1 /* $OpenBSD: serverloop.c,v 1.157 2009/02/12 03:16:01 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 <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 78 extern ServerOptions options; 79 80 /* XXX */ 81 extern Kex *xxx_kex; 82 extern Authctxt *the_authctxt; 83 extern int use_privsep; 84 85 static Buffer stdin_buffer; /* Buffer for stdin data. */ 86 static Buffer stdout_buffer; /* Buffer for stdout data. */ 87 static Buffer stderr_buffer; /* Buffer for stderr data. */ 88 static int fdin; /* Descriptor for stdin (for writing) */ 89 static int fdout; /* Descriptor for stdout (for reading); 90 May be same number as fdin. */ 91 static int fderr; /* Descriptor for stderr. May be -1. */ 92 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 93 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 94 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 95 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 96 static int stdin_eof = 0; /* EOF message received from client. */ 97 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 98 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 99 static int fdin_is_tty = 0; /* fdin points to a tty. */ 100 static int connection_in; /* Connection to client (input). */ 101 static int connection_out; /* Connection to client (output). */ 102 static int connection_closed = 0; /* Connection to client closed. */ 103 static u_int buffer_high; /* "Soft" max buffer size. */ 104 static int no_more_sessions = 0; /* Disallow further sessions. */ 105 106 /* 107 * This SIGCHLD kludge is used to detect when the child exits. The server 108 * will exit after that, as soon as forwarded connections have terminated. 109 */ 110 111 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 112 113 /* Cleanup on signals (!use_privsep case only) */ 114 static volatile sig_atomic_t received_sigterm = 0; 115 116 /* prototypes */ 117 static void server_init_dispatch(void); 118 119 /* 120 * we write to this pipe if a SIGCHLD is caught in order to avoid 121 * the race between select() and child_terminated 122 */ 123 static int notify_pipe[2]; 124 static void 125 notify_setup(void) 126 { 127 if (pipe(notify_pipe) < 0) { 128 error("pipe(notify_pipe) failed %s", strerror(errno)); 129 } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) || 130 (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) { 131 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 132 close(notify_pipe[0]); 133 close(notify_pipe[1]); 134 } else { 135 set_nonblock(notify_pipe[0]); 136 set_nonblock(notify_pipe[1]); 137 return; 138 } 139 notify_pipe[0] = -1; /* read end */ 140 notify_pipe[1] = -1; /* write end */ 141 } 142 static void 143 notify_parent(void) 144 { 145 if (notify_pipe[1] != -1) 146 write(notify_pipe[1], "", 1); 147 } 148 static void 149 notify_prepare(fd_set *readset) 150 { 151 if (notify_pipe[0] != -1) 152 FD_SET(notify_pipe[0], readset); 153 } 154 static void 155 notify_done(fd_set *readset) 156 { 157 char c; 158 159 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 160 while (read(notify_pipe[0], &c, 1) != -1) 161 debug2("notify_done: reading"); 162 } 163 164 /*ARGSUSED*/ 165 static void 166 sigchld_handler(int sig) 167 { 168 int save_errno = errno; 169 child_terminated = 1; 170 signal(SIGCHLD, sigchld_handler); 171 notify_parent(); 172 errno = save_errno; 173 } 174 175 /*ARGSUSED*/ 176 static void 177 sigterm_handler(int sig) 178 { 179 received_sigterm = sig; 180 } 181 182 /* 183 * Make packets from buffered stderr data, and buffer it for sending 184 * to the client. 185 */ 186 static void 187 make_packets_from_stderr_data(void) 188 { 189 u_int len; 190 191 /* Send buffered stderr data to the client. */ 192 while (buffer_len(&stderr_buffer) > 0 && 193 packet_not_very_much_data_to_write()) { 194 len = buffer_len(&stderr_buffer); 195 if (packet_is_interactive()) { 196 if (len > 512) 197 len = 512; 198 } else { 199 /* Keep the packets at reasonable size. */ 200 if (len > packet_get_maxsize()) 201 len = packet_get_maxsize(); 202 } 203 packet_start(SSH_SMSG_STDERR_DATA); 204 packet_put_string(buffer_ptr(&stderr_buffer), len); 205 packet_send(); 206 buffer_consume(&stderr_buffer, len); 207 stderr_bytes += len; 208 } 209 } 210 211 /* 212 * Make packets from buffered stdout data, and buffer it for sending to the 213 * client. 