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 1.78 2001/10/04 15:05:40 markus Exp $");
  39
  40 #include "xmalloc.h"
  41 #include "packet.h"
  42 #include "buffer.h"
  43 #include "log.h"
  44 #include "servconf.h"
  45 #include "sshpty.h"
  46 #include "channels.h"
  47 #include "compat.h"
  48 #include "ssh1.h"
  49 #include "ssh2.h"
  50 #include "auth.h"
  51 #include "session.h"
  52 #include "dispatch.h"
  53 #include "auth-options.h"
  54 #include "serverloop.h"
  55 #include "misc.h"
  56 #include "kex.h"
  57
  58 extern ServerOptions options;
  59
  60 /* XXX */
  61 extern Kex *xxx_kex;
  62 static Authctxt *xxx_authctxt;
  63
  64 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  65 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  66 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  67 static int fdin;                /* Descriptor for stdin (for writing) */
  68 static int fdout;               /* Descriptor for stdout (for reading);
  69                                    May be same number as fdin. */
  70 static int fderr;               /* Descriptor for stderr.  May be -1. */
  71 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  72 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  73 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  74 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  75 static int stdin_eof = 0;       /* EOF message received from client. */
  76 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
  77 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
  78 static int fdin_is_tty = 0;     /* fdin points to a tty. */
  79 static int connection_in;       /* Connection to client (input). */
  80 static int connection_out;      /* Connection to client (output). */
  81 static int connection_closed = 0;       /* Connection to client closed. */
  82 static u_int buffer_high;       /* "Soft" max buffer size. */
  83
  84 /*
  85  * This SIGCHLD kludge is used to detect when the child exits.  The server
  86  * will exit after that, as soon as forwarded connections have terminated.
  87  */
  88
  89 static volatile int child_terminated;   /* The child has terminated. */
  90
  91 /* prototypes */
  92 static void server_init_dispatch(void);
  93
  94 int client_alive_timeouts = 0;
  95
  96 static void
  97 sigchld_handler(int sig)
  98 {
  99         int save_errno = errno;
 100         debug("Received SIGCHLD.");
 101         child_terminated = 1;
 102         mysignal(SIGCHLD, sigchld_handler);
 103         errno = save_errno;
 104 }
 105
 106 /*
 107  * Make packets from buffered stderr data, and buffer it for sending
 108  * to the client.
 109  */
 110 static void
 111 make_packets_from_stderr_data(void)
 112 {
 113         int len;
 114
 115         /* Send buffered stderr data to the client. */
 116         while (buffer_len(&stderr_buffer) > 0 &&
 117             packet_not_very_much_data_to_write()) {
 118                 len = buffer_len(&stderr_buffer);
 119                 if (packet_is_interactive()) {
 120                         if (len > 512)
 121                                 len = 512;
 122                 } else {
 123                         /* Keep the packets at reasonable size. */
 124                         if (len > packet_get_maxsize())
 125                                 len = packet_get_maxsize();
 126                 }
 127                 packet_start(SSH_SMSG_STDERR_DATA);
 128                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 129                 packet_send();
 130                 buffer_consume(&stderr_buffer, len);
 131                 stderr_bytes += len;
 132         }
 133 }
 134
 135 /*
 136  * Make packets from buffered stdout data, and buffer it for sending to the
 137  * client.
 138  */
 139 static void
 140 make_packets_from_stdout_data(void)
 141 {
 142         int len;
 143
 144         /* Send buffered stdout data to the client. */
 145         while (buffer_len(&stdout_buffer) > 0 &&
 146             packet_not_very_much_data_to_write()) {
 147                 len = buffer_len(&stdout_buffer);
 148                 if (packet_is_interactive()) {
 149                         if (len > 512)
 150                                 len = 512;
 151                 } else {
 152                         /* Keep the packets at reasonable size. */
 153                         if (len > packet_get_maxsize())
 154                                 len = packet_get_maxsize();
 155                 }
 156                 packet_start(SSH_SMSG_STDOUT_DATA);
 157                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 158                 packet_send();
 159                 buffer_consume(&stdout_buffer, len);
 160                 stdout_bytes += len;
 161         }
 162 }
 163
 164 /*
 165  * Sleep in select() until we can do something.  This will initialize the
 166  * select masks.  Upon return, the masks will indicate which descriptors
 167  * have data or can accept data.  Optionally, a maximum time can be specified
 168  * for the duration of the wait (0 = infinite).
