1 /* $OpenBSD: sshconnect.c,v 1.235 2012/08/17 01:30:00 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 static pid_t proxy_command_pid = 0; 61 62 /* import */ 63 extern Options options; 64 extern char *__progname; 65 extern uid_t original_real_uid; 66 extern uid_t original_effective_uid; 67 68 static int show_other_keys(struct hostkeys *, Key *); 69 static void warn_changed_key(Key *); 70 71 /* 72 * Connect to the given ssh server using a proxy command. 73 */ 74 static int 75 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 76 { 77 char *command_string, *tmp; 78 int pin[2], pout[2]; 79 pid_t pid; 80 char *shell, strport[NI_MAXSERV]; 81 82 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 83 shell = _PATH_BSHELL; 84 85 /* Convert the port number into a string. */ 86 snprintf(strport, sizeof strport, "%hu", port); 87 88 /* 89 * Build the final command string in the buffer by making the 90 * appropriate substitutions to the given proxy command. 91 * 92 * Use "exec" to avoid "sh -c" processes on some platforms 93 * (e.g. Solaris) 94 */ 95 xasprintf(&tmp, "exec %s", proxy_command); 96 command_string = percent_expand(tmp, "h", host, "p", strport, 97 "r", options.user, (char *)NULL); 98 xfree(tmp); 99 100 /* Create pipes for communicating with the proxy. */ 101 if (pipe(pin) < 0 || pipe(pout) < 0) 102 fatal("Could not create pipes to communicate with the proxy: %.100s", 103 strerror(errno)); 104 105 debug("Executing proxy command: %.500s", command_string); 106 107 /* Fork and execute the proxy command. */ 108 if ((pid = fork()) == 0) { 109 char *argv[10]; 110 111 /* Child. Permanently give up superuser privileges. */ 112 permanently_drop_suid(original_real_uid); 113 114 /* Redirect stdin and stdout. */ 115 close(pin[1]); 116 if (pin[0] != 0) { 117 if (dup2(pin[0], 0) < 0) 118 perror("dup2 stdin"); 119 close(pin[0]); 120 } 121 close(pout[0]); 122 if (dup2(pout[1], 1) < 0) 123 perror("dup2 stdout"); 124 /* Cannot be 1 because pin allocated two descriptors. */ 125 close(pout[1]); 126 127 /* Stderr is left as it is so that error messages get 128 printed on the user's terminal. */ 129 argv[0] = shell; 130 argv[1] = "-c"; 131 argv[2] = command_string; 132 argv[3] = NULL; 133 134 /* Execute the proxy command. Note that we gave up any 135 extra privileges above. */ 136 signal(SIGPIPE, SIG_DFL); 137 execv(argv[0], argv); 138 perror(argv[0]); 139 exit(1); 140 } 141 /* Parent. */ 142 if (pid < 0) 143 fatal("fork failed: %.100s", strerror(errno)); 144 else 145 proxy_command_pid = pid; /* save pid to clean up later */ 146 147 /* Close child side of the descriptors. */ 148 close(pin[0]); 149 close(pout[1]); 150 151 /* Free the command name. */ 152 xfree(command_string); 153 154 /* Set the connection file descriptors. */ 155 packet_set_connection(pout[0], pin[1]); 156 packet_set_timeout(options.server_alive_interval, 157 options.server_alive_count_max); 158 159 /* Indicate OK return */ 160 return 0; 161 } 162 163 void 164 ssh_kill_proxy_command(void) 165 { 166 /* 167 * Send SIGHUP to proxy command if used. We don't wait() in 168 * case it hangs and instead rely on init to reap the child 169 */ 170 if (proxy_command_pid > 1) 171 kill(proxy_command_pid, SIGHUP); 172 } 173 174 /* 175 * Creates a (possibly privileged) socket for use as the ssh connection. 176 */ 177 static int 178 ssh_create_socket(int privileged, struct addrinfo *ai) 179 { 180 int sock, gaierr; 181 struct addrinfo hints, *res; 182 183 /* 184 * If we are running as root and want to connect to a privileged 185 * port, bind our own socket to a privileged port. 186 */ 187 if (privileged) { 188 int p = IPPORT_RESERVED - 1; 189 PRIV_START; 190 sock = rresvport_af(&p, ai->ai_family); 191 PRIV_END; 192 if (sock < 0) 193 error("rresvport: af=%d %.100s", ai->ai_family, 194 strerror(errno)); 195 else 196 debug("Allocated local port %d.", p); 197 return sock; 198 } 199 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 200 if (sock < 0) { 201 error("socket: %.100s", strerror(errno)); 202 return -1; 203 } 204 fcntl(sock, F_SETFD, FD_CLOEXEC); 205 206 /* Bind the socket to an alternative local IP address */ 207 if (options.bind_address == NULL) 208 return sock; 209 210 memset(&hints, 0, sizeof(hints)); 211 hints.ai_family = ai->ai_family; 212 hints.ai_socktype = ai->ai_socktype; 213 hints.ai_protocol = ai->ai_protocol; 214 hints.ai_flags = AI_PASSIVE; 215 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 216 if (gaierr) { 217 error("getaddrinfo: %s: %s", options.bind_address, 218 ssh_gai_strerror(gaierr)); 219 close(sock); 220 return -1; 221 } 222 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 223 