1 /* $OpenBSD: sshconnect.c,v 1.234 2011/05/24 07:15:47 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 /* 423 * Waits for the server identification string, and sends our own 424 * identification string. 425 */ 426 void 427 ssh_exchange_identification(int timeout_ms) 428 { 429 char buf[256], remote_version[256]; /* must be same size! */ 430 int remote_major, remote_minor, mismatch; 431 int connection_in = packet_get_connection_in(); 432 int connection_out = packet_get_connection_out(); 433 int minor1 = PROTOCOL_MINOR_1; 434 u_int i, n; 435 size_t len; 436 int fdsetsz, remaining, rc; 437 struct timeval t_start, t_remaining; 438 fd_set *fdset; 439 440 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 441 fdset = xcalloc(1, fdsetsz); 442 443 /* Read other side's version identification. */ 444 remaining = timeout_ms; 445 for (n = 0;;) { 446 for (i = 0; i < sizeof(buf) - 1; i++) { 447 if (timeout_ms > 0) { 448 gettimeofday(&t_start, NULL); 449 ms_to_timeval(&t_remaining, remaining); 450 FD_SET(connection_in, fdset); 451 rc = select(connection_in + 1, fdset, NULL, 452 fdset, &t_remaining); 453 ms_subtract_diff(&t_start, &remaining); 454 if (rc == 0 || remaining <= 0) 455 fatal("Connection timed out during " 456 "banner exchange"); 457 if (rc == -1) { 458 if (errno == EINTR) 459 continue; 460 fatal("ssh_exchange_identification: " 461 "select: %s", strerror(errno)); 462 } 463 } 464 465 len = roaming_atomicio(read, connection_in, &buf[i], 1); 466 467 if (len != 1 && errno == EPIPE) 468 fatal("ssh_exchange_identification: " 469 "Connection closed by remote host"); 470 else if (len != 1) 471 fatal("ssh_exchange_identification: " 472 "read: %.100s", strerror(errno)); 473 if (buf[i] == '\r') { 474 buf[i] = '\n'; 475 buf[i + 1] = 0; 476 continue; /**XXX wait for \n */ 477 } 478 if (buf[i] == '\n') { 479 buf[i + 1] = 0; 480 break; 481 } 482 if (++n > 65536) 483 fatal("ssh_exchange_identification: " 484 "No banner received"); 485 } 486 buf[sizeof(buf) - 1] = 0; 487 if (strncmp(buf, "SSH-", 4) == 0) 488 break; 489 debug("ssh_exchange_identification: %s", buf); 490 } 491 server_version_string = xstrdup(buf); 492 xfree(fdset); 493 494 /* 495 * Check that the versions match. In future this might accept 496 * several versions and set appropriate flags to handle them. 497 */ 498 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 499 &remote_major, &remote_minor, remote_version) != 3) 500 fatal("Bad remote protocol version identification: '%.100s'", buf); 501 debug("Remote protocol version %d.%d, remote software version %.100s", 502 remote_major, remote_minor, remote_version); 503 504 compat_datafellows(remote_version); 505 mismatch = 0; 506 507 switch (remote_major) { 508 case 1: 509 if (remote_minor == 99 && 510 (options.protocol & SSH_PROTO_2) && 511 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 512 enable_compat20(); 513 break; 514 } 515 if (!(options.protocol & SSH_PROTO_1)) { 516 mismatch = 1; 517 break; 518 } 519 if (remote_minor < 3) { 520 fatal("Remote machine has too old SSH software version."); 521 } else if (remote_minor == 3 || remote_minor == 4) { 522 /* We speak 1.3, too. */ 523 enable_compat13(); 524 minor1 = 3; 525 if (options.forward_agent) { 526 logit("Agent forwarding disabled for protocol 1.3"); 527 options.forward_agent = 0; 528 } 529 } 530 break; 531 case 2: 532 if (options.protocol & SSH_PROTO_2) { 533 enable_compat20(); 534 break; 535 } 536 /* FALLTHROUGH */ 537 default: 538 mismatch = 1; 539 break; 540 } 541 if (mismatch) 542 fatal("Protocol major versions differ: %d vs. %d", 543 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 544 remote_major); 545 /* Send our own protocol version identification. */ 546 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 547 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 