serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.139 2006/07/11 20:07:25 stevesk Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42 #include <sys/socket.h>
  43
  44 #include <netinet/in.h>
  45
  46 #include <errno.h>
  47 #include <fcntl.h>
  48 #include <pwd.h>
  49 #include <signal.h>
  50 #include <termios.h>
  51
  52 #include "xmalloc.h"
  53 #include "packet.h"
  54 #include "buffer.h"
  55 #include "log.h"
  56 #include "servconf.h"
  57 #include "canohost.h"
  58 #include "sshpty.h"
  59 #include "channels.h"
  60 #include "compat.h"
  61 #include "ssh1.h"
  62 #include "ssh2.h"
  63 #include "auth.h"
  64 #include "session.h"
  65 #include "dispatch.h"
  66 #include "auth-options.h"
  67 #include "serverloop.h"
  68 #include "misc.h"
  69 #include "kex.h"
  70
  71 extern ServerOptions options;
  72
  73 /* XXX */
  74 extern Kex *xxx_kex;
  75 extern Authctxt *the_authctxt;
  76 extern int use_privsep;
  77
  78 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  79 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  80 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  81 static int fdin;                /* Descriptor for stdin (for writing) */
  82 static int fdout;               /* Descriptor for stdout (for reading);
  83                                    May be same number as fdin. */
  84 static int fderr;               /* Descriptor for stderr.  May be -1. */
  85 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  86 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  87 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  88 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  89 static int stdin_eof = 0;       /* EOF message received from client. */
  90 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  91 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  92 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  93 static int connection_in;       /* Connection to client (input). */
  94 static int connection_out;      /* Connection to client (output). */
  95 static int connection_closed = 0;       /* Connection to client closed. */
  96 static u_int buffer_high;       /* "Soft" max buffer size. */
  97 static int client_alive_timeouts = 0;
  98
  99 /*
 100  * This SIGCHLD kludge is used to detect when the child exits.  The server
 101  * will exit after that, as soon as forwarded connections have terminated.
 102  */
 103
 104 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 105
 106 /* Cleanup on signals (!use_privsep case only) */
 107 static volatile sig_atomic_t received_sigterm = 0;
 108
 109 /* prototypes */
 110 static void server_init_dispatch(void);
 111
 112 /*
 113  * we write to this pipe if a SIGCHLD is caught in order to avoid
 114  * the race between select() and child_terminated
 115  */
 116 static int notify_pipe[2];
 117 static void
 118 notify_setup(void)
 119 {
 120         if (pipe(notify_pipe) < 0) {
 121                 error("pipe(notify_pipe) failed %s", strerror(errno));
 122         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 123             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 124                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 125                 close(notify_pipe[0]);
 126                 close(notify_pipe[1]);
 127         } else {
 128                 set_nonblock(notify_pipe[0]);
 129                 set_nonblock(notify_pipe[1]);
 130                 return;
 131         }
 132         notify_pipe[0] = -1;    /* read end */
 133         notify_pipe[1] = -1;    /* write end */
 134 }
 135 static void
 136 notify_parent(void)
 137 {
 138         if (notify_pipe[1] != -1)
 139                 write(notify_pipe[1], "", 1);
 140 }
 141 static void
 142 notify_prepare(fd_set *readset)
 143 {
 144         if (notify_pipe[0] != -1)
 145                 FD_SET(notify_pipe[0], readset);
 146 }
 147 static void
 148 notify_done(fd_set *readset)
 149 {
 150         char c;
 151
 152         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 153                 while (read(notify_pipe[0], &c, 1) != -1)
 154                         debug2("notify_done: reading");
 155 }
 156
 157 /*ARGSUSED*/
 158 static void
 159 sigchld_handler(int sig)
 160 {
 161         int save_errno = errno;
 162         child_terminated = 1;
 163 #ifndef _UNICOS
 164         mysignal(SIGCHLD, sigchld_handler);
 165 #endif
 166         notify_parent();
 167         errno = save_errno;
 168 }
 169
 170 /*ARGSUSED*/
 171 static void
 172 sigterm_handler(int sig)
 173 {
 174         received_sigterm = sig;
 175 }
 176
 177 /*
 178  * Make packets from buffered stderr data, and buffer it for sending
 179  * to the client.
