net/ipv4/netfilter/ip_conntrack_pptp.c

   1 /*
   2  * ip_conntrack_pptp.c  - Version 3.0
   3  *
   4  * Connection tracking support for PPTP (Point to Point Tunneling Protocol).
   5  * PPTP is a a protocol for creating virtual private networks.
   6  * It is a specification defined by Microsoft and some vendors
   7  * working with Microsoft.  PPTP is built on top of a modified
   8  * version of the Internet Generic Routing Encapsulation Protocol.
   9  * GRE is defined in RFC 1701 and RFC 1702.  Documentation of
  10  * PPTP can be found in RFC 2637
  11  *
  12  * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org>
  13  *
  14  * Development of this code funded by Astaro AG (http://www.astaro.com/)
  15  *
  16  * Limitations:
  17  *       - We blindly assume that control connections are always
  18  *         established in PNS->PAC direction.  This is a violation
  19  *         of RFFC2673
  20  *       - We can only support one single call within each session
  21  *
  22  * TODO:
  23  *       - testing of incoming PPTP calls
  24  *
  25  * Changes:
  26  *      2002-02-05 - Version 1.3
  27  *        - Call ip_conntrack_unexpect_related() from
  28  *          pptp_timeout_related() to destroy expectations in case
  29  *          CALL_DISCONNECT_NOTIFY or tcp fin packet was seen
  30  *          (Philip Craig <philipc@snapgear.com>)
  31  *        - Add Version information at module loadtime
  32  *      2002-02-10 - Version 1.6
  33  *        - move to C99 style initializers
  34  *        - remove second expectation if first arrives
  35  *      2004-10-22 - Version 2.0
  36  *        - merge Mandrake's 2.6.x port with recent 2.6.x API changes
  37  *        - fix lots of linear skb assumptions from Mandrake's port
  38  *      2005-06-10 - Version 2.1
  39  *        - use ip_conntrack_expect_free() instead of kfree() on the
  40  *          expect's (which are from the slab for quite some time)
  41  *      2005-06-10 - Version 3.0
  42  *        - port helper to post-2.6.11 API changes,
  43  *          funded by Oxcoda NetBox Blue (http://www.netboxblue.com/)
  44  *
  45  */
  46
  47 #include <linux/config.h>
  48 #include <linux/module.h>
  49 #include <linux/netfilter.h>
  50 #include <linux/ip.h>
  51 #include <net/checksum.h>
  52 #include <net/tcp.h>
  53
  54 #include <linux/netfilter_ipv4/lockhelp.h>
  55 #include <linux/netfilter_ipv4/ip_conntrack.h>
  56 #include <linux/netfilter_ipv4/ip_conntrack_core.h>
  57 #include <linux/netfilter_ipv4/ip_conntrack_helper.h>
  58 #include <linux/netfilter_ipv4/ip_conntrack_proto_gre.h>
  59 #include <linux/netfilter_ipv4/ip_conntrack_pptp.h>
  60
  61 #define IP_CT_PPTP_VERSION "3.0"
  62
  63 MODULE_LICENSE("GPL");
  64 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>");
  65 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP");
  66
  67 DECLARE_LOCK(ip_pptp_lock);
  68
  69 int
  70 (*ip_nat_pptp_hook_outbound)(struct sk_buff **pskb,
  71                           struct ip_conntrack *ct,
  72                           enum ip_conntrack_info ctinfo,
  73                           struct PptpControlHeader *ctlh,
  74                           union pptp_ctrl_union *pptpReq);
  75
  76 int
  77 (*ip_nat_pptp_hook_inbound)(struct sk_buff **pskb,
  78                           struct ip_conntrack *ct,
  79                           enum ip_conntrack_info ctinfo,
  80                           struct PptpControlHeader *ctlh,
  81                           union pptp_ctrl_union *pptpReq);
  82
  83 int
  84 (*ip_nat_pptp_hook_exp_gre)(struct ip_conntrack_expect *expect_orig,
  85                             struct ip_conntrack_expect *expect_reply);
  86
  87 void
  88 (*ip_nat_pptp_hook_expectfn)(struct ip_conntrack *ct,
  89                              struct ip_conntrack_expect *exp);
  90
  91 #if 0
  92 #include "ip_conntrack_pptp_priv.h"
  93 #define DEBUGP(format, args...) printk(KERN_DEBUG "%s:%s: " format, __FILE__, __FUNCTION__, ## args)
  94 #else
  95 #define DEBUGP(format, args...)
