End to end, dabbling

app/schemas/io.heckel.ntfy.db.Database/12.json

@@ -2,11 +2,11 @@
   "formatVersion": 1,
   "database": {
     "version": 12,
-    "identityHash": "9363ad5196e88862acceb1bb9ee91124",
+    "identityHash": "250db1985385d64d880124071eab96fc",
     "entities": [
       {
         "tableName": "Subscription",
-        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER NOT NULL, `baseUrl` TEXT NOT NULL, `topic` TEXT NOT NULL, `instant` INTEGER NOT NULL, `mutedUntil` INTEGER NOT NULL, `minPriority` INTEGER NOT NULL, `autoDelete` INTEGER NOT NULL, `lastNotificationId` TEXT, `icon` TEXT, `upAppId` TEXT, `upConnectorToken` TEXT, `displayName` TEXT, PRIMARY KEY(`id`))",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`id` INTEGER NOT NULL, `baseUrl` TEXT NOT NULL, `topic` TEXT NOT NULL, `instant` INTEGER NOT NULL, `mutedUntil` INTEGER NOT NULL, `minPriority` INTEGER NOT NULL, `autoDelete` INTEGER NOT NULL, `lastNotificationId` TEXT, `icon` TEXT, `upAppId` TEXT, `upConnectorToken` TEXT, `displayName` TEXT, `encryptionKey` BLOB, PRIMARY KEY(`id`))",
         "fields": [
           {
             "fieldPath": "id",
@@ -79,6 +79,12 @@
             "columnName": "displayName",
             "affinity": "TEXT",
             "notNull": false
+          },
+          {
+            "fieldPath": "encryptionKey",
+            "columnName": "encryptionKey",
+            "affinity": "BLOB",
+            "notNull": false
           }
         ],
         "primaryKey": {
@@ -326,7 +332,7 @@
     "views": [],
     "setupQueries": [
       "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
-      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '9363ad5196e88862acceb1bb9ee91124')"
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '250db1985385d64d880124071eab96fc')"
     ]
   }
 }

app/src/main/java/io/heckel/ntfy/backup/Backuper.kt

@@ -2,6 +2,7 @@ package io.heckel.ntfy.backup
 
 import android.content.Context
 import android.net.Uri
+import android.util.Base64
 import com.google.gson.Gson
 import com.google.gson.GsonBuilder
 import com.google.gson.stream.JsonReader
@@ -102,6 +103,7 @@ class Backuper(val context: Context) {
                     upAppId = s.upAppId,
                     upConnectorToken = s.upConnectorToken,
                     displayName = s.displayName,
+                    encryptionKey = Base64.decode(s.encryptionKey, Base64.DEFAULT)
                 ))
             } catch (e: Exception) {
                 Log.w(TAG, "Unable to restore subscription ${s.id} (${topicUrl(s.baseUrl, s.topic)}): ${e.message}. Ignoring.", e)
@@ -226,7 +228,8 @@ class Backuper(val context: Context) {
                 icon = s.icon,
                 upAppId = s.upAppId,
                 upConnectorToken = s.upConnectorToken,
-                displayName = s.displayName
+                displayName = s.displayName,
+                encryptionKey = if (s.encryptionKey != null) Base64.encodeToString(s.encryptionKey, Base64.DEFAULT) else null
             )
         }
     }
@@ -334,7 +337,8 @@ data class Subscription(
     val icon: String?,
     val upAppId: String?,
     val upConnectorToken: String?,
-    val displayName: String?
+    val displayName: String?,
+    val encryptionKey: String? // as base64
 )
 
 data class Notification(
@@ -343,7 +347,7 @@ data class Notification(
     val timestamp: Long,
     val title: String,
     val message: String,
-    val encoding: String, // "base64" or ""
+    val encoding: String, // "base64", "jwe", or ""
     val priority: Int, // 1=min, 3=default, 5=max
     val tags: String,
     val click: String, // URL/intent to open on notification click