 180  */
 181 static void
 182 make_packets_from_stderr_data(void)
 183 {
 184         u_int len;
 185
 186         /* Send buffered stderr data to the client. */
 187         while (buffer_len(&stderr_buffer) > 0 &&
 188             packet_not_very_much_data_to_write()) {
 189                 len = buffer_len(&stderr_buffer);
 190                 if (packet_is_interactive()) {
 191                         if (len > 512)
 192                                 len = 512;
 193                 } else {
 194                         /* Keep the packets at reasonable size. */
 195                         if (len > packet_get_maxsize())
 196                                 len = packet_get_maxsize();
 197                 }
 198                 packet_start(SSH_SMSG_STDERR_DATA);
 199                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 200                 packet_send();
 201                 buffer_consume(&stderr_buffer, len);
 202                 stderr_bytes += len;
 203         }
 204 }
 205
 206 /*
 207  * Make packets from buffered stdout data, and buffer it for sending to the
 208  * client.
 209  */
 210 static void
 211 make_packets_from_stdout_data(void)
 212 {
 213         u_int len;
 214
 215         /* Send buffered stdout data to the client. */
 216         while (buffer_len(&stdout_buffer) > 0 &&
 217             packet_not_very_much_data_to_write()) {
 218                 len = buffer_len(&stdout_buffer);
 219                 if (packet_is_interactive()) {
 220                         if (len > 512)
 221                                 len = 512;
 222                 } else {
 223                         /* Keep the packets at reasonable size. */
 224                         if (len > packet_get_maxsize())
 225                                 len = packet_get_maxsize();
 226                 }
 227                 packet_start(SSH_SMSG_STDOUT_DATA);
 228                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 229                 packet_send();
 230                 buffer_consume(&stdout_buffer, len);
 231                 stdout_bytes += len;
 232         }
 233 }
 234
 235 static void
 236 client_alive_check(void)
 237 {
 238         int channel_id;
 239
 240         /* timeout, check to see how many we have had */
 241         if (++client_alive_timeouts > options.client_alive_count_max)
 242                 packet_disconnect("Timeout, your session not responding.");
 243
 244         /*
 245          * send a bogus global/channel request with "wantreply",
 246          * we should get back a failure
 247          */
 248         if ((channel_id = channel_find_open()) == -1) {
 249                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 250                 packet_put_cstring("keepalive@openssh.com");
 251                 packet_put_char(1);     /* boolean: want reply */
 252         } else {
 253                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 254         }
 255         packet_send();
 256 }
 257
 258 /*
 259  * Sleep in select() until we can do something.  This will initialize the
 260  * select masks.  Upon return, the masks will indicate which descriptors
 261  * have data or can accept data.  Optionally, a maximum time can be specified
 262  * for the duration of the wait (0 = infinite).
 263  */
 264 static void
 265 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 266     u_int *nallocp, u_int max_time_milliseconds)
 267 {
 268         struct timeval tv, *tvp;
 269         int ret;
 270         int client_alive_scheduled = 0;
 271
 272         /*
 273          * if using client_alive, set the max timeout accordingly,
 274          * and indicate that this particular timeout was for client
 275          * alive by setting the client_alive_scheduled flag.
 276          *
 277          * this could be randomized somewhat to make traffic
 278          * analysis more difficult, but we're not doing it yet.
 279          */
 280         if (compat20 &&
 281             max_time_milliseconds == 0 && options.client_alive_interval) {
 282                 client_alive_scheduled = 1;
 283                 max_time_milliseconds = options.client_alive_interval * 1000;
 284         }
 285
 286         /* Allocate and update select() masks for channel descriptors. */
 287         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 288
 289         if (compat20) {
 290 #if 0
 291                 /* wrong: bad condition XXX */
 292                 if (channel_not_very_much_buffered_data())
 293 #endif
 294                 FD_SET(connection_in, *readsetp);
 295         } else {
 296                 /*
 297                  * Read packets from the client unless we have too much
 298                  * buffered stdin or channel data.
 299                  */
 300                 if (buffer_len(&stdin_buffer) < buffer_high &&
 301                     channel_not_very_much_buffered_data())
 302                         FD_SET(connection_in, *readsetp);
 303                 /*
 304                  * If there is not too much data already buffered going to
 305                  * the client, try to get some more data from the program.
 306                  */
 307                 if (packet_not_very_much_data_to_write()) {
 308                         if (!fdout_eof)
 309                                 FD_SET(fdout, *readsetp);
 310                         if (!fderr_eof)
 311                                 FD_SET(fderr, *readsetp);
 312                 }
 313                 /*
 314                  * If we have buffered data, try to write some of that data
 315                  * to the program.
 316                  */
 317                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 318                         FD_SET(fdin, *writesetp);
 319         }
 320         notify_prepare(*readsetp);
 321
 322         /*
 323          * If we have buffered packet data going to the client, mark that
 324          * descriptor.
