crypto/openssh/sshconnect.c

   1 /* $OpenBSD: sshconnect.c,v 1.214 2009/05/28 16:50:16 andreas 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 #ifdef HAVE_SYS_TIME_H
  23 # include <sys/time.h>
  24 #endif
  25
  26 #include <netinet/in.h>
  27 #include <arpa/inet.h>
  28
  29 #include <ctype.h>
  30 #include <errno.h>
  31 #include <netdb.h>
  32 #ifdef HAVE_PATHS_H
  33 #include <paths.h>
  34 #endif
  35 #include <pwd.h>
  36 #include <stdarg.h>
  37 #include <stdio.h>
  38 #include <stdlib.h>
  39 #include <string.h>
  40 #include <unistd.h>
  41
  42 #include "xmalloc.h"
  43 #include "key.h"
  44 #include "hostfile.h"
  45 #include "ssh.h"
  46 #include "rsa.h"
  47 #include "buffer.h"
  48 #include "packet.h"
  49 #include "uidswap.h"
  50 #include "compat.h"
  51 #include "key.h"
  52 #include "sshconnect.h"
  53 #include "hostfile.h"
  54 #include "log.h"
  55 #include "readconf.h"
  56 #include "atomicio.h"
  57 #include "misc.h"
  58 #include "dns.h"
  59 #include "roaming.h"
  60 #include "version.h"
  61
  62 char *client_version_string = NULL;
  63 char *server_version_string = NULL;
  64
  65 static int matching_host_key_dns = 0;
  66
  67 /* import */
  68 extern Options options;
  69 extern char *__progname;
  70 extern uid_t original_real_uid;
  71 extern uid_t original_effective_uid;
  72 extern pid_t proxy_command_pid;
  73
  74 static int show_other_keys(const char *, Key *);
  75 static void warn_changed_key(Key *);
  76
  77 /*
  78  * Connect to the given ssh server using a proxy command.
  79  */
  80 static int
  81 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  82 {
  83         char *command_string, *tmp;
  84         int pin[2], pout[2];
  85         pid_t pid;
  86         char *shell, strport[NI_MAXSERV];
  87
  88         if ((shell = getenv("SHELL")) == NULL)
  89                 shell = _PATH_BSHELL;
  90
  91         /* Convert the port number into a string. */
  92         snprintf(strport, sizeof strport, "%hu", port);
  93
  94         /*
  95          * Build the final command string in the buffer by making the
  96          * appropriate substitutions to the given proxy command.
  97          *
  98          * Use "exec" to avoid "sh -c" processes on some platforms
  99          * (e.g. Solaris)
 100          */
 101         xasprintf(&tmp, "exec %s", proxy_command);
 102         command_string = percent_expand(tmp, "h", host,
 103             "p", strport, (char *)NULL);
 104         xfree(tmp);
 105
 106         /* Create pipes for communicating with the proxy. */
 107         if (pipe(pin) < 0 || pipe(pout) < 0)
 108                 fatal("Could not create pipes to communicate with the proxy: %.100s",
 109                     strerror(errno));
 110
 111         debug("Executing proxy command: %.500s", command_string);
 112
 113         /* Fork and execute the proxy command. */
 114         if ((pid = fork()) == 0) {
 115                 char *argv[10];
 116
 117                 /* Child.  Permanently give up superuser privileges. */
 118                 permanently_drop_suid(original_real_uid);
 119
 120                 /* Redirect stdin and stdout. */
 121                 close(pin[1]);
 122                 if (pin[0] != 0) {
 123                         if (dup2(pin[0], 0) < 0)
 124                                 perror("dup2 stdin");
 125                         close(pin[0]);
 126                 }
 127                 close(pout[0]);
 128                 if (dup2(pout[1], 1) < 0)
 129                         perror("dup2 stdout");
 130                 /* Cannot be 1 because pin allocated two descriptors. */
 131                 close(pout[1]);
 132
 133                 /* Stderr is left as it is so that error messages get
 134                    printed on the user's terminal. */
 135                 argv[0] = shell;
 136                 argv[1] = "-c";
 137                 argv[2] = command_string;
 138                 argv[3] = NULL;
 139
 140                 /* Execute the proxy command.  Note that we gave up any
 141                    extra privileges above. */
 142                 execv(argv[0], argv);
 143                 perror(argv[0]);
 144                 exit(1);
 145         }
 146         /* Parent. */
 147         if (pid < 0)
 148                 fatal("fork failed: %.100s", strerror(errno));
 149         else
 150                 proxy_command_pid = pid; /* save pid to clean up later */
 151
 152         /* Close child side of the descriptors. */
 153         close(pin[0]);
 154         close(pout[1]);
 155
 156         /* Free the command name. */
 157         xfree(command_string);
 158
 159         /* Set the connection file descriptors. */
 160         packet_set_connection(pout[0], pin[1]);
 161         packet_set_timeout(options.server_alive_interval,
 162             options.server_alive_count_max);
 163
 164         /* Indicate OK return */
 165         return 0;
 166 }
 167
 168 /*
 169  * Set TCP receive buffer if requested.
