1 /*
2 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
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).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.jfr.internal;
27
28 import java.io.IOException;
29 import java.io.ObjectInputStream;
30 import java.io.ObjectOutputStream;
31 import java.security.AccessControlContext;
32 import java.security.AccessController;
33 import java.security.PrivilegedAction;
34 import java.util.Collections;
35 import java.util.HashSet;
36 import java.util.Objects;
37 import java.util.Set;
38
39 // User must never be able to subclass directly.
40 //
41 // Never put Control or Setting Control in a collections
42 // so overridable versions of hashCode or equals are
43 // executed in the wrong context. TODO: wrap this class
44 // in SsecureControl directly when it is instantiated and
45 // forward calls using AccessControlContext
46 abstract public class Control {
47 private final AccessControlContext context;
48 private final static int CACHE_SIZE = 5;
49 private final Set<?>[] cachedUnions = new HashSet<?>[CACHE_SIZE];
50 private final String[] cachedValues = new String[CACHE_SIZE];
51 private String defaultValue;
52 private String lastValue;
53
54 // called by exposed subclass in external API
55 public Control(AccessControlContext acc) {
56 Objects.requireNonNull(acc);
57 this.context = acc;
58
59 }
60
61 // only to be called by trusted VM code
62 public Control(String defaultValue) {
63 this.defaultValue = defaultValue;
64 this.context = null;
65 }
66
67 // For user code to override, must never be called from jdk.jfr.internal
68 // for user defined settings
69 public abstract String combine(Set<String> values);
70
71 // For user code to override, must never be called from jdk.jfr.internal
72 // for user defined settings
73 public abstract void setValue(String value);
74
75 // For user code to override, must never be called from jdk.jfr.internal
76 // for user defined settings
77 public abstract String getValue();
78
79 // Package private, user code should not have access to this method
80 final void apply(Set<String> values) {
81 setValueSafe(findCombineSafe(values));
82 }
83
84 // Package private, user code should not have access to this method.
85 // Only called during event registration
86 final void setDefault() {
87 if (defaultValue == null) {
88 defaultValue = getValueSafe();
89 }
90 apply(defaultValue);
91 }
92
93 final String getValueSafe() {
94 if (context == null) {
95 // VM events requires no access control context
96 return getValue();
97 } else {
98 return AccessController.doPrivileged(new PrivilegedAction<String>() {
99 @Override
100 public String run() {
101 try {
102 return getValue();
103 } catch (Throwable t) {
104 // Prevent malicious user to propagate exception callback in the wrong context
105 Logger.log(LogTag.JFR_SETTING, LogLevel.WARN, "Exception occured when trying to get value for " + getClass());
106 }
107 return defaultValue != null ? defaultValue : ""; // Need to return something
108 }
109 }, context);
110 }
111 }
112
113 private void apply(String value) {
114 if (lastValue != null && Objects.equals(value, lastValue)) {
115 return;
116 }
117 setValueSafe(value);
118 }
119
120 final void setValueSafe(String value) {
121 if (context == null) {
122 // VM events requires no access control context
123 try {
124 setValue(value);
125 } catch (Throwable t) {
126 Logger.log(LogTag.JFR_SETTING, LogLevel.WARN, "Exception occured when setting value \"" + value + "\" for " + getClass());
127 }
128 } else {
129 AccessController.doPrivileged(new PrivilegedAction<Void>() {
130 @Override
131 public Void run() {
132 try {
133 setValue(value);
134 } catch (Throwable t) {
135 // Prevent malicious user to propagate exception callback in the wrong context
136 Logger.log(LogTag.JFR_SETTING, LogLevel.WARN, "Exception occured when setting value \"" + value + "\" for " + getClass());
137 }
138 return null;
139 }
140 }, context);
141 }
142 lastValue = value;
143 }
144
145
146 private String combineSafe(Set<String> values) {
147 if (context == null) {
148 // VM events requires no access control context
149 return combine(values);
150 }
151 return AccessController.doPrivileged(new PrivilegedAction<String>() {
152 @Override
153 public String run() {
154 try {
155 combine(Collections.unmodifiableSet(values));
156 } catch (Throwable t) {
157 // Prevent malicious user to propagate exception callback in the wrong context
158 Logger.log(LogTag.JFR_SETTING, LogLevel.WARN, "Exception occured when combining " + values + " for " + getClass());
159 }
160 return null;
161 }
162 }, context);
163 }
164
165 private final String findCombineSafe(Set<String> values) {
166 if (values.size() == 1) {
167 return values.iterator().next();
168 }
169 for (int i = 0; i < CACHE_SIZE; i++) {
170 if (Objects.equals(cachedUnions[i], values)) {
171 return cachedValues[i];
172 }
173 }
174 String result = combineSafe(values);
175 for (int i = 0; i < CACHE_SIZE - 1; i++) {
176 cachedUnions[i + 1] = cachedUnions[i];
177 cachedValues[i + 1] = cachedValues[i];
178 }
179 cachedValues[0] = result;
180 cachedUnions[0] = values;
181 return result;
182 }
183
184
185 // package private, user code should not have access to this method
186 final String getDefaultValue() {
187 return defaultValue;
188 }
189
190 // package private, user code should not have access to this method
191 final String getLastValue() {
192 return lastValue;
193 }
194
195 // Precaution to prevent a malicious user from instantiating instances
196 // of a control where the context has not been set up.
197 @Override
198 public final Object clone() throws java.lang.CloneNotSupportedException {
199 throw new CloneNotSupportedException();
200 }
201
202 private final void writeObject(ObjectOutputStream out) throws IOException {
203 throw new IOException("Object cannot be serialized");
204 }
205
206 private final void readObject(ObjectInputStream in) throws IOException {
207 throw new IOException("Class cannot be deserialized");
208 }
209 }