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