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 struct rtable *rt; 163 struct net_device *tdev; 164 struct iphdr *iph; 165 int max_headroom; 166 167 if (sk_pppox(po)->sk_state & PPPOX_DEAD) 168 goto tx_drop; 169 170 rt = pptp_route_output(po, &fl4); 171 if (IS_ERR(rt)) 172 goto tx_drop; 173 174 tdev = rt->dst.dev; 175 176 max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph) + sizeof(*hdr) + 2; 177 178 if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { 179 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); 180 181 if (!new_skb) 182 goto tx_error; 183 184 if (skb->sk) 185 skb_set_owner_w(new_skb, skb->sk); 186 consume_skb(skb); 187 skb = new_skb; 188 } 189 190 /* Ensure we can safely access protocol field and LCP code */ 191 if (!pskb_may_pull(skb, 3)) 192 goto tx_error; 193 194 data = skb->data; 195 islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7; 196 197 /* compress protocol field */ 198 if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp) 199 skb_pull(skb, 1); 200 201 /* Put in the address/control bytes if necessary */ 202 if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) { 203 data = skb_push(skb, 2); 204 data[0] = PPP_ALLSTATIONS; 205 data[1] = PPP_UI; 206 } 207 208 len = skb->len; 209 210 seq_recv = opt->seq_recv; 211 212 if (opt->ack_sent == seq_recv) 213 header_len -= sizeof(hdr->ack); 214 215 /* Push down and install GRE header */ 216 skb_push(skb, header_len); 217 hdr = (struct pptp_gre_header *)(skb->data); 218 219 hdr->gre_hd.flags = GRE_KEY | GRE_VERSION_1 | GRE_SEQ; 220 hdr->gre_hd.protocol = GRE_PROTO_PPP; 221 hdr->call_id = htons(opt->dst_addr.call_id); 222 223 hdr->seq = htonl(++opt->seq_sent); 224 if (opt->ack_sent != seq_recv) { 225 /* send ack with this message */ 226 hdr->gre_hd.flags |= GRE_ACK; 227 hdr->ack = htonl(seq_recv); 228 opt->ack_sent = seq_recv; 229 } 230 hdr->payload_len = htons(len); 231 232 /* Push down and install the IP header. */ 233 234 skb_reset_transport_header(skb); 235 skb_push(skb, sizeof(*iph)); 236 skb_reset_network_header(skb); 237 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt)); 238 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED); 239 240 iph = ip_hdr(skb); 241 iph->version = 4; 242 iph->ihl = sizeof(struct iphdr) >> 2; 243 if (ip_dont_fragment(sk, &rt->dst)) 244 iph->frag_off = htons(IP_DF); 245 else 246 iph->frag_off = 0; 247 iph->protocol = IPPROTO_GRE; 248 iph->tos = 0; 249 iph->daddr = fl4.daddr; 250 iph->saddr = fl4.saddr; 251 iph->ttl = ip4_dst_hoplimit(&rt->dst); 252 iph->tot_len = htons(skb->len); 253 254 skb_dst_drop(skb); 255 skb_dst_set(skb, &rt->dst); 256 257 nf_reset_ct(skb); 258 259 skb->ip_summed = CHECKSUM_NONE; 260 ip_select_ident(net, skb, NULL); 261 ip_send_check(iph); 262 263 ip_local_out(net, skb->sk, skb); 264 return 1; 265 266 tx_error: 267 ip_rt_put(rt); 268 tx_drop: 269 kfree_skb(skb); 270 return 1; 271 } 272 273 static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb) 274 { 275 struct pppox_sock *po = pppox_sk(sk); 276 struct pptp_opt *opt = &po->proto.pptp; 277 int headersize, payload_len, seq; 278 __u8 *payload; 279 struct pptp_gre_header *header; 280 281 if (!