app/src/main/java/io/heckel/ntfy/db/Database.kt

@@ -23,13 +23,14 @@ data class Subscription(
     @ColumnInfo(name = "upAppId") val upAppId: String?, // UnifiedPush application package name
     @ColumnInfo(name = "upConnectorToken") val upConnectorToken: String?, // UnifiedPush connector token
     @ColumnInfo(name = "displayName") val displayName: String?,
+    @ColumnInfo(name = "encryptionKey") val encryptionKey: ByteArray?,
     @Ignore val totalCount: Int = 0, // Total notifications
     @Ignore val newCount: Int = 0, // New notifications
     @Ignore val lastActive: Long = 0, // Unix timestamp
     @Ignore val state: ConnectionState = ConnectionState.NOT_APPLICABLE
 ) {
-    constructor(id: Long, baseUrl: String, topic: String, instant: Boolean, mutedUntil: Long, minPriority: Int, autoDelete: Long, lastNotificationId: String, icon: String, upAppId: String, upConnectorToken: String, displayName: String?) :
+    constructor(id: Long, baseUrl: String, topic: String, instant: Boolean, mutedUntil: Long, minPriority: Int, autoDelete: Long, lastNotificationId: String, icon: String, upAppId: String, upConnectorToken: String, displayName: String?, encryptionKey: ByteArray?) :
-            this(id, baseUrl, topic, instant, mutedUntil, minPriority, autoDelete, lastNotificationId, icon, upAppId, upConnectorToken, displayName, 0, 0, 0, ConnectionState.NOT_APPLICABLE)
+            this(id, baseUrl, topic, instant, mutedUntil, minPriority, autoDelete, lastNotificationId, icon, upAppId, upConnectorToken, displayName, encryptionKey, 0, 0, 0, ConnectionState.NOT_APPLICABLE)
 }
 
 enum class ConnectionState {
@@ -49,6 +50,7 @@ data class SubscriptionWithMetadata(
     val upAppId: String?,
     val upConnectorToken: String?,
     val displayName: String?,
+    val encryptionKey: ByteArray?,
     val totalCount: Int,
     val newCount: Int,
     val lastActive: Long
@@ -61,7 +63,7 @@ data class Notification(
     @ColumnInfo(name = "timestamp") val timestamp: Long, // Unix timestamp
     @ColumnInfo(name = "title") val title: String,
     @ColumnInfo(name = "message") val message: String,
-    @ColumnInfo(name = "encoding") val encoding: String, // "base64" or ""
+    @ColumnInfo(name = "encoding") val encoding: String, // "" (raw UTF-8), "base64", or "jwe" (encryption)
     @ColumnInfo(name = "notificationId") val notificationId: Int, // Android notification popup ID
     @ColumnInfo(name = "priority", defaultValue = "3") val priority: Int, // 1=min, 3=default, 5=max
     @ColumnInfo(name = "tags") val tags: String,
@@ -269,6 +271,8 @@ abstract class Database : RoomDatabase() {
             override fun migrate(db: SupportSQLiteDatabase) {
                 db.execSQL("ALTER TABLE Subscription ADD COLUMN lastNotificationId TEXT")
                 db.execSQL("ALTER TABLE Subscription ADD COLUMN displayName TEXT")
+                db.execSQL("ALTER TABLE Subscription ADD COLUMN encryptionKey BLOB")
+                db.execSQL("ALTER TABLE Notification ADD COLUMN encryption TEXT NOT NULL DEFAULT('')")
             }
         }
     }
@@ -278,7 +282,7 @@ abstract class Database : RoomDatabase() {
 interface SubscriptionDao {
     @Query("""
         SELECT 
-          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName,
+          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName, s.encryptionKey,
           COUNT(n.id) totalCount, 
           COUNT(CASE n.notificationId WHEN 0 THEN NULL ELSE n.id END) newCount, 
           IFNULL(MAX(n.timestamp),0) AS lastActive
@@ -291,7 +295,7 @@ interface SubscriptionDao {
 
