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
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(sk: sk_pppox(po: sock));
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(lock: &chan_lock);
100 if (!sa->call_id) {
101 call_id = find_next_zero_bit(addr: callid_bitmap, MAX_CALLID, offset: call_id + 1);
102 if (call_id == MAX_CALLID) {
103 call_id = find_next_zero_bit(addr: callid_bitmap, MAX_CALLID, offset: 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(nr: sa->call_id, addr: callid_bitmap);
114 rcu_assign_pointer(callid_sock[sa->call_id], sock);
115 spin_unlock(lock: &chan_lock);
116
117 return 0;
118
119out_err:
120 spin_unlock(lock: &chan_lock);
121 return -1;
122}
123
124static void del_chan(struct pppox_sock *sock)
125{
126 spin_lock(lock: &chan_lock);
127 clear_bit(nr: sock->proto.pptp.src_addr.call_id, addr: callid_bitmap);
128 RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL);
129 spin_unlock(lock: &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, oif: sk->sk_bound_dev_if, mark: sk->sk_mark, tos: 0,
140 scope: RT_SCOPE_UNIVERSE, IPPROTO_GRE, flags: 0,
141 daddr: po->proto.pptp.dst_addr.sin_addr.s_addr,
142 saddr: po->proto.pptp.src_addr.sin_addr.s_addr,
143 dport: 0, sport: 0, uid: sock_net_uid(net, sk));
144 security_sk_classify_flow(sk, flic: flowi4_to_flowi_common(fl4));
145
146 return ip_route_output_flow(net, flp: 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 (sk_pppox(po)->sk_state & PPPOX_DEAD)
168 goto tx_drop;
169
170 rt = pptp_route_output(po, fl4: &fl4);
171 if (IS_ERR(ptr: 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, headroom: max_headroom);
180
181 if (!new_skb)
182 goto tx_error;
183
184 if (skb->sk)
185 skb_set_owner_w(skb: new_skb, sk: 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, len: 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, len: 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, len: 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, len: 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, len: 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, dst: &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(dst: &rt->dst);
252 iph->tot_len = htons(skb->len);
253
254 skb_dst_drop(skb);
255 skb_dst_set(skb, dst: &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(ip: iph);
262
263 ip_local_out(net, sk: 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 if (sock_queue_rcv_skb(sk, skb))
283 goto drop;
284 return NET_RX_SUCCESS;
285 }
286
287 header = (struct pptp_gre_header *)(skb->data);
288 headersize = sizeof(*header);
289
290 /* test if acknowledgement present */
291 if (GRE_IS_ACK(header->gre_hd.flags)) {
292 __u32 ack;
293
294 if (!pskb_may_pull(skb, len: headersize))
295 goto drop;
296 header = (struct pptp_gre_header *)(skb->data);
297
298 /* ack in different place if S = 0 */
299 ack = GRE_IS_SEQ(header->gre_hd.flags) ? ntohl(header->ack) :
300 ntohl(header->seq);
301 if (ack > opt->ack_recv)
302 opt->ack_recv = ack;
303 /* also handle sequence number wrap-around */
304 if (WRAPPED(ack, opt->ack_recv))
305 opt->ack_recv = ack;
306 } else {
307 headersize -= sizeof(header->ack);
308 }
309 /* test if payload present */
310 if (!GRE_IS_SEQ(header->gre_hd.flags))
311 goto drop;
312
313 payload_len = ntohs(header->payload_len);
