1/* $OpenBSD: sshconnect.c,v 1.237 2013/02/22 19:13:56 markus Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Code to connect to a remote host, and to perform the client side of the 7 * login (authentication) dialog. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16#include "includes.h" 17 18#include <sys/types.h> 19#include <sys/wait.h> 20#include <sys/stat.h> 21#include <sys/socket.h> 22#ifdef HAVE_SYS_TIME_H 23# include <sys/time.h> 24#endif 25 26#include <netinet/in.h> 27#include <arpa/inet.h> 28 29#include <ctype.h> 30#include <errno.h> 31#include <fcntl.h> 32#include <netdb.h> 33#ifdef HAVE_PATHS_H 34#include <paths.h> 35#endif 36#include <pwd.h> 37#include <signal.h> 38#include <stdarg.h> 39#include <stdio.h> 40#include <stdlib.h> 41#include <string.h> 42#include <unistd.h> 43 44#include "xmalloc.h" 45#include "key.h" 46#include "hostfile.h" 47#include "ssh.h" 48#include "rsa.h" 49#include "buffer.h" 50#include "packet.h" 51#include "uidswap.h" 52#include "compat.h" 53#include "key.h" 54#include "sshconnect.h" 55#include "hostfile.h" 56#include "log.h" 57#include "readconf.h" 58#include "atomicio.h" 59#include "misc.h" 60#include "dns.h" 61#include "roaming.h" 62#include "ssh2.h" 63#include "version.h" 64 65char *client_version_string = NULL; 66char *server_version_string = NULL; 67 68static int matching_host_key_dns = 0; 69 70static pid_t proxy_command_pid = 0; 71 72/* import */ 73extern Options options; 74extern char *__progname; 75extern uid_t original_real_uid; 76extern uid_t original_effective_uid; 77 78static int show_other_keys(struct hostkeys *, Key *); 79static void warn_changed_key(Key *); 80 81/* 82 * Connect to the given ssh server using a proxy command. 83 */ 84static int 85ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 86{ 87 char *command_string, *tmp; 88 int pin[2], pout[2]; 89 pid_t pid; 90 char *shell, strport[NI_MAXSERV]; 91 92 if (!strcmp(proxy_command, "-")) { 93 packet_set_connection(STDIN_FILENO, STDOUT_FILENO); 94 packet_set_timeout(options.server_alive_interval, 95 options.server_alive_count_max); 96 return 0; 97 } 98 99 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 100 shell = _PATH_BSHELL; 101 102 /* Convert the port number into a string. */ 103 snprintf(strport, sizeof strport, "%hu", port); 104 105 /* 106 * Build the final command string in the buffer by making the 107 * appropriate substitutions to the given proxy command. 108 * 109 * Use "exec" to avoid "sh -c" processes on some platforms 110 * (e.g. Solaris) 111 */ 112 xasprintf(&tmp, "exec %s", proxy_command); 113 command_string = percent_expand(tmp, "h", host, "p", strport, 114 "r", options.user, (char *)NULL); 115 xfree(tmp); 116 117 /* Create pipes for communicating with the proxy. */ 118 if (pipe(pin) < 0 || pipe(pout) < 0) 119 fatal("Could not create pipes to communicate with the proxy: %.100s", 120 strerror(errno)); 121 122 debug("Executing proxy command: %.500s", command_string); 123 124 /* Fork and execute the proxy command. */ 125 if ((pid = fork()) == 0) { 126 char *argv[10]; 127 128 /* Child. Permanently give up superuser privileges. */ 129 permanently_drop_suid(original_real_uid); 130 131 /* Redirect stdin and stdout. */ 132 close(pin[1]); 133 if (pin[0] != 0) { 134 if (dup2(pin[0], 0) < 0) 135 perror("dup2 stdin"); 136 close(pin[0]); 137 } 138 close(pout[0]); 139 if (dup2(pout[1], 1) < 0) 140 perror("dup2 stdout"); 141 /* Cannot be 1 because pin allocated two descriptors. */ 142 close(pout[1]); 143 144 /* Stderr is left as it is so that error messages get 145 printed on the user's terminal. */ 146 argv[0] = shell; 147 argv[1] = "-c"; 148 argv[2] = command_string; 149 argv[3] = NULL; 150 151 /* Execute the proxy command. Note that we gave up any 152 extra privileges above. */ 153 signal(SIGPIPE, SIG_DFL); 154 execv(argv[0], argv); 155 perror(argv[0]); 156 exit(1); 157 } 158 /* Parent. */ 159 if (pid < 0) 160 fatal("fork failed: %.100s", strerror(errno)); 161 else 162 proxy_command_pid = pid; /* save pid to clean up later */ 163 164 /* Close child side of the descriptors. */ 165 close(pin[0]); 166 close(pout[1]); 167 168 /* Free the command name. */ 169 xfree(command_string); 170 171 /* Set the connection file descriptors. */ 172 packet_set_connection(pout[0], pin[1]); 173 packet_set_timeout(options.server_alive_interval, 174 options.server_alive_count_max); 175 176 /* Indicate OK return */ 177 return 0; 178} 179 180void 181ssh_kill_proxy_command(void) 182{ 183 /* 184 * Send SIGHUP to proxy command if used. We don't wait() in 185 * case it hangs and instead rely on init to reap the child 186 */ 187 if (proxy_command_pid > 1) 188 kill(proxy_command_pid, SIGHUP); 189} 190 191/* 192 * Creates a (possibly privileged) socket for use as the ssh connection. 