serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.135 2006/03/25 18:30:55 deraadt Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42
  43 #include <signal.h>
  44 #include <termios.h>
  45
  46 #include "xmalloc.h"
  47 #include "packet.h"
  48 #include "buffer.h"
  49 #include "log.h"
  50 #include "servconf.h"
  51 #include "canohost.h"
  52 #include "sshpty.h"
  53 #include "channels.h"
  54 #include "compat.h"
  55 #include "ssh1.h"
  56 #include "ssh2.h"
  57 #include "auth.h"
  58 #include "session.h"
  59 #include "dispatch.h"
  60 #include "auth-options.h"
  61 #include "serverloop.h"
  62 #include "misc.h"
  63 #include "kex.h"
  64
  65 extern ServerOptions options;
  66
  67 /* XXX */
  68 extern Kex *xxx_kex;
  69 extern Authctxt *the_authctxt;
  70 extern int use_privsep;
  71
  72 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  73 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  74 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  75 static int fdin;                /* Descriptor for stdin (for writing) */
  76 static int fdout;               /* Descriptor for stdout (for reading);
  77                                    May be same number as fdin. */
  78 static int fderr;               /* Descriptor for stderr.  May be -1. */
  79 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  80 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  81 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  82 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  83 static int stdin_eof = 0;       /* EOF message received from client. */
  84 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  85 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  86 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  87 static int connection_in;       /* Connection to client (input). */
  88 static int connection_out;      /* Connection to client (output). */
  89 static int connection_closed = 0;       /* Connection to client closed. */
  90 static u_int buffer_high;       /* "Soft" max buffer size. */
  91 static int client_alive_timeouts = 0;
  92
  93 /*
  94  * This SIGCHLD kludge is used to detect when the child exits.  The server
  95  * will exit after that, as soon as forwarded connections have terminated.
  96  */
  97
  98 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  99
 100 /* Cleanup on signals (!use_privsep case only) */
 101 static volatile sig_atomic_t received_sigterm = 0;
 102
 103 /* prototypes */
 104 static void server_init_dispatch(void);
 105
 106 /*
 107  * we write to this pipe if a SIGCHLD is caught in order to avoid
 108  * the race between select() and child_terminated
 109  */
 110 static int notify_pipe[2];
 111 static void
 112 notify_setup(void)
 113 {
 114         if (pipe(notify_pipe) < 0) {
 115                 error("pipe(notify_pipe) failed %s", strerror(errno));
 116         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 117             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 118                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 119                 close(notify_pipe[0]);
 120                 close(notify_pipe[1]);
 121         } else {
 122                 set_nonblock(notify_pipe[0]);
 123                 set_nonblock(notify_pipe[1]);
 124                 return;
 125         }
 126         notify_pipe[0] = -1;    /* read end */
 127         notify_pipe[1] = -1;    /* write end */
 128 }
 129 static void
 130 notify_parent(void)
 131 {
 132         if (notify_pipe[1] != -1)
 133                 write(notify_pipe[1], "", 1);
 134 }
 135 static void
 136 notify_prepare(fd_set *readset)
 137 {
 138         if (notify_pipe[0] != -1)
 139                 FD_SET(notify_pipe[0], readset);
 140 }
 141 static void
 142 notify_done(fd_set *readset)
 143 {
 144         char c;
 145
 146         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 147                 while (read(notify_pipe[0], &c, 1) != -1)
 148                         debug2("notify_done: reading");
 149 }
 150
 151 /*ARGSUSED*/
 152 static void
 153 sigchld_handler(int sig)
 154 {
 155         int save_errno = errno;
 156         child_terminated = 1;
 157 #ifndef _UNICOS
 158         mysignal(SIGCHLD, sigchld_handler);
 159 #endif
 160         notify_parent();
 161         errno = save_errno;
 162 }
 163
 164 /*ARGSUSED*/
 165 static void
 166 sigterm_handler(int sig)
 167 {
 168         received_sigterm = sig;
 169 }
 170
 171 /*
 172  * Make packets from buffered stderr data, and buffer it for sending
 173  * to the client.
