crypto/openssh/sshconnect.c

   1 /* $OpenBSD: sshconnect.c,v 1.212 2008/10/14 18:11:33 stevesk Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Code to connect to a remote host, and to perform the client side of the
   7  * login (authentication) dialog.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  */
  15
  16 #include "includes.h"
  17
  18 #include <sys/types.h>
  19 #include <sys/wait.h>
  20 #include <sys/stat.h>
  21 #include <sys/socket.h>
  22 #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 static int show_other_keys(const char *, Key *);
  74 static void warn_changed_key(Key *);
  75
  76 /*
  77  * Connect to the given ssh server using a proxy command.
  78  */
  79 static int
  80 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command)
  81 {
  82         char *command_string, *tmp;
  83         int pin[2], pout[2];
  84         pid_t pid;
  85         char *shell, strport[NI_MAXSERV];
  86
  87         if ((shell = getenv("SHELL")) == NULL)
  88                 shell = _PATH_BSHELL;
  89
  90         /* Convert the port number into a string. */
  91         snprintf(strport, sizeof strport, "%hu", port);
  92
  93         /*
  94          * Build the final command string in the buffer by making the
  95          * appropriate substitutions to the given proxy command.
  96          *
  97          * Use "exec" to avoid "sh -c" processes on some platforms
  98          * (e.g. Solaris)
  99          */
 100         xasprintf(&tmp, "exec %s", proxy_command);
 101         command_string = percent_expand(tmp, "h", host,
 102             "p", strport, (char *)NULL);
 103         xfree(tmp);
 104
 105         /* Create pipes for communicating with the proxy. */
 106         if (pipe(pin) < 0 || pipe(pout) < 0)
 107                 fatal("Could not create pipes to communicate with the proxy: %.100s",
 108                     strerror(errno));
 109
 110         debug("Executing proxy command: %.500s", command_string);
 111
 112         /* Fork and execute the proxy command. */
 113         if ((pid = fork()) == 0) {
 114                 char *argv[10];
 115
 116                 /* Child.  Permanently give up superuser privileges. */
 117                 permanently_drop_suid(original_real_uid);
 118
 119                 /* Redirect stdin and stdout. */
 120                 close(pin[1]);
 121                 if (pin[0] != 0) {
 122                         if (dup2(pin[0], 0) < 0)
 123                                 perror("dup2 stdin");
 124                         close(pin[0]);
 125                 }
 126                 close(pout[0]);
 127                 if (dup2(pout[1], 1) < 0)
 128                         perror("dup2 stdout");
 129                 /* Cannot be 1 because pin allocated two descriptors. */
 130                 close(pout[1]);
 131
 132                 /* Stderr is left as it is so that error messages get
 133                    printed on the user's terminal. */
 134                 argv[0] = shell;
 135                 argv[1] = "-c";
 136                 argv[2] = command_string;
 137                 argv[3] = NULL;
 138
 139                 /* Execute the proxy command.  Note that we gave up any
 140                    extra privileges above. */
 141                 execv(argv[0], argv);
 142                 perror(argv[0]);
 143                 exit(1);
 144         }
 145         /* Parent. */
 146         if (pid < 0)
 147                 fatal("fork failed: %.100s", strerror(errno));
 148         else
 149                 proxy_command_pid = pid; /* save pid to clean up later */
 150
 151         /* Close child side of the descriptors. */
 152         close(pin[0]);
 153         close(pout[1]);
 154
 155         /* Free the command name. */
 156         xfree(command_string);
 157
 158         /* Set the connection file descriptors. */
 159         packet_set_connection(pout[0], pin[1]);
 160         packet_set_timeout(options.server_alive_interval,
 161             options.server_alive_count_max);
 162
 163         /* Indicate OK return */
 164         return 0;
 165 }
 166
 167 /*
 168  * Creates a (possibly privileged) socket for use as the ssh connection.
 169  */
 170 static int
 171 ssh_create_socket(int privileged, struct addrinfo *ai)
 172 {
 173         int sock, gaierr;
 174         struct addrinfo hints, *res;
 175
 176         /*
 177          * If we are running as root and want to connect to a privileged
 178          * port, bind our own socket to a privileged port.
