1 /* $OpenBSD: sshconnect.c,v 1.234 2011/05/24 07:15:47 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo (at) 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 65 char *client_version_string = NULL; 66 char *server_version_string = NULL; 67 68 static int matching_host_key_dns = 0; 69 70 static pid_t proxy_command_pid = 0; 71 72 /* import */ 73 extern Options options; 74 extern char *__progname; 75 extern uid_t original_real_uid; 76 extern uid_t original_effective_uid; 77 78 static int show_other_keys(struct hostkeys *, Key *); 79 static void warn_changed_key(Key *); 80 81 /* 82 * Connect to the given ssh server using a proxy command. 83 */ 84 static int 85 ssh_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 ((shell = getenv("SHELL")) == NULL || *shell == '\0') 93 shell = _PATH_BSHELL; 94 95 /* Convert the port number into a string. */ 96 snprintf(strport, sizeof strport, "%hu", port); 97 98 /* 99 * Build the final command string in the buffer by making the 100 * appropriate substitutions to the given proxy command. 101 * 102 * Use "exec" to avoid "sh -c" processes on some platforms 103 * (e.g. Solaris) 104 */ 105 xasprintf(&tmp, "exec %s", proxy_command); 106 command_string = percent_expand(tmp, "h", host, "p", strport, 107 "r", options.user, (char *)NULL); 108 xfree(tmp); 109 110 /* Create pipes for communicating with the proxy. */ 111 if (pipe(pin) < 0 || pipe(pout) < 0) 112 fatal("Could not create pipes to communicate with the proxy: %.100s", 113 strerror(errno)); 114 115 debug("Executing proxy command: %.500s", command_string); 116 117 /* Fork and execute the proxy command. */ 118 if ((pid = fork()) == 0) { 119 char *argv[10]; 120 121 /* Child. Permanently give up superuser privileges. */ 122 permanently_drop_suid(original_real_uid); 123 124 /* Redirect stdin and stdout. */ 125 close(pin[1]); 126 if (pin[0] != 0) { 127 if (dup2(pin[0], 0) < 0) 128 perror("dup2 stdin"); 129 close(pin[0]); 130 } 131 close(pout[0]); 132 if (dup2(pout[1], 1) < 0) 133 perror("dup2 stdout"); 134 /* Cannot be 1 because pin allocated two descriptors. */ 135 close(pout[1]); 136 137 /* Stderr is left as it is so that error messages get 138 printed on the user's terminal. */ 139 argv[0] = shell; 140 argv[1] = "-c"; 141 argv[2] = command_string; 142 argv[3] = NULL; 143 144 /* Execute the proxy command. Note that we gave up any 145 extra privileges above. */ 146 signal(SIGPIPE, SIG_DFL); 147 execv(argv[0], argv); 148 perror(argv[0]); 149 exit(1); 150 } 151 /* Parent. */ 152 if (pid < 0) 153 fatal("fork failed: %.100s", strerror(errno)); 154 else 155 proxy_command_pid = pid; /* save pid to clean up later */ 156 157 /* Close child side of the descriptors. */ 158 close(pin[0]); 159 close(pout[1]); 160 161 /* Free the command name. */ 162 xfree(command_string); 163 164 /* Set the connection file descriptors. */ 165 packet_set_connection(pout[0], pin[1]); 166 packet_set_timeout(options.server_alive_interval, 167 options.server_alive_count_max); 168 169 /* Indicate OK return */ 170 return 0; 171 } 172 173 void 174 ssh_kill_proxy_command(void) 175 { 176 /* 177 * Send SIGHUP to proxy command if used. We don't wait() in 178 * case it hangs and instead rely on init to reap the child 179 */ 180 if (proxy_command_pid > 1) 181 kill(proxy_command_pid, SIGHUP); 182 } 183 184 /* 185 * Creates a (possibly privileged) socket for use as the ssh connection. 186 */ 187 static int 188 ssh_create_socket(int privileged, struct addrinfo *ai) 189 { 190 int sock, gaierr; 191 struct addrinfo hints, *res; 192 193 /* 194 * If we are running as root and want to connect to a privileged 195 * port, bind our own socket to a privileged port. 196 */ 197 if (privileged) { 198 int p = IPPORT_RESERVED - 1; 199 PRIV_START; 200 sock = rresvport_af(&p, ai->ai_family); 201 PRIV_END; 202 if (sock < 0) 203 error("rresvport: af=%d %.100s", ai->ai_family, 204 strerror(errno)); 205 else 206 debug("Allocated local port %d.", p); 207 return sock; 208 } 209 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 210 if (sock < 0) { 211 error("socket: %.100s", strerror(errno)); 212 return -1; 213 } 214 fcntl(sock, F_SETFD, FD_CLOEXEC); 215 216 /* Bind the socket to an alternative local IP address */ 217 if (options.bind_address == NULL) 218 return sock; 219 220 memset(&hints, 0, sizeof(hints)); 221 hints.ai_family = ai->ai_family; 222 hints.ai_socktype = ai->ai_socktype; 223 hints.ai_protocol = ai->ai_protocol; 224 hints.ai_flags = AI_PASSIVE; 225 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 226 if (gaierr) { 227 error("getaddrinfo: %s: %s", options.bind_address, 228 ssh_gai_strerror(gaierr)); 229 