serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.143 2006/07/26 02:35:17 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/param.h>
  42 #include <sys/wait.h>
  43 #include <sys/socket.h>
  44 #ifdef HAVE_SYS_TIME_H
  45 # include <sys/time.h>
  46 #endif
  47
  48 #include <netinet/in.h>
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <pwd.h>
  53 #include <signal.h>
  54 #include <string.h>
  55 #include <termios.h>
  56 #include <unistd.h>
  57
  58 #include "xmalloc.h"
  59 #include "packet.h"
  60 #include "buffer.h"
  61 #include "log.h"
  62 #include "servconf.h"
  63 #include "canohost.h"
  64 #include "sshpty.h"
  65 #include "channels.h"
  66 #include "compat.h"
  67 #include "ssh1.h"
  68 #include "ssh2.h"
  69 #include "auth.h"
  70 #include "session.h"
  71 #include "dispatch.h"
  72 #include "auth-options.h"
  73 #include "serverloop.h"
  74 #include "misc.h"
  75 #include "kex.h"
  76
  77 extern ServerOptions options;
  78
  79 /* XXX */
  80 extern Kex *xxx_kex;
  81 extern Authctxt *the_authctxt;
  82 extern int use_privsep;
  83
  84 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  85 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  86 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  87 static int fdin;                /* Descriptor for stdin (for writing) */
  88 static int fdout;               /* Descriptor for stdout (for reading);
  89                                    May be same number as fdin. */
  90 static int fderr;               /* Descriptor for stderr.  May be -1. */
  91 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  92 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  93 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  94 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  95 static int stdin_eof = 0;       /* EOF message received from client. */
  96 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  97 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  98 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  99 static int connection_in;       /* Connection to client (input). */
 100 static int connection_out;      /* Connection to client (output). */
 101 static int connection_closed = 0;       /* Connection to client closed. */
 102 static u_int buffer_high;       /* "Soft" max buffer size. */
 103 static int client_alive_timeouts = 0;
 104
 105 /*
 106  * This SIGCHLD kludge is used to detect when the child exits.  The server
 107  * will exit after that, as soon as forwarded connections have terminated.
 108  */
 109
 110 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 111
 112 /* Cleanup on signals (!use_privsep case only) */
 113 static volatile sig_atomic_t received_sigterm = 0;
 114
 115 /* prototypes */
 116 static void server_init_dispatch(void);
 117
 118 /*
 119  * we write to this pipe if a SIGCHLD is caught in order to avoid
 120  * the race between select() and child_terminated
 121  */
 122 static int notify_pipe[2];
 123 static void
 124 notify_setup(void)
 125 {
 126         if (pipe(notify_pipe) < 0) {
 127                 error("pipe(notify_pipe) failed %s", strerror(errno));
 128         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 129             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 130                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 131                 close(notify_pipe[0]);
 132                 close(notify_pipe[1]);
 133         } else {
 134                 set_nonblock(notify_pipe[0]);
 135                 set_nonblock(notify_pipe[1]);
 136                 return;
 137         }
 138         notify_pipe[0] = -1;    /* read end */
 139         notify_pipe[1] = -1;    /* write end */
 140 }
 141 static void
 142 notify_parent(void)
 143 {
 144         if (notify_pipe[1] != -1)
 145                 write(notify_pipe[1], "", 1);
 146 }
 147 static void
 148 notify_prepare(fd_set *readset)
 149 {
 150         if (notify_pipe[0] != -1)
 151                 FD_SET(notify_pipe[0], readset);
 152 }
 153 static void
 154 notify_done(fd_set *readset)
 155 {
 156         char c;
 157
 158         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 159                 while (read(notify_pipe[0], &c, 1) != -1)
 160                         debug2("notify_done: reading");
 161 }
 162
 163 /*ARGSUSED*/
 164 static void
 165 sigchld_handler(int sig)
 166 {
 167         int save_errno = errno;
 168         child_terminated = 1;
 169 #ifndef _UNICOS
 170         mysignal(SIGCHLD, sigchld_handler);
 171 #endif
 172         notify_parent();
 173         errno = save_errno;
 174 }
 175
 176 /*ARGSUSED*/
 177 static void
 178 sigterm_handler(int sig)
 179 {
 180         received_sigterm = sig;
 181 }
 182
 183 /*
 184  * Make packets from buffered stderr data, and buffer it for sending
 185  * to the client.
