Class: java.lang.SecurityManager
- public class SecurityManager
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 SecurityManager.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.
Methods
-
SecurityManagertop
public SecurityManager()Constructs a newSecurityManager.If there is a security manager already installed, this method first calls the security manager's
checkPermissionmethod with theRuntimePermission("createSecurityManager")permission to ensure the calling thread has permission to create a new security manager. This may result in throwing aSecurityException. -
checkAccepttop
public void checkAccept(String host, int port)Throws aSecurityExceptionif the calling thread is not permitted to accept a socket connection from the specified host and port number.This method is invoked for the current security manager by the
acceptmethod of classServerSocket.This method calls
checkPermissionwith theSocketPermission(host+":"+port,"accept")permission.If you override this method, then you should make a call to
super.checkAcceptat the point the overridden method would normally throw an exception. -
checkAccesstop
public void checkAccess(Thread t)Throws aSecurityExceptionif the calling thread is not allowed to modify the thread argument.This method is invoked for the current security manager by the
stop,suspend,resume,setPriority,setName, andsetDaemonmethods of classThread.If the thread argument is a system thread (belongs to the thread group with a
nullparent) then this method callscheckPermissionwith theRuntimePermission("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.checkAccessshould be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method. -
checkAccesstop
public void checkAccess(ThreadGroup g)Throws aSecurityExceptionif the calling thread is not allowed to modify the thread group argument.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, anddestroymethods of classThreadGroup.If the thread group argument is the system thread group ( has a
nullparent) then this method callscheckPermissionwith theRuntimePermission("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.checkAccessshould be called by the first statement in the overridden method, or the equivalent security check should be placed in the overridden method. -
checkAwtEventQueueAccesstop
public void checkAwtEventQueueAccess()Throws aSecurityExceptionif the calling thread is not allowed to access the AWT event queue.This method calls
checkPermissionwith theAWTPermission("accessEventQueue")permission.If you override this method, then you should make a call to
super.checkAwtEventQueueAccessat the point the overridden method would normally throw an exception. -
checkConnecttop
public void checkConnect(String host, int port)Throws aSecurityExceptionif the calling thread is not allowed to open a socket connection to the specified host and port number.A port number of
-1indicates that the calling method is attempting to determine the IP address of the specified host name.This method calls
checkPermissionwith theSocketPermission(host+":"+port,"connect")permission if the port is not equal to -1. If the port is equal to -1, then it callscheckPermissionwith theSocketPermission(host,"resolve")permission.If you override this method, then you should make a call to
super.checkConnectat the point the overridden method would normally throw an exception. -
checkConnecttop
Throws aSecurityExceptionif the specified security context is not allowed to open a socket connection to the specified host and port number.A port number of
-1indicates that the calling method is attempting to determine the IP address of the specified host name.If
contextis not an instance ofAccessControlContextthen aSecurityExceptionis thrown.Otherwise, the port number is checked. If it is not equal to -1, the
context'scheckPermissionmethod is called with aSocketPermission(host+":"+port,"connect")permission. If the port is equal to -1, then thecontext'scheckPermissionmethod is called with aSocketPermission(host,"resolve")permission.If you override this method, then you should make a call to
super.checkConnectat the point the overridden method would normally throw an exception. -
checkCreateClassLoadertop
public void checkCreateClassLoader()Throws aSecurityExceptionif the calling thread is not allowed to create a new class loader.This method calls
checkPermissionwith theRuntimePermission("createClassLoader")permission.If you override this method, then you should make a call to
super.checkCreateClassLoaderat the point the overridden method would normally throw an exception. -
checkDeletetop
public void checkDelete(String file)Throws aSecurityExceptionif the calling thread is not allowed to delete the specified file.This method is invoked for the current security manager by the
deletemethod of classFile.This method calls
checkPermissionwith theFilePermission(file,"delete")permission.If you override this method, then you should make a call to
super.checkDeleteat the point the overridden method would normally throw an exception. -
checkExectop
public void checkExec(String cmd)Throws aSecurityExceptionif the calling thread is not allowed to create a subprocess.This method is invoked for the current security manager by the
execmethods of classRuntime.This method calls
checkPermissionwith theFilePermission(cmd,"execute")permission if cmd is an absolute path, otherwise it callscheckPermissionwithFilePermission("<<ALL FILES>>","execute").If you override this method, then you should make a call to
super.checkExecat the point the overridden method would normally throw an exception. -
checkExittop
public void checkExit(int status)Throws aSecurityExceptionif the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.This method is invoked for the current security manager by the
exitmethod of classRuntime. A status of0indicates success; other values indicate various errors.This method calls
checkPermissionwith theRuntimePermission("exitVM")permission.If you override this method, then you should make a call to
super.checkExitat the point the overridden method would normally throw an exception. -
checkLinktop
public void checkLink(String lib)Throws aSecurityExceptionif the calling thread is not allowed to dynamic link the library code specified by the string argument file. The argument is either a simple library name or a complete filename.This method is invoked for the current security manager by methods
loadandloadLibraryof classRuntime.This method calls
checkPermissionwith theRuntimePermission("loadLibrary."+lib)permission.If you override this method, then you should make a call to
super.checkLinkat the point the overridden method would normally throw an exception. -
checkListentop
public void checkListen(int port)Throws aSecurityExceptionif the calling thread is not allowed to wait for a connection request on the specified local port number.If port is not 0, this method calls
