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, 2001 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 1.76 2001/07/17 21:04:58 markus 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 static Authctxt *xxx_authctxt;
  63
  64 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  65 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  66 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  67 static int fdin;                /* Descriptor for stdin (for writing) */
  68 static int fdout;               /* Descriptor for stdout (for reading);
  69                                    May be same number as fdin. */
  70 static int fderr;               /* Descriptor for stderr.  May be -1. */
  71 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  72 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  73 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  74 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  75 static int stdin_eof = 0;       /* EOF message received from client. */
  76 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  77 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  78 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  79 static int connection_in;       /* Connection to client (input). */
  80 static int connection_out;      /* Connection to client (output). */
  81 static int connection_closed = 0;       /* Connection to client closed. */
  82 static u_int buffer_high;       /* "Soft" max buffer size. */
  83
  84 /*
  85  * This SIGCHLD kludge is used to detect when the child exits.  The server
  86  * will exit after that, as soon as forwarded connections have terminated.
  87  */
  88
  89 static volatile int child_terminated;   /* The child has terminated. */
  90
  91 /* prototypes */
  92 static void server_init_dispatch(void);
  93
  94 int client_alive_timeouts = 0;
  95
  96 static void
  97 sigchld_handler(int sig)
  98 {
  99         int save_errno = errno;
 100         debug("Received SIGCHLD.");
 101         child_terminated = 1;
 102         mysignal(SIGCHLD, sigchld_handler);
 103         errno = save_errno;
 104 }
 105
 106 /*
 107  * Make packets from buffered stderr data, and buffer it for sending
 108  * to the client.
 109  */
 110 static void
 111 make_packets_from_stderr_data(void)
 112 {
 113         int len;
 114
 115         /* Send buffered stderr data to the client. */
 116         while (buffer_len(&stderr_buffer) > 0 &&
 117             packet_not_very_much_data_to_write()) {
 118                 len = buffer_len(&stderr_buffer);
 119                 if (packet_is_interactive()) {
 120                         if (len > 512)
 121                                 len = 512;
 122                 } else {
 123                         /* Keep the packets at reasonable size. */
 124                         if (len > packet_get_maxsize())
 125                                 len = packet_get_maxsize();
 126                 }
 127                 packet_start(SSH_SMSG_STDERR_DATA);
 128                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 129                 packet_send();
 130                 buffer_consume(&stderr_buffer, len);
 131                 stderr_bytes += len;
 132         }
 133 }
 134
 135 /*
 136  * Make packets from buffered stdout data, and buffer it for sending to the
 137  * client.
 138  */
 139 static void
 140 make_packets_from_stdout_data(void)
 141 {
 142         int len;
 143
 144         /* Send buffered stdout data to the client. */
 145         while (buffer_len(&stdout_buffer) > 0 &&
 146             packet_not_very_much_data_to_write()) {
 147                 len = buffer_len(&stdout_buffer);
 148                 if (packet_is_interactive()) {
 149                         if (len > 512)
 150                                 len = 512;
 151                 } else {
 152                         /* Keep the packets at reasonable size. */
 153                         if (len > packet_get_maxsize())
 154                                 len = packet_get_maxsize();
 155                 }
 156                 packet_start(SSH_SMSG_STDOUT_DATA);
 157                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 158                 packet_send();
 159                 buffer_consume(&stdout_buffer, len);
 160                 stdout_bytes += len;
 161         }
 162 }
 163
 164 /*
 165  * Sleep in select() until we can do something.  This will initialize the
 166  * select masks.  Upon return, the masks will indicate which descriptors
 167  * have data or can accept data.  Optionally, a maximum time can be specified
 168  * for the duration of the wait (0 = infinite).
 169  */
 170 static void
 171 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 172     int *nallocp, u_int max_time_milliseconds)
 173 {
 174         struct timeval tv, *tvp;
 175         int ret;
 176         int client_alive_scheduled = 0;
 177
 178         /*
 179          * if using client_alive, set the max timeout accordingly,
 180          * and indicate that this particular timeout was for client
 181          * alive by setting the client_alive_scheduled flag.
 182          *
 183          * this could be randomized somewhat to make traffic
 184          * analysis more difficult, but we're not doing it yet.
