serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.159 2009/05/28 16:50:16 andreas 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 #include "roaming.h"
  82
  83 extern ServerOptions options;
  84
  85 /* XXX */
  86 extern Kex *xxx_kex;
  87 extern Authctxt *the_authctxt;
  88 extern int use_privsep;
  89
  90 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  91 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  92 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  93 static int fdin;                /* Descriptor for stdin (for writing) */
  94 static int fdout;               /* Descriptor for stdout (for reading);
  95                                    May be same number as fdin. */
  96 static int fderr;               /* Descriptor for stderr.  May be -1. */
  97 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  98 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  99 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
 100 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
 101 static int stdin_eof = 0;       /* EOF message received from client. */
 102 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
 103 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
 104 static int fdin_is_tty = 0;     /* fdin points to a tty. */
 105 static int connection_in;       /* Connection to client (input). */
 106 static int connection_out;      /* Connection to client (output). */
 107 static int connection_closed = 0;       /* Connection to client closed. */
 108 static u_int buffer_high;       /* "Soft" max buffer size. */
 109 static int no_more_sessions = 0; /* Disallow further sessions. */
 110
 111 /*
 112  * This SIGCHLD kludge is used to detect when the child exits.  The server
 113  * will exit after that, as soon as forwarded connections have terminated.
 114  */
 115
 116 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 117
 118 /* Cleanup on signals (!use_privsep case only) */
 119 static volatile sig_atomic_t received_sigterm = 0;
 120
 121 /* prototypes */
 122 static void server_init_dispatch(void);
 123
 124 /*
 125  * we write to this pipe if a SIGCHLD is caught in order to avoid
 126  * the race between select() and child_terminated
 127  */
 128 static int notify_pipe[2];
 129 static void
 130 notify_setup(void)
 131 {
 132         if (pipe(notify_pipe) < 0) {
 133                 error("pipe(notify_pipe) failed %s", strerror(errno));
 134         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 135             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 136                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 137                 close(notify_pipe[0]);
 138                 close(notify_pipe[1]);
 139         } else {
 140                 set_nonblock(notify_pipe[0]);
 141                 set_nonblock(notify_pipe[1]);
 142                 return;
 143         }
 144         notify_pipe[0] = -1;    /* read end */
 145         notify_pipe[1] = -1;    /* write end */
 146 }
 147 static void
 148 notify_parent(void)
 149 {
 150         if (notify_pipe[1] != -1)
 151                 write(notify_pipe[1], "", 1);
 152 }
 153 static void
 154 notify_prepare(fd_set *readset)
 155 {
 156         if (notify_pipe[0] != -1)
 157                 FD_SET(notify_pipe[0], readset);
 158 }
 159 static void
 160 notify_done(fd_set *readset)
 161 {
 162         char c;
 163
 164         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 165                 while (read(notify_pipe[0], &c, 1) != -1)
 166                         debug2("notify_done: reading");
 167 }
 168
 169 /*ARGSUSED*/
 170 static void
 171 sigchld_handler(int sig)
 172 {
 173         int save_errno = errno;
 174         child_terminated = 1;
 175 #ifndef _UNICOS
 176         mysignal(SIGCHLD, sigchld_handler);
 177 #endif
 178         notify_parent();
 179         errno = save_errno;
 180 }
 181
 182 /*ARGSUSED*/
 183 static void
 184 sigterm_handler(int sig)
 185 {
 186         received_sigterm = sig;
 187 }
 188
 189 /*
 190  * Make packets from buffered stderr data, and buffer it for sending
 191  * to the client.
 192  */
 193 static void
 194 make_packets_from_stderr_data(void)
 195 {
 196         u_int len;
 197
 198         /* Send buffered stderr data to the client. */
 199         while (buffer_len(&stderr_buffer) > 0 &&
 200             packet_not_very_much_data_to_write()) {
 201                 len = buffer_len(&stderr_buffer);
 202                 if (packet_is_interactive()) {
 203                         if (len > 512)
 204                                 len = 512;
 205                 } else {
 206                         /* Keep the packets at reasonable size. */
 207                         if (len > packet_get_maxsize())
 208                                 len = packet_get_maxsize();
 209                 }
 210                 packet_start(SSH_SMSG_STDERR_DATA);
 211                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 212                 packet_send();
 213                 buffer_consume(&stderr_buffer, len);
 214                 stderr_bytes += len;
 215         }
 216 }
 217
 218 /*
 219  * Make packets from buffered stdout data, and buffer it for sending to the
 220  * client.
