java.lang
Class SecurityManager

java.lang.Object   
  java.lang.SecurityManager

Direct Known Subclasses:

RMISecurityManager

public class SecurityManager
extends Object   

The security manager is a class that allows applications to implement a security policy. It allows an application to determine, before performing a possibly unsafe or sensitive operation, what the operation is and whether it is being attempted in a security context that allows the operation to be performed. The application can allow or disallow the operation.

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.

Since:

JDK1.0

See Also:

ClassLoader , SecurityException , checkTopLevelWindow , getSecurityManager , setSecurityManager , AccessController , AccessControlContext , AccessControlException , Permission , BasicPermission , FilePermission , SocketPermission , PropertyPermission , RuntimePermission , AWTPermission , Policy , SecurityPermission , ProtectionDomain

Field Summary

protected boolean

inCheck Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Constructor Summary

SecurityManager ()
Constructs a new SecurityManager.

Method Summary

void	checkAccept (String host, int port) Throws a SecurityException if the calling thread is not permitted to accept a socket connection from the specified host and port number.
void	checkAccess (Thread t) Throws a SecurityException if the calling thread is not allowed to modify the thread argument.
void	checkAccess (ThreadGroup g) Throws a SecurityException if the calling thread is not allowed to modify the thread group argument.
void	checkAwtEventQueueAccess () Throws a SecurityException if the calling thread is not allowed to access the AWT event queue.
void	checkConnect (String host, int port) Throws a SecurityException if the calling thread is not allowed to open a socket connection to the specified host and port number.
void	checkConnect (String host, int port, Object context) Throws a SecurityException if the specified security context is not allowed to open a socket connection to the specified host and port number.
void	checkCreateClassLoader () Throws a SecurityException if the calling thread is not allowed to create a new class loader.
void	checkDelete (String file) Throws a SecurityException if the calling thread is not allowed to delete the specified file.
void	checkExec (String cmd) Throws a SecurityException if the calling thread is not allowed to create a subprocess.
void	checkExit (int status) Throws a SecurityException if the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.
void	checkLink (String lib) Throws a SecurityException if the calling thread is not allowed to dynamic link the library code specified by the string argument file.
void	checkListen (int port) Throws a SecurityException if the calling thread is not allowed to wait for a connection request on the specified local port number.
void	checkMemberAccess (Class <?> clazz, int which) Throws a SecurityException if the calling thread is not allowed to access members.
void	checkMulticast (InetAddress maddr) Throws a SecurityException if the calling thread is not allowed to use (join/leave/send/receive) IP multicast.
void	checkMulticast (InetAddress maddr, byte ttl) Deprecated. Use #checkPermission(java.security.Permission) instead
void	checkPackageAccess (String pkg) Throws a SecurityException if the calling thread is not allowed to access the package specified by the argument.
void	checkPackageDefinition (String pkg) Throws a SecurityException if the calling thread is not allowed to define classes in the package specified by the argument.
void	checkPermission (Permission perm) Throws a SecurityException if the requested access, specified by the given permission, is not permitted based on the security policy currently in effect.
void	checkPermission (Permission perm, Object context) Throws a SecurityException if the specified security context is denied access to the resource specified by the given permission.
void	checkPrintJobAccess () Throws a SecurityException if the calling thread is not allowed to initiate a print job request.
void	checkPropertiesAccess () Throws a SecurityException if the calling thread is not allowed to access or modify the system properties.
void	checkPropertyAccess (String key) Throws a SecurityException if the calling thread is not allowed to access the system property with the specified key name.
void	checkRead (FileDescriptor fd) Throws a SecurityException if the calling thread is not allowed to read from the specified file descriptor.
void	checkRead (String file) Throws a SecurityException if the calling thread is not allowed to read the file specified by the string argument.
void	checkRead (String file, Object context) Throws a SecurityException if the specified security context is not allowed to read the file specified by the string argument.
void	checkSecurityAccess (String target) Determines whether the permission with the specified permission target name should be granted or denied.
void	checkSetFactory () Throws a SecurityException if the calling thread is not allowed to set the socket factory used by ServerSocket or Socket, or the stream handler factory used by URL.
void	checkSystemClipboardAccess () Throws a SecurityException if the calling thread is not allowed to access the system clipboard.
boolean	checkTopLevelWindow (Object window) Returns false if the calling thread is not trusted to bring up the top-level window indicated by the window argument.
void	checkWrite (FileDescriptor fd) Throws a SecurityException if the calling thread is not allowed to write to the specified file descriptor.
void	checkWrite (String file) Throws a SecurityException if the calling thread is not allowed to write to the file specified by the string argument.
protected int	classDepth (String name) Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
protected int	classLoaderDepth () Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
protected ClassLoader	currentClassLoader () Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
protected Class <?>	currentLoadedClass () Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
protected Class []	getClassContext () Returns the current execution stack as an array of classes.
boolean	getInCheck () Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
Object	getSecurityContext () Creates an object that encapsulates the current execution environment.
ThreadGroup	getThreadGroup () Returns the thread group into which to instantiate any new thread being created at the time this is being called.
protected boolean	inClass (String name) Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.
protected boolean	inClassLoader () Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Methods inherited from class java.lang.Object