 169  */
 170 static void
 171 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 172     int *nallocp, u_int max_time_milliseconds)
 173 {
 174         struct timeval tv, *tvp;
 175         int ret;
 176         int client_alive_scheduled = 0;
 177
 178         /*
 179          * if using client_alive, set the max timeout accordingly,
 180          * and indicate that this particular timeout was for client
 181          * alive by setting the client_alive_scheduled flag.
 182          *
 183          * this could be randomized somewhat to make traffic
 184          * analysis more difficult, but we're not doing it yet.
 185          */
 186         if (compat20 &&
 187             max_time_milliseconds == 0 && options.client_alive_interval) {
 188                 client_alive_scheduled = 1;
 189                 max_time_milliseconds = options.client_alive_interval * 1000;
 190         }
 191
 192         /* When select fails we restart from here. */
 193 retry_select:
 194
 195         /* Allocate and update select() masks for channel descriptors. */
 196         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 197
 198         if (compat20) {
 199 #if 0
 200                 /* wrong: bad condition XXX */
 201                 if (channel_not_very_much_buffered_data())
 202 #endif
 203                 FD_SET(connection_in, *readsetp);
 204         } else {
 205                 /*
 206                  * Read packets from the client unless we have too much
 207                  * buffered stdin or channel data.
 208                  */
 209                 if (buffer_len(&stdin_buffer) < buffer_high &&
 210                     channel_not_very_much_buffered_data())
 211                         FD_SET(connection_in, *readsetp);
 212                 /*
 213                  * If there is not too much data already buffered going to
 214                  * the client, try to get some more data from the program.
 215                  */
 216                 if (packet_not_very_much_data_to_write()) {
 217                         if (!fdout_eof)
 218                                 FD_SET(fdout, *readsetp);
 219                         if (!fderr_eof)
 220                                 FD_SET(fderr, *readsetp);
 221                 }
 222                 /*
 223                  * If we have buffered data, try to write some of that data
 224                  * to the program.
 225                  */
 226                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 227                         FD_SET(fdin, *writesetp);
 228         }
 229
 230         /*
 231          * If we have buffered packet data going to the client, mark that
 232          * descriptor.
 233          */
 234         if (packet_have_data_to_write())
 235                 FD_SET(connection_out, *writesetp);
 236
 237         /*
 238          * If child has terminated and there is enough buffer space to read
 239          * from it, then read as much as is available and exit.
 240          */
 241         if (child_terminated && packet_not_very_much_data_to_write())
 242                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 243                         max_time_milliseconds = 100;
 244
 245         if (max_time_milliseconds == 0)
 246                 tvp = NULL;
 247         else {
 248                 tv.tv_sec = max_time_milliseconds / 1000;
 249                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 250                 tvp = &tv;
 251         }
 252         if (tvp!=NULL)
 253                 debug3("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds);
 254
 255         /* Wait for something to happen, or the timeout to expire. */
 256         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 257
 258         if (ret == -1) {
 259                 if (errno != EINTR)
 260                         error("select: %.100s", strerror(errno));
 261                 else
 262                         goto retry_select;
 263         }
 264         if (ret == 0 && client_alive_scheduled) {
 265                 /* timeout, check to see how many we have had */
 266                 client_alive_timeouts++;
 267
 268                 if (client_alive_timeouts > options.client_alive_count_max ) {
 269                         packet_disconnect(
 270                                 "Timeout, your session not responding.");
 271                 } else {
 272                         /*
 273                          * send a bogus channel request with "wantreply"
 274                          * we should get back a failure
 275                          */
 276                         int id;
 277
 278                         id = channel_find_open();
 279                         if (id != -1) {
 280                                 channel_request_start(id,
 281                                   "keepalive@openssh.com", 1);
 282                                 packet_send();
 283                         } else
 284                                 packet_disconnect(
 285                                         "No open channels after timeout!");
 286                 }
 287         }
 288 }
 289
 290 /*
 291  * Processes input from the client and the program.  Input data is stored
 292  * in buffers and processed later.
