1 /* $OpenBSD: sshconnect.c,v 1.203 2007/12/27 14:22:08 dtucker 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 <sys/types.h> 17 #include <sys/wait.h> 18 #include <sys/stat.h> 19 #include <sys/socket.h> 20 #include <sys/time.h> 21 22 #include <netinet/in.h> 23 24 #include <ctype.h> 25 #include <errno.h> 26 #include <netdb.h> 27 #include <paths.h> 28 #include <signal.h> 29 #include <pwd.h> 30 #include <stdio.h> 31 #include <stdlib.h> 32 #include <string.h> 33 #include <unistd.h> 34 35 #include "xmalloc.h" 36 #include "ssh.h" 37 #include "rsa.h" 38 #include "buffer.h" 39 #include "packet.h" 40 #include "uidswap.h" 41 #include "compat.h" 42 #include "key.h" 43 #include "sshconnect.h" 44 #include "hostfile.h" 45 #include "log.h" 46 #include "readconf.h" 47 #include "atomicio.h" 48 #include "misc.h" 49 #include "dns.h" 50 #include "version.h" 51 52 char *client_version_string = NULL; 53 char *server_version_string = NULL; 54 55 static int matching_host_key_dns = 0; 56 57 /* import */ 58 extern Options options; 59 extern char *__progname; 60 extern uid_t original_real_uid; 61 extern uid_t original_effective_uid; 62 extern pid_t proxy_command_pid; 63 64 static int show_other_keys(const char *, Key *); 65 static void warn_changed_key(Key *); 66 67 static void 68 ms_subtract_diff(struct timeval *start, int *ms) 69 { 70 struct timeval diff, finish; 71 72 gettimeofday(&finish, NULL); 73 timersub(&finish, start, &diff); 74 *ms -= (diff.tv_sec * 1000) + (diff.tv_usec / 1000); 75 } 76 77 static void 78 ms_to_timeval(struct timeval *tv, int ms) 79 { 80 tv->tv_sec = ms / 1000; 81 tv->tv_usec = (ms % 1000) * 1000; 82 } 83 84 /* 85 * Connect to the given ssh server using a proxy command. 86 */ 87 static int 88 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 89 { 90 char *command_string, *tmp; 91 int pin[2], pout[2]; 92 pid_t pid; 93 char *shell, strport[NI_MAXSERV]; 94 95 if ((shell = getenv("SHELL")) == NULL) 96 shell = _PATH_BSHELL; 97 98 /* Convert the port number into a string. */ 99 snprintf(strport, sizeof strport, "%hu", port); 100 101 /* 102 * Build the final command string in the buffer by making the 103 * appropriate substitutions to the given proxy command. 104 * 105 * Use "exec" to avoid "sh -c" processes on some platforms 106 * (e.g. Solaris) 107 */ 108 xasprintf(&tmp, "exec %s", proxy_command); 109 command_string = percent_expand(tmp, "h", host, 110 "p", strport, (char *)NULL); 111 xfree(tmp); 112 113 /* Create pipes for communicating with the proxy. */ 114 if (pipe(pin) < 0 || pipe(pout) < 0) 115 fatal("Could not create pipes to communicate with the proxy: %.100s", 116 strerror(errno)); 117 118 debug("Executing proxy command: %.500s", command_string); 119 120 /* Fork and execute the proxy command. */ 121 if ((pid = fork()) == 0) { 122 char *argv[10]; 123 124 /* Child. Permanently give up superuser privileges. */ 125 permanently_drop_suid(original_real_uid); 126 127 /* Redirect stdin and stdout. */ 128 close(pin[1]); 129 if (pin[0] != 0) { 130 if (dup2(pin[0], 0) < 0) 131 perror("dup2 stdin"); 132 close(pin[0]); 133 } 134 close(pout[0]); 135 if (dup2(pout[1], 1) < 0) 136 perror("dup2 stdout"); 137 /* Cannot be 1 because pin allocated two descriptors. */ 138 close(pout[1]); 139 140 /* Stderr is left as it is so that error messages get 141 printed on the user's terminal. */ 142 argv[0] = shell; 143 argv[1] = "-c"; 144 argv[2] = command_string; 145 argv[3] = NULL; 146 147 /* Execute the proxy command. Note that we gave up any 148 extra privileges above. */ 149 execv(argv[0], argv); 150 perror(argv[0]); 151 exit(1); 152 } 153 /* Parent. */ 154 if (pid < 0) 155 fatal("fork failed: %.100s", strerror(errno)); 156 else 157 proxy_command_pid = pid; /* save pid to clean up later */ 158 159 /* Close child side of the descriptors. */ 160 close(pin[0]); 161 close(pout[1]); 162 163 /* Free the command name. */ 164 xfree(command_string); 165 166 /* Set the connection file descriptors. */ 167 packet_set_connection(pout[0], pin[1]); 168 169 /* Indicate OK return */ 170 return 0; 171 } 172 173 /* 174 * Creates a (possibly privileged) socket for use as the ssh connection. 