crypto/openssh/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.159 2009/05/28 16:50:16 andreas Exp $ */
   2 /* $FreeBSD$ */
   3 /*
   4  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   5  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   6  *                    All rights reserved
   7  * Server main loop for handling the interactive session.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  * SSH2 support by Markus Friedl.
  16  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  29  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  30  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  31  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  32  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 #include "includes.h"
  40
  41 #include <sys/types.h>
  42 #include <sys/param.h>
  43 #include <sys/wait.h>
  44 #include <sys/socket.h>
  45 #ifdef HAVE_SYS_TIME_H
  46 # include <sys/time.h>
  47 #endif
  48
  49 #include <netinet/in.h>
  50
  51 #include <errno.h>
  52 #include <fcntl.h>
  53 #include <pwd.h>
  54 #include <signal.h>
  55 #include <string.h>
  56 #include <termios.h>
  57 #include <unistd.h>
  58 #include <stdarg.h>
  59
  60 #include "openbsd-compat/sys-queue.h"
  61 #include "xmalloc.h"
  62 #include "packet.h"
  63 #include "buffer.h"
  64 #include "log.h"
  65 #include "servconf.h"
  66 #include "canohost.h"
  67 #include "sshpty.h"
  68 #include "channels.h"
  69 #include "compat.h"
  70 #include "ssh1.h"
  71 #include "ssh2.h"
  72 #include "key.h"
  73 #include "cipher.h"
  74 #include "kex.h"
  75 #include "hostfile.h"
  76 #include "auth.h"
  77 #include "session.h"
  78 #include "dispatch.h"
  79 #include "auth-options.h"
  80 #include "serverloop.h"
  81 #include "misc.h"
  82 #include "roaming.h"
  83
  84 extern ServerOptions options;
  85
  86 /* XXX */
  87 extern Kex *xxx_kex;
  88 extern Authctxt *the_authctxt;
  89 extern int use_privsep;
  90
  91 static Buffer stdin_buffer;     /* Buffer for stdin data. */
  92 static Buffer stdout_buffer;    /* Buffer for stdout data. */
  93 static Buffer stderr_buffer;    /* Buffer for stderr data. */
  94 static int fdin;                /* Descriptor for stdin (for writing) */
  95 static int fdout;               /* Descriptor for stdout (for reading);
  96                                    May be same number as fdin. */
  97 static int fderr;               /* Descriptor for stderr.  May be -1. */
  98 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
  99 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
 100 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
 101 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
 102 static int stdin_eof = 0;       /* EOF message received from client. */
 103 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
 104 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
 105 static int fdin_is_tty = 0;     /* fdin points to a tty. */
 106 static int connection_in;       /* Connection to client (input). */
 107 static int connection_out;      /* Connection to client (output). */
 108 static int connection_closed = 0;       /* Connection to client closed. */
 109 static u_int buffer_high;       /* "Soft" max buffer size. */
 110 static int no_more_sessions = 0; /* Disallow further sessions. */
 111
 112 /*
 113  * This SIGCHLD kludge is used to detect when the child exits.  The server
 114  * will exit after that, as soon as forwarded connections have terminated.
 115  */
 116
 117 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
 118
 119 /* Cleanup on signals (!use_privsep case only) */
 120 static volatile sig_atomic_t received_sigterm = 0;
 121
 122 /* prototypes */
 123 static void server_init_dispatch(void);
 124
 125 /*
 126  * we write to this pipe if a SIGCHLD is caught in order to avoid
 127  * the race between select() and child_terminated
 128  */
 129 static int notify_pipe[2];
 130 static void
 131 notify_setup(void)
 132 {
 133         if (pipe(notify_pipe) < 0) {
 134                 error("pipe(notify_pipe) failed %s", strerror(errno));
 135         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
 136             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
 137                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 138                 close(notify_pipe[0]);
 139                 close(notify_pipe[1]);
 140         } else {
 141                 set_nonblock(notify_pipe[0]);
 142                 set_nonblock(notify_pipe[1]);
 143                 return;
 144         }
 145         notify_pipe[0] = -1;    /* read end */
 146         notify_pipe[1] = -1;    /* write end */
 147 }
 148 static void
 149 notify_parent(void)
 150 {
 151         if (notify_pipe[1] != -1)
 152                 write(notify_pipe[1], "", 1);
 153 }
 154 static void
 155 notify_prepare(fd_set *readset)
 156 {
 157         if (notify_pipe[0] != -1)
 158                 FD_SET(notify_pipe[0], readset);
 159 }
 160 static void
 161 notify_done(fd_set *readset)
 162 {
 163         char c;
 164
 165         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 166                 while (read(notify_pipe[0], &c, 1) != -1)
 167                         debug2("notify_done: reading");
 168 }
 169
 170 /*ARGSUSED*/
 171 static void
 172 sigchld_handler(int sig)
 173 {
 174         int save_errno = errno;
 175         child_terminated = 1;
 176 #ifndef _UNICOS
 177         mysignal(SIGCHLD, sigchld_handler);
 178 #endif
 179         notify_parent();
 180         errno = save_errno;
 181 }
 182
 183 /*ARGSUSED*/
 184 static void
 185 sigterm_handler(int sig)
 186 {
 187         received_sigterm = sig;
 188 }
 189
 190 /*
 191  * Make packets from buffered stderr data, and buffer it for sending
 192  * to the client.