214 */ 215 static void 216 make_packets_from_stdout_data(void) 217 { 218 u_int len; 219 220 /* Send buffered stdout data to the client. */ 221 while (buffer_len(&stdout_buffer) > 0 && 222 packet_not_very_much_data_to_write()) { 223 len = buffer_len(&stdout_buffer); 224 if (packet_is_interactive()) { 225 if (len > 512) 226 len = 512; 227 } else { 228 /* Keep the packets at reasonable size. */ 229 if (len > packet_get_maxsize()) 230 len = packet_get_maxsize(); 231 } 232 packet_start(SSH_SMSG_STDOUT_DATA); 233 packet_put_string(buffer_ptr(&stdout_buffer), len); 234 packet_send(); 235 buffer_consume(&stdout_buffer, len); 236 stdout_bytes += len; 237 } 238 } 239 240 static void 241 client_alive_check(void) 242 { 243 int channel_id; 244 245 /* timeout, check to see how many we have had */ 246 if (++keep_alive_timeouts > options.client_alive_count_max) { 247 logit("Timeout, client not responding."); 248 cleanup_exit(255); 249 } 250 251 /* 252 * send a bogus global/channel request with "wantreply", 253 * we should get back a failure 254 */ 255 if ((channel_id = channel_find_open()) == -1) { 256 packet_start(SSH2_MSG_GLOBAL_REQUEST); 257 packet_put_cstring("keepalive@openssh.com"); 258 packet_put_char(1); /* boolean: want reply */ 259 } else { 260 channel_request_start(channel_id, "keepalive@openssh.com", 1); 261 } 262 packet_send(); 263 } 264 265 /* 266 * Sleep in select() until we can do something. This will initialize the 267 * select masks. Upon return, the masks will indicate which descriptors 268 * have data or can accept data. Optionally, a maximum time can be specified 269 * for the duration of the wait (0 = infinite). 270 */ 271 static void 272 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 273 u_int *nallocp, u_int max_time_milliseconds) 274 { 275 struct timeval tv, *tvp; 276 int ret; 277 int client_alive_scheduled = 0; 278 279 /* 280 * if using client_alive, set the max timeout accordingly, 281 * and indicate that this particular timeout was for client 282 * alive by setting the client_alive_scheduled flag. 283 * 284 * this could be randomized somewhat to make traffic 285 * analysis more difficult, but we're not doing it yet. 286 */ 287 if (compat20 && 288 max_time_milliseconds == 0 && options.client_alive_interval) { 289 client_alive_scheduled = 1; 290 max_time_milliseconds = options.client_alive_interval * 1000; 291 } 292 293 /* Allocate and update select() masks for channel descriptors. */ 294 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0); 295 296 if (compat20) { 297 #if 0 298 /* wrong: bad condition XXX */ 299 if (channel_not_very_much_buffered_data()) 300 #endif 301 FD_SET(connection_in, *readsetp); 302 } else { 303 /* 304 * Read packets from the client unless we have too much 305 * buffered stdin or channel data. 306 */ 307 if (buffer_len(&stdin_buffer) < buffer_high && 308 channel_not_very_much_buffered_data()) 309 FD_SET(connection_in, *readsetp); 310 /* 311 * If there is not too much data already buffered going to 312 * the client, try to get some more data from the program. 313 */ 314 if (packet_not_very_much_data_to_write()) { 315 if (!fdout_eof) 316 FD_SET(fdout, *readsetp); 317 if (!fderr_eof) 318 FD_SET(fderr, *readsetp); 319 } 320 /* 321 * If we have buffered data, try to write some of that data 322 * to the program. 323 */ 324 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 325 FD_SET(fdin, *writesetp); 326 } 327 notify_prepare(*readsetp); 328 329 /* 330 * If we have buffered packet data going to the client, mark that 331 * descriptor. 332 */ 333 if (packet_have_data_to_write()) 334 FD_SET(connection_out, *writesetp); 335 336 /* 337 * If child has terminated and there is enough buffer space to read 338 * from it, then read as much as is available and exit. 339 */ 340 if (child_terminated && packet_not_very_much_data_to_write()) 341 if (max_time_milliseconds == 0 || client_alive_scheduled) 342 max_time_milliseconds = 100; 343 344 if (max_time_milliseconds == 0) 345 tvp = NULL; 346 else { 347 tv.tv_sec = max_time_milliseconds / 1000; 348 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 349 tvp = &tv; 350 } 351 352 /* Wait for something to happen, or the timeout to expire. */ 353 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 354 355 if (ret == -1) { 356 memset(*readsetp, 0, *nallocp); 357 memset(*writesetp, 0, *nallocp); 358 if (errno != EINTR) 359 error("select: %.100s", strerror(errno)); 360 } else if (ret == 0 && client_alive_scheduled) 361 client_alive_check(); 362 363 notify_done(*readsetp); 364 } 365 366 /* 367 * Processes input from the client and the program. Input data is stored 368 * in buffers and processed later. 