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1/* $OpenBSD: channels.h,v 1.162 2025/10/07 08:02:32 djm Exp $ */
2
3/*
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * All rights reserved
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 */
14/*
15 * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38#ifndef CHANNEL_H
39#define CHANNEL_H
40
41/* Definitions for channel types. */
42#define SSH_CHANNEL_X11_LISTENER 1 /* Listening for inet X11 conn. */
43#define SSH_CHANNEL_PORT_LISTENER 2 /* Listening on a port. */
44#define SSH_CHANNEL_OPENING 3 /* waiting for confirmation */
45#define SSH_CHANNEL_OPEN 4 /* normal open two-way channel */
46#define SSH_CHANNEL_CLOSED 5 /* waiting for close confirmation */
47#define SSH_CHANNEL_AUTH_SOCKET 6 /* authentication socket */
48#define SSH_CHANNEL_X11_OPEN 7 /* reading first X11 packet */
49#define SSH_CHANNEL_LARVAL 10 /* larval session */
50#define SSH_CHANNEL_RPORT_LISTENER 11 /* Listening to a R-style port */
51#define SSH_CHANNEL_CONNECTING 12
52#define SSH_CHANNEL_DYNAMIC 13
53#define SSH_CHANNEL_ZOMBIE 14 /* Almost dead. */
54#define SSH_CHANNEL_MUX_LISTENER 15 /* Listener for mux conn. */
55#define SSH_CHANNEL_MUX_CLIENT 16 /* Conn. to mux client */
56#define SSH_CHANNEL_ABANDONED 17 /* Abandoned session, eg mux */
57#define SSH_CHANNEL_UNIX_LISTENER 18 /* Listening on a domain socket. */
58#define SSH_CHANNEL_RUNIX_LISTENER 19 /* Listening to a R-style domain socket. */
59#define SSH_CHANNEL_MUX_PROXY 20 /* proxy channel for mux-client */
60#define SSH_CHANNEL_RDYNAMIC_OPEN 21 /* reverse SOCKS, parsing request */
61#define SSH_CHANNEL_RDYNAMIC_FINISH 22 /* reverse SOCKS, finishing connect */
62#define SSH_CHANNEL_MAX_TYPE 23
63
64#define CHANNEL_CANCEL_PORT_STATIC -1
65
66/* nonblocking flags for channel_new */
67#define CHANNEL_NONBLOCK_LEAVE 0 /* don't modify non-blocking state */
68#define CHANNEL_NONBLOCK_SET 1 /* set non-blocking state */
69#define CHANNEL_NONBLOCK_STDIO 2 /* set non-blocking and restore on close */
70
71/* c->restore_block mask flags */
72#define CHANNEL_RESTORE_RFD 0x01
73#define CHANNEL_RESTORE_WFD 0x02
74#define CHANNEL_RESTORE_EFD 0x04
75
76/* TCP forwarding */
77#define FORWARD_DENY 0
78#define FORWARD_REMOTE (1)
79#define FORWARD_LOCAL (1<<1)
80#define FORWARD_ALLOW (FORWARD_REMOTE|FORWARD_LOCAL)
81
82#define FORWARD_ADM 0x100
83#define FORWARD_USER 0x101
84
85/* default pattern-lists used to classify channel types as bulk */
86#define CHANNEL_BULK_TTY ""
87#define CHANNEL_BULK_NOTTY "direct-*,forwarded-*,tun-*,x11-*,session*"
88
89struct ssh;
90struct Channel;
91typedef struct Channel Channel;
92
93typedef void channel_open_fn(struct ssh *, int, int, void *);
94typedef void channel_callback_fn(struct ssh *, int, int, void *);
95typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
96typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
97typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
98 u_char **, size_t *);
99
100/* Channel success/failure callbacks */
101typedef void channel_confirm_cb(struct ssh *, int, struct Channel *, void *);
102typedef void channel_confirm_abandon_cb(struct ssh *, struct Channel *, void *);
103struct channel_confirm {
104 TAILQ_ENTRY(channel_confirm) entry;
105 channel_confirm_cb *cb;
106 channel_confirm_abandon_cb *abandon_cb;
107 void *ctx;
108};
109TAILQ_HEAD(channel_confirms, channel_confirm);
110
111/* Context for non-blocking connects */
112struct channel_connect {
113 char *host;
114 int port;
115 struct addrinfo *ai, *aitop;
116};
117
118/* Callbacks for mux channels back into client-specific code */
119typedef int mux_callback_fn(struct ssh *, struct Channel *);
120
121/*
122 * NB. channel IDs on the wire and in c->remote_id are uint32, but local
123 * channel IDs (e.g. c->self) only ever use the int32 subset of this range,
124 * because we use local channel ID -1 for housekeeping. Remote channels have
125 * a dedicated "have_remote_id" flag to indicate their validity.