error("bind: %s: %s", options.bind_address, strerror(errno)); 224 close(sock); 225 freeaddrinfo(res); 226 return -1; 227 } 228 freeaddrinfo(res); 229 return sock; 230 } 231 232 static int 233 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 234 socklen_t addrlen, int *timeoutp) 235 { 236 fd_set *fdset; 237 struct timeval tv, t_start; 238 socklen_t optlen; 239 int optval, rc, result = -1; 240 241 gettimeofday(&t_start, NULL); 242 243 if (*timeoutp <= 0) { 244 result = connect(sockfd, serv_addr, addrlen); 245 goto done; 246 } 247 248 set_nonblock(sockfd); 249 rc = connect(sockfd, serv_addr, addrlen); 250 if (rc == 0) { 251 unset_nonblock(sockfd); 252 result = 0; 253 goto done; 254 } 255 if (errno != EINPROGRESS) { 256 result = -1; 257 goto done; 258 } 259 260 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 261 sizeof(fd_mask)); 262 FD_SET(sockfd, fdset); 263 ms_to_timeval(&tv, *timeoutp); 264 265 for (;;) { 266 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 267 if (rc != -1 || errno != EINTR) 268 break; 269 } 270 271 switch (rc) { 272 case 0: 273 /* Timed out */ 274 errno = ETIMEDOUT; 275 break; 276 case -1: 277 /* Select error */ 278 debug("select: %s", strerror(errno)); 279 break; 280 case 1: 281 /* Completed or failed */ 282 optval = 0; 283 optlen = sizeof(optval); 284 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 285 &optlen) == -1) { 286 debug("getsockopt: %s", strerror(errno)); 287 break; 288 } 289 if (optval != 0) { 290 errno = optval; 291 break; 292 } 293 result = 0; 294 unset_nonblock(sockfd); 295 break; 296 default: 297 /* Should not occur */ 298 fatal("Bogus return (%d) from select()", rc); 299 } 300 301 xfree(fdset); 302 303 done: 304 if (result == 0 && *timeoutp > 0) { 305 ms_subtract_diff(&t_start, timeoutp); 306 if (*timeoutp <= 0) { 307 errno = ETIMEDOUT; 308 result = -1; 309 } 310 } 311 312 return (result); 313 } 314 315 /* 316 * Opens a TCP/IP connection to the remote server on the given host. 317 * The address of the remote host will be returned in hostaddr. 318 * If port is 0, the default port will be used. If needpriv is true, 319 * a privileged port will be allocated to make the connection. 320 * This requires super-user privileges if needpriv is true. 321 * Connection_attempts specifies the maximum number of tries (one per 322 * second). If proxy_command is non-NULL, it specifies the command (with %h 323 * and %p substituted for host and port, respectively) to use to contact 324 * the daemon. 325 */ 326 int 327 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 328 u_short port, int family, int connection_attempts, int *timeout_ms, 329 int want_keepalive, int needpriv, const char *proxy_command) 330 { 331 int gaierr; 332 int on = 1; 333 int sock = -1, attempt; 334 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 335 struct addrinfo hints, *ai, *aitop; 336 337 debug2("ssh_connect: needpriv %d", needpriv); 338 339 /* If a proxy command is given, connect using it. */ 340 if (proxy_command != NULL) 341 return ssh_proxy_connect(host, port, proxy_command); 342 343 /* No proxy command. */ 344 345 memset(&hints, 0, sizeof(hints)); 346 hints.ai_family = family; 347 hints.ai_socktype = SOCK_STREAM; 348 snprintf(strport, sizeof strport, "%u", port); 349 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 350 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 351 host, ssh_gai_strerror(gaierr)); 352 353 for (attempt = 0; attempt < connection_attempts; attempt++) { 354 if (attempt > 0) { 355 /* Sleep a moment before retrying. */ 356 sleep(1); 357 debug("Trying again..."); 358 } 359 /* 360 * Loop through addresses for this host, and try each one in 361 * sequence until the connection succeeds. 362 */ 363 for (ai = aitop; ai; ai = ai->ai_next) { 364 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 365 continue; 366 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 367 ntop, sizeof(ntop), strport, sizeof(strport), 368 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 369 error("ssh_connect: getnameinfo failed"); 370 continue; 371 } 372 debug("Connecting to %.200s [%.100s] port %s.", 373 host, ntop, strport); 374 375 /* Create a socket for connecting. */ 376 sock = ssh_create_socket(needpriv, ai); 377 if (sock < 0) 378 /* Any error is already output */ 379 continue; 380 381 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 382 timeout_ms) >= 0) { 383 /* Successful connection. */ 384 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 385 break; 386 } else { 387 debug("connect to address %s port %s: %s", 388 ntop, strport, strerror(errno)); 389 close(sock); 390 sock = -1; 391 } 392 } 393 if (sock != -1) 394 