 174  */
 175 static void
 176 make_packets_from_stderr_data(void)
 177 {
 178         u_int len;
 179
 180         /* Send buffered stderr data to the client. */
 181         while (buffer_len(&stderr_buffer) > 0 &&
 182             packet_not_very_much_data_to_write()) {
 183                 len = buffer_len(&stderr_buffer);
 184                 if (packet_is_interactive()) {
 185                         if (len > 512)
 186                                 len = 512;
 187                 } else {
 188                         /* Keep the packets at reasonable size. */
 189                         if (len > packet_get_maxsize())
 190                                 len = packet_get_maxsize();
 191                 }
 192                 packet_start(SSH_SMSG_STDERR_DATA);
 193                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 194                 packet_send();
 195                 buffer_consume(&stderr_buffer, len);
 196                 stderr_bytes += len;
 197         }
 198 }
 199
 200 /*
 201  * Make packets from buffered stdout data, and buffer it for sending to the
 202  * client.
 203  */
 204 static void
 205 make_packets_from_stdout_data(void)
 206 {
 207         u_int len;
 208
 209         /* Send buffered stdout data to the client. */
 210         while (buffer_len(&stdout_buffer) > 0 &&
 211             packet_not_very_much_data_to_write()) {
 212                 len = buffer_len(&stdout_buffer);
 213                 if (packet_is_interactive()) {
 214                         if (len > 512)
 215                                 len = 512;
 216                 } else {
 217                         /* Keep the packets at reasonable size. */
 218                         if (len > packet_get_maxsize())
 219                                 len = packet_get_maxsize();
 220                 }
 221                 packet_start(SSH_SMSG_STDOUT_DATA);
 222                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 223                 packet_send();
 224                 buffer_consume(&stdout_buffer, len);
 225                 stdout_bytes += len;
 226         }
 227 }
 228
 229 static void
 230 client_alive_check(void)
 231 {
 232         int channel_id;
 233
 234         /* timeout, check to see how many we have had */
 235         if (++client_alive_timeouts > options.client_alive_count_max)
 236                 packet_disconnect("Timeout, your session not responding.");
 237
 238         /*
 239          * send a bogus global/channel request with "wantreply",
 240          * we should get back a failure
 241          */
 242         if ((channel_id = channel_find_open()) == -1) {
 243                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 244                 packet_put_cstring("keepalive@openssh.com");
 245                 packet_put_char(1);     /* boolean: want reply */
 246         } else {
 247                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 248         }
 249         packet_send();
 250 }
 251
 252 /*
 253  * Sleep in select() until we can do something.  This will initialize the
 254  * select masks.  Upon return, the masks will indicate which descriptors
 255  * have data or can accept data.  Optionally, a maximum time can be specified
 256  * for the duration of the wait (0 = infinite).
 257  */
 258 static void
 259 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 260     u_int *nallocp, u_int max_time_milliseconds)
 261 {
 262         struct timeval tv, *tvp;
 263         int ret;
 264         int client_alive_scheduled = 0;
 265
 266         /*
 267          * if using client_alive, set the max timeout accordingly,
 268          * and indicate that this particular timeout was for client
 269          * alive by setting the client_alive_scheduled flag.
 270          *
 271          * this could be randomized somewhat to make traffic
 272          * analysis more difficult, but we're not doing it yet.
 273          */
 274         if (compat20 &&
 275             max_time_milliseconds == 0 && options.client_alive_interval) {
 276                 client_alive_scheduled = 1;
 277                 max_time_milliseconds = options.client_alive_interval * 1000;
 278         }
 279
 280         /* Allocate and update select() masks for channel descriptors. */
 281         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 282
 283         if (compat20) {
 284 #if 0
 285                 /* wrong: bad condition XXX */
 286                 if (channel_not_very_much_buffered_data())
 287 #endif
 288                 FD_SET(connection_in, *readsetp);
 289         } else {
 290                 /*
 291                  * Read packets from the client unless we have too much
 292                  * buffered stdin or channel data.
 293                  */
 294                 if (buffer_len(&stdin_buffer) < buffer_high &&
 295                     channel_not_very_much_buffered_data())
 296                         FD_SET(connection_in, *readsetp);
 297                 /*
 298                  * If there is not too much data already buffered going to
 299                  * the client, try to get some more data from the program.
 300                  */
 301                 if (packet_not_very_much_data_to_write()) {
 302                         if (!fdout_eof)
 303                                 FD_SET(fdout, *readsetp);
 304                         if (!fderr_eof)
 305                                 FD_SET(fderr, *readsetp);
 306                 }
 307                 /*
 308                  * If we have buffered data, try to write some of that data
 309                  * to the program.
 310                  */
 311                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 312                         FD_SET(fdin, *writesetp);
 313         }
 314         notify_prepare(*readsetp);
 315
 316         /*
 317          * If we have buffered packet data going to the client, mark that
 318          * descriptor.
