crypto/openssh-5/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.148 2008/02/22 20:44:02 dtucker Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/param.h>
  42 #include <sys/wait.h>
  43 #include <sys/socket.h>
  44 #ifdef HAVE_SYS_TIME_H
  45 # include <sys/time.h>
  46 #endif
  47
  48 #include <netinet/in.h>
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <pwd.h>
  53 #include <signal.h>
  54 #include <string.h>
  55 #include <termios.h>
  56 #include <unistd.h>
  57 #include <stdarg.h>
  58
  59 #include "xmalloc.h"
  60 #include "packet.h"
  61 #include "buffer.h"
  62 #include "log.h"
  63 #include "servconf.h"
  64 #include "canohost.h"
  65 #include "sshpty.h"
  66 #include "channels.h"
  67 #include "compat.h"
  68 #include "ssh1.h"
  69 #include "ssh2.h"
  70 #include "key.h"
  71 #include "cipher.h"
  72 #include "kex.h"
  73 #include "hostfile.h"
  74 #include "auth.h"
  75 #include "session.h"
  76 #include "dispatch.h"
  77 #include "auth-options.h"
  78 #include "serverloop.h"
  79 #include "misc.h"
  80
  81 extern ServerOptions options;
  82
  83 /* XXX */
  84 extern Kex *xxx_kex;
  85 extern Authctxt *the_authctxt;
  86 extern int use_privsep;
  87
  88 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  89 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  90 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  91 static int fdin;                /* Descriptor for stdin (for writing) */
  92 static int fdout;               /* Descriptor for stdout (for reading);
  93                                    May be same number as fdin. */
  94 static int fderr;               /* Descriptor for stderr.  May be -1. */
  95 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  96 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
  97 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
  98 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
  99 static int stdin_eof = 0;       /* EOF message received from client. */
 100 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
 101 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
 102 static int fdin_is_tty = 0;     /* fdin points to a tty. */
 103 static int connection_in;       /* Connection to client (input). */
 104 static int connection_out;      /* Connection to client (output). */
 105 static int connection_closed = 0;       /* Connection to client closed. */
 106 static u_int buffer_high;       /* "Soft" max buffer size. */
 107
 108 /*
 109  * This SIGCHLD kludge is used to detect when the child exits.  The server
 110  * will exit after that, as soon as forwarded connections have terminated.
 111  */
 112
 113 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 114
 115 /* Cleanup on signals (!use_privsep case only) */
 116 static volatile sig_atomic_t received_sigterm = 0;
 117
 118 /* prototypes */
 119 static void server_init_dispatch(void);
 120
 121 /*
 122  * we write to this pipe if a SIGCHLD is caught in order to avoid
 123  * the race between select() and child_terminated
 124  */
 125 static int notify_pipe[2];
 126 static void
 127 notify_setup(void)
 128 {
 129         if (pipe(notify_pipe) < 0) {
 130                 error("pipe(notify_pipe) failed %s", strerror(errno));
 131         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 132             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 133                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 134                 close(notify_pipe[0]);
 135                 close(notify_pipe[1]);
 136         } else {
 137                 set_nonblock(notify_pipe[0]);
 138                 set_nonblock(notify_pipe[1]);
 139                 return;
 140         }
 141         notify_pipe[0] = -1;    /* read end */
 142         notify_pipe[1] = -1;    /* write end */
 143 }
 144 static void
 145 notify_parent(void)
 146 {
 147         if (notify_pipe[1] != -1)
 148                 write(notify_pipe[1], "", 1);
 149 }
 150 static void
 151 notify_prepare(fd_set *readset)
 152 {
 153         if (notify_pipe[0] != -1)
 154                 FD_SET(notify_pipe[0], readset);
 155 }
 156 static void
 157 notify_done(fd_set *readset)
 158 {
 159         char c;
 160
 161         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 162                 while (read(notify_pipe[0], &c, 1) != -1)
 163                         debug2("notify_done: reading");
 164 }
 165
 166 /*ARGSUSED*/
 167 static void
 168 sigchld_handler(int sig)
 169 {
 170         int save_errno = errno;
 171         child_terminated = 1;
 172 #ifndef _UNICOS
 173         mysignal(SIGCHLD, sigchld_handler);
 174 #endif
 175         notify_parent();
 176         errno = save_errno;
 177 }
 178
 179 /*ARGSUSED*/
 180 static void
 181 sigterm_handler(int sig)
 182 {
 183         received_sigterm = sig;
 184 }
 185
 186 /*
 187  * Make packets from buffered stderr data, and buffer it for sending
 188  * to the client.
