serverloop.c revision 181097
1/* $OpenBSD: serverloop.c,v 1.145 2006/10/11 12:38:03 markus Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38#include "includes.h" 39 40#include <sys/types.h> 41#include <sys/param.h> 42#include <sys/wait.h> 43#include <sys/socket.h> 44#ifdef HAVE_SYS_TIME_H 45# include <sys/time.h> 46#endif 47 48#include <netinet/in.h> 49 50#include <errno.h> 51#include <fcntl.h> 52#include <pwd.h> 53#include <signal.h> 54#include <string.h> 55#include <termios.h> 56#include <unistd.h> 57#include <stdarg.h> 58 59#include "xmalloc.h" 60#include "packet.h" 61#include "buffer.h" 62#include "log.h" 63#include "servconf.h" 64#include "canohost.h" 65#include "sshpty.h" 66#include "channels.h" 67#include "compat.h" 68#include "ssh1.h" 69#include "ssh2.h" 70#include "key.h" 71#include "cipher.h" 72#include "kex.h" 73#include "hostfile.h" 74#include "auth.h" 75#include "session.h" 76#include "dispatch.h" 77#include "auth-options.h" 78#include "serverloop.h" 79#include "misc.h" 80 81extern ServerOptions options; 82 83/* XXX */ 84extern Kex *xxx_kex; 85extern Authctxt *the_authctxt; 86extern int use_privsep; 87 88static Buffer stdin_buffer; /* Buffer for stdin data. */ 89static Buffer stdout_buffer; /* Buffer for stdout data. */ 90static Buffer stderr_buffer; /* Buffer for stderr data. */ 91static int fdin; /* Descriptor for stdin (for writing) */ 92static int fdout; /* Descriptor for stdout (for reading); 93 May be same number as fdin. */ 94static int fderr; /* Descriptor for stderr. May be -1. */ 95static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 96static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 97static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 98static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 99static int stdin_eof = 0; /* EOF message received from client. */ 100static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 101static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 102static int fdin_is_tty = 0; /* fdin points to a tty. */ 103static int connection_in; /* Connection to client (input). */ 104static int connection_out; /* Connection to client (output). */ 105static int connection_closed = 0; /* Connection to client closed. */ 106static u_int buffer_high; /* "Soft" max buffer size. */ 107static int client_alive_timeouts = 0; 108 109/* 110 * This SIGCHLD kludge is used to detect when the child exits. The server 111 * will exit after that, as soon as forwarded connections have terminated. 112 */ 113 114static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 115 116/* Cleanup on signals (!use_privsep case only) */ 117static volatile sig_atomic_t received_sigterm = 0; 118 119/* prototypes */ 120static void server_init_dispatch(void); 121 122/* 123 * we write to this pipe if a SIGCHLD is caught in order to avoid 124 * the race between select() and child_terminated 125 */ 126static int notify_pipe[2]; 127static void 128notify_setup(void) 129{ 130 if (pipe(notify_pipe) < 0) { 131 error("pipe(notify_pipe) failed %s", strerror(errno)); 132 } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) || 133 (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) { 134 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 135 close(notify_pipe[0]); 136 close(notify_pipe[1]); 137 } else { 138 set_nonblock(notify_pipe[0]); 139 set_nonblock(notify_pipe[1]); 140 return; 141 } 142 notify_pipe[0] = -1; /* read end */ 143 notify_pipe[1] = -1; /* write end */ 144} 145static void 146notify_parent(void) 147{ 148 if (notify_pipe[1] != -1) 149 write(notify_pipe[1], "", 1); 150} 151static void 152notify_prepare(fd_set *readset) 153{ 154 if (notify_pipe[0] != -1) 155 FD_SET(notify_pipe[0], readset); 156} 157static void 158notify_done(fd_set *readset) 159{ 160 char c; 161 162 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 163 while (read(notify_pipe[0], &c, 1) != -1) 164 debug2("notify_done: reading"); 165} 166 167/*ARGSUSED*/ 168static void 169sigchld_handler(int sig) 170{ 171 int save_errno = errno; 172 child_terminated = 1; 173#ifndef _UNICOS 174 mysignal(SIGCHLD, sigchld_handler); 175#endif 176 notify_parent(); 177 errno = save_errno; 178} 179 180/*ARGSUSED*/ 181static void 182sigterm_handler(int sig) 183{ 184 received_sigterm = sig; 185} 186 187/* 188 * Make packets from buffered stderr data, and buffer it for sending 189 * to the client. 