aboutsummaryrefslogtreecommitdiff
path: root/libssh/client.c
blob: 07dc0f83095aa86a31687fc77e422172670ef834 (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
/*
 * client.c - SSH client functions
 *
 * This file is part of the SSH Library
 *
 * Copyright (c) 2003-2008 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 <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifndef _WIN32
#include <arpa/inet.h>
#endif

#include "libssh/priv.h"
#include "libssh/ssh2.h"

#define set_status(opt,status) do {\
        if (opt->connect_status_function) \
            opt->connect_status_function(opt->connect_status_arg, status); \
    } while (0)

/**
 * @internal
 *
 * @brief Get a banner from a socket.
 *
 * The caller has to free memroy.
 *
 * @param  session      The session to get the banner from.
 *
 * @return A newly allocated string with the banner or NULL on error.
 */
char *ssh_get_banner(SSH_SESSION *session) {
  char buffer[128] = {0};
  char *str = NULL;
  int i;

  enter_function();

  for (i = 0; i < 127; i++) {
    if (ssh_socket_read(session->socket, &buffer[i], 1) != SSH_OK) {
      ssh_set_error(session, SSH_FATAL, "Remote host closed connection");
      leave_function();
      return NULL;
    }

    if (buffer[i] == '\r') {
      buffer[i] = '\0';
    }
    if (buffer[i] == '\n') {
      buffer[i] = '\0';
      str = strdup(buffer);
      if (str == NULL) {
        leave_function();
        return NULL;
      }
      leave_function();
      return str;
    }
  }

  ssh_set_error(session, SSH_FATAL, "Too large banner");

  leave_function();
  return NULL;
}

/**
 * @internal
 *
 * @brief Analyze the SSH banner to find out if we have a SSHv1 or SSHv2
 * server.
 *
 * @param  session      The session to analyze the banner from.
 * @param  ssh1         The variable which is set if it is a SSHv1 server.
 * @param  ssh2         The variable which is set if it is a SSHv2 server.
 *
 * @return 0 on success, < 0 on error.
 *
 * @see ssh_get_banner()
 */
static int ssh_analyze_banner(SSH_SESSION *session, int *ssh1, int *ssh2) {
  char *banner = session->serverbanner;

  if (strncmp(banner, "SSH-", 4) != 0) {
    ssh_set_error(session, SSH_FATAL, "Protocol mismatch: %s", banner);
    return -1;
  }

  /*
   * Typical banners e.g. are:
   * SSH-1.5-blah
   * SSH-1.99-blah
   * SSH-2.0-blah
   */
  switch(banner[4]) {
    case '1':
      *ssh1 = 1;
      if (banner[6] == '9') {
        *ssh2 = 1;
      } else {
        *ssh2 = 0;
      }
      break;
    case '2':
      *ssh1 = 0;
      *ssh2 = 1;
      break;
    default:
      ssh_set_error(session, SSH_FATAL, "Protocol mismatch: %s", banner);
      return -1;
  }

  return 0;
}

/** @internal
 * @brief Sends a SSH banner to the server.
 *
 * @param session      The SSH session to use.
 *
 * @param server       Send client or server banner.
 *
 * @return 0 on success, < 0 on error.
 */
int ssh_send_banner(SSH_SESSION *session, int server) {
  const char *banner = NULL;
  char buffer[128] = {0};

  enter_function();

  banner = session->version == 1 ? CLIENTBANNER1 : CLIENTBANNER2;

  if (session->options->banner) {
    banner = session->options->banner;
  }

  if (server) {
    session->serverbanner = strdup(banner);
    if (session->serverbanner == NULL) {
      leave_function();
      return -1;
    }
  } else {
    session->clientbanner = strdup(banner);
    if (session->clientbanner == NULL) {
      leave_function();
      return -1;
    }
  }

  snprintf(buffer, 128, "%s\r\n", banner);

  if (ssh_socket_write(session->socket, buffer, strlen(buffer)) == SSH_ERROR) {
    leave_function();
    return -1;
  }

  if (ssh_socket_blocking_flush(session->socket) != SSH_OK) {
    leave_function();
    return -1;
  }

