idna: *Profile.process to throw labelError if verifyDNSLength = true and s ends with trailing dot.

From UTS46, no trailing dots are allowed when ToASCII is called with verifyDNSLength = true. This negates the need for an additional l.verifyDNSLength flag in the previous commit.

See https://www.unicode.org/L2/L2021/21170-utc169-properties-recs.pdf under section F2

Fixes golang/go#47182

Author: elliotwutingfeng

internal/export/idna/idna10.0.0.go

@@ -348,10 +348,10 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 	// TODO: allow for a quick check of the tables data.
 	// It seems like we should only create this error on ToASCII, but the
 	// UTS 46 conformance tests suggests we should always check this.
-	if err == nil && p.verifyDNSLength && s == "" {
+	if err == nil && p.verifyDNSLength && (s == "" || s[len(s)-1] == '.') {
 		err = &labelError{s, "A4"}
 	}
-	labels := labelIter{orig: s, verifyDNSLength: p.verifyDNSLength}
+	labels := labelIter{orig: s}
 	for ; !labels.done(); labels.next() {
 		label := labels.label()
 		if label == "" {
@@ -413,12 +413,9 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 	}
 	s = labels.result()
 	if toASCII && p.verifyDNSLength && err == nil {
-		// Compute the length of the domain name minus the root label and its dot.
+		// Compute the length of the domain name.
 		n := len(s)
-		if n > 0 && s[n-1] == '.' {
-			n--
-		}
-		if len(s) < 1 || n > 253 {
+		if n < 1 || n > 253 {
 			err = &labelError{s, "A4"}
 		}
 	}
@@ -538,12 +535,11 @@ func validateAndMap(p *Profile, s string) (vm string, bidi bool, err error) {
 
 // A labelIter allows iterating over domain name labels.
 type labelIter struct {
-	orig            string
-	slice           []string
-	curStart        int
-	curEnd          int
-	i               int
-	verifyDNSLength bool
+	orig     string
+	slice    []string
+	curStart int
+	curEnd   int
+	i        int
 }
 
 func (l *labelIter) reset() {
@@ -575,8 +571,7 @@ func (l *labelIter) label() string {
 	return l.orig[l.curStart:l.curEnd]
 }
 
-// next sets the value to the next label. It skips the last label if it is empty
-// and l.verifyDNSLength is false.
+// next sets the value to the next label. It skips the last label if it is empty.
 func (l *labelIter) next() {
 	l.i++
 	if l.slice != nil {
@@ -585,7 +580,7 @@ func (l *labelIter) next() {
 		}
 	} else {
 		l.curStart = l.curEnd + 1
-		if !l.verifyDNSLength && l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
+		if l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
 			l.curStart = len(l.orig)
 		}
 	}

internal/export/idna/idna10.0.0_test.go

@@ -67,8 +67,12 @@ func TestLabelErrors(t *testing.T) {
 		{lengthA, ".b", ".b", "A4"},
 		{lengthA, "\u3002b", ".b", "A4"},
 		{lengthA, "..b", "..b", "A4"},
+		{lengthA, "b.", "b.", "A4"},
+		{lengthA, "ƀ.", "xn--lha.", "A4"},
 		{lengthA, "b..", "b..", "A4"},
 		{lengthA, "ƀ..", "xn--lha..", "A4"},
+		{lengthA, "b...", "b...", "A4"},
+		{lengthA, "ƀ...", "xn--lha...", "A4"},
 
 		// Sharpened Bidi rules for Unicode 10.0.0. Apply for ALL labels in ANY
 		// of the labels is RTL.
@@ -81,8 +85,12 @@ func TestLabelErrors(t *testing.T) {
 		{resolve, ".b", ".b", ""},
 		{resolve, "\u3002b", ".b", ""},
 		{resolve, "..b", "..b", ""},
+		{resolve, "b.", "b.", ""},
+		{resolve, "ƀ.", "xn--lha.", ""},
 		{resolve, "b..", "b..", ""},
 		{resolve, "ƀ..", "xn--lha..", ""},
+		{resolve, "b...", "b...", ""},
+		{resolve, "ƀ...", "xn--lha...", ""},
 		{resolve, "\xed", "", "P1"},
 
