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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 <[email protected]>
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
44static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1);
45static struct pppox_sock __rcu **callid_sock;
46
47static DEFINE_SPINLOCK(chan_lock);
48
49static struct proto pptp_sk_proto __read_mostly;
50static const struct ppp_channel_ops pptp_chan_ops;
51static const struct proto_ops pptp_ops;
52
53static 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
72static 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
94static 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
119out_err:
120 spin_unlock(&chan_lock);
121 return -1;
122}
123
124static 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
132static 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
149static 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
266tx_error:
267 ip_rt_put(rt);
268tx_drop:
269 kfree_skb(skb);
270 return 1;
271}
272
273static 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;
326allow_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 }
342drop:
343 kfree_skb(skb);
344 return NET_RX_DROP;
345}
346
347static 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 }
377drop:
378 kfree_skb(skb);
379 return NET_RX_DROP;
380}
381
382static 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
410out:
411 release_sock(sk);
412 return error;
413}
414
415static 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
484static 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
501static 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
533static 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
542static 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;
572out:
573 return error;
574}
575
576static 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
607static const struct ppp_channel_ops pptp_chan_ops = {
608 .start_xmit = pptp_xmit,
609 .ioctl = pptp_ppp_ioctl,
610};
611
612static struct proto pptp_sk_proto __read_mostly = {
613 .name = "PPTP",
614 .owner = THIS_MODULE,
615 .obj_size = sizeof(struct pppox_sock),
616};
617
618static 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
638static const struct pppox_proto pppox_pptp_proto = {
639 .create = pptp_create,
640 .owner = THIS_MODULE,
641};
642
643static const struct gre_protocol gre_pptp_protocol = {
644 .handler = pptp_rcv,
645};
646
647static 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
676out_unregister_sk_proto:
677 proto_unregister(&pptp_sk_proto);
678out_gre_del_protocol:
679 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
680out_mem_free:
681 vfree(callid_sock);
682
683 return err;
684}
685
686static 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
694module_init(pptp_init_module);
695module_exit(pptp_exit_module);
696
697MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");
698MODULE_AUTHOR("D. Kozlov <[email protected]>");
699MODULE_LICENSE("GPL");
700MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP);