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 1.264 2006/02/20 17:19:54 stevesk Exp $");
  44
  45 #include <sys/types.h>
  46 #ifdef HAVE_SYS_STAT_H
  47 # include <sys/stat.h>
  48 #endif
  49 #include <sys/resource.h>
  50 #include <sys/ioctl.h>
  51 #include <sys/un.h>
  52
  53 #include <paths.h>
  54 #include <signal.h>
  55
  56 #include <openssl/evp.h>
  57 #include <openssl/err.h>
  58
  59 #include "ssh.h"
  60 #include "ssh1.h"
  61 #include "ssh2.h"
  62 #include "compat.h"
  63 #include "cipher.h"
  64 #include "xmalloc.h"
  65 #include "packet.h"
  66 #include "buffer.h"
  67 #include "bufaux.h"
  68 #include "channels.h"
  69 #include "key.h"
  70 #include "authfd.h"
  71 #include "authfile.h"
  72 #include "pathnames.h"
  73 #include "dispatch.h"
  74 #include "clientloop.h"
  75 #include "log.h"
  76 #include "readconf.h"
  77 #include "sshconnect.h"
  78 #include "misc.h"
  79 #include "kex.h"
  80 #include "mac.h"
  81 #include "sshpty.h"
  82 #include "match.h"
  83 #include "msg.h"
  84 #include "monitor_fdpass.h"
  85 #include "uidswap.h"
  86
  87 #ifdef SMARTCARD
  88 #include "scard.h"
  89 #endif
  90
  91 extern char *__progname;
  92
  93 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
  94 int debug_flag = 0;
  95
  96 /* Flag indicating whether a tty should be allocated */
  97 int tty_flag = 0;
  98 int no_tty_flag = 0;
  99 int force_tty_flag = 0;
 100
 101 /* don't exec a shell */
 102 int no_shell_flag = 0;
 103
 104 /*
 105  * Flag indicating that nothing should be read from stdin.  This can be set
 106  * on the command line.
 107  */
 108 int stdin_null_flag = 0;
 109
 110 /*
 111  * Flag indicating that ssh should fork after authentication.  This is useful
 112  * so that the passphrase can be entered manually, and then ssh goes to the
 113  * background.
 114  */
 115 int fork_after_authentication_flag = 0;
 116
 117 /*
 118  * General data structure for command line options and options configurable
 119  * in configuration files.  See readconf.h.
 120  */
 121 Options options;
 122
 123 /* optional user configfile */
 124 char *config = NULL;
 125
 126 /*
 127  * Name of the host we are connecting to.  This is the name given on the
 128  * command line, or the HostName specified for the user-supplied name in a
 129  * configuration file.
 130  */
 131 char *host;
 132
 133 /* socket address the host resolves to */
 134 struct sockaddr_storage hostaddr;
 135
 136 /* Private host keys. */
 137 Sensitive sensitive_data;
 138
 139 /* Original real UID. */
 140 uid_t original_real_uid;
 141 uid_t original_effective_uid;
 142
 143 /* command to be executed */
 144 Buffer command;
 145
 146 /* Should we execute a command or invoke a subsystem? */
 147 int subsystem_flag = 0;
 148
 149 /* # of replies received for global requests */
 150 static int client_global_request_id = 0;
 151
 152 /* pid of proxycommand child process */
 153 pid_t proxy_command_pid = 0;
 154
 155 /* fd to control socket */
 156 int control_fd = -1;
 157
 158 /* Multiplexing control command */
 159 static u_int mux_command = 0;
 160
 161 /* Only used in control client mode */
 162 volatile sig_atomic_t control_client_terminate = 0;
 163 u_int control_server_pid = 0;
 164
 165 /* Prints a help message to the user.  This function never returns. */
 166
 167 static void
 168 usage(void)
 169 {
 170         fprintf(stderr,
 171 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 172 "           [-D [bind_address:]port] [-e escape_char] [-F configfile]\n"
 173 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 174 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 175 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 176 "           [-w tunnel:tunnel] [user@]hostname [command]\n"
 177         );
 178         exit(255);
 179 }
 180
 181 static int ssh_session(void);
 182 static int ssh_session2(void);
 183 static void load_public_identity_files(void);
 184 static void control_client(const char *path);
 185
 186 /*
 187  * Main program for the ssh client.
 188  */
 189 int
 190 main(int ac, char **av)
 191 {
 192         int i, opt, exit_status;
 193         char *p, *cp, *line, buf[256];
 194         struct stat st;
 195         struct passwd *pw;
 196         int dummy;
 197         extern int optind, optreset;
 198         extern char *optarg;
 199         struct servent *sp;
 200         Forward fwd;
 201
 202         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
 203         sanitise_stdfd();
 204
 205         __progname = ssh_get_progname(av[0]);
 206         init_rng();
 207
 208         /*
 209          * Save the original real uid.  It will be needed later (uid-swapping
 210          * may clobber the real uid).
 211          */
 212         original_real_uid = getuid();
 213         original_effective_uid = geteuid();
 214
 215         /*
 216          * Use uid-swapping to give up root privileges for the duration of
 217          * option processing.  We will re-instantiate the rights when we are
 218          * ready to create the privileged port, and will permanently drop
 219          * them when the port has been created (actually, when the connection
 220          * has been made, as we may need to create the port several times).
 221          */
 222         PRIV_END;
 223
 224 #ifdef HAVE_SETRLIMIT
 225         /* If we are installed setuid root be careful to not drop core. */
 226         if (original_real_uid != original_effective_uid) {
 227                 struct rlimit rlim;
 228                 rlim.rlim_cur = rlim.rlim_max = 0;
 229                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 230                         fatal("setrlimit failed: %.100s", strerror(errno));
 231         }
 232 #endif
 233         /* Get user data. */
 234         pw = getpwuid(original_real_uid);
 235         if (!pw) {
 236                 logit("You don't exist, go away!");
 237                 exit(255);
 238         }
 239         /* Take a copy of the returned structure. */
 240         pw = pwcopy(pw);
 241
 242         /*
 243          * Set our umask to something reasonable, as some files are created
 244          * with the default umask.  This will make them world-readable but
 245          * writable only by the owner, which is ok for all files for which we
 246          * don't set the modes explicitly.