 189  */
 190 static void
 191 make_packets_from_stderr_data(void)
 192 {
 193         u_int len;
 194
 195         /* Send buffered stderr data to the client. */
 196         while (buffer_len(&stderr_buffer) > 0 &&
 197             packet_not_very_much_data_to_write()) {
 198                 len = buffer_len(&stderr_buffer);
 199                 if (packet_is_interactive()) {
 200                         if (len > 512)
 201                                 len = 512;
 202                 } else {
 203                         /* Keep the packets at reasonable size. */
 204                         if (len > packet_get_maxsize())
 205                                 len = packet_get_maxsize();
 206                 }
 207                 packet_start(SSH_SMSG_STDERR_DATA);
 208                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 209                 packet_send();
 210                 buffer_consume(&stderr_buffer, len);
 211                 stderr_bytes += len;
 212         }
 213 }
 214
 215 /*
 216  * Make packets from buffered stdout data, and buffer it for sending to the
 217  * client.
 218  */
 219 static void
 220 make_packets_from_stdout_data(void)
 221 {
 222         u_int len;
 223
 224         /* Send buffered stdout data to the client. */
 225         while (buffer_len(&stdout_buffer) > 0 &&
 226             packet_not_very_much_data_to_write()) {
 227                 len = buffer_len(&stdout_buffer);
 228                 if (packet_is_interactive()) {
 229                         if (len > 512)
 230                                 len = 512;
 231                 } else {
 232                         /* Keep the packets at reasonable size. */
 233                         if (len > packet_get_maxsize())
 234                                 len = packet_get_maxsize();
 235                 }
 236                 packet_start(SSH_SMSG_STDOUT_DATA);
 237                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 238                 packet_send();
 239                 buffer_consume(&stdout_buffer, len);
 240                 stdout_bytes += len;
 241         }
 242 }
 243
 244 static void
 245 client_alive_check(void)
 246 {
 247         int channel_id;
 248
 249         /* timeout, check to see how many we have had */
 250         if (++keep_alive_timeouts > options.client_alive_count_max) {
 251                 logit("Timeout, client not responding.");
 252                 cleanup_exit(255);
 253         }
 254
 255         /*
 256          * send a bogus global/channel request with "wantreply",
 257          * we should get back a failure
 258          */
 259         if ((channel_id = channel_find_open()) == -1) {
 260                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 261                 packet_put_cstring("keepalive@openssh.com");
 262                 packet_put_char(1);     /* boolean: want reply */
 263         } else {
 264                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 265         }
 266         packet_send();
 267 }
 268
 269 /*
 270  * Sleep in select() until we can do something.  This will initialize the
 271  * select masks.  Upon return, the masks will indicate which descriptors
 272  * have data or can accept data.  Optionally, a maximum time can be specified
 273  * for the duration of the wait (0 = infinite).
 274  */
 275 static void
 276 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 277     u_int *nallocp, u_int max_time_milliseconds)
 278 {
 279         struct timeval tv, *tvp;
 280         int ret;
 281         int client_alive_scheduled = 0;
 282         int program_alive_scheduled = 0;
 283
 284         /*
 285          * if using client_alive, set the max timeout accordingly,
 286          * and indicate that this particular timeout was for client
 287          * alive by setting the client_alive_scheduled flag.
 288          *
 289          * this could be randomized somewhat to make traffic
 290          * analysis more difficult, but we're not doing it yet.
 291          */
 292         if (compat20 &&
 293             max_time_milliseconds == 0 && options.client_alive_interval) {
 294                 client_alive_scheduled = 1;
 295                 max_time_milliseconds = options.client_alive_interval * 1000;
 296         }
 297
 298         /* Allocate and update select() masks for channel descriptors. */
 299         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 300
 301         if (compat20) {
 302 #if 0
 303                 /* wrong: bad condition XXX */
 304                 if (channel_not_very_much_buffered_data())
 305 #endif
 306                 FD_SET(connection_in, *readsetp);
 307         } else {
 308                 /*
 309                  * Read packets from the client unless we have too much
 310                  * buffered stdin or channel data.
 311                  */
 312                 if (buffer_len(&stdin_buffer) < buffer_high &&
 313                     channel_not_very_much_buffered_data())
 314                         FD_SET(connection_in, *readsetp);
 315                 /*
 316                  * If there is not too much data already buffered going to
 317                  * the client, try to get some more data from the program.
 318                  */
 319                 if (packet_not_very_much_data_to_write()) {
 320                         program_alive_scheduled = child_terminated;
 321                         if (!fdout_eof)
 322                                 FD_SET(fdout, *readsetp);
 323                         if (!fderr_eof)
 324                                 FD_SET(fderr, *readsetp);
 325                 }
 326                 /*
 327                  * If we have buffered data, try to write some of that data
 328                  * to the program.
