ssh.c

   1 /* $OpenBSD: ssh.c,v 1.278 2006/07/03 08:54:20 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/un.h>
  52
  53 #include <ctype.h>
  54 #ifdef HAVE_PATHS_H
  55 #include <paths.h>
  56 #endif
  57 #include <signal.h>
  58
  59 #include <openssl/evp.h>
  60 #include <openssl/err.h>
  61
  62 #include "ssh.h"
  63 #include "ssh1.h"
  64 #include "ssh2.h"
  65 #include "compat.h"
  66 #include "cipher.h"
  67 #include "xmalloc.h"
  68 #include "packet.h"
  69 #include "buffer.h"
  70 #include "bufaux.h"
  71 #include "channels.h"
  72 #include "key.h"
  73 #include "authfd.h"
  74 #include "authfile.h"
  75 #include "pathnames.h"
  76 #include "dispatch.h"
  77 #include "clientloop.h"
  78 #include "log.h"
  79 #include "readconf.h"
  80 #include "sshconnect.h"
  81 #include "misc.h"
  82 #include "kex.h"
  83 #include "mac.h"
  84 #include "sshpty.h"
  85 #include "match.h"
  86 #include "msg.h"
  87 #include "monitor_fdpass.h"
  88 #include "uidswap.h"
  89 #include "version.h"
  90
  91 #ifdef SMARTCARD
  92 #include "scard.h"
  93 #endif
  94
  95 extern char *__progname;
  96
  97 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
  98 int debug_flag = 0;
  99
 100 /* Flag indicating whether a tty should be allocated */
 101 int tty_flag = 0;
 102 int no_tty_flag = 0;
 103 int force_tty_flag = 0;
 104
 105 /* don't exec a shell */
 106 int no_shell_flag = 0;
 107
 108 /*
 109  * Flag indicating that nothing should be read from stdin.  This can be set
 110  * on the command line.
 111  */
 112 int stdin_null_flag = 0;
 113
 114 /*
 115  * Flag indicating that ssh should fork after authentication.  This is useful
 116  * so that the passphrase can be entered manually, and then ssh goes to the
 117  * background.
 118  */
 119 int fork_after_authentication_flag = 0;
 120
 121 /*
 122  * General data structure for command line options and options configurable
 123  * in configuration files.  See readconf.h.
 124  */
 125 Options options;
 126
 127 /* optional user configfile */
 128 char *config = NULL;
 129
 130 /*
 131  * Name of the host we are connecting to.  This is the name given on the
 132  * command line, or the HostName specified for the user-supplied name in a
 133  * configuration file.
 134  */
 135 char *host;
 136
 137 /* socket address the host resolves to */
 138 struct sockaddr_storage hostaddr;
 139
 140 /* Private host keys. */
 141 Sensitive sensitive_data;
 142
 143 /* Original real UID. */
 144 uid_t original_real_uid;
 145 uid_t original_effective_uid;
 146
 147 /* command to be executed */
 148 Buffer command;
 149
 150 /* Should we execute a command or invoke a subsystem? */
 151 int subsystem_flag = 0;
 152
 153 /* # of replies received for global requests */
 154 static int client_global_request_id = 0;
 155
 156 /* pid of proxycommand child process */
 157 pid_t proxy_command_pid = 0;
 158
 159 /* fd to control socket */
 160 int control_fd = -1;
 161
 162 /* Multiplexing control command */
 163 static u_int mux_command = 0;
 164
 165 /* Only used in control client mode */
 166 volatile sig_atomic_t control_client_terminate = 0;
 167 u_int control_server_pid = 0;
 168
 169 /* Prints a help message to the user.  This function never returns. */
 170
 171 static void
 172 usage(void)
 173 {
 174         fprintf(stderr,
 175 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 176 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 177 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 178 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 179 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 180 "           [-w local_tun[:remote_tun]] [user@]hostname [command]\n"
 181         );
 182         exit(255);
 183 }
 184
 185 static int ssh_session(void);
 186 static int ssh_session2(void);
 187 static void load_public_identity_files(void);
 188 static void control_client(const char *path);
 189
 190 /*
 191  * Main program for the ssh client.
 192  */
 193 int
 194 main(int ac, char **av)
 195 {
 196         int i, opt, exit_status;
 197         char *p, *cp, *line, buf[256];
 198         struct stat st;
 199         struct passwd *pw;
 200         int dummy;
 201         extern int optind, optreset;
 202         extern char *optarg;
 203         struct servent *sp;
 204         Forward fwd;
 205
 206         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 207         sanitise_stdfd();
 208
 209         __progname = ssh_get_progname(av[0]);
 210         init_rng();
 211
 212         /*
 213          * Save the original real uid.  It will be needed later (uid-swapping
 214          * may clobber the real uid).
 215          */
 216         original_real_uid = getuid();
 217         original_effective_uid = geteuid();
 218
 219         /*
 220          * Use uid-swapping to give up root privileges for the duration of
 221          * option processing.  We will re-instantiate the rights when we are
 222          * ready to create the privileged port, and will permanently drop
 223          * them when the port has been created (actually, when the connection
 224          * has been made, as we may need to create the port several times).
 225          */
 226         PRIV_END;
 227
 228 #ifdef HAVE_SETRLIMIT
 229         /* If we are installed setuid root be careful to not drop core. */
 230         if (original_real_uid != original_effective_uid) {
 231                 struct rlimit rlim;
 232                 rlim.rlim_cur = rlim.rlim_max = 0;
 233                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 234                         fatal("setrlimit failed: %.100s", strerror(errno));
 235         }
 236 #endif
 237         /* Get user data. */
 238         pw = getpwuid(original_real_uid);
 239         if (!pw) {
 240                 logit("You don't exist, go away!");
 241                 exit(255);
 242         }
 243         /* Take a copy of the returned structure. */
 244         pw = pwcopy(pw);
 245
 246         /*
 247          * Set our umask to something reasonable, as some files are created
 248          * with the default umask.  This will make them world-readable but
 249          * writable only by the owner, which is ok for all files for which we
 250          * don't set the modes explicitly.
