mux.c revision 1.4
1/* $OpenBSD: mux.c,v 1.4 2008/06/12 15:19:17 djm Exp $ */ 2/* 3 * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18/* ssh session multiplexing support */ 19 20/* 21 * TODO: 22 * 1. partial reads in muxserver_accept_control (maybe make channels 23 * from accepted connections) 24 * 2. Better signalling from master to slave, especially passing of 25 * error messages 26 * 3. Better fall-back from mux slave error to new connection. 27 * 3. Add/delete forwardings via slave 28 * 4. ExitOnForwardingFailure (after #3 obviously) 29 * 5. Maybe extension mechanisms for multi-X11/multi-agent forwarding 30 * 6. Document the mux mini-protocol somewhere. 31 * 7. Support ~^Z in mux slaves. 32 * 8. Inspect or control sessions in master. 33 * 9. If we ever support the "signal" channel request, send signals on 34 * sessions in master. 35 */ 36 37#include <sys/types.h> 38#include <sys/param.h> 39#include <sys/queue.h> 40#include <sys/stat.h> 41#include <sys/socket.h> 42#include <sys/un.h> 43 44#include <errno.h> 45#include <fcntl.h> 46#include <signal.h> 47#include <stdarg.h> 48#include <stddef.h> 49#include <stdlib.h> 50#include <stdio.h> 51#include <string.h> 52#include <unistd.h> 53#include <util.h> 54#include <paths.h> 55 56#include "xmalloc.h" 57#include "log.h" 58#include "ssh.h" 59#include "pathnames.h" 60#include "misc.h" 61#include "match.h" 62#include "buffer.h" 63#include "channels.h" 64#include "msg.h" 65#include "packet.h" 66#include "monitor_fdpass.h" 67#include "sshpty.h" 68#include "key.h" 69#include "readconf.h" 70#include "clientloop.h" 71 72/* from ssh.c */ 73extern int tty_flag; 74extern Options options; 75extern int stdin_null_flag; 76extern char *host; 77int subsystem_flag; 78extern Buffer command; 79 80/* Context for session open confirmation callback */ 81struct mux_session_confirm_ctx { 82 int want_tty; 83 int want_subsys; 84 int want_x_fwd; 85 int want_agent_fwd; 86 Buffer cmd; 87 char *term; 88 struct termios tio; 89 char **env; 90}; 91 92/* fd to control socket */ 93int muxserver_sock = -1; 94 95/* Multiplexing control command */ 96u_int muxclient_command = 0; 97 98/* Set when signalled. */ 99static volatile sig_atomic_t muxclient_terminate = 0; 100 101/* PID of multiplex server */ 102static u_int muxserver_pid = 0; 103 104 105/* ** Multiplexing master support */ 106 107/* Prepare a mux master to listen on a Unix domain socket. */ 108void 109muxserver_listen(void) 110{ 111 struct sockaddr_un addr; 112 mode_t old_umask; 113 114 if (options.control_path == NULL || 115 options.control_master == SSHCTL_MASTER_NO) 116 return; 117 118 debug("setting up multiplex master socket"); 119 120 memset(&addr, '\0', sizeof(addr)); 121 addr.sun_family = AF_UNIX; 122 addr.sun_len = offsetof(struct sockaddr_un, sun_path) + 123 strlen(options.control_path) + 1; 124 125 if (strlcpy(addr.sun_path, options.control_path, 126 sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) 127 fatal("ControlPath too long"); 128 129 if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) 130 fatal("%s socket(): %s", __func__, strerror(errno)); 131 132 old_umask = umask(0177); 133 if (bind(muxserver_sock, (struct sockaddr *)&addr, addr.sun_len) == -1) { 134 muxserver_sock = -1; 135 if (errno == EINVAL || errno == EADDRINUSE) 136 fatal("ControlSocket %s already exists", 137 options.control_path); 138 else 139 fatal("%s bind(): %s", __func__, strerror(errno)); 140 } 141 umask(old_umask); 142 143 if (listen(muxserver_sock, 64) == -1) 144 fatal("%s listen(): %s", __func__, strerror(errno)); 145 146 set_nonblock(muxserver_sock); 147} 148 149/* Callback on open confirmation in mux master for a mux client session. */ 150static void 151mux_session_confirm(int id, void *arg) 152{ 153 struct mux_session_confirm_ctx *cctx = arg; 154 const char *display; 155 Channel *c; 156 int i; 157 158 if (cctx == NULL) 159 fatal("%s: cctx == NULL", __func__); 160 if ((c = channel_lookup(id)) == NULL) 161 fatal("%s: no channel for id %d", __func__, id); 162 163 display = getenv("DISPLAY"); 164 if (cctx->want_x_fwd && options.forward_x11 && display != NULL) { 165 char *proto, *data; 166 /* Get reasonable local authentication information. */ 167 client_x11_get_proto(display, options.xauth_location, 168 options.forward_x11_trusted, &proto, &data); 169 /* Request forwarding with authentication spoofing. */ 170 debug("Requesting X11 forwarding with authentication spoofing."); 171 x11_request_forwarding_with_spoofing(id, display, proto, data); 172 /* XXX wait for reply */ 173 } 174 175 if (cctx->want_agent_fwd && options.forward_agent) { 176 debug("Requesting authentication agent forwarding."); 177 channel_request_start(id, "auth-agent-req@openssh.com", 0); 178 packet_send(); 179 } 180 181 client_session2_setup(id, cctx->want_tty, cctx->want_subsys, 182 cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env); 183 184 c->open_confirm_ctx = NULL; 185 buffer_free(&cctx->cmd); 186 xfree(cctx->term); 187 if (cctx->env != NULL) { 188 for (i = 0; cctx->env[i] != NULL; i++) 189 xfree(cctx->env[i]); 190 xfree(cctx->env); 191 } 192 xfree(cctx); 193} 194 195/* 196 * Accept a connection on the mux master socket and process the 197 * client's request. Returns flag indicating whether mux master should 198 * begin graceful close. 199 */ 200int 201muxserver_accept_control(void) 202{ 203 Buffer m; 204 Channel *c; 205 int client_fd, new_fd[3], ver, allowed, window, packetmax; 206 socklen_t addrlen; 207 struct sockaddr_storage addr; 208 struct mux_session_confirm_ctx *cctx; 209 char *cmd; 210 u_int i, j, len, env_len, mux_command, flags, escape_char; 211 uid_t euid; 212 gid_t egid; 213 int start_close = 0; 214 215 /* 216 * Accept connection on control socket 217 */ 218 memset(&addr, 0, sizeof(addr)); 219 addrlen = sizeof(addr); 220 if ((client_fd = accept(muxserver_sock, 221 (struct sockaddr*)&addr, &addrlen)) == -1) { 222 error("%s accept: %s", __func__, strerror(errno)); 223 return 0; 224 } 225 226 if (getpeereid(client_fd, &euid, &egid) < 0) { 227 error("%s getpeereid failed: %s", __func__, strerror(errno)); 228 close(client_fd); 229 return 0; 230 } 231 if ((euid != 0) && (getuid() != euid)) { 232 error("control mode uid mismatch: peer euid %u != uid %u", 233 (u_int) euid, (u_int) getuid()); 234 close(client_fd); 235 return 0; 236 } 237 238 /* XXX handle asynchronously */ 239 unset_nonblock(client_fd); 240 241 /* Read command */ 242 buffer_init(&m); 243 if (ssh_msg_recv(client_fd, &m) == -1) { 244 error("%s: client msg_recv failed", __func__); 245 close(client_fd); 246 buffer_free(&m); 247 return 0; 248 } 249 if ((ver = buffer_get_char(&m)) != SSHMUX_VER) { 250 error("%s: wrong client version %d", __func__, ver); 251 buffer_free(&m); 252 close(client_fd); 253 return 0; 254 } 255 256 allowed = 1; 257 mux_command = buffer_get_int(&m); 258 flags = buffer_get_int(&m); 259 260 buffer_clear(&m); 261 262 switch (mux_command) { 263 case SSHMUX_COMMAND_OPEN: 264 if (options.control_master == SSHCTL_MASTER_ASK || 265 options.control_master == SSHCTL_MASTER_AUTO_ASK) 266 allowed = ask_permission("Allow shared connection " 267 "to %s? ", host); 268 /* continue below */ 269 break; 270 case SSHMUX_COMMAND_TERMINATE: 271 if (options.control_master == SSHCTL_MASTER_ASK || 272 options.control_master == SSHCTL_MASTER_AUTO_ASK) 273 allowed = ask_permission("Terminate shared connection " 274 "to %s? ", host); 275 if (allowed) 276 start_close = 1; 277 /* FALLTHROUGH */ 278 case SSHMUX_COMMAND_ALIVE_CHECK: 279 /* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */ 280 