 185          */
 186         if (compat20 &&
 187             max_time_milliseconds == 0 && options.client_alive_interval) {
 188                 client_alive_scheduled = 1;
 189                 max_time_milliseconds = options.client_alive_interval * 1000;
 190         }
 191
 192         /* When select fails we restart from here. */
 193 retry_select:
 194
 195         /* Allocate and update select() masks for channel descriptors. */
 196         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 197
 198         if (compat20) {
 199                 /* wrong: bad condition XXX */
 200                 if (channel_not_very_much_buffered_data())
 201                         FD_SET(connection_in, *readsetp);
 202         } else {
 203                 /*
 204                  * Read packets from the client unless we have too much
 205                  * buffered stdin or channel data.
 206                  */
 207                 if (buffer_len(&stdin_buffer) < buffer_high &&
 208                     channel_not_very_much_buffered_data())
 209                         FD_SET(connection_in, *readsetp);
 210                 /*
 211                  * If there is not too much data already buffered going to
 212                  * the client, try to get some more data from the program.
 213                  */
 214                 if (packet_not_very_much_data_to_write()) {
 215                         if (!fdout_eof)
 216                                 FD_SET(fdout, *readsetp);
 217                         if (!fderr_eof)
 218                                 FD_SET(fderr, *readsetp);
 219                 }
 220                 /*
 221                  * If we have buffered data, try to write some of that data
 222                  * to the program.
 223                  */
 224                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 225                         FD_SET(fdin, *writesetp);
 226         }
 227
 228         /*
 229          * If we have buffered packet data going to the client, mark that
 230          * descriptor.
 231          */
 232         if (packet_have_data_to_write())
 233                 FD_SET(connection_out, *writesetp);
 234
 235         /*
 236          * If child has terminated and there is enough buffer space to read
 237          * from it, then read as much as is available and exit.
 238          */
 239         if (child_terminated && packet_not_very_much_data_to_write())
 240                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 241                         max_time_milliseconds = 100;
 242
 243         if (max_time_milliseconds == 0)
 244                 tvp = NULL;
 245         else {
 246                 tv.tv_sec = max_time_milliseconds / 1000;
 247                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 248                 tvp = &tv;
 249         }
 250         if (tvp!=NULL)
 251                 debug3("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds);
 252
 253         /* Wait for something to happen, or the timeout to expire. */
 254         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 255
 256         if (ret == -1) {
 257                 if (errno != EINTR)
 258                         error("select: %.100s", strerror(errno));
 259                 else
 260                         goto retry_select;
 261         }
 262         if (ret == 0 && client_alive_scheduled) {
 263                 /* timeout, check to see how many we have had */
 264                 client_alive_timeouts++;
 265
 266                 if (client_alive_timeouts > options.client_alive_count_max ) {
 267                         packet_disconnect(
 268                                 "Timeout, your session not responding.");
 269                 } else {
 270                         /*
 271                          * send a bogus channel request with "wantreply"
 272                          * we should get back a failure
 273                          */
 274                         int id;
 275
 276                         id = channel_find_open();
 277                         if (id != -1) {
 278                                 channel_request_start(id,
 279                                   "keepalive@openssh.com", 1);
 280                                 packet_send();
 281                         } else
 282                                 packet_disconnect(
 283                                         "No open channels after timeout!");
 284                 }
 285         }
 286 }
 287
 288 /*
 289  * Processes input from the client and the program.  Input data is stored
 290  * in buffers and processed later.
 291  */
 292 static void
 293 process_input(fd_set * readset)
 294 {
 295         int len;
 296         char buf[16384];
 297
 298         /* Read and buffer any input data from the client. */
 299         if (FD_ISSET(connection_in, readset)) {
 300                 len = read(connection_in, buf, sizeof(buf));
 301                 if (len == 0) {
 302                         verbose("Connection closed by remote host.");
 303                         connection_closed = 1;
 304                         if (compat20)
 305                                 return;
 306                         fatal_cleanup();
 307                 } else if (len < 0) {
 308                         if (errno != EINTR && errno != EAGAIN) {
 309                                 verbose("Read error from remote host: %.100s", strerror(errno));
 310                                 fatal_cleanup();
 311                         }
 312                 } else {
 313                         /* Buffer any received data. */
 314                         packet_process_incoming(buf, len);
 315                 }
 316         }
 317         if (compat20)
 318                 return;
 319
 320         /* Read and buffer any available stdout data from the program. */
 321         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 322                 len = read(fdout, buf, sizeof(buf));
 323                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 324                         /* do nothing */
 325                 } else if (len <= 0) {
 326                         fdout_eof = 1;
 327                 } else {
 328                         buffer_append(&stdout_buffer, buf, len);
 329                         fdout_bytes += len;
 330                 }
 331         }
 332         /* Read and buffer any available stderr data from the program. */
 333         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 334                 len = read(fderr, buf, sizeof(buf));
 335                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 336                         /* do nothing */
 337                 } else if (len <= 0) {
 338                         fderr_eof = 1;
 339                 } else {
 340                         buffer_append(&stderr_buffer, buf, len);
 341                 }
 342         }
 343 }
 344
 345 /*
 346  * Sends data from internal buffers to client program stdin.
