clientloop.c

   1 /*
   2  *
   3  * clientloop.c
   4  *
   5  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   6  *
   7  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   8  *                    All rights reserved
   9  *
  10  *
  11  * Created: Sat Sep 23 12:23:57 1995 ylo
  12  *
  13  * The main loop for the interactive session (client side).
  14  *
  15  */
  16
  17 #include "includes.h"
  18 RCSID("$Id$");
  19
  20 #include "xmalloc.h"
  21 #include "ssh.h"
  22 #include "packet.h"
  23 #include "buffer.h"
  24 #include "authfd.h"
  25 #include "readconf.h"
  26
  27 #include "compat.h"
  28 #include "channels.h"
  29 #include "dispatch.h"
  30
  31
  32 /* Flag indicating that stdin should be redirected from /dev/null. */
  33 extern int stdin_null_flag;
  34
  35 /*
  36  * Name of the host we are connecting to.  This is the name given on the
  37  * command line, or the HostName specified for the user-supplied name in a
  38  * configuration file.
  39  */
  40 extern char *host;
  41
  42 /*
  43  * Flag to indicate that we have received a window change signal which has
  44  * not yet been processed.  This will cause a message indicating the new
  45  * window size to be sent to the server a little later.  This is volatile
  46  * because this is updated in a signal handler.
  47  */
  48 static volatile int received_window_change_signal = 0;
  49
  50 /* Terminal modes, as saved by enter_raw_mode. */
  51 static struct termios saved_tio;
  52
  53 /*
  54  * Flag indicating whether we are in raw mode.  This is used by
  55  * enter_raw_mode and leave_raw_mode.
  56  */
  57 static int in_raw_mode = 0;
  58
  59 /* Flag indicating whether the user\'s terminal is in non-blocking mode. */
  60 static int in_non_blocking_mode = 0;
  61
  62 /* Common data for the client loop code. */
  63 static int escape_pending;      /* Last character was the escape character */
  64 static int last_was_cr;         /* Last character was a newline. */
  65 static int exit_status;         /* Used to store the exit status of the command. */
  66 static int stdin_eof;           /* EOF has been encountered on standard error. */
  67 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  68 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  69 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  70 static unsigned int buffer_high;/* Soft max buffer size. */
  71 static int max_fd;              /* Maximum file descriptor number in select(). */
  72 static int connection_in;       /* Connection to server (input). */
  73 static int connection_out;      /* Connection to server (output). */
  74 static unsigned long stdin_bytes, stdout_bytes, stderr_bytes;
  75 static int quit_pending;        /* Set to non-zero to quit the client loop. */
  76 static int escape_char;         /* Escape character. */
  77
  78 /* Returns the user\'s terminal to normal mode if it had been put in raw mode. */
  79
  80 void
  81 leave_raw_mode()
  82 {
  83         if (!in_raw_mode)
  84                 return;
  85         in_raw_mode = 0;
  86         if (tcsetattr(fileno(stdin), TCSADRAIN, &saved_tio) < 0)
  87                 perror("tcsetattr");
  88
  89         fatal_remove_cleanup((void (*) (void *)) leave_raw_mode, NULL);
  90 }
  91
  92 /* Puts the user\'s terminal in raw mode. */
  93
  94 void
  95 enter_raw_mode()
  96 {
  97         struct termios tio;
  98
  99         if (tcgetattr(fileno(stdin), &tio) < 0)
 100                 perror("tcgetattr");
 101         saved_tio = tio;
 102         tio.c_iflag |= IGNPAR;
 103         tio.c_iflag &= ~(ISTRIP | INLCR | IGNCR | ICRNL | IXON | IXANY | IXOFF);
 104         tio.c_lflag &= ~(ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHONL);
 105 #ifdef IEXTEN
 106         tio.c_lflag &= ~IEXTEN;
 107 #endif                          /* IEXTEN */
 108         tio.c_oflag &= ~OPOST;
 109         tio.c_cc[VMIN] = 1;
 110         tio.c_cc[VTIME] = 0;
 111         if (tcsetattr(fileno(stdin), TCSADRAIN, &tio) < 0)
 112                 perror("tcsetattr");
 113         in_raw_mode = 1;
 114
 115         fatal_add_cleanup((void (*) (void *)) leave_raw_mode, NULL);
 116 }
 117
 118 /* Restores stdin to blocking mode. */
 119
 120 void
 121 leave_non_blocking()
 122 {
 123         if (in_non_blocking_mode) {
 124                 (void) fcntl(fileno(stdin), F_SETFL, 0);
 125                 in_non_blocking_mode = 0;
 126                 fatal_remove_cleanup((void (*) (void *)) leave_non_blocking, NULL);
 127         }
 128 }
 129
 130 /* Puts stdin terminal in non-blocking mode. */
 131
 132 void
 133 enter_non_blocking()
 134 {
 135         in_non_blocking_mode = 1;
 136         (void) fcntl(fileno(stdin), F_SETFL, O_NONBLOCK);
 137         fatal_add_cleanup((void (*) (void *)) leave_non_blocking, NULL);
 138 }
 139
 140 /*
 141  * Signal handler for the window change signal (SIGWINCH).  This just sets a
 142  * flag indicating that the window has changed.
