1 /* $OpenBSD: serverloop.c,v 1.167 2013/05/17 00:13:14 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 #include "roaming.h" 78 79 extern ServerOptions options; 80 81 /* XXX */ 82 extern Kex *xxx_kex; 83 extern Authctxt *the_authctxt; 84 extern int use_privsep; 85 86 static Buffer stdin_buffer; /* Buffer for stdin data. */ 87 static Buffer stdout_buffer; /* Buffer for stdout data. */ 88 static Buffer stderr_buffer; /* Buffer for stderr data. */ 89 static int fdin; /* Descriptor for stdin (for writing) */ 90 static int fdout; /* Descriptor for stdout (for reading); 91 May be same number as fdin. */ 92 static int fderr; /* Descriptor for stderr. May be -1. */ 93 static long stdin_bytes = 0; /* Number of bytes written to stdin. */ 94 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */ 95 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */ 96 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 97 static int stdin_eof = 0; /* EOF message received from client. */ 98 static int fdout_eof = 0; /* EOF encountered reading from fdout. */ 99 static int fderr_eof = 0; /* EOF encountered readung from fderr. */ 100 static int fdin_is_tty = 0; /* fdin points to a tty. */ 101 static int connection_in; /* Connection to client (input). */ 102 static int connection_out; /* Connection to client (output). */ 103 static int connection_closed = 0; /* Connection to client closed. */ 104 static u_int buffer_high; /* "Soft" max buffer size. */ 105 static int no_more_sessions = 0; /* Disallow further sessions. */ 106 107 /* 108 * This SIGCHLD kludge is used to detect when the child exits. The server 109 * will exit after that, as soon as forwarded connections have terminated. 110 */ 111 112 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 113 114 /* Cleanup on signals (!use_privsep case only) */ 115 static volatile sig_atomic_t received_sigterm = 0; 116 117 /* prototypes */ 118 static void server_init_dispatch(void); 119 120 /* 121 * we write to this pipe if a SIGCHLD is caught in order to avoid 122 * the race between select() and child_terminated 123 */ 124 static int notify_pipe[2]; 125 static void 126 notify_setup(void) 127 { 128 if (pipe(notify_pipe) < 0) { 129 error("pipe(notify_pipe) failed %s", strerror(errno)); 130 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 131 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 132 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 133 close(notify_pipe[0]); 134 close(notify_pipe[1]); 135 } else { 136 set_nonblock(notify_pipe[0]); 137 set_nonblock(notify_pipe[1]); 138 return; 139 } 140 notify_pipe[0] = -1; /* read end */ 141 notify_pipe[1] = -1; /* write end */ 142 } 143 static void 144 notify_parent(void) 145 { 146 if (notify_pipe[1] != -1) 147 (void)write(notify_pipe[1], "", 1); 148 } 149 static void 150 notify_prepare(fd_set *readset) 151 { 152 if (notify_pipe[0] != -1) 153 FD_SET(notify_pipe[0], readset); 154 } 155 static void 156 notify_done(fd_set *readset) 157 { 158 char c; 159 160 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 161 while (read(notify_pipe[0], &c, 1) != -1) 162 debug2("notify_done: reading"); 163 } 164 165 /*ARGSUSED*/ 166 static void 167 sigchld_handler(int sig) 168 { 169 int save_errno = errno; 170 child_terminated = 1; 171 signal(SIGCHLD, sigchld_handler); 172 notify_parent(); 173 errno = save_errno; 174 } 175 176 /*ARGSUSED*/ 177 static void 178 sigterm_handler(int sig) 179 { 180 received_sigterm = sig; 181 } 182 183 /* 184 * Make packets from buffered stderr data, and buffer it for sending 185 * to the client. 186 */ 187 static void 188 make_packets_from_stderr_data(void) 189 { 190 u_int len; 191 192 /* Send buffered stderr data to the client. */ 193 while (buffer_len(&stderr_buffer) > 0 && 194 packet_not_very_much_data_to_write()) { 195 len = buffer_len(&stderr_buffer); 196 if (packet_is_interactive()) { 197 if (len > 512) 198 len = 512; 199 } else { 200 /* Keep the packets at reasonable size. */ 201 if (len > packet_get_maxsize()) 202 len = packet_get_maxsize(); 203 } 204 packet_start(SSH_SMSG_STDERR_DATA); 205 packet_put_string(buffer_ptr(&stderr_buffer), len); 206 packet_send(); 207 buffer_consume(&stderr_buffer, len); 208 stderr_bytes += len; 209 } 210 } 211 212 /* 213 * Make packets from buffered stdout data, and buffer it for sending to the 214 * client. 