 329                  */
 330                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 331                         FD_SET(fdin, *writesetp);
 332         }
 333         notify_prepare(*readsetp);
 334
 335         /*
 336          * If we have buffered packet data going to the client, mark that
 337          * descriptor.
 338          */
 339         if (packet_have_data_to_write())
 340                 FD_SET(connection_out, *writesetp);
 341
 342         /*
 343          * If child has terminated and there is enough buffer space to read
 344          * from it, then read as much as is available and exit.
 345          */
 346         if (child_terminated && packet_not_very_much_data_to_write())
 347                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 348                         max_time_milliseconds = 100;
 349
 350         if (max_time_milliseconds == 0)
 351                 tvp = NULL;
 352         else {
 353                 tv.tv_sec = max_time_milliseconds / 1000;
 354                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 355                 tvp = &tv;
 356         }
 357
 358         /* Wait for something to happen, or the timeout to expire. */
 359         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 360
 361         if (ret == -1) {
 362                 memset(*readsetp, 0, *nallocp);
 363                 memset(*writesetp, 0, *nallocp);
 364                 if (errno != EINTR)
 365                         error("select: %.100s", strerror(errno));
 366         } else {
 367                 if (ret == 0 && client_alive_scheduled)
 368                         client_alive_check();
 369                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 370                         if (!fdout_eof)
 371                                 FD_SET(fdout, *readsetp);
 372                         if (!fderr_eof)
 373                                 FD_SET(fderr, *readsetp);
 374                 }
 375         }
 376
 377         notify_done(*readsetp);
 378 }
 379
 380 /*
 381  * Processes input from the client and the program.  Input data is stored
 382  * in buffers and processed later.
 383  */
 384 static void
 385 process_input(fd_set *readset)
 386 {
 387         int len;
 388         char buf[16384];
 389
 390         /* Read and buffer any input data from the client. */
 391         if (FD_ISSET(connection_in, readset)) {
 392                 len = read(connection_in, buf, sizeof(buf));
 393                 if (len == 0) {
 394                         verbose("Connection closed by %.100s",
 395                             get_remote_ipaddr());
 396                         connection_closed = 1;
 397                         if (compat20)
 398                                 return;
 399                         cleanup_exit(255);
 400                 } else if (len < 0) {
 401                         if (errno != EINTR && errno != EAGAIN) {
 402                                 verbose("Read error from remote host "
 403                                     "%.100s: %.100s",
 404                                     get_remote_ipaddr(), strerror(errno));
 405                                 cleanup_exit(255);
 406                         }
 407                 } else {
 408                         /* Buffer any received data. */
 409                         packet_process_incoming(buf, len);
 410                 }
 411         }
 412         if (compat20)
 413                 return;
 414
 415         /* Read and buffer any available stdout data from the program. */
 416         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 417                 errno = 0;
 418                 len = read(fdout, buf, sizeof(buf));
 419                 if (len < 0 && (errno == EINTR ||
 420                     (errno == EAGAIN && !child_terminated))) {
 421                         /* do nothing */
 422 #ifndef PTY_ZEROREAD
 423                 } else if (len <= 0) {
 424 #else
 425                 } else if ((!isatty(fdout) && len <= 0) ||
 426                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 427 #endif
 428                         fdout_eof = 1;
 429                 } else {
 430                         buffer_append(&stdout_buffer, buf, len);
 431                         fdout_bytes += len;
 432                 }
 433         }
 434         /* Read and buffer any available stderr data from the program. */
 435         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 436                 errno = 0;
 437                 len = read(fderr, buf, sizeof(buf));
 438                 if (len < 0 && (errno == EINTR ||
 439                     (errno == EAGAIN && !child_terminated))) {
 440                         /* do nothing */
 441 #ifndef PTY_ZEROREAD
 442                 } else if (len <= 0) {
 443 #else
 444                 } else if ((!isatty(fderr) && len <= 0) ||
 445                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 446 #endif
 447                         fderr_eof = 1;
 448                 } else {
 449                         buffer_append(&stderr_buffer, buf, len);
 450                 }
 451         }
 452 }
 453
 454 /*
 455  * Sends data from internal buffers to client program stdin.
