[openstack-dev] [keysstone] External authentication

boden boden at linux.vnet.ibm.com
Thu Sep 27 12:24:47 UTC 2012

I was recently looking into this same topic and came across the related
blueprint: https://blueprints.launchpad.net/keystone/+spec/sql-identiy-pam

I have been trying to reach the blueprint author by email for a few days
to understand if there has been any community interest in his blueprint,
but no response from him yet.

IMO PAM support in Keystone decoupled from the underlying Identity
Driver would be a nice value-add. This would allow consumers to use PAM
transparently across all concrete identity drivers (LDAP, SQL, etc.)
opening the door for numerous authentication mechanisms (as you mentioned).

I recently implemented a prototype for PAM support in Keystone, and
although similar to what you describe it appears to be more generic...

Rather than going into the details of the design, let me state the core
use cases that my prototype supports:
* As a keystone admin, I want the ability to specify 1 or more
authentication module classes in keystone.conf that can conditionally be
used to authenticate a POST /tokens request in the keystone service.
* As a keystone admin, I want to be able to use keystone PAM classes
irrespective of the concrete identity driver type (SQL, LDAP, KVS, etc.).
* As an keystone PAM developer, I want my module implementation to have
access to the request body/header in the POST /tokens request so that I
can get/put properties from/into it and also conditionally determine if
my module is applicable for the current request.
* As a keystone PAM developer, I want my module implementation to have a
reference to the concrete identity driver being used so that I can
interface with it as needed.
* As a keystone admin, I want my concrete identity driver's
authentication functionality used when no PAM classes are specified in
keystone.conf (i.e. what we have today) or when none of the PAM classes
are applicable to the given POST /tokens request.

I realize the proper way to socialize this idea is via a blueprint.
However given this idea encompasses the existing blueprint I linked
above I was hoping to 1st sync up with the existing blueprint author.

That said, I'm doing a little fishing here -- anyone have interest in
this idea?


On 9/27/2012 4:15 AM, Ralf Haferkamp wrote:
> On Tue, Sep 25, 2012 at 04:06:36PM -0700, heckj wrote:
>> Ralf - 
>> Keystone supports this by having an internal API that allows you to write
>> your own authentication backend for the various components. For this sort of
>> use, I'd recommend writing your own backend for Identity that interacts with
>> and translates from the back-end systems you're interested in using.
> Hm, I am trying to implement this in a way that is independed of the identity
> backend that is actually used. And currently it is only meant to handle the
> authentication part. Information about which Users, Roles and Tenants are
> present is still handled by the existing Drivers. So implementing another
> Identity backend for this seemed wrong (if possible at all). Keystone, when
> configured for external Authentication, would just trust apache (or another
> entity external to keystone) for doing authentication and providing information
> about the authenticated user. This is I think very helpful to support things
> like Kerberos Authentication (or X.509 Client Certificates) which do not rely
> on the username/password scheme that "normal" keystone authentication currently
> requires.
> Currently I have implemented my prototype in this way:
> - implemented a wsgi.Middleware, that when added into keystone's
>   public-/admin_api pipelines, extracts apache's information about the
>   authenticated user from the Enviroment and adds that information to
>   keystone's request context.
> - in TokenControler.authenticate(), if the above information is present in the
>   context, I check if that user is present (and not disabled) in the currently
>   configured identitiy backend and issue a new token for that user. (That means
>   there's no need for any username/password to be present in the POSTed JSON
>   document)
> So this should really work independed of the identity backend that is in use
> and doesn't require the introduction of a new backend I think.
> regards,
>     Ralf
>> Chris Hoge at U Oregon did something very much like this with the UOregon SSO
>> system (I heard about it at OSCON this past July). 
>> The relevant internal API for Identity is documented in
>> http://docs.openstack.org/developer/keystone/keystone.identity.html#module-keystone.identity.core,
>> and you can read the backends that implement that set of methods in
>> keystone/identity/backends - kvs.py, sql.py, etc.
>> - joe
>> On Sep 25, 2012, at 2:20 AM, Ralf Haferkamp <rhafer at suse.de> wrote:
>>> I've been thinking about adding support for External Authentication to
>>> keystone. By "External Authentication" I mean that e.g. when I run keystone
>>> behind apache it would be nice if I could just let apache handle the
>>> authentication (via mod_auth_kerb for example) and have keystone issue a Token
>>> based on the information that apache provides about the authenticated user
>>> (e.g. the username is usually passed via the REMOTE_USER env variable).
>>> I am currently wondering how the client should indicate to the server that
>>> External Auth should be used? One could add another parameter to the JSON doc
>>> that's POSTed during keystone authentication instead of the username/password
>>> tuple, but is that really needed or should keystone just check of the presence
>>> of specific ENV variables (e.g. REMOTE_USER as set by apache2) when external
>>> auth is enabled. In my current prototype implementation I do just that. What
>>> would be the preferable approach here?
>>> BTW, has anybody else been working on this already? Does this even sound like a
>>> feature worth adding?
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