369 */ 370 static void 371 process_input(fd_set *readset) 372 { 373 int len; 374 char buf[16384]; 375 376 /* Read and buffer any input data from the client. */ 377 if (FD_ISSET(connection_in, readset)) { 378 len = read(connection_in, buf, sizeof(buf)); 379 if (len == 0) { 380 verbose("Connection closed by %.100s", 381 get_remote_ipaddr()); 382 connection_closed = 1; 383 if (compat20) 384 return; 385 cleanup_exit(255); 386 } else if (len < 0) { 387 if (errno != EINTR && errno != EAGAIN) { 388 verbose("Read error from remote host " 389 "%.100s: %.100s", 390 get_remote_ipaddr(), strerror(errno)); 391 cleanup_exit(255); 392 } 393 } else { 394 /* Buffer any received data. */ 395 packet_process_incoming(buf, len); 396 } 397 } 398 if (compat20) 399 return; 400 401 /* Read and buffer any available stdout data from the program. */ 402 if (!fdout_eof && FD_ISSET(fdout, readset)) { 403 len = read(fdout, buf, sizeof(buf)); 404 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 405 /* do nothing */ 406 } else if (len <= 0) { 407 fdout_eof = 1; 408 } else { 409 buffer_append(&stdout_buffer, buf, len); 410 fdout_bytes += len; 411 } 412 } 413 /* Read and buffer any available stderr data from the program. */ 414 if (!fderr_eof && FD_ISSET(fderr, readset)) { 415 len = read(fderr, buf, sizeof(buf)); 416 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 417 /* do nothing */ 418 } else if (len <= 0) { 419 fderr_eof = 1; 420 } else { 421 buffer_append(&stderr_buffer, buf, len); 422 } 423 } 424 } 425 426 /* 427 * Sends data from internal buffers to client program stdin. 428 */ 429 static void 430 process_output(fd_set *writeset) 431 { 432 struct termios tio; 433 u_char *data; 434 u_int dlen; 435 int len; 436 437 /* Write buffered data to program stdin. */ 438 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 439 data = buffer_ptr(&stdin_buffer); 440 dlen = buffer_len(&stdin_buffer); 441 len = write(fdin, data, dlen); 442 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 443 /* do nothing */ 444 } else if (len <= 0) { 445 if (fdin != fdout) 446 close(fdin); 447 else 448 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 449 fdin = -1; 450 } else { 451 /* Successful write. */ 452 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 453 tcgetattr(fdin, &tio) == 0 && 454 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 455 /* 456 * Simulate echo to reduce the impact of 457 * traffic analysis 458 */ 459 packet_send_ignore(len); 460 packet_send(); 461 } 462 /* Consume the data from the buffer. */ 463 buffer_consume(&stdin_buffer, len); 464 /* Update the count of bytes written to the program. */ 465 stdin_bytes += len; 466 } 467 } 468 /* Send any buffered packet data to the client. */ 469 if (FD_ISSET(connection_out, writeset)) 470 packet_write_poll(); 471 } 472 473 /* 474 * Wait until all buffered output has been sent to the client. 475 * This is used when the program terminates. 476 */ 477 static void 478 drain_output(void) 479 { 480 /* Send any buffered stdout data to the client. */ 481 if (buffer_len(&stdout_buffer) > 0) { 482 packet_start(SSH_SMSG_STDOUT_DATA); 483 packet_put_string(buffer_ptr(&stdout_buffer), 484 buffer_len(&stdout_buffer)); 485 packet_send(); 486 /* Update the count of sent bytes. */ 487 stdout_bytes += buffer_len(&stdout_buffer); 488 } 489 /* Send any buffered stderr data to the client. */ 490 if (buffer_len(&stderr_buffer) > 0) { 491 packet_start(SSH_SMSG_STDERR_DATA); 492 packet_put_string(buffer_ptr(&stderr_buffer), 493 buffer_len(&stderr_buffer)); 494 packet_send(); 495 /* Update the count of sent bytes. */ 496 stderr_bytes += buffer_len(&stderr_buffer); 497 } 498 /* Wait until all buffered data has been written to the client. */ 499 packet_write_wait(); 500 } 501 502 static void 503 process_buffered_input_packets(void) 504 { 505 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 506 } 507 508 /* 509 * Performs the interactive session. This handles data transmission between 510 * the client and the program. Note that the notion of stdin, stdout, and 511 * stderr in this function is sort of reversed: this function writes to 512 * stdin (of the child program), and reads from stdout and stderr (of the 513 * child program). 