1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.shiro.crypto;
20
21 import org.apache.shiro.util.ByteSource;
22
23 import java.security.SecureRandom;
24
25 /**
26 * Default implementation of the {@link RandomNumberGenerator RandomNumberGenerator} interface, backed by a
27 * {@link SecureRandom SecureRandom} instance.
28 * <p/>
29 * This class is a little easier to use than using the JDK's {@code SecureRandom} class directly. It also
30 * allows for JavaBeans-style of customization, convenient for Shiro's INI configuration or other IoC configuration
31 * mechanism.
32 *
33 * @since 1.1
34 */
35 public class SecureRandomNumberGenerator implements RandomNumberGenerator {
36
37 protected static final int DEFAULT_NEXT_BYTES_SIZE = 16; //16 bytes == 128 bits (a common number in crypto)
38
39 private int defaultNextBytesSize;
40 private SecureRandom secureRandom;
41
42 /**
43 * Creates a new instance with a default backing {@link SecureRandom SecureRandom} and a
44 * {@link #getDefaultNextBytesSize() defaultNextBytesSize} of {@code 16}, which equals 128 bits, a size commonly
45 * used in cryptographic algorithms.
46 */
47 public SecureRandomNumberGenerator() {
48 this.defaultNextBytesSize = DEFAULT_NEXT_BYTES_SIZE;
49 this.secureRandom = new SecureRandom();
50 }
51
52 /**
53 * Seeds the backing {@link SecureRandom SecureRandom} instance with additional seed data.
54 *
55 * @param bytes the seed bytes
56 * @see SecureRandom#setSeed(byte[])
57 */
58 public void setSeed(byte[] bytes) {
59 this.secureRandom.setSeed(bytes);
60 }
61
62 /**
63 * Returns the {@link SecureRandom SecureRandom} backing this instance.
64 *
65 * @return the {@link SecureRandom SecureRandom} backing this instance.
66 */
67 public SecureRandom getSecureRandom() {
68 return secureRandom;
69 }
70
71 /**
72 * Sets the {@link SecureRandom SecureRandom} to back this instance.
73 *
74 * @param random the {@link SecureRandom SecureRandom} to back this instance.
75 * @throws NullPointerException if the method argument is null
76 */
77 public void setSecureRandom(SecureRandom random) throws NullPointerException {
78 if (random == null) {
79 throw new NullPointerException("SecureRandom argument cannot be null.");
80 }
81 this.secureRandom = random;
82 }
83
84 /**
85 * Returns the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}. Defaults to
86 * {@code 16}, which equals 128 bits, a size commonly used in cryptographic algorithms.
87 *
88 * @return the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}.
89 */
90 public int getDefaultNextBytesSize() {
91 return defaultNextBytesSize;
92 }
93
94 /**
95 * Sets the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}. Defaults to
96 * {@code 16}, which equals 128 bits, a size commonly used in cryptographic algorithms.
97 *
98 * @param defaultNextBytesSize the size of the generated byte array for calls to {@link #nextBytes() nextBytes()}.
99 * @throws IllegalArgumentException if the argument is 0 or negative
100 */
101 public void setDefaultNextBytesSize(int defaultNextBytesSize) throws IllegalArgumentException {
102 if ( defaultNextBytesSize <= 0) {
103 throw new IllegalArgumentException("size value must be a positive integer (1 or larger)");
104 }
105 this.defaultNextBytesSize = defaultNextBytesSize;
106 }
107
108 public ByteSource nextBytes() {
109 return nextBytes(getDefaultNextBytesSize());
110 }
111
112 public ByteSource nextBytes(int numBytes) {
113 if (numBytes <= 0) {
114 throw new IllegalArgumentException("numBytes argument must be a positive integer (1 or larger)");
115 }
116 byte[] bytes = new byte[numBytes];
117 this.secureRandom.nextBytes(bytes);
118 return ByteSource.Util.bytes(bytes);
119 }
120 }