crypto/openssh-4/sshconnect.c

   1 /* $OpenBSD: sshconnect.c,v 1.200 2006/10/10 10:12:45 markus 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 "version.h"
  60
  61 char *client_version_string = NULL;
  62 char *server_version_string = NULL;
  63
  64 static int matching_host_key_dns = 0;
  65
  66 /* import */
  67 extern Options options;
  68 extern char *__progname;
  69 extern uid_t original_real_uid;
  70 extern uid_t original_effective_uid;
  71 extern pid_t proxy_command_pid;
  72
  73 #ifndef INET6_ADDRSTRLEN                /* for non IPv6 machines */
  74 #define INET6_ADDRSTRLEN 46
  75 #endif
  76
  77 static int show_other_keys(const char *, Key *);
  78 static void warn_changed_key(Key *);
  79
  80 /*
  81  * Connect to the given ssh server using a proxy command.
  82  */
  83 static int
  84 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  85 {
  86         char *command_string, *tmp;
  87         int pin[2], pout[2];
  88         pid_t pid;
  89         char strport[NI_MAXSERV];
  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] = _PATH_BSHELL;
 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
 162         /* Indicate OK return */
 163         return 0;
 164 }
 165
 166 /*
 167  * Creates a (possibly privileged) socket for use as the ssh connection.
 168  */
 169 static int
 170 ssh_create_socket(int privileged, struct addrinfo *ai)
 171 {
 172         int sock, gaierr;
 173         struct addrinfo hints, *res;
 174
 175         /*
 176          * If we are running as root and want to connect to a privileged
 177          * port, bind our own socket to a privileged port.
 178          */
 179         if (privileged) {
 180                 int p = IPPORT_RESERVED - 1;
 181                 PRIV_START;
 182                 sock = rresvport_af(&p, ai->ai_family);
 183                 PRIV_END;
 184                 if (sock < 0)
 185                         error("rresvport: af=%d %.100s", ai->ai_family,
 186                             strerror(errno));
 187                 else
 188                         debug("Allocated local port %d.", p);
 189                 return sock;
 190         }
 191         sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 192         if (sock < 0)
 193                 error("socket: %.100s", strerror(errno));
 194
 195         /* Bind the socket to an alternative local IP address */
 196         if (options.bind_address == NULL)
 197                 return sock;
 198
 199         memset(&hints, 0, sizeof(hints));
 200         hints.ai_family = ai->ai_family;
 201         hints.ai_socktype = ai->ai_socktype;
 202         hints.ai_protocol = ai->ai_protocol;
 203         hints.ai_flags = AI_PASSIVE;
 204         gaierr = getaddrinfo(options.bind_address, "0", &hints, &res);
 205         if (gaierr) {
 206                 error("getaddrinfo: %s: %s", options.bind_address,
 207                     gai_strerror(gaierr));
 208                 close(sock);
 209                 return -1;
 210         }
 211         if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
 212                 error("bind: %s: %s", options.bind_address, strerror(errno));
 213                 close(sock);
 214                 freeaddrinfo(res);
 215                 return -1;
 216         }
 217         freeaddrinfo(res);
 218         return sock;
 219 }
 220
 221 static int
 222 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
 223     socklen_t addrlen, int timeout)
 224 {
 225         fd_set *fdset;
 226         struct timeval tv;
 227         socklen_t optlen;
 228         int optval, rc, result = -1;
 229
 230         if (timeout <= 0)
 231                 return (connect(sockfd, serv_addr, addrlen));
 232
 233         set_nonblock(sockfd);
 234         rc = connect(sockfd, serv_addr, addrlen);
 235         if (rc == 0) {
 236                 unset_nonblock(sockfd);
 237                 return (0);
 238         }
 239         if (errno != EINPROGRESS)
 240                 return (-1);
 241
 242         fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
 243             sizeof(fd_mask));
 244         FD_SET(sockfd, fdset);
 245         tv.tv_sec = timeout;
 246         tv.tv_usec = 0;
 247
 248         for (;;) {
 249                 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
 250                 if (rc != -1 || errno != EINTR)
 251                         break;
 252         }
 253
 254         switch (rc) {
 255         case 0:
 256                 /* Timed out */
 257                 errno = ETIMEDOUT;
 258                 break;
 259         case -1:
 260                 /* Select error */
 261                 debug("select: %s", strerror(errno));
 262                 break;
 263         case 1:
 264                 /* Completed or failed */
 265                 optval = 0;
 266                 optlen = sizeof(optval);
 267                 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
 268                     &optlen) == -1) {
 269                         debug("getsockopt: %s", strerror(errno));
 270                         break;
 271                 }
 272                 if (optval != 0) {
 273                         errno = optval;
 274                         break;
 275                 }
 276                 result = 0;
 277                 unset_nonblock(sockfd);
 278                 break;
 279         default:
 280                 /* Should not occur */
 281                 fatal("Bogus return (%d) from select()", rc);
 282         }
 283
 284         xfree(fdset);
 285         return (result);
 286 }
 287
 288 /*
 289  * Opens a TCP/IP connection to the remote server on the given host.