 325          */
 326         if (packet_have_data_to_write())
 327                 FD_SET(connection_out, *writesetp);
 328
 329         /*
 330          * If child has terminated and there is enough buffer space to read
 331          * from it, then read as much as is available and exit.
 332          */
 333         if (child_terminated && packet_not_very_much_data_to_write())
 334                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 335                         max_time_milliseconds = 100;
 336
 337         if (max_time_milliseconds == 0)
 338                 tvp = NULL;
 339         else {
 340                 tv.tv_sec = max_time_milliseconds / 1000;
 341                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 342                 tvp = &tv;
 343         }
 344
 345         /* Wait for something to happen, or the timeout to expire. */
 346         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 347
 348         if (ret == -1) {
 349                 memset(*readsetp, 0, *nallocp);
 350                 memset(*writesetp, 0, *nallocp);
 351                 if (errno != EINTR)
 352                         error("select: %.100s", strerror(errno));
 353         } else if (ret == 0 && client_alive_scheduled)
 354                 client_alive_check();
 355
 356         notify_done(*readsetp);
 357 }
 358
 359 /*
 360  * Processes input from the client and the program.  Input data is stored
 361  * in buffers and processed later.
 362  */
 363 static void
 364 process_input(fd_set *readset)
 365 {
 366         int len;
 367         char buf[16384];
 368
 369         /* Read and buffer any input data from the client. */
 370         if (FD_ISSET(connection_in, readset)) {
 371                 len = read(connection_in, buf, sizeof(buf));
 372                 if (len == 0) {
 373                         verbose("Connection closed by %.100s",
 374                             get_remote_ipaddr());
 375                         connection_closed = 1;
 376                         if (compat20)
 377                                 return;
 378                         cleanup_exit(255);
 379                 } else if (len < 0) {
 380                         if (errno != EINTR && errno != EAGAIN) {
 381                                 verbose("Read error from remote host "
 382                                     "%.100s: %.100s",
 383                                     get_remote_ipaddr(), strerror(errno));
 384                                 cleanup_exit(255);
 385                         }
 386                 } else {
 387                         /* Buffer any received data. */
 388                         packet_process_incoming(buf, len);
 389                 }
 390         }
 391         if (compat20)
 392                 return;
 393
 394         /* Read and buffer any available stdout data from the program. */
 395         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 396                 errno = 0;
 397                 len = read(fdout, buf, sizeof(buf));
 398                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 399                         /* do nothing */
 400 #ifndef PTY_ZEROREAD
 401                 } else if (len <= 0) {
 402 #else
 403                 } else if ((!isatty(fdout) && len <= 0) ||
 404                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 405 #endif
 406                         fdout_eof = 1;
 407                 } else {
 408                         buffer_append(&stdout_buffer, buf, len);
 409                         fdout_bytes += len;
 410                 }
 411         }
 412         /* Read and buffer any available stderr data from the program. */
 413         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 414                 errno = 0;
 415                 len = read(fderr, buf, sizeof(buf));
 416                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 417                         /* do nothing */
 418 #ifndef PTY_ZEROREAD
 419                 } else if (len <= 0) {
 420 #else
 421                 } else if ((!isatty(fderr) && len <= 0) ||
 422                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 423 #endif
 424                         fderr_eof = 1;
 425                 } else {
 426                         buffer_append(&stderr_buffer, buf, len);
 427                 }
 428         }
 429 }
 430
 431 /*
 432  * Sends data from internal buffers to client program stdin.
 433  */
 434 static void
 435 process_output(fd_set *writeset)
 436 {
 437         struct termios tio;
 438         u_char *data;
 439         u_int dlen;
 440         int len;
 441
 442         /* Write buffered data to program stdin. */
 443         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 444                 data = buffer_ptr(&stdin_buffer);
 445                 dlen = buffer_len(&stdin_buffer);
 446                 len = write(fdin, data, dlen);
 447                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 448                         /* do nothing */
 449                 } else if (len <= 0) {
 450                         if (fdin != fdout)
 451                                 close(fdin);
 452                         else
 453                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 454                         fdin = -1;
 455                 } else {
 456                         /* Successful write. */
 457                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 458                             tcgetattr(fdin, &tio) == 0 &&
 459                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 460                                 /*
 461                                  * Simulate echo to reduce the impact of
 462                                  * traffic analysis
 463                                  */
 464                                 packet_send_ignore(len);
 465                                 packet_send();
 466                         }
 467                         /* Consume the data from the buffer. */
 468                         buffer_consume(&stdin_buffer, len);
 469                         /* Update the count of bytes written to the program. */
 470                         stdin_bytes += len;
 471                 }
 472         }
 473         /* Send any buffered packet data to the client. */
 474         if (FD_ISSET(connection_out, writeset))
 475                 packet_write_poll();
 476 }
 477
 478 /*
 479  * Wait until all buffered output has been sent to the client.