 293  */
 294 static void
 295 process_input(fd_set * readset)
 296 {
 297         int len;
 298         char buf[16384];
 299
 300         /* Read and buffer any input data from the client. */
 301         if (FD_ISSET(connection_in, readset)) {
 302                 len = read(connection_in, buf, sizeof(buf));
 303                 if (len == 0) {
 304                         verbose("Connection closed by remote host.");
 305                         connection_closed = 1;
 306                         if (compat20)
 307                                 return;
 308                         fatal_cleanup();
 309                 } else if (len < 0) {
 310                         if (errno != EINTR && errno != EAGAIN) {
 311                                 verbose("Read error from remote host: %.100s", strerror(errno));
 312                                 fatal_cleanup();
 313                         }
 314                 } else {
 315                         /* Buffer any received data. */
 316                         packet_process_incoming(buf, len);
 317                 }
 318         }
 319         if (compat20)
 320                 return;
 321
 322         /* Read and buffer any available stdout data from the program. */
 323         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 324                 len = read(fdout, buf, sizeof(buf));
 325                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 326                         /* do nothing */
 327                 } else if (len <= 0) {
 328                         fdout_eof = 1;
 329                 } else {
 330                         buffer_append(&stdout_buffer, buf, len);
 331                         fdout_bytes += len;
 332                 }
 333         }
 334         /* Read and buffer any available stderr data from the program. */
 335         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 336                 len = read(fderr, buf, sizeof(buf));
 337                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 338                         /* do nothing */
 339                 } else if (len <= 0) {
 340                         fderr_eof = 1;
 341                 } else {
 342                         buffer_append(&stderr_buffer, buf, len);
 343                 }
 344         }
 345 }
 346
 347 /*
 348  * Sends data from internal buffers to client program stdin.
 349  */
 350 static void
 351 process_output(fd_set * writeset)
 352 {
 353         struct termios tio;
 354         u_char *data;
 355         u_int dlen;
 356         int len;
 357
 358         /* Write buffered data to program stdin. */
 359         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 360                 data = buffer_ptr(&stdin_buffer);
 361                 dlen = buffer_len(&stdin_buffer);
 362                 len = write(fdin, data, dlen);
 363                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 364                         /* do nothing */
 365                 } else if (len <= 0) {
 366 #ifdef USE_PIPES
 367                         close(fdin);
 368 #else
 369                         if (fdin != fdout)
 370                                 close(fdin);
 371                         else
 372                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 373 #endif
 374                         fdin = -1;
 375                 } else {
 376                         /* Successful write. */
 377                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 378                             tcgetattr(fdin, &tio) == 0 &&
 379                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 380                                 /*
 381                                  * Simulate echo to reduce the impact of
 382                                  * traffic analysis
 383                                  */
 384                                 packet_send_ignore(len);
 385                                 packet_send();
 386                         }
 387                         /* Consume the data from the buffer. */
 388                         buffer_consume(&stdin_buffer, len);
 389                         /* Update the count of bytes written to the program. */
 390                         stdin_bytes += len;
 391                 }
 392         }
 393         /* Send any buffered packet data to the client. */
 394         if (FD_ISSET(connection_out, writeset))
 395                 packet_write_poll();
 396 }
 397
 398 /*
 399  * Wait until all buffered output has been sent to the client.
 400  * This is used when the program terminates.
