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 RCSID("$OpenBSD: serverloop.c,v 1.125 2006/02/07 01:42:00 stevesk Exp $");
  39
  40 #include <termios.h>
  41
  42 #include "xmalloc.h"
  43 #include "packet.h"
  44 #include "buffer.h"
  45 #include "log.h"
  46 #include "servconf.h"
  47 #include "canohost.h"
  48 #include "sshpty.h"
  49 #include "channels.h"
  50 #include "compat.h"
  51 #include "ssh1.h"
  52 #include "ssh2.h"
  53 #include "auth.h"
  54 #include "session.h"
  55 #include "dispatch.h"
  56 #include "auth-options.h"
  57 #include "serverloop.h"
  58 #include "misc.h"
  59 #include "kex.h"
  60
  61 extern ServerOptions options;
  62
  63 /* XXX */
  64 extern Kex *xxx_kex;
  65 extern Authctxt *the_authctxt;
  66 extern int use_privsep;
  67
  68 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  69 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  70 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  71 static int fdin;                /* Descriptor for stdin (for writing) */
  72 static int fdout;               /* Descriptor for stdout (for reading);
  73                                    May be same number as fdin. */
  74 static int fderr;               /* Descriptor for stderr.  May be -1. */
  75 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  76 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  77 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  78 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  79 static int stdin_eof = 0;       /* EOF message received from client. */
  80 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  81 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  82 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  83 static int connection_in;       /* Connection to client (input). */
  84 static int connection_out;      /* Connection to client (output). */
  85 static int connection_closed = 0;       /* Connection to client closed. */
  86 static u_int buffer_high;       /* "Soft" max buffer size. */
  87 static int client_alive_timeouts = 0;
  88
  89 /*
  90  * This SIGCHLD kludge is used to detect when the child exits.  The server
  91  * will exit after that, as soon as forwarded connections have terminated.
  92  */
  93
  94 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  95
  96 /* Cleanup on signals (!use_privsep case only) */
  97 static volatile sig_atomic_t received_sigterm = 0;
  98
  99 /* prototypes */
 100 static void server_init_dispatch(void);
 101
 102 /*
 103  * we write to this pipe if a SIGCHLD is caught in order to avoid
 104  * the race between select() and child_terminated
 105  */
 106 static int notify_pipe[2];
 107 static void
 108 notify_setup(void)
 109 {
 110         if (pipe(notify_pipe) < 0) {
 111                 error("pipe(notify_pipe) failed %s", strerror(errno));
 112         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 113             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 114                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 115                 close(notify_pipe[0]);
 116                 close(notify_pipe[1]);
 117         } else {
 118                 set_nonblock(notify_pipe[0]);
 119                 set_nonblock(notify_pipe[1]);
 120                 return;
 121         }
 122         notify_pipe[0] = -1;    /* read end */
 123         notify_pipe[1] = -1;    /* write end */
 124 }
 125 static void
 126 notify_parent(void)
 127 {
 128         if (notify_pipe[1] != -1)
 129                 write(notify_pipe[1], "", 1);
 130 }
 131 static void
 132 notify_prepare(fd_set *readset)
 133 {
 134         if (notify_pipe[0] != -1)
 135                 FD_SET(notify_pipe[0], readset);
 136 }
 137 static void
 138 notify_done(fd_set *readset)
 139 {
 140         char c;
 141
 142         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 143                 while (read(notify_pipe[0], &c, 1) != -1)
 144                         debug2("notify_done: reading");
 145 }
 146
 147 static void
 148 sigchld_handler(int sig)
 149 {
 150         int save_errno = errno;
 151         debug("Received SIGCHLD.");
 152         child_terminated = 1;
 153 #ifndef _UNICOS
 154         mysignal(SIGCHLD, sigchld_handler);
 155 #endif
 156         notify_parent();
 157         errno = save_errno;
 158 }
 159
 160 static void
 161 sigterm_handler(int sig)
 162 {
 163         received_sigterm = sig;
 164 }
 165
 166 /*
 167  * Make packets from buffered stderr data, and buffer it for sending
 168  * to the client.
