crypto/openssh-4/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.145 2006/10/11 12:38:03 markus 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/param.h>
  42 #include <sys/wait.h>
  43 #include <sys/socket.h>
  44 #ifdef HAVE_SYS_TIME_H
  45 # include <sys/time.h>
  46 #endif
  47
  48 #include <netinet/in.h>
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <pwd.h>
  53 #include <signal.h>
  54 #include <string.h>
  55 #include <termios.h>
  56 #include <unistd.h>
  57 #include <stdarg.h>
  58
  59 #include "xmalloc.h"
  60 #include "packet.h"
  61 #include "buffer.h"
  62 #include "log.h"
  63 #include "servconf.h"
  64 #include "canohost.h"
  65 #include "sshpty.h"
  66 #include "channels.h"
  67 #include "compat.h"
  68 #include "ssh1.h"
  69 #include "ssh2.h"
  70 #include "key.h"
  71 #include "cipher.h"
  72 #include "kex.h"
  73 #include "hostfile.h"
  74 #include "auth.h"
  75 #include "session.h"
  76 #include "dispatch.h"
  77 #include "auth-options.h"
  78 #include "serverloop.h"
  79 #include "misc.h"
  80
  81 extern ServerOptions options;
  82
  83 /* XXX */
  84 extern Kex *xxx_kex;
  85 extern Authctxt *the_authctxt;
  86 extern int use_privsep;
  87
  88 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  89 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  90 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  91 static int fdin;                /* Descriptor for stdin (for writing) */
  92 static int fdout;               /* Descriptor for stdout (for reading);
  93                                    May be same number as fdin. */
  94 static int fderr;               /* Descriptor for stderr.  May be -1. */
  95 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  96 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  97 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  98 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  99 static int stdin_eof = 0;       /* EOF message received from client. */
 100 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
 101 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
 102 static int fdin_is_tty = 0;     /* fdin points to a tty. */
 103 static int connection_in;       /* Connection to client (input). */
 104 static int connection_out;      /* Connection to client (output). */
 105 static int connection_closed = 0;       /* Connection to client closed. */
 106 static u_int buffer_high;       /* "Soft" max buffer size. */
 107 static int client_alive_timeouts = 0;
 108
 109 /*
 110  * This SIGCHLD kludge is used to detect when the child exits.  The server
 111  * will exit after that, as soon as forwarded connections have terminated.
 112  */
 113
 114 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 115
 116 /* Cleanup on signals (!use_privsep case only) */
 117 static volatile sig_atomic_t received_sigterm = 0;
 118
 119 /* prototypes */
 120 static void server_init_dispatch(void);
 121
 122 /*
 123  * we write to this pipe if a SIGCHLD is caught in order to avoid
 124  * the race between select() and child_terminated
 125  */
 126 static int notify_pipe[2];
 127 static void
 128 notify_setup(void)
 129 {
 130         if (pipe(notify_pipe) < 0) {
 131                 error("pipe(notify_pipe) failed %s", strerror(errno));
 132         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 133             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 134                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 135                 close(notify_pipe[0]);
 136                 close(notify_pipe[1]);
 137         } else {
 138                 set_nonblock(notify_pipe[0]);
 139                 set_nonblock(notify_pipe[1]);
 140                 return;
 141         }
 142         notify_pipe[0] = -1;    /* read end */
 143         notify_pipe[1] = -1;    /* write end */
 144 }
 145 static void
 146 notify_parent(void)
 147 {
 148         if (notify_pipe[1] != -1)
 149                 write(notify_pipe[1], "", 1);
 150 }
 151 static void
 152 notify_prepare(fd_set *readset)
 153 {
 154         if (notify_pipe[0] != -1)
 155                 FD_SET(notify_pipe[0], readset);
 156 }
 157 static void
 158 notify_done(fd_set *readset)
 159 {
 160         char c;
 161
 162         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 163                 while (read(notify_pipe[0], &c, 1) != -1)
 164                         debug2("notify_done: reading");
 165 }
 166
 167 /*ARGSUSED*/
 168 static void
 169 sigchld_handler(int sig)
 170 {
 171         int save_errno = errno;
 172         child_terminated = 1;
 173 #ifndef _UNICOS
 174         mysignal(SIGCHLD, sigchld_handler);
 175 #endif
 176         notify_parent();
 177         errno = save_errno;
 178 }
 179
 180 /*ARGSUSED*/
 181 static void
 182 sigterm_handler(int sig)
 183 {
 184         received_sigterm = sig;
 185 }
 186
 187 /*
 188  * Make packets from buffered stderr data, and buffer it for sending
 189  * to the client.
