metasploit-framework/lib/rex/encoder/alpha2/alpha_mixed.rb

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#!/usr/bin/env ruby
require 'rex/encoder/alpha2/generic'
module Rex
module Encoder
module Alpha2
class AlphaMixed < Generic
def self.gen_decoder_prefix(reg, offset)
if (offset > 32)
raise "Critical: Offset is greater than 32"
end
# use inc ebx as a nop here so we still pad correctly
if (offset <= 16)
nop = 'C' * offset
mod = 'I' * (16 - offset) + nop + '7QZ' # dec ecx,,, push ecx, pop edx
edxmod = 'J' * (17 - offset)
else
mod = 'A' * (offset - 16)
nop = 'C' * (16 - mod.length)
mod << nop + '7QZ'
edxmod = 'B' * (17 - (offset - 16))
end
regprefix = {
'EAX' => 'PY' + mod, # push eax, pop ecx
'ECX' => 'I' + mod, # dec ecx
'EDX' => edxmod + nop + '7RY', # dec edx,,, push edx, pop ecx
'EBX' => 'SY' + mod, # push ebx, pop ecx
'ESP' => 'TY' + mod, # push esp, pop ecx
'EBP' => 'UY' + mod, # push ebp, pop ecx
'ESI' => 'VY' + mod, # push esi, pop ecx
'EDI' => 'WY' + mod, # push edi, pop ecx
}
reg.upcase!
if (not regprefix.keys.include? reg)
raise ArgumentError.new("Invalid register name")
end
return regprefix[reg]
end
def self.gen_decoder(reg, offset)
decoder =
gen_decoder_prefix(reg, offset) +
"jA" + # push 0x41
"X" + # pop eax
"P" + # push eax
"0A0" + # xor byte [ecx+30], al
"A" + # inc ecx <---
"kAAQ" + # imul eax, [ecx+42], 51 -> 10 |
"2AB" + # xor al, [ecx + 42] |
"2BB" + # xor al, [edx + 42] |
"0BB" + # xor [edx + 42], al |
"A" + # inc ecx |
"B" + # inc edx |
"X" + # pop eax |
"P" + # push eax |
"8AB" + # cmp [ecx + 42], al |
"uJ" + # jnz short -------------------------
"I" # first encoded char, fixes the above J
return decoder
end
end end end end