Android Applications Pentesting
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It's highly recommended to start reading this page to know about the most important parts related to Android security and the most dangerous components in an Android application:
This is the main tool you need to connect to an android device (emulated or physical). It allows you to control your device over USB or Network from a computer, copy files back and forth, install and uninstall apps, run shell commands, perform backups, read logs and more.
Take a look to the following list of _**_to learn how to use adb.
Sometimes it is interesting to modify the application code to access hidden information (maybe well obfuscated passwords or flags). Then, it could be interesting to decompile the apk, modify the code and recompile it. . This could be very useful as an alternative for several tests during the dynamic analysis that are going to presented. Then, keep always in mid this possibility.
Download APKs: , , ,
First of all, check if the application is debuggeable. A production APK shouldn't be (or others will be able to connect to it). You can check if an application is debbugeable looking in the manifest for the attribute debuggable="true" inside the tag <application Example: <application theme="@2131296387" debuggable="true"
Backup: The android:allowBackup attribute defines whether application data can be backed up and restored by a user who has enabled usb debugging. If backup flag is set to true, it allows an attacker to take the backup of the application data via adb even if the device is not rooted. Therefore applications that handle and store sensitive information such as card details, passwords etc. should have this setting explicitly set to false because by default it is set to true to prevent such risks.
<application android:allowBackup="false"
NetworkSecurity: The application network security can be overwritten the defaults values with android:networkSecurityConfig="@xml/network_security_config". A file with that name may be put in res/xml. This file will configure important security settings like certificate pins or if it allows HTTP traffic. You can read here more information about all the things that can be configure, but check this example about how to configure HTTP traffic for some domains:
<domain-config cleartextTrafficPermitted="true"> <domain includeSubdomains="true">formation-software.co.uk </domain></domain-config>
minSdkVersion, targetSDKVersion, maxSdkVersion: They indicate the versions of Android the app will run on. It's important to keep them in mind because from a security perspective, supporting old version will allow known vulnerable versions of android to run it.
Reading resources.arsc/strings.xml you can find some interesting info:
API Keys
Custom schemas
Other interesting info developers save in this file
Tapjacking is an attack where a malicious application is launched and positions itself on top of a victim application. Once it visibly obscures the victim app, its user interface is designed in such a way as to trick the user to interact with it, while it is passing the interaction along to the victim app. In effect, it is blinding the user from knowing they are actually performing actions on the victim app.
In order to detect apps vulnerable to this attacked you should search for exported activities in the android manifest (note that an activity with an intent-filter is automatically exported by default). Once you have found the exported activities, check if they require any permission. This is because the malicious application will need that permission also.
Finally, it's important to check the code for possible setFilterTouchesWhenObscured configurations. If set to true, a button can be automatically disabled if it is obscured:
Sometimes it is essential that an application be able to verify that an action is being performed with the full knowledge and consent of the user, such as granting a permission request, making a purchase or clicking on an advertisement. Unfortunately, a malicious application could try to spoof the user into performing these actions, unaware, by concealing the intended purpose of the view. As a remedy, the framework offers a touch filtering mechanism that can be used to improve the security of views that provide access to sensitive functionality.
External storage can be accessed in /storage/emulated/0 , /sdcard , /mnt/sdcard
Shared preferences: Android allow to each application to easily save xml files in the path /data/data/<packagename>/shared_prefs/ and sometimes it's possible to find sensitive information in clear-text in that folder.
Databases: Android allow to each application to easily save sqlite databases in the path /data/data/<packagename>/databases/ and sometimes it's possible to find sensitive information in clear-text in that folder.
For some reason sometimes developers accept all the certificates even if for example the hostname does not match with lines of code like the following one:
A good way to test this is to try to capture the traffic using some proxy like Burp without authorising Burp CA inside the device. Also, you can generate with Burp a certificate for a different hostname and use it.
Some developers save sensitive data in the local storage and encrypt it with a key hardcoded/predictable in the code. This shouldn't be done as some reversing could allow attackers to extract the confidential information.
Developers shouldn't use deprecated algorithms to perform authorisation checks, store or send data. Some of these algorithms are: RC4, MD4, MD5, SHA1... If hashes are used to store passwords for example, hashes brute-force resistant should be used with salt.