 221  */
 222 static void
 223 make_packets_from_stdout_data(void)
 224 {
 225         u_int len;
 226
 227         /* Send buffered stdout data to the client. */
 228         while (buffer_len(&stdout_buffer) > 0 &&
 229             packet_not_very_much_data_to_write()) {
 230                 len = buffer_len(&stdout_buffer);
 231                 if (packet_is_interactive()) {
 232                         if (len > 512)
 233                                 len = 512;
 234                 } else {
 235                         /* Keep the packets at reasonable size. */
 236                         if (len > packet_get_maxsize())
 237                                 len = packet_get_maxsize();
 238                 }
 239                 packet_start(SSH_SMSG_STDOUT_DATA);
 240                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 241                 packet_send();
 242                 buffer_consume(&stdout_buffer, len);
 243                 stdout_bytes += len;
 244         }
 245 }
 246
 247 static void
 248 client_alive_check(void)
 249 {
 250         int channel_id;
 251
 252         /* timeout, check to see how many we have had */
 253         if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
 254                 logit("Timeout, client not responding.");
 255                 cleanup_exit(255);
 256         }
 257
 258         /*
 259          * send a bogus global/channel request with "wantreply",
 260          * we should get back a failure
 261          */
 262         if ((channel_id = channel_find_open()) == -1) {
 263                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 264                 packet_put_cstring("keepalive@openssh.com");
 265                 packet_put_char(1);     /* boolean: want reply */
 266         } else {
 267                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 268         }
 269         packet_send();
 270 }
 271
 272 /*
 273  * Sleep in select() until we can do something.  This will initialize the
 274  * select masks.  Upon return, the masks will indicate which descriptors
 275  * have data or can accept data.  Optionally, a maximum time can be specified
 276  * for the duration of the wait (0 = infinite).
 277  */
 278 static void
 279 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 280     u_int *nallocp, u_int max_time_milliseconds)
 281 {
 282         struct timeval tv, *tvp;
 283         int ret;
 284         int client_alive_scheduled = 0;
 285         int program_alive_scheduled = 0;
 286
 287         /*
 288          * if using client_alive, set the max timeout accordingly,
 289          * and indicate that this particular timeout was for client
 290          * alive by setting the client_alive_scheduled flag.
 291          *
 292          * this could be randomized somewhat to make traffic
 293          * analysis more difficult, but we're not doing it yet.
 294          */
 295         if (compat20 &&
 296             max_time_milliseconds == 0 && options.client_alive_interval) {
 297                 client_alive_scheduled = 1;
 298                 max_time_milliseconds = options.client_alive_interval * 1000;
 299         }
 300
 301         /* Allocate and update select() masks for channel descriptors. */
 302         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 303
 304         if (compat20) {
 305 #if 0
 306                 /* wrong: bad condition XXX */
 307                 if (channel_not_very_much_buffered_data())
 308 #endif
 309                 FD_SET(connection_in, *readsetp);
 310         } else {
 311                 /*
 312                  * Read packets from the client unless we have too much
 313                  * buffered stdin or channel data.
 314                  */
 315                 if (buffer_len(&stdin_buffer) < buffer_high &&
 316                     channel_not_very_much_buffered_data())
 317                         FD_SET(connection_in, *readsetp);
 318                 /*
 319                  * If there is not too much data already buffered going to
 320                  * the client, try to get some more data from the program.
 321                  */
 322                 if (packet_not_very_much_data_to_write()) {
 323                         program_alive_scheduled = child_terminated;
 324                         if (!fdout_eof)
 325                                 FD_SET(fdout, *readsetp);
 326                         if (!fderr_eof)
 327                                 FD_SET(fderr, *readsetp);
 328                 }
 329                 /*
 330                  * If we have buffered data, try to write some of that data
 331                  * to the program.
 332                  */
 333                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 334                         FD_SET(fdin, *writesetp);
 335         }
 336         notify_prepare(*readsetp);
 337
 338         /*
 339          * If we have buffered packet data going to the client, mark that
 340          * descriptor.
 341          */
 342         if (packet_have_data_to_write())
 343                 FD_SET(connection_out, *writesetp);
 344
 345         /*
 346          * If child has terminated and there is enough buffer space to read
 347          * from it, then read as much as is available and exit.