 170  * Note: tuning needs to happen after the socket is
 171  * created but before the connection happens
 172  * so winscale is negotiated properly -cjr
 173  */
 174 static void
 175 ssh_set_socket_recvbuf(int sock)
 176 {
 177         void *buf = (void *)&options.tcp_rcv_buf;
 178         int sz = sizeof(options.tcp_rcv_buf);
 179         int socksize;
 180         int socksizelen = sizeof(int);
 181
 182         debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf);
 183         if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) {
 184           getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen);
 185           debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize);
 186         }
 187         else
 188                 error("Couldn't set socket receive buffer to %d: %.100s",
 189                     options.tcp_rcv_buf, strerror(errno));
 190 }
 191
 192
 193 /*
 194  * Creates a (possibly privileged) socket for use as the ssh connection.
 195  */
 196 static int
 197 ssh_create_socket(int privileged, struct addrinfo *ai)
 198 {
 199         int sock, gaierr;
 200         struct addrinfo hints, *res;
 201
 202         /*
 203          * If we are running as root and want to connect to a privileged
 204          * port, bind our own socket to a privileged port.
 205          */
 206         if (privileged) {
 207                 int p = IPPORT_RESERVED - 1;
 208                 PRIV_START;
 209                 sock = rresvport_af(&p, ai->ai_family);
 210                 PRIV_END;
 211                 if (sock < 0)
 212                         error("rresvport: af=%d %.100s", ai->ai_family,
 213                             strerror(errno));
 214                 else
 215                         debug("Allocated local port %d.", p);
 216
 217                 if (options.tcp_rcv_buf > 0)
 218                         ssh_set_socket_recvbuf(sock);
 219                 return sock;
 220         }
 221         sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 222         if (sock < 0)
 223                 error("socket: %.100s", strerror(errno));
 224
 225         if (options.tcp_rcv_buf > 0)
 226                 ssh_set_socket_recvbuf(sock);
 227
 228         /* Bind the socket to an alternative local IP address */
 229         if (options.bind_address == NULL)
 230                 return sock;
 231
 232         memset(&hints, 0, sizeof(hints));
 233         hints.ai_family = ai->ai_family;
 234         hints.ai_socktype = ai->ai_socktype;
 235         hints.ai_protocol = ai->ai_protocol;
 236         hints.ai_flags = AI_PASSIVE;
 237         gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
 238         if (gaierr) {
 239                 error("getaddrinfo: %s: %s", options.bind_address,
 240                     ssh_gai_strerror(gaierr));
 241                 close(sock);
 242                 return -1;
 243         }
 244         if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
 245                 error("bind: %s: %s", options.bind_address, strerror(errno));
 246                 close(sock);
 247                 freeaddrinfo(res);
 248                 return -1;
 249         }
 250         freeaddrinfo(res);
 251         return sock;
 252 }
 253
 254 static int
 255 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
 256     socklen_t addrlen, int *timeoutp)
 257 {
 258         fd_set *fdset;
 259         struct timeval tv, t_start;
 260         socklen_t optlen;
 261         int optval, rc, result = -1;
 262
 263         gettimeofday(&t_start, NULL);
 264
 265         if (*timeoutp <= 0) {
 266                 result = connect(sockfd, serv_addr, addrlen);
 267                 goto done;
 268         }
 269
 270         set_nonblock(sockfd);
 271         rc = connect(sockfd, serv_addr, addrlen);
 272         if (rc == 0) {
 273                 unset_nonblock(sockfd);
 274                 result = 0;
 275                 goto done;
 276         }
 277         if (errno != EINPROGRESS) {
 278                 result = -1;
 279                 goto done;
 280         }
 281
 282         fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
 283             sizeof(fd_mask));
 284         FD_SET(sockfd, fdset);
 285         ms_to_timeval(&tv, *timeoutp);
 286
 287         for (;;) {
 288                 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
 289                 if (rc != -1 || errno != EINTR)
 290                         break;
 291         }
 292
 293         switch (rc) {
 294         case 0:
 295                 /* Timed out */
 296                 errno = ETIMEDOUT;
 297                 break;
 298         case -1:
 299                 /* Select error */
 300                 debug("select: %s", strerror(errno));
 301                 break;
 302         case 1:
 303                 /* Completed or failed */
 304                 optval = 0;
 305                 optlen = sizeof(optval);
 306                 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
 307                     &optlen) == -1) {
 308                         debug("getsockopt: %s", strerror(errno));
 309                         break;
 310                 }
 311                 if (optval != 0) {
 312                         errno = optval;
 313                         break;
 314                 }
 315                 result = 0;
 316                 unset_nonblock(sockfd);
 317                 break;
 318         default:
 319                 /* Should not occur */
 320                 fatal("Bogus return (%d) from select()", rc);
 321         }
 322
 323         xfree(fdset);
 324
 325  done:
 326         if (result == 0 && *timeoutp > 0) {
 327                 ms_subtract_diff(&t_start, timeoutp);
 328                 if (*timeoutp <= 0) {
 329                         errno = ETIMEDOUT;
 330                         result = -1;
 331                 }
 332         }
 333
 334         return (result);
 335 }
 336
 337 /*
 338  * Opens a TCP/IP connection to the remote server on the given host.
 339  * The address of the remote host will be returned in hostaddr.
 340  * If port is 0, the default port will be used.  If needpriv is true,
 341  * a privileged port will be allocated to make the connection.
 342  * This requires super-user privileges if needpriv is true.