548 compat20 ? PROTOCOL_MINOR_2 : minor1, 549 SSH_VERSION, compat20 ? "\r\n" : "\n"); 550 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 551 != strlen(buf)) 552 fatal("write: %.100s", strerror(errno)); 553 client_version_string = xstrdup(buf); 554 chop(client_version_string); 555 chop(server_version_string); 556 debug("Local version string %.100s", client_version_string); 557 } 558 559 /* defaults to 'no' */ 560 static int 561 confirm(const char *prompt) 562 { 563 const char *msg, *again = "Please type 'yes' or 'no': "; 564 char *p; 565 int ret = -1; 566 567 if (options.batch_mode) 568 return 0; 569 for (msg = prompt;;msg = again) { 570 p = read_passphrase(msg, RP_ECHO); 571 if (p == NULL || 572 (p[0] == '\0') || (p[0] == '\n') || 573 strncasecmp(p, "no", 2) == 0) 574 ret = 0; 575 if (p && strncasecmp(p, "yes", 3) == 0) 576 ret = 1; 577 if (p) 578 xfree(p); 579 if (ret != -1) 580 return ret; 581 } 582 } 583 584 static int 585 check_host_cert(const char *host, const Key *host_key) 586 { 587 const char *reason; 588 589 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 590 error("%s", reason); 591 return 0; 592 } 593 if (buffer_len(&host_key->cert->critical) != 0) { 594 error("Certificate for %s contains unsupported " 595 "critical options(s)", host); 596 return 0; 597 } 598 return 1; 599 } 600 601 static int 602 sockaddr_is_local(struct sockaddr *hostaddr) 603 { 604 switch (hostaddr->sa_family) { 605 case AF_INET: 606 return (ntohl(((struct sockaddr_in *)hostaddr)-> 607 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 608 case AF_INET6: 609 return IN6_IS_ADDR_LOOPBACK( 610 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 611 default: 612 return 0; 613 } 614 } 615 616 /* 617 * Prepare the hostname and ip address strings that are used to lookup 618 * host keys in known_hosts files. These may have a port number appended. 619 */ 620 void 621 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 622 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 623 { 624 char ntop[NI_MAXHOST]; 625 626 /* 627 * We don't have the remote ip-address for connections 628 * using a proxy command 629 */ 630 if (hostfile_ipaddr != NULL) { 631 if (options.proxy_command == NULL) { 632 if (getnameinfo(hostaddr, hostaddr->sa_len, 633 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 634 fatal("check_host_key: getnameinfo failed"); 635 *hostfile_ipaddr = put_host_port(ntop, port); 636 } else { 637 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 638 "command>"); 639 } 640 } 641 642 /* 643 * Allow the user to record the key under a different name or 644 * differentiate a non-standard port. This is useful for ssh 645 * tunneling over forwarded connections or if you run multiple 646 * sshd's on different ports on the same machine. 647 */ 648 if (hostfile_hostname != NULL) { 649 if (options.host_key_alias != NULL) { 650 *hostfile_hostname = xstrdup(options.host_key_alias); 651 debug("using hostkeyalias: %s", *hostfile_hostname); 652 } else { 653 *hostfile_hostname = put_host_port(hostname, port); 654 } 655 } 656 } 657 658 /* 659 * check whether the supplied host key is valid, return -1 if the key 660 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 661 */ 662 #define RDRW 0 663 #define RDONLY 1 664 #define ROQUIET 2 665 static int 666 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 667 Key *host_key, int readonly, 668 char **user_hostfiles, u_int num_user_hostfiles, 669 char **system_hostfiles, u_int num_system_hostfiles) 670 { 671 HostStatus host_status; 672 HostStatus ip_status; 673 Key *raw_key = NULL; 674 char *ip = NULL, *host = NULL; 675 char hostline[1000], *hostp, *fp, *ra; 676 char msg[1024]; 677 const char *type; 678 const struct hostkey_entry *host_found, *ip_found; 679 int len, cancelled_forwarding = 0; 680 int local = sockaddr_is_local(hostaddr); 681 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 682 struct hostkeys *host_hostkeys, *ip_hostkeys; 683 u_int i; 684 685 /* 686 * Force accepting of the host key for loopback/localhost. The 687 * problem is that if the home directory is NFS-mounted to multiple 688 * machines, localhost will refer to a different machine in each of 689 * them, and the user will get bogus HOST_CHANGED warnings. This 690 * essentially disables host authentication for localhost; however, 691 * this is probably not a real problem. 