michael@0: /*
michael@0:  * rdb.c
michael@0:  *
michael@0:  * Implements a replay database for packet security
michael@0:  *
michael@0:  * David A. McGrew
michael@0:  * Cisco Systems, Inc.
michael@0:  */
michael@0: 
michael@0: /*
michael@0:  *	
michael@0:  * Copyright (c) 2001-2006, Cisco Systems, Inc.
michael@0:  * All rights reserved.
michael@0:  * 
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  * 
michael@0:  *   Redistributions of source code must retain the above copyright
michael@0:  *   notice, this list of conditions and the following disclaimer.
michael@0:  * 
michael@0:  *   Redistributions in binary form must reproduce the above
michael@0:  *   copyright notice, this list of conditions and the following
michael@0:  *   disclaimer in the documentation and/or other materials provided
michael@0:  *   with the distribution.
michael@0:  * 
michael@0:  *   Neither the name of the Cisco Systems, Inc. nor the names of its
michael@0:  *   contributors may be used to endorse or promote products derived
michael@0:  *   from this software without specific prior written permission.
michael@0:  * 
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
michael@0:  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
michael@0:  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
michael@0:  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
michael@0:  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
michael@0:  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
michael@0:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
michael@0:  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
michael@0:  * OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  *
michael@0:  */
michael@0: 
michael@0: 
michael@0: #include "rdb.h"
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * this implementation of a replay database works as follows:
michael@0:  * 
michael@0:  * window_start is the index of the first packet in the window
michael@0:  * bitmask      a bit-buffer, containing the most recently entered
michael@0:  *              index as the leftmost bit 
michael@0:  *
michael@0:  */
michael@0: 
michael@0: /* rdb_init initalizes rdb */
michael@0: 
michael@0: err_status_t
michael@0: rdb_init(rdb_t *rdb) {
michael@0:   v128_set_to_zero(&rdb->bitmask);
michael@0:   rdb->window_start = 0;
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: /*
michael@0:  * rdb_check checks to see if index appears in rdb
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: rdb_check(const rdb_t *rdb, uint32_t p_index) {
michael@0:   
michael@0:   /* if the index appears after (or at very end of) the window, its good */
michael@0:   if (p_index >= rdb->window_start + rdb_bits_in_bitmask)
michael@0:     return err_status_ok;
michael@0:   
michael@0:   /* if the index appears before the window, its bad */
michael@0:   if (p_index < rdb->window_start)
michael@0:     return err_status_replay_old;
michael@0: 
michael@0:   /* otherwise, the index appears within the window, so check the bitmask */
michael@0:   if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1)
michael@0:     return err_status_replay_fail;    
michael@0:       
michael@0:   /* otherwise, the index is okay */
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: /*
michael@0:  * rdb_add_index adds index to rdb_t (and does *not* check if
michael@0:  * index appears in db)
michael@0:  *
michael@0:  * this function should be called only after rdb_check has
michael@0:  * indicated that the index does not appear in the rdb, e.g., a mutex
michael@0:  * should protect the rdb between these calls
michael@0:  */
michael@0: 
michael@0: err_status_t
michael@0: rdb_add_index(rdb_t *rdb, uint32_t p_index) {
michael@0:   int delta;  
michael@0: 
michael@0:   /* here we *assume* that p_index > rdb->window_start */
michael@0: 
michael@0:   delta = (p_index - rdb->window_start);    
michael@0:   if (delta < (int)rdb_bits_in_bitmask) {
michael@0: 
michael@0:     /* if the p_index is within the window, set the appropriate bit */
michael@0:     v128_set_bit(&rdb->bitmask, delta);
michael@0: 
michael@0:   } else { 
michael@0:     
michael@0:     delta -= rdb_bits_in_bitmask - 1;
michael@0: 
michael@0:     /* shift the window forward by delta bits*/
michael@0:     v128_left_shift(&rdb->bitmask, delta);
michael@0:     v128_set_bit(&rdb->bitmask, rdb_bits_in_bitmask-1);
michael@0:     rdb->window_start += delta;
michael@0: 
michael@0:   }    
michael@0: 
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: err_status_t
michael@0: rdb_increment(rdb_t *rdb) {
michael@0: 
michael@0:   if (rdb->window_start++ > 0x7fffffff)
michael@0:     return err_status_key_expired;
michael@0:   return err_status_ok;
michael@0: }
michael@0: 
michael@0: uint32_t
michael@0: rdb_get_value(const rdb_t *rdb) {
michael@0:   return rdb->window_start;
michael@0: }