SecurityManager (GNU Classpath 0.94-pre Documentation)

SecurityManager is a class you can extend to create your own Java security policy. By default, there is no SecurityManager installed in 1.1, which means that all things are permitted to all people. The security manager, if set, is consulted before doing anything with potentially dangerous results, and throws a SecurityException if the action is forbidden.

A typical check is as follows, just before the dangerous operation:

 SecurityManager sm = System.getSecurityManager();
 if (sm != null)
   sm.checkABC(argument, ...);

Note that this is thread-safe, by caching the security manager in a local variable rather than risking a NullPointerException if the mangager is changed between the check for null and before the permission check.

The special method checkPermission is a catchall, and the default implementation calls AccessController.checkPermission. In fact, all the other methods default to calling checkPermission.

Sometimes, the security check needs to happen from a different context, such as when called from a worker thread. In such cases, use getSecurityContext to take a snapshot that can be passed to the worker thread:

 Object context = null;
 SecurityManager sm = System.getSecurityManager();
 if (sm != null)
   context = sm.getSecurityContext(); // defaults to an AccessControlContext
 // now, in worker thread
 if (sm != null)
   sm.checkPermission(permission, context);

Permissions fall into these categories: File, Socket, Net, Security, Runtime, Property, AWT, Reflect, and Serializable. Each of these permissions have a property naming convention, that follows a hierarchical naming convention, to make it easy to grant or deny several permissions at once. Some permissions also take a list of permitted actions, such as "read" or "write", to fine-tune control even more. The permission java.security.AllPermission grants all permissions.

The default methods in this class deny all things to all people. You must explicitly grant permission for anything you want to be legal when subclassing this class.

Since: 1.0

UNKNOWN: still missing 1.4 functionality

Field Summary
protected boolean	inCheck Tells whether or not the SecurityManager is currently performing a security check.

Constructor Summary
	SecurityManager() Construct a new security manager.

Method Summary
void	checkAccept(String host, int port) Check if the current thread is allowed to accept a connection from a particular host on a particular port.
void	checkAccess(Thread thread) Check if the current thread is allowed to modify another Thread.
void	checkAccess(ThreadGroup g) Check if the current thread is allowed to modify a ThreadGroup.
void	checkAwtEventQueueAccess() Check if the current thread is allowed to use the AWT event queue.
void	checkConnect(String host, int port) Check if the current thread is allowed to connect to a given host on a given port.
void	checkConnect(String host, int port, Object context) Check if the current thread is allowed to connect to a given host on a given port, using the given security context.
void	checkCreateClassLoader() Check if the current thread is allowed to create a ClassLoader.
void	checkDelete(String filename) Check if the current thread is allowed to delete the given file.
void	checkExec(String program) Check if the current thread is allowed to execute the given program.
void	checkExit(int status) Check if the current thread is allowed to exit the JVM with the given status.
void	checkLink(String filename) Check if the current thread is allowed to link in the given native library.
void	checkListen(int port) Check if the current thread is allowed to listen to a specific port for data.
void	checkMemberAccess(Class<?> c, int memberType) Check if the current thread is allowed to get certain types of Methods, Fields and Constructors from a Class object.
void	checkMulticast(InetAddress addr) Check if the current thread is allowed to read and write multicast to a particular address.
void	checkMulticast(InetAddress addr, byte ttl) Check if the current thread is allowed to read and write multicast to a particular address with a particular ttl (time-to-live) value.
void	checkPackageAccess(String packageName) Check if the current thread is allowed to access the specified package at all.
void	checkPackageDefinition(String packageName) Check if the current thread is allowed to define a class into the specified package.
void	checkPermission(Permission perm) Check if the current thread is allowed to perform an operation that requires the specified `Permission`.
void	checkPermission(Permission perm, Object context) Check if the current thread is allowed to perform an operation that requires the specified `Permission`.
void	checkPrintJobAccess() Check if the current thread is allowed to create a print job.
void	checkPropertiesAccess() Check if the current thread is allowed to read or write all the system properties at once.
void	checkPropertyAccess(String key) Check if the current thread is allowed to read a particular system property (writes are checked directly via checkPermission).
void	checkRead(FileDescriptor desc) Check if the current thread is allowed to read the given file using the FileDescriptor.
void	checkRead(String filename) Check if the current thread is allowed to read the given file.
void	checkRead(String filename, Object context) Check if the current thread is allowed to read the given file. using the given security context.
void	checkSecurityAccess(String action) Test whether a particular security action may be taken.
void	checkSetFactory() Check if the current thread is allowed to set the current socket factory.
void	checkSystemClipboardAccess() Check if the current thread is allowed to use the system clipboard.
boolean	checkTopLevelWindow(Object window) Check if the current thread is allowed to create a top-level window.
void	checkWrite(FileDescriptor desc) Check if the current thread is allowed to write the given file using the FileDescriptor.
void	checkWrite(String filename) Check if the current thread is allowed to write the given file.
protected int	classDepth(String className) Get the depth of a particular class on the execution stack.
protected int	classLoaderDepth() Get the depth on the execution stack of the most recent non-system class.
protected ClassLoader	currentClassLoader() Find the ClassLoader of the first non-system class on the execution stack.
protected Class<?>	currentLoadedClass() Find the first non-system class on the execution stack.
protected Class[]	getClassContext() Get a list of all the classes currently executing methods on the Java stack. getClassContext()[0] is the currently executing method (ie. the class that CALLED getClassContext, not SecurityManager).
boolean	getInCheck() Tells whether or not the SecurityManager is currently performing a security check.
Object	getSecurityContext() Get an implementation-dependent Object that contains enough information about the current environment to be able to perform standard security checks later.
ThreadGroup	getThreadGroup() Get the ThreadGroup that a new Thread should belong to by default.
protected boolean	inClass(String className) Tell whether the specified class is on the execution stack.
protected boolean	inClassLoader() Tell whether there is a class loaded with an explicit ClassLoader on the stack.

Check if the current thread is allowed to accept a connection from a particular host on a particular port. This method is called by ServerSocket.implAccept(). The default implementation checks SocketPermission(host + ":" + port, "accept"). If you override this, call super.checkAccept rather than throwing an exception.

Parameters: host the host which wishes to connect port the port the connection will be on

Throws: SecurityException if permission is denied NullPointerException if host is null

Class SecurityManager