serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.135 2006/03/25 18:30:55 deraadt 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
  43 #include <signal.h>
  44 #include <termios.h>
  45
  46 #include "xmalloc.h"
  47 #include "packet.h"
  48 #include "buffer.h"
  49 #include "log.h"
  50 #include "servconf.h"
  51 #include "canohost.h"
  52 #include "sshpty.h"
  53 #include "channels.h"
  54 #include "compat.h"
  55 #include "ssh1.h"
  56 #include "ssh2.h"
  57 #include "auth.h"
  58 #include "session.h"
  59 #include "dispatch.h"
  60 #include "auth-options.h"
  61 #include "serverloop.h"
  62 #include "misc.h"
  63 #include "kex.h"
  64
  65 extern ServerOptions options;
  66
  67 /* XXX */
  68 extern Kex *xxx_kex;
  69 extern Authctxt *the_authctxt;
  70 extern int use_privsep;
  71
  72 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  73 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  74 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  75 static int fdin;                /* Descriptor for stdin (for writing) */
  76 static int fdout;               /* Descriptor for stdout (for reading);
  77                                    May be same number as fdin. */
  78 static int fderr;               /* Descriptor for stderr.  May be -1. */
  79 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  80 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  81 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  82 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  83 static int stdin_eof = 0;       /* EOF message received from client. */
  84 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  85 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  86 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  87 static int connection_in;       /* Connection to client (input). */
  88 static int connection_out;      /* Connection to client (output). */
  89 static int connection_closed = 0;       /* Connection to client closed. */
  90 static u_int buffer_high;       /* "Soft" max buffer size. */
  91 static int client_alive_timeouts = 0;
  92
  93 /*
  94  * This SIGCHLD kludge is used to detect when the child exits.  The server
  95  * will exit after that, as soon as forwarded connections have terminated.
  96  */
  97
  98 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  99
 100 /* Cleanup on signals (!use_privsep case only) */
 101 static volatile sig_atomic_t received_sigterm = 0;
 102
 103 /* prototypes */
 104 static void server_init_dispatch(void);
 105
 106 /*
 107  * we write to this pipe if a SIGCHLD is caught in order to avoid
 108  * the race between select() and child_terminated
 109  */
 110 static int notify_pipe[2];
 111 static void
 112 notify_setup(void)
 113 {
 114         if (pipe(notify_pipe) < 0) {
 115                 error("pipe(notify_pipe) failed %s", strerror(errno));
 116         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 117             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 118                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 119                 close(notify_pipe[0]);
 120                 close(notify_pipe[1]);
 121         } else {
 122                 set_nonblock(notify_pipe[0]);
 123                 set_nonblock(notify_pipe[1]);
 124                 return;
 125         }
 126         notify_pipe[0] = -1;    /* read end */
 127         notify_pipe[1] = -1;    /* write end */
 128 }
 129 static void
 130 notify_parent(void)
 131 {
 132         if (notify_pipe[1] != -1)
 133                 write(notify_pipe[1], "", 1);
 134 }
 135 static void
 136 notify_prepare(fd_set *readset)
 137 {
 138         if (notify_pipe[0] != -1)
 139                 FD_SET(notify_pipe[0], readset);
 140 }
 141 static void
 142 notify_done(fd_set *readset)
 143 {
 144         char c;
 145
 146         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 147                 while (read(notify_pipe[0], &c, 1) != -1)
 148                         debug2("notify_done: reading");
 149 }
 150
 151 /*ARGSUSED*/
 152 static void
 153 sigchld_handler(int sig)
 154 {
 155         int save_errno = errno;
 156         child_terminated = 1;
 157 #ifndef _UNICOS
 158         mysignal(SIGCHLD, sigchld_handler);
 159 #endif
 160         notify_parent();
 161         errno = save_errno;
 162 }
 163
 164 /*ARGSUSED*/
 165 static void
 166 sigterm_handler(int sig)
 167 {
 168         received_sigterm = sig;
 169 }
 170
 171 /*
 172  * Make packets from buffered stderr data, and buffer it for sending
 173  * to the client.
