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   1 /***************************************************************************
   2  *   Copyright (C) 2005 by Dominic Rath                                    *
   3  *   Dominic.Rath@gmx.de                                                   *
   4  *                                                                         *
   5  *   Copyright (C) 2007,2008 Øyvind Harboe                                 *
   6  *   oyvind.harboe@zylin.com                                               *
   7  *                                                                         *
   8  *   Copyright (C) 2008 by Spencer Oliver                                  *
   9  *   spen@spen-soft.co.uk                                                  *
  10  *                                                                         *
  11  *   This program is free software; you can redistribute it and/or modify  *
  12  *   it under the terms of the GNU General Public License as published by  *
  13  *   the Free Software Foundation; either version 2 of the License, or     *
  14  *   (at your option) any later version.                                   *
  15  *                                                                         *
  16  *   This program is distributed in the hope that it will be useful,       *
  17  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  18  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  19  *   GNU General Public License for more details.                          *
  20  *                                                                         *
  21  *   You should have received a copy of the GNU General Public License     *
  22  *   along with this program; if not, write to the                         *
  23  *   Free Software Foundation, Inc.,                                       *
  24  *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
  25  ***************************************************************************/
  26 #ifdef HAVE_CONFIG_H
  27 #include "config.h"
  28 #endif
  29
  30 #include "telnet_server.h"
  31 #include "target_request.h"
  32
  33 static unsigned short telnet_port = 4444;
  34
  35 static char *negotiate =
  36                 "\xFF\xFB\x03"          /* IAC WILL Suppress Go Ahead */
  37                 "\xFF\xFB\x01"          /* IAC WILL Echo */
  38                 "\xFF\xFD\x03"          /* IAC DO Suppress Go Ahead */
  39                 "\xFF\xFE\x01";         /* IAC DON'T Echo */
  40
  41 #define CTRL(c) (c - '@')
  42
  43 /* The only way we can detect that the socket is closed is the first time
  44  * we write to it, we will fail. Subsequent write operations will
  45  * succeed. Shudder!
  46  */
  47 int telnet_write(connection_t *connection, const void *data, int len)
  48 {
  49         telnet_connection_t *t_con = connection->priv;
  50         if (t_con->closed)
  51                 return ERROR_SERVER_REMOTE_CLOSED;
  52
  53         if (write_socket(connection->fd, data, len) == len)
  54         {
  55                 return ERROR_OK;
  56         }
  57         t_con->closed = 1;
  58         return ERROR_SERVER_REMOTE_CLOSED;
  59 }
  60
  61 int telnet_prompt(connection_t *connection)
  62 {
  63         telnet_connection_t *t_con = connection->priv;
  64
  65         telnet_write(connection, "\r", 1); /* the prompt is always placed at the line beginning */
  66         return telnet_write(connection, t_con->prompt, strlen(t_con->prompt));
  67 }
  68
  69 int telnet_outputline(connection_t *connection, const char *line)
  70 {
  71         int len;
  72
  73         /* process lines in buffer */
  74         while (*line) {
  75                 char *line_end = strchr(line, '\n');
  76
  77                 if (line_end)
  78                         len = line_end-line;
  79                 else
  80                         len = strlen(line);
  81
  82                 telnet_write(connection, line, len);
  83                 if (line_end)
  84                 {
  85                         telnet_write(connection, "\r\n", 2);
  86                         line += len + 1;
  87                 }
  88                 else
  89                 {
  90                         line += len;
  91                 }
  92         }
  93
  94         return ERROR_OK;
  95 }
  96
  97 int telnet_output(struct command_context_s *cmd_ctx, const char* line)
  98 {
  99         connection_t *connection = cmd_ctx->output_handler_priv;
 100
 101         return telnet_outputline(connection, line);
 102 }
 103
 104 void telnet_log_callback(void *priv, const char *file, int line,
 105                 const char *function, const char *string)
 106 {
 107         connection_t *connection = priv;
 108         telnet_connection_t *t_con = connection->priv;
 109         int i;
 110
 111         /* if there is no prompt, simply output the message */
 112         if (t_con->line_cursor < 0)
 113         {
 114                 telnet_outputline(connection, string);
 115                 return;
 116         }
 117
 118         /* clear the command line */
 119         telnet_write(connection, "\r", 1);
 120         for (i = strlen(t_con->prompt) + t_con->line_size; i > 0; i -= 16)
 121                 telnet_write(connection, "                ", i > 16 ? 16 : i);
 122         telnet_write(connection, "\r", 1);
 123
 124         /* output the message */
 125         telnet_outputline(connection, string);
 126
 127         /* put the command line to its previous state */
 128         telnet_prompt(connection);
 129         telnet_write(connection, t_con->line, t_con->line_size);
 130         for (i = t_con->line_size; i > t_con->line_cursor; i--)
 131                 telnet_write(connection, "\b", 1);
 132 }
 133
 134 int telnet_new_connection(connection_t *connection)
 135 {
 136         telnet_connection_t *telnet_connection = malloc(sizeof(telnet_connection_t));
