Android Pentesting

Resources

OWASP Mobile Application Pentesting Gitbook:

https://mobile-security.gitbook.io/mobile-security-testing-guide/overview/0x03-overview

OWASP Mobile Top 10 :

https://owasp.org/www-project-mobile-top-10/

SecJuic Introduction to Frida and Objection:

https://www.secjuice.com/objection-frida-guide/

HackTricks Website with IOS/Android Pentest Checklists :

https://book.hacktricks.xyz/mobile-apps-pentesting/android-checklist

InjuredAndroid

https://github.com/B3nac/InjuredAndroid

Tools

Jadix-gui

https://github.com/skylot/jadx

Apktool

https://github.com/iBotPeaches/Apktool

Objection

https://github.com/sensepost/objection

Static Analysis

static analysis

Pull APK From Google Playstore

First, you need to install the apk from google playstore in your enumerator.

Drop the shell with adb adb shell.

To list every packages application that install in your enumlator.

pm list packages

Now find the path of the this apk located. pm path [package name]

generic_x86:/ $ pm path b3nac.injuredandroid
package:/data/app/b3nac.injuredandroid-fBw3LmlBTAq04Q5CC8sHg==/base.apk

Now we know where is the file path. Exit from adb and pull the apk form that path.

adb pull /data/app/b3nac.injuredandroid-fBw3LmlBTAq04Q5CC8sHg==/base.apk injuredAndroid_pulled.apk

Android Mainifest.xml

The Android Manifest is an XML file which contains important metadata about the Android app. This includes the package name, activity names, main activity (the entry point to the app), Android version support, hardware features support, permissions, and other configurations.

Decompiled APK

apktool d apkname.apk

┌─[sheinn101@parrot]─[~/ctf/android]
└──╼ [??]$ apktool d injuredAndroid.apk 
I: Using Apktool 2.5.0-dirty on injuredAndroid.apk
I: Loading resource table...
I: Decoding AndroidManifest.xml with resources...
I: Loading resource table from file: /home/sheinn101/.local/share/apktool/framework/1.apk
I: Regular manifest package...
I: Decoding file-resources...
I: Decoding values */* XMLs...
I: Baksmaling classes.dex...
I: Copying assets and libs...
I: Copying unknown files...
I: Copying original files...
┌─[sheinn101@parrot]─[~/ctf/android/injuredAndroid]
└──╼ [??]$ ls
AndroidManifest.xml  apktool.yml  assets  kotlin  lib  original  res  smali  unknown
┌─[sheinn101@parrot]─[~/ctf/android/injuredAndroid]
└──╼ [??]$

Find Hardcoded Strings

Often hardcoded strings can be found in resources/strings.xml and also in activity source code.Sometimes you may find client credentials, urls exposed, apikeys, firebase url, etc...

Exported Activity

An exported activity is the one that can be accessed by external components or apps. We can say that exported activities are like Public functions in Java, any other parent class or even package can call them. Let's say you are on your home screen and now you want to start the Twitter app so you’ll click on the app icon to invoke its launcher activity but technically you were already in some activity(home page) and then you started another activity(launching the Twitter app). Now if the launcher activity of the Twitter app isn’t exported(not public) then no one will be able to invoke the activity and the app won’t start. That is why there has to at least one activity exported so other components of android can start it.That can also be XSS attack.

Find android:exported=true in AndroidManifest.xml

Let's find ,we can access that activity anywhere from the phone (could be from different application).

To exploit this, enter adb shell and type this am start [activity name]

Don't forget to add forward slash in front of activity name /.b25lActivity

┌─[sheinn101@parrot]─[~/Documents/bug_program/h1/monday]
└──╼ [??]$ adb shell
picasso:/ $ am start b3nac.injuredandroid/.b25lActivity
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=b3nac.injuredandroid/.b25lActivity }
picasso:/ $

It will automatically pop up that activity in our phone.

In real world or bug bounty hunting , you need to make sure that activity has any sensitive data or can allow us some UI (like admin panel) which we don't have access to it.

Enumerating AWS Storage Bucket

https://github.com/initstring/cloud_enum

python3 cloud_enum.py -k injuredandroid

Enumerating Firebase Databases

https://github.com/Sambal0x/firebaseEnum

┌─[sheinn101@parrot]─[~/ctf/android/firebaseEnum]
└──╼ [??]$ python3 firebaseEnum.py -k injuredandroid

______ _          _                    _____                      
|  ___(_)        | |                  |  ___|                     
| |_   _ _ __ ___| |__   __ _ ___  ___| |__ _ __  _   _ _ __ ___  
|  _| | | '__/ _ \ '_ \ / _` / __|/ _ \  __| '_ \| | | | '_ ` _ \ 
| |   | | | |  __/ |_) | (_| \__ \  __/ |__| | | | |_| | | | | | |
\_|   |_|_|  \___|_.__/ \__,_|___/\___\____/_| |_|\__,_|_| |_| |_|
                                                                  
                                                                  
 github.com/sambal0x                                                                     


==========================
 Keyword based Enumeration
==========================

[+] Mutations list imported: 227 items
[+] Mutated results: 909 items
[+] Checking for open firebase databases...
    5/909 complete..