break; /* Successful connection. */ 395 } 396 397 freeaddrinfo(aitop); 398 399 /* Return failure if we didn't get a successful connection. */ 400 if (sock == -1) { 401 error("ssh: connect to host %s port %s: %s", 402 host, strport, strerror(errno)); 403 return (-1); 404 } 405 406 debug("Connection established."); 407 408 /* Set SO_KEEPALIVE if requested. */ 409 if (want_keepalive && 410 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 411 sizeof(on)) < 0) 412 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 413 414 /* Set the connection. */ 415 packet_set_connection(sock, sock); 416 packet_set_timeout(options.server_alive_interval, 417 options.server_alive_count_max); 418 419 return 0; 420 } 421 422 static void 423 send_client_banner(int connection_out, int minor1) 424 { 425 char buf[256]; 426 427 /* Send our own protocol version identification. */ 428 if (compat20) { 429 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n", 430 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION); 431 } else { 432 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n", 433 PROTOCOL_MAJOR_1, minor1, SSH_VERSION); 434 } 435 if (roaming_atomicio(vwrite, connection_out, client_version_string, 436 strlen(client_version_string)) != strlen(client_version_string)) 437 fatal("write: %.100s", strerror(errno)); 438 chop(client_version_string); 439 debug("Local version string %.100s", client_version_string); 440 } 441 442 /* 443 * Waits for the server identification string, and sends our own 444 * identification string. 445 */ 446 void 447 ssh_exchange_identification(int timeout_ms) 448 { 449 char buf[256], remote_version[256]; /* must be same size! */ 450 int remote_major, remote_minor, mismatch; 451 int connection_in = packet_get_connection_in(); 452 int connection_out = packet_get_connection_out(); 453 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0; 454 u_int i, n; 455 size_t len; 456 int fdsetsz, remaining, rc; 457 struct timeval t_start, t_remaining; 458 fd_set *fdset; 459 460 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 461 fdset = xcalloc(1, fdsetsz); 462 463 /* 464 * If we are SSH2-only then we can send the banner immediately and 465 * save a round-trip. 466 */ 467 if (options.protocol == SSH_PROTO_2) { 468 enable_compat20(); 469 send_client_banner(connection_out, 0); 470 client_banner_sent = 1; 471 } 472 473 /* Read other side's version identification. */ 474 remaining = timeout_ms; 475 for (n = 0;;) { 476 for (i = 0; i < sizeof(buf) - 1; i++) { 477 if (timeout_ms > 0) { 478 gettimeofday(&t_start, NULL); 479 ms_to_timeval(&t_remaining, remaining); 480 FD_SET(connection_in, fdset); 481 rc = select(connection_in + 1, fdset, NULL, 482 fdset, &t_remaining); 483 ms_subtract_diff(&t_start, &remaining); 484 if (rc == 0 || remaining <= 0) 485 fatal("Connection timed out during " 486 "banner exchange"); 487 if (rc == -1) { 488 if (errno == EINTR) 489 continue; 490 fatal("ssh_exchange_identification: " 491 "select: %s", strerror(errno)); 492 } 493 } 494 495 len = roaming_atomicio(read, connection_in, &buf[i], 1); 496 497 if (len != 1 && errno == EPIPE) 498 fatal("ssh_exchange_identification: " 499 "Connection closed by remote host"); 500 else if (len != 1) 501 fatal("ssh_exchange_identification: " 502 "read: %.100s", strerror(errno)); 503 if (buf[i] == '\r') { 504 buf[i] = '\n'; 505 buf[i + 1] = 0; 506 continue; /**XXX wait for \n */ 507 } 508 if (buf[i] == '\n') { 509 buf[i + 1] = 0; 510 break; 511 } 512 if (++n > 65536) 513 fatal("ssh_exchange_identification: " 514 "No banner received"); 515 } 516 buf[sizeof(buf) - 1] = 0; 517 if (strncmp(buf, "SSH-", 4) == 0) 518 break; 519 debug("ssh_exchange_identification: %s", buf); 520 } 521 server_version_string = xstrdup(buf); 522 xfree(fdset); 523 524 /* 525 * Check that the versions match. In future this might accept 526 * several versions and set appropriate flags to handle them. 527 */ 528 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 529 &remote_major, &remote_minor, remote_version) != 3) 530 fatal("Bad remote protocol version identification: '%.100s'", buf); 531 debug("Remote protocol version %d.%d, remote software version %.100s", 532 remote_major, remote_minor, remote_version); 533 534 compat_datafellows(remote_version); 535 mismatch = 0; 536 537 switch (remote_major) { 538 case 1: 539 if (remote_minor == 99 && 540 (options.protocol & SSH_PROTO_2) && 541 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 542 enable_compat20(); 543 break; 544 } 545 if (!