Category: HackTheBox

For this years halloween I decided to participate in the Hack The Boo CTF competition from Hack the Box. Despite this being my first solo public CTF competition, I still managed to climb to leaderboards and reach top 50 (48th to be exact). In total I managed to capture 7 out of the 10 flags, some easier than others. In this post I will delve into how I managed to solve the forensics and web challenges, as those where the areas my skills stuck out the most.

Tasked with defending the antidote's research, a diverse group of students united against a relentless cyber onslaught. As codes clashed and defenses were

Administrator is a medium-difficulty Windows machine designed around a complete domain compromise scenario, where credentials for a low-privileged user are provided. To gain access to the michael account, ACLs (Access Control Lists) over privileged objects are enumerated, leading us to discover that the user olivia has GenericAll permissions over michael, allowing us to reset his password. With access as michael, it is revealed that he can force a password change on the user benjamin, whose password is reset. This grants access to FTP where a backup.psafe3 file is discovered, cracked, and reveals credentials for several users. These credentials are sprayed across the domain, revealing valid credentials for the user emily. Further enumeration shows that emily has GenericWrite permissions over the user ethan, allowing us to perform a targeted Kerberoasting attack. The recovered hash is cracked and reveals valid credentials for ethan, who is found to have DCSync rights ultimately allowing retrieval of the Administrator account hash and full domain compromise.

Blazorized is a Windows machine, starting with a website written using the Blazor .NET framework that allows downloading a DLL file that can be reverse engineered to find a JWT secret and use it to get access to the admin panel. The admin panel is vulnerable to an SQL injection to get code execution. To pivot to the next user, the WriteSPN privilege can be abused to perform a targeted Kerberoast attack on another user. The targeted user is able to write a logon script that ultimately gives access to a user that allows performing a DCSync attack on the domain.

Checker is a hard-level Linux machine running Teampass and Bookstack on separate ports. The Teampass version has a SQL injection vulnerability CVE-2023-1545 that can be exploited to obtain user password hashes. By cracking these hashes, we get the password for the Teampass user bob. Logging into Teampass reveals credentials for both Bookstack user bob and the SSH user reader. Attempting SSH login as reader user shows that two-factor authentication is enabled. Meanwhile, the Bookstack version is vulnerable to CVE-2023-6199, a local file read flaw via Blind SSRF, which can be exploited to retrieve the 2FA secret key for the reader user’s SSH account, enabling successful SSH login. We reverse engineer a binary for privilege escalation to root to discover a command injection vulnerability, which we then exploit using a custom script.

We start with a quick nmap scan and see that there are only two ports open.

Infiltrator is an Insane Windows Active Directory machine that starts with a website that an attacker can scrape for possible usernames on the machine. One user doesn't have Kerberos pre-authentication enabled, and his password can be cracked. Afterwards, an intricate attack chain focused on Active Directory permissions allows the attacker to get access to the machine over WinRM as the user M.harris. Once on the machine, the attacker can identify that the whole company communicates through the Output Messenger application. Infiltrating the application, switching users, reverse engineering a binary, and using the application's API, he can eventually land a shell as the user O.martinez on the remote machine. Afterwards, he discovers a network capture file with a backup archive and a BitLocker volume recovery key. Unlocking the volume, another backup folder contains an ntds.dit file from which he can read sensitive user information and find a valid password for the user lan_managment. This new user can read the GMSA password of the user infiltrator_svc$. This last user can exploit a vulnerable ESC4 certificate template. Finally, he can get the Administrator's hash and compromise the whole domain through the certificate exploitation.

The "Office" machine on HackTheBox is a challenging Windows-based environment that incorporates a variety of vulnerabilities. These include exploiting a Joomla web application, analyzing PCAP files to extract Kerberos credentials, leveraging LibreOffice macros by manipulating registry settings, abusing MSKRP to dump DPAPI credentials, and exploiting Group Policies due to excessive privileges in Active Directory.

TheFrizz is a medium-difficulty Windows machine featuring a web application showcasing Walkerville Elementary School and a Gibbon CMS instance. The Gibbon-LMS instance is susceptible to unauthenticated arbitrary file write (CVE-2023-45878), which is used to write a PHP shell to the web application and gain access to the target. After gaining access to the system, a database settings file containing credentials to access MySQL includes a hash and salt for the user f.frizzle that can be cracked. After cracking the password, we authenticate to the target using SSH with GSSAPI/Kerberos. We request a TGT, which is then used to authenticate via Kerberos authentication. A deleted 7Zip archive is discovered in the fiona user's recycling bin which is extracted revealing a WAPT setup and includes a configuration file with base64-encoded credentials used to authenticate as the M.Schoolbus user. M.Schoolbus is a member of the Group Policy Creator Owners, which allows them to create GPOs within the domain, which is leveraged to escalate privileges to NT Authority\System.

University is an Insane Windows Active Directory machine that starts with a university webpage. The web application allows exporting user profile pages to

Vintage is a hard difficulty Windows machine designed around an assumed breach scenario, where the attacker is provided with low-privileged user credentials. The machine features an Active Directory environment without ADCS installed, and NTLM authentication is disabled. There is a 'Pre-Created computer account', meaning the password is the same as the sAMAccountName of the machine account. The 'Domain Computer' organisational unit (OU) has a configuration allowing attackers to read the service account password, which has gMSA configured. After obtaining the password, the service account can add itself to a privileged group. The group has complete control over a disabled user. The attacker is supposed to restore the disabled user and set a Service Principal Name (SPN) to perform Kerberoasting. After recovering the password, the user account has reused the same password. The newly compromised user has a password stored in the Credential Manager. The user can add itself to another privileged group configured for Resource-Based Constrained Delegation (RBCD) on the Domain Controller, allowing the attacker to compromise it.

Yummy is a hard box that starts with a Restaurant web app using Caddy web service, on port 80, where an attacker finds an arbitrary file read HTTP Location header, which is not handled and sanitized properly by the default Caddy configuration. This allows an attacker to find several cronjob scripts that allow downloading the web app source code. Reading the source code, the web app uses JWT RSA keypairs to forge an admin token and escalate privileges on the web app. The admin panel has an SQL injection, allowing arbitrary file write over a file running periodically (cronjob). Improper directory permissions allow the attacker to move laterally to www-data and eventually a dev user. The dev user can execute rsync binary as root, which helps escalate privileges to root.

With the increasing use of open-source Command and Control (C2) frameworks by threat actors, it has become crucial for blue teams to develop strategies to detect and mitigate these threats. In this exercise, our red team simulated an attack using a popular open-source C2 framework to help improve defenses. We were provided with PCAP files, EVTX logs, and API traces, which we will analyze to uncover the attack's methodology.