ntfy/server/server_firebase.go
2022-05-29 20:48:14 -04:00

218 lines
7.5 KiB
Go

package server
import (
"context"
"encoding/json"
"fmt"
"strings"
firebase "firebase.google.com/go/v4"
"firebase.google.com/go/v4/messaging"
"google.golang.org/api/option"
"heckel.io/ntfy/auth"
)
const (
fcmMessageLimit = 4000
fcmApnsBodyMessageLimit = 100
)
func createFirebaseSubscriber(credentialsFile string, auther auth.Auther) (subscriber, error) {
fb, err := firebase.NewApp(context.Background(), nil, option.WithCredentialsFile(credentialsFile))
if err != nil {
return nil, err
}
msg, err := fb.Messaging(context.Background())
if err != nil {
return nil, err
}
return func(m *message) error {
fbm, err := toFirebaseMessage(m, auther)
if err != nil {
return err
}
_, err = msg.Send(context.Background(), fbm)
return err
}, nil
}
// toFirebaseMessage converts a message to a Firebase message.
//
// Normal messages ("message"):
// - For Android, we can receive data messages from Firebase and process them as code, so we just send all fields
// in the "data" attribute. In the Android app, we then turn those into a notification and display it.
// - On iOS, we are not allowed to receive data-only messages, so we build messages with an "alert" (with title and
// message), and still send the rest of the data along in the "aps" attribute. We can then locally modify the
// message in the Notification Service Extension.
//
// Keepalive messages ("keepalive"):
// - On Android, we subscribe to the "~control" topic, which is used to restart the foreground service (if it died,
// e.g. after an app update). We send these keepalive messages regularly (see Config.FirebaseKeepaliveInterval).
// - On iOS, we subscribe to the "~poll" topic, which is used to poll all topics regularly. This is because iOS
// does not allow any background or scheduled activity at all.
//
// Poll request messages ("poll_request"):
// - Normal messages are turned into poll request messages if anonymous users are not allowed to read the message.
// On Android, this will trigger the app to poll the topic and thereby displaying new messages.
// - If UpstreamBaseURL is set, messages are forwarded as poll requests to an upstream server and then forwarded
// to Firebase here. This is mainly for iOS to support self-hosted servers.
func toFirebaseMessage(m *message, auther auth.Auther) (*messaging.Message, error) {
var data map[string]string // Mostly matches https://ntfy.sh/docs/subscribe/api/#json-message-format
var apnsConfig *messaging.APNSConfig
switch m.Event {
case keepaliveEvent, openEvent:
data = map[string]string{
"id": m.ID,
"time": fmt.Sprintf("%d", m.Time),
"event": m.Event,
"topic": m.Topic,
}
apnsConfig = createAPNSBackgroundConfig(data)
case pollRequestEvent:
data = map[string]string{
"id": m.ID,
"time": fmt.Sprintf("%d", m.Time),
"event": m.Event,
"topic": m.Topic,
"message": m.Message,
"poll_id": m.PollID,
}
apnsConfig = createAPNSAlertConfig(m, data)
case messageEvent:
allowForward := true
if auther != nil {
allowForward = auther.Authorize(nil, m.Topic, auth.PermissionRead) == nil
}
if allowForward {
data = map[string]string{
"id": m.ID,
"time": fmt.Sprintf("%d", m.Time),
"event": m.Event,
"topic": m.Topic,
"priority": fmt.Sprintf("%d", m.Priority),
"tags": strings.Join(m.Tags, ","),
"click": m.Click,
"title": m.Title,
"message": m.Message,
"encoding": m.Encoding,
}
if len(m.Actions) > 0 {
actions, err := json.Marshal(m.Actions)
if err != nil {
return nil, err
}
data["actions"] = string(actions)
}
if m.Attachment != nil {
data["attachment_name"] = m.Attachment.Name
data["attachment_type"] = m.Attachment.Type
data["attachment_size"] = fmt.Sprintf("%d", m.Attachment.Size)
data["attachment_expires"] = fmt.Sprintf("%d", m.Attachment.Expires)
data["attachment_url"] = m.Attachment.URL
}
apnsConfig = createAPNSAlertConfig(m, data)
} else {
// If anonymous read for a topic is not allowed, we cannot send the message along
// via Firebase. Instead, we send a "poll_request" message, asking the client to poll.