  leave_function();
  return 0;
}

#define DH_STATE_INIT 0
#define DH_STATE_INIT_TO_SEND 1
#define DH_STATE_INIT_SENT 2
#define DH_STATE_NEWKEYS_TO_SEND 3
#define DH_STATE_NEWKEYS_SENT 4
#define DH_STATE_FINISHED 5
static int dh_handshake(SSH_SESSION *session) {
  STRING *e = NULL;
  STRING *f = NULL;
  STRING *pubkey = NULL;
  STRING *signature = NULL;
  int rc = SSH_ERROR;

  enter_function();

  switch (session->dh_handshake_state) {
    case DH_STATE_INIT:
      if (buffer_add_u8(session->out_buffer, SSH2_MSG_KEXDH_INIT) < 0) {
        goto error;
      }

      if (dh_generate_x(session) < 0) {
        goto error;
      }
      if (dh_generate_e(session) < 0) {
        goto error;
      }

      e = dh_get_e(session);
      if (e == NULL) {
        goto error;
      }

      if (buffer_add_ssh_string(session->out_buffer, e) < 0) {
        goto error;
      }
      string_burn(e);
      string_free(e);

      rc = packet_send(session);
      if (rc == SSH_ERROR) {
        goto error;
      }

      session->dh_handshake_state = DH_STATE_INIT_TO_SEND;
    case DH_STATE_INIT_TO_SEND:
      rc = packet_flush(session, 0);
      if (rc != SSH_OK) {
        goto error;
      }
      session->dh_handshake_state = DH_STATE_INIT_SENT;
    case DH_STATE_INIT_SENT:
      rc = packet_wait(session, SSH2_MSG_KEXDH_REPLY, 1);
      if (rc != SSH_OK) {
        goto error;
      }

      pubkey = buffer_get_ssh_string(session->in_buffer);
      if (pubkey == NULL){
        ssh_set_error(session,SSH_FATAL, "No public key in packet");
        rc = SSH_ERROR;
        goto error;
      }
      dh_import_pubkey(session, pubkey);

      f = buffer_get_ssh_string(session->in_buffer);
      if (f == NULL) {
        ssh_set_error(session,SSH_FATAL, "No F number in packet");
        rc = SSH_ERROR;
        goto error;
      }
      if (dh_import_f(session, f) < 0) {
        ssh_set_error(session, SSH_FATAL, "Cannot import f number");
        rc = SSH_ERROR;
        goto error;
      }
      string_burn(f);
      string_free(f);

      signature = buffer_get_ssh_string(session->in_buffer);
      if (signature == NULL) {
        ssh_set_error(session, SSH_FATAL, "No signature in packet");
        rc = SSH_ERROR;
        goto error;
      }
      session->dh_server_signature = signature;
      if (dh_build_k(session) < 0) {
        ssh_set_error(session, SSH_FATAL, "Cannot build k number");
        rc = SSH_ERROR;
        goto error;
      }

      /* Send the MSG_NEWKEYS */
      if (buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS) < 0) {
        rc = SSH_ERROR;
        goto error;
      }

      rc = packet_send(session);
      if (rc == SSH_ERROR) {
        goto error;
      }

      session->dh_handshake_state = DH_STATE_NEWKEYS_TO_SEND;
    case DH_STATE_NEWKEYS_TO_SEND:
      rc = packet_flush(session, 0);
      if (rc != SSH_OK) {
        goto error;
      }
      ssh_log(session, SSH_LOG_RARE, "SSH_MSG_NEWKEYS sent\n");

      session->dh_handshake_state = DH_STATE_NEWKEYS_SENT;
    case DH_STATE_NEWKEYS_SENT:
      rc = packet_wait(session, SSH2_MSG_NEWKEYS, 1);
      if (rc != SSH_OK) {
        goto error;
      }
      ssh_log(session, SSH_LOG_RARE, "Got SSH_MSG_NEWKEYS\n");

      rc = make_sessionid(session);
      if (rc != SSH_OK) {
        goto error;
      }

      /*
       * Set the cryptographic functions for the next crypto
       * (it is needed for generate_session_keys for key lenghts)
       */
      if (crypt_set_algorithms(session)) {
        rc = SSH_ERROR;
        goto error;
      }

      if (generate_session_keys(session) < 0) {
        rc = SSH_ERROR;
        goto error;
      }