 143  */
 144
 145 void
 146 window_change_handler(int sig)
 147 {
 148         received_window_change_signal = 1;
 149         signal(SIGWINCH, window_change_handler);
 150 }
 151
 152 /*
 153  * Signal handler for signals that cause the program to terminate.  These
 154  * signals must be trapped to restore terminal modes.
 155  */
 156
 157 void
 158 signal_handler(int sig)
 159 {
 160         if (in_raw_mode)
 161                 leave_raw_mode();
 162         if (in_non_blocking_mode)
 163                 leave_non_blocking();
 164         channel_stop_listening();
 165         packet_close();
 166         fatal("Killed by signal %d.", sig);
 167 }
 168
 169 /*
 170  * Returns current time in seconds from Jan 1, 1970 with the maximum
 171  * available resolution.
 172  */
 173
 174 double
 175 get_current_time()
 176 {
 177         struct timeval tv;
 178         gettimeofday(&tv, NULL);
 179         return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0;
 180 }
 181
 182 /*
 183  * This is called when the interactive is entered.  This checks if there is
 184  * an EOF coming on stdin.  We must check this explicitly, as select() does
 185  * not appear to wake up when redirecting from /dev/null.
 186  */
 187
 188 void
 189 client_check_initial_eof_on_stdin()
 190 {
 191         int len;
 192         char buf[1];
 193
 194         /*
 195          * If standard input is to be "redirected from /dev/null", we simply
 196          * mark that we have seen an EOF and send an EOF message to the
 197          * server. Otherwise, we try to read a single character; it appears
 198          * that for some files, such /dev/null, select() never wakes up for
 199          * read for this descriptor, which means that we never get EOF.  This
 200          * way we will get the EOF if stdin comes from /dev/null or similar.
 201          */
 202         if (stdin_null_flag) {
 203                 /* Fake EOF on stdin. */
 204                 debug("Sending eof.");
 205                 stdin_eof = 1;
 206                 packet_start(SSH_CMSG_EOF);
 207                 packet_send();
 208         } else {
 209                 enter_non_blocking();
 210
 211                 /* Check for immediate EOF on stdin. */
 212                 len = read(fileno(stdin), buf, 1);
 213                 if (len == 0) {
 214                         /* EOF.  Record that we have seen it and send EOF to server. */
 215                         debug("Sending eof.");
 216                         stdin_eof = 1;
 217                         packet_start(SSH_CMSG_EOF);
 218                         packet_send();
 219                 } else if (len > 0) {
 220                         /*
 221                          * Got data.  We must store the data in the buffer,
 222                          * and also process it as an escape character if
 223                          * appropriate.
 224                          */
 225                         if ((unsigned char) buf[0] == escape_char)
 226                                 escape_pending = 1;
 227                         else {
 228                                 buffer_append(&stdin_buffer, buf, 1);
 229                                 stdin_bytes += 1;
 230                         }
 231                 }
 232                 leave_non_blocking();
 233         }
 234 }
 235
 236
 237 /*
 238  * Make packets from buffered stdin data, and buffer them for sending to the
 239  * connection.
