To set up the problem to solve.  Asking for points that are missed.

(Purposefully omitting the trailing dot, not talking about 'root' because that 
could get confusing.)

Trust anchor for "one/17" (i.e., key_id=17)

Trust anchor for "two.one/145"

Received data for "three.two.one" signed by "two.one/9342"

What would cause "two.one/9342" to be signed by "one/17" and not by 
"two.one/145"?  (I think this captures the question of interest.)

1. "two.one/145" is in the MISSING state from STD 69.
2. "two.one/145" was revoked but the validator didn't remove it.
3. "two.one/145" is stale, as the validator is not using STD 69.
4. "two.one" was re-delegated, the previous holder still uses "two.one/145"
5. (open for more scenarios of "why")

What should the validator do with the response?

For cases 1,2,3, the chain ought to be accepted.

For case 4, although the appropriate DNS response (according to the DNS 
protocol) was received, the application calling it might not want to take 
action based on the response (action such as open a connection and/or flow 
data).

Is there a way, within the DNS, to differentiate amongst the reasons why the 
response is signed up to "one" and not "two.one"?

Is there a way the application can tell?

With DANE as "an application" in mind:  When it comes to DANE, what bothers me 
is this, in "DNS-Based Authentication for TLS", the section "The Certificate 
Usage Field" (that is RFC 6698, section 2.1.1), for value "3 -- Certificate 
usage 3".  For that value, this is stated: "PKIX validation is not tested for 
certificate usage 3".  My reading of this is that the "problem" with PKIX 
certificate authorities has just been shifted over to DNS hosting services (in 
this case for "one"), concerns about the DNS hoster are on par with concerns 
regarding the certificate authorities.  (In essence, either could re-delegate a 
name.)  (Yes, this is a tangential off-shoot, anticipating questions about how 
DANE plays with this.)  In essence, usage 3 removes the benefit of pinning, 
which the application could use to detect a re-delegation.

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