[cabfpub] Proposed new ballot on IP Addresses in SANs

Dean Coclin Dean_Coclin at symantec.com
Mon Apr 25 22:32:04 UTC 2016

I’m not sure if this is relevant but one of the problems we ran into with the Code Signing BRs was that we had added language that a timestamp server must be compliant with RFC 3161. When the auditors took a look at that they said, “Do you really want us to develop audit criteria for every aspect of RFC 3161? If so, that will be a very difficult and expensive audit”. So we backed off on that broad description and were able to describe the items in 3161 we felt were important and auditable.


I raise this only because I’m hearing a similar discussion below with respect to RFC 5280. Perhaps it’s not the same but I only raise it so that if it is expected that auditors will pick apart the RFC and develop audit criteria against it, the audit scope may dramatically increase. Alternatively, are there specific items in the RFC that you might want to call out as important and have them listed separately ?



From: public-bounces at cabforum.org [mailto:public-bounces at cabforum.org] On Behalf Of Ryan Sleevi
Sent: Friday, April 22, 2016 5:45 PM
To: Peter Bowen <pzb at amzn.com>
Cc: Rick Andrews <Rick_Andrews at symantec.com>; public at cabforum.org
Subject: Re: [cabfpub] Proposed new ballot on IP Addresses in SANs




On Fri, Apr 22, 2016 at 12:45 PM, Peter Bowen <pzb at amzn.com <mailto:pzb at amzn.com> > wrote:

So it would seem that this solution might not be the best option.


"Not the best" isn't the goal. It's "Don't violate RFC5280" that should be the goal.


Multiple SANs is a complete red-herring as to the issue. There's no requirement that such certificates have them.


Common name deprecation is equally a red-herring. If it offers a viable path for these clients, without the attendant security issues and *fundamental violation of RFC5280*, it's worth exploring.


That there's been no further explanation other than "Meh" is, unquestionably, not a position we can endorse, but even moreso, a policy of "Oh well, we'll violate them anyways" is just grossly irresponsible.


The best solution would be for clients to be updated to follow RFC 2818 and check iPAddress entries in the SAN.


Indeed, and Microsoft can solve this very easily, without the same risks and compatibility issues of nameConstraints.


We considered the RFC5280 non-criticality of nameConstraints because it offered significant positive security value for a majority of clients, without compatibility risks. The iPAddresses provide no positive security value - other than allowing CAs to sell to users with buggy software that their vendor doesn't want to fix - and come with significant compatibility and security risks.


To me, it seems that allowing string-ified IP address in dNSName entries in the SAN when the same IP address is included as an iPAddress entry in the SAN is a reasonable tradeoff.  It is no worse than including the same in the common name.  As you have pointed out, a string-ified IP address can never match a hostname, so there is no chance of confusion 


I've already explained to you why this is incorrect. It's unfortunate that you continue to suggest this line of thinking. A string-ified IP address is not a valid hostname.


If you have a client that properly conforms to RFC 2818, then this is a no-op for you — you will look at the IPaddress entry and never try to match on DNSname.  You had expressed concern that Mozilla would need to update its code, but Gerv had indicated back in August that this was not necessary (https://cabforum.org/pipermail/public/2015-August/005850.html).


That's not what is in the ballot. What is in the ballot can and will cause compatibility issues. It also suggests that Chrome would need to adopt Firefox's peculiar behaviour (only validating presented identifiers as they're encountered, rather than at parse time). That's not something we are comfortable with implementing, and especially not foisting upon the ecosystem to know about the "special" rules the CA/B Forum embraces. There's already enough magic in the WebPKI - we shouldn't knowingly introduce more.


I appreciate that conformance is a great goal, but not causing customer pain is also a laudable goal.  In this case it seems the risk is low and the customer value is high.


There has yet to be a demonstration of the customer value compared to the solution posed 8 months ago.  There's clearly a demonstration of CA value - they do less work - and of browser value - Microsoft does less work - but there has yet to be an articulation of why the solution is non-viable. The closest comment is Jeremy saying they've investigated, it's not practical - but provided zero evidence or technical detail that would allow a reasoned weighing of the risk versus reward. Instead, we see CAs eager to violate RFC5280, easy to cause compatibility issues with clients, and w/o apparent care for the long-term damage to the ecosystem they would be doing.

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