java.io
Class FilePermission

java.lang.Object
  java.security.Permission
      java.io.FilePermission

All Implemented Interfaces:

java.security.Guard, Serializable

public final class FilePermission

extends java.security.Permission

implements Serializable

This class represents access to a file or directory. A FilePermission consists of a pathname and a set of actions valid for that pathname.

Pathname is the pathname of the file or directory granted the specified actions. A pathname that ends in "/*" (where "/" is the file separator character, File.separatorChar) indicates all the files and directories contained in that directory. A pathname that ends with "/-" indicates (recursively) all files and subdirectories contained in that directory. A pathname consisting of the special token "<<ALL FILES>>" matches any file.

Note: A pathname consisting of a single "*" indicates all the files in the current directory, while a pathname consisting of a single "-" indicates all the files in the current directory and (recursively) all files and subdirectories contained in the current directory.

The actions to be granted are passed to the constructor in a string containing a list of one or more comma-separated keywords. The possible keywords are "read", "write", "execute", and "delete". Their meaning is defined as follows:

read

read permission

write

write permission

execute

execute permission. Allows Runtime.exec to be called. Corresponds to SecurityManager.checkExec.

delete

delete permission. Allows File.delete to be called. Corresponds to SecurityManager.checkDelete.

The actions string is converted to lowercase before processing.

Be careful when granting FilePermissions. Think about the implications of granting read and especially write access to various files and directories. The "<<ALL FILES>>" permission with write action is especially dangerous. This grants permission to write to the entire file system. One thing this effectively allows is replacement of the system binary, including the JVM runtime environment.

Please note: Code can always read a file from the same directory it's in (or a subdirectory of that directory); it does not need explicit permission to do so.

Since:

1.2

Author:

Marianne Mueller, Roland Schemers

See Also:

Permission, Permissions, PermissionCollection

Field Summary

private String	actions the actions string.
private static int	ALL All actions (read,write,execute,delete)
private String	cpath
private static int	DELETE Delete action.
private boolean	directory
private static int	EXECUTE Execute action.
private int	mask
private static int	NONE No actions.
private static int	READ Read action.
private boolean	recursive
private static char	RECURSIVE_CHAR
private static long	serialVersionUID
private static char	WILD_CHAR
private static int	WRITE Write action.

Fields inherited from class java.security.Permission

Constructor Summary

(package private)	FilePermission(String path, int mask) Creates a new FilePermission object using an action mask.
	FilePermission(String path, String actions) Creates a new FilePermission object with the specified actions.

Method Summary

boolean	equals(Object obj) Checks two FilePermission objects for equality.
String	getActions() Returns the "canonical string representation" of the actions.
private static String	getActions(int mask) Return the canonical string representation of the actions.
(package private) int	getMask() Return the current action mask.
private static int	getMask(String actions) Converts an actions String to an actions mask.
int	hashCode() Returns the hash code value for this object.
boolean	implies(java.security.Permission p) Checks if this FilePermission object "implies" the specified permission.
(package private) boolean	impliesIgnoreMask(FilePermission that) Checks if the Permission's actions are a proper subset of the this object's actions.
private void	init(int mask) initialize a FilePermission object.
java.security.PermissionCollection	newPermissionCollection() Returns a new PermissionCollection object for storing FilePermission objects.
private void	readObject(ObjectInputStream s) readObject is called to restore the state of the FilePermission from a stream.
private void	writeObject(ObjectOutputStream s) WriteObject is called to save the state of the FilePermission to a stream.

Methods inherited from class java.security.Permission

checkGuard, getName, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

EXECUTE

private static final int EXECUTE

Execute action.

See Also:

Constant Field Values

WRITE

private static final int WRITE

Write action.

See Also:

Constant Field Values

READ

private static final int READ

Read action.

See Also:

Constant Field Values

DELETE

private static final int DELETE

Delete action.

See Also:

Constant Field Values

ALL

private static final int ALL

All actions (read,write,execute,delete)

See Also:

Constant Field Values

NONE

private static final int NONE

No actions.

See Also:

Constant Field Values

mask

private transient int mask

directory

private transient boolean directory

recursive

private transient boolean recursive

actions

private String actions

the actions string.

cpath

private transient String cpath

RECURSIVE_CHAR

private static final char RECURSIVE_CHAR

See Also:

Constant Field Values

WILD_CHAR

private static final char WILD_CHAR

See Also:

Constant Field Values

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

FilePermission

public FilePermission(String path,
                      String actions)

Creates a new FilePermission object with the specified actions. path is the pathname of a file or directory, and actions contains a comma-separated list of the desired actions granted on the file or directory. Possible actions are "read", "write", "execute", and "delete".