175 */ 176 static int 177 ssh_create_socket(int privileged, struct addrinfo *ai) 178 { 179 int sock, gaierr; 180 struct addrinfo hints, *res; 181 182 /* 183 * If we are running as root and want to connect to a privileged 184 * port, bind our own socket to a privileged port. 185 */ 186 if (privileged) { 187 int p = IPPORT_RESERVED - 1; 188 PRIV_START; 189 sock = rresvport_af(&p, ai->ai_family); 190 PRIV_END; 191 if (sock < 0) 192 error("rresvport: af=%d %.100s", ai->ai_family, 193 strerror(errno)); 194 else 195 debug("Allocated local port %d.", p); 196 return sock; 197 } 198 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 199 if (sock < 0) 200 error("socket: %.100s", strerror(errno)); 201 202 /* Bind the socket to an alternative local IP address */ 203 if (options.bind_address == NULL) 204 return sock; 205 206 memset(&hints, 0, sizeof(hints)); 207 hints.ai_family = ai->ai_family; 208 hints.ai_socktype = ai->ai_socktype; 209 hints.ai_protocol = ai->ai_protocol; 210 hints.ai_flags = AI_PASSIVE; 211 gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); 212 if (gaierr) { 213 error("getaddrinfo: %s: %s", options.bind_address, 214 ssh_gai_strerror(gaierr)); 215 close(sock); 216 return -1; 217 } 218 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 219 error("bind: %s: %s", options.bind_address, strerror(errno)); 220 close(sock); 221 freeaddrinfo(res); 222 return -1; 223 } 224 freeaddrinfo(res); 225 return sock; 226 } 227 228 static int 229 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 230 socklen_t addrlen, int *timeoutp) 231 { 232 fd_set *fdset; 233 struct timeval tv, t_start; 234 socklen_t optlen; 235 int optval, rc, result = -1; 236 237 gettimeofday(&t_start, NULL); 238 239 if (*timeoutp <= 0) { 240 result = connect(sockfd, serv_addr, addrlen); 241 goto done; 242 } 243 244 set_nonblock(sockfd); 245 rc = connect(sockfd, serv_addr, addrlen); 246 if (rc == 0) { 247 unset_nonblock(sockfd); 248 result = 0; 249 goto done; 250 } 251 if (errno != EINPROGRESS) { 252 result = -1; 253 goto done; 254 } 255 256 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 257 sizeof(fd_mask)); 258 FD_SET(sockfd, fdset); 259 ms_to_timeval(&tv, *timeoutp); 260 261 for (;;) { 262 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 263 if (rc != -1 || errno != EINTR) 264 break; 265 } 266 267 switch (rc) { 268 case 0: 269 /* Timed out */ 270 errno = ETIMEDOUT; 271 break; 272 case -1: 273 /* Select error */ 274 debug("select: %s", strerror(errno)); 275 break; 276 case 1: 277 /* Completed or failed */ 278 optval = 0; 279 optlen = sizeof(optval); 280 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 281 &optlen) == -1) { 282 debug("getsockopt: %s", strerror(errno)); 283 break; 284 } 285 if (optval != 0) { 286 errno = optval; 287 break; 288 } 289 result = 0; 290 unset_nonblock(sockfd); 291 break; 292 default: 293 /* Should not occur */ 294 fatal("Bogus return (%d) from select()", rc); 295 } 296 297 xfree(fdset); 298 299 done: 300 if (result == 0 && *timeoutp > 0) { 301 ms_subtract_diff(&t_start, timeoutp); 302 if (*timeoutp <= 0) { 303 errno = ETIMEDOUT; 304 result = -1; 305 } 306 } 307 308 return (result); 309 } 310 311 /* 312 * Opens a TCP/IP connection to the remote server on the given host. 313 * The address of the remote host will be returned in hostaddr. 314 * If port is 0, the default port will be used. If needpriv is true, 315 * a privileged port will be allocated to make the connection. 316 * This requires super-user privileges if needpriv is true. 317 * Connection_attempts specifies the maximum number of tries (one per 318 * second). If proxy_command is non-NULL, it specifies the command (with %h 319 * and %p substituted for host and port, respectively) to use to contact 320 * the daemon. 