(sk->sk_state & PPPOX_CONNECTED)) { 282 if (sock_queue_rcv_skb(sk, skb)) 283 goto drop; 284 return NET_RX_SUCCESS; 285 } 286 287 header = (struct pptp_gre_header *)(skb->data); 288 headersize = sizeof(*header); 289 290 /* test if acknowledgement present */ 291 if (GRE_IS_ACK(header->gre_hd.flags)) { 292 __u32 ack; 293 294 if (!pskb_may_pull(skb, headersize)) 295 goto drop; 296 header = (struct pptp_gre_header *)(skb->data); 297 298 /* ack in different place if S = 0 */ 299 ack = GRE_IS_SEQ(header->gre_hd.flags) ? ntohl(header->ack) : 300 ntohl(header->seq); 301 if (ack > opt->ack_recv) 302 opt->ack_recv = ack; 303 /* also handle sequence number wrap-around */ 304 if (WRAPPED(ack, opt->ack_recv)) 305 opt->ack_recv = ack; 306 } else { 307 headersize -= sizeof(header->ack); 308 } 309 /* test if payload present */ 310 if (!GRE_IS_SEQ(header->gre_hd.flags)) 311 goto drop; 312 313 payload_len = ntohs(header->payload_len); 314 seq = ntohl(header->seq); 315 316 /* check for incomplete packet (length smaller than expected) */ 317 if (!pskb_may_pull(skb, headersize + payload_len)) 318 goto drop; 319 320 payload = skb->data + headersize; 321 /* check for expected sequence number */ 322 if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) { 323 if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) && 324 (PPP_PROTOCOL(payload) == PPP_LCP) && 325 ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP))) 326 goto allow_packet; 327 } else { 328 opt->seq_recv = seq; 329 allow_packet: 330 skb_pull(skb, headersize); 331 332 if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) { 333 /* chop off address/control */ 334 if (skb->len < 3) 335 goto drop; 336 skb_pull(skb, 2); 337 } 338 339 skb->ip_summed = CHECKSUM_NONE; 340 skb_set_network_header(skb, skb->head-skb->data); 341 ppp_input(&po->chan, skb); 342 343 return NET_RX_SUCCESS; 344 } 345 drop: 346 kfree_skb(skb); 347 return NET_RX_DROP; 348 } 349 350 static int pptp_rcv(struct sk_buff *skb) 351 { 352 struct pppox_sock *po; 353 struct pptp_gre_header *header; 354 struct iphdr *iph; 355 356 if (skb->pkt_type != PACKET_HOST) 357 goto drop; 358 359 if (!pskb_may_pull(skb, 12)) 360 goto drop; 361 362 iph = ip_hdr(skb); 363 364 header = (struct pptp_gre_header *)skb->data; 365 366 if (header->gre_hd.protocol != GRE_PROTO_PPP || /* PPTP-GRE protocol for PPTP */ 367 GRE_IS_CSUM(header->gre_hd.flags) || /* flag CSUM should be clear */ 368 GRE_IS_ROUTING(header->gre_hd.flags) || /* flag ROUTING should be clear */ 369 !GRE_IS_KEY(header->gre_hd.flags) || /* flag KEY should be set */ 370 (header->gre_hd.flags & GRE_FLAGS)) /* flag Recursion Ctrl should be clear */ 371 /* if invalid, discard this packet */ 372 goto drop; 373 374 po = lookup_chan(ntohs(header->call_id), iph->saddr); 375 if (po) { 376 skb_dst_drop(skb); 377 nf_reset_ct(skb); 378 return sk_receive_skb(sk_pppox(po), skb, 0); 379 } 380 drop: 381 kfree_skb(skb); 382 return NET_RX_DROP; 383 } 384 385 static int pptp_bind(struct socket *sock, struct sockaddr *uservaddr, 386 int sockaddr_len) 387 { 388 struct sock *sk = sock->sk; 389 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 390 struct pppox_sock *po = pppox_sk(sk); 391 int error = 0; 392 393 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 394 return -EINVAL; 395 396 lock_sock(sk); 397 398 if (sk->sk_state & PPPOX_DEAD) { 399 error = -EALREADY; 400 goto out; 401 } 402 403 if (sk->sk_state & PPPOX_BOUND) { 404 error = -EBUSY; 405 goto out; 406 } 407 408 if (add_chan(po, &sp->sa_addr.pptp)) 409 error = -EBUSY; 410 else 411 sk->sk_state |= PPPOX_BOUND; 412 413 out: 414 release_sock(sk); 415 return error; 416 } 417 418 static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr, 