1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * Code to connect to a remote host, and to perform the client side of the 6 * login (authentication) dialog. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 */ 14 15 #include "includes.h" 16 RCSID("$OpenBSD: sshconnect.c,v 1.158 2004/06/21 17:36:31 avsm Exp $"); 17 18 #include <openssl/bn.h> 19 20 #include "ssh.h" 21 #include "xmalloc.h" 22 #include "rsa.h" 23 #include "buffer.h" 24 #include "packet.h" 25 #include "uidswap.h" 26 #include "compat.h" 27 #include "key.h" 28 #include "sshconnect.h" 29 #include "hostfile.h" 30 #include "log.h" 31 #include "readconf.h" 32 #include "atomicio.h" 33 #include "misc.h" 34 35 #include "dns.h" 36 37 char *client_version_string = NULL; 38 char *server_version_string = NULL; 39 40 int matching_host_key_dns = 0; 41 42 /* import */ 43 extern Options options; 44 extern char *__progname; 45 extern uid_t original_real_uid; 46 extern uid_t original_effective_uid; 47 extern pid_t proxy_command_pid; 48 49 #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ 50 #define INET6_ADDRSTRLEN 46 51 #endif 52 53 static int show_other_keys(const char *, Key *); 54 static void warn_changed_key(Key *); 55 56 /* 57 * Connect to the given ssh server using a proxy command. 58 */ 59 static int 60 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 61 { 62 Buffer command; 63 const char *cp; 64 char *command_string; 65 int pin[2], pout[2]; 66 pid_t pid; 67 char strport[NI_MAXSERV]; 68 69 /* Convert the port number into a string. */ 70 snprintf(strport, sizeof strport, "%hu", port); 71 72 /* 73 * Build the final command string in the buffer by making the 74 * appropriate substitutions to the given proxy command. 75 * 76 * Use "exec" to avoid "sh -c" processes on some platforms 77 * (e.g. Solaris) 78 */ 79 buffer_init(&command); 80 buffer_append(&command, "exec ", 5); 81 82 for (cp = proxy_command; *cp; cp++) { 83 if (cp[0] == '%' && cp[1] == '%') { 84 buffer_append(&command, "%", 1); 85 cp++; 86 continue; 87 } 88 if (cp[0] == '%' && cp[1] == 'h') { 89 buffer_append(&command, host, strlen(host)); 90 cp++; 91 continue; 92 } 93 if (cp[0] == '%' && cp[1] == 'p') { 94 buffer_append(&command, strport, strlen(strport)); 95 cp++; 96 continue; 97 } 98 buffer_append(&command, cp, 1); 99 } 100 buffer_append(&command, "\0", 1); 101 102 /* Get the final command string. */ 103 command_string = buffer_ptr(&command); 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 seteuid(original_real_uid); 118 setuid(original_real_uid); 119 120 /* Redirect stdin and stdout. */ 121 close(pin[1]); 122 if (pin[0] != 0) { 123 if (dup2(pin[0], 0) < 0) 124 perror("dup2 stdin"); 125 close(pin[0]); 126 } 127 close(pout[0]); 128 if (dup2(pout[1], 1) < 0) 129 perror("dup2 stdout"); 130 /* Cannot be 1 because pin allocated two descriptors. */ 131 close(pout[1]); 132 133 /* Stderr is left as it is so that error messages get 134 printed on the user's terminal. */ 135 argv[0] = _PATH_BSHELL; 136 argv[1] = "-c"; 137 argv[2] = command_string; 138 argv[3] = NULL; 139 140 /* Execute the proxy command. Note that we gave up any 141 extra privileges above. */ 142 execv(argv[0], argv); 143 perror(argv[0]); 144 exit(1); 145 } 146 /* Parent. */ 147 if (pid < 0) 148 fatal("fork failed: %.100s", strerror(errno)); 149 else 150 proxy_command_pid = pid; /* save pid to clean up later */ 151 152 /* Close child side of the descriptors. */ 153 close(pin[0]); 154 close(pout[1]); 155 156 /* Free the command name. */ 157 buffer_free(&command); 158 159 /* Set the connection file descriptors. */ 160 packet_set_connection(pout[0], pin[1]); 161 162 /* Indicate OK return */ 163 return 0; 164 } 165 166 /* 167 * Creates a (possibly privileged) socket for use as the ssh connection. 