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 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 1.181 2002/07/03 14:21:05 markus 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 "channels.h"
  57 #include "key.h"
  58 #include "authfd.h"
  59 #include "authfile.h"
  60 #include "pathnames.h"
  61 #include "clientloop.h"
  62 #include "log.h"
  63 #include "readconf.h"
  64 #include "sshconnect.h"
  65 #include "tildexpand.h"
  66 #include "dispatch.h"
  67 #include "misc.h"
  68 #include "kex.h"
  69 #include "mac.h"
  70 #include "sshtty.h"
  71
  72 #ifdef SMARTCARD
  73 #include "scard.h"
  74 #endif
  75
  76 #ifdef HAVE___PROGNAME
  77 extern char *__progname;
  78 #else
  79 char *__progname;
  80 #endif
  81
  82 /* Flag indicating whether IPv4 or IPv6.  This can be set on the command line.
  83    Default value is AF_UNSPEC means both IPv4 and IPv6. */
  84 #ifdef IPV4_DEFAULT
  85 int IPv4or6 = AF_INET;
  86 #else
  87 int IPv4or6 = AF_UNSPEC;
  88 #endif
  89
  90 /* Flag indicating whether debug mode is on.  This can be set on the command line. */
  91 int debug_flag = 0;
  92
  93 /* Flag indicating whether a tty should be allocated */
  94 int tty_flag = 0;
  95 int no_tty_flag = 0;
  96 int force_tty_flag = 0;
  97
  98 /* don't exec a shell */
  99 int no_shell_flag = 0;
 100
 101 /*
 102  * Flag indicating that nothing should be read from stdin.  This can be set
 103  * on the command line.
 104  */
 105 int stdin_null_flag = 0;
 106
 107 /*
 108  * Flag indicating that ssh should fork after authentication.  This is useful
 109  * so that the passphrase can be entered manually, and then ssh goes to the
 110  * background.
 111  */
 112 int fork_after_authentication_flag = 0;
 113
 114 /*
 115  * General data structure for command line options and options configurable
 116  * in configuration files.  See readconf.h.
 117  */
 118 Options options;
 119
 120 /* optional user configfile */
 121 char *config = NULL;
 122
 123 /*
 124  * Name of the host we are connecting to.  This is the name given on the
 125  * command line, or the HostName specified for the user-supplied name in a
 126  * configuration file.
 127  */
 128 char *host;
 129
 130 /* socket address the host resolves to */
 131 struct sockaddr_storage hostaddr;
 132
 133 /* Private host keys. */
 134 Sensitive sensitive_data;
 135
 136 /* Original real UID. */
 137 uid_t original_real_uid;
 138 uid_t original_effective_uid;
 139
 140 /* command to be executed */
 141 Buffer command;
 142
 143 /* Should we execute a command or invoke a subsystem? */
 144 int subsystem_flag = 0;
 145
 146 /* # of replies received for global requests */
 147 static int client_global_request_id = 0;
 148
 149 /* Prints a help message to the user.  This function never returns. */
 150
 151 static void
 152 usage(void)
 153 {
 154         fprintf(stderr, "Usage: %s [options] host [command]\n", __progname);
 155         fprintf(stderr, "Options:\n");
 156         fprintf(stderr, "  -l user     Log in using this user name.\n");
 157         fprintf(stderr, "  -n          Redirect input from " _PATH_DEVNULL ".\n");
 158         fprintf(stderr, "  -F config   Config file (default: ~/%s).\n",
 159              _PATH_SSH_USER_CONFFILE);
 160         fprintf(stderr, "  -A          Enable authentication agent forwarding.\n");
 161         fprintf(stderr, "  -a          Disable authentication agent forwarding (default).\n");
 162 #ifdef AFS
 163         fprintf(stderr, "  -k          Disable Kerberos ticket and AFS token forwarding.\n");
 164 #endif                          /* AFS */
 165         fprintf(stderr, "  -X          Enable X11 connection forwarding.\n");
 166         fprintf(stderr, "  -x          Disable X11 connection forwarding (default).\n");
 167         fprintf(stderr, "  -i file     Identity for public key authentication "
 168             "(default: ~/.ssh/identity)\n");
 169 #ifdef SMARTCARD
 170         fprintf(stderr, "  -I reader   Set smartcard reader.\n");
 171 #endif
 172         fprintf(stderr, "  -t          Tty; allocate a tty even if command is given.\n");
 173         fprintf(stderr, "  -T          Do not allocate a tty.\n");
 174         fprintf(stderr, "  -v          Verbose; display verbose debugging messages.\n");
 175         fprintf(stderr, "              Multiple -v increases verbosity.\n");
 176         fprintf(stderr, "  -V          Display version number only.\n");
 177         fprintf(stderr, "  -P          Don't allocate a privileged port.\n");
 178         fprintf(stderr, "  -q          Quiet; don't display any warning messages.\n");
 179         fprintf(stderr, "  -f          Fork into background after authentication.\n");
 180         fprintf(stderr, "  -e char     Set escape character; ``none'' = disable (default: ~).\n");
 181
 182         fprintf(stderr, "  -c cipher   Select encryption algorithm\n");
 183         fprintf(stderr, "  -m macs     Specify MAC algorithms for protocol version 2.\n");
 184         fprintf(stderr, "  -p port     Connect to this port.  Server must be on the same port.\n");
 185         fprintf(stderr, "  -L listen-port:host:port   Forward local port to remote address\n");
 186         fprintf(stderr, "  -R listen-port:host:port   Forward remote port to local address\n");
 187         fprintf(stderr, "              These cause %s to listen for connections on a port, and\n", __progname);
 188         fprintf(stderr, "              forward them to the other side by connecting to host:port.\n");
 189         fprintf(stderr, "  -D port     Enable dynamic application-level port forwarding.\n");
 190         fprintf(stderr, "  -C          Enable compression.\n");
 191         fprintf(stderr, "  -N          Do not execute a shell or command.\n");
 192         fprintf(stderr, "  -g          Allow remote hosts to connect to forwarded ports.\n");
 193         fprintf(stderr, "  -1          Force protocol version 1.\n");
 194         fprintf(stderr, "  -2          Force protocol version 2.\n");
 195         fprintf(stderr, "  -4          Use IPv4 only.\n");
 196         fprintf(stderr, "  -6          Use IPv6 only.\n");
 197         fprintf(stderr, "  -o 'option' Process the option as if it was read from a configuration file.\n");
 198         fprintf(stderr, "  -s          Invoke command (mandatory) as SSH2 subsystem.\n");
 199         fprintf(stderr, "  -b addr     Local IP address.\n");
 200         exit(1);
 201 }
 202
 203 static int ssh_session(void);
 204 static int ssh_session2(void);
 205 static void load_public_identity_files(void);
 206
 207 /*
 208  * Main program for the ssh client.