193 */ 194static int 195ssh_create_socket(int privileged, struct addrinfo *ai) 196{ 197 int sock, gaierr; 198 struct addrinfo hints, *res; 199 200 /* 201 * If we are running as root and want to connect to a privileged 202 * port, bind our own socket to a privileged port. 203 */ 204 if (privileged) { 205 int p = IPPORT_RESERVED - 1; 206 PRIV_START; 207 sock = rresvport_af(&p, ai->ai_family); 208 PRIV_END; 209 if (sock < 0) 210 error("rresvport: af=%d %.100s", ai->ai_family, 211 strerror(errno)); 212 else 213 debug("Allocated local port %d.", p); 214 return sock; 215 } 216 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 217 if (sock < 0) { 218 error("socket: %.100s", strerror(errno)); 219 return -1; 220 } 221 fcntl(sock, F_SETFD, FD_CLOEXEC); 222 223 /* Bind the socket to an alternative local IP address */ 224 if (options.bind_address == NULL) 225 return sock; 226 227 memset(&hints, 0, sizeof(hints)); 228 hints.ai_family = ai->ai_family; 229 hints.ai_socktype = ai->ai_socktype; 230 hints.ai_protocol = ai->ai_protocol; 231 hints.ai_flags = AI_PASSIVE; 232 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 233 if (gaierr) { 234 error("getaddrinfo: %s: %s", options.bind_address, 235 ssh_gai_strerror(gaierr)); 236 close(sock); 237 return -1; 238 } 239 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 240 error("bind: %s: %s", options.bind_address, strerror(errno)); 241 close(sock); 242 freeaddrinfo(res); 243 return -1; 244 } 245 freeaddrinfo(res); 246 return sock; 247} 248 249static int 250timeout_connect(int sockfd, const struct sockaddr *serv_addr, 251 socklen_t addrlen, int *timeoutp) 252{ 253 fd_set *fdset; 254 struct timeval tv, t_start; 255 socklen_t optlen; 256 int optval, rc, result = -1; 257 258 gettimeofday(&t_start, NULL); 259 260 if (*timeoutp <= 0) { 261 result = connect(sockfd, serv_addr, addrlen); 262 goto done; 263 } 264 265 set_nonblock(sockfd); 266 rc = connect(sockfd, serv_addr, addrlen); 267 if (rc == 0) { 268 unset_nonblock(sockfd); 269 result = 0; 270 goto done; 271 } 272 if (errno != EINPROGRESS) { 273 result = -1; 274 goto done; 275 } 276 277 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 278 sizeof(fd_mask)); 279 FD_SET(sockfd, fdset); 280 ms_to_timeval(&tv, *timeoutp); 281 282 for (;;) { 283 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 284 if (rc != -1 || errno != EINTR) 285 break; 286 } 287 288 switch (rc) { 289 case 0: 290 /* Timed out */ 291 errno = ETIMEDOUT; 292 break; 293 case -1: 294 /* Select error */ 295 debug("select: %s", strerror(errno)); 296 break; 297 case 1: 298 /* Completed or failed */ 299 optval = 0; 300 optlen = sizeof(optval); 301 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 302 &optlen) == -1) { 303 debug("getsockopt: %s", strerror(errno)); 304 break; 305 } 306 if (optval != 0) { 307 errno = optval; 308 break; 309 } 310 result = 0; 311 unset_nonblock(sockfd); 312 break; 313 default: 314 /* Should not occur */ 315 fatal("Bogus return (%d) from select()", rc); 316 } 317 318 xfree(fdset); 319 320 done: 321 if (result == 0 && *timeoutp > 0) { 322 ms_subtract_diff(&t_start, timeoutp); 323 if (*timeoutp <= 0) { 324 errno = ETIMEDOUT; 325 result = -1; 326 } 327 } 328 329 return (result); 330} 331 332/* 333 * Opens a TCP/IP connection to the remote server on the given host. 334 * The address of the remote host will be returned in hostaddr. 335 * If port is 0, the default port will be used. If needpriv is true, 336 * a privileged port will be allocated to make the connection. 337 * This requires super-user privileges if needpriv is true. 338 * Connection_attempts specifies the maximum number of tries (one per 339 * second). If proxy_command is non-NULL, it specifies the command (with %h 340 * and %p substituted for host and port, respectively) to use to contact 341 * the daemon. 342 */ 343int 344ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 345 u_short port, int family, int connection_attempts, int *timeout_ms, 346 int want_keepalive, int needpriv, const char *proxy_command) 347{ 348 int gaierr; 349 int on = 1; 350 int sock = -1, attempt; 351 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 352 struct addrinfo hints, *ai, *aitop; 353 354 debug2("ssh_connect: needpriv %d", needpriv); 355 356 /* If a proxy command is given, connect using it. */ 357 if (proxy_command != NULL) 358 return ssh_proxy_connect(host, port, proxy_command); 359 360 /* No proxy command. */ 361 362 memset(&hints, 0, sizeof(hints)); 363 hints.ai_family = family; 364 hints.ai_socktype = SOCK_STREAM; 365 snprintf(strport, sizeof strport, "%u", port); 366 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 367 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 368 host, ssh_gai_strerror(gaierr)); 369 370 for (attempt = 0; attempt < connection_attempts; attempt++) { 371 if (attempt > 0) { 372 /* Sleep a moment before retrying. */ 373 sleep(1); 374 debug("Trying again..."); 375 } 376 /* 377 * Loop through addresses for this host, and try each one in 378 * sequence until the connection succeeds. 