1 /* $OpenBSD: serverloop.c,v 1.144 2006/08/03 03:34:42 deraadt Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include "includes.h" 39 40 #include <sys/types.h> 41 #include <sys/param.h> 42 #include <sys/wait.h> 43 #include <sys/socket.h> 44 #ifdef HAVE_SYS_TIME_H 45 # include <sys/time.h> 46 #endif 47 48 #include <netinet/in.h> 49 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <pwd.h> 53 #include <signal.h> 54 #include <string.h> 55 #include <termios.h> 56 #include <unistd.h> 57 #include <stdarg.h> 58 59 #include "xmalloc.h" 60 #include "packet.h" 61 #include "buffer.h" 62 #include "log.h" 63 #include "servconf.h" 64 #include "canohost.h" 65 #include "sshpty.h" 66 #include "channels.h" 67 #include "compat.h" 68 #include "ssh1.h" 69 #include "ssh2.h" 70 #include "key.h" 71 #include "cipher.h" 72 #include "kex.h" 73 #include "hostfile.h" 74 #include "auth.h" 75 #include "session.h" 76 #include "dispatch.h" 77 #include "auth-options.h" 78 #include "serverloop.h" 79 #include "misc.h" 80 81 extern ServerOptions options; 82 83 /* XXX */ 84 extern Kex *xxx_kex; 85 extern Authctxt *the_authctxt; 86 extern int use_privsep; 87 88 static Buffer stdin_buffer; /* Buffer for stdin data. */ 89 static Buffer stdout_buffer; /* Buffer for stdout data. */ 90 static Buffer stderr_buffer; /* Buffer for stderr data. */ 91 static int fdin; /* Descriptor for stdin (for writing) */ 92 static int fdout; /* Descriptor for stdout (for reading); 93 May be same number as fdin. */ 94 static int fderr; /* Descriptor for stderr. May be -1. */ 95 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 96 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 97 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 98 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 99 static int stdin_eof = 0; /* EOF message received from client. */ 100 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 101 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 102 static int fdin_is_tty = 0; /* fdin points to a tty. */ 103 static int connection_in; /* Connection to client (input). */ 104 static int connection_out; /* Connection to client (output). */ 105 static int connection_closed = 0; /* Connection to client closed. */ 106 static u_int buffer_high; /* "Soft" max buffer size. */ 107 static int client_alive_timeouts = 0; 108 109 /* 110 * This SIGCHLD kludge is used to detect when the child exits. The server 111 * will exit after that, as soon as forwarded connections have terminated. 112 */ 113 114 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 115 116 /* Cleanup on signals (!use_privsep case only) */ 117 static volatile sig_atomic_t received_sigterm = 0; 118 119 /* prototypes */ 120 static void server_init_dispatch(void); 121 122 /* 123 * we write to this pipe if a SIGCHLD is caught in order to avoid 124 * the race between select() and child_terminated 125 */ 126 static int notify_pipe[2]; 127 static void 128 notify_setup(void) 129 { 130 if (pipe(notify_pipe) < 0) { 131 error("pipe(notify_pipe) failed %s", strerror(errno)); 132 } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) || 133 (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) { 134 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 135 close(notify_pipe[0]); 136 close(notify_pipe[1]); 137 } else { 138 set_nonblock(notify_pipe[0]); 139 set_nonblock(notify_pipe[1]); 140 return; 141 } 142 notify_pipe[0] = -1; /* read end */ 143 notify_pipe[1] = -1; /* write end */ 144 } 145 static void 146 notify_parent(void) 147 { 148 if (notify_pipe[1] != -1) 149 write(notify_pipe[1], "", 1); 150 } 151 static void 152 notify_prepare(fd_set *readset) 153 { 154 if (notify_pipe[0] != -1) 155 FD_SET(notify_pipe[0], readset); 156 } 157 static void 158 notify_done(fd_set *readset) 159 { 160 char c; 161 162 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 163 while (read(notify_pipe[0], &c, 1) != -1) 164 debug2("notify_done: reading"); 165 } 166 167 /*ARGSUSED*/ 168 static void 169 sigchld_handler(int sig) 170 { 171 int save_errno = errno; 172 child_terminated = 1; 173 #ifndef _UNICOS 174 mysignal(SIGCHLD, sigchld_handler); 175 #endif 176 notify_parent(); 177 errno = save_errno; 178 } 179 180 /*ARGSUSED*/ 181 static void 182 sigterm_handler(int sig) 183 { 184 received_sigterm = sig; 185 } 186 187 /* 188 * Make packets from buffered stderr data, and buffer it for sending 189 * to the client. 