1 /* $OpenBSD: sshconnect.c,v 1.251 2014/07/15 15:54:14 millert 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 #include <rpc/rpc.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 "misc.h" 59 #include "readconf.h" 60 #include "atomicio.h" 61 #include "dns.h" 62 #include "roaming.h" 63 #include "monitor_fdpass.h" 64 #include "ssh2.h" 65 #include "version.h" 66 67 char *client_version_string = NULL; 68 char *server_version_string = NULL; 69 Key *previous_host_key = NULL; 70 71 static int matching_host_key_dns = 0; 72 73 static pid_t proxy_command_pid = 0; 74 75 /* import */ 76 extern Options options; 77 extern char *__progname; 78 extern uid_t original_real_uid; 79 extern uid_t original_effective_uid; 80 81 static int show_other_keys(struct hostkeys *, Key *); 82 static void warn_changed_key(Key *); 83 84 /* Expand a proxy command */ 85 static char * 86 expand_proxy_command(const char *proxy_command, const char *user, 87 const char *host, int port) 88 { 89 char *tmp, *ret, strport[NI_MAXSERV]; 90 91 snprintf(strport, sizeof strport, "%d", port); 92 xasprintf(&tmp, "exec %s", proxy_command); 93 ret = percent_expand(tmp, "h", host, "p", strport, 94 "r", options.user, (char *)NULL); 95 free(tmp); 96 return ret; 97 } 98 99 /* 100 * Connect to the given ssh server using a proxy command that passes a 101 * a connected fd back to us. 102 */ 103 static int 104 ssh_proxy_fdpass_connect(const char *host, u_short port, 105 const char *proxy_command) 106 { 107 char *command_string; 108 int sp[2], sock; 109 pid_t pid; 110 char *shell; 111 112 if ((shell = getenv("SHELL")) == NULL) 113 shell = _PATH_BSHELL; 114 115 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) 116 fatal("Could not create socketpair to communicate with " 117 "proxy dialer: %.100s", strerror(errno)); 118 119 command_string = expand_proxy_command(proxy_command, options.user, 120 host, port); 121 debug("Executing proxy dialer command: %.500s", command_string); 122 123 /* Fork and execute the proxy command. */ 124 if ((pid = fork()) == 0) { 125 char *argv[10]; 126 127 /* Child. Permanently give up superuser privileges. */ 128 permanently_drop_suid(original_real_uid); 129 130 close(sp[1]); 131 /* Redirect stdin and stdout. */ 132 if (sp[0] != 0) { 133 if (dup2(sp[0], 0) < 0) 134 perror("dup2 stdin"); 135 } 136 if (sp[0] != 1) { 137 if (dup2(sp[0], 1) < 0) 138 perror("dup2 stdout"); 139 } 140 if (sp[0] >= 2) 141 close(sp[0]); 142 143 /* 144 * Stderr is left as it is so that error messages get 145 * printed on the user's terminal. 146 */ 147 argv[0] = shell; 148 argv[1] = "-c"; 149 argv[2] = command_string; 150 argv[3] = NULL; 151 152 /* 153 * Execute the proxy command. 154 * Note that we gave up any extra privileges above. 155 */ 156 execv(argv[0], argv); 157 perror(argv[0]); 158 exit(1); 159 } 160 /* Parent. */ 161 if (pid < 0) 162 fatal("fork failed: %.100s", strerror(errno)); 163 close(sp[0]); 164 free(command_string); 165 166 if ((sock = mm_receive_fd(sp[1])) == -1) 167 fatal("proxy dialer did not pass back a connection"); 168 169 while (waitpid(pid, NULL, 0) == -1) 170 if (errno != EINTR) 171 fatal("Couldn't wait for child: %s", strerror(errno)); 172 173 /* Set the connection file descriptors. */ 174 packet_set_connection(sock, sock); 175 176 return 0; 177 } 178 179 /* 180 * Connect to the given ssh server using a proxy command. 