1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Connection tracking support for PPTP (Point to Point Tunneling Protocol). 4 * PPTP is a a protocol for creating virtual private networks. 5 * It is a specification defined by Microsoft and some vendors 6 * working with Microsoft. PPTP is built on top of a modified 7 * version of the Internet Generic Routing Encapsulation Protocol. 8 * GRE is defined in RFC 1701 and RFC 1702. Documentation of 9 * PPTP can be found in RFC 2637 10 * 11 * (C) 2000-2005 by Harald Welte <laforge@gnumonks.org> 12 * 13 * Development of this code funded by Astaro AG (http://www.astaro.com/) 14 * 15 * (C) 2006-2012 Patrick McHardy <kaber@trash.net> 16 * 17 * Limitations: 18 * - We blindly assume that control connections are always 19 * established in PNS->PAC direction. This is a violation 20 * of RFC 2637 21 * - We can only support one single call within each session 22 * TODO: 23 * - testing of incoming PPTP calls 24 */ 25 26 #include <linux/module.h> 27 #include <linux/skbuff.h> 28 #include <linux/in.h> 29 #include <linux/tcp.h> 30 31 #include <net/netfilter/nf_conntrack.h> 32 #include <net/netfilter/nf_conntrack_core.h> 33 #include <net/netfilter/nf_conntrack_helper.h> 34 #include <net/netfilter/nf_conntrack_zones.h> 35 #include <linux/netfilter/nf_conntrack_proto_gre.h> 36 #include <linux/netfilter/nf_conntrack_pptp.h> 37 38 #define NF_CT_PPTP_VERSION "3.1" 39 40 MODULE_LICENSE("GPL"); 41 MODULE_AUTHOR("Harald Welte <laforge@gnumonks.org>"); 42 MODULE_DESCRIPTION("Netfilter connection tracking helper module for PPTP"); 43 MODULE_ALIAS("ip_conntrack_pptp"); 44 MODULE_ALIAS_NFCT_HELPER("pptp"); 45 46 static DEFINE_SPINLOCK(nf_pptp_lock); 47 48 int 49 (*nf_nat_pptp_hook_outbound)(struct sk_buff *skb, 50 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 51 unsigned int protoff, struct PptpControlHeader *ctlh, 52 union pptp_ctrl_union *pptpReq) __read_mostly; 53 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_outbound); 54 55 int 56 (*nf_nat_pptp_hook_inbound)(struct sk_buff *skb, 57 struct nf_conn *ct, enum ip_conntrack_info ctinfo, 58 unsigned int protoff, struct PptpControlHeader *ctlh, 59 union pptp_ctrl_union *pptpReq) __read_mostly; 60 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_inbound); 61 62 void 63 (*nf_nat_pptp_hook_exp_gre)(struct nf_conntrack_expect *expect_orig, 64 struct nf_conntrack_expect *expect_reply) 65 __read_mostly; 66 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_exp_gre); 67 68 void 69 (*nf_nat_pptp_hook_expectfn)(struct nf_conn *ct, 70 struct nf_conntrack_expect *exp) __read_mostly; 71 EXPORT_SYMBOL_GPL(nf_nat_pptp_hook_expectfn); 72 73 #if defined(DEBUG) || defined(CONFIG_DYNAMIC_DEBUG) 74 /* PptpControlMessageType names */ 75 const char *const pptp_msg_name[] = { 76 "UNKNOWN_MESSAGE", 77 "START_SESSION_REQUEST", 78 "START_SESSION_REPLY", 79 "STOP_SESSION_REQUEST", 80 "STOP_SESSION_REPLY", 81 "ECHO_REQUEST", 82 "ECHO_REPLY", 83 "OUT_CALL_REQUEST", 84 "OUT_CALL_REPLY", 85 "IN_CALL_REQUEST", 86 "IN_CALL_REPLY", 87 "IN_CALL_CONNECT", 88 "CALL_CLEAR_REQUEST", 89 "CALL_DISCONNECT_NOTIFY", 90 "WAN_ERROR_NOTIFY", 91 "SET_LINK_INFO" 92 }; 93 EXPORT_SYMBOL(pptp_msg_name); 94 #endif 95 96 #define SECS *HZ 97 #define MINS * 60 SECS 98 #define HOURS * 60 MINS 99 100 #define PPTP_GRE_TIMEOUT (10 MINS) 101 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 102 103 static void pptp_expectfn(struct nf_conn *ct, 104 struct nf_conntrack_expect *exp) 105 { 106 struct net *net = nf_ct_net(ct); 107 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn; 108 pr_debug("increasing timeouts\n"); 109 110 /* increase timeout of GRE data channel conntrack entry */ 111 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 112 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 113 114 /* Can you see how rusty this code is, compared with the pre-2.6.11 115 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 116 117 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn); 