321 */ 322 int 323 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 324 u_short port, int family, int connection_attempts, int *timeout_ms, 325 int want_keepalive, int needpriv, const char *proxy_command) 326 { 327 int gaierr; 328 int on = 1; 329 int sock = -1, attempt; 330 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 331 struct addrinfo hints, *ai, *aitop; 332 333 debug2("ssh_connect: needpriv %d", needpriv); 334 335 /* If a proxy command is given, connect using it. */ 336 if (proxy_command != NULL) 337 return ssh_proxy_connect(host, port, proxy_command); 338 339 /* No proxy command. */ 340 341 memset(&hints, 0, sizeof(hints)); 342 hints.ai_family = family; 343 hints.ai_socktype = SOCK_STREAM; 344 snprintf(strport, sizeof strport, "%u", port); 345 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 346 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 347 host, ssh_gai_strerror(gaierr)); 348 349 for (attempt = 0; attempt < connection_attempts; attempt++) { 350 if (attempt > 0) { 351 /* Sleep a moment before retrying. */ 352 sleep(1); 353 debug("Trying again..."); 354 } 355 /* 356 * Loop through addresses for this host, and try each one in 357 * sequence until the connection succeeds. 358 */ 359 for (ai = aitop; ai; ai = ai->ai_next) { 360 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 361 continue; 362 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 363 ntop, sizeof(ntop), strport, sizeof(strport), 364 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 365 error("ssh_connect: getnameinfo failed"); 366 continue; 367 } 368 debug("Connecting to %.200s [%.100s] port %s.", 369 host, ntop, strport); 370 371 /* Create a socket for connecting. */ 372 sock = ssh_create_socket(needpriv, ai); 373 if (sock < 0) 374 /* Any error is already output */ 375 continue; 376 377 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 378 timeout_ms) >= 0) { 379 /* Successful connection. */ 380 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 381 break; 382 } else { 383 debug("connect to address %s port %s: %s", 384 ntop, strport, strerror(errno)); 385 close(sock); 386 sock = -1; 387 } 388 } 389 if (sock != -1) 390 break; /* Successful connection. */ 391 } 392 393 freeaddrinfo(aitop); 394 395 /* Return failure if we didn't get a successful connection. */ 396 if (sock == -1) { 397 error("ssh: connect to host %s port %s: %s", 398 host, strport, strerror(errno)); 399 return (-1); 400 } 401 402 debug("Connection established."); 403 404 /* Set SO_KEEPALIVE if requested. */ 405 if (want_keepalive && 406 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 407 sizeof(on)) < 0) 408 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 409 410 /* Set the connection. */ 411 packet_set_connection(sock, sock); 412 413 return 0; 414 } 415 416 /* 417 * Waits for the server identification string, and sends our own 418 * identification string. 419 */ 420 static void 421 ssh_exchange_identification(int timeout_ms) 422 { 423 char buf[256], remote_version[256]; /* must be same size! */ 424 int remote_major, remote_minor, mismatch; 425 int connection_in = packet_get_connection_in(); 426 int connection_out = packet_get_connection_out(); 427 int minor1 = PROTOCOL_MINOR_1; 428 u_int i, n; 429 size_t len; 430 int fdsetsz, remaining, rc; 431 struct timeval t_start, t_remaining; 432 fd_set *fdset; 433 434 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 435 fdset = xcalloc(1, fdsetsz); 436 437 /* Read other side's version identification. */ 438 remaining = timeout_ms; 439 for (n = 0;;) { 440 for (i = 0; i < sizeof(buf) - 1; i++) { 441 if (timeout_ms > 0) { 442 gettimeofday(&t_start, NULL); 443 ms_to_timeval(&t_remaining, remaining); 444 FD_SET(connection_in, fdset); 445 rc = select(connection_in + 1, fdset, NULL, 446 fdset, &t_remaining); 447 ms_subtract_diff(&t_start, &remaining); 448 if (rc == 0 || remaining <= 0) 449 fatal("Connection timed out during " 450 "banner exchange"); 451 if (rc == -1) { 452 if (errno == EINTR) 453 continue; 454 fatal("ssh_exchange_identification: " 455 "select: %s", strerror(errno)); 456 } 457 } 458 459 len = atomicio(read, connection_in, &buf[i], 1); 460 461 if (len != 1 && errno == EPIPE) 462 fatal("ssh_exchange_identification: " 463 "Connection closed by remote host"); 464 else if (len != 1) 465 fatal("ssh_exchange_identification: " 466 "read: %.100s", strerror(errno)); 467 if (buf[i] == '\r') { 