The SecurityManager class contains many methods with names that begin with the word check. These methods are called by various methods in the Java libraries before those methods perform certain potentially sensitive operations. The invocation of such a check method typically looks like this:

     SecurityManager security = System.getSecurityManager();
     if (security != null) {
         security.checkXXX(argument,  . . . );
     }
 

The security manager is thereby given an opportunity to prevent completion of the operation by throwing an exception. A security manager routine simply returns if the operation is permitted, but throws a SecurityException if the operation is not permitted. The only exception to this convention is checkTopLevelWindow, which returns a boolean value.

The current security manager is set by the setSecurityManager method in class System. The current security manager is obtained by the getSecurityManager method.

The special method checkPermission(java.security.Permission) determines whether an access request indicated by a specified permission should be granted or denied. The default implementation calls

   AccessController.checkPermission(perm);
 

If a requested access is allowed, checkPermission returns quietly. If denied, a SecurityException is thrown.

As of Java 2 SDK v1.2, the default implementation of each of the other check methods in SecurityManager is to call the SecurityManager checkPermission method to determine if the calling thread has permission to perform the requested operation.

Note that the checkPermission method with just a single permission argument always performs security checks within the context of the currently executing thread. Sometimes a security check that should be made within a given context will actually need to be done from within a different context (for example, from within a worker thread). The getSecurityContext method and the checkPermission method that includes a context argument are provided for this situation. The getSecurityContext method returns a "snapshot" of the current calling context. (The default implementation returns an AccessControlContext object.) A sample call is the following:

   Object context = null;
   SecurityManager sm = System.getSecurityManager();
   if (sm != null) context = sm.getSecurityContext();
 

The checkPermission method that takes a context object in addition to a permission makes access decisions based on that context, rather than on that of the current execution thread. Code within a different context can thus call that method, passing the permission and the previously-saved context object. A sample call, using the SecurityManager sm obtained as in the previous example, is the following:

   if (sm != null) sm.checkPermission(permission, context);
 

Permissions fall into these categories: File, Socket, Net, Security, Runtime, Property, AWT, Reflect, and Serializable. The classes managing these various permission categories are java.io.FilePermission, java.net.SocketPermission, java.net.NetPermission, java.security.SecurityPermission, java.lang.RuntimePermission, java.util.PropertyPermission, java.awt.AWTPermission, java.lang.reflect.ReflectPermission, and java.io.SerializablePermission.

All but the first two (FilePermission and SocketPermission) are subclasses of java.security.BasicPermission, which itself is an abstract subclass of the top-level class for permissions, which is java.security.Permission. BasicPermission defines the functionality needed for all permissions that contain a name that follows the hierarchical property naming convention (for example, "exitVM", "setFactory", "queuePrintJob", etc). An asterisk may appear at the end of the name, following a ".", or by itself, to signify a wildcard match. For example: "a.*" or "*" is valid, "*a" or "a*b" is not valid.

FilePermission and SocketPermission are subclasses of the top-level class for permissions (java.security.Permission). Classes like these that have a more complicated name syntax than that used by BasicPermission subclass directly from Permission rather than from BasicPermission. For example, for a java.io.FilePermission object, the permission name is the path name of a file (or directory).

Some of the permission classes have an "actions" list that tells the actions that are permitted for the object. For example, for a java.io.FilePermission object, the actions list (such as "read, write") specifies which actions are granted for the specified file (or for files in the specified directory).

Other permission classes are for "named" permissions - ones that contain a name but no actions list; you either have the named permission or you don't.

Note: There is also a java.security.AllPermission permission that implies all permissions. It exists to simplify the work of system administrators who might need to perform multiple tasks that require all (or numerous) permissions.

See Permissions in the JDK for permission-related information. This document includes, for example, a table listing the various SecurityManager check methods and the permission(s) the default implementation of each such method requires. It also contains a table of all the version 1.2 methods that require permissions, and for each such method tells which permission it requires.

For more information about SecurityManager changes made in the JDK and advice regarding porting of 1.1-style security managers, see the security documentation.

If there is a security manager already installed, this method first calls the security manager's checkPermission method with the RuntimePermission("createSecurityManager") permission to ensure the calling thread has permission to create a new security manager. This may result in throwing a SecurityException.