 247          */
 248         umask(022);
 249
 250         /* Initialize option structure to indicate that no values have been set. */
 251         initialize_options(&options);
 252
 253         /* Parse command-line arguments. */
 254         host = NULL;
 255
 256 again:
 257         while ((opt = getopt(ac, av,
 258             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVw:XY")) != -1) {
 259                 switch (opt) {
 260                 case '1':
 261                         options.protocol = SSH_PROTO_1;
 262                         break;
 263                 case '2':
 264                         options.protocol = SSH_PROTO_2;
 265                         break;
 266                 case '4':
 267                         options.address_family = AF_INET;
 268                         break;
 269                 case '6':
 270                         options.address_family = AF_INET6;
 271                         break;
 272                 case 'n':
 273                         stdin_null_flag = 1;
 274                         break;
 275                 case 'f':
 276                         fork_after_authentication_flag = 1;
 277                         stdin_null_flag = 1;
 278                         break;
 279                 case 'x':
 280                         options.forward_x11 = 0;
 281                         break;
 282                 case 'X':
 283                         options.forward_x11 = 1;
 284                         break;
 285                 case 'Y':
 286                         options.forward_x11 = 1;
 287                         options.forward_x11_trusted = 1;
 288                         break;
 289                 case 'g':
 290                         options.gateway_ports = 1;
 291                         break;
 292                 case 'O':
 293                         if (strcmp(optarg, "check") == 0)
 294                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 295                         else if (strcmp(optarg, "exit") == 0)
 296                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 297                         else
 298                                 fatal("Invalid multiplex command.");
 299                         break;
 300                 case 'P':       /* deprecated */
 301                         options.use_privileged_port = 0;
 302                         break;
 303                 case 'a':
 304                         options.forward_agent = 0;
 305                         break;
 306                 case 'A':
 307                         options.forward_agent = 1;
 308                         break;
 309                 case 'k':
 310                         options.gss_deleg_creds = 0;
 311                         break;
 312                 case 'i':
 313                         if (stat(optarg, &st) < 0) {
 314                                 fprintf(stderr, "Warning: Identity file %s "
 315                                     "not accessible: %s.\n", optarg,
 316                                     strerror(errno));
 317                                 break;
 318                         }
 319                         if (options.num_identity_files >=
 320                             SSH_MAX_IDENTITY_FILES)
 321                                 fatal("Too many identity files specified "
 322                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 323                         options.identity_files[options.num_identity_files++] =
 324                             xstrdup(optarg);
 325                         break;
 326                 case 'I':
 327 #ifdef SMARTCARD
 328                         options.smartcard_device = xstrdup(optarg);
 329 #else
 330                         fprintf(stderr, "no support for smartcards.\n");
 331 #endif
 332                         break;
 333                 case 't':
 334                         if (tty_flag)
 335                                 force_tty_flag = 1;
 336                         tty_flag = 1;
 337                         break;
 338                 case 'v':
 339                         if (debug_flag == 0) {
 340                                 debug_flag = 1;
 341                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 342                         } else {
 343                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 344                                         options.log_level++;
 345                                 break;
 346                         }
 347                         /* FALLTHROUGH */
 348                 case 'V':
 349                         fprintf(stderr, "%s, %s\n",
 350                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 351                         if (opt == 'V')
 352                                 exit(0);
 353                         break;
 354                 case 'w':
 355                         if (options.tun_open == -1)
 356                                 options.tun_open = SSH_TUNMODE_DEFAULT;
 357                         options.tun_local = a2tun(optarg, &options.tun_remote);
 358                         if (options.tun_local == SSH_TUNID_ERR) {
 359                                 fprintf(stderr, "Bad tun device '%s'\n", optarg);
 360                                 exit(255);
 361                         }
 362                         break;
 363                 case 'q':
 364                         options.log_level = SYSLOG_LEVEL_QUIET;
 365                         break;
 366                 case 'e':
 367                         if (optarg[0] == '^' && optarg[2] == 0 &&
 368                             (u_char) optarg[1] >= 64 &&
 369                             (u_char) optarg[1] < 128)
 370                                 options.escape_char = (u_char) optarg[1] & 31;
 371                         else if (strlen(optarg) == 1)
 372                                 options.escape_char = (u_char) optarg[0];
 373                         else if (strcmp(optarg, "none") == 0)
 374                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 375                         else {
 376                                 fprintf(stderr, "Bad escape character '%s'.\n",
 377                                     optarg);
 378                                 exit(255);
 379                         }
 380                         break;
 381                 case 'c':
 382                         if (ciphers_valid(optarg)) {
 383                                 /* SSH2 only */
 384                                 options.ciphers = xstrdup(optarg);
 385                                 options.cipher = SSH_CIPHER_INVALID;
 386                         } else {
 387                                 /* SSH1 only */
 388                                 options.cipher = cipher_number(optarg);
 389                                 if (options.cipher == -1) {
 390                                         fprintf(stderr,
 391                                             "Unknown cipher type '%s'\n",
 392                                             optarg);
 393                                         exit(255);
 394                                 }
 395                                 if (options.cipher == SSH_CIPHER_3DES)
 396                                         options.ciphers = "3des-cbc";
 397                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 398                                         options.ciphers = "blowfish-cbc";
 399                                 else
 400                                         options.ciphers = (char *)-1;
 401                         }
 402                         break;
 403                 case 'm':
 404                         if (mac_valid(optarg))
 405                                 options.macs = xstrdup(optarg);
 406                         else {
 407                                 fprintf(stderr, "Unknown mac type '%s'\n",
 408                                     optarg);
 409                                 exit(255);