     @Query("""
         SELECT 
-          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName,
+          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName, s.encryptionKey,
           COUNT(n.id) totalCount, 
           COUNT(CASE n.notificationId WHEN 0 THEN NULL ELSE n.id END) newCount, 
           IFNULL(MAX(n.timestamp),0) AS lastActive
@@ -304,7 +308,7 @@ interface SubscriptionDao {
 
     @Query("""
         SELECT 
-          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName,
+          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName, s.encryptionKey,
           COUNT(n.id) totalCount, 
           COUNT(CASE n.notificationId WHEN 0 THEN NULL ELSE n.id END) newCount, 
           IFNULL(MAX(n.timestamp),0) AS lastActive
@@ -317,7 +321,7 @@ interface SubscriptionDao {
 
     @Query("""
         SELECT 
-          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName,
+          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName, s.encryptionKey,
           COUNT(n.id) totalCount, 
           COUNT(CASE n.notificationId WHEN 0 THEN NULL ELSE n.id END) newCount, 
           IFNULL(MAX(n.timestamp),0) AS lastActive
@@ -330,7 +334,7 @@ interface SubscriptionDao {
 
     @Query("""
         SELECT 
-          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName,
+          s.id, s.baseUrl, s.topic, s.instant, s.mutedUntil, s.minPriority, s.autoDelete, s.lastNotificationId, s.icon, s.upAppId, s.upConnectorToken, s.displayName, s.encryptionKey,
           COUNT(n.id) totalCount, 
           COUNT(CASE n.notificationId WHEN 0 THEN NULL ELSE n.id END) newCount, 
           IFNULL(MAX(n.timestamp),0) AS lastActive

app/src/main/java/io/heckel/ntfy/db/Repository.kt

@@ -385,6 +385,7 @@ class Repository(private val sharedPrefs: SharedPreferences, private val databas
                 upAppId = s.upAppId,
                 upConnectorToken = s.upConnectorToken,
                 displayName = s.displayName,
+                encryptionKey = s.encryptionKey,
                 totalCount = s.totalCount,
                 newCount = s.newCount,
                 lastActive = s.lastActive,
@@ -410,6 +411,7 @@ class Repository(private val sharedPrefs: SharedPreferences, private val databas
             upAppId = s.upAppId,
             upConnectorToken = s.upConnectorToken,
             displayName = s.displayName,
+            encryptionKey = s.encryptionKey,
             totalCount = s.totalCount,
             newCount = s.newCount,
             lastActive = s.lastActive,

app/src/main/java/io/heckel/ntfy/service/JsonConnection.kt

@@ -3,6 +3,7 @@ package io.heckel.ntfy.service
 import io.heckel.ntfy.db.*
 import io.heckel.ntfy.util.Log
 import io.heckel.ntfy.msg.ApiService
+import io.heckel.ntfy.util.Encryption
 import io.heckel.ntfy.util.topicUrl
 import kotlinx.coroutines.*
 import okhttp3.Call
@@ -42,7 +43,8 @@ class JsonConnection(
                     since = notification.id
                     val subscriptionId = topicsToSubscriptionIds[topic] ?: return@notify
                     val subscription = repository.getSubscription(subscriptionId) ?: return@notify
-                    val notificationWithSubscriptionId = notification.copy(subscriptionId = subscription.id)
+                    val notificationDecrypted = Encryption.maybeDecrypt(subscription, notification)
+                    val notificationWithSubscriptionId = notificationDecrypted.copy(subscriptionId = subscription.id)
                     notificationListener(subscription, notificationWithSubscriptionId)
                 }
                 val failed = AtomicBoolean(false)

