This repository has been archived by the owner on Jan 10, 2023. It is now read-only.
-
Notifications
You must be signed in to change notification settings - Fork 11
/
tunip.c
1229 lines (1053 loc) · 34.1 KB
/
tunip.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
/* IPSec ESP and AH support.
Copyright (c) 1999 Pierre Beyssac
Copyright (C) 2002 Geoffrey Keating
Copyright (C) 2003-2007 Maurice Massar
Copyright (C) 2004 Tomas Mraz
Copyright (C) 2005 Michael Tilstra
Copyright (C) 2006 Daniel Roethlisberger
Copyright (C) 2007 Paolo Zarpellon (tap+Cygwin support)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
$Id$
*/
/* borrowed from pipsecd (-; */
/*-
* Copyright (c) 1999 Pierre Beyssac
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <assert.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <netinet/in_systm.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#ifndef __SKYOS__
#include <netinet/ip_icmp.h>
#endif
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <syslog.h>
#include <time.h>
#include <sys/select.h>
#include <signal.h>
#ifdef __CYGWIN__
#include <pthread.h>
#endif
#if !defined(__sun__) && !defined(__SKYOS__)
#include <err.h>
#endif
#include <gcrypt.h>
#include "sysdep.h"
#include "config.h"
#include "vpnc.h"
#include "tunip.h"
#ifndef MAX
#define MAX(a,b) ((a)>(b)?(a):(b))
#endif
#ifndef FD_COPY
#define FD_COPY(f, t) ((void)memcpy((t), (f), sizeof(*(f))))
#endif
/* A real ESP header (RFC 2406) */
typedef struct esp_encap_header {
uint32_t spi; /* security parameters index */
uint32_t seq_id; /* sequence id (unimplemented) */
/* variable-length payload data + padding */
/* unsigned char next_header */
/* optional auth data */
} __attribute__((packed)) esp_encap_header_t;
struct encap_method {
int fixed_header_size;
int (*recv) (struct sa_block *s, unsigned char *buf, unsigned int bufsize);
void (*send_peer) (struct sa_block *s, unsigned char *buf, unsigned int bufsize);
int (*recv_peer) (struct sa_block *s, uint32_t seq_id);
};
/* Yuck! Global variables... */
#define MAX_HEADER 72
#define MAX_PACKET 4096
int volatile do_kill;
static uint8_t global_buffer_rx[MAX_HEADER + MAX_PACKET + ETH_HLEN];
static uint8_t global_buffer_tx[MAX_HEADER + MAX_PACKET + ETH_HLEN];
/*
* in_cksum --
* Checksum routine for Internet Protocol family headers (C Version)
*/
static u_short in_cksum(u_short *addr, int len)
{
register int nleft = len;
register u_short *w = addr;
register int sum = 0;
u_short answer = 0;
/*
* Our algorithm is simple, using a 32 bit accumulator (sum), we add
* sequential 16 bit words to it, and at the end, fold back all the
* carry bits from the top 16 bits into the lower 16 bits.
*/
while (nleft > 1) {
sum += *w++;
nleft -= 2;
}
/* mop up an odd byte, if necessary */
if (nleft == 1) {
*(u_char *) (&answer) = *(u_char *) w;
sum += answer;
}
/* add back carry outs from top 16 bits to low 16 bits */
sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
answer = ~sum; /* truncate to 16 bits */
return (answer);
}
/*
* Decapsulate from a raw IP packet
*/
static int encap_rawip_recv(struct sa_block *s, unsigned char *buf, unsigned int bufsize)
{
ssize_t r;
struct ip *p = (struct ip *)buf;
struct sockaddr_in from;
socklen_t fromlen = sizeof(from);
r = recvfrom(s->esp_fd, buf, bufsize, 0, (struct sockaddr *)&from, &fromlen);
if (r == -1) {
logmsg(LOG_ERR, "recvfrom: %m");
return -1;
}
if (from.sin_addr.s_addr != s->dst.s_addr) {
logmsg(LOG_ALERT, "packet from unknown host %s", inet_ntoa(from.sin_addr));
return -1;
}
if (r < (p->ip_hl << 2) + s->ipsec.em->fixed_header_size) {