 480  * This is used when the program terminates.
 481  */
 482 static void
 483 drain_output(void)
 484 {
 485         /* Send any buffered stdout data to the client. */
 486         if (buffer_len(&stdout_buffer) > 0) {
 487                 packet_start(SSH_SMSG_STDOUT_DATA);
 488                 packet_put_string(buffer_ptr(&stdout_buffer),
 489                                   buffer_len(&stdout_buffer));
 490                 packet_send();
 491                 /* Update the count of sent bytes. */
 492                 stdout_bytes += buffer_len(&stdout_buffer);
 493         }
 494         /* Send any buffered stderr data to the client. */
 495         if (buffer_len(&stderr_buffer) > 0) {
 496                 packet_start(SSH_SMSG_STDERR_DATA);
 497                 packet_put_string(buffer_ptr(&stderr_buffer),
 498                                   buffer_len(&stderr_buffer));
 499                 packet_send();
 500                 /* Update the count of sent bytes. */
 501                 stderr_bytes += buffer_len(&stderr_buffer);
 502         }
 503         /* Wait until all buffered data has been written to the client. */
 504         packet_write_wait();
 505 }
 506
 507 static void
 508 process_buffered_input_packets(void)
 509 {
 510         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 511 }
 512
 513 /*
 514  * Performs the interactive session.  This handles data transmission between
 515  * the client and the program.  Note that the notion of stdin, stdout, and
 516  * stderr in this function is sort of reversed: this function writes to
 517  * stdin (of the child program), and reads from stdout and stderr (of the
 518  * child program).
 519  */
 520 void
 521 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 522 {
 523         fd_set *readset = NULL, *writeset = NULL;
 524         int max_fd = 0;
 525         u_int nalloc = 0;
 526         int wait_status;        /* Status returned by wait(). */
 527         pid_t wait_pid;         /* pid returned by wait(). */
 528         int waiting_termination = 0;    /* Have displayed waiting close message. */
 529         u_int max_time_milliseconds;
 530         u_int previous_stdout_buffer_bytes;
 531         u_int stdout_buffer_bytes;
 532         int type;
 533
 534         debug("Entering interactive session.");
 535
 536         /* Initialize the SIGCHLD kludge. */
 537         child_terminated = 0;
 538         mysignal(SIGCHLD, sigchld_handler);
 539
 540         if (!use_privsep) {
 541                 signal(SIGTERM, sigterm_handler);
 542                 signal(SIGINT, sigterm_handler);
 543                 signal(SIGQUIT, sigterm_handler);
 544         }
 545
 546         /* Initialize our global variables. */
 547         fdin = fdin_arg;
 548         fdout = fdout_arg;
 549         fderr = fderr_arg;
 550
 551         /* nonblocking IO */
 552         set_nonblock(fdin);
 553         set_nonblock(fdout);
 554         /* we don't have stderr for interactive terminal sessions, see below */
 555         if (fderr != -1)
 556                 set_nonblock(fderr);
 557
 558         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 559                 fdin_is_tty = 1;
 560
 561         connection_in = packet_get_connection_in();
 562         connection_out = packet_get_connection_out();
 563
 564         notify_setup();
 565
 566         previous_stdout_buffer_bytes = 0;
 567
 568         /* Set approximate I/O buffer size. */
 569         if (packet_is_interactive())
 570                 buffer_high = 4096;
 571         else
 572                 buffer_high = 64 * 1024;
 573
 574 #if 0
 575         /* Initialize max_fd to the maximum of the known file descriptors. */
 576         max_fd = MAX(connection_in, connection_out);
 577         max_fd = MAX(max_fd, fdin);
 578         max_fd = MAX(max_fd, fdout);
 579         if (fderr != -1)
 580                 max_fd = MAX(max_fd, fderr);
 581 #endif
 582
 583         /* Initialize Initialize buffers. */
 584         buffer_init(&stdin_buffer);
 585         buffer_init(&stdout_buffer);
 586         buffer_init(&stderr_buffer);
 587
 588         /*
 589          * If we have no separate fderr (which is the case when we have a pty
 590          * - there we cannot make difference between data sent to stdout and
 591          * stderr), indicate that we have seen an EOF from stderr.  This way
 592          * we don't need to check the descriptor everywhere.
