1 /* $OpenBSD: sshconnect.c,v 1.224 2010/04/16 21:14:27 djm 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 <fcntl.h> 27 #include <netdb.h> 28 #include <paths.h> 29 #include <signal.h> 30 #include <pwd.h> 31 #include <stdio.h> 32 #include <stdlib.h> 33 #include <string.h> 34 #include <unistd.h> 35 36 #include "xmalloc.h" 37 #include "ssh.h" 38 #include "rsa.h" 39 #include "buffer.h" 40 #include "packet.h" 41 #include "uidswap.h" 42 #include "compat.h" 43 #include "key.h" 44 #include "sshconnect.h" 45 #include "hostfile.h" 46 #include "log.h" 47 #include "readconf.h" 48 #include "atomicio.h" 49 #include "misc.h" 50 #include "dns.h" 51 #include "roaming.h" 52 #include "ssh2.h" 53 #include "version.h" 54 55 char *client_version_string = NULL; 56 char *server_version_string = NULL; 57 58 static int matching_host_key_dns = 0; 59 60 /* import */ 61 extern Options options; 62 extern char *__progname; 63 extern uid_t original_real_uid; 64 extern uid_t original_effective_uid; 65 extern pid_t proxy_command_pid; 66 67 static int show_other_keys(const char *, Key *); 68 static void warn_changed_key(Key *); 69 70 /* 71 * Connect to the given ssh server using a proxy command. 72 */ 73 static int 74 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 75 { 76 char *command_string, *tmp; 77 int pin[2], pout[2]; 78 pid_t pid; 79 char *shell, strport[NI_MAXSERV]; 80 81 if ((shell = getenv("SHELL")) == NULL) 82 shell = _PATH_BSHELL; 83 84 /* Convert the port number into a string. */ 85 snprintf(strport, sizeof strport, "%hu", port); 86 87 /* 88 * Build the final command string in the buffer by making the 89 * appropriate substitutions to the given proxy command. 90 * 91 * Use "exec" to avoid "sh -c" processes on some platforms 92 * (e.g. Solaris) 93 */ 94 xasprintf(&tmp, "exec %s", proxy_command); 95 command_string = percent_expand(tmp, "h", host, "p", strport, 96 "r", options.user, (char *)NULL); 97 xfree(tmp); 98 99 /* Create pipes for communicating with the proxy. */ 100 if (pipe(pin) < 0 || pipe(pout) < 0) 101 fatal("Could not create pipes to communicate with the proxy: %.100s", 102 strerror(errno)); 103 104 debug("Executing proxy command: %.500s", command_string); 105 106 /* Fork and execute the proxy command. */ 107 if ((pid = fork()) == 0) { 108 char *argv[10]; 109 110 /* Child. Permanently give up superuser privileges. */ 111 permanently_drop_suid(original_real_uid); 112 113 /* Redirect stdin and stdout. */ 114 close(pin[1]); 115 if (pin[0] != 0) { 116 if (dup2(pin[0], 0) < 0) 117 perror("dup2 stdin"); 118 close(pin[0]); 119 } 120 close(pout[0]); 121 if (dup2(pout[1], 1) < 0) 122 perror("dup2 stdout"); 123 /* Cannot be 1 because pin allocated two descriptors. */ 124 close(pout[1]); 125 126 /* Stderr is left as it is so that error messages get 127 printed on the user's terminal. */ 128 argv[0] = shell; 129 argv[1] = "-c"; 130 argv[2] = command_string; 131 argv[3] = NULL; 132 133 /* Execute the proxy command. Note that we gave up any 134 extra privileges above. */ 135 execv(argv[0], argv); 136 perror(argv[0]); 137 exit(1); 138 } 139 /* Parent. */ 140 if (pid < 0) 141 fatal("fork failed: %.100s", strerror(errno)); 142 else 143 proxy_command_pid = pid; /* save pid to clean up later */ 144 145 /* Close child side of the descriptors. */ 146 close(pin[0]); 147 close(pout[1]); 148 149 /* Free the command name. */ 150 xfree(command_string); 151 152 /* Set the connection file descriptors. */ 153 packet_set_connection(pout[0], pin[1]); 154 packet_set_timeout(options.server_alive_interval, 155 options.server_alive_count_max); 156 157 /* Indicate OK return */ 158 return 0; 159 } 160 161 /* 162 * Creates a (possibly privileged) socket for use as the ssh connection. 163 */ 164 static int 165 ssh_create_socket(int privileged, struct addrinfo *ai) 166 { 167 int sock, gaierr; 168 struct addrinfo hints, *res; 169 170 /* 171 * If we are running as root and want to connect to a privileged 172 * port, bind our own socket to a privileged port. 173 */ 174 if (privileged) { 175 int p = IPPORT_RESERVED - 1; 176 PRIV_START; 177 sock = rresvport_af(&p, ai->ai_family); 178 PRIV_END; 179 if (sock < 0) 180 error("rresvport: af=%d %.100s", ai->ai_family, 181 strerror(errno)); 182 else 183 debug("Allocated local port %d.", p); 184 return sock; 185 } 186 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 187 if (sock < 0) { 188 error("socket: %.100s", strerror(errno)); 189 return -1; 190 } 191 fcntl(sock, F_SETFD, FD_CLOEXEC); 192 193 /* Bind the socket to an alternative local IP address */ 194 