logmsg(LOG_ALERT, "packet too short. got %zd, expected %d", r, (p->ip_hl << 2) + s->ipsec.em->fixed_header_size);
return -1;
}
#ifdef NEED_IPLEN_FIX
p->ip_len = r;
#else
p->ip_len = ntohs(r);
#endif
s->ipsec.rx.buf = buf;
s->ipsec.rx.buflen = r;
s->ipsec.rx.bufpayload = (p->ip_hl << 2);
s->ipsec.rx.bufsize = bufsize;
return r;
}
/*
* Decapsulate from an UDP packet
*/
static int encap_udp_recv(struct sa_block *s, unsigned char *buf, unsigned int bufsize)
{
ssize_t r;
r = recv(s->esp_fd, buf, bufsize, 0);
if (r == -1) {
logmsg(LOG_ERR, "recvfrom: %m");
return -1;
}
if (s->ipsec.natt_active_mode == NATT_ACTIVE_DRAFT_OLD && r > 8) {
r -= 8;
memmove(buf, buf + 8, r);
}
if( r == 1 && *buf == 0xff )
{
DEBUGTOP(1, printf("UDP NAT keepalive packet received\n"));
return -1;
}
if (r < s->ipsec.em->fixed_header_size) {
logmsg(LOG_ALERT, "packet too short from %s. got %zd, expected %d",
inet_ntoa(s->dst), r, s->ipsec.em->fixed_header_size);
return -1;
}
s->ipsec.rx.buf = buf;
s->ipsec.rx.buflen = r;
s->ipsec.rx.bufpayload = 0;
s->ipsec.rx.bufsize = bufsize;
return r;
}
/*
* Decapsulate packet
*/
static int encap_any_decap(struct sa_block *s)
{
s->ipsec.rx.buflen -= s->ipsec.rx.bufpayload + s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size;
s->ipsec.rx.buf += s->ipsec.rx.bufpayload + s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size;
if (s->ipsec.rx.buflen == 0)
return 0;
return 1;
}
/*
* Send decapsulated packet to tunnel device
*/
static int tun_send_ip(struct sa_block *s)
{
int sent, len;
uint8_t *start;
start = s->ipsec.rx.buf;
len = s->ipsec.rx.buflen;
if (opt_if_mode == IF_MODE_TAP) {
#ifndef __sun__
/*
* Add ethernet header before s->ipsec.rx.buf where
* at least ETH_HLEN bytes should be available.
*/
struct ether_header *eth_hdr = (struct ether_header *) (s->ipsec.rx.buf - ETH_HLEN);
memcpy(eth_hdr->ether_dhost, s->tun_hwaddr, ETH_ALEN);
memcpy(eth_hdr->ether_shost, s->tun_hwaddr, ETH_ALEN);
/* Use a different MAC as source */
eth_hdr->ether_shost[0] ^= 0x80; /* toggle some visible bit */
eth_hdr->ether_type = htons(ETHERTYPE_IP);
start = (uint8_t *) eth_hdr;
len += ETH_HLEN;
#endif
}
#if defined(__APPLE__)
if(strncmp(s->tun_name, "utun", 4)==0) {
sent = utun_write(s->tun_fd, start, len);
} else {
sent = tun_write(s->tun_fd, start, len);
}
#else
sent = tun_write(s->tun_fd, start, len);
#endif
if (sent != len)
logmsg(LOG_ERR, "truncated in: %d -> %d\n", len, sent);
hex_dump("Tx pkt", start, len, NULL);
return 1;
}
/*
* Compute HMAC for an arbitrary stream of bytes
*/
static int hmac_compute(int md_algo,
const unsigned char *data, unsigned int data_size,
unsigned char *digest, unsigned char do_store,
const unsigned char *secret, unsigned short secret_size)
{
gcry_md_hd_t md_ctx;
int ret;
unsigned char *hmac_digest;
unsigned int hmac_len;
/* See RFC 2104 */
gcry_md_open(&md_ctx, md_algo, GCRY_MD_FLAG_HMAC);
assert(md_ctx != NULL);
ret = gcry_md_setkey(md_ctx, secret, secret_size);
assert(ret == 0);
gcry_md_write(md_ctx, data, data_size);
gcry_md_final(md_ctx);
hmac_digest = gcry_md_read(md_ctx, 0);
hmac_len = 12; /*gcry_md_get_algo_dlen(md_algo); see RFC .. only use 96 bit */
if (do_store) {
memcpy(digest, hmac_digest, hmac_len);
ret = 0;
} else
ret = memcmp(digest, hmac_digest, hmac_len);
gcry_md_close(md_ctx);
return ret;
}
/*
* Encapsulate a packet in ESP
*/
static void encap_esp_encapsulate(struct sa_block *s)
{
esp_encap_header_t *eh;
unsigned char *iv, *cleartext;
size_t i, padding, pad_blksz;
unsigned int cleartextlen;
/*
* Add padding as necessary
*
* done: this should be checked, RFC 2406 section 2.4 is quite
* obscure on that point.