 290  * The address of the remote host will be returned in hostaddr.
 291  * If port is 0, the default port will be used.  If needpriv is true,
 292  * a privileged port will be allocated to make the connection.
 293  * This requires super-user privileges if needpriv is true.
 294  * Connection_attempts specifies the maximum number of tries (one per
 295  * second).  If proxy_command is non-NULL, it specifies the command (with %h
 296  * and %p substituted for host and port, respectively) to use to contact
 297  * the daemon.
 298  */
 299 int
 300 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
 301     u_short port, int family, int connection_attempts,
 302     int needpriv, const char *proxy_command)
 303 {
 304         int gaierr;
 305         int on = 1;
 306         int sock = -1, attempt;
 307         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 308         struct addrinfo hints, *ai, *aitop;
 309
 310         debug2("ssh_connect: needpriv %d", needpriv);
 311
 312         /* If a proxy command is given, connect using it. */
 313         if (proxy_command != NULL)
 314                 return ssh_proxy_connect(host, port, proxy_command);
 315
 316         /* No proxy command. */
 317
 318         memset(&hints, 0, sizeof(hints));
 319         hints.ai_family = family;
 320         hints.ai_socktype = SOCK_STREAM;
 321         snprintf(strport, sizeof strport, "%u", port);
 322         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
 323                 fatal("%s: %.100s: %s", __progname, host,
 324                     gai_strerror(gaierr));
 325
 326         for (attempt = 0; attempt < connection_attempts; attempt++) {
 327                 if (attempt > 0) {
 328                         /* Sleep a moment before retrying. */
 329                         sleep(1);
 330                         debug("Trying again...");
 331                 }
 332                 /*
 333                  * Loop through addresses for this host, and try each one in
 334                  * sequence until the connection succeeds.
 335                  */
 336                 for (ai = aitop; ai; ai = ai->ai_next) {
 337                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 338                                 continue;
 339                         if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
 340                             ntop, sizeof(ntop), strport, sizeof(strport),
 341                             NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 342                                 error("ssh_connect: getnameinfo failed");
 343                                 continue;
 344                         }
 345                         debug("Connecting to %.200s [%.100s] port %s.",
 346                                 host, ntop, strport);
 347
 348                         /* Create a socket for connecting. */
 349                         sock = ssh_create_socket(needpriv, ai);
 350                         if (sock < 0)
 351                                 /* Any error is already output */
 352                                 continue;
 353
 354                         if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
 355                             options.connection_timeout) >= 0) {
 356                                 /* Successful connection. */
 357                                 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
 358                                 break;
 359                         } else {
 360                                 debug("connect to address %s port %s: %s",
 361                                     ntop, strport, strerror(errno));
 362                                 close(sock);
 363                                 sock = -1;
 364                         }
 365                 }
 366                 if (sock != -1)
 367                         break;  /* Successful connection. */
 368         }
 369
 370         freeaddrinfo(aitop);
 371
 372         /* Return failure if we didn't get a successful connection. */
 373         if (sock == -1) {
 374                 error("ssh: connect to host %s port %s: %s",
 375                     host, strport, strerror(errno));
 376                 return (-1);
 377         }
 378
 379         debug("Connection established.");
 380
 381         /* Set SO_KEEPALIVE if requested. */
 382         if (options.tcp_keep_alive &&
 383             setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
 384             sizeof(on)) < 0)
 385                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 386
 387         /* Set the connection. */
 388         packet_set_connection(sock, sock);
 389
 390         return 0;
 391 }
 392
 393 /*
 394  * Waits for the server identification string, and sends our own
 395  * identification string.
