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+/*
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+ * Constant-time equality testing of memory regions.
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+ *
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+ * Authors:
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+ *
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+ * James Yonan <james@openvpn.net>
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+ * Daniel Borkmann <dborkman@redhat.com>
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+ *
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+ * This file is provided under a dual BSD/GPLv2 license. When using or
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+ * redistributing this file, you may do so under either license.
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+ *
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+ * GPL LICENSE SUMMARY
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+ *
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+ * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of version 2 of the GNU General Public License as
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+ * published by the Free Software Foundation.
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+ *
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+ * This program is distributed in the hope that it will be useful, but
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+ * WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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+ * General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program; if not, write to the Free Software
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+ * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
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+ * The full GNU General Public License is included in this distribution
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+ * in the file called LICENSE.GPL.
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+ *
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+ * BSD LICENSE
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+ *
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+ * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
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+ *
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+ * Redistribution and use in source and binary forms, with or without
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+ * modification, are permitted provided that the following conditions
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+ * are met:
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+ *
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+ * * Redistributions of source code must retain the above copyright
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+ * notice, this list of conditions and the following disclaimer.
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+ * * Redistributions in binary form must reproduce the above copyright
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+ * notice, this list of conditions and the following disclaimer in
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+ * the documentation and/or other materials provided with the
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+ * distribution.
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+ * * Neither the name of OpenVPN Technologies nor the names of its
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+ * contributors may be used to endorse or promote products derived
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+ * from this software without specific prior written permission.
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+ *
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+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+ */
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+
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+#include <crypto/algapi.h>
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+
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+#ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
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+
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+/* Generic path for arbitrary size */
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+static inline unsigned long
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+__crypto_memneq_generic(const void *a, const void *b, size_t size)
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+{
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+ unsigned long neq = 0;
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+
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+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
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+ while (size >= sizeof(unsigned long)) {
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+ neq |= *(unsigned long *)a ^ *(unsigned long *)b;
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+ a += sizeof(unsigned long);
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+ b += sizeof(unsigned long);
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+ size -= sizeof(unsigned long);
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+ }
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+#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
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+ while (size > 0) {
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+ neq |= *(unsigned char *)a ^ *(unsigned char *)b;
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+ a += 1;
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+ b += 1;
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+ size -= 1;
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+ }
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+ return neq;
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+}
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+
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+/* Loop-free fast-path for frequently used 16-byte size */
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+static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
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+{
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+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
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+ if (sizeof(unsigned long) == 8)
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+ return ((*(unsigned long *)(a) ^ *(unsigned long *)(b))
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+ | (*(unsigned long *)(a+8) ^ *(unsigned long *)(b+8)));
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+ else if (sizeof(unsigned int) == 4)
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+ return ((*(unsigned int *)(a) ^ *(unsigned int *)(b))
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+ | (*(unsigned int *)(a+4) ^ *(unsigned int *)(b+4))
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+ | (*(unsigned int *)(a+8) ^ *(unsigned int *)(b+8))
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+ | (*(unsigned int *)(a+12) ^ *(unsigned int *)(b+12)));
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+ else
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+#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
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+ return ((*(unsigned char *)(a) ^ *(unsigned char *)(b))
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+ | (*(unsigned char *)(a+1) ^ *(unsigned char *)(b+1))
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+ | (*(unsigned char *)(a+2) ^ *(unsigned char *)(b+2))
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+ | (*(unsigned char *)(a+3) ^ *(unsigned char *)(b+3))
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+ | (*(unsigned char *)(a+4) ^ *(unsigned char *)(b+4))
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+ | (*(unsigned char *)(a+5) ^ *(unsigned char *)(b+5))
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+ | (*(unsigned char *)(a+6) ^ *(unsigned char *)(b+6))
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+ | (*(unsigned char *)(a+7) ^ *(unsigned char *)(b+7))
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+ | (*(unsigned char *)(a+8) ^ *(unsigned char *)(b+8))
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+ | (*(unsigned char *)(a+9) ^ *(unsigned char *)(b+9))
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+ | (*(unsigned char *)(a+10) ^ *(unsigned char *)(b+10))
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+ | (*(unsigned char *)(a+11) ^ *(unsigned char *)(b+11))
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+ | (*(unsigned char *)(a+12) ^ *(unsigned char *)(b+12))
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+ | (*(unsigned char *)(a+13) ^ *(unsigned char *)(b+13))
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+ | (*(unsigned char *)(a+14) ^ *(unsigned char *)(b+14))
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+ | (*(unsigned char *)(a+15) ^ *(unsigned char *)(b+15)));
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+}
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+
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+/* Compare two areas of memory without leaking timing information,
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+ * and with special optimizations for common sizes. Users should
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+ * not call this function directly, but should instead use
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+ * crypto_memneq defined in crypto/algapi.h.
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+ */
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+noinline unsigned long __crypto_memneq(const void *a, const void *b,
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+ size_t size)
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+{
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+ switch (size) {
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+ case 16:
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+ return __crypto_memneq_16(a, b);
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+ default:
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+ return __crypto_memneq_generic(a, b, size);
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+ }
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+}
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+EXPORT_SYMBOL(__crypto_memneq);
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+
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+#endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */
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James Yonan