ssh.c

   1 /*
   2  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   3  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   4  *                    All rights reserved
   5  * Ssh client program.  This program can be used to log into a remote machine.
   6  * The software supports strong authentication, encryption, and forwarding
   7  * of X11, TCP/IP, and authentication connections.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  * Copyright (c) 1999 Niels Provos.  All rights reserved.
  16  * Copyright (c) 2000, 2001, 2002, 2003 Markus Friedl.  All rights reserved.
  17  *
  18  * Modified to work with SSL by Niels Provos <provos@citi.umich.edu>
  19  * in Canada (German citizen).
  20  *
  21  * Redistribution and use in source and binary forms, with or without
  22  * modification, are permitted provided that the following conditions
  23  * are met:
  24  * 1. Redistributions of source code must retain the above copyright
  25  *    notice, this list of conditions and the following disclaimer.
  26  * 2. Redistributions in binary form must reproduce the above copyright
  27  *    notice, this list of conditions and the following disclaimer in the
  28  *    documentation and/or other materials provided with the distribution.
  29  *
  30  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  31  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  32  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  33  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  34  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  35  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  36  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  37  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  38  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  39  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  40  */
  41
  42 #include "includes.h"
  43 RCSID("$OpenBSD: ssh.c,v 1.261 2006/02/12 06:45:34 djm Exp $");
  44
  45 #include <sys/resource.h>
  46 #include <sys/ioctl.h>
  47
  48 #include <paths.h>
  49
  50 #include <openssl/evp.h>
  51 #include <openssl/err.h>
  52
  53 #include "ssh.h"
  54 #include "ssh1.h"
  55 #include "ssh2.h"
  56 #include "compat.h"
  57 #include "cipher.h"
  58 #include "xmalloc.h"
  59 #include "packet.h"
  60 #include "buffer.h"
  61 #include "bufaux.h"
  62 #include "channels.h"
  63 #include "key.h"
  64 #include "authfd.h"
  65 #include "authfile.h"
  66 #include "pathnames.h"
  67 #include "dispatch.h"
  68 #include "clientloop.h"
  69 #include "log.h"
  70 #include "readconf.h"
  71 #include "sshconnect.h"
  72 #include "misc.h"
  73 #include "kex.h"
  74 #include "mac.h"
  75 #include "sshpty.h"
  76 #include "match.h"
  77 #include "msg.h"
  78 #include "monitor_fdpass.h"
  79 #include "uidswap.h"
  80
  81 #ifdef SMARTCARD
  82 #include "scard.h"
  83 #endif
  84
  85 extern char *__progname;
  86
  87 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
  88 int debug_flag = 0;
  89
  90 /* Flag indicating whether a tty should be allocated */
  91 int tty_flag = 0;
  92 int no_tty_flag = 0;
  93 int force_tty_flag = 0;
  94
  95 /* don't exec a shell */
  96 int no_shell_flag = 0;
  97
  98 /*
  99  * Flag indicating that nothing should be read from stdin.  This can be set
 100  * on the command line.
 101  */
 102 int stdin_null_flag = 0;
 103
 104 /*
 105  * Flag indicating that ssh should fork after authentication.  This is useful
 106  * so that the passphrase can be entered manually, and then ssh goes to the
 107  * background.
 108  */
 109 int fork_after_authentication_flag = 0;
 110
 111 /*
 112  * General data structure for command line options and options configurable
 113  * in configuration files.  See readconf.h.
 114  */
 115 Options options;
 116
 117 /* optional user configfile */
 118 char *config = NULL;
 119
 120 /*
 121  * Name of the host we are connecting to.  This is the name given on the
 122  * command line, or the HostName specified for the user-supplied name in a
 123  * configuration file.
 124  */
 125 char *host;
 126
 127 /* socket address the host resolves to */
 128 struct sockaddr_storage hostaddr;
 129
 130 /* Private host keys. */
 131 Sensitive sensitive_data;
 132
 133 /* Original real UID. */
 134 uid_t original_real_uid;
 135 uid_t original_effective_uid;
 136
 137 /* command to be executed */
 138 Buffer command;
 139
 140 /* Should we execute a command or invoke a subsystem? */
 141 int subsystem_flag = 0;
 142
 143 /* # of replies received for global requests */
 144 static int client_global_request_id = 0;
 145
 146 /* pid of proxycommand child process */
 147 pid_t proxy_command_pid = 0;
 148
 149 /* fd to control socket */
 150 int control_fd = -1;
 151
 152 /* Multiplexing control command */
 153 static u_int mux_command = 0;
 154
 155 /* Only used in control client mode */
 156 volatile sig_atomic_t control_client_terminate = 0;
 157 u_int control_server_pid = 0;
 158
 159 /* Prints a help message to the user.  This function never returns. */
 160
 161 static void
 162 usage(void)
 163 {
 164         fprintf(stderr,
 165 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 166 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 167 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 168 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 169 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 170 "           [-w tunnel:tunnel] [user@]hostname [command]\n"
 171         );
 172         exit(255);
 173 }
 174
 175 static int ssh_session(void);
 176 static int ssh_session2(void);
 177 static void load_public_identity_files(void);
 178 static void control_client(const char *path);
 179
 180 /*
 181  * Main program for the ssh client.
 182  */
 183 int
 184 main(int ac, char **av)
 185 {
 186         int i, opt, exit_status;
 187         char *p, *cp, *line, buf[256];
 188         struct stat st;
 189         struct passwd *pw;
 190         int dummy;
 191         extern int optind, optreset;
 192         extern char *optarg;
 193         struct servent *sp;
 194         Forward fwd;
 195
 196         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 197         sanitise_stdfd();
 198
 199         __progname = ssh_get_progname(av[0]);
 200         init_rng();
 201
 202         /*
 203          * Save the original real uid.  It will be needed later (uid-swapping
 204          * may clobber the real uid).
