1 /* $OpenBSD: serverloop.c,v 1.160 2011/05/15 08:09:01 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo (at) 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 "openbsd-compat/sys-queue.h" 60 #include "xmalloc.h" 61 #include "packet.h" 62 #include "buffer.h" 63 #include "log.h" 64 #include "servconf.h" 65 #include "canohost.h" 66 #include "sshpty.h" 67 #include "channels.h" 68 #include "compat.h" 69 #include "ssh1.h" 70 #include "ssh2.h" 71 #include "key.h" 72 #include "cipher.h" 73 #include "kex.h" 74 #include "hostfile.h" 75 #include "auth.h" 76 #include "session.h" 77 #include "dispatch.h" 78 #include "auth-options.h" 79 #include "serverloop.h" 80 #include "misc.h" 81 #include "roaming.h" 82 83 extern ServerOptions options; 84 85 /* XXX */ 86 extern Kex *xxx_kex; 87 extern Authctxt *the_authctxt; 88 extern int use_privsep; 89 90 static Buffer stdin_buffer; /* Buffer for stdin data. */ 91 static Buffer stdout_buffer; /* Buffer for stdout data. */ 92 static Buffer stderr_buffer; /* Buffer for stderr data. */ 93 static int fdin; /* Descriptor for stdin (for writing) */ 94 static int fdout; /* Descriptor for stdout (for reading); 95 May be same number as fdin. */ 96 static int fderr; /* Descriptor for stderr. May be -1. */ 97 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 98 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 99 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 100 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 101 static int stdin_eof = 0; /* EOF message received from client. */ 102 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 103 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 104 static int fdin_is_tty = 0; /* fdin points to a tty. */ 105 static int connection_in; /* Connection to client (input). */ 106 static int connection_out; /* Connection to client (output). */ 107 static int connection_closed = 0; /* Connection to client closed. */ 108 static u_int buffer_high; /* "Soft" max buffer size. */ 109 static int no_more_sessions = 0; /* Disallow further sessions. */ 110 111 /* 112 * This SIGCHLD kludge is used to detect when the child exits. The server 113 * will exit after that, as soon as forwarded connections have terminated. 114 */ 115 116 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 117 118 /* Cleanup on signals (!use_privsep case only) */ 119 static volatile sig_atomic_t received_sigterm = 0; 120 121 /* prototypes */ 122 static void server_init_dispatch(void); 123 124 /* 125 * we write to this pipe if a SIGCHLD is caught in order to avoid 126 * the race between select() and child_terminated 127 */ 128 static int notify_pipe[2]; 129 static void 130 notify_setup(void) 131 { 132 if (pipe(notify_pipe) < 0) { 133 error("pipe(notify_pipe) failed %s", strerror(errno)); 134 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 135 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 136 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 137 close(notify_pipe[0]); 138 close(notify_pipe[1]); 139 } else { 140 set_nonblock(notify_pipe[0]); 141 set_nonblock(notify_pipe[1]); 142 return; 143 } 144 notify_pipe[0] = -1; /* read end */ 145 notify_pipe[1] = -1; /* write end */ 146 } 147 static void 148 notify_parent(void) 149 { 150 if (notify_pipe[1] != -1) 151 write(notify_pipe[1], "", 1); 152 } 153 static void 154 notify_prepare(fd_set *readset) 155 { 156 if (notify_pipe[0] != -1) 157 FD_SET(notify_pipe[0], readset); 158 } 159 static void 160 notify_done(fd_set *readset) 161 { 162 char c; 163 164 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 165 while (read(notify_pipe[0], &c, 1) != -1) 166 debug2("notify_done: reading"); 167 } 168 169 /*ARGSUSED*/ 170 static void 171 sigchld_handler(int sig) 172 { 173 int save_errno = errno; 174 child_terminated = 1; 175 #ifndef _UNICOS 176 mysignal(SIGCHLD, sigchld_handler); 177 #endif 178 notify_parent(); 179 errno = save_errno; 180 } 181 182 /*ARGSUSED*/ 183 static void 184 sigterm_handler(int sig) 185 { 186 received_sigterm = sig; 187 } 188 189 /* 190 * Make packets from buffered stderr data, and buffer it for sending 191 * to the client. 