* seems fine
*/
pad_blksz = s->ipsec.blk_len;
while (pad_blksz & 3) /* must be multiple of 4 */
pad_blksz <<= 1;
padding = pad_blksz - ((s->ipsec.tx.buflen + 2 - s->ipsec.tx.var_header_size - s->ipsec.tx.bufpayload) % pad_blksz);
DEBUG(3, printf("sending packet: len = %d, padding = %lu\n", s->ipsec.tx.buflen, (unsigned long)padding));
if (padding == pad_blksz)
padding = 0;
for (i = 1; i <= padding; i++) {
s->ipsec.tx.buf[s->ipsec.tx.buflen] = i;
s->ipsec.tx.buflen++;
}
/* Add trailing padlen and next_header */
s->ipsec.tx.buf[s->ipsec.tx.buflen++] = padding;
s->ipsec.tx.buf[s->ipsec.tx.buflen++] = IPPROTO_IPIP;
cleartext = s->ipsec.tx.buf + s->ipsec.tx.var_header_size + s->ipsec.tx.bufpayload;
cleartextlen = s->ipsec.tx.buflen - s->ipsec.tx.var_header_size - s->ipsec.tx.bufpayload;
eh = (esp_encap_header_t *) (s->ipsec.tx.buf + s->ipsec.tx.bufpayload);
eh->spi = s->ipsec.tx.spi;
eh->seq_id = htonl(s->ipsec.tx.seq_id++);
/* Copy initialization vector in packet */
iv = (unsigned char *)(eh + 1);
gcry_create_nonce(iv, s->ipsec.iv_len);
hex_dump("iv", iv, s->ipsec.iv_len, NULL);
hex_dump("sending ESP packet (before crypt)", s->ipsec.tx.buf, s->ipsec.tx.buflen, NULL);
if (s->ipsec.cry_algo) {
gcry_cipher_setiv(s->ipsec.tx.cry_ctx, iv, s->ipsec.iv_len);
gcry_cipher_encrypt(s->ipsec.tx.cry_ctx, cleartext, cleartextlen, NULL, 0);
}
hex_dump("sending ESP packet (after crypt)", s->ipsec.tx.buf, s->ipsec.tx.buflen, NULL);
/* Handle optional authentication field */
if (s->ipsec.md_algo) {
hmac_compute(s->ipsec.md_algo,
s->ipsec.tx.buf + s->ipsec.tx.bufpayload,
s->ipsec.tx.var_header_size + cleartextlen,
s->ipsec.tx.buf + s->ipsec.tx.bufpayload
+ s->ipsec.tx.var_header_size + cleartextlen,
1, s->ipsec.tx.key_md, s->ipsec.md_len);
s->ipsec.tx.buflen += 12; /*gcry_md_get_algo_dlen(md_algo); see RFC .. only use 96 bit */
hex_dump("sending ESP packet (after ah)", s->ipsec.tx.buf, s->ipsec.tx.buflen, NULL);
}
}
/*
* Encapsulate a packet in IP ESP and send to the peer.
* "buf" should have exactly MAX_HEADER free bytes at its beginning
* to account for encapsulation data (not counted in "size").