 193  */
 194 static void
 195 make_packets_from_stderr_data(void)
 196 {
 197         u_int len;
 198
 199         /* Send buffered stderr data to the client. */
 200         while (buffer_len(&stderr_buffer) > 0 &&
 201             packet_not_very_much_data_to_write()) {
 202                 len = buffer_len(&stderr_buffer);
 203                 if (packet_is_interactive()) {
 204                         if (len > 512)
 205                                 len = 512;
 206                 } else {
 207                         /* Keep the packets at reasonable size. */
 208                         if (len > packet_get_maxsize())
 209                                 len = packet_get_maxsize();
 210                 }
 211                 packet_start(SSH_SMSG_STDERR_DATA);
 212                 packet_put_string(buffer_ptr(&stderr_buffer), len);
 213                 packet_send();
 214                 buffer_consume(&stderr_buffer, len);
 215                 stderr_bytes += len;
 216         }
 217 }
 218
 219 /*
 220  * Make packets from buffered stdout data, and buffer it for sending to the
 221  * client.
 222  */
 223 static void
 224 make_packets_from_stdout_data(void)
 225 {
 226         u_int len;
 227
 228         /* Send buffered stdout data to the client. */
 229         while (buffer_len(&stdout_buffer) > 0 &&
 230             packet_not_very_much_data_to_write()) {
 231                 len = buffer_len(&stdout_buffer);
 232                 if (packet_is_interactive()) {
 233                         if (len > 512)
 234                                 len = 512;
 235                 } else {
 236                         /* Keep the packets at reasonable size. */
 237                         if (len > packet_get_maxsize())
 238                                 len = packet_get_maxsize();
 239                 }
 240                 packet_start(SSH_SMSG_STDOUT_DATA);
 241                 packet_put_string(buffer_ptr(&stdout_buffer), len);
 242                 packet_send();
 243                 buffer_consume(&stdout_buffer, len);
 244                 stdout_bytes += len;
 245         }
 246 }
 247
 248 static void
 249 client_alive_check(void)
 250 {
 251         int channel_id;
 252
 253         /* timeout, check to see how many we have had */
 254         if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
 255                 logit("Timeout, client not responding.");
 256                 cleanup_exit(255);
 257         }
 258
 259         /*
 260          * send a bogus global/channel request with "wantreply",
 261          * we should get back a failure
 262          */
 263         if ((channel_id = channel_find_open()) == -1) {
 264                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 265                 packet_put_cstring("keepalive@openssh.com");
 266                 packet_put_char(1);     /* boolean: want reply */
 267         } else {
 268                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 269         }
 270         packet_send();
 271 }
 272
 273 /*
 274  * Sleep in select() until we can do something.  This will initialize the
 275  * select masks.  Upon return, the masks will indicate which descriptors
 276  * have data or can accept data.  Optionally, a maximum time can be specified
 277  * for the duration of the wait (0 = infinite).
 278  */
 279 static void
 280 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 281     u_int *nallocp, u_int max_time_milliseconds)
 282 {
 283         struct timeval tv, *tvp;
 284         int ret;
 285         int client_alive_scheduled = 0;
 286         int program_alive_scheduled = 0;
 287
 288         /*
 289          * if using client_alive, set the max timeout accordingly,
 290          * and indicate that this particular timeout was for client
 291          * alive by setting the client_alive_scheduled flag.
 292          *
 293          * this could be randomized somewhat to make traffic
 294          * analysis more difficult, but we're not doing it yet.
 295          */
 296         if (compat20 &&
 297             max_time_milliseconds == 0 && options.client_alive_interval) {
 298                 client_alive_scheduled = 1;
 299                 max_time_milliseconds = options.client_alive_interval * 1000;
 300         }
 301
 302         /* Allocate and update select() masks for channel descriptors. */
 303         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
 304
 305         if (compat20) {
 306 #if 0
 307                 /* wrong: bad condition XXX */
 308                 if (channel_not_very_much_buffered_data())
 309 #endif
 310                 FD_SET(connection_in, *readsetp);
 311         } else {
 312                 /*
 313                  * Read packets from the client unless we have too much
 314                  * buffered stdin or channel data.
 315                  */
 316                 if (buffer_len(&stdin_buffer) < buffer_high &&
 317                     channel_not_very_much_buffered_data())
 318                         FD_SET(connection_in, *readsetp);
 319                 /*
 320                  * If there is not too much data already buffered going to
 321                  * the client, try to get some more data from the program.