 179          */
 180         if (privileged) {
 181                 int p = IPPORT_RESERVED - 1;
 182                 PRIV_START;
 183                 sock = rresvport_af(&p, ai->ai_family);
 184                 PRIV_END;
 185                 if (sock < 0)
 186                         error("rresvport: af=%d %.100s", ai->ai_family,
 187                             strerror(errno));
 188                 else
 189                         debug("Allocated local port %d.", p);
 190                 return sock;
 191         }
 192         sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
 193         if (sock < 0)
 194                 error("socket: %.100s", strerror(errno));
 195
 196         /* Bind the socket to an alternative local IP address */
 197         if (options.bind_address == NULL)
 198                 return sock;
 199
 200         memset(&hints, 0, sizeof(hints));
 201         hints.ai_family = ai->ai_family;
 202         hints.ai_socktype = ai->ai_socktype;
 203         hints.ai_protocol = ai->ai_protocol;
 204         hints.ai_flags = AI_PASSIVE;
 205         gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res);
 206         if (gaierr) {
 207                 error("getaddrinfo: %s: %s", options.bind_address,
 208                     ssh_gai_strerror(gaierr));
 209                 close(sock);
 210                 return -1;
 211         }
 212         if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) {
 213                 error("bind: %s: %s", options.bind_address, strerror(errno));
 214                 close(sock);
 215                 freeaddrinfo(res);
 216                 return -1;
 217         }
 218         freeaddrinfo(res);
 219         return sock;
 220 }
 221
 222 static int
 223 timeout_connect(int sockfd, const struct sockaddr *serv_addr,
 224     socklen_t addrlen, int *timeoutp)
 225 {
 226         fd_set *fdset;
 227         struct timeval tv, t_start;
 228         socklen_t optlen;
 229         int optval, rc, result = -1;
 230
 231         gettimeofday(&t_start, NULL);
 232
 233         if (*timeoutp <= 0) {
 234                 result = connect(sockfd, serv_addr, addrlen);
 235                 goto done;
 236         }
 237
 238         set_nonblock(sockfd);
 239         rc = connect(sockfd, serv_addr, addrlen);
 240         if (rc == 0) {
 241                 unset_nonblock(sockfd);
 242                 result = 0;
 243                 goto done;
 244         }
 245         if (errno != EINPROGRESS) {
 246                 result = -1;
 247                 goto done;
 248         }
 249
 250         fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS),
 251             sizeof(fd_mask));
 252         FD_SET(sockfd, fdset);
 253         ms_to_timeval(&tv, *timeoutp);
 254
 255         for (;;) {
 256                 rc = select(sockfd + 1, NULL, fdset, NULL, &tv);
 257                 if (rc != -1 || errno != EINTR)
 258                         break;
 259         }
 260
 261         switch (rc) {
 262         case 0:
 263                 /* Timed out */
 264                 errno = ETIMEDOUT;
 265                 break;
 266         case -1:
 267                 /* Select error */
 268                 debug("select: %s", strerror(errno));
 269                 break;
 270         case 1:
 271                 /* Completed or failed */
 272                 optval = 0;
 273                 optlen = sizeof(optval);
 274                 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval,
 275                     &optlen) == -1) {
 276                         debug("getsockopt: %s", strerror(errno));
 277                         break;
 278                 }
 279                 if (optval != 0) {
 280                         errno = optval;
 281                         break;
 282                 }
 283                 result = 0;
 284                 unset_nonblock(sockfd);
 285                 break;
 286         default:
 287                 /* Should not occur */
 288                 fatal("Bogus return (%d) from select()", rc);
 289         }
 290
 291         xfree(fdset);
 292
 293  done:
 294         if (result == 0 && *timeoutp > 0) {
 295                 ms_subtract_diff(&t_start, timeoutp);
 296                 if (*timeoutp <= 0) {
 297                         errno = ETIMEDOUT;
 298                         result = -1;
 299                 }
 300         }
 301
 302         return (result);
 303 }
 304
 305 /*
 306  * Opens a TCP/IP connection to the remote server on the given host.
 307  * The address of the remote host will be returned in hostaddr.
 308  * If port is 0, the default port will be used.  If needpriv is true,
 309  * a privileged port will be allocated to make the connection.
 310  * This requires super-user privileges if needpriv is true.
 311  * Connection_attempts specifies the maximum number of tries (one per
 312  * second).  If proxy_command is non-NULL, it specifies the command (with %h
 313  * and %p substituted for host and port, respectively) to use to contact
 314  * the daemon.
 315  */
 316 int
 317 ssh_connect(const char *host, struct sockaddr_storage * hostaddr,
 318     u_short port, int family, int connection_attempts, int *timeout_ms,
 319     int want_keepalive, int needpriv, const char *proxy_command)
 320 {
 321         int gaierr;
 322         int on = 1;
 323         int sock = -1, attempt;
 324         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 325         struct addrinfo hints, *ai, *aitop;
 326
 327         debug2("ssh_connect: needpriv %d", needpriv);
 328
 329         /* If a proxy command is given, connect using it. */
 330         if (proxy_command != NULL)
 331                 return ssh_proxy_connect(host, port, proxy_command);
 332
 333         /* No proxy command. */
 334
 335         memset(&hints, 0, sizeof(hints));
 336         hints.ai_family = family;
 337         hints.ai_socktype = SOCK_STREAM;
 338         snprintf(strport, sizeof strport, "%u", port);
 339         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0)
 340                 fatal("%s: Could not resolve hostname %.100s: %s", __progname,
 341                     host, ssh_gai_strerror(gaierr));
 342
 343         for (attempt = 0; attempt < connection_attempts; attempt++) {
 344                 if (attempt > 0) {
 345                         /* Sleep a moment before retrying. */
 346                         sleep(1);
 347                         debug("Trying again...");
 348                 }
 349                 /*
 350                  * Loop through addresses for this host, and try each one in
 351                  * sequence until the connection succeeds.
