1 /* 2 * Connection tracking support for PPTP (Point to Point Tunneling Protocol). 3 * PPTP is a a protocol for creating virtual private networks. 4 * It is a specification defined by Microsoft and some vendors 5 * working with Microsoft. PPTP is built on top of a modified 6 * version of the Internet Generic Routing Encapsulation Protocol. 7 * GRE is defined in RFC 1701 and RFC 1702. Documentation of 8 * PPTP can be found in RFC 2637 9 * 10 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> 11 * 12 * Development of this code funded by Astaro AG (http://www.astaro.com/) 13 * 14 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 15 * 16 * Limitations: 17 * - We blindly assume that control connections are always 18 * established in PNS->PAC direction. This is a violation 19 * of RFC 2637 20 * - We can only support one single call within each session 21 * TODO: 22 * - testing of incoming PPTP calls 23 */ 24 25 #include <linux/module.h> 26 #include <linux/skbuff.h> 27 #include <linux/in.h> 28 #include <linux/tcp.h> 29 30 #include <net/netfilter/nf_conntrack.h> 31 #include <net/netfilter/nf_conntrack_core.h> 32 #include <net/netfilter/nf_conntrack_helper.h> 33 #include <net/netfilter/nf_conntrack_zones.h> 34 #include <linux/netfilter/nf_conntrack_proto_gre.h> 35 #include <linux/netfilter/nf_conntrack_pptp.h> 36 37 #define NF_CT_PPTP_VERSION "3.1" 38 39 MODULE_LICENSE("GPL"); 40 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 41 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP"); 42 MODULE_ALIAS("ip_conntrack_pptp"); 43 MODULE_ALIAS_NFCT_HELPER("pptp"); 44 45 static DEFINE_SPINLOCK(nf_pptp_lock); 46 47 int 48 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb, 49 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 50 unsigned int protoff, struct PptpControlHeader *ctlh, 51 union pptp_ctrl_union *pptpReq) __read_mostly; 52 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound); 53 54 int 55 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb, 56 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 57 unsigned int protoff, struct PptpControlHeader *ctlh, 58 union pptp_ctrl_union *pptpReq) __read_mostly; 59 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound); 60 61 void 62 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig, 63 struct nf_conntrack_expect *expect_reply) 64 __read_mostly; 65 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre); 66 67 void 68 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct, 69 struct nf_conntrack_expect *exp) __read_mostly; 70 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn); 71 72 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG) 73 /* PptpControlMessageType names */ 74 const char *const pptp_msg_name[] = { 75 "UNKNOWN_MESSAGE", 76 "START_SESSION_REQUEST", 77 "START_SESSION_REPLY", 78 "STOP_SESSION_REQUEST", 79 "STOP_SESSION_REPLY", 80 "ECHO_REQUEST", 81 "ECHO_REPLY", 82 "OUT_CALL_REQUEST", 83 "OUT_CALL_REPLY", 84 "IN_CALL_REQUEST", 85 "IN_CALL_REPLY", 86 "IN_CALL_CONNECT", 87 "CALL_CLEAR_REQUEST", 88 "CALL_DISCONNECT_NOTIFY", 89 "WAN_ERROR_NOTIFY", 90 "SET_LINK_INFO" 91 }; 92 EXPORT_SYMBOL(pptp_msg_name); 93 #endif 94 95 #define SECS *HZ 96 #define MINS * 60 SECS 97 #define HOURS * 60 MINS 98 99 #define PPTP_GRE_TIMEOUT (10 MINS) 100 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 101 102 static void pptp_expectfn(struct nf_conn *ct, 103 struct nf_conntrack_expect *exp) 104 { 105 struct net *net = nf_ct_net(ct); 106 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn; 107 pr_debug("increasing timeouts\n"); 108 109 /* increase timeout of GRE data channel conntrack entry */ 110 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 111 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 112 113 /* Can you see how rusty this code is, compared with the pre-2.6.11 114 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 115 116 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn); 117 