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/*
* rdb.c
*
* Implements a replay database for packet security
*
* David A. McGrew
* Cisco Systems, Inc.
*/
/*
*
* Copyright (c) 2001-2017, Cisco Systems, 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 the Cisco Systems, Inc. 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 HOLDERS 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.
*
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "rdb.h"
#define rdb_bits_in_bitmask (8 * sizeof(v128_t))
/*
* this implementation of a replay database works as follows:
*
* window_start is the index of the first packet in the window
* bitmask a bit-buffer, containing the most recently entered
* index as the leftmost bit
*
*/
/* srtp_rdb_init initalizes rdb */
srtp_err_status_t srtp_rdb_init(srtp_rdb_t *rdb)
{
v128_set_to_zero(&rdb->bitmask);
rdb->window_start = 0;
return srtp_err_status_ok;
}
/*
* srtp_rdb_check checks to see if index appears in rdb
*/
srtp_err_status_t srtp_rdb_check(const srtp_rdb_t *rdb, uint32_t p_index)
{
/* if the index appears after (or at very end of) the window, its good */
if (p_index >= rdb->window_start + rdb_bits_in_bitmask) {
return srtp_err_status_ok;
}
/* if the index appears before the window, its bad */
if (p_index < rdb->window_start) {
return srtp_err_status_replay_old;
}
/* otherwise, the index appears within the window, so check the bitmask */
if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1) {
return srtp_err_status_replay_fail;
}
/* otherwise, the index is okay */
return srtp_err_status_ok;
}
/*
* srtp_rdb_add_index adds index to srtp_rdb_t (and does *not* check if
* index appears in db)
*
* this function should be called only after srtp_rdb_check has
* indicated that the index does not appear in the rdb, e.g., a mutex
* should protect the rdb between these calls
*/
srtp_err_status_t srtp_rdb_add_index(srtp_rdb_t *rdb, uint32_t p_index)
{
unsigned int delta;
if (p_index < rdb->window_start)
return srtp_err_status_replay_fail;
delta = (p_index - rdb->window_start);
if (delta < rdb_bits_in_bitmask) {
/* if the p_index is within the window, set the appropriate bit */
v128_set_bit(&rdb->bitmask, delta);
} else {
delta -= rdb_bits_in_bitmask - 1;
/* shift the window forward by delta bits*/
v128_left_shift(&rdb->bitmask, delta);
v128_set_bit(&rdb->bitmask, rdb_bits_in_bitmask - 1);
rdb->window_start += delta;
}
return srtp_err_status_ok;
}
srtp_err_status_t srtp_rdb_increment(srtp_rdb_t *rdb)
{
if (rdb->window_start >= 0x7fffffff) {
return srtp_err_status_key_expired;
}
++rdb->window_start;
return srtp_err_status_ok;
}
uint32_t srtp_rdb_get_value(const srtp_rdb_t *rdb)
{
return rdb->window_start;
}
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