aboutsummaryrefslogtreecommitdiff
path: root/include/libssh/callbacks.h
blob: a7fdb5b6c52d9a1b67c38133faf1d8d5e38d02cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
/*
 * This file is part of the SSH Library
 *
 * Copyright (c) 2009 Aris Adamantiadis <aris@0xbadc0de.be>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/* callback.h
 * This file includes the public declarations for the libssh callback mechanism
 */

#ifndef _SSH_CALLBACK_H
#define _SSH_CALLBACK_H

#include <libssh/libssh.h>
#include <string.h>

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @defgroup libssh_callbacks The libssh callbacks
 * @ingroup libssh
 *
 * Callback which can be replaced in libssh.
 *
 * @{
 */

/** @internal
 * @brief callback to process simple codes
 * @param code value to transmit
 * @param user Userdata to pass in callback
 */
typedef void (*ssh_callback_int) (int code, void *user);

/** @internal
 * @brief callback for data received messages.
 * @param data data retrieved from the socket or stream
 * @param len number of bytes available from this stream
 * @param user user-supplied pointer sent along with all callback messages
 * @returns number of bytes processed by the callee. The remaining bytes will
 * be sent in the next callback message, when more data is available.
 */
typedef int (*ssh_callback_data) (const void *data, size_t len, void *user);

typedef void (*ssh_callback_int_int) (int code, int errno_code, void *user);

typedef int (*ssh_message_callback) (ssh_session, ssh_message message, void *user);
typedef int (*ssh_channel_callback_int) (ssh_channel channel, int code, void *user);
typedef int (*ssh_channel_callback_data) (ssh_channel channel, int code, void *data, size_t len, void *user);

/**
 * @brief SSH log callback. All logging messages will go through this callback
 * @param session Current session handler
 * @param priority Priority of the log, the smaller being the more important
 * @param message the actual message
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_log_callback) (ssh_session session, int priority,
    const char *message, void *userdata);

/**
 * @brief SSH Connection status callback.
 * @param session Current session handler
 * @param status Percentage of connection status, going from 0.0 to 1.0
 * once connection is done.
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_status_callback) (ssh_session session, float status,
		void *userdata);

/**
 * @brief SSH global request callback. All global request will go through this
 * callback.
 * @param session Current session handler
 * @param message the actual message
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_global_request_callback) (ssh_session session,
                                        ssh_message message, void *userdata);

/**
 * @brief Handles an SSH new channel open X11 request. This happens when the server
 * sends back an X11 connection attempt. This is a client-side API
 * @param session current session handler
 * @param userdata Userdata to be passed to the callback function.
 * @returns a valid ssh_channel handle if the request is to be allowed
 * @returns NULL if the request should not be allowed
 * @warning The channel pointer returned by this callback must be closed by the application.
 */
typedef ssh_channel (*ssh_channel_open_request_x11_callback) (ssh_session session,
      const char * originator_address, int originator_port, void *userdata);

/**
 * The structure to replace libssh functions with appropriate callbacks.
 */
struct ssh_callbacks_struct {
  /** DON'T SET THIS use ssh_callbacks_init() instead. */
  size_t size;
  /**
   * User-provided data. User is free to set anything he wants here
   */
  void *userdata;
  /**
   * This functions will be called if e.g. a keyphrase is needed.
   */
  ssh_auth_callback auth_function;
  /**
   * This function will be called each time a loggable event happens.
   */
  ssh_log_callback log_function;
  /**
   * This function gets called during connection time to indicate the
   * percentage of connection steps completed.
   */
  void (*connect_status_function)(void *userdata, float status);
  /**
   * This function will be called each time a global request is received.
   */
  ssh_global_request_callback global_request_function;
  /** This function will be called when an incoming X11 request is received.
   */
  ssh_channel_open_request_x11_callback channel_open_request_x11_function;
};
typedef struct ssh_callbacks_struct *ssh_callbacks;

