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1: /* PKCS7.java -- 2: Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. 3: 4: This file is a part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2 of the License, or (at 9: your option) any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; if not, write to the Free Software 18: Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 19: USA 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: 39: package gnu.javax.crypto.pad; 40: 41: import gnu.java.security.Configuration; 42: import gnu.java.security.Registry; 43: import gnu.java.security.util.Util; 44: 45: import java.util.logging.Logger; 46: 47: /** 48: * The implementation of the PKCS7 padding algorithm. 49: * <p> 50: * This algorithm is described for 8-byte blocks in [RFC-1423] and extended to 51: * block sizes of up to 256 bytes in [PKCS-7]. 52: * <p> 53: * References: 54: * <ol> 55: * <li><a href="http://www.ietf.org/rfc/rfc1423.txt">RFC-1423</a>: Privacy 56: * Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and 57: * Identifiers.</li> 58: * <li><a href="http://www.ietf.org/">IETF</a>.</li> 59: * <li><a href="http://www.rsasecurity.com/rsalabs/pkcs/pkcs-7/">[PKCS-7]</a> 60: * PKCS #7: Cryptographic Message Syntax Standard - An RSA Laboratories 61: * Technical Note.</li> 62: * <li><a href="http://www.rsasecurity.com/">RSA Security</a>.</li> 63: * </ol> 64: */ 65: public final class PKCS7 66: extends BasePad 67: { 68: private static final Logger log = Logger.getLogger(PKCS7.class.getName()); 69: 70: /** 71: * Trivial package-private constructor for use by the <i>Factory</i> class. 72: * 73: * @see PadFactory 74: */ 75: PKCS7() 76: { 77: super(Registry.PKCS7_PAD); 78: } 79: 80: public void setup() 81: { 82: if (blockSize < 2 || blockSize > 256) 83: throw new IllegalArgumentException(); 84: } 85: 86: public byte[] pad(byte[] in, int offset, int length) 87: { 88: int padLength = blockSize; 89: if (length % blockSize != 0) 90: padLength = blockSize - length % blockSize; 91: byte[] result = new byte[padLength]; 92: for (int i = 0; i < padLength;) 93: result[i++] = (byte) padLength; 94: if (Configuration.DEBUG) 95: log.fine("padding: 0x" + Util.toString(result)); 96: return result; 97: } 98: 99: public int unpad(byte[] in, int offset, int length) 100: throws WrongPaddingException 101: { 102: int limit = offset + length; 103: int result = in[limit - 1] & 0xFF; 104: for (int i = 0; i < result; i++) 105: if (result != (in[--limit] & 0xFF)) 106: throw new WrongPaddingException(); 107: if (Configuration.DEBUG) 108: log.fine("padding length: " + result); 109: return result; 110: } 111: }