 347  */
 348 static void
 349 process_output(fd_set * writeset)
 350 {
 351         struct termios tio;
 352         int len;
 353
 354         /* Write buffered data to program stdin. */
 355         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 356                 len = write(fdin, buffer_ptr(&stdin_buffer),
 357                     buffer_len(&stdin_buffer));
 358                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 359                         /* do nothing */
 360                 } else if (len <= 0) {
 361 #ifdef USE_PIPES
 362                         close(fdin);
 363 #else
 364                         if (fdin != fdout)
 365                                 close(fdin);
 366                         else
 367                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 368 #endif
 369                         fdin = -1;
 370                 } else {
 371                         /* Successful write. */
 372                         if (fdin_is_tty && tcgetattr(fdin, &tio) == 0 &&
 373                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 374                                 /*
 375                                  * Simulate echo to reduce the impact of
 376                                  * traffic analysis
 377                                  */
 378                                 packet_send_ignore(len);
 379                                 packet_send();
 380                         }
 381                         /* Consume the data from the buffer. */
 382                         buffer_consume(&stdin_buffer, len);
 383                         /* Update the count of bytes written to the program. */
 384                         stdin_bytes += len;
 385                 }
 386         }
 387         /* Send any buffered packet data to the client. */
 388         if (FD_ISSET(connection_out, writeset))
 389                 packet_write_poll();
 390 }
 391
 392 /*
 393  * Wait until all buffered output has been sent to the client.
 394  * This is used when the program terminates.
 395  */
 396 static void
 397 drain_output(void)
 398 {
 399         /* Send any buffered stdout data to the client. */
 400         if (buffer_len(&stdout_buffer) > 0) {
 401                 packet_start(SSH_SMSG_STDOUT_DATA);
 402                 packet_put_string(buffer_ptr(&stdout_buffer),
 403                                   buffer_len(&stdout_buffer));
 404                 packet_send();
 405                 /* Update the count of sent bytes. */
 406                 stdout_bytes += buffer_len(&stdout_buffer);
 407         }
 408         /* Send any buffered stderr data to the client. */
 409         if (buffer_len(&stderr_buffer) > 0) {
 410                 packet_start(SSH_SMSG_STDERR_DATA);
 411                 packet_put_string(buffer_ptr(&stderr_buffer),
 412                                   buffer_len(&stderr_buffer));
 413                 packet_send();
 414                 /* Update the count of sent bytes. */
 415                 stderr_bytes += buffer_len(&stderr_buffer);
 416         }
 417         /* Wait until all buffered data has been written to the client. */
 418         packet_write_wait();
 419 }
 420
 421 static void
 422 process_buffered_input_packets(void)
 423 {
 424         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 425 }
 426
 427 /*
 428  * Performs the interactive session.  This handles data transmission between
 429  * the client and the program.  Note that the notion of stdin, stdout, and
 430  * stderr in this function is sort of reversed: this function writes to
 431  * stdin (of the child program), and reads from stdout and stderr (of the
 432  * child program).
