1 /* $OpenBSD: sshconnect.c,v 1.214 2009/05/28 16:50:16 andreas 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 <netdb.h> 32 #ifdef HAVE_PATHS_H 33 #include <paths.h> 34 #endif 35 #include <pwd.h> 36 #include <stdarg.h> 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <unistd.h> 41 42 #include "xmalloc.h" 43 #include "key.h" 44 #include "hostfile.h" 45 #include "ssh.h" 46 #include "rsa.h" 47 #include "buffer.h" 48 #include "packet.h" 49 #include "uidswap.h" 50 #include "compat.h" 51 #include "key.h" 52 #include "sshconnect.h" 53 #include "hostfile.h" 54 #include "log.h" 55 #include "readconf.h" 56 #include "atomicio.h" 57 #include "misc.h" 58 #include "dns.h" 59 #include "roaming.h" 60 #include "version.h" 61 62 char *client_version_string = NULL; 63 char *server_version_string = NULL; 64 65 static int matching_host_key_dns = 0; 66 67 /* import */ 68 extern Options options; 69 extern char *__progname; 70 extern uid_t original_real_uid; 71 extern uid_t original_effective_uid; 72 extern pid_t proxy_command_pid; 73 74 static int show_other_keys(const char *, Key *); 75 static void warn_changed_key(Key *); 76 77 /* 78 * Connect to the given ssh server using a proxy command. 79 */ 80 static int 81 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 82 { 83 char *command_string, *tmp; 84 int pin[2], pout[2]; 85 pid_t pid; 86 char *shell, strport[NI_MAXSERV]; 87 88 if ((shell = getenv("SHELL")) == NULL) 89 shell = _PATH_BSHELL; 90 91 /* Convert the port number into a string. */ 92 snprintf(strport, sizeof strport, "%hu", port); 93 94 /* 95 * Build the final command string in the buffer by making the 96 * appropriate substitutions to the given proxy command. 97 * 98 * Use "exec" to avoid "sh -c" processes on some platforms 99 * (e.g. Solaris) 100 */ 101 xasprintf(&tmp, "exec %s", proxy_command); 102 command_string = percent_expand(tmp, "h", host, 103 "p", strport, (char *)NULL); 104 xfree(tmp); 105 106 /* Create pipes for communicating with the proxy. */ 107 if (pipe(pin) < 0 || pipe(pout) < 0) 108 fatal("Could not create pipes to communicate with the proxy: %.100s", 109 strerror(errno)); 110 111 debug("Executing proxy command: %.500s", command_string); 112 113 /* Fork and execute the proxy command. */ 114 if ((pid = fork()) == 0) { 115 char *argv[10]; 116 117 /* Child. Permanently give up superuser privileges. */ 118 permanently_drop_suid(original_real_uid); 119 120 /* Redirect stdin and stdout. */ 121 close(pin[1]); 122 if (pin[0] != 0) { 123 if (dup2(pin[0], 0) < 0) 124 perror("dup2 stdin"); 125 close(pin[0]); 126 } 127 close(pout[0]); 128 if (dup2(pout[1], 1) < 0) 129 perror("dup2 stdout"); 130 /* Cannot be 1 because pin allocated two descriptors. */ 131 close(pout[1]); 132 133 /* Stderr is left as it is so that error messages get 134 printed on the user's terminal. */ 135 argv[0] = shell; 136 argv[1] = "-c"; 137 argv[2] = command_string; 138 argv[3] = NULL; 139 140 /* Execute the proxy command. Note that we gave up any 141 extra privileges above. */ 142 execv(argv[0], argv); 143 perror(argv[0]); 144 exit(1); 145 } 146 /* Parent. */ 147 if (pid < 0) 148 fatal("fork failed: %.100s", strerror(errno)); 149 else 150 proxy_command_pid = pid; /* save pid to clean up later */ 151 152 /* Close child side of the descriptors. */ 153 close(pin[0]); 154 close(pout[1]); 155 156 /* Free the command name. */ 157 xfree(command_string); 158 159 /* Set the connection file descriptors. */ 160 packet_set_connection(pout[0], pin[1]); 161 packet_set_timeout(options.server_alive_interval, 162 options.server_alive_count_max); 163 164 /* Indicate OK return */ 165 return 0; 166 } 167 168 /* 169 * Set TCP receive buffer if requested. 170 * Note: tuning needs to happen after the socket is 171 * created but before the connection happens 172 * so winscale is negotiated properly -cjr 173 */ 174 static void 175 ssh_set_socket_recvbuf(int sock) 176 { 177 void *buf = (void *)&options.tcp_rcv_buf; 178 int sz = sizeof(options.tcp_rcv_buf); 179 int socksize; 180 int socksizelen = sizeof(int); 181 182 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 183 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 184 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 185 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 186 } 187 else 188 error("Couldn't set socket receive buffer to %d: %.100s", 189 options.tcp_rcv_buf, strerror(errno)); 190 } 191 192 193 /* 194 * Creates a (possibly privileged) socket for use as the ssh connection. 