 169  */
 170 static void
 171 make_packets_from_stderr_data(void)
 172 {
 173         u_int len;
 174
 175         /* Send buffered stderr data to the client. */
 176         while (buffer_len(&stderr_buffer) > 0 &&
 177             packet_not_very_much_data_to_write()) {
 178                 len = buffer_len(&stderr_buffer);
 179                 if (packet_is_interactive()) {
 180                         if (len > 512)
 181                                 len = 512;
 182                 } else {
 183                         /* Keep the packets at reasonable size. */
 184                         if (len > packet_get_maxsize())
 185                                 len = packet_get_maxsize();
 186                 }
 187                 packet_start(SSH_SMSG_STDERR_DATA);
 188                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 189                 packet_send();
 190                 buffer_consume(&stderr_buffer, len);
 191                 stderr_bytes += len;
 192         }
 193 }
 194
 195 /*
 196  * Make packets from buffered stdout data, and buffer it for sending to the
 197  * client.
 198  */
 199 static void
 200 make_packets_from_stdout_data(void)
 201 {
 202         u_int len;
 203
 204         /* Send buffered stdout data to the client. */
 205         while (buffer_len(&stdout_buffer) > 0 &&
 206             packet_not_very_much_data_to_write()) {
 207                 len = buffer_len(&stdout_buffer);
 208                 if (packet_is_interactive()) {
 209                         if (len > 512)
 210                                 len = 512;
 211                 } else {
 212                         /* Keep the packets at reasonable size. */
 213                         if (len > packet_get_maxsize())
 214                                 len = packet_get_maxsize();
 215                 }
 216                 packet_start(SSH_SMSG_STDOUT_DATA);
 217                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 218                 packet_send();
 219                 buffer_consume(&stdout_buffer, len);
 220                 stdout_bytes += len;
 221         }
 222 }
 223
 224 static void
 225 client_alive_check(void)
 226 {
 227         int channel_id;
 228
 229         /* timeout, check to see how many we have had */
 230         if (++client_alive_timeouts > options.client_alive_count_max)
 231                 packet_disconnect("Timeout, your session not responding.");
 232
 233         /*
 234          * send a bogus global/channel request with "wantreply",
 235          * we should get back a failure
 236          */
 237         if ((channel_id = channel_find_open()) == -1) {
 238                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 239                 packet_put_cstring("keepalive@openssh.com");
 240                 packet_put_char(1);     /* boolean: want reply */
 241         } else {
 242                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 243         }
 244         packet_send();
 245 }
 246
 247 /*
 248  * Sleep in select() until we can do something.  This will initialize the
 249  * select masks.  Upon return, the masks will indicate which descriptors
 250  * have data or can accept data.  Optionally, a maximum time can be specified
 251  * for the duration of the wait (0 = infinite).
 252  */
 253 static void
 254 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 255     u_int *nallocp, u_int max_time_milliseconds)
 256 {
 257         struct timeval tv, *tvp;
 258         int ret;
 259         int client_alive_scheduled = 0;
 260
 261         /*
 262          * if using client_alive, set the max timeout accordingly,
 263          * and indicate that this particular timeout was for client
 264          * alive by setting the client_alive_scheduled flag.
 265          *
 266          * this could be randomized somewhat to make traffic
 267          * analysis more difficult, but we're not doing it yet.
 268          */
 269         if (compat20 &&
 270             max_time_milliseconds == 0 && options.client_alive_interval) {
 271                 client_alive_scheduled = 1;
 272                 max_time_milliseconds = options.client_alive_interval * 1000;
 273         }
 274
 275         /* Allocate and update select() masks for channel descriptors. */
 276         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 277
 278         if (compat20) {
 279 #if 0
 280                 /* wrong: bad condition XXX */
 281                 if (channel_not_very_much_buffered_data())
 282 #endif
 283                 FD_SET(connection_in, *readsetp);
 284         } else {
 285                 /*
 286                  * Read packets from the client unless we have too much
 287                  * buffered stdin or channel data.
 288                  */
 289                 if (buffer_len(&stdin_buffer) < buffer_high &&
 290                     channel_not_very_much_buffered_data())
 291                         FD_SET(connection_in, *readsetp);
 292                 /*
 293                  * If there is not too much data already buffered going to
 294                  * the client, try to get some more data from the program.
 295                  */
 296                 if (packet_not_very_much_data_to_write()) {
 297                         if (!fdout_eof)
 298                                 FD_SET(fdout, *readsetp);
 299                         if (!fderr_eof)
 300                                 FD_SET(fderr, *readsetp);
 301                 }
 302                 /*
 303                  * If we have buffered data, try to write some of that data
 304                  * to the program.
 305                  */
 306                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 307                         FD_SET(fdin, *writesetp);
 308         }
 309         notify_prepare(*readsetp);
 310
 311         /*
 312          * If we have buffered packet data going to the client, mark that
 313          * descriptor.
