# HG changeset patch
# User weijun
# Date 1594566449 -3600
# Node ID 0e9efa336f0012dde71be94313b2be5b08a1faf0
# Parent  ce29e542f3fa6bca7ad2403ac60b28cbb67b2a60
8238804: Enhance key handling process
Reviewed-by: rriggs, mullan, ahgross, rhalade, mbalao, andrew

diff -r ce29e542f3fa -r 0e9efa336f00 src/share/classes/java/security/MessageDigest.java
--- a/src/share/classes/java/security/MessageDigest.java	Wed Jul 15 21:15:05 2020 +0100
+++ b/src/share/classes/java/security/MessageDigest.java	Sun Jul 12 16:07:29 2020 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1996, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1996, 2020, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -433,6 +433,12 @@
     /**
      * Compares two digests for equality. Does a simple byte compare.
      *
+     * @implNote
+     * All bytes in {@code digesta} are examined to determine equality.
+     * The calculation time depends only on the length of {@code digesta}.
+     * It does not depend on the length of {@code digestb} or the contents
+     * of {@code digesta} and {@code digestb}.
+     *
      * @param digesta one of the digests to compare.
      *
      * @param digestb the other digest to compare.
@@ -444,14 +450,22 @@
         if (digesta == null || digestb == null) {
             return false;
         }
-        if (digesta.length != digestb.length) {
-            return false;
+
+        int lenA = digesta.length;
+        int lenB = digestb.length;
+
+        if (lenB == 0) {
+            return lenA == 0;
         }
 
         int result = 0;
+        result |= lenA - lenB;
+
         // time-constant comparison
-        for (int i = 0; i < digesta.length; i++) {
-            result |= digesta[i] ^ digestb[i];
+        for (int i = 0; i < lenA; i++) {
+            // If i >= lenB, indexB is 0; otherwise, i.
+            int indexB = ((i - lenB) >>> 31) * i;
+            result |= digesta[i] ^ digestb[indexB];
         }
         return result == 0;
     }