[dns-operations] K-root in CN leaking outside of CN
songlinjian at gmail.com
Mon Nov 8 07:45:44 UTC 2021
If it is urgent, I suggest the K root operator withdraw the route of the
instance in Guangzhou immediately.
On Mon, 8 Nov 2021 at 15:23, Davey Song <songlinjian at gmail.com> wrote:
> Hi Manu,
> Is it still the case? I will try to outreach the people of AS4134 and
> Best regards,
> On Sat, 6 Nov 2021 at 12:18, Manu Bretelle <chantr4 at gmail.com> wrote:
>> Hi all,
>> Based on https://root-servers.org/, there are a few root servers
>> operated from Mainland China.
>> How do we ensure that those are not advertised outside of China so DNS
>> answers are not poisoned by the GFW?
>> Are there any contracts that root in CN are supposed to follow to prevent
>> this? Is the onus put on both the CN ASNs and their respective non-CN ASNs
>> peers to not advertise/not accept the root range on those specific peering
>> links? If so, how is it ensured that every operator knows about those rules?
>> Is there any monitoring performed by root operators to ensure that leaks
>> are being detected and possibly addressed?
>> I don't believe this specific leak I am seeing is malicious, but rather
>> is just a misconfiguration and I really wonder how this could be
>> prevented/addressed early on.
>> I have ran some probes in other regions and do not have proof that this
>> is happening more widely than a specific AS, but this was not exhaustive
>> and I could have very likely missed something.
>> As for this specific problem, we have reached out to both the AS that is
>> accepting the leak and RIPE NCC as we identified the issue, provided the
>> ISP possible workaround in the meantime.
>> Both DNSSEC and Qname minimization would have helped the resolver
>> detecting bogus answers, or just getting to com. in the first place, while
>> this would have helped, there is still an ongoing leak.
>> Longer story for the ones that want to dig more into it....
>> I am asking because we (FB/Meta) got reports from an ISP in MX which
>> users were not able to access whatsapp.net. For instance, answer would
>> be 22.214.171.124.... which is not quite the right answer....
>> Some initial debugging from the ISP seemed to point to k-root acting up.
>> e.g something alike:
>> # dig +trace d.ns.facebook.com
>> ; <<>> DiG 9.11.13 <<>> +trace d.ns.facebook.com
>> ;; global options: +cmd
>> . 518379 IN NS m.root-servers.net.
>> . 518379 IN NS e.root-servers.net.
>> . 518379 IN NS g.root-servers.net.
>> . 518379 IN NS j.root-servers.net.
>> . 518379 IN NS k.root-servers.net.
>> . 518379 IN NS b.root-servers.net.
>> . 518379 IN NS l.root-servers.net.
>> . 518379 IN NS a.root-servers.net.
>> . 518379 IN NS i.root-servers.net.
>> . 518379 IN NS d.root-servers.net.
>> . 518379 IN NS f.root-servers.net.
>> . 518379 IN NS h.root-servers.net.
>> . 518379 IN NS c.root-servers.net.
>> . 518379 IN RRSIG NS 8 0 518400
>> 20211117170000 20211104160000 14748 .
>> DhAuTFRWzboxlbqQw3nyYlH0Ot8lSatzhx0Cl0rNIBTboFQiWIUMgtVi PeRj0Q==
>> ;; Received 1125 bytes from 127.0.0.1#53(127.0.0.1) in 0 ms
>> ;; expected opt record in response
>> d.ns.facebook.com. 65 IN A 126.96.36.199
>> ;; Received 51 bytes from 188.8.131.52#53(k.root-servers.net) in 231 ms
>> Looking a bit more into it:
>> Querying d.ns.facebook.com/A against k-root directly from MX probes:
>> $ blaeu-resolve -m 33184386 -q A d.ns.facebook.com
>>  : 13 occurrences
>> [184.108.40.206] : 1 occurrences
>> [220.127.116.11] : 1 occurrences
>> [18.104.22.168] : 2 occurrences
>> [22.214.171.124] : 1 occurrences
>> [126.96.36.199] : 1 occurrences
>> Test #33184386 done at 2021-11-05T20:36:59Z
>> Getting an answer in the first place is kind of unexpected but I will not
>> focus on the ones returning the correct answer (e.g 188.8.131.52).
>> Checking the probes that return those results:
>> ripe-atlas report --renderer dns_compact 33184386
>> Probe #27558: 2021-11-05 13:36:59 NOERROR qr ra rd d.ns.facebook.com. 98
>> A 184.108.40.206
>> Probe #31355: 2021-11-05 13:37:01 NOERROR qr ra rd d.ns.facebook.com.
>> 146 A 220.127.116.11
>> Probe #52013: 2021-11-05 13:37:01 NOERROR qr ra rd d.ns.facebook.com.
>> 179 A 18.104.22.168
>> Probe #52660: 2021-11-05 13:37:00 NOERROR qr ra rd d.ns.facebook.com.
>> 150 A 22.214.171.124
>> Those probes will fail to reach 126.96.36.199 (k-root) over TCP.
>> Checking which id.server is returned by the k-roots reached by those
>> ripe-atlas measure dns --query-argument id.server --query-type TXT
>> --query-class CHAOS --from-country MX --target 188.8.131.52
>> where the interesting snippet is:
>> $ ripe-atlas report --renderer dns_compact 33184807
>> Probe #27558: 2021-11-05 14:08:54 NOERROR qr rd id.server. 0 TXT
>> Probe #31355: 2021-11-05 14:08:55 NOERROR qr rd id.server. 0 TXT
>> Probe #52013: 2021-11-05 14:08:55 NOERROR qr rd id.server. 0 TXT
>> Probe #52660: 2021-11-05 14:08:55 NOERROR qr rd id.server. 0 TXT
>> Traceroute from those probes to k-root:
>> Looking at the traceroutes
>> ripe-atlas report --renderer traceroute --traceroute-show-asns 33184963
>> shows that the last AS before reaching a CN AS and also the first
>> transiting AS from the probe is AS32098
>> which when checking their looking glass: https://lg.transtelco.net/ uses
>> Transtelco Inc. (AS PATH: 32098)
>> Asia Pacific Network Information Centre (AS PATH: 4134)
>> Not found (AS PATH: 58466)
>> China Academy of Information and Communications Technology (AS PATH:
>> Reseaux IP Europeens Network Coordination Centre (RIPE NCC) (AS PATH:
>> dns-operations mailing list
>> dns-operations at lists.dns-oarc.net
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