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