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RDRAND used directly when default engines loaded in openssl-1.0.1-beta1 through openssl-1.0.1e
From: coderman <coderman () gmail com>
Date: Sat, 14 Dec 2013 04:33:31 -0800

as per the FreeBSD announcement[0] and others[1][2] direct use of
RDRAND as sole entropy source is not recommended.

from Westmere onward you could use AES-NI to make crypto fast in
OpenSSL.  a common theme is to initialize OpenSSL via
ENGINE_load_builtin_engines() which lets OpenSSL take advantage of
this acceleration.

with Sandy Bridge you also got RDRAND. now load_builtin_engines
results in the application using RDRAND directly for all entropy, in
addition to accelerating AES.

if you are using an application linked with openssl-1.0.1-beta1
through openssl-1.0.1e you should do one of the following:

a.) rebuild your OpenSSL with OPENSSL_NO_RDRAND defined.

b.) call RAND_set_rand_engine(NULL) after ENGINE_load_builtin_engines().

c.) git pull latest openssl with commit: "Don't use rdrand engine as
default unless explicitly requested." - Dr. Stephen Henson

the OPENSSL_NO_RDRAND option is recommended; an inadvertent call to
load engines elsewhere could re-enable this bad rng behavior.

best regards,

0. "FreeBSD Developer Summit: Security Working Group, /dev/random"

1. "Surreptitiously Tampering with Computer Chips"

2. "How does the NSA break SSL? ... Weak random number generators"

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