aboutsummaryrefslogtreecommitdiff
path: root/src/session.c
blob: d4b3643f3be6c544898eb68f75212059ebd83173 (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
/*
 * session.c - non-networking functions
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2005-2008 by Aris Adamantiadis
 *
 * The SSH 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.
 *
 * The SSH 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 the SSH Library; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

#include "config.h"

#include <string.h>
#include <stdlib.h>

#include "libssh/priv.h"
#include "libssh/libssh.h"
#include "libssh/crypto.h"
#include "libssh/server.h"
#include "libssh/socket.h"
#include "libssh/ssh2.h"
#include "libssh/agent.h"
#include "libssh/packet.h"
#include "libssh/session.h"
#include "libssh/misc.h"
#include "libssh/buffer.h"
#include "libssh/poll.h"

#define FIRST_CHANNEL 42 // why not ? it helps to find bugs.

/**
 * @defgroup libssh_session The SSH session functions.
 * @ingroup libssh
 *
 * Functions that manage a session.
 *
 * @{
 */

/**
 * @brief Create a new ssh session.
 *
 * @returns             A new ssh_session pointer, NULL on error.
 */
ssh_session ssh_new(void) {
  ssh_session session;
  char *id = NULL;
  int rc;

  session = malloc(sizeof (struct ssh_session_struct));
  if (session == NULL) {
    return NULL;
  }
  ZERO_STRUCTP(session);

  session->next_crypto = crypto_new();
  if (session->next_crypto == NULL) {
    goto err;
  }

  session->socket = ssh_socket_new(session);
  if (session->socket == NULL) {
    goto err;
  }

  session->out_buffer = ssh_buffer_new();
  if (session->out_buffer == NULL) {
    goto err;
  }

  session->in_buffer=ssh_buffer_new();
  if (session->in_buffer == NULL) {
    goto err;
  }

  session->alive = 0;
  session->auth_methods = 0;
  ssh_set_blocking(session, 1);
  session->maxchannel = FIRST_CHANNEL;

#ifndef _WIN32
    session->agent = agent_new(session);
    if (session->agent == NULL) {
      goto err;
    }
#endif /* _WIN32 */

    /* OPTIONS */
    session->opts.StrictHostKeyChecking = 1;
    session->opts.port = 22;
    session->opts.fd = -1;
    session->opts.ssh2 = 1;
    session->opts.compressionlevel=7;
#ifdef WITH_SSH1
    session->opts.ssh1 = 1;
#else
    session->opts.ssh1 = 0;
#endif

    session->opts.identity = ssh_list_new();
    if (session->opts.identity == NULL) {
      goto err;
    }

#ifdef HAVE_ECC
    id = strdup("%d/id_ecdsa");
    if (id == NULL) {
      goto err;
    }
    rc = ssh_list_append(session->opts.identity, id);
    if (rc == SSH_ERROR) {
      goto err;
    }
#endif

    id = strdup("%d/id_rsa");
    if (id == NULL) {
      goto err;
    }
    rc = ssh_list_append(session->opts.identity, id);
    if (rc == SSH_ERROR) {
      goto err;
    }

    id = strdup("%d/id_dsa");
    if (id == NULL) {
      goto err;
    }
    rc = ssh_list_append(session->opts.identity, id);
    if (rc == SSH_ERROR) {
      goto err;
    }

    id = strdup("%d/identity");
    if (id == NULL) {
      goto err;
    }
    rc = ssh_list_append(session->opts.identity, id);
    if (rc == SSH_ERROR) {
      goto err;
    }

    return session;

err:
    free(id);
    ssh_free(session);
    return NULL;
}

/**
 * @brief Deallocate a SSH session handle.
 *
 * @param[in] session   The SSH session to free.
 *
 * @see ssh_disconnect()
 * @see ssh_new()
 */
void ssh_free(ssh_session session) {
  int i;
  struct ssh_iterator *it;

  if (session == NULL) {
    return;
  }

  /*
   * Delete all channels
   *
   * This needs the first thing we clean up cause if there is still an open
   * channel we call ssh_channel_close() first. So we need a working socket
   * and poll context for it.
   */
  for (it = ssh_list_get_iterator(session->channels);
       it != NULL;
       it = ssh_list_get_iterator(session->channels)) {
      ssh_channel_do_free(ssh_iterator_value(ssh_channel,it));
      ssh_list_remove(session->channels, it);
  }
  ssh_list_free(session->channels);
  session->channels = NULL;

