xref: /linux/net/xfrm/xfrm_replay.c (revision 0d456bad36d42d16022be045c8a53ddbb59ee478) 
1 /*
2  * xfrm_replay.c - xfrm replay detection, derived from xfrm_state.c.
3  *
4  * Copyright (C) 2010 secunet Security Networks AG
5  * Copyright (C) 2010 Steffen Klassert <steffen.klassert@secunet.com>
6  *
7  * This program is free software; you can redistribute it and/or modify it
8  * under the terms and conditions of the GNU General Public License,
9  * version 2, as published by the Free Software Foundation.
10  *
11  * This program is distributed in the hope it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
14  * more details.
15  *
16  * You should have received a copy of the GNU General Public License along with
17  * this program; if not, write to the Free Software Foundation, Inc.,
18  * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
19  */
20 
21 #include <linux/export.h>
22 #include <net/xfrm.h>
23 
24 u32 xfrm_replay_seqhi(struct xfrm_state *x, __be32 net_seq)
25 {
26 	u32 seq, seq_hi, bottom;
27 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
28 
29 	if (!(x->props.flags & XFRM_STATE_ESN))
30 		return 0;
31 
32 	seq = ntohl(net_seq);
33 	seq_hi = replay_esn->seq_hi;
34 	bottom = replay_esn->seq - replay_esn->replay_window + 1;
35 
36 	if (likely(replay_esn->seq >= replay_esn->replay_window - 1)) {
37 		/* A. same subspace */
38 		if (unlikely(seq < bottom))
39 			seq_hi++;
40 	} else {
41 		/* B. window spans two subspaces */
42 		if (unlikely(seq >= bottom))
43 			seq_hi--;
44 	}
45 
46 	return seq_hi;
47 }
48 
49 static void xfrm_replay_notify(struct xfrm_state *x, int event)
50 {
51 	struct km_event c;
52 	/* we send notify messages in case
53 	 *  1. we updated on of the sequence numbers, and the seqno difference
54 	 *     is at least x->replay_maxdiff, in this case we also update the
55 	 *     timeout of our timer function
56 	 *  2. if x->replay_maxage has elapsed since last update,
57 	 *     and there were changes
58 	 *
59 	 *  The state structure must be locked!
60 	 */
61 
62 	switch (event) {
63 	case XFRM_REPLAY_UPDATE:
64 		if (x->replay_maxdiff &&
65 		    (x->replay.seq - x->preplay.seq < x->replay_maxdiff) &&
66 		    (x->replay.oseq - x->preplay.oseq < x->replay_maxdiff)) {
67 			if (x->xflags & XFRM_TIME_DEFER)
68 				event = XFRM_REPLAY_TIMEOUT;
69 			else
70 				return;
71 		}
72 
73 		break;
74 
75 	case XFRM_REPLAY_TIMEOUT:
76 		if (memcmp(&x->replay, &x->preplay,
77 			   sizeof(struct xfrm_replay_state)) == 0) {
78 			x->xflags |= XFRM_TIME_DEFER;
79 			return;
80 		}
81 
82 		break;
83 	}
84 
85 	memcpy(&x->preplay, &x->replay, sizeof(struct xfrm_replay_state));
86 	c.event = XFRM_MSG_NEWAE;
87 	c.data.aevent = event;
88 	km_state_notify(x, &c);
89 
90 	if (x->replay_maxage &&
91 	    !mod_timer(&x->rtimer, jiffies + x->replay_maxage))
92 		x->xflags &= ~XFRM_TIME_DEFER;
93 }
94 
95 static int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
96 {
97 	int err = 0;
98 	struct net *net = xs_net(x);
99 
100 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
101 		XFRM_SKB_CB(skb)->seq.output.low = ++x->replay.oseq;
102 		if (unlikely(x->replay.oseq == 0)) {
103 			x->replay.oseq--;
104 			xfrm_audit_state_replay_overflow(x, skb);
105 			err = -EOVERFLOW;
106 
107 			return err;
108 		}
109 		if (xfrm_aevent_is_on(net))
110 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
111 	}
112 
113 	return err;
114 }
115 
116 static int xfrm_replay_check(struct xfrm_state *x,
117 		      struct sk_buff *skb, __be32 net_seq)
118 {
119 	u32 diff;
120 	u32 seq = ntohl(net_seq);
121 
122 	if (!x->props.replay_window)
123 		return 0;
124 
125 	if (unlikely(seq == 0))
126 		goto err;
127 
128 	if (likely(seq > x->replay.seq))
129 		return 0;
130 
131 	diff = x->replay.seq - seq;
132 	if (diff >= min_t(unsigned int, x->props.replay_window,
133 			  sizeof(x->replay.bitmap) * 8)) {
134 		x->stats.replay_window++;
135 		goto err;
136 	}
137 
138 	if (x->replay.bitmap & (1U << diff)) {
139 		x->stats.replay++;
140 		goto err;
141 	}
142 	return 0;
143 
144 err:
145 	xfrm_audit_state_replay(x, skb, net_seq);
146 	return -EINVAL;
147 }
148 