195 */ 196 static int 197 ssh_create_socket(int privileged, struct addrinfo *ai) 198 { 199 int sock, gaierr; 200 struct addrinfo hints, *res; 201 202 /* 203 * If we are running as root and want to connect to a privileged 204 * port, bind our own socket to a privileged port. 205 */ 206 if (privileged) { 207 int p = IPPORT_RESERVED - 1; 208 PRIV_START; 209 sock = rresvport_af(&p, ai->ai_family); 210 PRIV_END; 211 if (sock < 0) 212 error("rresvport: af=%d %.100s", ai->ai_family, 213 strerror(errno)); 214 else 215 debug("Allocated local port %d.", p); 216 217 if (options.tcp_rcv_buf > 0) 218 ssh_set_socket_recvbuf(sock); 219 return sock; 220 } 221 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 222 if (sock < 0) 223 error("socket: %.100s", strerror(errno)); 224 225 if (options.tcp_rcv_buf > 0) 226 ssh_set_socket_recvbuf(sock); 227 228 /* Bind the socket to an alternative local IP address */ 229 if (options.bind_address == NULL) 230 return sock; 231 232 memset(&hints, 0, sizeof(hints)); 233 hints.ai_family = ai->ai_family; 234 hints.ai_socktype = ai->ai_socktype; 235 hints.ai_protocol = ai->ai_protocol; 236 hints.ai_flags = AI_PASSIVE; 237 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 238 if (gaierr) { 239 error("getaddrinfo: %s: %s", options.bind_address, 240 ssh_gai_strerror(gaierr)); 241 close(sock); 242 return -1; 243 } 244 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 245 error("bind: %s: %s", options.bind_address, strerror(errno)); 246 close(sock); 247 freeaddrinfo(res); 248 return -1; 249 } 250 freeaddrinfo(res); 251 return sock; 252 } 253 254 static int 255 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 256 socklen_t addrlen, int *timeoutp) 257 { 258 fd_set *fdset; 259 struct timeval tv, t_start; 260 socklen_t optlen; 261 int optval, rc, result = -1; 262 263 gettimeofday(&t_start, NULL); 264 265 if (*timeoutp <= 0) { 266 result = connect(sockfd, serv_addr, addrlen); 267 goto done; 268 } 269 270 set_nonblock(sockfd); 271 rc = connect(sockfd, serv_addr, addrlen); 272 if (rc == 0) { 273 unset_nonblock(sockfd); 274 result = 0; 275 goto done; 276 } 277 if (errno != EINPROGRESS) { 278 result = -1; 279 goto done; 280 } 281 282 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 283 sizeof(fd_mask)); 284 FD_SET(sockfd, fdset); 285 ms_to_timeval(&tv, *timeoutp); 286 287 for (;;) { 288 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 289 if (rc != -1 || errno != EINTR) 290 break; 291 } 292 293 switch (rc) { 294 case 0: 295 /* Timed out */ 296 errno = ETIMEDOUT; 297 break; 298 case -1: 299 /* Select error */ 300 debug("select: %s", strerror(errno)); 301 break; 302 case 1: 303 /* Completed or failed */ 304 optval = 0; 305 optlen = sizeof(optval); 306 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 307 &optlen) == -1) { 308 debug("getsockopt: %s", strerror(errno)); 309 break; 310 } 311 if (optval != 0) { 312 errno = optval; 313 break; 314 } 315 result = 0; 316 unset_nonblock(sockfd); 317 break; 318 default: 319 /* Should not occur */ 320 fatal("Bogus return (%d) from select()", rc); 321 } 322 323 xfree(fdset); 324 325 done: 326 if (result == 0 && *timeoutp > 0) { 327 ms_subtract_diff(&t_start, timeoutp); 328 if (*timeoutp <= 0) { 329 errno = ETIMEDOUT; 330 result = -1; 331 } 332 } 333 334 return (result); 335 } 336 337 /* 338 * Opens a TCP/IP connection to the remote server on the given host. 339 * The address of the remote host will be returned in hostaddr. 340 * If port is 0, the default port will be used. If needpriv is true, 341 * a privileged port will be allocated to make the connection. 342 * This requires super-user privileges if needpriv is true. 343 * Connection_attempts specifies the maximum number of tries (one per 344 * second). If proxy_command is non-NULL, it specifies the command (with %h 345 * and %p substituted for host and port, respectively) to use to contact 346 * the daemon. 