serverloop.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  * Server main loop for handling the interactive session.
   6  *
   7  * As far as I am concerned, the code I have written for this software
   8  * can be used freely for any purpose.  Any derived versions of this
   9  * software must be clearly marked as such, and if the derived work is
  10  * incompatible with the protocol description in the RFC file, it must be
  11  * called by a name other than "ssh" or "Secure Shell".
  12  *
  13  * SSH2 support by Markus Friedl.
  14  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  15  *
  16  * Redistribution and use in source and binary forms, with or without
  17  * modification, are permitted provided that the following conditions
  18  * are met:
  19  * 1. Redistributions of source code must retain the above copyright
  20  *    notice, this list of conditions and the following disclaimer.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  *
  25  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  26  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  27  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  28  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  29  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  30  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  31  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  32  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  33  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  34  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  35  */
  36
  37 #include "includes.h"
  38 RCSID("$OpenBSD: serverloop.c,v 1.70 2001/06/23 15:12:19 itojun Exp $");
  39
  40 #include "xmalloc.h"
  41 #include "packet.h"
  42 #include "buffer.h"
  43 #include "log.h"
  44 #include "servconf.h"
  45 #include "sshpty.h"
  46 #include "channels.h"
  47 #include "compat.h"
  48 #include "ssh1.h"
  49 #include "ssh2.h"
  50 #include "auth.h"
  51 #include "session.h"
  52 #include "dispatch.h"
  53 #include "auth-options.h"
  54 #include "serverloop.h"
  55 #include "misc.h"
  56 #include "kex.h"
  57
  58 extern ServerOptions options;
  59
  60 /* XXX */
  61 extern Kex *xxx_kex;
  62
  63 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  64 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  65 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  66 static int fdin;                /* Descriptor for stdin (for writing) */
  67 static int fdout;               /* Descriptor for stdout (for reading);
  68                                    May be same number as fdin. */
  69 static int fderr;               /* Descriptor for stderr.  May be -1. */
  70 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  71 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  72 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  73 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  74 static int stdin_eof = 0;       /* EOF message received from client. */
  75 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  76 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  77 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  78 static int connection_in;       /* Connection to client (input). */
  79 static int connection_out;      /* Connection to client (output). */
  80 static int connection_closed = 0;       /* Connection to client closed. */
  81 static u_int buffer_high;       /* "Soft" max buffer size. */
  82
  83 /*
  84  * This SIGCHLD kludge is used to detect when the child exits.  The server
  85  * will exit after that, as soon as forwarded connections have terminated.
  86  */
  87
  88 static volatile int child_terminated;   /* The child has terminated. */
  89
  90 /* prototypes */
  91 static void server_init_dispatch(void);
  92
  93 int client_alive_timeouts = 0;
  94
  95 static void
  96 sigchld_handler(int sig)
  97 {
  98         int save_errno = errno;
  99         debug("Received SIGCHLD.");
 100         child_terminated = 1;
 101         mysignal(SIGCHLD, sigchld_handler);
 102         errno = save_errno;
 103 }
 104
 105 /*
 106  * Make packets from buffered stderr data, and buffer it for sending
 107  * to the client.
 108  */
 109 static void
 110 make_packets_from_stderr_data(void)
 111 {
 112         int len;
 113
 114         /* Send buffered stderr data to the client. */
 115         while (buffer_len(&stderr_buffer) > 0 &&
 116             packet_not_very_much_data_to_write()) {
 117                 len = buffer_len(&stderr_buffer);
 118                 if (packet_is_interactive()) {
 119                         if (len > 512)
 120                                 len = 512;
 121                 } else {
 122                         /* Keep the packets at reasonable size. */
 123                         if (len > packet_get_maxsize())
 124                                 len = packet_get_maxsize();
 125                 }
 126                 packet_start(SSH_SMSG_STDERR_DATA);
 127                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 128                 packet_send();
 129                 buffer_consume(&stderr_buffer, len);
 130                 stderr_bytes += len;
 131         }
 132 }
 133
 134 /*
 135  * Make packets from buffered stdout data, and buffer it for sending to the
 136  * client.