app/src/main/java/io/heckel/ntfy/service/WsConnection.kt

@@ -7,6 +7,7 @@ import android.os.Looper
 import io.heckel.ntfy.db.*
 import io.heckel.ntfy.msg.ApiService.Companion.requestBuilder
 import io.heckel.ntfy.msg.NotificationParser
+import io.heckel.ntfy.util.Encryption
 import io.heckel.ntfy.util.Log
 import io.heckel.ntfy.util.topicShortUrl
 import io.heckel.ntfy.util.topicUrlWs
@@ -144,7 +145,8 @@ class WsConnection(
                 val notification = notificationWithTopic.notification
                 val subscriptionId = topicsToSubscriptionIds[topic] ?: return@synchronize
                 val subscription = repository.getSubscription(subscriptionId) ?: return@synchronize
-                val notificationWithSubscriptionId = notification.copy(subscriptionId = subscription.id)
+                val notificationDecrypted = Encryption.maybeDecrypt(subscription, notification)
+                val notificationWithSubscriptionId = notificationDecrypted.copy(subscriptionId = subscription.id)
                 notificationListener(subscription, notificationWithSubscriptionId)
                 since.set(notification.id)
             }

app/src/main/java/io/heckel/ntfy/ui/DetailActivity.kt

@@ -118,6 +118,7 @@ class DetailActivity : AppCompatActivity(), ActionMode.Callback, NotificationFra
                     upAppId = null,
                     upConnectorToken = null,
                     displayName = null,
+                    encryptionKey = null,
                     totalCount = 0,
                     newCount = 0,
                     lastActive = Date().time/1000
@@ -133,7 +134,9 @@ class DetailActivity : AppCompatActivity(), ActionMode.Callback, NotificationFra
                 // Fetch cached messages
                 try {
                     val user = repository.getUser(subscription.baseUrl) // May be null
-                    val notifications = api.poll(subscription.id, subscription.baseUrl, subscription.topic, user)
+                    val notifications = api
+                        .poll(subscription.id, subscription.baseUrl, subscription.topic, user)
+                        .map { n -> Encryption.maybeDecrypt(subscription, n) }
                     notifications.forEach { notification -> repository.addNotification(notification) }
                 } catch (e: Exception) {
                     Log.e(TAG, "Unable to fetch notifications: ${e.message}", e)
@@ -466,7 +469,9 @@ class DetailActivity : AppCompatActivity(), ActionMode.Callback, NotificationFra
             try {
                 val subscription = repository.getSubscription(subscriptionId) ?: return@launch
                 val user = repository.getUser(subscription.baseUrl) // May be null
-                val notifications = api.poll(subscription.id, subscription.baseUrl, subscription.topic, user, subscription.lastNotificationId)
+                val notifications = api
+                    .poll(subscription.id, subscription.baseUrl, subscription.topic, user, subscription.lastNotificationId)
+                    .map { n -> Encryption.maybeDecrypt(subscription, n) }
                 val newNotifications = repository.onlyNewNotifications(subscriptionId, notifications)
                 val toastMessage = if (newNotifications.isEmpty()) {
                     getString(R.string.refresh_message_no_results)

app/src/main/java/io/heckel/ntfy/ui/DetailSettingsActivity.kt

@@ -4,7 +4,6 @@ import android.content.ContentResolver
 import android.content.ClipData
 import android.content.ClipboardManager
 import android.content.Context
-import android.graphics.BitmapFactory
 import android.net.Uri
 import android.os.Bundle
 import android.text.TextUtils
@@ -111,6 +110,7 @@ class DetailSettingsActivity : AppCompatActivity() {
                 loadMutedUntilPref()
                 loadMinPriorityPref()
                 loadAutoDeletePref()
+                loadPasswordPref()
                 loadIconSetPref()
                 loadIconRemovePref()
             } else {
@@ -254,6 +254,30 @@ class DetailSettingsActivity : AppCompatActivity() {
             }
         }
 