 593          */
 594         if (fderr == -1)
 595                 fderr_eof = 1;
 596
 597         server_init_dispatch();
 598
 599         /* Main loop of the server for the interactive session mode. */
 600         for (;;) {
 601
 602                 /* Process buffered packets from the client. */
 603                 process_buffered_input_packets();
 604
 605                 /*
 606                  * If we have received eof, and there is no more pending
 607                  * input data, cause a real eof by closing fdin.
 608                  */
 609                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 610                         if (fdin != fdout)
 611                                 close(fdin);
 612                         else
 613                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 614                         fdin = -1;
 615                 }
 616                 /* Make packets from buffered stderr data to send to the client. */
 617                 make_packets_from_stderr_data();
 618
 619                 /*
 620                  * Make packets from buffered stdout data to send to the
 621                  * client. If there is very little to send, this arranges to
 622                  * not send them now, but to wait a short while to see if we
 623                  * are getting more data. This is necessary, as some systems
 624                  * wake up readers from a pty after each separate character.
 625                  */
 626                 max_time_milliseconds = 0;
 627                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 628                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 629                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 630                         /* try again after a while */
 631                         max_time_milliseconds = 10;
 632                 } else {
 633                         /* Send it now. */
 634                         make_packets_from_stdout_data();
 635                 }
 636                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 637
 638                 /* Send channel data to the client. */
 639                 if (packet_not_very_much_data_to_write())
 640                         channel_output_poll();
 641
 642                 /*
 643                  * Bail out of the loop if the program has closed its output
 644                  * descriptors, and we have no more data to send to the
 645                  * client, and there is no pending buffered data.
 646                  */
 647                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 648                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 649                         if (!channel_still_open())
 650                                 break;
 651                         if (!waiting_termination) {
 652                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 653                                 char *cp;
 654                                 waiting_termination = 1;
 655                                 buffer_append(&stderr_buffer, s, strlen(s));
 656
 657                                 /* Display list of open channels. */
 658                                 cp = channel_open_message();
 659                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 660                                 xfree(cp);
 661                         }
 662                 }
 663                 max_fd = MAX(connection_in, connection_out);
 664                 max_fd = MAX(max_fd, fdin);
 665                 max_fd = MAX(max_fd, fdout);
 666                 max_fd = MAX(max_fd, fderr);
 667                 max_fd = MAX(max_fd, notify_pipe[0]);
 668
 669                 /* Sleep in select() until we can do something. */
 670                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 671                     &nalloc, max_time_milliseconds);
 672
 673                 if (received_sigterm) {
 674                         logit("Exiting on signal %d", received_sigterm);
 675                         /* Clean up sessions, utmp, etc. */
 676                         cleanup_exit(255);
 677                 }
 678
 679                 /* Process any channel events. */
 680                 channel_after_select(readset, writeset);
 681
 682                 /* Process input from the client and from program stdout/stderr. */
 683                 process_input(readset);
 684
 685                 /* Process output to the client and to program stdin. */
 686                 process_output(writeset);
 687         }
 688         if (readset)
 689                 xfree(readset);
 690         if (writeset)
 691                 xfree(writeset);
 692
 693         /* Cleanup and termination code. */
 694
 695         /* Wait until all output has been sent to the client. */
 696         drain_output();
 697
 698         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 699             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 700
 701         /* Free and clear the buffers. */
 702         buffer_free(&stdin_buffer);
 703         buffer_free(&stdout_buffer);
 704         buffer_free(&stderr_buffer);
 705
 706         /* Close the file descriptors. */
 707         if (fdout != -1)
 708                 close(fdout);
 709         fdout = -1;
 710         fdout_eof = 1;
 711         if (fderr != -1)
 712                 close(fderr);
 713         fderr = -1;
 714         fderr_eof = 1;
 715         if (fdin != -1)
 716                 close(fdin);
 717         fdin = -1;
 718
 719         channel_free_all();
 720
 721         /* We no longer want our SIGCHLD handler to be called. */
 722         mysignal(SIGCHLD, SIG_DFL);
 723
 724         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 725                 if (errno != EINTR)
 726                         packet_disconnect("wait: %.100s", strerror(errno));
 727         if (wait_pid != pid)
 728                 error("Strange, wait returned pid %ld, expected %ld",
 729                     (long)wait_pid, (long)pid);
 730
 731         /* Check if it exited normally. */
 732         if (WIFEXITED(wait_status)) {
 733                 /* Yes, normal exit.  Get exit status and send it to the client. */
 734                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 735                 packet_start(SSH_SMSG_EXITSTATUS);
 736                 packet_put_int(WEXITSTATUS(wait_status));
 737                 packet_send();
 738                 packet_write_wait();
 739
 740                 /*
 741                  * Wait for exit confirmation.  Note that there might be
 742                  * other packets coming before it; however, the program has
 743                  * already died so we just ignore them.  The client is
 744                  * supposed to respond with the confirmation when it receives
 745                  * the exit status.
