serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.135 2006/03/25 18:30:55 deraadt Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42
  43 #include <signal.h>
  44 #include <termios.h>
  45
  46 #include "xmalloc.h"
  47 #include "packet.h"
  48 #include "buffer.h"
  49 #include "log.h"
  50 #include "servconf.h"
  51 #include "canohost.h"
  52 #include "sshpty.h"
  53 #include "channels.h"
  54 #include "compat.h"
  55 #include "ssh1.h"
  56 #include "ssh2.h"
  57 #include "auth.h"
  58 #include "session.h"
  59 #include "dispatch.h"
  60 #include "auth-options.h"
  61 #include "serverloop.h"
  62 #include "misc.h"
  63 #include "kex.h"
  64
  65 extern ServerOptions options;
  66
  67 /* XXX */
  68 extern Kex *xxx_kex;
  69 extern Authctxt *the_authctxt;
  70 extern int use_privsep;
  71
  72 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  73 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  74 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  75 static int fdin;                /* Descriptor for stdin (for writing) */
  76 static int fdout;               /* Descriptor for stdout (for reading);
  77                                    May be same number as fdin. */
  78 static int fderr;               /* Descriptor for stderr.  May be -1. */
  79 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  80 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  81 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  82 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  83 static int stdin_eof = 0;       /* EOF message received from client. */
  84 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  85 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  86 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  87 static int connection_in;       /* Connection to client (input). */
  88 static int connection_out;      /* Connection to client (output). */
  89 static int connection_closed = 0;       /* Connection to client closed. */
  90 static u_int buffer_high;       /* "Soft" max buffer size. */
  91 static int client_alive_timeouts = 0;
  92
  93 /*
  94  * This SIGCHLD kludge is used to detect when the child exits.  The server
  95  * will exit after that, as soon as forwarded connections have terminated.
  96  */
  97
  98 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  99
 100 /* Cleanup on signals (!use_privsep case only) */
 101 static volatile sig_atomic_t received_sigterm = 0;
 102
 103 /* prototypes */
 104 static void server_init_dispatch(void);
 105
 106 /*
 107  * we write to this pipe if a SIGCHLD is caught in order to avoid
 108  * the race between select() and child_terminated
 109  */
 110 static int notify_pipe[2];
 111 static void
 112 notify_setup(void)
 113 {
 114         if (pipe(notify_pipe) < 0) {
 115                 error("pipe(notify_pipe) failed %s", strerror(errno));
 116         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 117             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 118                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 119                 close(notify_pipe[0]);
 120                 close(notify_pipe[1]);
 121         } else {
 122                 set_nonblock(notify_pipe[0]);
 123                 set_nonblock(notify_pipe[1]);
 124                 return;
 125         }
 126         notify_pipe[0] = -1;    /* read end */
 127         notify_pipe[1] = -1;    /* write end */
 128 }
 129 static void
 130 notify_parent(void)
 131 {
 132         if (notify_pipe[1] != -1)
 133                 write(notify_pipe[1], "", 1);
 134 }
 135 static void
 136 notify_prepare(fd_set *readset)
 137 {
 138         if (notify_pipe[0] != -1)
 139                 FD_SET(notify_pipe[0], readset);
 140 }
 141 static void
 142 notify_done(fd_set *readset)
 143 {
 144         char c;
 145
 146         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 147                 while (read(notify_pipe[0], &c, 1) != -1)
 148                         debug2("notify_done: reading");
 149 }
 150
 151 /*ARGSUSED*/
 152 static void
 153 sigchld_handler(int sig)
 154 {
 155         int save_errno = errno;
 156         child_terminated = 1;
 157 #ifndef _UNICOS
 158         mysignal(SIGCHLD, sigchld_handler);
 159 #endif
 160         notify_parent();
 161         errno = save_errno;
 162 }
 163
 164 /*ARGSUSED*/
 165 static void
 166 sigterm_handler(int sig)
 167 {
 168         received_sigterm = sig;
 169 }
 170
 171 /*
 172  * Make packets from buffered stderr data, and buffer it for sending
 173  * to the client.
 174  */
 175 static void
 176 make_packets_from_stderr_data(void)
 177 {
 178         u_int len;
 179
 180         /* Send buffered stderr data to the client. */
 181         while (buffer_len(&stderr_buffer) > 0 &&
 182             packet_not_very_much_data_to_write()) {
 183                 len = buffer_len(&stderr_buffer);
 184                 if (packet_is_interactive()) {
 185                         if (len > 512)
 186                                 len = 512;
 187                 } else {
 188                         /* Keep the packets at reasonable size. */
 189                         if (len > packet_get_maxsize())
 190                                 len = packet_get_maxsize();
 191                 }
 192                 packet_start(SSH_SMSG_STDERR_DATA);
 193                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 194                 packet_send();
 195                 buffer_consume(&stderr_buffer, len);
 196                 stderr_bytes += len;
 197         }
 198 }
 199
 200 /*
 201  * Make packets from buffered stdout data, and buffer it for sending to the
 202  * client.