692 */ 693 if (options.no_host_authentication_for_localhost == 1 && local && 694 options.host_key_alias == NULL) { 695 debug("Forcing accepting of host key for " 696 "loopback/localhost."); 697 return 0; 698 } 699 700 /* 701 * Prepare the hostname and address strings used for hostkey lookup. 702 * In some cases, these will have a port number appended. 703 */ 704 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 705 706 /* 707 * Turn off check_host_ip if the connection is to localhost, via proxy 708 * command or if we don't have a hostname to compare with 709 */ 710 if (options.check_host_ip && (local || 711 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 712 options.check_host_ip = 0; 713 714 host_hostkeys = init_hostkeys(); 715 for (i = 0; i < num_user_hostfiles; i++) 716 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 717 for (i = 0; i < num_system_hostfiles; i++) 718 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 719 720 ip_hostkeys = NULL; 721 if (!want_cert && options.check_host_ip) { 722 ip_hostkeys = init_hostkeys(); 723 for (i = 0; i < num_user_hostfiles; i++) 724 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 725 for (i = 0; i < num_system_hostfiles; i++) 726 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 727 } 728 729 retry: 730 /* Reload these as they may have changed on cert->key downgrade */ 731 want_cert = key_is_cert(host_key); 732 type = key_type(host_key); 733 734 /* 735 * Check if the host key is present in the user's list of known 736 * hosts or in the systemwide list. 737 */ 738 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 739 &host_found); 740 741 /* 742 * Also perform check for the ip address, skip the check if we are 743 * localhost, looking for a certificate, or the hostname was an ip 744 * address to begin with. 745 */ 746 if (!want_cert && ip_hostkeys != NULL) { 747 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 748 &ip_found); 749 if (host_status == HOST_CHANGED && 750 (ip_status != HOST_CHANGED || 751 (ip_found != NULL && 752 !key_equal(ip_found->key, host_found->key)))) 753 host_ip_differ = 1; 754 } else 755 ip_status = host_status; 756 757 switch (host_status) { 758 case HOST_OK: 759 /* The host is known and the key matches. */ 760 debug("Host '%.200s' is known and matches the %s host %s.", 761 host, type, want_cert ? "certificate" : "key"); 762 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 763 host_found->file, host_found->line); 764 if (want_cert && !check_host_cert(hostname, host_key)) 765 goto fail; 766 if (options.check_host_ip && ip_status == HOST_NEW) { 767 if (readonly || want_cert) 768 logit("%s host key for IP address " 769 "'%.128s' not in list of known hosts.", 770 type, ip); 771 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 772 host_key, options.hash_known_hosts)) 773 logit("Failed to add the %s host key for IP " 774 "address '%.128s' to the list of known " 775 "hosts (%.30s).", type, ip, 776 user_hostfiles[0]); 777 else 778 logit("Warning: Permanently added the %s host " 779 "key for IP address '%.128s' to the list " 780 "of known hosts.", type, ip); 781 } else if (options.visual_host_key) { 782 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 783 ra = key_fingerprint(host_key, SSH_FP_MD5, 