5 files changed, 29 insertions, 3 deletions
diff --git a/src/encoding/asn1/asn1.go b/src/encoding/asn1/asn1.go
index aa99ca5cc5..7172c1c786 100644
--- a/src/encoding/asn1/asn1.go
+++ b/src/encoding/asn1/asn1.go
@@ -579,6 +579,8 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 				result, err = parseObjectIdentifier(innerBytes)
 			case tagUTCTime:
 				result, err = parseUTCTime(innerBytes)
+			case tagGeneralizedTime:
+				result, err = parseGeneralizedTime(innerBytes)
 			case tagOctetString:
 				result = innerBytes
 			default:
diff --git a/src/encoding/asn1/asn1_test.go b/src/encoding/asn1/asn1_test.go
index 4e864d08ac..1a2ae2569f 100644
--- a/src/encoding/asn1/asn1_test.go
+++ b/src/encoding/asn1/asn1_test.go
@@ -358,6 +358,8 @@ func newBool(b bool) *bool { return &b }
 var parseFieldParametersTestData []parseFieldParametersTest = []parseFieldParametersTest{
 	{"", fieldParameters{}},
 	{"ia5", fieldParameters{stringType: tagIA5String}},
+	{"generalized", fieldParameters{timeType: tagGeneralizedTime}},
+	{"utc", fieldParameters{timeType: tagUTCTime}},
 	{"printable", fieldParameters{stringType: tagPrintableString}},
 	{"optional", fieldParameters{optional: true}},
 	{"explicit", fieldParameters{explicit: true, tag: new(int)}},
@@ -366,7 +368,7 @@ var parseFieldParametersTestData []parseFieldParametersTest = []parseFieldParame
 	{"default:42", fieldParameters{defaultValue: newInt64(42)}},
 	{"tag:17", fieldParameters{tag: newInt(17)}},
 	{"optional,explicit,default:42,tag:17", fieldParameters{optional: true, explicit: true, defaultValue: newInt64(42), tag: newInt(17)}},
-	{"optional,explicit,default:42,tag:17,rubbish1", fieldParameters{true, true, false, newInt64(42), newInt(17), 0, false, false}},
+	{"optional,explicit,default:42,tag:17,rubbish1", fieldParameters{true, true, false, newInt64(42), newInt(17), 0, 0, false, false}},
 	{"set", fieldParameters{set: true}},
 }
 
diff --git a/src/encoding/asn1/common.go b/src/encoding/asn1/common.go
index 33a117ece1..ab85e0496f 100644
--- a/src/encoding/asn1/common.go
+++ b/src/encoding/asn1/common.go
@@ -74,6 +74,7 @@ type fieldParameters struct {
 	defaultValue *int64 // a default value for INTEGER typed fields (maybe nil).
 	tag          *int   // the EXPLICIT or IMPLICIT tag (maybe nil).
 	stringType   int    // the string tag to use when marshaling.
+	timeType     int    // the time tag to use when marshaling.
 	set          bool   // true iff this should be encoded as a SET
 	omitEmpty    bool   // true iff this should be omitted if empty when marshaling.
 
@@ -94,6 +95,10 @@ func parseFieldParameters(str string) (ret fieldParameters) {
 			if ret.tag == nil {
 				ret.tag = new(int)
 			}
+		case part == "generalized":
+			ret.timeType = tagGeneralizedTime
+		case part == "utc":
+			ret.timeType = tagUTCTime
 		case part == "ia5":
 			ret.stringType = tagIA5String
 		case part == "printable":
diff --git a/src/encoding/asn1/marshal.go b/src/encoding/asn1/marshal.go
index bf92c04c9f..67a019db2d 100644
--- a/src/encoding/asn1/marshal.go
+++ b/src/encoding/asn1/marshal.go
@@ -410,9 +410,11 @@ func stripTagAndLength(in []byte) []byte {
 
 func marshalBody(out *forkableWriter, value reflect.Value, params fieldParameters) (err error) {
 	switch value.Type() {
+	case flagType:
+		return nil
 	case timeType:
 		t := value.Interface().(time.Time)
-		if outsideUTCRange(t) {
+		if params.timeType == tagGeneralizedTime || outsideUTCRange(t) {
 			return marshalGeneralizedTime(out, t)
 		} else {
 			return marshalUTCTime(out, t)
@@ -552,6 +554,10 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 	}
 	class := classUniversal
 
+	if params.timeType != 0 && tag != tagUTCTime {
+		return StructuralError{"explicit time type given to non-time member"}
+	}
+
 	if params.stringType != 0 && tag != tagPrintableString {
 		return StructuralError{"explicit string type given to non-string member"}
 	}
@@ -575,7 +581,7 @@ func marshalField(out *forkableWriter, v reflect.Value, params fieldParameters)
 			tag = params.stringType
 		}
 	case tagUTCTime:
-		if outsideUTCRange(v.Interface().(time.Time)) {
+		if params.timeType == tagGeneralizedTime || outsideUTCRange(v.Interface().(time.Time)) {
 			tag = tagGeneralizedTime
 		}
 	}
diff --git a/src/encoding/asn1/marshal_test.go b/src/encoding/asn1/marshal_test.go
index 5b0115f28c..cdca8aa336 100644
--- a/src/encoding/asn1/marshal_test.go
+++ b/src/encoding/asn1/marshal_test.go
@@ -42,6 +42,14 @@ type explicitTagTest struct {
 	A int `asn1:"explicit,tag:5"`
 }
 
+type flagTest struct {
+	A Flag `asn1:"tag:0,optional"`
+}
+
+type generalizedTimeTest struct {
+	A time.Time `asn1:"generalized"`
+}
+
 type ia5StringTest struct {
 	A string `asn1:"ia5"`
 }
@@ -92,10 +100,13 @@ var marshalTests = []marshalTest{
 	{[]byte{1, 2, 3}, "0403010203"},
 	{implicitTagTest{64}, "3003850140"},
 	{explicitTagTest{64}, "3005a503020140"},
+	{flagTest{true}, "30028000"},
+	{flagTest{false}, "3000"},
 	{time.Unix(0, 0).UTC(), "170d3730303130313030303030305a"},
 	{time.Unix(1258325776, 0).UTC(), "170d3039313131353232353631365a"},
 	{time.Unix(1258325776, 0).In(PST), "17113039313131353134353631362d30383030"},
 	{farFuture(), "180f32313030303430353132303130315a"},
+	{generalizedTimeTest{time.Unix(1258325776, 0).UTC()}, "3011180f32303039313131353232353631365a"},
 	{BitString{[]byte{0x80}, 1}, "03020780"},
 	{BitString{[]byte{0x81, 0xf0}, 12}, "03030481f0"},
 	{ObjectIdentifier([]int{1, 2, 3, 4}), "06032a0304"},