 314          */
 315         if (packet_have_data_to_write())
 316                 FD_SET(connection_out, *writesetp);
 317
 318         /*
 319          * If child has terminated and there is enough buffer space to read
 320          * from it, then read as much as is available and exit.
 321          */
 322         if (child_terminated && packet_not_very_much_data_to_write())
 323                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 324                         max_time_milliseconds = 100;
 325
 326         if (max_time_milliseconds == 0)
 327                 tvp = NULL;
 328         else {
 329                 tv.tv_sec = max_time_milliseconds / 1000;
 330                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 331                 tvp = &tv;
 332         }
 333
 334         /* Wait for something to happen, or the timeout to expire. */
 335         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 336
 337         if (ret == -1) {
 338                 memset(*readsetp, 0, *nallocp);
 339                 memset(*writesetp, 0, *nallocp);
 340                 if (errno != EINTR)
 341                         error("select: %.100s", strerror(errno));
 342         } else if (ret == 0 && client_alive_scheduled)
 343                 client_alive_check();
 344
 345         notify_done(*readsetp);
 346 }
 347
 348 /*
 349  * Processes input from the client and the program.  Input data is stored
 350  * in buffers and processed later.
 351  */
 352 static void
 353 process_input(fd_set * readset)
 354 {
 355         int len;
 356         char buf[16384];
 357
 358         /* Read and buffer any input data from the client. */
 359         if (FD_ISSET(connection_in, readset)) {
 360                 len = read(connection_in, buf, sizeof(buf));
 361                 if (len == 0) {
 362                         verbose("Connection closed by %.100s",
 363                             get_remote_ipaddr());
 364                         connection_closed = 1;
 365                         if (compat20)
 366                                 return;
 367                         cleanup_exit(255);
 368                 } else if (len < 0) {
 369                         if (errno != EINTR && errno != EAGAIN) {
 370                                 verbose("Read error from remote host "
 371                                     "%.100s: %.100s",
 372                                     get_remote_ipaddr(), strerror(errno));
 373                                 cleanup_exit(255);
 374                         }
 375                 } else {
 376                         /* Buffer any received data. */
 377                         packet_process_incoming(buf, len);
 378                 }
 379         }
 380         if (compat20)
 381                 return;
 382
 383         /* Read and buffer any available stdout data from the program. */
 384         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 385                 len = read(fdout, buf, sizeof(buf));
 386                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 387                         /* do nothing */
 388                 } else if (len <= 0) {
 389                         fdout_eof = 1;
 390                 } else {
 391                         buffer_append(&stdout_buffer, buf, len);
 392                         fdout_bytes += len;
 393                 }
 394         }
 395         /* Read and buffer any available stderr data from the program. */
 396         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 397                 len = read(fderr, buf, sizeof(buf));
 398                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 399                         /* do nothing */
 400                 } else if (len <= 0) {
 401                         fderr_eof = 1;
 402                 } else {
 403                         buffer_append(&stderr_buffer, buf, len);
 404                 }
 405         }
 406 }
 407
 408 /*
 409  * Sends data from internal buffers to client program stdin.
 410  */
 411 static void
 412 process_output(fd_set * writeset)
 413 {
 414         struct termios tio;
 415         u_char *data;
 416         u_int dlen;
 417         int len;
 418
 419         /* Write buffered data to program stdin. */
 420         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 421                 data = buffer_ptr(&stdin_buffer);
 422                 dlen = buffer_len(&stdin_buffer);
 423                 len = write(fdin, data, dlen);
 424                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 425                         /* do nothing */
 426                 } else if (len <= 0) {
 427                         if (fdin != fdout)
 428                                 close(fdin);
 429                         else
 430                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 431                         fdin = -1;
 432                 } else {
 433                         /* Successful write. */
 434                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 435                             tcgetattr(fdin, &tio) == 0 &&
 436                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 437                                 /*
 438                                  * Simulate echo to reduce the impact of
 439                                  * traffic analysis
 440                                  */
 441                                 packet_send_ignore(len);
 442                                 packet_send();
 443                         }
 444                         /* Consume the data from the buffer. */
 445                         buffer_consume(&stdin_buffer, len);
 446                         /* Update the count of bytes written to the program. */
 447                         stdin_bytes += len;
 448                 }
 449         }
 450         /* Send any buffered packet data to the client. */
 451         if (FD_ISSET(connection_out, writeset))
 452                 packet_write_poll();
 453 }
 454
 455 /*
 456  * Wait until all buffered output has been sent to the client.