 746                  */
 747                 do {
 748                         type = packet_read();
 749                 }
 750                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 751
 752                 debug("Received exit confirmation.");
 753                 return;
 754         }
 755         /* Check if the program terminated due to a signal. */
 756         if (WIFSIGNALED(wait_status))
 757                 packet_disconnect("Command terminated on signal %d.",
 758                                   WTERMSIG(wait_status));
 759
 760         /* Some weird exit cause.  Just exit. */
 761         packet_disconnect("wait returned status %04x.", wait_status);
 762         /* NOTREACHED */
 763 }
 764
 765 static void
 766 collect_children(void)
 767 {
 768         pid_t pid;
 769         sigset_t oset, nset;
 770         int status;
 771
 772         /* block SIGCHLD while we check for dead children */
 773         sigemptyset(&nset);
 774         sigaddset(&nset, SIGCHLD);
 775         sigprocmask(SIG_BLOCK, &nset, &oset);
 776         if (child_terminated) {
 777                 debug("Received SIGCHLD.");
 778                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 779                     (pid < 0 && errno == EINTR))
 780                         if (pid > 0)
 781                                 session_close_by_pid(pid, status);
 782                 child_terminated = 0;
 783         }
 784         sigprocmask(SIG_SETMASK, &oset, NULL);
 785 }
 786
 787 void
 788 server_loop2(Authctxt *authctxt)
 789 {
 790         fd_set *readset = NULL, *writeset = NULL;
 791         int rekeying = 0, max_fd, nalloc = 0;
 792
 793         debug("Entering interactive session for SSH2.");
 794
 795         mysignal(SIGCHLD, sigchld_handler);
 796         child_terminated = 0;
 797         connection_in = packet_get_connection_in();
 798         connection_out = packet_get_connection_out();
 799
 800         if (!use_privsep) {
 801                 signal(SIGTERM, sigterm_handler);
 802                 signal(SIGINT, sigterm_handler);
 803                 signal(SIGQUIT, sigterm_handler);
 804         }
 805
 806         notify_setup();
 807
 808         max_fd = MAX(connection_in, connection_out);
 809         max_fd = MAX(max_fd, notify_pipe[0]);
 810
 811         server_init_dispatch();
 812
 813         for (;;) {
 814                 process_buffered_input_packets();
 815
 816                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 817
 818                 if (!rekeying && packet_not_very_much_data_to_write())
 819                         channel_output_poll();
 820                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 821                     &nalloc, 0);
 822
 823                 if (received_sigterm) {
 824                         logit("Exiting on signal %d", received_sigterm);
 825                         /* Clean up sessions, utmp, etc. */
 826                         cleanup_exit(255);
 827                 }
 828
 829                 collect_children();
 830                 if (!rekeying) {
 831                         channel_after_select(readset, writeset);
 832                         if (packet_need_rekeying()) {
 833                                 debug("need rekeying");
 834                                 xxx_kex->done = 0;
 835                                 kex_send_kexinit(xxx_kex);
 836                         }
 837                 }
 838                 process_input(readset);
 839                 if (connection_closed)
 840                         break;
 841                 process_output(writeset);
 842         }
 843         collect_children();
 844
 845         if (readset)
 846                 xfree(readset);
 847         if (writeset)
 848                 xfree(writeset);
 849
 850         /* free all channels, no more reads and writes */
 851         channel_free_all();
 852
 853         /* free remaining sessions, e.g. remove wtmp entries */
 854         session_destroy_all(NULL);
 855 }
 856
 857 static void
 858 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 859 {
 860         debug("Got %d/%u for keepalive", type, seq);
 861         /*
 862          * reset timeout, since we got a sane answer from the client.
 863          * even if this was generated by something other than
 864          * the bogus CHANNEL_REQUEST we send for keepalives.
 865          */
 866         client_alive_timeouts = 0;
 867 }
 868
 869 static void
 870 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 871 {
 872         char *data;
 873         u_int data_len;
 874
 875         /* Stdin data from the client.  Append it to the buffer. */
 876         /* Ignore any data if the client has closed stdin. */
 877         if (fdin == -1)
 878                 return;
 879         data = packet_get_string(&data_len);
 880         packet_check_eom();
 881         buffer_append(&stdin_buffer, data, data_len);
 882         memset(data, 0, data_len);
 883         xfree(data);
 884 }
 885
 886 static void
 887 server_input_eof(int type, u_int32_t seq, void *ctxt)
 888 {
 889         /*
 890          * Eof from the client.  The stdin descriptor to the
 891          * program will be closed when all buffered data has
 892          * drained.