 		// Raw punycode

internal/export/idna/idna9.0.0.go

@@ -348,10 +348,10 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 	}
 	// It seems like we should only create this error on ToASCII, but the
 	// UTS 46 conformance tests suggests we should always check this.
-	if err == nil && p.verifyDNSLength && s == "" {
+	if err == nil && p.verifyDNSLength && (s == "" || s[len(s)-1] == '.') {
 		err = &labelError{s, "A4"}
 	}
-	labels := labelIter{orig: s, verifyDNSLength: p.verifyDNSLength}
+	labels := labelIter{orig: s}
 	for ; !labels.done(); labels.next() {
 		label := labels.label()
 		if label == "" {
@@ -404,12 +404,9 @@ func (p *Profile) process(s string, toASCII bool) (string, error) {
 	}
 	s = labels.result()
 	if toASCII && p.verifyDNSLength && err == nil {
-		// Compute the length of the domain name minus the root label and its dot.
+		// Compute the length of the domain name.
 		n := len(s)
-		if n > 0 && s[n-1] == '.' {
-			n--
-		}
-		if len(s) < 1 || n > 253 {
+		if n < 1 || n > 253 {
 			err = &labelError{s, "A4"}
 		}
 	}
@@ -500,12 +497,11 @@ func validateAndMap(p *Profile, s string) (string, error) {
 
 // A labelIter allows iterating over domain name labels.
 type labelIter struct {
-	orig            string
-	slice           []string
-	curStart        int
-	curEnd          int
-	i               int
-	verifyDNSLength bool
+	orig     string
+	slice    []string
+	curStart int
+	curEnd   int
+	i        int
 }
 
 func (l *labelIter) reset() {
@@ -537,8 +533,7 @@ func (l *labelIter) label() string {
 	return l.orig[l.curStart:l.curEnd]
 }
 
-// next sets the value to the next label. It skips the last label if it is empty
-// and l.verifyDNSLength is false.
+// next sets the value to the next label. It skips the last label if it is empty.
 func (l *labelIter) next() {
 	l.i++
 	if l.slice != nil {
@@ -547,7 +542,7 @@ func (l *labelIter) next() {
 		}
 	} else {
 		l.curStart = l.curEnd + 1
-		if !l.verifyDNSLength && l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
+		if l.curStart == len(l.orig)-1 && l.orig[l.curStart] == '.' {
 			l.curStart = len(l.orig)
 		}
 	}

internal/export/idna/idna9.0.0_test.go

@@ -71,15 +71,23 @@ func TestLabelErrors(t *testing.T) {
 		{lengthA, ".b", "b", ""},
 		{lengthA, "\u3002b", "b", ""},
 		{lengthA, "..b", "b", ""},
+		{lengthA, "b.", "b.", "A4"},
+		{lengthA, "ƀ.", "xn--lha.", "A4"},
 		{lengthA, "b..", "b..", "A4"},
 		{lengthA, "ƀ..", "xn--lha..", "A4"},
+		{lengthA, "b...", "b...", "A4"},
+		{lengthA, "ƀ...", "xn--lha...", "A4"},
 
 		{resolve, "a..b", "a..b", ""},
 		{resolve, ".b", "b", ""},
 		{resolve, "\u3002b", "b", ""},
 		{resolve, "..b", "b", ""},
+		{resolve, "b.", "b.", ""},
+		{resolve, "ƀ.", "xn--lha.", ""},
 		{resolve, "b..", "b..", ""},
 		{resolve, "ƀ..", "xn--lha..", ""},
+		{resolve, "b...", "b...", ""},
+		{resolve, "ƀ...", "xn--lha...", ""},
 		{resolve, "\xed", "", "P1"},
 
 		// Raw punycode