1 /* $OpenBSD: serverloop.c,v 1.159 2009/05/28 16:50:16 andreas 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 <sys/types.h> 39 #include <sys/wait.h> 40 #include <sys/socket.h> 41 #include <sys/time.h> 42 #include <sys/param.h> 43 #include <sys/queue.h> 44 45 #include <netinet/in.h> 46 47 #include <errno.h> 48 #include <fcntl.h> 49 #include <pwd.h> 50 #include <signal.h> 51 #include <string.h> 52 #include <termios.h> 53 #include <unistd.h> 54 #include <stdarg.h> 55 56 #include "xmalloc.h" 57 #include "packet.h" 58 #include "buffer.h" 59 #include "log.h" 60 #include "servconf.h" 61 #include "canohost.h" 62 #include "sshpty.h" 63 #include "channels.h" 64 #include "compat.h" 65 #include "ssh1.h" 66 #include "ssh2.h" 67 #include "key.h" 68 #include "cipher.h" 69 #include "kex.h" 70 #include "hostfile.h" 71 #include "auth.h" 72 #include "session.h" 73 #include "dispatch.h" 74 #include "auth-options.h" 75 #include "serverloop.h" 76 #include "misc.h" 77 #include "roaming.h" 78 79 extern ServerOptions options; 80 81 /* XXX */ 82 extern Kex *xxx_kex; 83 extern Authctxt *the_authctxt; 84 extern int use_privsep; 85 86 static Buffer stdin_buffer; /* Buffer for stdin data. */ 87 static Buffer stdout_buffer; /* Buffer for stdout data. */ 88 static Buffer stderr_buffer; /* Buffer for stderr data. */ 89 static int fdin; /* Descriptor for stdin (for writing) */ 90 static int fdout; /* Descriptor for stdout (for reading); 91 May be same number as fdin. */ 92 static int fderr; /* Descriptor for stderr. May be -1. */ 93 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 94 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 95 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 96 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 97 static int stdin_eof = 0; /* EOF message received from client. */ 98 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 99 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 100 static int fdin_is_tty = 0; /* fdin points to a tty. */ 101 static int connection_in; /* Connection to client (input). */ 102 static int connection_out; /* Connection to client (output). */ 103 static int connection_closed = 0; /* Connection to client closed. */ 104 static u_int buffer_high; /* "Soft" max buffer size. */ 105 static int no_more_sessions = 0; /* Disallow further sessions. */ 106 107 /* 108 * This SIGCHLD kludge is used to detect when the child exits. The server 109 * will exit after that, as soon as forwarded connections have terminated. 110 */ 111 112 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 113 114 /* Cleanup on signals (!use_privsep case only) */ 115 static volatile sig_atomic_t received_sigterm = 0; 116 117 /* prototypes */ 118 static void server_init_dispatch(void); 119 120 /* 121 * we write to this pipe if a SIGCHLD is caught in order to avoid 122 * the race between select() and child_terminated 123 */ 124 static int notify_pipe[2]; 125 static void 126 notify_setup(void) 127 { 128 if (pipe(notify_pipe) < 0) { 129 error("pipe(notify_pipe) failed %s", strerror(errno)); 130 } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) || 131 (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) { 132 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 133 close(notify_pipe[0]); 134 close(notify_pipe[1]); 135 } else { 136 set_nonblock(notify_pipe[0]); 137 set_nonblock(notify_pipe[1]); 138 return; 139 } 140 notify_pipe[0] = -1; /* read end */ 141 notify_pipe[1] = -1; /* write end */ 142 } 143 static void 144 notify_parent(void) 145 { 146 if (notify_pipe[1] != -1) 147 write(notify_pipe[1], "", 1); 148 } 149 static void 150 notify_prepare(fd_set *readset) 151 { 152 if (notify_pipe[0] != -1) 153 FD_SET(notify_pipe[0], readset); 154 } 155 static void 156 notify_done(fd_set *readset) 157 { 158 char c; 159 160 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 161 while (read(notify_pipe[0], &c, 1) != -1) 162 debug2("notify_done: reading"); 163 } 164 165 /*ARGSUSED*/ 166 static void 167 sigchld_handler(int sig) 168 { 169 int save_errno = errno; 170 child_terminated = 1; 171 signal(SIGCHLD, sigchld_handler); 172 notify_parent(); 173 errno = save_errno; 174 } 175 176 /*ARGSUSED*/ 177 static void 178 sigterm_handler(int sig) 179 { 180 received_sigterm = sig; 181 } 182 183 /* 184 * Make packets from buffered stderr data, and buffer it for sending 185 * to the client. 