1 /* $OpenBSD: sshconnect.c,v 1.224 2010/04/16 21:14:27 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Code to connect to a remote host, and to perform the client side of the 7 * login (authentication) dialog. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16 #include "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 <stdarg.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include <unistd.h> 42 43 #include "xmalloc.h" 44 #include "key.h" 45 #include "hostfile.h" 46 #include "ssh.h" 47 #include "rsa.h" 48 #include "buffer.h" 49 #include "packet.h" 50 #include "uidswap.h" 51 #include "compat.h" 52 #include "key.h" 53 #include "sshconnect.h" 54 #include "hostfile.h" 55 #include "log.h" 56 #include "readconf.h" 57 #include "atomicio.h" 58 #include "misc.h" 59 #include "dns.h" 60 #include "roaming.h" 61 #include "ssh2.h" 62 #include "version.h" 63 64 char *client_version_string = NULL; 65 char *server_version_string = NULL; 66 67 static int matching_host_key_dns = 0; 68 69 /* import */ 70 extern Options options; 71 extern char *__progname; 72 extern uid_t original_real_uid; 73 extern uid_t original_effective_uid; 74 extern pid_t proxy_command_pid; 75 76 static int show_other_keys(const char *, Key *); 77 static void warn_changed_key(Key *); 78 79 /* 80 * Connect to the given ssh server using a proxy command. 81 */ 82 static int 83 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 84 { 85 char *command_string, *tmp; 86 int pin[2], pout[2]; 87 pid_t pid; 88 char *shell, strport[NI_MAXSERV]; 89 90 if ((shell = getenv("SHELL")) == NULL) 91 shell = _PATH_BSHELL; 92 93 /* Convert the port number into a string. */ 94 snprintf(strport, sizeof strport, "%hu", port); 95 96 /* 97 * Build the final command string in the buffer by making the 98 * appropriate substitutions to the given proxy command. 99 * 100 * Use "exec" to avoid "sh -c" processes on some platforms 101 * (e.g. Solaris) 102 */ 103 xasprintf(&tmp, "exec %s", proxy_command); 104 command_string = percent_expand(tmp, "h", host, "p", strport, 105 "r", options.user, (char *)NULL); 106 xfree(tmp); 107 108 /* Create pipes for communicating with the proxy. */ 109 if (pipe(pin) < 0 || pipe(pout) < 0) 110 fatal("Could not create pipes to communicate with the proxy: %.100s", 111 strerror(errno)); 112 113 debug("Executing proxy command: %.500s", command_string); 114 115 /* Fork and execute the proxy command. */ 116 if ((pid = fork()) == 0) { 117 char *argv[10]; 118 119 /* Child. Permanently give up superuser privileges. */ 120 permanently_drop_suid(original_real_uid); 121 122 /* Redirect stdin and stdout. */ 123 close(pin[1]); 124 if (pin[0] != 0) { 125 if (dup2(pin[0], 0) < 0) 126 perror("dup2 stdin"); 127 close(pin[0]); 128 } 129 close(pout[0]); 130 if (dup2(pout[1], 1) < 0) 131 perror("dup2 stdout"); 132 /* Cannot be 1 because pin allocated two descriptors. */ 133 close(pout[1]); 134 135 /* Stderr is left as it is so that error messages get 136 printed on the user's terminal. */ 137 argv[0] = shell; 138 argv[1] = "-c"; 139 argv[2] = command_string; 140 argv[3] = NULL; 141 142 /* Execute the proxy command. Note that we gave up any 143 extra privileges above. */ 144 execv(argv[0], argv); 145 perror(argv[0]); 146 exit(1); 147 } 148 /* Parent. */ 149 if (pid < 0) 150 fatal("fork failed: %.100s", strerror(errno)); 151 else 152 proxy_command_pid = pid; /* save pid to clean up later */ 153 154 /* Close child side of the descriptors. */ 155 close(pin[0]); 156 close(pout[1]); 157 158 /* Free the command name. */ 159 xfree(command_string); 160 161 /* Set the connection file descriptors. */ 162 packet_set_connection(pout[0], pin[1]); 163 packet_set_timeout(options.server_alive_interval, 164 options.server_alive_count_max); 165 166 /* Indicate OK return */ 167 return 0; 168 } 169 170 /* 171 * Set TCP receive buffer if requested. 172 * Note: tuning needs to happen after the socket is 173 * created but before the connection happens 174 * so winscale is negotiated properly -cjr 175 */ 176 static void 177 ssh_set_socket_recvbuf(int sock) 178 { 179 void *buf = (void *)&options.tcp_rcv_buf; 180 int sz = sizeof(options.tcp_rcv_buf); 181 int socksize; 182 int socksizelen = sizeof(int); 183 184 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 185 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 186 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 187 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 188 } 189 else 190 error("Couldn't set socket receive buffer to %d: %.100s", 191 options.tcp_rcv_buf, strerror(errno)); 192 } 193 194 195 /* 196 * Creates a (possibly privileged) socket for use as the ssh connection. 