190 */ 191static void 192make_packets_from_stderr_data(void) 193{ 194 u_int len; 195 196 /* Send buffered stderr data to the client. */ 197 while (buffer_len(&stderr_buffer) > 0 && 198 packet_not_very_much_data_to_write()) { 199 len = buffer_len(&stderr_buffer); 200 if (packet_is_interactive()) { 201 if (len > 512) 202 len = 512; 203 } else { 204 /* Keep the packets at reasonable size. */ 205 if (len > packet_get_maxsize()) 206 len = packet_get_maxsize(); 207 } 208 packet_start(SSH_SMSG_STDERR_DATA); 209 packet_put_string(buffer_ptr(&stderr_buffer), len); 210 packet_send(); 211 buffer_consume(&stderr_buffer, len); 212 stderr_bytes += len; 213 } 214} 215 216/* 217 * Make packets from buffered stdout data, and buffer it for sending to the 218 * client. 219 */ 220static void 221make_packets_from_stdout_data(void) 222{ 223 u_int len; 224 225 /* Send buffered stdout data to the client. */ 226 while (buffer_len(&stdout_buffer) > 0 && 227 packet_not_very_much_data_to_write()) { 228 len = buffer_len(&stdout_buffer); 229 if (packet_is_interactive()) { 230 if (len > 512) 231 len = 512; 232 } else { 233 /* Keep the packets at reasonable size. */ 234 if (len > packet_get_maxsize()) 235 len = packet_get_maxsize(); 236 } 237 packet_start(SSH_SMSG_STDOUT_DATA); 238 packet_put_string(buffer_ptr(&stdout_buffer), len); 239 packet_send(); 240 buffer_consume(&stdout_buffer, len); 241 stdout_bytes += len; 242 } 243} 244 245static void 246client_alive_check(void) 247{ 248 int channel_id; 249 250 /* timeout, check to see how many we have had */ 251 if (++client_alive_timeouts > options.client_alive_count_max) { 252 logit("Timeout, client not responding."); 253 cleanup_exit(255); 254 } 255 256 /* 257 * send a bogus global/channel request with "wantreply", 258 * we should get back a failure 259 */ 260 if ((channel_id = channel_find_open()) == -1) { 261 packet_start(SSH2_MSG_GLOBAL_REQUEST); 262 packet_put_cstring("keepalive@openssh.com"); 263 packet_put_char(1); /* boolean: want reply */ 264 } else { 265 channel_request_start(channel_id, "keepalive@openssh.com", 1); 266 } 267 packet_send(); 268} 269 270/* 271 * Sleep in select() until we can do something. This will initialize the 272 * select masks. Upon return, the masks will indicate which descriptors 273 * have data or can accept data. Optionally, a maximum time can be specified 274 * for the duration of the wait (0 = infinite). 275 */ 276static void 277wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 278 u_int *nallocp, u_int max_time_milliseconds) 279{ 280 struct timeval tv, *tvp; 281 int ret; 282 int client_alive_scheduled = 0; 283 284 /* 285 * if using client_alive, set the max timeout accordingly, 286 * and indicate that this particular timeout was for client 287 * alive by setting the client_alive_scheduled flag. 288 * 289 * this could be randomized somewhat to make traffic 290 * analysis more difficult, but we're not doing it yet. 291 */ 292 if (compat20 && 293 max_time_milliseconds == 0 && options.client_alive_interval) { 294 client_alive_scheduled = 1; 295 max_time_milliseconds = options.client_alive_interval * 1000; 296 } 297 298 /* Allocate and update select() masks for channel descriptors. */ 299 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0); 300 301 if (compat20) { 302#if 0 303 /* wrong: bad condition XXX */ 304 if (channel_not_very_much_buffered_data()) 305#endif 306 FD_SET(connection_in, *readsetp); 307 } else { 308 /* 309 * Read packets from the client unless we have too much 310 * buffered stdin or channel data. 311 */ 312 if (buffer_len(&stdin_buffer) < buffer_high && 313 channel_not_very_much_buffered_data()) 314 FD_SET(connection_in, *readsetp); 315 /* 316 * If there is not too much data already buffered going to 317 * the client, try to get some more data from the program. 318 */ 319 if (packet_not_very_much_data_to_write()) { 320 if (!fdout_eof) 321 FD_SET(fdout, *readsetp); 322 if (!fderr_eof) 323 FD_SET(fderr, *readsetp); 324 } 325 /* 326 * If we have buffered data, try to write some of that data 327 * to the program. 328 */ 329 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 330 FD_SET(fdin, *writesetp); 331 } 332 notify_prepare(*readsetp); 333 334 /* 335 * If we have buffered packet data going to the client, mark that 336 * descriptor. 