serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.137 2006/07/06 16:03:53 stevesk Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42 #include <sys/socket.h>
  43
  44 #include <netinet/in.h>
  45
  46 #include <pwd.h>
  47 #include <signal.h>
  48 #include <termios.h>
  49
  50 #include "xmalloc.h"
  51 #include "packet.h"
  52 #include "buffer.h"
  53 #include "log.h"
  54 #include "servconf.h"
  55 #include "canohost.h"
  56 #include "sshpty.h"
  57 #include "channels.h"
  58 #include "compat.h"
  59 #include "ssh1.h"
  60 #include "ssh2.h"
  61 #include "auth.h"
  62 #include "session.h"
  63 #include "dispatch.h"
  64 #include "auth-options.h"
  65 #include "serverloop.h"
  66 #include "misc.h"
  67 #include "kex.h"
  68
  69 extern ServerOptions options;
  70
  71 /* XXX */
  72 extern Kex *xxx_kex;
  73 extern Authctxt *the_authctxt;
  74 extern int use_privsep;
  75
  76 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  77 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  78 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  79 static int fdin;                /* Descriptor for stdin (for writing) */
  80 static int fdout;               /* Descriptor for stdout (for reading);
  81                                    May be same number as fdin. */
  82 static int fderr;               /* Descriptor for stderr.  May be -1. */
  83 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  84 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  85 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  86 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  87 static int stdin_eof = 0;       /* EOF message received from client. */
  88 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  89 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  90 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  91 static int connection_in;       /* Connection to client (input). */
  92 static int connection_out;      /* Connection to client (output). */
  93 static int connection_closed = 0;       /* Connection to client closed. */
  94 static u_int buffer_high;       /* "Soft" max buffer size. */
  95 static int client_alive_timeouts = 0;
  96
  97 /*
  98  * This SIGCHLD kludge is used to detect when the child exits.  The server
  99  * will exit after that, as soon as forwarded connections have terminated.
 100  */
 101
 102 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 103
 104 /* Cleanup on signals (!use_privsep case only) */
 105 static volatile sig_atomic_t received_sigterm = 0;
 106
 107 /* prototypes */
 108 static void server_init_dispatch(void);
 109
 110 /*
 111  * we write to this pipe if a SIGCHLD is caught in order to avoid
 112  * the race between select() and child_terminated
 113  */
 114 static int notify_pipe[2];
 115 static void
 116 notify_setup(void)
 117 {
 118         if (pipe(notify_pipe) < 0) {
 119                 error("pipe(notify_pipe) failed %s", strerror(errno));
 120         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 121             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 122                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 123                 close(notify_pipe[0]);
 124                 close(notify_pipe[1]);
 125         } else {
 126                 set_nonblock(notify_pipe[0]);
 127                 set_nonblock(notify_pipe[1]);
 128                 return;
 129         }
 130         notify_pipe[0] = -1;    /* read end */
 131         notify_pipe[1] = -1;    /* write end */
 132 }
 133 static void
 134 notify_parent(void)
 135 {
 136         if (notify_pipe[1] != -1)
 137                 write(notify_pipe[1], "", 1);
 138 }
 139 static void
 140 notify_prepare(fd_set *readset)
 141 {
 142         if (notify_pipe[0] != -1)
 143                 FD_SET(notify_pipe[0], readset);
 144 }
 145 static void
 146 notify_done(fd_set *readset)
 147 {
 148         char c;
 149
 150         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 151                 while (read(notify_pipe[0], &c, 1) != -1)
 152                         debug2("notify_done: reading");
 153 }
 154
 155 /*ARGSUSED*/
 156 static void
 157 sigchld_handler(int sig)
 158 {
 159         int save_errno = errno;
 160         child_terminated = 1;
 161 #ifndef _UNICOS
 162         mysignal(SIGCHLD, sigchld_handler);
 163 #endif
 164         notify_parent();
 165         errno = save_errno;
 166 }
 167
 168 /*ARGSUSED*/
 169 static void
 170 sigterm_handler(int sig)
 171 {
 172         received_sigterm = sig;
 173 }
 174
 175 /*
 176  * Make packets from buffered stderr data, and buffer it for sending
 177  * to the client.