192 */ 193 static void 194 make_packets_from_stderr_data(void) 195 { 196 u_int len; 197 198 /* Send buffered stderr data to the client. */ 199 while (buffer_len(&stderr_buffer) > 0 && 200 packet_not_very_much_data_to_write()) { 201 len = buffer_len(&stderr_buffer); 202 if (packet_is_interactive()) { 203 if (len > 512) 204 len = 512; 205 } else { 206 /* Keep the packets at reasonable size. */ 207 if (len > packet_get_maxsize()) 208 len = packet_get_maxsize(); 209 } 210 packet_start(SSH_SMSG_STDERR_DATA); 211 packet_put_string(buffer_ptr(&stderr_buffer), len); 212 packet_send(); 213 buffer_consume(&stderr_buffer, len); 214 stderr_bytes += len; 215 } 216 } 217 218 /* 219 * Make packets from buffered stdout data, and buffer it for sending to the 220 * client. 221 */ 222 static void 223 make_packets_from_stdout_data(void) 224 { 225 u_int len; 226 227 /* Send buffered stdout data to the client. */ 228 while (buffer_len(&stdout_buffer) > 0 && 229 packet_not_very_much_data_to_write()) { 230 len = buffer_len(&stdout_buffer); 231 if (packet_is_interactive()) { 232 if (len > 512) 233 len = 512; 234 } else { 235 /* Keep the packets at reasonable size. */ 236 if (len > packet_get_maxsize()) 237 len = packet_get_maxsize(); 238 } 239 packet_start(SSH_SMSG_STDOUT_DATA); 240 packet_put_string(buffer_ptr(&stdout_buffer), len); 241 packet_send(); 242 buffer_consume(&stdout_buffer, len); 243 stdout_bytes += len; 244 } 245 } 246 247 static void 248 client_alive_check(void) 249 { 250 int channel_id; 251 252 /* timeout, check to see how many we have had */ 253 if (packet_inc_alive_timeouts() > options.client_alive_count_max) { 254 logit("Timeout, client not responding."); 255 cleanup_exit(255); 256 } 257 258 /* 259 * send a bogus global/channel request with "wantreply", 260 * we should get back a failure 261 */ 262 if ((channel_id = channel_find_open()) == -1) { 263 packet_start(SSH2_MSG_GLOBAL_REQUEST); 264 packet_put_cstring("keepalive (at) openssh.com"); 265 packet_put_char(1); /* boolean: want reply */ 266 } else { 267 channel_request_start(channel_id, "keepalive (at) openssh.com", 1); 268 } 269 packet_send(); 270 } 271 272 /* 273 * Sleep in select() until we can do something. This will initialize the 274 * select masks. Upon return, the masks will indicate which descriptors 275 * have data or can accept data. Optionally, a maximum time can be specified 276 * for the duration of the wait (0 = infinite). 277 */ 278 static void 279 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 280 u_int *nallocp, u_int max_time_milliseconds) 281 { 282 struct timeval tv, *tvp; 283 int ret; 284 int client_alive_scheduled = 0; 285 int program_alive_scheduled = 0; 286 287 /* 288 * if using client_alive, set the max timeout accordingly, 289 * and indicate that this particular timeout was for client 290 * alive by setting the client_alive_scheduled flag. 291 * 292 * this could be randomized somewhat to make traffic 293 * analysis more difficult, but we're not doing it yet. 294 */ 295 if (compat20 && 296 max_time_milliseconds == 0 && options.client_alive_interval) { 297 client_alive_scheduled = 1; 298 max_time_milliseconds = options.client_alive_interval * 1000; 299 } 300 301 /* Allocate and update select() masks for channel descriptors. */ 302 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0); 303 304 if (compat20) { 305 #if 0 306 /* wrong: bad condition XXX */ 307 if (channel_not_very_much_buffered_data()) 308 #endif 309 FD_SET(connection_in, *readsetp); 310 } else { 311 /* 312 * Read packets from the client unless we have too much 313 * buffered stdin or channel data. 314 */ 315 if (buffer_len(&stdin_buffer) < buffer_high && 316 channel_not_very_much_buffered_data()) 317 FD_SET(connection_in, *readsetp); 318 /* 319 * If there is not too much data already buffered going to 320 * the client, try to get some more data from the program. 321 */ 322 if (packet_not_very_much_data_to_write()) { 323 program_alive_scheduled = child_terminated; 324 if (!fdout_eof) 325 FD_SET(fdout, *readsetp); 326 if (!fderr_eof) 327 FD_SET(fderr, *readsetp); 328 } 329 /* 330 * If we have buffered data, try to write some of that data 331 * to the program. 332 */ 333 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 334 FD_SET(fdin, *writesetp); 335 } 336 notify_prepare(*readsetp); 337 338 /* 339 * If we have buffered packet data going to the client, mark that 340 * descriptor. 