337 */ 338 if (packet_have_data_to_write()) 339 FD_SET(connection_out, *writesetp); 340 341 /* 342 * If child has terminated and there is enough buffer space to read 343 * from it, then read as much as is available and exit. 344 */ 345 if (child_terminated && packet_not_very_much_data_to_write()) 346 if (max_time_milliseconds == 0 || client_alive_scheduled) 347 max_time_milliseconds = 100; 348 349 if (max_time_milliseconds == 0) 350 tvp = NULL; 351 else { 352 tv.tv_sec = max_time_milliseconds / 1000; 353 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 354 tvp = &tv; 355 } 356 357 /* Wait for something to happen, or the timeout to expire. */ 358 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 359 360 if (ret == -1) { 361 memset(*readsetp, 0, *nallocp); 362 memset(*writesetp, 0, *nallocp); 363 if (errno != EINTR) 364 error("select: %.100s", strerror(errno)); 365 } else if (ret == 0 && client_alive_scheduled) 366 client_alive_check(); 367 368 notify_done(*readsetp); 369} 370 371/* 372 * Processes input from the client and the program. Input data is stored 373 * in buffers and processed later. 374 */ 375static void 376process_input(fd_set *readset) 377{ 378 int len; 379 char buf[16384]; 380 381 /* Read and buffer any input data from the client. */ 382 if (FD_ISSET(connection_in, readset)) { 383 len = read(connection_in, buf, sizeof(buf)); 384 if (len == 0) { 385 verbose("Connection closed by %.100s", 386 get_remote_ipaddr()); 387 connection_closed = 1; 388 if (compat20) 389 return; 390 cleanup_exit(255); 391 } else if (len < 0) { 392 if (errno != EINTR && errno != EAGAIN) { 393 verbose("Read error from remote host " 394 "%.100s: %.100s", 395 get_remote_ipaddr(), strerror(errno)); 396 cleanup_exit(255); 397 } 398 } else { 399 /* Buffer any received data. */ 400 packet_process_incoming(buf, len); 401 } 402 } 403 if (compat20) 404 return; 405 406 /* Read and buffer any available stdout data from the program. */ 407 if (!fdout_eof && FD_ISSET(fdout, readset)) { 408 errno = 0; 409 len = read(fdout, buf, sizeof(buf)); 410 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 411 /* do nothing */ 412#ifndef PTY_ZEROREAD 413 } else if (len <= 0) { 414#else 415 } else if ((!isatty(fdout) && len <= 0) || 416 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) { 417#endif 418 fdout_eof = 1; 419 } else { 420 buffer_append(&stdout_buffer, buf, len); 421 fdout_bytes += len; 422 } 423 } 424 /* Read and buffer any available stderr data from the program. */ 425 if (!fderr_eof && FD_ISSET(fderr, readset)) { 426 errno = 0; 427 len = read(fderr, buf, sizeof(buf)); 428 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 429 /* do nothing */ 430#ifndef PTY_ZEROREAD 431 } else if (len <= 0) { 432#else 433 } else if ((!isatty(fderr) && len <= 0) || 434 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) { 435#endif 436 fderr_eof = 1; 437 } else { 438 buffer_append(&stderr_buffer, buf, len); 439 } 440 } 441} 442 443/* 444 * Sends data from internal buffers to client program stdin. 445 */ 446static void 447process_output(fd_set *writeset) 448{ 449 struct termios tio; 450 u_char *data; 451 u_int dlen; 452 int len; 453 454 /* Write buffered data to program stdin. */ 455 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 456 data = buffer_ptr(&stdin_buffer); 457 dlen = buffer_len(&stdin_buffer); 458 len = write(fdin, data, dlen); 459 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 460 /* do nothing */ 461 } else if (len <= 0) { 462 if (fdin != fdout) 463 close(fdin); 464 else 465 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 466 fdin = -1; 467 } else { 468 /* Successful write. */ 469 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 470 tcgetattr(fdin, &tio) == 0 && 471 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 472 /* 473 * Simulate echo to reduce the impact of 474 * traffic analysis 475 */ 476 packet_send_ignore(len); 477 packet_send(); 478 } 479 /* Consume the data from the buffer. */ 480 buffer_consume(&stdin_buffer, len); 481 /* Update the count of bytes written to the program. */ 482 stdin_bytes += len; 483 } 484 } 485 /* Send any buffered packet data to the client. */ 486 if (FD_ISSET(connection_out, writeset)) 487 packet_write_poll(); 488} 489 490/* 491 * Wait until all buffered output has been sent to the client. 