 251          */
 252         umask(022);
 253
 254         /* Initialize option structure to indicate that no values have been set. */
 255         initialize_options(&options);
 256
 257         /* Parse command-line arguments. */
 258         host = NULL;
 259
 260  again:
 261         while ((opt = getopt(ac, av,
 262             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVw:XY")) != -1) {
 263                 switch (opt) {
 264                 case '1':
 265                         options.protocol = SSH_PROTO_1;
 266                         break;
 267                 case '2':
 268                         options.protocol = SSH_PROTO_2;
 269                         break;
 270                 case '4':
 271                         options.address_family = AF_INET;
 272                         break;
 273                 case '6':
 274                         options.address_family = AF_INET6;
 275                         break;
 276                 case 'n':
 277                         stdin_null_flag = 1;
 278                         break;
 279                 case 'f':
 280                         fork_after_authentication_flag = 1;
 281                         stdin_null_flag = 1;
 282                         break;
 283                 case 'x':
 284                         options.forward_x11 = 0;
 285                         break;
 286                 case 'X':
 287                         options.forward_x11 = 1;
 288                         break;
 289                 case 'Y':
 290                         options.forward_x11 = 1;
 291                         options.forward_x11_trusted = 1;
 292                         break;
 293                 case 'g':
 294                         options.gateway_ports = 1;
 295                         break;
 296                 case 'O':
 297                         if (strcmp(optarg, "check") == 0)
 298                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 299                         else if (strcmp(optarg, "exit") == 0)
 300                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 301                         else
 302                                 fatal("Invalid multiplex command.");
 303                         break;
 304                 case 'P':       /* deprecated */
 305                         options.use_privileged_port = 0;
 306                         break;
 307                 case 'a':
 308                         options.forward_agent = 0;
 309                         break;
 310                 case 'A':
 311                         options.forward_agent = 1;
 312                         break;
 313                 case 'k':
 314                         options.gss_deleg_creds = 0;
 315                         break;
 316                 case 'i':
 317                         if (stat(optarg, &st) < 0) {
 318                                 fprintf(stderr, "Warning: Identity file %s "
 319                                     "not accessible: %s.\n", optarg,
 320                                     strerror(errno));
 321                                 break;
 322                         }
 323                         if (options.num_identity_files >=
 324                             SSH_MAX_IDENTITY_FILES)
 325                                 fatal("Too many identity files specified "
 326                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 327                         options.identity_files[options.num_identity_files++] =
 328                             xstrdup(optarg);
 329                         break;
 330                 case 'I':
 331 #ifdef SMARTCARD
 332                         options.smartcard_device = xstrdup(optarg);
 333 #else
 334                         fprintf(stderr, "no support for smartcards.\n");
 335 #endif
 336                         break;
 337                 case 't':
 338                         if (tty_flag)
 339                                 force_tty_flag = 1;
 340                         tty_flag = 1;
 341                         break;
 342                 case 'v':
 343                         if (debug_flag == 0) {
 344                                 debug_flag = 1;
 345                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 346                         } else {
 347                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 348                                         options.log_level++;
 349                                 break;
 350                         }
 351                         /* FALLTHROUGH */
 352                 case 'V':
 353                         fprintf(stderr, "%s, %s\n",
 354                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 355                         if (opt == 'V')
 356                                 exit(0);
 357                         break;
 358                 case 'w':
 359                         if (options.tun_open == -1)
 360                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 361                         options.tun_local = a2tun(optarg, &options.tun_remote);
 362                         if (options.tun_local == SSH_TUNID_ERR) {
 363                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 364                                 exit(255);
 365                         }
 366                         break;
 367                 case 'q':
 368                         options.log_level = SYSLOG_LEVEL_QUIET;
 369                         break;
 370                 case 'e':
 371                         if (optarg[0] == '^' && optarg[2] == 0 &&
 372                             (u_char) optarg[1] >= 64 &&
 373                             (u_char) optarg[1] < 128)
 374                                 options.escape_char = (u_char) optarg[1] & 31;
 375                         else if (strlen(optarg) == 1)
 376                                 options.escape_char = (u_char) optarg[0];
 377                         else if (strcmp(optarg, "none") == 0)
 378                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 379                         else {
 380                                 fprintf(stderr, "Bad escape character '%s'.\n",
 381                                     optarg);
 382                                 exit(255);
 383                         }
 384                         break;
 385                 case 'c':
 386                         if (ciphers_valid(optarg)) {
 387                                 /* SSH2 only */
 388                                 options.ciphers = xstrdup(optarg);
 389                                 options.cipher = SSH_CIPHER_INVALID;
 390                         } else {
 391                                 /* SSH1 only */
 392                                 options.cipher = cipher_number(optarg);
 393                                 if (options.cipher == -1) {
 394                                         fprintf(stderr,
 395                                             "Unknown cipher type '%s'\n",
 396                                             optarg);
 397                                         exit(255);
 398                                 }
 399                                 if (options.cipher == SSH_CIPHER_3DES)
 400                                         options.ciphers = "3des-cbc";
 401                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 402                                         options.ciphers = "blowfish-cbc";
 403                                 else
 404                                         options.ciphers = (char *)-1;
 405                         }
 406                         break;
 407                 case 'm':
 408                         if (mac_valid(optarg))
 409                                 options.macs = xstrdup(optarg);
 410                         else {
 411                                 fprintf(stderr, "Unknown mac type '%s'\n",
 412                                     optarg);
 413                                 exit(255);