 203  */
 204 static void
 205 make_packets_from_stdout_data(void)
 206 {
 207         u_int len;
 208
 209         /* Send buffered stdout data to the client. */
 210         while (buffer_len(&stdout_buffer) > 0 &&
 211             packet_not_very_much_data_to_write()) {
 212                 len = buffer_len(&stdout_buffer);
 213                 if (packet_is_interactive()) {
 214                         if (len > 512)
 215                                 len = 512;
 216                 } else {
 217                         /* Keep the packets at reasonable size. */
 218                         if (len > packet_get_maxsize())
 219                                 len = packet_get_maxsize();
 220                 }
 221                 packet_start(SSH_SMSG_STDOUT_DATA);
 222                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 223                 packet_send();
 224                 buffer_consume(&stdout_buffer, len);
 225                 stdout_bytes += len;
 226         }
 227 }
 228
 229 static void
 230 client_alive_check(void)
 231 {
 232         int channel_id;
 233
 234         /* timeout, check to see how many we have had */
 235         if (++client_alive_timeouts > options.client_alive_count_max)
 236                 packet_disconnect("Timeout, your session not responding.");
 237
 238         /*
 239          * send a bogus global/channel request with "wantreply",
 240          * we should get back a failure
 241          */
 242         if ((channel_id = channel_find_open()) == -1) {
 243                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 244                 packet_put_cstring("keepalive@openssh.com");
 245                 packet_put_char(1);     /* boolean: want reply */
 246         } else {
 247                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 248         }
 249         packet_send();
 250 }
 251
 252 /*
 253  * Sleep in select() until we can do something.  This will initialize the
 254  * select masks.  Upon return, the masks will indicate which descriptors
 255  * have data or can accept data.  Optionally, a maximum time can be specified
 256  * for the duration of the wait (0 = infinite).
 257  */
 258 static void
 259 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 260     u_int *nallocp, u_int max_time_milliseconds)
 261 {
 262         struct timeval tv, *tvp;
 263         int ret;
 264         int client_alive_scheduled = 0;
 265
 266         /*
 267          * if using client_alive, set the max timeout accordingly,
 268          * and indicate that this particular timeout was for client
 269          * alive by setting the client_alive_scheduled flag.
 270          *
 271          * this could be randomized somewhat to make traffic
 272          * analysis more difficult, but we're not doing it yet.
 273          */
 274         if (compat20 &&
 275             max_time_milliseconds == 0 && options.client_alive_interval) {
 276                 client_alive_scheduled = 1;
 277                 max_time_milliseconds = options.client_alive_interval * 1000;
 278         }
 279
 280         /* Allocate and update select() masks for channel descriptors. */
 281         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 282
 283         if (compat20) {
 284 #if 0
 285                 /* wrong: bad condition XXX */
 286                 if (channel_not_very_much_buffered_data())
 287 #endif
 288                 FD_SET(connection_in, *readsetp);
 289         } else {
 290                 /*
 291                  * Read packets from the client unless we have too much
 292                  * buffered stdin or channel data.
 293                  */
 294                 if (buffer_len(&stdin_buffer) < buffer_high &&
 295                     channel_not_very_much_buffered_data())
 296                         FD_SET(connection_in, *readsetp);
 297                 /*
 298                  * If there is not too much data already buffered going to
 299                  * the client, try to get some more data from the program.
 300                  */
 301                 if (packet_not_very_much_data_to_write()) {
 302                         if (!fdout_eof)
 303                                 FD_SET(fdout, *readsetp);
 304                         if (!fderr_eof)
 305                                 FD_SET(fderr, *readsetp);
 306                 }
 307                 /*
 308                  * If we have buffered data, try to write some of that data
 309                  * to the program.
 310                  */
 311                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 312                         FD_SET(fdin, *writesetp);
 313         }
 314         notify_prepare(*readsetp);
 315
 316         /*
 317          * If we have buffered packet data going to the client, mark that
 318          * descriptor.
 319          */
 320         if (packet_have_data_to_write())
 321                 FD_SET(connection_out, *writesetp);
 322
 323         /*
 324          * If child has terminated and there is enough buffer space to read
 325          * from it, then read as much as is available and exit.
 326          */
 327         if (child_terminated && packet_not_very_much_data_to_write())
 328                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 329                         max_time_milliseconds = 100;
 330
 331         if (max_time_milliseconds == 0)
 332                 tvp = NULL;
 333         else {
 334                 tv.tv_sec = max_time_milliseconds / 1000;
 335                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 336                 tvp = &tv;
 337         }
 338
 339         /* Wait for something to happen, or the timeout to expire. */
 340         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 341
 342         if (ret == -1) {
 343                 memset(*readsetp, 0, *nallocp);
 344                 memset(*writesetp, 0, *nallocp);
 345                 if (errno != EINTR)
 346                         error("select: %.100s", strerror(errno));
 347         } else if (ret == 0 && client_alive_scheduled)
 348                 client_alive_check();
 349
 350         notify_done(*readsetp);
 351 }
 352
 353 /*
 354  * Processes input from the client and the program.  Input data is stored
 355  * in buffers and processed later.
 356  */
 357 static void
 358 process_input(fd_set *readset)
 359 {
 360         int len;
 361         char buf[16384];
 362
 363         /* Read and buffer any input data from the client. */
 364         if (FD_ISSET(connection_in, readset)) {
 365                 len = read(connection_in, buf, sizeof(buf));
 366                 if (len == 0) {
 367                         verbose("Connection closed by %.100s",
 368                             get_remote_ipaddr());
 369                         connection_closed = 1;
 370                         if (compat20)
 371                                 return;
 372                         cleanup_exit(255);
 373                 } else if (len < 0) {
 374                         if (errno != EINTR && errno != EAGAIN) {
 375                                 verbose("Read error from remote host "
 376                                     "%.100s: %.100s",
 377                                     get_remote_ipaddr(), strerror(errno));
 378                                 cleanup_exit(255);
 379                         }
 380                 } else {
 381                         /* Buffer any received data. */
 382                         packet_process_incoming(buf, len);
 383                 }
 384         }
 385         if (compat20)
 386                 return;
 387
 388         /* Read and buffer any available stdout data from the program. */
 389         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 390                 errno = 0;
 391                 len = read(fdout, buf, sizeof(buf));
 392                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 393                         /* do nothing */
 394 #ifndef PTY_ZEROREAD
 395                 } else if (len <= 0) {
 396 #else
 397                 } else if ((!isatty(fdout) && len <= 0) ||
 398                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 399 #endif
 400                         fdout_eof = 1;
 401                 } else {
 402                         buffer_append(&stdout_buffer, buf, len);
 403                         fdout_bytes += len;
 404                 }
 405         }
 406         /* Read and buffer any available stderr data from the program. */
 407         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 408                 errno = 0;
 409                 len = read(fderr, buf, sizeof(buf));
 410                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 411                         /* do nothing */
 412 #ifndef PTY_ZEROREAD
 413                 } else if (len <= 0) {
 414 #else
 415                 } else if ((!isatty(fderr) && len <= 0) ||
 416                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 417 #endif
 418                         fderr_eof = 1;
 419                 } else {
 420                         buffer_append(&stderr_buffer, buf, len);
 421                 }
 422         }
 423 }
 424
 425 /*
 426  * Sends data from internal buffers to client program stdin.
 427  */
 428 static void
 429 process_output(fd_set *writeset)
 430 {
 431         struct termios tio;
 432         u_char *data;
 433         u_int dlen;
 434         int len;
 435
 436         /* Write buffered data to program stdin. */
 437         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 438                 data = buffer_ptr(&stdin_buffer);
 439                 dlen = buffer_len(&stdin_buffer);
 440                 len = write(fdin, data, dlen);
 441                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 442                         /* do nothing */
 443                 } else if (len <= 0) {
 444                         if (fdin != fdout)
 445                                 close(fdin);
 446                         else
 447                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 448                         fdin = -1;
 449                 } else {
 450                         /* Successful write. */
 451                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 452                             tcgetattr(fdin, &tio) == 0 &&
 453                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 454                                 /*
 455                                  * Simulate echo to reduce the impact of
 456                                  * traffic analysis
 457                                  */
 458                                 packet_send_ignore(len);
 459                                 packet_send();
 460                         }
 461                         /* Consume the data from the buffer. */
 462                         buffer_consume(&stdin_buffer, len);
 463                         /* Update the count of bytes written to the program. */
 464                         stdin_bytes += len;
 465                 }
 466         }
 467         /* Send any buffered packet data to the client. */
 468         if (FD_ISSET(connection_out, writeset))
 469                 packet_write_poll();
 470 }
 471
 472 /*
 473  * Wait until all buffered output has been sent to the client.
