golang/go

net: LookupTXT fails when TXT record contains multiple strings

DenBeke opened this issue · 2 comments

DenBeke commented

What version of Go are you using (go version)?
Go 1.4

What operating system and processor architecture are you using?
OS X 10.10.3

What did you do?
DNS TXT lookup on _spf.facebook.com:

package main

import "fmt"
import "net"

func main() {
    txt, err := net.LookupTXT("_spf.facebook.com")
    fmt.Println(err)
    fmt.Println(txt)
}

What did you expect to see?
"v=spf1 ip4:69.63.179.25 ip4:69.63.178.128/25 ip4:69.63.184.0/25 ip4:66.220.144.128/25 ip4:66.220.155.0/24 ip4:69.171.232.0/25 i" "p4:66.220.157.0/25 ip4:69.171.244.0/24 mx -all"

dig _spf.facebook.com TXT returns this:

;; QUESTION SECTION:
;_spf.facebook.com.     IN  TXT

;; ANSWER SECTION:
_spf.facebook.com.  3599    IN  TXT "v=spf1 ip4:69.63.179.25 ip4:69.63.178.128/25 ip4:69.63.184.0/25 ip4:66.220.144.128/25 ip4:66.220.155.0/24 ip4:69.171.232.0/25 i" "p4:66.220.157.0/25 ip4:69.171.244.0/24 mx -all"

What did you see instead?
lookup _spf.facebook.com on 8.8.8.8:53: no such host

Go fails to lookup TXT records which consist of multiple character strings.
RFC 1035 3.3.14.

3.3.14. TXT RDATA format

    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
    /                   TXT-DATA                    /
    +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

where:

TXT-DATA        One or more <character-string>s.

<character-string> is defined in section 3.3. of the same RFC 1035

<character-string> is a single
length octet followed by that number of characters.  <character-string>
is treated as binary information, and can be up to 256 characters in
length (including the length octet).
gopherbot commented

CL https://golang.org/cl/8966 mentions this issue.