492 * This is used when the program terminates. 493 */ 494static void 495drain_output(void) 496{ 497 /* Send any buffered stdout data to the client. */ 498 if (buffer_len(&stdout_buffer) > 0) { 499 packet_start(SSH_SMSG_STDOUT_DATA); 500 packet_put_string(buffer_ptr(&stdout_buffer), 501 buffer_len(&stdout_buffer)); 502 packet_send(); 503 /* Update the count of sent bytes. */ 504 stdout_bytes += buffer_len(&stdout_buffer); 505 } 506 /* Send any buffered stderr data to the client. */ 507 if (buffer_len(&stderr_buffer) > 0) { 508 packet_start(SSH_SMSG_STDERR_DATA); 509 packet_put_string(buffer_ptr(&stderr_buffer), 510 buffer_len(&stderr_buffer)); 511 packet_send(); 512 /* Update the count of sent bytes. */ 513 stderr_bytes += buffer_len(&stderr_buffer); 514 } 515 /* Wait until all buffered data has been written to the client. */ 516 packet_write_wait(); 517} 518 519static void 520process_buffered_input_packets(void) 521{ 522 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 523} 524 525/* 526 * Performs the interactive session. This handles data transmission between 527 * the client and the program. Note that the notion of stdin, stdout, and 528 * stderr in this function is sort of reversed: this function writes to 529 * stdin (of the child program), and reads from stdout and stderr (of the 530 * child program). 531 */ 532void 533server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 534{ 535 fd_set *readset = NULL, *writeset = NULL; 536 int max_fd = 0; 537 u_int nalloc = 0; 538 int wait_status; /* Status returned by wait(). */ 539 pid_t wait_pid; /* pid returned by wait(). */ 540 int waiting_termination = 0; /* Have displayed waiting close message. */ 541 u_int max_time_milliseconds; 542 u_int previous_stdout_buffer_bytes; 543 u_int stdout_buffer_bytes; 544 int type; 545 546 debug("Entering interactive session."); 547 548 /* Initialize the SIGCHLD kludge. */ 549 child_terminated = 0; 550 mysignal(SIGCHLD, sigchld_handler); 551 552 if (!use_privsep) { 553 signal(SIGTERM, sigterm_handler); 554 signal(SIGINT, sigterm_handler); 555 signal(SIGQUIT, sigterm_handler); 556 } 557 558 /* Initialize our global variables. */ 559 fdin = fdin_arg; 560 fdout = fdout_arg; 561 fderr = fderr_arg; 562 563 /* nonblocking IO */ 564 set_nonblock(fdin); 565 set_nonblock(fdout); 566 /* we don't have stderr for interactive terminal sessions, see below */ 567 if (fderr != -1) 568 set_nonblock(fderr); 569 570 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 571 fdin_is_tty = 1; 572 573 connection_in = packet_get_connection_in(); 574 connection_out = packet_get_connection_out(); 575 576 notify_setup(); 577 578 previous_stdout_buffer_bytes = 0; 579 580 /* Set approximate I/O buffer size. */ 581 if (packet_is_interactive()) 582 buffer_high = 4096; 583 else 584 buffer_high = 64 * 1024; 585 586#if 0 587 /* Initialize max_fd to the maximum of the known file descriptors. */ 588 max_fd = MAX(connection_in, connection_out); 589 max_fd = MAX(max_fd, fdin); 590 max_fd = MAX(max_fd, fdout); 591 if (fderr != -1) 592 max_fd = MAX(max_fd, fderr); 593#endif 594 595 /* Initialize Initialize buffers. */ 596 buffer_init(&stdin_buffer); 597 buffer_init(&stdout_buffer); 598 buffer_init(&stderr_buffer); 599 600 /* 601 * If we have no separate fderr (which is the case when we have a pty 602 * - there we cannot make difference between data sent to stdout and 603 * stderr), indicate that we have seen an EOF from stderr. This way 604 * we don't need to check the descriptor everywhere. 605 */ 606 if (fderr == -1) 607 fderr_eof = 1; 608 609 server_init_dispatch(); 610 611 /* Main loop of the server for the interactive session mode. */ 612 for (;;) { 613 614 /* Process buffered packets from the client. */ 615 process_buffered_input_packets(); 616 617 /* 618 * If we have received eof, and there is no more pending 619 * input data, cause a real eof by closing fdin. 620 */ 621 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 622 if (fdin != fdout) 623 close(fdin); 624 else 625 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 626 fdin = -1; 627 } 628 /* Make packets from buffered stderr data to send to the client. */ 629 make_packets_from_stderr_data(); 630 631 /* 632 * Make packets from buffered stdout data to send to the 633 * client. If there is very little to send, this arranges to 634 * not send them now, but to wait a short while to see if we 635 * are getting more data. This is necessary, as some systems 636 * wake up readers from a pty after each separate character. 