341 */ 342 if (packet_have_data_to_write()) 343 FD_SET(connection_out, *writesetp); 344 345 /* 346 * If child has terminated and there is enough buffer space to read 347 * from it, then read as much as is available and exit. 348 */ 349 if (child_terminated && packet_not_very_much_data_to_write()) 350 if (max_time_milliseconds == 0 || client_alive_scheduled) 351 max_time_milliseconds = 100; 352 353 if (max_time_milliseconds == 0) 354 tvp = NULL; 355 else { 356 tv.tv_sec = max_time_milliseconds / 1000; 357 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 358 tvp = &tv; 359 } 360 361 /* Wait for something to happen, or the timeout to expire. */ 362 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 363 364 if (ret == -1) { 365 memset(*readsetp, 0, *nallocp); 366 memset(*writesetp, 0, *nallocp); 367 if (errno != EINTR) 368 error("select: %.100s", strerror(errno)); 369 } else { 370 if (ret == 0 && client_alive_scheduled) 371 client_alive_check(); 372 if (!compat20 && program_alive_scheduled && fdin_is_tty) { 373 if (!fdout_eof) 374 FD_SET(fdout, *readsetp); 375 if (!fderr_eof) 376 FD_SET(fderr, *readsetp); 377 } 378 } 379 380 notify_done(*readsetp); 381 } 382 383 /* 384 * Processes input from the client and the program. Input data is stored 385 * in buffers and processed later. 386 */ 387 static void 388 process_input(fd_set *readset) 389 { 390 int len; 391 char buf[16384]; 392 393 /* Read and buffer any input data from the client. */ 394 if (FD_ISSET(connection_in, readset)) { 395 int cont = 0; 396 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 397 if (len == 0) { 398 if (cont) 399 return; 400 verbose("Connection closed by %.100s", 401 get_remote_ipaddr()); 402 connection_closed = 1; 403 if (compat20) 404 return; 405 cleanup_exit(255); 406 } else if (len < 0) { 407 if (errno != EINTR && errno != EAGAIN && 408 errno != EWOULDBLOCK) { 409 verbose("Read error from remote host " 410 "%.100s: %.100s", 411 get_remote_ipaddr(), strerror(errno)); 412 cleanup_exit(255); 413 } 414 } else { 415 /* Buffer any received data. */ 416 packet_process_incoming(buf, len); 417 } 418 } 419 if (compat20) 420 return; 421 422 /* Read and buffer any available stdout data from the program. */ 423 if (!fdout_eof && FD_ISSET(fdout, readset)) { 424 errno = 0; 425 len = read(fdout, buf, sizeof(buf)); 426 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 427 errno == EWOULDBLOCK) && !child_terminated))) { 428 /* do nothing */ 429 #ifndef PTY_ZEROREAD 430 } else if (len <= 0) { 431 #else 432 } else if ((!isatty(fdout) && len <= 0) || 433 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) { 434 #endif 435 fdout_eof = 1; 436 } else { 437 buffer_append(&stdout_buffer, buf, len); 438 fdout_bytes += len; 439 } 440 } 441 /* Read and buffer any available stderr data from the program. */ 442 if (!fderr_eof && FD_ISSET(fderr, readset)) { 443 errno = 0; 444 len = read(fderr, buf, sizeof(buf)); 445 if (len < 0 && (errno == EINTR || ((errno == EAGAIN || 446 errno == EWOULDBLOCK) && !child_terminated))) { 447 /* do nothing */ 448 #ifndef PTY_ZEROREAD 449 } else if (len <= 0) { 450 #else 451 } else if ((!isatty(fderr) && len <= 0) || 452 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) { 453 #endif 454 fderr_eof = 1; 455 } else { 456 buffer_append(&stderr_buffer, buf, len); 457 } 458 } 459 } 460 461 /* 462 * Sends data from internal buffers to client program stdin. 463 */ 464 static void 465 process_output(fd_set *writeset) 466 { 467 struct termios tio; 468 u_char *data; 469 u_int dlen; 470 int len; 471 472 /* Write buffered data to program stdin. */ 473 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 474 data = buffer_ptr(&stdin_buffer); 475 dlen = buffer_len(&stdin_buffer); 476 len = write(fdin, data, dlen); 477 if (len < 0 && 478 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) { 479 /* do nothing */ 480 } else if (len <= 0) { 481 if (fdin != fdout) 482 close(fdin); 483 else 484 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 485 fdin = -1; 486 } else { 487 /* Successful write. */ 488 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 489 tcgetattr(fdin, &tio) == 0 && 490 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 491 /* 492 * Simulate echo to reduce the impact of 493 * traffic analysis 494 */ 495 packet_send_ignore(len); 496 packet_send(); 497 } 498 /* Consume the data from the buffer. */ 499 buffer_consume(&stdin_buffer, len); 500 /* Update the count of bytes written to the program. */ 501 stdin_bytes += len; 502 } 503 } 504 /* Send any buffered packet data to the client. */ 505 if (FD_ISSET(connection_out, writeset)) 506 packet_write_poll(); 507 } 508 509 /* 510 * Wait until all buffered output has been sent to the client. 511 * This is used when the program terminates. 