 343  * Connection_attempts specifies the maximum number of tries (one per
 344  * second).  If proxy_command is non-NULL, it specifies the command (with %h
 345  * and %p substituted for host and port, respectively) to use to contact
 346  * the daemon.
 347  */
 348 int
 349 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
 350     u_short port, int family, int connection_attempts, int *timeout_ms,
 351     int want_keepalive, int needpriv, const char *proxy_command)
 352 {
 353         int gaierr;
 354         int on = 1;
 355         int sock = -1, attempt;
 356         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 357         struct addrinfo hints, *ai, *aitop;
 358
 359         debug2("ssh_connect: needpriv %d", needpriv);
 360
 361         /* If a proxy command is given, connect using it. */
 362         if (proxy_command != NULL)
 363                 return ssh_proxy_connect(host, port, proxy_command);
 364
 365         /* No proxy command. */
 366
 367         memset(&hints, 0, sizeof(hints));
 368         hints.ai_family = family;
 369         hints.ai_socktype = SOCK_STREAM;
 370         snprintf(strport, sizeof strport, "%u", port);
 371         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
 372                 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
 373                     host, ssh_gai_strerror(gaierr));
 374
 375         for (attempt = 0; attempt < connection_attempts; attempt++) {
 376                 if (attempt > 0) {
 377                         /* Sleep a moment before retrying. */
 378                         sleep(1);
 379                         debug("Trying again...");
 380                 }
 381                 /*
 382                  * Loop through addresses for this host, and try each one in
 383                  * sequence until the connection succeeds.
 384                  */
 385                 for (ai = aitop; ai; ai = ai->ai_next) {
 386                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 387                                 continue;
 388                         if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
 389                             ntop, sizeof(ntop), strport, sizeof(strport),
 390                             NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 391                                 error("ssh_connect: getnameinfo failed");
 392                                 continue;
 393                         }
 394                         debug("Connecting to %.200s [%.100s] port %s.",
 395                                 host, ntop, strport);
 396
 397                         /* Create a socket for connecting. */
 398                         sock = ssh_create_socket(needpriv, ai);
 399                         if (sock < 0)
 400                                 /* Any error is already output */
 401                                 continue;
 402
 403                         if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
 404                             timeout_ms) >= 0) {
 405                                 /* Successful connection. */
 406                                 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
 407                                 break;
 408                         } else {
 409                                 debug("connect to address %s port %s: %s",
 410                                     ntop, strport, strerror(errno));
 411                                 close(sock);
 412                                 sock = -1;
 413                         }
 414                 }
 415                 if (sock != -1)
 416                         break;  /* Successful connection. */
 417         }
 418
 419         freeaddrinfo(aitop);
 420
 421         /* Return failure if we didn't get a successful connection. */
 422         if (sock == -1) {
 423                 error("ssh: connect to host %s port %s: %s",
 424                     host, strport, strerror(errno));
 425                 return (-1);
 426         }
 427
 428         debug("Connection established.");
 429
 430         /* Set SO_KEEPALIVE if requested. */
 431         if (want_keepalive &&
 432             setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
 433             sizeof(on)) < 0)
 434                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 435
 436         /* Set the connection. */
 437         packet_set_connection(sock, sock);
 438         packet_set_timeout(options.server_alive_interval,
 439             options.server_alive_count_max);
 440
 441         return 0;
 442 }
 443
 444 /*
 445  * Waits for the server identification string, and sends our own
 446  * identification string.
 447  */
 448 void
 449 ssh_exchange_identification(int timeout_ms)
 450 {
 451         char buf[256], remote_version[256];     /* must be same size! */
 452         int remote_major, remote_minor, mismatch;
 453         int connection_in = packet_get_connection_in();
 454         int connection_out = packet_get_connection_out();
 455         int minor1 = PROTOCOL_MINOR_1;
 456         u_int i, n;
 457         size_t len;
 458         int fdsetsz, remaining, rc;
 459         struct timeval t_start, t_remaining;
 460         fd_set *fdset;
 461
 462         fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
 463         fdset = xcalloc(1, fdsetsz);
 464
 465         /* Read other side's version identification. */
 466         remaining = timeout_ms;
 467         for (n = 0;;) {
 468                 for (i = 0; i < sizeof(buf) - 1; i++) {
 469                         if (timeout_ms > 0) {
 470                                 gettimeofday(&t_start, NULL);
 471                                 ms_to_timeval(&t_remaining, remaining);
 472                                 FD_SET(connection_in, fdset);
 473                                 rc = select(connection_in + 1, fdset, NULL,
 474                                     fdset, &t_remaining);
 475                                 ms_subtract_diff(&t_start, &remaining);
 476                                 if (rc == 0 || remaining <= 0)
 477                                         fatal("Connection timed out during "
 478                                             "banner exchange");
 479                                 if (rc == -1) {
 480                                         if (errno == EINTR)
 481                                                 continue;
 482                                         fatal("ssh_exchange_identification: "
 483                                             "select: %s", strerror(errno));
 484                                 }
 485                         }
 486
 487                         len = roaming_atomicio(read, connection_in, &buf[i], 1);
 488
 489                         if (len != 1 && errno == EPIPE)
 490                                 fatal("ssh_exchange_identification: "
 491                                     "Connection closed by remote host");
 492                         else if (len != 1)
 493                                 fatal("ssh_exchange_identification: "
 494                                     "read: %.100s", strerror(errno));
 495                         if (buf[i] == '\r') {
 496                                 buf[i] = '\n';
 497                                 buf[i + 1] = 0;
 498                                 continue;               /**XXX wait for \n */
 499                         }
 500                         if (buf[i] == '\n') {
 501                                 buf[i + 1] = 0;
 502                                 break;
 503                         }
 504                         if (++n > 65536)
 505                                 fatal("ssh_exchange_identification: "
 506                                     "No banner received");
 507                 }
 508                 buf[sizeof(buf) - 1] = 0;
 509                 if (strncmp(buf, "SSH-", 4) == 0)
 510                         break;
 511                 debug("ssh_exchange_identification: %s", buf);
 512         }
 513         server_version_string = xstrdup(buf);
 514         xfree(fdset);
 515
 516         /*
 517          * Check that the versions match.  In future this might accept
 518          * several versions and set appropriate flags to handle them.
