Open Stack

Excerpts from John Dickinson's message of 2014-05-21 17:23:02 -0700:
> 
> On May 21, 2014, at 4:26 PM, Adam Young <ayoung at redhat.com> wrote:
> 
> > On 05/21/2014 03:36 PM, Kurt Griffiths wrote:
> >> Good to know, thanks for clarifying. One thing I’m still fuzzy on, however, is why we want to deprecate use of UUID tokens in the first place? I’m just trying to understand the history here...
> > Because they are wasteful, and because they are the chattiest part of OpenStack.  I can go into it in nauseating detail if you really want, including the plans for future enhancements and the weaknesses of bearer tokens.
> > 
> > 
> > A token is nothing more than a snap shot of the data you get from Keystone distributed.  It is stored in Memcached and in the Horizon session uses the hash of it for a key.
> > 
> > You can do the same thing.  Once you know the token has been transferred once to a service, assuming that service has caching on, you can pass the hash of the key instead of the whole thing.  
> 
> So this would mean that a Swift client would auth against Keystone to get the PKI token, send that to Swift, and then get back from Swift a "short" token that can be used for subsequent requests? It's an interesting idea to consider, but it is a new sort of protocol for clients to implement.
> 

Doesn't this mean that Swift would have to store the token it first
received, so that it can verify that the hash matches the token and to
extract the session information contained within?

It seems like the keystone auth middleware should be able to help with
this quite a bit, and I think it already does, but a pointer to the
documentation on how to make use of it would help close the loop here.

> > 
> > Actually, you can do that up front, as auth_token middleware will just default to an online lookup. However, we are planning on moving to ephemeral tokens (not saved in the database) and an online lookup won't be possible with those.  The people that manage Keystone will be happy with that, and forcing an online lookup will make them sad.
> 
> An "online lookup" is one that calls the Keystone service to validate a token? Which implies that by disabling online lookup there is enough info in the token to validate it without any call to Keystone?
> 

Yes, PKI tokens can be validated by the service without phoning back
home to Keystone. However, currently the service must still ask Keystone
for a list of revoked tokens periodically. In the near future that will
morph into a list of token revocation events, which should make the
backend simpler for Keystone to implement. I assume the middleware will
also do most of the heavy lifting there too.

> I understand how it's advantageous to offload token validation away from Keystone itself (helps with scaling), but the current "solution" here seems to be pushing a lot of pain to consumers and deployers of data APIs (eg Marconi and Swift and others).
> 

I tend to agree, though if the middleware implements the caching/hashing
that Adam describes, then it may only be a few changes to the way that
is configured.

> > 
> > Hash is MD5 up through what is released in Icehouse.  The next version of auth_token middleware will support a configurable algorithm.  The default should be updated to sha256 in the near future.
> 
> If a service (like Horizon) is hashing the token and using that as a session key, then why does it matter what the auth_token middleware supports? Isn't the hashing handled in the service itself? I'm thinking in the context of how we would implement this idea in Swift (exploring possibilities, not committing to a patch).
> 

The impression I got is that Horizon is a special case, and that most
services would just use the keystone auth middleware directly.