> Before making each of these safer we should make sshd not link with so
> many things in the first place.

Indeed. E.g., Arch Linux does not transitively link sshd against liblzma.
Fedora does because of this innocuous-looking patch:
https://src.fedoraproject.org/rpms/openssh/blob/rawhide/f/openssh-7.4p1-systemd.patch
which is what ultimately allowed this to happen. This drags in libsystemd
for sd_notify, and libsystemd is linked to way too much stuff including
liblzma. Either we need a split libsdnotify that contains only sd_notify, or
we should just stop using sd_notify at all. It increases the attack surface
of daemons a lot just to allow the service to be "Type=notify" rather than
one of the other available approaches. Arch Linux is also systemd-based
nowadays, but still does not link OpenSSH against libsystemd.