215 lines
9.2 KiB
Java
215 lines
9.2 KiB
Java
/*
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* Copyright (c) 2007, 2017, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.nio.file.attribute;
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import java.nio.file.*;
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import java.util.List;
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import java.io.IOException;
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/**
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* A file attribute view that supports reading or updating a file's Access
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* Control Lists (ACL) or file owner attributes.
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*
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* <p> ACLs are used to specify access rights to file system objects. An ACL is
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* an ordered list of {@link AclEntry access-control-entries}, each specifying a
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* {@link UserPrincipal} and the level of access for that user principal. This
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* file attribute view defines the {@link #getAcl() getAcl}, and {@link
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* #setAcl(List) setAcl} methods to read and write ACLs based on the ACL
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* model specified in <a href="http://www.ietf.org/rfc/rfc3530.txt"><i>RFC 3530:
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* Network File System (NFS) version 4 Protocol</i></a>. This file attribute view
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* is intended for file system implementations that support the NFSv4 ACL model
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* or have a <em>well-defined</em> mapping between the NFSv4 ACL model and the ACL
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* model used by the file system. The details of such mapping are implementation
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* dependent and are therefore unspecified.
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*
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* <p> This class also extends {@code FileOwnerAttributeView} so as to define
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* methods to get and set the file owner.
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*
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* <p> When a file system provides access to a set of {@link FileStore
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* file-systems} that are not homogeneous then only some of the file systems may
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* support ACLs. The {@link FileStore#supportsFileAttributeView
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* supportsFileAttributeView} method can be used to test if a file system
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* supports ACLs.
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*
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* <h2>Interoperability</h2>
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*
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* RFC 3530 allows for special user identities to be used on platforms that
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* support the POSIX defined access permissions. The special user identities
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* are "{@code OWNER@}", "{@code GROUP@}", and "{@code EVERYONE@}". When both
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* the {@code AclFileAttributeView} and the {@link PosixFileAttributeView}
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* are supported then these special user identities may be included in ACL {@link
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* AclEntry entries} that are read or written. The file system's {@link
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* UserPrincipalLookupService} may be used to obtain a {@link UserPrincipal}
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* to represent these special identities by invoking the {@link
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* UserPrincipalLookupService#lookupPrincipalByName lookupPrincipalByName}
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* method.
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*
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* <p> <b>Usage Example:</b>
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* Suppose we wish to add an entry to an existing ACL to grant "joe" access:
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* <pre>
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* // lookup "joe"
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* UserPrincipal joe = file.getFileSystem().getUserPrincipalLookupService()
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* .lookupPrincipalByName("joe");
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*
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* // get view
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* AclFileAttributeView view = Files.getFileAttributeView(file, AclFileAttributeView.class);
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*
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* // create ACE to give "joe" read access
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* AclEntry entry = AclEntry.newBuilder()
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* .setType(AclEntryType.ALLOW)
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* .setPrincipal(joe)
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* .setPermissions(AclEntryPermission.READ_DATA, AclEntryPermission.READ_ATTRIBUTES)
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* .build();
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*
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* // read ACL, insert ACE, re-write ACL
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* List<AclEntry> acl = view.getAcl();
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* acl.add(0, entry); // insert before any DENY entries
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* view.setAcl(acl);
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* </pre>
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*
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* <h2> Dynamic Access </h2>
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* <p> Where dynamic access to file attributes is required, the attributes
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* supported by this attribute view are as follows:
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* <blockquote>
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* <table class="striped">
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* <caption style="display:none">Supported attributes</caption>
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* <thead>
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* <tr>
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* <th scope="col"> Name </th>
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* <th scope="col"> Type </th>
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* </tr>
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* </thead>
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* <tbody>
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* <tr>
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* <th scope="row"> "acl" </th>
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* <td> {@link List}<{@link AclEntry}> </td>
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* </tr>
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* <tr>
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* <th scope="row"> "owner" </th>
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* <td> {@link UserPrincipal} </td>
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* </tr>
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* </tbody>
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* </table>
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* </blockquote>
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*
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* <p> The {@link Files#getAttribute getAttribute} method may be used to read
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* the ACL or owner attributes as if by invoking the {@link #getAcl getAcl} or
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* {@link #getOwner getOwner} methods.