514 */ 515 void 516 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 517 { 518 fd_set *readset = NULL, *writeset = NULL; 519 int max_fd = 0; 520 u_int nalloc = 0; 521 int wait_status; /* Status returned by wait(). */ 522 pid_t wait_pid; /* pid returned by wait(). */ 523 int waiting_termination = 0; /* Have displayed waiting close message. */ 524 u_int max_time_milliseconds; 525 u_int previous_stdout_buffer_bytes; 526 u_int stdout_buffer_bytes; 527 int type; 528 529 debug("Entering interactive session."); 530 531 /* Initialize the SIGCHLD kludge. */ 532 child_terminated = 0; 533 signal(SIGCHLD, sigchld_handler); 534 535 if (!use_privsep) { 536 signal(SIGTERM, sigterm_handler); 537 signal(SIGINT, sigterm_handler); 538 signal(SIGQUIT, sigterm_handler); 539 } 540 541 /* Initialize our global variables. */ 542 fdin = fdin_arg; 543 fdout = fdout_arg; 544 fderr = fderr_arg; 545 546 /* nonblocking IO */ 547 set_nonblock(fdin); 548 set_nonblock(fdout); 549 /* we don't have stderr for interactive terminal sessions, see below */ 550 if (fderr != -1) 551 set_nonblock(fderr); 552 553 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 554 fdin_is_tty = 1; 555 556 connection_in = packet_get_connection_in(); 557 connection_out = packet_get_connection_out(); 558 559 notify_setup(); 560 561 previous_stdout_buffer_bytes = 0; 562 563 /* Set approximate I/O buffer size. */ 564 if (packet_is_interactive()) 565 buffer_high = 4096; 566 else 567 buffer_high = 64 * 1024; 568 569 #if 0 570 /* Initialize max_fd to the maximum of the known file descriptors. */ 571 max_fd = MAX(connection_in, connection_out); 572 max_fd = MAX(max_fd, fdin); 573 max_fd = MAX(max_fd, fdout); 574 if (fderr != -1) 575 max_fd = MAX(max_fd, fderr); 576 #endif 577 578 /* Initialize Initialize buffers. */ 579 buffer_init(&stdin_buffer); 580 buffer_init(&stdout_buffer); 581 buffer_init(&stderr_buffer); 582 583 /* 584 * If we have no separate fderr (which is the case when we have a pty 585 * - there we cannot make difference between data sent to stdout and 586 * stderr), indicate that we have seen an EOF from stderr. This way 587 * we don't need to check the descriptor everywhere. 588 */ 589 if (fderr == -1) 590 fderr_eof = 1; 591 592 server_init_dispatch(); 593 594 /* Main loop of the server for the interactive session mode. */ 595 for (;;) { 596 597 /* Process buffered packets from the client. */ 598 process_buffered_input_packets(); 599 600 /* 601 * If we have received eof, and there is no more pending 602 * input data, cause a real eof by closing fdin. 603 */ 604 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 605 if (fdin != fdout) 606 close(fdin); 607 else 608 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 609 fdin = -1; 610 } 611 /* Make packets from buffered stderr data to send to the client. */ 612 make_packets_from_stderr_data(); 613 614 /* 615 * Make packets from buffered stdout data to send to the 616 * client. If there is very little to send, this arranges to 617 * not send them now, but to wait a short while to see if we 618 * are getting more data. This is necessary, as some systems 619 * wake up readers from a pty after each separate character. 