#ifdef WITH_PCAP
  if (session->pcap_ctx) {
      ssh_pcap_context_free(session->pcap_ctx);
      session->pcap_ctx = NULL;
  }
#endif

  ssh_socket_free(session->socket);
  session->socket = NULL;

  if (session->default_poll_ctx) {
      ssh_poll_ctx_free(session->default_poll_ctx);
  }

  ssh_buffer_free(session->in_buffer);
  ssh_buffer_free(session->out_buffer);
  session->in_buffer = session->out_buffer = NULL;

  if (session->in_hashbuf != NULL) {
      ssh_buffer_free(session->in_hashbuf);
  }
  if (session->out_hashbuf != NULL) {
      ssh_buffer_free(session->out_hashbuf);
  }

  crypto_free(session->current_crypto);
  crypto_free(session->next_crypto);

#ifndef _WIN32
  agent_free(session->agent);
#endif /* _WIN32 */

  ssh_key_free(session->srv.dsa_key);
  ssh_key_free(session->srv.rsa_key);

  if (session->ssh_message_list) {
      ssh_message msg;

      for (msg = ssh_list_pop_head(ssh_message, session->ssh_message_list);
           msg != NULL;
           msg = ssh_list_pop_head(ssh_message, session->ssh_message_list)) {
          ssh_message_free(msg);
      }
      ssh_list_free(session->ssh_message_list);
  }

  if (session->packet_callbacks) {
    ssh_list_free(session->packet_callbacks);
  }

  /* options */
  if (session->opts.identity) {
      char *id;

      for (id = ssh_list_pop_head(char *, session->opts.identity);
           id != NULL;
           id = ssh_list_pop_head(char *, session->opts.identity)) {
          SAFE_FREE(id);
      }
      ssh_list_free(session->opts.identity);
  }

  SAFE_FREE(session->serverbanner);
  SAFE_FREE(session->clientbanner);
  SAFE_FREE(session->banner);

  SAFE_FREE(session->opts.bindaddr);
  SAFE_FREE(session->opts.username);
  SAFE_FREE(session->opts.host);
  SAFE_FREE(session->opts.sshdir);
  SAFE_FREE(session->opts.knownhosts);
  SAFE_FREE(session->opts.ProxyCommand);

  for (i = 0; i < 10; i++) {
      if (session->opts.wanted_methods[i]) {
          SAFE_FREE(session->opts.wanted_methods[i]);
      }
  }

  /* burn connection, it could hang sensitive datas */
  BURN_BUFFER(session, sizeof(struct ssh_session_struct));
  SAFE_FREE(session);
}

/**
 * @brief get the server banner
 *
 * @param[in] session   The SSH session
 *
 * @return Returns the server banner string or NULL.
 */
const char* ssh_get_serverbanner(ssh_session session) {
	if(!session) {
		return NULL;
	}
	return session->serverbanner;
}

/**
 * @brief Disconnect impolitely from a remote host by closing the socket.
 *
 * Suitable if you forked and want to destroy this session.
 *
 * @param[in]  session  The SSH session to disconnect.
 */
void ssh_silent_disconnect(ssh_session session) {
  if (session == NULL) {
    return;
  }

  ssh_socket_close(session->socket);
  session->alive = 0;
  ssh_disconnect(session);
}

/**
 * @brief Set the session in blocking/nonblocking mode.
 *
 * @param[in]  session  The ssh session to change.
 *
 * @param[in]  blocking Zero for nonblocking mode.
 */
void ssh_set_blocking(ssh_session session, int blocking) {
	if (session == NULL) {
    return;
  }
  session->flags &= ~SSH_SESSION_FLAG_BLOCKING;
  session->flags |= blocking ? SSH_SESSION_FLAG_BLOCKING : 0;
}

