1 /* $OpenBSD: serverloop.c,v 1.170 2014/02/02 03:44:31 djm Exp $ */ 2 /* $FreeBSD$ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Server main loop for handling the interactive session. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 * 15 * SSH2 support by Markus Friedl. 16 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 __RCSID("$FreeBSD$"); 41 42 #include <sys/types.h> 43 #include <sys/param.h> 44 #include <sys/wait.h> 45 #include <sys/socket.h> 46 #ifdef HAVE_SYS_TIME_H 47 # include <sys/time.h> 48 #endif 49 50 #include <netinet/in.h> 51 52 #include <errno.h> 53 #include <fcntl.h> 54 #include <pwd.h> 55 #include <signal.h> 56 #include <string.h> 57 #include <termios.h> 58 #include <unistd.h> 59 #include <stdarg.h> 60 61 #include "openbsd-compat/sys-queue.h" 62 #include "xmalloc.h" 63 #include "packet.h" 64 #include "buffer.h" 65 #include "log.h" 66 #include "servconf.h" 67 #include "canohost.h" 68 #include "sshpty.h" 69 #include "channels.h" 70 #include "compat.h" 71 #include "ssh1.h" 72 #include "ssh2.h" 73 #include "key.h" 74 #include "cipher.h" 75 #include "kex.h" 76 #include "hostfile.h" 77 #include "auth.h" 78 #include "session.h" 79 #include "dispatch.h" 80 #include "auth-options.h" 81 #include "serverloop.h" 82 #include "misc.h" 83 #include "roaming.h" 84 85 extern ServerOptions options; 86 87 /* XXX */ 88 extern Kex *xxx_kex; 89 extern Authctxt *the_authctxt; 90 extern int use_privsep; 91 92 static Buffer stdin_buffer; /* Buffer for stdin data. */ 93 static Buffer stdout_buffer; /* Buffer for stdout data. */ 94 static Buffer stderr_buffer; /* Buffer for stderr data. */ 95 static int fdin; /* Descriptor for stdin (for writing) */ 96 static int fdout; /* Descriptor for stdout (for reading); 97 May be same number as fdin. */ 98 static int fderr; /* Descriptor for stderr. May be -1. */ 99 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 100 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 101 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 102 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 103 static int stdin_eof = 0; /* EOF message received from client. */ 104 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 105 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 106 static int fdin_is_tty = 0; /* fdin points to a tty. */ 107 static int connection_in; /* Connection to client (input). */ 108 static int connection_out; /* Connection to client (output). */ 109 static int connection_closed = 0; /* Connection to client closed. */ 110 static u_int buffer_high; /* "Soft" max buffer size. */ 111 static int no_more_sessions = 0; /* Disallow further sessions. */ 112 113 /* 114 * This SIGCHLD kludge is used to detect when the child exits. The server 115 * will exit after that, as soon as forwarded connections have terminated. 116 */ 117 118 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 119 120 /* Cleanup on signals (!use_privsep case only) */ 121 static volatile sig_atomic_t received_sigterm = 0; 122 123 /* prototypes */ 124 static void server_init_dispatch(void); 125 126 /* 127 * we write to this pipe if a SIGCHLD is caught in order to avoid 128 * the race between select() and child_terminated 129 */ 130 static int notify_pipe[2]; 131 static void 132 notify_setup(void) 133 { 134 if (pipe(notify_pipe) < 0) { 135 error("pipe(notify_pipe) failed %s", strerror(errno)); 136 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 137 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 138 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 139 close(notify_pipe[0]); 140 close(notify_pipe[1]); 141 } else { 142 set_nonblock(notify_pipe[0]); 143 set_nonblock(notify_pipe[1]); 144 return; 145 } 146 notify_pipe[0] = -1; /* read end */ 147 notify_pipe[1] = -1; /* write end */ 148 } 149 static void 150 notify_parent(void) 151 { 152 if (notify_pipe[1] != -1) 153 (void)write(notify_pipe[1], "", 1); 154 } 155 static void 156 notify_prepare(fd_set *readset) 157 { 158 if (notify_pipe[0] != -1) 159 FD_SET(notify_pipe[0], readset); 160 } 161 static void 162 notify_done(fd_set *readset) 163 { 164 char c; 165 166 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 167 while (read(notify_pipe[0], &c, 1) != -1) 168 debug2("notify_done: reading"); 169 } 170 171 /*ARGSUSED*/ 172 static void 173 sigchld_handler(int sig) 174 { 175 int save_errno = errno; 176 child_terminated = 1; 177 #ifndef _UNICOS 178 mysignal(SIGCHLD, sigchld_handler); 179 #endif 180 notify_parent(); 181 errno = save_errno; 182 } 183 184 /*ARGSUSED*/ 185 static void 186 sigterm_handler(int sig) 187 { 188 received_sigterm = sig; 189 } 190 191 /* 192 * Make packets from buffered stderr data, and buffer it for sending 193 * to the client. 