asn1: fix parsing of elements after a string in a structure.

Fixes #516.

R=rsc
CC=golang-dev, golang-dev
https://golang.org/cl/184080

src/pkg/asn1/asn1.go

@@ -609,6 +609,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		return
 	}
 	innerBytes := bytes[offset : offset+t.length]
+	offset += t.length
 
 	// We deal with the structures defined in this package first.
 	switch fieldType {
@@ -619,13 +620,11 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		if err1 == nil {
 			reflect.ArrayCopy(sliceValue, reflect.NewValue(newSlice).(reflect.ArrayOrSliceValue))
 		}
-		offset += t.length
 		err = err1
 		return
 	case bitStringType:
 		structValue := v.(*reflect.StructValue)
 		bs, err1 := parseBitString(innerBytes)
-		offset += t.length
 		if err1 == nil {
 			structValue.Set(reflect.NewValue(bs).(*reflect.StructValue))
 		}
@@ -634,7 +633,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 	case timeType:
 		ptrValue := v.(*reflect.PtrValue)
 		time, err1 := parseUTCTime(innerBytes)
-		offset += t.length
 		if err1 == nil {
 			ptrValue.Set(reflect.NewValue(time).(*reflect.PtrValue))
 		}
@@ -644,7 +642,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 	switch val := v.(type) {
 	case *reflect.BoolValue:
 		parsedBool, err1 := parseBool(innerBytes)
-		offset += t.length
 		if err1 == nil {
 			val.Set(parsedBool)
 		}
@@ -652,7 +649,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		return
 	case *reflect.IntValue:
 		parsedInt, err1 := parseInt(innerBytes)
-		offset += t.length
 		if err1 == nil {
 			val.Set(parsedInt)
 		}
@@ -660,7 +656,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 		return
 	case *reflect.Int64Value:
 		parsedInt, err1 := parseInt64(innerBytes)
-		offset += t.length
 		if err1 == nil {
 			val.Set(parsedInt)
 		}
@@ -671,7 +666,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 
 		if structType.NumField() > 0 &&
 			structType.Field(0).Type == rawContentsType {
-			bytes := bytes[initOffset : offset+t.length]
+			bytes := bytes[initOffset:offset]
 			val.Field(0).SetValue(reflect.NewValue(RawContent(bytes)))
 		}
 
@@ -686,7 +681,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 				return
 			}
 		}
-		offset += t.length
 		// We allow extra bytes at the end of the SEQUENCE because
 		// adding elements to the end has been used in X.509 as the
 		// version numbers have increased.
@@ -699,7 +693,6 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 			return
 		}
 		newSlice, err1 := parseSequenceOf(innerBytes, sliceType, sliceType.Elem())
-		offset += t.length
 		if err1 == nil {
 			val.Set(newSlice)
 		}

src/pkg/asn1/asn1_test.go

@@ -263,6 +263,11 @@ type TestContextSpecificTags2 struct {
 	B int
 }
 
+type TestElementsAfterString struct {
+	S    string
+	A, B int
+}
+
 var unmarshalTestData []unmarshalTest = []unmarshalTest{
 	unmarshalTest{[]byte{0x02, 0x01, 0x42}, newInt(0x42)},
 	unmarshalTest{[]byte{0x30, 0x08, 0x06, 0x06, 0x2a, 0x86, 0x48, 0x86, 0xf7, 0x0d}, &TestObjectIdentifierStruct{[]int{1, 2, 840, 113549}}},
@@ -277,6 +282,7 @@ var unmarshalTestData []unmarshalTest = []unmarshalTest{
 	unmarshalTest{[]byte{0x30, 0x08, 0xa1, 0x03, 0x02, 0x01, 0x01, 0x02, 0x01, 0x02}, &TestContextSpecificTags2{1, 2}},
 	unmarshalTest{[]byte{0x01, 0x01, 0x00}, newBool(false)},
 	unmarshalTest{[]byte{0x01, 0x01, 0x01}, newBool(true)},
+	unmarshalTest{[]byte{0x30, 0x0b, 0x13, 0x03, 0x66, 0x6f, 0x6f, 0x02, 0x01, 0x22, 0x02, 0x01, 0x33}, &TestElementsAfterString{"foo", 0x22, 0x33}},
 }
 
 func TestUnmarshal(t *testing.T) {