/** These are callbacks used specifically in SSH servers.
 */

/**
 * @brief SSH authentication callback.
 * @param session Current session handler
 * @param user User that wants to authenticate
 * @param password Password used for authentication
 * @param userdata Userdata to be passed to the callback function.
 * @returns SSH_AUTH_OK Authentication is accepted.
 * @returns SSH_AUTH_PARTIAL Partial authentication, more authentication means are needed.
 * @returns SSH_AUTH_DENIED Authentication failed.
 */
typedef int (*ssh_auth_password_callback) (ssh_session session, const char *user, const char *password,
		void *userdata);

/**
 * @brief SSH authentication callback. Tries to authenticates user with the "none" method
 * which is anonymous or passwordless.
 * @param session Current session handler
 * @param user User that wants to authenticate
 * @param userdata Userdata to be passed to the callback function.
 * @returns SSH_AUTH_OK Authentication is accepted.
 * @returns SSH_AUTH_PARTIAL Partial authentication, more authentication means are needed.
 * @returns SSH_AUTH_DENIED Authentication failed.
 */
typedef int (*ssh_auth_none_callback) (ssh_session session, const char *user, void *userdata);

/**
 * @brief SSH authentication callback. Tries to authenticates user with the "gssapi-with-mic" method
 * @param session Current session handler
 * @param user Authenticated login of the user, including realm.
 * @param userdata Userdata to be passed to the callback function.
 * @returns SSH_AUTH_OK Authentication is accepted.
 * @returns SSH_AUTH_PARTIAL Partial authentication, more authentication means are needed.
 * @returns SSH_AUTH_DENIED Authentication failed.
 */
typedef int (*ssh_auth_gssapi_mic_callback) (ssh_session session, const char *user, void *userdata);


/**
 * @brief Handles an SSH service request
 * @param session current session handler
 * @param service name of the service (e.g. "ssh-userauth") requested
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the request is to be allowed
 * @returns -1 if the request should not be allowed
 */

typedef int (*ssh_service_request_callback) (ssh_session session, const char *service, void *userdata);

/**
 * @brief Handles an SSH new channel open session request
 * @param session current session handler
 * @param userdata Userdata to be passed to the callback function.
 * @returns a valid ssh_channel handle if the request is to be allowed
 * @returns NULL if the request should not be allowed
 * @warning The channel pointer returned by this callback must be closed by the application.
 */
typedef ssh_channel (*ssh_channel_open_request_session_callback) (ssh_session session, void *userdata);

/*
 * @brief handle the beginning of a GSSAPI authentication, server side.
 * @param session current session handler
 * @param user the username of the client
 * @param n_oid number of available oids
 * @param oids OIDs provided by the client
 * @returns an ssh_string containing the chosen OID, that's supported by both
 * client and server.
 * @warning It is not necessary to fill this callback in if libssh is linked
 * with libgssapi.
 */
typedef ssh_string (*ssh_gssapi_select_oid_callback) (ssh_session session, const char *user,
		int n_oid, ssh_string *oids, void *userdata);

/*
 * @brief handle the negociation of a security context, server side.
 * @param session current session handler
 * @param[in] input_token input token provided by client
 * @param[out] output_token output of the gssapi accept_sec_context method,
 * 				NULL after completion.
 * @returns SSH_OK if the token was generated correctly or accept_sec_context
 * returned GSS_S_COMPLETE
 * @returns SSH_ERROR in case of error
 * @warning It is not necessary to fill this callback in if libssh is linked
 * with libgssapi.
 */
typedef int (*ssh_gssapi_accept_sec_ctx_callback) (ssh_session session,
		ssh_string input_token, ssh_string *output_token, void *userdata);

/*
 * @brief Verify and authenticates a MIC, server side.
 * @param session current session handler
 * @param[in] mic input mic to be verified provided by client
 * @param[in] mic_buffer buffer of data to be signed.
 * @param[in] mic_buffer_size size of mic_buffer
 * @returns SSH_OK if the MIC was authenticated correctly
 * @returns SSH_ERROR in case of error
 * @warning It is not necessary to fill this callback in if libssh is linked
 * with libgssapi.
 */
typedef int (*ssh_gssapi_verify_mic_callback) (ssh_session session,
		ssh_string mic, void *mic_buffer, size_t mic_buffer_size, void *userdata);

