1 /*
2 * Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
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9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
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25
26 package java.nio.file.attribute;
27
28 import java.nio.file.*;
29 import java.util.List;
30 import java.io.IOException;
31
32 /**
33 * A file attribute view that supports reading or updating a file's Access
34 * Control Lists (ACL) or file owner attributes.
35 *
36 * <p> ACLs are used to specify access rights to file system objects. An ACL is
37 * an ordered list of {@link AclEntry access-control-entries}, each specifying a
38 * {@link UserPrincipal} and the level of access for that user principal. This
39 * file attribute view defines the {@link #getAcl() getAcl}, and {@link
40 * #setAcl(List) setAcl} methods to read and write ACLs based on the ACL
41 * model specified in <a href="http://www.ietf.org/rfc/rfc3530.txt"><i>RFC 3530:
42 * Network File System (NFS) version 4 Protocol</i></a>. This file attribute view
43 * is intended for file system implementations that support the NFSv4 ACL model
44 * or have a <em>well-defined</em> mapping between the NFSv4 ACL model and the ACL
45 * model used by the file system. The details of such mapping are implementation
46 * dependent and are therefore unspecified.
47 *
48 * <p> This class also extends {@code FileOwnerAttributeView} so as to define
49 * methods to get and set the file owner.
50 *
51 * <p> When a file system provides access to a set of {@link FileStore
52 * file-systems} that are not homogeneous then only some of the file systems may
53 * support ACLs. The {@link FileStore#supportsFileAttributeView
54 * supportsFileAttributeView} method can be used to test if a file system
55 * supports ACLs.
56 *
57 * <a name="interop"><h4>Interoperability</h4></a>
58 *
59 * RFC 3530 allows for special user identities to be used on platforms that
60 * support the POSIX defined access permissions. The special user identities
61 * are "{@code OWNER@}", "{@code GROUP@}", and "{@code EVERYONE@}". When both
62 * the {@code AclFileAttributeView} and the {@link PosixFileAttributeView}
63 * are supported then these special user identities may be included in ACL {@link
64 * AclEntry entries} that are read or written. The file system's {@link
65 * UserPrincipalLookupService} may be used to obtain a {@link UserPrincipal}
66 * to represent these special identities by invoking the {@link
67 * UserPrincipalLookupService#lookupPrincipalByName lookupPrincipalByName}
68 * method. </p>
69 *
70 * <p> <b>Usage Example:</b>
71 * Suppose we wish to add an entry to an existing ACL to grant "joe" access:
72 * <pre>
73 * // lookup "joe"
74 * UserPrincipal joe = file.getFileSystem().getUserPrincipalLookupService()
75 * .lookupPrincipalByName("joe");
76 *
77 * // get view
78 * AclFileAttributeView view = Files.getFileAttributeView(file, AclFileAttributeView.class);
79 *
80 * // create ACE to give "joe" read access
81 * AclEntry entry = AclEntry.newBuilder()
82 * .setType(AclEntryType.ALLOW)
83 * .setPrincipal(joe)
84 * .setPermissions(AclEntryPermission.READ_DATA, AclEntryPermission.READ_ATTRIBUTES)
85 * .build();
86 *
87 * // read ACL, insert ACE, re-write ACL
88 * List<AclEntry> acl = view.getAcl();
89 * acl.add(0, entry); // insert before any DENY entries
90 * view.setAcl(acl);
91 * </pre>
92 *
93 * <h4> Dynamic Access </h4>
94 * <p> Where dynamic access to file attributes is required, the attributes
95 * supported by this attribute view are as follows:
96 * <blockquote>
97 * <table border="1" cellpadding="8">
98 * <tr>
99 * <th> Name </th>
100 * <th> Type </th>
101 * </tr>
102 * <tr>
103 * <td> "acl" </td>
104 * <td> {@link List}<{@link AclEntry}> </td>
105 * </tr>
106 * <tr>
107 * <td> "owner" </td>
108 * <td> {@link UserPrincipal} </td>
109 * </tr>
110 * </table>
111 * </blockquote>
112 *
113 * <p> The {@link Files#getAttribute getAttribute} method may be used to read
114 * the ACL or owner attributes as if by invoking the {@link #getAcl getAcl} or
115 * {@link #getOwner getOwner} methods.
