crypto/openssh-5/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.153 2008/06/30 12:15:39 djm 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 "openbsd-compat/sys-queue.h"
  60 #include "xmalloc.h"
  61 #include "packet.h"
  62 #include "buffer.h"
  63 #include "log.h"
  64 #include "servconf.h"
  65 #include "canohost.h"
  66 #include "sshpty.h"
  67 #include "channels.h"
  68 #include "compat.h"
  69 #include "ssh1.h"
  70 #include "ssh2.h"
  71 #include "key.h"
  72 #include "cipher.h"
  73 #include "kex.h"
  74 #include "hostfile.h"
  75 #include "auth.h"
  76 #include "session.h"
  77 #include "dispatch.h"
  78 #include "auth-options.h"
  79 #include "serverloop.h"
  80 #include "misc.h"
  81
  82 extern ServerOptions options;
  83
  84 /* XXX */
  85 extern Kex *xxx_kex;
  86 extern Authctxt *the_authctxt;
  87 extern int use_privsep;
  88
  89 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  90 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  91 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  92 static int fdin;                /* Descriptor for stdin (for writing) */
  93 static int fdout;               /* Descriptor for stdout (for reading);
  94                                    May be same number as fdin. */
  95 static int fderr;               /* Descriptor for stderr.  May be -1. */
  96 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  97 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  98 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  99 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
 100 static int stdin_eof = 0;       /* EOF message received from client. */
 101 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
 102 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
 103 static int fdin_is_tty = 0;     /* fdin points to a tty. */
 104 static int connection_in;       /* Connection to client (input). */
 105 static int connection_out;      /* Connection to client (output). */
 106 static int connection_closed = 0;       /* Connection to client closed. */
 107 static u_int buffer_high;       /* "Soft" max buffer size. */
 108 static int no_more_sessions = 0; /* Disallow further sessions. */
 109
 110 /*
 111  * This SIGCHLD kludge is used to detect when the child exits.  The server
 112  * will exit after that, as soon as forwarded connections have terminated.
 113  */
 114
 115 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 116
 117 /* Cleanup on signals (!use_privsep case only) */
 118 static volatile sig_atomic_t received_sigterm = 0;
 119
 120 /* prototypes */
 121 static void server_init_dispatch(void);
 122
 123 /*
 124  * we write to this pipe if a SIGCHLD is caught in order to avoid
 125  * the race between select() and child_terminated
 126  */
 127 static int notify_pipe[2];
 128 static void
 129 notify_setup(void)
 130 {
 131         if (pipe(notify_pipe) < 0) {
 132                 error("pipe(notify_pipe) failed %s", strerror(errno));
 133         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 134             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 135                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 136                 close(notify_pipe[0]);
 137                 close(notify_pipe[1]);
 138         } else {
 139                 set_nonblock(notify_pipe[0]);
 140                 set_nonblock(notify_pipe[1]);
 141                 return;
 142         }
 143         notify_pipe[0] = -1;    /* read end */
 144         notify_pipe[1] = -1;    /* write end */
 145 }
 146 static void
 147 notify_parent(void)
 148 {
 149         if (notify_pipe[1] != -1)
 150                 write(notify_pipe[1], "", 1);
 151 }
 152 static void
 153 notify_prepare(fd_set *readset)
 154 {
 155         if (notify_pipe[0] != -1)
 156                 FD_SET(notify_pipe[0], readset);
 157 }
 158 static void
 159 notify_done(fd_set *readset)
 160 {
 161         char c;
 162
 163         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 164                 while (read(notify_pipe[0], &c, 1) != -1)
 165                         debug2("notify_done: reading");
 166 }
 167
 168 /*ARGSUSED*/
 169 static void
 170 sigchld_handler(int sig)
 171 {
 172         int save_errno = errno;
 173         child_terminated = 1;
 174 #ifndef _UNICOS
 175         mysignal(SIGCHLD, sigchld_handler);
 176 #endif
 177         notify_parent();
 178         errno = save_errno;
 179 }
 180
 181 /*ARGSUSED*/
 182 static void
 183 sigterm_handler(int sig)
 184 {
 185         received_sigterm = sig;
 186 }
 187
 188 /*
 189  * Make packets from buffered stderr data, and buffer it for sending
 190  * to the client.
