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/*
Copyright (c) 2012-2015, Matthias Schiffer <mschiffer@universe-factory.net>
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 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 HOLDER 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.
*/
/**
\file
Definitions for the common packet format used by most methods
*/
#include "common.h"
/** Common initialization for a new session */
void fastd_method_common_init(fastd_method_common_t *session, bool initiator) {
memset(session, 0, sizeof(*session));
session->valid_till = ctx.now + KEY_VALID;
session->refresh_after = ctx.now + KEY_REFRESH - fastd_rand(0, KEY_REFRESH_SPLAY);
if (initiator) {
session->send_nonce[COMMON_NONCEBYTES-1] = 3;
}
else {
session->send_nonce[COMMON_NONCEBYTES-1] = 2;
session->receive_nonce[COMMON_NONCEBYTES-1] = 1;
}
}
/** Checks if a received nonce is valid */
bool fastd_method_is_nonce_valid(const fastd_method_common_t *session, const uint8_t nonce[COMMON_NONCEBYTES], int64_t *age) {
if ((nonce[0] & 1) != (session->receive_nonce[0] & 1))
return false;
size_t i;
*age = 0;
for (i = 0; i < COMMON_NONCEBYTES; i++) {
*age <<= 8;
*age += session->receive_nonce[i] - nonce[i];
}
*age >>= 1;
if (*age >= 0) {
if (fastd_timed_out(session->reorder_timeout))
return false;
if (*age > 64)
return false;
}
return true;
}
/**
Checks if a possibly reordered packet should be accepted
Returns a tristate: undef if it should not be accepted (duplicate or too old),
false if the packet is okay and not reordered and true
if it is reordered.
*/
fastd_tristate_t fastd_method_reorder_check(fastd_peer_t *peer, fastd_method_common_t *session, const uint8_t nonce[COMMON_NONCEBYTES], int64_t age) {
if (age < 0) {
size_t shift = -age;
if (shift >= 64)
session->receive_reorder_seen = 0;
else
session->receive_reorder_seen <<= shift;
if (shift <= 64)
session->receive_reorder_seen |= ((uint64_t)1 << (shift-1));
memcpy(session->receive_nonce, nonce, COMMON_NONCEBYTES);
session->reorder_timeout = ctx.now + REORDER_TIME;
return FASTD_TRISTATE_FALSE;
}
else if (age == 0 || session->receive_reorder_seen & ((uint64_t)1 << (age-1))) {
pr_debug("dropping duplicate packet from %P (age %u)", peer, (unsigned)age);
return FASTD_TRISTATE_UNDEF;
}
else {
pr_debug2("accepting reordered packet from %P (age %u)", peer, (unsigned)age);
session->receive_reorder_seen |= ((uint64_t)1 << (age-1));
return FASTD_TRISTATE_TRUE;
}
}
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