 319          */
 320         if (packet_have_data_to_write())
 321                 FD_SET(connection_out, *writesetp);
 322
 323         /*
 324          * If child has terminated and there is enough buffer space to read
 325          * from it, then read as much as is available and exit.
 326          */
 327         if (child_terminated && packet_not_very_much_data_to_write())
 328                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 329                         max_time_milliseconds = 100;
 330
 331         if (max_time_milliseconds == 0)
 332                 tvp = NULL;
 333         else {
 334                 tv.tv_sec = max_time_milliseconds / 1000;
 335                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 336                 tvp = &tv;
 337         }
 338
 339         /* Wait for something to happen, or the timeout to expire. */
 340         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 341
 342         if (ret == -1) {
 343                 memset(*readsetp, 0, *nallocp);
 344                 memset(*writesetp, 0, *nallocp);
 345                 if (errno != EINTR)
 346                         error("select: %.100s", strerror(errno));
 347         } else if (ret == 0 && client_alive_scheduled)
 348                 client_alive_check();
 349
 350         notify_done(*readsetp);
 351 }
 352
 353 /*
 354  * Processes input from the client and the program.  Input data is stored
 355  * in buffers and processed later.
 356  */
 357 static void
 358 process_input(fd_set *readset)
 359 {
 360         int len;
 361         char buf[16384];
 362
 363         /* Read and buffer any input data from the client. */
 364         if (FD_ISSET(connection_in, readset)) {
 365                 len = read(connection_in, buf, sizeof(buf));
 366                 if (len == 0) {
 367                         verbose("Connection closed by %.100s",
 368                             get_remote_ipaddr());
 369                         connection_closed = 1;
 370                         if (compat20)
 371                                 return;
 372                         cleanup_exit(255);
 373                 } else if (len < 0) {
 374                         if (errno != EINTR && errno != EAGAIN) {
 375                                 verbose("Read error from remote host "
 376                                     "%.100s: %.100s",
 377                                     get_remote_ipaddr(), strerror(errno));
 378                                 cleanup_exit(255);
 379                         }
 380                 } else {
 381                         /* Buffer any received data. */
 382                         packet_process_incoming(buf, len);
 383                 }
 384         }
 385         if (compat20)
 386                 return;
 387
 388         /* Read and buffer any available stdout data from the program. */
 389         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 390                 len = read(fdout, buf, sizeof(buf));
 391                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 392                         /* do nothing */
 393                 } else if (len <= 0) {
 394                         fdout_eof = 1;
 395                 } else {
 396                         buffer_append(&stdout_buffer, buf, len);
 397                         fdout_bytes += len;
 398                 }
 399         }
 400         /* Read and buffer any available stderr data from the program. */
 401         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 402                 len = read(fderr, buf, sizeof(buf));
 403                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 404                         /* do nothing */
 405                 } else if (len <= 0) {
 406                         fderr_eof = 1;
 407                 } else {
 408                         buffer_append(&stderr_buffer, buf, len);
 409                 }
 410         }
 411 }
 412
 413 /*
 414  * Sends data from internal buffers to client program stdin.
 415  */
 416 static void
 417 process_output(fd_set *writeset)
 418 {
 419         struct termios tio;
 420         u_char *data;
 421         u_int dlen;
 422         int len;
 423
 424         /* Write buffered data to program stdin. */
 425         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 426                 data = buffer_ptr(&stdin_buffer);
 427                 dlen = buffer_len(&stdin_buffer);
 428                 len = write(fdin, data, dlen);
 429                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 430                         /* do nothing */
 431                 } else if (len <= 0) {
 432                         if (fdin != fdout)
 433                                 close(fdin);
 434                         else
 435                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 436                         fdin = -1;
 437                 } else {
 438                         /* Successful write. */
 439                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 440                             tcgetattr(fdin, &tio) == 0 &&
 441                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 442                                 /*
 443                                  * Simulate echo to reduce the impact of
 444                                  * traffic analysis
 445                                  */
 446                                 packet_send_ignore(len);
 447                                 packet_send();
 448                         }
 449                         /* Consume the data from the buffer. */
 450                         buffer_consume(&stdin_buffer, len);
 451                         /* Update the count of bytes written to the program. */
 452                         stdin_bytes += len;
 453                 }
 454         }
 455         /* Send any buffered packet data to the client. */
 456         if (FD_ISSET(connection_out, writeset))
 457                 packet_write_poll();
 458 }
 459
 460 /*
 461  * Wait until all buffered output has been sent to the client.
 462  * This is used when the program terminates.