 190  */
 191 static void
 192 make_packets_from_stderr_data(void)
 193 {
 194         u_int len;
 195
 196         /* Send buffered stderr data to the client. */
 197         while (buffer_len(&stderr_buffer) > 0 &&
 198             packet_not_very_much_data_to_write()) {
 199                 len = buffer_len(&stderr_buffer);
 200                 if (packet_is_interactive()) {
 201                         if (len > 512)
 202                                 len = 512;
 203                 } else {
 204                         /* Keep the packets at reasonable size. */
 205                         if (len > packet_get_maxsize())
 206                                 len = packet_get_maxsize();
 207                 }
 208                 packet_start(SSH_SMSG_STDERR_DATA);
 209                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 210                 packet_send();
 211                 buffer_consume(&stderr_buffer, len);
 212                 stderr_bytes += len;
 213         }
 214 }
 215
 216 /*
 217  * Make packets from buffered stdout data, and buffer it for sending to the
 218  * client.
 219  */
 220 static void
 221 make_packets_from_stdout_data(void)
 222 {
 223         u_int len;
 224
 225         /* Send buffered stdout data to the client. */
 226         while (buffer_len(&stdout_buffer) > 0 &&
 227             packet_not_very_much_data_to_write()) {
 228                 len = buffer_len(&stdout_buffer);
 229                 if (packet_is_interactive()) {
 230                         if (len > 512)
 231                                 len = 512;
 232                 } else {
 233                         /* Keep the packets at reasonable size. */
 234                         if (len > packet_get_maxsize())
 235                                 len = packet_get_maxsize();
 236                 }
 237                 packet_start(SSH_SMSG_STDOUT_DATA);
 238                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 239                 packet_send();
 240                 buffer_consume(&stdout_buffer, len);
 241                 stdout_bytes += len;
 242         }
 243 }
 244
 245 static void
 246 client_alive_check(void)
 247 {
 248         int channel_id;
 249
 250         /* timeout, check to see how many we have had */
 251         if (++client_alive_timeouts > options.client_alive_count_max) {
 252                 logit("Timeout, client not responding.");
 253                 cleanup_exit(255);
 254         }
 255
 256         /*
 257          * send a bogus global/channel request with "wantreply",
 258          * we should get back a failure
 259          */
 260         if ((channel_id = channel_find_open()) == -1) {
 261                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 262                 packet_put_cstring("keepalive@openssh.com");
 263                 packet_put_char(1);     /* boolean: want reply */
 264         } else {
 265                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 266         }
 267         packet_send();
 268 }
 269
 270 /*
 271  * Sleep in select() until we can do something.  This will initialize the
 272  * select masks.  Upon return, the masks will indicate which descriptors
 273  * have data or can accept data.  Optionally, a maximum time can be specified
 274  * for the duration of the wait (0 = infinite).
 275  */
 276 static void
 277 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 278     u_int *nallocp, u_int max_time_milliseconds)
 279 {
 280         struct timeval tv, *tvp;
 281         int ret;
 282         int client_alive_scheduled = 0;
 283         int program_alive_scheduled = 0;
 284
 285         /*
 286          * if using client_alive, set the max timeout accordingly,
 287          * and indicate that this particular timeout was for client
 288          * alive by setting the client_alive_scheduled flag.
 289          *
 290          * this could be randomized somewhat to make traffic
 291          * analysis more difficult, but we're not doing it yet.
 292          */
 293         if (compat20 &&
 294             max_time_milliseconds == 0 && options.client_alive_interval) {
 295                 client_alive_scheduled = 1;
 296                 max_time_milliseconds = options.client_alive_interval * 1000;
 297         }
 298
 299         /* Allocate and update select() masks for channel descriptors. */
 300         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 301
 302         if (compat20) {
 303 #if 0
 304                 /* wrong: bad condition XXX */
 305                 if (channel_not_very_much_buffered_data())
 306 #endif
 307                 FD_SET(connection_in, *readsetp);
 308         } else {
 309                 /*
 310                  * Read packets from the client unless we have too much
 311                  * buffered stdin or channel data.
 312                  */
 313                 if (buffer_len(&stdin_buffer) < buffer_high &&
 314                     channel_not_very_much_buffered_data())
 315                         FD_SET(connection_in, *readsetp);
 316                 /*
 317                  * If there is not too much data already buffered going to
 318                  * the client, try to get some more data from the program.
 319                  */
 320                 if (packet_not_very_much_data_to_write()) {
 321                         program_alive_scheduled = child_terminated;
 322                         if (!fdout_eof)
 323                                 FD_SET(fdout, *readsetp);
 324                         if (!fderr_eof)
 325                                 FD_SET(fderr, *readsetp);
 326                 }
 327                 /*
 328                  * If we have buffered data, try to write some of that data
 329                  * to the program.
