Be consistent about domain name label character escaping (#1122)
* Improve sprintName tests * Fix sprintName handling of escaped dots * Make sprintName consistently drop dangling incomplete escapes * Be consistent about domain name label character escaping Fixes #1121 * Replace strings.IndexByte with faster special-purpose function
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parent
064ba4b789
commit
978b9a827a
15
msg.go
15
msg.go
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@ -398,17 +398,12 @@ Loop:
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return "", lenmsg, ErrLongDomain
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return "", lenmsg, ErrLongDomain
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}
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}
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for _, b := range msg[off : off+c] {
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for _, b := range msg[off : off+c] {
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switch b {
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if isDomainNameLabelSpecial(b) {
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case '.', '(', ')', ';', ' ', '@':
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fallthrough
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case '"', '\\':
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s = append(s, '\\', b)
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s = append(s, '\\', b)
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default:
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} else if b < ' ' || b > '~' {
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if b < ' ' || b > '~' { // unprintable, use \DDD
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s = append(s, escapeByte(b)...)
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s = append(s, escapeByte(b)...)
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} else {
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} else {
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s = append(s, b)
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s = append(s, b)
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}
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}
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}
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}
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}
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s = append(s, '.')
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s = append(s, '.')
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52
types.go
52
types.go
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@ -445,45 +445,38 @@ func sprintName(s string) string {
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var dst strings.Builder
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var dst strings.Builder
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for i := 0; i < len(s); {
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for i := 0; i < len(s); {
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if i+1 < len(s) && s[i] == '\\' && s[i+1] == '.' {
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if s[i] == '.' {
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if dst.Len() != 0 {
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if dst.Len() != 0 {
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dst.WriteString(s[i : i+2])
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dst.WriteByte('.')
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}
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}
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i += 2
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i++
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continue
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continue
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}
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}
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b, n := nextByte(s, i)
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b, n := nextByte(s, i)
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if n == 0 {
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if n == 0 {
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i++
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// Drop "dangling" incomplete escapes.
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continue
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if dst.Len() == 0 {
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}
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return s[:i]
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if b == '.' {
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if dst.Len() != 0 {
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dst.WriteByte('.')
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}
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}
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i += n
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break
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continue
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}
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}
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switch b {
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if isDomainNameLabelSpecial(b) {
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case ' ', '\'', '@', ';', '(', ')', '"', '\\': // additional chars to escape
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if dst.Len() == 0 {
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if dst.Len() == 0 {
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dst.Grow(len(s) * 2)
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dst.Grow(len(s) * 2)
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dst.WriteString(s[:i])
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dst.WriteString(s[:i])
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}
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}
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dst.WriteByte('\\')
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dst.WriteByte('\\')
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dst.WriteByte(b)
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dst.WriteByte(b)
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default:
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} else if b < ' ' || b > '~' { // unprintable, use \DDD
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if ' ' <= b && b <= '~' {
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if dst.Len() == 0 {
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if dst.Len() != 0 {
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dst.Grow(len(s) * 2)
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dst.WriteByte(b)
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dst.WriteString(s[:i])
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}
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}
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} else {
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dst.WriteString(escapeByte(b))
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if dst.Len() == 0 {
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} else {
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dst.Grow(len(s) * 2)
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if dst.Len() != 0 {
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dst.WriteString(s[:i])
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dst.WriteByte(b)
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}
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dst.WriteString(escapeByte(b))
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}
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}
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}
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}
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i += n
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i += n
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@ -585,6 +578,17 @@ func escapeByte(b byte) string {
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return escapedByteLarge[int(b)*4 : int(b)*4+4]
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return escapedByteLarge[int(b)*4 : int(b)*4+4]
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}
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}
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// isDomainNameLabelSpecial returns true if
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// a domain name label byte should be prefixed
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// with an escaping backslash.
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func isDomainNameLabelSpecial(b byte) bool {
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switch b {
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case '.', ' ', '\'', '@', ';', '(', ')', '"', '\\':
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return true
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}
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return false
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}
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func nextByte(s string, offset int) (byte, int) {
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func nextByte(s string, offset int) (byte, int) {
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if offset >= len(s) {
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if offset >= len(s) {
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return 0, 0
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return 0, 0
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@ -74,10 +74,33 @@ func TestSplitN(t *testing.T) {
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}
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}
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func TestSprintName(t *testing.T) {
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func TestSprintName(t *testing.T) {
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got := sprintName("abc\\.def\007\"\127@\255\x05\xef\\")
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tests := map[string]string{
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// Non-numeric escaping of special printable characters.
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" '@;()\"\\..example": `\ \'\@\;\(\)\"\..example`,
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"\\032\\039\\064\\059\\040\\041\\034\\046\\092.example": `\ \'\@\;\(\)\"\.\\.example`,
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if want := "abc\\.def\\007\\\"W\\@\\173\\005\\239"; got != want {
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// Numeric escaping of nonprintable characters.
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t.Errorf("expected %q, got %q", want, got)
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"\x00\x07\x09\x0a\x1f.\x7f\x80\xad\xef\xff": `\000\007\009\010\031.\127\128\173\239\255`,
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"\\000\\007\\009\\010\\031.\\127\\128\\173\\239\\255": `\000\007\009\010\031.\127\128\173\239\255`,
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// No escaping of other printable characters, at least after a prior escape.
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";[a-zA-Z0-9_]+/*.~": `\;[a-zA-Z0-9_]+/*.~`,
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";\\091\\097\\045\\122\\065\\045\\090\\048\\045\\057\\095\\093\\043\\047\\042.\\126": `\;[a-zA-Z0-9_]+/*.~`,
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// "\\091\\097\\045\\122\\065\\045\\090\\048\\045\\057\\095\\093\\043\\047\\042.\\126": `[a-zA-Z0-9_]+/*.~`,
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// Incomplete "dangling" escapes are dropped regardless of prior escaping.
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"a\\": `a`,
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";\\": `\;`,
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// Escaped dots stay escaped regardless of prior escaping.
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"a\\.\\046.\\.\\046": `a\.\..\.\.`,
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"a\\046\\..\\046\\.": `a\.\..\.\.`,
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}
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for input, want := range tests {
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got := sprintName(input)
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if got != want {
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t.Errorf("input %q: expected %q, got %q", input, want, got)
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}
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}
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}
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}
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}
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