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 1.126 2006/02/10 01:44:26 stevesk Exp $");
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42
  43 #include <termios.h>
  44
  45 #include "xmalloc.h"
  46 #include "packet.h"
  47 #include "buffer.h"
  48 #include "log.h"
  49 #include "servconf.h"
  50 #include "canohost.h"
  51 #include "sshpty.h"
  52 #include "channels.h"
  53 #include "compat.h"
  54 #include "ssh1.h"
  55 #include "ssh2.h"
  56 #include "auth.h"
  57 #include "session.h"
  58 #include "dispatch.h"
  59 #include "auth-options.h"
  60 #include "serverloop.h"
  61 #include "misc.h"
  62 #include "kex.h"
  63
  64 extern ServerOptions options;
  65
  66 /* XXX */
  67 extern Kex *xxx_kex;
  68 extern Authctxt *the_authctxt;
  69 extern int use_privsep;
  70
  71 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  72 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  73 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  74 static int fdin;                /* Descriptor for stdin (for writing) */
  75 static int fdout;               /* Descriptor for stdout (for reading);
  76                                    May be same number as fdin. */
  77 static int fderr;               /* Descriptor for stderr.  May be -1. */
  78 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  79 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  80 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  81 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  82 static int stdin_eof = 0;       /* EOF message received from client. */
  83 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  84 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  85 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  86 static int connection_in;       /* Connection to client (input). */
  87 static int connection_out;      /* Connection to client (output). */
  88 static int connection_closed = 0;       /* Connection to client closed. */
  89 static u_int buffer_high;       /* "Soft" max buffer size. */
  90 static int client_alive_timeouts = 0;
  91
  92 /*
  93  * This SIGCHLD kludge is used to detect when the child exits.  The server
  94  * will exit after that, as soon as forwarded connections have terminated.
  95  */
  96
  97 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  98
  99 /* Cleanup on signals (!use_privsep case only) */
 100 static volatile sig_atomic_t received_sigterm = 0;
 101
 102 /* prototypes */
 103 static void server_init_dispatch(void);
 104
 105 /*
 106  * we write to this pipe if a SIGCHLD is caught in order to avoid
 107  * the race between select() and child_terminated
 108  */
 109 static int notify_pipe[2];
 110 static void
 111 notify_setup(void)
 112 {
 113         if (pipe(notify_pipe) < 0) {
 114                 error("pipe(notify_pipe) failed %s", strerror(errno));
 115         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 116             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 117                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 118                 close(notify_pipe[0]);
 119                 close(notify_pipe[1]);
 120         } else {
 121                 set_nonblock(notify_pipe[0]);
 122                 set_nonblock(notify_pipe[1]);
 123                 return;
 124         }
 125         notify_pipe[0] = -1;    /* read end */
 126         notify_pipe[1] = -1;    /* write end */
 127 }
 128 static void
 129 notify_parent(void)
 130 {
 131         if (notify_pipe[1] != -1)
 132                 write(notify_pipe[1], "", 1);
 133 }
 134 static void
 135 notify_prepare(fd_set *readset)
 136 {
 137         if (notify_pipe[0] != -1)
 138                 FD_SET(notify_pipe[0], readset);
 139 }
 140 static void
 141 notify_done(fd_set *readset)
 142 {
 143         char c;
 144
 145         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 146                 while (read(notify_pipe[0], &c, 1) != -1)
 147                         debug2("notify_done: reading");
 148 }
 149
 150 static void
 151 sigchld_handler(int sig)
 152 {
 153         int save_errno = errno;
 154         debug("Received SIGCHLD.");
 155         child_terminated = 1;
 156 #ifndef _UNICOS
 157         mysignal(SIGCHLD, sigchld_handler);
 158 #endif
 159         notify_parent();
 160         errno = save_errno;
 161 }
 162
 163 static void
 164 sigterm_handler(int sig)
 165 {
 166         received_sigterm = sig;
 167 }
 168
 169 /*
 170  * Make packets from buffered stderr data, and buffer it for sending
 171  * to the client.