if (options.bind_address == NULL) 195 return sock; 196 197 memset(&hints, 0, sizeof(hints)); 198 hints.ai_family = ai->ai_family; 199 hints.ai_socktype = ai->ai_socktype; 200 hints.ai_protocol = ai->ai_protocol; 201 hints.ai_flags = AI_PASSIVE; 202 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 203 if (gaierr) { 204 error("getaddrinfo: %s: %s", options.bind_address, 205 ssh_gai_strerror(gaierr)); 206 close(sock); 207 return -1; 208 } 209 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 210 error("bind: %s: %s", options.bind_address, strerror(errno)); 211 close(sock); 212 freeaddrinfo(res); 213 return -1; 214 } 215 freeaddrinfo(res); 216 return sock; 217 } 218 219 static int 220 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 221 socklen_t addrlen, int *timeoutp) 222 { 223 fd_set *fdset; 224 struct timeval tv, t_start; 225 socklen_t optlen; 226 int optval, rc, result = -1; 227 228 gettimeofday(&t_start, NULL); 229 230 if (*timeoutp <= 0) { 231 result = connect(sockfd, serv_addr, addrlen); 232 goto done; 233 } 234 235 set_nonblock(sockfd); 236 rc = connect(sockfd, serv_addr, addrlen); 237 if (rc == 0) { 238 unset_nonblock(sockfd); 239 result = 0; 240 goto done; 241 } 242 if (errno != EINPROGRESS) { 243 result = -1; 244 goto done; 245 } 246 247 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 248 sizeof(fd_mask)); 249 FD_SET(sockfd, fdset); 250 ms_to_timeval(&tv, *timeoutp); 251 252 for (;;) { 253 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 254 if (rc != -1 || errno != EINTR) 255 break; 256 } 257 258 switch (rc) { 259 case 0: 260 /* Timed out */ 261 errno = ETIMEDOUT; 262 break; 263 case -1: 264 /* Select error */ 265 debug("select: %s", strerror(errno)); 266 break; 267 case 1: 268 /* Completed or failed */ 269 optval = 0; 270 optlen = sizeof(optval); 271 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 272 &optlen) == -1) { 273 debug("getsockopt: %s", strerror(errno)); 274 break; 275 } 276 if (optval != 0) { 277 errno = optval; 278 break; 279 } 280 result = 0; 281 unset_nonblock(sockfd); 282 break; 283 default: 284 /* Should not occur */ 285 fatal("Bogus return (%d) from select()", rc); 286 } 287 288 xfree(fdset); 289 290 done: 291 if (result == 0 && *timeoutp > 0) { 292 ms_subtract_diff(&t_start, timeoutp); 293 if (*timeoutp <= 0) { 294 errno = ETIMEDOUT; 295 result = -1; 296 } 297 } 298 299 return (result); 300 } 301 302 /* 303 * Opens a TCP/IP connection to the remote server on the given host. 304 * The address of the remote host will be returned in hostaddr. 305 * If port is 0, the default port will be used. If needpriv is true, 306 * a privileged port will be allocated to make the connection. 307 * This requires super-user privileges if needpriv is true. 308 * Connection_attempts specifies the maximum number of tries (one per 309 * second). If proxy_command is non-NULL, it specifies the command (with %h 310 * and %p substituted for host and port, respectively) to use to contact 311 * the daemon. 312 */ 313 int 314 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 315 u_short port, int family, int connection_attempts, int *timeout_ms, 316 int want_keepalive, int needpriv, const char *proxy_command) 317 { 318 int gaierr; 319 int on = 1; 320 int sock = -1, attempt; 321 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 322 struct addrinfo hints, *ai, *aitop; 323 324 debug2("ssh_connect: needpriv %d", needpriv); 325 326 /* If a proxy command is given, connect using it. */ 327 if (proxy_command != NULL) 328 return ssh_proxy_connect(host, port, proxy_command); 329 330 /* No proxy command. */ 331 332 memset(&hints, 0, sizeof(hints)); 333 hints.ai_family = family; 334 hints.ai_socktype = SOCK_STREAM; 335 snprintf(strport, sizeof strport, "%u", port); 336 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 337 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 338 host, ssh_gai_strerror(gaierr)); 339 340 for (attempt = 0; attempt < connection_attempts; attempt++) { 341 if (attempt > 0) { 342 /* Sleep a moment before retrying. */ 343 sleep(1); 344 debug("Trying again..."); 345 } 346 /* 347 * Loop through addresses for this host, and try each one in 348 * sequence until the connection succeeds. 