 463  */
 464 static void
 465 drain_output(void)
 466 {
 467         /* Send any buffered stdout data to the client. */
 468         if (buffer_len(&stdout_buffer) > 0) {
 469                 packet_start(SSH_SMSG_STDOUT_DATA);
 470                 packet_put_string(buffer_ptr(&stdout_buffer),
 471                                   buffer_len(&stdout_buffer));
 472                 packet_send();
 473                 /* Update the count of sent bytes. */
 474                 stdout_bytes += buffer_len(&stdout_buffer);
 475         }
 476         /* Send any buffered stderr data to the client. */
 477         if (buffer_len(&stderr_buffer) > 0) {
 478                 packet_start(SSH_SMSG_STDERR_DATA);
 479                 packet_put_string(buffer_ptr(&stderr_buffer),
 480                                   buffer_len(&stderr_buffer));
 481                 packet_send();
 482                 /* Update the count of sent bytes. */
 483                 stderr_bytes += buffer_len(&stderr_buffer);
 484         }
 485         /* Wait until all buffered data has been written to the client. */
 486         packet_write_wait();
 487 }
 488
 489 static void
 490 process_buffered_input_packets(void)
 491 {
 492         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 493 }
 494
 495 /*
 496  * Performs the interactive session.  This handles data transmission between
 497  * the client and the program.  Note that the notion of stdin, stdout, and
 498  * stderr in this function is sort of reversed: this function writes to
 499  * stdin (of the child program), and reads from stdout and stderr (of the
 500  * child program).
 501  */
 502 void
 503 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 504 {
 505         fd_set *readset = NULL, *writeset = NULL;
 506         int max_fd = 0;
 507         u_int nalloc = 0;
 508         int wait_status;        /* Status returned by wait(). */
 509         pid_t wait_pid;         /* pid returned by wait(). */
 510         int waiting_termination = 0;    /* Have displayed waiting close message. */
 511         u_int max_time_milliseconds;
 512         u_int previous_stdout_buffer_bytes;
 513         u_int stdout_buffer_bytes;
 514         int type;
 515
 516         debug("Entering interactive session.");
 517
 518         /* Initialize the SIGCHLD kludge. */
 519         child_terminated = 0;
 520         mysignal(SIGCHLD, sigchld_handler);
 521
 522         if (!use_privsep) {
 523                 signal(SIGTERM, sigterm_handler);
 524                 signal(SIGINT, sigterm_handler);
 525                 signal(SIGQUIT, sigterm_handler);
 526         }
 527
 528         /* Initialize our global variables. */
 529         fdin = fdin_arg;
 530         fdout = fdout_arg;
 531         fderr = fderr_arg;
 532
 533         /* nonblocking IO */
 534         set_nonblock(fdin);
 535         set_nonblock(fdout);
 536         /* we don't have stderr for interactive terminal sessions, see below */
 537         if (fderr != -1)
 538                 set_nonblock(fderr);
 539
 540         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 541                 fdin_is_tty = 1;
 542
 543         connection_in = packet_get_connection_in();
 544         connection_out = packet_get_connection_out();
 545
 546         notify_setup();
 547
 548         previous_stdout_buffer_bytes = 0;
 549
 550         /* Set approximate I/O buffer size. */
 551         if (packet_is_interactive())
 552                 buffer_high = 4096;
 553         else
 554                 buffer_high = 64 * 1024;
 555
 556 #if 0
 557         /* Initialize max_fd to the maximum of the known file descriptors. */
 558         max_fd = MAX(connection_in, connection_out);
 559         max_fd = MAX(max_fd, fdin);
 560         max_fd = MAX(max_fd, fdout);
 561         if (fderr != -1)
 562                 max_fd = MAX(max_fd, fderr);
 563 #endif
 564
 565         /* Initialize Initialize buffers. */
 566         buffer_init(&stdin_buffer);
 567         buffer_init(&stdout_buffer);
 568         buffer_init(&stderr_buffer);
 569
 570         /*
 571          * If we have no separate fderr (which is the case when we have a pty
 572          * - there we cannot make difference between data sent to stdout and
 573          * stderr), indicate that we have seen an EOF from stderr.  This way
 574          * we don't need to check the descriptor everywhere.
 575          */
 576         if (fderr == -1)
 577                 fderr_eof = 1;
 578
 579         server_init_dispatch();
 580
 581         /* Main loop of the server for the interactive session mode. */
 582         for (;;) {
 583
 584                 /* Process buffered packets from the client. */
 585                 process_buffered_input_packets();
 586
 587                 /*
 588                  * If we have received eof, and there is no more pending
 589                  * input data, cause a real eof by closing fdin.