 457  * This is used when the program terminates.
 458  */
 459 static void
 460 drain_output(void)
 461 {
 462         /* Send any buffered stdout data to the client. */
 463         if (buffer_len(&stdout_buffer) > 0) {
 464                 packet_start(SSH_SMSG_STDOUT_DATA);
 465                 packet_put_string(buffer_ptr(&stdout_buffer),
 466                                   buffer_len(&stdout_buffer));
 467                 packet_send();
 468                 /* Update the count of sent bytes. */
 469                 stdout_bytes += buffer_len(&stdout_buffer);
 470         }
 471         /* Send any buffered stderr data to the client. */
 472         if (buffer_len(&stderr_buffer) > 0) {
 473                 packet_start(SSH_SMSG_STDERR_DATA);
 474                 packet_put_string(buffer_ptr(&stderr_buffer),
 475                                   buffer_len(&stderr_buffer));
 476                 packet_send();
 477                 /* Update the count of sent bytes. */
 478                 stderr_bytes += buffer_len(&stderr_buffer);
 479         }
 480         /* Wait until all buffered data has been written to the client. */
 481         packet_write_wait();
 482 }
 483
 484 static void
 485 process_buffered_input_packets(void)
 486 {
 487         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 488 }
 489
 490 /*
 491  * Performs the interactive session.  This handles data transmission between
 492  * the client and the program.  Note that the notion of stdin, stdout, and
 493  * stderr in this function is sort of reversed: this function writes to
 494  * stdin (of the child program), and reads from stdout and stderr (of the
 495  * child program).
 496  */
 497 void
 498 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 499 {
 500         fd_set *readset = NULL, *writeset = NULL;
 501         int max_fd = 0;
 502         u_int nalloc = 0;
 503         int wait_status;        /* Status returned by wait(). */
 504         pid_t wait_pid;         /* pid returned by wait(). */
 505         int waiting_termination = 0;    /* Have displayed waiting close message. */
 506         u_int max_time_milliseconds;
 507         u_int previous_stdout_buffer_bytes;
 508         u_int stdout_buffer_bytes;
 509         int type;
 510
 511         debug("Entering interactive session.");
 512
 513         /* Initialize the SIGCHLD kludge. */
 514         child_terminated = 0;
 515         mysignal(SIGCHLD, sigchld_handler);
 516
 517         if (!use_privsep) {
 518                 signal(SIGTERM, sigterm_handler);
 519                 signal(SIGINT, sigterm_handler);
 520                 signal(SIGQUIT, sigterm_handler);
 521         }
 522
 523         /* Initialize our global variables. */
 524         fdin = fdin_arg;
 525         fdout = fdout_arg;
 526         fderr = fderr_arg;
 527
 528         /* nonblocking IO */
 529         set_nonblock(fdin);
 530         set_nonblock(fdout);
 531         /* we don't have stderr for interactive terminal sessions, see below */
 532         if (fderr != -1)
 533                 set_nonblock(fderr);
 534
 535         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 536                 fdin_is_tty = 1;
 537
 538         connection_in = packet_get_connection_in();
 539         connection_out = packet_get_connection_out();
 540
 541         notify_setup();
 542
 543         previous_stdout_buffer_bytes = 0;
 544
 545         /* Set approximate I/O buffer size. */
 546         if (packet_is_interactive())
 547                 buffer_high = 4096;
 548         else
 549                 buffer_high = 64 * 1024;
 550
 551 #if 0
 552         /* Initialize max_fd to the maximum of the known file descriptors. */
 553         max_fd = MAX(connection_in, connection_out);
 554         max_fd = MAX(max_fd, fdin);
 555         max_fd = MAX(max_fd, fdout);
 556         if (fderr != -1)
 557                 max_fd = MAX(max_fd, fderr);
 558 #endif
 559
 560         /* Initialize Initialize buffers. */
 561         buffer_init(&stdin_buffer);
 562         buffer_init(&stdout_buffer);
 563         buffer_init(&stderr_buffer);
 564
 565         /*
 566          * If we have no separate fderr (which is the case when we have a pty
 567          * - there we cannot make difference between data sent to stdout and
 568          * stderr), indicate that we have seen an EOF from stderr.  This way
 569          * we don't need to check the descriptor everywhere.
 570          */
 571         if (fderr == -1)
 572                 fderr_eof = 1;
 573
 574         server_init_dispatch();
 575
 576         /* Main loop of the server for the interactive session mode. */
 577         for (;;) {
 578
 579                 /* Process buffered packets from the client. */
 580                 process_buffered_input_packets();
 581
 582                 /*
 583                  * If we have received eof, and there is no more pending
 584                  * input data, cause a real eof by closing fdin.