215 */ 216 static void 217 make_packets_from_stdout_data(void) 218 { 219 u_int len; 220 221 /* Send buffered stdout data to the client. */ 222 while (buffer_len(&stdout_buffer) > 0 && 223 packet_not_very_much_data_to_write()) { 224 len = buffer_len(&stdout_buffer); 225 if (packet_is_interactive()) { 226 if (len > 512) 227 len = 512; 228 } else { 229 /* Keep the packets at reasonable size. */ 230 if (len > packet_get_maxsize()) 231 len = packet_get_maxsize(); 232 } 233 packet_start(SSH_SMSG_STDOUT_DATA); 234 packet_put_string(buffer_ptr(&stdout_buffer), len); 235 packet_send(); 236 buffer_consume(&stdout_buffer, len); 237 stdout_bytes += len; 238 } 239 } 240 241 static void 242 client_alive_check(void) 243 { 244 int channel_id; 245 246 /* timeout, check to see how many we have had */ 247 if (packet_inc_alive_timeouts() > options.client_alive_count_max) { 248 logit("Timeout, client not responding."); 249 cleanup_exit(255); 250 } 251 252 /* 253 * send a bogus global/channel request with "wantreply", 254 * we should get back a failure 255 */ 256 if ((channel_id = channel_find_open()) == -1) { 257 packet_start(SSH2_MSG_GLOBAL_REQUEST); 258 packet_put_cstring("keepalive@openssh.com"); 259 packet_put_char(1); /* boolean: want reply */ 260 } else { 261 channel_request_start(channel_id, "keepalive@openssh.com", 1); 262 } 263 packet_send(); 264 } 265 266 /* 267 * Sleep in select() until we can do something. This will initialize the 268 * select masks. Upon return, the masks will indicate which descriptors 269 * have data or can accept data. Optionally, a maximum time can be specified 270 * for the duration of the wait (0 = infinite). 271 */ 272 static void 273 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp, 274 u_int *nallocp, u_int64_t max_time_milliseconds) 275 { 276 struct timeval tv, *tvp; 277 int ret; 278 time_t minwait_secs = 0; 279 int client_alive_scheduled = 0; 280 281 /* Allocate and update select() masks for channel descriptors. */ 282 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 283 &minwait_secs, 0); 284 285 if (minwait_secs != 0) 286 max_time_milliseconds = MIN(max_time_milliseconds, 287 (u_int)minwait_secs * 1000); 288 289 /* 290 * if using client_alive, set the max timeout accordingly, 291 * and indicate that this particular timeout was for client 292 * alive by setting the client_alive_scheduled flag. 293 * 294 * this could be randomized somewhat to make traffic 295 * analysis more difficult, but we're not doing it yet. 296 */ 297 if (compat20 && 298 max_time_milliseconds == 0 && options.client_alive_interval) { 299 client_alive_scheduled = 1; 300 max_time_milliseconds = options.client_alive_interval * 1000; 301 } 302 303 if (compat20) { 304 #if 0 305 /* wrong: bad condition XXX */ 306 if (channel_not_very_much_buffered_data()) 307 #endif 308 FD_SET(connection_in, *readsetp); 309 } else { 310 /* 311 * Read packets from the client unless we have too much 312 * buffered stdin or channel data. 313 */ 314 if (buffer_len(&stdin_buffer) < buffer_high && 315 channel_not_very_much_buffered_data()) 316 FD_SET(connection_in, *readsetp); 317 /* 318 * If there is not too much data already buffered going to 319 * the client, try to get some more data from the program. 320 */ 321 if (packet_not_very_much_data_to_write()) { 322 if (!fdout_eof) 323 FD_SET(fdout, *readsetp); 324 if (!fderr_eof) 325 FD_SET(fderr, *readsetp); 326 } 327 /* 328 * If we have buffered data, try to write some of that data 329 * to the program. 330 */ 331 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 332 FD_SET(fdin, *writesetp); 333 } 334 notify_prepare(*readsetp); 335 336 /* 337 * If we have buffered packet data going to the client, mark that 338 * descriptor. 339 */ 340 if (packet_have_data_to_write()) 341 FD_SET(connection_out, *writesetp); 342 343 /* 344 * If child has terminated and there is enough buffer space to read 345 * from it, then read as much as is available and exit. 346 */ 347 if (child_terminated && packet_not_very_much_data_to_write()) 348 if (max_time_milliseconds == 0 || client_alive_scheduled) 349 max_time_milliseconds = 100; 350 351 if (max_time_milliseconds == 0) 352 tvp = NULL; 353 else { 354 tv.tv_sec = max_time_milliseconds / 1000; 355 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 356 tvp = &tv; 357 } 358 359 /* Wait for something to happen, or the timeout to expire. */ 360 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 361 362 if (ret == -1) { 363 memset(*readsetp, 0, *nallocp); 364 memset(*writesetp, 0, *nallocp); 365 if (errno != EINTR) 366 error("select: %.100s", strerror(errno)); 367 } else if (ret == 0 && client_alive_scheduled) 368 client_alive_check(); 369 370 notify_done(*readsetp); 371 } 372 373 /* 374 * Processes input from the client and the program. Input data is stored 375 * in buffers and processed later. 