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 = (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 void xfrm_replay_advance_esn(struct xfrm_state *x, __be32 net_seq)
 424 {
 425         unsigned int bitnr, nr, i;
 426         int wrap;
 427         u32 diff, pos, seq, seq_hi;
 428         struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
 429
 430         if (!replay_esn->replay_window)
 431                 return;
 432
 433         seq = ntohl(net_seq);
 434         pos = (replay_esn->seq - 1) % replay_esn->replay_window;
 435         seq_hi = xfrm_replay_seqhi(x, net_seq);
 436         wrap = seq_hi - replay_esn->seq_hi;
 437
 438         if ((!wrap && seq > replay_esn->seq) || wrap > 0) {
 439                 if (likely(!wrap))
 440                         diff = seq - replay_esn->seq;
 441                 else
 442                         diff = ~replay_esn->seq + seq + 1;
 443
 444                 if (diff < replay_esn->replay_window) {
 445                         for (i = 1; i < diff; i++) {
 446                                 bitnr = (pos + i) % replay_esn->replay_window;
 447                                 nr = bitnr >> 5;
 448                                 bitnr = bitnr & 0x1F;
 449                                 replay_esn->bmp[nr] &=  ~(1U << bitnr);
 450                         }
 451                 } else {
 452                         nr = (replay_esn->replay_window - 1) >> 5;
 453                         for (i = 0; i <= nr; i++)
 454                                 replay_esn->bmp[i] = 0;
 455                 }
 456
 457                 bitnr = (pos + diff) % replay_esn->replay_window;
 458                 replay_esn->seq = seq;
 459
 460                 if (unlikely(wrap > 0))
 461                         replay_esn->seq_hi++;
 462         } else {
 463                 diff = replay_esn->seq - seq;
 464
 465                 if (pos >= diff)
 466                         bitnr = (pos - diff) % replay_esn->replay_window;
 467                 else
 468                         bitnr = replay_esn->replay_window - (diff - pos);
 469         }
 470
 471         nr = bitnr >> 5;
 472         bitnr = bitnr & 0x1F;
 473         replay_esn->bmp[nr] |= (1U << bitnr);
 474
 475         if (xfrm_aevent_is_on(xs_net(x)))
 476                 x->repl->notify(x, XFRM_REPLAY_UPDATE);
 477 }
 478
 479 static struct xfrm_replay xfrm_replay_legacy = {
 480         .advance        = xfrm_replay_advance,
 481         .check          = xfrm_replay_check,
 482         .notify         = xfrm_replay_notify,
 483         .overflow       = xfrm_replay_overflow,
 484 };
 485
 486 static struct xfrm_replay xfrm_replay_bmp = {
 487         .advance        = xfrm_replay_advance_bmp,
 488         .check          = xfrm_replay_check_bmp,
 489         .notify         = xfrm_replay_notify_bmp,
 490         .overflow       = xfrm_replay_overflow_bmp,
 491 };
 492
 493 static struct xfrm_replay xfrm_replay_esn = {
 494         .advance        = xfrm_replay_advance_esn,
 495         .check          = xfrm_replay_check_esn,
 496         .notify         = xfrm_replay_notify_bmp,
 497         .overflow       = xfrm_replay_overflow_esn,
 498 };
 499
 500 int xfrm_init_replay(struct xfrm_state *x)
 501 {
 502         struct xfrm_replay_state_esn *replay_esn = x->replay_esn;
 503
 504         if (replay_esn) {
 505                 if (replay_esn->replay_window >
 506                     replay_esn->bmp_len * sizeof(__u32) * 8)
 507                         return -EINVAL;
 508
 509         if ((x->props.flags & XFRM_STATE_ESN) && replay_esn->replay_window == 0)
 510                 return -EINVAL;
 511
 512         if ((x->props.flags & XFRM_STATE_ESN) && x->replay_esn)
 513                 x->repl = &xfrm_replay_esn;
 514         else
 515                 x->repl = &xfrm_replay_bmp;
 516         } else
 517                 x->repl = &xfrm_replay_legacy;
 518
 519         return 0;
 520 }
 521 EXPORT_SYMBOL(xfrm_init_replay);