 172  */
 173 static void
 174 make_packets_from_stderr_data(void)
 175 {
 176         u_int len;
 177
 178         /* Send buffered stderr data to the client. */
 179         while (buffer_len(&stderr_buffer) > 0 &&
 180             packet_not_very_much_data_to_write()) {
 181                 len = buffer_len(&stderr_buffer);
 182                 if (packet_is_interactive()) {
 183                         if (len > 512)
 184                                 len = 512;
 185                 } else {
 186                         /* Keep the packets at reasonable size. */
 187                         if (len > packet_get_maxsize())
 188                                 len = packet_get_maxsize();
 189                 }
 190                 packet_start(SSH_SMSG_STDERR_DATA);
 191                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 192                 packet_send();
 193                 buffer_consume(&stderr_buffer, len);
 194                 stderr_bytes += len;
 195         }
 196 }
 197
 198 /*
 199  * Make packets from buffered stdout data, and buffer it for sending to the
 200  * client.
 201  */
 202 static void
 203 make_packets_from_stdout_data(void)
 204 {
 205         u_int len;
 206
 207         /* Send buffered stdout data to the client. */
 208         while (buffer_len(&stdout_buffer) > 0 &&
 209             packet_not_very_much_data_to_write()) {
 210                 len = buffer_len(&stdout_buffer);
 211                 if (packet_is_interactive()) {
 212                         if (len > 512)
 213                                 len = 512;
 214                 } else {
 215                         /* Keep the packets at reasonable size. */
 216                         if (len > packet_get_maxsize())
 217                                 len = packet_get_maxsize();
 218                 }
 219                 packet_start(SSH_SMSG_STDOUT_DATA);
 220                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 221                 packet_send();
 222                 buffer_consume(&stdout_buffer, len);
 223                 stdout_bytes += len;
 224         }
 225 }
 226
 227 static void
 228 client_alive_check(void)
 229 {
 230         int channel_id;
 231
 232         /* timeout, check to see how many we have had */
 233         if (++client_alive_timeouts > options.client_alive_count_max)
 234                 packet_disconnect("Timeout, your session not responding.");
 235
 236         /*
 237          * send a bogus global/channel request with "wantreply",
 238          * we should get back a failure
 239          */
 240         if ((channel_id = channel_find_open()) == -1) {
 241                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 242                 packet_put_cstring("keepalive@openssh.com");
 243                 packet_put_char(1);     /* boolean: want reply */
 244         } else {
 245                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 246         }
 247         packet_send();
 248 }
 249
 250 /*
 251  * Sleep in select() until we can do something.  This will initialize the
 252  * select masks.  Upon return, the masks will indicate which descriptors
 253  * have data or can accept data.  Optionally, a maximum time can be specified
 254  * for the duration of the wait (0 = infinite).
 255  */
 256 static void
 257 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 258     u_int *nallocp, u_int max_time_milliseconds)
 259 {
 260         struct timeval tv, *tvp;
 261         int ret;
 262         int client_alive_scheduled = 0;
 263
 264         /*
 265          * if using client_alive, set the max timeout accordingly,
 266          * and indicate that this particular timeout was for client
 267          * alive by setting the client_alive_scheduled flag.
 268          *
 269          * this could be randomized somewhat to make traffic
 270          * analysis more difficult, but we're not doing it yet.
 271          */
 272         if (compat20 &&
 273             max_time_milliseconds == 0 && options.client_alive_interval) {
 274                 client_alive_scheduled = 1;
 275                 max_time_milliseconds = options.client_alive_interval * 1000;
 276         }
 277
 278         /* Allocate and update select() masks for channel descriptors. */
 279         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 280
 281         if (compat20) {
 282 #if 0
 283                 /* wrong: bad condition XXX */
 284                 if (channel_not_very_much_buffered_data())
 285 #endif
 286                 FD_SET(connection_in, *readsetp);
 287         } else {
 288                 /*
 289                  * Read packets from the client unless we have too much
 290                  * buffered stdin or channel data.
 291                  */
 292                 if (buffer_len(&stdin_buffer) < buffer_high &&
 293                     channel_not_very_much_buffered_data())
 294                         FD_SET(connection_in, *readsetp);
 295                 /*
 296                  * If there is not too much data already buffered going to
 297                  * the client, try to get some more data from the program.
 298                  */
 299                 if (packet_not_very_much_data_to_write()) {
 300                         if (!fdout_eof)
 301                                 FD_SET(fdout, *readsetp);
 302                         if (!fderr_eof)
 303                                 FD_SET(fderr, *readsetp);
 304                 }
 305                 /*
 306                  * If we have buffered data, try to write some of that data
 307                  * to the program.
 308                  */
 309                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 310                         FD_SET(fdin, *writesetp);
 311         }
 312         notify_prepare(*readsetp);
 313
 314         /*
 315          * If we have buffered packet data going to the client, mark that
 316          * descriptor.
