Improve error message when no backups could be found for restore

app/src/main/java/com/stevesoltys/backup/metadata/Metadata.kt

@@ -17,7 +17,7 @@ internal const val JSON_TOKEN = "token"
 internal const val JSON_ANDROID_VERSION = "androidVersion"
 internal const val JSON_DEVICE_NAME = "deviceName"
 
-class FormatException(cause: Throwable) : Exception(cause)
+class DecryptionFailedException(cause: Throwable) : Exception(cause)
 
 class EncryptedBackupMetadata private constructor(val token: Long, val inputStream: InputStream?, val error: Boolean) {
     constructor(token: Long, inputStream: InputStream) : this(token, inputStream, false)

app/src/main/java/com/stevesoltys/backup/metadata/MetadataReader.kt

@@ -13,14 +13,14 @@ import javax.crypto.AEADBadTagException
 
 interface MetadataReader {
 
-    @Throws(FormatException::class, SecurityException::class, UnsupportedVersionException::class, IOException::class)
+    @Throws(SecurityException::class, DecryptionFailedException::class, UnsupportedVersionException::class, IOException::class)
     fun readMetadata(inputStream: InputStream, expectedToken: Long): BackupMetadata
 
 }
 
 class MetadataReaderImpl(private val crypto: Crypto) : MetadataReader {
 
-    @Throws(FormatException::class, SecurityException::class, UnsupportedVersionException::class, IOException::class)
+    @Throws(SecurityException::class, DecryptionFailedException::class, UnsupportedVersionException::class, IOException::class)
     override fun readMetadata(inputStream: InputStream, expectedToken: Long): BackupMetadata {
         val version = inputStream.read().toByte()
         if (version < 0) throw IOException()
@@ -28,14 +28,13 @@ class MetadataReaderImpl(private val crypto: Crypto) : MetadataReader {
         val metadataBytes = try {
             crypto.decryptSegment(inputStream)
         } catch (e: AEADBadTagException) {
-            // TODO use yet another exception?
-            throw SecurityException(e)
+            throw DecryptionFailedException(e)
         }
         return decode(metadataBytes, version, expectedToken)
     }
 
     @VisibleForTesting
-    @Throws(FormatException::class, SecurityException::class)
+    @Throws(SecurityException::class)
     internal fun decode(bytes: ByteArray, expectedVersion: Byte, expectedToken: Long): BackupMetadata {
         // NOTE: We don't do extensive validation of the parsed input here,
         // because it was encrypted with authentication, so we should be able to trust it.
@@ -59,7 +58,7 @@ class MetadataReaderImpl(private val crypto: Crypto) : MetadataReader {
                     deviceName = json.getString(JSON_DEVICE_NAME)
             )
         } catch (e: JSONException) {
-            throw FormatException(e)
+            throw SecurityException(e)
         }
     }
 

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

@@ -10,7 +10,7 @@ import android.content.pm.PackageInfo
 import android.os.ParcelFileDescriptor
 import android.util.Log
 import com.stevesoltys.backup.header.UnsupportedVersionException
-import com.stevesoltys.backup.metadata.FormatException
+import com.stevesoltys.backup.metadata.DecryptionFailedException
 import com.stevesoltys.backup.metadata.MetadataReader
 import com.stevesoltys.backup.settings.getBackupToken
 import libcore.io.IoUtils.closeQuietly
@@ -50,12 +50,12 @@ internal class RestoreCoordinator(
             } catch (e: IOException) {
                 Log.e(TAG, "Error while getting restore sets", e)
                 return null
-            } catch (e: FormatException) {
-                Log.e(TAG, "Error while getting restore sets", e)
-                return null
             } catch (e: SecurityException) {
                 Log.e(TAG, "Error while getting restore sets", e)
                 return null
+            } catch (e: DecryptionFailedException) {
+                Log.e(TAG, "Error while decrypting restore set", e)
+                continue
             } catch (e: UnsupportedVersionException) {
                 Log.w(TAG, "Backup with unsupported version read", e)
                 continue

app/src/main/java/com/stevesoltys/backup/ui/recoverycode/RecoveryCodeViewModel.kt

@@ -47,9 +47,6 @@ class RecoveryCodeViewModel(application: Application) : AndroidViewModel(applica
         } catch (e: InvalidWordCountException) {
             throw AssertionError(e)
         }
-
-        // TODO if (isRestore) check if we can decrypt a backup
-
         val mnemonic = input.joinToString(" ")
         val seed = SeedCalculator(JavaxPBKDF2WithHmacSHA512.INSTANCE).calculateSeed(mnemonic, "")
         Backup.keyManager.storeBackupKey(seed)

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

@@ -54,7 +54,8 @@
 
     <TextView
         android:id="@+id/errorView"
-        android:layout_width="wrap_content"
+        android:layout_width="0dp"
+        android:layout_margin="16dp"
         android:layout_height="wrap_content"
         android:textColor="@android:color/holo_red_dark"
         android:textSize="18sp"
@@ -63,7 +64,8 @@
         app:layout_constraintEnd_toEndOf="parent"
         app:layout_constraintStart_toStartOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/titleView"
-        tools:text="There was an error retrieving your backups." />
+        tools:text="@string/restore_set_empty_result"
+        tools:visibility="visible" />
 
     <TextView
         android:id="@+id/backView"

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

@@ -90,8 +90,8 @@
     <string name="restore_back">Don\'t restore</string>
     <string name="restore_invalid_location_title">No backups found</string>
     <string name="restore_invalid_location_message">We could not find any backups at this location.\n\nPlease choose another location that contains a %s folder.</string>
-    <string name="restore_set_error">An error occurred loading the backups.</string>
-    <string name="restore_set_empty_result">No backups found at given location.</string>
+    <string name="restore_set_error">An error occurred while loading the backups.</string>
+    <string name="restore_set_empty_result">No suitable backups found at given location.\n\nThis is most likely due to a wrong recovery code or a storage error.</string>
     <string name="restore_restoring">Restoring Backup</string>
     <string name="restore_current_package">Restoring %s…</string>
     <string name="restore_finished_success">Restore complete.</string>

app/src/test/java/com/stevesoltys/backup/metadata/MetadataReaderTest.kt

@@ -47,21 +47,21 @@ class MetadataReaderTest {
     }
 
     @Test
-    fun `malformed JSON throws FormatException`() {
-        assertThrows(FormatException::class.java) {
+    fun `malformed JSON throws SecurityException`() {
+        assertThrows(SecurityException::class.java) {
             decoder.decode("{".toByteArray(Utf8), metadata.version, metadata.token)
         }
     }
 
     @Test
-    fun `missing fields throws FormatException`() {
+    fun `missing fields throws SecurityException`() {
         val json = JSONObject()
         json.put(JSON_VERSION, metadata.version.toInt())
         json.put(JSON_TOKEN, metadata.token)
         json.put(JSON_ANDROID_VERSION, metadata.androidVersion)
         val jsonBytes = json.toString().toByteArray(Utf8)
 
-        assertThrows(FormatException::class.java) {
+        assertThrows(SecurityException::class.java) {
             decoder.decode(jsonBytes, metadata.version, metadata.token)
         }
     }