ssh.c

   1 /* $OpenBSD: ssh.c,v 1.285 2006/07/11 20:27:56 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 #ifdef HAVE_PATHS_H
  58 #include <paths.h>
  59 #endif
  60 #include <pwd.h>
  61 #include <signal.h>
  62
  63 #include <openssl/evp.h>
  64 #include <openssl/err.h>
  65
  66 #include "ssh.h"
  67 #include "ssh1.h"
  68 #include "ssh2.h"
  69 #include "compat.h"
  70 #include "cipher.h"
  71 #include "xmalloc.h"
  72 #include "packet.h"
  73 #include "buffer.h"
  74 #include "bufaux.h"
  75 #include "channels.h"
  76 #include "key.h"
  77 #include "authfd.h"
  78 #include "authfile.h"
  79 #include "pathnames.h"
  80 #include "dispatch.h"
  81 #include "clientloop.h"
  82 #include "log.h"
  83 #include "readconf.h"
  84 #include "sshconnect.h"
  85 #include "misc.h"
  86 #include "kex.h"
  87 #include "mac.h"
  88 #include "sshpty.h"
  89 #include "match.h"
  90 #include "msg.h"
  91 #include "monitor_fdpass.h"
  92 #include "uidswap.h"
  93 #include "version.h"
  94
  95 #ifdef SMARTCARD
  96 #include "scard.h"
  97 #endif
  98
  99 extern char *__progname;
 100
 101 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
 102 int debug_flag = 0;
 103
 104 /* Flag indicating whether a tty should be allocated */
 105 int tty_flag = 0;
 106 int no_tty_flag = 0;
 107 int force_tty_flag = 0;
 108
 109 /* don't exec a shell */
 110 int no_shell_flag = 0;
 111
 112 /*
 113  * Flag indicating that nothing should be read from stdin.  This can be set
 114  * on the command line.
 115  */
 116 int stdin_null_flag = 0;
 117
 118 /*
 119  * Flag indicating that ssh should fork after authentication.  This is useful
 120  * so that the passphrase can be entered manually, and then ssh goes to the
 121  * background.
 122  */
 123 int fork_after_authentication_flag = 0;
 124
 125 /*
 126  * General data structure for command line options and options configurable
 127  * in configuration files.  See readconf.h.
 128  */
 129 Options options;
 130
 131 /* optional user configfile */
 132 char *config = NULL;
 133
 134 /*
 135  * Name of the host we are connecting to.  This is the name given on the
 136  * command line, or the HostName specified for the user-supplied name in a
 137  * configuration file.
 138  */
 139 char *host;
 140
 141 /* socket address the host resolves to */
 142 struct sockaddr_storage hostaddr;
 143
 144 /* Private host keys. */
 145 Sensitive sensitive_data;
 146
 147 /* Original real UID. */
 148 uid_t original_real_uid;
 149 uid_t original_effective_uid;
 150
 151 /* command to be executed */
 152 Buffer command;
 153
 154 /* Should we execute a command or invoke a subsystem? */
 155 int subsystem_flag = 0;
 156
 157 /* # of replies received for global requests */
 158 static int client_global_request_id = 0;
 159
 160 /* pid of proxycommand child process */
 161 pid_t proxy_command_pid = 0;
 162
 163 /* fd to control socket */
 164 int control_fd = -1;
 165
 166 /* Multiplexing control command */
 167 static u_int mux_command = 0;
 168
 169 /* Only used in control client mode */
 170 volatile sig_atomic_t control_client_terminate = 0;
 171 u_int control_server_pid = 0;
 172
 173 /* Prints a help message to the user.  This function never returns. */
 174
 175 static void
 176 usage(void)
 177 {
 178         fprintf(stderr,
 179 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 180 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 181 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 182 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 183 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 184 "           [-w local_tun[:remote_tun]] [user@]hostname [command]\n"
 185         );
 186         exit(255);
 187 }
 188
 189 static int ssh_session(void);
 190 static int ssh_session2(void);
 191 static void load_public_identity_files(void);
 192 static void control_client(const char *path);
 193
 194 /*
 195  * Main program for the ssh client.
 196  */
 197 int
 198 main(int ac, char **av)
 199 {
 200         int i, opt, exit_status;
 201         char *p, *cp, *line, buf[256];
 202         struct stat st;
 203         struct passwd *pw;
 204         int dummy;
 205         extern int optind, optreset;
 206         extern char *optarg;
 207         struct servent *sp;
 208         Forward fwd;
 209
 210         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 211         sanitise_stdfd();
 212
 213         __progname = ssh_get_progname(av[0]);
 214         init_rng();
 215
 216         /*
 217          * Save the original real uid.  It will be needed later (uid-swapping
 218          * may clobber the real uid).
 219          */
 220         original_real_uid = getuid();
 221         original_effective_uid = geteuid();
 222
 223         /*
 224          * Use uid-swapping to give up root privileges for the duration of
 225          * option processing.  We will re-instantiate the rights when we are
 226          * ready to create the privileged port, and will permanently drop
 227          * them when the port has been created (actually, when the connection
 228          * has been made, as we may need to create the port several times).
 229          */
 230         PRIV_END;
 231
 232 #ifdef HAVE_SETRLIMIT
 233         /* If we are installed setuid root be careful to not drop core. */
 234         if (original_real_uid != original_effective_uid) {
 235                 struct rlimit rlim;
 236                 rlim.rlim_cur = rlim.rlim_max = 0;
 237                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 238                         fatal("setrlimit failed: %.100s", strerror(errno));
 239         }
 240 #endif
 241         /* Get user data. */
 242         pw = getpwuid(original_real_uid);
 243         if (!pw) {
 244                 logit("You don't exist, go away!");
 245                 exit(255);
 246         }
 247         /* Take a copy of the returned structure. */
 248         pw = pwcopy(pw);
 249
 250         /*
 251          * Set our umask to something reasonable, as some files are created
 252          * with the default umask.  This will make them world-readable but
 253          * writable only by the owner, which is ok for all files for which we
 254          * don't set the modes explicitly.
