1 /* $OpenBSD: serverloop.c,v 1.172 2014/07/15 15:54:14 millert 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 "misc.h" 61 #include "servconf.h" 62 #include "canohost.h" 63 #include "sshpty.h" 64 #include "channels.h" 65 #include "compat.h" 66 #include "ssh1.h" 67 #include "ssh2.h" 68 #include "key.h" 69 #include "cipher.h" 70 #include "kex.h" 71 #include "hostfile.h" 72 #include "auth.h" 73 #include "session.h" 74 #include "dispatch.h" 75 #include "auth-options.h" 76 #include "serverloop.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 = 301 (u_int64_t)options.client_alive_interval * 1000; 302 } 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 if (!fdout_eof) 324 FD_SET(fdout, *readsetp); 325 if (!fderr_eof) 326 FD_SET(fderr, *readsetp); 327 } 328 /* 329 * If we have buffered data, try to write some of that data 330 * to the program. 331 */ 332 if (fdin != -1 && buffer_len(&stdin_buffer) > 0) 333 FD_SET(fdin, *writesetp); 334 } 335 notify_prepare(*readsetp); 336 337 /* 338 * If we have buffered packet data going to the client, mark that 339 * descriptor. 340 */ 341 if (packet_have_data_to_write()) 342 FD_SET(connection_out, *writesetp); 343 344 /* 345 * If child has terminated and there is enough buffer space to read 346 * from it, then read as much as is available and exit. 347 */ 348 if (child_terminated && packet_not_very_much_data_to_write()) 349 if (max_time_milliseconds == 0 || client_alive_scheduled) 350 max_time_milliseconds = 100; 351 352 if (max_time_milliseconds == 0) 353 tvp = NULL; 354 else { 355 tv.tv_sec = max_time_milliseconds / 1000; 356 tv.tv_usec = 1000 * (max_time_milliseconds % 1000); 357 tvp = &tv; 358 } 359 360 /* Wait for something to happen, or the timeout to expire. */ 361 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 362 363 if (ret == -1) { 364 memset(*readsetp, 0, *nallocp); 365 memset(*writesetp, 0, *nallocp); 366 if (errno != EINTR) 367 error("select: %.100s", strerror(errno)); 368 } else if (ret == 0 && client_alive_scheduled) 369 client_alive_check(); 370 371 notify_done(*readsetp); 372 } 373 374 /* 375 * Processes input from the client and the program. Input data is stored 376 * in buffers and processed later. 377 */ 378 static void 379 process_input(fd_set *readset) 380 { 381 int len; 382 char buf[16384]; 383 384 /* Read and buffer any input data from the client. */ 385 if (FD_ISSET(connection_in, readset)) { 386 int cont = 0; 387 len = roaming_read(connection_in, buf, sizeof(buf), &cont); 388 if (len == 0) { 389 if (cont) 390 return; 391 verbose("Connection closed by %.100s", 392 get_remote_ipaddr()); 393 connection_closed = 1; 394 if (compat20) 395 return; 396 cleanup_exit(255); 397 } else if (len < 0) { 398 if (errno != EINTR && errno != EAGAIN) { 399 verbose("Read error from remote host " 400 "%.100s: %.100s", 401 get_remote_ipaddr(), strerror(errno)); 402 cleanup_exit(255); 403 } 404 } else { 405 /* Buffer any received data. */ 406 packet_process_incoming(buf, len); 407 } 408 } 409 if (compat20) 410 return; 411 412 /* Read and buffer any available stdout data from the program. */ 413 if (!fdout_eof && FD_ISSET(fdout, readset)) { 414 len = read(fdout, buf, sizeof(buf)); 415 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 416 /* do nothing */ 417 } else if (len <= 0) { 418 fdout_eof = 1; 419 } else { 420 buffer_append(&stdout_buffer, buf, len); 421 fdout_bytes += len; 422 } 423 } 424 /* Read and buffer any available stderr data from the program. */ 425 if (!fderr_eof && FD_ISSET(fderr, readset)) { 426 len = read(fderr, buf, sizeof(buf)); 427 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 428 /* do nothing */ 429 } else if (len <= 0) { 430 fderr_eof = 1; 431 } else { 432 buffer_append(&stderr_buffer, buf, len); 433 } 434 } 435 } 436 437 /* 438 * Sends data from internal buffers to client program stdin. 