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
61 err_status_t
rdb_init(rdb_t * rdb)62 rdb_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
72 err_status_t
rdb_check(const rdb_t * rdb,uint32_t index)73 rdb_check(const rdb_t *rdb, uint32_t index) {
74
75 /* if the index appears after (or at very end of) the window, its good */
76 if (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 (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, (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
100 err_status_t
rdb_add_index(rdb_t * rdb,uint32_t index)101 rdb_add_index(rdb_t *rdb, uint32_t index) {
102 int delta;
103
104 /* here we *assume* that index > rdb->window_start */
105
106 delta = (index - rdb->window_start);
107 if (delta < rdb_bits_in_bitmask) {
108
109 /* if the 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
126 err_status_t
rdb_increment(rdb_t * rdb)127 rdb_increment(rdb_t *rdb) {
128
129 if (rdb->window_start++ > 0x7fffffff)
130 return err_status_key_expired;
131 return err_status_ok;
132 }
133
134 uint32_t
rdb_get_value(const rdb_t * rdb)135 rdb_get_value(const rdb_t *rdb) {
136 return rdb->window_start;
137 }
138