/drivers/net/ppp/pptp.c

  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), sk->sk_bound_dev_if);
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),
448				   sk->sk_bound_dev_if);
449	if (IS_ERR(rt)) {
450		error = -EHOSTUNREACH;
451		goto end;
452	}
453	sk_setup_caps(sk, &rt->dst);
454
455	po->chan.mtu = dst_mtu(&rt->dst);
456	if (!po->chan.mtu)
457		po->chan.mtu = PPP_MRU;
458	po->chan.mtu -= PPTP_HEADER_OVERHEAD;
459
460	po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header);
461	error = ppp_register_channel(&po->chan);
462	if (error) {
463		pr_err("PPTP: failed to register PPP channel (%d)\n", error);
464		goto end;
465	}
466
467	opt->dst_addr = sp->sa_addr.pptp;
468	sk->sk_state |= PPPOX_CONNECTED;
469
470 end:
471	release_sock(sk);
472	return error;
473}
474
475static int pptp_getname(struct socket *sock, struct sockaddr *uaddr,
476	int peer)
477{
478	int len = sizeof(struct sockaddr_pppox);
479	struct sockaddr_pppox sp;
480
481	memset(&sp.sa_addr, 0, sizeof(sp.sa_addr));
482
483	sp.sa_family    = AF_PPPOX;
484	sp.sa_protocol  = PX_PROTO_PPTP;
485	sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr;
486
487	memcpy(uaddr, &sp, len);
488
489	return len;
490}
491
492static int pptp_release(struct socket *sock)
493{
494	struct sock *sk = sock->sk;
495	struct pppox_sock *po;
496	int error = 0;
497
498	if (!sk)
499		return 0;
500
501	lock_sock(sk);
502
503	if (sock_flag(sk, SOCK_DEAD)) {
504		release_sock(sk);
505		return -EBADF;
506	}
507
508	po = pppox_sk(sk);
509	del_chan(po);
510	synchronize_rcu();
511
512	pppox_unbind_sock(sk);
513	sk->sk_state = PPPOX_DEAD;
514
515	sock_orphan(sk);
516	sock->sk = NULL;
517
518	release_sock(sk);
519	sock_put(sk);
520
521	return error;
522}
523
524static void pptp_sock_destruct(struct sock *sk)
525{
526	if (!(sk->sk_state & PPPOX_DEAD)) {
527		del_chan(pppox_sk(sk));
528		pppox_unbind_sock(sk);
529	}
530	skb_queue_purge(&sk->sk_receive_queue);
531	dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1));
532}
533
534static int pptp_create(struct net *net, struct socket *sock, int kern)
535{
536	int error = -ENOMEM;
537	struct sock *sk;
538	struct pppox_sock *po;
539	struct pptp_opt *opt;
540
541	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, kern);
542	if (!sk)
543		goto out;
544
545	sock_init_data(sock, sk);
546
547	sock->state = SS_UNCONNECTED;
548	sock->ops   = &pptp_ops;
549
550	sk->sk_backlog_rcv = pptp_rcv_core;
551	sk->sk_state       = PPPOX_NONE;
552	sk->sk_type        = SOCK_STREAM;
553	sk->sk_family      = PF_PPPOX;
554	sk->sk_protocol    = PX_PROTO_PPTP;
555	sk->sk_destruct    = pptp_sock_destruct;
556
557	po = pppox_sk(sk);
558	opt = &po->proto.pptp;
559
560	opt->seq_sent = 0; opt->seq_recv = 0xffffffff;
561	opt->ack_recv = 0; opt->ack_sent = 0xffffffff;
562
563	error = 0;
564out:
565	return error;
566}
567
568static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
569	unsigned long arg)
570{
571	struct sock *sk = (struct sock *) chan->private;
572	struct pppox_sock *po = pppox_sk(sk);
573	struct pptp_opt *opt = &po->proto.pptp;
574	void __user *argp = (void __user *)arg;
575	int __user *p = argp;
576	int err, val;
577
578	err = -EFAULT;
579	switch (cmd) {
580	case PPPIOCGFLAGS:
581		val = opt->ppp_flags;
582		if (put_user(val, p))
583			break;
584		err = 0;
585		break;
586	case PPPIOCSFLAGS:
587		if (get_user(val, p))
588			break;
589		opt->ppp_flags = val & ~SC_RCV_BITS;
590		err = 0;
591		break;
592	default:
593		err = -ENOTTY;
594	}
595
596	return err;
597}
598
599static const struct ppp_channel_ops pptp_chan_ops = {
600	.start_xmit = pptp_xmit,
601	.ioctl      = pptp_ppp_ioctl,
602};
603
604static struct proto pptp_sk_proto __read_mostly = {
605	.name     = "PPTP",
606	.owner    = THIS_MODULE,
607	.obj_size = sizeof(struct pppox_sock),
608};
609
610static const struct proto_ops pptp_ops = {
611	.family     = AF_PPPOX,
612	.owner      = THIS_MODULE,
613	.release    = pptp_release,
614	.bind       = pptp_bind,
615	.connect    = pptp_connect,
616	.socketpair = sock_no_socketpair,
617	.accept     = sock_no_accept,
618	.getname    = pptp_getname,
619	.listen     = sock_no_listen,
620	.shutdown   = sock_no_shutdown,
621	.setsockopt = sock_no_setsockopt,
622	.getsockopt = sock_no_getsockopt,
623	.sendmsg    = sock_no_sendmsg,
624	.recvmsg    = sock_no_recvmsg,
625	.mmap       = sock_no_mmap,
626	.ioctl      = pppox_ioctl,
627#ifdef CONFIG_COMPAT
628	.compat_ioctl = pppox_compat_ioctl,
629#endif
630};
631
632static const struct pppox_proto pppox_pptp_proto = {
633	.create = pptp_create,
634	.owner  = THIS_MODULE,
635};
636
637static const struct gre_protocol gre_pptp_protocol = {
638	.handler = pptp_rcv,
639};
640
641static int __init pptp_init_module(void)
642{
643	int err = 0;
644	pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n");
645
646	callid_sock = vzalloc(array_size(sizeof(void *), (MAX_CALLID + 1)));
647	if (!callid_sock)
648		return -ENOMEM;
649
650	err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
651	if (err) {
652		pr_err("PPTP: can't add gre protocol\n");
653		goto out_mem_free;
654	}
655
656	err = proto_register(&pptp_sk_proto, 0);
657	if (err) {
658		pr_err("PPTP: can't register sk_proto\n");
659		goto out_gre_del_protocol;
660	}
661
662	err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto);
663	if (err) {
664		pr_err("PPTP: can't register pppox_proto\n");
665		goto out_unregister_sk_proto;
666	}
667
668	return 0;
669
670out_unregister_sk_proto:
671	proto_unregister(&pptp_sk_proto);
672out_gre_del_protocol:
673	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
674out_mem_free:
675	vfree(callid_sock);
676
677	return err;
678}
679
680static void __exit pptp_exit_module(void)
681{
682	unregister_pppox_proto(PX_PROTO_PPTP);
683	proto_unregister(&pptp_sk_proto);
684	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
685	vfree(callid_sock);
686}
687
688module_init(pptp_init_module);
689module_exit(pptp_exit_module);
690
691MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");
692MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
693MODULE_LICENSE("GPL");
694MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP);