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   1 /***************************************************************************
   2  *   Copyright (C) 2005 by Dominic Rath                                    *
   3  *   Dominic.Rath@gmx.de                                                   *
   4  *                                                                         *
   5  *   Copyright (C) 2007-2010 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
  27 #ifdef HAVE_CONFIG_H
  28 #include "config.h"
  29 #endif
  30
  31 #include "telnet_server.h"
  32 #include <target/target_request.h>
  33
  34 static const char *telnet_port;
  35
  36 static char *negotiate =
  37         "\xFF\xFB\x03"                  /* IAC WILL Suppress Go Ahead */
  38         "\xFF\xFB\x01"                  /* IAC WILL Echo */
  39         "\xFF\xFD\x03"                  /* IAC DO Suppress Go Ahead */
  40         "\xFF\xFE\x01";                 /* IAC DON'T Echo */
  41
  42 #define CTRL(c) (c - '@')
  43
  44 /* The only way we can detect that the socket is closed is the first time
  45  * we write to it, we will fail. Subsequent write operations will
  46  * succeed. Shudder!
  47  */
  48 static int telnet_write(struct connection *connection, const void *data,
  49         int len)
  50 {
  51         struct telnet_connection *t_con = connection->priv;
  52         if (t_con->closed)
  53                 return ERROR_SERVER_REMOTE_CLOSED;
  54
  55         if (connection_write(connection, data, len) == len)
  56                 return ERROR_OK;
  57         t_con->closed = 1;
  58         return ERROR_SERVER_REMOTE_CLOSED;
  59 }
  60
  61 static int telnet_prompt(struct connection *connection)
  62 {
  63         struct telnet_connection *t_con = connection->priv;
  64
  65         return telnet_write(connection, t_con->prompt, strlen(t_con->prompt));
  66 }
  67
  68 static int telnet_outputline(struct connection *connection, const char *line)
  69 {
  70         int len;
  71
  72         /* process lines in buffer */
  73         while (*line) {
  74                 char *line_end = strchr(line, '\n');
  75
  76                 if (line_end)
  77                         len = line_end-line;
  78                 else
  79                         len = strlen(line);
  80
  81                 telnet_write(connection, line, len);
  82                 if (line_end) {
  83                         telnet_write(connection, "\r\n", 2);
  84                         line += len + 1;
  85                 } else
  86                         line += len;
  87         }
  88
  89         return ERROR_OK;
  90 }
  91
  92 static int telnet_output(struct command_context *cmd_ctx, const char *line)
  93 {
  94         struct connection *connection = cmd_ctx->output_handler_priv;
  95
  96         return telnet_outputline(connection, line);
  97 }
  98
  99 static void telnet_log_callback(void *priv, const char *file, unsigned line,
 100         const char *function, const char *string)
 101 {
 102         struct connection *connection = priv;
 103         struct telnet_connection *t_con = connection->priv;
 104         int i;
 105
 106         /* if there is no prompt, simply output the message */
 107         if (t_con->line_cursor < 0) {
 108                 telnet_outputline(connection, string);
 109                 return;
 110         }
 111
 112         /* clear the command line */
 113         for (i = strlen(t_con->prompt) + t_con->line_size; i > 0; i -= 16)
 114                 telnet_write(connection, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b", i > 16 ? 16 : i);
 115         for (i = strlen(t_con->prompt) + t_con->line_size; i > 0; i -= 16)
 116                 telnet_write(connection, "                ", i > 16 ? 16 : i);
 117         for (i = strlen(t_con->prompt) + t_con->line_size; i > 0; i -= 16)
 118                 telnet_write(connection, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b", i > 16 ? 16 : i);
 119
 120         /* output the message */
 121         telnet_outputline(connection, string);
 122
 123         /* put the command line to its previous state */
 124         telnet_prompt(connection);
 125         telnet_write(connection, t_con->line, t_con->line_size);
 126         for (i = t_con->line_size; i > t_con->line_cursor; i--)
 127                 telnet_write(connection, "\b", 1);
 128 }
 129
 130 static int telnet_new_connection(struct connection *connection)
 131 {
 132         struct telnet_connection *telnet_connection = malloc(sizeof(struct telnet_connection));
 133         struct telnet_service *telnet_service = connection->service->priv;
 134         int i;
