telnet_server.c 18 KB
Newer Older
1
2
3
4
/***************************************************************************
 *   Copyright (C) 2005 by Dominic Rath                                    *
 *   Dominic.Rath@gmx.de                                                   *
 *                                                                         *
5
 *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
6
7
 *   oyvind.harboe@zylin.com                                               *
 *                                                                         *
8
9
10
 *   Copyright (C) 2008 by Spencer Oliver                                  *
 *   spen@spen-soft.co.uk                                                  *
 *                                                                         *
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program 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 General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "telnet_server.h"
#include "target_request.h"

zwelch's avatar
zwelch committed
33
static unsigned short telnet_port = 4444;
34
35
36
37
38
39
40
41
42

int handle_exit_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);
int handle_telnet_port_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc);

static char *negotiate =
		"\xFF\xFB\x03"		/* IAC WILL Suppress Go Ahead */
		"\xFF\xFB\x01"		/* IAC WILL Echo */
		"\xFF\xFD\x03"		/* IAC DO Suppress Go Ahead */
		"\xFF\xFE\x01";		/* IAC DON'T Echo */
43

44
#define CTRL(c) (c - '@')
45

46
47
48
49
/* The only way we can detect that the socket is closed is the first time
 * we write to it, we will fail. Subsequent write operations will
 * succeed. Shudder!
 */
50
int telnet_write(connection_t *connection, const void *data, int len)
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
{
	telnet_connection_t *t_con = connection->priv;
	if (t_con->closed)
		return ERROR_SERVER_REMOTE_CLOSED;

	if (write_socket(connection->fd, data, len) == len)
	{
		return ERROR_OK;
	}
	t_con->closed = 1;
	return ERROR_SERVER_REMOTE_CLOSED;
}

int telnet_prompt(connection_t *connection)
{
	telnet_connection_t *t_con = connection->priv;

68
	telnet_write(connection, "\r", 1); /* the prompt is always placed at the line beginning */
69
70
71
	return telnet_write(connection, t_con->prompt, strlen(t_con->prompt));
}

72
int telnet_outputline(connection_t *connection, const char *line)
73
{
74
	int len;
75

76
	/* process lines in buffer */
77
78
	while (*line) {
		char *line_end = strchr(line, '\n');
79

80
81
82
		if (line_end)
			len = line_end-line;
		else
oharboe's avatar
oharboe committed
83
			len = strlen(line);
84

85
86
		telnet_write(connection, line, len);
		if (line_end)
87
		{
oharboe's avatar
oharboe committed
88
			telnet_write(connection, "\r\n", 2);
zwelch's avatar
zwelch committed
89
			line += len + 1;
90
		}
91
92
		else
		{
oharboe's avatar
oharboe committed
93
			line += len;
94
95
		}
	}
96

97
	return ERROR_OK;
98
99
}

oharboe's avatar
oharboe committed
100
int telnet_output(struct command_context_s *cmd_ctx, const char* line)
101
102
{
	connection_t *connection = cmd_ctx->output_handler_priv;
103

104
105
106
	return telnet_outputline(connection, line);
}

107
void telnet_log_callback(void *priv, const char *file, int line,
108
		const char *function, const char *string)
109
110
{
	connection_t *connection = priv;
111
112
	telnet_connection_t *t_con = connection->priv;
	int i;
113
114
115
116
117
118
119
120

	/* if there is no prompt, simply output the message */
	if (t_con->line_cursor < 0)
	{
		telnet_outputline(connection, string);
		return;
	}

121
122
	/* clear the command line */
	telnet_write(connection, "\r", 1);
zwelch's avatar
zwelch committed
123
124
	for (i = strlen(t_con->prompt) + t_con->line_size; i > 0; i -= 16)
		telnet_write(connection, "                ", i > 16 ? 16 : i);
125
	telnet_write(connection, "\r", 1);
126
127

