[cifs-protocol] DirSync ACLs and Deleted Objects - TrackingID#2310230040015878

[Andrew Bartlett]

> Do you mean "whether an object is returned or not"?

Yes.
To expand further: In DirSync as described the behaviour is that a
deleted object only returns the GUID and deletion state.
What I mean by a filter attack is that because not all Deleted objects
are returned, only those that match the filter, we can work out if the
object matched the filter by noting if it was returned (just a GUID and
deletion state), or not (no object returned).
What I'm getting at is that it appears that the object ACLs, including
list children, ACLs, are applied for other objects - we don't have an
information leak for 'live' objects.  But that isn't documented.
And there seems to be some special codepath (required to keep this
protocol plausibly working) for Deleted objects, either for all deleted
objects or a specific exemption for the CN=Deleted Objects SD.  
Thanks so much for your assistance!
Andrew Bartlett
On Fri, 2023-10-27 at 19:29 +0000, Obaid Farooqi wrote:
> Hi Andrew:I'll help you with this issue.I need a little
> clarification. I did not understand what you have in the following
> sentence between dashes:"They are stripped of most information, but a
> filter attack (eg search for CN=a*) can be used to discover the
> values - an object is returned nor not - showing that the objects are
> readable in that context."
> Do you mean "whether an object is returned or not"?
> Regards,Obaid FarooqiEscalation Engineer | Microsoft
> -----Original Message-----From: Obaid FarooqiSent: Monday, October
> 23, 2023 5:18 PMTo: Andrew Bartlett <abartlet at samba.org>Cc: cifs-
> protocol mailing list <cifs-protocol at lists.samba.org>; Microsoft
> Support <supportmail at microsoft.com>Subject: DirSync ACLs and Deleted
> Objects - TrackingID#2310230040015878
> Hi Andrew:Thanks for contacting Microsoft. I have created a case to
> track this issue. A member of the open specifications team will be in
> touch soon.
> Regards,Obaid FarooqiEscalation Engineer | Microsoft
> -----Original Message-----From: Andrew Bartlett <abartlet at samba.org>S
> ent: Monday, October 23, 2023 4:15 PMTo: cifs-protocol mailing list <
> cifs-protocol at lists.samba.org>; Interoperability Documentation Help <
> dochelp at microsoft.com>Subject: [EXTERNAL] DirSync ACLs and Deleted
> Objects
> Hi Dochelp,
> MS-ADTS 3.1.1.3.4.1.3 LDAP_SERVER_DIRSYNC_OID describes
> LDAP_DIRSYNC_OBJECT_SECURITY as:
> Windows Server 2003 operating system and later: If  this flag is
> present, the client can only view objects and attributes  that are
> otherwise accessible to the client. If this flag is not present,
> the  server checks if the client has access rights to read the
> changes in the NC.
>   Windows 2000 operating system: Not supported.
> 
> However, there is an exception.  Objects that are deleted are
> returned, despite the ACL on CN=Deleted objects.  They are stripped
> of most information, but a filter attack (eg search for CN=a*) can be
> used to discover the values - an object is returned nor not - showing
> that the objects are readable in that context.
> MSRC has just closed my case (82978) as it was determined this issue
> doesn't cross any MSRC recognized security boundaries.
> However, neither is this documented.  There is nothing in the above
> reference nor in MS-DRSR 5.115.3 ProcessDirSyncSearchRequest that
> explains how ACLs are applied to DirSync in the normal case, nor the
> apparent exception for CN=Deleted Objects.
> The reason I say 'apparent exception' is that, if the ACL that blocks
> 'list children' on CN=Deleted Objects were honoured, then:
> bin/ldbsearch -H ldap://192.168.122.230 -Uandrew%password ou=spy2\*
> --controls=dirsync:1:1:0Can't load /usr/local/samba/etc/smb.conf -
> run testparm to debug it
> # record 1dn:objectGUID: 0ae90a39-9fbe-4a77-8651-
> abefa1f1eaceisDeleted: TRUEisRecycled: TRUE
> Should not be able to return anything, and shouldn't indicate that an
> object known previously as spy2 existed.
> From testing, it appears that only this special DN is excluded - if
> we have an object that is hidden because the parent denies 'List
> Children', then these don't show up.  So, if we are going to get our
> DirSync behaviour more consistent, we would like to be sure of
> exactly what the rules are here.
> Thanks,
> Andrew Bartlett
> --Andrew Bartlett (he/him)       https://samba.org/~abartlet/
> Samba Team Member (since 2001) https://samba.org/
> Samba Team Lead                https://catalyst.net.nz/services/samba
> Catalyst.Net Ltd
> Proudly developing Samba for Catalyst.Net Ltd - a Catalyst IT group
> company
> Samba Development and Support: https://catalyst.net.nz/services/samba
> 
> Catalyst IT - Expert Open Source Solutions
> 
> 
-- 
Andrew Bartlett (he/him)       https://samba.org/~abartlet/Samba Team Member (since 2001) https://samba.orgSamba Team Lead                https://catalyst.net.nz/services/sambaCatalyst.Net Ltd
Proudly developing Samba for Catalyst.Net Ltd - a Catalyst IT group
company
Samba Development and Support: https://catalyst.net.nz/services/samba
Catalyst IT - Expert Open Source Solutions
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.samba.org/pipermail/cifs-protocol/attachments/20231030/4e8be675/attachment.htm>