SSH gets protection against side channel attacks

Damien Miller ( djm@ ) has just committed a new feature for SSH that should help protect against all the various memory side channel attacks that have surfaced recently.

Add protection for private keys at rest in RAM against speculation and memory sidechannel attacks like Spectre, Meltdown, Rowhammer and Rambleed. This change encrypts private keys when they are not in use with a symmetic key that is derived from a relatively large "prekey" consisting of random data (currently 16KB).

Attackers must recover the entire prekey with high accuracy before they can attempt to decrypt the shielded private key, but the current generation of attacks have bit error rates that, when applied cumulatively to the entire prekey, make this unlikely.
Implementation-wise, keys are encrypted "shielded" when loaded and then automatically and transparently unshielded when used for signatures or when being saved/serialised.
Hopefully we can remove this in a few years time when computer architecture has become less unsafe.
been in snaps for a bit already; thanks deraadt@
ok dtucker@ deraadt@

Many thanks to Damien and all the others involved for working on this improvement!