 137  */
 138 static void
 139 make_packets_from_stdout_data(void)
 140 {
 141         int len;
 142
 143         /* Send buffered stdout data to the client. */
 144         while (buffer_len(&stdout_buffer) > 0 &&
 145             packet_not_very_much_data_to_write()) {
 146                 len = buffer_len(&stdout_buffer);
 147                 if (packet_is_interactive()) {
 148                         if (len > 512)
 149                                 len = 512;
 150                 } else {
 151                         /* Keep the packets at reasonable size. */
 152                         if (len > packet_get_maxsize())
 153                                 len = packet_get_maxsize();
 154                 }
 155                 packet_start(SSH_SMSG_STDOUT_DATA);
 156                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 157                 packet_send();
 158                 buffer_consume(&stdout_buffer, len);
 159                 stdout_bytes += len;
 160         }
 161 }
 162
 163 /*
 164  * Sleep in select() until we can do something.  This will initialize the
 165  * select masks.  Upon return, the masks will indicate which descriptors
 166  * have data or can accept data.  Optionally, a maximum time can be specified
 167  * for the duration of the wait (0 = infinite).
 168  */
 169 static void
 170 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 171     u_int max_time_milliseconds)
 172 {
 173         struct timeval tv, *tvp;
 174         int ret;
 175         int client_alive_scheduled = 0;
 176
 177         /*
 178          * if using client_alive, set the max timeout accordingly,
 179          * and indicate that this particular timeout was for client
 180          * alive by setting the client_alive_scheduled flag.
 181          *
 182          * this could be randomized somewhat to make traffic
 183          * analysis more difficult, but we're not doing it yet.
 184          */
 185         if (max_time_milliseconds == 0 && options.client_alive_interval) {
 186                 client_alive_scheduled = 1;
 187                 max_time_milliseconds = options.client_alive_interval * 1000;
 188         } else
 189                 client_alive_scheduled = 0;
 190
 191         /* When select fails we restart from here. */
 192 retry_select:
 193
 194         /* Allocate and update select() masks for channel descriptors. */
 195         channel_prepare_select(readsetp, writesetp, maxfdp, 0);
 196
 197         if (compat20) {
 198                 /* wrong: bad condition XXX */
 199                 if (channel_not_very_much_buffered_data())
 200                         FD_SET(connection_in, *readsetp);
 201         } else {
 202                 /*
 203                  * Read packets from the client unless we have too much
 204                  * buffered stdin or channel data.
 205                  */
 206                 if (buffer_len(&stdin_buffer) < buffer_high &&
 207                     channel_not_very_much_buffered_data())
 208                         FD_SET(connection_in, *readsetp);
 209                 /*
 210                  * If there is not too much data already buffered going to
 211                  * the client, try to get some more data from the program.
 212                  */
 213                 if (packet_not_very_much_data_to_write()) {
 214                         if (!fdout_eof)
 215                                 FD_SET(fdout, *readsetp);
 216                         if (!fderr_eof)
 217                                 FD_SET(fderr, *readsetp);
 218                 }
 219                 /*
 220                  * If we have buffered data, try to write some of that data
 221                  * to the program.
 222                  */
 223                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 224                         FD_SET(fdin, *writesetp);
 225         }
 226
 227         /*
 228          * If we have buffered packet data going to the client, mark that
 229          * descriptor.
 230          */
 231         if (packet_have_data_to_write())
 232                 FD_SET(connection_out, *writesetp);
 233
 234         /*
 235          * If child has terminated and there is enough buffer space to read
 236          * from it, then read as much as is available and exit.