190 */ 191 static void 192 make_packets_from_stderr_data(void) 193 { 194 u_int len; 195 196 /* Send buffered stderr data to the client. */ 197 while (buffer_len(&stderr_buffer) > 0 && 198 packet_not_very_much_data_to_write()) { 199 len = buffer_len(&stderr_buffer); 200 if (packet_is_interactive()) { 201 if (len > 512) 202 len = 512; 203 } else { 204 /* Keep the packets at reasonable size. */ 205 if (len > packet_get_maxsize()) 206 len = packet_get_maxsize(); 207 } 208 packet_start(SSH_SMSG_STDERR_DATA); 209 packet_put_string(buffer_ptr(&stderr_buffer), len); 210 packet_send(); 211 buffer_consume(&stderr_buffer, len); 212 stderr_bytes += len; 213 } 214 } 215 216 /* 217 * Make packets from buffered stdout data, and buffer it for sending to the 218 * client. 219 */ 220 static void 221 make_packets_from_stdout_data(void) 222 { 223 u_int len; 224 225 /* Send buffered stdout data to the client. */ 226 while (buffer_len(&stdout_buffer) > 0 && 227 packet_not_very_much_data_to_write()) { 228 len = buffer_len(&stdout_buffer); 229 if (packet_is_interactive()) { 230 if (len > 512) 231 len = 512; 232 } else { 233 /* Keep the packets at reasonable size. */ 234 if (len > packet_get_maxsize()) 235 len = packet_get_maxsize(); 236 } 237 packet_start(SSH_SMSG_STDOUT_DATA); 238 packet_put_string(buffer_ptr(&stdout_buffer), len); 239 packet_send(); 240 buffer_consume(&stdout_buffer, len); 241 stdout_bytes += len; 242 } 243 } 244 245 static void 246 client_alive_check(void) 247 { 248 int channel_id; 249 250 /* timeout, check to see how many we have had */ 251 if (++client_alive_timeouts > options.client_alive_count_max) 252 packet_disconnect("Timeout, your session not responding."); 253 254 /* 255 * send a bogus global/channel request with "wantreply", 256 * we should get back a failure 257 */ 258 if ((channel_id = channel_find_open()) == -1) { 259 packet_start(SSH2_MSG_GLOBAL_REQUEST); 260 packet_put_cstring("keepalive@openssh.com"); 261 packet_put_char(1); /* boolean: want reply */ 262 } else { 263 channel_request_start(channel_id, "keepalive@openssh.com", 1); 264 } 265 packet_send(); 266 } 267 268 /* 269 * Sleep in select() until we can do something. This will initialize the 270 * select masks. Upon return, the masks will indicate which descriptors 271 * have data or can accept data. Optionally, a maximum time can be specified 272 * for the duration of the wait (0 = infinite). 273 */ 274 static void 275 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 276 u_int *nallocp, u_int max_time_milliseconds) 277 { 278 struct timeval tv, *tvp; 279 int ret; 280 int client_alive_scheduled = 0; 281 282 /* 283 * if using client_alive, set the max timeout accordingly, 284 * and indicate that this particular timeout was for client 285 * alive by setting the client_alive_scheduled flag. 286 * 287 * this could be randomized somewhat to make traffic 288 * analysis more difficult, but we're not doing it yet. 289 */ 290 if (compat20 && 291 max_time_milliseconds == 0 && options.client_alive_interval) { 292 client_alive_scheduled = 1; 293 max_time_milliseconds = options.client_alive_interval * 1000; 294 } 295 296 /* Allocate and update select() masks for channel descriptors. */ 297 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0); 298 299 if (compat20) { 300 #if 0 301 /* wrong: bad condition XXX */ 302 if (channel_not_very_much_buffered_data()) 303 #endif 304 FD_SET(connection_in, *readsetp); 305 } else { 306 /* 307 * Read packets from the client unless we have too much 308 * buffered stdin or channel data. 309 */ 310 if (buffer_len(&stdin_buffer) < buffer_high && 311 channel_not_very_much_buffered_data()) 312 FD_SET(connection_in, *readsetp); 313 /* 314 * If there is not too much data already buffered going to 315 * the client, try to get some more data from the program. 316 */ 317 if (packet_not_very_much_data_to_write()) { 318 if (!fdout_eof) 319 FD_SET(fdout, *readsetp); 320 if (!fderr_eof) 321 FD_SET(fderr, *readsetp); 322 } 323 /* 324 * If we have buffered data, try to write some of that data 325 * to the program. 326 */ 327 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 328 FD_SET(fdin, *writesetp); 329 } 330 notify_prepare(*readsetp); 331 332 /* 333 * If we have buffered packet data going to the client, mark that 334 * descriptor. 