crypto/openssh-4/sshconnect.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  * Code to connect to a remote host, and to perform the client side of the
   6  * login (authentication) dialog.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  */
  14
  15 #include "includes.h"
  16 RCSID("$OpenBSD: sshconnect.c,v 1.168 2005/07/17 07:17:55 djm Exp $");
  17
  18 #include <openssl/bn.h>
  19
  20 #include "ssh.h"
  21 #include "xmalloc.h"
  22 #include "rsa.h"
  23 #include "buffer.h"
  24 #include "packet.h"
  25 #include "uidswap.h"
  26 #include "compat.h"
  27 #include "key.h"
  28 #include "sshconnect.h"
  29 #include "hostfile.h"
  30 #include "log.h"
  31 #include "readconf.h"
  32 #include "atomicio.h"
  33 #include "misc.h"
  34
  35 #include "dns.h"
  36
  37 char *client_version_string = NULL;
  38 char *server_version_string = NULL;
  39
  40 int matching_host_key_dns = 0;
  41
  42 /* import */
  43 extern Options options;
  44 extern char *__progname;
  45 extern uid_t original_real_uid;
  46 extern uid_t original_effective_uid;
  47 extern pid_t proxy_command_pid;
  48
  49 #ifndef INET6_ADDRSTRLEN                /* for non IPv6 machines */
  50 #define INET6_ADDRSTRLEN 46
  51 #endif
  52
  53 static int show_other_keys(const char *, Key *);
  54 static void warn_changed_key(Key *);
  55
  56 /*
  57  * Connect to the given ssh server using a proxy command.
  58  */
  59 static int
  60 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  61 {
  62         char *command_string, *tmp;
  63         int pin[2], pout[2];
  64         pid_t pid;
  65         char strport[NI_MAXSERV];
  66         size_t len;
  67
  68         /* Convert the port number into a string. */
  69         snprintf(strport, sizeof strport, "%hu", port);
  70
  71         /*
  72          * Build the final command string in the buffer by making the
  73          * appropriate substitutions to the given proxy command.
  74          *
  75          * Use "exec" to avoid "sh -c" processes on some platforms
  76          * (e.g. Solaris)
  77          */
  78         len = strlen(proxy_command) + 6;
  79         tmp = xmalloc(len);
  80         strlcpy(tmp, "exec ", len);
  81         strlcat(tmp, proxy_command, len);
  82         command_string = percent_expand(tmp, "h", host,
  83             "p", strport, (char *)NULL);
  84         xfree(tmp);
  85
  86         /* Create pipes for communicating with the proxy. */
  87         if (pipe(pin) < 0 || pipe(pout) < 0)
  88                 fatal("Could not create pipes to communicate with the proxy: %.100s",
  89                     strerror(errno));
  90
  91         debug("Executing proxy command: %.500s", command_string);
  92
  93         /* Fork and execute the proxy command. */
  94         if ((pid = fork()) == 0) {
  95                 char *argv[10];
  96
  97                 /* Child.  Permanently give up superuser privileges. */
  98                 seteuid(original_real_uid);
  99                 setuid(original_real_uid);
 100
 101                 /* Redirect stdin and stdout. */
 102                 close(pin[1]);
 103                 if (pin[0] != 0) {
 104                         if (dup2(pin[0], 0) < 0)
 105                                 perror("dup2 stdin");
 106                         close(pin[0]);
 107                 }
 108                 close(pout[0]);
 109                 if (dup2(pout[1], 1) < 0)
 110                         perror("dup2 stdout");
 111                 /* Cannot be 1 because pin allocated two descriptors. */
 112                 close(pout[1]);
 113
 114                 /* Stderr is left as it is so that error messages get
 115                    printed on the user's terminal. */
 116                 argv[0] = _PATH_BSHELL;
 117                 argv[1] = "-c";
 118                 argv[2] = command_string;
 119                 argv[3] = NULL;
 120
 121                 /* Execute the proxy command.  Note that we gave up any
 122                    extra privileges above. */
 123                 execv(argv[0], argv);
 124                 perror(argv[0]);
 125                 exit(1);
 126         }
 127         /* Parent. */
 128         if (pid < 0)
 129                 fatal("fork failed: %.100s", strerror(errno));
 130         else
 131                 proxy_command_pid = pid; /* save pid to clean up later */
 132
 133         /* Close child side of the descriptors. */
 134         close(pin[0]);
 135         close(pout[1]);
 136
 137         /* Free the command name. */
 138         xfree(command_string);
 139
 140         /* Set the connection file descriptors. */
 141         packet_set_connection(pout[0], pin[1]);
 142
 143         /* Indicate OK return */
 144         return 0;
 145 }
 146
 147 /*
 148  * Creates a (possibly privileged) socket for use as the ssh connection.