 348          */
 349         if (child_terminated && packet_not_very_much_data_to_write())
 350                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 351                         max_time_milliseconds = 100;
 352
 353         if (max_time_milliseconds == 0)
 354                 tvp = NULL;
 355         else {
 356                 tv.tv_sec = max_time_milliseconds / 1000;
 357                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 358                 tvp = &tv;
 359         }
 360
 361         /* Wait for something to happen, or the timeout to expire. */
 362         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 363
 364         if (ret == -1) {
 365                 memset(*readsetp, 0, *nallocp);
 366                 memset(*writesetp, 0, *nallocp);
 367                 if (errno != EINTR)
 368                         error("select: %.100s", strerror(errno));
 369         } else {
 370                 if (ret == 0 && client_alive_scheduled)
 371                         client_alive_check();
 372                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 373                         if (!fdout_eof)
 374                                 FD_SET(fdout, *readsetp);
 375                         if (!fderr_eof)
 376                                 FD_SET(fderr, *readsetp);
 377                 }
 378         }
 379
 380         notify_done(*readsetp);
 381 }
 382
 383 /*
 384  * Processes input from the client and the program.  Input data is stored
 385  * in buffers and processed later.
 386  */
 387 static void
 388 process_input(fd_set *readset)
 389 {
 390         int len;
 391         char buf[16384];
 392
 393         /* Read and buffer any input data from the client. */
 394         if (FD_ISSET(connection_in, readset)) {
 395                 int cont = 0;
 396                 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
 397                 if (len == 0) {
 398                         if (cont)
 399                                 return;
 400                         verbose("Connection closed by %.100s",
 401                             get_remote_ipaddr());
 402                         connection_closed = 1;
 403                         if (compat20)
 404                                 return;
 405                         cleanup_exit(255);
 406                 } else if (len < 0) {
 407                         if (errno != EINTR && errno != EAGAIN &&
 408                             errno != EWOULDBLOCK) {
 409                                 verbose("Read error from remote host "
 410                                     "%.100s: %.100s",
 411                                     get_remote_ipaddr(), strerror(errno));
 412                                 cleanup_exit(255);
 413                         }
 414                 } else {
 415                         /* Buffer any received data. */
 416                         packet_process_incoming(buf, len);
 417                 }
 418         }
 419         if (compat20)
 420                 return;
 421
 422         /* Read and buffer any available stdout data from the program. */
 423         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 424                 errno = 0;
 425                 len = read(fdout, buf, sizeof(buf));
 426                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 427                     errno == EWOULDBLOCK) && !child_terminated))) {
 428                         /* do nothing */
 429 #ifndef PTY_ZEROREAD
 430                 } else if (len <= 0) {
 431 #else
 432                 } else if ((!isatty(fdout) && len <= 0) ||
 433                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 434 #endif
 435                         fdout_eof = 1;
 436                 } else {
 437                         buffer_append(&stdout_buffer, buf, len);
 438                         fdout_bytes += len;
 439                 }
 440         }
 441         /* Read and buffer any available stderr data from the program. */
 442         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 443                 errno = 0;
 444                 len = read(fderr, buf, sizeof(buf));
 445                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 446                     errno == EWOULDBLOCK) && !child_terminated))) {
 447                         /* do nothing */
 448 #ifndef PTY_ZEROREAD
 449                 } else if (len <= 0) {
 450 #else
 451                 } else if ((!isatty(fderr) && len <= 0) ||
 452                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 453 #endif
 454                         fderr_eof = 1;
 455                 } else {
 456                         buffer_append(&stderr_buffer, buf, len);
 457                 }
 458         }
 459 }
 460
 461 /*
 462  * Sends data from internal buffers to client program stdin.
 463  */
 464 static void
 465 process_output(fd_set *writeset)
 466 {
 467         struct termios tio;
 468         u_char *data;
 469         u_int dlen;
 470         int len;
 471
 472         /* Write buffered data to program stdin. */
 473         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 474                 data = buffer_ptr(&stdin_buffer);
 475                 dlen = buffer_len(&stdin_buffer);
 476                 len = write(fdin, data, dlen);
 477                 if (len < 0 &&
 478                     (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
 479                         /* do nothing */
 480                 } else if (len <= 0) {
 481                         if (fdin != fdout)
 482                                 close(fdin);
 483                         else
 484                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 485                         fdin = -1;
 486                 } else {
 487                         /* Successful write. */
 488                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 489                             tcgetattr(fdin, &tio) == 0 &&
 490                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 491                                 /*
 492                                  * Simulate echo to reduce the impact of
 493                                  * traffic analysis
 494                                  */
 495                                 packet_send_ignore(len);
 496                                 packet_send();
 497                         }
 498                         /* Consume the data from the buffer. */
 499                         buffer_consume(&stdin_buffer, len);
 500                         /* Update the count of bytes written to the program. */
 501                         stdin_bytes += len;
 502                 }
 503         }
 504         /* Send any buffered packet data to the client. */
 505         if (FD_ISSET(connection_out, writeset))
 506                 packet_write_poll();
 507 }
 508
 509 /*
 510  * Wait until all buffered output has been sent to the client.
 511  * This is used when the program terminates.
