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Re: Controls and criticality

On Nov 2, 2008, at 11:00 AM, Pierangelo Masarati wrote:

Kurt Zeilenga wrote:
In short,
if the control is critical, the server cannot ignore it. It must either make use of it as prescribed or fail.
if the control is non-critical, the server can choose to ignore it. However, it should only do so before making use of it as prescribed.
Some controls specifications are simply broken. No part of the 'making use of the control' should depend on the value of criticality.

I'm not questioning this. I'm questioning the fact that the DSA allows a client to be happy with using a control with a criticality that could endanger the data integrity or security (and, all in all, violates the control's specs).

Also, I understand that rejecting an operation because it was performed with a non-critical control is in contrast with RFC4511.

Absolutely not. In making use of the control, critical or not, the server can certainly return an error.
Now RFC 4511 does allow for a server to, if it can, process the operation without the control. But the server certain cannot process a part the operation with the semantics implied by the operation and a part without.

Handling of dontUseCopy needs to be fixed in slapd (see ITS#5785) for conformance with RFC4511, although this would allow slapd to process a control whose criticality setting is in violation of its specs.

The server is not responsible for odd service if client fails to mark dontUseCopy critical.

I'm even more concerned about handling of RFC4370, which is now handled in full conformance of RFC4511, but I'd rather prefer that slapd rejects it if requested with criticality set to FALSE.

The server shouldn't even consider criticality in its processing until after deciding not to make use of a control, whether to fail due or ignore the control.

To me, slapd should reject those cases with protocolError.

This kind of breaks the separation between the controls criticality processing and control processing.

I tend to prefer 'be liberal in what you accept'. However, if I were to redesign LDAP from scratch, I'd remove the concept of a non- critical control in favor of requiring the client to fall-back. At present, most clients don't provide any fall-back. But I digress.