 474  * This is used when the program terminates.
 475  */
 476 static void
 477 drain_output(void)
 478 {
 479         /* Send any buffered stdout data to the client. */
 480         if (buffer_len(&stdout_buffer) > 0) {
 481                 packet_start(SSH_SMSG_STDOUT_DATA);
 482                 packet_put_string(buffer_ptr(&stdout_buffer),
 483                                   buffer_len(&stdout_buffer));
 484                 packet_send();
 485                 /* Update the count of sent bytes. */
 486                 stdout_bytes += buffer_len(&stdout_buffer);
 487         }
 488         /* Send any buffered stderr data to the client. */
 489         if (buffer_len(&stderr_buffer) > 0) {
 490                 packet_start(SSH_SMSG_STDERR_DATA);
 491                 packet_put_string(buffer_ptr(&stderr_buffer),
 492                                   buffer_len(&stderr_buffer));
 493                 packet_send();
 494                 /* Update the count of sent bytes. */
 495                 stderr_bytes += buffer_len(&stderr_buffer);
 496         }
 497         /* Wait until all buffered data has been written to the client. */
 498         packet_write_wait();
 499 }
 500
 501 static void
 502 process_buffered_input_packets(void)
 503 {
 504         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 505 }
 506
 507 /*
 508  * Performs the interactive session.  This handles data transmission between
 509  * the client and the program.  Note that the notion of stdin, stdout, and
 510  * stderr in this function is sort of reversed: this function writes to
 511  * stdin (of the child program), and reads from stdout and stderr (of the
 512  * child program).
 513  */
 514 void
 515 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 516 {
 517         fd_set *readset = NULL, *writeset = NULL;
 518         int max_fd = 0;
 519         u_int nalloc = 0;
 520         int wait_status;        /* Status returned by wait(). */
 521         pid_t wait_pid;         /* pid returned by wait(). */
 522         int waiting_termination = 0;    /* Have displayed waiting close message. */
 523         u_int max_time_milliseconds;
 524         u_int previous_stdout_buffer_bytes;
 525         u_int stdout_buffer_bytes;
 526         int type;
 527
 528         debug("Entering interactive session.");
 529
 530         /* Initialize the SIGCHLD kludge. */
 531         child_terminated = 0;
 532         mysignal(SIGCHLD, sigchld_handler);
 533
 534         if (!use_privsep) {
 535                 signal(SIGTERM, sigterm_handler);
 536                 signal(SIGINT, sigterm_handler);
 537                 signal(SIGQUIT, sigterm_handler);
 538         }
 539
 540         /* Initialize our global variables. */
 541         fdin = fdin_arg;
 542         fdout = fdout_arg;
 543         fderr = fderr_arg;
 544
 545         /* nonblocking IO */
 546         set_nonblock(fdin);
 547         set_nonblock(fdout);
 548         /* we don't have stderr for interactive terminal sessions, see below */
 549         if (fderr != -1)
 550                 set_nonblock(fderr);
 551
 552         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 553                 fdin_is_tty = 1;
 554
 555         connection_in = packet_get_connection_in();
 556         connection_out = packet_get_connection_out();
 557
 558         notify_setup();
 559
 560         previous_stdout_buffer_bytes = 0;
 561
 562         /* Set approximate I/O buffer size. */
 563         if (packet_is_interactive())
 564                 buffer_high = 4096;
 565         else
 566                 buffer_high = 64 * 1024;
 567
 568 #if 0
 569         /* Initialize max_fd to the maximum of the known file descriptors. */
 570         max_fd = MAX(connection_in, connection_out);
 571         max_fd = MAX(max_fd, fdin);
 572         max_fd = MAX(max_fd, fdout);
 573         if (fderr != -1)
 574                 max_fd = MAX(max_fd, fderr);
 575 #endif
 576
 577         /* Initialize Initialize buffers. */
 578         buffer_init(&stdin_buffer);
 579         buffer_init(&stdout_buffer);
 580         buffer_init(&stderr_buffer);
 581
 582         /*
 583          * If we have no separate fderr (which is the case when we have a pty
 584          * - there we cannot make difference between data sent to stdout and
 585          * stderr), indicate that we have seen an EOF from stderr.  This way
 586          * we don't need to check the descriptor everywhere.