512 */ 513 static void 514 drain_output(void) 515 { 516 /* Send any buffered stdout data to the client. */ 517 if (buffer_len(&stdout_buffer) > 0) { 518 packet_start(SSH_SMSG_STDOUT_DATA); 519 packet_put_string(buffer_ptr(&stdout_buffer), 520 buffer_len(&stdout_buffer)); 521 packet_send(); 522 /* Update the count of sent bytes. */ 523 stdout_bytes += buffer_len(&stdout_buffer); 524 } 525 /* Send any buffered stderr data to the client. */ 526 if (buffer_len(&stderr_buffer) > 0) { 527 packet_start(SSH_SMSG_STDERR_DATA); 528 packet_put_string(buffer_ptr(&stderr_buffer), 529 buffer_len(&stderr_buffer)); 530 packet_send(); 531 /* Update the count of sent bytes. */ 532 stderr_bytes += buffer_len(&stderr_buffer); 533 } 534 /* Wait until all buffered data has been written to the client. */ 535 packet_write_wait(); 536 } 537 538 static void 539 process_buffered_input_packets(void) 540 { 541 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 542 } 543 544 /* 545 * Performs the interactive session. This handles data transmission between 546 * the client and the program. Note that the notion of stdin, stdout, and 547 * stderr in this function is sort of reversed: this function writes to 548 * stdin (of the child program), and reads from stdout and stderr (of the 549 * child program). 550 */ 551 void 552 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 553 { 554 fd_set *readset = NULL, *writeset = NULL; 555 int max_fd = 0; 556 u_int nalloc = 0; 557 int wait_status; /* Status returned by wait(). */ 558 pid_t wait_pid; /* pid returned by wait(). */ 559 int waiting_termination = 0; /* Have displayed waiting close message. */ 560 u_int max_time_milliseconds; 561 u_int previous_stdout_buffer_bytes; 562 u_int stdout_buffer_bytes; 563 int type; 564 565 debug("Entering interactive session."); 566 567 /* Initialize the SIGCHLD kludge. */ 568 child_terminated = 0; 569 mysignal(SIGCHLD, sigchld_handler); 570 571 if (!use_privsep) { 572 signal(SIGTERM, sigterm_handler); 573 signal(SIGINT, sigterm_handler); 574 signal(SIGQUIT, sigterm_handler); 575 } 576 577 /* Initialize our global variables. */ 578 fdin = fdin_arg; 579 fdout = fdout_arg; 580 fderr = fderr_arg; 581 582 /* nonblocking IO */ 583 set_nonblock(fdin); 584 set_nonblock(fdout); 585 /* we don't have stderr for interactive terminal sessions, see below */ 586 if (fderr != -1) 587 set_nonblock(fderr); 588 589 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 590 fdin_is_tty = 1; 591 592 connection_in = packet_get_connection_in(); 593 connection_out = packet_get_connection_out(); 594 595 notify_setup(); 596 597 previous_stdout_buffer_bytes = 0; 598 599 /* Set approximate I/O buffer size. */ 600 if (packet_is_interactive()) 601 buffer_high = 4096; 602 else 603 buffer_high = 64 * 1024; 604 605 #if 0 606 /* Initialize max_fd to the maximum of the known file descriptors. */ 607 max_fd = MAX(connection_in, connection_out); 608 max_fd = MAX(max_fd, fdin); 609 max_fd = MAX(max_fd, fdout); 610 if (fderr != -1) 611 max_fd = MAX(max_fd, fderr); 612 #endif 613 614 /* Initialize Initialize buffers. */ 615 buffer_init(&stdin_buffer); 616 buffer_init(&stdout_buffer); 617 buffer_init(&stderr_buffer); 618 619 /* 620 * If we have no separate fderr (which is the case when we have a pty 621 * - there we cannot make difference between data sent to stdout and 622 * stderr), indicate that we have seen an EOF from stderr. This way 623 * we don't need to check the descriptor everywhere. 624 */ 625 if (fderr == -1) 626 fderr_eof = 1; 627 628 server_init_dispatch(); 629 630 /* Main loop of the server for the interactive session mode. */ 631 for (;;) { 632 633 /* Process buffered packets from the client. */ 634 process_buffered_input_packets(); 635 636 /* 637 * If we have received eof, and there is no more pending 638 * input data, cause a real eof by closing fdin. 639 */ 640 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 641 if (fdin != fdout) 642 close(fdin); 643 else 644 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 645 fdin = -1; 646 } 647 /* Make packets from buffered stderr data to send to the client. */ 648 make_packets_from_stderr_data(); 649 650 /* 651 * Make packets from buffered stdout data to send to the 652 * client. If there is very little to send, this arranges to 653 * not send them now, but to wait a short while to see if we 654 * are getting more data. This is necessary, as some systems 655 * wake up readers from a pty after each separate character. 