419 int sockaddr_len, int flags) 420 { 421 struct sock *sk = sock->sk; 422 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr; 423 struct pppox_sock *po = pppox_sk(sk); 424 struct pptp_opt *opt = &po->proto.pptp; 425 struct rtable *rt; 426 struct flowi4 fl4; 427 int error = 0; 428 429 if (sockaddr_len < sizeof(struct sockaddr_pppox)) 430 return -EINVAL; 431 432 if (sp->sa_protocol != PX_PROTO_PPTP) 433 return -EINVAL; 434 435 if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr)) 436 return -EALREADY; 437 438 lock_sock(sk); 439 /* Check for already bound sockets */ 440 if (sk->sk_state & PPPOX_CONNECTED) { 441 error = -EBUSY; 442 goto end; 443 } 444 445 /* Check for already disconnected sockets, on attempts to disconnect */ 446 if (sk->sk_state & PPPOX_DEAD) { 447 error = -EALREADY; 448 goto end; 449 } 450 451 if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) { 452 error = -EINVAL; 453 goto end; 454 } 455 456 po->chan.private = sk; 457 po->chan.ops = &pptp_chan_ops; 458 459 rt = pptp_route_output(po, &fl4); 460 if (IS_ERR(rt)) { 461 error = -EHOSTUNREACH; 462 goto end; 463 } 464 sk_setup_caps(sk, &rt->dst); 465 466 po->chan.mtu = dst_mtu(&rt->dst); 467 if (!po->chan.mtu) 468 po->chan.mtu = PPP_MRU; 469 po->chan.mtu -= PPTP_HEADER_OVERHEAD; 470 471 po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header); 472 po->chan.direct_xmit = true; 473 error = ppp_register_channel(&po->chan); 474 if (error) { 475 pr_err("PPTP: failed to register PPP channel (%d)\n", error); 476 goto end; 477 } 478 479 opt->dst_addr = sp->sa_addr.pptp; 480 sk->sk_state |= PPPOX_CONNECTED; 481 482 end: 483 release_sock(sk); 484 return error; 485 } 486 487 static int pptp_getname(struct socket *sock, struct sockaddr *uaddr, 488 int peer) 489 { 490 int len = sizeof(struct sockaddr_pppox); 491 struct sockaddr_pppox sp; 492 493 memset(&sp.sa_addr, 0, sizeof(sp.sa_addr)); 494 495 sp.sa_family = AF_PPPOX; 496 sp.sa_protocol = PX_PROTO_PPTP; 497 sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr; 498 499 memcpy(uaddr, &sp, len); 500 501 return len; 502 } 503 504 static int pptp_release(struct socket *sock) 505 { 506 struct sock *sk = sock->sk; 507 struct pppox_sock *po; 508 int error = 0; 509 510 if (!sk) 511 return 0; 512 513 lock_sock(sk); 514 515 if (sock_flag(sk, SOCK_DEAD)) { 516 release_sock(sk); 517 return -EBADF; 518 } 519 520 po = pppox_sk(sk); 521 del_chan(po); 522 synchronize_rcu(); 523 524 pppox_unbind_sock(sk); 525 sk->sk_state = PPPOX_DEAD; 526 527 sock_orphan(sk); 528 sock->sk = NULL; 529 530 release_sock(sk); 531 sock_put(sk); 532 533 return error; 534 } 535 536 static void pptp_sock_destruct(struct sock *sk) 537 { 538 if (!(sk->sk_state & PPPOX_DEAD)) { 539 del_chan(pppox_sk(sk)); 540 pppox_unbind_sock(sk); 541 } 542 skb_queue_purge(&sk->sk_receive_queue); 543 dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1)); 544 } 545 546 static int pptp_create(struct net *net, struct socket *sock, int kern) 547 { 548 int error = -ENOMEM; 549 struct sock *sk; 550 struct pppox_sock *po; 551 struct pptp_opt *opt; 552 553 sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, kern); 554 if (!sk) 555 goto out; 556 557 sock_init_data(sock, sk); 558 559 sock->state = SS_UNCONNECTED; 560 sock->ops = &pptp_ops; 561 562 sk->sk_backlog_rcv = pptp_rcv_core; 563 sk->sk_state = PPPOX_NONE; 564 sk->sk_type = SOCK_STREAM; 565 sk->sk_family = PF_PPPOX; 566 sk->sk_protocol = PX_PROTO_PPTP; 