(options.protocol & SSH_PROTO_1)) { 546 mismatch = 1; 547 break; 548 } 549 if (remote_minor < 3) { 550 fatal("Remote machine has too old SSH software version."); 551 } else if (remote_minor == 3 || remote_minor == 4) { 552 /* We speak 1.3, too. */ 553 enable_compat13(); 554 minor1 = 3; 555 if (options.forward_agent) { 556 logit("Agent forwarding disabled for protocol 1.3"); 557 options.forward_agent = 0; 558 } 559 } 560 break; 561 case 2: 562 if (options.protocol & SSH_PROTO_2) { 563 enable_compat20(); 564 break; 565 } 566 /* FALLTHROUGH */ 567 default: 568 mismatch = 1; 569 break; 570 } 571 if (mismatch) 572 fatal("Protocol major versions differ: %d vs. %d", 573 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 574 remote_major); 575 if (!client_banner_sent) 576 send_client_banner(connection_out, minor1); 577 chop(server_version_string); 578 } 579 580 /* defaults to 'no' */ 581 static int 582 confirm(const char *prompt) 583 { 584 const char *msg, *again = "Please type 'yes' or 'no': "; 585 char *p; 586 int ret = -1; 587 588 if (options.batch_mode) 589 return 0; 590 for (msg = prompt;;msg = again) { 591 p = read_passphrase(msg, RP_ECHO); 592 if (p == NULL || 593 (p[0] == '\0') || (p[0] == '\n') || 594 strncasecmp(p, "no", 2) == 0) 595 ret = 0; 596 if (p && strncasecmp(p, "yes", 3) == 0) 597 ret = 1; 598 if (p) 599 xfree(p); 600 if (ret != -1) 601 return ret; 602 } 603 } 604 605 static int 606 check_host_cert(const char *host, const Key *host_key) 607 { 608 const char *reason; 609 610 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 611 error("%s", reason); 612 return 0; 613 } 614 if (buffer_len(&host_key->cert->critical) != 0) { 615 error("Certificate for %s contains unsupported " 616 "critical options(s)", host); 617 return 0; 618 } 619 return 1; 620 } 621 622 static int 623 sockaddr_is_local(struct sockaddr *hostaddr) 624 { 625 switch (hostaddr->sa_family) { 626 case AF_INET: 627 return (ntohl(((struct sockaddr_in *)hostaddr)-> 628 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 629 case AF_INET6: 630 return IN6_IS_ADDR_LOOPBACK( 631 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 632 default: 633 return 0; 634 } 635 } 636 637 /* 638 * Prepare the hostname and ip address strings that are used to lookup 639 * host keys in known_hosts files. These may have a port number appended. 640 */ 641 void 642 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 643 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 644 { 645 char ntop[NI_MAXHOST]; 646 647 /* 648 * We don't have the remote ip-address for connections 649 * using a proxy command 650 */ 651 if (hostfile_ipaddr != NULL) { 652 if (options.proxy_command == NULL) { 653 if (getnameinfo(hostaddr, hostaddr->sa_len, 654 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 655 fatal("check_host_key: getnameinfo failed"); 656 *hostfile_ipaddr = put_host_port(ntop, port); 657 } else { 658 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 659 "command>"); 660 } 661 } 662 663 /* 664 * Allow the user to record the key under a different name or 665 * differentiate a non-standard port. This is useful for ssh 666 * tunneling over forwarded connections or if you run multiple 667 * sshd's on different ports on the same machine. 668 */ 669 if (hostfile_hostname != NULL) { 670 if (options.host_key_alias != NULL) { 671 *hostfile_hostname = xstrdup(options.host_key_alias); 672 debug("using hostkeyalias: %s", *hostfile_hostname); 673 } else { 674 *hostfile_hostname = put_host_port(hostname, port); 675 } 676 } 677 } 678 679 /* 680 * check whether the supplied host key is valid, return -1 if the key 681 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 682 */ 683 #define RDRW 0 684 #define RDONLY 1 685 #define ROQUIET 2 686 static int 687 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 688 Key *host_key, int readonly, 689 char **user_hostfiles, u_int num_user_hostfiles, 690 char **system_hostfiles, u_int num_system_hostfiles) 691 { 692 HostStatus host_status; 693 HostStatus ip_status; 694 Key *raw_key = NULL; 695 char *ip = NULL, *host = NULL; 696 char hostline[1000], *hostp, *fp, *ra; 697 char msg[1024]; 698 const char *type; 699 const struct hostkey_entry *host_found, *ip_found; 700 int len, cancelled_forwarding = 0; 701 int local = sockaddr_is_local(hostaddr); 702 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 703 struct hostkeys *host_hostkeys, *ip_hostkeys; 704 u_int i; 705 706 /* 707 * Force accepting of the host key for loopback/localhost. The 708 * problem is that if the home directory is NFS-mounted to multiple 709 * machines, localhost will refer to a different machine in each of 710 * them, and the user will get bogus HOST_CHANGED warnings. This 711 * essentially disables host authentication for localhost; however, 712 * this is probably not a real problem. 