https://bugs.openldap.org/show_bug.cgi?id=10254
Issue ID: 10254 Summary: Allow upgrading password hash on bind Product: OpenLDAP Version: unspecified Hardware: All OS: All Status: UNCONFIRMED Keywords: needs_review Severity: normal Priority: --- Component: overlays Assignee: bugs@openldap.org Reporter: me@floriswesterman.nl Target Milestone: ---
Many OpenLDAP installations are likely to contain relatively old password hashes such as SSHA and CRYPT, as modern alternatives such as Argon are only recent additions. Due to the nature of password hashes, it is of course not possible to "unhash" the old values and rehash them with a more modern algorithm. The presence of these old password hashes poses a liability in case of information leaks or hacks.
Currently, the only way to upgrade a password hash is to wait for the user to change their password. This can be sped up by expiring passwords and forcing users to change them. However, this can be slow and frequent password rotation is no longer considered a best practice.
It would be a very helpful addition to add support for upgrading a password hash on bind. This is implemented in the 389 directory server: https://www.port389.org/docs/389ds/design/pwupgrade-on-bind.html
Essentially, when a user binds, the password is checked like normal. In case of a successful bind, the proposed feature would check the hash algorithm used for the password; and in case it is not equal to the current `olcPasswordHash` value, the user-provided password is rehashed using the new algorithm and stored. This way, the old hashes are phased out more quickly, without being a disturbance to users.