forked from mkj/dropbear
-
Notifications
You must be signed in to change notification settings - Fork 0
/
common-channel.c
1267 lines (1011 loc) · 34.7 KB
/
common-channel.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
/*
* Dropbear SSH
*
* Copyright (c) 2002-2004 Matt Johnston
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
/* Handle the multiplexed channels, such as sessions, x11, agent connections */
#include "includes.h"
#include "session.h"
#include "packet.h"
#include "ssh.h"
#include "buffer.h"
#include "circbuffer.h"
#include "dbutil.h"
#include "channel.h"
#include "listener.h"
#include "runopts.h"
#include "netio.h"
static void send_msg_channel_open_failure(unsigned int remotechan, int reason,
const char *text, const char *lang);
static void send_msg_channel_open_confirmation(const struct Channel* channel,
unsigned int recvwindow,
unsigned int recvmaxpacket);
static int writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen);
static void send_msg_channel_window_adjust(const struct Channel *channel,
unsigned int incr);
static void send_msg_channel_data(struct Channel *channel, int isextended);
static void send_msg_channel_eof(struct Channel *channel);
static void send_msg_channel_close(struct Channel *channel);
static void remove_channel(struct Channel *channel);
static unsigned int write_pending(const struct Channel * channel);
static void check_close(struct Channel *channel);
static void close_chan_fd(struct Channel *channel, int fd, int how);
#define FD_UNINIT (-2)
#define FD_CLOSED (-1)
#define ERRFD_IS_READ(channel) ((channel)->extrabuf == NULL)
#define ERRFD_IS_WRITE(channel) (!ERRFD_IS_READ(channel))
/* allow space for:
* 1 byte byte SSH_MSG_CHANNEL_DATA
* 4 bytes uint32 recipient channel
* 4 bytes string data
*/
#define RECV_MAX_CHANNEL_DATA_LEN (RECV_MAX_PAYLOAD_LEN-(1+4+4))
/* Initialise all the channels */
void chaninitialise(const struct ChanType *chantypes[]) {
/* may as well create space for a single channel */
ses.channels = (struct Channel**)m_malloc(sizeof(struct Channel*));
ses.chansize = 1;
ses.channels[0] = NULL;
ses.chancount = 0;
ses.chantypes = chantypes;
#if DROPBEAR_LISTENERS
listeners_initialise();
#endif
}
/* Clean up channels, freeing allocated memory */
void chancleanup() {
unsigned int i;
TRACE(("enter chancleanup"))
for (i = 0; i < ses.chansize; i++) {
if (ses.channels[i] != NULL) {
TRACE(("channel %d closing", i))
remove_channel(ses.channels[i]);
}
}
m_free(ses.channels);
TRACE(("leave chancleanup"))
}
/* Create a new channel entry, send a reply confirm or failure */
/* If remotechan, transwindow and transmaxpacket are not know (for a new
* outgoing connection, with them to be filled on confirmation), they should
* all be set to 0 */
static struct Channel* newchannel(unsigned int remotechan,
const struct ChanType *type,
unsigned int transwindow, unsigned int transmaxpacket) {
struct Channel * newchan;
unsigned int i, j;
TRACE(("enter newchannel"))
/* first see if we can use existing channels */
for (i = 0; i < ses.chansize; i++) {
if (ses.channels[i] == NULL) {
break;
}
}
/* otherwise extend the list */
if (i == ses.chansize) {
if (ses.chansize >= MAX_CHANNELS) {
TRACE(("leave newchannel: max chans reached"))
return NULL;
}
/* extend the channels */
ses.channels = (struct Channel**)m_realloc(ses.channels,
(ses.chansize+CHAN_EXTEND_SIZE)*sizeof(struct Channel*));
ses.chansize += CHAN_EXTEND_SIZE;
/* set the new channels to null */
for (j = i; j < ses.chansize; j++) {
ses.channels[j] = NULL;
}
}
newchan = (struct Channel*)m_malloc(sizeof(struct Channel));
newchan->type = type;
newchan->index = i;
newchan->sent_close = newchan->recv_close = 0;
newchan->sent_eof = newchan->recv_eof = 0;
newchan->remotechan = remotechan;
newchan->transwindow = transwindow;
newchan->transmaxpacket = transmaxpacket;
newchan->typedata = NULL;
newchan->writefd = FD_UNINIT;
newchan->readfd = FD_UNINIT;
newchan->errfd = FD_CLOSED; /* this isn't always set to start with */
newchan->await_open = 0;
newchan->writebuf = cbuf_new(opts.recv_window);
newchan->recvwindow = opts.recv_window;
newchan->extrabuf = NULL; /* The user code can set it up */
newchan->recvdonelen = 0;
newchan->recvmaxpacket = RECV_MAX_CHANNEL_DATA_LEN;
newchan->prio = DROPBEAR_CHANNEL_PRIO_EARLY; /* inithandler sets it */
ses.channels[i] = newchan;
ses.chancount++;
TRACE(("leave newchannel"))
return newchan;
}
/* Returns the channel structure corresponding to the channel in the current
* data packet (ses.payload must be positioned appropriately).
