Name Constraints, was Re: [caops-wg] Re: ca signing policy file

[Frank Siebenlist]

I don't care about the collisions - that's a non-issue as far as I'm 
concerned.

The only sticky point I see, is the ability for any of your trusted CAs 
to issue certificates outside of their administrative domain and only to 
rely on essentially paper agreements to prevent this.

Note that with Kerberos cross-realm authentication, one realm is unable 
to issue credentials for the director of the other institute...

With your proposed scheme, any "trusted" CA in Italy, Germany, even 
Holland..., would have the theoretical opportunity to issue a 
certificate that would impersonate the director of Berkeley, NCSA, 
Livermore, Los Alamos... and we would have no way to enforce any policy 
in real-time that could prevent it.

If this acceptable to all our end user organizations, we should happily 
adopt the web-browser trust model with paper CA policy statements... and 
I'm serious here.

So what are the real "trust-requirements" we are working from?

Regards, Frank.


Mike Helm wrote:
> Frank Siebenlist writes:
>   
>> In other words, the Subject's DN should start with an identifier that 
>> essentially identifies the administrative domain in which the names are 
>> issued, e.g. \DOMAIN=ESNET.NET, followed by a 
>> \CN=abbf16d0-3b5f-11da-8cd6-0800200c9a66
>> In that way, a CA could be restraint to issue random names within a 
>> certain domain.
>>     
>
> Here's the subject name I had from Thawte:
> E = helm at fionn.es.net, CN = Michael Helm
>
> That's it.
>
> The E= was just for my convenience.  I could create other certificates
> with a different E= attribute if I needed to.
>
> Name collisions by themselves - so what?  I have the same
> name on my driver's license and on my library card.  Nobody
> gets worked up over that.  What I think you want, is
> to make sure that same name string isn't certified to
> two different people.  But we don't have technical means
> guarantee this. Even the current name constraints / signing policy
> scheme cannot prevent this, it can only make it a little more
> difficult.
>
> You can eliminate most "legitimate" collisions by including
> some link to the issuer in any authentication determination.
> That's the administrative domain.
>
> You find some CA issues duplicate DN's from other domains?
> Don't use them.   In any event, having an issuer field will 
> limit what damage they can do.
>
> You find some collision?   You don't like it?  Take it up with the CA's that
> did it.  They are highly motivated not to have this problem.
>
> Why is this such a huge problem?  I have never understood the amount of 
> time & energy spent on it in our community.  I sure wish we didn't have
> the current signing policy file scheme.
>
>   

-- 
Frank Siebenlist               franks at mcs.anl.gov
The Globus Alliance - Argonne National Laboratory