Bug Summary

File:libs/srtp/crypto/replay/rdbx.c
Location:line 141, column 12
Description:Value stored to 'guess_seq' during its initialization is never read

Annotated Source Code

1/*
2 * rdbx.c
3 *
4 * a replay database with extended range, using a rollover counter
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#include "rdbx.h"
47
48
49/*
50 * from RFC 3711:
51 *
52 * A receiver reconstructs the index i of a packet with sequence
53 * number SEQ using the estimate
54 *
55 * i = 2^16 * v + SEQ,
56 *
57 * where v is chosen from the set { ROC-1, ROC, ROC+1 } such that i is
58 * closest to the value 2^16 * ROC + s_l. If the value r+1 is used,
59 * then the rollover counter r in the cryptographic context is
60 * incremented by one (if the packet containing s is authentic).
61 */
62
63
64
65/*
66 * rdbx implementation notes
67 *
68 * A xtd_seq_num_t is essentially a sequence number for which some of
69 * the data on the wire are implicit. It logically consists of a
70 * rollover counter and a sequence number; the sequence number is the
71 * explicit part, and the rollover counter is the implicit part.
72 *
73 * Upon receiving a sequence_number (e.g. in a newly received SRTP
74 * packet), the complete xtd_seq_num_t can be estimated by using a
75 * local xtd_seq_num_t as a basis. This is done using the function
76 * index_guess(&local, &guess, seq_from_packet). This function
77 * returns the difference of the guess and the local value. The local
78 * xtd_seq_num_t can be moved forward to the guess using the function
79 * index_advance(&guess, delta), where delta is the difference.
80 *
81 *
82 * A rdbx_t consists of a xtd_seq_num_t and a bitmask. The index is highest
83 * sequence number that has been received, and the bitmask indicates
84 * which of the recent indicies have been received as well. The
85 * highest bit in the bitmask corresponds to the index in the bitmask.
86 */
87
88
89void
90index_init(xtd_seq_num_t *pi) {
91#ifdef NO_64BIT_MATH
92 *pi = make64(0,0);
93#else
94 *pi = 0;
95#endif
96}
97
98void
99index_advance(xtd_seq_num_t *pi, sequence_number_t s) {
100#ifdef NO_64BIT_MATH
101 /* a > ~b means a+b will generate a carry */
102 /* s is uint16 here */
103 *pi = make64(high32(*pi) + (s > ~low32(*pi) ? 1 : 0),low32(*pi) + s);
104#else
105 *pi += s;
106#endif
107}
108
109
110/*
111 * index_guess(local, guess, s)
112 *
113 * given a xtd_seq_num_t local (which represents the last
114 * known-to-be-good received xtd_seq_num_t) and a sequence number s
115 * (from a newly arrived packet), sets the contents of *guess to
116 * contain the best guess of the packet index to which s corresponds,
117 * and returns the difference between *guess and *local
118 *
119 * nota bene - the output is a signed integer, DON'T cast it to a
120 * unsigned integer!