 401  */
 402 static void
 403 drain_output(void)
 404 {
 405         /* Send any buffered stdout data to the client. */
 406         if (buffer_len(&stdout_buffer) > 0) {
 407                 packet_start(SSH_SMSG_STDOUT_DATA);
 408                 packet_put_string(buffer_ptr(&stdout_buffer),
 409                                   buffer_len(&stdout_buffer));
 410                 packet_send();
 411                 /* Update the count of sent bytes. */
 412                 stdout_bytes += buffer_len(&stdout_buffer);
 413         }
 414         /* Send any buffered stderr data to the client. */
 415         if (buffer_len(&stderr_buffer) > 0) {
 416                 packet_start(SSH_SMSG_STDERR_DATA);
 417                 packet_put_string(buffer_ptr(&stderr_buffer),
 418                                   buffer_len(&stderr_buffer));
 419                 packet_send();
 420                 /* Update the count of sent bytes. */
 421                 stderr_bytes += buffer_len(&stderr_buffer);
 422         }
 423         /* Wait until all buffered data has been written to the client. */
 424         packet_write_wait();
 425 }
 426
 427 static void
 428 process_buffered_input_packets(void)
 429 {
 430         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 431 }
 432
 433 /*
 434  * Performs the interactive session.  This handles data transmission between
 435  * the client and the program.  Note that the notion of stdin, stdout, and
 436  * stderr in this function is sort of reversed: this function writes to
 437  * stdin (of the child program), and reads from stdout and stderr (of the
 438  * child program).
 439  */
 440 void
 441 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 442 {
 443         fd_set *readset = NULL, *writeset = NULL;
 444         int max_fd = 0, nalloc = 0;
 445         int wait_status;        /* Status returned by wait(). */
 446         pid_t wait_pid;         /* pid returned by wait(). */
 447         int waiting_termination = 0;    /* Have displayed waiting close message. */
 448         u_int max_time_milliseconds;
 449         u_int previous_stdout_buffer_bytes;
 450         u_int stdout_buffer_bytes;
 451         int type;
 452
 453         debug("Entering interactive session.");
 454
 455         /* Initialize the SIGCHLD kludge. */
 456         child_terminated = 0;
 457         mysignal(SIGCHLD, sigchld_handler);
 458
 459         /* Initialize our global variables. */
 460         fdin = fdin_arg;
 461         fdout = fdout_arg;
 462         fderr = fderr_arg;
 463
 464         /* nonblocking IO */
 465         set_nonblock(fdin);
 466         set_nonblock(fdout);
 467         /* we don't have stderr for interactive terminal sessions, see below */
 468         if (fderr != -1)
 469                 set_nonblock(fderr);
 470
 471         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 472                 fdin_is_tty = 1;
 473
 474         connection_in = packet_get_connection_in();
 475         connection_out = packet_get_connection_out();
 476
 477         previous_stdout_buffer_bytes = 0;
 478
 479         /* Set approximate I/O buffer size. */
 480         if (packet_is_interactive())
 481                 buffer_high = 4096;
 482         else
 483                 buffer_high = 64 * 1024;
 484
 485 #if 0
 486         /* Initialize max_fd to the maximum of the known file descriptors. */
 487         max_fd = MAX(connection_in, connection_out);
 488         max_fd = MAX(max_fd, fdin);
 489         max_fd = MAX(max_fd, fdout);
 490         if (fderr != -1)
 491                 max_fd = MAX(max_fd, fderr);
 492 #endif
 493
 494         /* Initialize Initialize buffers. */
 495         buffer_init(&stdin_buffer);
 496         buffer_init(&stdout_buffer);
 497         buffer_init(&stderr_buffer);
 498
 499         /*
 500          * If we have no separate fderr (which is the case when we have a pty
 501          * - there we cannot make difference between data sent to stdout and
 502          * stderr), indicate that we have seen an EOF from stderr.  This way
 503          * we don\'t need to check the descriptor everywhere.