637 */ 638 max_time_milliseconds = 0; 639 stdout_buffer_bytes = buffer_len(&stdout_buffer); 640 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 641 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 642 /* try again after a while */ 643 max_time_milliseconds = 10; 644 } else { 645 /* Send it now. */ 646 make_packets_from_stdout_data(); 647 } 648 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 649 650 /* Send channel data to the client. */ 651 if (packet_not_very_much_data_to_write()) 652 channel_output_poll(); 653 654 /* 655 * Bail out of the loop if the program has closed its output 656 * descriptors, and we have no more data to send to the 657 * client, and there is no pending buffered data. 658 */ 659 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 660 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 661 if (!channel_still_open()) 662 break; 663 if (!waiting_termination) { 664 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 665 char *cp; 666 waiting_termination = 1; 667 buffer_append(&stderr_buffer, s, strlen(s)); 668 669 /* Display list of open channels. */ 670 cp = channel_open_message(); 671 buffer_append(&stderr_buffer, cp, strlen(cp)); 672 xfree(cp); 673 } 674 } 675 max_fd = MAX(connection_in, connection_out); 676 max_fd = MAX(max_fd, fdin); 677 max_fd = MAX(max_fd, fdout); 678 max_fd = MAX(max_fd, fderr); 679 max_fd = MAX(max_fd, notify_pipe[0]); 680 681 /* Sleep in select() until we can do something. */ 682 wait_until_can_do_something(&readset, &writeset, &max_fd, 683 &nalloc, max_time_milliseconds); 684 685 if (received_sigterm) { 686 logit("Exiting on signal %d", received_sigterm); 687 /* Clean up sessions, utmp, etc. */ 688 cleanup_exit(255); 689 } 690 691 /* Process any channel events. */ 692 channel_after_select(readset, writeset); 693 694 /* Process input from the client and from program stdout/stderr. */ 695 process_input(readset); 696 697 /* Process output to the client and to program stdin. */ 698 process_output(writeset); 699 } 700 if (readset) 701 xfree(readset); 702 if (writeset) 703 xfree(writeset); 704 705 /* Cleanup and termination code. */ 706 707 /* Wait until all output has been sent to the client. */ 708 drain_output(); 709 710 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 711 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 712 713 /* Free and clear the buffers. */ 714 buffer_free(&stdin_buffer); 715 buffer_free(&stdout_buffer); 716 buffer_free(&stderr_buffer); 717 718 /* Close the file descriptors. */ 719 if (fdout != -1) 720 close(fdout); 721 fdout = -1; 722 fdout_eof = 1; 723 if (fderr != -1) 724 close(fderr); 725 fderr = -1; 726 fderr_eof = 1; 727 if (fdin != -1) 728 close(fdin); 729 fdin = -1; 730 731 channel_free_all(); 732 733 /* We no longer want our SIGCHLD handler to be called. */ 734 mysignal(SIGCHLD, SIG_DFL); 735 736 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 737 if (errno != EINTR) 738 packet_disconnect("wait: %.100s", strerror(errno)); 739 if (wait_pid != pid) 740 error("Strange, wait returned pid %ld, expected %ld", 741 (long)wait_pid, (long)pid); 742 743 /* Check if it exited normally. */ 744 if (WIFEXITED(wait_status)) { 745 /* Yes, normal exit. Get exit status and send it to the client. */ 746 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 747 packet_start(SSH_SMSG_EXITSTATUS); 748 packet_put_int(WEXITSTATUS(wait_status)); 749 packet_send(); 750 packet_write_wait(); 751 752 /* 753 * Wait for exit confirmation. Note that there might be 754 * other packets coming before it; however, the program has 755 * already died so we just ignore them. The client is 756 * supposed to respond with the confirmation when it receives 757 * the exit status. 