376 */ 377 static void 378 process_input(fd_set *readset) 379 { 380 int len; 381 char buf[16384]; 382 383 /* Read and buffer any input data from the client. */ 384 if (FD_ISSET(connection_in, readset)) { 385 int cont = 0; 386 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 387 if (len == 0) { 388 if (cont) 389 return; 390 verbose("Connection closed by %.100s", 391 get_remote_ipaddr()); 392 connection_closed = 1; 393 if (compat20) 394 return; 395 cleanup_exit(255); 396 } else if (len < 0) { 397 if (errno != EINTR && errno != EAGAIN) { 398 verbose("Read error from remote host " 399 "%.100s: %.100s", 400 get_remote_ipaddr(), strerror(errno)); 401 cleanup_exit(255); 402 } 403 } else { 404 /* Buffer any received data. */ 405 packet_process_incoming(buf, len); 406 } 407 } 408 if (compat20) 409 return; 410 411 /* Read and buffer any available stdout data from the program. */ 412 if (!fdout_eof && FD_ISSET(fdout, readset)) { 413 len = read(fdout, buf, sizeof(buf)); 414 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 415 /* do nothing */ 416 } else if (len <= 0) { 417 fdout_eof = 1; 418 } else { 419 buffer_append(&stdout_buffer, buf, len); 420 fdout_bytes += len; 421 } 422 } 423 /* Read and buffer any available stderr data from the program. */ 424 if (!fderr_eof && FD_ISSET(fderr, readset)) { 425 len = read(fderr, buf, sizeof(buf)); 426 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 427 /* do nothing */ 428 } else if (len <= 0) { 429 fderr_eof = 1; 430 } else { 431 buffer_append(&stderr_buffer, buf, len); 432 } 433 } 434 } 435 436 /* 437 * Sends data from internal buffers to client program stdin. 438 */ 439 static void 440 process_output(fd_set *writeset) 441 { 442 struct termios tio; 443 u_char *data; 444 u_int dlen; 445 int len; 446 447 /* Write buffered data to program stdin. */ 448 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 449 data = buffer_ptr(&stdin_buffer); 450 dlen = buffer_len(&stdin_buffer); 451 len = write(fdin, data, dlen); 452 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 453 /* do nothing */ 454 } else if (len <= 0) { 455 if (fdin != fdout) 456 close(fdin); 457 else 458 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 459 fdin = -1; 460 } else { 461 /* Successful write. */ 462 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 463 tcgetattr(fdin, &tio) == 0 && 464 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 465 /* 466 * Simulate echo to reduce the impact of 467 * traffic analysis 468 */ 469 packet_send_ignore(len); 470 packet_send(); 471 } 472 /* Consume the data from the buffer. */ 473 buffer_consume(&stdin_buffer, len); 474 /* Update the count of bytes written to the program. */ 475 stdin_bytes += len; 476 } 477 } 478 /* Send any buffered packet data to the client. */ 479 if (FD_ISSET(connection_out, writeset)) 480 packet_write_poll(); 481 } 482 483 /* 484 * Wait until all buffered output has been sent to the client. 485 * This is used when the program terminates. 486 */ 487 static void 488 drain_output(void) 489 { 490 /* Send any buffered stdout data to the client. */ 491 if (buffer_len(&stdout_buffer) > 0) { 492 packet_start(SSH_SMSG_STDOUT_DATA); 493 packet_put_string(buffer_ptr(&stdout_buffer), 494 buffer_len(&stdout_buffer)); 495 packet_send(); 496 /* Update the count of sent bytes. */ 497 stdout_bytes += buffer_len(&stdout_buffer); 498 } 499 /* Send any buffered stderr data to the client. */ 500 if (buffer_len(&stderr_buffer) > 0) { 501 packet_start(SSH_SMSG_STDERR_DATA); 502 packet_put_string(buffer_ptr(&stderr_buffer), 503 buffer_len(&stderr_buffer)); 504 packet_send(); 505 /* Update the count of sent bytes. */ 506 stderr_bytes += buffer_len(&stderr_buffer); 507 } 508 /* Wait until all buffered data has been written to the client. */ 509 packet_write_wait(); 510 } 511 512 static void 513 process_buffered_input_packets(void) 514 { 515 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 516 } 517 518 /* 519 * Performs the interactive session. This handles data transmission between 520 * the client and the program. Note that the notion of stdin, stdout, and 521 * stderr in this function is sort of reversed: this function writes to 522 * stdin (of the child program), and reads from stdout and stderr (of the 523 * child program). 