 137         telnet_service_t *telnet_service = connection->service->priv;
 138         int i;
 139
 140         connection->priv = telnet_connection;
 141
 142         /* initialize telnet connection information */
 143         telnet_connection->closed = 0;
 144         telnet_connection->line_size = 0;
 145         telnet_connection->line_cursor = 0;
 146         telnet_connection->option_size = 0;
 147         telnet_connection->prompt = strdup("> ");
 148         telnet_connection->state = TELNET_STATE_DATA;
 149
 150         /* output goes through telnet connection */
 151         command_set_output_handler(connection->cmd_ctx, telnet_output, connection);
 152
 153         /* negotiate telnet options */
 154         telnet_write(connection, negotiate, strlen(negotiate));
 155
 156         /* print connection banner */
 157         if (telnet_service->banner)
 158         {
 159                 telnet_write(connection, telnet_service->banner, strlen(telnet_service->banner));
 160                 telnet_write(connection, "\r\n", 2);
 161         }
 162
 163         telnet_prompt(connection);
 164
 165         /* initialize history */
 166         for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
 167         {
 168                 telnet_connection->history[i] = NULL;
 169         }
 170         telnet_connection->next_history = 0;
 171         telnet_connection->current_history = 0;
 172
 173         log_add_callback(telnet_log_callback, connection);
 174
 175         return ERROR_OK;
 176 }
 177
 178 void telnet_clear_line(connection_t *connection, telnet_connection_t *t_con)
 179 {
 180         /* move to end of line */
 181         if (t_con->line_cursor < t_con->line_size)
 182         {
 183                 telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
 184         }
 185
 186         /* backspace, overwrite with space, backspace */
 187         while (t_con->line_size > 0)
 188         {
 189                 telnet_write(connection, "\b \b", 3);
 190                 t_con->line_size--;
 191         }
 192         t_con->line_cursor = 0;
 193 }
 194
 195 int telnet_input(connection_t *connection)
 196 {
 197         int bytes_read;
 198         char buffer[TELNET_BUFFER_SIZE];
 199         char *buf_p;
 200         telnet_connection_t *t_con = connection->priv;
 201         command_context_t *command_context = connection->cmd_ctx;
 202
 203         bytes_read = read_socket(connection->fd, buffer, TELNET_BUFFER_SIZE);
 204
 205         if (bytes_read == 0)
 206                 return ERROR_SERVER_REMOTE_CLOSED;
 207         else if (bytes_read == -1)
 208         {
 209                 LOG_ERROR("error during read: %s", strerror(errno));
 210                 return ERROR_SERVER_REMOTE_CLOSED;
 211         }
 212
 213         buf_p = buffer;
 214         while (bytes_read)
 215         {
 216                 switch (t_con->state)
 217                 {
 218                         case TELNET_STATE_DATA:
 219                                 if (*buf_p == '\xff')
 220                                 {
 221                                         t_con->state = TELNET_STATE_IAC;
 222                                 }
 223                                 else
 224                                 {
 225                                         if (isprint(*buf_p)) /* printable character */
 226                                         {
 227                                                 /* watch buffer size leaving one spare character for string null termination */
 228                                                 if (t_con->line_size == TELNET_LINE_MAX_SIZE-1)
 229                                                 {
 230                                                         /* output audible bell if buffer is full */
 231                                                         telnet_write(connection, "\x07", 1); /* "\a" does not work, at least on windows */
 232                                                 }
 233                                                 else if (t_con->line_cursor == t_con->line_size)
 234                                                 {
 235                                                         telnet_write(connection, buf_p, 1);
 236                                                         t_con->line[t_con->line_size++] = *buf_p;
 237                                                         t_con->line_cursor++;
 238                                                 }
 239                                                 else
 240                                                 {
 241                                                         int i;
 242                                                         memmove(t_con->line + t_con->line_cursor + 1, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
 243                                                         t_con->line[t_con->line_cursor] = *buf_p;
 244                                                         t_con->line_size++;
 245                                                         telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
 246                                                         t_con->line_cursor++;
 247                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 248                                                         {
 249                                                                 telnet_write(connection, "\b", 1);
 250                                                         }
 251                                                 }
 252                                         }
 253                                         else /* non-printable */
 254                                         {
 255                                                 if (*buf_p == 0x1b) /* escape */
 256                                                 {