 456  */
 457 static void
 458 process_output(fd_set *writeset)
 459 {
 460         struct termios tio;
 461         u_char *data;
 462         u_int dlen;
 463         int len;
 464
 465         /* Write buffered data to program stdin. */
 466         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 467                 data = buffer_ptr(&stdin_buffer);
 468                 dlen = buffer_len(&stdin_buffer);
 469                 len = write(fdin, data, dlen);
 470                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
 471                         /* do nothing */
 472                 } else if (len <= 0) {
 473                         if (fdin != fdout)
 474                                 close(fdin);
 475                         else
 476                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 477                         fdin = -1;
 478                 } else {
 479                         /* Successful write. */
 480                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 481                             tcgetattr(fdin, &tio) == 0 &&
 482                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 483                                 /*
 484                                  * Simulate echo to reduce the impact of
 485                                  * traffic analysis
 486                                  */
 487                                 packet_send_ignore(len);
 488                                 packet_send();
 489                         }
 490                         /* Consume the data from the buffer. */
 491                         buffer_consume(&stdin_buffer, len);
 492                         /* Update the count of bytes written to the program. */
 493                         stdin_bytes += len;
 494                 }
 495         }
 496         /* Send any buffered packet data to the client. */
 497         if (FD_ISSET(connection_out, writeset))
 498                 packet_write_poll();
 499 }
 500
 501 /*
 502  * Wait until all buffered output has been sent to the client.
 503  * This is used when the program terminates.
 504  */
 505 static void
 506 drain_output(void)
 507 {
 508         /* Send any buffered stdout data to the client. */
 509         if (buffer_len(&stdout_buffer) > 0) {
 510                 packet_start(SSH_SMSG_STDOUT_DATA);
 511                 packet_put_string(buffer_ptr(&stdout_buffer),
 512                                   buffer_len(&stdout_buffer));
 513                 packet_send();
 514                 /* Update the count of sent bytes. */
 515                 stdout_bytes += buffer_len(&stdout_buffer);
 516         }
 517         /* Send any buffered stderr data to the client. */
 518         if (buffer_len(&stderr_buffer) > 0) {
 519                 packet_start(SSH_SMSG_STDERR_DATA);
 520                 packet_put_string(buffer_ptr(&stderr_buffer),
 521                                   buffer_len(&stderr_buffer));
 522                 packet_send();
 523                 /* Update the count of sent bytes. */
 524                 stderr_bytes += buffer_len(&stderr_buffer);
 525         }
 526         /* Wait until all buffered data has been written to the client. */
 527         packet_write_wait();
 528 }
 529
 530 static void
 531 process_buffered_input_packets(void)
 532 {
 533         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 534 }
 535
 536 /*
 537  * Performs the interactive session.  This handles data transmission between
 538  * the client and the program.  Note that the notion of stdin, stdout, and
 539  * stderr in this function is sort of reversed: this function writes to
 540  * stdin (of the child program), and reads from stdout and stderr (of the
 541  * child program).
 542  */
 543 void
 544 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 545 {
 546         fd_set *readset = NULL, *writeset = NULL;
 547         int max_fd = 0;
 548         u_int nalloc = 0;
 549         int wait_status;        /* Status returned by wait(). */
 550         pid_t wait_pid;         /* pid returned by wait(). */
 551         int waiting_termination = 0;    /* Have displayed waiting close message. */
 552         u_int max_time_milliseconds;
 553         u_int previous_stdout_buffer_bytes;
 554         u_int stdout_buffer_bytes;
 555         int type;
 556
 557         debug("Entering interactive session.");
 558
 559         /* Initialize the SIGCHLD kludge. */
 560         child_terminated = 0;
 561         mysignal(SIGCHLD, sigchld_handler);
 562
 563         if (!use_privsep) {
 564                 signal(SIGTERM, sigterm_handler);
 565                 signal(SIGINT, sigterm_handler);
 566                 signal(SIGQUIT, sigterm_handler);
 567         }
 568
 569         /* Initialize our global variables. */
 570         fdin = fdin_arg;
 571         fdout = fdout_arg;
 572         fderr = fderr_arg;
 573
 574         /* nonblocking IO */
 575         set_nonblock(fdin);
 576         set_nonblock(fdout);
 577         /* we don't have stderr for interactive terminal sessions, see below */
 578         if (fderr != -1)
 579                 set_nonblock(fderr);
 580
 581         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 582                 fdin_is_tty = 1;
 583
 584         connection_in = packet_get_connection_in();
 585         connection_out = packet_get_connection_out();
 586
 587         notify_setup();
 588
 589         previous_stdout_buffer_bytes = 0;
 590
 591         /* Set approximate I/O buffer size. */
 592         if (packet_is_interactive())
 593                 buffer_high = 4096;
 594         else
 595                 buffer_high = 64 * 1024;
 596
 597 #if 0
 598         /* Initialize max_fd to the maximum of the known file descriptors. */
 599         max_fd = MAX(connection_in, connection_out);
 600         max_fd = MAX(max_fd, fdin);
 601         max_fd = MAX(max_fd, fdout);
 602         if (fderr != -1)
 603                 max_fd = MAX(max_fd, fderr);
 604 #endif
 605
 606         /* Initialize Initialize buffers. */
 607         buffer_init(&stdin_buffer);
 608         buffer_init(&stdout_buffer);
 609         buffer_init(&stderr_buffer);
 610
 611         /*
 612          * If we have no separate fderr (which is the case when we have a pty
 613          * - there we cannot make difference between data sent to stdout and
 614          * stderr), indicate that we have seen an EOF from stderr.  This way
 615          * we don't need to check the descriptor everywhere.
