OpenSSH 9.9

New features
------------

 * ssh(1), sshd(8): add support for a new hybrid post-quantum key
   exchange based on the FIPS 203 Module-Lattice Key Enapsulation
   mechanism (ML-KEM) combined with X25519 ECDH as described by
   https://datatracker.ietf.org/doc/html/draft-kampanakis-curdle-ssh-pq-ke-03
   This algorithm "mlkem768x25519-sha256" is available by default.

 * ssh(1): the ssh_config "Include" directive can now expand
   environment as well as the same set of %-tokens "Match Exec"
   supports.

 * sshd(8): add a sshd_config "RefuseConnection" option that, if set
   will terminate the connection at the first authentication request.

 * sshd(8): add a "refuseconnection" penalty class to sshd_config
   PerSourcePenalties that is applied when a connection is dropped by
   the new RefuseConnection keyword.

 * sshd(8): add a "Match invalid-user" predicate to sshd_config Match
   options that matches when the target username is not valid on the
   server.

 * ssh(1), sshd(8): update the Streamlined NTRUPrime code to a
   substantially faster implementation.

 * ssh(1), sshd(8): the hybrid Streamlined NTRUPrime/X25519 key
   exchange algorithm now has an IANA-assigned name in addition to
   the "@openssh.com" vendor extension name. This algorithm is now
   also available under this name IANAsntrup761x25519-sha512IANA

 * ssh(1), sshd(8), ssh-agent(1): prevent private keys from being
   included in core dump files for most of their lifespans. This is
   in addition to pre-existing controls in ssh-agent(1) and sshd(8)
   that prevented coredumps. This feature is supported on OpenBSD,
   Linux and FreeBSD.

 * All: convert key handling to use the libcrypto EVP_PKEY API, with
   the exception of DSA.

 * sshd(8): add a random amount of jitter (up to 4 seconds) to the
   grace login time to make its expiry unpredictable.