buffer_clear(&m); 281 buffer_put_int(&m, allowed); 282 buffer_put_int(&m, getpid()); 283 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { 284 error("%s: client msg_send failed", __func__); 285 close(client_fd); 286 buffer_free(&m); 287 return start_close; 288 } 289 buffer_free(&m); 290 close(client_fd); 291 return start_close; 292 default: 293 error("Unsupported command %d", mux_command); 294 buffer_free(&m); 295 close(client_fd); 296 return 0; 297 } 298 299 /* Reply for SSHMUX_COMMAND_OPEN */ 300 buffer_clear(&m); 301 buffer_put_int(&m, allowed); 302 buffer_put_int(&m, getpid()); 303 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { 304 error("%s: client msg_send failed", __func__); 305 close(client_fd); 306 buffer_free(&m); 307 return 0; 308 } 309 310 if (!allowed) { 311 error("Refused control connection"); 312 close(client_fd); 313 buffer_free(&m); 314 return 0; 315 } 316 317 buffer_clear(&m); 318 if (ssh_msg_recv(client_fd, &m) == -1) { 319 error("%s: client msg_recv failed", __func__); 320 close(client_fd); 321 buffer_free(&m); 322 return 0; 323 } 324 if ((ver = buffer_get_char(&m)) != SSHMUX_VER) { 325 error("%s: wrong client version %d", __func__, ver); 326 buffer_free(&m); 327 close(client_fd); 328 return 0; 329 } 330 331 cctx = xcalloc(1, sizeof(*cctx)); 332 cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0; 333 cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0; 334 cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0; 335 cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0; 336 cctx->term = buffer_get_string(&m, &len); 337 escape_char = buffer_get_int(&m); 338 339 cmd = buffer_get_string(&m, &len); 340 buffer_init(&cctx->cmd); 341 buffer_append(&cctx->cmd, cmd, strlen(cmd)); 342 343 env_len = buffer_get_int(&m); 344 env_len = MIN(env_len, 4096); 345 debug3("%s: receiving %d env vars", __func__, env_len); 346 if (env_len != 0) { 347 cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env)); 348 for (i = 0; i < env_len; i++) 349 cctx->env[i] = buffer_get_string(&m, &len); 350 cctx->env[i] = NULL; 351 } 352 353 debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__, 354 cctx->want_tty, cctx->want_subsys, cmd); 355 xfree(cmd); 356 357 /* Gather fds from client */ 358 for(i = 0; i < 3; i++) { 359 if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) { 360 error("%s: failed to receive fd %d from slave", 361 __func__, i); 362 for (j = 0; j < i; j++) 363 close(new_fd[j]); 364 for (j = 0; j < env_len; j++) 365 xfree(cctx->env[j]); 366 if (env_len > 0) 367 xfree(cctx->env); 368 xfree(cctx->term); 369 buffer_free(&cctx->cmd); 370 close(client_fd); 371 xfree(cctx); 372 return 0; 373 } 374 } 375 376 debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__, 377 new_fd[0], new_fd[1], new_fd[2]); 378 379 /* Try to pick up ttymodes from client before it goes raw */ 380 if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1) 381 error("%s: tcgetattr: %s", __func__, strerror(errno)); 382 383 /* This roundtrip is just for synchronisation of ttymodes */ 384 buffer_clear(&m); 385 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) { 386 error("%s: client msg_send failed", __func__); 387 close(client_fd); 388 close(new_fd[0]); 389 close(new_fd[1]); 390 close(new_fd[2]); 391 buffer_free(&m); 392 xfree(cctx->term); 393 if (env_len != 0) { 394 for (i = 0; i < env_len; i++) 395 xfree(cctx->env[i]); 396 xfree(cctx->env); 397 } 398 return 0; 399 } 400 buffer_free(&m); 401 402 /* enable nonblocking unless tty */ 403 if (!isatty(new_fd[0])) 404 set_nonblock(new_fd[0]); 405 if (!isatty(new_fd[1])) 406 set_nonblock(new_fd[1]); 407 if (!isatty(new_fd[2])) 408 set_nonblock(new_fd[2]); 409 410 set_nonblock(client_fd); 411 412 window = CHAN_SES_WINDOW_DEFAULT; 413 packetmax = CHAN_SES_PACKET_DEFAULT; 