add update_checksum, size, and length methods

git-svn-id: file:///home/svn/framework3/trunk@10036 4d416f70-5f16-0410-b530-b9f4589650da

lib/rex/peparsey/pe.rb

@@ -202,5 +202,11 @@ class Pe < PeBase
 		_isource.read(offset, len)
 	end
 
+	def size
+		_isource.size
+	end
+	def length
+		_isource.size
+	end
 
 end end end

lib/rex/peparsey/pebase.rb

@@ -1650,6 +1650,31 @@ class PeBase
 
 		rname.to_s
 	end
+	
+	def update_checksum
+		off = _dos_header.e_lfanew + IMAGE_FILE_HEADER_SIZE + 0x40
+		_isource.rawdata[off, 4] = [0].pack('V')
+
+		rem = _isource.size % 4
+		sum_me = ''
+		sum_me << _isource.rawdata
+		sum_me << "\x00" * (4 - rem) if rem > 0
+
+		cksum = 0
+		sum_me.unpack('V*').each { |el|
+			cksum = (cksum & 0xffffffff) + (cksum >> 32) + el
+			if cksum > 2**32
+				cksum = (cksum & 0xffffffff) + (cksum >> 32)
+			end
+		}
+
+		cksum = (cksum & 0xffff) + (cksum >> 16)
+		cksum += (cksum >> 16)
+		cksum &= 0xffff
+
+		cksum += _isource.size
+
+		_isource.rawdata[off, 4] = [cksum].pack('V')
+	end
 
 end end end
-