 174  */
 175 static void
 176 make_packets_from_stderr_data(void)
 177 {
 178         u_int len;
 179
 180         /* Send buffered stderr data to the client. */
 181         while (buffer_len(&stderr_buffer) > 0 &&
 182             packet_not_very_much_data_to_write()) {
 183                 len = buffer_len(&stderr_buffer);
 184                 if (packet_is_interactive()) {
 185                         if (len > 512)
 186                                 len = 512;
 187                 } else {
 188                         /* Keep the packets at reasonable size. */
 189                         if (len > packet_get_maxsize())
 190                                 len = packet_get_maxsize();
 191                 }
 192                 packet_start(SSH_SMSG_STDERR_DATA);
 193                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 194                 packet_send();
 195                 buffer_consume(&stderr_buffer, len);
 196                 stderr_bytes += len;
 197         }
 198 }
 199
 200 /*
 201  * Make packets from buffered stdout data, and buffer it for sending to the
 202  * client.
 203  */
 204 static void
 205 make_packets_from_stdout_data(void)
 206 {
 207         u_int len;
 208
 209         /* Send buffered stdout data to the client. */
 210         while (buffer_len(&stdout_buffer) > 0 &&
 211             packet_not_very_much_data_to_write()) {
 212                 len = buffer_len(&stdout_buffer);
 213                 if (packet_is_interactive()) {
 214                         if (len > 512)
 215                                 len = 512;
 216                 } else {
 217                         /* Keep the packets at reasonable size. */
 218                         if (len > packet_get_maxsize())
 219                                 len = packet_get_maxsize();
 220                 }
 221                 packet_start(SSH_SMSG_STDOUT_DATA);
 222                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 223                 packet_send();
 224                 buffer_consume(&stdout_buffer, len);
 225                 stdout_bytes += len;
 226         }
 227 }
 228
 229 static void
 230 client_alive_check(void)
 231 {
 232         int channel_id;
 233
 234         /* timeout, check to see how many we have had */
 235         if (++client_alive_timeouts > options.client_alive_count_max)
 236                 packet_disconnect("Timeout, your session not responding.");
 237
 238         /*
 239          * send a bogus global/channel request with "wantreply",
 240          * we should get back a failure
 241          */
 242         if ((channel_id = channel_find_open()) == -1) {
 243                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 244                 packet_put_cstring("keepalive@openssh.com");
 245                 packet_put_char(1);     /* boolean: want reply */
 246         } else {
 247                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 248         }
 249         packet_send();
 250 }
 251
 252 /*
 253  * Sleep in select() until we can do something.  This will initialize the
 254  * select masks.  Upon return, the masks will indicate which descriptors
 255  * have data or can accept data.  Optionally, a maximum time can be specified
 256  * for the duration of the wait (0 = infinite).
 257  */
 258 static void
 259 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 260     u_int *nallocp, u_int max_time_milliseconds)
 261 {
 262         struct timeval tv, *tvp;
 263         int ret;
 264         int client_alive_scheduled = 0;
 265
 266         /*
 267          * if using client_alive, set the max timeout accordingly,
 268          * and indicate that this particular timeout was for client
 269          * alive by setting the client_alive_scheduled flag.
 270          *
 271          * this could be randomized somewhat to make traffic
 272          * analysis more difficult, but we're not doing it yet.
 273          */
 274         if (compat20 &&
 275             max_time_milliseconds == 0 && options.client_alive_interval) {
 276                 client_alive_scheduled = 1;
 277                 max_time_milliseconds = options.client_alive_interval * 1000;
 278         }
 279
 280         /* Allocate and update select() masks for channel descriptors. */
 281         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 282
 283         if (compat20) {
 284 #if 0
 285                 /* wrong: bad condition XXX */
 286                 if (channel_not_very_much_buffered_data())
 287 #endif
 288                 FD_SET(connection_in, *readsetp);
 289         } else {
 290                 /*
 291                  * Read packets from the client unless we have too much
 292                  * buffered stdin or channel data.
 293                  */
 294                 if (buffer_len(&stdin_buffer) < buffer_high &&
 295                     channel_not_very_much_buffered_data())
 296                         FD_SET(connection_in, *readsetp);
 297                 /*
 298                  * If there is not too much data already buffered going to
 299                  * the client, try to get some more data from the program.
 300                  */
 301                 if (packet_not_very_much_data_to_write()) {
 302                         if (!fdout_eof)
 303                                 FD_SET(fdout, *readsetp);
 304                         if (!fderr_eof)
 305                                 FD_SET(fderr, *readsetp);
 306                 }
 307                 /*
 308                  * If we have buffered data, try to write some of that data
 309                  * to the program.
 310                  */
 311                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 312                         FD_SET(fdin, *writesetp);
 313         }
 314         notify_prepare(*readsetp);
 315
 316         /*
 317          * If we have buffered packet data going to the client, mark that
 318          * descriptor.
 319          */
 320         if (packet_have_data_to_write())
 321                 FD_SET(connection_out, *writesetp);
 322
 323         /*
 324          * If child has terminated and there is enough buffer space to read
 325          * from it, then read as much as is available and exit.
