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 1.233 2005/03/01 17:22:06 jmc Exp $");
  44
  45 #include <openssl/evp.h>
  46 #include <openssl/err.h>
  47
  48 #include "ssh.h"
  49 #include "ssh1.h"
  50 #include "ssh2.h"
  51 #include "compat.h"
  52 #include "cipher.h"
  53 #include "xmalloc.h"
  54 #include "packet.h"
  55 #include "buffer.h"
  56 #include "bufaux.h"
  57 #include "channels.h"
  58 #include "key.h"
  59 #include "authfd.h"
  60 #include "authfile.h"
  61 #include "pathnames.h"
  62 #include "dispatch.h"
  63 #include "clientloop.h"
  64 #include "log.h"
  65 #include "readconf.h"
  66 #include "sshconnect.h"
  67 #include "misc.h"
  68 #include "kex.h"
  69 #include "mac.h"
  70 #include "sshpty.h"
  71 #include "match.h"
  72 #include "msg.h"
  73 #include "monitor_fdpass.h"
  74 #include "uidswap.h"
  75
  76 #ifdef SMARTCARD
  77 #include "scard.h"
  78 #endif
  79
  80 extern char *__progname;
  81
  82 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
  83 int debug_flag = 0;
  84
  85 /* Flag indicating whether a tty should be allocated */
  86 int tty_flag = 0;
  87 int no_tty_flag = 0;
  88 int force_tty_flag = 0;
  89
  90 /* don't exec a shell */
  91 int no_shell_flag = 0;
  92
  93 /*
  94  * Flag indicating that nothing should be read from stdin.  This can be set
  95  * on the command line.
  96  */
  97 int stdin_null_flag = 0;
  98
  99 /*
 100  * Flag indicating that ssh should fork after authentication.  This is useful
 101  * so that the passphrase can be entered manually, and then ssh goes to the
 102  * background.
 103  */
 104 int fork_after_authentication_flag = 0;
 105
 106 /*
 107  * General data structure for command line options and options configurable
 108  * in configuration files.  See readconf.h.
 109  */
 110 Options options;
 111
 112 /* optional user configfile */
 113 char *config = NULL;
 114
 115 /*
 116  * Name of the host we are connecting to.  This is the name given on the
 117  * command line, or the HostName specified for the user-supplied name in a
 118  * configuration file.
 119  */
 120 char *host;
 121
 122 /* socket address the host resolves to */
 123 struct sockaddr_storage hostaddr;
 124
 125 /* Private host keys. */
 126 Sensitive sensitive_data;
 127
 128 /* Original real UID. */
 129 uid_t original_real_uid;
 130 uid_t original_effective_uid;
 131
 132 /* command to be executed */
 133 Buffer command;
 134
 135 /* Should we execute a command or invoke a subsystem? */
 136 int subsystem_flag = 0;
 137
 138 /* # of replies received for global requests */
 139 static int client_global_request_id = 0;
 140
 141 /* pid of proxycommand child process */
 142 pid_t proxy_command_pid = 0;
 143
 144 /* fd to control socket */
 145 int control_fd = -1;
 146
 147 /* Multiplexing control command */
 148 static u_int mux_command = SSHMUX_COMMAND_OPEN;
 149
 150 /* Only used in control client mode */
 151 volatile sig_atomic_t control_client_terminate = 0;
 152 u_int control_server_pid = 0;
 153
 154 /* Prints a help message to the user.  This function never returns. */
 155
 156 static void
 157 usage(void)
 158 {
 159         fprintf(stderr,
 160 "usage: ssh [-1246AaCfgkMNnqsTtVvXxY] [-b bind_address] [-c cipher_spec]\n"
 161 "           [-D port] [-e escape_char] [-F configfile]\n"
 162 "           [-i identity_file] [-L [bind_address:]port:host:hostport]\n"
 163 "           [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]\n"
 164 "           [-R [bind_address:]port:host:hostport] [-S ctl_path]\n"
 165 "           [user@]hostname [command]\n"
 166         );
 167         exit(1);
 168 }
 169
 170 static int ssh_session(void);
 171 static int ssh_session2(void);
 172 static void load_public_identity_files(void);
 173 static void control_client(const char *path);
 174
 175 /*
 176  * Main program for the ssh client.
 177  */
 178 int
 179 main(int ac, char **av)
 180 {
 181         int i, opt, exit_status;
 182         char *p, *cp, *line, buf[256];
 183         struct stat st;
 184         struct passwd *pw;
 185         int dummy;
 186         extern int optind, optreset;
 187         extern char *optarg;
 188         Forward fwd;
 189
 190         __progname = ssh_get_progname(av[0]);
 191         init_rng();
 192
 193         /*
 194          * Save the original real uid.  It will be needed later (uid-swapping
 195          * may clobber the real uid).
 196          */
 197         original_real_uid = getuid();
 198         original_effective_uid = geteuid();
 199
 200         /*
 201          * Use uid-swapping to give up root privileges for the duration of
 202          * option processing.  We will re-instantiate the rights when we are
 203          * ready to create the privileged port, and will permanently drop
 204          * them when the port has been created (actually, when the connection
 205          * has been made, as we may need to create the port several times).
 206          */
 207         PRIV_END;
 208
 209 #ifdef HAVE_SETRLIMIT
 210         /* If we are installed setuid root be careful to not drop core. */
 211         if (original_real_uid != original_effective_uid) {
 212                 struct rlimit rlim;
 213                 rlim.rlim_cur = rlim.rlim_max = 0;
 214                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 215                         fatal("setrlimit failed: %.100s", strerror(errno));
 216         }
 217 #endif
 218         /* Get user data. */
 219         pw = getpwuid(original_real_uid);
 220         if (!pw) {
 221                 logit("You don't exist, go away!");
 222                 exit(1);
 223         }
 224         /* Take a copy of the returned structure. */
 225         pw = pwcopy(pw);
 226
 227         /*
 228          * Set our umask to something reasonable, as some files are created
 229          * with the default umask.  This will make them world-readable but
 230          * writable only by the owner, which is ok for all files for which we
 231          * don't set the modes explicitly.
