Even I have PermitEmptyPasswords no (standard configuration from qa0404),
when the password is deleted from /etc/shadow (ie: there is empty field
with pasword in shadow file), the ssh daemon allow to anybody log in when
supply any non-empty pasword (but did not allow to log-in when user type no
I newer see this bug before.
It seems that there is serious bug in openssh server daemon in log-in
This is intertwined with the nullok option to pam_unix, which allows access to
any account which has an empty crypted password field (in /etc/passwd or in
/etc/shadow). So while sshd will reject an empty password immediately if
configured to do so, it will pass a non-empty password along to pam_unix, which
will allow access.
If you remove the "nullok" option from the lines in /etc/pam.d/system-auth which
refer to /lib/security/pam_unix.so, does this resolve the problem?