updated digest.go: fixes

pkg/digest/digest.go

@@ -155,6 +155,7 @@ func MakeSHA512Digest(src []byte) string {
 
 func (dig Digest) MarshalJSON() ([]byte, error) {
 	writer := bytes.NewBuffer(nil)
+	writer.WriteString(`"`)
 	switch dig.algorithm {
 	case SHA256:
 		writer.WriteString("sha256")
@@ -165,14 +166,18 @@ func (dig Digest) MarshalJSON() ([]byte, error) {
 	}
 	writer.WriteString(":")
 	writer.WriteString(hex.EncodeToString(dig.decoded))
+	writer.WriteString(`"`)
+
 	return writer.Bytes(), nil
 }
 
 func (dig *Digest) UnmarshalJSON(data []byte) error {
 	var err error
-	digobj := &Digest{}
+	digobj := Digest{}
 
 	str := strings.ToLower(string(data))
+	str = strings.TrimPrefix(str, `"`)
+	str = strings.TrimSuffix(str, `"`)
 	str = strings.TrimPrefix(str, "sha256:")
 	str = strings.TrimPrefix(str, "sha384:")
 	str = strings.TrimPrefix(str, "sha512:")
@@ -180,7 +185,7 @@ func (dig *Digest) UnmarshalJSON(data []byte) error {
 	decoded, err := hex.DecodeString(str)
 	if err != nil {
 		err := errors.New("Can't decode digest")
-		return digobj, err
+		return err
 	}
 	digobj.decoded = decoded
 	switch len(decoded) {
@@ -192,7 +197,7 @@ func (dig *Digest) UnmarshalJSON(data []byte) error {
 		digobj.algorithm = SHA512
 	default:
 		err = errors.New("Unknown digest type")
-		return digobj, err
+		return err
 	}
 	*dig = digobj
 	return err