335 */ 336 if (packet_have_data_to_write()) 337 FD_SET(connection_out, *writesetp); 338 339 /* 340 * If child has terminated and there is enough buffer space to read 341 * from it, then read as much as is available and exit. 342 */ 343 if (child_terminated && packet_not_very_much_data_to_write()) 344 if (max_time_milliseconds == 0 || client_alive_scheduled) 345 max_time_milliseconds = 100; 346 347 if (max_time_milliseconds == 0) 348 tvp = NULL; 349 else { 350 tv.tv_sec = max_time_milliseconds / 1000; 351 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 352 tvp = &tv; 353 } 354 355 /* Wait for something to happen, or the timeout to expire. */ 356 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 357 358 if (ret == -1) { 359 memset(*readsetp, 0, *nallocp); 360 memset(*writesetp, 0, *nallocp); 361 if (errno != EINTR) 362 error("select: %.100s", strerror(errno)); 363 } else if (ret == 0 && client_alive_scheduled) 364 client_alive_check(); 365 366 notify_done(*readsetp); 367 } 368 369 /* 370 * Processes input from the client and the program. Input data is stored 371 * in buffers and processed later. 372 */ 373 static void 374 process_input(fd_set *readset) 375 { 376 int len; 377 char buf[16384]; 378 379 /* Read and buffer any input data from the client. */ 380 if (FD_ISSET(connection_in, readset)) { 381 len = read(connection_in, buf, sizeof(buf)); 382 if (len == 0) { 383 verbose("Connection closed by %.100s", 384 get_remote_ipaddr()); 385 connection_closed = 1; 386 if (compat20) 387 return; 388 cleanup_exit(255); 389 } else if (len < 0) { 390 if (errno != EINTR && errno != EAGAIN) { 391 verbose("Read error from remote host " 392 "%.100s: %.100s", 393 get_remote_ipaddr(), strerror(errno)); 394 cleanup_exit(255); 395 } 396 } else { 397 /* Buffer any received data. */ 398 packet_process_incoming(buf, len); 399 } 400 } 401 if (compat20) 402 return; 403 404 /* Read and buffer any available stdout data from the program. */ 405 if (!fdout_eof && FD_ISSET(fdout, readset)) { 406 errno = 0; 407 len = read(fdout, buf, sizeof(buf)); 408 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 409 /* do nothing */ 410 #ifndef PTY_ZEROREAD 411 } else if (len <= 0) { 412 #else 413 } else if ((!isatty(fdout) && len <= 0) || 414 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) { 415 #endif 416 fdout_eof = 1; 417 } else { 418 buffer_append(&stdout_buffer, buf, len); 419 fdout_bytes += len; 420 } 421 } 422 /* Read and buffer any available stderr data from the program. */ 423 if (!fderr_eof && FD_ISSET(fderr, readset)) { 424 errno = 0; 425 len = read(fderr, buf, sizeof(buf)); 426 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 427 /* do nothing */ 428 #ifndef PTY_ZEROREAD 429 } else if (len <= 0) { 430 #else 431 } else if ((!isatty(fderr) && len <= 0) || 432 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) { 433 #endif 434 fderr_eof = 1; 435 } else { 436 buffer_append(&stderr_buffer, buf, len); 437 } 438 } 439 } 440 441 /* 442 * Sends data from internal buffers to client program stdin. 443 */ 444 static void 445 process_output(fd_set *writeset) 446 { 447 struct termios tio; 448 u_char *data; 449 u_int dlen; 450 int len; 451 452 /* Write buffered data to program stdin. */ 453 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 454 data = buffer_ptr(&stdin_buffer); 455 dlen = buffer_len(&stdin_buffer); 456 len = write(fdin, data, dlen); 457 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 458 /* do nothing */ 459 } else if (len <= 0) { 460 if (fdin != fdout) 461 close(fdin); 462 else 463 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 464 fdin = -1; 465 } else { 466 /* Successful write. */ 467 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 468 tcgetattr(fdin, &tio) == 0 && 469 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 470 /* 471 * Simulate echo to reduce the impact of 472 * traffic analysis 473 */ 474 packet_send_ignore(len); 475 packet_send(); 476 } 477 /* Consume the data from the buffer. */ 478 buffer_consume(&stdin_buffer, len); 479 /* Update the count of bytes written to the program. */ 480 stdin_bytes += len; 481 } 482 } 483 /* Send any buffered packet data to the client. */ 484 if (FD_ISSET(connection_out, writeset)) 485 packet_write_poll(); 486 } 487 488 /* 489 * Wait until all buffered output has been sent to the client. 