Install apps silently, with granted INSTALL_PACKAGES permission

I have been implementing installation without user consent recently - it was a kiosk application for API level 21+ where I had full control over environment.

The basic requirements are

• API level 21+
• root access to install the updater as a system privileged app.

The following method reads and installs APK from InputStream:

public static boolean installPackage(Context context, InputStream in, String packageName)
            throws IOException {
        PackageInstaller packageInstaller = context.getPackageManager().getPackageInstaller();
        PackageInstaller.SessionParams params = new PackageInstaller.SessionParams(
                PackageInstaller.SessionParams.MODE_FULL_INSTALL);
        params.setAppPackageName(packageName);
        // set params
        int sessionId = packageInstaller.createSession(params);
        PackageInstaller.Session session = packageInstaller.openSession(sessionId);
        OutputStream out = session.openWrite("COSU", 0, -1);
        byte[] buffer = new byte[65536];
        int c;
        while ((c = in.read(buffer)) != -1) {
            out.write(buffer, 0, c);
        }
        session.fsync(out);
        in.close();
        out.close();

        Intent intent = new Intent(context, MainActivity.class);
        intent.putExtra("info", "somedata");  // for extra data if needed..

        Random generator = new Random();

        PendingIntent i = PendingIntent.getActivity(context, generator.nextInt(), intent,PendingIntent.FLAG_UPDATE_CURRENT);
            session.commit(i.getIntentSender());


        return true;
    }

The following code calls the installation

 try {
     InputStream is = getResources().openRawResource(R.raw.someapk_source);
                    installPackage(MainActivity.this, is, "com.example.apk");
     } catch (IOException e) {
                    Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_SHORT).show();
     }

for the whole thing to work you desperately need INSTALL_PACKAGES permission, or the code above will fail silently

<uses-permission
        android:name="android.permission.INSTALL_PACKAGES" />

to get this permission you must install your APK as System application which REQUIRES root (however AFTER you have installed your updater application it seem to work WITHOUT root)

To install as system application I created a signed APK and pushed it with

adb push updater.apk /sdcard/updater.apk

and then moved it to system/priv-app - which requires remounting FS (this is why the root is required)

adb shell
su
mount -o rw,remount /system
mv /sdcard/updater.apk /system/priv-app
chmod 644 /system/priv-app/updater.apk

for some reason it didn't work with simple debug version, but logcat shows useful info if your application in priv-app is not picked up for some reason.

Your first bet is to look into Android's native PackageInstaller. I would recommend modifying that app the way you like, or just extract required functionality.

---

Specifically, if you look into PackageInstallerActivity and its method onClickListener:

 public void onClick(View v) {
    if(v == mOk) {
        // Start subactivity to actually install the application
        Intent newIntent = new Intent();
        ...
        newIntent.setClass(this, InstallAppProgress.class);
        ...
        startActivity(newIntent);
        finish();
    } else if(v == mCancel) {
        // Cancel and finish
        finish();
    }
}

Then you'll notice that actual installer is located in InstallAppProgress class. Inspecting that class you'll find that initView is the core installer function, and the final thing it does is call to PackageManager's installPackage function:

public void initView() {
...
pm.installPackage(mPackageURI, observer, installFlags, installerPackageName);
}

Next step is to inspect PackageManager, which is abstract class. You'll find installPackage(...) function there. The bad news is that it's marked with @hide. This means it's not directly available (you won't be able to compile with call to this method).

 /**
  * @hide
  * ....
  */
  public abstract void installPackage(Uri packageURI,
             IPackageInstallObserver observer, 
             int flags,String installerPackageName); 

But you will be able to access this methods via reflection.

If you are interested in how PackageManager's installPackage function is implemented, take a look at PackageManagerService.

Summary

You'll need to get package manager object via Context's getPackageManager(). Then you will call installPackage function via reflection.