 257                                                         t_con->state = TELNET_STATE_ESCAPE;
 258                                                         t_con->last_escape = '\x00';
 259                                                 }
 260                                                 else if ((*buf_p == 0xd) || (*buf_p == 0xa)) /* CR/LF */
 261                                                 {
 262                                                         int retval;
 263
 264                                                         /* skip over combinations with CR/LF and NUL characters */
 265                                                         if ((bytes_read > 1) && ((*(buf_p + 1) == 0xa) || (*(buf_p + 1) == 0xd)))
 266                                                         {
 267                                                                 buf_p++;
 268                                                                 bytes_read--;
 269                                                         }
 270                                                         if ((bytes_read > 1) && (*(buf_p + 1) == 0))
 271                                                         {
 272                                                                 buf_p++;
 273                                                                 bytes_read--;
 274                                                         }
 275                                                         t_con->line[t_con->line_size] = 0;
 276
 277                                                         telnet_write(connection, "\r\n\x00", 3);
 278
 279                                                         if (strcmp(t_con->line, "history") == 0)
 280                                                         {
 281                                                                 int i;
 282                                                                 for (i = 1; i < TELNET_LINE_HISTORY_SIZE; i++)
 283                                                                 {
 284                                                                         /* the t_con->next_history line contains empty string (unless NULL), thus it is not printed */
 285                                                                         char *history_line = t_con->history[(t_con->next_history + i) % TELNET_LINE_HISTORY_SIZE];
 286                                                                         if (history_line)
 287                                                                         {
 288                                                                                 telnet_write(connection, history_line, strlen(history_line));
 289                                                                                 telnet_write(connection, "\r\n\x00", 3);
 290                                                                         }
 291                                                                 }
 292                                                                 t_con->line_size = 0;
 293                                                                 t_con->line_cursor = 0;
 294                                                                 continue;
 295                                                         }
 296
 297                                                         /* save only non-blank not repeating lines in the history */
 298                                                         char *prev_line = t_con->history[(t_con->current_history > 0) ? t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1];
 299                                                         if (*t_con->line && (prev_line == NULL || strcmp(t_con->line, prev_line)))
 300                                                         {
 301                                                                 /* if the history slot is already taken, free it */
 302                                                                 if (t_con->history[t_con->next_history])
 303                                                                 {
 304                                                                         free(t_con->history[t_con->next_history]);
 305                                                                 }
 306
 307                                                                 /* add line to history */
 308                                                                 t_con->history[t_con->next_history] = strdup(t_con->line);
 309
 310                                                                 /* wrap history at TELNET_LINE_HISTORY_SIZE */
 311                                                                 t_con->next_history = (t_con->next_history + 1) % TELNET_LINE_HISTORY_SIZE;
 312
 313                                                                 /* current history line starts at the new entry */
 314                                                                 t_con->current_history = t_con->next_history;
 315
 316                                                                 if (t_con->history[t_con->current_history])
 317                                                                 {
 318                                                                         free(t_con->history[t_con->current_history]);
 319                                                                 }
 320                                                                 t_con->history[t_con->current_history] = strdup("");
 321                                                         }
 322
 323                                                         t_con->line_size = 0;
 324
 325                                                         t_con->line_cursor = -1; /* to supress prompt in log callback during command execution */
 326
 327                                                         retval = command_run_line(command_context, t_con->line);
 328