 149  */
 150 static int
 151 ssh_create_socket(int privileged, struct addrinfo *ai)
 152 {
 153         int sock, gaierr;
 154         struct addrinfo hints, *res;
 155
 156         /*
 157          * If we are running as root and want to connect to a privileged
 158          * port, bind our own socket to a privileged port.
 159          */
 160         if (privileged) {
 161                 int p = IPPORT_RESERVED - 1;
 162                 PRIV_START;
 163                 sock = rresvport_af(&p, ai->ai_family);
 164                 PRIV_END;
 165                 if (sock < 0)
 166                         error("rresvport: af=%d %.100s", ai->ai_family,
 167                             strerror(errno));
 168                 else
 169                         debug("Allocated local port %d.", p);
 170                 return sock;
 171         }
 172         sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 173         if (sock < 0)
 174                 error("socket: %.100s", strerror(errno));
 175
 176         /* Bind the socket to an alternative local IP address */
 177         if (options.bind_address == NULL)
 178                 return sock;
 179
 180         memset(&hints, 0, sizeof(hints));
 181         hints.ai_family = ai->ai_family;
 182         hints.ai_socktype = ai->ai_socktype;
 183         hints.ai_protocol = ai->ai_protocol;
 184         hints.ai_flags = AI_PASSIVE;
 185         gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
 186         if (gaierr) {
 187                 error("getaddrinfo: %s: %s", options.bind_address,
 188                     gai_strerror(gaierr));
 189                 close(sock);
 190                 return -1;
 191         }
 192         if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
 193                 error("bind: %s: %s", options.bind_address, strerror(errno));
 194                 close(sock);
 195                 freeaddrinfo(res);
 196                 return -1;
 197         }
 198         freeaddrinfo(res);
 199         return sock;
 200 }
 201
 202 static int
 203 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
 204     socklen_t addrlen, int timeout)
 205 {
 206         fd_set *fdset;
 207         struct timeval tv;
 208         socklen_t optlen;
 209         int fdsetsz, optval, rc, result = -1;
 210
 211         if (timeout <= 0)
 212                 return (connect(sockfd, serv_addr, addrlen));
 213
 214         set_nonblock(sockfd);
 215         rc = connect(sockfd, serv_addr, addrlen);
 216         if (rc == 0) {
 217                 unset_nonblock(sockfd);
 218                 return (0);
 219         }
 220         if (errno != EINPROGRESS)
 221                 return (-1);
 222
 223         fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask);
 224         fdset = (fd_set *)xmalloc(fdsetsz);
 225
 226         memset(fdset, 0, fdsetsz);
 227         FD_SET(sockfd, fdset);
 228         tv.tv_sec = timeout;
 229         tv.tv_usec = 0;
 230
 231         for (;;) {
 232                 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
 233                 if (rc != -1 || errno != EINTR)
 234                         break;
 235         }
 236
 237         switch (rc) {
 238         case 0:
 239                 /* Timed out */
 240                 errno = ETIMEDOUT;
 241                 break;
 242         case -1:
 243                 /* Select error */
 244                 debug("select: %s", strerror(errno));
 245                 break;
 246         case 1:
 247                 /* Completed or failed */
 248                 optval = 0;
 249                 optlen = sizeof(optval);
 250                 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
 251                     &optlen) == -1) {
 252                         debug("getsockopt: %s", strerror(errno));
 253                         break;
 254                 }
 255                 if (optval != 0) {
 256                         errno = optval;
 257                         break;
 258                 }
 259                 result = 0;
 260                 unset_nonblock(sockfd);
 261                 break;
 262         default:
 263                 /* Should not occur */
 264                 fatal("Bogus return (%d) from select()", rc);
 265         }
 266
 267         xfree(fdset);
 268         return (result);
 269 }
 270
 271 /*
 272  * Opens a TCP/IP connection to the remote server on the given host.
 273  * The address of the remote host will be returned in hostaddr.
 274  * If port is 0, the default port will be used.  If needpriv is true,
 275  * a privileged port will be allocated to make the connection.
 276  * This requires super-user privileges if needpriv is true.
 277  * Connection_attempts specifies the maximum number of tries (one per
 278  * second).  If proxy_command is non-NULL, it specifies the command (with %h
 279  * and %p substituted for host and port, respectively) to use to contact
 280  * the daemon.