439 */ 440 static void 441 process_output(fd_set *writeset) 442 { 443 struct termios tio; 444 u_char *data; 445 u_int dlen; 446 int len; 447 448 /* Write buffered data to program stdin. */ 449 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) { 450 data = buffer_ptr(&stdin_buffer); 451 dlen = buffer_len(&stdin_buffer); 452 len = write(fdin, data, dlen); 453 if (len < 0 && (errno == EINTR || errno == EAGAIN)) { 454 /* do nothing */ 455 } else if (len <= 0) { 456 if (fdin != fdout) 457 close(fdin); 458 else 459 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 460 fdin = -1; 461 } else { 462 /* Successful write. */ 463 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' && 464 tcgetattr(fdin, &tio) == 0 && 465 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) { 466 /* 467 * Simulate echo to reduce the impact of 468 * traffic analysis 469 */ 470 packet_send_ignore(len); 471 packet_send(); 472 } 473 /* Consume the data from the buffer. */ 474 buffer_consume(&stdin_buffer, len); 475 /* Update the count of bytes written to the program. */ 476 stdin_bytes += len; 477 } 478 } 479 /* Send any buffered packet data to the client. */ 480 if (FD_ISSET(connection_out, writeset)) 481 packet_write_poll(); 482 } 483 484 /* 485 * Wait until all buffered output has been sent to the client. 486 * This is used when the program terminates. 487 */ 488 static void 489 drain_output(void) 490 { 491 /* Send any buffered stdout data to the client. */ 492 if (buffer_len(&stdout_buffer) > 0) { 493 packet_start(SSH_SMSG_STDOUT_DATA); 494 packet_put_string(buffer_ptr(&stdout_buffer), 495 buffer_len(&stdout_buffer)); 496 packet_send(); 497 /* Update the count of sent bytes. */ 498 stdout_bytes += buffer_len(&stdout_buffer); 499 } 500 /* Send any buffered stderr data to the client. */ 501 if (buffer_len(&stderr_buffer) > 0) { 502 packet_start(SSH_SMSG_STDERR_DATA); 503 packet_put_string(buffer_ptr(&stderr_buffer), 504 buffer_len(&stderr_buffer)); 505 packet_send(); 506 /* Update the count of sent bytes. */ 507 stderr_bytes += buffer_len(&stderr_buffer); 508 } 509 /* Wait until all buffered data has been written to the client. */ 510 packet_write_wait(); 511 } 512 513 static void 514 process_buffered_input_packets(void) 515 { 516 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL); 517 } 518 519 /* 520 * Performs the interactive session. This handles data transmission between 521 * the client and the program. Note that the notion of stdin, stdout, and 522 * stderr in this function is sort of reversed: this function writes to 523 * stdin (of the child program), and reads from stdout and stderr (of the 524 * child program). 525 */ 526 void 527 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg) 528 { 529 fd_set *readset = NULL, *writeset = NULL; 530 int max_fd = 0; 531 u_int nalloc = 0; 532 int wait_status; /* Status returned by wait(). */ 533 pid_t wait_pid; /* pid returned by wait(). */ 534 int waiting_termination = 0; /* Have displayed waiting close message. */ 535 u_int64_t max_time_milliseconds; 536 u_int previous_stdout_buffer_bytes; 537 u_int stdout_buffer_bytes; 538 int type; 539 540 debug("Entering interactive session."); 541 542 /* Initialize the SIGCHLD kludge. */ 543 child_terminated = 0; 544 signal(SIGCHLD, sigchld_handler); 545 546 if (!use_privsep) { 547 signal(SIGTERM, sigterm_handler); 548 signal(SIGINT, sigterm_handler); 549 signal(SIGQUIT, sigterm_handler); 550 } 551 552 /* Initialize our global variables. */ 553 fdin = fdin_arg; 554 fdout = fdout_arg; 555 fderr = fderr_arg; 556 557 /* nonblocking IO */ 558 set_nonblock(fdin); 