 232          */
 233         umask(022);
 234
 235         /* Initialize option structure to indicate that no values have been set. */
 236         initialize_options(&options);
 237
 238         /* Parse command-line arguments. */
 239         host = NULL;
 240
 241 again:
 242         while ((opt = getopt(ac, av,
 243             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:MNO:PR:S:TVXY")) != -1) {
 244                 switch (opt) {
 245                 case '1':
 246                         options.protocol = SSH_PROTO_1;
 247                         break;
 248                 case '2':
 249                         options.protocol = SSH_PROTO_2;
 250                         break;
 251                 case '4':
 252                         options.address_family = AF_INET;
 253                         break;
 254                 case '6':
 255                         options.address_family = AF_INET6;
 256                         break;
 257                 case 'n':
 258                         stdin_null_flag = 1;
 259                         break;
 260                 case 'f':
 261                         fork_after_authentication_flag = 1;
 262                         stdin_null_flag = 1;
 263                         break;
 264                 case 'x':
 265                         options.forward_x11 = 0;
 266                         break;
 267                 case 'X':
 268                         options.forward_x11 = 1;
 269                         break;
 270                 case 'Y':
 271                         options.forward_x11 = 1;
 272                         options.forward_x11_trusted = 1;
 273                         break;
 274                 case 'g':
 275                         options.gateway_ports = 1;
 276                         break;
 277                 case 'O':
 278                         if (strcmp(optarg, "check") == 0)
 279                                 mux_command = SSHMUX_COMMAND_ALIVE_CHECK;
 280                         else if (strcmp(optarg, "exit") == 0)
 281                                 mux_command = SSHMUX_COMMAND_TERMINATE;
 282                         else
 283                                 fatal("Invalid multiplex command.");
 284                         break;
 285                 case 'P':       /* deprecated */
 286                         options.use_privileged_port = 0;
 287                         break;
 288                 case 'a':
 289                         options.forward_agent = 0;
 290                         break;
 291                 case 'A':
 292                         options.forward_agent = 1;
 293                         break;
 294                 case 'k':
 295                         options.gss_deleg_creds = 0;
 296                         break;
 297                 case 'i':
 298                         if (stat(optarg, &st) < 0) {
 299                                 fprintf(stderr, "Warning: Identity file %s "
 300                                     "not accessible: %s.\n", optarg,
 301                                     strerror(errno));
 302                                 break;
 303                         }
 304                         if (options.num_identity_files >=
 305                             SSH_MAX_IDENTITY_FILES)
 306                                 fatal("Too many identity files specified "
 307                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 308                         options.identity_files[options.num_identity_files++] =
 309                             xstrdup(optarg);
 310                         break;
 311                 case 'I':
 312 #ifdef SMARTCARD
 313                         options.smartcard_device = xstrdup(optarg);
 314 #else
 315                         fprintf(stderr, "no support for smartcards.\n");
 316 #endif
 317                         break;
 318                 case 't':
 319                         if (tty_flag)
 320                                 force_tty_flag = 1;
 321                         tty_flag = 1;
 322                         break;
 323                 case 'v':
 324                         if (debug_flag == 0) {
 325                                 debug_flag = 1;
 326                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 327                         } else {
 328                                 if (options.log_level < SYSLOG_LEVEL_DEBUG3)
 329                                         options.log_level++;
 330                                 break;
 331                         }
 332                         /* FALLTHROUGH */
 333                 case 'V':
 334                         fprintf(stderr, "%s, %s\n",
 335                             SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
 336                         if (opt == 'V')
 337                                 exit(0);
 338                         break;
 339                 case 'q':
 340                         options.log_level = SYSLOG_LEVEL_QUIET;
 341                         break;
 342                 case 'e':
 343                         if (optarg[0] == '^' && optarg[2] == 0 &&
 344                             (u_char) optarg[1] >= 64 &&
 345                             (u_char) optarg[1] < 128)
 346                                 options.escape_char = (u_char) optarg[1] & 31;
 347                         else if (strlen(optarg) == 1)
 348                                 options.escape_char = (u_char) optarg[0];
 349                         else if (strcmp(optarg, "none") == 0)
 350                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 351                         else {
 352                                 fprintf(stderr, "Bad escape character '%s'.\n",
 353                                     optarg);
 354                                 exit(1);
 355                         }
 356                         break;
 357                 case 'c':
 358                         if (ciphers_valid(optarg)) {
 359                                 /* SSH2 only */
 360                                 options.ciphers = xstrdup(optarg);
 361                                 options.cipher = SSH_CIPHER_INVALID;
 362                         } else {
 363                                 /* SSH1 only */
 364                                 options.cipher = cipher_number(optarg);
 365                                 if (options.cipher == -1) {
 366                                         fprintf(stderr,
 367                                             "Unknown cipher type '%s'\n",
 368                                             optarg);
 369                                         exit(1);
 370                                 }
 371                                 if (options.cipher == SSH_CIPHER_3DES)
 372                                         options.ciphers = "3des-cbc";
 373                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 374                                         options.ciphers = "blowfish-cbc";
 375                                 else
 376                                         options.ciphers = (char *)-1;
 377                         }
 378                         break;
 379                 case 'm':
 380                         if (mac_valid(optarg))
 381                                 options.macs = xstrdup(optarg);
 382                         else {
 383                                 fprintf(stderr, "Unknown mac type '%s'\n",
 384                                     optarg);
 385                                 exit(1);
 386                         }
 387                         break;
 388                 case 'M':
 389                         options.control_master =