A pathname that ends in "/*" (where "/" is the file separator character, File.separatorChar) indicates a directory and all the files contained in that directory. A pathname that ends with "/-" indicates a directory and (recursively) all files and subdirectories contained in that directory. The special pathname "<<ALL FILES>>" matches all files.

A pathname consisting of a single "*" indicates all the files in the current directory, while a pathname consisting of a single "-" indicates all the files in the current directory and (recursively) all files and subdirectories contained in the current directory.

Parameters:

path - the pathname of the file/directory.

actions - the action string.

FilePermission

FilePermission(String path,
               int mask)

Creates a new FilePermission object using an action mask. More efficient than the FilePermission(String, String) constructor. Can be used from within code that needs to create a FilePermission object to pass into the implies method.

Parameters:

path - the pathname of the file/directory.

mask - the action mask to use.

Method Detail

init

private void init(int mask)

initialize a FilePermission object. Common to all constructors. Also called during de-serialization.

Parameters:

mask - the actions mask to use.

implies

public boolean implies(java.security.Permission p)

Checks if this FilePermission object "implies" the specified permission.

More specifically, this method returns true if:

• p is an instanceof FilePermission,

• p's actions are a proper subset of this object's actions, and

• p's pathname is implied by this object's pathname. For example, "/tmp/*" implies "/tmp/foo", since "/tmp/*" encompasses the "/tmp" directory and all files in that directory, including the one named "foo".

Parameters:

p - the permission to check against.

Returns:

true if the specified permission is implied by this object, false if not.

impliesIgnoreMask

boolean impliesIgnoreMask(FilePermission that)

Checks if the Permission's actions are a proper subset of the this object's actions. Returns the effective mask iff the this FilePermission's path also implies that FilePermission's path.

Parameters:

that - the FilePermission to check against.

Returns:

the effective mask

equals

public boolean equals(Object obj)

Checks two FilePermission objects for equality. Checks that obj is a FilePermission, and has the same pathname and actions as this object.

Parameters:

obj - the object we are testing for equality with this object.

Returns:

true if obj is a FilePermission, and has the same pathname and actions as this FilePermission object.

hashCode

public int hashCode()

Returns the hash code value for this object.

Returns:

a hash code value for this object.

getMask

private static int getMask(String actions)

Converts an actions String to an actions mask.

Returns:

the actions mask.

getMask

int getMask()

Return the current action mask. Used by the FilePermissionCollection.

Returns:

the actions mask.

getActions

private static String getActions(int mask)

Return the canonical string representation of the actions. Always returns present actions in the following order: read, write, execute, delete.

Returns:

the canonical string representation of the actions.

getActions

public String getActions()

Returns the "canonical string representation" of the actions. That is, this method always returns present actions in the following order: read, write, execute, delete. For example, if this FilePermission object allows both write and read actions, a call to getActions will return the string "read,write".

Returns:

the canonical string representation of the actions.

newPermissionCollection

public java.security.PermissionCollection newPermissionCollection()

Returns a new PermissionCollection object for storing FilePermission objects.

FilePermission objects must be stored in a manner that allows them to be inserted into the collection in any order, but that also enables the PermissionCollection implies method to be implemented in an efficient (and consistent) manner.

For example, if you have two FilePermissions:

1. "/tmp/-", "read"
2. "/tmp/scratch/foo", "write"

and you are calling the implies method with the FilePermission:

   "/tmp/scratch/foo", "read,write", 
 

then the implies function must take into account both the "/tmp/-" and "/tmp/scratch/foo" permissions, so the effective permission is "read,write", and implies returns true. The "implies" semantics for FilePermissions are handled properly by the PermissionCollection object returned by this newPermissionCollection method.

Returns:

a new PermissionCollection object suitable for storing FilePermissions.

writeObject

private void writeObject(ObjectOutputStream s)
                  throws IOException

WriteObject is called to save the state of the FilePermission to a stream. The actions are serialized, and the superclass takes care of the name.

Throws:

IOException

readObject

private void readObject(ObjectInputStream s)
                 throws IOException,
                        ClassNotFoundException

readObject is called to restore the state of the FilePermission from a stream.

Throws:

IOException

ClassNotFoundException