 519          */
 520         if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
 521             &remote_major, &remote_minor, remote_version) != 3)
 522                 fatal("Bad remote protocol version identification: '%.100s'", buf);
 523         debug("Remote protocol version %d.%d, remote software version %.100s",
 524             remote_major, remote_minor, remote_version);
 525
 526         compat_datafellows(remote_version);
 527         mismatch = 0;
 528
 529         switch (remote_major) {
 530         case 1:
 531                 if (remote_minor == 99 &&
 532                     (options.protocol & SSH_PROTO_2) &&
 533                     !(options.protocol & SSH_PROTO_1_PREFERRED)) {
 534                         enable_compat20();
 535                         break;
 536                 }
 537                 if (!(options.protocol & SSH_PROTO_1)) {
 538                         mismatch = 1;
 539                         break;
 540                 }
 541                 if (remote_minor < 3) {
 542                         fatal("Remote machine has too old SSH software version.");
 543                 } else if (remote_minor == 3 || remote_minor == 4) {
 544                         /* We speak 1.3, too. */
 545                         enable_compat13();
 546                         minor1 = 3;
 547                         if (options.forward_agent) {
 548                                 logit("Agent forwarding disabled for protocol 1.3");
 549                                 options.forward_agent = 0;
 550                         }
 551                 }
 552                 break;
 553         case 2:
 554                 if (options.protocol & SSH_PROTO_2) {
 555                         enable_compat20();
 556                         break;
 557                 }
 558                 /* FALLTHROUGH */
 559         default:
 560                 mismatch = 1;
 561                 break;
 562         }
 563         if (mismatch)
 564                 fatal("Protocol major versions differ: %d vs. %d",
 565                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 566                     remote_major);
 567         /* Send our own protocol version identification. */
 568         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
 569             compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 570             compat20 ? PROTOCOL_MINOR_2 : minor1,
 571             SSH_RELEASE, compat20 ? "\r\n" : "\n");
 572         if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf))
 573             != strlen(buf))
 574                 fatal("write: %.100s", strerror(errno));
 575         client_version_string = xstrdup(buf);
 576         chop(client_version_string);
 577         chop(server_version_string);
 578         debug("Local version string %.100s", client_version_string);
 579 }
 580
 581 /* defaults to 'no' */
 582 static int
 583 confirm(const char *prompt)
 584 {
 585         const char *msg, *again = "Please type 'yes' or 'no': ";
 586         char *p;
 587         int ret = -1;
 588
 589         if (options.batch_mode)
 590                 return 0;
 591         for (msg = prompt;;msg = again) {
 592                 p = read_passphrase(msg, RP_ECHO);
 593                 if (p == NULL ||
 594                     (p[0] == '\0') || (p[0] == '\n') ||
 595                     strncasecmp(p, "no", 2) == 0)
 596                         ret = 0;
 597                 if (p && strncasecmp(p, "yes", 3) == 0)
 598                         ret = 1;
 599                 if (p)
 600                         xfree(p);
 601                 if (ret != -1)
 602                         return ret;
 603         }
 604 }
 605
 606 /*
 607  * check whether the supplied host key is valid, return -1 if the key
 608  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
 609  */
 610 #define RDRW    0
 611 #define RDONLY  1
 612 #define ROQUIET 2
 613 static int
 614 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 615     Key *host_key, int readonly, const char *user_hostfile,
 616     const char *system_hostfile)
 617 {
 618         Key *file_key;
 619         const char *type = key_type(host_key);
 620         char *ip = NULL, *host = NULL;
 621         char hostline[1000], *hostp, *fp, *ra;
 622         HostStatus host_status;
 623         HostStatus ip_status;
 624         int r, local = 0, host_ip_differ = 0;
 625         int salen;
 626         char ntop[NI_MAXHOST];
 627         char msg[1024];
 628         int len, host_line, ip_line, cancelled_forwarding = 0;
 629         const char *host_file = NULL, *ip_file = NULL;
 630
 631         /*
 632          * Force accepting of the host key for loopback/localhost. The
 633          * problem is that if the home directory is NFS-mounted to multiple
 634          * machines, localhost will refer to a different machine in each of
 635          * them, and the user will get bogus HOST_CHANGED warnings.  This
 636          * essentially disables host authentication for localhost; however,
 637          * this is probably not a real problem.
