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