186 */ 187 static void 188 make_packets_from_stderr_data(void) 189 { 190 u_int len; 191 192 /* Send buffered stderr data to the client. */ 193 while (buffer_len(&stderr_buffer) > 0 && 194 packet_not_very_much_data_to_write()) { 195 len = buffer_len(&stderr_buffer); 196 if (packet_is_interactive()) { 197 if (len > 512) 198 len = 512; 199 } else { 200 /* Keep the packets at reasonable size. */ 201 if (len > packet_get_maxsize()) 202 len = packet_get_maxsize(); 203 } 204 packet_start(SSH_SMSG_STDERR_DATA); 205 packet_put_string(buffer_ptr(&stderr_buffer), len); 206 packet_send(); 207 buffer_consume(&stderr_buffer, len); 208 stderr_bytes += len; 209 } 210 } 211 212 /* 213 * Make packets from buffered stdout data, and buffer it for sending to the 214 * client. 215 */ 216 static void 217 make_packets_from_stdout_data(void) 218 { 219 u_int len; 220 221 /* Send buffered stdout data to the client. */ 222 while (buffer_len(&stdout_buffer) > 0 && 223 packet_not_very_much_data_to_write()) { 224 len = buffer_len(&stdout_buffer); 225 if (packet_is_interactive()) { 226 if (len > 512) 227 len = 512; 228 } else { 229 /* Keep the packets at reasonable size. */ 230 if (len > packet_get_maxsize()) 231 len = packet_get_maxsize(); 232 } 233 packet_start(SSH_SMSG_STDOUT_DATA); 234 packet_put_string(buffer_ptr(&stdout_buffer), len); 235 packet_send(); 236 buffer_consume(&stdout_buffer, len); 237 stdout_bytes += len; 238 } 239 } 240 241 static void 242 client_alive_check(void) 243 { 244 int channel_id; 245 246 /* timeout, check to see how many we have had */ 247 if (packet_inc_alive_timeouts() > options.client_alive_count_max) { 248 logit("Timeout, client not responding."); 249 cleanup_exit(255); 250 } 251 252 /* 253 * send a bogus global/channel request with "wantreply", 254 * we should get back a failure 255 */ 256 if ((channel_id = channel_find_open()) == -1) { 257 packet_start(SSH2_MSG_GLOBAL_REQUEST); 258 packet_put_cstring("keepalive@openssh.com"); 259 packet_put_char(1); /* boolean: want reply */ 260 } else { 261 channel_request_start(channel_id, "keepalive@openssh.com", 1); 262 } 263 packet_send(); 264 } 265 266 /* 267 * Sleep in select() until we can do something. This will initialize the 268 * select masks. Upon return, the masks will indicate which descriptors 269 * have data or can accept data. Optionally, a maximum time can be specified 270 * for the duration of the wait (0 = infinite). 271 */ 272 static void 273 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 274 u_int *nallocp, u_int max_time_milliseconds) 275 { 276 struct timeval tv, *tvp; 277 int ret; 278 int client_alive_scheduled = 0; 279 280 /* 281 * if using client_alive, set the max timeout accordingly, 282 * and indicate that this particular timeout was for client 283 * alive by setting the client_alive_scheduled flag. 284 * 285 * this could be randomized somewhat to make traffic 286 * analysis more difficult, but we're not doing it yet. 287 */ 288 if (compat20 && 289 max_time_milliseconds == 0 && options.client_alive_interval) { 290 client_alive_scheduled = 1; 291 max_time_milliseconds = options.client_alive_interval * 1000; 292 } 293 294 /* Allocate and update select() masks for channel descriptors. */ 295 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0); 296 297 if (compat20) { 298 #if 0 299 /* wrong: bad condition XXX */ 300 if (channel_not_very_much_buffered_data()) 301 #endif 302 FD_SET(connection_in, *readsetp); 303 } else { 304 /* 305 * Read packets from the client unless we have too much 306 * buffered stdin or channel data. 307 */ 308 if (buffer_len(&stdin_buffer) < buffer_high && 309 channel_not_very_much_buffered_data()) 310 FD_SET(connection_in, *readsetp); 311 /* 312 * If there is not too much data already buffered going to 313 * the client, try to get some more data from the program. 314 */ 315 if (packet_not_very_much_data_to_write()) { 316 if (!fdout_eof) 317 FD_SET(fdout, *readsetp); 318 if (!fderr_eof) 319 FD_SET(fderr, *readsetp); 320 } 321 /* 322 * If we have buffered data, try to write some of that data 323 * to the program. 324 */ 325 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 326 FD_SET(fdin, *writesetp); 327 } 328 notify_prepare(*readsetp); 329 330 /* 331 * If we have buffered packet data going to the client, mark that 332 * descriptor. 