1 /* 2 * Copyright (c) 2021, 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 sun.security.util; 27 28 /** 29 * A time-instance comparison of two byte arrays. 30 */ 31 public class ByteArrays { 32 // See the MessageDigest.isEqual(byte[] digesta, byte[] digestb) 33 // implementation. This is a potential enhancement of the 34 // MessageDigest class. isEqual(byte[] a, int aFromIndex, int aToIndex, byte[] b, int bFromIndex, int bToIndex)35 public static boolean isEqual(byte[] a, int aFromIndex, int aToIndex, 36 byte[] b, int bFromIndex, int bToIndex) { 37 if (a == b) { 38 return true; 39 } 40 41 if (a == null || b == null) { 42 return false; 43 } 44 45 if (a.length == 0) { 46 return b.length == 0; 47 } 48 49 int lenA = aToIndex - aFromIndex; 50 int lenB = bToIndex - bFromIndex; 51 52 if (lenB == 0) { 53 return lenA == 0; 54 } 55 56 int result = 0; 57 result |= lenA - lenB; 58 59 // time-constant comparison 60 for (int indexA = 0; indexA < lenA; indexA++) { 61 int indexB = ((indexA - lenB) >>> 31) * indexA; 62 result |= a[aFromIndex + indexA] ^ b[bFromIndex + indexB]; 63 } 64 65 return result == 0; 66 } 67 } 68