 178  */
 179 static void
 180 make_packets_from_stderr_data(void)
 181 {
 182         u_int len;
 183
 184         /* Send buffered stderr data to the client. */
 185         while (buffer_len(&stderr_buffer) > 0 &&
 186             packet_not_very_much_data_to_write()) {
 187                 len = buffer_len(&stderr_buffer);
 188                 if (packet_is_interactive()) {
 189                         if (len > 512)
 190                                 len = 512;
 191                 } else {
 192                         /* Keep the packets at reasonable size. */
 193                         if (len > packet_get_maxsize())
 194                                 len = packet_get_maxsize();
 195                 }
 196                 packet_start(SSH_SMSG_STDERR_DATA);
 197                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 198                 packet_send();
 199                 buffer_consume(&stderr_buffer, len);
 200                 stderr_bytes += len;
 201         }
 202 }
 203
 204 /*
 205  * Make packets from buffered stdout data, and buffer it for sending to the
 206  * client.
 207  */
 208 static void
 209 make_packets_from_stdout_data(void)
 210 {
 211         u_int len;
 212
 213         /* Send buffered stdout data to the client. */
 214         while (buffer_len(&stdout_buffer) > 0 &&
 215             packet_not_very_much_data_to_write()) {
 216                 len = buffer_len(&stdout_buffer);
 217                 if (packet_is_interactive()) {
 218                         if (len > 512)
 219                                 len = 512;
 220                 } else {
 221                         /* Keep the packets at reasonable size. */
 222                         if (len > packet_get_maxsize())
 223                                 len = packet_get_maxsize();
 224                 }
 225                 packet_start(SSH_SMSG_STDOUT_DATA);
 226                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 227                 packet_send();
 228                 buffer_consume(&stdout_buffer, len);
 229                 stdout_bytes += len;
 230         }
 231 }
 232
 233 static void
 234 client_alive_check(void)
 235 {
 236         int channel_id;
 237
 238         /* timeout, check to see how many we have had */
 239         if (++client_alive_timeouts > options.client_alive_count_max)
 240                 packet_disconnect("Timeout, your session not responding.");
 241
 242         /*
 243          * send a bogus global/channel request with "wantreply",
 244          * we should get back a failure
 245          */
 246         if ((channel_id = channel_find_open()) == -1) {
 247                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 248                 packet_put_cstring("keepalive@openssh.com");
 249                 packet_put_char(1);     /* boolean: want reply */
 250         } else {
 251                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 252         }
 253         packet_send();
 254 }
 255
 256 /*
 257  * Sleep in select() until we can do something.  This will initialize the
 258  * select masks.  Upon return, the masks will indicate which descriptors
 259  * have data or can accept data.  Optionally, a maximum time can be specified
 260  * for the duration of the wait (0 = infinite).
 261  */
 262 static void
 263 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 264     u_int *nallocp, u_int max_time_milliseconds)
 265 {
 266         struct timeval tv, *tvp;
 267         int ret;
 268         int client_alive_scheduled = 0;
 269
 270         /*
 271          * if using client_alive, set the max timeout accordingly,
 272          * and indicate that this particular timeout was for client
 273          * alive by setting the client_alive_scheduled flag.
 274          *
 275          * this could be randomized somewhat to make traffic
 276          * analysis more difficult, but we're not doing it yet.
 277          */
 278         if (compat20 &&
 279             max_time_milliseconds == 0 && options.client_alive_interval) {
 280                 client_alive_scheduled = 1;
 281                 max_time_milliseconds = options.client_alive_interval * 1000;
 282         }
 283
 284         /* Allocate and update select() masks for channel descriptors. */
 285         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 286
 287         if (compat20) {
 288 #if 0
 289                 /* wrong: bad condition XXX */
 290                 if (channel_not_very_much_buffered_data())
 291 #endif
 292                 FD_SET(connection_in, *readsetp);
 293         } else {
 294                 /*
 295                  * Read packets from the client unless we have too much
 296                  * buffered stdin or channel data.
 297                  */
 298                 if (buffer_len(&stdin_buffer) < buffer_high &&
 299                     channel_not_very_much_buffered_data())
 300                         FD_SET(connection_in, *readsetp);
 301                 /*
 302                  * If there is not too much data already buffered going to
 303                  * the client, try to get some more data from the program.
 304                  */
 305                 if (packet_not_very_much_data_to_write()) {
 306                         if (!fdout_eof)
 307                                 FD_SET(fdout, *readsetp);
 308                         if (!fderr_eof)
 309                                 FD_SET(fderr, *readsetp);
 310                 }
 311                 /*
 312                  * If we have buffered data, try to write some of that data
 313                  * to the program.
 314                  */
 315                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 316                         FD_SET(fdin, *writesetp);
 317         }
 318         notify_prepare(*readsetp);
 319
 320         /*
 321          * If we have buffered packet data going to the client, mark that
 322          * descriptor.
