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channels.h
1 /* $OpenBSD: channels.h,v 1.137 2021/04/03 06:18:40 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 struct ssh;
86 struct Channel;
87 typedef struct Channel Channel;
88 struct fwd_perm_list;
89 
90 typedef void channel_open_fn(struct ssh *, int, int, void *);
91 typedef void channel_callback_fn(struct ssh *, int, void *);
92 typedef int channel_infilter_fn(struct ssh *, struct Channel *, char *, int);
93 typedef void channel_filter_cleanup_fn(struct ssh *, int, void *);
94 typedef u_char *channel_outfilter_fn(struct ssh *, struct Channel *,
95  u_char **, size_t *);
96 
97 /* Channel success/failure callbacks */
98 typedef void channel_confirm_cb(struct ssh *, int, struct Channel *, void *);
99 typedef void channel_confirm_abandon_cb(struct ssh *, struct Channel *, void *);
100 struct channel_confirm {
101  TAILQ_ENTRY(channel_confirm) entry;
102  channel_confirm_cb *cb;
103  channel_confirm_abandon_cb *abandon_cb;
104  void *ctx;
105 };
106 TAILQ_HEAD(channel_confirms, channel_confirm);
107 
108 /* Context for non-blocking connects */
109 struct channel_connect {
110  char *host;
111  int port;
112  struct addrinfo *ai, *aitop;
113 };
114 
115 /* Callbacks for mux channels back into client-specific code */
116 typedef int mux_callback_fn(struct ssh *, struct Channel *);
117 
118 /*
119  * NB. channel IDs on the wire and in c->remote_id are uint32, but local
120  * channel IDs (e.g. c->self) only ever use the int32 subset of this range,
121  * because we use local channel ID -1 for housekeeping. Remote channels have
122  * a dedicated "have_remote_id" flag to indicate their validity.
123  */
124 
125 struct Channel {
126  int type; /* channel type/state */
127 
128  int self; /* my own channel identifier */
129  uint32_t remote_id; /* channel identifier for remote peer */
130  int have_remote_id; /* non-zero if remote_id is valid */
131 
132  u_int istate; /* input from channel (state of receive half) */
133  u_int ostate; /* output to channel (state of transmit half) */
134  int flags; /* close sent/rcvd */
135  int rfd; /* read fd */
136  int wfd; /* write fd */
137  int efd; /* extended fd */
138  int sock; /* sock fd */
139  int ctl_chan; /* control channel (multiplexed connections) */
140  int isatty; /* rfd is a tty */
141 #ifdef _AIX
142  int wfd_isatty; /* wfd is a tty */
143 #endif
144  int client_tty; /* (client) TTY has been requested */
145  int force_drain; /* force close on iEOF */
146  time_t notbefore; /* Pause IO until deadline (time_t) */
147  int delayed; /* post-select handlers for newly created
148  * channels are delayed until the first call
149  * to a matching pre-select handler.