  96 #endif
  97
  98 #define SECS *HZ
  99 #define MINS * 60 SECS
 100 #define HOURS * 60 MINS
 101 #define DAYS * 24 HOURS
 102
 103 #define PPTP_GRE_TIMEOUT                (10 MINS)
 104 #define PPTP_GRE_STREAM_TIMEOUT         (5 DAYS)
 105
 106 static void pptp_expectfn(struct ip_conntrack *ct,
 107                          struct ip_conntrack_expect *exp)
 108 {
 109         DEBUGP("increasing timeouts\n");
 110
 111         /* increase timeout of GRE data channel conntrack entry */
 112         ct->proto.gre.timeout = PPTP_GRE_TIMEOUT;
 113         ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT;
 114
 115         /* Can you see how rusty this code is, compared with the pre-2.6.11
 116          * one? That's what happened to my shiny newnat of 2002 ;( -HW */
 117
 118         if (!ip_nat_pptp_hook_expectfn) {
 119                 struct ip_conntrack_tuple inv_t;
 120                 struct ip_conntrack_expect *exp_other;
 121
 122                 /* obviously this tuple inversion only works until you do NAT */
 123                 invert_tuplepr(&inv_t, &exp->tuple);
 124                 DEBUGP("trying to unexpect other dir: ");
 125                 DUMP_TUPLE(&inv_t);
 126
 127                 exp_other = __ip_conntrack_exp_find(&inv_t);
 128                 if (exp_other) {
 129                         /* delete other expectation.  */
 130                         DEBUGP("found\n");
 131                         ip_conntrack_unexpect_related(exp_other);
 132                 } else {
 133                         DEBUGP("not found\n");
 134                 }
 135         } else {
 136                 /* we need more than simple inversion */
 137                 ip_nat_pptp_hook_expectfn(ct, exp);
 138         }
 139 }
 140
 141 static int timeout_ct_or_exp(const struct ip_conntrack_tuple *t)
 142 {
 143         struct ip_conntrack_tuple_hash *h;
 144         struct ip_conntrack_expect *exp;
 145
 146         DEBUGP("trying to timeout ct or exp for tuple ");
 147         DUMP_TUPLE(t);
 148
 149         h = __ip_conntrack_find(t, NULL);
 150         if (h)  {
 151                 struct ip_conntrack *sibling = tuplehash_to_ctrack(h);
 152                 DEBUGP("setting timeout of conntrack %p to 0\n", sibling);
 153                 sibling->proto.gre.timeout = 0;
 154                 sibling->proto.gre.stream_timeout = 0;
 155                 /* refresh_acct will not modify counters if skb == NULL */
 156                 ip_ct_refresh_acct(sibling, 0, NULL, 0);
 157                 return 1;
 158         } else {
 159                 exp = __ip_conntrack_exp_find(t);
 160                 if (exp) {
 161                         DEBUGP("unexpect_related of expect %p\n", exp);
 162                         ip_conntrack_unexpect_related(exp);
 163                         return 1;
 164                 }
 165         }
 166
 167         return 0;
 168 }
 169
 170
 171 /* timeout GRE data connections */
 172 static int pptp_timeout_related(struct ip_conntrack *ct)
 173 {
 174         struct ip_conntrack_tuple t;
 175         int ret;
 176
 177         /* Since ct->sibling_list has literally rusted away in 2.6.11,
 178          * we now need another way to find out about our sibling
 179          * contrack and expects... -HW */
 180
 181         /* try original (pns->pac) tuple */
 182         memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t));
 183         t.dst.protonum = IPPROTO_GRE;
 184         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 185         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 186
 187         ret = timeout_ct_or_exp(&t);
 188
 189         /* try reply (pac->pns) tuple */
 190         memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t));
 191         t.dst.protonum = IPPROTO_GRE;
 192         t.src.u.gre.key = htons(ct->help.ct_pptp_info.pac_call_id);
 193         t.dst.u.gre.key = htons(ct->help.ct_pptp_info.pns_call_id);
 194
 195         ret += timeout_ct_or_exp(&t);
 196
 197         return ret;
 198 }
 199
 200 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */
 201 static inline int
 202 exp_gre(struct ip_conntrack *master,
