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# Class java.lang.SecurityManager

    java.lang.Object
       |
       +----java.lang.SecurityManager

public class SecurityManager
extends Object

The security manager is an abstract 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 the operation is being performed by a class created via a class loader rather than installed locally. Classes loaded via a class loader (especially if they have been downloaded over a network) may be less trustworthy than classes from files installed locally. 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 default implementation of each of the `check` XXX methods is to assume that the caller does not have permission to perform the requested operation.

See Also:
  ClassLoader, SecurityException, checkTopLevelWindow, getSecurityManager, setSecurityManager

##

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

##

SecurityManager()
  Constructs a new `SecurityManager`.

##

checkAccept(String, int)
  Throws a `SecurityException` if the calling thread is not permitted to accept a socket connection from the specified host and port number.
checkAccess(Thread)
  Throws a `SecurityException` if the calling thread is not allowed to modify the thread argument.
checkAccess(ThreadGroup)
  Throws a `SecurityException` if the calling thread is not allowed to modify the thread group argument.
checkAwtEventQueueAccess()
  Tests if a client can get access to the AWT event queue.
checkConnect(String, int)
  Throws a `SecurityException` if the calling thread is not allowed to open a socket connection to the specified host and port number.
checkConnect(String, int, Object)
  Throws a `SecurityException` if the specified security context is not allowed to open a socket connection to the specified host and port number.
checkCreateClassLoader()
  Throws a `SecurityException` if the calling thread is not allowed to create a new class loader.
checkDelete(String)
  Throws a `SecurityException` if the calling thread is not allowed to delete the specified file.
checkExec(String)
  Throws a `SecurityException` if the calling thread is not allowed to create a subprocss.
checkExit(int)
  Throws a `SecurityException` if the calling thread is not allowed to cause the Java Virtual Machine to halt with the specified status code.
checkLink(String)
  Throws a `SecurityException` if the calling thread is not allowed to dynamic link the library code specified by the string argument file.
checkListen(int)
  Throws a `SecurityException` if the calling thread is not allowed to wait for a connection request on the specified local port number.
checkMemberAccess(Class, int)
  Tests if a client is allowed to access members.
checkMulticast(InetAddress)
  Tests if current execution context is allowed to use (join/leave/send/receive) IP multicast.
checkMulticast(InetAddress, byte)
  Tests to see if current execution context is allowed to use (join/leave/send/receive) IP multicast.
checkPackageAccess(String)
  Throws a `SecurityException` if the calling thread is not allowed to access the package specified by the argument.
checkPackageDefinition(String)
  Throws a `SecurityException` if the calling thread is not allowed to define classes in the package specified by the argument.
checkPrintJobAccess()
  Tests if a client can initiate a print job request.
checkPropertiesAccess()
  Throws a `SecurityException` if the calling thread is not allowed to access or modify the system properties.
checkPropertyAccess(String)
  Throws a `SecurityException` if the calling thread is not allowed to access the system property with the specified `key` name.
checkRead(FileDescriptor)
  Throws a `SecurityException` if the calling thread is not allowed to read from the specified file descriptor.
checkRead(String)
  Throws a `SecurityException` if the calling thread is not allowed to read the file specified by the string argument.
checkRead(String, Object)
  Throws a `SecurityException` if the specified security context is not allowed to read the file specified by the string argument.
checkSecurityAccess(String)
  Tests access to certain operations for a security API action.
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`.
checkSystemClipboardAccess()
  Tests if a client can get access to the system clipboard.
checkTopLevelWindow(Object)
  Returns `false` if the calling thread is not trusted to bring up the top-level window indicated by the `window` argument.
checkWrite(FileDescriptor)
  Throws a `SecurityException` if the calling thread is not allowed to write to the specified file descriptor.
checkWrite(String)
  Throws a `SecurityException` if the calling thread is not allowed to write to the file specified by the string argument.
classDepth(String)
  Returns the stack depth of the specified class.
classLoaderDepth()
  Returns the stack depth of the most recently executing method from a class defined using a class loader.
currentClassLoader()
  Returns an object describing the most recent class loader executing on the stack.
currentLoadedClass()
  Returns the current Class with a ClassLoader on the execution stack.
getClassContext()
  Returns the current execution stack as an array of classes.
getInCheck()
  Tests if there is a security check in progress.
getSecurityContext()
  Creates an object that encapsulates the current execution environment.
getThreadGroup()
  Returns the thread group into which to instantiate any new thread being created at the time this is being called.
inClass(String)
  Tests if the specified String is in this Class.
inClassLoader()
  Tests if the current ClassLoader is equal to `null`.

##

inCheck

      protected boolean inCheck

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

##

SecurityManager

      protected SecurityManager()

  Constructs a new `SecurityManager`. An application is not allowed to create a new security manager if there is already a current security manager.

