xref: /openssh-portable/channels.h (revision 6d755706)
1 /* $OpenBSD: channels.h,v 1.134 2020/07/05 23:59:45 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 /* TCP forwarding */
67 #define FORWARD_DENY		0
68 #define FORWARD_REMOTE		(1)
69 #define FORWARD_LOCAL		(1<<1)
70 #define FORWARD_ALLOW		(FORWARD_REMOTE|FORWARD_LOCAL)
71 
72 #define FORWARD_ADM		0x100
73 #define FORWARD_USER		0x101
74 
75 struct ssh;
76 struct Channel;
77 typedef struct Channel Channel;
78 struct fwd_perm_list;
79 
80 typedef void channel_open_fn(struct ssh *, int, int, void *);
81 typedef void channel_callback_fn(struct ssh *, int, void *);
82 typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
83 typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
84 typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
85     u_char **, size_t *);
86 
87 /* Channel success/failure callbacks */
88 typedef void channel_confirm_cb(struct ssh *, int, struct Channel *, void *);
89 typedef void channel_confirm_abandon_cb(struct ssh *, struct Channel *, void *);
90 struct channel_confirm {
91 	TAILQ_ENTRY(channel_confirm) entry;
92 	channel_confirm_cb *cb;
93 	channel_confirm_abandon_cb *abandon_cb;
94 	void *ctx;
95 };
96 TAILQ_HEAD(channel_confirms, channel_confirm);
97 
98 /* Context for non-blocking connects */
99 struct channel_connect {
100 	char *host;
101 	int port;
102 	struct addrinfo *ai, *aitop;
103 };
104 
105 /* Callbacks for mux channels back into client-specific code */
106 typedef int mux_callback_fn(struct ssh *, struct Channel *);
107 
108 /*
109  * NB. channel IDs on the wire and in c->remote_id are uint32, but local
110  * channel IDs (e.g. c->self) only ever use the int32 subset of this range,
111  * because we use local channel ID -1 for housekeeping. Remote channels have
112  * a dedicated "have_remote_id" flag to indicate their validity.
113  */
114 
115 struct Channel {
116 	int     type;		/* channel type/state */
117 
118 	int     self;		/* my own channel identifier */
119 	uint32_t remote_id;	/* channel identifier for remote peer */
120 	int	have_remote_id;	/* non-zero if remote_id is valid */
121 
122 	u_int   istate;		/* input from channel (state of receive half) */
123 	u_int   ostate;		/* output to channel  (state of transmit half) */
124 	int     flags;		/* close sent/rcvd */
125 	int     rfd;		/* read fd */
126 	int     wfd;		/* write fd */
127 	int     efd;		/* extended fd */
128 	int     sock;		/* sock fd */
129 	int     ctl_chan;	/* control channel (multiplexed connections) */
130 	int     isatty;		/* rfd is a tty */
131 #ifdef _AIX
132 	int     wfd_isatty;	/* wfd is a tty */
133 #endif
134 	int	client_tty;	/* (client) TTY has been requested */
135 	int     force_drain;	/* force close on iEOF */
136 	time_t	notbefore;	/* Pause IO until deadline (time_t) */
137 	int     delayed;	/* post-select handlers for newly created
138 				 * channels are delayed until the first call
139 				 * to a matching pre-select handler.