 433  */
 434 void
 435 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 436 {
 437         fd_set *readset = NULL, *writeset = NULL;
 438         int max_fd = 0, nalloc = 0;
 439         int wait_status;        /* Status returned by wait(). */
 440         pid_t wait_pid;         /* pid returned by wait(). */
 441         int waiting_termination = 0;    /* Have displayed waiting close message. */
 442         u_int max_time_milliseconds;
 443         u_int previous_stdout_buffer_bytes;
 444         u_int stdout_buffer_bytes;
 445         int type;
 446
 447         debug("Entering interactive session.");
 448
 449         /* Initialize the SIGCHLD kludge. */
 450         child_terminated = 0;
 451         signal(SIGCHLD, sigchld_handler);
 452
 453         /* Initialize our global variables. */
 454         fdin = fdin_arg;
 455         fdout = fdout_arg;
 456         fderr = fderr_arg;
 457
 458         /* nonblocking IO */
 459         set_nonblock(fdin);
 460         set_nonblock(fdout);
 461         /* we don't have stderr for interactive terminal sessions, see below */
 462         if (fderr != -1)
 463                 set_nonblock(fderr);
 464
 465         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 466                 fdin_is_tty = 1;
 467
 468         connection_in = packet_get_connection_in();
 469         connection_out = packet_get_connection_out();
 470
 471         previous_stdout_buffer_bytes = 0;
 472
 473         /* Set approximate I/O buffer size. */
 474         if (packet_is_interactive())
 475                 buffer_high = 4096;
 476         else
 477                 buffer_high = 64 * 1024;
 478
 479 #if 0
 480         /* Initialize max_fd to the maximum of the known file descriptors. */
 481         max_fd = MAX(connection_in, connection_out);
 482         max_fd = MAX(max_fd, fdin);
 483         max_fd = MAX(max_fd, fdout);
 484         if (fderr != -1)
 485                 max_fd = MAX(max_fd, fderr);
 486 #endif
 487
 488         /* Initialize Initialize buffers. */
 489         buffer_init(&stdin_buffer);
 490         buffer_init(&stdout_buffer);
 491         buffer_init(&stderr_buffer);
 492
 493         /*
 494          * If we have no separate fderr (which is the case when we have a pty
 495          * - there we cannot make difference between data sent to stdout and
 496          * stderr), indicate that we have seen an EOF from stderr.  This way
 497          * we don\'t need to check the descriptor everywhere.
 498          */
 499         if (fderr == -1)
 500                 fderr_eof = 1;
 501
 502         server_init_dispatch();
 503
 504         /* Main loop of the server for the interactive session mode. */
 505         for (;;) {
 506
 507                 /* Process buffered packets from the client. */
 508                 process_buffered_input_packets();
 509
 510                 /*
 511                  * If we have received eof, and there is no more pending
 512                  * input data, cause a real eof by closing fdin.
 513                  */
 514                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 515 #ifdef USE_PIPES
 516                         close(fdin);
 517 #else
 518                         if (fdin != fdout)
 519                                 close(fdin);
 520                         else
 521                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 522 #endif
 523                         fdin = -1;
 524                 }
 525                 /* Make packets from buffered stderr data to send to the client. */
 526                 make_packets_from_stderr_data();
 527
 528                 /*
 529                  * Make packets from buffered stdout data to send to the
 530                  * client. If there is very little to send, this arranges to
 531                  * not send them now, but to wait a short while to see if we
 532                  * are getting more data. This is necessary, as some systems
 533                  * wake up readers from a pty after each separate character.
 534                  */
 535                 max_time_milliseconds = 0;
 536                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 537                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 538                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 539                         /* try again after a while */
 540                         max_time_milliseconds = 10;
 541                 } else {
 542                         /* Send it now. */
 543                         make_packets_from_stdout_data();
 544                 }
 545                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 546
 547                 /* Send channel data to the client. */
 548                 if (packet_not_very_much_data_to_write())
 549                         channel_output_poll();
 550
 551                 /*
 552                  * Bail out of the loop if the program has closed its output
 553                  * descriptors, and we have no more data to send to the
 554                  * client, and there is no pending buffered data.