 237          */
 238         if (child_terminated && packet_not_very_much_data_to_write())
 239                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 240                         max_time_milliseconds = 100;
 241
 242         if (max_time_milliseconds == 0)
 243                 tvp = NULL;
 244         else {
 245                 tv.tv_sec = max_time_milliseconds / 1000;
 246                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 247                 tvp = &tv;
 248         }
 249         if (tvp!=NULL)
 250                 debug3("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds);
 251
 252         /* Wait for something to happen, or the timeout to expire. */
 253         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 254
 255         if (ret == -1) {
 256                 if (errno != EINTR)
 257                         error("select: %.100s", strerror(errno));
 258                 else
 259                         goto retry_select;
 260         }
 261         if (ret == 0 && client_alive_scheduled) {
 262                 /* timeout, check to see how many we have had */
 263                 client_alive_timeouts++;
 264
 265                 if (client_alive_timeouts > options.client_alive_count_max ) {
 266                         packet_disconnect(
 267                                 "Timeout, your session not responding.");
 268                 } else {
 269                         /*
 270                          * send a bogus channel request with "wantreply"
 271                          * we should get back a failure
 272                          */
 273                         int id;
 274
 275                         id = channel_find_open();
 276                         if (id != -1) {
 277                                 channel_request_start(id,
 278                                   "keepalive@openssh.com", 1);
 279                                 packet_send();
 280                         } else
 281                                 packet_disconnect(
 282                                         "No open channels after timeout!");
 283                 }
 284         }
 285 }
 286
 287 /*
 288  * Processes input from the client and the program.  Input data is stored
 289  * in buffers and processed later.
 290  */
 291 static void
 292 process_input(fd_set * readset)
 293 {
 294         int len;
 295         char buf[16384];
 296
 297         /* Read and buffer any input data from the client. */
 298         if (FD_ISSET(connection_in, readset)) {
 299                 len = read(connection_in, buf, sizeof(buf));
 300                 if (len == 0) {
 301                         verbose("Connection closed by remote host.");
 302                         connection_closed = 1;
 303                         if (compat20)
 304                                 return;
 305                         fatal_cleanup();
 306                 } else if (len < 0) {
 307                         if (errno != EINTR && errno != EAGAIN) {
 308                                 verbose("Read error from remote host: %.100s", strerror(errno));
 309                                 fatal_cleanup();
 310                         }
 311                 } else {
 312                         /* Buffer any received data. */
 313                         packet_process_incoming(buf, len);
 314                 }
 315         }
 316         if (compat20)
 317                 return;
 318
 319         /* Read and buffer any available stdout data from the program. */
 320         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 321                 len = read(fdout, buf, sizeof(buf));
 322                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 323                         /* do nothing */
 324                 } else if (len <= 0) {
 325                         fdout_eof = 1;
 326                 } else {
 327                         buffer_append(&stdout_buffer, buf, len);
 328                         fdout_bytes += len;
 329                 }
 330         }
 331         /* Read and buffer any available stderr data from the program. */
 332         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 333                 len = read(fderr, buf, sizeof(buf));
 334                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 335                         /* do nothing */
 336                 } else if (len <= 0) {
 337                         fderr_eof = 1;
 338                 } else {
 339                         buffer_append(&stderr_buffer, buf, len);
 340                 }
 341         }
 342 }
 343
 344 /*
 345  * Sends data from internal buffers to client program stdin.
