1 /* $OpenBSD: sshconnect.c,v 1.208 2008/06/12 23:24:58 ian 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 /* 68 * Connect to the given ssh server using a proxy command. 69 */ 70 static int 71 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 72 { 73 char *command_string, *tmp; 74 int pin[2], pout[2]; 75 pid_t pid; 76 char *shell, strport[NI_MAXSERV]; 77 78 if ((shell = getenv("SHELL")) == NULL) 79 shell = _PATH_BSHELL; 80 81 /* Convert the port number into a string. */ 82 snprintf(strport, sizeof strport, "%hu", port); 83 84 /* 85 * Build the final command string in the buffer by making the 86 * appropriate substitutions to the given proxy command. 87 * 88 * Use "exec" to avoid "sh -c" processes on some platforms 89 * (e.g. Solaris) 90 */ 91 xasprintf(&tmp, "exec %s", proxy_command); 92 command_string = percent_expand(tmp, "h", host, 93 "p", strport, (char *)NULL); 94 xfree(tmp); 95 96 /* Create pipes for communicating with the proxy. */ 97 if (pipe(pin) < 0 || pipe(pout) < 0) 98 fatal("Could not create pipes to communicate with the proxy: %.100s", 99 strerror(errno)); 100 101 debug("Executing proxy command: %.500s", command_string); 102 103 /* Fork and execute the proxy command. */ 104 if ((pid = fork()) == 0) { 105 char *argv[10]; 106 107 /* Child. Permanently give up superuser privileges. */ 108 permanently_drop_suid(original_real_uid); 109 110 /* Redirect stdin and stdout. */ 111 close(pin[1]); 112 if (pin[0] != 0) { 113 if (dup2(pin[0], 0) < 0) 114 perror("dup2 stdin"); 115 close(pin[0]); 116 } 117 close(pout[0]); 118 if (dup2(pout[1], 1) < 0) 119 perror("dup2 stdout"); 120 /* Cannot be 1 because pin allocated two descriptors. */ 121 close(pout[1]); 122 123 /* Stderr is left as it is so that error messages get 124 printed on the user's terminal. */ 125 argv[0] = shell; 126 argv[1] = "-c"; 127 argv[2] = command_string; 128 argv[3] = NULL; 129 130 /* Execute the proxy command. Note that we gave up any 131 extra privileges above. */ 132 execv(argv[0], argv); 133 perror(argv[0]); 134 exit(1); 135 } 136 /* Parent. */ 137 if (pid < 0) 138 fatal("fork failed: %.100s", strerror(errno)); 139 else 140 proxy_command_pid = pid; /* save pid to clean up later */ 141 142 /* Close child side of the descriptors. */ 143 close(pin[0]); 144 close(pout[1]); 145 146 /* Free the command name. */ 147 xfree(command_string); 148 149 /* Set the connection file descriptors. */ 150 packet_set_connection(pout[0], pin[1]); 151 packet_set_timeout(options.server_alive_interval, 152 options.server_alive_count_max); 153 154 /* Indicate OK return */ 155 return 0; 156 } 157 158 /* 159 * Creates a (possibly privileged) socket for use as the ssh connection. 160 */ 161 static int 162 ssh_create_socket(int privileged, struct addrinfo *ai) 163 { 164 int sock, gaierr; 165 struct addrinfo hints, *res; 166 167 /* 168 * If we are running as root and want to connect to a privileged 169 * port, bind our own socket to a privileged port. 170 */ 171 if (privileged) { 172 int p = IPPORT_RESERVED - 1; 173 PRIV_START; 174 sock = rresvport_af(&p, ai->ai_family); 175 PRIV_END; 176 if (sock < 0) 177 error("rresvport: af=%d %.100s", ai->ai_family, 178 strerror(errno)); 179 else 180 debug("Allocated local port %d.", p); 181 return sock; 182 } 183 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 184 if (sock < 0) 185 error("socket: %.100s", strerror(errno)); 186 187 /* Bind the socket to an alternative local IP address */ 188 if (options.bind_address == NULL) 189 return sock; 190 191 memset(&hints, 0, sizeof(hints)); 192 hints.ai_family = ai->ai_family; 193 hints.ai_socktype = ai->ai_socktype; 194 hints.ai_protocol = ai->ai_protocol; 195 hints.ai_flags = AI_PASSIVE; 196 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 197 if (gaierr) { 198 error("getaddrinfo: %s: %s", options.bind_address, 199 ssh_gai_strerror(gaierr)); 200 close(sock); 201 return -1; 202 } 203 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 204 error("bind: %s: %s", options.bind_address, strerror(errno)); 205 close(sock); 206 freeaddrinfo(res); 207 return -1; 208 } 