On Tue, 23 Oct 2012, Guangqing Deng wrote:
2012/10/23 Alexander Gurvitz <[email protected]>
Hello.
http://tools.ietf.org/html/rfc6394#section-3.1 :
Continuing to require PKIX validation also limits the degree to which
DNS operators (as distinct from the holders of domains) can interfere
with TLS authentication through this mechanism. As above, even if a
DNS operator falsifies DANE records, it cannot masquerade as the
target server unless it can also obtain a certificate for the target
domain.
This seems like a mistake to me - DNS operator can always issue a fraudulent
usage 2/3 record,
and thus skip the CA validation.
Remind that the section 3.1 just discusses the “CA Constraints” which refers to
usage 0 TLSA record but not usage 2/3 TLSA records, which
is discussed in other sections. So, the statement “even if a DNS operator
falsifies DANE records, it cannot masquerade as the target
server unless it can also obtain a certificate for the target domain” is
correct.
But it can, just by updating the A/AAAA record to a server it owns.
I vague remember pointing out this exact mistake in the draft. I guess
we all kind of missed updating it in the end.
Paul
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