150  * this way post-select handlers are not
151  * accidentally called if a FD gets reused */
152  int restore_block; /* fd mask to restore blocking status */
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_max;
170  u_int local_consumed;
171  u_int local_maxpacket;
172  int dynamic_window;
173  int extended_usage;
174  int single_connection;
175  u_int tcpwinsz;
176 
177  char *ctype; /* 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 
206 #define CHAN_EXTENDED_IGNORE 0
207 #define CHAN_EXTENDED_READ 1
208 #define CHAN_EXTENDED_WRITE 2
209 
210 /* default window/packet sizes for tcp/x11-fwd-channel */
211 #define CHAN_SES_PACKET_DEFAULT (32*1024)
212 #define CHAN_SES_WINDOW_DEFAULT (64*CHAN_SES_PACKET_DEFAULT)
213 #define CHAN_TCP_PACKET_DEFAULT (32*1024)
214 #define CHAN_TCP_WINDOW_DEFAULT (64*CHAN_TCP_PACKET_DEFAULT)
215 #define CHAN_X11_PACKET_DEFAULT (16*1024)
216 #define CHAN_X11_WINDOW_DEFAULT (4*CHAN_X11_PACKET_DEFAULT)
217 
218 /* possible input states */
219 #define CHAN_INPUT_OPEN 0
220 #define CHAN_INPUT_WAIT_DRAIN 1
221 #define CHAN_INPUT_WAIT_OCLOSE 2
222 #define CHAN_INPUT_CLOSED 3
223 
224 /* possible output states */
225 #define CHAN_OUTPUT_OPEN 0
226 #define CHAN_OUTPUT_WAIT_DRAIN 1
227 #define CHAN_OUTPUT_WAIT_IEOF 2
228 #define CHAN_OUTPUT_CLOSED 3
229 
230 #define CHAN_CLOSE_SENT 0x01
231 #define CHAN_CLOSE_RCVD 0x02
232 #define CHAN_EOF_SENT 0x04
233 #define CHAN_EOF_RCVD 0x08
234 #define CHAN_LOCAL 0x10
235 
236 /* Read buffer size */
237 #define CHAN_RBUF CHAN_SES_PACKET_DEFAULT
238 
239 /* Maximum channel input buffer size */
240 #define CHAN_INPUT_MAX (16*1024*1024)
241 
242 /* Hard limit on number of channels */
243 #define CHANNELS_MAX_CHANNELS (16*1024)
244 
245 /* check whether 'efd' is still in use */
246 #define CHANNEL_EFD_INPUT_ACTIVE(c) \
247  (c->extended_usage == CHAN_EXTENDED_READ && \
248  (c->efd != -1 || \
249  sshbuf_len(c->extended) > 0))
250 #define CHANNEL_EFD_OUTPUT_ACTIVE(c) \
251  (c->extended_usage == CHAN_EXTENDED_WRITE && \
252  c->efd != -1 && (!(c->flags & (CHAN_EOF_RCVD|CHAN_CLOSE_RCVD)) || \
253  sshbuf_len(c->extended) > 0))
254 
255 /* Add channel management structures to SSH transport instance */
256 void channel_init_channels(struct ssh *ssh);
257 
258 /* channel management */
259 
260 Channel *channel_by_id(struct ssh *, int);
261 Channel *channel_by_remote_id(struct ssh *, u_int);
262 Channel *channel_lookup(struct ssh *, int);
263 Channel *channel_new(struct ssh *, char *, int, int, int, int,
264  u_int, u_int, int, char *, int);
265 void channel_set_fds(struct ssh *, int, int, int, int, int,
266  int, int, u_int);
267 void channel_free(struct ssh *, Channel *);
268 void channel_free_all(struct ssh *);
269 void channel_stop_listening(struct ssh *);
270 
271 void channel_send_open(struct ssh *, int);
272 void channel_request_start(struct ssh *, int, char *, int);
273 void channel_register_cleanup(struct ssh *, int,
274  channel_callback_fn *, int);
275 void channel_register_open_confirm(struct ssh *, int,
276  channel_open_fn *, void *);
277 void channel_register_filter(struct ssh *, int, channel_infilter_fn *,
278  channel_outfilter_fn *, channel_filter_cleanup_fn *, void *);
279 void channel_register_status_confirm(struct ssh *, int,
280  channel_confirm_cb *, channel_confirm_abandon_cb *, void *);
281 void channel_cancel_cleanup(struct ssh *, int);
282 int channel_close_fd(struct ssh *, Channel *, int *);
283 void channel_send_window_changes(struct ssh *);
284 
285 /* mux proxy support */
286 
287 int channel_proxy_downstream(struct ssh *, Channel *mc);
288 int channel_proxy_upstream(Channel *, int, u_int32_t, struct ssh *);