 323          */
 324         if (packet_have_data_to_write())
 325                 FD_SET(connection_out, *writesetp);
 326
 327         /*
 328          * If child has terminated and there is enough buffer space to read
 329          * from it, then read as much as is available and exit.
 330          */
 331         if (child_terminated && packet_not_very_much_data_to_write())
 332                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 333                         max_time_milliseconds = 100;
 334
 335         if (max_time_milliseconds == 0)
 336                 tvp = NULL;
 337         else {
 338                 tv.tv_sec = max_time_milliseconds / 1000;
 339                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 340                 tvp = &tv;
 341         }
 342
 343         /* Wait for something to happen, or the timeout to expire. */
 344         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 345
 346         if (ret == -1) {
 347                 memset(*readsetp, 0, *nallocp);
 348                 memset(*writesetp, 0, *nallocp);
 349                 if (errno != EINTR)
 350                         error("select: %.100s", strerror(errno));
 351         } else if (ret == 0 && client_alive_scheduled)
 352                 client_alive_check();
 353
 354         notify_done(*readsetp);
 355 }
 356
 357 /*
 358  * Processes input from the client and the program.  Input data is stored
 359  * in buffers and processed later.
 360  */
 361 static void
 362 process_input(fd_set *readset)
 363 {
 364         int len;
 365         char buf[16384];
 366
 367         /* Read and buffer any input data from the client. */
 368         if (FD_ISSET(connection_in, readset)) {
 369                 len = read(connection_in, buf, sizeof(buf));
 370                 if (len == 0) {
 371                         verbose("Connection closed by %.100s",
 372                             get_remote_ipaddr());
 373                         connection_closed = 1;
 374                         if (compat20)
 375                                 return;
 376                         cleanup_exit(255);
 377                 } else if (len < 0) {
 378                         if (errno != EINTR && errno != EAGAIN) {
 379                                 verbose("Read error from remote host "
 380                                     "%.100s: %.100s",
 381                                     get_remote_ipaddr(), strerror(errno));
 382                                 cleanup_exit(255);
 383                         }
 384                 } else {
 385                         /* Buffer any received data. */
 386                         packet_process_incoming(buf, len);
 387                 }
 388         }
 389         if (compat20)
 390                 return;
 391
 392         /* Read and buffer any available stdout data from the program. */
 393         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 394                 errno = 0;
 395                 len = read(fdout, buf, sizeof(buf));
 396                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 397                         /* do nothing */
 398 #ifndef PTY_ZEROREAD
 399                 } else if (len <= 0) {
 400 #else
 401                 } else if ((!isatty(fdout) && len <= 0) ||
 402                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 403 #endif
 404                         fdout_eof = 1;
 405                 } else {
 406                         buffer_append(&stdout_buffer, buf, len);
 407                         fdout_bytes += len;
 408                 }
 409         }
 410         /* Read and buffer any available stderr data from the program. */
 411         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 412                 errno = 0;
 413                 len = read(fderr, buf, sizeof(buf));
 414                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 415                         /* do nothing */
 416 #ifndef PTY_ZEROREAD
 417                 } else if (len <= 0) {
 418 #else
 419                 } else if ((!isatty(fderr) && len <= 0) ||
 420                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 421 #endif
 422                         fderr_eof = 1;
 423                 } else {
 424                         buffer_append(&stderr_buffer, buf, len);
 425                 }
 426         }
 427 }
 428
 429 /*
 430  * Sends data from internal buffers to client program stdin.
 431  */
 432 static void
 433 process_output(fd_set *writeset)
 434 {
 435         struct termios tio;
 436         u_char *data;
 437         u_int dlen;
 438         int len;
 439
 440         /* Write buffered data to program stdin. */
 441         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 442                 data = buffer_ptr(&stdin_buffer);
 443                 dlen = buffer_len(&stdin_buffer);
 444                 len = write(fdin, data, dlen);
 445                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 446                         /* do nothing */
 447                 } else if (len <= 0) {
 448                         if (fdin != fdout)
 449                                 close(fdin);
 450                         else
 451                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 452                         fdin = -1;
 453                 } else {
 454                         /* Successful write. */
 455                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 456                             tcgetattr(fdin, &tio) == 0 &&
 457                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 458                                 /*
 459                                  * Simulate echo to reduce the impact of
 460                                  * traffic analysis
 461                                  */
 462                                 packet_send_ignore(len);
 463                                 packet_send();
 464                         }
 465                         /* Consume the data from the buffer. */
 466                         buffer_consume(&stdin_buffer, len);
 467                         /* Update the count of bytes written to the program. */
 468                         stdin_bytes += len;
 469                 }
 470         }
 471         /* Send any buffered packet data to the client. */
 472         if (FD_ISSET(connection_out, writeset))
 473                 packet_write_poll();
 474 }
 475
 476 /*
 477  * Wait until all buffered output has been sent to the client.
