1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Point-to-Point Tunneling Protocol for Linux 4 * 5 * Authors: Dmitry Kozlov <xeb@mail.ru> 6 */ 7 8 #include <linux/string.h> 9 #include <linux/module.h> 10 #include <linux/kernel.h> 11 #include <linux/slab.h> 12 #include <linux/errno.h> 13 #include <linux/netdevice.h> 14 #include <linux/net.h> 15 #include <linux/skbuff.h> 16 #include <linux/vmalloc.h> 17 #include <linux/init.h> 18 #include <linux/ppp_channel.h> 19 #include <linux/ppp_defs.h> 20 #include <linux/if_pppox.h> 21 #include <linux/ppp-ioctl.h> 22 #include <linux/notifier.h> 23 #include <linux/file.h> 24 #include <linux/in.h> 25 #include <linux/ip.h> 26 #include <linux/rcupdate.h> 27 #include <linux/security.h> 28 #include <linux/spinlock.h> 29 30 #include <net/sock.h> 31 #include <net/protocol.h> 32 #include <net/ip.h> 33 #include <net/icmp.h> 34 #include <net/route.h> 35 #include <net/gre.h> 36 #include <net/pptp.h> 37 38 #include <linux/uaccess.h> 39 40 #define PPTP_DRIVER_VERSION "0.8.5" 41 42 #define MAX_CALLID 65535 43 44 static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1); 45 static struct pppox_sock __rcu **callid_sock; 46 47 static DEFINE_SPINLOCK(chan_lock); 48 49 static struct proto pptp_sk_proto __read_mostly; 50 static const struct ppp_channel_ops pptp_chan_ops; 51 static const struct proto_ops pptp_ops; 52 53 static struct pppox_sock *lookup_chan(u16 call_id, __be32 s_addr) 54 { 55 struct pppox_sock *sock; 56 struct pptp_opt *opt; 57 58 rcu_read_lock(); 59 sock = rcu_dereference(callid_sock[call_id]); 60 if (sock) { 61 opt = &sock->proto.pptp; 62 if (opt->dst_addr.sin_addr.s_addr != s_addr) 63 sock = NULL; 64 else 65 sock_hold(sk_pppox(sock)); 66 } 67 rcu_read_unlock(); 68 69 return sock; 70 } 71 72 static int lookup_chan_dst(u16 call_id, __be32 d_addr) 73 { 74 struct pppox_sock *sock; 75 struct pptp_opt *opt; 76 int i; 77 78 rcu_read_lock(); 79 i = 1; 80 for_each_set_bit_from(i, callid_bitmap, MAX_CALLID) { 81 sock = rcu_dereference(callid_sock[i]); 82 if (!sock) 83 continue; 84 opt = &sock->proto.pptp; 85 if (opt->dst_addr.call_id == call_id && 86 opt->dst_addr.sin_addr.s_addr == d_addr) 87 break; 88 } 89 rcu_read_unlock(); 90 91 return i < MAX_CALLID; 92 } 93 94 static int add_chan(struct pppox_sock *sock, 95 struct pptp_addr *sa) 96 { 97 static int call_id; 98 99 spin_lock(&chan_lock); 100 if (!sa->call_id) { 101 call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, call_id + 1); 102 if (call_id == MAX_CALLID) { 103 call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, 1); 104 if (call_id == MAX_CALLID) 105 goto out_err; 106 } 107 sa->call_id = call_id; 108 } else if (test_bit(sa->call_id, callid_bitmap)) { 109 goto out_err; 110 } 111 112 sock->proto.pptp.src_addr = *sa; 113 set_bit(sa->call_id, callid_bitmap); 114 rcu_assign_pointer(callid_sock[sa->call_id], sock); 115 spin_unlock(&chan_lock); 116 117 return 0; 118 119 out_err: 120 spin_unlock(&chan_lock); 121 return -1; 122 } 123 124 static void del_chan(struct pppox_sock *sock) 125 { 126 spin_lock(&chan_lock); 127 clear_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap); 128 RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL); 129 spin_unlock(&chan_lock); 130 } 131 132 static struct rtable *pptp_route_output(const struct pppox_sock *po, 133 struct flowi4 *fl4) 134 { 135 const struct sock *sk = &po->sk; 136 struct net *net; 137 138 net = sock_net(sk); 139 flowi4_init_output(fl4, sk->sk_bound_dev_if, sk->sk_mark, 0, 140 RT_SCOPE_UNIVERSE, IPPROTO_GRE, 0, 141 