/**
 * @brief Return the blocking mode of libssh
 * @param[in] session The SSH session
 * @returns 0 if the session is nonblocking,
 * @returns 1 if the functions may block.
 */
int ssh_is_blocking(ssh_session session){
	return (session->flags&SSH_SESSION_FLAG_BLOCKING) ? 1 : 0;
}

/* Waits until the output socket is empty */
static int ssh_flush_termination(void *c){
  ssh_session session = c;
  if (ssh_socket_buffered_write_bytes(session->socket) == 0 ||
      session->session_state == SSH_SESSION_STATE_ERROR)
    return 1;
  else
    return 0;
}

/**
 * @brief Blocking flush of the outgoing buffer
 * @param[in] session The SSH session
 * @param[in] timeout Set an upper limit on the time for which this function
 *                    will block, in milliseconds. Specifying -1
 *                    means an infinite timeout. This parameter is passed to
 *                    the poll() function.
 * @returns           SSH_OK on success, SSH_AGAIN if timeout occurred,
 *                    SSH_ERROR otherwise.
 */

int ssh_blocking_flush(ssh_session session, int timeout){
    int rc;
    if (session == NULL) {
        return SSH_ERROR;
    }

    rc = ssh_handle_packets_termination(session, timeout,
            ssh_flush_termination, session);
    if (rc == SSH_ERROR) {
        return rc;
    }
    if (!ssh_flush_termination(session)) {
        rc = SSH_AGAIN;
    }

    return rc;
}

/**
 * @brief Check if we are connected.
 *
 * @param[in]  session  The session to check if it is connected.
 *
 * @return              1 if we are connected, 0 if not.
 */
int ssh_is_connected(ssh_session session) {
    if (session == NULL) {
        return 0;
    }

    return session->alive;
}

/**
 * @brief Get the fd of a connection.
 *
 * In case you'd need the file descriptor of the connection to the server/client.
 *
 * @param[in] session   The ssh session to use.
 *
 * @return              The file descriptor of the connection, or -1 if it is
 *                      not connected
 */
socket_t ssh_get_fd(ssh_session session) {
  if (session == NULL) {
    return -1;
  }

  return ssh_socket_get_fd_in(session->socket);
}

/**
 * @brief Tell the session it has data to read on the file descriptor without
 * blocking.
 *
 * @param[in] session   The ssh session to use.
 */
void ssh_set_fd_toread(ssh_session session) {
  if (session == NULL) {
    return;
  }

  ssh_socket_set_read_wontblock(session->socket);
}

/**
 * @brief Tell the session it may write to the file descriptor without blocking.
 *
 * @param[in] session   The ssh session to use.
 */
void ssh_set_fd_towrite(ssh_session session) {
  if (session == NULL) {
    return;
  }

  ssh_socket_set_write_wontblock(session->socket);
}

/**
 * @brief Tell the session it has an exception to catch on the file descriptor.
 *
 * \param[in] session   The ssh session to use.
 */
void ssh_set_fd_except(ssh_session session) {
  if (session == NULL) {
    return;
  }

  ssh_socket_set_except(session->socket);
}

/**
 * @internal
 *
 * @brief Poll the current session for an event and call the appropriate
 * callbacks. This function will not loop until the timeout is expired.
 *
 * This will block until one event happens.
 *
 * @param[in] session   The session handle to use.
 *
 * @param[in] timeout   Set an upper limit on the time for which this function
 *                      will block, in milliseconds. Specifying SSH_TIMEOUT_INFINITE
 *                      (-1) means an infinite timeout.
 *                      Specifying SSH_TIMEOUT_USER means to use the timeout
 *                      specified in options. 0 means poll will return immediately.
 *                      This parameter is passed to the poll() function.
 *
 * @return              SSH_OK on success, SSH_ERROR otherwise.
 */
int ssh_handle_packets(ssh_session session, int timeout) {
    ssh_poll_handle spoll_in,spoll_out;
    ssh_poll_ctx ctx;
    int tm = timeout;
    int rc;

    if (session == NULL || session->socket == NULL) {
        return SSH_ERROR;
    }