140 				 * this way post-select handlers are not
141 				 * accidentally called if a FD gets reused */
142 	struct sshbuf *input;	/* data read from socket, to be sent over
143 				 * encrypted connection */
144 	struct sshbuf *output;	/* data received over encrypted connection for
145 				 * send on socket */
146 	struct sshbuf *extended;
147 
148 	char    *path;
149 		/* path for unix domain sockets, or host name for forwards */
150 	int     listening_port;	/* port being listened for forwards */
151 	char   *listening_addr;	/* addr being listened for forwards */
152 	int     host_port;	/* remote port to connect for forwards */
153 	char   *remote_name;	/* remote hostname */
154 
155 	u_int	remote_window;
156 	u_int	remote_maxpacket;
157 	u_int	local_window;
158 	u_int	local_window_max;
159 	u_int	local_consumed;
160 	u_int	local_maxpacket;
161 	int     extended_usage;
162 	int	single_connection;
163 
164 	char   *ctype;		/* type */
165 
166 	/* callback */
167 	channel_open_fn		*open_confirm;
168 	void			*open_confirm_ctx;
169 	channel_callback_fn	*detach_user;
170 	int			detach_close;
171 	struct channel_confirms	status_confirms;
172 
173 	/* filter */
174 	channel_infilter_fn	*input_filter;
175 	channel_outfilter_fn	*output_filter;
176 	void			*filter_ctx;
177 	channel_filter_cleanup_fn *filter_cleanup;
178 
179 	/* keep boundaries */
180 	int     		datagram;
181 
182 	/* non-blocking connect */
183 	/* XXX make this a pointer so the structure can be opaque */
184 	struct channel_connect	connect_ctx;
185 
186 	/* multiplexing protocol hook, called for each packet received */
187 	mux_callback_fn		*mux_rcb;
188 	void			*mux_ctx;
189 	int			mux_pause;
190 	int     		mux_downstream_id;
191 };
192 
193 #define CHAN_EXTENDED_IGNORE		0
194 #define CHAN_EXTENDED_READ		1
195 #define CHAN_EXTENDED_WRITE		2
196 
197 /* default window/packet sizes for tcp/x11-fwd-channel */
198 #define CHAN_SES_PACKET_DEFAULT	(32*1024)
199 #define CHAN_SES_WINDOW_DEFAULT	(64*CHAN_SES_PACKET_DEFAULT)
200 #define CHAN_TCP_PACKET_DEFAULT	(32*1024)
201 #define CHAN_TCP_WINDOW_DEFAULT	(64*CHAN_TCP_PACKET_DEFAULT)
202 #define CHAN_X11_PACKET_DEFAULT	(16*1024)
203 #define CHAN_X11_WINDOW_DEFAULT	(4*CHAN_X11_PACKET_DEFAULT)
204 
205 /* possible input states */
206 #define CHAN_INPUT_OPEN			0
207 #define CHAN_INPUT_WAIT_DRAIN		1
208 #define CHAN_INPUT_WAIT_OCLOSE		2
209 #define CHAN_INPUT_CLOSED		3
210 
211 /* possible output states */
212 #define CHAN_OUTPUT_OPEN		0
213 #define CHAN_OUTPUT_WAIT_DRAIN		1
214 #define CHAN_OUTPUT_WAIT_IEOF		2
215 #define CHAN_OUTPUT_CLOSED		3
216 
217 #define CHAN_CLOSE_SENT			0x01
218 #define CHAN_CLOSE_RCVD			0x02
219 #define CHAN_EOF_SENT			0x04
220 #define CHAN_EOF_RCVD			0x08
221 #define CHAN_LOCAL			0x10
222 
223 /* Read buffer size */
224 #define CHAN_RBUF	(16*1024)
225 
226 /* Hard limit on number of channels */
227 #define CHANNELS_MAX_CHANNELS	(16*1024)
228 
229 /* check whether 'efd' is still in use */
230 #define CHANNEL_EFD_INPUT_ACTIVE(c) \
231 	(c->extended_usage == CHAN_EXTENDED_READ && \
232 	(c->efd != -1 || \
233 	sshbuf_len(c->extended) > 0))
234 #define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
235 	(c->extended_usage == CHAN_EXTENDED_WRITE && \
236 	c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
237 	sshbuf_len(c->extended) > 0))
238 
239 /* Add channel management structures to SSH transport instance */
240 void channel_init_channels(struct ssh *ssh);
241 
242 /* channel management */
243 
244 Channel	*channel_by_id(struct ssh *, int);
245 Channel	*channel_by_remote_id(struct ssh *, u_int);
246 Channel	*channel_lookup(struct ssh *, int);
247 Channel *channel_new(struct ssh *, char *, int, int, int, int,
248 	    u_int, u_int, int, char *, int);
249 void	 channel_set_fds(struct ssh *, int, int, int, int, int,
250 	    int, int, u_int);
251 void	 channel_free(struct ssh *, Channel *);
252 void	 channel_free_all(struct ssh *);
253 void	 channel_stop_listening(struct ssh *);
254 
255 void	 channel_send_open(struct ssh *, int);
256 void	 channel_request_start(struct ssh *, int, char *, int);
257 void	 channel_register_cleanup(struct ssh *, int,
258 	    channel_callback_fn *, int);
259 void	 channel_register_open_confirm(struct ssh *, int,