 135
 136         connection->priv = telnet_connection;
 137
 138         /* initialize telnet connection information */
 139         telnet_connection->closed = 0;
 140         telnet_connection->line_size = 0;
 141         telnet_connection->line_cursor = 0;
 142         telnet_connection->option_size = 0;
 143         telnet_connection->prompt = strdup("> ");
 144         telnet_connection->state = TELNET_STATE_DATA;
 145
 146         /* output goes through telnet connection */
 147         command_set_output_handler(connection->cmd_ctx, telnet_output, connection);
 148
 149         /* negotiate telnet options */
 150         telnet_write(connection, negotiate, strlen(negotiate));
 151
 152         /* print connection banner */
 153         if (telnet_service->banner) {
 154                 telnet_write(connection, telnet_service->banner, strlen(telnet_service->banner));
 155                 telnet_write(connection, "\r\n", 2);
 156         }
 157
 158         /* the prompt is always placed at the line beginning */
 159         telnet_write(connection, "\r", 1);
 160         telnet_prompt(connection);
 161
 162         /* initialize history */
 163         for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++)
 164                 telnet_connection->history[i] = NULL;
 165         telnet_connection->next_history = 0;
 166         telnet_connection->current_history = 0;
 167
 168         log_add_callback(telnet_log_callback, connection);
 169
 170         return ERROR_OK;
 171 }
 172
 173 static void telnet_clear_line(struct connection *connection,
 174         struct telnet_connection *t_con)
 175 {
 176         /* move to end of line */
 177         if (t_con->line_cursor < t_con->line_size)
 178                 telnet_write(connection,
 179                         t_con->line + t_con->line_cursor,
 180                         t_con->line_size - t_con->line_cursor);
 181
 182         /* backspace, overwrite with space, backspace */
 183         while (t_con->line_size > 0) {
 184                 telnet_write(connection, "\b \b", 3);
 185                 t_con->line_size--;
 186         }
 187         t_con->line_cursor = 0;
 188 }
 189
 190 static int telnet_input(struct connection *connection)
 191 {
 192         int bytes_read;
 193         unsigned char buffer[TELNET_BUFFER_SIZE];
 194         unsigned char *buf_p;
 195         struct telnet_connection *t_con = connection->priv;
 196         struct command_context *command_context = connection->cmd_ctx;
 197
 198         bytes_read = connection_read(connection, buffer, TELNET_BUFFER_SIZE);
 199
 200         if (bytes_read == 0)
 201                 return ERROR_SERVER_REMOTE_CLOSED;
 202         else if (bytes_read == -1) {
 203                 LOG_ERROR("error during read: %s", strerror(errno));
 204                 return ERROR_SERVER_REMOTE_CLOSED;
 205         }
 206
 207         buf_p = buffer;
 208         while (bytes_read) {
 209                 switch (t_con->state) {
 210                         case TELNET_STATE_DATA:
 211                                 if (*buf_p == 0xff)
 212                                         t_con->state = TELNET_STATE_IAC;
 213                                 else {
 214                                         if (isprint(*buf_p)) {  /* printable character */
 215                                                 /* watch buffer size leaving one spare character for
 216                                                  * string null termination */
 217                                                 if (t_con->line_size == TELNET_LINE_MAX_SIZE-1) {
 218                                                         /* output audible bell if buffer is full
 219                                                          * "\a" does not work, at least on windows */
 220                                                         telnet_write(connection, "\x07", 1);
 221                                                 } else if (t_con->line_cursor == t_con->line_size) {
 222                                                         telnet_write(connection, buf_p, 1);
 223                                                         t_con->line[t_con->line_size++] = *buf_p;
 224                                                         t_con->line_cursor++;
 225                                                 } else {
 226                                                         int i;
 227                                                         memmove(t_con->line + t_con->line_cursor + 1,
 228                                                                         t_con->line + t_con->line_cursor,