168 */ 169 static int 170 ssh_create_socket(int privileged, struct addrinfo *ai) 171 { 172 int sock, gaierr; 173 struct addrinfo hints, *res; 174 175 /* 176 * If we are running as root and want to connect to a privileged 177 * port, bind our own socket to a privileged port. 178 */ 179 if (privileged) { 180 int p = IPPORT_RESERVED - 1; 181 PRIV_START; 182 sock = rresvport_af(&p, ai->ai_family); 183 PRIV_END; 184 if (sock < 0) 185 error("rresvport: af=%d %.100s", ai->ai_family, 186 strerror(errno)); 187 else 188 debug("Allocated local port %d.", p); 189 return sock; 190 } 191 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 192 if (sock < 0) 193 error("socket: %.100s", strerror(errno)); 194 195 /* Bind the socket to an alternative local IP address */ 196 if (options.bind_address == NULL) 197 return sock; 198 199 memset(&hints, 0, sizeof(hints)); 200 hints.ai_family = ai->ai_family; 201 hints.ai_socktype = ai->ai_socktype; 202 hints.ai_protocol = ai->ai_protocol; 203 hints.ai_flags = AI_PASSIVE; 204 gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); 205 if (gaierr) { 206 error("getaddrinfo: %s: %s", options.bind_address, 207 gai_strerror(gaierr)); 208 close(sock); 209 return -1; 210 } 211 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 212 error("bind: %s: %s", options.bind_address, strerror(errno)); 213 close(sock); 214 freeaddrinfo(res); 215 return -1; 216 } 217 freeaddrinfo(res); 218 return sock; 219 } 220 221 static int 222 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 223 socklen_t addrlen, int timeout) 224 { 225 fd_set *fdset; 226 struct timeval tv; 227 socklen_t optlen; 228 int fdsetsz, optval, rc, result = -1; 229 230 if (timeout <= 0) 231 return (connect(sockfd, serv_addr, addrlen)); 232 233 set_nonblock(sockfd); 234 rc = connect(sockfd, serv_addr, addrlen); 235 if (rc == 0) { 236 unset_nonblock(sockfd); 237 return (0); 238 } 239 if (errno != EINPROGRESS) 240 return (-1); 241 242 fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); 243 fdset = (fd_set *)xmalloc(fdsetsz); 244 245 memset(fdset, 0, fdsetsz); 246 FD_SET(sockfd, fdset); 247 tv.tv_sec = timeout; 248 tv.tv_usec = 0; 249 250 for(;;) { 251 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 252 if (rc != -1 || errno != EINTR) 253 break; 254 } 255 256 switch(rc) { 257 case 0: 258 /* Timed out */ 259 errno = ETIMEDOUT; 260 break; 261 case -1: 262 /* Select error */ 263 debug("select: %s", strerror(errno)); 264 break; 265 case 1: 266 /* Completed or failed */ 267 optval = 0; 268 optlen = sizeof(optval); 269 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 270 &optlen) == -1) { 271 debug("getsockopt: %s", strerror(errno)); 272 break; 273 } 274 if (optval != 0) { 275 errno = optval; 276 break; 277 } 278 result = 0; 279 unset_nonblock(sockfd); 280 break; 281 default: 282 /* Should not occur */ 283 fatal("Bogus return (%d) from select()", rc); 284 } 285 286 xfree(fdset); 287 return (result); 288 } 289 290 /* 291 * Opens a TCP/IP connection to the remote server on the given host. 292 * The address of the remote host will be returned in hostaddr. 293 * If port is 0, the default port will be used. If needpriv is true, 294 * a privileged port will be allocated to make the connection. 295 * This requires super-user privileges if needpriv is true. 296 * Connection_attempts specifies the maximum number of tries (one per 297 * second). If proxy_command is non-NULL, it specifies the command (with %h 298 * and %p substituted for host and port, respectively) to use to contact 299 * the daemon. 300 * Return values: 301 * 0 for OK 302 * ECONNREFUSED if we got a "Connection Refused" by the peer on any address 303 * ECONNABORTED if we failed without a "Connection refused" 304 * Suitable error messages for the connection failure will already have been 305 * printed. 