1 /*
2  * Copyright (C) 2018 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.server.backup;
18 
19 import static com.android.server.backup.BackupManagerService.TAG;
20 
21 import android.util.Slog;
22 
23 import java.io.File;
24 import java.io.FileInputStream;
25 import java.io.FileOutputStream;
26 import java.io.IOException;
27 
28 /** User settings which are persisted across reboots. */
29 final class UserBackupManagerFilePersistedSettings {
30     // File containing backup-enabled state. Contains a single byte to denote enabled status.
31     // Nonzero is enabled; file missing or a zero byte is disabled.
32     private static final String BACKUP_ENABLE_FILE = "backup_enabled";
33 
readBackupEnableState(int userId)34     static boolean readBackupEnableState(int userId) {
35         boolean enabled = readBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId));
36         Slog.d(TAG, "user:" + userId + " readBackupEnableState enabled:" + enabled);
37         return enabled;
38     }
39 
writeBackupEnableState(int userId, boolean enable)40     static void writeBackupEnableState(int userId, boolean enable) {
41         Slog.d(TAG, "user:" + userId + " writeBackupEnableState enable:" + enable);
42         writeBackupEnableState(UserBackupManagerFiles.getBaseStateDir(userId), enable);
43     }
44 
readBackupEnableState(File baseDir)45     private static boolean readBackupEnableState(File baseDir) {
46         File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
47         if (enableFile.exists()) {
48             try (FileInputStream fin = new FileInputStream(enableFile)) {
49                 int state = fin.read();
50                 if (state != 0 && state != 1) {
51                     // TODO (b/148587496) handle instead of only logging
52                     Slog.e(TAG, "Unexpected enabled state:" + state);
53                 }
54                 return state != 0;
55             } catch (IOException e) {
56                 // can't read the file; fall through to assume disabled
57                 Slog.e(TAG, "Cannot read enable state; assuming disabled");
58             }
59         } else {
60             Slog.i(TAG, "isBackupEnabled() => false due to absent settings file");
61         }
62         return false;
63     }
64 
writeBackupEnableState(File baseDir, boolean enable)65     private static void writeBackupEnableState(File baseDir, boolean enable) {
66         File enableFile = new File(baseDir, BACKUP_ENABLE_FILE);
67         File stage = new File(baseDir, BACKUP_ENABLE_FILE + "-stage");
68         try (FileOutputStream fout = new FileOutputStream(stage)) {
69             fout.write(enable ? 1 : 0);
70             fout.close();
71             boolean renamed = stage.renameTo(enableFile);
72             if (!renamed) {
73                 // TODO (b/148587496) handle instead of only logging
74                 Slog.e(TAG, "Write enable failed as could not rename staging file to actual");
75             }
76             // will be synced immediately by the try-with-resources call to close()
77         } catch (IOException | RuntimeException e) {
78             Slog.e(
79                     TAG,
80                     "Unable to record backup enable state; reverting to disabled: "
81                             + e.getMessage());
82             enableFile.delete();
83             stage.delete();
84         }
85     }
86 }
87