encoding/asn1: Fix parsing of non-printable strings in

sequences.

Use the same criteria for when to modify the tag type when
parsing a string in a sequence as when parsing a bare string
field.

Fixes #6726.

R=golang-dev, bradfitz, gobot, agl
CC=golang-dev
https://golang.org/cl/22460043

src/pkg/encoding/asn1/asn1.go

@@ -451,11 +451,13 @@ func parseSequenceOf(bytes []byte, sliceType reflect.Type, elemType reflect.Type
 		if err != nil {
 			return
 		}
-		// We pretend that GENERAL STRINGs are PRINTABLE STRINGs so
-		// that a sequence of them can be parsed into a []string.
-		if t.tag == tagGeneralString {
+		// We pretend that various other string types are PRINTABLE STRINGs
+		// so that a sequence of them can be parsed into a []string.
+		switch t.tag {
+		case tagIA5String, tagGeneralString, tagT61String, tagUTF8String:
 			t.tag = tagPrintableString
 		}
+
 		if t.class != classUniversal || t.isCompound != compoundType || t.tag != expectedTag {
 			err = StructuralError{"sequence tag mismatch"}
 			return

src/pkg/encoding/asn1/asn1_test.go

@@ -6,6 +6,7 @@ package asn1
 
 import (
 	"bytes"
+	"fmt"
 	"math/big"
 	"reflect"
 	"testing"
@@ -776,3 +777,29 @@ var derEncodedPaypalNULCertBytes = []byte{
 	0xc8, 0x64, 0x8c, 0xb5, 0x50, 0x23, 0x82, 0x6f, 0xdb, 0xb8, 0x22, 0x1c, 0x43,
 	0x96, 0x07, 0xa8, 0xbb,
 }
+
+var stringSliceTestData = [][]string{
+	{"foo", "bar"},
+	{"foo", "\\bar"},
+	{"foo", "\"bar\""},
+	{"foo", "åäö"},
+}
+
+func TestStringSlice(t *testing.T) {
+	for _, test := range stringSliceTestData {
+		bs, err := Marshal(test)
+		if err != nil {
+			t.Error(err)
+		}
+
+		var res []string
+		_, err = Unmarshal(bs, &res)
+		if err != nil {
+			t.Error(err)
+		}
+
+		if fmt.Sprintf("%v", res) != fmt.Sprintf("%v", test) {
+			t.Errorf("incorrect marshal/unmarshal; %v != %v", res, test)
+		}
+	}
+}