 322                  */
 323                 if (packet_not_very_much_data_to_write()) {
 324                         program_alive_scheduled = child_terminated;
 325                         if (!fdout_eof)
 326                                 FD_SET(fdout, *readsetp);
 327                         if (!fderr_eof)
 328                                 FD_SET(fderr, *readsetp);
 329                 }
 330                 /*
 331                  * If we have buffered data, try to write some of that data
 332                  * to the program.
 333                  */
 334                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
 335                         FD_SET(fdin, *writesetp);
 336         }
 337         notify_prepare(*readsetp);
 338
 339         /*
 340          * If we have buffered packet data going to the client, mark that
 341          * descriptor.
 342          */
 343         if (packet_have_data_to_write())
 344                 FD_SET(connection_out, *writesetp);
 345
 346         /*
 347          * If child has terminated and there is enough buffer space to read
 348          * from it, then read as much as is available and exit.
 349          */
 350         if (child_terminated && packet_not_very_much_data_to_write())
 351                 if (max_time_milliseconds == 0 || client_alive_scheduled)
 352                         max_time_milliseconds = 100;
 353
 354         if (max_time_milliseconds == 0)
 355                 tvp = NULL;
 356         else {
 357                 tv.tv_sec = max_time_milliseconds / 1000;
 358                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
 359                 tvp = &tv;
 360         }
 361
 362         /* Wait for something to happen, or the timeout to expire. */
 363         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 364
 365         if (ret == -1) {
 366                 memset(*readsetp, 0, *nallocp);
 367                 memset(*writesetp, 0, *nallocp);
 368                 if (errno != EINTR)
 369                         error("select: %.100s", strerror(errno));
 370         } else {
 371                 if (ret == 0 && client_alive_scheduled)
 372                         client_alive_check();
 373                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
 374                         if (!fdout_eof)
 375                                 FD_SET(fdout, *readsetp);
 376                         if (!fderr_eof)
 377                                 FD_SET(fderr, *readsetp);
 378                 }
 379         }
 380
 381         notify_done(*readsetp);
 382 }
 383
 384 /*
 385  * Processes input from the client and the program.  Input data is stored
 386  * in buffers and processed later.
 387  */
 388 static void
 389 process_input(fd_set *readset)
 390 {
 391         int len;
 392         char buf[16384];
 393
 394         /* Read and buffer any input data from the client. */
 395         if (FD_ISSET(connection_in, readset)) {
 396                 int cont = 0;
 397                 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
 398                 if (len == 0) {
 399                         if (cont)
 400                                 return;
 401                         verbose("Connection closed by %.100s",
 402                             get_remote_ipaddr());
 403                         connection_closed = 1;
 404                         if (compat20)
 405                                 return;
 406                         cleanup_exit(255);
 407                 } else if (len < 0) {
 408                         if (errno != EINTR && errno != EAGAIN &&
 409                             errno != EWOULDBLOCK) {
 410                                 verbose("Read error from remote host "
 411                                     "%.100s: %.100s",
 412                                     get_remote_ipaddr(), strerror(errno));
 413                                 cleanup_exit(255);
 414                         }
 415                 } else {
 416                         /* Buffer any received data. */
 417                         packet_process_incoming(buf, len);
 418                 }
 419         }
 420         if (compat20)
 421                 return;
 422
 423         /* Read and buffer any available stdout data from the program. */
 424         if (!fdout_eof && FD_ISSET(fdout, readset)) {
 425                 errno = 0;
 426                 len = read(fdout, buf, sizeof(buf));
 427                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 428                     errno == EWOULDBLOCK) && !child_terminated))) {
 429                         /* do nothing */
 430 #ifndef PTY_ZEROREAD
 431                 } else if (len <= 0) {
 432 #else
 433                 } else if ((!isatty(fdout) && len <= 0) ||
 434                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
 435 #endif
 436                         fdout_eof = 1;
 437                 } else {
 438                         buffer_append(&stdout_buffer, buf, len);
 439                         fdout_bytes += len;
 440                 }
 441         }
 442         /* Read and buffer any available stderr data from the program. */
 443         if (!fderr_eof && FD_ISSET(fderr, readset)) {
 444                 errno = 0;
 445                 len = read(fderr, buf, sizeof(buf));
 446                 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
 447                     errno == EWOULDBLOCK) && !child_terminated))) {
 448                         /* do nothing */
 449 #ifndef PTY_ZEROREAD
 450                 } else if (len <= 0) {
 451 #else
 452                 } else if ((!isatty(fderr) && len <= 0) ||
 453                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
 454 #endif
 455                         fderr_eof = 1;
 456                 } else {
 457                         buffer_append(&stderr_buffer, buf, len);
 458                 }
 459         }
 460 }
 461
 462 /*
 463  * Sends data from internal buffers to client program stdin.