 587          */
 588         if (fderr == -1)
 589                 fderr_eof = 1;
 590
 591         server_init_dispatch();
 592
 593         /* Main loop of the server for the interactive session mode. */
 594         for (;;) {
 595
 596                 /* Process buffered packets from the client. */
 597                 process_buffered_input_packets();
 598
 599                 /*
 600                  * If we have received eof, and there is no more pending
 601                  * input data, cause a real eof by closing fdin.
 602                  */
 603                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 604                         if (fdin != fdout)
 605                                 close(fdin);
 606                         else
 607                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 608                         fdin = -1;
 609                 }
 610                 /* Make packets from buffered stderr data to send to the client. */
 611                 make_packets_from_stderr_data();
 612
 613                 /*
 614                  * Make packets from buffered stdout data to send to the
 615                  * client. If there is very little to send, this arranges to
 616                  * not send them now, but to wait a short while to see if we
 617                  * are getting more data. This is necessary, as some systems
 618                  * wake up readers from a pty after each separate character.
 619                  */
 620                 max_time_milliseconds = 0;
 621                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 622                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 623                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 624                         /* try again after a while */
 625                         max_time_milliseconds = 10;
 626                 } else {
 627                         /* Send it now. */
 628                         make_packets_from_stdout_data();
 629                 }
 630                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 631
 632                 /* Send channel data to the client. */
 633                 if (packet_not_very_much_data_to_write())
 634                         channel_output_poll();
 635
 636                 /*
 637                  * Bail out of the loop if the program has closed its output
 638                  * descriptors, and we have no more data to send to the
 639                  * client, and there is no pending buffered data.
 640                  */
 641                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 642                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 643                         if (!channel_still_open())
 644                                 break;
 645                         if (!waiting_termination) {
 646                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 647                                 char *cp;
 648                                 waiting_termination = 1;
 649                                 buffer_append(&stderr_buffer, s, strlen(s));
 650
 651                                 /* Display list of open channels. */
 652                                 cp = channel_open_message();
 653                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 654                                 xfree(cp);
 655                         }
 656                 }
 657                 max_fd = MAX(connection_in, connection_out);
 658                 max_fd = MAX(max_fd, fdin);
 659                 max_fd = MAX(max_fd, fdout);
 660                 max_fd = MAX(max_fd, fderr);
 661                 max_fd = MAX(max_fd, notify_pipe[0]);
 662
 663                 /* Sleep in select() until we can do something. */
 664                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 665                     &nalloc, max_time_milliseconds);
 666
 667                 if (received_sigterm) {
 668                         logit("Exiting on signal %d", received_sigterm);
 669                         /* Clean up sessions, utmp, etc. */
 670                         cleanup_exit(255);
 671                 }
 672
 673                 /* Process any channel events. */
 674                 channel_after_select(readset, writeset);
 675
 676                 /* Process input from the client and from program stdout/stderr. */
 677                 process_input(readset);
 678
 679                 /* Process output to the client and to program stdin. */
 680                 process_output(writeset);
 681         }
 682         if (readset)
 683                 xfree(readset);
 684         if (writeset)
 685                 xfree(writeset);
 686
 687         /* Cleanup and termination code. */
 688
 689         /* Wait until all output has been sent to the client. */
 690         drain_output();
 691
 692         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 693             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 694
 695         /* Free and clear the buffers. */
 696         buffer_free(&stdin_buffer);
 697         buffer_free(&stdout_buffer);
 698         buffer_free(&stderr_buffer);
 699
 700         /* Close the file descriptors. */
 701         if (fdout != -1)
 702                 close(fdout);
 703         fdout = -1;
 704         fdout_eof = 1;
 705         if (fderr != -1)
 706                 close(fderr);
 707         fderr = -1;
 708         fderr_eof = 1;
 709         if (fdin != -1)
 710                 close(fdin);
 711         fdin = -1;
 712
 713         channel_free_all();
 714
 715         /* We no longer want our SIGCHLD handler to be called. */
 716         mysignal(SIGCHLD, SIG_DFL);
 717
 718         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 719                 if (errno != EINTR)
 720                         packet_disconnect("wait: %.100s", strerror(errno));
 721         if (wait_pid != pid)
 722                 error("Strange, wait returned pid %ld, expected %ld",
 723                     (long)wait_pid, (long)pid);
 724
 725         /* Check if it exited normally. */
 726         if (WIFEXITED(wait_status)) {
 727                 /* Yes, normal exit.  Get exit status and send it to the client. */
 728                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 729                 packet_start(SSH_SMSG_EXITSTATUS);
 730                 packet_put_int(WEXITSTATUS(wait_status));
 731                 packet_send();
 732                 packet_write_wait();
 733
 734                 /*
 735                  * Wait for exit confirmation.  Note that there might be
 736                  * other packets coming before it; however, the program has
 737                  * already died so we just ignore them.  The client is
 738                  * supposed to respond with the confirmation when it receives
 739                  * the exit status.
