Java.lang.SecurityManager.checkExec() Method

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Description

The java.lang.SecurityManager.checkExec(String cmd) method throws a SecurityException if the calling thread is not allowed to create a subprocess. This method is invoked for the current security manager by the exec methods of class Runtime.

This method calls checkPermission with the FilePermission(cmd,"execute") permission if cmd is an absolute path, otherwise it calls checkPermission with FilePermission("<<ALL FILES>>","execute"). If you override this method, then you should make a call to super.checkExec at the point the overridden method would normally throw an exception.

Declaration

Following is the declaration for java.lang.SecurityManager.checkExec() method

public void checkExec(String cmd)

Parameters

  • cmd -- the specified system command.

Return Value

This method does not return a value.

Exception

  • SecurityException -- if the calling thread does not have permission to create a subprocess.

  • NullPointerException -- if the cmd argument is null.

Example

Our examples require that the permissions for each command is blocked. A new policy file was set that allows only the creating and setting of our Security Manager. The file is in C:/java.policy and contains the following text:

grant {
  permission java.lang.RuntimePermission "setSecurityManager";
  permission java.lang.RuntimePermission "createSecurityManager";
  permission java.lang.RuntimePermission "usePolicy";
};

The following example shows the usage of lang.SecurityManager.checkExec() method.

package com.tutorialspoint;

public class SecurityManagerDemo {

   public static void main(String[] args) {

      // set the policy file as the system securuty policy
      System.setProperty("java.security.policy", "file:/C:/java.policy");

      // create a security manager
      SecurityManager sm = new SecurityManager();

      // set the system security manager
      System.setSecurityManager(sm);

      // perform the check
      sm.checkExec("notepad.exe");

      // print a message if we passed the check
      System.out.println("Allowed!");
   }
}

Let us compile and run the above program, this will produce the following result:

Exception in thread "main" java.security.AccessControlException: access denied (java.io.FilePermission <<ALL FILES>> execute)



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