close(sock); 230 return -1; 231 } 232 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 233 error("bind: %s: %s", options.bind_address, strerror(errno)); 234 close(sock); 235 freeaddrinfo(res); 236 return -1; 237 } 238 freeaddrinfo(res); 239 return sock; 240 } 241 242 static int 243 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 244 socklen_t addrlen, int *timeoutp) 245 { 246 fd_set *fdset; 247 struct timeval tv, t_start; 248 socklen_t optlen; 249 int optval, rc, result = -1; 250 251 gettimeofday(&t_start, NULL); 252 253 if (*timeoutp <= 0) { 254 result = connect(sockfd, serv_addr, addrlen); 255 goto done; 256 } 257 258 set_nonblock(sockfd); 259 rc = connect(sockfd, serv_addr, addrlen); 260 if (rc == 0) { 261 unset_nonblock(sockfd); 262 result = 0; 263 goto done; 264 } 265 if (errno != EINPROGRESS) { 266 result = -1; 267 goto done; 268 } 269 270 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 271 sizeof(fd_mask)); 272 FD_SET(sockfd, fdset); 273 ms_to_timeval(&tv, *timeoutp); 274 275 for (;;) { 276 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 277 if (rc != -1 || errno != EINTR) 278 break; 279 } 280 281 switch (rc) { 282 case 0: 283 /* Timed out */ 284 errno = ETIMEDOUT; 285 break; 286 case -1: 287 /* Select error */ 288 debug("select: %s", strerror(errno)); 289 break; 290 case 1: 291 /* Completed or failed */ 292 optval = 0; 293 optlen = sizeof(optval); 294 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 295 &optlen) == -1) { 296 debug("getsockopt: %s", strerror(errno)); 297 break; 298 } 299 if (optval != 0) { 300 errno = optval; 301 break; 302 } 303 result = 0; 304 unset_nonblock(sockfd); 305 break; 306 default: 307 /* Should not occur */ 308 fatal("Bogus return (%d) from select()", rc); 309 } 310 311 xfree(fdset); 312 313 done: 314 if (result == 0 && *timeoutp > 0) { 315 ms_subtract_diff(&t_start, timeoutp); 316 if (*timeoutp <= 0) { 317 errno = ETIMEDOUT; 318 result = -1; 319 } 320 } 321 322 return (result); 323 } 324 325 /* 326 * Opens a TCP/IP connection to the remote server on the given host. 327 * The address of the remote host will be returned in hostaddr. 328 * If port is 0, the default port will be used. If needpriv is true, 329 * a privileged port will be allocated to make the connection. 330 * This requires super-user privileges if needpriv is true. 331 * Connection_attempts specifies the maximum number of tries (one per 332 * second). If proxy_command is non-NULL, it specifies the command (with %h 333 * and %p substituted for host and port, respectively) to use to contact 334 * the daemon. 335 */ 336 int 337 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 338 u_short port, int family, int connection_attempts, int *timeout_ms, 339 int want_keepalive, int needpriv, const char *proxy_command) 340 { 341 int gaierr; 342 int on = 1; 343 int sock = -1, attempt; 344 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 345 struct addrinfo hints, *ai, *aitop; 346 347 debug2("ssh_connect: needpriv %d", needpriv); 348 349 /* If a proxy command is given, connect using it. */ 350 if (proxy_command != NULL) 351 return ssh_proxy_connect(host, port, proxy_command); 352 353 /* No proxy command. */ 354 355 memset(&hints, 0, sizeof(hints)); 356 hints.ai_family = family; 357 hints.ai_socktype = SOCK_STREAM; 358 snprintf(strport, sizeof strport, "%u", port); 359 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 360 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 361 host, ssh_gai_strerror(gaierr)); 362 363 for (attempt = 0; attempt < connection_attempts; attempt++) { 364 if (attempt > 0) { 365 /* Sleep a moment before retrying. */ 366 sleep(1); 367 debug("Trying again..."); 368 } 369 /* 370 * Loop through addresses for this host, and try each one in 371 * sequence until the connection succeeds. 372 */ 373 for (ai = aitop; ai; ai = ai->ai_next) { 374 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 375 continue; 376 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 377 ntop, sizeof(ntop), strport, sizeof(strport), 378 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 379 error("ssh_connect: getnameinfo failed"); 380 continue; 381 } 382 debug("Connecting to %.200s [%.100s] port %s.", 383 host, ntop, strport); 384 385 /* Create a socket for connecting. */ 386 sock = ssh_create_socket(needpriv, ai); 387 if (sock < 0) 388 /* Any error is already output */ 389 continue; 390 391 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 392 timeout_ms) >= 0) { 393 /* Successful connection. */ 394 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 395 break; 396 } else { 397 debug("connect to address %s