1 /* $OpenBSD: sshconnect.c,v 1.236 2012/09/14 16:51:34 markus Exp $ */ 2 /* $OpenBSD: sshconnect.c,v 1.237 2013/02/22 19:13:56 markus Exp $ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Code to connect to a remote host, and to perform the client side of the 8 * login (authentication) dialog. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 */ 16 17 #include "includes.h" 18 19 #include <sys/types.h> 20 #include <sys/wait.h> 21 #include <sys/stat.h> 22 #include <sys/socket.h> 23 #ifdef HAVE_SYS_TIME_H 24 # include <sys/time.h> 25 #endif 26 27 #include <netinet/in.h> 28 #include <arpa/inet.h> 29 30 #include <ctype.h> 31 #include <errno.h> 32 #include <fcntl.h> 33 #include <netdb.h> 34 #ifdef HAVE_PATHS_H 35 #include <paths.h> 36 #endif 37 #include <pwd.h> 38 #include <signal.h> 39 #include <stdarg.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include <unistd.h> 44 45 #include "xmalloc.h" 46 #include "key.h" 47 #include "hostfile.h" 48 #include "ssh.h" 49 #include "rsa.h" 50 #include "buffer.h" 51 #include "packet.h" 52 #include "uidswap.h" 53 #include "compat.h" 54 #include "key.h" 55 #include "sshconnect.h" 56 #include "hostfile.h" 57 #include "log.h" 58 #include "readconf.h" 59 #include "atomicio.h" 60 #include "misc.h" 61 #include "dns.h" 62 #include "roaming.h" 63 #include "ssh2.h" 64 #include "version.h" 65 66 char *client_version_string = NULL; 67 char *server_version_string = NULL; 68 69 static int matching_host_key_dns = 0; 70 71 static pid_t proxy_command_pid = 0; 72 73 /* import */ 74 extern Options options; 75 extern char *__progname; 76 extern uid_t original_real_uid; 77 extern uid_t original_effective_uid; 78 79 static int show_other_keys(struct hostkeys *, Key *); 80 static void warn_changed_key(Key *); 81 82 /* 83 * Connect to the given ssh server using a proxy command. 84 */ 85 static int 86 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 87 { 88 char *command_string, *tmp; 89 int pin[2], pout[2]; 90 pid_t pid; 91 char *shell, strport[NI_MAXSERV]; 92 93 if (!strcmp(proxy_command, "-")) { 94 packet_set_connection(STDIN_FILENO, STDOUT_FILENO); 95 packet_set_timeout(options.server_alive_interval, 96 options.server_alive_count_max); 97 return 0; 98 } 99 100 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 101 shell = _PATH_BSHELL; 102 103 /* Convert the port number into a string. */ 104 snprintf(strport, sizeof strport, "%hu", port); 105 106 /* 107 * Build the final command string in the buffer by making the 108 * appropriate substitutions to the given proxy command. 109 * 110 * Use "exec" to avoid "sh -c" processes on some platforms 111 * (e.g. Solaris) 112 */ 113 xasprintf(&tmp, "exec %s", proxy_command); 114 command_string = percent_expand(tmp, "h", host, "p", strport, 115 "r", options.user, (char *)NULL); 116 xfree(tmp); 117 118 /* Create pipes for communicating with the proxy. */ 119 if (pipe(pin) < 0 || pipe(pout) < 0) 120 fatal("Could not create pipes to communicate with the proxy: %.100s", 121 strerror(errno)); 122 123 debug("Executing proxy command: %.500s", command_string); 124 125 /* Fork and execute the proxy command. */ 126 if ((pid = fork()) == 0) { 127 char *argv[10]; 128 129 /* Child. Permanently give up superuser privileges. */ 130 permanently_drop_suid(original_real_uid); 131 132 /* Redirect stdin and stdout. */ 133 close(pin[1]); 134 if (pin[0] != 0) { 135 if (dup2(pin[0], 0) < 0) 136 perror("dup2 stdin"); 137 close(pin[0]); 138 } 139 close(pout[0]); 140 if (dup2(pout[1], 1) < 0) 141 perror("dup2 stdout"); 142 /* Cannot be 1 because pin allocated two descriptors. */ 143 close(pout[1]); 144 145 /* Stderr is left as it is so that error messages get 146 printed on the user's terminal. */ 147 argv[0] = shell; 148 argv[1] = "-c"; 149 argv[2] = command_string; 150 argv[3] = NULL; 151 152 /* Execute the proxy command. Note that we gave up any 153 extra privileges above. */ 154 signal(SIGPIPE, SIG_DFL); 155 execv(argv[0], argv); 156 perror(argv[0]); 157 exit(1); 158 } 159 /* Parent. */ 160 if (pid < 0) 161 fatal("fork failed: %.100s", strerror(errno)); 162 else 163 proxy_command_pid = pid; /* save pid to clean up later */ 164 165 /* Close child side of the descriptors. */ 166 close(pin[0]); 167 close(pout[1]); 168 169 /* Free the command name. */ 170 xfree(command_string); 171 172 /* Set the connection file descriptors. */ 173 packet_set_connection(pout[0], pin[1]); 174 packet_set_timeout(options.server_alive_interval, 175 options.server_alive_count_max); 176 177 /* Indicate OK return */ 178 return 0; 179 } 180 181 void 182 ssh_kill_proxy_command(void) 183 { 184 /* 185 * Send SIGHUP to proxy command if used. We don't wait() in 186 * case it hangs and instead rely on init to reap the child 187 */ 188 if (proxy_command_pid > 1) 189 kill(proxy_command_pid, SIGHUP); 190 } 191 192 /* 193 * Set TCP receive buffer if requested. 194 * Note: tuning needs to happen after the socket is created but before the 195 * connection happens so winscale is negotiated properly. 