sshconnect.c

   1 /* $OpenBSD: sshconnect.c,v 1.193 2006/07/22 20:48:23 stevesk Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Code to connect to a remote host, and to perform the client side of the
   7  * login (authentication) dialog.
   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
  16 #include "includes.h"
  17
  18 #include <sys/types.h>
  19 #include <sys/wait.h>
  20 #include <sys/stat.h>
  21 #include <sys/socket.h>
  22
  23 #include <netinet/in.h>
  24
  25 #include <ctype.h>
  26 #include <errno.h>
  27 #include <netdb.h>
  28 #ifdef HAVE_PATHS_H
  29 #include <paths.h>
  30 #endif
  31 #include <pwd.h>
  32 #include <string.h>
  33 #include <unistd.h>
  34
  35 #include "ssh.h"
  36 #include "xmalloc.h"
  37 #include "rsa.h"
  38 #include "buffer.h"
  39 #include "packet.h"
  40 #include "uidswap.h"
  41 #include "compat.h"
  42 #include "key.h"
  43 #include "sshconnect.h"
  44 #include "hostfile.h"
  45 #include "log.h"
  46 #include "readconf.h"
  47 #include "atomicio.h"
  48 #include "misc.h"
  49 #include "dns.h"
  50 #include "version.h"
  51
  52 char *client_version_string = NULL;
  53 char *server_version_string = NULL;
  54
  55 static int matching_host_key_dns = 0;
  56
  57 /* import */
  58 extern Options options;
  59 extern char *__progname;
  60 extern uid_t original_real_uid;
  61 extern uid_t original_effective_uid;
  62 extern pid_t proxy_command_pid;
  63
  64 #ifndef INET6_ADDRSTRLEN                /* for non IPv6 machines */
  65 #define INET6_ADDRSTRLEN 46
  66 #endif
  67
  68 static int show_other_keys(const char *, Key *);
  69 static void warn_changed_key(Key *);
  70
  71 /*
  72  * Connect to the given ssh server using a proxy command.
  73  */
  74 static int
  75 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  76 {
  77         char *command_string, *tmp;
  78         int pin[2], pout[2];
  79         pid_t pid;
  80         char strport[NI_MAXSERV];
  81
  82         /* Convert the port number into a string. */
  83         snprintf(strport, sizeof strport, "%hu", port);
  84
  85         /*
  86          * Build the final command string in the buffer by making the
  87          * appropriate substitutions to the given proxy command.
  88          *
  89          * Use "exec" to avoid "sh -c" processes on some platforms
  90          * (e.g. Solaris)
  91          */
  92         xasprintf(&tmp, "exec %s", proxy_command);
  93         command_string = percent_expand(tmp, "h", host,
  94             "p", strport, (char *)NULL);
  95         xfree(tmp);
  96
  97         /* Create pipes for communicating with the proxy. */
  98         if (pipe(pin) < 0 || pipe(pout) < 0)
  99                 fatal("Could not create pipes to communicate with the proxy: %.100s",
 100                     strerror(errno));
 101
 102         debug("Executing proxy command: %.500s", command_string);
 103
 104         /* Fork and execute the proxy command. */
 105         if ((pid = fork()) == 0) {
 106                 char *argv[10];
 107
 108                 /* Child.  Permanently give up superuser privileges. */
 109                 permanently_drop_suid(original_real_uid);
 110
 111                 /* Redirect stdin and stdout. */
 112                 close(pin[1]);
 113                 if (pin[0] != 0) {
 114                         if (dup2(pin[0], 0) < 0)
 115                                 perror("dup2 stdin");
 116                         close(pin[0]);
 117                 }
 118                 close(pout[0]);
 119                 if (dup2(pout[1], 1) < 0)
 120                         perror("dup2 stdout");
 121                 /* Cannot be 1 because pin allocated two descriptors. */
 122                 close(pout[1]);
 123
 124                 /* Stderr is left as it is so that error messages get
 125                    printed on the user's terminal. */
 126                 argv[0] = _PATH_BSHELL;
 127                 argv[1] = "-c";
 128                 argv[2] = command_string;
 129                 argv[3] = NULL;
 130
 131                 /* Execute the proxy command.  Note that we gave up any
 132                    extra privileges above. */
 133                 execv(argv[0], argv);
 134                 perror(argv[0]);
 135                 exit(1);
 136         }
 137         /* Parent. */
 138         if (pid < 0)
 139                 fatal("fork failed: %.100s", strerror(errno));
 140         else
 141                 proxy_command_pid = pid; /* save pid to clean up later */
 142
 143         /* Close child side of the descriptors. */
 144         close(pin[0]);
 145         close(pout[1]);
 146
 147         /* Free the command name. */
 148         xfree(command_string);
 149
 150         /* Set the connection file descriptors. */
 151         packet_set_connection(pout[0], pin[1]);
 152
 153         /* Indicate OK return */
 154         return 0;
 155 }
 156
 157 /*
 158  * Creates a (possibly privileged) socket for use as the ssh connection.