 205          */
 206         original_real_uid = getuid();
 207         original_effective_uid = geteuid();
 208
 209         /*
 210          * Use uid-swapping to give up root privileges for the duration of
 211          * option processing.  We will re-instantiate the rights when we are
 212          * ready to create the privileged port, and will permanently drop
 213          * them when the port has been created (actually, when the connection
 214          * has been made, as we may need to create the port several times).
 215          */
 216         PRIV_END;
 217
 218 #ifdef HAVE_SETRLIMIT
 219         /* If we are installed setuid root be careful to not drop core. */
 220         if (original_real_uid != original_effective_uid) {
 221                 struct rlimit rlim;
 222                 rlim.rlim_cur = rlim.rlim_max = 0;
 223                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 224                         fatal("setrlimit failed: %.100s", strerror(errno));
 225         }
 226 #endif
 227         /* Get user data. */
 228         pw = getpwuid(original_real_uid);
 229         if (!pw) {
 230                 logit("You don't exist, go away!");
 231                 exit(255);
 232         }
 233         /* Take a copy of the returned structure. */
 234         pw = pwcopy(pw);
 235
 236         /*
 237          * Set our umask to something reasonable, as some files are created
 238          * with the default umask.  This will make them world-readable but
 239          * writable only by the owner, which is ok for all files for which we
 240          * don't set the modes explicitly.
 241          */
 242         umask(022);
 243
 244         /* Initialize option structure to indicate that no values have been set. */
 245         initialize_options(&options);
 246
 247         /* Parse command-line arguments. */
 248         host = NULL;
 249
 250 again:
 251         while ((opt = getopt(ac, av,
 252             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVw:XY")) != -1) {
 253                 switch (opt) {
 254                 case '1':
 255                         options.protocol = SSH_PROTO_1;
 256                         break;
 257                 case '2':
 258                         options.protocol = SSH_PROTO_2;
 259                         break;
 260                 case '4':
 261                         options.address_family = AF_INET;
 262                         break;
 263                 case '6':
 264                         options.address_family = AF_INET6;
 265                         break;
 266                 case 'n':
 267                         stdin_null_flag = 1;
 268                         break;
 269                 case 'f':
 270                         fork_after_authentication_flag = 1;
 271                         stdin_null_flag = 1;
 272                         break;
 273                 case 'x':
 274                         options.forward_x11 = 0;
 275                         break;
 276                 case 'X':
 277                         options.forward_x11 = 1;
 278                         break;
 279                 case 'Y':
 280                         options.forward_x11 = 1;
 281                         options.forward_x11_trusted = 1;
 282                         break;
 283                 case 'g':
 284                         options.gateway_ports = 1;
 285                         break;
 286                 case 'O':
 287                         if (strcmp(optarg, "check") == 0)
 288                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 289                         else if (strcmp(optarg, "exit") == 0)
 290                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 291                         else
 292                                 fatal("Invalid multiplex command.");
 293                         break;
 294                 case 'P':       /* deprecated */
 295                         options.use_privileged_port = 0;
 296                         break;
 297                 case 'a':
 298                         options.forward_agent = 0;
 299                         break;
 300                 case 'A':
 301                         options.forward_agent = 1;
 302                         break;
 303                 case 'k':
 304                         options.gss_deleg_creds = 0;
 305                         break;
 306                 case 'i':
 307                         if (stat(optarg, &st) < 0) {
 308                                 fprintf(stderr, "Warning: Identity file %s "
 309                                     "not accessible: %s.\n", optarg,
 310                                     strerror(errno));
 311                                 break;
 312                         }
 313                         if (options.num_identity_files >=
 314                             SSH_MAX_IDENTITY_FILES)
 315                                 fatal("Too many identity files specified "
 316                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 317                         options.identity_files[options.num_identity_files++] =
 318                             xstrdup(optarg);
 319                         break;
 320                 case 'I':
 321 #ifdef SMARTCARD
 322                         options.smartcard_device = xstrdup(optarg);
 323 #else
 324                         fprintf(stderr, "no support for smartcards.\n");
 325 #endif
 326                         break;
 327                 case 't':
 328                         if (tty_flag)
 329                                 force_tty_flag = 1;
 330                         tty_flag = 1;
 331                         break;
 332                 case 'v':
 333                         if (debug_flag == 0) {
 334                                 debug_flag = 1;
 335                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 336                         } else {
 337                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 338                                         options.log_level++;
 339                                 break;
 340                         }
 341                         /* FALLTHROUGH */
 342                 case 'V':
 343                         fprintf(stderr, "%s, %s\n",
 344                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 345                         if (opt == 'V')
 346                                 exit(0);
 347                         break;
 348                 case 'w':
 349                         if (options.tun_open == -1)
 350                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 351                         options.tun_local = a2tun(optarg, &options.tun_remote);
 352                         if (options.tun_local == SSH_TUNID_ERR) {
 353                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 354                                 exit(255);
 355                         }
 356                         break;
 357                 case 'q':
 358                         options.log_level = SYSLOG_LEVEL_QUIET;
 359                         break;
 360                 case 'e':
 361                         if (optarg[0] == '^' && optarg[2] == 0 &&
 362                             (u_char) optarg[1] >= 64 &&
 363                             (u_char) optarg[1] < 128)
 364                                 options.escape_char = (u_char) optarg[1] & 31;
 365                         else if (strlen(optarg) == 1)
 366                                 options.escape_char = (u_char) optarg[0];
 367                         else if (strcmp(optarg, "none") == 0)
 368                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 369                         else {
 370                                 fprintf(stderr, "Bad escape character '%s'.\n",
 371                                     optarg);
 372                                 exit(255);
 373                         }
 374                         break;
 375                 case 'c':
 376                         if (ciphers_valid(optarg)) {
 377                                 /* SSH2 only */
 378                                 options.ciphers = xstrdup(optarg);
 379                                 options.cipher = SSH_CIPHER_INVALID;
 380                         } else {
 381                                 /* SSH1 only */
 382                                 options.cipher = cipher_number(optarg);
 383                                 if (options.cipher == -1) {
 384                                         fprintf(stderr,
 385                                             "Unknown cipher type '%s'\n",