/**
 * This structure can be used to implement a libssh server, with appropriate callbacks.
 */

struct ssh_server_callbacks_struct {
  /** DON'T SET THIS use ssh_callbacks_init() instead. */
  size_t size;
  /**
   * User-provided data. User is free to set anything he wants here
   */
  void *userdata;
  /** This function gets called when a client tries to authenticate through
   * password method.
   */
  ssh_auth_password_callback auth_password_function;

  /** This function gets called when a client tries to authenticate through
   * none method.
   */
  ssh_auth_none_callback auth_none_function;

  /** This function gets called when a client tries to authenticate through
   * gssapi-mic method.
   */
  ssh_auth_gssapi_mic_callback auth_gssapi_mic_function;
  /** This functions gets called when a service request is issued by the
   * client
   */
  ssh_service_request_callback service_request_function;
  /** This functions gets called when a new channel request is issued by
   * the client
   */
  ssh_channel_open_request_session_callback channel_open_request_session_function;
  /** This function will be called when a new gssapi authentication is attempted.
   */
  ssh_gssapi_select_oid_callback gssapi_select_oid_function;
  /** This function will be called when a gssapi token comes in.
   */
  ssh_gssapi_accept_sec_ctx_callback gssapi_accept_sec_ctx_function;
  /* This function will be called when a MIC needs to be verified.
   */
  ssh_gssapi_verify_mic_callback gssapi_verify_mic_function;
};
typedef struct ssh_server_callbacks_struct *ssh_server_callbacks;

/**
 * @brief Set the session server callback functions.
 *
 * This functions sets the callback structure to use your own callback
 * functions for user authentication, new channels and requests.
 *
 * @code
 * struct ssh_server_callbacks_struct cb = {
 *   .userdata = data,
 *   .auth_password_function = my_auth_function
 * };
 * ssh_callbacks_init(&cb);
 * ssh_set_server_callbacks(session, &cb);
 * @endcode
 *
 * @param  session      The session to set the callback structure.
 *
 * @param  cb           The callback structure itself.
 *
 * @return SSH_OK on success, SSH_ERROR on error.
 */
LIBSSH_API int ssh_set_server_callbacks(ssh_session session, ssh_server_callbacks cb);

/**
 * These are the callbacks exported by the socket structure
 * They are called by the socket module when a socket event appears
 */
struct ssh_socket_callbacks_struct {
  /**
   * User-provided data. User is free to set anything he wants here
   */
  void *userdata;
	/**
	 * This function will be called each time data appears on socket. The data
	 * not consumed will appear on the next data event.
	 */
  ssh_callback_data data;
  /** This function will be called each time a controlflow state changes, i.e.
   * the socket is available for reading or writing.
   */
  ssh_callback_int controlflow;
  /** This function will be called each time an exception appears on socket. An
   * exception can be a socket problem (timeout, ...) or an end-of-file.
   */
  ssh_callback_int_int exception;
  /** This function is called when the ssh_socket_connect was used on the socket
   * on nonblocking state, and the connection successed.
   */
  ssh_callback_int_int connected;
};
typedef struct ssh_socket_callbacks_struct *ssh_socket_callbacks;

#define SSH_SOCKET_FLOW_WRITEWILLBLOCK 1
#define SSH_SOCKET_FLOW_WRITEWONTBLOCK 2

#define SSH_SOCKET_EXCEPTION_EOF 	     1
#define SSH_SOCKET_EXCEPTION_ERROR     2

#define SSH_SOCKET_CONNECTED_OK 			1
#define SSH_SOCKET_CONNECTED_ERROR 		2
#define SSH_SOCKET_CONNECTED_TIMEOUT 	3

/**
 * @brief Initializes an ssh_callbacks_struct
 * A call to this macro is mandatory when you have set a new
 * ssh_callback_struct structure. Its goal is to maintain the binary
 * compatibility with future versions of libssh as the structure
 * evolves with time.
 */
#define ssh_callbacks_init(p) do {\
	(p)->size=sizeof(*(p)); \
} while(0);

/**
 * @internal
 * @brief tests if a callback can be called without crash
 *  verifies that the struct size if big enough
 *  verifies that the callback pointer exists
 * @param p callback pointer
 * @param c callback name
 * @returns nonzero if callback can be called
 */
#define ssh_callbacks_exists(p,c) (\
  (p != NULL) && ( (char *)&((p)-> c) < (char *)(p) + (p)->size ) && \
  ((p)-> c != NULL) \
  )