 410                         }
 411                         break;
 412                 case 'M':
 413                         if (options.control_master == SSHCTL_MASTER_YES)
 414                                 options.control_master = SSHCTL_MASTER_ASK;
 415                         else
 416                                 options.control_master = SSHCTL_MASTER_YES;
 417                         break;
 418                 case 'p':
 419                         options.port = a2port(optarg);
 420                         if (options.port == 0) {
 421                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 422                                 exit(255);
 423                         }
 424                         break;
 425                 case 'l':
 426                         options.user = optarg;
 427                         break;
 428
 429                 case 'L':
 430                         if (parse_forward(&fwd, optarg))
 431                                 add_local_forward(&options, &fwd);
 432                         else {
 433                                 fprintf(stderr,
 434                                     "Bad local forwarding specification '%s'\n",
 435                                     optarg);
 436                                 exit(255);
 437                         }
 438                         break;
 439
 440                 case 'R':
 441                         if (parse_forward(&fwd, optarg)) {
 442                                 add_remote_forward(&options, &fwd);
 443                         } else {
 444                                 fprintf(stderr,
 445                                     "Bad remote forwarding specification "
 446                                     "'%s'\n", optarg);
 447                                 exit(255);
 448                         }
 449                         break;
 450
 451                 case 'D':
 452                         cp = p = xstrdup(optarg);
 453                         memset(&fwd, '\0', sizeof(fwd));
 454                         fwd.connect_host = "socks";
 455                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 456                                 fprintf(stderr, "Bad dynamic forwarding "
 457                                     "specification '%.100s'\n", optarg);
 458                                 exit(255);
 459                         }
 460                         if (cp != NULL) {
 461                                 fwd.listen_port = a2port(cp);
 462                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 463                         } else {
 464                                 fwd.listen_port = a2port(fwd.listen_host);
 465                                 fwd.listen_host = NULL;
 466                         }
 467
 468                         if (fwd.listen_port == 0) {
 469                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 470                                     optarg);
 471                                 exit(255);
 472                         }
 473                         add_local_forward(&options, &fwd);
 474                         xfree(p);
 475                         break;
 476
 477                 case 'C':
 478                         options.compression = 1;
 479                         break;
 480                 case 'N':
 481                         no_shell_flag = 1;
 482                         no_tty_flag = 1;
 483                         break;
 484                 case 'T':
 485                         no_tty_flag = 1;
 486                         break;
 487                 case 'o':
 488                         dummy = 1;
 489                         line = xstrdup(optarg);
 490                         if (process_config_line(&options, host ? host : "",
 491                             line, "command-line", 0, &dummy) != 0)
 492                                 exit(255);
 493                         xfree(line);
 494                         break;
 495                 case 's':
 496                         subsystem_flag = 1;
 497                         break;
 498                 case 'S':
 499                         if (options.control_path != NULL)
 500                                 free(options.control_path);
 501                         options.control_path = xstrdup(optarg);
 502                         break;
 503                 case 'b':
 504                         options.bind_address = optarg;
 505                         break;
 506                 case 'F':
 507                         config = optarg;
 508                         break;
 509                 default:
 510                         usage();
 511                 }
 512         }
 513
 514         ac -= optind;
 515         av += optind;
 516
 517         if (ac > 0 && !host && **av != '-') {
 518                 if (strrchr(*av, '@')) {
 519                         p = xstrdup(*av);
 520                         cp = strrchr(p, '@');
 521                         if (cp == NULL || cp == p)
 522                                 usage();
 523                         options.user = p;
 524                         *cp = '\0';
 525                         host = ++cp;
 526                 } else
 527                         host = *av;
 528                 if (ac > 1) {
 529                         optind = optreset = 1;
 530                         goto again;
 531                 }
 532                 ac--, av++;
 533         }
 534
 535         /* Check that we got a host name. */
 536         if (!host)
 537                 usage();
 538
 539         SSLeay_add_all_algorithms();
 540         ERR_load_crypto_strings();
 541
 542         /* Initialize the command to execute on remote host. */
 543         buffer_init(&command);
 544
 545         /*
 546          * Save the command to execute on the remote host in a buffer. There
 547          * is no limit on the length of the command, except by the maximum
 548          * packet size.  Also sets the tty flag if there is no command.
 549          */
 550         if (!ac) {
 551                 /* No command specified - execute shell on a tty. */
 552                 tty_flag = 1;
 553                 if (subsystem_flag) {
 554                         fprintf(stderr,
 555                             "You must specify a subsystem to invoke.\n");
 556                         usage();
 557                 }
 558         } else {
 559                 /* A command has been specified.  Store it into the buffer. */
 560                 for (i = 0; i < ac; i++) {
 561                         if (i)
 562                                 buffer_append(&command, " ", 1);
 563                         buffer_append(&command, av[i], strlen(av[i]));
 564                 }
 565         }
 566
 567         /* Cannot fork to background if no command. */
 568         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 569                 fatal("Cannot fork into background without a command to execute.");
 570
 571         /* Allocate a tty by default if no command specified. */
 572         if (buffer_len(&command) == 0)
 573                 tty_flag = 1;
 574
 575         /* Force no tty */
 576         if (no_tty_flag)
 577                 tty_flag = 0;
 578         /* Do not allocate a tty if stdin is not a tty. */
 579         if ((!isatty(fileno(stdin)) || stdin_null_flag) && !force_tty_flag) {
 580                 if (tty_flag)
 581                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 582                 tty_flag = 0;
 583         }
 584
 585         /*
 586          * Initialize "log" output.  Since we are the client all output
 587          * actually goes to stderr.
 588          */
 589         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 590             SYSLOG_FACILITY_USER, 1);
 591
 592         /*
 593          * Read per-user configuration file.  Ignore the system wide config
 594          * file if the user specifies a config file on the command line.
