[Fedora-directory-devel] Re: How to implement Extended DNs for Samba4?

Howard Chu hyc at symas.com
Tue Oct 21 10:35:54 GMT 2008

Pierangelo Masarati wrote:
> Howard Chu wrote:
>>> Currently OpenLDAP uses the refint and memberOf modules, knowing that
>>> this attribute is simply a DN, nothing more.  These modules (and
>>> probably the input validation) will no doubt be unable to cope with the
>>> 'extended' DN form.
>>> Is it reasonable to ask that OpenLDAP carry a module so Samba-specific
>>> in it's application (reading the objectSid and entryUUID and formatting
>>> the link that way)?  Should we try to just fill this in with another
>>> search as part of the search entry callback? (at great performance
>>> cost).
>>> Any thoughts?
>> We already carry a bunch of Samba-related modules in our contrib branch.
>> I don't see any problem with adding this one. In this case all you need
>> is a module to implement parsing and processing of your magic Extended
>> DN control.
>> Frankly, I can see this being generally useful, if you define the
>> semantics broadly enough. For example, the request control could take a
>> data argument providing:
>>      MagicData ::= SEQUENCE of DerefSpec
>>      DerefSpec ::= SEQUENCE {
>>          DerefAttr    attributedescription,
>>          attributes    attrlist }
>>      attrlist ::= SEQUENCE of attr attributedescription
>> So for each DerefAttr, dereference the name and extract the attributes
>> from the target entry, and return them all in the response control.
> I see a few issues:
> - the resulting values do not conform to RFC4514; this could create
> interoperability issues with other modules plugged in that receive
> mucked DN-valued attrs, including the entry's name itself

I think you misunderstood my proposal. I'm not suggesting we muck with the 
returned DNs at all; the extra information will only appear in the response 

> - according to the definition of 1.2.840.113556.1.4.529, the GUID and
> the DN parts must always be present; we do not have any GUID (unless we
> think of casting entryUUID to GUID or something the like)

entryUUID == GUID.

> In any case, the module would need to perform a subsearch  anyway for
> each DN-valued attr that is being returned, in order to gather the
> required information, possibly with the exception of the entry's DN (in
> this case, it would suffice to add the attributes needed by the extended
> DN to the requested attrs).

Right. But perhaps we should stop referring to it as an "extended DN," since 
we're not altering the DN at all. Call it something like Subsearch or 
Dereference control (or something...). We just need to provide 
ldap_create_subsearch_control() and ldap_parse_subsearchresponse_control().

   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/

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