 352                  */
 353                 for (ai = aitop; ai; ai = ai->ai_next) {
 354                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 355                                 continue;
 356                         if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
 357                             ntop, sizeof(ntop), strport, sizeof(strport),
 358                             NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 359                                 error("ssh_connect: getnameinfo failed");
 360                                 continue;
 361                         }
 362                         debug("Connecting to %.200s [%.100s] port %s.",
 363                                 host, ntop, strport);
 364
 365                         /* Create a socket for connecting. */
 366                         sock = ssh_create_socket(needpriv, ai);
 367                         if (sock < 0)
 368                                 /* Any error is already output */
 369                                 continue;
 370
 371                         if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
 372                             timeout_ms) >= 0) {
 373                                 /* Successful connection. */
 374                                 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
 375                                 break;
 376                         } else {
 377                                 debug("connect to address %s port %s: %s",
 378                                     ntop, strport, strerror(errno));
 379                                 close(sock);
 380                                 sock = -1;
 381                         }
 382                 }
 383                 if (sock != -1)
 384                         break;  /* Successful connection. */
 385         }
 386
 387         freeaddrinfo(aitop);
 388
 389         /* Return failure if we didn't get a successful connection. */
 390         if (sock == -1) {
 391                 error("ssh: connect to host %s port %s: %s",
 392                     host, strport, strerror(errno));
 393                 return (-1);
 394         }
 395
 396         debug("Connection established.");
 397
 398         /* Set SO_KEEPALIVE if requested. */
 399         if (want_keepalive &&
 400             setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
 401             sizeof(on)) < 0)
 402                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 403
 404         /* Set the connection. */
 405         packet_set_connection(sock, sock);
 406         packet_set_timeout(options.server_alive_interval,
 407             options.server_alive_count_max);
 408
 409         return 0;
 410 }
 411
 412 /*
 413  * Waits for the server identification string, and sends our own
 414  * identification string.
 415  */
 416 static void
 417 ssh_exchange_identification(int timeout_ms)
 418 {
 419         char buf[256], remote_version[256];     /* must be same size! */
 420         int remote_major, remote_minor, mismatch;
 421         int connection_in = packet_get_connection_in();
 422         int connection_out = packet_get_connection_out();
 423         int minor1 = PROTOCOL_MINOR_1;
 424         u_int i, n;
 425         size_t len;
 426         int fdsetsz, remaining, rc;
 427         struct timeval t_start, t_remaining;
 428         fd_set *fdset;
 429
 430         fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask);
 431         fdset = xcalloc(1, fdsetsz);
 432
 433         /* Read other side's version identification. */
 434         remaining = timeout_ms;
 435         for (n = 0;;) {
 436                 for (i = 0; i < sizeof(buf) - 1; i++) {
 437                         if (timeout_ms > 0) {
 438                                 gettimeofday(&t_start, NULL);
 439                                 ms_to_timeval(&t_remaining, remaining);
 440                                 FD_SET(connection_in, fdset);
 441                                 rc = select(connection_in + 1, fdset, NULL,
 442                                     fdset, &t_remaining);
 443                                 ms_subtract_diff(&t_start, &remaining);
 444                                 if (rc == 0 || remaining <= 0)
 445                                         fatal("Connection timed out during "
 446                                             "banner exchange");
 447                                 if (rc == -1) {
 448                                         if (errno == EINTR)
 449                                                 continue;
 450                                         fatal("ssh_exchange_identification: "
 451                                             "select: %s", strerror(errno));
 452                                 }
 453                         }
 454
 455                         len = atomicio(read, connection_in, &buf[i], 1);
 456
 457                         if (len != 1 && errno == EPIPE)
 458                                 fatal("ssh_exchange_identification: "
 459                                     "Connection closed by remote host");
 460                         else if (len != 1)
 461                                 fatal("ssh_exchange_identification: "
 462                                     "read: %.100s", strerror(errno));
 463                         if (buf[i] == '\r') {
 464                                 buf[i] = '\n';
 465                                 buf[i + 1] = 0;
 466                                 continue;               /**XXX wait for \n */
 467                         }
 468                         if (buf[i] == '\n') {
 469                                 buf[i + 1] = 0;
 470                                 break;
 471                         }
 472                         if (++n > 65536)
 473                                 fatal("ssh_exchange_identification: "
 474                                     "No banner received");
 475                 }
 476                 buf[sizeof(buf) - 1] = 0;
 477                 if (strncmp(buf, "SSH-", 4) == 0)
 478                         break;
 479                 debug("ssh_exchange_identification: %s", buf);
 480         }
 481         server_version_string = xstrdup(buf);
 482         xfree(fdset);
 483
 484         /*
 485          * Check that the versions match.  In future this might accept
 486          * several versions and set appropriate flags to handle them.