 229                                                                         t_con->line_size - t_con->line_cursor);
 230                                                         t_con->line[t_con->line_cursor] = *buf_p;
 231                                                         t_con->line_size++;
 232                                                         telnet_write(connection,
 233                                                                         t_con->line + t_con->line_cursor,
 234                                                                         t_con->line_size - t_con->line_cursor);
 235                                                         t_con->line_cursor++;
 236                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 237                                                                 telnet_write(connection, "\b", 1);
 238                                                 }
 239                                         } else {        /* non-printable */
 240                                                 if (*buf_p == 0x1b) {   /* escape */
 241                                                         t_con->state = TELNET_STATE_ESCAPE;
 242                                                         t_con->last_escape = '\x00';
 243                                                 } else if ((*buf_p == 0xd) || (*buf_p == 0xa)) {        /* CR/LF */
 244                                                         int retval;
 245
 246                                                         /* skip over combinations with CR/LF and NUL characters */
 247                                                         if ((bytes_read > 1) && ((*(buf_p + 1) == 0xa) ||
 248                                                                         (*(buf_p + 1) == 0xd))) {
 249                                                                 buf_p++;
 250                                                                 bytes_read--;
 251                                                         }
 252                                                         if ((bytes_read > 1) && (*(buf_p + 1) == 0)) {
 253                                                                 buf_p++;
 254                                                                 bytes_read--;
 255                                                         }
 256                                                         t_con->line[t_con->line_size] = 0;
 257
 258                                                         telnet_write(connection, "\r\n\x00", 3);
 259
 260                                                         if (strcmp(t_con->line, "history") == 0) {
 261                                                                 int i;
 262                                                                 for (i = 1; i < TELNET_LINE_HISTORY_SIZE; i++) {
 263                                                                         /* the t_con->next_history line contains empty string
 264                                                                          * (unless NULL), thus it is not printed */
 265                                                                         char *history_line = t_con->history[(t_con->
 266                                                                                         next_history + i) %
 267                                                                                         TELNET_LINE_HISTORY_SIZE];
 268                                                                         if (history_line) {
 269                                                                                 telnet_write(connection, history_line,
 270                                                                                                 strlen(history_line));
 271                                                                                 telnet_write(connection, "\r\n\x00", 3);
 272                                                                         }
 273                                                                 }
 274                                                                 t_con->line_size = 0;
 275                                                                 t_con->line_cursor = 0;
 276                                                                 continue;
 277                                                         }
 278
 279                                                         /* save only non-blank not repeating lines in the history */
 280                                                         char *prev_line = t_con->history[(t_con->current_history > 0) ?