713 */ 714 if (options.no_host_authentication_for_localhost == 1 && local && 715 options.host_key_alias == NULL) { 716 debug("Forcing accepting of host key for " 717 "loopback/localhost."); 718 return 0; 719 } 720 721 /* 722 * Prepare the hostname and address strings used for hostkey lookup. 723 * In some cases, these will have a port number appended. 724 */ 725 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 726 727 /* 728 * Turn off check_host_ip if the connection is to localhost, via proxy 729 * command or if we don't have a hostname to compare with 730 */ 731 if (options.check_host_ip && (local || 732 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 733 options.check_host_ip = 0; 734 735 host_hostkeys = init_hostkeys(); 736 for (i = 0; i < num_user_hostfiles; i++) 737 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 738 for (i = 0; i < num_system_hostfiles; i++) 739 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 740 741 ip_hostkeys = NULL; 742 if (!want_cert && options.check_host_ip) { 743 ip_hostkeys = init_hostkeys(); 744 for (i = 0; i < num_user_hostfiles; i++) 745 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 746 for (i = 0; i < num_system_hostfiles; i++) 747 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 748 } 749 750 retry: 751 /* Reload these as they may have changed on cert->key downgrade */ 752 want_cert = key_is_cert(host_key); 753 type = key_type(host_key); 754 755 /* 756 * Check if the host key is present in the user's list of known 757 * hosts or in the systemwide list. 758 */ 759 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 760 &host_found); 761 762 /* 763 * Also perform check for the ip address, skip the check if we are 764 * localhost, looking for a certificate, or the hostname was an ip 765 * address to begin with. 766 */ 767 if (!want_cert && ip_hostkeys != NULL) { 768 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 769 &ip_found); 770 if (host_status == HOST_CHANGED && 771 (ip_status != HOST_CHANGED || 772 (ip_found != NULL && 773 !key_equal(ip_found->key, host_found->key)))) 774 host_ip_differ = 1; 775 } else 776 ip_status = host_status; 777 778 switch (host_status) { 779 case HOST_OK: 780 /* The host is known and the key matches. */ 781 debug("Host '%.200s' is known and matches the %s host %s.", 782 host, type, want_cert ? "certificate" : "key"); 783 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 784 host_found->file, host_found->line); 785 if (want_cert && !check_host_cert(hostname, host_key)) 786 goto fail; 787 if (options.check_host_ip && ip_status == HOST_NEW) { 788 if (readonly || want_cert) 789 logit("%s host key for IP address " 790 "'%.128s' not in list of known hosts.", 791 type, ip); 792 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 793 host_key, options.hash_known_hosts)) 794 logit("Failed to add the %s host key for IP " 795 "address '%.128s' to the list of known " 796 "hosts (%.30s).", type, ip, 797 user_hostfiles[0]); 798 else 799 logit("Warning: Permanently added the %s host " 800 "key for IP address '%.128s' to the list " 801 "of known hosts.", type, ip); 802 } else if (options.visual_host_key) { 803 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 804 ra = key_fingerprint(host_key, SSH_FP_MD5, 805 SSH_FP_RANDOMART); 806 logit("Host key fingerprint is %s\n%s\n", fp, ra); 807 xfree(ra); 808 xfree(fp); 809 } 810 break; 811 case HOST_NEW: 812 if (options.host_key_alias == NULL && port != 0 && 813 port != SSH_DEFAULT_PORT) { 814 debug("checking without port identifier"); 815 if (check_host_key(hostname, hostaddr, 0, host_key, 816 ROQUIET, user_hostfiles, num_user_hostfiles, 817 system_hostfiles, num_system_hostfiles) == 0) { 818 debug("found matching key w/out port"); 819 break; 820 } 821 } 822 if (readonly || want_cert) 823 goto fail; 824 /* The host is new. */ 825 if (options.strict_host_key_checking == 1) { 826 /* 827 * User has requested strict host key checking. We 828 * will not add the host key automatically. The only 829 * alternative left is to abort. 830 */ 831 error("No %s host key is known for %.200s and you " 832 "have requested strict checking.", type, host); 833 goto fail; 834 } else if (options.strict_host_key_checking == 2) { 835 char msg1[1024], msg2[1024]; 836 837 if (show_other_keys(host_hostkeys, host_key)) 838 snprintf(msg1, sizeof(msg1), 839 "\nbut keys of different type are already" 840 " known for this host."); 841 else 842 snprintf(msg1, sizeof(msg1), "."); 843 /* The default */ 844 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 845 ra = key_fingerprint(host_key, SSH_FP_MD5, 846 SSH_FP_RANDOMART); 847 msg2[0] = '\0'; 848 if (options.verify_host_key_dns) { 849 if (matching_host_key_dns) 850 snprintf(msg2, sizeof(msg2), 851 "Matching host key fingerprint" 852 " found in DNS.