 240  */
 241
 242 void
 243 client_make_packets_from_stdin_data()
 244 {
 245         unsigned int len;
 246
 247         /* Send buffered stdin data to the server. */
 248         while (buffer_len(&stdin_buffer) > 0 &&
 249                packet_not_very_much_data_to_write()) {
 250                 len = buffer_len(&stdin_buffer);
 251                 /* Keep the packets at reasonable size. */
 252                 if (len > packet_get_maxsize())
 253                         len = packet_get_maxsize();
 254                 packet_start(SSH_CMSG_STDIN_DATA);
 255                 packet_put_string(buffer_ptr(&stdin_buffer), len);
 256                 packet_send();
 257                 buffer_consume(&stdin_buffer, len);
 258                 /* If we have a pending EOF, send it now. */
 259                 if (stdin_eof && buffer_len(&stdin_buffer) == 0) {
 260                         packet_start(SSH_CMSG_EOF);
 261                         packet_send();
 262                 }
 263         }
 264 }
 265
 266 /*
 267  * Checks if the client window has changed, and sends a packet about it to
 268  * the server if so.  The actual change is detected elsewhere (by a software
 269  * interrupt on Unix); this just checks the flag and sends a message if
 270  * appropriate.
 271  */
 272
 273 void
 274 client_check_window_change()
 275 {
 276         /* Send possible window change message to the server. */
 277         if (received_window_change_signal) {
 278                 struct winsize ws;
 279
 280                 /* Clear the window change indicator. */
 281                 received_window_change_signal = 0;
 282
 283                 /* Read new window size. */
 284                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) >= 0) {
 285                         /* Successful, send the packet now. */
 286                         packet_start(SSH_CMSG_WINDOW_SIZE);
 287                         packet_put_int(ws.ws_row);
 288                         packet_put_int(ws.ws_col);
 289                         packet_put_int(ws.ws_xpixel);
 290                         packet_put_int(ws.ws_ypixel);
 291                         packet_send();
 292                 }
 293         }
 294 }
 295
 296 /*
 297  * Waits until the client can do something (some data becomes available on
 298  * one of the file descriptors).
 299  */
 300
 301 void
 302 client_wait_until_can_do_something(fd_set * readset, fd_set * writeset)
 303 {
 304         /* Initialize select masks. */
 305         FD_ZERO(readset);
 306
 307         /* Read from the connection, unless our buffers are full. */
 308         if (buffer_len(&stdout_buffer) < buffer_high &&
 309             buffer_len(&stderr_buffer) < buffer_high &&
 310             channel_not_very_much_buffered_data())
 311                 FD_SET(connection_in, readset);
 312
 313         /*
 314          * Read from stdin, unless we have seen EOF or have very much
 315          * buffered data to send to the server.
 316          */
 317         if (!stdin_eof && packet_not_very_much_data_to_write())
 318                 FD_SET(fileno(stdin), readset);
 319
 320         FD_ZERO(writeset);
 321
 322         /* Add any selections by the channel mechanism. */
 323         channel_prepare_select(readset, writeset);
 324
 325         /* Select server connection if have data to write to the server. */
 326         if (packet_have_data_to_write())
 327                 FD_SET(connection_out, writeset);
 328
 329         /* Select stdout if have data in buffer. */
 330         if (buffer_len(&stdout_buffer) > 0)
 331                 FD_SET(fileno(stdout), writeset);
 332
 333         /* Select stderr if have data in buffer. */
 334         if (buffer_len(&stderr_buffer) > 0)
 335                 FD_SET(fileno(stderr), writeset);
 336
 337         /* Update maximum file descriptor number, if appropriate. */
 338         if (channel_max_fd() > max_fd)
 339                 max_fd = channel_max_fd();
 340
 341         /*
 342          * Wait for something to happen.  This will suspend the process until
 343          * some selected descriptor can be read, written, or has some other
 344          * event pending. Note: if you want to implement SSH_MSG_IGNORE
 345          * messages to fool traffic analysis, this might be the place to do
 346          * it: just have a random timeout for the select, and send a random
 347          * SSH_MSG_IGNORE packet when the timeout expires.