209 freeaddrinfo(res); 210 return sock; 211 } 212 213 static int 214 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 215 socklen_t addrlen, int *timeoutp) 216 { 217 fd_set *fdset; 218 struct timeval tv, t_start; 219 socklen_t optlen; 220 int optval, rc, result = -1; 221 222 gettimeofday(&t_start, NULL); 223 224 if (*timeoutp <= 0) { 225 result = connect(sockfd, serv_addr, addrlen); 226 goto done; 227 } 228 229 set_nonblock(sockfd); 230 rc = connect(sockfd, serv_addr, addrlen); 231 if (rc == 0) { 232 unset_nonblock(sockfd); 233 result = 0; 234 goto done; 235 } 236 if (errno != EINPROGRESS) { 237 result = -1; 238 goto done; 239 } 240 241 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 242 sizeof(fd_mask)); 243 FD_SET(sockfd, fdset); 244 ms_to_timeval(&tv, *timeoutp); 245 246 for (;;) { 247 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 248 if (rc != -1 || errno != EINTR) 249 break; 250 } 251 252 switch (rc) { 253 case 0: 254 /* Timed out */ 255 errno = ETIMEDOUT; 256 break; 257 case -1: 258 /* Select error */ 259 debug("select: %s", strerror(errno)); 260 break; 261 case 1: 262 /* Completed or failed */ 263 optval = 0; 264 optlen = sizeof(optval); 265 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 266 &optlen) == -1) { 267 debug("getsockopt: %s", strerror(errno)); 268 break; 269 } 270 if (optval != 0) { 271 errno = optval; 272 break; 273 } 274 result = 0; 275 unset_nonblock(sockfd); 276 break; 277 default: 278 /* Should not occur */ 279 fatal("Bogus return (%d) from select()", rc); 280 } 281 282 xfree(fdset); 283 284 done: 285 if (result == 0 && *timeoutp > 0) { 286 ms_subtract_diff(&t_start, timeoutp); 287 if (*timeoutp <= 0) { 288 errno = ETIMEDOUT; 289 result = -1; 290 } 291 } 292 293 return (result); 294 } 295 296 /* 297 * Opens a TCP/IP connection to the remote server on the given host. 298 * The address of the remote host will be returned in hostaddr. 299 * If port is 0, the default port will be used. If needpriv is true, 300 * a privileged port will be allocated to make the connection. 301 * This requires super-user privileges if needpriv is true. 302 * Connection_attempts specifies the maximum number of tries (one per 303 * second). If proxy_command is non-NULL, it specifies the command (with %h 304 * and %p substituted for host and port, respectively) to use to contact 305 * the daemon. 306 */ 307 int 308 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 309 u_short port, int family, int connection_attempts, int *timeout_ms, 310 int want_keepalive, int needpriv, const char *proxy_command) 311 { 312 int gaierr; 313 int on = 1; 314 int sock = -1, attempt; 315 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 316 struct addrinfo hints, *ai, *aitop; 317 318 debug2("ssh_connect: needpriv %d", needpriv); 319 320 /* If a proxy command is given, connect using it. */ 321 if (proxy_command != NULL) 322 return ssh_proxy_connect(host, port, proxy_command); 323 324 /* No proxy command. */ 325 326 memset(&hints, 0, sizeof(hints)); 327 hints.ai_family = family; 328 hints.ai_socktype = SOCK_STREAM; 329 snprintf(strport, sizeof strport, "%u", port); 330 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 331 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 332 host, ssh_gai_strerror(gaierr)); 333 334 for (attempt = 0; attempt < connection_attempts; attempt++) { 335 if (attempt > 0) { 336 /* Sleep a moment before retrying. */ 337 sleep(1); 338 debug("Trying again..."); 339 } 340 /* 341 * Loop through addresses for this host, and try each one in 342 * sequence until the connection succeeds. 