 590                  */
 591                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 592                         if (fdin != fdout)
 593                                 close(fdin);
 594                         else
 595                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 596                         fdin = -1;
 597                 }
 598                 /* Make packets from buffered stderr data to send to the client. */
 599                 make_packets_from_stderr_data();
 600
 601                 /*
 602                  * Make packets from buffered stdout data to send to the
 603                  * client. If there is very little to send, this arranges to
 604                  * not send them now, but to wait a short while to see if we
 605                  * are getting more data. This is necessary, as some systems
 606                  * wake up readers from a pty after each separate character.
 607                  */
 608                 max_time_milliseconds = 0;
 609                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 610                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 611                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 612                         /* try again after a while */
 613                         max_time_milliseconds = 10;
 614                 } else {
 615                         /* Send it now. */
 616                         make_packets_from_stdout_data();
 617                 }
 618                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 619
 620                 /* Send channel data to the client. */
 621                 if (packet_not_very_much_data_to_write())
 622                         channel_output_poll();
 623
 624                 /*
 625                  * Bail out of the loop if the program has closed its output
 626                  * descriptors, and we have no more data to send to the
 627                  * client, and there is no pending buffered data.
 628                  */
 629                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 630                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 631                         if (!channel_still_open())
 632                                 break;
 633                         if (!waiting_termination) {
 634                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 635                                 char *cp;
 636                                 waiting_termination = 1;
 637                                 buffer_append(&stderr_buffer, s, strlen(s));
 638
 639                                 /* Display list of open channels. */
 640                                 cp = channel_open_message();
 641                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 642                                 xfree(cp);
 643                         }
 644                 }
 645                 max_fd = MAX(connection_in, connection_out);
 646                 max_fd = MAX(max_fd, fdin);
 647                 max_fd = MAX(max_fd, fdout);
 648                 max_fd = MAX(max_fd, fderr);
 649                 max_fd = MAX(max_fd, notify_pipe[0]);
 650
 651                 /* Sleep in select() until we can do something. */
 652                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 653                     &nalloc, max_time_milliseconds);
 654
 655                 if (received_sigterm) {
 656                         logit("Exiting on signal %d", received_sigterm);
 657                         /* Clean up sessions, utmp, etc. */
 658                         cleanup_exit(255);
 659                 }
 660
 661                 /* Process any channel events. */
 662                 channel_after_select(readset, writeset);
 663
 664                 /* Process input from the client and from program stdout/stderr. */
 665                 process_input(readset);
 666
 667                 /* Process output to the client and to program stdin. */
 668                 process_output(writeset);
 669         }
 670         if (readset)
 671                 xfree(readset);
 672         if (writeset)
 673                 xfree(writeset);
 674
 675         /* Cleanup and termination code. */
 676
 677         /* Wait until all output has been sent to the client. */
 678         drain_output();
 679
 680         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 681             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 682
 683         /* Free and clear the buffers. */
 684         buffer_free(&stdin_buffer);
 685         buffer_free(&stdout_buffer);
 686         buffer_free(&stderr_buffer);
 687
 688         /* Close the file descriptors. */
 689         if (fdout != -1)
 690                 close(fdout);
 691         fdout = -1;
 692         fdout_eof = 1;
 693         if (fderr != -1)
 694                 close(fderr);
 695         fderr = -1;
 696         fderr_eof = 1;
 697         if (fdin != -1)
 698                 close(fdin);
 699         fdin = -1;
 700
 701         channel_free_all();
 702
 703         /* We no longer want our SIGCHLD handler to be called. */
 704         mysignal(SIGCHLD, SIG_DFL);
 705
 706         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 707                 if (errno != EINTR)
 708                         packet_disconnect("wait: %.100s", strerror(errno));
 709         if (wait_pid != pid)
 710                 error("Strange, wait returned pid %ld, expected %ld",
 711                     (long)wait_pid, (long)pid);
 712
 713         /* Check if it exited normally. */
 714         if (WIFEXITED(wait_status)) {
 715                 /* Yes, normal exit.  Get exit status and send it to the client. */
 716                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 717                 packet_start(SSH_SMSG_EXITSTATUS);
 718                 packet_put_int(WEXITSTATUS(wait_status));
 719                 packet_send();
 720                 packet_write_wait();
 721
 722                 /*
 723                  * Wait for exit confirmation.  Note that there might be
 724                  * other packets coming before it; however, the program has
 725                  * already died so we just ignore them.  The client is
 726                  * supposed to respond with the confirmation when it receives
 727                  * the exit status.