197 */ 198 static int 199 ssh_create_socket(int privileged, struct addrinfo *ai) 200 { 201 int sock, gaierr; 202 struct addrinfo hints, *res; 203 204 /* 205 * If we are running as root and want to connect to a privileged 206 * port, bind our own socket to a privileged port. 207 */ 208 if (privileged) { 209 int p = IPPORT_RESERVED - 1; 210 PRIV_START; 211 sock = rresvport_af(&p, ai->ai_family); 212 PRIV_END; 213 if (sock < 0) 214 error("rresvport: af=%d %.100s", ai->ai_family, 215 strerror(errno)); 216 else 217 debug("Allocated local port %d.", p); 218 219 if (options.tcp_rcv_buf > 0) 220 ssh_set_socket_recvbuf(sock); 221 return sock; 222 } 223 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 224 if (sock < 0) { 225 error("socket: %.100s", strerror(errno)); 226 return -1; 227 } 228 fcntl(sock, F_SETFD, FD_CLOEXEC); 229 230 if (options.tcp_rcv_buf > 0) 231 ssh_set_socket_recvbuf(sock); 232 233 /* Bind the socket to an alternative local IP address */ 234 if (options.bind_address == NULL) 235 return sock; 236 237 memset(&hints, 0, sizeof(hints)); 238 hints.ai_family = ai->ai_family; 239 hints.ai_socktype = ai->ai_socktype; 240 hints.ai_protocol = ai->ai_protocol; 241 hints.ai_flags = AI_PASSIVE; 242 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 243 if (gaierr) { 244 error("getaddrinfo: %s: %s", options.bind_address, 245 ssh_gai_strerror(gaierr)); 246 close(sock); 247 return -1; 248 } 249 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 250 error("bind: %s: %s", options.bind_address, strerror(errno)); 251 close(sock); 252 freeaddrinfo(res); 253 return -1; 254 } 255 freeaddrinfo(res); 256 return sock; 257 } 258 259 static int 260 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 261 socklen_t addrlen, int *timeoutp) 262 { 263 fd_set *fdset; 264 struct timeval tv, t_start; 265 socklen_t optlen; 266 int optval, rc, result = -1; 267 268 gettimeofday(&t_start, NULL); 269 270 if (*timeoutp <= 0) { 271 result = connect(sockfd, serv_addr, addrlen); 272 goto done; 273 } 274 275 set_nonblock(sockfd); 276 rc = connect(sockfd, serv_addr, addrlen); 277 if (rc == 0) { 278 unset_nonblock(sockfd); 279 result = 0; 280 goto done; 281 } 282 if (errno != EINPROGRESS) { 283 result = -1; 284 goto done; 285 } 286 287 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 288 sizeof(fd_mask)); 289 FD_SET(sockfd, fdset); 290 ms_to_timeval(&tv, *timeoutp); 291 292 for (;;) { 293 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 294 if (rc != -1 || errno != EINTR) 295 break; 296 } 297 298 switch (rc) { 299 case 0: 300 /* Timed out */ 301 errno = ETIMEDOUT; 302 break; 303 case -1: 304 /* Select error */ 305 debug("select: %s", strerror(errno)); 306 break; 307 case 1: 308 /* Completed or failed */ 309 optval = 0; 310 optlen = sizeof(optval); 311 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 312 &optlen) == -1) { 313 debug("getsockopt: %s", strerror(errno)); 314 break; 315 } 316 if (optval != 0) { 317 errno = optval; 318 break; 319 } 320 result = 0; 321 unset_nonblock(sockfd); 322 break; 323 default: 324 /* Should not occur */ 325 fatal("Bogus return (%d) from select()", rc); 326 } 327 328 xfree(fdset); 329 330 done: 331 if (result == 0 && *timeoutp > 0) { 332 ms_subtract_diff(&t_start, timeoutp); 333 if (*timeoutp <= 0) { 334 errno = ETIMEDOUT; 335 result = -1; 336 } 337 } 338 339 return (result); 340 } 341 342 /* 343 * Opens a TCP/IP connection to the remote server on the given host. 344 * The address of the remote host will be returned in hostaddr. 345 * If port is 0, the default port will be used. If needpriv is true, 346 * a privileged port will be allocated to make the connection. 347 * This requires super-user privileges if needpriv is true. 348 * Connection_attempts specifies the maximum number of tries (one per 349 * second). If proxy_command is non-NULL, it specifies the command (with %h 350 * and %p substituted for host and port, respectively) to use to contact 351 * the daemon. 352 */ 353 int 354 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 355 u_short port, int family, int connection_attempts, int *timeout_ms, 356 int want_keepalive, int needpriv, const char *proxy_command) 357 { 358 int gaierr; 359 int on = 1; 360 int sock = -1, attempt; 361 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 362 struct addrinfo hints, *ai, *aitop; 363 364 debug2("ssh_connect: needpriv %d", needpriv); 365 366 /* If a proxy command is given, connect using it. */ 367 if (proxy_command != NULL) 368 return ssh_proxy_connect(host, port, proxy_command); 369 370 /* No proxy command. */ 371 372 memset(&hints, 0, sizeof(hints)); 373 hints.ai_family = family; 374 hints.ai_socktype = SOCK_STREAM; 375 snprintf(strport, sizeof strport, "%u", port); 376 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 377 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 378 host, ssh_gai_strerror(gaierr)); 379 380 for (attempt = 0; attempt < connection_attempts; attempt++) { 381 if (attempt > 0) { 382 /* Sleep a moment before retrying. */ 383 sleep(1); 384 debug("Trying again..."); 385 } 386 /* 387 * Loop through addresses for this host, and try each one in 388 * sequence until the connection succeeds. 