559 set_nonblock(fdout); 560 /* we don't have stderr for interactive terminal sessions, see below */ 561 if (fderr != -1) 562 set_nonblock(fderr); 563 564 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin)) 565 fdin_is_tty = 1; 566 567 connection_in = packet_get_connection_in(); 568 connection_out = packet_get_connection_out(); 569 570 notify_setup(); 571 572 previous_stdout_buffer_bytes = 0; 573 574 /* Set approximate I/O buffer size. */ 575 if (packet_is_interactive()) 576 buffer_high = 4096; 577 else 578 buffer_high = 64 * 1024; 579 580 #if 0 581 /* Initialize max_fd to the maximum of the known file descriptors. */ 582 max_fd = MAX(connection_in, connection_out); 583 max_fd = MAX(max_fd, fdin); 584 max_fd = MAX(max_fd, fdout); 585 if (fderr != -1) 586 max_fd = MAX(max_fd, fderr); 587 #endif 588 589 /* Initialize Initialize buffers. */ 590 buffer_init(&stdin_buffer); 591 buffer_init(&stdout_buffer); 592 buffer_init(&stderr_buffer); 593 594 /* 595 * If we have no separate fderr (which is the case when we have a pty 596 * - there we cannot make difference between data sent to stdout and 597 * stderr), indicate that we have seen an EOF from stderr. This way 598 * we don't need to check the descriptor everywhere. 599 */ 600 if (fderr == -1) 601 fderr_eof = 1; 602 603 server_init_dispatch(); 604 605 /* Main loop of the server for the interactive session mode. */ 606 for (;;) { 607 608 /* Process buffered packets from the client. */ 609 process_buffered_input_packets(); 610 611 /* 612 * If we have received eof, and there is no more pending 613 * input data, cause a real eof by closing fdin. 614 */ 615 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) { 616 if (fdin != fdout) 617 close(fdin); 618 else 619 shutdown(fdin, SHUT_WR); /* We will no longer send. */ 620 fdin = -1; 621 } 622 /* Make packets from buffered stderr data to send to the client. */ 623 make_packets_from_stderr_data(); 624 625 /* 626 * Make packets from buffered stdout data to send to the 627 * client. If there is very little to send, this arranges to 628 * not send them now, but to wait a short while to see if we 629 * are getting more data. This is necessary, as some systems 630 * wake up readers from a pty after each separate character. 631 */ 632 max_time_milliseconds = 0; 633 stdout_buffer_bytes = buffer_len(&stdout_buffer); 634 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 && 635 stdout_buffer_bytes != previous_stdout_buffer_bytes) { 636 /* try again after a while */ 637 max_time_milliseconds = 10; 638 } else { 639 /* Send it now. */ 640 make_packets_from_stdout_data(); 641 } 642 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer); 643 644 /* Send channel data to the client. */ 645 if (packet_not_very_much_data_to_write()) 646 channel_output_poll(); 647 648 /* 649 * Bail out of the loop if the program has closed its output 650 * descriptors, and we have no more data to send to the 651 * client, and there is no pending buffered data. 652 */ 653 if (fdout_eof && fderr_eof && !packet_have_data_to_write() && 654 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) { 655 if (!channel_still_open()) 656 break; 657 if (!waiting_termination) { 658 const char *s = "Waiting for forwarded connections to terminate...