 330                  */
 331                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 332                         FD_SET(fdin, *writesetp);
 333         }
 334         notify_prepare(*readsetp);
 335
 336         /*
 337          * If we have buffered packet data going to the client, mark that
 338          * descriptor.
 339          */
 340         if (packet_have_data_to_write())
 341                 FD_SET(connection_out, *writesetp);
 342
 343         /*
 344          * If child has terminated and there is enough buffer space to read
 345          * from it, then read as much as is available and exit.
 346          */
 347         if (child_terminated && packet_not_very_much_data_to_write())
 348                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 349                         max_time_milliseconds = 100;
 350
 351         if (max_time_milliseconds == 0)
 352                 tvp = NULL;
 353         else {
 354                 tv.tv_sec = max_time_milliseconds / 1000;
 355                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 356                 tvp = &tv;
 357         }
 358
 359         /* Wait for something to happen, or the timeout to expire. */
 360         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 361
 362         if (ret == -1) {
 363                 memset(*readsetp, 0, *nallocp);
 364                 memset(*writesetp, 0, *nallocp);
 365                 if (errno != EINTR)
 366                         error("select: %.100s", strerror(errno));
 367         } else {
 368                 if (ret == 0 && client_alive_scheduled)
 369                         client_alive_check();
 370                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 371                         if (!fdout_eof)
 372                                 FD_SET(fdout, *readsetp);
 373                         if (!fderr_eof)
 374                                 FD_SET(fderr, *readsetp);
 375                 }
 376         }
 377
 378         notify_done(*readsetp);
 379 }
 380
 381 /*
 382  * Processes input from the client and the program.  Input data is stored
 383  * in buffers and processed later.
 384  */
 385 static void
 386 process_input(fd_set *readset)
 387 {
 388         int len;
 389         char buf[16384];
 390
 391         /* Read and buffer any input data from the client. */
 392         if (FD_ISSET(connection_in, readset)) {
 393                 len = read(connection_in, buf, sizeof(buf));
 394                 if (len == 0) {
 395                         verbose("Connection closed by %.100s",
 396                             get_remote_ipaddr());
 397                         connection_closed = 1;
 398                         if (compat20)
 399                                 return;
 400                         cleanup_exit(255);
 401                 } else if (len < 0) {
 402                         if (errno != EINTR && errno != EAGAIN) {
 403                                 verbose("Read error from remote host "
 404                                     "%.100s: %.100s",
 405                                     get_remote_ipaddr(), strerror(errno));
 406                                 cleanup_exit(255);
 407                         }
 408                 } else {
 409                         /* Buffer any received data. */
 410                         packet_process_incoming(buf, len);
 411                 }
 412         }
 413         if (compat20)
 414                 return;
 415
 416         /* Read and buffer any available stdout data from the program. */
 417         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 418                 errno = 0;
 419                 len = read(fdout, buf, sizeof(buf));
 420                 if (len < 0 && (errno == EINTR ||
 421                     (errno == EAGAIN && !child_terminated))) {
 422                         /* do nothing */
 423 #ifndef PTY_ZEROREAD
 424                 } else if (len <= 0) {
 425 #else
 426                 } else if ((!isatty(fdout) && len <= 0) ||
 427                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 428 #endif
 429                         fdout_eof = 1;
 430                 } else {
 431                         buffer_append(&stdout_buffer, buf, len);
 432                         fdout_bytes += len;
 433                 }
 434         }
 435         /* Read and buffer any available stderr data from the program. */
 436         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 437                 errno = 0;
 438                 len = read(fderr, buf, sizeof(buf));
 439                 if (len < 0 && (errno == EINTR ||
 440                     (errno == EAGAIN && !child_terminated))) {
 441                         /* do nothing */
 442 #ifndef PTY_ZEROREAD
 443                 } else if (len <= 0) {
 444 #else
 445                 } else if ((!isatty(fderr) && len <= 0) ||
 446                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 447 #endif
 448                         fderr_eof = 1;
 449                 } else {
 450                         buffer_append(&stderr_buffer, buf, len);
 451                 }
 452         }
 453 }
 454
 455 /*
 456  * Sends data from internal buffers to client program stdin.
