ssh.c

   1 /* $OpenBSD: ssh.c,v 1.286 2006/07/12 22:28:52 stevesk 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  * Ssh client program.  This program can be used to log into a remote machine.
   7  * The software supports strong authentication, encryption, and forwarding
   8  * of X11, TCP/IP, and authentication connections.
   9  *
  10  * As far as I am concerned, the code I have written for this software
  11  * can be used freely for any purpose.  Any derived versions of this
  12  * software must be clearly marked as such, and if the derived work is
  13  * incompatible with the protocol description in the RFC file, it must be
  14  * called by a name other than "ssh" or "Secure Shell".
  15  *
  16  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  17  * Copyright (c) 2000, 2001, 2002, 2003 Markus Friedl.  All rights reserved.
  18  *
  19  * Modified to work with SSL by Niels Provos <provos@citi.umich.edu>
  20  * in Canada (German citizen).
  21  *
  22  * Redistribution and use in source and binary forms, with or without
  23  * modification, are permitted provided that the following conditions
  24  * are met:
  25  * 1. Redistributions of source code must retain the above copyright
  26  *    notice, this list of conditions and the following disclaimer.
  27  * 2. Redistributions in binary form must reproduce the above copyright
  28  *    notice, this list of conditions and the following disclaimer in the
  29  *    documentation and/or other materials provided with the distribution.
  30  *
  31  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  32  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  33  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  34  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  35  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  36  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  37  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  38  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  39  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  40  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  41  */
  42
  43 #include "includes.h"
  44
  45 #include <sys/types.h>
  46 #ifdef HAVE_SYS_STAT_H
  47 # include <sys/stat.h>
  48 #endif
  49 #include <sys/resource.h>
  50 #include <sys/ioctl.h>
  51 #include <sys/socket.h>
  52 #include <sys/un.h>
  53
  54 #include <ctype.h>
  55 #include <errno.h>
  56 #include <fcntl.h>
  57 #if defined(HAVE_NETDB_H)
  58 # include <netdb.h>
  59 #endif
  60 #ifdef HAVE_PATHS_H
  61 #include <paths.h>
  62 #endif
  63 #include <pwd.h>
  64 #include <signal.h>
  65
  66 #include <openssl/evp.h>
  67 #include <openssl/err.h>
  68
  69 #include "ssh.h"
  70 #include "ssh1.h"
  71 #include "ssh2.h"
  72 #include "compat.h"
  73 #include "cipher.h"
  74 #include "xmalloc.h"
  75 #include "packet.h"
  76 #include "buffer.h"
  77 #include "bufaux.h"
  78 #include "channels.h"
  79 #include "key.h"
  80 #include "authfd.h"
  81 #include "authfile.h"
  82 #include "pathnames.h"
  83 #include "dispatch.h"
  84 #include "clientloop.h"
  85 #include "log.h"
  86 #include "readconf.h"
  87 #include "sshconnect.h"
  88 #include "misc.h"
  89 #include "kex.h"
  90 #include "mac.h"
  91 #include "sshpty.h"
  92 #include "match.h"
  93 #include "msg.h"
  94 #include "monitor_fdpass.h"
  95 #include "uidswap.h"
  96 #include "version.h"
  97
  98 #ifdef SMARTCARD
  99 #include "scard.h"
 100 #endif
 101
 102 extern char *__progname;
 103
 104 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
 105 int debug_flag = 0;
 106
 107 /* Flag indicating whether a tty should be allocated */
 108 int tty_flag = 0;
 109 int no_tty_flag = 0;
 110 int force_tty_flag = 0;
 111
 112 /* don't exec a shell */
 113 int no_shell_flag = 0;
 114
 115 /*
 116  * Flag indicating that nothing should be read from stdin.  This can be set
 117  * on the command line.
 118  */
 119 int stdin_null_flag = 0;
 120
 121 /*
 122  * Flag indicating that ssh should fork after authentication.  This is useful
 123  * so that the passphrase can be entered manually, and then ssh goes to the
 124  * background.
 125  */
 126 int fork_after_authentication_flag = 0;
 127
 128 /*
 129  * General data structure for command line options and options configurable
 130  * in configuration files.  See readconf.h.
 131  */
 132 Options options;
 133
 134 /* optional user configfile */
 135 char *config = NULL;
 136
 137 /*
 138  * Name of the host we are connecting to.  This is the name given on the
 139  * command line, or the HostName specified for the user-supplied name in a
 140  * configuration file.
 141  */
 142 char *host;
 143
 144 /* socket address the host resolves to */
 145 struct sockaddr_storage hostaddr;
 146
 147 /* Private host keys. */
 148 Sensitive sensitive_data;
 149
 150 /* Original real UID. */
 151 uid_t original_real_uid;
 152 uid_t original_effective_uid;
 153
 154 /* command to be executed */
 155 Buffer command;
 156
 157 /* Should we execute a command or invoke a subsystem? */
 158 int subsystem_flag = 0;
 159
 160 /* # of replies received for global requests */
 161 static int client_global_request_id = 0;
 162
 163 /* pid of proxycommand child process */
 164 pid_t proxy_command_pid = 0;
 165
 166 /* fd to control socket */
 167 int control_fd = -1;
 168
 169 /* Multiplexing control command */
 170 static u_int mux_command = 0;
 171
 172 /* Only used in control client mode */
 173 volatile sig_atomic_t control_client_terminate = 0;
 174 u_int control_server_pid = 0;
 175
 176 /* Prints a help message to the user.  This function never returns. */
 177
 178 static void
 179 usage(void)
 180 {
 181         fprintf(stderr,
 182 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 183 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 184 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 185 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 186 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 187 "           [-w local_tun[:remote_tun]] [user@]hostname [command]\n"
 188         );
 189         exit(255);
 190 }
 191
 192 static int ssh_session(void);
 193 static int ssh_session2(void);
 194 static void load_public_identity_files(void);
 195 static void control_client(const char *path);
 196
 197 /*
 198  * Main program for the ssh client.
