Re: clarifications needed re safe form editor cert matching algorithm

This is an error I'm trying to do some research on, maybe someone can
shed some light on it.  There are thousands of legitimate sites that
have this problem, either because they don't use an alt-name, or the
certificate is being used on some other subdomain of their domain.

In the case where one certificate is being used by another host within
the domain that it was legitimately issued for, I'm not entirely sure
what the threat model is.  Sure, this is a great way for CAs to make
money (by either making a site buy a new certificate for every host or
making them buy a wildcard cert), but beyond this, what's the need to warn?

Yes, the DNS can be hacked to add in a new hostname, but at that point
there are bigger problems.

serge

Ian Fette wrote:
> bankofamerica.com <http://bankofamerica.com> does not use an alt-name.
> What's the point? (And for those of us who aren't using IE7, I'm
> assuming you just get a common name mismatch error, or what?) if eBay
> uses it, then I think you need to be worried about breaking it.
> 
> On 10/11/07, *Close, Tyler J.* <tyler.close@hp.com
> <mailto:tyler.close@hp.com>> wrote:
> 
>     Perhaps there's some way to finesse this part of the algorithm by
>     reference to RFC 2818. I'll work on it.
>      
>     Many sites don't seem to be using this cert feature. For a fun
>     example, visit the following URL using IE7.
>      
>     https://bankofamerica.com/
>      
>     --Tyler
> 
>         ------------------------------------------------------------------------
>         *From:* Ian Fette [mailto:ifette@google.com
>         <mailto:ifette@google.com>]
>         *Sent:* Thursday, October 11, 2007 12:48 PM
>         *To:* Close, Tyler J.
>         *Cc:* public-wsc-wg@w3.org <mailto:public-wsc-wg@w3.org>
>         *Subject:* Re: clarifications needed re safe form editor cert
>         matching algorithm
> 
>         It is in huge use. For example. if you go to
>         https://signin.ebay.com and look at the cert - the CN is
>         signin.ebay.com <http://signin.ebay.com> but the certificate
>         subject alt name lists:
> 
>         Not Critical
>         DNS Name: signin.cafr.ebay.ca <http://signin.cafr.ebay.ca>
>         DNS Name: signin.ebay.ca <http://signin.ebay.ca>
>         DNS Name: signin.ebay.com.au <http://signin.ebay.com.au>
>         DNS Name: signin.ebay.com.cn <http://signin.ebay.com.cn>
>         DNS Name: signin.express.ebay.com <http://signin.express.ebay.com>
>         DNS Name: signin.half.ebay.com <http://signin.half.ebay.com>
>         DNS Name: signin.liveauctions.ebay.com
>         <http://signin.liveauctions.ebay.com>
>         DNS Name: signin.shopping.ebay.com <http://signin.shopping.ebay.com>
>         DNS Name: signin.tw.ebay.com <http://signin.tw.ebay.com>
>         DNS Name: signin.ebay.com <http://signin.ebay.com>
> 
>         and if you go to https://signin.ebay.de you again get a cert
>         with CN= signin.ebay.com <http://signin.ebay.com> but alt names of:
>         Not Critical
>         DNS Name: signin.befr.ebay.be <http://signin.befr.ebay.be>
>         DNS Name: signin.benl.ebay.be <http://signin.benl.ebay.be>
>         DNS Name: signin.ebay.at <http://signin.ebay.at>
>         DNS Name: signin.ebay.be <http://signin.ebay.be>
>         DNS Name: signin.ebay.co.uk <http://signin.ebay.co.uk>
>         DNS Name: signin.ebay.de <http://signin.ebay.de>
>         DNS Name: signin.ebay.es <http://signin.ebay.es>
>         DNS Name: signin.ebay.fr <http://signin.ebay.fr>
>         DNS Name: signin.ebay.ie <http://signin.ebay.ie>
>         DNS Name: signin.ebay.nl <http://signin.ebay.nl>
>         DNS Name: signin.express.ebay.co.uk
>         <http://signin.express.ebay.co.uk>
>         DNS Name: signin.ebay.com <http://signin.ebay.com>
> 
> 
>         So yeah, it's important.
>         On 10/11/07, *Close, Tyler J.* <tyler.close@hp.com
>         <mailto:tyler.close@hp.com>> wrote:
> 
> 
> 
> 
>             Thomas Roessler wrote:
>             > going through the matching algorithm while folding it in...
>             >
>             > - The current language confuses attributes and fields.  I
>             suspect
>             >   that you mean the various attributes of the Subject
>             certificate
>             >   field.  Please confirm.
> 
>             The CN, O, L, ST and C values I refer to are the ones in the set
>             referred to by the Subject field in the end entity
>             certificate. Not sure
>             how to be any more specific about this in PKIXese.
> 
>             > - I notice that you have some rules that concern matching
>             the CN
>             >   attribute, but none concerning subjectAltName.  I'm happy to
>             >   simply track this point as an issue.
> 
>             Could you point me to a document covering the semantics of
>             subjectAltName? Is it in use in X.509 certs on the Web?
> 
>             > Also, I'll open an issue to track the "PKI orthodoxy"
>             remarks that
>             > Hal had made at the face-to-face, and will link to that
>             issue from
>             > the draft.
> 
>             Thanks,
>             --Tyler
> 
> 
> 

-- 
/*
Serge Egelman

PhD Candidate
Vice President for External Affairs, Graduate Student Assembly
Carnegie Mellon University

Legislative Concerns Chair
National Association of Graduate-Professional Students
*/

Received on Thursday, 11 October 2007 21:32:38 UTC