The sntrup761 code sourced from supercop uses variable length
arrays. Although widely supported, they are not part of the ANSI
C89 spec so if the compiler does not support VLAs, disable the
sntrup761x25519-sha512@openssh.com KEX method by replacing the kex
functions with no-op ones similar to what we do in kexecdh.c.
This should allow OpenSSH to build with a plain C89 compiler again.
Spotted by tim@, ok djm@.
exchange method based on Streamlined NTRU Prime (coupled with X25519).
The previous sntrup4591761x25519-sha512@tinyssh.org method is
replaced with sntrup761x25519-sha512@openssh.com. Per the authors,
sntrup4591761 was replaced almost two years ago by sntrup761.
The sntrup761 implementaion, like sntrup4591761 before it, is public
domain code extracted from the SUPERCOP cryptography benchmark
suite (https://bench.cr.yp.to/supercop.html).
Thanks for Daniel J Bernstein for guidance on algorithm selection.
Patch from Tobias Heider; feedback & ok markus@ and myself
(note this both the updated method and the one that it replaced are
disabled by default)
OpenBSD-Commit-ID: 2bf582b772d81ee24e911bb6f4b2aecfd39338ae