 159  */
 160 static int
 161 ssh_create_socket(int privileged, struct addrinfo *ai)
 162 {
 163         int sock, gaierr;
 164         struct addrinfo hints, *res;
 165
 166         /*
 167          * If we are running as root and want to connect to a privileged
 168          * port, bind our own socket to a privileged port.
 169          */
 170         if (privileged) {
 171                 int p = IPPORT_RESERVED - 1;
 172                 PRIV_START;
 173                 sock = rresvport_af(&p, ai->ai_family);
 174                 PRIV_END;
 175                 if (sock < 0)
 176                         error("rresvport: af=%d %.100s", ai->ai_family,
 177                             strerror(errno));
 178                 else
 179                         debug("Allocated local port %d.", p);
 180                 return sock;
 181         }
 182         sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 183         if (sock < 0)
 184                 error("socket: %.100s", strerror(errno));
 185
 186         /* Bind the socket to an alternative local IP address */
 187         if (options.bind_address == NULL)
 188                 return sock;
 189
 190         memset(&hints, 0, sizeof(hints));
 191         hints.ai_family = ai->ai_family;
 192         hints.ai_socktype = ai->ai_socktype;
 193         hints.ai_protocol = ai->ai_protocol;
 194         hints.ai_flags = AI_PASSIVE;
 195         gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
 196         if (gaierr) {
 197                 error("getaddrinfo: %s: %s", options.bind_address,
 198                     gai_strerror(gaierr));
 199                 close(sock);
 200                 return -1;
 201         }
 202         if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
 203                 error("bind: %s: %s", options.bind_address, strerror(errno));
 204                 close(sock);
 205                 freeaddrinfo(res);
 206                 return -1;
 207         }
 208         freeaddrinfo(res);
 209         return sock;
 210 }
 211
 212 static int
 213 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
 214     socklen_t addrlen, int timeout)
 215 {
 216         fd_set *fdset;
 217         struct timeval tv;
 218         socklen_t optlen;
 219         int optval, rc, result = -1;
 220
 221         if (timeout <= 0)
 222                 return (connect(sockfd, serv_addr, addrlen));
 223
 224         set_nonblock(sockfd);
 225         rc = connect(sockfd, serv_addr, addrlen);
 226         if (rc == 0) {
 227                 unset_nonblock(sockfd);
 228                 return (0);
 229         }
 230         if (errno != EINPROGRESS)
 231                 return (-1);
 232
 233         fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
 234             sizeof(fd_mask));
 235         FD_SET(sockfd, fdset);
 236         tv.tv_sec = timeout;
 237         tv.tv_usec = 0;
 238
 239         for (;;) {
 240                 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
 241                 if (rc != -1 || errno != EINTR)
 242                         break;
 243         }
 244
 245         switch (rc) {
 246         case 0:
 247                 /* Timed out */
 248                 errno = ETIMEDOUT;
 249                 break;
 250         case -1:
 251                 /* Select error */
 252                 debug("select: %s", strerror(errno));
 253                 break;
 254         case 1:
 255                 /* Completed or failed */
 256                 optval = 0;
 257                 optlen = sizeof(optval);
 258                 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
 259                     &optlen) == -1) {
 260                         debug("getsockopt: %s", strerror(errno));
 261                         break;
 262                 }
 263                 if (optval != 0) {
 264                         errno = optval;
 265                         break;
 266                 }
 267                 result = 0;
 268                 unset_nonblock(sockfd);
 269                 break;
 270         default:
 271                 /* Should not occur */
 272                 fatal("Bogus return (%d) from select()", rc);
 273         }
 274
 275         xfree(fdset);
 276         return (result);
 277 }
 278
 279 /*
 280  * Opens a TCP/IP connection to the remote server on the given host.
 281  * The address of the remote host will be returned in hostaddr.
 282  * If port is 0, the default port will be used.  If needpriv is true,
 283  * a privileged port will be allocated to make the connection.
 284  * This requires super-user privileges if needpriv is true.
 285  * Connection_attempts specifies the maximum number of tries (one per
 286  * second).  If proxy_command is non-NULL, it specifies the command (with %h
 287  * and %p substituted for host and port, respectively) to use to contact
 288  * the daemon.