343 */ 344 for (ai = aitop; ai; ai = ai->ai_next) { 345 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 346 continue; 347 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 348 ntop, sizeof(ntop), strport, sizeof(strport), 349 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 350 error("ssh_connect: getnameinfo failed"); 351 continue; 352 } 353 debug("Connecting to %.200s [%.100s] port %s.", 354 host, ntop, strport); 355 356 /* Create a socket for connecting. */ 357 sock = ssh_create_socket(needpriv, ai); 358 if (sock < 0) 359 /* Any error is already output */ 360 continue; 361 362 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 363 timeout_ms) >= 0) { 364 /* Successful connection. */ 365 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 366 break; 367 } else { 368 debug("connect to address %s port %s: %s", 369 ntop, strport, strerror(errno)); 370 close(sock); 371 sock = -1; 372 } 373 } 374 if (sock != -1) 375 break; /* Successful connection. */ 376 } 377 378 freeaddrinfo(aitop); 379 380 /* Return failure if we didn't get a successful connection. */ 381 if (sock == -1) { 382 error("ssh: connect to host %s port %s: %s", 383 host, strport, strerror(errno)); 384 return (-1); 385 } 386 387 debug("Connection established."); 388 389 /* Set SO_KEEPALIVE if requested. */ 390 if (want_keepalive && 391 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 392 sizeof(on)) < 0) 393 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 394 395 /* Set the connection. */ 396 packet_set_connection(sock, sock); 397 packet_set_timeout(options.server_alive_interval, 398 options.server_alive_count_max); 399 400 return 0; 401 } 402 403 /* 404 * Waits for the server identification string, and sends our own 405 * identification string. 406 */ 407 static void 408 ssh_exchange_identification(int timeout_ms) 409 { 410 char buf[256], remote_version[256]; /* must be same size! */ 411 int remote_major, remote_minor, mismatch; 412 int connection_in = packet_get_connection_in(); 413 int connection_out = packet_get_connection_out(); 414 int minor1 = PROTOCOL_MINOR_1; 415 u_int i, n; 416 size_t len; 417 int fdsetsz, remaining, rc; 418 struct timeval t_start, t_remaining; 419 fd_set *fdset; 420 421 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 422 fdset = xcalloc(1, fdsetsz); 423 424 /* Read other side's version identification. */ 425 remaining = timeout_ms; 426 for (n = 0;;) { 427 for (i = 0; i < sizeof(buf) - 1; i++) { 428 if (timeout_ms > 0) { 429 gettimeofday(&t_start, NULL); 430 ms_to_timeval(&t_remaining, remaining); 431 FD_SET(connection_in, fdset); 432 rc = select(connection_in + 1, fdset, NULL, 433 fdset, &t_remaining); 434 ms_subtract_diff(&t_start, &remaining); 435 if (rc == 0 || remaining <= 0) 436 fatal("Connection timed out during " 437 "banner exchange"); 438 if (rc == -1) { 439 if (errno == EINTR) 440 continue; 441 fatal("ssh_exchange_identification: " 442 "select: %s", strerror(errno)); 443 } 444 } 445 446 len = atomicio(read, connection_in, &buf[i], 1); 447 448 if (len != 1 && errno == EPIPE) 449 fatal("ssh_exchange_identification: " 450 "Connection closed by remote host"); 451 else if (len != 1) 452 fatal("ssh_exchange_identification: " 453 "read: %.100s", strerror(errno)); 454 if (buf[i] == '\r') { 455 buf[i] = '\n'; 456 buf[i + 1] = 0; 457 continue; /**XXX wait for \n */ 458 } 459 if (buf[i] == '\n') { 460 buf[i + 1] = 0; 461 break; 462 } 463 if (++n > 65536) 464 fatal("ssh_exchange_identification: " 465 "No banner received"); 466 } 467 buf[sizeof(buf) - 1] = 0; 468 if (strncmp(buf, "SSH-", 4) == 0) 469 break; 470 debug("ssh_exchange_identification: %s", buf); 471 } 472 server_version_string = xstrdup(buf); 473 xfree(fdset); 474 475 /* 476 * Check that the versions match. In future this might accept 477 * several versions and set appropriate flags to handle them. 478 */ 479 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 480 &remote_major, &remote_minor, remote_version) != 3) 481 fatal("Bad remote protocol version identification: '%.100s'", buf); 482 debug("Remote protocol version %d.%d, remote software version %.100s", 483 remote_major, remote_minor, remote_version); 484 485 compat_datafellows(remote_version); 486 mismatch = 0; 487 488 switch (remote_major) { 489 case 1: 490 if (remote_minor == 99 && 491 (options.protocol & SSH_PROTO_2) && 492 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 493 enable_compat20(); 494 break; 495 } 496 if (!