serverloop.c revision 294693
1/* $OpenBSD: serverloop.c,v 1.170 2014/02/02 03:44:31 djm Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38#include "includes.h" 39 40#include <sys/types.h> 41#include <sys/param.h> 42#include <sys/wait.h> 43#include <sys/socket.h> 44#ifdef HAVE_SYS_TIME_H 45# include <sys/time.h> 46#endif 47 48#include <netinet/in.h> 49 50#include <errno.h> 51#include <fcntl.h> 52#include <pwd.h> 53#include <signal.h> 54#include <string.h> 55#include <termios.h> 56#include <unistd.h> 57#include <stdarg.h> 58 59#include "openbsd-compat/sys-queue.h" 60#include "xmalloc.h" 61#include "packet.h" 62#include "buffer.h" 63#include "log.h" 64#include "servconf.h" 65#include "canohost.h" 66#include "sshpty.h" 67#include "channels.h" 68#include "compat.h" 69#include "ssh1.h" 70#include "ssh2.h" 71#include "key.h" 72#include "cipher.h" 73#include "kex.h" 74#include "hostfile.h" 75#include "auth.h" 76#include "session.h" 77#include "dispatch.h" 78#include "auth-options.h" 79#include "serverloop.h" 80#include "misc.h" 81#include "roaming.h" 82 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 (void)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_int64_t 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 = 308 (u_int64_t)options.client_alive_interval * 1000; 309 } 310 311 if (compat20) { 312#if 0 313 /* wrong: bad condition XXX */ 314 if (channel_not_very_much_buffered_data()) 315#endif 316 FD_SET(connection_in, *readsetp); 317 } else { 318 /* 319 * Read packets from the client unless we have too much 320 * buffered stdin or channel data. 321 */ 322 if (buffer_len(&stdin_buffer) < buffer_high && 323 channel_not_very_much_buffered_data()) 324 FD_SET(connection_in, *readsetp); 325 /* 326 * If there is not too much data already buffered going to 327 * the client, try to get some more data from the program. 328 */ 329 if (packet_not_very_much_data_to_write()) { 330 program_alive_scheduled = child_terminated; 331 if (!fdout_eof) 332 FD_SET(fdout, *readsetp); 333 if (!fderr_eof) 334 FD_SET(fderr, *readsetp); 335 } 336 /* 337 * If we have buffered data, try to write some of that data 338 * to the program. 339 */ 340 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 341 FD_SET(fdin, *writesetp); 342 } 343 notify_prepare(*readsetp); 344 345 /* 346 * If we have buffered packet data going to the client, mark that 347 * descriptor. 348 */ 349 if (packet_have_data_to_write()) 350 FD_SET(connection_out, *writesetp); 351 352 /* 353 * If child has terminated and there is enough buffer space to read 354 * from it, then read as much as is available and exit. 355 */ 356 if (child_terminated && packet_not_very_much_data_to_write()) 357 if (max_time_milliseconds == 0 || client_alive_scheduled) 358 max_time_milliseconds = 100; 359 360 if (max_time_milliseconds == 0) 361 tvp = NULL; 362 else { 363 tv.tv_sec = max_time_milliseconds / 1000; 364 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 365 tvp = &tv; 366 } 367 368 /* Wait for something to happen, or the timeout to expire. */ 369 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 370 371 if (ret == -1) { 372 memset(*readsetp, 0, *nallocp); 373 memset(*writesetp, 0, *nallocp); 374 if (errno != EINTR) 375 error("select: %.100s", strerror(errno)); 376 } else { 377 if (ret == 0 && client_alive_scheduled) 378 client_alive_check(); 379 if (!compat20 && program_alive_scheduled && fdin_is_tty) { 380 if (!fdout_eof) 381 FD_SET(fdout, *readsetp); 382 if (!fderr_eof) 383 FD_SET(fderr, *readsetp); 384 } 385 } 386 387 notify_done(*readsetp); 388} 389 390/* 391 * Processes input from the client and the program. Input data is stored 392 * in buffers and processed later. 