784 SSH_FP_RANDOMART); 785 logit("Host key fingerprint is %s\n%s\n", fp, ra); 786 xfree(ra); 787 xfree(fp); 788 } 789 break; 790 case HOST_NEW: 791 if (options.host_key_alias == NULL && port != 0 && 792 port != SSH_DEFAULT_PORT) { 793 debug("checking without port identifier"); 794 if (check_host_key(hostname, hostaddr, 0, host_key, 795 ROQUIET, user_hostfiles, num_user_hostfiles, 796 system_hostfiles, num_system_hostfiles) == 0) { 797 debug("found matching key w/out port"); 798 break; 799 } 800 } 801 if (readonly || want_cert) 802 goto fail; 803 /* The host is new. */ 804 if (options.strict_host_key_checking == 1) { 805 /* 806 * User has requested strict host key checking. We 807 * will not add the host key automatically. The only 808 * alternative left is to abort. 809 */ 810 error("No %s host key is known for %.200s and you " 811 "have requested strict checking.", type, host); 812 goto fail; 813 } else if (options.strict_host_key_checking == 2) { 814 char msg1[1024], msg2[1024]; 815 816 if (show_other_keys(host_hostkeys, host_key)) 817 snprintf(msg1, sizeof(msg1), 818 "\nbut keys of different type are already" 819 " known for this host."); 820 else 821 snprintf(msg1, sizeof(msg1), "."); 822 /* The default */ 823 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 824 ra = key_fingerprint(host_key, SSH_FP_MD5, 825 SSH_FP_RANDOMART); 826 msg2[0] = '\0'; 827 if (options.verify_host_key_dns) { 828 if (matching_host_key_dns) 829 snprintf(msg2, sizeof(msg2), 830 "Matching host key fingerprint" 831 " found in DNS.\n"); 832 else 833 snprintf(msg2, sizeof(msg2), 834 "No matching host key fingerprint" 835 " found in DNS.\n"); 836 } 837 snprintf(msg, sizeof(msg), 838 "The authenticity of host '%.200s (%s)' can't be " 839 "established%s\n" 840 "%s key fingerprint is %s.%s%s\n%s" 841 "Are you sure you want to continue connecting " 842 "(yes/no)? ", 843 host, ip, msg1, type, fp, 844 options.visual_host_key ? "\n" : "", 845 options.visual_host_key ? ra : "", 846 msg2); 847 xfree(ra); 848 xfree(fp); 849 if (!confirm(msg)) 850 goto fail; 851 } 852 /* 853 * If not in strict mode, add the key automatically to the 854 * local known_hosts file. 855 */ 856 if (options.check_host_ip && ip_status == HOST_NEW) { 857 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 858 hostp = hostline; 859 if (options.hash_known_hosts) { 860 /* Add hash of host and IP separately */ 861 r = add_host_to_hostfile(user_hostfiles[0], 862 host, host_key, options.hash_known_hosts) && 863 add_host_to_hostfile(user_hostfiles[0], ip, 864 host_key, options.hash_known_hosts); 865 } else { 866 /* Add unhashed "host,ip" */ 867 r = add_host_to_hostfile(user_hostfiles[0], 868 hostline, host_key, 869 options.hash_known_hosts); 870 } 871 } else { 872 r = add_host_to_hostfile(user_hostfiles[0], host, 873 host_key, options.hash_known_hosts); 874 hostp = host; 875 } 876 877 if (!r) 878 logit("Failed to add the host to the list of known " 879 "hosts (%.500s).", user_hostfiles[0]); 880 else 881 logit("Warning: Permanently added '%.200s' (%s) to the " 882 "list of known hosts.", hostp, type); 883 break; 884 case HOST_REVOKED: 885 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 886 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 887 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 888 error("The %s host key for %s is marked as revoked.", type, host); 889 error("This could mean that a stolen key is being used to"); 890 error("impersonate this host."); 891 892 /* 893 * If strict host key checking is in use, the user will have 894 * to edit the key manually and we can only abort. 895 */ 896 if (options.strict_host_key_checking) { 897 error("%s host key for %.200s was revoked and you have " 898 "requested strict checking.", type, host); 899 goto fail; 900 } 901 goto continue_unsafe; 902 903 case HOST_CHANGED: 904 if (want_cert) { 905 /* 906 * This is only a debug() since it is valid to have 907 * CAs with wildcard DNS matches that don't match 908 * all hosts that one might visit. 