 289  */
 290 int
 291 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
 292     u_short port, int family, int connection_attempts,
 293     int needpriv, const char *proxy_command)
 294 {
 295         int gaierr;
 296         int on = 1;
 297         int sock = -1, attempt;
 298         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 299         struct addrinfo hints, *ai, *aitop;
 300
 301         debug2("ssh_connect: needpriv %d", needpriv);
 302
 303         /* If a proxy command is given, connect using it. */
 304         if (proxy_command != NULL)
 305                 return ssh_proxy_connect(host, port, proxy_command);
 306
 307         /* No proxy command. */
 308
 309         memset(&hints, 0, sizeof(hints));
 310         hints.ai_family = family;
 311         hints.ai_socktype = SOCK_STREAM;
 312         snprintf(strport, sizeof strport, "%u", port);
 313         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
 314                 fatal("%s: %.100s: %s", __progname, host,
 315                     gai_strerror(gaierr));
 316
 317         for (attempt = 0; attempt < connection_attempts; attempt++) {
 318                 if (attempt > 0)
 319                         debug("Trying again...");
 320
 321                 /*
 322                  * Loop through addresses for this host, and try each one in
 323                  * sequence until the connection succeeds.
 324                  */
 325                 for (ai = aitop; ai; ai = ai->ai_next) {
 326                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 327                                 continue;
 328                         if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
 329                             ntop, sizeof(ntop), strport, sizeof(strport),
 330                             NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 331                                 error("ssh_connect: getnameinfo failed");
 332                                 continue;
 333                         }
 334                         debug("Connecting to %.200s [%.100s] port %s.",
 335                                 host, ntop, strport);
 336
 337                         /* Create a socket for connecting. */
 338                         sock = ssh_create_socket(needpriv, ai);
 339                         if (sock < 0)
 340                                 /* Any error is already output */
 341                                 continue;
 342
 343                         if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
 344                             options.connection_timeout) >= 0) {
 345                                 /* Successful connection. */
 346                                 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
 347                                 break;
 348                         } else {
 349                                 debug("connect to address %s port %s: %s",
 350                                     ntop, strport, strerror(errno));
 351                                 close(sock);
 352                                 sock = -1;
 353                         }
 354                 }
 355                 if (sock != -1)
 356                         break;  /* Successful connection. */
 357
 358                 /* Sleep a moment before retrying. */
 359                 sleep(1);
 360         }
 361
 362         freeaddrinfo(aitop);
 363
 364         /* Return failure if we didn't get a successful connection. */
 365         if (sock == -1) {
 366                 error("ssh: connect to host %s port %s: %s",
 367                     host, strport, strerror(errno));
 368                 return (-1);
 369         }
 370
 371         debug("Connection established.");
 372
 373         /* Set SO_KEEPALIVE if requested. */
 374         if (options.tcp_keep_alive &&
 375             setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
 376             sizeof(on)) < 0)
 377                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 378
 379         /* Set the connection. */
 380         packet_set_connection(sock, sock);
 381
 382         return 0;
 383 }
 384
 385 /*
 386  * Waits for the server identification string, and sends our own
 387  * identification string.
 388  */
 389 static void
 390 ssh_exchange_identification(void)
 391 {
 392         char buf[256], remote_version[256];     /* must be same size! */
 393         int remote_major, remote_minor, mismatch;
 394         int connection_in = packet_get_connection_in();
 395         int connection_out = packet_get_connection_out();
 396         int minor1 = PROTOCOL_MINOR_1;
 397         u_int i, n;
 398
 399         /* Read other side's version identification. */
 400         for (n = 0;;) {
 401                 for (i = 0; i < sizeof(buf) - 1; i++) {
 402                         size_t len = atomicio(read, connection_in, &buf[i], 1);
 403
 404                         if (len != 1 && errno == EPIPE)
 405                                 fatal("ssh_exchange_identification: Connection closed by remote host");
 406                         else if (len != 1)
 407                                 fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
 408                         if (buf[i] == '\r') {
 409                                 buf[i] = '\n';
 410                                 buf[i + 1] = 0;
 411                                 continue;               /**XXX wait for \n */
 412                         }
 413                         if (buf[i] == '\n') {
 414                                 buf[i + 1] = 0;
 415                                 break;
 416                         }
 417                         if (++n > 65536)
 418                                 fatal("ssh_exchange_identification: No banner received");
 419                 }
 420                 buf[sizeof(buf) - 1] = 0;
 421                 if (strncmp(buf, "SSH-", 4) == 0)
 422                         break;
 423                 debug("ssh_exchange_identification: %s", buf);
 424         }
 425         server_version_string = xstrdup(buf);
 426
 427         /*
 428          * Check that the versions match.  In future this might accept
 429          * several versions and set appropriate flags to handle them.