	/* output the message */
128
	telnet_outputline(connection, string);
129

130
	/* put the command line to its previous state */
oharboe's avatar
oharboe committed
131
	telnet_prompt(connection);
132
	telnet_write(connection, t_con->line, t_con->line_size);
zwelch's avatar
zwelch committed
133
	for (i = t_con->line_size; i > t_con->line_cursor; i--)
134
		telnet_write(connection, "\b", 1);
135
136
137
138
139
140
141
}

int telnet_new_connection(connection_t *connection)
{
	telnet_connection_t *telnet_connection = malloc(sizeof(telnet_connection_t));
	telnet_service_t *telnet_service = connection->service->priv;
	int i;
142

143
	connection->priv = telnet_connection;
144

145
146
147
148
149
150
151
	/* initialize telnet connection information */
	telnet_connection->closed = 0;
	telnet_connection->line_size = 0;
	telnet_connection->line_cursor = 0;
	telnet_connection->option_size = 0;
	telnet_connection->prompt = strdup("> ");
	telnet_connection->state = TELNET_STATE_DATA;
152

153
154
	/* output goes through telnet connection */
	command_set_output_handler(connection->cmd_ctx, telnet_output, connection);
155

156
157
	/* negotiate telnet options */
	telnet_write(connection, negotiate, strlen(negotiate));
158

159
160
161
162
	/* print connection banner */
	if (telnet_service->banner)
	{
		telnet_write(connection, telnet_service->banner, strlen(telnet_service->banner));
oharboe's avatar
oharboe committed
163
		telnet_write(connection, "\r\n", 2);
164
	}
165

166
	telnet_prompt(connection);
167

168
169
170
171
172
173
174
175
	/* initialize history */
	for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
	{
		telnet_connection->history[i] = NULL;
	}
	telnet_connection->next_history = 0;
	telnet_connection->current_history = 0;

176
	log_add_callback(telnet_log_callback, connection);
177

178
179
180
181
182
183
184
185
186
187
	return ERROR_OK;
}

void telnet_clear_line(connection_t *connection, telnet_connection_t *t_con)
{
	/* move to end of line */
	if (t_con->line_cursor < t_con->line_size)
	{
		telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
	}
oharboe's avatar
oharboe committed
188

189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
	/* backspace, overwrite with space, backspace */
	while (t_con->line_size > 0)
	{
		telnet_write(connection, "\b \b", 3);
		t_con->line_size--;
	}
	t_con->line_cursor = 0;
}

int telnet_input(connection_t *connection)
{
	int bytes_read;
	char buffer[TELNET_BUFFER_SIZE];
	char *buf_p;
	telnet_connection_t *t_con = connection->priv;
	command_context_t *command_context = connection->cmd_ctx;
205

206
	bytes_read = read_socket(connection->fd, buffer, TELNET_BUFFER_SIZE);
207

208
209
210
211
	if (bytes_read == 0)
		return ERROR_SERVER_REMOTE_CLOSED;
	else if (bytes_read == -1)
	{
212
		LOG_ERROR("error during read: %s", strerror(errno));
213
214
		return ERROR_SERVER_REMOTE_CLOSED;
	}
215

216
217
218
219
220
221
222
223
224
225
226
227
228
229
	buf_p = buffer;
	while (bytes_read)
	{
		switch (t_con->state)
		{
			case TELNET_STATE_DATA:
				if (*buf_p == '\xff')
				{
					t_con->state = TELNET_STATE_IAC;
				}
				else
				{
					if (isprint(*buf_p)) /* printable character */
					{
230
231
232
233
234
235
236
						/* watch buffer size leaving one spare character for string null termination */
						if (t_con->line_size == TELNET_LINE_MAX_SIZE-1)
						{
							/* output audible bell if buffer is full */
							telnet_write(connection, "\x07", 1); /* "\a" does not work, at least on windows */
						}
						else if (t_con->line_cursor == t_con->line_size)
237
						{
238
							telnet_write(connection, buf_p, 1);
239
240
241
242
243
244
245
							t_con->line[t_con->line_size++] = *buf_p;
							t_con->line_cursor++;
						}
						else
						{
							int i;
							memmove(t_con->line + t_con->line_cursor + 1, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
246
							t_con->line[t_con->line_cursor] = *buf_p;
247
248
							t_con->line_size++;
							telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
249
							t_con->line_cursor++;
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
							for (i = t_con->line_cursor; i < t_con->line_size; i++)
							{
								telnet_write(connection, "\b", 1);
							}
						}
					}
					else /* non-printable */
					{
						if (*buf_p == 0x1b) /* escape */
						{
							t_con->state = TELNET_STATE_ESCAPE;
							t_con->last_escape = '\x00';
						}
						else if ((*buf_p == 0xd) || (*buf_p == 0xa)) /* CR/LF */
						{
							int retval;
266
267
268