379 */ 380 for (ai = aitop; ai; ai = ai->ai_next) { 381 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 382 continue; 383 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 384 ntop, sizeof(ntop), strport, sizeof(strport), 385 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 386 error("ssh_connect: getnameinfo failed"); 387 continue; 388 } 389 debug("Connecting to %.200s [%.100s] port %s.", 390 host, ntop, strport); 391 392 /* Create a socket for connecting. */ 393 sock = ssh_create_socket(needpriv, ai); 394 if (sock < 0) 395 /* Any error is already output */ 396 continue; 397 398 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 399 timeout_ms) >= 0) { 400 /* Successful connection. */ 401 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 402 break; 403 } else { 404 debug("connect to address %s port %s: %s", 405 ntop, strport, strerror(errno)); 406 close(sock); 407 sock = -1; 408 } 409 } 410 if (sock != -1) 411 break; /* Successful connection. */ 412 } 413 414 freeaddrinfo(aitop); 415 416 /* Return failure if we didn't get a successful connection. */ 417 if (sock == -1) { 418 error("ssh: connect to host %s port %s: %s", 419 host, strport, strerror(errno)); 420 return (-1); 421 } 422 423 debug("Connection established."); 424 425 /* Set SO_KEEPALIVE if requested. */ 426 if (want_keepalive && 427 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 428 sizeof(on)) < 0) 429 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 430 431 /* Set the connection. */ 432 packet_set_connection(sock, sock); 433 packet_set_timeout(options.server_alive_interval, 434 options.server_alive_count_max); 435 436 return 0; 437} 438 439static void 440send_client_banner(int connection_out, int minor1) 441{ 442 /* Send our own protocol version identification. */ 443 if (compat20) { 444 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n", 445 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION); 446 } else { 447 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n", 448 PROTOCOL_MAJOR_1, minor1, SSH_VERSION); 449 } 450 if (roaming_atomicio(vwrite, connection_out, client_version_string, 451 strlen(client_version_string)) != strlen(client_version_string)) 452 fatal("write: %.100s", strerror(errno)); 453 chop(client_version_string); 454 debug("Local version string %.100s", client_version_string); 455} 456 457/* 458 * Waits for the server identification string, and sends our own 459 * identification string. 460 */ 461void 462ssh_exchange_identification(int timeout_ms) 463{ 464 char buf[256], remote_version[256]; /* must be same size! */ 465 int remote_major, remote_minor, mismatch; 466 int connection_in = packet_get_connection_in(); 467 int connection_out = packet_get_connection_out(); 468 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0; 469 u_int i, n; 470 size_t len; 471 int fdsetsz, remaining, rc; 472 struct timeval t_start, t_remaining; 473 fd_set *fdset; 474 475 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 476 fdset = xcalloc(1, fdsetsz); 477 478 /* 479 * If we are SSH2-only then we can send the banner immediately and 480 * save a round-trip. 481 */ 482 if (options.protocol == SSH_PROTO_2) { 483 enable_compat20(); 484 send_client_banner(connection_out, 0); 485 client_banner_sent = 1; 486 } 487 488 /* Read other side's version identification. */ 489 remaining = timeout_ms; 490 for (n = 0;;) { 491 for (i = 0; i < sizeof(buf) - 1; i++) { 492 if (timeout_ms > 0) { 493 gettimeofday(&t_start, NULL); 494 ms_to_timeval(&t_remaining, remaining); 495 FD_SET(connection_in, fdset); 496 rc = select(connection_in + 1, fdset, NULL, 497 fdset, &t_remaining); 498 ms_subtract_diff(&t_start, &remaining); 499 if (rc == 0 || remaining <= 0) 500 fatal("Connection timed out during " 501 "banner exchange"); 502 if (rc == -1) { 503 if (errno == EINTR) 504 continue; 505 fatal("ssh_exchange_identification: " 506 "select: %s", strerror(errno)); 507 } 508 } 509 510 len = roaming_atomicio(read, connection_in, &buf[i], 1); 511 512 if (len != 1 && errno == EPIPE) 513 fatal("ssh_exchange_identification: " 514 "Connection closed by remote host"); 515 else if (len != 1) 516 fatal("ssh_exchange_identification: " 517 "read: %.100s", strerror(errno)); 518 if (buf[i] == '\r') { 519 buf[i] = '\n'; 520 buf[i + 1] = 0; 521 continue; /**XXX wait for \n */ 522 } 523 if (buf[i] == '\n') { 524 buf[i + 1] = 0; 525 break; 526 } 527 if (++n > 65536) 528 fatal("ssh_exchange_identification: " 529 "No banner received"); 530 } 531 buf[sizeof(buf) - 1] = 0; 532 if (strncmp(buf, "SSH-", 4) == 0) 533 break; 534 debug("ssh_exchange_identification: %s", buf); 535 } 536 server_version_string = xstrdup(buf); 537 xfree(fdset); 538 539 /* 540 * Check that the versions match. In future this might accept 541 * several versions and set appropriate flags to handle them. 542 */ 543 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 544 &remote_major, &remote_minor, remote_version) != 3) 545 fatal("Bad remote protocol version identification: '%.100s'", buf); 546 debug("Remote protocol version %d.