 317          */
 318         if (packet_have_data_to_write())
 319                 FD_SET(connection_out, *writesetp);
 320
 321         /*
 322          * If child has terminated and there is enough buffer space to read
 323          * from it, then read as much as is available and exit.
 324          */
 325         if (child_terminated && packet_not_very_much_data_to_write())
 326                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 327                         max_time_milliseconds = 100;
 328
 329         if (max_time_milliseconds == 0)
 330                 tvp = NULL;
 331         else {
 332                 tv.tv_sec = max_time_milliseconds / 1000;
 333                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 334                 tvp = &tv;
 335         }
 336
 337         /* Wait for something to happen, or the timeout to expire. */
 338         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 339
 340         if (ret == -1) {
 341                 memset(*readsetp, 0, *nallocp);
 342                 memset(*writesetp, 0, *nallocp);
 343                 if (errno != EINTR)
 344                         error("select: %.100s", strerror(errno));
 345         } else if (ret == 0 && client_alive_scheduled)
 346                 client_alive_check();
 347
 348         notify_done(*readsetp);
 349 }
 350
 351 /*
 352  * Processes input from the client and the program.  Input data is stored
 353  * in buffers and processed later.
 354  */
 355 static void
 356 process_input(fd_set * readset)
 357 {
 358         int len;
 359         char buf[16384];
 360
 361         /* Read and buffer any input data from the client. */
 362         if (FD_ISSET(connection_in, readset)) {
 363                 len = read(connection_in, buf, sizeof(buf));
 364                 if (len == 0) {
 365                         verbose("Connection closed by %.100s",
 366                             get_remote_ipaddr());
 367                         connection_closed = 1;
 368                         if (compat20)
 369                                 return;
 370                         cleanup_exit(255);
 371                 } else if (len < 0) {
 372                         if (errno != EINTR && errno != EAGAIN) {
 373                                 verbose("Read error from remote host "
 374                                     "%.100s: %.100s",
 375                                     get_remote_ipaddr(), strerror(errno));
 376                                 cleanup_exit(255);
 377                         }
 378                 } else {
 379                         /* Buffer any received data. */
 380                         packet_process_incoming(buf, len);
 381                 }
 382         }
 383         if (compat20)
 384                 return;
 385
 386         /* Read and buffer any available stdout data from the program. */
 387         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 388                 len = read(fdout, buf, sizeof(buf));
 389                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 390                         /* do nothing */
 391                 } else if (len <= 0) {
 392                         fdout_eof = 1;
 393                 } else {
 394                         buffer_append(&stdout_buffer, buf, len);
 395                         fdout_bytes += len;
 396                 }
 397         }
 398         /* Read and buffer any available stderr data from the program. */
 399         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 400                 len = read(fderr, buf, sizeof(buf));
 401                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 402                         /* do nothing */
 403                 } else if (len <= 0) {
 404                         fderr_eof = 1;
 405                 } else {
 406                         buffer_append(&stderr_buffer, buf, len);
 407                 }
 408         }
 409 }
 410
 411 /*
 412  * Sends data from internal buffers to client program stdin.
 413  */
 414 static void
 415 process_output(fd_set * writeset)
 416 {
 417         struct termios tio;
 418         u_char *data;
 419         u_int dlen;
 420         int len;
 421
 422         /* Write buffered data to program stdin. */
 423         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 424                 data = buffer_ptr(&stdin_buffer);
 425                 dlen = buffer_len(&stdin_buffer);
 426                 len = write(fdin, data, dlen);
 427                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 428                         /* do nothing */
 429                 } else if (len <= 0) {
 430                         if (fdin != fdout)
 431                                 close(fdin);
 432                         else
 433                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 434                         fdin = -1;
 435                 } else {
 436                         /* Successful write. */
 437                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 438                             tcgetattr(fdin, &tio) == 0 &&
 439                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 440                                 /*
 441                                  * Simulate echo to reduce the impact of
 442                                  * traffic analysis
 443                                  */
 444                                 packet_send_ignore(len);
 445                                 packet_send();
 446                         }
 447                         /* Consume the data from the buffer. */
 448                         buffer_consume(&stdin_buffer, len);
 449                         /* Update the count of bytes written to the program. */
 450                         stdin_bytes += len;
 451                 }
 452         }
 453         /* Send any buffered packet data to the client. */
 454         if (FD_ISSET(connection_out, writeset))
 455                 packet_write_poll();
 456 }
 457
 458 /*
 459  * Wait until all buffered output has been sent to the client.
 460  * This is used when the program terminates.
