xref: /openbmc/linux/net/xfrm/xfrm_replay.c (revision d0b73b48) 
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;
246 
247 	if (!replay_esn->replay_window)
248 		return;
249 
250 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
251 
252 	if (seq > replay_esn->seq) {
253 		diff = seq - replay_esn->seq;
254 
255 		if (diff < replay_esn->replay_window) {
256 			for (i = 1; i < diff; i++) {
257 				bitnr = (pos + i) % replay_esn->replay_window;
258 				nr = bitnr >> 5;
259 				bitnr = bitnr & 0x1F;
260 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
261 			}
262 		} else {
263 			nr = (replay_esn->replay_window - 1) >> 5;
264 			for (i = 0; i <= nr; i++)
265 				replay_esn->bmp[i] = 0;
266 		}
267 
268 		bitnr = (pos + diff) % replay_esn->replay_window;
269 		replay_esn->seq = seq;
270 	} else {
271 		diff = replay_esn->seq - seq;
272 
273 		if (pos >= diff)
274 			bitnr = (pos - diff) % replay_esn->replay_window;
275 		else
276 			bitnr = replay_esn->replay_window - (diff - pos);
277 	}
278 
279 	nr = bitnr >> 5;
280 	bitnr = bitnr & 0x1F;
281 	replay_esn->bmp[nr] |= (1U << bitnr);
282 
283 	if (xfrm_aevent_is_on(xs_net(x)))
284 		x->repl->notify(x, XFRM_REPLAY_UPDATE);
285 }
286 
287 static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
288 {
289 	struct km_event c;
290 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
291 	struct xfrm_replay_state_esn *preplay_esn = x->preplay_esn;
292 
293 	/* we send notify messages in case
294 	 *  1. we updated on of the sequence numbers, and the seqno difference
295 	 *     is at least x->replay_maxdiff, in this case we also update the
296 	 *     timeout of our timer function
297 	 *  2. if x->replay_maxage has elapsed since last update,
298 	 *     and there were changes
299 	 *
300 	 *  The state structure must be locked!
301 	 */
302 
303 	switch (event) {
304 	case XFRM_REPLAY_UPDATE:
305 		if (x->replay_maxdiff &&
306 		    (replay_esn->seq - preplay_esn->seq < x->replay_maxdiff) &&
307 		    (replay_esn->oseq - preplay_esn->oseq < x->replay_maxdiff)) {
308 			if (x->xflags & XFRM_TIME_DEFER)
309 				event = XFRM_REPLAY_TIMEOUT;
310 			else
311 				return;
312 		}
313 
314 		break;
315 
316 	case XFRM_REPLAY_TIMEOUT:
317 		if (memcmp(x->replay_esn, x->preplay_esn,
318 			   xfrm_replay_state_esn_len(replay_esn)) == 0) {
319 			x->xflags |= XFRM_TIME_DEFER;
320 			return;
321 		}
322 
323 		break;
324 	}
325 
326 	memcpy(x->preplay_esn, x->replay_esn,
327 	       xfrm_replay_state_esn_len(replay_esn));
328 	c.event = XFRM_MSG_NEWAE;
329 	c.data.aevent = event;
330 	km_state_notify(x, &c);
331 
332 	if (x->replay_maxage &&
333 	    !mod_timer(&x->rtimer, jiffies + x->replay_maxage))
334 		x->xflags &= ~XFRM_TIME_DEFER;
335 }
336 
337 static int xfrm_replay_overflow_esn(struct xfrm_state *x, struct sk_buff *skb)
338 {
339 	int err = 0;
340 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
341 	struct net *net = xs_net(x);
342 
343 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
344 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
345 		XFRM_SKB_CB(skb)->seq.output.hi = replay_esn->oseq_hi;
346 
347 		if (unlikely(replay_esn->oseq == 0)) {
348 			XFRM_SKB_CB(skb)->seq.output.hi = ++replay_esn->oseq_hi;
349 
350 			if (replay_esn->oseq_hi == 0) {
351 				replay_esn->oseq--;
352 				replay_esn->oseq_hi--;
353 				xfrm_audit_state_replay_overflow(x, skb);
354 				err = -EOVERFLOW;
355 
356 				return err;
357 			}
358 		}
359 		if (xfrm_aevent_is_on(net))
360 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
361 	}
362 
363 	return err;
364 }
365 
366 static int xfrm_replay_check_esn(struct xfrm_state *x,
367 				 struct sk_buff *skb, __be32 net_seq)
368 {
369 	unsigned int bitnr, nr;
370 	u32 diff;
371 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
372 	u32 pos;
373 	u32 seq = ntohl(net_seq);
374 	u32 wsize = replay_esn->replay_window;
375 	u32 top = replay_esn->seq;
376 	u32 bottom = top - wsize + 1;
377 
378 	if (!wsize)
379 		return 0;
380 
381 	if (unlikely(seq == 0 && replay_esn->seq_hi == 0 &&
382 		     (replay_esn->seq < replay_esn->replay_window - 1)))
383 		goto err;
384 
385 	diff = top - seq;
386 