%d, remote software version %.100s", 547 remote_major, remote_minor, remote_version); 548 549 compat_datafellows(remote_version); 550 mismatch = 0; 551 552 switch (remote_major) { 553 case 1: 554 if (remote_minor == 99 && 555 (options.protocol & SSH_PROTO_2) && 556 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 557 enable_compat20(); 558 break; 559 } 560 if (!(options.protocol & SSH_PROTO_1)) { 561 mismatch = 1; 562 break; 563 } 564 if (remote_minor < 3) { 565 fatal("Remote machine has too old SSH software version."); 566 } else if (remote_minor == 3 || remote_minor == 4) { 567 /* We speak 1.3, too. */ 568 enable_compat13(); 569 minor1 = 3; 570 if (options.forward_agent) { 571 logit("Agent forwarding disabled for protocol 1.3"); 572 options.forward_agent = 0; 573 } 574 } 575 break; 576 case 2: 577 if (options.protocol & SSH_PROTO_2) { 578 enable_compat20(); 579 break; 580 } 581 /* FALLTHROUGH */ 582 default: 583 mismatch = 1; 584 break; 585 } 586 if (mismatch) 587 fatal("Protocol major versions differ: %d vs. %d", 588 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 589 remote_major); 590 if (!client_banner_sent) 591 send_client_banner(connection_out, minor1); 592 chop(server_version_string); 593} 594 595/* defaults to 'no' */ 596static int 597confirm(const char *prompt) 598{ 599 const char *msg, *again = "Please type 'yes' or 'no': "; 600 char *p; 601 int ret = -1; 602 603 if (options.batch_mode) 604 return 0; 605 for (msg = prompt;;msg = again) { 606 p = read_passphrase(msg, RP_ECHO); 607 if (p == NULL || 608 (p[0] == '\0') || (p[0] == '\n') || 609 strncasecmp(p, "no", 2) == 0) 610 ret = 0; 611 if (p && strncasecmp(p, "yes", 3) == 0) 612 ret = 1; 613 if (p) 614 xfree(p); 615 if (ret != -1) 616 return ret; 617 } 618} 619 620static int 621check_host_cert(const char *host, const Key *host_key) 622{ 623 const char *reason; 624 625 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 626 error("%s", reason); 627 return 0; 628 } 629 if (buffer_len(&host_key->cert->critical) != 0) { 630 error("Certificate for %s contains unsupported " 631 "critical options(s)", host); 632 return 0; 633 } 634 return 1; 635} 636 637static int 638sockaddr_is_local(struct sockaddr *hostaddr) 639{ 640 switch (hostaddr->sa_family) { 641 case AF_INET: 642 return (ntohl(((struct sockaddr_in *)hostaddr)-> 643 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 644 case AF_INET6: 645 return IN6_IS_ADDR_LOOPBACK( 646 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 647 default: 648 return 0; 649 } 650} 651 652/* 653 * Prepare the hostname and ip address strings that are used to lookup 654 * host keys in known_hosts files. These may have a port number appended. 655 */ 656void 657get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 658 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 659{ 660 char ntop[NI_MAXHOST]; 661 socklen_t addrlen; 662 663 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 664 case -1: 665 addrlen = 0; 666 break; 667 case AF_INET: 668 addrlen = sizeof(struct sockaddr_in); 669 break; 670 case AF_INET6: 671 addrlen = sizeof(struct sockaddr_in6); 672 break; 673 default: 674 addrlen = sizeof(struct sockaddr); 675 break; 676 } 677 678 /* 679 * We don't have the remote ip-address for connections 680 * using a proxy command 681 */ 682 if (hostfile_ipaddr != NULL) { 683 if (options.proxy_command == NULL) { 684 if (getnameinfo(hostaddr, addrlen, 685 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 686 fatal("check_host_key: getnameinfo failed"); 687 *hostfile_ipaddr = put_host_port(ntop, port); 688 } else { 689 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 690 "command>"); 691 } 692 } 693 694 /* 695 * Allow the user to record the key under a different name or 696 * differentiate a non-standard port. This is useful for ssh 697 * tunneling over forwarded connections or if you run multiple 698 * sshd's on different ports on the same machine. 