[cifs-protocol] Structure of prefixMap over LDAP

Fri Jan 15 10:28:29 MST 2010

Hi Kamen:
I'll look into it and will get back to you with my findings.

Regards,
Obaid Farooqi
Sr. Support Escalation Engineer | Microsoft

-----Original Message-----
From: Kamen Mazdrashki [mailto:kamen.mazdrashki at postpath.com] 
Sent: Friday, January 15, 2010 3:09 AM
To: Obaid Farooqi; abartlet at samba.org
Cc: pfif at tridgell.net; cifs-protocol at samba.org
Subject: RE: [cifs-protocol] Structure of prefixMap over LDAP

Hi Obaid,

Could you please point out where those default 39 entries for prefixMap are described?
I am looking at: http://msdn.microsoft.com/en-us/library/cc228445%28PROT.13%29.aspx
and there are only 19 default prefixes listed here.

Thanks,
Kamen Mazdrashki
kamen.mazdrashki at postpath.com
http://repo.or.cz/w/Samba/kamenim.git
-------------------------------------
CISCO SYSTEMS BULGARIA EOOD
http://www.cisco.com/global/BG/

> -----Original Message-----
> From: cifs-protocol-bounces at cifs.org [mailto:cifs-protocol- 
> bounces at cifs.org] On Behalf Of Obaid Farooqi
> Sent: Thursday, January 14, 2010 8:27 PM
> To: abartlet at samba.org
> Cc: pfif at tridgell.net; cifs-protocol at samba.org
> Subject: Re: [cifs-protocol] Structure of prefixMap over LDAP
> 
> Hi Andrew:
> Please let me know if the following answers your question. If yes, 
> I'll consider this issue resolved.
> 
> Regards,
> Obaid Farooqi
> Sr. Support Escalation Engineer | Microsoft
> 
> -----Original Message-----
> From: Obaid Farooqi
> Sent: Wednesday, January 06, 2010 2:03 PM
> To: 'abartlet at samba.org'
> Cc: 'cifs-protocol at samba.org'; 'pfif at tridgell.net'
> Subject: RE: Structure of prefixMap over LDAP
> 
> Hi Andrew,
> 
> We understand the reasons for your inquiry as to the exact content and 
> format of the LDAP attribute prefixMap.  We’d like to propose that we 
> explain the content and format of the attribute in this mail, and 
> after that, discuss whether it belongs in the documentation.
> 
> As you’ve no doubt already determined, prefixMap is related to the 
> ‘Prefix Table’ documented in MS-DRSR and used in ATTRTYP-to-OID 
> conversion; it’s also documented in MS-DRSR (section 5.16.4.)  The 
> prefixMap attribute itself though serves no purpose in the context of 
> "replication-protocol" beyond locally storing the state necessary for 
> a replication partner to decompress an implementation-specific means 
> of representing OIDs.  The attribute itself is never requested or 
> written over-the-wire by any Windows implementation nor is it 
> necessary for a partner DC to know how the map is stored.  DRSR does 
> not reference the attribute by name or refer to where the map is 
> maintained in any more general sense; it only provides the necessary 
> detail to define how the OIDs are decompressed to their native form on the partner DC.
> 
> More specifically – prefixMap is a cache of the parts of the Prefix 
> Table that relate to user-defined attributes (which is a subset of the 
> whole Prefix Table used in MS-DRSR.)  Theoretically, this structure 
> could have been built on the fly and not cached.  Certainly this cache 
> could have been stored somewhere else, besides in an attribute of the 
> directory, e.g. on a protocol-inaccessible area in memory or on disk 
> (i.e. not in abstract state).  We certainly didn’t envisage any need 
> or value in a client reading it or writing it – we would have included 
> the entire Prefix Table were that the case.  So if we don’t want any 
> client to ever read or write it then “why is it an attribute?”.  
> Basically, because it was a convenient place for our implementation to 
> locally store it – our directory implementation IS a handy place to 
> store things.  Plus, for the purposes of debugging our implementation, 
> being able to read implementation-specific values via LDAP is very 
> practical (since we read everything else that way too).
> 
> 
> 
> Anyway, the prefixMap structure contains user-defined attribute info 
> for ATTRTYP-to-OID conversion.  This means e.g. for Windows 2008 R2 it 
> does not contain the ATTRTYP-to-OID conversion info for the first 39 
> attributes in the Prefix Table as used by MS-DRSR, just the ‘rest’ of 
> them.  When this attribute has a value, it is stored as a binary blob 
> with the following formatting:
> 
> 1. First 4 bytes are a DWORD showing the total number of prefixes 
> represented in the map.  That is, the number of elements in the series 
> of data structures described below.
> 
> 2. Next 4 bytes are a DWORD showing the total size of the binary blob, 
> including both these first 8 bytes and any remaining bytes 
> representing OID prefixes.
> 
> 3. Following these first 8 bytes is a series of variable length data 
> structures, each element in the series representing a single mapping 
> between an OID prefix and the internal WORD value representing the 
> prefix.  The WORD is used as the high-word of a DWORD holding an 
> internal attribute type.  These internal attribute types are not 
> useful via LDAP, they are used only in the replication protocol. Each 
> element of the series has this format:
> 	- First 2 bytes are a WORD holding the internal WORD value.
> 	- Next 2 bytes are a WORD holding the length of the actual OID 
> prefix.  Call this value N.
> 	- Next N bytes are the BER encoding of the OID prefix.
> 
> Please let me know if this answers your question. If yes, I'll 
> consider this issue resolved.
> 
> Regards,
> Obaid Farooqi
> Sr. Support Escalation Engineer | Microsoft
> 
> 
> 
> -----Original Message-----
> From: Andrew Bartlett [mailto:abartlet at samba.org]
> Sent: Tuesday, December 15, 2009 1:39 AM
> To: Obaid Farooqi
> Cc: cifs-protocol at samba.org; pfif at tridgell.net
> Subject: RE: Structure of prefixMap over LDAP
> 
> On Tue, 2009-12-15 at 06:22 +0000, Obaid Farooqi wrote:
> > Hi Andrew:
> > In an effort to fully understand your goals, please explain what you 
> > are looking  to achieve through the addition of documentation that 
> > defines the internal structure of the prefixMap attribute.
> 
> As a start:
> 
> The ability to generate a matching prefixMap attribute, should any 
> client request it.  The ability to verify prefixMap values over DRS 
> and LDAP to confirm consistency.  The ability to include prefixMap 
> values in comparison tests we may make between AD and Samba4.  An 
> understanding of how the contents of this attribute interacts with 
> msDs-intID and other prefix mapping functionality.
> 
> Finally, I'm simply looking to ensure that the documentation set 
> explains the format of every value (generated or otherwise) in AD, so 
> we don't have to come back to this later.
> 
> Thanks,
> 
> Andrew Bartlett
> 
> --
> Andrew Bartlett
>                       http://samba.org/~abartlet/ Authentication 
> Developer, Samba Team           http://samba.org Samba Developer, 
> Cisco Inc.
> 
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