 595          */
 596         if (config != NULL) {
 597                 if (!read_config_file(config, host, &options, 0))
 598                         fatal("Can't open user config file %.100s: "
 599                             "%.100s", config, strerror(errno));
 600         } else  {
 601                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 602                     _PATH_SSH_USER_CONFFILE);
 603                 (void)read_config_file(buf, host, &options, 1);
 604
 605                 /* Read systemwide configuration file after use config. */
 606                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 607                     &options, 0);
 608         }
 609
 610         /* Fill configuration defaults. */
 611         fill_default_options(&options);
 612
 613         channel_set_af(options.address_family);
 614
 615         /* reinit */
 616         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 617
 618         seed_rng();
 619
 620         if (options.user == NULL)
 621                 options.user = xstrdup(pw->pw_name);
 622
 623         if (options.hostname != NULL)
 624                 host = options.hostname;
 625
 626         /* force lowercase for hostkey matching */
 627         if (options.host_key_alias != NULL) {
 628                 for (p = options.host_key_alias; *p; p++)
 629                         if (isupper(*p))
 630                                 *p = tolower(*p);
 631         }
 632
 633         /* Get default port if port has not been set. */
 634         if (options.port == 0) {
 635                 sp = getservbyname(SSH_SERVICE_NAME, "tcp");
 636                 options.port = sp ? ntohs(sp->s_port) : SSH_DEFAULT_PORT;
 637         }
 638
 639         if (options.proxy_command != NULL &&
 640             strcmp(options.proxy_command, "none") == 0)
 641                 options.proxy_command = NULL;
 642         if (options.control_path != NULL &&
 643             strcmp(options.control_path, "none") == 0)
 644                 options.control_path = NULL;
 645
 646         if (options.control_path != NULL) {
 647                 char me[NI_MAXHOST];
 648
 649                 if (gethostname(me, sizeof(me)) == -1)
 650                         fatal("gethostname: %s", strerror(errno));
 651                 snprintf(buf, sizeof(buf), "%d", options.port);
 652                 cp = tilde_expand_filename(options.control_path,
 653                     original_real_uid);
 654                 options.control_path = percent_expand(cp, "p", buf, "h", host,
 655                     "r", options.user, "l", me, (char *)NULL);
 656                 xfree(cp);
 657         }
 658         if (mux_command != 0 && options.control_path == NULL)
 659                 fatal("No ControlPath specified for \"-O\" command");
 660         if (options.control_path != NULL)
 661                 control_client(options.control_path);
 662
 663         /* Open a connection to the remote host. */
 664         if (ssh_connect(host, &hostaddr, options.port,
 665             options.address_family, options.connection_attempts,
 666 #ifdef HAVE_CYGWIN
 667             options.use_privileged_port,
 668 #else
 669             original_effective_uid == 0 && options.use_privileged_port,
 670 #endif
 671             options.proxy_command) != 0)
 672                 exit(255);
 673
 674         /*
 675          * If we successfully made the connection, load the host private key
 676          * in case we will need it later for combined rsa-rhosts
 677          * authentication. This must be done before releasing extra
 678          * privileges, because the file is only readable by root.
 679          * If we cannot access the private keys, load the public keys
 680          * instead and try to execute the ssh-keysign helper instead.
 681          */
 682         sensitive_data.nkeys = 0;
 683         sensitive_data.keys = NULL;
 684         sensitive_data.external_keysign = 0;
 685         if (options.rhosts_rsa_authentication ||
 686             options.hostbased_authentication) {
 687                 sensitive_data.nkeys = 3;
 688                 sensitive_data.keys = xmalloc(sensitive_data.nkeys *
 689                     sizeof(Key));
 690
 691                 PRIV_START;
 692                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 693                     _PATH_HOST_KEY_FILE, "", NULL);
 694                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 695                     _PATH_HOST_DSA_KEY_FILE, "", NULL);
 696                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 697                     _PATH_HOST_RSA_KEY_FILE, "", NULL);
 698                 PRIV_END;
 699
 700                 if (options.hostbased_authentication == 1 &&
 701                     sensitive_data.keys[0] == NULL &&
 702                     sensitive_data.keys[1] == NULL &&
 703                     sensitive_data.keys[2] == NULL) {
 704                         sensitive_data.keys[1] = key_load_public(
 705                             _PATH_HOST_DSA_KEY_FILE, NULL);
 706                         sensitive_data.keys[2] = key_load_public(
 707                             _PATH_HOST_RSA_KEY_FILE, NULL);
 708                         sensitive_data.external_keysign = 1;
 709                 }
 710         }
 711         /*
 712          * Get rid of any extra privileges that we may have.  We will no
 713          * longer need them.  Also, extra privileges could make it very hard
 714          * to read identity files and other non-world-readable files from the
 715          * user's home directory if it happens to be on a NFS volume where
 716          * root is mapped to nobody.
 717          */
 718         if (original_effective_uid == 0) {
 719                 PRIV_START;
 720                 permanently_set_uid(pw);
 721         }
 722
 723         /*
 724          * Now that we are back to our own permissions, create ~/.ssh
 725          * directory if it doesn't already exist.
