Proj 16: Protection Level Downgrade (15-30 pts)

What You Need for This Project

Purpose

To practice using Drozer to examine Android internals. The attack will fail unless you have a really old version of Android, below 5.0, which is unlikely.

Connecting with ADB

On Kali, in a Terminal, execute this command:
ip addr
Find your IP address, as highlighted in the image below.

To find your Android device, execute this command, replacing the IP address with the IP address you found above, including the CIDR suffix "/24".

netdiscover -r 172.16.123.155/24
Netdiscover finds the devices on your network. Find the one that is not from "VMware", as highlighted in the image below.

Execute this command to connect to your Android device, replacing the IP address with the IP address of the device you determined in the previous step.

adb connect 172.16.123.171
Adb connects, as shown below.

Launching the Drozer Agent

On your Android emulator, launch the Drozer agent and make sure the Server is running, as shown below.

If you don't have a Drozer agent on your emulator, execute these commands to install one:

wget https://github.com/mwrlabs/drozer/releases/download/2.3.4/drozer-agent-2.3.4.apk
adb install drozer-agent-2.3.4.apk

Port Forwarding

On Kali, execute this command to expose the agent's port.
adb forward tcp:31415 tcp:31415
The command completes without errors, as shown below.

Installing the Twitter App

On your Android emulator, install Twitter from the App store, as shown below.

Viewing Twitter App Permissions

In Kali, in a Terminal, at the # bash prompt, execute these commands:
drozer console connect
run app.package.info -a com.twitter.android
Information about the app appears, starting with general information as shown below.

At the end, there are three permissions the Twitter app defines, as shown below:

I was unable to find out what "READ_DATA" does in detail, but we can learn more about the other two permissions.

To see the appm components, execute this command:

run app.package.attacksurface com.twitter.android
Twitter uses several activities, "broadcast receivers", and services, but no "content providers", as shown below.

Understanding the AUTH_APP Permission

To see more about the activities, execute this command:
run app.activity.info -a com.twitter.android
We see that the AUTH_APP permission controls access to the AuthorizeAppActivity activity, as shown below.

Understanding the RESTRICTED Permission

To see more about the broadcast receivers, execute this command:
run app.broadcast.info -a com.twitter.android
We see that the RESTRICTED permission controls access to the AppBroadcastReceiver receiver, as shown below.

Viewing the Protection Levels

To see the protection levels of these permissions, execute these commands:
run information.permissions --permission com.twitter.android.permission.READ_DATA
run information.permissions --permission com.twitter.android.permission.RESTRICTED
run information.permissions --permission com.twitter.android.permission.AUTH_APP
exit
As shown below, READ_DATA and RESTRICTED have the signature protection level, and AUTH_APP is marked as dangerous.

The signature-level permissions are only available to apps signed with the same certificate, and the dangerous permission will pop a box up, requesting permission from the user.

Downgrading Java

Drozer can't sign apps with recent Java versions, so we need to downgrade Java.

Execute these commands to do that.

apt update
apt install openjdk-8-jdk -y
If an "Outdated processor microcode" box appears, press Enter.

Execute this command to reboot Kali.

reboot
Execute this command to select the default version of javac, the Java compiler:
update-alternatives --config javac
Find "java-8" on the list and select it. When I did it, that was item 2 as shown below.

Execute this command to select the default version of java:

update-alternatives --config java
Find "java-8" on the list and select it. When I did it, that was item 2 as shown below.

Building a Drozer App

To build a Drozer app that requests the permissions defined by Twitter, in Kali, in a Terminal, at the # bash prompt, execute this command:
drozer agent build --permission \
com.twitter.android.permission.READ_DATA \
com.twitter.android.permission.RESTRICTED \
com.twitter.android.permission.AUTH_APP 
The agent is built and placed in the /tmp directory. Note the path to the agent, highlighted in the image below.