 487          */
 488         if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
 489             &remote_major, &remote_minor, remote_version) != 3)
 490                 fatal("Bad remote protocol version identification: '%.100s'", buf);
 491         debug("Remote protocol version %d.%d, remote software version %.100s",
 492             remote_major, remote_minor, remote_version);
 493
 494         compat_datafellows(remote_version);
 495         mismatch = 0;
 496
 497         switch (remote_major) {
 498         case 1:
 499                 if (remote_minor == 99 &&
 500                     (options.protocol & SSH_PROTO_2) &&
 501                     !(options.protocol & SSH_PROTO_1_PREFERRED)) {
 502                         enable_compat20();
 503                         break;
 504                 }
 505                 if (!(options.protocol & SSH_PROTO_1)) {
 506                         mismatch = 1;
 507                         break;
 508                 }
 509                 if (remote_minor < 3) {
 510                         fatal("Remote machine has too old SSH software version.");
 511                 } else if (remote_minor == 3 || remote_minor == 4) {
 512                         /* We speak 1.3, too. */
 513                         enable_compat13();
 514                         minor1 = 3;
 515                         if (options.forward_agent) {
 516                                 logit("Agent forwarding disabled for protocol 1.3");
 517                                 options.forward_agent = 0;
 518                         }
 519                 }
 520                 break;
 521         case 2:
 522                 if (options.protocol & SSH_PROTO_2) {
 523                         enable_compat20();
 524                         break;
 525                 }
 526                 /* FALLTHROUGH */
 527         default:
 528                 mismatch = 1;
 529                 break;
 530         }
 531         if (mismatch)
 532                 fatal("Protocol major versions differ: %d vs. %d",
 533                     (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 534                     remote_major);
 535         /* Send our own protocol version identification. */
 536         snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s",
 537             compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1,
 538             compat20 ? PROTOCOL_MINOR_2 : minor1,
 539             SSH_VERSION, compat20 ? "\r\n" : "\n");
 540         if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf))
 541                 fatal("write: %.100s", strerror(errno));
 542         client_version_string = xstrdup(buf);
 543         chop(client_version_string);
 544         chop(server_version_string);
 545         debug("Local version string %.100s", client_version_string);
 546 }
 547
 548 /* defaults to 'no' */
 549 static int
 550 confirm(const char *prompt)
 551 {
 552         const char *msg, *again = "Please type 'yes' or 'no': ";
 553         char *p;
 554         int ret = -1;
 555
 556         if (options.batch_mode)
 557                 return 0;
 558         for (msg = prompt;;msg = again) {
 559                 p = read_passphrase(msg, RP_ECHO);
 560                 if (p == NULL ||
 561                     (p[0] == '\0') || (p[0] == '\n') ||
 562                     strncasecmp(p, "no", 2) == 0)
 563                         ret = 0;
 564                 if (p && strncasecmp(p, "yes", 3) == 0)
 565                         ret = 1;
 566                 if (p)
 567                         xfree(p);
 568                 if (ret != -1)
 569                         return ret;
 570         }
 571 }
 572
 573 /*
 574  * check whether the supplied host key is valid, return -1 if the key
 575  * is not valid. the user_hostfile will not be updated if 'readonly' is true.
 576  */
 577 #define RDRW    0
 578 #define RDONLY  1
 579 #define ROQUIET 2
 580 static int
 581 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
 582     Key *host_key, int readonly, const char *user_hostfile,
 583     const char *system_hostfile)
 584 {
 585         Key *file_key;
 586         const char *type = key_type(host_key);
 587         char *ip = NULL, *host = NULL;
 588         char hostline[1000], *hostp, *fp, *ra;
 589         HostStatus host_status;
 590         HostStatus ip_status;
 591         int r, local = 0, host_ip_differ = 0;
 592         int salen;
 593         char ntop[NI_MAXHOST];
 594         char msg[1024];
 595         int len, host_line, ip_line, cancelled_forwarding = 0;
 596         const char *host_file = NULL, *ip_file = NULL;
 597
 598         /*
 599          * Force accepting of the host key for loopback/localhost. The
 600          * problem is that if the home directory is NFS-mounted to multiple
 601          * machines, localhost will refer to a different machine in each of
 602          * them, and the user will get bogus HOST_CHANGED warnings.  This
 603          * essentially disables host authentication for localhost; however,
 604          * this is probably not a real problem.
 605          */
 606         /**  hostaddr == 0! */
 607         switch (hostaddr->sa_family) {
 608         case AF_INET:
 609                 local = (ntohl(((struct sockaddr_in *)hostaddr)->
 610                     sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
 611                 salen = sizeof(struct sockaddr_in);
 612                 break;
 613         case AF_INET6:
 614                 local = IN6_IS_ADDR_LOOPBACK(
 615                     &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
 616                 salen = sizeof(struct sockaddr_in6);
 617                 break;
 618         default:
 619                 local = 0;
 620                 salen = sizeof(struct sockaddr_storage);
 621                 break;
 622         }
 623         if (options.no_host_authentication_for_localhost == 1 && local &&
 624             options.host_key_alias == NULL) {
 625                 debug("Forcing accepting of host key for "
 626                     "loopback/localhost.");
 627                 return 0;
 628         }
 629
 630         /*
 631          * We don't have the remote ip-address for connections
 632          * using a proxy command
 633          */
 634         if (options.proxy_command == NULL) {
 635                 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop),
 636                     NULL, 0, NI_NUMERICHOST) != 0)
 637                         fatal("check_host_key: getnameinfo failed");
 638                 ip = put_host_port(ntop, port);
 639         } else {
 640                 ip = xstrdup("<no hostip for proxy command>");
 641         }
 642
 643         /*
 644          * Turn off check_host_ip if the connection is to localhost, via proxy
 645          * command or if we don't have a hostname to compare with
 646          */
 647         if (options.check_host_ip && (local ||
 648             strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
 649                 options.check_host_ip = 0;
 650
 651         /*
 652          * Allow the user to record the key under a different name or
 653          * differentiate a non-standard port.  This is useful for ssh
 654          * tunneling over forwarded connections or if you run multiple
 655          * sshd's on different ports on the same machine.
