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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) .
| Code Block | ||
|---|---|---|
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// Trusted.java
import java.security.*;
public class Trusted {
// load native libraries
static{
System.loadLibrary("NativeMethodLib1");
System.loadLibrary("NativeMethodLib2");
...
}
// private native methods
private native void nativeOperation1(byte[] data, int offset, int len);
private native void nativeOperation2(...)
...
// wrapper methods perform SecurityManager and input validation checks
public void doOperation1(byte[] data, int offset, int len) {
// permission needed to invoke native method
securityManagerCheck();
if (data == null) {
throw new NullPointerException();
}
// copy mutable input
data = data.clone();
// validate input
if ((offset < 0) || (len < 0) || (offset > (data.length - len))) {
throw new IllegalArgumentException();
}
nativeOperation1(data, offset, len);
}
public void doOperation2(...){
...
}
} |
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