 186  */
 187 static void
 188 make_packets_from_stderr_data(void)
 189 {
 190         u_int len;
 191
 192         /* Send buffered stderr data to the client. */
 193         while (buffer_len(&stderr_buffer) > 0 &&
 194             packet_not_very_much_data_to_write()) {
 195                 len = buffer_len(&stderr_buffer);
 196                 if (packet_is_interactive()) {
 197                         if (len > 512)
 198                                 len = 512;
 199                 } else {
 200                         /* Keep the packets at reasonable size. */
 201                         if (len > packet_get_maxsize())
 202                                 len = packet_get_maxsize();
 203                 }
 204                 packet_start(SSH_SMSG_STDERR_DATA);
 205                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 206                 packet_send();
 207                 buffer_consume(&stderr_buffer, len);
 208                 stderr_bytes += len;
 209         }
 210 }
 211
 212 /*
 213  * Make packets from buffered stdout data, and buffer it for sending to the
 214  * client.
 215  */
 216 static void
 217 make_packets_from_stdout_data(void)
 218 {
 219         u_int len;
 220
 221         /* Send buffered stdout data to the client. */
 222         while (buffer_len(&stdout_buffer) > 0 &&
 223             packet_not_very_much_data_to_write()) {
 224                 len = buffer_len(&stdout_buffer);
 225                 if (packet_is_interactive()) {
 226                         if (len > 512)
 227                                 len = 512;
 228                 } else {
 229                         /* Keep the packets at reasonable size. */
 230                         if (len > packet_get_maxsize())
 231                                 len = packet_get_maxsize();
 232                 }
 233                 packet_start(SSH_SMSG_STDOUT_DATA);
 234                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 235                 packet_send();
 236                 buffer_consume(&stdout_buffer, len);
 237                 stdout_bytes += len;
 238         }
 239 }
 240
 241 static void
 242 client_alive_check(void)
 243 {
 244         int channel_id;
 245
 246         /* timeout, check to see how many we have had */
 247         if (++client_alive_timeouts > options.client_alive_count_max)
 248                 packet_disconnect("Timeout, your session not responding.");
 249
 250         /*
 251          * send a bogus global/channel request with "wantreply",
 252          * we should get back a failure
 253          */
 254         if ((channel_id = channel_find_open()) == -1) {
 255                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 256                 packet_put_cstring("keepalive@openssh.com");
 257                 packet_put_char(1);     /* boolean: want reply */
 258         } else {
 259                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 260         }
 261         packet_send();
 262 }
 263
 264 /*
 265  * Sleep in select() until we can do something.  This will initialize the
 266  * select masks.  Upon return, the masks will indicate which descriptors
 267  * have data or can accept data.  Optionally, a maximum time can be specified
 268  * for the duration of the wait (0 = infinite).
 269  */
 270 static void
 271 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 272     u_int *nallocp, u_int max_time_milliseconds)
 273 {
 274         struct timeval tv, *tvp;
 275         int ret;
 276         int client_alive_scheduled = 0;
 277
 278         /*
 279          * if using client_alive, set the max timeout accordingly,
 280          * and indicate that this particular timeout was for client
 281          * alive by setting the client_alive_scheduled flag.
 282          *
 283          * this could be randomized somewhat to make traffic
 284          * analysis more difficult, but we're not doing it yet.
 285          */
 286         if (compat20 &&
 287             max_time_milliseconds == 0 && options.client_alive_interval) {
 288                 client_alive_scheduled = 1;
 289                 max_time_milliseconds = options.client_alive_interval * 1000;
 290         }
 291
 292         /* Allocate and update select() masks for channel descriptors. */
 293         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 294
 295         if (compat20) {
 296 #if 0
 297                 /* wrong: bad condition XXX */
 298                 if (channel_not_very_much_buffered_data())
 299 #endif
 300                 FD_SET(connection_in, *readsetp);
 301         } else {
 302                 /*
 303                  * Read packets from the client unless we have too much
 304                  * buffered stdin or channel data.
 305                  */
 306                 if (buffer_len(&stdin_buffer) < buffer_high &&
 307                     channel_not_very_much_buffered_data())
 308                         FD_SET(connection_in, *readsetp);
 309                 /*
 310                  * If there is not too much data already buffered going to
 311                  * the client, try to get some more data from the program.
 312                  */
 313                 if (packet_not_very_much_data_to_write()) {
 314                         if (!fdout_eof)
 315                                 FD_SET(fdout, *readsetp);
 316                         if (!fderr_eof)
 317                                 FD_SET(fderr, *readsetp);
 318                 }
 319                 /*
 320                  * If we have buffered data, try to write some of that data
 321                  * to the program.
 322                  */
 323                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 324                         FD_SET(fdin, *writesetp);
 325         }
 326         notify_prepare(*readsetp);
 327
 328         /*
 329          * If we have buffered packet data going to the client, mark that
 330          * descriptor.
