‘Samsung no longer lets Android apps adjust data SD card’

When updating its smartphones to Android 4.4, Samsung seems to have made adjustments to the options for apps to modify data on the SD card. For example, it no longer seems possible for apps to be able to write content outside their ‘own’ folder.

Android Police discovered this on the basis of some Android 4.4 updates distributed over-the-air by Samsung. Restrictions are imposed on applications in the software: where it was previously possible after permission to modify content on the SD card, this is no longer possible with the new firmwares. Applications that ask for the necessary permission write_external_storage now seem to only get read access on the sd card. However, it is still possible to modify content on the internal memory with write_external_storage.

Google had previously imposed restrictions on modifying data on the SD card by apps. This was accomplished by creating a new permission called write_media_storage to gain write access to the SD card and then make it inaccessible to application developers. Smartphone makers such as Samsung, however, put a stop to this by automatically granting permission for write_media_storage when requesting write_external_storage, so developers did not have to do it themselves. This ‘tweak’ seems to come to an end at Samsung with the release of its Android 4.4 ROMs.

The changes in Samsung’s software appear to have something to do with new regulations for SD cards and Android applications that Google released concurrently with the release of Android 4.4. For example, Android Police discovered in the Android documentation that by default applications should only have write access to their own folder on both the internal memory and the SD card of an Android device. For example, the app with package name com.example.foo has automatic access to the folder Android/data/com.example.foo. The permission write_external_storage may only give write access to the internal memory, while only read access is given for the SD card. In this way, apps can request permission to modify data on the internal memory, but it remains limited on the SD card to its own folder that is created for the app.

The new rules in Samsung’s Android 4.4 ROMs can cause problems for apps that want to write content to the SD card. This can be, for example, apps with which photos are taken or images or videos are edited. File managers are also limited in their options. For system applications it is still possible to obtain full write access to the SD card: for this they use the aforementioned write_media_storage permission.

It is unclear whether Google has asked Android device manufacturers to limit the ability for apps to modify content on the SD card. It is also unclear whether manufacturers other than Samsung will implement the same changes in their Android 4.4 ROMs. It is possible that the restrictions for apps can be bypassed with root access.

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