 386                                             optarg);
 387                                         exit(255);
 388                                 }
 389                                 if (options.cipher == SSH_CIPHER_3DES)
 390                                         options.ciphers = "3des-cbc";
 391                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 392                                         options.ciphers = "blowfish-cbc";
 393                                 else
 394                                         options.ciphers = (char *)-1;
 395                         }
 396                         break;
 397                 case 'm':
 398                         if (mac_valid(optarg))
 399                                 options.macs = xstrdup(optarg);
 400                         else {
 401                                 fprintf(stderr, "Unknown mac type '%s'\n",
 402                                     optarg);
 403                                 exit(255);
 404                         }
 405                         break;
 406                 case 'M':
 407                         if (options.control_master == SSHCTL_MASTER_YES)
 408                                 options.control_master = SSHCTL_MASTER_ASK;
 409                         else
 410                                 options.control_master = SSHCTL_MASTER_YES;
 411                         break;
 412                 case 'p':
 413                         options.port = a2port(optarg);
 414                         if (options.port == 0) {
 415                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 416                                 exit(255);
 417                         }
 418                         break;
 419                 case 'l':
 420                         options.user = optarg;
 421                         break;
 422
 423                 case 'L':
 424                         if (parse_forward(&fwd, optarg))
 425                                 add_local_forward(&options, &fwd);
 426                         else {
 427                                 fprintf(stderr,
 428                                     "Bad local forwarding specification '%s'\n",
 429                                     optarg);
 430                                 exit(255);
 431                         }
 432                         break;
 433
 434                 case 'R':
 435                         if (parse_forward(&fwd, optarg)) {
 436                                 add_remote_forward(&options, &fwd);
 437                         } else {
 438                                 fprintf(stderr,
 439                                     "Bad remote forwarding specification "
 440                                     "'%s'\n", optarg);
 441                                 exit(255);
 442                         }
 443                         break;
 444
 445                 case 'D':
 446                         cp = p = xstrdup(optarg);
 447                         memset(&fwd, '\0', sizeof(fwd));
 448                         fwd.connect_host = "socks";
 449                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 450                                 fprintf(stderr, "Bad dynamic forwarding "
 451                                     "specification '%.100s'\n", optarg);
 452                                 exit(255);
 453                         }
 454                         if (cp != NULL) {
 455                                 fwd.listen_port = a2port(cp);
 456                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 457                         } else {
 458                                 fwd.listen_port = a2port(fwd.listen_host);
 459                                 fwd.listen_host = NULL;
 460                         }
 461
 462                         if (fwd.listen_port == 0) {
 463                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 464                                     optarg);
 465                                 exit(255);
 466                         }
 467                         add_local_forward(&options, &fwd);
 468                         xfree(p);
 469                         break;
 470
 471                 case 'C':
 472                         options.compression = 1;
 473                         break;
 474                 case 'N':
 475                         no_shell_flag = 1;
 476                         no_tty_flag = 1;
 477                         break;
 478                 case 'T':
 479                         no_tty_flag = 1;
 480                         break;
 481                 case 'o':
 482                         dummy = 1;
 483                         line = xstrdup(optarg);
 484                         if (process_config_line(&options, host ? host : "",
 485                             line, "command-line", 0, &dummy) != 0)
 486                                 exit(255);
 487                         xfree(line);
 488                         break;
 489                 case 's':
 490                         subsystem_flag = 1;
 491                         break;
 492                 case 'S':
 493                         if (options.control_path != NULL)
 494                                 free(options.control_path);
 495                         options.control_path = xstrdup(optarg);
 496                         break;
 497                 case 'b':
 498                         options.bind_address = optarg;
 499                         break;
 500                 case 'F':
 501                         config = optarg;
 502                         break;
 503                 default:
 504                         usage();
 505                 }
 506         }
 507
 508         ac -= optind;
 509         av += optind;
 510
 511         if (ac > 0 && !host && **av != '-') {
 512                 if (strrchr(*av, '@')) {
 513                         p = xstrdup(*av);
 514                         cp = strrchr(p, '@');
 515                         if (cp == NULL || cp == p)
 516                                 usage();
 517                         options.user = p;
 518                         *cp = '\0';
 519                         host = ++cp;
 520                 } else
 521                         host = *av;
 522                 if (ac > 1) {
 523                         optind = optreset = 1;
 524                         goto again;
 525                 }
 526                 ac--, av++;
 527         }
 528
 529         /* Check that we got a host name. */
 530         if (!host)
 531                 usage();
 532
 533         SSLeay_add_all_algorithms();
 534         ERR_load_crypto_strings();
 535
 536         /* Initialize the command to execute on remote host. */
 537         buffer_init(&command);
 538
 539         /*
 540          * Save the command to execute on the remote host in a buffer. There
 541          * is no limit on the length of the command, except by the maximum
 542          * packet size.  Also sets the tty flag if there is no command.
 543          */
 544         if (!ac) {
 545                 /* No command specified - execute shell on a tty. */
 546                 tty_flag = 1;
 547                 if (subsystem_flag) {
 548                         fprintf(stderr,
 549                             "You must specify a subsystem to invoke.\n");
 550                         usage();
 551                 }
 552         } else {
 553                 /* A command has been specified.  Store it into the buffer. */
 554                 for (i = 0; i < ac; i++) {
 555                         if (i)
 556                                 buffer_append(&command, " ", 1);
 557                         buffer_append(&command, av[i], strlen(av[i]));
 558                 }
 559         }
 560
 561         /* Cannot fork to background if no command. */
 562         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 563                 fatal("Cannot fork into background without a command to execute.");
 564
 565         /* Allocate a tty by default if no command specified. */
 566         if (buffer_len(&command) == 0)
 567                 tty_flag = 1;
 568
 569         /* Force no tty */
 570         if (no_tty_flag)
 571                 tty_flag = 0;
 572         /* Do not allocate a tty if stdin is not a tty. */
 573         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 574                 if (tty_flag)
 575                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 576                 tty_flag = 0;
 577         }
 578
 579         /*
 580          * Initialize "log" output.  Since we are the client all output
 581          * actually goes to stderr.