149 static void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq)
150 {
151 	u32 diff;
152 	u32 seq = ntohl(net_seq);
153 
154 	if (!x->props.replay_window)
155 		return;
156 
157 	if (seq > x->replay.seq) {
158 		diff = seq - x->replay.seq;
159 		if (diff < x->props.replay_window)
160 			x->replay.bitmap = ((x->replay.bitmap) << diff) | 1;
161 		else
162 			x->replay.bitmap = 1;
163 		x->replay.seq = seq;
164 	} else {
165 		diff = x->replay.seq - seq;
166 		x->replay.bitmap |= (1U << diff);
167 	}
168 
169 	if (xfrm_aevent_is_on(xs_net(x)))
170 		x->repl->notify(x, XFRM_REPLAY_UPDATE);
171 }
172 
173 static int xfrm_replay_overflow_bmp(struct xfrm_state *x, struct sk_buff *skb)
174 {
175 	int err = 0;
176 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
177 	struct net *net = xs_net(x);
178 
179 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
180 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
181 		if (unlikely(replay_esn->oseq == 0)) {
182 			replay_esn->oseq--;
183 			xfrm_audit_state_replay_overflow(x, skb);
184 			err = -EOVERFLOW;
185 
186 			return err;
187 		}
188 		if (xfrm_aevent_is_on(net))
189 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
190 	}
191 
192 	return err;
193 }
194 
195 static int xfrm_replay_check_bmp(struct xfrm_state *x,
196 				 struct sk_buff *skb, __be32 net_seq)
197 {
198 	unsigned int bitnr, nr;
199 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
200 	u32 pos;
201 	u32 seq = ntohl(net_seq);
202 	u32 diff =  replay_esn->seq - seq;
203 
204 	if (!replay_esn->replay_window)
205 		return 0;
206 
207 	if (unlikely(seq == 0))
208 		goto err;
209 
210 	if (likely(seq > replay_esn->seq))
211 		return 0;
212 
213 	if (diff >= replay_esn->replay_window) {
214 		x->stats.replay_window++;
215 		goto err;
216 	}
217 
218 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
219 
220 	if (pos >= diff)
221 		bitnr = (pos - diff) % replay_esn->replay_window;
222 	else
223 		bitnr = replay_esn->replay_window - (diff - pos);
224 
225 	nr = bitnr >> 5;
226 	bitnr = bitnr & 0x1F;
227 	if (replay_esn->bmp[nr] & (1U << bitnr))
228 		goto err_replay;
229 
230 	return 0;
231 
232 err_replay:
233 	x->stats.replay++;
234 err:
235 	xfrm_audit_state_replay(x, skb, net_seq);
236 	return -EINVAL;
237 }
238 
239 static void xfrm_replay_advance_bmp(struct xfrm_state *x, __be32 net_seq)
240 {
241 	unsigned int bitnr, nr, i;
242 	u32 diff;
243 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
244 	u32 seq = ntohl(net_seq);
245 	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
246 
247 	if (!replay_esn->replay_window)
248 		return;
249 
250 	if (seq > replay_esn->seq) {
251 		diff = seq - replay_esn->seq;
252 
253 		if (diff < replay_esn->replay_window) {
254 			for (i = 1; i < diff; i++) {
255 				bitnr = (pos + i) % replay_esn->replay_window;
256 				nr = bitnr >> 5;
257 				bitnr = bitnr & 0x1F;
258 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
259 			}
260 		} else {
261 			nr = (replay_esn->replay_window - 1) >> 5;
262 			for (i = 0; i <= nr; i++)
263 				replay_esn->bmp[i] = 0;
264 		}
265 
266 		bitnr = (pos + diff) % replay_esn->replay_window;
267 		replay_esn->seq = seq;
268 	} else {
269 		diff = replay_esn->seq - seq;
270 
271 		if (pos >= diff)
272 			bitnr = (pos - diff) % replay_esn->replay_window;
273 		else
274 			bitnr = replay_esn->replay_window - (diff - pos);
275 	}
276 
277 	nr = bitnr >> 5;
278 	bitnr = bitnr & 0x1F;
279 	replay_esn->bmp[nr] |= (1U << bitnr);
280 
281 	if (xfrm_aevent_is_on(xs_net(x)))
282 		x->repl->notify(x, XFRM_REPLAY_UPDATE);
283 }
284 
285 static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
286 {
287 	struct km_event c;
288 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
289 	struct xfrm_replay_state_esn *preplay_esn = x->preplay_esn;
290 
291 	/* we send notify messages in case
292 	 *  1. we updated on of the sequence numbers, and the seqno difference
293 	 *     is at least x->replay_maxdiff, in this case we also update the
294 	 *     timeout of our timer function
295 	 *  2. if x->replay_maxage has elapsed since last update,
296 	 *     and there were changes
297 	 *
298 	 *  The state structure must be locked!
