net/netfilter/nf_conntrack_pptp.c

   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         BUG_ON(!tcph);
 548         nexthdr_off += tcph->doff * 4;
 549         datalen = tcplen - tcph->doff * 4;
 550
 551         pptph = skb_header_pointer(skb, nexthdr_off, sizeof(_pptph), &_pptph);
 552         if (!pptph) {
 553                 pr_debug("no full PPTP header, can't track\n");
 554                 return NF_ACCEPT;
 555         }
 556         nexthdr_off += sizeof(_pptph);
 557         datalen -= sizeof(_pptph);
 558
 559         /* if it's not a control message we can't do anything with it */
 560         if (ntohs(pptph->packetType) != PPTP_PACKET_CONTROL ||
 561             ntohl(pptph->magicCookie) != PPTP_MAGIC_COOKIE) {
 562                 pr_debug("not a control packet\n");
 563                 return NF_ACCEPT;
 564         }
 565
 566         ctlh = skb_header_pointer(skb, nexthdr_off, sizeof(_ctlh), &_ctlh);
 567         if (!ctlh)
 568                 return NF_ACCEPT;
 569         nexthdr_off += sizeof(_ctlh);
 570         datalen -= sizeof(_ctlh);
 571
 572         reqlen = datalen;
 573         msg = ntohs(ctlh->messageType);
 574         if (msg > 0 && msg <= PPTP_MSG_MAX && reqlen < pptp_msg_size[msg])
 575                 return NF_ACCEPT;
 576         if (reqlen > sizeof(*pptpReq))
 577                 reqlen = sizeof(*pptpReq);
 578
 579         pptpReq = skb_header_pointer(skb, nexthdr_off, reqlen, &_pptpReq);
 580         if (!pptpReq)
 581                 return NF_ACCEPT;
 582
 583         oldsstate = info->sstate;
 584         oldcstate = info->cstate;
 585
 586         spin_lock_bh(&nf_pptp_lock);
 587
 588         /* FIXME: We just blindly assume that the control connection is always
 589          * established from PNS->PAC.  However, RFC makes no guarantee */
 590         if (dir == IP_CT_DIR_ORIGINAL)
 591                 /* client -> server (PNS -> PAC) */
 592                 ret = pptp_outbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 593                                         ctinfo);
 594         else
 595                 /* server -> client (PAC -> PNS) */
 596                 ret = pptp_inbound_pkt(skb, protoff, ctlh, pptpReq, reqlen, ct,
 597                                        ctinfo);
 598         pr_debug("sstate: %d->%d, cstate: %d->%d\n",
 599                  oldsstate, info->sstate, oldcstate, info->cstate);
 600         spin_unlock_bh(&nf_pptp_lock);
 601
 602         return ret;
 603 }
 604
 605 static const struct nf_conntrack_expect_policy pptp_exp_policy = {
 606         .max_expected   = 2,
 607         .timeout        = 5 * 60,
 608 };
 609
 610 /* control protocol helper */
 611 static struct nf_conntrack_helper pptp __read_mostly = {
 612         .name                   = "pptp",
 613         .me                     = THIS_MODULE,
 614         .tuple.src.l3num        = AF_INET,
 615         .tuple.src.u.tcp.port   = cpu_to_be16(PPTP_CONTROL_PORT),
 616         .tuple.dst.protonum     = IPPROTO_TCP,
 617         .help                   = conntrack_pptp_help,
 618         .destroy                = pptp_destroy_siblings,
 619         .expect_policy          = &pptp_exp_policy,
 620 };
 621
 622 static int __init nf_conntrack_pptp_init(void)
 623 {
 624         NF_CT_HELPER_BUILD_BUG_ON(sizeof(struct nf_ct_pptp_master));
 625
 626         return nf_conntrack_helper_register(&pptp);
 627 }
 628
 629 static void __exit nf_conntrack_pptp_fini(void)
 630 {
 631         nf_conntrack_helper_unregister(&pptp);
 632 }
 633
 634 module_init(nf_conntrack_pptp_init);
 635 module_exit(nf_conntrack_pptp_fini);