[dns-privacy] Two issues on draft-ietf-dprive-dnsodtls-04.txt

[Stephane Bortzmeyer <[e-mail]>]

On Fri, Jan 22, 2016 at 05:51:22AM +0000,
 Tirumaleswar Reddy (tireddy) <[e-mail]> wrote 
 a message of 62 lines which said:

> This revision addresses comments from Christian and refers to draft-dgr-dprive-dtls-and-tls-profiles.
>         Title           : DNS over DTLS (DNSoD)
> 	Filename        : draft-ietf-dprive-dnsodtls-04.txt

> If the DNS client receives a hard ICMP error [RFC1122], it MUST
> immediately cease attempts to re-transmit its ClientHello.

Isn't there a risk of downgrade attack here? ICMP errors are not
authentified so an active attacker, even if off-path, could convince a
client to disable DNS over DTLS. May be add a reference RFC 5927 to
emphasize that the credibility of ICMP errors should be challenged?
(RFC 5927 is for TCP, I do not find an equivalent for UDP, where the
problem is more complicated, we cannot use the sequence numbers to
check the ICMP message.)

> The existing Query ID allows multiple requests and responses to be
> interleaved in whatever order they can be fulfilled by the DNS
> server.

Only the Query ID? RFC 7766 (a DTLS session, in one way, is a bit like
a TCP connection) says "Since pipelined responses can arrive out of
order, clients MUST match responses to outstanding queries on the same
TCP connection using the Message ID.  If the response contains a
question section, the client MUST match the QNAME, QCLASS, and QTYPE
fields." For DNS over ordinary UDP, I do not find a RFC with clear
rules but RFC 3833 section 2.2 and RFC 5452 section 4 both use more
than the Query ID. Since we are protected by DTLS, we may be more lax
but draft-ietf-dprive-dns-over-tls-04 is not "Since pipelined
responses can arrive out-of-order, clients MUST match responses to
outstanding queries using the ID field, query name, type, and class."

> Implementing DNSoD on root servers is outside the scope of this
> document.

Should be deleted (why only the root servers?)