656 */ 657 max_time_milliseconds = 0; 658 stdout_buffer_bytes = buffer_len(&stdout_buffer); 659 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 660 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 661 /* try again after a while */ 662 max_time_milliseconds = 10; 663 } else { 664 /* Send it now. */ 665 make_packets_from_stdout_data(); 666 } 667 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 668 669 /* Send channel data to the client. */ 670 if (packet_not_very_much_data_to_write()) 671 channel_output_poll(); 672 673 /* 674 * Bail out of the loop if the program has closed its output 675 * descriptors, and we have no more data to send to the 676 * client, and there is no pending buffered data. 677 */ 678 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 679 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 680 if (!channel_still_open()) 681 break; 682 if (!waiting_termination) { 683 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 684 char *cp; 685 waiting_termination = 1; 686 buffer_append(&stderr_buffer, s, strlen(s)); 687 688 /* Display list of open channels. */ 689 cp = channel_open_message(); 690 buffer_append(&stderr_buffer, cp, strlen(cp)); 691 xfree(cp); 692 } 693 } 694 max_fd = MAX(connection_in, connection_out); 695 max_fd = MAX(max_fd, fdin); 696 max_fd = MAX(max_fd, fdout); 697 max_fd = MAX(max_fd, fderr); 698 max_fd = MAX(max_fd, notify_pipe[0]); 699 700 /* Sleep in select() until we can do something. */ 701 wait_until_can_do_something(&readset, &writeset, &max_fd, 702 &nalloc, max_time_milliseconds); 703 704 if (received_sigterm) { 705 logit("Exiting on signal %d", received_sigterm); 706 /* Clean up sessions, utmp, etc. */ 707 cleanup_exit(255); 708 } 709 710 /* Process any channel events. */ 711 channel_after_select(readset, writeset); 712 713 /* Process input from the client and from program stdout/stderr. */ 714 process_input(readset); 715 716 /* Process output to the client and to program stdin. */ 717 process_output(writeset); 718 } 719 if (readset) 720 xfree(readset); 721 if (writeset) 722 xfree(writeset); 723 724 /* Cleanup and termination code. */ 725 726 /* Wait until all output has been sent to the client. */ 727 drain_output(); 728 729 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 730 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 731 732 /* Free and clear the buffers. */ 733 buffer_free(&stdin_buffer); 734 buffer_free(&stdout_buffer); 735 buffer_free(&stderr_buffer); 736 737 /* Close the file descriptors. */ 738 if (fdout != -1) 739 close(fdout); 740 fdout = -1; 741 fdout_eof = 1; 742 if (fderr != -1) 743 close(fderr); 744 fderr = -1; 745 fderr_eof = 1; 746 if (fdin != -1) 747 close(fdin); 748 fdin = -1; 749 750 channel_free_all(); 751 752 /* We no longer want our SIGCHLD handler to be called. */ 753 mysignal(SIGCHLD, SIG_DFL); 754 755 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 756 if (errno != EINTR) 757 packet_disconnect("wait: %.100s", strerror(errno)); 758 if (wait_pid != pid) 759 error("Strange, wait returned pid %ld, expected %ld", 760 (long)wait_pid, (long)pid); 761 762 /* Check if it exited normally. */ 763 if (WIFEXITED(wait_status)) { 764 /* Yes, normal exit. Get exit status and send it to the client. */ 765 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 766 packet_start(SSH_SMSG_EXITSTATUS); 767 packet_put_int(WEXITSTATUS(wait_status)); 768 packet_send(); 769 packet_write_wait(); 770 771 /* 772 * Wait for exit confirmation. Note that there might be 773 * other packets coming before it; however, the program has 774 * already died so we just ignore them. The client is 775 * supposed to respond with the confirmation when it receives 776 * the exit status. 777 */ 778 do { 779 type = packet_read(); 780 } 781 while (type != SSH_CMSG_EXIT_CONFIRMATION); 782 783 debug("Received exit confirmation."); 784 return; 785 } 786 /* Check if the program terminated due to a signal. */ 787 if (WIFSIGNALED(wait_status)) 788 packet_disconnect("Command terminated on signal %d.", 789 WTERMSIG(wait_status)); 790 791 /* Some weird exit cause. Just exit. */ 792 packet_disconnect("wait returned status %04x.", wait_status); 793 /* NOTREACHED */ 794 } 795 796 static void 797 collect_children(void) 798 { 799 pid_t pid; 800 sigset_t oset, nset; 801 int status; 802 803 /* block SIGCHLD while we check for dead children */ 804 sigemptyset(&nset); 