 329                                                         t_con->line_cursor = 0;
 330
 331                                                         if (retval == ERROR_COMMAND_CLOSE_CONNECTION)
 332                                                                 return ERROR_SERVER_REMOTE_CLOSED;
 333
 334                                                         retval = telnet_prompt(connection);
 335                                                         if (retval == ERROR_SERVER_REMOTE_CLOSED)
 336                                                                 return ERROR_SERVER_REMOTE_CLOSED;
 337
 338                                                 }
 339                                                 else if ((*buf_p == 0x7f) || (*buf_p == 0x8)) /* delete character */
 340                                                 {
 341                                                         if (t_con->line_cursor > 0)
 342                                                         {
 343                                                                 if (t_con->line_cursor != t_con->line_size)
 344                                                                 {
 345                                                                         int i;
 346                                                                         telnet_write(connection, "\b", 1);
 347                                                                         t_con->line_cursor--;
 348                                                                         t_con->line_size--;
 349                                                                         memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
 350
 351                                                                         telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
 352                                                                         telnet_write(connection, " \b", 2);
 353                                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 354                                                                         {
 355                                                                                 telnet_write(connection, "\b", 1);
 356                                                                         }
 357                                                                 }
 358                                                                 else
 359                                                                 {
 360                                                                         t_con->line_size--;
 361                                                                         t_con->line_cursor--;
 362                                                                         /* back space: move the 'printer' head one char back, overwrite with space, move back again */
 363                                                                         telnet_write(connection, "\b \b", 3);
 364                                                                 }
 365                                                         }
 366                                                 }
 367                                                 else if (*buf_p == 0x15) /* clear line */
 368                                                 {
 369                                                         telnet_clear_line(connection, t_con);
 370                                                 }
 371                                                 else if (*buf_p == CTRL('B')) /* cursor left */
 372                                                 {
 373                                                         if (t_con->line_cursor > 0)
 374                                                         {
 375                                                                 telnet_write(connection, "\b", 1);
 376                                                                 t_con->line_cursor--;
 377                                                         }
 378                                                         t_con->state = TELNET_STATE_DATA;
 379                                                 }
 380                                                 else if (*buf_p == CTRL('F')) /* cursor right */
 381                                                 {
 382                                                         if (t_con->line_cursor < t_con->line_size)
 383                                                         {
 384                                                                 telnet_write(connection, t_con->line + t_con->line_cursor++, 1);
 385                                                         }
 386                                                         t_con->state = TELNET_STATE_DATA;
 387                                                 }
 388                                                 else
 389                                                 {
 390                                                         LOG_DEBUG("unhandled nonprintable: %2.2x", *buf_p);
 391                                                 }
 392                                         }
 393                                 }
 394                                 break;
 395                         case TELNET_STATE_IAC:
 396                                 switch (*buf_p)
 397                                 {
 398                                         case '\xfe':
 399                                                 t_con->state = TELNET_STATE_DONT;
 400                                                 break;
 401                                         case '\xfd':
 402                                                 t_con->state = TELNET_STATE_DO;
 403                                                 break;
 404                                         case '\xfc':