196 */ 197 static void 198 ssh_set_socket_recvbuf(int sock) 199 { 200 void *buf = (void *)&options.tcp_rcv_buf; 201 int socksize, sz = sizeof(options.tcp_rcv_buf); 202 socklen_t len = sizeof(int); 203 204 debug("setsockopt attempting to set SO_RCVBUF to %d", 205 options.tcp_rcv_buf); 206 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 207 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len); 208 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), 209 socksize); 210 } else 211 error("Couldn't set socket receive buffer to %d: %.100s", 212 options.tcp_rcv_buf, strerror(errno)); 213 } 214 215 /* 216 * Creates a (possibly privileged) socket for use as the ssh connection. 217 */ 218 static int 219 ssh_create_socket(int privileged, struct addrinfo *ai) 220 { 221 int sock, gaierr; 222 struct addrinfo hints, *res; 223 224 /* 225 * If we are running as root and want to connect to a privileged 226 * port, bind our own socket to a privileged port. 227 */ 228 if (privileged) { 229 int p = IPPORT_RESERVED - 1; 230 PRIV_START; 231 sock = rresvport_af(&p, ai->ai_family); 232 PRIV_END; 233 if (sock < 0) 234 error("rresvport: af=%d %.100s", ai->ai_family, 235 strerror(errno)); 236 else 237 debug("Allocated local port %d.", p); 238 if (options.tcp_rcv_buf > 0) 239 ssh_set_socket_recvbuf(sock); 240 return sock; 241 } 242 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 243 if (sock < 0) { 244 error("socket: %.100s", strerror(errno)); 245 return -1; 246 } 247 fcntl(sock, F_SETFD, FD_CLOEXEC); 248 249 if (options.tcp_rcv_buf > 0) 250 ssh_set_socket_recvbuf(sock); 251 252 /* Bind the socket to an alternative local IP address */ 253 if (options.bind_address == NULL) 254 return sock; 255 256 memset(&hints, 0, sizeof(hints)); 257 hints.ai_family = ai->ai_family; 258 hints.ai_socktype = ai->ai_socktype; 259 hints.ai_protocol = ai->ai_protocol; 260 hints.ai_flags = AI_PASSIVE; 261 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 262 if (gaierr) { 263 error("getaddrinfo: %s: %s", options.bind_address, 264 ssh_gai_strerror(gaierr)); 265 close(sock); 266 return -1; 267 } 268 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 269 error("bind: %s: %s", options.bind_address, strerror(errno)); 270 close(sock); 271 freeaddrinfo(res); 272 return -1; 273 } 274 freeaddrinfo(res); 275 return sock; 276 } 277 278 static int 279 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 280 socklen_t addrlen, int *timeoutp) 281 { 282 fd_set *fdset; 283 struct timeval tv, t_start; 284 socklen_t optlen; 285 int optval, rc, result = -1; 286 287 gettimeofday(&t_start, NULL); 288 289 if (*timeoutp <= 0) { 290 result = connect(sockfd, serv_addr, addrlen); 291 goto done; 292 } 293 294 set_nonblock(sockfd); 295 rc = connect(sockfd, serv_addr, addrlen); 296 if (rc == 0) { 297 unset_nonblock(sockfd); 298 result = 0; 299 goto done; 300 } 301 if (errno != EINPROGRESS) { 302 result = -1; 303 goto done; 304 } 305 306 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 307 sizeof(fd_mask)); 308 FD_SET(sockfd, fdset); 309 ms_to_timeval(&tv, *timeoutp); 310 311 for (;;) { 312 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 313 if (rc != -1 || errno != EINTR) 314 break; 315 } 316 317 switch (rc) { 318 case 0: 319 /* Timed out */ 320 errno = ETIMEDOUT; 321 break; 322 case -1: 323 /* Select error */ 324 debug("select: %s", strerror(errno)); 325 break; 326 case 1: 327 /* Completed or failed */ 328 optval = 0; 329 optlen = sizeof(optval); 330 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 331 &optlen) == -1) { 332 debug("getsockopt: %s", strerror(errno)); 333 break; 334 } 335 if (optval != 0) { 336 errno = optval; 337 break; 338 } 339 result = 0; 340 unset_nonblock(sockfd); 341 break; 342 default: 343 /* Should not occur */ 344 fatal("Bogus return (%d) from select()", rc); 345 } 346 347 xfree(fdset); 348 349 done: 350 if (result == 0 && *timeoutp > 0) { 351 ms_subtract_diff(&t_start, timeoutp); 352 if (*timeoutp <= 0) { 353 errno = ETIMEDOUT; 354 result = -1; 355 } 356 } 357 358 return (result); 359 } 360 361 /* 362 * Opens a TCP/IP connection to the remote server on the given host. 363 * The address of the remote host will be returned in hostaddr. 364 * If port is 0, the default port will be used. If needpriv is true, 365 * a privileged port will be allocated to make the connection. 366 * This requires super-user privileges if needpriv is true. 367 * Connection_attempts specifies the maximum number of tries (one per 368 * second). If proxy_command is non-NULL, it specifies the command (with %h 369 * and %p substituted for host and port, respectively) to use to contact 370 * the daemon. 