Add a unique ID to the device folder name to avoid collisions

when using several devices of the same model with the same account

Android.mk

@@ -1,5 +1,13 @@
 LOCAL_PATH := $(call my-dir)
 
+include $(CLEAR_VARS)
+LOCAL_MODULE := default-permissions_com.stevesoltys.backup.xml
+LOCAL_MODULE_CLASS := ETC
+LOCAL_MODULE_TAGS := optional
+LOCAL_MODULE_PATH := $(TARGET_OUT_ETC)/default-permissions
+LOCAL_SRC_FILES := $(LOCAL_MODULE)
+include $(BUILD_PREBUILT)
+
 include $(CLEAR_VARS)
 LOCAL_MODULE := permissions_com.stevesoltys.backup.xml
 LOCAL_MODULE_CLASS := ETC

app/src/main/AndroidManifest.xml

@@ -14,7 +14,9 @@
         android:name="android.permission.BACKUP"
         tools:ignore="ProtectedPermissions" />
 
-    <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+    <!-- This is needed to retrieve the serial number of the device,
+         so we can store the backups for each device in a unique location -->
+    <uses-permission android:name="android.permission.READ_PHONE_STATE" />
 
     <application
         android:name=".Backup"
@@ -35,7 +37,7 @@
 
         <activity
             android:name="com.stevesoltys.backup.activity.MainActivity"
-            android:label="@string/app_name"/>
+            android:label="@string/app_name" />
 
         <activity
             android:name="com.stevesoltys.backup.activity.backup.CreateBackupActivity"

app/src/main/java/com/stevesoltys/backup/Backup.kt

@@ -1,14 +1,27 @@
 package com.stevesoltys.backup
 
+import android.Manifest
+import android.Manifest.permission.READ_PHONE_STATE
 import android.app.Application
 import android.app.backup.IBackupManager
 import android.content.Context.BACKUP_SERVICE
+import android.content.pm.PackageManager.PERMISSION_GRANTED
+import android.os.Build
 import android.os.ServiceManager.getService
+import android.util.Log
 import com.stevesoltys.backup.crypto.KeyManager
 import com.stevesoltys.backup.crypto.KeyManagerImpl
+import com.stevesoltys.backup.settings.getDeviceName
+import com.stevesoltys.backup.settings.setDeviceName
+import io.github.novacrypto.hashing.Sha256
+import io.github.novacrypto.hashing.Sha256.sha256
+import io.github.novacrypto.hashing.Sha256.sha256Twice
+import java.lang.AssertionError
 
 const val JOB_ID_BACKGROUND_BACKUP = 1
 
+private val TAG = Backup::class.java.simpleName
+
 /**
  * @author Steve Soltys
  * @author Torsten Grote
@@ -24,4 +37,25 @@ class Backup : Application() {
         }
     }
 
+    override fun onCreate() {
+        super.onCreate()
+        storeDeviceName()
+    }
+
+    private fun storeDeviceName() {
+        if (getDeviceName(this) != null) return  // we already have a stored device name
+
+        val permission = READ_PHONE_STATE
+        if (checkSelfPermission(permission) != PERMISSION_GRANTED) {
+            throw AssertionError("You need to grant the $permission permission.")
+        }
+        // TODO consider just using a hash for the entire device name and store metadata in an encrypted file
+        val id = sha256Twice(Build.getSerial().toByteArray(Utf8))
+                .copyOfRange(0, 8)
+                .encodeBase64()
+        val name = "${Build.MANUFACTURER} ${Build.MODEL} ($id)"
+        Log.i(TAG, "Initialized device name to: $name")
+        setDeviceName(this, name)
+    }
+
 }

app/src/main/java/com/stevesoltys/backup/Base64Utils.kt

@@ -0,0 +1,18 @@
+package com.stevesoltys.backup
+
+import java.nio.charset.Charset
+import java.util.*
+
+val Utf8: Charset = Charset.forName("UTF-8")
+
+fun ByteArray.encodeBase64(): String {
+    return Base64.getUrlEncoder().withoutPadding().encodeToString(this)
+}
+
+fun String.encodeBase64(): String {
+    return toByteArray(Utf8).encodeBase64()
+}
+
+fun String.decodeBase64(): String {
+    return String(Base64.getUrlDecoder().decode(this))
+}

app/src/main/java/com/stevesoltys/backup/header/Header.kt

@@ -1,7 +1,5 @@
 package com.stevesoltys.backup.header
 
-import java.nio.charset.Charset
-
 internal const val VERSION: Byte = 0
 internal const val MAX_PACKAGE_LENGTH_SIZE = 255
 internal const val MAX_KEY_LENGTH_SIZE = MAX_PACKAGE_LENGTH_SIZE
@@ -39,5 +37,3 @@ class SegmentHeader(
         check(nonce.size == IV_SIZE)
     }
 }
-
-val Utf8: Charset = Charset.forName("UTF-8")

