[Freeipa-devel] Ticket #2866 - referential integrity in IPA

[Martin Kosek]

On 09/04/2012 04:40 PM, Rich Megginson wrote:
> On 09/03/2012 08:42 AM, Martin Kosek wrote:
>> On 08/27/2012 06:29 PM, Rich Megginson wrote:
>>> On 08/27/2012 10:24 AM, Martin Kosek wrote:
>>>> On 08/17/2012 04:00 PM, Rich Megginson wrote:
>>>>> On 08/17/2012 07:44 AM, Martin Kosek wrote:
>>>>>> Hi guys,
>>>>>>
>>>>>> I am now investigating ticket #2866:
>>>>>> https://fedorahosted.org/freeipa/ticket/2866
>>>>>>
>>>>>> And I am thinking about possible solutions for this problem. In a
>>>>>> nutshell, we do not properly check referential integrity in some IPA
>>>>>> objects where we keep one-way DN references to other objects, e.g. in
>>>>>> - managedBy attribute for a host object
>>>>>> - memberhost attribute for HBAC rule object
>>>>>> - memberuser attribute for user object
>>>>>> - memberallowcmd or memberdenycmd for SUDO command object (reported in
>>>>>> #2866)
>>>>>> ...
>>>>>>
>>>>>> Currently, I see 2 approaches to solve this:
>>>>>> 1) Add relevant checks to our ipalib plugins where problematic
>>>>>> operations with these operations are being executed (like we do for
>>>>>> selinuxusermap's seealso attribute in HBAC plugin)
>>>>>> This of course would not prevent direct LDAP deletes.
>>>>>>
>>>>>> 2) Implement a preop DS plugin that would hook to MODRDN and DELETE
>>>>>> callbacks and check that this object's DN is not referenced in other
>>>>>> objects. And if it does, it would reject such modification. Second
>>>>>> option would be to delete the attribute value with now invalid
>>>>>> reference. This would be probably  more suitable for example for
>>>>>> references to user objects.
>>>>>>
>>>>>> Any comments to these possible approaches are welcome.
>>>>>>
>>>>>> Rich, do you think that as an alternative to these 2 approaches,
>>>>>> memberOf plugin could be eventually modified to do this task?
>>>>> This is very similar to the referential integrity plugin already in 389,
>>>>> except
>>>>> instead of cleaning up references to moved and deleted entries, you want
>>>>> it to
>>>>> prevent moving or deleting an entry if that entry is referenced by the
>>>>> managedby/memberhost/memberuser/memberallowcmd/memberdenycmd of some other
>>>>> entry.
>>>> I think that using or enhancing current DS referential integrity plugin
>>>> will be
>>>> the best and the most consistent way to go.
>>>>
>>>> We already use that plugin for some user attributes like "manager" or
>>>> "secretary". seeAlso is already covered by default, so for example seeAlso
>>>> attribute in SELinux usermap object referencing an HBAC rule will get removed
>>>> when relevant HBAC rule is removed (I just checked that).
>>>>
>>>>> Note that the managed entry plugin (mep) already handles this for the
>>>>> managedby
>>>>> attribute.
>>>> I assume you are referencing "mepmanagedby" and "mepmanagedentry" attributes
>>>> which then produce errors like this one:
>>>>
>>>> # ipa netgroup-del foo
>>>> ipa: ERROR: Server is unwilling to perform: Deleting a managed entry is not
>>>> allowed. It needs to be manually unlinked first.
>>>>
>>>> managedBy attribute used by hosts objects I had in mind seems to not be
>>>> covered.
>>>>
>>>> But you are right, this is pretty much what I wanted. Though in case of MEP,
>>>> there is a link in both referenced objects, but in our case, we have just the
>>>> one-way link.
>>>>
>>>>> Are you already using the memberof plugin for
>>>>> memberhost/memberuser/memberallowcmd/memberdenycmd?
>>>>>
>>>>> This doesn't seem like a job for memberof, this seems like more of a new
>>>>> check
>>>>> for the referential integrity plugin.
>>>>>
>>>> I am now considering if current move/delete clean up already present in
>>>> Referential Integrity plugin would not be sufficient for us.
>>>>
>>>> Rich, please correct me if I am wrong, but in that case, we would just need to
>>>> add relevant attribute names
>>>> (memberhost/memberuser/memberallowcmd/memberdenycmd...) to Referential
>>>> Integrity plugin configuration as nsslapd-pluginarg7, nsslapd-pluginarg8, ...
>>>> I wonder if there would be some performance issues if we add attributes to the
>>>> list this way.
>>> No, not if they are indexed for presence and equality.
>>>
>> Hello Rich,
>> I am back to investigate this ticket. In order to be able to deliver some
>> working solution to IPA 3.0, I plan to take advantage of current Referential
>> Integrity Plugin to clean up dangling references.
>>
>> This is the plan I plan to take:
>> 1) Add pres,eq indexes for all un-indexed attributes that we want to check:
>> sourcehost
>> memberservice
>> managedby
>> memberallowcmd
>> memberdenycmd
>> ipasudorunas
>> ipasudorunasgroup
> ok
>>
>> 2) Add missing "pres" index for attributes we want to check, but only have eq
>> index:
>> manager
>> secretary
>> memberuser
>> memberhost
>>
>> I assume this step is also needed in order to keep the server performance.
> yes
>>
>> 3) Add all these attributes do Referential Integrity Plugin attribute list of
>> not already
> ok
>>
>> 4) Also add Index task (nsIndexAttribute) for all these new indexes so that
>> they are created during IPA server upgrade.
> ok
>>
>> Is this procedure OK DS-wise?
> Yes
>>
>> I also have question regarding the following note in RHDS doc chapter 3.6.
>> Maintaining Referential Integrity:
>>
>> "The Referential Integrity Plug-in should only be enabled on one supplier
>> replica in a multi-master replication environment to avoid conflict resolution
>> loops..."
>>
>> Currently, we enable this plugin on all IPA replicas. Is this something we need
>> to be concerned about and fix ASAP (before we do all this RefInt effort)?
> 
> Mark/Nathan - I know you guys have looked at this issue.

Hello guys,

any update on that? Just checking before I implement this extended referential
check in IPA.

Thanks,
Martin