crypto/openssh/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.162 2012/06/20 04:42:58 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/param.h>
  42 #include <sys/wait.h>
  43 #include <sys/socket.h>
  44 #ifdef HAVE_SYS_TIME_H
  45 # include <sys/time.h>
  46 #endif
  47
  48 #include <netinet/in.h>
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <pwd.h>
  53 #include <signal.h>
  54 #include <string.h>
  55 #include <termios.h>
  56 #include <unistd.h>
  57 #include <stdarg.h>
  58
  59 #include "openbsd-compat/sys-queue.h"
  60 #include "xmalloc.h"
  61 #include "packet.h"
  62 #include "buffer.h"
  63 #include "log.h"
  64 #include "servconf.h"
  65 #include "canohost.h"
  66 #include "sshpty.h"
  67 #include "channels.h"
  68 #include "compat.h"
  69 #include "ssh1.h"
  70 #include "ssh2.h"
  71 #include "key.h"
  72 #include "cipher.h"
  73 #include "kex.h"
  74 #include "hostfile.h"
  75 #include "auth.h"
  76 #include "session.h"
  77 #include "dispatch.h"
  78 #include "auth-options.h"
  79 #include "serverloop.h"
  80 #include "misc.h"
  81 #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, FD_CLOEXEC) == -1) ||
 135             (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -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         time_t minwait_secs = 0;
 285         int client_alive_scheduled = 0;
 286         int program_alive_scheduled = 0;
 287
 288         /* Allocate and update select() masks for channel descriptors. */
 289         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
 290             &minwait_secs, 0);
 291
 292         if (minwait_secs != 0)
 293                 max_time_milliseconds = MIN(max_time_milliseconds,
 294                     (u_int)minwait_secs * 1000);
 295
 296         /*
 297          * if using client_alive, set the max timeout accordingly,
 298          * and indicate that this particular timeout was for client
 299          * alive by setting the client_alive_scheduled flag.
 300          *
 301          * this could be randomized somewhat to make traffic
 302          * analysis more difficult, but we're not doing it yet.
 303          */
 304         if (compat20 &&
 305             max_time_milliseconds == 0 && options.client_alive_interval) {
 306                 client_alive_scheduled = 1;
 307                 max_time_milliseconds = options.client_alive_interval * 1000;
 308         }
 309
 310         if (compat20) {
 311 #if 0
 312                 /* wrong: bad condition XXX */
 313                 if (channel_not_very_much_buffered_data())
 314 #endif
 315                 FD_SET(connection_in, *readsetp);
 316         } else {
 317                 /*
 318                  * Read packets from the client unless we have too much
 319                  * buffered stdin or channel data.
 320                  */
 321                 if (buffer_len(&stdin_buffer) < buffer_high &&
 322                     channel_not_very_much_buffered_data())
 323                         FD_SET(connection_in, *readsetp);
 324                 /*
 325                  * If there is not too much data already buffered going to
 326                  * the client, try to get some more data from the program.
 327                  */
 328                 if (packet_not_very_much_data_to_write()) {
 329                         program_alive_scheduled = child_terminated;
 330                         if (!fdout_eof)
 331                                 FD_SET(fdout, *readsetp);
 332                         if (!fderr_eof)
 333                                 FD_SET(fderr, *readsetp);
 334                 }
 335                 /*
 336                  * If we have buffered data, try to write some of that data
 337                  * to the program.
 338                  */
 339                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 340                         FD_SET(fdin, *writesetp);
 341         }
 342         notify_prepare(*readsetp);
 343
 344         /*
 345          * If we have buffered packet data going to the client, mark that
 346          * descriptor.
 347          */
 348         if (packet_have_data_to_write())
 349                 FD_SET(connection_out, *writesetp);
 350
 351         /*
 352          * If child has terminated and there is enough buffer space to read
 353          * from it, then read as much as is available and exit.
