xref: /openbmc/linux/net/xfrm/xfrm_replay.c (revision 565d76cb) 
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 <net/xfrm.h>
22 
23 u32 xfrm_replay_seqhi(struct xfrm_state *x, __be32 net_seq)
24 {
25 	u32 seq, seq_hi, bottom;
26 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
27 
28 	if (!(x->props.flags & XFRM_STATE_ESN))
29 		return 0;
30 
31 	seq = ntohl(net_seq);
32 	seq_hi = replay_esn->seq_hi;
33 	bottom = replay_esn->seq - replay_esn->replay_window + 1;
34 
35 	if (likely(replay_esn->seq >= replay_esn->replay_window - 1)) {
36 		/* A. same subspace */
37 		if (unlikely(seq < bottom))
38 			seq_hi++;
39 	} else {
40 		/* B. window spans two subspaces */
41 		if (unlikely(seq >= bottom))
42 			seq_hi--;
43 	}
44 
45 	return seq_hi;
46 }
47 
48 static void xfrm_replay_notify(struct xfrm_state *x, int event)
49 {
50 	struct km_event c;
51 	/* we send notify messages in case
52 	 *  1. we updated on of the sequence numbers, and the seqno difference
53 	 *     is at least x->replay_maxdiff, in this case we also update the
54 	 *     timeout of our timer function
55 	 *  2. if x->replay_maxage has elapsed since last update,
56 	 *     and there were changes
57 	 *
58 	 *  The state structure must be locked!
59 	 */
60 
61 	switch (event) {
62 	case XFRM_REPLAY_UPDATE:
63 		if (x->replay_maxdiff &&
64 		    (x->replay.seq - x->preplay.seq < x->replay_maxdiff) &&
65 		    (x->replay.oseq - x->preplay.oseq < x->replay_maxdiff)) {
66 			if (x->xflags & XFRM_TIME_DEFER)
67 				event = XFRM_REPLAY_TIMEOUT;
68 			else
69 				return;
70 		}
71 
72 		break;
73 
74 	case XFRM_REPLAY_TIMEOUT:
75 		if (memcmp(&x->replay, &x->preplay,
76 			   sizeof(struct xfrm_replay_state)) == 0) {
77 			x->xflags |= XFRM_TIME_DEFER;
78 			return;
79 		}
80 
81 		break;
82 	}
83 
84 	memcpy(&x->preplay, &x->replay, sizeof(struct xfrm_replay_state));
85 	c.event = XFRM_MSG_NEWAE;
86 	c.data.aevent = event;
87 	km_state_notify(x, &c);
88 
89 	if (x->replay_maxage &&
90 	    !mod_timer(&x->rtimer, jiffies + x->replay_maxage))
91 		x->xflags &= ~XFRM_TIME_DEFER;
92 }
93 
94 static int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
95 {
96 	int err = 0;
97 	struct net *net = xs_net(x);
98 
99 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
100 		XFRM_SKB_CB(skb)->seq.output.low = ++x->replay.oseq;
101 		if (unlikely(x->replay.oseq == 0)) {
102 			x->replay.oseq--;
103 			xfrm_audit_state_replay_overflow(x, skb);
104 			err = -EOVERFLOW;
105 
106 			return err;
107 		}
108 		if (xfrm_aevent_is_on(net))
109 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
110 	}
111 
112 	return err;
113 }
114 
115 static int xfrm_replay_check(struct xfrm_state *x,
116 		      struct sk_buff *skb, __be32 net_seq)
117 {
118 	u32 diff;
119 	u32 seq = ntohl(net_seq);
120 
121 	if (unlikely(seq == 0))
122 		goto err;
123 
124 	if (likely(seq > x->replay.seq))
125 		return 0;
126 
127 	diff = x->replay.seq - seq;
128 	if (diff >= min_t(unsigned int, x->props.replay_window,
129 			  sizeof(x->replay.bitmap) * 8)) {
130 		x->stats.replay_window++;
131 		goto err;
132 	}
133 
134 	if (x->replay.bitmap & (1U << diff)) {
135 		x->stats.replay++;
136 		goto err;
137 	}
138 	return 0;
139 
140 err:
141 	xfrm_audit_state_replay(x, skb, net_seq);
142 	return -EINVAL;
143 }
144 
145 static void xfrm_replay_advance(struct xfrm_state *x, __be32 net_seq)
146 {
147 	u32 diff;
148 	u32 seq = ntohl(net_seq);
149 
150 	if (!x->props.replay_window)
151 		return;
152 
153 	if (seq > x->replay.seq) {
154 		diff = seq - x->replay.seq;
155 		if (diff < x->props.replay_window)
156 			x->replay.bitmap = ((x->replay.bitmap) << diff) | 1;
157 		else
158 			x->replay.bitmap = 1;
159 		x->replay.seq = seq;
160 	} else {
161 		diff = x->replay.seq - seq;
162 		x->replay.bitmap |= (1U << diff);
163 	}
164 
165 	if (xfrm_aevent_is_on(xs_net(x)))
166 		xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
167 }
168 
169 static int xfrm_replay_overflow_bmp(struct xfrm_state *x, struct sk_buff *skb)
