Instead of guessing the right function to use, we malloc() 15 bytes more than
we need, and compute the aligned offset within. The AlignedBuffer class takes
care of passing the original pointer to free().
This simplifies the core crypto routines, especially the error handling. In
fact there was already one error path where we were failing to call free().
"Both the privacy and the authenticity properties of OCB degrade as
per s^2 / 2^128, where s is the total number of blocks that the
adversary acquires.... In order to ensure that s^2 / 2^128 remains
small, a given key should be used to encrypt at most 2^48 blocks (2^55
bits or 4 petabytes)"
-- http://tools.ietf.org/html/draft-krovetz-ocb-03
We deem it unlikely that a legitimate user will send 4 PB through a Mosh
session. If it happens, we simply kill the session. The server and
client use the same key, so we actually need to die after 2^47 blocks.
Closes#77.
This is a precaution to avoid saving sensitive data to disk, e.g. session keys.
We expect that corefiles are not world readable, but they're still sitting on
the physical disk and it's safer just to disable creating them.
GitHub issue #71 deals with a similar concern.
Keith Winstein