 326          */
 327         if (child_terminated && packet_not_very_much_data_to_write())
 328                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 329                         max_time_milliseconds = 100;
 330
 331         if (max_time_milliseconds == 0)
 332                 tvp = NULL;
 333         else {
 334                 tv.tv_sec = max_time_milliseconds / 1000;
 335                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 336                 tvp = &tv;
 337         }
 338
 339         /* Wait for something to happen, or the timeout to expire. */
 340         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 341
 342         if (ret == -1) {
 343                 memset(*readsetp, 0, *nallocp);
 344                 memset(*writesetp, 0, *nallocp);
 345                 if (errno != EINTR)
 346                         error("select: %.100s", strerror(errno));
 347         } else if (ret == 0 && client_alive_scheduled)
 348                 client_alive_check();
 349
 350         notify_done(*readsetp);
 351 }
 352
 353 /*
 354  * Processes input from the client and the program.  Input data is stored
 355  * in buffers and processed later.
 356  */
 357 static void
 358 process_input(fd_set *readset)
 359 {
 360         int len;
 361         char buf[16384];
 362
 363         /* Read and buffer any input data from the client. */
 364         if (FD_ISSET(connection_in, readset)) {
 365                 len = read(connection_in, buf, sizeof(buf));
 366                 if (len == 0) {
 367                         verbose("Connection closed by %.100s",
 368                             get_remote_ipaddr());
 369                         connection_closed = 1;
 370                         if (compat20)
 371                                 return;
 372                         cleanup_exit(255);
 373                 } else if (len < 0) {
 374                         if (errno != EINTR && errno != EAGAIN) {
 375                                 verbose("Read error from remote host "
 376                                     "%.100s: %.100s",
 377                                     get_remote_ipaddr(), strerror(errno));
 378                                 cleanup_exit(255);
 379                         }
 380                 } else {
 381                         /* Buffer any received data. */
 382                         packet_process_incoming(buf, len);
 383                 }
 384         }
 385         if (compat20)
 386                 return;
 387
 388         /* Read and buffer any available stdout data from the program. */
 389         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 390                 errno = 0;
 391                 len = read(fdout, buf, sizeof(buf));
 392                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 393                         /* do nothing */
 394 #ifdef PTY_ZEROREAD
 395                 } else if (len <= 0) {
 396 #else
 397                 } else if (len < 0 || (len == 0 && errno != 0)) {
 398 #endif
 399                         fdout_eof = 1;
 400                 } else {
 401                         buffer_append(&stdout_buffer, buf, len);
 402                         fdout_bytes += len;
 403                 }
 404         }
 405         /* Read and buffer any available stderr data from the program. */
 406         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 407                 errno = 0;
 408                 len = read(fderr, buf, sizeof(buf));
 409                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 410                         /* do nothing */
 411 #ifdef PTY_ZEROREAD
 412                 } else if (len <= 0) {
 413 #else
 414                 } else if (len < 0 || (len == 0 && errno != 0)) {
 415 #endif
 416                         fderr_eof = 1;
 417                 } else {
 418                         buffer_append(&stderr_buffer, buf, len);
 419                 }
 420         }
 421 }
 422
 423 /*
 424  * Sends data from internal buffers to client program stdin.
 425  */
 426 static void
 427 process_output(fd_set *writeset)
 428 {
 429         struct termios tio;
 430         u_char *data;
 431         u_int dlen;
 432         int len;
 433
 434         /* Write buffered data to program stdin. */
 435         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 436                 data = buffer_ptr(&stdin_buffer);
 437                 dlen = buffer_len(&stdin_buffer);
 438                 len = write(fdin, data, dlen);
 439                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 440                         /* do nothing */
 441                 } else if (len <= 0) {
 442                         if (fdin != fdout)
 443                                 close(fdin);
 444                         else
 445                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 446                         fdin = -1;
 447                 } else {
 448                         /* Successful write. */
 449                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 450                             tcgetattr(fdin, &tio) == 0 &&
 451                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 452                                 /*
 453                                  * Simulate echo to reduce the impact of
 454                                  * traffic analysis
 455                                  */
 456                                 packet_send_ignore(len);
 457                                 packet_send();
 458                         }
 459                         /* Consume the data from the buffer. */
 460                         buffer_consume(&stdin_buffer, len);
 461                         /* Update the count of bytes written to the program. */
 462                         stdin_bytes += len;
 463                 }
 464         }
 465         /* Send any buffered packet data to the client. */
 466         if (FD_ISSET(connection_out, writeset))
 467                 packet_write_poll();
 468 }
 469
 470 /*
 471  * Wait until all buffered output has been sent to the client.