(options.protocol & SSH_PROTO_1)) { 497 mismatch = 1; 498 break; 499 } 500 if (remote_minor < 3) { 501 fatal("Remote machine has too old SSH software version."); 502 } else if (remote_minor == 3 || remote_minor == 4) { 503 /* We speak 1.3, too. */ 504 enable_compat13(); 505 minor1 = 3; 506 if (options.forward_agent) { 507 logit("Agent forwarding disabled for protocol 1.3"); 508 options.forward_agent = 0; 509 } 510 } 511 break; 512 case 2: 513 if (options.protocol & SSH_PROTO_2) { 514 enable_compat20(); 515 break; 516 } 517 /* FALLTHROUGH */ 518 default: 519 mismatch = 1; 520 break; 521 } 522 if (mismatch) 523 fatal("Protocol major versions differ: %d vs. %d", 524 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 525 remote_major); 526 /* Send our own protocol version identification. */ 527 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", 528 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 529 compat20 ? PROTOCOL_MINOR_2 : minor1, 530 SSH_VERSION); 531 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) 532 fatal("write: %.100s", strerror(errno)); 533 client_version_string = xstrdup(buf); 534 chop(client_version_string); 535 chop(server_version_string); 536 debug("Local version string %.100s", client_version_string); 537 } 538 539 /* defaults to 'no' */ 540 static int 541 confirm(const char *prompt) 542 { 543 const char *msg, *again = "Please type 'yes' or 'no': "; 544 char *p; 545 int ret = -1; 546 547 if (options.batch_mode) 548 return 0; 549 for (msg = prompt;;msg = again) { 550 p = read_passphrase(msg, RP_ECHO); 551 if (p == NULL || 552 (p[0] == '\0') || (p[0] == '\n') || 553 strncasecmp(p, "no", 2) == 0) 554 ret = 0; 555 if (p && strncasecmp(p, "yes", 3) == 0) 556 ret = 1; 557 if (p) 558 xfree(p); 559 if (ret != -1) 560 return ret; 561 } 562 } 563 564 /* 565 * check whether the supplied host key is valid, return -1 if the key 566 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 567 */ 568 #define RDRW 0 569 #define RDONLY 1 570 #define ROQUIET 2 571 static int 572 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 573 Key *host_key, int readonly, const char *user_hostfile, 574 const char *system_hostfile) 575 { 576 Key *file_key; 577 const char *type = key_type(host_key); 578 char *ip = NULL, *host = NULL; 579 char hostline[1000], *hostp, *fp, *ra; 580 HostStatus host_status; 581 HostStatus ip_status; 582 int r, local = 0, host_ip_differ = 0; 583 char ntop[NI_MAXHOST]; 584 char msg[1024]; 585 int len, host_line, ip_line; 586 const char *host_file = NULL, *ip_file = NULL; 587 int display_randomart; 588 589 /* 590 * Force accepting of the host key for loopback/localhost. The 591 * problem is that if the home directory is NFS-mounted to multiple 592 * machines, localhost will refer to a different machine in each of 593 * them, and the user will get bogus HOST_CHANGED warnings. This 594 * essentially disables host authentication for localhost; however, 595 * this is probably not a real problem. 596 */ 597 /** hostaddr == 0! */ 598 switch (hostaddr->sa_family) { 599 case AF_INET: 600 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 601 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 602 break; 603 case AF_INET6: 604 local = IN6_IS_ADDR_LOOPBACK( 605 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 606 break; 607 default: 608 local = 0; 609 break; 610 } 611 if (options.no_host_authentication_for_localhost == 1 && local && 612 options.host_key_alias == NULL) { 613 debug("Forcing accepting of host key for " 614 "loopback/localhost."); 615 return 0; 616 } 617 618 /* 619 * We don't have the remote ip-address for connections 620 * using a proxy command 621 */ 622 if (options.proxy_command == NULL) { 623 if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop), 624 NULL, 0, NI_NUMERICHOST) != 0) 625 fatal("check_host_key: getnameinfo failed"); 626 ip = put_host_port(ntop, port); 627 } else { 628 ip = xstrdup("<no hostip for proxy command>"); 629 } 630 631 /* 632 * check_host_ip may be set to zero in the next step, so if it 633 * conveys a request to display the random art, save it away. 634 */ 635 display_randomart = (options.check_host_ip == SSHCTL_CHECKHOSTIP_FPR); 636 637 /* 638 * Turn off check_host_ip if the connection is to localhost, via proxy 639 * command or if we don't have a hostname to compare with 640 */ 641 if (options.check_host_ip && (local || 642 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 643 options.check_host_ip = 0; 644 645 /* 646 * Allow the user to record the key under a different name or 647 * differentiate a non-standard port. This is useful for ssh 648 * tunneling over forwarded connections or if you run multiple 649 * sshd's on different ports on the same machine. 