 281                                                                         t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1];
 282                                                         if (*t_con->line && (prev_line == NULL ||
 283                                                                         strcmp(t_con->line, prev_line))) {
 284                                                                 /* if the history slot is already taken, free it */
 285                                                                 if (t_con->history[t_con->next_history])
 286                                                                         free(t_con->history[t_con->next_history]);
 287
 288                                                                 /* add line to history */
 289                                                                 t_con->history[t_con->next_history] = strdup(t_con->line);
 290
 291                                                                 /* wrap history at TELNET_LINE_HISTORY_SIZE */
 292                                                                 t_con->next_history = (t_con->next_history + 1) %
 293                                                                                 TELNET_LINE_HISTORY_SIZE;
 294
 295                                                                 /* current history line starts at the new entry */
 296                                                                 t_con->current_history =
 297                                                                                 t_con->next_history;
 298
 299                                                                 if (t_con->history[t_con->current_history])
 300                                                                         free(t_con->history[t_con->current_history]);
 301                                                                 t_con->history[t_con->current_history] = strdup("");
 302                                                         }
 303
 304                                                         t_con->line_size = 0;
 305
 306                                                         /* to suppress prompt in log callback during command execution */
 307                                                         t_con->line_cursor = -1;
 308
 309                                                         retval = command_run_line(command_context, t_con->line);
 310
 311                                                         t_con->line_cursor = 0;
 312
 313                                                         if (retval == ERROR_COMMAND_CLOSE_CONNECTION)
 314                                                                 return ERROR_SERVER_REMOTE_CLOSED;
 315
 316                                                         /* the prompt is always * placed at the line beginning */
 317                                                         telnet_write(connection, "\r", 1);
 318
 319                                                         retval = telnet_prompt(connection);
 320                                                         if (retval == ERROR_SERVER_REMOTE_CLOSED)
 321                                                                 return ERROR_SERVER_REMOTE_CLOSED;
 322
 323                                                 } else if ((*buf_p == 0x7f) || (*buf_p == 0x8)) {       /* delete character */
 324                                                         if (t_con->line_cursor > 0) {
 325                                                                 if (t_con->line_cursor != t_con->line_size) {
 326                                                                         int i;
 327                                                                         telnet_write(connection, "\b", 1);
 328                                                                         t_con->line_cursor--;
 329                                                                         t_con->line_size--;
 330                                                                         memmove(t_con->line + t_con->line_cursor,
 331                                                                                         t_con->line + t_con->line_cursor + 1,
 332                                                                                         t_con->line_size -
 333                                                                                         t_con->line_cursor);
 334
 335                                                                         telnet_write(connection,
 336                                                                                         t_con->line + t_con->line_cursor,
 337                                                                                         t_con->line_size -
 338                                                                                         t_con->line_cursor);
 339                                                                         telnet_write(connection, " \b", 2);
 340                                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 341                                                                                 telnet_write(connection, "\b", 1);
 342                                                                 } else {
 343                                                                         t_con->line_size--;
 344                                                                         t_con->line_cursor--;
 345                                                                         /* back space: move the 'printer' head one char
 346                                                                          * back, overwrite with space, move back again */
 347                                                                         telnet_write(connection, "\b \b", 3);
 348                                                                 }
 349                                                         }
 350                                                 } else if (*buf_p == 0x15) /* clear line */
 351                                                         telnet_clear_line(connection, t_con);