 331          */
 332         if (packet_have_data_to_write())
 333                 FD_SET(connection_out, *writesetp);
 334
 335         /*
 336          * If child has terminated and there is enough buffer space to read
 337          * from it, then read as much as is available and exit.
 338          */
 339         if (child_terminated && packet_not_very_much_data_to_write())
 340                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 341                         max_time_milliseconds = 100;
 342
 343         if (max_time_milliseconds == 0)
 344                 tvp = NULL;
 345         else {
 346                 tv.tv_sec = max_time_milliseconds / 1000;
 347                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 348                 tvp = &tv;
 349         }
 350
 351         /* Wait for something to happen, or the timeout to expire. */
 352         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 353
 354         if (ret == -1) {
 355                 memset(*readsetp, 0, *nallocp);
 356                 memset(*writesetp, 0, *nallocp);
 357                 if (errno != EINTR)
 358                         error("select: %.100s", strerror(errno));
 359         } else if (ret == 0 && client_alive_scheduled)
 360                 client_alive_check();
 361
 362         notify_done(*readsetp);
 363 }
 364
 365 /*
 366  * Processes input from the client and the program.  Input data is stored
 367  * in buffers and processed later.
 368  */
 369 static void
 370 process_input(fd_set *readset)
 371 {
 372         int len;
 373         char buf[16384];
 374
 375         /* Read and buffer any input data from the client. */
 376         if (FD_ISSET(connection_in, readset)) {
 377                 len = read(connection_in, buf, sizeof(buf));
 378                 if (len == 0) {
 379                         verbose("Connection closed by %.100s",
 380                             get_remote_ipaddr());
 381                         connection_closed = 1;
 382                         if (compat20)
 383                                 return;
 384                         cleanup_exit(255);
 385                 } else if (len < 0) {
 386                         if (errno != EINTR && errno != EAGAIN) {
 387                                 verbose("Read error from remote host "
 388                                     "%.100s: %.100s",
 389                                     get_remote_ipaddr(), strerror(errno));
 390                                 cleanup_exit(255);
 391                         }
 392                 } else {
 393                         /* Buffer any received data. */
 394                         packet_process_incoming(buf, len);
 395                 }
 396         }
 397         if (compat20)
 398                 return;
 399
 400         /* Read and buffer any available stdout data from the program. */
 401         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 402                 errno = 0;
 403                 len = read(fdout, buf, sizeof(buf));
 404                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 405                         /* do nothing */
 406 #ifndef PTY_ZEROREAD
 407                 } else if (len <= 0) {
 408 #else
 409                 } else if ((!isatty(fdout) && len <= 0) ||
 410                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 411 #endif
 412                         fdout_eof = 1;
 413                 } else {
 414                         buffer_append(&stdout_buffer, buf, len);
 415                         fdout_bytes += len;
 416                 }
 417         }
 418         /* Read and buffer any available stderr data from the program. */
 419         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 420                 errno = 0;
 421                 len = read(fderr, buf, sizeof(buf));
 422                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 423                         /* do nothing */
 424 #ifndef PTY_ZEROREAD
 425                 } else if (len <= 0) {
 426 #else
 427                 } else if ((!isatty(fderr) && len <= 0) ||
 428                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 429 #endif
 430                         fderr_eof = 1;
 431                 } else {
 432                         buffer_append(&stderr_buffer, buf, len);
 433                 }
 434         }
 435 }
 436
 437 /*
 438  * Sends data from internal buffers to client program stdin.
 439  */
 440 static void
 441 process_output(fd_set *writeset)
 442 {
 443         struct termios tio;
 444         u_char *data;
 445         u_int dlen;
 446         int len;
 447
 448         /* Write buffered data to program stdin. */
 449         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 450                 data = buffer_ptr(&stdin_buffer);
 451                 dlen = buffer_len(&stdin_buffer);
 452                 len = write(fdin, data, dlen);
 453                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 454                         /* do nothing */
 455                 } else if (len <= 0) {
 456                         if (fdin != fdout)
 457                                 close(fdin);
 458                         else
 459                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 460                         fdin = -1;
 461                 } else {
 462                         /* Successful write. */
 463                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 464                             tcgetattr(fdin, &tio) == 0 &&
 465                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 466                                 /*
 467                                  * Simulate echo to reduce the impact of
 468                                  * traffic analysis
 469                                  */
 470                                 packet_send_ignore(len);
 471                                 packet_send();
 472                         }
 473                         /* Consume the data from the buffer. */
 474                         buffer_consume(&stdin_buffer, len);
 475                         /* Update the count of bytes written to the program. */
 476                         stdin_bytes += len;
 477                 }
 478         }
 479         /* Send any buffered packet data to the client. */
 480         if (FD_ISSET(connection_out, writeset))
 481                 packet_write_poll();
 482 }
 483
 484 /*
 485  * Wait until all buffered output has been sent to the client.