 616          */
 617         if (fderr == -1)
 618                 fderr_eof = 1;
 619
 620         server_init_dispatch();
 621
 622         /* Main loop of the server for the interactive session mode. */
 623         for (;;) {
 624
 625                 /* Process buffered packets from the client. */
 626                 process_buffered_input_packets();
 627
 628                 /*
 629                  * If we have received eof, and there is no more pending
 630                  * input data, cause a real eof by closing fdin.
 631                  */
 632                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 633                         if (fdin != fdout)
 634                                 close(fdin);
 635                         else
 636                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 637                         fdin = -1;
 638                 }
 639                 /* Make packets from buffered stderr data to send to the client. */
 640                 make_packets_from_stderr_data();
 641
 642                 /*
 643                  * Make packets from buffered stdout data to send to the
 644                  * client. If there is very little to send, this arranges to
 645                  * not send them now, but to wait a short while to see if we
 646                  * are getting more data. This is necessary, as some systems
 647                  * wake up readers from a pty after each separate character.
 648                  */
 649                 max_time_milliseconds = 0;
 650                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 651                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 652                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 653                         /* try again after a while */
 654                         max_time_milliseconds = 10;
 655                 } else {
 656                         /* Send it now. */
 657                         make_packets_from_stdout_data();
 658                 }
 659                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 660
 661                 /* Send channel data to the client. */
 662                 if (packet_not_very_much_data_to_write())
 663                         channel_output_poll();
 664
 665                 /*
 666                  * Bail out of the loop if the program has closed its output
 667                  * descriptors, and we have no more data to send to the
 668                  * client, and there is no pending buffered data.
 669                  */
 670                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 671                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 672                         if (!channel_still_open())
 673                                 break;
 674                         if (!waiting_termination) {
 675                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 676                                 char *cp;
 677                                 waiting_termination = 1;
 678                                 buffer_append(&stderr_buffer, s, strlen(s));
 679
 680                                 /* Display list of open channels. */
 681                                 cp = channel_open_message();
 682                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 683                                 xfree(cp);
 684                         }
 685                 }
 686                 max_fd = MAX(connection_in, connection_out);
 687                 max_fd = MAX(max_fd, fdin);
 688                 max_fd = MAX(max_fd, fdout);
 689                 max_fd = MAX(max_fd, fderr);
 690                 max_fd = MAX(max_fd, notify_pipe[0]);
 691
 692                 /* Sleep in select() until we can do something. */
 693                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 694                     &nalloc, max_time_milliseconds);
 695
 696                 if (received_sigterm) {
 697                         logit("Exiting on signal %d", received_sigterm);
 698                         /* Clean up sessions, utmp, etc. */
 699                         cleanup_exit(255);
 700                 }
 701
 702                 /* Process any channel events. */
 703                 channel_after_select(readset, writeset);
 704
 705                 /* Process input from the client and from program stdout/stderr. */
 706                 process_input(readset);
 707
 708                 /* Process output to the client and to program stdin. */
 709                 process_output(writeset);
 710         }
 711         if (readset)
 712                 xfree(readset);
 713         if (writeset)
 714                 xfree(writeset);
 715
 716         /* Cleanup and termination code. */
 717
 718         /* Wait until all output has been sent to the client. */
 719         drain_output();
 720
 721         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 722             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 723
 724         /* Free and clear the buffers. */
 725         buffer_free(&stdin_buffer);
 726         buffer_free(&stdout_buffer);
 727         buffer_free(&stderr_buffer);
 728
 729         /* Close the file descriptors. */
 730         if (fdout != -1)
 731                 close(fdout);
 732         fdout = -1;
 733         fdout_eof = 1;
 734         if (fderr != -1)
 735                 close(fderr);
 736         fderr = -1;
 737         fderr_eof = 1;
 738         if (fdin != -1)
 739                 close(fdin);
 740         fdin = -1;
 741
 742         channel_free_all();
 743
 744         /* We no longer want our SIGCHLD handler to be called. */
 745         mysignal(SIGCHLD, SIG_DFL);
 746
 747         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 748                 if (errno != EINTR)
 749                         packet_disconnect("wait: %.100s", strerror(errno));
 750         if (wait_pid != pid)
 751                 error("Strange, wait returned pid %ld, expected %ld",
 752                     (long)wait_pid, (long)pid);
 753
 754         /* Check if it exited normally. */
 755         if (WIFEXITED(wait_status)) {
 756                 /* Yes, normal exit.  Get exit status and send it to the client. */
 757                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 758                 packet_start(SSH_SMSG_EXITSTATUS);
 759                 packet_put_int(WEXITSTATUS(wait_status));
 760                 packet_send();
 761                 packet_write_wait();
 762
 763                 /*
 764                  * Wait for exit confirmation.  Note that there might be
 765                  * other packets coming before it; however, the program has
 766                  * already died so we just ignore them.  The client is
 767                  * supposed to respond with the confirmation when it receives
 768                  * the exit status.