* A valid channel is always returns, it will fail fatally with an unknown
* channel */
static struct Channel* getchannel_msg(const char* kind) {
unsigned int chan;
chan = buf_getint(ses.payload);
if (chan >= ses.chansize || ses.channels[chan] == NULL) {
if (kind) {
dropbear_exit("%s for unknown channel %d", kind, chan);
} else {
dropbear_exit("Unknown channel %d", chan);
}
}
return ses.channels[chan];
}
struct Channel* getchannel() {
return getchannel_msg(NULL);
}
/* Iterate through the channels, performing IO if available */
void channelio(const fd_set *readfds, const fd_set *writefds) {
/* Listeners such as TCP, X11, agent-auth */
struct Channel *channel;
unsigned int i;
/* foreach channel */
for (i = 0; i < ses.chansize; i++) {
/* Close checking only needs to occur for channels that had IO events */
int do_check_close = 0;
channel = ses.channels[i];
if (channel == NULL) {
/* only process in-use channels */
continue;
}
/* read data and send it over the wire */
if (channel->readfd >= 0 && FD_ISSET(channel->readfd, readfds)) {
TRACE(("send normal readfd"))
send_msg_channel_data(channel, 0);
do_check_close = 1;
}
/* read stderr data and send it over the wire */
if (ERRFD_IS_READ(channel) && channel->errfd >= 0
&& FD_ISSET(channel->errfd, readfds)) {
TRACE(("send normal errfd"))
send_msg_channel_data(channel, 1);
do_check_close = 1;
}
/* write to program/pipe stdin */
if (channel->writefd >= 0 && FD_ISSET(channel->writefd, writefds)) {
writechannel(channel, channel->writefd, channel->writebuf, NULL, NULL);
do_check_close = 1;
}
/* stderr for client mode */
if (ERRFD_IS_WRITE(channel)
&& channel->errfd >= 0 && FD_ISSET(channel->errfd, writefds)) {
writechannel(channel, channel->errfd, channel->extrabuf, NULL, NULL);
do_check_close = 1;
}
if (ses.channel_signal_pending) {
/* SIGCHLD can change channel state for server sessions */
do_check_close = 1;
}
/* handle any channel closing etc */
if (do_check_close) {
check_close(channel);
}
}
#if DROPBEAR_LISTENERS
handle_listeners(readfds);
#endif
}
/* Returns true if there is data remaining to be written to stdin or
* stderr of a channel's endpoint. */
static unsigned int write_pending(const struct Channel * channel) {
if (channel->writefd >= 0 && cbuf_getused(channel->writebuf) > 0) {
return 1;
} else if (channel->errfd >= 0 && channel->extrabuf &&
cbuf_getused(channel->extrabuf) > 0) {
return 1;
}
return 0;
}
/* EOF/close handling */
static void check_close(struct Channel *channel) {
int close_allowed = 0;
TRACE2(("check_close: writefd %d, readfd %d, errfd %d, sent_close %d, recv_close %d",
channel->writefd, channel->readfd,
channel->errfd, channel->sent_close, channel->recv_close))
TRACE2(("writebuf size %d extrabuf size %d",
channel->writebuf ? cbuf_getused(channel->writebuf) : 0,
channel->extrabuf ? cbuf_getused(channel->extrabuf) : 0))
/* if a type-specific check_close is defined we will only exit
once that has been triggered. this is only used for a server "session"
channel, to ensure that the shell has exited (and the exit status
retrieved) before we close things up. */
if (!channel->type->check_close
|| channel->sent_close
|| channel->type->check_close(channel)) {
close_allowed = 1;
}
/* In flushing mode we close FDs as soon as pipes are empty.
