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) 2001-2017, 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 #ifdef HAVE_CONFIG_H
47 #include <config.h>
48 #endif
49
50 #include "rdb.h"
51
52 /*
53 * this implementation of a replay database works as follows:
54 *
55 * window_start is the index of the first packet in the window
56 * bitmask a bit-buffer, containing the most recently entered
57 * index as the leftmost bit
58 *
59 */
60
61 /* srtp_rdb_init initalizes rdb */
srtp_rdb_init(srtp_rdb_t * rdb)62 srtp_err_status_t srtp_rdb_init(srtp_rdb_t *rdb)
63 {
64 v128_set_to_zero(&rdb->bitmask);
65 rdb->window_start = 0;
66 return srtp_err_status_ok;
67 }
68
69 /*
70 * srtp_rdb_check checks to see if index appears in rdb
71 */
srtp_rdb_check(const srtp_rdb_t * rdb,uint32_t p_index)72 srtp_err_status_t srtp_rdb_check(const srtp_rdb_t *rdb, uint32_t p_index)
73 {
74 /* if the index appears after (or at very end of) the window, its good */
75 if (p_index >= rdb->window_start + rdb_bits_in_bitmask) {
76 return srtp_err_status_ok;
77 }
78
79 /* if the index appears before the window, its bad */
80 if (p_index < rdb->window_start) {
81 return srtp_err_status_replay_old;
82 }
83
84 /* otherwise, the index appears within the window, so check the bitmask */
85 if (v128_get_bit(&rdb->bitmask, (p_index - rdb->window_start)) == 1) {
86 return srtp_err_status_replay_fail;
87 }
88
89 /* otherwise, the index is okay */
90 return srtp_err_status_ok;
91 }
92
93 /*
94 * srtp_rdb_add_index adds index to srtp_rdb_t (and does *not* check if
95 * index appears in db)
96 *
97 * this function should be called only after srtp_rdb_check has
98 * indicated that the index does not appear in the rdb, e.g., a mutex
99 * should protect the rdb between these calls
100 */
srtp_rdb_add_index(srtp_rdb_t * rdb,uint32_t p_index)101 srtp_err_status_t srtp_rdb_add_index(srtp_rdb_t *rdb, uint32_t p_index)
102 {
103 unsigned int delta;
104
105 if (p_index < rdb->window_start)
106 return srtp_err_status_replay_fail;
107
108 delta = (p_index - rdb->window_start);
109 if (delta < rdb_bits_in_bitmask) {
110 /* if the p_index is within the window, set the appropriate bit */
111 v128_set_bit(&rdb->bitmask, delta);
112
113 } else {
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 return srtp_err_status_ok;
123 }
124
srtp_rdb_increment(srtp_rdb_t * rdb)125 srtp_err_status_t srtp_rdb_increment(srtp_rdb_t *rdb)
126 {
127 if (rdb->window_start >= 0x7fffffff) {
128 return srtp_err_status_key_expired;
129 }
130 ++rdb->window_start;
131 return srtp_err_status_ok;
132 }
133
srtp_rdb_get_value(const srtp_rdb_t * rdb)134 uint32_t srtp_rdb_get_value(const srtp_rdb_t *rdb)
135 {
136 return rdb->window_start;
137 }
138