 769                  */
 770                 do {
 771                         type = packet_read();
 772                 }
 773                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 774
 775                 debug("Received exit confirmation.");
 776                 return;
 777         }
 778         /* Check if the program terminated due to a signal. */
 779         if (WIFSIGNALED(wait_status))
 780                 packet_disconnect("Command terminated on signal %d.",
 781                                   WTERMSIG(wait_status));
 782
 783         /* Some weird exit cause.  Just exit. */
 784         packet_disconnect("wait returned status %04x.", wait_status);
 785         /* NOTREACHED */
 786 }
 787
 788 static void
 789 collect_children(void)
 790 {
 791         pid_t pid;
 792         sigset_t oset, nset;
 793         int status;
 794
 795         /* block SIGCHLD while we check for dead children */
 796         sigemptyset(&nset);
 797         sigaddset(&nset, SIGCHLD);
 798         sigprocmask(SIG_BLOCK, &nset, &oset);
 799         if (child_terminated) {
 800                 debug("Received SIGCHLD.");
 801                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 802                     (pid < 0 && errno == EINTR))
 803                         if (pid > 0)
 804                                 session_close_by_pid(pid, status);
 805                 child_terminated = 0;
 806         }
 807         sigprocmask(SIG_SETMASK, &oset, NULL);
 808 }
 809
 810 void
 811 server_loop2(Authctxt *authctxt)
 812 {
 813         fd_set *readset = NULL, *writeset = NULL;
 814         int rekeying = 0, max_fd, nalloc = 0;
 815
 816         debug("Entering interactive session for SSH2.");
 817
 818         mysignal(SIGCHLD, sigchld_handler);
 819         child_terminated = 0;
 820         connection_in = packet_get_connection_in();
 821         connection_out = packet_get_connection_out();
 822
 823         if (!use_privsep) {
 824                 signal(SIGTERM, sigterm_handler);
 825                 signal(SIGINT, sigterm_handler);
 826                 signal(SIGQUIT, sigterm_handler);
 827         }
 828
 829         notify_setup();
 830
 831         max_fd = MAX(connection_in, connection_out);
 832         max_fd = MAX(max_fd, notify_pipe[0]);
 833
 834         server_init_dispatch();
 835
 836         for (;;) {
 837                 process_buffered_input_packets();
 838
 839                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 840
 841                 if (!rekeying && packet_not_very_much_data_to_write())
 842                         channel_output_poll();
 843                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 844                     &nalloc, 0);
 845
 846                 if (received_sigterm) {
 847                         logit("Exiting on signal %d", received_sigterm);
 848                         /* Clean up sessions, utmp, etc. */
 849                         cleanup_exit(255);
 850                 }
 851
 852                 collect_children();
 853                 if (!rekeying) {
 854                         channel_after_select(readset, writeset);
 855                         if (packet_need_rekeying()) {
 856                                 debug("need rekeying");
 857                                 xxx_kex->done = 0;
 858                                 kex_send_kexinit(xxx_kex);
 859                         }
 860                 }
 861                 process_input(readset);
 862                 if (connection_closed)
 863                         break;
 864                 process_output(writeset);
 865         }
 866         collect_children();
 867
 868         if (readset)
 869                 xfree(readset);
 870         if (writeset)
 871                 xfree(writeset);
 872
 873         /* free all channels, no more reads and writes */
 874         channel_free_all();
 875
 876         /* free remaining sessions, e.g. remove wtmp entries */
 877         session_destroy_all(NULL);
 878 }
 879
 880 static void
 881 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 882 {
 883         debug("Got %d/%u for keepalive", type, seq);
 884         /*
 885          * reset timeout, since we got a sane answer from the client.
 886          * even if this was generated by something other than
 887          * the bogus CHANNEL_REQUEST we send for keepalives.
