0x7F char causes "Unable to parse DNS TXT" in powerdns-recursor

[mbevand]

When the latest powerdns-recursor version (3.6.1) attempts to resolve a TXT record containing the character 0x7F (DEL), it errors out (see error below). This is because 837f4b4 was an incomplete fix: "> 127" should be replaced with "> 126".

STL error: Unable to parse DNS TXT '"\x7f"'

[mbevand]

Any update? It is a one-line patch to fix this issue... I created a record to help you guys test and validate the fix. If x.x.x.x is a PowerDNS resolver run:

$ dig @x.x.x.x -t txt bug.zorinaq.com

Actual result: dig times out... and pdns_recursor logs show "Unable to parse DNS TXT '"\x7f"'

Expected result: dig showing:

; <<>> DiG 9.9.5-3-Ubuntu <<>> @x.x.x.x -t txt bug.zorinaq.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5858
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;bug.zorinaq.com. IN TXT

;; ANSWER SECTION:
bug.zorinaq.com. 299 IN TXT "\127"

[...]

[txdv]

Your blog stated you had a patch. Where is the patch?

[Habbie]

The patch is described in the first post on this page.

[Habbie]

Bug confirmed in 3.5.3

[Habbie]

Works for me on 3.6.1 though!

Can you verify that you really are running 3.6.1? Then, can you tell us exactly how you built it and on what system?

[mbevand]

As Habbie said, the patch is described in the first post on this page (replacing "> 127" with "> 126" at line 395 of this patch: 837f4b4).

I built 3.6.1 on Ubuntu 14.04 with a simple ./configure && make (and running pdns-recursor from the source tree.) Although it has been 2 weeks since I did it so I don't recall the exact details and did not take notes other than submitting this bug. I will double-check tonight my steps...

[mbevand]

Hmm, I am indeed unable to reproduce it with 3.6.1. The bug only exists with 3.5.3. Something else must have changed in the logic causing 3.6.1 to work despite "> 127" in this if condition.

[Habbie]

973efd3 fixed this. Closing ticket!