net/xfrm/xfrm_replay.c

   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);