It's recommended to obfuscate the APK to difficult the reverse engineer labour to attackers.
If the app is sensitive (like bank apps), it should perform it's own checks to see if the mobile is rooted and act in consequence.
If the app is sensitive (like bank apps), it should check if an emulator is being used.
If the app is sensitive (like bank apps), it should check it's own integrity before executing it to check if it was modified.
Read the following page to learn how to easily access javascript code of React applications:
Xamarin apps are written in C#, in order to access the C# code decompressed, you need to get the files from the apk:
Code execution: Runtime.exec(), ProcessBuilder(), native code:system()
Send SMSs: sendTextMessage, sendMultipartTestMessage
Native functions declared as native: public native, System.loadLibrary, System.load
First of all, you need an environment where you can install the application and all the environment (Burp CA cert, Drozer and Frida mainly). Therefore, a rooted device (emulated or not) is extremely recommended.
You can even see the logs of your application in the web and connect through adb.
Thanks to the ADB connection you can use Drozer and Frida inside the emulators.
You can use some emulator like:
If you want to try to install an image and then you want to delete it you can do that on Windows:C:\Users\<User>\AppData\Local\Android\sdk\system-images\ or Mac: /Users/myeongsic/Library/Android/sdk/system-image
As most people will use Genymotion, note this trick. To install google services (like AppStore) you need to click on the red marked button of the following image:
Also, notice that in the configuration of the Android VM in Genymotion you can select Bridge Network mode (this will be useful if you will be connecting to the Android VM from a different VM with the tools).
Or you could use a physical device (you need to activate the debugging options and it will be cool if you can root it):
Settings.
(FromAndroid 8.0) Select System.
Select About phone.
Press Build number 7 times.
Go back and you will find the Developer options.
Once you have installed the application, the first thing you should do is to try it and investigate what does it do, how does it work and get comfortable with it. I will suggest to perform this initial dynamic analysis using MobSF dynamic analysis + pidcat, so will will be able to learn how the application works while MobSF capture a lot of interesting data you can review later on.
Note that from later versions that Android 4.0, applications are only able to access their own logs. So applications cannot access other apps logs. Anyway, it's still recommended to not log sensitive information.
Copy/Paste Buffer Caching
Android provides clipboard-based framework to provide copy-paste function in android applications. But this creates serious issue when some other application can access the clipboard which contain some sensitive data. Copy/Paste function should be disabled for sensitive part of the application. For example, disable copying credit card details.
If an application crashes during runtime and it saves logs somewhere then those logs can be of help to an attacker especially in cases when android application cannot be reverse engineered. Then, avoid creating logs when applications crashes and if logs are sent over the network then ensure that they are sent over an SSL channel. As pentester, try to take a look to these logs.
Most of the application uses other services in their application like Google Adsense but sometimes they leak some sensitive data or the data which is not required to sent to that service. This may happen because of the developer not implementing feature properly. You can look by intercepting the traffic of the application and see whether any sensitive data is sent to 3rd parties or not.
Most of the applications will use internal SQLite databases to save information. During the pentest take a look to the databases created, the names of tables and columns and all the data saved because you could find sensitive information (which would be a vulnerability).
Databases should be located in /data/data/the.package.name/databases like /data/data/com.mwr.example.sieve/databases
If the database is saving confidential information and is encrypted but you can find the password inside the application it's still a vulnerability.
Enumerate the tables using .tables and enumerate the columns of the tables doing .schema <table_name>
You can also start an exported activity from adb:
PackageName is com.example.demo
Exported ActivityName is com.example.test.MainActivity
Sensitive information leakage
Activities can also return results. If you manage to find an exported and unprotected activity calling the setResult method and returning sensitive information, there is a sensitive information leakage.
Note that you can omit the package name and the mobile will automatically call the app that should open that link.
In order to find the code that will be executed in the App, go to the activity called by the deeplink and search the function onNewIntent.
Every time you find a deep link check that it's not receiving sensitive data (like passwords) via URL parameters, because any other application could impersonate the deep link and steal that data!