 464  */
 465 static void
 466 process_output(fd_set *writeset)
 467 {
 468         struct termios tio;
 469         u_char *data;
 470         u_int dlen;
 471         int len;
 472
 473         /* Write buffered data to program stdin. */
 474         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
 475                 data = buffer_ptr(&stdin_buffer);
 476                 dlen = buffer_len(&stdin_buffer);
 477                 len = write(fdin, data, dlen);
 478                 if (len < 0 &&
 479                     (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
 480                         /* do nothing */
 481                 } else if (len <= 0) {
 482                         if (fdin != fdout)
 483                                 close(fdin);
 484                         else
 485                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 486                         fdin = -1;
 487                 } else {
 488                         /* Successful write. */
 489                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
 490                             tcgetattr(fdin, &tio) == 0 &&
 491                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
 492                                 /*
 493                                  * Simulate echo to reduce the impact of
 494                                  * traffic analysis
 495                                  */
 496                                 packet_send_ignore(len);
 497                                 packet_send();
 498                         }
 499                         /* Consume the data from the buffer. */
 500                         buffer_consume(&stdin_buffer, len);
 501                         /* Update the count of bytes written to the program. */
 502                         stdin_bytes += len;
 503                 }
 504         }
 505         /* Send any buffered packet data to the client. */
 506         if (FD_ISSET(connection_out, writeset))
 507                 packet_write_poll();
 508 }
 509
 510 /*
 511  * Wait until all buffered output has been sent to the client.
 512  * This is used when the program terminates.
 513  */
 514 static void
 515 drain_output(void)
 516 {
 517         /* Send any buffered stdout data to the client. */
 518         if (buffer_len(&stdout_buffer) > 0) {
 519                 packet_start(SSH_SMSG_STDOUT_DATA);
 520                 packet_put_string(buffer_ptr(&stdout_buffer),
 521                                   buffer_len(&stdout_buffer));
 522                 packet_send();
 523                 /* Update the count of sent bytes. */
 524                 stdout_bytes += buffer_len(&stdout_buffer);
 525         }
 526         /* Send any buffered stderr data to the client. */
 527         if (buffer_len(&stderr_buffer) > 0) {
 528                 packet_start(SSH_SMSG_STDERR_DATA);
 529                 packet_put_string(buffer_ptr(&stderr_buffer),
 530                                   buffer_len(&stderr_buffer));
 531                 packet_send();
 532                 /* Update the count of sent bytes. */
 533                 stderr_bytes += buffer_len(&stderr_buffer);
 534         }
 535         /* Wait until all buffered data has been written to the client. */
 536         packet_write_wait();
 537 }
 538
 539 static void
 540 process_buffered_input_packets(void)
 541 {
 542         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
 543 }
 544
 545 /*
 546  * Performs the interactive session.  This handles data transmission between
 547  * the client and the program.  Note that the notion of stdin, stdout, and
 548  * stderr in this function is sort of reversed: this function writes to
 549  * stdin (of the child program), and reads from stdout and stderr (of the
 550  * child program).
 551  */
 552 void
 553 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
 554 {
 555         fd_set *readset = NULL, *writeset = NULL;
 556         int max_fd = 0;
 557         u_int nalloc = 0;
 558         int wait_status;        /* Status returned by wait(). */
 559         pid_t wait_pid;         /* pid returned by wait(). */
 560         int waiting_termination = 0;    /* Have displayed waiting close message. */
 561         u_int max_time_milliseconds;
 562         u_int previous_stdout_buffer_bytes;
 563         u_int stdout_buffer_bytes;
 564         int type;
 565
 566         debug("Entering interactive session.");
 567
 568         /* Initialize the SIGCHLD kludge. */
 569         child_terminated = 0;
 570         mysignal(SIGCHLD, sigchld_handler);
 571
 572         if (!use_privsep) {
 573                 signal(SIGTERM, sigterm_handler);
 574                 signal(SIGINT, sigterm_handler);
 575                 signal(SIGQUIT, sigterm_handler);
 576         }
 577
 578         /* Initialize our global variables. */
 579         fdin = fdin_arg;
 580         fdout = fdout_arg;
 581         fderr = fderr_arg;
 582
 583         /* nonblocking IO */
 584         set_nonblock(fdin);
 585         set_nonblock(fdout);
 586         /* we don't have stderr for interactive terminal sessions, see below */
 587         if (fderr != -1)
 588                 set_nonblock(fderr);
 589
 590         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
 591                 fdin_is_tty = 1;
 592
 593         connection_in = packet_get_connection_in();
 594         connection_out = packet_get_connection_out();
 595
 596         notify_setup();
 597
 598         previous_stdout_buffer_bytes = 0;
 599
 600         /* Set approximate I/O buffer size. */
 601         if (packet_is_interactive())
 602                 buffer_high = 4096;
 603         else
 604                 buffer_high = 64 * 1024;
 605
 606 #if 0
 607         /* Initialize max_fd to the maximum of the known file descriptors. */
 608         max_fd = MAX(connection_in, connection_out);
 609         max_fd = MAX(max_fd, fdin);
 610         max_fd = MAX(max_fd, fdout);
 611         if (fderr != -1)
 612                 max_fd = MAX(max_fd, fderr);
 613 #endif
 614
 615         /* Initialize Initialize buffers. */
 616         buffer_init(&stdin_buffer);
 617         buffer_init(&stdout_buffer);
 618         buffer_init(&stderr_buffer);
 619
 620         /*
 621          * If we have no separate fderr (which is the case when we have a pty
 622          * - there we cannot make difference between data sent to stdout and
 623          * stderr), indicate that we have seen an EOF from stderr.  This way
 624          * we don't need to check the descriptor everywhere.