 346  */
 347 static void
 348 process_output(fd_set * writeset)
 349 {
 350         struct termios tio;
 351         int len;
 352
 353         /* Write buffered data to program stdin. */
 354         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 355                 len = write(fdin, buffer_ptr(&stdin_buffer),
 356                     buffer_len(&stdin_buffer));
 357                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 358                         /* do nothing */
 359                 } else if (len <= 0) {
 360 #ifdef USE_PIPES
 361                         close(fdin);
 362 #else
 363                         if (fdin != fdout)
 364                                 close(fdin);
 365                         else
 366                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 367 #endif
 368                         fdin = -1;
 369                 } else {
 370                         /* Successful write. */
 371                         if (fdin_is_tty && tcgetattr(fdin, &tio) == 0 &&
 372                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 373                                 /*
 374                                  * Simulate echo to reduce the impact of
 375                                  * traffic analysis
 376                                  */
 377                                 packet_send_ignore(len);
 378                                 packet_send();
 379                         }
 380                         /* Consume the data from the buffer. */
 381                         buffer_consume(&stdin_buffer, len);
 382                         /* Update the count of bytes written to the program. */
 383                         stdin_bytes += len;
 384                 }
 385         }
 386         /* Send any buffered packet data to the client. */
 387         if (FD_ISSET(connection_out, writeset))
 388                 packet_write_poll();
 389 }
 390
 391 /*
 392  * Wait until all buffered output has been sent to the client.
 393  * This is used when the program terminates.
 394  */
 395 static void
 396 drain_output(void)
 397 {
 398         /* Send any buffered stdout data to the client. */
 399         if (buffer_len(&stdout_buffer) > 0) {
 400                 packet_start(SSH_SMSG_STDOUT_DATA);
 401                 packet_put_string(buffer_ptr(&stdout_buffer),
 402                                   buffer_len(&stdout_buffer));
 403                 packet_send();
 404                 /* Update the count of sent bytes. */
 405                 stdout_bytes += buffer_len(&stdout_buffer);
 406         }
 407         /* Send any buffered stderr data to the client. */
 408         if (buffer_len(&stderr_buffer) > 0) {
 409                 packet_start(SSH_SMSG_STDERR_DATA);
 410                 packet_put_string(buffer_ptr(&stderr_buffer),
 411                                   buffer_len(&stderr_buffer));
 412                 packet_send();
 413                 /* Update the count of sent bytes. */
 414                 stderr_bytes += buffer_len(&stderr_buffer);
 415         }
 416         /* Wait until all buffered data has been written to the client. */
 417         packet_write_wait();
 418 }
 419
 420 static void
 421 process_buffered_input_packets(void)
 422 {
 423         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 424 }
 425
 426 /*
 427  * Performs the interactive session.  This handles data transmission between
 428  * the client and the program.  Note that the notion of stdin, stdout, and
 429  * stderr in this function is sort of reversed: this function writes to
 430  * stdin (of the child program), and reads from stdout and stderr (of the
 431  * child program).
 432  */
 433 void
 434 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 435 {
 436         fd_set *readset = NULL, *writeset = NULL;
 437         int max_fd;
 438         int wait_status;        /* Status returned by wait(). */
 439         pid_t wait_pid;         /* pid returned by wait(). */
 440         int waiting_termination = 0;    /* Have displayed waiting close message. */
 441         u_int max_time_milliseconds;
 442         u_int previous_stdout_buffer_bytes;
 443         u_int stdout_buffer_bytes;
 444         int type;
 445
 446         debug("Entering interactive session.");
 447
 448         /* Initialize the SIGCHLD kludge. */
 449         child_terminated = 0;
 450         signal(SIGCHLD, sigchld_handler);
 451
 452         /* Initialize our global variables. */
 453         fdin = fdin_arg;
 454         fdout = fdout_arg;
 455         fderr = fderr_arg;
 456
 457         /* nonblocking IO */
 458         set_nonblock(fdin);
 459         set_nonblock(fdout);
 460         /* we don't have stderr for interactive terminal sessions, see below */
 461         if (fderr != -1)
 462                 set_nonblock(fderr);
 463
 464         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 465                 fdin_is_tty = 1;
 466
 467         connection_in = packet_get_connection_in();
 468         connection_out = packet_get_connection_out();
 469
 470         previous_stdout_buffer_bytes = 0;
 471
 472         /* Set approximate I/O buffer size. */
 473         if (packet_is_interactive())
 474                 buffer_high = 4096;
 475         else
 476                 buffer_high = 64 * 1024;
 477
 478         /* Initialize max_fd to the maximum of the known file descriptors. */
 479         max_fd = MAX(fdin, fdout);
 480         if (fderr != -1)
 481                 max_fd = MAX(max_fd, fderr);
 482         max_fd = MAX(max_fd, connection_in);
 483         max_fd = MAX(max_fd, connection_out);
 484
 485         /* Initialize Initialize buffers. */
 486         buffer_init(&stdin_buffer);
 487         buffer_init(&stdout_buffer);
 488         buffer_init(&stderr_buffer);
 489
 490         /*
 491          * If we have no separate fderr (which is the case when we have a pty
 492          * - there we cannot make difference between data sent to stdout and
 493          * stderr), indicate that we have seen an EOF from stderr.  This way
 494          * we don\'t need to check the descriptor everywhere.