 405                                                 t_con->state = TELNET_STATE_WONT;
 406                                                 break;
 407                                         case '\xfb':
 408                                                 t_con->state = TELNET_STATE_WILL;
 409                                                 break;
 410                                 }
 411                                 break;
 412                         case TELNET_STATE_SB:
 413                                 break;
 414                         case TELNET_STATE_SE:
 415                                 break;
 416                         case TELNET_STATE_WILL:
 417                         case TELNET_STATE_WONT:
 418                         case TELNET_STATE_DO:
 419                         case TELNET_STATE_DONT:
 420                                 t_con->state = TELNET_STATE_DATA;
 421                                 break;
 422                         case TELNET_STATE_ESCAPE:
 423                                 if (t_con->last_escape == '[')
 424                                 {
 425                                         if (*buf_p == 'D') /* cursor left */
 426                                         {
 427                                                 if (t_con->line_cursor > 0)
 428                                                 {
 429                                                         telnet_write(connection, "\b", 1);
 430                                                         t_con->line_cursor--;
 431                                                 }
 432                                                 t_con->state = TELNET_STATE_DATA;
 433                                         }
 434                                         else if (*buf_p == 'C') /* cursor right */
 435                                         {
 436                                                 if (t_con->line_cursor < t_con->line_size)
 437                                                 {
 438                                                         telnet_write(connection, t_con->line + t_con->line_cursor++, 1);
 439                                                 }
 440                                                 t_con->state = TELNET_STATE_DATA;
 441                                         }
 442                                         else if (*buf_p == 'A') /* cursor up */
 443                                         {
 444                                                 int last_history = (t_con->current_history > 0) ? t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1;
 445                                                 if (t_con->history[last_history])
 446                                                 {
 447                                                         telnet_clear_line(connection, t_con);
 448                                                         t_con->line_size = strlen(t_con->history[last_history]);
 449                                                         t_con->line_cursor = t_con->line_size;
 450                                                         memcpy(t_con->line, t_con->history[last_history], t_con->line_size);
 451                                                         telnet_write(connection, t_con->line, t_con->line_size);
 452                                                         t_con->current_history = last_history;
 453                                                 }
 454                                                 t_con->state = TELNET_STATE_DATA;
 455                                         }
 456                                         else if (*buf_p == 'B') /* cursor down */
 457                                         {
 458                                                 int next_history = (t_con->current_history + 1) % TELNET_LINE_HISTORY_SIZE;
 459                                                 if (t_con->history[next_history])
 460                                                 {
 461                                                         telnet_clear_line(connection, t_con);
 462                                                         t_con->line_size = strlen(t_con->history[next_history]);
 463                                                         t_con->line_cursor = t_con->line_size;
 464                                                         memcpy(t_con->line, t_con->history[next_history], t_con->line_size);
 465                                                         telnet_write(connection, t_con->line, t_con->line_size);
 466                                                         t_con->current_history = next_history;
 467                                                 }
 468                                                 t_con->state = TELNET_STATE_DATA;
 469                                         }
 470                                         else if (*buf_p == '3')
 471                                         {
 472                                                 t_con->last_escape = *buf_p;
 473                                         }
 474                                         else
 475                                         {
 476                                                 t_con->state = TELNET_STATE_DATA;
 477                                         }
 478                                 }
 479                                 else if (t_con->last_escape == '3')
 480                                 {
 481                                         /* Remove character */
 482                                         if (*buf_p == '~')
 483                                         {
 484                                                 if (t_con->line_cursor < t_con->line_size)
 485                                                 {
 486                                                         int i;
 487                                                         t_con->line_size--;