      /* Verify the host's signature. FIXME do it sooner */
      signature = session->dh_server_signature;
      session->dh_server_signature = NULL;
      if (signature_verify(session, signature)) {
        rc = SSH_ERROR;
        goto error;
      }

      /* forget it for now ... */
      string_burn(signature);
      string_free(signature);

      /*
       * Once we got SSH2_MSG_NEWKEYS we can switch next_crypto and
       * current_crypto
       */
      if (session->current_crypto) {
        crypto_free(session->current_crypto);
      }

      /* FIXME later, include a function to change keys */
      session->current_crypto = session->next_crypto;

      session->next_crypto = crypto_new();
      if (session->next_crypto == NULL) {
        rc = SSH_ERROR;
        goto error;
      }

      session->dh_handshake_state = DH_STATE_FINISHED;

      leave_function();
      return SSH_OK;
    default:
      ssh_set_error(session, SSH_FATAL, "Invalid state in dh_handshake(): %d",
          session->dh_handshake_state);

      leave_function();
      return SSH_ERROR;
  }

  /* not reached */
error:
  string_burn(e);
  string_free(e);
  string_burn(f);
  string_free(f);
  string_burn(pubkey);
  string_free(pubkey);
  string_burn(signature);
  string_free(signature);

  leave_function();
  return rc;
}

/**
 * @internal
 *
 * @brief Request a service from the SSH server.
 *
 * Service requests are for example: ssh-userauth, ssh-connection, etc.
 *
 * @param  session      The session to use to ask for a service request.
 * @param  service      The service request.
 *
 * @return 0 on success, < 0 on error.
 */
int ssh_service_request(SSH_SESSION *session, const char *service) {
  STRING *service_s = NULL;

  enter_function();

  if (buffer_add_u8(session->out_buffer, SSH2_MSG_SERVICE_REQUEST) < 0) {
    leave_function();
    return -1;
  }

  service_s = string_from_char(service);
  if (service_s == NULL) {
    leave_function();
    return -1;
  }

  if (buffer_add_ssh_string(session->out_buffer,service_s) < 0) {
    string_free(service_s);
    leave_function();
    return -1;
  }
  string_free(service_s);

  if (packet_send(session) != SSH_OK) {
    ssh_set_error(session, SSH_FATAL,
        "Sending SSH2_MSG_SERVICE_REQUEST failed.");
    leave_function();
    return -1;
  }

  ssh_log(session, SSH_LOG_PACKET,
      "Sent SSH_MSG_SERVICE_REQUEST (service %s)", service);

  if (packet_wait(session,SSH2_MSG_SERVICE_ACCEPT,1) != SSH_OK) {
    ssh_set_error(session, SSH_FATAL, "Did not receive SERVICE_ACCEPT");
    leave_function();
    return -1;
  }

  ssh_log(session, SSH_LOG_PACKET,
      "Received SSH_MSG_SERVICE_ACCEPT (service %s)", service);

  leave_function();
  return 0;
}

/** \addtogroup ssh_session
 * @{
 */

/** \brief connect to the ssh server
 * \param session ssh session
 * \return SSH_OK on success, SSH_ERROR on error
 * \see ssh_new()
 * \see ssh_disconnect()
 */
int ssh_connect(SSH_SESSION *session) {
  SSH_OPTIONS *options = session->options;
  int ssh1 = 0;
  int ssh2 = 0;
  int fd = -1;

  if (session == NULL) {
    ssh_set_error(session, SSH_FATAL, "Invalid session pointer");
    return SSH_ERROR;
  }

  if (session->options == NULL) {
    ssh_set_error(session, SSH_FATAL, "No options set");
    return SSH_ERROR;
  }
  options = session->options;

  enter_function();

  session->alive = 0;
  session->client = 1;

  if (ssh_crypto_init() < 0) {
    leave_function();
    return SSH_ERROR;
  }
  if (ssh_socket_init() < 0) {
    leave_function();
    return SSH_ERROR;
  }

  if (options->fd == -1 && options->host == NULL) {
    ssh_set_error(session, SSH_FATAL, "Hostname required");
    leave_function();
    return SSH_ERROR;
  }
  if (options->fd != -1) {
    fd = options->fd;
  } else {
    fd = ssh_connect_host(session, options->host, options->bindaddr,
        options->port, options->timeout, options->timeout_usec);
  }
  if (fd < 0) {
    leave_function();
    return SSH_ERROR;
  }
  set_status(options, 0.2);

  ssh_socket_set_fd(session->socket, fd);

  session->alive = 1;
  session->serverbanner = ssh_get_banner(session);
  if (session->serverbanner == NULL) {
    ssh_socket_close(session->socket);
    session->alive = 0;
    leave_function();
    return SSH_ERROR;
  }
  set_status(options, 0.4);

  ssh_log(session, SSH_LOG_RARE,
      "SSH server banner: %s", session->serverbanner);