 478  * This is used when the program terminates.
 479  */
 480 static void
 481 drain_output(void)
 482 {
 483         /* Send any buffered stdout data to the client. */
 484         if (buffer_len(&stdout_buffer) > 0) {
 485                 packet_start(SSH_SMSG_STDOUT_DATA);
 486                 packet_put_string(buffer_ptr(&stdout_buffer),
 487                                   buffer_len(&stdout_buffer));
 488                 packet_send();
 489                 /* Update the count of sent bytes. */
 490                 stdout_bytes += buffer_len(&stdout_buffer);
 491         }
 492         /* Send any buffered stderr data to the client. */
 493         if (buffer_len(&stderr_buffer) > 0) {
 494                 packet_start(SSH_SMSG_STDERR_DATA);
 495                 packet_put_string(buffer_ptr(&stderr_buffer),
 496                                   buffer_len(&stderr_buffer));
 497                 packet_send();
 498                 /* Update the count of sent bytes. */
 499                 stderr_bytes += buffer_len(&stderr_buffer);
 500         }
 501         /* Wait until all buffered data has been written to the client. */
 502         packet_write_wait();
 503 }
 504
 505 static void
 506 process_buffered_input_packets(void)
 507 {
 508         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 509 }
 510
 511 /*
 512  * Performs the interactive session.  This handles data transmission between
 513  * the client and the program.  Note that the notion of stdin, stdout, and
 514  * stderr in this function is sort of reversed: this function writes to
 515  * stdin (of the child program), and reads from stdout and stderr (of the
 516  * child program).
 517  */
 518 void
 519 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 520 {
 521         fd_set *readset = NULL, *writeset = NULL;
 522         int max_fd = 0;
 523         u_int nalloc = 0;
 524         int wait_status;        /* Status returned by wait(). */
 525         pid_t wait_pid;         /* pid returned by wait(). */
 526         int waiting_termination = 0;    /* Have displayed waiting close message. */
 527         u_int max_time_milliseconds;
 528         u_int previous_stdout_buffer_bytes;
 529         u_int stdout_buffer_bytes;
 530         int type;
 531
 532         debug("Entering interactive session.");
 533
 534         /* Initialize the SIGCHLD kludge. */
 535         child_terminated = 0;
 536         mysignal(SIGCHLD, sigchld_handler);
 537
 538         if (!use_privsep) {
 539                 signal(SIGTERM, sigterm_handler);
 540                 signal(SIGINT, sigterm_handler);
 541                 signal(SIGQUIT, sigterm_handler);
 542         }
 543
 544         /* Initialize our global variables. */
 545         fdin = fdin_arg;
 546         fdout = fdout_arg;
 547         fderr = fderr_arg;
 548
 549         /* nonblocking IO */
 550         set_nonblock(fdin);
 551         set_nonblock(fdout);
 552         /* we don't have stderr for interactive terminal sessions, see below */
 553         if (fderr != -1)
 554                 set_nonblock(fderr);
 555
 556         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 557                 fdin_is_tty = 1;
 558
 559         connection_in = packet_get_connection_in();
 560         connection_out = packet_get_connection_out();
 561
 562         notify_setup();
 563
 564         previous_stdout_buffer_bytes = 0;
 565
 566         /* Set approximate I/O buffer size. */
 567         if (packet_is_interactive())
 568                 buffer_high = 4096;
 569         else
 570                 buffer_high = 64 * 1024;
 571
 572 #if 0
 573         /* Initialize max_fd to the maximum of the known file descriptors. */
 574         max_fd = MAX(connection_in, connection_out);
 575         max_fd = MAX(max_fd, fdin);
 576         max_fd = MAX(max_fd, fdout);
 577         if (fderr != -1)
 578                 max_fd = MAX(max_fd, fderr);
 579 #endif
 580
 581         /* Initialize Initialize buffers. */
 582         buffer_init(&stdin_buffer);
 583         buffer_init(&stdout_buffer);
 584         buffer_init(&stderr_buffer);
 585
 586         /*
 587          * If we have no separate fderr (which is the case when we have a pty
 588          * - there we cannot make difference between data sent to stdout and
 589          * stderr), indicate that we have seen an EOF from stderr.  This way
 590          * we don't need to check the descriptor everywhere.
