|Intermediate||18 July 2019||Zayotic|
This box had quite a good number of misconfigurations and vulnerabilities. Initial access was through copying a shadow backup file to a smb share accessible anonymously using a file copy vulnerability in proftpd. Then lateral movement and privilege escalation was achieved by exploiting rce a locally running librenms instance and finally abusing sudo permissions on mysql to get root.
Nmap scan report for 192.168.191.129 Host is up (0.00028s latency). PORT STATE SERVICE VERSION 21/tcp open ftp ProFTPD 1.3.5 22/tcp open ssh OpenSSH 7.4p1 Debian 10+deb9u6 (protocol 2.0) | ssh-hostkey: | 2048 9d:f8:5f:87:20:e5:8c:fa:68:47:7d:71:62:08:ad:b9 (RSA) | 256 04:2a:bb:06:56:ea:d1:93:1c:d2:78:0a:00:46:9d:85 (ECDSA) |_ 256 28:ad:ac:dc:7e:2a:1c:f6:4c:6b:47:f2:d6:22:5b:52 (ED25519) 80/tcp open http WebFS httpd 1.21 |_http-server-header: webfs/1.21 |_http-title: Site doesn't have a title (text/html). 139/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP) 445/tcp open netbios-ssn Samba smbd 4.5.16-Debian (workgroup: WORKGROUP) Service Info: Host: SYMFONOS2; OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel Host script results: |_clock-skew: mean: 2h00m00s, deviation: 3h27m51s, median: 0s |_nbstat: NetBIOS name: SYMFONOS2, NetBIOS user: <unknown>, NetBIOS MAC: <unknown> (unknown) | smb-os-discovery: | OS: Windows 6.1 (Samba 4.5.16-Debian) | Computer name: symfonos2 | NetBIOS computer name: SYMFONOS2\x00 | Domain name: \x00 | FQDN: symfonos2 |_ System time: 2021-01-25T07:02:21-06:00 | smb-security-mode: | account_used: guest | authentication_level: user | challenge_response: supported |_ message_signing: disabled (dangerous, but default) | smb2-security-mode: | 2.02: |_ Message signing enabled but not required | smb2-time: | date: 2021-01-25T13:02:21 |_ start_date: N/A
Running smbmap on the target we see we can access the anonymous share without credentials:
smbmap -R -H 192.168.191.129
Using smbclient to download log.txt from the anonymous share.
smbclient \\\\192.168.191.129\\anonymous -N -c 'get backups\log.txt log.txt'
From log.txt, we discover a backup of the shadow file is created in /var/backups/
Checking for known vulnerabilities of the proftp version using searchsploit, we find several.
The command execution exploits available rely on creating a php file on the existing webserver that would be executed. However, the web server is running webfs which only serves static content.
We can only take advantage of the file copy vulnerability. From log.txt, the smb configuration gives the location of the anonymous share:
We can exfiltrate information to the anonymous share by exploiting file copy on proftpd. Using the PoC shown here https://www.exploit-db.com/exploits/36742 , let’s get the shadow.bak file. You can either use netcat or telnet. In this case I use netcat.
nc -vn 192.168.191.129 21
Running smbmap command again we see that we have shadow.bak file.
Shell as aeolus⌗
After downloading the shadow file from the smb we can crack it with john and rockyou wordlist.
john --wordlist=/usr/share/wordlists/rockyou.txt shadow.bak
Using sergioteamo as the password we can access ssh as aeolus.
Doing some basic manual enumeration, we see some ports listening on localhost.
8080 would most likely be a webserver, so I’ll tunnel to it first using an ssh port forward.
ssh -L 8000:127.0.0.1:8080 email@example.com
When we visit http://127.0.0.1:8000 on the browser, we find that LibreNMS is running here.
Using searchsploit again we find two existing vulnerabilities for version 1.46.
Since we can’t verify the version of librenms currently running, we’ll try the exploits and see if they work. I’ll go for the RCE.
Using the exploit script provided here https://www.exploit-db.com/exploits/47044 , we need to provide url, session cookies, rhost and rport where the reverse shell will be received.
Login using the earlier discovered credentials aeolus : sergioteamo, then retrieve the cookies using burpsuite.
Run the exploit as below and catch the reverse shell using netcat.
We are now the cronus user.
Getting a root shell⌗
Running sudo -l reveals cronus can run mysql as root with no password.
Dropping into mysql as root user, we can get a root shell using the below command.
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