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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 | } | ||