1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Connection tracking support for PPTP (Point to Point Tunneling Protocol). 4 * PPTP is 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 static const char *const pptp_msg_name_array[PPTP_MSG_MAX + 1] = { 76 [0] = "UNKNOWN_MESSAGE", 77 [PPTP_START_SESSION_REQUEST] = "START_SESSION_REQUEST", 78 [PPTP_START_SESSION_REPLY] = "START_SESSION_REPLY", 79 [PPTP_STOP_SESSION_REQUEST] = "STOP_SESSION_REQUEST", 80 [PPTP_STOP_SESSION_REPLY] = "STOP_SESSION_REPLY", 81 [PPTP_ECHO_REQUEST] = "ECHO_REQUEST", 82 [PPTP_ECHO_REPLY] = "ECHO_REPLY", 83 [PPTP_OUT_CALL_REQUEST] = "OUT_CALL_REQUEST", 84 [PPTP_OUT_CALL_REPLY] = "OUT_CALL_REPLY", 85 [PPTP_IN_CALL_REQUEST] = "IN_CALL_REQUEST", 86 [PPTP_IN_CALL_REPLY] = "IN_CALL_REPLY", 87 [PPTP_IN_CALL_CONNECT] = "IN_CALL_CONNECT", 88 [PPTP_CALL_CLEAR_REQUEST] = "CALL_CLEAR_REQUEST", 89 [PPTP_CALL_DISCONNECT_NOTIFY] = "CALL_DISCONNECT_NOTIFY", 90 [PPTP_WAN_ERROR_NOTIFY] = "WAN_ERROR_NOTIFY", 91 [PPTP_SET_LINK_INFO] = "SET_LINK_INFO" 92 }; 93 94 const char *pptp_msg_name(u_int16_t msg) 95 { 96 if (msg > PPTP_MSG_MAX) 97 return pptp_msg_name_array[0]; 98 99 return pptp_msg_name_array[msg]; 100 } 101 EXPORT_SYMBOL(pptp_msg_name); 102 #endif 103 104 #define SECS *HZ 105 #define MINS * 60 SECS 106 #define HOURS * 60 MINS 107 108 #define PPTP_GRE_TIMEOUT (10 MINS) 109 #define PPTP_GRE_STREAM_TIMEOUT (5 HOURS) 110 111 static void pptp_expectfn(struct nf_conn *ct, 112 struct nf_conntrack_expect *exp) 113 { 114 struct net *net = nf_ct_net(ct); 115 typeof(nf_nat_pptp_hook_expectfn) nf_nat_pptp_expectfn; 116 pr_debug("increasing timeouts\n"); 117 118 /* increase timeout of GRE data channel conntrack entry */ 119 ct->proto.gre.timeout = PPTP_GRE_TIMEOUT; 120 ct->proto.gre.stream_timeout = PPTP_GRE_STREAM_TIMEOUT; 121 122 /* Can you see how rusty this code is, compared with the pre-2.6.11 123 * one? That's what happened to my shiny newnat of 2002 ;( -HW */ 124 125 nf_nat_pptp_expectfn = rcu_dereference(nf_nat_pptp_hook_expectfn); 126 if (nf_nat_pptp_expectfn && ct->master->status & IPS_NAT_MASK) 127 nf_nat_pptp_expectfn(ct, exp); 128 else { 129 struct nf_conntrack_tuple inv_t; 130 struct nf_conntrack_expect *exp_other; 131 132 /* obviously this tuple inversion only works until you do NAT */ 133 nf_ct_invert_tuple(&inv_t, &exp->tuple); 134 pr_debug("trying to unexpect other dir: "); 135 nf_ct_dump_tuple(&inv_t); 136 137 exp_other = nf_ct_expect_find_get(net, nf_ct_zone(ct), &inv_t); 138 if (exp_other) { 139 /* delete other expectation. */ 140 pr_debug("found\n"); 141 nf_ct_unexpect_related(exp_other); 142 nf_ct_expect_put(exp_other); 143 } else { 144 pr_debug("not found\n"); 145 } 146 } 147 } 148 149 static int destroy_sibling_or_exp(struct net *net, struct nf_conn *ct, 150 const struct nf_conntrack_tuple *t) 151 { 152 const struct nf_conntrack_tuple_hash *h; 153 const struct nf_conntrack_zone *zone; 154 struct nf_conntrack_expect *exp; 155 struct nf_conn *sibling; 156 157 pr_debug("trying to timeout ct or