Reconnecting with ADB

Execute this command to connect to your Android device, replacing the IP address with the IP address of the device you determined previously.
adb connect 172.16.123.171
Adb connects, as shown below.

Monitoring the Log

Execute these commands to clear old log entries and monitor the Android log:
adb logcat -c
adb logcat | grep perm
Leave this window running, as shown below.

Installing the Agent

On Kali, open a second Terminal window. Execute these commands to remove the old agent and install the new one.

In the second command, adjusting the path to lead to the APK file you built previously with Drozer.

adb uninstall com.mwr.dz
adb install /tmp/tmpzXbifs/agent.apk
The agent installs, as shown in the upper window in the image below.

The log shows that the app was not granted these two permissions:

as shown in the lower window in the image below.

This makes sense, because those are signature-level permissions, and the Drozer agent is not signed with the Twitter certificate.

Uninstalling Twitter and the Drozer Agent

On Kali, execute these commands:
adb uninstall com.mwr.dz
adb uninstall com.twitter.android
The operations succeed, as shown below.

Building a Drozer Agent that Defines Twitter Permissions

In Kali, in a Terminal, at the # bash prompt, execute this command:
drozer agent build --define-permission \
com.twitter.android.permission.READ_DATA normal \
com.twitter.android.permission.RESTRICTED normal \
com.twitter.android.permission.AUTH_APP normal --permission \
com.twitter.android.permission.READ_DATA \
com.twitter.android.permission.RESTRICTED \
com.twitter.android.permission.AUTH_APP
The agent is built and placed in the /tmp directory. Note the path to the agent, highlighted in the image below.

Installing the New Agent

On Kali, open a second Terminal window. Execute these commands to remove the old agent and install the new one.

In the second command, adjusting the path to lead to the APK file you built previously with Drozer.

adb install /tmp/tmp_URMcR/agent.apk
The agent installs, as shown below.

Installing the Twitter App Again

On your Android emulator, install Twitter from the App store again, as shown below.

If you are using Android 5.0 or above, the installation should fail with the error message shown below.

Saving a Screen Image

Make sure the "Can't install app" message is visible, as shown above.

Save a full-desktop image. On a Mac, press Shift+Commmand+3. On a PC, press Shift+PrntScrn and paste into Paint.

YOU MUST SUBMIT A FULL-SCREEN IMAGE FOR FULL CREDIT!

Save the image with the filename "YOUR NAME Proj 16a", replacing "YOUR NAME" with your real name.


Extra Credit: Use Android 4.3 (15 pts)

Install an Android 4.3 emulator.

I used the one shown below.

You can't use the Gapps button to install Google Play. Instead, you need to install these two components one by one, rebooting after each installation.

https://samsclass.info/128/proj/Genymotion-ARM-Translation_v1.1.zip

https://samsclass.info/128/proj/gapps-jb-20130813-signed.zip

Then repeat the project. This time Twitter will install.

Launch the Drozer agent, configure port forwarding, and execute these commands to see Twitter's protection levels:

drozer console connect
run information.permissions --permission com.twitter.android.permission.READ_DATA
run information.permissions --permission com.twitter.android.permission.RESTRICTED
run information.permissions --permission com.twitter.android.permission.AUTH_APP
exit
The permissions are all normal, as shown below.

Saving a Screen Image

Make sure the three "normal" messages are visible, as shown above.

Save a full-desktop image. On a Mac, press Shift+Commmand+3. On a PC, press Shift+PrntScrn and paste into Paint.

YOU MUST SUBMIT A FULL-SCREEN IMAGE FOR FULL CREDIT!

Save the image with the filename "YOUR NAME Proj 16b", replacing "YOUR NAME" with your real name.

Turning in your Project

Email the image(s) to to cnit.128sam@gmail.com with the subject line: Proj 15 from YOUR NAME

References

drozer build agent # On recent Kali
How to downgrade java on ubuntu/kali linux

Posted 2-8-19 by Sam Bowne
Second image description fixed 3-11-19