699 */ 700 if (hostfile_hostname != NULL) { 701 if (options.host_key_alias != NULL) { 702 *hostfile_hostname = xstrdup(options.host_key_alias); 703 debug("using hostkeyalias: %s", *hostfile_hostname); 704 } else { 705 *hostfile_hostname = put_host_port(hostname, port); 706 } 707 } 708} 709 710/* 711 * check whether the supplied host key is valid, return -1 if the key 712 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 713 */ 714#define RDRW 0 715#define RDONLY 1 716#define ROQUIET 2 717static int 718check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 719 Key *host_key, int readonly, 720 char **user_hostfiles, u_int num_user_hostfiles, 721 char **system_hostfiles, u_int num_system_hostfiles) 722{ 723 HostStatus host_status; 724 HostStatus ip_status; 725 Key *raw_key = NULL; 726 char *ip = NULL, *host = NULL; 727 char hostline[1000], *hostp, *fp, *ra; 728 char msg[1024]; 729 const char *type; 730 const struct hostkey_entry *host_found, *ip_found; 731 int len, cancelled_forwarding = 0; 732 int local = sockaddr_is_local(hostaddr); 733 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 734 struct hostkeys *host_hostkeys, *ip_hostkeys; 735 u_int i; 736 737 /* 738 * Force accepting of the host key for loopback/localhost. The 739 * problem is that if the home directory is NFS-mounted to multiple 740 * machines, localhost will refer to a different machine in each of 741 * them, and the user will get bogus HOST_CHANGED warnings. This 742 * essentially disables host authentication for localhost; however, 743 * this is probably not a real problem. 744 */ 745 if (options.no_host_authentication_for_localhost == 1 && local && 746 options.host_key_alias == NULL) { 747 debug("Forcing accepting of host key for " 748 "loopback/localhost."); 749 return 0; 750 } 751 752 /* 753 * Prepare the hostname and address strings used for hostkey lookup. 754 * In some cases, these will have a port number appended. 755 */ 756 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 757 758 /* 759 * Turn off check_host_ip if the connection is to localhost, via proxy 760 * command or if we don't have a hostname to compare with 761 */ 762 if (options.check_host_ip && (local || 763 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 764 options.check_host_ip = 0; 765 766 host_hostkeys = init_hostkeys(); 767 for (i = 0; i < num_user_hostfiles; i++) 768 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 769 for (i = 0; i < num_system_hostfiles; i++) 770 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 771 772 ip_hostkeys = NULL; 773 if (!want_cert && options.check_host_ip) { 774 ip_hostkeys = init_hostkeys(); 775 for (i = 0; i < num_user_hostfiles; i++) 776 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 777 for (i = 0; i < num_system_hostfiles; i++) 778 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 779 } 780 781 retry: 782 /* Reload these as they may have changed on cert->key downgrade */ 783 want_cert = key_is_cert(host_key); 784 type = key_type(host_key); 785 786 /* 787 * Check if the host key is present in the user's list of known 788 * hosts or in the systemwide list. 789 */ 790 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 791 &host_found); 792 793 /* 794 * Also perform check for the ip address, skip the check if we are 795 * localhost, looking for a certificate, or the hostname was an ip 796 * address to begin with. 797 */ 798 if (!want_cert && ip_hostkeys != NULL) { 799 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 800 &ip_found); 801 if (host_status == HOST_CHANGED && 802 (ip_status != HOST_CHANGED || 803 (ip_found != NULL && 804 !key_equal(ip_found->key, host_found->key)))) 805 host_ip_differ = 1; 806 } else 807 ip_status = host_status; 808 809 switch (host_status) { 810 case HOST_OK: 811 /* The host is known and the key matches. */ 812 debug("Host '%.200s' is known and matches the %s host %s.", 813 host, type, want_cert ? "certificate" : "key"); 814 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 815 host_found->file, host_found->line); 816 if (want_cert && !check_host_cert(hostname, host_key)) 817 goto fail; 818 if (options.check_host_ip && ip_status == HOST_NEW) { 819 if (readonly || want_cert) 820 logit("%s host key for IP address " 821 "'%.128s' not in list of known hosts.", 822 type, ip); 823 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 824 host_key, options.hash_known_hosts)) 825 logit("Failed to add the %s host key for IP " 826 "address '%.128s' to the list of known " 827 "hosts (%.30s).", type, ip, 828 user_hostfiles[0]); 829 else 830 logit("Warning: Permanently added the %s host " 831 "key for IP address '%.128s' to the list " 832 "of known hosts.", type, ip); 833 } else if (options.visual_host_key) { 834 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 835 ra = key_fingerprint(host_key, SSH_FP_MD5, 836 SSH_FP_RANDOMART); 837 logit("Host key fingerprint is %s\n%s\n", fp, ra); 838 xfree(ra); 839 xfree(fp); 840 } 841 break; 842 case HOST_NEW: 843 if (options.host_key_alias == NULL && port != 0 && 844 port != SSH_DEFAULT_PORT) { 845 debug("checking without port identifier"); 846 if (check_host_key(hostname, hostaddr, 0, host_key, 847 ROQUIET, user_hostfiles, num_user_hostfiles, 848 system_hostfiles, num_system_hostfiles) == 0) { 849 debug("found matching key w/out port"); 850 break; 851 } 852 } 853 if (readonly || want_cert) 854 goto fail; 855 /* The host is new. */ 856 if (options.strict_host_key_checking == 1) { 857 /* 858 * User has requested strict host key checking. We 859 * will not add the host key automatically. The only 860 * alternative left is to abort. 