 430          */
 431         if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
 432             &remote_major, &remote_minor, remote_version) != 3)
 433                 fatal("Bad remote protocol version identification: '%.100s'", buf);
 434         debug("Remote protocol version %d.%d, remote software version %.100s",
 435             remote_major, remote_minor, remote_version);
 436
 437         compat_datafellows(remote_version);
 438         mismatch = 0;
 439
 440         switch (remote_major) {
 441         case 1:
 442                 if (remote_minor == 99 &&
 443                     (options.protocol & SSH_PROTO_2) &&
 444                     !(options.protocol & SSH_PROTO_1_PREFERRED)) {
 445                         enable_compat20();
 446                         break;
 447                 }
 448                 if (!(options.protocol & SSH_PROTO_1)) {
 449                         mismatch = 1;
 450                         break;
 451                 }
 452                 if (remote_minor < 3) {
 453                         fatal("Remote machine has too old SSH software version.");
 454                 } else if (remote_minor == 3 || remote_minor == 4) {
 455                         /* We speak 1.3, too. */
 456                         enable_compat13();
 457                         minor1 = 3;
 458                         if (options.forward_agent) {
 459                                 logit("Agent forwarding disabled for protocol 1.3");
 460                                 options.forward_agent = 0;
 461                         }
 462                 }
 463                 break;
 464         case 2:
 465                 if (options.protocol & SSH_PROTO_2) {
 466                         enable_compat20();
 467                         break;
 468                 }
 469                 /* FALLTHROUGH */
 470         default:
 471                 mismatch = 1;
 472                 break;
 473         }
 474         if (mismatch)
 475                 fatal("Protocol major versions differ: %d vs. %d",
 476                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 477                     remote_major);
 478         /* Send our own protocol version identification. */
 479         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
 480             compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 481             compat20 ? PROTOCOL_MINOR_2 : minor1,
 482             SSH_VERSION);
 483         if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
 484                 fatal("write: %.100s", strerror(errno));
 485         client_version_string = xstrdup(buf);
 486         chop(client_version_string);
 487         chop(server_version_string);
 488         debug("Local version string %.100s", client_version_string);
 489 }
 490
 491 /* defaults to 'no' */
 492 static int
 493 confirm(const char *prompt)
 494 {
 495         const char *msg, *again = "Please type 'yes' or 'no': ";
 496         char *p;
 497         int ret = -1;
 498
 499         if (options.batch_mode)
 500                 return 0;
 501         for (msg = prompt;;msg = again) {
 502                 p = read_passphrase(msg, RP_ECHO);
 503                 if (p == NULL ||
 504                     (p[0] == '\0') || (p[0] == '\n') ||
 505                     strncasecmp(p, "no", 2) == 0)
 506                         ret = 0;
 507                 if (p && strncasecmp(p, "yes", 3) == 0)
 508                         ret = 1;
 509                 if (p)
 510                         xfree(p);
 511                 if (ret != -1)
 512                         return ret;
 513         }
 514 }
 515
 516 /*
 517  * check whether the supplied host key is valid, return -1 if the key
 518  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
 519  */
 520 static int
 521 check_host_key(char *hostname, struct sockaddr *hostaddr, Key *host_key,
 522     int readonly, const char *user_hostfile, const char *system_hostfile)
 523 {
 524         Key *file_key;
 525         const char *type = key_type(host_key);
 526         char *ip = NULL, *host = NULL;
 527         char hostline[1000], *hostp, *fp;
 528         HostStatus host_status;
 529         HostStatus ip_status;
 530         int r, local = 0, host_ip_differ = 0;
 531         int salen;
 532         char ntop[NI_MAXHOST];
 533         char msg[1024];
 534         int len, host_line, ip_line;
 535         const char *host_file = NULL, *ip_file = NULL;
 536
 537         /*
 538          * Force accepting of the host key for loopback/localhost. The
 539          * problem is that if the home directory is NFS-mounted to multiple
 540          * machines, localhost will refer to a different machine in each of
 541          * them, and the user will get bogus HOST_CHANGED warnings.  This
 542          * essentially disables host authentication for localhost; however,
 543          * this is probably not a real problem.
