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)
This commit is contained in:
Nicola Tuveri
Dr. Matthias St. Pierre
parent
f667820c16
commit
b26befb541
3 changed files with 75 additions and 23 deletions
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@ -2,7 +2,9 @@
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=head1 NAME
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BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range - generate pseudo-random number
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BN_rand, BN_priv_rand, BN_pseudo_rand,
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BN_rand_range, BN_priv_rand_range, BN_pseudo_rand_range
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- generate pseudo-random number
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=head1 SYNOPSIS
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@ -10,10 +12,14 @@ BN_rand, BN_pseudo_rand, BN_rand_range, BN_pseudo_rand_range - generate pseudo-r
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int BN_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_priv_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom);
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int BN_rand_range(BIGNUM *rnd, BIGNUM *range);
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int BN_priv_rand_range(BIGNUM *rnd, BIGNUM *range);
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int BN_pseudo_rand_range(BIGNUM *rnd, BIGNUM *range);
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=head1 DESCRIPTION
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@ -37,7 +43,16 @@ If B<bits> is 1 then B<top> cannot also be B<BN_RAND_FLG_TOPTWO>.
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BN_rand_range() generates a cryptographically strong pseudo-random
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number B<rnd> in the range 0 E<lt>= B<rnd> E<lt> B<range>.
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The PRNG must be seeded prior to calling BN_rand() or BN_rand_range().
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BN_priv_rand() and BN_priv_rand_range() have the same semantics as
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BN_rand() and BN_rand_range() respectively. They are intended to be
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used for generating values that should remain private, and mirror the
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same difference between L<RAND_bytes(3)> and L<RAND_priv_bytes(3)>.
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=head1 NOTES
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Always check the error return value of these functions and do not take
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randomness for granted: an error occurs if the CSPRNG has not been
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seeded with enough randomness to ensure an unpredictable byte sequence.
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=head1 RETURN VALUES
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@ -46,20 +61,34 @@ The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 HISTORY
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Starting with OpenSSL release 1.1.0,
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BN_pseudo_rand() has been identical to BN_rand()
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and
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BN_pseudo_rand_range() has been identical to BN_rand_range().
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=over 2
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=item *
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Starting with OpenSSL release 1.1.0, BN_pseudo_rand() has been identical
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to BN_rand() and BN_pseudo_rand_range() has been identical to
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BN_rand_range().
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The "pseudo" functions should not be used and may be deprecated in
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a future release.
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=item *
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BN_priv_rand() and BN_priv_rand_range() were added in OpenSSL 1.1.1.
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=back
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=head1 SEE ALSO
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L<ERR_get_error(3)>, L<RAND_add(3)>, L<RAND_bytes(3)>
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L<ERR_get_error(3)>,
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND_priv_bytes(3)>,
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L<RAND(7)>,
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L<RAND_DRBG(7)>
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=head1 COPYRIGHT
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Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
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Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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@ -20,13 +20,21 @@ Deprecated:
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=head1 DESCRIPTION
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RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes
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into B<buf>. An error occurs if the CSPRNG has not been seeded with
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enough randomness to ensure an unpredictable byte sequence.
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into B<buf>.
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RAND_priv_bytes() has the same semantics as RAND_bytes(). It is intended to
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be used for generating long-term private keys. If using the default
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RAND_METHOD, this function uses a separate instance of the PRNG so that
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a compromise of the global generator will not affect such key generation.
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be used for generating values that should remain private. If using the
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default RAND_METHOD, this function uses a separate "private" PRNG
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instance so that a compromise of the "public" PRNG instance will not
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affect the secrecy of these private values, as described in L<RAND(7)>
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and L<RAND_DRBG(7)>.
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=head1 NOTES
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Always check the error return value of RAND_bytes() and
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RAND_priv_bytes() and do not take randomness for granted: an error occurs
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if the CSPRNG has not been seeded with enough randomness to ensure an
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unpredictable byte sequence.
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=head1 RETURN VALUES
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@ -37,14 +45,26 @@ obtained by L<ERR_get_error(3)>.
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=head1 HISTORY
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=over 2
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=item *
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RAND_pseudo_bytes() was deprecated in OpenSSL 1.1.0; use RAND_bytes() instead.
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=item *
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RAND_priv_bytes() was added in OpenSSL 1.1.1.
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=back
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=head1 SEE ALSO
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND_priv_bytes(3)>,
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L<ERR_get_error(3)>,
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L<RAND(7)>
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L<RAND(7)>,
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L<RAND_DRBG(7)>
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=head1 COPYRIGHT
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@ -24,16 +24,19 @@ to be initialized ('seeded') explicitly.
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It seeds and reseeds itself automatically using trusted random sources
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provided by the operating system.
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As a normal application developer, you don't have to worry about any details,
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As a normal application developer, you do not have to worry about any details,
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just use L<RAND_bytes(3)> to obtain random data.
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Having said that, there is one important rule to obey: Always check the error
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return value of L<RAND_bytes(3)> and don't take randomness for granted.
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return value of L<RAND_bytes(3)> and do not take randomness for granted.
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For long-term secrets, you can use L<RAND_priv_bytes(3)> instead.
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For values that should remain secret, you can use L<RAND_priv_bytes(3)>
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instead.
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This method does not provide 'better' randomness, it uses the same type of CSPRNG.
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The intention behind using a dedicated CSPRNG exclusively for long-term secrets is
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that none of its output should be visible to an attacker (e.g used as salt value),
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in order to reveal as little information as possible about its internal state.
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The intention behind using a dedicated CSPRNG exclusively for private
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values is that none of its output should be visible to an attacker (e.g.,
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used as salt value), in order to reveal as little information as
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possible about its internal state, and that a compromise of the "public"
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CSPRNG instance will not affect the secrecy of these private values.
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In the rare case where the default implementation does not satisfy your special
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requirements, there are two options:
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@ -61,10 +64,10 @@ of cryptographic principles and understand the implications of your changes.
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND_priv_bytes(3)>,
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L<RAND_get_rand_method(3)>
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L<RAND_set_rand_method(3)>
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L<RAND_get_rand_method(3)>,
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L<RAND_set_rand_method(3)>,
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L<RAND_OpenSSL(3)>,
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L<RAND_DRBG(7)>,
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L<RAND_DRBG(7)>
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=head1 COPYRIGHT
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