861 */ 862 error("No %s host key is known for %.200s and you " 863 "have requested strict checking.", type, host); 864 goto fail; 865 } else if (options.strict_host_key_checking == 2) { 866 char msg1[1024], msg2[1024]; 867 868 if (show_other_keys(host_hostkeys, host_key)) 869 snprintf(msg1, sizeof(msg1), 870 "\nbut keys of different type are already" 871 " known for this host."); 872 else 873 snprintf(msg1, sizeof(msg1), "."); 874 /* The default */ 875 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 876 ra = key_fingerprint(host_key, SSH_FP_MD5, 877 SSH_FP_RANDOMART); 878 msg2[0] = '\0'; 879 if (options.verify_host_key_dns) { 880 if (matching_host_key_dns) 881 snprintf(msg2, sizeof(msg2), 882 "Matching host key fingerprint" 883 " found in DNS.\n"); 884 else 885 snprintf(msg2, sizeof(msg2), 886 "No matching host key fingerprint" 887 " found in DNS.\n"); 888 } 889 snprintf(msg, sizeof(msg), 890 "The authenticity of host '%.200s (%s)' can't be " 891 "established%s\n" 892 "%s key fingerprint is %s.%s%s\n%s" 893 "Are you sure you want to continue connecting " 894 "(yes/no)? ", 895 host, ip, msg1, type, fp, 896 options.visual_host_key ? "\n" : "", 897 options.visual_host_key ? ra : "", 898 msg2); 899 xfree(ra); 900 xfree(fp); 901 if (!confirm(msg)) 902 goto fail; 903 } 904 /* 905 * If not in strict mode, add the key automatically to the 906 * local known_hosts file. 907 */ 908 if (options.check_host_ip && ip_status == HOST_NEW) { 909 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 910 hostp = hostline; 911 if (options.hash_known_hosts) { 912 /* Add hash of host and IP separately */ 913 r = add_host_to_hostfile(user_hostfiles[0], 914 host, host_key, options.hash_known_hosts) && 915 add_host_to_hostfile(user_hostfiles[0], ip, 916 host_key, options.hash_known_hosts); 917 } else { 918 /* Add unhashed "host,ip" */ 919 r = add_host_to_hostfile(user_hostfiles[0], 920 hostline, host_key, 921 options.hash_known_hosts); 922 } 923 } else { 924 r = add_host_to_hostfile(user_hostfiles[0], host, 925 host_key, options.hash_known_hosts); 926 hostp = host; 927 } 928 929 if (!r) 930 logit("Failed to add the host to the list of known " 931 "hosts (%.500s).", user_hostfiles[0]); 932 else 933 logit("Warning: Permanently added '%.200s' (%s) to the " 934 "list of known hosts.", hostp, type); 935 break; 936 case HOST_REVOKED: 937 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 938 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 939 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 940 error("The %s host key for %s is marked as revoked.", type, host); 941 error("This could mean that a stolen key is being used to"); 942 error("impersonate this host."); 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 was revoked and you have " 950 "requested strict checking.", type, host); 951 goto fail; 952 } 953 goto continue_unsafe; 954 955 case HOST_CHANGED: 956 if (want_cert) { 957 /* 958 * This is only a debug() since it is valid to have 959 * CAs with wildcard DNS matches that don't match 960 * all hosts that one might visit. 961 */ 962 debug("Host certificate authority does not " 963 "match %s in %s:%lu", CA_MARKER, 964 host_found->file, host_found->line); 965 goto fail; 966 } 967 if (readonly == ROQUIET) 968 goto fail; 969 if (options.check_host_ip && host_ip_differ) { 970 char *key_msg; 971 if (ip_status == HOST_NEW) 972 key_msg = "is unknown"; 973 else if (ip_status == HOST_OK) 974 key_msg = "is unchanged"; 975 else 976 key_msg = "has a different value"; 977 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 978 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 979 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 980 error("The %s host key for %s has changed,", type, host); 981 error("and the key for the corresponding IP address %s", ip); 982 error("%s. This could either mean that", key_msg); 983 error("DNS SPOOFING is happening or the IP address for the host"); 984 error("and its host key have changed at the same time."); 985 if (ip_status != HOST_NEW) 986 error("Offending key for IP in %s:%lu", 987 ip_found->file, ip_found->line); 988 } 989 /* The host key has changed. */ 990 warn_changed_key(host_key); 991 error("Add correct host key in %.100s to get rid of this message.", 992 user_hostfiles[0]); 993 error("Offending %s key in %s:%lu", key_type(host_found->key), 994 host_found->file, host_found->line); 995 996 /* 997 * If strict host key checking is in use, the user will have 998 * to edit the key manually and we can only abort. 