144 lines
4.1 KiB
C
144 lines
4.1 KiB
C
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/*
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* rdb.c
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*
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* Implements a replay database for packet security
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*
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* David A. McGrew
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* Cisco Systems, Inc.
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*/
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/*
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*
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* Copyright (c) 2001-2017, Cisco Systems, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* Neither the name of the Cisco Systems, Inc. nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#include "rdb.h"
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/*
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* this implementation of a replay database works as follows:
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*
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* window_start is the index of the first packet in the window
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* bitmask a bit-buffer, containing the most recently entered
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* index as the leftmost bit
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*
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*/
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/* srtp_rdb_init initalizes rdb */
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srtp_err_status_t srtp_rdb_init (srtp_rdb_t *rdb)
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{
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v128_set_to_zero(&rdb->bitmask);
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rdb->window_start = 0;
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return srtp_err_status_ok;
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}
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/*
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* srtp_rdb_check checks to see if index appears in rdb
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*/
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srtp_err_status_t srtp_rdb_check (const srtp_rdb_t *rdb, uint32_t p_index)
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{
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/* if the index appears after (or at very end of) the window, its good */
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if (p_index >= rdb->window_start + rdb_bits_in_bitmask) {
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return srtp_err_status_ok;
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}
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/* if the index appears before the window, its bad */
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if (p_index < rdb->window_start) {
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return srtp_err_status_replay_old;
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}
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/* otherwise, the index appears within the window, so check the bitmask */
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if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1) {
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return srtp_err_status_replay_fail;
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}
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/* otherwise, the index is okay */
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return srtp_err_status_ok;
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}
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/*
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* srtp_rdb_add_index adds index to srtp_rdb_t (and does *not* check if
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* index appears in db)
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*
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* this function should be called only after srtp_rdb_check has
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* indicated that the index does not appear in the rdb, e.g., a mutex
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* should protect the rdb between these calls
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*/
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srtp_err_status_t srtp_rdb_add_index (srtp_rdb_t *rdb, uint32_t p_index)
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{
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int delta;
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/* here we *assume* that p_index > rdb->window_start */
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delta = (p_index - rdb->window_start);
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if (delta < rdb_bits_in_bitmask) {
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/* if the p_index is within the window, set the appropriate bit */
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v128_set_bit(&rdb->bitmask, delta);
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} else {
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delta -= rdb_bits_in_bitmask - 1;
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/* shift the window forward by delta bits*/
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v128_left_shift(&rdb->bitmask, delta);
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v128_set_bit(&rdb->bitmask, rdb_bits_in_bitmask - 1);
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rdb->window_start += delta;
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}
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return srtp_err_status_ok;
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}
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srtp_err_status_t srtp_rdb_increment (srtp_rdb_t *rdb)
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{
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if (rdb->window_start >= 0x7fffffff) {
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return srtp_err_status_key_expired;
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}
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++rdb->window_start;
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return srtp_err_status_ok;
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}
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uint32_t srtp_rdb_get_value (const srtp_rdb_t *rdb)
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{
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return rdb->window_start;
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}
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