tor/changes/bug10402
Nick Mathewson 7b87003957 Never allow OpenSSL engines to replace the RAND_SSLeay method
This fixes bug 10402, where the rdrand engine would use the rdrand
instruction, not as an additional entropy source, but as a replacement
for the entire userspace PRNG.  That's obviously stupid: even if you
don't think that RDRAND is a likely security risk, the right response
to an alleged new alleged entropy source is never to throw away all
previously used entropy sources.

Thanks to coderman and rl1987 for diagnosing and tracking this down.
2013-12-18 11:53:07 -05:00

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o Major bugfixes:
- Do not allow OpenSSL engines to replace the PRNG, even when
HardwareAccel is set. The only default builtin PRNG engine uses
the Intel RDRAND instruction to replace the entire PRNG, and
ignores all attempts to seed it with more entropy. That's
cryptographically stupid: the right response to a new alleged
entropy source is never to discard all previously used entropy
sources. Fixes bug 10402; works around behavior introduced in
OpenSSL 1.0.0. Diagnosis and investigation thanks to "coderman"
and "rl1987".