 348          */
 349
 350         if (select(max_fd + 1, readset, writeset, NULL, NULL) < 0) {
 351                 char buf[100];
 352                 /* Some systems fail to clear these automatically. */
 353                 FD_ZERO(readset);
 354                 FD_ZERO(writeset);
 355                 if (errno == EINTR)
 356                         return;
 357                 /* Note: we might still have data in the buffers. */
 358                 snprintf(buf, sizeof buf, "select: %s\r\n", strerror(errno));
 359                 buffer_append(&stderr_buffer, buf, strlen(buf));
 360                 stderr_bytes += strlen(buf);
 361                 quit_pending = 1;
 362         }
 363 }
 364
 365 void
 366 client_suspend_self()
 367 {
 368         struct winsize oldws, newws;
 369
 370         /* Flush stdout and stderr buffers. */
 371         if (buffer_len(&stdout_buffer) > 0)
 372                 atomicio(write, fileno(stdout), buffer_ptr(&stdout_buffer),
 373                     buffer_len(&stdout_buffer));
 374         if (buffer_len(&stderr_buffer) > 0)
 375                 atomicio(write, fileno(stderr), buffer_ptr(&stderr_buffer),
 376                     buffer_len(&stderr_buffer));
 377
 378         leave_raw_mode();
 379
 380         /*
 381          * Free (and clear) the buffer to reduce the amount of data that gets
 382          * written to swap.
 383          */
 384         buffer_free(&stdin_buffer);
 385         buffer_free(&stdout_buffer);
 386         buffer_free(&stderr_buffer);
 387
 388         /* Save old window size. */
 389         ioctl(fileno(stdin), TIOCGWINSZ, &oldws);
 390
 391         /* Send the suspend signal to the program itself. */
 392         kill(getpid(), SIGTSTP);
 393
 394         /* Check if the window size has changed. */
 395         if (ioctl(fileno(stdin), TIOCGWINSZ, &newws) >= 0 &&
 396             (oldws.ws_row != newws.ws_row ||
 397              oldws.ws_col != newws.ws_col ||
 398              oldws.ws_xpixel != newws.ws_xpixel ||
 399              oldws.ws_ypixel != newws.ws_ypixel))
 400                 received_window_change_signal = 1;
 401
 402         /* OK, we have been continued by the user. Reinitialize buffers. */
 403         buffer_init(&stdin_buffer);
 404         buffer_init(&stdout_buffer);
 405         buffer_init(&stderr_buffer);
 406
 407         enter_raw_mode();
 408 }
 409
 410 void
 411 client_process_input(fd_set * readset)
 412 {
 413         int len, pid;
 414         char buf[8192], *s;
 415
 416         /*
 417          * Read input from the server, and add any such data to the buffer of
 418          * the packet subsystem.
 419          */
 420         if (FD_ISSET(connection_in, readset)) {
 421                 /* Read as much as possible. */
 422                 len = read(connection_in, buf, sizeof(buf));
 423                 if (len == 0) {
 424                         /* Received EOF.  The remote host has closed the connection. */
 425                         snprintf(buf, sizeof buf, "Connection to %.300s closed by remote host.\r\n",
 426                                  host);
 427                         buffer_append(&stderr_buffer, buf, strlen(buf));
 428                         stderr_bytes += strlen(buf);
 429                         quit_pending = 1;
 430                         return;
 431                 }
 432                 /*
 433                  * There is a kernel bug on Solaris that causes select to
 434                  * sometimes wake up even though there is no data available.
 435                  */
 436                 if (len < 0 && errno == EAGAIN)
 437                         len = 0;
 438
 439                 if (len < 0) {
 440                         /* An error has encountered.  Perhaps there is a network problem. */
 441                         snprintf(buf, sizeof buf, "Read from remote host %.300s: %.100s\r\n",
 442                                  host, strerror(errno));
 443                         buffer_append(&stderr_buffer, buf, strlen(buf));
 444                         stderr_bytes += strlen(buf);
 445                         quit_pending = 1;
 446                         return;
 447                 }
 448                 packet_process_incoming(buf, len);
 449         }
 450         /* Read input from stdin. */
 451         if (FD_ISSET(fileno(stdin), readset)) {
 452                 /* Read as much as possible. */
 453                 len = read(fileno(stdin), buf, sizeof(buf));
 454                 if (len <= 0) {
 455                         /*
 456                          * Received EOF or error.  They are treated
 457                          * similarly, except that an error message is printed
 458                          * if it was an error condition.
 459                          */
 460                         if (len < 0) {
 461                                 snprintf(buf, sizeof buf, "read: %.100s\r\n", strerror(errno));
 462                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 463                                 stderr_bytes += strlen(buf);
 464                         }
 465                         /* Mark that we have seen EOF. */
 466                         stdin_eof = 1;
 467                         /*
 468                          * Send an EOF message to the server unless there is
 469                          * data in the buffer.  If there is data in the
 470                          * buffer, no message will be sent now.  Code
 471                          * elsewhere will send the EOF when the buffer
 472                          * becomes empty if stdin_eof is set.