 893          */
 894         debug("EOF received for stdin.");
 895         packet_check_eom();
 896         stdin_eof = 1;
 897 }
 898
 899 static void
 900 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 901 {
 902         u_int row = packet_get_int();
 903         u_int col = packet_get_int();
 904         u_int xpixel = packet_get_int();
 905         u_int ypixel = packet_get_int();
 906
 907         debug("Window change received.");
 908         packet_check_eom();
 909         if (fdin != -1)
 910                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 911 }
 912
 913 static Channel *
 914 server_request_direct_tcpip(void)
 915 {
 916         Channel *c;
 917         int sock;
 918         char *target, *originator;
 919         int target_port, originator_port;
 920
 921         target = packet_get_string(NULL);
 922         target_port = packet_get_int();
 923         originator = packet_get_string(NULL);
 924         originator_port = packet_get_int();
 925         packet_check_eom();
 926
 927         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 928             originator, originator_port, target, target_port);
 929
 930         /* XXX check permission */
 931         sock = channel_connect_to(target, target_port);
 932         xfree(target);
 933         xfree(originator);
 934         if (sock < 0)
 935                 return NULL;
 936         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 937             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 938             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 939         return c;
 940 }
 941
 942 static Channel *
 943 server_request_tun(void)
 944 {
 945         Channel *c = NULL;
 946         int mode, tun;
 947         int sock;
 948
 949         mode = packet_get_int();
 950         switch (mode) {
 951         case SSH_TUNMODE_POINTOPOINT:
 952         case SSH_TUNMODE_ETHERNET:
 953                 break;
 954         default:
 955                 packet_send_debug("Unsupported tunnel device mode.");
 956                 return NULL;
 957         }
 958         if ((options.permit_tun & mode) == 0) {
 959                 packet_send_debug("Server has rejected tunnel device "
 960                     "forwarding");
 961                 return NULL;
 962         }
 963
 964         tun = packet_get_int();
 965         if (forced_tun_device != -1) {
 966                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 967                         goto done;
 968                 tun = forced_tun_device;
 969         }
 970         sock = tun_open(tun, mode);
 971         if (sock < 0)
 972                 goto done;
 973         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 974             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 975         c->datagram = 1;
 976 #if defined(SSH_TUN_FILTER)
 977         if (mode == SSH_TUNMODE_POINTOPOINT)
 978                 channel_register_filter(c->self, sys_tun_infilter,
 979                     sys_tun_outfilter);
 980 #endif
 981
 982  done:
 983         if (c == NULL)
 984                 packet_send_debug("Failed to open the tunnel device.");
 985         return c;
 986 }
 987
 988 static Channel *
 989 server_request_session(void)
 990 {
 991         Channel *c;
 992
 993         debug("input_session_request");
 994         packet_check_eom();
 995         /*
 996          * A server session has no fd to read or write until a
 997          * CHANNEL_REQUEST for a shell is made, so we set the type to
 998          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 999          * CHANNEL_REQUEST messages is registered.
