[dns-operations] DNSSEC validation - salliemae.com
warren at kumari.net
Wed Aug 7 13:51:33 UTC 2019
On Wed, Aug 7, 2019 at 9:36 AM Robert Blayzor <rblayzor.bulk at inoc.net> wrote:
> We run multiple unbound recursive DNS servers using DNSSEC validation.
> We've been getting complaints about users not being able to get to
> salliemae.com. From what we have seen, salliemae.com's DNSSEC is
> completely broken. Bad sigs, no sigs on records, etc.
> For example: SOA sig fails, but "www" for salliemae.com has no signature
> (that I can see).
> User complains that using our servers they can't get to the site (and
> rightfully so, I guess), but then states that if they switch to Google
> or Cloudfalre (220.127.116.11 or 18.104.22.168) it works.
> If I try to do validation tests for the SOA record Google or Cloudflare,
> I get the same failures, but they DO return a valid A records for "www".
> I thought DNSSEC validation was to be "all or nothing". How can you be
> doing DNSSEC validation but still passing back RR's that do not pass due
> to not having any signature ?
Well, according to dnsviz, there *is* a validation path which works
for www -- http://dnsviz.net/d/www.salliemae.com/dnssec/
The signature is over rrsets, and there are indeed valid ones for
everything needed for www.salliemae.com (edited for readability):
$ dig ns salliemae.com @a.gtld-servers.com
salliemae.com. 172800 IN NS ns81.a2.incapsecuredns.net.
salliemae.com. 172800 IN NS ns22.a1.incapsecuredns.net.
salliemae.com. 172800 IN NS ns107.a0.incapsecuredns.net.
$ dig +short ds salliemae.com @a.gtld-servers.com
15630 7 2 6FA7705AF8AFA8AF4AA620F3F49D67BC81935C3F8EAF8D37137DFCE8 2CE022D0
15630 7 1 8E14C4E3F8E9104FAEB16E3CAD39AE9876855D43
$ dig +dnssec dnskey www.salliemae.com @ns81.a2.incapsecuredns.net.
www.salliemae.com. 520 IN CNAME ltfhaea.x.incapdns.net.
www.salliemae.com. 520 IN RRSIG CNAME 7 3 600 20190905152127
20190806152127 33962 salliemae.com.
DNSSEC for salliemae.com itself is distinctly "odd" --
http://dnsviz.net/d/salliemae.com/dnssec/ -- I'd be fascinated to know
just how they managed that.
Anyway, none of the broken names there are needed to build a valid chain...
> Who is right?
Well, one thing is for sure, it isn't salliemae :-P
> XMPP: rblayzor.AT.inoc.net
> PGP: https://pgp.inoc.net/rblayzor/
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I don't think the execution is relevant when it was obviously a bad
idea in the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair
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