[Cerowrt-devel] Problems with DNSsec on Comcast, with Cero 3.10.38-1/DNSmasq 4-26-2014

Dave Taht dave.taht at gmail.com
Thu Jan 8 14:52:23 EST 2015

OK, I built this latest dnsmasq as a test for cerowrt-3.10-50 users:

login to the router
cd /tmp
wget http://snapon.lab.bufferbloat.net/~cero2/dnsmasq/dnsmasq-full_2.73-3_ar71xx.ipk
opkg install ./dnsmasq-full_2.73-3_ar71xx.ipk
(ignore the warnings about not overwriting several files)

I did a few tests on the former dnssec problematic sites and
everything looked kosher. As for the variety of the dnssec testing web
sites.... about half seem down or mis-behaving. Sigh. the ongoing
costs of keeping core internet test tools going strikes again...

In an orgy of self-flagellation, and *only because I have native ipv6*
I also turned off dns queries over ipv4 entirely (this is option
peerdns '0'  in /etc/config/networks on cerowrt's ge00 config), and
will pound on it a few days/weeks. I send this email prior to actually
trying that, however....

On Thu, Jan 8, 2015 at 10:07 AM, Simon Kelley <simon at thekelleys.org.uk> wrote:
> Hash: SHA256
> On 08/01/15 17:44, Dave Taht wrote:
>> Wow, this thread goes back a ways. Is ds.test-ipv6.com still
>> configured wrong, and does it pass now? It passes for me (but I am
>> behind a more modern openwrt box right now)
> ds.test-ipv6.com is still showing the same behaviour it was back in
> April (!) as far as I can see.

My bad. The "modern openwrt" I am behind does not have the dnsmasq-full
package installed.

> Queries to test-ipv6.com (which is what
> tripped up Jim in the first place) work fine on the latest dnsmasq,
> code, forwarding to
>> Is there another site that demonstrates this problem?
> There were three in Aaron Wood's original posting (subject: Had to
> disable dnssec today)
> - - Bank of America (sso-fi.bankofamerica.com)
> - - Weather Underground (cdnjs.cloudflare.com)
> - - Akamai (e3191.dscc.akamaiedge.net.0.1.cn.akamaiedge.net)
> All three work for me with the new code. I didn't try old dnsmasq, to
> see if the repair was from that or the DNS configuration.
>> BTW: For a while there (on comcast), in production, I ran with
>> pure ipv6 for dns (it reduced ipv4 nat pressure significantly!),
>> but it hung after a few days and I never got back to it. Were any
>> problems like this experienced and/or fixed for dnsmasq in the past
>> 8 months or so?
> http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=5782649ad95382dd558df97b33b64e854d8789fb
> is a possible candidate.


>> Anyway... enough incremental fixes have landed all across the board
>> in openwrt, and the chaos calmer process seems to have settled
>> down enough, to consider doing an entirely updated cerowrt based on
>> 3.14 and pushing things like dnsmasq further forward...
>> ... but I, personally, am still, not in the position to easily
>> build and test a new dnsmasq package for cerowrt and have no
>> funding or time for further development based on chaos calmer.
>> Hopefully someone else in the openwrt or cerowrt world can take up
>> the slack. I see that several bleeding edge sub-distros of openwrt
>> have also emerged on their forums...
>> (Yet.... I will still try to produce a test dnsmasq version from
>> the cerowrt-3.10 tree but I doubt it would be safe to do an opkg
>> update for it.)
> There shouldn't be any non backwards-compatible changes in dnsmasq to
> bite you. Don't know about other stuff.

So far so good.

> Cheers,
> Simon.
>> On Thu, Jan 8, 2015 at 8:34 AM, Simon Kelley
>> <simon at thekelleys.org.uk> wrote: OK, it's taken some time, but with
>> this insight, I've recoded the relevant stuff to look for the
>> limits of the signed DNS tree from the DNS root down. That's
>> clearly the correct way to do it, and should avoid the original
>> problem here, caused by sending DNSSEC queries  to DNSSEC-unaware
>> servers in the unsigned parts of the tree.
>> This was quite a big change, and it could do with some serious
>> testing. Available now on the dnsmasq git repo, or as 2.73test3 in
>> a tarball.
>> There are other DNSSEC fixes in there too, Check the changelog.
>> Cheers,
>> Simon.
>> On 04/10/14 22:45, Anders Kaseorg wrote:
>>>>> On Fri, 3 Oct 2014, Anders Kaseorg wrote:
>>>>>>> secure no DS means that the original unsigned answer
>>>>>>> should be accepted, except that it shouldn't. There's no
>>>>>>> way to distinguish between secure lack of DS because
>>>>>>> we've reached an unsigned branch of the tree, and secure
>>>>>>> lack of DS because we're not at a zone cut, except if we
>>>>>>> know where the zone cuts are, and we don't.
>>>>>> Having just looked through RFC 5155 for clues: isn’t that
>>>>>> the purpose of the NS type bit in the NSEC3 record?  In
>>>>>> this example, DS university would give an NSEC3 record with
>>>>>> the NS bit clear. That signals that we should go down a
>>>>>> level and query DS campus. In this case we find a signed DS
>>>>>> there.  But if we were to find an NSEC3 with the NS bit
>>>>>> set, then we’d know that we’ve really found an unsigned
>>>>>> zone and can stop going down.
>>>>> Aha: and this is exactly the answer given at
>>>>> http://tools.ietf.org/html/rfc6840#section-4.4 .
>>>>> Anders
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> =i31t

Dave Täht


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