Lack of Certificate Inspection: Android Application fails to verify the identity of the certificate presented to it. Most of the application ignore the warnings and accept any self-signed certificate presented. Some Application instead pass the traffic through an HTTP connection.
Weak Handshake Negotiation: Application and server perform an SSL/TLS handshake but use an insecure cipher suite which is vulnerable to MITM attacks. So any attacker can easily decrypt that connection.
Privacy Information Leakage: Most of the times it happens that Applications do authentication through a secure channel but rest all connection through non-secure channel. That doesn’t add to security of application because rest sensitive data like session cookie or user data can be intercepted by an malicious user.
By default, when making an SSL connection, the client(android app) checks that the server’s certificate has a verifiable chain of trust back to a trusted (root) certificate and matches the requested hostname. This lead to problem of Man in the Middle Attacks(MITM). In certificate Pinnning, an Android Application itself contains the certificate of server and only transmit data if the same certificate is presented. It's recommended to apply SSL Pinning for the sites where sensitive information is going to be sent.
For applications targeting API Level 24+ it isn't enough to install the Burp CA certificate in the device. To bypass this new protection you need to modify the Network Security Config file. So, you could modify this file to authorise your CA certificate or you can **[read this page for a tutorial on how to force the application to accept again all the installed certificate sin the device](make-apk-accept-ca-certificate.md).**
We have already discuss what is SSL Pinning just 2 paragraphs before. When it's implemented in an application you will need to bypass it to inspect the HTTPS traffic or you won't see it. Here I'm going to present a few options I've used to bypass this protection:
You can also try to automatically bypass SSL Pinning using MobSF dynamic analysis (explained below)
Note that in this step you should look for common web vulnerabilities. A lot of information about web vulnerabilities be found in this book so I'm not going to mention them here.
This vulnerability resembles Open Redirect in web security. Since class Intent is Parcelable, objects belonging to this class can be passed as extra data in another Intent object.
Many developers make use of this feature and create proxy components (activities, broadcast receivers and services) that take an embedded Intent and pass it to dangerous methods like startActivity(...), sendBroadcast(...), etc.
This is dangerous because an attacker can force the app to launch a non-exported component that cannot be launched directly from another app, or to grant the attacker access to its content providers. WebView also sometimes changes a URL from a string to an Intent object, using the Intent.parseUri(...) method, and passes it to startActivity(...).
Probably you know about this kind of vulnerabilities from the Web. You have to be specially careful with this vulnerabilities in an Android application:
SQL Injection: When dealing with dynamic queries or Content-Providers ensure you are using parameterized queries.
Eternal cookies: In several cases when the android application finish the session the cookie isn't revoked or it could be even saved to disk
Vulnerability assessment of the application using a nice web-based frontend. You can also perform dynamic analysis (but you need to prepare the environment).
Notice that MobSF can analyse Android(apk), IOS(ipa) and Windows(apx) applications (Windows applications must be analyzed from a MobSF installed in a Windows host). Also, if you create a ZIP file with the source code if an Android or an IOS app (go to the root folder of the application, select everything and create a ZIPfile), it will be able to analyse it also.
MobSF also allows you to diff/Compare analysis and to integrate VirusTotal (you will need to set your API key in MobSF/settings.py and enable it: VT_ENABLED = TRUE VT_API_KEY = <Your API key> VT_UPLOAD = TRUE). You can also set VT_UPLOAD to False, then the hash will be upload instead of the file.
MobSF can also be very helpful for dynamic analysis in Android, but in that case you will need to install MobSF and genymotion in your host (a VM or Docker won't work). Note: You need to start first a VM in genymotion and then MobSF. The MobSF dynamic analyser can:
Dump application data (URLs, logs, clipboard, screenshots made by you, screenshots made by "Exported Activity Tester", emails, SQLite databases, XML files, and other created files). All of this is done automatically except for the screenshots, you need to press when you want a screenshot or you need to press "Exported Activity Tester" to obtain screenshots of all the exported activities.
Capture HTTPS traffic
Use Frida to obtain runtime information
From android versions > 5, it will automatically start Frida and will set global proxy settings to capture traffic. It will only capture traffic from the tested application.