 191  */
 192 static void
 193 make_packets_from_stderr_data(void)
 194 {
 195         u_int len;
 196
 197         /* Send buffered stderr data to the client. */
 198         while (buffer_len(&stderr_buffer) > 0 &&
 199             packet_not_very_much_data_to_write()) {
 200                 len = buffer_len(&stderr_buffer);
 201                 if (packet_is_interactive()) {
 202                         if (len > 512)
 203                                 len = 512;
 204                 } else {
 205                         /* Keep the packets at reasonable size. */
 206                         if (len > packet_get_maxsize())
 207                                 len = packet_get_maxsize();
 208                 }
 209                 packet_start(SSH_SMSG_STDERR_DATA);
 210                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 211                 packet_send();
 212                 buffer_consume(&stderr_buffer, len);
 213                 stderr_bytes += len;
 214         }
 215 }
 216
 217 /*
 218  * Make packets from buffered stdout data, and buffer it for sending to the
 219  * client.
 220  */
 221 static void
 222 make_packets_from_stdout_data(void)
 223 {
 224         u_int len;
 225
 226         /* Send buffered stdout data to the client. */
 227         while (buffer_len(&stdout_buffer) > 0 &&
 228             packet_not_very_much_data_to_write()) {
 229                 len = buffer_len(&stdout_buffer);
 230                 if (packet_is_interactive()) {
 231                         if (len > 512)
 232                                 len = 512;
 233                 } else {
 234                         /* Keep the packets at reasonable size. */
 235                         if (len > packet_get_maxsize())
 236                                 len = packet_get_maxsize();
 237                 }
 238                 packet_start(SSH_SMSG_STDOUT_DATA);
 239                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 240                 packet_send();
 241                 buffer_consume(&stdout_buffer, len);
 242                 stdout_bytes += len;
 243         }
 244 }
 245
 246 static void
 247 client_alive_check(void)
 248 {
 249         int channel_id;
 250
 251         /* timeout, check to see how many we have had */
 252         if (++keep_alive_timeouts > options.client_alive_count_max) {
 253                 logit("Timeout, client not responding.");
 254                 cleanup_exit(255);
 255         }
 256
 257         /*
 258          * send a bogus global/channel request with "wantreply",
 259          * we should get back a failure
 260          */
 261         if ((channel_id = channel_find_open()) == -1) {
 262                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 263                 packet_put_cstring("keepalive@openssh.com");
 264                 packet_put_char(1);     /* boolean: want reply */
 265         } else {
 266                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 267         }
 268         packet_send();
 269 }
 270
 271 /*
 272  * Sleep in select() until we can do something.  This will initialize the
 273  * select masks.  Upon return, the masks will indicate which descriptors
 274  * have data or can accept data.  Optionally, a maximum time can be specified
 275  * for the duration of the wait (0 = infinite).
 276  */
 277 static void
 278 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 279     u_int *nallocp, u_int max_time_milliseconds)
 280 {
 281         struct timeval tv, *tvp;
 282         int ret;
 283         int client_alive_scheduled = 0;
 284         int program_alive_scheduled = 0;
 285
 286         /*
 287          * if using client_alive, set the max timeout accordingly,
 288          * and indicate that this particular timeout was for client
 289          * alive by setting the client_alive_scheduled flag.
 290          *
 291          * this could be randomized somewhat to make traffic
 292          * analysis more difficult, but we're not doing it yet.
 293          */
 294         if (compat20 &&
 295             max_time_milliseconds == 0 && options.client_alive_interval) {
 296                 client_alive_scheduled = 1;
 297                 max_time_milliseconds = options.client_alive_interval * 1000;
 298         }
 299
 300         /* Allocate and update select() masks for channel descriptors. */
 301         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 302
 303         if (compat20) {
 304 #if 0
 305                 /* wrong: bad condition XXX */
 306                 if (channel_not_very_much_buffered_data())
 307 #endif
 308                 FD_SET(connection_in, *readsetp);
 309         } else {
 310                 /*
 311                  * Read packets from the client unless we have too much
 312                  * buffered stdin or channel data.
 313                  */
 314                 if (buffer_len(&stdin_buffer) < buffer_high &&
 315                     channel_not_very_much_buffered_data())
 316                         FD_SET(connection_in, *readsetp);
 317                 /*
 318                  * If there is not too much data already buffered going to
 319                  * the client, try to get some more data from the program.
 320                  */
 321                 if (packet_not_very_much_data_to_write()) {
 322                         program_alive_scheduled = child_terminated;
 323                         if (!fdout_eof)
 324                                 FD_SET(fdout, *readsetp);
 325                         if (!fderr_eof)
 326                                 FD_SET(fderr, *readsetp);
 327                 }
 328                 /*
 329                  * If we have buffered data, try to write some of that data
 330                  * to the program.