 203         u_int32_t seq,
 204         u_int16_t callid,
 205         u_int16_t peer_callid)
 206 {
 207         struct ip_conntrack_tuple inv_tuple;
 208         struct ip_conntrack_tuple exp_tuples[] = {
 209                 /* tuple in original direction, PNS->PAC */
 210                 { .src = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.ip,
 211                            .u = { .gre = { .key = peer_callid } }
 212                          },
 213                   .dst = { .ip = master->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.ip,
 214                            .u = { .gre = { .key = callid } },
 215                            .protonum = IPPROTO_GRE
 216                          },
 217                  },
 218                 /* tuple in reply direction, PAC->PNS */
 219                 { .src = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip,
 220                            .u = { .gre = { .key = callid } }
 221                          },
 222                   .dst = { .ip = master->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip,
 223                            .u = { .gre = { .key = peer_callid } },
 224                            .protonum = IPPROTO_GRE
 225                          },
 226                  }
 227         };
 228
 229         struct ip_conntrack_expect *exp_orig, *exp_reply;
 230
 231         exp_orig = ip_conntrack_expect_alloc();
 232         if (exp_orig == NULL)
 233                 return 1;
 234
 235         exp_reply = ip_conntrack_expect_alloc();
 236         if (exp_reply == NULL) {
 237                 ip_conntrack_expect_free(exp_orig);
 238                 return 1;
 239         }
 240
 241         memcpy(&exp_orig->tuple, &exp_tuples[0], sizeof(exp_orig->tuple));
 242
 243         exp_orig->mask.src.ip = 0xffffffff;
 244         exp_orig->mask.src.u.all = 0;
 245         exp_orig->mask.dst.u.all = 0;
 246         exp_orig->mask.dst.u.gre.key = 0xffff;
 247         exp_orig->mask.dst.ip = 0xffffffff;
 248         exp_orig->mask.dst.protonum = 0xff;
 249
 250         exp_orig->master = master;
 251         exp_orig->expectfn = pptp_expectfn;
 252
 253         exp_orig->dir = IP_CT_DIR_ORIGINAL;
 254
 255         /* both expectations are identical apart from tuple */
 256         memcpy(exp_reply, exp_orig, sizeof(*exp_reply));
 257         memcpy(&exp_reply->tuple, &exp_tuples[1], sizeof(exp_reply->tuple));
 258
 259         exp_reply->dir = !exp_orig->dir;
 260
 261         if (ip_nat_pptp_hook_exp_gre)
 262                 return ip_nat_pptp_hook_exp_gre(exp_orig, exp_reply);
 263         else {
 264
 265                 DEBUGP("calling expect_related PNS->PAC");
 266                 DUMP_TUPLE(&exp_orig->tuple);
 267
 268                 if (ip_conntrack_expect_related(exp_orig) != 0) {
 269                         ip_conntrack_expect_free(exp_orig);
 270                         ip_conntrack_expect_free(exp_reply);
 271                         DEBUGP("cannot expect_related()\n");
 272                         return 1;
 273                 }
 274
 275                 DEBUGP("calling expect_related PAC->PNS");
 276                 DUMP_TUPLE(&exp_reply->tuple);
 277
 278                 if (ip_conntrack_expect_related(exp_reply) != 0) {
 279                         ip_conntrack_unexpect_related(exp_orig);
 280                         ip_conntrack_expect_free(exp_reply);
 281                         DEBUGP("cannot expect_related()\n");
 282                         return 1;
 283                 }
 284
 285                 /* Add GRE keymap entries */
 286                 if (ip_ct_gre_keymap_add(master, &exp_reply->tuple, 0) != 0) {
 287                         ip_conntrack_unexpect_related(exp_orig);
 288                         ip_conntrack_unexpect_related(exp_reply);
 289                         DEBUGP("cannot keymap_add() exp\n");
 290                         return 1;
 291                 }
 292
 293                 invert_tuplepr(&inv_tuple, &exp_reply->tuple);
 294                 if (ip_ct_gre_keymap_add(master, &inv_tuple, 1) != 0) {