 209  */
 210 int
 211 main(int ac, char **av)
 212 {
 213         int i, opt, exit_status;
 214         u_short fwd_port, fwd_host_port;
 215         char sfwd_port[6], sfwd_host_port[6];
 216         char *p, *cp, buf[256];
 217         struct stat st;
 218         struct passwd *pw;
 219         int dummy;
 220         extern int optind, optreset;
 221         extern char *optarg;
 222
 223         __progname = get_progname(av[0]);
 224         init_rng();
 225
 226         /*
 227          * Save the original real uid.  It will be needed later (uid-swapping
 228          * may clobber the real uid).
 229          */
 230         original_real_uid = getuid();
 231         original_effective_uid = geteuid();
 232
 233 #ifdef HAVE_SETRLIMIT
 234         /* If we are installed setuid root be careful to not drop core. */
 235         if (original_real_uid != original_effective_uid) {
 236                 struct rlimit rlim;
 237                 rlim.rlim_cur = rlim.rlim_max = 0;
 238                 if (setrlimit(RLIMIT_CORE, &rlim) < 0)
 239                         fatal("setrlimit failed: %.100s", strerror(errno));
 240         }
 241 #endif
 242         /* Get user data. */
 243         pw = getpwuid(original_real_uid);
 244         if (!pw) {
 245                 log("You don't exist, go away!");
 246                 exit(1);
 247         }
 248         /* Take a copy of the returned structure. */
 249         pw = pwcopy(pw);
 250
 251         /*
 252          * Use uid-swapping to give up root privileges for the duration of
 253          * option processing.  We will re-instantiate the rights when we are
 254          * ready to create the privileged port, and will permanently drop
 255          * them when the port has been created (actually, when the connection
 256          * has been made, as we may need to create the port several times).
 257          */
 258         PRIV_END;
 259
 260         /*
 261          * Set our umask to something reasonable, as some files are created
 262          * with the default umask.  This will make them world-readable but
 263          * writable only by the owner, which is ok for all files for which we
 264          * don't set the modes explicitly.
 265          */
 266         umask(022);
 267
 268         /* Initialize option structure to indicate that no values have been set. */
 269         initialize_options(&options);
 270
 271         /* Parse command-line arguments. */
 272         host = NULL;
 273
 274 again:
 275         while ((opt = getopt(ac, av,
 276             "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:NPR:TVX")) != -1) {
 277                 switch (opt) {
 278                 case '1':
 279                         options.protocol = SSH_PROTO_1;
 280                         break;
 281                 case '2':
 282                         options.protocol = SSH_PROTO_2;
 283                         break;
 284                 case '4':
 285                         IPv4or6 = AF_INET;
 286                         break;
 287                 case '6':
 288                         IPv4or6 = AF_INET6;
 289                         break;
 290                 case 'n':
 291                         stdin_null_flag = 1;
 292                         break;
 293                 case 'f':
 294                         fork_after_authentication_flag = 1;
 295                         stdin_null_flag = 1;
 296                         break;
 297                 case 'x':
 298                         options.forward_x11 = 0;
 299                         break;
 300                 case 'X':
 301                         options.forward_x11 = 1;
 302                         break;
 303                 case 'g':
 304                         options.gateway_ports = 1;
 305                         break;
 306                 case 'P':
 307                         options.use_privileged_port = 0;
 308                         break;
 309                 case 'a':
 310                         options.forward_agent = 0;
 311                         break;
 312                 case 'A':
 313                         options.forward_agent = 1;
 314                         break;
 315 #ifdef AFS
 316                 case 'k':
 317                         options.kerberos_tgt_passing = 0;
 318                         options.afs_token_passing = 0;
 319                         break;
 320 #endif
 321                 case 'i':
 322                         if (stat(optarg, &st) < 0) {
 323                                 fprintf(stderr, "Warning: Identity file %s "
 324                                     "does not exist.\n", optarg);
 325                                 break;
 326                         }
 327                         if (options.num_identity_files >=
 328                             SSH_MAX_IDENTITY_FILES)
 329                                 fatal("Too many identity files specified "
 330                                     "(max %d)", SSH_MAX_IDENTITY_FILES);
 331                         options.identity_files[options.num_identity_files++] =
 332                             xstrdup(optarg);
 333                         break;
 334                 case 'I':
 335 #ifdef SMARTCARD
 336                         options.smartcard_device = xstrdup(optarg);
 337 #else
 338                         fprintf(stderr, "no support for smartcards.\n");
 339 #endif
 340                         break;
 341                 case 't':
 342                         if (tty_flag)
 343                                 force_tty_flag = 1;
 344                         tty_flag = 1;
 345                         break;
 346                 case 'v':
 347                         if (0 == debug_flag) {
 348                                 debug_flag = 1;
 349                                 options.log_level = SYSLOG_LEVEL_DEBUG1;
 350                         } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
 351                                 options.log_level++;
 352                                 break;
 353                         } else
 354                                 fatal("Too high debugging level.");
 355                         /* fallthrough */
 356                 case 'V':
 357                         fprintf(stderr,
