-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi Mehmed,
On 21/09/15 13:17, Mehmed Kahric via Unbound-users wrote: > Hi, > > I have a similar issue as reported in Bug 669. > > For some (one for now) CNAMEs we have a empty A record answer from > Unbound. Proper answer came from remote DNS as showed in Unbound > log and tcpdump. Identical issue came from both us Unbound > instances: - CentOS 6, Unbound 1.5.1 from EPEL, configured as > recursive caching with forward-zone; - CentOS 7, Unbound 1.4.20 > from base, configured as authoritative, validating, recursive > caching. > > Log from first Unbound instance (with verbosity level 4) and from > tcpdump is in attachment, and dig from client (with output) is: What happens is the query for www.sensoray.com gives a CNAME to sensoray.com and an A record. But when queried specifically for the sensoray.com name the A record does not exist, the A record in the CNAME answer was a lie! You can test this yourself, with dig sensoray.com @8.8.8.8 and this returns no A record. (according to the verbosity 4 logs you give) The A record is inserted in the same way some cache-poisoning attacks work. The cache-poisoning attack mitigations in unbound remove it. (and unbound logs that it is scrubbed out of the answer). Best regards, Wouter > > --- C:\Users\Moi>dig www.sensoray.com @192.168.10.14 > > ; <<>> DiG 9.10.2-P3 <<>> www.sensoray.com @192.168.10.14 ;; global > options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: > NOERROR, id: 38559 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, > AUTHORITY: 0, ADDITIONAL: 1 > > ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; > QUESTION SECTION: ;www.sensoray.com. IN A > > ;; ANSWER SECTION: www.sensoray.com. 5433 IN CNAME > sensoray.com. > > ;; Query time: 218 msec ;; SERVER: 192.168.10.14#53(192.168.10.14) > ;; WHEN: Fri Sep 18 11:13:30 Central Europe Daylight Time 2015 ;; > MSG SIZE rcvd: 59 > > C:\Users\Moi>dig sensoray.com @192.168.10.14 > > ; <<>> DiG 9.10.2-P3 <<>> sensoray.com @192.168.10.14 ;; global > options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: > NOERROR, id: 5722 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, > AUTHORITY: 0, ADDITIONAL: 1 > > ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; > QUESTION SECTION: ;sensoray.com. IN A > > ;; Query time: 31 msec ;; SERVER: 192.168.10.14#53(192.168.10.14) > ;; WHEN: Fri Sep 18 11:13:37 Central Europe Daylight Time 2015 ;; > MSG SIZE rcvd: 41 > > --- > > > Regards, Mehmed > -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJWAQ+qAAoJEJ9vHC1+BF+NBaoQAKCxfaHOoV1n59p7ujexXbom Ai/89fCcumvoWG7x1SpEnkKOD/3bSYh4/gYQsXb+f5Cwpf+L8mXWUeVtuWg03GWl 8MCcbRfhTFLrKS2Uaa3agLRSNkXo/hKDkixlsnf67rnAGPNonJ/FSg0VF0Q7bC5s IGpdCYmyF4L/W2xlkW+0gh5WWD05cCFXNu4l7/Gg7esxdmY72H9otqtJQNODU9t7 t/9xwIMOeDMKIdkHsXfKru73rGCuq1+VSAyzaPrjV9dv3S/9eg22QgF5CbVxUl++ rUxm/KCY8UqTJbSXB5hv7qB0d2viJuX2UJgkNKuSzWmaCq9aMy9zyOJ3OXTtduz8 G925GS7UrLpBMTEotPeDYn7d2cJCwdaMUNnRkfjqIGdvz6Aw5WbmnlwQLimiBRoJ U8pDw2zzRn/u5j6YFrocVjgn0DUjeod9UA0tnTdLtuocE7HM65UY+AwNnwonxg7u Xj1XQlIvhSw9JMHB8uVYDJGKZDkqDIoyEkifR47DK6/Xo/D3s17PPlHFBfOcskd0 kbb00MoR4wvUXlHZm5S4/5l9l5+ZbMDBJc6910/+53tn8M+gH/i6vWMTyCjT6gko 5cUKaHGN5wsm5VsUb396rGkLnyQUw0z0T5S016bAgPsoK9Yx0djhoVU9cezVEE4v OvmFyxkjassU5o0ZJnll =elOW -----END PGP SIGNATURE-----