/** @brief Prototype for a packet callback, to be called when a new packet arrives
 * @param session The current session of the packet
 * @param type packet type (see ssh2.h)
 * @param packet buffer containing the packet, excluding size, type and padding fields
 * @param user user argument to the callback
 * and are called each time a packet shows up
 * @returns SSH_PACKET_USED Packet was parsed and used
 * @returns SSH_PACKET_NOT_USED Packet was not used or understood, processing must continue
 */
typedef int (*ssh_packet_callback) (ssh_session session, uint8_t type, ssh_buffer packet, void *user);

/** return values for a ssh_packet_callback */
/** Packet was used and should not be parsed by another callback */
#define SSH_PACKET_USED 1
/** Packet was not used and should be passed to any other callback
 * available */
#define SSH_PACKET_NOT_USED 2


/** @brief This macro declares a packet callback handler
 * @code
 * SSH_PACKET_CALLBACK(mycallback){
 * ...
 * }
 * @endcode
 */
#define SSH_PACKET_CALLBACK(name) \
	int name (ssh_session session, uint8_t type, ssh_buffer packet, void *user)

struct ssh_packet_callbacks_struct {
	/** Index of the first packet type being handled */
	uint8_t start;
	/** Number of packets being handled by this callback struct */
	uint8_t n_callbacks;
	/** A pointer to n_callbacks packet callbacks */
	ssh_packet_callback *callbacks;
  /**
   * User-provided data. User is free to set anything he wants here
   */
	void *user;
};

typedef struct ssh_packet_callbacks_struct *ssh_packet_callbacks;

/**
 * @brief Set the session callback functions.
 *
 * This functions sets the callback structure to use your own callback
 * functions for auth, logging and status.
 *
 * @code
 * struct ssh_callbacks_struct cb = {
 *   .userdata = data,
 *   .auth_function = my_auth_function
 * };
 * ssh_callbacks_init(&cb);
 * ssh_set_callbacks(session, &cb);
 * @endcode
 *
 * @param  session      The session to set the callback structure.
 *
 * @param  cb           The callback structure itself.
 *
 * @return SSH_OK on success, SSH_ERROR on error.
 */
LIBSSH_API int ssh_set_callbacks(ssh_session session, ssh_callbacks cb);

/**
 * @brief SSH channel data callback. Called when data is available on a channel
 * @param session Current session handler
 * @param channel the actual channel
 * @param data the data that has been read on the channel
 * @param len the length of the data
 * @param is_stderr is 0 for stdout or 1 for stderr
 * @param userdata Userdata to be passed to the callback function.
 */
typedef int (*ssh_channel_data_callback) (ssh_session session,
                                           ssh_channel channel,
                                           void *data,
                                           uint32_t len,
                                           int is_stderr,
                                           void *userdata);

/**
 * @brief SSH channel eof callback. Called when a channel receives EOF
 * @param session Current session handler
 * @param channel the actual channel
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_eof_callback) (ssh_session session,
                                           ssh_channel channel,
                                           void *userdata);

/**
 * @brief SSH channel close callback. Called when a channel is closed by remote peer
 * @param session Current session handler
 * @param channel the actual channel
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_close_callback) (ssh_session session,
                                            ssh_channel channel,
                                            void *userdata);

/**
 * @brief SSH channel signal callback. Called when a channel has received a signal
 * @param session Current session handler
 * @param channel the actual channel
 * @param signal the signal name (without the SIG prefix)
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_signal_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *signal,
                                            void *userdata);

/**
 * @brief SSH channel exit status callback. Called when a channel has received an exit status
 * @param session Current session handler
 * @param channel the actual channel
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_exit_status_callback) (ssh_session session,
                                            ssh_channel channel,
                                            int exit_status,
                                            void *userdata);