389 */ 390 for (ai = aitop; ai; ai = ai->ai_next) { 391 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 392 continue; 393 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 394 ntop, sizeof(ntop), strport, sizeof(strport), 395 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 396 error("ssh_connect: getnameinfo failed"); 397 continue; 398 } 399 debug("Connecting to %.200s [%.100s] port %s.", 400 host, ntop, strport); 401 402 /* Create a socket for connecting. */ 403 sock = ssh_create_socket(needpriv, ai); 404 if (sock < 0) 405 /* Any error is already output */ 406 continue; 407 408 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 409 timeout_ms) >= 0) { 410 /* Successful connection. */ 411 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 412 break; 413 } else { 414 debug("connect to address %s port %s: %s", 415 ntop, strport, strerror(errno)); 416 close(sock); 417 sock = -1; 418 } 419 } 420 if (sock != -1) 421 break; /* Successful connection. */ 422 } 423 424 freeaddrinfo(aitop); 425 426 /* Return failure if we didn't get a successful connection. */ 427 if (sock == -1) { 428 error("ssh: connect to host %s port %s: %s", 429 host, strport, strerror(errno)); 430 return (-1); 431 } 432 433 debug("Connection established."); 434 435 /* Set SO_KEEPALIVE if requested. */ 436 if (want_keepalive && 437 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 438 sizeof(on)) < 0) 439 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 440 441 /* Set the connection. */ 442 packet_set_connection(sock, sock); 443 packet_set_timeout(options.server_alive_interval, 444 options.server_alive_count_max); 445 446 return 0; 447 } 448 449 /* 450 * Waits for the server identification string, and sends our own 451 * identification string. 452 */ 453 void 454 ssh_exchange_identification(int timeout_ms) 455 { 456 char buf[256], remote_version[256]; /* must be same size! */ 457 int remote_major, remote_minor, mismatch; 458 int connection_in = packet_get_connection_in(); 459 int connection_out = packet_get_connection_out(); 460 int minor1 = PROTOCOL_MINOR_1; 461 u_int i, n; 462 size_t len; 463 int fdsetsz, remaining, rc; 464 struct timeval t_start, t_remaining; 465 fd_set *fdset; 466 467 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 468 fdset = xcalloc(1, fdsetsz); 469 470 /* Read other side's version identification. */ 471 remaining = timeout_ms; 472 for (n = 0;;) { 473 for (i = 0; i < sizeof(buf) - 1; i++) { 474 if (timeout_ms > 0) { 475 gettimeofday(&t_start, NULL); 476 ms_to_timeval(&t_remaining, remaining); 477 FD_SET(connection_in, fdset); 478 rc = select(connection_in + 1, fdset, NULL, 479 fdset, &t_remaining); 480 ms_subtract_diff(&t_start, &remaining); 481 if (rc == 0 || remaining <= 0) 482 fatal("Connection timed out during " 483 "banner exchange"); 484 if (rc == -1) { 485 if (errno == EINTR) 486 continue; 487 fatal("ssh_exchange_identification: " 488 "select: %s", strerror(errno)); 489 } 490 } 491 492 len = roaming_atomicio(read, connection_in, &buf[i], 1); 493 494 if (len != 1 && errno == EPIPE) 495 fatal("ssh_exchange_identification: " 496 "Connection closed by remote host"); 497 else if (len != 1) 498 fatal("ssh_exchange_identification: " 499 "read: %.100s", strerror(errno)); 500 if (buf[i] == '\r') { 501 buf[i] = '\n'; 502 buf[i + 1] = 0; 503 continue; /**XXX wait for \n */ 504 } 505 if (buf[i] == '\n') { 506 buf[i + 1] = 0; 507 break; 508 } 509 if (++n > 65536) 510 fatal("ssh_exchange_identification: " 511 "No banner received"); 512 } 513 buf[sizeof(buf) - 1] = 0; 514 if (strncmp(buf, "SSH-", 4) == 0) 515 break; 516 debug("ssh_exchange_identification: %s", buf); 517 } 518 server_version_string = xstrdup(buf); 519 xfree(fdset); 520 521 /* 522 * Check that the versions match. In future this might accept 523 * several versions and set appropriate flags to handle them. 524 */ 525 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 526 &remote_major, &remote_minor, remote_version) != 3) 527 fatal("Bad remote protocol version identification: '%.100s'", buf); 528 debug("Remote protocol version %d.