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authorCem Keylan <cem@ckyln.com>2020-10-16 17:41:25 +0300
committerCem Keylan <cem@ckyln.com>2020-10-16 17:41:25 +0300
commite2abcdca396661cbe0ae2ddb13d5c2b85682c13a (patch)
treeacf9b5c80b645617f882c45224c6e07251711842 /lib/libc/string/timingsafe_memcmp.c
downloadotools-e2abcdca396661cbe0ae2ddb13d5c2b85682c13a.tar.gz
initial commit
Diffstat (limited to 'lib/libc/string/timingsafe_memcmp.c')
-rw-r--r--lib/libc/string/timingsafe_memcmp.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/lib/libc/string/timingsafe_memcmp.c b/lib/libc/string/timingsafe_memcmp.c
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+++ b/lib/libc/string/timingsafe_memcmp.c
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+/* $OpenBSD: timingsafe_memcmp.c,v 1.2 2015/08/31 02:53:57 guenther Exp $ */
+/*
+ * Copyright (c) 2014 Google Inc.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <limits.h>
+#include <string.h>
+
+int
+timingsafe_memcmp(const void *b1, const void *b2, size_t len)
+{
+ const unsigned char *p1 = b1, *p2 = b2;
+ size_t i;
+ int res = 0, done = 0;
+
+ for (i = 0; i < len; i++) {
+ /* lt is -1 if p1[i] < p2[i]; else 0. */
+ int lt = (p1[i] - p2[i]) >> CHAR_BIT;
+
+ /* gt is -1 if p1[i] > p2[i]; else 0. */
+ int gt = (p2[i] - p1[i]) >> CHAR_BIT;
+
+ /* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
+ int cmp = lt - gt;
+
+ /* set res = cmp if !done. */
+ res |= cmp & ~done;
+
+ /* set done if p1[i] != p2[i]. */
+ done |= lt | gt;
+ }
+
+ return (res);
+}
+DEF_WEAK(timingsafe_memcmp);