 414                         }
 415                         break;
 416                 case 'M':
 417                         if (options.control_master == SSHCTL_MASTER_YES)
 418                                 options.control_master = SSHCTL_MASTER_ASK;
 419                         else
 420                                 options.control_master = SSHCTL_MASTER_YES;
 421                         break;
 422                 case 'p':
 423                         options.port = a2port(optarg);
 424                         if (options.port == 0) {
 425                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 426                                 exit(255);
 427                         }
 428                         break;
 429                 case 'l':
 430                         options.user = optarg;
 431                         break;
 432
 433                 case 'L':
 434                         if (parse_forward(&fwd, optarg))
 435                                 add_local_forward(&options, &fwd);
 436                         else {
 437                                 fprintf(stderr,
 438                                     "Bad local forwarding specification '%s'\n",
 439                                     optarg);
 440                                 exit(255);
 441                         }
 442                         break;
 443
 444                 case 'R':
 445                         if (parse_forward(&fwd, optarg)) {
 446                                 add_remote_forward(&options, &fwd);
 447                         } else {
 448                                 fprintf(stderr,
 449                                     "Bad remote forwarding specification "
 450                                     "'%s'\n", optarg);
 451                                 exit(255);
 452                         }
 453                         break;
 454
 455                 case 'D':
 456                         cp = p = xstrdup(optarg);
 457                         memset(&fwd, '\0', sizeof(fwd));
 458                         fwd.connect_host = "socks";
 459                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 460                                 fprintf(stderr, "Bad dynamic forwarding "
 461                                     "specification '%.100s'\n", optarg);
 462                                 exit(255);
 463                         }
 464                         if (cp != NULL) {
 465                                 fwd.listen_port = a2port(cp);
 466                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 467                         } else {
 468                                 fwd.listen_port = a2port(fwd.listen_host);
 469                                 fwd.listen_host = NULL;
 470                         }
 471
 472                         if (fwd.listen_port == 0) {
 473                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 474                                     optarg);
 475                                 exit(255);
 476                         }
 477                         add_local_forward(&options, &fwd);
 478                         xfree(p);
 479                         break;
 480
 481                 case 'C':
 482                         options.compression = 1;
 483                         break;
 484                 case 'N':
 485                         no_shell_flag = 1;
 486                         no_tty_flag = 1;
 487                         break;
 488                 case 'T':
 489                         no_tty_flag = 1;
 490                         break;
 491                 case 'o':
 492                         dummy = 1;
 493                         line = xstrdup(optarg);
 494                         if (process_config_line(&options, host ? host : "",
 495                             line, "command-line", 0, &dummy) != 0)
 496                                 exit(255);
 497                         xfree(line);
 498                         break;
 499                 case 's':
 500                         subsystem_flag = 1;
 501                         break;
 502                 case 'S':
 503                         if (options.control_path != NULL)
 504                                 free(options.control_path);
 505                         options.control_path = xstrdup(optarg);
 506                         break;
 507                 case 'b':
 508                         options.bind_address = optarg;
 509                         break;
 510                 case 'F':
 511                         config = optarg;
 512                         break;
 513                 default:
 514                         usage();
 515                 }
 516         }
 517
 518         ac -= optind;
 519         av += optind;
 520
 521         if (ac > 0 && !host && **av != '-') {
 522                 if (strrchr(*av, '@')) {
 523                         p = xstrdup(*av);
 524                         cp = strrchr(p, '@');
 525                         if (cp == NULL || cp == p)
 526                                 usage();
 527                         options.user = p;
 528                         *cp = '\0';
 529                         host = ++cp;
 530                 } else
 531                         host = *av;
 532                 if (ac > 1) {
 533                         optind = optreset = 1;
 534                         goto again;
 535                 }
 536                 ac--, av++;
 537         }
 538
 539         /* Check that we got a host name. */
 540         if (!host)
 541                 usage();
 542
 543         SSLeay_add_all_algorithms();
 544         ERR_load_crypto_strings();
 545
 546         /* Initialize the command to execute on remote host. */
 547         buffer_init(&command);
 548
 549         /*
 550          * Save the command to execute on the remote host in a buffer. There
 551          * is no limit on the length of the command, except by the maximum
 552          * packet size.  Also sets the tty flag if there is no command.
 553          */
 554         if (!ac) {
 555                 /* No command specified - execute shell on a tty. */
 556                 tty_flag = 1;
 557                 if (subsystem_flag) {
 558                         fprintf(stderr,
 559                             "You must specify a subsystem to invoke.\n");
 560                         usage();
 561                 }
 562         } else {
 563                 /* A command has been specified.  Store it into the buffer. */
 564                 for (i = 0; i < ac; i++) {
 565                         if (i)
 566                                 buffer_append(&command, " ", 1);
 567                         buffer_append(&command, av[i], strlen(av[i]));
 568                 }
 569         }
 570
 571         /* Cannot fork to background if no command. */
 572         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 573                 fatal("Cannot fork into background without a command to execute.");
 574
 575         /* Allocate a tty by default if no command specified. */
 576         if (buffer_len(&command) == 0)
 577                 tty_flag = 1;
 578
 579         /* Force no tty */
 580         if (no_tty_flag)
 581                 tty_flag = 0;
 582         /* Do not allocate a tty if stdin is not a tty. */
 583         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 584                 if (tty_flag)
 585                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 586                 tty_flag = 0;
 587         }
 588
 589         /*
 590          * Initialize "log" output.  Since we are the client all output
 591          * actually goes to stderr.
 592          */
 593         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 594             SYSLOG_FACILITY_USER, 1);
 595
 596         /*
 597          * Read per-user configuration file.  Ignore the system wide config
 598          * file if the user specifies a config file on the command line.