  Throws: SecurityException
    if a security manager already exists.
  See Also:
    getSecurityManager

##

getInCheck

      public boolean getInCheck()

  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

      protected ClassLoader currentClassLoader()

  Returns an object describing the most recent class loader executing on the stack.

  Returns:
    the class loader of the most recent occurrence on the stack of a method from a class defined using a class loader; returns `null` if there is no occurrence on the stack of a method from a class defined using a class loader.

currentLoadedClass

      protected Class currentLoadedClass()

  Returns the current Class with a ClassLoader on the execution stack.

classDepth

      protected int classDepth(String name)

  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

      protected int classLoaderDepth()

  Returns the stack depth of the most recently executing method from a class defined using a class loader.

  Returns:
    the depth on the stack frame of the most recent occurrence of a method from a class defined using a class loader; returns `-1` if there is no occurrence of a method from a class defined using a class loader.

inClass

      protected boolean inClass(String name)

  Tests if the specified String is in this Class.

  Parameters:
    name - the fully qualified name of the class.
  Returns:
    `true` if a method from a class with the specified name is on the execution stack; `false` otherwise.

inClassLoader

      protected boolean inClassLoader()

  Tests if the current ClassLoader is equal to `null`.

  Returns:
    `true` if a method from a class defined using a class loader is on the execution stack.

getSecurityContext

      public Object getSecurityContext()

  Creates an object that encapsulates the current execution environment. The result of this method is used by the three-argument `checkConnect` method and by the two-argument `checkRead` method.

  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.

  Returns:
    an implementation-dependent object that encapsulates sufficient information about the current execution environment to perform some security checks later.
  See Also:
    checkConnect, checkRead

checkCreateClassLoader

      public void checkCreateClassLoader()

  Throws a `SecurityException` if the calling thread is not allowed to create a new class loader.

  The `checkCreateClassLoader` method for class `SecurityManager` always throws a `SecurityException`.

  Throws: SecurityException
    if the caller does not have permission to create a new class loader.
  See Also:
    ClassLoader

checkAccess

      public void checkAccess(Thread g)

  Throws a `SecurityException` if 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`, and `setDaemon` methods of class `Thread`.

  The `checkAccess` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    g - the thread to be checked.
  Throws: SecurityException
    if the caller does not have permission to modify the thread.
  See Also:
    getSecurityManager, resume, setDaemon, setName, setPriority, stop, suspend

checkAccess

      public void checkAccess(ThreadGroup g)

  Throws a `SecurityException` if 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`, and `destroy` methods of class `ThreadGroup`.

  The `checkAccess` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    g - the thread group to be checked.
  Throws: SecurityException
    if the caller does not have permission to modify the thread group.
  See Also:
    getSecurityManager, destroy, resume, setDaemon, setMaxPriority, stop, suspend

checkExit

      public 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.

  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.

  The `checkExit` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    status - the exit status.
  Throws: SecurityException
    if the caller does not have permission to halt the Java Virtual Machine with the specified status.
  See Also:
    exit, getSecurityManager

checkExec

      public void checkExec(String cmd)

  Throws a `SecurityException` if the calling thread is not allowed to create a subprocss.

  This method is invoked for the current security manager by the `exec` methods of class `Runtime`.

  The `checkExec` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    cmd - the specified system command.
  Throws: SecurityException
    if the caller does not have permission to create a subprocess.
  See Also:
    exec, exec, exec, exec, getSecurityManager

checkLink

      public 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. The argument is either a simple library name or a complete filename.

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

  The `checkLink` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    lib - the name of the library.
  Throws: SecurityException
    if the caller does not have permission to dynamically link the library.
  See Also:
    load, loadLibrary, getSecurityManager

checkRead

      public void checkRead(FileDescriptor fd)

  Throws a `SecurityException` if the calling thread is not allowed to read from the specified file descriptor.

  The `checkRead` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    fd - the system-dependent file descriptor.
  Throws: SecurityException
    if the caller does not have permission to access the specified file descriptor.
  See Also:
    FileDescriptor

checkRead

      public void checkRead(String file)

  Throws a `SecurityException` if the calling thread is not allowed to read the file specified by the string argument.

  The `checkRead` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    file - the system-dependent file name.
  Throws: SecurityException
    if the caller does not have permission to access the specified file.

checkRead

      public 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. The context must be a security context returned by a previous call to `getSecurityContext`.

  The `checkRead` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    file - the system-dependent filename.
    context - a system-dependent security context.
  Throws: SecurityException
    if the specified security context does not have permission to read the specified file.
  See Also:
    getSecurityContext

checkWrite

      public void checkWrite(FileDescriptor fd)

  Throws a `SecurityException` if the calling thread is not allowed to write to the specified file descriptor.

  The `checkWrite` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    fd - the system-dependent file descriptor.
  Throws: SecurityException
    if the caller does not have permission to access the specified file descriptor.
  See Also:
    FileDescriptor

checkWrite

      public void checkWrite(String file)

  Throws a `SecurityException` if the calling thread is not allowed to write to the file specified by the string argument.