 281  */
 282 int
 283 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
 284     u_short port, int family, int connection_attempts,
 285     int needpriv, const char *proxy_command)
 286 {
 287         int gaierr;
 288         int on = 1;
 289         int sock = -1, attempt;
 290         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 291         struct addrinfo hints, *ai, *aitop;
 292
 293         debug2("ssh_connect: needpriv %d", needpriv);
 294
 295         /* If a proxy command is given, connect using it. */
 296         if (proxy_command != NULL)
 297                 return ssh_proxy_connect(host, port, proxy_command);
 298
 299         /* No proxy command. */
 300
 301         memset(&hints, 0, sizeof(hints));
 302         hints.ai_family = family;
 303         hints.ai_socktype = SOCK_STREAM;
 304         snprintf(strport, sizeof strport, "%u", port);
 305         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
 306                 fatal("%s: %.100s: %s", __progname, host,
 307                     gai_strerror(gaierr));
 308
 309         /*
 310          * Try to connect several times.  On some machines, the first time
 311          * will sometimes fail.  In general socket code appears to behave
 312          * quite magically on many machines.
 313                  */
 314         for (attempt = 0; ;) {
 315                 if (attempt > 0)
 316                         debug("Trying again...");
 317
 318                 /* Loop through addresses for this host, and try each one in
 319                    sequence until the connection succeeds. */
 320                 for (ai = aitop; ai; ai = ai->ai_next) {
 321                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 322                                 continue;
 323                         if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
 324                             ntop, sizeof(ntop), strport, sizeof(strport),
 325                             NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 326                                 error("ssh_connect: getnameinfo failed");
 327                                 continue;
 328                         }
 329                         debug("Connecting to %.200s [%.100s] port %s.",
 330                                 host, ntop, strport);
 331
 332                         /* Create a socket for connecting. */
 333                         sock = ssh_create_socket(needpriv, ai);
 334                         if (sock < 0)
 335                                 /* Any error is already output */
 336                                 continue;
 337
 338                         if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
 339                             options.connection_timeout) >= 0) {
 340                                 /* Successful connection. */
 341                                 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
 342                                 break;
 343                         } else {
 344                                 debug("connect to address %s port %s: %s",
 345                                     ntop, strport, strerror(errno));
 346                                 /*
 347                                  * Close the failed socket; there appear to
 348                                  * be some problems when reusing a socket for
 349                                  * which connect() has already returned an
 350                                  * error.
 351                                  */
 352                                 close(sock);
 353                         }
 354                 }
 355                 if (ai)
 356                         break;  /* Successful connection. */
 357
 358                 attempt++;
 359                 if (attempt >= connection_attempts)
 360                         break;
 361                 /* Sleep a moment before retrying. */
 362                 sleep(1);
 363         }
 364
 365         freeaddrinfo(aitop);
 366
 367         /* Return failure if we didn't get a successful connection. */
 368         if (attempt >= connection_attempts) {
 369                 error("ssh: connect to host %s port %s: %s",
 370                     host, strport, strerror(errno));
 371                 return (-1);
 372         }
 373
 374         debug("Connection established.");
 375
 376         /* Set SO_KEEPALIVE if requested. */
 377         if (options.tcp_keep_alive &&
 378             setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
 379             sizeof(on)) < 0)
 380                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 381
 382         /* Set the connection. */
 383         packet_set_connection(sock, sock);
 384
 385         return 0;
 386 }
 387
 388 /*
 389  * Waits for the server identification string, and sends our own
 390  * identification string.
 391  */
 392 static void
 393 ssh_exchange_identification(void)
 394 {
 395         char buf[256], remote_version[256];     /* must be same size! */
 396         int remote_major, remote_minor, mismatch;
 397         int connection_in = packet_get_connection_in();
 398         int connection_out = packet_get_connection_out();
 399         int minor1 = PROTOCOL_MINOR_1;
 400         u_int i;
 401
 402         /* Read other side's version identification. */
 403         for (;;) {
 404                 for (i = 0; i < sizeof(buf) - 1; i++) {
 405                         size_t len = atomicio(read, connection_in, &buf[i], 1);
 406
 407                         if (len != 1 && errno == EPIPE)
 408                                 fatal("ssh_exchange_identification: Connection closed by remote host");
 409                         else if (len != 1)
 410                                 fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
 411                         if (buf[i] == '\r') {
 412                                 buf[i] = '\n';
 413                                 buf[i + 1] = 0;
 414                                 continue;               /**XXX wait for \n */
 415                         }
 416                         if (buf[i] == '\n') {
 417                                 buf[i + 1] = 0;
 418                                 break;
 419                         }
 420                 }
 421                 buf[sizeof(buf) - 1] = 0;
 422                 if (strncmp(buf, "SSH-", 4) == 0)
 423                         break;
 424                 debug("ssh_exchange_identification: %s", buf);
 425         }
 426         server_version_string = xstrdup(buf);
 427
 428         /*
 429          * Check that the versions match.  In future this might accept
 430          * several versions and set appropriate flags to handle them.