 582          */
 583         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 584             SYSLOG_FACILITY_USER, 1);
 585
 586         /*
 587          * Read per-user configuration file.  Ignore the system wide config
 588          * file if the user specifies a config file on the command line.
 589          */
 590         if (config != NULL) {
 591                 if (!read_config_file(config, host, &options, 0))
 592                         fatal("Can't open user config file %.100s: "
 593                             "%.100s", config, strerror(errno));
 594         } else  {
 595                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 596                     _PATH_SSH_USER_CONFFILE);
 597                 (void)read_config_file(buf, host, &options, 1);
 598
 599                 /* Read systemwide configuration file after use config. */
 600                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 601                     &options, 0);
 602         }
 603
 604         /* Fill configuration defaults. */
 605         fill_default_options(&options);
 606
 607         channel_set_af(options.address_family);
 608
 609         /* reinit */
 610         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 611
 612         seed_rng();
 613
 614         if (options.user == NULL)
 615                 options.user = xstrdup(pw->pw_name);
 616
 617         if (options.hostname != NULL)
 618                 host = options.hostname;
 619
 620         /* force lowercase for hostkey matching */
 621         if (options.host_key_alias != NULL) {
 622                 for (p = options.host_key_alias; *p; p++)
 623                         if (isupper(*p))
 624                                 *p = tolower(*p);
 625         }
 626
 627         /* Get default port if port has not been set. */
 628         if (options.port == 0) {
 629                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 630                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 631         }
 632
 633         if (options.proxy_command != NULL &&
 634             strcmp(options.proxy_command, "none") == 0)
 635                 options.proxy_command = NULL;
 636         if (options.control_path != NULL &&
 637             strcmp(options.control_path, "none") == 0)
 638                 options.control_path = NULL;
 639
 640         if (options.control_path != NULL) {
 641                 char me[NI_MAXHOST];
 642
 643                 if (gethostname(me, sizeof(me)) == -1)
 644                         fatal("gethostname: %s", strerror(errno));
 645                 snprintf(buf, sizeof(buf), "%d", options.port);
 646                 cp = tilde_expand_filename(options.control_path,
 647                     original_real_uid);
 648                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 649                     "r", options.user, "l", me, (char *)NULL);
 650                 xfree(cp);
 651         }
 652         if (mux_command != 0 && options.control_path == NULL)
 653                 fatal("No ControlPath specified for \"-O\" command");
 654         if (options.control_path != NULL)
 655                 control_client(options.control_path);
 656
 657         /* Open a connection to the remote host. */
 658         if (ssh_connect(host, &hostaddr, options.port,
 659             options.address_family, options.connection_attempts,
 660 #ifdef HAVE_CYGWIN
 661             options.use_privileged_port,
 662 #else
 663             original_effective_uid == 0 && options.use_privileged_port,
 664 #endif
 665             options.proxy_command) != 0)
 666                 exit(255);
 667
 668         /*
 669          * If we successfully made the connection, load the host private key
 670          * in case we will need it later for combined rsa-rhosts
 671          * authentication. This must be done before releasing extra
 672          * privileges, because the file is only readable by root.
 673          * If we cannot access the private keys, load the public keys
 674          * instead and try to execute the ssh-keysign helper instead.
 675          */
 676         sensitive_data.nkeys = 0;
 677         sensitive_data.keys = NULL;
 678         sensitive_data.external_keysign = 0;
 679         if (options.rhosts_rsa_authentication ||
 680             options.hostbased_authentication) {
 681                 sensitive_data.nkeys = 3;
 682                 sensitive_data.keys = xmalloc(sensitive_data.nkeys *
 683                     sizeof(Key));
 684
 685                 PRIV_START;
 686                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 687                     _PATH_HOST_KEY_FILE, "", NULL);
 688                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 689                     _PATH_HOST_DSA_KEY_FILE, "", NULL);
 690                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 691                     _PATH_HOST_RSA_KEY_FILE, "", NULL);
 692                 PRIV_END;
 693
 694                 if (options.hostbased_authentication == 1 &&
 695                     sensitive_data.keys[0] == NULL &&
 696                     sensitive_data.keys[1] == NULL &&
 697                     sensitive_data.keys[2] == NULL) {
 698                         sensitive_data.keys[1] = key_load_public(
 699                             _PATH_HOST_DSA_KEY_FILE, NULL);
 700                         sensitive_data.keys[2] = key_load_public(
 701                             _PATH_HOST_RSA_KEY_FILE, NULL);
 702                         sensitive_data.external_keysign = 1;
 703                 }
 704         }
 705         /*
 706          * Get rid of any extra privileges that we may have.  We will no
 707          * longer need them.  Also, extra privileges could make it very hard
 708          * to read identity files and other non-world-readable files from the
 709          * user's home directory if it happens to be on a NFS volume where
 710          * root is mapped to nobody.
 711          */
 712         if (original_effective_uid == 0) {
 713                 PRIV_START;
 714                 permanently_set_uid(pw);
 715         }
 716
 717         /*
 718          * Now that we are back to our own permissions, create ~/.ssh
 719          * directory if it doesn't already exist.