 354          */
 355         if (child_terminated && packet_not_very_much_data_to_write())
 356                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 357                         max_time_milliseconds = 100;
 358
 359         if (max_time_milliseconds == 0)
 360                 tvp = NULL;
 361         else {
 362                 tv.tv_sec = max_time_milliseconds / 1000;
 363                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 364                 tvp = &tv;
 365         }
 366
 367         /* Wait for something to happen, or the timeout to expire. */
 368         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 369
 370         if (ret == -1) {
 371                 memset(*readsetp, 0, *nallocp);
 372                 memset(*writesetp, 0, *nallocp);
 373                 if (errno != EINTR)
 374                         error("select: %.100s", strerror(errno));
 375         } else {
 376                 if (ret == 0 && client_alive_scheduled)
 377                         client_alive_check();
 378                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 379                         if (!fdout_eof)
 380                                 FD_SET(fdout, *readsetp);
 381                         if (!fderr_eof)
 382                                 FD_SET(fderr, *readsetp);
 383                 }
 384         }
 385
 386         notify_done(*readsetp);
 387 }
 388
 389 /*
 390  * Processes input from the client and the program.  Input data is stored
 391  * in buffers and processed later.
 392  */
 393 static void
 394 process_input(fd_set *readset)
 395 {
 396         int len;
 397         char buf[16384];
 398
 399         /* Read and buffer any input data from the client. */
 400         if (FD_ISSET(connection_in, readset)) {
 401                 int cont = 0;
 402                 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
 403                 if (len == 0) {
 404                         if (cont)
 405                                 return;
 406                         verbose("Connection closed by %.100s",
 407                             get_remote_ipaddr());
 408                         connection_closed = 1;
 409                         if (compat20)
 410                                 return;
 411                         cleanup_exit(255);
 412                 } else if (len < 0) {
 413                         if (errno != EINTR && errno != EAGAIN &&
 414                             errno != EWOULDBLOCK) {
 415                                 verbose("Read error from remote host "
 416                                     "%.100s: %.100s",
 417                                     get_remote_ipaddr(), strerror(errno));
 418                                 cleanup_exit(255);
 419                         }
 420                 } else {
 421                         /* Buffer any received data. */
 422                         packet_process_incoming(buf, len);
 423                 }
 424         }
 425         if (compat20)
 426                 return;
 427
 428         /* Read and buffer any available stdout data from the program. */
 429         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 430                 errno = 0;
 431                 len = read(fdout, buf, sizeof(buf));
 432                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 433                     errno == EWOULDBLOCK) && !child_terminated))) {
 434                         /* do nothing */
 435 #ifndef PTY_ZEROREAD
 436                 } else if (len <= 0) {
 437 #else
 438                 } else if ((!isatty(fdout) && len <= 0) ||
 439                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 440 #endif
 441                         fdout_eof = 1;
 442                 } else {
 443                         buffer_append(&stdout_buffer, buf, len);
 444                         fdout_bytes += len;
 445                 }
 446         }
 447         /* Read and buffer any available stderr data from the program. */
 448         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 449                 errno = 0;
 450                 len = read(fderr, buf, sizeof(buf));
 451                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 452                     errno == EWOULDBLOCK) && !child_terminated))) {
 453                         /* do nothing */
 454 #ifndef PTY_ZEROREAD
 455                 } else if (len <= 0) {
 456 #else
 457                 } else if ((!isatty(fderr) && len <= 0) ||
 458                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 459 #endif
 460                         fderr_eof = 1;
 461                 } else {
 462                         buffer_append(&stderr_buffer, buf, len);
 463                 }
 464         }
 465 }
 466
 467 /*
 468  * Sends data from internal buffers to client program stdin.