 473                          */
 474                         if (buffer_len(&stdin_buffer) == 0) {
 475                                 packet_start(SSH_CMSG_EOF);
 476                                 packet_send();
 477                         }
 478                 } else if (escape_char == -1) {
 479                         /*
 480                          * Normal successful read, and no escape character.
 481                          * Just append the data to buffer.
 482                          */
 483                         buffer_append(&stdin_buffer, buf, len);
 484                         stdin_bytes += len;
 485                 } else {
 486                         /*
 487                          * Normal, successful read.  But we have an escape character
 488                          * and have to process the characters one by one.
 489                          */
 490                         unsigned int i;
 491                         for (i = 0; i < len; i++) {
 492                                 unsigned char ch;
 493                                 /* Get one character at a time. */
 494                                 ch = buf[i];
 495
 496                                 if (escape_pending) {
 497                                         /* We have previously seen an escape character. */
 498                                         /* Clear the flag now. */
 499                                         escape_pending = 0;
 500                                         /* Process the escaped character. */
 501                                         switch (ch) {
 502                                         case '.':
 503                                                 /* Terminate the connection. */
 504                                                 snprintf(buf, sizeof buf, "%c.\r\n", escape_char);
 505                                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 506                                                 stderr_bytes += strlen(buf);
 507                                                 quit_pending = 1;
 508                                                 return;
 509
 510                                         case 'Z' - 64:
 511                                                 /* Suspend the program. */
 512                                                 /* Print a message to that effect to the user. */
 513                                                 snprintf(buf, sizeof buf, "%c^Z\r\n", escape_char);
 514                                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 515                                                 stderr_bytes += strlen(buf);
 516
 517                                                 /* Restore terminal modes and suspend. */
 518                                                 client_suspend_self();
 519
 520                                                 /* We have been continued. */
 521                                                 continue;
 522
 523                                         case '&':
 524                                                 /*
 525                                                  * Detach the program (continue to serve connections,
 526                                                  * but put in background and no more new connections).
 527                                                  */
 528                                                 if (!stdin_eof) {
 529                                                         /*
 530                                                          * Sending SSH_CMSG_EOF alone does not always appear
 531                                                          * to be enough.  So we try to send an EOF character
 532                                                          * first.
 533                                                          */
 534                                                         packet_start(SSH_CMSG_STDIN_DATA);
 535                                                         packet_put_string("\004", 1);
 536                                                         packet_send();
 537                                                         /* Close stdin. */
 538                                                         stdin_eof = 1;
 539                                                         if (buffer_len(&stdin_buffer) == 0) {
 540                                                                 packet_start(SSH_CMSG_EOF);
 541                                                                 packet_send();
 542                                                         }
 543                                                 }
 544                                                 /* Restore tty modes. */
 545                                                 leave_raw_mode();
 546
 547                                                 /* Stop listening for new connections. */
 548                                                 channel_stop_listening();
 549
 550                                                 printf("%c& [backgrounded]\n", escape_char);
 551
 552                                                 /* Fork into background. */
 553                                                 pid = fork();
 554                                                 if (pid < 0) {
 555                                                         error("fork: %.100s", strerror(errno));
 556                                                         continue;
 557                                                 }
 558                                                 if (pid != 0) { /* This is the parent. */
 559                                                         /* The parent just exits. */
 560                                                         exit(0);
 561                                                 }
 562                                                 /* The child continues serving connections. */
 563                                                 continue;
 564
 565                                         case '?':
 566                                                 snprintf(buf, sizeof buf,
 567 "%c?\r\n\
 568 Supported escape sequences:\r\n\
 569 ~.  - terminate connection\r\n\
 570 ~^Z - suspend ssh\r\n\
 571 ~#  - list forwarded connections\r\n\
 572 ~&  - background ssh (when waiting for connections to terminate)\r\n\
 573 ~?  - this message\r\n\
 574 ~~  - send the escape character by typing it twice\r\n\
 575 (Note that escapes are only recognized immediately after newline.)\r\n",
 576                                                          escape_char);
 577                                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 578                                                 continue;
 579
 580                                         case '#':
 581                                                 snprintf(buf, sizeof buf, "%c#\r\n", escape_char);
 582                                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 583                                                 s = channel_open_message();
 584                                                 buffer_append(&stderr_buffer, s, strlen(s));
 585                                                 xfree(s);
 586                                                 continue;
 587
 588                                         default:
 589                                                 if (ch != escape_char) {
 590                                                         /*
 591                                                          * Escape character followed by non-special character.