 555                  */
 556                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 557                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 558                         if (!channel_still_open())
 559                                 break;
 560                         if (!waiting_termination) {
 561                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 562                                 char *cp;
 563                                 waiting_termination = 1;
 564                                 buffer_append(&stderr_buffer, s, strlen(s));
 565
 566                                 /* Display list of open channels. */
 567                                 cp = channel_open_message();
 568                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 569                                 xfree(cp);
 570                         }
 571                 }
 572                 max_fd = MAX(connection_in, connection_out);
 573                 max_fd = MAX(max_fd, fdin);
 574                 max_fd = MAX(max_fd, fdout);
 575                 max_fd = MAX(max_fd, fderr);
 576
 577                 /* Sleep in select() until we can do something. */
 578                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 579                     &nalloc, max_time_milliseconds);
 580
 581                 /* Process any channel events. */
 582                 channel_after_select(readset, writeset);
 583
 584                 /* Process input from the client and from program stdout/stderr. */
 585                 process_input(readset);
 586
 587                 /* Process output to the client and to program stdin. */
 588                 process_output(writeset);
 589         }
 590         if (readset)
 591                 xfree(readset);
 592         if (writeset)
 593                 xfree(writeset);
 594
 595         /* Cleanup and termination code. */
 596
 597         /* Wait until all output has been sent to the client. */
 598         drain_output();
 599
 600         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 601               stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 602
 603         /* Free and clear the buffers. */
 604         buffer_free(&stdin_buffer);
 605         buffer_free(&stdout_buffer);
 606         buffer_free(&stderr_buffer);
 607
 608         /* Close the file descriptors. */
 609         if (fdout != -1)
 610                 close(fdout);
 611         fdout = -1;
 612         fdout_eof = 1;
 613         if (fderr != -1)
 614                 close(fderr);
 615         fderr = -1;
 616         fderr_eof = 1;
 617         if (fdin != -1)
 618                 close(fdin);
 619         fdin = -1;
 620
 621         channel_free_all();
 622
 623         /* We no longer want our SIGCHLD handler to be called. */
 624         signal(SIGCHLD, SIG_DFL);
 625
 626         wait_pid = waitpid(-1, &wait_status, child_terminated ? WNOHANG : 0);
 627         if (wait_pid == -1)
 628                 packet_disconnect("wait: %.100s", strerror(errno));
 629         else if (wait_pid != pid)
 630                 error("Strange, wait returned pid %d, expected %d",
 631                     wait_pid, pid);
 632
 633         /* Check if it exited normally. */
 634         if (WIFEXITED(wait_status)) {
 635                 /* Yes, normal exit.  Get exit status and send it to the client. */
 636                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 637                 packet_start(SSH_SMSG_EXITSTATUS);
 638                 packet_put_int(WEXITSTATUS(wait_status));
 639                 packet_send();
 640                 packet_write_wait();
 641
 642                 /*
 643                  * Wait for exit confirmation.  Note that there might be
 644                  * other packets coming before it; however, the program has
 645                  * already died so we just ignore them.  The client is
 646                  * supposed to respond with the confirmation when it receives
 647                  * the exit status.
 648                  */
 649                 do {
 650                         int plen;
 651                         type = packet_read(&plen);
 652                 }
 653                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 654
 655                 debug("Received exit confirmation.");
 656                 return;
 657         }
 658         /* Check if the program terminated due to a signal. */
 659         if (WIFSIGNALED(wait_status))
 660                 packet_disconnect("Command terminated on signal %d.",
 661                                   WTERMSIG(wait_status));
 662
 663         /* Some weird exit cause.  Just exit. */
 664         packet_disconnect("wait returned status %04x.", wait_status);
 665         /* NOTREACHED */
 666 }
 667
 668 void
 669 server_loop2(Authctxt *authctxt)
 670 {
 671         fd_set *readset = NULL, *writeset = NULL;
 672         int rekeying = 0, max_fd, status, nalloc = 0;
 673         pid_t pid;
 674
 675         debug("Entering interactive session for SSH2.");
 676
 677         mysignal(SIGCHLD, sigchld_handler);
 678         child_terminated = 0;
 679         connection_in = packet_get_connection_in();
 680         connection_out = packet_get_connection_out();
 681
 682         max_fd = MAX(connection_in, connection_out);
 683         xxx_authctxt = authctxt;
 684
 685         server_init_dispatch();
 686
 687         for (;;) {
 688                 process_buffered_input_packets();
 689
 690                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 691
 692                 if (!rekeying && packet_not_very_much_data_to_write())
 693                         channel_output_poll();
 694                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 695                     &nalloc, 0);
 696                 if (child_terminated) {
 697                         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 698                                 session_close_by_pid(pid, status);
 699                         child_terminated = 0;
 700                 }
 701                 if (!rekeying)
 702                         channel_after_select(readset, writeset);
 703                 process_input(readset);
 704                 if (connection_closed)
 705                         break;
 706                 process_output(writeset);
 707         }
 708         if (readset)
 709                 xfree(readset);
 710         if (writeset)
 711                 xfree(writeset);
 712
 713         signal(SIGCHLD, SIG_DFL);
 714
 715         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 716                 session_close_by_pid(pid, status);
 717         /*
 718          * there is a race between channel_free_all() killing children and
 719          * children dying before kill()
 720          */
 721         channel_detach_all();
 722         channel_stop_listening();
 723
 724         while (session_have_children()) {
 725                 pid = waitpid(-1, &status, 0);
 726                 if (pid > 0)
 727                         session_close_by_pid(pid, status);
 728                 else {
 729                         error("waitpid returned %d: %s", pid, strerror(errno));
 730                         break;
 731                 }
 732         }
 733         channel_free_all();
 734 }
 735
 736 static void
 737 server_input_channel_failure(int type, int plen, void *ctxt)
 738 {
 739         debug("Got CHANNEL_FAILURE for keepalive");
 740         /*
 741          * reset timeout, since we got a sane answer from the client.