This is used to drain out FDs when the process exits, in the case
where the FD doesn't have EOF - "sleep 10&echo hello" case */
if (channel->flushing) {
if (channel->readfd >= 0 && !fd_read_pending(channel->readfd)) {
close_chan_fd(channel, channel->readfd, SHUT_RD);
}
if (ERRFD_IS_READ(channel)
&& channel->errfd >= 0 && !fd_read_pending(channel->errfd)) {
close_chan_fd(channel, channel->errfd, SHUT_RD);
}
}
if (channel->recv_close && !write_pending(channel) && close_allowed) {
if (!channel->sent_close) {
TRACE(("Sending MSG_CHANNEL_CLOSE in response to same."))
send_msg_channel_close(channel);
}
remove_channel(channel);
return;
}
if ((channel->recv_eof && !write_pending(channel))
/* have a server "session" and child has exited */
|| (channel->type->check_close && close_allowed)) {
close_chan_fd(channel, channel->writefd, SHUT_WR);
}
/* If we're not going to send any more data, send EOF */
if (!channel->sent_eof
&& channel->readfd == FD_CLOSED
&& (ERRFD_IS_WRITE(channel) || channel->errfd == FD_CLOSED)) {
send_msg_channel_eof(channel);
}
/* And if we can't receive any more data from them either, close up */
if (channel->readfd == FD_CLOSED
&& channel->writefd == FD_CLOSED
&& (ERRFD_IS_WRITE(channel) || channel->errfd == FD_CLOSED)
&& !channel->sent_close
&& close_allowed
&& !write_pending(channel)) {
TRACE(("sending close, readfd is closed"))
send_msg_channel_close(channel);
}
}
/* Check whether a deferred (EINPROGRESS) connect() was successful, and
* if so, set up the channel properly. Otherwise, the channel is cleaned up, so
* it is important that the channel reference isn't used after a call to this
* function */
void channel_connect_done(int result, int sock, void* user_data, const char* errstring) {
struct Channel *channel = user_data;
TRACE(("enter channel_connect_done"))
if (result == DROPBEAR_SUCCESS)
{
channel->readfd = channel->writefd = sock;
channel->bidir_fd = 1;
channel->conn_pending = NULL;
send_msg_channel_open_confirmation(channel, channel->recvwindow,
channel->recvmaxpacket);
TRACE(("leave channel_connect_done: success"))
}
else
{
send_msg_channel_open_failure(channel->remotechan,
SSH_OPEN_CONNECT_FAILED, errstring, "");
remove_channel(channel);
TRACE(("leave check_in_progress: fail. internal errstring: %s", errstring))
}
}
/* Send the close message and set the channel as closed */
static void send_msg_channel_close(struct Channel *channel) {
TRACE(("enter send_msg_channel_close %p", (void*)channel))
if (channel->type->closehandler) {
channel->type->closehandler(channel);
}
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_CLOSE);
buf_putint(ses.writepayload, channel->remotechan);
encrypt_packet();
channel->sent_eof = 1;
channel->sent_close = 1;
close_chan_fd(channel, channel->readfd, SHUT_RD);
close_chan_fd(channel, channel->errfd, SHUT_RDWR);
close_chan_fd(channel, channel->writefd, SHUT_WR);
TRACE(("leave send_msg_channel_close"))
}
/* call this when trans/eof channels are closed */
static void send_msg_channel_eof(struct Channel *channel) {
TRACE(("enter send_msg_channel_eof"))
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_EOF);
buf_putint(ses.writepayload, channel->remotechan);
encrypt_packet();
channel->sent_eof = 1;
TRACE(("leave send_msg_channel_eof"))
}
#ifndef HAVE_WRITEV
static int writechannel_fallback(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *UNUSED(moredata), unsigned int *morelen) {
unsigned char *circ_p1, *circ_p2;
unsigned int circ_len1, circ_len2;
ssize_t written;
if (morelen) {
/* fallback doesn't consume moredata */
*morelen = 0;