490 * This is used when the program terminates. 491 */ 492 static void 493 drain_output(void) 494 { 495 /* Send any buffered stdout data to the client. */ 496 if (buffer_len(&stdout_buffer) > 0) { 497 packet_start(SSH_SMSG_STDOUT_DATA); 498 packet_put_string(buffer_ptr(&stdout_buffer), 499 buffer_len(&stdout_buffer)); 500 packet_send(); 501 /* Update the count of sent bytes. */ 502 stdout_bytes += buffer_len(&stdout_buffer); 503 } 504 /* Send any buffered stderr data to the client. */ 505 if (buffer_len(&stderr_buffer) > 0) { 506 packet_start(SSH_SMSG_STDERR_DATA); 507 packet_put_string(buffer_ptr(&stderr_buffer), 508 buffer_len(&stderr_buffer)); 509 packet_send(); 510 /* Update the count of sent bytes. */ 511 stderr_bytes += buffer_len(&stderr_buffer); 512 } 513 /* Wait until all buffered data has been written to the client. */ 514 packet_write_wait(); 515 } 516 517 static void 518 process_buffered_input_packets(void) 519 { 520 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 521 } 522 523 /* 524 * Performs the interactive session. This handles data transmission between 525 * the client and the program. Note that the notion of stdin, stdout, and 526 * stderr in this function is sort of reversed: this function writes to 527 * stdin (of the child program), and reads from stdout and stderr (of the 528 * child program). 529 */ 530 void 531 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 532 { 533 fd_set *readset = NULL, *writeset = NULL; 534 int max_fd = 0; 535 u_int nalloc = 0; 536 int wait_status; /* Status returned by wait(). */ 537 pid_t wait_pid; /* pid returned by wait(). */ 538 int waiting_termination = 0; /* Have displayed waiting close message. */ 539 u_int max_time_milliseconds; 540 u_int previous_stdout_buffer_bytes; 541 u_int stdout_buffer_bytes; 542 int type; 543 544 debug("Entering interactive session."); 545 546 /* Initialize the SIGCHLD kludge. */ 547 child_terminated = 0; 548 mysignal(SIGCHLD, sigchld_handler); 549 550 if (!use_privsep) { 551 signal(SIGTERM, sigterm_handler); 552 signal(SIGINT, sigterm_handler); 553 signal(SIGQUIT, sigterm_handler); 554 } 555 556 /* Initialize our global variables. */ 557 fdin = fdin_arg; 558 fdout = fdout_arg; 559 fderr = fderr_arg; 560 561 /* nonblocking IO */ 562 set_nonblock(fdin); 563 set_nonblock(fdout); 564 /* we don't have stderr for interactive terminal sessions, see below */ 565 if (fderr != -1) 566 set_nonblock(fderr); 567 568 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 569 fdin_is_tty = 1; 570 571 connection_in = packet_get_connection_in(); 572 connection_out = packet_get_connection_out(); 573 574 notify_setup(); 575 576 previous_stdout_buffer_bytes = 0; 577 578 /* Set approximate I/O buffer size. */ 579 if (packet_is_interactive()) 580 buffer_high = 4096; 581 else 582 buffer_high = 64 * 1024; 583 584 #if 0 585 /* Initialize max_fd to the maximum of the known file descriptors. */ 586 max_fd = MAX(connection_in, connection_out); 587 max_fd = MAX(max_fd, fdin); 588 max_fd = MAX(max_fd, fdout); 589 if (fderr != -1) 590 max_fd = MAX(max_fd, fderr); 591 #endif 592 593 /* Initialize Initialize buffers. */ 594 buffer_init(&stdin_buffer); 595 buffer_init(&stdout_buffer); 596 buffer_init(&stderr_buffer); 597 598 /* 599 * If we have no separate fderr (which is the case when we have a pty 600 * - there we cannot make difference between data sent to stdout and 601 * stderr), indicate that we have seen an EOF from stderr. This way 602 * we don't need to check the descriptor everywhere. 603 */ 604 if (fderr == -1) 605 fderr_eof = 1; 606 607 server_init_dispatch(); 608 609 /* Main loop of the server for the interactive session mode. */ 610 for (;;) { 611 612 /* Process buffered packets from the client. */ 613 process_buffered_input_packets(); 614 615 /* 616 * If we have received eof, and there is no more pending 617 * input data, cause a real eof by closing fdin. 618 */ 619 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 620 if (fdin != fdout) 621 close(fdin); 622 else 623 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 624 fdin = -1; 625 } 626 /* Make packets from buffered stderr data to send to the client. */ 627 make_packets_from_stderr_data(); 628 629 /* 630 * Make packets from buffered stdout data to send to the 631 * client. If there is very little to send, this arranges to 632 * not send them now, but to wait a short while to see if we 633 * are getting more data. This is necessary, as some systems 634 * wake up readers from a pty after each separate character. 