524 */ 525 void 526 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 527 { 528 fd_set *readset = NULL, *writeset = NULL; 529 int max_fd = 0; 530 u_int nalloc = 0; 531 int wait_status; /* Status returned by wait(). */ 532 pid_t wait_pid; /* pid returned by wait(). */ 533 int waiting_termination = 0; /* Have displayed waiting close message. */ 534 u_int64_t max_time_milliseconds; 535 u_int previous_stdout_buffer_bytes; 536 u_int stdout_buffer_bytes; 537 int type; 538 539 debug("Entering interactive session."); 540 541 /* Initialize the SIGCHLD kludge. */ 542 child_terminated = 0; 543 signal(SIGCHLD, sigchld_handler); 544 545 if (!use_privsep) { 546 signal(SIGTERM, sigterm_handler); 547 signal(SIGINT, sigterm_handler); 548 signal(SIGQUIT, sigterm_handler); 549 } 550 551 /* Initialize our global variables. */ 552 fdin = fdin_arg; 553 fdout = fdout_arg; 554 fderr = fderr_arg; 555 556 /* nonblocking IO */ 557 set_nonblock(fdin); 558 set_nonblock(fdout); 559 /* we don't have stderr for interactive terminal sessions, see below */ 560 if (fderr != -1) 561 set_nonblock(fderr); 562 563 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 564 fdin_is_tty = 1; 565 566 connection_in = packet_get_connection_in(); 567 connection_out = packet_get_connection_out(); 568 569 notify_setup(); 570 571 previous_stdout_buffer_bytes = 0; 572 573 /* Set approximate I/O buffer size. */ 574 if (packet_is_interactive()) 575 buffer_high = 4096; 576 else 577 buffer_high = 64 * 1024; 578 579 #if 0 580 /* Initialize max_fd to the maximum of the known file descriptors. */ 581 max_fd = MAX(connection_in, connection_out); 582 max_fd = MAX(max_fd, fdin); 583 max_fd = MAX(max_fd, fdout); 584 if (fderr != -1) 585 max_fd = MAX(max_fd, fderr); 586 #endif 587 588 /* Initialize Initialize buffers. */ 589 buffer_init(&stdin_buffer); 590 buffer_init(&stdout_buffer); 591 buffer_init(&stderr_buffer); 592 593 /* 594 * If we have no separate fderr (which is the case when we have a pty 595 * - there we cannot make difference between data sent to stdout and 596 * stderr), indicate that we have seen an EOF from stderr. This way 597 * we don't need to check the descriptor everywhere. 598 */ 599 if (fderr == -1) 600 fderr_eof = 1; 601 602 server_init_dispatch(); 603 604 /* Main loop of the server for the interactive session mode. */ 605 for (;;) { 606 607 /* Process buffered packets from the client. */ 608 process_buffered_input_packets(); 609 610 /* 611 * If we have received eof, and there is no more pending 612 * input data, cause a real eof by closing fdin. 613 */ 614 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 615 if (fdin != fdout) 616 close(fdin); 617 else 618 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 619 fdin = -1; 620 } 621 /* Make packets from buffered stderr data to send to the client. */ 622 make_packets_from_stderr_data(); 623 624 /* 625 * Make packets from buffered stdout data to send to the 626 * client. If there is very little to send, this arranges to 627 * not send them now, but to wait a short while to see if we 628 * are getting more data. This is necessary, as some systems 629 * wake up readers from a pty after each separate character. 