 544          */
 545         /**  hostaddr == 0! */
 546         switch (hostaddr->sa_family) {
 547         case AF_INET:
 548                 local = (ntohl(((struct sockaddr_in *)hostaddr)->
 549                     sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
 550                 salen = sizeof(struct sockaddr_in);
 551                 break;
 552         case AF_INET6:
 553                 local = IN6_IS_ADDR_LOOPBACK(
 554                     &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
 555                 salen = sizeof(struct sockaddr_in6);
 556                 break;
 557         default:
 558                 local = 0;
 559                 salen = sizeof(struct sockaddr_storage);
 560                 break;
 561         }
 562         if (options.no_host_authentication_for_localhost == 1 && local &&
 563             options.host_key_alias == NULL) {
 564                 debug("Forcing accepting of host key for "
 565                     "loopback/localhost.");
 566                 return 0;
 567         }
 568
 569         /*
 570          * We don't have the remote ip-address for connections
 571          * using a proxy command
 572          */
 573         if (options.proxy_command == NULL) {
 574                 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
 575                     NULL, 0, NI_NUMERICHOST) != 0)
 576                         fatal("check_host_key: getnameinfo failed");
 577                 ip = put_host_port(ntop, options.port);
 578         } else {
 579                 ip = xstrdup("<no hostip for proxy command>");
 580         }
 581         /*
 582          * Turn off check_host_ip if the connection is to localhost, via proxy
 583          * command or if we don't have a hostname to compare with
 584          */
 585         if (options.check_host_ip && (local ||
 586             strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
 587                 options.check_host_ip = 0;
 588
 589         /*
 590          * Allow the user to record the key under a different name or
 591          * differentiate a non-standard port.  This is useful for ssh
 592          * tunneling over forwarded connections or if you run multiple
 593          * sshd's on different ports on the same machine.
 594          */
 595         if (options.host_key_alias != NULL) {
 596                 host = xstrdup(options.host_key_alias);
 597                 debug("using hostkeyalias: %s", host);
 598         } else {
 599                 host = put_host_port(hostname, options.port);
 600         }
 601
 602         /*
 603          * Store the host key from the known host file in here so that we can
 604          * compare it with the key for the IP address.
 605          */
 606         file_key = key_new(host_key->type);
 607
 608         /*
 609          * Check if the host key is present in the user's list of known
 610          * hosts or in the systemwide list.
 611          */
 612         host_file = user_hostfile;
 613         host_status = check_host_in_hostfile(host_file, host, host_key,
 614             file_key, &host_line);
 615         if (host_status == HOST_NEW) {
 616                 host_file = system_hostfile;
 617                 host_status = check_host_in_hostfile(host_file, host, host_key,
 618                     file_key, &host_line);
 619         }
 620         /*
 621          * Also perform check for the ip address, skip the check if we are
 622          * localhost or the hostname was an ip address to begin with
 623          */
 624         if (options.check_host_ip) {
 625                 Key *ip_key = key_new(host_key->type);
 626
 627                 ip_file = user_hostfile;
 628                 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
 629                     ip_key, &ip_line);
 630                 if (ip_status == HOST_NEW) {
 631                         ip_file = system_hostfile;
 632                         ip_status = check_host_in_hostfile(ip_file, ip,
 633                             host_key, ip_key, &ip_line);
 634                 }
 635                 if (host_status == HOST_CHANGED &&
 636                     (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
 637                         host_ip_differ = 1;
 638
 639                 key_free(ip_key);
 640         } else
 641                 ip_status = host_status;
 642
 643         key_free(file_key);
 644
 645         switch (host_status) {
 646         case HOST_OK:
 647                 /* The host is known and the key matches. */
 648                 debug("Host '%.200s' is known and matches the %s host key.",
 649                     host, type);
 650                 debug("Found key in %s:%d", host_file, host_line);
 651                 if (options.check_host_ip && ip_status == HOST_NEW) {
 652                         if (readonly)
 653                                 logit("%s host key for IP address "
 654                                     "'%.128s' not in list of known hosts.",
 655                                     type, ip);
 656                         else if (!add_host_to_hostfile(user_hostfile, ip,
 657                             host_key, options.hash_known_hosts))
 658                                 logit("Failed to add the %s host key for IP "
 659                                     "address '%.128s' to the list of known "
 660                                     "hosts (%.30s).", type, ip, user_hostfile);
 661                         else
 662                                 logit("Warning: Permanently added the %s host "
 663                                     "key for IP address '%.128s' to the list "
 664                                     "of known hosts.", type, ip);
 665                 }
 666                 break;
 667         case HOST_NEW:
 668                 if (readonly)
 669                         goto fail;
 670                 /* The host is new. */
 671                 if (options.strict_host_key_checking == 1) {
 672                         /*
 673                          * User has requested strict host key checking.  We
 674                          * will not add the host key automatically.  The only
 675                          * alternative left is to abort.