118 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK) 119 nf_nat_pptp_expectfn(ct, exp); 120 else { 121 struct nf_conntrack_tuple inv_t; 122 struct nf_conntrack_expect *exp_other; 123 124 /* obviously this tuple inversion only works until you do NAT */ 125 nf_ct_invert_tuple(&inv_t, &exp->tuple); 126 pr_debug("trying to unexpect other dir: "); 127 nf_ct_dump_tuple(&inv_t); 128 129 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 130 if (exp_other) { 131 /* delete other expectation. */ 132 pr_debug("found\n"); 133 nf_ct_unexpect_related(exp_other); 134 nf_ct_expect_put(exp_other); 135 } else { 136 pr_debug("not found\n"); 137 } 138 } 139 } 140 141 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 142 const struct nf_conntrack_tuple *t) 143 { 144 const struct nf_conntrack_tuple_hash *h; 145 const struct nf_conntrack_zone *zone; 146 struct nf_conntrack_expect *exp; 147 struct nf_conn *sibling; 148 149 pr_debug("trying to timeout ct or exp for tuple "); 150 nf_ct_dump_tuple(t); 151 152 zone = nf_ct_zone(ct); 153 h = nf_conntrack_find_get(net, zone, t); 154 if (h) { 155 sibling = nf_ct_tuplehash_to_ctrack(h); 156 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 157 sibling->proto.gre.timeout = 0; 158 sibling->proto.gre.stream_timeout = 0; 159 nf_ct_kill(sibling); 160 nf_ct_put(sibling); 161 return 1; 162 } else { 163 exp = nf_ct_expect_find_get(net, zone, t); 164 if (exp) { 165 pr_debug("unexpect_related of expect %p\n", exp); 166 nf_ct_unexpect_related(exp); 167 nf_ct_expect_put(exp); 168 return 1; 169 } 170 } 171 return 0; 172 } 173 174 /* timeout GRE data connections */ 175 static void pptp_destroy_siblings(struct nf_conn *ct) 176 { 177 struct net *net = nf_ct_net(ct); 178 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 179 struct nf_conntrack_tuple t; 180 181 nf_ct_gre_keymap_destroy(ct); 182 183 /* try original (pns->pac) tuple */ 184 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 185 t.dst.protonum = IPPROTO_GRE; 186 t.src.u.gre.key = ct_pptp_info->pns_call_id; 187 t.dst.u.gre.key = ct_pptp_info->pac_call_id; 188 if (!destroy_sibling_or_exp(net, ct, &t)) 189 pr_debug("failed to timeout original pns->pac ct/exp\n"); 190 191 /* try reply (pac->pns) tuple */ 192 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 193 t.dst.protonum = IPPROTO_GRE; 194 t.src.u.gre.key = ct_pptp_info->pac_call_id; 195 t.dst.u.gre.key = ct_pptp_info->pns_call_id; 196 if (!destroy_sibling_or_exp(net, ct, &t)) 197 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 198 } 199 200 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 201 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 202 { 203 struct nf_conntrack_expect *exp_orig, *exp_reply; 204 enum ip_conntrack_dir dir; 205 int ret = 1; 206 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre; 207 208 exp_orig = nf_ct_expect_alloc(ct); 209 if (exp_orig == NULL) 210 goto out; 211 212 exp_reply = nf_ct_expect_alloc(ct); 213 if (exp_reply == NULL) 214 goto out_put_orig; 215 216 /* original direction, PNS->PAC */ 217 dir = IP_CT_DIR_ORIGINAL; 218 nf_ct_expect_init(exp_orig, NF_CT_EXPECT_CLASS_DEFAULT, 219 nf_ct_l3num(ct), 220 &ct->tuplehash[dir].tuple.src.u3, 221 &ct->tuplehash[dir].tuple.dst.u3, 222 IPPROTO_GRE, &peer_callid, &callid); 223 exp_orig->expectfn = pptp_expectfn; 224 225 /* reply direction, PAC->PNS */ 226 dir = IP_CT_DIR_REPLY; 227 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT, 228 nf_ct_l3num(ct), 229 &ct->tuplehash[dir].tuple.src.u3, 230 &ct->tuplehash[dir].tuple.dst.u3, 231 IPPROTO_GRE, &callid, &peer_callid); 232 exp_reply->expectfn = pptp_expectfn; 233 234 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre); 235 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK) 236 nf_nat_pptp_exp_gre(exp_orig, exp_reply); 237 if (nf_ct_expect_related(exp_orig) != 0) 238 goto out_put_both; 239 if (nf_ct_expect_related(exp_reply) != 0) 240 goto out_unexpect_orig; 241 242 /* Add GRE keymap entries */ 243 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 244 goto out_unexpect_both; 245 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 246 nf_ct_gre_keymap_destroy(ct); 247 goto out_unexpect_both; 248 } 249 ret = 0; 250 251 out_put_both: 252 nf_ct_expect_put(exp_reply); 253 out_put_orig: 254 nf_ct_expect_put(exp_orig); 255 out: 256 return ret; 257 258 out_unexpect_both: 259 nf_ct_unexpect_related(exp_reply); 260 out_unexpect_orig: 261 nf_ct_unexpect_related(exp_orig); 262 goto out_put_both; 263 } 264 265 static int 266 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, 267 struct PptpControlHeader *ctlh, 268 union pptp_ctrl_union *pptpReq, 269 unsigned int reqlen, 270 struct nf_conn *ct, 271 enum ip_conntrack_info ctinfo) 272 { 273 struct nf_ct_pptp_master *info = nfct_help_data(ct); 274 u_int16_t msg; 275 __be16 cid = 0, pcid = 0; 276 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound; 277 278 msg = ntohs(ctlh->messageType); 279 pr_debug("inbound control message %s\n", pptp_msg_name[msg]); 280 281 switch (msg) { 282 case PPTP_START_SESSION_REPLY: 283 /* server confirms new control session */ 284 if (info->sstate < PPTP_SESSION_REQUESTED) 285 goto invalid; 286 if (pptpReq->srep.resultCode == PPTP_START_OK) 287 info->sstate = PPTP_SESSION_CONFIRMED; 288 else 289 info->sstate = PPTP_SESSION_ERROR; 290 break; 291 292 case PPTP_STOP_SESSION_REPLY: 293 /* server confirms end of control session */ 294 if (info->sstate > PPTP_SESSION_STOPREQ) 295 goto invalid; 296 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 297 info->sstate = PPTP_SESSION_NONE; 298 else 299 info->sstate = PPTP_SESSION_ERROR; 300 break; 301 302 case PPTP_OUT_CALL_REPLY: 303 /* server accepted call, we now expect GRE frames */ 304 if (info->sstate != PPTP_SESSION_CONFIRMED) 305 goto invalid; 306 if (info->cstate != PPTP_CALL_OUT_REQ && 307 info->cstate != PPTP_CALL_OUT_CONF) 308 goto invalid; 309 310 cid = pptpReq->ocack.callID; 311 pcid = pptpReq->ocack.peersCallID; 312 if (info->pns_call_id != pcid) 313 goto invalid; 314 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name[msg], 315 ntohs(cid), ntohs(pcid)); 316 317 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 318 info->cstate = PPTP_CALL_OUT_CONF; 319 info->pac_call_id = cid; 320 exp_gre(ct, cid, pcid); 321 } else 322 info->cstate = PPTP_CALL_NONE; 323 break; 324 325 case PPTP_IN_CALL_REQUEST: 326 /* server tells us about incoming call request */ 327 if (info->sstate != PPTP_SESSION_CONFIRMED) 328 goto invalid; 329 330 cid = pptpReq->icreq.callID; 331 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 332 info->cstate = PPTP_CALL_IN_REQ; 333 info->pac_call_id = cid; 334 break; 335 336 case PPTP_IN_CALL_CONNECT: 337 /* server tells us about incoming call established */ 338 if (info->sstate != PPTP_SESSION_CONFIRMED) 339 goto invalid; 340 if (info->cstate != PPTP_CALL_IN_REP && 341 info->cstate != PPTP_CALL_IN_CONF) 342 goto invalid; 343 344 pcid = pptpReq->iccon.peersCallID; 345 cid = info->pac_call_id; 346 347 if (info->pns_call_id != pcid) 348 goto invalid; 349 350 pr_debug("%s, PCID=%X\n", pptp_msg_name[msg], ntohs(pcid)); 351 info->cstate = PPTP_CALL_IN_CONF; 352 353 /* we expect a GRE connection from PAC to PNS */ 354 exp_gre(ct, cid, pcid); 355 break; 356 357 case PPTP_CALL_DISCONNECT_NOTIFY: 358 /* server confirms disconnect */ 359 cid = pptpReq->disc.callID; 360 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 361 info->cstate = PPTP_CALL_NONE; 362 363 /* untrack this call id, unexpect GRE packets */ 364 pptp_destroy_siblings(ct); 365 break; 366 367 case PPTP_WAN_ERROR_NOTIFY: 368 case PPTP_SET_LINK_INFO: 369 case PPTP_ECHO_REQUEST: 370 case PPTP_ECHO_REPLY: 371 /* I don't have to explain these ;) */ 372 break; 373 374 default: 375 goto invalid; 376 } 377 378 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound); 379 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK) 380 return nf_nat_pptp_inbound(skb, ct, ctinfo, 381 