620 */ 621 max_time_milliseconds = 0; 622 stdout_buffer_bytes = buffer_len(&stdout_buffer); 623 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 624 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 625 /* try again after a while */ 626 max_time_milliseconds = 10; 627 } else { 628 /* Send it now. */ 629 make_packets_from_stdout_data(); 630 } 631 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 632 633 /* Send channel data to the client. */ 634 if (packet_not_very_much_data_to_write()) 635 channel_output_poll(); 636 637 /* 638 * Bail out of the loop if the program has closed its output 639 * descriptors, and we have no more data to send to the 640 * client, and there is no pending buffered data. 641 */ 642 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 643 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 644 if (!channel_still_open()) 645 break; 646 if (!waiting_termination) { 647 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 648 char *cp; 649 waiting_termination = 1; 650 buffer_append(&stderr_buffer, s, strlen(s)); 651 652 /* Display list of open channels. */ 653 cp = channel_open_message(); 654 buffer_append(&stderr_buffer, cp, strlen(cp)); 655 xfree(cp); 656 } 657 } 658 max_fd = MAX(connection_in, connection_out); 659 max_fd = MAX(max_fd, fdin); 660 max_fd = MAX(max_fd, fdout); 661 max_fd = MAX(max_fd, fderr); 662 max_fd = MAX(max_fd, notify_pipe[0]); 663 664 /* Sleep in select() until we can do something. */ 665 wait_until_can_do_something(&readset, &writeset, &max_fd, 666 &nalloc, max_time_milliseconds); 667 668 if (received_sigterm) { 669 logit("Exiting on signal %d", received_sigterm); 670 /* Clean up sessions, utmp, etc. */ 671 cleanup_exit(255); 672 } 673 674 /* Process any channel events. */ 675 channel_after_select(readset, writeset); 676 677 /* Process input from the client and from program stdout/stderr. */ 678 process_input(readset); 679 680 /* Process output to the client and to program stdin. */ 681 process_output(writeset); 682 } 683 if (readset) 684 xfree(readset); 685 if (writeset) 686 xfree(writeset); 687 688 /* Cleanup and termination code. */ 689 690 /* Wait until all output has been sent to the client. */ 691 drain_output(); 692 693 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 694 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 695 696 /* Free and clear the buffers. */ 697 buffer_free(&stdin_buffer); 698 buffer_free(&stdout_buffer); 699 buffer_free(&stderr_buffer); 700 701 /* Close the file descriptors. */ 702 if (fdout != -1) 703 close(fdout); 704 fdout = -1; 705 fdout_eof = 1; 706 if (fderr != -1) 707 close(fderr); 708 fderr = -1; 709 fderr_eof = 1; 710 if (fdin != -1) 711 close(fdin); 712 fdin = -1; 713 714 channel_free_all(); 715 716 /* We no longer want our SIGCHLD handler to be called. */ 717 signal(SIGCHLD, SIG_DFL); 718 719 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 720 if (errno != EINTR) 721 packet_disconnect("wait: %.100s", strerror(errno)); 722 if (wait_pid != pid) 723 error("Strange, wait returned pid %ld, expected %ld", 724 (long)wait_pid, (long)pid); 725 726 /* Check if it exited normally. */ 727 if (WIFEXITED(wait_status)) { 728 /* Yes, normal exit. Get exit status and send it to the client. */ 729 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 730 packet_start(SSH_SMSG_EXITSTATUS); 731 packet_put_int(WEXITSTATUS(wait_status)); 732 packet_send(); 733 packet_write_wait(); 734 735 /* 736 * Wait for exit confirmation. Note that there might be 737 * other packets coming before it; however, the program has 738 * already died so we just ignore them. The client is 739 * supposed to respond with the confirmation when it receives 740 * the exit status. 741 */ 742 do { 743 type = packet_read(); 744 } 745 while (type != SSH_CMSG_EXIT_CONFIRMATION); 746 747 debug("Received exit confirmation."); 748 return; 749 } 750 /* Check if the program terminated due to a signal. */ 751 if (WIFSIGNALED(wait_status)) 752 packet_disconnect("Command terminated on signal %d.", 753 WTERMSIG(wait_status)); 754 755 /* Some weird exit cause. Just exit. */ 756 packet_disconnect("wait returned status %04x.", wait_status); 757 /* NOTREACHED */ 758 } 759 760 static void 761 collect_children(void) 762 { 763 pid_t pid; 764 sigset_t oset, nset; 765 int status; 766 767 /* block SIGCHLD while we check for dead children */ 768 sigemptyset(&nset); 769 sigaddset(&nset, SIGCHLD); 770 sigprocmask(SIG_BLOCK, &nset, &oset); 771 if (child_terminated) { 772 debug("Received SIGCHLD."); 773 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 774 (pid < 0 && errno == EINTR)) 775 if (pid > 0) 776 session_close_by_pid(pid, status); 777 child_terminated = 0; 778 } 779 