exp for tuple "); 158 nf_ct_dump_tuple(t); 159 160 zone = nf_ct_zone(ct); 161 h = nf_conntrack_find_get(net, zone, t); 162 if (h) { 163 sibling = nf_ct_tuplehash_to_ctrack(h); 164 pr_debug("setting timeout of conntrack %p to 0\n", sibling); 165 sibling->proto.gre.timeout = 0; 166 sibling->proto.gre.stream_timeout = 0; 167 nf_ct_kill(sibling); 168 nf_ct_put(sibling); 169 return 1; 170 } else { 171 exp = nf_ct_expect_find_get(net, zone, t); 172 if (exp) { 173 pr_debug("unexpect_related of expect %p\n", exp); 174 nf_ct_unexpect_related(exp); 175 nf_ct_expect_put(exp); 176 return 1; 177 } 178 } 179 return 0; 180 } 181 182 /* timeout GRE data connections */ 183 static void pptp_destroy_siblings(struct nf_conn *ct) 184 { 185 struct net *net = nf_ct_net(ct); 186 const struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct); 187 struct nf_conntrack_tuple t; 188 189 nf_ct_gre_keymap_destroy(ct); 190 191 /* try original (pns->pac) tuple */ 192 memcpy(&t, &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple, sizeof(t)); 193 t.dst.protonum = IPPROTO_GRE; 194 t.src.u.gre.key = ct_pptp_info->pns_call_id; 195 t.dst.u.gre.key = ct_pptp_info->pac_call_id; 196 if (!destroy_sibling_or_exp(net, ct, &t)) 197 pr_debug("failed to timeout original pns->pac ct/exp\n"); 198 199 /* try reply (pac->pns) tuple */ 200 memcpy(&t, &ct->tuplehash[IP_CT_DIR_REPLY].tuple, sizeof(t)); 201 t.dst.protonum = IPPROTO_GRE; 202 t.src.u.gre.key = ct_pptp_info->pac_call_id; 203 t.dst.u.gre.key = ct_pptp_info->pns_call_id; 204 if (!destroy_sibling_or_exp(net, ct, &t)) 205 pr_debug("failed to timeout reply pac->pns ct/exp\n"); 206 } 207 208 /* expect GRE connections (PNS->PAC and PAC->PNS direction) */ 209 static int exp_gre(struct nf_conn *ct, __be16 callid, __be16 peer_callid) 210 { 211 struct nf_conntrack_expect *exp_orig, *exp_reply; 212 enum ip_conntrack_dir dir; 213 int ret = 1; 214 typeof(nf_nat_pptp_hook_exp_gre) nf_nat_pptp_exp_gre; 215 216 exp_orig = nf_ct_expect_alloc(ct); 217 if (exp_orig == NULL) 218 goto out; 219 220 exp_reply = nf_ct_expect_alloc(ct); 221 if (exp_reply == NULL) 222 goto out_put_orig; 223 224 /* original direction, PNS->PAC */ 225 dir = IP_CT_DIR_ORIGINAL; 226 nf_ct_expect_init(exp_orig, 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, &peer_callid, &callid); 231 exp_orig->expectfn = pptp_expectfn; 232 233 /* reply direction, PAC->PNS */ 234 dir = IP_CT_DIR_REPLY; 235 nf_ct_expect_init(exp_reply, NF_CT_EXPECT_CLASS_DEFAULT, 236 nf_ct_l3num(ct), 237 &ct->tuplehash[dir].tuple.src.u3, 238 &ct->tuplehash[dir].tuple.dst.u3, 239 IPPROTO_GRE, &callid, &peer_callid); 240 exp_reply->expectfn = pptp_expectfn; 241 242 nf_nat_pptp_exp_gre = rcu_dereference(nf_nat_pptp_hook_exp_gre); 243 if (nf_nat_pptp_exp_gre && ct->status & IPS_NAT_MASK) 244 nf_nat_pptp_exp_gre(exp_orig, exp_reply); 245 if (nf_ct_expect_related(exp_orig, 0) != 0) 246 goto out_put_both; 247 if (nf_ct_expect_related(exp_reply, 0) != 0) 248 goto out_unexpect_orig; 249 250 /* Add GRE keymap entries */ 251 