 742          * even if this was generated by something other than
 743          * the bogus CHANNEL_REQUEST we send for keepalives.
 744          */
 745         client_alive_timeouts = 0;
 746 }
 747
 748
 749 static void
 750 server_input_stdin_data(int type, int plen, void *ctxt)
 751 {
 752         char *data;
 753         u_int data_len;
 754
 755         /* Stdin data from the client.  Append it to the buffer. */
 756         /* Ignore any data if the client has closed stdin. */
 757         if (fdin == -1)
 758                 return;
 759         data = packet_get_string(&data_len);
 760         packet_integrity_check(plen, (4 + data_len), type);
 761         buffer_append(&stdin_buffer, data, data_len);
 762         memset(data, 0, data_len);
 763         xfree(data);
 764 }
 765
 766 static void
 767 server_input_eof(int type, int plen, void *ctxt)
 768 {
 769         /*
 770          * Eof from the client.  The stdin descriptor to the
 771          * program will be closed when all buffered data has
 772          * drained.
 773          */
 774         debug("EOF received for stdin.");
 775         packet_integrity_check(plen, 0, type);
 776         stdin_eof = 1;
 777 }
 778
 779 static void
 780 server_input_window_size(int type, int plen, void *ctxt)
 781 {
 782         int row = packet_get_int();
 783         int col = packet_get_int();
 784         int xpixel = packet_get_int();
 785         int ypixel = packet_get_int();
 786
 787         debug("Window change received.");
 788         packet_integrity_check(plen, 4 * 4, type);
 789         if (fdin != -1)
 790                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 791 }
 792
 793 static Channel *
 794 server_request_direct_tcpip(char *ctype)
 795 {
 796         Channel *c;
 797         int sock;
 798         char *target, *originator;
 799         int target_port, originator_port;
 800
 801         target = packet_get_string(NULL);
 802         target_port = packet_get_int();
 803         originator = packet_get_string(NULL);
 804         originator_port = packet_get_int();
 805         packet_done();
 806
 807         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 808            originator, originator_port, target, target_port);
 809
 810         /* XXX check permission */
 811         sock = channel_connect_to(target, target_port);
 812         xfree(target);
 813         xfree(originator);
 814         if (sock < 0)
 815                 return NULL;
 816         c = channel_new(ctype, SSH_CHANNEL_CONNECTING,
 817             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 818             CHAN_TCP_PACKET_DEFAULT, 0, xstrdup("direct-tcpip"), 1);
 819         if (c == NULL) {
 820                 error("server_request_direct_tcpip: channel_new failed");
 821                 close(sock);
 822         }
 823         return c;
 824 }
 825
 826 static Channel *
 827 server_request_session(char *ctype)
 828 {
 829         Channel *c;
 830
 831         debug("input_session_request");
 832         packet_done();
 833         /*
 834          * A server session has no fd to read or write until a
 835          * CHANNEL_REQUEST for a shell is made, so we set the type to
 836          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 837          * CHANNEL_REQUEST messages is registered.