 199  */
 200 int
 201 main(int ac, char **av)
 202 {
 203         int i, opt, exit_status;
 204         char *p, *cp, *line, buf[256];
 205         struct stat st;
 206         struct passwd *pw;
 207         int dummy;
 208         extern int optind, optreset;
 209         extern char *optarg;
 210         struct servent *sp;
 211         Forward fwd;
 212
 213         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 214         sanitise_stdfd();
 215
 216         __progname = ssh_get_progname(av[0]);
 217         init_rng();
 218
 219         /*
 220          * Save the original real uid.  It will be needed later (uid-swapping
 221          * may clobber the real uid).
 222          */
 223         original_real_uid = getuid();
 224         original_effective_uid = geteuid();
 225
 226         /*
 227          * Use uid-swapping to give up root privileges for the duration of
 228          * option processing.  We will re-instantiate the rights when we are
 229          * ready to create the privileged port, and will permanently drop
 230          * them when the port has been created (actually, when the connection
 231          * has been made, as we may need to create the port several times).
 232          */
 233         PRIV_END;
 234
 235 #ifdef HAVE_SETRLIMIT
 236         /* If we are installed setuid root be careful to not drop core. */
 237         if (original_real_uid != original_effective_uid) {
 238                 struct rlimit rlim;
 239                 rlim.rlim_cur = rlim.rlim_max = 0;
 240                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 241                         fatal("setrlimit failed: %.100s", strerror(errno));
 242         }
 243 #endif
 244         /* Get user data. */
 245         pw = getpwuid(original_real_uid);
 246         if (!pw) {
 247                 logit("You don't exist, go away!");
 248                 exit(255);
 249         }
 250         /* Take a copy of the returned structure. */
 251         pw = pwcopy(pw);
 252
 253         /*
 254          * Set our umask to something reasonable, as some files are created
 255          * with the default umask.  This will make them world-readable but
 256          * writable only by the owner, which is ok for all files for which we
 257          * don't set the modes explicitly.
 258          */
 259         umask(022);
 260
 261         /* Initialize option structure to indicate that no values have been set. */
 262         initialize_options(&options);
 263
 264         /* Parse command-line arguments. */
 265         host = NULL;
 266
 267  again:
 268         while ((opt = getopt(ac, av,
 269             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVw:XY")) != -1) {
 270                 switch (opt) {
 271                 case '1':
 272                         options.protocol = SSH_PROTO_1;
 273                         break;
 274                 case '2':
 275                         options.protocol = SSH_PROTO_2;
 276                         break;
 277                 case '4':
 278                         options.address_family = AF_INET;
 279                         break;
 280                 case '6':
 281                         options.address_family = AF_INET6;
 282                         break;
 283                 case 'n':
 284                         stdin_null_flag = 1;
 285                         break;
 286                 case 'f':
 287                         fork_after_authentication_flag = 1;
 288                         stdin_null_flag = 1;
 289                         break;
 290                 case 'x':
 291                         options.forward_x11 = 0;
 292                         break;
 293                 case 'X':
 294                         options.forward_x11 = 1;
 295                         break;
 296                 case 'Y':
 297                         options.forward_x11 = 1;
 298                         options.forward_x11_trusted = 1;
 299                         break;
 300                 case 'g':
 301                         options.gateway_ports = 1;
 302                         break;
 303                 case 'O':
 304                         if (strcmp(optarg, "check") == 0)
 305                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 306                         else if (strcmp(optarg, "exit") == 0)
 307                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 308                         else
 309                                 fatal("Invalid multiplex command.");
 310                         break;
 311                 case 'P':       /* deprecated */
 312                         options.use_privileged_port = 0;
 313                         break;
 314                 case 'a':
 315                         options.forward_agent = 0;
 316                         break;
 317                 case 'A':
 318                         options.forward_agent = 1;
 319                         break;
 320                 case 'k':
 321                         options.gss_deleg_creds = 0;
 322                         break;
 323                 case 'i':
 324                         if (stat(optarg, &st) < 0) {
 325                                 fprintf(stderr, "Warning: Identity file %s "
 326                                     "not accessible: %s.\n", optarg,
 327                                     strerror(errno));
 328                                 break;
 329                         }
 330                         if (options.num_identity_files >=
 331                             SSH_MAX_IDENTITY_FILES)
 332                                 fatal("Too many identity files specified "
 333                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 334                         options.identity_files[options.num_identity_files++] =
 335                             xstrdup(optarg);
 336                         break;
 337                 case 'I':
 338 #ifdef SMARTCARD
 339                         options.smartcard_device = xstrdup(optarg);
 340 #else
 341                         fprintf(stderr, "no support for smartcards.\n");
 342 #endif
 343                         break;
 344                 case 't':
 345                         if (tty_flag)
 346                                 force_tty_flag = 1;
 347                         tty_flag = 1;
 348                         break;
 349                 case 'v':
 350                         if (debug_flag == 0) {
 351                                 debug_flag = 1;
 352                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 353                         } else {
 354                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 355                                         options.log_level++;
 356                                 break;
 357                         }
 358                         /* FALLTHROUGH */
 359                 case 'V':
 360                         fprintf(stderr, "%s, %s\n",
 361                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 362                         if (opt == 'V')
 363                                 exit(0);
 364                         break;
 365                 case 'w':
 366                         if (options.tun_open == -1)
 367                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 368                         options.tun_local = a2tun(optarg, &options.tun_remote);
 369                         if (options.tun_local == SSH_TUNID_ERR) {
 370                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 371                                 exit(255);
 372                         }
 373                         break;
 374                 case 'q':
 375                         options.log_level = SYSLOG_LEVEL_QUIET;
 376                         break;
 377                 case 'e':
 378                         if (optarg[0] == '^' && optarg[2] == 0 &&
 379                             (u_char) optarg[1] >= 64 &&
 380                             (u_char) optarg[1] < 128)
 381                                 options.escape_char = (u_char) optarg[1] & 31;
 382                         else if (strlen(optarg) == 1)
 383                                 options.escape_char = (u_char) optarg[0];
 384                         else if (strcmp(optarg, "none") == 0)
 385                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 386                         else {
 387                                 fprintf(stderr, "Bad escape character '%s'.\n",
 388                                     optarg);
 389                                 exit(255);
 390                         }
 391                         break;
 392                 case 'c':
 393                         if (ciphers_valid(optarg)) {
 394                                 /* SSH2 only */
 395                                 options.ciphers = xstrdup(optarg);
 396                                 options.cipher = SSH_CIPHER_INVALID;
 397                         } else {