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK) 118 nf_nat_pptp_expectfn(ct, exp); 119 else { 120 struct nf_conntrack_tuple inv_t; 121 struct nf_conntrack_expect *exp_other; 122 123 /* obviously this tuple inversion only works until you do NAT */ 124 nf_ct_invert_tuplepr(&inv_t, &exp->tuple); 125 pr_debug("trying to unexpect other dir: "); 126 nf_ct_dump_tuple(&inv_t); 127 128 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 129 if (exp_other) { 130 /* delete other expectation. */ 131 pr_debug("found\n"); 132 nf_ct_unexpect_related(exp_other); 133 nf_ct_expect_put(exp_other); 134 } else { 135 pr_debug("not found\n"); 136 } 137 } 138 } 139 140 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 141 const struct nf_conntrack_tuple *t) 142 { 143 const struct nf_conntrack_tuple_hash *h; 144 const struct nf_conntrack_zone *zone; 145 struct nf_conntrack_expect *exp; 146 struct nf_conn *sibling; 147 148 pr_debug("trying to timeout ct or exp for tuple "); 149 nf_ct_dump_tuple(t); 150 151 zone = nf_ct_zone(ct); 152 h = nf_conntrack_find_get(net, zone, t); 153 if (h) { 154 sibling = nf_ct_tuplehash_to_ctrack(h); 155 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 156 sibling->proto.gre.timeout = 0; 157 sibling->proto.gre.stream_timeout = 0; 158 nf_ct_kill(sibling); 159 nf_ct_put(sibling); 160 return 1; 161 } else { 162 exp = nf_ct_expect_find_get(net, zone, t); 163 if (exp) { 164 pr_debug("unexpect_related of expect %p\n", exp); 165 nf_ct_unexpect_related(exp); 166 nf_ct_expect_put(exp); 167 return 1; 168 } 169 } 170 return 0; 171 } 172 173 /* timeout GRE data connections */ 174 static void pptp_destroy_siblings(struct nf_conn *ct) 175 { 176 struct net *net = nf_ct_net(ct); 177 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 178 struct nf_conntrack_tuple t; 179 180 nf_ct_gre_keymap_destroy(ct); 181 182 /* try original (pns->pac) tuple */ 183 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 184 t.dst.protonum = IPPROTO_GRE; 185 t.src.u.gre.key = ct_pptp_info->pns_call_id; 186 t.dst.u.gre.key = ct_pptp_info->pac_call_id; 187 if (!destroy_sibling_or_exp(net, ct, &t)) 188 pr_debug("failed to timeout original pns->pac ct/exp\n"); 189 190 /* try reply (pac->pns) tuple */ 191 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 192 t.dst.protonum = IPPROTO_GRE; 193 t.src.u.gre.key = ct_pptp_info->pac_call_id; 194 t.dst.u.gre.key = ct_pptp_info->pns_call_id; 195 if (!destroy_sibling_or_exp(net, ct, &t)) 196 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 197 } 198 199 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 200 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 201 { 202 struct nf_conntrack_expect *exp_orig, *exp_reply; 203 enum ip_conntrack_dir dir; 204 int ret = 1; 205 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre; 206 207 exp_orig = nf_ct_expect_alloc(ct); 208 if (exp_orig == NULL) 209 goto out; 210 211 exp_reply = nf_ct_expect_alloc(ct); 212 if (exp_reply == NULL) 213 goto out_put_orig; 214 215 /* original direction, PNS->PAC */ 216 dir = IP_CT_DIR_ORIGINAL; 217 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT, 218 nf_ct_l3num(ct), 219 &ct->tuplehash[dir].tuple.src.u3, 220 &ct->tuplehash[dir].tuple.dst.u3, 221 IPPROTO_GRE, &peer_callid, &callid); 222 exp_orig->expectfn = pptp_expectfn; 223 224 /* reply direction, PAC->PNS */ 225 dir = IP_CT_DIR_REPLY; 226 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT, 227 nf_ct_l3num(ct), 228 &ct->tuplehash[dir].tuple.src.u3, 229 &ct->tuplehash[dir].tuple.dst.u3, 230 IPPROTO_GRE, &callid, &peer_callid); 231 exp_reply->expectfn = pptp_expectfn; 232 233 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre); 234 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK) 235 nf_nat_pptp_exp_gre(exp_orig, exp_reply); 236 if (nf_ct_expect_related(exp_orig) != 0) 237 goto out_put_both; 238 if (nf_ct_expect_related(exp_reply) != 0) 239 goto out_unexpect_orig; 240 241 /* Add GRE keymap entries */ 242 