 469  */
 470 static void
 471 process_output(fd_set *writeset)
 472 {
 473         struct termios tio;
 474         u_char *data;
 475         u_int dlen;
 476         int len;
 477
 478         /* Write buffered data to program stdin. */
 479         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 480                 data = buffer_ptr(&stdin_buffer);
 481                 dlen = buffer_len(&stdin_buffer);
 482                 len = write(fdin, data, dlen);
 483                 if (len < 0 &&
 484                     (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
 485                         /* do nothing */
 486                 } else if (len <= 0) {
 487                         if (fdin != fdout)
 488                                 close(fdin);
 489                         else
 490                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 491                         fdin = -1;
 492                 } else {
 493                         /* Successful write. */
 494                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 495                             tcgetattr(fdin, &tio) == 0 &&
 496                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 497                                 /*
 498                                  * Simulate echo to reduce the impact of
 499                                  * traffic analysis
 500                                  */
 501                                 packet_send_ignore(len);
 502                                 packet_send();
 503                         }
 504                         /* Consume the data from the buffer. */
 505                         buffer_consume(&stdin_buffer, len);
 506                         /* Update the count of bytes written to the program. */
 507                         stdin_bytes += len;
 508                 }
 509         }
 510         /* Send any buffered packet data to the client. */
 511         if (FD_ISSET(connection_out, writeset))
 512                 packet_write_poll();
 513 }
 514
 515 /*
 516  * Wait until all buffered output has been sent to the client.
 517  * This is used when the program terminates.
 518  */
 519 static void
 520 drain_output(void)
 521 {
 522         /* Send any buffered stdout data to the client. */
 523         if (buffer_len(&stdout_buffer) > 0) {
 524                 packet_start(SSH_SMSG_STDOUT_DATA);
 525                 packet_put_string(buffer_ptr(&stdout_buffer),
 526                                   buffer_len(&stdout_buffer));
 527                 packet_send();
 528                 /* Update the count of sent bytes. */
 529                 stdout_bytes += buffer_len(&stdout_buffer);
 530         }
 531         /* Send any buffered stderr data to the client. */
 532         if (buffer_len(&stderr_buffer) > 0) {
 533                 packet_start(SSH_SMSG_STDERR_DATA);
 534                 packet_put_string(buffer_ptr(&stderr_buffer),
 535                                   buffer_len(&stderr_buffer));
 536                 packet_send();
 537                 /* Update the count of sent bytes. */
 538                 stderr_bytes += buffer_len(&stderr_buffer);
 539         }
 540         /* Wait until all buffered data has been written to the client. */
 541         packet_write_wait();
 542 }
 543
 544 static void
 545 process_buffered_input_packets(void)
 546 {
 547         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 548 }
 549
 550 /*
 551  * Performs the interactive session.  This handles data transmission between
 552  * the client and the program.  Note that the notion of stdin, stdout, and
 553  * stderr in this function is sort of reversed: this function writes to
 554  * stdin (of the child program), and reads from stdout and stderr (of the
 555  * child program).
 556  */
 557 void
 558 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 559 {
 560         fd_set *readset = NULL, *writeset = NULL;
 561         int max_fd = 0;
 562         u_int nalloc = 0;
 563         int wait_status;        /* Status returned by wait(). */
 564         pid_t wait_pid;         /* pid returned by wait(). */
 565         int waiting_termination = 0;    /* Have displayed waiting close message. */
 566         u_int max_time_milliseconds;
 567         u_int previous_stdout_buffer_bytes;
 568         u_int stdout_buffer_bytes;
 569         int type;
 570
 571         debug("Entering interactive session.");
 572
 573         /* Initialize the SIGCHLD kludge. */
 574         child_terminated = 0;
 575         mysignal(SIGCHLD, sigchld_handler);
 576
 577         if (!use_privsep) {
 578                 signal(SIGTERM, sigterm_handler);
 579                 signal(SIGINT, sigterm_handler);
 580                 signal(SIGQUIT, sigterm_handler);
 581         }
 582
 583         /* Initialize our global variables. */
 584         fdin = fdin_arg;
 585         fdout = fdout_arg;
 586         fderr = fderr_arg;
 587
 588         /* nonblocking IO */
 589         set_nonblock(fdin);
 590         set_nonblock(fdout);
 591         /* we don't have stderr for interactive terminal sessions, see below */
 592         if (fderr != -1)
 593                 set_nonblock(fderr);
 594
 595         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 596                 fdin_is_tty = 1;
 597
 598         connection_in = packet_get_connection_in();
 599         connection_out = packet_get_connection_out();
 600
 601         notify_setup();
 602
 603         previous_stdout_buffer_bytes = 0;
 604
 605         /* Set approximate I/O buffer size. */
 606         if (packet_is_interactive())
 607                 buffer_high = 4096;
 608         else
 609                 buffer_high = 64 * 1024;
 610
 611 #if 0
 612         /* Initialize max_fd to the maximum of the known file descriptors. */
 613         max_fd = MAX(connection_in, connection_out);
 614         max_fd = MAX(max_fd, fdin);
 615         max_fd = MAX(max_fd, fdout);
 616         if (fderr != -1)
 617                 max_fd = MAX(max_fd, fderr);
 618 #endif
 619
 620         /* Initialize Initialize buffers. */
 621         buffer_init(&stdin_buffer);
 622         buffer_init(&stdout_buffer);
 623         buffer_init(&stderr_buffer);
 624
 625         /*
 626          * If we have no separate fderr (which is the case when we have a pty
 627          * - there we cannot make difference between data sent to stdout and
 628          * stderr), indicate that we have seen an EOF from stderr.  This way
 629          * we don't need to check the descriptor everywhere.
