Open Stack

Dear Henry and Joe

I will try to respond to some of both of your points.

Firstly I agree with Henry that segmenting an openstack installation 
into multiple independent domains is an important functionality to 
provide. But coupled with this, we should also have the ability to 
provide interdomain access as well. Otherwise you end up with 
un-interoperable silos. For example, two organisations may have separate 
domains on the same openstack system, and later decide they want to 
cooperate and have some of their users share information. This should be 
achievable with configuration or policy changes without having to 
rebuild the entire openstack system. So I would extend Henry's no 1 goal 
to be "interoperable domains"  rather than standalone domains.

It seems to me that Henry's second goal can be relatively easily 
achieved by having a proper RBAC/ABAC interface between the service 
(PEP) and the policy engine (PDP). This will allow different PDPs to be 
plugged in that support much more fine grained and sophisticated 
policies e.g. conditions based on time of day/week/month, different 
authentication levels etc without the user's role(s) necessarily needing 
to change. And this naturally leads onto the comments made by Joe.

Joe, if we have a set of goals of varying levels of importance and 
priority, rather than picking the top priority goal and making a 
tailored solution to it, that solves this goal and only this goal, isnt 
it better to produce a more generic abstracted solution that can also 
solve many of the other goals as well? The former leads to more 
spaghetti code with different special parameters and APIs for different 
goals ie. a complex system that is very difficult to understand, whereas 
the latter leads to a conceptually much simpler system with cleaner code 
and more flexibility.

Here is a case in point. The current RBAC interface requires in your 
words "all the data that comes in from the roles (name, user, tenant, 
etc).....to provide authorization". This requires many different special 
parameters to be passed to the policy engine via the API, and if you 
want to add groups in the future, then this causes yet another parameter 
to be added to the interface. However, if you go up a level of 
abstraction and say that you pass a set of subject attributes to the 
policy engine, and the API is written in this way, then you have an 
infinitely extensible interface that does not need to change when groups 
are added. Group is just another subject attribute that can be passed 
along with role, user, tenant, name etc. The API design is future proof 
to whichever new subject attributes come along next year or next decade.

Joe, the above should also help to answer your question about type/value 
pairs. In the subject attributes example above, the type value pairs 
passed via the API might be
name=David
user=1234
tenant=xyz
role=prof
Once you have this type of ABAC interface, it becomes trivial to add new 
features, by simply adding a new attribute type and value to those 
passed to the PDP, for example, to base authz also on the strength of 
authentication, you might add
LOA=2 (level of assurance as per the NIST recommendation)
to the set of subject attributes.
A flexible policy based PDP can easily take this new attribute into 
account when policies are written and decisions are made, without 
needing to change the policy code base. You simply change the policy.
You will of course need to change the service PEP, since it will need to 
pick up this new attribute from the Keystone authentication service, and 
pass it to the policy engine.