 457  */
 458 static void
 459 process_output(fd_set *writeset)
 460 {
 461         struct termios tio;
 462         u_char *data;
 463         u_int dlen;
 464         int len;
 465
 466         /* Write buffered data to program stdin. */
 467         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 468                 data = buffer_ptr(&stdin_buffer);
 469                 dlen = buffer_len(&stdin_buffer);
 470                 len = write(fdin, data, dlen);
 471                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 472                         /* do nothing */
 473                 } else if (len <= 0) {
 474                         if (fdin != fdout)
 475                                 close(fdin);
 476                         else
 477                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 478                         fdin = -1;
 479                 } else {
 480                         /* Successful write. */
 481                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 482                             tcgetattr(fdin, &tio) == 0 &&
 483                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 484                                 /*
 485                                  * Simulate echo to reduce the impact of
 486                                  * traffic analysis
 487                                  */
 488                                 packet_send_ignore(len);
 489                                 packet_send();
 490                         }
 491                         /* Consume the data from the buffer. */
 492                         buffer_consume(&stdin_buffer, len);
 493                         /* Update the count of bytes written to the program. */
 494                         stdin_bytes += len;
 495                 }
 496         }
 497         /* Send any buffered packet data to the client. */
 498         if (FD_ISSET(connection_out, writeset))
 499                 packet_write_poll();
 500 }
 501
 502 /*
 503  * Wait until all buffered output has been sent to the client.
 504  * This is used when the program terminates.
 505  */
 506 static void
 507 drain_output(void)
 508 {
 509         /* Send any buffered stdout data to the client. */
 510         if (buffer_len(&stdout_buffer) > 0) {
 511                 packet_start(SSH_SMSG_STDOUT_DATA);
 512                 packet_put_string(buffer_ptr(&stdout_buffer),
 513                                   buffer_len(&stdout_buffer));
 514                 packet_send();
 515                 /* Update the count of sent bytes. */
 516                 stdout_bytes += buffer_len(&stdout_buffer);
 517         }
 518         /* Send any buffered stderr data to the client. */
 519         if (buffer_len(&stderr_buffer) > 0) {
 520                 packet_start(SSH_SMSG_STDERR_DATA);
 521                 packet_put_string(buffer_ptr(&stderr_buffer),
 522                                   buffer_len(&stderr_buffer));
 523                 packet_send();
 524                 /* Update the count of sent bytes. */
 525                 stderr_bytes += buffer_len(&stderr_buffer);
 526         }
 527         /* Wait until all buffered data has been written to the client. */
 528         packet_write_wait();
 529 }
 530
 531 static void
 532 process_buffered_input_packets(void)
 533 {
 534         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 535 }
 536
 537 /*
 538  * Performs the interactive session.  This handles data transmission between
 539  * the client and the program.  Note that the notion of stdin, stdout, and
 540  * stderr in this function is sort of reversed: this function writes to
 541  * stdin (of the child program), and reads from stdout and stderr (of the
 542  * child program).
 543  */
 544 void
 545 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 546 {
 547         fd_set *readset = NULL, *writeset = NULL;
 548         int max_fd = 0;
 549         u_int nalloc = 0;
 550         int wait_status;        /* Status returned by wait(). */
 551         pid_t wait_pid;         /* pid returned by wait(). */
 552         int waiting_termination = 0;    /* Have displayed waiting close message. */
 553         u_int max_time_milliseconds;
 554         u_int previous_stdout_buffer_bytes;
 555         u_int stdout_buffer_bytes;
 556         int type;
 557
 558         debug("Entering interactive session.");
 559
 560         /* Initialize the SIGCHLD kludge. */
 561         child_terminated = 0;
 562         mysignal(SIGCHLD, sigchld_handler);
 563
 564         if (!use_privsep) {
 565                 signal(SIGTERM, sigterm_handler);
 566                 signal(SIGINT, sigterm_handler);
 567                 signal(SIGQUIT, sigterm_handler);
 568         }
 569
 570         /* Initialize our global variables. */
 571         fdin = fdin_arg;
 572         fdout = fdout_arg;
 573         fderr = fderr_arg;
 574
 575         /* nonblocking IO */
 576         set_nonblock(fdin);
 577         set_nonblock(fdout);
 578         /* we don't have stderr for interactive terminal sessions, see below */
 579         if (fderr != -1)
 580                 set_nonblock(fderr);
 581
 582         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 583                 fdin_is_tty = 1;
 584
 585         connection_in = packet_get_connection_in();
 586         connection_out = packet_get_connection_out();
 587
 588         notify_setup();
 589
 590         previous_stdout_buffer_bytes = 0;
 591
 592         /* Set approximate I/O buffer size. */
 593         if (packet_is_interactive())
 594                 buffer_high = 4096;
 595         else
 596                 buffer_high = 64 * 1024;
 597
 598 #if 0
 599         /* Initialize max_fd to the maximum of the known file descriptors. */
 600         max_fd = MAX(connection_in, connection_out);
 601         max_fd = MAX(max_fd, fdin);
 602         max_fd = MAX(max_fd, fdout);
 603         if (fderr != -1)
 604                 max_fd = MAX(max_fd, fderr);
 605 #endif
 606
 607         /* Initialize Initialize buffers. */
 608         buffer_init(&stdin_buffer);
 609         buffer_init(&stdout_buffer);
 610         buffer_init(&stderr_buffer);
 611
 612         /*
 613          * If we have no separate fderr (which is the case when we have a pty
 614          * - there we cannot make difference between data sent to stdout and
 615          * stderr), indicate that we have seen an EOF from stderr.  This way
 616          * we don't need to check the descriptor everywhere.