306 */ 307 int 308 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 309 u_short port, int family, int connection_attempts, 310 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 struct servent *sp; 318 /* 319 * Did we get only other errors than "Connection refused" (which 320 * should block fallback to rsh and similar), or did we get at least 321 * one "Connection refused"? 322 */ 323 int full_failure = 1; 324 325 debug2("ssh_connect: needpriv %d", needpriv); 326 327 /* Get default port if port has not been set. */ 328 if (port == 0) { 329 sp = getservbyname(SSH_SERVICE_NAME, "tcp"); 330 if (sp) 331 port = ntohs(sp->s_port); 332 else 333 port = SSH_DEFAULT_PORT; 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: %.100s: %s", __progname, host, 347 gai_strerror(gaierr)); 348 349 /* 350 * Try to connect several times. On some machines, the first time 351 * will sometimes fail. In general socket code appears to behave 352 * quite magically on many machines. 353 */ 354 for (attempt = 0; ;) { 355 if (attempt > 0) 356 debug("Trying again..."); 357 358 /* Loop through addresses for this host, and try each one in 359 sequence until the connection succeeds. */ 360 for (ai = aitop; ai; ai = ai->ai_next) { 361 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 362 continue; 363 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 364 ntop, sizeof(ntop), strport, sizeof(strport), 365 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 366 error("ssh_connect: getnameinfo failed"); 367 continue; 368 } 369 debug("Connecting to %.200s [%.100s] port %s.", 370 host, ntop, strport); 371 372 /* Create a socket for connecting. */ 373 sock = ssh_create_socket(needpriv, ai); 374 if (sock < 0) 375 /* Any error is already output */ 376 continue; 377 378 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 379 options.connection_timeout) >= 0) { 380 /* Successful connection. */ 381 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 382 break; 383 } else { 384 if (errno == ECONNREFUSED) 385 full_failure = 0; 386 debug("connect to address %s port %s: %s", 387 ntop, strport, strerror(errno)); 388 /* 389 * Close the failed socket; there appear to 390 * be some problems when reusing a socket for 391 * which connect() has already returned an 392 * error. 393 */ 394 close(sock); 395 } 396 } 397 if (ai) 398 break; /* Successful connection. */ 399 400 attempt++; 401 if (attempt >= connection_attempts) 402 break; 403 /* Sleep a moment before retrying. */ 404 sleep(1); 405 } 406 407 freeaddrinfo(aitop); 408 409 /* Return failure if we didn't get a successful connection. */ 410 if (attempt >= connection_attempts) { 411 logit("ssh: connect to host %s port %s: %s", 412 host, strport, strerror(errno)); 413 return full_failure ? ECONNABORTED : ECONNREFUSED; 414 } 415 416 debug("Connection established."); 417 418 /* Set SO_KEEPALIVE if requested. */ 419 if (options.tcp_keep_alive && 420 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 421 sizeof(on)) < 0) 422 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 423 424 /* Set the connection. */ 425 packet_set_connection(sock, sock); 426 427 return 0; 428 } 429 430 /* 431 * Waits for the server identification string, and sends our own 432 * identification string. 