\r\n"; 659 char *cp; 660 waiting_termination = 1; 661 buffer_append(&stderr_buffer, s, strlen(s)); 662 663 /* Display list of open channels. */ 664 cp = channel_open_message(); 665 buffer_append(&stderr_buffer, cp, strlen(cp)); 666 free(cp); 667 } 668 } 669 max_fd = MAX(connection_in, connection_out); 670 max_fd = MAX(max_fd, fdin); 671 max_fd = MAX(max_fd, fdout); 672 max_fd = MAX(max_fd, fderr); 673 max_fd = MAX(max_fd, notify_pipe[0]); 674 675 /* Sleep in select() until we can do something. */ 676 wait_until_can_do_something(&readset, &writeset, &max_fd, 677 &nalloc, max_time_milliseconds); 678 679 if (received_sigterm) { 680 logit("Exiting on signal %d", (int)received_sigterm); 681 /* Clean up sessions, utmp, etc. */ 682 cleanup_exit(255); 683 } 684 685 /* Process any channel events. */ 686 channel_after_select(readset, writeset); 687 688 /* Process input from the client and from program stdout/stderr. */ 689 process_input(readset); 690 691 /* Process output to the client and to program stdin. */ 692 process_output(writeset); 693 } 694 free(readset); 695 free(writeset); 696 697 /* Cleanup and termination code. */ 698 699 /* Wait until all output has been sent to the client. */ 700 drain_output(); 701 702 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.", 703 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes); 704 705 /* Free and clear the buffers. */ 706 buffer_free(&stdin_buffer); 707 buffer_free(&stdout_buffer); 708 buffer_free(&stderr_buffer); 709 710 /* Close the file descriptors. */ 711 if (fdout != -1) 712 close(fdout); 713 fdout = -1; 714 fdout_eof = 1; 715 if (fderr != -1) 716 close(fderr); 717 fderr = -1; 718 fderr_eof = 1; 719 if (fdin != -1) 720 close(fdin); 721 fdin = -1; 722 723 channel_free_all(); 724 725 /* We no longer want our SIGCHLD handler to be called. */ 726 signal(SIGCHLD, SIG_DFL); 727 728 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0) 729 if (errno != EINTR) 730 packet_disconnect("wait: %.100s", strerror(errno)); 731 if (wait_pid != pid) 732 error("Strange, wait returned pid %ld, expected %ld", 733 (long)wait_pid, (long)pid); 734 735 /* Check if it exited normally. */ 736 if (WIFEXITED(wait_status)) { 737 /* Yes, normal exit. Get exit status and send it to the client. */ 738 debug("Command exited with status %d.", WEXITSTATUS(wait_status)); 739 packet_start(SSH_SMSG_EXITSTATUS); 740 packet_put_int(WEXITSTATUS(wait_status)); 741 packet_send(); 742 packet_write_wait(); 743 744 /* 745 * Wait for exit confirmation. Note that there might be 746 * other packets coming before it; however, the program has 747 * already died so we just ignore them. The client is 748 * supposed to respond with the confirmation when it receives 749 * the exit status. 750 */ 751 do { 752 type = packet_read(); 753 } 754 while (type != SSH_CMSG_EXIT_CONFIRMATION); 755 756 debug("Received exit confirmation."); 757 return; 758 } 759 /* Check if the program terminated due to a signal. */ 760 if (WIFSIGNALED(wait_status)) 761 packet_disconnect("Command terminated on signal %d.", 762 WTERMSIG(wait_status)); 763 764 /* Some weird exit cause. Just exit. */ 765 packet_disconnect("wait returned status %04x.", wait_status); 766 /* NOTREACHED */ 767 } 768 769 static void 770 collect_children(void) 771 { 772 pid_t pid; 773 sigset_t oset, nset; 774 int status; 775 776 /* block SIGCHLD while we check for dead children */ 777 sigemptyset(&nset); 778 sigaddset(&nset, SIGCHLD); 779 sigprocmask(SIG_BLOCK, &nset, &oset); 780 if (child_terminated) { 781 debug("Received SIGCHLD."); 782 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 783 (pid < 0 && errno == EINTR)) 784 if (pid > 0) 785 session_close_by_pid(pid, status); 786 child_terminated = 0; 787 } 788 sigprocmask(SIG_SETMASK, &oset, NULL); 789 } 790 791 void 792 server_loop2(Authctxt *authctxt) 793 { 794 fd_set *readset = NULL, *writeset = NULL; 795 int rekeying = 0, max_fd; 796 u_int nalloc = 0; 797 u_int64_t rekey_timeout_ms = 0; 798 799 debug("Entering interactive session for SSH2."); 800 801 signal(SIGCHLD, sigchld_handler); 802 child_terminated = 0; 803 connection_in = packet_get_connection_in(); 804 connection_out = packet_get_connection_out(); 