333 */ 334 if (packet_have_data_to_write()) 335 FD_SET(connection_out, *writesetp); 336 337 /* 338 * If child has terminated and there is enough buffer space to read 339 * from it, then read as much as is available and exit. 340 */ 341 if (child_terminated && packet_not_very_much_data_to_write()) 342 if (max_time_milliseconds == 0 || client_alive_scheduled) 343 max_time_milliseconds = 100; 344 345 if (max_time_milliseconds == 0) 346 tvp = NULL; 347 else { 348 tv.tv_sec = max_time_milliseconds / 1000; 349 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 350 tvp = &tv; 351 } 352 353 /* Wait for something to happen, or the timeout to expire. */ 354 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 355 356 if (ret == -1) { 357 memset(*readsetp, 0, *nallocp); 358 memset(*writesetp, 0, *nallocp); 359 if (errno != EINTR) 360 error("select: %.100s", strerror(errno)); 361 } else if (ret == 0 && client_alive_scheduled) 362 client_alive_check(); 363 364 notify_done(*readsetp); 365 } 366 367 /* 368 * Processes input from the client and the program. Input data is stored 369 * in buffers and processed later. 370 */ 371 static void 372 process_input(fd_set *readset) 373 { 374 int len; 375 char buf[16384]; 376 377 /* Read and buffer any input data from the client. */ 378 if (FD_ISSET(connection_in, readset)) { 379 int cont = 0; 380 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 381 if (len == 0) { 382 if (cont) 383 return; 384 verbose("Connection closed by %.100s", 385 get_remote_ipaddr()); 386 connection_closed = 1; 387 if (compat20) 388 return; 389 cleanup_exit(255); 390 } else if (len < 0) { 391 if (errno != EINTR && errno != EAGAIN) { 392 verbose("Read error from remote host " 393 "%.100s: %.100s", 394 get_remote_ipaddr(), strerror(errno)); 395 cleanup_exit(255); 396 } 397 } else { 398 /* Buffer any received data. */ 399 packet_process_incoming(buf, len); 400 } 401 } 402 if (compat20) 403 return; 404 405 /* Read and buffer any available stdout data from the program. */ 406 if (!fdout_eof && FD_ISSET(fdout, readset)) { 407 len = read(fdout, buf, sizeof(buf)); 408 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 409 /* do nothing */ 410 } else if (len <= 0) { 411 fdout_eof = 1; 412 } else { 413 buffer_append(&stdout_buffer, buf, len); 414 fdout_bytes += len; 415 } 416 } 417 /* Read and buffer any available stderr data from the program. */ 418 if (!fderr_eof && FD_ISSET(fderr, readset)) { 419 len = read(fderr, buf, sizeof(buf)); 420 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 421 /* do nothing */ 422 } else if (len <= 0) { 423 fderr_eof = 1; 424 } else { 425 buffer_append(&stderr_buffer, buf, len); 426 } 427 } 428 } 429 430 /* 431 * Sends data from internal buffers to client program stdin. 432 */ 433 static void 434 process_output(fd_set *writeset) 435 { 436 struct termios tio; 437 u_char *data; 438 u_int dlen; 439 int len; 440 441 /* Write buffered data to program stdin. */ 442 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 443 data = buffer_ptr(&stdin_buffer); 444 dlen = buffer_len(&stdin_buffer); 445 len = write(fdin, data, dlen); 446 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 447 /* do nothing */ 448 } else if (len <= 0) { 449 if (fdin != fdout) 450 close(fdin); 451 else 452 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 453 fdin = -1; 454 } else { 455 /* Successful write. */ 456 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 457 tcgetattr(fdin, &tio) == 0 && 458 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 459 /* 460 * Simulate echo to reduce the impact of 461 * traffic analysis 462 */ 463 packet_send_ignore(len); 464 packet_send(); 465 } 466 /* Consume the data from the buffer. */ 467 buffer_consume(&stdin_buffer, len); 468 /* Update the count of bytes written to the program. */ 469 stdin_bytes += len; 470 } 471 } 472 /* Send any buffered packet data to the client. */ 473 if (FD_ISSET(connection_out, writeset)) 474 packet_write_poll(); 475 } 476 477 /* 478 * Wait until all buffered output has been sent to the client. 479 * This is used when the program terminates. 