[Freeipa-devel] Managed permission versioning

Martin Kosek mkosek at redhat.com
Wed Apr 23 16:26:17 UTC 2014

On 04/23/2014 05:19 PM, Simo Sorce wrote:
> On Wed, 2014-04-23 at 16:10 +0200, Martin Kosek wrote:
>> On 04/21/2014 02:48 PM, Simo Sorce wrote:
>>> On Mon, 2014-04-21 at 08:39 -0400, Rob Crittenden wrote:
>>>> Simo Sorce wrote:
>>>>> On Thu, 2014-04-17 at 18:25 -0400, Rob Crittenden wrote:
>>>>>> Simo Sorce wrote:
>>>>>>> On Thu, 2014-04-17 at 15:00 -0400, Rob Crittenden wrote:
>>>>>>>> Simo Sorce wrote:
>>>>>>>>> On Thu, 2014-04-17 at 15:48 +0200, Martin Kosek wrote:
>>>>>>>>>> I would like to discuss more on the managed read permissions upgrades [1].
>>>>>>>>>> Right now, we simply merge an old permission with the new one, making sure that
>>>>>>>>>> we only add new attributes instead of just replacing them, to prevent a managed
>>>>>>>>>> permission to be spoiled by a lower FreeIPA server version which runs an updates.
>>>>>>>>>> I was thinking about it some more and seems to me we could run in problems when
>>>>>>>>>> we for example find out that some permission is too relaxed and we want to
>>>>>>>>>> remove some default attribute. Or when we want to update the permission filter.
>>>>>>>>>> Or when object has anonymous and authenticated permission and we want to move
>>>>>>>>>> attribute from anonymous to authenticated permission.
>>>>>>>>>> Changes like this can happen, especially in the first release and we do not
>>>>>>>>>> have means to address them. What about simply versioning the permissions as we
>>>>>>>>>> do with our configs? I.e.
>>>>>>>>>> 1) Introduce new MUST numeric attribute ipaPermVersion
>>>>>>>>>> 2) Add 'version' field to managed permissions:
>>>>>>>>>>        managed_permissions = {
>>>>>>>>>>            'System: Read Roles': {
>>>>>>>>>>                'version': 1,
>>>>>>>>>>                'replaces_global_anonymous_aci': True,
>>>>>>>>>>                'ipapermbindruletype': 'permission',
>>>>>>>>>>                'ipapermright': {'read', 'search', 'compare'},
>>>>>>>>>>                'ipapermdefaultattr': {
>>>>>>>>>>                    'businesscategory', 'cn', 'description', 'member', 'memberof',
>>>>>>>>>>                    'o', 'objectclass', 'ou', 'owner', 'seealso',
>>>>>>>>>>                },
>>>>>>>>>>                'default_privileges': {'RBAC Readers'},
>>>>>>>>>>            },
>>>>>>>>>>        }
>>>>>>>>>> 3) Modify updater to only update the permission if it's version is higher than
>>>>>>>>>> the one in LDAP. In that case, it should simply replace the managed permission
>>>>>>>>>> attributes with the new one, no merging (except the attributes that we allow
>>>>>>>>>> users to change).
>>>>>>>>>> When we want to change the permission, we simply do the changes, bump the
>>>>>>>>>> version and we are done and we do not need to fear some older FreeIPA will
>>>>>>>>>> overwrite it. That of course assumes that the versioning would be available
>>>>>>>>>> from FreeIPA 4.0.
>>>>>>>>>> Makes sense?
>>>>>>>>>> [1] http://www.freeipa.org/page/V3/Managed_Read_permissions
>>>>>>>>> Uhmm, yes, and no, let me explain.
>>>>>>>>> What you say *does* make sense, but you are being too focused :-)
>>>>>>>>> The upgrade issue is not limited to permissions, but affects everything.
>>>>>>>>> I think that what we need is to add a "ipa schema version" attribute
>>>>>>>>> somewhere in cn=etc, and then always check this number in the updater
>>>>>>>>> script. if this number is higher than what we know we immediately stop
>>>>>>>>> and do not perform updates that affect anything but our own server data.
>>>>>>>>> This will protect the whole tree from unintentional changes caused by an
>>>>>>>>> older replica.
>>>>>>>>> Makes sense ?
>>>>>>>> This could lead to new features not working. Those features would rely
>>>>>>>> on containers, ACIs, etc to exist but they wouldn't if the updates
>>>>>>>> aren't run.
>>>>>>> Sorry I don't get this, if they are new features, then the version will
>>>>>>> be "older" and the update *will* run and at the end raise the version.
>>>>>>> We just prevent old updates from running and current updates from
>>>>>>> running multiple times, for the shared tree.
>>>>>>> Do we depend on having updates run multiple times for the data in the
>>>>>>> shared tree ?
>>>>>>> Note that I am not saying that all updates should stop, any update for
>>>>>>> cn=config would still need to be run on each server (although setting a
>>>>>>> version there too would probably be beneficial).
>>>>>> Ok, so the update runs, adds data, which gets replicated out to
>>>>>> potentially old servers, and we're at the place you said we wouldn't be.
>>>>> I am not following you, the aim here is not to avoid replicating new
>>>>> data to old server, the aim is that if you update the rpm of an older
>>>>> replica and the rpm runs the ldap updater with the *old* code, we do not
>>>>> end up with that updater *undoing* what a more recent update did.
>>>>>> Updates are all loaded and sorted so that all changes to a given DN
>>>>>> should be applied at once, so it isn't like applying a old update and a
>>>>>> new update are two separate operations. In fact, it would likely be a
>>>>>> no-op in the case that they have already been applied.
>>>>>> Do you have any examples to clarify your concerns? I'm not following you.
>>>>> Sure at some point version freeipa version 4.2 is released and it has an
>>>>> update that changes a default object so that now attribute 'foo' is
>>>>> added, this is done through the updater.
>>>>> Later on we release freeipa version 5.0 and we realize we will have
>>>>> again to remove attribute 'foo' because we never really needed it, plus
>>>>> if it is still there it causes issues to new feature XYZ.
>>>>> The admin installs 5.0 and all are happy, then a week later he runs a
>>>>> simply yum update on th eolder replicas still running 4.2 and 4.2.1 is
>>>>> available, and gets installed and ... bah the 4.2.1 updater re-adds
>>>>> attribute 'foo' back ... and 5.0 servers are now broken.
>>>>> If we have an updater version field when the 4.2.1 update goes on it
>>>>> will see that all updates that were necessary (and more) have already
>>>>> been added and just quits.
>>>> Ok, this won't happen in a modify case. When changing data we only 
>>>> change a known existing value, so exact match is required.
>>>> The only risk is in adding and deleting data.
>>>> So if we delete a permission named "Do cool stuff" in 5.0 and that was 
>>>> something previously added in 4.2 then yeah, re-running the 4.2 updates 
>>>> will re-apply the data. Similarly deletes would always be applied.
>>>> I would not be keen on adding a global version value though, as we've 
>>>> had issues with updates in the past where re-running the updater would 
>>>> fix things. This would short circuit that.
>>> Well we could allow the updater to run on "same version" values, this
>>> would preserve this ability while still blocking older updaters.
>>> Besides modifies can be affected too, say we have default value of 10,
>>> we change it to 20 in 4.2 then change it back to 10 in 5.0 as we found
>>> an issue with the new value. If you run 4.2 updater it puts it back to
>>> 20.
>>> All cases of flipping values are also affected.
>>>> Something more fine-grained might work but carries its own problems.
>>> I think in this case we really want a domain level version, as the tree
>>> is shared and we want updates to be consistent, so the update need to be
>>> applied in full or not at all IMO.
>>> We do have some fine-grained approach as we will have a separate version
>>> for he shared tree than the cn=config tree (and I guess another one for
>>> the CA tree).
>>> Each tree is a Silo, and should have its own tree version.
>>> Simo.
>> I think you are just designing
>> https://fedorahosted.org/freeipa/ticket/2961
>> The idea to only run updates when the version of the tree is the same or higher
>> than your FreeIPA package's.
> It is exactly the inverse :-)
> Run updates if the version is equal or *lower*.