 625          */
 626         if (fderr == -1)
 627                 fderr_eof = 1;
 628
 629         server_init_dispatch();
 630
 631         /* Main loop of the server for the interactive session mode. */
 632         for (;;) {
 633
 634                 /* Process buffered packets from the client. */
 635                 process_buffered_input_packets();
 636
 637                 /*
 638                  * If we have received eof, and there is no more pending
 639                  * input data, cause a real eof by closing fdin.
 640                  */
 641                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
 642                         if (fdin != fdout)
 643                                 close(fdin);
 644                         else
 645                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
 646                         fdin = -1;
 647                 }
 648                 /* Make packets from buffered stderr data to send to the client. */
 649                 make_packets_from_stderr_data();
 650
 651                 /*
 652                  * Make packets from buffered stdout data to send to the
 653                  * client. If there is very little to send, this arranges to
 654                  * not send them now, but to wait a short while to see if we
 655                  * are getting more data. This is necessary, as some systems
 656                  * wake up readers from a pty after each separate character.
 657                  */
 658                 max_time_milliseconds = 0;
 659                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
 660                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
 661                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
 662                         /* try again after a while */
 663                         max_time_milliseconds = 10;
 664                 } else {
 665                         /* Send it now. */
 666                         make_packets_from_stdout_data();
 667                 }
 668                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
 669
 670                 /* Send channel data to the client. */
 671                 if (packet_not_very_much_data_to_write())
 672                         channel_output_poll();
 673
 674                 /*
 675                  * Bail out of the loop if the program has closed its output
 676                  * descriptors, and we have no more data to send to the
 677                  * client, and there is no pending buffered data.
 678                  */
 679                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
 680                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
 681                         if (!channel_still_open())
 682                                 break;
 683                         if (!waiting_termination) {
 684                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
 685                                 char *cp;
 686                                 waiting_termination = 1;
 687                                 buffer_append(&stderr_buffer, s, strlen(s));
 688
 689                                 /* Display list of open channels. */
 690                                 cp = channel_open_message();
 691                                 buffer_append(&stderr_buffer, cp, strlen(cp));
 692                                 xfree(cp);
 693                         }
 694                 }
 695                 max_fd = MAX(connection_in, connection_out);
 696                 max_fd = MAX(max_fd, fdin);
 697                 max_fd = MAX(max_fd, fdout);
 698                 max_fd = MAX(max_fd, fderr);
 699                 max_fd = MAX(max_fd, notify_pipe[0]);
 700
 701                 /* Sleep in select() until we can do something. */
 702                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 703                     &nalloc, max_time_milliseconds);
 704
 705                 if (received_sigterm) {
 706                         logit("Exiting on signal %d", received_sigterm);
 707                         /* Clean up sessions, utmp, etc. */
 708                         cleanup_exit(255);
 709                 }
 710
 711                 /* Process any channel events. */
 712                 channel_after_select(readset, writeset);
 713
 714                 /* Process input from the client and from program stdout/stderr. */
 715                 process_input(readset);
 716
 717                 /* Process output to the client and to program stdin. */
 718                 process_output(writeset);
 719         }
 720         if (readset)
 721                 xfree(readset);
 722         if (writeset)
 723                 xfree(writeset);
 724
 725         /* Cleanup and termination code. */
 726
 727         /* Wait until all output has been sent to the client. */
 728         drain_output();
 729
 730         debug("End of interactive session; stdin %ld, stdout (read %ld, " "sent %ld), stderr %ld bytes.",
 731             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
 732
 733         /* Free and clear the buffers. */
 734         buffer_free(&stdin_buffer);
 735         buffer_free(&stdout_buffer);
 736         buffer_free(&stderr_buffer);
 737
 738         /* Close the file descriptors. */
 739         if (fdout != -1)
 740                 close(fdout);
 741         fdout = -1;
 742         fdout_eof = 1;
 743         if (fderr != -1)
 744                 close(fderr);
 745         fderr = -1;
 746         fderr_eof = 1;
 747         if (fdin != -1)
 748                 close(fdin);
 749         fdin = -1;
 750
 751         channel_free_all();
 752
 753         /* We no longer want our SIGCHLD handler to be called. */
 754         mysignal(SIGCHLD, SIG_DFL);
 755
 756         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
 757                 if (errno != EINTR)
 758                         packet_disconnect("wait: %.100s", strerror(errno));
 759         if (wait_pid != pid)
 760                 error("Strange, wait returned pid %ld, expected %ld",
 761                     (long)wait_pid, (long)pid);
 762
 763         /* Check if it exited normally. */
 764         if (WIFEXITED(wait_status)) {
 765                 /* Yes, normal exit.  Get exit status and send it to the client. */
 766                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
 767                 packet_start(SSH_SMSG_EXITSTATUS);
 768                 packet_put_int(WEXITSTATUS(wait_status));
 769                 packet_send();
 770                 packet_write_wait();
 771
 772                 /*
 773                  * Wait for exit confirmation.  Note that there might be
 774                  * other packets coming before it; however, the program has
 775                  * already died so we just ignore them.  The client is
 776                  * supposed to respond with the confirmation when it receives
 777                  * the exit status.