758 */ 759 do { 760 type = packet_read(); 761 } 762 while (type != SSH_CMSG_EXIT_CONFIRMATION); 763 764 debug("Received exit confirmation."); 765 return; 766 } 767 /* Check if the program terminated due to a signal. */ 768 if (WIFSIGNALED(wait_status)) 769 packet_disconnect("Command terminated on signal %d.", 770 WTERMSIG(wait_status)); 771 772 /* Some weird exit cause. Just exit. */ 773 packet_disconnect("wait returned status %04x.", wait_status); 774 /* NOTREACHED */ 775} 776 777static void 778collect_children(void) 779{ 780 pid_t pid; 781 sigset_t oset, nset; 782 int status; 783 784 /* block SIGCHLD while we check for dead children */ 785 sigemptyset(&nset); 786 sigaddset(&nset, SIGCHLD); 787 sigprocmask(SIG_BLOCK, &nset, &oset); 788 if (child_terminated) { 789 debug("Received SIGCHLD."); 790 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 791 (pid < 0 && errno == EINTR)) 792 if (pid > 0) 793 session_close_by_pid(pid, status); 794 child_terminated = 0; 795 } 796 sigprocmask(SIG_SETMASK, &oset, NULL); 797} 798 799void 800server_loop2(Authctxt *authctxt) 801{ 802 fd_set *readset = NULL, *writeset = NULL; 803 int rekeying = 0, max_fd, nalloc = 0; 804 805 debug("Entering interactive session for SSH2."); 806 807 mysignal(SIGCHLD, sigchld_handler); 808 child_terminated = 0; 809 connection_in = packet_get_connection_in(); 810 connection_out = packet_get_connection_out(); 811 812 if (!use_privsep) { 813 signal(SIGTERM, sigterm_handler); 814 signal(SIGINT, sigterm_handler); 815 signal(SIGQUIT, sigterm_handler); 816 } 817 818 notify_setup(); 819 820 max_fd = MAX(connection_in, connection_out); 821 max_fd = MAX(max_fd, notify_pipe[0]); 822 823 server_init_dispatch(); 824 825 for (;;) { 826 process_buffered_input_packets(); 827 828 rekeying = (xxx_kex != NULL && !xxx_kex->done); 829 830 if (!rekeying && packet_not_very_much_data_to_write()) 831 channel_output_poll(); 832 wait_until_can_do_something(&readset, &writeset, &max_fd, 833 &nalloc, 0); 834 835 if (received_sigterm) { 836 logit("Exiting on signal %d", received_sigterm); 837 /* Clean up sessions, utmp, etc. */ 838 cleanup_exit(255); 839 } 840 841 collect_children(); 842 if (!rekeying) { 843 channel_after_select(readset, writeset); 844 if (packet_need_rekeying()) { 845 debug("need rekeying"); 846 xxx_kex->done = 0; 847 kex_send_kexinit(xxx_kex); 848 } 849 } 850 process_input(readset); 851 if (connection_closed) 852 break; 853 process_output(writeset); 854 } 855 collect_children(); 856 857 if (readset) 858 xfree(readset); 859 if (writeset) 860 xfree(writeset); 861 862 /* free all channels, no more reads and writes */ 863 channel_free_all(); 864 865 /* free remaining sessions, e.g. remove wtmp entries */ 866 session_destroy_all(NULL); 867} 868 869static void 870server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 871{ 872 debug("Got %d/%u for keepalive", type, seq); 873 /* 874 * reset timeout, since we got a sane answer from the client. 875 * even if this was generated by something other than 876 * the bogus CHANNEL_REQUEST we send for keepalives. 877 */ 878 client_alive_timeouts = 0; 879} 880 881static void 882server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 883{ 884 char *data; 885 u_int data_len; 886 887 /* Stdin data from the client. Append it to the buffer. */ 888 /* Ignore any data if the client has closed stdin. */ 889 if (fdin == -1) 890 return; 891 data = packet_get_string(&data_len); 892 packet_check_eom(); 893 buffer_append(&stdin_buffer, data, data_len); 894 memset(data, 0, data_len); 895 xfree(data); 896} 897 898static void 899server_input_eof(int type, u_int32_t seq, void *ctxt) 900{ 901 /* 902 * Eof from the client. The stdin descriptor to the 903 * program will be closed when all buffered data has 904 * drained. 905 */ 906 debug("EOF received for stdin."); 907 packet_check_eom(); 908 stdin_eof = 1; 909} 910 911static void 912server_input_window_size(int type, u_int32_t seq, void *ctxt) 913{ 914 u_int row = packet_get_int(); 915 u_int col = packet_get_int(); 916 u_int xpixel = packet_get_int(); 917 u_int ypixel = packet_get_int(); 918 919 debug("Window change received."); 920 packet_check_eom(); 921 if (fdin != -1) 922 pty_change_window_size(fdin, row, col, xpixel, ypixel); 923} 924 925static Channel * 926server_request_direct_tcpip(void) 927{ 928 Channel *c; 929 int sock; 930 char *target, *originator; 931 int target_port, originator_port; 932 933 target = packet_get_string(NULL); 934 target_port = packet_get_int(); 935 originator = packet_get_string(NULL); 936 originator_port = packet_get_int(); 937 packet_check_eom(); 938 939 debug("server_request_direct_tcpip: originator %s port %d, target %s port %d", 940 originator, originator_port, target, target_port); 941 942 /* XXX