 585                  */
 586                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 587                         if (fdin != fdout)
 588                                 close(fdin);
 589                         else
 590                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 591                         fdin = -1;
 592                 }
 593                 /* Make packets from buffered stderr data to send to the client. */
 594                 make_packets_from_stderr_data();
 595
 596                 /*
 597                  * Make packets from buffered stdout data to send to the
 598                  * client. If there is very little to send, this arranges to
 599                  * not send them now, but to wait a short while to see if we
 600                  * are getting more data. This is necessary, as some systems
 601                  * wake up readers from a pty after each separate character.
 602                  */
 603                 max_time_milliseconds = 0;
 604                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 605                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 606                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 607                         /* try again after a while */
 608                         max_time_milliseconds = 10;
 609                 } else {
 610                         /* Send it now. */
 611                         make_packets_from_stdout_data();
 612                 }
 613                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 614
 615                 /* Send channel data to the client. */
 616                 if (packet_not_very_much_data_to_write())
 617                         channel_output_poll();
 618
 619                 /*
 620                  * Bail out of the loop if the program has closed its output
 621                  * descriptors, and we have no more data to send to the
 622                  * client, and there is no pending buffered data.
 623                  */
 624                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 625                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 626                         if (!channel_still_open())
 627                                 break;
 628                         if (!waiting_termination) {
 629                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 630                                 char *cp;
 631                                 waiting_termination = 1;
 632                                 buffer_append(&stderr_buffer, s, strlen(s));
 633
 634                                 /* Display list of open channels. */
 635                                 cp = channel_open_message();
 636                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 637                                 xfree(cp);
 638                         }
 639                 }
 640                 max_fd = MAX(connection_in, connection_out);
 641                 max_fd = MAX(max_fd, fdin);
 642                 max_fd = MAX(max_fd, fdout);
 643                 max_fd = MAX(max_fd, fderr);
 644                 max_fd = MAX(max_fd, notify_pipe[0]);
 645
 646                 /* Sleep in select() until we can do something. */
 647                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 648                     &nalloc, max_time_milliseconds);
 649
 650                 if (received_sigterm) {
 651                         logit("Exiting on signal %d", received_sigterm);
 652                         /* Clean up sessions, utmp, etc. */
 653                         cleanup_exit(255);
 654                 }
 655
 656                 /* Process any channel events. */
 657                 channel_after_select(readset, writeset);
 658
 659                 /* Process input from the client and from program stdout/stderr. */
 660                 process_input(readset);
 661
 662                 /* Process output to the client and to program stdin. */
 663                 process_output(writeset);
 664         }
 665         if (readset)
 666                 xfree(readset);
 667         if (writeset)
 668                 xfree(writeset);
 669
 670         /* Cleanup and termination code. */
 671
 672         /* Wait until all output has been sent to the client. */
 673         drain_output();
 674
 675         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 676             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 677
 678         /* Free and clear the buffers. */
 679         buffer_free(&stdin_buffer);
 680         buffer_free(&stdout_buffer);
 681         buffer_free(&stderr_buffer);
 682
 683         /* Close the file descriptors. */
 684         if (fdout != -1)
 685                 close(fdout);
 686         fdout = -1;
 687         fdout_eof = 1;
 688         if (fderr != -1)
 689                 close(fderr);
 690         fderr = -1;
 691         fderr_eof = 1;
 692         if (fdin != -1)
 693                 close(fdin);
 694         fdin = -1;
 695
 696         channel_free_all();
 697
 698         /* We no longer want our SIGCHLD handler to be called. */
 699         mysignal(SIGCHLD, SIG_DFL);
 700
 701         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 702                 if (errno != EINTR)
 703                         packet_disconnect("wait: %.100s", strerror(errno));
 704         if (wait_pid != pid)
 705                 error("Strange, wait returned pid %ld, expected %ld",
 706                     (long)wait_pid, (long)pid);
 707
 708         /* Check if it exited normally. */
 709         if (WIFEXITED(wait_status)) {
 710                 /* Yes, normal exit.  Get exit status and send it to the client. */
 711                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 712                 packet_start(SSH_SMSG_EXITSTATUS);
 713                 packet_put_int(WEXITSTATUS(wait_status));
 714                 packet_send();
 715                 packet_write_wait();
 716
 717                 /*
 718                  * Wait for exit confirmation.  Note that there might be
 719                  * other packets coming before it; however, the program has
 720                  * already died so we just ignore them.  The client is
 721                  * supposed to respond with the confirmation when it receives
 722                  * the exit status.