 630          */
 631         if (fderr == -1)
 632                 fderr_eof = 1;
 633
 634         server_init_dispatch();
 635
 636         /* Main loop of the server for the interactive session mode. */
 637         for (;;) {
 638
 639                 /* Process buffered packets from the client. */
 640                 process_buffered_input_packets();
 641
 642                 /*
 643                  * If we have received eof, and there is no more pending
 644                  * input data, cause a real eof by closing fdin.
 645                  */
 646                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 647                         if (fdin != fdout)
 648                                 close(fdin);
 649                         else
 650                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 651                         fdin = -1;
 652                 }
 653                 /* Make packets from buffered stderr data to send to the client. */
 654                 make_packets_from_stderr_data();
 655
 656                 /*
 657                  * Make packets from buffered stdout data to send to the
 658                  * client. If there is very little to send, this arranges to
 659                  * not send them now, but to wait a short while to see if we
 660                  * are getting more data. This is necessary, as some systems
 661                  * wake up readers from a pty after each separate character.
 662                  */
 663                 max_time_milliseconds = 0;
 664                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 665                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 666                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 667                         /* try again after a while */
 668                         max_time_milliseconds = 10;
 669                 } else {
 670                         /* Send it now. */
 671                         make_packets_from_stdout_data();
 672                 }
 673                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 674
 675                 /* Send channel data to the client. */
 676                 if (packet_not_very_much_data_to_write())
 677                         channel_output_poll();
 678
 679                 /*
 680                  * Bail out of the loop if the program has closed its output
 681                  * descriptors, and we have no more data to send to the
 682                  * client, and there is no pending buffered data.
 683                  */
 684                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 685                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 686                         if (!channel_still_open())
 687                                 break;
 688                         if (!waiting_termination) {
 689                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 690                                 char *cp;
 691                                 waiting_termination = 1;
 692                                 buffer_append(&stderr_buffer, s, strlen(s));
 693
 694                                 /* Display list of open channels. */
 695                                 cp = channel_open_message();
 696                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 697                                 xfree(cp);
 698                         }
 699                 }
 700                 max_fd = MAX(connection_in, connection_out);
 701                 max_fd = MAX(max_fd, fdin);
 702                 max_fd = MAX(max_fd, fdout);
 703                 max_fd = MAX(max_fd, fderr);
 704                 max_fd = MAX(max_fd, notify_pipe[0]);
 705
 706                 /* Sleep in select() until we can do something. */
 707                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 708                     &nalloc, max_time_milliseconds);
 709
 710                 if (received_sigterm) {
 711                         logit("Exiting on signal %d", received_sigterm);
 712                         /* Clean up sessions, utmp, etc. */
 713                         cleanup_exit(255);
 714                 }
 715
 716                 /* Process any channel events. */
 717                 channel_after_select(readset, writeset);
 718
 719                 /* Process input from the client and from program stdout/stderr. */
 720                 process_input(readset);
 721
 722                 /* Process output to the client and to program stdin. */
 723                 process_output(writeset);
 724         }
 725         if (readset)
 726                 xfree(readset);
 727         if (writeset)
 728                 xfree(writeset);
 729
 730         /* Cleanup and termination code. */
 731
 732         /* Wait until all output has been sent to the client. */
 733         drain_output();
 734
 735         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
 736             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 737
 738         /* Free and clear the buffers. */