194 */ 195 static void 196 make_packets_from_stderr_data(void) 197 { 198 u_int len; 199 200 /* Send buffered stderr data to the client. */ 201 while (buffer_len(&stderr_buffer) > 0 && 202 packet_not_very_much_data_to_write()) { 203 len = buffer_len(&stderr_buffer); 204 if (packet_is_interactive()) { 205 if (len > 512) 206 len = 512; 207 } else { 208 /* Keep the packets at reasonable size. */ 209 if (len > packet_get_maxsize()) 210 len = packet_get_maxsize(); 211 } 212 packet_start(SSH_SMSG_STDERR_DATA); 213 packet_put_string(buffer_ptr(&stderr_buffer), len); 214 packet_send(); 215 buffer_consume(&stderr_buffer, len); 216 stderr_bytes += len; 217 } 218 } 219 220 /* 221 * Make packets from buffered stdout data, and buffer it for sending to the 222 * client. 223 */ 224 static void 225 make_packets_from_stdout_data(void) 226 { 227 u_int len; 228 229 /* Send buffered stdout data to the client. */ 230 while (buffer_len(&stdout_buffer) > 0 && 231 packet_not_very_much_data_to_write()) { 232 len = buffer_len(&stdout_buffer); 233 if (packet_is_interactive()) { 234 if (len > 512) 235 len = 512; 236 } else { 237 /* Keep the packets at reasonable size. */ 238 if (len > packet_get_maxsize()) 239 len = packet_get_maxsize(); 240 } 241 packet_start(SSH_SMSG_STDOUT_DATA); 242 packet_put_string(buffer_ptr(&stdout_buffer), len); 243 packet_send(); 244 buffer_consume(&stdout_buffer, len); 245 stdout_bytes += len; 246 } 247 } 248 249 static void 250 client_alive_check(void) 251 { 252 int channel_id; 253 254 /* timeout, check to see how many we have had */ 255 if (packet_inc_alive_timeouts() > options.client_alive_count_max) { 256 logit("Timeout, client not responding."); 257 cleanup_exit(255); 258 } 259 260 /* 261 * send a bogus global/channel request with "wantreply", 262 * we should get back a failure 263 */ 264 if ((channel_id = channel_find_open()) == -1) { 265 packet_start(SSH2_MSG_GLOBAL_REQUEST); 266 packet_put_cstring("keepalive@openssh.com"); 267 packet_put_char(1); /* boolean: want reply */ 268 } else { 269 channel_request_start(channel_id, "keepalive@openssh.com", 1); 270 } 271 packet_send(); 272 } 273 274 /* 275 * Sleep in select() until we can do something. This will initialize the 276 * select masks. Upon return, the masks will indicate which descriptors 277 * have data or can accept data. Optionally, a maximum time can be specified 278 * for the duration of the wait (0 = infinite). 279 */ 280 static void 281 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 282 u_int *nallocp, u_int64_t max_time_milliseconds) 283 { 284 struct timeval tv, *tvp; 285 int ret; 286 time_t minwait_secs = 0; 287 int client_alive_scheduled = 0; 288 int program_alive_scheduled = 0; 289 290 /* Allocate and update select() masks for channel descriptors. */ 291 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 292 &minwait_secs, 0); 293 294 if (minwait_secs != 0) 295 max_time_milliseconds = MIN(max_time_milliseconds, 296 (u_int)minwait_secs * 1000); 297 298 /* 299 * if using client_alive, set the max timeout accordingly, 300 * and indicate that this particular timeout was for client 301 * alive by setting the client_alive_scheduled flag. 302 * 303 * this could be randomized somewhat to make traffic 304 * analysis more difficult, but we're not doing it yet. 305 */ 306 if (compat20 && 307 max_time_milliseconds == 0 && options.client_alive_interval) { 308 client_alive_scheduled = 1; 309 max_time_milliseconds = 310 (u_int64_t)options.client_alive_interval * 1000; 311 } 312 313 if (compat20) { 314 #if 0 315 /* wrong: bad condition XXX */ 316 if (channel_not_very_much_buffered_data()) 317 #endif 318 FD_SET(connection_in, *readsetp); 319 } else { 320 /* 321 * Read packets from the client unless we have too much 322 * buffered stdin or channel data. 323 */ 324 if (buffer_len(&stdin_buffer) < buffer_high && 325 channel_not_very_much_buffered_data()) 326 FD_SET(connection_in, *readsetp); 327 /* 328 * If there is not too much data already buffered going to 329 * the client, try to get some more data from the program. 330 */ 331 if (packet_not_very_much_data_to_write()) { 332 program_alive_scheduled = child_terminated; 333 if (!fdout_eof) 334 FD_SET(fdout, *readsetp); 335 if (!fderr_eof) 336 FD_SET(fderr, *readsetp); 337 } 338 /* 339 * If we have buffered data, try to write some of that data 340 * to the program. 341 */ 342 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 343 FD_SET(fdin, *writesetp); 344 } 345 notify_prepare(*readsetp); 346 347 /* 348 * If we have buffered packet data going to the client, mark that 349 * descriptor. 