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*
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* <p> The {@link Files#setAttribute setAttribute} method may be used to
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* update the ACL or owner attributes as if by invoking the {@link #setAcl setAcl}
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* or {@link #setOwner setOwner} methods.
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*
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* <h2> Setting the ACL when creating a file </h2>
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*
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* <p> Implementations supporting this attribute view may also support setting
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* the initial ACL when creating a file or directory. The initial ACL
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* may be provided to methods such as {@link Files#createFile createFile} or {@link
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* Files#createDirectory createDirectory} as an {@link FileAttribute} with {@link
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* FileAttribute#name name} {@code "acl:acl"} and a {@link FileAttribute#value
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* value} that is the list of {@code AclEntry} objects.
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*
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* <p> Where an implementation supports an ACL model that differs from the NFSv4
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* defined ACL model then setting the initial ACL when creating the file must
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* translate the ACL to the model supported by the file system. Methods that
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* create a file should reject (by throwing {@link IOException IOException})
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* any attempt to create a file that would be less secure as a result of the
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* translation.
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*
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* @since 1.7
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*/
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public interface AclFileAttributeView
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extends FileOwnerAttributeView
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{
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/**
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* Returns the name of the attribute view. Attribute views of this type
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* have the name {@code "acl"}.
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*/
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@Override
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String name();
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/**
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* Reads the access control list.
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*
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* <p> When the file system uses an ACL model that differs from the NFSv4
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* defined ACL model, then this method returns an ACL that is the translation
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* of the ACL to the NFSv4 ACL model.
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*
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* <p> The returned list is modifiable so as to facilitate changes to the
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* existing ACL. The {@link #setAcl setAcl} method is used to update
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* the file's ACL attribute.
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*
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* @return an ordered list of {@link AclEntry entries} representing the
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* ACL
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*
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* @throws IOException
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* if an I/O error occurs
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* @throws SecurityException
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* In the case of the default provider, a security manager is
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* installed, and it denies {@link RuntimePermission}{@code ("accessUserInformation")}
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* or its {@link SecurityManager#checkRead(String) checkRead} method
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* denies read access to the file.
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*/
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List<AclEntry> getAcl() throws IOException;
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/**
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* Updates (replace) the access control list.
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*
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* <p> Where the file system supports Access Control Lists, and it uses an
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* ACL model that differs from the NFSv4 defined ACL model, then this method
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* must translate the ACL to the model supported by the file system. This
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* method should reject (by throwing {@link IOException IOException}) any
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* attempt to write an ACL that would appear to make the file more secure
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* than would be the case if the ACL were updated. Where an implementation
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* does not support a mapping of {@link AclEntryType#AUDIT} or {@link
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* AclEntryType#ALARM} entries, then this method ignores these entries when
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* writing the ACL.
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*
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* <p> If an ACL entry contains a {@link AclEntry#principal user-principal}
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* that is not associated with the same provider as this attribute view then
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* {@link ProviderMismatchException} is thrown. Additional validation, if
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* any, is implementation dependent.
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*
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* <p> If the file system supports other security related file attributes
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* (such as a file {@link PosixFileAttributes#permissions
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* access-permissions} for example), the updating the access control list
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* may also cause these security related attributes to be updated.
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*
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* @param acl
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* the new access control list
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*
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* @throws IOException
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* if an I/O error occurs or the ACL is invalid
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* @throws SecurityException
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* In the case of the default provider, a security manager is
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* installed, it denies {@link RuntimePermission}{@code ("accessUserInformation")}
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* or its {@link SecurityManager#checkWrite(String) checkWrite}
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* method denies write access to the file.
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*/
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void setAcl(List<AclEntry> acl) throws IOException;
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}
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