 255          */
 256         umask(022);
 257
 258         /* Initialize option structure to indicate that no values have been set. */
 259         initialize_options(&options);
 260
 261         /* Parse command-line arguments. */
 262         host = NULL;
 263
 264  again:
 265         while ((opt = getopt(ac, av,
 266             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVw:XY")) != -1) {
 267                 switch (opt) {
 268                 case '1':
 269                         options.protocol = SSH_PROTO_1;
 270                         break;
 271                 case '2':
 272                         options.protocol = SSH_PROTO_2;
 273                         break;
 274                 case '4':
 275                         options.address_family = AF_INET;
 276                         break;
 277                 case '6':
 278                         options.address_family = AF_INET6;
 279                         break;
 280                 case 'n':
 281                         stdin_null_flag = 1;
 282                         break;
 283                 case 'f':
 284                         fork_after_authentication_flag = 1;
 285                         stdin_null_flag = 1;
 286                         break;
 287                 case 'x':
 288                         options.forward_x11 = 0;
 289                         break;
 290                 case 'X':
 291                         options.forward_x11 = 1;
 292                         break;
 293                 case 'Y':
 294                         options.forward_x11 = 1;
 295                         options.forward_x11_trusted = 1;
 296                         break;
 297                 case 'g':
 298                         options.gateway_ports = 1;
 299                         break;
 300                 case 'O':
 301                         if (strcmp(optarg, "check") == 0)
 302                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 303                         else if (strcmp(optarg, "exit") == 0)
 304                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 305                         else
 306                                 fatal("Invalid multiplex command.");
 307                         break;
 308                 case 'P':       /* deprecated */
 309                         options.use_privileged_port = 0;
 310                         break;
 311                 case 'a':
 312                         options.forward_agent = 0;
 313                         break;
 314                 case 'A':
 315                         options.forward_agent = 1;
 316                         break;
 317                 case 'k':
 318                         options.gss_deleg_creds = 0;
 319                         break;
 320                 case 'i':
 321                         if (stat(optarg, &st) < 0) {
 322                                 fprintf(stderr, "Warning: Identity file %s "
 323                                     "not accessible: %s.\n", optarg,
 324                                     strerror(errno));
 325                                 break;
 326                         }
 327                         if (options.num_identity_files >=
 328                             SSH_MAX_IDENTITY_FILES)
 329                                 fatal("Too many identity files specified "
 330                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 331                         options.identity_files[options.num_identity_files++] =
 332                             xstrdup(optarg);
 333                         break;
 334                 case 'I':
 335 #ifdef SMARTCARD
 336                         options.smartcard_device = xstrdup(optarg);
 337 #else
 338                         fprintf(stderr, "no support for smartcards.\n");
 339 #endif
 340                         break;
 341                 case 't':
 342                         if (tty_flag)
 343                                 force_tty_flag = 1;
 344                         tty_flag = 1;
 345                         break;
 346                 case 'v':
 347                         if (debug_flag == 0) {
 348                                 debug_flag = 1;
 349                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 350                         } else {
 351                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 352                                         options.log_level++;
 353                                 break;
 354                         }
 355                         /* FALLTHROUGH */
 356                 case 'V':
 357                         fprintf(stderr, "%s, %s\n",
 358                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 359                         if (opt == 'V')
 360                                 exit(0);
 361                         break;
 362                 case 'w':
 363                         if (options.tun_open == -1)
 364                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 365                         options.tun_local = a2tun(optarg, &options.tun_remote);
 366                         if (options.tun_local == SSH_TUNID_ERR) {
 367                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 368                                 exit(255);
 369                         }
 370                         break;
 371                 case 'q':
 372                         options.log_level = SYSLOG_LEVEL_QUIET;
 373                         break;
 374                 case 'e':
 375                         if (optarg[0] == '^' && optarg[2] == 0 &&
 376                             (u_char) optarg[1] >= 64 &&
 377                             (u_char) optarg[1] < 128)
 378                                 options.escape_char = (u_char) optarg[1] & 31;
 379                         else if (strlen(optarg) == 1)
 380                                 options.escape_char = (u_char) optarg[0];
 381                         else if (strcmp(optarg, "none") == 0)
 382                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 383                         else {
 384                                 fprintf(stderr, "Bad escape character '%s'.\n",
 385                                     optarg);
 386                                 exit(255);
 387                         }
 388                         break;
 389                 case 'c':
 390                         if (ciphers_valid(optarg)) {
 391                                 /* SSH2 only */
 392                                 options.ciphers = xstrdup(optarg);
 393                                 options.cipher = SSH_CIPHER_INVALID;
 394                         } else {
 395                                 /* SSH1 only */
 396                                 options.cipher = cipher_number(optarg);
 397                                 if (options.cipher == -1) {
 398                                         fprintf(stderr,
 399                                             "Unknown cipher type '%s'\n",
 400                                             optarg);
 401                                         exit(255);
 402                                 }
 403                                 if (options.cipher == SSH_CIPHER_3DES)
 404                                         options.ciphers = "3des-cbc";
 405                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 406                                         options.ciphers = "blowfish-cbc";
 407                                 else
 408                                         options.ciphers = (char *)-1;
 409                         }
 410                         break;
 411                 case 'm':
 412                         if (mac_valid(optarg))
 413                                 options.macs = xstrdup(optarg);
 414                         else {
 415                                 fprintf(stderr, "Unknown mac type '%s'\n",
 416                                     optarg);
 417                                 exit(255);