650 */ 651 if (options.host_key_alias != NULL) { 652 host = xstrdup(options.host_key_alias); 653 debug("using hostkeyalias: %s", host); 654 } else { 655 host = put_host_port(hostname, port); 656 } 657 658 /* 659 * Store the host key from the known host file in here so that we can 660 * compare it with the key for the IP address. 661 */ 662 file_key = key_new(host_key->type); 663 664 /* 665 * Check if the host key is present in the user's list of known 666 * hosts or in the systemwide list. 667 */ 668 host_file = user_hostfile; 669 host_status = check_host_in_hostfile(host_file, host, host_key, 670 file_key, &host_line); 671 if (host_status == HOST_NEW) { 672 host_file = system_hostfile; 673 host_status = check_host_in_hostfile(host_file, host, host_key, 674 file_key, &host_line); 675 } 676 /* 677 * Also perform check for the ip address, skip the check if we are 678 * localhost or the hostname was an ip address to begin with 679 */ 680 if (options.check_host_ip) { 681 Key *ip_key = key_new(host_key->type); 682 683 ip_file = user_hostfile; 684 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 685 ip_key, &ip_line); 686 if (ip_status == HOST_NEW) { 687 ip_file = system_hostfile; 688 ip_status = check_host_in_hostfile(ip_file, ip, 689 host_key, ip_key, &ip_line); 690 } 691 if (host_status == HOST_CHANGED && 692 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 693 host_ip_differ = 1; 694 695 key_free(ip_key); 696 } else 697 ip_status = host_status; 698 699 key_free(file_key); 700 701 switch (host_status) { 702 case HOST_OK: 703 /* The host is known and the key matches. */ 704 debug("Host '%.200s' is known and matches the %s host key.", 705 host, type); 706 debug("Found key in %s:%d", host_file, host_line); 707 if (options.check_host_ip && ip_status == HOST_NEW) { 708 if (readonly) 709 logit("%s host key for IP address " 710 "'%.128s' not in list of known hosts.", 711 type, ip); 712 else if (!add_host_to_hostfile(user_hostfile, ip, 713 host_key, options.hash_known_hosts)) 714 logit("Failed to add the %s host key for IP " 715 "address '%.128s' to the list of known " 716 "hosts (%.30s).", type, ip, user_hostfile); 717 else 718 logit("Warning: Permanently added the %s host " 719 "key for IP address '%.128s' to the list " 720 "of known hosts.", type, ip); 721 } else if (display_randomart) { 722 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 723 ra = key_fingerprint(host_key, SSH_FP_MD5, 724 SSH_FP_RANDOMART); 725 logit("Host key fingerprint is %s\n%s\n", fp, ra); 726 xfree(ra); 727 xfree(fp); 728 } 729 break; 730 case HOST_NEW: 731 if (options.host_key_alias == NULL && port != 0 && 732 port != SSH_DEFAULT_PORT) { 733 debug("checking without port identifier"); 734 if (check_host_key(hostname, hostaddr, 0, host_key, 2, 735 user_hostfile, system_hostfile) == 0) { 736 debug("found matching key w/out port"); 737 break; 738 } 739 } 740 if (readonly) 741 goto fail; 742 /* The host is new. */ 743 if (options.strict_host_key_checking == 1) { 744 /* 745 * User has requested strict host key checking. We 746 * will not add the host key automatically. The only 747 * alternative left is to abort. 748 */ 749 error("No %s host key is known for %.200s and you " 750 "have requested strict checking.", type, host); 751 goto fail; 752 } else if (options.strict_host_key_checking == 2) { 753 char msg1[1024], msg2[1024]; 754 755 if (show_other_keys(host, host_key)) 756 snprintf(msg1, sizeof(msg1), 757 "\nbut keys of different type are already" 758 " known for this host."); 759 else 760 snprintf(msg1, sizeof(msg1), "."); 761 /* The default */ 762 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 763 ra = key_fingerprint(host_key, SSH_FP_MD5, 764 SSH_FP_RANDOMART); 765 msg2[0] = '\0'; 766 if (options.verify_host_key_dns) { 767 if (matching_host_key_dns) 768 snprintf(msg2, sizeof(msg2), 769 "Matching host key fingerprint" 770 " found in DNS.