347 */ 348 int 349 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 350 u_short port, int family, int connection_attempts, int *timeout_ms, 351 int want_keepalive, int needpriv, const char *proxy_command) 352 { 353 int gaierr; 354 int on = 1; 355 int sock = -1, attempt; 356 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 357 struct addrinfo hints, *ai, *aitop; 358 359 debug2("ssh_connect: needpriv %d", needpriv); 360 361 /* If a proxy command is given, connect using it. */ 362 if (proxy_command != NULL) 363 return ssh_proxy_connect(host, port, proxy_command); 364 365 /* No proxy command. */ 366 367 memset(&hints, 0, sizeof(hints)); 368 hints.ai_family = family; 369 hints.ai_socktype = SOCK_STREAM; 370 snprintf(strport, sizeof strport, "%u", port); 371 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 372 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 373 host, ssh_gai_strerror(gaierr)); 374 375 for (attempt = 0; attempt < connection_attempts; attempt++) { 376 if (attempt > 0) { 377 /* Sleep a moment before retrying. */ 378 sleep(1); 379 debug("Trying again..."); 380 } 381 /* 382 * Loop through addresses for this host, and try each one in 383 * sequence until the connection succeeds. 384 */ 385 for (ai = aitop; ai; ai = ai->ai_next) { 386 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 387 continue; 388 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 389 ntop, sizeof(ntop), strport, sizeof(strport), 390 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 391 error("ssh_connect: getnameinfo failed"); 392 continue; 393 } 394 debug("Connecting to %.200s [%.100s] port %s.", 395 host, ntop, strport); 396 397 /* Create a socket for connecting. */ 398 sock = ssh_create_socket(needpriv, ai); 399 if (sock < 0) 400 /* Any error is already output */ 401 continue; 402 403 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 404 timeout_ms) >= 0) { 405 /* Successful connection. */ 406 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 407 break; 408 } else { 409 debug("connect to address %s port %s: %s", 410 ntop, strport, strerror(errno)); 411 close(sock); 412 sock = -1; 413 } 414 } 415 if (sock != -1) 416 break; /* Successful connection. */ 417 } 418 419 freeaddrinfo(aitop); 420 421 /* Return failure if we didn't get a successful connection. */ 422 if (sock == -1) { 423 error("ssh: connect to host %s port %s: %s", 424 host, strport, strerror(errno)); 425 return (-1); 426 } 427 428 debug("Connection established."); 429 430 /* Set SO_KEEPALIVE if requested. */ 431 if (want_keepalive && 432 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 433 sizeof(on)) < 0) 434 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 435 436 /* Set the connection. */ 437 packet_set_connection(sock, sock); 438 packet_set_timeout(options.server_alive_interval, 439 options.server_alive_count_max); 440 441 return 0; 442 } 443 444 /* 445 * Waits for the server identification string, and sends our own 446 * identification string. 447 */ 448 void 449 ssh_exchange_identification(int timeout_ms) 450 { 451 char buf[256], remote_version[256]; /* must be same size! */ 452 int remote_major, remote_minor, mismatch; 453 int connection_in = packet_get_connection_in(); 454 int connection_out = packet_get_connection_out(); 455 int minor1 = PROTOCOL_MINOR_1; 456 u_int i, n; 457 size_t len; 458 int fdsetsz, remaining, rc; 459 struct timeval t_start, t_remaining; 460 fd_set *fdset; 461 462 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 463 fdset = xcalloc(1, fdsetsz); 464 465 /* Read other side's version identification. */ 466 remaining = timeout_ms; 467 for (n = 0;;) { 468 for (i = 0; i < sizeof(buf) - 1; i++) { 469 if (timeout_ms > 0) { 470 gettimeofday(&t_start, NULL); 471 ms_to_timeval(&t_remaining, remaining); 472 FD_SET(connection_in, fdset); 473 rc = select(connection_in + 1, fdset, NULL, 474 fdset, &t_remaining); 475 ms_subtract_diff(&t_start, &remaining); 476 if (rc == 0 || remaining <= 0) 477 fatal("Connection timed out during " 478 "banner exchange"); 479 if (rc == -1) { 480 if (errno == EINTR) 481 continue; 482 fatal("ssh_exchange_identification: " 483 "select: %s", strerror(errno)); 484 } 485 } 486 487 len = roaming_atomicio(read, connection_in, &buf[i], 1); 488 489 if (len != 1 && errno == EPIPE) 490 fatal("ssh_exchange_identification: " 491 "Connection closed by remote host"); 492 else if (len != 1) 493 fatal("ssh_exchange_identification: " 494 "read: %.100s", strerror(errno)); 495 if (buf[i] == '\r') { 496 buf[i] = '\n'; 497 buf[i + 1] = 0; 498 continue; /**XXX wait for \n */ 499 } 500 if (buf[i] == '\n') { 501 buf[i + 1] = 0; 502 break; 503 } 504 if (++n > 65536) 505 fatal("ssh_exchange_identification: " 506 "No banner received"); 507 } 508 buf[sizeof(buf) - 1] = 0; 509 if (strncmp(buf, "SSH-", 4) == 0) 510 break; 511 debug("ssh_exchange_identification: %s", buf); 512 } 513 server_version_string = xstrdup(buf); 514 xfree(fdset); 515 516 /* 517 * Check that the versions match. In future this might accept 518 * several versions and set appropriate flags to handle them. 519 */ 520 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 521 &remote_major, &remote_minor, remote_version) != 3) 522 fatal("Bad remote protocol version identification: '%.100s'", buf); 523 debug("Remote protocol version %d.