393 */ 394static void 395process_input(fd_set *readset) 396{ 397 int len; 398 char buf[16384]; 399 400 /* Read and buffer any input data from the client. */ 401 if (FD_ISSET(connection_in, readset)) { 402 int cont = 0; 403 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 404 if (len == 0) { 405 if (cont) 406 return; 407 verbose("Connection closed by %.100s", 408 get_remote_ipaddr()); 409 connection_closed = 1; 410 if (compat20) 411 return; 412 cleanup_exit(255); 413 } else if (len < 0) { 414 if (errno != EINTR && errno != EAGAIN && 415 errno != EWOULDBLOCK) { 416 verbose("Read error from remote host " 417 "%.100s: %.100s", 418 get_remote_ipaddr(), strerror(errno)); 419 cleanup_exit(255); 420 } 421 } else { 422 /* Buffer any received data. */ 423 packet_process_incoming(buf, len); 424 } 425 } 426 if (compat20) 427 return; 428 429 /* Read and buffer any available stdout data from the program. */ 430 if (!fdout_eof && FD_ISSET(fdout, readset)) { 431 errno = 0; 432 len = read(fdout, buf, sizeof(buf)); 433 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 434 errno == EWOULDBLOCK) && !child_terminated))) { 435 /* do nothing */ 436#ifndef PTY_ZEROREAD 437 } else if (len <= 0) { 438#else 439 } else if ((!isatty(fdout) && len <= 0) || 440 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) { 441#endif 442 fdout_eof = 1; 443 } else { 444 buffer_append(&stdout_buffer, buf, len); 445 fdout_bytes += len; 446 } 447 } 448 /* Read and buffer any available stderr data from the program. */ 449 if (!fderr_eof && FD_ISSET(fderr, readset)) { 450 errno = 0; 451 len = read(fderr, buf, sizeof(buf)); 452 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 453 errno == EWOULDBLOCK) && !child_terminated))) { 454 /* do nothing */ 455#ifndef PTY_ZEROREAD 456 } else if (len <= 0) { 457#else 458 } else if ((!isatty(fderr) && len <= 0) || 459 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) { 460#endif 461 fderr_eof = 1; 462 } else { 463 buffer_append(&stderr_buffer, buf, len); 464 } 465 } 466} 467 468/* 469 * Sends data from internal buffers to client program stdin. 470 */ 471static void 472process_output(fd_set *writeset) 473{ 474 struct termios tio; 475 u_char *data; 476 u_int dlen; 477 int len; 478 479 /* Write buffered data to program stdin. */ 480 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 481 data = buffer_ptr(&stdin_buffer); 482 dlen = buffer_len(&stdin_buffer); 483 len = write(fdin, data, dlen); 484 if (len < 0 && 485 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) { 486 /* do nothing */ 487 } else if (len <= 0) { 488 if (fdin != fdout) 489 close(fdin); 490 else 491 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 492 fdin = -1; 493 } else { 494 /* Successful write. */ 495 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 496 tcgetattr(fdin, &tio) == 0 && 497 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 498 /* 499 * Simulate echo to reduce the impact of 500 * traffic analysis 501 */ 502 packet_send_ignore(len); 503 packet_send(); 504 } 505 /* Consume the data from the buffer. */ 506 buffer_consume(&stdin_buffer, len); 507 /* Update the count of bytes written to the program. */ 508 stdin_bytes += len; 509 } 510 } 511 /* Send any buffered packet data to the client. */ 512 if (FD_ISSET(connection_out, writeset)) 513 packet_write_poll(); 514} 515 516/* 517 * Wait until all buffered output has been sent to the client. 518 * This is used when the program terminates. 519 */ 520static void 521drain_output(void) 522{ 523 /* Send any buffered stdout data to the client. */ 524 if (buffer_len(&stdout_buffer) > 0) { 525 packet_start(SSH_SMSG_STDOUT_DATA); 526 packet_put_string(buffer_ptr(&stdout_buffer), 527 buffer_len(&stdout_buffer)); 528 packet_send(); 529 /* Update the count of sent bytes. */ 530 stdout_bytes += buffer_len(&stdout_buffer); 531 } 532 /* Send any buffered stderr data to the client. */ 533 if (buffer_len(&stderr_buffer) > 0) { 534 packet_start(SSH_SMSG_STDERR_DATA); 535 packet_put_string(buffer_ptr(&stderr_buffer), 536 buffer_len(&stderr_buffer)); 537 packet_send(); 538 /* Update the count of sent bytes. */ 539 stderr_bytes += buffer_len(&stderr_buffer); 540 } 541 /* Wait until all buffered data has been written to the client. */ 542 packet_write_wait(); 543} 544 545static void 546process_buffered_input_packets(void) 547{ 548 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 549} 550 551/* 552 * Performs the interactive session. This handles data transmission between 553 * the client and the program. Note that the notion of stdin, stdout, and 554 * stderr in this function is sort of reversed: this function writes to 555 * stdin (of the child program), and reads from stdout and stderr (of the 556 * child program). 