*/
static void encap_esp_send_peer(struct sa_block *s, unsigned char *buf, unsigned int bufsize)
{
ssize_t sent;
struct ip *tip, ip;
struct sockaddr_in dstaddr;
buf += MAX_HEADER;
/* Keep a pointer to the old IP header */
tip = (struct ip *)buf;
s->ipsec.tx.buf = buf;
s->ipsec.tx.buflen = bufsize;
/* Prepend our encapsulation header and new IP header */
s->ipsec.tx.var_header_size = (s->ipsec.em->fixed_header_size + s->ipsec.iv_len);
s->ipsec.tx.buf -= sizeof(struct ip) + s->ipsec.tx.var_header_size;
s->ipsec.tx.buflen += sizeof(struct ip) + s->ipsec.tx.var_header_size;
s->ipsec.tx.bufpayload = sizeof(struct ip);
/* Fill non-mutable fields */
ip.ip_v = IPVERSION;
ip.ip_hl = 5;
/*gcry_md_get_algo_dlen(md_algo); see RFC .. only use 96 bit */
ip.ip_id = htons(s->ipsec.ip_id++);
ip.ip_p = IPPROTO_ESP;
ip.ip_src = s->src;
ip.ip_dst = s->dst;
/* Fill mutable fields */
ip.ip_tos = (bufsize < sizeof(struct ip)) ? 0 : tip->ip_tos;
ip.ip_off = 0;
ip.ip_ttl = IPDEFTTL;
ip.ip_sum = 0;
encap_esp_encapsulate(s);
ip.ip_len = s->ipsec.tx.buflen;
#ifdef NEED_IPLEN_FIX
ip.ip_len = htons(ip.ip_len);
#endif
ip.ip_sum = in_cksum((u_short *) s->ipsec.tx.buf, sizeof(struct ip));
memcpy(s->ipsec.tx.buf, &ip, sizeof ip);
dstaddr.sin_family = AF_INET;
dstaddr.sin_addr = s->dst;
dstaddr.sin_port = 0;
sent = sendto(s->esp_fd, s->ipsec.tx.buf, s->ipsec.tx.buflen, 0, (struct sockaddr *)&dstaddr, sizeof(struct sockaddr_in));
if (sent == -1) {
logmsg(LOG_ERR, "esp sendto: %m");
return;
}
if (sent != s->ipsec.tx.buflen)
logmsg(LOG_ALERT, "esp truncated out (%lld out of %d)", (long long)sent, s->ipsec.tx.buflen);
}
/*
* Encapsulate a packet in UDP ESP and send to the peer.
* "buf" should have exactly MAX_HEADER free bytes at its beginning
* to account for encapsulation data (not counted in "size").
*/
static void encap_udp_send_peer(struct sa_block *s, unsigned char *buf, unsigned int bufsize)
{
ssize_t sent;
struct ip *tip;
uint8_t tos;
buf += MAX_HEADER;
/* get the TOS value of the original frame */
tip = (struct ip *)buf;
tos = (bufsize < sizeof(struct ip)) ? 0 : tip->ip_tos;
s->ipsec.tx.buf = buf;
s->ipsec.tx.buflen = bufsize;
/* Prepend our encapsulation header and new IP header */
s->ipsec.tx.var_header_size = (s->ipsec.em->fixed_header_size + s->ipsec.iv_len);
s->ipsec.tx.buf -= s->ipsec.tx.var_header_size;
s->ipsec.tx.buflen += s->ipsec.tx.var_header_size;
s->ipsec.tx.bufpayload = 0;
encap_esp_encapsulate(s);
if (s->ipsec.natt_active_mode == NATT_ACTIVE_DRAFT_OLD) {
s->ipsec.tx.buf -= 8;
s->ipsec.tx.buflen += 8;
memset(s->ipsec.tx.buf, 0, 8);
}
/* set outer TOS header to the one of the original frame */
/* but only if it differs from the already set TOS */
if (tos != s->ipsec.current_udp_tos) {
if (setsockopt(s->esp_fd, IPPROTO_IP, IP_TOS, &tos, sizeof(tos))) {
logmsg(LOG_ERR, "udp setsockopt: %m");
}
s->ipsec.current_udp_tos = tos;
}
sent = send(s->esp_fd, s->ipsec.tx.buf, s->ipsec.tx.buflen, 0);
if (sent == -1) {
logmsg(LOG_ERR, "udp sendto: %m");
return;
}
if (sent != s->ipsec.tx.buflen)
logmsg(LOG_ALERT, "udp truncated out (%lld out of %d)",
(long long)sent, s->ipsec.tx.buflen);
}
static int encap_esp_validate_seqid(struct sa_block *s, uint32_t seq_id)
{
/*
* For incoming, s->ipsec.rx.seq_id is the next *expected* packet,
* being the sequence number *after* the latest we have received.
