add helper to export key metadata for pass for iOS

helper/helper.go

@@ -72,6 +72,41 @@ func PassGetHexSubkeyIDsJSON(key *crypto.Key) []byte {
 	return result
 }
 
+type passKeyInfo struct {
+	UserIDs        []string `json:"userIDs"`
+	CreationTime   int64    `json:"creationTime"`
+	ExpirationTime int64    `json:"expirationTime"` // 0 means no expiration
+}
+
+func PassGetKeyInfoJSON(key *crypto.Key) []byte {
+	entity := key.GetEntity()
+
+	userIDs := make([]string, 0, len(entity.Identities))
+	for name := range entity.Identities {
+		userIDs = append(userIDs, name)
+	}
+
+	creationTime := entity.PrimaryKey.CreationTime.Unix()
+
+	var expirationTime int64
+	identity := entity.PrimaryIdentity()
+	if identity != nil && identity.SelfSignature != nil && identity.SelfSignature.KeyLifetimeSecs != nil && *identity.SelfSignature.KeyLifetimeSecs != 0 {
+		expirationTime = creationTime + int64(*identity.SelfSignature.KeyLifetimeSecs)
+	}
+
+	info := passKeyInfo{
+		UserIDs:        userIDs,
+		CreationTime:   creationTime,
+		ExpirationTime: expirationTime,
+	}
+
+	result, err := json.Marshal(info)
+	if err != nil {
+		return nil
+	}
+	return result
+}
+
 
 func PassDecryptWithSessionKey(pgpMessage *crypto.PGPMessage, sk *crypto.SessionKey) (plain_message  *crypto.PlainMessage, err error) {
 	var p packet.Packet