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Make Passphrase comparison constant time
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parent
729b33a116
commit
176ad09d19
3 changed files with 57 additions and 1 deletions
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@ -47,4 +47,41 @@ public final class BCUtil {
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return bitStrength;
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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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* @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 = (expected.length < supplied.length) ? 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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@ -8,6 +8,8 @@ import javax.annotation.Nonnull;
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import javax.annotation.Nullable;
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import java.util.Arrays;
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import static org.pgpainless.util.BCUtil.constantTimeAreEqual;
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public class Passphrase {
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public final Object lock = new Object();
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@ -162,6 +164,7 @@ public class Passphrase {
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return false;
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}
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Passphrase other = (Passphrase) obj;
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return Arrays.equals(getChars(), other.getChars());
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return (getChars() == null && other.getChars() == null) ||
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constantTimeAreEqual(getChars(), other.getChars());
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}
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}
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@ -5,6 +5,8 @@
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package org.pgpainless.util;
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import static org.junit.jupiter.api.Assertions.assertEquals;
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import static org.junit.jupiter.api.Assertions.assertFalse;
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import static org.junit.jupiter.api.Assertions.assertTrue;
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import java.io.IOException;
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import java.security.InvalidAlgorithmParameterException;
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@ -88,4 +90,18 @@ public class BCUtilTest {
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assertEquals(pubColSize, secColSize);
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}
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@Test
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public void constantTimeAreEqualsTest() {
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char[] b = "Hello".toCharArray();
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assertTrue(BCUtil.constantTimeAreEqual(b, b));
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assertTrue(BCUtil.constantTimeAreEqual("Hello".toCharArray(), "Hello".toCharArray()));
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assertTrue(BCUtil.constantTimeAreEqual(new char[0], new char[0]));
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assertTrue(BCUtil.constantTimeAreEqual(new char[] {'H', 'e', 'l', 'l', 'o'}, "Hello".toCharArray()));
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assertFalse(BCUtil.constantTimeAreEqual("Hello".toCharArray(), "Hello World".toCharArray()));
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assertFalse(BCUtil.constantTimeAreEqual(null, "Hello".toCharArray()));
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assertFalse(BCUtil.constantTimeAreEqual("Hello".toCharArray(), null));
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assertFalse(BCUtil.constantTimeAreEqual(null, null));
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}
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}
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