}
/* Write the first portion of the circular buffer */
cbuf_readptrs(cbuf, &circ_p1, &circ_len1, &circ_p2, &circ_len2);
written = write(fd, circ_p1, circ_len1);
if (written < 0) {
if (errno != EINTR && errno != EAGAIN) {
TRACE(("channel IO write error fd %d %s", fd, strerror(errno)))
close_chan_fd(channel, fd, SHUT_WR);
return DROPBEAR_FAILURE;
}
} else {
cbuf_incrread(cbuf, written);
channel->recvdonelen += written;
}
return DROPBEAR_SUCCESS;
}
#endif /* !HAVE_WRITEV */
#ifdef HAVE_WRITEV
static int writechannel_writev(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen) {
struct iovec iov[3];
unsigned char *circ_p1, *circ_p2;
unsigned int circ_len1, circ_len2;
int io_count = 0;
ssize_t written;
cbuf_readptrs(cbuf, &circ_p1, &circ_len1, &circ_p2, &circ_len2);
if (circ_len1 > 0) {
TRACE(("circ1 %d", circ_len1))
iov[io_count].iov_base = circ_p1;
iov[io_count].iov_len = circ_len1;
io_count++;
}
if (circ_len2 > 0) {
TRACE(("circ2 %d", circ_len2))
iov[io_count].iov_base = circ_p2;
iov[io_count].iov_len = circ_len2;
io_count++;
}
if (morelen) {
assert(moredata);
TRACE(("more %d", *morelen))
iov[io_count].iov_base = (void*)moredata;
iov[io_count].iov_len = *morelen;
io_count++;
}
if (io_count == 0) {
/* writechannel may sometimes be called twice in a main loop iteration.
From common_recv_msg_channel_data() then channelio().
The second call may not have any data to write, so we just return. */
TRACE(("leave writechannel, no data"))
return DROPBEAR_SUCCESS;
}
if (morelen) {
/* Default return value, none consumed */
*morelen = 0;
}
written = writev(fd, iov, io_count);
if (written < 0) {
if (errno != EINTR && errno != EAGAIN) {
TRACE(("channel IO write error fd %d %s", fd, strerror(errno)))
close_chan_fd(channel, fd, SHUT_WR);
return DROPBEAR_FAILURE;
}
} else {
int cbuf_written = MIN(circ_len1+circ_len2, (unsigned int)written);
cbuf_incrread(cbuf, cbuf_written);
if (morelen) {
*morelen = written - cbuf_written;
}
channel->recvdonelen += written;
}
return DROPBEAR_SUCCESS;
}
#endif /* HAVE_WRITEV */
/* Called to write data out to the local side of the channel.
Writes the circular buffer contents and also the "moredata" buffer
if not null. Will ignore EAGAIN.
Returns DROPBEAR_FAILURE if writing to fd had an error and the channel is being closed, DROPBEAR_SUCCESS otherwise */
static int writechannel(struct Channel* channel, int fd, circbuffer *cbuf,
const unsigned char *moredata, unsigned int *morelen) {
int ret = DROPBEAR_SUCCESS;
TRACE(("enter writechannel fd %d", fd))
#ifdef HAVE_WRITEV
ret = writechannel_writev(channel, fd, cbuf, moredata, morelen);
#else
ret = writechannel_fallback(channel, fd, cbuf, moredata, morelen);
#endif
/* Window adjust handling */
if (channel->recvdonelen >= RECV_WINDOWEXTEND) {
send_msg_channel_window_adjust(channel, channel->recvdonelen);
channel->recvwindow += channel->recvdonelen;
channel->recvdonelen = 0;
}
dropbear_assert(channel->recvwindow <= opts.recv_window);
dropbear_assert(channel->recvwindow <= cbuf_getavail(channel->writebuf));
dropbear_assert(channel->extrabuf == NULL ||
channel->recvwindow <= cbuf_getavail(channel->extrabuf));
TRACE(("leave writechannel"))
return ret;
}
/* Set the file descriptors for the main select in session.c
* This avoid channels which don't have any window available, are closed, etc*/
void setchannelfds(fd_set *readfds, fd_set *writefds, int allow_reads) {
unsigned int i;
struct Channel * channel;
for (i = 0; i < ses.chansize; i++) {
channel = ses.channels[i];
if (channel == NULL) {
continue;
}
/* Stuff to put over the wire.