 599          */
 600         if (config != NULL) {
 601                 if (!read_config_file(config, host, &options, 0))
 602                         fatal("Can't open user config file %.100s: "
 603                             "%.100s", config, strerror(errno));
 604         } else  {
 605                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 606                     _PATH_SSH_USER_CONFFILE);
 607                 (void)read_config_file(buf, host, &options, 1);
 608
 609                 /* Read systemwide configuration file after use config. */
 610                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 611                     &options, 0);
 612         }
 613
 614         /* Fill configuration defaults. */
 615         fill_default_options(&options);
 616
 617         channel_set_af(options.address_family);
 618
 619         /* reinit */
 620         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 621
 622         seed_rng();
 623
 624         if (options.user == NULL)
 625                 options.user = xstrdup(pw->pw_name);
 626
 627         if (options.hostname != NULL)
 628                 host = options.hostname;
 629
 630         /* force lowercase for hostkey matching */
 631         if (options.host_key_alias != NULL) {
 632                 for (p = options.host_key_alias; *p; p++)
 633                         if (isupper(*p))
 634                                 *p = (char)tolower(*p);
 635         }
 636
 637         /* Get default port if port has not been set. */
 638         if (options.port == 0) {
 639                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 640                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 641         }
 642
 643         if (options.proxy_command != NULL &&
 644             strcmp(options.proxy_command, "none") == 0)
 645                 options.proxy_command = NULL;
 646         if (options.control_path != NULL &&
 647             strcmp(options.control_path, "none") == 0)
 648                 options.control_path = NULL;
 649
 650         if (options.control_path != NULL) {
 651                 char thishost[NI_MAXHOST];
 652
 653                 if (gethostname(thishost, sizeof(thishost)) == -1)
 654                         fatal("gethostname: %s", strerror(errno));
 655                 snprintf(buf, sizeof(buf), "%d", options.port);
 656                 cp = tilde_expand_filename(options.control_path,
 657                     original_real_uid);
 658                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 659                     "r", options.user, "l", thishost, (char *)NULL);
 660                 xfree(cp);
 661         }
 662         if (mux_command != 0 && options.control_path == NULL)
 663                 fatal("No ControlPath specified for \"-O\" command");
 664         if (options.control_path != NULL)
 665                 control_client(options.control_path);
 666
 667         /* Open a connection to the remote host. */
 668         if (ssh_connect(host, &hostaddr, options.port,
 669             options.address_family, options.connection_attempts,
 670 #ifdef HAVE_CYGWIN
 671             options.use_privileged_port,
 672 #else
 673             original_effective_uid == 0 && options.use_privileged_port,
 674 #endif
 675             options.proxy_command) != 0)
 676                 exit(255);
 677
 678         /*
 679          * If we successfully made the connection, load the host private key
 680          * in case we will need it later for combined rsa-rhosts
 681          * authentication. This must be done before releasing extra
 682          * privileges, because the file is only readable by root.
 683          * If we cannot access the private keys, load the public keys
 684          * instead and try to execute the ssh-keysign helper instead.
 685          */
 686         sensitive_data.nkeys = 0;
 687         sensitive_data.keys = NULL;
 688         sensitive_data.external_keysign = 0;
 689         if (options.rhosts_rsa_authentication ||
 690             options.hostbased_authentication) {
 691                 sensitive_data.nkeys = 3;
 692                 sensitive_data.keys = xcalloc(sensitive_data.nkeys,
 693                     sizeof(Key));
 694
 695                 PRIV_START;
 696                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 697                     _PATH_HOST_KEY_FILE, "", NULL, NULL);
 698                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 699                     _PATH_HOST_DSA_KEY_FILE, "", NULL, NULL);
 700                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 701                     _PATH_HOST_RSA_KEY_FILE, "", NULL, NULL);
 702                 PRIV_END;
 703
 704                 if (options.hostbased_authentication == 1 &&
 705                     sensitive_data.keys[0] == NULL &&
 706                     sensitive_data.keys[1] == NULL &&
 707                     sensitive_data.keys[2] == NULL) {
 708                         sensitive_data.keys[1] = key_load_public(
 709                             _PATH_HOST_DSA_KEY_FILE, NULL);
 710                         sensitive_data.keys[2] = key_load_public(
 711                             _PATH_HOST_RSA_KEY_FILE, NULL);
 712                         sensitive_data.external_keysign = 1;
 713                 }
 714         }
 715         /*
 716          * Get rid of any extra privileges that we may have.  We will no
 717          * longer need them.  Also, extra privileges could make it very hard
 718          * to read identity files and other non-world-readable files from the
 719          * user's home directory if it happens to be on a NFS volume where
 720          * root is mapped to nobody.
 721          */
 722         if (original_effective_uid == 0) {
 723                 PRIV_START;
 724                 permanently_set_uid(pw);
 725         }
 726
 727         /*
 728          * Now that we are back to our own permissions, create ~/.ssh
 729          * directory if it doesn't already exist.
 730          */
 731         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 732         if (stat(buf, &st) < 0)
 733                 if (mkdir(buf, 0700) < 0)
 734                         error("Could not create directory '%.200s'.", buf);
 735
 736         /* load options.identity_files */
 737         load_public_identity_files();
 738
 739         /* Expand ~ in known host file names. */
 740         /* XXX mem-leaks: */
 741         options.system_hostfile =
 742             tilde_expand_filename(options.system_hostfile, original_real_uid);
 743         options.user_hostfile =
 744             tilde_expand_filename(options.user_hostfile, original_real_uid);
 745         options.system_hostfile2 =
 746             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 747         options.user_hostfile2 =
 748             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 749
 750         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 751
 752         /* Log into the remote system.  This never returns if the login fails. */
 753         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 754
 755         /* We no longer need the private host keys.  Clear them now. */
 756         if (sensitive_data.nkeys != 0) {
 757                 for (i = 0; i < sensitive_data.nkeys; i++) {
 758                         if (sensitive_data.keys[i] != NULL) {
 759                                 /* Destroys contents safely */
 760                                 debug3("clear hostkey %d", i);
 761                                 key_free(sensitive_data.keys[i]);
 762                                 sensitive_data.keys[i] = NULL;
 763                         }
 764                 }
 765                 xfree(sensitive_data.keys);
 766         }
 767         for (i = 0; i < options.num_identity_files; i++) {
 768                 if (options.identity_files[i]) {
 769                         xfree(options.identity_files[i]);
 770                         options.identity_files[i] = NULL;
 771                 }
 772                 if (options.identity_keys[i]) {
 773                         key_free(options.identity_keys[i]);
 774                         options.identity_keys[i] = NULL;
 775                 }
 776         }
 777
 778         exit_status = compat20 ? ssh_session2() : ssh_session();
 779         packet_close();
 780
 781         if (options.control_path != NULL && control_fd != -1)
 782                 unlink(options.control_path);
 783
 784         /*
 785          * Send SIGHUP to proxy command if used. We don't wait() in
 786          * case it hangs and instead rely on init to reap the child
 787          */
 788         if (proxy_command_pid > 1)
 789                 kill(proxy_command_pid, SIGHUP);
 790
 791         return exit_status;
 792 }
 793
 794 static void
 795 ssh_init_forwarding(void)
 796 {
 797         int success = 0;
 798         int i;
 799
 800         /* Initiate local TCP/IP port forwardings. */
 801         for (i = 0; i < options.num_local_forwards; i++) {
 802                 debug("Local connections to %.200s:%d forwarded to remote "
 803                     "address %.200s:%d",
 804                     (options.local_forwards[i].listen_host == NULL) ?