 512  */
 513 static void
 514 drain_output(void)
 515 {
 516         /* Send any buffered stdout data to the client. */
 517         if (buffer_len(&stdout_buffer) > 0) {
 518                 packet_start(SSH_SMSG_STDOUT_DATA);
 519                 packet_put_string(buffer_ptr(&stdout_buffer),
 520                                   buffer_len(&stdout_buffer));
 521                 packet_send();
 522                 /* Update the count of sent bytes. */
 523                 stdout_bytes += buffer_len(&stdout_buffer);
 524         }
 525         /* Send any buffered stderr data to the client. */
 526         if (buffer_len(&stderr_buffer) > 0) {
 527                 packet_start(SSH_SMSG_STDERR_DATA);
 528                 packet_put_string(buffer_ptr(&stderr_buffer),
 529                                   buffer_len(&stderr_buffer));
 530                 packet_send();
 531                 /* Update the count of sent bytes. */
 532                 stderr_bytes += buffer_len(&stderr_buffer);
 533         }
 534         /* Wait until all buffered data has been written to the client. */
 535         packet_write_wait();
 536 }
 537
 538 static void
 539 process_buffered_input_packets(void)
 540 {
 541         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 542 }
 543
 544 /*
 545  * Performs the interactive session.  This handles data transmission between
 546  * the client and the program.  Note that the notion of stdin, stdout, and
 547  * stderr in this function is sort of reversed: this function writes to
 548  * stdin (of the child program), and reads from stdout and stderr (of the
 549  * child program).
 550  */
 551 void
 552 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 553 {
 554         fd_set *readset = NULL, *writeset = NULL;
 555         int max_fd = 0;
 556         u_int nalloc = 0;
 557         int wait_status;        /* Status returned by wait(). */
 558         pid_t wait_pid;         /* pid returned by wait(). */
 559         int waiting_termination = 0;    /* Have displayed waiting close message. */
 560         u_int max_time_milliseconds;
 561         u_int previous_stdout_buffer_bytes;
 562         u_int stdout_buffer_bytes;
 563         int type;
 564
 565         debug("Entering interactive session.");
 566
 567         /* Initialize the SIGCHLD kludge. */
 568         child_terminated = 0;
 569         mysignal(SIGCHLD, sigchld_handler);
 570
 571         if (!use_privsep) {
 572                 signal(SIGTERM, sigterm_handler);
 573                 signal(SIGINT, sigterm_handler);
 574                 signal(SIGQUIT, sigterm_handler);
 575         }
 576
 577         /* Initialize our global variables. */
 578         fdin = fdin_arg;
 579         fdout = fdout_arg;
 580         fderr = fderr_arg;
 581
 582         /* nonblocking IO */
 583         set_nonblock(fdin);
 584         set_nonblock(fdout);
 585         /* we don't have stderr for interactive terminal sessions, see below */
 586         if (fderr != -1)
 587                 set_nonblock(fderr);
 588
 589         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 590                 fdin_is_tty = 1;
 591
 592         connection_in = packet_get_connection_in();
 593         connection_out = packet_get_connection_out();
 594
 595         notify_setup();
 596
 597         previous_stdout_buffer_bytes = 0;
 598
 599         /* Set approximate I/O buffer size. */
 600         if (packet_is_interactive())
 601                 buffer_high = 4096;
 602         else
 603                 buffer_high = 64 * 1024;
 604
 605 #if 0
 606         /* Initialize max_fd to the maximum of the known file descriptors. */
 607         max_fd = MAX(connection_in, connection_out);
 608         max_fd = MAX(max_fd, fdin);
 609         max_fd = MAX(max_fd, fdout);
 610         if (fderr != -1)
 611                 max_fd = MAX(max_fd, fderr);
 612 #endif
 613
 614         /* Initialize Initialize buffers. */
 615         buffer_init(&stdin_buffer);
 616         buffer_init(&stdout_buffer);
 617         buffer_init(&stderr_buffer);
 618
 619         /*
 620          * If we have no separate fderr (which is the case when we have a pty
 621          * - there we cannot make difference between data sent to stdout and
 622          * stderr), indicate that we have seen an EOF from stderr.  This way
 623          * we don't need to check the descriptor everywhere.
 624          */
 625         if (fderr == -1)
 626                 fderr_eof = 1;
 627
 628         server_init_dispatch();
 629
 630         /* Main loop of the server for the interactive session mode. */
 631         for (;;) {
 632
 633                 /* Process buffered packets from the client. */
 634                 process_buffered_input_packets();
 635
 636                 /*
 637                  * If we have received eof, and there is no more pending
 638                  * input data, cause a real eof by closing fdin.