170 {
171 	int err = 0;
172 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
173 	struct net *net = xs_net(x);
174 
175 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
176 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
177 		if (unlikely(replay_esn->oseq == 0)) {
178 			replay_esn->oseq--;
179 			xfrm_audit_state_replay_overflow(x, skb);
180 			err = -EOVERFLOW;
181 
182 			return err;
183 		}
184 		if (xfrm_aevent_is_on(net))
185 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
186 	}
187 
188 	return err;
189 }
190 
191 static int xfrm_replay_check_bmp(struct xfrm_state *x,
192 				 struct sk_buff *skb, __be32 net_seq)
193 {
194 	unsigned int bitnr, nr;
195 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
196 	u32 seq = ntohl(net_seq);
197 	u32 diff =  replay_esn->seq - seq;
198 	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
199 
200 	if (unlikely(seq == 0))
201 		goto err;
202 
203 	if (likely(seq > replay_esn->seq))
204 		return 0;
205 
206 	if (diff >= replay_esn->replay_window) {
207 		x->stats.replay_window++;
208 		goto err;
209 	}
210 
211 	if (pos >= diff) {
212 		bitnr = (pos - diff) % replay_esn->replay_window;
213 		nr = bitnr >> 5;
214 		bitnr = bitnr & 0x1F;
215 		if (replay_esn->bmp[nr] & (1U << bitnr))
216 			goto err_replay;
217 	} else {
218 		bitnr = replay_esn->replay_window - (diff - pos);
219 		nr = bitnr >> 5;
220 		bitnr = bitnr & 0x1F;
221 		if (replay_esn->bmp[nr] & (1U << bitnr))
222 			goto err_replay;
223 	}
224 	return 0;
225 
226 err_replay:
227 	x->stats.replay++;
228 err:
229 	xfrm_audit_state_replay(x, skb, net_seq);
230 	return -EINVAL;
231 }
232 
233 static void xfrm_replay_advance_bmp(struct xfrm_state *x, __be32 net_seq)
234 {
235 	unsigned int bitnr, nr, i;
236 	u32 diff;
237 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
238 	u32 seq = ntohl(net_seq);
239 	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
240 
241 	if (!replay_esn->replay_window)
242 		return;
243 
244 	if (seq > replay_esn->seq) {
245 		diff = seq - replay_esn->seq;
246 
247 		if (diff < replay_esn->replay_window) {
248 			for (i = 1; i < diff; i++) {
249 				bitnr = (pos + i) % replay_esn->replay_window;
250 				nr = bitnr >> 5;
251 				bitnr = bitnr & 0x1F;
252 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
253 			}
254 
255 			bitnr = (pos + diff) % replay_esn->replay_window;
256 			nr = bitnr >> 5;
257 			bitnr = bitnr & 0x1F;
258 			replay_esn->bmp[nr] |= (1U << bitnr);
259 		} else {
260 			nr = replay_esn->replay_window >> 5;
261 			for (i = 0; i <= nr; i++)
262 				replay_esn->bmp[i] = 0;
263 
264 			bitnr = (pos + diff) % replay_esn->replay_window;
265 			nr = bitnr >> 5;
266 			bitnr = bitnr & 0x1F;
267 			replay_esn->bmp[nr] |= (1U << bitnr);
268 		}
269 
270 		replay_esn->seq = seq;
271 	} else {
272 		diff = replay_esn->seq - seq;
273 
274 		if (pos >= diff) {
275 			bitnr = (pos - diff) % replay_esn->replay_window;
276 			nr = bitnr >> 5;
277 			bitnr = bitnr & 0x1F;
278 			replay_esn->bmp[nr] |= (1U << bitnr);
279 		} else {
280 			bitnr = replay_esn->replay_window - (diff - pos);
281 			nr = bitnr >> 5;
282 			bitnr = bitnr & 0x1F;
283 			replay_esn->bmp[nr] |= (1U << bitnr);
284 		}
285 	}
286 
287 	if (xfrm_aevent_is_on(xs_net(x)))
288 		xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
289 }
290 
291 static void xfrm_replay_notify_bmp(struct xfrm_state *x, int event)
292 {
293 	struct km_event c;
294 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
295 	struct xfrm_replay_state_esn *preplay_esn = x->preplay_esn;
296 
297 	/* we send notify messages in case
298 	 *  1. we updated on of the sequence numbers, and the seqno difference
299 	 *     is at least x->replay_maxdiff, in this case we also update the
300 	 *     timeout of our timer function
301 	 *  2. if x->replay_maxage has elapsed since last update,
302 	 *     and there were changes
303 	 *
304 	 *  The state structure must be locked!
