push: implement parsing native notifications (#87)

pkg/connector/push.go

@@ -2,17 +2,85 @@ package connector
 
 import (
 	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/json"
 	"fmt"
 
+	"github.com/gotd/td/bin"
+	"github.com/gotd/td/crypto"
 	"github.com/gotd/td/tg"
+	"github.com/tidwall/gjson"
 	"go.mau.fi/util/random"
 	"maunium.net/go/mautrix/bridgev2"
+	"maunium.net/go/mautrix/bridgev2/networkid"
 )
 
-var _ bridgev2.PushableNetworkAPI = (*TelegramClient)(nil)
+var (
+	_ bridgev2.PushableNetworkAPI = (*TelegramClient)(nil)
+	_ bridgev2.PushParsingNetwork = (*TelegramConnector)(nil)
+)
 
 var PushAppSandbox = false
 
+// TODO
+type PushNotificationData map[string]any
+
+func (tg *TelegramConnector) ParsePushNotification(ctx context.Context, data json.RawMessage) (networkid.UserLoginID, any, error) {
+	val := gjson.GetBytes(data, "p")
+	if val.Type != gjson.String {
+		return "", nil, fmt.Errorf("missing or invalid p field")
+	}
+	valBytes, err := base64.RawURLEncoding.DecodeString(val.Str)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to base64 decode p field: %w", err)
+	}
+	var em crypto.EncryptedMessage
+	err = em.DecodeWithoutCopy(&bin.Buffer{Buf: valBytes})
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to decode auth key and message ID: %w", err)
+	}
+	userIDs, err := tg.Bridge.DB.UserLogin.GetAllUserIDsWithLogins(ctx)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to get users with logins: %w", err)
+	}
+	var matchingAuthKey *crypto.AuthKey
+	var userLoginID networkid.UserLoginID
+UserLoop:
+	for _, userID := range userIDs {
+		user, err := tg.Bridge.GetExistingUserByMXID(ctx, userID)
+		if err != nil {
+			return "", nil, fmt.Errorf("failed to get user %s: %w", userID, err)
+		}
+		for _, login := range user.GetUserLogins() {
+			key := login.Metadata.(*UserLoginMetadata).PushEncryptionKey
+			if len(key) != 256 {
+				continue
+			}
+			authKey := crypto.Key(key).WithID()
+			if authKey.ID == em.AuthKeyID {
+				matchingAuthKey = &authKey
+				userLoginID = login.ID
+				break UserLoop
+			}
+		}
+	}
+	if matchingAuthKey == nil {
+		return "", nil, fmt.Errorf("no matching auth key found")
+	}
+	c := crypto.NewClientCipher(rand.Reader)
+	plaintext, err := c.DecryptRaw(*matchingAuthKey, &em)
+	if err != nil {
+		return userLoginID, nil, fmt.Errorf("failed to decrypt payload: %w", err)
+	}
+	pmd := make(PushNotificationData)
+	err = json.Unmarshal(plaintext, &pmd)
+	if err != nil {
+		return userLoginID, nil, fmt.Errorf("failed to unmarshal decrypted payload: %w", err)
+	}
+	return userLoginID, pmd, nil
+}
+
 func (t *TelegramClient) RegisterPushNotifications(ctx context.Context, pushType bridgev2.PushType, token string) error {
 	meta := t.userLogin.Metadata.(*UserLoginMetadata)
 	if meta.PushEncryptionKey == nil {