							/* skip over combinations with CR/LF and NUL characters */
							if ((bytes_read > 1) && ((*(buf_p + 1) == 0xa) || (*(buf_p + 1) == 0xd)))
269
270
271
272
							{
								buf_p++;
								bytes_read--;
							}
273
							if ((bytes_read > 1) && (*(buf_p + 1) == 0))
274
275
276
277
278
							{
								buf_p++;
								bytes_read--;
							}
							t_con->line[t_con->line_size] = 0;
279

280
							telnet_write(connection, "\r\n\x00", 3);
281

282
283
284
							if (strcmp(t_con->line, "history") == 0)
							{
								int i;
285
								for (i = 1; i < TELNET_LINE_HISTORY_SIZE; i++)
286
								{
287
288
289
									/* the t_con->next_history line contains empty string (unless NULL), thus it is not printed */
									char *history_line = t_con->history[(t_con->next_history + i) % TELNET_LINE_HISTORY_SIZE];
									if (history_line)
290
									{
291
										telnet_write(connection, history_line, strlen(history_line));
292
293
294
295
296
297
298
										telnet_write(connection, "\r\n\x00", 3);
									}
								}
								t_con->line_size = 0;
								t_con->line_cursor = 0;
								continue;
							}
299
300
301
302

							/* save only non-blank not repeating lines in the history */
							char *prev_line = t_con->history[(t_con->current_history > 0) ? t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1];
							if (*t_con->line && (prev_line == NULL || strcmp(t_con->line, prev_line)))
303
304
305
306
307
308
							{
								/* if the history slot is already taken, free it */
								if (t_con->history[t_con->next_history])
								{
									free(t_con->history[t_con->next_history]);
								}
309

310
311
312
313
314
								/* add line to history */
								t_con->history[t_con->next_history] = strdup(t_con->line);

								/* wrap history at TELNET_LINE_HISTORY_SIZE */
								t_con->next_history = (t_con->next_history + 1) % TELNET_LINE_HISTORY_SIZE;
315

316
317
								/* current history line starts at the new entry */
								t_con->current_history = t_con->next_history;
318

319
320
321
322
323
324
								if (t_con->history[t_con->current_history])
								{
									free(t_con->history[t_con->current_history]);
								}
								t_con->history[t_con->current_history] = strdup("");
							}
325

326
							t_con->line_size = 0;
327

328
							t_con->line_cursor = -1; /* to supress prompt in log callback during command execution */
329

330
							retval = command_run_line(command_context, t_con->line);
331

332
333
							t_con->line_cursor = 0;

334
335
336
337
338
339
							if (retval == ERROR_COMMAND_CLOSE_CONNECTION)
								return ERROR_SERVER_REMOTE_CLOSED;

							retval = telnet_prompt(connection);
							if (retval == ERROR_SERVER_REMOTE_CLOSED)
								return ERROR_SERVER_REMOTE_CLOSED;
340

