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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * Point-to-Point Tunneling Protocol for Linux4 *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 6553543 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 else65 sock_hold(sk_pppox(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(&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;162 163 164 struct rtable *rt;165 struct net_device *tdev;166 struct iphdr *iph;167 int max_headroom;168 169 if (sk_pppox(po)->sk_state & PPPOX_DEAD)170 goto tx_error;171 172 rt = pptp_route_output(po, &fl4);173 if (IS_ERR(rt))174 goto tx_error;175 176 tdev = rt->dst.dev;177 178 max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph) + sizeof(*hdr) + 2;179 180 if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {181 struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);182 if (!new_skb) {183 ip_rt_put(rt);184 goto tx_error;185 }186 if (skb->sk)187 skb_set_owner_w(new_skb, skb->sk);188 consume_skb(skb);189 skb = new_skb;190 }191 192 data = skb->data;193 islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7;194 195 /* compress protocol field */196 if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp)197 skb_pull(skb, 1);198 199 /* Put in the address/control bytes if necessary */200 if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) {201 data = skb_push(skb, 2);202 data[0] = PPP_ALLSTATIONS;203 data[1] = PPP_UI;204 }205 206 len = skb->len;207 208 seq_recv = opt->seq_recv;209 210 if (opt->ack_sent == seq_recv)211 header_len -= sizeof(hdr->ack);212 213 /* Push down and install GRE header */214 skb_push(skb, header_len);215 hdr = (struct pptp_gre_header *)(skb->data);216 217 hdr->gre_hd.flags = GRE_KEY | GRE_VERSION_1 | GRE_SEQ;218 hdr->gre_hd.protocol = GRE_PROTO_PPP;219 hdr->call_id = htons(opt->dst_addr.call_id);220 221 hdr->seq = htonl(++opt->seq_sent);222 if (opt->ack_sent != seq_recv) {223 /* send ack with this message */224 hdr->gre_hd.flags |= GRE_ACK;225 hdr->ack = htonl(seq_recv);226 opt->ack_sent = seq_recv;227 }228 hdr->payload_len = htons(len);229 230 /* Push down and install the IP header. */231 232 skb_reset_transport_header(skb);233 skb_push(skb, sizeof(*iph));234 skb_reset_network_header(skb);235 memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));236 IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);237 238 iph = ip_hdr(skb);239 iph->version = 4;240 iph->ihl = sizeof(struct iphdr) >> 2;241 if (ip_dont_fragment(sk, &rt->dst))242 iph->frag_off = htons(IP_DF);243 else244 iph->frag_off = 0;245 iph->protocol = IPPROTO_GRE;246 iph->tos = 0;247 iph->daddr = fl4.daddr;248 iph->saddr = fl4.saddr;249 iph->ttl = ip4_dst_hoplimit(&rt->dst);250 iph->tot_len = htons(skb->len);251 252 skb_dst_drop(skb);253 skb_dst_set(skb, &rt->dst);254 255 nf_reset_ct(skb);256 257 skb->ip_summed = CHECKSUM_NONE;258 ip_select_ident(net, skb, NULL);259 ip_send_check(iph);260 261 ip_local_out(net, skb->sk, skb);262 return 1;263 264tx_error:265 kfree_skb(skb);266 return 1;267}268 269static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb)270{271 struct pppox_sock *po = pppox_sk(sk);272 struct pptp_opt *opt = &po->proto.pptp;273 int headersize, payload_len, seq;274 __u8 *payload;275 struct pptp_gre_header *header;276 277 if (!