po->proto.pptp.dst_addr.sin_addr.s_addr, 142 po->proto.pptp.src_addr.sin_addr.s_addr, 143 0, 0, sock_net_uid(net, sk)); 144 security_sk_classify_flow(sk, flowi4_to_flowi_common(fl4)); 145 146 return ip_route_output_flow(net, fl4, sk); 147 } 148 149 static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) 150 { 151 struct sock *sk = chan->private; 152 struct pppox_sock *po = pppox_sk(sk); 153 struct net *net = sock_net(sk); 154 struct pptp_opt *opt = &po->proto.pptp; 155 struct pptp_gre_header *hdr; 156 unsigned int header_len = sizeof(*hdr); 157 struct flowi4 fl4; 158 int islcp; 159 int len; 160 unsigned char *data; 161 __u32 seq_recv; 162 163 164 struct rtable *rt; 165 struct net_device *tdev; 166 struct iphdr *iph; 167 int max_headroom; 168 169 if (sk_pppox(po)->sk_state & PPPOX_DEAD) 170 goto tx_error; 171 172 rt = pptp_route_output(po, &fl4); 173 if (IS_ERR(rt)) 174 goto tx_error; 175 176 tdev = rt->dst.dev; 177 178 max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph) + sizeof(*hdr) + 2; 179 180 if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { 181 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); 182 if (!new_skb) { 183 ip_rt_put(rt); 184 goto tx_error; 185 } 186 if (skb->sk) 187 skb_set_owner_w(new_skb, skb->sk); 188 consume_skb(skb); 189 skb = new_skb; 190 } 191 192 data = skb->data; 193 islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7; 194 195 /* compress protocol field */ 196 if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp) 197 skb_pull(skb, 1); 198 199 /* Put in the address/control bytes if necessary */ 200 if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) { 201 data = skb_push(skb, 2); 202 data[0] = PPP_ALLSTATIONS; 203 data[1] = PPP_UI; 204 } 205 206 len = skb->len; 207 208 seq_recv = opt->seq_recv; 209 210 if (opt->ack_sent == seq_recv) 211 header_len -= sizeof(hdr->ack); 212 213 /* Push down and install GRE header */ 214 skb_push(skb, header_len); 215 hdr = (struct pptp_gre_header *)(skb->data); 216 217 hdr->gre_hd.flags = GRE_KEY | GRE_VERSION_1 | GRE_SEQ; 218 hdr->gre_hd.protocol = GRE_PROTO_PPP; 219 hdr->call_id = htons(opt->dst_addr.call_id); 220 221 hdr->seq = htonl(++opt->seq_sent); 222 if (opt->ack_sent != seq_recv) { 223 /* send ack with this message */ 224 hdr->gre_hd.flags |= GRE_ACK; 225 hdr->ack = htonl(seq_recv); 226 opt->ack_sent = seq_recv; 227 } 228 hdr->payload_len = htons(len); 229 230 /* Push down and install the IP header. */ 231 232 skb_reset_transport_header(skb); 233 skb_push(skb, sizeof(*iph)); 234 skb_reset_network_header(skb); 235 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 236 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED); 237 238 iph = ip_hdr(skb); 239 iph->version = 4; 240 iph->ihl = sizeof(struct iphdr) >> 2; 241 if (ip_dont_fragment(sk, &rt->dst)) 242 iph->frag_off = htons(IP_DF); 243 else 244 iph->frag_off = 0; 245 iph->protocol = IPPROTO_GRE; 246 iph->tos = 0; 247 iph->daddr = fl4.daddr; 248 iph->saddr = fl4.saddr; 249 iph->ttl = ip4_dst_hoplimit(&rt->dst); 250 iph->tot_len = htons(skb->len); 251 252 skb_dst_drop(skb); 253 skb_dst_set(skb, &rt->dst); 254 255 nf_reset_ct(skb); 256 257 skb->ip_summed = CHECKSUM_NONE; 258 ip_select_ident(net, skb, NULL); 259 ip_send_check(iph); 260 261 ip_local_out(net, skb->sk, skb); 262 return 1; 263 264 tx_error: 265 kfree_skb(skb); 266 return 1; 267 } 268 269 static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb) 270 { 271 struct pppox_sock *po = pppox_sk(sk); 272 struct pptp_opt *opt = &po->proto.pptp; 273 int headersize, payload_len, seq; 274 __u8 *payload; 275 struct pptp_gre_header *header; 276 277 if (!