371 */ 372 int 373 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 374 u_short port, int family, int connection_attempts, int *timeout_ms, 375 int want_keepalive, int needpriv, const char *proxy_command) 376 { 377 int gaierr; 378 int on = 1; 379 int sock = -1, attempt; 380 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 381 struct addrinfo hints, *ai, *aitop; 382 383 debug2("ssh_connect: needpriv %d", needpriv); 384 385 /* If a proxy command is given, connect using it. */ 386 if (proxy_command != NULL) 387 return ssh_proxy_connect(host, port, proxy_command); 388 389 /* No proxy command. */ 390 391 memset(&hints, 0, sizeof(hints)); 392 hints.ai_family = family; 393 hints.ai_socktype = SOCK_STREAM; 394 snprintf(strport, sizeof strport, "%u", port); 395 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 396 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 397 host, ssh_gai_strerror(gaierr)); 398 399 for (attempt = 0; attempt < connection_attempts; attempt++) { 400 if (attempt > 0) { 401 /* Sleep a moment before retrying. */ 402 sleep(1); 403 debug("Trying again..."); 404 } 405 /* 406 * Loop through addresses for this host, and try each one in 407 * sequence until the connection succeeds. 408 */ 409 for (ai = aitop; ai; ai = ai->ai_next) { 410 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 411 continue; 412 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 413 ntop, sizeof(ntop), strport, sizeof(strport), 414 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 415 error("ssh_connect: getnameinfo failed"); 416 continue; 417 } 418 debug("Connecting to %.200s [%.100s] port %s.", 419 host, ntop, strport); 420 421 /* Create a socket for connecting. */ 422 sock = ssh_create_socket(needpriv, ai); 423 if (sock < 0) 424 /* Any error is already output */ 425 continue; 426 427 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 428 timeout_ms) >= 0) { 429 /* Successful connection. */ 430 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 431 break; 432 } else { 433 debug("connect to address %s port %s: %s", 434 ntop, strport, strerror(errno)); 435 close(sock); 436 sock = -1; 437 } 438 } 439 if (sock != -1) 440 break; /* Successful connection. */ 441 } 442 443 freeaddrinfo(aitop); 444 445 /* Return failure if we didn't get a successful connection. */ 446 if (sock == -1) { 447 error("ssh: connect to host %s port %s: %s", 448 host, strport, strerror(errno)); 449 return (-1); 450 } 451 452 debug("Connection established."); 453 454 /* Set SO_KEEPALIVE if requested. */ 455 if (want_keepalive && 456 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 457 sizeof(on)) < 0) 458 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 459 460 /* Set the connection. */ 461 packet_set_connection(sock, sock); 462 packet_set_timeout(options.server_alive_interval, 463 options.server_alive_count_max); 464 465 return 0; 466 } 467 468 static void 469 send_client_banner(int connection_out, int minor1) 470 { 471 /* Send our own protocol version identification. */ 472 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s%s", 473 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 474 compat20 ? PROTOCOL_MINOR_2 : minor1, 475 SSH_VERSION, options.hpn_disabled ? "" : SSH_VERSION_HPN, 476 *options.version_addendum == '\0' ? "" : " ", 477 options.version_addendum, compat20 ? "\r\n" : "\n"); 478 if (roaming_atomicio(vwrite, connection_out, client_version_string, 479 strlen(client_version_string)) != strlen(client_version_string)) 480 fatal("write: %.100s", strerror(errno)); 481 chop(client_version_string); 482 debug("Local version string %.100s", client_version_string); 483 } 484 485 /* 486 * Waits for the server identification string, and sends our own 487 * identification string. 488 */ 489 void 490 ssh_exchange_identification(int timeout_ms) 491 { 492 char buf[256], remote_version[256]; /* must be same size! */ 493 int remote_major, remote_minor, mismatch; 494 int connection_in = packet_get_connection_in(); 495 int connection_out = packet_get_connection_out(); 496 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0; 497 u_int i, n; 498 size_t len; 499 int fdsetsz, remaining, rc; 500 struct timeval t_start, t_remaining; 501 fd_set *fdset; 502 503 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 504 fdset = xcalloc(1, fdsetsz); 505 506 /* 507 * If we are SSH2-only then we can send the banner immediately and 508 * save a round-trip. 509 */ 510 if (options.protocol == SSH_PROTO_2) { 511 enable_compat20(); 512 send_client_banner(connection_out, 0); 513 client_banner_sent = 1; 514 } 515 516 /* Read other side's version identification. */ 517 remaining = timeout_ms; 518 for (n = 0;;) { 519 for (i = 0; i < sizeof(buf) - 1; i++) { 520 if (timeout_ms > 0) { 521 gettimeofday(&t_start, NULL); 522 ms_to_timeval(&t_remaining, remaining); 523 FD_SET(connection_in, fdset); 524 rc = select(connection_in + 1, fdset, NULL, 525 fdset, &t_remaining); 526 ms_subtract_diff(&t_start, &remaining); 527 if (rc == 0 || remaining <= 0) 528 fatal("Connection timed out during " 529 "banner exchange"); 530 if (rc == -1) { 531 if (errno == EINTR) 532 continue; 533 fatal("ssh_exchange_identification: " 534 "select: %s", strerror(errno)); 535 } 536 } 537 538 len = roaming_atomicio(read, connection_in, &buf[i], 1); 539 540 if (len != 1 && errno == EPIPE) 541 fatal("ssh_exchange_identification: " 542 "Connection closed by remote