 461  */
 462 static void
 463 drain_output(void)
 464 {
 465         /* Send any buffered stdout data to the client. */
 466         if (buffer_len(&stdout_buffer) > 0) {
 467                 packet_start(SSH_SMSG_STDOUT_DATA);
 468                 packet_put_string(buffer_ptr(&stdout_buffer),
 469                                   buffer_len(&stdout_buffer));
 470                 packet_send();
 471                 /* Update the count of sent bytes. */
 472                 stdout_bytes += buffer_len(&stdout_buffer);
 473         }
 474         /* Send any buffered stderr data to the client. */
 475         if (buffer_len(&stderr_buffer) > 0) {
 476                 packet_start(SSH_SMSG_STDERR_DATA);
 477                 packet_put_string(buffer_ptr(&stderr_buffer),
 478                                   buffer_len(&stderr_buffer));
 479                 packet_send();
 480                 /* Update the count of sent bytes. */
 481                 stderr_bytes += buffer_len(&stderr_buffer);
 482         }
 483         /* Wait until all buffered data has been written to the client. */
 484         packet_write_wait();
 485 }
 486
 487 static void
 488 process_buffered_input_packets(void)
 489 {
 490         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 491 }
 492
 493 /*
 494  * Performs the interactive session.  This handles data transmission between
 495  * the client and the program.  Note that the notion of stdin, stdout, and
 496  * stderr in this function is sort of reversed: this function writes to
 497  * stdin (of the child program), and reads from stdout and stderr (of the
 498  * child program).
 499  */
 500 void
 501 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 502 {
 503         fd_set *readset = NULL, *writeset = NULL;
 504         int max_fd = 0;
 505         u_int nalloc = 0;
 506         int wait_status;        /* Status returned by wait(). */
 507         pid_t wait_pid;         /* pid returned by wait(). */
 508         int waiting_termination = 0;    /* Have displayed waiting close message. */
 509         u_int max_time_milliseconds;
 510         u_int previous_stdout_buffer_bytes;
 511         u_int stdout_buffer_bytes;
 512         int type;
 513
 514         debug("Entering interactive session.");
 515
 516         /* Initialize the SIGCHLD kludge. */
 517         child_terminated = 0;
 518         mysignal(SIGCHLD, sigchld_handler);
 519
 520         if (!use_privsep) {
 521                 signal(SIGTERM, sigterm_handler);
 522                 signal(SIGINT, sigterm_handler);
 523                 signal(SIGQUIT, sigterm_handler);
 524         }
 525
 526         /* Initialize our global variables. */
 527         fdin = fdin_arg;
 528         fdout = fdout_arg;
 529         fderr = fderr_arg;
 530
 531         /* nonblocking IO */
 532         set_nonblock(fdin);
 533         set_nonblock(fdout);
 534         /* we don't have stderr for interactive terminal sessions, see below */
 535         if (fderr != -1)
 536                 set_nonblock(fderr);
 537
 538         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 539                 fdin_is_tty = 1;
 540
 541         connection_in = packet_get_connection_in();
 542         connection_out = packet_get_connection_out();
 543
 544         notify_setup();
 545
 546         previous_stdout_buffer_bytes = 0;
 547
 548         /* Set approximate I/O buffer size. */
 549         if (packet_is_interactive())
 550                 buffer_high = 4096;
 551         else
 552                 buffer_high = 64 * 1024;
 553
 554 #if 0
 555         /* Initialize max_fd to the maximum of the known file descriptors. */
 556         max_fd = MAX(connection_in, connection_out);
 557         max_fd = MAX(max_fd, fdin);
 558         max_fd = MAX(max_fd, fdout);
 559         if (fderr != -1)
 560                 max_fd = MAX(max_fd, fderr);
 561 #endif
 562
 563         /* Initialize Initialize buffers. */
 564         buffer_init(&stdin_buffer);
 565         buffer_init(&stdout_buffer);
 566         buffer_init(&stderr_buffer);
 567
 568         /*
 569          * If we have no separate fderr (which is the case when we have a pty
 570          * - there we cannot make difference between data sent to stdout and
 571          * stderr), indicate that we have seen an EOF from stderr.  This way
 572          * we don't need to check the descriptor everywhere.
 573          */
 574         if (fderr == -1)
 575                 fderr_eof = 1;
 576
 577         server_init_dispatch();
 578
 579         /* Main loop of the server for the interactive session mode. */
 580         for (;;) {
 581
 582                 /* Process buffered packets from the client. */
 583                 process_buffered_input_packets();
 584
 585                 /*
 586                  * If we have received eof, and there is no more pending
 587                  * input data, cause a real eof by closing fdin.