 726          */
 727         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 728         if (stat(buf, &st) < 0)
 729                 if (mkdir(buf, 0700) < 0)
 730                         error("Could not create directory '%.200s'.", buf);
 731
 732         /* load options.identity_files */
 733         load_public_identity_files();
 734
 735         /* Expand ~ in known host file names. */
 736         /* XXX mem-leaks: */
 737         options.system_hostfile =
 738             tilde_expand_filename(options.system_hostfile, original_real_uid);
 739         options.user_hostfile =
 740             tilde_expand_filename(options.user_hostfile, original_real_uid);
 741         options.system_hostfile2 =
 742             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 743         options.user_hostfile2 =
 744             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 745
 746         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 747
 748         /* Log into the remote system.  This never returns if the login fails. */
 749         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 750
 751         /* We no longer need the private host keys.  Clear them now. */
 752         if (sensitive_data.nkeys != 0) {
 753                 for (i = 0; i < sensitive_data.nkeys; i++) {
 754                         if (sensitive_data.keys[i] != NULL) {
 755                                 /* Destroys contents safely */
 756                                 debug3("clear hostkey %d", i);
 757                                 key_free(sensitive_data.keys[i]);
 758                                 sensitive_data.keys[i] = NULL;
 759                         }
 760                 }
 761                 xfree(sensitive_data.keys);
 762         }
 763         for (i = 0; i < options.num_identity_files; i++) {
 764                 if (options.identity_files[i]) {
 765                         xfree(options.identity_files[i]);
 766                         options.identity_files[i] = NULL;
 767                 }
 768                 if (options.identity_keys[i]) {
 769                         key_free(options.identity_keys[i]);
 770                         options.identity_keys[i] = NULL;
 771                 }
 772         }
 773
 774         exit_status = compat20 ? ssh_session2() : ssh_session();
 775         packet_close();
 776
 777         if (options.control_path != NULL && control_fd != -1)
 778                 unlink(options.control_path);
 779
 780         /*
 781          * Send SIGHUP to proxy command if used. We don't wait() in
 782          * case it hangs and instead rely on init to reap the child
 783          */
 784         if (proxy_command_pid > 1)
 785                 kill(proxy_command_pid, SIGHUP);
 786
 787         return exit_status;
 788 }
 789
 790 static void
 791 ssh_init_forwarding(void)
 792 {
 793         int success = 0;
 794         int i;
 795
 796         /* Initiate local TCP/IP port forwardings. */
 797         for (i = 0; i < options.num_local_forwards; i++) {
 798                 debug("Local connections to %.200s:%d forwarded to remote "
 799                     "address %.200s:%d",
 800                     (options.local_forwards[i].listen_host == NULL) ?
 801                     (options.gateway_ports ? "*" : "LOCALHOST") :
 802                     options.local_forwards[i].listen_host,
 803                     options.local_forwards[i].listen_port,
 804                     options.local_forwards[i].connect_host,
 805                     options.local_forwards[i].connect_port);
 806                 success += channel_setup_local_fwd_listener(
 807                     options.local_forwards[i].listen_host,
 808                     options.local_forwards[i].listen_port,
 809                     options.local_forwards[i].connect_host,
 810                     options.local_forwards[i].connect_port,
 811                     options.gateway_ports);
 812         }
 813         if (i > 0 && success == 0)
 814                 error("Could not request local forwarding.");
 815
 816         /* Initiate remote TCP/IP port forwardings. */
 817         for (i = 0; i < options.num_remote_forwards; i++) {
 818                 debug("Remote connections from %.200s:%d forwarded to "
 819                     "local address %.200s:%d",
 820                     (options.remote_forwards[i].listen_host == NULL) ?
 821                     "LOCALHOST" : options.remote_forwards[i].listen_host,
 822                     options.remote_forwards[i].listen_port,
 823                     options.remote_forwards[i].connect_host,
 824                     options.remote_forwards[i].connect_port);
 825                 channel_request_remote_forwarding(
 826                     options.remote_forwards[i].listen_host,
 827                     options.remote_forwards[i].listen_port,
 828                     options.remote_forwards[i].connect_host,
 829                     options.remote_forwards[i].connect_port);
 830         }
 831 }
 832
 833 static void
 834 check_agent_present(void)
 835 {
 836         if (options.forward_agent) {
 837                 /* Clear agent forwarding if we don't have an agent. */
 838                 if (!ssh_agent_present())
 839                         options.forward_agent = 0;
 840         }
 841 }
 842
 843 static int
 844 ssh_session(void)
 845 {
 846         int type;
 847         int interactive = 0;
 848         int have_tty = 0;
 849         struct winsize ws;
 850         char *cp;
 851         const char *display;
 852
 853         /* Enable compression if requested. */
 854         if (options.compression) {
 855                 debug("Requesting compression at level %d.", options.compression_level);
 856
 857                 if (options.compression_level < 1 || options.compression_level > 9)
 858                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 859
 860                 /* Send the request. */
 861                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 862                 packet_put_int(options.compression_level);
 863                 packet_send();
 864                 packet_write_wait();
 865                 type = packet_read();
 866                 if (type == SSH_SMSG_SUCCESS)
 867                         packet_start_compression(options.compression_level);
 868                 else if (type == SSH_SMSG_FAILURE)
 869                         logit("Warning: Remote host refused compression.");
 870                 else
 871                         packet_disconnect("Protocol error waiting for compression response.");
 872         }
 873         /* Allocate a pseudo tty if appropriate. */
 874         if (tty_flag) {
 875                 debug("Requesting pty.");
 876
 877                 /* Start the packet. */
 878                 packet_start(SSH_CMSG_REQUEST_PTY);
 879
 880                 /* Store TERM in the packet.  There is no limit on the
 881                    length of the string. */
 882                 cp = getenv("TERM");
 883                 if (!cp)
 884                         cp = "";
 885                 packet_put_cstring(cp);
 886
 887                 /* Store window size in the packet. */
 888                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 889                         memset(&ws, 0, sizeof(ws));
 890                 packet_put_int(ws.ws_row);
 891                 packet_put_int(ws.ws_col);
 892                 packet_put_int(ws.ws_xpixel);
 893                 packet_put_int(ws.ws_ypixel);
 894
 895                 /* Store tty modes in the packet. */
 896                 tty_make_modes(fileno(stdin), NULL);
 897
 898                 /* Send the packet, and wait for it to leave. */
 899                 packet_send();
 900                 packet_write_wait();
 901
 902                 /* Read response from the server. */
 903                 type = packet_read();
 904                 if (type == SSH_SMSG_SUCCESS) {
 905                         interactive = 1;
 906                         have_tty = 1;
 907                 } else if (type == SSH_SMSG_FAILURE)
 908                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 909                 else
 910                         packet_disconnect("Protocol error waiting for pty request response.");
 911         }
 912         /* Request X11 forwarding if enabled and DISPLAY is set. */
 913         display = getenv("DISPLAY");
 914         if (options.forward_x11 && display != NULL) {
 915                 char *proto, *data;
 916                 /* Get reasonable local authentication information. */
 917                 client_x11_get_proto(display, options.xauth_location,
 918                     options.forward_x11_trusted, &proto, &data);
 919                 /* Request forwarding with authentication spoofing. */
 920                 debug("Requesting X11 forwarding with authentication spoofing.");
 921                 x11_request_forwarding_with_spoofing(0, display, proto, data);
 922
 923                 /* Read response from the server. */
 924                 type = packet_read();
 925                 if (type == SSH_SMSG_SUCCESS) {
 926                         interactive = 1;
 927                 } else if (type == SSH_SMSG_FAILURE) {
 928                         logit("Warning: Remote host denied X11 forwarding.");
 929                 } else {
 930                         packet_disconnect("Protocol error waiting for X11 forwarding");
 931                 }
 932         }
 933         /* Tell the packet module whether this is an interactive session. */
 934         packet_set_interactive(interactive);
 935
 936         /* Request authentication agent forwarding if appropriate. */
 937         check_agent_present();
 938
 939         if (options.forward_agent) {
 940                 debug("Requesting authentication agent forwarding.");
 941                 auth_request_forwarding();
 942
 943                 /* Read response from the server. */
 944                 type = packet_read();
 945                 packet_check_eom();
 946                 if (type != SSH_SMSG_SUCCESS)
 947                         logit("Warning: Remote host denied authentication agent forwarding.");
 948         }
 949
 950         /* Initiate port forwardings. */
 951         ssh_init_forwarding();
 952
 953         /* If requested, let ssh continue in the background. */
 954         if (fork_after_authentication_flag)
 955                 if (daemon(1, 1) < 0)
 956                         fatal("daemon() failed: %.200s", strerror(errno));
 957
 958         /*
 959          * If a command was specified on the command line, execute the
 960          * command now. Otherwise request the server to start a shell.
