1/* $OpenBSD: channels.h,v 1.156 2024/05/23 23:47:16 jsg 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
85struct ssh;
86struct Channel;
87typedef struct Channel Channel;
88
89typedef void channel_open_fn(struct ssh *, int, int, void *);
90typedef void channel_callback_fn(struct ssh *, int, int, void *);
91typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
92typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
93typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
94    u_char **, size_t *);
95
96/* Channel success/failure callbacks */
97typedef void channel_confirm_cb(struct ssh *, int, struct Channel *, void *);
98typedef void channel_confirm_abandon_cb(struct ssh *, struct Channel *, void *);
99struct channel_confirm {
100	TAILQ_ENTRY(channel_confirm) entry;
101	channel_confirm_cb *cb;
102	channel_confirm_abandon_cb *abandon_cb;
103	void *ctx;
104};
105TAILQ_HEAD(channel_confirms, channel_confirm);
106
107/* Context for non-blocking connects */
108struct channel_connect {
109	char *host;
110	int port;
111	struct addrinfo *ai, *aitop;
112};
113
114/* Callbacks for mux channels back into client-specific code */
115typedef int mux_callback_fn(struct ssh *, struct Channel *);
116
117/*
118 * NB. channel IDs on the wire and in c->remote_id are uint32, but local
119 * channel IDs (e.g. c->self) only ever use the int32 subset of this range,
120 * because we use local channel ID -1 for housekeeping. Remote channels have
121 * a dedicated "have_remote_id" flag to indicate their validity.
122 */
123
124struct Channel {
125	int     type;		/* channel type/state */
126
127	int     self;		/* my own channel identifier */
128	uint32_t remote_id;	/* channel identifier for remote peer */
129	int	have_remote_id;	/* non-zero if remote_id is valid */
130
131	u_int   istate;		/* input from channel (state of receive half) */
132	u_int   ostate;		/* output to channel  (state of transmit half) */
133	int     flags;		/* close sent/rcvd */
134	int     rfd;		/* read fd */
135	int     wfd;		/* write fd */
136	int     efd;		/* extended fd */
137	int     sock;		/* sock fd */
138	u_int	io_want;	/* bitmask of SSH_CHAN_IO_* */
139	u_int	io_ready;	/* bitmask of SSH_CHAN_IO_* */
140	int	pfds[4];	/* pollfd entries for rfd/wfd/efd/sock */
141	int     ctl_chan;	/* control channel (multiplexed connections) */
142	int     isatty;		/* rfd is a tty */
143	int	client_tty;	/* (client) TTY has been requested */
144	int     force_drain;	/* force close on iEOF */
145	time_t	notbefore;	/* Pause IO until deadline (time_t) */
146	int     delayed;	/* post-IO handlers for newly created
147				 * channels are delayed until the first call
148				 * to a matching pre-IO handler.
149				 * this way post-IO handlers are not
150				 * accidentally called if a FD gets reused */
151	int	restore_block;	/* fd mask to restore blocking status */
152	int	restore_flags[3];/* flags to restore */
153	struct sshbuf *input;	/* data read from socket, to be sent over
154				 * encrypted connection */
155	struct sshbuf *output;	/* data received over encrypted connection for
156				 * send on socket */
157	struct sshbuf *extended;
158
159	char    *path;
160		/* path for unix domain sockets, or host name for forwards */
161	int     listening_port;	/* port being listened for forwards */
162	char   *listening_addr;	/* addr being listened for forwards */
163	int     host_port;	/* remote port to connect for forwards */
164	char   *remote_name;	/* remote hostname */
165
166	u_int	remote_window;
167	u_int	remote_maxpacket;
168	u_int	local_window;
169	u_int	local_window_exceeded;
170	u_int	local_window_max;
171	u_int	local_consumed;
172	u_int	local_maxpacket;
173	int     extended_usage;
174	int	single_connection;
175
176	char   *ctype;		/* const type - NB. not freed on channel_free */
177	char   *xctype;		/* extended type */
178
179	/* callback */
180	channel_open_fn		*open_confirm;
181	void			*open_confirm_ctx;
182	channel_callback_fn	*detach_user;
183	int			detach_close;
184	struct channel_confirms	status_confirms;
185
186	/* filter */
187	channel_infilter_fn	*input_filter;