349 */ 350 for (ai = aitop; ai; ai = ai->ai_next) { 351 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 352 continue; 353 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 354 ntop, sizeof(ntop), strport, sizeof(strport), 355 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 356 error("ssh_connect: getnameinfo failed"); 357 continue; 358 } 359 debug("Connecting to %.200s [%.100s] port %s.", 360 host, ntop, strport); 361 362 /* Create a socket for connecting. */ 363 sock = ssh_create_socket(needpriv, ai); 364 if (sock < 0) 365 /* Any error is already output */ 366 continue; 367 368 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 369 timeout_ms) >= 0) { 370 /* Successful connection. */ 371 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 372 break; 373 } else { 374 debug("connect to address %s port %s: %s", 375 ntop, strport, strerror(errno)); 376 close(sock); 377 sock = -1; 378 } 379 } 380 if (sock != -1) 381 break; /* Successful connection. */ 382 } 383 384 freeaddrinfo(aitop); 385 386 /* Return failure if we didn't get a successful connection. */ 387 if (sock == -1) { 388 error("ssh: connect to host %s port %s: %s", 389 host, strport, strerror(errno)); 390 return (-1); 391 } 392 393 debug("Connection established."); 394 395 /* Set SO_KEEPALIVE if requested. */ 396 if (want_keepalive && 397 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 398 sizeof(on)) < 0) 399 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 400 401 /* Set the connection. */ 402 packet_set_connection(sock, sock); 403 packet_set_timeout(options.server_alive_interval, 404 options.server_alive_count_max); 405 406 return 0; 407 } 408 409 /* 410 * Waits for the server identification string, and sends our own 411 * identification string. 412 */ 413 void 414 ssh_exchange_identification(int timeout_ms) 415 { 416 char buf[256], remote_version[256]; /* must be same size! */ 417 int remote_major, remote_minor, mismatch; 418 int connection_in = packet_get_connection_in(); 419 int connection_out = packet_get_connection_out(); 420 int minor1 = PROTOCOL_MINOR_1; 421 u_int i, n; 422 size_t len; 423 int fdsetsz, remaining, rc; 424 struct timeval t_start, t_remaining; 425 fd_set *fdset; 426 427 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 428 fdset = xcalloc(1, fdsetsz); 429 430 /* Read other side's version identification. */ 431 remaining = timeout_ms; 432 for (n = 0;;) { 433 for (i = 0; i < sizeof(buf) - 1; i++) { 434 if (timeout_ms > 0) { 435 gettimeofday(&t_start, NULL); 436 ms_to_timeval(&t_remaining, remaining); 437 FD_SET(connection_in, fdset); 438 rc = select(connection_in + 1, fdset, NULL, 439 fdset, &t_remaining); 440 ms_subtract_diff(&t_start, &remaining); 441 if (rc == 0 || remaining <= 0) 442 fatal("Connection timed out during " 443 "banner exchange"); 444 if (rc == -1) { 445 if (errno == EINTR) 446 continue; 447 fatal("ssh_exchange_identification: " 448 "select: %s", strerror(errno)); 449 } 450 } 451 452 len = roaming_atomicio(read, connection_in, &buf[i], 1); 453 454 if (len != 1 && errno == EPIPE) 455 fatal("ssh_exchange_identification: " 456 "Connection closed by remote host"); 457 else if (len != 1) 458 fatal("ssh_exchange_identification: " 459 "read: %.100s", strerror(errno)); 460 if (buf[i] == '\r') { 461 buf[i] = '\n'; 462 buf[i + 1] = 0; 463 continue; /**XXX wait for \n */ 464 } 465 if (buf[i] == '\n') { 466 buf[i + 1] = 0; 467 break; 468 } 469 if (++n > 65536) 470 fatal("ssh_exchange_identification: " 471 "No banner received"); 472 } 473 buf[sizeof(buf) - 1] = 0; 474 if (strncmp(buf, "SSH-", 4) == 0) 475 break; 476 debug("ssh_exchange_identification: %s", buf); 477 } 478 server_version_string = xstrdup(buf); 479 xfree(fdset); 480 481 /* 482 * Check that the versions match. In future this might accept 483 * several versions and set appropriate flags to handle them. 484 */ 485 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 486 &remote_major, &remote_minor, remote_version) != 3) 487 fatal("Bad remote protocol version identification: '%.100s'", buf); 488 debug("Remote protocol version %d.%d, remote software version %.100s", 489 remote_major, remote_minor, remote_version); 490 491 compat_datafellows(remote_version); 492 mismatch = 0; 493 494 switch (remote_major) { 495 case 1: 496 if (remote_minor == 99 && 497 (options.protocol & SSH_PROTO_2) && 498 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 499 enable_compat20(); 500 break; 501 } 502 if (!