 504          */
 505         if (fderr == -1)
 506                 fderr_eof = 1;
 507
 508         server_init_dispatch();
 509
 510         /* Main loop of the server for the interactive session mode. */
 511         for (;;) {
 512
 513                 /* Process buffered packets from the client. */
 514                 process_buffered_input_packets();
 515
 516                 /*
 517                  * If we have received eof, and there is no more pending
 518                  * input data, cause a real eof by closing fdin.
 519                  */
 520                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 521 #ifdef USE_PIPES
 522                         close(fdin);
 523 #else
 524                         if (fdin != fdout)
 525                                 close(fdin);
 526                         else
 527                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 528 #endif
 529                         fdin = -1;
 530                 }
 531                 /* Make packets from buffered stderr data to send to the client. */
 532                 make_packets_from_stderr_data();
 533
 534                 /*
 535                  * Make packets from buffered stdout data to send to the
 536                  * client. If there is very little to send, this arranges to
 537                  * not send them now, but to wait a short while to see if we
 538                  * are getting more data. This is necessary, as some systems
 539                  * wake up readers from a pty after each separate character.
 540                  */
 541                 max_time_milliseconds = 0;
 542                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 543                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 544                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 545                         /* try again after a while */
 546                         max_time_milliseconds = 10;
 547                 } else {
 548                         /* Send it now. */
 549                         make_packets_from_stdout_data();
 550                 }
 551                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 552
 553                 /* Send channel data to the client. */
 554                 if (packet_not_very_much_data_to_write())
 555                         channel_output_poll();
 556
 557                 /*
 558                  * Bail out of the loop if the program has closed its output
 559                  * descriptors, and we have no more data to send to the
 560                  * client, and there is no pending buffered data.
 561                  */
 562                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 563                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 564                         if (!channel_still_open())
 565                                 break;
 566                         if (!waiting_termination) {
 567                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 568                                 char *cp;
 569                                 waiting_termination = 1;
 570                                 buffer_append(&stderr_buffer, s, strlen(s));
 571
 572                                 /* Display list of open channels. */
 573                                 cp = channel_open_message();
 574                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 575                                 xfree(cp);
 576                         }
 577                 }
 578                 max_fd = MAX(connection_in, connection_out);
 579                 max_fd = MAX(max_fd, fdin);
 580                 max_fd = MAX(max_fd, fdout);
 581                 max_fd = MAX(max_fd, fderr);
 582
 583                 /* Sleep in select() until we can do something. */
 584                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 585                     &nalloc, max_time_milliseconds);
 586
 587                 /* Process any channel events. */
 588                 channel_after_select(readset, writeset);
 589
 590                 /* Process input from the client and from program stdout/stderr. */
 591                 process_input(readset);
 592
 593                 /* Process output to the client and to program stdin. */
 594                 process_output(writeset);
 595         }
 596         if (readset)
 597                 xfree(readset);
 598         if (writeset)
 599                 xfree(writeset);
 600
 601         /* Cleanup and termination code. */
 602
 603         /* Wait until all output has been sent to the client. */
 604         drain_output();
 605
 606         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 607               stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 608
 609         /* Free and clear the buffers. */
 610         buffer_free(&stdin_buffer);
 611         buffer_free(&stdout_buffer);
 612         buffer_free(&stderr_buffer);
 613
 614         /* Close the file descriptors. */
 615         if (fdout != -1)
 616                 close(fdout);
 617         fdout = -1;
 618         fdout_eof = 1;
 619         if (fderr != -1)
 620                 close(fderr);
 621         fderr = -1;
 622         fderr_eof = 1;
 623         if (fdin != -1)
 624                 close(fdin);
 625         fdin = -1;
 626
 627         channel_free_all();
 628
 629         /* We no longer want our SIGCHLD handler to be called. */
 630         mysignal(SIGCHLD, SIG_DFL);
 631
 632         wait_pid = waitpid(-1, &wait_status, child_terminated ? WNOHANG : 0);
 633         if (wait_pid == -1)
 634                 packet_disconnect("wait: %.100s", strerror(errno));
 635         else if (wait_pid != pid)
 636                 error("Strange, wait returned pid %d, expected %d",
 637                     wait_pid, pid);
 638
 639         /* Check if it exited normally. */
 640         if (WIFEXITED(wait_status)) {
 641                 /* Yes, normal exit.  Get exit status and send it to the client. */
 642                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 643                 packet_start(SSH_SMSG_EXITSTATUS);
 644                 packet_put_int(WEXITSTATUS(wait_status));
 645                 packet_send();
 646                 packet_write_wait();
 647
 648                 /*
 649                  * Wait for exit confirmation.  Note that there might be
 650                  * other packets coming before it; however, the program has
 651                  * already died so we just ignore them.  The client is
 652                  * supposed to respond with the confirmation when it receives
 653                  * the exit status.
