1/* $OpenBSD: serverloop.c,v 1.164 2012/12/07 01:51:35 dtucker Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38#include "includes.h" 39 40#include <sys/types.h> 41#include <sys/param.h> 42#include <sys/wait.h> 43#include <sys/socket.h> 44#ifdef HAVE_SYS_TIME_H 45# include <sys/time.h> 46#endif 47 48#include <netinet/in.h> 49 50#include <errno.h> 51#include <fcntl.h> 52#include <pwd.h> 53#include <signal.h> 54#include <string.h> 55#include <termios.h> 56#include <unistd.h> 57#include <stdarg.h> 58 59#include "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 83extern ServerOptions options; 84 85/* XXX */ 86extern Kex *xxx_kex; 87extern Authctxt *the_authctxt; 88extern int use_privsep; 89 90static Buffer stdin_buffer; /* Buffer for stdin data. */ 91static Buffer stdout_buffer; /* Buffer for stdout data. */ 92static Buffer stderr_buffer; /* Buffer for stderr data. */ 93static int fdin; /* Descriptor for stdin (for writing) */ 94static int fdout; /* Descriptor for stdout (for reading); 95 May be same number as fdin. */ 96static int fderr; /* Descriptor for stderr. May be -1. */ 97static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 98static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 99static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 100static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 101static int stdin_eof = 0; /* EOF message received from client. */ 102static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 103static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 104static int fdin_is_tty = 0; /* fdin points to a tty. */ 105static int connection_in; /* Connection to client (input). */ 106static int connection_out; /* Connection to client (output). */ 107static int connection_closed = 0; /* Connection to client closed. */ 108static u_int buffer_high; /* "Soft" max buffer size. */ 109static 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 116static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 117 118/* Cleanup on signals (!use_privsep case only) */ 119static volatile sig_atomic_t received_sigterm = 0; 120 121/* prototypes */ 122static 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 */ 128static int notify_pipe[2]; 129static void 130notify_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} 147static void 148notify_parent(void) 149{ 150 if (notify_pipe[1] != -1) 151 write(notify_pipe[1], "", 1); 152} 153static void 154notify_prepare(fd_set *readset) 155{ 156 if (notify_pipe[0] != -1) 157 FD_SET(notify_pipe[0], readset); 158} 159static void 160notify_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*/ 170static void 171sigchld_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*/ 183static void 184sigterm_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 */ 193static void 194make_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 */ 222static void 223make_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 247static void 248client_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 */ 278static void 279wait_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 */ 393static void 394process_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 */ 470static void 471process_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 */ 519static void 520drain_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 544static void 545process_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 */ 557void 558server_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", (int)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 802static void 803collect_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 824void 825server_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", (int)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 894static void 895server_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 906static void 907server_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 923static void 924server_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 936static void 937server_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 950static Channel * 951server_request_direct_tcpip(void) 952{ 953 Channel *c = NULL; 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 fine grained permissions */ 967 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 968 !no_port_forwarding_flag) { 969 c = channel_connect_to(target, target_port, 970 "direct-tcpip", "direct-tcpip"); 971 } else { 972 logit("refused local port forward: " 973 "originator %s port %d, target %s port %d", 974 originator, originator_port, target, target_port); 975 } 976 977 xfree(originator); 978 xfree(target); 979 980 return c; 981} 982 983static Channel * 984server_request_tun(void) 985{ 986 Channel *c = NULL; 987 int mode, tun; 988 int sock; 989 990 mode = packet_get_int(); 991 switch (mode) { 992 case SSH_TUNMODE_POINTOPOINT: 993 case SSH_TUNMODE_ETHERNET: 994 break; 995 default: 996 packet_send_debug("Unsupported tunnel device mode."); 997 return NULL; 998 } 999 if ((options.permit_tun & mode) == 0) { 1000 packet_send_debug("Server has rejected tunnel device " 1001 "forwarding"); 1002 return NULL; 1003 } 1004 1005 tun = packet_get_int(); 1006 if (forced_tun_device != -1) { 1007 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 1008 goto done; 1009 tun = forced_tun_device; 1010 } 1011 sock = tun_open(tun, mode); 1012 if (sock < 0) 1013 goto done; 1014 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1015 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 1016 c->datagram = 1; 1017#if defined(SSH_TUN_FILTER) 1018 if (mode == SSH_TUNMODE_POINTOPOINT) 1019 channel_register_filter(c->self, sys_tun_infilter, 1020 sys_tun_outfilter, NULL, NULL); 1021#endif 1022 1023 done: 1024 if (c == NULL) 1025 packet_send_debug("Failed to open the tunnel device."); 1026 return c; 1027} 1028 1029static Channel * 1030server_request_session(void) 1031{ 1032 Channel *c; 1033 1034 debug("input_session_request"); 1035 packet_check_eom(); 1036 1037 if (no_more_sessions) { 1038 packet_disconnect("Possible attack: attempt to open a session " 1039 "after additional sessions disabled"); 1040 } 1041 1042 /* 1043 * A server session has no fd to read or write until a 1044 * CHANNEL_REQUEST for a shell is made, so we set the type to 1045 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1046 * CHANNEL_REQUEST messages is registered. 