 472  * This is used when the program terminates.
 473  */
 474 static void
 475 drain_output(void)
 476 {
 477         /* Send any buffered stdout data to the client. */
 478         if (buffer_len(&stdout_buffer) > 0) {
 479                 packet_start(SSH_SMSG_STDOUT_DATA);
 480                 packet_put_string(buffer_ptr(&stdout_buffer),
 481                                   buffer_len(&stdout_buffer));
 482                 packet_send();
 483                 /* Update the count of sent bytes. */
 484                 stdout_bytes += buffer_len(&stdout_buffer);
 485         }
 486         /* Send any buffered stderr data to the client. */
 487         if (buffer_len(&stderr_buffer) > 0) {
 488                 packet_start(SSH_SMSG_STDERR_DATA);
 489                 packet_put_string(buffer_ptr(&stderr_buffer),
 490                                   buffer_len(&stderr_buffer));
 491                 packet_send();
 492                 /* Update the count of sent bytes. */
 493                 stderr_bytes += buffer_len(&stderr_buffer);
 494         }
 495         /* Wait until all buffered data has been written to the client. */
 496         packet_write_wait();
 497 }
 498
 499 static void
 500 process_buffered_input_packets(void)
 501 {
 502         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 503 }
 504
 505 /*
 506  * Performs the interactive session.  This handles data transmission between
 507  * the client and the program.  Note that the notion of stdin, stdout, and
 508  * stderr in this function is sort of reversed: this function writes to
 509  * stdin (of the child program), and reads from stdout and stderr (of the
 510  * child program).
 511  */
 512 void
 513 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 514 {
 515         fd_set *readset = NULL, *writeset = NULL;
 516         int max_fd = 0;
 517         u_int nalloc = 0;
 518         int wait_status;        /* Status returned by wait(). */
 519         pid_t wait_pid;         /* pid returned by wait(). */
 520         int waiting_termination = 0;    /* Have displayed waiting close message. */
 521         u_int max_time_milliseconds;
 522         u_int previous_stdout_buffer_bytes;
 523         u_int stdout_buffer_bytes;
 524         int type;
 525
 526         debug("Entering interactive session.");
 527
 528         /* Initialize the SIGCHLD kludge. */
 529         child_terminated = 0;
 530         mysignal(SIGCHLD, sigchld_handler);
 531
 532         if (!use_privsep) {
 533                 signal(SIGTERM, sigterm_handler);
 534                 signal(SIGINT, sigterm_handler);
 535                 signal(SIGQUIT, sigterm_handler);
 536         }
 537
 538         /* Initialize our global variables. */
 539         fdin = fdin_arg;
 540         fdout = fdout_arg;
 541         fderr = fderr_arg;
 542
 543         /* nonblocking IO */
 544         set_nonblock(fdin);
 545         set_nonblock(fdout);
 546         /* we don't have stderr for interactive terminal sessions, see below */
 547         if (fderr != -1)
 548                 set_nonblock(fderr);
 549
 550         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 551                 fdin_is_tty = 1;
 552
 553         connection_in = packet_get_connection_in();
 554         connection_out = packet_get_connection_out();
 555
 556         notify_setup();
 557
 558         previous_stdout_buffer_bytes = 0;
 559
 560         /* Set approximate I/O buffer size. */
 561         if (packet_is_interactive())
 562                 buffer_high = 4096;
 563         else
 564                 buffer_high = 64 * 1024;
 565
 566 #if 0
 567         /* Initialize max_fd to the maximum of the known file descriptors. */
 568         max_fd = MAX(connection_in, connection_out);
 569         max_fd = MAX(max_fd, fdin);
 570         max_fd = MAX(max_fd, fdout);
 571         if (fderr != -1)
 572                 max_fd = MAX(max_fd, fderr);
 573 #endif
 574
 575         /* Initialize Initialize buffers. */
 576         buffer_init(&stdin_buffer);
 577         buffer_init(&stdout_buffer);
 578         buffer_init(&stderr_buffer);
 579
 580         /*
 581          * If we have no separate fderr (which is the case when we have a pty
 582          * - there we cannot make difference between data sent to stdout and
 583          * stderr), indicate that we have seen an EOF from stderr.  This way
 584          * we don't need to check the descriptor everywhere.