Avoid queueing data to send if we're in the middle of a
key re-exchange (!dataallowed), but still read from the
FD if there's the possibility of "~."" to kill an
interactive session (the read_mangler) */
if (channel->transwindow > 0
&& ((ses.dataallowed && allow_reads) || channel->read_mangler)) {
if (channel->readfd >= 0) {
FD_SET(channel->readfd, readfds);
}
if (ERRFD_IS_READ(channel) && channel->errfd >= 0) {
FD_SET(channel->errfd, readfds);
}
}
/* Stuff from the wire */
if (channel->writefd >= 0 && cbuf_getused(channel->writebuf) > 0) {
FD_SET(channel->writefd, writefds);
}
if (ERRFD_IS_WRITE(channel) && channel->errfd >= 0
&& cbuf_getused(channel->extrabuf) > 0) {
FD_SET(channel->errfd, writefds);
}
} /* foreach channel */
#if DROPBEAR_LISTENERS
set_listener_fds(readfds);
#endif
}
/* handle the channel EOF event, by closing the channel filedescriptor. The
* channel isn't closed yet, it is left until the incoming (from the program
* etc) FD is also EOF */
void recv_msg_channel_eof() {
struct Channel * channel;
TRACE(("enter recv_msg_channel_eof"))
channel = getchannel_msg("EOF");
channel->recv_eof = 1;
check_close(channel);
TRACE(("leave recv_msg_channel_eof"))
}
/* Handle channel closure(), respond in kind and close the channels */
void recv_msg_channel_close() {
struct Channel * channel;
TRACE(("enter recv_msg_channel_close"))
channel = getchannel_msg("Close");
channel->recv_eof = 1;
channel->recv_close = 1;
check_close(channel);
TRACE(("leave recv_msg_channel_close"))
}
/* Remove a channel entry, this is only executed after both sides have sent
* channel close */
static void remove_channel(struct Channel * channel) {
TRACE(("enter remove_channel"))
TRACE(("channel index is %d", channel->index))
cbuf_free(channel->writebuf);
channel->writebuf = NULL;
if (channel->extrabuf) {
cbuf_free(channel->extrabuf);
channel->extrabuf = NULL;
}
if (IS_DROPBEAR_SERVER || (channel->writefd != STDOUT_FILENO)) {
/* close the FDs in case they haven't been done
* yet (they might have been shutdown etc) */
TRACE(("CLOSE writefd %d", channel->writefd))
m_close(channel->writefd);
TRACE(("CLOSE readfd %d", channel->readfd))
m_close(channel->readfd);
TRACE(("CLOSE errfd %d", channel->errfd))
m_close(channel->errfd);
}
if (channel->type->cleanup) {
channel->type->cleanup(channel);
}
if (channel->conn_pending) {
cancel_connect(channel->conn_pending);
}
ses.channels[channel->index] = NULL;
m_free(channel);
ses.chancount--;
update_channel_prio();
TRACE(("leave remove_channel"))
}
/* Handle channel specific requests, passing off to corresponding handlers
* such as chansession or x11fwd */
void recv_msg_channel_request() {
struct Channel *channel;
channel = getchannel();
TRACE(("enter recv_msg_channel_request %p", (void*)channel))
if (channel->type->reqhandler) {
channel->type->reqhandler(channel);
} else {
int wantreply;
buf_eatstring(ses.payload);
wantreply = buf_getbool(ses.payload);
if (wantreply) {
send_msg_channel_failure(channel);
}
}
TRACE(("leave recv_msg_channel_request"))
}
/* Reads data from the server's program/shell/etc, and puts it in a
* channel_data packet to send.