 588                  */
 589                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 590                         if (fdin != fdout)
 591                                 close(fdin);
 592                         else
 593                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 594                         fdin = -1;
 595                 }
 596                 /* Make packets from buffered stderr data to send to the client. */
 597                 make_packets_from_stderr_data();
 598
 599                 /*
 600                  * Make packets from buffered stdout data to send to the
 601                  * client. If there is very little to send, this arranges to
 602                  * not send them now, but to wait a short while to see if we
 603                  * are getting more data. This is necessary, as some systems
 604                  * wake up readers from a pty after each separate character.
 605                  */
 606                 max_time_milliseconds = 0;
 607                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 608                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 609                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 610                         /* try again after a while */
 611                         max_time_milliseconds = 10;
 612                 } else {
 613                         /* Send it now. */
 614                         make_packets_from_stdout_data();
 615                 }
 616                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 617
 618                 /* Send channel data to the client. */
 619                 if (packet_not_very_much_data_to_write())
 620                         channel_output_poll();
 621
 622                 /*
 623                  * Bail out of the loop if the program has closed its output
 624                  * descriptors, and we have no more data to send to the
 625                  * client, and there is no pending buffered data.
 626                  */
 627                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 628                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 629                         if (!channel_still_open())
 630                                 break;
 631                         if (!waiting_termination) {
 632                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 633                                 char *cp;
 634                                 waiting_termination = 1;
 635                                 buffer_append(&stderr_buffer, s, strlen(s));
 636
 637                                 /* Display list of open channels. */
 638                                 cp = channel_open_message();
 639                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 640                                 xfree(cp);
 641                         }
 642                 }
 643                 max_fd = MAX(connection_in, connection_out);
 644                 max_fd = MAX(max_fd, fdin);
 645                 max_fd = MAX(max_fd, fdout);
 646                 max_fd = MAX(max_fd, fderr);
 647                 max_fd = MAX(max_fd, notify_pipe[0]);
 648
 649                 /* Sleep in select() until we can do something. */
 650                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 651                     &nalloc, max_time_milliseconds);
 652
 653                 if (received_sigterm) {
 654                         logit("Exiting on signal %d", received_sigterm);
 655                         /* Clean up sessions, utmp, etc. */
 656                         cleanup_exit(255);
 657                 }
 658
 659                 /* Process any channel events. */
 660                 channel_after_select(readset, writeset);
 661
 662                 /* Process input from the client and from program stdout/stderr. */
 663                 process_input(readset);
 664
 665                 /* Process output to the client and to program stdin. */
 666                 process_output(writeset);
 667         }
 668         if (readset)
 669                 xfree(readset);
 670         if (writeset)
 671                 xfree(writeset);
 672
 673         /* Cleanup and termination code. */
 674
 675         /* Wait until all output has been sent to the client. */
 676         drain_output();
 677
 678         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 679             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 680
 681         /* Free and clear the buffers. */
 682         buffer_free(&stdin_buffer);
 683         buffer_free(&stdout_buffer);
 684         buffer_free(&stderr_buffer);
 685
 686         /* Close the file descriptors. */
 687         if (fdout != -1)
 688                 close(fdout);
 689         fdout = -1;
 690         fdout_eof = 1;
 691         if (fderr != -1)
 692                 close(fderr);
 693         fderr = -1;
 694         fderr_eof = 1;
 695         if (fdin != -1)
 696                 close(fdin);
 697         fdin = -1;
 698
 699         channel_free_all();
 700
 701         /* We no longer want our SIGCHLD handler to be called. */
 702         mysignal(SIGCHLD, SIG_DFL);
 703
 704         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 705                 if (errno != EINTR)
 706                         packet_disconnect("wait: %.100s", strerror(errno));
 707         if (wait_pid != pid)
 708                 error("Strange, wait returned pid %ld, expected %ld",
 709                     (long)wait_pid, (long)pid);
 710
 711         /* Check if it exited normally. */
 712         if (WIFEXITED(wait_status)) {
 713                 /* Yes, normal exit.  Get exit status and send it to the client. */
 714                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 715                 packet_start(SSH_SMSG_EXITSTATUS);
 716                 packet_put_int(WEXITSTATUS(wait_status));
 717                 packet_send();
 718                 packet_write_wait();
 719
 720                 /*
 721                  * Wait for exit confirmation.  Note that there might be
 722                  * other packets coming before it; however, the program has
 723                  * already died so we just ignore them.  The client is
 724                  * supposed to respond with the confirmation when it receives
 725                  * the exit status.