387 	if (likely(top >= wsize - 1)) {
388 		/* A. same subspace */
389 		if (likely(seq > top) || seq < bottom)
390 			return 0;
391 	} else {
392 		/* B. window spans two subspaces */
393 		if (likely(seq > top && seq < bottom))
394 			return 0;
395 		if (seq >= bottom)
396 			diff = ~seq + top + 1;
397 	}
398 
399 	if (diff >= replay_esn->replay_window) {
400 		x->stats.replay_window++;
401 		goto err;
402 	}
403 
404 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
405 
406 	if (pos >= diff)
407 		bitnr = (pos - diff) % replay_esn->replay_window;
408 	else
409 		bitnr = replay_esn->replay_window - (diff - pos);
410 
411 	nr = bitnr >> 5;
412 	bitnr = bitnr & 0x1F;
413 	if (replay_esn->bmp[nr] & (1U << bitnr))
414 		goto err_replay;
415 
416 	return 0;
417 
418 err_replay:
419 	x->stats.replay++;
420 err:
421 	xfrm_audit_state_replay(x, skb, net_seq);
422 	return -EINVAL;
423 }
424 
425 static int xfrm_replay_recheck_esn(struct xfrm_state *x,
426 				   struct sk_buff *skb, __be32 net_seq)
427 {
428 	if (unlikely(XFRM_SKB_CB(skb)->seq.input.hi !=
429 		     htonl(xfrm_replay_seqhi(x, net_seq)))) {
430 			x->stats.replay_window++;
431 			return -EINVAL;
432 	}
433 
434 	return xfrm_replay_check_esn(x, skb, net_seq);
435 }
436 
437 static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
438 {
439 	unsigned int bitnr, nr, i;
440 	int wrap;
441 	u32 diff, pos, seq, seq_hi;
442 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
443 
444 	if (!replay_esn->replay_window)
445 		return;
446 
447 	seq = ntohl(net_seq);
448 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
449 	seq_hi = xfrm_replay_seqhi(x, net_seq);
450 	wrap = seq_hi - replay_esn->seq_hi;
451 
452 	if ((!wrap && seq > replay_esn->seq) || wrap > 0) {
453 		if (likely(!wrap))
454 			diff = seq - replay_esn->seq;
455 		else
456 			diff = ~replay_esn->seq + seq + 1;
457 
458 		if (diff < replay_esn->replay_window) {
459 			for (i = 1; i < diff; i++) {
460 				bitnr = (pos + i) % replay_esn->replay_window;
461 				nr = bitnr >> 5;
462 				bitnr = bitnr & 0x1F;
463 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
464 			}
465 		} else {
466 			nr = (replay_esn->replay_window - 1) >> 5;
467 			for (i = 0; i <= nr; i++)
468 				replay_esn->bmp[i] = 0;
469 		}
470 
471 		bitnr = (pos + diff) % replay_esn->replay_window;
472 		replay_esn->seq = seq;
473 
474 		if (unlikely(wrap > 0))
475 			replay_esn->seq_hi++;
476 	} else {
477 		diff = replay_esn->seq - seq;
478 
479 		if (pos >= diff)
480 			bitnr = (pos - diff) % replay_esn->replay_window;
481 		else
482 			bitnr = replay_esn->replay_window - (diff - pos);
483 	}
484 
485 	nr = bitnr >> 5;
486 	bitnr = bitnr & 0x1F;
487 	replay_esn->bmp[nr] |= (1U << bitnr);
488 
489 	if (xfrm_aevent_is_on(xs_net(x)))
490 		x->repl->notify(x, XFRM_REPLAY_UPDATE);
491 }
492 
493 static struct xfrm_replay xfrm_replay_legacy = {
494 	.advance	= xfrm_replay_advance,
495 	.check		= xfrm_replay_check,
496 	.recheck	= xfrm_replay_check,
497 	.notify		= xfrm_replay_notify,
498 	.overflow	= xfrm_replay_overflow,
499 };
500 
501 static struct xfrm_replay xfrm_replay_bmp = {
502 	.advance	= xfrm_replay_advance_bmp,
503 	.check		= xfrm_replay_check_bmp,
504 	.recheck	= xfrm_replay_check_bmp,
505 	.notify		= xfrm_replay_notify_bmp,
506 	.overflow	= xfrm_replay_overflow_bmp,
507 };
508 
509 static struct xfrm_replay xfrm_replay_esn = {
510 	.advance	= xfrm_replay_advance_esn,
511 	.check		= xfrm_replay_check_esn,
512 	.recheck	= xfrm_replay_recheck_esn,
513 	.notify		= xfrm_replay_notify_bmp,
514 	.overflow	= xfrm_replay_overflow_esn,
515 };
516 
517 int xfrm_init_replay(struct xfrm_state *x)
518 {
519 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
520 
521 	if (replay_esn) {
522 		if (replay_esn->replay_window >
523 		    replay_esn->bmp_len * sizeof(__u32) * 8)
524 			return -EINVAL;
525 
526 		if (x->props.flags & XFRM_STATE_ESN) {
527 			if (replay_esn->replay_window == 0)
528 				return -EINVAL;
529 			x->repl = &xfrm_replay_esn;
530 		} else
531 			x->repl = &xfrm_replay_bmp;
532 	} else
533 		x->repl = &xfrm_replay_legacy;
534 
535 	return 0;
536 }
537 EXPORT_SYMBOL(xfrm_init_replay);
538