999 */ 1000 if (options.strict_host_key_checking) { 1001 error("%s host key for %.200s has changed and you have " 1002 "requested strict checking.", type, host); 1003 goto fail; 1004 } 1005 1006 continue_unsafe: 1007 /* 1008 * If strict host key checking has not been requested, allow 1009 * the connection but without MITM-able authentication or 1010 * forwarding. 1011 */ 1012 if (options.password_authentication) { 1013 error("Password authentication is disabled to avoid " 1014 "man-in-the-middle attacks."); 1015 options.password_authentication = 0; 1016 cancelled_forwarding = 1; 1017 } 1018 if (options.kbd_interactive_authentication) { 1019 error("Keyboard-interactive authentication is disabled" 1020 " to avoid man-in-the-middle attacks."); 1021 options.kbd_interactive_authentication = 0; 1022 options.challenge_response_authentication = 0; 1023 cancelled_forwarding = 1; 1024 } 1025 if (options.challenge_response_authentication) { 1026 error("Challenge/response authentication is disabled" 1027 " to avoid man-in-the-middle attacks."); 1028 options.challenge_response_authentication = 0; 1029 cancelled_forwarding = 1; 1030 } 1031 if (options.forward_agent) { 1032 error("Agent forwarding is disabled to avoid " 1033 "man-in-the-middle attacks."); 1034 options.forward_agent = 0; 1035 cancelled_forwarding = 1; 1036 } 1037 if (options.forward_x11) { 1038 error("X11 forwarding is disabled to avoid " 1039 "man-in-the-middle attacks."); 1040 options.forward_x11 = 0; 1041 cancelled_forwarding = 1; 1042 } 1043 if (options.num_local_forwards > 0 || 1044 options.num_remote_forwards > 0) { 1045 error("Port forwarding is disabled to avoid " 1046 "man-in-the-middle attacks."); 1047 options.num_local_forwards = 1048 options.num_remote_forwards = 0; 1049 cancelled_forwarding = 1; 1050 } 1051 if (options.tun_open != SSH_TUNMODE_NO) { 1052 error("Tunnel forwarding is disabled to avoid " 1053 "man-in-the-middle attacks."); 1054 options.tun_open = SSH_TUNMODE_NO; 1055 cancelled_forwarding = 1; 1056 } 1057 if (options.exit_on_forward_failure && cancelled_forwarding) 1058 fatal("Error: forwarding disabled due to host key " 1059 "check failure"); 1060 1061 /* 1062 * XXX Should permit the user to change to use the new id. 1063 * This could be done by converting the host key to an 1064 * identifying sentence, tell that the host identifies itself 1065 * by that sentence, and ask the user if he/she wishes to 1066 * accept the authentication. 1067 */ 1068 break; 1069 case HOST_FOUND: 1070 fatal("internal error"); 1071 break; 1072 } 1073 1074 if (options.check_host_ip && host_status != HOST_CHANGED && 1075 ip_status == HOST_CHANGED) { 1076 snprintf(msg, sizeof(msg), 1077 "Warning: the %s host key for '%.200s' " 1078 "differs from the key for the IP address '%.128s'" 1079 "\nOffending key for IP in %s:%lu", 1080 type, host, ip, ip_found->file, ip_found->line); 1081 if (host_status == HOST_OK) { 1082 len = strlen(msg); 1083 snprintf(msg + len, sizeof(msg) - len, 1084 "\nMatching host key in %s:%lu", 1085 host_found->file, host_found->line); 1086 } 1087 if (options.strict_host_key_checking == 1) { 1088 logit("%s", msg); 1089 error("Exiting, you have requested strict checking."); 1090 goto fail; 1091 } else if (options.strict_host_key_checking == 2) { 1092 strlcat(msg, "\nAre you sure you want " 1093 "to continue connecting (yes/no)? ", sizeof(msg)); 1094 if (!confirm(msg)) 1095 goto fail; 1096 } else { 1097 logit("%s", msg); 1098 } 1099 } 1100 1101 xfree(ip); 1102 xfree(host); 1103 if (host_hostkeys != NULL) 1104 free_hostkeys(host_hostkeys); 1105 if (ip_hostkeys != NULL) 1106 free_hostkeys(ip_hostkeys); 1107 return 0; 1108 1109fail: 1110 if (want_cert && host_status != HOST_REVOKED) { 1111 /* 1112 * No matching certificate. Downgrade cert to raw key and 1113 * search normally. 1114 */ 1115 debug("No matching CA found. Retry with plain key"); 1116 raw_key = key_from_private(host_key); 1117 if (key_drop_cert(raw_key) != 0) 1118 fatal("Couldn't drop certificate"); 1119 host_key = raw_key; 1120 goto retry; 1121 } 1122 if (raw_key != NULL) 1123 key_free(raw_key); 1124 xfree(ip); 1125 xfree(host); 1126 if (host_hostkeys != NULL) 1127 free_hostkeys(host_hostkeys); 1128 if (ip_hostkeys != NULL) 1129 free_hostkeys(ip_hostkeys); 1130 return -1; 1131} 1132 1133/* returns 0 if key verifies or -1 if key does NOT verify */ 1134int 1135verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1136{ 1137 int flags = 0; 1138 char *fp; 1139 1140 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1141 debug("Server host key: %s %s", key_type(host_key), fp); 1142 xfree(fp); 1143 1144 /* XXX certs are not yet supported for DNS */ 1145 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1146 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1147 if (flags & DNS_VERIFY_FOUND) { 1148 1149 if (options.verify_host_key_dns == 1 && 1150 flags & DNS_VERIFY_MATCH && 1151 flags & DNS_VERIFY_SECURE) 1152 return 0; 1153 1154 if (flags & DNS_VERIFY_MATCH) { 1155 matching_host_key_dns = 1; 1156 } else { 1157 warn_changed_key(host_key); 1158 error("Update the SSHFP RR in DNS with the new " 1159 "host key to get rid of this message."); 1160 } 1161 } 1162 } 1163 1164 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1165 options.user_hostfiles, options.num_user_hostfiles, 1166 options.system_hostfiles, options.num_system_hostfiles); 1167} 1168 1169/* 1170 * Starts a dialog with the server, and authenticates the current user on the 1171 * server. This does not need any extra privileges. The basic connection 1172 * to the server must already have been established before this is called. 