\n"); 771 else 772 snprintf(msg2, sizeof(msg2), 773 "No matching host key fingerprint" 774 " found in DNS.\n"); 775 } 776 snprintf(msg, sizeof(msg), 777 "The authenticity of host '%.200s (%s)' can't be " 778 "established%s\n" 779 "%s key fingerprint is %s.\n%s\n%s" 780 "Are you sure you want to continue connecting " 781 "(yes/no)? ", 782 host, ip, msg1, type, fp, ra, msg2); 783 xfree(ra); 784 xfree(fp); 785 if (!confirm(msg)) 786 goto fail; 787 } 788 /* 789 * If not in strict mode, add the key automatically to the 790 * local known_hosts file. 791 */ 792 if (options.check_host_ip && ip_status == HOST_NEW) { 793 snprintf(hostline, sizeof(hostline), "%s,%s", 794 host, ip); 795 hostp = hostline; 796 if (options.hash_known_hosts) { 797 /* Add hash of host and IP separately */ 798 r = add_host_to_hostfile(user_hostfile, host, 799 host_key, options.hash_known_hosts) && 800 add_host_to_hostfile(user_hostfile, ip, 801 host_key, options.hash_known_hosts); 802 } else { 803 /* Add unhashed "host,ip" */ 804 r = add_host_to_hostfile(user_hostfile, 805 hostline, host_key, 806 options.hash_known_hosts); 807 } 808 } else { 809 r = add_host_to_hostfile(user_hostfile, host, host_key, 810 options.hash_known_hosts); 811 hostp = host; 812 } 813 814 if (!r) 815 logit("Failed to add the host to the list of known " 816 "hosts (%.500s).", user_hostfile); 817 else 818 logit("Warning: Permanently added '%.200s' (%s) to the " 819 "list of known hosts.", hostp, type); 820 break; 821 case HOST_CHANGED: 822 if (readonly == ROQUIET) 823 goto fail; 824 if (options.check_host_ip && host_ip_differ) { 825 char *key_msg; 826 if (ip_status == HOST_NEW) 827 key_msg = "is unknown"; 828 else if (ip_status == HOST_OK) 829 key_msg = "is unchanged"; 830 else 831 key_msg = "has a different value"; 832 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 833 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 834 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 835 error("The %s host key for %s has changed,", type, host); 836 error("and the key for the corresponding IP address %s", ip); 837 error("%s. This could either mean that", key_msg); 838 error("DNS SPOOFING is happening or the IP address for the host"); 839 error("and its host key have changed at the same time."); 840 if (ip_status != HOST_NEW) 841 error("Offending key for IP in %s:%d", ip_file, ip_line); 842 } 843 /* The host key has changed. */ 844 warn_changed_key(host_key); 845 error("Add correct host key in %.100s to get rid of this message.", 846 user_hostfile); 847 error("Offending key in %s:%d", host_file, host_line); 848 849 /* 850 * If strict host key checking is in use, the user will have 851 * to edit the key manually and we can only abort. 852 */ 853 if (options.strict_host_key_checking) { 854 error("%s host key for %.200s has changed and you have " 855 "requested strict checking.", type, host); 856 goto fail; 857 } 858 859 /* 860 * If strict host key checking has not been requested, allow 861 * the connection but without MITM-able authentication or 862 * forwarding. 863 */ 864 if (options.password_authentication) { 865 error("Password authentication is disabled to avoid " 866 "man-in-the-middle attacks."); 867 options.password_authentication = 0; 868 } 869 if (options.kbd_interactive_authentication) { 870 error("Keyboard-interactive authentication is disabled" 871 " to avoid man-in-the-middle attacks."); 872 options.kbd_interactive_authentication = 0; 873 options.challenge_response_authentication = 0; 874 } 875 if (options.challenge_response_authentication) { 876 error("Challenge/response authentication is disabled" 877 " to avoid man-in-the-middle attacks."); 878 options.challenge_response_authentication = 0; 879 } 880 if (options.forward_agent) { 