 592                                                          * Append both to the input buffer.
 593                                                          */
 594                                                         buf[0] = escape_char;
 595                                                         buf[1] = ch;
 596                                                         buffer_append(&stdin_buffer, buf, 2);
 597                                                         stdin_bytes += 2;
 598                                                         continue;
 599                                                 }
 600                                                 /*
 601                                                  * Note that escape character typed twice
 602                                                  * falls through here; the latter gets processed
 603                                                  * as a normal character below.
 604                                                  */
 605                                                 break;
 606                                         }
 607                                 } else {
 608                                         /*
 609                                          * The previous character was not an escape char. Check if this
 610                                          * is an escape.
 611                                          */
 612                                         if (last_was_cr && ch == escape_char) {
 613                                                 /* It is. Set the flag and continue to next character. */
 614                                                 escape_pending = 1;
 615                                                 continue;
 616                                         }
 617                                 }
 618
 619                                 /*
 620                                  * Normal character.  Record whether it was a newline,
 621                                  * and append it to the buffer.
 622                                  */
 623                                 last_was_cr = (ch == '\r' || ch == '\n');
 624                                 buf[0] = ch;
 625                                 buffer_append(&stdin_buffer, buf, 1);
 626                                 stdin_bytes += 1;
 627                                 continue;
 628                         }
 629                 }
 630         }
 631 }
 632
 633 void
 634 client_process_output(fd_set * writeset)
 635 {
 636         int len;
 637         char buf[100];
 638
 639         /* Write buffered output to stdout. */
 640         if (FD_ISSET(fileno(stdout), writeset)) {
 641                 /* Write as much data as possible. */
 642                 len = write(fileno(stdout), buffer_ptr(&stdout_buffer),
 643                     buffer_len(&stdout_buffer));
 644                 if (len <= 0) {
 645                         if (errno == EAGAIN)
 646                                 len = 0;
 647                         else {
 648                                 /*
 649                                  * An error or EOF was encountered.  Put an
 650                                  * error message to stderr buffer.
 651                                  */
 652                                 snprintf(buf, sizeof buf, "write stdout: %.50s\r\n", strerror(errno));
 653                                 buffer_append(&stderr_buffer, buf, strlen(buf));
 654                                 stderr_bytes += strlen(buf);
 655                                 quit_pending = 1;
 656                                 return;
 657                         }
 658                 }
 659                 /* Consume printed data from the buffer. */
 660                 buffer_consume(&stdout_buffer, len);
 661         }
 662         /* Write buffered output to stderr. */
 663         if (FD_ISSET(fileno(stderr), writeset)) {
 664                 /* Write as much data as possible. */
 665                 len = write(fileno(stderr), buffer_ptr(&stderr_buffer),
 666                     buffer_len(&stderr_buffer));
 667                 if (len <= 0) {
 668                         if (errno == EAGAIN)
 669                                 len = 0;
 670                         else {
 671                                 /* EOF or error, but can't even print error message. */
 672                                 quit_pending = 1;
 673                                 return;
 674                         }
 675                 }
 676                 /* Consume printed characters from the buffer. */
 677                 buffer_consume(&stderr_buffer, len);
 678         }
 679 }
 680
 681 /*
 682  * Get packets from the connection input buffer, and process them as long as
 683  * there are packets available.
 684  *
 685  * Any unknown packets received during the actual
 686  * session cause the session to terminate.  This is
 687  * intended to make debugging easier since no
 688  * confirmations are sent.  Any compatible protocol
 689  * extensions must be negotiated during the
 690  * preparatory phase.
 691  */
 692
 693 void
 694 client_process_buffered_input_packets()
 695 {
 696         dispatch_run(DISPATCH_NONBLOCK, &quit_pending);
 697 }
 698
 699 /*
 700  * Implements the interactive session with the server.  This is called after
 701  * the user has been authenticated, and a command has been started on the
 702  * remote host.  If escape_char != -1, it is the character used as an escape
 703  * character for terminating or suspending the session.
