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

[Martin Kosek]

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.

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.

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.

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.

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.