 639                  */
 640                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 641                         if (fdin != fdout)
 642                                 close(fdin);
 643                         else
 644                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 645                         fdin = -1;
 646                 }
 647                 /* Make packets from buffered stderr data to send to the client. */
 648                 make_packets_from_stderr_data();
 649
 650                 /*
 651                  * Make packets from buffered stdout data to send to the
 652                  * client. If there is very little to send, this arranges to
 653                  * not send them now, but to wait a short while to see if we
 654                  * are getting more data. This is necessary, as some systems
 655                  * wake up readers from a pty after each separate character.
 656                  */
 657                 max_time_milliseconds = 0;
 658                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 659                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 660                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 661                         /* try again after a while */
 662                         max_time_milliseconds = 10;
 663                 } else {
 664                         /* Send it now. */
 665                         make_packets_from_stdout_data();
 666                 }
 667                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 668
 669                 /* Send channel data to the client. */
 670                 if (packet_not_very_much_data_to_write())
 671                         channel_output_poll();
 672
 673                 /*
 674                  * Bail out of the loop if the program has closed its output
 675                  * descriptors, and we have no more data to send to the
 676                  * client, and there is no pending buffered data.
 677                  */
 678                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 679                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 680                         if (!channel_still_open())
 681                                 break;
 682                         if (!waiting_termination) {
 683                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 684                                 char *cp;
 685                                 waiting_termination = 1;
 686                                 buffer_append(&stderr_buffer, s, strlen(s));
 687
 688                                 /* Display list of open channels. */
 689                                 cp = channel_open_message();
 690                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 691                                 xfree(cp);
 692                         }
 693                 }
 694                 max_fd = MAX(connection_in, connection_out);
 695                 max_fd = MAX(max_fd, fdin);
 696                 max_fd = MAX(max_fd, fdout);
 697                 max_fd = MAX(max_fd, fderr);
 698                 max_fd = MAX(max_fd, notify_pipe[0]);
 699
 700                 /* Sleep in select() until we can do something. */
 701                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 702                     &nalloc, max_time_milliseconds);
 703
 704                 if (received_sigterm) {
 705                         logit("Exiting on signal %d", received_sigterm);
 706                         /* Clean up sessions, utmp, etc. */
 707                         cleanup_exit(255);
 708                 }
 709
 710                 /* Process any channel events. */
 711                 channel_after_select(readset, writeset);
 712
 713                 /* Process input from the client and from program stdout/stderr. */
 714                 process_input(readset);
 715
 716                 /* Process output to the client and to program stdin. */
 717                 process_output(writeset);
 718         }
 719         if (readset)
 720                 xfree(readset);
 721         if (writeset)
 722                 xfree(writeset);
 723
 724         /* Cleanup and termination code. */
 725
 726         /* Wait until all output has been sent to the client. */
 727         drain_output();
 728
 729         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 730             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 731
 732         /* Free and clear the buffers. */
 733         buffer_free(&stdin_buffer);
 734         buffer_free(&stdout_buffer);
 735         buffer_free(&stderr_buffer);
 736
 737         /* Close the file descriptors. */
 738         if (fdout != -1)
 739                 close(fdout);
 740         fdout = -1;
 741         fdout_eof = 1;
 742         if (fderr != -1)
 743                 close(fderr);
 744         fderr = -1;
 745         fderr_eof = 1;
 746         if (fdin != -1)
 747                 close(fdin);
 748         fdin = -1;
 749
 750         channel_free_all();
 751
 752         /* We no longer want our SIGCHLD handler to be called. */
 753         mysignal(SIGCHLD, SIG_DFL);
 754
 755         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 756                 if (errno != EINTR)
 757                         packet_disconnect("wait: %.100s", strerror(errno));
 758         if (wait_pid != pid)
 759                 error("Strange, wait returned pid %ld, expected %ld",
 760                     (long)wait_pid, (long)pid);
 761
 762         /* Check if it exited normally. */
 763         if (WIFEXITED(wait_status)) {
 764                 /* Yes, normal exit.  Get exit status and send it to the client. */
 765                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 766                 packet_start(SSH_SMSG_EXITSTATUS);
 767                 packet_put_int(WEXITSTATUS(wait_status));
 768                 packet_send();
 769                 packet_write_wait();
 770
 771                 /*
 772                  * Wait for exit confirmation.  Note that there might be
 773                  * other packets coming before it; however, the program has
 774                  * already died so we just ignore them.  The client is
 775                  * supposed to respond with the confirmation when it receives
 776                  * the exit status.