%d, remote software version %.100s", 524 remote_major, remote_minor, remote_version); 525 526 compat_datafellows(remote_version); 527 mismatch = 0; 528 529 switch (remote_major) { 530 case 1: 531 if (remote_minor == 99 && 532 (options.protocol & SSH_PROTO_2) && 533 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 534 enable_compat20(); 535 break; 536 } 537 if (!(options.protocol & SSH_PROTO_1)) { 538 mismatch = 1; 539 break; 540 } 541 if (remote_minor < 3) { 542 fatal("Remote machine has too old SSH software version."); 543 } else if (remote_minor == 3 || remote_minor == 4) { 544 /* We speak 1.3, too. */ 545 enable_compat13(); 546 minor1 = 3; 547 if (options.forward_agent) { 548 logit("Agent forwarding disabled for protocol 1.3"); 549 options.forward_agent = 0; 550 } 551 } 552 break; 553 case 2: 554 if (options.protocol & SSH_PROTO_2) { 555 enable_compat20(); 556 break; 557 } 558 /* FALLTHROUGH */ 559 default: 560 mismatch = 1; 561 break; 562 } 563 if (mismatch) 564 fatal("Protocol major versions differ: %d vs. %d", 565 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 566 remote_major); 567 /* Send our own protocol version identification. */ 568 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 569 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 570 compat20 ? PROTOCOL_MINOR_2 : minor1, 571 SSH_RELEASE, compat20 ? "\r\n" : "\n"); 572 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 573 != strlen(buf)) 574 fatal("write: %.100s", strerror(errno)); 575 client_version_string = xstrdup(buf); 576 chop(client_version_string); 577 chop(server_version_string); 578 debug("Local version string %.100s", client_version_string); 579 } 580 581 /* defaults to 'no' */ 582 static int 583 confirm(const char *prompt) 584 { 585 const char *msg, *again = "Please type 'yes' or 'no': "; 586 char *p; 587 int ret = -1; 588 589 if (options.batch_mode) 590 return 0; 591 for (msg = prompt;;msg = again) { 592 p = read_passphrase(msg, RP_ECHO); 593 if (p == NULL || 594 (p[0] == '\0') || (p[0] == '\n') || 595 strncasecmp(p, "no", 2) == 0) 596 ret = 0; 597 if (p && strncasecmp(p, "yes", 3) == 0) 598 ret = 1; 599 if (p) 600 xfree(p); 601 if (ret != -1) 602 return ret; 603 } 604 } 605 606 /* 607 * check whether the supplied host key is valid, return -1 if the key 608 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 609 */ 610 #define RDRW 0 611 #define RDONLY 1 612 #define ROQUIET 2 613 static int 614 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 615 Key *host_key, int readonly, const char *user_hostfile, 616 const char *system_hostfile) 617 { 618 Key *file_key; 619 const char *type = key_type(host_key); 620 char *ip = NULL, *host = NULL; 621 char hostline[1000], *hostp, *fp, *ra; 622 HostStatus host_status; 623 HostStatus ip_status; 624 int r, local = 0, host_ip_differ = 0; 625 int salen; 626 char ntop[NI_MAXHOST]; 627 char msg[1024]; 628 int len, host_line, ip_line, cancelled_forwarding = 0; 629 const char *host_file = NULL, *ip_file = NULL; 630 631 /* 632 * Force accepting of the host key for loopback/localhost. The 633 * problem is that if the home directory is NFS-mounted to multiple 634 * machines, localhost will refer to a different machine in each of 635 * them, and the user will get bogus HOST_CHANGED warnings. This 636 * essentially disables host authentication for localhost; however, 637 * this is probably not a real problem. 