The length of the array is the number of methods on the execution stack. The element at index 0 is the class of the currently executing method, the element at index 1 is the class of that method's caller, and so on.

This method will return null in the following three cases:

1. All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
2. All methods on the execution stack up to the first "privileged" caller (see java.security.AccessController.doPrivileged(java.security.PrivilegedAction)) are from classes defined using the system class loader or one of its ancestors.
3. A call to checkPermission with java.security.AllPermission does not result in a SecurityException.

This method will return null in the following three cases:

1. All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
2. All methods on the execution stack up to the first "privileged" caller (see java.security.AccessController.doPrivileged(java.security.PrivilegedAction)) are from classes defined using the system class loader or one of its ancestors.
3. A call to checkPermission with java.security.AllPermission does not result in a SecurityException.

This method will return -1 in the following three cases:

1. All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
2. All methods on the execution stack up to the first "privileged" caller (see java.security.AccessController.doPrivileged(java.security.PrivilegedAction)) are from classes defined using the system class loader or one of its ancestors.
3. A call to checkPermission with java.security.AllPermission does not result in a SecurityException.

The default implementation of this method is to return an AccessControlContext object.

This method calls AccessController.checkPermission with the given permission.

If context is an instance of AccessControlContext then the AccessControlContext.checkPermission method is invoked with the specified permission.

If context is not an instance of AccessControlContext then a SecurityException is thrown.

This method calls checkPermission with the RuntimePermission("createClassLoader") permission.

If you override this method, then you should make a call to super.checkCreateClassLoader at the point the overridden method would normally throw an exception.

This method is invoked for the current security manager by the stop, suspend, resume, setPriority, setName, and setDaemon methods of class Thread.

If the thread argument is a system thread (belongs to the thread group with a null parent) then this method calls checkPermission with the RuntimePermission("modifyThread") permission. If the thread argument is not a system thread, this method just returns silently.

Applications that want a stricter policy should override this method. If this method is overridden, the method that overrides it should additionally check to see if the calling thread has the RuntimePermission("modifyThread") permission, and if so, return silently. This is to ensure that code granted that permission (such as the JDK itself) is allowed to manipulate any thread.

If this method is overridden, then super.checkAccess should be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method.

This method is invoked for the current security manager when a new child thread or child thread group is created, and by the setDaemon, setMaxPriority, stop, suspend, resume, and destroy methods of class ThreadGroup.

If the thread group argument is the system thread group ( has a null parent) then this method calls checkPermission with the RuntimePermission("modifyThreadGroup") permission. If the thread group argument is not the system thread group, this method just returns silently.

Applications that want a stricter policy should override this method. If this method is overridden, the method that overrides it should additionally check to see if the calling thread has the RuntimePermission("modifyThreadGroup") permission, and if so, return silently. This is to ensure that code granted that permission (such as the JDK itself) is allowed to manipulate any thread.

If this method is overridden, then super.checkAccess should be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method.

This method is invoked for the current security manager by the exit method of class Runtime. A status of 0 indicates success; other values indicate various errors.

This method calls checkPermission with the RuntimePermission("exitVM."+status) permission.

If you override this method, then you should make a call to super.checkExit at the point the overridden method would normally throw an exception.

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.

This method is invoked for the current security manager by methods load and loadLibrary of class Runtime.

This method calls checkPermission with the RuntimePermission("loadLibrary."+lib) permission.

If you override this method, then you should make a call to super.checkLink at the point the overridden method would normally throw an exception.

This method calls checkPermission with the RuntimePermission("readFileDescriptor") permission.

If you override this method, then you should make a call to super.checkRead at the point the overridden method would normally throw an exception.

This method calls checkPermission with the FilePermission(file,"read") permission.

If you override this method, then you should make a call to super.checkRead at the point the overridden method would normally throw an exception.

If context is an instance of AccessControlContext then the AccessControlContext.checkPermission method will be invoked with the FilePermission(file,"read") permission.

If context is not an instance of AccessControlContext then a SecurityException is thrown.

If you override this method, then you should make a call to super.checkRead at the point the overridden method would normally throw an exception.