557 */ 558void 559server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 560{ 561 fd_set *readset = NULL, *writeset = NULL; 562 int max_fd = 0; 563 u_int nalloc = 0; 564 int wait_status; /* Status returned by wait(). */ 565 pid_t wait_pid; /* pid returned by wait(). */ 566 int waiting_termination = 0; /* Have displayed waiting close message. */ 567 u_int64_t max_time_milliseconds; 568 u_int previous_stdout_buffer_bytes; 569 u_int stdout_buffer_bytes; 570 int type; 571 572 debug("Entering interactive session."); 573 574 /* Initialize the SIGCHLD kludge. */ 575 child_terminated = 0; 576 mysignal(SIGCHLD, sigchld_handler); 577 578 if (!use_privsep) { 579 signal(SIGTERM, sigterm_handler); 580 signal(SIGINT, sigterm_handler); 581 signal(SIGQUIT, sigterm_handler); 582 } 583 584 /* Initialize our global variables. */ 585 fdin = fdin_arg; 586 fdout = fdout_arg; 587 fderr = fderr_arg; 588 589 /* nonblocking IO */ 590 set_nonblock(fdin); 591 set_nonblock(fdout); 592 /* we don't have stderr for interactive terminal sessions, see below */ 593 if (fderr != -1) 594 set_nonblock(fderr); 595 596 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 597 fdin_is_tty = 1; 598 599 connection_in = packet_get_connection_in(); 600 connection_out = packet_get_connection_out(); 601 602 notify_setup(); 603 604 previous_stdout_buffer_bytes = 0; 605 606 /* Set approximate I/O buffer size. */ 607 if (packet_is_interactive()) 608 buffer_high = 4096; 609 else 610 buffer_high = 64 * 1024; 611 612#if 0 613 /* Initialize max_fd to the maximum of the known file descriptors. */ 614 max_fd = MAX(connection_in, connection_out); 615 max_fd = MAX(max_fd, fdin); 616 max_fd = MAX(max_fd, fdout); 617 if (fderr != -1) 618 max_fd = MAX(max_fd, fderr); 619#endif 620 621 /* Initialize Initialize buffers. */ 622 buffer_init(&stdin_buffer); 623 buffer_init(&stdout_buffer); 624 buffer_init(&stderr_buffer); 625 626 /* 627 * If we have no separate fderr (which is the case when we have a pty 628 * - there we cannot make difference between data sent to stdout and 629 * stderr), indicate that we have seen an EOF from stderr. This way 630 * we don't need to check the descriptor everywhere. 631 */ 632 if (fderr == -1) 633 fderr_eof = 1; 634 635 server_init_dispatch(); 636 637 /* Main loop of the server for the interactive session mode. */ 638 for (;;) { 639 640 /* Process buffered packets from the client. */ 641 process_buffered_input_packets(); 642 643 /* 644 * If we have received eof, and there is no more pending 645 * input data, cause a real eof by closing fdin. 646 */ 647 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 648 if (fdin != fdout) 649 close(fdin); 650 else 651 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 652 fdin = -1; 653 } 654 /* Make packets from buffered stderr data to send to the client. */ 655 make_packets_from_stderr_data(); 656 657 /* 658 * Make packets from buffered stdout data to send to the 659 * client. If there is very little to send, this arranges to 660 * not send them now, but to wait a short while to see if we 661 * are getting more data. This is necessary, as some systems 662 * wake up readers from a pty after each separate character. 663 */ 664 max_time_milliseconds = 0; 665 stdout_buffer_bytes = buffer_len(&stdout_buffer); 666 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 667 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 668 /* try again after a while */ 669 max_time_milliseconds = 10; 670 } else { 671 /* Send it now. */ 672 make_packets_from_stdout_data(); 673 } 674 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 675 676 /* Send channel data to the client. */ 677 if (packet_not_very_much_data_to_write()) 678 channel_output_poll(); 679 680 /* 681 * Bail out of the loop if the program has closed its output 682 * descriptors, and we have no more data to send to the 683 * client, and there is no pending buffered data. 684 */ 685 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 686 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 687 if (!channel_still_open()) 688 break; 689 if (!waiting_termination) { 690 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 691 char *cp; 692 waiting_termination = 1; 693 buffer_append(&stderr_buffer, s, strlen(s)); 694 695 /* Display list of open channels. */ 696 