 398                                 /* SSH1 only */
 399                                 options.cipher = cipher_number(optarg);
 400                                 if (options.cipher == -1) {
 401                                         fprintf(stderr,
 402                                             "Unknown cipher type '%s'\n",
 403                                             optarg);
 404                                         exit(255);
 405                                 }
 406                                 if (options.cipher == SSH_CIPHER_3DES)
 407                                         options.ciphers = "3des-cbc";
 408                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 409                                         options.ciphers = "blowfish-cbc";
 410                                 else
 411                                         options.ciphers = (char *)-1;
 412                         }
 413                         break;
 414                 case 'm':
 415                         if (mac_valid(optarg))
 416                                 options.macs = xstrdup(optarg);
 417                         else {
 418                                 fprintf(stderr, "Unknown mac type '%s'\n",
 419                                     optarg);
 420                                 exit(255);
 421                         }
 422                         break;
 423                 case 'M':
 424                         if (options.control_master == SSHCTL_MASTER_YES)
 425                                 options.control_master = SSHCTL_MASTER_ASK;
 426                         else
 427                                 options.control_master = SSHCTL_MASTER_YES;
 428                         break;
 429                 case 'p':
 430                         options.port = a2port(optarg);
 431                         if (options.port == 0) {
 432                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 433                                 exit(255);
 434                         }
 435                         break;
 436                 case 'l':
 437                         options.user = optarg;
 438                         break;
 439
 440                 case 'L':
 441                         if (parse_forward(&fwd, optarg))
 442                                 add_local_forward(&options, &fwd);
 443                         else {
 444                                 fprintf(stderr,
 445                                     "Bad local forwarding specification '%s'\n",
 446                                     optarg);
 447                                 exit(255);
 448                         }
 449                         break;
 450
 451                 case 'R':
 452                         if (parse_forward(&fwd, optarg)) {
 453                                 add_remote_forward(&options, &fwd);
 454                         } else {
 455                                 fprintf(stderr,
 456                                     "Bad remote forwarding specification "
 457                                     "'%s'\n", optarg);
 458                                 exit(255);
 459                         }
 460                         break;
 461
 462                 case 'D':
 463                         cp = p = xstrdup(optarg);
 464                         memset(&fwd, '\0', sizeof(fwd));
 465                         fwd.connect_host = "socks";
 466                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 467                                 fprintf(stderr, "Bad dynamic forwarding "
 468                                     "specification '%.100s'\n", optarg);
 469                                 exit(255);
 470                         }
 471                         if (cp != NULL) {
 472                                 fwd.listen_port = a2port(cp);
 473                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 474                         } else {
 475                                 fwd.listen_port = a2port(fwd.listen_host);
 476                                 fwd.listen_host = NULL;
 477                         }
 478
 479                         if (fwd.listen_port == 0) {
 480                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 481                                     optarg);
 482                                 exit(255);
 483                         }
 484                         add_local_forward(&options, &fwd);
 485                         xfree(p);
 486                         break;
 487
 488                 case 'C':
 489                         options.compression = 1;
 490                         break;
 491                 case 'N':
 492                         no_shell_flag = 1;
 493                         no_tty_flag = 1;
 494                         break;
 495                 case 'T':
 496                         no_tty_flag = 1;
 497                         break;
 498                 case 'o':
 499                         dummy = 1;
 500                         line = xstrdup(optarg);
 501                         if (process_config_line(&options, host ? host : "",
 502                             line, "command-line", 0, &dummy) != 0)
 503                                 exit(255);
 504                         xfree(line);
 505                         break;
 506                 case 's':
 507                         subsystem_flag = 1;
 508                         break;
 509                 case 'S':
 510                         if (options.control_path != NULL)
 511                                 free(options.control_path);
 512                         options.control_path = xstrdup(optarg);
 513                         break;
 514                 case 'b':
 515                         options.bind_address = optarg;
 516                         break;
 517                 case 'F':
 518                         config = optarg;
 519                         break;
 520                 default:
 521                         usage();
 522                 }
 523         }
 524
 525         ac -= optind;
 526         av += optind;
 527
 528         if (ac > 0 && !host && **av != '-') {
 529                 if (strrchr(*av, '@')) {
 530                         p = xstrdup(*av);
 531                         cp = strrchr(p, '@');
 532                         if (cp == NULL || cp == p)
 533                                 usage();
 534                         options.user = p;
 535                         *cp = '\0';
 536                         host = ++cp;
 537                 } else
 538                         host = *av;
 539                 if (ac > 1) {
 540                         optind = optreset = 1;
 541                         goto again;
 542                 }
 543                 ac--, av++;
 544         }
 545
 546         /* Check that we got a host name. */
 547         if (!host)
 548                 usage();
 549
 550         SSLeay_add_all_algorithms();
 551         ERR_load_crypto_strings();
 552
 553         /* Initialize the command to execute on remote host. */
 554         buffer_init(&command);
 555
 556         /*
 557          * Save the command to execute on the remote host in a buffer. There
 558          * is no limit on the length of the command, except by the maximum
 559          * packet size.  Also sets the tty flag if there is no command.
 560          */
 561         if (!ac) {
 562                 /* No command specified - execute shell on a tty. */
 563                 tty_flag = 1;
 564                 if (subsystem_flag) {
 565                         fprintf(stderr,
 566                             "You must specify a subsystem to invoke.\n");
 567                         usage();
 568                 }
 569         } else {
 570                 /* A command has been specified.  Store it into the buffer. */
 571                 for (i = 0; i < ac; i++) {
 572                         if (i)
 573                                 buffer_append(&command, " ", 1);
 574                         buffer_append(&command, av[i], strlen(av[i]));
 575                 }
 576         }
 577
 578         /* Cannot fork to background if no command. */
 579         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 580                 fatal("Cannot fork into background without a command to execute.");
 581
 582         /* Allocate a tty by default if no command specified. */
 583         if (buffer_len(&command) == 0)
 584                 tty_flag = 1;
 585
 586         /* Force no tty */
 587         if (no_tty_flag)
 588                 tty_flag = 0;
 589         /* Do not allocate a tty if stdin is not a tty. */
 590         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 591                 if (tty_flag)
 592                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 593                 tty_flag = 0;
 594         }
 595
 596         /*
 597          * Initialize "log" output.  Since we are the client all output
 598          * actually goes to stderr.