 331                  */
 332                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 333                         FD_SET(fdin, *writesetp);
 334         }
 335         notify_prepare(*readsetp);
 336
 337         /*
 338          * If we have buffered packet data going to the client, mark that
 339          * descriptor.
 340          */
 341         if (packet_have_data_to_write())
 342                 FD_SET(connection_out, *writesetp);
 343
 344         /*
 345          * If child has terminated and there is enough buffer space to read
 346          * from it, then read as much as is available and exit.
 347          */
 348         if (child_terminated && packet_not_very_much_data_to_write())
 349                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 350                         max_time_milliseconds = 100;
 351
 352         if (max_time_milliseconds == 0)
 353                 tvp = NULL;
 354         else {
 355                 tv.tv_sec = max_time_milliseconds / 1000;
 356                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 357                 tvp = &tv;
 358         }
 359
 360         /* Wait for something to happen, or the timeout to expire. */
 361         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 362
 363         if (ret == -1) {
 364                 memset(*readsetp, 0, *nallocp);
 365                 memset(*writesetp, 0, *nallocp);
 366                 if (errno != EINTR)
 367                         error("select: %.100s", strerror(errno));
 368         } else {
 369                 if (ret == 0 && client_alive_scheduled)
 370                         client_alive_check();
 371                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 372                         if (!fdout_eof)
 373                                 FD_SET(fdout, *readsetp);
 374                         if (!fderr_eof)
 375                                 FD_SET(fderr, *readsetp);
 376                 }
 377         }
 378
 379         notify_done(*readsetp);
 380 }
 381
 382 /*
 383  * Processes input from the client and the program.  Input data is stored
 384  * in buffers and processed later.
 385  */
 386 static void
 387 process_input(fd_set *readset)
 388 {
 389         int len;
 390         char buf[16384];
 391
 392         /* Read and buffer any input data from the client. */
 393         if (FD_ISSET(connection_in, readset)) {
 394                 len = read(connection_in, buf, sizeof(buf));
 395                 if (len == 0) {
 396                         verbose("Connection closed by %.100s",
 397                             get_remote_ipaddr());
 398                         connection_closed = 1;
 399                         if (compat20)
 400                                 return;
 401                         cleanup_exit(255);
 402                 } else if (len < 0) {
 403                         if (errno != EINTR && errno != EAGAIN &&
 404                             errno != EWOULDBLOCK) {
 405                                 verbose("Read error from remote host "
 406                                     "%.100s: %.100s",
 407                                     get_remote_ipaddr(), strerror(errno));
 408                                 cleanup_exit(255);
 409                         }
 410                 } else {
 411                         /* Buffer any received data. */
 412                         packet_process_incoming(buf, len);
 413                 }
 414         }
 415         if (compat20)
 416                 return;
 417
 418         /* Read and buffer any available stdout data from the program. */
 419         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 420                 errno = 0;
 421                 len = read(fdout, buf, sizeof(buf));
 422                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 423                     errno == EWOULDBLOCK) && !child_terminated))) {
 424                         /* do nothing */
 425 #ifndef PTY_ZEROREAD
 426                 } else if (len <= 0) {
 427 #else
 428                 } else if ((!isatty(fdout) && len <= 0) ||
 429                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 430 #endif
 431                         fdout_eof = 1;
 432                 } else {
 433                         buffer_append(&stdout_buffer, buf, len);
 434                         fdout_bytes += len;
 435                 }
 436         }
 437         /* Read and buffer any available stderr data from the program. */
 438         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 439                 errno = 0;
 440                 len = read(fderr, buf, sizeof(buf));
 441                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 442                     errno == EWOULDBLOCK) && !child_terminated))) {
 443                         /* do nothing */
 444 #ifndef PTY_ZEROREAD
 445                 } else if (len <= 0) {
 446 #else
 447                 } else if ((!isatty(fderr) && len <= 0) ||
 448                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 449 #endif
 450                         fderr_eof = 1;
 451                 } else {
 452                         buffer_append(&stderr_buffer, buf, len);
 453                 }
 454         }
 455 }
 456
 457 /*
 458  * Sends data from internal buffers to client program stdin.