881 error("Agent forwarding is disabled to avoid " 882 "man-in-the-middle attacks."); 883 options.forward_agent = 0; 884 } 885 if (options.forward_x11) { 886 error("X11 forwarding is disabled to avoid " 887 "man-in-the-middle attacks."); 888 options.forward_x11 = 0; 889 } 890 if (options.num_local_forwards > 0 || 891 options.num_remote_forwards > 0) { 892 error("Port forwarding is disabled to avoid " 893 "man-in-the-middle attacks."); 894 options.num_local_forwards = 895 options.num_remote_forwards = 0; 896 } 897 if (options.tun_open != SSH_TUNMODE_NO) { 898 error("Tunnel forwarding is disabled to avoid " 899 "man-in-the-middle attacks."); 900 options.tun_open = SSH_TUNMODE_NO; 901 } 902 /* 903 * XXX Should permit the user to change to use the new id. 904 * This could be done by converting the host key to an 905 * identifying sentence, tell that the host identifies itself 906 * by that sentence, and ask the user if he/she whishes to 907 * accept the authentication. 908 */ 909 break; 910 case HOST_FOUND: 911 fatal("internal error"); 912 break; 913 } 914 915 if (options.check_host_ip && host_status != HOST_CHANGED && 916 ip_status == HOST_CHANGED) { 917 snprintf(msg, sizeof(msg), 918 "Warning: the %s host key for '%.200s' " 919 "differs from the key for the IP address '%.128s'" 920 "\nOffending key for IP in %s:%d", 921 type, host, ip, ip_file, ip_line); 922 if (host_status == HOST_OK) { 923 len = strlen(msg); 924 snprintf(msg + len, sizeof(msg) - len, 925 "\nMatching host key in %s:%d", 926 host_file, host_line); 927 } 928 if (options.strict_host_key_checking == 1) { 929 logit("%s", msg); 930 error("Exiting, you have requested strict checking."); 931 goto fail; 932 } else if (options.strict_host_key_checking == 2) { 933 strlcat(msg, "\nAre you sure you want " 934 "to continue connecting (yes/no)? ", sizeof(msg)); 935 if (!confirm(msg)) 936 goto fail; 937 } else { 938 logit("%s", msg); 939 } 940 } 941 942 xfree(ip); 943 xfree(host); 944 return 0; 945 946 fail: 947 xfree(ip); 948 xfree(host); 949 return -1; 950 } 951 952 /* returns 0 if key verifies or -1 if key does NOT verify */ 953 int 954 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 955 { 956 struct stat st; 957 int flags = 0; 958 959 if (options.verify_host_key_dns && 960 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 961 962 if (flags & DNS_VERIFY_FOUND) { 963 964 if (options.verify_host_key_dns == 1 && 965 flags & DNS_VERIFY_MATCH && 966 flags & DNS_VERIFY_SECURE) 967 return 0; 968 969 if (flags & DNS_VERIFY_MATCH) { 970 matching_host_key_dns = 1; 971 } else { 972 warn_changed_key(host_key); 973 error("Update the SSHFP RR in DNS with the new " 974 "host key to get rid of this message."); 975 } 976 } 977 } 978 979 /* return ok if the key can be found in an old keyfile */ 980 if (stat(options.system_hostfile2, &st) == 0 || 981 stat(options.user_hostfile2, &st) == 0) { 982 if (check_host_key(host, hostaddr, options.port, host_key, 983 RDONLY, options.user_hostfile2, 984 options.system_hostfile2) == 0) 985 return 0; 986 } 987 return check_host_key(host, hostaddr, options.port, host_key, 988 RDRW, options.user_hostfile, options.system_hostfile); 989 } 990 991 /* 992 * Starts a dialog with the server, and authenticates the current user on the 993 * server. This does not need any extra privileges. The basic connection 994 * to the server must already have been established before this is called. 995 * If login fails, this function prints an error and never returns. 996 * This function does not require super-user privileges. 