Eddie Harari reported that the OpenSSH SSH daemon allows user
enumeration through timing differences when trying to authenticate
users. When sshd tries to authenticate a non-existing user, it will pick
up a fixed fake password structure with a hash based on the Blowfish
algorithm. If real users passwords are hashed using SHA256/SHA512, then
a remote attacker can take advantage of this flaw by sending large
passwords, receiving shorter response times from the server for
non-existing users.