 418                         }
 419                         break;
 420                 case 'M':
 421                         if (options.control_master == SSHCTL_MASTER_YES)
 422                                 options.control_master = SSHCTL_MASTER_ASK;
 423                         else
 424                                 options.control_master = SSHCTL_MASTER_YES;
 425                         break;
 426                 case 'p':
 427                         options.port = a2port(optarg);
 428                         if (options.port == 0) {
 429                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 430                                 exit(255);
 431                         }
 432                         break;
 433                 case 'l':
 434                         options.user = optarg;
 435                         break;
 436
 437                 case 'L':
 438                         if (parse_forward(&fwd, optarg))
 439                                 add_local_forward(&options, &fwd);
 440                         else {
 441                                 fprintf(stderr,
 442                                     "Bad local forwarding specification '%s'\n",
 443                                     optarg);
 444                                 exit(255);
 445                         }
 446                         break;
 447
 448                 case 'R':
 449                         if (parse_forward(&fwd, optarg)) {
 450                                 add_remote_forward(&options, &fwd);
 451                         } else {
 452                                 fprintf(stderr,
 453                                     "Bad remote forwarding specification "
 454                                     "'%s'\n", optarg);
 455                                 exit(255);
 456                         }
 457                         break;
 458
 459                 case 'D':
 460                         cp = p = xstrdup(optarg);
 461                         memset(&fwd, '\0', sizeof(fwd));
 462                         fwd.connect_host = "socks";
 463                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 464                                 fprintf(stderr, "Bad dynamic forwarding "
 465                                     "specification '%.100s'\n", optarg);
 466                                 exit(255);
 467                         }
 468                         if (cp != NULL) {
 469                                 fwd.listen_port = a2port(cp);
 470                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 471                         } else {
 472                                 fwd.listen_port = a2port(fwd.listen_host);
 473                                 fwd.listen_host = NULL;
 474                         }
 475
 476                         if (fwd.listen_port == 0) {
 477                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 478                                     optarg);
 479                                 exit(255);
 480                         }
 481                         add_local_forward(&options, &fwd);
 482                         xfree(p);
 483                         break;
 484
 485                 case 'C':
 486                         options.compression = 1;
 487                         break;
 488                 case 'N':
 489                         no_shell_flag = 1;
 490                         no_tty_flag = 1;
 491                         break;
 492                 case 'T':
 493                         no_tty_flag = 1;
 494                         break;
 495                 case 'o':
 496                         dummy = 1;
 497                         line = xstrdup(optarg);
 498                         if (process_config_line(&options, host ? host : "",
 499                             line, "command-line", 0, &dummy) != 0)
 500                                 exit(255);
 501                         xfree(line);
 502                         break;
 503                 case 's':
 504                         subsystem_flag = 1;
 505                         break;
 506                 case 'S':
 507                         if (options.control_path != NULL)
 508                                 free(options.control_path);
 509                         options.control_path = xstrdup(optarg);
 510                         break;
 511                 case 'b':
 512                         options.bind_address = optarg;
 513                         break;
 514                 case 'F':
 515                         config = optarg;
 516                         break;
 517                 default:
 518                         usage();
 519                 }
 520         }
 521
 522         ac -= optind;
 523         av += optind;
 524
 525         if (ac > 0 && !host && **av != '-') {
 526                 if (strrchr(*av, '@')) {
 527                         p = xstrdup(*av);
 528                         cp = strrchr(p, '@');
 529                         if (cp == NULL || cp == p)
 530                                 usage();
 531                         options.user = p;
 532                         *cp = '\0';
 533                         host = ++cp;
 534                 } else
 535                         host = *av;
 536                 if (ac > 1) {
 537                         optind = optreset = 1;
 538                         goto again;
 539                 }
 540                 ac--, av++;
 541         }
 542
 543         /* Check that we got a host name. */
 544         if (!host)
 545                 usage();
 546
 547         SSLeay_add_all_algorithms();
 548         ERR_load_crypto_strings();
 549
 550         /* Initialize the command to execute on remote host. */
 551         buffer_init(&command);
 552
 553         /*
 554          * Save the command to execute on the remote host in a buffer. There
 555          * is no limit on the length of the command, except by the maximum
 556          * packet size.  Also sets the tty flag if there is no command.
 557          */
 558         if (!ac) {
 559                 /* No command specified - execute shell on a tty. */
 560                 tty_flag = 1;
 561                 if (subsystem_flag) {
 562                         fprintf(stderr,
 563                             "You must specify a subsystem to invoke.\n");
 564                         usage();
 565                 }
 566         } else {
 567                 /* A command has been specified.  Store it into the buffer. */
 568                 for (i = 0; i < ac; i++) {
 569                         if (i)
 570                                 buffer_append(&command, " ", 1);
 571                         buffer_append(&command, av[i], strlen(av[i]));
 572                 }
 573         }
 574
 575         /* Cannot fork to background if no command. */
 576         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 577                 fatal("Cannot fork into background without a command to execute.");
 578
 579         /* Allocate a tty by default if no command specified. */
 580         if (buffer_len(&command) == 0)
 581                 tty_flag = 1;
 582
 583         /* Force no tty */
 584         if (no_tty_flag)
 585                 tty_flag = 0;
 586         /* Do not allocate a tty if stdin is not a tty. */
 587         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 588                 if (tty_flag)
 589                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 590                 tty_flag = 0;
 591         }
 592
 593         /*
 594          * Initialize "log" output.  Since we are the client all output
 595          * actually goes to stderr.
 596          */
 597         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 598             SYSLOG_FACILITY_USER, 1);
 599
 600         /*
 601          * Read per-user configuration file.  Ignore the system wide config
 602          * file if the user specifies a config file on the command line.