480 */ 481 static void 482 drain_output(void) 483 { 484 /* Send any buffered stdout data to the client. */ 485 if (buffer_len(&stdout_buffer) > 0) { 486 packet_start(SSH_SMSG_STDOUT_DATA); 487 packet_put_string(buffer_ptr(&stdout_buffer), 488 buffer_len(&stdout_buffer)); 489 packet_send(); 490 /* Update the count of sent bytes. */ 491 stdout_bytes += buffer_len(&stdout_buffer); 492 } 493 /* Send any buffered stderr data to the client. */ 494 if (buffer_len(&stderr_buffer) > 0) { 495 packet_start(SSH_SMSG_STDERR_DATA); 496 packet_put_string(buffer_ptr(&stderr_buffer), 497 buffer_len(&stderr_buffer)); 498 packet_send(); 499 /* Update the count of sent bytes. */ 500 stderr_bytes += buffer_len(&stderr_buffer); 501 } 502 /* Wait until all buffered data has been written to the client. */ 503 packet_write_wait(); 504 } 505 506 static void 507 process_buffered_input_packets(void) 508 { 509 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 510 } 511 512 /* 513 * Performs the interactive session. This handles data transmission between 514 * the client and the program. Note that the notion of stdin, stdout, and 515 * stderr in this function is sort of reversed: this function writes to 516 * stdin (of the child program), and reads from stdout and stderr (of the 517 * child program). 518 */ 519 void 520 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 521 { 522 fd_set *readset = NULL, *writeset = NULL; 523 int max_fd = 0; 524 u_int nalloc = 0; 525 int wait_status; /* Status returned by wait(). */ 526 pid_t wait_pid; /* pid returned by wait(). */ 527 int waiting_termination = 0; /* Have displayed waiting close message. */ 528 u_int max_time_milliseconds; 529 u_int previous_stdout_buffer_bytes; 530 u_int stdout_buffer_bytes; 531 int type; 532 533 debug("Entering interactive session."); 534 535 /* Initialize the SIGCHLD kludge. */ 536 child_terminated = 0; 537 signal(SIGCHLD, sigchld_handler); 538 539 if (!use_privsep) { 540 signal(SIGTERM, sigterm_handler); 541 signal(SIGINT, sigterm_handler); 542 signal(SIGQUIT, sigterm_handler); 543 } 544 545 /* Initialize our global variables. */ 546 fdin = fdin_arg; 547 fdout = fdout_arg; 548 fderr = fderr_arg; 549 550 /* nonblocking IO */ 551 set_nonblock(fdin); 552 set_nonblock(fdout); 553 /* we don't have stderr for interactive terminal sessions, see below */ 554 if (fderr != -1) 555 set_nonblock(fderr); 556 557 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 558 fdin_is_tty = 1; 559 560 connection_in = packet_get_connection_in(); 561 connection_out = packet_get_connection_out(); 562 563 notify_setup(); 564 565 previous_stdout_buffer_bytes = 0; 566 567 /* Set approximate I/O buffer size. */ 568 if (packet_is_interactive()) 569 buffer_high = 4096; 570 else 571 buffer_high = 64 * 1024; 572 573 #if 0 574 /* Initialize max_fd to the maximum of the known file descriptors. */ 575 max_fd = MAX(connection_in, connection_out); 576 max_fd = MAX(max_fd, fdin); 577 max_fd = MAX(max_fd, fdout); 578 if (fderr != -1) 579 max_fd = MAX(max_fd, fderr); 580 #endif 581 582 /* Initialize Initialize buffers. */ 583 buffer_init(&stdin_buffer); 584 buffer_init(&stdout_buffer); 585 buffer_init(&stderr_buffer); 586 587 /* 588 * If we have no separate fderr (which is the case when we have a pty 589 * - there we cannot make difference between data sent to stdout and 590 * stderr), indicate that we have seen an EOF from stderr. This way 591 * we don't need to check the descriptor everywhere. 592 */ 593 if (fderr == -1) 594 fderr_eof = 1; 595 596 server_init_dispatch(); 597 598 /* Main loop of the server for the interactive session mode. */ 599 for (;;) { 600 601 /* Process buffered packets from the client. */ 602 process_buffered_input_packets(); 603 604 /* 605 * If we have received eof, and there is no more pending 606 * input data, cause a real eof by closing fdin. 607 */ 608 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 609 if (fdin != fdout) 610 close(fdin); 611 else 612 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 613 fdin = -1; 614 } 615 /* Make packets from buffered stderr data to send to the client. */ 616 make_packets_from_stderr_data(); 617 618 /* 619 * Make packets from buffered stdout data to send to the 620 * client. If there is very little to send, this arranges to 621 * not send them now, but to wait a short while to see if we 622 * are getting more data. This is necessary, as some systems 623 * wake up readers from a pty after each separate character. 