314 seq = ntohl(header->seq);
315
316 /* check for incomplete packet (length smaller than expected) */
317 if (!pskb_may_pull(skb, len: headersize + payload_len))
318 goto drop;
319
320 payload = skb->data + headersize;
321 /* check for expected sequence number */
322 if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) {
323 if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) &&
324 (PPP_PROTOCOL(payload) == PPP_LCP) &&
325 ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP)))
326 goto allow_packet;
327 } else {
328 opt->seq_recv = seq;
329allow_packet:
330 skb_pull(skb, len: headersize);
331
332 if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) {
333 /* chop off address/control */
334 if (skb->len < 3)
335 goto drop;
336 skb_pull(skb, len: 2);
337 }
338
339 skb->ip_summed = CHECKSUM_NONE;
340 skb_set_network_header(skb, offset: skb->head-skb->data);
341 ppp_input(&po->chan, skb);
342
343 return NET_RX_SUCCESS;
344 }
345drop:
346 kfree_skb(skb);
347 return NET_RX_DROP;
348}
349
350static int pptp_rcv(struct sk_buff *skb)
351{
352 struct pppox_sock *po;
353 struct pptp_gre_header *header;
354 struct iphdr *iph;
355
356 if (skb->pkt_type != PACKET_HOST)
357 goto drop;
358
359 if (!pskb_may_pull(skb, len: 12))
360 goto drop;
361
362 iph = ip_hdr(skb);
363
364 header = (struct pptp_gre_header *)skb->data;
365
366 if (header->gre_hd.protocol != GRE_PROTO_PPP || /* PPTP-GRE protocol for PPTP */
367 GRE_IS_CSUM(header->gre_hd.flags) || /* flag CSUM should be clear */
368 GRE_IS_ROUTING(header->gre_hd.flags) || /* flag ROUTING should be clear */
369 !GRE_IS_KEY(header->gre_hd.flags) || /* flag KEY should be set */
370 (header->gre_hd.flags & GRE_FLAGS)) /* flag Recursion Ctrl should be clear */
371 /* if invalid, discard this packet */
372 goto drop;
373
374 po = lookup_chan(ntohs(header->call_id), s_addr: iph->saddr);
375 if (po) {
376 skb_dst_drop(skb);
377 nf_reset_ct(skb);
378 return sk_receive_skb(sk: sk_pppox(po), skb, nested: 0);
379 }
380drop:
381 kfree_skb(skb);
382 return NET_RX_DROP;
383}
384
385static int pptp_bind(struct socket *sock, struct sockaddr_unsized *uservaddr,
386 int sockaddr_len)
387{
388 struct sock *sk = sock->sk;
389 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
390 struct pppox_sock *po = pppox_sk(sk);
391 int error = 0;
392
393 if (sockaddr_len < sizeof(struct sockaddr_pppox))
394 return -EINVAL;
395
396 lock_sock(sk);
397
398 if (sk->sk_state & PPPOX_DEAD) {
399 error = -EALREADY;
400 goto out;
401 }
402
403 if (sk->sk_state & PPPOX_BOUND) {
404 error = -EBUSY;
405 goto out;
406 }
407
408 if (add_chan(sock: po, sa: &sp->sa_addr.pptp))
409 error = -EBUSY;
410 else
411 sk->sk_state |= PPPOX_BOUND;
412
413out:
414 release_sock(sk);
415 return error;
416}
417
418static int pptp_connect(struct socket *sock, struct sockaddr_unsized *uservaddr,
419 int sockaddr_len, int flags)
420{
421 struct sock *sk = sock->sk;
422 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
423 struct pppox_sock *po = pppox_sk(sk);
424 struct pptp_opt *opt = &po->proto.pptp;
425 struct rtable *rt;
426 struct flowi4 fl4;
427 int error = 0;
428
429 if (sockaddr_len < sizeof(struct sockaddr_pppox))
430 return -EINVAL;
431
432 if (sp->sa_protocol != PX_PROTO_PPTP)
433 return -EINVAL;
434
