2 * Support for SSH connection sharing, i.e. permitting one PuTTY to
3 * open its own channels over the SSH session being run by another.
7 * Discussion and technical documentation
8 * ======================================
10 * The basic strategy for PuTTY's implementation of SSH connection
11 * sharing is to have a single 'upstream' PuTTY process, which manages
12 * the real SSH connection and all the cryptography, and then zero or
13 * more 'downstream' PuTTYs, which never talk to the real host but
14 * only talk to the upstream through local IPC (Unix-domain sockets or
15 * Windows named pipes).
17 * The downstreams communicate with the upstream using a protocol
18 * derived from SSH itself, which I'll document in detail below. In
19 * brief, though: the downstream->upstream protocol uses a trivial
20 * binary packet protocol (just length/type/data) to encapsulate
21 * unencrypted SSH messages, and downstreams talk to the upstream more
22 * or less as if it was an SSH server itself. (So downstreams can
23 * themselves open multiple SSH channels, for example, by sending
24 * multiple SSH2_MSG_CHANNEL_OPENs; they can send CHANNEL_REQUESTs of
25 * their choice within each channel, and they handle their own
26 * WINDOW_ADJUST messages.)
28 * The upstream would ideally handle these downstreams by just putting
29 * their messages into the queue for proper SSH-2 encapsulation and
30 * encryption and sending them straight on to the server. However,
31 * that's not quite feasible as written, because client-side channel
32 * IDs could easily conflict (between multiple downstreams, or between
33 * a downstream and the upstream). To protect against that, the
34 * upstream rewrites the client-side channel IDs in messages it passes
35 * on to the server, so that it's performing what you might describe
36 * as 'channel-number NAT'. Then the upstream remembers which of its
37 * own channel IDs are channels it's managing itself, and which are
38 * placeholders associated with a particular downstream, so that when
39 * replies come in from the server they can be sent on to the relevant
40 * downstream (after un-NATting the channel number, of course).
42 * Global requests from downstreams are only accepted if the upstream
43 * knows what to do about them; currently the only such requests are
44 * the ones having to do with remote-to-local port forwarding (in
45 * which, again, the upstream remembers that some of the forwardings
46 * it's asked the server to set up were on behalf of particular
47 * downstreams, and sends the incoming CHANNEL_OPENs to those
48 * downstreams when connections come in).
50 * Other fiddly pieces of this mechanism are X forwarding and
51 * (OpenSSH-style) agent forwarding. Both of these have a fundamental
52 * problem arising from the protocol design: that the CHANNEL_OPEN
53 * from the server introducing a forwarded connection does not carry
54 * any indication of which session channel gave rise to it; so if
55 * session channels from multiple downstreams enable those forwarding
56 * methods, it's hard for the upstream to know which downstream to
57 * send the resulting connections back to.
59 * For X forwarding, we can work around this in a really painful way
60 * by using the fake X11 authorisation data sent to the server as part
61 * of the forwarding setup: upstream ensures that every X forwarding
62 * request carries distinguishable fake auth data, and then when X
63 * connections come in it waits to see the auth data in the X11 setup
64 * message before it decides which downstream to pass the connection
67 * For agent forwarding, that workaround is unavailable. As a result,
68 * this system (and, as far as I can think of, any other system too)
69 * has the fundamental constraint that it can only forward one SSH
70 * agent - it can't forward two agents to different session channels.
71 * So downstreams can request agent forwarding if they like, but if
72 * they do, they'll get whatever SSH agent is known to the upstream
73 * (if any) forwarded to their sessions.
75 * Downstream-to-upstream protocol
76 * -------------------------------
78 * Here I document in detail the protocol spoken between PuTTY
79 * downstreams and upstreams over local IPC. The IPC mechanism can
80 * vary between host platforms, but the protocol is the same.
82 * The protocol commences with a version exchange which is exactly
83 * like the SSH-2 one, in that each side sends a single line of text
86 * <protocol>-<version>-<softwareversion> [comments] \r\n
88 * The only difference is that in real SSH-2, <protocol> is the string
89 * "SSH", whereas in this protocol the string is
90 * "SSHCONNECTION@putty.projects.tartarus.org".
92 * (The SSH RFCs allow many protocol-level identifier namespaces to be
93 * extended by implementors without central standardisation as long as
94 * they suffix "@" and a domain name they control to their new ids.
95 * RFC 4253 does not define this particular name to be changeable at
96 * all, but I like to think this is obviously how it would have done
97 * so if the working group had foreseen the need :-)
99 * Thereafter, all data exchanged consists of a sequence of binary
100 * packets concatenated end-to-end, each of which is of the form
102 * uint32 length of packet, N
103 * byte[N] N bytes of packet data
105 * and, since these are SSH-2 messages, the first data byte is taken
106 * to be the packet type code.
108 * These messages are interpreted as those of an SSH connection, after
109 * userauth completes, and without any repeat key exchange.
110 * Specifically, any message from the SSH Connection Protocol is
111 * permitted, and also SSH_MSG_IGNORE, SSH_MSG_DEBUG,
112 * SSH_MSG_DISCONNECT and SSH_MSG_UNIMPLEMENTED from the SSH Transport
115 * This protocol imposes a few additional requirements, over and above
116 * those of the standard SSH Connection Protocol:
118 * Message sizes are not permitted to exceed 0x4010 (16400) bytes,
119 * including their length header.
121 * When the server (i.e. really the PuTTY upstream) sends
122 * SSH_MSG_CHANNEL_OPEN with channel type "x11", and the client
123 * (downstream) responds with SSH_MSG_CHANNEL_OPEN_CONFIRMATION, that
124 * confirmation message MUST include an initial window size of at
125 * least 256. (Rationale: this is a bit of a fudge which makes it
126 * easier, by eliminating the possibility of nasty edge cases, for an
127 * upstream to arrange not to pass the CHANNEL_OPEN on to downstream
128 * until after it's seen the X11 auth data to decide which downstream
129 * it needs to go to.)
141 struct ssh_sharing_state {
142 const struct plug_function_table *fn;
143 /* the above variable absolutely *must* be the first in this structure */
145 char *sockname; /* the socket name, kept for cleanup */
146 Socket listensock; /* the master listening Socket */
147 tree234 *connections; /* holds ssh_sharing_connstates */
148 unsigned nextid; /* preferred id for next connstate */
149 Ssh ssh; /* instance of the ssh backend */
150 char *server_verstring; /* server version string after "SSH-" */
153 struct share_globreq;
155 struct ssh_sharing_connstate {
156 const struct plug_function_table *fn;
157 /* the above variable absolutely *must* be the first in this structure */
159 unsigned id; /* used to identify this downstream in log messages */
161 Socket sock; /* the Socket for this connection */
162 struct ssh_sharing_state *parent;
164 int crLine; /* coroutine state for share_receive */
166 int sent_verstring, got_verstring, curr_packetlen;
168 unsigned char recvbuf[0x4010];
172 * Assorted state we have to remember about this downstream, so
173 * that we can clean it up appropriately when the downstream goes
177 /* Channels which don't have a downstream id, i.e. we've passed a
178 * CHANNEL_OPEN down from the server but not had an
179 * OPEN_CONFIRMATION or OPEN_FAILURE back. If downstream goes
180 * away, we respond to all of these with OPEN_FAILURE. */
181 tree234 *halfchannels; /* stores 'struct share_halfchannel' */
183 /* Channels which do have a downstream id. We need to index these
184 * by both server id and upstream id, so we can find a channel
185 * when handling either an upward or a downward message referring
187 tree234 *channels_by_us; /* stores 'struct share_channel' */
188 tree234 *channels_by_server; /* stores 'struct share_channel' */
190 /* Another class of channel which doesn't have a downstream id.
191 * The difference between these and halfchannels is that xchannels
192 * do have an *upstream* id, because upstream has already accepted
193 * the channel request from the server. This arises in the case of
194 * X forwarding, where we have to accept the request and read the
195 * X authorisation data before we know whether the channel needs
196 * to be forwarded to a downstream. */
197 tree234 *xchannels_by_us; /* stores 'struct share_xchannel' */
198 tree234 *xchannels_by_server; /* stores 'struct share_xchannel' */
200 /* Remote port forwarding requests in force. */
201 tree234 *forwardings; /* stores 'struct share_forwarding' */
203 /* Global requests we've sent on to the server, pending replies. */
204 struct share_globreq *globreq_head, *globreq_tail;
207 struct share_halfchannel {
211 /* States of a share_channel. */
216 /* Downstream has sent CHANNEL_OPEN but server hasn't replied yet.