1000          */
1001         c = channel_new("session", SSH_CHANNEL_LARVAL,
1002             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1003             0, "server-session", 1);
1004         if (session_open(the_authctxt, c->self) != 1) {
1005                 debug("session open failed, free channel %d", c->self);
1006                 channel_free(c);
1007                 return NULL;
1008         }
1009         channel_register_cleanup(c->self, session_close_by_channel, 0);
1010         return c;
1011 }
1012
1013 static void
1014 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1015 {
1016         Channel *c = NULL;
1017         char *ctype;
1018         int rchan;
1019         u_int rmaxpack, rwindow, len;
1020
1021         ctype = packet_get_string(&len);
1022         rchan = packet_get_int();
1023         rwindow = packet_get_int();
1024         rmaxpack = packet_get_int();
1025
1026         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1027             ctype, rchan, rwindow, rmaxpack);
1028
1029         if (strcmp(ctype, "session") == 0) {
1030                 c = server_request_session();
1031         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1032                 c = server_request_direct_tcpip();
1033         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1034                 c = server_request_tun();
1035         }
1036         if (c != NULL) {
1037                 debug("server_input_channel_open: confirm %s", ctype);
1038                 c->remote_id = rchan;
1039                 c->remote_window = rwindow;
1040                 c->remote_maxpacket = rmaxpack;
1041                 if (c->type != SSH_CHANNEL_CONNECTING) {
1042                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1043                         packet_put_int(c->remote_id);
1044                         packet_put_int(c->self);
1045                         packet_put_int(c->local_window);
1046                         packet_put_int(c->local_maxpacket);
1047                         packet_send();
1048                 }
1049         } else {
1050                 debug("server_input_channel_open: failure %s", ctype);
1051                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1052                 packet_put_int(rchan);
1053                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1054                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1055                         packet_put_cstring("open failed");
1056                         packet_put_cstring("");
1057                 }
1058                 packet_send();
1059         }
1060         xfree(ctype);
1061 }
1062
1063 static void
1064 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1065 {
1066         char *rtype;
1067         int want_reply;
1068         int success = 0;
1069
1070         rtype = packet_get_string(NULL);
1071         want_reply = packet_get_char();
1072         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1073
1074         /* -R style forwarding */
1075         if (strcmp(rtype, "tcpip-forward") == 0) {
1076                 struct passwd *pw;
1077                 char *listen_address;
1078                 u_short listen_port;
1079
1080                 pw = the_authctxt->pw;
1081                 if (pw == NULL || !the_authctxt->valid)
1082                         fatal("server_input_global_request: no/invalid user");
1083                 listen_address = packet_get_string(NULL);
1084                 listen_port = (u_short)packet_get_int();
1085                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1086                     listen_address, listen_port);
1087
1088                 /* check permissions */
1089                 if (!options.allow_tcp_forwarding ||
1090                     no_port_forwarding_flag
1091 #ifndef NO_IPPORT_RESERVED_CONCEPT
1092                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1093 #endif
1094                     ) {
1095                         success = 0;
1096                         packet_send_debug("Server has disabled port forwarding.");
1097                 } else {
1098                         /* Start listening on the port */
1099                         success = channel_setup_remote_fwd_listener(
1100                             listen_address, listen_port, options.gateway_ports);
1101                 }
1102                 xfree(listen_address);
1103         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1104                 char *cancel_address;
1105                 u_short cancel_port;
1106
1107                 cancel_address = packet_get_string(NULL);
1108                 cancel_port = (u_short)packet_get_int();
1109                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1110                     cancel_address, cancel_port);
1111
1112                 success = channel_cancel_rport_listener(cancel_address,
1113                     cancel_port);
1114                 xfree(cancel_address);
1115         }
1116         if (want_reply) {
1117                 packet_start(success ?
1118                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1119                 packet_send();
1120                 packet_write_wait();
1121         }
1122         xfree(rtype);
1123 }
1124
1125 static void
1126 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1127 {
1128         Channel *c;
1129         int id, reply, success = 0;
1130         char *rtype;
1131
1132         id = packet_get_int();
1133         rtype = packet_get_string(NULL);
1134         reply = packet_get_char();
1135
1136         debug("server_input_channel_req: channel %d request %s reply %d",
1137             id, rtype, reply);
1138
1139         if ((c = channel_lookup(id)) == NULL)
1140                 packet_disconnect("server_input_channel_req: "
1141                     "unknown channel %d", id);
1142         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1143                 success = session_input_channel_req(c, rtype);
1144         if (reply) {
1145                 packet_start(success ?
1146                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1147                 packet_put_int(c->remote_id);
1148                 packet_send();
1149         }
1150         xfree(rtype);
1151 }
1152
1153 static void
1154 server_init_dispatch_20(void)
1155 {
1156         debug("server_init_dispatch_20");
1157         dispatch_init(&dispatch_protocol_error);
1158         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1159         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1160         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1161         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1162         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1163         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1164         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1165         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1166         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1167         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1168         /* client_alive */
1169         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1170         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1171         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1172         /* rekeying */
1173         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1174 }
1175 static void
1176 server_init_dispatch_13(void)
1177 {
1178         debug("server_init_dispatch_13");
1179         dispatch_init(NULL);
1180         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1181         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1182         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1183         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1184         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1185         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1186         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1187         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1188         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1189 }
1190 static void
1191 server_init_dispatch_15(void)
1192 {
1193         server_init_dispatch_13();
1194         debug("server_init_dispatch_15");
1195         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1196         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1197 }
1198 static void
1199 server_init_dispatch(void)
1200 {
1201         if (compat20)
1202                 server_init_dispatch_20();
1203         else if (compat13)
1204                 server_init_dispatch_13();
1205         else
1206                 server_init_dispatch_15();
1207 }