 358                             "%s, SSH protocols %d.%d/%d.%d, OpenSSL 0x%8.8lx\n",
 359                             SSH_VERSION,
 360                             PROTOCOL_MAJOR_1, PROTOCOL_MINOR_1,
 361                             PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2,
 362                             SSLeay());
 363                         if (opt == 'V')
 364                                 exit(0);
 365                         break;
 366                 case 'q':
 367                         options.log_level = SYSLOG_LEVEL_QUIET;
 368                         break;
 369                 case 'e':
 370                         if (optarg[0] == '^' && optarg[2] == 0 &&
 371                             (u_char) optarg[1] >= 64 &&
 372                             (u_char) optarg[1] < 128)
 373                                 options.escape_char = (u_char) optarg[1] & 31;
 374                         else if (strlen(optarg) == 1)
 375                                 options.escape_char = (u_char) optarg[0];
 376                         else if (strcmp(optarg, "none") == 0)
 377                                 options.escape_char = SSH_ESCAPECHAR_NONE;
 378                         else {
 379                                 fprintf(stderr, "Bad escape character '%s'.\n",
 380                                     optarg);
 381                                 exit(1);
 382                         }
 383                         break;
 384                 case 'c':
 385                         if (ciphers_valid(optarg)) {
 386                                 /* SSH2 only */
 387                                 options.ciphers = xstrdup(optarg);
 388                                 options.cipher = SSH_CIPHER_ILLEGAL;
 389                         } else {
 390                                 /* SSH1 only */
 391                                 options.cipher = cipher_number(optarg);
 392                                 if (options.cipher == -1) {
 393                                         fprintf(stderr,
 394                                             "Unknown cipher type '%s'\n",
 395                                             optarg);
 396                                         exit(1);
 397                                 }
 398                                 if (options.cipher == SSH_CIPHER_3DES)
 399                                         options.ciphers = "3des-cbc";
 400                                 else if (options.cipher == SSH_CIPHER_BLOWFISH)
 401                                         options.ciphers = "blowfish-cbc";
 402                                 else
 403                                         options.ciphers = (char *)-1;
 404                         }
 405                         break;
 406                 case 'm':
 407                         if (mac_valid(optarg))
 408                                 options.macs = xstrdup(optarg);
 409                         else {
 410                                 fprintf(stderr, "Unknown mac type '%s'\n",
 411                                     optarg);
 412                                 exit(1);
 413                         }
 414                         break;
 415                 case 'p':
 416                         options.port = a2port(optarg);
 417                         if (options.port == 0) {
 418                                 fprintf(stderr, "Bad port '%s'\n", optarg);
 419                                 exit(1);
 420                         }
 421                         break;
 422                 case 'l':
 423                         options.user = optarg;
 424                         break;
 425
 426                 case 'L':
 427                 case 'R':
 428                         if (sscanf(optarg, "%5[0-9]:%255[^:]:%5[0-9]",
 429                             sfwd_port, buf, sfwd_host_port) != 3 &&
 430                             sscanf(optarg, "%5[0-9]/%255[^/]/%5[0-9]",
 431                             sfwd_port, buf, sfwd_host_port) != 3) {
 432                                 fprintf(stderr,
 433                                     "Bad forwarding specification '%s'\n",
 434                                     optarg);
 435                                 usage();
 436                                 /* NOTREACHED */
 437                         }
 438                         if ((fwd_port = a2port(sfwd_port)) == 0 ||
 439                             (fwd_host_port = a2port(sfwd_host_port)) == 0) {
 440                                 fprintf(stderr,
 441                                     "Bad forwarding port(s) '%s'\n", optarg);
 442                                 exit(1);
 443                         }
 444                         if (opt == 'L')
 445                                 add_local_forward(&options, fwd_port, buf,
 446                                     fwd_host_port);
 447                         else if (opt == 'R')
 448                                 add_remote_forward(&options, fwd_port, buf,
 449                                     fwd_host_port);
 450                         break;
 451
 452                 case 'D':
 453                         fwd_port = a2port(optarg);
 454                         if (fwd_port == 0) {
 455                                 fprintf(stderr, "Bad dynamic port '%s'\n",
 456                                     optarg);
 457                                 exit(1);
 458                         }
 459                         add_local_forward(&options, fwd_port, "socks4", 0);
 460                         break;
 461
 462                 case 'C':
 463                         options.compression = 1;
 464                         break;
 465                 case 'N':
 466                         no_shell_flag = 1;
 467                         no_tty_flag = 1;
 468                         break;
 469                 case 'T':
 470                         no_tty_flag = 1;
 471                         break;
 472                 case 'o':
 473                         dummy = 1;
 474                         if (process_config_line(&options, host ? host : "",
 475                             optarg, "command-line", 0, &dummy) != 0)
 476                                 exit(1);