%d, remote software version %.100s", 529 remote_major, remote_minor, remote_version); 530 531 compat_datafellows(remote_version); 532 mismatch = 0; 533 534 switch (remote_major) { 535 case 1: 536 if (remote_minor == 99 && 537 (options.protocol & SSH_PROTO_2) && 538 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 539 enable_compat20(); 540 break; 541 } 542 if (!(options.protocol & SSH_PROTO_1)) { 543 mismatch = 1; 544 break; 545 } 546 if (remote_minor < 3) { 547 fatal("Remote machine has too old SSH software version."); 548 } else if (remote_minor == 3 || remote_minor == 4) { 549 /* We speak 1.3, too. */ 550 enable_compat13(); 551 minor1 = 3; 552 if (options.forward_agent) { 553 logit("Agent forwarding disabled for protocol 1.3"); 554 options.forward_agent = 0; 555 } 556 } 557 break; 558 case 2: 559 if (options.protocol & SSH_PROTO_2) { 560 enable_compat20(); 561 break; 562 } 563 /* FALLTHROUGH */ 564 default: 565 mismatch = 1; 566 break; 567 } 568 if (mismatch) 569 fatal("Protocol major versions differ: %d vs. %d", 570 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 571 remote_major); 572 /* Send our own protocol version identification. */ 573 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 574 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 575 compat20 ? PROTOCOL_MINOR_2 : minor1, 576 SSH_RELEASE, compat20 ? "\r\n" : "\n"); 577 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 578 != strlen(buf)) 579 fatal("write: %.100s", strerror(errno)); 580 client_version_string = xstrdup(buf); 581 chop(client_version_string); 582 chop(server_version_string); 583 debug("Local version string %.100s", client_version_string); 584 } 585 586 /* defaults to 'no' */ 587 static int 588 confirm(const char *prompt) 589 { 590 const char *msg, *again = "Please type 'yes' or 'no': "; 591 char *p; 592 int ret = -1; 593 594 if (options.batch_mode) 595 return 0; 596 for (msg = prompt;;msg = again) { 597 p = read_passphrase(msg, RP_ECHO); 598 if (p == NULL || 599 (p[0] == '\0') || (p[0] == '\n') || 600 strncasecmp(p, "no", 2) == 0) 601 ret = 0; 602 if (p && strncasecmp(p, "yes", 3) == 0) 603 ret = 1; 604 if (p) 605 xfree(p); 606 if (ret != -1) 607 return ret; 608 } 609 } 610 611 static int 612 check_host_cert(const char *host, const Key *host_key) 613 { 614 const char *reason; 615 616 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 617 error("%s", reason); 618 return 0; 619 } 620 if (buffer_len(&host_key->cert->critical) != 0) { 621 error("Certificate for %s contains unsupported " 622 "critical options(s)", host); 623 return 0; 624 } 625 return 1; 626 } 627 628 /* 629 * check whether the supplied host key is valid, return -1 if the key 630 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 631 */ 632 #define RDRW 0 633 #define RDONLY 1 634 #define ROQUIET 2 635 static int 636 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 637 Key *host_key, int readonly, const char *user_hostfile, 638 const char *system_hostfile) 639 { 640 Key *file_key, *raw_key = NULL; 641 const char *type; 642 char *ip = NULL, *host = NULL; 643 char hostline[1000], *hostp, *fp, *ra; 644 HostStatus host_status; 645 HostStatus ip_status; 646 int r, want_cert, local = 0, host_ip_differ = 0; 647 int salen; 648 char ntop[NI_MAXHOST]; 649 char msg[1024]; 650 int len, host_line, ip_line, cancelled_forwarding = 0; 651 const char *host_file = NULL, *ip_file = NULL; 652 653 /* 654 * Force accepting of the host key for loopback/localhost. The 655 * problem is that if the home directory is NFS-mounted to multiple 656 * machines, localhost will refer to a different machine in each of 657 * them, and the user will get bogus HOST_CHANGED warnings. This 658 * essentially disables host authentication for localhost; however, 659 * this is probably not a real problem. 660 */ 661 /** hostaddr == 0! */ 662 switch (hostaddr->sa_family) { 663 case AF_INET: 664 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 665 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 666 salen = sizeof(struct sockaddr_in); 667 break; 668 case AF_INET6: 669 local = IN6_IS_ADDR_LOOPBACK( 670 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 671 salen = sizeof(struct sockaddr_in6); 672 break; 673 default: 674 local = 0; 675 salen = sizeof(struct sockaddr_storage); 676 break; 677 } 678 if (options.no_host_authentication_for_localhost == 1 && local && 679 options.host_key_alias == NULL) { 680 debug("Forcing accepting of host key for " 681 "loopback/localhost."); 682 return 0; 683 } 684 685 /* 686 * We don't have the remote ip-address for connections 687 * using a proxy command 688 */ 689 if (options.proxy_command == NULL) { 690 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), 691 NULL, 0, NI_NUMERICHOST) != 0) 692 fatal("check_host_key: getnameinfo failed"); 693 ip = put_host_port(ntop, port); 694 } else { 695 ip = xstrdup("<no hostip for proxy command>"); 696 } 697 698 /* 699 * Turn off check_host_ip if the connection is to localhost, via proxy 700 * command or if we don't have a hostname to compare with 701 */ 702 if (options.check_host_ip && (local || 703 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 704 options.check_host_ip = 0; 705 706 /* 707 * Allow the user to record the key under a different name or 708 * differentiate a non-standard port. This is useful for ssh 709 * tunneling over forwarded connections or if you run multiple 710 * sshd's on different ports on the same machine. 