 486  * This is used when the program terminates.
 487  */
 488 static void
 489 drain_output(void)
 490 {
 491         /* Send any buffered stdout data to the client. */
 492         if (buffer_len(&stdout_buffer) > 0) {
 493                 packet_start(SSH_SMSG_STDOUT_DATA);
 494                 packet_put_string(buffer_ptr(&stdout_buffer),
 495                                   buffer_len(&stdout_buffer));
 496                 packet_send();
 497                 /* Update the count of sent bytes. */
 498                 stdout_bytes += buffer_len(&stdout_buffer);
 499         }
 500         /* Send any buffered stderr data to the client. */
 501         if (buffer_len(&stderr_buffer) > 0) {
 502                 packet_start(SSH_SMSG_STDERR_DATA);
 503                 packet_put_string(buffer_ptr(&stderr_buffer),
 504                                   buffer_len(&stderr_buffer));
 505                 packet_send();
 506                 /* Update the count of sent bytes. */
 507                 stderr_bytes += buffer_len(&stderr_buffer);
 508         }
 509         /* Wait until all buffered data has been written to the client. */
 510         packet_write_wait();
 511 }
 512
 513 static void
 514 process_buffered_input_packets(void)
 515 {
 516         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 517 }
 518
 519 /*
 520  * Performs the interactive session.  This handles data transmission between
 521  * the client and the program.  Note that the notion of stdin, stdout, and
 522  * stderr in this function is sort of reversed: this function writes to
 523  * stdin (of the child program), and reads from stdout and stderr (of the
 524  * child program).
 525  */
 526 void
 527 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 528 {
 529         fd_set *readset = NULL, *writeset = NULL;
 530         int max_fd = 0;
 531         u_int nalloc = 0;
 532         int wait_status;        /* Status returned by wait(). */
 533         pid_t wait_pid;         /* pid returned by wait(). */
 534         int waiting_termination = 0;    /* Have displayed waiting close message. */
 535         u_int max_time_milliseconds;
 536         u_int previous_stdout_buffer_bytes;
 537         u_int stdout_buffer_bytes;
 538         int type;
 539
 540         debug("Entering interactive session.");
 541
 542         /* Initialize the SIGCHLD kludge. */
 543         child_terminated = 0;
 544         mysignal(SIGCHLD, sigchld_handler);
 545
 546         if (!use_privsep) {
 547                 signal(SIGTERM, sigterm_handler);
 548                 signal(SIGINT, sigterm_handler);
 549                 signal(SIGQUIT, sigterm_handler);
 550         }
 551
 552         /* Initialize our global variables. */
 553         fdin = fdin_arg;
 554         fdout = fdout_arg;
 555         fderr = fderr_arg;
 556
 557         /* nonblocking IO */
 558         set_nonblock(fdin);
 559         set_nonblock(fdout);
 560         /* we don't have stderr for interactive terminal sessions, see below */
 561         if (fderr != -1)
 562                 set_nonblock(fderr);
 563
 564         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 565                 fdin_is_tty = 1;
 566
 567         connection_in = packet_get_connection_in();
 568         connection_out = packet_get_connection_out();
 569
 570         notify_setup();
 571
 572         previous_stdout_buffer_bytes = 0;
 573
 574         /* Set approximate I/O buffer size. */
 575         if (packet_is_interactive())
 576                 buffer_high = 4096;
 577         else
 578                 buffer_high = 64 * 1024;
 579
 580 #if 0
 581         /* Initialize max_fd to the maximum of the known file descriptors. */
 582         max_fd = MAX(connection_in, connection_out);
 583         max_fd = MAX(max_fd, fdin);
 584         max_fd = MAX(max_fd, fdout);
 585         if (fderr != -1)
 586                 max_fd = MAX(max_fd, fderr);
 587 #endif
 588
 589         /* Initialize Initialize buffers. */
 590         buffer_init(&stdin_buffer);
 591         buffer_init(&stdout_buffer);
 592         buffer_init(&stderr_buffer);
 593
 594         /*
 595          * If we have no separate fderr (which is the case when we have a pty
 596          * - there we cannot make difference between data sent to stdout and
 597          * stderr), indicate that we have seen an EOF from stderr.  This way
 598          * we don't need to check the descriptor everywhere.