 617          */
 618         if (fderr == -1)
 619                 fderr_eof = 1;
 620
 621         server_init_dispatch();
 622
 623         /* Main loop of the server for the interactive session mode. */
 624         for (;;) {
 625
 626                 /* Process buffered packets from the client. */
 627                 process_buffered_input_packets();
 628
 629                 /*
 630                  * If we have received eof, and there is no more pending
 631                  * input data, cause a real eof by closing fdin.
 632                  */
 633                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 634                         if (fdin != fdout)
 635                                 close(fdin);
 636                         else
 637                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 638                         fdin = -1;
 639                 }
 640                 /* Make packets from buffered stderr data to send to the client. */
 641                 make_packets_from_stderr_data();
 642
 643                 /*
 644                  * Make packets from buffered stdout data to send to the
 645                  * client. If there is very little to send, this arranges to
 646                  * not send them now, but to wait a short while to see if we
 647                  * are getting more data. This is necessary, as some systems
 648                  * wake up readers from a pty after each separate character.
 649                  */
 650                 max_time_milliseconds = 0;
 651                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 652                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 653                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 654                         /* try again after a while */
 655                         max_time_milliseconds = 10;
 656                 } else {
 657                         /* Send it now. */
 658                         make_packets_from_stdout_data();
 659                 }
 660                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 661
 662                 /* Send channel data to the client. */
 663                 if (packet_not_very_much_data_to_write())
 664                         channel_output_poll();
 665
 666                 /*
 667                  * Bail out of the loop if the program has closed its output
 668                  * descriptors, and we have no more data to send to the
 669                  * client, and there is no pending buffered data.
 670                  */
 671                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 672                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 673                         if (!channel_still_open())
 674                                 break;
 675                         if (!waiting_termination) {
 676                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 677                                 char *cp;
 678                                 waiting_termination = 1;
 679                                 buffer_append(&stderr_buffer, s, strlen(s));
 680
 681                                 /* Display list of open channels. */
 682                                 cp = channel_open_message();
 683                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 684                                 xfree(cp);
 685                         }
 686                 }
 687                 max_fd = MAX(connection_in, connection_out);
 688                 max_fd = MAX(max_fd, fdin);
 689                 max_fd = MAX(max_fd, fdout);
 690                 max_fd = MAX(max_fd, fderr);
 691                 max_fd = MAX(max_fd, notify_pipe[0]);
 692
 693                 /* Sleep in select() until we can do something. */
 694                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 695                     &nalloc, max_time_milliseconds);
 696
 697                 if (received_sigterm) {
 698                         logit("Exiting on signal %d", received_sigterm);
 699                         /* Clean up sessions, utmp, etc. */
 700                         cleanup_exit(255);
 701                 }
 702
 703                 /* Process any channel events. */
 704                 channel_after_select(readset, writeset);
 705
 706                 /* Process input from the client and from program stdout/stderr. */
 707                 process_input(readset);
 708
 709                 /* Process output to the client and to program stdin. */
 710                 process_output(writeset);
 711         }
 712         if (readset)
 713                 xfree(readset);
 714         if (writeset)
 715                 xfree(writeset);
 716
 717         /* Cleanup and termination code. */
 718
 719         /* Wait until all output has been sent to the client. */
 720         drain_output();
 721
 722         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 723             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 724
 725         /* Free and clear the buffers. */
 726         buffer_free(&stdin_buffer);
 727         buffer_free(&stdout_buffer);
 728         buffer_free(&stderr_buffer);
 729
 730         /* Close the file descriptors. */
 731         if (fdout != -1)
 732                 close(fdout);
 733         fdout = -1;
 734         fdout_eof = 1;
 735         if (fderr != -1)
 736                 close(fderr);
 737         fderr = -1;
 738         fderr_eof = 1;
 739         if (fdin != -1)
 740                 close(fdin);
 741         fdin = -1;
 742
 743         channel_free_all();
 744
 745         /* We no longer want our SIGCHLD handler to be called. */
 746         mysignal(SIGCHLD, SIG_DFL);
 747
 748         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 749                 if (errno != EINTR)
 750                         packet_disconnect("wait: %.100s", strerror(errno));
 751         if (wait_pid != pid)
 752                 error("Strange, wait returned pid %ld, expected %ld",
 753                     (long)wait_pid, (long)pid);
 754
 755         /* Check if it exited normally. */
 756         if (WIFEXITED(wait_status)) {
 757                 /* Yes, normal exit.  Get exit status and send it to the client. */
 758                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 759                 packet_start(SSH_SMSG_EXITSTATUS);
 760                 packet_put_int(WEXITSTATUS(wait_status));
 761                 packet_send();
 762                 packet_write_wait();
 763
 764                 /*
 765                  * Wait for exit confirmation.  Note that there might be
 766                  * other packets coming before it; however, the program has
 767                  * already died so we just ignore them.  The client is
 768                  * supposed to respond with the confirmation when it receives
 769                  * the exit status.