 726                  */
 727                 do {
 728                         type = packet_read();
 729                 }
 730                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 731
 732                 debug("Received exit confirmation.");
 733                 return;
 734         }
 735         /* Check if the program terminated due to a signal. */
 736         if (WIFSIGNALED(wait_status))
 737                 packet_disconnect("Command terminated on signal %d.",
 738                                   WTERMSIG(wait_status));
 739
 740         /* Some weird exit cause.  Just exit. */
 741         packet_disconnect("wait returned status %04x.", wait_status);
 742         /* NOTREACHED */
 743 }
 744
 745 static void
 746 collect_children(void)
 747 {
 748         pid_t pid;
 749         sigset_t oset, nset;
 750         int status;
 751
 752         /* block SIGCHLD while we check for dead children */
 753         sigemptyset(&nset);
 754         sigaddset(&nset, SIGCHLD);
 755         sigprocmask(SIG_BLOCK, &nset, &oset);
 756         if (child_terminated) {
 757                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 758                     (pid < 0 && errno == EINTR))
 759                         if (pid > 0)
 760                                 session_close_by_pid(pid, status);
 761                 child_terminated = 0;
 762         }
 763         sigprocmask(SIG_SETMASK, &oset, NULL);
 764 }
 765
 766 void
 767 server_loop2(Authctxt *authctxt)
 768 {
 769         fd_set *readset = NULL, *writeset = NULL;
 770         int rekeying = 0, max_fd, nalloc = 0;
 771
 772         debug("Entering interactive session for SSH2.");
 773
 774         mysignal(SIGCHLD, sigchld_handler);
 775         child_terminated = 0;
 776         connection_in = packet_get_connection_in();
 777         connection_out = packet_get_connection_out();
 778
 779         if (!use_privsep) {
 780                 signal(SIGTERM, sigterm_handler);
 781                 signal(SIGINT, sigterm_handler);
 782                 signal(SIGQUIT, sigterm_handler);
 783         }
 784
 785         notify_setup();
 786
 787         max_fd = MAX(connection_in, connection_out);
 788         max_fd = MAX(max_fd, notify_pipe[0]);
 789
 790         server_init_dispatch();
 791
 792         for (;;) {
 793                 process_buffered_input_packets();
 794
 795                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 796
 797                 if (!rekeying && packet_not_very_much_data_to_write())
 798                         channel_output_poll();
 799                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 800                     &nalloc, 0);
 801
 802                 if (received_sigterm) {
 803                         logit("Exiting on signal %d", received_sigterm);
 804                         /* Clean up sessions, utmp, etc. */
 805                         cleanup_exit(255);
 806                 }
 807
 808                 collect_children();
 809                 if (!rekeying) {
 810                         channel_after_select(readset, writeset);
 811                         if (packet_need_rekeying()) {
 812                                 debug("need rekeying");
 813                                 xxx_kex->done = 0;
 814                                 kex_send_kexinit(xxx_kex);
 815                         }
 816                 }
 817                 process_input(readset);
 818                 if (connection_closed)
 819                         break;
 820                 process_output(writeset);
 821         }
 822         collect_children();
 823
 824         if (readset)
 825                 xfree(readset);
 826         if (writeset)
 827                 xfree(writeset);
 828
 829         /* free all channels, no more reads and writes */
 830         channel_free_all();
 831
 832         /* free remaining sessions, e.g. remove wtmp entries */
 833         session_destroy_all(NULL);
 834 }
 835
 836 static void
 837 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 838 {
 839         debug("Got %d/%u for keepalive", type, seq);
 840         /*
 841          * reset timeout, since we got a sane answer from the client.
 842          * even if this was generated by something other than
 843          * the bogus CHANNEL_REQUEST we send for keepalives.
 844          */
 845         client_alive_timeouts = 0;
 846 }
 847
 848 static void
 849 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 850 {
 851         char *data;
 852         u_int data_len;
 853
 854         /* Stdin data from the client.  Append it to the buffer. */
 855         /* Ignore any data if the client has closed stdin. */
 856         if (fdin == -1)
 857                 return;
 858         data = packet_get_string(&data_len);
 859         packet_check_eom();
 860         buffer_append(&stdin_buffer, data, data_len);
 861         memset(data, 0, data_len);
 862         xfree(data);
 863 }
 864
 865 static void
 866 server_input_eof(int type, u_int32_t seq, void *ctxt)
 867 {
 868         /*
 869          * Eof from the client.  The stdin descriptor to the
 870          * program will be closed when all buffered data has
 871          * drained.