/**
 * @brief SSH channel exit signal callback. Called when a channel has received an exit signal
 * @param session Current session handler
 * @param channel the actual channel
 * @param signal the signal name (without the SIG prefix)
 * @param core a boolean telling wether a core has been dumped or not
 * @param errmsg the description of the exception
 * @param lang the language of the description (format: RFC 3066)
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_exit_signal_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *signal,
                                            int core,
                                            const char *errmsg,
                                            const char *lang,
                                            void *userdata);

/**
 * @brief SSH channel PTY request from a client.
 * @param channel the channel
 * @param term The type of terminal emulation
 * @param width width of the terminal, in characters
 * @param height height of the terminal, in characters
 * @param pxwidth width of the terminal, in pixels
 * @param pxheight height of the terminal, in pixels
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the pty request is accepted
 * @returns -1 if the request is denied
 */
typedef int (*ssh_channel_pty_request_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *term,
                                            int width, int height,
                                            int pxwidth, int pwheight,
                                            void *userdata);

/**
 * @brief SSH channel Shell request from a client.
 * @param channel the channel
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the shell request is accepted
 * @returns 1 if the request is denied
 */
typedef int (*ssh_channel_shell_request_callback) (ssh_session session,
                                            ssh_channel channel,
                                            void *userdata);
/**
 * @brief SSH auth-agent-request from the client. This request is
 * sent by a client when agent forwarding is available.
 * Server is free to ignore this callback, no answer is expected.
 * @param channel the channel
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_auth_agent_req_callback) (ssh_session session,
                                            ssh_channel channel,
                                            void *userdata);

/**
 * @brief SSH X11 request from the client. This request is
 * sent by a client when X11 forwarding is requested(and available).
 * Server is free to ignore this callback, no answer is expected.
 * @param channel the channel
 * @param userdata Userdata to be passed to the callback function.
 */
typedef void (*ssh_channel_x11_req_callback) (ssh_session session,
                                            ssh_channel channel,
                                            int single_connection,
                                            const char *auth_protocol,
                                            const char *auth_cookie,
                                            uint32_t screen_number,
                                            void *userdata);
/**
 * @brief SSH channel PTY windows change (terminal size) from a client.
 * @param channel the channel
 * @param width width of the terminal, in characters
 * @param height height of the terminal, in characters
 * @param pxwidth width of the terminal, in pixels
 * @param pxheight height of the terminal, in pixels
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the pty request is accepted
 * @returns -1 if the request is denied
 */
typedef int (*ssh_channel_pty_window_change_callback) (ssh_session session,
                                            ssh_channel channel,
                                            int width, int height,
                                            int pxwidth, int pwheight,
                                            void *userdata);

/**
 * @brief SSH channel Exec request from a client.
 * @param channel the channel
 * @param command the shell command to be executed
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the exec request is accepted
 * @returns 1 if the request is denied
 */
typedef int (*ssh_channel_exec_request_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *command,
                                            void *userdata);

/**
 * @brief SSH channel environment request from a client.
 * @param channel the channel
 * @param env_name name of the environment value to be set
 * @param env_value value of the environment value to be set
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the env request is accepted
 * @returns 1 if the request is denied
 * @warning some environment variables can be dangerous if changed (e.g.
 * 			LD_PRELOAD) and should not be fulfilled.
 */
typedef int (*ssh_channel_env_request_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *env_name,
                                            const char *env_value,
                                            void *userdata);
/**
 * @brief SSH channel subsystem request from a client.
 * @param channel the channel
 * @param subsystem the subsystem required
 * @param userdata Userdata to be passed to the callback function.
 * @returns 0 if the subsystem request is accepted
 * @returns 1 if the request is denied
 */
typedef int (*ssh_channel_subsystem_request_callback) (ssh_session session,
                                            ssh_channel channel,
                                            const char *subsystem,
                                            void *userdata);


