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doc: document that 'openssl rand' is cryptographically secure 

Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/11213)
This commit is contained in:
Dr. Matthias St. Pierre 2020-03-02 00:25:29 +01:00
parent a24e62f54b
commit 88398d2a35
2 changed files with 29 additions and 9 deletions
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14
doc/man1/openssl-rand.pod.in
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@ -20,8 +20,14 @@ I<num>
=head1 DESCRIPTION =head1 DESCRIPTION
This command outputs I<num> pseudo-random bytes after seeding This command generates I<num> random bytes using a cryptographically
the random number generator once. secure pseudo random number generator (CSPRNG).
The random bytes are generated using the L<RAND_bytes(3)> function,
which provides a security level of 256 bits, provided it managed to
seed itself successfully from a trusted operating system entropy source.
Otherwise, the command will fail with a non-zero error code.
For more details, see L<RAND_bytes(3)>, L<RAND(7)>, and L<RAND_DRBG(7)>.
=head1 OPTIONS =head1 OPTIONS
@ -52,7 +58,9 @@ Show the output as a hex string.
=head1 SEE ALSO =head1 SEE ALSO
L<openssl(1)>, L<openssl(1)>,
L<RAND_bytes(3)> L<RAND_bytes(3)>,
L<RAND(7)>,
L<RAND_DRBG(7)>
=head1 COPYRIGHT =head1 COPYRIGHT

24
doc/man3/RAND_bytes.pod
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@ -23,8 +23,8 @@ L<openssl_user_macros(7)>:
=head1 DESCRIPTION =head1 DESCRIPTION
RAND_bytes() puts B<num> cryptographically strong pseudo-random bytes RAND_bytes() generates B<num> random bytes using a cryptographically
into B<buf>. 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 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 be used for generating values that should remain private. If using the
@ -44,10 +44,22 @@ ignored.
=head1 NOTES =head1 NOTES
Always check the error return value of RAND_bytes() and By default, the OpenSSL CSPRNG supports a security level of 256 bits, provided it
RAND_priv_bytes() and do not take randomness for granted: an error occurs was able to seed itself from a trusted entropy source.
if the CSPRNG has not been seeded with enough randomness to ensure an On all major platforms supported by OpenSSL (including the Unix-like platforms
unpredictable byte sequence. 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 =head1 RETURN VALUES