port %s: %s", 398 ntop, strport, strerror(errno)); 399 close(sock); 400 sock = -1; 401 } 402 } 403 if (sock != -1) 404 break; /* Successful connection. */ 405 } 406 407 freeaddrinfo(aitop); 408 409 /* Return failure if we didn't get a successful connection. */ 410 if (sock == -1) { 411 error("ssh: connect to host %s port %s: %s", 412 host, strport, strerror(errno)); 413 return (-1); 414 } 415 416 debug("Connection established."); 417 418 /* Set SO_KEEPALIVE if requested. */ 419 if (want_keepalive && 420 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 421 sizeof(on)) < 0) 422 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 423 424 /* Set the connection. */ 425 packet_set_connection(sock, sock); 426 packet_set_timeout(options.server_alive_interval, 427 options.server_alive_count_max); 428 429 return 0; 430 } 431 432 /* 433 * Waits for the server identification string, and sends our own 434 * identification string. 435 */ 436 void 437 ssh_exchange_identification(int timeout_ms) 438 { 439 char buf[256], remote_version[256]; /* must be same size! */ 440 int remote_major, remote_minor, mismatch; 441 int connection_in = packet_get_connection_in(); 442 int connection_out = packet_get_connection_out(); 443 int minor1 = PROTOCOL_MINOR_1; 444 u_int i, n; 445 size_t len; 446 int fdsetsz, remaining, rc; 447 struct timeval t_start, t_remaining; 448 fd_set *fdset; 449 450 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 451 fdset = xcalloc(1, fdsetsz); 452 453 /* Read other side's version identification. */ 454 remaining = timeout_ms; 455 for (n = 0;;) { 456 for (i = 0; i < sizeof(buf) - 1; i++) { 457 if (timeout_ms > 0) { 458 gettimeofday(&t_start, NULL); 459 ms_to_timeval(&t_remaining, remaining); 460 FD_SET(connection_in, fdset); 461 rc = select(connection_in + 1, fdset, NULL, 462 fdset, &t_remaining); 463 ms_subtract_diff(&t_start, &remaining); 464 if (rc == 0 || remaining <= 0) 465 fatal("Connection timed out during " 466 "banner exchange"); 467 if (rc == -1) { 468 if (errno == EINTR) 469 continue; 470 fatal("ssh_exchange_identification: " 471 "select: %s", strerror(errno)); 472 } 473 } 474 475 len = roaming_atomicio(read, connection_in, &buf[i], 1); 476 477 if (len != 1 && errno == EPIPE) 478 fatal("ssh_exchange_identification: " 479 "Connection closed by remote host"); 480 else if (len != 1) 481 fatal("ssh_exchange_identification: " 482 "read: %.100s", strerror(errno)); 483 if (buf[i] == '\r') { 484 buf[i] = '\n'; 485 buf[i + 1] = 0; 486 continue; /**XXX wait for \n */ 487 } 488 if (buf[i] == '\n') { 489 buf[i + 1] = 0; 490 break; 491 } 492 if (++n > 65536) 493 fatal("ssh_exchange_identification: " 494 "No banner received"); 495 } 496 buf[sizeof(buf) - 1] = 0; 497 if (strncmp(buf, "SSH-", 4) == 0) 498 break; 499 debug("ssh_exchange_identification: %s", buf); 500 } 501 server_version_string = xstrdup(buf); 502 xfree(fdset); 503 504 /* 505 * Check that the versions match. In future this might accept 506 * several versions and set appropriate flags to handle them. 507 */ 508 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 509 &remote_major, &remote_minor, remote_version) != 3) 510 fatal("Bad remote protocol version identification: '%.100s'", buf); 511 debug("Remote protocol version %d.%d, remote software version %.100s", 512 remote_major, remote_minor, remote_version); 513 514 compat_datafellows(remote_version); 515 mismatch = 0; 516 517 switch (remote_major) { 518 case 1: 519 if (remote_minor == 99 && 520 (options.protocol & SSH_PROTO_2) && 521 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 522 enable_compat20(); 523 break; 524 } 525 if (!(options.protocol & SSH_PROTO_1)) { 526 mismatch = 1; 527 break; 528 } 529 if (remote_minor < 3) { 530 fatal("Remote machine has too old SSH software version."); 531 } else if (remote_minor == 3 || remote_minor == 4) { 532 /* We speak 1.3, too. */ 533 enable_compat13(); 534 minor1 = 3; 535 if (options.forward_agent) { 536 logit("Agent forwarding disabled for protocol 1.3"); 537 options.forward_agent = 0; 538 } 539 } 540 break; 541 case 2: 542 if (options.protocol & SSH_PROTO_2) { 543 enable_compat20(); 544 break; 545 } 546 /* FALLTHROUGH */ 547 default: 548 mismatch = 1; 549 break; 550 } 551 if (mismatch) 552 fatal("Protocol major versions differ: %d vs. %d", 553 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 554 remote_major); 555 /* Send our own protocol version identification. */ 556 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 557 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 558 compat20 ? PROTOCOL_MINOR_2 : minor1, 559 SSH_VERSION, compat20 ? "\r\n" : "\n"); 