 603          */
 604         if (config != NULL) {
 605                 if (!read_config_file(config, host, &options, 0))
 606                         fatal("Can't open user config file %.100s: "
 607                             "%.100s", config, strerror(errno));
 608         } else  {
 609                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 610                     _PATH_SSH_USER_CONFFILE);
 611                 (void)read_config_file(buf, host, &options, 1);
 612
 613                 /* Read systemwide configuration file after use config. */
 614                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 615                     &options, 0);
 616         }
 617
 618         /* Fill configuration defaults. */
 619         fill_default_options(&options);
 620
 621         channel_set_af(options.address_family);
 622
 623         /* reinit */
 624         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 625
 626         seed_rng();
 627
 628         if (options.user == NULL)
 629                 options.user = xstrdup(pw->pw_name);
 630
 631         if (options.hostname != NULL)
 632                 host = options.hostname;
 633
 634         /* force lowercase for hostkey matching */
 635         if (options.host_key_alias != NULL) {
 636                 for (p = options.host_key_alias; *p; p++)
 637                         if (isupper(*p))
 638                                 *p = (char)tolower(*p);
 639         }
 640
 641         /* Get default port if port has not been set. */
 642         if (options.port == 0) {
 643                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 644                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 645         }
 646
 647         if (options.proxy_command != NULL &&
 648             strcmp(options.proxy_command, "none") == 0)
 649                 options.proxy_command = NULL;
 650         if (options.control_path != NULL &&
 651             strcmp(options.control_path, "none") == 0)
 652                 options.control_path = NULL;
 653
 654         if (options.control_path != NULL) {
 655                 char thishost[NI_MAXHOST];
 656
 657                 if (gethostname(thishost, sizeof(thishost)) == -1)
 658                         fatal("gethostname: %s", strerror(errno));
 659                 snprintf(buf, sizeof(buf), "%d", options.port);
 660                 cp = tilde_expand_filename(options.control_path,
 661                     original_real_uid);
 662                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 663                     "r", options.user, "l", thishost, (char *)NULL);
 664                 xfree(cp);
 665         }
 666         if (mux_command != 0 && options.control_path == NULL)
 667                 fatal("No ControlPath specified for \"-O\" command");
 668         if (options.control_path != NULL)
 669                 control_client(options.control_path);
 670
 671         /* Open a connection to the remote host. */
 672         if (ssh_connect(host, &hostaddr, options.port,
 673             options.address_family, options.connection_attempts,
 674 #ifdef HAVE_CYGWIN
 675             options.use_privileged_port,
 676 #else
 677             original_effective_uid == 0 && options.use_privileged_port,
 678 #endif
 679             options.proxy_command) != 0)
 680                 exit(255);
 681
 682         /*
 683          * If we successfully made the connection, load the host private key
 684          * in case we will need it later for combined rsa-rhosts
 685          * authentication. This must be done before releasing extra
 686          * privileges, because the file is only readable by root.
 687          * If we cannot access the private keys, load the public keys
 688          * instead and try to execute the ssh-keysign helper instead.
 689          */
 690         sensitive_data.nkeys = 0;
 691         sensitive_data.keys = NULL;
 692         sensitive_data.external_keysign = 0;
 693         if (options.rhosts_rsa_authentication ||
 694             options.hostbased_authentication) {
 695                 sensitive_data.nkeys = 3;
 696                 sensitive_data.keys = xcalloc(sensitive_data.nkeys,
 697                     sizeof(Key));
 698
 699                 PRIV_START;
 700                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 701                     _PATH_HOST_KEY_FILE, "", NULL, NULL);
 702                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 703                     _PATH_HOST_DSA_KEY_FILE, "", NULL, NULL);
 704                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 705                     _PATH_HOST_RSA_KEY_FILE, "", NULL, NULL);
 706                 PRIV_END;
 707
 708                 if (options.hostbased_authentication == 1 &&
 709                     sensitive_data.keys[0] == NULL &&
 710                     sensitive_data.keys[1] == NULL &&
 711                     sensitive_data.keys[2] == NULL) {
 712                         sensitive_data.keys[1] = key_load_public(
 713                             _PATH_HOST_DSA_KEY_FILE, NULL);
 714                         sensitive_data.keys[2] = key_load_public(
 715                             _PATH_HOST_RSA_KEY_FILE, NULL);
 716                         sensitive_data.external_keysign = 1;
 717                 }
 718         }
 719         /*
 720          * Get rid of any extra privileges that we may have.  We will no
 721          * longer need them.  Also, extra privileges could make it very hard
 722          * to read identity files and other non-world-readable files from the
 723          * user's home directory if it happens to be on a NFS volume where
 724          * root is mapped to nobody.
 725          */
 726         if (original_effective_uid == 0) {
 727                 PRIV_START;
 728                 permanently_set_uid(pw);
 729         }
 730
 731         /*
 732          * Now that we are back to our own permissions, create ~/.ssh
 733          * directory if it doesn't already exist.
 734          */
 735         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 736         if (stat(buf, &st) < 0)
 737                 if (mkdir(buf, 0700) < 0)
 738                         error("Could not create directory '%.200s'.", buf);
 739
 740         /* load options.identity_files */
 741         load_public_identity_files();
 742
 743         /* Expand ~ in known host file names. */
 744         /* XXX mem-leaks: */
 745         options.system_hostfile =
 746             tilde_expand_filename(options.system_hostfile, original_real_uid);
 747         options.user_hostfile =
 748             tilde_expand_filename(options.user_hostfile, original_real_uid);
 749         options.system_hostfile2 =
 750             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 751         options.user_hostfile2 =
 752             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 753
 754         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 755
 756         /* Log into the remote system.  This never returns if the login fails. */
 757         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 758
 759         /* We no longer need the private host keys.  Clear them now. */
 760         if (sensitive_data.nkeys != 0) {
 761                 for (i = 0; i < sensitive_data.nkeys; i++) {
 762                         if (sensitive_data.keys[i] != NULL) {
 763                                 /* Destroys contents safely */
 764                                 debug3("clear hostkey %d", i);
 765                                 key_free(sensitive_data.keys[i]);
 766                                 sensitive_data.keys[i] = NULL;
 767                         }
 768                 }
 769                 xfree(sensitive_data.keys);
 770         }
 771         for (i = 0; i < options.num_identity_files; i++) {
 772                 if (options.identity_files[i]) {
 773                         xfree(options.identity_files[i]);
 774                         options.identity_files[i] = NULL;
 775                 }
 776                 if (options.identity_keys[i]) {
 777                         key_free(options.identity_keys[i]);
 778                         options.identity_keys[i] = NULL;
 779                 }
 780         }
 781
 782         exit_status = compat20 ? ssh_session2() : ssh_session();
 783         packet_close();
 784
 785         if (options.control_path != NULL && control_fd != -1)
 786                 unlink(options.control_path);
 787
 788         /*
 789          * Send SIGHUP to proxy command if used. We don't wait() in
 790          * case it hangs and instead rely on init to reap the child
 791          */
 792         if (proxy_command_pid > 1)
 793                 kill(proxy_command_pid, SIGHUP);
 794
 795         return exit_status;
 796 }
 797
 798 static void
 799 ssh_init_forwarding(void)
 800 {
 801         int success = 0;
 802         int i;
 803
 804         /* Initiate local TCP/IP port forwardings. */
 805         for (i = 0; i < options.num_local_forwards; i++) {
 806                 debug("Local connections to %.200s:%d forwarded to remote "
 807                     "address %.200s:%d",
 808                     (options.local_forwards[i].listen_host == NULL) ?