app/src/main/java/com/stevesoltys/backup/header/HeaderReader.kt

@@ -1,5 +1,6 @@
 package com.stevesoltys.backup.header
 
+import com.stevesoltys.backup.Utf8
 import java.io.EOFException
 import java.io.IOException
 import java.io.InputStream

app/src/main/java/com/stevesoltys/backup/header/HeaderWriter.kt

@@ -1,5 +1,6 @@
 package com.stevesoltys.backup.header
 
+import com.stevesoltys.backup.Utf8
 import java.io.IOException
 import java.io.OutputStream
 import java.nio.ByteBuffer

app/src/main/java/com/stevesoltys/backup/settings/SettingsManager.kt

@@ -5,8 +5,8 @@ import android.net.Uri
 import android.preference.PreferenceManager.getDefaultSharedPreferences
 
 private const val PREF_KEY_BACKUP_URI = "backupUri"
+private const val PREF_KEY_DEVICE_NAME = "deviceName"
 private const val PREF_KEY_BACKUP_PASSWORD = "backupLegacyPassword"
-private const val PREF_KEY_BACKUPS_SCHEDULED = "backupsScheduled"
 
 fun setBackupFolderUri(context: Context, uri: Uri) {
     getDefaultSharedPreferences(context)
@@ -21,6 +21,17 @@ fun getBackupFolderUri(context: Context): Uri? {
     return Uri.parse(uriStr)
 }
 
+fun setDeviceName(context: Context, name: String) {
+    getDefaultSharedPreferences(context)
+            .edit()
+            .putString(PREF_KEY_DEVICE_NAME, name)
+            .apply()
+}
+
+fun getDeviceName(context: Context): String? {
+    return getDefaultSharedPreferences(context).getString(PREF_KEY_DEVICE_NAME, null)
+}
+
 /**
  * This is insecure and not supposed to be part of a release,
  * but rather an intermediate step towards a generated passphrase.
@@ -38,6 +49,7 @@ fun getBackupPassword(context: Context): String? {
     return getDefaultSharedPreferences(context).getString(PREF_KEY_BACKUP_PASSWORD, null)
 }
 
+@Deprecated("Our own scheduling will be removed")
 fun setBackupsScheduled(context: Context) {
     getDefaultSharedPreferences(context)
             .edit()
@@ -45,6 +57,7 @@ fun setBackupsScheduled(context: Context) {
             .apply()
 }
 
+@Deprecated("Our own scheduling will be removed")
 fun areBackupsScheduled(context: Context): Boolean {
     return getDefaultSharedPreferences(context).getBoolean(PREF_KEY_BACKUPS_SCHEDULED, false)
 }

app/src/main/java/com/stevesoltys/backup/transport/PluginManager.kt

@@ -1,13 +1,13 @@
 package com.stevesoltys.backup.transport
 
 import android.content.Context
-import android.os.Build
 import com.stevesoltys.backup.Backup
 import com.stevesoltys.backup.crypto.CipherFactoryImpl
 import com.stevesoltys.backup.crypto.CryptoImpl
 import com.stevesoltys.backup.header.HeaderReaderImpl
 import com.stevesoltys.backup.header.HeaderWriterImpl
 import com.stevesoltys.backup.settings.getBackupFolderUri
+import com.stevesoltys.backup.settings.getDeviceName
 import com.stevesoltys.backup.transport.backup.BackupCoordinator
 import com.stevesoltys.backup.transport.backup.FullBackup
 import com.stevesoltys.backup.transport.backup.InputFactory
@@ -24,7 +24,7 @@ class PluginManager(context: Context) {
 
     // We can think about using an injection framework such as Dagger to simplify this.
 
-    private val storage = DocumentsStorage(context, getBackupFolderUri(context), getDeviceName())
+    private val storage = DocumentsStorage(context, getBackupFolderUri(context), getDeviceName(context)!!)
 
     private val headerWriter = HeaderWriterImpl()
     private val headerReader = HeaderReaderImpl()
@@ -47,10 +47,4 @@ class PluginManager(context: Context) {
 
     internal val restoreCoordinator = RestoreCoordinator(restorePlugin, kvRestore, fullRestore)
 