 872          */
 873         debug("EOF received for stdin.");
 874         packet_check_eom();
 875         stdin_eof = 1;
 876 }
 877
 878 static void
 879 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 880 {
 881         int row = packet_get_int();
 882         int col = packet_get_int();
 883         int xpixel = packet_get_int();
 884         int ypixel = packet_get_int();
 885
 886         debug("Window change received.");
 887         packet_check_eom();
 888         if (fdin != -1)
 889                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 890 }
 891
 892 static Channel *
 893 server_request_direct_tcpip(void)
 894 {
 895         Channel *c;
 896         int sock;
 897         char *target, *originator;
 898         int target_port, originator_port;
 899
 900         target = packet_get_string(NULL);
 901         target_port = packet_get_int();
 902         originator = packet_get_string(NULL);
 903         originator_port = packet_get_int();
 904         packet_check_eom();
 905
 906         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 907             originator, originator_port, target, target_port);
 908
 909         /* XXX check permission */
 910         sock = channel_connect_to(target, target_port);
 911         xfree(target);
 912         xfree(originator);
 913         if (sock < 0)
 914                 return NULL;
 915         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 916             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 917             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 918         return c;
 919 }
 920
 921 static Channel *
 922 server_request_tun(void)
 923 {
 924         Channel *c = NULL;
 925         int mode, tun;
 926         int sock;
 927
 928         mode = packet_get_int();
 929         switch (mode) {
 930         case SSH_TUNMODE_POINTOPOINT:
 931         case SSH_TUNMODE_ETHERNET:
 932                 break;
 933         default:
 934                 packet_send_debug("Unsupported tunnel device mode.");
 935                 return NULL;
 936         }
 937         if ((options.permit_tun & mode) == 0) {
 938                 packet_send_debug("Server has rejected tunnel device "
 939                     "forwarding");
 940                 return NULL;
 941         }
 942
 943         tun = packet_get_int();
 944         if (forced_tun_device != -1) {
 945                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 946                         goto done;
 947                 tun = forced_tun_device;
 948         }
 949         sock = tun_open(tun, mode);
 950         if (sock < 0)
 951                 goto done;
 952         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 953             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 954         c->datagram = 1;
 955 #if defined(SSH_TUN_FILTER)
 956         if (mode == SSH_TUNMODE_POINTOPOINT)
 957                 channel_register_filter(c->self, sys_tun_infilter,
 958                     sys_tun_outfilter);
 959 #endif
 960
 961  done:
 962         if (c == NULL)
 963                 packet_send_debug("Failed to open the tunnel device.");
 964         return c;
 965 }
 966
 967 static Channel *
 968 server_request_session(void)
 969 {
 970         Channel *c;
 971
 972         debug("input_session_request");
 973         packet_check_eom();
 974         /*
 975          * A server session has no fd to read or write until a
 976          * CHANNEL_REQUEST for a shell is made, so we set the type to
 977          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 978          * CHANNEL_REQUEST messages is registered.