\n"); 853 else 854 snprintf(msg2, sizeof(msg2), 855 "No matching host key fingerprint" 856 " found in DNS.\n"); 857 } 858 snprintf(msg, sizeof(msg), 859 "The authenticity of host '%.200s (%s)' can't be " 860 "established%s\n" 861 "%s key fingerprint is %s.%s%s\n%s" 862 "Are you sure you want to continue connecting " 863 "(yes/no)? ", 864 host, ip, msg1, type, fp, 865 options.visual_host_key ? "\n" : "", 866 options.visual_host_key ? ra : "", 867 msg2); 868 xfree(ra); 869 xfree(fp); 870 if (!confirm(msg)) 871 goto fail; 872 } 873 /* 874 * If not in strict mode, add the key automatically to the 875 * local known_hosts file. 876 */ 877 if (options.check_host_ip && ip_status == HOST_NEW) { 878 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 879 hostp = hostline; 880 if (options.hash_known_hosts) { 881 /* Add hash of host and IP separately */ 882 r = add_host_to_hostfile(user_hostfiles[0], 883 host, host_key, options.hash_known_hosts) && 884 add_host_to_hostfile(user_hostfiles[0], ip, 885 host_key, options.hash_known_hosts); 886 } else { 887 /* Add unhashed "host,ip" */ 888 r = add_host_to_hostfile(user_hostfiles[0], 889 hostline, host_key, 890 options.hash_known_hosts); 891 } 892 } else { 893 r = add_host_to_hostfile(user_hostfiles[0], host, 894 host_key, options.hash_known_hosts); 895 hostp = host; 896 } 897 898 if (!r) 899 logit("Failed to add the host to the list of known " 900 "hosts (%.500s).", user_hostfiles[0]); 901 else 902 logit("Warning: Permanently added '%.200s' (%s) to the " 903 "list of known hosts.", hostp, type); 904 break; 905 case HOST_REVOKED: 906 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 907 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 908 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 909 error("The %s host key for %s is marked as revoked.", type, host); 910 error("This could mean that a stolen key is being used to"); 911 error("impersonate this host."); 912 913 /* 914 * If strict host key checking is in use, the user will have 915 * to edit the key manually and we can only abort. 916 */ 917 if (options.strict_host_key_checking) { 918 error("%s host key for %.200s was revoked and you have " 919 "requested strict checking.", type, host); 920 goto fail; 921 } 922 goto continue_unsafe; 923 924 case HOST_CHANGED: 925 if (want_cert) { 926 /* 927 * This is only a debug() since it is valid to have 928 * CAs with wildcard DNS matches that don't match 929 * all hosts that one might visit. 930 */ 931 debug("Host certificate authority does not " 932 "match %s in %s:%lu", CA_MARKER, 933 host_found->file, host_found->line); 934 goto fail; 935 } 936 if (readonly == ROQUIET) 937 goto fail; 938 if (options.check_host_ip && host_ip_differ) { 939 char *key_msg; 940 if (ip_status == HOST_NEW) 941 key_msg = "is unknown"; 942 else if (ip_status == HOST_OK) 943 key_msg = "is unchanged"; 944 else 945 key_msg = "has a different value"; 946 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 947 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 948 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 949 error("The %s host key for %s has changed,", type, host); 950 error("and the key for the corresponding IP address %s", ip); 951 error("%s. This could either mean that", key_msg); 952 error("DNS SPOOFING is happening or the IP address for the host"); 953 error("and its host key have changed at the same time."); 954 if (ip_status != HOST_NEW) 955 error("Offending key for IP in %s:%lu", 956 ip_found->file, ip_found->line); 957 } 958 /* The host key has changed. */ 959 warn_changed_key(host_key); 960 error("Add correct host key in %.100s to get rid of this message.", 961 user_hostfiles[0]); 962 error("Offending %s key in %s:%lu", key_type(host_found->key), 963 host_found->file, host_found->line); 964 965 /* 966 * If strict host key checking is in use, the user will have 967 * to edit the key manually and we can only abort. 968 */ 969 if (options.strict_host_key_checking) { 970 error("%s host key for %.200s has changed and you have " 971 "requested strict checking.", type, host); 972 goto fail; 973 } 974 975 continue_unsafe: 976 /* 977 * If strict host key checking has not been requested, allow 978 * the connection but without MITM-able authentication or 979 * forwarding. 