638 */ 639 /** hostaddr == 0! */ 640 switch (hostaddr->sa_family) { 641 case AF_INET: 642 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 643 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 644 salen = sizeof(struct sockaddr_in); 645 break; 646 case AF_INET6: 647 local = IN6_IS_ADDR_LOOPBACK( 648 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 649 salen = sizeof(struct sockaddr_in6); 650 break; 651 default: 652 local = 0; 653 salen = sizeof(struct sockaddr_storage); 654 break; 655 } 656 if (options.no_host_authentication_for_localhost == 1 && local && 657 options.host_key_alias == NULL) { 658 debug("Forcing accepting of host key for " 659 "loopback/localhost."); 660 return 0; 661 } 662 663 /* 664 * We don't have the remote ip-address for connections 665 * using a proxy command 666 */ 667 if (options.proxy_command == NULL) { 668 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), 669 NULL, 0, NI_NUMERICHOST) != 0) 670 fatal("check_host_key: getnameinfo failed"); 671 ip = put_host_port(ntop, port); 672 } else { 673 ip = xstrdup("<no hostip for proxy command>"); 674 } 675 676 /* 677 * Turn off check_host_ip if the connection is to localhost, via proxy 678 * command or if we don't have a hostname to compare with 679 */ 680 if (options.check_host_ip && (local || 681 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 682 options.check_host_ip = 0; 683 684 /* 685 * Allow the user to record the key under a different name or 686 * differentiate a non-standard port. This is useful for ssh 687 * tunneling over forwarded connections or if you run multiple 688 * sshd's on different ports on the same machine. 689 */ 690 if (options.host_key_alias != NULL) { 691 host = xstrdup(options.host_key_alias); 692 debug("using hostkeyalias: %s", host); 693 } else { 694 host = put_host_port(hostname, port); 695 } 696 697 /* 698 * Store the host key from the known host file in here so that we can 699 * compare it with the key for the IP address. 700 */ 701 file_key = key_new(host_key->type); 702 703 /* 704 * Check if the host key is present in the user's list of known 705 * hosts or in the systemwide list. 706 */ 707 host_file = user_hostfile; 708 host_status = check_host_in_hostfile(host_file, host, host_key, 709 file_key, &host_line); 710 if (host_status == HOST_NEW) { 711 host_file = system_hostfile; 712 host_status = check_host_in_hostfile(host_file, host, host_key, 713 file_key, &host_line); 714 } 715 /* 716 * Also perform check for the ip address, skip the check if we are 717 * localhost or the hostname was an ip address to begin with 718 */ 719 if (options.check_host_ip) { 720 Key *ip_key = key_new(host_key->type); 721 722 ip_file = user_hostfile; 723 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 724 ip_key, &ip_line); 725 if (ip_status == HOST_NEW) { 726 ip_file = system_hostfile; 727 ip_status = check_host_in_hostfile(ip_file, ip, 728 host_key, ip_key, &ip_line); 729 } 730 if (host_status == HOST_CHANGED && 731 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 732 host_ip_differ = 1; 733 734 key_free(ip_key); 735 } else 736 ip_status = host_status; 737 738 key_free(file_key); 739 740 switch (host_status) { 741 case HOST_OK: 742 /* The host is known and the key matches. */ 743 debug("Host '%.200s' is known and matches the %s host key.", 744 host, type); 745 debug("Found key in %s:%d", host_file, host_line); 746 if (options.check_host_ip && ip_status == HOST_NEW) { 747 if (readonly) 748 logit("%s host key for IP address " 749 "'%.128s' not in list of known hosts.", 750 type, ip); 751 else if (!add_host_to_hostfile(user_hostfile, ip, 752 host_key, options.hash_known_hosts)) 753 logit("Failed to add the %s host key for IP " 754 "address '%.128s' to the list of known " 755 "hosts (%.30s).", type, ip, user_hostfile); 756 else 757 logit("Warning: Permanently added the %s host " 758 "key for IP address '%.128s' to the list " 759 "of known hosts.", type, ip); 760 } else if (options.visual_host_key) { 761 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 762 ra = key_fingerprint(host_key, SSH_FP_MD5, 763 SSH_FP_RANDOMART); 764 logit("Host key fingerprint is %s\n%s\n", fp, ra); 765 xfree(ra); 766 xfree(fp); 767 } 768 break; 769 case HOST_NEW: 770 if (options.host_key_alias == NULL && port != 0 && 771 port != SSH_DEFAULT_PORT) { 772 debug("checking without port identifier"); 773 if (check_host_key(hostname, hostaddr, 0, host_key, 774 ROQUIET, user_hostfile, system_hostfile) == 0) { 775 debug("found matching key w/out port"); 776 break; 777 } 778 } 779 if (readonly) 780 goto fail; 781 /* The host is new. */ 782 if (options.strict_host_key_checking == 1) { 783 /* 784 * User has requested strict host key checking. We 785 * will not add the host key automatically. The only 786 * alternative left is to abort. 