 431          */
 432         if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
 433             &remote_major, &remote_minor, remote_version) != 3)
 434                 fatal("Bad remote protocol version identification: '%.100s'", buf);
 435         debug("Remote protocol version %d.%d, remote software version %.100s",
 436             remote_major, remote_minor, remote_version);
 437
 438         compat_datafellows(remote_version);
 439         mismatch = 0;
 440
 441         switch (remote_major) {
 442         case 1:
 443                 if (remote_minor == 99 &&
 444                     (options.protocol & SSH_PROTO_2) &&
 445                     !(options.protocol & SSH_PROTO_1_PREFERRED)) {
 446                         enable_compat20();
 447                         break;
 448                 }
 449                 if (!(options.protocol & SSH_PROTO_1)) {
 450                         mismatch = 1;
 451                         break;
 452                 }
 453                 if (remote_minor < 3) {
 454                         fatal("Remote machine has too old SSH software version.");
 455                 } else if (remote_minor == 3 || remote_minor == 4) {
 456                         /* We speak 1.3, too. */
 457                         enable_compat13();
 458                         minor1 = 3;
 459                         if (options.forward_agent) {
 460                                 logit("Agent forwarding disabled for protocol 1.3");
 461                                 options.forward_agent = 0;
 462                         }
 463                 }
 464                 break;
 465         case 2:
 466                 if (options.protocol & SSH_PROTO_2) {
 467                         enable_compat20();
 468                         break;
 469                 }
 470                 /* FALLTHROUGH */
 471         default:
 472                 mismatch = 1;
 473                 break;
 474         }
 475         if (mismatch)
 476                 fatal("Protocol major versions differ: %d vs. %d",
 477                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 478                     remote_major);
 479         /* Send our own protocol version identification. */
 480         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
 481             compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 482             compat20 ? PROTOCOL_MINOR_2 : minor1,
 483             SSH_VERSION);
 484         if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
 485                 fatal("write: %.100s", strerror(errno));
 486         client_version_string = xstrdup(buf);
 487         chop(client_version_string);
 488         chop(server_version_string);
 489         debug("Local version string %.100s", client_version_string);
 490 }
 491
 492 /* defaults to 'no' */
 493 static int
 494 confirm(const char *prompt)
 495 {
 496         const char *msg, *again = "Please type 'yes' or 'no': ";
 497         char *p;
 498         int ret = -1;
 499
 500         if (options.batch_mode)
 501                 return 0;
 502         for (msg = prompt;;msg = again) {
 503                 p = read_passphrase(msg, RP_ECHO);
 504                 if (p == NULL ||
 505                     (p[0] == '\0') || (p[0] == '\n') ||
 506                     strncasecmp(p, "no", 2) == 0)
 507                         ret = 0;
 508                 if (p && strncasecmp(p, "yes", 3) == 0)
 509                         ret = 1;
 510                 if (p)
 511                         xfree(p);
 512                 if (ret != -1)
 513                         return ret;
 514         }
 515 }
 516
 517 /*
 518  * check whether the supplied host key is valid, return -1 if the key
 519  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
 520  */
 521 static int
 522 check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key,
 523     int readonly, const char *user_hostfile, const char *system_hostfile)
 524 {
 525         Key *file_key;
 526         const char *type = key_type(host_key);
 527         char *ip = NULL;
 528         char hostline[1000], *hostp, *fp;
 529         HostStatus host_status;
 530         HostStatus ip_status;
 531         int r, local = 0, host_ip_differ = 0;
 532         int salen;
 533         char ntop[NI_MAXHOST];
 534         char msg[1024];
 535         int len, host_line, ip_line;
 536         const char *host_file = NULL, *ip_file = NULL;
 537
 538         /*
 539          * Force accepting of the host key for loopback/localhost. The
 540          * problem is that if the home directory is NFS-mounted to multiple
 541          * machines, localhost will refer to a different machine in each of
 542          * them, and the user will get bogus HOST_CHANGED warnings.  This
 543          * essentially disables host authentication for localhost; however,
 544          * this is probably not a real problem.