711 */ 712 if (options.host_key_alias != NULL) { 713 host = xstrdup(options.host_key_alias); 714 debug("using hostkeyalias: %s", host); 715 } else { 716 host = put_host_port(hostname, port); 717 } 718 719 retry: 720 want_cert = key_is_cert(host_key); 721 type = key_type(host_key); 722 723 /* 724 * Store the host key from the known host file in here so that we can 725 * compare it with the key for the IP address. 726 */ 727 file_key = key_new(key_is_cert(host_key) ? KEY_UNSPEC : host_key->type); 728 729 /* 730 * Check if the host key is present in the user's list of known 731 * hosts or in the systemwide list. 732 */ 733 host_file = user_hostfile; 734 host_status = check_host_in_hostfile(host_file, host, host_key, 735 file_key, &host_line); 736 if (host_status == HOST_NEW) { 737 host_file = system_hostfile; 738 host_status = check_host_in_hostfile(host_file, host, host_key, 739 file_key, &host_line); 740 } 741 /* 742 * Also perform check for the ip address, skip the check if we are 743 * localhost, looking for a certificate, or the hostname was an ip 744 * address to begin with. 745 */ 746 if (!want_cert && options.check_host_ip) { 747 Key *ip_key = key_new(host_key->type); 748 749 ip_file = user_hostfile; 750 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 751 ip_key, &ip_line); 752 if (ip_status == HOST_NEW) { 753 ip_file = system_hostfile; 754 ip_status = check_host_in_hostfile(ip_file, ip, 755 host_key, ip_key, &ip_line); 756 } 757 if (host_status == HOST_CHANGED && 758 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 759 host_ip_differ = 1; 760 761 key_free(ip_key); 762 } else 763 ip_status = host_status; 764 765 key_free(file_key); 766 767 switch (host_status) { 768 case HOST_OK: 769 /* The host is known and the key matches. */ 770 debug("Host '%.200s' is known and matches the %s host %s.", 771 host, type, want_cert ? "certificate" : "key"); 772 debug("Found %s in %s:%d", 773 want_cert ? "CA key" : "key", host_file, host_line); 774 if (want_cert && !check_host_cert(hostname, host_key)) 775 goto fail; 776 if (options.check_host_ip && ip_status == HOST_NEW) { 777 if (readonly || want_cert) 778 logit("%s host key for IP address " 779 "'%.128s' not in list of known hosts.", 780 type, ip); 781 else if (!add_host_to_hostfile(user_hostfile, ip, 782 host_key, options.hash_known_hosts)) 783 logit("Failed to add the %s host key for IP " 784 "address '%.128s' to the list of known " 785 "hosts (%.30s).", type, ip, user_hostfile); 786 else 787 logit("Warning: Permanently added the %s host " 788 "key for IP address '%.128s' to the list " 789 "of known hosts.", type, ip); 790 } else if (options.visual_host_key) { 791 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 792 ra = key_fingerprint(host_key, SSH_FP_MD5, 793 SSH_FP_RANDOMART); 794 logit("Host key fingerprint is %s\n%s\n", fp, ra); 795 xfree(ra); 796 xfree(fp); 797 } 798 break; 799 case HOST_NEW: 800 if (options.host_key_alias == NULL && port != 0 && 801 port != SSH_DEFAULT_PORT) { 802 debug("checking without port identifier"); 803 if (check_host_key(hostname, hostaddr, 0, host_key, 804 ROQUIET, user_hostfile, system_hostfile) == 0) { 805 debug("found matching key w/out port"); 806 break; 807 } 808 } 809 if (readonly || want_cert) 810 goto fail; 811 /* The host is new. */ 812 if (options.strict_host_key_checking == 1) { 813 /* 814 * User has requested strict host key checking. We 815 * will not add the host key automatically. The only 816 * alternative left is to abort. 817 */ 818 error("No %s host key is known for %.200s and you " 819 "have requested strict checking.", type, host); 820 goto fail; 821 } else if (options.strict_host_key_checking == 2) { 822 char msg1[1024], msg2[1024]; 823 824 if (show_other_keys(host, host_key)) 825 snprintf(msg1, sizeof(msg1), 826 "\nbut keys of different type are already" 827 " known for this host."); 828 else 829 snprintf(msg1, sizeof(msg1), "."); 830 /* The default */ 831 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 832 ra = key_fingerprint(host_key, SSH_FP_MD5, 833 SSH_FP_RANDOMART); 834 msg2[0] = '\0'; 835 if (options.verify_host_key_dns) { 836 if (matching_host_key_dns) 837 snprintf(msg2, sizeof(msg2), 838 "Matching host key fingerprint" 839 " found in DNS.