 495          */
 496         if (fderr == -1)
 497                 fderr_eof = 1;
 498
 499         server_init_dispatch();
 500
 501         /* Main loop of the server for the interactive session mode. */
 502         for (;;) {
 503
 504                 /* Process buffered packets from the client. */
 505                 process_buffered_input_packets();
 506
 507                 /*
 508                  * If we have received eof, and there is no more pending
 509                  * input data, cause a real eof by closing fdin.
 510                  */
 511                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 512 #ifdef USE_PIPES
 513                         close(fdin);
 514 #else
 515                         if (fdin != fdout)
 516                                 close(fdin);
 517                         else
 518                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 519 #endif
 520                         fdin = -1;
 521                 }
 522                 /* Make packets from buffered stderr data to send to the client. */
 523                 make_packets_from_stderr_data();
 524
 525                 /*
 526                  * Make packets from buffered stdout data to send to the
 527                  * client. If there is very little to send, this arranges to
 528                  * not send them now, but to wait a short while to see if we
 529                  * are getting more data. This is necessary, as some systems
 530                  * wake up readers from a pty after each separate character.
 531                  */
 532                 max_time_milliseconds = 0;
 533                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 534                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 535                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 536                         /* try again after a while */
 537                         max_time_milliseconds = 10;
 538                 } else {
 539                         /* Send it now. */
 540                         make_packets_from_stdout_data();
 541                 }
 542                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 543
 544                 /* Send channel data to the client. */
 545                 if (packet_not_very_much_data_to_write())
 546                         channel_output_poll();
 547
 548                 /*
 549                  * Bail out of the loop if the program has closed its output
 550                  * descriptors, and we have no more data to send to the
 551                  * client, and there is no pending buffered data.
 552                  */
 553                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 554                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 555                         if (!channel_still_open())
 556                                 break;
 557                         if (!waiting_termination) {
 558                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 559                                 char *cp;
 560                                 waiting_termination = 1;
 561                                 buffer_append(&stderr_buffer, s, strlen(s));
 562
 563                                 /* Display list of open channels. */
 564                                 cp = channel_open_message();
 565                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 566                                 xfree(cp);
 567                         }
 568                 }
 569                 /* Sleep in select() until we can do something. */
 570                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 571                     max_time_milliseconds);
 572
 573                 /* Process any channel events. */
 574                 channel_after_select(readset, writeset);
 575
 576                 /* Process input from the client and from program stdout/stderr. */
 577                 process_input(readset);
 578
 579                 /* Process output to the client and to program stdin. */
 580                 process_output(writeset);
 581         }
 582         if (readset)
 583                 xfree(readset);
 584         if (writeset)
 585                 xfree(writeset);
 586
 587         /* Cleanup and termination code. */
 588
 589         /* Wait until all output has been sent to the client. */
 590         drain_output();
 591
 592         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 593               stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 594
 595         /* Free and clear the buffers. */
 596         buffer_free(&stdin_buffer);
 597         buffer_free(&stdout_buffer);