 778                  */
 779                 do {
 780                         type = packet_read();
 781                 }
 782                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
 783
 784                 debug("Received exit confirmation.");
 785                 return;
 786         }
 787         /* Check if the program terminated due to a signal. */
 788         if (WIFSIGNALED(wait_status))
 789                 packet_disconnect("Command terminated on signal %d.",
 790                                   WTERMSIG(wait_status));
 791
 792         /* Some weird exit cause.  Just exit. */
 793         packet_disconnect("wait returned status %04x.", wait_status);
 794         /* NOTREACHED */
 795 }
 796
 797 static void
 798 collect_children(void)
 799 {
 800         pid_t pid;
 801         sigset_t oset, nset;
 802         int status;
 803
 804         /* block SIGCHLD while we check for dead children */
 805         sigemptyset(&nset);
 806         sigaddset(&nset, SIGCHLD);
 807         sigprocmask(SIG_BLOCK, &nset, &oset);
 808         if (child_terminated) {
 809                 debug("Received SIGCHLD.");
 810                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 811                     (pid < 0 && errno == EINTR))
 812                         if (pid > 0)
 813                                 session_close_by_pid(pid, status);
 814                 child_terminated = 0;
 815         }
 816         sigprocmask(SIG_SETMASK, &oset, NULL);
 817 }
 818
 819 void
 820 server_loop2(Authctxt *authctxt)
 821 {
 822         fd_set *readset = NULL, *writeset = NULL;
 823         int rekeying = 0, max_fd, nalloc = 0;
 824
 825         debug("Entering interactive session for SSH2.");
 826
 827         mysignal(SIGCHLD, sigchld_handler);
 828         child_terminated = 0;
 829         connection_in = packet_get_connection_in();
 830         connection_out = packet_get_connection_out();
 831
 832         if (!use_privsep) {
 833                 signal(SIGTERM, sigterm_handler);
 834                 signal(SIGINT, sigterm_handler);
 835                 signal(SIGQUIT, sigterm_handler);
 836         }
 837
 838         notify_setup();
 839
 840         max_fd = MAX(connection_in, connection_out);
 841         max_fd = MAX(max_fd, notify_pipe[0]);
 842
 843         server_init_dispatch();
 844
 845         for (;;) {
 846                 process_buffered_input_packets();
 847
 848                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
 849
 850                 if (!rekeying && packet_not_very_much_data_to_write())
 851                         channel_output_poll();
 852                 wait_until_can_do_something(&readset, &writeset, &max_fd,
 853                     &nalloc, 0);
 854
 855                 if (received_sigterm) {
 856                         logit("Exiting on signal %d", received_sigterm);
 857                         /* Clean up sessions, utmp, etc. */
 858                         cleanup_exit(255);
 859                 }
 860
 861                 collect_children();
 862                 if (!rekeying) {
 863                         channel_after_select(readset, writeset);
 864                         if (packet_need_rekeying()) {
 865                                 debug("need rekeying");
 866                                 xxx_kex->done = 0;
 867                                 kex_send_kexinit(xxx_kex);
 868                         }
 869                 }
 870                 process_input(readset);
 871                 if (connection_closed)
 872                         break;
 873                 process_output(writeset);
 874         }
 875         collect_children();
 876
 877         if (readset)
 878                 xfree(readset);
 879         if (writeset)
 880                 xfree(writeset);
 881
 882         /* free all channels, no more reads and writes */
 883         channel_free_all();
 884
 885         /* free remaining sessions, e.g. remove wtmp entries */
 886         session_destroy_all(NULL);
 887 }
 888
 889 static void
 890 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 891 {
 892         debug("Got %d/%u for keepalive", type, seq);
 893         /*
 894          * reset timeout, since we got a sane answer from the client.
 895          * even if this was generated by something other than
 896          * the bogus CHANNEL_REQUEST we send for keepalives.
 897          */
 898         packet_set_alive_timeouts(0);
 899 }
 900
 901 static void
 902 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
 903 {
 904         char *data;
 905         u_int data_len;
 906
 907         /* Stdin data from the client.  Append it to the buffer. */
 908         /* Ignore any data if the client has closed stdin. */
 909         if (fdin == -1)
 910                 return;
 911         data = packet_get_string(&data_len);
 912         packet_check_eom();
 913         buffer_append(&stdin_buffer, data, data_len);
 914         memset(data, 0, data_len);
 915         xfree(data);
 916 }
 917
 918 static void
 919 server_input_eof(int type, u_int32_t seq, void *ctxt)
 920 {
 921         /*
 922          * Eof from the client.  The stdin descriptor to the
 923          * program will be closed when all buffered data has
 924          * drained.