(options.protocol & SSH_PROTO_1)) { 503 mismatch = 1; 504 break; 505 } 506 if (remote_minor < 3) { 507 fatal("Remote machine has too old SSH software version."); 508 } else if (remote_minor == 3 || remote_minor == 4) { 509 /* We speak 1.3, too. */ 510 enable_compat13(); 511 minor1 = 3; 512 if (options.forward_agent) { 513 logit("Agent forwarding disabled for protocol 1.3"); 514 options.forward_agent = 0; 515 } 516 } 517 break; 518 case 2: 519 if (options.protocol & SSH_PROTO_2) { 520 enable_compat20(); 521 break; 522 } 523 /* FALLTHROUGH */ 524 default: 525 mismatch = 1; 526 break; 527 } 528 if (mismatch) 529 fatal("Protocol major versions differ: %d vs. %d", 530 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 531 remote_major); 532 /* Send our own protocol version identification. */ 533 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 534 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 535 compat20 ? PROTOCOL_MINOR_2 : minor1, 536 SSH_VERSION, compat20 ? "\r\n" : "\n"); 537 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 538 != strlen(buf)) 539 fatal("write: %.100s", strerror(errno)); 540 client_version_string = xstrdup(buf); 541 chop(client_version_string); 542 chop(server_version_string); 543 debug("Local version string %.100s", client_version_string); 544 } 545 546 /* defaults to 'no' */ 547 static int 548 confirm(const char *prompt) 549 { 550 const char *msg, *again = "Please type 'yes' or 'no': "; 551 char *p; 552 int ret = -1; 553 554 if (options.batch_mode) 555 return 0; 556 for (msg = prompt;;msg = again) { 557 p = read_passphrase(msg, RP_ECHO); 558 if (p == NULL || 559 (p[0] == '\0') || (p[0] == '\n') || 560 strncasecmp(p, "no", 2) == 0) 561 ret = 0; 562 if (p && strncasecmp(p, "yes", 3) == 0) 563 ret = 1; 564 if (p) 565 xfree(p); 566 if (ret != -1) 567 return ret; 568 } 569 } 570 571 static int 572 check_host_cert(const char *host, const Key *host_key) 573 { 574 const char *reason; 575 576 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 577 error("%s", reason); 578 return 0; 579 } 580 if (buffer_len(&host_key->cert->critical) != 0) { 581 error("Certificate for %s contains unsupported " 582 "critical options(s)", host); 583 return 0; 584 } 585 return 1; 586 } 587 588 /* 589 * check whether the supplied host key is valid, return -1 if the key 590 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 591 */ 592 #define RDRW 0 593 #define RDONLY 1 594 #define ROQUIET 2 595 static int 596 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 597 Key *host_key, int readonly, const char *user_hostfile, 598 const char *system_hostfile) 599 { 600 Key *file_key, *raw_key = NULL; 601 const char *type; 602 char *ip = NULL, *host = NULL; 603 char hostline[1000], *hostp, *fp, *ra; 604 HostStatus host_status; 605 HostStatus ip_status; 606 int r, want_cert, local = 0, host_ip_differ = 0; 607 char ntop[NI_MAXHOST]; 608 char msg[1024]; 609 int len, host_line, ip_line, cancelled_forwarding = 0; 610 const char *host_file = NULL, *ip_file = NULL; 611 612 /* 613 * Force accepting of the host key for loopback/localhost. The 614 * problem is that if the home directory is NFS-mounted to multiple 615 * machines, localhost will refer to a different machine in each of 616 * them, and the user will get bogus HOST_CHANGED warnings. This 617 * essentially disables host authentication for localhost; however, 618 * this is probably not a real problem. 619 */ 620 /** hostaddr == 0! */ 621 switch (hostaddr->sa_family) { 622 case AF_INET: 623 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 624 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 625 break; 626 case AF_INET6: 627 local = IN6_IS_ADDR_LOOPBACK( 628 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 629 break; 630 default: 631 local = 0; 632 break; 633 } 634 if (options.no_host_authentication_for_localhost == 1 && local && 635 options.host_key_alias == NULL) { 636 debug("Forcing accepting of host key for " 637 "loopback/localhost."); 638 return 0; 639 } 640 641 /* 642 * We don't have the remote ip-address for connections 643 * using a proxy command 644 */ 645 if (options.proxy_command == NULL) { 646 if (getnameinfo(hostaddr, hostaddr->sa_len, ntop, sizeof(ntop), 647 NULL, 0, NI_NUMERICHOST) != 0) 648 fatal("check_host_key: getnameinfo failed"); 649 ip = put_host_port(ntop, port); 650 } else { 651 ip = xstrdup("<no hostip for proxy command>"); 652 } 653 654 /* 655 * Turn off check_host_ip if the connection is to localhost, via proxy 656 * command or if we don't have a hostname to compare with 657 */ 658 if (options.check_host_ip && (local || 659 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 660 options.check_host_ip = 0; 661 662 /* 663 * Allow the user to record the key under a different name or 664 * differentiate a non-standard port. This is useful for ssh 665 * tunneling over forwarded connections or if you run multiple 666 * sshd's on different ports on the same machine. 