[openstack-dev] [opnfv-tech-discuss] [Keystone][Multisite] Huge token size

Adam Young ayoung at redhat.com
Mon Mar 16 14:52:10 UTC 2015

On 03/16/2015 05:33 AM, joehuang wrote:
> [Topic]: Huge token size
> Hello,
> As you may or may not be aware of, a requirement project proposal 
> Multisite[1] was started in OPNFV in order to identify gaps in 
> implementing OpenStack across multiple sites.
> Although the proposal has not been approvedyet, we’ve started to run 
> some experiments to try out different methods. One of the problem we 
> identify in those experiments is that, when we want  to use a shared 
> KeyStone for 101 Regions ( including ~500 endpoints ). The token size 
> is huge (The token format is PKI), please see details in the attachments:
> token_catalog.txt, 162KB: catalog list included in the token
> token_pki.txt, 536KB: non-compressed token size
> token_pkiz.txt, 40KB: compressed token size
> I understand that KeyStone has a way like endpoint_filter to reduce 
> the size of token, however this requires to manage many (hard to id 
> the exact number) endpoints can be seen by a project, and the size is 
> not easy to exactly controlled.
> Do you guys have any insights in how to reduce the token size if PKI 
> token used? Is there any BP relates to this issue? Or should we fire 
> one to tackle this?

Right now there is an effort for non-multisite to get a handle on the 
problem.  The Fernet token format will make it possible for a token to 
be ephemeral.  The scheme is this:

Encode the minimal amount of Data into the token possible.

Always validate the token on the Keystone server.

On the Keystone server, the token validation is performed by checking 
the message HMAC, and then expanding out the data.

This concept is expandable to multi site in two ways.

For a completely trusted and symmetric multisite deployement, the 
keystone servers can share keys.  The Kite project was 
http://git.openstack.org/cgit/openstack/kite origianlly spun up to 
manage this sort of symmetric key sharing, and is a natural extension.

If two keystone server need to sign for and validate separate serts of 
data (future work)  the form of signing could be returned to Asymmetric 
Crypto.  This would lead to a minimal tokne size of about 800 Bytes (I 
haven't tested exactly).  It would mean that any service responsible for 
validating tokens would need to fetch and cache the responses for things 
like catalog and role assignments.

The epehemeral nature of the Fernet specification means that revocation 
data needs to bepersisted separate from the token, so it is not 100% 
ephemeral, but the amount of stored data should be (I estimate) two 
orders of magnatude smaller, maybe three.  Password changes, project 
deactivations,  and role revocations will still cause some traffic 
there.  These will need to be synchronized across token validation servers.

Great topic for discussion in Vancouver.

> [1]https://wiki.opnfv.org/requirements_projects/multisite
> Best Regards
> Chaoyi Huang ( Joe Huang )
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