 390                             (options.control_master >= 1) ? 2 : 1;
 391                         break;
 392                 case 'p':
 393                         options.port = a2port(optarg);
 394                         if (options.port == 0) {
 395                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 396                                 exit(1);
 397                         }
 398                         break;
 399                 case 'l':
 400                         options.user = optarg;
 401                         break;
 402
 403                 case 'L':
 404                         if (parse_forward(&fwd, optarg))
 405                                 add_local_forward(&options, &fwd);
 406                         else {
 407                                 fprintf(stderr,
 408                                     "Bad local forwarding specification '%s'\n",
 409                                     optarg);
 410                                 exit(1);
 411                         }
 412                         break;
 413
 414                 case 'R':
 415                         if (parse_forward(&fwd, optarg)) {
 416                                 add_remote_forward(&options, &fwd);
 417                         } else {
 418                                 fprintf(stderr,
 419                                     "Bad remote forwarding specification "
 420                                     "'%s'\n", optarg);
 421                                 exit(1);
 422                         }
 423                         break;
 424
 425                 case 'D':
 426                         cp = p = xstrdup(optarg);
 427                         memset(&fwd, '\0', sizeof(fwd));
 428                         fwd.connect_host = "socks";
 429                         if ((fwd.listen_host = hpdelim(&cp)) == NULL) {
 430                                 fprintf(stderr, "Bad dynamic forwarding "
 431                                     "specification '%.100s'\n", optarg);
 432                                 exit(1);
 433                         }
 434                         if (cp != NULL) {
 435                                 fwd.listen_port = a2port(cp);
 436                                 fwd.listen_host = cleanhostname(fwd.listen_host);
 437                         } else {
 438                                 fwd.listen_port = a2port(fwd.listen_host);
 439                                 fwd.listen_host = "";
 440                         }
 441
 442                         if (fwd.listen_port == 0) {
 443                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 444                                     optarg);
 445                                 exit(1);
 446                         }
 447                         add_local_forward(&options, &fwd);
 448                         xfree(p);
 449                         break;
 450
 451                 case 'C':
 452                         options.compression = 1;
 453                         break;
 454                 case 'N':
 455                         no_shell_flag = 1;
 456                         no_tty_flag = 1;
 457                         break;
 458                 case 'T':
 459                         no_tty_flag = 1;
 460                         break;
 461                 case 'o':
 462                         dummy = 1;
 463                         line = xstrdup(optarg);
 464                         if (process_config_line(&options, host ? host : "",
 465                             line, "command-line", 0, &dummy) != 0)
 466                                 exit(1);
 467                         xfree(line);
 468                         break;
 469                 case 's':
 470                         subsystem_flag = 1;
 471                         break;
 472                 case 'S':
 473                         if (options.control_path != NULL)
 474                                 free(options.control_path);
 475                         options.control_path = xstrdup(optarg);
 476                         break;
 477                 case 'b':
 478                         options.bind_address = optarg;
 479                         break;
 480                 case 'F':
 481                         config = optarg;
 482                         break;
 483                 default:
 484                         usage();
 485                 }
 486         }
 487
 488         ac -= optind;
 489         av += optind;
 490
 491         if (ac > 0 && !host && **av != '-') {
 492                 if (strrchr(*av, '@')) {
 493                         p = xstrdup(*av);
 494                         cp = strrchr(p, '@');
 495                         if (cp == NULL || cp == p)
 496                                 usage();
 497                         options.user = p;
 498                         *cp = '\0';
 499                         host = ++cp;
 500                 } else
 501                         host = *av;
 502                 if (ac > 1) {
 503                         optind = optreset = 1;
 504                         goto again;
 505                 }
 506                 ac--, av++;
 507         }
 508
 509         /* Check that we got a host name. */
 510         if (!host)
 511                 usage();
 512
 513         SSLeay_add_all_algorithms();
 514         ERR_load_crypto_strings();
 515
 516         /* Initialize the command to execute on remote host. */
 517         buffer_init(&command);
 518
 519         /*
 520          * Save the command to execute on the remote host in a buffer. There
 521          * is no limit on the length of the command, except by the maximum
 522          * packet size.  Also sets the tty flag if there is no command.
 523          */
 524         if (!ac) {
 525                 /* No command specified - execute shell on a tty. */
 526                 tty_flag = 1;
 527                 if (subsystem_flag) {
 528                         fprintf(stderr,
 529                             "You must specify a subsystem to invoke.\n");
 530                         usage();
 531                 }
 532         } else {
 533                 /* A command has been specified.  Store it into the buffer. */
 534                 for (i = 0; i < ac; i++) {
 535                         if (i)
 536                                 buffer_append(&command, " ", 1);
 537                         buffer_append(&command, av[i], strlen(av[i]));
 538                 }
 539         }
 540
 541         /* Cannot fork to background if no command. */
 542         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 543                 fatal("Cannot fork into background without a command to execute.");
 544
 545         /* Allocate a tty by default if no command specified. */
 546         if (buffer_len(&command) == 0)
 547                 tty_flag = 1;
 548
 549         /* Force no tty */
 550         if (no_tty_flag)
 551                 tty_flag = 0;
 552         /* Do not allocate a tty if stdin is not a tty. */
 553         if (!isatty(fileno(stdin)) && !force_tty_flag) {
 554                 if (tty_flag)
 555                         logit("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 556                 tty_flag = 0;
 557         }
 558
 559         /*
 560          * Initialize "log" output.  Since we are the client all output
 561          * actually goes to stderr.
 562          */
 563         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 564             SYSLOG_FACILITY_USER, 1);
 565
 566         /*
 567          * Read per-user configuration file.  Ignore the system wide config
 568          * file if the user specifies a config file on the command line.
