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