414 if (cctx->want_tty) { 415 window >>= 1; 416 packetmax >>= 1; 417 } 418 419 c = channel_new("session", SSH_CHANNEL_OPENING, 420 new_fd[0], new_fd[1], new_fd[2], window, packetmax, 421 CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0); 422 423 c->ctl_fd = client_fd; 424 if (cctx->want_tty && escape_char != 0xffffffff) { 425 channel_register_filter(c->self, 426 client_simple_escape_filter, NULL, 427 client_filter_cleanup, 428 client_new_escape_filter_ctx((int)escape_char)); 429 } 430 431 debug3("%s: channel_new: %d", __func__, c->self); 432 433 channel_send_open(c->self); 434 channel_register_open_confirm(c->self, mux_session_confirm, cctx); 435 return 0; 436} 437 438/* ** Multiplexing client support */ 439 440/* Exit signal handler */ 441static void 442control_client_sighandler(int signo) 443{ 444 muxclient_terminate = signo; 445} 446 447/* 448 * Relay signal handler - used to pass some signals from mux client to 449 * mux master. 450 */ 451static void 452control_client_sigrelay(int signo) 453{ 454 int save_errno = errno; 455 456 if (muxserver_pid > 1) 457 kill(muxserver_pid, signo); 458 459 errno = save_errno; 460} 461 462/* Check mux client environment variables before passing them to mux master. */ 463static int 464env_permitted(char *env) 465{ 466 int i, ret; 467 char name[1024], *cp; 468 469 if ((cp = strchr(env, '=')) == NULL || cp == env) 470 return (0); 471 ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env); 472 if (ret <= 0 || (size_t)ret >= sizeof(name)) 473 fatal("env_permitted: name '%.100s...' too long", env); 474 475 for (i = 0; i < options.num_send_env; i++) 476 if (match_pattern(name, options.send_env[i])) 477 return (1); 478 479 return (0); 480} 481 482/* Multiplex client main loop. */ 483void 484muxclient(const char *path) 485{ 486 struct sockaddr_un addr; 487 int i, r, fd, sock, exitval[2], num_env; 488 Buffer m; 489 char *term; 490 extern char **environ; 491 u_int flags; 492 493 if (muxclient_command == 0) 494 muxclient_command = SSHMUX_COMMAND_OPEN; 495 496 switch (options.control_master) { 497 case SSHCTL_MASTER_AUTO: 498 case SSHCTL_MASTER_AUTO_ASK: 499 debug("auto-mux: Trying existing master"); 500 /* FALLTHROUGH */ 501 case SSHCTL_MASTER_NO: 502 break; 503 default: 504 return; 505 } 506 507 memset(&addr, '\0', sizeof(addr)); 508 addr.sun_family = AF_UNIX; 509 addr.sun_len = offsetof(struct sockaddr_un, sun_path) + 510 strlen(path) + 1; 511 512 if (strlcpy(addr.sun_path, path, 513 sizeof(addr.sun_path)) >= sizeof(addr.sun_path)) 514 fatal("ControlPath too long"); 515 516 if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0) 517 fatal("%s socket(): %s", __func__, strerror(errno)); 518 519 if (connect(sock, (struct sockaddr *)&addr, addr.sun_len) == -1) { 520 if (muxclient_command != SSHMUX_COMMAND_OPEN) { 521 fatal("Control socket connect(%.100s): %s", path, 522 strerror(errno)); 523 } 524 if (errno == ENOENT) 525 debug("Control socket \"%.100s\" does not exist", path); 526 else { 527 error("Control socket connect(%.100s): %s", path, 528 strerror(errno)); 529 } 530 close(sock); 531 return; 532 } 533 534 if (stdin_null_flag) { 535 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1) 536 fatal("open(/dev/null): %s", strerror(errno)); 537 if (dup2(fd, STDIN_FILENO) == -1) 538 fatal("dup2: %s", strerror(errno)); 539 if (fd > STDERR_FILENO) 540 close(fd); 541 } 542 543 term = getenv("TERM"); 544 545 flags = 0; 546 if (tty_flag) 547 flags |= SSHMUX_FLAG_TTY; 548 if (subsystem_flag) 549 flags |= SSHMUX_FLAG_SUBSYS; 550 if (options.forward_x11) 551 flags |= SSHMUX_FLAG_X11_FWD; 552 if (options.forward_agent) 553 flags |= SSHMUX_FLAG_AGENT_FWD; 554 555 signal(SIGPIPE, SIG_IGN); 556 557 buffer_init(&m); 558 559 /* Send our command to server */ 560 buffer_put_int(&m, muxclient_command); 