435 if (lookup_chan_dst(call_id: sp->sa_addr.pptp.call_id, d_addr: sp->sa_addr.pptp.sin_addr.s_addr))
436 return -EALREADY;
437
438 lock_sock(sk);
439 /* Check for already bound sockets */
440 if (sk->sk_state & PPPOX_CONNECTED) {
441 error = -EBUSY;
442 goto end;
443 }
444
445 /* Check for already disconnected sockets, on attempts to disconnect */
446 if (sk->sk_state & PPPOX_DEAD) {
447 error = -EALREADY;
448 goto end;
449 }
450
451 if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) {
452 error = -EINVAL;
453 goto end;
454 }
455
456 po->chan.private = sk;
457 po->chan.ops = &pptp_chan_ops;
458
459 rt = pptp_route_output(po, fl4: &fl4);
460 if (IS_ERR(ptr: rt)) {
461 error = -EHOSTUNREACH;
462 goto end;
463 }
464 sk_setup_caps(sk, dst: &rt->dst);
465
466 po->chan.mtu = dst_mtu(dst: &rt->dst);
467 if (!po->chan.mtu)
468 po->chan.mtu = PPP_MRU;
469 po->chan.mtu -= PPTP_HEADER_OVERHEAD;
470
471 po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header);
472 po->chan.direct_xmit = true;
473 error = ppp_register_channel(&po->chan);
474 if (error) {
475 pr_err("PPTP: failed to register PPP channel (%d)\n", error);
476 goto end;
477 }
478
479 opt->dst_addr = sp->sa_addr.pptp;
480 sk->sk_state |= PPPOX_CONNECTED;
481
482 end:
483 release_sock(sk);
484 return error;
485}
486
487static int pptp_getname(struct socket *sock, struct sockaddr *uaddr,
488 int peer)
489{
490 int len = sizeof(struct sockaddr_pppox);
491 struct sockaddr_pppox sp;
492
493 memset(&sp.sa_addr, 0, sizeof(sp.sa_addr));
494
495 sp.sa_family = AF_PPPOX;
496 sp.sa_protocol = PX_PROTO_PPTP;
497 sp.sa_addr.pptp = pppox_sk(sk: sock->sk)->proto.pptp.src_addr;
498
499 memcpy(uaddr, &sp, len);
500
501 return len;
502}
503
504static int pptp_release(struct socket *sock)
505{
506 struct sock *sk = sock->sk;
507 struct pppox_sock *po;
508 int error = 0;
509
510 if (!sk)
511 return 0;
512
513 lock_sock(sk);
514
515 if (sock_flag(sk, flag: SOCK_DEAD)) {
516 release_sock(sk);
517 return -EBADF;
518 }
519
520 po = pppox_sk(sk);
521 del_chan(sock: po);
522 synchronize_rcu();
523
524 pppox_unbind_sock(sk);
525 sk->sk_state = PPPOX_DEAD;
526
527 sock_orphan(sk);
528 sock->sk = NULL;
529
530 release_sock(sk);
531 sock_put(sk);
532
533 return error;
534}
535
536static void pptp_sock_destruct(struct sock *sk)
537{
538 if (!(sk->sk_state & PPPOX_DEAD)) {
539 del_chan(sock: pppox_sk(sk));
540 pppox_unbind_sock(sk);
541 }
542 skb_queue_purge(list: &sk->sk_receive_queue);
543 dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1));
544}
545
546static int pptp_create(struct net *net, struct socket *sock, int kern)
547{
548 int error = -ENOMEM;
549 struct sock *sk;
550 struct pppox_sock *po;
551 struct pptp_opt *opt;
552
553 sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, prot: &pptp_sk_proto, kern);
554 if (!sk)
555 goto out;
556
557 sock_init_data(sock, sk);
558
559 sock->state = SS_UNCONNECTED;
560 sock->ops = &pptp_ops;
561
562 sk->sk_backlog_rcv = pptp_rcv_core;
563 sk->sk_state = PPPOX_NONE;
564 sk->sk_type = SOCK_STREAM;
565 sk->sk_family = PF_PPPOX;
566 sk->sk_protocol = PX_PROTO_PPTP;
567 sk->sk_destruct = pptp_sock_destruct;
568
569 po = pppox_sk(sk);
570 opt = &po->proto.pptp;
571
572 opt->seq_sent = 0; opt->seq_recv = 0xffffffff;
573 opt->ack_recv = 0; opt->ack_sent = 0xffffffff;
574