997 */ 998 void 999 ssh_login(Sensitive *sensitive, const char *orighost, 1000 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 1001 { 1002 char *host, *cp; 1003 char *server_user, *local_user; 1004 1005 local_user = xstrdup(pw->pw_name); 1006 server_user = options.user ? options.user : local_user; 1007 1008 /* Convert the user-supplied hostname into all lowercase. */ 1009 host = xstrdup(orighost); 1010 for (cp = host; *cp; cp++) 1011 if (isupper(*cp)) 1012 *cp = (char)tolower(*cp); 1013 1014 /* Exchange protocol version identification strings with the server. */ 1015 ssh_exchange_identification(timeout_ms); 1016 1017 /* Put the connection into non-blocking mode. */ 1018 packet_set_nonblocking(); 1019 1020 /* key exchange */ 1021 /* authenticate user */ 1022 if (compat20) { 1023 ssh_kex2(host, hostaddr); 1024 ssh_userauth2(local_user, server_user, host, sensitive); 1025 } else { 1026 ssh_kex(host, hostaddr); 1027 ssh_userauth1(local_user, server_user, host, sensitive); 1028 } 1029 xfree(local_user); 1030 } 1031 1032 void 1033 ssh_put_password(char *password) 1034 { 1035 int size; 1036 char *padded; 1037 1038 if (datafellows & SSH_BUG_PASSWORDPAD) { 1039 packet_put_cstring(password); 1040 return; 1041 } 1042 size = roundup(strlen(password) + 1, 32); 1043 padded = xcalloc(1, size); 1044 strlcpy(padded, password, size); 1045 packet_put_string(padded, size); 1046 memset(padded, 0, size); 1047 xfree(padded); 1048 } 1049 1050 static int 1051 show_key_from_file(const char *file, const char *host, int keytype) 1052 { 1053 Key *found; 1054 char *fp, *ra; 1055 int line, ret; 1056 1057 found = key_new(keytype); 1058 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1059 keytype, found, &line))) { 1060 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1061 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); 1062 logit("WARNING: %s key found for host %s\n" 1063 "in %s:%d\n" 1064 "%s key fingerprint %s.\n%s\n", 1065 key_type(found), host, file, line, 1066 key_type(found), fp, ra); 1067 xfree(ra); 1068 xfree(fp); 1069 } 1070 key_free(found); 1071 return (ret); 1072 } 1073 1074 /* print all known host keys for a given host, but skip keys of given type */ 1075 static int 1076 show_other_keys(const char *host, Key *key) 1077 { 1078 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1079 int i, found = 0; 1080 1081 for (i = 0; type[i] != -1; i++) { 1082 if (type[i] == key->type) 1083 continue; 1084 if (type[i] != KEY_RSA1 && 1085 show_key_from_file(options.user_hostfile2, host, type[i])) { 1086 found = 1; 1087 continue; 1088 } 1089 if (type[i] != KEY_RSA1 && 1090 show_key_from_file(options.system_hostfile2, host, type[i])) { 1091 found = 1; 1092 continue; 1093 } 1094 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1095 found = 1; 1096 continue; 1097 } 1098 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1099 found = 1; 1100 continue; 1101 } 1102 debug2("no key of type %d for host %s", type[i], host); 1103 } 1104 return (found); 1105 } 1106 1107 static void 1108 warn_changed_key(Key *host_key) 1109 { 1110 char *fp; 1111 const char *type = key_type(host_key); 1112 1113 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1114 1115 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1116 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1117 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1118 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1119 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1120 error("It is also possible that the %s host key has just been changed.", type); 1121 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1122 type, fp); 1123 error("Please contact your system administrator."); 1124 1125 xfree(fp); 1126 } 1127 1128 /* 1129 * Execute a local command 1130 */ 1131 int 1132 ssh_local_cmd(const char *args) 1133 { 1134 char *shell; 1135 pid_t pid; 1136 int status; 1137 1138 if (!options.permit_local_command || 1139 args == NULL || !*args) 1140 return (1); 1141 1142 if ((shell = getenv("SHELL")) == NULL) 1143 shell = _PATH_BSHELL; 1144 1145 pid = fork(); 1146 if (pid == 0) { 1147 debug3("Executing %s -c \"%s\"", shell, args); 1148 execl(shell, shell, "-c", args, (char *)NULL); 1149 error("Couldn't execute %s -c \"%s\": %s", 1150 shell, args, strerror(errno)); 1151 _exit(1); 1152 } else if (pid == -1) 1153 fatal("fork failed: %.100s", strerror(errno)); 1154 while (waitpid(pid, &status, 0) == -1) 1155 if (errno != EINTR) 1156 fatal("Couldn't wait for child: %s", strerror(errno)); 1157 1158 if (!WIFEXITED(status)) 1159 return (1); 1160 1161 return (WEXITSTATUS(status)); 1162 } 1163