Re: clarifications needed re safe form editor cert matching algorithm

If there were a way for the cert owner to express that they intended that
cert to be used on a different CN (subdomain / whatever) then I would be all
for it. There is such a way, and it's called Certificate Subject Alt Name.
The fact that companies are too cheap to spend $60 at Godaddy for a 6-in-1
cert isn't really sufficient motivation for me to say "let's go ahead and
drastically diverge from spec/common practice". (As a note, I originally
thought this was a good idea a few months ago, I think I even brought it up
with Johnathan over drinks at one point, but now having thought about it I'm
seeing a large number of downsides and very few upsides, with the potential
exception of www=hostname.) The reason I don't want to treat certs
differently is that the cert is expressing the preference of the server /
site owner. The owner purchased a cert for a particular (set) of CNs. If
they wanted to specify alternate CNs, they could have done so for $60 -
$20(price of normal cert) = $40. [prices based off of godaddy, sorry Phil.]
I'm not really comfortable divining intentions as to why a company chose not
to spend that extra $40 - maybe they were cheap, maybe they didn't actually
want to extend trust to all their subdomains, I have no way of knowing,
except for looking at the CN and Subject Alt Name extension. I just don't
see the upside in the general case - I see it for www vs hostname, but not
beyond that. I don't think any of us have good numbers for how common the
error is beyond that (not just anecdotes, but numbers), and given that I'm
very uneasy.

On 10/12/07, Serge Egelman <> wrote:
> Given that the attestation for a non-EV cert is control over the domain,
> this still applies to subdomains.  So I'm not sure why all low-grade
> certs shouldn't use wildcards (other than more profit for CAs).  Why
> shouldn't we just treat them this way with regard to which warnings we
> show?
> Granted, I agree with you guys about the theoretical problems.  The
> issue is weighing these against being pragmatic.  We will not be able to
> create effective warnings if we only consider "perfect" situations.  We
> need to consider what is actually happening.
> serge
> Thomas Roessler wrote:
> > On 2007-10-12 10:30:50 -0700, Ian Fette wrote:
> >
> >> LOL... all I'm saying is this. For the case of www vs bare
> >> hostname, I can see this being common enough to warrant
> >> investigation. For the other cases, I see a lot of risk in terms
> >> of opening up new attack vectors, changing defaults, breaking
> >> standards etc, but I'm not sure I really see the benefit.
> >
> > Considering that the "real" fix for the problem is a wildcard cert,
> > I'm leaning toward agreeing with you on this one, my prior remark
> > nonwithstanding.
> >
> --
> /*
> 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 Friday, 12 October 2007 18:43:35 UTC