initial working version

internal/dnstt/parser_test.go

@@ -0,0 +1,93 @@
+package dnstt
+
+import (
+	"encoding/base32"
+	"testing"
+)
+
+func TestExtractQueryDecodesDNSTTClientID(t *testing.T) {
+	clientID := []byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08}
+	encoded := base32.StdEncoding.WithPadding(base32.NoPadding).EncodeToString(append(clientID, 0xaa, 0xbb))
+	packet := dnsQuery(encoded, "tunnel.example.com")
+
+	domain, gotClientID := ExtractQuery(packet, []string{"tunnel.example.com"})
+
+	if domain != "tunnel.example.com" {
+		t.Fatalf("domain = %q, want tunnel.example.com", domain)
+	}
+	if gotClientID != "0102030405060708" {
+		t.Fatalf("client ID = %q, want 0102030405060708", gotClientID)
+	}
+}
+
+func TestExtractQueryMatchesBareDomainWithoutClientID(t *testing.T) {
+	packet := dnsQuery("", "tunnel.example.com")
+
+	domain, gotClientID := ExtractQuery(packet, []string{"tunnel.example.com"})
+
+	if domain != "tunnel.example.com" {
+		t.Fatalf("domain = %q, want tunnel.example.com", domain)
+	}
+	if gotClientID != "" {
+		t.Fatalf("client ID = %q, want empty", gotClientID)
+	}
+}
+
+func TestExtractQueryIgnoresUnregisteredDomain(t *testing.T) {
+	packet := dnsQuery("abcd", "other.example.com")
+
+	domain, gotClientID := ExtractQuery(packet, []string{"tunnel.example.com"})
+
+	if domain != "" || gotClientID != "" {
+		t.Fatalf("got domain=%q clientID=%q, want both empty", domain, gotClientID)
+	}
+}
+
+func TestExtractQueryReturnsDomainWhenPrefixIsNotClientID(t *testing.T) {
+	packet := dnsQuery("not-base32-!", "tunnel.example.com")
+
+	domain, gotClientID := ExtractQuery(packet, []string{"tunnel.example.com"})
+
+	if domain != "tunnel.example.com" {
+		t.Fatalf("domain = %q, want tunnel.example.com", domain)
+	}
+	if gotClientID != "" {
+		t.Fatalf("client ID = %q, want empty", gotClientID)
+	}
+}
+
+func dnsQuery(prefix string, domain string) []byte {
+	packet := []byte{
+		0x12, 0x34, // transaction ID
+		0x01, 0x00, // flags
+		0x00, 0x01, // questions
+		0x00, 0x00, // answers
+		0x00, 0x00, // authority
+		0x00, 0x00, // additional
+	}
+
+	labels := splitDomain(domain)
+	if prefix != "" {
+		labels = append([]string{prefix}, labels...)
+	}
+	for _, label := range labels {
+		packet = append(packet, byte(len(label)))
+		packet = append(packet, label...)
+	}
+	packet = append(packet, 0x00)       // root label
+	packet = append(packet, 0x00, 0x10) // TXT
+	packet = append(packet, 0x00, 0x01) // IN
+	return packet
+}
+
+func splitDomain(domain string) []string {
+	var labels []string
+	start := 0
+	for i := 0; i <= len(domain); i++ {
+		if i == len(domain) || domain[i] == '.' {
+			labels = append(labels, domain[start:i])
+			start = i + 1
+		}
+	}
+	return labels
+}