  /* Here we analyse the different protocols the server allows. */
  if (ssh_analyze_banner(session, &ssh1, &ssh2) < 0) {
    ssh_socket_close(session->socket);
    session->alive = 0;
    leave_function();
    return SSH_ERROR;
  }

  /* Here we decide which version of the protocol to use. */
  if (ssh2 && options->ssh2allowed) {
    session->version = 2;
  } else if(ssh1 && options->ssh1allowed) {
    session->version = 1;
  } else {
    ssh_set_error(session, SSH_FATAL,
        "No version of SSH protocol usable (banner: %s)",
        session->serverbanner);
    ssh_socket_close(session->socket);
    session->alive = 0;
    leave_function();
    return SSH_ERROR;
  }

  if (ssh_send_banner(session, 0) < 0) {
    ssh_set_error(session, SSH_FATAL, "Sending the banner failed");
    ssh_socket_close(session->socket);
    session->alive = 0;
    leave_function();
    return SSH_ERROR;
  }
  set_status(options, 0.5);

  switch (session->version) {
    case 2:
      if (ssh_get_kex(session,0) < 0) {
        ssh_socket_close(session->socket);
        session->alive = 0;
        leave_function();
        return SSH_ERROR;
      }
      set_status(options,0.6);

      ssh_list_kex(session, &session->server_kex);
      if (set_kex(session) < 0) {
        ssh_socket_close(session->socket);
        session->alive = 0;
        leave_function();
        return SSH_ERROR;
      }
      if (ssh_send_kex(session, 0) < 0) {
        ssh_socket_close(session->socket);
        session->alive = 0;
        leave_function();
        return SSH_ERROR;
      }
      set_status(options,0.8);

      if (dh_handshake(session) < 0) {
        ssh_socket_close(session->socket);
        session->alive = 0;
        leave_function();
        return SSH_ERROR;
      }
      set_status(options,1.0);

      session->connected = 1;
      break;
    case 1:
      if (ssh_get_kex1(session) < 0) {
        ssh_socket_close(session->socket);
        session->alive = 0;
        leave_function();
        return SSH_ERROR;
      }
      set_status(options,0.6);

      session->connected = 1;
      break;
  }

  leave_function();
  return 0;
}

/**
 * @brief Get the issue banner from the server.
 *
 * This is the banner showing a disclaimer to users who log in,
 * typically their right or the fact that they will be monitored.
 *
 * @param session       The SSH session to use.
 *
 * @return A newly allocated string with the banner, NULL on error.
 */
char *ssh_get_issue_banner(SSH_SESSION *session) {
  if (session == NULL || session->banner == NULL) {
    return NULL;
  }

  return string_to_char(session->banner);
}

/**
 * @brief Disconnect from a session (client or server).
 *
 * @param session       The SSH session to disconnect.
 */
void ssh_disconnect(SSH_SESSION *session) {
  STRING *str = NULL;

  enter_function();

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

  if (ssh_socket_is_open(session->socket)) {
    if (buffer_add_u8(session->out_buffer, SSH2_MSG_DISCONNECT) < 0) {
      goto error;
    }
    if (buffer_add_u32(session->out_buffer,
          htonl(SSH2_DISCONNECT_BY_APPLICATION)) < 0) {
      goto error;
    }

    str = string_from_char("Bye Bye");
    if (str == NULL) {
      goto error;
    }

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

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

error:
  leave_function();
  ssh_cleanup(session);
}

const char *ssh_copyright(void) {
    return SSH_STRINGIFY(LIBSSH_VERSION) " (c) 2003-2008 Aris Adamantiadis "
    "(aris@0xbadc0de.be) Distributed under the LGPL, please refer to COPYING"
    "file for informations about your rights";
}
/** @} */
/* vim: set ts=2 sw=2 et cindent: */