667 */ 668 if (options.host_key_alias != NULL) { 669 host = xstrdup(options.host_key_alias); 670 debug("using hostkeyalias: %s", host); 671 } else { 672 host = put_host_port(hostname, port); 673 } 674 675 retry: 676 want_cert = key_is_cert(host_key); 677 type = key_type(host_key); 678 679 /* 680 * Store the host key from the known host file in here so that we can 681 * compare it with the key for the IP address. 682 */ 683 file_key = key_new(key_is_cert(host_key) ? KEY_UNSPEC : host_key->type); 684 685 /* 686 * Check if the host key is present in the user's list of known 687 * hosts or in the systemwide list. 688 */ 689 host_file = user_hostfile; 690 host_status = check_host_in_hostfile(host_file, host, host_key, 691 file_key, &host_line); 692 if (host_status == HOST_NEW) { 693 host_file = system_hostfile; 694 host_status = check_host_in_hostfile(host_file, host, host_key, 695 file_key, &host_line); 696 } 697 /* 698 * Also perform check for the ip address, skip the check if we are 699 * localhost, looking for a certificate, or the hostname was an ip 700 * address to begin with. 701 */ 702 if (!want_cert && options.check_host_ip) { 703 Key *ip_key = key_new(host_key->type); 704 705 ip_file = user_hostfile; 706 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 707 ip_key, &ip_line); 708 if (ip_status == HOST_NEW) { 709 ip_file = system_hostfile; 710 ip_status = check_host_in_hostfile(ip_file, ip, 711 host_key, ip_key, &ip_line); 712 } 713 if (host_status == HOST_CHANGED && 714 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 715 host_ip_differ = 1; 716 717 key_free(ip_key); 718 } else 719 ip_status = host_status; 720 721 key_free(file_key); 722 723 switch (host_status) { 724 case HOST_OK: 725 /* The host is known and the key matches. */ 726 debug("Host '%.200s' is known and matches the %s host %s.", 727 host, type, want_cert ? "certificate" : "key"); 728 debug("Found %s in %s:%d", 729 want_cert ? "CA key" : "key", host_file, host_line); 730 if (want_cert && !check_host_cert(hostname, host_key)) 731 goto fail; 732 if (options.check_host_ip && ip_status == HOST_NEW) { 733 if (readonly || want_cert) 734 logit("%s host key for IP address " 735 "'%.128s' not in list of known hosts.", 736 type, ip); 737 else if (!add_host_to_hostfile(user_hostfile, ip, 738 host_key, options.hash_known_hosts)) 739 logit("Failed to add the %s host key for IP " 740 "address '%.128s' to the list of known " 741 "hosts (%.30s).", type, ip, user_hostfile); 742 else 743 logit("Warning: Permanently added the %s host " 744 "key for IP address '%.128s' to the list " 745 "of known hosts.", type, ip); 746 } else if (options.visual_host_key) { 747 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 748 ra = key_fingerprint(host_key, SSH_FP_MD5, 749 SSH_FP_RANDOMART); 750 logit("Host key fingerprint is %s\n%s\n", fp, ra); 751 xfree(ra); 752 xfree(fp); 753 } 754 break; 755 case HOST_NEW: 756 if (options.host_key_alias == NULL && port != 0 && 757 port != SSH_DEFAULT_PORT) { 758 debug("checking without port identifier"); 759 if (check_host_key(hostname, hostaddr, 0, host_key, 760 ROQUIET, user_hostfile, system_hostfile) == 0) { 761 debug("found matching key w/out port"); 762 break; 763 } 764 } 765 if (readonly || want_cert) 766 goto fail; 767 /* The host is new. */ 768 if (options.strict_host_key_checking == 1) { 769 /* 770 * User has requested strict host key checking. We 771 * will not add the host key automatically. The only 772 * alternative left is to abort. 773 */ 774 error("No %s host key is known for %.200s and you " 775 "have requested strict checking.", type, host); 776 goto fail; 777 } else if (options.strict_host_key_checking == 2) { 778 char msg1[1024], msg2[1024]; 779 780 if (show_other_keys(host, host_key)) 781 snprintf(msg1, sizeof(msg1), 782 "\nbut keys of different type are already" 783 " known for this host."); 784 else 785 snprintf(msg1, sizeof(msg1), "."); 786 /* The default */ 787 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 788 ra = key_fingerprint(host_key, SSH_FP_MD5, 789 SSH_FP_RANDOMART); 790 msg2[0] = '\0'; 791 if (options.verify_host_key_dns) { 792 if (matching_host_key_dns) 793 snprintf(msg2, sizeof(msg2), 794 "Matching host key fingerprint" 795 " found in DNS.\n"); 796 else 797 snprintf(msg2, sizeof(msg2), 798 "No matching host key fingerprint" 799 " found in DNS.\n"); 800 } 801 snprintf(msg, sizeof(msg), 802 "The authenticity of host '%.200s (%s)' can't be " 803 "established%s\n" 804 "%s key fingerprint is %s.