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 243 goto out_unexpect_both; 244 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 245 nf_ct_gre_keymap_destroy(ct); 246 goto out_unexpect_both; 247 } 248 ret = 0; 249 250 out_put_both: 251 nf_ct_expect_put(exp_reply); 252 out_put_orig: 253 nf_ct_expect_put(exp_orig); 254 out: 255 return ret; 256 257 out_unexpect_both: 258 nf_ct_unexpect_related(exp_reply); 259 out_unexpect_orig: 260 nf_ct_unexpect_related(exp_orig); 261 goto out_put_both; 262 } 263 264 static int 265 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, 266 struct PptpControlHeader *ctlh, 267 union pptp_ctrl_union *pptpReq, 268 unsigned int reqlen, 269 struct nf_conn *ct, 270 enum ip_conntrack_info ctinfo) 271 { 272 struct nf_ct_pptp_master *info = nfct_help_data(ct); 273 u_int16_t msg; 274 __be16 cid = 0, pcid = 0; 275 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound; 276 277 msg = ntohs(ctlh->messageType); 278 pr_debug("inbound control message %s\n", pptp_msg_name[msg]); 279 280 switch (msg) { 281 case PPTP_START_SESSION_REPLY: 282 /* server confirms new control session */ 283 if (info->sstate < PPTP_SESSION_REQUESTED) 284 goto invalid; 285 if (pptpReq->srep.resultCode == PPTP_START_OK) 286 info->sstate = PPTP_SESSION_CONFIRMED; 287 else 288 info->sstate = PPTP_SESSION_ERROR; 289 break; 290 291 case PPTP_STOP_SESSION_REPLY: 292 /* server confirms end of control session */ 293 if (info->sstate > PPTP_SESSION_STOPREQ) 294 goto invalid; 295 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 296 info->sstate = PPTP_SESSION_NONE; 297 else 298 info->sstate = PPTP_SESSION_ERROR; 299 break; 300 301 case PPTP_OUT_CALL_REPLY: 302 /* server accepted call, we now expect GRE frames */ 303 if (info->sstate != PPTP_SESSION_CONFIRMED) 304 goto invalid; 305 if (info->cstate != PPTP_CALL_OUT_REQ && 306 info->cstate != PPTP_CALL_OUT_CONF) 307 goto invalid; 308 309 cid = pptpReq->ocack.callID; 310 pcid = pptpReq->ocack.peersCallID; 311 if (info->pns_call_id != pcid) 312 goto invalid; 313 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg], 314 ntohs(cid), ntohs(pcid)); 315 316 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 317 info->cstate = PPTP_CALL_OUT_CONF; 318 info->pac_call_id = cid; 319 exp_gre(ct, cid, pcid); 320 } else 321 info->cstate = PPTP_CALL_NONE; 322 break; 323 324 case PPTP_IN_CALL_REQUEST: 325 /* server tells us about incoming call request */ 326 if (info->sstate != PPTP_SESSION_CONFIRMED) 327 goto invalid; 328 329 cid = pptpReq->icreq.callID; 330 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 331 info->cstate = PPTP_CALL_IN_REQ; 332 info->pac_call_id = cid; 333 break; 334 335 case PPTP_IN_CALL_CONNECT: 336 /* server tells us about incoming call established */ 337 if (info->sstate != PPTP_SESSION_CONFIRMED) 338 goto invalid; 339 if (info->cstate != PPTP_CALL_IN_REP && 340 info->cstate != PPTP_CALL_IN_CONF) 341 goto invalid; 342 343 pcid = pptpReq->iccon.peersCallID; 344 cid = info->pac_call_id; 345 346 if (info->pns_call_id != pcid) 347 goto invalid; 348 349 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid)); 350 info->cstate = PPTP_CALL_IN_CONF; 351 352 /* we expect a GRE connection from PAC to PNS */ 353 exp_gre(ct, cid, pcid); 354 break; 355 356 case PPTP_CALL_DISCONNECT_NOTIFY: 357 /* server confirms disconnect */ 358 cid = pptpReq->disc.callID; 359 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 360 info->cstate = PPTP_CALL_NONE; 361 362 /* untrack this call id, unexpect GRE packets */ 363 pptp_destroy_siblings(ct); 364 break; 365 366 case PPTP_WAN_ERROR_NOTIFY: 367 case PPTP_SET_LINK_INFO: 368 case PPTP_ECHO_REQUEST: 369 case PPTP_ECHO_REPLY: 370 /* I don't have to explain these ;) */ 371 break; 372 373 default: 374 goto invalid; 375 } 376 377 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound); 378 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK) 379 return nf_nat_pptp_inbound(skb, ct, ctinfo, 380 protoff, ctlh, pptpReq); 