 888          */
 889         keep_alive_timeouts = 0;
 890 }
 891
 892 static void
 893 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 894 {
 895         char *data;
 896         u_int data_len;
 897
 898         /* Stdin data from the client.  Append it to the buffer. */
 899         /* Ignore any data if the client has closed stdin. */
 900         if (fdin == -1)
 901                 return;
 902         data = packet_get_string(&data_len);
 903         packet_check_eom();
 904         buffer_append(&stdin_buffer, data, data_len);
 905         memset(data, 0, data_len);
 906         xfree(data);
 907 }
 908
 909 static void
 910 server_input_eof(int type, u_int32_t seq, void *ctxt)
 911 {
 912         /*
 913          * Eof from the client.  The stdin descriptor to the
 914          * program will be closed when all buffered data has
 915          * drained.
 916          */
 917         debug("EOF received for stdin.");
 918         packet_check_eom();
 919         stdin_eof = 1;
 920 }
 921
 922 static void
 923 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 924 {
 925         u_int row = packet_get_int();
 926         u_int col = packet_get_int();
 927         u_int xpixel = packet_get_int();
 928         u_int ypixel = packet_get_int();
 929
 930         debug("Window change received.");
 931         packet_check_eom();
 932         if (fdin != -1)
 933                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 934 }
 935
 936 static Channel *
 937 server_request_direct_tcpip(void)
 938 {
 939         Channel *c;
 940         int sock;
 941         char *target, *originator;
 942         int target_port, originator_port;
 943
 944         target = packet_get_string(NULL);
 945         target_port = packet_get_int();
 946         originator = packet_get_string(NULL);
 947         originator_port = packet_get_int();
 948         packet_check_eom();
 949
 950         debug("server_request_direct_tcpip: originator %s port %d, target %s port %d",
 951             originator, originator_port, target, target_port);
 952
 953         /* XXX check permission */
 954         sock = channel_connect_to(target, target_port);
 955         xfree(target);
 956         xfree(originator);
 957         if (sock < 0)
 958                 return NULL;
 959         c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING,
 960             sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT,
 961             CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1);
 962         return c;
 963 }
 964
 965 static Channel *
 966 server_request_tun(void)
 967 {
 968         Channel *c = NULL;
 969         int mode, tun;
 970         int sock;
 971
 972         mode = packet_get_int();
 973         switch (mode) {
 974         case SSH_TUNMODE_POINTOPOINT:
 975         case SSH_TUNMODE_ETHERNET:
 976                 break;
 977         default:
 978                 packet_send_debug("Unsupported tunnel device mode.");
 979                 return NULL;
 980         }
 981         if ((options.permit_tun & mode) == 0) {
 982                 packet_send_debug("Server has rejected tunnel device "
 983                     "forwarding");
 984                 return NULL;
 985         }
 986
 987         tun = packet_get_int();
 988         if (forced_tun_device != -1) {
 989                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 990                         goto done;
 991                 tun = forced_tun_device;
 992         }
 993         sock = tun_open(tun, mode);
 994         if (sock < 0)
 995                 goto done;
 996         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 997             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 998         c->datagram = 1;
 999 #if defined(SSH_TUN_FILTER)
1000         if (mode == SSH_TUNMODE_POINTOPOINT)
1001                 channel_register_filter(c->self, sys_tun_infilter,
1002                     sys_tun_outfilter);
1003 #endif
1004
1005  done:
1006         if (c == NULL)
1007                 packet_send_debug("Failed to open the tunnel device.");
1008         return c;
1009 }
1010
1011 static Channel *
1012 server_request_session(void)
1013 {
1014         Channel *c;
1015
1016         debug("input_session_request");
1017         packet_check_eom();
1018         /*
1019          * A server session has no fd to read or write until a
1020          * CHANNEL_REQUEST for a shell is made, so we set the type to
1021          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1022          * CHANNEL_REQUEST messages is registered.