\n"); 840 else 841 snprintf(msg2, sizeof(msg2), 842 "No matching host key fingerprint" 843 " found in DNS.\n"); 844 } 845 snprintf(msg, sizeof(msg), 846 "The authenticity of host '%.200s (%s)' can't be " 847 "established%s\n" 848 "%s key fingerprint is %s.%s%s\n%s" 849 "Are you sure you want to continue connecting " 850 "(yes/no)? ", 851 host, ip, msg1, type, fp, 852 options.visual_host_key ? "\n" : "", 853 options.visual_host_key ? ra : "", 854 msg2); 855 xfree(ra); 856 xfree(fp); 857 if (!confirm(msg)) 858 goto fail; 859 } 860 /* 861 * If not in strict mode, add the key automatically to the 862 * local known_hosts file. 863 */ 864 if (options.check_host_ip && ip_status == HOST_NEW) { 865 snprintf(hostline, sizeof(hostline), "%s,%s", 866 host, ip); 867 hostp = hostline; 868 if (options.hash_known_hosts) { 869 /* Add hash of host and IP separately */ 870 r = add_host_to_hostfile(user_hostfile, host, 871 host_key, options.hash_known_hosts) && 872 add_host_to_hostfile(user_hostfile, ip, 873 host_key, options.hash_known_hosts); 874 } else { 875 /* Add unhashed "host,ip" */ 876 r = add_host_to_hostfile(user_hostfile, 877 hostline, host_key, 878 options.hash_known_hosts); 879 } 880 } else { 881 r = add_host_to_hostfile(user_hostfile, host, host_key, 882 options.hash_known_hosts); 883 hostp = host; 884 } 885 886 if (!r) 887 logit("Failed to add the host to the list of known " 888 "hosts (%.500s).", user_hostfile); 889 else 890 logit("Warning: Permanently added '%.200s' (%s) to the " 891 "list of known hosts.", hostp, type); 892 break; 893 case HOST_REVOKED: 894 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 895 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 896 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 897 error("The %s host key for %s is marked as revoked.", type, host); 898 error("This could mean that a stolen key is being used to"); 899 error("impersonate this host."); 900 901 /* 902 * If strict host key checking is in use, the user will have 903 * to edit the key manually and we can only abort. 904 */ 905 if (options.strict_host_key_checking) { 906 error("%s host key for %.200s was revoked and you have " 907 "requested strict checking.", type, host); 908 goto fail; 909 } 910 goto continue_unsafe; 911 912 case HOST_CHANGED: 913 if (want_cert) { 914 /* 915 * This is only a debug() since it is valid to have 916 * CAs with wildcard DNS matches that don't match 917 * all hosts that one might visit. 918 */ 919 debug("Host certificate authority does not " 920 "match %s in %s:%d", CA_MARKER, 921 host_file, host_line); 922 goto fail; 923 } 924 if (readonly == ROQUIET) 925 goto fail; 926 if (options.check_host_ip && host_ip_differ) { 927 char *key_msg; 928 if (ip_status == HOST_NEW) 929 key_msg = "is unknown"; 930 else if (ip_status == HOST_OK) 931 key_msg = "is unchanged"; 932 else 933 key_msg = "has a different value"; 934 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 935 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 936 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 937 error("The %s host key for %s has changed,", type, host); 938 error("and the key for the corresponding IP address %s", ip); 939 error("%s. This could either mean that", key_msg); 940 error("DNS SPOOFING is happening or the IP address for the host"); 941 error("and its host key have changed at the same time."); 942 if (ip_status != HOST_NEW) 943 error("Offending key for IP in %s:%d", ip_file, ip_line); 944 } 945 /* The host key has changed. */ 946 warn_changed_key(host_key); 947 error("Add correct host key in %.100s to get rid of this message.", 948 user_hostfile); 949 error("Offending key in %s:%d", host_file, host_line); 950 951 /* 952 * If strict host key checking is in use, the user will have 953 * to edit the key manually and we can only abort. 954 */ 955 if (options.strict_host_key_checking) { 956 error("%s host key for %.200s has changed and you have " 957 "requested strict checking.", type, host); 958 goto fail; 959 } 960 961 continue_unsafe: 962 /* 963 * If strict host key checking has not been requested, allow 964 * the connection but without MITM-able authentication or 965 * forwarding. 