 638          */
 639         /**  hostaddr == 0! */
 640         switch (hostaddr->sa_family) {
 641         case AF_INET:
 642                 local = (ntohl(((struct sockaddr_in *)hostaddr)->
 643                     sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
 644                 salen = sizeof(struct sockaddr_in);
 645                 break;
 646         case AF_INET6:
 647                 local = IN6_IS_ADDR_LOOPBACK(
 648                     &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
 649                 salen = sizeof(struct sockaddr_in6);
 650                 break;
 651         default:
 652                 local = 0;
 653                 salen = sizeof(struct sockaddr_storage);
 654                 break;
 655         }
 656         if (options.no_host_authentication_for_localhost == 1 && local &&
 657             options.host_key_alias == NULL) {
 658                 debug("Forcing accepting of host key for "
 659                     "loopback/localhost.");
 660                 return 0;
 661         }
 662
 663         /*
 664          * We don't have the remote ip-address for connections
 665          * using a proxy command
 666          */
 667         if (options.proxy_command == NULL) {
 668                 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
 669                     NULL, 0, NI_NUMERICHOST) != 0)
 670                         fatal("check_host_key: getnameinfo failed");
 671                 ip = put_host_port(ntop, port);
 672         } else {
 673                 ip = xstrdup("<no hostip for proxy command>");
 674         }
 675
 676         /*
 677          * Turn off check_host_ip if the connection is to localhost, via proxy
 678          * command or if we don't have a hostname to compare with
 679          */
 680         if (options.check_host_ip && (local ||
 681             strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
 682                 options.check_host_ip = 0;
 683
 684         /*
 685          * Allow the user to record the key under a different name or
 686          * differentiate a non-standard port.  This is useful for ssh
 687          * tunneling over forwarded connections or if you run multiple
 688          * sshd's on different ports on the same machine.
 689          */
 690         if (options.host_key_alias != NULL) {
 691                 host = xstrdup(options.host_key_alias);
 692                 debug("using hostkeyalias: %s", host);
 693         } else {
 694                 host = put_host_port(hostname, port);
 695         }
 696
 697         /*
 698          * Store the host key from the known host file in here so that we can
 699          * compare it with the key for the IP address.
 700          */
 701         file_key = key_new(host_key->type);
 702
 703         /*
 704          * Check if the host key is present in the user's list of known
 705          * hosts or in the systemwide list.
 706          */
 707         host_file = user_hostfile;
 708         host_status = check_host_in_hostfile(host_file, host, host_key,
 709             file_key, &host_line);
 710         if (host_status == HOST_NEW) {
 711                 host_file = system_hostfile;
 712                 host_status = check_host_in_hostfile(host_file, host, host_key,
 713                     file_key, &host_line);
 714         }
 715         /*
 716          * Also perform check for the ip address, skip the check if we are
 717          * localhost or the hostname was an ip address to begin with
 718          */
 719         if (options.check_host_ip) {
 720                 Key *ip_key = key_new(host_key->type);
 721
 722                 ip_file = user_hostfile;
 723                 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
 724                     ip_key, &ip_line);
 725                 if (ip_status == HOST_NEW) {
 726                         ip_file = system_hostfile;
 727                         ip_status = check_host_in_hostfile(ip_file, ip,
 728                             host_key, ip_key, &ip_line);
 729                 }
 730                 if (host_status == HOST_CHANGED &&
 731                     (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
 732                         host_ip_differ = 1;
 733
 734                 key_free(ip_key);
 735         } else
 736                 ip_status = host_status;
 737
 738         key_free(file_key);
 739
 740         switch (host_status) {
 741         case HOST_OK:
 742                 /* The host is known and the key matches. */
 743                 debug("Host '%.200s' is known and matches the %s host key.",
 744                     host, type);
 745                 debug("Found key in %s:%d", host_file, host_line);
 746                 if (options.check_host_ip && ip_status == HOST_NEW) {
 747                         if (readonly)
 748                                 logit("%s host key for IP address "
 749                                     "'%.128s' not in list of known hosts.",
 750                                     type, ip);
 751                         else if (!add_host_to_hostfile(user_hostfile, ip,
 752                             host_key, options.hash_known_hosts))
 753                                 logit("Failed to add the %s host key for IP "
 754                                     "address '%.128s' to the list of known "
 755                                     "hosts (%.30s).", type, ip, user_hostfile);
 756                         else
 757                                 logit("Warning: Permanently added the %s host "
 758                                     "key for IP address '%.128s' to the list "
 759                                     "of known hosts.", type, ip);
 760                 } else if (options.visual_host_key) {
 761                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 762                         ra = key_fingerprint(host_key, SSH_FP_MD5,
 763                             SSH_FP_RANDOMART);
 764                         logit("Host key fingerprint is %s\n%s\n", fp, ra);
 765                         xfree(ra);
 766                         xfree(fp);
 767                 }
 768                 break;
 769         case HOST_NEW:
 770                 if (options.host_key_alias == NULL && port != 0 &&
 771                     port != SSH_DEFAULT_PORT) {
 772                         debug("checking without port identifier");
 773                         if (check_host_key(hostname, hostaddr, 0, host_key,
 774                             ROQUIET, user_hostfile, system_hostfile) == 0) {
 775                                 debug("found matching key w/out port");
 776                                 break;
 777                         }
 778                 }
 779                 if (readonly)
 780                         goto fail;
 781                 /* The host is new. */
 782                 if (options.strict_host_key_checking == 1) {
 783                         /*
 784                          * User has requested strict host key checking.  We
 785                          * will not add the host key automatically.  The only
 786                          * alternative left is to abort.
