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/*
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* Copyright (c) 2003, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package com.sun.crypto.provider;
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import javax.crypto.ShortBufferException;
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/**
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* This class implements padding as specified in the W3 XML ENC standard.
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*
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* @author Valerie Peng
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*
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*
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* @see Padding
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*/
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final class ISO10126Padding implements Padding {
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private int blockSize;
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ISO10126Padding(int blockSize) {
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this.blockSize = blockSize;
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}
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/**
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* Adds the given number of padding bytes to the data input.
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* The value of the padding bytes is determined
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* by the specific padding mechanism that implements this
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* interface.
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*
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* @param in the input buffer with the data to pad
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* @param off the offset in <code>in</code> where the padding bytes
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* are appended
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* @param len the number of padding bytes to add
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*
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* @exception ShortBufferException if <code>in</code> is too small to hold
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* the padding bytes
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*/
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public void padWithLen(byte[] in, int off, int len)
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throws ShortBufferException
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{
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if (in == null)
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return;
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if ((off + len) > in.length) {
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throw new ShortBufferException("Buffer too small to hold padding");
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}
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byte paddingOctet = (byte) (len & 0xff);
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byte[] padding = new byte[len];
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SunJCE.getRandom().nextBytes(padding);
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padding[len-1] = paddingOctet;
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System.arraycopy(padding, 0, in, off, len);
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return;
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}
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/**
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* Returns the index where the padding starts.
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*
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* <p>Given a buffer with padded data, this method returns the
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* index where the padding starts.
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*
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* @param in the buffer with the padded data
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* @param off the offset in <code>in</code> where the padded data starts
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* @param len the length of the padded data
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*
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* @return the index where the padding starts, or -1 if the input is
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* not properly padded
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*/
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public int unpad(byte[] in, int off, int len) {
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if ((in == null) ||
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(len == 0)) { // this can happen if input is really a padded buffer
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return 0;
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}
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byte lastByte = in[off + len - 1];
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int padValue = (int)lastByte & 0x0ff;
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if ((padValue < 0x01)
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|| (padValue > blockSize)) {
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return -1;
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}
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int start = off + len - ((int)lastByte & 0x0ff);
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if (start < off) {
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return -1;
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}
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return start;
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}
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/**
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* Determines how long the padding will be for a given input length.
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*
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* @param len the length of the data to pad
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*
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* @return the length of the padding
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*/
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public int padLength(int len) {
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int paddingOctet = blockSize - (len % blockSize);
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return paddingOctet;
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}
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}
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