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| 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 | +} | |