 477                         break;
 478                 case 's':
 479                         subsystem_flag = 1;
 480                         break;
 481                 case 'b':
 482                         options.bind_address = optarg;
 483                         break;
 484                 case 'F':
 485                         config = optarg;
 486                         break;
 487                 default:
 488                         usage();
 489                 }
 490         }
 491
 492         ac -= optind;
 493         av += optind;
 494
 495         if (ac > 0 && !host && **av != '-') {
 496                 if (strchr(*av, '@')) {
 497                         p = xstrdup(*av);
 498                         cp = strchr(p, '@');
 499                         if (cp == NULL || cp == p)
 500                                 usage();
 501                         options.user = p;
 502                         *cp = '\0';
 503                         host = ++cp;
 504                 } else
 505                         host = *av;
 506                 ac--, av++;
 507                 if (ac > 0) {
 508                         optind = 0;
 509                         optreset = 1;
 510                         goto again;
 511                 }
 512         }
 513
 514         /* Check that we got a host name. */
 515         if (!host)
 516                 usage();
 517
 518         SSLeay_add_all_algorithms();
 519         ERR_load_crypto_strings();
 520         channel_set_af(IPv4or6);
 521
 522         /* Initialize the command to execute on remote host. */
 523         buffer_init(&command);
 524
 525         /*
 526          * Save the command to execute on the remote host in a buffer. There
 527          * is no limit on the length of the command, except by the maximum
 528          * packet size.  Also sets the tty flag if there is no command.
 529          */
 530         if (!ac) {
 531                 /* No command specified - execute shell on a tty. */
 532                 tty_flag = 1;
 533                 if (subsystem_flag) {
 534                         fprintf(stderr,
 535                             "You must specify a subsystem to invoke.\n");
 536                         usage();
 537                 }
 538         } else {
 539                 /* A command has been specified.  Store it into the buffer. */
 540                 for (i = 0; i < ac; i++) {
 541                         if (i)
 542                                 buffer_append(&command, " ", 1);
 543                         buffer_append(&command, av[i], strlen(av[i]));
 544                 }
 545         }
 546
 547         /* Cannot fork to background if no command. */
 548         if (fork_after_authentication_flag && buffer_len(&command) == 0 && !no_shell_flag)
 549                 fatal("Cannot fork into background without a command to execute.");
 550
 551         /* Allocate a tty by default if no command specified. */
 552         if (buffer_len(&command) == 0)
 553                 tty_flag = 1;
 554
 555         /* Force no tty */
 556         if (no_tty_flag)
 557                 tty_flag = 0;
 558         /* Do not allocate a tty if stdin is not a tty. */
 559         if (!isatty(fileno(stdin)) && !force_tty_flag) {
 560                 if (tty_flag)
 561                         log("Pseudo-terminal will not be allocated because stdin is not a terminal.");
 562                 tty_flag = 0;
 563         }
 564
 565         /*
 566          * Initialize "log" output.  Since we are the client all output
 567          * actually goes to stderr.
 568          */
 569         log_init(av[0], options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
 570             SYSLOG_FACILITY_USER, 1);
 571
 572         /*
 573          * Read per-user configuration file.  Ignore the system wide config
 574          * file if the user specifies a config file on the command line.
 575          */
 576         if (config != NULL) {
 577                 if (!read_config_file(config, host, &options))
 578                         fatal("Can't open user config file %.100s: "
 579                             "%.100s", config, strerror(errno));
 580         } else  {
 581                 snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir,
 582                     _PATH_SSH_USER_CONFFILE);
 583                 (void)read_config_file(buf, host, &options);
 584
 585                 /* Read systemwide configuration file after use config. */
 586                 (void)read_config_file(_PATH_HOST_CONFIG_FILE, host, &options);
 587         }
 588
 589         /* Fill configuration defaults. */
 590         fill_default_options(&options);
 591
 592         /* reinit */
 593         log_init(av[0], options.log_level, SYSLOG_FACILITY_USER, 1);
 594
 595         seed_rng();
 596
 597         if (options.user == NULL)
 598                 options.user = xstrdup(pw->pw_name);
 599
 600         if (options.hostname != NULL)
 601                 host = options.hostname;
 602
 603         /* Disable rhosts authentication if not running as root. */
 604 #ifdef HAVE_CYGWIN
 605         /* Ignore uid if running under Windows */
 606         if (!options.use_privileged_port) {
 607 #else
 608         if (original_effective_uid != 0 || !options.use_privileged_port) {
 609 #endif
 610                 debug("Rhosts Authentication disabled, "
 611                     "originating port will not be trusted.");
 612                 options.rhosts_authentication = 0;
 613         }
 614         /* Open a connection to the remote host. */
 615
 616         if (ssh_connect(host, &hostaddr, options.port, IPv4or6,
 617             options.connection_attempts,
 618 #ifdef HAVE_CYGWIN
 619             options.use_privileged_port,
 620 #else
 621             original_effective_uid == 0 && options.use_privileged_port,
 622 #endif
 623             options.proxy_command) != 0)
 624                 exit(1);
 625
 626         /*
 627          * If we successfully made the connection, load the host private key
 628          * in case we will need it later for combined rsa-rhosts
 629          * authentication. This must be done before releasing extra
 630          * privileges, because the file is only readable by root.