121 */
122
123int
124index_guess(const xtd_seq_num_t *local,
125 xtd_seq_num_t *guess,
126 sequence_number_t s) {
127#ifdef NO_64BIT_MATH
128 uint32_t local_roc = ((high32(*local) << 16) |
129 (low32(*local) >> 16));
130 uint16_t local_seq = (uint16_t) (low32(*local));
131#else
132 uint32_t local_roc = (uint32_t)(*local >> 16);
133 uint16_t local_seq = (uint16_t) *local;
134#endif
135#ifdef NO_64BIT_MATH
136 uint32_t guess_roc = ((high32(*guess) << 16) |
137 (low32(*guess) >> 16));
138 uint16_t guess_seq = (uint16_t) (low32(*guess));
139#else
140 uint32_t guess_roc = (uint32_t)(*guess >> 16);
141 uint16_t guess_seq = (uint16_t) *guess;
Value stored to 'guess_seq' during its initialization is never read
142#endif
143 int difference;
144
145 if (local_seq < seq_num_median(1 << (8*sizeof(sequence_number_t) - 1))) {
146 if (s - local_seq > seq_num_median(1 << (8*sizeof(sequence_number_t) - 1))) {
147 guess_roc = local_roc - 1;
148 difference = s - local_seq - seq_num_max(1 << (8*sizeof(sequence_number_t)));
149 } else {
150 guess_roc = local_roc;
151 difference = s - local_seq;
152 }
153 } else {
154 if (local_seq - seq_num_median(1 << (8*sizeof(sequence_number_t) - 1)) > s) {
155 guess_roc = local_roc + 1;
156 difference = s - local_seq + seq_num_max(1 << (8*sizeof(sequence_number_t)));
157 } else {
158 guess_roc = local_roc;
159 difference = s - local_seq;
160 }
161 }
162 guess_seq = s;
163
164 /* Note: guess_roc is 32 bits, so this generates a 48-bit result! */
165#ifdef NO_64BIT_MATH
166 *guess = make64(guess_roc >> 16,
167 (guess_roc << 16) | guess_seq);
168#else
169 *guess = (((uint64_t) guess_roc) << 16) | guess_seq;
170#endif
171
172 return difference;
173}
174
175/*
176 * rdbx
177 *
178 */
179
180
181/*
182 * rdbx_init(&r, ws) initializes the rdbx_t pointed to by r with window size ws
183 */
184
185err_status_t
186rdbx_init(rdbx_t *rdbx, unsigned long ws) {
187 if (ws == 0)
188 return err_status_bad_param;
189
190 if (bitvector_alloc(&rdbx->bitmask, ws) != 0)
191 return err_status_alloc_fail;
192
193 index_init(&rdbx->index);
194
195 return err_status_ok;
196}
197
198/*
199 * rdbx_dealloc(&r) frees memory for the rdbx_t pointed to by r
200 */
201
202err_status_t
203rdbx_dealloc(rdbx_t *rdbx) {
204 bitvector_dealloc(&rdbx->bitmask);
205
206 return err_status_ok;
207}
208
209/*
210 * rdbx_set_roc(rdbx, roc) initalizes the rdbx_t at the location rdbx
211 * to have the rollover counter value roc. If that value is less than
212 * the current rollover counter value, then the function returns
213 * err_status_replay_old; otherwise, err_status_ok is returned.
214 *
215 */
216
217err_status_t
218rdbx_set_roc(rdbx_t *rdbx, uint32_t roc) {
219 bitvector_set_to_zero(&rdbx->bitmask);
220
221#ifdef NO_64BIT_MATH
222 #error not yet implemented
223#else
224
225 /* make sure that we're not moving backwards */
226 if (roc < (rdbx->index >> 16))
227 return err_status_replay_old;
228
229 rdbx->index &= 0xffff; /* retain lowest 16 bits */
230 rdbx->index |= ((uint64_t)roc) << 16; /* set ROC */
231#endif
232
233 return err_status_ok;
234}
235
236/*
237 * rdbx_get_packet_index(rdbx) returns the value of the packet index
238 * for the rdbx_t pointed to by rdbx
239 *
240 */
241
242xtd_seq_num_t
243rdbx_get_packet_index(const rdbx_t *rdbx) {
244 return rdbx->index;
245}
246
247/*
248 * rdbx_get_window_size(rdbx) returns the value of the window size
249 * for the rdbx_t pointed to by rdbx
250 *
251 */
252
253unsigned long
254rdbx_get_window_size(const rdbx_t *rdbx) {
255 return bitvector_get_length(&rdbx->bitmask)( ((&rdbx->bitmask)->length) );
256}
257
258/*