1047 */ 1048 c = channel_new("session", SSH_CHANNEL_LARVAL, 1049 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1050 0, "server-session", 1); 1051 if (session_open(the_authctxt, c->self) != 1) { 1052 debug("session open failed, free channel %d", c->self); 1053 channel_free(c); 1054 return NULL; 1055 } 1056 channel_register_cleanup(c->self, session_close_by_channel, 0); 1057 return c; 1058} 1059 1060static void 1061server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1062{ 1063 Channel *c = NULL; 1064 char *ctype; 1065 int rchan; 1066 u_int rmaxpack, rwindow, len; 1067 1068 ctype = packet_get_string(&len); 1069 rchan = packet_get_int(); 1070 rwindow = packet_get_int(); 1071 rmaxpack = packet_get_int(); 1072 1073 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1074 ctype, rchan, rwindow, rmaxpack); 1075 1076 if (strcmp(ctype, "session") == 0) { 1077 c = server_request_session(); 1078 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1079 c = server_request_direct_tcpip(); 1080 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1081 c = server_request_tun(); 1082 } 1083 if (c != NULL) { 1084 debug("server_input_channel_open: confirm %s", ctype); 1085 c->remote_id = rchan; 1086 c->remote_window = rwindow; 1087 c->remote_maxpacket = rmaxpack; 1088 if (c->type != SSH_CHANNEL_CONNECTING) { 1089 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1090 packet_put_int(c->remote_id); 1091 packet_put_int(c->self); 1092 packet_put_int(c->local_window); 1093 packet_put_int(c->local_maxpacket); 1094 packet_send(); 1095 } 1096 } else { 1097 debug("server_input_channel_open: failure %s", ctype); 1098 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1099 packet_put_int(rchan); 1100 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1101 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1102 packet_put_cstring("open failed"); 1103 packet_put_cstring(""); 1104 } 1105 packet_send(); 1106 } 1107 xfree(ctype); 1108} 1109 1110static void 1111server_input_global_request(int type, u_int32_t seq, void *ctxt) 1112{ 1113 char *rtype; 1114 int want_reply; 1115 int success = 0, allocated_listen_port = 0; 1116 1117 rtype = packet_get_string(NULL); 1118 want_reply = packet_get_char(); 1119 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1120 1121 /* -R style forwarding */ 1122 if (strcmp(rtype, "tcpip-forward") == 0) { 1123 struct passwd *pw; 1124 char *listen_address; 1125 u_short listen_port; 1126 1127 pw = the_authctxt->pw; 1128 if (pw == NULL || !the_authctxt->valid) 1129 fatal("server_input_global_request: no/invalid user"); 1130 listen_address = packet_get_string(NULL); 1131 listen_port = (u_short)packet_get_int(); 1132 debug("server_input_global_request: tcpip-forward listen %s port %d", 1133 listen_address, listen_port); 1134 1135 /* check permissions */ 1136 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 1137 no_port_forwarding_flag || 1138 (!want_reply && listen_port == 0) 1139#ifndef NO_IPPORT_RESERVED_CONCEPT 1140 || (listen_port != 0 && listen_port < IPPORT_RESERVED && 1141 pw->pw_uid != 0) 1142#endif 1143 ) { 1144 success = 0; 1145 packet_send_debug("Server has disabled port forwarding."); 1146 } else { 1147 /* Start listening on the port */ 1148 success = channel_setup_remote_fwd_listener( 1149 listen_address, listen_port, 1150 &allocated_listen_port, options.gateway_ports); 1151 } 1152 xfree(listen_address); 1153 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1154 char *cancel_address; 1155 u_short cancel_port; 1156 1157 cancel_address = packet_get_string(NULL); 1158 cancel_port = (u_short)packet_get_int(); 1159 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1160 cancel_address, cancel_port); 1161 1162 success = channel_cancel_rport_listener(cancel_address, 1163 cancel_port); 1164 xfree(cancel_address); 1165 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1166 no_more_sessions = 1; 1167 success = 1; 1168 } 1169 if (want_reply) { 1170 packet_start(success ? 1171 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1172 if (success && allocated_listen_port > 0) 1173 packet_put_int(allocated_listen_port); 1174 packet_send(); 1175 packet_write_wait(); 1176 } 1177 xfree(rtype); 1178} 1179 1180static void 1181server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1182{ 1183 Channel *c; 1184 int id, reply, success = 0; 1185 char *rtype; 1186 1187 id = packet_get_int(); 1188 rtype = packet_get_string(NULL); 1189 reply = packet_get_char(); 1190 1191 debug("server_input_channel_req: channel %d request %s reply %d", 1192 id, rtype, reply); 1193 1194 if ((c = channel_lookup(id)) == NULL) 1195 packet_disconnect("server_input_channel_req: " 1196 "unknown channel %d", id); 1197 if (!strcmp(rtype, "eow@openssh.com")) { 1198 packet_check_eom(); 1199 chan_rcvd_eow(c); 1200 } else if ((c->type == SSH_CHANNEL_LARVAL || 1201 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1202 success = session_input_channel_req(c, rtype); 1203 if (reply) { 1204 packet_start(success ? 1205 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1206 packet_put_int(c->remote_id); 1207 packet_send(); 1208 } 1209 xfree(rtype); 1210} 1211 1212static void 1213server_init_dispatch_20(void) 1214{ 1215 debug("server_init_dispatch_20"); 1216 dispatch_init(&dispatch_protocol_error); 1217 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1218 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1219 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1220 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1221 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1222 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1223 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1224 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1225 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1226 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1227 /* client_alive */ 1228 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1229 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1230 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1231 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1232 /* rekeying */ 1233 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1234} 1235static void 1236server_init_dispatch_13(void) 1237{ 1238 debug("server_init_dispatch_13"); 1239 dispatch_init(NULL); 1240 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1241 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1242 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1243 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1244 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1245 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1246 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1247 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1248 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1249} 1250static void 1251server_init_dispatch_15(void) 1252{ 1253 server_init_dispatch_13(); 1254 debug("server_init_dispatch_15"); 1255 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1256 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1257} 1258static void 1259server_init_dispatch(void) 1260{ 1261 if (compat20) 1262 server_init_dispatch_20(); 1263 else if (compat13) 1264 server_init_dispatch_13(); 1265 else 1266 server_init_dispatch_15(); 1267} 1268