 459  */
 460 static void
 461 process_output(fd_set *writeset)
 462 {
 463         struct termios tio;
 464         u_char *data;
 465         u_int dlen;
 466         int len;
 467
 468         /* Write buffered data to program stdin. */
 469         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 470                 data = buffer_ptr(&stdin_buffer);
 471                 dlen = buffer_len(&stdin_buffer);
 472                 len = write(fdin, data, dlen);
 473                 if (len < 0 &&
 474                     (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
 475                         /* do nothing */
 476                 } else if (len <= 0) {
 477                         if (fdin != fdout)
 478                                 close(fdin);
 479                         else
 480                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 481                         fdin = -1;
 482                 } else {
 483                         /* Successful write. */
 484                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 485                             tcgetattr(fdin, &tio) == 0 &&
 486                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 487                                 /*
 488                                  * Simulate echo to reduce the impact of
 489                                  * traffic analysis
 490                                  */
 491                                 packet_send_ignore(len);
 492                                 packet_send();
 493                         }
 494                         /* Consume the data from the buffer. */
 495                         buffer_consume(&stdin_buffer, len);
 496                         /* Update the count of bytes written to the program. */
 497                         stdin_bytes += len;
 498                 }
 499         }
 500         /* Send any buffered packet data to the client. */
 501         if (FD_ISSET(connection_out, writeset))
 502                 packet_write_poll();
 503 }
 504
 505 /*
 506  * Wait until all buffered output has been sent to the client.
 507  * This is used when the program terminates.
 508  */
 509 static void
 510 drain_output(void)
 511 {
 512         /* Send any buffered stdout data to the client. */
 513         if (buffer_len(&stdout_buffer) > 0) {
 514                 packet_start(SSH_SMSG_STDOUT_DATA);
 515                 packet_put_string(buffer_ptr(&stdout_buffer),
 516                                   buffer_len(&stdout_buffer));
 517                 packet_send();
 518                 /* Update the count of sent bytes. */
 519                 stdout_bytes += buffer_len(&stdout_buffer);
 520         }
 521         /* Send any buffered stderr data to the client. */
 522         if (buffer_len(&stderr_buffer) > 0) {
 523                 packet_start(SSH_SMSG_STDERR_DATA);
 524                 packet_put_string(buffer_ptr(&stderr_buffer),
 525                                   buffer_len(&stderr_buffer));
 526                 packet_send();
 527                 /* Update the count of sent bytes. */
 528                 stderr_bytes += buffer_len(&stderr_buffer);
 529         }
 530         /* Wait until all buffered data has been written to the client. */
 531         packet_write_wait();
 532 }
 533
 534 static void
 535 process_buffered_input_packets(void)
 536 {
 537         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 538 }
 539
 540 /*
 541  * Performs the interactive session.  This handles data transmission between
 542  * the client and the program.  Note that the notion of stdin, stdout, and
 543  * stderr in this function is sort of reversed: this function writes to
 544  * stdin (of the child program), and reads from stdout and stderr (of the
 545  * child program).
 546  */
 547 void
 548 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 549 {
 550         fd_set *readset = NULL, *writeset = NULL;
 551         int max_fd = 0;
 552         u_int nalloc = 0;
 553         int wait_status;        /* Status returned by wait(). */
 554         pid_t wait_pid;         /* pid returned by wait(). */
 555         int waiting_termination = 0;    /* Have displayed waiting close message. */
 556         u_int max_time_milliseconds;
 557         u_int previous_stdout_buffer_bytes;
 558         u_int stdout_buffer_bytes;
 559         int type;
 560
 561         debug("Entering interactive session.");
 562
 563         /* Initialize the SIGCHLD kludge. */
 564         child_terminated = 0;
 565         mysignal(SIGCHLD, sigchld_handler);
 566
 567         if (!use_privsep) {
 568                 signal(SIGTERM, sigterm_handler);
 569                 signal(SIGINT, sigterm_handler);
 570                 signal(SIGQUIT, sigterm_handler);
 571         }
 572
 573         /* Initialize our global variables. */
 574         fdin = fdin_arg;
 575         fdout = fdout_arg;
 576         fderr = fderr_arg;
 577
 578         /* nonblocking IO */
 579         set_nonblock(fdin);
 580         set_nonblock(fdout);
 581         /* we don't have stderr for interactive terminal sessions, see below */
 582         if (fderr != -1)
 583                 set_nonblock(fderr);
 584
 585         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 586                 fdin_is_tty = 1;
 587
 588         connection_in = packet_get_connection_in();
 589         connection_out = packet_get_connection_out();
 590
 591         notify_setup();
 592
 593         previous_stdout_buffer_bytes = 0;
 594
 595         /* Set approximate I/O buffer size. */
 596         if (packet_is_interactive())
 597                 buffer_high = 4096;
 598         else
 599                 buffer_high = 64 * 1024;
 600
 601 #if 0
 602         /* Initialize max_fd to the maximum of the known file descriptors. */
 603         max_fd = MAX(connection_in, connection_out);
 604         max_fd = MAX(max_fd, fdin);
 605         max_fd = MAX(max_fd, fdout);
 606         if (fderr != -1)
 607                 max_fd = MAX(max_fd, fderr);
 608 #endif
 609
 610         /* Initialize Initialize buffers. */
 611         buffer_init(&stdin_buffer);
 612         buffer_init(&stdout_buffer);
 613         buffer_init(&stderr_buffer);
 614
 615         /*
 616          * If we have no separate fderr (which is the case when we have a pty
 617          * - there we cannot make difference between data sent to stdout and
 618          * stderr), indicate that we have seen an EOF from stderr.  This way
 619          * we don't need to check the descriptor everywhere.