217 * If downstream goes away when a channel is in this state, we
218 * must wait for the server's response before starting to send
219 * CLOSE. Channels in this state are also not held in
220 * channels_by_server, because their server_id field is
225 struct share_channel {
226 unsigned downstream_id, upstream_id, server_id;
227 int downstream_maxpkt;
230 * Some channels (specifically, channels on which downstream has
231 * sent "x11-req") have the additional function of storing a set
232 * of downstream X authorisation data and a handle to an upstream
235 struct X11FakeAuth *x11_auth_upstream;
238 int x11_auth_datalen;
242 struct share_forwarding {
245 int active; /* has the server sent REQUEST_SUCCESS? */
248 struct share_xchannel_message {
249 struct share_xchannel_message *next;
255 struct share_xchannel {
256 unsigned upstream_id, server_id;
259 * xchannels come in two flavours: live and dead. Live ones are
260 * waiting for an OPEN_CONFIRMATION or OPEN_FAILURE from
261 * downstream; dead ones have had an OPEN_FAILURE, so they only
262 * exist as a means of letting us conveniently respond to further
263 * channel messages from the server until such time as the server
264 * sends us CHANNEL_CLOSE.
269 * When we receive OPEN_CONFIRMATION, we will need to send a
270 * WINDOW_ADJUST to the server to synchronise the windows. For
271 * this purpose we need to know what window we have so far offered
272 * the server. We record this as exactly the value in the
273 * OPEN_CONFIRMATION that upstream sent us, adjusted by the amount
274 * by which the two X greetings differed in length.
279 * Linked list of SSH messages from the server relating to this
280 * channel, which we queue up until downstream sends us an
281 * OPEN_CONFIRMATION and we can belatedly send them all on.
283 struct share_xchannel_message *msghead, *msgtail;
287 GLOBREQ_TCPIP_FORWARD,
288 GLOBREQ_CANCEL_TCPIP_FORWARD
291 struct share_globreq {
292 struct share_globreq *next;
295 struct share_forwarding *fwd;
298 static int share_connstate_cmp(void *av, void *bv)
300 const struct ssh_sharing_connstate *a =
301 (const struct ssh_sharing_connstate *)av;
302 const struct ssh_sharing_connstate *b =
303 (const struct ssh_sharing_connstate *)bv;
307 else if (a->id > b->id)
313 static unsigned share_find_unused_id
314 (struct ssh_sharing_state *sharestate, unsigned first)
316 int low_orig, low, mid, high, high_orig;
317 struct ssh_sharing_connstate *cs;
321 * Find the lowest unused downstream ID greater or equal to
324 * Begin by seeing if 'first' itself is available. If it is, we'll
325 * just return it; if it's already in the tree, we'll find the
326 * tree index where it appears and use that for the next stage.
329 struct ssh_sharing_connstate dummy;
331 cs = findrelpos234(sharestate->connections, &dummy, NULL,
332 REL234_GE, &low_orig);
338 * Now binary-search using the counted B-tree, to find the largest
339 * ID which is in a contiguous sequence from the beginning of that
343 high = high_orig = count234(sharestate->connections);
344 while (high - low > 1) {
345 mid = (high + low) / 2;
346 cs = index234(sharestate->connections, mid);
347 if (cs->id == first + (mid - low_orig))
348 low = mid; /* this one is still in the sequence */
350 high = mid; /* this one is past the end */
354 * Now low is the tree index of the largest ID in the initial
355 * sequence. So the return value is one more than low's id, and we
356 * know low's id is given by the formula in the binary search loop
359 * (If an SSH connection went on for _enormously_ long, we might
360 * reach a point where all ids from 'first' to UINT_MAX were in
361 * use. In that situation the formula below would wrap round by
362 * one and return zero, which is conveniently the right way to
363 * signal 'no id available' from this function.)
365 ret = first + (low - low_orig) + 1;
367 struct ssh_sharing_connstate dummy;
369 assert(NULL == find234(sharestate->connections, &dummy, NULL));
374 static int share_halfchannel_cmp(void *av, void *bv)
376 const struct share_halfchannel *a = (const struct share_halfchannel *)av;
377 const struct share_halfchannel *b = (const struct share_halfchannel *)bv;
379 if (a->server_id < b->server_id)
381 else if (a->server_id > b->server_id)
387 static int share_channel_us_cmp(void *av, void *bv)
389 const struct share_channel *a = (const struct share_channel *)av;
390 const struct share_channel *b = (const struct share_channel *)bv;
392 if (a->upstream_id < b->upstream_id)
394 else if (a->upstream_id > b->upstream_id)
400 static int share_channel_server_cmp(void *av, void *bv)
402 const struct share_channel *a = (const struct share_channel *)av;
403 const struct share_channel *b = (const struct share_channel *)bv;
405 if (a->server_id < b->server_id)
407 else if (a->server_id > b->server_id)
413 static int share_xchannel_us_cmp(void *av, void *bv)
415 const struct share_xchannel *a = (const struct share_xchannel *)av;
416 const struct share_xchannel *b = (const struct share_xchannel *)bv;
418 if (a->upstream_id < b->upstream_id)
420 else if (a->upstream_id > b->upstream_id)
426 static int share_xchannel_server_cmp(void *av, void *bv)
428 const struct share_xchannel *a = (const struct share_xchannel *)av;
429 const struct share_xchannel *b = (const struct share_xchannel *)bv;
431 if (a->server_id < b->server_id)
433 else if (a->server_id > b->server_id)
439 static int share_forwarding_cmp(void *av, void *bv)
441 const struct share_forwarding *a = (const struct share_forwarding *)av;
442 const struct share_forwarding *b = (const struct share_forwarding *)bv;
445 if ((i = strcmp(a->host, b->host)) != 0)
447 else if (a->port < b->port)
449 else if (a->port > b->port)
455 static void share_xchannel_free(struct share_xchannel *xc)
457 while (xc->msghead) {
458 struct share_xchannel_message *tmp = xc->msghead;
459 xc->msghead = tmp->next;
465 static void share_connstate_free(struct ssh_sharing_connstate *cs)
467 struct share_halfchannel *hc;
468 struct share_xchannel *xc;
469 struct share_channel *chan;
470 struct share_forwarding *fwd;
472 while ((hc = (struct share_halfchannel *)
473 delpos234(cs->halfchannels, 0)) != NULL)
475 freetree234(cs->halfchannels);
477 /* All channels live in 'channels_by_us' but only some in
478 * 'channels_by_server', so we use the former to find the list of
480 freetree234(cs->channels_by_server);
481 while ((chan = (struct share_channel *)
482 delpos234(cs->channels_by_us, 0)) != NULL)
484 freetree234(cs->channels_by_us);
486 /* But every xchannel is in both trees, so it doesn't matter which
487 * we use to free them. */
488 while ((xc = (struct share_xchannel *)
489 delpos234(cs->xchannels_by_us, 0)) != NULL)
490 share_xchannel_free(xc);
491 freetree234(cs->xchannels_by_us);
492 freetree234(cs->xchannels_by_server);
494 while ((fwd = (struct share_forwarding *)
495 delpos234(cs->forwardings, 0)) != NULL)
497 freetree234(cs->forwardings);
499 while (cs->globreq_head) {
500 struct share_globreq *globreq = cs->globreq_head;
501 cs->globreq_head = cs->globreq_head->next;
508 void sharestate_free(void *v)
510 struct ssh_sharing_state *sharestate = (struct ssh_sharing_state *)v;
511 struct ssh_sharing_connstate *cs;
513 platform_ssh_share_cleanup(sharestate->sockname);
515 while ((cs = (struct ssh_sharing_connstate *)
516 delpos234(sharestate->connections, 0)) != NULL) {
517 share_connstate_free(cs);
519 freetree234(sharestate->connections);
520 if (sharestate->listensock) {
521 sk_close(sharestate->listensock);
522 sharestate->listensock = NULL;
524 sfree(sharestate->server_verstring);
525 sfree(sharestate->sockname);
529 static struct share_halfchannel *share_add_halfchannel
530 (struct ssh_sharing_connstate *cs, unsigned server_id)