*
* Since it must always be true that packet s->ipsec.rx.seq_id-1
* has been received, there's no need to explicitly record that.
*
* So the backlog bitmap covers the 32 packets prior to that, with
* the LSB representing packet (s->ipsec.rx.seq_id - 2), and the
* MSB representing (s->ipsec.rx.seq_id - 33). A received packet
* is represented by a zero bit, and a missing packet is
* represented by a one.
*
* Thus we can allow out-of-order reception of packets that are
* within a reasonable interval of the latest packet received.
*/
if (seq_id == s->ipsec.rx.seq_id) {
/* The common case. This is the packet we expected next. */
s->ipsec.rx.seq_backlog <<= 1;
s->ipsec.rx.seq_id++;
logmsg(LOG_DEBUG, "Accepting expected ESP packet with seq %u\n",
seq_id);
return 0;
} else if (seq_id + 33 < s->ipsec.rx.seq_id) {
/* Too old. We can't know if it's a replay. */
logmsg(LOG_NOTICE,
"Discarding ancient ESP packet with seq %u (expected %u)\n",
seq_id, s->ipsec.rx.seq_id);
return -EINVAL;
} else if (seq_id < s->ipsec.rx.seq_id) {
/* Within the backlog window, so we remember whether we've seen it or not. */
uint32_t mask = 1 << (s->ipsec.rx.seq_id - seq_id - 2);
if (s->ipsec.rx.seq_backlog & mask) {
logmsg(LOG_DEBUG,
"Accepting out-of-order ESP packet with seq %u (expected %u)\n",
seq_id, s->ipsec.rx.seq_id);
s->ipsec.rx.seq_backlog &= ~mask;
return 0;
}
logmsg(LOG_NOTICE,
"Discarding replayed ESP packet with seq %u\n", seq_id);
return -EINVAL;
} else {
/* The packet we were expecting has gone missing; this one is newer. */
int delta = seq_id - s->ipsec.rx.seq_id;
if (delta >= 32) {
/* We jumped a long way into the future. We have not seen
* any of the previous 32 packets so set the backlog bitmap
* to all ones. */
s->ipsec.rx.seq_backlog = 0xffffffff;
} else if (delta == 31) {
/* Avoid undefined behaviour that shifting by 32 would incur.
* The (clear) top bit represents the packet which is currently
* s->ipsec.rx.seq_id - 1, which we know was already received. */
s->ipsec.rx.seq_backlog = 0x7fffffff;
} else {
/* We have missed (delta) packets. Shift the backlog by that
* amount *plus* the one we would have shifted it anyway if
* we'd received the packet we were expecting. The zero bit
* representing the packet which is currently s->ipsec.rx.seq_id - 1,
* which we know has been received, ends up at bit position
* (1<<delta). Then we set all the bits lower than that, which
* represent the missing packets. */
s->ipsec.rx.seq_backlog <<= delta + 1;
s->ipsec.rx.seq_backlog |= (1<<delta) - 1;
}
logmsg(LOG_DEBUG,
"Accepting later-than-expected ESP packet with seq %u (expected %u)\n",
seq_id, s->ipsec.rx.seq_id);
s->ipsec.rx.seq_id = seq_id + 1;
return 0;
}
}
static int encap_esp_recv_peer(struct sa_block *s, uint32_t seq_id)
{
int len, i;
size_t blksz;
unsigned char padlen, next_header;
unsigned char *pad;
unsigned char *iv;
s->ipsec.rx.var_header_size = s->ipsec.iv_len;
iv = s->ipsec.rx.buf + s->ipsec.rx.bufpayload + s->ipsec.em->fixed_header_size;
len = s->ipsec.rx.buflen - s->ipsec.rx.bufpayload - s->ipsec.em->fixed_header_size - s->ipsec.rx.var_header_size;
if (len < 0) {
logmsg(LOG_ALERT, "Packet too short");
return -1;
}
/* Handle optional authentication field */
if (s->ipsec.md_algo) {
