(THIS CODING RULE OR GUIDELINE IS UNDER CONSTRUCTION)
Many static methods in standard Java APIs vary their behavior according to the immediate caller's class. Such methods are considered to be caller-sensitive. For example, the
java.lang.System.loadLibrary(library) method uses the immediate caller's class loader to find and dynamically load the specified library containing native method definitions. Because native code bypasses all of the security checks enforced by the Java Runtime Environment and other built-in protections provided by the Java virtual machine, only trusted code should be allowed to load native libraries. None of the loadLibrary methods in the standard APIs should be invoked on behalf of untrusted code since untrusted code may not have the necessary permissions to load the same libraries using its own class loader instance [Oracle 2014].
Noncompliant Code Example
In this noncompliant example, the Trusted class has permission to load libraries while the Untrusted class does not. However, the Trusted class provides a library loading service through a public method thus allowing the Untrusted class to load any libraries it desires.
In this compliant example, the Trusted class loads any necessary native libraries during initialization and then provides access through public native method wrappers. These wrappers perform the necessary security checks and data validation to ensure that untrusted code cannot exploit the native methods (see JNI00-J. Define wrappers around native methods) .
Detecting calls, such as
java.lang.System.loadLibrary(), that perform tasks using the immediate caller's class loader can be detected automatically. Determining whether the use of these calls is safe cannot be done automatically.
CWE-111. Direct use of unsafe JNI
Guideline 9-9. Safely invoke standard APIs that perform tasks using the immediate caller's class loader instance