serverloop.c

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