805 806 if (!use_privsep) { 807 signal(SIGTERM, sigterm_handler); 808 signal(SIGINT, sigterm_handler); 809 signal(SIGQUIT, sigterm_handler); 810 } 811 812 notify_setup(); 813 814 max_fd = MAX(connection_in, connection_out); 815 max_fd = MAX(max_fd, notify_pipe[0]); 816 817 server_init_dispatch(); 818 819 for (;;) { 820 process_buffered_input_packets(); 821 822 rekeying = (xxx_kex != NULL && !xxx_kex->done); 823 824 if (!rekeying && packet_not_very_much_data_to_write()) 825 channel_output_poll(); 826 if (options.rekey_interval > 0 && compat20 && !rekeying) 827 rekey_timeout_ms = packet_get_rekey_timeout() * 1000; 828 else 829 rekey_timeout_ms = 0; 830 831 wait_until_can_do_something(&readset, &writeset, &max_fd, 832 &nalloc, rekey_timeout_ms); 833 834 if (received_sigterm) { 835 logit("Exiting on signal %d", (int)received_sigterm); 836 /* Clean up sessions, utmp, etc. */ 837 cleanup_exit(255); 838 } 839 840 collect_children(); 841 if (!rekeying) { 842 channel_after_select(readset, writeset); 843 if (packet_need_rekeying()) { 844 debug("need rekeying"); 845 xxx_kex->done = 0; 846 kex_send_kexinit(xxx_kex); 847 } 848 } 849 process_input(readset); 850 if (connection_closed) 851 break; 852 process_output(writeset); 853 } 854 collect_children(); 855 856 free(readset); 857 free(writeset); 858 859 /* free all channels, no more reads and writes */ 860 channel_free_all(); 861 862 /* free remaining sessions, e.g. remove wtmp entries */ 863 session_destroy_all(NULL); 864 } 865 866 static void 867 server_input_keep_alive(int type, u_int32_t seq, void *ctxt) 868 { 869 debug("Got %d/%u for keepalive", type, seq); 870 /* 871 * reset timeout, since we got a sane answer from the client. 872 * even if this was generated by something other than 873 * the bogus CHANNEL_REQUEST we send for keepalives. 874 */ 875 packet_set_alive_timeouts(0); 876 } 877 878 static void 879 server_input_stdin_data(int type, u_int32_t seq, void *ctxt) 880 { 881 char *data; 882 u_int data_len; 883 884 /* Stdin data from the client. Append it to the buffer. */ 885 /* Ignore any data if the client has closed stdin. */ 886 if (fdin == -1) 887 return; 888 data = packet_get_string(&data_len); 889 packet_check_eom(); 890 buffer_append(&stdin_buffer, data, data_len); 891 explicit_bzero(data, data_len); 892 free(data); 893 } 894 895 static void 896 server_input_eof(int type, u_int32_t seq, void *ctxt) 897 { 898 /* 899 * Eof from the client. The stdin descriptor to the 900 * program will be closed when all buffered data has 901 * drained. 902 */ 903 debug("EOF received for stdin."); 904 packet_check_eom(); 905 stdin_eof = 1; 906 } 907 908 static void 909 server_input_window_size(int type, u_int32_t seq, void *ctxt) 910 { 911 u_int row = packet_get_int(); 912 u_int col = packet_get_int(); 913 u_int xpixel = packet_get_int(); 914 u_int ypixel = packet_get_int(); 915 916 debug("Window change received."); 917 packet_check_eom(); 918 if (fdin != -1) 919 pty_change_window_size(fdin, row, col, xpixel, ypixel); 920 } 921 922 static Channel * 923 server_request_direct_tcpip(void) 924 { 925 Channel *c = NULL; 926 char *target, *originator; 927 u_short target_port, originator_port; 928 929 target = packet_get_string(NULL); 930 target_port = packet_get_int(); 931 originator = packet_get_string(NULL); 932 originator_port = packet_get_int(); 933 packet_check_eom(); 934 935 debug("server_request_direct_tcpip: originator %s port %d, target %s " 936 "port %d", originator, originator_port, target, target_port); 937 938 /* XXX fine grained permissions */ 939 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 940 !no_port_forwarding_flag) { 941 c = channel_connect_to_port(target, target_port, 942 "direct-tcpip", "direct-tcpip"); 