[Freeipa-devel] #4389: DS deref broken after ACI refactoring

[Jakub Hrozek]

On Fri, Jun 20, 2014 at 04:06:16PM +0200, Martin Kosek wrote:
> Hello all,
> 
> I would like to discuss what should we do with the latest issue we found in
> SSSD-DS communication which is broken after the ACI refactoring.

It's not just SSSD-DS communication, any client, including ldapsearch
currently fails.

> 
> I was working with Ludwig, there is a problem in the way how deref plugin
> checks the access to the referenced entry. Instead of checking the target entry
> itself, Ludwig found out that the deref plugin checks a dummy entry created
> from the dereferenced DN, not the real entry. Details in DS ticket:
> https://fedorahosted.org/389/ticket/47821
> 
> Previously, we allowed read access globally so it worked fine. Now, when we
> have targeted ACIs using objectclass targetfilter, the access control goes
> wrong, deref plugin does not return all attributes and SSSD does not work (see
> 4389).
> 
> Question is, what should we do in 4.0. We could have the DS team to fix the
> deref plugin, but this would break SSSD connected to old RHEL/CentOs 6.x
> replicas which would not have the fix. So we need to be cautious about this one.

Why? SSSD Simply uses a client control. See
http://tools.ietf.org/html/draft-masarati-ldap-deref-00 for all the
details.

> 
> I see couple ways:
> 1) Fix DS deref plugin in F20 and next RHEL 6.x and specify the RHEL-6.x as
> minimal version of FreeIPA/DS required when replicating with FreeIPA 4.0. This
> option is a bit clumsy.

The fact that this 'fix' seems to be backwards incompatible sounds
strange to me. How exactly did you intend to fix the plugin? If the fix
was about changing DS to check the target entry instead of some dummy
entry, then I see no impact on the client.

> 
> 2) Add temporary ACIs allowing access to attributes that SSSD needs for deref
> calls. I tested it with Jakub's example call and it fixed this query:
> 
> # ipa permission-add --subtree
> cn=computers,cn=accounts,dc=idm,dc=lab,dc=eng,dc=brq,dc=redhat,dc=com
> --right={read,search,compare} --attrs={objectclass,memberof,managedby}
> --bindtype all deref_managedby
> # kinit -kt /etc/krb5.keytab
> 
> # ldapsearch -Y GSSAPI -h vm-236.idm.lab.eng.brq.redhat.com -b
> fqdn=vm-086.idm.lab.bos.redhat.com,cn=computers,cn=accounts,dc=idm,dc=lab,dc=eng,dc=brq,dc=redhat,dc=com
> -E 'deref=managedBy:objectClass'
> ...
> dn: fqdn=vm-086.idm.lab.bos.redhat.com,cn=computers,cn=accounts,dc=idm,dc=lab,
>  dc=eng,dc=brq,dc=redhat,dc=com
> control: 1.3.6.1.4.1.4203.666.5.16 false MIQAAAEgMIQAAAEaBAltYW5hZ2VkQnkEaGZxZ
>  G49dm0tMDg2LmlkbS5sYWIuYm9zLnJlZGhhdC5jb20sY249Y29tcHV0ZXJzLGNuPWFjY291bnRzLG
>  RjPWlkbSxkYz1sYWIsZGM9ZW5nLGRjPWJycSxkYz1yZWRoYXQsZGM9Y29toIQAAACfMIQAAACZBAt
>  vYmplY3RDbGFzczGEAAAAhgQJaXBhb2JqZWN0BA1pZWVlODAyZGV2aWNlBAZuc2hvc3QECmlwYXNl
>  cnZpY2UEB3BraXVzZXIEB2lwYWhvc3QEDGtyYnByaW5jaXBhbAQPa3JicHJpbmNpcGFsYXV4BAppc
>  GFzc2hob3N0BAN0b3AEFGlwYVNzaEdyb3VwT2ZQdWJLZXlz
> # managedBy: <objectClass=ipaobject>;<objectClass=ieee802device>;<objectClass
>  =nshost>;<objectClass=ipaservice>;<objectClass=pkiuser>;<objectClass=ipahost
>  >;<objectClass=krbprincipal>;<objectClass=krbprincipalaux>;<objectClass=ipas
>  shhost>;<objectClass=top>;<objectClass=ipaSshGroupOfPubKeys>;fqdn=vm-086.idm
>  .lab.bos.redhat.com,cn=computers,cn=accounts,dc=idm,dc=lab,dc=eng,dc=brq,dc=
>  redhat,dc=com
> 
> Jakub, what else would we need to allow? After this change, login/sudo seemed
> to work for me on F20.

Are you asking about the list of attributes we dereference or the list
of attributes we read from the dereferenced entries?

For IPA we only care about memberof, but keep in mind that attribute
maps in SSSD are configurable.

> 
> The ACIs would be removed when all our supported DS versions have the deref
> plugin fixed.
> 
> -- 
> Martin Kosek <mkosek at redhat.com>
> Supervisor, Software Engineering - Identity Management Team
> Red Hat Inc.