560 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 561 != strlen(buf)) 562 fatal("write: %.100s", strerror(errno)); 563 client_version_string = xstrdup(buf); 564 chop(client_version_string); 565 chop(server_version_string); 566 debug("Local version string %.100s", client_version_string); 567 } 568 569 /* defaults to 'no' */ 570 static int 571 confirm(const char *prompt) 572 { 573 const char *msg, *again = "Please type 'yes' or 'no': "; 574 char *p; 575 int ret = -1; 576 577 if (options.batch_mode) 578 return 0; 579 for (msg = prompt;;msg = again) { 580 p = read_passphrase(msg, RP_ECHO); 581 if (p == NULL || 582 (p[0] == '\0') || (p[0] == '\n') || 583 strncasecmp(p, "no", 2) == 0) 584 ret = 0; 585 if (p && strncasecmp(p, "yes", 3) == 0) 586 ret = 1; 587 if (p) 588 xfree(p); 589 if (ret != -1) 590 return ret; 591 } 592 } 593 594 static int 595 check_host_cert(const char *host, const Key *host_key) 596 { 597 const char *reason; 598 599 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 600 error("%s", reason); 601 return 0; 602 } 603 if (buffer_len(&host_key->cert->critical) != 0) { 604 error("Certificate for %s contains unsupported " 605 "critical options(s)", host); 606 return 0; 607 } 608 return 1; 609 } 610 611 static int 612 sockaddr_is_local(struct sockaddr *hostaddr) 613 { 614 switch (hostaddr->sa_family) { 615 case AF_INET: 616 return (ntohl(((struct sockaddr_in *)hostaddr)-> 617 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 618 case AF_INET6: 619 return IN6_IS_ADDR_LOOPBACK( 620 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 621 default: 622 return 0; 623 } 624 } 625 626 /* 627 * Prepare the hostname and ip address strings that are used to lookup 628 * host keys in known_hosts files. These may have a port number appended. 629 */ 630 void 631 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 632 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 633 { 634 char ntop[NI_MAXHOST]; 635 socklen_t addrlen; 636 637 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 638 case -1: 639 addrlen = 0; 640 break; 641 case AF_INET: 642 addrlen = sizeof(struct sockaddr_in); 643 break; 644 case AF_INET6: 645 addrlen = sizeof(struct sockaddr_in6); 646 break; 647 default: 648 addrlen = sizeof(struct sockaddr); 649 break; 650 } 651 652 /* 653 * We don't have the remote ip-address for connections 654 * using a proxy command 655 */ 656 if (hostfile_ipaddr != NULL) { 657 if (options.proxy_command == NULL) { 658 if (getnameinfo(hostaddr, addrlen, 659 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 660 fatal("check_host_key: getnameinfo failed"); 661 *hostfile_ipaddr = put_host_port(ntop, port); 662 } else { 663 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 664 "command>"); 665 } 666 } 667 668 /* 669 * Allow the user to record the key under a different name or 670 * differentiate a non-standard port. This is useful for ssh 671 * tunneling over forwarded connections or if you run multiple 672 * sshd's on different ports on the same machine. 673 */ 674 if (hostfile_hostname != NULL) { 675 if (options.host_key_alias != NULL) { 676 *hostfile_hostname = xstrdup(options.host_key_alias); 677 debug("using hostkeyalias: %s", *hostfile_hostname); 678 } else { 679 *hostfile_hostname = put_host_port(hostname, port); 680 } 681 } 682 } 683 684 /* 685 * check whether the supplied host key is valid, return -1 if the key 686 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 687 */ 688 #define RDRW 0 689 #define RDONLY 1 690 #define ROQUIET 2 691 static int 692 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 693 Key *host_key, int readonly, 694 char **user_hostfiles, u_int num_user_hostfiles, 695 char **system_hostfiles, u_int num_system_hostfiles) 696 { 697 HostStatus host_status; 698 HostStatus ip_status; 699 Key *raw_key = NULL; 700 char *ip = NULL, *host = NULL; 701 char hostline[1000], *hostp, *fp, *ra; 702 char msg[1024]; 703 const char *type; 704 const struct hostkey_entry *host_found, *ip_found; 705 int len, cancelled_forwarding = 0; 706 int local = sockaddr_is_local(hostaddr); 707 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 708 struct hostkeys *host_hostkeys, *ip_hostkeys; 709 u_int i; 710 711 /* 712 * Force accepting of the host key for loopback/localhost. The 713 * problem is that if the home directory is NFS-mounted to multiple 714 * machines, localhost will refer to a different machine in each of 715 * them, and the user will get bogus HOST_CHANGED warnings. This 716 * essentially disables host authentication for localhost; however, 717 * this is probably not a real problem. 