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util/dnsname: add FQDN type, use throughout codebase.
Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson
committed by
Dave Anderson
Dave Anderson
parent
7a1813fd24
commit
1a371b93be
@@ -5,45 +5,134 @@
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// Package dnsname contains string functions for working with DNS names.
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package dnsname
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import "strings"
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import (
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"fmt"
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"strings"
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)
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var separators = map[byte]bool{
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' ': true,
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'.': true,
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'@': true,
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'_': true,
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}
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const (
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// maxLabelLength is the maximum length of a label permitted by RFC 1035.
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maxLabelLength = 63
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// maxNameLength is the maximum length of a DNS name.
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maxNameLength = 253
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)
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func islower(c byte) bool {
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return 'a' <= c && c <= 'z'
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}
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// A FQDN is a fully-qualified DNS name or name suffix.
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type FQDN string
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func isupper(c byte) bool {
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return 'A' <= c && c <= 'Z'
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}
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func isalpha(c byte) bool {
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return islower(c) || isupper(c)
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}
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func isalphanum(c byte) bool {
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return isalpha(c) || ('0' <= c && c <= '9')
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}
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func isdnschar(c byte) bool {
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return isalphanum(c) || c == '-'
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}
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func tolower(c byte) byte {
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if isupper(c) {
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return c + 'a' - 'A'
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} else {
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return c
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func ToFQDN(s string) (FQDN, error) {
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if isValidFQDN(s) {
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return FQDN(s), nil
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}
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if len(s) == 0 {
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return FQDN("."), nil
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}
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if s[len(s)-1] == '.' {
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s = s[:len(s)-1]
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}
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if len(s) > maxNameLength {
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return "", fmt.Errorf("%q is too long to be a DNS name", s)
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}
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fs := strings.Split(s, ".")
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for _, f := range fs {
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if !validLabel(f) {
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return "", fmt.Errorf("%q is not a valid DNS label", f)
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}
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}
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return FQDN(s + "."), nil
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}
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// maxLabelLength is the maximal length of a label permitted by RFC 1035.
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const maxLabelLength = 63
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func validLabel(s string) bool {
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if len(s) == 0 || len(s) > maxLabelLength {
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return false
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}
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if !isalphanum(s[0]) || !isalphanum(s[len(s)-1]) {
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return false
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}
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for i := 1; i < len(s)-1; i++ {
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if !isalphanum(s[i]) && s[i] != '-' {
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return false
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}
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}
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return true
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}
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// WithTrailingDot returns f as a string, with a trailing dot.
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func (f FQDN) WithTrailingDot() string {
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return string(f)
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}
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// WithoutTrailingDot returns f as a string, with the trailing dot
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// removed.
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func (f FQDN) WithoutTrailingDot() string {
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return string(f[:len(f)-1])
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}
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func (f FQDN) NumLabels() int {
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if f == "." {
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return 0
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}
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return strings.Count(f.WithTrailingDot(), ".")
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}
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func (f FQDN) Contains(other FQDN) bool {
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if f == other {
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return true
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}
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cmp := f.WithTrailingDot()
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if cmp != "." {
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cmp = "." + cmp
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}
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return strings.HasSuffix(other.WithTrailingDot(), cmp)
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}
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// isValidFQDN reports whether s is already a valid FQDN, without
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// allocating.
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func isValidFQDN(s string) bool {
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if len(s) == 0 {
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return false
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}
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if len(s) > maxNameLength {
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return false
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}
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// DNS root name.
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if s == "." {
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return true
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}
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// Missing trailing dot.
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if s[len(s)-1] != '.' {
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return false
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}
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// Leading dots not allowed.
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if s[0] == '.' {
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return false
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}
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st := 0
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for i := 0; i < len(s); i++ {
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if s[i] != '.' {
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continue
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}
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label := s[st:i]
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if len(label) == 0 || len(label) > maxLabelLength {
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return false
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}
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if !isalphanum(label[0]) || !isalphanum(label[len(label)-1]) {
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return false
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}
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for j := 1; j < len(label)-1; j++ {
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if !isalphanum(label[j]) && label[j] != '-' {
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return false
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}
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}
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st = i + 1
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}
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return true
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}
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// SanitizeLabel takes a string intended to be a DNS name label
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// and turns it into a valid name label according to RFC 1035.