350 */ 351 if (packet_have_data_to_write()) 352 FD_SET(connection_out, *writesetp); 353 354 /* 355 * If child has terminated and there is enough buffer space to read 356 * from it, then read as much as is available and exit. 357 */ 358 if (child_terminated && packet_not_very_much_data_to_write()) 359 if (max_time_milliseconds == 0 || client_alive_scheduled) 360 max_time_milliseconds = 100; 361 362 if (max_time_milliseconds == 0) 363 tvp = NULL; 364 else { 365 tv.tv_sec = max_time_milliseconds / 1000; 366 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 367 tvp = &tv; 368 } 369 370 /* Wait for something to happen, or the timeout to expire. */ 371 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 372 373 if (ret == -1) { 374 memset(*readsetp, 0, *nallocp); 375 memset(*writesetp, 0, *nallocp); 376 if (errno != EINTR) 377 error("select: %.100s", strerror(errno)); 378 } else { 379 if (ret == 0 && client_alive_scheduled) 380 client_alive_check(); 381 if (!compat20 && program_alive_scheduled && fdin_is_tty) { 382 if (!fdout_eof) 383 FD_SET(fdout, *readsetp); 384 if (!fderr_eof) 385 FD_SET(fderr, *readsetp); 386 } 387 } 388 389 notify_done(*readsetp); 390 } 391 392 /* 393 * Processes input from the client and the program. Input data is stored 394 * in buffers and processed later. 395 */ 396 static void 397 process_input(fd_set *readset) 398 { 399 int len; 400 char buf[16384]; 401 402 /* Read and buffer any input data from the client. */ 403 if (FD_ISSET(connection_in, readset)) { 404 int cont = 0; 405 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 406 if (len == 0) { 407 if (cont) 408 return; 409 verbose("Connection closed by %.100s", 410 get_remote_ipaddr()); 411 connection_closed = 1; 412 if (compat20) 413 return; 414 cleanup_exit(255); 415 } else if (len < 0) { 416 if (errno != EINTR && errno != EAGAIN && 417 errno != EWOULDBLOCK) { 418 verbose("Read error from remote host " 419 "%.100s: %.100s", 420 get_remote_ipaddr(), strerror(errno)); 421 cleanup_exit(255); 422 } 423 } else { 424 /* Buffer any received data. */ 425 packet_process_incoming(buf, len); 426 } 427 } 428 if (compat20) 429 return; 430 431 /* Read and buffer any available stdout data from the program. */ 432 if (!fdout_eof && FD_ISSET(fdout, readset)) { 433 errno = 0; 434 len = read(fdout, buf, sizeof(buf)); 435 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 436 errno == EWOULDBLOCK) && !child_terminated))) { 437 /* do nothing */ 438 #ifndef PTY_ZEROREAD 439 } else if (len <= 0) { 440 #else 441 } else if ((!isatty(fdout) && len <= 0) || 442 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) { 443 #endif 444 fdout_eof = 1; 445 } else { 446 buffer_append(&stdout_buffer, buf, len); 447 fdout_bytes += len; 448 } 449 } 450 /* Read and buffer any available stderr data from the program. */ 451 if (!fderr_eof && FD_ISSET(fderr, readset)) { 452 errno = 0; 453 len = read(fderr, buf, sizeof(buf)); 454 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 455 errno == EWOULDBLOCK) && !child_terminated))) { 456 /* do nothing */ 457 #ifndef PTY_ZEROREAD 458 } else if (len <= 0) { 459 #else 460 } else if ((!isatty(fderr) && len <= 0) || 461 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) { 462 #endif 463 fderr_eof = 1; 464 } else { 465 buffer_append(&stderr_buffer, buf, len); 466 } 467 } 468 } 469 470 /* 471 * Sends data from internal buffers to client program stdin. 472 */ 473 static void 474 process_output(fd_set *writeset) 475 { 476 struct termios tio; 477 u_char *data; 478 u_int dlen; 479 int len; 480 481 /* Write buffered data to program stdin. */ 482 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 483 data = buffer_ptr(&stdin_buffer); 484 dlen = buffer_len(&stdin_buffer); 485 len = write(fdin, data, dlen); 486 if (len < 0 && 487 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) { 488 /* do nothing */ 489 } else if (len <= 0) { 490 if (fdin != fdout) 491 close(fdin); 492 else 493 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 494 fdin = -1; 495 } else { 496 /* Successful write. */ 497 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 498 tcgetattr(fdin, &tio) == 0 && 499 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 500 /* 501 * Simulate echo to reduce the impact of 502 * traffic analysis 503 */ 504 packet_send_ignore(len); 505 packet_send(); 506 } 507 /* Consume the data from the buffer. */ 508 buffer_consume(&stdin_buffer, len); 509 /* Update the count of bytes written to the program. */ 510 stdin_bytes += len; 511 } 512 } 513 /* Send any buffered packet data to the client. */ 514 if (FD_ISSET(connection_out, writeset)) 515 packet_write_poll(); 516 } 517 518 /* 519 * Wait until all buffered output has been sent to the client. 