 704  */
 705
 706 void client_init_dispatch(void);
 707
 708 int
 709 client_loop(int have_pty, int escape_char_arg)
 710 {
 711         extern Options options;
 712         double start_time, total_time;
 713         int len;
 714         char buf[100];
 715
 716         debug("Entering interactive session.");
 717
 718         start_time = get_current_time();
 719
 720         /* Initialize variables. */
 721         escape_pending = 0;
 722         last_was_cr = 1;
 723         exit_status = -1;
 724         stdin_eof = 0;
 725         buffer_high = 64 * 1024;
 726         connection_in = packet_get_connection_in();
 727         connection_out = packet_get_connection_out();
 728         max_fd = connection_in;
 729         if (connection_out > max_fd)
 730                 max_fd = connection_out;
 731         stdin_bytes = 0;
 732         stdout_bytes = 0;
 733         stderr_bytes = 0;
 734         quit_pending = 0;
 735         escape_char = escape_char_arg;
 736
 737         /* Initialize buffers. */
 738         buffer_init(&stdin_buffer);
 739         buffer_init(&stdout_buffer);
 740         buffer_init(&stderr_buffer);
 741
 742         client_init_dispatch();
 743
 744         /* Set signal handlers to restore non-blocking mode.  */
 745         signal(SIGINT, signal_handler);
 746         signal(SIGQUIT, signal_handler);
 747         signal(SIGTERM, signal_handler);
 748         signal(SIGPIPE, SIG_IGN);
 749         if (have_pty)
 750                 signal(SIGWINCH, window_change_handler);
 751
 752         if (have_pty)
 753                 enter_raw_mode();
 754
 755         /* Check if we should immediately send of on stdin. */
 756         client_check_initial_eof_on_stdin();
 757
 758         /* Main loop of the client for the interactive session mode. */
 759         while (!quit_pending) {
 760                 fd_set readset, writeset;
 761
 762                 /* Process buffered packets sent by the server. */
 763                 client_process_buffered_input_packets();
 764
 765                 /*
 766                  * Make packets of buffered stdin data, and buffer them for
 767                  * sending to the server.
 768                  */
 769                 client_make_packets_from_stdin_data();
 770
 771                 /*
 772                  * Make packets from buffered channel data, and buffer them
 773                  * for sending to the server.
 774                  */
 775                 if (packet_not_very_much_data_to_write())
 776                         channel_output_poll();
 777
 778                 /*
 779                  * Check if the window size has changed, and buffer a message
 780                  * about it to the server if so.
 781                  */
 782                 client_check_window_change();
 783
 784                 if (quit_pending)
 785                         break;
 786
 787                 /*
 788                  * Wait until we have something to do (something becomes
 789                  * available on one of the descriptors).
 790                  */
 791                 client_wait_until_can_do_something(&readset, &writeset);
 792
 793                 if (quit_pending)
 794                         break;
 795
 796                 /* Do channel operations. */
 797                 channel_after_select(&readset, &writeset);
 798
 799                 /*
 800                  * Process input from the connection and from stdin. Buffer
 801                  * any data that is available.
 802                  */
 803                 client_process_input(&readset);
 804
 805                 /*
 806                  * Process output to stdout and stderr.   Output to the
 807                  * connection is processed elsewhere (above).
 808                  */
 809                 client_process_output(&writeset);
 810
 811                 /* Send as much buffered packet data as possible to the sender. */
 812                 if (FD_ISSET(connection_out, &writeset))
 813                         packet_write_poll();
 814         }
 815
 816         /* Terminate the session. */
 817
 818         /* Stop watching for window change. */
 819         if (have_pty)
 820                 signal(SIGWINCH, SIG_DFL);
 821
 822         /* Stop listening for connections. */
 823         channel_stop_listening();
 824
 825         /*
 826          * In interactive mode (with pseudo tty) display a message indicating
 827          * that the connection has been closed.