787 */ 788 error("No %s host key is known for %.200s and you " 789 "have requested strict checking.", type, host); 790 goto fail; 791 } else if (options.strict_host_key_checking == 2) { 792 char msg1[1024], msg2[1024]; 793 794 if (show_other_keys(host, host_key)) 795 snprintf(msg1, sizeof(msg1), 796 "\nbut keys of different type are already" 797 " known for this host."); 798 else 799 snprintf(msg1, sizeof(msg1), "."); 800 /* The default */ 801 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 802 ra = key_fingerprint(host_key, SSH_FP_MD5, 803 SSH_FP_RANDOMART); 804 msg2[0] = '\0'; 805 if (options.verify_host_key_dns) { 806 if (matching_host_key_dns) 807 snprintf(msg2, sizeof(msg2), 808 "Matching host key fingerprint" 809 " found in DNS.\n"); 810 else 811 snprintf(msg2, sizeof(msg2), 812 "No matching host key fingerprint" 813 " found in DNS.\n"); 814 } 815 snprintf(msg, sizeof(msg), 816 "The authenticity of host '%.200s (%s)' can't be " 817 "established%s\n" 818 "%s key fingerprint is %s.%s%s\n%s" 819 "Are you sure you want to continue connecting " 820 "(yes/no)? ", 821 host, ip, msg1, type, fp, 822 options.visual_host_key ? "\n" : "", 823 options.visual_host_key ? ra : "", 824 msg2); 825 xfree(ra); 826 xfree(fp); 827 if (!confirm(msg)) 828 goto fail; 829 } 830 /* 831 * If not in strict mode, add the key automatically to the 832 * local known_hosts file. 833 */ 834 if (options.check_host_ip && ip_status == HOST_NEW) { 835 snprintf(hostline, sizeof(hostline), "%s,%s", 836 host, ip); 837 hostp = hostline; 838 if (options.hash_known_hosts) { 839 /* Add hash of host and IP separately */ 840 r = add_host_to_hostfile(user_hostfile, host, 841 host_key, options.hash_known_hosts) && 842 add_host_to_hostfile(user_hostfile, ip, 843 host_key, options.hash_known_hosts); 844 } else { 845 /* Add unhashed "host,ip" */ 846 r = add_host_to_hostfile(user_hostfile, 847 hostline, host_key, 848 options.hash_known_hosts); 849 } 850 } else { 851 r = add_host_to_hostfile(user_hostfile, host, host_key, 852 options.hash_known_hosts); 853 hostp = host; 854 } 855 856 if (!r) 857 logit("Failed to add the host to the list of known " 858 "hosts (%.500s).", user_hostfile); 859 else 860 logit("Warning: Permanently added '%.200s' (%s) to the " 861 "list of known hosts.", hostp, type); 862 break; 863 case HOST_CHANGED: 864 if (readonly == ROQUIET) 865 goto fail; 866 if (options.check_host_ip && host_ip_differ) { 867 char *key_msg; 868 if (ip_status == HOST_NEW) 869 key_msg = "is unknown"; 870 else if (ip_status == HOST_OK) 871 key_msg = "is unchanged"; 872 else 873 key_msg = "has a different value"; 874 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 875 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 876 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 877 error("The %s host key for %s has changed,", type, host); 878 error("and the key for the corresponding IP address %s", ip); 879 error("%s. This could either mean that", key_msg); 880 error("DNS SPOOFING is happening or the IP address for the host"); 881 error("and its host key have changed at the same time."); 882 if (ip_status != HOST_NEW) 883 error("Offending key for IP in %s:%d", ip_file, ip_line); 884 } 885 /* The host key has changed. */ 886 warn_changed_key(host_key); 887 error("Add correct host key in %.100s to get rid of this message.", 888 user_hostfile); 889 error("Offending key in %s:%d", host_file, host_line); 890 891 /* 892 * If strict host key checking is in use, the user will have 893 * to edit the key manually and we can only abort. 894 */ 895 if (options.strict_host_key_checking) { 896 error("%s host key for %.200s has changed and you have " 897 "requested strict checking.", type, host); 898 goto fail; 899 } 900 901 /* 902 * If strict host key checking has not been requested, allow 903 * the connection but without MITM-able authentication or 904 * forwarding. 