520 * This is used when the program terminates. 521 */ 522 static void 523 drain_output(void) 524 { 525 /* Send any buffered stdout data to the client. */ 526 if (buffer_len(&stdout_buffer) > 0) { 527 packet_start(SSH_SMSG_STDOUT_DATA); 528 packet_put_string(buffer_ptr(&stdout_buffer), 529 buffer_len(&stdout_buffer)); 530 packet_send(); 531 /* Update the count of sent bytes. */ 532 stdout_bytes += buffer_len(&stdout_buffer); 533 } 534 /* Send any buffered stderr data to the client. */ 535 if (buffer_len(&stderr_buffer) > 0) { 536 packet_start(SSH_SMSG_STDERR_DATA); 537 packet_put_string(buffer_ptr(&stderr_buffer), 538 buffer_len(&stderr_buffer)); 539 packet_send(); 540 /* Update the count of sent bytes. */ 541 stderr_bytes += buffer_len(&stderr_buffer); 542 } 543 /* Wait until all buffered data has been written to the client. */ 544 packet_write_wait(); 545 } 546 547 static void 548 process_buffered_input_packets(void) 549 { 550 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 551 } 552 553 /* 554 * Performs the interactive session. This handles data transmission between 555 * the client and the program. Note that the notion of stdin, stdout, and 556 * stderr in this function is sort of reversed: this function writes to 557 * stdin (of the child program), and reads from stdout and stderr (of the 558 * child program). 559 */ 560 void 561 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 562 { 563 fd_set *readset = NULL, *writeset = NULL; 564 int max_fd = 0; 565 u_int nalloc = 0; 566 int wait_status; /* Status returned by wait(). */ 567 pid_t wait_pid; /* pid returned by wait(). */ 568 int waiting_termination = 0; /* Have displayed waiting close message. */ 569 u_int64_t max_time_milliseconds; 570 u_int previous_stdout_buffer_bytes; 571 u_int stdout_buffer_bytes; 572 int type; 573 574 debug("Entering interactive session."); 575 576 /* Initialize the SIGCHLD kludge. */ 577 child_terminated = 0; 578 mysignal(SIGCHLD, sigchld_handler); 579 580 if (!use_privsep) { 581 signal(SIGTERM, sigterm_handler); 582 signal(SIGINT, sigterm_handler); 583 signal(SIGQUIT, sigterm_handler); 584 } 585 586 /* Initialize our global variables. */ 587 fdin = fdin_arg; 588 fdout = fdout_arg; 589 fderr = fderr_arg; 590 591 /* nonblocking IO */ 592 set_nonblock(fdin); 593 set_nonblock(fdout); 594 /* we don't have stderr for interactive terminal sessions, see below */ 595 if (fderr != -1) 596 set_nonblock(fderr); 597 598 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 599 fdin_is_tty = 1; 600 601 connection_in = packet_get_connection_in(); 602 connection_out = packet_get_connection_out(); 603 604 notify_setup(); 605 606 previous_stdout_buffer_bytes = 0; 607 608 /* Set approximate I/O buffer size. */ 609 if (packet_is_interactive()) 610 buffer_high = 4096; 611 else 612 buffer_high = 64 * 1024; 613 614 #if 0 615 /* Initialize max_fd to the maximum of the known file descriptors. */ 616 max_fd = MAX(connection_in, connection_out); 617 max_fd = MAX(max_fd, fdin); 618 max_fd = MAX(max_fd, fdout); 619 if (fderr != -1) 620 max_fd = MAX(max_fd, fderr); 621 #endif 622 623 /* Initialize Initialize buffers. */ 624 buffer_init(&stdin_buffer); 625 buffer_init(&stdout_buffer); 626 buffer_init(&stderr_buffer); 627 628 /* 629 * If we have no separate fderr (which is the case when we have a pty 630 * - there we cannot make difference between data sent to stdout and 631 * stderr), indicate that we have seen an EOF from stderr. This way 632 * we don't need to check the descriptor everywhere. 633 */ 634 if (fderr == -1) 635 fderr_eof = 1; 636 637 server_init_dispatch(); 638 639 /* Main loop of the server for the interactive session mode. */ 640 for (;;) { 641 642 /* Process buffered packets from the client. */ 643 process_buffered_input_packets(); 644 645 /* 646 * If we have received eof, and there is no more pending 647 * input data, cause a real eof by closing fdin. 648 */ 649 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 650 if (fdin != fdout) 651 close(fdin); 652 else 653 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 654 fdin = -1; 655 } 656 /* Make packets from buffered stderr data to send to the client. */ 657 make_packets_from_stderr_data(); 658 659 /* 660 * Make packets from buffered stdout data to send to the 661 * client. If there is very little to send, this arranges to 662 * not send them now, but to wait a short while to see if we 663 * are getting more data. This is necessary, as some systems 664 * wake up readers from a pty after each separate character. 