532 struct share_halfchannel *hc = snew(struct share_halfchannel);
533 hc->server_id = server_id;
534 if (add234(cs->halfchannels, hc) != hc) {
543 static struct share_halfchannel *share_find_halfchannel
544 (struct ssh_sharing_connstate *cs, unsigned server_id)
546 struct share_halfchannel dummyhc;
547 dummyhc.server_id = server_id;
548 return find234(cs->halfchannels, &dummyhc, NULL);
551 static void share_remove_halfchannel(struct ssh_sharing_connstate *cs,
552 struct share_halfchannel *hc)
554 del234(cs->halfchannels, hc);
558 static struct share_channel *share_add_channel
559 (struct ssh_sharing_connstate *cs, unsigned downstream_id,
560 unsigned upstream_id, unsigned server_id, int state, int maxpkt)
562 struct share_channel *chan = snew(struct share_channel);
563 chan->downstream_id = downstream_id;
564 chan->upstream_id = upstream_id;
565 chan->server_id = server_id;
567 chan->downstream_maxpkt = maxpkt;
568 chan->x11_auth_upstream = NULL;
569 chan->x11_auth_data = NULL;
570 chan->x11_auth_proto = -1;
571 chan->x11_auth_datalen = 0;
572 chan->x11_one_shot = 0;
573 if (add234(cs->channels_by_us, chan) != chan) {
577 if (chan->state != UNACKNOWLEDGED) {
578 if (add234(cs->channels_by_server, chan) != chan) {
579 del234(cs->channels_by_us, chan);
587 static void share_channel_set_server_id(struct ssh_sharing_connstate *cs,
588 struct share_channel *chan,
589 unsigned server_id, int newstate)
591 chan->server_id = server_id;
592 chan->state = newstate;
593 assert(newstate != UNACKNOWLEDGED);
594 add234(cs->channels_by_server, chan);
597 static struct share_channel *share_find_channel_by_upstream
598 (struct ssh_sharing_connstate *cs, unsigned upstream_id)
600 struct share_channel dummychan;
601 dummychan.upstream_id = upstream_id;
602 return find234(cs->channels_by_us, &dummychan, NULL);
605 static struct share_channel *share_find_channel_by_server
606 (struct ssh_sharing_connstate *cs, unsigned server_id)
608 struct share_channel dummychan;
609 dummychan.server_id = server_id;
610 return find234(cs->channels_by_server, &dummychan, NULL);
613 static void share_remove_channel(struct ssh_sharing_connstate *cs,
614 struct share_channel *chan)
616 del234(cs->channels_by_us, chan);
617 del234(cs->channels_by_server, chan);
618 if (chan->x11_auth_upstream)
619 ssh_sharing_remove_x11_display(cs->parent->ssh,
620 chan->x11_auth_upstream);
621 sfree(chan->x11_auth_data);
625 static struct share_xchannel *share_add_xchannel
626 (struct ssh_sharing_connstate *cs,
627 unsigned upstream_id, unsigned server_id)
629 struct share_xchannel *xc = snew(struct share_xchannel);
630 xc->upstream_id = upstream_id;
631 xc->server_id = server_id;
633 xc->msghead = xc->msgtail = NULL;
634 if (add234(cs->xchannels_by_us, xc) != xc) {
638 if (add234(cs->xchannels_by_server, xc) != xc) {
639 del234(cs->xchannels_by_us, xc);
646 static struct share_xchannel *share_find_xchannel_by_upstream
647 (struct ssh_sharing_connstate *cs, unsigned upstream_id)
649 struct share_xchannel dummyxc;
650 dummyxc.upstream_id = upstream_id;
651 return find234(cs->xchannels_by_us, &dummyxc, NULL);
654 static struct share_xchannel *share_find_xchannel_by_server
655 (struct ssh_sharing_connstate *cs, unsigned server_id)
657 struct share_xchannel dummyxc;
658 dummyxc.server_id = server_id;
659 return find234(cs->xchannels_by_server, &dummyxc, NULL);
662 static void share_remove_xchannel(struct ssh_sharing_connstate *cs,
663 struct share_xchannel *xc)
665 del234(cs->xchannels_by_us, xc);
666 del234(cs->xchannels_by_server, xc);
667 share_xchannel_free(xc);
670 static struct share_forwarding *share_add_forwarding
671 (struct ssh_sharing_connstate *cs,
672 const char *host, int port)
674 struct share_forwarding *fwd = snew(struct share_forwarding);
675 fwd->host = dupstr(host);
678 if (add234(cs->forwardings, fwd) != fwd) {
686 static struct share_forwarding *share_find_forwarding
687 (struct ssh_sharing_connstate *cs, const char *host, int port)
689 struct share_forwarding dummyfwd, *ret;
690 dummyfwd.host = dupstr(host);
691 dummyfwd.port = port;
692 ret = find234(cs->forwardings, &dummyfwd, NULL);
693 sfree(dummyfwd.host);
697 static void share_remove_forwarding(struct ssh_sharing_connstate *cs,
698 struct share_forwarding *fwd)
700 del234(cs->forwardings, fwd);
704 static void send_packet_to_downstream(struct ssh_sharing_connstate *cs,
705 int type, const void *pkt, int pktlen,
706 struct share_channel *chan)
708 if (!cs->sock) /* throw away all packets destined for a dead downstream */
711 if (type == SSH2_MSG_CHANNEL_DATA) {
713 * Special case which we take care of at a low level, so as to
714 * be sure to apply it in all cases. On rare occasions we
715 * might find that we have a channel for which the
716 * downstream's maximum packet size exceeds the max packet
717 * size we presented to the server on its behalf. (This can
718 * occur in X11 forwarding, where we have to send _our_
719 * CHANNEL_OPEN_CONFIRMATION before we discover which if any
720 * downstream the channel is destined for, so if that
721 * downstream turns out to present a smaller max packet size
722 * then we're in this situation.)
724 * If that happens, we just chop up the packet into pieces and
725 * send them as separate CHANNEL_DATA packets.
727 const char *upkt = (const char *)pkt;
728 char header[13]; /* 4 length + 1 type + 4 channel id + 4 string len */
730 int len = toint(GET_32BIT(upkt + 4));
731 upkt += 8; /* skip channel id + length field */
733 if (len < 0 || len > pktlen - 8)
737 int this_len = (len > chan->downstream_maxpkt ?
738 chan->downstream_maxpkt : len);
739 PUT_32BIT(header, this_len + 9);
741 PUT_32BIT(header + 5, chan->downstream_id);
742 PUT_32BIT(header + 9, this_len);
743 sk_write(cs->sock, header, 13);
744 sk_write(cs->sock, upkt, this_len);
750 * Just do the obvious thing.
754 PUT_32BIT(header, pktlen + 1);
756 sk_write(cs->sock, header, 5);
757 sk_write(cs->sock, pkt, pktlen);
761 static void share_try_cleanup(struct ssh_sharing_connstate *cs)
764 struct share_halfchannel *hc;
765 struct share_channel *chan;
766 struct share_forwarding *fwd;
769 * Any half-open channels, i.e. those for which we'd received
770 * CHANNEL_OPEN from the server but not passed back a response
771 * from downstream, should be responded to with OPEN_FAILURE.
773 while ((hc = (struct share_halfchannel *)
774 index234(cs->halfchannels, 0)) != NULL) {
775 static const char reason[] = "PuTTY downstream no longer available";
776 static const char lang[] = "en";
777 unsigned char packet[256];
780 PUT_32BIT(packet + pos, hc->server_id); pos += 4;
781 PUT_32BIT(packet + pos, SSH2_OPEN_CONNECT_FAILED); pos += 4;
782 PUT_32BIT(packet + pos, strlen(reason)); pos += 4;
783 memcpy(packet + pos, reason, strlen(reason)); pos += strlen(reason);
784 PUT_32BIT(packet + pos, strlen(lang)); pos += 4;
785 memcpy(packet + pos, lang, strlen(lang)); pos += strlen(lang);
786 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
787 SSH2_MSG_CHANNEL_OPEN_FAILURE,
788 packet, pos, "cleanup after"
789 " downstream went away");
791 share_remove_halfchannel(cs, hc);
795 * Any actually open channels should have a CHANNEL_CLOSE sent for
796 * them, unless we've already done so. We won't be able to
797 * actually clean them up until CHANNEL_CLOSE comes back from the
798 * server, though (unless the server happens to have sent a CLOSE
801 * Another annoying exception is UNACKNOWLEDGED channels, i.e.
802 * we've _sent_ a CHANNEL_OPEN to the server but not received an
803 * OPEN_CONFIRMATION or OPEN_FAILURE. We must wait for a reply
804 * before closing the channel, because until we see that reply we
805 * won't have the server's channel id to put in the close message.