381 return NF_ACCEPT; 382 383 invalid: 384 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 385 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 386 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 387 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 388 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 389 return NF_ACCEPT; 390 } 391 392 static int 393 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, 394 struct PptpControlHeader *ctlh, 395 union pptp_ctrl_union *pptpReq, 396 unsigned int reqlen, 397 struct nf_conn *ct, 398 enum ip_conntrack_info ctinfo) 399 { 400 struct nf_ct_pptp_master *info = nfct_help_data(ct); 401 u_int16_t msg; 402 __be16 cid = 0, pcid = 0; 403 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound; 404 405 msg = ntohs(ctlh->messageType); 406 pr_debug("outbound control message %s\n", pptp_msg_name[msg]); 407 408 switch (msg) { 409 case PPTP_START_SESSION_REQUEST: 410 /* client requests for new control session */ 411 if (info->sstate != PPTP_SESSION_NONE) 412 goto invalid; 413 info->sstate = PPTP_SESSION_REQUESTED; 414 break; 415 416 case PPTP_STOP_SESSION_REQUEST: 417 /* client requests end of control session */ 418 info->sstate = PPTP_SESSION_STOPREQ; 419 break; 420 421 case PPTP_OUT_CALL_REQUEST: 422 /* client initiating connection to server */ 423 if (info->sstate != PPTP_SESSION_CONFIRMED) 424 goto invalid; 425 info->cstate = PPTP_CALL_OUT_REQ; 426 /* track PNS call id */ 427 cid = pptpReq->ocreq.callID; 428 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 429 info->pns_call_id = cid; 430 break; 431 432 case PPTP_IN_CALL_REPLY: 433 /* client answers incoming call */ 434 if (info->cstate != PPTP_CALL_IN_REQ && 435 info->cstate != PPTP_CALL_IN_REP) 436 goto invalid; 437 438 cid = pptpReq->icack.callID; 439 pcid = pptpReq->icack.peersCallID; 440 if (info->pac_call_id != pcid) 441 goto invalid; 442 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg], 443 ntohs(cid), ntohs(pcid)); 444 445 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 446 /* part two of the three-way handshake */ 447 info->cstate = PPTP_CALL_IN_REP; 448 info->pns_call_id = cid; 449 } else 450 info->cstate = PPTP_CALL_NONE; 451 break; 452 453 case PPTP_CALL_CLEAR_REQUEST: 454 /* client requests hangup of call */ 455 if (info->sstate != PPTP_SESSION_CONFIRMED) 456 goto invalid; 457 /* FUTURE: iterate over all calls and check if 458 * call ID is valid. We don't do this without newnat, 459 * because we only know about last call */ 460 info->cstate = PPTP_CALL_CLEAR_REQ; 461 break; 462 463 case PPTP_SET_LINK_INFO: 464 case PPTP_ECHO_REQUEST: 465 case PPTP_ECHO_REPLY: 466 /* I don't have to explain these ;) */ 467 break; 468 469 default: 470 goto invalid; 471 } 472 473 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound); 474 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK) 475 return nf_nat_pptp_outbound(skb, ct, ctinfo, 476 protoff, ctlh, pptpReq); 477 return NF_ACCEPT; 478 479 invalid: 480 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 481 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 482 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 483 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 484 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 485 return NF_ACCEPT; 486 } 487 488 static const unsigned int pptp_msg_size[] = { 489 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 490 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 491 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 492 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 493 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 494 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 495 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 496 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 497 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 498 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 499 