1023          */
1024         c = channel_new("session", SSH_CHANNEL_LARVAL,
1025             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1026             0, "server-session", 1);
1027         if (session_open(the_authctxt, c->self) != 1) {
1028                 debug("session open failed, free channel %d", c->self);
1029                 channel_free(c);
1030                 return NULL;
1031         }
1032         channel_register_cleanup(c->self, session_close_by_channel, 0);
1033         return c;
1034 }
1035
1036 static void
1037 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1038 {
1039         Channel *c = NULL;
1040         char *ctype;
1041         int rchan;
1042         u_int rmaxpack, rwindow, len;
1043
1044         ctype = packet_get_string(&len);
1045         rchan = packet_get_int();
1046         rwindow = packet_get_int();
1047         rmaxpack = packet_get_int();
1048
1049         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1050             ctype, rchan, rwindow, rmaxpack);
1051
1052         if (strcmp(ctype, "session") == 0) {
1053                 c = server_request_session();
1054         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1055                 c = server_request_direct_tcpip();
1056         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1057                 c = server_request_tun();
1058         }
1059         if (c != NULL) {
1060                 debug("server_input_channel_open: confirm %s", ctype);
1061                 c->remote_id = rchan;
1062                 c->remote_window = rwindow;
1063                 c->remote_maxpacket = rmaxpack;
1064                 if (c->type != SSH_CHANNEL_CONNECTING) {
1065                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1066                         packet_put_int(c->remote_id);
1067                         packet_put_int(c->self);
1068                         packet_put_int(c->local_window);
1069                         packet_put_int(c->local_maxpacket);
1070                         packet_send();
1071                 }
1072         } else {
1073                 debug("server_input_channel_open: failure %s", ctype);
1074                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1075                 packet_put_int(rchan);
1076                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1077                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1078                         packet_put_cstring("open failed");
1079                         packet_put_cstring("");
1080                 }
1081                 packet_send();
1082         }
1083         xfree(ctype);
1084 }
1085
1086 static void
1087 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1088 {
1089         char *rtype;
1090         int want_reply;
1091         int success = 0;
1092
1093         rtype = packet_get_string(NULL);
1094         want_reply = packet_get_char();
1095         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1096
1097         /* -R style forwarding */
1098         if (strcmp(rtype, "tcpip-forward") == 0) {
1099                 struct passwd *pw;
1100                 char *listen_address;
1101                 u_short listen_port;
1102
1103                 pw = the_authctxt->pw;
1104                 if (pw == NULL || !the_authctxt->valid)
1105                         fatal("server_input_global_request: no/invalid user");
1106                 listen_address = packet_get_string(NULL);
1107                 listen_port = (u_short)packet_get_int();
1108                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1109                     listen_address, listen_port);
1110
1111                 /* check permissions */
1112                 if (!options.allow_tcp_forwarding ||
1113                     no_port_forwarding_flag
1114 #ifndef NO_IPPORT_RESERVED_CONCEPT
1115                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1116 #endif
1117                     ) {
1118                         success = 0;
1119                         packet_send_debug("Server has disabled port forwarding.");
1120                 } else {
1121                         /* Start listening on the port */
1122                         success = channel_setup_remote_fwd_listener(
1123                             listen_address, listen_port, options.gateway_ports);
1124                 }
1125                 xfree(listen_address);
1126         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1127                 char *cancel_address;
1128                 u_short cancel_port;
1129
1130                 cancel_address = packet_get_string(NULL);
1131                 cancel_port = (u_short)packet_get_int();
1132                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1133                     cancel_address, cancel_port);
1134
1135                 success = channel_cancel_rport_listener(cancel_address,
1136                     cancel_port);
1137                 xfree(cancel_address);
1138         }
1139         if (want_reply) {
1140                 packet_start(success ?
1141                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1142                 packet_send();
1143                 packet_write_wait();
1144         }
1145         xfree(rtype);
1146 }
1147
1148 static void
1149 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1150 {
1151         Channel *c;
1152         int id, reply, success = 0;
1153         char *rtype;
1154
1155         id = packet_get_int();
1156         rtype = packet_get_string(NULL);
1157         reply = packet_get_char();
1158
1159         debug("server_input_channel_req: channel %d request %s reply %d",
1160             id, rtype, reply);
1161
1162         if ((c = channel_lookup(id)) == NULL)
1163                 packet_disconnect("server_input_channel_req: "
1164                     "unknown channel %d", id);
1165         if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN)
1166                 success = session_input_channel_req(c, rtype);
1167         if (reply) {
1168                 packet_start(success ?
1169                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1170                 packet_put_int(c->remote_id);
1171                 packet_send();
1172         }
1173         xfree(rtype);
1174 }
1175
1176 static void
1177 server_init_dispatch_20(void)
1178 {
1179         debug("server_init_dispatch_20");
1180         dispatch_init(&dispatch_protocol_error);
1181         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1182         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1183         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1184         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1185         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1186         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1187         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1188         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1189         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1190         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1191         /* client_alive */
1192         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1193         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1194         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1195         /* rekeying */
1196         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1197 }
1198 static void
1199 server_init_dispatch_13(void)
1200 {
1201         debug("server_init_dispatch_13");
1202         dispatch_init(NULL);
1203         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1204         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1205         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1206         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1207         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1208         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1209         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1210         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1211         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1212 }
1213 static void
1214 server_init_dispatch_15(void)
1215 {
1216         server_init_dispatch_13();
1217         debug("server_init_dispatch_15");
1218         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1219         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1220 }
1221 static void
1222 server_init_dispatch(void)
1223 {
1224         if (compat20)
1225                 server_init_dispatch_20();
1226         else if (compat13)
1227                 server_init_dispatch_13();
1228         else
1229                 server_init_dispatch_15();
1230 }