 631          * If we cannot access the private keys, load the public keys
 632          * instead and try to execute the ssh-keysign helper instead.
 633          */
 634         sensitive_data.nkeys = 0;
 635         sensitive_data.keys = NULL;
 636         sensitive_data.external_keysign = 0;
 637         if (options.rhosts_rsa_authentication ||
 638             options.hostbased_authentication) {
 639                 sensitive_data.nkeys = 3;
 640                 sensitive_data.keys = xmalloc(sensitive_data.nkeys *
 641                     sizeof(Key));
 642
 643                 PRIV_START;
 644                 sensitive_data.keys[0] = key_load_private_type(KEY_RSA1,
 645                     _PATH_HOST_KEY_FILE, "", NULL);
 646                 sensitive_data.keys[1] = key_load_private_type(KEY_DSA,
 647                     _PATH_HOST_DSA_KEY_FILE, "", NULL);
 648                 sensitive_data.keys[2] = key_load_private_type(KEY_RSA,
 649                     _PATH_HOST_RSA_KEY_FILE, "", NULL);
 650                 PRIV_END;
 651
 652                 if (options.hostbased_authentication == 1 &&
 653                     sensitive_data.keys[0] == NULL &&
 654                     sensitive_data.keys[1] == NULL &&
 655                     sensitive_data.keys[2] == NULL) {
 656                         sensitive_data.keys[1] = key_load_public(
 657                             _PATH_HOST_DSA_KEY_FILE, NULL);
 658                         sensitive_data.keys[2] = key_load_public(
 659                             _PATH_HOST_RSA_KEY_FILE, NULL);
 660                         sensitive_data.external_keysign = 1;
 661                 }
 662         }
 663         /*
 664          * Get rid of any extra privileges that we may have.  We will no
 665          * longer need them.  Also, extra privileges could make it very hard
 666          * to read identity files and other non-world-readable files from the
 667          * user's home directory if it happens to be on a NFS volume where
 668          * root is mapped to nobody.
 669          */
 670         seteuid(original_real_uid);
 671         setuid(original_real_uid);
 672
 673         /*
 674          * Now that we are back to our own permissions, create ~/.ssh
 675          * directory if it doesn\'t already exist.
 676          */
 677         snprintf(buf, sizeof buf, "%.100s%s%.100s", pw->pw_dir, strcmp(pw->pw_dir, "/") ? "/" : "", _PATH_SSH_USER_DIR);
 678         if (stat(buf, &st) < 0)
 679                 if (mkdir(buf, 0700) < 0)
 680                         error("Could not create directory '%.200s'.", buf);
 681
 682         /* load options.identity_files */
 683         load_public_identity_files();
 684
 685         /* Expand ~ in known host file names. */
 686         /* XXX mem-leaks: */
 687         options.system_hostfile =
 688             tilde_expand_filename(options.system_hostfile, original_real_uid);
 689         options.user_hostfile =
 690             tilde_expand_filename(options.user_hostfile, original_real_uid);
 691         options.system_hostfile2 =
 692             tilde_expand_filename(options.system_hostfile2, original_real_uid);
 693         options.user_hostfile2 =
 694             tilde_expand_filename(options.user_hostfile2, original_real_uid);
 695
 696         signal(SIGPIPE, SIG_IGN); /* ignore SIGPIPE early */
 697
 698         /* Log into the remote system.  This never returns if the login fails. */
 699         ssh_login(&sensitive_data, host, (struct sockaddr *)&hostaddr, pw);
 700
 701         /* We no longer need the private host keys.  Clear them now. */
 702         if (sensitive_data.nkeys != 0) {
 703                 for (i = 0; i < sensitive_data.nkeys; i++) {
 704                         if (sensitive_data.keys[i] != NULL) {
 705                                 /* Destroys contents safely */
 706                                 debug3("clear hostkey %d", i);
 707                                 key_free(sensitive_data.keys[i]);
 708                                 sensitive_data.keys[i] = NULL;
 709                         }
 710                 }
 711                 xfree(sensitive_data.keys);
 712         }
 713         for (i = 0; i < options.num_identity_files; i++) {
 714                 if (options.identity_files[i]) {
 715                         xfree(options.identity_files[i]);
 716                         options.identity_files[i] = NULL;
 717                 }
 718                 if (options.identity_keys[i]) {
 719                         key_free(options.identity_keys[i]);
 720                         options.identity_keys[i] = NULL;
 721                 }
 722         }
 723
 724         exit_status = compat20 ? ssh_session2() : ssh_session();
 725         packet_close();
 726         return exit_status;
 727 }
 728
 729 static void
 730 x11_get_proto(char **_proto, char **_data)
 731 {
 732         char line[512];
 733         static char proto[512], data[512];
 734         FILE *f;
 735         int got_data = 0, i;
 736         char *display;
 737
 738         *_proto = proto;
 739         *_data = data;
 740         proto[0] = data[0] = '\0';
 741         if (options.xauth_location && (display = getenv("DISPLAY"))) {
 742                 /* Try to get Xauthority information for the display. */
 743                 if (strncmp(display, "localhost:", 10) == 0)
 744                         /*
 745                          * Handle FamilyLocal case where $DISPLAY does
 746                          * not match an authorization entry.  For this we
 747                          * just try "xauth list unix:displaynum.screennum".
 748                          * XXX: "localhost" match to determine FamilyLocal
 749                          *      is not perfect.