980 */ 981 if (options.password_authentication) { 982 error("Password authentication is disabled to avoid " 983 "man-in-the-middle attacks."); 984 options.password_authentication = 0; 985 cancelled_forwarding = 1; 986 } 987 if (options.kbd_interactive_authentication) { 988 error("Keyboard-interactive authentication is disabled" 989 " to avoid man-in-the-middle attacks."); 990 options.kbd_interactive_authentication = 0; 991 options.challenge_response_authentication = 0; 992 cancelled_forwarding = 1; 993 } 994 if (options.challenge_response_authentication) { 995 error("Challenge/response authentication is disabled" 996 " to avoid man-in-the-middle attacks."); 997 options.challenge_response_authentication = 0; 998 cancelled_forwarding = 1; 999 } 1000 if (options.forward_agent) { 1001 error("Agent forwarding is disabled to avoid " 1002 "man-in-the-middle attacks."); 1003 options.forward_agent = 0; 1004 cancelled_forwarding = 1; 1005 } 1006 if (options.forward_x11) { 1007 error("X11 forwarding is disabled to avoid " 1008 "man-in-the-middle attacks."); 1009 options.forward_x11 = 0; 1010 cancelled_forwarding = 1; 1011 } 1012 if (options.num_local_forwards > 0 || 1013 options.num_remote_forwards > 0) { 1014 error("Port forwarding is disabled to avoid " 1015 "man-in-the-middle attacks."); 1016 options.num_local_forwards = 1017 options.num_remote_forwards = 0; 1018 cancelled_forwarding = 1; 1019 } 1020 if (options.tun_open != SSH_TUNMODE_NO) { 1021 error("Tunnel forwarding is disabled to avoid " 1022 "man-in-the-middle attacks."); 1023 options.tun_open = SSH_TUNMODE_NO; 1024 cancelled_forwarding = 1; 1025 } 1026 if (options.exit_on_forward_failure && cancelled_forwarding) 1027 fatal("Error: forwarding disabled due to host key " 1028 "check failure"); 1029 1030 /* 1031 * XXX Should permit the user to change to use the new id. 1032 * This could be done by converting the host key to an 1033 * identifying sentence, tell that the host identifies itself 1034 * by that sentence, and ask the user if he/she wishes to 1035 * accept the authentication. 1036 */ 1037 break; 1038 case HOST_FOUND: 1039 fatal("internal error"); 1040 break; 1041 } 1042 1043 if (options.check_host_ip && host_status != HOST_CHANGED && 1044 ip_status == HOST_CHANGED) { 1045 snprintf(msg, sizeof(msg), 1046 "Warning: the %s host key for '%.200s' " 1047 "differs from the key for the IP address '%.128s'" 1048 "\nOffending key for IP in %s:%lu", 1049 type, host, ip, ip_found->file, ip_found->line); 1050 if (host_status == HOST_OK) { 1051 len = strlen(msg); 1052 snprintf(msg + len, sizeof(msg) - len, 1053 "\nMatching host key in %s:%lu", 1054 host_found->file, host_found->line); 1055 } 1056 if (options.strict_host_key_checking == 1) { 1057 logit("%s", msg); 1058 error("Exiting, you have requested strict checking."); 1059 goto fail; 1060 } else if (options.strict_host_key_checking == 2) { 1061 strlcat(msg, "\nAre you sure you want " 1062 "to continue connecting (yes/no)? ", sizeof(msg)); 1063 if (!confirm(msg)) 1064 goto fail; 1065 } else { 1066 logit("%s", msg); 1067 } 1068 } 1069 1070 xfree(ip); 1071 xfree(host); 1072 if (host_hostkeys != NULL) 1073 free_hostkeys(host_hostkeys); 1074 if (ip_hostkeys != NULL) 1075 free_hostkeys(ip_hostkeys); 1076 return 0; 1077 1078 fail: 1079 if (want_cert && host_status != HOST_REVOKED) { 1080 /* 1081 * No matching certificate. Downgrade cert to raw key and 1082 * search normally. 1083 */ 1084 debug("No matching CA found. Retry with plain key"); 1085 raw_key = key_from_private(host_key); 1086 if (key_drop_cert(raw_key) != 0) 1087 fatal("Couldn't drop certificate"); 1088 host_key = raw_key; 1089 goto retry; 1090 } 1091 if (raw_key != NULL) 1092 key_free(raw_key); 1093 xfree(ip); 1094 xfree(host); 1095 if (host_hostkeys != NULL) 1096 free_hostkeys(host_hostkeys); 1097 if (ip_hostkeys != NULL) 1098 free_hostkeys(ip_hostkeys); 1099 return -1; 1100 } 1101 1102 /* returns 0 if key verifies or -1 if key does NOT verify */ 1103 int 1104 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1105 { 1106 int flags = 0; 1107 char *fp; 1108 1109 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1110 debug("Server host key: %s %s", key_type(host_key), fp); 1111 xfree(fp); 1112 1113 /* XXX certs are not yet supported for DNS */ 1114 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1115 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1116 if (flags & DNS_VERIFY_FOUND) { 1117 1118 if (options.verify_host_key_dns == 1 && 1119 flags & DNS_VERIFY_MATCH && 1120 flags & DNS_VERIFY_SECURE) 1121 return 0; 1122 1123 if (flags & DNS_VERIFY_MATCH) { 1124 matching_host_key_dns = 1; 1125 } else { 1126 warn_changed_key(host_key); 1127 error("Update the SSHFP RR in DNS with the new " 1128 "host key to get rid of this message."); 1129 } 1130 } 1131 } 1132 1133 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1134 options.user_hostfiles, options.num_user_hostfiles, 1135 options.system_hostfiles, options.num_system_hostfiles); 1136 } 1137 1138 /* 1139 * Starts a dialog with the server, and authenticates the current user on the 1140 * server. This does not need any extra privileges. The basic connection 1141 * to the server must already have been established before this is called. 