718 */ 719 if (options.no_host_authentication_for_localhost == 1 && local && 720 options.host_key_alias == NULL) { 721 debug("Forcing accepting of host key for " 722 "loopback/localhost."); 723 return 0; 724 } 725 726 /* 727 * Prepare the hostname and address strings used for hostkey lookup. 728 * In some cases, these will have a port number appended. 729 */ 730 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 731 732 /* 733 * Turn off check_host_ip if the connection is to localhost, via proxy 734 * command or if we don't have a hostname to compare with 735 */ 736 if (options.check_host_ip && (local || 737 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 738 options.check_host_ip = 0; 739 740 host_hostkeys = init_hostkeys(); 741 for (i = 0; i < num_user_hostfiles; i++) 742 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 743 for (i = 0; i < num_system_hostfiles; i++) 744 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 745 746 ip_hostkeys = NULL; 747 if (!want_cert && options.check_host_ip) { 748 ip_hostkeys = init_hostkeys(); 749 for (i = 0; i < num_user_hostfiles; i++) 750 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 751 for (i = 0; i < num_system_hostfiles; i++) 752 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 753 } 754 755 retry: 756 /* Reload these as they may have changed on cert->key downgrade */ 757 want_cert = key_is_cert(host_key); 758 type = key_type(host_key); 759 760 /* 761 * Check if the host key is present in the user's list of known 762 * hosts or in the systemwide list. 763 */ 764 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 765 &host_found); 766 767 /* 768 * Also perform check for the ip address, skip the check if we are 769 * localhost, looking for a certificate, or the hostname was an ip 770 * address to begin with. 771 */ 772 if (!want_cert && ip_hostkeys != NULL) { 773 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 774 &ip_found); 775 if (host_status == HOST_CHANGED && 776 (ip_status != HOST_CHANGED || 777 (ip_found != NULL && 778 !key_equal(ip_found->key, host_found->key)))) 779 host_ip_differ = 1; 780 } else 781 ip_status = host_status; 782 783 switch (host_status) { 784 case HOST_OK: 785 /* The host is known and the key matches. */ 786 debug("Host '%.200s' is known and matches the %s host %s.", 787 host, type, want_cert ? "certificate" : "key"); 788 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 789 host_found->file, host_found->line); 790 if (want_cert && !check_host_cert(hostname, host_key)) 791 goto fail; 792 if (options.check_host_ip && ip_status == HOST_NEW) { 793 if (readonly || want_cert) 794 logit("%s host key for IP address " 795 "'%.128s' not in list of known hosts.", 796 type, ip); 797 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 798 host_key, options.hash_known_hosts)) 799 logit("Failed to add the %s host key for IP " 800 "address '%.128s' to the list of known " 801 "hosts (%.30s).", type, ip, 802 user_hostfiles[0]); 803 else 804 logit("Warning: Permanently added the %s host " 805 "key for IP address '%.128s' to the list " 806 "of known hosts.", type, ip); 807 } else if (options.visual_host_key) { 808 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 809 ra = key_fingerprint(host_key, SSH_FP_MD5, 810 SSH_FP_RANDOMART); 811 logit("Host key fingerprint is %s\n%s\n", fp, ra); 812 xfree(ra); 813 xfree(fp); 814 } 815 break; 816 case HOST_NEW: 817 if (options.host_key_alias == NULL && port != 0 && 818 port != SSH_DEFAULT_PORT) { 819 debug("checking without port identifier"); 820 if (check_host_key(hostname, hostaddr, 0, host_key, 821 ROQUIET, user_hostfiles, num_user_hostfiles, 822 system_hostfiles, num_system_hostfiles) == 0) { 823 debug("found matching key w/out port"); 824 break; 825 } 826 } 827 if (readonly || want_cert) 828 goto fail; 829 /* The host is new. */ 830 if (options.strict_host_key_checking == 1) { 831 /* 832 * User has requested strict host key checking. We 833 * will not add the host key automatically. The only 834 * alternative left is to abort. 835 */ 836 error("No %s host key is known for %.200s and you " 837 "have requested strict checking.", type, host); 838 goto fail; 839 } else if (options.strict_host_key_checking == 2) { 840 char msg1[1024], msg2[1024]; 841 842 if (show_other_keys(host_hostkeys, host_key)) 843 snprintf(msg1, sizeof(msg1), 844 "\nbut keys of different type are already" 845 " known for this host."); 846 else 847 snprintf(msg1, sizeof(msg1), "."); 848 /* The default */ 849 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 850 ra = key_fingerprint(host_key, SSH_FP_MD5, 851 SSH_FP_RANDOMART); 852 msg2[0] = '\0'; 853 if (options.verify_host_key_dns) { 854 if (matching_host_key_dns) 855 snprintf(msg2, sizeof(msg2), 856 "Matching host key fingerprint" 857 " found in DNS.