An access control bypass flaw was found in modrdn. In particular if a user has a rdn like uid=username, then the user can change its own rdn to any value that is a superstring of the current name bypassing access control.

This issue could be reproduced by the following:

ldapmodrnd -Y GSSAPI -r uid=testuser,cn=users,cn=accounts,dc=test,dc=ipa uid=testuser_extended_without_permission

The above succeeds and renames the user.

No authentication whatsoever is necessary. An anonymous user can completely hose a server (if not worse) by just renaming any entry it pleases.

If ACIs are employed to hide entries and those entries are targeted by
name then it is also possible to reveal those contents by renaming the
entry and falling off the ACI protection.


Acknowledgements:

This issue was discovered by Simo Sorce of Red Hat.