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Android Declassification Infrastructure. Matan David Yuval Evron Project Advisor: Roei Schuster. A Short Reminder…. Android’s built-in permissions are very coarse grained. We aim to provide a better solution at the application level (without having to change the OS).
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Android Declassification Infrastructure Matan David Yuval Evron Project Advisor: Roei Schuster
A Short Reminder… • Android’s built-in permissions are very coarse grained. • We aim to provide a better solution at the application level (without having to change the OS). • Security is of the essence.
A Short Reminder… • We introduced a new permission mechanism – “A Declassifier”. • The Declassifier would request high permission levels, while exporting lower, finer grained, permissions to third parties.
BroadcastReceiver • Utilizes Android’s permissions mechanism. • Filters incoming intents by caller permissions. (i.e. Does this app have sufficient permissions?) • Enables a callback mechanism which allows sending back the answer privately. • Each 3rd party app creates its own BroadcastReceiver to handle the returned result.
BroadcastReceiver – A Closer Look • Upon installation, our Declassifier requests all of the Native OS permissions it plans on using. • In the Manifest, the Declassifier creates custom permissions that the 3rd party apps will need to use. OS Declassifier APP PHONE_STATE_READ_PHONE_TYPE_PERMISSION PHONE_STATE_READ_SUBSCRIBER_ID_PERMISSION READ_PHONE_STATE PHONE_STATE_READ_CALL_STATE_PERMISSION PHONE_STATE_READ_SIM_SERIAL_NUMBER_PERMISSION PHONE_STATE_READ_DEVICE_ID_PERMISSION
BroadcastReceiver – A Closer Look • Upon installation, the 3rd party app requests only the permissions it needs from the Declassifier (It never asks for a Native OS permission).
BroadcastReceiver – A Closer Look • The app sends a BroadcastReceiver request, with all the information encapsulated inside an Intent. Intent i = newIntent("com.example.Declassifier.CALENDAR_EVENT_BY_TITLE_ACTION"); i.putExtra("Title",titleNameStr); • One of the parameters the app supplies in the request, is a custom BroadcastReceiver which will handle the Declassifier’s result (The Callback mechanism).
BroadcastReceiver – A Closer Look Calendar_App_GetEventByTitle_BReventByTitleReceiver= new Calendar_App_GetEventByTitle_BR(); sendOrderedBroadcast(i,"android.permission.READ_CALENDAR", eventByTitleReceiver, null, Activity.RESULT_OK, null, null); • At this stage, the Declassifier filters out requests which to not satisfy the relevant permissions. • In a similar way, the 3rd party app filters out returned results from unauthorized sources. • With this model, we ensure that Intents reach the designated destination and make their way back securely.
Where We Are Today • Contacts • Calendar • SD Card • Phone State
Contacts • Contact phone by Name. • Contact address by Name. • Contact e-mail address by Name. • Contact picture by Name. • Queries are interchangeable (you can search for contact name by phone number as well).
Calendar 1. Calendar Event by Title 2. Calendar Event by Date 3. Calendar Event by Location • Some queries may produce several results. i.e. entering “June” as a date will present all event in the month of June.
SD Card Management • Each application gets its own folder using its unique UID. • Writing and Reading is limited to this folder only, using the Declassifier’s interface. • Now no application is granted the WRITE_EXTERNAL_STORAGE permission and thus, can not manipulate the information on the SD Card.
Phone State • READ_PHONE_STATE permission may seem a bit vague to the average user. • It actually grants access to many of the phone’s settings (IMEI, IMSI, Cellular data connection state, Call state, Sim serial number, etc.). • Our Declassifier subdivides the READ_PHONE_STATE permission to sub permissions.
Stay Tuned…. • Audio Record Requests – We found that when granted RECORD_AUDIO permission, audio recording is possible at any time without any user consent. • Wifi – The ACCESS_WIFI_STATE permission grants the app the ability to know the wireless connection’s current state, to connect to a Wi-Fi network, etc. These permissions present a security risk, as well as a coarse permission granularity as to how applications may use the Wi-Fi / Audio devices on the Android Phone.