protoff, ctlh, pptpReq); 382 return NF_ACCEPT; 383 384 invalid: 385 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 386 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 387 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 388 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 389 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 390 return NF_ACCEPT; 391 } 392 393 static int 394 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, 395 struct PptpControlHeader *ctlh, 396 union pptp_ctrl_union *pptpReq, 397 unsigned int reqlen, 398 struct nf_conn *ct, 399 enum ip_conntrack_info ctinfo) 400 { 401 struct nf_ct_pptp_master *info = nfct_help_data(ct); 402 u_int16_t msg; 403 __be16 cid = 0, pcid = 0; 404 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound; 405 406 msg = ntohs(ctlh->messageType); 407 pr_debug("outbound control message %s\n", pptp_msg_name[msg]); 408 409 switch (msg) { 410 case PPTP_START_SESSION_REQUEST: 411 /* client requests for new control session */ 412 if (info->sstate != PPTP_SESSION_NONE) 413 goto invalid; 414 info->sstate = PPTP_SESSION_REQUESTED; 415 break; 416 417 case PPTP_STOP_SESSION_REQUEST: 418 /* client requests end of control session */ 419 info->sstate = PPTP_SESSION_STOPREQ; 420 break; 421 422 case PPTP_OUT_CALL_REQUEST: 423 /* client initiating connection to server */ 424 if (info->sstate != PPTP_SESSION_CONFIRMED) 425 goto invalid; 426 info->cstate = PPTP_CALL_OUT_REQ; 427 /* track PNS call id */ 428 cid = pptpReq->ocreq.callID; 429 pr_debug("%s, CID=%X\n", pptp_msg_name[msg], ntohs(cid)); 430 info->pns_call_id = cid; 431 break; 432 433 case PPTP_IN_CALL_REPLY: 434 /* client answers incoming call */ 435 if (info->cstate != PPTP_CALL_IN_REQ && 436 info->cstate != PPTP_CALL_IN_REP) 437 goto invalid; 438 439 cid = pptpReq->icack.callID; 440 pcid = pptpReq->icack.peersCallID; 441 if (info->pac_call_id != pcid) 442 goto invalid; 443 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name[msg], 444 ntohs(cid), ntohs(pcid)); 445 446 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 447 /* part two of the three-way handshake */ 448 info->cstate = PPTP_CALL_IN_REP; 449 info->pns_call_id = cid; 450 } else 451 info->cstate = PPTP_CALL_NONE; 452 break; 453 454 case PPTP_CALL_CLEAR_REQUEST: 455 /* client requests hangup of call */ 456 if (info->sstate != PPTP_SESSION_CONFIRMED) 457 goto invalid; 458 /* FUTURE: iterate over all calls and check if 459 * call ID is valid. We don't do this without newnat, 460 * because we only know about last call */ 461 info->cstate = PPTP_CALL_CLEAR_REQ; 462 break; 463 464 case PPTP_SET_LINK_INFO: 465 case PPTP_ECHO_REQUEST: 466 case PPTP_ECHO_REPLY: 467 /* I don't have to explain these ;) */ 468 break; 469 470 default: 471 goto invalid; 472 } 473 474 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound); 475 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK) 476 return nf_nat_pptp_outbound(skb, ct, ctinfo, 477 protoff, ctlh, pptpReq); 478 return NF_ACCEPT; 479 480 invalid: 481 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 482 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 483 msg <= PPTP_MSG_MAX ? pptp_msg_name[msg] : pptp_msg_name[0], 484 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 485 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 486 return NF_ACCEPT; 487 } 488 489 static const unsigned int pptp_msg_size[] = { 490 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 491 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 492 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 493 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 494 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 495 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 496 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 497 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 498 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 499 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 500 