 770                  */
 771                 do {
 772                         type = packet_read();
 773                 }
 774                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 775
 776                 debug("Received exit confirmation.");
 777                 return;
 778         }
 779         /* Check if the program terminated due to a signal. */
 780         if (WIFSIGNALED(wait_status))
 781                 packet_disconnect("Command terminated on signal %d.",
 782                                   WTERMSIG(wait_status));
 783
 784         /* Some weird exit cause.  Just exit. */
 785         packet_disconnect("wait returned status %04x.", wait_status);
 786         /* NOTREACHED */
 787 }
 788
 789 static void
 790 collect_children(void)
 791 {
 792         pid_t pid;
 793         sigset_t oset, nset;
 794         int status;
 795
 796         /* block SIGCHLD while we check for dead children */
 797         sigemptyset(&nset);
 798         sigaddset(&nset, SIGCHLD);
 799         sigprocmask(SIG_BLOCK, &nset, &oset);
 800         if (child_terminated) {
 801                 debug("Received SIGCHLD.");
 802                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 803                     (pid < 0 && errno == EINTR))
 804                         if (pid > 0)
 805                                 session_close_by_pid(pid, status);
 806                 child_terminated = 0;
 807         }
 808         sigprocmask(SIG_SETMASK, &oset, NULL);
 809 }
 810
 811 void
 812 server_loop2(Authctxt *authctxt)
 813 {
 814         fd_set *readset = NULL, *writeset = NULL;
 815         int rekeying = 0, max_fd, nalloc = 0;
 816
 817         debug("Entering interactive session for SSH2.");
 818
 819         mysignal(SIGCHLD, sigchld_handler);
 820         child_terminated = 0;
 821         connection_in = packet_get_connection_in();
 822         connection_out = packet_get_connection_out();
 823
 824         if (!use_privsep) {
 825                 signal(SIGTERM, sigterm_handler);
 826                 signal(SIGINT, sigterm_handler);
 827                 signal(SIGQUIT, sigterm_handler);
 828         }
 829
 830         notify_setup();
 831
 832         max_fd = MAX(connection_in, connection_out);
 833         max_fd = MAX(max_fd, notify_pipe[0]);
 834
 835         server_init_dispatch();
 836
 837         for (;;) {
 838                 process_buffered_input_packets();
 839
 840                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 841
 842                 if (!rekeying && packet_not_very_much_data_to_write())
 843                         channel_output_poll();
 844                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 845                     &nalloc, 0);
 846
 847                 if (received_sigterm) {
 848                         logit("Exiting on signal %d", received_sigterm);
 849                         /* Clean up sessions, utmp, etc. */
 850                         cleanup_exit(255);
 851                 }
 852
 853                 collect_children();
 854                 if (!rekeying) {
 855                         channel_after_select(readset, writeset);
 856                         if (packet_need_rekeying()) {
 857                                 debug("need rekeying");
 858                                 xxx_kex->done = 0;
 859                                 kex_send_kexinit(xxx_kex);
 860                         }
 861                 }
 862                 process_input(readset);
 863                 if (connection_closed)
 864                         break;
 865                 process_output(writeset);
 866         }
 867         collect_children();
 868
 869         if (readset)
 870                 xfree(readset);
 871         if (writeset)
 872                 xfree(writeset);
 873
 874         /* free all channels, no more reads and writes */
 875         channel_free_all();
 876
 877         /* free remaining sessions, e.g. remove wtmp entries */
 878         session_destroy_all(NULL);
 879 }
 880
 881 static void
 882 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 883 {
 884         debug("Got %d/%u for keepalive", type, seq);
 885         /*
 886          * reset timeout, since we got a sane answer from the client.
 887          * even if this was generated by something other than
 888          * the bogus CHANNEL_REQUEST we send for keepalives.