 599          */
 600         if (fderr == -1)
 601                 fderr_eof = 1;
 602
 603         server_init_dispatch();
 604
 605         /* Main loop of the server for the interactive session mode. */
 606         for (;;) {
 607
 608                 /* Process buffered packets from the client. */
 609                 process_buffered_input_packets();
 610
 611                 /*
 612                  * If we have received eof, and there is no more pending
 613                  * input data, cause a real eof by closing fdin.
 614                  */
 615                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 616                         if (fdin != fdout)
 617                                 close(fdin);
 618                         else
 619                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 620                         fdin = -1;
 621                 }
 622                 /* Make packets from buffered stderr data to send to the client. */
 623                 make_packets_from_stderr_data();
 624
 625                 /*
 626                  * Make packets from buffered stdout data to send to the
 627                  * client. If there is very little to send, this arranges to
 628                  * not send them now, but to wait a short while to see if we
 629                  * are getting more data. This is necessary, as some systems
 630                  * wake up readers from a pty after each separate character.
 631                  */
 632                 max_time_milliseconds = 0;
 633                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 634                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 635                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 636                         /* try again after a while */
 637                         max_time_milliseconds = 10;
 638                 } else {
 639                         /* Send it now. */
 640                         make_packets_from_stdout_data();
 641                 }
 642                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 643
 644                 /* Send channel data to the client. */
 645                 if (packet_not_very_much_data_to_write())
 646                         channel_output_poll();
 647
 648                 /*
 649                  * Bail out of the loop if the program has closed its output
 650                  * descriptors, and we have no more data to send to the
 651                  * client, and there is no pending buffered data.
 652                  */
 653                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 654                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 655                         if (!channel_still_open())
 656                                 break;
 657                         if (!waiting_termination) {
 658                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 659                                 char *cp;
 660                                 waiting_termination = 1;
 661                                 buffer_append(&stderr_buffer, s, strlen(s));
 662
 663                                 /* Display list of open channels. */
 664                                 cp = channel_open_message();
 665                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 666                                 xfree(cp);
 667                         }
 668                 }
 669                 max_fd = MAX(connection_in, connection_out);
 670                 max_fd = MAX(max_fd, fdin);
 671                 max_fd = MAX(max_fd, fdout);
 672                 max_fd = MAX(max_fd, fderr);
 673                 max_fd = MAX(max_fd, notify_pipe[0]);
 674
 675                 /* Sleep in select() until we can do something. */
 676                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 677                     &nalloc, max_time_milliseconds);
 678
 679                 if (received_sigterm) {
 680                         logit("Exiting on signal %d", received_sigterm);
 681                         /* Clean up sessions, utmp, etc. */
 682                         cleanup_exit(255);
 683                 }
 684
 685                 /* Process any channel events. */
 686                 channel_after_select(readset, writeset);
 687
 688                 /* Process input from the client and from program stdout/stderr. */
 689                 process_input(readset);
 690
 691                 /* Process output to the client and to program stdin. */
 692                 process_output(writeset);
 693         }
 694         if (readset)
 695                 xfree(readset);
 696         if (writeset)
 697                 xfree(writeset);
 698
 699         /* Cleanup and termination code. */
 700
 701         /* Wait until all output has been sent to the client. */
 702         drain_output();
 703
 704         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 705             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 706
 707         /* Free and clear the buffers. */
 708         buffer_free(&stdin_buffer);
 709         buffer_free(&stdout_buffer);
 710         buffer_free(&stderr_buffer);
 711
 712         /* Close the file descriptors. */
 713         if (fdout != -1)
 714                 close(fdout);
 715         fdout = -1;
 716         fdout_eof = 1;
 717         if (fderr != -1)
 718                 close(fderr);
 719         fderr = -1;
 720         fderr_eof = 1;
 721         if (fdin != -1)
 722                 close(fdin);
 723         fdin = -1;
 724
 725         channel_free_all();
 726
 727         /* We no longer want our SIGCHLD handler to be called. */
 728         mysignal(SIGCHLD, SIG_DFL);
 729
 730         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 731                 if (errno != EINTR)
 732                         packet_disconnect("wait: %.100s", strerror(errno));
 733         if (wait_pid != pid)
 734                 error("Strange, wait returned pid %ld, expected %ld",
 735                     (long)wait_pid, (long)pid);
 736
 737         /* Check if it exited normally. */
 738         if (WIFEXITED(wait_status)) {
 739                 /* Yes, normal exit.  Get exit status and send it to the client. */
 740                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 741                 packet_start(SSH_SMSG_EXITSTATUS);
 742                 packet_put_int(WEXITSTATUS(wait_status));
 743                 packet_send();
 744                 packet_write_wait();
 745
 746                 /*
 747                  * Wait for exit confirmation.  Note that there might be
 748                  * other packets coming before it; however, the program has
 749                  * already died so we just ignore them.  The client is
 750                  * supposed to respond with the confirmation when it receives
 751                  * the exit status.