    spoll_in = ssh_socket_get_poll_handle_in(session->socket);
    spoll_out = ssh_socket_get_poll_handle_out(session->socket);
    if (session->server) {
        ssh_poll_add_events(spoll_in, POLLIN);
    }
    ctx = ssh_poll_get_ctx(spoll_in);

    if (!ctx) {
        ctx = ssh_poll_get_default_ctx(session);
        ssh_poll_ctx_add(ctx, spoll_in);
        if (spoll_in != spoll_out) {
            ssh_poll_ctx_add(ctx, spoll_out);
        }
    }

    if (timeout == SSH_TIMEOUT_USER) {
        if (ssh_is_blocking(session))
          tm = ssh_make_milliseconds(session->opts.timeout,
                                     session->opts.timeout_usec);
        else
          tm = 0;
    }
    rc = ssh_poll_ctx_dopoll(ctx, tm);
    if (rc == SSH_ERROR) {
        session->session_state = SSH_SESSION_STATE_ERROR;
    }

    return rc;
}

/**
 * @internal
 *
 * @brief Poll the current session for an event and call the appropriate
 * callbacks.
 *
 * This will block until termination function returns true, or timeout expired.
 *
 * @param[in] session   The session handle to use.
 *
 * @param[in] timeout   Set an upper limit on the time for which this function
 *                      will block, in milliseconds. Specifying SSH_TIMEOUT_INFINITE
 *                      (-1) means an infinite timeout.
 *                      Specifying SSH_TIMEOUT_USER means to use the timeout
 *                      specified in options. 0 means poll will return immediately.
 *                      SSH_TIMEOUT_DEFAULT uses blocking parameters of the session.
 *                      This parameter is passed to the poll() function.
 *
 * @param[in] fct       Termination function to be used to determine if it is
 *                      possible to stop polling.
 * @param[in] user      User parameter to be passed to fct termination function.
 * @return              SSH_OK on success, SSH_ERROR otherwise.
 */
int ssh_handle_packets_termination(ssh_session session,
                                   int timeout,
                                   ssh_termination_function fct,
                                   void *user)
{
    struct ssh_timestamp ts;
    int ret = SSH_OK;
    int tm;

    if (timeout == SSH_TIMEOUT_USER) {
        if (ssh_is_blocking(session)) {
            timeout = ssh_make_milliseconds(session->opts.timeout,
                                            session->opts.timeout_usec);
        } else {
            timeout = SSH_TIMEOUT_NONBLOCKING;
        }
    } else if (timeout == SSH_TIMEOUT_DEFAULT) {
        if (ssh_is_blocking(session)) {
            timeout = SSH_TIMEOUT_INFINITE;
        } else {
            timeout = SSH_TIMEOUT_NONBLOCKING;
        }
    }

    ssh_timestamp_init(&ts);
    tm = timeout;
    while(!fct(user)) {
        ret = ssh_handle_packets(session, tm);
        if (ret == SSH_ERROR) {
            break;
        }
        if (ssh_timeout_elapsed(&ts,timeout)) {
            ret = fct(user) ? SSH_OK : SSH_AGAIN;
            break;
        }

        tm = ssh_timeout_update(&ts, timeout);
    }

    return ret;
}

/**
 * @brief Get session status
 *
 * @param session       The ssh session to use.
 *
 * @returns A bitmask including SSH_CLOSED, SSH_READ_PENDING, SSH_WRITE_PENDING
 *          or SSH_CLOSED_ERROR which respectively means the session is closed,
 *          has data to read on the connection socket and session was closed
 *          due to an error.
 */
int ssh_get_status(ssh_session session) {
  int socketstate;
  int r = 0;

  if (session == NULL) {
    return 0;
  }

  socketstate = ssh_socket_get_status(session->socket);

  if (session->session_state == SSH_SESSION_STATE_DISCONNECTED) {
    r |= SSH_CLOSED;
  }
  if (socketstate & SSH_READ_PENDING) {
    r |= SSH_READ_PENDING;
  }
  if (socketstate & SSH_WRITE_PENDING) {
      r |= SSH_WRITE_PENDING;
  }
  if ((session->session_state == SSH_SESSION_STATE_DISCONNECTED &&
       (socketstate & SSH_CLOSED_ERROR)) ||
      session->session_state == SSH_SESSION_STATE_ERROR) {
    r |= SSH_CLOSED_ERROR;
  }