 545          */
 546         /**  hostaddr == 0! */
 547         switch (hostaddr->sa_family) {
 548         case AF_INET:
 549                 local = (ntohl(((struct sockaddr_in *)hostaddr)->
 550                     sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
 551                 salen = sizeof(struct sockaddr_in);
 552                 break;
 553         case AF_INET6:
 554                 local = IN6_IS_ADDR_LOOPBACK(
 555                     &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
 556                 salen = sizeof(struct sockaddr_in6);
 557                 break;
 558         default:
 559                 local = 0;
 560                 salen = sizeof(struct sockaddr_storage);
 561                 break;
 562         }
 563         if (options.no_host_authentication_for_localhost == 1 && local &&
 564             options.host_key_alias == NULL) {
 565                 debug("Forcing accepting of host key for "
 566                     "loopback/localhost.");
 567                 return 0;
 568         }
 569
 570         /*
 571          * We don't have the remote ip-address for connections
 572          * using a proxy command
 573          */
 574         if (options.proxy_command == NULL) {
 575                 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
 576                     NULL, 0, NI_NUMERICHOST) != 0)
 577                         fatal("check_host_key: getnameinfo failed");
 578                 ip = xstrdup(ntop);
 579         } else {
 580                 ip = xstrdup("<no hostip for proxy command>");
 581         }
 582         /*
 583          * Turn off check_host_ip if the connection is to localhost, via proxy
 584          * command or if we don't have a hostname to compare with
 585          */
 586         if (options.check_host_ip &&
 587             (local || strcmp(host, ip) == 0 || options.proxy_command != NULL))
 588                 options.check_host_ip = 0;
 589
 590         /*
 591          * Allow the user to record the key under a different name. This is
 592          * useful for ssh tunneling over forwarded connections or if you run
 593          * multiple sshd's on different ports on the same machine.
 594          */
 595         if (options.host_key_alias != NULL) {
 596                 host = options.host_key_alias;
 597                 debug("using hostkeyalias: %s", host);
 598         }
 599
 600         /*
 601          * Store the host key from the known host file in here so that we can
 602          * compare it with the key for the IP address.
 603          */
 604         file_key = key_new(host_key->type);
 605
 606         /*
 607          * Check if the host key is present in the user\'s list of known
 608          * hosts or in the systemwide list.
 609          */
 610         host_file = user_hostfile;
 611         host_status = check_host_in_hostfile(host_file, host, host_key,
 612             file_key, &host_line);
 613         if (host_status == HOST_NEW) {
 614                 host_file = system_hostfile;
 615                 host_status = check_host_in_hostfile(host_file, host, host_key,
 616                     file_key, &host_line);
 617         }
 618         /*
 619          * Also perform check for the ip address, skip the check if we are
 620          * localhost or the hostname was an ip address to begin with
 621          */
 622         if (options.check_host_ip) {
 623                 Key *ip_key = key_new(host_key->type);
 624
 625                 ip_file = user_hostfile;
 626                 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
 627                     ip_key, &ip_line);
 628                 if (ip_status == HOST_NEW) {
 629                         ip_file = system_hostfile;
 630                         ip_status = check_host_in_hostfile(ip_file, ip,
 631                             host_key, ip_key, &ip_line);
 632                 }
 633                 if (host_status == HOST_CHANGED &&
 634                     (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
 635                         host_ip_differ = 1;
 636
 637                 key_free(ip_key);
 638         } else
 639                 ip_status = host_status;
 640
 641         key_free(file_key);
 642
 643         switch (host_status) {
 644         case HOST_OK:
 645                 /* The host is known and the key matches. */
 646                 debug("Host '%.200s' is known and matches the %s host key.",
 647                     host, type);
 648                 debug("Found key in %s:%d", host_file, host_line);
 649                 if (options.check_host_ip && ip_status == HOST_NEW) {
 650                         if (readonly)
 651                                 logit("%s host key for IP address "
 652                                     "'%.128s' not in list of known hosts.",
 653                                     type, ip);
 654                         else if (!add_host_to_hostfile(user_hostfile, ip,
 655                             host_key, options.hash_known_hosts))
 656                                 logit("Failed to add the %s host key for IP "
 657                                     "address '%.128s' to the list of known "
 658                                     "hosts (%.30s).", type, ip, user_hostfile);
 659                         else
 660                                 logit("Warning: Permanently added the %s host "
 661                                     "key for IP address '%.128s' to the list "
 662                                     "of known hosts.", type, ip);
 663                 }
 664                 break;
 665         case HOST_NEW:
 666                 if (readonly)
 667                         goto fail;
 668                 /* The host is new. */
 669                 if (options.strict_host_key_checking == 1) {
 670                         /*
 671                          * User has requested strict host key checking.  We
 672                          * will not add the host key automatically.  The only
 673                          * alternative left is to abort.