966 */ 967 if (options.password_authentication) { 968 error("Password authentication is disabled to avoid " 969 "man-in-the-middle attacks."); 970 options.password_authentication = 0; 971 cancelled_forwarding = 1; 972 } 973 if (options.kbd_interactive_authentication) { 974 error("Keyboard-interactive authentication is disabled" 975 " to avoid man-in-the-middle attacks."); 976 options.kbd_interactive_authentication = 0; 977 options.challenge_response_authentication = 0; 978 cancelled_forwarding = 1; 979 } 980 if (options.challenge_response_authentication) { 981 error("Challenge/response authentication is disabled" 982 " to avoid man-in-the-middle attacks."); 983 options.challenge_response_authentication = 0; 984 cancelled_forwarding = 1; 985 } 986 if (options.forward_agent) { 987 error("Agent forwarding is disabled to avoid " 988 "man-in-the-middle attacks."); 989 options.forward_agent = 0; 990 cancelled_forwarding = 1; 991 } 992 if (options.forward_x11) { 993 error("X11 forwarding is disabled to avoid " 994 "man-in-the-middle attacks."); 995 options.forward_x11 = 0; 996 cancelled_forwarding = 1; 997 } 998 if (options.num_local_forwards > 0 || 999 options.num_remote_forwards > 0) { 1000 error("Port forwarding is disabled to avoid " 1001 "man-in-the-middle attacks."); 1002 options.num_local_forwards = 1003 options.num_remote_forwards = 0; 1004 cancelled_forwarding = 1; 1005 } 1006 if (options.tun_open != SSH_TUNMODE_NO) { 1007 error("Tunnel forwarding is disabled to avoid " 1008 "man-in-the-middle attacks."); 1009 options.tun_open = SSH_TUNMODE_NO; 1010 cancelled_forwarding = 1; 1011 } 1012 if (options.exit_on_forward_failure && cancelled_forwarding) 1013 fatal("Error: forwarding disabled due to host key " 1014 "check failure"); 1015 1016 /* 1017 * XXX Should permit the user to change to use the new id. 1018 * This could be done by converting the host key to an 1019 * identifying sentence, tell that the host identifies itself 1020 * by that sentence, and ask the user if he/she wishes to 1021 * accept the authentication. 1022 */ 1023 break; 1024 case HOST_FOUND: 1025 fatal("internal error"); 1026 break; 1027 } 1028 1029 if (options.check_host_ip && host_status != HOST_CHANGED && 1030 ip_status == HOST_CHANGED) { 1031 snprintf(msg, sizeof(msg), 1032 "Warning: the %s host key for '%.200s' " 1033 "differs from the key for the IP address '%.128s'" 1034 "\nOffending key for IP in %s:%d", 1035 type, host, ip, ip_file, ip_line); 1036 if (host_status == HOST_OK) { 1037 len = strlen(msg); 1038 snprintf(msg + len, sizeof(msg) - len, 1039 "\nMatching host key in %s:%d", 1040 host_file, host_line); 1041 } 1042 if (options.strict_host_key_checking == 1) { 1043 logit("%s", msg); 1044 error("Exiting, you have requested strict checking."); 1045 goto fail; 1046 } else if (options.strict_host_key_checking == 2) { 1047 strlcat(msg, "\nAre you sure you want " 1048 "to continue connecting (yes/no)? ", sizeof(msg)); 1049 if (!confirm(msg)) 1050 goto fail; 1051 } else { 1052 logit("%s", msg); 1053 } 1054 } 1055 1056 xfree(ip); 1057 xfree(host); 1058 return 0; 1059 1060 fail: 1061 if (want_cert && host_status != HOST_REVOKED) { 1062 /* 1063 * No matching certificate. Downgrade cert to raw key and 1064 * search normally. 1065 */ 1066 debug("No matching CA found. Retry with plain key"); 1067 raw_key = key_from_private(host_key); 1068 if (key_drop_cert(raw_key) != 0) 1069 fatal("Couldn't drop certificate"); 1070 host_key = raw_key; 1071 goto retry; 1072 } 1073 if (raw_key != NULL) 1074 key_free(raw_key); 1075 xfree(ip); 1076 xfree(host); 1077 return -1; 1078 } 1079 1080 /* returns 0 if key verifies or -1 if key does NOT verify */ 1081 int 1082 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1083 { 1084 struct stat st; 1085 int flags = 0; 1086 1087 /* XXX certs are not yet supported for DNS */ 1088 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1089 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1090 1091 if (flags & DNS_VERIFY_FOUND) { 1092 1093 if (options.verify_host_key_dns == 1 && 1094 flags & DNS_VERIFY_MATCH && 1095 flags & DNS_VERIFY_SECURE) 1096 return 0; 1097 1098 if (flags & DNS_VERIFY_MATCH) { 1099 matching_host_key_dns = 1; 1100 } else { 1101 warn_changed_key(host_key); 1102 error("Update the SSHFP RR in DNS with the new " 1103 "host key to get rid of this message."); 1104 } 1105 } 1106 } 1107 1108 /* return ok if the key can be found in an old keyfile */ 1109 if (stat(options.system_hostfile2, &st) == 0 || 1110 stat(options.user_hostfile2, &st) == 0) { 1111 if (check_host_key(host, hostaddr, options.port, host_key, 1112 RDONLY, options.user_hostfile2, 1113 options.system_hostfile2) == 0) 1114 return 0; 1115 } 1116 return check_host_key(host, hostaddr, options.port, host_key, 1117 RDRW, options.user_hostfile, options.system_hostfile); 1118 } 1119 1120 /* 1121 * Starts a dialog with the server, and authenticates the current user on the 1122 * server. This does not need any extra privileges. The basic connection 1123 * to the server must already have been established before this is called. 1124 * If login fails, this function prints an error and never returns. 