 591          */
 592         if (fderr == -1)
 593                 fderr_eof = 1;
 594
 595         server_init_dispatch();
 596
 597         /* Main loop of the server for the interactive session mode. */
 598         for (;;) {
 599
 600                 /* Process buffered packets from the client. */
 601                 process_buffered_input_packets();
 602
 603                 /*
 604                  * If we have received eof, and there is no more pending
 605                  * input data, cause a real eof by closing fdin.
 606                  */
 607                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 608                         if (fdin != fdout)
 609                                 close(fdin);
 610                         else
 611                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 612                         fdin = -1;
 613                 }
 614                 /* Make packets from buffered stderr data to send to the client. */
 615                 make_packets_from_stderr_data();
 616
 617                 /*
 618                  * Make packets from buffered stdout data to send to the
 619                  * client. If there is very little to send, this arranges to
 620                  * not send them now, but to wait a short while to see if we
 621                  * are getting more data. This is necessary, as some systems
 622                  * wake up readers from a pty after each separate character.
 623                  */
 624                 max_time_milliseconds = 0;
 625                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 626                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 627                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 628                         /* try again after a while */
 629                         max_time_milliseconds = 10;
 630                 } else {
 631                         /* Send it now. */
 632                         make_packets_from_stdout_data();
 633                 }
 634                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 635
 636                 /* Send channel data to the client. */
 637                 if (packet_not_very_much_data_to_write())
 638                         channel_output_poll();
 639
 640                 /*
 641                  * Bail out of the loop if the program has closed its output
 642                  * descriptors, and we have no more data to send to the
 643                  * client, and there is no pending buffered data.
 644                  */
 645                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 646                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 647                         if (!channel_still_open())
 648                                 break;
 649                         if (!waiting_termination) {
 650                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 651                                 char *cp;
 652                                 waiting_termination = 1;
 653                                 buffer_append(&stderr_buffer, s, strlen(s));
 654
 655                                 /* Display list of open channels. */
 656                                 cp = channel_open_message();
 657                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 658                                 xfree(cp);
 659                         }
 660                 }
 661                 max_fd = MAX(connection_in, connection_out);
 662                 max_fd = MAX(max_fd, fdin);
 663                 max_fd = MAX(max_fd, fdout);
 664                 max_fd = MAX(max_fd, fderr);
 665                 max_fd = MAX(max_fd, notify_pipe[0]);
 666
 667                 /* Sleep in select() until we can do something. */
 668                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 669                     &nalloc, max_time_milliseconds);
 670
 671                 if (received_sigterm) {
 672                         logit("Exiting on signal %d", received_sigterm);
 673                         /* Clean up sessions, utmp, etc. */
 674                         cleanup_exit(255);
 675                 }
 676
 677                 /* Process any channel events. */
 678                 channel_after_select(readset, writeset);
 679
 680                 /* Process input from the client and from program stdout/stderr. */
 681                 process_input(readset);
 682
 683                 /* Process output to the client and to program stdin. */
 684                 process_output(writeset);
 685         }
 686         if (readset)
 687                 xfree(readset);
 688         if (writeset)
 689                 xfree(writeset);
 690
 691         /* Cleanup and termination code. */
 692
 693         /* Wait until all output has been sent to the client. */
 694         drain_output();
 695
 696         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 697             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 698
 699         /* Free and clear the buffers. */
 700         buffer_free(&stdin_buffer);
 701         buffer_free(&stdout_buffer);
 702         buffer_free(&stderr_buffer);
 703
 704         /* Close the file descriptors. */
 705         if (fdout != -1)
 706                 close(fdout);
 707         fdout = -1;
 708         fdout_eof = 1;
 709         if (fderr != -1)
 710                 close(fderr);
 711         fderr = -1;
 712         fderr_eof = 1;
 713         if (fdin != -1)
 714                 close(fdin);
 715         fdin = -1;
 716
 717         channel_free_all();
 718
 719         /* We no longer want our SIGCHLD handler to be called. */
 720         mysignal(SIGCHLD, SIG_DFL);
 721
 722         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 723                 if (errno != EINTR)
 724                         packet_disconnect("wait: %.100s", strerror(errno));
 725         if (wait_pid != pid)
 726                 error("Strange, wait returned pid %ld, expected %ld",
 727                     (long)wait_pid, (long)pid);
 728
 729         /* Check if it exited normally. */
 730         if (WIFEXITED(wait_status)) {
 731                 /* Yes, normal exit.  Get exit status and send it to the client. */
 732                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 733                 packet_start(SSH_SMSG_EXITSTATUS);
 734                 packet_put_int(WEXITSTATUS(wait_status));
 735                 packet_send();
 736                 packet_write_wait();
 737
 738                 /*
 739                  * Wait for exit confirmation.  Note that there might be
 740                  * other packets coming before it; however, the program has
 741                  * already died so we just ignore them.  The client is
 742                  * supposed to respond with the confirmation when it receives
 743                  * the exit status.
