Subject: RE: Cached OCSP responses vs. single entry CRLs

From: "Ryan M. Hurst" <[email-masked]>
Date: Fri, 5 Dec 2003 15:30:21 -0800

Carl there are a number of reasons, one of the most significant being
backwards compatibility; many existing client implementations do not
support partitioned CRLs and there is not way to tell from a CDP if the
data on the other end represents a partitioned CRL or a full one.

Additionally there are commercial OCSP responders out there that support
this concept, yet very few CAs support the use of portioned CRLs to that
granularity.

Ryan

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Carl Wallace
Sent: Friday, December 05, 2003 1:09 PM
To: [email-masked]
Subject: Cached OCSP responses vs. single entry CRLs

Why use OCSP to convey pre-produced revocation information in the way
that's
being discussed?  Why not use single entry CRLs?  The functionality is
similar and they could be propagated using existing technology (e.g.
directories, 3280 compliant path processing clients, etc.).

---

From: Jean-Marc Desperrier <[email-masked]>
Date: Tue, 09 Dec 2003 21:19:49 +0100

Ryan M. Hurst wrote:

>[...] there is not way to tell from a CDP if the
But then clean client should check the content of the IDP extension 
after getting the CRL and check it's distribution point matches the 
distribution field of the CDP, and if not refuse the CRL, and supposedly 
try the next crldp inside the cert.
RFC3280 6.3.3 (b)(2)(i)

I'm a bit sceptic it really works, but if the CRL's IDP is marked 
critical as it should, maybe a good number of client will duly reject 
the CRL when they can not support that case.

---

From: "Ryan M. Hurst" <[email-masked]>
Date: Tue, 9 Dec 2003 19:01:40 -0800

I have seen engines that do not deal with extension criticality in CRLs, some of the java implementations I have seen in-fact; these would trust these partial CRLs as a full CRL. Now I know folks will say thats a bad implementation, and I am not arguing that what these clients have done is right but its yet another example of how CRLs fail in this area due to the history of implementations out there.

Another example is where the client does properly deal with critical extensions in the CRL, in this case almost all implementations I have seen would show the CRL as bad and fail validation (as it should), I dont know of one that would try the next URL in the CDP to see if it was the full CRL. And even if it did thats extra data to be downloaded to discover its not the rigth CRL.

Ryan

From: Jean-Marc Desperrier
Sent: Tue 12/9/2003 12:19 PM
To: [email-masked]
Subject: Re: Cached OCSP responses vs. single entry CRLs

---

From: "Santosh Chokhani" <[email-masked]>
Date: Wed, 10 Dec 2003 08:28:13 -0500

Ryan:
 
Assuming the CA and the client software are working properly, there will be
one DP (URL) in the CDP and that will point to the proper partition.  The
client will get the CRL from that URL.  The DP in the IDP of the CRL will be
matched to the DP in the CDP of certificate and all will be well.
 
If there is a glitch on the network or active adversary, then these won't
match, but in those circumstances there are innumerable (albeit finite) way
to cause denial of service, CRL partitioning notwithstanding.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Ryan M. Hurst
Sent: Tuesday, December 09, 2003 10:02 PM
To: Jean-Marc Desperrier; [email-masked]
Subject: RE: Cached OCSP responses vs. single entry CRLs

I have seen engines that do not deal with extension criticality in CRLs,
some of the java implementations I have seen in-fact; these would trust
these partial CRLs as a full CRL. Now I know folks will say thats a bad
implementation, and I am not arguing that what these clients have done is
right but its yet another example of how CRLs fail in this area due to the
history of implementations out there.
 
Another example is where the client does properly deal with critical
extensions in the CRL, in this case almost all implementations I have seen
would show the CRL as bad and fail validation (as it should), I dont know of
one that would try the next URL in the CDP to see if it was the full CRL.
And even if it did thats extra data to be downloaded to discover its not the
rigth CRL.
 
Ryan

  _____  

RFC3280 6.3.3 (b)(2)(i)

---

From: Michael Ströder <[email-masked]>
Date: Wed, 10 Dec 2003 17:14:58 +0100

Jean-Marc Desperrier wrote:
> 
> I'm a bit sceptic it really works,

So am I.

> but if the CRL's IDP is marked 

I saw at least one widely-deployed software of a major vendor simply crash 
when CRL IDP was marked critical.

Ciao, Michael.

---

From: "Santosh Chokhani" <[email-masked]>
Date: Wed, 10 Dec 2003 14:41:27 -0500

Michael:

The standard requires the IDP to be critical and not the CRLDP.  If a client
does not process CRLDP, it will have to rely on a CRL.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Michael Ströder
Sent: Wednesday, December 10, 2003 11:15 AM
To: Jean-Marc Desperrier
Cc: [email-masked]
Subject: Re: Cached OCSP responses vs. single entry CRLs

So am I.

Ciao, Michael.

---

From: "Ryan M. Hurst" <[email-masked]>
Date: Wed, 10 Dec 2003 13:58:34 -0800

Sure, if the client supports paritioned CRLs and most deployed clients MSFT or otherwise do not; ttp issues want to service as many possible relying parties as possible since this is often a significant factor a subscriber takes into consideration when choosing a ttp.

Ryan

From: Santosh Chokhani
Sent: Wed 12/10/2003 5:28 AM
To: [email-masked]
Subject: RE: Cached OCSP responses vs. single entry CRLs

Ryan:

Assuming the CA and the client software are working properly, there will be one DP (URL) in the CDP and that will point to the proper partition.  The client will get the CRL from that URL.  The DP in the IDP of the CRL will be matched to the DP in the CDP of certificate and all will be well.

If there is a glitch on the network or active adversary, then these won't match, but in those circumstances there are innumerable (albeit finite) way to cause denial of service, CRL partitioning notwithstanding.
-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Ryan M. Hurst
Sent: Tuesday, December 09, 2003 10:02 PM
To: Jean-Marc Desperrier; [email-masked]
Subject: RE: Cached OCSP responses vs. single entry CRLs

Ryan