468 buf[i] = '\n'; 469 buf[i + 1] = 0; 470 continue; /**XXX wait for \n */ 471 } 472 if (buf[i] == '\n') { 473 buf[i + 1] = 0; 474 break; 475 } 476 if (++n > 65536) 477 fatal("ssh_exchange_identification: " 478 "No banner received"); 479 } 480 buf[sizeof(buf) - 1] = 0; 481 if (strncmp(buf, "SSH-", 4) == 0) 482 break; 483 debug("ssh_exchange_identification: %s", buf); 484 } 485 server_version_string = xstrdup(buf); 486 xfree(fdset); 487 488 /* 489 * Check that the versions match. In future this might accept 490 * several versions and set appropriate flags to handle them. 491 */ 492 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 493 &remote_major, &remote_minor, remote_version) != 3) 494 fatal("Bad remote protocol version identification: '%.100s'", buf); 495 debug("Remote protocol version %d.%d, remote software version %.100s", 496 remote_major, remote_minor, remote_version); 497 498 compat_datafellows(remote_version); 499 mismatch = 0; 500 501 switch (remote_major) { 502 case 1: 503 if (remote_minor == 99 && 504 (options.protocol & SSH_PROTO_2) && 505 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 506 enable_compat20(); 507 break; 508 } 509 if (!(options.protocol & SSH_PROTO_1)) { 510 mismatch = 1; 511 break; 512 } 513 if (remote_minor < 3) { 514 fatal("Remote machine has too old SSH software version."); 515 } else if (remote_minor == 3 || remote_minor == 4) { 516 /* We speak 1.3, too. */ 517 enable_compat13(); 518 minor1 = 3; 519 if (options.forward_agent) { 520 logit("Agent forwarding disabled for protocol 1.3"); 521 options.forward_agent = 0; 522 } 523 } 524 break; 525 case 2: 526 if (options.protocol & SSH_PROTO_2) { 527 enable_compat20(); 528 break; 529 } 530 /* FALLTHROUGH */ 531 default: 532 mismatch = 1; 533 break; 534 } 535 if (mismatch) 536 fatal("Protocol major versions differ: %d vs. %d", 537 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 538 remote_major); 539 /* Send our own protocol version identification. */ 540 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", 541 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 542 compat20 ? PROTOCOL_MINOR_2 : minor1, 543 SSH_VERSION); 544 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) 545 fatal("write: %.100s", strerror(errno)); 546 client_version_string = xstrdup(buf); 547 chop(client_version_string); 548 chop(server_version_string); 549 debug("Local version string %.100s", client_version_string); 550 } 551 552 /* defaults to 'no' */ 553 static int 554 confirm(const char *prompt) 555 { 556 const char *msg, *again = "Please type 'yes' or 'no': "; 557 char *p; 558 int ret = -1; 559 560 if (options.batch_mode) 561 return 0; 562 for (msg = prompt;;msg = again) { 563 p = read_passphrase(msg, RP_ECHO); 564 if (p == NULL || 565 (p[0] == '\0') || (p[0] == '\n') || 566 strncasecmp(p, "no", 2) == 0) 567 ret = 0; 568 if (p && strncasecmp(p, "yes", 3) == 0) 569 ret = 1; 570 if (p) 571 xfree(p); 572 if (ret != -1) 573 return ret; 574 } 575 } 576 577 /* 578 * check whether the supplied host key is valid, return -1 if the key 579 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 580 */ 581 #define RDRW 0 582 #define RDONLY 1 583 #define ROQUIET 2 584 static int 585 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 586 Key *host_key, int readonly, const char *user_hostfile, 587 const char *system_hostfile) 588 { 589 Key *file_key; 590 const char *type = key_type(host_key); 591 char *ip = NULL, *host = NULL; 592 char hostline[1000], *hostp, *fp; 593 HostStatus host_status; 594 HostStatus ip_status; 595 int r, local = 0, host_ip_differ = 0; 596 char ntop[NI_MAXHOST]; 597 char msg[1024]; 598 int len, host_line, ip_line; 599 const char *host_file = NULL, *ip_file = NULL; 600 601 /* 602 * Force accepting of the host key for loopback/localhost. The 603 * problem is that if the home directory is NFS-mounted to multiple 604 * machines, localhost will refer to a different machine in each of 605 * them, and the user will get bogus HOST_CHANGED warnings. This 606 * essentially disables host authentication for localhost; however, 607 * this is probably not a real problem. 