 744                  */
 745                 do {
 746                         type = packet_read();
 747                 }
 748                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 749
 750                 debug("Received exit confirmation.");
 751                 return;
 752         }
 753         /* Check if the program terminated due to a signal. */
 754         if (WIFSIGNALED(wait_status))
 755                 packet_disconnect("Command terminated on signal %d.",
 756                                   WTERMSIG(wait_status));
 757
 758         /* Some weird exit cause.  Just exit. */
 759         packet_disconnect("wait returned status %04x.", wait_status);
 760         /* NOTREACHED */
 761 }
 762
 763 static void
 764 collect_children(void)
 765 {
 766         pid_t pid;
 767         sigset_t oset, nset;
 768         int status;
 769
 770         /* block SIGCHLD while we check for dead children */
 771         sigemptyset(&nset);
 772         sigaddset(&nset, SIGCHLD);
 773         sigprocmask(SIG_BLOCK, &nset, &oset);
 774         if (child_terminated) {
 775                 debug("Received SIGCHLD.");
 776                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 777                     (pid < 0 && errno == EINTR))
 778                         if (pid > 0)
 779                                 session_close_by_pid(pid, status);
 780                 child_terminated = 0;
 781         }
 782         sigprocmask(SIG_SETMASK, &oset, NULL);
 783 }
 784
 785 void
 786 server_loop2(Authctxt *authctxt)
 787 {
 788         fd_set *readset = NULL, *writeset = NULL;
 789         int rekeying = 0, max_fd, nalloc = 0;
 790
 791         debug("Entering interactive session for SSH2.");
 792
 793         mysignal(SIGCHLD, sigchld_handler);
 794         child_terminated = 0;
 795         connection_in = packet_get_connection_in();
 796         connection_out = packet_get_connection_out();
 797
 798         if (!use_privsep) {
 799                 signal(SIGTERM, sigterm_handler);
 800                 signal(SIGINT, sigterm_handler);
 801                 signal(SIGQUIT, sigterm_handler);
 802         }
 803
 804         notify_setup();
 805
 806         max_fd = MAX(connection_in, connection_out);
 807         max_fd = MAX(max_fd, notify_pipe[0]);
 808
 809         server_init_dispatch();
 810
 811         for (;;) {
 812                 process_buffered_input_packets();
 813
 814                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 815
 816                 if (!rekeying && packet_not_very_much_data_to_write())
 817                         channel_output_poll();
 818                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 819                     &nalloc, 0);
 820
 821                 if (received_sigterm) {
 822                         logit("Exiting on signal %d", received_sigterm);
 823                         /* Clean up sessions, utmp, etc. */
 824                         cleanup_exit(255);
 825                 }
 826
 827                 collect_children();
 828                 if (!rekeying) {
 829                         channel_after_select(readset, writeset);
 830                         if (packet_need_rekeying()) {
 831                                 debug("need rekeying");
 832                                 xxx_kex->done = 0;
 833                                 kex_send_kexinit(xxx_kex);
 834                         }
 835                 }
 836                 process_input(readset);
 837                 if (connection_closed)
 838                         break;
 839                 process_output(writeset);
 840         }
 841         collect_children();
 842
 843         if (readset)
 844                 xfree(readset);
 845         if (writeset)
 846                 xfree(writeset);
 847
 848         /* free all channels, no more reads and writes */
 849         channel_free_all();
 850
 851         /* free remaining sessions, e.g. remove wtmp entries */
 852         session_destroy_all(NULL);
 853 }
 854
 855 static void
 856 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 857 {
 858         debug("Got %d/%u for keepalive", type, seq);
 859         /*
 860          * reset timeout, since we got a sane answer from the client.
 861          * even if this was generated by something other than
 862          * the bogus CHANNEL_REQUEST we send for keepalives.
 863          */
 864         client_alive_timeouts = 0;
 865 }
 866
 867 static void
 868 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 869 {
 870         char *data;
 871         u_int data_len;
 872
 873         /* Stdin data from the client.  Append it to the buffer. */
 874         /* Ignore any data if the client has closed stdin. */
 875         if (fdin == -1)
 876                 return;
 877         data = packet_get_string(&data_len);
 878         packet_check_eom();
 879         buffer_append(&stdin_buffer, data, data_len);
 880         memset(data, 0, data_len);
 881         xfree(data);
 882 }
 883
 884 static void
 885 server_input_eof(int type, u_int32_t seq, void *ctxt)
 886 {
 887         /*
 888          * Eof from the client.  The stdin descriptor to the
 889          * program will be closed when all buffered data has
 890          * drained.