When you find a firebase url , keep that in mind , may be there is some area are not protected. You can check with .json like this.

Dynamic Analysis

Disable SSL Pinning

Patching Apk using Objection

We can use objection for automatically patch the application to bypass SSL Pinning.

Installation : pip3 install objection

┌─[sheinn101@parrot]─[~/ctf/android]
└──╼ [??]$ objection patchapk --source injuredAndroid.apk 
No architecture specified. Determining it using `adb`...
Detected target device architecture as: arm64-v8a
Using latest Github gadget version: 15.1.10
Patcher will be using Gadget version: 15.1.10
Detected apktool version as: 2.5.0-dirty
Running apktool empty-framework-dir...
I: Removing 1.apk framework file...
Unpacking injuredAndroid.apk
App already has android.permission.INTERNET
Target class not specified, searching for launchable activity instead...
Reading smali from: /tmp/tmpeohig7rk.apktemp/smali/b3nac/injuredandroid/MainActivity.smali
Injecting loadLibrary call at line: 10
Attempting to fix the constructors .locals count
Current locals value is 0, updating to 1:
Writing patched smali back to: /tmp/tmpeohig7rk.apktemp/smali/b3nac/injuredandroid/MainActivity.smali
Copying Frida gadget to libs path...
Rebuilding the APK with the frida-gadget loaded...
Rebuilding the APK may have failed. Read the following output to determine if apktool actually had an error: 
Built new APK with injected loadLibrary and frida-gadget
Performing zipalign
Zipalign completed
Signing new APK.
Signed the new APK
Copying final apk from /tmp/tmpeohig7rk.apktemp.aligned.objection.apk to injuredAndroid.objection.apk in current directory...
Cleaning up temp files...

Sometime this method does not work properly. You can do manually to patch.

Manual Patching

Patch the apk with apktool

apktool -d apkname.apk and download frida-gadget.so from github.

wget https://github.com/frida/frida/releases/download/15.1.10/frida-gadget-15.1.10-android-x86.so.xz

Move that file to the lib/x86_64/ folder, you should add lib in front of that filename because sometimes the app can crash. (libfrida-gadget.so).

Add this code to MainActivity.smali file.

const-string v0, "frida-gadget"
invoke-static {v0}, Ljava/lang/System;->loadLibrary(Ljava/lang/String;)V

And then rebuild the apk with apktool

apktool b injuredAndroid -o injured_patch.apk

Note: add this first if it's not already there.In this case we already have this.

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

Signing The APK

# create keystore
keytool -genkey -v -keystore demo.keystore -alias demokeys -keyalg RSA -keysize 2048 -validity 10000
# sign the apk
jarsigner -sigalg SHA1withRSA -digestalg SHA1 -keystore demo.keystore -storepass demopass injured_patch.apk demokeys
# verify the signature
jarsigner -verify injured_patch.apk
# zipalign the APK
zipalign 4 injured_patch.apk injured_path_final.apk

Install the apk in enumerator and then when you open that you will see white screen for a little while and type this command to hook with frida.

objection explore

Insecure Logging

• > adb logcat -c (clear the log)

• > adb logcat | grep "password"

Drozer usage

Port Forward

adb forward tcp:31415 tcp:31415

Connect Drozer

drozer console connect

Show App Info

run app.package.info -a com.android.insecurebankv2

Show Activity Info

run app.activity.info -a com.android.insecurebankv2

Show Content Provider

run app.provider.finduri com.android.insecurebankv2

Check Vulnerable Injection in Content Provider

run scanner.provider.injection -a com.android.insecurebankv2

Show Broadcast Receiver

run app.broadcast.info -a com.android.insecurebankv2 -i

run app.broadcast.send --action theBroadcast --extra string 095634534345 --extra string newpass NewPassword

run app.package.attacksurface com.android.insecurebankv2

Run Acitivity Directly

run app.activity.start --component com.android.insecurebankv2 com.android.insecurebankv2.ViewStatement run activity directly

ADB

Insecure Login Mechanism

$ adb shell am start -n com.android.insecurebankv2/com.android.insecurebankv2.PostLogin

• When backupallow is true , we can backup data even we don't have root privilege.

Tool to extract that backup file

https://github.com/nelenkov/android-backup-extractor

$ adb backup com.android.insecurebankv2

Checking Log

$ adb logcat | grep "$(adb shell ps | grep com.android.insecurebankv2 | awk '{print $2}')"

Can also use pidcat

pidcat [packageName]

Will update more.