 739         buffer_free(&stdin_buffer);
 740         buffer_free(&stdout_buffer);
 741         buffer_free(&stderr_buffer);
 742
 743         /* Close the file descriptors. */
 744         if (fdout != -1)
 745                 close(fdout);
 746         fdout = -1;
 747         fdout_eof = 1;
 748         if (fderr != -1)
 749                 close(fderr);
 750         fderr = -1;
 751         fderr_eof = 1;
 752         if (fdin != -1)
 753                 close(fdin);
 754         fdin = -1;
 755
 756         channel_free_all();
 757
 758         /* We no longer want our SIGCHLD handler to be called. */
 759         mysignal(SIGCHLD, SIG_DFL);
 760
 761         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 762                 if (errno != EINTR)
 763                         packet_disconnect("wait: %.100s", strerror(errno));
 764         if (wait_pid != pid)
 765                 error("Strange, wait returned pid %ld, expected %ld",
 766                     (long)wait_pid, (long)pid);
 767
 768         /* Check if it exited normally. */
 769         if (WIFEXITED(wait_status)) {
 770                 /* Yes, normal exit.  Get exit status and send it to the client. */
 771                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 772                 packet_start(SSH_SMSG_EXITSTATUS);
 773                 packet_put_int(WEXITSTATUS(wait_status));
 774                 packet_send();
 775                 packet_write_wait();
 776
 777                 /*
 778                  * Wait for exit confirmation.  Note that there might be
 779                  * other packets coming before it; however, the program has
 780                  * already died so we just ignore them.  The client is
 781                  * supposed to respond with the confirmation when it receives
 782                  * the exit status.
 783                  */
 784                 do {
 785                         type = packet_read();
 786                 }
 787                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 788
 789                 debug("Received exit confirmation.");
 790                 return;
 791         }
 792         /* Check if the program terminated due to a signal. */
 793         if (WIFSIGNALED(wait_status))
 794                 packet_disconnect("Command terminated on signal %d.",
 795                                   WTERMSIG(wait_status));
 796
 797         /* Some weird exit cause.  Just exit. */
 798         packet_disconnect("wait returned status %04x.", wait_status);
 799         /* NOTREACHED */
 800 }
 801
 802 static void
 803 collect_children(void)
 804 {
 805         pid_t pid;
 806         sigset_t oset, nset;
 807         int status;
 808
 809         /* block SIGCHLD while we check for dead children */
 810         sigemptyset(&nset);
 811         sigaddset(&nset, SIGCHLD);
 812         sigprocmask(SIG_BLOCK, &nset, &oset);
 813         if (child_terminated) {
 814                 debug("Received SIGCHLD.");
 815                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 816                     (pid < 0 && errno == EINTR))
 817                         if (pid > 0)
 818                                 session_close_by_pid(pid, status);
 819                 child_terminated = 0;
 820         }
 821         sigprocmask(SIG_SETMASK, &oset, NULL);
 822 }
 823
 824 void
 825 server_loop2(Authctxt *authctxt)
 826 {
 827         fd_set *readset = NULL, *writeset = NULL;
 828         int rekeying = 0, max_fd, nalloc = 0;
 829
 830         debug("Entering interactive session for SSH2.");
 831
 832         mysignal(SIGCHLD, sigchld_handler);
 833         child_terminated = 0;
 834         connection_in = packet_get_connection_in();
 835         connection_out = packet_get_connection_out();
 836
 837         if (!use_privsep) {
 838                 signal(SIGTERM, sigterm_handler);
 839                 signal(SIGINT, sigterm_handler);
 840                 signal(SIGQUIT, sigterm_handler);
 841         }
 842
 843         notify_setup();
 844
 845         max_fd = MAX(connection_in, connection_out);
 846         max_fd = MAX(max_fd, notify_pipe[0]);
 847
 848         server_init_dispatch();
 849
 850         for (;;) {
 851                 process_buffered_input_packets();
 852
 853                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 854
 855                 if (!rekeying && packet_not_very_much_data_to_write())
 856                         channel_output_poll();
 857                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 858                     &nalloc, 0);
 859
 860                 if (received_sigterm) {
 861                         logit("Exiting on signal %d", received_sigterm);
 862                         /* Clean up sessions, utmp, etc. */
 863                         cleanup_exit(255);
 864                 }
 865
 866                 collect_children();
 867                 if (!rekeying) {
 868                         channel_after_select(readset, writeset);
 869                         if (packet_need_rekeying()) {