 891          */
 892         debug("EOF received for stdin.");
 893         packet_check_eom();
 894         stdin_eof = 1;
 895 }
 896
 897 static void
 898 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 899 {
 900         u_int row = packet_get_int();
 901         u_int col = packet_get_int();
 902         u_int xpixel = packet_get_int();
 903         u_int ypixel = packet_get_int();
 904
 905         debug("Window change received.");
 906         packet_check_eom();
 907         if (fdin != -1)
 908                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 909 }
 910
 911 static Channel *
 912 server_request_direct_tcpip(void)
 913 {
 914         Channel *c;
 915         int sock;
 916         char *target, *originator;
 917         int target_port, originator_port;
 918
 919         target = packet_get_string(NULL);
 920         target_port = packet_get_int();
 921         originator = packet_get_string(NULL);
 922         originator_port = packet_get_int();
 923         packet_check_eom();
 924
 925         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 926             originator, originator_port, target, target_port);
 927
 928         /* XXX check permission */
 929         sock = channel_connect_to(target, target_port);
 930         xfree(target);
 931         xfree(originator);
 932         if (sock < 0)
 933                 return NULL;
 934         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 935             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 936             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 937         return c;
 938 }
 939
 940 static Channel *
 941 server_request_tun(void)
 942 {
 943         Channel *c = NULL;
 944         int mode, tun;
 945         int sock;
 946
 947         mode = packet_get_int();
 948         switch (mode) {
 949         case SSH_TUNMODE_POINTOPOINT:
 950         case SSH_TUNMODE_ETHERNET:
 951                 break;
 952         default:
 953                 packet_send_debug("Unsupported tunnel device mode.");
 954                 return NULL;
 955         }
 956         if ((options.permit_tun & mode) == 0) {
 957                 packet_send_debug("Server has rejected tunnel device "
 958                     "forwarding");
 959                 return NULL;
 960         }
 961
 962         tun = packet_get_int();
 963         if (forced_tun_device != -1) {
 964                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 965                         goto done;
 966                 tun = forced_tun_device;
 967         }
 968         sock = tun_open(tun, mode);
 969         if (sock < 0)
 970                 goto done;
 971         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 972             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 973         c->datagram = 1;
 974 #if defined(SSH_TUN_FILTER)
 975         if (mode == SSH_TUNMODE_POINTOPOINT)
 976                 channel_register_filter(c->self, sys_tun_infilter,
 977                     sys_tun_outfilter);
 978 #endif
 979
 980  done:
 981         if (c == NULL)
 982                 packet_send_debug("Failed to open the tunnel device.");
 983         return c;
 984 }
 985
 986 static Channel *
 987 server_request_session(void)
 988 {
 989         Channel *c;
 990
 991         debug("input_session_request");
 992         packet_check_eom();
 993         /*
 994          * A server session has no fd to read or write until a
 995          * CHANNEL_REQUEST for a shell is made, so we set the type to
 996          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 997          * CHANNEL_REQUEST messages is registered.