126 */
127
128struct Channel {
129 int type; /* channel type/state */
130
131 int self; /* my own channel identifier */
132 uint32_t remote_id; /* channel identifier for remote peer */
133 int have_remote_id; /* non-zero if remote_id is valid */
134
135 u_int istate; /* input from channel (state of receive half) */
136 u_int ostate; /* output to channel (state of transmit half) */
137 int flags; /* close sent/rcvd */
138 int rfd; /* read fd */
139 int wfd; /* write fd */
140 int efd; /* extended fd */
141 int sock; /* sock fd */
142 u_int io_want; /* bitmask of SSH_CHAN_IO_* */
143 u_int io_ready; /* bitmask of SSH_CHAN_IO_* */
144 int pfds[4]; /* pollfd entries for rfd/wfd/efd/sock */
145 int ctl_chan; /* control channel (multiplexed connections) */
146 uint32_t ctl_child_id; /* child session for mux controllers */
147 int have_ctl_child_id;/* non-zero if ctl_child_id is valid */
148 int remote_has_tty; /* remote side has a tty */
149 int isatty; /* rfd is a tty */
150 int client_tty; /* (client) TTY has been requested */
151 int force_drain; /* force close on iEOF */
152 time_t notbefore; /* Pause IO until deadline (time_t) */
153 int delayed; /* post-IO handlers for newly created
154 * channels are delayed until the first call
155 * to a matching pre-IO handler.
156 * this way post-IO handlers are not
157 * accidentally called if a FD gets reused */
158 int restore_block; /* fd mask to restore blocking status */
159 int restore_flags[3];/* flags to restore */
160 struct sshbuf *input; /* data read from socket, to be sent over
161 * encrypted connection */
162 struct sshbuf *output; /* data received over encrypted connection for
163 * send on socket */
164 struct sshbuf *extended;
165
166 char *path;
167 /* path for unix domain sockets, or host name for forwards */
168 int listening_port; /* port being listened for forwards */
169 char *listening_addr; /* addr being listened for forwards */
170 int host_port; /* remote port to connect for forwards */
171 char *remote_name; /* remote hostname */
172
173 u_int remote_window;
174 u_int remote_maxpacket;
175 u_int local_window;
176 u_int local_window_exceeded;
177 u_int local_window_max;
178 u_int local_consumed;
179 u_int local_maxpacket;
180 int extended_usage;
181 int single_connection;
182
183 char *ctype; /* const type - NB. not freed on channel_free */
184 char *xctype; /* extended type */
185 int bulk; /* channel is non-interactive */
186
187 /* callback */
188 channel_open_fn *open_confirm;
189 void *open_confirm_ctx;
190 channel_callback_fn *detach_user;
191 int detach_close;
192 struct channel_confirms status_confirms;
193
194 /* filter */
195 channel_infilter_fn *input_filter;
196 channel_outfilter_fn *output_filter;
197 void *filter_ctx;
198 channel_filter_cleanup_fn *filter_cleanup;
199
200 /* keep boundaries */
201 int datagram;
202
203 /* non-blocking connect */
204 /* XXX make this a pointer so the structure can be opaque */
205 struct channel_connect connect_ctx;
206
207 /* multiplexing protocol hook, called for each packet received */
208 mux_callback_fn *mux_rcb;
209 void *mux_ctx;
210 int mux_pause;
211 int mux_downstream_id;
212
213 /* Inactivity timeouts */
214
215 /* Last traffic seen for OPEN channels */
216 time_t lastused;
217 /* Inactivity timeout deadline in seconds (0 = no timeout) */
218 int inactive_deadline;
219};
220
221#define CHAN_EXTENDED_IGNORE 0
222#define CHAN_EXTENDED_READ 1
223#define CHAN_EXTENDED_WRITE 2
224
225/* default window/packet sizes for tcp/x11-fwd-channel */
226#define CHAN_SES_PACKET_DEFAULT (32*1024)
227#define CHAN_SES_WINDOW_DEFAULT (64*CHAN_SES_PACKET_DEFAULT)