 295                         ip_conntrack_unexpect_related(exp_orig);
 296                         ip_conntrack_unexpect_related(exp_reply);
 297                         ip_ct_gre_keymap_destroy(master);
 298                         DEBUGP("cannot keymap_add() exp_inv\n");
 299                         return 1;
 300                 }
 301
 302         }
 303
 304         return 0;
 305 }
 306
 307 static inline int
 308 pptp_inbound_pkt(struct sk_buff **pskb,
 309                  struct tcphdr *tcph,
 310                  unsigned int ctlhoff,
 311                  size_t datalen,
 312                  struct ip_conntrack *ct,
 313                  enum ip_conntrack_info ctinfo)
 314 {
 315         struct PptpControlHeader _ctlh, *ctlh;
 316         unsigned int reqlen;
 317         union pptp_ctrl_union _pptpReq, *pptpReq;
 318         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 319         u_int16_t msg, *cid, *pcid;
 320         u_int32_t seq;
 321
 322         ctlh = skb_header_pointer(*pskb, ctlhoff, sizeof(_ctlh), &_ctlh);
 323         if (unlikely(!ctlh)) {
 324                 DEBUGP("error during skb_header_pointer\n");
 325                 return NF_ACCEPT;
 326         }
 327
 328         reqlen = datalen - sizeof(struct pptp_pkt_hdr) - sizeof(_ctlh);
 329         pptpReq = skb_header_pointer(*pskb, ctlhoff+sizeof(_ctlh),
 330                                      reqlen, &_pptpReq);
 331         if (unlikely(!pptpReq)) {
 332                 DEBUGP("error during skb_header_pointer\n");
 333                 return NF_ACCEPT;
 334         }
 335
 336         msg = ntohs(ctlh->messageType);
 337         DEBUGP("inbound control message %s\n", strMName[msg]);
 338
 339         switch (msg) {
 340         case PPTP_START_SESSION_REPLY:
 341                 if (reqlen < sizeof(_pptpReq.srep)) {
 342                         DEBUGP("%s: short packet\n", strMName[msg]);
 343                         break;
 344                 }
 345
 346                 /* server confirms new control session */
 347                 if (info->sstate < PPTP_SESSION_REQUESTED) {
 348                         DEBUGP("%s without START_SESS_REQUEST\n",
 349                                 strMName[msg]);
 350                         break;
 351                 }
 352                 if (pptpReq->srep.resultCode == PPTP_START_OK)
 353                         info->sstate = PPTP_SESSION_CONFIRMED;
 354                 else
 355                         info->sstate = PPTP_SESSION_ERROR;
 356                 break;
 357
 358         case PPTP_STOP_SESSION_REPLY:
 359                 if (reqlen < sizeof(_pptpReq.strep)) {
 360                         DEBUGP("%s: short packet\n", strMName[msg]);
 361                         break;
 362                 }
 363
 364                 /* server confirms end of control session */
 365                 if (info->sstate > PPTP_SESSION_STOPREQ) {
 366                         DEBUGP("%s without STOP_SESS_REQUEST\n",
 367                                 strMName[msg]);
 368                         break;
 369                 }
 370                 if (pptpReq->strep.resultCode == PPTP_STOP_OK)
 371                         info->sstate = PPTP_SESSION_NONE;
 372                 else
 373                         info->sstate = PPTP_SESSION_ERROR;
 374                 break;
 375
 376         case PPTP_OUT_CALL_REPLY:
 377                 if (reqlen < sizeof(_pptpReq.ocack)) {
 378                         DEBUGP("%s: short packet\n", strMName[msg]);
 379                         break;
 380                 }
 381
 382                 /* server accepted call, we now expect GRE frames */
 383                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 384                         DEBUGP("%s but no session\n", strMName[msg]);
 385                         break;
 386                 }
 387                 if (info->cstate != PPTP_CALL_OUT_REQ &&
 388                     info->cstate != PPTP_CALL_OUT_CONF) {
 389                         DEBUGP("%s without OUTCALL_REQ\n", strMName[msg]);
 390                         break;
 391                 }
 392                 if (pptpReq->ocack.resultCode != PPTP_OUTCALL_CONNECT) {
