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Re: DNSSEC and unknown algorithms

Wes Hardaker wrote:
On Thu, 16 Dec 2004 15:34:51 -0500, David Blacka <davidb@verisignlabs.com> said: 


David> In protocol-09, section 5.2, there are two paragraphs
David> describing what to do when a resolver encounters a delegation
David> to a zone signed only with unknown algorithms:

proto-09-5.2> If the validator does not support any of the algorithms
proto-09-5.2> listed in an authenticated DS RRset, then the resolver
proto-09-5.2> has no supported authentication path leading from the
proto-09-5.2> parent to the child.  The resolver should treat this
proto-09-5.2> case as it would the case of an authenticated NSEC RRset
proto-09-5.2> proving that no DS RRset exists, as described above.

If you follow the advice in that last sentence, doesn't it allow for
someone to craft a DS packet with a unassigned algorithm ID and send
it to the requester and they'll actually immediately treat that packet
as a proof of non-existence?  Why would you ever treat a response you
can't authenticate as an authenticated NSEC?  Treating it as an
unauthenticated NSEC I can understand, but not as an authenticated
one.


No.

This is actually discussed earlier in section (5.2). The validator is working with verified DS records from the parent. I.e., the parent is signed with a known algorithm. So you aren't making a security decision based on unauthenticated data here (which is what I'm worried that some misguided implementation might do).

--
David Blacka    <davidb@verisignlabs.com>
Sr. Engineer    VeriSign Applied Research

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