807 for (i = 0; (chan = (struct share_channel *)
808 index234(cs->channels_by_us, i)) != NULL; i++) {
809 unsigned char packet[256];
812 if (chan->state != SENT_CLOSE && chan->state != UNACKNOWLEDGED) {
813 PUT_32BIT(packet + pos, chan->server_id); pos += 4;
814 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
815 SSH2_MSG_CHANNEL_CLOSE,
816 packet, pos, "cleanup after"
817 " downstream went away");
818 if (chan->state != RCVD_CLOSE) {
819 chan->state = SENT_CLOSE;
821 /* In this case, we _can_ clear up the channel now. */
822 ssh_delete_sharing_channel(cs->parent->ssh, chan->upstream_id);
823 share_remove_channel(cs, chan);
824 i--; /* don't accidentally skip one as a result */
830 * Any remote port forwardings we're managing on behalf of this
831 * downstream should be cancelled. Again, we must defer those for
832 * which we haven't yet seen REQUEST_SUCCESS/FAILURE.
834 * We take a fire-and-forget approach during cleanup, not
835 * bothering to set want_reply.
837 for (i = 0; (fwd = (struct share_forwarding *)
838 index234(cs->forwardings, i)) != NULL; i++) {
840 static const char request[] = "cancel-tcpip-forward";
841 char *packet = snewn(256 + strlen(fwd->host), char);
844 PUT_32BIT(packet + pos, strlen(request)); pos += 4;
845 memcpy(packet + pos, request, strlen(request));
846 pos += strlen(request);
848 packet[pos++] = 0; /* !want_reply */
850 PUT_32BIT(packet + pos, strlen(fwd->host)); pos += 4;
851 memcpy(packet + pos, fwd->host, strlen(fwd->host));
852 pos += strlen(fwd->host);
854 PUT_32BIT(packet + pos, fwd->port); pos += 4;
856 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
857 SSH2_MSG_GLOBAL_REQUEST,
858 packet, pos, "cleanup after"
859 " downstream went away");
861 share_remove_forwarding(cs, fwd);
862 i--; /* don't accidentally skip one as a result */
866 if (count234(cs->halfchannels) == 0 &&
867 count234(cs->channels_by_us) == 0 &&
868 count234(cs->forwardings) == 0) {
870 * Now we're _really_ done, so we can get rid of cs completely.
872 del234(cs->parent->connections, cs);
873 ssh_sharing_downstream_disconnected(cs->parent->ssh, cs->id);
874 share_connstate_free(cs);
878 static void share_begin_cleanup(struct ssh_sharing_connstate *cs)
884 share_try_cleanup(cs);
887 static void share_disconnect(struct ssh_sharing_connstate *cs,
890 static const char lang[] = "en";
891 int msglen = strlen(message);
892 char *packet = snewn(msglen + 256, char);
895 PUT_32BIT(packet + pos, SSH2_DISCONNECT_PROTOCOL_ERROR); pos += 4;
897 PUT_32BIT(packet + pos, msglen); pos += 4;
898 memcpy(packet + pos, message, msglen);
901 PUT_32BIT(packet + pos, strlen(lang)); pos += 4;
902 memcpy(packet + pos, lang, strlen(lang)); pos += strlen(lang);
904 send_packet_to_downstream(cs, SSH2_MSG_DISCONNECT, packet, pos, NULL);
906 share_begin_cleanup(cs);
909 static int share_closing(Plug plug, const char *error_msg, int error_code,
912 struct ssh_sharing_connstate *cs = (struct ssh_sharing_connstate *)plug;
914 ssh_sharing_logf(cs->parent->ssh, cs->id, "%s", error_msg);
915 share_begin_cleanup(cs);
919 static int getstring_inner(const void *vdata, int datalen,
920 char **out, int *outlen)
922 const unsigned char *data = (const unsigned char *)vdata;
928 len = toint(GET_32BIT(data));
929 if (len < 0 || len > datalen - 4)
933 *outlen = len + 4; /* total size including length field */
935 *out = dupprintf("%.*s", len, (char *)data + 4);
939 static char *getstring(const void *data, int datalen)
942 if (getstring_inner(data, datalen, &ret, NULL))
948 static int getstring_size(const void *data, int datalen)
951 if (getstring_inner(data, datalen, NULL, &ret))
958 * Append a message to the end of an xchannel's queue, with the length
959 * and type code filled in and the data block allocated but
962 struct share_xchannel_message *share_xchannel_add_message
963 (struct share_xchannel *xc, int type, int len)
965 unsigned char *block;
966 struct share_xchannel_message *msg;
969 * Be a little tricksy here by allocating a single memory block
970 * containing both the 'struct share_xchannel_message' and the
971 * actual data. Simplifies freeing it later.
973 block = smalloc(sizeof(struct share_xchannel_message) + len);
974 msg = (struct share_xchannel_message *)block;
975 msg->data = block + sizeof(struct share_xchannel_message);
980 * Queue it in the xchannel.
983 xc->msgtail->next = msg;
992 void share_dead_xchannel_respond(struct ssh_sharing_connstate *cs,
993 struct share_xchannel *xc)
996 * Handle queued incoming messages from the server destined for an
997 * xchannel which is dead (i.e. downstream sent OPEN_FAILURE).
1000 while (xc->msghead) {
1001 struct share_xchannel_message *msg = xc->msghead;
1002 xc->msghead = msg->next;
1004 if (msg->type == SSH2_MSG_CHANNEL_REQUEST && msg->datalen > 4) {
1006 * A CHANNEL_REQUEST is responded to by sending
1007 * CHANNEL_FAILURE, if it has want_reply set.
1009 int wantreplypos = getstring_size(msg->data, msg->datalen);
1010 if (wantreplypos > 0 && wantreplypos < msg->datalen &&
1011 msg->data[wantreplypos] != 0) {
1012 unsigned char id[4];
1013 PUT_32BIT(id, xc->server_id);
1014 ssh_send_packet_from_downstream
1015 (cs->parent->ssh, cs->id, SSH2_MSG_CHANNEL_FAILURE, id, 4,
1016 "downstream refused X channel open");
1018 } else if (msg->type == SSH2_MSG_CHANNEL_CLOSE) {
1020 * On CHANNEL_CLOSE we can discard the channel completely.
1029 ssh_delete_sharing_channel(cs->parent->ssh, xc->upstream_id);
1030 share_remove_xchannel(cs, xc);
1034 void share_xchannel_confirmation(struct ssh_sharing_connstate *cs,
1035 struct share_xchannel *xc,
1036 struct share_channel *chan,
1037 unsigned downstream_window)
1039 unsigned char window_adjust[8];
1042 * Send all the queued messages downstream.
1044 while (xc->msghead) {
1045 struct share_xchannel_message *msg = xc->msghead;
1046 xc->msghead = msg->next;
1048 if (msg->datalen >= 4)
1049 PUT_32BIT(msg->data, chan->downstream_id);
1050 send_packet_to_downstream(cs, msg->type,
1051 msg->data, msg->datalen, chan);
1057 * Send a WINDOW_ADJUST back upstream, to synchronise the window
1058 * size downstream thinks it's presented with the one we've
1059 * actually presented.
1061 PUT_32BIT(window_adjust, xc->server_id);
1062 PUT_32BIT(window_adjust + 4, downstream_window - xc->window);
1063 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1064 SSH2_MSG_CHANNEL_WINDOW_ADJUST,
1065 window_adjust, 8, "window adjustment after"
1066 " downstream accepted X channel");
1069 void share_xchannel_failure(struct ssh_sharing_connstate *cs,
1070 struct share_xchannel *xc)
1073 * If downstream refuses to open our X channel at all for some
1074 * reason, we must respond by sending an emergency CLOSE upstream.
1076 unsigned char id[4];
1077 PUT_32BIT(id, xc->server_id);
1078 ssh_send_packet_from_downstream
1079 (cs->parent->ssh, cs->id, SSH2_MSG_CHANNEL_CLOSE, id, 4,
1080 "downstream refused X channel open");
1083 * Now mark the xchannel as dead, and respond to anything sent on
1084 * it until we see CLOSE for it in turn.
1087 share_dead_xchannel_respond(cs, xc);
1090 void share_setup_x11_channel(void *csv, void *chanv,
1091 unsigned upstream_id, unsigned server_id,
1092 unsigned server_currwin, unsigned server_maxpkt,
1093 unsigned client_adjusted_window,
1094 const char *peer_addr, int peer_port, int endian,
1095 int protomajor, int protominor,
1096 const void *initial_data, int initial_len)
1098 struct ssh_sharing_connstate *cs = (struct ssh_sharing_connstate *)csv;
1099 struct share_channel *chan = (struct share_channel *)chanv;
1100 struct share_xchannel *xc;
1101 struct share_xchannel_message *msg;
1108 * Create an xchannel containing data we've already received from
1109 * the X client, and preload it with a CHANNEL_DATA message
1110 * containing our own made-up authorisation greeting and any
1111 * additional data sent from the server so far.
