Add RFC4034 domain comparison + NSEC Cover

Author: monoidic

nsecx.go

@@ -93,3 +93,62 @@ func (rr *NSEC3) Match(name string) bool {
 	}
 	return false
 }
+
+// compares domains according to the canonical ordering specified in RFC4034
+// returns an integer value similar to strcmp
+// (0 for equal values, -1 if s1 < s2, 1 if s1 > s2)
+func DomainCompare(s1, s2 string) int {
+	s1 = strings.ToLower(s1)
+	s2 = strings.ToLower(s2)
+
+	if s1 == s2 {
+		return 0
+	}
+
+	s1_labels := SplitDomainName(s1)
+	s2_labels := SplitDomainName(s2)
+
+	if s1_labels == nil { // s1 is root
+		return -1
+	}
+	if s2_labels == nil { // s2 is root
+		return 1
+	}
+
+	reverse_arr(s1_labels)
+	reverse_arr(s2_labels)
+
+	s1_label_len := len(s1_labels)
+	s2_label_len := len(s2_labels)
+
+	var min_label_len int
+	var default_ret int // based on label count, if the common prefix matches
+
+	if s1_label_len < s2_label_len {
+		min_label_len = s1_label_len
+		default_ret = -1
+	} else {
+		min_label_len = s2_label_len
+		default_ret = 1
+	}
+
+	for i := 0; i < min_label_len; i++ {
+		cmp := strings.Compare(s1_labels[i], s2_labels[i])
+		if cmp != 0 {
+			return cmp
+		}
+	}
+
+	return default_ret
+}
+
+// Match returns true if the given name is covered by the NSEC record
+func (rr *NSEC) Cover(name string) bool {
+	return DomainCompare(rr.Hdr.Name, name) <= 0 && DomainCompare(name, rr.NextDomain) == -1
+}
+
+func reverse_arr(arr []string) {
+	for i, j := 0, len(arr) - 1; i < j; i, j = i+1, j-1 {
+		arr[i], arr[j] = arr[j], arr[i]
+	}
+}

nsecx_test.go

@@ -168,3 +168,51 @@ func BenchmarkHashName(b *testing.B) {
 		})
 	}
 }
+
+func TestDomainCompare(t *testing.T) {
+	domains := []string{ // from RFC 4034
+		"example.",
+		"a.example.",
+		"yljkjljk.a.example.",
+		"Z.a.example.",
+		"zABC.a.EXAMPLE.",
+		"z.example.",
+		"\x01.z.example.",
+		"*.z.example.",
+		"\xc8.z.example.",
+	}
+
+	len_domains := len(domains)
+
+	for i, domain := range domains {
+		if i != 0 {
+			prev_domain := domains[i-1]
+			if !(DomainCompare(prev_domain, domain) == -1 && DomainCompare(domain, prev_domain) == 1) {
+				t.Fatalf("prev comparison failure between %s and %s", prev_domain, domain)
+			}
+		}
+
+		if DomainCompare(domain, domain) != 0 {
+			t.Fatalf("self comparison failure for %s", domain)
+		}
+
+		if i != len_domains-1 {
+			next_domain := domains[i+1]
+			if !(DomainCompare(domain, next_domain) == -1 && DomainCompare(next_domain, domain) == 1) {
+				t.Fatalf("next comparison failure between %s and %s, %d and %d", domain, next_domain, DomainCompare(domain, next_domain), DomainCompare(next_domain, domain))
+			}
+		}
+	}
+}
+
+func TestNsecCover(t *testing.T) {
+	nsec := testRR("aaa.ee.	3600	IN	NSEC	aac.ee. NS RRSIG NSEC").(*NSEC)
+
+	if !nsec.Cover("aaaa.ee.") {
+		t.Fatal("nsec cover positive example failure")
+	}
+
+	if nsec.Cover("aad.ee.") {
+		t.Fatal("nsec cover negative example failure")
+	}
+}