 569          */
 570         if (config != NULL) {
 571                 if (!read_config_file(config, host, &options, 0))
 572                         fatal("Can't open user config file %.100s: "
 573                             "%.100s", config, strerror(errno));
 574         } else  {
 575                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 576                     _PATH_SSH_USER_CONFFILE);
 577                 (void)read_config_file(buf, host, &options, 1);
 578
 579                 /* Read systemwide configuration file after use config. */
 580                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host,
 581                     &options, 0);
 582         }
 583
 584         /* Fill configuration defaults. */
 585         fill_default_options(&options);
 586
 587         channel_set_af(options.address_family);
 588
 589         /* reinit */
 590         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 591
 592         seed_rng();
 593
 594         if (options.user == NULL)
 595                 options.user = xstrdup(pw->pw_name);
 596
 597         if (options.hostname != NULL)
 598                 host = options.hostname;
 599
 600         /* force lowercase for hostkey matching */
 601         if (options.host_key_alias != NULL) {
 602                 for (p = options.host_key_alias; *p; p++)
 603                         if (isupper(*p))
 604                                 *p = tolower(*p);
 605         }
 606
 607         if (options.proxy_command != NULL &&
 608             strcmp(options.proxy_command, "none") == 0)
 609                 options.proxy_command = NULL;
 610
 611         if (options.control_path != NULL) {
 612                 options.control_path = tilde_expand_filename(
 613                    options.control_path, original_real_uid);
 614         }
 615         if (options.control_path != NULL && options.control_master == 0)
 616                 control_client(options.control_path); /* This doesn't return */
 617
 618         /* Open a connection to the remote host. */
 619         if (ssh_connect(host, &hostaddr, options.port,
 620             options.address_family, options.connection_attempts,
 621 #ifdef HAVE_CYGWIN
 622             options.use_privileged_port,
 623 #else
 624             original_effective_uid == 0 && options.use_privileged_port,
 625 #endif
 626             options.proxy_command) != 0)
 627                 exit(1);
 628
 629         /*
 630          * If we successfully made the connection, load the host private key
 631          * in case we will need it later for combined rsa-rhosts
 632          * authentication. This must be done before releasing extra
 633          * privileges, because the file is only readable by root.
 634          * If we cannot access the private keys, load the public keys
 635          * instead and try to execute the ssh-keysign helper instead.
 636          */
 637         sensitive_data.nkeys = 0;
 638         sensitive_data.keys = NULL;
 639         sensitive_data.external_keysign = 0;
 640         if (options.rhosts_rsa_authentication ||
 641             options.hostbased_authentication) {
 642                 sensitive_data.nkeys = 3;
 643                 sensitive_data.keys = xmalloc(sensitive_data.nkeys *
 644                     sizeof(Key));
 645
 646                 PRIV_START;
 647                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 648                     _PATH_HOST_KEY_FILE, "", NULL);
 649                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 650                     _PATH_HOST_DSA_KEY_FILE, "", NULL);
 651                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 652                     _PATH_HOST_RSA_KEY_FILE, "", NULL);
 653                 PRIV_END;
 654
 655                 if (options.hostbased_authentication == 1 &&
 656                     sensitive_data.keys[0] == NULL &&
 657                     sensitive_data.keys[1] == NULL &&
 658                     sensitive_data.keys[2] == NULL) {
 659                         sensitive_data.keys[1] = key_load_public(
 660                             _PATH_HOST_DSA_KEY_FILE, NULL);
 661                         sensitive_data.keys[2] = key_load_public(
 662                             _PATH_HOST_RSA_KEY_FILE, NULL);
 663                         sensitive_data.external_keysign = 1;
 664                 }
 665         }
 666         /*
 667          * Get rid of any extra privileges that we may have.  We will no
 668          * longer need them.  Also, extra privileges could make it very hard
 669          * to read identity files and other non-world-readable files from the
 670          * user's home directory if it happens to be on a NFS volume where
 671          * root is mapped to nobody.
 672          */
 673         if (original_effective_uid == 0) {
 674                 PRIV_START;
 675                 permanently_set_uid(pw);
 676         }
 677
 678         /*
 679          * Now that we are back to our own permissions, create ~/.ssh
 680          * directory if it doesn\'t already exist.
 681          */
 682         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 683         if (stat(buf, &st) < 0)
 684                 if (mkdir(buf, 0700) < 0)
 685                         error("Could not create directory '%.200s'.", buf);
 686
 687         /* load options.identity_files */
 688         load_public_identity_files();
 689
 690         /* Expand ~ in known host file names. */
 691         /* XXX mem-leaks: */
 692         options.system_hostfile =
 693             tilde_expand_filename(options.system_hostfile, original_real_uid);
 694         options.user_hostfile =
 695             tilde_expand_filename(options.user_hostfile, original_real_uid);
 696         options.system_hostfile2 =
 697             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 698         options.user_hostfile2 =
 699             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 700
 701         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 702
 703         /* Log into the remote system.  This never returns if the login fails. */
 704         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 705
 706         /* We no longer need the private host keys.  Clear them now. */
 707         if (sensitive_data.nkeys != 0) {
 708                 for (i = 0; i < sensitive_data.nkeys; i++) {
 709                         if (sensitive_data.keys[i] != NULL) {
 710                                 /* Destroys contents safely */
 711                                 debug3("clear hostkey %d", i);
 712                                 key_free(sensitive_data.keys[i]);
 713                                 sensitive_data.keys[i] = NULL;
 714                         }
 715                 }
 716                 xfree(sensitive_data.keys);
 717         }
 718         for (i = 0; i < options.num_identity_files; i++) {
 719                 if (options.identity_files[i]) {
 720                         xfree(options.identity_files[i]);
 721                         options.identity_files[i] = NULL;
 722                 }
 723                 if (options.identity_keys[i]) {
 724                         key_free(options.identity_keys[i]);
 725                         options.identity_keys[i] = NULL;
 726                 }
 727         }
 728
 729         exit_status = compat20 ? ssh_session2() : ssh_session();
 730         packet_close();
 731
 732         if (options.control_path != NULL && control_fd != -1)
 733                 unlink(options.control_path);
 734
 735         /*
 736          * Send SIGHUP to proxy command if used. We don't wait() in
 737          * case it hangs and instead rely on init to reap the child
 738          */
 739         if (proxy_command_pid > 1)
 740                 kill(proxy_command_pid, SIGHUP);
 741
 742         return exit_status;
 743 }
 744
 745 #define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1"
 746
 747 static void
 748 x11_get_proto(char **_proto, char **_data)
 749 {
 750         char cmd[1024];
 751         char line[512];
 752         char xdisplay[512];
 753         static char proto[512], data[512];
 754         FILE *f;
 755         int got_data = 0, generated = 0, do_unlink = 0, i;
 756         char *display, *xauthdir, *xauthfile;
 757         struct stat st;
 758
 759         xauthdir = xauthfile = NULL;
 760         *_proto = proto;
 761         *_data = data;
 762         proto[0] = data[0] = '\0';
 763
 764         if (!options.xauth_location ||
 765             (stat(options.xauth_location, &st) == -1)) {
 766                 debug("No xauth program.");
 767         } else {
 768                 if ((display = getenv("DISPLAY")) == NULL) {
 769                         debug("x11_get_proto: DISPLAY not set");
 770                         return;
 771                 }
 772                 /*
 773                  * Handle FamilyLocal case where $DISPLAY does
 774                  * not match an authorization entry.  For this we
 775                  * just try "xauth list unix:displaynum.screennum".