1113 xc = share_add_xchannel(cs, upstream_id, server_id);
1114 greeting = x11_make_greeting(endian, protomajor, protominor,
1115 chan->x11_auth_proto,
1116 chan->x11_auth_data, chan->x11_auth_datalen,
1117 peer_addr, peer_port, &greeting_len);
1118 msg = share_xchannel_add_message(xc, SSH2_MSG_CHANNEL_DATA,
1119 8 + greeting_len + initial_len);
1120 /* leave the channel id field unfilled - we don't know the
1121 * downstream id yet, of course */
1122 PUT_32BIT(msg->data + 4, greeting_len + initial_len);
1123 memcpy(msg->data + 8, greeting, greeting_len);
1124 memcpy(msg->data + 8 + greeting_len, initial_data, initial_len);
1127 xc->window = client_adjusted_window + greeting_len;
1130 * Send on a CHANNEL_OPEN to downstream.
1132 pktlen = 27 + strlen(peer_addr);
1133 pkt = snewn(pktlen, unsigned char);
1134 PUT_32BIT(pkt, 3); /* strlen("x11") */
1135 memcpy(pkt+4, "x11", 3);
1136 PUT_32BIT(pkt+7, server_id);
1137 PUT_32BIT(pkt+11, server_currwin);
1138 PUT_32BIT(pkt+15, server_maxpkt);
1139 PUT_32BIT(pkt+19, strlen(peer_addr));
1140 memcpy(pkt+23, peer_addr, strlen(peer_addr));
1141 PUT_32BIT(pkt+23+strlen(peer_addr), peer_port);
1142 send_packet_to_downstream(cs, SSH2_MSG_CHANNEL_OPEN, pkt, pktlen, NULL);
1146 * If this was a once-only X forwarding, clean it up now.
1148 if (chan->x11_one_shot) {
1149 ssh_sharing_remove_x11_display(cs->parent->ssh,
1150 chan->x11_auth_upstream);
1151 chan->x11_auth_upstream = NULL;
1152 sfree(chan->x11_auth_data);
1153 chan->x11_auth_proto = -1;
1154 chan->x11_auth_datalen = 0;
1155 chan->x11_one_shot = 0;
1159 void share_got_pkt_from_server(void *csv, int type,
1160 unsigned char *pkt, int pktlen)
1162 struct ssh_sharing_connstate *cs = (struct ssh_sharing_connstate *)csv;
1163 struct share_globreq *globreq;
1165 unsigned upstream_id, server_id;
1166 struct share_channel *chan;
1167 struct share_xchannel *xc;
1170 case SSH2_MSG_REQUEST_SUCCESS:
1171 case SSH2_MSG_REQUEST_FAILURE:
1172 globreq = cs->globreq_head;
1173 if (globreq->type == GLOBREQ_TCPIP_FORWARD) {
1174 if (type == SSH2_MSG_REQUEST_FAILURE) {
1175 share_remove_forwarding(cs, globreq->fwd);
1177 globreq->fwd->active = TRUE;
1179 } else if (globreq->type == GLOBREQ_CANCEL_TCPIP_FORWARD) {
1180 if (type == SSH2_MSG_REQUEST_SUCCESS) {
1181 share_remove_forwarding(cs, globreq->fwd);
1184 if (globreq->want_reply) {
1185 send_packet_to_downstream(cs, type, pkt, pktlen, NULL);
1187 cs->globreq_head = globreq->next;
1189 if (cs->globreq_head == NULL)
1190 cs->globreq_tail = NULL;
1193 /* Retry cleaning up this connection, in case that reply
1194 * was the last thing we were waiting for. */
1195 share_try_cleanup(cs);
1200 case SSH2_MSG_CHANNEL_OPEN:
1201 id_pos = getstring_size(pkt, pktlen);
1202 assert(id_pos >= 0);
1203 server_id = GET_32BIT(pkt + id_pos);
1204 share_add_halfchannel(cs, server_id);
1206 send_packet_to_downstream(cs, type, pkt, pktlen, NULL);
1209 case SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
1210 case SSH2_MSG_CHANNEL_OPEN_FAILURE:
1211 case SSH2_MSG_CHANNEL_CLOSE:
1212 case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
1213 case SSH2_MSG_CHANNEL_DATA:
1214 case SSH2_MSG_CHANNEL_EXTENDED_DATA:
1215 case SSH2_MSG_CHANNEL_EOF:
1216 case SSH2_MSG_CHANNEL_REQUEST:
1217 case SSH2_MSG_CHANNEL_SUCCESS:
1218 case SSH2_MSG_CHANNEL_FAILURE:
1220 * All these messages have the recipient channel id as the
1221 * first uint32 field in the packet. Substitute the downstream
1222 * channel id for our one and pass the packet downstream.
1224 assert(pktlen >= 4);
1225 upstream_id = GET_32BIT(pkt);
1226 if ((chan = share_find_channel_by_upstream(cs, upstream_id)) != NULL) {
1228 * The normal case: this id refers to an open channel.
1230 PUT_32BIT(pkt, chan->downstream_id);
1231 send_packet_to_downstream(cs, type, pkt, pktlen, chan);
1234 * Update the channel state, for messages that need it.
1236 if (type == SSH2_MSG_CHANNEL_OPEN_CONFIRMATION) {
1237 if (chan->state == UNACKNOWLEDGED && pktlen >= 8) {
1238 share_channel_set_server_id(cs, chan, GET_32BIT(pkt+4),
1241 /* Retry cleaning up this connection, so that we
1242 * can send an immediate CLOSE on this channel for
1243 * which we now know the server id. */
1244 share_try_cleanup(cs);
1247 } else if (type == SSH2_MSG_CHANNEL_OPEN_FAILURE) {
1248 ssh_delete_sharing_channel(cs->parent->ssh, chan->upstream_id);
1249 share_remove_channel(cs, chan);
1250 } else if (type == SSH2_MSG_CHANNEL_CLOSE) {
1251 if (chan->state == SENT_CLOSE) {
1252 ssh_delete_sharing_channel(cs->parent->ssh,
1254 share_remove_channel(cs, chan);
1256 /* Retry cleaning up this connection, in case this
1257 * channel closure was the last thing we were
1259 share_try_cleanup(cs);
1262 chan->state = RCVD_CLOSE;
1265 } else if ((xc = share_find_xchannel_by_upstream(cs, upstream_id))
1268 * The unusual case: this id refers to an xchannel. Add it
1269 * to the xchannel's queue.
1271 struct share_xchannel_message *msg;
1273 msg = share_xchannel_add_message(xc, type, pktlen);
1274 memcpy(msg->data, pkt, pktlen);
1276 /* If the xchannel is dead, then also respond to it (which
1277 * may involve deleting the channel). */
1279 share_dead_xchannel_respond(cs, xc);
1284 assert(!"This packet type should never have come from ssh.c");
1289 static void share_got_pkt_from_downstream(struct ssh_sharing_connstate *cs,
1291 unsigned char *pkt, int pktlen)
1294 struct share_forwarding *fwd;
1296 unsigned old_id, new_id, server_id;
1297 struct share_globreq *globreq;
1298 struct share_channel *chan;
1299 struct share_halfchannel *hc;
1300 struct share_xchannel *xc;
1304 case SSH2_MSG_DISCONNECT:
1306 * This message stops here: if downstream is disconnecting
1307 * from us, that doesn't mean we want to disconnect from the
1308 * SSH server. Close the downstream connection and start
1311 share_begin_cleanup(cs);
1314 case SSH2_MSG_GLOBAL_REQUEST:
1316 * The only global requests we understand are "tcpip-forward"
1317 * and "cancel-tcpip-forward". Since those require us to
1318 * maintain state, we must assume that other global requests
1319 * will probably require that too, and so we don't forward on
1320 * any request we don't understand.
1322 request_name = getstring(pkt, pktlen);
1323 if (request_name == NULL) {
1324 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1328 if (!strcmp(request_name, "tcpip-forward")) {
1329 int wantreplypos, orig_wantreply, port, ret;
1332 sfree(request_name);
1335 * Pick the packet apart to find the want_reply field and
1336 * the host/port we're going to ask to listen on.