* chan is the remote channel, isextended is 0 if it is normal data, 1
* if it is extended data. if it is extended, then the type is in
* exttype */
static void send_msg_channel_data(struct Channel *channel, int isextended) {
int len;
size_t maxlen, size_pos;
int fd;
CHECKCLEARTOWRITE();
TRACE(("enter send_msg_channel_data"))
dropbear_assert(!channel->sent_close);
if (isextended) {
fd = channel->errfd;
} else {
fd = channel->readfd;
}
TRACE(("enter send_msg_channel_data isextended %d fd %d", isextended, fd))
dropbear_assert(fd >= 0);
maxlen = MIN(channel->transwindow, channel->transmaxpacket);
/* -(1+4+4) is SSH_MSG_CHANNEL_DATA, channel number, string length, and
* exttype if is extended */
maxlen = MIN(maxlen,
ses.writepayload->size - 1 - 4 - 4 - (isextended ? 4 : 0));
TRACE(("maxlen %zd", maxlen))
if (maxlen == 0) {
TRACE(("leave send_msg_channel_data: no window"))
return;
}
buf_putbyte(ses.writepayload,
isextended ? SSH_MSG_CHANNEL_EXTENDED_DATA : SSH_MSG_CHANNEL_DATA);
buf_putint(ses.writepayload, channel->remotechan);
if (isextended) {
buf_putint(ses.writepayload, SSH_EXTENDED_DATA_STDERR);
}
/* a dummy size first ...*/
size_pos = ses.writepayload->pos;
buf_putint(ses.writepayload, 0);
/* read the data */
len = read(fd, buf_getwriteptr(ses.writepayload, maxlen), maxlen);
if (len <= 0) {
if (len == 0 || errno != EINTR) {
/* This will also get hit in the case of EAGAIN. The only
time we expect to receive EAGAIN is when we're flushing a FD,
in which case it can be treated the same as EOF */
close_chan_fd(channel, fd, SHUT_RD);
}
buf_setpos(ses.writepayload, 0);
buf_setlen(ses.writepayload, 0);
TRACE(("leave send_msg_channel_data: len %d read err %d or EOF for fd %d",
len, errno, fd))
return;
}
if (channel->read_mangler) {
channel->read_mangler(channel, buf_getwriteptr(ses.writepayload, len), &len);
if (len == 0) {
buf_setpos(ses.writepayload, 0);
buf_setlen(ses.writepayload, 0);
return;
}
}
TRACE(("send_msg_channel_data: len %d fd %d", len, fd))
buf_incrwritepos(ses.writepayload, len);
/* ... real size here */
buf_setpos(ses.writepayload, size_pos);
buf_putint(ses.writepayload, len);
channel->transwindow -= len;
encrypt_packet();
TRACE(("leave send_msg_channel_data"))
}
/* We receive channel data */
void recv_msg_channel_data() {
struct Channel *channel;
channel = getchannel();
common_recv_msg_channel_data(channel, channel->writefd, channel->writebuf);
}
/* Shared for data and stderr data - when we receive data, put it in a buffer
* for writing to the local file descriptor */
void common_recv_msg_channel_data(struct Channel *channel, int fd,
circbuffer * cbuf) {
unsigned int datalen;
unsigned int maxdata;
unsigned int buflen;
unsigned int len;
unsigned int consumed;
int res;
TRACE(("enter recv_msg_channel_data"))
if (channel->recv_eof) {
dropbear_exit("Received data after eof");
}
if (fd < 0 || !cbuf) {
/* If we have encountered failed write, the far side might still
* be sending data without having yet received our close notification.
* We just drop the data. */
return;
}
datalen = buf_getint(ses.payload);
TRACE(("length %d", datalen))
maxdata = cbuf_getavail(cbuf);
/* Whilst the spec says we "MAY ignore data past the end" this could
* lead to corrupted file transfers etc (chunks missed etc). It's better to
* just die horribly */
if (datalen > maxdata) {
dropbear_exit("Oversized packet");
}
dropbear_assert(channel->recvwindow >= datalen);
channel->recvwindow -= datalen;
dropbear_assert(channel->recvwindow <= opts.recv_window);
#if defined(DBMULTI_scp) && DROPBEAR_MULTI
TRACE(("%s: data = '%s'", __func__, buf_getptr(ses.payload, datalen)))
size_t cmdlen = ses.payload->len;
while (cmdlen > 60) {
char * cmd = (char *)buf_getptr(ses.payload, datalen);
char lastsym = cmd[cmdlen-1];
cmd[cmdlen-1] = 0;
char * x = strstr(cmd, "\"WinSCP: this is begin-of-file\" ; scp -r ");
cmd[cmdlen-1] = lastsym;
if (!x)
break;
static char exe[80] = {0};
static int exelen = 0;
if (!exelen) {
exelen = readlink("/proc/self/exe", exe, sizeof(exe)-1);
if (exelen > 0) {
TRACE(("exe name = '%s'", exe))
exe[exelen++] = ' ';
exe[exelen] = 0;
}
}
if (exelen < 3)
break;
if (ses.payload->len + exelen >= ses.payload->size)
break;
cmd[cmdlen-1] = 0;
char * scp = strstr(x, "scp -r ");
cmd[cmdlen-1] = lastsym;
memmove(scp + exelen, scp, (size_t)cmd + cmdlen - (size_t)scp);
memcpy(scp, exe, exelen);
ses.payload->len += exelen;
datalen += exelen;
TRACE(("%s: DATA = '%s'", __func__, buf_getptr(ses.payload, datalen)))
break;
}
#endif
/* Attempt to write the data immediately without having to put it in the circular buffer */
consumed = datalen;
res = writechannel(channel, fd, cbuf, buf_getptr(ses.payload, datalen), &consumed);
datalen -= consumed;
buf_incrpos(ses.payload, consumed);
/* We may have to run throught twice, if the buffer wraps around. Can't
* just "leave it for next time" like with writechannel, since this
* is payload data.