This method calls checkPermission with the RuntimePermission("writeFileDescriptor") permission.

If you override this method, then you should make a call to super.checkWrite at the point the overridden method would normally throw an exception.

This method calls checkPermission with the FilePermission(file,"write") permission.

If you override this method, then you should make a call to super.checkWrite at the point the overridden method would normally throw an exception.

This method is invoked for the current security manager by the delete method of class File.

This method calls checkPermission with the FilePermission(file,"delete") permission.

If you override this method, then you should make a call to super.checkDelete at the point the overridden method would normally throw an exception.

A port number of -1 indicates that the calling method is attempting to determine the IP address of the specified host name.

This method calls checkPermission with the SocketPermission(host+":"+port,"connect") permission if the port is not equal to -1. If the port is equal to -1, then it calls checkPermission with the SocketPermission(host,"resolve") permission.

If you override this method, then you should make a call to super.checkConnect at the point the overridden method would normally throw an exception.

A port number of -1 indicates that the calling method is attempting to determine the IP address of the specified host name.

If context is not an instance of AccessControlContext then a SecurityException is thrown.

Otherwise, the port number is checked. If it is not equal to -1, the context's checkPermission method is called with a SocketPermission(host+":"+port,"connect") permission. If the port is equal to -1, then the context's checkPermission method is called with a SocketPermission(host,"resolve") permission.

If you override this method, then you should make a call to super.checkConnect at the point the overridden method would normally throw an exception.

If port is not 0, this method calls checkPermission with the SocketPermission("localhost:"+port,"listen"). If port is zero, this method calls checkPermission with SocketPermission("localhost:1024-","listen").

If you override this method, then you should make a call to super.checkListen at the point the overridden method would normally throw an exception.

This method is invoked for the current security manager by the accept method of class ServerSocket.

This method calls checkPermission with the SocketPermission(host+":"+port,"accept") permission.

If you override this method, then you should make a call to super.checkAccept at the point the overridden method would normally throw an exception.

This method calls checkPermission with the java.net.SocketPermission(maddr.getHostAddress(), "accept,connect") permission.

If you override this method, then you should make a call to super.checkMulticast at the point the overridden method would normally throw an exception.

This method calls checkPermission with the java.net.SocketPermission(maddr.getHostAddress(), "accept,connect") permission.

If you override this method, then you should make a call to super.checkMulticast at the point the overridden method would normally throw an exception.

This method is used by the getProperties and setProperties methods of class System.

This method calls checkPermission with the PropertyPermission("*", "read,write") permission.

If you override this method, then you should make a call to super.checkPropertiesAccess at the point the overridden method would normally throw an exception.

This method is used by the getProperty method of class System.

This method calls checkPermission with the PropertyPermission(key, "read") permission.

If you override this method, then you should make a call to super.checkPropertyAccess at the point the overridden method would normally throw an exception.

See class Window for more information on trusted and untrusted windows.

This method calls checkPermission with the AWTPermission("showWindowWithoutWarningBanner") permission, and returns true if a SecurityException is not thrown, otherwise it returns false.

If you override this method, then you should make a call to super.checkTopLevelWindow at the point the overridden method would normally return false, and the value of super.checkTopLevelWindow should be returned.

This method calls checkPermission with the RuntimePermission("queuePrintJob") permission.

If you override this method, then you should make a call to super.checkPrintJobAccess at the point the overridden method would normally throw an exception.

This method calls checkPermission with the AWTPermission("accessClipboard") permission.

If you override this method, then you should make a call to super.checkSystemClipboardAccess at the point the overridden method would normally throw an exception.

This method calls checkPermission with the AWTPermission("accessEventQueue") permission.

If you override this method, then you should make a call to super.checkAwtEventQueueAccess at the point the overridden method would normally throw an exception.

This method is used by the loadClass method of class loaders.

This method first gets a list of restricted packages by obtaining a comma-separated list from a call to java.security.Security.getProperty("package.access"), and checks to see if pkg starts with or equals any of the restricted packages. If it does, then checkPermission gets called with the RuntimePermission("accessClassInPackage."+pkg) permission.

If this method is overridden, then super.checkPackageAccess should be called as the first line in the overridden method.