 599          */
 600         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 601             SYSLOG_FACILITY_USER, 1);
 602
 603         /*
 604          * Read per-user configuration file.  Ignore the system wide config
 605          * file if the user specifies a config file on the command line.
 606          */
 607         if (config != NULL) {
 608                 if (!read_config_file(config, host, &options, 0))
 609                         fatal("Can't open user config file %.100s: "
 610                             "%.100s", config, strerror(errno));
 611         } else  {
 612                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 613                     _PATH_SSH_USER_CONFFILE);
 614                 (void)read_config_file(buf, host, &options, 1);
 615
 616                 /* Read systemwide configuration file after use config. */
 617                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 618                     &options, 0);
 619         }
 620
 621         /* Fill configuration defaults. */
 622         fill_default_options(&options);
 623
 624         channel_set_af(options.address_family);
 625
 626         /* reinit */
 627         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 628
 629         seed_rng();
 630
 631         if (options.user == NULL)
 632                 options.user = xstrdup(pw->pw_name);
 633
 634         if (options.hostname != NULL)
 635                 host = options.hostname;
 636
 637         /* force lowercase for hostkey matching */
 638         if (options.host_key_alias != NULL) {
 639                 for (p = options.host_key_alias; *p; p++)
 640                         if (isupper(*p))
 641                                 *p = (char)tolower(*p);
 642         }
 643
 644         /* Get default port if port has not been set. */
 645         if (options.port == 0) {
 646                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 647                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 648         }
 649
 650         if (options.proxy_command != NULL &&
 651             strcmp(options.proxy_command, "none") == 0)
 652                 options.proxy_command = NULL;
 653         if (options.control_path != NULL &&
 654             strcmp(options.control_path, "none") == 0)
 655                 options.control_path = NULL;
 656
 657         if (options.control_path != NULL) {
 658                 char thishost[NI_MAXHOST];
 659
 660                 if (gethostname(thishost, sizeof(thishost)) == -1)
 661                         fatal("gethostname: %s", strerror(errno));
 662                 snprintf(buf, sizeof(buf), "%d", options.port);
 663                 cp = tilde_expand_filename(options.control_path,
 664                     original_real_uid);
 665                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 666                     "r", options.user, "l", thishost, (char *)NULL);
 667                 xfree(cp);
 668         }
 669         if (mux_command != 0 && options.control_path == NULL)
 670                 fatal("No ControlPath specified for \"-O\" command");
 671         if (options.control_path != NULL)
 672                 control_client(options.control_path);
 673
 674         /* Open a connection to the remote host. */
 675         if (ssh_connect(host, &hostaddr, options.port,
 676             options.address_family, options.connection_attempts,
 677 #ifdef HAVE_CYGWIN
 678             options.use_privileged_port,
 679 #else
 680             original_effective_uid == 0 && options.use_privileged_port,
 681 #endif
 682             options.proxy_command) != 0)
 683                 exit(255);
 684
 685         /*
 686          * If we successfully made the connection, load the host private key
 687          * in case we will need it later for combined rsa-rhosts
 688          * authentication. This must be done before releasing extra
 689          * privileges, because the file is only readable by root.
 690          * If we cannot access the private keys, load the public keys
 691          * instead and try to execute the ssh-keysign helper instead.
 692          */
 693         sensitive_data.nkeys = 0;
 694         sensitive_data.keys = NULL;
 695         sensitive_data.external_keysign = 0;
 696         if (options.rhosts_rsa_authentication ||
 697             options.hostbased_authentication) {
 698                 sensitive_data.nkeys = 3;
 699                 sensitive_data.keys = xcalloc(sensitive_data.nkeys,
 700                     sizeof(Key));
 701
 702                 PRIV_START;
 703                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 704                     _PATH_HOST_KEY_FILE, "", NULL, NULL);
 705                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 706                     _PATH_HOST_DSA_KEY_FILE, "", NULL, NULL);
 707                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 708                     _PATH_HOST_RSA_KEY_FILE, "", NULL, NULL);
 709                 PRIV_END;
 710
 711                 if (options.hostbased_authentication == 1 &&
 712                     sensitive_data.keys[0] == NULL &&
 713                     sensitive_data.keys[1] == NULL &&
 714                     sensitive_data.keys[2] == NULL) {
 715                         sensitive_data.keys[1] = key_load_public(
 716                             _PATH_HOST_DSA_KEY_FILE, NULL);
 717                         sensitive_data.keys[2] = key_load_public(
 718                             _PATH_HOST_RSA_KEY_FILE, NULL);
 719                         sensitive_data.external_keysign = 1;
 720                 }
 721         }
 722         /*
 723          * Get rid of any extra privileges that we may have.  We will no
 724          * longer need them.  Also, extra privileges could make it very hard
 725          * to read identity files and other non-world-readable files from the
 726          * user's home directory if it happens to be on a NFS volume where
 727          * root is mapped to nobody.
 728          */
 729         if (original_effective_uid == 0) {
 730                 PRIV_START;
 731                 permanently_set_uid(pw);
 732         }
 733
 734         /*
 735          * Now that we are back to our own permissions, create ~/.ssh
 736          * directory if it doesn't already exist.