host"); 543 else if (len != 1) 544 fatal("ssh_exchange_identification: " 545 "read: %.100s", strerror(errno)); 546 if (buf[i] == '\r') { 547 buf[i] = '\n'; 548 buf[i + 1] = 0; 549 continue; /**XXX wait for \n */ 550 } 551 if (buf[i] == '\n') { 552 buf[i + 1] = 0; 553 break; 554 } 555 if (++n > 65536) 556 fatal("ssh_exchange_identification: " 557 "No banner received"); 558 } 559 buf[sizeof(buf) - 1] = 0; 560 if (strncmp(buf, "SSH-", 4) == 0) 561 break; 562 debug("ssh_exchange_identification: %s", buf); 563 } 564 server_version_string = xstrdup(buf); 565 xfree(fdset); 566 567 /* 568 * Check that the versions match. In future this might accept 569 * several versions and set appropriate flags to handle them. 570 */ 571 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 572 &remote_major, &remote_minor, remote_version) != 3) 573 fatal("Bad remote protocol version identification: '%.100s'", buf); 574 debug("Remote protocol version %d.%d, remote software version %.100s", 575 remote_major, remote_minor, remote_version); 576 577 compat_datafellows(remote_version); 578 mismatch = 0; 579 580 switch (remote_major) { 581 case 1: 582 if (remote_minor == 99 && 583 (options.protocol & SSH_PROTO_2) && 584 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 585 enable_compat20(); 586 break; 587 } 588 if (!(options.protocol & SSH_PROTO_1)) { 589 mismatch = 1; 590 break; 591 } 592 if (remote_minor < 3) { 593 fatal("Remote machine has too old SSH software version."); 594 } else if (remote_minor == 3 || remote_minor == 4) { 595 /* We speak 1.3, too. */ 596 enable_compat13(); 597 minor1 = 3; 598 if (options.forward_agent) { 599 logit("Agent forwarding disabled for protocol 1.3"); 600 options.forward_agent = 0; 601 } 602 } 603 break; 604 case 2: 605 if (options.protocol & SSH_PROTO_2) { 606 enable_compat20(); 607 break; 608 } 609 /* FALLTHROUGH */ 610 default: 611 mismatch = 1; 612 break; 613 } 614 if (mismatch) 615 fatal("Protocol major versions differ: %d vs. %d", 616 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 617 remote_major); 618 if (!client_banner_sent) 619 send_client_banner(connection_out, minor1); 620 chop(server_version_string); 621 } 622 623 /* defaults to 'no' */ 624 static int 625 confirm(const char *prompt) 626 { 627 const char *msg, *again = "Please type 'yes' or 'no': "; 628 char *p; 629 int ret = -1; 630 631 if (options.batch_mode) 632 return 0; 633 for (msg = prompt;;msg = again) { 634 p = read_passphrase(msg, RP_ECHO); 635 if (p == NULL || 636 (p[0] == '\0') || (p[0] == '\n') || 637 strncasecmp(p, "no", 2) == 0) 638 ret = 0; 639 if (p && strncasecmp(p, "yes", 3) == 0) 640 ret = 1; 641 if (p) 642 xfree(p); 643 if (ret != -1) 644 return ret; 645 } 646 } 647 648 static int 649 check_host_cert(const char *host, const Key *host_key) 650 { 651 const char *reason; 652 653 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 654 error("%s", reason); 655 return 0; 656 } 657 if (buffer_len(&host_key->cert->critical) != 0) { 658 error("Certificate for %s contains unsupported " 659 "critical options(s)", host); 660 return 0; 661 } 662 return 1; 663 } 664 665 static int 666 sockaddr_is_local(struct sockaddr *hostaddr) 667 { 668 switch (hostaddr->sa_family) { 669 case AF_INET: 670 return (ntohl(((struct sockaddr_in *)hostaddr)-> 671 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 672 case AF_INET6: 673 return IN6_IS_ADDR_LOOPBACK( 674 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 675 default: 676 return 0; 677 } 678 } 679 680 /* 681 * Prepare the hostname and ip address strings that are used to lookup 682 * host keys in known_hosts files. These may have a port number appended. 683 */ 684 void 685 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 686 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 687 { 688 char ntop[NI_MAXHOST]; 689 socklen_t addrlen; 690 691 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 692 case -1: 693 addrlen = 0; 694 break; 695 case AF_INET: 696 addrlen = sizeof(struct sockaddr_in); 697 break; 698 case AF_INET6: 699 addrlen = sizeof(struct sockaddr_in6); 700 break; 701 default: 702 addrlen = sizeof(struct sockaddr); 703 break; 704 } 705 706 /* 707 * We don't have the remote ip-address for connections 708 * using a proxy command 709 */ 710 if (hostfile_ipaddr != NULL) { 711 if (options.proxy_command == NULL) { 712 if (getnameinfo(hostaddr, addrlen, 713 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 714 fatal("check_host_key: getnameinfo failed"); 715 *hostfile_ipaddr = put_host_port(ntop, port); 716 } else { 717 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 718 "command>"); 719 } 720 } 721 722 /* 723 * Allow the user to record the key under a different name or 724 * differentiate a non-standard port. This is useful for ssh 725 * tunneling over forwarded connections or if you run multiple 726 * sshd's on different ports on the same machine. 