665 */ 666 max_time_milliseconds = 0; 667 stdout_buffer_bytes = buffer_len(&stdout_buffer); 668 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 669 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 670 /* try again after a while */ 671 max_time_milliseconds = 10; 672 } else { 673 /* Send it now. */ 674 make_packets_from_stdout_data(); 675 } 676 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 677 678 /* Send channel data to the client. */ 679 if (packet_not_very_much_data_to_write()) 680 channel_output_poll(); 681 682 /* 683 * Bail out of the loop if the program has closed its output 684 * descriptors, and we have no more data to send to the 685 * client, and there is no pending buffered data. 686 */ 687 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 688 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 689 if (!channel_still_open()) 690 break; 691 if (!waiting_termination) { 692 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 693 char *cp; 694 waiting_termination = 1; 695 buffer_append(&stderr_buffer, s, strlen(s)); 696 697 /* Display list of open channels. */ 698 cp = channel_open_message(); 699 buffer_append(&stderr_buffer, cp, strlen(cp)); 700 free(cp); 701 } 702 } 703 max_fd = MAX(connection_in, connection_out); 704 max_fd = MAX(max_fd, fdin); 705 max_fd = MAX(max_fd, fdout); 706 max_fd = MAX(max_fd, fderr); 707 max_fd = MAX(max_fd, notify_pipe[0]); 708 709 /* Sleep in select() until we can do something. */ 710 wait_until_can_do_something(&readset, &writeset, &max_fd, 711 &nalloc, max_time_milliseconds); 712 713 if (received_sigterm) { 714 logit("Exiting on signal %d", (int)received_sigterm); 715 /* Clean up sessions, utmp, etc. */ 716 cleanup_exit(255); 717 } 718 719 /* Process any channel events. */ 720 channel_after_select(readset, writeset); 721 722 /* Process input from the client and from program stdout/stderr. */ 723 process_input(readset); 724 725 /* Process output to the client and to program stdin. */ 726 process_output(writeset); 727 } 728 free(readset); 729 free(writeset); 730 731 /* Cleanup and termination code. */ 732 733 /* Wait until all output has been sent to the client. */ 734 drain_output(); 735 736 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 737 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 738 739 /* Free and clear the buffers. */ 740 buffer_free(&stdin_buffer); 741 buffer_free(&stdout_buffer); 742 buffer_free(&stderr_buffer); 743 744 /* Close the file descriptors. */ 745 if (fdout != -1) 746 close(fdout); 747 fdout = -1; 748 fdout_eof = 1; 749 if (fderr != -1) 750 close(fderr); 751 fderr = -1; 752 fderr_eof = 1; 753 if (fdin != -1) 754 close(fdin); 755 fdin = -1; 756 757 channel_free_all(); 758 759 /* We no longer want our SIGCHLD handler to be called. */ 760 mysignal(SIGCHLD, SIG_DFL); 761 762 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 763 if (errno != EINTR) 764 packet_disconnect("wait: %.100s", strerror(errno)); 765 if (wait_pid != pid) 766 error("Strange, wait returned pid %ld, expected %ld", 767 (long)wait_pid, (long)pid); 768 769 /* Check if it exited normally. */ 770 if (WIFEXITED(wait_status)) { 771 /* Yes, normal exit. Get exit status and send it to the client. */ 772 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 773 packet_start(SSH_SMSG_EXITSTATUS); 774 packet_put_int(WEXITSTATUS(wait_status)); 775 packet_send(); 776 packet_write_wait(); 777 778 /* 779 * Wait for exit confirmation. Note that there might be 780 * other packets coming before it; however, the program has 781 * already died so we just ignore them. The client is 782 * supposed to respond with the confirmation when it receives 783 * the exit status. 784 */ 785 do { 786 type = packet_read(); 787 } 788 while (type != SSH_CMSG_EXIT_CONFIRMATION); 789 790 debug("Received exit confirmation."); 791 return; 792 } 793 /* Check if the program terminated due to a signal. */ 794 if (WIFSIGNALED(wait_status)) 795 packet_disconnect("Command terminated on signal %d.", 796 WTERMSIG(wait_status)); 797 798 /* Some weird exit cause. Just exit. */ 799 packet_disconnect("wait returned status %04x.", wait_status); 800 /* NOTREACHED */ 801 } 802 803 static void 804 collect_children(void) 805 { 806 pid_t pid; 807 sigset_t oset, nset; 808 int status; 809 810 /* block SIGCHLD while we check for dead children */ 811 sigemptyset(&nset); 812 sigaddset(&nset, SIGCHLD); 813 sigprocmask(SIG_BLOCK, &nset, &oset); 814 if (child_terminated) { 815 debug("Received SIGCHLD."); 816 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 