 787                          */
 788                         error("No %s host key is known for %.200s and you "
 789                             "have requested strict checking.", type, host);
 790                         goto fail;
 791                 } else if (options.strict_host_key_checking == 2) {
 792                         char msg1[1024], msg2[1024];
 793
 794                         if (show_other_keys(host, host_key))
 795                                 snprintf(msg1, sizeof(msg1),
 796                                     "\nbut keys of different type are already"
 797                                     " known for this host.");
 798                         else
 799                                 snprintf(msg1, sizeof(msg1), ".");
 800                         /* The default */
 801                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 802                         ra = key_fingerprint(host_key, SSH_FP_MD5,
 803                             SSH_FP_RANDOMART);
 804                         msg2[0] = '\0';
 805                         if (options.verify_host_key_dns) {
 806                                 if (matching_host_key_dns)
 807                                         snprintf(msg2, sizeof(msg2),
 808                                             "Matching host key fingerprint"
 809                                             " found in DNS.\n");
 810                                 else
 811                                         snprintf(msg2, sizeof(msg2),
 812                                             "No matching host key fingerprint"
 813                                             " found in DNS.\n");
 814                         }
 815                         snprintf(msg, sizeof(msg),
 816                             "The authenticity of host '%.200s (%s)' can't be "
 817                             "established%s\n"
 818                             "%s key fingerprint is %s.%s%s\n%s"
 819                             "Are you sure you want to continue connecting "
 820                             "(yes/no)? ",
 821                             host, ip, msg1, type, fp,
 822                             options.visual_host_key ? "\n" : "",
 823                             options.visual_host_key ? ra : "",
 824                             msg2);
 825                         xfree(ra);
 826                         xfree(fp);
 827                         if (!confirm(msg))
 828                                 goto fail;
 829                 }
 830                 /*
 831                  * If not in strict mode, add the key automatically to the
 832                  * local known_hosts file.
 833                  */
 834                 if (options.check_host_ip && ip_status == HOST_NEW) {
 835                         snprintf(hostline, sizeof(hostline), "%s,%s",
 836                             host, ip);
 837                         hostp = hostline;
 838                         if (options.hash_known_hosts) {
 839                                 /* Add hash of host and IP separately */
 840                                 r = add_host_to_hostfile(user_hostfile, host,
 841                                     host_key, options.hash_known_hosts) &&
 842                                     add_host_to_hostfile(user_hostfile, ip,
 843                                     host_key, options.hash_known_hosts);
 844                         } else {
 845                                 /* Add unhashed "host,ip" */
 846                                 r = add_host_to_hostfile(user_hostfile,
 847                                     hostline, host_key,
 848                                     options.hash_known_hosts);
 849                         }
 850                 } else {
 851                         r = add_host_to_hostfile(user_hostfile, host, host_key,
 852                             options.hash_known_hosts);
 853                         hostp = host;
 854                 }
 855
 856                 if (!r)
 857                         logit("Failed to add the host to the list of known "
 858                             "hosts (%.500s).", user_hostfile);
 859                 else
 860                         logit("Warning: Permanently added '%.200s' (%s) to the "
 861                             "list of known hosts.", hostp, type);
 862                 break;
 863         case HOST_CHANGED:
 864                 if (readonly == ROQUIET)
 865                         goto fail;
 866                 if (options.check_host_ip && host_ip_differ) {
 867                         char *key_msg;
 868                         if (ip_status == HOST_NEW)
 869                                 key_msg = "is unknown";
 870                         else if (ip_status == HOST_OK)
 871                                 key_msg = "is unchanged";
 872                         else
 873                                 key_msg = "has a different value";
 874                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 875                         error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
 876                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 877                         error("The %s host key for %s has changed,", type, host);
 878                         error("and the key for the corresponding IP address %s", ip);
 879                         error("%s. This could either mean that", key_msg);
 880                         error("DNS SPOOFING is happening or the IP address for the host");
 881                         error("and its host key have changed at the same time.");
 882                         if (ip_status != HOST_NEW)
 883                                 error("Offending key for IP in %s:%d", ip_file, ip_line);
 884                 }
 885                 /* The host key has changed. */
 886                 warn_changed_key(host_key);
 887                 error("Add correct host key in %.100s to get rid of this message.",
 888                     user_hostfile);
 889                 error("Offending key in %s:%d", host_file, host_line);
 890
 891                 /*
 892                  * If strict host key checking is in use, the user will have
 893                  * to edit the key manually and we can only abort.
 894                  */
 895                 if (options.strict_host_key_checking) {
 896                         error("%s host key for %.200s has changed and you have "
 897                             "requested strict checking.", type, host);
 898                         goto fail;
 899                 }
 900
 901                 /*
 902                  * If strict host key checking has not been requested, allow
 903                  * the connection but without MITM-able authentication or
 904                  * forwarding.