 979          */
 980         c = channel_new("session", SSH_CHANNEL_LARVAL,
 981             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 982             0, "server-session", 1);
 983         if (session_open(the_authctxt, c->self) != 1) {
 984                 debug("session open failed, free channel %d", c->self);
 985                 channel_free(c);
 986                 return NULL;
 987         }
 988         channel_register_cleanup(c->self, session_close_by_channel, 0);
 989         return c;
 990 }
 991
 992 static void
 993 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 994 {
 995         Channel *c = NULL;
 996         char *ctype;
 997         int rchan;
 998         u_int rmaxpack, rwindow, len;
 999
1000         ctype = packet_get_string(&len);
1001         rchan = packet_get_int();
1002         rwindow = packet_get_int();
1003         rmaxpack = packet_get_int();
1004
1005         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1006             ctype, rchan, rwindow, rmaxpack);
1007
1008         if (strcmp(ctype, "session") == 0) {
1009                 c = server_request_session();
1010         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1011                 c = server_request_direct_tcpip();
1012         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1013                 c = server_request_tun();
1014         }
1015         if (c != NULL) {
1016                 debug("server_input_channel_open: confirm %s", ctype);
1017                 c->remote_id = rchan;
1018                 c->remote_window = rwindow;
1019                 c->remote_maxpacket = rmaxpack;
1020                 if (c->type != SSH_CHANNEL_CONNECTING) {
1021                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1022                         packet_put_int(c->remote_id);
1023                         packet_put_int(c->self);
1024                         packet_put_int(c->local_window);
1025                         packet_put_int(c->local_maxpacket);
1026                         packet_send();
1027                 }
1028         } else {
1029                 debug("server_input_channel_open: failure %s", ctype);
1030                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1031                 packet_put_int(rchan);
1032                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1033                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1034                         packet_put_cstring("open failed");
1035                         packet_put_cstring("");
1036                 }
1037                 packet_send();
1038         }
1039         xfree(ctype);
1040 }
1041
1042 static void
1043 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1044 {
1045         char *rtype;
1046         int want_reply;
1047         int success = 0;
1048
1049         rtype = packet_get_string(NULL);
1050         want_reply = packet_get_char();
1051         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1052
1053         /* -R style forwarding */
1054         if (strcmp(rtype, "tcpip-forward") == 0) {
1055                 struct passwd *pw;
1056                 char *listen_address;
1057                 u_short listen_port;
1058
1059                 pw = the_authctxt->pw;
1060                 if (pw == NULL || !the_authctxt->valid)
1061                         fatal("server_input_global_request: no/invalid user");
1062                 listen_address = packet_get_string(NULL);
1063                 listen_port = (u_short)packet_get_int();
1064                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1065                     listen_address, listen_port);
1066
1067                 /* check permissions */
1068                 if (!options.allow_tcp_forwarding ||
1069                     no_port_forwarding_flag
1070 #ifndef NO_IPPORT_RESERVED_CONCEPT
1071                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1072 #endif
1073                     ) {
1074                         success = 0;
1075                         packet_send_debug("Server has disabled port forwarding.");
1076                 } else {
1077                         /* Start listening on the port */
1078                         success = channel_setup_remote_fwd_listener(
1079                             listen_address, listen_port, options.gateway_ports);
1080                 }
1081                 xfree(listen_address);
1082         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1083                 char *cancel_address;
1084                 u_short cancel_port;
1085
1086                 cancel_address = packet_get_string(NULL);
1087                 cancel_port = (u_short)packet_get_int();
1088                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1089                     cancel_address, cancel_port);
1090
1091                 success = channel_cancel_rport_listener(cancel_address,
1092                     cancel_port);
1093         }
1094         if (want_reply) {
1095                 packet_start(success ?
1096                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1097                 packet_send();
1098                 packet_write_wait();
1099         }
1100         xfree(rtype);
1101 }
1102 static void
1103 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1104 {
1105         Channel *c;
1106         int id, reply, success = 0;
1107         char *rtype;
1108
1109         id = packet_get_int();
1110         rtype = packet_get_string(NULL);
1111         reply = packet_get_char();
1112
1113         debug("server_input_channel_req: channel %d request %s reply %d",
1114             id, rtype, reply);
1115
1116         if ((c = channel_lookup(id)) == NULL)
1117                 packet_disconnect("server_input_channel_req: "
1118                     "unknown channel %d", id);
1119         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1120                 success = session_input_channel_req(c, rtype);
1121         if (reply) {
1122                 packet_start(success ?
1123                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1124                 packet_put_int(c->remote_id);
1125                 packet_send();
1126         }
1127         xfree(rtype);
1128 }
1129
1130 static void
1131 server_init_dispatch_20(void)
1132 {
1133         debug("server_init_dispatch_20");
1134         dispatch_init(&dispatch_protocol_error);
1135         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1136         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1137         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1138         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1139         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1140         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1141         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1142         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1143         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1144         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1145         /* client_alive */
1146         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1147         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1148         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1149         /* rekeying */
1150         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1151 }
1152 static void
1153 server_init_dispatch_13(void)
1154 {
1155         debug("server_init_dispatch_13");
1156         dispatch_init(NULL);
1157         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1158         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1159         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1160         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1161         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1162         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1163         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1164         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1165         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1166 }
1167 static void
1168 server_init_dispatch_15(void)
1169 {
1170         server_init_dispatch_13();
1171         debug("server_init_dispatch_15");
1172         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1173         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1174 }
1175 static void
1176 server_init_dispatch(void)
1177 {
1178         if (compat20)
1179                 server_init_dispatch_20();
1180         else if (compat13)
1181                 server_init_dispatch_13();
1182         else
1183                 server_init_dispatch_15();
1184 }