 998          */
 999         c = channel_new("session", SSH_CHANNEL_LARVAL,
1000             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1001             0, "server-session", 1);
1002         if (session_open(the_authctxt, c->self) != 1) {
1003                 debug("session open failed, free channel %d", c->self);
1004                 channel_free(c);
1005                 return NULL;
1006         }
1007         channel_register_cleanup(c->self, session_close_by_channel, 0);
1008         return c;
1009 }
1010
1011 static void
1012 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1013 {
1014         Channel *c = NULL;
1015         char *ctype;
1016         int rchan;
1017         u_int rmaxpack, rwindow, len;
1018
1019         ctype = packet_get_string(&len);
1020         rchan = packet_get_int();
1021         rwindow = packet_get_int();
1022         rmaxpack = packet_get_int();
1023
1024         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1025             ctype, rchan, rwindow, rmaxpack);
1026
1027         if (strcmp(ctype, "session") == 0) {
1028                 c = server_request_session();
1029         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1030                 c = server_request_direct_tcpip();
1031         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1032                 c = server_request_tun();
1033         }
1034         if (c != NULL) {
1035                 debug("server_input_channel_open: confirm %s", ctype);
1036                 c->remote_id = rchan;
1037                 c->remote_window = rwindow;
1038                 c->remote_maxpacket = rmaxpack;
1039                 if (c->type != SSH_CHANNEL_CONNECTING) {
1040                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1041                         packet_put_int(c->remote_id);
1042                         packet_put_int(c->self);
1043                         packet_put_int(c->local_window);
1044                         packet_put_int(c->local_maxpacket);
1045                         packet_send();
1046                 }
1047         } else {
1048                 debug("server_input_channel_open: failure %s", ctype);
1049                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1050                 packet_put_int(rchan);
1051                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1052                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1053                         packet_put_cstring("open failed");
1054                         packet_put_cstring("");
1055                 }
1056                 packet_send();
1057         }
1058         xfree(ctype);
1059 }
1060
1061 static void
1062 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1063 {
1064         char *rtype;
1065         int want_reply;
1066         int success = 0;
1067
1068         rtype = packet_get_string(NULL);
1069         want_reply = packet_get_char();
1070         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1071
1072         /* -R style forwarding */
1073         if (strcmp(rtype, "tcpip-forward") == 0) {
1074                 struct passwd *pw;
1075                 char *listen_address;
1076                 u_short listen_port;
1077
1078                 pw = the_authctxt->pw;
1079                 if (pw == NULL || !the_authctxt->valid)
1080                         fatal("server_input_global_request: no/invalid user");
1081                 listen_address = packet_get_string(NULL);
1082                 listen_port = (u_short)packet_get_int();
1083                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1084                     listen_address, listen_port);
1085
1086                 /* check permissions */
1087                 if (!options.allow_tcp_forwarding ||
1088                     no_port_forwarding_flag
1089 #ifndef NO_IPPORT_RESERVED_CONCEPT
1090                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1091 #endif
1092                     ) {
1093                         success = 0;
1094                         packet_send_debug("Server has disabled port forwarding.");
1095                 } else {
1096                         /* Start listening on the port */
1097                         success = channel_setup_remote_fwd_listener(
1098                             listen_address, listen_port, options.gateway_ports);
1099                 }
1100                 xfree(listen_address);
1101         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1102                 char *cancel_address;
1103                 u_short cancel_port;
1104
1105                 cancel_address = packet_get_string(NULL);
1106                 cancel_port = (u_short)packet_get_int();
1107                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1108                     cancel_address, cancel_port);
1109
1110                 success = channel_cancel_rport_listener(cancel_address,
1111                     cancel_port);
1112                 xfree(cancel_address);
1113         }
1114         if (want_reply) {
1115                 packet_start(success ?
1116                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1117                 packet_send();
1118                 packet_write_wait();
1119         }
1120         xfree(rtype);
1121 }
1122
1123 static void
1124 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1125 {
1126         Channel *c;
1127         int id, reply, success = 0;
1128         char *rtype;
1129
1130         id = packet_get_int();
1131         rtype = packet_get_string(NULL);
1132         reply = packet_get_char();
1133
1134         debug("server_input_channel_req: channel %d request %s reply %d",
1135             id, rtype, reply);
1136
1137         if ((c = channel_lookup(id)) == NULL)
1138                 packet_disconnect("server_input_channel_req: "
1139                     "unknown channel %d", id);
1140         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1141                 success = session_input_channel_req(c, rtype);
1142         if (reply) {
1143                 packet_start(success ?
1144                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1145                 packet_put_int(c->remote_id);
1146                 packet_send();
1147         }
1148         xfree(rtype);
1149 }
1150
1151 static void
1152 server_init_dispatch_20(void)
1153 {
1154         debug("server_init_dispatch_20");
1155         dispatch_init(&dispatch_protocol_error);
1156         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1157         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1158         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1159         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1160         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1161         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1162         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1163         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1164         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1165         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1166         /* client_alive */
1167         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1168         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1169         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1170         /* rekeying */
1171         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1172 }
1173 static void
1174 server_init_dispatch_13(void)
1175 {
1176         debug("server_init_dispatch_13");
1177         dispatch_init(NULL);
1178         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1179         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1180         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1181         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1182         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1183         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1184         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1185         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1186         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1187 }
1188 static void
1189 server_init_dispatch_15(void)
1190 {
1191         server_init_dispatch_13();
1192         debug("server_init_dispatch_15");
1193         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1194         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1195 }
1196 static void
1197 server_init_dispatch(void)
1198 {
1199         if (compat20)
1200                 server_init_dispatch_20();
1201         else if (compat13)
1202                 server_init_dispatch_13();
1203         else
1204                 server_init_dispatch_15();
1205 }