1/*
2 * rdb.c
3 *
4 * Implements a replay database for packet security
5 *
6 * David A. McGrew
7 * Cisco Systems, Inc.
8 */
9
10/*
11 *
12 * Copyright (c) 2001-2006, Cisco Systems, Inc.
13 * All rights reserved.
14 *
15 * Redistribution and use in source and binary forms, with or without
16 * modification, are permitted provided that the following conditions
17 * are met:
18 *
19 *   Redistributions of source code must retain the above copyright
20 *   notice, this list of conditions and the following disclaimer.
21 *
22 *   Redistributions in binary form must reproduce the above
23 *   copyright notice, this list of conditions and the following
24 *   disclaimer in the documentation and/or other materials provided
25 *   with the distribution.
26 *
27 *   Neither the name of the Cisco Systems, Inc. nor the names of its
28 *   contributors may be used to endorse or promote products derived
29 *   from this software without specific prior written permission.
30 *
31 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
34 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
35 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
36 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
37 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
38 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
39 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
40 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
41 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
42 * OF THE POSSIBILITY OF SUCH DAMAGE.
43 *
44 */
45
46
47#include "rdb.h"
48
49
50/*
51 * this implementation of a replay database works as follows:
52 *
53 * window_start is the index of the first packet in the window
54 * bitmask      a bit-buffer, containing the most recently entered
55 *              index as the leftmost bit
56 *
57 */
58
59/* rdb_init initalizes rdb */
60
61err_status_t
62rdb_init(rdb_t *rdb) {
63  v128_set_to_zero(&rdb->bitmask);
64  rdb->window_start = 0;
65  return err_status_ok;
66}
67
68/*
69 * rdb_check checks to see if index appears in rdb
70 */
71
72err_status_t
73rdb_check(const rdb_t *rdb, uint32_t p_index) {
74
75  /* if the index appears after (or at very end of) the window, its good */
76  if (p_index >= rdb->window_start + rdb_bits_in_bitmask)
77    return err_status_ok;
78
79  /* if the index appears before the window, its bad */
80  if (p_index < rdb->window_start)
81    return err_status_replay_old;
82
83  /* otherwise, the index appears within the window, so check the bitmask */
84  if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1)
85    return err_status_replay_fail;
86
87  /* otherwise, the index is okay */
88  return err_status_ok;
89}
90
91/*
92 * rdb_add_index adds index to rdb_t (and does *not* check if
93 * index appears in db)
94 *
95 * this function should be called only after rdb_check has
96 * indicated that the index does not appear in the rdb, e.g., a mutex
97 * should protect the rdb between these calls
98 */
99
100err_status_t
101rdb_add_index(rdb_t *rdb, uint32_t p_index) {
102  int delta;
103
104  /* here we *assume* that p_index > rdb->window_start */
105
106  delta = (p_index - rdb->window_start);
107  if (delta < rdb_bits_in_bitmask) {
108
109    /* if the p_index is within the window, set the appropriate bit */
110    v128_set_bit(&rdb->bitmask, delta);
111
112  } else {
113
114    delta -= rdb_bits_in_bitmask - 1;
115
116    /* shift the window forward by delta bits*/
117    v128_left_shift(&rdb->bitmask, delta);
118    v128_set_bit(&rdb->bitmask, rdb_bits_in_bitmask-1);
119    rdb->window_start += delta;
120
121  }
122
123  return err_status_ok;
124}
125
126err_status_t
127rdb_increment(rdb_t *rdb) {
128
129  if (rdb->window_start++ > 0x7fffffff)
130    return err_status_key_expired;
131  return err_status_ok;
132}
133
134uint32_t
135rdb_get_value(const rdb_t *rdb) {
136  return rdb->window_start;
137}
138