433 */ 434 static void 435 ssh_exchange_identification(void) 436 { 437 char buf[256], remote_version[256]; /* must be same size! */ 438 int remote_major, remote_minor, i, mismatch; 439 int connection_in = packet_get_connection_in(); 440 int connection_out = packet_get_connection_out(); 441 int minor1 = PROTOCOL_MINOR_1; 442 443 /* Read other side\'s version identification. */ 444 for (;;) { 445 for (i = 0; i < sizeof(buf) - 1; i++) { 446 int len = atomicio(read, connection_in, &buf[i], 1); 447 if (len < 0) 448 fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); 449 if (len != 1) 450 fatal("ssh_exchange_identification: Connection closed by remote host"); 451 if (buf[i] == '\r') { 452 buf[i] = '\n'; 453 buf[i + 1] = 0; 454 continue; /**XXX wait for \n */ 455 } 456 if (buf[i] == '\n') { 457 buf[i + 1] = 0; 458 break; 459 } 460 } 461 buf[sizeof(buf) - 1] = 0; 462 if (strncmp(buf, "SSH-", 4) == 0) 463 break; 464 debug("ssh_exchange_identification: %s", buf); 465 } 466 server_version_string = xstrdup(buf); 467 468 /* 469 * Check that the versions match. In future this might accept 470 * several versions and set appropriate flags to handle them. 471 */ 472 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 473 &remote_major, &remote_minor, remote_version) != 3) 474 fatal("Bad remote protocol version identification: '%.100s'", buf); 475 debug("Remote protocol version %d.%d, remote software version %.100s", 476 remote_major, remote_minor, remote_version); 477 478 compat_datafellows(remote_version); 479 mismatch = 0; 480 481 switch (remote_major) { 482 case 1: 483 if (remote_minor == 99 && 484 (options.protocol & SSH_PROTO_2) && 485 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 486 enable_compat20(); 487 break; 488 } 489 if (!(options.protocol & SSH_PROTO_1)) { 490 mismatch = 1; 491 break; 492 } 493 if (remote_minor < 3) { 494 fatal("Remote machine has too old SSH software version."); 495 } else if (remote_minor == 3 || remote_minor == 4) { 496 /* We speak 1.3, too. */ 497 enable_compat13(); 498 minor1 = 3; 499 if (options.forward_agent) { 500 logit("Agent forwarding disabled for protocol 1.3"); 501 options.forward_agent = 0; 502 } 503 } 504 break; 505 case 2: 506 if (options.protocol & SSH_PROTO_2) { 507 enable_compat20(); 508 break; 509 } 510 /* FALLTHROUGH */ 511 default: 512 mismatch = 1; 513 break; 514 } 515 if (mismatch) 516 fatal("Protocol major versions differ: %d vs. %d", 517 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 518 remote_major); 519 /* Send our own protocol version identification. */ 520 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", 521 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 522 compat20 ? PROTOCOL_MINOR_2 : minor1, 523 SSH_VERSION); 524 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) 525 fatal("write: %.100s", strerror(errno)); 526 client_version_string = xstrdup(buf); 527 chop(client_version_string); 528 chop(server_version_string); 529 debug("Local version string %.100s", client_version_string); 530 } 531 532 /* defaults to 'no' */ 533 static int 534 confirm(const char *prompt) 535 { 536 const char *msg, *again = "Please type 'yes' or 'no': "; 537 char *p; 538 int ret = -1; 539 540 if (options.batch_mode) 541 return 0; 542 for (msg = prompt;;msg = again) { 543 p = read_passphrase(msg, RP_ECHO); 544 if (p == NULL || 545 (p[0] == '\0') || (p[0] == '\n') || 546 strncasecmp(p, "no", 2) == 0) 547 ret = 0; 548 if (p && strncasecmp(p, "yes", 3) == 0) 549 ret = 1; 550 if (p) 551 xfree(p); 552 if (ret != -1) 553 return ret; 554 } 555 } 556 557 /* 558 * check whether the supplied host key is valid, return -1 if the key 559 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 560 */ 561 static int 562 check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, 563 int readonly, const char *user_hostfile, const char *system_hostfile) 564 { 565 Key *file_key; 566 const char *type = key_type(host_key); 567 char *ip = NULL; 568 char hostline[1000], *hostp, *fp; 569 HostStatus host_status; 570 HostStatus ip_status; 571 int local = 0, host_ip_differ = 0; 572 int salen; 573 char ntop[NI_MAXHOST]; 574 char msg[1024]; 575 int len, host_line, ip_line; 576 const char *host_file = NULL, *ip_file = NULL; 577 578 /* 579 * Force accepting of the host key for loopback/localhost. The 580 * problem is that if the home directory is NFS-mounted to multiple 581 * machines, localhost will refer to a different machine in each of 582 * them, and the user will get bogus HOST_CHANGED warnings. This 583 * essentially disables host authentication for localhost; however, 584 * this is probably not a real problem. 