188	channel_outfilter_fn	*output_filter;
189	void			*filter_ctx;
190	channel_filter_cleanup_fn *filter_cleanup;
191
192	/* keep boundaries */
193	int			datagram;
194
195	/* non-blocking connect */
196	/* XXX make this a pointer so the structure can be opaque */
197	struct channel_connect	connect_ctx;
198
199	/* multiplexing protocol hook, called for each packet received */
200	mux_callback_fn		*mux_rcb;
201	void			*mux_ctx;
202	int			mux_pause;
203	int			mux_downstream_id;
204
205	/* Inactivity timeouts */
206
207	/* Last traffic seen for OPEN channels */
208	time_t			lastused;
209	/* Inactivity timeout deadline in seconds (0 = no timeout) */
210	int			inactive_deadline;
211};
212
213#define CHAN_EXTENDED_IGNORE		0
214#define CHAN_EXTENDED_READ		1
215#define CHAN_EXTENDED_WRITE		2
216
217/* default window/packet sizes for tcp/x11-fwd-channel */
218#define CHAN_SES_PACKET_DEFAULT	(32*1024)
219#define CHAN_SES_WINDOW_DEFAULT	(64*CHAN_SES_PACKET_DEFAULT)
220#define CHAN_TCP_PACKET_DEFAULT	(32*1024)
221#define CHAN_TCP_WINDOW_DEFAULT	(64*CHAN_TCP_PACKET_DEFAULT)
222#define CHAN_X11_PACKET_DEFAULT	(16*1024)
223#define CHAN_X11_WINDOW_DEFAULT	(4*CHAN_X11_PACKET_DEFAULT)
224
225/* possible input states */
226#define CHAN_INPUT_OPEN			0
227#define CHAN_INPUT_WAIT_DRAIN		1
228#define CHAN_INPUT_WAIT_OCLOSE		2
229#define CHAN_INPUT_CLOSED		3
230
231/* possible output states */
232#define CHAN_OUTPUT_OPEN		0
233#define CHAN_OUTPUT_WAIT_DRAIN		1
234#define CHAN_OUTPUT_WAIT_IEOF		2
235#define CHAN_OUTPUT_CLOSED		3
236
237#define CHAN_CLOSE_SENT			0x01
238#define CHAN_CLOSE_RCVD			0x02
239#define CHAN_EOF_SENT			0x04
240#define CHAN_EOF_RCVD			0x08
241#define CHAN_LOCAL			0x10
242
243/* file descriptor events */
244#define SSH_CHAN_IO_RFD			0x01
245#define SSH_CHAN_IO_WFD			0x02
246#define SSH_CHAN_IO_EFD_R		0x04
247#define SSH_CHAN_IO_EFD_W		0x08
248#define SSH_CHAN_IO_EFD			(SSH_CHAN_IO_EFD_R|SSH_CHAN_IO_EFD_W)
249#define SSH_CHAN_IO_SOCK_R		0x10
250#define SSH_CHAN_IO_SOCK_W		0x20
251#define SSH_CHAN_IO_SOCK		(SSH_CHAN_IO_SOCK_R|SSH_CHAN_IO_SOCK_W)
252
253/* Read buffer size */
254#define CHAN_RBUF	(16*1024)
255
256/* Maximum size for direct reads to buffers */
257#define CHANNEL_MAX_READ	CHAN_SES_PACKET_DEFAULT
258
259/* Maximum channel input buffer size */
260#define CHAN_INPUT_MAX	(16*1024*1024)
261
262/* Hard limit on number of channels */
263#define CHANNELS_MAX_CHANNELS	(16*1024)
264
265/* check whether 'efd' is still in use */
266#define CHANNEL_EFD_INPUT_ACTIVE(c) \
267	(c->extended_usage == CHAN_EXTENDED_READ && \
268	(c->efd != -1 || \
269	sshbuf_len(c->extended) > 0))
270#define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
271	(c->extended_usage == CHAN_EXTENDED_WRITE && \
272	c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
273	sshbuf_len(c->extended) > 0))
274
275/* Add channel management structures to SSH transport instance */
276void channel_init_channels(struct ssh *ssh);
277
278/* channel management */
279
280Channel	*channel_by_id(struct ssh *, int);
281Channel	*channel_by_remote_id(struct ssh *, u_int);
282Channel	*channel_lookup(struct ssh *, int);
283Channel *channel_new(struct ssh *, char *, int, int, int, int,
284	    u_int, u_int, int, const char *, int);
285void	 channel_set_fds(struct ssh *, int, int, int, int, int,
286	    int, int, u_int);
287void	 channel_free(struct ssh *, Channel *);
288void	 channel_free_all(struct ssh *);
289void	 channel_stop_listening(struct ssh *);
290void	 channel_force_close(struct ssh *, Channel *, int);
291void	 channel_set_xtype(struct ssh *, int, const char *);
292
293void	 channel_send_open(struct ssh *, int);
294void	 channel_request_start(struct ssh *, int, char *, int);
295void	 channel_register_cleanup(struct ssh *, int,
296	    channel_callback_fn *, int);
297void	 channel_register_open_confirm(struct ssh *, int,
298	    channel_open_fn *, void *);
299void	 channel_register_filter(struct ssh *, int, channel_infilter_fn *,
300	    channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
301void	 channel_register_status_confirm(struct ssh *, int,