 805                     (options.gateway_ports ? "*" : "LOCALHOST") :
 806                     options.local_forwards[i].listen_host,
 807                     options.local_forwards[i].listen_port,
 808                     options.local_forwards[i].connect_host,
 809                     options.local_forwards[i].connect_port);
 810                 success += channel_setup_local_fwd_listener(
 811                     options.local_forwards[i].listen_host,
 812                     options.local_forwards[i].listen_port,
 813                     options.local_forwards[i].connect_host,
 814                     options.local_forwards[i].connect_port,
 815                     options.gateway_ports);
 816         }
 817         if (i > 0 && success == 0)
 818                 error("Could not request local forwarding.");
 819
 820         /* Initiate remote TCP/IP port forwardings. */
 821         for (i = 0; i < options.num_remote_forwards; i++) {
 822                 debug("Remote connections from %.200s:%d forwarded to "
 823                     "local address %.200s:%d",
 824                     (options.remote_forwards[i].listen_host == NULL) ?
 825                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 826                     options.remote_forwards[i].listen_port,
 827                     options.remote_forwards[i].connect_host,
 828                     options.remote_forwards[i].connect_port);
 829                 channel_request_remote_forwarding(
 830                     options.remote_forwards[i].listen_host,
 831                     options.remote_forwards[i].listen_port,
 832                     options.remote_forwards[i].connect_host,
 833                     options.remote_forwards[i].connect_port);
 834         }
 835 }
 836
 837 static void
 838 check_agent_present(void)
 839 {
 840         if (options.forward_agent) {
 841                 /* Clear agent forwarding if we don't have an agent. */
 842                 if (!ssh_agent_present())
 843                         options.forward_agent = 0;
 844         }
 845 }
 846
 847 static int
 848 ssh_session(void)
 849 {
 850         int type;
 851         int interactive = 0;
 852         int have_tty = 0;
 853         struct winsize ws;
 854         char *cp;
 855         const char *display;
 856
 857         /* Enable compression if requested. */
 858         if (options.compression) {
 859                 debug("Requesting compression at level %d.", options.compression_level);
 860
 861                 if (options.compression_level < 1 || options.compression_level > 9)
 862                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 863
 864                 /* Send the request. */
 865                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 866                 packet_put_int(options.compression_level);
 867                 packet_send();
 868                 packet_write_wait();
 869                 type = packet_read();
 870                 if (type == SSH_SMSG_SUCCESS)
 871                         packet_start_compression(options.compression_level);
 872                 else if (type == SSH_SMSG_FAILURE)
 873                         logit("Warning: Remote host refused compression.");
 874                 else
 875                         packet_disconnect("Protocol error waiting for compression response.");
 876         }
 877         /* Allocate a pseudo tty if appropriate. */
 878         if (tty_flag) {
 879                 debug("Requesting pty.");
 880
 881                 /* Start the packet. */
 882                 packet_start(SSH_CMSG_REQUEST_PTY);
 883
 884                 /* Store TERM in the packet.  There is no limit on the
 885                    length of the string. */
 886                 cp = getenv("TERM");
 887                 if (!cp)
 888                         cp = "";
 889                 packet_put_cstring(cp);
 890
 891                 /* Store window size in the packet. */
 892                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 893                         memset(&ws, 0, sizeof(ws));
 894                 packet_put_int((u_int)ws.ws_row);
 895                 packet_put_int((u_int)ws.ws_col);
 896                 packet_put_int((u_int)ws.ws_xpixel);
 897                 packet_put_int((u_int)ws.ws_ypixel);
 898
 899                 /* Store tty modes in the packet. */
 900                 tty_make_modes(fileno(stdin), NULL);
 901
 902                 /* Send the packet, and wait for it to leave. */
 903                 packet_send();
 904                 packet_write_wait();
 905
 906                 /* Read response from the server. */
 907                 type = packet_read();
 908                 if (type == SSH_SMSG_SUCCESS) {
 909                         interactive = 1;
 910                         have_tty = 1;
 911                 } else if (type == SSH_SMSG_FAILURE)
 912                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 913                 else
 914                         packet_disconnect("Protocol error waiting for pty request response.");
 915         }
 916         /* Request X11 forwarding if enabled and DISPLAY is set. */
 917         display = getenv("DISPLAY");
 918         if (options.forward_x11 && display != NULL) {
 919                 char *proto, *data;
 920                 /* Get reasonable local authentication information. */
 921                 client_x11_get_proto(display, options.xauth_location,
 922                     options.forward_x11_trusted, &proto, &data);
 923                 /* Request forwarding with authentication spoofing. */
 924                 debug("Requesting X11 forwarding with authentication spoofing.");
 925                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 926
 927                 /* Read response from the server. */
 928                 type = packet_read();
 929                 if (type == SSH_SMSG_SUCCESS) {
 930                         interactive = 1;
 931                 } else if (type == SSH_SMSG_FAILURE) {
 932                         logit("Warning: Remote host denied X11 forwarding.");
 933                 } else {
 934                         packet_disconnect("Protocol error waiting for X11 forwarding");
 935                 }
 936         }
 937         /* Tell the packet module whether this is an interactive session. */
 938         packet_set_interactive(interactive);
 939
 940         /* Request authentication agent forwarding if appropriate. */
 941         check_agent_present();
 942
 943         if (options.forward_agent) {
 944                 debug("Requesting authentication agent forwarding.");
 945                 auth_request_forwarding();
 946
 947                 /* Read response from the server. */
 948                 type = packet_read();
 949                 packet_check_eom();
 950                 if (type != SSH_SMSG_SUCCESS)
 951                         logit("Warning: Remote host denied authentication agent forwarding.");
 952         }
 953
 954         /* Initiate port forwardings. */
 955         ssh_init_forwarding();
 956
 957         /* If requested, let ssh continue in the background. */
 958         if (fork_after_authentication_flag)
 959                 if (daemon(1, 1) < 0)
 960                         fatal("daemon() failed: %.200s", strerror(errno));
 961
 962         /*
 963          * If a command was specified on the command line, execute the
 964          * command now. Otherwise request the server to start a shell.
