Incorrect Provision of Specified Functionality

Description

When providing functionality to an external party, it is important that the product behaves in accordance with the details specified. When requirements of nuances are not documented, the functionality may produce unintended behaviors for the caller, possibly leading to an exploitable state.

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 the following snippet from a doPost() servlet method, the server returns "200 OK" (default) even if an error occurs.

try {


  // Something that may throw an exception.
  ...

} catch (Throwable t) {
  logger.error("Caught: " + t.toString());
  return;
}

Example Two

In the following example, an HTTP 404 status code is returned in the event of an IOException encountered in a Java servlet. A 404 code is typically meant to indicate a non-existent resource and would be somewhat misleading in this case.

try {


  // something that might throw IOException
  ...

} catch (IOException ioe) {
  response.sendError(SC_NOT_FOUND);
}

See Also