635 */ 636 max_time_milliseconds = 0; 637 stdout_buffer_bytes = buffer_len(&stdout_buffer); 638 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 639 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 640 /* try again after a while */ 641 max_time_milliseconds = 10; 642 } else { 643 /* Send it now. */ 644 make_packets_from_stdout_data(); 645 } 646 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 647 648 /* Send channel data to the client. */ 649 if (packet_not_very_much_data_to_write()) 650 channel_output_poll(); 651 652 /* 653 * Bail out of the loop if the program has closed its output 654 * descriptors, and we have no more data to send to the 655 * client, and there is no pending buffered data. 656 */ 657 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 658 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 659 if (!channel_still_open()) 660 break; 661 if (!waiting_termination) { 662 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 663 char *cp; 664 waiting_termination = 1; 665 buffer_append(&stderr_buffer, s, strlen(s)); 666 667 /* Display list of open channels. */ 668 cp = channel_open_message(); 669 buffer_append(&stderr_buffer, cp, strlen(cp)); 670 xfree(cp); 671 } 672 } 673 max_fd = MAX(connection_in, connection_out); 674 max_fd = MAX(max_fd, fdin); 675 max_fd = MAX(max_fd, fdout); 676 max_fd = MAX(max_fd, fderr); 677 max_fd = MAX(max_fd, notify_pipe[0]); 678 679 /* Sleep in select() until we can do something. */ 680 wait_until_can_do_something(&readset, &writeset, &max_fd, 681 &nalloc, max_time_milliseconds); 682 683 if (received_sigterm) { 684 logit("Exiting on signal %d", received_sigterm); 685 /* Clean up sessions, utmp, etc. */ 686 cleanup_exit(255); 687 } 688 689 /* Process any channel events. */ 690 channel_after_select(readset, writeset); 691 692 /* Process input from the client and from program stdout/stderr. */ 693 process_input(readset); 694 695 /* Process output to the client and to program stdin. */ 696 process_output(writeset); 697 } 698 if (readset) 699 xfree(readset); 700 if (writeset) 701 xfree(writeset); 702 703 /* Cleanup and termination code. */ 704 705 /* Wait until all output has been sent to the client. */ 706 drain_output(); 707 708 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 709 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 710 711 /* Free and clear the buffers. */ 712 buffer_free(&stdin_buffer); 713 buffer_free(&stdout_buffer); 714 buffer_free(&stderr_buffer); 715 716 /* Close the file descriptors. */ 717 if (fdout != -1) 718 close(fdout); 719 fdout = -1; 720 fdout_eof = 1; 721 if (fderr != -1) 722 close(fderr); 723 fderr = -1; 724 fderr_eof = 1; 725 if (fdin != -1) 726 close(fdin); 727 fdin = -1; 728 729 channel_free_all(); 730 731 /* We no longer want our SIGCHLD handler to be called. */ 732 mysignal(SIGCHLD, SIG_DFL); 733 734 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 735 if (errno != EINTR) 736 packet_disconnect("wait: %.100s", strerror(errno)); 737 if (wait_pid != pid) 738 error("Strange, wait returned pid %ld, expected %ld", 739 (long)wait_pid, (long)pid); 740 741 /* Check if it exited normally. */ 742 if (WIFEXITED(wait_status)) { 743 /* Yes, normal exit. Get exit status and send it to the client. */ 744 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 745 packet_start(SSH_SMSG_EXITSTATUS); 746 packet_put_int(WEXITSTATUS(wait_status)); 747 packet_send(); 748 packet_write_wait(); 749 750 /* 751 * Wait for exit confirmation. Note that there might be 752 * other packets coming before it; however, the program has 753 * already died so we just ignore them. The client is 754 * supposed to respond with the confirmation when it receives 755 * the exit status. 