 752                  */
 753                 do {
 754                         type = packet_read();
 755                 }
 756                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 757
 758                 debug("Received exit confirmation.");
 759                 return;
 760         }
 761         /* Check if the program terminated due to a signal. */
 762         if (WIFSIGNALED(wait_status))
 763                 packet_disconnect("Command terminated on signal %d.",
 764                                   WTERMSIG(wait_status));
 765
 766         /* Some weird exit cause.  Just exit. */
 767         packet_disconnect("wait returned status %04x.", wait_status);
 768         /* NOTREACHED */
 769 }
 770
 771 static void
 772 collect_children(void)
 773 {
 774         pid_t pid;
 775         sigset_t oset, nset;
 776         int status;
 777
 778         /* block SIGCHLD while we check for dead children */
 779         sigemptyset(&nset);
 780         sigaddset(&nset, SIGCHLD);
 781         sigprocmask(SIG_BLOCK, &nset, &oset);
 782         if (child_terminated) {
 783                 debug("Received SIGCHLD.");
 784                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 785                     (pid < 0 && errno == EINTR))
 786                         if (pid > 0)
 787                                 session_close_by_pid(pid, status);
 788                 child_terminated = 0;
 789         }
 790         sigprocmask(SIG_SETMASK, &oset, NULL);
 791 }
 792
 793 void
 794 server_loop2(Authctxt *authctxt)
 795 {
 796         fd_set *readset = NULL, *writeset = NULL;
 797         int rekeying = 0, max_fd, nalloc = 0;
 798
 799         debug("Entering interactive session for SSH2.");
 800
 801         mysignal(SIGCHLD, sigchld_handler);
 802         child_terminated = 0;
 803         connection_in = packet_get_connection_in();
 804         connection_out = packet_get_connection_out();
 805
 806         if (!use_privsep) {
 807                 signal(SIGTERM, sigterm_handler);
 808                 signal(SIGINT, sigterm_handler);
 809                 signal(SIGQUIT, sigterm_handler);
 810         }
 811
 812         notify_setup();
 813
 814         max_fd = MAX(connection_in, connection_out);
 815         max_fd = MAX(max_fd, notify_pipe[0]);
 816
 817         server_init_dispatch();
 818
 819         for (;;) {
 820                 process_buffered_input_packets();
 821
 822                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 823
 824                 if (!rekeying && packet_not_very_much_data_to_write())
 825                         channel_output_poll();
 826                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 827                     &nalloc, 0);
 828
 829                 if (received_sigterm) {
 830                         logit("Exiting on signal %d", received_sigterm);
 831                         /* Clean up sessions, utmp, etc. */
 832                         cleanup_exit(255);
 833                 }
 834
 835                 collect_children();
 836                 if (!rekeying) {
 837                         channel_after_select(readset, writeset);
 838                         if (packet_need_rekeying()) {
 839                                 debug("need rekeying");
 840                                 xxx_kex->done = 0;
 841                                 kex_send_kexinit(xxx_kex);
 842                         }
 843                 }
 844                 process_input(readset);
 845                 if (connection_closed)
 846                         break;
 847                 process_output(writeset);
 848         }
 849         collect_children();
 850
 851         if (readset)
 852                 xfree(readset);
 853         if (writeset)
 854                 xfree(writeset);
 855
 856         /* free all channels, no more reads and writes */
 857         channel_free_all();
 858
 859         /* free remaining sessions, e.g. remove wtmp entries */
 860         session_destroy_all(NULL);
 861 }
 862
 863 static void
 864 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 865 {
 866         debug("Got %d/%u for keepalive", type, seq);
 867         /*
 868          * reset timeout, since we got a sane answer from the client.
 869          * even if this was generated by something other than
 870          * the bogus CHANNEL_REQUEST we send for keepalives.