727 */ 728 if (hostfile_hostname != NULL) { 729 if (options.host_key_alias != NULL) { 730 *hostfile_hostname = xstrdup(options.host_key_alias); 731 debug("using hostkeyalias: %s", *hostfile_hostname); 732 } else { 733 *hostfile_hostname = put_host_port(hostname, port); 734 } 735 } 736 } 737 738 /* 739 * check whether the supplied host key is valid, return -1 if the key 740 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 741 */ 742 #define RDRW 0 743 #define RDONLY 1 744 #define ROQUIET 2 745 static int 746 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 747 Key *host_key, int readonly, 748 char **user_hostfiles, u_int num_user_hostfiles, 749 char **system_hostfiles, u_int num_system_hostfiles) 750 { 751 HostStatus host_status; 752 HostStatus ip_status; 753 Key *raw_key = NULL; 754 char *ip = NULL, *host = NULL; 755 char hostline[1000], *hostp, *fp, *ra; 756 char msg[1024]; 757 const char *type; 758 const struct hostkey_entry *host_found, *ip_found; 759 int len, cancelled_forwarding = 0; 760 int local = sockaddr_is_local(hostaddr); 761 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 762 struct hostkeys *host_hostkeys, *ip_hostkeys; 763 u_int i; 764 765 /* 766 * Force accepting of the host key for loopback/localhost. The 767 * problem is that if the home directory is NFS-mounted to multiple 768 * machines, localhost will refer to a different machine in each of 769 * them, and the user will get bogus HOST_CHANGED warnings. This 770 * essentially disables host authentication for localhost; however, 771 * this is probably not a real problem. 772 */ 773 if (options.no_host_authentication_for_localhost == 1 && local && 774 options.host_key_alias == NULL) { 775 debug("Forcing accepting of host key for " 776 "loopback/localhost."); 777 return 0; 778 } 779 780 /* 781 * Prepare the hostname and address strings used for hostkey lookup. 782 * In some cases, these will have a port number appended. 783 */ 784 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 785 786 /* 787 * Turn off check_host_ip if the connection is to localhost, via proxy 788 * command or if we don't have a hostname to compare with 789 */ 790 if (options.check_host_ip && (local || 791 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 792 options.check_host_ip = 0; 793 794 host_hostkeys = init_hostkeys(); 795 for (i = 0; i < num_user_hostfiles; i++) 796 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 797 for (i = 0; i < num_system_hostfiles; i++) 798 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 799 800 ip_hostkeys = NULL; 801 if (!want_cert && options.check_host_ip) { 802 ip_hostkeys = init_hostkeys(); 803 for (i = 0; i < num_user_hostfiles; i++) 804 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 805 for (i = 0; i < num_system_hostfiles; i++) 806 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 807 } 808 809 retry: 810 /* Reload these as they may have changed on cert->key downgrade */ 811 want_cert = key_is_cert(host_key); 812 type = key_type(host_key); 813 814 /* 815 * Check if the host key is present in the user's list of known 816 * hosts or in the systemwide list. 817 */ 818 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 819 &host_found); 820 821 /* 822 * Also perform check for the ip address, skip the check if we are 823 * localhost, looking for a certificate, or the hostname was an ip 824 * address to begin with. 825 */ 826 if (!want_cert && ip_hostkeys != NULL) { 827 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 828 &ip_found); 829 if (host_status == HOST_CHANGED && 830 (ip_status != HOST_CHANGED || 831 (ip_found != NULL && 832 !key_equal(ip_found->key, host_found->key)))) 833 host_ip_differ = 1; 834 } else 835 ip_status = host_status; 836 837 switch (host_status) { 838 case HOST_OK: 839 /* The host is known and the key matches. */ 840 debug("Host '%.200s' is known and matches the %s host %s.", 841 host, type, want_cert ? "certificate" : "key"); 842 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 843 host_found->file, host_found->line); 844 if (want_cert && !check_host_cert(hostname, host_key)) 845 goto fail; 846 if (options.check_host_ip && ip_status == HOST_NEW) { 847 if (readonly || want_cert) 848 logit("%s host key for IP address " 849 "'%.128s' not in list of known hosts.", 850 type, ip); 851 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 852 host_key, options.hash_known_hosts)) 853 logit("Failed to add the %s host key for IP " 854 "address '%.128s' to the list of known " 855 "hosts (%.30s).", type, ip, 856 user_hostfiles[0]); 857 else 858 logit("Warning: Permanently added the %s host " 859 "key for IP address '%.128s' to the list " 860 "of known hosts.", type, ip); 861 } else if (options.visual_host_key) { 862 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 863 ra = key_fingerprint(host_key, SSH_FP_MD5, 864 SSH_FP_RANDOMART); 865 logit("Host key fingerprint is %s\n%s\n", fp, ra); 866 xfree(ra); 867 xfree(fp); 868 } 869 break; 870 case HOST_NEW: 871 if (options.host_key_alias == NULL && port != 0 && 872 port != SSH_DEFAULT_PORT) { 873 debug("checking without port identifier"); 874 if (check_host_key(hostname, hostaddr, 0, host_key, 875 ROQUIET, user_hostfiles, num_user_hostfiles, 876 system_hostfiles, num_system_hostfiles) == 0) { 877 debug("found matching key w/out port"); 878 break; 879 } 880 } 881 if (readonly || want_cert) 882 goto fail; 883 /* The host is new. */ 884 if (options.strict_host_key_checking == 1) { 885 /* 886 * User has requested strict host key checking. We 887 * will not add the host key automatically. The only 888 * alternative left is to abort. 