 396  */
 397 static void
 398 ssh_exchange_identification(void)
 399 {
 400         char buf[256], remote_version[256];     /* must be same size! */
 401         int remote_major, remote_minor, mismatch;
 402         int connection_in = packet_get_connection_in();
 403         int connection_out = packet_get_connection_out();
 404         int minor1 = PROTOCOL_MINOR_1;
 405         u_int i, n;
 406
 407         /* Read other side's version identification. */
 408         for (n = 0;;) {
 409                 for (i = 0; i < sizeof(buf) - 1; i++) {
 410                         size_t len = atomicio(read, connection_in, &buf[i], 1);
 411
 412                         if (len != 1 && errno == EPIPE)
 413                                 fatal("ssh_exchange_identification: Connection closed by remote host");
 414                         else if (len != 1)
 415                                 fatal("ssh_exchange_identification: read: %.100s", strerror(errno));
 416                         if (buf[i] == '\r') {
 417                                 buf[i] = '\n';
 418                                 buf[i + 1] = 0;
 419                                 continue;               /**XXX wait for \n */
 420                         }
 421                         if (buf[i] == '\n') {
 422                                 buf[i + 1] = 0;
 423                                 break;
 424                         }
 425                         if (++n > 65536)
 426                                 fatal("ssh_exchange_identification: No banner received");
 427                 }
 428                 buf[sizeof(buf) - 1] = 0;
 429                 if (strncmp(buf, "SSH-", 4) == 0)
 430                         break;
 431                 debug("ssh_exchange_identification: %s", buf);
 432         }
 433         server_version_string = xstrdup(buf);
 434
 435         /*
 436          * Check that the versions match.  In future this might accept
 437          * several versions and set appropriate flags to handle them.
 438          */
 439         if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
 440             &remote_major, &remote_minor, remote_version) != 3)
 441                 fatal("Bad remote protocol version identification: '%.100s'", buf);
 442         debug("Remote protocol version %d.%d, remote software version %.100s",
 443             remote_major, remote_minor, remote_version);
 444
 445         compat_datafellows(remote_version);
 446         mismatch = 0;
 447
 448         switch (remote_major) {
 449         case 1:
 450                 if (remote_minor == 99 &&
 451                     (options.protocol & SSH_PROTO_2) &&
 452                     !(options.protocol & SSH_PROTO_1_PREFERRED)) {
 453                         enable_compat20();
 454                         break;
 455                 }
 456                 if (!(options.protocol & SSH_PROTO_1)) {
 457                         mismatch = 1;
 458                         break;
 459                 }
 460                 if (remote_minor < 3) {
 461                         fatal("Remote machine has too old SSH software version.");
 462                 } else if (remote_minor == 3 || remote_minor == 4) {
 463                         /* We speak 1.3, too. */
 464                         enable_compat13();
 465                         minor1 = 3;
 466                         if (options.forward_agent) {
 467                                 logit("Agent forwarding disabled for protocol 1.3");
 468                                 options.forward_agent = 0;
 469                         }
 470                 }
 471                 break;
 472         case 2:
 473                 if (options.protocol & SSH_PROTO_2) {
 474                         enable_compat20();
 475                         break;
 476                 }
 477                 /* FALLTHROUGH */
 478         default:
 479                 mismatch = 1;
 480                 break;
 481         }
 482         if (mismatch)
 483                 fatal("Protocol major versions differ: %d vs. %d",
 484                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 485                     remote_major);
 486         /* Send our own protocol version identification. */
 487         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
 488             compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 489             compat20 ? PROTOCOL_MINOR_2 : minor1,
 490             SSH_VERSION);
 491         if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
 492                 fatal("write: %.100s", strerror(errno));
 493         client_version_string = xstrdup(buf);
 494         chop(client_version_string);
 495         chop(server_version_string);
 496         debug("Local version string %.100s", client_version_string);
 497 }
 498
 499 /* defaults to 'no' */
 500 static int
 501 confirm(const char *prompt)
 502 {
 503         const char *msg, *again = "Please type 'yes' or 'no': ";