-
-    private fun getDeviceName(): String {
-        // TODO add device specific unique ID to the end
-        return "${Build.MANUFACTURER} ${Build.MODEL}"
-    }
-
 }

app/src/main/java/com/stevesoltys/backup/transport/backup/FullBackupPlugin.kt

@@ -8,6 +8,7 @@ interface FullBackupPlugin {
 
     fun getQuota(): Long
 
+    // TODO consider using a salted hash for the package name to not leak it to the storage server
     @Throws(IOException::class)
     fun getOutputStream(targetPackage: PackageInfo): OutputStream
 

app/src/main/java/com/stevesoltys/backup/transport/backup/KVBackup.kt

@@ -5,12 +5,11 @@ import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.crypto.Crypto
+import com.stevesoltys.backup.encodeBase64
 import com.stevesoltys.backup.header.HeaderWriter
-import com.stevesoltys.backup.header.Utf8
 import com.stevesoltys.backup.header.VersionHeader
 import libcore.io.IoUtils.closeQuietly
 import java.io.IOException
-import java.util.Base64.getUrlEncoder
 
 class KVBackupState(internal val packageName: String)
 
@@ -139,7 +138,7 @@ class KVBackup(
             }
             // encode key
             val key = changeSet.key
-            val base64Key = getUrlEncoder().withoutPadding().encodeToString(key.toByteArray(Utf8))
+            val base64Key = key.encodeBase64()
             val dataSize = changeSet.dataSize
 
             // read and encrypt value

app/src/main/java/com/stevesoltys/backup/transport/backup/KVBackupPlugin.kt

@@ -11,6 +11,7 @@ interface KVBackupPlugin {
      */
     fun getQuota(): Long
 
+    // TODO consider using a salted hash for the package name (and key) to not leak it to the storage server
     /**
      * Return true if there are records stored for the given package.
      */

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsProviderBackupPlugin.kt

@@ -6,8 +6,6 @@ import com.stevesoltys.backup.transport.backup.FullBackupPlugin
 import com.stevesoltys.backup.transport.backup.KVBackupPlugin
 import java.io.IOException
 
-private const val NO_MEDIA = ".nomedia"
-
 class DocumentsProviderBackupPlugin(
         private val storage: DocumentsStorage,
         packageManager: PackageManager) : BackupPlugin {
@@ -25,9 +23,6 @@ class DocumentsProviderBackupPlugin(
         // get or create root backup dir
         val rootDir = storage.rootBackupDir ?: throw IOException()
 
-        // create .nomedia file to prevent Android's MediaScanner from trying to index the backup
-        rootDir.createOrGetFile(NO_MEDIA)
-
         // create backup folders
         val kvDir = storage.defaultKvBackupDir
         val fullDir = storage.defaultFullBackupDir

app/src/main/java/com/stevesoltys/backup/transport/backup/plugins/DocumentsStorage.kt

@@ -13,6 +13,7 @@ import java.io.OutputStream
 const val DIRECTORY_FULL_BACKUP = "full"
 const val DIRECTORY_KEY_VALUE_BACKUP = "kv"
 private const val ROOT_DIR_NAME = ".AndroidBackup"
+private const val NO_MEDIA = ".nomedia"
 private const val MIME_TYPE = "application/octet-stream"
 
 private val TAG = DocumentsStorage::class.java.simpleName
@@ -25,7 +26,10 @@ class DocumentsStorage(context: Context, parentFolder: Uri?, deviceName: String)
         val folderUri = parentFolder ?: return@lazy null
         val parent = DocumentFile.fromTreeUri(context, folderUri) ?: throw AssertionError()
         try {
-            parent.createOrGetDirectory(ROOT_DIR_NAME)
+            val rootDir = parent.createOrGetDirectory(ROOT_DIR_NAME)
+            // create .nomedia file to prevent Android's MediaScanner from trying to index the backup
+            rootDir.createOrGetFile(NO_MEDIA)
+            rootDir
         } catch (e: IOException) {
             Log.e(TAG, "Error creating root backup dir.", e)
             null

app/src/main/java/com/stevesoltys/backup/transport/restore/KVRestore.kt

@@ -7,12 +7,12 @@ import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.crypto.Crypto
+import com.stevesoltys.backup.decodeBase64
 import com.stevesoltys.backup.header.HeaderReader
 import com.stevesoltys.backup.header.UnsupportedVersionException
 import libcore.io.IoUtils.closeQuietly
 import java.io.IOException
 import java.util.*
-import java.util.Base64.getUrlDecoder
 
 private class KVRestoreState(
         internal val token: Long,
@@ -132,7 +132,7 @@ internal class KVRestore(
     }
 
     private class DecodedKey(internal val base64Key: String) : Comparable<DecodedKey> {
-        internal val key = String(getUrlDecoder().decode(base64Key))
+        internal val key = base64Key.decodeBase64()
 
         override fun compareTo(other: DecodedKey) = key.compareTo(other.key)
     }

app/src/test/java/com/stevesoltys/backup/header/HeaderReaderTest.kt

@@ -1,5 +1,6 @@
 package com.stevesoltys.backup.header
 
+import com.stevesoltys.backup.Utf8
 import com.stevesoltys.backup.assertContains
 import com.stevesoltys.backup.getRandomString
 import org.junit.jupiter.api.Assertions.*