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_ORIGINAL, &exp_orig->tuple) != 0) 252 goto out_unexpect_both; 253 if (nf_ct_gre_keymap_add(ct, IP_CT_DIR_REPLY, &exp_reply->tuple) != 0) { 254 nf_ct_gre_keymap_destroy(ct); 255 goto out_unexpect_both; 256 } 257 ret = 0; 258 259 out_put_both: 260 nf_ct_expect_put(exp_reply); 261 out_put_orig: 262 nf_ct_expect_put(exp_orig); 263 out: 264 return ret; 265 266 out_unexpect_both: 267 nf_ct_unexpect_related(exp_reply); 268 out_unexpect_orig: 269 nf_ct_unexpect_related(exp_orig); 270 goto out_put_both; 271 } 272 273 static int 274 pptp_inbound_pkt(struct sk_buff *skb, unsigned int protoff, 275 struct PptpControlHeader *ctlh, 276 union pptp_ctrl_union *pptpReq, 277 unsigned int reqlen, 278 struct nf_conn *ct, 279 enum ip_conntrack_info ctinfo) 280 { 281 struct nf_ct_pptp_master *info = nfct_help_data(ct); 282 u_int16_t msg; 283 __be16 cid = 0, pcid = 0; 284 typeof(nf_nat_pptp_hook_inbound) nf_nat_pptp_inbound; 285 286 msg = ntohs(ctlh->messageType); 287 pr_debug("inbound control message %s\n", pptp_msg_name(msg)); 288 289 switch (msg) { 290 case PPTP_START_SESSION_REPLY: 291 /* server confirms new control session */ 292 if (info->sstate < PPTP_SESSION_REQUESTED) 293 goto invalid; 294 if (pptpReq->srep.resultCode == PPTP_START_OK) 295 info->sstate = PPTP_SESSION_CONFIRMED; 296 else 297 info->sstate = PPTP_SESSION_ERROR; 298 break; 299 300 case PPTP_STOP_SESSION_REPLY: 301 /* server confirms end of control session */ 302 if (info->sstate > PPTP_SESSION_STOPREQ) 303 goto invalid; 304 if (pptpReq->strep.resultCode == PPTP_STOP_OK) 305 info->sstate = PPTP_SESSION_NONE; 306 else 307 info->sstate = PPTP_SESSION_ERROR; 308 break; 309 310 case PPTP_OUT_CALL_REPLY: 311 /* server accepted call, we now expect GRE frames */ 312 if (info->sstate != PPTP_SESSION_CONFIRMED) 313 goto invalid; 314 if (info->cstate != PPTP_CALL_OUT_REQ && 315 info->cstate != PPTP_CALL_OUT_CONF) 316 goto invalid; 317 318 cid = pptpReq->ocack.callID; 319 pcid = pptpReq->ocack.peersCallID; 320 if (info->pns_call_id != pcid) 321 goto invalid; 322 pr_debug("%s, CID=%X, PCID=%X\n", pptp_msg_name(msg), 323 ntohs(cid), ntohs(pcid)); 324 325 if (pptpReq->ocack.resultCode == PPTP_OUTCALL_CONNECT) { 326 info->cstate = PPTP_CALL_OUT_CONF; 327 info->pac_call_id = cid; 328 exp_gre(ct, cid, pcid); 329 } else 330 info->cstate = PPTP_CALL_NONE; 331 break; 332 333 case PPTP_IN_CALL_REQUEST: 334 /* server tells us about incoming call request */ 335 if (info->sstate != PPTP_SESSION_CONFIRMED) 336 goto invalid; 337 338 cid = pptpReq->icreq.callID; 339 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 340 info->cstate = PPTP_CALL_IN_REQ; 341 info->pac_call_id = cid; 342 break; 343 344 case PPTP_IN_CALL_CONNECT: 345 /* server tells us about incoming call established */ 346 if (info->sstate != PPTP_SESSION_CONFIRMED) 347 goto invalid; 348 if (info->cstate != PPTP_CALL_IN_REP && 349 info->cstate != PPTP_CALL_IN_CONF) 350 goto invalid; 351 352 pcid = pptpReq->iccon.peersCallID; 353 cid = info->pac_call_id; 