 728                  */
 729                 do {
 730                         type = packet_read();
 731                 }
 732                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 733
 734                 debug("Received exit confirmation.");
 735                 return;
 736         }
 737         /* Check if the program terminated due to a signal. */
 738         if (WIFSIGNALED(wait_status))
 739                 packet_disconnect("Command terminated on signal %d.",
 740                                   WTERMSIG(wait_status));
 741
 742         /* Some weird exit cause.  Just exit. */
 743         packet_disconnect("wait returned status %04x.", wait_status);
 744         /* NOTREACHED */
 745 }
 746
 747 static void
 748 collect_children(void)
 749 {
 750         pid_t pid;
 751         sigset_t oset, nset;
 752         int status;
 753
 754         /* block SIGCHLD while we check for dead children */
 755         sigemptyset(&nset);
 756         sigaddset(&nset, SIGCHLD);
 757         sigprocmask(SIG_BLOCK, &nset, &oset);
 758         if (child_terminated) {
 759                 debug("Received SIGCHLD.");
 760                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 761                     (pid < 0 && errno == EINTR))
 762                         if (pid > 0)
 763                                 session_close_by_pid(pid, status);
 764                 child_terminated = 0;
 765         }
 766         sigprocmask(SIG_SETMASK, &oset, NULL);
 767 }
 768
 769 void
 770 server_loop2(Authctxt *authctxt)
 771 {
 772         fd_set *readset = NULL, *writeset = NULL;
 773         int rekeying = 0, max_fd, nalloc = 0;
 774
 775         debug("Entering interactive session for SSH2.");
 776
 777         mysignal(SIGCHLD, sigchld_handler);
 778         child_terminated = 0;
 779         connection_in = packet_get_connection_in();
 780         connection_out = packet_get_connection_out();
 781
 782         if (!use_privsep) {
 783                 signal(SIGTERM, sigterm_handler);
 784                 signal(SIGINT, sigterm_handler);
 785                 signal(SIGQUIT, sigterm_handler);
 786         }
 787
 788         notify_setup();
 789
 790         max_fd = MAX(connection_in, connection_out);
 791         max_fd = MAX(max_fd, notify_pipe[0]);
 792
 793         server_init_dispatch();
 794
 795         for (;;) {
 796                 process_buffered_input_packets();
 797
 798                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 799
 800                 if (!rekeying && packet_not_very_much_data_to_write())
 801                         channel_output_poll();
 802                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 803                     &nalloc, 0);
 804
 805                 if (received_sigterm) {
 806                         logit("Exiting on signal %d", received_sigterm);
 807                         /* Clean up sessions, utmp, etc. */
 808                         cleanup_exit(255);
 809                 }
 810
 811                 collect_children();
 812                 if (!rekeying) {
 813                         channel_after_select(readset, writeset);
 814                         if (packet_need_rekeying()) {
 815                                 debug("need rekeying");
 816                                 xxx_kex->done = 0;
 817                                 kex_send_kexinit(xxx_kex);
 818                         }
 819                 }
 820                 process_input(readset);
 821                 if (connection_closed)
 822                         break;
 823                 process_output(writeset);
 824         }
 825         collect_children();
 826
 827         if (readset)
 828                 xfree(readset);
 829         if (writeset)
 830                 xfree(writeset);
 831
 832         /* free all channels, no more reads and writes */
 833         channel_free_all();
 834
 835         /* free remaining sessions, e.g. remove wtmp entries */
 836         session_destroy_all(NULL);
 837 }
 838
 839 static void
 840 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 841 {
 842         debug("Got %d/%u for keepalive", type, seq);
 843         /*
 844          * reset timeout, since we got a sane answer from the client.
 845          * even if this was generated by something other than
 846          * the bogus CHANNEL_REQUEST we send for keepalives.
 847          */
 848         client_alive_timeouts = 0;
 849 }
 850
 851 static void
 852 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 853 {
 854         char *data;
 855         u_int data_len;
 856
 857         /* Stdin data from the client.  Append it to the buffer. */
 858         /* Ignore any data if the client has closed stdin. */
 859         if (fdin == -1)
 860                 return;
 861         data = packet_get_string(&data_len);
 862         packet_check_eom();
 863         buffer_append(&stdin_buffer, data, data_len);
 864         memset(data, 0, data_len);
 865         xfree(data);
 866 }
 867
 868 static void
 869 server_input_eof(int type, u_int32_t seq, void *ctxt)
 870 {
 871         /*
 872          * Eof from the client.  The stdin descriptor to the
 873          * program will be closed when all buffered data has
 874          * drained.