 720          */
 721         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 722         if (stat(buf, &st) < 0)
 723                 if (mkdir(buf, 0700) < 0)
 724                         error("Could not create directory '%.200s'.", buf);
 725
 726         /* load options.identity_files */
 727         load_public_identity_files();
 728
 729         /* Expand ~ in known host file names. */
 730         /* XXX mem-leaks: */
 731         options.system_hostfile =
 732             tilde_expand_filename(options.system_hostfile, original_real_uid);
 733         options.user_hostfile =
 734             tilde_expand_filename(options.user_hostfile, original_real_uid);
 735         options.system_hostfile2 =
 736             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 737         options.user_hostfile2 =
 738             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 739
 740         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 741
 742         /* Log into the remote system.  This never returns if the login fails. */
 743         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 744
 745         /* We no longer need the private host keys.  Clear them now. */
 746         if (sensitive_data.nkeys != 0) {
 747                 for (i = 0; i < sensitive_data.nkeys; i++) {
 748                         if (sensitive_data.keys[i] != NULL) {
 749                                 /* Destroys contents safely */
 750                                 debug3("clear hostkey %d", i);
 751                                 key_free(sensitive_data.keys[i]);
 752                                 sensitive_data.keys[i] = NULL;
 753                         }
 754                 }
 755                 xfree(sensitive_data.keys);
 756         }
 757         for (i = 0; i < options.num_identity_files; i++) {
 758                 if (options.identity_files[i]) {
 759                         xfree(options.identity_files[i]);
 760                         options.identity_files[i] = NULL;
 761                 }
 762                 if (options.identity_keys[i]) {
 763                         key_free(options.identity_keys[i]);
 764                         options.identity_keys[i] = NULL;
 765                 }
 766         }
 767
 768         exit_status = compat20 ? ssh_session2() : ssh_session();
 769         packet_close();
 770
 771         if (options.control_path != NULL && control_fd != -1)
 772                 unlink(options.control_path);
 773
 774         /*
 775          * Send SIGHUP to proxy command if used. We don't wait() in
 776          * case it hangs and instead rely on init to reap the child
 777          */
 778         if (proxy_command_pid > 1)
 779                 kill(proxy_command_pid, SIGHUP);
 780
 781         return exit_status;
 782 }
 783
 784 static void
 785 ssh_init_forwarding(void)
 786 {
 787         int success = 0;
 788         int i;
 789
 790         /* Initiate local TCP/IP port forwardings. */
 791         for (i = 0; i < options.num_local_forwards; i++) {
 792                 debug("Local connections to %.200s:%d forwarded to remote "
 793                     "address %.200s:%d",
 794                     (options.local_forwards[i].listen_host == NULL) ?
 795                     (options.gateway_ports ? "*" : "LOCALHOST") :
 796                     options.local_forwards[i].listen_host,
 797                     options.local_forwards[i].listen_port,
 798                     options.local_forwards[i].connect_host,
 799                     options.local_forwards[i].connect_port);
 800                 success += channel_setup_local_fwd_listener(
 801                     options.local_forwards[i].listen_host,
 802                     options.local_forwards[i].listen_port,
 803                     options.local_forwards[i].connect_host,
 804                     options.local_forwards[i].connect_port,
 805                     options.gateway_ports);
 806         }
 807         if (i > 0 && success == 0)
 808                 error("Could not request local forwarding.");
 809
 810         /* Initiate remote TCP/IP port forwardings. */
 811         for (i = 0; i < options.num_remote_forwards; i++) {
 812                 debug("Remote connections from %.200s:%d forwarded to "
 813                     "local address %.200s:%d",
 814                     (options.remote_forwards[i].listen_host == NULL) ?
 815                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 816                     options.remote_forwards[i].listen_port,
 817                     options.remote_forwards[i].connect_host,
 818                     options.remote_forwards[i].connect_port);
 819                 channel_request_remote_forwarding(
 820                     options.remote_forwards[i].listen_host,
 821                     options.remote_forwards[i].listen_port,
 822                     options.remote_forwards[i].connect_host,
 823                     options.remote_forwards[i].connect_port);
 824         }
 825 }
 826
 827 static void
 828 check_agent_present(void)
 829 {
 830         if (options.forward_agent) {
 831                 /* Clear agent forwarding if we don't have an agent. */
 832                 if (!ssh_agent_present())
 833                         options.forward_agent = 0;
 834         }
 835 }
 836
 837 static int
 838 ssh_session(void)
 839 {
 840         int type;
 841         int interactive = 0;
 842         int have_tty = 0;
 843         struct winsize ws;
 844         char *cp;
 845         const char *display;
 846
 847         /* Enable compression if requested. */
 848         if (options.compression) {
 849                 debug("Requesting compression at level %d.", options.compression_level);
 850
 851                 if (options.compression_level < 1 || options.compression_level > 9)
 852                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 853
 854                 /* Send the request. */
 855                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 856                 packet_put_int(options.compression_level);
 857                 packet_send();
 858                 packet_write_wait();
 859                 type = packet_read();
 860                 if (type == SSH_SMSG_SUCCESS)
 861                         packet_start_compression(options.compression_level);
 862                 else if (type == SSH_SMSG_FAILURE)
 863                         logit("Warning: Remote host refused compression.");
 864                 else
 865                         packet_disconnect("Protocol error waiting for compression response.");
 866         }
 867         /* Allocate a pseudo tty if appropriate. */
 868         if (tty_flag) {
 869                 debug("Requesting pty.");
 870
 871                 /* Start the packet. */
 872                 packet_start(SSH_CMSG_REQUEST_PTY);
 873
 874                 /* Store TERM in the packet.  There is no limit on the
 875                    length of the string. */
 876                 cp = getenv("TERM");
 877                 if (!cp)
 878                         cp = "";
 879                 packet_put_cstring(cp);
 880
 881                 /* Store window size in the packet. */
 882                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 883                         memset(&ws, 0, sizeof(ws));