805 sigaddset(&nset, SIGCHLD); 806 sigprocmask(SIG_BLOCK, &nset, &oset); 807 if (child_terminated) { 808 debug("Received SIGCHLD."); 809 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 810 (pid < 0 && errno == EINTR)) 811 if (pid > 0) 812 session_close_by_pid(pid, status); 813 child_terminated = 0; 814 } 815 sigprocmask(SIG_SETMASK, &oset, NULL); 816 } 817 818 void 819 server_loop2(Authctxt *authctxt) 820 { 821 fd_set *readset = NULL, *writeset = NULL; 822 int rekeying = 0, max_fd, nalloc = 0; 823 824 debug("Entering interactive session for SSH2."); 825 826 mysignal(SIGCHLD, sigchld_handler); 827 child_terminated = 0; 828 connection_in = packet_get_connection_in(); 829 connection_out = packet_get_connection_out(); 830 831 if (!use_privsep) { 832 signal(SIGTERM, sigterm_handler); 833 signal(SIGINT, sigterm_handler); 834 signal(SIGQUIT, sigterm_handler); 835 } 836 837 notify_setup(); 838 839 max_fd = MAX(connection_in, connection_out); 840 max_fd = MAX(max_fd, notify_pipe[0]); 841 842 server_init_dispatch(); 843 844 for (;;) { 845 process_buffered_input_packets(); 846 847 rekeying = (xxx_kex != NULL && !xxx_kex->done); 848 849 if (!rekeying && packet_not_very_much_data_to_write()) 850 channel_output_poll(); 851 wait_until_can_do_something(&readset, &writeset, &max_fd, 852 &nalloc, 0); 853 854 if (received_sigterm) { 855 logit("Exiting on signal %d", received_sigterm); 856 /* Clean up sessions, utmp, etc. */ 857 cleanup_exit(255); 858 } 859 860 collect_children(); 861 if (!rekeying) { 862 channel_after_select(readset, writeset); 863 if (packet_need_rekeying()) { 864 debug("need rekeying"); 865 xxx_kex->done = 0; 866 kex_send_kexinit(xxx_kex); 867 } 868 } 869 process_input(readset); 870 if (connection_closed) 871 break; 872 process_output(writeset); 873 } 874 collect_children(); 875 876 if (readset) 877 xfree(readset); 878 if (writeset) 879 xfree(writeset); 880 881 /* free all channels, no more reads and writes */ 882 channel_free_all(); 883 884 /* free remaining sessions, e.g. remove wtmp entries */ 885 session_destroy_all(NULL); 886 } 887 888 static void 889 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 890 { 891 debug("Got %d/%u for keepalive", type, seq); 892 /* 893 * reset timeout, since we got a sane answer from the client. 894 * even if this was generated by something other than 895 * the bogus CHANNEL_REQUEST we send for keepalives. 896 */ 897 packet_set_alive_timeouts(0); 898 } 899 900 static void 901 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 902 { 903 char *data; 904 u_int data_len; 905 906 /* Stdin data from the client. Append it to the buffer. */ 907 /* Ignore any data if the client has closed stdin. */ 908 if (fdin == -1) 909 return; 910 data = packet_get_string(&data_len); 911 packet_check_eom(); 912 buffer_append(&stdin_buffer, data, data_len); 913 memset(data, 0, data_len); 914 xfree(data); 915 } 916 917 static void 918 server_input_eof(int type, u_int32_t seq, void *ctxt) 919 { 920 /* 921 * Eof from the client. The stdin descriptor to the 922 * program will be closed when all buffered data has 923 * drained. 924 */ 925 debug("EOF received for stdin."); 926 packet_check_eom(); 927 stdin_eof = 1; 928 } 929 930 static void 931 server_input_window_size(int type, u_int32_t seq, void *ctxt) 932 { 933 u_int row = packet_get_int(); 934 u_int col = packet_get_int(); 935 u_int xpixel = packet_get_int(); 936 u_int ypixel = packet_get_int(); 937 938 debug("Window change received."); 939 packet_check_eom(); 940 if (fdin != -1) 941 pty_change_window_size(fdin, row, col, xpixel, ypixel); 942 } 943 944 static Channel * 945 server_request_direct_tcpip(void) 946 { 947 Channel *c; 948 char *target, *originator; 949 u_short target_port, originator_port; 950 951 target = packet_get_string(NULL); 952 target_port = packet_get_int(); 953 originator = packet_get_string(NULL); 954 originator_port = packet_get_int(); 955 packet_check_eom(); 956 957 debug("server_request_direct_tcpip: originator %s port %d, target %s " 958 "port %d", originator, originator_port, target, target_port); 959 960 /* XXX check permission */ 961 c = channel_connect_to(target, target_port, 962 "direct-tcpip", "direct-tcpip"); 963 964 xfree(originator); 965 xfree(target); 966 967 return c; 968 } 969 970 static Channel * 971 server_request_tun(void) 972 { 973 Channel *c = NULL; 974 int mode, tun; 975 int sock; 976 977 mode = packet_get_int(); 978 switch (mode) { 979 