+        private fun loadPasswordPref() {
+            val prefId = context?.getString(R.string.detail_settings_notifications_password_key) ?: return
+            val pref: EditTextPreference? = findPreference(prefId)
+            pref?.isVisible = true // Hack: Show all settings at once, because subscription is loaded asynchronously
+            pref?.text = ""
+            pref?.preferenceDataStore = object : PreferenceDataStore() {
+                override fun putString(key: String?, value: String?) {
+                    val newPassword = value ?: return
+                    val encryptionKey = if (newPassword.trim().isEmpty()) null else Encryption.deriveKey(newPassword, topicUrl(subscription))
+                    save(subscription.copy(encryptionKey = encryptionKey))
+                }
+                override fun getString(key: String?, defValue: String?): String {
+                    return ""
+                }
+            }
+            pref?.summaryProvider = Preference.SummaryProvider<EditTextPreference> { pref ->
+                if (TextUtils.isEmpty(pref.text)) {
+                    "No password set"
+                } else {
+                    "Password saved"
+                }
+            }
+        }
+
         private fun loadIconSetPref() {
             val prefId = context?.getString(R.string.detail_settings_appearance_icon_set_key) ?: return
             iconSetPref = findPreference(prefId) ?: return

app/src/main/java/io/heckel/ntfy/ui/MainActivity.kt

@@ -43,7 +43,6 @@ import io.heckel.ntfy.work.PollWorker
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.launch
-import java.security.SecureRandom
 import java.util.*
 import java.util.concurrent.TimeUnit
 import kotlin.random.Random
@@ -206,6 +205,20 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
         schedulePeriodicPollWorker()
         schedulePeriodicServiceRestartWorker()
         schedulePeriodicDeleteWorker()
+
+        testenc()
+    }
+
+    fun testenc() {
+        try {
+            val key = Encryption.deriveKey("secr3t password", "https://ntfy.sh/mysecret")
+            Log.d("encryption", "key ${key.toHex()}")
+            val ciphertext = "eyJhbGciOiJkaXIiLCJlbmMiOiJBMjU2R0NNIn0..vbe1Qv_-mKYbUgce.EfmOUIUi7lxXZG_o4bqXZ9pmpr1Rzs4Y5QLE2XD2_aw_SQ.y2hadrN5b2LEw7_PJHhbcA"
+            val plaintext = Encryption.decrypt(ciphertext, key)
+            Log.d("encryption", "decryptString: $plaintext")
+        } catch (e: Exception) {
+            Log.e("encryption", "failed", e)
+        }
     }
 
     override fun onResume() {
@@ -439,6 +452,7 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
             upAppId = null,
             upConnectorToken = null,
             displayName = null,
+            encryptionKey = null,
             totalCount = 0,
             newCount = 0,
             lastActive = Date().time/1000
@@ -455,7 +469,9 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
         lifecycleScope.launch(Dispatchers.IO) {
             try {
                 val user = repository.getUser(subscription.baseUrl) // May be null
-                val notifications = api.poll(subscription.id, subscription.baseUrl, subscription.topic, user)
+                val notifications = api
+                    .poll(subscription.id, subscription.baseUrl, subscription.topic, user)
+                    .map { n -> Encryption.maybeDecrypt(subscription, n) }
                 notifications.forEach { notification -> repository.addNotification(notification) }
             } catch (e: Exception) {
                 Log.e(TAG, "Unable to fetch notifications: ${e.message}", e)
@@ -492,7 +508,9 @@ class MainActivity : AppCompatActivity(), ActionMode.Callback, AddFragment.Subsc
                 Log.d(TAG, "subscription: ${subscription}")
                 try {
                     val user = repository.getUser(subscription.baseUrl) // May be null
-                    val notifications = api.poll(subscription.id, subscription.baseUrl, subscription.topic, user, subscription.lastNotificationId)
+                    val notifications = api
+                        .poll(subscription.id, subscription.baseUrl, subscription.topic, user, subscription.lastNotificationId)
+                        .map { n -> Encryption.maybeDecrypt(subscription, n) }
                     val newNotifications = repository.onlyNewNotifications(subscription.id, notifications)
                     newNotifications.forEach { notification ->
                         newNotificationsCount++