struct ssh_channel_callbacks_struct {
  /** DON'T SET THIS use ssh_callbacks_init() instead. */
  size_t size;
  /**
   * User-provided data. User is free to set anything he wants here
   */
  void *userdata;
  /**
   * This functions will be called when there is data available.
   */
  ssh_channel_data_callback channel_data_function;
  /**
   * This functions will be called when the channel has received an EOF.
   */
  ssh_channel_eof_callback channel_eof_function;
  /**
   * This functions will be called when the channel has been closed by remote
   */
  ssh_channel_close_callback channel_close_function;
  /**
   * This functions will be called when a signal has been received
   */
  ssh_channel_signal_callback channel_signal_function;
  /**
   * This functions will be called when an exit status has been received
   */
  ssh_channel_exit_status_callback channel_exit_status_function;
  /**
   * This functions will be called when an exit signal has been received
   */
  ssh_channel_exit_signal_callback channel_exit_signal_function;
  /**
   * This function will be called when a client requests a PTY
   */
  ssh_channel_pty_request_callback channel_pty_request_function;
  /**
   * This function will be called when a client requests a shell
   */
  ssh_channel_shell_request_callback channel_shell_request_function;
  /** This function will be called when a client requests agent
   * authentication forwarding.
   */
  ssh_channel_auth_agent_req_callback channel_auth_agent_req_function;
  /** This function will be called when a client requests X11
   * forwarding.
   */
  ssh_channel_x11_req_callback channel_x11_req_function;
  /** This function will be called when a client requests a
   * window change.
   */
  ssh_channel_pty_window_change_callback channel_pty_window_change_function;
  /** This function will be called when a client requests a
   * command execution.
   */
  ssh_channel_exec_request_callback channel_exec_request_function;
  /** This function will be called when a client requests an environment
   * variable to be set.
   */
  ssh_channel_env_request_callback channel_env_request_function;
  /** This function will be called when a client requests a subsystem
   * (like sftp).
   */
  ssh_channel_subsystem_request_callback channel_subsystem_request_function;
};

typedef struct ssh_channel_callbacks_struct *ssh_channel_callbacks;

/**
 * @brief Set the channel callback functions.
 *
 * This functions sets the callback structure to use your own callback
 * functions for channel data and exceptions
 *
 * @code
 * struct ssh_channel_callbacks_struct cb = {
 *   .userdata = data,
 *   .channel_data = my_channel_data_function
 * };
 * ssh_callbacks_init(&cb);
 * ssh_set_channel_callbacks(channel, &cb);
 * @endcode
 *
 * @param  channel      The channel to set the callback structure.
 *
 * @param  cb           The callback structure itself.
 *
 * @return SSH_OK on success, SSH_ERROR on error.
 */
LIBSSH_API int ssh_set_channel_callbacks(ssh_channel channel,
                                         ssh_channel_callbacks cb);

/** @} */

/** @group libssh_threads
 * @{
 */

typedef int (*ssh_thread_callback) (void **lock);

typedef unsigned long (*ssh_thread_id_callback) (void);
struct ssh_threads_callbacks_struct {
	const char *type;
  ssh_thread_callback mutex_init;
  ssh_thread_callback mutex_destroy;
  ssh_thread_callback mutex_lock;
  ssh_thread_callback mutex_unlock;
  ssh_thread_id_callback thread_id;
};

/**
 * @brief sets the thread callbacks necessary if your program is using
 * libssh in a multithreaded fashion. This function must be called first,
 * outside of any threading context (in your main() for instance), before
 * ssh_init().
 * @param cb pointer to a ssh_threads_callbacks_struct structure, which contains
 * the different callbacks to be set.
 * @see ssh_threads_callbacks_struct
 * @see SSH_THREADS_PTHREAD
 */
LIBSSH_API int ssh_threads_set_callbacks(struct ssh_threads_callbacks_struct
    *cb);

/**
 * @brief returns a pointer on the pthread threads callbacks, to be used with
 * ssh_threads_set_callbacks.
 * @warning you have to link with the library ssh_threads.
 * @see ssh_threads_set_callbacks
 */
LIBSSH_API struct ssh_threads_callbacks_struct *ssh_threads_get_pthread(void);

/**
 * @brief returns a pointer on the noop threads callbacks, to be used with
 * ssh_threads_set_callbacks. These callbacks do nothing and are being used by
 * default.
 * @see ssh_threads_set_callbacks
 */
LIBSSH_API struct ssh_threads_callbacks_struct *ssh_threads_get_noop(void);

/** @} */
#ifdef __cplusplus
}
#endif

#endif /*_SSH_CALLBACK_H */

/* @} */