943 } else { 944 logit("refused local port forward: " 945 "originator %s port %d, target %s port %d", 946 originator, originator_port, target, target_port); 947 } 948 949 free(originator); 950 free(target); 951 952 return c; 953 } 954 955 static Channel * 956 server_request_direct_streamlocal(void) 957 { 958 Channel *c = NULL; 959 char *target, *originator; 960 u_short originator_port; 961 962 target = packet_get_string(NULL); 963 originator = packet_get_string(NULL); 964 originator_port = packet_get_int(); 965 packet_check_eom(); 966 967 debug("server_request_direct_streamlocal: originator %s port %d, target %s", 968 originator, originator_port, target); 969 970 /* XXX fine grained permissions */ 971 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 972 !no_port_forwarding_flag) { 973 c = channel_connect_to_path(target, 974 "direct-streamlocal@openssh.com", "direct-streamlocal"); 975 } else { 976 logit("refused streamlocal port forward: " 977 "originator %s port %d, target %s", 978 originator, originator_port, target); 979 } 980 981 free(originator); 982 free(target); 983 984 return c; 985 } 986 987 static Channel * 988 server_request_tun(void) 989 { 990 Channel *c = NULL; 991 int mode, tun; 992 int sock; 993 994 mode = packet_get_int(); 995 switch (mode) { 996 case SSH_TUNMODE_POINTOPOINT: 997 case SSH_TUNMODE_ETHERNET: 998 break; 999 default: 1000 packet_send_debug("Unsupported tunnel device mode."); 1001 return NULL; 1002 } 1003 if ((options.permit_tun & mode) == 0) { 1004 packet_send_debug("Server has rejected tunnel device " 1005 "forwarding"); 1006 return NULL; 1007 } 1008 1009 tun = packet_get_int(); 1010 if (forced_tun_device != -1) { 1011 if (tun != SSH_TUNID_ANY && forced_tun_device != tun) 1012 goto done; 1013 tun = forced_tun_device; 1014 } 1015 sock = tun_open(tun, mode); 1016 if (sock < 0) 1017 goto done; 1018 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1, 1019 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 1020 c->datagram = 1; 1021 1022 done: 1023 if (c == NULL) 1024 packet_send_debug("Failed to open the tunnel device."); 1025 return c; 1026 } 1027 1028 static Channel * 1029 server_request_session(void) 1030 { 1031 Channel *c; 1032 1033 debug("input_session_request"); 1034 packet_check_eom(); 1035 1036 if (no_more_sessions) { 1037 packet_disconnect("Possible attack: attempt to open a session " 1038 "after additional sessions disabled"); 1039 } 1040 1041 /* 1042 * A server session has no fd to read or write until a 1043 * CHANNEL_REQUEST for a shell is made, so we set the type to 1044 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 1045 * CHANNEL_REQUEST messages is registered. 1046 */ 1047 c = channel_new("session", SSH_CHANNEL_LARVAL, 1048 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 1049 0, "server-session", 1); 1050 if (session_open(the_authctxt, c->self) != 1) { 1051 debug("session open failed, free channel %d", c->self); 1052 channel_free(c); 1053 return NULL; 1054 } 1055 channel_register_cleanup(c->self, session_close_by_channel, 0); 1056 return c; 1057 } 1058 1059 static void 1060 server_input_channel_open(int type, u_int32_t seq, void *ctxt) 1061 { 1062 Channel *c = NULL; 1063 char *ctype; 1064 int rchan; 1065 u_int rmaxpack, rwindow, len; 1066 1067 ctype = packet_get_string(&len); 1068 rchan = packet_get_int(); 1069 rwindow = packet_get_int(); 1070 rmaxpack = packet_get_int(); 1071 1072 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 1073 ctype, rchan, rwindow, rmaxpack); 1074 1075 if (strcmp(ctype, "session") == 0) { 1076 c = server_request_session(); 1077 } else if (strcmp(ctype, "direct-tcpip") == 0) { 1078 c = server_request_direct_tcpip(); 1079 