889 */ 890 error("No %s host key is known for %.200s and you " 891 "have requested strict checking.", type, host); 892 goto fail; 893 } else if (options.strict_host_key_checking == 2) { 894 char msg1[1024], msg2[1024]; 895 896 if (show_other_keys(host_hostkeys, host_key)) 897 snprintf(msg1, sizeof(msg1), 898 "\nbut keys of different type are already" 899 " known for this host."); 900 else 901 snprintf(msg1, sizeof(msg1), "."); 902 /* The default */ 903 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 904 ra = key_fingerprint(host_key, SSH_FP_MD5, 905 SSH_FP_RANDOMART); 906 msg2[0] = '\0'; 907 if (options.verify_host_key_dns) { 908 if (matching_host_key_dns) 909 snprintf(msg2, sizeof(msg2), 910 "Matching host key fingerprint" 911 " found in DNS.\n"); 912 else 913 snprintf(msg2, sizeof(msg2), 914 "No matching host key fingerprint" 915 " found in DNS.\n"); 916 } 917 snprintf(msg, sizeof(msg), 918 "The authenticity of host '%.200s (%s)' can't be " 919 "established%s\n" 920 "%s key fingerprint is %s.%s%s\n%s" 921 "Are you sure you want to continue connecting " 922 "(yes/no)? ", 923 host, ip, msg1, type, fp, 924 options.visual_host_key ? "\n" : "", 925 options.visual_host_key ? ra : "", 926 msg2); 927 xfree(ra); 928 xfree(fp); 929 if (!confirm(msg)) 930 goto fail; 931 } 932 /* 933 * If not in strict mode, add the key automatically to the 934 * local known_hosts file. 935 */ 936 if (options.check_host_ip && ip_status == HOST_NEW) { 937 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 938 hostp = hostline; 939 if (options.hash_known_hosts) { 940 /* Add hash of host and IP separately */ 941 r = add_host_to_hostfile(user_hostfiles[0], 942 host, host_key, options.hash_known_hosts) && 943 add_host_to_hostfile(user_hostfiles[0], ip, 944 host_key, options.hash_known_hosts); 945 } else { 946 /* Add unhashed "host,ip" */ 947 r = add_host_to_hostfile(user_hostfiles[0], 948 hostline, host_key, 949 options.hash_known_hosts); 950 } 951 } else { 952 r = add_host_to_hostfile(user_hostfiles[0], host, 953 host_key, options.hash_known_hosts); 954 hostp = host; 955 } 956 957 if (!r) 958 logit("Failed to add the host to the list of known " 959 "hosts (%.500s).", user_hostfiles[0]); 960 else 961 logit("Warning: Permanently added '%.200s' (%s) to the " 962 "list of known hosts.", hostp, type); 963 break; 964 case HOST_REVOKED: 965 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 966 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 967 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 968 error("The %s host key for %s is marked as revoked.", type, host); 969 error("This could mean that a stolen key is being used to"); 970 error("impersonate this host."); 971 972 /* 973 * If strict host key checking is in use, the user will have 974 * to edit the key manually and we can only abort. 975 */ 976 if (options.strict_host_key_checking) { 977 error("%s host key for %.200s was revoked and you have " 978 "requested strict checking.", type, host); 979 goto fail; 980 } 981 goto continue_unsafe; 982 983 case HOST_CHANGED: 984 if (want_cert) { 985 /* 986 * This is only a debug() since it is valid to have 987 * CAs with wildcard DNS matches that don't match 988 * all hosts that one might visit. 989 */ 990 debug("Host certificate authority does not " 991 "match %s in %s:%lu", CA_MARKER, 992 host_found->file, host_found->line); 993 goto fail; 994 } 995 if (readonly == ROQUIET) 996 goto fail; 997 if (options.check_host_ip && host_ip_differ) { 998 char *key_msg; 999 if (ip_status == HOST_NEW) 1000 key_msg = "is unknown"; 1001 else if (ip_status == HOST_OK) 1002 key_msg = "is unchanged"; 1003 else 1004 key_msg = "has a different value"; 1005 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1006 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1007 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1008 error("The %s host key for %s has changed,", type, host); 1009 error("and the key for the corresponding IP address %s", ip); 1010 error("%s. This could either mean that", key_msg); 1011 error("DNS SPOOFING is happening or the IP address for the host"); 1012 error("and its host key have changed at the same time."); 1013 if (ip_status != HOST_NEW) 1014 error("Offending key for IP in %s:%lu", 1015 ip_found->file, ip_found->line); 1016 } 1017 /* The host key has changed. */ 1018 warn_changed_key(host_key); 1019 error("Add correct host key in %.100s to get rid of this message.", 1020 user_hostfiles[0]); 1021 error("Offending %s key in %s:%lu", key_type(host_found->key), 1022 host_found->file, host_found->line); 1023 1024 /* 1025 * If strict host key checking is in use, the user will have 1026 * to edit the key manually and we can only abort. 