341
342
343
344
345
346
347
348
349
350
351
352
						}
						else if ((*buf_p == 0x7f) || (*buf_p == 0x8)) /* delete character */
						{
							if (t_con->line_cursor > 0)
							{
								if (t_con->line_cursor != t_con->line_size)
								{
									int i;
									telnet_write(connection, "\b", 1);
									t_con->line_cursor--;
									t_con->line_size--;
									memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
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
									telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
									telnet_write(connection, " \b", 2);
									for (i = t_con->line_cursor; i < t_con->line_size; i++)
									{
										telnet_write(connection, "\b", 1);
									}
								}
								else
								{
									t_con->line_size--;
									t_con->line_cursor--;
									/* back space: move the 'printer' head one char back, overwrite with space, move back again */
									telnet_write(connection, "\b \b", 3);
								}
							}
						}
						else if (*buf_p == 0x15) /* clear line */
						{
							telnet_clear_line(connection, t_con);
						}
						else if (*buf_p == CTRL('B')) /* cursor left */
						{
							if (t_con->line_cursor > 0)
							{
								telnet_write(connection, "\b", 1);
								t_con->line_cursor--;
							}
							t_con->state = TELNET_STATE_DATA;
						}
						else if (*buf_p == CTRL('F')) /* cursor right */
						{
							if (t_con->line_cursor < t_con->line_size)
							{
								telnet_write(connection, t_con->line + t_con->line_cursor++, 1);
							}
							t_con->state = TELNET_STATE_DATA;
						}
						else
						{
393
							LOG_DEBUG("unhandled nonprintable: %2.2x", *buf_p);
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
						}
					}
				}
				break;
			case TELNET_STATE_IAC:
				switch (*buf_p)
				{
					case '\xfe':
						t_con->state = TELNET_STATE_DONT;
						break;
					case '\xfd':
						t_con->state = TELNET_STATE_DO;
						break;
					case '\xfc':
						t_con->state = TELNET_STATE_WONT;
						break;
					case '\xfb':
						t_con->state = TELNET_STATE_WILL;
						break;
				}
				break;
			case TELNET_STATE_SB:
				break;
			case TELNET_STATE_SE:
				break;
			case TELNET_STATE_WILL:
			case TELNET_STATE_WONT:
			case TELNET_STATE_DO:
			case TELNET_STATE_DONT:
				t_con->state = TELNET_STATE_DATA;
				break;
			case TELNET_STATE_ESCAPE:
				if (t_con->last_escape == '[')
				{
					if (*buf_p == 'D') /* cursor left */
					{
						if (t_con->line_cursor > 0)
						{
							telnet_write(connection, "\b", 1);
							t_con->line_cursor--;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'C') /* cursor right */
					{
						if (t_con->line_cursor < t_con->line_size)
						{
							telnet_write(connection, t_con->line + t_con->line_cursor++, 1);
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'A') /* cursor up */
					{
						int last_history = (t_con->current_history > 0) ? t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1;
						if (t_con->history[last_history])
						{
							telnet_clear_line(connection, t_con);
							t_con->line_size = strlen(t_con->history[last_history]);
							t_con->line_cursor = t_con->line_size;
453
							memcpy(t_con->line, t_con->history[last_history], t_con->line_size);
454
455
456
457
458
459
460
461
462
463
464
465
466
							telnet_write(connection, t_con->line, t_con->line_size);
							t_con->current_history = last_history;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == 'B') /* cursor down */
					{
						int next_history = (t_con->current_history + 1) % TELNET_LINE_HISTORY_SIZE;
						if (t_con->history[next_history])
						{
							telnet_clear_line(connection, t_con);
							t_con->line_size = strlen(t_con->history[next_history]);
							t_con->line_cursor = t_con->line_size;
467
							memcpy(t_con->line, t_con->history[next_history], t_con->line_size);
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
							telnet_write(connection, t_con->line, t_con->line_size);
							t_con->current_history = next_history;
						}
						t_con->state = TELNET_STATE_DATA;
					}
					else if (*buf_p == '3')
					{
						t_con->last_escape = *buf_p;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else if (t_con->last_escape == '3')
				{
					/* Remove character */
					if (*buf_p == '~')
					{
						if (t_con->line_cursor < t_con->line_size)
						{
							int i;
							t_con->line_size--;
							/* remove char from line buffer */
							memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
493