 884                 packet_put_int(ws.ws_row);
 885                 packet_put_int(ws.ws_col);
 886                 packet_put_int(ws.ws_xpixel);
 887                 packet_put_int(ws.ws_ypixel);
 888
 889                 /* Store tty modes in the packet. */
 890                 tty_make_modes(fileno(stdin), NULL);
 891
 892                 /* Send the packet, and wait for it to leave. */
 893                 packet_send();
 894                 packet_write_wait();
 895
 896                 /* Read response from the server. */
 897                 type = packet_read();
 898                 if (type == SSH_SMSG_SUCCESS) {
 899                         interactive = 1;
 900                         have_tty = 1;
 901                 } else if (type == SSH_SMSG_FAILURE)
 902                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 903                 else
 904                         packet_disconnect("Protocol error waiting for pty request response.");
 905         }
 906         /* Request X11 forwarding if enabled and DISPLAY is set. */
 907         display = getenv("DISPLAY");
 908         if (options.forward_x11 && display != NULL) {
 909                 char *proto, *data;
 910                 /* Get reasonable local authentication information. */
 911                 client_x11_get_proto(display, options.xauth_location,
 912                     options.forward_x11_trusted, &proto, &data);
 913                 /* Request forwarding with authentication spoofing. */
 914                 debug("Requesting X11 forwarding with authentication spoofing.");
 915                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 916
 917                 /* Read response from the server. */
 918                 type = packet_read();
 919                 if (type == SSH_SMSG_SUCCESS) {
 920                         interactive = 1;
 921                 } else if (type == SSH_SMSG_FAILURE) {
 922                         logit("Warning: Remote host denied X11 forwarding.");
 923                 } else {
 924                         packet_disconnect("Protocol error waiting for X11 forwarding");
 925                 }
 926         }
 927         /* Tell the packet module whether this is an interactive session. */
 928         packet_set_interactive(interactive);
 929
 930         /* Request authentication agent forwarding if appropriate. */
 931         check_agent_present();
 932
 933         if (options.forward_agent) {
 934                 debug("Requesting authentication agent forwarding.");
 935                 auth_request_forwarding();
 936
 937                 /* Read response from the server. */
 938                 type = packet_read();
 939                 packet_check_eom();
 940                 if (type != SSH_SMSG_SUCCESS)
 941                         logit("Warning: Remote host denied authentication agent forwarding.");
 942         }
 943
 944         /* Initiate port forwardings. */
 945         ssh_init_forwarding();
 946
 947         /* If requested, let ssh continue in the background. */
 948         if (fork_after_authentication_flag)
 949                 if (daemon(1, 1) < 0)
 950                         fatal("daemon() failed: %.200s", strerror(errno));
 951
 952         /*
 953          * If a command was specified on the command line, execute the
 954          * command now. Otherwise request the server to start a shell.
 955          */
 956         if (buffer_len(&command) > 0) {
 957                 int len = buffer_len(&command);
 958                 if (len > 900)
 959                         len = 900;
 960                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 961                 packet_start(SSH_CMSG_EXEC_CMD);
 962                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 963                 packet_send();
 964                 packet_write_wait();
 965         } else {
 966                 debug("Requesting shell.");
 967                 packet_start(SSH_CMSG_EXEC_SHELL);
 968                 packet_send();
 969                 packet_write_wait();
 970         }
 971
 972         /* Enter the interactive session. */
 973         return client_loop(have_tty, tty_flag ?
 974             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
 975 }
 976
 977 static void
 978 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
 979 {
 980         int id, len;
 981
 982         id = packet_get_int();
 983         len = buffer_len(&command);
 984         if (len > 900)
 985                 len = 900;
 986         packet_check_eom();
 987         if (type == SSH2_MSG_CHANNEL_FAILURE)
 988                 fatal("Request for subsystem '%.*s' failed on channel %d",
 989                     len, (u_char *)buffer_ptr(&command), id);
 990 }
 991
 992 void
 993 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
 994 {
 995         int i;
 996
 997         i = client_global_request_id++;
 998         if (i >= options.num_remote_forwards)
 999                 return;
1000         debug("remote forward %s for: listen %d, connect %s:%d",
1001             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1002             options.remote_forwards[i].listen_port,
1003             options.remote_forwards[i].connect_host,
1004             options.remote_forwards[i].connect_port);
1005         if (type == SSH2_MSG_REQUEST_FAILURE)
1006                 logit("Warning: remote port forwarding failed for listen "
1007                     "port %d", options.remote_forwards[i].listen_port);
1008 }
1009
1010 static void
1011 ssh_control_listener(void)
1012 {
1013         struct sockaddr_un addr;
1014         mode_t old_umask;
1015         int addr_len;
1016
1017         if (options.control_path == NULL ||
1018             options.control_master == SSHCTL_MASTER_NO)
1019                 return;
1020
1021         debug("setting up multiplex master socket");
1022
1023         memset(&addr, '\0', sizeof(addr));
1024         addr.sun_family = AF_UNIX;
1025         addr_len = offsetof(struct sockaddr_un, sun_path) +
1026             strlen(options.control_path) + 1;
1027
1028         if (strlcpy(addr.sun_path, options.control_path,
1029             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1030                 fatal("ControlPath too long");
1031
1032         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1033                 fatal("%s socket(): %s", __func__, strerror(errno));
1034
1035         old_umask = umask(0177);
1036         if (bind(control_fd, (struct sockaddr*)&addr, addr_len) == -1) {
1037                 control_fd = -1;
1038                 if (errno == EINVAL || errno == EADDRINUSE)
1039                         fatal("ControlSocket %s already exists",
1040                             options.control_path);
1041                 else
1042                         fatal("%s bind(): %s", __func__, strerror(errno));
1043         }
1044         umask(old_umask);
1045
1046         if (listen(control_fd, 64) == -1)
1047                 fatal("%s listen(): %s", __func__, strerror(errno));
1048
1049         set_nonblock(control_fd);
1050 }
1051
1052 /* request pty/x11/agent/tcpfwd/shell for channel */
1053 static void
1054 ssh_session2_setup(int id, void *arg)
1055 {
1056         extern char **environ;
1057         const char *display;
