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Hi Adam,

I apologize if my questions were answered before.  I wasn't aware that what I perceive as a very serious security concern was openly discussed.  The arguments against revocation support, as you've described them, seem to be:

 - it's complicated/messy/expensive to implement and/or execute
 - Kerberos doesn't need it, so why would we?

I'm not sure why either of these arguments would justify the potential security hole that a lack of revocation represents, but I suppose a 'short enough' token lifespan could minimize that hole.  But how short a span are you suggesting as being acceptable?

The delay between when a user's access permissions change (whether roles, password or even account deactivation) and when the ticket reflects that change is my concern.  The default in Keystone has been 24h, which is clearly too long.  Something on the order of 5 minutes would be ideal, but then ticket issuance could become the bottleneck.  Validity that's much longer could be a real problem, though.  Maybe not at the cloud administration level, but for a given project I can imagine someone being fired and their access being revoked.  How long is an acceptable period for that ticket to still be valid?  How much damage could be done by someone who should no longer have access to an account if their access cannot be revoked, by anyone, at all?

I'm hearing that you, as the implementer of this feature, don't consider the lack of revocation to be an issue.  What am I missing?  Is support for revocation so repugnant that the potential security hole is preferable?  I can see that from a developer's perspective, but I don't understand why someone deploying Keystone wouldn't avoid PKI tokens until revocation support became available.

Thanks,


Maru 
 


On 2012-08-01, at 9:47 PM, Adam Young wrote:

> On 08/01/2012 09:19 PM, Maru Newby wrote:
>> 
>> I see that support for PKI Signed Tokens has been added to Keystone without support for token revocation.  I tried to raise this issue on the bug report:
>> 
>> https://bugs.launchpad.net/keystone/+bug/1003962/comments/4
>> 
>> And the review:
>> 
>> https://review.openstack.org/#/c/7754/
>> 
>> I'm curious as to whether anybody shares my concern and if there is a specific reason why nobody responded to my question as to why revocation is not required for this new token scheme.   Anybody?
> 
> It was discussed back when I wrote the Blueprint.  While it is possible to do revocations with PKI,  it is expensive and requires a lot of extra checking.  Revocation is a policy decision, and the assumption is that people that are going to use PKI tokens are comfortable with out revocation.  Kerberos service tickets have the same limitation, and Kerberos has been in deployment that way for close to 25 years.
> 
> Assuming that PKI ticket lifespan is short enough,  revocation should not be required.  What will be tricky is to balance the needs of long lived tokens (delayed operations, long running operations) against the needs for reasonable token timeout.
> 
> PKI Token revocation would look like CRLs in the Certificate world.  While they are used, they are clunky.  Each time a token gets revoked, a blast message would have to go out to all registered parties informing them of the revocation.  Keystone does not yet have a message queue interface, so doing that is prohibitive in the first implementation.
> 
> Note that users can get disabled, and token chaining will no longer work:  you won't be able to use a token to get a new token from Keystone.
> 
> 
>> 
>> Thanks,
>> 
>> 
>> Maru
>> 
>> 
>> 
>> 
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