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Robert Clausecker
1af027e583
Prevent a potentially sufficiently smart compiler from optimising
away our attempts to clear sensitive buffers.
A related change was discussed and rejected in D16059, but I don't
believe the reasoning there applies: the code clearly documents its
intent that the `memset` calls clear sensitive buffers so they don't
hang around. `explicit_bzero` is the appropriate function for this
purpose. A potential performance disadvantage seems less important:
the functions in crypt are specifically designed to be slow, so a
few extra calls to guarantee that sensitive buffers are cleared does
not significantly affect runtime.
See also: D16059
Reviewed by: delphij, kevans
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D47037
(cherry picked from commit a2c0d2026f)