What is android allowBackup

Question

Since the new ADT preview version  version 21   they have a new lint warning that tells me the next thing on the manifest file  in the application tag       Should explicitly set android allowBackup to true or false  it s true by default  and that can have some security implications for the application s data    In the official website  they ve written      A couple of new checks  you must explicitly decide whether your app allows backups  and a label check  There s a new command line flag for setting the library path  Many improvements to the incremental lint analysis while editing    What is this warning  What is the backup feature  and how do I use it   Also  why does the warning tell me it has security implications  What are the disadvantages and advantages of disabling this feature     There are two concepts of backup for the manifest     android allowBackup  allows to backup and restore via adb  as shown here       Whether to allow the application to participate in the backup and   restore infrastructure  If this attribute is set to false  no backup   or restore of the application will ever be performed  even by a   full-system backup that would otherwise cause all application data to   be saved via adb  The default value of this attribute is true    This is considered a security issue because people could backup your app via ADB and then get private data of your app into their PC   However  I think it s not that of a problem  since most users don t know what adb is  and if they do  they will also know how to root the device  ADB functions would only work if the device has the debugging feature enabled  and this needs the user to enable it   So  only users that connect their devices to the PC and enable the debugging feature would be affected  If they have a malicious app on their PC that uses the ADB tools  this could be problematic since the app could read the private storage data   I think Google should just add a feature that is disabled by default  in the developer category  to allow backup amp restore of apps via ADB     android backupAgent  allows to use the backup and restore feature of the cloud  as shown here and here       The name of the class that implement s the application s backup agent    a subclass of BackupAgent  The attribute value should be a fully   qualified class name  such as   com example project MyBackupAgent      However  as a shorthand  if the first character of the name is a   period  for example    MyBackupAgent    it is appended to the package   name specified in the  element  There is no default  The   name must be specified    This isn t a security issue

User · Answer

This is not explicitly mentioned  but based on the following docs  I think it is implied that an app needs to declare and implement a BackupAgent in order for data backup to work  even in the case when allowBackup is set to true  which is the default value    http   developer android com reference android R attr html allowBackup http   developer android com reference android app backup BackupManager html http   developer android com guide topics data backup html

User · Answer

For this lint warning  as for all other lint warnings  note that you can get a fuller explanation than just what is in the one line error message  you don t have to search the web for more info   If you are using lint via Eclipse  either open the lint warnings view  where you can select the lint error and see a longer explanation  or invoke the quick fix  Ctrl-1  on the error line  and one of the suggestions is  Explain this issue   which will also pop up a fuller explanation  If you are not using Eclipse  you can generate an HTML report from lint  lint --html  lt filename gt   which includes full explanations next to the warnings  or you can ask lint to explain a particular issue  For example  the issue related to allowBackup has the id AllowBackup  shown at the end of the error message   so the fuller explanation is       lint --show AllowBackup AllowBackup ----------- Summary  Ensure that allowBackup is explicitly set in the application s manifest  Priority  3   10 Severity  Warning Category  Security   The allowBackup attribute determines if an application s data can be backed up and restored  as documented here       By default  this flag is set to true  When this flag is set to true  application data can be backed up and restored by the user using adb backup and adb restore       This may have security consequences for an application  adb backup allows users who have enabled USB debugging to copy application data off of the device  Once backed up  all application data can be read by the user  adb restore allows creation of application data from a source specified by the user  Following a restore  applications should not assume that the data  file permissions  and directory permissions were created by the application itself       Setting allowBackup  false  opts an application out of both backup and restore       To fix this warning  decide whether your application should support backup and explicitly set android allowBackup  true false    Click here for More information

User · Answer

It is privacy concern  It is recommended to disallow users to backup an app if it contains sensitive data  Having access to backup files  i e  when android allowBackup  true    it is possible to modify read the content of an app even on a non-rooted device   Solution -  use android allowBackup  false  in the manifest file   You can read this post to have more information   Hacking Android Apps Using Backup Techniques

User · Answer

Here is what backup in this sense really means      Android s backup service allows you to copy your persistent application data to remote  cloud  storage  in order to provide a restore point for the application data and settings  If a user performs a factory reset or converts to a new Android-powered device  the system automatically restores your backup data when the application is re-installed  This way  your users don t need to reproduce their previous data or application settings     Taken from http   developer android com guide topics data backup html  You can register for this backup service as a developer here  https   developer android com google backup signup html  The type of data that can be backed up are files  databases  sharedPreferences  cache  and lib   These are generally stored in your device s  data data  com myapp  directory  which is read-protected and cannot be accessed unless you have root privileges   UPDATE  You can see this flag listed on BackupManager s api doc  BackupManager

[android] What is "android:allowBackup"?

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