Open Stack

On 09/18/2014 05:14 PM, Doug Hellmann wrote:
> On Sep 18, 2014, at 4:34 PM, David Chadwick <d.w.chadwick at kent.ac.uk> wrote:
>
>>
>> On 18/09/2014 21:04, Doug Hellmann wrote:
>>> On Sep 18, 2014, at 12:36 PM, David Chadwick
>>> <d.w.chadwick at kent.ac.uk> wrote:
>>>
>>>> Our recent work on federation suggests we need an improvement to
>>>> the way the policy engine works. My understanding is that most
>>>> functions are protected by the policy engine, but some are not. The
>>>> latter functions are publicly accessible. But there is no way in
>>>> the policy engine to specify public access to a function and there
>>>> ought to be. This will allow an administrator to configure the
>>>> policy for a function to range from very lax (publicly accessible)
>>>> to very strict (admin only). A policy of "" means that any
>>>> authenticated user can access the function. But there is no way in
>>>> the policy to specify that an unauthenticated user (i.e. public)
>>>> has access to a function.
>>>>
>>>> We have already identified one function (get trusted IdPs
>>>> "identity:list_identity_providers") that needs to be publicly
>>>> accessible in order for users to choose which IdP to use for
>>>> federated login. However some organisations may not wish to make
>>>> this API call publicly accessible, whilst others may wish to
>>>> restrict it to Horizon only etc. This indicates that that the
>>>> policy needs to be set by the administrator, and not by changes to
>>>> the code (i.e. to either call the policy engine or not, or to have
>>>> two different API calls).
>>> I don’t know what list_identity_providers does.
>> it lists the IDPs that Keystone trusts to authenticate users
>>
>>> Can you give a little
>>> more detail about why some providers would want to make it not public
>> I am not convinced that many cloud services will want to keep this list
>> secret. Today if you do federated login, the public web page of the
>> service provider typically lists the logos or names of its trusted IDPs
>> (usually Facebook and Google). Also all academic federations publish
>> their full lists of IdPs. But it has been suggested that some commercial
>> cloud providers may not wish to publicise this list and instead require
>> the end users to know which IDP they are going to use for federated
>> login. In which case the list should not be public.
More to the point: there is going to need to be a public list.  It might 
not have everything, but it will have a subset, and the user needs to 
know what they are before they can authenticate.  This absolutely needs 
to be available before the user logs in.


Keystone is kindof a one off here, in that it is the only service that 
does not run auth_token middleware (ATM for short) Every other service 
that does can choose to split the token unpacking and the autentication 
steps:  there is a config option that says whether or not to treat a 
missing token as an authentication error.


Keystone  should make use of  ATM, but in an short-circuited way as it 
does not need to make remote calls to fetch things from Keystone.  If 
the token constriuction pipeline were pulled out of the current paste 
API, this would be quite manageble.


I tinkered with pulling /auth and /token out from the /main /admin /v3 
pipelines in the past. We need to stop the port 5000 and 35357 silliness 
anyway, so this might just be the motivation we need.

One of the problems we have with moving things around is that we are not 
RESTful:  most of the clients know A-Priori where the resources are, and 
moving them would break things.  However, AUTH_URL is usually separate 
from the endpoint returned in the service catalog. We could probably get 
away with pulling that into its own suburl without changing the rest of 
Keystone.  Then it could be in its own paste pipeline without us having 
to rewrite half of Keystone.

Good topic for the upcoming summit.



>>
>>
>>> if we plan to make it public by default? If we think there’s a
>>> security issue, shouldn’t we just protect it?
>>>
>> Its more a commercial in confidence issue (I dont want the world to know
>> who I have agreements with) rather than a security issue, since the IDPs
>> are typically already well known and already protect themselves against
>> attacks from hackers on the Internet.
> OK. The weak “someone might want to” requirement aside, and again showing my ignorance of implementation details, do we truly have to add a new feature to disable the policy check? Is there no way to have an “always allow” policy using the current syntax?
>
> Doug
>
>> regards
>>
>> David
>>
>>>> If we can invent some policy syntax that indicates public access,
>>>> e.g. reserved keyword of public, then Keystone can always call the
>>>> policy file for every function and there would be no need to
>>>> differentiate between protected APIs and non-protected APIs as all
>>>> would be protected to a greater or lesser extent according to the
>>>> administrator's policy.
>>>>
>>>> Comments please
>>> It seems reasonable to have a way to mark a function as fully public,
>>> if we expect to really have those kinds of functions.
>>>
>>> Doug
>>>
>>>> regards
>>>>
>>>> David
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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