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 501 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 502 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 503 }; 504 505 /* track caller id inside control connection, call expect_related */ 506 static int 507 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 508 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 509 510 { 511 int dir = CTINFO2DIR(ctinfo); 512 const struct nf_ct_pptp_master *info = nfct_help_data(ct); 513 const struct tcphdr *tcph; 514 struct tcphdr _tcph; 515 const struct pptp_pkt_hdr *pptph; 516 struct pptp_pkt_hdr _pptph; 517 struct PptpControlHeader _ctlh, *ctlh; 518 union pptp_ctrl_union _pptpReq, *pptpReq; 519 unsigned int tcplen = skb->len - protoff; 520 unsigned int datalen, reqlen, nexthdr_off; 521 int oldsstate, oldcstate; 522 int ret; 523 u_int16_t msg; 524 525 #if IS_ENABLED(CONFIG_NF_NAT) 526 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) { 527 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT); 528 529 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC)) 530 return NF_DROP; 531 } 532 #endif 533 /* don't do any tracking before tcp handshake complete */ 534 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 535 return NF_ACCEPT; 536 537 nexthdr_off = protoff; 538 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 539 BUG_ON(!tcph); 540 nexthdr_off += tcph->doff * 4; 541 datalen = tcplen - tcph->doff * 4; 542 543 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 544 if (!pptph) { 545 pr_debug("no full PPTP header, can't track\n"); 546 return NF_ACCEPT; 547 } 548 nexthdr_off += sizeof(_pptph); 549 datalen -= sizeof(_pptph); 550 551 /* if it's not a control message we can't do anything with it */ 552 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 553 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 554 pr_debug("not a control packet\n"); 555 return NF_ACCEPT; 556 } 557 558 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 559 if (!ctlh) 560 return NF_ACCEPT; 561 nexthdr_off += sizeof(_ctlh); 562 datalen -= sizeof(_ctlh); 563 564 reqlen = datalen; 565 msg = ntohs(ctlh->messageType); 566 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 567 return NF_ACCEPT; 568 if (reqlen > sizeof(*pptpReq)) 569 reqlen = sizeof(*pptpReq); 570 571 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 572 if (!pptpReq) 573 return NF_ACCEPT; 574 575 oldsstate = info->sstate; 576 oldcstate = info->cstate; 577 578 spin_lock_bh(&nf_pptp_lock); 579 580 /* FIXME: We just blindly assume that the control connection is always 581 * established from PNS->PAC. However, RFC makes no guarantee */ 582 if (dir == IP_CT_DIR_ORIGINAL) 583 /* client -> server (PNS -> PAC) */ 584 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 585 ctinfo); 586 else 587 /* server -> client (PAC -> PNS) */ 588 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 589 ctinfo); 590 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 591 oldsstate, info->sstate, oldcstate, info->cstate); 592 spin_unlock_bh(&nf_pptp_lock); 593 594 return ret; 595 } 596 597 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 598 .max_expected = 2, 599 .timeout = 5 * 60, 600 }; 601 602 /* control protocol helper */ 603 static struct nf_conntrack_helper pptp __read_mostly = { 604 .name = "pptp", 605 .me = THIS_MODULE, 606 .tuple.src.l3num = AF_INET, 607 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 608 .tuple.dst.protonum = IPPROTO_TCP, 609 .help = conntrack_pptp_help, 610 .destroy = pptp_destroy_siblings, 611 .expect_policy = &pptp_exp_policy, 612 }; 613 614 static int __init nf_conntrack_pptp_init(void) 615 { 616 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master)); 617 618 return nf_conntrack_helper_register(&pptp); 619 } 620 621 static void __exit nf_conntrack_pptp_fini(void) 622 { 623 nf_conntrack_helper_unregister(&pptp); 624 } 625 626 module_init(nf_conntrack_pptp_init); 627 module_exit(nf_conntrack_pptp_fini); 628