 585          */
 586         if (fderr == -1)
 587                 fderr_eof = 1;
 588
 589         server_init_dispatch();
 590
 591         /* Main loop of the server for the interactive session mode. */
 592         for (;;) {
 593
 594                 /* Process buffered packets from the client. */
 595                 process_buffered_input_packets();
 596
 597                 /*
 598                  * If we have received eof, and there is no more pending
 599                  * input data, cause a real eof by closing fdin.
 600                  */
 601                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 602                         if (fdin != fdout)
 603                                 close(fdin);
 604                         else
 605                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 606                         fdin = -1;
 607                 }
 608                 /* Make packets from buffered stderr data to send to the client. */
 609                 make_packets_from_stderr_data();
 610
 611                 /*
 612                  * Make packets from buffered stdout data to send to the
 613                  * client. If there is very little to send, this arranges to
 614                  * not send them now, but to wait a short while to see if we
 615                  * are getting more data. This is necessary, as some systems
 616                  * wake up readers from a pty after each separate character.
 617                  */
 618                 max_time_milliseconds = 0;
 619                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 620                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 621                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 622                         /* try again after a while */
 623                         max_time_milliseconds = 10;
 624                 } else {
 625                         /* Send it now. */
 626                         make_packets_from_stdout_data();
 627                 }
 628                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 629
 630                 /* Send channel data to the client. */
 631                 if (packet_not_very_much_data_to_write())
 632                         channel_output_poll();
 633
 634                 /*
 635                  * Bail out of the loop if the program has closed its output
 636                  * descriptors, and we have no more data to send to the
 637                  * client, and there is no pending buffered data.
 638                  */
 639                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 640                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 641                         if (!channel_still_open())
 642                                 break;
 643                         if (!waiting_termination) {
 644                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 645                                 char *cp;
 646                                 waiting_termination = 1;
 647                                 buffer_append(&stderr_buffer, s, strlen(s));
 648
 649                                 /* Display list of open channels. */
 650                                 cp = channel_open_message();
 651                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 652                                 xfree(cp);
 653                         }
 654                 }
 655                 max_fd = MAX(connection_in, connection_out);
 656                 max_fd = MAX(max_fd, fdin);
 657                 max_fd = MAX(max_fd, fdout);
 658                 max_fd = MAX(max_fd, fderr);
 659                 max_fd = MAX(max_fd, notify_pipe[0]);
 660
 661                 /* Sleep in select() until we can do something. */
 662                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 663                     &nalloc, max_time_milliseconds);
 664
 665                 if (received_sigterm) {
 666                         logit("Exiting on signal %d", received_sigterm);
 667                         /* Clean up sessions, utmp, etc. */
 668                         cleanup_exit(255);
 669                 }
 670
 671                 /* Process any channel events. */
 672                 channel_after_select(readset, writeset);
 673
 674                 /* Process input from the client and from program stdout/stderr. */
 675                 process_input(readset);
 676
 677                 /* Process output to the client and to program stdin. */
 678                 process_output(writeset);
 679         }
 680         if (readset)
 681                 xfree(readset);
 682         if (writeset)
 683                 xfree(writeset);
 684
 685         /* Cleanup and termination code. */
 686
 687         /* Wait until all output has been sent to the client. */
 688         drain_output();
 689
 690         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 691             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 692
 693         /* Free and clear the buffers. */
 694         buffer_free(&stdin_buffer);
 695         buffer_free(&stdout_buffer);
 696         buffer_free(&stderr_buffer);
 697
 698         /* Close the file descriptors. */
 699         if (fdout != -1)
 700                 close(fdout);
 701         fdout = -1;
 702         fdout_eof = 1;
 703         if (fderr != -1)
 704                 close(fderr);
 705         fderr = -1;
 706         fderr_eof = 1;
 707         if (fdin != -1)
 708                 close(fdin);
 709         fdin = -1;
 710
 711         channel_free_all();
 712
 713         /* We no longer want our SIGCHLD handler to be called. */
 714         mysignal(SIGCHLD, SIG_DFL);
 715
 716         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 717                 if (errno != EINTR)
 718                         packet_disconnect("wait: %.100s", strerror(errno));
 719         if (wait_pid != pid)
 720                 error("Strange, wait returned pid %ld, expected %ld",
 721                     (long)wait_pid, (long)pid);
 722
 723         /* Check if it exited normally. */
 724         if (WIFEXITED(wait_status)) {
 725                 /* Yes, normal exit.  Get exit status and send it to the client. */
 726                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 727                 packet_start(SSH_SMSG_EXITSTATUS);
 728                 packet_put_int(WEXITSTATUS(wait_status));
 729                 packet_send();
 730                 packet_write_wait();
 731
 732                 /*
 733                  * Wait for exit confirmation.  Note that there might be
 734                  * other packets coming before it; however, the program has
 735                  * already died so we just ignore them.  The client is
 736                  * supposed to respond with the confirmation when it receives
 737                  * the exit status.