909 */ 910 debug("Host certificate authority does not " 911 "match %s in %s:%lu", CA_MARKER, 912 host_found->file, host_found->line); 913 goto fail; 914 } 915 if (readonly == ROQUIET) 916 goto fail; 917 if (options.check_host_ip && host_ip_differ) { 918 char *key_msg; 919 if (ip_status == HOST_NEW) 920 key_msg = "is unknown"; 921 else if (ip_status == HOST_OK) 922 key_msg = "is unchanged"; 923 else 924 key_msg = "has a different value"; 925 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 926 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 927 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 928 error("The %s host key for %s has changed,", type, host); 929 error("and the key for the corresponding IP address %s", ip); 930 error("%s. This could either mean that", key_msg); 931 error("DNS SPOOFING is happening or the IP address for the host"); 932 error("and its host key have changed at the same time."); 933 if (ip_status != HOST_NEW) 934 error("Offending key for IP in %s:%lu", 935 ip_found->file, ip_found->line); 936 } 937 /* The host key has changed. */ 938 warn_changed_key(host_key); 939 error("Add correct host key in %.100s to get rid of this message.", 940 user_hostfiles[0]); 941 error("Offending %s key in %s:%lu", key_type(host_found->key), 942 host_found->file, host_found->line); 943 944 /* 945 * If strict host key checking is in use, the user will have 946 * to edit the key manually and we can only abort. 947 */ 948 if (options.strict_host_key_checking) { 949 error("%s host key for %.200s has changed and you have " 950 "requested strict checking.", type, host); 951 goto fail; 952 } 953 954 continue_unsafe: 955 /* 956 * If strict host key checking has not been requested, allow 957 * the connection but without MITM-able authentication or 958 * forwarding. 959 */ 960 if (options.password_authentication) { 961 error("Password authentication is disabled to avoid " 962 "man-in-the-middle attacks."); 963 options.password_authentication = 0; 964 cancelled_forwarding = 1; 965 } 966 if (options.kbd_interactive_authentication) { 967 error("Keyboard-interactive authentication is disabled" 968 " to avoid man-in-the-middle attacks."); 969 options.kbd_interactive_authentication = 0; 970 options.challenge_response_authentication = 0; 971 cancelled_forwarding = 1; 972 } 973 if (options.challenge_response_authentication) { 974 error("Challenge/response authentication is disabled" 975 " to avoid man-in-the-middle attacks."); 976 options.challenge_response_authentication = 0; 977 cancelled_forwarding = 1; 978 } 979 if (options.forward_agent) { 980 error("Agent forwarding is disabled to avoid " 981 "man-in-the-middle attacks."); 982 options.forward_agent = 0; 983 cancelled_forwarding = 1; 984 } 985 if (options.forward_x11) { 986 error("X11 forwarding is disabled to avoid " 987 "man-in-the-middle attacks."); 988 options.forward_x11 = 0; 989 cancelled_forwarding = 1; 990 } 991 if (options.num_local_forwards > 0 || 992 options.num_remote_forwards > 0) { 993 error("Port forwarding is disabled to avoid " 994 "man-in-the-middle attacks."); 995 options.num_local_forwards = 996 options.num_remote_forwards = 0; 997 cancelled_forwarding = 1; 998 } 999 if (options.tun_open != SSH_TUNMODE_NO) { 1000 error("Tunnel forwarding is disabled to avoid " 1001 "man-in-the-middle attacks."); 1002 options.tun_open = SSH_TUNMODE_NO; 1003 cancelled_forwarding = 1; 1004 } 1005 if (options.exit_on_forward_failure && cancelled_forwarding) 1006 fatal("Error: forwarding disabled due to host key " 1007 "check failure"); 1008 1009 /* 1010 * XXX Should permit the user to change to use the new id. 1011 * This could be done by converting the host key to an 1012 * identifying sentence, tell that the host identifies itself 1013 * by that sentence, and ask the user if he/she wishes to 1014 * accept the authentication. 