817 (pid < 0 && errno == EINTR)) 818 if (pid > 0) 819 session_close_by_pid(pid, status); 820 child_terminated = 0; 821 } 822 sigprocmask(SIG_SETMASK, &oset, NULL); 823 } 824 825 void 826 server_loop2(Authctxt *authctxt) 827 { 828 fd_set *readset = NULL, *writeset = NULL; 829 int rekeying = 0, max_fd; 830 u_int nalloc = 0; 831 u_int64_t rekey_timeout_ms = 0; 832 833 debug("Entering interactive session for SSH2."); 834 835 mysignal(SIGCHLD, sigchld_handler); 836 child_terminated = 0; 837 connection_in = packet_get_connection_in(); 838 connection_out = packet_get_connection_out(); 839 840 if (!use_privsep) { 841 signal(SIGTERM, sigterm_handler); 842 signal(SIGINT, sigterm_handler); 843 signal(SIGQUIT, sigterm_handler); 844 } 845 846 notify_setup(); 847 848 max_fd = MAX(connection_in, connection_out); 849 max_fd = MAX(max_fd, notify_pipe[0]); 850 851 server_init_dispatch(); 852 853 for (;;) { 854 process_buffered_input_packets(); 855 856 rekeying = (xxx_kex != NULL && !xxx_kex->done); 857 858 if (!rekeying && packet_not_very_much_data_to_write()) 859 channel_output_poll(); 860 if (options.rekey_interval > 0 && compat20 && !rekeying) 861 rekey_timeout_ms = packet_get_rekey_timeout() * 1000; 862 else 863 rekey_timeout_ms = 0; 864 865 wait_until_can_do_something(&readset, &writeset, &max_fd, 866 &nalloc, rekey_timeout_ms); 867 868 if (received_sigterm) { 869 logit("Exiting on signal %d", (int)received_sigterm); 870 /* Clean up sessions, utmp, etc. */ 871 cleanup_exit(255); 872 } 873 874 collect_children(); 875 if (!rekeying) { 876 channel_after_select(readset, writeset); 877 if (packet_need_rekeying()) { 878 debug("need rekeying"); 879 xxx_kex->done = 0; 880 kex_send_kexinit(xxx_kex); 881 } 882 } 883 process_input(readset); 884 if (connection_closed) 885 break; 886 process_output(writeset); 887 } 888 collect_children(); 889 890 free(readset); 891 free(writeset); 892 893 /* free all channels, no more reads and writes */ 894 channel_free_all(); 895 896 /* free remaining sessions, e.g. remove wtmp entries */ 897 session_destroy_all(NULL); 898 } 899 900 static void 901 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 902 { 903 debug("Got %d/%u for keepalive", type, seq); 904 /* 905 * reset timeout, since we got a sane answer from the client. 906 * even if this was generated by something other than 907 * the bogus CHANNEL_REQUEST we send for keepalives. 908 */ 909 packet_set_alive_timeouts(0); 910 } 911 912 static void 913 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 914 { 915 char *data; 916 u_int data_len; 917 918 /* Stdin data from the client. Append it to the buffer. */ 919 /* Ignore any data if the client has closed stdin. */ 920 if (fdin == -1) 921 return; 922 data = packet_get_string(&data_len); 923 packet_check_eom(); 924 buffer_append(&stdin_buffer, data, data_len); 925 explicit_bzero(data, data_len); 926 free(data); 927 } 928 929 static void 930 server_input_eof(int type, u_int32_t seq, void *ctxt) 931 { 932 /* 933 * Eof from the client. The stdin descriptor to the 934 * program will be closed when all buffered data has 935 * drained. 936 */ 937 debug("EOF received for stdin."); 938 packet_check_eom(); 939 stdin_eof = 1; 940 } 941 942 static void 943 server_input_window_size(int type, u_int32_t seq, void *ctxt) 944 { 945 u_int row = packet_get_int(); 946 u_int col = packet_get_int(); 947 u_int xpixel = packet_get_int(); 948 u_int ypixel = packet_get_int(); 949 950 debug("Window change received."); 951 packet_check_eom(); 952 if (fdin != -1) 953 pty_change_window_size(fdin, row, col, xpixel, ypixel); 954 } 955 956 static Channel * 957 server_request_direct_tcpip(void) 958 { 959 Channel *c = NULL; 960 char *target, *originator; 961 u_short target_port, originator_port; 962 963 target = packet_get_string(NULL); 964 target_port = packet_get_int(); 965 originator = packet_get_string(NULL); 966 originator_port = packet_get_int(); 967 packet_check_eom(); 968 969 debug("server_request_direct_tcpip: originator %s port %d, target %s " 970 "port %d", originator, originator_port, target, target_port); 971 972 /* XXX fine grained permissions */ 973 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 974 !no_port_forwarding_flag) { 975 c = channel_connect_to(target, target_port, 976 "direct-tcpip", "direct-tcpip"); 977 } else { 978 logit("refused local port forward: " 979 "originator %s port %d, target %s port %d", 980 originator, originator_port, target, target_port); 981 } 982 983 free(originator); 984 free(target); 985 986 return c; 987 } 988 989 static Channel * 990 server_request_tun(void) 991 { 992 Channel *c = NULL; 