630 */ 631 max_time_milliseconds = 0; 632 stdout_buffer_bytes = buffer_len(&stdout_buffer); 633 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 634 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 635 /* try again after a while */ 636 max_time_milliseconds = 10; 637 } else { 638 /* Send it now. */ 639 make_packets_from_stdout_data(); 640 } 641 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 642 643 /* Send channel data to the client. */ 644 if (packet_not_very_much_data_to_write()) 645 channel_output_poll(); 646 647 /* 648 * Bail out of the loop if the program has closed its output 649 * descriptors, and we have no more data to send to the 650 * client, and there is no pending buffered data. 651 */ 652 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 653 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 654 if (!channel_still_open()) 655 break; 656 if (!waiting_termination) { 657 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 658 char *cp; 659 waiting_termination = 1; 660 buffer_append(&stderr_buffer, s, strlen(s)); 661 662 /* Display list of open channels. */ 663 cp = channel_open_message(); 664 buffer_append(&stderr_buffer, cp, strlen(cp)); 665 free(cp); 666 } 667 } 668 max_fd = MAX(connection_in, connection_out); 669 max_fd = MAX(max_fd, fdin); 670 max_fd = MAX(max_fd, fdout); 671 max_fd = MAX(max_fd, fderr); 672 max_fd = MAX(max_fd, notify_pipe[0]); 673 674 /* Sleep in select() until we can do something. */ 675 wait_until_can_do_something(&readset, &writeset, &max_fd, 676 &nalloc, max_time_milliseconds); 677 678 if (received_sigterm) { 679 logit("Exiting on signal %d", (int)received_sigterm); 680 /* Clean up sessions, utmp, etc. */ 681 cleanup_exit(255); 682 } 683 684 /* Process any channel events. */ 685 channel_after_select(readset, writeset); 686 687 /* Process input from the client and from program stdout/stderr. */ 688 process_input(readset); 689 690 /* Process output to the client and to program stdin. */ 691 process_output(writeset); 692 } 693 free(readset); 694 free(writeset); 695 696 /* Cleanup and termination code. */ 697 698 /* Wait until all output has been sent to the client. */ 699 drain_output(); 700 701 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 702 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 703 704 /* Free and clear the buffers. */ 705 buffer_free(&stdin_buffer); 706 buffer_free(&stdout_buffer); 707 buffer_free(&stderr_buffer); 708 709 /* Close the file descriptors. */ 710 if (fdout != -1) 711 close(fdout); 712 fdout = -1; 713 fdout_eof = 1; 714 if (fderr != -1) 715 close(fderr); 716 fderr = -1; 717 fderr_eof = 1; 718 if (fdin != -1) 719 close(fdin); 720 fdin = -1; 721 722 channel_free_all(); 723 724 /* We no longer want our SIGCHLD handler to be called. */ 725 signal(SIGCHLD, SIG_DFL); 726 727 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 728 if (errno != EINTR) 729 packet_disconnect("wait: %.100s", strerror(errno)); 730 if (wait_pid != pid) 731 error("Strange, wait returned pid %ld, expected %ld", 732 (long)wait_pid, (long)pid); 733 734 /* Check if it exited normally. */ 735 if (WIFEXITED(wait_status)) { 736 /* Yes, normal exit. Get exit status and send it to the client. */ 737 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 738 packet_start(SSH_SMSG_EXITSTATUS); 739 packet_put_int(WEXITSTATUS(wait_status)); 740 packet_send(); 741 packet_write_wait(); 742 743 /* 744 * Wait for exit confirmation. Note that there might be 745 * other packets coming before it; however, the program has 746 * already died so we just ignore them. The client is 747 * supposed to respond with the confirmation when it receives 748 * the exit status. 749 */ 750 do { 751 type = packet_read(); 752 } 753 while (type != SSH_CMSG_EXIT_CONFIRMATION); 754 755 debug("Received exit confirmation."); 756 return; 757 } 758 /* Check if the program terminated due to a signal. */ 759 if (WIFSIGNALED(wait_status)) 760 packet_disconnect("Command terminated on signal %d.", 761 WTERMSIG(wait_status)); 762 763 /* Some weird exit cause. Just exit. */ 764 packet_disconnect("wait returned status %04x.", wait_status); 765 /* NOTREACHED */ 766 } 767 768 static void 769 collect_children(void) 770 { 771 pid_t pid; 772 sigset_t oset, nset; 773 int status; 774 775 /* block SIGCHLD while we check for dead children */ 776 sigemptyset(&nset); 777 sigaddset(&nset, SIGCHLD); 778 sigprocmask(SIG_BLOCK, &nset, &oset); 779 if (child_terminated) { 780 debug("Received SIGCHLD."); 781 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 782 (pid < 0 && errno == EINTR)) 783 if (pid > 0) 784 session_close_by_pid(pid, status); 785 child_terminated = 0; 786 } 787 sigprocmask(SIG_SETMASK, &oset, NULL); 788 } 789 790 void 791 server_loop2(Authctxt *authctxt) 792 { 793 fd_set *readset = NULL, *writeset = NULL; 794 int rekeying = 0, max_fd, nalloc = 0; 795 u_int64_t rekey_timeout_ms = 0; 796 797 