Frida
By default, it will also use some Frida Scripts to bypass SSL pinning, root detection and debugger detection and to monitor interesting APIs. MobSF can also invoke exported activities, grab screenshots of them and save them for the report.
To start the dynamic testing press the green bottom: "Start Instrumentation". Press the "Frida Live Logs" to see the logs generated by the Frida scripts and "Live API Monitor" to see all the invocation to hooked methods, arguments passed and returned values (this will appear after pressing "Start Instrumentation").
MobSF also allows you to load your own Frida scripts (to send the results of your Friday scripts to MobSF use the function send()). It also has several pre-written scripts you can load (you can add more in MobSF/DynamicAnalyzer/tools/frida_scripts/others/), just select them, press "Load" and press "Start Instrumentation" (you will be able to see the logs of that scripts inside "Frida Live Logs").
Moreover, you have some Auxiliary Frida functionalities:
Enumerate Loaded Classes: It will print all the loaded classes
Capture Strings: It will print all the capture strings while using the application (super noisy)
Capture String Comparisons: Could be very useful. It will show the 2 strings being compared and if the result was True or False.
Enumerate Class Methods: Put the class name (like "java.io.File") and it will print all the methods of the class.
Search Class Pattern: Search classes by pattern
Trace Class Methods: Trace a whole class (see inputs and outputs of all methods of th class). Remember that by default MobSF traces several interesting Android Api methods.
Once you have selected the auxiliary module you want to use you need to press "Start Intrumentation" and you will see all the outputs in "Frida Live Logs".
Shell
Mobsf also brings you a shell with some adb commands, MobSF commands, and common shell commands at the bottom of the dynamic analysis page. Some interesting commands:
HTTP tools
Once you finish the dynamic analysis with MobSF you can press on "Start Web API Fuzzer" to fuzz http requests an look for vulnerabilities.
This is a great tool to perform static analysis with a GUI
This tool is designed to look for several security related Android application vulnerabilities, either in source code or packaged APKs. The tool is also capable of creating a "Proof-of-Concept" deployable APK and ADB commands, to exploit some of the found vulnerabilities (Exposed activities, intents, tapjacking...). As with Drozer, there is no need to root the test device.
Displays all extracted files for easy reference
Automatically decompile APK files to Java and Smali format
Analyze AndroidManifest.xml for common vulnerabilities and behavior
Static source code analysis for common vulnerabilities and behavior
Device info
Intents
Command execution
SQLite references
Logging references
Content providers
Broadcast recievers
Service references
File references
Crypto references
Hardcoded secrets
URL's
Network connections
SSL references
WebView references
SUPER is a command-line application that can be used in Windows, MacOS X and Linux, that analyzes .apk files in search for vulnerabilities. It does this by decompressing APKs and applying a series of rules to detect those vulnerabilities.
All rules are centered in a rules.json file, and each company or tester could create its own rules to analyze what they need.
The concept is that you drag and drop your mobile application file (an .apk or .ipa file) on the StaCoAn application and it will generate a visual and portable report for you. You can tweak the settings and wordlists to get a customized experience.
Androwarn is a tool whose main aim is to detect and warn the user about potential malicious behaviours developped by an Android application.
This tool looks for common behavior of "bad" applications like: Telephony identifiers exfiltration, Audio/video flow interception, PIM data modification, Arbitrary code execution...
MARA is a Mobile Application Reverse engineering and Analysis Framework. It is a tool that puts together commonly used mobile application reverse engineering and analysis tools, to assist in testing mobile applications against the OWASP mobile security threats. Its objective is to make this task easier and friendlier to mobile application developers and security professionals.
It is able to:
Extract Java and Smali code using different tools
Extract private information from the APK using regexps.
Analyze the Manifest.
Note that depending the service and configuration you use to obfuscate the code. Secrets may or may not ended obfuscated.
ProGuard is an open source command-line tool that shrinks, optimizes and obfuscates Java code. It is able to optimize bytecode as well as detect and remove unused instructions. ProGuard is free software and is distributed under the GNU General Public License, version 2.
ProGuard is distributed as part of the Android SDK and runs when building the application in release mode.
You can upload an obfuscated APK to their platform.