 620          */
 621         if (fderr == -1)
 622                 fderr_eof = 1;
 623
 624         server_init_dispatch();
 625
 626         /* Main loop of the server for the interactive session mode. */
 627         for (;;) {
 628
 629                 /* Process buffered packets from the client. */
 630                 process_buffered_input_packets();
 631
 632                 /*
 633                  * If we have received eof, and there is no more pending
 634                  * input data, cause a real eof by closing fdin.
 635                  */
 636                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 637                         if (fdin != fdout)
 638                                 close(fdin);
 639                         else
 640                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 641                         fdin = -1;
 642                 }
 643                 /* Make packets from buffered stderr data to send to the client. */
 644                 make_packets_from_stderr_data();
 645
 646                 /*
 647                  * Make packets from buffered stdout data to send to the
 648                  * client. If there is very little to send, this arranges to
 649                  * not send them now, but to wait a short while to see if we
 650                  * are getting more data. This is necessary, as some systems
 651                  * wake up readers from a pty after each separate character.
 652                  */
 653                 max_time_milliseconds = 0;
 654                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 655                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 656                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 657                         /* try again after a while */
 658                         max_time_milliseconds = 10;
 659                 } else {
 660                         /* Send it now. */
 661                         make_packets_from_stdout_data();
 662                 }
 663                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 664
 665                 /* Send channel data to the client. */
 666                 if (packet_not_very_much_data_to_write())
 667                         channel_output_poll();
 668
 669                 /*
 670                  * Bail out of the loop if the program has closed its output
 671                  * descriptors, and we have no more data to send to the
 672                  * client, and there is no pending buffered data.
 673                  */
 674                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 675                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 676                         if (!channel_still_open())
 677                                 break;
 678                         if (!waiting_termination) {
 679                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 680                                 char *cp;
 681                                 waiting_termination = 1;
 682                                 buffer_append(&stderr_buffer, s, strlen(s));
 683
 684                                 /* Display list of open channels. */
 685                                 cp = channel_open_message();
 686                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 687                                 xfree(cp);
 688                         }
 689                 }
 690                 max_fd = MAX(connection_in, connection_out);
 691                 max_fd = MAX(max_fd, fdin);
 692                 max_fd = MAX(max_fd, fdout);
 693                 max_fd = MAX(max_fd, fderr);
 694                 max_fd = MAX(max_fd, notify_pipe[0]);
 695
 696                 /* Sleep in select() until we can do something. */
 697                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 698                     &nalloc, max_time_milliseconds);
 699
 700                 if (received_sigterm) {
 701                         logit("Exiting on signal %d", received_sigterm);
 702                         /* Clean up sessions, utmp, etc. */
 703                         cleanup_exit(255);
 704                 }
 705
 706                 /* Process any channel events. */
 707                 channel_after_select(readset, writeset);
 708
 709                 /* Process input from the client and from program stdout/stderr. */
 710                 process_input(readset);
 711
 712                 /* Process output to the client and to program stdin. */
 713                 process_output(writeset);
 714         }
 715         if (readset)
 716                 xfree(readset);
 717         if (writeset)
 718                 xfree(writeset);
 719
 720         /* Cleanup and termination code. */
 721
 722         /* Wait until all output has been sent to the client. */
 723         drain_output();
 724
 725         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 726             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 727
 728         /* Free and clear the buffers. */
 729         buffer_free(&stdin_buffer);
 730         buffer_free(&stdout_buffer);
 731         buffer_free(&stderr_buffer);
 732
 733         /* Close the file descriptors. */
 734         if (fdout != -1)
 735                 close(fdout);
 736         fdout = -1;
 737         fdout_eof = 1;
 738         if (fderr != -1)
 739                 close(fderr);
 740         fderr = -1;
 741         fderr_eof = 1;
 742         if (fdin != -1)
 743                 close(fdin);
 744         fdin = -1;
 745
 746         channel_free_all();
 747
 748         /* We no longer want our SIGCHLD handler to be called. */
 749         mysignal(SIGCHLD, SIG_DFL);
 750
 751         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 752                 if (errno != EINTR)
 753                         packet_disconnect("wait: %.100s", strerror(errno));
 754         if (wait_pid != pid)
 755                 error("Strange, wait returned pid %ld, expected %ld",
 756                     (long)wait_pid, (long)pid);
 757
 758         /* Check if it exited normally. */
 759         if (WIFEXITED(wait_status)) {
 760                 /* Yes, normal exit.  Get exit status and send it to the client. */
 761                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 762                 packet_start(SSH_SMSG_EXITSTATUS);
 763                 packet_put_int(WEXITSTATUS(wait_status));
 764                 packet_send();
 765                 packet_write_wait();
 766
 767                 /*
 768                  * Wait for exit confirmation.  Note that there might be
 769                  * other packets coming before it; however, the program has
 770                  * already died so we just ignore them.  The client is
 771                  * supposed to respond with the confirmation when it receives
 772                  * the exit status.