app/src/test/java/com/stevesoltys/backup/transport/CoordinatorIntegrationTest.kt

@@ -10,17 +10,16 @@ import android.os.ParcelFileDescriptor
 import com.stevesoltys.backup.crypto.CipherFactoryImpl
 import com.stevesoltys.backup.crypto.CryptoImpl
 import com.stevesoltys.backup.crypto.KeyManagerTestImpl
-import com.stevesoltys.backup.transport.backup.*
+import com.stevesoltys.backup.encodeBase64
 import com.stevesoltys.backup.header.HeaderReaderImpl
 import com.stevesoltys.backup.header.HeaderWriterImpl
-import com.stevesoltys.backup.header.Utf8
+import com.stevesoltys.backup.transport.backup.*
 import com.stevesoltys.backup.transport.restore.*
 import io.mockk.*
 import org.junit.jupiter.api.Assertions.*
 import org.junit.jupiter.api.Test
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
-import java.util.*
 import kotlin.random.Random
 
 internal class CoordinatorIntegrationTest : TransportTest() {
@@ -53,9 +52,9 @@ internal class CoordinatorIntegrationTest : TransportTest() {
     private val appData = ByteArray(42).apply { Random.nextBytes(this) }
     private val appData2 = ByteArray(1337).apply { Random.nextBytes(this) }
     private val key = "RestoreKey"
-    private val key64 = Base64.getUrlEncoder().withoutPadding().encodeToString(key.toByteArray(Utf8))
+    private val key64 = key.encodeBase64()
     private val key2 = "RestoreKey2"
-    private val key264 = Base64.getUrlEncoder().withoutPadding().encodeToString(key2.toByteArray(Utf8))
+    private val key264 = key2.encodeBase64()
 
     init {
         every { backupPlugin.kvBackupPlugin } returns kvBackupPlugin

app/src/test/java/com/stevesoltys/backup/transport/backup/KVBackupTest.kt

@@ -2,9 +2,9 @@ package com.stevesoltys.backup.transport.backup
 
 import android.app.backup.BackupDataInput
 import android.app.backup.BackupTransport.*
+import com.stevesoltys.backup.Utf8
 import com.stevesoltys.backup.getRandomString
 import com.stevesoltys.backup.header.MAX_KEY_LENGTH_SIZE
-import com.stevesoltys.backup.header.Utf8
 import com.stevesoltys.backup.header.VersionHeader
 import io.mockk.Runs
 import io.mockk.every

app/src/test/java/com/stevesoltys/backup/transport/restore/KVRestoreTest.kt

@@ -3,9 +3,9 @@ package com.stevesoltys.backup.transport.restore
 import android.app.backup.BackupDataOutput
 import android.app.backup.BackupTransport.TRANSPORT_ERROR
 import android.app.backup.BackupTransport.TRANSPORT_OK
+import com.stevesoltys.backup.encodeBase64
 import com.stevesoltys.backup.getRandomByteArray
 import com.stevesoltys.backup.header.UnsupportedVersionException
-import com.stevesoltys.backup.header.Utf8
 import com.stevesoltys.backup.header.VERSION
 import com.stevesoltys.backup.header.VersionHeader
 import io.mockk.*
@@ -14,7 +14,6 @@ import org.junit.jupiter.api.Assertions.assertThrows
 import org.junit.jupiter.api.Test
 import java.io.IOException
 import java.io.InputStream
-import java.util.Base64.getUrlEncoder
 import kotlin.random.Random
 
 internal class KVRestoreTest : RestoreTest() {
@@ -24,10 +23,10 @@ internal class KVRestoreTest : RestoreTest() {
     private val restore = KVRestore(plugin, outputFactory, headerReader, crypto)
 
     private val key = "Restore Key"
-    private val key64 = getUrlEncoder().withoutPadding().encodeToString(key.toByteArray(Utf8))
+    private val key64 = key.encodeBase64()
     private val versionHeader = VersionHeader(VERSION, packageInfo.packageName, key)
     private val key2 = "Restore Key2"
-    private val key264 = getUrlEncoder().withoutPadding().encodeToString(key2.toByteArray(Utf8))
+    private val key264 = key2.encodeBase64()
     private val versionHeader2 = VersionHeader(VERSION, packageInfo.packageName, key2)
 
     @Test

default-permissions_com.stevesoltys.backup.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8" standalone="yes"?>
+<exceptions>
+    <exception package="com.stevesoltys.backup">
+        <permission name="android.permission.READ_PHONE_STATE" fixed="true"/>
+    </exception>
+</exceptions>