(sk->sk_state & PPPOX_CONNECTED)) {278 if (sock_queue_rcv_skb(sk, skb))279 goto drop;280 return NET_RX_SUCCESS;281 }282 283 header = (struct pptp_gre_header *)(skb->data);284 headersize = sizeof(*header);285 286 /* test if acknowledgement present */287 if (GRE_IS_ACK(header->gre_hd.flags)) {288 __u32 ack;289 290 if (!pskb_may_pull(skb, headersize))291 goto drop;292 header = (struct pptp_gre_header *)(skb->data);293 294 /* ack in different place if S = 0 */295 ack = GRE_IS_SEQ(header->gre_hd.flags) ? ntohl(header->ack) :296 ntohl(header->seq);297 if (ack > opt->ack_recv)298 opt->ack_recv = ack;299 /* also handle sequence number wrap-around */300 if (WRAPPED(ack, opt->ack_recv))301 opt->ack_recv = ack;302 } else {303 headersize -= sizeof(header->ack);304 }305 /* test if payload present */306 if (!GRE_IS_SEQ(header->gre_hd.flags))307 goto drop;308 309 payload_len = ntohs(header->payload_len);310 seq = ntohl(header->seq);311 312 /* check for incomplete packet (length smaller than expected) */313 if (!pskb_may_pull(skb, headersize + payload_len))314 goto drop;315 316 payload = skb->data + headersize;317 /* check for expected sequence number */318 if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) {319 if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) &&320 (PPP_PROTOCOL(payload) == PPP_LCP) &&321 ((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP)))322 goto allow_packet;323 } else {324 opt->seq_recv = seq;325allow_packet:326 skb_pull(skb, headersize);327 328 if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) {329 /* chop off address/control */330 if (skb->len < 3)331 goto drop;332 skb_pull(skb, 2);333 }334 335 skb->ip_summed = CHECKSUM_NONE;336 skb_set_network_header(skb, skb->head-skb->data);337 ppp_input(&po->chan, skb);338 339 return NET_RX_SUCCESS;340 }341drop:342 kfree_skb(skb);343 return NET_RX_DROP;344}345 346static int pptp_rcv(struct sk_buff *skb)347{348 struct pppox_sock *po;349 struct pptp_gre_header *header;350 struct iphdr *iph;351 352 if (skb->pkt_type != PACKET_HOST)353 goto drop;354 355 if (!pskb_may_pull(skb, 12))356 goto drop;357 358 iph = ip_hdr(skb);359 360 header = (struct pptp_gre_header *)skb->data;361 362 if (header->gre_hd.protocol != GRE_PROTO_PPP || /* PPTP-GRE protocol for PPTP */363 GRE_IS_CSUM(header->gre_hd.flags) || /* flag CSUM should be clear */364 GRE_IS_ROUTING(header->gre_hd.flags) || /* flag ROUTING should be clear */365 !GRE_IS_KEY(header->gre_hd.flags) || /* flag KEY should be set */366 (header->gre_hd.flags & GRE_FLAGS)) /* flag Recursion Ctrl should be clear */367 /* if invalid, discard this packet */368 goto drop;369 370 po = lookup_chan(ntohs(header->call_id), iph->saddr);371 if (po) {372 skb_dst_drop(skb);373 nf_reset_ct(skb);374 return sk_receive_skb(sk_pppox(po), skb, 0);375 }376drop:377 kfree_skb(skb);378 return NET_RX_DROP;379}380 381static int pptp_bind(struct socket *sock, struct sockaddr *uservaddr,382 int sockaddr_len)383{384 struct sock *sk = sock->sk;385 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;386 struct pppox_sock *po = pppox_sk(sk);387 int error = 0;388 389 if (sockaddr_len < sizeof(struct sockaddr_pppox))390 return -EINVAL;391 392 lock_sock(sk);393 394 if (sk->sk_state & PPPOX_DEAD) {395 error = -EALREADY;396 goto out;397 }398 399 if (sk->sk_state & PPPOX_BOUND) {400 error = -EBUSY;401 goto out;402 }403 404 if (add_chan(po, &sp->sa_addr.pptp))405 error = -EBUSY;406 