sigprocmask(SIG_SETMASK, &oset, NULL); 780 } 781 782 void 783 server_loop2(Authctxt *authctxt) 784 { 785 fd_set *readset = NULL, *writeset = NULL; 786 int rekeying = 0, max_fd, nalloc = 0; 787 788 debug("Entering interactive session for SSH2."); 789 790 signal(SIGCHLD, sigchld_handler); 791 child_terminated = 0; 792 connection_in = packet_get_connection_in(); 793 connection_out = packet_get_connection_out(); 794 795 if (!use_privsep) { 796 signal(SIGTERM, sigterm_handler); 797 signal(SIGINT, sigterm_handler); 798 signal(SIGQUIT, sigterm_handler); 799 } 800 801 notify_setup(); 802 803 max_fd = MAX(connection_in, connection_out); 804 max_fd = MAX(max_fd, notify_pipe[0]); 805 806 server_init_dispatch(); 807 808 for (;;) { 809 process_buffered_input_packets(); 810 811 rekeying = (xxx_kex != NULL && !xxx_kex->done); 812 813 if (!rekeying && packet_not_very_much_data_to_write()) 814 channel_output_poll(); 815 wait_until_can_do_something(&readset, &writeset, &max_fd, 816 &nalloc, 0); 817 818 if (received_sigterm) { 819 logit("Exiting on signal %d", received_sigterm); 820 /* Clean up sessions, utmp, etc. */ 821 cleanup_exit(255); 822 } 823 824 collect_children(); 825 if (!rekeying) { 826 channel_after_select(readset, writeset); 827 if (packet_need_rekeying()) { 828 debug("need rekeying"); 829 xxx_kex->done = 0; 830 kex_send_kexinit(xxx_kex); 831 } 832 } 833 process_input(readset); 834 if (connection_closed) 835 break; 836 process_output(writeset); 837 } 838 collect_children(); 839 840 if (readset) 841 xfree(readset); 842 if (writeset) 843 xfree(writeset); 844 845 /* free all channels, no more reads and writes */ 846 channel_free_all(); 847 848 /* free remaining sessions, e.g. remove wtmp entries */ 849 session_destroy_all(NULL); 850 } 851 852 static void 853 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 854 { 855 debug("Got %d/%u for keepalive", type, seq); 856 /* 857 * reset timeout, since we got a sane answer from the client. 858 * even if this was generated by something other than 859 * the bogus CHANNEL_REQUEST we send for keepalives. 860 */ 861 keep_alive_timeouts = 0; 862 } 863 864 static void 865 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 866 { 867 char *data; 868 u_int data_len; 869 870 /* Stdin data from the client. Append it to the buffer. */ 871 /* Ignore any data if the client has closed stdin. */ 872 if (fdin == -1) 873 return; 874 data = packet_get_string(&data_len); 875 packet_check_eom(); 876 buffer_append(&stdin_buffer, data, data_len); 877 memset(data, 0, data_len); 878 xfree(data); 879 } 880 881 static void 882 server_input_eof(int type, u_int32_t seq, void *ctxt) 883 { 884 /* 885 * Eof from the client. The stdin descriptor to the 886 * program will be closed when all buffered data has 887 * drained. 888 */ 889 debug("EOF received for stdin."); 890 packet_check_eom(); 891 stdin_eof = 1; 892 } 893 894 static void 895 server_input_window_size(int type, u_int32_t seq, void *ctxt) 896 { 897 u_int row = packet_get_int(); 898 u_int col = packet_get_int(); 899 u_int xpixel = packet_get_int(); 900 u_int ypixel = packet_get_int(); 901 902 debug("Window change received."); 903 packet_check_eom(); 904 if (fdin != -1) 905 pty_change_window_size(fdin, row, col, xpixel, ypixel); 906 } 907 908 static Channel * 909 server_request_direct_tcpip(void) 910 { 911 Channel *c; 912 char *target, *originator; 913 u_short target_port, originator_port; 914 915 target = packet_get_string(NULL); 916 target_port = packet_get_int(); 917 originator = packet_get_string(NULL); 918 originator_port = packet_get_int(); 919 packet_check_eom(); 920 921 debug("server_request_direct_tcpip: originator %s port %d, target %s " 922 "port %d", originator, originator_port, target, target_port); 923 924 /* XXX check permission */ 925 c = channel_connect_to(target, target_port, 926 "direct-tcpip", "direct-tcpip"); 927 928 xfree(originator); 929 xfree(target); 930 931 return c; 932 } 933 934 static Channel * 935 server_request_tun(void) 936 { 937 Channel *c = NULL; 938 int mode, tun; 939 int sock; 940 941 mode = packet_get_int(); 942 switch (mode) { 943 case SSH_TUNMODE_POINTOPOINT: 944 case SSH_TUNMODE_ETHERNET: 945 break; 946 default: 947 packet_send_debug("Unsupported tunnel