%s%s\n%s" 805 "Are you sure you want to continue connecting " 806 "(yes/no)? ", 807 host, ip, msg1, type, fp, 808 options.visual_host_key ? "\n" : "", 809 options.visual_host_key ? ra : "", 810 msg2); 811 xfree(ra); 812 xfree(fp); 813 if (!confirm(msg)) 814 goto fail; 815 } 816 /* 817 * If not in strict mode, add the key automatically to the 818 * local known_hosts file. 819 */ 820 if (options.check_host_ip && ip_status == HOST_NEW) { 821 snprintf(hostline, sizeof(hostline), "%s,%s", 822 host, ip); 823 hostp = hostline; 824 if (options.hash_known_hosts) { 825 /* Add hash of host and IP separately */ 826 r = add_host_to_hostfile(user_hostfile, host, 827 host_key, options.hash_known_hosts) && 828 add_host_to_hostfile(user_hostfile, ip, 829 host_key, options.hash_known_hosts); 830 } else { 831 /* Add unhashed "host,ip" */ 832 r = add_host_to_hostfile(user_hostfile, 833 hostline, host_key, 834 options.hash_known_hosts); 835 } 836 } else { 837 r = add_host_to_hostfile(user_hostfile, host, host_key, 838 options.hash_known_hosts); 839 hostp = host; 840 } 841 842 if (!r) 843 logit("Failed to add the host to the list of known " 844 "hosts (%.500s).", user_hostfile); 845 else 846 logit("Warning: Permanently added '%.200s' (%s) to the " 847 "list of known hosts.", hostp, type); 848 break; 849 case HOST_REVOKED: 850 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 851 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 852 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 853 error("The %s host key for %s is marked as revoked.", type, host); 854 error("This could mean that a stolen key is being used to"); 855 error("impersonate this host."); 856 857 /* 858 * If strict host key checking is in use, the user will have 859 * to edit the key manually and we can only abort. 860 */ 861 if (options.strict_host_key_checking) { 862 error("%s host key for %.200s was revoked and you have " 863 "requested strict checking.", type, host); 864 goto fail; 865 } 866 goto continue_unsafe; 867 868 case HOST_CHANGED: 869 if (want_cert) { 870 /* 871 * This is only a debug() since it is valid to have 872 * CAs with wildcard DNS matches that don't match 873 * all hosts that one might visit. 874 */ 875 debug("Host certificate authority does not " 876 "match %s in %s:%d", CA_MARKER, 877 host_file, host_line); 878 goto fail; 879 } 880 if (readonly == ROQUIET) 881 goto fail; 882 if (options.check_host_ip && host_ip_differ) { 883 char *key_msg; 884 if (ip_status == HOST_NEW) 885 key_msg = "is unknown"; 886 else if (ip_status == HOST_OK) 887 key_msg = "is unchanged"; 888 else 889 key_msg = "has a different value"; 890 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 891 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 892 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 893 error("The %s host key for %s has changed,", type, host); 894 error("and the key for the corresponding IP address %s", ip); 895 error("%s. This could either mean that", key_msg); 896 error("DNS SPOOFING is happening or the IP address for the host"); 897 error("and its host key have changed at the same time."); 898 if (ip_status != HOST_NEW) 899 error("Offending key for IP in %s:%d", ip_file, ip_line); 900 } 901 /* The host key has changed. */ 902 warn_changed_key(host_key); 903 error("Add correct host key in %.100s to get rid of this message.", 904 user_hostfile); 905 error("Offending key in %s:%d", host_file, host_line); 906 907 /* 908 * If strict host key checking is in use, the user will have 909 * to edit the key manually and we can only abort. 910 */ 911 if (options.strict_host_key_checking) { 912 error("%s host key for %.200s has changed and you have " 913 "requested strict checking.", type, host); 914 goto fail; 915 } 916 917 continue_unsafe: 918 /* 919 * If strict host key checking has not been requested, allow 920 * the connection but without MITM-able authentication or 921 * forwarding. 922 */ 923 if (options.password_authentication) { 924 error("Password authentication is disabled to avoid " 925 "man-in-the-middle attacks."); 926 options.password_authentication = 0; 927 cancelled_forwarding = 1; 928 } 929 if (options.kbd_interactive_authentication) { 930 error("Keyboard-interactive authentication is disabled" 931 " to avoid man-in-the-middle attacks."); 932 options.kbd_interactive_authentication = 0; 933 options.challenge_response_authentication = 0; 934 cancelled_forwarding = 1; 935 } 936 if (options.challenge_response_authentication) { 937 error("Challenge/response authentication is disabled" 938 " to avoid man-in-the-middle attacks."); 939 