linux/net/xfrm/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 <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
  24u32 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
  49static 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
  95static 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
 116static 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
 144err:
 145        xfrm_audit_state_replay(x, skb, net_seq);
 146        return -EINVAL;
 147}
 148
 149static 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
 173static 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
 195static 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
 232err_replay:
 233        x->stats.replay++;
 234err:
 235        xfrm_audit_state_replay(x, skb, net_seq);
 236        return -EINVAL;
 237}
 238
 239static 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
 285static 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
 335static 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
 364static 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
 416err_replay:
 417        x->stats.replay++;
 418err:
 419        xfrm_audit_state_replay(x, skb, net_seq);
 420        return -EINVAL;
 421}
 422
 423static 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
 435static 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
 491static 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
 499static 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
 507static 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
 515int 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}
 536EXPORT_SYMBOL(xfrm_init_replay);
 537
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