 676                          */
 677                         error("No %s host key is known for %.200s and you "
 678                             "have requested strict checking.", type, host);
 679                         goto fail;
 680                 } else if (options.strict_host_key_checking == 2) {
 681                         char msg1[1024], msg2[1024];
 682
 683                         if (show_other_keys(host, host_key))
 684                                 snprintf(msg1, sizeof(msg1),
 685                                     "\nbut keys of different type are already"
 686                                     " known for this host.");
 687                         else
 688                                 snprintf(msg1, sizeof(msg1), ".");
 689                         /* The default */
 690                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 691                         msg2[0] = '\0';
 692                         if (options.verify_host_key_dns) {
 693                                 if (matching_host_key_dns)
 694                                         snprintf(msg2, sizeof(msg2),
 695                                             "Matching host key fingerprint"
 696                                             " found in DNS.\n");
 697                                 else
 698                                         snprintf(msg2, sizeof(msg2),
 699                                             "No matching host key fingerprint"
 700                                             " found in DNS.\n");
 701                         }
 702                         snprintf(msg, sizeof(msg),
 703                             "The authenticity of host '%.200s (%s)' can't be "
 704                             "established%s\n"
 705                             "%s key fingerprint is %s.\n%s"
 706                             "Are you sure you want to continue connecting "
 707                             "(yes/no)? ",
 708                             host, ip, msg1, type, fp, msg2);
 709                         xfree(fp);
 710                         if (!confirm(msg))
 711                                 goto fail;
 712                 }
 713                 /*
 714                  * If not in strict mode, add the key automatically to the
 715                  * local known_hosts file.
 716                  */
 717                 if (options.check_host_ip && ip_status == HOST_NEW) {
 718                         snprintf(hostline, sizeof(hostline), "%s,%s",
 719                             host, ip);
 720                         hostp = hostline;
 721                         if (options.hash_known_hosts) {
 722                                 /* Add hash of host and IP separately */
 723                                 r = add_host_to_hostfile(user_hostfile, host,
 724                                     host_key, options.hash_known_hosts) &&
 725                                     add_host_to_hostfile(user_hostfile, ip,
 726                                     host_key, options.hash_known_hosts);
 727                         } else {
 728                                 /* Add unhashed "host,ip" */
 729                                 r = add_host_to_hostfile(user_hostfile,
 730                                     hostline, host_key,
 731                                     options.hash_known_hosts);
 732                         }
 733                 } else {
 734                         r = add_host_to_hostfile(user_hostfile, host, host_key,
 735                             options.hash_known_hosts);
 736                         hostp = host;
 737                 }
 738
 739                 if (!r)
 740                         logit("Failed to add the host to the list of known "
 741                             "hosts (%.500s).", user_hostfile);
 742                 else
 743                         logit("Warning: Permanently added '%.200s' (%s) to the "
 744                             "list of known hosts.", hostp, type);
 745                 break;
 746         case HOST_CHANGED:
 747                 if (options.check_host_ip && host_ip_differ) {
 748                         char *key_msg;
 749                         if (ip_status == HOST_NEW)
 750                                 key_msg = "is unknown";
 751                         else if (ip_status == HOST_OK)
 752                                 key_msg = "is unchanged";
 753                         else
 754                                 key_msg = "has a different value";
 755                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 756                         error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
 757                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 758                         error("The %s host key for %s has changed,", type, host);
 759                         error("and the key for the according IP address %s", ip);
 760                         error("%s. This could either mean that", key_msg);
 761                         error("DNS SPOOFING is happening or the IP address for the host");
 762                         error("and its host key have changed at the same time.");
 763                         if (ip_status != HOST_NEW)
 764                                 error("Offending key for IP in %s:%d", ip_file, ip_line);
 765                 }
 766                 /* The host key has changed. */
 767                 warn_changed_key(host_key);
 768                 error("Add correct host key in %.100s to get rid of this message.",
 769                     user_hostfile);
 770                 error("Offending key in %s:%d", host_file, host_line);
 771
 772                 /*
 773                  * If strict host key checking is in use, the user will have
 774                  * to edit the key manually and we can only abort.
 775                  */
 776                 if (options.strict_host_key_checking) {
 777                         error("%s host key for %.200s has changed and you have "
 778                             "requested strict checking.", type, host);
 779                         goto fail;
 780                 }
 781
 782                 /*
 783                  * If strict host key checking has not been requested, allow
 784                  * the connection but without MITM-able authentication or
 785                  * agent forwarding.
