new stuffs

git-svn-id: file:///home/svn/incoming/trunk@2608 4d416f70-5f16-0410-b530-b9f4589650da

lib/rex/arch/x86.rb

@@ -3,6 +3,10 @@
 module Rex
 module Arch
 
+#
+# everything here is mostly stole from vlad's perl x86 stuff
+#
+
 module X86
 
 	#
@@ -21,30 +25,71 @@ module X86
 		return self.const_get(str.upcase)
 	end
 
+
+	def self.encode_modrm(dst, src)
+		_check_reg(dst, src)
+		return (0xc0 | src | dst << 3).chr
+	end
+
 	def self.push_byte(byte)
 		# push byte will sign extend...
 		if byte < 128 && byte >= -128
 			return "\x6a" + (byte & 0xff).chr
 		end
-		raise ::ArgumentError, "Can only take signed byte values!", caller()
+		raise ::RangeError, "Can only take signed byte values!", caller()
 	end
-
-	def self.check_reg(reg)
-		if reg > 7 || reg < 0
-			raise ArgumentError, "Invalid register #{reg}", caller()
-		end
-	end
-
 	def self.pop_dword(dst)
-		check_reg(dst)
+		_check_reg(dst)
 		return (0x58 | dst).chr
 	end
 
-	def self.set(dst, val, badchars)
-		# I'm a lazy bum fix this!"
-		data = push_byte(val) + pop_dword(dst)
+	def self.clear(reg, badchars = '')
+		_check_reg(reg)
+		opcodes = Rex::StringUtils.remove_badchars("\x29\x2b\x31\x33", badchars)
+		if opcodes.empty?
+			raise RuntimeError, "Could not find a usable opcode", caller()
+		end
+
+		return opcodes[rand(opcodes.length)].chr + encode_modrm(reg, reg)
+	end
+
+	def self.mov_byte(reg, val)
+		_check_reg(reg)
+		# chr will raise RangeError if val not between 0 .. 255
+		return (0xb0 | reg).chr + val.chr
+	end
+
+	def self.set(dst, val, badchars = '')
+		_check_reg(dst)
+
+		begin
+			return _check_badchars(push_byte(val) + pop_dword(dst), badchars)
+		rescue RuntimeError, RangeError
+		end
+
+		begin
+			return _check_badchars(clear(dst, badchars) + mov_byte(dst, val), badchars)
+		rescue RuntimeError, RangeError
+		end
+
+		raise RuntimeError, "No valid set instruction could be created!", caller()
+	end
+
+	def self._check_reg(*regs)
+		regs.each { |reg|
+			if reg > 7 || reg < 0
+				raise ArgumentError, "Invalid register #{reg}", caller()
+			end
+		}
+		return nil
+	end
+
+	def self._check_badchars(data, badchars)
+		idx = Rex::StringUtils.badchar_index(data, badchars)
+		if idx
+			raise RuntimeError, "Bad character at #{idx}", caller()
+		end
 		return data
-		# !!! check bad chars!
 	end
 
 end