561 buffer_put_int(&m, flags); 562 if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1) 563 fatal("%s: msg_send", __func__); 564 buffer_clear(&m); 565 566 /* Get authorisation status and PID of controlee */ 567 if (ssh_msg_recv(sock, &m) == -1) 568 fatal("%s: msg_recv", __func__); 569 if (buffer_get_char(&m) != SSHMUX_VER) 570 fatal("%s: wrong version", __func__); 571 if (buffer_get_int(&m) != 1) 572 fatal("Connection to master denied"); 573 muxserver_pid = buffer_get_int(&m); 574 575 buffer_clear(&m); 576 577 switch (muxclient_command) { 578 case SSHMUX_COMMAND_ALIVE_CHECK: 579 fprintf(stderr, "Master running (pid=%d)\r\n", 580 muxserver_pid); 581 exit(0); 582 case SSHMUX_COMMAND_TERMINATE: 583 fprintf(stderr, "Exit request sent.\r\n"); 584 exit(0); 585 case SSHMUX_COMMAND_OPEN: 586 buffer_put_cstring(&m, term ? term : ""); 587 if (options.escape_char == SSH_ESCAPECHAR_NONE) 588 buffer_put_int(&m, 0xffffffff); 589 else 590 buffer_put_int(&m, options.escape_char); 591 buffer_append(&command, "\0", 1); 592 buffer_put_cstring(&m, buffer_ptr(&command)); 593 594 if (options.num_send_env == 0 || environ == NULL) { 595 buffer_put_int(&m, 0); 596 } else { 597 /* Pass environment */ 598 num_env = 0; 599 for (i = 0; environ[i] != NULL; i++) { 600 if (env_permitted(environ[i])) 601 num_env++; /* Count */ 602 } 603 buffer_put_int(&m, num_env); 604 for (i = 0; environ[i] != NULL && num_env >= 0; i++) { 605 if (env_permitted(environ[i])) { 606 num_env--; 607 buffer_put_cstring(&m, environ[i]); 608 } 609 } 610 } 611 break; 612 default: 613 fatal("unrecognised muxclient_command %d", muxclient_command); 614 } 615 616 if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1) 617 fatal("%s: msg_send", __func__); 618 619 if (mm_send_fd(sock, STDIN_FILENO) == -1 || 620 mm_send_fd(sock, STDOUT_FILENO) == -1 || 621 mm_send_fd(sock, STDERR_FILENO) == -1) 622 fatal("%s: send fds failed", __func__); 623 624 /* Wait for reply, so master has a chance to gather ttymodes */ 625 buffer_clear(&m); 626 if (ssh_msg_recv(sock, &m) == -1) 627 fatal("%s: msg_recv", __func__); 628 if (buffer_get_char(&m) != SSHMUX_VER) 629 fatal("%s: wrong version", __func__); 630 buffer_free(&m); 631 632 signal(SIGHUP, control_client_sighandler); 633 signal(SIGINT, control_client_sighandler); 634 signal(SIGTERM, control_client_sighandler); 635 signal(SIGWINCH, control_client_sigrelay); 636 637 if (tty_flag) 638 enter_raw_mode(); 639 640 /* 641 * Stick around until the controlee closes the client_fd. 642 * Before it does, it is expected to write this process' exit 643 * value (one int). This process must read the value and wait for 644 * the closure of the client_fd; if this one closes early, the 645 * multiplex master will terminate early too (possibly losing data). 646 */ 647 exitval[0] = 0; 648 for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) { 649 r = read(sock, (char *)exitval + i, sizeof(exitval) - i); 650 if (r == 0) { 651 debug2("Received EOF from master"); 652 break; 653 } 654 if (r == -1) { 655 if (errno == EINTR) 656 continue; 657 fatal("%s: read %s", __func__, strerror(errno)); 658 } 659 i += r; 660 } 661 662 close(sock); 663 leave_raw_mode(); 664 if (i > (int)sizeof(int)) 665 fatal("%s: master returned too much data (%d > %lu)", 666 __func__, i, sizeof(int)); 667 if (muxclient_terminate) { 668 debug2("Exiting on signal %d", muxclient_terminate); 669 exitval[0] = 255; 670 } else if (i < (int)sizeof(int)) { 671 debug2("Control master terminated unexpectedly"); 672 exitval[0] = 255; 673 } else 674 debug2("Received exit status from master %d", exitval[0]); 675 676 if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET) 677 fprintf(stderr, "Shared connection to %s closed.\r\n", host); 678 679 exit(exitval[0]); 680} 681