* If the writechannel() failed then remaining data is discarded */
if (res == DROPBEAR_SUCCESS) {
len = datalen;
while (len > 0) {
buflen = cbuf_writelen(cbuf);
buflen = MIN(buflen, len);
memcpy(cbuf_writeptr(cbuf, buflen),
buf_getptr(ses.payload, buflen), buflen);
cbuf_incrwrite(cbuf, buflen);
buf_incrpos(ses.payload, buflen);
len -= buflen;
}
}
TRACE(("leave recv_msg_channel_data"))
}
/* Increment the outgoing data window for a channel - the remote end limits
* the amount of data which may be transmitted, this window is decremented
* as data is sent, and incremented upon receiving window-adjust messages */
void recv_msg_channel_window_adjust() {
struct Channel * channel;
unsigned int incr;
channel = getchannel();
incr = buf_getint(ses.payload);
TRACE(("received window increment %d", incr))
incr = MIN(incr, TRANS_MAX_WIN_INCR);
channel->transwindow += incr;
channel->transwindow = MIN(channel->transwindow, TRANS_MAX_WINDOW);
}
/* Increment the incoming data window for a channel, and let the remote
* end know */
static void send_msg_channel_window_adjust(const struct Channel* channel,
unsigned int incr) {
TRACE(("sending window adjust %d", incr))
CHECKCLEARTOWRITE();
buf_putbyte(ses.writepayload, SSH_MSG_CHANNEL_WINDOW_ADJUST);
buf_putint(ses.writepayload, channel->remotechan);
buf_putint(ses.writepayload, incr);
encrypt_packet();
}
/* Handle a new channel request, performing any channel-type-specific setup */
void recv_msg_channel_open() {
char *type;
unsigned int typelen;
unsigned int remotechan, transwindow, transmaxpacket;
struct Channel *channel;
const struct ChanType **cp;
const struct ChanType *chantype;
unsigned int errtype = SSH_OPEN_UNKNOWN_CHANNEL_TYPE;
int ret;
TRACE(("enter recv_msg_channel_open"))
/* get the packet contents */
type = buf_getstring(ses.payload, &typelen);
remotechan = buf_getint(ses.payload);
transwindow = buf_getint(ses.payload);
transwindow = MIN(transwindow, TRANS_MAX_WINDOW);
transmaxpacket = buf_getint(ses.payload);
transmaxpacket = MIN(transmaxpacket, TRANS_MAX_PAYLOAD_LEN);
/* figure what type of packet it is */
if (typelen > MAX_NAME_LEN) {
goto failure;
}
/* Get the channel type. Client and server style invokation will set up a
* different list for ses.chantypes at startup. We just iterate through
* this list and find the matching name */
for (cp = &ses.chantypes[0], chantype = (*cp);
chantype != NULL;
cp++, chantype = (*cp)) {
if (strcmp(type, chantype->name) == 0) {
break;
}
}
if (chantype == NULL) {
TRACE(("No matching type for '%s'", type))
goto failure;
}
TRACE(("matched type '%s'", type))
/* create the channel */
channel = newchannel(remotechan, chantype, transwindow, transmaxpacket);
if (channel == NULL) {
TRACE(("newchannel returned NULL"))
errtype = SSH_OPEN_RESOURCE_SHORTAGE;
goto failure;
}
if (channel->type->inithandler) {
ret = channel->type->inithandler(channel);
if (ret == SSH_OPEN_IN_PROGRESS) {
/* We'll send the confirmation later */
goto cleanup;
}
if (ret > 0) {
errtype = ret;
remove_channel(channel);
TRACE(("inithandler returned failure %d", ret))
goto failure;
}
}
if (channel->prio == DROPBEAR_CHANNEL_PRIO_EARLY) {
channel->prio = DROPBEAR_CHANNEL_PRIO_BULK;
}
/* success */
send_msg_channel_open_confirmation(channel, channel->recvwindow,