Missing Support for Integrity Check

Description

If integrity check values or "checksums" are omitted from a protocol, there is no way of determining if data has been corrupted in transmission. The lack of checksum functionality in a protocol removes the first application-level check of data that can be used. The end-to-end philosophy of checks states that integrity checks should be performed at the lowest level that they can be completely implemented. Excluding further sanity checks and input validation performed by applications, the protocol's checksum is the most important level of checksum, since it can be performed more completely than at any previous level and takes into account entire messages, as opposed to single packets.

Demonstrations

The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.

Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.

Example One

In this example, a request packet is received, and privileged information is sent to the requester:

while(true) {
  DatagramPacket rp = new DatagramPacket(rData,rData.length);
  outSock.receive(rp);
  InetAddress IPAddress = rp.getAddress();
  int port = rp.getPort();
  out = secret.getBytes();
  DatagramPacket sp =new DatagramPacket(out, out.length, IPAddress, port);
  outSock.send(sp);
}

The response containing secret data has no integrity check associated with it, allowing an attacker to alter the message without detection.

See Also