354 355 if (info->pns_call_id != pcid) 356 goto invalid; 357 358 pr_debug("%s, PCID=%X\n", pptp_msg_name(msg), ntohs(pcid)); 359 info->cstate = PPTP_CALL_IN_CONF; 360 361 /* we expect a GRE connection from PAC to PNS */ 362 exp_gre(ct, cid, pcid); 363 break; 364 365 case PPTP_CALL_DISCONNECT_NOTIFY: 366 /* server confirms disconnect */ 367 cid = pptpReq->disc.callID; 368 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 369 info->cstate = PPTP_CALL_NONE; 370 371 /* untrack this call id, unexpect GRE packets */ 372 pptp_destroy_siblings(ct); 373 break; 374 375 case PPTP_WAN_ERROR_NOTIFY: 376 case PPTP_SET_LINK_INFO: 377 case PPTP_ECHO_REQUEST: 378 case PPTP_ECHO_REPLY: 379 /* I don't have to explain these ;) */ 380 break; 381 382 default: 383 goto invalid; 384 } 385 386 nf_nat_pptp_inbound = rcu_dereference(nf_nat_pptp_hook_inbound); 387 if (nf_nat_pptp_inbound && ct->status & IPS_NAT_MASK) 388 return nf_nat_pptp_inbound(skb, ct, ctinfo, 389 protoff, ctlh, pptpReq); 390 return NF_ACCEPT; 391 392 invalid: 393 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 394 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 395 pptp_msg_name(msg), 396 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 397 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 398 return NF_ACCEPT; 399 } 400 401 static int 402 pptp_outbound_pkt(struct sk_buff *skb, unsigned int protoff, 403 struct PptpControlHeader *ctlh, 404 union pptp_ctrl_union *pptpReq, 405 unsigned int reqlen, 406 struct nf_conn *ct, 407 enum ip_conntrack_info ctinfo) 408 { 409 struct nf_ct_pptp_master *info = nfct_help_data(ct); 410 u_int16_t msg; 411 __be16 cid = 0, pcid = 0; 412 typeof(nf_nat_pptp_hook_outbound) nf_nat_pptp_outbound; 413 414 msg = ntohs(ctlh->messageType); 415 pr_debug("outbound control message %s\n", pptp_msg_name(msg)); 416 417 switch (msg) { 418 case PPTP_START_SESSION_REQUEST: 419 /* client requests for new control session */ 420 if (info->sstate != PPTP_SESSION_NONE) 421 goto invalid; 422 info->sstate = PPTP_SESSION_REQUESTED; 423 break; 424 425 case PPTP_STOP_SESSION_REQUEST: 426 /* client requests end of control session */ 427 info->sstate = PPTP_SESSION_STOPREQ; 428 break; 429 430 case PPTP_OUT_CALL_REQUEST: 431 /* client initiating connection to server */ 432 if (info->sstate != PPTP_SESSION_CONFIRMED) 433 goto invalid; 434 info->cstate = PPTP_CALL_OUT_REQ; 435 /* track PNS call id */ 436 cid = pptpReq->ocreq.callID; 437 pr_debug("%s, CID=%X\n", pptp_msg_name(msg), ntohs(cid)); 438 info->pns_call_id = cid; 439 break; 440 441 case PPTP_IN_CALL_REPLY: 442 /* client answers incoming call */ 443 if (info->cstate != PPTP_CALL_IN_REQ && 444 info->cstate != PPTP_CALL_IN_REP) 445 goto invalid; 446 447 cid = pptpReq->icack.callID; 448 pcid = pptpReq->icack.peersCallID; 449 if (info->pac_call_id != pcid) 450 goto invalid; 451 pr_debug("%s, CID=%X PCID=%X\n", pptp_msg_name(msg), 452 ntohs(cid), ntohs(pcid)); 453 454 if (pptpReq->icack.resultCode == PPTP_INCALL_ACCEPT) { 455 /* part two of the