checkPermissionwith theSocketPermission("localhost:"+port,"listen"). If port is zero, this method callscheckPermissionwithSocketPermission("localhost:1024-","listen").If you override this method, then you should make a call to
super.checkListenat the point the overridden method would normally throw an exception. -
checkMemberAccesstop
public void checkMemberAccess(Class<?> clazz, int which)Throws aSecurityExceptionif the calling thread is not allowed to access members.The default policy is to allow access to PUBLIC members, as well as access to classes that have the same class loader as the caller. In all other cases, this method calls
checkPermissionwith theRuntimePermission("accessDeclaredMembers")permission.If this method is overridden, then a call to
super.checkMemberAccesscannot be made, as the default implementation ofcheckMemberAccessrelies on the code being checked being at a stack depth of 4. -
checkMulticasttop
public void checkMulticast(InetAddress maddr)Throws aSecurityExceptionif the calling thread is not allowed to use (join/leave/send/receive) IP multicast.This method calls
checkPermissionwith thejava.net.SocketPermission(maddr.getHostAddress(), "accept,connect")permission.If you override this method, then you should make a call to
super.checkMulticastat the point the overridden method would normally throw an exception. -
checkMulticasttop
public void checkMulticast(InetAddress maddr, byte ttl)Throws aSecurityExceptionif the calling thread is not allowed to use (join/leave/send/receive) IP multicast.This method calls
checkPermissionwith thejava.net.SocketPermission(maddr.getHostAddress(), "accept,connect")permission.If you override this method, then you should make a call to
super.checkMulticastat the point the overridden method would normally throw an exception. -
checkPackageAccesstop
public void checkPackageAccess(String pkg)Throws aSecurityExceptionif the calling thread is not allowed to access the package specified by the argument.This method is used by the
loadClassmethod 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 ifpkgstarts with or equals any of the restricted packages. If it does, thencheckPermissiongets called with theRuntimePermission("accessClassInPackage."+pkg)permission.If this method is overridden, then
super.checkPackageAccessshould be called as the first line in the overridden method. -
checkPackageDefinitiontop
public void checkPackageDefinition(String pkg)Throws aSecurityExceptionif the calling thread is not allowed to define classes in the package specified by the argument.This method is used by the
loadClassmethod of some 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.definition"), and checks to see ifpkgstarts with or equals any of the restricted packages. If it does, thencheckPermissiongets called with theRuntimePermission("defineClassInPackage."+pkg)permission.If this method is overridden, then
super.checkPackageDefinitionshould be called as the first line in the overridden method. -
checkPermissiontop
public void checkPermission(Permission perm)Throws aSecurityExceptionif the requested access, specified by the given permission, is not permitted based on the security policy currently in effect.This method calls
AccessController.checkPermissionwith the given permission. -
checkPermissiontop
public void checkPermission(Permission perm, Object context)Throws aSecurityExceptionif the specified security context is denied access to the resource specified by the given permission. The context must be a security context returned by a previous call togetSecurityContextand the access control decision is based upon the configured security policy for that security context.If
contextis an instance ofAccessControlContextthen theAccessControlContext.checkPermissionmethod is invoked with the specified permission.If
contextis not an instance ofAccessControlContextthen aSecurityExceptionis thrown. -
checkPrintJobAccesstop
public void checkPrintJobAccess()Throws aSecurityExceptionif the calling thread is not allowed to initiate a print job request.This method calls
checkPermissionwith theRuntimePermission("queuePrintJob")permission.If you override this method, then you should make a call to
super.checkPrintJobAccessat the point the overridden method would normally throw an exception. -
checkPropertiesAccesstop
public void checkPropertiesAccess()Throws aSecurityExceptionif the calling thread is not allowed to access or modify the system properties.This method is used by the
getPropertiesandsetPropertiesmethods of classSystem.This method calls
checkPermissionwith thePropertyPermission("*", "read,write")permission.If you override this method, then you should make a call to
super.checkPropertiesAccessat the point the overridden method would normally throw an exception. -
checkPropertyAccesstop
public void checkPropertyAccess(String key)Throws aSecurityExceptionif the calling thread is not allowed to access the system property with the specifiedkeyname.This method is used by the
getPropertymethod of classSystem.This method calls
checkPermissionwith thePropertyPermission(key, "read")permission.If you override this method, then you should make a call to
super.checkPropertyAccessat the point the overridden method would normally throw an exception. -
checkReadtop
public void checkRead(FileDescriptor fd)Throws aSecurityExceptionif the calling thread is not allowed to read from the specified file descriptor.This method calls
checkPermissionwith theRuntimePermission("readFileDescriptor")permission.If you override this method, then you should make a call to
super.checkReadat the point the overridden method would normally throw an exception. -
checkReadtop
public void checkRead(String file)Throws aSecurityExceptionif the calling thread is not allowed to read the file specified by the string argument.This method calls
checkPermissionwith theFilePermission(file,"read")permission.If you override this method, then you should make a call to
super.checkReadat the point the overridden method would normally throw an exception. -
checkReadtop
Throws aSecurityExceptionif the specified security context is not allowed to read the file specified by the string argument. The context must be a security context returned by a previous call togetSecurityContext.If
contextis an instance ofAccessControlContextthen theAccessControlContext.checkPermissionmethod will be invoked with theFilePermission(file,"read")permission.If
contextis not an instance ofAccessControlContextthen aSecurityExceptionis thrown.If you override this method, then you should make a call to
super.checkReadat the point the overridden method would normally throw an exception. -
checkSecurityAccesstop
public void checkSecurityAccess(String target)Determines whether the permission with the specified permission target name should be granted or denied.If the requested permission is allowed, this method returns quietly. If denied, a SecurityException is raised.