 961          */
 962         if (buffer_len(&command) > 0) {
 963                 int len = buffer_len(&command);
 964                 if (len > 900)
 965                         len = 900;
 966                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 967                 packet_start(SSH_CMSG_EXEC_CMD);
 968                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 969                 packet_send();
 970                 packet_write_wait();
 971         } else {
 972                 debug("Requesting shell.");
 973                 packet_start(SSH_CMSG_EXEC_SHELL);
 974                 packet_send();
 975                 packet_write_wait();
 976         }
 977
 978         /* Enter the interactive session. */
 979         return client_loop(have_tty, tty_flag ?
 980             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
 981 }
 982
 983 static void
 984 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
 985 {
 986         int id, len;
 987
 988         id = packet_get_int();
 989         len = buffer_len(&command);
 990         if (len > 900)
 991                 len = 900;
 992         packet_check_eom();
 993         if (type == SSH2_MSG_CHANNEL_FAILURE)
 994                 fatal("Request for subsystem '%.*s' failed on channel %d",
 995                     len, (u_char *)buffer_ptr(&command), id);
 996 }
 997
 998 void
 999 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1000 {
1001         int i;
1002
1003         i = client_global_request_id++;
1004         if (i >= options.num_remote_forwards)
1005                 return;
1006         debug("remote forward %s for: listen %d, connect %s:%d",
1007             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1008             options.remote_forwards[i].listen_port,
1009             options.remote_forwards[i].connect_host,
1010             options.remote_forwards[i].connect_port);
1011         if (type == SSH2_MSG_REQUEST_FAILURE)
1012                 logit("Warning: remote port forwarding failed for listen "
1013                     "port %d", options.remote_forwards[i].listen_port);
1014 }
1015
1016 static void
1017 ssh_control_listener(void)
1018 {
1019         struct sockaddr_un addr;
1020         mode_t old_umask;
1021         int addr_len;
1022
1023         if (options.control_path == NULL ||
1024             options.control_master == SSHCTL_MASTER_NO)
1025                 return;
1026
1027         debug("setting up multiplex master socket");
1028
1029         memset(&addr, '\0', sizeof(addr));
1030         addr.sun_family = AF_UNIX;
1031         addr_len = offsetof(struct sockaddr_un, sun_path) +
1032             strlen(options.control_path) + 1;
1033
1034         if (strlcpy(addr.sun_path, options.control_path,
1035             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1036                 fatal("ControlPath too long");
1037
1038         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1039                 fatal("%s socket(): %s", __func__, strerror(errno));
1040
1041         old_umask = umask(0177);
1042         if (bind(control_fd, (struct sockaddr*)&addr, addr_len) == -1) {
1043                 control_fd = -1;
1044                 if (errno == EINVAL || errno == EADDRINUSE)
1045                         fatal("ControlSocket %s already exists",
1046                             options.control_path);
1047                 else
1048                         fatal("%s bind(): %s", __func__, strerror(errno));
1049         }
1050         umask(old_umask);
1051
1052         if (listen(control_fd, 64) == -1)
1053                 fatal("%s listen(): %s", __func__, strerror(errno));
1054
1055         set_nonblock(control_fd);
1056 }
1057
1058 /* request pty/x11/agent/tcpfwd/shell for channel */
1059 static void
1060 ssh_session2_setup(int id, void *arg)
1061 {
1062         extern char **environ;
1063         const char *display;
1064         int interactive = tty_flag;
1065
1066         display = getenv("DISPLAY");
1067         if (options.forward_x11 && display != NULL) {
1068                 char *proto, *data;
1069                 /* Get reasonable local authentication information. */
1070                 client_x11_get_proto(display, options.xauth_location,
1071                     options.forward_x11_trusted, &proto, &data);
1072                 /* Request forwarding with authentication spoofing. */
1073                 debug("Requesting X11 forwarding with authentication spoofing.");
1074                 x11_request_forwarding_with_spoofing(id, display, proto, data);
1075                 interactive = 1;
1076                 /* XXX wait for reply */
1077         }
1078
1079         check_agent_present();
1080         if (options.forward_agent) {
1081                 debug("Requesting authentication agent forwarding.");
1082                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1083                 packet_send();
1084         }
1085
1086         if (options.tun_open != SSH_TUNMODE_NO) {
1087                 Channel *c;
1088                 int fd;
1089
1090                 debug("Requesting tun.");
1091                 if ((fd = tun_open(options.tun_local,
1092                     options.tun_open)) >= 0) {
1093                         c = channel_new("tun", SSH_CHANNEL_OPENING, fd, fd, -1,
1094                             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1095                             0, "tun", 1);
1096                         c->datagram = 1;
1097 #if defined(SSH_TUN_FILTER)
1098                         if (options.tun_open == SSH_TUNMODE_POINTOPOINT)
1099                                 channel_register_filter(c->self, sys_tun_infilter,
1100                                     sys_tun_outfilter);
1101 #endif
1102                         packet_start(SSH2_MSG_CHANNEL_OPEN);
1103                         packet_put_cstring("tun@openssh.com");
1104                         packet_put_int(c->self);
1105                         packet_put_int(c->local_window_max);
1106                         packet_put_int(c->local_maxpacket);
1107                         packet_put_int(options.tun_open);
1108                         packet_put_int(options.tun_remote);
