are you affected?
- is your sshd running on musl? (alpine, openwrt, buildroot, yocto)
- is it not using pam? alpine's openssh-server doesn't by default, or maybe you set UsePAM no
- are password logins still on? they are by default
- is there an account with just * as its password? key-only users, ldap users, root on alpine
- and some other account with a real password?
- then that * account takes any password between 257 and 1024 characters
on alpine's official aws and azure images that's the default alpine user, and it has passwordless doas. so it's root
on debian, ubuntu, fedora or anything else with glibc? going through pam? dropbear? openbsd? you're fine
~~NO! Exactly the opposite, that is the problem. Key-only is a prerequisite for this.~~
~~Edit: see also, the first thing that pops up under the link.~~
I was wrong, see below.
The "are you affected?" section directly contradicts this. It outright states you must have password authentication enabled. Otherwise, SSH never gives you a chance to even attempt a password.
Bottom of the page says what to do and gives 2 options to mitigate:
So if you disable password auth and only allow key auth, then you are unaffected (safe).
The introis a bit confusing but it means that if you have password auth on - then even if your regular ssh login requires a key, you are not safe.
Ah. Thanks for the correction. The intro + where I originally learned this from made me overreact a bit, it seems.