app/src/main/java/io/heckel/ntfy/up/BroadcastReceiver.kt

@@ -80,6 +80,7 @@ class BroadcastReceiver : android.content.BroadcastReceiver() {
                     upAppId = appId,
                     upConnectorToken = connectorToken,
                     displayName = null,
+                    encryptionKey = null,
                     totalCount = 0,
                     newCount = 0,
                     lastActive = Date().time/1000

app/src/main/java/io/heckel/ntfy/util/Encryption.kt

@@ -0,0 +1,68 @@
+package io.heckel.ntfy.util
+
+import android.util.Base64
+import io.heckel.ntfy.db.Notification
+import io.heckel.ntfy.db.Subscription
+import io.heckel.ntfy.msg.NotificationParser
+import java.security.MessageDigest
+import javax.crypto.Cipher
+import javax.crypto.SecretKeyFactory
+import javax.crypto.spec.GCMParameterSpec
+import javax.crypto.spec.PBEKeySpec
+import javax.crypto.spec.SecretKeySpec
+
+fun ByteArray.toHex(): String = joinToString(separator = "") { eachByte -> "%02x".format(eachByte) }
+
+object Encryption {
+    private const val TAG = "NtfyEncryption"
+    private const val keyDerivIter = 50000
+    private const val keyLenBits = 256
+    private const val gcmTagLenBits = 128
+    private const val encodingJwe = "jwe"
+    private val parser = NotificationParser()
+
+    fun maybeDecrypt(subscription: Subscription, notification: Notification): Notification {
+        if (notification.encoding != encodingJwe) {
+            return notification
+        } else if (subscription.encryptionKey == null) {
+            Log.w(TAG, "Notification is encrypted, but key is missing: $notification; leaving encrypted message intact")
+            return notification
+        }
+        return try {
+            val plaintext = decrypt(notification.message, subscription.encryptionKey)
+            val decryptedNotification = parser.parse(plaintext) ?: throw Exception("Cannot parse decrypted message: $plaintext")
+            if (decryptedNotification.id != notification.id || decryptedNotification.timestamp != notification.timestamp) {
+                throw Exception("Message ID or timestamp mismatch in decrypted message: $plaintext")
+            }
+            decryptedNotification
+        } catch (e: Exception) {
+            Log.w(TAG, "Unable to decrypt message, falling back to original", e)
+            notification
+        }
+    }
+
+    fun deriveKey(password: String, topicUrl: String): ByteArray {
+        val salt = MessageDigest.getInstance("SHA-256").digest(topicUrl.toByteArray())
+        val factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256")
+        val spec = PBEKeySpec(password.toCharArray(), salt, keyDerivIter, keyLenBits)
+        return factory.generateSecret(spec).encoded
+    }
+
+    fun decrypt(input: String, key: ByteArray): String {
+        val parts = input.split(".")
+        if (parts.size != 5 || parts[1] != "") {
+            throw Exception("Unexpected format")
+        }
+        val encodedHeader = parts[0]
+        val iv = Base64.decode(parts[2], Base64.URL_SAFE)
+        val ciphertext = Base64.decode(parts[3], Base64.URL_SAFE)
+        val tag = Base64.decode(parts[4], Base64.URL_SAFE)
+        val ciphertextWithTag = ciphertext + tag
+        val secretKeySpec = SecretKeySpec(key, "AES")
+        val gcmParameterSpec = GCMParameterSpec(gcmTagLenBits, iv)
+        val cipher: Cipher = Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(Cipher.DECRYPT_MODE, secretKeySpec, gcmParameterSpec)
+        cipher.updateAAD(encodedHeader.toByteArray())
+        return String(cipher.doFinal(ciphertextWithTag))
+    }
+}