1125 * This function does not require super-user privileges. 1126 */ 1127 void 1128 ssh_login(Sensitive *sensitive, const char *orighost, 1129 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 1130 { 1131 char *host, *cp; 1132 char *server_user, *local_user; 1133 1134 local_user = xstrdup(pw->pw_name); 1135 server_user = options.user ? options.user : local_user; 1136 1137 /* Convert the user-supplied hostname into all lowercase. */ 1138 host = xstrdup(orighost); 1139 for (cp = host; *cp; cp++) 1140 if (isupper(*cp)) 1141 *cp = (char)tolower(*cp); 1142 1143 /* Exchange protocol version identification strings with the server. */ 1144 ssh_exchange_identification(timeout_ms); 1145 1146 /* Put the connection into non-blocking mode. */ 1147 packet_set_nonblocking(); 1148 1149 /* key exchange */ 1150 /* authenticate user */ 1151 if (compat20) { 1152 ssh_kex2(host, hostaddr); 1153 ssh_userauth2(local_user, server_user, host, sensitive); 1154 } else { 1155 ssh_kex(host, hostaddr); 1156 ssh_userauth1(local_user, server_user, host, sensitive); 1157 } 1158 xfree(local_user); 1159 } 1160 1161 void 1162 ssh_put_password(char *password) 1163 { 1164 int size; 1165 char *padded; 1166 1167 if (datafellows & SSH_BUG_PASSWORDPAD) { 1168 packet_put_cstring(password); 1169 return; 1170 } 1171 size = roundup(strlen(password) + 1, 32); 1172 padded = xcalloc(1, size); 1173 strlcpy(padded, password, size); 1174 packet_put_string(padded, size); 1175 memset(padded, 0, size); 1176 xfree(padded); 1177 } 1178 1179 static int 1180 show_key_from_file(const char *file, const char *host, int keytype) 1181 { 1182 Key *found; 1183 char *fp, *ra; 1184 int line, ret; 1185 1186 found = key_new(keytype); 1187 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1188 keytype, found, &line))) { 1189 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1190 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); 1191 logit("WARNING: %s key found for host %s\n" 1192 "in %s:%d\n" 1193 "%s key fingerprint %s.\n%s\n", 1194 key_type(found), host, file, line, 1195 key_type(found), fp, ra); 1196 xfree(ra); 1197 xfree(fp); 1198 } 1199 key_free(found); 1200 return (ret); 1201 } 1202 1203 /* print all known host keys for a given host, but skip keys of given type */ 1204 static int 1205 show_other_keys(const char *host, Key *key) 1206 { 1207 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1208 int i, found = 0; 1209 1210 for (i = 0; type[i] != -1; i++) { 1211 if (type[i] == key->type) 1212 continue; 1213 if (type[i] != KEY_RSA1 && 1214 show_key_from_file(options.user_hostfile2, host, type[i])) { 1215 found = 1; 1216 continue; 1217 } 1218 if (type[i] != KEY_RSA1 && 1219 show_key_from_file(options.system_hostfile2, host, type[i])) { 1220 found = 1; 1221 continue; 1222 } 1223 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1224 found = 1; 1225 continue; 1226 } 1227 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1228 found = 1; 1229 continue; 1230 } 1231 debug2("no key of type %d for host %s", type[i], host); 1232 } 1233 return (found); 1234 } 1235 1236 static void 1237 warn_changed_key(Key *host_key) 1238 { 1239 char *fp; 1240 const char *type = key_type(host_key); 1241 1242 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1243 1244 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1245 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1246 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1247 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1248 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1249 error("It is also possible that the %s host key has just been changed.", type); 1250 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1251 type, fp); 1252 error("Please contact your system administrator."); 1253 1254 xfree(fp); 1255 } 1256 1257 /* 1258 * Execute a local command 1259 */ 1260 int 1261 ssh_local_cmd(const char *args) 1262 { 1263 char *shell; 1264 pid_t pid; 1265 int status; 1266 1267 if (!options.permit_local_command || 1268 args == NULL || !*args) 1269 return (1); 1270 1271 if ((shell = getenv("SHELL")) == NULL) 1272 shell = _PATH_BSHELL; 1273 1274 pid = fork(); 1275 if (pid == 0) { 1276 debug3("Executing %s -c \"%s\"", shell, args); 1277 execl(shell, shell, "-c", args, (char *)NULL); 1278 error("Couldn't execute %s -c \"%s\": %s", 1279 shell, args, strerror(errno)); 1280 _exit(1); 1281 } else if (pid == -1) 1282 fatal("fork failed: %.100s", strerror(errno)); 1283 while (waitpid(pid, &status, 0) == -1) 1284 if (errno != EINTR) 1285 fatal("Couldn't wait for child: %s", strerror(errno)); 1286 1287 if (!WIFEXITED(status)) 1288 return (1); 1289 1290 return (WEXITSTATUS(status)); 1291 } 1292