cp = channel_open_message(); 697 buffer_append(&stderr_buffer, cp, strlen(cp)); 698 free(cp); 699 } 700 } 701 max_fd = MAX(connection_in, connection_out); 702 max_fd = MAX(max_fd, fdin); 703 max_fd = MAX(max_fd, fdout); 704 max_fd = MAX(max_fd, fderr); 705 max_fd = MAX(max_fd, notify_pipe[0]); 706 707 /* Sleep in select() until we can do something. */ 708 wait_until_can_do_something(&readset, &writeset, &max_fd, 709 &nalloc, max_time_milliseconds); 710 711 if (received_sigterm) { 712 logit("Exiting on signal %d", (int)received_sigterm); 713 /* Clean up sessions, utmp, etc. */ 714 cleanup_exit(255); 715 } 716 717 /* Process any channel events. */ 718 channel_after_select(readset, writeset); 719 720 /* Process input from the client and from program stdout/stderr. */ 721 process_input(readset); 722 723 /* Process output to the client and to program stdin. */ 724 process_output(writeset); 725 } 726 free(readset); 727 free(writeset); 728 729 /* Cleanup and termination code. */ 730 731 /* Wait until all output has been sent to the client. */ 732 drain_output(); 733 734 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 735 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 736 737 /* Free and clear the buffers. */ 738 buffer_free(&stdin_buffer); 739 buffer_free(&stdout_buffer); 740 buffer_free(&stderr_buffer); 741 742 /* Close the file descriptors. */ 743 if (fdout != -1) 744 close(fdout); 745 fdout = -1; 746 fdout_eof = 1; 747 if (fderr != -1) 748 close(fderr); 749 fderr = -1; 750 fderr_eof = 1; 751 if (fdin != -1) 752 close(fdin); 753 fdin = -1; 754 755 channel_free_all(); 756 757 /* We no longer want our SIGCHLD handler to be called. */ 758 mysignal(SIGCHLD, SIG_DFL); 759 760 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 761 if (errno != EINTR) 762 packet_disconnect("wait: %.100s", strerror(errno)); 763 if (wait_pid != pid) 764 error("Strange, wait returned pid %ld, expected %ld", 765 (long)wait_pid, (long)pid); 766 767 /* Check if it exited normally. */ 768 if (WIFEXITED(wait_status)) { 769 /* Yes, normal exit. Get exit status and send it to the client. */ 770 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 771 packet_start(SSH_SMSG_EXITSTATUS); 772 packet_put_int(WEXITSTATUS(wait_status)); 773 packet_send(); 774 packet_write_wait(); 775 776 /* 777 * Wait for exit confirmation. Note that there might be 778 * other packets coming before it; however, the program has 779 * already died so we just ignore them. The client is 780 * supposed to respond with the confirmation when it receives 781 * the exit status. 782 */ 783 do { 784 type = packet_read(); 785 } 786 while (type != SSH_CMSG_EXIT_CONFIRMATION); 787 788 debug("Received exit confirmation."); 789 return; 790 } 791 /* Check if the program terminated due to a signal. */ 792 if (WIFSIGNALED(wait_status)) 793 packet_disconnect("Command terminated on signal %d.", 794 WTERMSIG(wait_status)); 795 796 /* Some weird exit cause. Just exit. */ 797 packet_disconnect("wait returned status %04x.", wait_status); 798 /* NOTREACHED */ 799} 800 801static void 802collect_children(void) 803{ 804 pid_t pid; 805 sigset_t oset, nset; 806 int status; 807 808 /* block SIGCHLD while we check for dead children */ 809 sigemptyset(&nset); 810 sigaddset(&nset, SIGCHLD); 811 sigprocmask(SIG_BLOCK, &nset, &oset); 812 if (child_terminated) { 813 debug("Received SIGCHLD."); 814 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 815 (pid < 0 && errno == EINTR)) 816 if (pid > 0) 817 session_close_by_pid(pid, status); 818 child_terminated = 0; 819 } 820 sigprocmask(SIG_SETMASK, &oset, NULL); 821} 822 823void 824server_loop2(Authctxt *authctxt) 825{ 826 fd_set *readset = NULL, *writeset = NULL; 827 int rekeying = 0, max_fd; 828 u_int nalloc = 0; 829 u_int64_t rekey_timeout_ms = 0; 830 831 debug("Entering interactive session for SSH2."); 832 833 mysignal(SIGCHLD, sigchld_handler); 834 child_terminated = 0; 835 connection_in = packet_get_connection_in(); 836 connection_out = packet_get_connection_out(); 837 838 if (!use_privsep) { 839 signal(SIGTERM, sigterm_handler); 840 signal(SIGINT, sigterm_handler); 841 signal(SIGQUIT, sigterm_handler); 842 } 843 844 notify_setup(); 845 846 max_fd = MAX(connection_in, connection_out); 847 