Umh, right - this is what I actually meant (but not typed) :-)

>>  I am thinking this should work properly except the
>> case when you have shared version replicas. It would not work for example if
>> you have stable FreeIPA 3.3 servers and then you try installing FreeIPA 4.0
>> replica.
> The ticket you mention is different, it says to not run certain updates
> if the version is past a certain version, that is also a useful feature,
> but only for tasks really.

Ah, correct - LDAP updates like

# Add the default PAC type to configuration
dn: cn=ipaConfig,cn=etc,$SUFFIX
addifnew: ipaKrbAuthzData: MS-PAC

will still add ipaKrbAuthzData back if someone purposefully deleted the attribute.

>> Now until you move all your FreeIPA 3.4 servers to FreeIPA 4.0, you will be cut
>> out of LDAP updates. For example, if we release security release FreeIPA 3.4.1,
>> it's LDAP updates would not be updated as tree version would be 4.0.
> True, but if we release a security release 3.4.1 that requires updates
> to the tree then we have 2 options:
> A) The 4.0 versioned tree is not vulnerable because of previous ldap
> updates, so no updates are necessary.
> B) We also release 4.0.1 because the vulnerability is also there, so all
> you need to do is update one of the 4.0 release and the tree will be
> updated.

Ok, we just need to be aware of this.

>> As for new permissions, with your scheme we would need to go through all
>> permissions and forcefully overwrite what is in LDAP instead of just comparing
>> the permission versions and updating if necessary.
> I do not understand this comment, sorry.
> Simo.

This comment was specific to how managed permission updater works. With a
version per permission, updater could just look at own managed permission
versions and versions of managed permissions in LDAP and run update only for
those that have lower version.

With global tree version, updater will need to run through all own managed
permission definitions and overwrite what's in LDAP to be sure that all updates
are done.


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