116 *
117 * <p> The {@link Files#setAttribute setAttribute} method may be used to
118 * update the ACL or owner attributes as if by invoking the {@link #setAcl setAcl}
119 * or {@link #setOwner setOwner} methods.
120 *
121 * <h4> Setting the ACL when creating a file </h4>
122 *
123 * <p> Implementations supporting this attribute view may also support setting
124 * the initial ACL when creating a file or directory. The initial ACL
125 * may be provided to methods such as {@link Files#createFile createFile} or {@link
126 * Files#createDirectory createDirectory} as an {@link FileAttribute} with {@link
127 * FileAttribute#name name} {@code "acl:acl"} and a {@link FileAttribute#value
128 * value} that is the list of {@code AclEntry} objects.
129 *
130 * <p> Where an implementation supports an ACL model that differs from the NFSv4
131 * defined ACL model then setting the initial ACL when creating the file must
132 * translate the ACL to the model supported by the file system. Methods that
133 * create a file should reject (by throwing {@link IOException IOException})
134 * any attempt to create a file that would be less secure as a result of the
135 * translation.
136 *
137 * @since 1.7
138 */
139
140 public interface AclFileAttributeView
141 extends FileOwnerAttributeView
142 {
143 /**
144 * Returns the name of the attribute view. Attribute views of this type
145 * have the name {@code "acl"}.
146 */
147 @Override
148 String name();
149
150 /**
151 * Reads the access control list.
152 *
153 * <p> When the file system uses an ACL model that differs from the NFSv4
154 * defined ACL model, then this method returns an ACL that is the translation
155 * of the ACL to the NFSv4 ACL model.
156 *
157 * <p> The returned list is modifiable so as to facilitate changes to the
158 * existing ACL. The {@link #setAcl setAcl} method is used to update
159 * the file's ACL attribute.
160 *
161 * @return an ordered list of {@link AclEntry entries} representing the
162 * ACL
163 *
164 * @throws IOException
165 * if an I/O error occurs
166 * @throws SecurityException
167 * In the case of the default provider, a security manager is
168 * installed, and it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
169 * or its {@link SecurityManager#checkRead(String) checkRead} method
170 * denies read access to the file.
171 */
172 List<AclEntry> getAcl() throws IOException;
173
174 /**
175 * Updates (replace) the access control list.
176 *
177 * <p> Where the file system supports Access Control Lists, and it uses an
178 * ACL model that differs from the NFSv4 defined ACL model, then this method
179 * must translate the ACL to the model supported by the file system. This
180 * method should reject (by throwing {@link IOException IOException}) any
181 * attempt to write an ACL that would appear to make the file more secure
182 * than would be the case if the ACL were updated. Where an implementation
183 * does not support a mapping of {@link AclEntryType#AUDIT} or {@link
184 * AclEntryType#ALARM} entries, then this method ignores these entries when
185 * writing the ACL.
186 *
187 * <p> If an ACL entry contains a {@link AclEntry#principal user-principal}
188 * that is not associated with the same provider as this attribute view then
189 * {@link ProviderMismatchException} is thrown. Additional validation, if
190 * any, is implementation dependent.
191 *
192 * <p> If the file system supports other security related file attributes
193 * (such as a file {@link PosixFileAttributes#permissions
194 * access-permissions} for example), the updating the access control list
195 * may also cause these security related attributes to be updated.
196 *
197 * @param acl
198 * the new access control list
199 *
200 * @throws IOException
201 * if an I/O error occurs or the ACL is invalid
202 * @throws SecurityException
203 * In the case of the default provider, a security manager is
204 * installed, it denies {@link RuntimePermission}<tt>("accessUserInformation")</tt>
205 * or its {@link SecurityManager#checkWrite(String) checkWrite}
206 * method denies write access to the file.
207 */
208 void setAcl(List<AclEntry> acl) throws IOException;
209 }