data = map[string]string{
"id": m.ID,
"time": fmt.Sprintf("%d", m.Time),
"event": pollRequestEvent,
"topic": m.Topic,
}
// TODO Handle APNS?
}
}
var androidConfig *messaging.AndroidConfig
if m.Priority >= 4 {
androidConfig = &messaging.AndroidConfig{
Priority: "high",
}
}
return maybeTruncateFCMMessage(&messaging.Message{
Topic: m.Topic,
Data: data,
Android: androidConfig,
APNS: apnsConfig,
}), nil
}
// maybeTruncateFCMMessage performs best-effort truncation of FCM messages.
// The docs say the limit is 4000 characters, but during testing it wasn't quite clear
// what fields matter; so we're just capping the serialized JSON to 4000 bytes.
func maybeTruncateFCMMessage(m *messaging.Message) *messaging.Message {
s, err := json.Marshal(m)
if err != nil {
return m
}
if len(s) > fcmMessageLimit {
over := len(s) - fcmMessageLimit + 16 // = len("truncated":"1",), sigh ...
message, ok := m.Data["message"]
if ok && len(message) > over {
m.Data["truncated"] = "1"
m.Data["message"] = message[:len(message)-over]
}
}
return m
}
// createAPNSAlertConfig creates an APNS config for iOS notifications that show up as an alert (only relevant for iOS).
// We must set the Alert struct ("alert"), and we need to set MutableContent ("mutable-content"), so the Notification Service
// Extension in iOS can modify the message.
func createAPNSAlertConfig(m *message, data map[string]string) *messaging.APNSConfig {
apnsData := make(map[string]interface{})
for k, v := range data {
apnsData[k] = v
}
return &messaging.APNSConfig{
Payload: &messaging.APNSPayload{
CustomData: apnsData,
Aps: &messaging.Aps{
MutableContent: true,
Alert: &messaging.ApsAlert{
Title: m.Title,
Body: maybeTruncateAPNSBodyMessage(m.Message),
},
},
},
}
}
// createAPNSBackgroundConfig creates an APNS config for a silent background message (only relevant for iOS). Apple only
// allows us to send 2-3 of these notifications per hour, and delivery not guaranteed. We use this only for the ~poll
// topic, which triggers the iOS app to poll all topics for changes.
//
// See https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app
func createAPNSBackgroundConfig(data map[string]string) *messaging.APNSConfig {
apnsData := make(map[string]interface{})
for k, v := range data {
apnsData[k] = v
}
return &messaging.APNSConfig{
Headers: map[string]string{
"apns-push-type": "background",
"apns-priority": "5",
},
Payload: &messaging.APNSPayload{
Aps: &messaging.Aps{
ContentAvailable: true,
},
CustomData: apnsData,
},
}
}
// maybeTruncateAPNSBodyMessage truncates the body for APNS.
//
// The "body" of the push notification can contain the entire message, which would count doubly for the overall length
// of the APNS payload. I set a limit of 100 characters before truncating the notification "body" with ellipsis.
// The message would not be changed (unless truncated for being too long). Note: if the payload is too large (>4KB),
// APNS will simply reject / discard the notification, meaning it will never arrive on the iOS device.
func maybeTruncateAPNSBodyMessage(s string) string {
if len(s) >= fcmApnsBodyMessageLimit {
over := len(s) - fcmApnsBodyMessageLimit + 3 // len("...")
return s[:len(s)-over] + "..."
}
return s
}