HI!
What really strikes users is the lack of feedback in case a unique constraint or other constraint fails.
Let's look at error messages of slapo-unique first. I'm experimenting with a pretty simple patch for returning the effective uniqueness filter in the diagnosticMessage.
Example output with this patch (line wrapped):
$ ldapadd -f test.ldif adding new entry "uid=foo,ou=Users,dc=example,dc=com" ldap_add: Constraint violation (19) additional info: non-unique attributes found with (|(uid=foo)(uidNumber=20000))
Even this minimum information is already somewhat useful. Of course it would be even more nice to get the list of non-unique attribute values returned. (I vaguely remember some idea for a "What Failed?" response control.)
Now formerly one of the arguments against returning more information in the diagnosticMessage was that this would reveal content information to an attacker which is obtained by an internal search with a more privileged authz-ID.
Yes, that's right.
But this problem exists anyway because an attacker can probe values by adding entries with non-unique attributes and determine whether an attribute value exists or not by distinguishing the result code constraintViolation(19) vs. insufficientAccessRights(50). Even worse this even works in case the attacker does not have read access anywhere!
This leads to the question whether some sort of access control or limit check should be applied in unique_search().
What do you think?
Ciao, Michael.