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 1080 c = server_request_direct_streamlocal(); 1081 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 1082 c = server_request_tun(); 1083 } 1084 if (c != NULL) { 1085 debug("server_input_channel_open: confirm %s", ctype); 1086 c->remote_id = rchan; 1087 c->remote_window = rwindow; 1088 c->remote_maxpacket = rmaxpack; 1089 if (c->type != SSH_CHANNEL_CONNECTING) { 1090 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 1091 packet_put_int(c->remote_id); 1092 packet_put_int(c->self); 1093 packet_put_int(c->local_window); 1094 packet_put_int(c->local_maxpacket); 1095 packet_send(); 1096 } 1097 } else { 1098 debug("server_input_channel_open: failure %s", ctype); 1099 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 1100 packet_put_int(rchan); 1101 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED); 1102 if (!(datafellows & SSH_BUG_OPENFAILURE)) { 1103 packet_put_cstring("open failed"); 1104 packet_put_cstring(""); 1105 } 1106 packet_send(); 1107 } 1108 free(ctype); 1109 } 1110 1111 static void 1112 server_input_global_request(int type, u_int32_t seq, void *ctxt) 1113 { 1114 char *rtype; 1115 int want_reply; 1116 int success = 0, allocated_listen_port = 0; 1117 1118 rtype = packet_get_string(NULL); 1119 want_reply = packet_get_char(); 1120 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 1121 1122 /* -R style forwarding */ 1123 if (strcmp(rtype, "tcpip-forward") == 0) { 1124 struct passwd *pw; 1125 struct Forward fwd; 1126 1127 pw = the_authctxt->pw; 1128 if (pw == NULL || !the_authctxt->valid) 1129 fatal("server_input_global_request: no/invalid user"); 1130 memset(&fwd, 0, sizeof(fwd)); 1131 fwd.listen_host = packet_get_string(NULL); 1132 fwd.listen_port = (u_short)packet_get_int(); 1133 debug("server_input_global_request: tcpip-forward listen %s port %d", 1134 fwd.listen_host, fwd.listen_port); 1135 1136 /* check permissions */ 1137 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 1138 no_port_forwarding_flag || 1139 (!want_reply && fwd.listen_port == 0) || 1140 (fwd.listen_port != 0 && fwd.listen_port < IPPORT_RESERVED && 1141 pw->pw_uid != 0)) { 1142 success = 0; 1143 packet_send_debug("Server has disabled port forwarding."); 1144 } else { 1145 /* Start listening on the port */ 1146 success = channel_setup_remote_fwd_listener(&fwd, 1147 &allocated_listen_port, &options.fwd_opts); 1148 } 1149 free(fwd.listen_host); 1150 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 1151 struct Forward fwd; 1152 1153 memset(&fwd, 0, sizeof(fwd)); 1154 fwd.listen_host = packet_get_string(NULL); 1155 fwd.listen_port = (u_short)packet_get_int(); 1156 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 1157 fwd.listen_host, fwd.listen_port); 1158 1159 success = channel_cancel_rport_listener(&fwd); 1160 free(fwd.listen_host); 1161 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 1162 struct Forward fwd; 1163 1164 memset(&fwd, 0, sizeof(fwd)); 1165 fwd.listen_path = packet_get_string(NULL); 1166 debug("server_input_global_request: streamlocal-forward listen path %s", 1167 fwd.listen_path); 1168 1169 /* check permissions */ 1170 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 1171 || no_port_forwarding_flag) { 1172 success = 0; 1173 packet_send_debug("Server has disabled port forwarding."); 1174 } else { 1175 /* Start listening on the socket */ 1176 success = channel_setup_remote_fwd_listener( 1177 &fwd, NULL, &options.fwd_opts); 1178 } 1179 free(fwd.listen_path); 1180 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 1181 struct Forward fwd; 1182 1183 memset(&fwd, 0, sizeof(fwd)); 1184 fwd.listen_path = packet_get_string(NULL); 1185 debug("%s: cancel-streamlocal-forward path %s", __func__, 1186 fwd.listen_path); 1187 1188 success = channel_cancel_rport_listener(&fwd); 1189 free(fwd.listen_path); 1190 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 1191 no_more_sessions = 1; 1192 success = 1; 1193 } 1194 if (want_reply) { 1195 packet_start(success ? 