 504         char *p;
 505         int ret = -1;
 506
 507         if (options.batch_mode)
 508                 return 0;
 509         for (msg = prompt;;msg = again) {
 510                 p = read_passphrase(msg, RP_ECHO);
 511                 if (p == NULL ||
 512                     (p[0] == '\0') || (p[0] == '\n') ||
 513                     strncasecmp(p, "no", 2) == 0)
 514                         ret = 0;
 515                 if (p && strncasecmp(p, "yes", 3) == 0)
 516                         ret = 1;
 517                 if (p)
 518                         xfree(p);
 519                 if (ret != -1)
 520                         return ret;
 521         }
 522 }
 523
 524 /*
 525  * check whether the supplied host key is valid, return -1 if the key
 526  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
 527  */
 528 #define RDRW    0
 529 #define RDONLY  1
 530 #define ROQUIET 2
 531 static int
 532 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 533     Key *host_key, int readonly, const char *user_hostfile,
 534     const char *system_hostfile)
 535 {
 536         Key *file_key;
 537         const char *type = key_type(host_key);
 538         char *ip = NULL, *host = NULL;
 539         char hostline[1000], *hostp, *fp;
 540         HostStatus host_status;
 541         HostStatus ip_status;
 542         int r, local = 0, host_ip_differ = 0;
 543         int salen;
 544         char ntop[NI_MAXHOST];
 545         char msg[1024];
 546         int len, host_line, ip_line;
 547         const char *host_file = NULL, *ip_file = NULL;
 548
 549         /*
 550          * Force accepting of the host key for loopback/localhost. The
 551          * problem is that if the home directory is NFS-mounted to multiple
 552          * machines, localhost will refer to a different machine in each of
 553          * them, and the user will get bogus HOST_CHANGED warnings.  This
 554          * essentially disables host authentication for localhost; however,
 555          * this is probably not a real problem.
 556          */
 557         /**  hostaddr == 0! */
 558         switch (hostaddr->sa_family) {
 559         case AF_INET:
 560                 local = (ntohl(((struct sockaddr_in *)hostaddr)->
 561                     sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
 562                 salen = sizeof(struct sockaddr_in);
 563                 break;
 564         case AF_INET6:
 565                 local = IN6_IS_ADDR_LOOPBACK(
 566                     &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
 567                 salen = sizeof(struct sockaddr_in6);
 568                 break;
 569         default:
 570                 local = 0;
 571                 salen = sizeof(struct sockaddr_storage);
 572                 break;
 573         }
 574         if (options.no_host_authentication_for_localhost == 1 && local &&
 575             options.host_key_alias == NULL) {
 576                 debug("Forcing accepting of host key for "
 577                     "loopback/localhost.");
 578                 return 0;
 579         }
 580
 581         /*
 582          * We don't have the remote ip-address for connections
 583          * using a proxy command
 584          */
 585         if (options.proxy_command == NULL) {
 586                 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
 587                     NULL, 0, NI_NUMERICHOST) != 0)
 588                         fatal("check_host_key: getnameinfo failed");
 589                 ip = put_host_port(ntop, port);
 590         } else {
 591                 ip = xstrdup("<no hostip for proxy command>");
 592         }
 593         /*
 594          * Turn off check_host_ip if the connection is to localhost, via proxy
 595          * command or if we don't have a hostname to compare with
 596          */
 597         if (options.check_host_ip && (local ||
 598             strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
 599                 options.check_host_ip = 0;
 600
 601         /*
 602          * Allow the user to record the key under a different name or
 603          * differentiate a non-standard port.  This is useful for ssh
 604          * tunneling over forwarded connections or if you run multiple
 605          * sshd's on different ports on the same machine.
 606          */
 607         if (options.host_key_alias != NULL) {
 608                 host = xstrdup(options.host_key_alias);
 609                 debug("using hostkeyalias: %s", host);
 610         } else {
 611                 host = put_host_port(hostname, port);
 612         }
 613
 614         /*
 615          * Store the host key from the known host file in here so that we can
 616          * compare it with the key for the IP address.
 617          */
 618         file_key = key_new(host_key->type);
 619
 620         /*
 621          * Check if the host key is present in the user's list of known
 622          * hosts or in the systemwide list.