 737          */
 738         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 739         if (stat(buf, &st) < 0)
 740                 if (mkdir(buf, 0700) < 0)
 741                         error("Could not create directory '%.200s'.", buf);
 742
 743         /* load options.identity_files */
 744         load_public_identity_files();
 745
 746         /* Expand ~ in known host file names. */
 747         /* XXX mem-leaks: */
 748         options.system_hostfile =
 749             tilde_expand_filename(options.system_hostfile, original_real_uid);
 750         options.user_hostfile =
 751             tilde_expand_filename(options.user_hostfile, original_real_uid);
 752         options.system_hostfile2 =
 753             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 754         options.user_hostfile2 =
 755             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 756
 757         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 758
 759         /* Log into the remote system.  This never returns if the login fails. */
 760         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 761
 762         /* We no longer need the private host keys.  Clear them now. */
 763         if (sensitive_data.nkeys != 0) {
 764                 for (i = 0; i < sensitive_data.nkeys; i++) {
 765                         if (sensitive_data.keys[i] != NULL) {
 766                                 /* Destroys contents safely */
 767                                 debug3("clear hostkey %d", i);
 768                                 key_free(sensitive_data.keys[i]);
 769                                 sensitive_data.keys[i] = NULL;
 770                         }
 771                 }
 772                 xfree(sensitive_data.keys);
 773         }
 774         for (i = 0; i < options.num_identity_files; i++) {
 775                 if (options.identity_files[i]) {
 776                         xfree(options.identity_files[i]);
 777                         options.identity_files[i] = NULL;
 778                 }
 779                 if (options.identity_keys[i]) {
 780                         key_free(options.identity_keys[i]);
 781                         options.identity_keys[i] = NULL;
 782                 }
 783         }
 784
 785         exit_status = compat20 ? ssh_session2() : ssh_session();
 786         packet_close();
 787
 788         if (options.control_path != NULL && control_fd != -1)
 789                 unlink(options.control_path);
 790
 791         /*
 792          * Send SIGHUP to proxy command if used. We don't wait() in
 793          * case it hangs and instead rely on init to reap the child
 794          */
 795         if (proxy_command_pid > 1)
 796                 kill(proxy_command_pid, SIGHUP);
 797
 798         return exit_status;
 799 }
 800
 801 static void
 802 ssh_init_forwarding(void)
 803 {
 804         int success = 0;
 805         int i;
 806
 807         /* Initiate local TCP/IP port forwardings. */
 808         for (i = 0; i < options.num_local_forwards; i++) {
 809                 debug("Local connections to %.200s:%d forwarded to remote "
 810                     "address %.200s:%d",
 811                     (options.local_forwards[i].listen_host == NULL) ?
 812                     (options.gateway_ports ? "*" : "LOCALHOST") :
 813                     options.local_forwards[i].listen_host,
 814                     options.local_forwards[i].listen_port,
 815                     options.local_forwards[i].connect_host,
 816                     options.local_forwards[i].connect_port);
 817                 success += channel_setup_local_fwd_listener(
 818                     options.local_forwards[i].listen_host,
 819                     options.local_forwards[i].listen_port,
 820                     options.local_forwards[i].connect_host,
 821                     options.local_forwards[i].connect_port,
 822                     options.gateway_ports);
 823         }
 824         if (i > 0 && success != i && options.exit_on_forward_failure)
 825                 fatal("Could not request local forwarding.");
 826         if (i > 0 && success == 0)
 827                 error("Could not request local forwarding.");
 828
 829         /* Initiate remote TCP/IP port forwardings. */
 830         for (i = 0; i < options.num_remote_forwards; i++) {
 831                 debug("Remote connections from %.200s:%d forwarded to "
 832                     "local address %.200s:%d",
 833                     (options.remote_forwards[i].listen_host == NULL) ?
 834                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 835                     options.remote_forwards[i].listen_port,
 836                     options.remote_forwards[i].connect_host,
 837                     options.remote_forwards[i].connect_port);
 838                 if (channel_request_remote_forwarding(
 839                     options.remote_forwards[i].listen_host,
 840                     options.remote_forwards[i].listen_port,
 841                     options.remote_forwards[i].connect_host,
 842                     options.remote_forwards[i].connect_port) < 0) {
 843                         if (options.exit_on_forward_failure)
 844                                 fatal("Could not request remote forwarding.");
 845                         else
 846                                 logit("Warning: Could not request remote "
 847                                     "forwarding.");
 848                 }
 849         }
 850 }
 851
 852 static void
 853 check_agent_present(void)
 854 {
 855         if (options.forward_agent) {
 856                 /* Clear agent forwarding if we don't have an agent. */
 857                 if (!ssh_agent_present())
 858                         options.forward_agent = 0;
 859         }
 860 }
 861
 862 static int
 863 ssh_session(void)
 864 {
 865         int type;
 866         int interactive = 0;
 867         int have_tty = 0;
 868         struct winsize ws;
 869         char *cp;
 870         const char *display;
 871
 872         /* Enable compression if requested. */
 873         if (options.compression) {
 874                 debug("Requesting compression at level %d.", options.compression_level);
 875
 876                 if (options.compression_level < 1 || options.compression_level > 9)
 877                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 878
 879                 /* Send the request. */
 880                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 881                 packet_put_int(options.compression_level);
 882                 packet_send();
 883                 packet_write_wait();
 884                 type = packet_read();
 885                 if (type == SSH_SMSG_SUCCESS)
 886                         packet_start_compression(options.compression_level);
 887                 else if (type == SSH_SMSG_FAILURE)
 888                         logit("Warning: Remote host refused compression.");
 889                 else
 890                         packet_disconnect("Protocol error waiting for compression response.");
 891         }
 892         /* Allocate a pseudo tty if appropriate. */
 893         if (tty_flag) {
 894                 debug("Requesting pty.");
 895
 896                 /* Start the packet. */
 897                 packet_start(SSH_CMSG_REQUEST_PTY);
 898
 899                 /* Store TERM in the packet.  There is no limit on the
 900                    length of the string. */
 901                 cp = getenv("TERM");
 902                 if (!cp)
 903                         cp = "";
 904                 packet_put_cstring(cp);
 905
 906                 /* Store window size in the packet. */
 907                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 908                         memset(&ws, 0, sizeof(ws));
 909                 packet_put_int((u_int)ws.ws_row);
 910                 packet_put_int((u_int)ws.ws_col);
 911                 packet_put_int((u_int)ws.ws_xpixel);
 912                 packet_put_int((u_int)ws.ws_ypixel);
 913
 914                 /* Store tty modes in the packet. */
 915                 tty_make_modes(fileno(stdin), NULL);
 916
 917                 /* Send the packet, and wait for it to leave. */
 918                 packet_send();
 919                 packet_write_wait();
 920
 921                 /* Read response from the server. */
 922                 type = packet_read();
 923                 if (type == SSH_SMSG_SUCCESS) {
 924                         interactive = 1;
 925                         have_tty = 1;
 926                 } else if (type == SSH_SMSG_FAILURE)
 927                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 928                 else
 929                         packet_disconnect("Protocol error waiting for pty request response.");
 930         }
 931         /* Request X11 forwarding if enabled and DISPLAY is set. */
 932         display = getenv("DISPLAY");
 933         if (options.forward_x11 && display != NULL) {
 934                 char *proto, *data;
 935                 /* Get reasonable local authentication information. */
 936                 client_x11_get_proto(display, options.xauth_location,
 937                     options.forward_x11_trusted, &proto, &data);
 938                 /* Request forwarding with authentication spoofing. */
 939                 debug("Requesting X11 forwarding with authentication spoofing.");
 940                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 941
 942                 /* Read response from the server. */
 943                 type = packet_read();
 944                 if (type == SSH_SMSG_SUCCESS) {
 945                         interactive = 1;
 946                 } else if (type == SSH_SMSG_FAILURE) {
 947                         logit("Warning: Remote host denied X11 forwarding.");
 948                 } else {
 949                         packet_disconnect("Protocol error waiting for X11 forwarding");
 950                 }
 951         }
 952         /* Tell the packet module whether this is an interactive session. */
 953         packet_set_interactive(interactive);
 954
 955         /* Request authentication agent forwarding if appropriate. */
 956         check_agent_present();
 957
 958         if (options.forward_agent) {
 959                 debug("Requesting authentication agent forwarding.");
 960                 auth_request_forwarding();
 961
 962                 /* Read response from the server. */
 963                 type = packet_read();
 964                 packet_check_eom();
 965                 if (type != SSH_SMSG_SUCCESS)
 966                         logit("Warning: Remote host denied authentication agent forwarding.");
 967         }
 968
 969         /* Initiate port forwardings. */
 970         ssh_init_forwarding();
 971
 972         /* If requested, let ssh continue in the background. */
 973         if (fork_after_authentication_flag)
 974                 if (daemon(1, 1) < 0)
 975                         fatal("daemon() failed: %.200s", strerror(errno));
 976
 977         /*
 978          * If a command was specified on the command line, execute the
 979          * command now. Otherwise request the server to start a shell.