228#define CHAN_TCP_PACKET_DEFAULT (32*1024)
229#define CHAN_TCP_WINDOW_DEFAULT (64*CHAN_TCP_PACKET_DEFAULT)
230#define CHAN_X11_PACKET_DEFAULT (16*1024)
231#define CHAN_X11_WINDOW_DEFAULT (4*CHAN_X11_PACKET_DEFAULT)
232
233/* possible input states */
234#define CHAN_INPUT_OPEN 0
235#define CHAN_INPUT_WAIT_DRAIN 1
236#define CHAN_INPUT_WAIT_OCLOSE 2
237#define CHAN_INPUT_CLOSED 3
238
239/* possible output states */
240#define CHAN_OUTPUT_OPEN 0
241#define CHAN_OUTPUT_WAIT_DRAIN 1
242#define CHAN_OUTPUT_WAIT_IEOF 2
243#define CHAN_OUTPUT_CLOSED 3
244
245#define CHAN_CLOSE_SENT 0x01
246#define CHAN_CLOSE_RCVD 0x02
247#define CHAN_EOF_SENT 0x04
248#define CHAN_EOF_RCVD 0x08
249#define CHAN_LOCAL 0x10
250
251/* file descriptor events */
252#define SSH_CHAN_IO_RFD 0x01
253#define SSH_CHAN_IO_WFD 0x02
254#define SSH_CHAN_IO_EFD_R 0x04
255#define SSH_CHAN_IO_EFD_W 0x08
256#define SSH_CHAN_IO_EFD (SSH_CHAN_IO_EFD_R|SSH_CHAN_IO_EFD_W)
257#define SSH_CHAN_IO_SOCK_R 0x10
258#define SSH_CHAN_IO_SOCK_W 0x20
259#define SSH_CHAN_IO_SOCK (SSH_CHAN_IO_SOCK_R|SSH_CHAN_IO_SOCK_W)
260
261/* Read buffer size */
262#define CHAN_RBUF (16*1024)
263
264/* Maximum size for direct reads to buffers */
265#define CHANNEL_MAX_READ CHAN_SES_PACKET_DEFAULT
266
267/* Maximum channel input buffer size */
268#define CHAN_INPUT_MAX (16*1024*1024)
269
270/* Hard limit on number of channels */
271#define CHANNELS_MAX_CHANNELS (16*1024)
272
273/* check whether 'efd' is still in use */
274#define CHANNEL_EFD_INPUT_ACTIVE(c) \
275 (c->extended_usage == CHAN_EXTENDED_READ && \
276 (c->efd != -1 || \
277 sshbuf_len(c->extended) > 0))
278#define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
279 (c->extended_usage == CHAN_EXTENDED_WRITE && \
280 c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
281 sshbuf_len(c->extended) > 0))
282
283/* Add/remove channel management structures to/from SSH transport instance */
284void channel_init_channels(struct ssh *ssh);
285void channel_free_channels(struct ssh *ssh);
286
287/* channel management */
288
289Channel *channel_by_id(struct ssh *, int);
290Channel *channel_by_remote_id(struct ssh *, u_int);
291Channel *channel_lookup(struct ssh *, int);
292Channel *channel_new(struct ssh *, char *, int, int, int, int,
293 u_int, u_int, int, const char *, int);
294void channel_set_fds(struct ssh *, int, int, int, int, int,
295 int, int, u_int);
296void channel_set_tty(struct ssh *, Channel *);
297void channel_free(struct ssh *, Channel *);
298void channel_free_all(struct ssh *);
299void channel_stop_listening(struct ssh *);
300void channel_force_close(struct ssh *, Channel *, int);
301void channel_set_xtype(struct ssh *, int, const char *);
302
303void channel_send_open(struct ssh *, int);
304void channel_request_start(struct ssh *, int, char *, int);
305void channel_register_cleanup(struct ssh *, int,
306 channel_callback_fn *, int);
307void channel_register_open_confirm(struct ssh *, int,
308 channel_open_fn *, void *);
309void channel_register_filter(struct ssh *, int, channel_infilter_fn *,
310 channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
311void channel_register_status_confirm(struct ssh *, int,
312 channel_confirm_cb *, channel_confirm_abandon_cb *, void *);
313void channel_cancel_cleanup(struct ssh *, int);
314int channel_close_fd(struct ssh *, Channel *, int *);
315void channel_send_window_changes(struct ssh *);
316int channel_has_bulk(struct ssh *);
317
318/* channel inactivity timeouts */
319void channel_add_timeout(struct ssh *, const char *, int);
320void channel_clear_timeouts(struct ssh *);
321
322/* mux proxy support */
323
324int channel_proxy_downstream(struct ssh *, Channel *mc);