 905                  */
 906                 if (options.password_authentication) {
 907                         error("Password authentication is disabled to avoid "
 908                             "man-in-the-middle attacks.");
 909                         options.password_authentication = 0;
 910                         cancelled_forwarding = 1;
 911                 }
 912                 if (options.kbd_interactive_authentication) {
 913                         error("Keyboard-interactive authentication is disabled"
 914                             " to avoid man-in-the-middle attacks.");
 915                         options.kbd_interactive_authentication = 0;
 916                         options.challenge_response_authentication = 0;
 917                         cancelled_forwarding = 1;
 918                 }
 919                 if (options.challenge_response_authentication) {
 920                         error("Challenge/response authentication is disabled"
 921                             " to avoid man-in-the-middle attacks.");
 922                         options.challenge_response_authentication = 0;
 923                         cancelled_forwarding = 1;
 924                 }
 925                 if (options.forward_agent) {
 926                         error("Agent forwarding is disabled to avoid "
 927                             "man-in-the-middle attacks.");
 928                         options.forward_agent = 0;
 929                         cancelled_forwarding = 1;
 930                 }
 931                 if (options.forward_x11) {
 932                         error("X11 forwarding is disabled to avoid "
 933                             "man-in-the-middle attacks.");
 934                         options.forward_x11 = 0;
 935                         cancelled_forwarding = 1;
 936                 }
 937                 if (options.num_local_forwards > 0 ||
 938                     options.num_remote_forwards > 0) {
 939                         error("Port forwarding is disabled to avoid "
 940                             "man-in-the-middle attacks.");
 941                         options.num_local_forwards =
 942                             options.num_remote_forwards = 0;
 943                         cancelled_forwarding = 1;
 944                 }
 945                 if (options.tun_open != SSH_TUNMODE_NO) {
 946                         error("Tunnel forwarding is disabled to avoid "
 947                             "man-in-the-middle attacks.");
 948                         options.tun_open = SSH_TUNMODE_NO;
 949                         cancelled_forwarding = 1;
 950                 }
 951                 if (options.exit_on_forward_failure && cancelled_forwarding)
 952                         fatal("Error: forwarding disabled due to host key "
 953                             "check failure");
 954
 955                 /*
 956                  * XXX Should permit the user to change to use the new id.
 957                  * This could be done by converting the host key to an
 958                  * identifying sentence, tell that the host identifies itself
 959                  * by that sentence, and ask the user if he/she whishes to
 960                  * accept the authentication.
 961                  */
 962                 break;
 963         case HOST_FOUND:
 964                 fatal("internal error");
 965                 break;
 966         }
 967
 968         if (options.check_host_ip && host_status != HOST_CHANGED &&
 969             ip_status == HOST_CHANGED) {
 970                 snprintf(msg, sizeof(msg),
 971                     "Warning: the %s host key for '%.200s' "
 972                     "differs from the key for the IP address '%.128s'"
 973                     "\nOffending key for IP in %s:%d",
 974                     type, host, ip, ip_file, ip_line);
 975                 if (host_status == HOST_OK) {
 976                         len = strlen(msg);
 977                         snprintf(msg + len, sizeof(msg) - len,
 978                             "\nMatching host key in %s:%d",
 979                             host_file, host_line);
 980                 }
 981                 if (options.strict_host_key_checking == 1) {
 982                         logit("%s", msg);
 983                         error("Exiting, you have requested strict checking.");
 984                         goto fail;
 985                 } else if (options.strict_host_key_checking == 2) {
 986                         strlcat(msg, "\nAre you sure you want "
 987                             "to continue connecting (yes/no)? ", sizeof(msg));
 988                         if (!confirm(msg))
 989                                 goto fail;
 990                 } else {
 991                         logit("%s", msg);
 992                 }
 993         }
 994
 995         xfree(ip);
 996         xfree(host);
 997         return 0;
 998
 999 fail:
1000         xfree(ip);
1001         xfree(host);
1002         return -1;
1003 }
1004
1005 /* returns 0 if key verifies or -1 if key does NOT verify */
1006 int
1007 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
1008 {
1009         struct stat st;
1010         int flags = 0;
1011
1012         if (options.verify_host_key_dns &&
1013             verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
1014
1015                 if (flags & DNS_VERIFY_FOUND) {
1016
1017                         if (options.verify_host_key_dns == 1 &&
1018                             flags & DNS_VERIFY_MATCH &&
1019                             flags & DNS_VERIFY_SECURE)
1020                                 return 0;
1021
1022                         if (flags & DNS_VERIFY_MATCH) {
1023                                 matching_host_key_dns = 1;
1024                         } else {
1025                                 warn_changed_key(host_key);
1026                                 error("Update the SSHFP RR in DNS with the new "
1027                                     "host key to get rid of this message.");
1028                         }
1029                 }
1030         }
1031
1032         /* return ok if the key can be found in an old keyfile */
1033         if (stat(options.system_hostfile2, &st) == 0 ||
1034             stat(options.user_hostfile2, &st) == 0) {
1035                 if (check_host_key(host, hostaddr, options.port, host_key,
1036                     RDONLY, options.user_hostfile2,
1037                     options.system_hostfile2) == 0)
1038                         return 0;
1039         }
1040         return check_host_key(host, hostaddr, options.port, host_key,
1041             RDRW, options.user_hostfile, options.system_hostfile);
1042 }
1043
1044 /*
1045  * Starts a dialog with the server, and authenticates the current user on the
1046  * server.  This does not need any extra privileges.  The basic connection
1047  * to the server must already have been established before this is called.