 875          */
 876         debug("EOF received for stdin.");
 877         packet_check_eom();
 878         stdin_eof = 1;
 879 }
 880
 881 static void
 882 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 883 {
 884         u_int row = packet_get_int();
 885         u_int col = packet_get_int();
 886         u_int xpixel = packet_get_int();
 887         u_int ypixel = packet_get_int();
 888
 889         debug("Window change received.");
 890         packet_check_eom();
 891         if (fdin != -1)
 892                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 893 }
 894
 895 static Channel *
 896 server_request_direct_tcpip(void)
 897 {
 898         Channel *c;
 899         int sock;
 900         char *target, *originator;
 901         int target_port, originator_port;
 902
 903         target = packet_get_string(NULL);
 904         target_port = packet_get_int();
 905         originator = packet_get_string(NULL);
 906         originator_port = packet_get_int();
 907         packet_check_eom();
 908
 909         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 910             originator, originator_port, target, target_port);
 911
 912         /* XXX check permission */
 913         sock = channel_connect_to(target, target_port);
 914         xfree(target);
 915         xfree(originator);
 916         if (sock < 0)
 917                 return NULL;
 918         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 919             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 920             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 921         return c;
 922 }
 923
 924 static Channel *
 925 server_request_tun(void)
 926 {
 927         Channel *c = NULL;
 928         int mode, tun;
 929         int sock;
 930
 931         mode = packet_get_int();
 932         switch (mode) {
 933         case SSH_TUNMODE_POINTOPOINT:
 934         case SSH_TUNMODE_ETHERNET:
 935                 break;
 936         default:
 937                 packet_send_debug("Unsupported tunnel device mode.");
 938                 return NULL;
 939         }
 940         if ((options.permit_tun & mode) == 0) {
 941                 packet_send_debug("Server has rejected tunnel device "
 942                     "forwarding");
 943                 return NULL;
 944         }
 945
 946         tun = packet_get_int();
 947         if (forced_tun_device != -1) {
 948                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 949                         goto done;
 950                 tun = forced_tun_device;
 951         }
 952         sock = tun_open(tun, mode);
 953         if (sock < 0)
 954                 goto done;
 955         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 956             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 957         c->datagram = 1;
 958 #if defined(SSH_TUN_FILTER)
 959         if (mode == SSH_TUNMODE_POINTOPOINT)
 960                 channel_register_filter(c->self, sys_tun_infilter,
 961                     sys_tun_outfilter);
 962 #endif
 963
 964  done:
 965         if (c == NULL)
 966                 packet_send_debug("Failed to open the tunnel device.");
 967         return c;
 968 }
 969
 970 static Channel *
 971 server_request_session(void)
 972 {
 973         Channel *c;
 974
 975         debug("input_session_request");
 976         packet_check_eom();
 977         /*
 978          * A server session has no fd to read or write until a
 979          * CHANNEL_REQUEST for a shell is made, so we set the type to
 980          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 981          * CHANNEL_REQUEST messages is registered.