608 */ 609 /** hostaddr == 0! */ 610 switch (hostaddr->sa_family) { 611 case AF_INET: 612 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 613 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 614 break; 615 case AF_INET6: 616 local = IN6_IS_ADDR_LOOPBACK( 617 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 618 break; 619 default: 620 local = 0; 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, hostaddr->sa_len, 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 * Turn off check_host_ip if the connection is to localhost, via proxy 644 * command or if we don't have a hostname to compare with 645 */ 646 if (options.check_host_ip && (local || 647 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 648 options.check_host_ip = 0; 649 650 /* 651 * Allow the user to record the key under a different name or 652 * differentiate a non-standard port. This is useful for ssh 653 * tunneling over forwarded connections or if you run multiple 654 * sshd's on different ports on the same machine. 655 */ 656 if (options.host_key_alias != NULL) { 657 host = xstrdup(options.host_key_alias); 658 debug("using hostkeyalias: %s", host); 659 } else { 660 host = put_host_port(hostname, port); 661 } 662 663 /* 664 * Store the host key from the known host file in here so that we can 665 * compare it with the key for the IP address. 666 */ 667 file_key = key_new(host_key->type); 668 669 /* 670 * Check if the host key is present in the user's list of known 671 * hosts or in the systemwide list. 672 */ 673 host_file = user_hostfile; 674 host_status = check_host_in_hostfile(host_file, host, host_key, 675 file_key, &host_line); 676 if (host_status == HOST_NEW) { 677 host_file = system_hostfile; 678 host_status = check_host_in_hostfile(host_file, host, host_key, 679 file_key, &host_line); 680 } 681 /* 682 * Also perform check for the ip address, skip the check if we are 683 * localhost or the hostname was an ip address to begin with 684 */ 685 if (options.check_host_ip) { 686 Key *ip_key = key_new(host_key->type); 687 688 ip_file = user_hostfile; 689 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 690 ip_key, &ip_line); 691 if (ip_status == HOST_NEW) { 692 ip_file = system_hostfile; 693 ip_status = check_host_in_hostfile(ip_file, ip, 694 host_key, ip_key, &ip_line); 695 } 696 if (host_status == HOST_CHANGED && 697 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 698 host_ip_differ = 1; 699 700 key_free(ip_key); 701 } else 702 ip_status = host_status; 703 704 key_free(file_key); 705 706 switch (host_status) { 707 case HOST_OK: 708 /* The host is known and the key matches. */ 709 debug("Host '%.200s' is known and matches the %s host key.", 710 host, type); 711 debug("Found key in %s:%d", host_file, host_line); 712 if (options.check_host_ip && ip_status == HOST_NEW) { 713 if (readonly) 714 logit("%s host key for IP address " 715 "'%.128s' not in list of known hosts.", 716 type, ip); 717 else if (!add_host_to_hostfile(user_hostfile, ip, 718 host_key, options.hash_known_hosts)) 719 logit("Failed to add the %s host key for IP " 720 "address '%.128s' to the list of known " 721 "hosts (%.30s).", type, ip, user_hostfile); 722 else 723 logit("Warning: Permanently added the %s host " 724 "key for IP address '%.128s' to the list " 725 "of known hosts.", type, ip); 726 } 727 break; 728 case HOST_NEW: 729 if (options.host_key_alias == NULL && port != 0 && 730 port != SSH_DEFAULT_PORT) { 731 debug("checking without port identifier"); 732 if (check_host_key(hostname, hostaddr, 0, host_key, 2, 733 user_hostfile, system_hostfile) == 0) { 734 debug("found matching key w/out port"); 735 break; 736 } 737 } 738 if (readonly) 739 goto fail; 740 /* The host is new. */ 741 if (options.strict_host_key_checking == 1) { 742 /* 743 * User has requested strict host key checking. We 744 * will not add the host key automatically. The only 745 * alternative left is to abort. 