905 */ 906 if (options.password_authentication) { 907 error("Password authentication is disabled to avoid " 908 "man-in-the-middle attacks."); 909 options.password_authentication = 0; 910 cancelled_forwarding = 1; 911 } 912 if (options.kbd_interactive_authentication) { 913 error("Keyboard-interactive authentication is disabled" 914 " to avoid man-in-the-middle attacks."); 915 options.kbd_interactive_authentication = 0; 916 options.challenge_response_authentication = 0; 917 cancelled_forwarding = 1; 918 } 919 if (options.challenge_response_authentication) { 920 error("Challenge/response authentication is disabled" 921 " to avoid man-in-the-middle attacks."); 922 options.challenge_response_authentication = 0; 923 cancelled_forwarding = 1; 924 } 925 if (options.forward_agent) { 926 error("Agent forwarding is disabled to avoid " 927 "man-in-the-middle attacks."); 928 options.forward_agent = 0; 929 cancelled_forwarding = 1; 930 } 931 if (options.forward_x11) { 932 error("X11 forwarding is disabled to avoid " 933 "man-in-the-middle attacks."); 934 options.forward_x11 = 0; 935 cancelled_forwarding = 1; 936 } 937 if (options.num_local_forwards > 0 || 938 options.num_remote_forwards > 0) { 939 error("Port forwarding is disabled to avoid " 940 "man-in-the-middle attacks."); 941 options.num_local_forwards = 942 options.num_remote_forwards = 0; 943 cancelled_forwarding = 1; 944 } 945 if (options.tun_open != SSH_TUNMODE_NO) { 946 error("Tunnel forwarding is disabled to avoid " 947 "man-in-the-middle attacks."); 948 options.tun_open = SSH_TUNMODE_NO; 949 cancelled_forwarding = 1; 950 } 951 if (options.exit_on_forward_failure && cancelled_forwarding) 952 fatal("Error: forwarding disabled due to host key " 953 "check failure"); 954 955 /* 956 * XXX Should permit the user to change to use the new id. 957 * This could be done by converting the host key to an 958 * identifying sentence, tell that the host identifies itself 959 * by that sentence, and ask the user if he/she whishes to 960 * accept the authentication. 961 */ 962 break; 963 case HOST_FOUND: 964 fatal("internal error"); 965 break; 966 } 967 968 if (options.check_host_ip && host_status != HOST_CHANGED && 969 ip_status == HOST_CHANGED) { 970 snprintf(msg, sizeof(msg), 971 "Warning: the %s host key for '%.200s' " 972 "differs from the key for the IP address '%.128s'" 973 "\nOffending key for IP in %s:%d", 974 type, host, ip, ip_file, ip_line); 975 if (host_status == HOST_OK) { 976 len = strlen(msg); 977 snprintf(msg + len, sizeof(msg) - len, 978 "\nMatching host key in %s:%d", 979 host_file, host_line); 980 } 981 if (options.strict_host_key_checking == 1) { 982 logit("%s", msg); 983 error("Exiting, you have requested strict checking."); 984 goto fail; 985 } else if (options.strict_host_key_checking == 2) { 986 strlcat(msg, "\nAre you sure you want " 987 "to continue connecting (yes/no)? ", sizeof(msg)); 988 if (!confirm(msg)) 989 goto fail; 990 } else { 991 logit("%s", msg); 992 } 993 } 994 995 xfree(ip); 996 xfree(host); 997 return 0; 998 999 fail: 1000 xfree(ip); 1001 xfree(host); 1002 return -1; 1003 } 1004 1005 /* returns 0 if key verifies or -1 if key does NOT verify */ 1006 int 1007 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1008 { 1009 struct stat st; 1010 int flags = 0; 1011 1012 if (options.verify_host_key_dns && 1013 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1014 1015 if (flags & DNS_VERIFY_FOUND) { 1016 1017 if (options.verify_host_key_dns == 1 && 1018 flags & DNS_VERIFY_MATCH && 1019 flags & DNS_VERIFY_SECURE) 1020 return 0; 1021 1022 if (flags & DNS_VERIFY_MATCH) { 1023 matching_host_key_dns = 1; 1024 } else { 1025 warn_changed_key(host_key); 1026 error("Update the SSHFP RR in DNS with the new " 1027 "host key to get rid of this message."); 1028 } 1029 } 1030 } 1031 1032 /* return ok if the key can be found in an old keyfile */ 1033 if (stat(options.system_hostfile2, &st) == 0 || 1034 stat(options.user_hostfile2, &st) == 0) { 1035 if (check_host_key(host, hostaddr, options.port, host_key, 1036 RDONLY, options.user_hostfile2, 1037 options.system_hostfile2) == 0) 1038 return 0; 1039 } 1040 return check_host_key(host, hostaddr, options.port, host_key, 1041 RDRW, options.user_hostfile, options.system_hostfile); 1042 } 1043 1044 /* 1045 * Starts a dialog with the server, and authenticates the current user on the 1046 * server. This does not need any extra privileges. The basic connection 1047 * to the server must already have been established before this is called. 1048 * If login fails, this function prints an error and never returns. 1049 * This function does not require super-user privileges. 