options.challenge_response_authentication = 0; 940 cancelled_forwarding = 1; 941 } 942 if (options.forward_agent) { 943 error("Agent forwarding is disabled to avoid " 944 "man-in-the-middle attacks."); 945 options.forward_agent = 0; 946 cancelled_forwarding = 1; 947 } 948 if (options.forward_x11) { 949 error("X11 forwarding is disabled to avoid " 950 "man-in-the-middle attacks."); 951 options.forward_x11 = 0; 952 cancelled_forwarding = 1; 953 } 954 if (options.num_local_forwards > 0 || 955 options.num_remote_forwards > 0) { 956 error("Port forwarding is disabled to avoid " 957 "man-in-the-middle attacks."); 958 options.num_local_forwards = 959 options.num_remote_forwards = 0; 960 cancelled_forwarding = 1; 961 } 962 if (options.tun_open != SSH_TUNMODE_NO) { 963 error("Tunnel forwarding is disabled to avoid " 964 "man-in-the-middle attacks."); 965 options.tun_open = SSH_TUNMODE_NO; 966 cancelled_forwarding = 1; 967 } 968 if (options.exit_on_forward_failure && cancelled_forwarding) 969 fatal("Error: forwarding disabled due to host key " 970 "check failure"); 971 972 /* 973 * XXX Should permit the user to change to use the new id. 974 * This could be done by converting the host key to an 975 * identifying sentence, tell that the host identifies itself 976 * by that sentence, and ask the user if he/she wishes to 977 * accept the authentication. 978 */ 979 break; 980 case HOST_FOUND: 981 fatal("internal error"); 982 break; 983 } 984 985 if (options.check_host_ip && host_status != HOST_CHANGED && 986 ip_status == HOST_CHANGED) { 987 snprintf(msg, sizeof(msg), 988 "Warning: the %s host key for '%.200s' " 989 "differs from the key for the IP address '%.128s'" 990 "\nOffending key for IP in %s:%d", 991 type, host, ip, ip_file, ip_line); 992 if (host_status == HOST_OK) { 993 len = strlen(msg); 994 snprintf(msg + len, sizeof(msg) - len, 995 "\nMatching host key in %s:%d", 996 host_file, host_line); 997 } 998 if (options.strict_host_key_checking == 1) { 999 logit("%s", msg); 1000 error("Exiting, you have requested strict checking."); 1001 goto fail; 1002 } else if (options.strict_host_key_checking == 2) { 1003 strlcat(msg, "\nAre you sure you want " 1004 "to continue connecting (yes/no)? ", sizeof(msg)); 1005 if (!confirm(msg)) 1006 goto fail; 1007 } else { 1008 logit("%s", msg); 1009 } 1010 } 1011 1012 xfree(ip); 1013 xfree(host); 1014 return 0; 1015 1016 fail: 1017 if (want_cert && host_status != HOST_REVOKED) { 1018 /* 1019 * No matching certificate. Downgrade cert to raw key and 1020 * search normally. 1021 */ 1022 debug("No matching CA found. Retry with plain key"); 1023 raw_key = key_from_private(host_key); 1024 if (key_drop_cert(raw_key) != 0) 1025 fatal("Couldn't drop certificate"); 1026 host_key = raw_key; 1027 goto retry; 1028 } 1029 if (raw_key != NULL) 1030 key_free(raw_key); 1031 xfree(ip); 1032 xfree(host); 1033 return -1; 1034 } 1035 1036 /* returns 0 if key verifies or -1 if key does NOT verify */ 1037 int 1038 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1039 { 1040 struct stat st; 1041 int flags = 0; 1042 1043 /* XXX certs are not yet supported for DNS */ 1044 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1045 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1046 1047 if (flags & DNS_VERIFY_FOUND) { 1048 1049 if (options.verify_host_key_dns == 1 && 1050 flags & DNS_VERIFY_MATCH && 1051 flags & DNS_VERIFY_SECURE) 1052 return 0; 1053 1054 if (flags & DNS_VERIFY_MATCH) { 1055 matching_host_key_dns = 1; 1056 } else { 1057 warn_changed_key(host_key); 1058 error("Update the SSHFP RR in DNS with the new " 1059 "host key to get rid of this message."); 1060 } 1061 } 1062 } 1063 1064 /* return ok if the key can be found in an old keyfile */ 1065 if (stat(options.system_hostfile2, &st) == 0 || 1066 stat(options.user_hostfile2, &st) == 0) { 1067 if (check_host_key(host, hostaddr, options.port, host_key, 1068 RDONLY, options.user_hostfile2, 1069 options.system_hostfile2) == 0) 1070 return 0; 1071 } 1072 return check_host_key(host, hostaddr, options.port, host_key, 1073 RDRW, options.user_hostfile, options.system_hostfile); 1074 } 1075 1076 /* 1077 * Starts a dialog with the server, and authenticates the current user on the 1078 * server. This does not need any extra privileges. The basic connection 1079 * to the server must already have been established before this is called. 1080 * If login fails, this function prints an error and never returns. 1081 * This function does not require super-user privileges. 