regards

David

On 23/11/2012 13:06, Henry Nash wrote:
> Hi
>
> So I'll let others, e.g. David, perhaps provide a more detailed
> description of ABAC etc., but setting out the high level goals is an
> excellent approach.
>
> For me the highest level goal is to improve the acceptability of
> openstack in the enterprise market so as to grow the % of
> installations based on it, both for public and private clouds.  In
> such installations "multi-tenancy" is crucial - unfortunately that
> word is much over used.  What I mean by it in this context is that a
> cloud provider can logically segment their openstack installation in
> order to give their customers (e.g. different enterprises hosted on a
> single public cloud, or, say, company divisions in a private cloud)
> what appears to be their own cloud, even though it is hosted on a
> shared openstack installation.  The cloud provider should be able to
> delegate the administration of appropriate aspects of the customers,
> so that they can self-administer.  For Keystone, as the security
> fabric, the focus should be around using Domains as the underpinning
> of this and extending them to provide the flexibility needed for the
> above.  Further, we need to connect that concept to the other parts
> of openstack - e.g. images, objects, availability zones, quotas etc.
> so that a cloud provider can really provide the logical view required
> by customers while getting the most use of the h/w used to back the
> whole cloud and keeping their admin costs low.  This, for me, is
> priorty #1
>
> As the above succeeds, then enterprises will start running up against
> some of the flexibility limitations we have in access control.  The
> larger the enterprise, generally, the more problem they'll find - and
> this is priority #2.  One that we are already hitting is the issue of
> needing an organisation role or group (which I consider the most
> glaring hole right now).  But let's look beyond that at a rather
> trivial flexibility issue.  A large enterprise (that will almost
> certainly be regularly audited) wants to minimise its exposure by
> limiting the access that certain users have during key production
> cycles (e.g time of day/week/month or whatever) - perhaps to remove
> modification rights to certain assets.  In today's keystone model
> there is no way of doing this without either a) A given user have
> different accounts they log in as at different times, or b) the
> administrator changing the role assignments each time.  Maybe they
> also want to insist on extra authentication items for ultra-sensitive
> operations and pretty soon you end up creating many different roles
> that you try and assign the user for particular situations - leading
> to what is called "role explosion".  This becomes increasingly hard
> to manage.  ABAC tries to provide a more flexible, granular and
> dynamic equivalent of today's static role assignment.  There are some
> that argue that all ABAC is really saying is "run this dynamic check
> using a pre-defined bunch of attributes" every time you need to
> validate access and if you replace today's static role assignment
> with that, you end up in the same place.  I'll let others comment on
> that.
>
> Given the above priorities,  I believe we should: - Really flesh out
> the implications of domains across openstack - If there is low
> hanging fruit within our current RBAC that will have dramatic effect
> on enterprise acceptability, let's grab it - Investigate/experiment
> how a more flexible attribute model could be introduced, potentially
> as some extension to RBAC
>
> Henry
>
>
> On 22 Nov 2012, at 20:24, Joseph Heck wrote:
>
>> Since we're listing out limitations (and this looks to be a pretty
>> good list), can we also define the goals that you are after and
>> why?
>>
>> I get the obvious management goals of supporting groups, but I'm
>> far less clear on what we're gaining by putting in the effort to
>> evolve to an ABAC system, as architecturally clear as that sounds.
>> I'm not deep on the literature or details of RBAC, ABAC, and
>> assorted systems - so some simplified clarity in goals and what
>> this will let us achieve would help me contribute to this
>> conversation significantly.
>>
>> So more specific points - does it matter if we have a "pure" RBAC
>> system or not?
>>
>> Roles today are an arbitrary (and currently globally unique)
>> identifier of a user to a project or domain (or perhaps group) -
>> can you give me an idea of what type/value pairs are and how
>> they're used for authorization? Today we have all the data that
>> comes in from the roles (name, user, tenant, etc) that can be used
>> along with the policy files (simple rule sets that compare
>> requested action to parameters provided by the authorization token)
>> to provide authorization - all of which occurs currently at the
>> service level. Does some of this translater to type/value pairs?
>> I'm not familiar with what is meant by these or what an example
>> might be.
>>
>> - joe
>>
>>
>> On Nov 22, 2012, at 11:26 AM, David Chadwick
>> <d.w.chadwick at kent.ac.uk> wrote:
>>> Hi Henry
>>>
>>> so why dont we start by discussing/listing/recording the
>>> limitations in the current RBAC system as a first step.
>>>
>>> Here is my initial list which I am sure you can supplement. BTW,
>>> is there a wiki page where we could create a standing document
>>> listing these limitations, so that they can be ticked off once
>>> solutions have been implemented (or added to when new ones are
>>> discovered?)
>>>
>>> 1. Roles have to be global and cannot be locally created by a
>>> cloud service 2. Roles only comprise a value, whereas in general
>>> you need type/value pairs for authorisation (sometimes this is
>>> called parameterised roles in the literature). 3. The current
>>> system limits the user to having to be a particular tenant, so
>>> this cannot be called a "pure" RBAC system, since more than roles
>>> control access. 4. There is no role-mapping capability which is
>>> needed for scalability, flexibility and federation. This  is
>>> referred to in the literature as separating organisation roles
>>> from workflow roles 5. The current system does not support
>>> delegation of authority whereby a role holder can delegate a role
>>> to another user.
>>>
>>> That's an initial first draft
>>>
>>> regards
>>>
>>> David
>>>
>>>
>>> On 22/11/2012 18:07, Henry Nash wrote:
>>>> Hi David,
>>>>
>>>> So on the idea of using suffix/prefixes for user and domain
