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Application code that calls security-sensitive methods must validate the arguments being passed to the methods. In particular, null values may be interpreted as benign by certain security-sensitive methods and but may override default settings. Although security-sensitive methods must should be coded defensively in the first place, sometimes the onus is on the client code to must validate the arguments it providesarguments that the method might otherwise accept as valid. Failure to do so can result in privilege escalation and execution of arbitrary code.

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When passed a null access control context, the two-argument doPrivileged() method will fail fails to reduce the current privileges to those of the previously saved context. Consequently, this code may can grant excess privileges when the accessControlContext argument is null. Programmers who intend to call AccessController.doPrivileged() with a null access control context should explicitly pass the null constant or use the one-argument version of AccessController.doPrivileged().

Compliant Solution 

This compliant solution prevents granting of excess privileges by ensuring that accessControlContext is non-null:

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Security-sensitive methods must be thoroughly understood and their parameters validated ( to prevent null arguments, for instance) in order to prevent corner cases with unexpected argument values (such as null arguments). If unexpected argument values are passed to security-sensitive methods, arbitrary code execution becomes possible, and privilege escalation becomes likely.

Bibliography

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