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-
- ##
- # This file is part of the Metasploit Framework and may be redistributed
- # according to the licenses defined in the Authors field below. In the
- # case of an unknown or missing license, this file defaults to the same
- # license as the core Framework (dual GPLv2 and Artistic). The latest
- # version of the Framework can always be obtained from metasploit.com.
- ##
-
- package Msf::Encoder::Pex;
- use strict;
- use base 'Msf::Encoder::XorDword';
- use Pex::Encoder;
- use Pex::x86;
-
- my $advanced = {
- };
-
- my $info = {
- 'Name' => 'Pex Call $+4 Double Word Xor Encoder',
- 'Version' => '$Revision: 1.20 $',
- 'Authors' =>
- [
- 'H D Moore <hdm [at] metasploit.com>',
- 'spoonm <ninjatools [at] hush.com>',
- ],
- 'Arch' => [ 'x86' ],
- 'OS' => [ ],
- 'Description' => 'Dynamically generated dword xor encoder',
- 'Refs' => [ ],
- };
-
- sub new {
- my $class = shift;
- return($class->SUPER::new({'Info' => $info, 'Advanced' => $advanced}, @_));
- }
-
- # Variable Length Decoder Using jmp/call 26/29 bytes.
- # Uses smaller encoder if payload is <= 512 bytes
- sub _GenEncoder {
- my $self = shift;
- my $xor = shift;
- my $len = shift;
- my $badchars = shift;
- my $xorkey = pack('V', $xor);
-
- # spoon's smaller variable-length encoder (updated to use call $+4 by vlad902)
- my $decoder =
- Pex::x86::Sub(-((($len -1) / 4) + 1), "ecx", $badchars).
- "\xe8\xff\xff\xff". # call $+4
- "\xff\xc0". # inc eax
- "\x5e". # pop esi
- "\x81\x76\x0e" . $xorkey. # xor_xor: xor [esi + 0x0e], $xorkey
- "\x83\xee\xfc". # sub esi, -4
- "\xe2\xf4"; # loop xor_xor
-
- return($decoder);
- }
-
- 1;
-