 786                  */
 787                 if (options.password_authentication) {
 788                         error("Password authentication is disabled to avoid "
 789                             "man-in-the-middle attacks.");
 790                         options.password_authentication = 0;
 791                 }
 792                 if (options.kbd_interactive_authentication) {
 793                         error("Keyboard-interactive authentication is disabled"
 794                             " to avoid man-in-the-middle attacks.");
 795                         options.kbd_interactive_authentication = 0;
 796                         options.challenge_response_authentication = 0;
 797                 }
 798                 if (options.challenge_response_authentication) {
 799                         error("Challenge/response authentication is disabled"
 800                             " to avoid man-in-the-middle attacks.");
 801                         options.challenge_response_authentication = 0;
 802                 }
 803                 if (options.forward_agent) {
 804                         error("Agent forwarding is disabled to avoid "
 805                             "man-in-the-middle attacks.");
 806                         options.forward_agent = 0;
 807                 }
 808                 if (options.forward_x11) {
 809                         error("X11 forwarding is disabled to avoid "
 810                             "man-in-the-middle attacks.");
 811                         options.forward_x11 = 0;
 812                 }
 813                 if (options.num_local_forwards > 0 ||
 814                     options.num_remote_forwards > 0) {
 815                         error("Port forwarding is disabled to avoid "
 816                             "man-in-the-middle attacks.");
 817                         options.num_local_forwards =
 818                             options.num_remote_forwards = 0;
 819                 }
 820                 /*
 821                  * XXX Should permit the user to change to use the new id.
 822                  * This could be done by converting the host key to an
 823                  * identifying sentence, tell that the host identifies itself
 824                  * by that sentence, and ask the user if he/she whishes to
 825                  * accept the authentication.
 826                  */
 827                 break;
 828         case HOST_FOUND:
 829                 fatal("internal error");
 830                 break;
 831         }
 832
 833         if (options.check_host_ip && host_status != HOST_CHANGED &&
 834             ip_status == HOST_CHANGED) {
 835                 snprintf(msg, sizeof(msg),
 836                     "Warning: the %s host key for '%.200s' "
 837                     "differs from the key for the IP address '%.128s'"
 838                     "\nOffending key for IP in %s:%d",
 839                     type, host, ip, ip_file, ip_line);
 840                 if (host_status == HOST_OK) {
 841                         len = strlen(msg);
 842                         snprintf(msg + len, sizeof(msg) - len,
 843                             "\nMatching host key in %s:%d",
 844                             host_file, host_line);
 845                 }
 846                 if (options.strict_host_key_checking == 1) {
 847                         logit("%s", msg);
 848                         error("Exiting, you have requested strict checking.");
 849                         goto fail;
 850                 } else if (options.strict_host_key_checking == 2) {
 851                         strlcat(msg, "\nAre you sure you want "
 852                             "to continue connecting (yes/no)? ", sizeof(msg));
 853                         if (!confirm(msg))
 854                                 goto fail;
 855                 } else {
 856                         logit("%s", msg);
 857                 }
 858         }
 859
 860         xfree(ip);
 861         xfree(host);
 862         return 0;
 863
 864 fail:
 865         xfree(ip);
 866         xfree(host);
 867         return -1;
 868 }
 869
 870 /* returns 0 if key verifies or -1 if key does NOT verify */
 871 int
 872 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 873 {
 874         struct stat st;
 875         int flags = 0;
 876
 877         if (options.verify_host_key_dns &&
 878             verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
 879
 880                 if (flags & DNS_VERIFY_FOUND) {
 881
 882                         if (options.verify_host_key_dns == 1 &&
 883                             flags & DNS_VERIFY_MATCH &&
 884                             flags & DNS_VERIFY_SECURE)
 885                                 return 0;
 886
 887                         if (flags & DNS_VERIFY_MATCH) {
 888                                 matching_host_key_dns = 1;
 889                         } else {
 890                                 warn_changed_key(host_key);
 891                                 error("Update the SSHFP RR in DNS with the new "
 892                                     "host key to get rid of this message.");
 893                         }
 894                 }
 895         }
 896
 897         /* return ok if the key can be found in an old keyfile */
 898         if (stat(options.system_hostfile2, &st) == 0 ||
 899             stat(options.user_hostfile2, &st) == 0) {
 900                 if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
 901                     options.user_hostfile2, options.system_hostfile2) == 0)
 902                         return 0;
 903         }
 904         return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
 905             options.user_hostfile, options.system_hostfile);
 906 }
 907
 908 /*
 909  * Starts a dialog with the server, and authenticates the current user on the
 910  * server.  This does not need any extra privileges.  The basic connection
 911  * to the server must already have been established before this is called.
 912  * If login fails, this function prints an error and never returns.
 913  * This function does not require super-user privileges.