1338 wantreplypos = getstring_size(pkt, pktlen);
1339 if (wantreplypos < 0 || wantreplypos >= pktlen) {
1340 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1343 orig_wantreply = pkt[wantreplypos];
1344 port = getstring_size(pkt + (wantreplypos + 1),
1345 pktlen - (wantreplypos + 1));
1346 port += (wantreplypos + 1);
1347 if (port < 0 || port > pktlen - 4) {
1348 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1351 host = getstring(pkt + (wantreplypos + 1),
1352 pktlen - (wantreplypos + 1));
1353 assert(host != NULL);
1354 port = GET_32BIT(pkt + port);
1357 * See if we can allocate space in ssh.c's tree of remote
1358 * port forwardings. If we can't, it's because another
1359 * client sharing this connection has already allocated
1360 * the identical port forwarding, so we take it on
1361 * ourselves to manufacture a failure packet and send it
1362 * back to downstream.
1364 ret = ssh_alloc_sharing_rportfwd(cs->parent->ssh, host, port, cs);
1366 if (orig_wantreply) {
1367 send_packet_to_downstream(cs, SSH2_MSG_REQUEST_FAILURE,
1372 * We've managed to make space for this forwarding
1373 * locally. Pass the request on to the SSH server, but
1374 * set want_reply even if it wasn't originally set, so
1375 * that we know whether this forwarding needs to be
1376 * cleaned up if downstream goes away.
1378 int old_wantreply = pkt[wantreplypos];
1379 pkt[wantreplypos] = 1;
1380 ssh_send_packet_from_downstream
1381 (cs->parent->ssh, cs->id, type, pkt, pktlen,
1382 old_wantreply ? NULL : "upstream added want_reply flag");
1383 fwd = share_add_forwarding(cs, host, port);
1384 ssh_sharing_queue_global_request(cs->parent->ssh, cs);
1387 globreq = snew(struct share_globreq);
1388 globreq->next = NULL;
1389 if (cs->globreq_tail)
1390 cs->globreq_tail->next = globreq;
1392 cs->globreq_head = globreq;
1394 globreq->want_reply = orig_wantreply;
1395 globreq->type = GLOBREQ_TCPIP_FORWARD;
1400 } else if (!strcmp(request_name, "cancel-tcpip-forward")) {
1401 int wantreplypos, orig_wantreply, port;
1403 struct share_forwarding *fwd;
1405 sfree(request_name);
1408 * Pick the packet apart to find the want_reply field and
1409 * the host/port we're going to ask to listen on.
1411 wantreplypos = getstring_size(pkt, pktlen);
1412 if (wantreplypos < 0 || wantreplypos >= pktlen) {
1413 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1416 orig_wantreply = pkt[wantreplypos];
1417 port = getstring_size(pkt + (wantreplypos + 1),
1418 pktlen - (wantreplypos + 1));
1419 port += (wantreplypos + 1);
1420 if (port < 0 || port > pktlen - 4) {
1421 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1424 host = getstring(pkt + (wantreplypos + 1),
1425 pktlen - (wantreplypos + 1));
1426 assert(host != NULL);
1427 port = GET_32BIT(pkt + port);
1430 * Look up the existing forwarding with these details.
1432 fwd = share_find_forwarding(cs, host, port);
1434 if (orig_wantreply) {
1435 send_packet_to_downstream(cs, SSH2_MSG_REQUEST_FAILURE,
1440 * Pass the cancel request on to the SSH server, but
1441 * set want_reply even if it wasn't originally set, so
1442 * that _we_ know whether the forwarding has been
1443 * deleted even if downstream doesn't want to know.
1445 int old_wantreply = pkt[wantreplypos];
1446 pkt[wantreplypos] = 1;
1447 ssh_send_packet_from_downstream
1448 (cs->parent->ssh, cs->id, type, pkt, pktlen,
1449 old_wantreply ? NULL : "upstream added want_reply flag");
1450 ssh_sharing_queue_global_request(cs->parent->ssh, cs);
1456 * Request we don't understand. Manufacture a failure
1457 * message if an answer was required.
1461 sfree(request_name);
1463 wantreplypos = getstring_size(pkt, pktlen);
1464 if (wantreplypos < 0 || wantreplypos >= pktlen) {
1465 err = dupprintf("Truncated GLOBAL_REQUEST packet");
1468 if (pkt[wantreplypos])
1469 send_packet_to_downstream(cs, SSH2_MSG_REQUEST_FAILURE,
1474 case SSH2_MSG_CHANNEL_OPEN:
1475 /* Sender channel id comes after the channel type string */
1476 id_pos = getstring_size(pkt, pktlen);
1477 if (id_pos < 0 || id_pos > pktlen - 12) {
1478 err = dupprintf("Truncated CHANNEL_OPEN packet");
1482 old_id = GET_32BIT(pkt + id_pos);
1483 new_id = ssh_alloc_sharing_channel(cs->parent->ssh, cs);
1484 share_add_channel(cs, old_id, new_id, 0, UNACKNOWLEDGED,
1485 GET_32BIT(pkt + id_pos + 8));
1486 PUT_32BIT(pkt + id_pos, new_id);
1487 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1488 type, pkt, pktlen, NULL);
1491 case SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
1493 err = dupprintf("Truncated CHANNEL_OPEN_CONFIRMATION packet");
1497 id_pos = 4; /* sender channel id is 2nd uint32 field in packet */
1498 old_id = GET_32BIT(pkt + id_pos);
1500 server_id = GET_32BIT(pkt);
1501 /* This server id may refer to either a halfchannel or an xchannel. */
1502 hc = NULL, xc = NULL; /* placate optimiser */
1503 if ((hc = share_find_halfchannel(cs, server_id)) != NULL) {
1504 new_id = ssh_alloc_sharing_channel(cs->parent->ssh, cs);
1505 } else if ((xc = share_find_xchannel_by_server(cs, server_id))
1507 new_id = xc->upstream_id;
1509 err = dupprintf("CHANNEL_OPEN_CONFIRMATION packet cited unknown channel %u", (unsigned)server_id);
1513 PUT_32BIT(pkt + id_pos, new_id);
1515 chan = share_add_channel(cs, old_id, new_id, server_id, OPEN,
1516 GET_32BIT(pkt + 12));
1519 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1520 type, pkt, pktlen, NULL);
1521 share_remove_halfchannel(cs, hc);
1523 unsigned downstream_window = GET_32BIT(pkt + 8);
1524 if (downstream_window < 256) {
1525 err = dupprintf("Initial window size for x11 channel must be at least 256 (got %u)", downstream_window);
1528 share_xchannel_confirmation(cs, xc, chan, downstream_window);
1529 share_remove_xchannel(cs, xc);
1534 case SSH2_MSG_CHANNEL_OPEN_FAILURE:
1536 err = dupprintf("Truncated CHANNEL_OPEN_FAILURE packet");
1540 server_id = GET_32BIT(pkt);
1541 /* This server id may refer to either a halfchannel or an xchannel. */
1542 if ((hc = share_find_halfchannel(cs, server_id)) != NULL) {
1543 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1544 type, pkt, pktlen, NULL);
1545 share_remove_halfchannel(cs, hc);
1546 } else if ((xc = share_find_xchannel_by_server(cs, server_id))
1548 share_xchannel_failure(cs, xc);
1550 err = dupprintf("CHANNEL_OPEN_FAILURE packet cited unknown channel %u", (unsigned)server_id);
1556 case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
1557 case SSH2_MSG_CHANNEL_DATA:
1558 case SSH2_MSG_CHANNEL_EXTENDED_DATA:
1559 case SSH2_MSG_CHANNEL_EOF:
1560 case SSH2_MSG_CHANNEL_CLOSE:
1561 case SSH2_MSG_CHANNEL_REQUEST:
1562 case SSH2_MSG_CHANNEL_SUCCESS:
1563 case SSH2_MSG_CHANNEL_FAILURE:
1564 case SSH2_MSG_IGNORE:
1565 case SSH2_MSG_DEBUG:
1566 if (type == SSH2_MSG_CHANNEL_REQUEST &&
1567 (request_name = getstring(pkt + 4, pktlen - 4)) != NULL) {
1569 * Agent forwarding requests from downstream are treated
1570 * specially. Because OpenSSHD doesn't let us enable agent
1571 * forwarding independently per session channel, and in
1572 * particular because the OpenSSH-defined agent forwarding
1573 * protocol does not mark agent-channel requests with the
1574 * id of the session channel they originate from, the only
1575 * way we can implement agent forwarding in a
1576 * connection-shared PuTTY is to forward the _upstream_
1577 * agent. Hence, we unilaterally deny agent forwarding
1578 * requests from downstreams if we aren't prepared to
1579 * forward an agent ourselves.