app/src/main/java/io/heckel/ntfy/util/Util.kt

@@ -46,6 +46,7 @@ import kotlin.math.abs
 import kotlin.math.absoluteValue
 
 fun topicUrl(baseUrl: String, topic: String) = "${baseUrl}/${topic}"
+fun topicUrl(subscription: Subscription) = topicUrl(subscription.baseUrl, subscription.topic)
 fun topicUrlUp(baseUrl: String, topic: String) = "${baseUrl}/${topic}?up=1" // UnifiedPush
 fun topicUrlJson(baseUrl: String, topic: String, since: String) = "${topicUrl(baseUrl, topic)}/json?since=$since"
 fun topicUrlWs(baseUrl: String, topic: String, since: String) = "${topicUrl(baseUrl, topic)}/ws?since=$since"

app/src/main/java/io/heckel/ntfy/work/PollWorker.kt

@@ -7,6 +7,7 @@ import io.heckel.ntfy.BuildConfig
 import io.heckel.ntfy.db.Repository
 import io.heckel.ntfy.msg.ApiService
 import io.heckel.ntfy.msg.NotificationDispatcher
+import io.heckel.ntfy.util.Encryption
 import io.heckel.ntfy.util.Log
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
@@ -40,13 +41,15 @@ class PollWorker(ctx: Context, params: WorkerParameters) : CoroutineWorker(ctx,
             subscriptions.forEach{ subscription ->
                 try {
                     val user = repository.getUser(subscription.baseUrl)
-                    val notifications = api.poll(
+                    val notifications = api
+                        .poll(
                             subscriptionId = subscription.id,
                             baseUrl = subscription.baseUrl,
                             topic = subscription.topic,
                             user = user,
                             since = subscription.lastNotificationId
                         )
+                        .map { n -> Encryption.maybeDecrypt(subscription, n) }
                     val newNotifications = repository
                         .onlyNewNotifications(subscription.id, notifications)
                         .map { it.copy(notificationId = Random.nextInt()) }

app/src/main/res/layout/preference_dialog_editpass_edited.xml

@@ -0,0 +1,59 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  ntfy EDIT:
+    This is a slightly edited copy of the original Android project layout
+    to reduce the marginBottom of the message to something reasonable (was: 48dp).
+
+  ~ Copyright (C) 2015 The Android Open Source Project
+  ~
+  ~ Licensed under the Apache License, Version 2.0 (the "License");
+  ~ you may not use this file except in compliance with the License.
+  ~ You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License
+  -->
+
+<ScrollView
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent"
+    android:layout_marginTop="48dp"
+    android:layout_marginBottom="48dp"
+    android:overScrollMode="ifContentScrolls">
+
+  <LinearLayout
+      android:layout_width="match_parent"
+      android:layout_height="wrap_content"
+      android:orientation="vertical">
+
+    <TextView
+        android:id="@android:id/message"
+        style="?android:attr/textAppearanceSmall"
+        android:layout_marginLeft="24dp"
+        android:layout_marginRight="24dp"
+        android:layout_marginStart="24dp"
+        android:layout_marginEnd="24dp"
+        android:layout_marginBottom="2dp"
+        android:layout_marginTop="4dp"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:textColor="?android:attr/textColorSecondary"/>
+
+    <EditText
+        android:id="@android:id/edit"
+        android:layout_marginLeft="20dp"
+        android:layout_marginRight="20dp"
+        android:layout_marginStart="20dp"
+        android:layout_marginEnd="20dp"
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:minHeight = "48dp"
+        android:inputType="textPassword"/>
+  </LinearLayout>
+</ScrollView>

app/src/main/res/values/strings.xml

@@ -347,6 +347,8 @@
     <string name="detail_settings_notifications_instant_title">Instant delivery</string>
     <string name="detail_settings_notifications_instant_summary_on">Notifications are delivered instantly. Requires a foreground service and consumes more battery.</string>
     <string name="detail_settings_notifications_instant_summary_off">Notifications are delivered using Firebase. Delivery may be delayed, but consumes less battery.</string>
+    <string name="detail_settings_notifications_password_title">Password</string>
+    <string name="detail_settings_notifications_password_dialog_summary">Choose a password to use to decrypt incoming end-to-end encrypted notifications. The derived key will be stored locally. If the password is incorrect, messages will not decrypt correctly.</string>
     <string name="detail_settings_appearance_header">Appearance</string>
     <string name="detail_settings_appearance_icon_set_title">Subscription icon</string>
     <string name="detail_settings_appearance_icon_set_summary">Set an icon to be displayed in notifications</string>