 598         buffer_free(&stderr_buffer);
 599
 600         /* Close the file descriptors. */
 601         if (fdout != -1)
 602                 close(fdout);
 603         fdout = -1;
 604         fdout_eof = 1;
 605         if (fderr != -1)
 606                 close(fderr);
 607         fderr = -1;
 608         fderr_eof = 1;
 609         if (fdin != -1)
 610                 close(fdin);
 611         fdin = -1;
 612
 613         channel_free_all();
 614
 615         /* We no longer want our SIGCHLD handler to be called. */
 616         signal(SIGCHLD, SIG_DFL);
 617
 618         wait_pid = waitpid(-1, &wait_status, child_terminated ? WNOHANG : 0);
 619         if (wait_pid == -1)
 620                 packet_disconnect("wait: %.100s", strerror(errno));
 621         else if (wait_pid != pid)
 622                 error("Strange, wait returned pid %d, expected %d",
 623                     wait_pid, pid);
 624
 625         /* Check if it exited normally. */
 626         if (WIFEXITED(wait_status)) {
 627                 /* Yes, normal exit.  Get exit status and send it to the client. */
 628                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 629                 packet_start(SSH_SMSG_EXITSTATUS);
 630                 packet_put_int(WEXITSTATUS(wait_status));
 631                 packet_send();
 632                 packet_write_wait();
 633
 634                 /*
 635                  * Wait for exit confirmation.  Note that there might be
 636                  * other packets coming before it; however, the program has
 637                  * already died so we just ignore them.  The client is
 638                  * supposed to respond with the confirmation when it receives
 639                  * the exit status.
 640                  */
 641                 do {
 642                         int plen;
 643                         type = packet_read(&plen);
 644                 }
 645                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 646
 647                 debug("Received exit confirmation.");
 648                 return;
 649         }
 650         /* Check if the program terminated due to a signal. */
 651         if (WIFSIGNALED(wait_status))
 652                 packet_disconnect("Command terminated on signal %d.",
 653                                   WTERMSIG(wait_status));
 654
 655         /* Some weird exit cause.  Just exit. */
 656         packet_disconnect("wait returned status %04x.", wait_status);
 657         /* NOTREACHED */
 658 }
 659
 660 void
 661 server_loop2(void)
 662 {
 663         fd_set *readset = NULL, *writeset = NULL;
 664         int rekeying = 0, max_fd, status;
 665         pid_t pid;
 666
 667         debug("Entering interactive session for SSH2.");
 668
 669         mysignal(SIGCHLD, sigchld_handler);
 670         child_terminated = 0;
 671         connection_in = packet_get_connection_in();
 672         connection_out = packet_get_connection_out();
 673
 674         max_fd = MAX(connection_in, connection_out);
 675
 676         server_init_dispatch();
 677
 678         for (;;) {
 679                 process_buffered_input_packets();
 680
 681                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 682
 683                 if (!rekeying && packet_not_very_much_data_to_write())
 684                         channel_output_poll();
 685                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 686                     rekeying);
 687                 if (child_terminated) {
 688                         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 689                                 session_close_by_pid(pid, status);
 690                         child_terminated = 0;
 691                 }
 692                 if (!rekeying)
 693                         channel_after_select(readset, writeset);
 694                 process_input(readset);
 695                 if (connection_closed)
 696                         break;
 697                 process_output(writeset);
 698         }
 699         if (readset)
 700                 xfree(readset);
 701         if (writeset)
 702                 xfree(writeset);
 703
 704         channel_free_all();
 705
 706         signal(SIGCHLD, SIG_DFL);
 707         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 708                 session_close_by_pid(pid, status);
 709 }
 710
 711 static void
 712 server_input_channel_failure(int type, int plen, void *ctxt)
 713 {
 714         debug("Got CHANNEL_FAILURE for keepalive");
 715         /*
 716          * reset timeout, since we got a sane answer from the client.
 717          * even if this was generated by something other than
 718          * the bogus CHANNEL_REQUEST we send for keepalives.