 623          */
 624         host_file = user_hostfile;
 625         host_status = check_host_in_hostfile(host_file, host, host_key,
 626             file_key, &host_line);
 627         if (host_status == HOST_NEW) {
 628                 host_file = system_hostfile;
 629                 host_status = check_host_in_hostfile(host_file, host, host_key,
 630                     file_key, &host_line);
 631         }
 632         /*
 633          * Also perform check for the ip address, skip the check if we are
 634          * localhost or the hostname was an ip address to begin with
 635          */
 636         if (options.check_host_ip) {
 637                 Key *ip_key = key_new(host_key->type);
 638
 639                 ip_file = user_hostfile;
 640                 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
 641                     ip_key, &ip_line);
 642                 if (ip_status == HOST_NEW) {
 643                         ip_file = system_hostfile;
 644                         ip_status = check_host_in_hostfile(ip_file, ip,
 645                             host_key, ip_key, &ip_line);
 646                 }
 647                 if (host_status == HOST_CHANGED &&
 648                     (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
 649                         host_ip_differ = 1;
 650
 651                 key_free(ip_key);
 652         } else
 653                 ip_status = host_status;
 654
 655         key_free(file_key);
 656
 657         switch (host_status) {
 658         case HOST_OK:
 659                 /* The host is known and the key matches. */
 660                 debug("Host '%.200s' is known and matches the %s host key.",
 661                     host, type);
 662                 debug("Found key in %s:%d", host_file, host_line);
 663                 if (options.check_host_ip && ip_status == HOST_NEW) {
 664                         if (readonly)
 665                                 logit("%s host key for IP address "
 666                                     "'%.128s' not in list of known hosts.",
 667                                     type, ip);
 668                         else if (!add_host_to_hostfile(user_hostfile, ip,
 669                             host_key, options.hash_known_hosts))
 670                                 logit("Failed to add the %s host key for IP "
 671                                     "address '%.128s' to the list of known "
 672                                     "hosts (%.30s).", type, ip, user_hostfile);
 673                         else
 674                                 logit("Warning: Permanently added the %s host "
 675                                     "key for IP address '%.128s' to the list "
 676                                     "of known hosts.", type, ip);
 677                 }
 678                 break;
 679         case HOST_NEW:
 680                 if (options.host_key_alias == NULL && port != 0 &&
 681                     port != SSH_DEFAULT_PORT) {
 682                         debug("checking without port identifier");
 683                         if (check_host_key(hostname, hostaddr, 0, host_key, 2,
 684                             user_hostfile, system_hostfile) == 0) {
 685                                 debug("found matching key w/out port");
 686                                 break;
 687                         }
 688                 }
 689                 if (readonly)
 690                         goto fail;
 691                 /* The host is new. */
 692                 if (options.strict_host_key_checking == 1) {
 693                         /*
 694                          * User has requested strict host key checking.  We
 695                          * will not add the host key automatically.  The only
 696                          * alternative left is to abort.
 697                          */
 698                         error("No %s host key is known for %.200s and you "
 699                             "have requested strict checking.", type, host);
 700                         goto fail;
 701                 } else if (options.strict_host_key_checking == 2) {
 702                         char msg1[1024], msg2[1024];
 703
 704                         if (show_other_keys(host, host_key))
 705                                 snprintf(msg1, sizeof(msg1),
 706                                     "\nbut keys of different type are already"
 707                                     " known for this host.");
 708                         else
 709                                 snprintf(msg1, sizeof(msg1), ".");
 710                         /* The default */
 711                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 712                         msg2[0] = '\0';
 713                         if (options.verify_host_key_dns) {
 714                                 if (matching_host_key_dns)
 715                                         snprintf(msg2, sizeof(msg2),
 716                                             "Matching host key fingerprint"
 717                                             " found in DNS.\n");
 718                                 else
 719                                         snprintf(msg2, sizeof(msg2),
 720                                             "No matching host key fingerprint"
 721                                             " found in DNS.\n");
 722                         }
 723                         snprintf(msg, sizeof(msg),
 724                             "The authenticity of host '%.200s (%s)' can't be "
 725                             "established%s\n"
 726                             "%s key fingerprint is %s.\n%s"
 727                             "Are you sure you want to continue connecting "
 728                             "(yes/no)? ",
 729                             host, ip, msg1, type, fp, msg2);
 730                         xfree(fp);
 731                         if (!confirm(msg))
 732                                 goto fail;
 733                 }
 734                 /*
 735                  * If not in strict mode, add the key automatically to the
 736                  * local known_hosts file.