 674                          */
 675                         error("No %s host key is known for %.200s and you "
 676                             "have requested strict checking.", type, host);
 677                         goto fail;
 678                 } else if (options.strict_host_key_checking == 2) {
 679                         char msg1[1024], msg2[1024];
 680
 681                         if (show_other_keys(host, host_key))
 682                                 snprintf(msg1, sizeof(msg1),
 683                                     "\nbut keys of different type are already"
 684                                     " known for this host.");
 685                         else
 686                                 snprintf(msg1, sizeof(msg1), ".");
 687                         /* The default */
 688                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 689                         msg2[0] = '\0';
 690                         if (options.verify_host_key_dns) {
 691                                 if (matching_host_key_dns)
 692                                         snprintf(msg2, sizeof(msg2),
 693                                             "Matching host key fingerprint"
 694                                             " found in DNS.\n");
 695                                 else
 696                                         snprintf(msg2, sizeof(msg2),
 697                                             "No matching host key fingerprint"
 698                                             " found in DNS.\n");
 699                         }
 700                         snprintf(msg, sizeof(msg),
 701                             "The authenticity of host '%.200s (%s)' can't be "
 702                             "established%s\n"
 703                             "%s key fingerprint is %s.\n%s"
 704                             "Are you sure you want to continue connecting "
 705                             "(yes/no)? ",
 706                             host, ip, msg1, type, fp, msg2);
 707                         xfree(fp);
 708                         if (!confirm(msg))
 709                                 goto fail;
 710                 }
 711                 /*
 712                  * If not in strict mode, add the key automatically to the
 713                  * local known_hosts file.
 714                  */
 715                 if (options.check_host_ip && ip_status == HOST_NEW) {
 716                         snprintf(hostline, sizeof(hostline), "%s,%s",
 717                             host, ip);
 718                         hostp = hostline;
 719                         if (options.hash_known_hosts) {
 720                                 /* Add hash of host and IP separately */
 721                                 r = add_host_to_hostfile(user_hostfile, host,
 722                                     host_key, options.hash_known_hosts) &&
 723                                     add_host_to_hostfile(user_hostfile, ip,
 724                                     host_key, options.hash_known_hosts);
 725                         } else {
 726                                 /* Add unhashed "host,ip" */
 727                                 r = add_host_to_hostfile(user_hostfile,
 728                                     hostline, host_key,
 729                                     options.hash_known_hosts);
 730                         }
 731                 } else {
 732                         r = add_host_to_hostfile(user_hostfile, host, host_key,
 733                             options.hash_known_hosts);
 734                         hostp = host;
 735                 }
 736
 737                 if (!r)
 738                         logit("Failed to add the host to the list of known "
 739                             "hosts (%.500s).", user_hostfile);
 740                 else
 741                         logit("Warning: Permanently added '%.200s' (%s) to the "
 742                             "list of known hosts.", hostp, type);
 743                 break;
 744         case HOST_CHANGED:
 745                 if (options.check_host_ip && host_ip_differ) {
 746                         char *key_msg;
 747                         if (ip_status == HOST_NEW)
 748                                 key_msg = "is unknown";
 749                         else if (ip_status == HOST_OK)
 750                                 key_msg = "is unchanged";
 751                         else
 752                                 key_msg = "has a different value";
 753                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 754                         error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
 755                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 756                         error("The %s host key for %s has changed,", type, host);
 757                         error("and the key for the according IP address %s", ip);
 758                         error("%s. This could either mean that", key_msg);
 759                         error("DNS SPOOFING is happening or the IP address for the host");
 760                         error("and its host key have changed at the same time.");
 761                         if (ip_status != HOST_NEW)
 762                                 error("Offending key for IP in %s:%d", ip_file, ip_line);
 763                 }
 764                 /* The host key has changed. */
 765                 warn_changed_key(host_key);
 766                 error("Add correct host key in %.100s to get rid of this message.",
 767                     user_hostfile);
 768                 error("Offending key in %s:%d", host_file, host_line);
 769
 770                 /*
 771                  * If strict host key checking is in use, the user will have
 772                  * to edit the key manually and we can only abort.