 870                                 debug("need rekeying");
 871                                 xxx_kex->done = 0;
 872                                 kex_send_kexinit(xxx_kex);
 873                         }
 874                 }
 875                 process_input(readset);
 876                 if (connection_closed)
 877                         break;
 878                 process_output(writeset);
 879         }
 880         collect_children();
 881
 882         if (readset)
 883                 xfree(readset);
 884         if (writeset)
 885                 xfree(writeset);
 886
 887         /* free all channels, no more reads and writes */
 888         channel_free_all();
 889
 890         /* free remaining sessions, e.g. remove wtmp entries */
 891         session_destroy_all(NULL);
 892 }
 893
 894 static void
 895 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 896 {
 897         debug("Got %d/%u for keepalive", type, seq);
 898         /*
 899          * reset timeout, since we got a sane answer from the client.
 900          * even if this was generated by something other than
 901          * the bogus CHANNEL_REQUEST we send for keepalives.
 902          */
 903         packet_set_alive_timeouts(0);
 904 }
 905
 906 static void
 907 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 908 {
 909         char *data;
 910         u_int data_len;
 911
 912         /* Stdin data from the client.  Append it to the buffer. */
 913         /* Ignore any data if the client has closed stdin. */
 914         if (fdin == -1)
 915                 return;
 916         data = packet_get_string(&data_len);
 917         packet_check_eom();
 918         buffer_append(&stdin_buffer, data, data_len);
 919         memset(data, 0, data_len);
 920         xfree(data);
 921 }
 922
 923 static void
 924 server_input_eof(int type, u_int32_t seq, void *ctxt)
 925 {
 926         /*
 927          * Eof from the client.  The stdin descriptor to the
 928          * program will be closed when all buffered data has
 929          * drained.
 930          */
 931         debug("EOF received for stdin.");
 932         packet_check_eom();
 933         stdin_eof = 1;
 934 }
 935
 936 static void
 937 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 938 {
 939         u_int row = packet_get_int();
 940         u_int col = packet_get_int();
 941         u_int xpixel = packet_get_int();
 942         u_int ypixel = packet_get_int();
 943
 944         debug("Window change received.");
 945         packet_check_eom();
 946         if (fdin != -1)
 947                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 948 }
 949
 950 static Channel *
 951 server_request_direct_tcpip(void)
 952 {
 953         Channel *c;
 954         char *target, *originator;
 955         u_short target_port, originator_port;
 956
 957         target = packet_get_string(NULL);
 958         target_port = packet_get_int();
 959         originator = packet_get_string(NULL);
 960         originator_port = packet_get_int();
 961         packet_check_eom();
 962
 963         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 964             "port %d", originator, originator_port, target, target_port);
 965
 966         /* XXX check permission */
 967         c = channel_connect_to(target, target_port,
 968             "direct-tcpip", "direct-tcpip");
 969
 970         xfree(originator);
 971         xfree(target);
 972
 973         return c;
 974 }
 975
 976 static Channel *
 977 server_request_tun(void)
 978 {
 979         Channel *c = NULL;
 980         int mode, tun;
 981         int sock;
 982
 983         mode = packet_get_int();
 984         switch (mode) {
 985         case SSH_TUNMODE_POINTOPOINT:
 986         case SSH_TUNMODE_ETHERNET:
 987                 break;
 988         default:
 989                 packet_send_debug("Unsupported tunnel device mode.");
 990                 return NULL;
 991         }
 992         if ((options.permit_tun & mode) == 0) {
 993                 packet_send_debug("Server has rejected tunnel device "
 994                     "forwarding");
 995                 return NULL;
 996         }
 997
 998         tun = packet_get_int();
 999         if (forced_tun_device != -1) {
1000                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
1001                         goto done;
1002                 tun = forced_tun_device;
1003         }
1004         sock = tun_open(tun, mode);
1005         if (sock < 0)
1006                 goto done;
1007         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1008             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
1009         c->datagram = 1;
1010 #if defined(SSH_TUN_FILTER)
1011         if (mode == SSH_TUNMODE_POINTOPOINT)
1012                 channel_register_filter(c->self, sys_tun_infilter,
1013                     sys_tun_outfilter, NULL, NULL);
1014 #endif
1015
1016  done:
1017         if (c == NULL)
1018                 packet_send_debug("Failed to open the tunnel device.");
1019         return c;