len -= 12; /*gcry_md_get_algo_dlen(peer->local_sa->md_algo); */
s->ipsec.rx.buflen -= 12;
if (hmac_compute(s->ipsec.md_algo,
s->ipsec.rx.buf + s->ipsec.rx.bufpayload,
s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size + len,
s->ipsec.rx.buf + s->ipsec.rx.bufpayload
+ s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size + len,
0,
s->ipsec.rx.key_md,
s->ipsec.md_len) != 0) {
logmsg(LOG_ALERT, "HMAC mismatch in ESP mode");
return -1;
}
}
if (encap_esp_validate_seqid(s, seq_id))
return -1;
blksz = s->ipsec.blk_len;
if (s->ipsec.cry_algo && ((len % blksz) != 0)) {
logmsg(LOG_ALERT,
"payload len %d not a multiple of algorithm block size %lu", len,
(unsigned long)blksz);
return -1;
}
hex_dump("receiving ESP packet (before decrypt)",
&s->ipsec.rx.buf[s->ipsec.rx.bufpayload + s->ipsec.em->fixed_header_size +
s->ipsec.rx.var_header_size], len, NULL);
if (s->ipsec.cry_algo) {
unsigned char *data;
data = (s->ipsec.rx.buf + s->ipsec.rx.bufpayload
+ s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size);
gcry_cipher_setiv(s->ipsec.rx.cry_ctx, iv, s->ipsec.iv_len);
gcry_cipher_decrypt(s->ipsec.rx.cry_ctx, data, len, NULL, 0);
}
hex_dump("receiving ESP packet (after decrypt)",
&s->ipsec.rx.buf[s->ipsec.rx.bufpayload + s->ipsec.em->fixed_header_size +
s->ipsec.rx.var_header_size], len, NULL);
padlen = s->ipsec.rx.buf[s->ipsec.rx.bufpayload
+ s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size + len - 2];
next_header = s->ipsec.rx.buf[s->ipsec.rx.bufpayload
+ s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size + len - 1];
if (padlen + 2 > len) {
logmsg(LOG_ALERT, "Inconsistent padlen");
return -1;
}
if (next_header != IPPROTO_IPIP) {
logmsg(LOG_ALERT, "Inconsistent next_header %d", next_header);
return -1;
}
DEBUG(3, printf("pad len: %d, next_header: %d\n", padlen, next_header));
len -= padlen + 2;
s->ipsec.rx.buflen -= padlen + 2;
/* Check padding */
pad = s->ipsec.rx.buf + s->ipsec.rx.bufpayload
+ s->ipsec.em->fixed_header_size + s->ipsec.rx.var_header_size + len;
for (i = 1; i <= padlen; i++) {
if (*pad != i) {
logmsg(LOG_ALERT, "Bad padding");
return -1;
}
pad++;
}
return 0;
}
static void encap_esp_new(struct encap_method *encap)
{
encap->recv = encap_rawip_recv;
encap->send_peer = encap_esp_send_peer;
encap->recv_peer = encap_esp_recv_peer;
encap->fixed_header_size = sizeof(esp_encap_header_t);
}
static void encap_udp_new(struct encap_method *encap)
{
encap->recv = encap_udp_recv;
encap->send_peer = encap_udp_send_peer;
encap->recv_peer = encap_esp_recv_peer;
encap->fixed_header_size = sizeof(esp_encap_header_t);
}
/*
* Process ARP
* Return 1 if packet has been processed, 0 otherwise
*/
static int process_arp(struct sa_block *s, uint8_t *frame)
{
#ifndef __sun__
int frame_size;
uint8_t tmp[4];
struct ether_header *eth = (struct ether_header *) frame;
struct ether_arp *arp = (struct ether_arp *) (frame + ETH_HLEN);
if (ntohs(eth->ether_type) != ETHERTYPE_ARP) {
return 0;
}
if (ntohs(arp->arp_hrd) != ARPHRD_ETHER ||
ntohs(arp->arp_pro) != 0x800 ||
arp->arp_hln != ETH_ALEN ||
arp->arp_pln != 4 ||
ntohs(arp->arp_op) != ARPOP_REQUEST ||
!memcmp(arp->arp_spa, arp->arp_tpa, 4) ||
memcmp(eth->ether_shost, s->tun_hwaddr, ETH_ALEN) ||