302	    channel_confirm_cb *, channel_confirm_abandon_cb *, void *);
303void	 channel_cancel_cleanup(struct ssh *, int);
304int	 channel_close_fd(struct ssh *, Channel *, int *);
305void	 channel_send_window_changes(struct ssh *);
306
307/* channel inactivity timeouts */
308void channel_add_timeout(struct ssh *, const char *, int);
309void channel_clear_timeouts(struct ssh *);
310
311/* mux proxy support */
312
313int	 channel_proxy_downstream(struct ssh *, Channel *mc);
314int	 channel_proxy_upstream(Channel *, int, u_int32_t, struct ssh *);
315
316/* protocol handler */
317
318int	 channel_input_data(int, u_int32_t, struct ssh *);
319int	 channel_input_extended_data(int, u_int32_t, struct ssh *);
320int	 channel_input_ieof(int, u_int32_t, struct ssh *);
321int	 channel_input_oclose(int, u_int32_t, struct ssh *);
322int	 channel_input_open_confirmation(int, u_int32_t, struct ssh *);
323int	 channel_input_open_failure(int, u_int32_t, struct ssh *);
324int	 channel_input_window_adjust(int, u_int32_t, struct ssh *);
325int	 channel_input_status_confirm(int, u_int32_t, struct ssh *);
326
327/* file descriptor handling (read/write) */
328struct pollfd;
329struct timespec;
330
331void	 channel_prepare_poll(struct ssh *, struct pollfd **,
332	    u_int *, u_int *, u_int, struct timespec *);
333void	 channel_after_poll(struct ssh *, struct pollfd *, u_int);
334int	 channel_output_poll(struct ssh *);
335
336int      channel_not_very_much_buffered_data(struct ssh *);
337void     channel_close_all(struct ssh *);
338int      channel_still_open(struct ssh *);
339int	 channel_tty_open(struct ssh *);
340const char *channel_format_extended_usage(const Channel *);
341char	*channel_open_message(struct ssh *);
342int	 channel_find_open(struct ssh *);
343
344/* tcp forwarding */
345struct Forward;
346struct ForwardOptions;
347void	 channel_set_af(struct ssh *, int af);
348void     channel_permit_all(struct ssh *, int);
349void	 channel_add_permission(struct ssh *, int, int, char *, int);
350void	 channel_clear_permission(struct ssh *, int, int);
351void	 channel_disable_admin(struct ssh *, int);
352void	 channel_update_permission(struct ssh *, int, int);
353Channel	*channel_connect_to_port(struct ssh *, const char *, u_short,
354	    char *, char *, int *, const char **);
355Channel *channel_connect_to_path(struct ssh *, const char *, char *, char *);
356Channel	*channel_connect_stdio_fwd(struct ssh *, const char*,
357	    int, int, int, int);
358Channel	*channel_connect_by_listen_address(struct ssh *, const char *,
359	    u_short, char *, char *);
360Channel	*channel_connect_by_listen_path(struct ssh *, const char *,
361	    char *, char *);
362int	 channel_request_remote_forwarding(struct ssh *, struct Forward *);
363int	 channel_setup_local_fwd_listener(struct ssh *, struct Forward *,
364	    struct ForwardOptions *);
365int	 channel_request_rforward_cancel(struct ssh *, struct Forward *);
366int	 channel_setup_remote_fwd_listener(struct ssh *, struct Forward *,
367	    int *, struct ForwardOptions *);
368int	 channel_cancel_rport_listener(struct ssh *, struct Forward *);
369int	 channel_cancel_lport_listener(struct ssh *, struct Forward *,
370	    int, struct ForwardOptions *);
371int	 permitopen_port(const char *);
372
373/* x11 forwarding */
374
375void	 channel_set_x11_refuse_time(struct ssh *, time_t);
376int	 x11_connect_display(struct ssh *);
377int	 x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
378void	 x11_request_forwarding_with_spoofing(struct ssh *, int,
379	    const char *, const char *, const char *, int);
380
381/* channel close */
382
383int	 chan_is_dead(struct ssh *, Channel *, int);
384void	 chan_mark_dead(struct ssh *, Channel *);
385
386/* channel events */
387
388void	 chan_rcvd_oclose(struct ssh *, Channel *);
389void	 chan_rcvd_eow(struct ssh *, Channel *);
390void	 chan_read_failed(struct ssh *, Channel *);
391void	 chan_ibuf_empty(struct ssh *, Channel *);
392void	 chan_rcvd_ieof(struct ssh *, Channel *);
393void	 chan_write_failed(struct ssh *, Channel *);
394void	 chan_obuf_empty(struct ssh *, Channel *);
395
396#endif
397