 871          */
 872         client_alive_timeouts = 0;
 873 }
 874
 875 static void
 876 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 877 {
 878         char *data;
 879         u_int data_len;
 880
 881         /* Stdin data from the client.  Append it to the buffer. */
 882         /* Ignore any data if the client has closed stdin. */
 883         if (fdin == -1)
 884                 return;
 885         data = packet_get_string(&data_len);
 886         packet_check_eom();
 887         buffer_append(&stdin_buffer, data, data_len);
 888         memset(data, 0, data_len);
 889         xfree(data);
 890 }
 891
 892 static void
 893 server_input_eof(int type, u_int32_t seq, void *ctxt)
 894 {
 895         /*
 896          * Eof from the client.  The stdin descriptor to the
 897          * program will be closed when all buffered data has
 898          * drained.
 899          */
 900         debug("EOF received for stdin.");
 901         packet_check_eom();
 902         stdin_eof = 1;
 903 }
 904
 905 static void
 906 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 907 {
 908         u_int row = packet_get_int();
 909         u_int col = packet_get_int();
 910         u_int xpixel = packet_get_int();
 911         u_int ypixel = packet_get_int();
 912
 913         debug("Window change received.");
 914         packet_check_eom();
 915         if (fdin != -1)
 916                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 917 }
 918
 919 static Channel *
 920 server_request_direct_tcpip(void)
 921 {
 922         Channel *c;
 923         int sock;
 924         char *target, *originator;
 925         int target_port, originator_port;
 926
 927         target = packet_get_string(NULL);
 928         target_port = packet_get_int();
 929         originator = packet_get_string(NULL);
 930         originator_port = packet_get_int();
 931         packet_check_eom();
 932
 933         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 934             originator, originator_port, target, target_port);
 935
 936         /* XXX check permission */
 937         sock = channel_connect_to(target, target_port);
 938         xfree(target);
 939         xfree(originator);
 940         if (sock < 0)
 941                 return NULL;
 942         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 943             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 944             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 945         return c;
 946 }
 947
 948 static Channel *
 949 server_request_tun(void)
 950 {
 951         Channel *c = NULL;
 952         int mode, tun;
 953         int sock;
 954
 955         mode = packet_get_int();
 956         switch (mode) {
 957         case SSH_TUNMODE_POINTOPOINT:
 958         case SSH_TUNMODE_ETHERNET:
 959                 break;
 960         default:
 961                 packet_send_debug("Unsupported tunnel device mode.");
 962                 return NULL;
 963         }
 964         if ((options.permit_tun & mode) == 0) {
 965                 packet_send_debug("Server has rejected tunnel device "
 966                     "forwarding");
 967                 return NULL;
 968         }
 969
 970         tun = packet_get_int();
 971         if (forced_tun_device != -1) {
 972                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 973                         goto done;
 974                 tun = forced_tun_device;
 975         }
 976         sock = tun_open(tun, mode);
 977         if (sock < 0)
 978                 goto done;
 979         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 980             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 981         c->datagram = 1;
 982 #if defined(SSH_TUN_FILTER)
 983         if (mode == SSH_TUNMODE_POINTOPOINT)
 984                 channel_register_filter(c->self, sys_tun_infilter,
 985                     sys_tun_outfilter);
 986 #endif
 987
 988  done:
 989         if (c == NULL)
 990                 packet_send_debug("Failed to open the tunnel device.");
 991         return c;
 992 }
 993
 994 static Channel *
 995 server_request_session(void)
 996 {
 997         Channel *c;
 998
 999         debug("input_session_request");
1000         packet_check_eom();
1001         /*
1002          * A server session has no fd to read or write until a
1003          * CHANNEL_REQUEST for a shell is made, so we set the type to
1004          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1005          * CHANNEL_REQUEST messages is registered.