 925          */
 926         debug("EOF received for stdin.");
 927         packet_check_eom();
 928         stdin_eof = 1;
 929 }
 930
 931 static void
 932 server_input_window_size(int type, u_int32_t seq, void *ctxt)
 933 {
 934         u_int row = packet_get_int();
 935         u_int col = packet_get_int();
 936         u_int xpixel = packet_get_int();
 937         u_int ypixel = packet_get_int();
 938
 939         debug("Window change received.");
 940         packet_check_eom();
 941         if (fdin != -1)
 942                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
 943 }
 944
 945 static Channel *
 946 server_request_direct_tcpip(void)
 947 {
 948         Channel *c;
 949         char *target, *originator;
 950         u_short target_port, originator_port;
 951
 952         target = packet_get_string(NULL);
 953         target_port = packet_get_int();
 954         originator = packet_get_string(NULL);
 955         originator_port = packet_get_int();
 956         packet_check_eom();
 957
 958         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 959             "port %d", originator, originator_port, target, target_port);
 960
 961         /* XXX check permission */
 962         c = channel_connect_to(target, target_port,
 963             "direct-tcpip", "direct-tcpip");
 964
 965         xfree(originator);
 966         xfree(target);
 967
 968         return c;
 969 }
 970
 971 static Channel *
 972 server_request_tun(void)
 973 {
 974         Channel *c = NULL;
 975         int mode, tun;
 976         int sock;
 977
 978         mode = packet_get_int();
 979         switch (mode) {
 980         case SSH_TUNMODE_POINTOPOINT:
 981         case SSH_TUNMODE_ETHERNET:
 982                 break;
 983         default:
 984                 packet_send_debug("Unsupported tunnel device mode.");
 985                 return NULL;
 986         }
 987         if ((options.permit_tun & mode) == 0) {
 988                 packet_send_debug("Server has rejected tunnel device "
 989                     "forwarding");
 990                 return NULL;
 991         }
 992
 993         tun = packet_get_int();
 994         if (forced_tun_device != -1) {
 995                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 996                         goto done;
 997                 tun = forced_tun_device;
 998         }
 999         sock = tun_open(tun, mode);
1000         if (sock < 0)
1001                 goto done;
1002         if (options.hpn_disabled)
1003                 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1004                     CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0,
1005                     "tun", 1);
1006         else
1007                 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1008                     options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0,
1009                     "tun", 1);
1010         c->datagram = 1;
1011 #if defined(SSH_TUN_FILTER)
1012         if (mode == SSH_TUNMODE_POINTOPOINT)
1013                 channel_register_filter(c->self, sys_tun_infilter,
1014                     sys_tun_outfilter, NULL, NULL);
1015 #endif
1016
1017  done:
1018         if (c == NULL)
1019                 packet_send_debug("Failed to open the tunnel device.");
1020         return c;
1021 }
1022
1023 static Channel *
1024 server_request_session(void)
1025 {
1026         Channel *c;
1027
1028         debug("input_session_request");
1029         packet_check_eom();
1030
1031         if (no_more_sessions) {
1032                 packet_disconnect("Possible attack: attempt to open a session "
1033                     "after additional sessions disabled");
1034         }
1035
1036         /*
1037          * A server session has no fd to read or write until a
1038          * CHANNEL_REQUEST for a shell is made, so we set the type to
1039          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1040          * CHANNEL_REQUEST messages is registered.