1082 */ 1083 void 1084 ssh_login(Sensitive *sensitive, const char *orighost, 1085 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 1086 { 1087 char *host, *cp; 1088 char *server_user, *local_user; 1089 1090 local_user = xstrdup(pw->pw_name); 1091 server_user = options.user ? options.user : local_user; 1092 1093 /* Convert the user-supplied hostname into all lowercase. */ 1094 host = xstrdup(orighost); 1095 for (cp = host; *cp; cp++) 1096 if (isupper(*cp)) 1097 *cp = (char)tolower(*cp); 1098 1099 /* Exchange protocol version identification strings with the server. */ 1100 ssh_exchange_identification(timeout_ms); 1101 1102 /* Put the connection into non-blocking mode. */ 1103 packet_set_nonblocking(); 1104 1105 /* key exchange */ 1106 /* authenticate user */ 1107 if (compat20) { 1108 ssh_kex2(host, hostaddr); 1109 ssh_userauth2(local_user, server_user, host, sensitive); 1110 } else { 1111 ssh_kex(host, hostaddr); 1112 ssh_userauth1(local_user, server_user, host, sensitive); 1113 } 1114 xfree(local_user); 1115 } 1116 1117 void 1118 ssh_put_password(char *password) 1119 { 1120 int size; 1121 char *padded; 1122 1123 if (datafellows & SSH_BUG_PASSWORDPAD) { 1124 packet_put_cstring(password); 1125 return; 1126 } 1127 size = roundup(strlen(password) + 1, 32); 1128 padded = xcalloc(1, size); 1129 strlcpy(padded, password, size); 1130 packet_put_string(padded, size); 1131 memset(padded, 0, size); 1132 xfree(padded); 1133 } 1134 1135 static int 1136 show_key_from_file(const char *file, const char *host, int keytype) 1137 { 1138 Key *found; 1139 char *fp, *ra; 1140 int line, ret; 1141 1142 found = key_new(keytype); 1143 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1144 keytype, found, &line))) { 1145 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1146 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); 1147 logit("WARNING: %s key found for host %s\n" 1148 "in %s:%d\n" 1149 "%s key fingerprint %s.\n%s\n", 1150 key_type(found), host, file, line, 1151 key_type(found), fp, ra); 1152 xfree(ra); 1153 xfree(fp); 1154 } 1155 key_free(found); 1156 return (ret); 1157 } 1158 1159 /* print all known host keys for a given host, but skip keys of given type */ 1160 static int 1161 show_other_keys(const char *host, Key *key) 1162 { 1163 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1164 int i, found = 0; 1165 1166 for (i = 0; type[i] != -1; i++) { 1167 if (type[i] == key->type) 1168 continue; 1169 if (type[i] != KEY_RSA1 && 1170 show_key_from_file(options.user_hostfile2, host, type[i])) { 1171 found = 1; 1172 continue; 1173 } 1174 if (type[i] != KEY_RSA1 && 1175 show_key_from_file(options.system_hostfile2, host, type[i])) { 1176 found = 1; 1177 continue; 1178 } 1179 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1180 found = 1; 1181 continue; 1182 } 1183 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1184 found = 1; 1185 continue; 1186 } 1187 debug2("no key of type %d for host %s", type[i], host); 1188 } 1189 return (found); 1190 } 1191 1192 static void 1193 warn_changed_key(Key *host_key) 1194 { 1195 char *fp; 1196 const char *type = key_type(host_key); 1197 1198 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1199 1200 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1201 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1202 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1203 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1204 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1205 error("It is also possible that the %s host key has just been changed.", type); 1206 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1207 type, fp); 1208 error("Please contact your system administrator."); 1209 1210 xfree(fp); 1211 } 1212 1213 /* 1214 * Execute a local command 1215 */ 1216 int 1217 ssh_local_cmd(const char *args) 1218 { 1219 char *shell; 1220 pid_t pid; 1221 int status; 1222 1223 if (!options.permit_local_command || 1224 args == NULL || !*args) 1225 return (1); 1226 1227 if ((shell = getenv("SHELL")) == NULL) 1228 shell = _PATH_BSHELL; 1229 1230 pid = fork(); 1231 if (pid == 0) { 1232 debug3("Executing %s -c \"%s\"", shell, args); 1233 execl(shell, shell, "-c", args, (char *)NULL); 1234 error("Couldn't execute %s -c \"%s\": %s", 1235 shell, args, strerror(errno)); 1236 _exit(1); 1237 } else if (pid == -1) 1238 fatal("fork failed: %.100s", strerror(errno)); 1239 while (waitpid(pid, &status, 0) == -1) 1240 if (errno != EINTR) 1241 fatal("Couldn't wait for child: %s", strerror(errno)); 1242 1243 if (!WIFEXITED(status)) 1244 return (1); 1245 1246 return (WEXITSTATUS(status)); 1247 } 1248