 965          */
 966         if (buffer_len(&command) > 0) {
 967                 int len = buffer_len(&command);
 968                 if (len > 900)
 969                         len = 900;
 970                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 971                 packet_start(SSH_CMSG_EXEC_CMD);
 972                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 973                 packet_send();
 974                 packet_write_wait();
 975         } else {
 976                 debug("Requesting shell.");
 977                 packet_start(SSH_CMSG_EXEC_SHELL);
 978                 packet_send();
 979                 packet_write_wait();
 980         }
 981
 982         /* Enter the interactive session. */
 983         return client_loop(have_tty, tty_flag ?
 984             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
 985 }
 986
 987 static void
 988 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
 989 {
 990         int id, len;
 991
 992         id = packet_get_int();
 993         len = buffer_len(&command);
 994         if (len > 900)
 995                 len = 900;
 996         packet_check_eom();
 997         if (type == SSH2_MSG_CHANNEL_FAILURE)
 998                 fatal("Request for subsystem '%.*s' failed on channel %d",
 999                     len, (u_char *)buffer_ptr(&command), id);
1000 }
1001
1002 void
1003 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1004 {
1005         int i;
1006
1007         i = client_global_request_id++;
1008         if (i >= options.num_remote_forwards)
1009                 return;
1010         debug("remote forward %s for: listen %d, connect %s:%d",
1011             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1012             options.remote_forwards[i].listen_port,
1013             options.remote_forwards[i].connect_host,
1014             options.remote_forwards[i].connect_port);
1015         if (type == SSH2_MSG_REQUEST_FAILURE)
1016                 logit("Warning: remote port forwarding failed for listen "
1017                     "port %d", options.remote_forwards[i].listen_port);
1018 }
1019
1020 static void
1021 ssh_control_listener(void)
1022 {
1023         struct sockaddr_un addr;
1024         mode_t old_umask;
1025         int addr_len;
1026
1027         if (options.control_path == NULL ||
1028             options.control_master == SSHCTL_MASTER_NO)
1029                 return;
1030
1031         debug("setting up multiplex master socket");
1032
1033         memset(&addr, '\0', sizeof(addr));
1034         addr.sun_family = AF_UNIX;
1035         addr_len = offsetof(struct sockaddr_un, sun_path) +
1036             strlen(options.control_path) + 1;
1037
1038         if (strlcpy(addr.sun_path, options.control_path,
1039             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1040                 fatal("ControlPath too long");
1041
1042         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1043                 fatal("%s socket(): %s", __func__, strerror(errno));
1044
1045         old_umask = umask(0177);
1046         if (bind(control_fd, (struct sockaddr *)&addr, addr_len) == -1) {
1047                 control_fd = -1;
1048                 if (errno == EINVAL || errno == EADDRINUSE)
1049                         fatal("ControlSocket %s already exists",
1050                             options.control_path);
1051                 else
1052                         fatal("%s bind(): %s", __func__, strerror(errno));
1053         }
1054         umask(old_umask);
1055
1056         if (listen(control_fd, 64) == -1)
1057                 fatal("%s listen(): %s", __func__, strerror(errno));
1058
1059         set_nonblock(control_fd);
1060 }
1061
1062 /* request pty/x11/agent/tcpfwd/shell for channel */
1063 static void
1064 ssh_session2_setup(int id, void *arg)
1065 {
1066         extern char **environ;
1067         const char *display;
1068         int interactive = tty_flag;
1069
1070         display = getenv("DISPLAY");
1071         if (options.forward_x11 && display != NULL) {
1072                 char *proto, *data;
1073                 /* Get reasonable local authentication information. */
1074                 client_x11_get_proto(display, options.xauth_location,
1075                     options.forward_x11_trusted, &proto, &data);
1076                 /* Request forwarding with authentication spoofing. */
1077                 debug("Requesting X11 forwarding with authentication spoofing.");
1078                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1079                 interactive = 1;
1080                 /* XXX wait for reply */
1081         }
1082
1083         check_agent_present();
1084         if (options.forward_agent) {
1085                 debug("Requesting authentication agent forwarding.");
1086                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1087                 packet_send();
1088         }
1089
1090         if (options.tun_open != SSH_TUNMODE_NO) {
1091                 Channel *c;
1092                 int fd;
1093
1094                 debug("Requesting tun.");
1095                 if ((fd = tun_open(options.tun_local,
1096                     options.tun_open)) >= 0) {
1097                         c = channel_new("tun", SSH_CHANNEL_OPENING, fd, fd, -1,
1098                             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1099                             0, "tun", 1);
1100                         c->datagram = 1;
1101 #if defined(SSH_TUN_FILTER)
1102                         if (options.tun_open == SSH_TUNMODE_POINTOPOINT)
1103                                 channel_register_filter(c->self, sys_tun_infilter,
1104                                     sys_tun_outfilter);
1105 #endif
1106                         packet_start(SSH2_MSG_CHANNEL_OPEN);
1107                         packet_put_cstring("tun@openssh.com");
1108                         packet_put_int(c->self);
1109                         packet_put_int(c->local_window_max);
1110                         packet_put_int(c->local_maxpacket);
1111                         packet_put_int(options.tun_open);
1112                         packet_put_int(options.tun_remote);
1113                         packet_send();
1114                 }
1115         }
1116
1117         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1118             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1119