>>>> names to remove the need to add a parameter to the API - I did
>>>> think about that for a while.  Since it is only the one API
>>>> (the authentication by username/password) that requires the
>>>> parameter and that there is no equivalent of "local site login"
>>>> as in your example, I am not sure the concatenation of the
>>>> strings buys us much.  I also thought about a system when the
>>>> domain name is automatically added/stripped from user/project
>>>> names - but in the end this seems fraught with the usual
>>>> problems that such schemes have.  I think it is also important
>>>> that we are clear about can and cannot be used as a unique tag
>>>> by the users of keystone.
>>>>
>>>> On your more general comment on a wider discussion on RBAC &
>>>> ABAC should be used, I think that is a good idea.  I think we
>>>> need to discuss a few things, e.g.:
>>>>
>>>> 1) We have RBAC now, similar to many such systems.  How much
>>>> more extensible do we need to make it? 2) Is ABAC our eventual
>>>> destination?  I actually think it should be.  But what does
>>>> that mean?  a) As a replacement for RBAC (i.e. since you should
>>>> be able to implement any RBAC scheme within a broader ABAC
>>>> implementation).  Or b) is it to stand alongside RBAC (i.e. a
>>>> cloud provider could chose which they use)?  If we were
>>>> designing from a clean sheet of paper, then a) might be the
>>>> obvious answer - but of course we're not.  It might still be
>>>> the right path, but we'd have to handle the migration very
>>>> carefully and as well as really understand what happens to the
>>>> existing APIs.
>>>>
>>>> I think 2) will take some serious discussion - but I'm all for
>>>> it.  However, we can't ignore 1).  There are restrictions today
>>>> in our RBAC that will prevent enterprises using Openstack OTB
>>>> (Out of The Box), some listed in these blueprints as well as
>>>> others like the one on "groups of users".  I think we need to
>>>> keep pushing such improvements forward (we all want market
>>>> share for Openstack), while keeping an eye to make sure we can
>>>> sensibly represent them in ABAC form in the future.  A good
>>>> example is indeed that  groups of users blueprint
>>>> (https://blueprints.launchpad.net/keystone/+spec/user-groups).
>>>> This is really about allowing the creation of local (i.e. to
>>>> the domain) organizational role/attributes (I happen to call it
>>>> a group) that can be mapped to global roles (since that's all
>>>> we support today as roles are shared secrets between services
>>>> and keystone).
>>>>
>>>> Henry
>>>>
>>>> On 22 Nov 2012, at 13:00, David Chadwick wrote:
>>>>
>>>>> Hi Henry
>>>>>
>>>>> On 21/11/2012 19:59, Henry Nash wrote:
>>>>>> Hi
>>>>>>
>>>>>> I have been working, with others, on a set of blueprints
>>>>>> (some already discussed on this list) that enhance the
>>>>>> definition and use of domains to make Openstack more
>>>>>> successful and acceptable to enterprise customers (both
>>>>>> when being hosted by a openstack-based cloud provider as
>>>>>> well as for private clouds).  I would welcome
>>>>>> comments/suggestions:
>>>>>>
>>>>>> *Optional private name spaces for domains*.  The initial
>>>>>> draft of this proposal has been discussed here before, but
>>>>>> I have now added details of the proposed changes :
>>>>>> https://blueprints.launchpad.net/keystone/+spec/domain-name-spaces
>>>>>
>>>>>
>>>>>>
I fully support your spec for domain-name-spaces from a conceptual 
perspective. It makes eminent sense. Concerning the implementation 
details, I am more agnostic. Have you considered for example, that 
usernames, projects etc. that have private names, could be simply 
converted into global names by prefixing them (or suffixing them) with 
the global domain name, without creating an extra "domain_name" 
parameter on the APIs. Would that work? Eduroam for example uses a 
similar scheme, by allowing local usernames to be used for 
authentication when you are logging in to the local site/domain, but you 
must use username at dns.name when logging in to a remote site (where 
dns.name is the DNS name of your domain).
>>>>>
>>>>>
>>>>>>
>>>>>> *Token scoping to a domain*.  More easily enabling the
>>>>>> operation of domain-wide admin roles:
>>>>>> https://blueprints.launchpad.net/keystone/+spec/domain-scoping
>>>>>
>>>>>
>>>>>>
No comments on this spec for now
>>>>>
>>>>>>
>>>>>> *Domain role assignment.*  Providing more flexibility in
>>>>>> terms of what the current functionality means to assign a
>>>>>> role to a user-domain pair:
>>>>>> https://blueprints.launchpad.net/keystone/+spec/domain-role-assignment
>>>>>
>>>>>
>>>>>>
I would like to open up this whole discussion to "how is RBAC or ABAC to 
be used in general" ie. how are roles to be assigned, how are 
permissions to be granted etc. It seems that you are only addressing one 
small aspect of a much larger discussion in your current document.
>>>>>
>>>>> One could consider for example that roles can have global or
>>>>> local names, just like usernames and projects can have in
>>>>> your first blueprint above. What follows from this would be
>>>>>
>>>>> i) if a role has a globally unique name it can potentially
>>>>> give privileged access to all resources in all domains on all
>>>>> clouds (rather like the dollar gives me access to resources
>>>>> all over the world)
>>>>>
>>>>> ii) if a role has a local name then it can only give
>>>>> privileged access to resources that are within the same name
>>>>> space as itself.
>>>>>
>>>>> iii) a local role can be converted into a global role by
>>>>> prefixing it with the name of its name space
>>>>>
>>>>> Another issue to consider is, why are users restricted to
>>>>> only accessing resources within their own tenant? This is a
>>>>> needless restriction, and will cause us problems when we come
>>>>> to delegation of authority. A user with a globally unique
>>>>> role should potentially have access to all resources in all
>>>>> tenants (subject to the policy of the cloud service
>>>>> provider).
>>>>>
>>>>> Perhaps if we try to take a more global look at the current
>>>>> RBAC mechanism we can specify a less restrictive,
>>>>> conceptually simpler, ABAC scheme that is a superset of the
>>>>> current restrictive RBAC scheme. And then try to migrate
>>>>> towards this
>>>>>
>>>>> regards
>>>>>
>>>>> David
>>>>>
>>>>>>
>>>>>> Henry
>>>>>>
>>>>>>
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