1581 * (If we are, then we dutifully pass agent forwarding
1582 * requests upstream. OpenSSHD has the curious behaviour
1583 * that all but the first such request will be rejected,
1584 * but all session channels opened after the first request
1585 * get agent forwarding enabled whether they ask for it or
1586 * not; but that's not our concern, since other SSH
1587 * servers supporting the same piece of protocol might in
1588 * principle at least manage to enable agent forwarding on
1589 * precisely the channels that requested it, even if the
1590 * subsequent CHANNEL_OPENs still can't be associated with
1591 * a parent session channel.)
1593 if (!strcmp(request_name, "auth-agent-req@openssh.com") &&
1594 !ssh_agent_forwarding_permitted(cs->parent->ssh)) {
1595 unsigned server_id = GET_32BIT(pkt);
1596 unsigned char recipient_id[4];
1597 chan = share_find_channel_by_server(cs, server_id);
1599 PUT_32BIT(recipient_id, chan->downstream_id);
1600 send_packet_to_downstream(cs, SSH2_MSG_CHANNEL_FAILURE,
1601 recipient_id, 4, NULL);
1603 char *buf = dupprintf("Agent forwarding request for "
1604 "unrecognised channel %u", server_id);
1605 share_disconnect(cs, buf);
1613 * Another thing we treat specially is X11 forwarding
1614 * requests. For these, we have to make up another set of
1615 * X11 auth data, and enter it into our SSH connection's
1616 * list of possible X11 authorisation credentials so that
1617 * when we see an X11 channel open request we can know
1618 * whether it's one to handle locally or one to pass on to
1619 * a downstream, and if the latter, which one.
1621 if (!strcmp(request_name, "x11-req")) {
1622 unsigned server_id = GET_32BIT(pkt);
1623 int want_reply, single_connection, screen;
1624 char *auth_proto_str, *auth_data;
1625 int auth_proto, protolen, datalen;
1628 chan = share_find_channel_by_server(cs, server_id);
1630 char *buf = dupprintf("X11 forwarding request for "
1631 "unrecognised channel %u", server_id);
1632 share_disconnect(cs, buf);
1638 * Pick apart the whole message to find the downstream
1641 /* we have already seen: 4 bytes channel id, 4+7 request name */
1643 err = dupprintf("Truncated CHANNEL_REQUEST(\"x11\") packet");
1646 want_reply = pkt[15] != 0;
1647 single_connection = pkt[16] != 0;
1648 auth_proto_str = getstring(pkt+17, pktlen-17);
1649 pos = 17 + getstring_size(pkt+17, pktlen-17);
1650 auth_data = getstring(pkt+pos, pktlen-pos);
1651 pos += getstring_size(pkt+pos, pktlen-pos);
1652 if (pktlen < pos+4) {
1653 err = dupprintf("Truncated CHANNEL_REQUEST(\"x11\") packet");
1656 screen = GET_32BIT(pkt+pos);
1658 auth_proto = x11_identify_auth_proto(auth_proto_str);
1659 if (auth_proto < 0) {
1660 /* Reject due to not understanding downstream's
1661 * requested authorisation method. */
1662 unsigned char recipient_id[4];
1663 PUT_32BIT(recipient_id, chan->downstream_id);
1664 send_packet_to_downstream(cs, SSH2_MSG_CHANNEL_FAILURE,
1665 recipient_id, 4, NULL);
1668 chan->x11_auth_proto = auth_proto;
1669 chan->x11_auth_data = x11_dehexify(auth_data,
1670 &chan->x11_auth_datalen);
1671 chan->x11_auth_upstream =
1672 ssh_sharing_add_x11_display(cs->parent->ssh, auth_proto,
1674 chan->x11_one_shot = single_connection;
1677 * Now construct a replacement X forwarding request,
1678 * containing our own auth data, and send that to the
1681 protolen = strlen(chan->x11_auth_upstream->protoname);
1682 datalen = strlen(chan->x11_auth_upstream->datastring);
1683 pktlen = 29+protolen+datalen;
1684 pkt = snewn(pktlen, unsigned char);
1685 PUT_32BIT(pkt, server_id);
1686 PUT_32BIT(pkt+4, 7); /* strlen("x11-req") */
1687 memcpy(pkt+8, "x11-req", 7);
1688 pkt[15] = want_reply;
1689 pkt[16] = single_connection;
1690 PUT_32BIT(pkt+17, protolen);
1691 memcpy(pkt+21, chan->x11_auth_upstream->protoname, protolen);
1692 PUT_32BIT(pkt+21+protolen, datalen);
1693 memcpy(pkt+25+protolen, chan->x11_auth_upstream->datastring,
1695 PUT_32BIT(pkt+25+protolen+datalen, screen);
1696 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1697 SSH2_MSG_CHANNEL_REQUEST,
1705 ssh_send_packet_from_downstream(cs->parent->ssh, cs->id,
1706 type, pkt, pktlen, NULL);
1707 if (type == SSH2_MSG_CHANNEL_CLOSE && pktlen >= 4) {
1708 server_id = GET_32BIT(pkt);
1709 chan = share_find_channel_by_server(cs, server_id);
1711 if (chan->state == RCVD_CLOSE) {
1712 ssh_delete_sharing_channel(cs->parent->ssh,
1714 share_remove_channel(cs, chan);
1716 chan->state = SENT_CLOSE;
1723 err = dupprintf("Unexpected packet type %d\n", type);
1727 * Any other packet type is unexpected. In particular, we
1728 * never pass GLOBAL_REQUESTs downstream, so we never expect
1729 * to see SSH2_MSG_REQUEST_{SUCCESS,FAILURE}.
1732 assert(err != NULL);
1733 share_disconnect(cs, err);
1740 * Coroutine macros similar to, but simplified from, those in ssh.c.
1742 #define crBegin(v) { int *crLine = &v; switch(v) { case 0:;
1743 #define crFinish(z) } *crLine = 0; return (z); }
1744 #define crGetChar(c) do \
1746 while (len == 0) { \
1747 *crLine =__LINE__; return 1; case __LINE__:; \
1750 (c) = (unsigned char)*data++; \
1753 static int share_receive(Plug plug, int urgent, char *data, int len)
1755 struct ssh_sharing_connstate *cs = (struct ssh_sharing_connstate *)plug;
1756 static const char expected_verstring_prefix[] =
1757 "SSHCONNECTION@putty.projects.tartarus.org-2.0-";
1760 crBegin(cs->crLine);
1763 * First read the version string from downstream.
1770 if (cs->recvlen >= sizeof(cs->recvbuf)) {
1771 char *buf = dupprintf("Version string far too long\n");
1772 share_disconnect(cs, buf);
1776 cs->recvbuf[cs->recvlen++] = c;
1780 * Now parse the version string to make sure it's at least vaguely
1781 * sensible, and log it.
1783 if (cs->recvlen < sizeof(expected_verstring_prefix)-1 ||
1784 memcmp(cs->recvbuf, expected_verstring_prefix,
1785 sizeof(expected_verstring_prefix) - 1)) {
1786 char *buf = dupprintf("Version string did not have expected prefix\n");
1787 share_disconnect(cs, buf);
1791 if (cs->recvlen > 0 && cs->recvbuf[cs->recvlen-1] == '\015')
1792 cs->recvlen--; /* trim off \r before \n */
1793 ssh_sharing_logf(cs->parent->ssh, cs->id,
1794 "Downstream version string: %.*s",
1795 cs->recvlen, cs->recvbuf);
1798 * Loop round reading packets.
1802 while (cs->recvlen < 4) {
1804 cs->recvbuf[cs->recvlen++] = c;
1806 cs->curr_packetlen = toint(GET_32BIT(cs->recvbuf) + 4);
1807 if (cs->curr_packetlen < 5 ||
1808 cs->curr_packetlen > sizeof(cs->recvbuf)) {
1809 char *buf = dupprintf("Bad packet length %u\n",
1810 (unsigned)cs->curr_packetlen);
1811 share_disconnect(cs, buf);
1815 while (cs->recvlen < cs->curr_packetlen) {
1817 cs->recvbuf[cs->recvlen++] = c;
1820 share_got_pkt_from_downstream(cs, cs->recvbuf[4],
1821 cs->recvbuf + 5, cs->recvlen - 5);
1828 static void share_sent(Plug plug, int bufsize)
1830 /* struct ssh_sharing_connstate *cs = (struct ssh_sharing_connstate *)plug; */
1833 * We do nothing here, because we expect that there won't be a
1834 * need to throttle and unthrottle the connection to a downstream.