 838          */
 839         c = channel_new(ctype, SSH_CHANNEL_LARVAL,
 840             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 841             0, xstrdup("server-session"), 1);
 842         if (c == NULL) {
 843                 error("server_request_session: channel_new failed");
 844                 return NULL;
 845         }
 846         if (session_open(xxx_authctxt, c->self) != 1) {
 847                 debug("session open failed, free channel %d", c->self);
 848                 channel_free(c);
 849                 return NULL;
 850         }
 851         channel_register_callback(c->self, SSH2_MSG_CHANNEL_REQUEST,
 852             session_input_channel_req, (void *)0);
 853         channel_register_cleanup(c->self, session_close_by_channel);
 854         return c;
 855 }
 856
 857 static void
 858 server_input_channel_open(int type, int plen, void *ctxt)
 859 {
 860         Channel *c = NULL;
 861         char *ctype;
 862         u_int len;
 863         int rchan;
 864         int rmaxpack;
 865         int rwindow;
 866
 867         ctype = packet_get_string(&len);
 868         rchan = packet_get_int();
 869         rwindow = packet_get_int();
 870         rmaxpack = packet_get_int();
 871
 872         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 873             ctype, rchan, rwindow, rmaxpack);
 874
 875         if (strcmp(ctype, "session") == 0) {
 876                 c = server_request_session(ctype);
 877         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 878                 c = server_request_direct_tcpip(ctype);
 879         }
 880         if (c != NULL) {
 881                 debug("server_input_channel_open: confirm %s", ctype);
 882                 c->remote_id = rchan;
 883                 c->remote_window = rwindow;
 884                 c->remote_maxpacket = rmaxpack;
 885                 if (c->type != SSH_CHANNEL_CONNECTING) {
 886                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 887                         packet_put_int(c->remote_id);
 888                         packet_put_int(c->self);
 889                         packet_put_int(c->local_window);
 890                         packet_put_int(c->local_maxpacket);
 891                         packet_send();
 892                 }
 893         } else {
 894                 debug("server_input_channel_open: failure %s", ctype);
 895                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 896                 packet_put_int(rchan);
 897                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
 898                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
 899                         packet_put_cstring("open failed");
 900                         packet_put_cstring("");
 901                 }
 902                 packet_send();
 903         }
 904         xfree(ctype);
 905 }
 906
 907 static void
 908 server_input_global_request(int type, int plen, void *ctxt)
 909 {
 910         char *rtype;
 911         int want_reply;
 912         int success = 0;
 913
 914         rtype = packet_get_string(NULL);
 915         want_reply = packet_get_char();
 916         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 917
 918         /* -R style forwarding */
 919         if (strcmp(rtype, "tcpip-forward") == 0) {
 920                 struct passwd *pw;
 921                 char *listen_address;
 922                 u_short listen_port;
 923
 924                 pw = auth_get_user();
 925                 if (pw == NULL)
 926                         fatal("server_input_global_request: no user");
 927                 listen_address = packet_get_string(NULL); /* XXX currently ignored */
 928                 listen_port = (u_short)packet_get_int();
 929                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 930                     listen_address, listen_port);
 931
 932                 /* check permissions */
 933                 if (!options.allow_tcp_forwarding ||
 934                     no_port_forwarding_flag ||
 935                     (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)) {
 936                         success = 0;
 937                         packet_send_debug("Server has disabled port forwarding.");
 938                 } else {
 939                         /* Start listening on the port */
 940                         success = channel_request_forwarding(
 941                             listen_address, listen_port,
 942                             /*unspec host_to_connect*/ "<unspec host>",
 943                             /*unspec port_to_connect*/ 0,
 944                             options.gateway_ports, /*remote*/ 1);
 945                 }
 946                 xfree(listen_address);
 947         }
 948         if (want_reply) {
 949                 packet_start(success ?
 950                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 951                 packet_send();
 952                 packet_write_wait();
 953         }
 954         xfree(rtype);
 955 }
 956
 957 static void
 958 server_init_dispatch_20(void)
 959 {
 960         debug("server_init_dispatch_20");
 961         dispatch_init(&dispatch_protocol_error);
 962         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 963         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 964         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 965         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 966         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 967         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 968         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 969         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request);
 970         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 971         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 972         /* client_alive */
 973         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_channel_failure);
 974         /* rekeying */
 975         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 976 }
 977 static void
 978 server_init_dispatch_13(void)
 979 {
 980         debug("server_init_dispatch_13");
 981         dispatch_init(NULL);
 982         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
 983         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
 984         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
 985         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
 986         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
 987         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
 988         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 989         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 990         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
 991 }
 992 static void
 993 server_init_dispatch_15(void)
 994 {
 995         server_init_dispatch_13();
 996         debug("server_init_dispatch_15");
 997         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
 998         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
 999 }
1000 static void
1001 server_init_dispatch(void)
1002 {
1003         if (compat20)
1004                 server_init_dispatch_20();
1005         else if (compat13)
1006                 server_init_dispatch_13();
1007         else
1008                 server_init_dispatch_15();
1009 }