1058         int interactive = tty_flag;
1059
1060         display = getenv("DISPLAY");
1061         if (options.forward_x11 && display != NULL) {
1062                 char *proto, *data;
1063                 /* Get reasonable local authentication information. */
1064                 client_x11_get_proto(display, options.xauth_location,
1065                     options.forward_x11_trusted, &proto, &data);
1066                 /* Request forwarding with authentication spoofing. */
1067                 debug("Requesting X11 forwarding with authentication spoofing.");
1068                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1069                 interactive = 1;
1070                 /* XXX wait for reply */
1071         }
1072
1073         check_agent_present();
1074         if (options.forward_agent) {
1075                 debug("Requesting authentication agent forwarding.");
1076                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1077                 packet_send();
1078         }
1079
1080         if (options.tun_open != SSH_TUNMODE_NO) {
1081                 Channel *c;
1082                 int fd;
1083
1084                 debug("Requesting tun.");
1085                 if ((fd = tun_open(options.tun_local,
1086                     options.tun_open)) >= 0) {
1087                         c = channel_new("tun", SSH_CHANNEL_OPENING, fd, fd, -1,
1088                             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1089                             0, "tun", 1);
1090                         c->datagram = 1;
1091 #if defined(SSH_TUN_FILTER)
1092                         if (options.tun_open == SSH_TUNMODE_POINTOPOINT)
1093                                 channel_register_filter(c->self, sys_tun_infilter,
1094                                     sys_tun_outfilter);
1095 #endif
1096                         packet_start(SSH2_MSG_CHANNEL_OPEN);
1097                         packet_put_cstring("tun@openssh.com");
1098                         packet_put_int(c->self);
1099                         packet_put_int(c->local_window_max);
1100                         packet_put_int(c->local_maxpacket);
1101                         packet_put_int(options.tun_open);
1102                         packet_put_int(options.tun_remote);
1103                         packet_send();
1104                 }
1105         }
1106
1107         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1108             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1109
1110         packet_set_interactive(interactive);
1111 }
1112
1113 /* open new channel for a session */
1114 static int
1115 ssh_session2_open(void)
1116 {
1117         Channel *c;
1118         int window, packetmax, in, out, err;
1119
1120         if (stdin_null_flag) {
1121                 in = open(_PATH_DEVNULL, O_RDONLY);
1122         } else {
1123                 in = dup(STDIN_FILENO);
1124         }
1125         out = dup(STDOUT_FILENO);
1126         err = dup(STDERR_FILENO);
1127
1128         if (in < 0 || out < 0 || err < 0)
1129                 fatal("dup() in/out/err failed");
1130
1131         /* enable nonblocking unless tty */
1132         if (!isatty(in))
1133                 set_nonblock(in);
1134         if (!isatty(out))
1135                 set_nonblock(out);
1136         if (!isatty(err))
1137                 set_nonblock(err);
1138
1139         window = CHAN_SES_WINDOW_DEFAULT;
1140         packetmax = CHAN_SES_PACKET_DEFAULT;
1141         if (tty_flag) {
1142                 window >>= 1;
1143                 packetmax >>= 1;
1144         }
1145         c = channel_new(
1146             "session", SSH_CHANNEL_OPENING, in, out, err,
1147             window, packetmax, CHAN_EXTENDED_WRITE,
1148             "client-session", /*nonblock*/0);
1149
1150         debug3("ssh_session2_open: channel_new: %d", c->self);
1151
1152         channel_send_open(c->self);
1153         if (!no_shell_flag)
1154                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1155
1156         return c->self;
1157 }
1158
1159 static int
1160 ssh_session2(void)
1161 {
1162         int id = -1;
1163
1164         /* XXX should be pre-session */
1165         ssh_init_forwarding();
1166         ssh_control_listener();
1167
1168         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1169                 id = ssh_session2_open();
1170
1171         /* Execute a local command */
1172         if (options.local_command != NULL &&
1173             options.permit_local_command)
1174                 ssh_local_cmd(options.local_command);
1175
1176         /* If requested, let ssh continue in the background. */
1177         if (fork_after_authentication_flag)
1178                 if (daemon(1, 1) < 0)
1179                         fatal("daemon() failed: %.200s", strerror(errno));
1180
1181         return client_loop(tty_flag, tty_flag ?
1182             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1183 }
1184
1185 static void
1186 load_public_identity_files(void)
1187 {
1188         char *filename;
1189         int i = 0;
1190         Key *public;
1191 #ifdef SMARTCARD
1192         Key **keys;
1193
1194         if (options.smartcard_device != NULL &&
1195             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1196             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1197                 int count = 0;
1198                 for (i = 0; keys[i] != NULL; i++) {
1199                         count++;
1200                         memmove(&options.identity_files[1], &options.identity_files[0],
1201                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1202                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1203                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1204                         options.num_identity_files++;
1205                         options.identity_keys[0] = keys[i];
1206                         options.identity_files[0] = sc_get_key_label(keys[i]);
1207                 }
1208                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1209                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1210                 i = count;
1211                 xfree(keys);
1212         }
1213 #endif /* SMARTCARD */
1214         for (; i < options.num_identity_files; i++) {
1215                 filename = tilde_expand_filename(options.identity_files[i],
1216                     original_real_uid);
1217                 public = key_load_public(filename, NULL);
1218                 debug("identity file %s type %d", filename,
1219                     public ? public->type : -1);
1220                 xfree(options.identity_files[i]);
1221                 options.identity_files[i] = filename;
1222                 options.identity_keys[i] = public;
1223         }
1224 }
1225
1226 static void
1227 control_client_sighandler(int signo)
1228 {
1229         control_client_terminate = signo;
1230 }
1231
1232 static void
1233 control_client_sigrelay(int signo)
1234 {
1235         if (control_server_pid > 1)
1236                 kill(control_server_pid, signo);
1237 }
1238
1239 static int
1240 env_permitted(char *env)
1241 {
1242         int i;
1243         char name[1024], *cp;
1244
1245         strlcpy(name, env, sizeof(name));