624 */ 625 max_time_milliseconds = 0; 626 stdout_buffer_bytes = buffer_len(&stdout_buffer); 627 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 628 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 629 /* try again after a while */ 630 max_time_milliseconds = 10; 631 } else { 632 /* Send it now. */ 633 make_packets_from_stdout_data(); 634 } 635 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 636 637 /* Send channel data to the client. */ 638 if (packet_not_very_much_data_to_write()) 639 channel_output_poll(); 640 641 /* 642 * Bail out of the loop if the program has closed its output 643 * descriptors, and we have no more data to send to the 644 * client, and there is no pending buffered data. 645 */ 646 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 647 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 648 if (!channel_still_open()) 649 break; 650 if (!waiting_termination) { 651 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 652 char *cp; 653 waiting_termination = 1; 654 buffer_append(&stderr_buffer, s, strlen(s)); 655 656 /* Display list of open channels. */ 657 cp = channel_open_message(); 658 buffer_append(&stderr_buffer, cp, strlen(cp)); 659 xfree(cp); 660 } 661 } 662 max_fd = MAX(connection_in, connection_out); 663 max_fd = MAX(max_fd, fdin); 664 max_fd = MAX(max_fd, fdout); 665 max_fd = MAX(max_fd, fderr); 666 max_fd = MAX(max_fd, notify_pipe[0]); 667 668 /* Sleep in select() until we can do something. */ 669 wait_until_can_do_something(&readset, &writeset, &max_fd, 670 &nalloc, max_time_milliseconds); 671 672 if (received_sigterm) { 673 logit("Exiting on signal %d", received_sigterm); 674 /* Clean up sessions, utmp, etc. */ 675 cleanup_exit(255); 676 } 677 678 /* Process any channel events. */ 679 channel_after_select(readset, writeset); 680 681 /* Process input from the client and from program stdout/stderr. */ 682 process_input(readset); 683 684 /* Process output to the client and to program stdin. */ 685 process_output(writeset); 686 } 687 if (readset) 688 xfree(readset); 689 if (writeset) 690 xfree(writeset); 691 692 /* Cleanup and termination code. */ 693 694 /* Wait until all output has been sent to the client. */ 695 drain_output(); 696 697 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 698 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 699 700 /* Free and clear the buffers. */ 701 buffer_free(&stdin_buffer); 702 buffer_free(&stdout_buffer); 703 buffer_free(&stderr_buffer); 704 705 /* Close the file descriptors. */ 706 if (fdout != -1) 707 close(fdout); 708 fdout = -1; 709 fdout_eof = 1; 710 if (fderr != -1) 711 close(fderr); 712 fderr = -1; 713 fderr_eof = 1; 714 if (fdin != -1) 715 close(fdin); 716 fdin = -1; 717 718 channel_free_all(); 719 720 /* We no longer want our SIGCHLD handler to be called. */ 721 signal(SIGCHLD, SIG_DFL); 722 723 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 724 if (errno != EINTR) 725 packet_disconnect("wait: %.100s", strerror(errno)); 726 if (wait_pid != pid) 727 error("Strange, wait returned pid %ld, expected %ld", 728 (long)wait_pid, (long)pid); 729 730 /* Check if it exited normally. */ 731 if (WIFEXITED(wait_status)) { 732 /* Yes, normal exit. Get exit status and send it to the client. */ 733 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 734 packet_start(SSH_SMSG_EXITSTATUS); 735 packet_put_int(WEXITSTATUS(wait_status)); 736 packet_send(); 737 packet_write_wait(); 738 739 /* 740 * Wait for exit confirmation. Note that there might be 741 * other packets coming before it; however, the program has 742 * already died so we just ignore them. The client is 743 * supposed to respond with the confirmation when it receives 744 * the exit status. 745 */ 746 do { 747 type = packet_read(); 748 } 749 while (type != SSH_CMSG_EXIT_CONFIRMATION); 750 751 debug("Received exit confirmation."); 752 return; 753 } 754 /* Check if the program terminated due to a signal. */ 755 if (WIFSIGNALED(wait_status)) 756 packet_disconnect("Command terminated on signal %d.", 757 WTERMSIG(wait_status)); 758 759 /* Some weird exit cause. Just exit. */ 760 packet_disconnect("wait returned status %04x.", wait_status); 761 /* NOTREACHED */ 762 } 763 764 static void 765 collect_children(void) 766 { 767 pid_t pid; 768 sigset_t oset, nset; 769 int status; 770 771 /* block SIGCHLD while we check for dead children */ 772 sigemptyset(&nset); 773 