 740                  */
 741                 do {
 742                         type = packet_read();
 743                 }
 744                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 745
 746                 debug("Received exit confirmation.");
 747                 return;
 748         }
 749         /* Check if the program terminated due to a signal. */
 750         if (WIFSIGNALED(wait_status))
 751                 packet_disconnect("Command terminated on signal %d.",
 752                                   WTERMSIG(wait_status));
 753
 754         /* Some weird exit cause.  Just exit. */
 755         packet_disconnect("wait returned status %04x.", wait_status);
 756         /* NOTREACHED */
 757 }
 758
 759 static void
 760 collect_children(void)
 761 {
 762         pid_t pid;
 763         sigset_t oset, nset;
 764         int status;
 765
 766         /* block SIGCHLD while we check for dead children */
 767         sigemptyset(&nset);
 768         sigaddset(&nset, SIGCHLD);
 769         sigprocmask(SIG_BLOCK, &nset, &oset);
 770         if (child_terminated) {
 771                 debug("Received SIGCHLD.");
 772                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 773                     (pid < 0 && errno == EINTR))
 774                         if (pid > 0)
 775                                 session_close_by_pid(pid, status);
 776                 child_terminated = 0;
 777         }
 778         sigprocmask(SIG_SETMASK, &oset, NULL);
 779 }
 780
 781 void
 782 server_loop2(Authctxt *authctxt)
 783 {
 784         fd_set *readset = NULL, *writeset = NULL;
 785         int rekeying = 0, max_fd, nalloc = 0;
 786
 787         debug("Entering interactive session for SSH2.");
 788
 789         mysignal(SIGCHLD, sigchld_handler);
 790         child_terminated = 0;
 791         connection_in = packet_get_connection_in();
 792         connection_out = packet_get_connection_out();
 793
 794         if (!use_privsep) {
 795                 signal(SIGTERM, sigterm_handler);
 796                 signal(SIGINT, sigterm_handler);
 797                 signal(SIGQUIT, sigterm_handler);
 798         }
 799
 800         notify_setup();
 801
 802         max_fd = MAX(connection_in, connection_out);
 803         max_fd = MAX(max_fd, notify_pipe[0]);
 804
 805         server_init_dispatch();
 806
 807         for (;;) {
 808                 process_buffered_input_packets();
 809
 810                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 811
 812                 if (!rekeying && packet_not_very_much_data_to_write())
 813                         channel_output_poll();
 814                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 815                     &nalloc, 0);
 816
 817                 if (received_sigterm) {
 818                         logit("Exiting on signal %d", received_sigterm);
 819                         /* Clean up sessions, utmp, etc. */
 820                         cleanup_exit(255);
 821                 }
 822
 823                 collect_children();
 824                 if (!rekeying) {
 825                         channel_after_select(readset, writeset);
 826                         if (packet_need_rekeying()) {
 827                                 debug("need rekeying");
 828                                 xxx_kex->done = 0;
 829                                 kex_send_kexinit(xxx_kex);
 830                         }
 831                 }
 832                 process_input(readset);
 833                 if (connection_closed)
 834                         break;
 835                 process_output(writeset);
 836         }
 837         collect_children();
 838
 839         if (readset)
 840                 xfree(readset);
 841         if (writeset)
 842                 xfree(writeset);
 843
 844         /* free all channels, no more reads and writes */
 845         channel_free_all();
 846
 847         /* free remaining sessions, e.g. remove wtmp entries */
 848         session_destroy_all(NULL);
 849 }
 850
 851 static void
 852 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 853 {
 854         debug("Got %d/%u for keepalive", type, seq);
 855         /*
 856          * reset timeout, since we got a sane answer from the client.
 857          * even if this was generated by something other than
 858          * the bogus CHANNEL_REQUEST we send for keepalives.
 859          */
 860         client_alive_timeouts = 0;
 861 }
 862
 863 static void
 864 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 865 {
 866         char *data;
 867         u_int data_len;
 868
 869         /* Stdin data from the client.  Append it to the buffer. */
 870         /* Ignore any data if the client has closed stdin. */
 871         if (fdin == -1)
 872                 return;
 873         data = packet_get_string(&data_len);
 874         packet_check_eom();
 875         buffer_append(&stdin_buffer, data, data_len);
 876         memset(data, 0, data_len);
 877         xfree(data);
 878 }
 879
 880 static void
 881 server_input_eof(int type, u_int32_t seq, void *ctxt)
 882 {
 883         /*
 884          * Eof from the client.  The stdin descriptor to the
 885          * program will be closed when all buffered data has
 886          * drained.