 809                     (options.gateway_ports ? "*" : "LOCALHOST") :
 810                     options.local_forwards[i].listen_host,
 811                     options.local_forwards[i].listen_port,
 812                     options.local_forwards[i].connect_host,
 813                     options.local_forwards[i].connect_port);
 814                 success += channel_setup_local_fwd_listener(
 815                     options.local_forwards[i].listen_host,
 816                     options.local_forwards[i].listen_port,
 817                     options.local_forwards[i].connect_host,
 818                     options.local_forwards[i].connect_port,
 819                     options.gateway_ports);
 820         }
 821         if (i > 0 && success != i && options.exit_on_forward_failure)
 822                 fatal("Could not request local forwarding.");
 823         if (i > 0 && success == 0)
 824                 error("Could not request local forwarding.");
 825
 826         /* Initiate remote TCP/IP port forwardings. */
 827         for (i = 0; i < options.num_remote_forwards; i++) {
 828                 debug("Remote connections from %.200s:%d forwarded to "
 829                     "local address %.200s:%d",
 830                     (options.remote_forwards[i].listen_host == NULL) ?
 831                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 832                     options.remote_forwards[i].listen_port,
 833                     options.remote_forwards[i].connect_host,
 834                     options.remote_forwards[i].connect_port);
 835                 if (channel_request_remote_forwarding(
 836                     options.remote_forwards[i].listen_host,
 837                     options.remote_forwards[i].listen_port,
 838                     options.remote_forwards[i].connect_host,
 839                     options.remote_forwards[i].connect_port) < 0) {
 840                         if (options.exit_on_forward_failure)
 841                                 fatal("Could not request remote forwarding.");
 842                         else
 843                                 logit("Warning: Could not request remote "
 844                                     "forwarding.");
 845                 }
 846         }
 847 }
 848
 849 static void
 850 check_agent_present(void)
 851 {
 852         if (options.forward_agent) {
 853                 /* Clear agent forwarding if we don't have an agent. */
 854                 if (!ssh_agent_present())
 855                         options.forward_agent = 0;
 856         }
 857 }
 858
 859 static int
 860 ssh_session(void)
 861 {
 862         int type;
 863         int interactive = 0;
 864         int have_tty = 0;
 865         struct winsize ws;
 866         char *cp;
 867         const char *display;
 868
 869         /* Enable compression if requested. */
 870         if (options.compression) {
 871                 debug("Requesting compression at level %d.", options.compression_level);
 872
 873                 if (options.compression_level < 1 || options.compression_level > 9)
 874                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 875
 876                 /* Send the request. */
 877                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 878                 packet_put_int(options.compression_level);
 879                 packet_send();
 880                 packet_write_wait();
 881                 type = packet_read();
 882                 if (type == SSH_SMSG_SUCCESS)
 883                         packet_start_compression(options.compression_level);
 884                 else if (type == SSH_SMSG_FAILURE)
 885                         logit("Warning: Remote host refused compression.");
 886                 else
 887                         packet_disconnect("Protocol error waiting for compression response.");
 888         }
 889         /* Allocate a pseudo tty if appropriate. */
 890         if (tty_flag) {
 891                 debug("Requesting pty.");
 892
 893                 /* Start the packet. */
 894                 packet_start(SSH_CMSG_REQUEST_PTY);
 895
 896                 /* Store TERM in the packet.  There is no limit on the
 897                    length of the string. */
 898                 cp = getenv("TERM");
 899                 if (!cp)
 900                         cp = "";
 901                 packet_put_cstring(cp);
 902
 903                 /* Store window size in the packet. */
 904                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 905                         memset(&ws, 0, sizeof(ws));
 906                 packet_put_int((u_int)ws.ws_row);
 907                 packet_put_int((u_int)ws.ws_col);
 908                 packet_put_int((u_int)ws.ws_xpixel);
 909                 packet_put_int((u_int)ws.ws_ypixel);
 910
 911                 /* Store tty modes in the packet. */
 912                 tty_make_modes(fileno(stdin), NULL);
 913
 914                 /* Send the packet, and wait for it to leave. */
 915                 packet_send();
 916                 packet_write_wait();
 917
 918                 /* Read response from the server. */
 919                 type = packet_read();
 920                 if (type == SSH_SMSG_SUCCESS) {
 921                         interactive = 1;
 922                         have_tty = 1;
 923                 } else if (type == SSH_SMSG_FAILURE)
 924                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 925                 else
 926                         packet_disconnect("Protocol error waiting for pty request response.");
 927         }
 928         /* Request X11 forwarding if enabled and DISPLAY is set. */
 929         display = getenv("DISPLAY");
 930         if (options.forward_x11 && display != NULL) {
 931                 char *proto, *data;
 932                 /* Get reasonable local authentication information. */
 933                 client_x11_get_proto(display, options.xauth_location,
 934                     options.forward_x11_trusted, &proto, &data);
 935                 /* Request forwarding with authentication spoofing. */
 936                 debug("Requesting X11 forwarding with authentication spoofing.");
 937                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 938
 939                 /* Read response from the server. */
 940                 type = packet_read();
 941                 if (type == SSH_SMSG_SUCCESS) {
 942                         interactive = 1;
 943                 } else if (type == SSH_SMSG_FAILURE) {
 944                         logit("Warning: Remote host denied X11 forwarding.");
 945                 } else {
 946                         packet_disconnect("Protocol error waiting for X11 forwarding");
 947                 }
 948         }
 949         /* Tell the packet module whether this is an interactive session. */
 950         packet_set_interactive(interactive);
 951
 952         /* Request authentication agent forwarding if appropriate. */
 953         check_agent_present();
 954
 955         if (options.forward_agent) {
 956                 debug("Requesting authentication agent forwarding.");
 957                 auth_request_forwarding();
 958
 959                 /* Read response from the server. */
 960                 type = packet_read();
 961                 packet_check_eom();
 962                 if (type != SSH_SMSG_SUCCESS)
 963                         logit("Warning: Remote host denied authentication agent forwarding.");
 964         }
 965
 966         /* Initiate port forwardings. */
 967         ssh_init_forwarding();
 968
 969         /* If requested, let ssh continue in the background. */
 970         if (fork_after_authentication_flag)
 971                 if (daemon(1, 1) < 0)
 972                         fatal("daemon() failed: %.200s", strerror(errno));
 973
 974         /*
 975          * If a command was specified on the command line, execute the
 976          * command now. Otherwise request the server to start a shell.