299 	 */
300 
301 	switch (event) {
302 	case XFRM_REPLAY_UPDATE:
303 		if (x->replay_maxdiff &&
304 		    (replay_esn->seq - preplay_esn->seq < x->replay_maxdiff) &&
305 		    (replay_esn->oseq - preplay_esn->oseq < x->replay_maxdiff)) {
306 			if (x->xflags & XFRM_TIME_DEFER)
307 				event = XFRM_REPLAY_TIMEOUT;
308 			else
309 				return;
310 		}
311 
312 		break;
313 
314 	case XFRM_REPLAY_TIMEOUT:
315 		if (memcmp(x->replay_esn, x->preplay_esn,
316 			   xfrm_replay_state_esn_len(replay_esn)) == 0) {
317 			x->xflags |= XFRM_TIME_DEFER;
318 			return;
319 		}
320 
321 		break;
322 	}
323 
324 	memcpy(x->preplay_esn, x->replay_esn,
325 	       xfrm_replay_state_esn_len(replay_esn));
326 	c.event = XFRM_MSG_NEWAE;
327 	c.data.aevent = event;
328 	km_state_notify(x, &c);
329 
330 	if (x->replay_maxage &&
331 	    !mod_timer(&x->rtimer, jiffies + x->replay_maxage))
332 		x->xflags &= ~XFRM_TIME_DEFER;
333 }
334 
335 static int xfrm_replay_overflow_esn(struct xfrm_state *x, struct sk_buff *skb)
336 {
337 	int err = 0;
338 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
339 	struct net *net = xs_net(x);
340 
341 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
342 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
343 		XFRM_SKB_CB(skb)->seq.output.hi = replay_esn->oseq_hi;
344 
345 		if (unlikely(replay_esn->oseq == 0)) {
346 			XFRM_SKB_CB(skb)->seq.output.hi = ++replay_esn->oseq_hi;
347 
348 			if (replay_esn->oseq_hi == 0) {
349 				replay_esn->oseq--;
350 				replay_esn->oseq_hi--;
351 				xfrm_audit_state_replay_overflow(x, skb);
352 				err = -EOVERFLOW;
353 
354 				return err;
355 			}
356 		}
357 		if (xfrm_aevent_is_on(net))
358 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
359 	}
360 
361 	return err;
362 }
363 
364 static int xfrm_replay_check_esn(struct xfrm_state *x,
365 				 struct sk_buff *skb, __be32 net_seq)
366 {
367 	unsigned int bitnr, nr;
368 	u32 diff;
369 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
370 	u32 pos;
371 	u32 seq = ntohl(net_seq);
372 	u32 wsize = replay_esn->replay_window;
373 	u32 top = replay_esn->seq;
374 	u32 bottom = top - wsize + 1;
375 
376 	if (!wsize)
377 		return 0;
378 
379 	if (unlikely(seq == 0 && replay_esn->seq_hi == 0 &&
380 		     (replay_esn->seq < replay_esn->replay_window - 1)))
381 		goto err;
382 
383 	diff = top - seq;
384 
385 	if (likely(top >= wsize - 1)) {
386 		/* A. same subspace */
387 		if (likely(seq > top) || seq < bottom)
388 			return 0;
389 	} else {
390 		/* B. window spans two subspaces */
391 		if (likely(seq > top && seq < bottom))
392 			return 0;
393 		if (seq >= bottom)
394 			diff = ~seq + top + 1;
395 	}
396 
397 	if (diff >= replay_esn->replay_window) {
398 		x->stats.replay_window++;
399 		goto err;
400 	}
401 
402 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
403 
404 	if (pos >= diff)
405 		bitnr = (pos - diff) % replay_esn->replay_window;
406 	else
407 		bitnr = replay_esn->replay_window - (diff - pos);
408 
409 	nr = bitnr >> 5;
410 	bitnr = bitnr & 0x1F;
411 	if (replay_esn->bmp[nr] & (1U << bitnr))
412 		goto err_replay;
413 
414 	return 0;
415 
416 err_replay:
417 	x->stats.replay++;
418 err:
419 	xfrm_audit_state_replay(x, skb, net_seq);
420 	return -EINVAL;
421 }
422 