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 500 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 501 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 502 }; 503 504 /* track caller id inside control connection, call expect_related */ 505 static int 506 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 507 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 508 509 { 510 int dir = CTINFO2DIR(ctinfo); 511 const struct nf_ct_pptp_master *info = nfct_help_data(ct); 512 const struct tcphdr *tcph; 513 struct tcphdr _tcph; 514 const struct pptp_pkt_hdr *pptph; 515 struct pptp_pkt_hdr _pptph; 516 struct PptpControlHeader _ctlh, *ctlh; 517 union pptp_ctrl_union _pptpReq, *pptpReq; 518 unsigned int tcplen = skb->len - protoff; 519 unsigned int datalen, reqlen, nexthdr_off; 520 int oldsstate, oldcstate; 521 int ret; 522 u_int16_t msg; 523 524 #if IS_ENABLED(CONFIG_NF_NAT) 525 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) { 526 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT); 527 528 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC)) 529 return NF_DROP; 530 } 531 #endif 532 /* don't do any tracking before tcp handshake complete */ 533 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 534 return NF_ACCEPT; 535 536 nexthdr_off = protoff; 537 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 538 BUG_ON(!tcph); 539 nexthdr_off += tcph->doff * 4; 540 datalen = tcplen - tcph->doff * 4; 541 542 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 543 if (!pptph) { 544 pr_debug("no full PPTP header, can't track\n"); 545 return NF_ACCEPT; 546 } 547 nexthdr_off += sizeof(_pptph); 548 datalen -= sizeof(_pptph); 549 550 /* if it's not a control message we can't do anything with it */ 551 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 552 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 553 pr_debug("not a control packet\n"); 554 return NF_ACCEPT; 555 } 556 557 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 558 if (!ctlh) 559 return NF_ACCEPT; 560 nexthdr_off += sizeof(_ctlh); 561 datalen -= sizeof(_ctlh); 562 563 reqlen = datalen; 564 msg = ntohs(ctlh->messageType); 565 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 566 return NF_ACCEPT; 567 if (reqlen > sizeof(*pptpReq)) 568 reqlen = sizeof(*pptpReq); 569 570 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 571 if (!pptpReq) 572 return NF_ACCEPT; 573 574 oldsstate = info->sstate; 575 oldcstate = info->cstate; 576 577 spin_lock_bh(&nf_pptp_lock); 578 579 /* FIXME: We just blindly assume that the control connection is always 580 * established from PNS->PAC. However, RFC makes no guarantee */ 581 if (dir == IP_CT_DIR_ORIGINAL) 582 /* client -> server (PNS -> PAC) */ 583 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 584 ctinfo); 585 else 586 /* server -> client (PAC -> PNS) */ 587 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 588 ctinfo); 589 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 590 oldsstate, info->sstate, oldcstate, info->cstate); 591 spin_unlock_bh(&nf_pptp_lock); 592 593 return ret; 594 } 595 596 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 597 .max_expected = 2, 598 .timeout = 5 * 60, 599 }; 600 601 /* control protocol helper */ 602 static struct nf_conntrack_helper pptp __read_mostly = { 603 .name = "pptp", 604 .me = THIS_MODULE, 605 .tuple.src.l3num = AF_INET, 606 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 607 .tuple.dst.protonum = IPPROTO_TCP, 608 .help = conntrack_pptp_help, 609 .destroy = pptp_destroy_siblings, 610 .expect_policy = &pptp_exp_policy, 611 }; 612 613 static int __init nf_conntrack_pptp_init(void) 614 { 615 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master)); 616 617 return nf_conntrack_helper_register(&pptp); 618 } 619 620 static void __exit nf_conntrack_pptp_fini(void) 621 { 622 nf_conntrack_helper_unregister(&pptp); 623 } 624 625 module_init(nf_conntrack_pptp_init); 626 module_exit(nf_conntrack_pptp_fini); 627