 393                         info->cstate = PPTP_CALL_NONE;
 394                         break;
 395                 }
 396
 397                 cid = &pptpReq->ocack.callID;
 398                 pcid = &pptpReq->ocack.peersCallID;
 399
 400                 info->pac_call_id = ntohs(*cid);
 401
 402                 if (htons(info->pns_call_id) != *pcid) {
 403                         DEBUGP("%s for unknown callid %u\n",
 404                                 strMName[msg], ntohs(*pcid));
 405                         break;
 406                 }
 407
 408                 DEBUGP("%s, CID=%X, PCID=%X\n", strMName[msg],
 409                         ntohs(*cid), ntohs(*pcid));
 410
 411                 info->cstate = PPTP_CALL_OUT_CONF;
 412
 413                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 414                                        + sizeof(struct PptpControlHeader)
 415                                        + ((void *)pcid - (void *)pptpReq);
 416
 417                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 418                         printk("ip_conntrack_pptp: error during exp_gre\n");
 419                 break;
 420
 421         case PPTP_IN_CALL_REQUEST:
 422                 if (reqlen < sizeof(_pptpReq.icack)) {
 423                         DEBUGP("%s: short packet\n", strMName[msg]);
 424                         break;
 425                 }
 426
 427                 /* server tells us about incoming call request */
 428                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 429                         DEBUGP("%s but no session\n", strMName[msg]);
 430                         break;
 431                 }
 432                 pcid = &pptpReq->icack.peersCallID;
 433                 DEBUGP("%s, PCID=%X\n", strMName[msg], ntohs(*pcid));
 434                 info->cstate = PPTP_CALL_IN_REQ;
 435                 info->pac_call_id = ntohs(*pcid);
 436                 break;
 437
 438         case PPTP_IN_CALL_CONNECT:
 439                 if (reqlen < sizeof(_pptpReq.iccon)) {
 440                         DEBUGP("%s: short packet\n", strMName[msg]);
 441                         break;
 442                 }
 443
 444                 /* server tells us about incoming call established */
 445                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 446                         DEBUGP("%s but no session\n", strMName[msg]);
 447                         break;
 448                 }
 449                 if (info->sstate != PPTP_CALL_IN_REP
 450                     && info->sstate != PPTP_CALL_IN_CONF) {
 451                         DEBUGP("%s but never sent IN_CALL_REPLY\n",
 452                                 strMName[msg]);
 453                         break;
 454                 }
 455
 456                 pcid = &pptpReq->iccon.peersCallID;
 457                 cid = &info->pac_call_id;
 458
 459                 if (info->pns_call_id != ntohs(*pcid)) {
 460                         DEBUGP("%s for unknown CallID %u\n",
 461                                 strMName[msg], ntohs(*cid));
 462                         break;
 463                 }
 464
 465                 DEBUGP("%s, PCID=%X\n", strMName[msg], ntohs(*pcid));
 466                 info->cstate = PPTP_CALL_IN_CONF;
 467
 468                 /* we expect a GRE connection from PAC to PNS */
 469                 seq = ntohl(tcph->seq) + sizeof(struct pptp_pkt_hdr)
 470                                        + sizeof(struct PptpControlHeader)
 471                                        + ((void *)pcid - (void *)pptpReq);
 472
 473                 if (exp_gre(ct, seq, *cid, *pcid) != 0)
 474                         printk("ip_conntrack_pptp: error during exp_gre\n");
 475
 476                 break;
 477
 478         case PPTP_CALL_DISCONNECT_NOTIFY:
 479                 if (reqlen < sizeof(_pptpReq.disc)) {
 480                         DEBUGP("%s: short packet\n", strMName[msg]);
 481                         break;
 482                 }
 483
 484                 /* server confirms disconnect */
 485                 cid = &pptpReq->disc.callID;