!memcmp(arp->arp_tpa, &s->our_address, 4)) {
/* whatever .. just drop it */
return 1;
}
/* send arp reply */
memcpy(eth->ether_dhost, s->tun_hwaddr, ETH_ALEN);
eth->ether_shost[0] ^= 0x80; /* Use a different MAC as source */
memcpy(tmp, arp->arp_spa, 4);
memcpy(arp->arp_spa, arp->arp_tpa, 4);
memcpy(arp->arp_tpa, tmp, 4);
memcpy(arp->arp_tha, s->tun_hwaddr, ETH_ALEN);
arp->arp_sha[0] ^= 0x80; /* Use a different MAC as source */
arp->arp_op = htons(ARPOP_REPLY);
frame_size = ETH_HLEN + sizeof(struct ether_arp);
#if defined(__APPLE__)
if(strncmp(s->tun_name, "utun", 4)==0) {
utun_write(s->tun_fd, frame, frame_size);
} else {
tun_write(s->tun_fd, frame, frame_size);
}
#else
tun_write(s->tun_fd, frame, frame_size);
#endif
hex_dump("ARP reply", frame, frame_size, NULL);
return 1;
#else
s = 0;
frame = 0;
return 0;
#endif
}
/*
* Process non-IP packets
* Return 1 if packet has been processed, 0 otherwise
*/
static int process_non_ip(uint8_t *frame)
{
struct ether_header *eth = (struct ether_header *) frame;
if (ntohs(eth->ether_type) != ETHERTYPE_IP) {
/* drop non-ip traffic */
return 1;
}
return 0;
}
static void process_tun(struct sa_block *s)
{
int pack;
int size = MAX_PACKET;
uint8_t *start = global_buffer_rx + MAX_HEADER;
if (opt_if_mode == IF_MODE_TAP) {
/* Make sure IP packet starts at buf + MAX_HEADER */
start -= ETH_HLEN;
size += ETH_HLEN;
}
/* Receive a packet from the tunnel interface */
#if defined(__APPLE__)
if(strncmp(s->tun_name, "utun", 4)==0) {
pack = utun_read(s->tun_fd, start, size);
} else {
pack = tun_read(s->tun_fd, start, size);
}
#else
pack = tun_read(s->tun_fd, start, size);
#endif
hex_dump("Rx pkt", start, pack, NULL);
if (opt_if_mode == IF_MODE_TAP) {
if (process_arp(s, start)) {
return;
}
if (process_non_ip(start)) {
return;
}
pack -= ETH_HLEN;
}
if (pack == -1) {
logmsg(LOG_ERR, "read: %m");
return;
}
/* Don't access the contents of the buffer other than byte aligned.
* 12: Offset of ip source address in ip header,
* 4: Length of IP address */
if (!memcmp(global_buffer_rx + MAX_HEADER + 12, &s->dst.s_addr, 4)) {
logmsg(LOG_ALERT, "routing loop to %s",
inet_ntoa(s->dst));
return;
}
/* Encapsulate and send to the other end of the tunnel */
s->ipsec.life.tx += pack;
s->ipsec.em->send_peer(s, global_buffer_rx, pack);
}
static void process_socket(struct sa_block *s)
{
/* Receive a packet from a socket */
int pack;
uint8_t *start = global_buffer_tx;
esp_encap_header_t *eh;
if (opt_if_mode == IF_MODE_TAP) {
start += ETH_HLEN;
}
pack = s->ipsec.em->recv(s, start, MAX_HEADER + MAX_PACKET);
if (pack == -1)
return;
eh = (esp_encap_header_t *) (s->ipsec.rx.buf + s->ipsec.rx.bufpayload);
if (eh->spi == 0) {
process_late_ike(s, s->ipsec.rx.buf + s->ipsec.rx.bufpayload + 4 /* SPI-size */,
s->ipsec.rx.buflen - s->ipsec.rx.bufpayload - 4);
return;
} else if (eh->spi != s->ipsec.rx.spi) {
logmsg(LOG_NOTICE, "unknown spi %#08x from peer", ntohl(eh->spi));
return;
} else if (ntohl(eh->spi) < 256) {
syslog(LOG_NOTICE, "illegal spi %d from peer - continuing", ntohl(eh->spi));
}
/* Check auth digest and/or decrypt */
if (s->ipsec.em->recv_peer(s, ntohl(eh->seq_id)) != 0)
return;
if (encap_any_decap(s) == 0) {
logmsg(LOG_DEBUG, "received update probe from peer");
} else {