 719          */
 720         client_alive_timeouts = 0;
 721 }
 722
 723
 724 static void
 725 server_input_stdin_data(int type, int plen, void *ctxt)
 726 {
 727         char *data;
 728         u_int data_len;
 729
 730         /* Stdin data from the client.  Append it to the buffer. */
 731         /* Ignore any data if the client has closed stdin. */
 732         if (fdin == -1)
 733                 return;
 734         data = packet_get_string(&data_len);
 735         packet_integrity_check(plen, (4 + data_len), type);
 736         buffer_append(&stdin_buffer, data, data_len);
 737         memset(data, 0, data_len);
 738         xfree(data);
 739 }
 740
 741 static void
 742 server_input_eof(int type, int plen, void *ctxt)
 743 {
 744         /*
 745          * Eof from the client.  The stdin descriptor to the
 746          * program will be closed when all buffered data has
 747          * drained.
 748          */
 749         debug("EOF received for stdin.");
 750         packet_integrity_check(plen, 0, type);
 751         stdin_eof = 1;
 752 }
 753
 754 static void
 755 server_input_window_size(int type, int plen, void *ctxt)
 756 {
 757         int row = packet_get_int();
 758         int col = packet_get_int();
 759         int xpixel = packet_get_int();
 760         int ypixel = packet_get_int();
 761
 762         debug("Window change received.");
 763         packet_integrity_check(plen, 4 * 4, type);
 764         if (fdin != -1)
 765                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 766 }
 767
 768 static Channel *
 769 server_request_direct_tcpip(char *ctype)
 770 {
 771         Channel *c;
 772         int sock;
 773         char *target, *originator;
 774         int target_port, originator_port;
 775
 776         target = packet_get_string(NULL);
 777         target_port = packet_get_int();
 778         originator = packet_get_string(NULL);
 779         originator_port = packet_get_int();
 780         packet_done();
 781
 782         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 783            originator, originator_port, target, target_port);
 784
 785         /* XXX check permission */
 786         sock = channel_connect_to(target, target_port);
 787         xfree(target);
 788         xfree(originator);
 789         if (sock < 0)
 790                 return NULL;
 791         c = channel_new(ctype, SSH_CHANNEL_CONNECTING,
 792             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 793             CHAN_TCP_PACKET_DEFAULT, 0, xstrdup("direct-tcpip"), 1);
 794         if (c == NULL) {
 795                 error("server_request_direct_tcpip: channel_new failed");
 796                 close(sock);
 797         }
 798         return c;
 799 }
 800
 801 static Channel *
 802 server_request_session(char *ctype)
 803 {
 804         Channel *c;
 805
 806         debug("input_session_request");
 807         packet_done();
 808         /*
 809          * A server session has no fd to read or write until a
 810          * CHANNEL_REQUEST for a shell is made, so we set the type to
 811          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 812          * CHANNEL_REQUEST messages is registered.