 773                  */
 774                 do {
 775                         type = packet_read();
 776                 }
 777                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 778
 779                 debug("Received exit confirmation.");
 780                 return;
 781         }
 782         /* Check if the program terminated due to a signal. */
 783         if (WIFSIGNALED(wait_status))
 784                 packet_disconnect("Command terminated on signal %d.",
 785                                   WTERMSIG(wait_status));
 786
 787         /* Some weird exit cause.  Just exit. */
 788         packet_disconnect("wait returned status %04x.", wait_status);
 789         /* NOTREACHED */
 790 }
 791
 792 static void
 793 collect_children(void)
 794 {
 795         pid_t pid;
 796         sigset_t oset, nset;
 797         int status;
 798
 799         /* block SIGCHLD while we check for dead children */
 800         sigemptyset(&nset);
 801         sigaddset(&nset, SIGCHLD);
 802         sigprocmask(SIG_BLOCK, &nset, &oset);
 803         if (child_terminated) {
 804                 debug("Received SIGCHLD.");
 805                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 806                     (pid < 0 && errno == EINTR))
 807                         if (pid > 0)
 808                                 session_close_by_pid(pid, status);
 809                 child_terminated = 0;
 810         }
 811         sigprocmask(SIG_SETMASK, &oset, NULL);
 812 }
 813
 814 void
 815 server_loop2(Authctxt *authctxt)
 816 {
 817         fd_set *readset = NULL, *writeset = NULL;
 818         int rekeying = 0, max_fd, nalloc = 0;
 819
 820         debug("Entering interactive session for SSH2.");
 821
 822         mysignal(SIGCHLD, sigchld_handler);
 823         child_terminated = 0;
 824         connection_in = packet_get_connection_in();
 825         connection_out = packet_get_connection_out();
 826
 827         if (!use_privsep) {
 828                 signal(SIGTERM, sigterm_handler);
 829                 signal(SIGINT, sigterm_handler);
 830                 signal(SIGQUIT, sigterm_handler);
 831         }
 832
 833         notify_setup();
 834
 835         max_fd = MAX(connection_in, connection_out);
 836         max_fd = MAX(max_fd, notify_pipe[0]);
 837
 838         server_init_dispatch();
 839
 840         for (;;) {
 841                 process_buffered_input_packets();
 842
 843                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 844
 845                 if (!rekeying && packet_not_very_much_data_to_write())
 846                         channel_output_poll();
 847                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 848                     &nalloc, 0);
 849
 850                 if (received_sigterm) {
 851                         logit("Exiting on signal %d", received_sigterm);
 852                         /* Clean up sessions, utmp, etc. */
 853                         cleanup_exit(255);
 854                 }
 855
 856                 collect_children();
 857                 if (!rekeying) {
 858                         channel_after_select(readset, writeset);
 859                         if (packet_need_rekeying()) {
 860                                 debug("need rekeying");
 861                                 xxx_kex->done = 0;
 862                                 kex_send_kexinit(xxx_kex);
 863                         }
 864                 }
 865                 process_input(readset);
 866                 if (connection_closed)
 867                         break;
 868                 process_output(writeset);
 869         }
 870         collect_children();
 871
 872         if (readset)
 873                 xfree(readset);
 874         if (writeset)
 875                 xfree(writeset);
 876
 877         /* free all channels, no more reads and writes */
 878         channel_free_all();
 879
 880         /* free remaining sessions, e.g. remove wtmp entries */
 881         session_destroy_all(NULL);
 882 }
 883
 884 static void
 885 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 886 {
 887         debug("Got %d/%u for keepalive", type, seq);
 888         /*
 889          * reset timeout, since we got a sane answer from the client.
