1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.codec.digest;
18
19 import java.security.SecureRandom;
20 import java.util.Random;
21
22 /**
23 * Base64-like method to convert binary bytes into ASCII chars.
24 * <p>
25 * TODO: Can Base64 be reused?
26 * </p>
27 * <p>
28 * This class is immutable and thread-safe.
29 * </p>
30 */
31 final class B64 {
32
33 /**
34 * Table with characters for Base64 transformation.
35 */
36 static final String B64T_STRING = "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
37
38 /**
39 * Table with characters for Base64 transformation.
40 */
41 static final char[] B64T_ARRAY = B64T_STRING.toCharArray();
42
43 /**
44 * Base64 like conversion of bytes to ASCII chars.
45 *
46 * @param b2
47 * A byte from the result.
48 * @param b1
49 * A byte from the result.
50 * @param b0
51 * A byte from the result.
52 * @param outLen
53 * The number of expected output chars.
54 * @param buffer
55 * Where the output chars is appended to.
56 */
57 static void b64from24bit(final byte b2, final byte b1, final byte b0, final int outLen,
58 final StringBuilder buffer) {
59 // The bit masking is necessary because the JVM byte type is signed!
60 int w = b2 << 16 & 0x00ffffff | b1 << 8 & 0x00ffff | b0 & 0xff;
61 // It's effectively a "for" loop but kept to resemble the original C code.
62 int n = outLen;
63 while (n-- > 0) {
64 buffer.append(B64T_ARRAY[w & 0x3f]);
65 w >>= 6;
66 }
67 }
68
69 /**
70 * Generates a string of random chars from the B64T set.
71 * <p>
72 * The salt is generated with {@link SecureRandom}.
73 * </p>
74 *
75 * @param num Number of chars to generate.
76 * @return a random salt {@link String}.
77 */
78 static String getRandomSalt(final int num) {
79 return getRandomSalt(num, new SecureRandom());
80 }
81
82 /**
83 * Generates a string of random chars from the B64T set.
84 * <p>
85 * The salt is generated with the {@link Random} provided.
86 * </p>
87 *
88 * @param num Number of chars to generate.
89 * @param random an instance of {@link Random}.
90 * @return a random salt {@link String}.
91 */
92 static String getRandomSalt(final int num, final Random random) {
93 final StringBuilder saltString = new StringBuilder(num);
94 for (int i = 1; i <= num; i++) {
95 saltString.append(B64T_STRING.charAt(random.nextInt(B64T_STRING.length())));
96 }
97 return saltString.toString();
98 }
99 }