1120         packet_set_interactive(interactive);
1121 }
1122
1123 /* open new channel for a session */
1124 static int
1125 ssh_session2_open(void)
1126 {
1127         Channel *c;
1128         int window, packetmax, in, out, err;
1129
1130         if (stdin_null_flag) {
1131                 in = open(_PATH_DEVNULL, O_RDONLY);
1132         } else {
1133                 in = dup(STDIN_FILENO);
1134         }
1135         out = dup(STDOUT_FILENO);
1136         err = dup(STDERR_FILENO);
1137
1138         if (in < 0 || out < 0 || err < 0)
1139                 fatal("dup() in/out/err failed");
1140
1141         /* enable nonblocking unless tty */
1142         if (!isatty(in))
1143                 set_nonblock(in);
1144         if (!isatty(out))
1145                 set_nonblock(out);
1146         if (!isatty(err))
1147                 set_nonblock(err);
1148
1149         window = CHAN_SES_WINDOW_DEFAULT;
1150         packetmax = CHAN_SES_PACKET_DEFAULT;
1151         if (tty_flag) {
1152                 window >>= 1;
1153                 packetmax >>= 1;
1154         }
1155         c = channel_new(
1156             "session", SSH_CHANNEL_OPENING, in, out, err,
1157             window, packetmax, CHAN_EXTENDED_WRITE,
1158             "client-session", /*nonblock*/0);
1159
1160         debug3("ssh_session2_open: channel_new: %d", c->self);
1161
1162         channel_send_open(c->self);
1163         if (!no_shell_flag)
1164                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1165
1166         return c->self;
1167 }
1168
1169 static int
1170 ssh_session2(void)
1171 {
1172         int id = -1;
1173
1174         /* XXX should be pre-session */
1175         ssh_init_forwarding();
1176         ssh_control_listener();
1177
1178         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1179                 id = ssh_session2_open();
1180
1181         /* Execute a local command */
1182         if (options.local_command != NULL &&
1183             options.permit_local_command)
1184                 ssh_local_cmd(options.local_command);
1185
1186         /* If requested, let ssh continue in the background. */
1187         if (fork_after_authentication_flag)
1188                 if (daemon(1, 1) < 0)
1189                         fatal("daemon() failed: %.200s", strerror(errno));
1190
1191         return client_loop(tty_flag, tty_flag ?
1192             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1193 }
1194
1195 static void
1196 load_public_identity_files(void)
1197 {
1198         char *filename, *cp, thishost[NI_MAXHOST];
1199         int i = 0;
1200         Key *public;
1201         struct passwd *pw;
1202 #ifdef SMARTCARD
1203         Key **keys;
1204
1205         if (options.smartcard_device != NULL &&
1206             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1207             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1208                 int count = 0;
1209                 for (i = 0; keys[i] != NULL; i++) {
1210                         count++;
1211                         memmove(&options.identity_files[1], &options.identity_files[0],
1212                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1213                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1214                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1215                         options.num_identity_files++;
1216                         options.identity_keys[0] = keys[i];
1217                         options.identity_files[0] = sc_get_key_label(keys[i]);
1218                 }
1219                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1220                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1221                 i = count;
1222                 xfree(keys);
1223         }
1224 #endif /* SMARTCARD */
1225         if ((pw = getpwuid(original_real_uid)) == NULL)
1226                 fatal("load_public_identity_files: getpwuid failed");
1227         if (gethostname(thishost, sizeof(thishost)) == -1)
1228                 fatal("load_public_identity_files: gethostname: %s",
1229                     strerror(errno));
1230         for (; i < options.num_identity_files; i++) {
1231                 cp = tilde_expand_filename(options.identity_files[i],
1232                     original_real_uid);
1233                 filename = percent_expand(cp, "d", pw->pw_dir,
1234                     "u", pw->pw_name, "l", thishost, "h", host,
1235                     "r", options.user, (char *)NULL);
1236                 xfree(cp);
1237                 public = key_load_public(filename, NULL);
1238                 debug("identity file %s type %d", filename,
1239                     public ? public->type : -1);
1240                 xfree(options.identity_files[i]);
1241                 options.identity_files[i] = filename;
1242                 options.identity_keys[i] = public;
1243         }
1244 }
1245
1246 static void
1247 control_client_sighandler(int signo)
1248 {
1249         control_client_terminate = signo;
1250 }
1251
1252 static void
1253 control_client_sigrelay(int signo)
1254 {
1255         if (control_server_pid > 1)
1256                 kill(control_server_pid, signo);
1257 }
1258
1259 static int
1260 env_permitted(char *env)
1261 {
1262         int i;
1263         char name[1024], *cp;
1264
1265         if (strlcpy(name, env, sizeof(name)) >= sizeof(name))
1266                 fatal("env_permitted: name too long");
1267         if ((cp = strchr(name, '=')) == NULL)
1268                 return (0);
1269
1270         *cp = '\0';
1271
1272         for (i = 0; i < options.num_send_env; i++)
1273                 if (match_pattern(name, options.send_env[i]))
1274                         return (1);
1275
1276         return (0);
1277 }
1278
1279 static void
1280 control_client(const char *path)
1281 {
1282         struct sockaddr_un addr;
1283         int i, r, fd, sock, exitval, num_env, addr_len;
1284         Buffer m;
1285         char *term;
1286         extern char **environ;
1287         u_int  flags;
1288
1289         if (mux_command == 0)
1290                 mux_command = SSHMUX_COMMAND_OPEN;
1291
1292         switch (options.control_master) {
1293         case SSHCTL_MASTER_AUTO:
1294         case SSHCTL_MASTER_AUTO_ASK:
1295                 debug("auto-mux: Trying existing master");
1296                 /* FALLTHROUGH */