 776                  * XXX: "localhost" match to determine FamilyLocal
 777                  *      is not perfect.
 778                  */
 779                 if (strncmp(display, "localhost:", 10) == 0) {
 780                         snprintf(xdisplay, sizeof(xdisplay), "unix:%s",
 781                             display + 10);
 782                         display = xdisplay;
 783                 }
 784                 if (options.forward_x11_trusted == 0) {
 785                         xauthdir = xmalloc(MAXPATHLEN);
 786                         xauthfile = xmalloc(MAXPATHLEN);
 787                         strlcpy(xauthdir, "/tmp/ssh-XXXXXXXXXX", MAXPATHLEN);
 788                         if (mkdtemp(xauthdir) != NULL) {
 789                                 do_unlink = 1;
 790                                 snprintf(xauthfile, MAXPATHLEN, "%s/xauthfile",
 791                                     xauthdir);
 792                                 snprintf(cmd, sizeof(cmd),
 793                                     "%s -f %s generate %s " SSH_X11_PROTO
 794                                     " untrusted timeout 1200 2>" _PATH_DEVNULL,
 795                                     options.xauth_location, xauthfile, display);
 796                                 debug2("x11_get_proto: %s", cmd);
 797                                 if (system(cmd) == 0)
 798                                         generated = 1;
 799                         }
 800                 }
 801                 snprintf(cmd, sizeof(cmd),
 802                     "%s %s%s list %s . 2>" _PATH_DEVNULL,
 803                     options.xauth_location,
 804                     generated ? "-f " : "" ,
 805                     generated ? xauthfile : "",
 806                     display);
 807                 debug2("x11_get_proto: %s", cmd);
 808                 f = popen(cmd, "r");
 809                 if (f && fgets(line, sizeof(line), f) &&
 810                     sscanf(line, "%*s %511s %511s", proto, data) == 2)
 811                         got_data = 1;
 812                 if (f)
 813                         pclose(f);
 814         }
 815
 816         if (do_unlink) {
 817                 unlink(xauthfile);
 818                 rmdir(xauthdir);
 819         }
 820         if (xauthdir)
 821                 xfree(xauthdir);
 822         if (xauthfile)
 823                 xfree(xauthfile);
 824
 825         /*
 826          * If we didn't get authentication data, just make up some
 827          * data.  The forwarding code will check the validity of the
 828          * response anyway, and substitute this data.  The X11
 829          * server, however, will ignore this fake data and use
 830          * whatever authentication mechanisms it was using otherwise
 831          * for the local connection.
 832          */
 833         if (!got_data) {
 834                 u_int32_t rnd = 0;
 835
 836                 logit("Warning: No xauth data; "
 837                     "using fake authentication data for X11 forwarding.");
 838                 strlcpy(proto, SSH_X11_PROTO, sizeof proto);
 839                 for (i = 0; i < 16; i++) {
 840                         if (i % 4 == 0)
 841                                 rnd = arc4random();
 842                         snprintf(data + 2 * i, sizeof data - 2 * i, "%02x",
 843                             rnd & 0xff);
 844                         rnd >>= 8;
 845                 }
 846         }
 847 }
 848
 849 static void
 850 ssh_init_forwarding(void)
 851 {
 852         int success = 0;
 853         int i;
 854
 855         /* Initiate local TCP/IP port forwardings. */
 856         for (i = 0; i < options.num_local_forwards; i++) {
 857                 debug("Local connections to %.200s:%d forwarded to remote "
 858                     "address %.200s:%d",
 859                     (options.local_forwards[i].listen_host == NULL) ?
 860                     (options.gateway_ports ? "*" : "LOCALHOST") :
 861                     options.local_forwards[i].listen_host,
 862                     options.local_forwards[i].listen_port,
 863                     options.local_forwards[i].connect_host,
 864                     options.local_forwards[i].connect_port);
 865                 success += channel_setup_local_fwd_listener(
 866                     options.local_forwards[i].listen_host,
 867                     options.local_forwards[i].listen_port,
 868                     options.local_forwards[i].connect_host,
 869                     options.local_forwards[i].connect_port,
 870                     options.gateway_ports);
 871         }
 872         if (i > 0 && success == 0)
 873                 error("Could not request local forwarding.");
 874
 875         /* Initiate remote TCP/IP port forwardings. */
 876         for (i = 0; i < options.num_remote_forwards; i++) {
 877                 debug("Remote connections from %.200s:%d forwarded to "
 878                     "local address %.200s:%d",
 879                     options.remote_forwards[i].listen_host,
 880                     options.remote_forwards[i].listen_port,
 881                     options.remote_forwards[i].connect_host,
 882                     options.remote_forwards[i].connect_port);
 883                 channel_request_remote_forwarding(
 884                     options.remote_forwards[i].listen_host,
 885                     options.remote_forwards[i].listen_port,
 886                     options.remote_forwards[i].connect_host,
 887                     options.remote_forwards[i].connect_port);
 888         }
 889 }
 890
 891 static void
 892 check_agent_present(void)
 893 {
 894         if (options.forward_agent) {
 895                 /* Clear agent forwarding if we don\'t have an agent. */
 896                 if (!ssh_agent_present())
 897                         options.forward_agent = 0;
 898         }
 899 }
 900
 901 static int
 902 ssh_session(void)
 903 {
 904         int type;
 905         int interactive = 0;