259 * rdbx_check(&r, delta) checks to see if the xtd_seq_num_t
260 * which is at rdbx->index + delta is in the rdb
261 */
262
263err_status_t
264rdbx_check(const rdbx_t *rdbx, int delta) {
265
266 if (delta > 0) { /* if delta is positive, it's good */
267 return err_status_ok;
268 } else if ((int)(bitvector_get_length(&rdbx->bitmask)( ((&rdbx->bitmask)->length) ) - 1) + delta < 0) {
269 /* if delta is lower than the bitmask, it's bad */
270 return err_status_replay_old;
271 } else if (bitvector_get_bit(&rdbx->bitmask,( ((((&rdbx->bitmask)->word[(((int)(( ((&rdbx->
bitmask)->length) ) - 1) + delta) >> 5)]) >> (
((int)(( ((&rdbx->bitmask)->length) ) - 1) + delta)
& 31)) & 1) )
272 (int)(bitvector_get_length(&rdbx->bitmask) - 1) + delta)( ((((&rdbx->bitmask)->word[(((int)(( ((&rdbx->
bitmask)->length) ) - 1) + delta) >> 5)]) >> (
((int)(( ((&rdbx->bitmask)->length) ) - 1) + delta)
& 31)) & 1) ) == 1) {
273 /* delta is within the window, so check the bitmask */
274 return err_status_replay_fail;
275 }
276 /* otherwise, the index is okay */
277
278 return err_status_ok;
279}
280
281/*
282 * rdbx_add_index adds the xtd_seq_num_t at rdbx->window_start + d to
283 * replay_db (and does *not* check if that xtd_seq_num_t appears in db)
284 *
285 * this function should be called only after replay_check has
286 * indicated that the index does not appear in the rdbx, e.g., a mutex
287 * should protect the rdbx between these calls if need be
288 */
289
290err_status_t
291rdbx_add_index(rdbx_t *rdbx, int delta) {
292
293 if (delta > 0) {
294 /* shift forward by delta */
295 index_advance(&rdbx->index, (sequence_number_t)delta);
296 bitvector_left_shift(&rdbx->bitmask, delta);
297 bitvector_set_bit(&rdbx->bitmask, bitvector_get_length(&rdbx->bitmask) - 1)( (((&rdbx->bitmask)->word[((( ((&rdbx->bitmask
)->length) ) - 1) >> 5)] |= ((uint32_t)1 << ((
( ((&rdbx->bitmask)->length) ) - 1) & 31)))) );
298 } else {
299 /* delta is in window */
300 bitvector_set_bit(&rdbx->bitmask, bitvector_get_length(&rdbx->bitmask) -1 + delta)( (((&rdbx->bitmask)->word[((( ((&rdbx->bitmask
)->length) ) -1 + delta) >> 5)] |= ((uint32_t)1 <<
((( ((&rdbx->bitmask)->length) ) -1 + delta) &
31)))) );
301 }
302
303 /* note that we need not consider the case that delta == 0 */
304
305 return err_status_ok;
306}
307
308
309
310/*
311 * rdbx_estimate_index(rdbx, guess, s)
312 *
313 * given an rdbx and a sequence number s (from a newly arrived packet),
314 * sets the contents of *guess to contain the best guess of the packet
315 * index to which s corresponds, and returns the difference between
316 * *guess and the locally stored synch info
317 */
318
319int
320rdbx_estimate_index(const rdbx_t *rdbx,
321 xtd_seq_num_t *guess,
322 sequence_number_t s) {
323
324 /*
325 * if the sequence number and rollover counter in the rdbx are
326 * non-zero, then use the index_guess(...) function, otherwise, just
327 * set the rollover counter to zero (since the index_guess(...)
328 * function might incorrectly guess that the rollover counter is
329 * 0xffffffff)
330 */
331
332#ifdef NO_64BIT_MATH
333 /* seq_num_median = 0x8000 */
334 if (high32(rdbx->index) > 0 ||
335 low32(rdbx->index) > seq_num_median(1 << (8*sizeof(sequence_number_t) - 1)))
336#else
337 if (rdbx->index > seq_num_median(1 << (8*sizeof(sequence_number_t) - 1)))
338#endif
339 return index_guess(&rdbx->index, guess, s);
340
341#ifdef NO_64BIT_MATH
342 *guess = make64(0,(uint32_t) s);
343#else
344 *guess = s;
345#endif
346
347#ifdef NO_64BIT_MATH
348 return s - (uint16_t) low32(rdbx->index);
349#else
350 return s - (uint16_t) rdbx->index;
351#endif
352}