device mode."); 948 return NULL; 949 } 950 if ((options.permit_tun & mode) == 0) { 951 packet_send_debug("Server has rejected tunnel device " 952 "forwarding"); 953 return NULL; 954 } 955 956 tun = packet_get_int(); 957 if (forced_tun_device != -1) { 958 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 959 goto done; 960 tun = forced_tun_device; 961 } 962 sock = tun_open(tun, mode); 963 if (sock < 0) 964 goto done; 965 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 966 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 967 c->datagram = 1; 968 969 done: 970 if (c == NULL) 971 packet_send_debug("Failed to open the tunnel device."); 972 return c; 973 } 974 975 static Channel * 976 server_request_session(void) 977 { 978 Channel *c; 979 980 debug("input_session_request"); 981 packet_check_eom(); 982 983 if (no_more_sessions) { 984 packet_disconnect("Possible attack: attempt to open a session " 985 "after additional sessions disabled"); 986 } 987 988 /* 989 * A server session has no fd to read or write until a 990 * CHANNEL_REQUEST for a shell is made, so we set the type to 991 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 992 * CHANNEL_REQUEST messages is registered. 993 */ 994 c = channel_new("session", SSH_CHANNEL_LARVAL, 995 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 996 0, "server-session", 1); 997 if (session_open(the_authctxt, c->self) != 1) { 998 debug("session open failed, free channel %d", c->self); 999 channel_free(c); 1000 return NULL; 1001 } 1002 channel_register_cleanup(c->self, session_close_by_channel, 0); 1003 return c; 1004 } 1005 1006 static void 1007 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1008 { 1009 Channel *c = NULL; 1010 char *ctype; 1011 int rchan; 1012 u_int rmaxpack, rwindow, len; 1013 1014 ctype = packet_get_string(&len); 1015 rchan = packet_get_int(); 1016 rwindow = packet_get_int(); 1017 rmaxpack = packet_get_int(); 1018 1019 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1020 ctype, rchan, rwindow, rmaxpack); 1021 1022 if (strcmp(ctype, "session") == 0) { 1023 c = server_request_session(); 1024 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1025 c = server_request_direct_tcpip(); 1026 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1027 c = server_request_tun(); 1028 } 1029 if (c != NULL) { 1030 debug("server_input_channel_open: confirm %s", ctype); 1031 c->remote_id = rchan; 1032 c->remote_window = rwindow; 1033 c->remote_maxpacket = rmaxpack; 1034 if (c->type != SSH_CHANNEL_CONNECTING) { 1035 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1036 packet_put_int(c->remote_id); 1037 packet_put_int(c->self); 1038 packet_put_int(c->local_window); 1039 packet_put_int(c->local_maxpacket); 1040 packet_send(); 1041 } 1042 } else { 1043 debug("server_input_channel_open: failure %s", ctype); 1044 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1045 packet_put_int(rchan); 1046 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1047 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1048 packet_put_cstring("open failed"); 1049 packet_put_cstring(""); 1050 } 1051 packet_send(); 1052 } 1053 xfree(ctype); 1054 } 1055 1056 static void 1057 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1058 { 1059 char *rtype; 1060 int want_reply; 1061 int success = 0, allocated_listen_port = 0; 1062 1063 rtype = packet_get_string(NULL); 1064 want_reply = packet_get_char(); 1065 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1066 1067 /* -R style forwarding */ 1068 if (strcmp(rtype, "tcpip-forward") == 0) { 1069 struct passwd *pw; 1070 char *listen_address; 1071 u_short listen_port; 1072 1073 pw = the_authctxt->pw; 1074 if (pw == NULL || !the_authctxt->valid) 1075 fatal("server_input_global_request: no/invalid user"); 1076 listen_address = packet_get_string(NULL); 1077 listen_port = (u_short)packet_get_int(); 1078 debug("server_input_global_request: tcpip-forward listen %s port %d", 1079 listen_address, listen_port); 1080 1081 /* check permissions */ 1082 if (!options.allow_tcp_forwarding || 1083 no_port_forwarding_flag || 1084 (!want_reply && listen_port == 0) || 1085 (listen_port != 0 && listen_port < IPPORT_RESERVED && 1086 pw->pw_uid != 0)) { 1087 success = 0; 