 737                  */
 738                 if (options.check_host_ip && ip_status == HOST_NEW) {
 739                         snprintf(hostline, sizeof(hostline), "%s,%s",
 740                             host, ip);
 741                         hostp = hostline;
 742                         if (options.hash_known_hosts) {
 743                                 /* Add hash of host and IP separately */
 744                                 r = add_host_to_hostfile(user_hostfile, host,
 745                                     host_key, options.hash_known_hosts) &&
 746                                     add_host_to_hostfile(user_hostfile, ip,
 747                                     host_key, options.hash_known_hosts);
 748                         } else {
 749                                 /* Add unhashed "host,ip" */
 750                                 r = add_host_to_hostfile(user_hostfile,
 751                                     hostline, host_key,
 752                                     options.hash_known_hosts);
 753                         }
 754                 } else {
 755                         r = add_host_to_hostfile(user_hostfile, host, host_key,
 756                             options.hash_known_hosts);
 757                         hostp = host;
 758                 }
 759
 760                 if (!r)
 761                         logit("Failed to add the host to the list of known "
 762                             "hosts (%.500s).", user_hostfile);
 763                 else
 764                         logit("Warning: Permanently added '%.200s' (%s) to the "
 765                             "list of known hosts.", hostp, type);
 766                 break;
 767         case HOST_CHANGED:
 768                 if (readonly == ROQUIET)
 769                         goto fail;
 770                 if (options.check_host_ip && host_ip_differ) {
 771                         char *key_msg;
 772                         if (ip_status == HOST_NEW)
 773                                 key_msg = "is unknown";
 774                         else if (ip_status == HOST_OK)
 775                                 key_msg = "is unchanged";
 776                         else
 777                                 key_msg = "has a different value";
 778                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 779                         error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
 780                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 781                         error("The %s host key for %s has changed,", type, host);
 782                         error("and the key for the according IP address %s", ip);
 783                         error("%s. This could either mean that", key_msg);
 784                         error("DNS SPOOFING is happening or the IP address for the host");
 785                         error("and its host key have changed at the same time.");
 786                         if (ip_status != HOST_NEW)
 787                                 error("Offending key for IP in %s:%d", ip_file, ip_line);
 788                 }
 789                 /* The host key has changed. */
 790                 warn_changed_key(host_key);
 791                 error("Add correct host key in %.100s to get rid of this message.",
 792                     user_hostfile);
 793                 error("Offending key in %s:%d", host_file, host_line);
 794
 795                 /*
 796                  * If strict host key checking is in use, the user will have
 797                  * to edit the key manually and we can only abort.
 798                  */
 799                 if (options.strict_host_key_checking) {
 800                         error("%s host key for %.200s has changed and you have "
 801                             "requested strict checking.", type, host);
 802                         goto fail;
 803                 }
 804
 805                 /*
 806                  * If strict host key checking has not been requested, allow
 807                  * the connection but without MITM-able authentication or
 808                  * forwarding.
 809                  */
 810                 if (options.password_authentication) {
 811                         error("Password authentication is disabled to avoid "
 812                             "man-in-the-middle attacks.");
 813                         options.password_authentication = 0;
 814                 }
 815                 if (options.kbd_interactive_authentication) {
 816                         error("Keyboard-interactive authentication is disabled"
 817                             " to avoid man-in-the-middle attacks.");
 818                         options.kbd_interactive_authentication = 0;
 819                         options.challenge_response_authentication = 0;
 820                 }
 821                 if (options.challenge_response_authentication) {
 822                         error("Challenge/response authentication is disabled"
 823                             " to avoid man-in-the-middle attacks.");
 824                         options.challenge_response_authentication = 0;
 825                 }
 826                 if (options.forward_agent) {
 827                         error("Agent forwarding is disabled to avoid "
 828                             "man-in-the-middle attacks.");
 829                         options.forward_agent = 0;
 830                 }
 831                 if (options.forward_x11) {
 832                         error("X11 forwarding is disabled to avoid "
 833                             "man-in-the-middle attacks.");
 834                         options.forward_x11 = 0;
 835                 }
 836                 if (options.num_local_forwards > 0 ||
 837                     options.num_remote_forwards > 0) {
 838                         error("Port forwarding is disabled to avoid "
 839                             "man-in-the-middle attacks.");
 840                         options.num_local_forwards =
 841                             options.num_remote_forwards = 0;
 842                 }
 843                 if (options.tun_open != SSH_TUNMODE_NO) {
 844                         error("Tunnel forwarding is disabled to avoid "
 845                             "man-in-the-middle attacks.");
 846                         options.tun_open = SSH_TUNMODE_NO;
 847                 }
 848                 /*
 849                  * XXX Should permit the user to change to use the new id.