 488                                                         /* remove char from line buffer */
 489                                                         memmove(t_con->line + t_con->line_cursor, t_con->line + t_con->line_cursor + 1, t_con->line_size - t_con->line_cursor);
 490
 491                                                         /* print remainder of buffer */
 492                                                         telnet_write(connection, t_con->line + t_con->line_cursor, t_con->line_size - t_con->line_cursor);
 493                                                         /* overwrite last char with whitespace */
 494                                                         telnet_write(connection, " \b", 2);
 495
 496                                                         /* move back to cursor position*/
 497                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 498                                                         {
 499                                                                 telnet_write(connection, "\b", 1);
 500                                                         }
 501                                                 }
 502
 503                                                 t_con->state = TELNET_STATE_DATA;
 504                                         }
 505                                         else
 506                                         {
 507                                                 t_con->state = TELNET_STATE_DATA;
 508                                         }
 509                                 }
 510                                 else if (t_con->last_escape == '\x00')
 511                                 {
 512                                         if (*buf_p == '[')
 513                                         {
 514                                                 t_con->last_escape = *buf_p;
 515                                         }
 516                                         else
 517                                         {
 518                                                 t_con->state = TELNET_STATE_DATA;
 519                                         }
 520                                 }
 521                                 else
 522                                 {
 523                                         LOG_ERROR("BUG: unexpected value in t_con->last_escape");
 524                                         t_con->state = TELNET_STATE_DATA;
 525                                 }
 526
 527                                 break;
 528                         default:
 529                                 LOG_ERROR("unknown telnet state");
 530                                 exit(-1);
 531                 }
 532
 533                 bytes_read--;
 534                 buf_p++;
 535         }
 536
 537         return ERROR_OK;
 538 }
 539
 540 int telnet_connection_closed(connection_t *connection)
 541 {
 542         telnet_connection_t *t_con = connection->priv;
 543         int i;
 544
 545         log_remove_callback(telnet_log_callback, connection);
 546
 547         if (t_con->prompt)
 548         {
 549                 free(t_con->prompt);
 550                 t_con->prompt = NULL;
 551         }
 552
 553         for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
 554         {
 555                 if (t_con->history[i])
 556                 {
 557                         free(t_con->history[i]);
 558                         t_con->history[i] = NULL;
 559                 }
 560         }
 561
 562         /* if this connection registered a debug-message receiver delete it */
 563         delete_debug_msg_receiver(connection->cmd_ctx, NULL);
 564
 565         if (connection->priv)
 566         {
 567                 free(connection->priv);
 568                 connection->priv = NULL;
 569         }
 570         else
 571         {
 572                 LOG_ERROR("BUG: connection->priv == NULL");
 573         }
 574
 575         return ERROR_OK;
 576 }
 577
 578 int telnet_set_prompt(connection_t *connection, char *prompt)
 579 {
 580         telnet_connection_t *t_con = connection->priv;
 581
 582         if (t_con->prompt != NULL)
 583                 free(t_con->prompt);
 584
 585         t_con->prompt = strdup(prompt);
 586
 587         return ERROR_OK;
 588 }
 589
 590 int telnet_init(char *banner)
 591 {
 592         telnet_service_t *telnet_service = malloc(sizeof(telnet_service_t));
 593
 594         if (telnet_port == 0)
 595         {
 596                 LOG_INFO("telnet port disabled");
 597                 free(telnet_service);
 598                 return ERROR_OK;
 599         }
 600
 601         telnet_service->banner = banner;
 602
 603         add_service("telnet", CONNECTION_TCP, telnet_port, 1, telnet_new_connection, telnet_input, telnet_connection_closed, telnet_service);
 604
 605         return ERROR_OK;
 606 }
 607
 608 /* daemon configuration command telnet_port */
 609 static int handle_telnet_port_command(struct command_context_s *cmd_ctx,
 610                 char *cmd, char **args, int argc)
 611 {
 612         return server_port_command(cmd_ctx, cmd, args, argc, &telnet_port);
 613 }
 614
 615 static int handle_exit_command(struct command_context_s *cmd_ctx,
 616                 char *cmd, char **args, int argc)
 617 {
 618         return ERROR_COMMAND_CLOSE_CONNECTION;
 619 }
 620
 621 int telnet_register_commands(command_context_t *command_context)
 622 {
 623         register_command(command_context, NULL, "exit",
 624                         &handle_exit_command, COMMAND_EXEC,
 625                         "exit telnet session");
 626
 627         register_command(command_context, NULL, "telnet_port",
 628                         &handle_telnet_port_command, COMMAND_ANY,
 629                         "port on which to listen for incoming telnet connections");
 630
 631         return ERROR_OK;
 632 }
 633
 634