 656          */
 657         if (options.host_key_alias != NULL) {
 658                 host = xstrdup(options.host_key_alias);
 659                 debug("using hostkeyalias: %s", host);
 660         } else {
 661                 host = put_host_port(hostname, port);
 662         }
 663
 664         /*
 665          * Store the host key from the known host file in here so that we can
 666          * compare it with the key for the IP address.
 667          */
 668         file_key = key_new(host_key->type);
 669
 670         /*
 671          * Check if the host key is present in the user's list of known
 672          * hosts or in the systemwide list.
 673          */
 674         host_file = user_hostfile;
 675         host_status = check_host_in_hostfile(host_file, host, host_key,
 676             file_key, &host_line);
 677         if (host_status == HOST_NEW) {
 678                 host_file = system_hostfile;
 679                 host_status = check_host_in_hostfile(host_file, host, host_key,
 680                     file_key, &host_line);
 681         }
 682         /*
 683          * Also perform check for the ip address, skip the check if we are
 684          * localhost or the hostname was an ip address to begin with
 685          */
 686         if (options.check_host_ip) {
 687                 Key *ip_key = key_new(host_key->type);
 688
 689                 ip_file = user_hostfile;
 690                 ip_status = check_host_in_hostfile(ip_file, ip, host_key,
 691                     ip_key, &ip_line);
 692                 if (ip_status == HOST_NEW) {
 693                         ip_file = system_hostfile;
 694                         ip_status = check_host_in_hostfile(ip_file, ip,
 695                             host_key, ip_key, &ip_line);
 696                 }
 697                 if (host_status == HOST_CHANGED &&
 698                     (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key)))
 699                         host_ip_differ = 1;
 700
 701                 key_free(ip_key);
 702         } else
 703                 ip_status = host_status;
 704
 705         key_free(file_key);
 706
 707         switch (host_status) {
 708         case HOST_OK:
 709                 /* The host is known and the key matches. */
 710                 debug("Host '%.200s' is known and matches the %s host key.",
 711                     host, type);
 712                 debug("Found key in %s:%d", host_file, host_line);
 713                 if (options.check_host_ip && ip_status == HOST_NEW) {
 714                         if (readonly)
 715                                 logit("%s host key for IP address "
 716                                     "'%.128s' not in list of known hosts.",
 717                                     type, ip);
 718                         else if (!add_host_to_hostfile(user_hostfile, ip,
 719                             host_key, options.hash_known_hosts))
 720                                 logit("Failed to add the %s host key for IP "
 721                                     "address '%.128s' to the list of known "
 722                                     "hosts (%.30s).", type, ip, user_hostfile);
 723                         else
 724                                 logit("Warning: Permanently added the %s host "
 725                                     "key for IP address '%.128s' to the list "
 726                                     "of known hosts.", type, ip);
 727                 } else if (options.visual_host_key) {
 728                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 729                         ra = key_fingerprint(host_key, SSH_FP_MD5,
 730                             SSH_FP_RANDOMART);
 731                         logit("Host key fingerprint is %s\n%s\n", fp, ra);
 732                         xfree(ra);
 733                         xfree(fp);
 734                 }
 735                 break;
 736         case HOST_NEW:
 737                 if (options.host_key_alias == NULL && port != 0 &&
 738                     port != SSH_DEFAULT_PORT) {
 739                         debug("checking without port identifier");
 740                         if (check_host_key(hostname, hostaddr, 0, host_key,
 741                             ROQUIET, user_hostfile, system_hostfile) == 0) {
 742                                 debug("found matching key w/out port");
 743                                 break;
 744                         }
 745                 }
 746                 if (readonly)
 747                         goto fail;
 748                 /* The host is new. */
 749                 if (options.strict_host_key_checking == 1) {
 750                         /*
 751                          * User has requested strict host key checking.  We
 752                          * will not add the host key automatically.  The only
 753                          * alternative left is to abort.