 777                  */
 778                 do {
 779                         type = packet_read();
 780                 }
 781                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 782
 783                 debug("Received exit confirmation.");
 784                 return;
 785         }
 786         /* Check if the program terminated due to a signal. */
 787         if (WIFSIGNALED(wait_status))
 788                 packet_disconnect("Command terminated on signal %d.",
 789                                   WTERMSIG(wait_status));
 790
 791         /* Some weird exit cause.  Just exit. */
 792         packet_disconnect("wait returned status %04x.", wait_status);
 793         /* NOTREACHED */
 794 }
 795
 796 static void
 797 collect_children(void)
 798 {
 799         pid_t pid;
 800         sigset_t oset, nset;
 801         int status;
 802
 803         /* block SIGCHLD while we check for dead children */
 804         sigemptyset(&nset);
 805         sigaddset(&nset, SIGCHLD);
 806         sigprocmask(SIG_BLOCK, &nset, &oset);
 807         if (child_terminated) {
 808                 debug("Received SIGCHLD.");
 809                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 810                     (pid < 0 && errno == EINTR))
 811                         if (pid > 0)
 812                                 session_close_by_pid(pid, status);
 813                 child_terminated = 0;
 814         }
 815         sigprocmask(SIG_SETMASK, &oset, NULL);
 816 }
 817
 818 void
 819 server_loop2(Authctxt *authctxt)
 820 {
 821         fd_set *readset = NULL, *writeset = NULL;
 822         int rekeying = 0, max_fd, nalloc = 0;
 823
 824         debug("Entering interactive session for SSH2.");
 825
 826         mysignal(SIGCHLD, sigchld_handler);
 827         child_terminated = 0;
 828         connection_in = packet_get_connection_in();
 829         connection_out = packet_get_connection_out();
 830
 831         if (!use_privsep) {
 832                 signal(SIGTERM, sigterm_handler);
 833                 signal(SIGINT, sigterm_handler);
 834                 signal(SIGQUIT, sigterm_handler);
 835         }
 836
 837         notify_setup();
 838
 839         max_fd = MAX(connection_in, connection_out);
 840         max_fd = MAX(max_fd, notify_pipe[0]);
 841
 842         server_init_dispatch();
 843
 844         for (;;) {
 845                 process_buffered_input_packets();
 846
 847                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 848
 849                 if (!rekeying && packet_not_very_much_data_to_write())
 850                         channel_output_poll();
 851                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 852                     &nalloc, 0);
 853
 854                 if (received_sigterm) {
 855                         logit("Exiting on signal %d", received_sigterm);
 856                         /* Clean up sessions, utmp, etc. */
 857                         cleanup_exit(255);
 858                 }
 859
 860                 collect_children();
 861                 if (!rekeying) {
 862                         channel_after_select(readset, writeset);
 863                         if (packet_need_rekeying()) {
 864                                 debug("need rekeying");
 865                                 xxx_kex->done = 0;
 866                                 kex_send_kexinit(xxx_kex);
 867                         }
 868                 }
 869                 process_input(readset);
 870                 if (connection_closed)
 871                         break;
 872                 process_output(writeset);
 873         }
 874         collect_children();
 875
 876         if (readset)
 877                 xfree(readset);
 878         if (writeset)
 879                 xfree(writeset);
 880
 881         /* free all channels, no more reads and writes */
 882         channel_free_all();
 883
 884         /* free remaining sessions, e.g. remove wtmp entries */
 885         session_destroy_all(NULL);
 886 }
 887
 888 static void
 889 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 890 {
 891         debug("Got %d/%u for keepalive", type, seq);
 892         /*
 893          * reset timeout, since we got a sane answer from the client.
 894          * even if this was generated by something other than
 895          * the bogus CHANNEL_REQUEST we send for keepalives.
 896          */
 897         packet_set_alive_timeouts(0);
 898 }
 899
 900 static void
 901 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 902 {
 903         char *data;
 904         u_int data_len;
 905
 906         /* Stdin data from the client.  Append it to the buffer. */
 907         /* Ignore any data if the client has closed stdin. */
 908         if (fdin == -1)
 909                 return;
 910         data = packet_get_string(&data_len);
 911         packet_check_eom();
 912         buffer_append(&stdin_buffer, data, data_len);
 913         memset(data, 0, data_len);
 914         xfree(data);
 915 }
 916
 917 static void
 918 server_input_eof(int type, u_int32_t seq, void *ctxt)
 919 {
 920         /*
 921          * Eof from the client.  The stdin descriptor to the
 922          * program will be closed when all buffered data has
 923          * drained.