1246         if ((cp = strchr(name, '=')) == NULL)
1247                 return (0);
1248
1249         *cp = '\0';
1250
1251         for (i = 0; i < options.num_send_env; i++)
1252                 if (match_pattern(name, options.send_env[i]))
1253                         return (1);
1254
1255         return (0);
1256 }
1257
1258 static void
1259 control_client(const char *path)
1260 {
1261         struct sockaddr_un addr;
1262         int i, r, fd, sock, exitval, num_env, addr_len;
1263         Buffer m;
1264         char *term;
1265         extern char **environ;
1266         u_int  flags;
1267
1268         if (mux_command == 0)
1269                 mux_command = SSHMUX_COMMAND_OPEN;
1270
1271         switch (options.control_master) {
1272         case SSHCTL_MASTER_AUTO:
1273         case SSHCTL_MASTER_AUTO_ASK:
1274                 debug("auto-mux: Trying existing master");
1275                 /* FALLTHROUGH */
1276         case SSHCTL_MASTER_NO:
1277                 break;
1278         default:
1279                 return;
1280         }
1281
1282         memset(&addr, '\0', sizeof(addr));
1283         addr.sun_family = AF_UNIX;
1284         addr_len = offsetof(struct sockaddr_un, sun_path) +
1285             strlen(path) + 1;
1286
1287         if (strlcpy(addr.sun_path, path,
1288             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1289                 fatal("ControlPath too long");
1290
1291         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1292                 fatal("%s socket(): %s", __func__, strerror(errno));
1293
1294         if (connect(sock, (struct sockaddr*)&addr, addr_len) == -1) {
1295                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1296                         fatal("Control socket connect(%.100s): %s", path,
1297                             strerror(errno));
1298                 }
1299                 if (errno == ENOENT)
1300                         debug("Control socket \"%.100s\" does not exist", path);
1301                 else {
1302                         error("Control socket connect(%.100s): %s", path,
1303                             strerror(errno));
1304                 }
1305                 close(sock);
1306                 return;
1307         }
1308
1309         if (stdin_null_flag) {
1310                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1311                         fatal("open(/dev/null): %s", strerror(errno));
1312                 if (dup2(fd, STDIN_FILENO) == -1)
1313                         fatal("dup2: %s", strerror(errno));
1314                 if (fd > STDERR_FILENO)
1315                         close(fd);
1316         }
1317
1318         term = getenv("TERM");
1319
1320         flags = 0;
1321         if (tty_flag)
1322                 flags |= SSHMUX_FLAG_TTY;
1323         if (subsystem_flag)
1324                 flags |= SSHMUX_FLAG_SUBSYS;
1325         if (options.forward_x11)
1326                 flags |= SSHMUX_FLAG_X11_FWD;
1327         if (options.forward_agent)
1328                 flags |= SSHMUX_FLAG_AGENT_FWD;
1329
1330         buffer_init(&m);
1331
1332         /* Send our command to server */
1333         buffer_put_int(&m, mux_command);
1334         buffer_put_int(&m, flags);
1335         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1336                 fatal("%s: msg_send", __func__);
1337         buffer_clear(&m);
1338
1339         /* Get authorisation status and PID of controlee */
1340         if (ssh_msg_recv(sock, &m) == -1)
1341                 fatal("%s: msg_recv", __func__);
1342         if (buffer_get_char(&m) != SSHMUX_VER)
1343                 fatal("%s: wrong version", __func__);
1344         if (buffer_get_int(&m) != 1)
1345                 fatal("Connection to master denied");
1346         control_server_pid = buffer_get_int(&m);
1347
1348         buffer_clear(&m);
1349
1350         switch (mux_command) {
1351         case SSHMUX_COMMAND_ALIVE_CHECK:
1352                 fprintf(stderr, "Master running (pid=%d)\r\n",
1353                     control_server_pid);
1354                 exit(0);
1355         case SSHMUX_COMMAND_TERMINATE:
1356                 fprintf(stderr, "Exit request sent.\r\n");
1357                 exit(0);
1358         case SSHMUX_COMMAND_OPEN:
1359                 /* continue below */
1360                 break;
1361         default:
1362                 fatal("silly mux_command %d", mux_command);
1363         }
1364
1365         /* SSHMUX_COMMAND_OPEN */
1366         buffer_put_cstring(&m, term ? term : "");
1367         buffer_append(&command, "\0", 1);
1368         buffer_put_cstring(&m, buffer_ptr(&command));
1369
1370         if (options.num_send_env == 0 || environ == NULL) {
1371                 buffer_put_int(&m, 0);
1372         } else {
1373                 /* Pass environment */
1374                 num_env = 0;
1375                 for (i = 0; environ[i] != NULL; i++)
1376                         if (env_permitted(environ[i]))
1377                                 num_env++; /* Count */
1378
1379                 buffer_put_int(&m, num_env);
1380
1381                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1382                         if (env_permitted(environ[i])) {
1383                                 num_env--;
1384                                 buffer_put_cstring(&m, environ[i]);
1385                         }
1386         }
1387
1388         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1389                 fatal("%s: msg_send", __func__);
1390
1391         mm_send_fd(sock, STDIN_FILENO);
1392         mm_send_fd(sock, STDOUT_FILENO);
1393         mm_send_fd(sock, STDERR_FILENO);
1394
1395         /* Wait for reply, so master has a chance to gather ttymodes */
1396         buffer_clear(&m);
1397         if (ssh_msg_recv(sock, &m) == -1)
1398                 fatal("%s: msg_recv", __func__);
1399         if (buffer_get_char(&m) != SSHMUX_VER)
1400                 fatal("%s: wrong version", __func__);
1401         buffer_free(&m);
1402
1403         signal(SIGHUP, control_client_sighandler);
1404         signal(SIGINT, control_client_sighandler);
1405         signal(SIGTERM, control_client_sighandler);
1406         signal(SIGWINCH, control_client_sigrelay);
1407
1408         if (tty_flag)
1409                 enter_raw_mode();
1410
1411         /* Stick around until the controlee closes the client_fd */
1412         exitval = 0;
1413         for (;!control_client_terminate;) {
1414                 r = read(sock, &exitval, sizeof(exitval));
1415                 if (r == 0) {
1416                         debug2("Received EOF from master");
1417                         break;
1418                 }
1419                 if (r > 0)
1420                         debug2("Received exit status from master %d", exitval);
1421                 if (r == -1 && errno != EINTR)
1422                         fatal("%s: read %s", __func__, strerror(errno));
1423         }
1424
1425         if (control_client_terminate)
1426                 debug2("Exiting on signal %d", control_client_terminate);
1427
1428         close(sock);
1429
1430         leave_raw_mode();
1431
1432         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1433                 fprintf(stderr, "Connection to master closed.\r\n");
1434
1435         exit(exitval);
1436 }