746 */ 747 error("No %s host key is known for %.200s and you " 748 "have requested strict checking.", type, host); 749 goto fail; 750 } else if (options.strict_host_key_checking == 2) { 751 char msg1[1024], msg2[1024]; 752 753 if (show_other_keys(host, host_key)) 754 snprintf(msg1, sizeof(msg1), 755 "\nbut keys of different type are already" 756 " known for this host."); 757 else 758 snprintf(msg1, sizeof(msg1), "."); 759 /* The default */ 760 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 761 msg2[0] = '\0'; 762 if (options.verify_host_key_dns) { 763 if (matching_host_key_dns) 764 snprintf(msg2, sizeof(msg2), 765 "Matching host key fingerprint" 766 " found in DNS.\n"); 767 else 768 snprintf(msg2, sizeof(msg2), 769 "No matching host key fingerprint" 770 " found in DNS.\n"); 771 } 772 snprintf(msg, sizeof(msg), 773 "The authenticity of host '%.200s (%s)' can't be " 774 "established%s\n" 775 "%s key fingerprint is %s.\n%s" 776 "Are you sure you want to continue connecting " 777 "(yes/no)? ", 778 host, ip, msg1, type, fp, msg2); 779 xfree(fp); 780 if (!confirm(msg)) 781 goto fail; 782 } 783 /* 784 * If not in strict mode, add the key automatically to the 785 * local known_hosts file. 786 */ 787 if (options.check_host_ip && ip_status == HOST_NEW) { 788 snprintf(hostline, sizeof(hostline), "%s,%s", 789 host, ip); 790 hostp = hostline; 791 if (options.hash_known_hosts) { 792 /* Add hash of host and IP separately */ 793 r = add_host_to_hostfile(user_hostfile, host, 794 host_key, options.hash_known_hosts) && 795 add_host_to_hostfile(user_hostfile, ip, 796 host_key, options.hash_known_hosts); 797 } else { 798 /* Add unhashed "host,ip" */ 799 r = add_host_to_hostfile(user_hostfile, 800 hostline, host_key, 801 options.hash_known_hosts); 802 } 803 } else { 804 r = add_host_to_hostfile(user_hostfile, host, host_key, 805 options.hash_known_hosts); 806 hostp = host; 807 } 808 809 if (!r) 810 logit("Failed to add the host to the list of known " 811 "hosts (%.500s).", user_hostfile); 812 else 813 logit("Warning: Permanently added '%.200s' (%s) to the " 814 "list of known hosts.", hostp, type); 815 break; 816 case HOST_CHANGED: 817 if (readonly == ROQUIET) 818 goto fail; 819 if (options.check_host_ip && host_ip_differ) { 820 char *key_msg; 821 if (ip_status == HOST_NEW) 822 key_msg = "is unknown"; 823 else if (ip_status == HOST_OK) 824 key_msg = "is unchanged"; 825 else 826 key_msg = "has a different value"; 827 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 828 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 829 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 830 error("The %s host key for %s has changed,", type, host); 831 error("and the key for the according IP address %s", ip); 832 error("%s. This could either mean that", key_msg); 833 error("DNS SPOOFING is happening or the IP address for the host"); 834 error("and its host key have changed at the same time."); 835 if (ip_status != HOST_NEW) 836 error("Offending key for IP in %s:%d", ip_file, ip_line); 837 } 838 /* The host key has changed. */ 839 warn_changed_key(host_key); 840 error("Add correct host key in %.100s to get rid of this message.", 841 user_hostfile); 842 error("Offending key in %s:%d", host_file, host_line); 843 844 /* 845 * If strict host key checking is in use, the user will have 846 * to edit the key manually and we can only abort. 847 */ 848 if (options.strict_host_key_checking) { 849 error("%s host key for %.200s has changed and you have " 850 "requested strict checking.", type, host); 851 goto fail; 852 } 853 854 /* 855 * If strict host key checking has not been requested, allow 856 * the connection but without MITM-able authentication or 857 * forwarding. 