It is a generic android deobfuscator. Simplify virtually executes an app to understand its behavior and then tries to optimize the code so it behaves identically but is easier for a human to understand. Each optimization type is simple and generic, so it doesn't matter what the specific type of obfuscation is used.
AndroL4b is an Android security virtual machine based on ubuntu-mate includes the collection of latest framework, tutorials and labs from different security geeks and researchers for reverse engineering and malware analysis.
For more information visit:
First of all, for analysing an APK you should take a look to the to the Java code using a decompiler. Please, .
Just taking a look to the strings of the APK you can search for passwords, URLs (), api keys, encryption, bluetooth uuids, tokens and anything interesting... look even for code execution backdoors or authentication backdoors (hardcoded admin credentials to the app).
Pay special attention to firebase URLs and check if it is bad configured.
Using any of the decompilers mentioned you will be able to read the Manifest.xml. You could also rename the apk file extension to .zip and unzip it. Reading the manifest you can find vulnerabilities:
how to find debuggeable applications in a phone and exploit them
Exported activities: Check for exported activities inside the manifest as this could be dangerous. Later in the dynamic analysis it will be explained how .
Content Providers: If an exported provider is being exposed, you could b able to access/modify interesting information. In dynamic analysis .
Check for FileProviders configurations inside the attribute android:name="android.support.FILE_PROVIDER_PATHS". .
Exposed Services: Depending on what the service is doing internally vulnerabilities could be exploited. In dynamic analysis .
Broadcast Receivers: during the dynamic analysis.
URL scheme: Read the code of the activity managing the schema and look for vulnerabilities managing the input of the user. More info about .
You can use with the --exploit-apk parameter to create a malicious application to test for possible Tapjacking vulnerabilities.
A example project implementing this kind of feature can be fund in .
The mitigation is relatively simple as the developer may choose not to receive touch events when a view is covered by another. Using the :
To enable touch filtering, call or set the android:filterTouchesWhenObscured layout attribute to true. When enabled, the framework will discard touches that are received whenever the view's window is obscured by another visible window. As a result, the view will not receive touches whenever a toast, dialog or other window appears above the view's window.
Files created on internal storage are accessible only by the app. This protection is implemented by Android and is sufficient for most applications. But developers often use MODE_WORLD_READBALE & MODE_WORLD_WRITABLE to give access to those files to a different application, but this doesn’t limit other apps(malicious) from accessing them.
During the static analysis check for the use of those modes, during the dynamic analysis check the permissions of the files created (maybe some of them are worldwide readable/writable).
Files created on external storage, such as SD Cards, are globally readable and writable. Because external storage can be removed by the user and also modified by any application, you should not store sensitive information using external storage. As with data from any untrusted source, you should perform input validation when handling data from external storage. We strongly recommend that you not store executables or class files on external storage prior to dynamic loading. If your app does retrieve executable files from external storage, the files should be signed and cryptographically verified prior to dynamic loading. Info taken from .
Use to check which compiler/packer/obfuscator was used to build the APK
Then, decompress all the DLsL using :
and finally you can use to read C# code from the DLLs.
You can create a free account in: . This platform allows you to upload and execute APKs, so it is useful to see how an apk is behaving.
(You can create x86 and arm devices, and according to latest x86 versions support ARM libraries without needing an slow arm emulator).
This is the main emulator I recommend to use and you can.
**** **(_Free version: Personal Edition, you need to create an account**._)
**** (Free, but it doesn't support Frida or Drozer).
Often Developers leave debugging information publicly. So any application with READ_LOGS permission can access those logs and can gain sensitive information through that.
While navigating through the application use (Recommended, it's easier to use and read) or to read the created logs and look for sensitive information.
Drozer allows you to assume the role of an Android app and interact with other apps. It can do anything that an installed application can do, such as make use of Android’s Inter-Process Communication (IPC) mechanism and interact with the underlying operating system. From . Drozer is s useful tool to exploit exported activities, exported services and Content Providers as you will learn in the following sections.
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_**_Also remember that the code of an activity starts with the onCreate method.
When an Activity is exported you can invoke its screen from an external app. Therefore, if an activity with sensitive information is exported you could bypass the authentication mechanisms to access it. ****
NOTE: MobSF will detect as malicious the use of singleTask/singleInstance as android:launchMode in an activity, but due to , apparently this is only dangerous on old versions (API versions < 21).