 977          */
 978         if (buffer_len(&command) > 0) {
 979                 int len = buffer_len(&command);
 980                 if (len > 900)
 981                         len = 900;
 982                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 983                 packet_start(SSH_CMSG_EXEC_CMD);
 984                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 985                 packet_send();
 986                 packet_write_wait();
 987         } else {
 988                 debug("Requesting shell.");
 989                 packet_start(SSH_CMSG_EXEC_SHELL);
 990                 packet_send();
 991                 packet_write_wait();
 992         }
 993
 994         /* Enter the interactive session. */
 995         return client_loop(have_tty, tty_flag ?
 996             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
 997 }
 998
 999 static void
1000 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
1001 {
1002         int id, len;
1003
1004         id = packet_get_int();
1005         len = buffer_len(&command);
1006         if (len > 900)
1007                 len = 900;
1008         packet_check_eom();
1009         if (type == SSH2_MSG_CHANNEL_FAILURE)
1010                 fatal("Request for subsystem '%.*s' failed on channel %d",
1011                     len, (u_char *)buffer_ptr(&command), id);
1012 }
1013
1014 void
1015 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1016 {
1017         int i;
1018
1019         i = client_global_request_id++;
1020         if (i >= options.num_remote_forwards)
1021                 return;
1022         debug("remote forward %s for: listen %d, connect %s:%d",
1023             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1024             options.remote_forwards[i].listen_port,
1025             options.remote_forwards[i].connect_host,
1026             options.remote_forwards[i].connect_port);
1027         if (type == SSH2_MSG_REQUEST_FAILURE) {
1028                 if (options.exit_on_forward_failure)
1029                         fatal("Error: remote port forwarding failed for "
1030                             "listen port %d",
1031                             options.remote_forwards[i].listen_port);
1032                 else
1033                         logit("Warning: remote port forwarding failed for "
1034                             "listen port %d",
1035                             options.remote_forwards[i].listen_port);
1036         }
1037 }
1038
1039 static void
1040 ssh_control_listener(void)
1041 {
1042         struct sockaddr_un addr;
1043         mode_t old_umask;
1044         int addr_len;
1045
1046         if (options.control_path == NULL ||
1047             options.control_master == SSHCTL_MASTER_NO)
1048                 return;
1049
1050         debug("setting up multiplex master socket");
1051
1052         memset(&addr, '\0', sizeof(addr));
1053         addr.sun_family = AF_UNIX;
1054         addr_len = offsetof(struct sockaddr_un, sun_path) +
1055             strlen(options.control_path) + 1;
1056
1057         if (strlcpy(addr.sun_path, options.control_path,
1058             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1059                 fatal("ControlPath too long");
1060
1061         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1062                 fatal("%s socket(): %s", __func__, strerror(errno));
1063
1064         old_umask = umask(0177);
1065         if (bind(control_fd, (struct sockaddr *)&addr, addr_len) == -1) {
1066                 control_fd = -1;
1067                 if (errno == EINVAL || errno == EADDRINUSE)
1068                         fatal("ControlSocket %s already exists",
1069                             options.control_path);
1070                 else
1071                         fatal("%s bind(): %s", __func__, strerror(errno));
1072         }
1073         umask(old_umask);
1074
1075         if (listen(control_fd, 64) == -1)
1076                 fatal("%s listen(): %s", __func__, strerror(errno));
1077
1078         set_nonblock(control_fd);
1079 }
1080
1081 /* request pty/x11/agent/tcpfwd/shell for channel */
1082 static void
1083 ssh_session2_setup(int id, void *arg)
1084 {
1085         extern char **environ;
1086         const char *display;
1087         int interactive = tty_flag;
1088
1089         display = getenv("DISPLAY");
1090         if (options.forward_x11 && display != NULL) {
1091                 char *proto, *data;
1092                 /* Get reasonable local authentication information. */
1093                 client_x11_get_proto(display, options.xauth_location,
1094                     options.forward_x11_trusted, &proto, &data);
1095                 /* Request forwarding with authentication spoofing. */
1096                 debug("Requesting X11 forwarding with authentication spoofing.");
1097                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1098                 interactive = 1;
1099                 /* XXX wait for reply */
1100         }
1101
1102         check_agent_present();
1103         if (options.forward_agent) {
1104                 debug("Requesting authentication agent forwarding.");
1105                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1106                 packet_send();
1107         }
1108
1109         if (options.tun_open != SSH_TUNMODE_NO) {
1110                 Channel *c;
1111                 int fd;
1112
1113                 debug("Requesting tun.");
1114                 if ((fd = tun_open(options.tun_local,
1115                     options.tun_open)) >= 0) {
1116                         c = channel_new("tun", SSH_CHANNEL_OPENING, fd, fd, -1,
1117                             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1118                             0, "tun", 1);
1119                         c->datagram = 1;
1120 #if defined(SSH_TUN_FILTER)
1121                         if (options.tun_open == SSH_TUNMODE_POINTOPOINT)
1122                                 channel_register_filter(c->self, sys_tun_infilter,
1123                                     sys_tun_outfilter);
1124 #endif
1125                         packet_start(SSH2_MSG_CHANNEL_OPEN);
1126                         packet_put_cstring("tun@openssh.com");
1127                         packet_put_int(c->self);
1128                         packet_put_int(c->local_window_max);
1129                         packet_put_int(c->local_maxpacket);
1130                         packet_put_int(options.tun_open);
1131                         packet_put_int(options.tun_remote);