 486                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*cid));
 487                 info->cstate = PPTP_CALL_NONE;
 488
 489                 /* untrack this call id, unexpect GRE packets */
 490                 pptp_timeout_related(ct);
 491                 break;
 492
 493         case PPTP_WAN_ERROR_NOTIFY:
 494                 break;
 495
 496         case PPTP_ECHO_REQUEST:
 497         case PPTP_ECHO_REPLY:
 498                 /* I don't have to explain these ;) */
 499                 break;
 500         default:
 501                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)
 502                         ? strMName[msg]:strMName[0], msg);
 503                 break;
 504         }
 505
 506
 507         if (ip_nat_pptp_hook_inbound)
 508                 return ip_nat_pptp_hook_inbound(pskb, ct, ctinfo, ctlh,
 509                                                 pptpReq);
 510
 511         return NF_ACCEPT;
 512
 513 }
 514
 515 static inline int
 516 pptp_outbound_pkt(struct sk_buff **pskb,
 517                   struct tcphdr *tcph,
 518                   unsigned int ctlhoff,
 519                   size_t datalen,
 520                   struct ip_conntrack *ct,
 521                   enum ip_conntrack_info ctinfo)
 522 {
 523         struct PptpControlHeader _ctlh, *ctlh;
 524         unsigned int reqlen;
 525         union pptp_ctrl_union _pptpReq, *pptpReq;
 526         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 527         u_int16_t msg, *cid, *pcid;
 528
 529         ctlh = skb_header_pointer(*pskb, ctlhoff, sizeof(_ctlh), &_ctlh);
 530         if (!ctlh)
 531                 return NF_ACCEPT;
 532
 533         reqlen = datalen - sizeof(struct pptp_pkt_hdr) - sizeof(_ctlh);
 534         pptpReq = skb_header_pointer(*pskb, ctlhoff+sizeof(_ctlh), reqlen,
 535                                      &_pptpReq);
 536         if (!pptpReq)
 537                 return NF_ACCEPT;
 538
 539         msg = ntohs(ctlh->messageType);
 540         DEBUGP("outbound control message %s\n", strMName[msg]);
 541
 542         switch (msg) {
 543         case PPTP_START_SESSION_REQUEST:
 544                 /* client requests for new control session */
 545                 if (info->sstate != PPTP_SESSION_NONE) {
 546                         DEBUGP("%s but we already have one",
 547                                 strMName[msg]);
 548                 }
 549                 info->sstate = PPTP_SESSION_REQUESTED;
 550                 break;
 551         case PPTP_STOP_SESSION_REQUEST:
 552                 /* client requests end of control session */
 553                 info->sstate = PPTP_SESSION_STOPREQ;
 554                 break;
 555
 556         case PPTP_OUT_CALL_REQUEST:
 557                 if (reqlen < sizeof(_pptpReq.ocreq)) {
 558                         DEBUGP("%s: short packet\n", strMName[msg]);
 559                         /* FIXME: break; */
 560                 }
 561
 562                 /* client initiating connection to server */
 563                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 564                         DEBUGP("%s but no session\n",
 565                                 strMName[msg]);
 566                         break;
 567                 }
 568                 info->cstate = PPTP_CALL_OUT_REQ;
 569                 /* track PNS call id */
 570                 cid = &pptpReq->ocreq.callID;
 571                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*cid));
 572                 info->pns_call_id = ntohs(*cid);
 573                 break;
 574         case PPTP_IN_CALL_REPLY:
 575                 if (reqlen < sizeof(_pptpReq.icack)) {
 576                         DEBUGP("%s: short packet\n", strMName[msg]);
 577                         break;
 578                 }
 579
 580                 /* client answers incoming call */
 581                 if (info->cstate != PPTP_CALL_IN_REQ
 582                     && info->cstate != PPTP_CALL_IN_REP) {
 583                         DEBUGP("%s without incall_req\n",
 584                                 strMName[msg]);
