compat: use real crypto_memneq

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

4 files changed, 181 insertions, 14 deletions

diff --git a/src/compat/Kbuild.include b/src/compat/Kbuild.include
index aaaffcb..aacc9f6 100644
--- a/src/compat/Kbuild.include
+++ b/src/compat/Kbuild.include
@@ -26,3 +26,8 @@ ifeq ($(wildcard $(srctree)/include/net/udp_tunnel.h),)
 ccflags-y += -I$(src)/compat/udp_tunnel/include
 wireguard-y += compat/udp_tunnel/udp_tunnel.o
 endif
+
+ifeq ($(shell grep -F "int crypto_memneq" "$(srctree)/include/crypto/algapi.h"),)
+ccflags-y += -include $(src)/compat/memneq/include.h
+wireguard-y += compat/memneq/memneq.o
+endif
diff --git a/src/compat/compat.h b/src/compat/compat.h
index 5d5f714..31ff0b5 100644
--- a/src/compat/compat.h
+++ b/src/compat/compat.h
@@ -194,20 +194,6 @@ static inline u32 prandom_u32_max(u32 ep_ro)
 }
 #endif
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 12, 59)
-static inline int crypto_memneq(const void *a, const void *b, size_t size)
-{
-	unsigned long neq = 0;
-	while (size > 0) {
-		neq |= *(u8 *)a ^ *(u8 *)b;
-		a += 1;
-		b += 1;
-		size -= 1;
-	}
-	return neq != 0UL ? 1 : 0;
-}
-#endif
-
 #if LINUX_VERSION_CODE < KERNEL_VERSION(3, 10, 75)
 #define U8_MAX ((u8)~0U)
 #define S8_MAX ((s8)(U8_MAX >> 1))
diff --git a/src/compat/memneq/include.h b/src/compat/memneq/include.h
new file mode 100644
index 0000000..2d18acd
--- /dev/null
+++ b/src/compat/memneq/include.h
@@ -0,0 +1,5 @@
+extern noinline unsigned long __crypto_memneq(const void *a, const void *b, size_t size);
+static inline int crypto_memneq(const void *a, const void *b, size_t size)
+{
+	return __crypto_memneq(a, b, size) != 0UL ? 1 : 0;
+}
diff --git a/src/compat/memneq/memneq.c b/src/compat/memneq/memneq.c
new file mode 100644
index 0000000..b85cd9e
--- /dev/null
+++ b/src/compat/memneq/memneq.c
@@ -0,0 +1,171 @@
+/*
+ * Constant-time equality testing of memory regions.
+ *
+ * Authors:
+ *
+ *   James Yonan <james@openvpn.net>
+ *   Daniel Borkmann <dborkman@redhat.com>
+ *
+ * This file is provided under a dual BSD/GPLv2 license.  When using or
+ * redistributing this file, you may do so under either license.
+ *
+ * GPL LICENSE SUMMARY
+ *
+ * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+ * The full GNU General Public License is included in this distribution
+ * in the file called LICENSE.GPL.
+ *
+ * BSD LICENSE
+ *
+ * Copyright(c) 2013 OpenVPN Technologies, Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *   * Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in
+ *     the documentation and/or other materials provided with the
+ *     distribution.
+ *   * Neither the name of OpenVPN Technologies nor the names of its
+ *     contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <crypto/algapi.h>
+
+/* Make the optimizer believe the variable can be manipulated arbitrarily. */
+#define COMPILER_OPTIMIZER_HIDE_VAR(var) __asm__ ("" : "=r" (var) : "0" (var))
+
+#ifndef __HAVE_ARCH_CRYPTO_MEMNEQ
+
+/* Generic path for arbitrary size */
+static inline unsigned long
+__crypto_memneq_generic(const void *a, const void *b, size_t size)
+{
+	unsigned long neq = 0;
+
+#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
+	while (size >= sizeof(unsigned long)) {
+		neq |= *(unsigned long *)a ^ *(unsigned long *)b;
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		a += sizeof(unsigned long);
+		b += sizeof(unsigned long);
+		size -= sizeof(unsigned long);
+	}
+#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
+	while (size > 0) {
+		neq |= *(unsigned char *)a ^ *(unsigned char *)b;
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		a += 1;
+		b += 1;
+		size -= 1;
+	}
+	return neq;
+}
+
+/* Loop-free fast-path for frequently used 16-byte size */
+static inline unsigned long __crypto_memneq_16(const void *a, const void *b)
+{
+	unsigned long neq = 0;
+
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+	if (sizeof(unsigned long) == 8) {
+		neq |= *(unsigned long *)(a)   ^ *(unsigned long *)(b);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned long *)(a+8) ^ *(unsigned long *)(b+8);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+	} else if (sizeof(unsigned int) == 4) {
+		neq |= *(unsigned int *)(a)    ^ *(unsigned int *)(b);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned int *)(a+4)  ^ *(unsigned int *)(b+4);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned int *)(a+8)  ^ *(unsigned int *)(b+8);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned int *)(a+12) ^ *(unsigned int *)(b+12);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+	} else
+#endif /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
+	{
+		neq |= *(unsigned char *)(a)    ^ *(unsigned char *)(b);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+1)  ^ *(unsigned char *)(b+1);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+2)  ^ *(unsigned char *)(b+2);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+3)  ^ *(unsigned char *)(b+3);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+4)  ^ *(unsigned char *)(b+4);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+5)  ^ *(unsigned char *)(b+5);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+6)  ^ *(unsigned char *)(b+6);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+7)  ^ *(unsigned char *)(b+7);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+8)  ^ *(unsigned char *)(b+8);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+9)  ^ *(unsigned char *)(b+9);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+10) ^ *(unsigned char *)(b+10);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+11) ^ *(unsigned char *)(b+11);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+12) ^ *(unsigned char *)(b+12);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+13) ^ *(unsigned char *)(b+13);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+14) ^ *(unsigned char *)(b+14);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+		neq |= *(unsigned char *)(a+15) ^ *(unsigned char *)(b+15);
+		COMPILER_OPTIMIZER_HIDE_VAR(neq);
+	}
+
+	return neq;
+}
+
+/* Compare two areas of memory without leaking timing information,
+ * and with special optimizations for common sizes.  Users should
+ * not call this function directly, but should instead use
+ * crypto_memneq defined in crypto/algapi.h.
+ */
+noinline unsigned long __crypto_memneq(const void *a, const void *b,
+				       size_t size)
+{
+	switch (size) {
+	case 16:
+		return __crypto_memneq_16(a, b);
+	default:
+		return __crypto_memneq_generic(a, b, size);
+	}
+}
+EXPORT_SYMBOL(__crypto_memneq);
+
+#endif /* __HAVE_ARCH_CRYPTO_MEMNEQ */