\n"); 858 else 859 snprintf(msg2, sizeof(msg2), 860 "No matching host key fingerprint" 861 " found in DNS.\n"); 862 } 863 snprintf(msg, sizeof(msg), 864 "The authenticity of host '%.200s (%s)' can't be " 865 "established%s\n" 866 "%s key fingerprint is %s.%s%s\n%s" 867 "Are you sure you want to continue connecting " 868 "(yes/no)? ", 869 host, ip, msg1, type, fp, 870 options.visual_host_key ? "\n" : "", 871 options.visual_host_key ? ra : "", 872 msg2); 873 xfree(ra); 874 xfree(fp); 875 if (!confirm(msg)) 876 goto fail; 877 } 878 /* 879 * If not in strict mode, add the key automatically to the 880 * local known_hosts file. 881 */ 882 if (options.check_host_ip && ip_status == HOST_NEW) { 883 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 884 hostp = hostline; 885 if (options.hash_known_hosts) { 886 /* Add hash of host and IP separately */ 887 r = add_host_to_hostfile(user_hostfiles[0], 888 host, host_key, options.hash_known_hosts) && 889 add_host_to_hostfile(user_hostfiles[0], ip, 890 host_key, options.hash_known_hosts); 891 } else { 892 /* Add unhashed "host,ip" */ 893 r = add_host_to_hostfile(user_hostfiles[0], 894 hostline, host_key, 895 options.hash_known_hosts); 896 } 897 } else { 898 r = add_host_to_hostfile(user_hostfiles[0], host, 899 host_key, options.hash_known_hosts); 900 hostp = host; 901 } 902 903 if (!r) 904 logit("Failed to add the host to the list of known " 905 "hosts (%.500s).", user_hostfiles[0]); 906 else 907 logit("Warning: Permanently added '%.200s' (%s) to the " 908 "list of known hosts.", hostp, type); 909 break; 910 case HOST_REVOKED: 911 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 912 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 913 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 914 error("The %s host key for %s is marked as revoked.", type, host); 915 error("This could mean that a stolen key is being used to"); 916 error("impersonate this host."); 917 918 /* 919 * If strict host key checking is in use, the user will have 920 * to edit the key manually and we can only abort. 921 */ 922 if (options.strict_host_key_checking) { 923 error("%s host key for %.200s was revoked and you have " 924 "requested strict checking.", type, host); 925 goto fail; 926 } 927 goto continue_unsafe; 928 929 case HOST_CHANGED: 930 if (want_cert) { 931 /* 932 * This is only a debug() since it is valid to have 933 * CAs with wildcard DNS matches that don't match 934 * all hosts that one might visit. 935 */ 936 debug("Host certificate authority does not " 937 "match %s in %s:%lu", CA_MARKER, 938 host_found->file, host_found->line); 939 goto fail; 940 } 941 if (readonly == ROQUIET) 942 goto fail; 943 if (options.check_host_ip && host_ip_differ) { 944 char *key_msg; 945 if (ip_status == HOST_NEW) 946 key_msg = "is unknown"; 947 else if (ip_status == HOST_OK) 948 key_msg = "is unchanged"; 949 else 950 key_msg = "has a different value"; 951 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 952 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 953 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 954 error("The %s host key for %s has changed,", type, host); 955 error("and the key for the corresponding IP address %s", ip); 956 error("%s. This could either mean that", key_msg); 957 error("DNS SPOOFING is happening or the IP address for the host"); 958 error("and its host key have changed at the same time."); 959 if (ip_status != HOST_NEW) 960 error("Offending key for IP in %s:%lu", 961 ip_found->file, ip_found->line); 962 } 963 /* The host key has changed. */ 964 warn_changed_key(host_key); 965 error("Add correct host key in %.100s to get rid of this message.", 966 user_hostfiles[0]); 967 error("Offending %s key in %s:%lu", key_type(host_found->key), 968 host_found->file, host_found->line); 969 970 /* 971 * If strict host key checking is in use, the user will have 972 * to edit the key manually and we can only abort. 973 */ 974 if (options.strict_host_key_checking) { 975 error("%s host key for %.200s has changed and you have " 976 "requested strict checking.", type, host); 977 goto fail; 978 } 979 980 continue_unsafe: 981 /* 982 * If strict host key checking has not been requested, allow 983 * the connection but without MITM-able authentication or 984 * forwarding. 