  return r;
}

/**
 * @brief Get the disconnect message from the server.
 *
 * @param[in] session   The ssh session to use.
 *
 * @return              The message sent by the server along with the
 *                      disconnect, or NULL in which case the reason of the
 *                      disconnect may be found with ssh_get_error.
 *
 * @see ssh_get_error()
 */
const char *ssh_get_disconnect_message(ssh_session session) {
  if (session == NULL) {
    return NULL;
  }

  if (session->session_state != SSH_SESSION_STATE_DISCONNECTED) {
    ssh_set_error(session, SSH_REQUEST_DENIED,
        "Connection not closed yet");
  } else if(!session->discon_msg) {
    ssh_set_error(session, SSH_FATAL,
        "Connection correctly closed but no disconnect message");
  } else {
    return session->discon_msg;
  }

  return NULL;
}

/**
 * @brief Get the protocol version of the session.
 *
 * @param session       The ssh session to use.
 *
 * @return 1 or 2, for ssh1 or ssh2, < 0 on error.
 */
int ssh_get_version(ssh_session session) {
  if (session == NULL) {
    return -1;
  }

  return session->version;
}

/**
 * @internal
 * @brief Callback to be called when the socket received an exception code.
 * @param user is a pointer to session
 */
void ssh_socket_exception_callback(int code, int errno_code, void *user){
    ssh_session session=(ssh_session)user;

    SSH_LOG(SSH_LOG_RARE,"Socket exception callback: %d (%d)",code, errno_code);
    session->session_state=SSH_SESSION_STATE_ERROR;
    ssh_set_error(session,SSH_FATAL,"Socket error: %s",strerror(errno_code));
    session->ssh_connection_callback(session);
}

/**
 * @brief Send a message that should be ignored
 *
 * @param[in] session   The SSH session
 * @param[in] data      Data to be sent
 *
 * @return              SSH_OK on success, SSH_ERROR otherwise.
 */
int ssh_send_ignore (ssh_session session, const char *data) {
    ssh_string str;

    if (ssh_socket_is_open(session->socket)) {
        if (buffer_add_u8(session->out_buffer, SSH2_MSG_IGNORE) < 0) {
            goto error;
        }

        str = ssh_string_from_char(data);
        if (str == NULL) {
            goto error;
        }

        if (buffer_add_ssh_string(session->out_buffer, str) < 0) {
            ssh_string_free(str);
            goto error;
        }

        packet_send(session);
        ssh_handle_packets(session, 0);

        ssh_string_free(str);
    }

    return SSH_OK;

error:
    buffer_reinit(session->out_buffer);
    return SSH_ERROR;
}

/**
 * @brief Send a debug message
 *
 * @param[in] session          The SSH session
 * @param[in] message          Data to be sent
 * @param[in] always_display   Message SHOULD be displayed by the server. It
 *                             SHOULD NOT be displayed unless debugging
 *                             information has been explicitly requested.
 *
 * @return                     SSH_OK on success, SSH_ERROR otherwise.
 */
int ssh_send_debug (ssh_session session, const char *message, int always_display) {
    ssh_string str;
    int rc;

    if (ssh_socket_is_open(session->socket)) {
        if (buffer_add_u8(session->out_buffer, SSH2_MSG_DEBUG) < 0) {
            goto error;
        }

        if (buffer_add_u8(session->out_buffer, always_display) < 0) {
            goto error;
        }

        str = ssh_string_from_char(message);
        if (str == NULL) {
            goto error;
        }

        rc = buffer_add_ssh_string(session->out_buffer, str);
        ssh_string_free(str);
        if (rc < 0) {
            goto error;
        }

        /* Empty language tag */
        if (buffer_add_u32(session->out_buffer, 0) < 0) {
            goto error;
        }

        packet_send(session);
        ssh_handle_packets(session, 0);
    }

    return SSH_OK;

error:
    buffer_reinit(session->out_buffer);
    return SSH_ERROR;
}

/** @} */

/* vim: set ts=4 sw=4 et cindent: */