*sshole · sshhole.com
sshhole.com
openssh on musl linux has been letting people into password-less accounts since 2016.

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

  • smiletolerantlyOPEnglish
    2·
    2 hours ago

    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.

    • AHemlocksLie@lemmy.zipEnglish
      2·
      2 hours ago

      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.

    • HelloRoot@lemy.lolEnglish
      2·
      2 hours ago

      Bottom of the page says what to do and gives 2 options to mitigate:

      # update. openssh 10.6p2 fixes it.
$ apk upgrade openssh

# can't update yet? turn password logins off.
$ echo "PasswordAuthentication no" > /etc/ssh/sshd_config.d/00-no-passwords.conf
$ rc-service sshd restart

      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.

      • smiletolerantlyOPEnglish
        3·
        2 hours ago

        Ah. Thanks for the correction. The intro + where I originally learned this from made me overreact a bit, it seems.