 850                  * This could be done by converting the host key to an
 851                  * identifying sentence, tell that the host identifies itself
 852                  * by that sentence, and ask the user if he/she whishes to
 853                  * accept the authentication.
 854                  */
 855                 break;
 856         case HOST_FOUND:
 857                 fatal("internal error");
 858                 break;
 859         }
 860
 861         if (options.check_host_ip && host_status != HOST_CHANGED &&
 862             ip_status == HOST_CHANGED) {
 863                 snprintf(msg, sizeof(msg),
 864                     "Warning: the %s host key for '%.200s' "
 865                     "differs from the key for the IP address '%.128s'"
 866                     "\nOffending key for IP in %s:%d",
 867                     type, host, ip, ip_file, ip_line);
 868                 if (host_status == HOST_OK) {
 869                         len = strlen(msg);
 870                         snprintf(msg + len, sizeof(msg) - len,
 871                             "\nMatching host key in %s:%d",
 872                             host_file, host_line);
 873                 }
 874                 if (options.strict_host_key_checking == 1) {
 875                         logit("%s", msg);
 876                         error("Exiting, you have requested strict checking.");
 877                         goto fail;
 878                 } else if (options.strict_host_key_checking == 2) {
 879                         strlcat(msg, "\nAre you sure you want "
 880                             "to continue connecting (yes/no)? ", sizeof(msg));
 881                         if (!confirm(msg))
 882                                 goto fail;
 883                 } else {
 884                         logit("%s", msg);
 885                 }
 886         }
 887
 888         xfree(ip);
 889         xfree(host);
 890         return 0;
 891
 892 fail:
 893         xfree(ip);
 894         xfree(host);
 895         return -1;
 896 }
 897
 898 /* returns 0 if key verifies or -1 if key does NOT verify */
 899 int
 900 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 901 {
 902         struct stat st;
 903         int flags = 0;
 904
 905         if (options.verify_host_key_dns &&
 906             verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
 907
 908                 if (flags & DNS_VERIFY_FOUND) {
 909
 910                         if (options.verify_host_key_dns == 1 &&
 911                             flags & DNS_VERIFY_MATCH &&
 912                             flags & DNS_VERIFY_SECURE)
 913                                 return 0;
 914
 915                         if (flags & DNS_VERIFY_MATCH) {
 916                                 matching_host_key_dns = 1;
 917                         } else {
 918                                 warn_changed_key(host_key);
 919                                 error("Update the SSHFP RR in DNS with the new "
 920                                     "host key to get rid of this message.");
 921                         }
 922                 }
 923         }
 924
 925         /* return ok if the key can be found in an old keyfile */
 926         if (stat(options.system_hostfile2, &st) == 0 ||
 927             stat(options.user_hostfile2, &st) == 0) {
 928                 if (check_host_key(host, hostaddr, options.port, host_key,
 929                     RDONLY, options.user_hostfile2,
 930                     options.system_hostfile2) == 0)
 931                         return 0;
 932         }
 933         return check_host_key(host, hostaddr, options.port, host_key,
 934             RDRW, options.user_hostfile, options.system_hostfile);
 935 }
 936
 937 /*
 938  * Starts a dialog with the server, and authenticates the current user on the
 939  * server.  This does not need any extra privileges.  The basic connection
 940  * to the server must already have been established before this is called.
 941  * If login fails, this function prints an error and never returns.
 942  * This function does not require super-user privileges.