305 	 */
306 
307 	switch (event) {
308 	case XFRM_REPLAY_UPDATE:
309 		if (x->replay_maxdiff &&
310 		    (replay_esn->seq - preplay_esn->seq < x->replay_maxdiff) &&
311 		    (replay_esn->oseq - preplay_esn->oseq < x->replay_maxdiff)) {
312 			if (x->xflags & XFRM_TIME_DEFER)
313 				event = XFRM_REPLAY_TIMEOUT;
314 			else
315 				return;
316 		}
317 
318 		break;
319 
320 	case XFRM_REPLAY_TIMEOUT:
321 		if (memcmp(x->replay_esn, x->preplay_esn,
322 			   xfrm_replay_state_esn_len(replay_esn)) == 0) {
323 			x->xflags |= XFRM_TIME_DEFER;
324 			return;
325 		}
326 
327 		break;
328 	}
329 
330 	memcpy(x->preplay_esn, x->replay_esn,
331 	       xfrm_replay_state_esn_len(replay_esn));
332 	c.event = XFRM_MSG_NEWAE;
333 	c.data.aevent = event;
334 	km_state_notify(x, &c);
335 
336 	if (x->replay_maxage &&
337 	    !mod_timer(&x->rtimer, jiffies + x->replay_maxage))
338 		x->xflags &= ~XFRM_TIME_DEFER;
339 }
340 
341 static int xfrm_replay_overflow_esn(struct xfrm_state *x, struct sk_buff *skb)
342 {
343 	int err = 0;
344 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
345 	struct net *net = xs_net(x);
346 
347 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
348 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
349 		XFRM_SKB_CB(skb)->seq.output.hi = replay_esn->oseq_hi;
350 
351 		if (unlikely(replay_esn->oseq == 0)) {
352 			XFRM_SKB_CB(skb)->seq.output.hi = ++replay_esn->oseq_hi;
353 
354 			if (replay_esn->oseq_hi == 0) {
355 				replay_esn->oseq--;
356 				replay_esn->oseq_hi--;
357 				xfrm_audit_state_replay_overflow(x, skb);
358 				err = -EOVERFLOW;
359 
360 				return err;
361 			}
362 		}
363 		if (xfrm_aevent_is_on(net))
364 			x->repl->notify(x, XFRM_REPLAY_UPDATE);
365 	}
366 
367 	return err;
368 }
369 
370 static int xfrm_replay_check_esn(struct xfrm_state *x,
371 				 struct sk_buff *skb, __be32 net_seq)
372 {
373 	unsigned int bitnr, nr;
374 	u32 diff;
375 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
376 	u32 seq = ntohl(net_seq);
377 	u32 pos = (replay_esn->seq - 1) % replay_esn->replay_window;
378 	u32 wsize = replay_esn->replay_window;
379 	u32 top = replay_esn->seq;
380 	u32 bottom = top - wsize + 1;
381 
382 	if (unlikely(seq == 0 && replay_esn->seq_hi == 0 &&
383 		     (replay_esn->seq < replay_esn->replay_window - 1)))
384 		goto err;
385 
386 	diff = top - seq;
387 
388 	if (likely(top >= wsize - 1)) {
389 		/* A. same subspace */
390 		if (likely(seq > top) || seq < bottom)
391 			return 0;
392 	} else {
393 		/* B. window spans two subspaces */
394 		if (likely(seq > top && seq < bottom))
395 			return 0;
396 		if (seq >= bottom)
397 			diff = ~seq + top + 1;
398 	}
399 
400 	if (diff >= replay_esn->replay_window) {
401 		x->stats.replay_window++;
402 		goto err;
403 	}
404 
405 	if (pos >= diff) {
406 		bitnr = (pos - diff) % replay_esn->replay_window;
407 		nr = bitnr >> 5;
408 		bitnr = bitnr & 0x1F;
409 		if (replay_esn->bmp[nr] & (1U << bitnr))
410 			goto err_replay;
411 	} else {
412 		bitnr = replay_esn->replay_window - (diff - pos);
413 		nr = bitnr >> 5;
414 		bitnr = bitnr & 0x1F;
415 		if (replay_esn->bmp[nr] & (1U << bitnr))
