upstream: 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@

OpenBSD-Commit-ID: 19767213c312e46f94b303a512ef8e9218a39bd4

1 files changed, 2 insertions, 2 deletions

diff --git a/authfd.h b/authfd.h
index a032fd542..060bed63f 100644
--- a/authfd.h
+++ b/authfd.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: authfd.h,v 1.44 2018/07/12 04:35:25 djm Exp $ */
+/* $OpenBSD: authfd.h,v 1.45 2019/06/21 04:21:04 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -29,7 +29,7 @@ void	ssh_close_authentication_socket(int sock);
 int     ssh_lock_agent(int sock, int lock, const char *password);
 int     ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp);
 void    ssh_free_identitylist(struct ssh_identitylist *idl);
-int     ssh_add_identity_constrained(int sock, const struct sshkey *key,
+int     ssh_add_identity_constrained(int sock, struct sshkey *key,
             const char *comment, u_int life, u_int confirm, u_int maxsign);
 int     ssh_remove_identity(int sock, struct sshkey *key);
 int     ssh_update_card(int sock, int add, const char *reader_id,