585 */ 586 /** hostaddr == 0! */ 587 switch (hostaddr->sa_family) { 588 case AF_INET: 589 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 590 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 591 salen = sizeof(struct sockaddr_in); 592 break; 593 case AF_INET6: 594 local = IN6_IS_ADDR_LOOPBACK( 595 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 596 salen = sizeof(struct sockaddr_in6); 597 break; 598 default: 599 local = 0; 600 salen = sizeof(struct sockaddr_storage); 601 break; 602 } 603 if (options.no_host_authentication_for_localhost == 1 && local && 604 options.host_key_alias == NULL) { 605 debug("Forcing accepting of host key for " 606 "loopback/localhost."); 607 return 0; 608 } 609 610 /* 611 * We don't have the remote ip-address for connections 612 * using a proxy command 613 */ 614 if (options.proxy_command == NULL) { 615 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), 616 NULL, 0, NI_NUMERICHOST) != 0) 617 fatal("check_host_key: getnameinfo failed"); 618 ip = xstrdup(ntop); 619 } else { 620 ip = xstrdup("<no hostip for proxy command>"); 621 } 622 /* 623 * Turn off check_host_ip if the connection is to localhost, via proxy 624 * command or if we don't have a hostname to compare with 625 */ 626 if (options.check_host_ip && 627 (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) 628 options.check_host_ip = 0; 629 630 /* 631 * Allow the user to record the key under a different name. This is 632 * useful for ssh tunneling over forwarded connections or if you run 633 * multiple sshd's on different ports on the same machine. 634 */ 635 if (options.host_key_alias != NULL) { 636 host = options.host_key_alias; 637 debug("using hostkeyalias: %s", host); 638 } 639 640 /* 641 * Store the host key from the known host file in here so that we can 642 * compare it with the key for the IP address. 643 */ 644 file_key = key_new(host_key->type); 645 646 /* 647 * Check if the host key is present in the user\'s list of known 648 * hosts or in the systemwide list. 649 */ 650 host_file = user_hostfile; 651 host_status = check_host_in_hostfile(host_file, host, host_key, 652 file_key, &host_line); 653 if (host_status == HOST_NEW) { 654 host_file = system_hostfile; 655 host_status = check_host_in_hostfile(host_file, host, host_key, 656 file_key, &host_line); 657 } 658 /* 659 * Also perform check for the ip address, skip the check if we are 660 * localhost or the hostname was an ip address to begin with 661 */ 662 if (options.check_host_ip) { 663 Key *ip_key = key_new(host_key->type); 664 665 ip_file = user_hostfile; 666 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 667 ip_key, &ip_line); 668 if (ip_status == HOST_NEW) { 669 ip_file = system_hostfile; 670 ip_status = check_host_in_hostfile(ip_file, ip, 671 host_key, ip_key, &ip_line); 672 } 673 if (host_status == HOST_CHANGED && 674 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 675 host_ip_differ = 1; 676 677 key_free(ip_key); 678 } else 679 ip_status = host_status; 680 681 key_free(file_key); 682 683 switch (host_status) { 684 case HOST_OK: 685 /* The host is known and the key matches. */ 686 debug("Host '%.200s' is known and matches the %s host key.", 687 host, type); 688 debug("Found key in %s:%d", host_file, host_line); 689 if (options.check_host_ip && ip_status == HOST_NEW) { 690 if (readonly) 691 logit("%s host key for IP address " 692 "'%.128s' not in list of known hosts.", 693 type, ip); 694 else if (!add_host_to_hostfile(user_hostfile, ip, 695 