416 			goto err_replay;
417 	}
418 	return 0;
419 
420 err_replay:
421 	x->stats.replay++;
422 err:
423 	xfrm_audit_state_replay(x, skb, net_seq);
424 	return -EINVAL;
425 }
426 
427 static void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
428 {
429 	unsigned int bitnr, nr, i;
430 	int wrap;
431 	u32 diff, pos, seq, seq_hi;
432 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
433 
434 	if (!replay_esn->replay_window)
435 		return;
436 
437 	seq = ntohl(net_seq);
438 	pos = (replay_esn->seq - 1) % replay_esn->replay_window;
439 	seq_hi = xfrm_replay_seqhi(x, net_seq);
440 	wrap = seq_hi - replay_esn->seq_hi;
441 
442 	if ((!wrap && seq > replay_esn->seq) || wrap > 0) {
443 		if (likely(!wrap))
444 			diff = seq - replay_esn->seq;
445 		else
446 			diff = ~replay_esn->seq + seq + 1;
447 
448 		if (diff < replay_esn->replay_window) {
449 			for (i = 1; i < diff; i++) {
450 				bitnr = (pos + i) % replay_esn->replay_window;
451 				nr = bitnr >> 5;
452 				bitnr = bitnr & 0x1F;
453 				replay_esn->bmp[nr] &=  ~(1U << bitnr);
454 			}
455 
456 			bitnr = (pos + diff) % replay_esn->replay_window;
457 			nr = bitnr >> 5;
458 			bitnr = bitnr & 0x1F;
459 			replay_esn->bmp[nr] |= (1U << bitnr);
460 		} else {
461 			nr = replay_esn->replay_window >> 5;
462 			for (i = 0; i <= nr; i++)
463 				replay_esn->bmp[i] = 0;
464 
465 			bitnr = (pos + diff) % replay_esn->replay_window;
466 			nr = bitnr >> 5;
467 			bitnr = bitnr & 0x1F;
468 			replay_esn->bmp[nr] |= (1U << bitnr);
469 		}
470 
471 		replay_esn->seq = seq;
472 
473 		if (unlikely(wrap > 0))
474 			replay_esn->seq_hi++;
475 	} else {
476 		diff = replay_esn->seq - seq;
477 
478 		if (pos >= diff) {
479 			bitnr = (pos - diff) % replay_esn->replay_window;
480 			nr = bitnr >> 5;
481 			bitnr = bitnr & 0x1F;
482 			replay_esn->bmp[nr] |= (1U << bitnr);
483 		} else {
484 			bitnr = replay_esn->replay_window - (diff - pos);
485 			nr = bitnr >> 5;
486 			bitnr = bitnr & 0x1F;
487 			replay_esn->bmp[nr] |= (1U << bitnr);
488 		}
489 	}
490 
491 	if (xfrm_aevent_is_on(xs_net(x)))
492 		xfrm_replay_notify(x, XFRM_REPLAY_UPDATE);
493 }
494 
495 static struct xfrm_replay xfrm_replay_legacy = {
496 	.advance	= xfrm_replay_advance,
497 	.check		= xfrm_replay_check,
498 	.notify		= xfrm_replay_notify,
499 	.overflow	= xfrm_replay_overflow,
500 };
501 
502 static struct xfrm_replay xfrm_replay_bmp = {
503 	.advance	= xfrm_replay_advance_bmp,
504 	.check		= 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 	.notify		= xfrm_replay_notify_bmp,
513 	.overflow	= xfrm_replay_overflow_esn,
514 };
515 
516 int xfrm_init_replay(struct xfrm_state *x)
517 {
518 	struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
519 
520 	if (replay_esn) {
521 		if (replay_esn->replay_window >
522 		    replay_esn->bmp_len * sizeof(__u32))
523 			return -EINVAL;
524 
525 	if ((x->props.flags & XFRM_STATE_ESN) && x->replay_esn)
526 		x->repl = &xfrm_replay_esn;
527 	else
528 		x->repl = &xfrm_replay_bmp;
529 	} else
530 		x->repl = &xfrm_replay_legacy;
531 
532 	return 0;
533 }
534 EXPORT_SYMBOL(xfrm_init_replay);
535