 773                  */
 774                 if (options.strict_host_key_checking) {
 775                         error("%s host key for %.200s has changed and you have "
 776                             "requested strict checking.", type, host);
 777                         goto fail;
 778                 }
 779
 780                 /*
 781                  * If strict host key checking has not been requested, allow
 782                  * the connection but without MITM-able authentication or
 783                  * agent forwarding.
 784                  */
 785                 if (options.password_authentication) {
 786                         error("Password authentication is disabled to avoid "
 787                             "man-in-the-middle attacks.");
 788                         options.password_authentication = 0;
 789                 }
 790                 if (options.kbd_interactive_authentication) {
 791                         error("Keyboard-interactive authentication is disabled"
 792                             " to avoid man-in-the-middle attacks.");
 793                         options.kbd_interactive_authentication = 0;
 794                         options.challenge_response_authentication = 0;
 795                 }
 796                 if (options.challenge_response_authentication) {
 797                         error("Challenge/response authentication is disabled"
 798                             " to avoid man-in-the-middle attacks.");
 799                         options.challenge_response_authentication = 0;
 800                 }
 801                 if (options.forward_agent) {
 802                         error("Agent forwarding is disabled to avoid "
 803                             "man-in-the-middle attacks.");
 804                         options.forward_agent = 0;
 805                 }
 806                 if (options.forward_x11) {
 807                         error("X11 forwarding is disabled to avoid "
 808                             "man-in-the-middle attacks.");
 809                         options.forward_x11 = 0;
 810                 }
 811                 if (options.num_local_forwards > 0 ||
 812                     options.num_remote_forwards > 0) {
 813                         error("Port forwarding is disabled to avoid "
 814                             "man-in-the-middle attacks.");
 815                         options.num_local_forwards =
 816                             options.num_remote_forwards = 0;
 817                 }
 818                 /*
 819                  * XXX Should permit the user to change to use the new id.
 820                  * This could be done by converting the host key to an
 821                  * identifying sentence, tell that the host identifies itself
 822                  * by that sentence, and ask the user if he/she whishes to
 823                  * accept the authentication.
 824                  */
 825                 break;
 826         case HOST_FOUND:
 827                 fatal("internal error");
 828                 break;
 829         }
 830
 831         if (options.check_host_ip && host_status != HOST_CHANGED &&
 832             ip_status == HOST_CHANGED) {
 833                 snprintf(msg, sizeof(msg),
 834                     "Warning: the %s host key for '%.200s' "
 835                     "differs from the key for the IP address '%.128s'"
 836                     "\nOffending key for IP in %s:%d",
 837                     type, host, ip, ip_file, ip_line);
 838                 if (host_status == HOST_OK) {
 839                         len = strlen(msg);
 840                         snprintf(msg + len, sizeof(msg) - len,
 841                             "\nMatching host key in %s:%d",
 842                             host_file, host_line);
 843                 }
 844                 if (options.strict_host_key_checking == 1) {
 845                         logit("%s", msg);
 846                         error("Exiting, you have requested strict checking.");
 847                         goto fail;
 848                 } else if (options.strict_host_key_checking == 2) {
 849                         strlcat(msg, "\nAre you sure you want "
 850                             "to continue connecting (yes/no)? ", sizeof(msg));
 851                         if (!confirm(msg))
 852                                 goto fail;
 853                 } else {
 854                         logit("%s", msg);
 855                 }
 856         }
 857
 858         xfree(ip);
 859         return 0;
 860
 861 fail:
 862         xfree(ip);
 863         return -1;
 864 }
 865
 866 /* returns 0 if key verifies or -1 if key does NOT verify */
 867 int
 868 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 869 {
 870         struct stat st;
 871         int flags = 0;
 872
 873         if (options.verify_host_key_dns &&
 874             verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
 875
 876                 if (flags & DNS_VERIFY_FOUND) {
 877
 878                         if (options.verify_host_key_dns == 1 &&
 879                             flags & DNS_VERIFY_MATCH &&
 880                             flags & DNS_VERIFY_SECURE)
 881                                 return 0;
 882
 883                         if (flags & DNS_VERIFY_MATCH) {
 884                                 matching_host_key_dns = 1;
 885                         } else {
 886                                 warn_changed_key(host_key);
 887                                 error("Update the SSHFP RR in DNS with the new "
 888                                     "host key to get rid of this message.");
 889                         }
 890                 }
 891         }
 892
 893         /* return ok if the key can be found in an old keyfile */
 894         if (stat(options.system_hostfile2, &st) == 0 ||
 895             stat(options.user_hostfile2, &st) == 0) {
 896                 if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1,
 897                     options.user_hostfile2, options.system_hostfile2) == 0)
 898                         return 0;
 899         }
 900         return check_host_key(host, hostaddr, host_key, /*readonly*/ 0,
 901             options.user_hostfile, options.system_hostfile);
 902 }
 903
 904 /*
 905  * Starts a dialog with the server, and authenticates the current user on the
 906  * server.  This does not need any extra privileges.  The basic connection
 907  * to the server must already have been established before this is called.