325int channel_proxy_upstream(Channel *, int, u_int32_t, struct ssh *);
326
327/* protocol handler */
328
329int channel_input_data(int, u_int32_t, struct ssh *);
330int channel_input_extended_data(int, u_int32_t, struct ssh *);
331int channel_input_ieof(int, u_int32_t, struct ssh *);
332int channel_input_oclose(int, u_int32_t, struct ssh *);
333int channel_input_open_confirmation(int, u_int32_t, struct ssh *);
334int channel_input_open_failure(int, u_int32_t, struct ssh *);
335int channel_input_window_adjust(int, u_int32_t, struct ssh *);
336int channel_input_status_confirm(int, u_int32_t, struct ssh *);
337
338/* file descriptor handling (read/write) */
339struct pollfd;
340struct timespec;
341
342void channel_prepare_poll(struct ssh *, struct pollfd **,
343 u_int *, u_int *, u_int, struct timespec *);
344void channel_after_poll(struct ssh *, struct pollfd *, u_int);
345int channel_output_poll(struct ssh *);
346
347int channel_not_very_much_buffered_data(struct ssh *);
348void channel_close_all(struct ssh *);
349int channel_still_open(struct ssh *);
350int channel_tty_open(struct ssh *);
351const char *channel_format_extended_usage(const Channel *);
352char *channel_open_message(struct ssh *);
353void channel_report_open(struct ssh *, int);
354int channel_find_open(struct ssh *);
355
356/* tcp forwarding */
357struct Forward;
358struct ForwardOptions;
359void channel_set_af(struct ssh *, int af);
360void channel_permit_all(struct ssh *, int);
361void channel_add_permission(struct ssh *, int, int, char *, int);
362void channel_clear_permission(struct ssh *, int, int);
363void channel_disable_admin(struct ssh *, int);
364void channel_update_permission(struct ssh *, int, int);
365Channel *channel_connect_to_port(struct ssh *, const char *, u_short,
366 char *, char *, int *, const char **);
367Channel *channel_connect_to_path(struct ssh *, const char *, char *, char *);
368Channel *channel_connect_stdio_fwd(struct ssh *, const char*,
369 int, int, int, int);
370Channel *channel_connect_by_listen_address(struct ssh *, const char *,
371 u_short, char *, char *);
372Channel *channel_connect_by_listen_path(struct ssh *, const char *,
373 char *, char *);
374int channel_request_remote_forwarding(struct ssh *, struct Forward *);
375int channel_setup_local_fwd_listener(struct ssh *, struct Forward *,
376 struct ForwardOptions *);
377int channel_request_rforward_cancel(struct ssh *, struct Forward *);
378int channel_setup_remote_fwd_listener(struct ssh *, struct Forward *,
379 int *, struct ForwardOptions *);
380int channel_cancel_rport_listener(struct ssh *, struct Forward *);
381int channel_cancel_lport_listener(struct ssh *, struct Forward *,
382 int, struct ForwardOptions *);
383int permitopen_port(const char *);
384
385/* x11 forwarding */
386
387void channel_set_x11_refuse_time(struct ssh *, time_t);
388int x11_connect_display(struct ssh *);
389int x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
390void x11_request_forwarding_with_spoofing(struct ssh *, int,
391 const char *, const char *, const char *, int);
392int x11_channel_used_recently(struct ssh *ssh);
393
394/* channel close */
395
396int chan_is_dead(struct ssh *, Channel *, int);
397void chan_mark_dead(struct ssh *, Channel *);
398
399/* channel events */
400
401void chan_rcvd_oclose(struct ssh *, Channel *);
402void chan_rcvd_eow(struct ssh *, Channel *);
403void chan_read_failed(struct ssh *, Channel *);
404void chan_ibuf_empty(struct ssh *, Channel *);
405void chan_rcvd_ieof(struct ssh *, Channel *);
406void chan_write_failed(struct ssh *, Channel *);
407void chan_obuf_empty(struct ssh *, Channel *);
408
409#endif