181 */ 182 static int 183 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 184 { 185 char *command_string; 186 int pin[2], pout[2]; 187 pid_t pid; 188 char *shell; 189 190 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 191 shell = _PATH_BSHELL; 192 193 /* Create pipes for communicating with the proxy. */ 194 if (pipe(pin) < 0 || pipe(pout) < 0) 195 fatal("Could not create pipes to communicate with the proxy: %.100s", 196 strerror(errno)); 197 198 command_string = expand_proxy_command(proxy_command, options.user, 199 host, port); 200 debug("Executing proxy command: %.500s", command_string); 201 202 /* Fork and execute the proxy command. */ 203 if ((pid = fork()) == 0) { 204 char *argv[10]; 205 206 /* Child. Permanently give up superuser privileges. */ 207 permanently_drop_suid(original_real_uid); 208 209 /* Redirect stdin and stdout. */ 210 close(pin[1]); 211 if (pin[0] != 0) { 212 if (dup2(pin[0], 0) < 0) 213 perror("dup2 stdin"); 214 close(pin[0]); 215 } 216 close(pout[0]); 217 if (dup2(pout[1], 1) < 0) 218 perror("dup2 stdout"); 219 /* Cannot be 1 because pin allocated two descriptors. */ 220 close(pout[1]); 221 222 /* Stderr is left as it is so that error messages get 223 printed on the user's terminal. */ 224 argv[0] = shell; 225 argv[1] = "-c"; 226 argv[2] = command_string; 227 argv[3] = NULL; 228 229 /* Execute the proxy command. Note that we gave up any 230 extra privileges above. */ 231 signal(SIGPIPE, SIG_DFL); 232 execv(argv[0], argv); 233 perror(argv[0]); 234 exit(1); 235 } 236 /* Parent. */ 237 if (pid < 0) 238 fatal("fork failed: %.100s", strerror(errno)); 239 else 240 proxy_command_pid = pid; /* save pid to clean up later */ 241 242 /* Close child side of the descriptors. */ 243 close(pin[0]); 244 close(pout[1]); 245 246 /* Free the command name. */ 247 free(command_string); 248 249 /* Set the connection file descriptors. */ 250 packet_set_connection(pout[0], pin[1]); 251 252 /* Indicate OK return */ 253 return 0; 254 } 255 256 void 257 ssh_kill_proxy_command(void) 258 { 259 /* 260 * Send SIGHUP to proxy command if used. We don't wait() in 261 * case it hangs and instead rely on init to reap the child 262 */ 263 if (proxy_command_pid > 1) 264 kill(proxy_command_pid, SIGHUP); 265 } 266 267 /* 268 * Set TCP receive buffer if requested. 269 * Note: tuning needs to happen after the socket is 270 * created but before the connection happens 271 * so winscale is negotiated properly -cjr 272 */ 273 static void 274 ssh_set_socket_recvbuf(int sock) 275 { 276 void *buf = (void *)&options.tcp_rcv_buf; 277 int sz = sizeof(options.tcp_rcv_buf); 278 int socksize; 279 int socksizelen = sizeof(int); 280 281 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 282 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 283 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 284 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 285 } 286 else 287 error("Couldn't set socket receive buffer to %d: %.100s", 288 options.tcp_rcv_buf, strerror(errno)); 289 } 290 291 292 /* 293 * Creates a (possibly privileged) socket for use as the ssh connection. 294 */ 295 static int 296 ssh_create_socket(int privileged, struct addrinfo *ai) 297 { 298 int sock, r, gaierr; 299 struct addrinfo hints, *res = NULL; 300 301 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 302 if (sock < 0) { 303 error("socket: %s", strerror(errno)); 304 return -1; 305 } 306 fcntl(sock, F_SETFD, FD_CLOEXEC); 307 308 if (options.tcp_rcv_buf > 0) 309 ssh_set_socket_recvbuf(sock); 310 311 /* Bind the socket to an alternative local IP address */ 312 if (options.bind_address == NULL && !privileged) 313 return sock; 314 315 if (options.bind_address) { 316 memset(&hints, 0, sizeof(hints)); 317 hints.ai_family = ai->ai_family; 318 hints.ai_socktype = ai->ai_socktype; 319 hints.ai_protocol = ai->ai_protocol; 320 hints.ai_flags = AI_PASSIVE; 321 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 322 if (gaierr) { 323 error("getaddrinfo: %s: %s", options.bind_address, 324 ssh_gai_strerror(gaierr)); 325 close(sock); 326 return -1; 327 } 328 } 329 /* 330 * If we are running as root and want to connect to a privileged 331 * port, bind our own socket to a privileged port. 332 */ 333 if (privileged) { 334 PRIV_START; 335 r = bindresvport_sa(sock, res ? res->ai_addr : NULL); 336 