985 */ 986 if (options.password_authentication) { 987 error("Password authentication is disabled to avoid " 988 "man-in-the-middle attacks."); 989 options.password_authentication = 0; 990 cancelled_forwarding = 1; 991 } 992 if (options.kbd_interactive_authentication) { 993 error("Keyboard-interactive authentication is disabled" 994 " to avoid man-in-the-middle attacks."); 995 options.kbd_interactive_authentication = 0; 996 options.challenge_response_authentication = 0; 997 cancelled_forwarding = 1; 998 } 999 if (options.challenge_response_authentication) { 1000 error("Challenge/response authentication is disabled" 1001 " to avoid man-in-the-middle attacks."); 1002 options.challenge_response_authentication = 0; 1003 cancelled_forwarding = 1; 1004 } 1005 if (options.forward_agent) { 1006 error("Agent forwarding is disabled to avoid " 1007 "man-in-the-middle attacks."); 1008 options.forward_agent = 0; 1009 cancelled_forwarding = 1; 1010 } 1011 if (options.forward_x11) { 1012 error("X11 forwarding is disabled to avoid " 1013 "man-in-the-middle attacks."); 1014 options.forward_x11 = 0; 1015 cancelled_forwarding = 1; 1016 } 1017 if (options.num_local_forwards > 0 || 1018 options.num_remote_forwards > 0) { 1019 error("Port forwarding is disabled to avoid " 1020 "man-in-the-middle attacks."); 1021 options.num_local_forwards = 1022 options.num_remote_forwards = 0; 1023 cancelled_forwarding = 1; 1024 } 1025 if (options.tun_open != SSH_TUNMODE_NO) { 1026 error("Tunnel forwarding is disabled to avoid " 1027 "man-in-the-middle attacks."); 1028 options.tun_open = SSH_TUNMODE_NO; 1029 cancelled_forwarding = 1; 1030 } 1031 if (options.exit_on_forward_failure && cancelled_forwarding) 1032 fatal("Error: forwarding disabled due to host key " 1033 "check failure"); 1034 1035 /* 1036 * XXX Should permit the user to change to use the new id. 1037 * This could be done by converting the host key to an 1038 * identifying sentence, tell that the host identifies itself 1039 * by that sentence, and ask the user if he/she wishes to 1040 * accept the authentication. 1041 */ 1042 break; 1043 case HOST_FOUND: 1044 fatal("internal error"); 1045 break; 1046 } 1047 1048 if (options.check_host_ip && host_status != HOST_CHANGED && 1049 ip_status == HOST_CHANGED) { 1050 snprintf(msg, sizeof(msg), 1051 "Warning: the %s host key for '%.200s' " 1052 "differs from the key for the IP address '%.128s'" 1053 "\nOffending key for IP in %s:%lu", 1054 type, host, ip, ip_found->file, ip_found->line); 1055 if (host_status == HOST_OK) { 1056 len = strlen(msg); 1057 snprintf(msg + len, sizeof(msg) - len, 1058 "\nMatching host key in %s:%lu", 1059 host_found->file, host_found->line); 1060 } 1061 if (options.strict_host_key_checking == 1) { 1062 logit("%s", msg); 1063 error("Exiting, you have requested strict checking."); 1064 goto fail; 1065 } else if (options.strict_host_key_checking == 2) { 1066 strlcat(msg, "\nAre you sure you want " 1067 "to continue connecting (yes/no)? ", sizeof(msg)); 1068 if (!confirm(msg)) 1069 goto fail; 1070 } else { 1071 logit("%s", msg); 1072 } 1073 } 1074 1075 xfree(ip); 1076 xfree(host); 1077 if (host_hostkeys != NULL) 1078 free_hostkeys(host_hostkeys); 1079 if (ip_hostkeys != NULL) 1080 free_hostkeys(ip_hostkeys); 1081 return 0; 1082 1083 fail: 1084 if (want_cert && host_status != HOST_REVOKED) { 1085 /* 1086 * No matching certificate. Downgrade cert to raw key and 1087 * search normally. 1088 */ 1089 debug("No matching CA found. Retry with plain key"); 1090 raw_key = key_from_private(host_key); 1091 if (key_drop_cert(raw_key) != 0) 1092 fatal("Couldn't drop certificate"); 1093 host_key = raw_key; 1094 goto retry; 1095 } 1096 if (raw_key != NULL) 1097 key_free(raw_key); 1098 xfree(ip); 1099 xfree(host); 1100 if (host_hostkeys != NULL) 1101 free_hostkeys(host_hostkeys); 1102 if (ip_hostkeys != NULL) 1103 free_hostkeys(ip_hostkeys); 1104 return -1; 1105 } 1106 1107 /* returns 0 if key verifies or -1 if key does NOT verify */ 1108 int 1109 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1110 { 1111 int flags = 0; 1112 char *fp; 1113 1114 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1115 debug("Server host key: %s %s", key_type(host_key), fp); 1116 xfree(fp); 1117 1118 /* XXX certs are not yet supported for DNS */ 1119 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1120 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1121 if (flags & DNS_VERIFY_FOUND) { 1122 1123 if (options.verify_host_key_dns == 1 && 1124 flags & DNS_VERIFY_MATCH && 1125 flags & DNS_VERIFY_SECURE) 1126 return 0; 1127 1128 if (flags & DNS_VERIFY_MATCH) { 1129 matching_host_key_dns = 1; 1130 } else { 1131 warn_changed_key(host_key); 1132 error("Update the SSHFP RR in DNS with the new " 1133 "host key to get rid of this message."); 1134 } 1135 } 1136 } 1137 1138 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1139 options.user_hostfiles, options.num_user_hostfiles, 1140 options.system_hostfiles, options.num_system_hostfiles); 1141 } 1142 1143 /* 1144 * Starts a dialog with the server, and authenticates the current user on the 1145 * server. This does not need any extra privileges. The basic connection 1146 * to the server must already have been established before this is called. 