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