756 */ 757 do { 758 type = packet_read(); 759 } 760 while (type != SSH_CMSG_EXIT_CONFIRMATION); 761 762 debug("Received exit confirmation."); 763 return; 764 } 765 /* Check if the program terminated due to a signal. */ 766 if (WIFSIGNALED(wait_status)) 767 packet_disconnect("Command terminated on signal %d.", 768 WTERMSIG(wait_status)); 769 770 /* Some weird exit cause. Just exit. */ 771 packet_disconnect("wait returned status %04x.", wait_status); 772 /* NOTREACHED */ 773 } 774 775 static void 776 collect_children(void) 777 { 778 pid_t pid; 779 sigset_t oset, nset; 780 int status; 781 782 /* block SIGCHLD while we check for dead children */ 783 sigemptyset(&nset); 784 sigaddset(&nset, SIGCHLD); 785 sigprocmask(SIG_BLOCK, &nset, &oset); 786 if (child_terminated) { 787 debug("Received SIGCHLD."); 788 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 789 (pid < 0 && errno == EINTR)) 790 if (pid > 0) 791 session_close_by_pid(pid, status); 792 child_terminated = 0; 793 } 794 sigprocmask(SIG_SETMASK, &oset, NULL); 795 } 796 797 void 798 server_loop2(Authctxt *authctxt) 799 { 800 fd_set *readset = NULL, *writeset = NULL; 801 int rekeying = 0, max_fd, nalloc = 0; 802 803 debug("Entering interactive session for SSH2."); 804 805 mysignal(SIGCHLD, sigchld_handler); 806 child_terminated = 0; 807 connection_in = packet_get_connection_in(); 808 connection_out = packet_get_connection_out(); 809 810 if (!use_privsep) { 811 signal(SIGTERM, sigterm_handler); 812 signal(SIGINT, sigterm_handler); 813 signal(SIGQUIT, sigterm_handler); 814 } 815 816 notify_setup(); 817 818 max_fd = MAX(connection_in, connection_out); 819 max_fd = MAX(max_fd, notify_pipe[0]); 820 821 server_init_dispatch(); 822 823 for (;;) { 824 process_buffered_input_packets(); 825 826 rekeying = (xxx_kex != NULL && !xxx_kex->done); 827 828 if (!rekeying && packet_not_very_much_data_to_write()) 829 channel_output_poll(); 830 wait_until_can_do_something(&readset, &writeset, &max_fd, 831 &nalloc, 0); 832 833 if (received_sigterm) { 834 logit("Exiting on signal %d", received_sigterm); 835 /* Clean up sessions, utmp, etc. */ 836 cleanup_exit(255); 837 } 838 839 collect_children(); 840 if (!rekeying) { 841 channel_after_select(readset, writeset); 842 if (packet_need_rekeying()) { 843 debug("need rekeying"); 844 xxx_kex->done = 0; 845 kex_send_kexinit(xxx_kex); 846 } 847 } 848 process_input(readset); 849 if (connection_closed) 850 break; 851 process_output(writeset); 852 } 853 collect_children(); 854 855 if (readset) 856 xfree(readset); 857 if (writeset) 858 xfree(writeset); 859 860 /* free all channels, no more reads and writes */ 861 channel_free_all(); 862 863 /* free remaining sessions, e.g. remove wtmp entries */ 864 session_destroy_all(NULL); 865 } 866 867 static void 868 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 869 { 870 debug("Got %d/%u for keepalive", type, seq); 871 /* 872 * reset timeout, since we got a sane answer from the client. 873 * even if this was generated by something other than 874 * the bogus CHANNEL_REQUEST we send for keepalives. 875 */ 876 client_alive_timeouts = 0; 877 } 878 879 static void 880 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 881 { 882 char *data; 883 u_int data_len; 884 885 /* Stdin data from the client. Append it to the buffer. */ 886 /* Ignore any data if the client has closed stdin. */ 887 if (fdin == -1) 888 return; 889 data = packet_get_string(&data_len); 890 packet_check_eom(); 891 buffer_append(&stdin_buffer, data, data_len); 892 memset(data, 0, data_len); 893 xfree(data); 894 } 895 896 static void 897 server_input_eof(int type, u_int32_t seq, void *ctxt) 898 { 899 /* 900 * Eof from the client. The stdin descriptor to the 901 * program will be closed when all buffered data has 902 * drained. 903 */ 904 debug("EOF received for stdin."); 905 packet_check_eom(); 906 stdin_eof = 1; 907 } 908 909 static void 910 server_input_window_size(int type, u_int32_t seq, void *ctxt) 911 { 912 u_int row = packet_get_int(); 913 u_int col = packet_get_int(); 914 u_int xpixel = packet_get_int(); 915 u_int ypixel = packet_get_int(); 916 917 debug("Window change received."); 918 packet_check_eom(); 919 if (fdin != -1) 920 pty_change_window_size(fdin, row, col, xpixel, ypixel); 921 } 922 923 static Channel * 924 server_request_direct_tcpip(void) 925 { 926 Channel *c; 927 int sock; 928 char *target, *originator; 929 int target_port, originator_port; 930 931 target = packet_get_string(NULL); 932 target_port = packet_get_int(); 933 originator = packet_get_string(NULL); 934 originator_port = packet_get_int(); 935 packet_check_eom(); 936 937 debug("server_request_direct_tcpip: originator %s port %d, target %s port %d", 938 originator, originator_port, target, target_port); 