This method creates a
SecurityPermissionobject for the given permission target name and callscheckPermissionwith it.See the documentation for
java.security.SecurityPermissionfor a list of possible permission target names.If you override this method, then you should make a call to
super.checkSecurityAccessat the point the overridden method would normally throw an exception. -
checkSetFactorytop
public void checkSetFactory()Throws aSecurityExceptionif the calling thread is not allowed to set the socket factory used byServerSocketorSocket, or the stream handler factory used byURL.This method calls
checkPermissionwith theRuntimePermission("setFactory")permission.If you override this method, then you should make a call to
super.checkSetFactoryat the point the overridden method would normally throw an exception. -
checkSystemClipboardAccesstop
public void checkSystemClipboardAccess()Throws aSecurityExceptionif the calling thread is not allowed to access the system clipboard.This method calls
checkPermissionwith theAWTPermission("accessClipboard")permission.If you override this method, then you should make a call to
super.checkSystemClipboardAccessat the point the overridden method would normally throw an exception. -
checkTopLevelWindowtop
public boolean checkTopLevelWindow(Object window)Returnsfalseif the calling thread is not trusted to bring up the top-level window indicated by thewindowargument. In this case, the caller can still decide to show the window, but the window should include some sort of visual warning. If the method returnstrue, then the window can be shown without any special restrictions.See class
Windowfor more information on trusted and untrusted windows.This method calls
checkPermissionwith theAWTPermission("showWindowWithoutWarningBanner")permission, and returnstrueif a SecurityException is not thrown, otherwise it returnsfalse.If you override this method, then you should make a call to
super.checkTopLevelWindowat the point the overridden method would normally returnfalse, and the value ofsuper.checkTopLevelWindowshould be returned. -
checkWritetop
public void checkWrite(FileDescriptor fd)Throws aSecurityExceptionif the calling thread is not allowed to write to the specified file descriptor.This method calls
checkPermissionwith theRuntimePermission("writeFileDescriptor")permission.If you override this method, then you should make a call to
super.checkWriteat the point the overridden method would normally throw an exception. -
checkWritetop
public void checkWrite(String file)Throws aSecurityExceptionif the calling thread is not allowed to write to the file specified by the string argument.This method calls
checkPermissionwith theFilePermission(file,"write")permission.If you override this method, then you should make a call to
super.checkWriteat the point the overridden method would normally throw an exception. -
classDepthtop
native protected int classDepth(String name)Returns the stack depth of the specified class. -
classLoaderDepthtop
protected int classLoaderDepth()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:
- All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
- 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.
- A call to
checkPermissionwithjava.security.AllPermissiondoes not result in a SecurityException.
-
currentClassLoadertop
protected ClassLoader currentClassLoader()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
nullin the following three cases:- All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
- 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.
- A call to
checkPermissionwithjava.security.AllPermissiondoes not result in a SecurityException.
-
currentLoadedClasstop
protected Class<?> currentLoadedClass()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
nullin the following three cases:- All methods on the execution stack are from classes defined using the system class loader or one of its ancestors.
- 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.
- A call to
checkPermissionwithjava.security.AllPermissiondoes not result in a SecurityException.
-
getClassContexttop
native 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
0is the class of the currently executing method, the element at index1is the class of that method's caller, and so on. -
getInChecktop
public boolean getInCheck()Tests if there is a security check in progress. -
getSecurityContexttop
public Object getSecurityContext()Creates an object that encapsulates the current execution environment. The result of this method is used, for example, by the three-argumentcheckConnectmethod and by the two-argumentcheckReadmethod. These methods are needed because a trusted method may be called on to read a file or open a socket on behalf of another method. The trusted method needs to determine if the other (possibly untrusted) method would be allowed to perform the operation on its own.The default implementation of this method is to return an
AccessControlContextobject. -
getThreadGrouptop
public ThreadGroup getThreadGroup()Returns the thread group into which to instantiate any new thread being created at the time this is being called. By default, it returns the thread group of the current thread. This should be overridden by a specific security manager to return the appropriate thread group. -
inClasstop
protected boolean inClass(String name)Tests if a method from a class with the specified name is on the execution stack. -
inClassLoadertop
protected boolean inClassLoader()Basically, tests if a method from a class defined using a class loader is on the execution stack.