 654                  */
 655                 do {
 656                         int plen;
 657                         type = packet_read(&plen);
 658                 }
 659                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 660
 661                 debug("Received exit confirmation.");
 662                 return;
 663         }
 664         /* Check if the program terminated due to a signal. */
 665         if (WIFSIGNALED(wait_status))
 666                 packet_disconnect("Command terminated on signal %d.",
 667                                   WTERMSIG(wait_status));
 668
 669         /* Some weird exit cause.  Just exit. */
 670         packet_disconnect("wait returned status %04x.", wait_status);
 671         /* NOTREACHED */
 672 }
 673
 674 void
 675 server_loop2(Authctxt *authctxt)
 676 {
 677         fd_set *readset = NULL, *writeset = NULL;
 678         int rekeying = 0, max_fd, status, nalloc = 0;
 679         pid_t pid;
 680
 681         debug("Entering interactive session for SSH2.");
 682
 683         mysignal(SIGCHLD, sigchld_handler);
 684         child_terminated = 0;
 685         connection_in = packet_get_connection_in();
 686         connection_out = packet_get_connection_out();
 687
 688         max_fd = MAX(connection_in, connection_out);
 689         xxx_authctxt = authctxt;
 690
 691         server_init_dispatch();
 692
 693         for (;;) {
 694                 process_buffered_input_packets();
 695
 696                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 697
 698                 if (!rekeying && packet_not_very_much_data_to_write())
 699                         channel_output_poll();
 700                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 701                     &nalloc, 0);
 702                 if (child_terminated) {
 703                         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 704                                 session_close_by_pid(pid, status);
 705                         child_terminated = 0;
 706                 }
 707                 if (!rekeying)
 708                         channel_after_select(readset, writeset);
 709                 process_input(readset);
 710                 if (connection_closed)
 711                         break;
 712                 process_output(writeset);
 713         }
 714         if (readset)
 715                 xfree(readset);
 716         if (writeset)
 717                 xfree(writeset);
 718
 719         mysignal(SIGCHLD, SIG_DFL);
 720
 721         while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
 722                 session_close_by_pid(pid, status);
 723         /*
 724          * there is a race between channel_free_all() killing children and
 725          * children dying before kill()
 726          */
 727         channel_detach_all();
 728         channel_stop_listening();
 729
 730         while (session_have_children()) {
 731                 pid = waitpid(-1, &status, 0);
 732                 if (pid > 0)
 733                         session_close_by_pid(pid, status);
 734                 else {
 735                         error("waitpid returned %d: %s", pid, strerror(errno));
 736                         break;
 737                 }
 738         }
 739         channel_free_all();
 740 }
 741
 742 static void
 743 server_input_channel_failure(int type, int plen, void *ctxt)
 744 {
 745         debug("Got CHANNEL_FAILURE for keepalive");
 746         /*
 747          * reset timeout, since we got a sane answer from the client.
 748          * even if this was generated by something other than
 749          * the bogus CHANNEL_REQUEST we send for keepalives.
 750          */
 751         client_alive_timeouts = 0;
 752 }
 753
 754
 755 static void
 756 server_input_stdin_data(int type, int plen, void *ctxt)
 757 {
 758         char *data;
 759         u_int data_len;
 760
 761         /* Stdin data from the client.  Append it to the buffer. */
 762         /* Ignore any data if the client has closed stdin. */
 763         if (fdin == -1)
 764                 return;
 765         data = packet_get_string(&data_len);
 766         packet_integrity_check(plen, (4 + data_len), type);
 767         buffer_append(&stdin_buffer, data, data_len);
 768         memset(data, 0, data_len);
 769         xfree(data);
 770 }
 771
 772 static void
 773 server_input_eof(int type, int plen, void *ctxt)
 774 {
 775         /*
 776          * Eof from the client.  The stdin descriptor to the
 777          * program will be closed when all buffered data has
 778          * drained.
 779          */
 780         debug("EOF received for stdin.");
 781         packet_integrity_check(plen, 0, type);
 782         stdin_eof = 1;
 783 }
 784
 785 static void
 786 server_input_window_size(int type, int plen, void *ctxt)
 787 {
 788         int row = packet_get_int();
 789         int col = packet_get_int();
 790         int xpixel = packet_get_int();
 791         int ypixel = packet_get_int();
 792
 793         debug("Window change received.");
 794         packet_integrity_check(plen, 4 * 4, type);
 795         if (fdin != -1)
 796                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 797 }
 798
 799 static Channel *
 800 server_request_direct_tcpip(char *ctype)
 801 {
 802         Channel *c;
 803         int sock;
 804         char *target, *originator;
 805         int target_port, originator_port;
 806
 807         target = packet_get_string(NULL);
 808         target_port = packet_get_int();
 809         originator = packet_get_string(NULL);
 810         originator_port = packet_get_int();
 811         packet_done();
 812
 813         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 814            originator, originator_port, target, target_port);
 815
 816         /* XXX check permission */
 817         sock = channel_connect_to(target, target_port);
 818         xfree(target);
 819         xfree(originator);
 820         if (sock < 0)
 821                 return NULL;
 822         c = channel_new(ctype, SSH_CHANNEL_CONNECTING,
 823             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 824             CHAN_TCP_PACKET_DEFAULT, 0, xstrdup("direct-tcpip"), 1);
 825         if (c == NULL) {
 826                 error("server_request_direct_tcpip: channel_new failed");
 827                 close(sock);
 828         }
 829         return c;
 830 }
 831
 832 static Channel *
 833 server_request_session(char *ctype)
 834 {
 835         Channel *c;
 836
 837         debug("input_session_request");
 838         packet_done();
 839         /*
 840          * A server session has no fd to read or write until a
 841          * CHANNEL_REQUEST for a shell is made, so we set the type to
 842          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 843          * CHANNEL_REQUEST messages is registered.