host_key)) 696 logit("Failed to add the %s host key for IP " 697 "address '%.128s' to the list of known " 698 "hosts (%.30s).", type, ip, user_hostfile); 699 else 700 logit("Warning: Permanently added the %s host " 701 "key for IP address '%.128s' to the list " 702 "of known hosts.", type, ip); 703 } 704 break; 705 case HOST_NEW: 706 if (readonly) 707 goto fail; 708 /* The host is new. */ 709 if (options.strict_host_key_checking == 1) { 710 /* 711 * User has requested strict host key checking. We 712 * will not add the host key automatically. The only 713 * alternative left is to abort. 714 */ 715 error("No %s host key is known for %.200s and you " 716 "have requested strict checking.", type, host); 717 goto fail; 718 } else if (options.strict_host_key_checking == 2) { 719 char msg1[1024], msg2[1024]; 720 721 if (show_other_keys(host, host_key)) 722 snprintf(msg1, sizeof(msg1), 723 "\nbut keys of different type are already" 724 " known for this host."); 725 else 726 snprintf(msg1, sizeof(msg1), "."); 727 /* The default */ 728 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 729 msg2[0] = '\0'; 730 if (options.verify_host_key_dns) { 731 if (matching_host_key_dns) 732 snprintf(msg2, sizeof(msg2), 733 "Matching host key fingerprint" 734 " found in DNS.\n"); 735 else 736 snprintf(msg2, sizeof(msg2), 737 "No matching host key fingerprint" 738 " found in DNS.\n"); 739 } 740 snprintf(msg, sizeof(msg), 741 "The authenticity of host '%.200s (%s)' can't be " 742 "established%s\n" 743 "%s key fingerprint is %s.\n%s" 744 "Are you sure you want to continue connecting " 745 "(yes/no)? ", 746 host, ip, msg1, type, fp, msg2); 747 xfree(fp); 748 if (!confirm(msg)) 749 goto fail; 750 } 751 if (options.check_host_ip && ip_status == HOST_NEW) { 752 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 753 hostp = hostline; 754 } else 755 hostp = host; 756 757 /* 758 * If not in strict mode, add the key automatically to the 759 * local known_hosts file. 760 */ 761 if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) 762 logit("Failed to add the host to the list of known " 763 "hosts (%.500s).", user_hostfile); 764 else 765 logit("Warning: Permanently added '%.200s' (%s) to the " 766 "list of known hosts.", hostp, type); 767 break; 768 case HOST_CHANGED: 769 if (options.check_host_ip && host_ip_differ) { 770 char *key_msg; 771 if (ip_status == HOST_NEW) 772 key_msg = "is unknown"; 773 else if (ip_status == HOST_OK) 774 key_msg = "is unchanged"; 775 else 776 key_msg = "has a different value"; 777 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 778 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 779 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 780 error("The %s host key for %s has changed,", type, host); 781 error("and the key for the according IP address %s", ip); 782 error("%s. This could either mean that", key_msg); 783 error("DNS SPOOFING is happening or the IP address for the host"); 784 error("and its host key have changed at the same time."); 785 if (ip_status != HOST_NEW) 786 error("Offending key for IP in %s:%d", ip_file, ip_line); 787 } 788 /* The host key has changed. */ 789 warn_changed_key(host_key); 790 error("Add correct host key in %.100s to get rid of this message.", 791 user_hostfile); 792 error("Offending key in %s:%d", host_file, host_line); 793 794 /* 795 * If strict host key checking is in use, the user will have 796 * to edit the key manually and we can only abort. 797 */ 798 if (options.strict_host_key_checking) { 799 error("%s host key for %.200s has changed and you have " 800 "requested strict checking.", type, host); 801 goto fail; 802 } 803 804 /* 805 * If strict host key checking has not been requested, allow 806 * the connection but without MITM-able authentication or 807 * agent forwarding. 