 908  * If login fails, this function prints an error and never returns.
 909  * This function does not require super-user privileges.
 910  */
 911 void
 912 ssh_login(Sensitive *sensitive, const char *orighost,
 913     struct sockaddr *hostaddr, struct passwd *pw)
 914 {
 915         char *host, *cp;
 916         char *server_user, *local_user;
 917
 918         local_user = xstrdup(pw->pw_name);
 919         server_user = options.user ? options.user : local_user;
 920
 921         /* Convert the user-supplied hostname into all lowercase. */
 922         host = xstrdup(orighost);
 923         for (cp = host; *cp; cp++)
 924                 if (isupper(*cp))
 925                         *cp = tolower(*cp);
 926
 927         /* Exchange protocol version identification strings with the server. */
 928         ssh_exchange_identification();
 929
 930         /* Put the connection into non-blocking mode. */
 931         packet_set_nonblocking();
 932
 933         /* key exchange */
 934         /* authenticate user */
 935         if (compat20) {
 936                 ssh_kex2(host, hostaddr);
 937                 ssh_userauth2(local_user, server_user, host, sensitive);
 938         } else {
 939                 ssh_kex(host, hostaddr);
 940                 ssh_userauth1(local_user, server_user, host, sensitive);
 941         }
 942 }
 943
 944 void
 945 ssh_put_password(char *password)
 946 {
 947         int size;
 948         char *padded;
 949
 950         if (datafellows & SSH_BUG_PASSWORDPAD) {
 951                 packet_put_cstring(password);
 952                 return;
 953         }
 954         size = roundup(strlen(password) + 1, 32);
 955         padded = xmalloc(size);
 956         memset(padded, 0, size);
 957         strlcpy(padded, password, size);
 958         packet_put_string(padded, size);
 959         memset(padded, 0, size);
 960         xfree(padded);
 961 }
 962
 963 static int
 964 show_key_from_file(const char *file, const char *host, int keytype)
 965 {
 966         Key *found;
 967         char *fp;
 968         int line, ret;
 969
 970         found = key_new(keytype);
 971         if ((ret = lookup_key_in_hostfile_by_type(file, host,
 972             keytype, found, &line))) {
 973                 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
 974                 logit("WARNING: %s key found for host %s\n"
 975                     "in %s:%d\n"
 976                     "%s key fingerprint %s.",
 977                     key_type(found), host, file, line,
 978                     key_type(found), fp);
 979                 xfree(fp);
 980         }
 981         key_free(found);
 982         return (ret);
 983 }
 984
 985 /* print all known host keys for a given host, but skip keys of given type */
 986 static int
 987 show_other_keys(const char *host, Key *key)
 988 {
 989         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
 990         int i, found = 0;
 991
 992         for (i = 0; type[i] != -1; i++) {
 993                 if (type[i] == key->type)
 994                         continue;
 995                 if (type[i] != KEY_RSA1 &&
 996                     show_key_from_file(options.user_hostfile2, host, type[i])) {
 997                         found = 1;
 998                         continue;
 999                 }
1000                 if (type[i] != KEY_RSA1 &&
1001                     show_key_from_file(options.system_hostfile2, host, type[i])) {
1002                         found = 1;
1003                         continue;
1004                 }
1005                 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1006                         found = 1;
1007                         continue;
1008                 }
1009                 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1010                         found = 1;
1011                         continue;
1012                 }
1013                 debug2("no key of type %d for host %s", type[i], host);
1014         }
1015         return (found);
1016 }
1017
1018 static void
1019 warn_changed_key(Key *host_key)
1020 {
1021         char *fp;
1022         const char *type = key_type(host_key);
1023
1024         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1025
1026         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1027         error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1028         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1029         error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1030         error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1031         error("It is also possible that the %s host key has just been changed.", type);
1032         error("The fingerprint for the %s key sent by the remote host is\n%s.",
1033             type, fp);
1034         error("Please contact your system administrator.");
1035
1036         xfree(fp);
1037 }