 813          */
 814         c = channel_new(ctype, SSH_CHANNEL_LARVAL,
 815             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 816             0, xstrdup("server-session"), 1);
 817         if (c == NULL) {
 818                 error("server_request_session: channel_new failed");
 819                 return NULL;
 820         }
 821         if (session_open(c->self) != 1) {
 822                 debug("session open failed, free channel %d", c->self);
 823                 channel_free(c);
 824                 return NULL;
 825         }
 826         channel_register_callback(c->self, SSH2_MSG_CHANNEL_REQUEST,
 827             session_input_channel_req, (void *)0);
 828         channel_register_cleanup(c->self, session_close_by_channel);
 829         return c;
 830 }
 831
 832 static void
 833 server_input_channel_open(int type, int plen, void *ctxt)
 834 {
 835         Channel *c = NULL;
 836         char *ctype;
 837         u_int len;
 838         int rchan;
 839         int rmaxpack;
 840         int rwindow;
 841
 842         ctype = packet_get_string(&len);
 843         rchan = packet_get_int();
 844         rwindow = packet_get_int();
 845         rmaxpack = packet_get_int();
 846
 847         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 848             ctype, rchan, rwindow, rmaxpack);
 849
 850         if (strcmp(ctype, "session") == 0) {
 851                 c = server_request_session(ctype);
 852         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 853                 c = server_request_direct_tcpip(ctype);
 854         }
 855         if (c != NULL) {
 856                 debug("server_input_channel_open: confirm %s", ctype);
 857                 c->remote_id = rchan;
 858                 c->remote_window = rwindow;
 859                 c->remote_maxpacket = rmaxpack;
 860                 if (c->type != SSH_CHANNEL_CONNECTING) {
 861                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 862                         packet_put_int(c->remote_id);
 863                         packet_put_int(c->self);
 864                         packet_put_int(c->local_window);
 865                         packet_put_int(c->local_maxpacket);
 866                         packet_send();
 867                 }
 868         } else {
 869                 debug("server_input_channel_open: failure %s", ctype);
 870                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 871                 packet_put_int(rchan);
 872                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
 873                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
 874                         packet_put_cstring("open failed");
 875                         packet_put_cstring("");
 876                 }
 877                 packet_send();
 878         }
 879         xfree(ctype);
 880 }
 881
 882 static void
 883 server_input_global_request(int type, int plen, void *ctxt)
 884 {
 885         char *rtype;
 886         int want_reply;
 887         int success = 0;
 888
 889         rtype = packet_get_string(NULL);
 890         want_reply = packet_get_char();
 891         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 892
 893         /* -R style forwarding */
 894         if (strcmp(rtype, "tcpip-forward") == 0) {
 895                 struct passwd *pw;
 896                 char *listen_address;
 897                 u_short listen_port;
 898
 899                 pw = auth_get_user();
 900                 if (pw == NULL)
 901                         fatal("server_input_global_request: no user");
 902                 listen_address = packet_get_string(NULL); /* XXX currently ignored */
 903                 listen_port = (u_short)packet_get_int();
 904                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 905                     listen_address, listen_port);
 906
 907                 /* check permissions */
 908                 if (!options.allow_tcp_forwarding ||
 909                     no_port_forwarding_flag ||
 910                     (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)) {
 911                         success = 0;
 912                         packet_send_debug("Server has disabled port forwarding.");
 913                 } else {
 914                         /* Start listening on the port */
 915                         success = channel_request_forwarding(
 916                             listen_address, listen_port,
 917                             /*unspec host_to_connect*/ "<unspec host>",
 918                             /*unspec port_to_connect*/ 0,
 919                             options.gateway_ports, /*remote*/ 1);
 920                 }
 921                 xfree(listen_address);
 922         }
 923         if (want_reply) {
 924                 packet_start(success ?
 925                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 926                 packet_send();
 927                 packet_write_wait();
 928         }
 929         xfree(rtype);
 930 }
 931
 932 static void
 933 server_init_dispatch_20(void)
 934 {
 935         debug("server_init_dispatch_20");
 936         dispatch_init(&dispatch_protocol_error);
 937         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 938         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 939         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 940         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 941         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 942         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 943         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 944         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request);
 945         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 946         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 947         /* client_alive */
 948         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_channel_failure);
 949         /* rekeying */
 950         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 951 }
 952 static void
 953 server_init_dispatch_13(void)
 954 {
 955         debug("server_init_dispatch_13");
 956         dispatch_init(NULL);
 957         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
 958         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
 959         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
 960         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
 961         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
 962         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
 963         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 964         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 965         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
 966 }
 967 static void
 968 server_init_dispatch_15(void)
 969 {
 970         server_init_dispatch_13();
 971         debug("server_init_dispatch_15");
 972         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
 973         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
 974 }
 975 static void
 976 server_init_dispatch(void)
 977 {
 978         if (compat20)
 979                 server_init_dispatch_20();
 980         else if (compat13)
 981                 server_init_dispatch_13();
 982         else
 983                 server_init_dispatch_15();
 984 }
 985