858 */ 859 if (options.password_authentication) { 860 error("Password authentication is disabled to avoid " 861 "man-in-the-middle attacks."); 862 options.password_authentication = 0; 863 } 864 if (options.kbd_interactive_authentication) { 865 error("Keyboard-interactive authentication is disabled" 866 " to avoid man-in-the-middle attacks."); 867 options.kbd_interactive_authentication = 0; 868 options.challenge_response_authentication = 0; 869 } 870 if (options.challenge_response_authentication) { 871 error("Challenge/response authentication is disabled" 872 " to avoid man-in-the-middle attacks."); 873 options.challenge_response_authentication = 0; 874 } 875 if (options.forward_agent) { 876 error("Agent forwarding is disabled to avoid " 877 "man-in-the-middle attacks."); 878 options.forward_agent = 0; 879 } 880 if (options.forward_x11) { 881 error("X11 forwarding is disabled to avoid " 882 "man-in-the-middle attacks."); 883 options.forward_x11 = 0; 884 } 885 if (options.num_local_forwards > 0 || 886 options.num_remote_forwards > 0) { 887 error("Port forwarding is disabled to avoid " 888 "man-in-the-middle attacks."); 889 options.num_local_forwards = 890 options.num_remote_forwards = 0; 891 } 892 if (options.tun_open != SSH_TUNMODE_NO) { 893 error("Tunnel forwarding is disabled to avoid " 894 "man-in-the-middle attacks."); 895 options.tun_open = SSH_TUNMODE_NO; 896 } 897 /* 898 * XXX Should permit the user to change to use the new id. 899 * This could be done by converting the host key to an 900 * identifying sentence, tell that the host identifies itself 901 * by that sentence, and ask the user if he/she whishes to 902 * accept the authentication. 903 */ 904 break; 905 case HOST_FOUND: 906 fatal("internal error"); 907 break; 908 } 909 910 if (options.check_host_ip && host_status != HOST_CHANGED && 911 ip_status == HOST_CHANGED) { 912 snprintf(msg, sizeof(msg), 913 "Warning: the %s host key for '%.200s' " 914 "differs from the key for the IP address '%.128s'" 915 "\nOffending key for IP in %s:%d", 916 type, host, ip, ip_file, ip_line); 917 if (host_status == HOST_OK) { 918 len = strlen(msg); 919 snprintf(msg + len, sizeof(msg) - len, 920 "\nMatching host key in %s:%d", 921 host_file, host_line); 922 } 923 if (options.strict_host_key_checking == 1) { 924 logit("%s", msg); 925 error("Exiting, you have requested strict checking."); 926 goto fail; 927 } else if (options.strict_host_key_checking == 2) { 928 strlcat(msg, "\nAre you sure you want " 929 "to continue connecting (yes/no)? ", sizeof(msg)); 930 if (!confirm(msg)) 931 goto fail; 932 } else { 933 logit("%s", msg); 934 } 935 } 936 937 xfree(ip); 938 xfree(host); 939 return 0; 940 941 fail: 942 xfree(ip); 943 xfree(host); 944 return -1; 945 } 946 947 /* returns 0 if key verifies or -1 if key does NOT verify */ 948 int 949 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 950 { 951 struct stat st; 952 int flags = 0; 953 954 if (options.verify_host_key_dns && 955 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 956 957 if (flags & DNS_VERIFY_FOUND) { 958 959 if (options.verify_host_key_dns == 1 && 960 flags & DNS_VERIFY_MATCH && 961 flags & DNS_VERIFY_SECURE) 962 return 0; 963 964 if (flags & DNS_VERIFY_MATCH) { 965 matching_host_key_dns = 1; 966 } else { 967 warn_changed_key(host_key); 968 error("Update the SSHFP RR in DNS with the new " 969 "host key to get rid of this message."); 970 } 971 } 972 } 973 974 /* return ok if the key can be found in an old keyfile */ 975 if (stat(options.system_hostfile2, &st) == 0 || 976 stat(options.user_hostfile2, &st) == 0) { 977 if (check_host_key(host, hostaddr, options.port, host_key, 978 RDONLY, options.user_hostfile2, 979 options.system_hostfile2) == 0) 980 return 0; 981 } 982 return check_host_key(host, hostaddr, options.port, host_key, 983 RDRW, options.user_hostfile, options.system_hostfile); 984 } 985 986 /* 987 * Starts a dialog with the server, and authenticates the current user on the 988 * server. This does not need any extra privileges. The basic connection 989 * to the server must already have been established before this is called. 990 * If login fails, this function prints an error and never returns. 991 * This function does not require super-user privileges. 