 738                  */
 739                 do {
 740                         type = packet_read();
 741                 }
 742                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 743
 744                 debug("Received exit confirmation.");
 745                 return;
 746         }
 747         /* Check if the program terminated due to a signal. */
 748         if (WIFSIGNALED(wait_status))
 749                 packet_disconnect("Command terminated on signal %d.",
 750                                   WTERMSIG(wait_status));
 751
 752         /* Some weird exit cause.  Just exit. */
 753         packet_disconnect("wait returned status %04x.", wait_status);
 754         /* NOTREACHED */
 755 }
 756
 757 static void
 758 collect_children(void)
 759 {
 760         pid_t pid;
 761         sigset_t oset, nset;
 762         int status;
 763
 764         /* block SIGCHLD while we check for dead children */
 765         sigemptyset(&nset);
 766         sigaddset(&nset, SIGCHLD);
 767         sigprocmask(SIG_BLOCK, &nset, &oset);
 768         if (child_terminated) {
 769                 debug("Received SIGCHLD.");
 770                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 771                     (pid < 0 && errno == EINTR))
 772                         if (pid > 0)
 773                                 session_close_by_pid(pid, status);
 774                 child_terminated = 0;
 775         }
 776         sigprocmask(SIG_SETMASK, &oset, NULL);
 777 }
 778
 779 void
 780 server_loop2(Authctxt *authctxt)
 781 {
 782         fd_set *readset = NULL, *writeset = NULL;
 783         int rekeying = 0, max_fd, nalloc = 0;
 784
 785         debug("Entering interactive session for SSH2.");
 786
 787         mysignal(SIGCHLD, sigchld_handler);
 788         child_terminated = 0;
 789         connection_in = packet_get_connection_in();
 790         connection_out = packet_get_connection_out();
 791
 792         if (!use_privsep) {
 793                 signal(SIGTERM, sigterm_handler);
 794                 signal(SIGINT, sigterm_handler);
 795                 signal(SIGQUIT, sigterm_handler);
 796         }
 797
 798         notify_setup();
 799
 800         max_fd = MAX(connection_in, connection_out);
 801         max_fd = MAX(max_fd, notify_pipe[0]);
 802
 803         server_init_dispatch();
 804
 805         for (;;) {
 806                 process_buffered_input_packets();
 807
 808                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 809
 810                 if (!rekeying && packet_not_very_much_data_to_write())
 811                         channel_output_poll();
 812                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 813                     &nalloc, 0);
 814
 815                 if (received_sigterm) {
 816                         logit("Exiting on signal %d", received_sigterm);
 817                         /* Clean up sessions, utmp, etc. */
 818                         cleanup_exit(255);
 819                 }
 820
 821                 collect_children();
 822                 if (!rekeying) {
 823                         channel_after_select(readset, writeset);
 824                         if (packet_need_rekeying()) {
 825                                 debug("need rekeying");
 826                                 xxx_kex->done = 0;
 827                                 kex_send_kexinit(xxx_kex);
 828                         }
 829                 }
 830                 process_input(readset);
 831                 if (connection_closed)
 832                         break;
 833                 process_output(writeset);
 834         }
 835         collect_children();
 836
 837         if (readset)
 838                 xfree(readset);
 839         if (writeset)
 840                 xfree(writeset);
 841
 842         /* free all channels, no more reads and writes */
 843         channel_free_all();
 844
 845         /* free remaining sessions, e.g. remove wtmp entries */
 846         session_destroy_all(NULL);
 847 }
 848
 849 static void
 850 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 851 {
 852         debug("Got %d/%u for keepalive", type, seq);
 853         /*
 854          * reset timeout, since we got a sane answer from the client.
 855          * even if this was generated by something other than
 856          * the bogus CHANNEL_REQUEST we send for keepalives.
 857          */
 858         client_alive_timeouts = 0;
 859 }
 860
 861 static void
 862 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 863 {
 864         char *data;
 865         u_int data_len;
 866
 867         /* Stdin data from the client.  Append it to the buffer. */
 868         /* Ignore any data if the client has closed stdin. */
 869         if (fdin == -1)
 870                 return;
 871         data = packet_get_string(&data_len);
 872         packet_check_eom();
 873         buffer_append(&stdin_buffer, data, data_len);
 874         memset(data, 0, data_len);
 875         xfree(data);
 876 }
 877
 878 static void
 879 server_input_eof(int type, u_int32_t seq, void *ctxt)
 880 {
 881         /*
 882          * Eof from the client.  The stdin descriptor to the
 883          * program will be closed when all buffered data has
 884          * drained.