1050 */ 1051 void 1052 ssh_login(Sensitive *sensitive, const char *orighost, 1053 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 1054 { 1055 char *host, *cp; 1056 char *server_user, *local_user; 1057 1058 local_user = xstrdup(pw->pw_name); 1059 server_user = options.user ? options.user : local_user; 1060 1061 /* Convert the user-supplied hostname into all lowercase. */ 1062 host = xstrdup(orighost); 1063 for (cp = host; *cp; cp++) 1064 if (isupper(*cp)) 1065 *cp = (char)tolower(*cp); 1066 1067 /* Exchange protocol version identification strings with the server. */ 1068 ssh_exchange_identification(timeout_ms); 1069 1070 /* Put the connection into non-blocking mode. */ 1071 packet_set_nonblocking(); 1072 1073 /* key exchange */ 1074 /* authenticate user */ 1075 if (compat20) { 1076 ssh_kex2(host, hostaddr); 1077 ssh_userauth2(local_user, server_user, host, sensitive); 1078 } else { 1079 ssh_kex(host, hostaddr); 1080 ssh_userauth1(local_user, server_user, host, sensitive); 1081 } 1082 xfree(local_user); 1083 } 1084 1085 void 1086 ssh_put_password(char *password) 1087 { 1088 int size; 1089 char *padded; 1090 1091 if (datafellows & SSH_BUG_PASSWORDPAD) { 1092 packet_put_cstring(password); 1093 return; 1094 } 1095 size = roundup(strlen(password) + 1, 32); 1096 padded = xcalloc(1, size); 1097 strlcpy(padded, password, size); 1098 packet_put_string(padded, size); 1099 memset(padded, 0, size); 1100 xfree(padded); 1101 } 1102 1103 static int 1104 show_key_from_file(const char *file, const char *host, int keytype) 1105 { 1106 Key *found; 1107 char *fp, *ra; 1108 int line, ret; 1109 1110 found = key_new(keytype); 1111 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1112 keytype, found, &line))) { 1113 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1114 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); 1115 logit("WARNING: %s key found for host %s\n" 1116 "in %s:%d\n" 1117 "%s key fingerprint %s.\n%s\n", 1118 key_type(found), host, file, line, 1119 key_type(found), fp, ra); 1120 xfree(ra); 1121 xfree(fp); 1122 } 1123 key_free(found); 1124 return (ret); 1125 } 1126 1127 /* print all known host keys for a given host, but skip keys of given type */ 1128 static int 1129 show_other_keys(const char *host, Key *key) 1130 { 1131 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1132 int i, found = 0; 1133 1134 for (i = 0; type[i] != -1; i++) { 1135 if (type[i] == key->type) 1136 continue; 1137 if (type[i] != KEY_RSA1 && 1138 show_key_from_file(options.user_hostfile2, host, type[i])) { 1139 found = 1; 1140 continue; 1141 } 1142 if (type[i] != KEY_RSA1 && 1143 show_key_from_file(options.system_hostfile2, host, type[i])) { 1144 found = 1; 1145 continue; 1146 } 1147 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1148 found = 1; 1149 continue; 1150 } 1151 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1152 found = 1; 1153 continue; 1154 } 1155 debug2("no key of type %d for host %s", type[i], host); 1156 } 1157 return (found); 1158 } 1159 1160 static void 1161 warn_changed_key(Key *host_key) 1162 { 1163 char *fp; 1164 const char *type = key_type(host_key); 1165 1166 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1167 1168 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1169 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1170 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1171 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1172 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1173 error("It is also possible that the %s host key has just been changed.", type); 1174 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1175 type, fp); 1176 error("Please contact your system administrator."); 1177 1178 xfree(fp); 1179 } 1180 1181 /* 1182 * Execute a local command 1183 */ 1184 int 1185 ssh_local_cmd(const char *args) 1186 { 1187 char *shell; 1188 pid_t pid; 1189 int status; 1190 1191 if (!options.permit_local_command || 1192 args == NULL || !*args) 1193 return (1); 1194 1195 if ((shell = getenv("SHELL")) == NULL) 1196 shell = _PATH_BSHELL; 1197 1198 pid = fork(); 1199 if (pid == 0) { 1200 debug3("Executing %s -c \"%s\"", shell, args); 1201 execl(shell, shell, "-c", args, (char *)NULL); 1202 error("Couldn't execute %s -c \"%s\": %s", 1203 shell, args, strerror(errno)); 1204 _exit(1); 1205 } else if (pid == -1) 1206 fatal("fork failed: %.100s", strerror(errno)); 1207 while (waitpid(pid, &status, 0) == -1) 1208 if (errno != EINTR) 1209 fatal("Couldn't wait for child: %s", strerror(errno)); 1210 1211 if (!WIFEXITED(status)) 1212 return (1); 1213 1214 return (WEXITSTATUS(status)); 1215 } 1216