sigaddset(&nset, SIGCHLD); 774 sigprocmask(SIG_BLOCK, &nset, &oset); 775 if (child_terminated) { 776 debug("Received SIGCHLD."); 777 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 778 (pid < 0 && errno == EINTR)) 779 if (pid > 0) 780 session_close_by_pid(pid, status); 781 child_terminated = 0; 782 } 783 sigprocmask(SIG_SETMASK, &oset, NULL); 784 } 785 786 void 787 server_loop2(Authctxt *authctxt) 788 { 789 fd_set *readset = NULL, *writeset = NULL; 790 int rekeying = 0, max_fd, nalloc = 0; 791 792 debug("Entering interactive session for SSH2."); 793 794 signal(SIGCHLD, sigchld_handler); 795 child_terminated = 0; 796 connection_in = packet_get_connection_in(); 797 connection_out = packet_get_connection_out(); 798 799 if (!use_privsep) { 800 signal(SIGTERM, sigterm_handler); 801 signal(SIGINT, sigterm_handler); 802 signal(SIGQUIT, sigterm_handler); 803 } 804 805 notify_setup(); 806 807 max_fd = MAX(connection_in, connection_out); 808 max_fd = MAX(max_fd, notify_pipe[0]); 809 810 server_init_dispatch(); 811 812 for (;;) { 813 process_buffered_input_packets(); 814 815 rekeying = (xxx_kex != NULL && !xxx_kex->done); 816 817 if (!rekeying && packet_not_very_much_data_to_write()) 818 channel_output_poll(); 819 wait_until_can_do_something(&readset, &writeset, &max_fd, 820 &nalloc, 0); 821 822 if (received_sigterm) { 823 logit("Exiting on signal %d", received_sigterm); 824 /* Clean up sessions, utmp, etc. */ 825 cleanup_exit(255); 826 } 827 828 collect_children(); 829 if (!rekeying) { 830 channel_after_select(readset, writeset); 831 if (packet_need_rekeying()) { 832 debug("need rekeying"); 833 xxx_kex->done = 0; 834 kex_send_kexinit(xxx_kex); 835 } 836 } 837 process_input(readset); 838 if (connection_closed) 839 break; 840 process_output(writeset); 841 } 842 collect_children(); 843 844 if (readset) 845 xfree(readset); 846 if (writeset) 847 xfree(writeset); 848 849 /* free all channels, no more reads and writes */ 850 channel_free_all(); 851 852 /* free remaining sessions, e.g. remove wtmp entries */ 853 session_destroy_all(NULL); 854 } 855 856 static void 857 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 858 { 859 debug("Got %d/%u for keepalive", type, seq); 860 /* 861 * reset timeout, since we got a sane answer from the client. 862 * even if this was generated by something other than 863 * the bogus CHANNEL_REQUEST we send for keepalives. 864 */ 865 packet_set_alive_timeouts(0); 866 } 867 868 static void 869 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 870 { 871 char *data; 872 u_int data_len; 873 874 /* Stdin data from the client. Append it to the buffer. */ 875 /* Ignore any data if the client has closed stdin. */ 876 if (fdin == -1) 877 return; 878 data = packet_get_string(&data_len); 879 packet_check_eom(); 880 buffer_append(&stdin_buffer, data, data_len); 881 memset(data, 0, data_len); 882 xfree(data); 883 } 884 885 static void 886 server_input_eof(int type, u_int32_t seq, void *ctxt) 887 { 888 /* 889 * Eof from the client. The stdin descriptor to the 890 * program will be closed when all buffered data has 891 * drained. 892 */ 893 debug("EOF received for stdin."); 894 packet_check_eom(); 895 stdin_eof = 1; 896 } 897 898 static void 899 server_input_window_size(int type, u_int32_t seq, void *ctxt) 900 { 901 u_int row = packet_get_int(); 902 u_int col = packet_get_int(); 903 u_int xpixel = packet_get_int(); 904 u_int ypixel = packet_get_int(); 905 906 debug("Window change received."); 907 packet_check_eom(); 908 if (fdin != -1) 909 pty_change_window_size(fdin, row, col, xpixel, ypixel); 910 } 911 912 static Channel * 913 server_request_direct_tcpip(void) 914 { 915 Channel *c; 916 char *target, *originator; 917 u_short target_port, originator_port; 918 919 target = packet_get_string(NULL); 920 target_port = packet_get_int(); 921 originator = packet_get_string(NULL); 922 originator_port = packet_get_int(); 923 packet_check_eom(); 924 925 debug("server_request_direct_tcpip: originator %s port %d, target %s " 926 "port %d", originator, originator_port, target, target_port); 927 928 /* XXX check permission */ 929 c = channel_connect_to(target, target_port, 930 "direct-tcpip", "direct-tcpip"); 931 932 xfree(originator); 933 xfree(target); 934 935 return c; 936 } 937 938 static Channel * 939 server_request_tun(void) 940 { 941 Channel *c = NULL; 