**** Content providers are basically used to share data. If an app has available content providers you may be able to extract sensitive data from them. It also interesting to test possible SQL injections and Path Traversals as they could be vulnerable. ****
_**_Remember that a the actions of a Service start in the method onStartCommand.
As service is basically something that can receive data, process it and returns (or not) a response. Then, if an application is exporting some services you should check the code to understand what is it doing and test it dynamically for extracting confidential info, bypassing authentication measures... ****
_**_Remember that a the actions of a Broadcast Receiver start in the method onReceive.
A broadcast receiver will be waiting for a type of message. Depending on ho the receiver handles the message it could be vulnerable.
You can look for deep links manually, using tools like MobSF or scripts like . You can open a declared scheme using adb or a browser:
You must check also if any deep link is using a parameter inside the path of the URL like: https://api.example.com/v1/users/{username} , in that case you can force a path traversal accessing something like: example://app/users?username=../../unwanted-endpoint%3fparam=value .
Note that if you find the correct endpoints inside the application you may be able to cause a Open Redirect (if part of the path is used as domain name), account takeover (if you can modify users details without CSRF token and the vuln endpoint used the correct method) and any other vuln. More .
An about links (/.well-known/assetlinks.json).
From the 3 scenarios presented we are going to discuss how to verify the identity of the certificate. The other 2 scenarios depends on the TLS configuration of the server and if the application sends unencrypted data. The pentester should check by it's own the TLS configuration of the server () and detect if any confidential information is sent by an unencrypted/vulnerable channel . More information about how to discover and fix these kind of vulnerabilities .
First of all, you should (must) install the certificate of the proxy tool that you are going to use, probably Burp. If you don't install the CA certificate of the proxy tool, you probably aren't going to see the encrypted traffic in the proxy. Please, .
Automatically modify the apk to bypass SSLPinning with . The best pro of this option, is that you won't need root to bypass the SSL Pinning, but you will need to delete the application and reinstall the new one, and this won't always work.
You could use Frida (discussed below) to bypass this protection. Here you have a guide to use Burp+Frida+Genymotion:
You can also try to automatically bypass SSL Pinning using : objection --gadget com.package.app explore --startup-command "android sslpinning disable"
Dynamic instrumentation toolkit for developers, reverse-engineers, and security researchers. Learn more at . It's amazing, you can access running application and hook methods on run time to change the behaviour, change values, extract values, run different code... If you want to pentest Android applications you need to know how to use Frida.
Learn how to use Frida: Some "GUI" for actions with Frida: Some other abstractions based on Frida: , You can find some Awesome Frida scripts here: ****
This tool could help you managing different tools during the dynamic analysis:
JavaScript Injection (XSS): Verify that JavaScript and Plugin support is disabled for any WebViews (disabled by default). .
Local File Inclusion: Verify that File System Access is disabled for any WebViews (enabled by default) (webview.getSettings().setAllowFileAccess(false);). .
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When http traffic is capture you can see an ugly view of the captured traffic on "HTTP(S) Traffic" bottom or a nicer view in "Start HTTPTools" green bottom. From the second option, you can send the captured requests to proxies like Burp or Owasp ZAP. To do so, power on Burp --> turn off Intercept --> in MobSB HTTPTools select the request --> press "Send to Fuzzer" --> select the proxy address (.
You can get the tool from . This tool with use some Hooks to let you know what is happening in the application while you perform a dynamic analysis.
Download the latest binaries from in the
StaCoAn is a crossplatform tool which aids developers, bugbounty hunters and ethical hackers performing on mobile applications*.
Download:
AndroBugs Framework is an Android vulnerability analysis system that helps developers or hackers find potential security vulnerabilities in Android applications.
The detection is performed with the static analysis of the application's Dalvik bytecode, represented as Smali, with the library.
Analyze APKs using: , , , ,
Analyze found domains using: , and
Deobfuscate APK via
Useful to detect malware:
From:
APKiD gives you information about how an APK was made. It identifies many compilers, packers, obfuscators, and other weird stuff. It's for Android.
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It is a great list of resources
Android quick course