1088 packet_send_debug("Server has disabled port forwarding."); 1089 } else { 1090 /* Start listening on the port */ 1091 success = channel_setup_remote_fwd_listener( 1092 listen_address, listen_port, 1093 &allocated_listen_port, options.gateway_ports); 1094 } 1095 xfree(listen_address); 1096 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1097 char *cancel_address; 1098 u_short cancel_port; 1099 1100 cancel_address = packet_get_string(NULL); 1101 cancel_port = (u_short)packet_get_int(); 1102 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1103 cancel_address, cancel_port); 1104 1105 success = channel_cancel_rport_listener(cancel_address, 1106 cancel_port); 1107 xfree(cancel_address); 1108 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1109 no_more_sessions = 1; 1110 success = 1; 1111 } 1112 if (want_reply) { 1113 packet_start(success ? 1114 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1115 if (success && allocated_listen_port > 0) 1116 packet_put_int(allocated_listen_port); 1117 packet_send(); 1118 packet_write_wait(); 1119 } 1120 xfree(rtype); 1121 } 1122 1123 static void 1124 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1125 { 1126 Channel *c; 1127 int id, reply, success = 0; 1128 char *rtype; 1129 1130 id = packet_get_int(); 1131 rtype = packet_get_string(NULL); 1132 reply = packet_get_char(); 1133 1134 debug("server_input_channel_req: channel %d request %s reply %d", 1135 id, rtype, reply); 1136 1137 if ((c = channel_lookup(id)) == NULL) 1138 packet_disconnect("server_input_channel_req: " 1139 "unknown channel %d", id); 1140 if (!strcmp(rtype, "eow@openssh.com")) { 1141 packet_check_eom(); 1142 chan_rcvd_eow(c); 1143 } else if ((c->type == SSH_CHANNEL_LARVAL || 1144 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1145 success = session_input_channel_req(c, rtype); 1146 if (reply) { 1147 packet_start(success ? 1148 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1149 packet_put_int(c->remote_id); 1150 packet_send(); 1151 } 1152 xfree(rtype); 1153 } 1154 1155 static void 1156 server_init_dispatch_20(void) 1157 { 1158 debug("server_init_dispatch_20"); 1159 dispatch_init(&dispatch_protocol_error); 1160 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1161 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1162 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1163 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1164 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1165 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1166 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1167 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1168 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1169 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1170 /* client_alive */ 1171 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1172 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1173 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1174 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1175 /* rekeying */ 1176 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1177 } 1178 static void 1179 server_init_dispatch_13(void) 1180 { 1181 debug("server_init_dispatch_13"); 1182 dispatch_init(NULL); 1183 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1184 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1185 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1186 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1187 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1188 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1189 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1190 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1191 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1192 } 1193 static void 1194 server_init_dispatch_15(void) 1195 { 1196 server_init_dispatch_13(); 1197 debug("server_init_dispatch_15"); 1198 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1199 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1200 } 1201 static void 1202 server_init_dispatch(void) 1203 { 1204 if (compat20) 1205 server_init_dispatch_20(); 1206 else if (compat13) 1207 server_init_dispatch_13(); 1208 else 1209 server_init_dispatch_15(); 1210 } 1211