  The `checkWrite` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    file - the system-dependent filename.
  Throws: SecurityException
    if the caller does not have permission to access the specified file.

checkDelete

      public void checkDelete(String file)

  Throws a `SecurityException` if the calling thread is not allowed to delete the specified file.

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

  The `checkDelete` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    file - the system-dependent filename.
  Throws: SecurityException
    if the caller does not have permission to delete the file.
  See Also:
    delete, getSecurityManager

checkConnect

      public 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.

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

  The `checkConnect` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    host - the host name port to connect to.
    port - the protocol port to connect to.
  Throws: SecurityException
    if the caller does not have permission to open a socket connection to the specified `host` and `port`.

checkConnect

      public 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.

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

  The `checkConnect` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    host - the host name port to connect to.
    port - the protocol port to connect to.
    context - a system-dependent security context.
  Throws: SecurityException
    if the specified security context does not have permission to open a socket connection to the specified `host` and `port`.
  See Also:
    getSecurityContext

checkListen

      public 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.

  The `checkListen` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    port - the local port.
  Throws: SecurityException
    if the caller does not have permission to listen on the specified port.

checkAccept

      public 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.

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

  The `checkAccept` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    host - the host name of the socket connection.
    port - the port number of the socket connection.
  Throws: SecurityException
    if the caller does not have permission to accept the connection.
  See Also:
    getSecurityManager, accept

checkMulticast

      public void checkMulticast(InetAddress maddr)

  Tests if current execution context is allowed to use (join/leave/send/receive) IP multicast.

  Parameters:
    multicast - Internet group address to be used.
  Throws: SecurityException
    if a security error has occurred.

checkMulticast

      public void checkMulticast(InetAddress maddr,
                                 byte ttl)

  Tests to see if current execution context is allowed to use (join/leave/send/receive) IP multicast.

  Parameters:
    multicast - Internet group address to be used.
    ttl - value in use, if it is multicast send.
  Throws: SecurityException
    if a security error has occurred.

checkPropertiesAccess

      public void checkPropertiesAccess()

  Throws a `SecurityException` if the calling thread is not allowed to access or modify the system properties.

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

  The `checkPropertiesAccess` method for class `SecurityManager` always throws a `SecurityException`.

  Throws: SecurityException
    if the caller does not have permission to access or modify the system properties.
  See Also:
    getProperties, setProperties

checkPropertyAccess

      public void checkPropertyAccess(String key)

  Throws a `SecurityException` if the calling thread is not allowed to access the system property with the specified `key` name.

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

  The `checkPropertiesAccess` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    key - a system property key.
  Throws: SecurityException
    if the caller does not have permission to access the specified system property.
  See Also:
    getProperty

checkTopLevelWindow

      public 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. 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 returns `true`, then the window can be shown without any special restrictions.

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

  The `checkSetFactory` method for class `SecurityManager` always returns `false`.

  Parameters:
    window - the new window that is being created.
  Returns:
    `true` if the caller is trusted to put up top-level windows; `false` otherwise.
  Throws: SecurityException
    if creation is disallowed entirely.
  See Also:
    Window

checkPrintJobAccess

      public void checkPrintJobAccess()

  Tests if a client can initiate a print job request.

checkSystemClipboardAccess

      public void checkSystemClipboardAccess()

  Tests if a client can get access to the system clipboard.

checkAwtEventQueueAccess

      public void checkAwtEventQueueAccess()

  Tests if a client can get access to the AWT event queue.

checkPackageAccess

      public void checkPackageAccess(String pkg)

  Throws a `SecurityException` if the calling thread is not allowed to access the package specified by the argument.

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

  The `checkPackageAccess` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    pkg - the package name.
  Throws: SecurityException
    if the caller does not have permission to access the specified package.
  See Also:
    loadClass

checkPackageDefinition

      public void checkPackageDefinition(String pkg)

  Throws a `SecurityException` if the calling thread is not allowed to define classes in the package specified by the argument.

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

  The `checkPackageDefinition` method for class `SecurityManager` always throws a `SecurityException`.

  Parameters:
    pkg - the package name.
  Throws: SecurityException
    if the caller does not have permission to define classes in the specified package.
  See Also:
    loadClass

checkSetFactory

      public 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`.

  The `checkSetFactory` method for class `SecurityManager` always throws a `SecurityException`.

  Throws: SecurityException
    if the caller does not have permission to specify a socket factory or a stream handler factory.
  See Also:
    setSocketFactory, setSocketImplFactory, setURLStreamHandlerFactory

checkMemberAccess

      public void checkMemberAccess(Class clazz,
                                    int which)

  Tests if a client is allowed to access members. If access is denied, throw a SecurityException. The default policy is to deny all accesses.

checkSecurityAccess

      public void checkSecurityAccess(String action)

  Tests access to certain operations for a security API action.

getThreadGroup

      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 overriden by specific security manager to return the appropriate thread group.

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