260 	    channel_open_fn *, void *);
261 void	 channel_register_filter(struct ssh *, int, channel_infilter_fn *,
262 	    channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
263 void	 channel_register_status_confirm(struct ssh *, int,
264 	    channel_confirm_cb *, channel_confirm_abandon_cb *, void *);
265 void	 channel_cancel_cleanup(struct ssh *, int);
266 int	 channel_close_fd(struct ssh *, int *);
267 void	 channel_send_window_changes(struct ssh *);
268 
269 /* mux proxy support */
270 
271 int	 channel_proxy_downstream(struct ssh *, Channel *mc);
272 int	 channel_proxy_upstream(Channel *, int, u_int32_t, struct ssh *);
273 
274 /* protocol handler */
275 
276 int	 channel_input_data(int, u_int32_t, struct ssh *);
277 int	 channel_input_extended_data(int, u_int32_t, struct ssh *);
278 int	 channel_input_ieof(int, u_int32_t, struct ssh *);
279 int	 channel_input_oclose(int, u_int32_t, struct ssh *);
280 int	 channel_input_open_confirmation(int, u_int32_t, struct ssh *);
281 int	 channel_input_open_failure(int, u_int32_t, struct ssh *);
282 int	 channel_input_port_open(int, u_int32_t, struct ssh *);
283 int	 channel_input_window_adjust(int, u_int32_t, struct ssh *);
284 int	 channel_input_status_confirm(int, u_int32_t, struct ssh *);
285 
286 /* file descriptor handling (read/write) */
287 
288 void	 channel_prepare_select(struct ssh *, fd_set **, fd_set **, int *,
289 	     u_int*, time_t*);
290 void     channel_after_select(struct ssh *, fd_set *, fd_set *);
291 void     channel_output_poll(struct ssh *);
292 
293 int      channel_not_very_much_buffered_data(struct ssh *);
294 void     channel_close_all(struct ssh *);
295 int      channel_still_open(struct ssh *);
296 const char *channel_format_extended_usage(const Channel *);
297 char	*channel_open_message(struct ssh *);
298 int	 channel_find_open(struct ssh *);
299 
300 /* tcp forwarding */
301 struct Forward;
302 struct ForwardOptions;
303 void	 channel_set_af(struct ssh *, int af);
304 void     channel_permit_all(struct ssh *, int);
305 void	 channel_add_permission(struct ssh *, int, int, char *, int);
306 void	 channel_clear_permission(struct ssh *, int, int);
307 void	 channel_disable_admin(struct ssh *, int);
308 void	 channel_update_permission(struct ssh *, int, int);
309 Channel	*channel_connect_to_port(struct ssh *, const char *, u_short,
310 	    char *, char *, int *, const char **);
311 Channel *channel_connect_to_path(struct ssh *, const char *, char *, char *);
312 Channel	*channel_connect_stdio_fwd(struct ssh *, const char*,
313 	    u_short, int, int);
314 Channel	*channel_connect_by_listen_address(struct ssh *, const char *,
315 	    u_short, char *, char *);
316 Channel	*channel_connect_by_listen_path(struct ssh *, const char *,
317 	    char *, char *);
318 int	 channel_request_remote_forwarding(struct ssh *, struct Forward *);
319 int	 channel_setup_local_fwd_listener(struct ssh *, struct Forward *,
320 	    struct ForwardOptions *);
321 int	 channel_request_rforward_cancel(struct ssh *, struct Forward *);
322 int	 channel_setup_remote_fwd_listener(struct ssh *, struct Forward *,
323 	    int *, struct ForwardOptions *);
324 int	 channel_cancel_rport_listener(struct ssh *, struct Forward *);
325 int	 channel_cancel_lport_listener(struct ssh *, struct Forward *,
326 	    int, struct ForwardOptions *);
327 int	 permitopen_port(const char *);
328 
329 /* x11 forwarding */
330 
331 void	 channel_set_x11_refuse_time(struct ssh *, u_int);
332 int	 x11_connect_display(struct ssh *);
333 int	 x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
334 void	 x11_request_forwarding_with_spoofing(struct ssh *, int,
335 	    const char *, const char *, const char *, int);
336 
337 /* channel close */
338 
339 int	 chan_is_dead(struct ssh *, Channel *, int);
340 void	 chan_mark_dead(struct ssh *, Channel *);
341 
342 /* channel events */
343 
344 void	 chan_rcvd_oclose(struct ssh *, Channel *);
345 void	 chan_rcvd_eow(struct ssh *, Channel *);
346 void	 chan_read_failed(struct ssh *, Channel *);
347 void	 chan_ibuf_empty(struct ssh *, Channel *);
348 void	 chan_rcvd_ieof(struct ssh *, Channel *);
349 void	 chan_write_failed(struct ssh *, Channel *);
350 void	 chan_obuf_empty(struct ssh *, Channel *);
351 
352 #endif
353