1297         case SSHCTL_MASTER_NO:
1298                 break;
1299         default:
1300                 return;
1301         }
1302
1303         memset(&addr, '\0', sizeof(addr));
1304         addr.sun_family = AF_UNIX;
1305         addr_len = offsetof(struct sockaddr_un, sun_path) +
1306             strlen(path) + 1;
1307
1308         if (strlcpy(addr.sun_path, path,
1309             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1310                 fatal("ControlPath too long");
1311
1312         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1313                 fatal("%s socket(): %s", __func__, strerror(errno));
1314
1315         if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
1316                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1317                         fatal("Control socket connect(%.100s): %s", path,
1318                             strerror(errno));
1319                 }
1320                 if (errno == ENOENT)
1321                         debug("Control socket \"%.100s\" does not exist", path);
1322                 else {
1323                         error("Control socket connect(%.100s): %s", path,
1324                             strerror(errno));
1325                 }
1326                 close(sock);
1327                 return;
1328         }
1329
1330         if (stdin_null_flag) {
1331                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1332                         fatal("open(/dev/null): %s", strerror(errno));
1333                 if (dup2(fd, STDIN_FILENO) == -1)
1334                         fatal("dup2: %s", strerror(errno));
1335                 if (fd > STDERR_FILENO)
1336                         close(fd);
1337         }
1338
1339         term = getenv("TERM");
1340
1341         flags = 0;
1342         if (tty_flag)
1343                 flags |= SSHMUX_FLAG_TTY;
1344         if (subsystem_flag)
1345                 flags |= SSHMUX_FLAG_SUBSYS;
1346         if (options.forward_x11)
1347                 flags |= SSHMUX_FLAG_X11_FWD;
1348         if (options.forward_agent)
1349                 flags |= SSHMUX_FLAG_AGENT_FWD;
1350
1351         buffer_init(&m);
1352
1353         /* Send our command to server */
1354         buffer_put_int(&m, mux_command);
1355         buffer_put_int(&m, flags);
1356         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1357                 fatal("%s: msg_send", __func__);
1358         buffer_clear(&m);
1359
1360         /* Get authorisation status and PID of controlee */
1361         if (ssh_msg_recv(sock, &m) == -1)
1362                 fatal("%s: msg_recv", __func__);
1363         if (buffer_get_char(&m) != SSHMUX_VER)
1364                 fatal("%s: wrong version", __func__);
1365         if (buffer_get_int(&m) != 1)
1366                 fatal("Connection to master denied");
1367         control_server_pid = buffer_get_int(&m);
1368
1369         buffer_clear(&m);
1370
1371         switch (mux_command) {
1372         case SSHMUX_COMMAND_ALIVE_CHECK:
1373                 fprintf(stderr, "Master running (pid=%d)\r\n",
1374                     control_server_pid);
1375                 exit(0);
1376         case SSHMUX_COMMAND_TERMINATE:
1377                 fprintf(stderr, "Exit request sent.\r\n");
1378                 exit(0);
1379         case SSHMUX_COMMAND_OPEN:
1380                 /* continue below */
1381                 break;
1382         default:
1383                 fatal("silly mux_command %d", mux_command);
1384         }
1385
1386         /* SSHMUX_COMMAND_OPEN */
1387         buffer_put_cstring(&m, term ? term : "");
1388         buffer_append(&command, "\0", 1);
1389         buffer_put_cstring(&m, buffer_ptr(&command));
1390
1391         if (options.num_send_env == 0 || environ == NULL) {
1392                 buffer_put_int(&m, 0);
1393         } else {
1394                 /* Pass environment */
1395                 num_env = 0;
1396                 for (i = 0; environ[i] != NULL; i++)
1397                         if (env_permitted(environ[i]))
1398                                 num_env++; /* Count */
1399
1400                 buffer_put_int(&m, num_env);
1401
1402                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1403                         if (env_permitted(environ[i])) {
1404                                 num_env--;
1405                                 buffer_put_cstring(&m, environ[i]);
1406                         }
1407         }
1408
1409         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1410                 fatal("%s: msg_send", __func__);
1411
1412         mm_send_fd(sock, STDIN_FILENO);
1413         mm_send_fd(sock, STDOUT_FILENO);
1414         mm_send_fd(sock, STDERR_FILENO);
1415
1416         /* Wait for reply, so master has a chance to gather ttymodes */
1417         buffer_clear(&m);
1418         if (ssh_msg_recv(sock, &m) == -1)
1419                 fatal("%s: msg_recv", __func__);
1420         if (buffer_get_char(&m) != SSHMUX_VER)
1421                 fatal("%s: wrong version", __func__);
1422         buffer_free(&m);
1423
1424         signal(SIGHUP, control_client_sighandler);
1425         signal(SIGINT, control_client_sighandler);
1426         signal(SIGTERM, control_client_sighandler);
1427         signal(SIGWINCH, control_client_sigrelay);
1428
1429         if (tty_flag)
1430                 enter_raw_mode();
1431
1432         /* Stick around until the controlee closes the client_fd */
1433         exitval = 0;
1434         for (;!control_client_terminate;) {
1435                 r = read(sock, &exitval, sizeof(exitval));
1436                 if (r == 0) {
1437                         debug2("Received EOF from master");
1438                         break;
1439                 }
1440                 if (r > 0)
1441                         debug2("Received exit status from master %d", exitval);
1442                 if (r == -1 && errno != EINTR)
1443                         fatal("%s: read %s", __func__, strerror(errno));
1444         }
1445
1446         if (control_client_terminate)
1447                 debug2("Exiting on signal %d", control_client_terminate);
1448
1449         close(sock);
1450
1451         leave_raw_mode();
1452
1453         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1454                 fprintf(stderr, "Connection to master closed.\r\n");
1455
1456         exit(exitval);
1457 }