three-way handshake */ 456 info->cstate = PPTP_CALL_IN_REP; 457 info->pns_call_id = cid; 458 } else 459 info->cstate = PPTP_CALL_NONE; 460 break; 461 462 case PPTP_CALL_CLEAR_REQUEST: 463 /* client requests hangup of call */ 464 if (info->sstate != PPTP_SESSION_CONFIRMED) 465 goto invalid; 466 /* FUTURE: iterate over all calls and check if 467 * call ID is valid. We don't do this without newnat, 468 * because we only know about last call */ 469 info->cstate = PPTP_CALL_CLEAR_REQ; 470 break; 471 472 case PPTP_SET_LINK_INFO: 473 case PPTP_ECHO_REQUEST: 474 case PPTP_ECHO_REPLY: 475 /* I don't have to explain these ;) */ 476 break; 477 478 default: 479 goto invalid; 480 } 481 482 nf_nat_pptp_outbound = rcu_dereference(nf_nat_pptp_hook_outbound); 483 if (nf_nat_pptp_outbound && ct->status & IPS_NAT_MASK) 484 return nf_nat_pptp_outbound(skb, ct, ctinfo, 485 protoff, ctlh, pptpReq); 486 return NF_ACCEPT; 487 488 invalid: 489 pr_debug("invalid %s: type=%d cid=%u pcid=%u " 490 "cstate=%d sstate=%d pns_cid=%u pac_cid=%u\n", 491 pptp_msg_name(msg), 492 msg, ntohs(cid), ntohs(pcid), info->cstate, info->sstate, 493 ntohs(info->pns_call_id), ntohs(info->pac_call_id)); 494 return NF_ACCEPT; 495 } 496 497 static const unsigned int pptp_msg_size[] = { 498 [PPTP_START_SESSION_REQUEST] = sizeof(struct PptpStartSessionRequest), 499 [PPTP_START_SESSION_REPLY] = sizeof(struct PptpStartSessionReply), 500 [PPTP_STOP_SESSION_REQUEST] = sizeof(struct PptpStopSessionRequest), 501 [PPTP_STOP_SESSION_REPLY] = sizeof(struct PptpStopSessionReply), 502 [PPTP_OUT_CALL_REQUEST] = sizeof(struct PptpOutCallRequest), 503 [PPTP_OUT_CALL_REPLY] = sizeof(struct PptpOutCallReply), 504 [PPTP_IN_CALL_REQUEST] = sizeof(struct PptpInCallRequest), 505 [PPTP_IN_CALL_REPLY] = sizeof(struct PptpInCallReply), 506 [PPTP_IN_CALL_CONNECT] = sizeof(struct PptpInCallConnected), 507 [PPTP_CALL_CLEAR_REQUEST] = sizeof(struct PptpClearCallRequest), 508 [PPTP_CALL_DISCONNECT_NOTIFY] = sizeof(struct PptpCallDisconnectNotify), 509 [PPTP_WAN_ERROR_NOTIFY] = sizeof(struct PptpWanErrorNotify), 510 [PPTP_SET_LINK_INFO] = sizeof(struct PptpSetLinkInfo), 511 }; 512 513 /* track caller id inside control connection, call expect_related */ 514 static int 515 conntrack_pptp_help(struct sk_buff *skb, unsigned int protoff, 516 struct nf_conn *ct, enum ip_conntrack_info ctinfo) 517 518 { 519 int dir = CTINFO2DIR(ctinfo); 520 const struct nf_ct_pptp_master *info = nfct_help_data(ct); 521 const struct tcphdr *tcph; 522 struct tcphdr _tcph; 523 const struct pptp_pkt_hdr *pptph; 524 struct pptp_pkt_hdr _pptph; 525 struct PptpControlHeader _ctlh, *ctlh; 526 union pptp_ctrl_union _pptpReq, *pptpReq; 527 unsigned int tcplen = skb->len - protoff; 528 unsigned int datalen, reqlen, nexthdr_off; 529 int oldsstate, oldcstate; 530 int ret; 531 u_int16_t msg; 532 533 #if IS_ENABLED(CONFIG_NF_NAT) 534 if (!nf_ct_is_confirmed(ct) && (ct->status & IPS_NAT_MASK)) { 535 struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT); 536 537 if (!nat && !nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC)) 538 return NF_DROP; 539 } 540 #endif 541 /* don't do any tracking before tcp handshake complete */ 542 if (ctinfo != IP_CT_ESTABLISHED && ctinfo != IP_CT_ESTABLISHED_REPLY) 543 return NF_ACCEPT; 544 545 nexthdr_off = protoff; 546 tcph = skb_header_pointer(skb, nexthdr_off, sizeof(_tcph), &_tcph); 547 if (!tcph) 548 return NF_ACCEPT; 549 550 nexthdr_off += tcph->doff * 4; 551 datalen = tcplen - tcph->doff * 4; 552 553 pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph); 554 if (!pptph) { 555 pr_debug("no full PPTP header, can't track\n"); 556 return NF_ACCEPT; 557 } 558 nexthdr_off += sizeof(_pptph); 559 datalen -= sizeof(_pptph); 560 561 /* if it's not a control message we can't do anything with it */ 562 if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL || 563 ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) { 564 pr_debug("not a control packet\n"); 565 return NF_ACCEPT; 566 } 567 568 ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh); 569 if (!ctlh) 570 return NF_ACCEPT; 571 nexthdr_off += sizeof(_ctlh); 572 datalen -= sizeof(_ctlh); 573 574 reqlen = datalen; 575 msg = ntohs(ctlh->messageType); 576 if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg]) 577 return NF_ACCEPT; 578 if (reqlen > sizeof(*pptpReq)) 579 reqlen = sizeof(*pptpReq); 580 581 pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq); 582 if (!pptpReq) 583 return NF_ACCEPT; 584 585 oldsstate = info->sstate; 586 oldcstate = info->cstate; 587 588 spin_lock_bh(&nf_pptp_lock); 589 590 /* FIXME: We just blindly assume that the control connection is always 591 * established from PNS->PAC. However, RFC makes no guarantee */ 592 if (dir == IP_CT_DIR_ORIGINAL) 593 /* client -> server (PNS -> PAC) */ 594 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 595 ctinfo); 596 else 597 /* server -> client (PAC -> PNS) */ 598 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct, 599 ctinfo); 600 pr_debug("sstate: %d->%d, cstate: %d->%d\n", 601 oldsstate, info->sstate, oldcstate, info->cstate); 602 spin_unlock_bh(&nf_pptp_lock); 603 604 return ret; 605 } 606 607 static const struct nf_conntrack_expect_policy pptp_exp_policy = { 608 .max_expected = 2, 609 .timeout = 5 * 60, 610 }; 611 612 /* control protocol helper */ 613 static struct nf_conntrack_helper pptp __read_mostly = { 614 .name = "pptp", 615 .me = THIS_MODULE, 616 .tuple.src.l3num = AF_INET, 617 .tuple.src.u.tcp.port = cpu_to_be16(PPTP_CONTROL_PORT), 618 .tuple.dst.protonum = IPPROTO_TCP, 619 .help = conntrack_pptp_help, 620 .destroy = pptp_destroy_siblings, 621 .expect_policy = &pptp_exp_policy, 622 }; 623 624 static int __init nf_conntrack_pptp_init(void) 625 { 626 NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master)); 627 628 return nf_conntrack_helper_register(&pptp); 629 } 630 631 static void __exit nf_conntrack_pptp_fini(void) 632 { 633 nf_conntrack_helper_unregister(&pptp); 634 } 635 636 module_init(nf_conntrack_pptp_init); 637 module_exit(nf_conntrack_pptp_fini); 638