1027 */ 1028 if (options.strict_host_key_checking) { 1029 error("%s host key for %.200s has changed and you have " 1030 "requested strict checking.", type, host); 1031 goto fail; 1032 } 1033 1034 continue_unsafe: 1035 /* 1036 * If strict host key checking has not been requested, allow 1037 * the connection but without MITM-able authentication or 1038 * forwarding. 1039 */ 1040 if (options.password_authentication) { 1041 error("Password authentication is disabled to avoid " 1042 "man-in-the-middle attacks."); 1043 options.password_authentication = 0; 1044 cancelled_forwarding = 1; 1045 } 1046 if (options.kbd_interactive_authentication) { 1047 error("Keyboard-interactive authentication is disabled" 1048 " to avoid man-in-the-middle attacks."); 1049 options.kbd_interactive_authentication = 0; 1050 options.challenge_response_authentication = 0; 1051 cancelled_forwarding = 1; 1052 } 1053 if (options.challenge_response_authentication) { 1054 error("Challenge/response authentication is disabled" 1055 " to avoid man-in-the-middle attacks."); 1056 options.challenge_response_authentication = 0; 1057 cancelled_forwarding = 1; 1058 } 1059 if (options.forward_agent) { 1060 error("Agent forwarding is disabled to avoid " 1061 "man-in-the-middle attacks."); 1062 options.forward_agent = 0; 1063 cancelled_forwarding = 1; 1064 } 1065 if (options.forward_x11) { 1066 error("X11 forwarding is disabled to avoid " 1067 "man-in-the-middle attacks."); 1068 options.forward_x11 = 0; 1069 cancelled_forwarding = 1; 1070 } 1071 if (options.num_local_forwards > 0 || 1072 options.num_remote_forwards > 0) { 1073 error("Port forwarding is disabled to avoid " 1074 "man-in-the-middle attacks."); 1075 options.num_local_forwards = 1076 options.num_remote_forwards = 0; 1077 cancelled_forwarding = 1; 1078 } 1079 if (options.tun_open != SSH_TUNMODE_NO) { 1080 error("Tunnel forwarding is disabled to avoid " 1081 "man-in-the-middle attacks."); 1082 options.tun_open = SSH_TUNMODE_NO; 1083 cancelled_forwarding = 1; 1084 } 1085 if (options.exit_on_forward_failure && cancelled_forwarding) 1086 fatal("Error: forwarding disabled due to host key " 1087 "check failure"); 1088 1089 /* 1090 * XXX Should permit the user to change to use the new id. 1091 * This could be done by converting the host key to an 1092 * identifying sentence, tell that the host identifies itself 1093 * by that sentence, and ask the user if he/she wishes to 1094 * accept the authentication. 1095 */ 1096 break; 1097 case HOST_FOUND: 1098 fatal("internal error"); 1099 break; 1100 } 1101 1102 if (options.check_host_ip && host_status != HOST_CHANGED && 1103 ip_status == HOST_CHANGED) { 1104 snprintf(msg, sizeof(msg), 1105 "Warning: the %s host key for '%.200s' " 1106 "differs from the key for the IP address '%.128s'" 1107 "\nOffending key for IP in %s:%lu", 1108 type, host, ip, ip_found->file, ip_found->line); 1109 if (host_status == HOST_OK) { 1110 len = strlen(msg); 1111 snprintf(msg + len, sizeof(msg) - len, 1112 "\nMatching host key in %s:%lu", 1113 host_found->file, host_found->line); 1114 } 1115 if (options.strict_host_key_checking == 1) { 1116 logit("%s", msg); 1117 error("Exiting, you have requested strict checking."); 1118 goto fail; 1119 } else if (options.strict_host_key_checking == 2) { 1120 strlcat(msg, "\nAre you sure you want " 1121 "to continue connecting (yes/no)? ", sizeof(msg)); 1122 if (!confirm(msg)) 1123 goto fail; 1124 } else { 1125 logit("%s", msg); 1126 } 1127 } 1128 1129 xfree(ip); 1130 xfree(host); 1131 if (host_hostkeys != NULL) 1132 free_hostkeys(host_hostkeys); 1133 if (ip_hostkeys != NULL) 1134 free_hostkeys(ip_hostkeys); 1135 return 0; 1136 1137 fail: 1138 if (want_cert && host_status != HOST_REVOKED) { 1139 /* 1140 * No matching certificate. Downgrade cert to raw key and 1141 * search normally. 1142 */ 1143 debug("No matching CA found. Retry with plain key"); 1144 raw_key = key_from_private(host_key); 1145 if (key_drop_cert(raw_key) != 0) 1146 fatal("Couldn't drop certificate"); 1147 host_key = raw_key; 1148 goto retry; 1149 } 1150 if (raw_key != NULL) 1151 key_free(raw_key); 1152 xfree(ip); 1153 xfree(host); 1154 if (host_hostkeys != NULL) 1155 free_hostkeys(host_hostkeys); 1156 if (ip_hostkeys != NULL) 1157 free_hostkeys(ip_hostkeys); 1158 return -1; 1159 } 1160 1161 /* returns 0 if key verifies or -1 if key does NOT verify */ 1162 int 1163 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1164 { 1165 int flags = 0; 1166 char *fp; 1167 1168 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1169 debug("Server host key: %s %s", key_type(host_key), fp); 1170 xfree(fp); 1171 1172 /* XXX certs are not yet supported for DNS */ 1173 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1174 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1175 if (flags & DNS_VERIFY_FOUND) { 1176 1177 if (options.verify_host_key_dns == 1 && 1178 flags & DNS_VERIFY_MATCH && 1179 flags & DNS_VERIFY_SECURE) 1180 return 0; 1181 1182 if (flags & DNS_VERIFY_MATCH) { 1183 matching_host_key_dns = 1; 1184 } else { 1185 warn_changed_key(host_key); 1186 error("Update the SSHFP RR in DNS with the new " 1187 "host key to get rid of this message."); 1188 } 1189 } 1190 } 1191 1192 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1193 options.user_hostfiles, options.num_user_hostfiles, 1194 options.system_hostfiles, options.num_system_hostfiles); 1195 } 1196 1197 /* 1198 * Starts a dialog with the server, and authenticates the current user on the 1199 * server. This does not need any extra privileges. The basic connection 1200 * to the server must already have been established before this is called. 1201 * If login fails, this function prints an error and never returns. 1202 * This function does not require super-user privileges. 1203 */ 1204 void 1205 ssh_login(Sensitive *sensitive, const char *orighost, 1206 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1207 { 1208 char *host, *cp; 1209 char *server_user, *local_user; 1210 1211 local_user = xstrdup(pw->pw_name); 1212 server_user = options.user ? options.user : local_user; 1213 1214 /* Convert the user-supplied hostname into all lowercase. */ 1215 host = xstrdup(orighost); 1216 for (cp = host; *cp; cp++) 1217 if (isupper(*cp)) 1218 *cp = (char)tolower(*cp); 1219 1220 /* Exchange protocol version identification strings with the server. */ 1221 ssh_exchange_identification(timeout_ms); 1222 1223 /* Put the connection into non-blocking mode. */ 1224 packet_set_nonblocking(); 1225 1226 /* key exchange */ 1227 /* authenticate user */ 1228 if (compat20) { 1229 ssh_kex2(host, hostaddr, port); 1230 ssh_userauth2(local_user, server_user, host, sensitive); 1231 } else { 1232 ssh_kex(host, hostaddr); 1233 ssh_userauth1(local_user, server_user, host, sensitive); 1234 } 1235 xfree(local_user); 1236 } 1237 1238 void 1239 ssh_put_password(char *password) 1240 { 1241 int size; 1242 char *padded; 1243 1244 if (datafellows & SSH_BUG_PASSWORDPAD) { 1245 packet_put_cstring(password); 1246 return; 1247 } 1248 size = roundup(strlen(password) + 1, 32); 1249 padded = xcalloc(1, size); 1250 strlcpy(padded, password, size); 1251 packet_put_string(padded, size); 1252 memset(padded, 0, size); 1253 xfree(padded); 1254 } 1255 1256 /* print all known host keys for a given host, but skip keys of given type */ 1257 static int 1258 show_other_keys(struct hostkeys *hostkeys, Key *key) 1259 { 1260 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1261 int i, ret = 0; 1262 char *fp, *ra; 1263 const struct hostkey_entry *found; 1264 1265 for (i = 0; type[i] != -1; i++) { 1266 if (type[i] == key->type) 1267 continue; 1268 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1269 continue; 1270 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1271 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1272 logit("WARNING: %s key found for host %s\n" 1273 "in %s:%lu\n" 1274 "%s key fingerprint %s.", 1275 key_type(found->key), 1276 found->host, found->file, found->line, 1277 key_type(found->key), fp); 1278 if (options.visual_host_key) 1279 logit("%s", ra); 1280 xfree(ra); 1281 xfree(fp); 1282 ret = 1; 1283 } 1284 return ret; 1285 } 1286 1287 static void 1288 warn_changed_key(Key *host_key) 1289 { 1290 char *fp; 1291 1292 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1293 1294 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1295 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1296 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1297 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1298 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1299 error("It is also possible that a host key has just been changed."); 1300 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1301 key_type(host_key), fp); 1302 error("Please contact your system administrator."); 1303 1304 xfree(fp); 1305 } 1306 1307 /* 1308 * Execute a local command 1309 */ 1310 int 1311 ssh_local_cmd(const char *args) 1312 { 1313 char *shell; 1314 pid_t pid; 1315 int status; 1316 void (*osighand)(int); 1317 1318 if (!options.permit_local_command || 1319 args == NULL || !*args) 1320 return (1); 1321 1322 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1323 shell = _PATH_BSHELL; 1324 1325 osighand = signal(SIGCHLD, SIG_DFL); 1326 pid = fork(); 1327 if (pid == 0) { 1328 signal(SIGPIPE, SIG_DFL); 1329 debug3("Executing %s -c \"%s\"", shell, args); 1330 execl(shell, shell, "-c", args, (char *)NULL); 1331 error("Couldn't execute %s -c \"%s\": %s", 1332 shell, args, strerror(errno)); 1333 _exit(1); 1334 } else if (pid == -1) 1335 fatal("fork failed: %.100s", strerror(errno)); 1336 while (waitpid(pid, &status, 0) == -1) 1337 if (errno != EINTR) 1338 fatal("Couldn't wait for child: %s", strerror(errno)); 1339 signal(SIGCHLD, osighand); 1340 1341 if (!WIFEXITED(status)) 1342 return (1); 1343 1344 return (WEXITSTATUS(status)); 1345 } 1346