 352                                                 else if (*buf_p == CTRL('B')) { /* cursor left */
 353                                                         if (t_con->line_cursor > 0) {
 354                                                                 telnet_write(connection, "\b", 1);
 355                                                                 t_con->line_cursor--;
 356                                                         }
 357                                                         t_con->state = TELNET_STATE_DATA;
 358                                                 } else if (*buf_p == CTRL('F')) {       /* cursor right */
 359                                                         if (t_con->line_cursor < t_con->line_size)
 360                                                                 telnet_write(connection, t_con->line + t_con->line_cursor++, 1);
 361                                                         t_con->state = TELNET_STATE_DATA;
 362                                                 } else
 363                                                         LOG_DEBUG("unhandled nonprintable: %2.2x", *buf_p);
 364                                         }
 365                                 }
 366                                 break;
 367                         case TELNET_STATE_IAC:
 368                                 switch (*buf_p) {
 369                                 case 0xfe:
 370                                         t_con->state = TELNET_STATE_DONT;
 371                                         break;
 372                                 case 0xfd:
 373                                         t_con->state = TELNET_STATE_DO;
 374                                         break;
 375                                 case 0xfc:
 376                                         t_con->state = TELNET_STATE_WONT;
 377                                         break;
 378                                 case 0xfb:
 379                                         t_con->state = TELNET_STATE_WILL;
 380                                         break;
 381                                 }
 382                                 break;
 383                         case TELNET_STATE_SB:
 384                                 break;
 385                         case TELNET_STATE_SE:
 386                                 break;
 387                         case TELNET_STATE_WILL:
 388                         case TELNET_STATE_WONT:
 389                         case TELNET_STATE_DO:
 390                         case TELNET_STATE_DONT:
 391                                 t_con->state = TELNET_STATE_DATA;
 392                                 break;
 393                         case TELNET_STATE_ESCAPE:
 394                                 if (t_con->last_escape == '[') {
 395                                         if (*buf_p == 'D') {    /* cursor left */
 396                                                 if (t_con->line_cursor > 0) {
 397                                                         telnet_write(connection, "\b", 1);
 398                                                         t_con->line_cursor--;
 399                                                 }
 400                                                 t_con->state = TELNET_STATE_DATA;
 401                                         } else if (*buf_p == 'C') {     /* cursor right */
 402                                                 if (t_con->line_cursor < t_con->line_size)
 403                                                         telnet_write(connection,
 404                                                                         t_con->line + t_con->line_cursor++, 1);
 405                                                 t_con->state = TELNET_STATE_DATA;
 406                                         } else if (*buf_p == 'A') {     /* cursor up */
 407                                                 int last_history = (t_con->current_history > 0) ?
 408                                                                 t_con->current_history - 1 : TELNET_LINE_HISTORY_SIZE-1;
 409                                                 if (t_con->history[last_history]) {
 410                                                         telnet_clear_line(connection, t_con);
 411                                                         t_con->line_size = strlen(t_con->history[last_history]);
 412                                                         t_con->line_cursor = t_con->line_size;
 413                                                         memcpy(t_con->line, t_con->history[last_history], t_con->line_size);
 414                                                         telnet_write(connection, t_con->line, t_con->line_size);
 415                                                         t_con->current_history = last_history;
 416                                                 }
 417                                                 t_con->state = TELNET_STATE_DATA;
 418                                         } else if (*buf_p == 'B') {     /* cursor down */
 419                                                 int next_history = (t_con->current_history + 1) % TELNET_LINE_HISTORY_SIZE;
 420                                                 if (t_con->history[next_history]) {
 421                                                         telnet_clear_line(connection, t_con);
 422                                                         t_con->line_size = strlen(t_con->history[next_history]);
 423                                                         t_con->line_cursor = t_con->line_size;
 424                                                         memcpy(t_con->line, t_con->history[next_history], t_con->line_size);
 425                                                         telnet_write(connection, t_con->line, t_con->line_size);
 426                                                         t_con->current_history = next_history;
 427                                                 }
 428                                                 t_con->state = TELNET_STATE_DATA;
 429                                         } else if (*buf_p == '3')