 585                         break;
 586                 }
 587                 if (pptpReq->icack.resultCode != PPTP_INCALL_ACCEPT) {
 588                         info->cstate = PPTP_CALL_NONE;
 589                         break;
 590                 }
 591                 pcid = &pptpReq->icack.peersCallID;
 592                 if (info->pac_call_id != ntohs(*pcid)) {
 593                         DEBUGP("%s for unknown call %u\n",
 594                                 strMName[msg], ntohs(*pcid));
 595                         break;
 596                 }
 597                 DEBUGP("%s, CID=%X\n", strMName[msg], ntohs(*pcid));
 598                 /* part two of the three-way handshake */
 599                 info->cstate = PPTP_CALL_IN_REP;
 600                 info->pns_call_id = ntohs(pptpReq->icack.callID);
 601                 break;
 602
 603         case PPTP_CALL_CLEAR_REQUEST:
 604                 /* client requests hangup of call */
 605                 if (info->sstate != PPTP_SESSION_CONFIRMED) {
 606                         DEBUGP("CLEAR_CALL but no session\n");
 607                         break;
 608                 }
 609                 /* FUTURE: iterate over all calls and check if
 610                  * call ID is valid.  We don't do this without newnat,
 611                  * because we only know about last call */
 612                 info->cstate = PPTP_CALL_CLEAR_REQ;
 613                 break;
 614         case PPTP_SET_LINK_INFO:
 615                 break;
 616         case PPTP_ECHO_REQUEST:
 617         case PPTP_ECHO_REPLY:
 618                 /* I don't have to explain these ;) */
 619                 break;
 620         default:
 621                 DEBUGP("invalid %s (TY=%d)\n", (msg <= PPTP_MSG_MAX)?
 622                         strMName[msg]:strMName[0], msg);
 623                 /* unknown: no need to create GRE masq table entry */
 624                 break;
 625         }
 626
 627         if (ip_nat_pptp_hook_outbound)
 628                 return ip_nat_pptp_hook_outbound(pskb, ct, ctinfo, ctlh,
 629                                                  pptpReq);
 630
 631         return NF_ACCEPT;
 632 }
 633
 634
 635 /* track caller id inside control connection, call expect_related */
 636 static int
 637 conntrack_pptp_help(struct sk_buff **pskb,
 638                     struct ip_conntrack *ct, enum ip_conntrack_info ctinfo)
 639
 640 {
 641         struct pptp_pkt_hdr _pptph, *pptph;
 642
 643         struct tcphdr _tcph, *tcph;
 644         u_int32_t tcplen = (*pskb)->len - (*pskb)->nh.iph->ihl * 4;
 645         u_int32_t datalen;
 646         void *datalimit;
 647         int dir = CTINFO2DIR(ctinfo);
 648         struct ip_ct_pptp_master *info = &ct->help.ct_pptp_info;
 649         unsigned int nexthdr_off;
 650
 651         int oldsstate, oldcstate;
 652         int ret;
 653
 654         /* don't do any tracking before tcp handshake complete */
 655         if (ctinfo != IP_CT_ESTABLISHED
 656             && ctinfo != IP_CT_ESTABLISHED+IP_CT_IS_REPLY) {
 657                 DEBUGP("ctinfo = %u, skipping\n", ctinfo);
 658                 return NF_ACCEPT;
 659         }
 660
 661         nexthdr_off = (*pskb)->nh.iph->ihl*4;
 662         tcph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4, sizeof(_tcph),
 663                                   &_tcph);
 664         if (!tcph)
 665                 return NF_ACCEPT;
 666
 667         /* not a complete TCP header? */
 668         if (tcplen < sizeof(struct tcphdr) || tcplen < tcph->doff * 4) {
 669                 DEBUGP("tcplen = %u\n", tcplen);
 670                 return NF_ACCEPT;
 671         }
 672
 673
 674         datalen = tcplen - tcph->doff * 4;
 675
 676         /* checksum invalid? */
 677         if (tcp_v4_check(tcph, tcplen, (*pskb)->nh.iph->saddr,
 678                          (*pskb)->nh.iph->daddr,
 679                          csum_partial((char *) tcph, tcplen, 0))) {
 680                 DEBUGP(" bad csum\n");
 681                 /* W2K PPTP server sends TCP packets with wrong checksum :(( */
 682                 //return NF_ACCEPT;
 683         }
 684