1142 * If login fails, this function prints an error and never returns. 1143 * This function does not require super-user privileges. 1144 */ 1145 void 1146 ssh_login(Sensitive *sensitive, const char *orighost, 1147 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1148 { 1149 char *host, *cp; 1150 char *server_user, *local_user; 1151 1152 local_user = xstrdup(pw->pw_name); 1153 server_user = options.user ? options.user : local_user; 1154 1155 /* Convert the user-supplied hostname into all lowercase. */ 1156 host = xstrdup(orighost); 1157 for (cp = host; *cp; cp++) 1158 if (isupper(*cp)) 1159 *cp = (char)tolower(*cp); 1160 1161 /* Exchange protocol version identification strings with the server. */ 1162 ssh_exchange_identification(timeout_ms); 1163 1164 /* Put the connection into non-blocking mode. */ 1165 packet_set_nonblocking(); 1166 1167 /* key exchange */ 1168 /* authenticate user */ 1169 if (compat20) { 1170 ssh_kex2(host, hostaddr, port); 1171 ssh_userauth2(local_user, server_user, host, sensitive); 1172 } else { 1173 ssh_kex(host, hostaddr); 1174 ssh_userauth1(local_user, server_user, host, sensitive); 1175 } 1176 xfree(local_user); 1177 } 1178 1179 void 1180 ssh_put_password(char *password) 1181 { 1182 int size; 1183 char *padded; 1184 1185 if (datafellows & SSH_BUG_PASSWORDPAD) { 1186 packet_put_cstring(password); 1187 return; 1188 } 1189 size = roundup(strlen(password) + 1, 32); 1190 padded = xcalloc(1, size); 1191 strlcpy(padded, password, size); 1192 packet_put_string(padded, size); 1193 memset(padded, 0, size); 1194 xfree(padded); 1195 } 1196 1197 /* print all known host keys for a given host, but skip keys of given type */ 1198 static int 1199 show_other_keys(struct hostkeys *hostkeys, Key *key) 1200 { 1201 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1202 int i, ret = 0; 1203 char *fp, *ra; 1204 const struct hostkey_entry *found; 1205 1206 for (i = 0; type[i] != -1; i++) { 1207 if (type[i] == key->type) 1208 continue; 1209 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1210 continue; 1211 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1212 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1213 logit("WARNING: %s key found for host %s\n" 1214 "in %s:%lu\n" 1215 "%s key fingerprint %s.", 1216 key_type(found->key), 1217 found->host, found->file, found->line, 1218 key_type(found->key), fp); 1219 if (options.visual_host_key) 1220 logit("%s", ra); 1221 xfree(ra); 1222 xfree(fp); 1223 ret = 1; 1224 } 1225 return ret; 1226 } 1227 1228 static void 1229 warn_changed_key(Key *host_key) 1230 { 1231 char *fp; 1232 1233 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1234 1235 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1236 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1237 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1238 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1239 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1240 error("It is also possible that a host key has just been changed."); 1241 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1242 key_type(host_key), fp); 1243 error("Please contact your system administrator."); 1244 1245 xfree(fp); 1246 } 1247 1248 /* 1249 * Execute a local command 1250 */ 1251 int 1252 ssh_local_cmd(const char *args) 1253 { 1254 char *shell; 1255 pid_t pid; 1256 int status; 1257 void (*osighand)(int); 1258 1259 if (!options.permit_local_command || 1260 args == NULL || !*args) 1261 return (1); 1262 1263 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1264 shell = _PATH_BSHELL; 1265 1266 osighand = signal(SIGCHLD, SIG_DFL); 1267 pid = fork(); 1268 if (pid == 0) { 1269 signal(SIGPIPE, SIG_DFL); 1270 debug3("Executing %s -c \"%s\"", shell, args); 1271 execl(shell, shell, "-c", args, (char *)NULL); 1272 error("Couldn't execute %s -c \"%s\": %s", 1273 shell, args, strerror(errno)); 1274 _exit(1); 1275 } else if (pid == -1) 1276 fatal("fork failed: %.100s", strerror(errno)); 1277 while (waitpid(pid, &status, 0) == -1) 1278 if (errno != EINTR) 1279 fatal("Couldn't wait for child: %s", strerror(errno)); 1280 signal(SIGCHLD, osighand); 1281 1282 if (!WIFEXITED(status)) 1283 return (1); 1284 1285 return (WEXITSTATUS(status)); 1286 } 1287