423 static int xfrm_replay_recheck_esn(struct xfrm_state *x,
424 				   struct sk_buff *skb, __be32 net_seq)
425 {
426 	if (unlikely(XFRM_SKB_CB(skb)->seq.input.hi !=
427 		     htonl(xfrm_replay_seqhi(x, net_seq)))) {
428 			x->stats.replay_window++;
429 			return -EINVAL;
430 	}
431 
432 	return xfrm_replay_check_esn(x, skb, net_seq);
433 }
434 
435 static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
436 {
437 	unsigned int bitnr, nr, i;
438 	int wrap;
439 	u32 diff, pos, seq, seq_hi;
440 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
441 
442 	if (!replay_esn->replay_window)
443 		return;
444 
445 	seq = ntohl(net_seq);
446 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
447 	seq_hi = xfrm_replay_seqhi(x, net_seq);
448 	wrap = seq_hi - replay_esn->seq_hi;
449 
450 	if ((!wrap && seq > replay_esn->seq) || wrap > 0) {
451 		if (likely(!wrap))
452 			diff = seq - replay_esn->seq;
453 		else
454 			diff = ~replay_esn->seq + seq + 1;
455 
456 		if (diff < replay_esn->replay_window) {
457 			for (i = 1; i < diff; i++) {
458 				bitnr = (pos + i) % replay_esn->replay_window;
459 				nr = bitnr >> 5;
460 				bitnr = bitnr & 0x1F;
461 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
462 			}
463 		} else {
464 			nr = (replay_esn->replay_window - 1) >> 5;
465 			for (i = 0; i <= nr; i++)
466 				replay_esn->bmp[i] = 0;
467 		}
468 
469 		bitnr = (pos + diff) % replay_esn->replay_window;
470 		replay_esn->seq = seq;
471 
472 		if (unlikely(wrap > 0))
473 			replay_esn->seq_hi++;
474 	} else {
475 		diff = replay_esn->seq - seq;
476 
477 		if (pos >= diff)
478 			bitnr = (pos - diff) % replay_esn->replay_window;
479 		else
480 			bitnr = replay_esn->replay_window - (diff - pos);
481 	}
482 
483 	nr = bitnr >> 5;
484 	bitnr = bitnr & 0x1F;
485 	replay_esn->bmp[nr] |= (1U << bitnr);
486 
487 	if (xfrm_aevent_is_on(xs_net(x)))
488 		x->repl->notify(x, XFRM_REPLAY_UPDATE);
489 }
490 
491 static struct xfrm_replay xfrm_replay_legacy = {
492 	.advance	= xfrm_replay_advance,
493 	.check		= xfrm_replay_check,
494 	.recheck	= xfrm_replay_check,
495 	.notify		= xfrm_replay_notify,
496 	.overflow	= xfrm_replay_overflow,
497 };
498 
499 static struct xfrm_replay xfrm_replay_bmp = {
500 	.advance	= xfrm_replay_advance_bmp,
501 	.check		= xfrm_replay_check_bmp,
502 	.recheck	= xfrm_replay_check_bmp,
503 	.notify		= xfrm_replay_notify_bmp,
504 	.overflow	= xfrm_replay_overflow_bmp,
505 };
506 
507 static struct xfrm_replay xfrm_replay_esn = {
508 	.advance	= xfrm_replay_advance_esn,
509 	.check		= xfrm_replay_check_esn,
510 	.recheck	= xfrm_replay_recheck_esn,
511 	.notify		= xfrm_replay_notify_bmp,
512 	.overflow	= xfrm_replay_overflow_esn,
513 };
514 
515 int xfrm_init_replay(struct xfrm_state *x)
516 {
517 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
518 
519 	if (replay_esn) {
520 		if (replay_esn->replay_window >
521 		    replay_esn->bmp_len * sizeof(__u32) * 8)
522 			return -EINVAL;
523 
524 		if (x->props.flags & XFRM_STATE_ESN) {
525 			if (replay_esn->replay_window == 0)
526 				return -EINVAL;
527 			x->repl = &xfrm_replay_esn;
528 		} else
529 			x->repl = &xfrm_replay_bmp;
530 	} else
531 		x->repl = &xfrm_replay_legacy;
532 
533 	return 0;
534 }
535 EXPORT_SYMBOL(xfrm_init_replay);
536