 828          */
 829         if (have_pty && options.log_level != SYSLOG_LEVEL_QUIET) {
 830                 snprintf(buf, sizeof buf, "Connection to %.64s closed.\r\n", host);
 831                 buffer_append(&stderr_buffer, buf, strlen(buf));
 832                 stderr_bytes += strlen(buf);
 833         }
 834         /* Output any buffered data for stdout. */
 835         while (buffer_len(&stdout_buffer) > 0) {
 836                 len = write(fileno(stdout), buffer_ptr(&stdout_buffer),
 837                     buffer_len(&stdout_buffer));
 838                 if (len <= 0) {
 839                         error("Write failed flushing stdout buffer.");
 840                         break;
 841                 }
 842                 buffer_consume(&stdout_buffer, len);
 843         }
 844
 845         /* Output any buffered data for stderr. */
 846         while (buffer_len(&stderr_buffer) > 0) {
 847                 len = write(fileno(stderr), buffer_ptr(&stderr_buffer),
 848                     buffer_len(&stderr_buffer));
 849                 if (len <= 0) {
 850                         error("Write failed flushing stderr buffer.");
 851                         break;
 852                 }
 853                 buffer_consume(&stderr_buffer, len);
 854         }
 855
 856         if (have_pty)
 857                 leave_raw_mode();
 858
 859         /* Clear and free any buffers. */
 860         memset(buf, 0, sizeof(buf));
 861         buffer_free(&stdin_buffer);
 862         buffer_free(&stdout_buffer);
 863         buffer_free(&stderr_buffer);
 864
 865         /* Report bytes transferred, and transfer rates. */
 866         total_time = get_current_time() - start_time;
 867         debug("Transferred: stdin %lu, stdout %lu, stderr %lu bytes in %.1f seconds",
 868               stdin_bytes, stdout_bytes, stderr_bytes, total_time);
 869         if (total_time > 0)
 870                 debug("Bytes per second: stdin %.1f, stdout %.1f, stderr %.1f",
 871                       stdin_bytes / total_time, stdout_bytes / total_time,
 872                       stderr_bytes / total_time);
 873
 874         /* Return the exit status of the program. */
 875         debug("Exit status %d", exit_status);
 876         return exit_status;
 877 }
 878
 879 /*********/
 880
 881 void
 882 client_input_stdout_data(int type, int plen)
 883 {
 884         unsigned int data_len;
 885         char *data = packet_get_string(&data_len);
 886         packet_integrity_check(plen, 4 + data_len, type);
 887         buffer_append(&stdout_buffer, data, data_len);
 888         stdout_bytes += data_len;
 889         memset(data, 0, data_len);
 890         xfree(data);
 891 }
 892 void
 893 client_input_stderr_data(int type, int plen)
 894 {
 895         unsigned int data_len;
 896         char *data = packet_get_string(&data_len);
 897         packet_integrity_check(plen, 4 + data_len, type);
 898         buffer_append(&stderr_buffer, data, data_len);
 899         stdout_bytes += data_len;
 900         memset(data, 0, data_len);
 901         xfree(data);
 902 }
 903 void
 904 client_input_exit_status(int type, int plen)
 905 {
 906         packet_integrity_check(plen, 4, type);
 907         exit_status = packet_get_int();
 908         /* Acknowledge the exit. */
 909         packet_start(SSH_CMSG_EXIT_CONFIRMATION);
 910         packet_send();
 911         /*
 912          * Must wait for packet to be sent since we are
 913          * exiting the loop.
 914          */
 915         packet_write_wait();
 916         /* Flag that we want to exit. */
 917         quit_pending = 1;
 918 }
 919
 920 void
 921 client_init_dispatch_13()
 922 {
 923         dispatch_init(NULL);
 924         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
 925         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
 926         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
 927         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
 928         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 929         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 930         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
 931         dispatch_set(SSH_SMSG_AGENT_OPEN, &auth_input_open_request);
 932         dispatch_set(SSH_SMSG_EXITSTATUS, &client_input_exit_status);
 933         dispatch_set(SSH_SMSG_STDERR_DATA, &client_input_stderr_data);
 934         dispatch_set(SSH_SMSG_STDOUT_DATA, &client_input_stdout_data);
 935         dispatch_set(SSH_SMSG_X11_OPEN, &x11_input_open);
 936 }
 937 void
 938 client_init_dispatch_15()
 939 {
 940         client_init_dispatch_13();
 941         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
 942         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, & channel_input_oclose);
 943 }
 944 void
 945 client_init_dispatch()
 946 {
 947         if (compat13)
 948                 client_init_dispatch_13();
 949         else
 950                 client_init_dispatch_15();
 951 }