 890          * even if this was generated by something other than
 891          * the bogus CHANNEL_REQUEST we send for keepalives.
 892          */
 893         keep_alive_timeouts = 0;
 894 }
 895
 896 static void
 897 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 898 {
 899         char *data;
 900         u_int data_len;
 901
 902         /* Stdin data from the client.  Append it to the buffer. */
 903         /* Ignore any data if the client has closed stdin. */
 904         if (fdin == -1)
 905                 return;
 906         data = packet_get_string(&data_len);
 907         packet_check_eom();
 908         buffer_append(&stdin_buffer, data, data_len);
 909         memset(data, 0, data_len);
 910         xfree(data);
 911 }
 912
 913 static void
 914 server_input_eof(int type, u_int32_t seq, void *ctxt)
 915 {
 916         /*
 917          * Eof from the client.  The stdin descriptor to the
 918          * program will be closed when all buffered data has
 919          * drained.
 920          */
 921         debug("EOF received for stdin.");
 922         packet_check_eom();
 923         stdin_eof = 1;
 924 }
 925
 926 static void
 927 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 928 {
 929         u_int row = packet_get_int();
 930         u_int col = packet_get_int();
 931         u_int xpixel = packet_get_int();
 932         u_int ypixel = packet_get_int();
 933
 934         debug("Window change received.");
 935         packet_check_eom();
 936         if (fdin != -1)
 937                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 938 }
 939
 940 static Channel *
 941 server_request_direct_tcpip(void)
 942 {
 943         Channel *c;
 944         char *target, *originator;
 945         int target_port, originator_port;
 946
 947         target = packet_get_string(NULL);
 948         target_port = packet_get_int();
 949         originator = packet_get_string(NULL);
 950         originator_port = packet_get_int();
 951         packet_check_eom();
 952
 953         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 954             "port %d", originator, originator_port, target, target_port);
 955
 956         /* XXX check permission */
 957         c = channel_connect_to(target, target_port,
 958             "direct-tcpip", "direct-tcpip");
 959
 960         xfree(originator);
 961         xfree(target);
 962
 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, NULL, NULL);
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         if (no_more_sessions) {
1021                 packet_disconnect("Possible attack: attempt to open a session "
1022                     "after additional sessions disabled");
1023         }
1024
1025         /*
1026          * A server session has no fd to read or write until a
1027          * CHANNEL_REQUEST for a shell is made, so we set the type to
1028          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1029          * CHANNEL_REQUEST messages is registered.
1030          */
1031         c = channel_new("session", SSH_CHANNEL_LARVAL,
1032             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1033             0, "server-session", 1);
1034         if (session_open(the_authctxt, c->self) != 1) {
1035                 debug("session open failed, free channel %d", c->self);
1036                 channel_free(c);
1037                 return NULL;
1038         }
1039         channel_register_cleanup(c->self, session_close_by_channel, 0);
1040         return c;
1041 }
1042
1043 static void
1044 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1045 {
1046         Channel *c = NULL;
1047         char *ctype;
1048         int rchan;
1049         u_int rmaxpack, rwindow, len;
1050
1051         ctype = packet_get_string(&len);
1052         rchan = packet_get_int();
1053         rwindow = packet_get_int();
1054         rmaxpack = packet_get_int();
1055
1056         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1057             ctype, rchan, rwindow, rmaxpack);
1058
1059         if (strcmp(ctype, "session") == 0) {
1060                 c = server_request_session();
1061         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1062                 c = server_request_direct_tcpip();
1063         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1064                 c = server_request_tun();
1065         }
1066         if (c != NULL) {
1067                 debug("server_input_channel_open: confirm %s", ctype);
1068                 c->remote_id = rchan;
1069                 c->remote_window = rwindow;
1070                 c->remote_maxpacket = rmaxpack;
1071                 if (c->type != SSH_CHANNEL_CONNECTING) {
1072                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1073                         packet_put_int(c->remote_id);
1074                         packet_put_int(c->self);
1075                         packet_put_int(c->local_window);
1076                         packet_put_int(c->local_maxpacket);
1077                         packet_send();
1078                 }
1079         } else {
1080                 debug("server_input_channel_open: failure %s", ctype);
1081                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1082                 packet_put_int(rchan);
1083                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1084                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1085                         packet_put_cstring("open failed");
1086                         packet_put_cstring("");
1087                 }
1088                 packet_send();
1089         }
1090         xfree(ctype);
1091 }
1092
1093 static void
1094 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1095 {
1096         char *rtype;
1097         int want_reply;
1098         int success = 0;
1099
1100         rtype = packet_get_string(NULL);
1101         want_reply = packet_get_char();
1102         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1103
1104         /* -R style forwarding */
1105         if (strcmp(rtype, "tcpip-forward") == 0) {
1106                 struct passwd *pw;
