Signing my android application as system app

Question

Signing my android application as system app

In my company, we would want total control for battery consumption in the field, using only 2g and gps could drain the battery awfully fast. What we decided is that we need to have root access to the mobile phone, So that when phone is idle, we would turn off those needless battery consumption. And also we would not allow users to uninstall it and clear data to it.

My Question is :

1. Where do I get these signature key?
2. Is it going to like a root access If ever I successfully managed to sign it?
3. What is the difference between Root vs Signed with key?

Answer 1

Well below is your answer,

1. You can find platform keys from HERE. The command to sign apk (for linux) is:

   java -jar signapk.jar -w platform.x509.pem platform.pk8 APPLICATION.apk APPLICATION_sign.apk

2. If you sign your apk with platform keys you won't required root access you can simply install it from "adb install" command, and yes in someway it is like root 'cos it can access all internal api but keep in mind if your app is system signed then you can't write external storage.

3. First of all don't combine both root is user where system app is application type which distinguish from normal application below link might clear your confusion regarding it.

   what-is-the-difference-between-android-user-app-with-root-access-and-a-system-ap

Answer 2

Answering your three questions:

1 - Where do I get these signature key?

From Android's own documentation in the section Release Keys

The Android tree includes test-keys under build/target/product/security

But the next part is where you should really pay attention

Since the test-keys are publicly known, anybody can sign their own .apk files with the same keys, which may allow them to replace or hijack system apps built into your OS image. For this reason it is critical to sign any publicly released or deployed Android OS image with a special set of release-keys that only you have access to.

So basically unless you can somehow gain access to manufacturer's pvt keys it might be difficult to achieve this. This is why a user in a previous comment was saying this is usually achieved by producing your own build.

2 - Is it going to like a root access If ever I successfully managed to sign it?

You will not get "root access" by doing it, but you will get access to an extremely high level of access. Specifically, what this achieves you is that you will be granted permissions with declared android:protectionLevel="signature" which is, arguably, the most exclusive one.

One other dangerous consequence (or fun, depending on how you look at it) of this is that you can now run your app under system user process android:sharedUserId="android.uid.system" - under android's "process sandboxed" security rules this would normally fail.

3 - What is the difference between Root vs Signed with key?

With an app signed with the platform key from your build, you can get the permissions mentioned above, or run your app with UID 1000 (system uid) which in android is much more powerful than the UIDs of other apps because of the permissions it can request, this is a behaviour specific of Android though. In a rooted device, you can use UID 0 (root) which has the broadest access in linux based systems, you can bypass most of the security sandboxing/checks/fences on the OS.

Hope this helps ;)