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@@ -133,3 +222,38 @@ func NumLabels(hostname string) int {
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}
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return strings.Count(hostname, ".")
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}
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var separators = map[byte]bool{
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' ': true,
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'.': true,
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'@': true,
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'_': true,
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}
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func islower(c byte) bool {
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return 'a' <= c && c <= 'z'
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}
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func isupper(c byte) bool {
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return 'A' <= c && c <= 'Z'
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}
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func isalpha(c byte) bool {
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return islower(c) || isupper(c)
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}
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func isalphanum(c byte) bool {
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return isalpha(c) || ('0' <= c && c <= '9')
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}
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func isdnschar(c byte) bool {
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return isalphanum(c) || c == '-'
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}
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func tolower(c byte) byte {
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if isupper(c) {
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return c + 'a' - 'A'
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} else {
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return c
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}
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}
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@@ -9,6 +9,87 @@ import (
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"testing"
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)
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func TestFQDN(t *testing.T) {
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tests := []struct {
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in string
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want FQDN
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wantErr bool
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wantLabels int
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}{
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{"", ".", false, 0},
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{".", ".", false, 0},
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{"foo.com", "foo.com.", false, 2},
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{"foo.com.", "foo.com.", false, 2},
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{"com", "com.", false, 1},
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{"www.tailscale.com", "www.tailscale.com.", false, 3},
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{"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.com", "", true, 0},
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{strings.Repeat("aaaaa.", 60) + "com", "", true, 0},
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{".com", "", true, 0},
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{"foo..com", "", true, 0},
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}
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for _, test := range tests {
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t.Run(test.in, func(t *testing.T) {
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got, err := ToFQDN(test.in)
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if got != test.want {
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t.Errorf("ToFQDN(%q) got %q, want %q", test.in, got, test.want)
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}
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if (err != nil) != test.wantErr {
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t.Errorf("ToFQDN(%q) err %v, wantErr=%v", test.in, err, test.wantErr)
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}
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if err != nil {
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return
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}
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gotDot := got.WithTrailingDot()
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if gotDot != string(test.want) {
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t.Errorf("ToFQDN(%q).WithTrailingDot() got %q, want %q", test.in, gotDot, test.want)
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}
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gotNoDot := got.WithoutTrailingDot()
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wantNoDot := string(test.want)[:len(test.want)-1]
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if gotNoDot != wantNoDot {
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t.Errorf("ToFQDN(%q).WithoutTrailingDot() got %q, want %q", test.in, gotNoDot, wantNoDot)
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}
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if gotLabels := got.NumLabels(); gotLabels != test.wantLabels {
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t.Errorf("ToFQDN(%q).NumLabels() got %v, want %v", test.in, gotLabels, test.wantLabels)
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}
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})
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}
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}
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func TestFQDNContains(t *testing.T) {
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tests := []struct {
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a, b string
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want bool
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}{
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{"", "", true},
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{"", "foo.com", true},
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{"foo.com", "", false},
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{"tailscale.com", "www.tailscale.com", true},
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{"www.tailscale.com", "tailscale.com", false},
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{"scale.com", "tailscale.com", false},
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{"foo.com", "foo.com", true},
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}
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for _, test := range tests {
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t.Run(test.a+"_"+test.b, func(t *testing.T) {
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a, err := ToFQDN(test.a)
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if err != nil {
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t.Fatalf("ToFQDN(%q): %v", test.a, err)
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}
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b, err := ToFQDN(test.b)
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if err != nil {
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t.Fatalf("ToFQDN(%q): %v", test.b, err)
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}
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if got := a.Contains(b); got != test.want {
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t.Errorf("ToFQDN(%q).Contains(%q) got %v, want %v", a, b, got, test.want)
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}
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})
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}
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}
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func TestSanitizeLabel(t *testing.T) {
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tests := []struct {
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name string
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