 685         if (tcph->fin || tcph->rst) {
 686                 DEBUGP("RST/FIN received, timeouting GRE\n");
 687                 /* can't do this after real newnat */
 688                 info->cstate = PPTP_CALL_NONE;
 689
 690                 /* untrack this call id, unexpect GRE packets */
 691                 pptp_timeout_related(ct);
 692         }
 693
 694         nexthdr_off += tcph->doff*4;
 695         pptph = skb_header_pointer(*pskb, (*pskb)->nh.iph->ihl*4 + tcph->doff*4,
 696                                    sizeof(_pptph), &_pptph);
 697         if (!pptph) {
 698                 DEBUGP("no full PPTP header, can't track\n");
 699                 return NF_ACCEPT;
 700         }
 701
 702         datalimit = (void *) pptph + datalen;
 703
 704         /* if it's not a control message we can't do anything with it */
 705         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 706             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 707                 DEBUGP("not a control packet\n");
 708                 return NF_ACCEPT;
 709         }
 710
 711         oldsstate = info->sstate;
 712         oldcstate = info->cstate;
 713
 714         LOCK_BH(&ip_pptp_lock);
 715
 716         nexthdr_off += sizeof(_pptph);
 717         /* FIXME: We just blindly assume that the control connection is always
 718          * established from PNS->PAC.  However, RFC makes no guarantee */
 719         if (dir == IP_CT_DIR_ORIGINAL)
 720                 /* client -> server (PNS -> PAC) */
 721                 ret = pptp_outbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 722                                         ctinfo);
 723         else
 724                 /* server -> client (PAC -> PNS) */
 725                 ret = pptp_inbound_pkt(pskb, tcph, nexthdr_off, datalen, ct,
 726                                        ctinfo);
 727         DEBUGP("sstate: %d->%d, cstate: %d->%d\n",
 728                 oldsstate, info->sstate, oldcstate, info->cstate);
 729         UNLOCK_BH(&ip_pptp_lock);
 730
 731         return ret;
 732 }
 733
 734 /* control protocol helper */
 735 static struct ip_conntrack_helper pptp = {
 736         .list = { NULL, NULL },
 737         .name = "pptp",
 738         .me = THIS_MODULE,
 739         .max_expected = 2,
 740         .timeout = 5 * 60,
 741         .tuple = { .src = { .ip = 0,
 742                             .u = { .tcp = { .port =
 743                                     __constant_htons(PPTP_CONTROL_PORT) } }
 744                           },
 745                    .dst = { .ip = 0,
 746                             .u = { .all = 0 },
 747                             .protonum = IPPROTO_TCP
 748                           }
 749                  },
 750         .mask = { .src = { .ip = 0,
 751                            .u = { .tcp = { .port = 0xffff } }
 752                          },
 753                   .dst = { .ip = 0,
 754                            .u = { .all = 0 },
 755                            .protonum = 0xff
 756                          }
 757                 },
 758         .help = conntrack_pptp_help
 759 };
 760
 761 /* ip_conntrack_pptp initialization */
 762 static int __init init(void)
 763 {
 764         int retcode;
 765
 766         DEBUGP(" registering helper\n");
 767         if ((retcode = ip_conntrack_helper_register(&pptp))) {
 768                 printk(KERN_ERR "Unable to register conntrack application "
 769                                 "helper for pptp: %d\n", retcode);
 770                 return -EIO;
 771         }
 772
 773         printk("ip_conntrack_pptp version %s loaded\n", IP_CT_PPTP_VERSION);
 774         return 0;
 775 }
 776
 777 static void __exit fini(void)
 778 {
 779         ip_conntrack_helper_unregister(&pptp);
 780         printk("ip_conntrack_pptp version %s unloaded\n", IP_CT_PPTP_VERSION);
 781 }
 782
 783 module_init(init);
 784 module_exit(fini);
 785
 786 EXPORT_SYMBOL(ip_pptp_lock);
 787 EXPORT_SYMBOL(ip_nat_pptp_hook_outbound);
 788 EXPORT_SYMBOL(ip_nat_pptp_hook_inbound);
 789 EXPORT_SYMBOL(ip_nat_pptp_hook_exp_gre);
 790 EXPORT_SYMBOL(ip_nat_pptp_hook_expectfn);