kdc outdated passwords (bug #14054)


See Bug 14054 - Kerberos Pre-Authentication updates badPwdCount for the 2 newest passwords in the history and results in ACCOUNT_LOCKED_OUT:

Authentications failing with WRONG_PASSWORD should not update the badPwdCount if the password was in the recent password history.

Often SMB clients like e.g. Windows, but maybe also others have a long lasting connection to a server. If the connection gets disconnected or causes NETWORK_SESSION_EXPIRED the client tries to reconnect/reauthenticate without prompting the user for credentials, they assume the password is still the same. But if the password was changed (by another client) in the meantime, the authentication with the old password will fail and would easily lock out the account. I saw Windows trying 8 times within one second.

With NTLM and plaintext authentication we already check the password history, see authsam_password_check_and_record.

We currently don't have that logic in the KDC, which is wrong and can cause an account to be locked out. Note that the auth_audit logging is not triggered for Kerberos with ACCOUNT_LOCKED_OUT.

A Windows KDC has such a logic so we should have something similar.

We also need to find out if "old password allowed period" applies to this on the KDC, but I don't think so as it's like an interactive authentication.

Edited by Stefan Metzmacher

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