939 940 /* XXX check permission */ 941 sock = channel_connect_to(target, target_port); 942 xfree(target); 943 xfree(originator); 944 if (sock < 0) 945 return NULL; 946 c = channel_new("direct-tcpip", SSH_CHANNEL_CONNECTING, 947 sock, sock, -1, CHAN_TCP_WINDOW_DEFAULT, 948 CHAN_TCP_PACKET_DEFAULT, 0, "direct-tcpip", 1); 949 return c; 950 } 951 952 static Channel * 953 server_request_tun(void) 954 { 955 Channel *c = NULL; 956 int mode, tun; 957 int sock; 958 959 mode = packet_get_int(); 960 switch (mode) { 961 case SSH_TUNMODE_POINTOPOINT: 962 case SSH_TUNMODE_ETHERNET: 963 break; 964 default: 965 packet_send_debug("Unsupported tunnel device mode."); 966 return NULL; 967 } 968 if ((options.permit_tun & mode) == 0) { 969 packet_send_debug("Server has rejected tunnel device " 970 "forwarding"); 971 return NULL; 972 } 973 974 tun = packet_get_int(); 975 if (forced_tun_device != -1) { 976 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 977 goto done; 978 tun = forced_tun_device; 979 } 980 sock = tun_open(tun, mode); 981 if (sock < 0) 982 goto done; 983 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 984 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 985 c->datagram = 1; 986 #if defined(SSH_TUN_FILTER) 987 if (mode == SSH_TUNMODE_POINTOPOINT) 988 channel_register_filter(c->self, sys_tun_infilter, 989 sys_tun_outfilter); 990 #endif 991 992 done: 993 if (c == NULL) 994 packet_send_debug("Failed to open the tunnel device."); 995 return c; 996 } 997 998 static Channel * 999 server_request_session(void) 1000 { 1001 Channel *c; 1002 1003 debug("input_session_request"); 1004 packet_check_eom(); 1005 /* 1006 * A server session has no fd to read or write until a 1007 * CHANNEL_REQUEST for a shell is made, so we set the type to 1008 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1009 * CHANNEL_REQUEST messages is registered. 1010 */ 1011 c = channel_new("session", SSH_CHANNEL_LARVAL, 1012 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1013 0, "server-session", 1); 1014 if (session_open(the_authctxt, c->self) != 1) { 1015 debug("session open failed, free channel %d", c->self); 1016 channel_free(c); 1017 return NULL; 1018 } 1019 channel_register_cleanup(c->self, session_close_by_channel, 0); 1020 return c; 1021 } 1022 1023 static void 1024 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1025 { 1026 Channel *c = NULL; 1027 char *ctype; 1028 int rchan; 1029 u_int rmaxpack, rwindow, len; 1030 1031 ctype = packet_get_string(&len); 1032 rchan = packet_get_int(); 1033 rwindow = packet_get_int(); 1034 rmaxpack = packet_get_int(); 1035 1036 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1037 ctype, rchan, rwindow, rmaxpack); 1038 1039 if (strcmp(ctype, "session") == 0) { 1040 c = server_request_session(); 1041 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1042 c = server_request_direct_tcpip(); 1043 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1044 c = server_request_tun(); 1045 } 1046 if (c != NULL) { 1047 debug("server_input_channel_open: confirm %s", ctype); 1048 c->remote_id = rchan; 1049 c->remote_window = rwindow; 1050 c->remote_maxpacket = rmaxpack; 1051 if (c->type != SSH_CHANNEL_CONNECTING) { 1052 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1053 packet_put_int(c->remote_id); 1054 packet_put_int(c->self); 1055 packet_put_int(c->local_window); 1056 packet_put_int(c->local_maxpacket); 1057 packet_send(); 1058 } 1059 } else { 1060 debug("server_input_channel_open: failure %s", ctype); 1061 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1062 packet_put_int(rchan); 1063 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1064 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1065 packet_put_cstring("open failed"); 1066 packet_put_cstring(""); 1067 } 1068 packet_send(); 1069 } 1070 xfree(ctype); 1071 } 1072 1073 static void 1074 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1075 { 1076 char *rtype; 1077 int want_reply; 1078 int success = 0; 1079 1080 rtype = packet_get_string(NULL); 1081 want_reply = packet_get_char(); 1082 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1083 1084 /* -R style forwarding */ 1085 if (strcmp(rtype, "tcpip-forward") == 0) { 1086 struct passwd *pw; 1087 char *listen_address; 1088 u_short listen_port; 1089 1090 pw = the_authctxt->pw; 1091 if (pw == NULL || !the_authctxt->valid) 1092 fatal("server_input_global_request: no/invalid user"); 1093 listen_address = packet_get_string(NULL); 1094 listen_port = (u_short)packet_get_int(); 1095 debug("server_input_global_request: tcpip-forward listen %s port %d", 1096 listen_address, listen_port); 1097 1098 /* check permissions */ 1099 if (!options.allow_tcp_forwarding || 1100 no_port_forwarding_flag 1101 #ifndef NO_IPPORT_RESERVED_CONCEPT 1102 || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0) 1103 #endif 1104 ) { 1105 success = 0; 1106 packet_send_debug("Server has disabled port forwarding."); 1107 } else { 1108 /* Start listening on the port */ 1109 success = channel_setup_remote_fwd_listener( 1110 listen_address, listen_port, options.gateway_ports); 1111 } 1112 xfree(listen_address); 1113 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1114 char *cancel_address; 1115 u_short cancel_port; 1116 1117 cancel_address = packet_get_string(NULL); 1118 cancel_port = (u_short)packet_get_int(); 1119 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1120 cancel_address, cancel_port); 1121 1122 success = channel_cancel_rport_listener(cancel_address, 1123 cancel_port); 1124 xfree(cancel_address); 1125 } 1126 if (want_reply) { 1127 packet_start(success ? 1128 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1129 packet_send(); 1130 packet_write_wait(); 1131 } 1132 xfree(rtype); 1133 } 1134 1135 static void 1136 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1137 { 1138 Channel *c; 1139 int id, reply, success = 0; 1140 char *rtype; 1141 1142 id = packet_get_int(); 1143 rtype = packet_get_string(NULL); 1144 reply = packet_get_char(); 1145 1146 debug("server_input_channel_req: channel %d request %s reply %d", 1147 id, rtype, reply); 1148 1149 if ((c = channel_lookup(id)) == NULL) 1150 packet_disconnect("server_input_channel_req: " 1151 "unknown channel %d", id); 1152 if (c->type == SSH_CHANNEL_LARVAL || c->type == SSH_CHANNEL_OPEN) 1153 success = session_input_channel_req(c, rtype); 1154 if (reply) { 1155 packet_start(success ? 1156 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1157 packet_put_int(c->remote_id); 1158 packet_send(); 1159 } 1160 xfree(rtype); 1161 } 1162 1163 static void 1164 server_init_dispatch_20(void) 1165 { 1166 debug("server_init_dispatch_20"); 1167 dispatch_init(&dispatch_protocol_error); 1168 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1169 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1170 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1171 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1172 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1173 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1174 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1175 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1176 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1177 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1178 /* client_alive */ 1179 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1180 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1181 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1182 /* rekeying */ 1183 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1184 } 1185 static void 1186 server_init_dispatch_13(void) 1187 { 1188 debug("server_init_dispatch_13"); 1189 dispatch_init(NULL); 1190 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1191 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1192 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1193 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1194 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1195 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1196 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1197 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1198 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1199 } 1200 static void 1201 server_init_dispatch_15(void) 1202 { 1203 server_init_dispatch_13(); 1204 debug("server_init_dispatch_15"); 1205 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1206 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1207 } 1208 static void 1209 server_init_dispatch(void) 1210 { 1211 if (compat20) 1212 server_init_dispatch_20(); 1213 else if (compat13) 1214 server_init_dispatch_13(); 1215 else 1216 server_init_dispatch_15(); 1217 } 1218