992 */ 993 void 994 ssh_login(Sensitive *sensitive, const char *orighost, 995 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 996 { 997 char *host, *cp; 998 char *server_user, *local_user; 999 1000 local_user = xstrdup(pw->pw_name); 1001 server_user = options.user ? options.user : local_user; 1002 1003 /* Convert the user-supplied hostname into all lowercase. */ 1004 host = xstrdup(orighost); 1005 for (cp = host; *cp; cp++) 1006 if (isupper(*cp)) 1007 *cp = (char)tolower(*cp); 1008 1009 /* Exchange protocol version identification strings with the server. */ 1010 ssh_exchange_identification(timeout_ms); 1011 1012 /* Put the connection into non-blocking mode. */ 1013 packet_set_nonblocking(); 1014 1015 /* key exchange */ 1016 /* authenticate user */ 1017 if (compat20) { 1018 ssh_kex2(host, hostaddr); 1019 ssh_userauth2(local_user, server_user, host, sensitive); 1020 } else { 1021 ssh_kex(host, hostaddr); 1022 ssh_userauth1(local_user, server_user, host, sensitive); 1023 } 1024 xfree(local_user); 1025 } 1026 1027 void 1028 ssh_put_password(char *password) 1029 { 1030 int size; 1031 char *padded; 1032 1033 if (datafellows & SSH_BUG_PASSWORDPAD) { 1034 packet_put_cstring(password); 1035 return; 1036 } 1037 size = roundup(strlen(password) + 1, 32); 1038 padded = xcalloc(1, size); 1039 strlcpy(padded, password, size); 1040 packet_put_string(padded, size); 1041 memset(padded, 0, size); 1042 xfree(padded); 1043 } 1044 1045 static int 1046 show_key_from_file(const char *file, const char *host, int keytype) 1047 { 1048 Key *found; 1049 char *fp; 1050 int line, ret; 1051 1052 found = key_new(keytype); 1053 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1054 keytype, found, &line))) { 1055 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1056 logit("WARNING: %s key found for host %s\n" 1057 "in %s:%d\n" 1058 "%s key fingerprint %s.", 1059 key_type(found), host, file, line, 1060 key_type(found), fp); 1061 xfree(fp); 1062 } 1063 key_free(found); 1064 return (ret); 1065 } 1066 1067 /* print all known host keys for a given host, but skip keys of given type */ 1068 static int 1069 show_other_keys(const char *host, Key *key) 1070 { 1071 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1072 int i, found = 0; 1073 1074 for (i = 0; type[i] != -1; i++) { 1075 if (type[i] == key->type) 1076 continue; 1077 if (type[i] != KEY_RSA1 && 1078 show_key_from_file(options.user_hostfile2, host, type[i])) { 1079 found = 1; 1080 continue; 1081 } 1082 if (type[i] != KEY_RSA1 && 1083 show_key_from_file(options.system_hostfile2, host, type[i])) { 1084 found = 1; 1085 continue; 1086 } 1087 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1088 found = 1; 1089 continue; 1090 } 1091 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1092 found = 1; 1093 continue; 1094 } 1095 debug2("no key of type %d for host %s", type[i], host); 1096 } 1097 return (found); 1098 } 1099 1100 static void 1101 warn_changed_key(Key *host_key) 1102 { 1103 char *fp; 1104 const char *type = key_type(host_key); 1105 1106 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1107 1108 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1109 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1110 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1111 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1112 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1113 error("It is also possible that the %s host key has just been changed.", type); 1114 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1115 type, fp); 1116 error("Please contact your system administrator."); 1117 1118 xfree(fp); 1119 } 1120 1121 /* 1122 * Execute a local command 1123 */ 1124 int 1125 ssh_local_cmd(const char *args) 1126 { 1127 char *shell; 1128 pid_t pid; 1129 int status; 1130 1131 if (!options.permit_local_command || 1132 args == NULL || !*args) 1133 return (1); 1134 1135 if ((shell = getenv("SHELL")) == NULL) 1136 shell = _PATH_BSHELL; 1137 1138 pid = fork(); 1139 if (pid == 0) { 1140 debug3("Executing %s -c \"%s\"", shell, args); 1141 execl(shell, shell, "-c", args, (char *)NULL); 1142 error("Couldn't execute %s -c \"%s\": %s", 1143 shell, args, strerror(errno)); 1144 _exit(1); 1145 } else if (pid == -1) 1146 fatal("fork failed: %.100s", strerror(errno)); 1147 while (waitpid(pid, &status, 0) == -1) 1148 if (errno != EINTR) 1149 fatal("Couldn't wait for child: %s", strerror(errno)); 1150 1151 if (!WIFEXITED(status)) 1152 return (1); 1153 1154 return (WEXITSTATUS(status)); 1155 } 1156