Subject: RE: Ignoring name constraints with self-issued certs

From: Sharon Boeyen <[email-masked]>
Date: Fri, 4 May 2001 14:41:05 -0400

Yep, I see that. Now would name constraints actually be a problem in that
type of environment. With name chaining the subject of the previous cert
would have the same value as the issuer and subject of the self-issued cert.
As long as name-constraints on that previous cert succeeded, there isn't a
problem is there? It's only in the case where the cert that contains the
name constraint is the one that is the direct neighbour to the self issued
cert.  I guess I agree with 
Steve then, (at least this time I don't need to make any changes to 509
right??)
 
Sharon
 
 From: Tim Polk [mailto:[email-masked]]
Sent: Friday, May 04, 2001 2:35 PM
To: Sharon Boeyen; 'Steve Hanna'; PKIX List
Subject: RE: Ignoring name constraints with self-issued certs

Sharon,

I can think of one scenario where the end certificate is legitimately
self-issued.  (There may be others.)

Consider a CA that uses separate keys for CRL signing or certificate
management operations.  If that CA issues certificates to itself for those
keys, a PKI client that verifies a signature on a CRL or a message needs to
validate the certificate containing that public key.  In that case, the end
certificate will be self-issued.

Thanks,

Tim

At 02:08 PM 5/4/01 -0400, Sharon Boeyen wrote:

Hi Steve, 

In discussion with PKIX folks when we were working on the defect report 
for name constraints, I don't recall any specific discussion of that type 
of a path (with a self issued cert at the end). The defect report doesn't 
change that particular text that you mention, but I suspect that the fact 
that it catches this 'hole' is probably more coincidental that deliberate. 

I'm curious whether you think there are legitimate situations where the 
final cert would be a self issued one, or whether you are suggesting that 
the fact that it could happen is a threat. Not that it would change the 
outcome, I'm just wondering which perspective you're coming from so that 
I can understand the issue better. 

Thanks 
Sharon

---

From: Steve Hanna <[email-masked]>
Date: Fri, 04 May 2001 15:51:51 -0400

Sharon Boeyen wrote:
> Yep, I see that. Now would name constraints actually be a problem in
> that type of environment. With name chaining the subject of the
> previous cert would have the same value as the issuer and subject of
> the self-issued cert. As long as name-constraints on that previous
> cert succeeded, there isn't a problem is there? It's only in the case
> where the cert that contains the name constraint is the one that is
> the direct neighbour to the self issued cert.  I guess I agree with 
> Steve then, (at least this time I don't need to make any changes to
> 509 right??)

A more serious problem is that a self-issued cert might have subject
alternative names. These names will not be constrained by any name
constraints or by name chaining. If the cert is not the last cert in the
path, these subject alternative names are not dangerous. If the cert is
the last cert in the path, they may cause client software to establish
an incorrect <name,key> binding. That's why we need to apply name
constraints to a self-issued certificate if it is the last cert in the
path.

-Steve