1835 * It should automatically throttle itself: if the SSH server
1836 * sends huge amounts of data on all channels then it'll run out
1837 * of window until our downstream sends it back some
1842 static int share_listen_closing(Plug plug, const char *error_msg,
1843 int error_code, int calling_back)
1845 struct ssh_sharing_state *sharestate = (struct ssh_sharing_state *)plug;
1847 ssh_sharing_logf(sharestate->ssh, 0,
1848 "listening socket: %s", error_msg);
1849 sk_close(sharestate->listensock);
1850 sharestate->listensock = NULL;
1854 static void share_send_verstring(struct ssh_sharing_connstate *cs)
1856 char *fullstring = dupcat("SSHCONNECTION@putty.projects.tartarus.org-2.0-",
1857 cs->parent->server_verstring, "\015\012", NULL);
1858 sk_write(cs->sock, fullstring, strlen(fullstring));
1861 cs->sent_verstring = TRUE;
1864 int share_ndownstreams(void *state)
1866 struct ssh_sharing_state *sharestate = (struct ssh_sharing_state *)state;
1867 return count234(sharestate->connections);
1870 void share_activate(void *state, const char *server_verstring)
1873 * Indication from ssh.c that we are now ready to begin serving
1874 * any downstreams that have already connected to us.
1876 struct ssh_sharing_state *sharestate = (struct ssh_sharing_state *)state;
1877 struct ssh_sharing_connstate *cs;
1881 * Trim the server's version string down to just the software
1882 * version component, removing "SSH-2.0-" or whatever at the
1885 for (i = 0; i < 2; i++) {
1886 server_verstring += strcspn(server_verstring, "-");
1887 if (*server_verstring)
1891 sharestate->server_verstring = dupstr(server_verstring);
1893 for (i = 0; (cs = (struct ssh_sharing_connstate *)
1894 index234(sharestate->connections, i)) != NULL; i++) {
1895 assert(!cs->sent_verstring);
1896 share_send_verstring(cs);
1900 static int share_listen_accepting(Plug plug,
1901 accept_fn_t constructor, accept_ctx_t ctx)
1903 static const struct plug_function_table connection_fn_table = {
1904 NULL, /* no log function, because that's for outgoing connections */
1908 NULL /* no accepting function, because we've already done it */
1910 struct ssh_sharing_state *sharestate = (struct ssh_sharing_state *)plug;
1911 struct ssh_sharing_connstate *cs;
1915 * A new downstream has connected to us.
1917 cs = snew(struct ssh_sharing_connstate);
1918 cs->fn = &connection_fn_table;
1919 cs->parent = sharestate;
1921 if ((cs->id = share_find_unused_id(sharestate, sharestate->nextid)) == 0 &&
1922 (cs->id = share_find_unused_id(sharestate, 1)) == 0) {
1926 sharestate->nextid = cs->id + 1;
1927 if (sharestate->nextid == 0)
1928 sharestate->nextid++; /* only happens in VERY long-running upstreams */
1930 cs->sock = constructor(ctx, (Plug) cs);
1931 if ((err = sk_socket_error(cs->sock)) != NULL) {
1936 sk_set_frozen(cs->sock, 0);
1938 add234(cs->parent->connections, cs);
1940 cs->sent_verstring = FALSE;
1941 if (sharestate->server_verstring)
1942 share_send_verstring(cs);
1944 cs->got_verstring = FALSE;
1947 cs->halfchannels = newtree234(share_halfchannel_cmp);
1948 cs->channels_by_us = newtree234(share_channel_us_cmp);
1949 cs->channels_by_server = newtree234(share_channel_server_cmp);
1950 cs->xchannels_by_us = newtree234(share_xchannel_us_cmp);
1951 cs->xchannels_by_server = newtree234(share_xchannel_server_cmp);
1952 cs->forwardings = newtree234(share_forwarding_cmp);
1953 cs->globreq_head = cs->globreq_tail = NULL;
1955 ssh_sharing_downstream_connected(sharestate->ssh, cs->id);
1960 /* Per-application overrides for what roles we can take (e.g. pscp
1961 * will never be an upstream) */
1962 extern const int share_can_be_downstream;
1963 extern const int share_can_be_upstream;
1966 * Init function for connection sharing. We either open a listening
1967 * socket and become an upstream, or connect to an existing one and
1968 * become a downstream, or do neither. We are responsible for deciding
1969 * which of these to do (including checking the Conf to see if
1970 * connection sharing is even enabled in the first place). If we
1971 * become a downstream, we return the Socket with which we connected
1972 * to the upstream; otherwise (whether or not we have established an
1973 * upstream) we return NULL.
1975 Socket ssh_connection_sharing_init(const char *host, int port,
1976 Conf *conf, Ssh ssh, void **state)
1978 static const struct plug_function_table listen_fn_table = {
1979 NULL, /* no log function, because that's for outgoing connections */
1980 share_listen_closing,
1981 NULL, /* no receive function on a listening socket */
1982 NULL, /* no sent function on a listening socket */
1983 share_listen_accepting
1986 int result, can_upstream, can_downstream;
1987 char *logtext, *ds_err, *us_err;
1990 struct ssh_sharing_state *sharestate;
1992 if (!conf_get_int(conf, CONF_ssh_connection_sharing))
1993 return NULL; /* do not share anything */
1994 can_upstream = share_can_be_upstream &&
1995 conf_get_int(conf, CONF_ssh_connection_sharing_upstream);
1996 can_downstream = share_can_be_downstream &&
1997 conf_get_int(conf, CONF_ssh_connection_sharing_downstream);
1998 if (!can_upstream && !can_downstream)
2002 * Decide on the string used to identify the connection point
2003 * between upstream and downstream (be it a Windows named pipe or
2004 * a Unix-domain socket or whatever else).
2006 * I wondered about making this a SHA hash of all sorts of pieces
2007 * of the PuTTY configuration - essentially everything PuTTY uses
2008 * to know where and how to make a connection, including all the
2009 * proxy details (or rather, all the _relevant_ ones - only
2010 * including settings that other settings didn't prevent from
2011 * having any effect), plus the username. However, I think it's
2012 * better to keep it really simple: the connection point
2013 * identifier is derived from the hostname and port used to index
2014 * the host-key cache (not necessarily where we _physically_
2015 * connected to, in cases involving proxies or CONF_loghost), plus
2016 * the username if one is specified.
2019 char *username = get_remote_username(conf);
2023 sockname = dupprintf("%s@%s", username, host);
2025 sockname = dupprintf("%s", host);
2028 sockname = dupprintf("%s@%s:%d", username, host, port);
2030 sockname = dupprintf("%s:%d", host, port);
2036 * The platform-specific code may transform this further in
2037 * order to conform to local namespace conventions (e.g. not
2038 * using slashes in filenames), but that's its job and not
2044 * Create a data structure for the listening plug if we turn out
2045 * to be an upstream.
2047 sharestate = snew(struct ssh_sharing_state);
2048 sharestate->fn = &listen_fn_table;
2049 sharestate->listensock = NULL;
2052 * Now hand off to a per-platform routine that either connects to
2053 * an existing upstream (using 'ssh' as the plug), establishes our
2054 * own upstream (using 'sharestate' as the plug), or forks off a
2055 * separate upstream and then connects to that. It will return a
2056 * code telling us which kind of socket it put in 'sock'.
2059 logtext = ds_err = us_err = NULL;
2060 result = platform_ssh_share(sockname, conf, (Plug)ssh,
2061 (Plug)sharestate, &sock, &logtext, &ds_err,
2062 &us_err, can_upstream, can_downstream);
2063 ssh_connshare_log(ssh, result, logtext, ds_err, us_err);
2070 * We aren't sharing our connection at all (e.g. something
2071 * went wrong setting the socket up). Free the upstream
2072 * structure and return NULL.
2074 assert(sock == NULL);
2080 case SHARE_DOWNSTREAM:
2082 * We are downstream, so free sharestate which it turns out we
2083 * don't need after all, and return the downstream socket as a
2084 * replacement for an ordinary SSH connection.
2091 case SHARE_UPSTREAM:
2093 * We are upstream. Set up sharestate properly and pass a copy
2094 * to the caller; return NULL, to tell ssh.c that it has to
2095 * make an ordinary connection after all.
2097 *state = sharestate;
2098 sharestate->listensock = sock;
2099 sharestate->connections = newtree234(share_connstate_cmp);
2100 sharestate->ssh = ssh;
2101 sharestate->server_verstring = NULL;
2102 sharestate->sockname = dupstr(sockname);
2103 sharestate->nextid = 1;