 924          */
 925         debug("EOF received for stdin.");
 926         packet_check_eom();
 927         stdin_eof = 1;
 928 }
 929
 930 static void
 931 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 932 {
 933         u_int row = packet_get_int();
 934         u_int col = packet_get_int();
 935         u_int xpixel = packet_get_int();
 936         u_int ypixel = packet_get_int();
 937
 938         debug("Window change received.");
 939         packet_check_eom();
 940         if (fdin != -1)
 941                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 942 }
 943
 944 static Channel *
 945 server_request_direct_tcpip(void)
 946 {
 947         Channel *c;
 948         char *target, *originator;
 949         u_short target_port, originator_port;
 950
 951         target = packet_get_string(NULL);
 952         target_port = packet_get_int();
 953         originator = packet_get_string(NULL);
 954         originator_port = packet_get_int();
 955         packet_check_eom();
 956
 957         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 958             "port %d", originator, originator_port, target, target_port);
 959
 960         /* XXX check permission */
 961         c = channel_connect_to(target, target_port,
 962             "direct-tcpip", "direct-tcpip");
 963
 964         xfree(originator);
 965         xfree(target);
 966
 967         return c;
 968 }
 969
 970 static Channel *
 971 server_request_tun(void)
 972 {
 973         Channel *c = NULL;
 974         int mode, tun;
 975         int sock;
 976
 977         mode = packet_get_int();
 978         switch (mode) {
 979         case SSH_TUNMODE_POINTOPOINT:
 980         case SSH_TUNMODE_ETHERNET:
 981                 break;
 982         default:
 983                 packet_send_debug("Unsupported tunnel device mode.");
 984                 return NULL;
 985         }
 986         if ((options.permit_tun & mode) == 0) {
 987                 packet_send_debug("Server has rejected tunnel device "
 988                     "forwarding");
 989                 return NULL;
 990         }
 991
 992         tun = packet_get_int();
 993         if (forced_tun_device != -1) {
 994                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 995                         goto done;
 996                 tun = forced_tun_device;
 997         }
 998         sock = tun_open(tun, mode);
 999         if (sock < 0)
1000                 goto done;
1001         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1002             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
1003         c->datagram = 1;
1004 #if defined(SSH_TUN_FILTER)
1005         if (mode == SSH_TUNMODE_POINTOPOINT)
1006                 channel_register_filter(c->self, sys_tun_infilter,
1007                     sys_tun_outfilter, NULL, NULL);
1008 #endif
1009
1010  done:
1011         if (c == NULL)
1012                 packet_send_debug("Failed to open the tunnel device.");
1013         return c;
1014 }
1015
1016 static Channel *
1017 server_request_session(void)
1018 {
1019         Channel *c;
1020
1021         debug("input_session_request");
1022         packet_check_eom();
1023
1024         if (no_more_sessions) {
1025                 packet_disconnect("Possible attack: attempt to open a session "
1026                     "after additional sessions disabled");
1027         }
1028
1029         /*
1030          * A server session has no fd to read or write until a
1031          * CHANNEL_REQUEST for a shell is made, so we set the type to
1032          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1033          * CHANNEL_REQUEST messages is registered.
1034          */
1035         c = channel_new("session", SSH_CHANNEL_LARVAL,
1036             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1037             0, "server-session", 1);
1038         if (session_open(the_authctxt, c->self) != 1) {
1039                 debug("session open failed, free channel %d", c->self);
1040                 channel_free(c);
1041                 return NULL;
1042         }
1043         channel_register_cleanup(c->self, session_close_by_channel, 0);
1044         return c;
1045 }
1046
1047 static void
1048 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1049 {
1050         Channel *c = NULL;
1051         char *ctype;
1052         int rchan;
1053         u_int rmaxpack, rwindow, len;
1054
1055         ctype = packet_get_string(&len);
1056         rchan = packet_get_int();
1057         rwindow = packet_get_int();
1058         rmaxpack = packet_get_int();
1059
1060         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1061             ctype, rchan, rwindow, rmaxpack);
1062
1063         if (strcmp(ctype, "session") == 0) {
1064                 c = server_request_session();
1065         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1066                 c = server_request_direct_tcpip();
1067         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1068                 c = server_request_tun();
1069         }
1070         if (c != NULL) {
1071                 debug("server_input_channel_open: confirm %s", ctype);
1072                 c->remote_id = rchan;
1073                 c->remote_window = rwindow;
1074                 c->remote_maxpacket = rmaxpack;
1075                 if (c->type != SSH_CHANNEL_CONNECTING) {
1076                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1077                         packet_put_int(c->remote_id);
1078                         packet_put_int(c->self);
1079                         packet_put_int(c->local_window);
1080                         packet_put_int(c->local_maxpacket);
1081                         packet_send();
1082                 }
1083         } else {
1084                 debug("server_input_channel_open: failure %s", ctype);
1085                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1086                 packet_put_int(rchan);
1087                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1088                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1089                         packet_put_cstring("open failed");
1090                         packet_put_cstring("");
1091                 }
1092                 packet_send();
1093         }
1094         xfree(ctype);
1095 }
1096
1097 static void
1098 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1099 {
1100         char *rtype;
1101         int want_reply;
1102         int success = 0, allocated_listen_port = 0;
1103
1104         rtype = packet_get_string(NULL);