 723                  */
 724                 do {
 725                         type = packet_read();
 726                 }
 727                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 728
 729                 debug("Received exit confirmation.");
 730                 return;
 731         }
 732         /* Check if the program terminated due to a signal. */
 733         if (WIFSIGNALED(wait_status))
 734                 packet_disconnect("Command terminated on signal %d.",
 735                                   WTERMSIG(wait_status));
 736
 737         /* Some weird exit cause.  Just exit. */
 738         packet_disconnect("wait returned status %04x.", wait_status);
 739         /* NOTREACHED */
 740 }
 741
 742 static void
 743 collect_children(void)
 744 {
 745         pid_t pid;
 746         sigset_t oset, nset;
 747         int status;
 748
 749         /* block SIGCHLD while we check for dead children */
 750         sigemptyset(&nset);
 751         sigaddset(&nset, SIGCHLD);
 752         sigprocmask(SIG_BLOCK, &nset, &oset);
 753         if (child_terminated) {
 754                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 755                     (pid < 0 && errno == EINTR))
 756                         if (pid > 0)
 757                                 session_close_by_pid(pid, status);
 758                 child_terminated = 0;
 759         }
 760         sigprocmask(SIG_SETMASK, &oset, NULL);
 761 }
 762
 763 void
 764 server_loop2(Authctxt *authctxt)
 765 {
 766         fd_set *readset = NULL, *writeset = NULL;
 767         int rekeying = 0, max_fd, nalloc = 0;
 768
 769         debug("Entering interactive session for SSH2.");
 770
 771         mysignal(SIGCHLD, sigchld_handler);
 772         child_terminated = 0;
 773         connection_in = packet_get_connection_in();
 774         connection_out = packet_get_connection_out();
 775
 776         if (!use_privsep) {
 777                 signal(SIGTERM, sigterm_handler);
 778                 signal(SIGINT, sigterm_handler);
 779                 signal(SIGQUIT, sigterm_handler);
 780         }
 781
 782         notify_setup();
 783
 784         max_fd = MAX(connection_in, connection_out);
 785         max_fd = MAX(max_fd, notify_pipe[0]);
 786
 787         server_init_dispatch();
 788
 789         for (;;) {
 790                 process_buffered_input_packets();
 791
 792                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 793
 794                 if (!rekeying && packet_not_very_much_data_to_write())
 795                         channel_output_poll();
 796                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 797                     &nalloc, 0);
 798
 799                 if (received_sigterm) {
 800                         logit("Exiting on signal %d", received_sigterm);
 801                         /* Clean up sessions, utmp, etc. */
 802                         cleanup_exit(255);
 803                 }
 804
 805                 collect_children();
 806                 if (!rekeying) {
 807                         channel_after_select(readset, writeset);
 808                         if (packet_need_rekeying()) {
 809                                 debug("need rekeying");
 810                                 xxx_kex->done = 0;
 811                                 kex_send_kexinit(xxx_kex);
 812                         }
 813                 }
 814                 process_input(readset);
 815                 if (connection_closed)
 816                         break;
 817                 process_output(writeset);
 818         }
 819         collect_children();
 820
 821         if (readset)
 822                 xfree(readset);
 823         if (writeset)
 824                 xfree(writeset);
 825
 826         /* free all channels, no more reads and writes */
 827         channel_free_all();
 828
 829         /* free remaining sessions, e.g. remove wtmp entries */
 830         session_destroy_all(NULL);
 831 }
 832
 833 static void
 834 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 835 {
 836         debug("Got %d/%u for keepalive", type, seq);
 837         /*
 838          * reset timeout, since we got a sane answer from the client.
 839          * even if this was generated by something other than
 840          * the bogus CHANNEL_REQUEST we send for keepalives.
 841          */
 842         client_alive_timeouts = 0;
 843 }
 844
 845 static void
 846 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 847 {
 848         char *data;
 849         u_int data_len;
 850
 851         /* Stdin data from the client.  Append it to the buffer. */
 852         /* Ignore any data if the client has closed stdin. */
 853         if (fdin == -1)
 854                 return;
 855         data = packet_get_string(&data_len);
 856         packet_check_eom();
 857         buffer_append(&stdin_buffer, data, data_len);
 858         memset(data, 0, data_len);
 859         xfree(data);
 860 }
 861
 862 static void
 863 server_input_eof(int type, u_int32_t seq, void *ctxt)
 864 {
 865         /*
 866          * Eof from the client.  The stdin descriptor to the
 867          * program will be closed when all buffered data has
 868          * drained.