 906         int have_tty = 0;
 907         struct winsize ws;
 908         char *cp;
 909
 910         /* Enable compression if requested. */
 911         if (options.compression) {
 912                 debug("Requesting compression at level %d.", options.compression_level);
 913
 914                 if (options.compression_level < 1 || options.compression_level > 9)
 915                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 916
 917                 /* Send the request. */
 918                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 919                 packet_put_int(options.compression_level);
 920                 packet_send();
 921                 packet_write_wait();
 922                 type = packet_read();
 923                 if (type == SSH_SMSG_SUCCESS)
 924                         packet_start_compression(options.compression_level);
 925                 else if (type == SSH_SMSG_FAILURE)
 926                         logit("Warning: Remote host refused compression.");
 927                 else
 928                         packet_disconnect("Protocol error waiting for compression response.");
 929         }
 930         /* Allocate a pseudo tty if appropriate. */
 931         if (tty_flag) {
 932                 debug("Requesting pty.");
 933
 934                 /* Start the packet. */
 935                 packet_start(SSH_CMSG_REQUEST_PTY);
 936
 937                 /* Store TERM in the packet.  There is no limit on the
 938                    length of the string. */
 939                 cp = getenv("TERM");
 940                 if (!cp)
 941                         cp = "";
 942                 packet_put_cstring(cp);
 943
 944                 /* Store window size in the packet. */
 945                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 946                         memset(&ws, 0, sizeof(ws));
 947                 packet_put_int(ws.ws_row);
 948                 packet_put_int(ws.ws_col);
 949                 packet_put_int(ws.ws_xpixel);
 950                 packet_put_int(ws.ws_ypixel);
 951
 952                 /* Store tty modes in the packet. */
 953                 tty_make_modes(fileno(stdin), NULL);
 954
 955                 /* Send the packet, and wait for it to leave. */
 956                 packet_send();
 957                 packet_write_wait();
 958
 959                 /* Read response from the server. */
 960                 type = packet_read();
 961                 if (type == SSH_SMSG_SUCCESS) {
 962                         interactive = 1;
 963                         have_tty = 1;
 964                 } else if (type == SSH_SMSG_FAILURE)
 965                         logit("Warning: Remote host failed or refused to allocate a pseudo tty.");
 966                 else
 967                         packet_disconnect("Protocol error waiting for pty request response.");
 968         }
 969         /* Request X11 forwarding if enabled and DISPLAY is set. */
 970         if (options.forward_x11 && getenv("DISPLAY") != NULL) {
 971                 char *proto, *data;
 972                 /* Get reasonable local authentication information. */
 973                 x11_get_proto(&proto, &data);
 974                 /* Request forwarding with authentication spoofing. */
 975                 debug("Requesting X11 forwarding with authentication spoofing.");
 976                 x11_request_forwarding_with_spoofing(0, proto, data);
 977
 978                 /* Read response from the server. */
 979                 type = packet_read();
 980                 if (type == SSH_SMSG_SUCCESS) {
 981                         interactive = 1;
 982                 } else if (type == SSH_SMSG_FAILURE) {
 983                         logit("Warning: Remote host denied X11 forwarding.");
 984                 } else {
 985                         packet_disconnect("Protocol error waiting for X11 forwarding");
 986                 }
 987         }
 988         /* Tell the packet module whether this is an interactive session. */
 989         packet_set_interactive(interactive);
 990
 991         /* Request authentication agent forwarding if appropriate. */
 992         check_agent_present();
 993
 994         if (options.forward_agent) {
 995                 debug("Requesting authentication agent forwarding.");
 996                 auth_request_forwarding();
 997
 998                 /* Read response from the server. */
 999                 type = packet_read();
1000                 packet_check_eom();
1001                 if (type != SSH_SMSG_SUCCESS)
1002                         logit("Warning: Remote host denied authentication agent forwarding.");
1003         }
1004
1005         /* Initiate port forwardings. */
1006         ssh_init_forwarding();
1007
1008         /* If requested, let ssh continue in the background. */
1009         if (fork_after_authentication_flag)
1010                 if (daemon(1, 1) < 0)
1011                         fatal("daemon() failed: %.200s", strerror(errno));
1012
1013         /*
1014          * If a command was specified on the command line, execute the
1015          * command now. Otherwise request the server to start a shell.
1016          */
1017         if (buffer_len(&command) > 0) {
1018                 int len = buffer_len(&command);
1019                 if (len > 900)
1020                         len = 900;
1021                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
1022                 packet_start(SSH_CMSG_EXEC_CMD);
1023                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
1024                 packet_send();
1025                 packet_write_wait();
1026         } else {
1027                 debug("Requesting shell.");
1028                 packet_start(SSH_CMSG_EXEC_SHELL);
1029                 packet_send();
1030                 packet_write_wait();
1031         }
1032
1033         /* Enter the interactive session. */
1034         return client_loop(have_tty, tty_flag ?
