN_rand.pod
+++ b/doc/man3/BN_rand.pod
@@ -2,7 +2,9 @@
 
 =head1 NAME
 
-BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range - generate pseudo-random number
+BN_rand, BN_priv_rand, BN_pseudo_rand,
+BN_rand_range, BN_priv_rand_range, BN_pseudo_rand_range
+- generate pseudo-random number
 
 =head1 SYNOPSIS
 
@@ -10,10 +12,14 @@ BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range - generate pseudo-r
 
  int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
 
+ int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom);
+
  int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
 
  int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
 
+ int BN_priv_rand_range(BIGNUM *rnd, BIGNUM *range);
+
  int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
 
 =head1 DESCRIPTION
@@ -37,7 +43,16 @@ If B<bits> is 1 then B<top> cannot also be B<BN_RAND_FLG_TOPTWO>.
 BN_rand_range() generates a cryptographically strong pseudo-random
 number B<rnd> in the range 0 E<lt>= B<rnd> E<lt> B<range>.
 
-The PRNG must be seeded prior to calling BN_rand() or BN_rand_range().
+BN_priv_rand() and BN_priv_rand_range() have the same semantics as
+BN_rand() and BN_rand_range() respectively.  They are intended to be
+used for generating values that should remain private, and mirror the
+same difference between L<RAND_bytes(3)> and L<RAND_priv_bytes(3)>.
+
+=head1 NOTES
+
+Always check the error return value of these functions and do not take
+randomness for granted: an error occurs if the CSPRNG has not been
+seeded with enough randomness to ensure an unpredictable byte sequence.
 
 =head1 RETURN VALUES
 
@@ -46,20 +61,34 @@ The error codes can be obtained by L<ERR_get_error(3)>.
 
 =head1 HISTORY
 
-Starting with OpenSSL release 1.1.0,
-BN_pseudo_rand() has been identical to BN_rand()
-and
-BN_pseudo_rand_range() has been identical to BN_rand_range().
+=over 2
+
+=item *
+
+Starting with OpenSSL release 1.1.0, BN_pseudo_rand() has been identical
+to BN_rand() and BN_pseudo_rand_range() has been identical to
+BN_rand_range().
 The "pseudo" functions should not be used and may be deprecated in
 a future release.
 
+=item *
+
+BN_priv_rand() and BN_priv_rand_range() were added in OpenSSL 1.1.1.
+
+=back
+
 =head1 SEE ALSO
 
-L<ERR_get_error(3)>, L<RAND_add(3)>, L<RAND_bytes(3)>
+L<ERR_get_error(3)>,
+L<RAND_add(3)>,
+L<RAND_bytes(3)>,
+L<RAND_priv_bytes(3)>,
+L<RAND(7)>,
+L<RAND_DRBG(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