Class FilePermission

All Implemented Interfaces:
Serializable, Guard 

public final class FilePermission
extends 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. Such a pathname is called a wildcard pathname. Otherwise, it's a simple pathname.

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", "delete", and "readlink". 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.
readlink
read link permission. Allows the target of a symbolic link to be read by invoking the readSymbolicLink method.

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
See Also:
Permission, Permissions, PermissionCollection

Constructors

Constructor and Description
FilePermission(String path, String actions)

Creates a new FilePermission object with the specified actions.

Methods

Modifier and Type Method and Description
boolean equals(Object obj)

Checks two FilePermission objects for equality.
String getActions()

Returns the "canonical string representation" of the actions.
int hashCode()

Returns the hash code value for this object.
boolean implies(Permission p)

Checks if this FilePermission object "implies" the specified permission.
PermissionCollection newPermissionCollection()

Returns a new PermissionCollection object for storing FilePermission objects.

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

Constructors

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", "delete", and "readlink".

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. The special pathname "<<ALL FILES>>" matches any file.

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.

A pathname containing an empty string represents an empty path.

Parameters:
path - the pathname of the file/directory.
actions - the action string.
Throws:
IllegalArgumentException - If actions is null, empty or contains an action other than the specified possible actions.

Methods

implies

public boolean implies(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 all files in the "/tmp" directory, including the one named "foo".

Precisely, a simple pathname implies another simple pathname if and only if they are equal. A simple pathname never implies a wildcard pathname. A wildcard pathname implies another wildcard pathname if and only if all simple pathnames implied by the latter are implied by the former. A wildcard pathname implies a simple pathname if and only if

  • if the wildcard flag is "*", the simple pathname's path must be right inside the wildcard pathname's path.
  • if the wildcard flag is "-", the simple pathname's path must be recursively inside the wildcard pathname's path.

"<<ALL FILES>>" implies every other pathname. No pathname, except for "<<ALL FILES>>" itself, implies "<<ALL FILES>>".

Specified by:
implies in class Permission
Parameters:
p - the permission to check against.
Returns:
true if the specified permission is not null and is implied by this object, false otherwise.

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.

Specified by:
equals in class Permission
Implementation Note:
More specifically, two pathnames are the same if and only if they have the same wildcard flag and their npath are equal. Or they are both "<<ALL FILES>>".
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, false otherwise.
See Also:
Object.hashCode(), HashMap

hashCode

public int hashCode()

Returns the hash code value for this object.

Specified by:
hashCode in class Permission
Returns:
a hash code value for this object.
See Also:
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

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, readlink. For example, if this FilePermission object allows both write and read actions, a call to getActions will return the string "read,write".

Specified by:
getActions in class Permission
Returns:
the canonical string representation of the actions.

newPermissionCollection

public 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.
Overrides:
newPermissionCollection in class Permission
Returns:
a new PermissionCollection object suitable for storing FilePermissions.

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/javase/8/docs/api/java/io/FilePermission.html