 887          */
 888         debug("EOF received for stdin.");
 889         packet_check_eom();
 890         stdin_eof = 1;
 891 }
 892
 893 static void
 894 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 895 {
 896         u_int row = packet_get_int();
 897         u_int col = packet_get_int();
 898         u_int xpixel = packet_get_int();
 899         u_int ypixel = packet_get_int();
 900
 901         debug("Window change received.");
 902         packet_check_eom();
 903         if (fdin != -1)
 904                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 905 }
 906
 907 static Channel *
 908 server_request_direct_tcpip(void)
 909 {
 910         Channel *c;
 911         int sock;
 912         char *target, *originator;
 913         int target_port, originator_port;
 914
 915         target = packet_get_string(NULL);
 916         target_port = packet_get_int();
 917         originator = packet_get_string(NULL);
 918         originator_port = packet_get_int();
 919         packet_check_eom();
 920
 921         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 922             originator, originator_port, target, target_port);
 923
 924         /* XXX check permission */
 925         sock = channel_connect_to(target, target_port);
 926         xfree(target);
 927         xfree(originator);
 928         if (sock < 0)
 929                 return NULL;
 930         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 931             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 932             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 933         return c;
 934 }
 935
 936 static Channel *
 937 server_request_tun(void)
 938 {
 939         Channel *c = NULL;
 940         int mode, tun;
 941         int sock;
 942
 943         mode = packet_get_int();
 944         switch (mode) {
 945         case SSH_TUNMODE_POINTOPOINT:
 946         case SSH_TUNMODE_ETHERNET:
 947                 break;
 948         default:
 949                 packet_send_debug("Unsupported tunnel device mode.");
 950                 return NULL;
 951         }
 952         if ((options.permit_tun & mode) == 0) {
 953                 packet_send_debug("Server has rejected tunnel device "
 954                     "forwarding");
 955                 return NULL;
 956         }
 957
 958         tun = packet_get_int();
 959         if (forced_tun_device != -1) {
 960                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 961                         goto done;
 962                 tun = forced_tun_device;
 963         }
 964         sock = tun_open(tun, mode);
 965         if (sock < 0)
 966                 goto done;
 967         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 968             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 969         c->datagram = 1;
 970 #if defined(SSH_TUN_FILTER)
 971         if (mode == SSH_TUNMODE_POINTOPOINT)
 972                 channel_register_filter(c->self, sys_tun_infilter,
 973                     sys_tun_outfilter);
 974 #endif
 975
 976  done:
 977         if (c == NULL)
 978                 packet_send_debug("Failed to open the tunnel device.");
 979         return c;
 980 }
 981
 982 static Channel *
 983 server_request_session(void)
 984 {
 985         Channel *c;
 986
 987         debug("input_session_request");
 988         packet_check_eom();
 989         /*
 990          * A server session has no fd to read or write until a
 991          * CHANNEL_REQUEST for a shell is made, so we set the type to
 992          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 993          * CHANNEL_REQUEST messages is registered.