max_fd = MAX(max_fd, notify_pipe[0]); 848 849 server_init_dispatch(); 850 851 for (;;) { 852 process_buffered_input_packets(); 853 854 rekeying = (xxx_kex != NULL && !xxx_kex->done); 855 856 if (!rekeying && packet_not_very_much_data_to_write()) 857 channel_output_poll(); 858 if (options.rekey_interval > 0 && compat20 && !rekeying) 859 rekey_timeout_ms = packet_get_rekey_timeout() * 1000; 860 else 861 rekey_timeout_ms = 0; 862 863 wait_until_can_do_something(&readset, &writeset, &max_fd, 864 &nalloc, rekey_timeout_ms); 865 866 if (received_sigterm) { 867 logit("Exiting on signal %d", (int)received_sigterm); 868 /* Clean up sessions, utmp, etc. */ 869 cleanup_exit(255); 870 } 871 872 collect_children(); 873 if (!rekeying) { 874 channel_after_select(readset, writeset); 875 if (packet_need_rekeying()) { 876 debug("need rekeying"); 877 xxx_kex->done = 0; 878 kex_send_kexinit(xxx_kex); 879 } 880 } 881 process_input(readset); 882 if (connection_closed) 883 break; 884 process_output(writeset); 885 } 886 collect_children(); 887 888 free(readset); 889 free(writeset); 890 891 /* free all channels, no more reads and writes */ 892 channel_free_all(); 893 894 /* free remaining sessions, e.g. remove wtmp entries */ 895 session_destroy_all(NULL); 896} 897 898static void 899server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 900{ 901 debug("Got %d/%u for keepalive", type, seq); 902 /* 903 * reset timeout, since we got a sane answer from the client. 904 * even if this was generated by something other than 905 * the bogus CHANNEL_REQUEST we send for keepalives. 906 */ 907 packet_set_alive_timeouts(0); 908} 909 910static void 911server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 912{ 913 char *data; 914 u_int data_len; 915 916 /* Stdin data from the client. Append it to the buffer. */ 917 /* Ignore any data if the client has closed stdin. */ 918 if (fdin == -1) 919 return; 920 data = packet_get_string(&data_len); 921 packet_check_eom(); 922 buffer_append(&stdin_buffer, data, data_len); 923 explicit_bzero(data, data_len); 924 free(data); 925} 926 927static void 928server_input_eof(int type, u_int32_t seq, void *ctxt) 929{ 930 /* 931 * Eof from the client. The stdin descriptor to the 932 * program will be closed when all buffered data has 933 * drained. 934 */ 935 debug("EOF received for stdin."); 936 packet_check_eom(); 937 stdin_eof = 1; 938} 939 940static void 941server_input_window_size(int type, u_int32_t seq, void *ctxt) 942{ 943 u_int row = packet_get_int(); 944 u_int col = packet_get_int(); 945 u_int xpixel = packet_get_int(); 946 u_int ypixel = packet_get_int(); 947 948 debug("Window change received."); 949 packet_check_eom(); 950 if (fdin != -1) 951 pty_change_window_size(fdin, row, col, xpixel, ypixel); 952} 953 954static Channel * 955server_request_direct_tcpip(void) 956{ 957 Channel *c = NULL; 958 char *target, *originator; 959 u_short target_port, originator_port; 960 961 target = packet_get_string(NULL); 962 target_port = packet_get_int(); 963 originator = packet_get_string(NULL); 964 originator_port = packet_get_int(); 965 packet_check_eom(); 966 967 debug("server_request_direct_tcpip: originator %s port %d, target %s " 968 "port %d", originator, originator_port, target, target_port); 969 970 /* XXX fine grained permissions */ 971 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 972 !no_port_forwarding_flag) { 973 c = channel_connect_to(target, target_port, 974 "direct-tcpip", "direct-tcpip"); 975 } else { 976 logit("refused local port forward: " 977 "originator %s port %d, target %s port %d", 978 originator, originator_port, target, target_port); 979 } 980 981 free(originator); 982 free(target); 983 984 return c; 985} 986 987static Channel * 988server_request_tun(void) 989{ 990 Channel *c = NULL; 991 int mode, tun; 992 int sock; 993 994 mode = packet_get_int(); 995 switch (mode) { 996 case SSH_TUNMODE_POINTOPOINT: 997 case SSH_TUNMODE_ETHERNET: 998 break; 999 default: 1000 packet_send_debug("Unsupported tunnel device mode."); 1001 return NULL; 1002 } 1003 if ((options.permit_tun & mode) == 0) { 1004 packet_send_debug("Server has rejected tunnel device " 1005 "forwarding"); 1006 return NULL; 1007 } 1008 1009 tun = packet_get_int(); 1010 if (forced_tun_device != -1) { 1011 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 1012 goto done; 1013 tun = forced_tun_device; 1014 } 1015 sock = tun_open(tun, mode); 1016 if (sock < 0) 1017 goto done; 1018 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1019 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 1020 c->datagram = 1; 1021#if defined(SSH_TUN_FILTER) 1022 if (mode == SSH_TUNMODE_POINTOPOINT) 1023 channel_register_filter(c->self, sys_tun_infilter, 1024 sys_tun_outfilter, NULL, NULL); 1025#endif 1026 1027 done: 1028 if (c == NULL) 1029 packet_send_debug("Failed to open the tunnel device."); 1030 return c; 1031} 1032 1033static Channel * 1034server_request_session(void) 1035{ 1036 Channel *c; 1037 1038 debug("input_session_request"); 1039 packet_check_eom(); 1040 1041 if (no_more_sessions) { 1042 packet_disconnect("Possible attack: attempt to open a session " 1043 "after additional sessions disabled"); 1044 } 1045 1046 /* 1047 * A server session has no fd to read or write until a 1048 * CHANNEL_REQUEST for a shell is made, so we set the type to 1049 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1050 * CHANNEL_REQUEST messages is registered. 1051 */ 1052 c = channel_new("session", SSH_CHANNEL_LARVAL, 1053 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1054 0, "server-session", 1); 1055 if (session_open(the_authctxt, c->self) != 1) { 1056 debug("session open failed, free channel %d", c->self); 1057 channel_free(c); 1058 return NULL; 1059 } 1060 channel_register_cleanup(c->self, session_close_by_channel, 0); 1061 return c; 1062} 1063 1064static void 1065server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1066{ 1067 Channel *c = NULL; 1068 char *ctype; 1069 int rchan; 1070 u_int rmaxpack, rwindow, len; 1071 1072 ctype = packet_get_string(&len); 1073 rchan = packet_get_int(); 1074 rwindow = packet_get_int(); 1075 rmaxpack = packet_get_int(); 1076 1077 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1078 ctype, rchan, rwindow, rmaxpack); 1079 1080 if (strcmp(ctype, "session") == 0) { 1081 c = server_request_session(); 1082 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1083 c = server_request_direct_tcpip(); 1084 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1085 c = server_request_tun(); 1086 } 1087 if (c != NULL) { 1088 debug("server_input_channel_open: confirm %s", ctype); 1089 c->remote_id = rchan; 1090 c->remote_window = rwindow; 1091 c->remote_maxpacket = rmaxpack; 1092 if (c->type != SSH_CHANNEL_CONNECTING) { 1093 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1094 packet_put_int(c->remote_id); 1095 packet_put_int(c->self); 1096 packet_put_int(c->local_window); 1097 packet_put_int(c->local_maxpacket); 1098 packet_send(); 1099 } 1100 } else { 1101 debug("server_input_channel_open: failure %s", ctype); 1102 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1103 packet_put_int(rchan); 1104 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1105 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1106 packet_put_cstring("open failed"); 1107 packet_put_cstring(""); 1108 } 1109 packet_send(); 1110 } 1111 free(ctype); 1112} 1113 1114static void 1115server_input_global_request(int type, u_int32_t seq, void *ctxt) 1116{ 1117 char *rtype; 1118 int want_reply; 1119 int success = 0, allocated_listen_port = 0; 1120 1121 rtype = packet_get_string(NULL); 1122 want_reply = packet_get_char(); 1123 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1124 1125 /* -R style forwarding */ 1126 if (strcmp(rtype, "tcpip-forward") == 0) { 1127 struct passwd *pw; 1128 char *listen_address; 1129 u_short listen_port; 1130 1131 pw = the_authctxt->pw; 1132 if (pw == NULL || !the_authctxt->valid) 1133 fatal("server_input_global_request: no/invalid user"); 1134 listen_address = packet_get_string(NULL); 1135 listen_port = (u_short)packet_get_int(); 1136 debug("server_input_global_request: tcpip-forward listen %s port %d", 1137 listen_address, listen_port); 1138 1139 /* check permissions */ 1140 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 1141 no_port_forwarding_flag || 1142 (!want_reply && listen_port == 0) 1143#ifndef NO_IPPORT_RESERVED_CONCEPT 1144 || (listen_port != 0 && listen_port < IPPORT_RESERVED && 1145 pw->pw_uid != 