1 files changed, 32 insertions, 6 deletions
diff --git a/libgo/go/encoding/asn1/marshal.go b/libgo/go/encoding/asn1/marshal.go
index 163bca575de..3fd6be8ad92 100644
--- a/libgo/go/encoding/asn1/marshal.go
+++ b/libgo/go/encoding/asn1/marshal.go
@@ -6,11 +6,13 @@ package asn1
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"math/big"
 	"reflect"
 	"time"
+	"unicode/utf8"
 )
 
 // A forkableWriter is an in-memory buffer that can be
@@ -280,6 +282,11 @@ func marshalIA5String(out *forkableWriter, s string) (err error) {
 	return
 }
 
+func marshalUTF8String(out *forkableWriter, s string) (err error) {
+	_, err = out.Write([]byte(s))
+	return
+}
+
 func marshalTwoDigits(out *forkableWriter, v int) (err error) {
 	err = out.WriteByte(byte('0' + (v/10)%10))
 	if err != nil {
@@ -446,10 +453,13 @@ func marshalBody(out *forkableWriter, value reflect.Value, params fieldParameter
 		}
 		return
 	case reflect.String:
-		if params.stringType == tagIA5String {
+		switch params.stringType {
+		case tagIA5String:
 			return marshalIA5String(out, v.String())
-		} else {
+		case tagPrintableString:
 			return marshalPrintableString(out, v.String())
+		default:
+			return marshalUTF8String(out, v.String())
 		}
 		return
 	}
@@ -492,11 +502,27 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 	}
 	class := classUniversal
 
-	if params.stringType != 0 {
-		if tag != tagPrintableString {
-			return StructuralError{"Explicit string type given to non-string member"}
+	if params.stringType != 0 && tag != tagPrintableString {
+		return StructuralError{"Explicit string type given to non-string member"}
+	}
+
+	if tag == tagPrintableString {
+		if params.stringType == 0 {
+			// This is a string without an explicit string type. We'll use
+			// a PrintableString if the character set in the string is
+			// sufficiently limited, otherwise we'll use a UTF8String.
+			for _, r := range v.String() {
+				if r >= utf8.RuneSelf || !isPrintable(byte(r)) {
+					if !utf8.ValidString(v.String()) {
+						return errors.New("asn1: string not valid UTF-8")
+					}
+					tag = tagUTF8String
+					break
+				}
+			}
+		} else {
+			tag = params.stringType
 		}
-		tag = params.stringType
 	}
 
 	if params.set {