1132                         packet_send();
1133                 }
1134         }
1135
1136         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1137             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1138
1139         packet_set_interactive(interactive);
1140 }
1141
1142 /* open new channel for a session */
1143 static int
1144 ssh_session2_open(void)
1145 {
1146         Channel *c;
1147         int window, packetmax, in, out, err;
1148
1149         if (stdin_null_flag) {
1150                 in = open(_PATH_DEVNULL, O_RDONLY);
1151         } else {
1152                 in = dup(STDIN_FILENO);
1153         }
1154         out = dup(STDOUT_FILENO);
1155         err = dup(STDERR_FILENO);
1156
1157         if (in < 0 || out < 0 || err < 0)
1158                 fatal("dup() in/out/err failed");
1159
1160         /* enable nonblocking unless tty */
1161         if (!isatty(in))
1162                 set_nonblock(in);
1163         if (!isatty(out))
1164                 set_nonblock(out);
1165         if (!isatty(err))
1166                 set_nonblock(err);
1167
1168         window = CHAN_SES_WINDOW_DEFAULT;
1169         packetmax = CHAN_SES_PACKET_DEFAULT;
1170         if (tty_flag) {
1171                 window >>= 1;
1172                 packetmax >>= 1;
1173         }
1174         c = channel_new(
1175             "session", SSH_CHANNEL_OPENING, in, out, err,
1176             window, packetmax, CHAN_EXTENDED_WRITE,
1177             "client-session", /*nonblock*/0);
1178
1179         debug3("ssh_session2_open: channel_new: %d", c->self);
1180
1181         channel_send_open(c->self);
1182         if (!no_shell_flag)
1183                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1184
1185         return c->self;
1186 }
1187
1188 static int
1189 ssh_session2(void)
1190 {
1191         int id = -1;
1192
1193         /* XXX should be pre-session */
1194         ssh_init_forwarding();
1195         ssh_control_listener();
1196
1197         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1198                 id = ssh_session2_open();
1199
1200         /* Execute a local command */
1201         if (options.local_command != NULL &&
1202             options.permit_local_command)
1203                 ssh_local_cmd(options.local_command);
1204
1205         /* If requested, let ssh continue in the background. */
1206         if (fork_after_authentication_flag)
1207                 if (daemon(1, 1) < 0)
1208                         fatal("daemon() failed: %.200s", strerror(errno));
1209
1210         return client_loop(tty_flag, tty_flag ?
1211             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1212 }
1213
1214 static void
1215 load_public_identity_files(void)
1216 {
1217         char *filename, *cp, thishost[NI_MAXHOST];
1218         int i = 0;
1219         Key *public;
1220         struct passwd *pw;
1221 #ifdef SMARTCARD
1222         Key **keys;
1223
1224         if (options.smartcard_device != NULL &&
1225             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1226             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1227                 int count = 0;
1228                 for (i = 0; keys[i] != NULL; i++) {
1229                         count++;
1230                         memmove(&options.identity_files[1], &options.identity_files[0],
1231                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1232                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1233                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1234                         options.num_identity_files++;
1235                         options.identity_keys[0] = keys[i];
1236                         options.identity_files[0] = sc_get_key_label(keys[i]);
1237                 }
1238                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1239                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1240                 i = count;
1241                 xfree(keys);
1242         }
1243 #endif /* SMARTCARD */
1244         if ((pw = getpwuid(original_real_uid)) == NULL)
1245                 fatal("load_public_identity_files: getpwuid failed");
1246         if (gethostname(thishost, sizeof(thishost)) == -1)
1247                 fatal("load_public_identity_files: gethostname: %s",
1248                     strerror(errno));
1249         for (; i < options.num_identity_files; i++) {
1250                 cp = tilde_expand_filename(options.identity_files[i],
1251                     original_real_uid);
1252                 filename = percent_expand(cp, "d", pw->pw_dir,
1253                     "u", pw->pw_name, "l", thishost, "h", host,
1254                     "r", options.user, (char *)NULL);
1255                 xfree(cp);
1256                 public = key_load_public(filename, NULL);
1257                 debug("identity file %s type %d", filename,
1258                     public ? public->type : -1);
1259                 xfree(options.identity_files[i]);
1260                 options.identity_files[i] = filename;
1261                 options.identity_keys[i] = public;
1262         }
1263 }
1264
1265 static void
1266 control_client_sighandler(int signo)
1267 {
1268         control_client_terminate = signo;
1269 }
1270
1271 static void
1272 control_client_sigrelay(int signo)
1273 {
1274         if (control_server_pid > 1)
1275                 kill(control_server_pid, signo);
1276 }
1277
1278 static int
1279 env_permitted(char *env)
1280 {
1281         int i, ret;
1282         char name[1024], *cp;
1283
1284         if ((cp = strchr(env, '=')) == NULL || cp == env)
1285                 return (0);
1286         ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
1287         if (ret <= 0 || (size_t)ret >= sizeof(name))
1288                 fatal("env_permitted: name '%.100s...' too long", env);
1289
1290         for (i = 0; i < options.num_send_env; i++)
1291                 if (match_pattern(name, options.send_env[i]))
1292                         return (1);
1293
1294         return (0);
1295 }
1296
1297 static void
1298 control_client(const char *path)
1299 {
1300         struct sockaddr_un addr;
1301         int i, r, fd, sock, exitval, num_env, addr_len;
1302         Buffer m;
1303         char *term;
1304         extern char **environ;
1305         u_int  flags;
1306
1307         if (mux_command == 0)
1308                 mux_command = SSHMUX_COMMAND_OPEN;
1309
1310         switch (options.control_master) {
1311         case SSHCTL_MASTER_AUTO:
