[dns-operations] Hall of DNS Shame (?)
edmonds at mycre.ws
Tue Jan 24 18:47:36 UTC 2017
Ondřej Surý wrote:
> I've been thinking lately (after seeing all the DNS protocol violations)
> that a collaborative list of all DNS protocol violations in the wild
> might be beneficial to both DNS implementors and also to increase a
> pressure on those operators to fix their issues.
> Perhaps we can have such list at some neutral place like DNS-OARC?
> Unfortunately I have a plenty of material I can contribute as of this
> My favorite one is log.kmplayer.com that just appends some extra \0
> bytes after the last RRSet in the answer. (Probably allocating a
> fixed sized buffer and sending it whole instead of just the part
> that was filled?)
I like this idea. The last time I wrote a DNS message parser I ended up
cribbing heavily from the behavior of existing implementations (and what
do you do if two implementations disagree over whether a message is
valid or not?).
It would be cool to have it entirely repository-driven, for example the
repository could have:
- A collection of broken DNS messages, with annotations like a list of
references to the RFC clauses violated.
dnstap would be a good format for storing the raw messages, because
it doesn't care if the messages are validly formatted or not. If you
can replicate the problem with a particular kdig command you can
easily save a trace of the raw query and response messages (plus
metadata) with something like:
kdig -E ./dnstap.out +qr [query options]
kdig -E ./dnstap.out +qr @188.8.131.52 log.kmplayer.com +norec
- A utility which extracts the first response message from a dnstap
trace file and exports the raw DNS message to be consumed by a
- DNS message parser drivers for the various message parsing libraries
(e.g., libknot, ldns, the BIND9 library, Go miekg/dns, dnsrend).
There should already be drivers for fuzzing that could be adopted in
some cases. Probably the drivers can do something simple like reading
a single wire-format binary DNS message from stdin.
- A driver script to execute the suite of broken messages against the
message parsers, and collect and present the results.
- An audit script which re-executes the collection of broken queries to
see if the nameservers are still broken.
The whole thing could be automated with GitHub/Travis-CI/etc. If the
presenter script had an HTML mode the output could be saved and
published to GitHub Pages automatically. Then you end up with a nice
"run kdig to generate trace file + add trace file to repository + send
pull request" workflow for adding/evaluating new entries.
That's a fair bit of work but it might be worth it if:
- There's a ton of broken nameservers out there.
- Highlighting the broken nameservers might get some of them fixed.
- Future implementers end up with a high quality collection of broken
real-world data to test their implementations against.
- It results in a cool DNS-OARC presentation :-)
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