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/*
* Copyright (C) 2016 Red Hat, Inc.
*
* Authors: Fridolin Pokorny
* Nikos Mavrogiannopoulos
*
* This file is part of GNUTLS.
*
* The GNUTLS library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
/* Functions that relate to DTLS sliding window handling.
*/
#ifndef DTLS_SW_NO_INCLUDES
#include "gnutls_int.h"
#include "errors.h"
#include "debug.h"
#include "dtls.h"
#include "record.h"
#endif
/*
* DTLS sliding window handling
*/
#define DTLS_EPOCH_SHIFT (6*CHAR_BIT)
#define DTLS_SEQ_NUM_MASK 0x0000FFFFFFFFFFFF
#define DTLS_WINDOW_HAVE_RECV_PACKET(W) ((W)->dtls_sw_have_recv != 0)
#define DTLS_WINDOW_INIT_AT(W, S) (W)->dtls_sw_bits = ((W)->dtls_sw_have_recv) = 0; (W)->dtls_sw_start = (S&DTLS_SEQ_NUM_MASK)
#define DTLS_WINDOW_INIT(W) DTLS_WINDOW_INIT_AT(W, 0)
#define DTLS_WINDOW_INSIDE(W, S) ((((S) & DTLS_SEQ_NUM_MASK) > (W)->dtls_sw_start) && \
(((S) & DTLS_SEQ_NUM_MASK) - (W)->dtls_sw_start <= (sizeof((W)->dtls_sw_bits) * CHAR_BIT)))
#define DTLS_WINDOW_OFFSET(W, S) ((((S) & DTLS_SEQ_NUM_MASK) - (W)->dtls_sw_start) - 1)
#define DTLS_WINDOW_RECEIVED(W, S) (((W)->dtls_sw_bits & ((uint64_t) 1 << DTLS_WINDOW_OFFSET(W, S))) != 0)
#define DTLS_WINDOW_MARK(W, S) ((W)->dtls_sw_bits |= ((uint64_t) 1 << DTLS_WINDOW_OFFSET(W, S)))
/* We forcefully advance the window once we have received more than
* 8 packets since the first one. That way we ensure that we don't
* get stuck on connections with many lost packets. */
#define DTLS_WINDOW_UPDATE(W) \
if (((W)->dtls_sw_bits & 0xffffffffffff0000LL) != 0) { \
(W)->dtls_sw_bits = (W)->dtls_sw_bits >> 1; \
(W)->dtls_sw_start++; \
} \
while ((W)->dtls_sw_bits & (uint64_t) 1) { \
(W)->dtls_sw_bits = (W)->dtls_sw_bits >> 1; \
(W)->dtls_sw_start++; \
}
#define LOAD_UINT64(out, ubytes) \
for (i = 0; i < 8; i++) { \
out <<= 8; \
out |= ubytes[i] & 0xff; \
}
void _dtls_reset_window(struct record_parameters_st *rp)
{
DTLS_WINDOW_INIT(rp);
}
/* Checks if a sequence number is not replayed. If a replayed
* packet is detected it returns a negative value (but no sensible error code).
* Otherwise zero.
*/
int _dtls_record_check(struct record_parameters_st *rp, uint64 * _seq)
{
uint64_t seq_num = 0;
unsigned i;
LOAD_UINT64(seq_num, _seq->i);
if ((seq_num >> DTLS_EPOCH_SHIFT) != rp->epoch) {
return gnutls_assert_val(-1);
}
if (!DTLS_WINDOW_HAVE_RECV_PACKET(rp)) {
DTLS_WINDOW_INIT_AT(rp, seq_num);
rp->dtls_sw_have_recv = 1;
return 0;
}
/* are we inside sliding window? */
if (!DTLS_WINDOW_INSIDE(rp, seq_num)) {
return gnutls_assert_val(-2);
}
/* already received? */
if (DTLS_WINDOW_RECEIVED(rp, seq_num)) {
return gnutls_assert_val(-3);
}
DTLS_WINDOW_MARK(rp, seq_num);
DTLS_WINDOW_UPDATE(rp);
return 0;
}
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