1006          */
1007         c = channel_new("session", SSH_CHANNEL_LARVAL,
1008             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1009             0, "server-session", 1);
1010         if (session_open(the_authctxt, c->self) != 1) {
1011                 debug("session open failed, free channel %d", c->self);
1012                 channel_free(c);
1013                 return NULL;
1014         }
1015         channel_register_cleanup(c->self, session_close_by_channel, 0);
1016         return c;
1017 }
1018
1019 static void
1020 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1021 {
1022         Channel *c = NULL;
1023         char *ctype;
1024         int rchan;
1025         u_int rmaxpack, rwindow, len;
1026
1027         ctype = packet_get_string(&len);
1028         rchan = packet_get_int();
1029         rwindow = packet_get_int();
1030         rmaxpack = packet_get_int();
1031
1032         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1033             ctype, rchan, rwindow, rmaxpack);
1034
1035         if (strcmp(ctype, "session") == 0) {
1036                 c = server_request_session();
1037         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1038                 c = server_request_direct_tcpip();
1039         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1040                 c = server_request_tun();
1041         }
1042         if (c != NULL) {
1043                 debug("server_input_channel_open: confirm %s", ctype);
1044                 c->remote_id = rchan;
1045                 c->remote_window = rwindow;
1046                 c->remote_maxpacket = rmaxpack;
1047                 if (c->type != SSH_CHANNEL_CONNECTING) {
1048                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1049                         packet_put_int(c->remote_id);
1050                         packet_put_int(c->self);
1051                         packet_put_int(c->local_window);
1052                         packet_put_int(c->local_maxpacket);
1053                         packet_send();
1054                 }
1055         } else {
1056                 debug("server_input_channel_open: failure %s", ctype);
1057                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1058                 packet_put_int(rchan);
1059                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1060                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1061                         packet_put_cstring("open failed");
1062                         packet_put_cstring("");
1063                 }
1064                 packet_send();
1065         }
1066         xfree(ctype);
1067 }
1068
1069 static void
1070 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1071 {
1072         char *rtype;
1073         int want_reply;
1074         int success = 0;
1075
1076         rtype = packet_get_string(NULL);
1077         want_reply = packet_get_char();
1078         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1079
1080         /* -R style forwarding */
1081         if (strcmp(rtype, "tcpip-forward") == 0) {
1082                 struct passwd *pw;
1083                 char *listen_address;
1084                 u_short listen_port;
1085
1086                 pw = the_authctxt->pw;
1087                 if (pw == NULL || !the_authctxt->valid)
1088                         fatal("server_input_global_request: no/invalid user");
1089                 listen_address = packet_get_string(NULL);
1090                 listen_port = (u_short)packet_get_int();
1091                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1092                     listen_address, listen_port);
1093
1094                 /* check permissions */
1095                 if (!options.allow_tcp_forwarding ||
1096                     no_port_forwarding_flag
1097 #ifndef NO_IPPORT_RESERVED_CONCEPT
1098                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1099 #endif
1100                     ) {
1101                         success = 0;
1102                         packet_send_debug("Server has disabled port forwarding.");
1103                 } else {
1104                         /* Start listening on the port */
1105                         success = channel_setup_remote_fwd_listener(
1106                             listen_address, listen_port, options.gateway_ports);
1107                 }
1108                 xfree(listen_address);
1109         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1110                 char *cancel_address;
1111                 u_short cancel_port;
1112
1113                 cancel_address = packet_get_string(NULL);
1114                 cancel_port = (u_short)packet_get_int();
1115                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1116                     cancel_address, cancel_port);
1117
1118                 success = channel_cancel_rport_listener(cancel_address,
1119                     cancel_port);
1120                 xfree(cancel_address);
1121         }
1122         if (want_reply) {
1123                 packet_start(success ?
1124                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1125                 packet_send();
1126                 packet_write_wait();
1127         }
1128         xfree(rtype);
1129 }
1130
1131 static void
1132 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1133 {
1134         Channel *c;
1135         int id, reply, success = 0;
1136         char *rtype;
1137
1138         id = packet_get_int();
1139         rtype = packet_get_string(NULL);
1140         reply = packet_get_char();
1141
1142         debug("server_input_channel_req: channel %d request %s reply %d",
1143             id, rtype, reply);
1144
1145         if ((c = channel_lookup(id)) == NULL)
1146                 packet_disconnect("server_input_channel_req: "
1147                     "unknown channel %d", id);
1148         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1149                 success = session_input_channel_req(c, rtype);
1150         if (reply) {
1151                 packet_start(success ?
1152                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1153                 packet_put_int(c->remote_id);
1154                 packet_send();
1155         }
1156         xfree(rtype);
1157 }
1158
1159 static void
1160 server_init_dispatch_20(void)
1161 {
1162         debug("server_init_dispatch_20");
1163         dispatch_init(&dispatch_protocol_error);
1164         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1165         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1166         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1167         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1168         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1169         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1170         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1171         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1172         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1173         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1174         /* client_alive */
1175         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1176         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1177         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1178         /* rekeying */
1179         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1180 }
1181 static void
1182 server_init_dispatch_13(void)
1183 {
1184         debug("server_init_dispatch_13");
1185         dispatch_init(NULL);
1186         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1187         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1188         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1189         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1190         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1191         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1192         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1193         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1194         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1195 }
1196 static void
1197 server_init_dispatch_15(void)
1198 {
1199         server_init_dispatch_13();
1200         debug("server_init_dispatch_15");
1201         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1202         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1203 }
1204 static void
1205 server_init_dispatch(void)
1206 {
1207         if (compat20)
1208                 server_init_dispatch_20();
1209         else if (compat13)
1210                 server_init_dispatch_13();
1211         else
1212                 server_init_dispatch_15();
1213 }