Wildcard domains as per RFC-4592

[Cottand]

Hi!

My understanding is this lib should support RFC-4592 (wildcard domains, as stated in the README). I am trying to use wildcard domains RRs with the following example:

// make a simple fake dns.ResponseWriter
type mockRw struct {
	stored *dns.Msg
}

func (m *mockRw) WriteMsg(msg *dns.Msg) error {
	m.stored = msg
	return nil
}

// returns a handler that returns TXT record
func ServerReplyTXT(txt string) dns.HandlerFunc {
	return func(w dns.ResponseWriter, req *dns.Msg) {
		m := new(dns.Msg)
		m.SetReply(req)

		m.Answer = make([]dns.RR, 1)
		m.Answer[0] = &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{txt}}
		_ = w.WriteMsg(m)
	}
}


func TestWildcardInLib(t *testing.T) {
	serveMux := dns.NewServeMux()

	serveMux.HandleFunc(".", ServerReplyTXT("root"))
	serveMux.HandleFunc("example.com.", ServerReplyTXT("example"))
	serveMux.HandleFunc("*.example.com.", ServerReplyTXT("wildcard"))

	rw := mockRw{stored: nil}

	msg := new(dns.Msg)
	msg.SetQuestion("banana.example.com", dns.TypeTXT)

	serveMux.ServeDNS(&rw, msg)
	println(rw.stored.Answer[0].String()) // prints: `example`, I expected `wildcard`

}

My understandig of RFC-4592 section 2.2.1 is that the above should print wildcard (because it matches *.example.com) but it prints example instead.

Did I misunderstand the RFC or perhaps am I using the library wrong? I did not find anything else mentioning 'wildcard' in the README and these tests do not seem to be testing matching wildcard domains.

Thanks in advance

[miekg]

I don't think this is implemented, nor, e.g., DS handling

…

On Sat, 3 Feb 2024, 15:58 Cottand, ***@***.***> wrote: Hi! My understanding is this lib should support RFC-4592 (wildcard domains, as stated in the README). I am trying to use wildcard domains RRs with the following example: // make a simple fake dns.ResponseWritertype mockRw struct { stored *dns.Msg } func (m *mockRw) WriteMsg(msg *dns.Msg) error { m.stored = msg return nil } // returns a handler that returns TXT recordfunc ServerReplyTXT(txt string) dns.HandlerFunc { return func(w dns.ResponseWriter, req *dns.Msg) { m := new(dns.Msg) m.SetReply(req) m.Answer = make([]dns.RR, 1) m.Answer[0] = &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{txt}} _ = w.WriteMsg(m) } } func TestWildcardInLib(t *testing.T) { serveMux := dns.NewServeMux() serveMux.HandleFunc(".", ServerReplyTXT("root")) serveMux.HandleFunc("example.com.", ServerReplyTXT("example")) serveMux.HandleFunc("*.example.com.", ServerReplyTXT("wildcard")) rw := mockRw{stored: nil} msg := new(dns.Msg) msg.SetQuestion("banana.example.com", dns.TypeTXT) serveMux.ServeDNS(&rw, msg) println(rw.stored.Answer[0].String()) // prints: `example`, I expected `wildcard` } My understandig of RFC-4592 section 2.2.10 <https://datatracker.ietf.org/doc/html/rfc4592#section-2.2.10> is that the above should print wildcard (because it matches *.example.com) but it prints example instead. Did I misunderstand the RFC or perhaps am I using the library wrong? I did not find anything else mentioning 'wildcard' in the README and these tests <https://github.com/miekg/dns/blob/master/serve_mux_test.go> do not seem to be testing matching wildcard domains. Thanks in advance — Reply to this email directly, view it on GitHub <#1534>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACWIW54UUFUVXH52BQZCB3YRZGCNAVCNFSM6AAAAABCYC2RPGVHI2DSMVQWIX3LMV43ASLTON2WKOZSGEYTMNJSGA4TENY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[Cottand]

Thanks for the quick reply

In that case, do you think it would be fair to either implement it, or remove RFC-4592 from the list of supported RFCs in the README?

Otherwise I would have expected it to work

[miekg]

No, but maybe the handlefunc docs or some other docs could be improved.

…

On Sat, 3 Feb 2024, 18:20 Cottand, ***@***.***> wrote: Thanks for the quick reply In that case, do you think it would be fair to either implement it, or remove RFC-4592 from the list of supported RFCs in the README? Otherwise I would have expected it to work — Reply to this email directly, view it on GitHub <#1534 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AACWIW3OG76K2SFRVYSE7OLYRZWXDAVCNFSM6AAAAABCYC2RPGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSMRVGQYDAMRVGI> . You are receiving this because you commented.Message ID: ***@***.***>

[Cottand]

Ok no worries, I will implement on my end, thank you.

In that case, would you mind clarifying how exactly is this library compliant with RFC-4592? Is there use of wildcards elsewhere?

[miekg]

ha, i see we do do DS handling, probably wildcard handling should be done as well

[Cottand]

that's good to hear!

[miekg]

[ Quoting ***@***.***> in "Re: [miekg/dns] Wildcard domains as..." ]

that's good to hear!

should be possible to lift this out of CoreDNS' loop, but I want have any spare cycles to do this any time soon /Miek

[Cottand]

If you point me to the file(s) in CoreDNS I can have a stab a it

[miekg]

[ Quoting ***@***.***> in "Re: [miekg/dns] Wildcard domains as..." ]

If you point me to the file in CoreDNS I can have a stab a it

maybe here: https://github.com/coredns/coredns/blob/master/plugin/file/lookup.go althought that is more complex. I think this checking for wildcard label if there is no match should be sufficient /Miek

…

-- Miek Gieben

[Cottand]

See #1536 as step 1. I chose not to add CoreDNS' complexity to the simple match function until I fully understood the code there