1196 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 1197 if (success && allocated_listen_port > 0) 1198 packet_put_int(allocated_listen_port); 1199 packet_send(); 1200 packet_write_wait(); 1201 } 1202 free(rtype); 1203 } 1204 1205 static void 1206 server_input_channel_req(int type, u_int32_t seq, void *ctxt) 1207 { 1208 Channel *c; 1209 int id, reply, success = 0; 1210 char *rtype; 1211 1212 id = packet_get_int(); 1213 rtype = packet_get_string(NULL); 1214 reply = packet_get_char(); 1215 1216 debug("server_input_channel_req: channel %d request %s reply %d", 1217 id, rtype, reply); 1218 1219 if ((c = channel_lookup(id)) == NULL) 1220 packet_disconnect("server_input_channel_req: " 1221 "unknown channel %d", id); 1222 if (!strcmp(rtype, "eow@openssh.com")) { 1223 packet_check_eom(); 1224 chan_rcvd_eow(c); 1225 } else if ((c->type == SSH_CHANNEL_LARVAL || 1226 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 1227 success = session_input_channel_req(c, rtype); 1228 if (reply && !(c->flags & CHAN_CLOSE_SENT)) { 1229 packet_start(success ? 1230 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 1231 packet_put_int(c->remote_id); 1232 packet_send(); 1233 } 1234 free(rtype); 1235 } 1236 1237 static void 1238 server_init_dispatch_20(void) 1239 { 1240 debug("server_init_dispatch_20"); 1241 dispatch_init(&dispatch_protocol_error); 1242 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 1243 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 1244 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 1245 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 1246 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 1247 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1248 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1249 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 1250 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1251 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1252 /* client_alive */ 1253 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1254 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1255 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1256 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1257 /* rekeying */ 1258 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 1259 } 1260 static void 1261 server_init_dispatch_13(void) 1262 { 1263 debug("server_init_dispatch_13"); 1264 dispatch_init(NULL); 1265 dispatch_set(SSH_CMSG_EOF, &server_input_eof); 1266 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data); 1267 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size); 1268 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close); 1269 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation); 1270 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data); 1271 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 1272 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 1273 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open); 1274 } 1275 static void 1276 server_init_dispatch_15(void) 1277 { 1278 server_init_dispatch_13(); 1279 debug("server_init_dispatch_15"); 1280 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof); 1281 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose); 1282 } 1283 static void 1284 server_init_dispatch(void) 1285 { 1286 if (compat20) 1287 server_init_dispatch_20(); 1288 else if (compat13) 1289 server_init_dispatch_13(); 1290 else 1291 server_init_dispatch_15(); 1292 } 1293