 980          */
 981         if (buffer_len(&command) > 0) {
 982                 int len = buffer_len(&command);
 983                 if (len > 900)
 984                         len = 900;
 985                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 986                 packet_start(SSH_CMSG_EXEC_CMD);
 987                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 988                 packet_send();
 989                 packet_write_wait();
 990         } else {
 991                 debug("Requesting shell.");
 992                 packet_start(SSH_CMSG_EXEC_SHELL);
 993                 packet_send();
 994                 packet_write_wait();
 995         }
 996
 997         /* Enter the interactive session. */
 998         return client_loop(have_tty, tty_flag ?
 999             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
1000 }
1001
1002 static void
1003 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
1004 {
1005         int id, len;
1006
1007         id = packet_get_int();
1008         len = buffer_len(&command);
1009         if (len > 900)
1010                 len = 900;
1011         packet_check_eom();
1012         if (type == SSH2_MSG_CHANNEL_FAILURE)
1013                 fatal("Request for subsystem '%.*s' failed on channel %d",
1014                     len, (u_char *)buffer_ptr(&command), id);
1015 }
1016
1017 void
1018 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1019 {
1020         int i;
1021
1022         i = client_global_request_id++;
1023         if (i >= options.num_remote_forwards)
1024                 return;
1025         debug("remote forward %s for: listen %d, connect %s:%d",
1026             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1027             options.remote_forwards[i].listen_port,
1028             options.remote_forwards[i].connect_host,
1029             options.remote_forwards[i].connect_port);
1030         if (type == SSH2_MSG_REQUEST_FAILURE) {
1031                 if (options.exit_on_forward_failure)
1032                         fatal("Error: remote port forwarding failed for "
1033                             "listen port %d",
1034                             options.remote_forwards[i].listen_port);
1035                 else
1036                         logit("Warning: remote port forwarding failed for "
1037                             "listen port %d",
1038                             options.remote_forwards[i].listen_port);
1039         }
1040 }
1041
1042 static void
1043 ssh_control_listener(void)
1044 {
1045         struct sockaddr_un addr;
1046         mode_t old_umask;
1047         int addr_len;
1048
1049         if (options.control_path == NULL ||
1050             options.control_master == SSHCTL_MASTER_NO)
1051                 return;
1052
1053         debug("setting up multiplex master socket");
1054
1055         memset(&addr, '\0', sizeof(addr));
1056         addr.sun_family = AF_UNIX;
1057         addr_len = offsetof(struct sockaddr_un, sun_path) +
1058             strlen(options.control_path) + 1;
1059
1060         if (strlcpy(addr.sun_path, options.control_path,
1061             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1062                 fatal("ControlPath too long");
1063
1064         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1065                 fatal("%s socket(): %s", __func__, strerror(errno));
1066
1067         old_umask = umask(0177);
1068         if (bind(control_fd, (struct sockaddr *)&addr, addr_len) == -1) {
1069                 control_fd = -1;
1070                 if (errno == EINVAL || errno == EADDRINUSE)
1071                         fatal("ControlSocket %s already exists",
1072                             options.control_path);
1073                 else
1074                         fatal("%s bind(): %s", __func__, strerror(errno));
1075         }
1076         umask(old_umask);
1077
1078         if (listen(control_fd, 64) == -1)
1079                 fatal("%s listen(): %s", __func__, strerror(errno));
1080
1081         set_nonblock(control_fd);
1082 }
1083
1084 /* request pty/x11/agent/tcpfwd/shell for channel */
1085 static void
1086 ssh_session2_setup(int id, void *arg)
1087 {
1088         extern char **environ;
1089         const char *display;
1090         int interactive = tty_flag;
1091
1092         display = getenv("DISPLAY");
1093         if (options.forward_x11 && display != NULL) {
1094                 char *proto, *data;
1095                 /* Get reasonable local authentication information. */
1096                 client_x11_get_proto(display, options.xauth_location,
1097                     options.forward_x11_trusted, &proto, &data);
1098                 /* Request forwarding with authentication spoofing. */
1099                 debug("Requesting X11 forwarding with authentication spoofing.");
1100                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1101                 interactive = 1;
1102                 /* XXX wait for reply */
1103         }
1104
1105         check_agent_present();
1106         if (options.forward_agent) {
1107                 debug("Requesting authentication agent forwarding.");
1108                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1109                 packet_send();
1110         }
1111
1112         if (options.tun_open != SSH_TUNMODE_NO) {
1113                 Channel *c;
1114                 int fd;
1115
1116                 debug("Requesting tun.");
1117                 if ((fd = tun_open(options.tun_local,
1118                     options.tun_open)) >= 0) {
1119                         c = channel_new("tun", SSH_CHANNEL_OPENING, fd, fd, -1,
1120                             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1121                             0, "tun", 1);
1122                         c->datagram = 1;
1123 #if defined(SSH_TUN_FILTER)
1124                         if (options.tun_open == SSH_TUNMODE_POINTOPOINT)
1125                                 channel_register_filter(c->self, sys_tun_infilter,
1126                                     sys_tun_outfilter);
1127 #endif
1128                         packet_start(SSH2_MSG_CHANNEL_OPEN);
1129                         packet_put_cstring("tun@openssh.com");
1130                         packet_put_int(c->self);
1131                         packet_put_int(c->local_window_max);
1132                         packet_put_int(c->local_maxpacket);
1133                         packet_put_int(options.tun_open);
1134                         packet_put_int(options.tun_remote);