/* Send the decapsulated packet to the tunnel interface */
s->ipsec.life.rx += s->ipsec.rx.buflen;
tun_send_ip(s);
}
}
#if defined(__CYGWIN__)
static void *tun_thread (void *arg)
{
struct sa_block *s = (struct sa_block *) arg;
while (!do_kill) {
process_tun(s);
}
return NULL;
}
#endif
static void vpnc_main_loop(struct sa_block *s)
{
fd_set rfds, refds;
int nfds=0;
int enable_keepalives;
int timed_mode;
ssize_t len;
struct timeval select_timeout;
struct timeval normal_timeout;
time_t next_ike_keepalive=0;
time_t next_ike_dpd=0;
#if defined(__CYGWIN__)
pthread_t tid;
#endif
/* non-esp marker, nat keepalive payload (0xFF) */
uint8_t keepalive_v2[5] = { 0x00, 0x00, 0x00, 0x00, 0xFF };
uint8_t keepalive_v1[1] = { 0xFF };
uint8_t *keepalive;
size_t keepalive_size;
/* the below code had keepalive_v2 for NATT_ACTIVE_RFC [FIXME]
* however, ASA 9.4(1) produced
* [IKEv1]: IKE Receiver: Runt ISAKMP packet discarded on Port 4500 from ip:port
* according to RFC 3948, the keepalive should be 0xFF
*
* 2.3. NAT-Keepalive Packet Format
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Source Port | Destination Port |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Length | Checksum |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | 0xFF |
* +-+-+-+-+-+-+-+-+
*
*/
if (s->ipsec.natt_active_mode == NATT_ACTIVE_DRAFT_OLD) {
keepalive = keepalive_v1;
keepalive_size = sizeof(keepalive_v1);
} else if (s->ipsec.natt_active_mode == NATT_ACTIVE_RFC) {
keepalive = keepalive_v1;
keepalive_size = sizeof(keepalive_v1);
} else { /* active_mode is CISCO_UDP */
keepalive = keepalive_v2;
keepalive_size = sizeof(keepalive_v2);
}
/* send keepalives if UDP encapsulation is enabled */
enable_keepalives = (s->ipsec.encap_mode != IPSEC_ENCAP_TUNNEL);
/* regular wakeups if keepalives on ike or dpd active */
timed_mode = ((enable_keepalives && s->ike_fd != s->esp_fd) || s->ike.do_dpd);
FD_ZERO(&rfds);
#if !defined(__CYGWIN__)
FD_SET(s->tun_fd, &rfds);
nfds = MAX(nfds, s->tun_fd +1);
#endif
FD_SET(s->esp_fd, &rfds);
nfds = MAX(nfds, s->esp_fd +1);
if (s->ike_fd != s->esp_fd) {
FD_SET(s->ike_fd, &rfds);
nfds = MAX(nfds, s->ike_fd +1);
}
#if defined(__CYGWIN__)
if (pthread_create(&tid, NULL, tun_thread, s)) {
logmsg(LOG_ERR, "Cannot create tun thread!\n");
return;
}
#endif
normal_timeout.tv_sec = 86400;
normal_timeout.tv_usec = 0;
if (s->ike.do_dpd) {
/* send initial dpd request */
next_ike_dpd = time(NULL) + s->ike.dpd_idle;
dpd_ike(s);
normal_timeout.tv_sec = s->ike.dpd_idle;
normal_timeout.tv_usec = 0;
}
if (enable_keepalives) {
normal_timeout.tv_sec = 9;
normal_timeout.tv_usec = 500000;
if (s->ike_fd != s->esp_fd) {
/* send initial nat ike keepalive packet */
next_ike_keepalive = time(NULL) + 9;
keepalive_ike(s);
}
}
select_timeout = normal_timeout;
while (!do_kill) {
int presult;
do {
struct timeval *tvp = NULL;
FD_COPY(&rfds, &refds);
if (s->ike.do_dpd || enable_keepalives)
tvp = &select_timeout;
presult = select(nfds, &refds, NULL, NULL, tvp);
if (presult == 0 && (s->ike.do_dpd || enable_keepalives)) {
/* reset to max timeout */
select_timeout = normal_timeout;
if (enable_keepalives) {
if (s->ike_fd != s->esp_fd) {
/* send nat ike keepalive packet */
next_ike_keepalive = time(NULL) + 9;