1312         case SSHCTL_MASTER_AUTO_ASK:
1313                 debug("auto-mux: Trying existing master");
1314                 /* FALLTHROUGH */
1315         case SSHCTL_MASTER_NO:
1316                 break;
1317         default:
1318                 return;
1319         }
1320
1321         memset(&addr, '\0', sizeof(addr));
1322         addr.sun_family = AF_UNIX;
1323         addr_len = offsetof(struct sockaddr_un, sun_path) +
1324             strlen(path) + 1;
1325
1326         if (strlcpy(addr.sun_path, path,
1327             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1328                 fatal("ControlPath too long");
1329
1330         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1331                 fatal("%s socket(): %s", __func__, strerror(errno));
1332
1333         if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
1334                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1335                         fatal("Control socket connect(%.100s): %s", path,
1336                             strerror(errno));
1337                 }
1338                 if (errno == ENOENT)
1339                         debug("Control socket \"%.100s\" does not exist", path);
1340                 else {
1341                         error("Control socket connect(%.100s): %s", path,
1342                             strerror(errno));
1343                 }
1344                 close(sock);
1345                 return;
1346         }
1347
1348         if (stdin_null_flag) {
1349                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1350                         fatal("open(/dev/null): %s", strerror(errno));
1351                 if (dup2(fd, STDIN_FILENO) == -1)
1352                         fatal("dup2: %s", strerror(errno));
1353                 if (fd > STDERR_FILENO)
1354                         close(fd);
1355         }
1356
1357         term = getenv("TERM");
1358
1359         flags = 0;
1360         if (tty_flag)
1361                 flags |= SSHMUX_FLAG_TTY;
1362         if (subsystem_flag)
1363                 flags |= SSHMUX_FLAG_SUBSYS;
1364         if (options.forward_x11)
1365                 flags |= SSHMUX_FLAG_X11_FWD;
1366         if (options.forward_agent)
1367                 flags |= SSHMUX_FLAG_AGENT_FWD;
1368
1369         buffer_init(&m);
1370
1371         /* Send our command to server */
1372         buffer_put_int(&m, mux_command);
1373         buffer_put_int(&m, flags);
1374         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1375                 fatal("%s: msg_send", __func__);
1376         buffer_clear(&m);
1377
1378         /* Get authorisation status and PID of controlee */
1379         if (ssh_msg_recv(sock, &m) == -1)
1380                 fatal("%s: msg_recv", __func__);
1381         if (buffer_get_char(&m) != SSHMUX_VER)
1382                 fatal("%s: wrong version", __func__);
1383         if (buffer_get_int(&m) != 1)
1384                 fatal("Connection to master denied");
1385         control_server_pid = buffer_get_int(&m);
1386
1387         buffer_clear(&m);
1388
1389         switch (mux_command) {
1390         case SSHMUX_COMMAND_ALIVE_CHECK:
1391                 fprintf(stderr, "Master running (pid=%d)\r\n",
1392                     control_server_pid);
1393                 exit(0);
1394         case SSHMUX_COMMAND_TERMINATE:
1395                 fprintf(stderr, "Exit request sent.\r\n");
1396                 exit(0);
1397         case SSHMUX_COMMAND_OPEN:
1398                 /* continue below */
1399                 break;
1400         default:
1401                 fatal("silly mux_command %d", mux_command);
1402         }
1403
1404         /* SSHMUX_COMMAND_OPEN */
1405         buffer_put_cstring(&m, term ? term : "");
1406         buffer_append(&command, "\0", 1);
1407         buffer_put_cstring(&m, buffer_ptr(&command));
1408
1409         if (options.num_send_env == 0 || environ == NULL) {
1410                 buffer_put_int(&m, 0);
1411         } else {
1412                 /* Pass environment */
1413                 num_env = 0;
1414                 for (i = 0; environ[i] != NULL; i++)
1415                         if (env_permitted(environ[i]))
1416                                 num_env++; /* Count */
1417
1418                 buffer_put_int(&m, num_env);
1419
1420                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1421                         if (env_permitted(environ[i])) {
1422                                 num_env--;
1423                                 buffer_put_cstring(&m, environ[i]);
1424                         }
1425         }
1426
1427         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1428                 fatal("%s: msg_send", __func__);
1429
1430         mm_send_fd(sock, STDIN_FILENO);
1431         mm_send_fd(sock, STDOUT_FILENO);
1432         mm_send_fd(sock, STDERR_FILENO);
1433
1434         /* Wait for reply, so master has a chance to gather ttymodes */
1435         buffer_clear(&m);
1436         if (ssh_msg_recv(sock, &m) == -1)
1437                 fatal("%s: msg_recv", __func__);
1438         if (buffer_get_char(&m) != SSHMUX_VER)
1439                 fatal("%s: wrong version", __func__);
1440         buffer_free(&m);
1441
1442         signal(SIGHUP, control_client_sighandler);
1443         signal(SIGINT, control_client_sighandler);
1444         signal(SIGTERM, control_client_sighandler);
1445         signal(SIGWINCH, control_client_sigrelay);
1446
1447         if (tty_flag)
1448                 enter_raw_mode();
1449
1450         /* Stick around until the controlee closes the client_fd */
1451         exitval = 0;
1452         for (;!control_client_terminate;) {
1453                 r = read(sock, &exitval, sizeof(exitval));
1454                 if (r == 0) {
1455                         debug2("Received EOF from master");
1456                         break;
1457                 }
1458                 if (r > 0)
1459                         debug2("Received exit status from master %d", exitval);
1460                 if (r == -1 && errno != EINTR)
1461                         fatal("%s: read %s", __func__, strerror(errno));
1462         }
1463
1464         if (control_client_terminate)
1465                 debug2("Exiting on signal %d", control_client_terminate);
1466
1467         close(sock);
1468
1469         leave_raw_mode();
1470
1471         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1472                 fprintf(stderr, "Connection to master closed.\r\n");
1473
1474         exit(exitval);
1475 }