 750                          */
 751                         snprintf(line, sizeof line, "%s list unix:%s 2>"
 752                             _PATH_DEVNULL, options.xauth_location, display+10);
 753                 else
 754                         snprintf(line, sizeof line, "%s list %.200s 2>"
 755                             _PATH_DEVNULL, options.xauth_location, display);
 756                 debug2("x11_get_proto %s", line);
 757                 f = popen(line, "r");
 758                 if (f && fgets(line, sizeof(line), f) &&
 759                     sscanf(line, "%*s %511s %511s", proto, data) == 2)
 760                         got_data = 1;
 761                 if (f)
 762                         pclose(f);
 763         }
 764         /*
 765          * If we didn't get authentication data, just make up some
 766          * data.  The forwarding code will check the validity of the
 767          * response anyway, and substitute this data.  The X11
 768          * server, however, will ignore this fake data and use
 769          * whatever authentication mechanisms it was using otherwise
 770          * for the local connection.
 771          */
 772         if (!got_data) {
 773                 u_int32_t rand = 0;
 774
 775                 strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto);
 776                 for (i = 0; i < 16; i++) {
 777                         if (i % 4 == 0)
 778                                 rand = arc4random();
 779                         snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff);
 780                         rand >>= 8;
 781                 }
 782         }
 783 }
 784
 785 static void
 786 ssh_init_forwarding(void)
 787 {
 788         int success = 0;
 789         int i;
 790
 791         /* Initiate local TCP/IP port forwardings. */
 792         for (i = 0; i < options.num_local_forwards; i++) {
 793                 debug("Connections to local port %d forwarded to remote address %.200s:%d",
 794                     options.local_forwards[i].port,
 795                     options.local_forwards[i].host,
 796                     options.local_forwards[i].host_port);
 797                 success += channel_setup_local_fwd_listener(
 798                     options.local_forwards[i].port,
 799                     options.local_forwards[i].host,
 800                     options.local_forwards[i].host_port,
 801                     options.gateway_ports);
 802         }
 803         if (i > 0 && success == 0)
 804                 error("Could not request local forwarding.");
 805
 806         /* Initiate remote TCP/IP port forwardings. */
 807         for (i = 0; i < options.num_remote_forwards; i++) {
 808                 debug("Connections to remote port %d forwarded to local address %.200s:%d",
 809                     options.remote_forwards[i].port,
 810                     options.remote_forwards[i].host,
 811                     options.remote_forwards[i].host_port);
 812                 channel_request_remote_forwarding(
 813                     options.remote_forwards[i].port,
 814                     options.remote_forwards[i].host,
 815                     options.remote_forwards[i].host_port);
 816         }
 817 }
 818
 819 static void
 820 check_agent_present(void)
 821 {
 822         if (options.forward_agent) {
 823                 /* Clear agent forwarding if we don\'t have an agent. */
 824                 int authfd = ssh_get_authentication_socket();
 825                 if (authfd < 0)
 826                         options.forward_agent = 0;
 827                 else
 828                         ssh_close_authentication_socket(authfd);
 829         }
 830 }
 831
 832 static int
 833 ssh_session(void)
 834 {
 835         int type;
 836         int interactive = 0;
 837         int have_tty = 0;
 838         struct winsize ws;
 839         char *cp;
 840
 841         /* Enable compression if requested. */
 842         if (options.compression) {
 843                 debug("Requesting compression at level %d.", options.compression_level);
 844
 845                 if (options.compression_level < 1 || options.compression_level > 9)
 846                         fatal("Compression level must be from 1 (fast) to 9 (slow, best).");
 847
 848                 /* Send the request. */
 849                 packet_start(SSH_CMSG_REQUEST_COMPRESSION);
 850                 packet_put_int(options.compression_level);
 851                 packet_send();
 852                 packet_write_wait();
 853                 type = packet_read();
 854                 if (type == SSH_SMSG_SUCCESS)
 855                         packet_start_compression(options.compression_level);
 856                 else if (type == SSH_SMSG_FAILURE)
 857                         log("Warning: Remote host refused compression.");
 858                 else
 859                         packet_disconnect("Protocol error waiting for compression response.");
 860         }
 861         /* Allocate a pseudo tty if appropriate. */
 862         if (tty_flag) {
 863                 debug("Requesting pty.");
 864
 865                 /* Start the packet. */
 866                 packet_start(SSH_CMSG_REQUEST_PTY);
 867
 868                 /* Store TERM in the packet.  There is no limit on the
 869                    length of the string. */
 870                 cp = getenv("TERM");
 871                 if (!cp)
 872                         cp = "";
 873                 packet_put_cstring(cp);
 874
 875                 /* Store window size in the packet. */
 876                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
 877                         memset(&ws, 0, sizeof(ws));
 878                 packet_put_int(ws.ws_row);
 879                 packet_put_int(ws.ws_col);
 880                 packet_put_int(ws.ws_xpixel);
 881                 packet_put_int(ws.ws_ypixel);
 882
 883                 /* Store tty modes in the packet. */
 884                 tty_make_modes(fileno(stdin), NULL);
 885
 886                 /* Send the packet, and wait for it to leave. */
 887                 packet_send();
 888                 packet_write_wait();
 889
 890                 /* Read response from the server. */