 889          */
 890         client_alive_timeouts = 0;
 891 }
 892
 893 static void
 894 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 895 {
 896         char *data;
 897         u_int data_len;
 898
 899         /* Stdin data from the client.  Append it to the buffer. */
 900         /* Ignore any data if the client has closed stdin. */
 901         if (fdin == -1)
 902                 return;
 903         data = packet_get_string(&data_len);
 904         packet_check_eom();
 905         buffer_append(&stdin_buffer, data, data_len);
 906         memset(data, 0, data_len);
 907         xfree(data);
 908 }
 909
 910 static void
 911 server_input_eof(int type, u_int32_t seq, void *ctxt)
 912 {
 913         /*
 914          * Eof from the client.  The stdin descriptor to the
 915          * program will be closed when all buffered data has
 916          * drained.
 917          */
 918         debug("EOF received for stdin.");
 919         packet_check_eom();
 920         stdin_eof = 1;
 921 }
 922
 923 static void
 924 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 925 {
 926         u_int row = packet_get_int();
 927         u_int col = packet_get_int();
 928         u_int xpixel = packet_get_int();
 929         u_int ypixel = packet_get_int();
 930
 931         debug("Window change received.");
 932         packet_check_eom();
 933         if (fdin != -1)
 934                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 935 }
 936
 937 static Channel *
 938 server_request_direct_tcpip(void)
 939 {
 940         Channel *c;
 941         int sock;
 942         char *target, *originator;
 943         int target_port, originator_port;
 944
 945         target = packet_get_string(NULL);
 946         target_port = packet_get_int();
 947         originator = packet_get_string(NULL);
 948         originator_port = packet_get_int();
 949         packet_check_eom();
 950
 951         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 952             originator, originator_port, target, target_port);
 953
 954         /* XXX check permission */
 955         sock = channel_connect_to(target, target_port);
 956         xfree(target);
 957         xfree(originator);
 958         if (sock < 0)
 959                 return NULL;
 960         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 961             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 962             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 963         return c;
 964 }
 965
 966 static Channel *
 967 server_request_tun(void)
 968 {
 969         Channel *c = NULL;
 970         int mode, tun;
 971         int sock;
 972
 973         mode = packet_get_int();
 974         switch (mode) {
 975         case SSH_TUNMODE_POINTOPOINT:
 976         case SSH_TUNMODE_ETHERNET:
 977                 break;
 978         default:
 979                 packet_send_debug("Unsupported tunnel device mode.");
 980                 return NULL;
 981         }
 982         if ((options.permit_tun & mode) == 0) {
 983                 packet_send_debug("Server has rejected tunnel device "
 984                     "forwarding");
 985                 return NULL;
 986         }
 987
 988         tun = packet_get_int();
 989         if (forced_tun_device != -1) {
 990                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 991                         goto done;
 992                 tun = forced_tun_device;
 993         }
 994         sock = tun_open(tun, mode);
 995         if (sock < 0)
 996                 goto done;
 997         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 998             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 999         c->datagram = 1;
1000 #if defined(SSH_TUN_FILTER)
1001         if (mode == SSH_TUNMODE_POINTOPOINT)
1002                 channel_register_filter(c->self, sys_tun_infilter,
1003                     sys_tun_outfilter);
1004 #endif
1005
1006  done:
1007         if (c == NULL)
1008                 packet_send_debug("Failed to open the tunnel device.");
1009         return c;
1010 }
1011
1012 static Channel *
1013 server_request_session(void)
1014 {
1015         Channel *c;
1016
1017         debug("input_session_request");
1018         packet_check_eom();
1019         /*
1020          * A server session has no fd to read or write until a
1021          * CHANNEL_REQUEST for a shell is made, so we set the type to
1022          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1023          * CHANNEL_REQUEST messages is registered.