1035             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
1036 }
1037
1038 static void
1039 ssh_subsystem_reply(int type, u_int32_t seq, void *ctxt)
1040 {
1041         int id, len;
1042
1043         id = packet_get_int();
1044         len = buffer_len(&command);
1045         if (len > 900)
1046                 len = 900;
1047         packet_check_eom();
1048         if (type == SSH2_MSG_CHANNEL_FAILURE)
1049                 fatal("Request for subsystem '%.*s' failed on channel %d",
1050                     len, (u_char *)buffer_ptr(&command), id);
1051 }
1052
1053 void
1054 client_global_request_reply_fwd(int type, u_int32_t seq, void *ctxt)
1055 {
1056         int i;
1057
1058         i = client_global_request_id++;
1059         if (i >= options.num_remote_forwards)
1060                 return;
1061         debug("remote forward %s for: listen %d, connect %s:%d",
1062             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
1063             options.remote_forwards[i].listen_port,
1064             options.remote_forwards[i].connect_host,
1065             options.remote_forwards[i].connect_port);
1066         if (type == SSH2_MSG_REQUEST_FAILURE)
1067                 logit("Warning: remote port forwarding failed for listen "
1068                     "port %d", options.remote_forwards[i].listen_port);
1069 }
1070
1071 static void
1072 ssh_control_listener(void)
1073 {
1074         struct sockaddr_un addr;
1075         mode_t old_umask;
1076         int addr_len;
1077
1078         if (options.control_path == NULL || options.control_master <= 0)
1079                 return;
1080
1081         memset(&addr, '\0', sizeof(addr));
1082         addr.sun_family = AF_UNIX;
1083         addr_len = offsetof(struct sockaddr_un, sun_path) +
1084             strlen(options.control_path) + 1;
1085
1086         if (strlcpy(addr.sun_path, options.control_path,
1087             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1088                 fatal("ControlPath too long");
1089
1090         if ((control_fd = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1091                 fatal("%s socket(): %s\n", __func__, strerror(errno));
1092
1093         old_umask = umask(0177);
1094         if (bind(control_fd, (struct sockaddr*)&addr, addr_len) == -1) {
1095                 control_fd = -1;
1096                 if (errno == EINVAL)
1097                         fatal("ControlSocket %s already exists",
1098                             options.control_path);
1099                 else
1100                         fatal("%s bind(): %s\n", __func__, strerror(errno));
1101         }
1102         umask(old_umask);
1103
1104         if (listen(control_fd, 64) == -1)
1105                 fatal("%s listen(): %s\n", __func__, strerror(errno));
1106
1107         set_nonblock(control_fd);
1108 }
1109
1110 /* request pty/x11/agent/tcpfwd/shell for channel */
1111 static void
1112 ssh_session2_setup(int id, void *arg)
1113 {
1114         extern char **environ;
1115
1116         int interactive = tty_flag;
1117         if (options.forward_x11 && getenv("DISPLAY") != NULL) {
1118                 char *proto, *data;
1119                 /* Get reasonable local authentication information. */
1120                 x11_get_proto(&proto, &data);
1121                 /* Request forwarding with authentication spoofing. */
1122                 debug("Requesting X11 forwarding with authentication spoofing.");
1123                 x11_request_forwarding_with_spoofing(id, proto, data);
1124                 interactive = 1;
1125                 /* XXX wait for reply */
1126         }
1127
1128         check_agent_present();
1129         if (options.forward_agent) {
1130                 debug("Requesting authentication agent forwarding.");
1131                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1132                 packet_send();
1133         }
1134
1135         client_session2_setup(id, tty_flag, subsystem_flag, getenv("TERM"),
1136             NULL, fileno(stdin), &command, environ, &ssh_subsystem_reply);
1137
1138         packet_set_interactive(interactive);
1139 }
1140
1141 /* open new channel for a session */
1142 static int
1143 ssh_session2_open(void)
1144 {
1145         Channel *c;
1146         int window, packetmax, in, out, err;
1147
1148         if (stdin_null_flag) {
1149                 in = open(_PATH_DEVNULL, O_RDONLY);
1150         } else {
1151                 in = dup(STDIN_FILENO);
1152         }
1153         out = dup(STDOUT_FILENO);
1154         err = dup(STDERR_FILENO);
1155
1156         if (in < 0 || out < 0 || err < 0)
1157                 fatal("dup() in/out/err failed");
1158
1159         /* enable nonblocking unless tty */
1160         if (!isatty(in))
1161                 set_nonblock(in);
1162         if (!isatty(out))
1163                 set_nonblock(out);
1164         if (!isatty(err))
1165                 set_nonblock(err);
1166
1167         window = CHAN_SES_WINDOW_DEFAULT;
1168         packetmax = CHAN_SES_PACKET_DEFAULT;
1169         if (tty_flag) {
1170                 window >>= 1;
1171                 packetmax >>= 1;
1172         }
1173         c = channel_new(
1174             "session", SSH_CHANNEL_OPENING, in, out, err,
1175             window, packetmax, CHAN_EXTENDED_WRITE,
1176             "client-session", /*nonblock*/0);
1177
1178         debug3("ssh_session2_open: channel_new: %d", c->self);
1179
1180         channel_send_open(c->self);
1181         if (!no_shell_flag)
1182                 channel_register_confirm(c->self, ssh_session2_setup, NULL);
1183
1184         return c->self;
1185 }
1186
1187 static int
1188 ssh_session2(void)
1189 {
1190         int id = -1;
1191
1192         /* XXX should be pre-session */
1193         ssh_init_forwarding();
1194         ssh_control_listener();
1195
1196         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1197                 id = ssh_session2_open();
1198
1199         /* If requested, let ssh continue in the background. */
1200         if (fork_after_authentication_flag)
1201                 if (daemon(1, 1) < 0)
1202                         fatal("daemon() failed: %.200s", strerror(errno));
1203
1204         return client_loop(tty_flag, tty_flag ?