 891                 type = packet_read();
 892                 if (type == SSH_SMSG_SUCCESS) {
 893                         interactive = 1;
 894                         have_tty = 1;
 895                 } else if (type == SSH_SMSG_FAILURE)
 896                         log("Warning: Remote host failed or refused to allocate a pseudo tty.");
 897                 else
 898                         packet_disconnect("Protocol error waiting for pty request response.");
 899         }
 900         /* Request X11 forwarding if enabled and DISPLAY is set. */
 901         if (options.forward_x11 && getenv("DISPLAY") != NULL) {
 902                 char *proto, *data;
 903                 /* Get reasonable local authentication information. */
 904                 x11_get_proto(&proto, &data);
 905                 /* Request forwarding with authentication spoofing. */
 906                 debug("Requesting X11 forwarding with authentication spoofing.");
 907                 x11_request_forwarding_with_spoofing(0, proto, data);
 908
 909                 /* Read response from the server. */
 910                 type = packet_read();
 911                 if (type == SSH_SMSG_SUCCESS) {
 912                         interactive = 1;
 913                 } else if (type == SSH_SMSG_FAILURE) {
 914                         log("Warning: Remote host denied X11 forwarding.");
 915                 } else {
 916                         packet_disconnect("Protocol error waiting for X11 forwarding");
 917                 }
 918         }
 919         /* Tell the packet module whether this is an interactive session. */
 920         packet_set_interactive(interactive);
 921
 922         /* Request authentication agent forwarding if appropriate. */
 923         check_agent_present();
 924
 925         if (options.forward_agent) {
 926                 debug("Requesting authentication agent forwarding.");
 927                 auth_request_forwarding();
 928
 929                 /* Read response from the server. */
 930                 type = packet_read();
 931                 packet_check_eom();
 932                 if (type != SSH_SMSG_SUCCESS)
 933                         log("Warning: Remote host denied authentication agent forwarding.");
 934         }
 935
 936         /* Initiate port forwardings. */
 937         ssh_init_forwarding();
 938
 939         /* If requested, let ssh continue in the background. */
 940         if (fork_after_authentication_flag)
 941                 if (daemon(1, 1) < 0)
 942                         fatal("daemon() failed: %.200s", strerror(errno));
 943
 944         /*
 945          * If a command was specified on the command line, execute the
 946          * command now. Otherwise request the server to start a shell.
 947          */
 948         if (buffer_len(&command) > 0) {
 949                 int len = buffer_len(&command);
 950                 if (len > 900)
 951                         len = 900;
 952                 debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
 953                 packet_start(SSH_CMSG_EXEC_CMD);
 954                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
 955                 packet_send();
 956                 packet_write_wait();
 957         } else {
 958                 debug("Requesting shell.");
 959                 packet_start(SSH_CMSG_EXEC_SHELL);
 960                 packet_send();
 961                 packet_write_wait();
 962         }
 963
 964         /* Enter the interactive session. */
 965         return client_loop(have_tty, tty_flag ?
 966             options.escape_char : SSH_ESCAPECHAR_NONE, 0);
 967 }
 968
 969 static void
 970 client_subsystem_reply(int type, u_int32_t seq, void *ctxt)
 971 {
 972         int id, len;
 973
 974         id = packet_get_int();
 975         len = buffer_len(&command);
 976         if (len > 900)
 977                 len = 900;
 978         packet_check_eom();
 979         if (type == SSH2_MSG_CHANNEL_FAILURE)
 980                 fatal("Request for subsystem '%.*s' failed on channel %d",
 981                     len, (u_char *)buffer_ptr(&command), id);
 982 }
 983
 984 void
 985 client_global_request_reply(int type, u_int32_t seq, void *ctxt)
 986 {
 987         int i;
 988
 989         i = client_global_request_id++;
 990         if (i >= options.num_remote_forwards) {
 991                 debug("client_global_request_reply: too many replies %d > %d",
 992                     i, options.num_remote_forwards);
 993                 return;
 994         }
 995         debug("remote forward %s for: listen %d, connect %s:%d",
 996             type == SSH2_MSG_REQUEST_SUCCESS ? "success" : "failure",
 997             options.remote_forwards[i].port,
 998             options.remote_forwards[i].host,
 999             options.remote_forwards[i].host_port);
1000         if (type == SSH2_MSG_REQUEST_FAILURE)
1001                 log("Warning: remote port forwarding failed for listen port %d",
1002                     options.remote_forwards[i].port);
1003 }
1004
1005 /* request pty/x11/agent/tcpfwd/shell for channel */
1006 static void
1007 ssh_session2_setup(int id, void *arg)
1008 {
1009         int len;
1010         int interactive = 0;
1011         struct termios tio;
1012
1013         debug("ssh_session2_setup: id %d", id);
1014
1015         if (tty_flag) {
1016                 struct winsize ws;
1017                 char *cp;
1018                 cp = getenv("TERM");
1019                 if (!cp)
1020                         cp = "";
1021                 /* Store window size in the packet. */
1022                 if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
1023                         memset(&ws, 0, sizeof(ws));
1024
1025                 channel_request_start(id, "pty-req", 0);
1026                 packet_put_cstring(cp);
1027                 packet_put_int(ws.ws_col);
1028                 packet_put_int(ws.ws_row);
1029                 packet_put_int(ws.ws_xpixel);
1030                 packet_put_int(ws.ws_ypixel);
1031                 tio = get_saved_tio();
1032                 tty_make_modes(/*ignored*/ 0, &tio);
1033                 packet_send();
1034                 interactive = 1;
1035                 /* XXX wait for reply */
1036         }