else407 sk->sk_state |= PPPOX_BOUND;408 409out:410 release_sock(sk);411 return error;412}413 414static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr,415 int sockaddr_len, int flags)416{417 struct sock *sk = sock->sk;418 struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;419 struct pppox_sock *po = pppox_sk(sk);420 struct pptp_opt *opt = &po->proto.pptp;421 struct rtable *rt;422 struct flowi4 fl4;423 int error = 0;424 425 if (sockaddr_len < sizeof(struct sockaddr_pppox))426 return -EINVAL;427 428 if (sp->sa_protocol != PX_PROTO_PPTP)429 return -EINVAL;430 431 if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr))432 return -EALREADY;433 434 lock_sock(sk);435 /* Check for already bound sockets */436 if (sk->sk_state & PPPOX_CONNECTED) {437 error = -EBUSY;438 goto end;439 }440 441 /* Check for already disconnected sockets, on attempts to disconnect */442 if (sk->sk_state & PPPOX_DEAD) {443 error = -EALREADY;444 goto end;445 }446 447 if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) {448 error = -EINVAL;449 goto end;450 }451 452 po->chan.private = sk;453 po->chan.ops = &pptp_chan_ops;454 455 rt = pptp_route_output(po, &fl4);456 if (IS_ERR(rt)) {457 error = -EHOSTUNREACH;458 goto end;459 }460 sk_setup_caps(sk, &rt->dst);461 462 po->chan.mtu = dst_mtu(&rt->dst);463 if (!po->chan.mtu)464 po->chan.mtu = PPP_MRU;465 po->chan.mtu -= PPTP_HEADER_OVERHEAD;466 467 po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header);468 error = ppp_register_channel(&po->chan);469 if (error) {470 pr_err("PPTP: failed to register PPP channel (%d)\n", error);471 goto end;472 }473 474 opt->dst_addr = sp->sa_addr.pptp;475 sk->sk_state |= PPPOX_CONNECTED;476 477 end:478 release_sock(sk);479 return error;480}481 482static int pptp_getname(struct socket *sock, struct sockaddr *uaddr,483 int peer)484{485 int len = sizeof(struct sockaddr_pppox);486 struct sockaddr_pppox sp;487 488 memset(&sp.sa_addr, 0, sizeof(sp.sa_addr));489 490 sp.sa_family = AF_PPPOX;491 sp.sa_protocol = PX_PROTO_PPTP;492 sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr;493 494 memcpy(uaddr, &sp, len);495 496 return len;497}498 499static int pptp_release(struct socket *sock)500{501 struct sock *sk = sock->sk;502 struct pppox_sock *po;503 int error = 0;504 505 if (!sk)506 return 0;507 508 lock_sock(sk);509 510 if (sock_flag(sk, SOCK_DEAD)) {511 release_sock(sk);512 return -EBADF;513 }514 515 po = pppox_sk(sk);516 del_chan(po);517 synchronize_rcu();518 519 pppox_unbind_sock(sk);520 sk->sk_state = PPPOX_DEAD;521 522 sock_orphan(sk);523 sock->sk = NULL;524 525 release_sock(sk);526 sock_put(sk);527 528 return error;529}530 531static void pptp_sock_destruct(struct sock *sk)532{533 if (!(sk->sk_state & PPPOX_DEAD)) {534 del_chan(pppox_sk(sk));535 pppox_unbind_sock(sk);536 }537 skb_queue_purge(&sk->sk_receive_queue);538 dst_release(rcu_dereference_protected(sk->sk_dst_cache, 1));539}540 541static int pptp_create(struct net *net, struct socket *sock, int kern)542{543 int error = -ENOMEM;544 struct sock *sk;545 struct pppox_sock *po;546 struct pptp_opt *opt;547 548 sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto, kern);549 if (!sk)550 goto out;551 552 sock_init_data(sock, sk);553 554 sock->state = SS_UNCONNECTED;555 sock->ops = &pptp_ops;556 557 sk->sk_backlog_rcv = pptp_rcv_core;558 sk->sk_state = PPPOX_NONE;559 sk->sk_type = SOCK_STREAM;560 sk->sk_family = PF_PPPOX;561 sk->sk_protocol = PX_PROTO_PPTP;562 sk->sk_destruct = pptp_sock_destruct;563 564 po = pppox_sk(sk);565 opt = &po->proto.pptp;566 567 opt->seq_sent = 0; opt->seq_recv = 0xffffffff;568 opt->ack_recv = 0; opt->ack_sent = 0xffffffff;569 570 error = 0;571out:572 return error;573}574 575static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,576 unsigned long arg)577{578 struct sock *sk = chan->private;579 struct pppox_sock *po = pppox_sk(sk);580 struct pptp_opt *opt = &po->proto.pptp;581 void __user *argp = (void __user *)arg;582 int __user *p = argp;583 int err, val;584 585 err = -EFAULT;586 switch (cmd) {587 case PPPIOCGFLAGS:588 val = opt->ppp_flags;589 if (put_user(val, p))590 break;591 err = 0;592 break;593 case PPPIOCSFLAGS:594 if (get_user(val, p))595 break;596 opt->ppp_flags = val & ~SC_RCV_BITS;597 err = 0;598 break;599 default:600 err = -ENOTTY;601 }602 603 return err;604}605 606static const struct ppp_channel_ops pptp_chan_ops = {607 .start_xmit = pptp_xmit,608 .ioctl = pptp_ppp_ioctl,609};610 611static struct proto pptp_sk_proto __read_mostly = {612 .name = "PPTP",613 .owner = THIS_MODULE,614 .obj_size = sizeof(struct pppox_sock),615};616 617static const struct proto_ops pptp_ops = {618 .family = AF_PPPOX,619 .owner = THIS_MODULE,620 .release = pptp_release,621 .bind = pptp_bind,622 .connect = pptp_connect,623 .socketpair = sock_no_socketpair,624 .accept = sock_no_accept,625 .getname = pptp_getname,626 .listen = sock_no_listen,627 .shutdown = sock_no_shutdown,628 .sendmsg = sock_no_sendmsg,629 .recvmsg = sock_no_recvmsg,630 .mmap = sock_no_mmap,631 .ioctl = pppox_ioctl,632#ifdef CONFIG_COMPAT633 .compat_ioctl = pppox_compat_ioctl,634#endif635};636 637static const struct pppox_proto pppox_pptp_proto = {638 .create = pptp_create,639 .owner = THIS_MODULE,640};641 642static const struct gre_protocol gre_pptp_protocol = {643 .handler = pptp_rcv,644};645 646static int __init pptp_init_module(void)647{648 int err = 0;649 pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n");650 651 callid_sock = vzalloc(array_size(sizeof(void *), (MAX_CALLID + 1)));652 if (!callid_sock)653 return -ENOMEM;654 655 err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP);656 if (err) {657 pr_err("PPTP: can't add gre protocol\n");658 goto out_mem_free;659 }660 661 err = proto_register(&pptp_sk_proto, 0);662 if (err) {663 pr_err("PPTP: can't register sk_proto\n");664 goto out_gre_del_protocol;665 }666 667 err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto);668 if (err) {669 pr_err("PPTP: can't register pppox_proto\n");670 goto out_unregister_sk_proto;671 }672 673 return 0;674 675out_unregister_sk_proto:676 proto_unregister(&pptp_sk_proto);677out_gre_del_protocol:678 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);679out_mem_free:680 vfree(callid_sock);681 682 return err;683}684 685static void __exit pptp_exit_module(void)686{687 unregister_pppox_proto(PX_PROTO_PPTP);688 proto_unregister(&pptp_sk_proto);689 gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);690 vfree(callid_sock);691}692 693module_init(pptp_init_module);694module_exit(pptp_exit_module);695 696MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");697MODULE_AUTHOR("D. Kozlov <xeb@mail.ru>");698MODULE_LICENSE("GPL");699MODULE_ALIAS_NET_PF_PROTO(PF_PPPOX, PX_PROTO_PPTP);700