1015 */ 1016 break; 1017 case HOST_FOUND: 1018 fatal("internal error"); 1019 break; 1020 } 1021 1022 if (options.check_host_ip && host_status != HOST_CHANGED && 1023 ip_status == HOST_CHANGED) { 1024 snprintf(msg, sizeof(msg), 1025 "Warning: the %s host key for '%.200s' " 1026 "differs from the key for the IP address '%.128s'" 1027 "\nOffending key for IP in %s:%lu", 1028 type, host, ip, ip_found->file, ip_found->line); 1029 if (host_status == HOST_OK) { 1030 len = strlen(msg); 1031 snprintf(msg + len, sizeof(msg) - len, 1032 "\nMatching host key in %s:%lu", 1033 host_found->file, host_found->line); 1034 } 1035 if (options.strict_host_key_checking == 1) { 1036 logit("%s", msg); 1037 error("Exiting, you have requested strict checking."); 1038 goto fail; 1039 } else if (options.strict_host_key_checking == 2) { 1040 strlcat(msg, "\nAre you sure you want " 1041 "to continue connecting (yes/no)? ", sizeof(msg)); 1042 if (!confirm(msg)) 1043 goto fail; 1044 } else { 1045 logit("%s", msg); 1046 } 1047 } 1048 1049 xfree(ip); 1050 xfree(host); 1051 if (host_hostkeys != NULL) 1052 free_hostkeys(host_hostkeys); 1053 if (ip_hostkeys != NULL) 1054 free_hostkeys(ip_hostkeys); 1055 return 0; 1056 1057 fail: 1058 if (want_cert && host_status != HOST_REVOKED) { 1059 /* 1060 * No matching certificate. Downgrade cert to raw key and 1061 * search normally. 1062 */ 1063 debug("No matching CA found. Retry with plain key"); 1064 raw_key = key_from_private(host_key); 1065 if (key_drop_cert(raw_key) != 0) 1066 fatal("Couldn't drop certificate"); 1067 host_key = raw_key; 1068 goto retry; 1069 } 1070 if (raw_key != NULL) 1071 key_free(raw_key); 1072 xfree(ip); 1073 xfree(host); 1074 if (host_hostkeys != NULL) 1075 free_hostkeys(host_hostkeys); 1076 if (ip_hostkeys != NULL) 1077 free_hostkeys(ip_hostkeys); 1078 return -1; 1079 } 1080 1081 /* returns 0 if key verifies or -1 if key does NOT verify */ 1082 int 1083 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1084 { 1085 int flags = 0; 1086 char *fp; 1087 1088 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1089 debug("Server host key: %s %s", key_type(host_key), fp); 1090 xfree(fp); 1091 1092 /* XXX certs are not yet supported for DNS */ 1093 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1094 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1095 if (flags & DNS_VERIFY_FOUND) { 1096 1097 if (options.verify_host_key_dns == 1 && 1098 flags & DNS_VERIFY_MATCH && 1099 flags & DNS_VERIFY_SECURE) 1100 return 0; 1101 1102 if (flags & DNS_VERIFY_MATCH) { 1103 matching_host_key_dns = 1; 1104 } else { 1105 warn_changed_key(host_key); 1106 error("Update the SSHFP RR in DNS with the new " 1107 "host key to get rid of this message."); 1108 } 1109 } 1110 } 1111 1112 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1113 options.user_hostfiles, options.num_user_hostfiles, 1114 options.system_hostfiles, options.num_system_hostfiles); 1115 } 1116 1117 /* 1118 * Starts a dialog with the server, and authenticates the current user on the 1119 * server. This does not need any extra privileges. The basic connection 1120 * to the server must already have been established before this is called. 1121 * If login fails, this function prints an error and never returns. 1122 * This function does not require super-user privileges. 1123 */ 1124 void 1125 ssh_login(Sensitive *sensitive, const char *orighost, 1126 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1127 { 1128 char *host, *cp; 1129 char *server_user, *local_user; 1130 1131 local_user = xstrdup(pw->pw_name); 1132 server_user = options.user ? options.user : local_user; 1133 1134 /* Convert the user-supplied hostname into all lowercase. */ 1135 host = xstrdup(orighost); 1136 for (cp = host; *cp; cp++) 1137 if (isupper(*cp)) 1138 *cp = (char)tolower(*cp); 1139 1140 /* Exchange protocol version identification strings with the server. */ 1141 ssh_exchange_identification(timeout_ms); 1142 1143 /* Put the connection into non-blocking mode. */ 1144 packet_set_nonblocking(); 1145 1146 /* key exchange */ 1147 /* authenticate user */ 1148 if (compat20) { 1149 ssh_kex2(host, hostaddr, port); 1150 ssh_userauth2(local_user, server_user, host, sensitive); 1151 } else { 1152 ssh_kex(host, hostaddr); 1153 ssh_userauth1(local_user, server_user, host, sensitive); 1154 } 1155 xfree(local_user); 1156 } 1157 1158 void 1159 ssh_put_password(char *password) 1160 { 1161 int size; 1162 char *padded; 1163 1164 if (datafellows & SSH_BUG_PASSWORDPAD) { 1165 packet_put_cstring(password); 1166 return; 1167 } 1168 size = roundup(strlen(password) + 1, 32); 1169 padded = xcalloc(1, size); 1170 strlcpy(padded, password, size); 1171 packet_put_string(padded, size); 1172 memset(padded, 0, size); 1173 xfree(padded); 1174 } 1175 1176 /* print all known host keys for a given host, but skip keys of given type */ 1177 static int 1178 show_other_keys(struct hostkeys *hostkeys, Key *key) 1179 { 1180 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1181 int i, ret = 0; 1182 char *fp, *ra; 1183 const struct hostkey_entry *found; 1184 1185 for (i = 0; type[i] != -1; i++) { 1186 if (type[i] == key->type) 1187 continue; 1188 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1189 continue; 1190 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1191 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1192 logit("WARNING: %s key found for host %s\n" 1193 "in %s:%lu\n" 1194 "%s key fingerprint %s.", 1195 key_type(found->key), 1196 found->host, found->file, found->line, 1197 key_type(found->key), fp); 1198 if (options.visual_host_key) 1199 logit("%s", ra); 1200 xfree(ra); 1201 xfree(fp); 1202 ret = 1; 1203 } 1204 return ret; 1205 } 1206 1207 static void 1208 warn_changed_key(Key *host_key) 1209 { 1210 char *fp; 1211 1212 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1213 1214 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1215 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1216 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1217 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1218 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1219 error("It is also possible that a host key has just been changed."); 1220 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1221 key_type(host_key), fp); 1222 error("Please contact your system administrator."); 1223 1224 xfree(fp); 1225 } 1226 1227 /* 1228 * Execute a local command 1229 */ 1230 int 1231 ssh_local_cmd(const char *args) 1232 { 1233 char *shell; 1234 pid_t pid; 1235 int status; 1236 void (*osighand)(int); 1237 1238 if (!options.permit_local_command || 1239 args == NULL || !*args) 1240 return (1); 1241 1242 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1243 shell = _PATH_BSHELL; 1244 1245 osighand = signal(SIGCHLD, SIG_DFL); 1246 pid = fork(); 1247 if (pid == 0) { 1248 signal(SIGPIPE, SIG_DFL); 1249 debug3("Executing %s -c \"%s\"", shell, args); 1250 execl(shell, shell, "-c", args, (char *)NULL); 1251 error("Couldn't execute %s -c \"%s\": %s", 1252 shell, args, strerror(errno)); 1253 _exit(1); 1254 } else if (pid == -1) 1255 fatal("fork failed: %.100s", strerror(errno)); 1256 while (waitpid(pid, &status, 0) == -1) 1257 if (errno != EINTR) 1258 fatal("Couldn't wait for child: %s", strerror(errno)); 1259 signal(SIGCHLD, osighand); 1260 1261 if (!WIFEXITED(status)) 1262 return (1); 1263 1264 return (WEXITSTATUS(status)); 1265 } 1266