575 error = 0;
576out:
577 return error;
578}
579
580static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
581 unsigned long arg)
582{
583 struct sock *sk = chan->private;
584 struct pppox_sock *po = pppox_sk(sk);
585 struct pptp_opt *opt = &po->proto.pptp;
586 void __user *argp = (void __user *)arg;
587 int __user *p = argp;
588 int err, val;
589
590 err = -EFAULT;
591 switch (cmd) {
592 case PPPIOCGFLAGS:
593 val = opt->ppp_flags;
594 if (put_user(val, p))
595 break;
596 err = 0;
597 break;
598 case PPPIOCSFLAGS:
599 if (get_user(val, p))
600 break;
601 opt->ppp_flags = val & ~SC_RCV_BITS;
602 err = 0;
603 break;
604 default:
605 err = -ENOTTY;
606 }
607
608 return err;
609}
610
611static const struct ppp_channel_ops pptp_chan_ops = {
612 .start_xmit = pptp_xmit,
613 .ioctl = pptp_ppp_ioctl,
614};
615
616static struct proto pptp_sk_proto __read_mostly = {
617 .name = "PPTP",
618 .owner = THIS_MODULE,
619 .obj_size = sizeof(struct pppox_sock),
620};
621
622static const struct proto_ops pptp_ops = {
623 .family = AF_PPPOX,
624 .owner = THIS_MODULE,
625 .release = pptp_release,
626 .bind = pptp_bind,
627 .connect = pptp_connect,
628 .socketpair = sock_no_socketpair,
629 .accept = sock_no_accept,
630 .getname = pptp_getname,
631 .listen = sock_no_listen,
632 .shutdown = sock_no_shutdown,
633 .sendmsg = sock_no_sendmsg,
634 .recvmsg = sock_no_recvmsg,
635 .mmap = sock_no_mmap,
636 .ioctl = pppox_ioctl,
637#ifdef CONFIG_COMPAT
638 .compat_ioctl = pppox_compat_ioctl,
639#endif
640};
641
642static const struct pppox_proto pppox_pptp_proto = {
643 .create = pptp_create,
644 .owner = THIS_MODULE,
645};
646
647static const struct gre_protocol gre_pptp_protocol = {
648 .handler = pptp_rcv,
649};
650
651static int __init pptp_init_module(void)
652{
653 int err = 0;
654 pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n");
655
656 callid_sock = vzalloc(array_size(sizeof(void *), (MAX_CALLID + 1)));
657 if (!callid_sock)
658 return -ENOMEM;
659
660 err = gre_add_protocol(proto: &gre_pptp_protocol, GREPROTO_PPTP);
661 if (err) {
662 pr_err("PPTP: can't add gre protocol\n");
663 goto out_mem_free;
664 }
665
666 err = proto_register(prot: &pptp_sk_proto, alloc_slab: 0);
667 if (err) {
668 pr_err("PPTP: can't register sk_proto\n");
669 goto out_gre_del_protocol;
670 }
671
672 err = register_pppox_proto(PX_PROTO_PPTP, pp: &pppox_pptp_proto);
673 if (err) {
674 pr_err("PPTP: can't register pppox_proto\n");
675 goto out_unregister_sk_proto;
676 }
677
678 return 0;
679
680out_unregister_sk_proto:
681 proto_unregister(prot: &pptp_sk_proto);
682out_gre_del_protocol:
683 gre_del_protocol(proto: &gre_pptp_protocol, GREPROTO_PPTP);
684out_mem_free:
685 vfree(addr: callid_sock);
686
687 return err;
688}
689
690static void __exit pptp_exit_module(void)
691{
692 unregister_pppox_proto(PX_PROTO_PPTP);
693 proto_unregister(prot: &pptp_sk_proto);
694 gre_del_protocol(proto: &gre_pptp_protocol, GREPROTO_PPTP);
695 vfree(addr: callid_sock);
696}
697
698module_init(pptp_init_module);
699module_exit(pptp_exit_module);
700
701MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");
702MODULE_AUTHOR("D. Kozlov <xeb@mail.ru>");
703MODULE_LICENSE("GPL");
704MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP);
705

source code of linux/drivers/net/ppp/pptp.c