 844          */
 845         c = channel_new(ctype, SSH_CHANNEL_LARVAL,
 846             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 847             0, xstrdup("server-session"), 1);
 848         if (c == NULL) {
 849                 error("server_request_session: channel_new failed");
 850                 return NULL;
 851         }
 852         if (session_open(xxx_authctxt, c->self) != 1) {
 853                 debug("session open failed, free channel %d", c->self);
 854                 channel_free(c);
 855                 return NULL;
 856         }
 857         channel_register_callback(c->self, SSH2_MSG_CHANNEL_REQUEST,
 858             session_input_channel_req, (void *)0);
 859         channel_register_cleanup(c->self, session_close_by_channel);
 860         return c;
 861 }
 862
 863 static void
 864 server_input_channel_open(int type, int plen, void *ctxt)
 865 {
 866         Channel *c = NULL;
 867         char *ctype;
 868         u_int len;
 869         int rchan;
 870         int rmaxpack;
 871         int rwindow;
 872
 873         ctype = packet_get_string(&len);
 874         rchan = packet_get_int();
 875         rwindow = packet_get_int();
 876         rmaxpack = packet_get_int();
 877
 878         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 879             ctype, rchan, rwindow, rmaxpack);
 880
 881         if (strcmp(ctype, "session") == 0) {
 882                 c = server_request_session(ctype);
 883         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 884                 c = server_request_direct_tcpip(ctype);
 885         }
 886         if (c != NULL) {
 887                 debug("server_input_channel_open: confirm %s", ctype);
 888                 c->remote_id = rchan;
 889                 c->remote_window = rwindow;
 890                 c->remote_maxpacket = rmaxpack;
 891                 if (c->type != SSH_CHANNEL_CONNECTING) {
 892                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 893                         packet_put_int(c->remote_id);
 894                         packet_put_int(c->self);
 895                         packet_put_int(c->local_window);
 896                         packet_put_int(c->local_maxpacket);
 897                         packet_send();
 898                 }
 899         } else {
 900                 debug("server_input_channel_open: failure %s", ctype);
 901                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 902                 packet_put_int(rchan);
 903                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
 904                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
 905                         packet_put_cstring("open failed");
 906                         packet_put_cstring("");
 907                 }
 908                 packet_send();
 909         }
 910         xfree(ctype);
 911 }
 912
 913 static void
 914 server_input_global_request(int type, int plen, void *ctxt)
 915 {
 916         char *rtype;
 917         int want_reply;
 918         int success = 0;
 919
 920         rtype = packet_get_string(NULL);
 921         want_reply = packet_get_char();
 922         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 923
 924         /* -R style forwarding */
 925         if (strcmp(rtype, "tcpip-forward") == 0) {
 926                 struct passwd *pw;
 927                 char *listen_address;
 928                 u_short listen_port;
 929
 930                 pw = auth_get_user();
 931                 if (pw == NULL)
 932                         fatal("server_input_global_request: no user");
 933                 listen_address = packet_get_string(NULL); /* XXX currently ignored */
 934                 listen_port = (u_short)packet_get_int();
 935                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 936                     listen_address, listen_port);
 937
 938                 /* check permissions */
 939                 if (!options.allow_tcp_forwarding ||
 940                     no_port_forwarding_flag ||
 941                     (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)) {
 942                         success = 0;
 943                         packet_send_debug("Server has disabled port forwarding.");
 944                 } else {
 945                         /* Start listening on the port */
 946                         success = channel_request_forwarding(
 947                             listen_address, listen_port,
 948                             /*unspec host_to_connect*/ "<unspec host>",
 949                             /*unspec port_to_connect*/ 0,
 950                             options.gateway_ports, /*remote*/ 1);
 951                 }
 952                 xfree(listen_address);
 953         }
 954         if (want_reply) {
 955                 packet_start(success ?
 956                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 957                 packet_send();
 958                 packet_write_wait();
 959         }
 960         xfree(rtype);
 961 }
 962
 963 static void
 964 server_init_dispatch_20(void)
 965 {
 966         debug("server_init_dispatch_20");
 967         dispatch_init(&dispatch_protocol_error);
 968         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 969         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 970         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 971         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 972         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 973         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 974         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 975         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request);
 976         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 977         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 978         /* client_alive */
 979         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_channel_failure);
 980         /* rekeying */
 981         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 982 }
 983 static void
 984 server_init_dispatch_13(void)
 985 {
 986         debug("server_init_dispatch_13");
 987         dispatch_init(NULL);
 988         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
 989         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
 990         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
 991         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
 992         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
 993         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
 994         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 995         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 996         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
 997 }
 998 static void
 999 server_init_dispatch_15(void)
1000 {
1001         server_init_dispatch_13();
1002         debug("server_init_dispatch_15");
1003         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1004         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1005 }
1006 static void
1007 server_init_dispatch(void)
1008 {
1009         if (compat20)
1010                 server_init_dispatch_20();
1011         else if (compat13)
1012                 server_init_dispatch_13();
1013         else
1014                 server_init_dispatch_15();
1015 }