Single-byte XOR Countdown Encoder - Metasploit


This page contains detailed information about how to use the encoder/x86/countdown metasploit module. For list of all metasploit modules, visit the Metasploit Module Library.

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Module Overview

Name: Single-byte XOR Countdown Encoder
Module: encoder/x86/countdown
Source code: modules/encoders/x86/countdown.rb
Disclosure date: -
Last modification time: 2018-09-01 02:40:26 +0000
Supported architecture(s): x86
Supported platform(s): All
Target service / protocol: -
Target network port(s): -
List of CVEs: -

This encoder uses the length of the payload as a position-dependent encoder key to produce a small decoder stub.

Module Ranking and Traits

Module Ranking:

  • normal: The exploit is otherwise reliable, but depends on a specific version and can't (or doesn't) reliably autodetect. More information about ranking can be found here.

Basic Usage

msf > use encoder/x86/countdown
msf encoder(countdown) > show targets
    ... a list of targets ...
msf encoder(countdown) > set TARGET target-id
msf encoder(countdown) > show options
    ... show and set options ...
msf encoder(countdown) > exploit

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Msfconsole Usage

Here is how the encoder/x86/countdown module looks in the msfconsole:

msf6 > use encoder/x86/countdown

msf6 encoder(x86/countdown) > show info

       Name: Single-byte XOR Countdown Encoder
     Module: encoder/x86/countdown
   Platform: All
       Arch: x86
       Rank: Normal

Provided by:
  vlad902 <[email protected]>

Description:
  This encoder uses the length of the payload as a position-dependent 
  encoder key to produce a small decoder stub.

Module Options

This is a complete list of options available in the encoder/x86/countdown module:

msf6 encoder(x86/countdown) > show options

Module options (encoder/x86/countdown):

   Name  Current Setting  Required  Description
   ----  ---------------  --------  -----------

Advanced Options

Here is a complete list of advanced options supported by the encoder/x86/countdown module:

msf6 encoder(x86/countdown) > show advanced

Module advanced options (encoder/x86/countdown):

   Name       Current Setting  Required  Description
   ----       ---------------  --------  -----------
   VERBOSE    false            no        Enable detailed status messages
   WORKSPACE                   no        Specify the workspace for this module

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Error Messages

This module may fail with the following error messages:

Error Messages

Check for the possible causes from the code snippets below found in the module source code. This can often times help in identifying the root cause of the problem.

No valid set instruction could be created!

Here is a relevant code snippet related to the "No valid set instruction could be created!" error message:

44:	        "\xe2\xfa"            # loop xor_loop
45:	
46:	      # Initialize the state context to 1
47:	      state.context = 1
48:	    rescue RuntimeError => e
49:	      raise BadcharError if e.message == "No valid set instruction could be created!"
50:	    end
51:	    return decoder
52:	  end
53:	
54:	  #

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See Also

Check also the following modules related to this module:

Authors

vlad902

Version

This page has been produced using Metasploit Framework version 6.1.24-dev. For more modules, visit the Metasploit Module Library.

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