1 /*
2 * Copyright (c) 1997, 2007, 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 com.sun.crypto.provider;
27
28 import javax.crypto.ShortBufferException;
29
30 /**
31 * This class implements padding as specified in the PKCS#5 standard.
32 *
33 * @author Gigi Ankeny
34 *
35 *
36 * @see Padding
37 */
38 final class PKCS5Padding implements Padding {
39
40 private int blockSize;
41
42 PKCS5Padding(int blockSize) {
43 this.blockSize = blockSize;
44 }
45
46 /**
47 * Adds the given number of padding bytes to the data input.
48 * The value of the padding bytes is determined
49 * by the specific padding mechanism that implements this
50 * interface.
51 *
52 * @param in the input buffer with the data to pad
53 * @param off the offset in <code>in</code> where the padding bytes
54 * are appended
55 * @param len the number of padding bytes to add
56 *
57 * @exception ShortBufferException if <code>in</code> is too small to hold
58 * the padding bytes
59 */
60 public void padWithLen(byte[] in, int off, int len)
61 throws ShortBufferException
62 {
63 if (in == null)
64 return;
65
66 if ((off + len) > in.length) {
67 throw new ShortBufferException("Buffer too small to hold padding");
68 }
69
70 byte paddingOctet = (byte) (len & 0xff);
71 for (int i = 0; i < len; i++) {
72 in[i + off] = paddingOctet;
73 }
74 return;
75 }
76
77 /**
78 * Returns the index where the padding starts.
79 *
80 * <p>Given a buffer with padded data, this method returns the
81 * index where the padding starts.
82 *
83 * @param in the buffer with the padded data
84 * @param off the offset in <code>in</code> where the padded data starts
85 * @param len the length of the padded data
86 *
87 * @return the index where the padding starts, or -1 if the input is
88 * not properly padded
89 */
90 public int unpad(byte[] in, int off, int len) {
91 if ((in == null) ||
92 (len == 0)) { // this can happen if input is really a padded buffer
93 return 0;
94 }
95
96 byte lastByte = in[off + len - 1];
97 int padValue = (int)lastByte & 0x0ff;
98 if ((padValue < 0x01)
99 || (padValue > blockSize)) {
100 return -1;
101 }
102
103 int start = off + len - ((int)lastByte & 0x0ff);
104 if (start < off) {
105 return -1;
106 }
107
108 for (int i = 0; i < ((int)lastByte & 0x0ff); i++) {
109 if (in[start+i] != lastByte) {
110 return -1;
111 }
112 }
113
114 return start;
115 }
116
117 /**
118 * Determines how long the padding will be for a given input length.
119 *
120 * @param len the length of the data to pad
121 *
122 * @return the length of the padding
123 */
124 public int padLength(int len) {
125 int paddingOctet = blockSize - (len % blockSize);
126 return paddingOctet;
127 }
128 }
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1 /*
2 * Copyright (c) 1997, 2017, 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 com.sun.crypto.provider;
27
28 import javax.crypto.ShortBufferException;
29 import java.util.Arrays;
30
31 /**
32 * This class implements padding as specified in the PKCS#5 standard.
33 *
34 * @author Gigi Ankeny
35 *
36 *
37 * @see Padding
38 */
39 final class PKCS5Padding implements Padding {
40
41 private int blockSize;
42
43 PKCS5Padding(int blockSize) {
44 this.blockSize = blockSize;
45 }
46
47 /**
48 * Adds the given number of padding bytes to the data input.
49 * The value of the padding bytes is determined
50 * by the specific padding mechanism that implements this
51 * interface.
52 *
53 * @param in the input buffer with the data to pad
54 * @param off the offset in <code>in</code> where the padding bytes
55 * are appended
56 * @param len the number of padding bytes to add
57 *
58 * @exception ShortBufferException if <code>in</code> is too small to hold
59 * the padding bytes
60 */
61 public void padWithLen(byte[] in, int off, int len)
62 throws ShortBufferException
63 {
64 if (in == null)
65 return;
66
67 int idx = Math.addExact(off, len);
68 if (idx > in.length) {
69 throw new ShortBufferException("Buffer too small to hold padding");
70 }
71
72 byte paddingOctet = (byte) (len & 0xff);
73 Arrays.fill(in, off, idx, paddingOctet);
74 return;
75 }
76
77 /**
78 * Returns the index where the padding starts.
79 *
80 * <p>Given a buffer with padded data, this method returns the
81 * index where the padding starts.
82 *
83 * @param in the buffer with the padded data
84 * @param off the offset in <code>in</code> where the padded data starts
85 * @param len the length of the padded data
86 *
87 * @return the index where the padding starts, or -1 if the input is
88 * not properly padded
89 */
90 public int unpad(byte[] in, int off, int len) {
91 if ((in == null) ||
92 (len == 0)) { // this can happen if input is really a padded buffer
93 return 0;
94 }
95 int idx = Math.addExact(off, len);
96 byte lastByte = in[idx - 1];
97 int padValue = (int)lastByte & 0x0ff;
98 if ((padValue < 0x01)
99 || (padValue > blockSize)) {
100 return -1;
101 }
102
103 int start = idx - padValue;
104 if (start < off) {
105 return -1;
106 }
107
108 for (int i = start; i < idx; i++) {
109 if (in[i] != lastByte) {
110 return -1;
111 }
112 }
113 return start;
114 }
115
116 /**
117 * Determines how long the padding will be for a given input length.
118 *
119 * @param len the length of the data to pad
120 *
121 * @return the length of the padding
122 */
123 public int padLength(int len) {
124 int paddingOctet = blockSize - (len % blockSize);
125 return paddingOctet;
126 }
127 }
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