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xfrm_replay.c
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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 <[email protected]>
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) && replay_esn->replay_window == 0)
525  return -EINVAL;
526 
527  if ((x->props.flags & XFRM_STATE_ESN) && x->replay_esn)
528  x->repl = &xfrm_replay_esn;
529  else
530  x->repl = &xfrm_replay_bmp;
531  } else
532  x->repl = &xfrm_replay_legacy;
533 
534  return 0;
535 }
536 EXPORT_SYMBOL(xfrm_init_replay);
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