1205             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1206 }
1207
1208 static void
1209 load_public_identity_files(void)
1210 {
1211         char *filename;
1212         int i = 0;
1213         Key *public;
1214 #ifdef SMARTCARD
1215         Key **keys;
1216
1217         if (options.smartcard_device != NULL &&
1218             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1219             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1220                 int count = 0;
1221                 for (i = 0; keys[i] != NULL; i++) {
1222                         count++;
1223                         memmove(&options.identity_files[1], &options.identity_files[0],
1224                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1225                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1226                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1227                         options.num_identity_files++;
1228                         options.identity_keys[0] = keys[i];
1229                         options.identity_files[0] = sc_get_key_label(keys[i]);
1230                 }
1231                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1232                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1233                 i = count;
1234                 xfree(keys);
1235         }
1236 #endif /* SMARTCARD */
1237         for (; i < options.num_identity_files; i++) {
1238                 filename = tilde_expand_filename(options.identity_files[i],
1239                     original_real_uid);
1240                 public = key_load_public(filename, NULL);
1241                 debug("identity file %s type %d", filename,
1242                     public ? public->type : -1);
1243                 xfree(options.identity_files[i]);
1244                 options.identity_files[i] = filename;
1245                 options.identity_keys[i] = public;
1246         }
1247 }
1248
1249 static void
1250 control_client_sighandler(int signo)
1251 {
1252         control_client_terminate = signo;
1253 }
1254
1255 static void
1256 control_client_sigrelay(int signo)
1257 {
1258         if (control_server_pid > 1)
1259                 kill(control_server_pid, signo);
1260 }
1261
1262 static int
1263 env_permitted(char *env)
1264 {
1265         int i;
1266         char name[1024], *cp;
1267
1268         strlcpy(name, env, sizeof(name));
1269         if ((cp = strchr(name, '=')) == NULL)
1270                 return (0);
1271
1272         *cp = '\0';
1273
1274         for (i = 0; i < options.num_send_env; i++)
1275                 if (match_pattern(name, options.send_env[i]))
1276                         return (1);
1277
1278         return (0);
1279 }
1280
1281 static void
1282 control_client(const char *path)
1283 {
1284         struct sockaddr_un addr;
1285         int i, r, fd, sock, exitval, num_env, addr_len;
1286         Buffer m;
1287         char *term;
1288         extern char **environ;
1289         u_int  flags;
1290
1291         if (stdin_null_flag) {
1292                 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
1293                         fatal("open(/dev/null): %s", strerror(errno));
1294                 if (dup2(fd, STDIN_FILENO) == -1)
1295                         fatal("dup2: %s", strerror(errno));
1296                 if (fd > STDERR_FILENO)
1297                         close(fd);
1298         }
1299
1300         memset(&addr, '\0', sizeof(addr));
1301         addr.sun_family = AF_UNIX;
1302         addr_len = offsetof(struct sockaddr_un, sun_path) +
1303             strlen(path) + 1;
1304
1305         if (strlcpy(addr.sun_path, path,
1306             sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
1307                 fatal("ControlPath too long");
1308
1309         if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
1310                 fatal("%s socket(): %s", __func__, strerror(errno));
1311
1312         if (connect(sock, (struct sockaddr*)&addr, addr_len) == -1)
1313                 fatal("Couldn't connect to %s: %s", path, strerror(errno));
1314
1315         if ((term = getenv("TERM")) == NULL)
1316                 term = "";
1317
1318         flags = 0;
1319         if (tty_flag)
1320                 flags |= SSHMUX_FLAG_TTY;
1321         if (subsystem_flag)
1322                 flags |= SSHMUX_FLAG_SUBSYS;
1323
1324         buffer_init(&m);
1325
1326         /* Send our command to server */
1327         buffer_put_int(&m, mux_command);
1328         buffer_put_int(&m, flags);
1329         if (ssh_msg_send(sock, /* version */1, &m) == -1)
1330                 fatal("%s: msg_send", __func__);
1331         buffer_clear(&m);
1332
1333         /* Get authorisation status and PID of controlee */
1334         if (ssh_msg_recv(sock, &m) == -1)
1335                 fatal("%s: msg_recv", __func__);
1336         if (buffer_get_char(&m) != 1)
1337                 fatal("%s: wrong version", __func__);
1338         if (buffer_get_int(&m) != 1)
1339                 fatal("Connection to master denied");
1340         control_server_pid = buffer_get_int(&m);
1341
1342         buffer_clear(&m);
1343
1344         switch (mux_command) {
1345         case SSHMUX_COMMAND_ALIVE_CHECK:
1346                 fprintf(stderr, "Master running (pid=%d)\r\n",
1347                     control_server_pid);
1348                 exit(0);
1349         case SSHMUX_COMMAND_TERMINATE:
1350                 fprintf(stderr, "Exit request sent.\r\n");
1351                 exit(0);
1352         case SSHMUX_COMMAND_OPEN:
1353                 /* continue below */
1354                 break;
1355         default:
1356                 fatal("silly mux_command %d", mux_command);
1357         }
1358
1359         /* SSHMUX_COMMAND_OPEN */
1360         buffer_put_cstring(&m, term);
1361         buffer_append(&command, "\0", 1);
1362         buffer_put_cstring(&m, buffer_ptr(&command));
1363
1364         if (options.num_send_env == 0 || environ == NULL) {
1365                 buffer_put_int(&m, 0);
1366         } else {
1367                 /* Pass environment */
1368                 num_env = 0;
1369                 for (i = 0; environ[i] != NULL; i++)
1370                         if (env_permitted(environ[i]))
1371                                 num_env++; /* Count */
1372
1373                 buffer_put_int(&m, num_env);
1374
1375                 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
1376                         if (env_permitted(environ[i])) {
1377                                 num_env--;
1378                                 buffer_put_cstring(&m, environ[i]);
1379                         }
1380         }
1381
1382         if (ssh_msg_send(sock, /* version */1, &m) == -1)
1383                 fatal("%s: msg_send", __func__);
1384
1385         mm_send_fd(sock, STDIN_FILENO);
1386         mm_send_fd(sock, STDOUT_FILENO);
1387         mm_send_fd(sock, STDERR_FILENO);
1388
1389         /* Wait for reply, so master has a chance to gather ttymodes */
1390         buffer_clear(&m);
1391         if (ssh_msg_recv(sock, &m) == -1)
1392                 fatal("%s: msg_recv", __func__);
1393         if (buffer_get_char(&m) != 1)
1394                 fatal("%s: wrong version", __func__);
1395         buffer_free(&m);
1396
1397         signal(SIGHUP, control_client_sighandler);
1398         signal(SIGINT, control_client_sighandler);
1399         signal(SIGTERM, control_client_sighandler);
1400         signal(SIGWINCH, control_client_sigrelay);
1401
1402         if (tty_flag)
1403                 enter_raw_mode();
1404
1405         /* Stick around until the controlee closes the client_fd */
1406         exitval = 0;
1407         for (;!control_client_terminate;) {
1408                 r = read(sock, &exitval, sizeof(exitval));
1409                 if (r == 0) {
1410                         debug2("Received EOF from master");
1411                         break;
1412                 }
1413                 if (r > 0)
1414                         debug2("Received exit status from master %d", exitval);
1415                 if (r == -1 && errno != EINTR)
1416                         fatal("%s: read %s", __func__, strerror(errno));
1417         }
1418
1419         if (control_client_terminate)
1420                 debug2("Exiting on signal %d", control_client_terminate);
1421
1422         close(sock);
1423
1424         leave_raw_mode();
1425
1426         if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
1427                 fprintf(stderr, "Connection to master closed.\r\n");
1428
1429         exit(exitval);
1430 }