 982          */
 983         c = channel_new("session", SSH_CHANNEL_LARVAL,
 984             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 985             0, "server-session", 1);
 986         if (session_open(the_authctxt, c->self) != 1) {
 987                 debug("session open failed, free channel %d", c->self);
 988                 channel_free(c);
 989                 return NULL;
 990         }
 991         channel_register_cleanup(c->self, session_close_by_channel, 0);
 992         return c;
 993 }
 994
 995 static void
 996 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 997 {
 998         Channel *c = NULL;
 999         char *ctype;
1000         int rchan;
1001         u_int rmaxpack, rwindow, len;
1002
1003         ctype = packet_get_string(&len);
1004         rchan = packet_get_int();
1005         rwindow = packet_get_int();
1006         rmaxpack = packet_get_int();
1007
1008         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1009             ctype, rchan, rwindow, rmaxpack);
1010
1011         if (strcmp(ctype, "session") == 0) {
1012                 c = server_request_session();
1013         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1014                 c = server_request_direct_tcpip();
1015         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1016                 c = server_request_tun();
1017         }
1018         if (c != NULL) {
1019                 debug("server_input_channel_open: confirm %s", ctype);
1020                 c->remote_id = rchan;
1021                 c->remote_window = rwindow;
1022                 c->remote_maxpacket = rmaxpack;
1023                 if (c->type != SSH_CHANNEL_CONNECTING) {
1024                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1025                         packet_put_int(c->remote_id);
1026                         packet_put_int(c->self);
1027                         packet_put_int(c->local_window);
1028                         packet_put_int(c->local_maxpacket);
1029                         packet_send();
1030                 }
1031         } else {
1032                 debug("server_input_channel_open: failure %s", ctype);
1033                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1034                 packet_put_int(rchan);
1035                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1036                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1037                         packet_put_cstring("open failed");
1038                         packet_put_cstring("");
1039                 }
1040                 packet_send();
1041         }
1042         xfree(ctype);
1043 }
1044
1045 static void
1046 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1047 {
1048         char *rtype;
1049         int want_reply;
1050         int success = 0;
1051
1052         rtype = packet_get_string(NULL);
1053         want_reply = packet_get_char();
1054         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1055
1056         /* -R style forwarding */
1057         if (strcmp(rtype, "tcpip-forward") == 0) {
1058                 struct passwd *pw;
1059                 char *listen_address;
1060                 u_short listen_port;
1061
1062                 pw = the_authctxt->pw;
1063                 if (pw == NULL || !the_authctxt->valid)
1064                         fatal("server_input_global_request: no/invalid user");
1065                 listen_address = packet_get_string(NULL);
1066                 listen_port = (u_short)packet_get_int();
1067                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1068                     listen_address, listen_port);
1069
1070                 /* check permissions */
1071                 if (!options.allow_tcp_forwarding ||
1072                     no_port_forwarding_flag
1073 #ifndef NO_IPPORT_RESERVED_CONCEPT
1074                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1075 #endif
1076                     ) {
1077                         success = 0;
1078                         packet_send_debug("Server has disabled port forwarding.");
1079                 } else {
1080                         /* Start listening on the port */
1081                         success = channel_setup_remote_fwd_listener(
1082                             listen_address, listen_port, options.gateway_ports);
1083                 }
1084                 xfree(listen_address);
1085         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1086                 char *cancel_address;
1087                 u_short cancel_port;
1088
1089                 cancel_address = packet_get_string(NULL);
1090                 cancel_port = (u_short)packet_get_int();
1091                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1092                     cancel_address, cancel_port);
1093
1094                 success = channel_cancel_rport_listener(cancel_address,
1095                     cancel_port);
1096                 xfree(cancel_address);
1097         }
1098         if (want_reply) {
1099                 packet_start(success ?
1100                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1101                 packet_send();
1102                 packet_write_wait();
1103         }
1104         xfree(rtype);
1105 }
1106
1107 static void
1108 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1109 {
1110         Channel *c;
1111         int id, reply, success = 0;
1112         char *rtype;
1113
1114         id = packet_get_int();
1115         rtype = packet_get_string(NULL);
1116         reply = packet_get_char();
1117
1118         debug("server_input_channel_req: channel %d request %s reply %d",
1119             id, rtype, reply);
1120
1121         if ((c = channel_lookup(id)) == NULL)
1122                 packet_disconnect("server_input_channel_req: "
1123                     "unknown channel %d", id);
1124         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1125                 success = session_input_channel_req(c, rtype);
1126         if (reply) {
1127                 packet_start(success ?
1128                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1129                 packet_put_int(c->remote_id);
1130                 packet_send();
1131         }
1132         xfree(rtype);
1133 }
1134
1135 static void
1136 server_init_dispatch_20(void)
1137 {
1138         debug("server_init_dispatch_20");
1139         dispatch_init(&dispatch_protocol_error);
1140         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1141         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1142         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1143         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1144         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1145         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1146         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1147         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1148         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1149         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1150         /* client_alive */
1151         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1152         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1153         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1154         /* rekeying */
1155         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1156 }
1157 static void
1158 server_init_dispatch_13(void)
1159 {
1160         debug("server_init_dispatch_13");
1161         dispatch_init(NULL);
1162         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1163         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1164         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1165         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1166         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1167         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1168         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1169         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1170         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1171 }
1172 static void
1173 server_init_dispatch_15(void)
1174 {
1175         server_init_dispatch_13();
1176         debug("server_init_dispatch_15");
1177         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1178         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1179 }
1180 static void
1181 server_init_dispatch(void)
1182 {
1183         if (compat20)
1184                 server_init_dispatch_20();
1185         else if (compat13)
1186                 server_init_dispatch_13();
1187         else
1188                 server_init_dispatch_15();
1189 }