 914  */
 915 void
 916 ssh_login(Sensitive *sensitive, const char *orighost,
 917     struct sockaddr *hostaddr, struct passwd *pw)
 918 {
 919         char *host, *cp;
 920         char *server_user, *local_user;
 921
 922         local_user = xstrdup(pw->pw_name);
 923         server_user = options.user ? options.user : local_user;
 924
 925         /* Convert the user-supplied hostname into all lowercase. */
 926         host = xstrdup(orighost);
 927         for (cp = host; *cp; cp++)
 928                 if (isupper(*cp))
 929                         *cp = (char)tolower(*cp);
 930
 931         /* Exchange protocol version identification strings with the server. */
 932         ssh_exchange_identification();
 933
 934         /* Put the connection into non-blocking mode. */
 935         packet_set_nonblocking();
 936
 937         /* key exchange */
 938         /* authenticate user */
 939         if (compat20) {
 940                 ssh_kex2(host, hostaddr);
 941                 ssh_userauth2(local_user, server_user, host, sensitive);
 942         } else {
 943                 ssh_kex(host, hostaddr);
 944                 ssh_userauth1(local_user, server_user, host, sensitive);
 945         }
 946         xfree(local_user);
 947 }
 948
 949 void
 950 ssh_put_password(char *password)
 951 {
 952         int size;
 953         char *padded;
 954
 955         if (datafellows & SSH_BUG_PASSWORDPAD) {
 956                 packet_put_cstring(password);
 957                 return;
 958         }
 959         size = roundup(strlen(password) + 1, 32);
 960         padded = xcalloc(1, size);
 961         strlcpy(padded, password, size);
 962         packet_put_string(padded, size);
 963         memset(padded, 0, size);
 964         xfree(padded);
 965 }
 966
 967 static int
 968 show_key_from_file(const char *file, const char *host, int keytype)
 969 {
 970         Key *found;
 971         char *fp;
 972         int line, ret;
 973
 974         found = key_new(keytype);
 975         if ((ret = lookup_key_in_hostfile_by_type(file, host,
 976             keytype, found, &line))) {
 977                 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
 978                 logit("WARNING: %s key found for host %s\n"
 979                     "in %s:%d\n"
 980                     "%s key fingerprint %s.",
 981                     key_type(found), host, file, line,
 982                     key_type(found), fp);
 983                 xfree(fp);
 984         }
 985         key_free(found);
 986         return (ret);
 987 }
 988
 989 /* print all known host keys for a given host, but skip keys of given type */
 990 static int
 991 show_other_keys(const char *host, Key *key)
 992 {
 993         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
 994         int i, found = 0;
 995
 996         for (i = 0; type[i] != -1; i++) {
 997                 if (type[i] == key->type)
 998                         continue;
 999                 if (type[i] != KEY_RSA1 &&
1000                     show_key_from_file(options.user_hostfile2, host, type[i])) {
1001                         found = 1;
1002                         continue;
1003                 }
1004                 if (type[i] != KEY_RSA1 &&
1005                     show_key_from_file(options.system_hostfile2, host, type[i])) {
1006                         found = 1;
1007                         continue;
1008                 }
1009                 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1010                         found = 1;
1011                         continue;
1012                 }
1013                 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1014                         found = 1;
1015                         continue;
1016                 }
1017                 debug2("no key of type %d for host %s", type[i], host);
1018         }
1019         return (found);
1020 }
1021
1022 static void
1023 warn_changed_key(Key *host_key)
1024 {
1025         char *fp;
1026         const char *type = key_type(host_key);
1027
1028         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1029
1030         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1031         error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1032         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1033         error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1034         error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1035         error("It is also possible that the %s host key has just been changed.", type);
1036         error("The fingerprint for the %s key sent by the remote host is\n%s.",
1037             type, fp);
1038         error("Please contact your system administrator.");
1039
1040         xfree(fp);
1041 }
1042
1043 /*
1044  * Execute a local command
1045  */
1046 int
1047 ssh_local_cmd(const char *args)
1048 {
1049         char *shell;
1050         pid_t pid;
1051         int status;
1052
1053         if (!options.permit_local_command ||
1054             args == NULL || !*args)
1055                 return (1);
1056
1057         if ((shell = getenv("SHELL")) == NULL)
1058                 shell = _PATH_BSHELL;
1059
1060         pid = fork();
1061         if (pid == 0) {
1062                 debug3("Executing %s -c \"%s\"", shell, args);
1063                 execl(shell, shell, "-c", args, (char *)NULL);
1064                 error("Couldn't execute %s -c \"%s\": %s",
1065                     shell, args, strerror(errno));
1066                 _exit(1);
1067         } else if (pid == -1)
1068                 fatal("fork failed: %.100s", strerror(errno));
1069         while (waitpid(pid, &status, 0) == -1)
1070                 if (errno != EINTR)
1071                         fatal("Couldn't wait for child: %s", strerror(errno));
1072
1073         if (!WIFEXITED(status))
1074                 return (1);
1075
1076         return (WEXITSTATUS(status));
1077 }