808 */ 809 if (options.password_authentication) { 810 error("Password authentication is disabled to avoid " 811 "man-in-the-middle attacks."); 812 options.password_authentication = 0; 813 } 814 if (options.kbd_interactive_authentication) { 815 error("Keyboard-interactive authentication is disabled" 816 " to avoid man-in-the-middle attacks."); 817 options.kbd_interactive_authentication = 0; 818 options.challenge_response_authentication = 0; 819 } 820 if (options.challenge_response_authentication) { 821 error("Challenge/response authentication is disabled" 822 " to avoid man-in-the-middle attacks."); 823 options.challenge_response_authentication = 0; 824 } 825 if (options.forward_agent) { 826 error("Agent forwarding is disabled to avoid " 827 "man-in-the-middle attacks."); 828 options.forward_agent = 0; 829 } 830 if (options.forward_x11) { 831 error("X11 forwarding is disabled to avoid " 832 "man-in-the-middle attacks."); 833 options.forward_x11 = 0; 834 } 835 if (options.num_local_forwards > 0 || 836 options.num_remote_forwards > 0) { 837 error("Port forwarding is disabled to avoid " 838 "man-in-the-middle attacks."); 839 options.num_local_forwards = 840 options.num_remote_forwards = 0; 841 } 842 /* 843 * XXX Should permit the user to change to use the new id. 844 * This could be done by converting the host key to an 845 * identifying sentence, tell that the host identifies itself 846 * by that sentence, and ask the user if he/she whishes to 847 * accept the authentication. 848 */ 849 break; 850 case HOST_FOUND: 851 fatal("internal error"); 852 break; 853 } 854 855 if (options.check_host_ip && host_status != HOST_CHANGED && 856 ip_status == HOST_CHANGED) { 857 snprintf(msg, sizeof(msg), 858 "Warning: the %s host key for '%.200s' " 859 "differs from the key for the IP address '%.128s'" 860 "\nOffending key for IP in %s:%d", 861 type, host, ip, ip_file, ip_line); 862 if (host_status == HOST_OK) { 863 len = strlen(msg); 864 snprintf(msg + len, sizeof(msg) - len, 865 "\nMatching host key in %s:%d", 866 host_file, host_line); 867 } 868 if (options.strict_host_key_checking == 1) { 869 logit("%s", msg); 870 error("Exiting, you have requested strict checking."); 871 goto fail; 872 } else if (options.strict_host_key_checking == 2) { 873 strlcat(msg, "\nAre you sure you want " 874 "to continue connecting (yes/no)? ", sizeof(msg)); 875 if (!confirm(msg)) 876 goto fail; 877 } else { 878 logit("%s", msg); 879 } 880 } 881 882 xfree(ip); 883 return 0; 884 885 fail: 886 xfree(ip); 887 return -1; 888 } 889 890 /* returns 0 if key verifies or -1 if key does NOT verify */ 891 int 892 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 893 { 894 struct stat st; 895 int flags = 0; 896 897 if (options.verify_host_key_dns && 898 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 899 900 if (flags & DNS_VERIFY_FOUND) { 901 902 if (options.verify_host_key_dns == 1 && 903 flags & DNS_VERIFY_MATCH && 904 flags & DNS_VERIFY_SECURE) 905 return 0; 906 907 if (flags & DNS_VERIFY_MATCH) { 908 matching_host_key_dns = 1; 909 } else { 910 warn_changed_key(host_key); 911 error("Update the SSHFP RR in DNS with the new " 912 "host key to get rid of this message."); 913 } 914 } 915 } 916 917 /* return ok if the key can be found in an old keyfile */ 918 if (stat(options.system_hostfile2, &st) == 0 || 919 stat(options.user_hostfile2, &st) == 0) { 920 if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, 921 options.user_hostfile2, options.system_hostfile2) == 0) 922 return 0; 923 } 924 return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, 925 options.user_hostfile, options.system_hostfile); 926 } 927 928 /* 929 * Starts a dialog with the server, and authenticates the current user on the 930 * server. This does not need any extra privileges. The basic connection 931 * to the server must already have been established before this is called. 