1173 * If login fails, this function prints an error and never returns. 1174 * This function does not require super-user privileges. 1175 */ 1176void 1177ssh_login(Sensitive *sensitive, const char *orighost, 1178 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1179{ 1180 char *host, *cp; 1181 char *server_user, *local_user; 1182 1183 local_user = xstrdup(pw->pw_name); 1184 server_user = options.user ? options.user : local_user; 1185 1186 /* Convert the user-supplied hostname into all lowercase. */ 1187 host = xstrdup(orighost); 1188 for (cp = host; *cp; cp++) 1189 if (isupper(*cp)) 1190 *cp = (char)tolower(*cp); 1191 1192 /* Exchange protocol version identification strings with the server. */ 1193 ssh_exchange_identification(timeout_ms); 1194 1195 /* Put the connection into non-blocking mode. */ 1196 packet_set_nonblocking(); 1197 1198 /* key exchange */ 1199 /* authenticate user */ 1200 if (compat20) { 1201 ssh_kex2(host, hostaddr, port); 1202 ssh_userauth2(local_user, server_user, host, sensitive); 1203 } else { 1204 ssh_kex(host, hostaddr); 1205 ssh_userauth1(local_user, server_user, host, sensitive); 1206 } 1207 xfree(local_user); 1208} 1209 1210void 1211ssh_put_password(char *password) 1212{ 1213 int size; 1214 char *padded; 1215 1216 if (datafellows & SSH_BUG_PASSWORDPAD) { 1217 packet_put_cstring(password); 1218 return; 1219 } 1220 size = roundup(strlen(password) + 1, 32); 1221 padded = xcalloc(1, size); 1222 strlcpy(padded, password, size); 1223 packet_put_string(padded, size); 1224 memset(padded, 0, size); 1225 xfree(padded); 1226} 1227 1228/* print all known host keys for a given host, but skip keys of given type */ 1229static int 1230show_other_keys(struct hostkeys *hostkeys, Key *key) 1231{ 1232 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1233 int i, ret = 0; 1234 char *fp, *ra; 1235 const struct hostkey_entry *found; 1236 1237 for (i = 0; type[i] != -1; i++) { 1238 if (type[i] == key->type) 1239 continue; 1240 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1241 continue; 1242 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1243 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1244 logit("WARNING: %s key found for host %s\n" 1245 "in %s:%lu\n" 1246 "%s key fingerprint %s.", 1247 key_type(found->key), 1248 found->host, found->file, found->line, 1249 key_type(found->key), fp); 1250 if (options.visual_host_key) 1251 logit("%s", ra); 1252 xfree(ra); 1253 xfree(fp); 1254 ret = 1; 1255 } 1256 return ret; 1257} 1258 1259static void 1260warn_changed_key(Key *host_key) 1261{ 1262 char *fp; 1263 1264 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1265 1266 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1267 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1268 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1269 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1270 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1271 error("It is also possible that a host key has just been changed."); 1272 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1273 key_type(host_key), fp); 1274 error("Please contact your system administrator."); 1275 1276 xfree(fp); 1277} 1278 1279/* 1280 * Execute a local command 1281 */ 1282int 1283ssh_local_cmd(const char *args) 1284{ 1285 char *shell; 1286 pid_t pid; 1287 int status; 1288 void (*osighand)(int); 1289 1290 if (!options.permit_local_command || 1291 args == NULL || !*args) 1292 return (1); 1293 1294 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1295 shell = _PATH_BSHELL; 1296 1297 osighand = signal(SIGCHLD, SIG_DFL); 1298 pid = fork(); 1299 if (pid == 0) { 1300 signal(SIGPIPE, SIG_DFL); 1301 debug3("Executing %s -c \"%s\"", shell, args); 1302 execl(shell, shell, "-c", args, (char *)NULL); 1303 error("Couldn't execute %s -c \"%s\": %s", 1304 shell, args, strerror(errno)); 1305 _exit(1); 1306 } else if (pid == -1) 1307 fatal("fork failed: %.100s", strerror(errno)); 1308 while (waitpid(pid, &status, 0) == -1) 1309 if (errno != EINTR) 1310 fatal("Couldn't wait for child: %s", strerror(errno)); 1311 signal(SIGCHLD, osighand); 1312 1313 if (!WIFEXITED(status)) 1314 return (1); 1315 1316 return (WEXITSTATUS(status)); 1317} 1318