55 lines
1.5 KiB
Java
55 lines
1.5 KiB
Java
// SPDX-FileCopyrightText: 2018 Paul Schaub <vanitasvitae@fsfe.org>
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//
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// SPDX-License-Identifier: Apache-2.0
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package org.pgpainless.util;
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public final class BCUtil {
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private BCUtil() {
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}
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/**
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* A constant time equals comparison - does not terminate early if
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* test will fail. For best results always pass the expected value
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* as the first parameter.
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*
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* TODO: This method was proposed as a patch to BC:
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* https://github.com/bcgit/bc-java/pull/1141
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* Replace usage of this method with upstream eventually.
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* Remove once BC 172 gets released, given it contains the patch.
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*
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* @param expected first array
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* @param supplied second array
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* @return true if arrays equal, false otherwise.
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*/
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public static boolean constantTimeAreEqual(
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char[] expected,
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char[] supplied) {
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if (expected == null || supplied == null) {
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return false;
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}
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if (expected == supplied) {
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return true;
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}
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int len = Math.min(expected.length, supplied.length);
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int nonEqual = expected.length ^ supplied.length;
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// do the char-wise comparison
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for (int i = 0; i != len; i++) {
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nonEqual |= (expected[i] ^ supplied[i]);
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}
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// If supplied is longer than expected, iterate over rest of supplied with NOPs
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for (int i = len; i < supplied.length; i++) {
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nonEqual |= ((byte) supplied[i] ^ (byte) ~supplied[i]);
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}
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return nonEqual == 0;
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}
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}
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