[cabfpub] Domain validation

Ryan Sleevi sleevi at google.com
Wed May 6 22:49:34 UTC 2015

On Wed, May 6, 2015 at 3:37 PM, Anoosh Saboori <ansaboor at microsoft.com>

>  Reviving this older thread. It seems that both:
> 1.       Forum has concerns around relying only on whois database or
> email address since the whois database might not be accurate
> 2.       MS still has concerns for #6 not being at par with the rest of
> validation mechanism proposed
> So, can we get to a point where both concerns are addressed by modifying
> the requirement as: “#6 continues to be accepted, only if other validation
> methods failed to work. CAs then keep documentation on why they decided to
> accept #6. “
I'm still not sure why Microsoft doesn't feel that #6 is not on-par with
the rest. It would be very helpful if you could elaborate what properties
you feel that the other methods offer that #6 does not. In digging through
your past replies, it only seems that you've highlighted it's "not as
strong" - but you haven't clarified what property is absent.

If I understand by reading between the lines, your concern is that method
#6 allows verification to happen by any attacker who can gain
filesystem-level access, whereas the other methods require some level of
password compromise (e.g. email, methods 1/2/4 from the original message),
remote code execution (e.g. TLS bindings, method 11 from the original
message), or has compromised the domain management (methods 7/8 from the
original message). Is that correct?

I'm surprised that Microsoft hasn't highlighted Item 9 (IP address
validation) as similarly weaker in guarantees. For example, in a shared
hosting service, foo.com and bar.com may both be hosted on the same IP, and
use SNI (for HTTPS) and the Host: header (for HTTP) to disambiguate which
host the client wishes to talk to. As presently worded, it seems like
bar.com MAY be able to apply for a certificate for foo.com.

Now, I know that's not the intent, but that strikes me as an area that
needs further clarification about what "controls an IP address" means (e.g.
does it mean looking in the appropriate RIR for that Netblock and
confirming the applicant through a Reliable Means of Communication?)
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