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 } 1183