 885          */
 886         debug("EOF received for stdin.");
 887         packet_check_eom();
 888         stdin_eof = 1;
 889 }
 890
 891 static void
 892 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 893 {
 894         u_int row = packet_get_int();
 895         u_int col = packet_get_int();
 896         u_int xpixel = packet_get_int();
 897         u_int ypixel = packet_get_int();
 898
 899         debug("Window change received.");
 900         packet_check_eom();
 901         if (fdin != -1)
 902                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 903 }
 904
 905 static Channel *
 906 server_request_direct_tcpip(void)
 907 {
 908         Channel *c;
 909         int sock;
 910         char *target, *originator;
 911         int target_port, originator_port;
 912
 913         target = packet_get_string(NULL);
 914         target_port = packet_get_int();
 915         originator = packet_get_string(NULL);
 916         originator_port = packet_get_int();
 917         packet_check_eom();
 918
 919         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 920             originator, originator_port, target, target_port);
 921
 922         /* XXX check permission */
 923         sock = channel_connect_to(target, target_port);
 924         xfree(target);
 925         xfree(originator);
 926         if (sock < 0)
 927                 return NULL;
 928         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 929             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 930             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 931         return c;
 932 }
 933
 934 static Channel *
 935 server_request_tun(void)
 936 {
 937         Channel *c = NULL;
 938         int mode, tun;
 939         int sock;
 940
 941         mode = packet_get_int();
 942         switch (mode) {
 943         case SSH_TUNMODE_POINTOPOINT:
 944         case SSH_TUNMODE_ETHERNET:
 945                 break;
 946         default:
 947                 packet_send_debug("Unsupported tunnel device mode.");
 948                 return NULL;
 949         }
 950         if ((options.permit_tun & mode) == 0) {
 951                 packet_send_debug("Server has rejected tunnel device "
 952                     "forwarding");
 953                 return NULL;
 954         }
 955
 956         tun = packet_get_int();
 957         if (forced_tun_device != -1) {
 958                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 959                         goto done;
 960                 tun = forced_tun_device;
 961         }
 962         sock = tun_open(tun, mode);
 963         if (sock < 0)
 964                 goto done;
 965         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 966             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 967         c->datagram = 1;
 968 #if defined(SSH_TUN_FILTER)
 969         if (mode == SSH_TUNMODE_POINTOPOINT)
 970                 channel_register_filter(c->self, sys_tun_infilter,
 971                     sys_tun_outfilter);
 972 #endif
 973
 974  done:
 975         if (c == NULL)
 976                 packet_send_debug("Failed to open the tunnel device.");
 977         return c;
 978 }
 979
 980 static Channel *
 981 server_request_session(void)
 982 {
 983         Channel *c;
 984
 985         debug("input_session_request");
 986         packet_check_eom();
 987         /*
 988          * A server session has no fd to read or write until a
 989          * CHANNEL_REQUEST for a shell is made, so we set the type to
 990          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 991          * CHANNEL_REQUEST messages is registered.