clone , equals , finalize , getClass , hashCode , notify , notifyAll , toString , wait , wait , wait

Field Detail

inCheck

@Deprecated
protected boolean inCheck

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

This field is true if there is a security check in progress; false otherwise.

Constructor Detail

SecurityManager

public SecurityManager()

Constructs a new SecurityManager.

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.

Throws:

SecurityException - if a security manager already exists and its checkPermission method doesn't allow creation of a new security manager.

See Also:

System.getSecurityManager() , checkPermission , RuntimePermission

Method Detail

getInCheck

@Deprecated
public boolean getInCheck()

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Tests if there is a security check in progress.

Returns:

the value of the inCheck field. This field should contain true if a security check is in progress, false otherwise.

See Also:

inCheck

getClassContext

protected Class   [] getClassContext()

Returns the current execution stack as an array of classes.

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.

Returns:

the execution stack.

currentClassLoader

@Deprecated
protected ClassLoader    currentClassLoader()

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Returns the class loader of the most recently executing method from a class defined using a non-system class loader. A non-system class loader is defined as being a class loader that is not equal to the system class loader (as returned by ClassLoader.getSystemClassLoader() ) or one of its ancestors.

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 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.

Returns:

the class loader of the most recent occurrence on the stack of a method from a class defined using a non-system class loader.

See Also:

getSystemClassLoader , checkPermission

currentLoadedClass

@Deprecated
protected Class   <?> currentLoadedClass()

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Returns the class of the most recently executing method from a class defined using a non-system class loader. A non-system class loader is defined as being a class loader that is not equal to the system class loader (as returned by ClassLoader.getSystemClassLoader() ) or one of its ancestors.

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 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.

Returns:

the class of the most recent occurrence on the stack of a method from a class defined using a non-system class loader.

See Also:

getSystemClassLoader , checkPermission

classDepth

@Deprecated
protected int classDepth(String    name)

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Returns the stack depth of the specified class.

Parameters:

name - the fully qualified name of the class to search for.

Returns:

the depth on the stack frame of the first occurrence of a method from a class with the specified name; -1 if such a frame cannot be found.

classLoaderDepth

@Deprecated
protected int classLoaderDepth()

Deprecated. This type of security checking is not recommended. It is recommended that the checkPermission call be used instead.

Returns the stack depth of the most recently executing method from a class defined using a non-system class loader. A non-system class loader is defined as being a class loader that is not equal to the system class loader (as returned by ClassLoader.getSystemClassLoader() ) or one of its ancestors.

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 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.

Returns:

the depth on the stack frame of the most recent occurrence of a method from a class defined using a non-system class loader.

See Also:

getSystemClassLoader