0) 1146#endif 1147 ) { 1148 success = 0; 1149 packet_send_debug("Server has disabled port forwarding."); 1150 } else { 1151 /* Start listening on the port */ 1152 success = channel_setup_remote_fwd_listener( 1153 listen_address, listen_port, 1154 &allocated_listen_port, options.gateway_ports); 1155 } 1156 free(listen_address); 1157 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1158 char *cancel_address; 1159 u_short cancel_port; 1160 1161 cancel_address = packet_get_string(NULL); 1162 cancel_port = (u_short)packet_get_int(); 1163 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1164 cancel_address, cancel_port); 1165 1166 success = channel_cancel_rport_listener(cancel_address, 1167 cancel_port); 1168 free(cancel_address); 1169 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1170 no_more_sessions = 1; 1171 success = 1; 1172 } 1173 if (want_reply) { 1174 packet_start(success ? 1175 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1176 if (success && allocated_listen_port > 0) 1177 packet_put_int(allocated_listen_port); 1178 packet_send(); 1179 packet_write_wait(); 1180 } 1181 free(rtype); 1182} 1183 1184static void 1185server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1186{ 1187 Channel *c; 1188 int id, reply, success = 0; 1189 char *rtype; 1190 1191 id = packet_get_int(); 1192 rtype = packet_get_string(NULL); 1193 reply = packet_get_char(); 1194 1195 debug("server_input_channel_req: channel %d request %s reply %d", 1196 id, rtype, reply); 1197 1198 if ((c = channel_lookup(id)) == NULL) 1199 packet_disconnect("server_input_channel_req: " 1200 "unknown channel %d", id); 1201 if (!strcmp(rtype, "eow@openssh.com")) { 1202 packet_check_eom(); 1203 chan_rcvd_eow(c); 1204 } else if ((c->type == SSH_CHANNEL_LARVAL || 1205 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1206 success = session_input_channel_req(c, rtype); 1207 if (reply) { 1208 packet_start(success ? 1209 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1210 packet_put_int(c->remote_id); 1211 packet_send(); 1212 } 1213 free(rtype); 1214} 1215 1216static void 1217server_init_dispatch_20(void) 1218{ 1219 debug("server_init_dispatch_20"); 1220 dispatch_init(&dispatch_protocol_error); 1221 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1222 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1223 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1224 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1225 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1226 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1227 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1228 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1229 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1230 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1231 /* client_alive */ 1232 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1233 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1234 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1235 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1236 /* rekeying */ 1237 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1238} 1239static void 1240server_init_dispatch_13(void) 1241{ 1242 debug("server_init_dispatch_13"); 1243 dispatch_init(NULL); 1244 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1245 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1246 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1247 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1248 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1249 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1250 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1251 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1252 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1253} 1254static void 1255server_init_dispatch_15(void) 1256{ 1257 server_init_dispatch_13(); 1258 debug("server_init_dispatch_15"); 1259 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1260 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1261} 1262static void 1263server_init_dispatch(void) 1264{ 1265 if (compat20) 1266 server_init_dispatch_20(); 1267 else if (compat13) 1268 server_init_dispatch_13(); 1269 else 1270 server_init_dispatch_15(); 1271} 1272