567 sk->sk_destruct = pptp_sock_destruct; 568 569 po = pppox_sk(sk); 570 opt = &po->proto.pptp; 571 572 opt->seq_sent = 0; opt->seq_recv = 0xffffffff; 573 opt->ack_recv = 0; opt->ack_sent = 0xffffffff; 574 575 error = 0; 576 out: 577 return error; 578 } 579 580 static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd, 581 unsigned long arg) 582 { 583 struct sock *sk = chan->private; 584 struct pppox_sock *po = pppox_sk(sk); 585 struct pptp_opt *opt = &po->proto.pptp; 586 void __user *argp = (void __user *)arg; 587 int __user *p = argp; 588 int err, val; 589 590 err = -EFAULT; 591 switch (cmd) { 592 case PPPIOCGFLAGS: 593 val = opt->ppp_flags; 594 if (put_user(val, p)) 595 break; 596 err = 0; 597 break; 598 case PPPIOCSFLAGS: 599 if (get_user(val, p)) 600 break; 601 opt->ppp_flags = val & ~SC_RCV_BITS; 602 err = 0; 603 break; 604 default: 605 err = -ENOTTY; 606 } 607 608 return err; 609 } 610 611 static const struct ppp_channel_ops pptp_chan_ops = { 612 .start_xmit = pptp_xmit, 613 .ioctl = pptp_ppp_ioctl, 614 }; 615 616 static struct proto pptp_sk_proto __read_mostly = { 617 .name = "PPTP", 618 .owner = THIS_MODULE, 619 .obj_size = sizeof(struct pppox_sock), 620 }; 621 622 static const struct proto_ops pptp_ops = { 623 .family = AF_PPPOX, 624 .owner = THIS_MODULE, 625 .release = pptp_release, 626 .bind = pptp_bind, 627 .connect = pptp_connect, 628 .socketpair = sock_no_socketpair, 629 .accept = sock_no_accept, 630 .getname = pptp_getname, 631 .listen = sock_no_listen, 632 .shutdown = sock_no_shutdown, 633 .sendmsg = sock_no_sendmsg, 634 .recvmsg = sock_no_recvmsg, 635 .mmap = sock_no_mmap, 636 .ioctl = pppox_ioctl, 637 #ifdef CONFIG_COMPAT 638 .compat_ioctl = pppox_compat_ioctl, 639 #endif 640 }; 641 642 static const struct pppox_proto pppox_pptp_proto = { 643 .create = pptp_create, 644 .owner = THIS_MODULE, 645 }; 646 647 static const struct gre_protocol gre_pptp_protocol = { 648 .handler = pptp_rcv, 649 }; 650 651 static int __init pptp_init_module(void) 652 { 653 int err = 0; 654 pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n"); 655 656 callid_sock = vzalloc(array_size(sizeof(void *), (MAX_CALLID + 1))); 657 if (!callid_sock) 658 return -ENOMEM; 659 660 err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 661 if (err) { 662 pr_err("PPTP: can't add gre protocol\n"); 663 goto out_mem_free; 664 } 665 666 err = proto_register(&pptp_sk_proto, 0); 667 if (err) { 668 pr_err("PPTP: can't register sk_proto\n"); 669 goto out_gre_del_protocol; 670 } 671 672 err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto); 673 if (err) { 674 pr_err("PPTP: can't register pppox_proto\n"); 675 goto out_unregister_sk_proto; 676 } 677 678 return 0; 679 680 out_unregister_sk_proto: 681 proto_unregister(&pptp_sk_proto); 682 out_gre_del_protocol: 683 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 684 out_mem_free: 685 vfree(callid_sock); 686 687 return err; 688 } 689 690 static void __exit pptp_exit_module(void) 691 { 692 unregister_pppox_proto(PX_PROTO_PPTP); 693 proto_unregister(&pptp_sk_proto); 694 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP); 695 vfree(callid_sock); 696 } 697 698 module_init(pptp_init_module); 699 module_exit(pptp_exit_module); 700 701 MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol"); 702 MODULE_AUTHOR("D. Kozlov <xeb@mail.ru>"); 703 MODULE_LICENSE("GPL"); 704 MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP); 705