case SSH_TUNMODE_POINTOPOINT: 980 case SSH_TUNMODE_ETHERNET: 981 break; 982 default: 983 packet_send_debug("Unsupported tunnel device mode."); 984 return NULL; 985 } 986 if ((options.permit_tun & mode) == 0) { 987 packet_send_debug("Server has rejected tunnel device " 988 "forwarding"); 989 return NULL; 990 } 991 992 tun = packet_get_int(); 993 if (forced_tun_device != -1) { 994 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 995 goto done; 996 tun = forced_tun_device; 997 } 998 sock = tun_open(tun, mode); 999 if (sock < 0) 1000 goto done; 1001 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1002 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 1003 c->datagram = 1; 1004 #if defined(SSH_TUN_FILTER) 1005 if (mode == SSH_TUNMODE_POINTOPOINT) 1006 channel_register_filter(c->self, sys_tun_infilter, 1007 sys_tun_outfilter, NULL, NULL); 1008 #endif 1009 1010 done: 1011 if (c == NULL) 1012 packet_send_debug("Failed to open the tunnel device."); 1013 return c; 1014 } 1015 1016 static Channel * 1017 server_request_session(void) 1018 { 1019 Channel *c; 1020 1021 debug("input_session_request"); 1022 packet_check_eom(); 1023 1024 if (no_more_sessions) { 1025 packet_disconnect("Possible attack: attempt to open a session " 1026 "after additional sessions disabled"); 1027 } 1028 1029 /* 1030 * A server session has no fd to read or write until a 1031 * CHANNEL_REQUEST for a shell is made, so we set the type to 1032 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1033 * CHANNEL_REQUEST messages is registered. 1034 */ 1035 c = channel_new("session", SSH_CHANNEL_LARVAL, 1036 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1037 0, "server-session", 1); 1038 if (session_open(the_authctxt, c->self) != 1) { 1039 debug("session open failed, free channel %d", c->self); 1040 channel_free(c); 1041 return NULL; 1042 } 1043 channel_register_cleanup(c->self, session_close_by_channel, 0); 1044 return c; 1045 } 1046 1047 static void 1048 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1049 { 1050 Channel *c = NULL; 1051 char *ctype; 1052 int rchan; 1053 u_int rmaxpack, rwindow, len; 1054 1055 ctype = packet_get_string(&len); 1056 rchan = packet_get_int(); 1057 rwindow = packet_get_int(); 1058 rmaxpack = packet_get_int(); 1059 1060 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1061 ctype, rchan, rwindow, rmaxpack); 1062 1063 if (strcmp(ctype, "session") == 0) { 1064 c = server_request_session(); 1065 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1066 c = server_request_direct_tcpip(); 1067 } else if (strcmp(ctype, "tun (at) openssh.com") == 0) { 1068 c = server_request_tun(); 1069 } 1070 if (c != NULL) { 1071 debug("server_input_channel_open: confirm %s", ctype); 1072 c->remote_id = rchan; 1073 c->remote_window = rwindow; 1074 c->remote_maxpacket = rmaxpack; 1075 if (c->type != SSH_CHANNEL_CONNECTING) { 1076 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1077 packet_put_int(c->remote_id); 1078 packet_put_int(c->self); 1079 packet_put_int(c->local_window); 1080 packet_put_int(c->local_maxpacket); 1081 packet_send(); 1082 } 1083 } else { 1084 debug("server_input_channel_open: failure %s", ctype); 1085 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1086 packet_put_int(rchan); 1087 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1088 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1089 packet_put_cstring("open failed"); 1090 packet_put_cstring(""); 1091 } 1092 packet_send(); 1093 } 1094 xfree(ctype); 1095 } 1096 1097 static void 1098 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1099 { 1100 char *rtype; 1101 int want_reply; 1102 int success = 0, allocated_listen_port = 0; 1103 1104 rtype = packet_get_string(NULL); 1105 want_reply = packet_get_char(); 1106 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1107 1108 /* -R style forwarding */ 1109 if (strcmp(rtype, "tcpip-forward") == 0) { 1110 struct passwd *pw; 1111 char *listen_address; 1112 u_short listen_port; 1113 1114 pw = the_authctxt->pw; 1115 if (pw == NULL || !the_authctxt->valid) 1116 fatal("server_input_global_request: no/invalid user"); 1117 listen_address = packet_get_string(NULL); 1118 listen_port = (u_short)packet_get_int(); 1119 debug("server_input_global_request: tcpip-forward listen %s port %d", 1120 listen_address, listen_port); 1121 1122 /* check permissions */ 1123 if (!options.allow_tcp_forwarding || 1124 no_port_forwarding_flag || 1125 (!want_reply && listen_port == 0) 1126 #ifndef NO_IPPORT_RESERVED_CONCEPT 1127 || (listen_port != 0 && listen_port < IPPORT_RESERVED && 1128 pw->pw_uid != 0) 1129 #endif 1130 ) { 1131 success = 0; 1132 packet_send_debug("Server has disabled port forwarding."); 1133 } else { 1134 /* Start listening on the port */ 1135 success = channel_setup_remote_fwd_listener( 1136 listen_address, listen_port, 1137 &allocated_listen_port, options.gateway_ports); 1138 } 1139 xfree(listen_address); 1140 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1141 char *cancel_address; 1142 u_short cancel_port; 1143 1144 cancel_address = packet_get_string(NULL); 1145 cancel_port = (u_short)packet_get_int(); 1146 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1147 cancel_address, cancel_port); 1148 1149 success = channel_cancel_rport_listener(cancel_address, 1150 cancel_port); 1151 xfree(cancel_address); 1152 } else if (strcmp(rtype, "no-more-sessions (at) openssh.com") == 0) { 1153 no_more_sessions = 1; 1154 success = 1; 1155 } 1156 if (want_reply) { 1157 packet_start(success ? 1158 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1159 if (success && allocated_listen_port > 0) 1160 packet_put_int(allocated_listen_port); 1161 packet_send(); 1162 packet_write_wait(); 1163 } 1164 xfree(rtype); 1165 } 1166 1167 static void 1168 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1169 { 1170 Channel *c; 1171 int id, reply, success = 0; 1172 char *rtype; 1173 1174 id = packet_get_int(); 1175 rtype = packet_get_string(NULL); 1176 reply = packet_get_char(); 1177 1178 debug("server_input_channel_req: channel %d request %s reply %d", 1179 id, rtype, reply); 1180 1181 if ((c = channel_lookup(id)) == NULL) 1182 packet_disconnect("server_input_channel_req: " 1183 "unknown channel %d", id); 1184 if (!strcmp(rtype, "eow (at) openssh.com")) { 1185 packet_check_eom(); 1186 chan_rcvd_eow(c); 1187 } else if ((c->type == SSH_CHANNEL_LARVAL || 1188 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1189 success = session_input_channel_req(c, rtype); 1190 if (reply) { 1191 packet_start(success ? 1192 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1193 packet_put_int(c->remote_id); 1194 packet_send(); 1195 } 1196 xfree(rtype); 1197 } 1198 1199 static void 1200 server_init_dispatch_20(void) 1201 { 1202 debug("server_init_dispatch_20"); 1203 dispatch_init(&dispatch_protocol_error); 1204 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1205 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1206 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1207 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1208 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1209 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1210 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1211 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1212 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1213 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1214 /* client_alive */ 1215 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1216 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1217 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1218 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1219 /* rekeying */ 1220 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1221 } 1222 static void 1223 server_init_dispatch_13(void) 1224 { 1225 debug("server_init_dispatch_13"); 1226 dispatch_init(NULL); 1227 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1228 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1229 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1230 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1231 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1232 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1233 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1234 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1235 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1236 } 1237 static void 1238 server_init_dispatch_15(void) 1239 { 1240 server_init_dispatch_13(); 1241 debug("server_init_dispatch_15"); 1242 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1243 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1244 } 1245 static void 1246 server_init_dispatch(void) 1247 { 1248 if (compat20) 1249 server_init_dispatch_20(); 1250 else if (compat13) 1251 server_init_dispatch_13(); 1252 else 1253 server_init_dispatch_15(); 1254 } 1255
