diff --git a/asn1/asn1.go b/asn1/asn1.go
index a027e11..105a7f7 100644
--- a/asn1/asn1.go
+++ b/asn1/asn1.go
@@ -559,6 +559,10 @@ func parseTagAndLength(bytes []byte, initOffset int) (ret tagAndLength, offset i
 						}
 						return
 					}
+					if len(bytes) <= reoffset+reTag.length {
+						err = asn1.StructuralError{"indefinete lenght: length too large"}
+						return
+					}
 					reTag, reoffset, _ = parseTagAndLength(bytes, reoffset+reTag.length)
 				}
 				log.Println("indefinite length found (not DER)")
@@ -928,7 +932,7 @@ func parseField(v reflect.Value, bytes []byte, initOffset int, params fieldParam
 
 		for i := 0; i < structType.NumField(); i++ {
 			if structType.Field(i).PkgPath != "" {
-				err = asn1.StructuralError{"struct contains unexported fields"}
+				err = asn1.StructuralError{Msg: "struct contains unexported fields"}
 				return
 			}
 		}
diff --git a/asn1/asn1_test.go b/asn1/asn1_test.go
index 6dbc83b..ebbc4b1 100644
--- a/asn1/asn1_test.go
+++ b/asn1/asn1_test.go
@@ -179,7 +179,7 @@ func TestBitString(t *testing.T) {
 }
 
 func TestBitStringAt(t *testing.T) {
-	bs := asn1.BitString{[]byte{0x82, 0x40}, 16}
+	bs := asn1.BitString{Bytes: []byte{0x82, 0x40}, BitLength: 16}
 	if bs.At(0) != 1 {
 		t.Error("#1: Failed")
 	}
@@ -217,7 +217,7 @@ var bitStringRightAlignTests = []bitStringRightAlignTest{
 
 func TestBitStringRightAlign(t *testing.T) {
 	for i, test := range bitStringRightAlignTests {
-		bs := asn1.BitString{test.in, test.inlen}
+		bs := asn1.BitString{Bytes: test.in, BitLength: test.inlen}
 		out := bs.RightAlign()
 		if !bytes.Equal(out, test.out) {
 			t.Errorf("#%d got: %x want: %x", i, out, test.out)
@@ -997,7 +997,7 @@ type exported struct {
 }
 
 func TestUnexportedStructField(t *testing.T) {
-	want := asn1.StructuralError{"struct contains unexported fields"}
+	want := asn1.StructuralError{Msg: "struct contains unexported fields"}
 
 	_, err := Marshal(unexported{X: 5, y: 1})
 	if err != want {
diff --git a/asn1/marshal.go b/asn1/marshal.go
index e396706..0b30e63 100644
--- a/asn1/marshal.go
+++ b/asn1/marshal.go
@@ -446,7 +446,7 @@ func makeBody(value reflect.Value, params fieldParameters) (e encoder, err error
 
 		for i := 0; i < t.NumField(); i++ {
 			if t.Field(i).PkgPath != "" {
-				return nil, asn1.StructuralError{"struct contains unexported fields"}
+				return nil, asn1.StructuralError{Msg: "struct contains unexported fields"}
 			}
 		}