Fail securely

Overview
Handling errors securely is a key aspect of secure coding. There are two different types of errors that deserve special attention. The first is exceptions that occur in the processing of a countermeasure itself. It's important that these exceptions do not enable behavior that the countermeasure would normally not allow. As a developer, you should consider that there are generally three possible outcomes from a security mechanism:
 * allow the operation
 * disallow the operation
 * exception

In general, you should design your security mechanism so that a failure will follow the same execution path as disallowing the operation. For example, security methods like isAuthorized, isAuthenticated, and validate should all return false if there is an exception during processing.

The other type of security-relevant exception is outside specific security mechanisms, but may affect the control flow that invokes such mechanisms.

For example:

isAdmin = true; try { codeWhichMayFail; isAdmin = isUserInRole( “Administrator” ); } catch (Exception ex) {  log.write(ex.toString); }

If codeWhichMayFail fails, the user is an admin by default. This is obviously a security risk.