check permission */ 943 sock = channel_connect_to(target, target_port); 944 xfree(target); 945 xfree(originator); 946 if (sock < 0) 947 return NULL; 948 c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING, 949 sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT, 950 CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1); 951 return c; 952} 953 954static Channel * 955server_request_tun(void) 956{ 957 Channel *c = NULL; 958 int mode, tun; 959 int sock; 960 961 mode = packet_get_int(); 962 switch (mode) { 963 case SSH_TUNMODE_POINTOPOINT: 964 case SSH_TUNMODE_ETHERNET: 965 break; 966 default: 967 packet_send_debug("Unsupported tunnel device mode."); 968 return NULL; 969 } 970 if ((options.permit_tun & mode) == 0) { 971 packet_send_debug("Server has rejected tunnel device " 972 "forwarding"); 973 return NULL; 974 } 975 976 tun = packet_get_int(); 977 if (forced_tun_device != -1) { 978 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 979 goto done; 980 tun = forced_tun_device; 981 } 982 sock = tun_open(tun, mode); 983 if (sock < 0) 984 goto done; 985 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 986 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 987 c->datagram = 1; 988#if defined(SSH_TUN_FILTER) 989 if (mode == SSH_TUNMODE_POINTOPOINT) 990 channel_register_filter(c->self, sys_tun_infilter, 991 sys_tun_outfilter); 992#endif 993 994 done: 995 if (c == NULL) 996 packet_send_debug("Failed to open the tunnel device."); 997 return c; 998} 999 1000static Channel * 1001server_request_session(void) 1002{ 1003 Channel *c; 1004 1005 debug("input_session_request"); 1006 packet_check_eom(); 1007 /* 1008 * A server session has no fd to read or write until a 1009 * CHANNEL_REQUEST for a shell is made, so we set the type to 1010 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1011 * CHANNEL_REQUEST messages is registered. 1012 */ 1013 c = channel_new("session", SSH_CHANNEL_LARVAL, 1014 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1015 0, "server-session", 1); 1016 if (session_open(the_authctxt, c->self) != 1) { 1017 debug("session open failed, free channel %d", c->self); 1018 channel_free(c); 1019 return NULL; 1020 } 1021 channel_register_cleanup(c->self, session_close_by_channel, 0); 1022 return c; 1023} 1024 1025static void 1026server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1027{ 1028 Channel *c = NULL; 1029 char *ctype; 1030 int rchan; 1031 u_int rmaxpack, rwindow, len; 1032 1033 ctype = packet_get_string(&len); 1034 rchan = packet_get_int(); 1035 rwindow = packet_get_int(); 1036 rmaxpack = packet_get_int(); 1037 1038 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1039 ctype, rchan, rwindow, rmaxpack); 1040 1041 if (strcmp(ctype, "session") == 0) { 1042 c = server_request_session(); 1043 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1044 c = server_request_direct_tcpip(); 1045 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1046 c = server_request_tun(); 1047 } 1048 if (c != NULL) { 1049 debug("server_input_channel_open: confirm %s", ctype); 1050 c->remote_id = rchan; 1051 c->remote_window = rwindow; 1052 c->remote_maxpacket = rmaxpack; 1053 if (c->type != SSH_CHANNEL_CONNECTING) { 1054 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1055 packet_put_int(c->remote_id); 1056 packet_put_int(c->self); 1057 packet_put_int(c->local_window); 1058 packet_put_int(c->local_maxpacket); 1059 packet_send(); 1060 } 1061 } else { 1062 debug("server_input_channel_open: failure %s", ctype); 1063 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1064 packet_put_int(rchan); 1065 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1066 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1067 packet_put_cstring("open failed"); 1068 packet_put_cstring(""); 1069 } 1070 packet_send(); 1071 } 1072 xfree(ctype); 1073} 1074 1075static void 1076server_input_global_request(int type, u_int32_t seq, void *ctxt) 1077{ 1078 char *rtype; 1079 int want_reply; 1080 int success = 0; 1081 1082 rtype = packet_get_string(NULL); 1083 want_reply = packet_get_char(); 1084 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1085 1086 /* -R style forwarding */ 1087 if (strcmp(rtype, "tcpip-forward") == 0) { 1088 struct passwd *pw; 1089 char *listen_address; 1090 u_short listen_port; 1091 1092 pw = the_authctxt->pw; 1093 if (pw == NULL || !the_authctxt->valid) 1094 fatal("server_input_global_request: no/invalid user"); 1095 listen_address = packet_get_string(NULL); 1096 listen_port = (u_short)packet_get_int(); 1097 debug("server_input_global_request: tcpip-forward listen %s port %d", 1098 listen_address, listen_port); 1099 1100 /* check permissions */ 1101 if (!options.allow_tcp_forwarding || 1102 no_port_forwarding_flag 1103#ifndef NO_IPPORT_RESERVED_CONCEPT 1104 || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0) 1105#endif 1106 ) { 1107 success = 0; 1108 packet_send_debug("Server has disabled port forwarding."); 1109 } else { 1110 /* Start listening on the port */ 1111 success = channel_setup_remote_fwd_listener( 1112 listen_address, listen_port, options.gateway_ports); 1113 } 1114 xfree(listen_address); 1115 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1116 char *cancel_address; 1117 u_short cancel_port; 1118 1119 cancel_address = packet_get_string(NULL); 1120 cancel_port = (u_short)packet_get_int(); 1121 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1122 cancel_address, cancel_port); 1123 1124 success = channel_cancel_rport_listener(cancel_address, 1125 cancel_port); 1126 xfree(cancel_address); 1127 } 1128 if (want_reply) { 1129 packet_start(success ? 1130 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1131 packet_send(); 1132 packet_write_wait(); 1133 } 1134 xfree(rtype); 1135} 1136 1137static void 1138server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1139{ 1140 Channel *c; 1141 int id, reply, success = 0; 1142 char *rtype; 1143 1144 id = packet_get_int(); 1145 rtype = packet_get_string(NULL); 1146 reply = packet_get_char(); 1147 1148 debug("server_input_channel_req: channel %d request %s reply %d", 1149 id, rtype, reply); 1150 1151 if ((c = channel_lookup(id)) == NULL) 1152 packet_disconnect("server_input_channel_req: " 1153 "unknown channel %d", id); 1154 if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN) 1155 success = session_input_channel_req(c, rtype); 1156 if (reply) { 1157 packet_start(success ? 1158 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1159 packet_put_int(c->remote_id); 1160 packet_send(); 1161 } 1162 xfree(rtype); 1163} 1164 1165static void 1166server_init_dispatch_20(void) 1167{ 1168 debug("server_init_dispatch_20"); 1169 dispatch_init(&dispatch_protocol_error); 1170 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1171 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1172 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1173 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1174 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1175 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1176 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1177 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1178 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1179 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1180 /* client_alive */ 1181 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1182 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1183 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1184 /* rekeying */ 1185 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1186} 1187static void 1188server_init_dispatch_13(void) 1189{ 1190 debug("server_init_dispatch_13"); 1191 dispatch_init(NULL); 1192 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1193 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1194 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1195 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1196 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1197 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1198 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1199 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1200 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1201} 1202static void 1203server_init_dispatch_15(void) 1204{ 1205 server_init_dispatch_13(); 1206 debug("server_init_dispatch_15"); 1207 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1208 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1209} 1210static void 1211server_init_dispatch(void) 1212{ 1213 if (compat20) 1214 server_init_dispatch_20(); 1215 else if (compat13) 1216 server_init_dispatch_13(); 1217 else 1218 server_init_dispatch_15(); 1219} 1220