 754                          */
 755                         error("No %s host key is known for %.200s and you "
 756                             "have requested strict checking.", type, host);
 757                         goto fail;
 758                 } else if (options.strict_host_key_checking == 2) {
 759                         char msg1[1024], msg2[1024];
 760
 761                         if (show_other_keys(host, host_key))
 762                                 snprintf(msg1, sizeof(msg1),
 763                                     "\nbut keys of different type are already"
 764                                     " known for this host.");
 765                         else
 766                                 snprintf(msg1, sizeof(msg1), ".");
 767                         /* The default */
 768                         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
 769                         ra = key_fingerprint(host_key, SSH_FP_MD5,
 770                             SSH_FP_RANDOMART);
 771                         msg2[0] = '\0';
 772                         if (options.verify_host_key_dns) {
 773                                 if (matching_host_key_dns)
 774                                         snprintf(msg2, sizeof(msg2),
 775                                             "Matching host key fingerprint"
 776                                             " found in DNS.\n");
 777                                 else
 778                                         snprintf(msg2, sizeof(msg2),
 779                                             "No matching host key fingerprint"
 780                                             " found in DNS.\n");
 781                         }
 782                         snprintf(msg, sizeof(msg),
 783                             "The authenticity of host '%.200s (%s)' can't be "
 784                             "established%s\n"
 785                             "%s key fingerprint is %s.%s%s\n%s"
 786                             "Are you sure you want to continue connecting "
 787                             "(yes/no)? ",
 788                             host, ip, msg1, type, fp,
 789                             options.visual_host_key ? "\n" : "",
 790                             options.visual_host_key ? ra : "",
 791                             msg2);
 792                         xfree(ra);
 793                         xfree(fp);
 794                         if (!confirm(msg))
 795                                 goto fail;
 796                 }
 797                 /*
 798                  * If not in strict mode, add the key automatically to the
 799                  * local known_hosts file.
 800                  */
 801                 if (options.check_host_ip && ip_status == HOST_NEW) {
 802                         snprintf(hostline, sizeof(hostline), "%s,%s",
 803                             host, ip);
 804                         hostp = hostline;
 805                         if (options.hash_known_hosts) {
 806                                 /* Add hash of host and IP separately */
 807                                 r = add_host_to_hostfile(user_hostfile, host,
 808                                     host_key, options.hash_known_hosts) &&
 809                                     add_host_to_hostfile(user_hostfile, ip,
 810                                     host_key, options.hash_known_hosts);
 811                         } else {
 812                                 /* Add unhashed "host,ip" */
 813                                 r = add_host_to_hostfile(user_hostfile,
 814                                     hostline, host_key,
 815                                     options.hash_known_hosts);
 816                         }
 817                 } else {
 818                         r = add_host_to_hostfile(user_hostfile, host, host_key,
 819                             options.hash_known_hosts);
 820                         hostp = host;
 821                 }
 822
 823                 if (!r)
 824                         logit("Failed to add the host to the list of known "
 825                             "hosts (%.500s).", user_hostfile);
 826                 else
 827                         logit("Warning: Permanently added '%.200s' (%s) to the "
 828                             "list of known hosts.", hostp, type);
 829                 break;
 830         case HOST_CHANGED:
 831                 if (readonly == ROQUIET)
 832                         goto fail;
 833                 if (options.check_host_ip && host_ip_differ) {
 834                         char *key_msg;
 835                         if (ip_status == HOST_NEW)
 836                                 key_msg = "is unknown";
 837                         else if (ip_status == HOST_OK)
 838                                 key_msg = "is unchanged";
 839                         else
 840                                 key_msg = "has a different value";
 841                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 842                         error("@       WARNING: POSSIBLE DNS SPOOFING DETECTED!          @");
 843                         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 844                         error("The %s host key for %s has changed,", type, host);
 845                         error("and the key for the corresponding IP address %s", ip);
 846                         error("%s. This could either mean that", key_msg);
 847                         error("DNS SPOOFING is happening or the IP address for the host");
 848                         error("and its host key have changed at the same time.");
 849                         if (ip_status != HOST_NEW)
 850                                 error("Offending key for IP in %s:%d", ip_file, ip_line);
 851                 }
 852                 /* The host key has changed. */
 853                 warn_changed_key(host_key);
 854                 error("Add correct host key in %.100s to get rid of this message.",
 855                     user_hostfile);
 856                 error("Offending key in %s:%d", host_file, host_line);
 857
 858                 /*
 859                  * If strict host key checking is in use, the user will have
 860                  * to edit the key manually and we can only abort.
 861                  */
 862                 if (options.strict_host_key_checking) {
 863                         error("%s host key for %.200s has changed and you have "
 864                             "requested strict checking.", type, host);
 865                         goto fail;
 866                 }
 867
 868                 /*
 869                  * If strict host key checking has not been requested, allow
 870                  * the connection but without MITM-able authentication or
 871                  * forwarding.