494
495
496
497
							/* print remainder of buffer */
							telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
							/* overwrite last char with whitespace */
							telnet_write(connection, " \b", 2);
498

499
500
501
502
503
504
							/* move back to cursor position*/
							for (i = t_con->line_cursor; i < t_con->line_size; i++)
							{
								telnet_write(connection, "\b", 1);
							}
						}
505

506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
						t_con->state = TELNET_STATE_DATA;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else if (t_con->last_escape == '\x00')
				{
					if (*buf_p == '[')
					{
						t_con->last_escape = *buf_p;
					}
					else
					{
						t_con->state = TELNET_STATE_DATA;
					}
				}
				else
				{
526
					LOG_ERROR("BUG: unexpected value in t_con->last_escape");
527
528
					t_con->state = TELNET_STATE_DATA;
				}
529

530
531
				break;
			default:
532
				LOG_ERROR("unknown telnet state");
533
534
535
536
537
538
				exit(-1);
		}

		bytes_read--;
		buf_p++;
	}
539

540
541
542
543
544
545
546
	return ERROR_OK;
}

int telnet_connection_closed(connection_t *connection)
{
	telnet_connection_t *t_con = connection->priv;
	int i;
547

548
	log_remove_callback(telnet_log_callback, connection);
549

550
551
552
553
554
	if (t_con->prompt)
	{
		free(t_con->prompt);
		t_con->prompt = NULL;
	}
555

556
557
558
559
560
561
562
563
	for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
	{
		if (t_con->history[i])
		{
			free(t_con->history[i]);
			t_con->history[i] = NULL;
		}
	}
564

565
566
	/* if this connection registered a debug-message receiver delete it */
	delete_debug_msg_receiver(connection->cmd_ctx, NULL);
567

568
569
570
571
572
573
574
	if (connection->priv)
	{
		free(connection->priv);
		connection->priv = NULL;
	}
	else
	{
575
		LOG_ERROR("BUG: connection->priv == NULL");
576
	}
577

578
579
580
581
582
583
584
	return ERROR_OK;
}

int telnet_set_prompt(connection_t *connection, char *prompt)
{
	telnet_connection_t *t_con = connection->priv;

585
	if (t_con->prompt != NULL)
586
587
		free(t_con->prompt);

588
	t_con->prompt = strdup(prompt);
589

590
591
592
593
594
595
	return ERROR_OK;
}

int telnet_init(char *banner)
{
	telnet_service_t *telnet_service = malloc(sizeof(telnet_service_t));
596

597
598
	if (telnet_port == 0)
	{
zwelch's avatar
zwelch committed
599
600
		LOG_INFO("telnet port disabled");
		return ERROR_OK;
601
	}
602

603
	telnet_service->banner = banner;
604

605
	add_service("telnet", CONNECTION_TCP, telnet_port, 1, telnet_new_connection, telnet_input, telnet_connection_closed, telnet_service);
606

607
608
609
610
611
612
613
	return ERROR_OK;
}

int telnet_register_commands(command_context_t *command_context)
{
	register_command(command_context, NULL, "exit", handle_exit_command,
					 COMMAND_EXEC, "exit telnet session");
614

615
	register_command(command_context, NULL, "telnet_port", handle_telnet_port_command,
oharboe's avatar
oharboe committed
616
					 COMMAND_ANY, "port on which to listen for incoming telnet connections");
617

618
619
620
621
622
623
624
	return ERROR_OK;
}

/* daemon configuration command telnet_port */
int handle_telnet_port_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
	if (argc == 0)
oharboe's avatar
oharboe committed
625
626
	{
		command_print(cmd_ctx, "%d", telnet_port);
627
		return ERROR_OK;
oharboe's avatar
oharboe committed
628
	}
629

630
	telnet_port = strtoul(args[0], NULL, 0);
631
632
633
634
635
636
637
638

	return ERROR_OK;
}

int handle_exit_command(struct command_context_s *cmd_ctx, char *cmd, char **args, int argc)
{
	return ERROR_COMMAND_CLOSE_CONNECTION;
}