 943  */
 944 void
 945 ssh_login(Sensitive *sensitive, const char *orighost,
 946     struct sockaddr *hostaddr, struct passwd *pw)
 947 {
 948         char *host, *cp;
 949         char *server_user, *local_user;
 950
 951         local_user = xstrdup(pw->pw_name);
 952         server_user = options.user ? options.user : local_user;
 953
 954         /* Convert the user-supplied hostname into all lowercase. */
 955         host = xstrdup(orighost);
 956         for (cp = host; *cp; cp++)
 957                 if (isupper(*cp))
 958                         *cp = (char)tolower(*cp);
 959
 960         /* Exchange protocol version identification strings with the server. */
 961         ssh_exchange_identification();
 962
 963         /* Put the connection into non-blocking mode. */
 964         packet_set_nonblocking();
 965
 966         /* key exchange */
 967         /* authenticate user */
 968         if (compat20) {
 969                 ssh_kex2(host, hostaddr);
 970                 ssh_userauth2(local_user, server_user, host, sensitive);
 971         } else {
 972                 ssh_kex(host, hostaddr);
 973                 ssh_userauth1(local_user, server_user, host, sensitive);
 974         }
 975         xfree(local_user);
 976 }
 977
 978 void
 979 ssh_put_password(char *password)
 980 {
 981         int size;
 982         char *padded;
 983
 984         if (datafellows & SSH_BUG_PASSWORDPAD) {
 985                 packet_put_cstring(password);
 986                 return;
 987         }
 988         size = roundup(strlen(password) + 1, 32);
 989         padded = xcalloc(1, size);
 990         strlcpy(padded, password, size);
 991         packet_put_string(padded, size);
 992         memset(padded, 0, size);
 993         xfree(padded);
 994 }
 995
 996 static int
 997 show_key_from_file(const char *file, const char *host, int keytype)
 998 {
 999         Key *found;
1000         char *fp;
1001         int line, ret;
1002
1003         found = key_new(keytype);
1004         if ((ret = lookup_key_in_hostfile_by_type(file, host,
1005             keytype, found, &line))) {
1006                 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1007                 logit("WARNING: %s key found for host %s\n"
1008                     "in %s:%d\n"
1009                     "%s key fingerprint %s.",
1010                     key_type(found), host, file, line,
1011                     key_type(found), fp);
1012                 xfree(fp);
1013         }
1014         key_free(found);
1015         return (ret);
1016 }
1017
1018 /* print all known host keys for a given host, but skip keys of given type */
1019 static int
1020 show_other_keys(const char *host, Key *key)
1021 {
1022         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1023         int i, found = 0;
1024
1025         for (i = 0; type[i] != -1; i++) {
1026                 if (type[i] == key->type)
1027                         continue;
1028                 if (type[i] != KEY_RSA1 &&
1029                     show_key_from_file(options.user_hostfile2, host, type[i])) {
1030                         found = 1;
1031                         continue;
1032                 }
1033                 if (type[i] != KEY_RSA1 &&
1034                     show_key_from_file(options.system_hostfile2, host, type[i])) {
1035                         found = 1;
1036                         continue;
1037                 }
1038                 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1039                         found = 1;
1040                         continue;
1041                 }
1042                 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1043                         found = 1;
1044                         continue;
1045                 }
1046                 debug2("no key of type %d for host %s", type[i], host);
1047         }
1048         return (found);
1049 }
1050
1051 static void
1052 warn_changed_key(Key *host_key)
1053 {
1054         char *fp;
1055         const char *type = key_type(host_key);
1056
1057         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1058
1059         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1060         error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1061         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1062         error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1063         error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1064         error("It is also possible that the %s host key has just been changed.", type);
1065         error("The fingerprint for the %s key sent by the remote host is\n%s.",
1066             type, fp);
1067         error("Please contact your system administrator.");
1068
1069         xfree(fp);
1070 }
1071
1072 /*
1073  * Execute a local command
1074  */
1075 int
1076 ssh_local_cmd(const char *args)
1077 {
1078         char *shell;
1079         pid_t pid;
1080         int status;
1081
1082         if (!options.permit_local_command ||
1083             args == NULL || !*args)
1084                 return (1);
1085
1086         if ((shell = getenv("SHELL")) == NULL)
1087                 shell = _PATH_BSHELL;
1088
1089         pid = fork();
1090         if (pid == 0) {
1091                 debug3("Executing %s -c \"%s\"", shell, args);
1092                 execl(shell, shell, "-c", args, (char *)NULL);
1093                 error("Couldn't execute %s -c \"%s\": %s",
1094                     shell, args, strerror(errno));
1095                 _exit(1);
1096         } else if (pid == -1)
1097                 fatal("fork failed: %.100s", strerror(errno));
1098         while (waitpid(pid, &status, 0) == -1)
1099                 if (errno != EINTR)
1100                         fatal("Couldn't wait for child: %s", strerror(errno));
1101
1102         if (!WIFEXITED(status))
1103                 return (1);
1104
1105         return (WEXITSTATUS(status));
1106 }