1020 }
1021
1022 static Channel *
1023 server_request_session(void)
1024 {
1025         Channel *c;
1026
1027         debug("input_session_request");
1028         packet_check_eom();
1029
1030         if (no_more_sessions) {
1031                 packet_disconnect("Possible attack: attempt to open a session "
1032                     "after additional sessions disabled");
1033         }
1034
1035         /*
1036          * A server session has no fd to read or write until a
1037          * CHANNEL_REQUEST for a shell is made, so we set the type to
1038          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1039          * CHANNEL_REQUEST messages is registered.
1040          */
1041         c = channel_new("session", SSH_CHANNEL_LARVAL,
1042             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1043             0, "server-session", 1);
1044         if (session_open(the_authctxt, c->self) != 1) {
1045                 debug("session open failed, free channel %d", c->self);
1046                 channel_free(c);
1047                 return NULL;
1048         }
1049         channel_register_cleanup(c->self, session_close_by_channel, 0);
1050         return c;
1051 }
1052
1053 static void
1054 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1055 {
1056         Channel *c = NULL;
1057         char *ctype;
1058         int rchan;
1059         u_int rmaxpack, rwindow, len;
1060
1061         ctype = packet_get_string(&len);
1062         rchan = packet_get_int();
1063         rwindow = packet_get_int();
1064         rmaxpack = packet_get_int();
1065
1066         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1067             ctype, rchan, rwindow, rmaxpack);
1068
1069         if (strcmp(ctype, "session") == 0) {
1070                 c = server_request_session();
1071         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1072                 c = server_request_direct_tcpip();
1073         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1074                 c = server_request_tun();
1075         }
1076         if (c != NULL) {
1077                 debug("server_input_channel_open: confirm %s", ctype);
1078                 c->remote_id = rchan;
1079                 c->remote_window = rwindow;
1080                 c->remote_maxpacket = rmaxpack;
1081                 if (c->type != SSH_CHANNEL_CONNECTING) {
1082                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1083                         packet_put_int(c->remote_id);
1084                         packet_put_int(c->self);
1085                         packet_put_int(c->local_window);
1086                         packet_put_int(c->local_maxpacket);
1087                         packet_send();
1088                 }
1089         } else {
1090                 debug("server_input_channel_open: failure %s", ctype);
1091                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1092                 packet_put_int(rchan);
1093                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1094                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1095                         packet_put_cstring("open failed");
1096                         packet_put_cstring("");
1097                 }
1098                 packet_send();
1099         }
1100         xfree(ctype);
1101 }
1102
1103 static void
1104 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1105 {
1106         char *rtype;
1107         int want_reply;
1108         int success = 0, allocated_listen_port = 0;
1109
1110         rtype = packet_get_string(NULL);
1111         want_reply = packet_get_char();
1112         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1113
1114         /* -R style forwarding */
1115         if (strcmp(rtype, "tcpip-forward") == 0) {
1116                 struct passwd *pw;
1117                 char *listen_address;
1118                 u_short listen_port;
1119
1120                 pw = the_authctxt->pw;
1121                 if (pw == NULL || !the_authctxt->valid)
1122                         fatal("server_input_global_request: no/invalid user");
1123                 listen_address = packet_get_string(NULL);
1124                 listen_port = (u_short)packet_get_int();
1125                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1126                     listen_address, listen_port);
1127
1128                 /* check permissions */
1129                 if (!options.allow_tcp_forwarding ||
1130                     no_port_forwarding_flag ||
1131                     (!want_reply && listen_port == 0)
1132 #ifndef NO_IPPORT_RESERVED_CONCEPT
1133                     || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1134                     pw->pw_uid != 0)
1135 #endif
1136                     ) {
1137                         success = 0;
1138                         packet_send_debug("Server has disabled port forwarding.");
1139                 } else {
1140                         /* Start listening on the port */
1141                         success = channel_setup_remote_fwd_listener(