app/src/main/res/values/values.xml

@@ -35,6 +35,7 @@
     <string name="detail_settings_notifications_muted_until_key" translatable="false">SubscriptionMutedUntil</string>
     <string name="detail_settings_notifications_min_priority_key" translatable="false">SubscriptionMinPriority</string>
     <string name="detail_settings_notifications_auto_delete_key" translatable="false">SubscriptionAutoDelete</string>
+    <string name="detail_settings_notifications_password_key" translatable="false">SubscriptionPassword</string>
     <string name="detail_settings_appearance_header_key" translatable="false">SubscriptionAppearance</string>
     <string name="detail_settings_appearance_icon_set_key" translatable="false">SubscriptionIconSet</string>
     <string name="detail_settings_appearance_icon_remove_key" translatable="false">SubscriptionIconRemove</string>

app/src/main/res/xml/detail_preferences.xml

@@ -28,6 +28,11 @@
                 app:entryValues="@array/detail_settings_notifications_auto_delete_values"
                 app:defaultValue="-1"
                 app:isPreferenceVisible="false"/> <!-- Same as Repository.AUTO_DELETE_USE_GLOBAL -->
+        <EditTextPreference
+                app:key="@string/detail_settings_notifications_password_key"
+                app:title="@string/detail_settings_notifications_password_title"
+                app:dialogLayout="@layout/preference_dialog_editpass_edited"
+                app:dialogMessage="@string/detail_settings_notifications_password_dialog_summary"/>
     </PreferenceCategory>
     <PreferenceCategory
         app:key="@string/detail_settings_appearance_header_key"

app/src/play/java/io/heckel/ntfy/firebase/FirebaseService.kt

@@ -1,7 +1,6 @@
 package io.heckel.ntfy.firebase
 
 import android.content.Intent
-import android.util.Base64
 import androidx.work.*
 import com.google.firebase.messaging.FirebaseMessagingService
 import com.google.firebase.messaging.RemoteMessage
@@ -11,10 +10,10 @@ import io.heckel.ntfy.db.Attachment
 import io.heckel.ntfy.db.Notification
 import io.heckel.ntfy.util.Log
 import io.heckel.ntfy.msg.ApiService
-import io.heckel.ntfy.msg.MESSAGE_ENCODING_BASE64
 import io.heckel.ntfy.msg.NotificationDispatcher
 import io.heckel.ntfy.msg.NotificationParser
 import io.heckel.ntfy.service.SubscriberService
+import io.heckel.ntfy.util.Encryption
 import io.heckel.ntfy.util.toPriority
 import io.heckel.ntfy.util.topicShortUrl
 import io.heckel.ntfy.work.PollWorker
@@ -124,7 +123,7 @@ class FirebaseService : FirebaseMessagingService() {
                     url = attachmentUrl,
                 )
             } else null
-            val notification = Notification(
+            val notificationOriginal = Notification(
                 id = id,
                 subscriptionId = subscription.id,
                 timestamp = timestamp,
@@ -139,6 +138,7 @@ class FirebaseService : FirebaseMessagingService() {
                 notificationId = Random.nextInt(),
                 deleted = false
             )
+            val notification = Encryption.maybeDecrypt(subscription, notificationOriginal)
             if (repository.addNotification(notification)) {
                 Log.d(TAG, "Dispatching notification: from=${remoteMessage.from}, fcmprio=${remoteMessage.priority}, fcmprio_orig=${remoteMessage.originalPriority}, data=${data}")
                 dispatcher.dispatch(subscription, notification)