 994          */
 995         c = channel_new("session", SSH_CHANNEL_LARVAL,
 996             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 997             0, "server-session", 1);
 998         if (session_open(the_authctxt, c->self) != 1) {
 999                 debug("session open failed, free channel %d", c->self);
1000                 channel_free(c);
1001                 return NULL;
1002         }
1003         channel_register_cleanup(c->self, session_close_by_channel, 0);
1004         return c;
1005 }
1006
1007 static void
1008 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1009 {
1010         Channel *c = NULL;
1011         char *ctype;
1012         int rchan;
1013         u_int rmaxpack, rwindow, len;
1014
1015         ctype = packet_get_string(&len);
1016         rchan = packet_get_int();
1017         rwindow = packet_get_int();
1018         rmaxpack = packet_get_int();
1019
1020         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1021             ctype, rchan, rwindow, rmaxpack);
1022
1023         if (strcmp(ctype, "session") == 0) {
1024                 c = server_request_session();
1025         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1026                 c = server_request_direct_tcpip();
1027         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1028                 c = server_request_tun();
1029         }
1030         if (c != NULL) {
1031                 debug("server_input_channel_open: confirm %s", ctype);
1032                 c->remote_id = rchan;
1033                 c->remote_window = rwindow;
1034                 c->remote_maxpacket = rmaxpack;
1035                 if (c->type != SSH_CHANNEL_CONNECTING) {
1036                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1037                         packet_put_int(c->remote_id);
1038                         packet_put_int(c->self);
1039                         packet_put_int(c->local_window);
1040                         packet_put_int(c->local_maxpacket);
1041                         packet_send();
1042                 }
1043         } else {
1044                 debug("server_input_channel_open: failure %s", ctype);
1045                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1046                 packet_put_int(rchan);
1047                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1048                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1049                         packet_put_cstring("open failed");
1050                         packet_put_cstring("");
1051                 }
1052                 packet_send();
1053         }
1054         xfree(ctype);
1055 }
1056
1057 static void
1058 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1059 {
1060         char *rtype;
1061         int want_reply;
1062         int success = 0;
1063
1064         rtype = packet_get_string(NULL);
1065         want_reply = packet_get_char();
1066         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1067
1068         /* -R style forwarding */
1069         if (strcmp(rtype, "tcpip-forward") == 0) {
1070                 struct passwd *pw;
1071                 char *listen_address;
1072                 u_short listen_port;
1073
1074                 pw = the_authctxt->pw;
1075                 if (pw == NULL || !the_authctxt->valid)
1076                         fatal("server_input_global_request: no/invalid user");
1077                 listen_address = packet_get_string(NULL);
1078                 listen_port = (u_short)packet_get_int();
1079                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1080                     listen_address, listen_port);
1081
1082                 /* check permissions */
1083                 if (!options.allow_tcp_forwarding ||
1084                     no_port_forwarding_flag
1085 #ifndef NO_IPPORT_RESERVED_CONCEPT
1086                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1087 #endif
1088                     ) {
1089                         success = 0;
1090                         packet_send_debug("Server has disabled port forwarding.");
1091                 } else {
1092                         /* Start listening on the port */
1093                         success = channel_setup_remote_fwd_listener(
1094                             listen_address, listen_port, options.gateway_ports);
1095                 }
1096                 xfree(listen_address);
1097         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1098                 char *cancel_address;
1099                 u_short cancel_port;
1100
1101                 cancel_address = packet_get_string(NULL);
1102                 cancel_port = (u_short)packet_get_int();
1103                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1104                     cancel_address, cancel_port);
1105
1106                 success = channel_cancel_rport_listener(cancel_address,
1107                     cancel_port);
1108                 xfree(cancel_address);
1109         }
1110         if (want_reply) {
1111                 packet_start(success ?
1112                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1113                 packet_send();
1114                 packet_write_wait();
1115         }
1116         xfree(rtype);
1117 }
1118
1119 static void
1120 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1121 {
1122         Channel *c;
1123         int id, reply, success = 0;
1124         char *rtype;
1125
1126         id = packet_get_int();
1127         rtype = packet_get_string(NULL);
1128         reply = packet_get_char();
1129
1130         debug("server_input_channel_req: channel %d request %s reply %d",
1131             id, rtype, reply);
1132
1133         if ((c = channel_lookup(id)) == NULL)
1134                 packet_disconnect("server_input_channel_req: "
1135                     "unknown channel %d", id);
1136         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1137                 success = session_input_channel_req(c, rtype);
1138         if (reply) {
1139                 packet_start(success ?
1140                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1141                 packet_put_int(c->remote_id);
1142                 packet_send();
1143         }
1144         xfree(rtype);
1145 }
1146
1147 static void
1148 server_init_dispatch_20(void)
1149 {
1150         debug("server_init_dispatch_20");
1151         dispatch_init(&dispatch_protocol_error);
1152         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1153         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1154         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1155         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1156         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1157         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1158         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1159         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1160         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1161         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1162         /* client_alive */
1163         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1164         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1165         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1166         /* rekeying */
1167         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1168 }
1169 static void
1170 server_init_dispatch_13(void)
1171 {
1172         debug("server_init_dispatch_13");
1173         dispatch_init(NULL);
1174         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1175         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1176         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1177         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1178         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1179         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1180         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1181         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1182         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1183 }
1184 static void
1185 server_init_dispatch_15(void)
1186 {
1187         server_init_dispatch_13();
1188         debug("server_init_dispatch_15");
1189         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1190         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1191 }
1192 static void
1193 server_init_dispatch(void)
1194 {
1195         if (compat20)
1196                 server_init_dispatch_20();
1197         else if (compat13)
1198                 server_init_dispatch_13();
1199         else
1200                 server_init_dispatch_15();
1201 }