 430                                                 t_con->last_escape = *buf_p;
 431                                         else
 432                                                 t_con->state = TELNET_STATE_DATA;
 433                                 } else if (t_con->last_escape == '3') {
 434                                         /* Remove character */
 435                                         if (*buf_p == '~') {
 436                                                 if (t_con->line_cursor < t_con->line_size) {
 437                                                         int i;
 438                                                         t_con->line_size--;
 439                                                         /* remove char from line buffer */
 440                                                         memmove(t_con->line + t_con->line_cursor,
 441                                                                         t_con->line + t_con->line_cursor + 1,
 442                                                                         t_con->line_size - t_con->line_cursor);
 443
 444                                                         /* print remainder of buffer */
 445                                                         telnet_write(connection, t_con->line + t_con->line_cursor,
 446                                                                         t_con->line_size - t_con->line_cursor);
 447                                                         /* overwrite last char with whitespace */
 448                                                         telnet_write(connection, " \b", 2);
 449
 450                                                         /* move back to cursor position*/
 451                                                         for (i = t_con->line_cursor; i < t_con->line_size; i++)
 452                                                                 telnet_write(connection, "\b", 1);
 453                                                 }
 454
 455                                                 t_con->state = TELNET_STATE_DATA;
 456                                         } else
 457                                                 t_con->state = TELNET_STATE_DATA;
 458                                 } else if (t_con->last_escape == '\x00') {
 459                                         if (*buf_p == '[')
 460                                                 t_con->last_escape = *buf_p;
 461                                         else
 462                                                 t_con->state = TELNET_STATE_DATA;
 463                                 } else {
 464                                         LOG_ERROR("BUG: unexpected value in t_con->last_escape");
 465                                         t_con->state = TELNET_STATE_DATA;
 466                                 }
 467
 468                                 break;
 469                         default:
 470                                 LOG_ERROR("unknown telnet state");
 471                                 exit(-1);
 472                 }
 473
 474                 bytes_read--;
 475                 buf_p++;
 476         }
 477
 478         return ERROR_OK;
 479 }
 480
 481 static int telnet_connection_closed(struct connection *connection)
 482 {
 483         struct telnet_connection *t_con = connection->priv;
 484         int i;
 485
 486         log_remove_callback(telnet_log_callback, connection);
 487
 488         if (t_con->prompt) {
 489                 free(t_con->prompt);
 490                 t_con->prompt = NULL;
 491         }
 492
 493         for (i = 0; i < TELNET_LINE_HISTORY_SIZE; i++) {
 494                 if (t_con->history[i]) {
 495                         free(t_con->history[i]);
 496                         t_con->history[i] = NULL;
 497                 }
 498         }
 499
 500         /* if this connection registered a debug-message receiver delete it */
 501         delete_debug_msg_receiver(connection->cmd_ctx, NULL);
 502
 503         if (connection->priv) {
 504                 free(connection->priv);
 505                 connection->priv = NULL;
 506         } else
 507                 LOG_ERROR("BUG: connection->priv == NULL");
 508
 509         return ERROR_OK;
 510 }
 511
 512 int telnet_init(char *banner)
 513 {
 514         if (strcmp(telnet_port, "disabled") == 0) {
 515                 LOG_INFO("telnet server disabled");
 516                 return ERROR_OK;
 517         }
 518
 519         struct telnet_service *telnet_service = malloc(sizeof(struct telnet_service));
 520
 521         telnet_service->banner = banner;
 522
 523         return add_service("telnet",
 524                 telnet_port,
 525                 1,
 526                 telnet_new_connection,
 527                 telnet_input,
 528                 telnet_connection_closed,
 529                 telnet_service);
 530 }
 531
 532 /* daemon configuration command telnet_port */
 533 COMMAND_HANDLER(handle_telnet_port_command)
 534 {
 535         return CALL_COMMAND_HANDLER(server_pipe_command, &telnet_port);
 536 }
 537
 538 COMMAND_HANDLER(handle_exit_command)
 539 {
 540         return ERROR_COMMAND_CLOSE_CONNECTION;
 541 }
 542
 543 static const struct command_registration telnet_command_handlers[] = {
 544         {
 545                 .name = "exit",
 546                 .handler = handle_exit_command,
 547                 .mode = COMMAND_EXEC,
 548                 .usage = "",
 549                 .help = "exit telnet session",
 550         },
 551         {
 552                 .name = "telnet_port",
 553                 .handler = handle_telnet_port_command,
 554                 .mode = COMMAND_ANY,
 555                 .help = "Specify port on which to listen "
 556                         "for incoming telnet connections.  "
 557                         "Read help on 'gdb_port'.",
 558                 .usage = "[port_num]",
 559         },
 560         COMMAND_REGISTRATION_DONE
 561 };
 562
 563 int telnet_register_commands(struct command_context *cmd_ctx)
 564 {
 565         telnet_port = strdup("4444");
 566         return register_commands(cmd_ctx, NULL, telnet_command_handlers);
 567 }