942 int mode, tun; 943 int sock; 944 945 mode = packet_get_int(); 946 switch (mode) { 947 case SSH_TUNMODE_POINTOPOINT: 948 case SSH_TUNMODE_ETHERNET: 949 break; 950 default: 951 packet_send_debug("Unsupported tunnel device mode."); 952 return NULL; 953 } 954 if ((options.permit_tun & mode) == 0) { 955 packet_send_debug("Server has rejected tunnel device " 956 "forwarding"); 957 return NULL; 958 } 959 960 tun = packet_get_int(); 961 if (forced_tun_device != -1) { 962 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 963 goto done; 964 tun = forced_tun_device; 965 } 966 sock = tun_open(tun, mode); 967 if (sock < 0) 968 goto done; 969 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 970 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 971 c->datagram = 1; 972 973 done: 974 if (c == NULL) 975 packet_send_debug("Failed to open the tunnel device."); 976 return c; 977 } 978 979 static Channel * 980 server_request_session(void) 981 { 982 Channel *c; 983 984 debug("input_session_request"); 985 packet_check_eom(); 986 987 if (no_more_sessions) { 988 packet_disconnect("Possible attack: attempt to open a session " 989 "after additional sessions disabled"); 990 } 991 992 /* 993 * A server session has no fd to read or write until a 994 * CHANNEL_REQUEST for a shell is made, so we set the type to 995 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 996 * CHANNEL_REQUEST messages is registered. 997 */ 998 c = channel_new("session", SSH_CHANNEL_LARVAL, 999 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1000 0, "server-session", 1); 1001 if (session_open(the_authctxt, c->self) != 1) { 1002 debug("session open failed, free channel %d", c->self); 1003 channel_free(c); 1004 return NULL; 1005 } 1006 channel_register_cleanup(c->self, session_close_by_channel, 0); 1007 return c; 1008 } 1009 1010 static void 1011 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1012 { 1013 Channel *c = NULL; 1014 char *ctype; 1015 int rchan; 1016 u_int rmaxpack, rwindow, len; 1017 1018 ctype = packet_get_string(&len); 1019 rchan = packet_get_int(); 1020 rwindow = packet_get_int(); 1021 rmaxpack = packet_get_int(); 1022 1023 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1024 ctype, rchan, rwindow, rmaxpack); 1025 1026 if (strcmp(ctype, "session") == 0) { 1027 c = server_request_session(); 1028 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1029 c = server_request_direct_tcpip(); 1030 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1031 c = server_request_tun(); 1032 } 1033 if (c != NULL) { 1034 debug("server_input_channel_open: confirm %s", ctype); 1035 c->remote_id = rchan; 1036 c->remote_window = rwindow; 1037 c->remote_maxpacket = rmaxpack; 1038 if (c->type != SSH_CHANNEL_CONNECTING) { 1039 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1040 packet_put_int(c->remote_id); 1041 packet_put_int(c->self); 1042 packet_put_int(c->local_window); 1043 packet_put_int(c->local_maxpacket); 1044 packet_send(); 1045 } 1046 } else { 1047 debug("server_input_channel_open: failure %s", ctype); 1048 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1049 packet_put_int(rchan); 1050 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1051 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1052 packet_put_cstring("open failed"); 1053 packet_put_cstring(""); 1054 } 1055 packet_send(); 1056 } 1057 xfree(ctype); 1058 } 1059 1060 static void 1061 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1062 { 1063 char *rtype; 1064 int want_reply; 1065 int success = 0, allocated_listen_port = 0; 1066 1067 rtype = packet_get_string(NULL); 1068 want_reply = packet_get_char(); 1069 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1070 1071 /* -R style forwarding */ 1072 if (strcmp(rtype, "tcpip-forward") == 0) { 1073 struct passwd *pw; 1074 char *listen_address; 1075 u_short listen_port; 1076 1077 pw = the_authctxt->pw; 1078 if (pw == NULL || !the_authctxt->valid) 1079 fatal("server_input_global_request: no/invalid user"); 1080 listen_address = packet_get_string(NULL); 1081 listen_port = (u_short)packet_get_int(); 1082 debug("server_input_global_request: tcpip-forward listen %s port %d", 1083 listen_address, listen_port); 1084 1085 /* check permissions */ 1086 if (!options.allow_tcp_forwarding || 1087 no_port_forwarding_flag || 1088 (!want_reply && listen_port == 0) || 1089 (listen_port != 0 && listen_port < IPPORT_RESERVED && 1090 pw->pw_uid != 0)) { 1091 success = 0; 1092 packet_send_debug("Server has disabled port forwarding."); 1093 } else { 1094 /* Start listening on the port */ 1095 success = channel_setup_remote_fwd_listener( 1096 listen_address, listen_port, 1097 &allocated_listen_port, options.gateway_ports); 1098 } 1099 xfree(listen_address); 1100 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1101 char *cancel_address; 1102 u_short cancel_port; 1103 1104 cancel_address = packet_get_string(NULL); 1105 cancel_port = (u_short)packet_get_int(); 1106 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1107 cancel_address, cancel_port); 1108 1109 success = channel_cancel_rport_listener(cancel_address, 1110 cancel_port); 1111 xfree(cancel_address); 1112 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1113 no_more_sessions = 1; 1114 success = 1; 1115 } 1116 if (want_reply) { 1117 packet_start(success ? 1118 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1119 if (success && allocated_listen_port > 0) 1120 packet_put_int(allocated_listen_port); 1121 packet_send(); 1122 packet_write_wait(); 1123 } 1124 xfree(rtype); 1125 } 1126 1127 static void 1128 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1129 { 1130 Channel *c; 1131 int id, reply, success = 0; 1132 char *rtype; 1133 1134 id = packet_get_int(); 1135 rtype = packet_get_string(NULL); 1136 reply = packet_get_char(); 1137 1138 debug("server_input_channel_req: channel %d request %s reply %d", 1139 id, rtype, reply); 1140 1141 if ((c = channel_lookup(id)) == NULL) 1142 packet_disconnect("server_input_channel_req: " 1143 "unknown channel %d", id); 1144 if (!strcmp(rtype, "eow@openssh.com")) { 1145 packet_check_eom(); 1146 chan_rcvd_eow(c); 1147 } else if ((c->type == SSH_CHANNEL_LARVAL || 1148 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1149 success = session_input_channel_req(c, rtype); 1150 if (reply) { 1151 packet_start(success ? 1152 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1153 packet_put_int(c->remote_id); 1154 packet_send(); 1155 } 1156 xfree(rtype); 1157 } 1158 1159 static void 1160 server_init_dispatch_20(void) 1161 { 1162 debug("server_init_dispatch_20"); 1163 dispatch_init(&dispatch_protocol_error); 1164 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1165 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1166 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1167 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1168 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1169 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1170 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1171 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1172 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1173 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1174 /* client_alive */ 1175 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1176 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1177 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1178 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1179 /* rekeying */ 1180 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1181 } 1182 static void 1183 server_init_dispatch_13(void) 1184 { 1185 debug("server_init_dispatch_13"); 1186 dispatch_init(NULL); 1187 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1188 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1189 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1190 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1191 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1192 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1193 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1194 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1195 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1196 } 1197 static void 1198 server_init_dispatch_15(void) 1199 { 1200 server_init_dispatch_13(); 1201 debug("server_init_dispatch_15"); 1202 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1203 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1204 } 1205 static void 1206 server_init_dispatch(void) 1207 { 1208 if (compat20) 1209 server_init_dispatch_20(); 1210 else if (compat13) 1211 server_init_dispatch_13(); 1212 else 1213 server_init_dispatch_15(); 1214 } 1215