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