932 * If login fails, this function prints an error and never returns. 933 * This function does not require super-user privileges. 934 */ 935 void 936 ssh_login(Sensitive *sensitive, const char *orighost, 937 struct sockaddr *hostaddr, struct passwd *pw) 938 { 939 char *host, *cp; 940 char *server_user, *local_user; 941 942 local_user = xstrdup(pw->pw_name); 943 server_user = options.user ? options.user : local_user; 944 945 /* Convert the user-supplied hostname into all lowercase. */ 946 host = xstrdup(orighost); 947 for (cp = host; *cp; cp++) 948 if (isupper(*cp)) 949 *cp = tolower(*cp); 950 951 /* Exchange protocol version identification strings with the server. */ 952 ssh_exchange_identification(); 953 954 /* Put the connection into non-blocking mode. */ 955 packet_set_nonblocking(); 956 957 /* key exchange */ 958 /* authenticate user */ 959 if (compat20) { 960 ssh_kex2(host, hostaddr); 961 ssh_userauth2(local_user, server_user, host, sensitive); 962 } else { 963 ssh_kex(host, hostaddr); 964 ssh_userauth1(local_user, server_user, host, sensitive); 965 } 966 } 967 968 void 969 ssh_put_password(char *password) 970 { 971 int size; 972 char *padded; 973 974 if (datafellows & SSH_BUG_PASSWORDPAD) { 975 packet_put_cstring(password); 976 return; 977 } 978 size = roundup(strlen(password) + 1, 32); 979 padded = xmalloc(size); 980 memset(padded, 0, size); 981 strlcpy(padded, password, size); 982 packet_put_string(padded, size); 983 memset(padded, 0, size); 984 xfree(padded); 985 } 986 987 static int 988 show_key_from_file(const char *file, const char *host, int keytype) 989 { 990 Key *found; 991 char *fp; 992 int line, ret; 993 994 found = key_new(keytype); 995 if ((ret = lookup_key_in_hostfile_by_type(file, host, 996 keytype, found, &line))) { 997 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 998 logit("WARNING: %s key found for host %s\n" 999 "in %s:%d\n" 1000 "%s key fingerprint %s.", 1001 key_type(found), host, file, line, 1002 key_type(found), fp); 1003 xfree(fp); 1004 } 1005 key_free(found); 1006 return (ret); 1007 } 1008 1009 /* print all known host keys for a given host, but skip keys of given type */ 1010 static int 1011 show_other_keys(const char *host, Key *key) 1012 { 1013 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1014 int i, found = 0; 1015 1016 for (i = 0; type[i] != -1; i++) { 1017 if (type[i] == key->type) 1018 continue; 1019 if (type[i] != KEY_RSA1 && 1020 show_key_from_file(options.user_hostfile2, host, type[i])) { 1021 found = 1; 1022 continue; 1023 } 1024 if (type[i] != KEY_RSA1 && 1025 show_key_from_file(options.system_hostfile2, host, type[i])) { 1026 found = 1; 1027 continue; 1028 } 1029 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1030 found = 1; 1031 continue; 1032 } 1033 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1034 found = 1; 1035 continue; 1036 } 1037 debug2("no key of type %d for host %s", type[i], host); 1038 } 1039 return (found); 1040 } 1041 1042 static void 1043 warn_changed_key(Key *host_key) 1044 { 1045 char *fp; 1046 const char *type = key_type(host_key); 1047 1048 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1049 1050 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1051 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1052 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1053 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1054 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1055 error("It is also possible that the %s host key has just been changed.", type); 1056 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1057 type, fp); 1058 error("Please contact your system administrator."); 1059 1060 xfree(fp); 1061 } 1062