1037         if (options.forward_x11 &&
1038             getenv("DISPLAY") != NULL) {
1039                 char *proto, *data;
1040                 /* Get reasonable local authentication information. */
1041                 x11_get_proto(&proto, &data);
1042                 /* Request forwarding with authentication spoofing. */
1043                 debug("Requesting X11 forwarding with authentication spoofing.");
1044                 x11_request_forwarding_with_spoofing(id, proto, data);
1045                 interactive = 1;
1046                 /* XXX wait for reply */
1047         }
1048
1049         check_agent_present();
1050         if (options.forward_agent) {
1051                 debug("Requesting authentication agent forwarding.");
1052                 channel_request_start(id, "auth-agent-req@openssh.com", 0);
1053                 packet_send();
1054         }
1055
1056         len = buffer_len(&command);
1057         if (len > 0) {
1058                 if (len > 900)
1059                         len = 900;
1060                 if (subsystem_flag) {
1061                         debug("Sending subsystem: %.*s", len, (u_char *)buffer_ptr(&command));
1062                         channel_request_start(id, "subsystem", /*want reply*/ 1);
1063                         /* register callback for reply */
1064                         /* XXX we assume that client_loop has already been called */
1065                         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &client_subsystem_reply);
1066                         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &client_subsystem_reply);
1067                 } else {
1068                         debug("Sending command: %.*s", len, (u_char *)buffer_ptr(&command));
1069                         channel_request_start(id, "exec", 0);
1070                 }
1071                 packet_put_string(buffer_ptr(&command), buffer_len(&command));
1072                 packet_send();
1073         } else {
1074                 channel_request_start(id, "shell", 0);
1075                 packet_send();
1076         }
1077
1078         packet_set_interactive(interactive);
1079 }
1080
1081 /* open new channel for a session */
1082 static int
1083 ssh_session2_open(void)
1084 {
1085         Channel *c;
1086         int window, packetmax, in, out, err;
1087
1088         if (stdin_null_flag) {
1089                 in = open(_PATH_DEVNULL, O_RDONLY);
1090         } else {
1091                 in = dup(STDIN_FILENO);
1092         }
1093         out = dup(STDOUT_FILENO);
1094         err = dup(STDERR_FILENO);
1095
1096         if (in < 0 || out < 0 || err < 0)
1097                 fatal("dup() in/out/err failed");
1098
1099         /* enable nonblocking unless tty */
1100         if (!isatty(in))
1101                 set_nonblock(in);
1102         if (!isatty(out))
1103                 set_nonblock(out);
1104         if (!isatty(err))
1105                 set_nonblock(err);
1106
1107         window = CHAN_SES_WINDOW_DEFAULT;
1108         packetmax = CHAN_SES_PACKET_DEFAULT;
1109         if (tty_flag) {
1110                 window >>= 1;
1111                 packetmax >>= 1;
1112         }
1113         c = channel_new(
1114             "session", SSH_CHANNEL_OPENING, in, out, err,
1115             window, packetmax, CHAN_EXTENDED_WRITE,
1116             xstrdup("client-session"), /*nonblock*/0);
1117
1118         debug3("ssh_session2_open: channel_new: %d", c->self);
1119
1120         channel_send_open(c->self);
1121         if (!no_shell_flag)
1122                 channel_register_confirm(c->self, ssh_session2_setup);
1123
1124         return c->self;
1125 }
1126
1127 static int
1128 ssh_session2(void)
1129 {
1130         int id = -1;
1131
1132         /* XXX should be pre-session */
1133         ssh_init_forwarding();
1134
1135         if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
1136                 id = ssh_session2_open();
1137
1138         /* If requested, let ssh continue in the background. */
1139         if (fork_after_authentication_flag)
1140                 if (daemon(1, 1) < 0)
1141                         fatal("daemon() failed: %.200s", strerror(errno));
1142
1143         return client_loop(tty_flag, tty_flag ?
1144             options.escape_char : SSH_ESCAPECHAR_NONE, id);
1145 }
1146
1147 static void
1148 load_public_identity_files(void)
1149 {
1150         char *filename;
1151         int i = 0;
1152         Key *public;
1153 #ifdef SMARTCARD
1154         Key **keys;
1155
1156         if (options.smartcard_device != NULL &&
1157             options.num_identity_files < SSH_MAX_IDENTITY_FILES &&
1158             (keys = sc_get_keys(options.smartcard_device, NULL)) != NULL ) {
1159                 int count = 0;
1160                 for (i = 0; keys[i] != NULL; i++) {
1161                         count++;
1162                         memmove(&options.identity_files[1], &options.identity_files[0],
1163                             sizeof(char *) * (SSH_MAX_IDENTITY_FILES - 1));
1164                         memmove(&options.identity_keys[1], &options.identity_keys[0],
1165                             sizeof(Key *) * (SSH_MAX_IDENTITY_FILES - 1));
1166                         options.num_identity_files++;
1167                         options.identity_keys[0] = keys[i];
1168                         options.identity_files[0] = xstrdup("smartcard key");;
1169                 }
1170                 if (options.num_identity_files > SSH_MAX_IDENTITY_FILES)
1171                         options.num_identity_files = SSH_MAX_IDENTITY_FILES;
1172                 i = count;
1173                 xfree(keys);
1174         }
1175 #endif /* SMARTCARD */
1176         for (; i < options.num_identity_files; i++) {
1177                 filename = tilde_expand_filename(options.identity_files[i],
1178                     original_real_uid);
1179                 public = key_load_public(filename, NULL);
1180                 debug("identity file %s type %d", filename,
1181                     public ? public->type : -1);
1182                 xfree(options.identity_files[i]);
1183                 options.identity_files[i] = filename;
1184                 options.identity_keys[i] = public;
1185         }
1186 }