1147 * If login fails, this function prints an error and never returns. 1148 * This function does not require super-user privileges. 1149 */ 1150 void 1151 ssh_login(Sensitive *sensitive, const char *orighost, 1152 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1153 { 1154 char *host, *cp; 1155 char *server_user, *local_user; 1156 1157 local_user = xstrdup(pw->pw_name); 1158 server_user = options.user ? options.user : local_user; 1159 1160 /* Convert the user-supplied hostname into all lowercase. */ 1161 host = xstrdup(orighost); 1162 for (cp = host; *cp; cp++) 1163 if (isupper(*cp)) 1164 *cp = (char)tolower(*cp); 1165 1166 /* Exchange protocol version identification strings with the server. */ 1167 ssh_exchange_identification(timeout_ms); 1168 1169 /* Put the connection into non-blocking mode. */ 1170 packet_set_nonblocking(); 1171 1172 /* key exchange */ 1173 /* authenticate user */ 1174 if (compat20) { 1175 ssh_kex2(host, hostaddr, port); 1176 ssh_userauth2(local_user, server_user, host, sensitive); 1177 } else { 1178 ssh_kex(host, hostaddr); 1179 ssh_userauth1(local_user, server_user, host, sensitive); 1180 } 1181 xfree(local_user); 1182 } 1183 1184 void 1185 ssh_put_password(char *password) 1186 { 1187 int size; 1188 char *padded; 1189 1190 if (datafellows & SSH_BUG_PASSWORDPAD) { 1191 packet_put_cstring(password); 1192 return; 1193 } 1194 size = roundup(strlen(password) + 1, 32); 1195 padded = xcalloc(1, size); 1196 strlcpy(padded, password, size); 1197 packet_put_string(padded, size); 1198 memset(padded, 0, size); 1199 xfree(padded); 1200 } 1201 1202 /* print all known host keys for a given host, but skip keys of given type */ 1203 static int 1204 show_other_keys(struct hostkeys *hostkeys, Key *key) 1205 { 1206 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1207 int i, ret = 0; 1208 char *fp, *ra; 1209 const struct hostkey_entry *found; 1210 1211 for (i = 0; type[i] != -1; i++) { 1212 if (type[i] == key->type) 1213 continue; 1214 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1215 continue; 1216 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1217 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1218 logit("WARNING: %s key found for host %s\n" 1219 "in %s:%lu\n" 1220 "%s key fingerprint %s.", 1221 key_type(found->key), 1222 found->host, found->file, found->line, 1223 key_type(found->key), fp); 1224 if (options.visual_host_key) 1225 logit("%s", ra); 1226 xfree(ra); 1227 xfree(fp); 1228 ret = 1; 1229 } 1230 return ret; 1231 } 1232 1233 static void 1234 warn_changed_key(Key *host_key) 1235 { 1236 char *fp; 1237 1238 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1239 1240 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1241 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1242 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1243 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1244 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1245 error("It is also possible that a host key has just been changed."); 1246 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1247 key_type(host_key), fp); 1248 error("Please contact your system administrator."); 1249 1250 xfree(fp); 1251 } 1252 1253 /* 1254 * Execute a local command 1255 */ 1256 int 1257 ssh_local_cmd(const char *args) 1258 { 1259 char *shell; 1260 pid_t pid; 1261 int status; 1262 void (*osighand)(int); 1263 1264 if (!options.permit_local_command || 1265 args == NULL || !*args) 1266 return (1); 1267 1268 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1269 shell = _PATH_BSHELL; 1270 1271 osighand = signal(SIGCHLD, SIG_DFL); 1272 pid = fork(); 1273 if (pid == 0) { 1274 signal(SIGPIPE, SIG_DFL); 1275 debug3("Executing %s -c \"%s\"", shell, args); 1276 execl(shell, shell, "-c", args, (char *)NULL); 1277 error("Couldn't execute %s -c \"%s\": %s", 1278 shell, args, strerror(errno)); 1279 _exit(1); 1280 } else if (pid == -1) 1281 fatal("fork failed: %.100s", strerror(errno)); 1282 while (waitpid(pid, &status, 0) == -1) 1283 if (errno != EINTR) 1284 fatal("Couldn't wait for child: %s", strerror(errno)); 1285 signal(SIGCHLD, osighand); 1286 1287 if (!WIFEXITED(status)) 1288 return (1); 1289 1290 return (WEXITSTATUS(status)); 1291 } 1292