1024          */
1025         c = channel_new("session", SSH_CHANNEL_LARVAL,
1026             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1027             0, "server-session", 1);
1028         if (session_open(the_authctxt, c->self) != 1) {
1029                 debug("session open failed, free channel %d", c->self);
1030                 channel_free(c);
1031                 return NULL;
1032         }
1033         channel_register_cleanup(c->self, session_close_by_channel, 0);
1034         return c;
1035 }
1036
1037 static void
1038 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1039 {
1040         Channel *c = NULL;
1041         char *ctype;
1042         int rchan;
1043         u_int rmaxpack, rwindow, len;
1044
1045         ctype = packet_get_string(&len);
1046         rchan = packet_get_int();
1047         rwindow = packet_get_int();
1048         rmaxpack = packet_get_int();
1049
1050         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1051             ctype, rchan, rwindow, rmaxpack);
1052
1053         if (strcmp(ctype, "session") == 0) {
1054                 c = server_request_session();
1055         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1056                 c = server_request_direct_tcpip();
1057         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1058                 c = server_request_tun();
1059         }
1060         if (c != NULL) {
1061                 debug("server_input_channel_open: confirm %s", ctype);
1062                 c->remote_id = rchan;
1063                 c->remote_window = rwindow;
1064                 c->remote_maxpacket = rmaxpack;
1065                 if (c->type != SSH_CHANNEL_CONNECTING) {
1066                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1067                         packet_put_int(c->remote_id);
1068                         packet_put_int(c->self);
1069                         packet_put_int(c->local_window);
1070                         packet_put_int(c->local_maxpacket);
1071                         packet_send();
1072                 }
1073         } else {
1074                 debug("server_input_channel_open: failure %s", ctype);
1075                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1076                 packet_put_int(rchan);
1077                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1078                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1079                         packet_put_cstring("open failed");
1080                         packet_put_cstring("");
1081                 }
1082                 packet_send();
1083         }
1084         xfree(ctype);
1085 }
1086
1087 static void
1088 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1089 {
1090         char *rtype;
1091         int want_reply;
1092         int success = 0;
1093
1094         rtype = packet_get_string(NULL);
1095         want_reply = packet_get_char();
1096         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1097
1098         /* -R style forwarding */
1099         if (strcmp(rtype, "tcpip-forward") == 0) {
1100                 struct passwd *pw;
1101                 char *listen_address;
1102                 u_short listen_port;
1103
1104                 pw = the_authctxt->pw;
1105                 if (pw == NULL || !the_authctxt->valid)
1106                         fatal("server_input_global_request: no/invalid user");
1107                 listen_address = packet_get_string(NULL);
1108                 listen_port = (u_short)packet_get_int();
1109                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1110                     listen_address, listen_port);
1111
1112                 /* check permissions */
1113                 if (!options.allow_tcp_forwarding ||
1114                     no_port_forwarding_flag
1115 #ifndef NO_IPPORT_RESERVED_CONCEPT
1116                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1117 #endif
1118                     ) {
1119                         success = 0;
1120                         packet_send_debug("Server has disabled port forwarding.");
1121                 } else {
1122                         /* Start listening on the port */
1123                         success = channel_setup_remote_fwd_listener(
1124                             listen_address, listen_port, options.gateway_ports);
1125                 }
1126                 xfree(listen_address);
1127         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1128                 char *cancel_address;
1129                 u_short cancel_port;
1130
1131                 cancel_address = packet_get_string(NULL);
1132                 cancel_port = (u_short)packet_get_int();
1133                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1134                     cancel_address, cancel_port);
1135
1136                 success = channel_cancel_rport_listener(cancel_address,
1137                     cancel_port);
1138                 xfree(cancel_address);
1139         }
1140         if (want_reply) {
1141                 packet_start(success ?
1142                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1143                 packet_send();
1144                 packet_write_wait();
1145         }
1146         xfree(rtype);
1147 }
1148
1149 static void
1150 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1151 {
1152         Channel *c;
1153         int id, reply, success = 0;
1154         char *rtype;
1155
1156         id = packet_get_int();
1157         rtype = packet_get_string(NULL);
1158         reply = packet_get_char();
1159
1160         debug("server_input_channel_req: channel %d request %s reply %d",
1161             id, rtype, reply);
1162
1163         if ((c = channel_lookup(id)) == NULL)
1164                 packet_disconnect("server_input_channel_req: "
1165                     "unknown channel %d", id);
1166         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1167                 success = session_input_channel_req(c, rtype);
1168         if (reply) {
1169                 packet_start(success ?
1170                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1171                 packet_put_int(c->remote_id);
1172                 packet_send();
1173         }
1174         xfree(rtype);
1175 }
1176
1177 static void
1178 server_init_dispatch_20(void)
1179 {
1180         debug("server_init_dispatch_20");
1181         dispatch_init(&dispatch_protocol_error);
1182         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1183         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1184         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1185         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1186         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1187         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1188         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1189         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1190         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1191         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1192         /* client_alive */
1193         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1194         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1195         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1196         /* rekeying */
1197         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1198 }
1199 static void
1200 server_init_dispatch_13(void)
1201 {
1202         debug("server_init_dispatch_13");
1203         dispatch_init(NULL);
1204         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1205         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1206         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1207         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1208         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1209         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1210         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1211         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1212         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1213 }
1214 static void
1215 server_init_dispatch_15(void)
1216 {
1217         server_init_dispatch_13();
1218         debug("server_init_dispatch_15");
1219         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1220         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1221 }
1222 static void
1223 server_init_dispatch(void)
1224 {
1225         if (compat20)
1226                 server_init_dispatch_20();
1227         else if (compat13)
1228                 server_init_dispatch_13();
1229         else
1230                 server_init_dispatch_15();
1231 }