1048  * If login fails, this function prints an error and never returns.
1049  * This function does not require super-user privileges.
1050  */
1051 void
1052 ssh_login(Sensitive *sensitive, const char *orighost,
1053     struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
1054 {
1055         char *host, *cp;
1056         char *server_user, *local_user;
1057
1058         local_user = xstrdup(pw->pw_name);
1059         server_user = options.user ? options.user : local_user;
1060
1061         /* Convert the user-supplied hostname into all lowercase. */
1062         host = xstrdup(orighost);
1063         for (cp = host; *cp; cp++)
1064                 if (isupper(*cp))
1065                         *cp = (char)tolower(*cp);
1066
1067         /* Exchange protocol version identification strings with the server. */
1068         ssh_exchange_identification(timeout_ms);
1069
1070         /* Put the connection into non-blocking mode. */
1071         packet_set_nonblocking();
1072
1073         /* key exchange */
1074         /* authenticate user */
1075         if (compat20) {
1076                 ssh_kex2(host, hostaddr);
1077                 ssh_userauth2(local_user, server_user, host, sensitive);
1078         } else {
1079                 ssh_kex(host, hostaddr);
1080                 ssh_userauth1(local_user, server_user, host, sensitive);
1081         }
1082         xfree(local_user);
1083 }
1084
1085 void
1086 ssh_put_password(char *password)
1087 {
1088         int size;
1089         char *padded;
1090
1091         if (datafellows & SSH_BUG_PASSWORDPAD) {
1092                 packet_put_cstring(password);
1093                 return;
1094         }
1095         size = roundup(strlen(password) + 1, 32);
1096         padded = xcalloc(1, size);
1097         strlcpy(padded, password, size);
1098         packet_put_string(padded, size);
1099         memset(padded, 0, size);
1100         xfree(padded);
1101 }
1102
1103 static int
1104 show_key_from_file(const char *file, const char *host, int keytype)
1105 {
1106         Key *found;
1107         char *fp, *ra;
1108         int line, ret;
1109
1110         found = key_new(keytype);
1111         if ((ret = lookup_key_in_hostfile_by_type(file, host,
1112             keytype, found, &line))) {
1113                 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1114                 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
1115                 logit("WARNING: %s key found for host %s\n"
1116                     "in %s:%d\n"
1117                     "%s key fingerprint %s.\n%s\n",
1118                     key_type(found), host, file, line,
1119                     key_type(found), fp, ra);
1120                 xfree(ra);
1121                 xfree(fp);
1122         }
1123         key_free(found);
1124         return (ret);
1125 }
1126
1127 /* print all known host keys for a given host, but skip keys of given type */
1128 static int
1129 show_other_keys(const char *host, Key *key)
1130 {
1131         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1132         int i, found = 0;
1133
1134         for (i = 0; type[i] != -1; i++) {
1135                 if (type[i] == key->type)
1136                         continue;
1137                 if (type[i] != KEY_RSA1 &&
1138                     show_key_from_file(options.user_hostfile2, host, type[i])) {
1139                         found = 1;
1140                         continue;
1141                 }
1142                 if (type[i] != KEY_RSA1 &&
1143                     show_key_from_file(options.system_hostfile2, host, type[i])) {
1144                         found = 1;
1145                         continue;
1146                 }
1147                 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1148                         found = 1;
1149                         continue;
1150                 }
1151                 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1152                         found = 1;
1153                         continue;
1154                 }
1155                 debug2("no key of type %d for host %s", type[i], host);
1156         }
1157         return (found);
1158 }
1159
1160 static void
1161 warn_changed_key(Key *host_key)
1162 {
1163         char *fp;
1164         const char *type = key_type(host_key);
1165
1166         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1167
1168         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1169         error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1170         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1171         error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1172         error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1173         error("It is also possible that the %s host key has just been changed.", type);
1174         error("The fingerprint for the %s key sent by the remote host is\n%s.",
1175             type, fp);
1176         error("Please contact your system administrator.");
1177
1178         xfree(fp);
1179 }
1180
1181 /*
1182  * Execute a local command
1183  */
1184 int
1185 ssh_local_cmd(const char *args)
1186 {
1187         char *shell;
1188         pid_t pid;
1189         int status;
1190
1191         if (!options.permit_local_command ||
1192             args == NULL || !*args)
1193                 return (1);
1194
1195         if ((shell = getenv("SHELL")) == NULL)
1196                 shell = _PATH_BSHELL;
1197
1198         pid = fork();
1199         if (pid == 0) {
1200                 debug3("Executing %s -c \"%s\"", shell, args);
1201                 execl(shell, shell, "-c", args, (char *)NULL);
1202                 error("Couldn't execute %s -c \"%s\": %s",
1203                     shell, args, strerror(errno));
1204                 _exit(1);
1205         } else if (pid == -1)
1206                 fatal("fork failed: %.100s", strerror(errno));
1207         while (waitpid(pid, &status, 0) == -1)
1208                 if (errno != EINTR)
1209                         fatal("Couldn't wait for child: %s", strerror(errno));
1210
1211         if (!WIFEXITED(status))
1212                 return (1);
1213
1214         return (WEXITSTATUS(status));
1215 }