1142                             listen_address, listen_port,
1143                             &allocated_listen_port, options.gateway_ports);
1144                 }
1145                 xfree(listen_address);
1146         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1147                 char *cancel_address;
1148                 u_short cancel_port;
1149
1150                 cancel_address = packet_get_string(NULL);
1151                 cancel_port = (u_short)packet_get_int();
1152                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1153                     cancel_address, cancel_port);
1154
1155                 success = channel_cancel_rport_listener(cancel_address,
1156                     cancel_port);
1157                 xfree(cancel_address);
1158         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1159                 no_more_sessions = 1;
1160                 success = 1;
1161         }
1162         if (want_reply) {
1163                 packet_start(success ?
1164                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1165                 if (success && allocated_listen_port > 0)
1166                         packet_put_int(allocated_listen_port);
1167                 packet_send();
1168                 packet_write_wait();
1169         }
1170         xfree(rtype);
1171 }
1172
1173 static void
1174 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1175 {
1176         Channel *c;
1177         int id, reply, success = 0;
1178         char *rtype;
1179
1180         id = packet_get_int();
1181         rtype = packet_get_string(NULL);
1182         reply = packet_get_char();
1183
1184         debug("server_input_channel_req: channel %d request %s reply %d",
1185             id, rtype, reply);
1186
1187         if ((c = channel_lookup(id)) == NULL)
1188                 packet_disconnect("server_input_channel_req: "
1189                     "unknown channel %d", id);
1190         if (!strcmp(rtype, "eow@openssh.com")) {
1191                 packet_check_eom();
1192                 chan_rcvd_eow(c);
1193         } else if ((c->type == SSH_CHANNEL_LARVAL ||
1194             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1195                 success = session_input_channel_req(c, rtype);
1196         if (reply) {
1197                 packet_start(success ?
1198                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1199                 packet_put_int(c->remote_id);
1200                 packet_send();
1201         }
1202         xfree(rtype);
1203 }
1204
1205 static void
1206 server_init_dispatch_20(void)
1207 {
1208         debug("server_init_dispatch_20");
1209         dispatch_init(&dispatch_protocol_error);
1210         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1211         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1212         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1213         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1214         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1215         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1216         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1217         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1218         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1219         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1220         /* client_alive */
1221         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1222         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1223         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1224         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1225         /* rekeying */
1226         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1227 }
1228 static void
1229 server_init_dispatch_13(void)
1230 {
1231         debug("server_init_dispatch_13");
1232         dispatch_init(NULL);
1233         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1234         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1235         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1236         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1237         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1238         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1239         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1240         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1241         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1242 }
1243 static void
1244 server_init_dispatch_15(void)
1245 {
1246         server_init_dispatch_13();
1247         debug("server_init_dispatch_15");
1248         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1249         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1250 }
1251 static void
1252 server_init_dispatch(void)
1253 {
1254         if (compat20)
1255                 server_init_dispatch_20();
1256         else if (compat13)
1257                 server_init_dispatch_13();
1258         else
1259                 server_init_dispatch_15();
1260 }