 872                  */
 873                 if (options.password_authentication) {
 874                         error("Password authentication is disabled to avoid "
 875                             "man-in-the-middle attacks.");
 876                         options.password_authentication = 0;
 877                         cancelled_forwarding = 1;
 878                 }
 879                 if (options.kbd_interactive_authentication) {
 880                         error("Keyboard-interactive authentication is disabled"
 881                             " to avoid man-in-the-middle attacks.");
 882                         options.kbd_interactive_authentication = 0;
 883                         options.challenge_response_authentication = 0;
 884                         cancelled_forwarding = 1;
 885                 }
 886                 if (options.challenge_response_authentication) {
 887                         error("Challenge/response authentication is disabled"
 888                             " to avoid man-in-the-middle attacks.");
 889                         options.challenge_response_authentication = 0;
 890                         cancelled_forwarding = 1;
 891                 }
 892                 if (options.forward_agent) {
 893                         error("Agent forwarding is disabled to avoid "
 894                             "man-in-the-middle attacks.");
 895                         options.forward_agent = 0;
 896                         cancelled_forwarding = 1;
 897                 }
 898                 if (options.forward_x11) {
 899                         error("X11 forwarding is disabled to avoid "
 900                             "man-in-the-middle attacks.");
 901                         options.forward_x11 = 0;
 902                         cancelled_forwarding = 1;
 903                 }
 904                 if (options.num_local_forwards > 0 ||
 905                     options.num_remote_forwards > 0) {
 906                         error("Port forwarding is disabled to avoid "
 907                             "man-in-the-middle attacks.");
 908                         options.num_local_forwards =
 909                             options.num_remote_forwards = 0;
 910                         cancelled_forwarding = 1;
 911                 }
 912                 if (options.tun_open != SSH_TUNMODE_NO) {
 913                         error("Tunnel forwarding is disabled to avoid "
 914                             "man-in-the-middle attacks.");
 915                         options.tun_open = SSH_TUNMODE_NO;
 916                         cancelled_forwarding = 1;
 917                 }
 918                 if (options.exit_on_forward_failure && cancelled_forwarding)
 919                         fatal("Error: forwarding disabled due to host key "
 920                             "check failure");
 921
 922                 /*
 923                  * XXX Should permit the user to change to use the new id.
 924                  * This could be done by converting the host key to an
 925                  * identifying sentence, tell that the host identifies itself
 926                  * by that sentence, and ask the user if he/she whishes to
 927                  * accept the authentication.
 928                  */
 929                 break;
 930         case HOST_FOUND:
 931                 fatal("internal error");
 932                 break;
 933         }
 934
 935         if (options.check_host_ip && host_status != HOST_CHANGED &&
 936             ip_status == HOST_CHANGED) {
 937                 snprintf(msg, sizeof(msg),
 938                     "Warning: the %s host key for '%.200s' "
 939                     "differs from the key for the IP address '%.128s'"
 940                     "\nOffending key for IP in %s:%d",
 941                     type, host, ip, ip_file, ip_line);
 942                 if (host_status == HOST_OK) {
 943                         len = strlen(msg);
 944                         snprintf(msg + len, sizeof(msg) - len,
 945                             "\nMatching host key in %s:%d",
 946                             host_file, host_line);
 947                 }
 948                 if (options.strict_host_key_checking == 1) {
 949                         logit("%s", msg);
 950                         error("Exiting, you have requested strict checking.");
 951                         goto fail;
 952                 } else if (options.strict_host_key_checking == 2) {
 953                         strlcat(msg, "\nAre you sure you want "
 954                             "to continue connecting (yes/no)? ", sizeof(msg));
 955                         if (!confirm(msg))
 956                                 goto fail;
 957                 } else {
 958                         logit("%s", msg);
 959                 }
 960         }
 961
 962         xfree(ip);
 963         xfree(host);
 964         return 0;
 965
 966 fail:
 967         xfree(ip);
 968         xfree(host);
 969         return -1;
 970 }
 971
 972 /* returns 0 if key verifies or -1 if key does NOT verify */
 973 int
 974 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key)
 975 {
 976         struct stat st;
 977         int flags = 0;
 978
 979         if (options.verify_host_key_dns &&
 980             verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) {
 981
 982                 if (flags & DNS_VERIFY_FOUND) {
 983
 984                         if (options.verify_host_key_dns == 1 &&
 985                             flags & DNS_VERIFY_MATCH &&
 986                             flags & DNS_VERIFY_SECURE)
 987                                 return 0;
 988
 989                         if (flags & DNS_VERIFY_MATCH) {
 990                                 matching_host_key_dns = 1;
 991                         } else {
 992                                 warn_changed_key(host_key);
 993                                 error("Update the SSHFP RR in DNS with the new "
 994                                     "host key to get rid of this message.");
 995                         }
 996                 }
 997         }
 998
 999         /* return ok if the key can be found in an old keyfile */
1000         if (stat(options.system_hostfile2, &st) == 0 ||
1001             stat(options.user_hostfile2, &st) == 0) {
1002                 if (check_host_key(host, hostaddr, options.port, host_key,
1003                     RDONLY, options.user_hostfile2,
1004                     options.system_hostfile2) == 0)
1005                         return 0;
1006         }
1007         return check_host_key(host, hostaddr, options.port, host_key,
1008             RDRW, options.user_hostfile, options.system_hostfile);
1009 }
1010
1011 /*
1012  * Starts a dialog with the server, and authenticates the current user on the
1013  * server.  This does not need any extra privileges.  The basic connection
1014  * to the server must already have been established before this is called.
1015  * If login fails, this function prints an error and never returns.
1016  * This function does not require super-user privileges.