1109                         packet_send();
1110                 }
1111         }
1112
1113         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1114             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1115
1116         packet_set_interactive(interactive);
1117 }
1118
1119 /* open new channel for a session */
1120 static int
1121 ssh_session2_open(void)
1122 {
1123         Channel *c;
1124         int window, packetmax, in, out, err;
1125
1126         if (stdin_null_flag) {
1127                 in = open(_PATH_DEVNULL, O_RDONLY);
1128         } else {
1129                 in = dup(STDIN_FILENO);
1130         }
1131         out = dup(STDOUT_FILENO);
1132         err = dup(STDERR_FILENO);
1133
1134         if (in < 0 || out < 0 || err < 0)
1135                 fatal("dup() in/out/err failed");
1136
1137         /* enable nonblocking unless tty */
1138         if (!isatty(in))
1139                 set_nonblock(in);
1140         if (!isatty(out))
1141                 set_nonblock(out);
1142         if (!isatty(err))
1143                 set_nonblock(err);
1144
1145         window = CHAN_SES_WINDOW_DEFAULT;
1146         packetmax = CHAN_SES_PACKET_DEFAULT;
1147         if (tty_flag) {
1148                 window >>= 1;
1149                 packetmax >>= 1;
1150         }
1151         c = channel_new(
1152             "session", SSH_CHANNEL_OPENING, in, out, err,
1153             window, packetmax, CHAN_EXTENDED_WRITE,
1154             "client-session", /*nonblock*/0);
1155
1156         debug3("ssh_session2_open: channel_new: %d", c->self);
1157
1158         channel_send_open(c->self);
1159         if (!no_shell_flag)
1160                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1161
1162         return c->self;
1163 }
1164
1165 static int
1166 ssh_session2(void)
1167 {
1168         int id = -1;
1169
1170         /* XXX should be pre-session */
1171         ssh_init_forwarding();
1172         ssh_control_listener();
1173
1174         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1175                 id = ssh_session2_open();
1176
1177         /* Execute a local command */
1178         if (options.local_command != NULL &&
1179             options.permit_local_command)
1180                 ssh_local_cmd(options.local_command);
1181
1182         /* If requested, let ssh continue in the background. */
1183         if (fork_after_authentication_flag)
1184                 if (daemon(1, 1) < 0)
1185                         fatal("daemon() failed: %.200s", strerror(errno));
1186
1187         return client_loop(tty_flag, tty_flag ?
1188             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1189 }
1190
1191 static void
1192 load_public_identity_files(void)
1193 {
1194         char *filename;
1195         int i = 0;
1196         Key *public;
1197 #ifdef SMARTCARD
1198         Key **keys;
1199
1200         if (options.smartcard_device != NULL &&
1201             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1202             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1203                 int count = 0;
1204                 for (i = 0; keys[i] != NULL; i++) {
1205                         count++;
1206                         memmove(&options.identity_files[1], &options.identity_files[0],
1207                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1208                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1209                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1210                         options.num_identity_files++;
1211                         options.identity_keys[0] = keys[i];
1212                         options.identity_files[0] = sc_get_key_label(keys[i]);
1213                 }
1214                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1215                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1216                 i = count;
1217                 xfree(keys);
1218         }
1219 #endif /* SMARTCARD */
1220         for (; i < options.num_identity_files; i++) {
1221                 filename = tilde_expand_filename(options.identity_files[i],
1222                     original_real_uid);
1223                 public = key_load_public(filename, NULL);
1224                 debug("identity file %s type %d", filename,
1225                     public ? public->type : -1);
1226                 xfree(options.identity_files[i]);
1227                 options.identity_files[i] = filename;
1228                 options.identity_keys[i] = public;
1229         }
1230 }
1231
1232 static void
1233 control_client_sighandler(int signo)
1234 {
1235         control_client_terminate = signo;
1236 }
1237
1238 static void
1239 control_client_sigrelay(int signo)
1240 {
1241         if (control_server_pid > 1)
1242                 kill(control_server_pid, signo);
1243 }
1244
1245 static int
1246 env_permitted(char *env)
1247 {
1248         int i;
1249         char name[1024], *cp;
1250
1251         strlcpy(name, env, sizeof(name));
1252         if ((cp = strchr(name, '=')) == NULL)
1253                 return (0);
1254
1255         *cp = '\0';
1256
1257         for (i = 0; i < options.num_send_env; i++)
1258                 if (match_pattern(name, options.send_env[i]))
1259                         return (1);
1260
1261         return (0);
1262 }
1263
1264 static void
1265 control_client(const char *path)
1266 {
1267         struct sockaddr_un addr;
1268         int i, r, fd, sock, exitval, num_env, addr_len;
1269         Buffer m;
1270         char *term;
1271         extern char **environ;
1272         u_int  flags;
1273
1274         if (mux_command == 0)
1275                 mux_command = SSHMUX_COMMAND_OPEN;
1276
1277         switch (options.control_master) {
1278         case SSHCTL_MASTER_AUTO:
1279         case SSHCTL_MASTER_AUTO_ASK:
1280                 debug("auto-mux: Trying existing master");
1281                 /* FALLTHROUGH */
1282         case SSHCTL_MASTER_NO:
1283                 break;
1284         default:
1285                 return;
1286         }
1287
1288         memset(&addr, '\0', sizeof(addr));
1289         addr.sun_family = AF_UNIX;