289 
290 /* protocol handler */
291 
292 int channel_input_data(int, u_int32_t, struct ssh *);
293 int channel_input_extended_data(int, u_int32_t, struct ssh *);
294 int channel_input_ieof(int, u_int32_t, struct ssh *);
295 int channel_input_oclose(int, u_int32_t, struct ssh *);
296 int channel_input_open_confirmation(int, u_int32_t, struct ssh *);
297 int channel_input_open_failure(int, u_int32_t, struct ssh *);
298 int channel_input_port_open(int, u_int32_t, struct ssh *);
299 int channel_input_window_adjust(int, u_int32_t, struct ssh *);
300 int channel_input_status_confirm(int, u_int32_t, struct ssh *);
301 
302 /* file descriptor handling (read/write) */
303 
304 void channel_prepare_select(struct ssh *, fd_set **, fd_set **, int *,
305  u_int*, time_t*);
306 void channel_after_select(struct ssh *, fd_set *, fd_set *);
307 void channel_output_poll(struct ssh *);
308 
309 int channel_not_very_much_buffered_data(struct ssh *);
310 void channel_close_all(struct ssh *);
311 int channel_still_open(struct ssh *);
312 const char *channel_format_extended_usage(const Channel *);
313 char *channel_open_message(struct ssh *);
314 int channel_find_open(struct ssh *);
315 
316 /* tcp forwarding */
317 struct Forward;
318 struct ForwardOptions;
319 void channel_set_af(struct ssh *, int af);
320 void channel_permit_all(struct ssh *, int);
321 void channel_add_permission(struct ssh *, int, int, char *, int);
322 void channel_clear_permission(struct ssh *, int, int);
323 void channel_disable_admin(struct ssh *, int);
324 void channel_update_permission(struct ssh *, int, int);
325 Channel *channel_connect_to_port(struct ssh *, const char *, u_short,
326  char *, char *, int *, const char **);
327 Channel *channel_connect_to_path(struct ssh *, const char *, char *, char *);
328 Channel *channel_connect_stdio_fwd(struct ssh *, const char*,
329  u_short, int, int, int);
330 Channel *channel_connect_by_listen_address(struct ssh *, const char *,
331  u_short, char *, char *);
332 Channel *channel_connect_by_listen_path(struct ssh *, const char *,
333  char *, char *);
334 int channel_request_remote_forwarding(struct ssh *, struct Forward *);
335 int channel_setup_local_fwd_listener(struct ssh *, struct Forward *,
336  struct ForwardOptions *);
337 int channel_request_rforward_cancel(struct ssh *, struct Forward *);
338 int channel_setup_remote_fwd_listener(struct ssh *, struct Forward *,
339  int *, struct ForwardOptions *);
340 int channel_cancel_rport_listener(struct ssh *, struct Forward *);
341 int channel_cancel_lport_listener(struct ssh *, struct Forward *,
342  int, struct ForwardOptions *);
343 int permitopen_port(const char *);
344 
345 /* x11 forwarding */
346 
347 void channel_set_x11_refuse_time(struct ssh *, u_int);
348 int x11_connect_display(struct ssh *);
349 int x11_create_display_inet(struct ssh *, int, int, int, int, u_int *, int **);
350 void x11_request_forwarding_with_spoofing(struct ssh *, int,
351  const char *, const char *, const char *, int);
352 
353 /* channel close */
354 
355 int chan_is_dead(struct ssh *, Channel *, int);
356 void chan_mark_dead(struct ssh *, Channel *);
357 
358 /* channel events */
359 
360 void chan_rcvd_oclose(struct ssh *, Channel *);
361 void chan_rcvd_eow(struct ssh *, Channel *);
362 void chan_read_failed(struct ssh *, Channel *);
363 void chan_ibuf_empty(struct ssh *, Channel *);
364 void chan_rcvd_ieof(struct ssh *, Channel *);
365 void chan_write_failed(struct ssh *, Channel *);
366 void chan_obuf_empty(struct ssh *, Channel *);
367 
368 /* hpn handler */
369 void channel_set_hpn(int, int);
370 
371 #endif
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