1017  */
1018 void
1019 ssh_login(Sensitive *sensitive, const char *orighost,
1020     struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms)
1021 {
1022         char *host, *cp;
1023         char *server_user, *local_user;
1024
1025         local_user = xstrdup(pw->pw_name);
1026         server_user = options.user ? options.user : local_user;
1027
1028         /* Convert the user-supplied hostname into all lowercase. */
1029         host = xstrdup(orighost);
1030         for (cp = host; *cp; cp++)
1031                 if (isupper(*cp))
1032                         *cp = (char)tolower(*cp);
1033
1034         /* Exchange protocol version identification strings with the server. */
1035         ssh_exchange_identification(timeout_ms);
1036
1037         /* Put the connection into non-blocking mode. */
1038         packet_set_nonblocking();
1039
1040         /* key exchange */
1041         /* authenticate user */
1042         if (compat20) {
1043                 ssh_kex2(host, hostaddr);
1044                 ssh_userauth2(local_user, server_user, host, sensitive);
1045         } else {
1046                 ssh_kex(host, hostaddr);
1047                 ssh_userauth1(local_user, server_user, host, sensitive);
1048         }
1049         xfree(local_user);
1050 }
1051
1052 void
1053 ssh_put_password(char *password)
1054 {
1055         int size;
1056         char *padded;
1057
1058         if (datafellows & SSH_BUG_PASSWORDPAD) {
1059                 packet_put_cstring(password);
1060                 return;
1061         }
1062         size = roundup(strlen(password) + 1, 32);
1063         padded = xcalloc(1, size);
1064         strlcpy(padded, password, size);
1065         packet_put_string(padded, size);
1066         memset(padded, 0, size);
1067         xfree(padded);
1068 }
1069
1070 static int
1071 show_key_from_file(const char *file, const char *host, int keytype)
1072 {
1073         Key *found;
1074         char *fp, *ra;
1075         int line, ret;
1076
1077         found = key_new(keytype);
1078         if ((ret = lookup_key_in_hostfile_by_type(file, host,
1079             keytype, found, &line))) {
1080                 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX);
1081                 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART);
1082                 logit("WARNING: %s key found for host %s\n"
1083                     "in %s:%d\n"
1084                     "%s key fingerprint %s.\n%s\n",
1085                     key_type(found), host, file, line,
1086                     key_type(found), fp, ra);
1087                 xfree(ra);
1088                 xfree(fp);
1089         }
1090         key_free(found);
1091         return (ret);
1092 }
1093
1094 /* print all known host keys for a given host, but skip keys of given type */
1095 static int
1096 show_other_keys(const char *host, Key *key)
1097 {
1098         int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1};
1099         int i, found = 0;
1100
1101         for (i = 0; type[i] != -1; i++) {
1102                 if (type[i] == key->type)
1103                         continue;
1104                 if (type[i] != KEY_RSA1 &&
1105                     show_key_from_file(options.user_hostfile2, host, type[i])) {
1106                         found = 1;
1107                         continue;
1108                 }
1109                 if (type[i] != KEY_RSA1 &&
1110                     show_key_from_file(options.system_hostfile2, host, type[i])) {
1111                         found = 1;
1112                         continue;
1113                 }
1114                 if (show_key_from_file(options.user_hostfile, host, type[i])) {
1115                         found = 1;
1116                         continue;
1117                 }
1118                 if (show_key_from_file(options.system_hostfile, host, type[i])) {
1119                         found = 1;
1120                         continue;
1121                 }
1122                 debug2("no key of type %d for host %s", type[i], host);
1123         }
1124         return (found);
1125 }
1126
1127 static void
1128 warn_changed_key(Key *host_key)
1129 {
1130         char *fp;
1131         const char *type = key_type(host_key);
1132
1133         fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX);
1134
1135         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1136         error("@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @");
1137         error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1138         error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1139         error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1140         error("It is also possible that the %s host key has just been changed.", type);
1141         error("The fingerprint for the %s key sent by the remote host is\n%s.",
1142             type, fp);
1143         error("Please contact your system administrator.");
1144
1145         xfree(fp);
1146 }
1147
1148 /*
1149  * Execute a local command
1150  */
1151 int
1152 ssh_local_cmd(const char *args)
1153 {
1154         char *shell;
1155         pid_t pid;
1156         int status;
1157
1158         if (!options.permit_local_command ||
1159             args == NULL || !*args)
1160                 return (1);
1161
1162         if ((shell = getenv("SHELL")) == NULL)
1163                 shell = _PATH_BSHELL;
1164
1165         pid = fork();
1166         if (pid == 0) {
1167                 debug3("Executing %s -c \"%s\"", shell, args);
1168                 execl(shell, shell, "-c", args, (char *)NULL);
1169                 error("Couldn't execute %s -c \"%s\": %s",
1170                     shell, args, strerror(errno));
1171                 _exit(1);
1172         } else if (pid == -1)
1173                 fatal("fork failed: %.100s", strerror(errno));
1174         while (waitpid(pid, &status, 0) == -1)
1175                 if (errno != EINTR)
1176                         fatal("Couldn't wait for child: %s", strerror(errno));
1177
1178         if (!WIFEXITED(status))
1179                 return (1);
1180
1181         return (WEXITSTATUS(status));
1182 }