1290         addr_len = offsetof(struct sockaddr_un, sun_path) +
1291             strlen(path) + 1;
1292
1293         if (strlcpy(addr.sun_path, path,
1294             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1295                 fatal("ControlPath too long");
1296
1297         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1298                 fatal("%s socket(): %s", __func__, strerror(errno));
1299
1300         if (connect(sock, (struct sockaddr*)&addr, addr_len) == -1) {
1301                 if (mux_command != SSHMUX_COMMAND_OPEN) {
1302                         fatal("Control socket connect(%.100s): %s", path,
1303                             strerror(errno));
1304                 }
1305                 if (errno == ENOENT)
1306                         debug("Control socket \"%.100s\" does not exist", path);
1307                 else {
1308                         error("Control socket connect(%.100s): %s", path,
1309                             strerror(errno));
1310                 }
1311                 close(sock);
1312                 return;
1313         }
1314
1315         if (stdin_null_flag) {
1316                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1317                         fatal("open(/dev/null): %s", strerror(errno));
1318                 if (dup2(fd, STDIN_FILENO) == -1)
1319                         fatal("dup2: %s", strerror(errno));
1320                 if (fd > STDERR_FILENO)
1321                         close(fd);
1322         }
1323
1324         term = getenv("TERM");
1325
1326         flags = 0;
1327         if (tty_flag)
1328                 flags |= SSHMUX_FLAG_TTY;
1329         if (subsystem_flag)
1330                 flags |= SSHMUX_FLAG_SUBSYS;
1331         if (options.forward_x11)
1332                 flags |= SSHMUX_FLAG_X11_FWD;
1333         if (options.forward_agent)
1334                 flags |= SSHMUX_FLAG_AGENT_FWD;
1335
1336         buffer_init(&m);
1337
1338         /* Send our command to server */
1339         buffer_put_int(&m, mux_command);
1340         buffer_put_int(&m, flags);
1341         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1342                 fatal("%s: msg_send", __func__);
1343         buffer_clear(&m);
1344
1345         /* Get authorisation status and PID of controlee */
1346         if (ssh_msg_recv(sock, &m) == -1)
1347                 fatal("%s: msg_recv", __func__);
1348         if (buffer_get_char(&m) != SSHMUX_VER)
1349                 fatal("%s: wrong version", __func__);
1350         if (buffer_get_int(&m) != 1)
1351                 fatal("Connection to master denied");
1352         control_server_pid = buffer_get_int(&m);
1353
1354         buffer_clear(&m);
1355
1356         switch (mux_command) {
1357         case SSHMUX_COMMAND_ALIVE_CHECK:
1358                 fprintf(stderr, "Master running (pid=%d)\r\n",
1359                     control_server_pid);
1360                 exit(0);
1361         case SSHMUX_COMMAND_TERMINATE:
1362                 fprintf(stderr, "Exit request sent.\r\n");
1363                 exit(0);
1364         case SSHMUX_COMMAND_OPEN:
1365                 /* continue below */
1366                 break;
1367         default:
1368                 fatal("silly mux_command %d", mux_command);
1369         }
1370
1371         /* SSHMUX_COMMAND_OPEN */
1372         buffer_put_cstring(&m, term ? term : "");
1373         buffer_append(&command, "\0", 1);
1374         buffer_put_cstring(&m, buffer_ptr(&command));
1375
1376         if (options.num_send_env == 0 || environ == NULL) {
1377                 buffer_put_int(&m, 0);
1378         } else {
1379                 /* Pass environment */
1380                 num_env = 0;
1381                 for (i = 0; environ[i] != NULL; i++)
1382                         if (env_permitted(environ[i]))
1383                                 num_env++; /* Count */
1384
1385                 buffer_put_int(&m, num_env);
1386
1387                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1388                         if (env_permitted(environ[i])) {
1389                                 num_env--;
1390                                 buffer_put_cstring(&m, environ[i]);
1391                         }
1392         }
1393
1394         if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
1395                 fatal("%s: msg_send", __func__);
1396
1397         mm_send_fd(sock, STDIN_FILENO);
1398         mm_send_fd(sock, STDOUT_FILENO);
1399         mm_send_fd(sock, STDERR_FILENO);
1400
1401         /* Wait for reply, so master has a chance to gather ttymodes */
1402         buffer_clear(&m);
1403         if (ssh_msg_recv(sock, &m) == -1)
1404                 fatal("%s: msg_recv", __func__);
1405         if (buffer_get_char(&m) != SSHMUX_VER)
1406                 fatal("%s: wrong version", __func__);
1407         buffer_free(&m);
1408
1409         signal(SIGHUP, control_client_sighandler);
1410         signal(SIGINT, control_client_sighandler);
1411         signal(SIGTERM, control_client_sighandler);
1412         signal(SIGWINCH, control_client_sigrelay);
1413
1414         if (tty_flag)
1415                 enter_raw_mode();
1416
1417         /* Stick around until the controlee closes the client_fd */
1418         exitval = 0;
1419         for (;!control_client_terminate;) {
1420                 r = read(sock, &exitval, sizeof(exitval));
1421                 if (r == 0) {
1422                         debug2("Received EOF from master");
1423                         break;
1424                 }
1425                 if (r > 0)
1426                         debug2("Received exit status from master %d", exitval);
1427                 if (r == -1 && errno != EINTR)
1428                         fatal("%s: read %s", __func__, strerror(errno));
1429         }
1430
1431         if (control_client_terminate)
1432                 debug2("Exiting on signal %d", control_client_terminate);
1433
1434         close(sock);
1435
1436         leave_raw_mode();
1437
1438         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1439                 fprintf(stderr, "Connection to master closed.\r\n");
1440
1441         exit(exitval);
1442 }