(sk->sk_state & PPPOX_CONNECTED)) { 278 if (sock_queue_rcv_skb(sk, skb)) 279 goto drop; 280 return NET_RX_SUCCESS; 281 } 282 283 header = (struct pptp_gre_header *)(skb->data); 284 headersize = sizeof(*header); 285 286 /* test if acknowledgement present */ 287 if (GRE_IS_ACK(header->gre_hd.flags)) { 288 __u32 ack; 289 290 if (!pskb_may_pull(skb, headersize)) 291 goto drop; 292 header = (struct pptp_gre_header *)(skb->data); 293 294 /* ack in different place if S = 0 */ 295 ack = GRE_IS_SEQ(header->gre_hd.flags) ? ntohl(header->ack) : 296 ntohl(header->seq); 297 if (ack > opt->ack_recv) 298 opt->ack_recv = ack; 299 /* also handle sequence number wrap-around */ 300 if (WRAPPED(ack, opt->ack_recv)) 301 opt->ack_recv = ack; 302 } else { 303 headersize -= sizeof(header->ack); 304 } 305 /* test if payload present */ 306 if (!GRE_IS_SEQ(header->gre_hd.flags)) 307 goto drop; 308 309 payload_len = ntohs(header->payload_len); 310 seq = ntohl(header->seq); 311 312 /* check for incomplete packet (length smaller than expected) */ 313 if (!pskb_may_pull(skb, headersize + payload_len)) 314 goto drop; 315 316 payload = skb->data + headersize; 317 /* check for expected sequence number */ 318 if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) { 319 if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) && 320 (PPP_PROTOCOL(payload) == PPP_LCP) && 321 ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP))) 322 goto allow_packet; 323 } else { 324 opt->seq_recv = seq; 325 allow_packet: 326 skb_pull(skb, headersize); 327 328 if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) { 329 /* chop off address/control */ 330 if (skb->len < 3) 331 goto drop; 332 skb_pull(skb, 2); 333 } 334 335 skb->ip_summed = CHECKSUM_NONE; 336 skb_set_network_header(skb, skb->head-skb->data); 337 ppp_input(&po->chan, skb); 338 339 return NET_RX_SUCCESS; 340 } 341 drop: 342 kfree_skb(skb); 343 return NET_RX_DROP; 344 } 345 346 static int pptp_rcv(struct sk_buff *skb) 347 { 348 struct pppox_sock *po; 349 struct pptp_gre_header *header; 350 struct iphdr *iph; 351 352 if (skb->pkt_type != PACKET_HOST) 353 goto drop; 354 355 if (!pskb_may_pull(skb, 12)) 356 goto drop; 357 358 iph = ip_hdr(skb); 359 360 header = (struct pptp_gre_header *)skb->data; 361 362 if (header->gre_hd.protocol != GRE_PROTO_PPP || /* PPTP-GRE protocol for PPTP */ 363 GRE_IS_CSUM(header->gre_hd.flags) || /* flag CSUM should be clear */ 364 GRE_IS_ROUTING(header->gre_hd.flags) || /* flag ROUTING should be clear */ 365 !GRE_IS_KEY(header->gre_hd.flags) || /* flag KEY should be set */ 366 (header->gre_hd.flags & GRE_FLAGS)) /* flag Recursion Ctrl should be clear */ 367 /* if invalid, discard this packet */ 368 goto drop; 369 370 po = lookup_chan(ntohs(header->call_id), iph->saddr); 371 if (po) { 372 skb_dst_drop(skb); 373 nf_reset_ct(skb); 374 return sk_receive_skb(sk_pppox(po), skb, 0); 375 } 376 drop: 377 kfree_skb(skb); 378 return NET_RX_DROP; 379 } 380 381 static int pptp_bind(struct socket *sock, struct sockaddr *uservaddr, 382 int sockaddr_len) 383 { 384 struct sock *sk = sock->sk; 385 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 386 struct pppox_sock *po = pppox_sk(sk); 387 int error = 0; 388 389 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 390 return -EINVAL; 391 392 lock_sock(sk); 393 394 if (sk->sk_state & PPPOX_DEAD) { 395 error = -EALREADY; 396 goto out; 397 } 398 399 if (sk->sk_state & PPPOX_BOUND) { 400 error = -EBUSY; 401 goto out; 402 } 403 404 if (add_chan(po, &sp->sa_addr.pptp)) 405 error = -EBUSY; 406 else 407 sk->sk_state |= PPPOX_BOUND; 408 409 out: 410 release_sock(sk); 411 return error; 412 } 413 414 static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr, 415 int sockaddr_len, int flags) 416 { 417 struct sock *sk = sock->sk; 418 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 419 struct pppox_sock *po = pppox_sk(sk); 420 struct pptp_opt *opt = &po->proto.pptp; 421 struct rtable *rt; 422 struct flowi4 fl4; 423 int error = 0; 424 425 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 426 return -EINVAL; 427 428 if (sp->sa_protocol != PX_PROTO_PPTP) 429 return -EINVAL; 430 431 if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr)) 432 return -EALREADY; 433 434 lock_sock(sk); 435 /* Check for already bound sockets */ 436 if (sk->sk_state & PPPOX_CONNECTED) { 437 error = -EBUSY; 438 goto end; 439 } 440 441 /* Check for already disconnected sockets, on attempts to disconnect */ 442 if (sk->sk_state & PPPOX_DEAD) { 443 error = -EALREADY; 444 goto end; 445 } 446 447 if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) { 448 error = -EINVAL; 449 goto end; 450 } 451 452 po->chan.private = sk; 453 po->chan.ops = &pptp_chan_ops; 454 455 rt = pptp_route_output(po, &fl4); 456 if (IS_ERR(rt)) { 457 error = -EHOSTUNREACH; 458 goto end; 459 } 460 sk_setup_caps(sk, &rt->dst); 461 462 po->chan.mtu = dst_mtu(&rt->dst); 463 if (!po->chan.mtu) 464 po->chan.mtu = PPP_MRU; 465 po->chan.mtu -= PPTP_HEADER_OVERHEAD; 466 467 po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header); 468 error = ppp_register_channel(&po->chan); 469 if (error) { 470 pr_err("PPTP: failed to register PPP channel (%d)\n", error); 471 goto end; 472 } 473 474 opt->dst_addr = sp->sa_addr.pptp; 475 sk->sk_state |= PPPOX_CONNECTED; 476 477 end: 478 release_sock(sk); 479 return error; 480 } 481 482 static int pptp_getname(struct socket *sock, struct sockaddr *uaddr, 483 int peer) 484 { 485 int len = sizeof(struct sockaddr_pppox); 486 struct sockaddr_pppox sp; 487 488 memset(&sp.sa_addr, 0, sizeof(sp.sa_addr)); 489 490 sp.sa_family = AF_PPPOX; 491 sp.sa_protocol = PX_PROTO_PPTP; 492 sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr; 493 494 memcpy(uaddr, &sp, len); 495 496 return len; 497 } 498 499 static int pptp_release(struct socket *sock) 500 { 501 struct sock *sk = sock->sk; 502 struct pppox_sock *po; 503 int error = 0; 504 505 if (!sk) 506 return 0; 507 508 lock_sock(sk); 509 510 if (sock_flag(sk, SOCK_DEAD)) { 511 release_sock(sk); 512 return -EBADF; 513 } 514 515 po = pppox_sk(sk); 516 del_chan(po); 517 synchronize_rcu(); 518 519 pppox_unbind_sock(sk); 520 sk->sk_state = PPPOX_DEAD; 521 522 sock_orphan(sk); 523 sock->sk = NULL; 524 525 release_sock(sk); 526 sock_put(sk); 527 528 return error; 529 } 530 531 static void pptp_sock_destruct(struct sock *sk) 532 { 533 if (!(sk->sk_state & PPPOX_DEAD)) { 534 del_chan(pppox_sk(sk)); 535 pppox_unbind_sock(sk); 536 } 537 skb_queue_purge(&sk->sk_receive_queue); 538 dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1)); 539 } 540 541 static int pptp_create(struct net *net, struct socket *sock, int kern) 542 { 543 int error = -ENOMEM; 544 struct sock *sk; 545 struct pppox_sock *po; 546 struct pptp_opt *opt; 547 548 sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, kern); 549 if (!sk) 550 goto out; 551 552 sock_init_data(sock, sk); 553 554 sock->state = SS_UNCONNECTED; 555 sock->ops = &pptp_ops; 556 557 sk->sk_backlog_rcv = pptp_rcv_core; 558 sk->sk_state = PPPOX_NONE; 