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