1107                 char *listen_address;
1108                 u_short listen_port;
1109
1110                 pw = the_authctxt->pw;
1111                 if (pw == NULL || !the_authctxt->valid)
1112                         fatal("server_input_global_request: no/invalid user");
1113                 listen_address = packet_get_string(NULL);
1114                 listen_port = (u_short)packet_get_int();
1115                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1116                     listen_address, listen_port);
1117
1118                 /* check permissions */
1119                 if (!options.allow_tcp_forwarding ||
1120                     no_port_forwarding_flag
1121 #ifndef NO_IPPORT_RESERVED_CONCEPT
1122                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1123 #endif
1124                     ) {
1125                         success = 0;
1126                         packet_send_debug("Server has disabled port forwarding.");
1127                 } else {
1128                         /* Start listening on the port */
1129                         success = channel_setup_remote_fwd_listener(
1130                             listen_address, listen_port, options.gateway_ports);
1131                 }
1132                 xfree(listen_address);
1133         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1134                 char *cancel_address;
1135                 u_short cancel_port;
1136
1137                 cancel_address = packet_get_string(NULL);
1138                 cancel_port = (u_short)packet_get_int();
1139                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1140                     cancel_address, cancel_port);
1141
1142                 success = channel_cancel_rport_listener(cancel_address,
1143                     cancel_port);
1144                 xfree(cancel_address);
1145         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1146                 no_more_sessions = 1;
1147                 success = 1;
1148         }
1149         if (want_reply) {
1150                 packet_start(success ?
1151                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1152                 packet_send();
1153                 packet_write_wait();
1154         }
1155         xfree(rtype);
1156 }
1157
1158 static void
1159 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1160 {
1161         Channel *c;
1162         int id, reply, success = 0;
1163         char *rtype;
1164
1165         id = packet_get_int();
1166         rtype = packet_get_string(NULL);
1167         reply = packet_get_char();
1168
1169         debug("server_input_channel_req: channel %d request %s reply %d",
1170             id, rtype, reply);
1171
1172         if ((c = channel_lookup(id)) == NULL)
1173                 packet_disconnect("server_input_channel_req: "
1174                     "unknown channel %d", id);
1175         if (!strcmp(rtype, "eow@openssh.com")) {
1176                 packet_check_eom();
1177                 chan_rcvd_eow(c);
1178         } else if ((c->type == SSH_CHANNEL_LARVAL ||
1179             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1180                 success = session_input_channel_req(c, rtype);
1181         if (reply) {
1182                 packet_start(success ?
1183                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1184                 packet_put_int(c->remote_id);
1185                 packet_send();
1186         }
1187         xfree(rtype);
1188 }
1189
1190 static void
1191 server_init_dispatch_20(void)
1192 {
1193         debug("server_init_dispatch_20");
1194         dispatch_init(&dispatch_protocol_error);
1195         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1196         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1197         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1198         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1199         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1200         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1201         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1202         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1203         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1204         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1205         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &channel_input_status_confirm);
1206         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &channel_input_status_confirm);
1207         /* client_alive */
1208         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1209         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1210         /* rekeying */
1211         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1212 }
1213 static void
1214 server_init_dispatch_13(void)
1215 {
1216         debug("server_init_dispatch_13");
1217         dispatch_init(NULL);
1218         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1219         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1220         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1221         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1222         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1223         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1224         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1225         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1226         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1227 }
1228 static void
1229 server_init_dispatch_15(void)
1230 {
1231         server_init_dispatch_13();
1232         debug("server_init_dispatch_15");
1233         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1234         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1235 }
1236 static void
1237 server_init_dispatch(void)
1238 {
1239         if (compat20)
1240                 server_init_dispatch_20();
1241         else if (compat13)
1242                 server_init_dispatch_13();
1243         else
1244                 server_init_dispatch_15();
1245 }