 869          */
 870         debug("EOF received for stdin.");
 871         packet_check_eom();
 872         stdin_eof = 1;
 873 }
 874
 875 static void
 876 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 877 {
 878         int row = packet_get_int();
 879         int col = packet_get_int();
 880         int xpixel = packet_get_int();
 881         int ypixel = packet_get_int();
 882
 883         debug("Window change received.");
 884         packet_check_eom();
 885         if (fdin != -1)
 886                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 887 }
 888
 889 static Channel *
 890 server_request_direct_tcpip(void)
 891 {
 892         Channel *c;
 893         int sock;
 894         char *target, *originator;
 895         int target_port, originator_port;
 896
 897         target = packet_get_string(NULL);
 898         target_port = packet_get_int();
 899         originator = packet_get_string(NULL);
 900         originator_port = packet_get_int();
 901         packet_check_eom();
 902
 903         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 904             originator, originator_port, target, target_port);
 905
 906         /* XXX check permission */
 907         sock = channel_connect_to(target, target_port);
 908         xfree(target);
 909         xfree(originator);
 910         if (sock < 0)
 911                 return NULL;
 912         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 913             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 914             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 915         return c;
 916 }
 917
 918 static Channel *
 919 server_request_tun(void)
 920 {
 921         Channel *c = NULL;
 922         int mode, tun;
 923         int sock;
 924
 925         mode = packet_get_int();
 926         switch (mode) {
 927         case SSH_TUNMODE_POINTOPOINT:
 928         case SSH_TUNMODE_ETHERNET:
 929                 break;
 930         default:
 931                 packet_send_debug("Unsupported tunnel device mode.");
 932                 return NULL;
 933         }
 934         if ((options.permit_tun & mode) == 0) {
 935                 packet_send_debug("Server has rejected tunnel device "
 936                     "forwarding");
 937                 return NULL;
 938         }
 939
 940         tun = packet_get_int();
 941         if (forced_tun_device != -1) {
 942                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 943                         goto done;
 944                 tun = forced_tun_device;
 945         }
 946         sock = tun_open(tun, mode);
 947         if (sock < 0)
 948                 goto done;
 949         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 950             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 951         c->datagram = 1;
 952 #if defined(SSH_TUN_FILTER)
 953         if (mode == SSH_TUNMODE_POINTOPOINT)
 954                 channel_register_filter(c->self, sys_tun_infilter,
 955                     sys_tun_outfilter);
 956 #endif
 957
 958  done:
 959         if (c == NULL)
 960                 packet_send_debug("Failed to open the tunnel device.");
 961         return c;
 962 }
 963
 964 static Channel *
 965 server_request_session(void)
 966 {
 967         Channel *c;
 968
 969         debug("input_session_request");
 970         packet_check_eom();
 971         /*
 972          * A server session has no fd to read or write until a
 973          * CHANNEL_REQUEST for a shell is made, so we set the type to
 974          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 975          * CHANNEL_REQUEST messages is registered.