559 sk->sk_type = SOCK_STREAM; 560 sk->sk_family = PF_PPPOX; 561 sk->sk_protocol = PX_PROTO_PPTP; 562 sk->sk_destruct = pptp_sock_destruct; 563 564 po = pppox_sk(sk); 565 opt = &po->proto.pptp; 566 567 opt->seq_sent = 0; opt->seq_recv = 0xffffffff; 568 opt->ack_recv = 0; opt->ack_sent = 0xffffffff; 569 570 error = 0; 571 out: 572 return error; 573 } 574 575 static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd, 576 unsigned long arg) 577 { 578 struct sock *sk = chan->private; 579 struct pppox_sock *po = pppox_sk(sk); 580 struct pptp_opt *opt = &po->proto.pptp; 581 void __user *argp = (void __user *)arg; 582 int __user *p = argp; 583 int err, val; 584 585 err = -EFAULT; 586 switch (cmd) { 587 case PPPIOCGFLAGS: 588 val = opt->ppp_flags; 589 if (put_user(val, p)) 590 break; 591 err = 0; 592 break; 593 case PPPIOCSFLAGS: 594 if (get_user(val, p)) 595 break; 596 opt->ppp_flags = val & ~SC_RCV_BITS; 597 err = 0; 598 break; 599 default: 600 err = -ENOTTY; 601 } 602 603 return err; 604 } 605 606 static const struct ppp_channel_ops pptp_chan_ops = { 607 .start_xmit = pptp_xmit, 608 .ioctl = pptp_ppp_ioctl, 609 }; 610 611 static struct proto pptp_sk_proto __read_mostly = { 612 .name = "PPTP", 613 .owner = THIS_MODULE, 614 .obj_size = sizeof(struct pppox_sock), 615 }; 616 617 static const struct proto_ops pptp_ops = { 618 .family = AF_PPPOX, 619 .owner = THIS_MODULE, 620 .release = pptp_release, 621 .bind = pptp_bind, 622 .connect = pptp_connect, 623 .socketpair = sock_no_socketpair, 624 .accept = sock_no_accept, 625 .getname = pptp_getname, 626 .listen = sock_no_listen, 627 .shutdown = sock_no_shutdown, 628 .sendmsg = sock_no_sendmsg, 629 .recvmsg = sock_no_recvmsg, 630 .mmap = sock_no_mmap, 631 .ioctl = pppox_ioctl, 632 #ifdef CONFIG_COMPAT 633 .compat_ioctl = pppox_compat_ioctl, 634 #endif 635 }; 636 637 static const struct pppox_proto pppox_pptp_proto = { 638 .create = pptp_create, 639 .owner = THIS_MODULE, 640 }; 641 642 static const struct gre_protocol gre_pptp_protocol = { 643 .handler = pptp_rcv, 644 }; 645 646 static int __init pptp_init_module(void) 647 { 648 int err = 0; 649 pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n"); 650 651 callid_sock = vzalloc(array_size(sizeof(void *), (MAX_CALLID + 1))); 652 if (!callid_sock) 653 return -ENOMEM; 654 655 err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 656 if (err) { 657 pr_err("PPTP: can't add gre protocol\n"); 658 goto out_mem_free; 659 } 660 661 err = proto_register(&pptp_sk_proto, 0); 662 if (err) { 663 pr_err("PPTP: can't register sk_proto\n"); 664 goto out_gre_del_protocol; 665 } 666 667 err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto); 668 if (err) { 669 pr_err("PPTP: can't register pppox_proto\n"); 670 goto out_unregister_sk_proto; 671 } 672 673 return 0; 674 675 out_unregister_sk_proto: 676 proto_unregister(&pptp_sk_proto); 677 out_gre_del_protocol: 678 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 679 out_mem_free: 680 vfree(callid_sock); 681 682 return err; 683 } 684 685 static void __exit pptp_exit_module(void) 686 { 687 unregister_pppox_proto(PX_PROTO_PPTP); 688 proto_unregister(&pptp_sk_proto); 689 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 690 vfree(callid_sock); 691 } 692 693 module_init(pptp_init_module); 694 module_exit(pptp_exit_module); 695 696 MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol"); 697 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)"); 698 MODULE_LICENSE("GPL"); 699 MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP); 700