1135                         packet_send();
1136                 }
1137         }
1138
1139         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1140             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1141
1142         packet_set_interactive(interactive);
1143 }
1144
1145 /* open new channel for a session */
1146 static int
1147 ssh_session2_open(void)
1148 {
1149         Channel *c;
1150         int window, packetmax, in, out, err;
1151
1152         if (stdin_null_flag) {
1153                 in = open(_PATH_DEVNULL, O_RDONLY);
1154         } else {
1155                 in = dup(STDIN_FILENO);
1156         }
1157         out = dup(STDOUT_FILENO);
1158         err = dup(STDERR_FILENO);
1159
1160         if (in < 0 || out < 0 || err < 0)
1161                 fatal("dup() in/out/err failed");
1162
1163         /* enable nonblocking unless tty */
1164         if (!isatty(in))
1165                 set_nonblock(in);
1166         if (!isatty(out))
1167                 set_nonblock(out);
1168         if (!isatty(err))
1169                 set_nonblock(err);
1170
1171         window = CHAN_SES_WINDOW_DEFAULT;
1172         packetmax = CHAN_SES_PACKET_DEFAULT;
1173         if (tty_flag) {
1174                 window >>= 1;
1175                 packetmax >>= 1;
1176         }
1177         c = channel_new(
1178             "session", SSH_CHANNEL_OPENING, in, out, err,
1179             window, packetmax, CHAN_EXTENDED_WRITE,
1180             "client-session", /*nonblock*/0);
1181
1182         debug3("ssh_session2_open: channel_new: %d", c->self);
1183
1184         channel_send_open(c->self);
1185         if (!no_shell_flag)
1186                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1187
1188         return c->self;
1189 }
1190
1191 static int
1192 ssh_session2(void)
1193 {
1194         int id = -1;
1195
1196         /* XXX should be pre-session */
1197         ssh_init_forwarding();
1198         ssh_control_listener();
1199
1200         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1201                 id = ssh_session2_open();
1202
1203         /* Execute a local command */
1204         if (options.local_command != NULL &&
1205             options.permit_local_command)
1206                 ssh_local_cmd(options.local_command);
1207
1208         /* If requested, let ssh continue in the background. */
1209         if (fork_after_authentication_flag)
1210                 if (daemon(1, 1) < 0)
1211                         fatal("daemon() failed: %.200s", strerror(errno));
1212
1213         return client_loop(tty_flag, tty_flag ?
1214             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1215 }
1216
1217 static void
1218 load_public_identity_files(void)
1219 {
1220         char *filename, *cp, thishost[NI_MAXHOST];
1221         int i = 0;
1222         Key *public;
1223         struct passwd *pw;
1224 #ifdef SMARTCARD
1225         Key **keys;
1226
1227         if (options.smartcard_device != NULL &&
1228             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1229             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1230                 int count = 0;
1231                 for (i = 0; keys[i] != NULL; i++) {
1232                         count++;
1233                         memmove(&options.identity_files[1], &options.identity_files[0],
1234                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1235                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1236                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1237                         options.num_identity_files++;
1238                         options.identity_keys[0] = keys[i];
1239                         options.identity_files[0] = sc_get_key_label(keys[i]);
1240                 }
1241                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1242                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1243                 i = count;
1244                 xfree(keys);
1245         }
1246 #endif /* SMARTCARD */
1247         if ((pw = getpwuid(original_real_uid)) == NULL)
1248                 fatal("load_public_identity_files: getpwuid failed");
1249         if (gethostname(thishost, sizeof(thishost)) == -1)
1250                 fatal("load_public_identity_files: gethostname: %s",
1251                     strerror(errno));
1252         for (; i < options.num_identity_files; i++) {
1253                 cp = tilde_expand_filename(options.identity_files[i],
1254                     original_real_uid);
1255                 filename = percent_expand(cp, "d", pw->pw_dir,
1256                     "u", pw->pw_name, "l", thishost, "h", host,
1257                     "r", options.user, (char *)NULL);
1258                 xfree(cp);
1259                 public = key_load_public(filename, NULL);
1260                 debug("identity file %s type %d", filename,
1261                     public ? public->type : -1);
1262                 xfree(options.identity_files[i]);
1263                 options.identity_files[i] = filename;
1264                 options.identity_keys[i] = public;
1265         }
1266 }
1267
1268 static void
1269 control_client_sighandler(int signo)
1270 {
1271         control_client_terminate = signo;
1272 }
1273
1274 static void
1275 control_client_sigrelay(int signo)
1276 {
1277         if (control_server_pid > 1)
1278                 kill(control_server_pid, signo);
1279 }
1280
1281 static int
1282 env_permitted(char *env)
1283 {
1284         int i, ret;
1285         char name[1024], *cp;
1286
1287         if ((cp = strchr(env, '=')) == NULL || cp == env)
1288                 return (0);
1289         ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
1290         if (ret <= 0 || (size_t)ret >= sizeof(name))
1291                 fatal("env_permitted: name '%.100s...' too long", env);
1292
1293         for (i = 0; i < options.num_send_env; i++)
1294                 if (match_pattern(name, options.send_env[i]))
1295                         return (1);
1296
1297         return (0);
1298 }
1299
1300 static void
1301 control_client(const char *path)
1302 {
1303         struct sockaddr_un addr;
1304         int i, r, fd, sock, exitval, num_env, addr_len;
1305         Buffer m;
1306         char *term;
1307         extern char **environ;
1308         u_int  flags;
1309
1310         if (mux_command == 0)
1311                 mux_command = SSHMUX_COMMAND_OPEN;
1312
1313         switch (options.control_master) {
1314         case SSHCTL_MASTER_AUTO:
1315         case SSHCTL_MASTER_AUTO_ASK:
1316                 debug("auto-mux: Trying existing master");
1317                 /* FALLTHROUGH */
1318         case SSHCTL_MASTER_NO:
1319                 break;
1320         default:
1321                 return;
1322         }
1323
1324         memset(&addr, '\0', sizeof(addr));
1325         addr.sun_family = AF_UNIX;
1326         addr_len = offsetof(struct sockaddr_un, sun_path) +
1327             strlen(path) + 1;
1328
1329         if (strlcpy(addr.sun_path, path,
1330             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1331                 fatal("ControlPath too long");
1332
1333         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1334                 fatal("%s socket(): %s", __func__, strerror(errno));
1335
1336         if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
1337                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1338                         fatal("Control socket connect(%.100s): %s", path,
1339                             strerror(errno));
1340                 }
1341                 if (errno == ENOENT)
1342                         debug("Control socket \"%.100s\" does not exist", path);
1343                 else {
1344                         error("Control socket connect(%.100s): %s", path,
1345                             strerror(errno));
1346                 }
1347                 close(sock);
1348                 return;
1349         }
1350
1351         if (stdin_null_flag) {
1352                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1353                         fatal("open(/dev/null): %s", strerror(errno));
1354                 if (dup2(fd, STDIN_FILENO) == -1)
1355                         fatal("dup2: %s", strerror(errno));
1356                 if (fd > STDERR_FILENO)
1357                         close(fd);
1358         }
1359
1360         term = getenv("TERM");
1361
1362         flags = 0;
1363         if (tty_flag)
1364                 flags |= SSHMUX_FLAG_TTY;
1365         if (subsystem_flag)
1366                 flags |= SSHMUX_FLAG_SUBSYS;
1367         if (options.forward_x11)
1368                 flags |= SSHMUX_FLAG_X11_FWD;
1369         if (options.forward_agent)
1370                 flags |= SSHMUX_FLAG_AGENT_FWD;
1371
1372         buffer_init(&m);
1373
1374         /* Send our command to server */
1375         buffer_put_int(&m, mux_command);
1376         buffer_put_int(&m, flags);
1377         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1378                 fatal("%s: msg_send", __func__);
1379         buffer_clear(&m);
1380
1381         /* Get authorisation status and PID of controlee */
1382         if (ssh_msg_recv(sock, &m) == -1)
1383                 fatal("%s: msg_recv", __func__);
1384         if (buffer_get_char(&m) != SSHMUX_VER)
1385                 fatal("%s: wrong version", __func__);
1386         if (buffer_get_int(&m) != 1)
1387                 fatal("Connection to master denied");
1388         control_server_pid = buffer_get_int(&m);
1389
1390         buffer_clear(&m);
1391
1392         switch (mux_command) {
1393         case SSHMUX_COMMAND_ALIVE_CHECK:
1394                 fprintf(stderr, "Master running (pid=%d)\r\n",
1395                     control_server_pid);
1396                 exit(0);
1397         case SSHMUX_COMMAND_TERMINATE:
1398                 fprintf(stderr, "Exit request sent.\r\n");
1399                 exit(0);
1400         case SSHMUX_COMMAND_OPEN:
1401                 /* continue below */
1402                 break;
1403         default:
1404                 fatal("silly mux_command %d", mux_command);
1405         }
1406
1407         /* SSHMUX_COMMAND_OPEN */
1408         buffer_put_cstring(&m, term ? term : "");
1409         buffer_append(&command, "\0", 1);
1410         buffer_put_cstring(&m, buffer_ptr(&command));
1411
1412         if (options.num_send_env == 0 || environ == NULL) {
1413                 buffer_put_int(&m, 0);
1414         } else {
1415                 /* Pass environment */
1416                 num_env = 0;
1417                 for (i = 0; environ[i] != NULL; i++)
1418                         if (env_permitted(environ[i]))
1419                                 num_env++; /* Count */
1420
1421                 buffer_put_int(&m, num_env);
1422
1423                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1424                         if (env_permitted(environ[i])) {
1425                                 num_env--;
1426                                 buffer_put_cstring(&m, environ[i]);
1427                         }
1428         }
1429
1430         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1431                 fatal("%s: msg_send", __func__);
1432
1433         mm_send_fd(sock, STDIN_FILENO);
1434         mm_send_fd(sock, STDOUT_FILENO);
1435         mm_send_fd(sock, STDERR_FILENO);
1436
1437         /* Wait for reply, so master has a chance to gather ttymodes */
1438         buffer_clear(&m);
1439         if (ssh_msg_recv(sock, &m) == -1)
1440                 fatal("%s: msg_recv", __func__);
1441         if (buffer_get_char(&m) != SSHMUX_VER)
1442                 fatal("%s: wrong version", __func__);
1443         buffer_free(&m);
1444
1445         signal(SIGHUP, control_client_sighandler);
1446         signal(SIGINT, control_client_sighandler);
1447         signal(SIGTERM, control_client_sighandler);
1448         signal(SIGWINCH, control_client_sigrelay);
1449
1450         if (tty_flag)
1451                 enter_raw_mode();
1452
1453         /* Stick around until the controlee closes the client_fd */
1454         exitval = 0;
1455         for (;!control_client_terminate;) {
1456                 r = read(sock, &exitval, sizeof(exitval));
1457                 if (r == 0) {
1458                         debug2("Received EOF from master");
1459                         break;
1460                 }
1461                 if (r > 0)
1462                         debug2("Received exit status from master %d", exitval);
1463                 if (r == -1 && errno != EINTR)
1464                         fatal("%s: read %s", __func__, strerror(errno));
1465         }
1466
1467         if (control_client_terminate)
1468                 debug2("Exiting on signal %d", control_client_terminate);
1469
1470         close(sock);
1471
1472         leave_raw_mode();
1473
1474         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1475                 fprintf(stderr, "Connection to master closed.\r\n");
1476
1477         exit(exitval);
1478 }