 992          */
 993         c = channel_new("session", SSH_CHANNEL_LARVAL,
 994             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 995             0, "server-session", 1);
 996         if (session_open(the_authctxt, c->self) != 1) {
 997                 debug("session open failed, free channel %d", c->self);
 998                 channel_free(c);
 999                 return NULL;
1000         }
1001         channel_register_cleanup(c->self, session_close_by_channel, 0);
1002         return c;
1003 }
1004
1005 static void
1006 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1007 {
1008         Channel *c = NULL;
1009         char *ctype;
1010         int rchan;
1011         u_int rmaxpack, rwindow, len;
1012
1013         ctype = packet_get_string(&len);
1014         rchan = packet_get_int();
1015         rwindow = packet_get_int();
1016         rmaxpack = packet_get_int();
1017
1018         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1019             ctype, rchan, rwindow, rmaxpack);
1020
1021         if (strcmp(ctype, "session") == 0) {
1022                 c = server_request_session();
1023         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1024                 c = server_request_direct_tcpip();
1025         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1026                 c = server_request_tun();
1027         }
1028         if (c != NULL) {
1029                 debug("server_input_channel_open: confirm %s", ctype);
1030                 c->remote_id = rchan;
1031                 c->remote_window = rwindow;
1032                 c->remote_maxpacket = rmaxpack;
1033                 if (c->type != SSH_CHANNEL_CONNECTING) {
1034                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1035                         packet_put_int(c->remote_id);
1036                         packet_put_int(c->self);
1037                         packet_put_int(c->local_window);
1038                         packet_put_int(c->local_maxpacket);
1039                         packet_send();
1040                 }
1041         } else {
1042                 debug("server_input_channel_open: failure %s", ctype);
1043                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1044                 packet_put_int(rchan);
1045                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1046                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1047                         packet_put_cstring("open failed");
1048                         packet_put_cstring("");
1049                 }
1050                 packet_send();
1051         }
1052         xfree(ctype);
1053 }
1054
1055 static void
1056 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1057 {
1058         char *rtype;
1059         int want_reply;
1060         int success = 0;
1061
1062         rtype = packet_get_string(NULL);
1063         want_reply = packet_get_char();
1064         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1065
1066         /* -R style forwarding */
1067         if (strcmp(rtype, "tcpip-forward") == 0) {
1068                 struct passwd *pw;
1069                 char *listen_address;
1070                 u_short listen_port;
1071
1072                 pw = the_authctxt->pw;
1073                 if (pw == NULL || !the_authctxt->valid)
1074                         fatal("server_input_global_request: no/invalid user");
1075                 listen_address = packet_get_string(NULL);
1076                 listen_port = (u_short)packet_get_int();
1077                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1078                     listen_address, listen_port);
1079
1080                 /* check permissions */
1081                 if (!options.allow_tcp_forwarding ||
1082                     no_port_forwarding_flag
1083 #ifndef NO_IPPORT_RESERVED_CONCEPT
1084                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1085 #endif
1086                     ) {
1087                         success = 0;
1088                         packet_send_debug("Server has disabled port forwarding.");
1089                 } else {
1090                         /* Start listening on the port */
1091                         success = channel_setup_remote_fwd_listener(
1092                             listen_address, listen_port, options.gateway_ports);
1093                 }
1094                 xfree(listen_address);
1095         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1096                 char *cancel_address;
1097                 u_short cancel_port;
1098
1099                 cancel_address = packet_get_string(NULL);
1100                 cancel_port = (u_short)packet_get_int();
1101                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1102                     cancel_address, cancel_port);
1103
1104                 success = channel_cancel_rport_listener(cancel_address,
1105                     cancel_port);
1106                 xfree(cancel_address);
1107         }
1108         if (want_reply) {
1109                 packet_start(success ?
1110                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1111                 packet_send();
1112                 packet_write_wait();
1113         }
1114         xfree(rtype);
1115 }
1116
1117 static void
1118 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1119 {
1120         Channel *c;
1121         int id, reply, success = 0;
1122         char *rtype;
1123
1124         id = packet_get_int();
1125         rtype = packet_get_string(NULL);
1126         reply = packet_get_char();
1127
1128         debug("server_input_channel_req: channel %d request %s reply %d",
1129             id, rtype, reply);
1130
1131         if ((c = channel_lookup(id)) == NULL)
1132                 packet_disconnect("server_input_channel_req: "
1133                     "unknown channel %d", id);
1134         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1135                 success = session_input_channel_req(c, rtype);
1136         if (reply) {
1137                 packet_start(success ?
1138                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1139                 packet_put_int(c->remote_id);
1140                 packet_send();
1141         }
1142         xfree(rtype);
1143 }
1144
1145 static void
1146 server_init_dispatch_20(void)
1147 {
1148         debug("server_init_dispatch_20");
1149         dispatch_init(&dispatch_protocol_error);
1150         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1151         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1152         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1153         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1154         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1155         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1156         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1157         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1158         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1159         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1160         /* client_alive */
1161         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1162         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1163         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1164         /* rekeying */
1165         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1166 }
1167 static void
1168 server_init_dispatch_13(void)
1169 {
1170         debug("server_init_dispatch_13");
1171         dispatch_init(NULL);
1172         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1173         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1174         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1175         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1176         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1177         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1178         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1179         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1180         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1181 }
1182 static void
1183 server_init_dispatch_15(void)
1184 {
1185         server_init_dispatch_13();
1186         debug("server_init_dispatch_15");
1187         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1188         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1189 }
1190 static void
1191 server_init_dispatch(void)
1192 {
1193         if (compat20)
1194                 server_init_dispatch_20();
1195         else if (compat13)
1196                 server_init_dispatch_13();
1197         else
1198                 server_init_dispatch_15();
1199 }