 976          */
 977         c = channel_new("session", SSH_CHANNEL_LARVAL,
 978             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 979             0, "server-session", 1);
 980         if (session_open(the_authctxt, c->self) != 1) {
 981                 debug("session open failed, free channel %d", c->self);
 982                 channel_free(c);
 983                 return NULL;
 984         }
 985         channel_register_cleanup(c->self, session_close_by_channel, 0);
 986         return c;
 987 }
 988
 989 static void
 990 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 991 {
 992         Channel *c = NULL;
 993         char *ctype;
 994         int rchan;
 995         u_int rmaxpack, rwindow, len;
 996
 997         ctype = packet_get_string(&len);
 998         rchan = packet_get_int();
 999         rwindow = packet_get_int();
1000         rmaxpack = packet_get_int();
1001
1002         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1003             ctype, rchan, rwindow, rmaxpack);
1004
1005         if (strcmp(ctype, "session") == 0) {
1006                 c = server_request_session();
1007         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1008                 c = server_request_direct_tcpip();
1009         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1010                 c = server_request_tun();
1011         }
1012         if (c != NULL) {
1013                 debug("server_input_channel_open: confirm %s", ctype);
1014                 c->remote_id = rchan;
1015                 c->remote_window = rwindow;
1016                 c->remote_maxpacket = rmaxpack;
1017                 if (c->type != SSH_CHANNEL_CONNECTING) {
1018                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1019                         packet_put_int(c->remote_id);
1020                         packet_put_int(c->self);
1021                         packet_put_int(c->local_window);
1022                         packet_put_int(c->local_maxpacket);
1023                         packet_send();
1024                 }
1025         } else {
1026                 debug("server_input_channel_open: failure %s", ctype);
1027                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1028                 packet_put_int(rchan);
1029                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1030                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1031                         packet_put_cstring("open failed");
1032                         packet_put_cstring("");
1033                 }
1034                 packet_send();
1035         }
1036         xfree(ctype);
1037 }
1038
1039 static void
1040 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1041 {
1042         char *rtype;
1043         int want_reply;
1044         int success = 0;
1045
1046         rtype = packet_get_string(NULL);
1047         want_reply = packet_get_char();
1048         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1049
1050         /* -R style forwarding */
1051         if (strcmp(rtype, "tcpip-forward") == 0) {
1052                 struct passwd *pw;
1053                 char *listen_address;
1054                 u_short listen_port;
1055
1056                 pw = the_authctxt->pw;
1057                 if (pw == NULL || !the_authctxt->valid)
1058                         fatal("server_input_global_request: no/invalid user");
1059                 listen_address = packet_get_string(NULL);
1060                 listen_port = (u_short)packet_get_int();
1061                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1062                     listen_address, listen_port);
1063
1064                 /* check permissions */
1065                 if (!options.allow_tcp_forwarding ||
1066                     no_port_forwarding_flag
1067 #ifndef NO_IPPORT_RESERVED_CONCEPT
1068                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1069 #endif
1070                     ) {
1071                         success = 0;
1072                         packet_send_debug("Server has disabled port forwarding.");
1073                 } else {
1074                         /* Start listening on the port */
1075                         success = channel_setup_remote_fwd_listener(
1076                             listen_address, listen_port, options.gateway_ports);
1077                 }
1078                 xfree(listen_address);
1079         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1080                 char *cancel_address;
1081                 u_short cancel_port;
1082
1083                 cancel_address = packet_get_string(NULL);
1084                 cancel_port = (u_short)packet_get_int();
1085                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1086                     cancel_address, cancel_port);
1087
1088                 success = channel_cancel_rport_listener(cancel_address,
1089                     cancel_port);
1090         }
1091         if (want_reply) {
1092                 packet_start(success ?
1093                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1094                 packet_send();
1095                 packet_write_wait();
1096         }
1097         xfree(rtype);
1098 }
1099 static void
1100 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1101 {
1102         Channel *c;
1103         int id, reply, success = 0;
1104         char *rtype;
1105
1106         id = packet_get_int();
1107         rtype = packet_get_string(NULL);
1108         reply = packet_get_char();
1109
1110         debug("server_input_channel_req: channel %d request %s reply %d",
1111             id, rtype, reply);
1112
1113         if ((c = channel_lookup(id)) == NULL)
1114                 packet_disconnect("server_input_channel_req: "
1115                     "unknown channel %d", id);
1116         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1117                 success = session_input_channel_req(c, rtype);
1118         if (reply) {
1119                 packet_start(success ?
1120                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1121                 packet_put_int(c->remote_id);
1122                 packet_send();
1123         }
1124         xfree(rtype);
1125 }
1126
1127 static void
1128 server_init_dispatch_20(void)
1129 {
1130         debug("server_init_dispatch_20");
1131         dispatch_init(&dispatch_protocol_error);
1132         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1133         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1134         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1135         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1136         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1137         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1138         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1139         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1140         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1141         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1142         /* client_alive */
1143         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1144         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1145         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1146         /* rekeying */
1147         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1148 }
1149 static void
1150 server_init_dispatch_13(void)
1151 {
1152         debug("server_init_dispatch_13");
1153         dispatch_init(NULL);
1154         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1155         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1156         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1157         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1158         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1159         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1160         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1161         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1162         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1163 }
1164 static void
1165 server_init_dispatch_15(void)
1166 {
1167         server_init_dispatch_13();
1168         debug("server_init_dispatch_15");
1169         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1170         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1171 }
1172 static void
1173 server_init_dispatch(void)
1174 {
1175         if (compat20)
1176                 server_init_dispatch_20();
1177         else if (compat13)
1178                 server_init_dispatch_13();
1179         else
1180                 server_init_dispatch_15();
1181 }