1041          */
1042         c = channel_new("session", SSH_CHANNEL_LARVAL,
1043             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1044             0, "server-session", 1);
1045         if (!options.hpn_disabled && options.tcp_rcv_buf_poll)
1046                 c->dynamic_window = 1;
1047         if (session_open(the_authctxt, c->self) != 1) {
1048                 debug("session open failed, free channel %d", c->self);
1049                 channel_free(c);
1050                 return NULL;
1051         }
1052         channel_register_cleanup(c->self, session_close_by_channel, 0);
1053         return c;
1054 }
1055
1056 static void
1057 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1058 {
1059         Channel *c = NULL;
1060         char *ctype;
1061         int rchan;
1062         u_int rmaxpack, rwindow, len;
1063
1064         ctype = packet_get_string(&len);
1065         rchan = packet_get_int();
1066         rwindow = packet_get_int();
1067         rmaxpack = packet_get_int();
1068
1069         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1070             ctype, rchan, rwindow, rmaxpack);
1071
1072         if (strcmp(ctype, "session") == 0) {
1073                 c = server_request_session();
1074         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1075                 c = server_request_direct_tcpip();
1076         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1077                 c = server_request_tun();
1078         }
1079         if (c != NULL) {
1080                 debug("server_input_channel_open: confirm %s", ctype);
1081                 c->remote_id = rchan;
1082                 c->remote_window = rwindow;
1083                 c->remote_maxpacket = rmaxpack;
1084                 if (c->type != SSH_CHANNEL_CONNECTING) {
1085                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1086                         packet_put_int(c->remote_id);
1087                         packet_put_int(c->self);
1088                         packet_put_int(c->local_window);
1089                         packet_put_int(c->local_maxpacket);
1090                         packet_send();
1091                 }
1092         } else {
1093                 debug("server_input_channel_open: failure %s", ctype);
1094                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1095                 packet_put_int(rchan);
1096                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1097                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1098                         packet_put_cstring("open failed");
1099                         packet_put_cstring("");
1100                 }
1101                 packet_send();
1102         }
1103         xfree(ctype);
1104 }
1105
1106 static void
1107 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1108 {
1109         char *rtype;
1110         int want_reply;
1111         int success = 0, allocated_listen_port = 0;
1112
1113         rtype = packet_get_string(NULL);
1114         want_reply = packet_get_char();
1115         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1116
1117         /* -R style forwarding */
1118         if (strcmp(rtype, "tcpip-forward") == 0) {
1119                 struct passwd *pw;
1120                 char *listen_address;
1121                 u_short listen_port;
1122
1123                 pw = the_authctxt->pw;
1124                 if (pw == NULL || !the_authctxt->valid)
1125                         fatal("server_input_global_request: no/invalid user");
1126                 listen_address = packet_get_string(NULL);
1127                 listen_port = (u_short)packet_get_int();
1128                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1129                     listen_address, listen_port);
1130
1131                 /* check permissions */
1132                 if (!options.allow_tcp_forwarding ||
1133                     no_port_forwarding_flag ||
1134                     (!want_reply && listen_port == 0)
1135 #ifndef NO_IPPORT_RESERVED_CONCEPT
1136                     || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1137                     pw->pw_uid != 0)
1138 #endif
1139                     ) {
1140                         success = 0;
1141                         packet_send_debug("Server has disabled port forwarding.");
1142                 } else {
1143                         /* Start listening on the port */
1144                         success = channel_setup_remote_fwd_listener(
1145                             listen_address, listen_port,
1146                             &allocated_listen_port, options.gateway_ports);
1147                 }
1148                 xfree(listen_address);
1149         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1150                 char *cancel_address;
1151                 u_short cancel_port;
1152
1153                 cancel_address = packet_get_string(NULL);
1154                 cancel_port = (u_short)packet_get_int();
1155                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1156                     cancel_address, cancel_port);
1157
1158                 success = channel_cancel_rport_listener(cancel_address,
1159                     cancel_port);
1160                 xfree(cancel_address);
1161         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1162                 no_more_sessions = 1;
1163                 success = 1;
1164         }
1165         if (want_reply) {
1166                 packet_start(success ?
1167                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1168                 if (success && allocated_listen_port > 0)
1169                         packet_put_int(allocated_listen_port);
1170                 packet_send();
1171                 packet_write_wait();
1172         }
1173         xfree(rtype);
1174 }
1175
1176 static void
1177 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1178 {
1179         Channel *c;
1180         int id, reply, success = 0;
1181         char *rtype;
1182
1183         id = packet_get_int();
1184         rtype = packet_get_string(NULL);
1185         reply = packet_get_char();
1186
1187         debug("server_input_channel_req: channel %d request %s reply %d",
1188             id, rtype, reply);
1189
1190         if ((c = channel_lookup(id)) == NULL)
1191                 packet_disconnect("server_input_channel_req: "
1192                     "unknown channel %d", id);
1193         if (!strcmp(rtype, "eow@openssh.com")) {
1194                 packet_check_eom();
1195                 chan_rcvd_eow(c);
1196         } else if ((c->type == SSH_CHANNEL_LARVAL ||
1197             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1198                 success = session_input_channel_req(c, rtype);
1199         if (reply) {
1200                 packet_start(success ?
1201                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1202                 packet_put_int(c->remote_id);
1203                 packet_send();
1204         }
1205         xfree(rtype);
1206 }
1207
1208 static void
1209 server_init_dispatch_20(void)
1210 {
1211         debug("server_init_dispatch_20");
1212         dispatch_init(&dispatch_protocol_error);
1213         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1214         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1215         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1216         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1217         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1218         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1219         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1220         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1221         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1222         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1223         /* client_alive */
1224         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1225         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1226         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1227         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1228         /* rekeying */
1229         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1230 }
1231 static void
1232 server_init_dispatch_13(void)
1233 {
1234         debug("server_init_dispatch_13");
1235         dispatch_init(NULL);
1236         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1237         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1238         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1239         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1240         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1241         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1242         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1243         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1244         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1245 }
1246 static void
1247 server_init_dispatch_15(void)
1248 {
1249         server_init_dispatch_13();
1250         debug("server_init_dispatch_15");
1251         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1252         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1253 }
1254 static void
1255 server_init_dispatch(void)
1256 {
1257         if (compat20)
1258                 server_init_dispatch_20();
1259         else if (compat13)
1260                 server_init_dispatch_13();
1261         else
1262                 server_init_dispatch_15();
1263 }