993 int mode, tun; 994 int sock; 995 996 mode = packet_get_int(); 997 switch (mode) { 998 case SSH_TUNMODE_POINTOPOINT: 999 case SSH_TUNMODE_ETHERNET: 1000 break; 1001 default: 1002 packet_send_debug("Unsupported tunnel device mode."); 1003 return NULL; 1004 } 1005 if ((options.permit_tun & mode) == 0) { 1006 packet_send_debug("Server has rejected tunnel device " 1007 "forwarding"); 1008 return NULL; 1009 } 1010 1011 tun = packet_get_int(); 1012 if (forced_tun_device != -1) { 1013 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 1014 goto done; 1015 tun = forced_tun_device; 1016 } 1017 sock = tun_open(tun, mode); 1018 if (sock < 0) 1019 goto done; 1020 if (options.hpn_disabled) 1021 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1022 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, 1023 "tun", 1); 1024 else 1025 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1026 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, 1027 "tun", 1); 1028 c->datagram = 1; 1029 #if defined(SSH_TUN_FILTER) 1030 if (mode == SSH_TUNMODE_POINTOPOINT) 1031 channel_register_filter(c->self, sys_tun_infilter, 1032 sys_tun_outfilter, NULL, NULL); 1033 #endif 1034 1035 done: 1036 if (c == NULL) 1037 packet_send_debug("Failed to open the tunnel device."); 1038 return c; 1039 } 1040 1041 static Channel * 1042 server_request_session(void) 1043 { 1044 Channel *c; 1045 1046 debug("input_session_request"); 1047 packet_check_eom(); 1048 1049 if (no_more_sessions) { 1050 packet_disconnect("Possible attack: attempt to open a session " 1051 "after additional sessions disabled"); 1052 } 1053 1054 /* 1055 * A server session has no fd to read or write until a 1056 * CHANNEL_REQUEST for a shell is made, so we set the type to 1057 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1058 * CHANNEL_REQUEST messages is registered. 1059 */ 1060 c = channel_new("session", SSH_CHANNEL_LARVAL, 1061 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1062 0, "server-session", 1); 1063 if (!options.hpn_disabled && options.tcp_rcv_buf_poll) 1064 c->dynamic_window = 1; 1065 if (session_open(the_authctxt, c->self) != 1) { 1066 debug("session open failed, free channel %d", c->self); 1067 channel_free(c); 1068 return NULL; 1069 } 1070 channel_register_cleanup(c->self, session_close_by_channel, 0); 1071 return c; 1072 } 1073 1074 static void 1075 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1076 { 1077 Channel *c = NULL; 1078 char *ctype; 1079 int rchan; 1080 u_int rmaxpack, rwindow, len; 1081 1082 ctype = packet_get_string(&len); 1083 rchan = packet_get_int(); 1084 rwindow = packet_get_int(); 1085 rmaxpack = packet_get_int(); 1086 1087 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1088 ctype, rchan, rwindow, rmaxpack); 1089 1090 if (strcmp(ctype, "session") == 0) { 1091 c = server_request_session(); 1092 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1093 c = server_request_direct_tcpip(); 1094 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1095 c = server_request_tun(); 1096 } 1097 if (c != NULL) { 1098 debug("server_input_channel_open: confirm %s", ctype); 1099 c->remote_id = rchan; 1100 c->remote_window = rwindow; 1101 c->remote_maxpacket = rmaxpack; 1102 if (c->type != SSH_CHANNEL_CONNECTING) { 1103 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1104 packet_put_int(c->remote_id); 1105 packet_put_int(c->self); 1106 packet_put_int(c->local_window); 1107 packet_put_int(c->local_maxpacket); 1108 packet_send(); 1109 } 1110 } else { 1111 debug("server_input_channel_open: failure %s", ctype); 1112 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1113 packet_put_int(rchan); 1114 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1115 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1116 packet_put_cstring("open failed"); 1117 packet_put_cstring(""); 1118 } 1119 packet_send(); 1120 } 1121 free(ctype); 1122 } 1123 1124 static void 1125 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1126 { 1127 char *rtype; 1128 int want_reply; 1129 int success = 0, allocated_listen_port = 0; 1130 1131 rtype = packet_get_string(NULL); 1132 want_reply = packet_get_char(); 1133 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1134 1135 /* -R style forwarding */ 1136 if (strcmp(rtype, "tcpip-forward") == 0) { 1137 struct passwd *pw; 1138 char *listen_address; 1139 u_short listen_port; 1140 1141 pw = the_authctxt->pw; 1142 if (pw == NULL || !the_authctxt->valid) 1143 fatal("server_input_global_request: no/invalid user"); 1144 listen_address = packet_get_string(NULL); 1145 listen_port = (u_short)packet_get_int(); 1146 debug("server_input_global_request: tcpip-forward listen %s port %d", 1147 listen_address, listen_port); 1148 1149 /* check permissions */ 1150 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 1151 no_port_forwarding_flag || 1152 (!want_reply && listen_port == 0) 1153 #ifndef NO_IPPORT_RESERVED_CONCEPT 1154 || (listen_port != 0 && listen_port < IPPORT_RESERVED && 1155 pw->pw_uid != 0) 1156 #endif 1157 ) { 1158 success = 0; 1159 packet_send_debug("Server has disabled port forwarding."); 1160 } else { 1161 /* Start listening on the port */ 1162 success = channel_setup_remote_fwd_listener( 1163 listen_address, listen_port, 1164 &allocated_listen_port, options.gateway_ports); 1165 } 1166 free(listen_address); 1167 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1168 char *cancel_address; 1169 u_short cancel_port; 1170 1171 cancel_address = packet_get_string(NULL); 1172 cancel_port = (u_short)packet_get_int(); 1173 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1174 cancel_address, cancel_port); 1175 1176 success = channel_cancel_rport_listener(cancel_address, 1177 cancel_port); 1178 free(cancel_address); 1179 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1180 no_more_sessions = 1; 1181 success = 1; 1182 } 1183 if (want_reply) { 1184 packet_start(success ? 1185 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1186 if (success && allocated_listen_port > 0) 1187 packet_put_int(allocated_listen_port); 1188 packet_send(); 1189 packet_write_wait(); 1190 } 1191 free(rtype); 1192 } 1193 1194 static void 1195 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1196 { 1197 Channel *c; 1198 int id, reply, success = 0; 1199 char *rtype; 1200 1201 id = packet_get_int(); 1202 rtype = packet_get_string(NULL); 1203 reply = packet_get_char(); 1204 1205 debug("server_input_channel_req: channel %d request %s reply %d", 1206 id, rtype, reply); 1207 1208 if ((c = channel_lookup(id)) == NULL) 1209 packet_disconnect("server_input_channel_req: " 1210 "unknown channel %d", id); 1211 if (!strcmp(rtype, "eow@openssh.com")) { 1212 packet_check_eom(); 1213 chan_rcvd_eow(c); 1214 } else if ((c->type == SSH_CHANNEL_LARVAL || 1215 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1216 success = session_input_channel_req(c, rtype); 1217 if (reply) { 1218 packet_start(success ? 1219 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1220 packet_put_int(c->remote_id); 1221 packet_send(); 1222 } 1223 free(rtype); 1224 } 1225 1226 static void 1227 server_init_dispatch_20(void) 1228 { 1229 debug("server_init_dispatch_20"); 1230 dispatch_init(&dispatch_protocol_error); 1231 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1232 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1233 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1234 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1235 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1236 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1237 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1238 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1239 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1240 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1241 /* client_alive */ 1242 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1243 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1244 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1245 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1246 /* rekeying */ 1247 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1248 } 1249 static void 1250 server_init_dispatch_13(void) 1251 { 1252 debug("server_init_dispatch_13"); 1253 dispatch_init(NULL); 1254 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1255 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1256 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1257 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1258 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1259 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1260 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1261 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1262 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1263 } 1264 static void 1265 server_init_dispatch_15(void) 1266 { 1267 server_init_dispatch_13(); 1268 debug("server_init_dispatch_15"); 1269 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1270 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1271 } 1272 static void 1273 server_init_dispatch(void) 1274 { 1275 if (compat20) 1276 server_init_dispatch_20(); 1277 else if (compat13) 1278 server_init_dispatch_13(); 1279 else 1280 server_init_dispatch_15(); 1281 } 1282