debug("Entering interactive session for SSH2."); 798 799 signal(SIGCHLD, sigchld_handler); 800 child_terminated = 0; 801 connection_in = packet_get_connection_in(); 802 connection_out = packet_get_connection_out(); 803 804 if (!use_privsep) { 805 signal(SIGTERM, sigterm_handler); 806 signal(SIGINT, sigterm_handler); 807 signal(SIGQUIT, sigterm_handler); 808 } 809 810 notify_setup(); 811 812 max_fd = MAX(connection_in, connection_out); 813 max_fd = MAX(max_fd, notify_pipe[0]); 814 815 server_init_dispatch(); 816 817 for (;;) { 818 process_buffered_input_packets(); 819 820 rekeying = (xxx_kex != NULL && !xxx_kex->done); 821 822 if (!rekeying && packet_not_very_much_data_to_write()) 823 channel_output_poll(); 824 if (options.rekey_interval > 0 && compat20 && !rekeying) 825 rekey_timeout_ms = packet_get_rekey_timeout() * 1000; 826 else 827 rekey_timeout_ms = 0; 828 829 wait_until_can_do_something(&readset, &writeset, &max_fd, 830 &nalloc, rekey_timeout_ms); 831 832 if (received_sigterm) { 833 logit("Exiting on signal %d", (int)received_sigterm); 834 /* Clean up sessions, utmp, etc. */ 835 cleanup_exit(255); 836 } 837 838 collect_children(); 839 if (!rekeying) { 840 channel_after_select(readset, writeset); 841 if (packet_need_rekeying()) { 842 debug("need rekeying"); 843 xxx_kex->done = 0; 844 kex_send_kexinit(xxx_kex); 845 } 846 } 847 process_input(readset); 848 if (connection_closed) 849 break; 850 process_output(writeset); 851 } 852 collect_children(); 853 854 free(readset); 855 free(writeset); 856 857 /* free all channels, no more reads and writes */ 858 channel_free_all(); 859 860 /* free remaining sessions, e.g. remove wtmp entries */ 861 session_destroy_all(NULL); 862 } 863 864 static void 865 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 866 { 867 debug("Got %d/%u for keepalive", type, seq); 868 /* 869 * reset timeout, since we got a sane answer from the client. 870 * even if this was generated by something other than 871 * the bogus CHANNEL_REQUEST we send for keepalives. 872 */ 873 packet_set_alive_timeouts(0); 874 } 875 876 static void 877 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 878 { 879 char *data; 880 u_int data_len; 881 882 /* Stdin data from the client. Append it to the buffer. */ 883 /* Ignore any data if the client has closed stdin. */ 884 if (fdin == -1) 885 return; 886 data = packet_get_string(&data_len); 887 packet_check_eom(); 888 buffer_append(&stdin_buffer, data, data_len); 889 memset(data, 0, data_len); 890 free(data); 891 } 892 893 static void 894 server_input_eof(int type, u_int32_t seq, void *ctxt) 895 { 896 /* 897 * Eof from the client. The stdin descriptor to the 898 * program will be closed when all buffered data has 899 * drained. 900 */ 901 debug("EOF received for stdin."); 902 packet_check_eom(); 903 stdin_eof = 1; 904 } 905 906 static void 907 server_input_window_size(int type, u_int32_t seq, void *ctxt) 908 { 909 u_int row = packet_get_int(); 910 u_int col = packet_get_int(); 911 u_int xpixel = packet_get_int(); 912 u_int ypixel = packet_get_int(); 913 914 debug("Window change received."); 915 packet_check_eom(); 916 if (fdin != -1) 917 pty_change_window_size(fdin, row, col, xpixel, ypixel); 918 } 919 920 static Channel * 921 server_request_direct_tcpip(void) 922 { 923 Channel *c = NULL; 924 char *target, *originator; 925 u_short target_port, originator_port; 926 927 target = packet_get_string(NULL); 928 target_port = packet_get_int(); 929 originator = packet_get_string(NULL); 930 originator_port = packet_get_int(); 931 packet_check_eom(); 932 933 debug("server_request_direct_tcpip: originator %s port %d, target %s " 934 "port %d", originator, originator_port, target, target_port); 935 936 /* XXX fine grained permissions */ 937 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 938 !no_port_forwarding_flag) { 939 c = channel_connect_to(target, target_port, 940 "direct-tcpip", "direct-tcpip"); 941 } else { 942 logit("refused local port forward: " 943 "originator %s port %d, target %s port %d", 944 originator, originator_port, target, target_port); 945 } 946 947 free(originator); 948 free(target); 949 950 return c; 951 } 952 953 static Channel * 954 server_request_tun(void) 955 { 956 Channel *c = NULL; 957 int mode, tun; 958 int sock; 959 960 mode = packet_get_int(); 961 switch (mode) { 962 case SSH_TUNMODE_POINTOPOINT: 963 case SSH_TUNMODE_ETHERNET: 964 break; 965 default: 966 packet_send_debug("Unsupported tunnel device mode."); 967 return NULL; 968 } 969 if ((options.permit_tun & mode) == 0) { 970 packet_send_debug("Server has rejected tunnel device " 971 "forwarding"); 972 return NULL; 973 } 974 975 tun = packet_get_int(); 976 if (forced_tun_device != -1) { 977 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 978 goto done; 979 tun = forced_tun_device; 980 } 981 sock = tun_open(tun, mode); 982 if (sock < 0) 983 goto done; 984 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 985 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 986 c->datagram = 1; 987 988 done: 989 if (c == NULL) 990 packet_send_debug("Failed to open the tunnel device."); 991 return c; 992 } 993 994 static Channel * 995 server_request_session(void) 996 { 997 Channel *c; 998 999 debug("input_session_request"); 1000 packet_check_eom(); 1001 1002 if (no_more_sessions) { 1003 packet_disconnect("Possible attack: attempt to open a session " 1004 "after additional sessions disabled"); 1005 } 1006 1007 /* 1008 * A server session has no fd to read or write until a 1009 * CHANNEL_REQUEST for a shell is made, so we set the type to 1010 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1011 * CHANNEL_REQUEST messages is registered. 1012 */ 1013 c = channel_new("session", SSH_CHANNEL_LARVAL, 1014 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1015 0, "server-session", 1); 1016 if (session_open(the_authctxt, c->self) != 1) { 1017 debug("session open failed, free channel %d", c->self); 1018 channel_free(c); 1019 return NULL; 1020 } 1021 channel_register_cleanup(c->self, session_close_by_channel, 0); 1022 return c; 1023 } 1024 1025 static void 1026 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1027 { 1028 Channel *c = NULL; 1029 char *ctype; 1030 int rchan; 1031 u_int rmaxpack, rwindow, len; 1032 1033 ctype = packet_get_string(&len); 1034 rchan = packet_get_int(); 1035 rwindow = packet_get_int(); 1036 rmaxpack = packet_get_int(); 1037 1038 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1039 ctype, rchan, rwindow, rmaxpack); 1040 1041 if (strcmp(ctype, "session") == 0) { 1042 c = server_request_session(); 1043 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1044 c = server_request_direct_tcpip(); 1045 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1046 c = server_request_tun(); 1047 } 1048 if (c != NULL) { 1049 debug("server_input_channel_open: confirm %s", ctype); 1050 c->remote_id = rchan; 1051 c->remote_window = rwindow; 1052 c->remote_maxpacket = rmaxpack; 1053 if (c->type != SSH_CHANNEL_CONNECTING) { 1054 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1055 packet_put_int(c->remote_id); 1056 packet_put_int(c->self); 1057 packet_put_int(c->local_window); 1058 packet_put_int(c->local_maxpacket); 1059 packet_send(); 1060 } 1061 } else { 1062 debug("server_input_channel_open: failure %s", ctype); 1063 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1064 packet_put_int(rchan); 1065 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1066 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1067 packet_put_cstring("open failed"); 1068 packet_put_cstring(""); 1069 } 1070 packet_send(); 1071 } 1072 free(ctype); 1073 } 1074 1075 static void 1076 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1077 { 1078 char *rtype; 1079 int want_reply; 1080 int success = 0, allocated_listen_port = 0; 1081 1082 rtype = packet_get_string(NULL); 1083 want_reply = packet_get_char(); 1084 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1085 1086 /* -R style forwarding */ 1087 if (strcmp(rtype, "tcpip-forward") == 0) { 1088 struct passwd *pw; 1089 char *listen_address; 1090 u_short listen_port; 1091 1092 pw = the_authctxt->pw; 1093 if (pw == NULL || !the_authctxt->valid) 1094 fatal("server_input_global_request: no/invalid user"); 1095 listen_address = packet_get_string(NULL); 1096 listen_port = (u_short)packet_get_int(); 1097 debug("server_input_global_request: tcpip-forward listen %s port %d", 1098 listen_address, listen_port); 1099 1100 /* check permissions */ 1101 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 1102 no_port_forwarding_flag || 1103 (!want_reply && listen_port == 0) || 1104 (listen_port != 0 && listen_port < IPPORT_RESERVED && 1105 pw->pw_uid != 0)) { 1106 success = 0; 1107 packet_send_debug("Server has disabled port forwarding."); 1108 } else { 1109 /* Start listening on the port */ 1110 success = channel_setup_remote_fwd_listener( 1111 listen_address, listen_port, 1112 &allocated_listen_port, options.gateway_ports); 1113 } 1114 free(listen_address); 1115 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1116 char *cancel_address; 1117 u_short cancel_port; 1118 1119 cancel_address = packet_get_string(NULL); 1120 cancel_port = (u_short)packet_get_int(); 1121 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1122 cancel_address, cancel_port); 1123 1124 success = channel_cancel_rport_listener(cancel_address, 1125 cancel_port); 1126 free(cancel_address); 1127 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1128 no_more_sessions = 1; 1129 success = 1; 1130 } 1131 if (want_reply) { 1132 packet_start(success ? 1133 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1134 if (success && allocated_listen_port > 0) 1135 packet_put_int(allocated_listen_port); 1136 packet_send(); 1137 packet_write_wait(); 1138 } 1139 free(rtype); 1140 } 1141 1142 static void 1143 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1144 { 1145 Channel *c; 1146 int id, reply, success = 0; 1147 char *rtype; 1148 1149 id = packet_get_int(); 1150 rtype = packet_get_string(NULL); 1151 reply = packet_get_char(); 1152 1153 debug("server_input_channel_req: channel %d request %s reply %d", 1154 id, rtype, reply); 1155 1156 if ((c = channel_lookup(id)) == NULL) 1157 packet_disconnect("server_input_channel_req: " 1158 "unknown channel %d", id); 1159 if (!strcmp(rtype, "eow@openssh.com")) { 1160 packet_check_eom(); 1161 chan_rcvd_eow(c); 1162 } else if ((c->type == SSH_CHANNEL_LARVAL || 1163 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1164 success = session_input_channel_req(c, rtype); 1165 if (reply) { 1166 packet_start(success ? 1167 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1168 packet_put_int(c->remote_id); 1169 packet_send(); 1170 } 1171 free(rtype); 1172 } 1173 1174 static void 1175 server_init_dispatch_20(void) 1176 { 1177 debug("server_init_dispatch_20"); 1178 dispatch_init(&dispatch_protocol_error); 1179 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1180 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1181 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1182 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1183 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1184 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1185 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1186 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1187 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1188 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1189 /* client_alive */ 1190 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1191 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1192 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1193 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1194 /* rekeying */ 1195 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1196 } 1197 static void 1198 server_init_dispatch_13(void) 1199 { 1200 debug("server_init_dispatch_13"); 1201 dispatch_init(NULL); 1202 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1203 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1204 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1205 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1206 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1207 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1208 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1209 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1210 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1211 } 1212 static void 1213 server_init_dispatch_15(void) 1214 { 1215 server_init_dispatch_13(); 1216 debug("server_init_dispatch_15"); 1217 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1218 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1219 } 1220 static void 1221 server_init_dispatch(void) 1222 { 1223 if (compat20) 1224 server_init_dispatch_20(); 1225 else if (compat13) 1226 server_init_dispatch_13(); 1227 else 1228 server_init_dispatch_15(); 1229 } 1230