[Freeipa-devel] Managed permission versioning

Rob Crittenden rcritten at redhat.com
Thu Apr 17 22:25:42 UTC 2014

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.

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.


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