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Revision 1.10, Fri Jul 8 03:44:42 2016 UTC (7 years, 10 months ago) by djm
Branch: MAIN
CVS Tags: OPENBSD_7_5_BASE, OPENBSD_7_5, OPENBSD_7_4_BASE, OPENBSD_7_4, OPENBSD_7_3_BASE, OPENBSD_7_3, OPENBSD_7_2_BASE, OPENBSD_7_2, OPENBSD_7_1_BASE, OPENBSD_7_1, OPENBSD_7_0_BASE, OPENBSD_7_0, OPENBSD_6_9_BASE, OPENBSD_6_9, OPENBSD_6_8_BASE, OPENBSD_6_8, OPENBSD_6_7_BASE, OPENBSD_6_7, OPENBSD_6_6_BASE, OPENBSD_6_6, OPENBSD_6_5_BASE, OPENBSD_6_5, OPENBSD_6_4_BASE, OPENBSD_6_4, OPENBSD_6_3_BASE, OPENBSD_6_3, OPENBSD_6_2_BASE, OPENBSD_6_2, OPENBSD_6_1_BASE, OPENBSD_6_1, OPENBSD_6_0_BASE, OPENBSD_6_0, HEAD
Changes since 1.9: +3 -1 lines 

Improve crypto ordering for Encrypt-then-MAC (EtM) mode MAC algorithms.

Previously we were computing the MAC, decrypting the packet and then
checking the MAC. This gave rise to the possibility of creating a
side-channel oracle in the decryption step, though no such oracle has
been identified.

This adds a mac_check() function that computes and checks the MAC in
one pass, and uses it to advance MAC checking for EtM algorithms to
before payload decryption.

Reported by Jean Paul Degabriele, Kenny Paterson, Torben Hansen and
Martin Albrecht. feedback and ok markus@

/* $OpenBSD: mac.h,v 1.10 2016/07/08 03:44:42 djm Exp $ */
/*
 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

#ifndef SSHMAC_H
#define SSHMAC_H

#include <sys/types.h>

struct sshmac {
	char	*name;
	int	enabled;
	u_int	mac_len;
	u_char	*key;
	u_int	key_len;
	int	type;
	int	etm;		/* Encrypt-then-MAC */
	struct ssh_hmac_ctx	*hmac_ctx;
	struct umac_ctx		*umac_ctx;
};

int	 mac_valid(const char *);
char	*mac_alg_list(char);
int	 mac_setup(struct sshmac *, char *);
int	 mac_init(struct sshmac *);
int	 mac_compute(struct sshmac *, u_int32_t, const u_char *, int,
    u_char *, size_t);
int	 mac_check(struct sshmac *, u_int32_t, const u_char *, size_t,
    const u_char *, size_t);
void	 mac_clear(struct sshmac *);

#endif /* SSHMAC_H */