| /* |
| * rdb.c |
| * |
| * Implements a replay database for packet security |
| * |
| * David A. McGrew |
| * Cisco Systems, Inc. |
| */ |
| |
| /* |
| * |
| * Copyright (c) 2001-2006, 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" |
| |
| |
| /* |
| * 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) |
| { |
| int delta; |
| |
| /* here we *assume* that p_index > rdb->window_start */ |
| |
| 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; |
| } |
| return srtp_err_status_ok; |
| } |
| |
| uint32_t srtp_rdb_get_value (const srtp_rdb_t *rdb) |
| { |
| return rdb->window_start; |
| } |