1105         want_reply = packet_get_char();
1106         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1107
1108         /* -R style forwarding */
1109         if (strcmp(rtype, "tcpip-forward") == 0) {
1110                 struct passwd *pw;
1111                 char *listen_address;
1112                 u_short listen_port;
1113
1114                 pw = the_authctxt->pw;
1115                 if (pw == NULL || !the_authctxt->valid)
1116                         fatal("server_input_global_request: no/invalid user");
1117                 listen_address = packet_get_string(NULL);
1118                 listen_port = (u_short)packet_get_int();
1119                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1120                     listen_address, listen_port);
1121
1122                 /* check permissions */
1123                 if (!options.allow_tcp_forwarding ||
1124                     no_port_forwarding_flag ||
1125                     (!want_reply && listen_port == 0)
1126 #ifndef NO_IPPORT_RESERVED_CONCEPT
1127                     || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1128                     pw->pw_uid != 0)
1129 #endif
1130                     ) {
1131                         success = 0;
1132                         packet_send_debug("Server has disabled port forwarding.");
1133                 } else {
1134                         /* Start listening on the port */
1135                         success = channel_setup_remote_fwd_listener(
1136                             listen_address, listen_port,
1137                             &allocated_listen_port, options.gateway_ports);
1138                 }
1139                 xfree(listen_address);
1140         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1141                 char *cancel_address;
1142                 u_short cancel_port;
1143
1144                 cancel_address = packet_get_string(NULL);
1145                 cancel_port = (u_short)packet_get_int();
1146                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1147                     cancel_address, cancel_port);
1148
1149                 success = channel_cancel_rport_listener(cancel_address,
1150                     cancel_port);
1151                 xfree(cancel_address);
1152         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1153                 no_more_sessions = 1;
1154                 success = 1;
1155         }
1156         if (want_reply) {
1157                 packet_start(success ?
1158                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1159                 if (success && allocated_listen_port > 0)
1160                         packet_put_int(allocated_listen_port);
1161                 packet_send();
1162                 packet_write_wait();
1163         }
1164         xfree(rtype);
1165 }
1166
1167 static void
1168 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1169 {
1170         Channel *c;
1171         int id, reply, success = 0;
1172         char *rtype;
1173
1174         id = packet_get_int();
1175         rtype = packet_get_string(NULL);
1176         reply = packet_get_char();
1177
1178         debug("server_input_channel_req: channel %d request %s reply %d",
1179             id, rtype, reply);
1180
1181         if ((c = channel_lookup(id)) == NULL)
1182                 packet_disconnect("server_input_channel_req: "
1183                     "unknown channel %d", id);
1184         if (!strcmp(rtype, "eow@openssh.com")) {
1185                 packet_check_eom();
1186                 chan_rcvd_eow(c);
1187         } else if ((c->type == SSH_CHANNEL_LARVAL ||
1188             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1189                 success = session_input_channel_req(c, rtype);
1190         if (reply) {
1191                 packet_start(success ?
1192                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1193                 packet_put_int(c->remote_id);
1194                 packet_send();
1195         }
1196         xfree(rtype);
1197 }
1198
1199 static void
1200 server_init_dispatch_20(void)
1201 {
1202         debug("server_init_dispatch_20");
1203         dispatch_init(&dispatch_protocol_error);
1204         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1205         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1206         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1207         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1208         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1209         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1210         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1211         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1212         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1213         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1214         /* client_alive */
1215         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1216         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1217         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1218         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1219         /* rekeying */
1220         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1221 }
1222 static void
1223 server_init_dispatch_13(void)
1224 {
1225         debug("server_init_dispatch_13");
1226         dispatch_init(NULL);
1227         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1228         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1229         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1230         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1231         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1232         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1233         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1234         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1235         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1236 }
1237 static void
1238 server_init_dispatch_15(void)
1239 {
1240         server_init_dispatch_13();
1241         debug("server_init_dispatch_15");
1242         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1243         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1244 }
1245 static void
1246 server_init_dispatch(void)
1247 {
1248         if (compat20)
1249                 server_init_dispatch_20();
1250         else if (compat13)
1251                 server_init_dispatch_13();
1252         else
1253                 server_init_dispatch_15();
1254 }