PRIV_END; 337 if (r < 0) { 338 error("bindresvport_sa: af=%d %s", ai->ai_family, 339 strerror(errno)); 340 goto fail; 341 } 342 } else { 343 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 344 error("bind: %s: %s", options.bind_address, 345 strerror(errno)); 346 fail: 347 close(sock); 348 freeaddrinfo(res); 349 return -1; 350 } 351 } 352 if (res != NULL) 353 freeaddrinfo(res); 354 return sock; 355 } 356 357 static int 358 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 359 socklen_t addrlen, int *timeoutp) 360 { 361 fd_set *fdset; 362 struct timeval tv, t_start; 363 socklen_t optlen; 364 int optval, rc, result = -1; 365 366 gettimeofday(&t_start, NULL); 367 368 if (*timeoutp <= 0) { 369 result = connect(sockfd, serv_addr, addrlen); 370 goto done; 371 } 372 373 set_nonblock(sockfd); 374 rc = connect(sockfd, serv_addr, addrlen); 375 if (rc == 0) { 376 unset_nonblock(sockfd); 377 result = 0; 378 goto done; 379 } 380 if (errno != EINPROGRESS) { 381 result = -1; 382 goto done; 383 } 384 385 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 386 sizeof(fd_mask)); 387 FD_SET(sockfd, fdset); 388 ms_to_timeval(&tv, *timeoutp); 389 390 for (;;) { 391 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 392 if (rc != -1 || errno != EINTR) 393 break; 394 } 395 396 switch (rc) { 397 case 0: 398 /* Timed out */ 399 errno = ETIMEDOUT; 400 break; 401 case -1: 402 /* Select error */ 403 debug("select: %s", strerror(errno)); 404 break; 405 case 1: 406 /* Completed or failed */ 407 optval = 0; 408 optlen = sizeof(optval); 409 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 410 &optlen) == -1) { 411 debug("getsockopt: %s", strerror(errno)); 412 break; 413 } 414 if (optval != 0) { 415 errno = optval; 416 break; 417 } 418 result = 0; 419 unset_nonblock(sockfd); 420 break; 421 default: 422 /* Should not occur */ 423 fatal("Bogus return (%d) from select()", rc); 424 } 425 426 free(fdset); 427 428 done: 429 if (result == 0 && *timeoutp > 0) { 430 ms_subtract_diff(&t_start, timeoutp); 431 if (*timeoutp <= 0) { 432 errno = ETIMEDOUT; 433 result = -1; 434 } 435 } 436 437 return (result); 438 } 439 440 /* 441 * Opens a TCP/IP connection to the remote server on the given host. 442 * The address of the remote host will be returned in hostaddr. 443 * If port is 0, the default port will be used. If needpriv is true, 444 * a privileged port will be allocated to make the connection. 445 * This requires super-user privileges if needpriv is true. 446 * Connection_attempts specifies the maximum number of tries (one per 447 * second). If proxy_command is non-NULL, it specifies the command (with %h 448 * and %p substituted for host and port, respectively) to use to contact 449 * the daemon. 450 */ 451 static int 452 ssh_connect_direct(const char *host, struct addrinfo *aitop, 453 struct sockaddr_storage *hostaddr, u_short port, int family, 454 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 455 { 456 int on = 1; 457 int sock = -1, attempt; 458 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 459 struct addrinfo *ai; 460 461 debug2("ssh_connect: needpriv %d", needpriv); 462 463 for (attempt = 0; attempt < connection_attempts; attempt++) { 464 if (attempt > 0) { 465 /* Sleep a moment before retrying. */ 466 sleep(1); 467 debug("Trying again..."); 468 } 469 /* 470 * Loop through addresses for this host, and try each one in 471 * sequence until the connection succeeds. 472 */ 473 for (ai = aitop; ai; ai = ai->ai_next) { 474 if (ai->ai_family != AF_INET && 475 ai->ai_family != AF_INET6) 476 continue; 477 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 478 ntop, sizeof(ntop), strport, sizeof(strport), 479 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 480 error("ssh_connect: getnameinfo failed"); 481 continue; 482 } 483 debug("Connecting to %.200s [%.100s] port %s.", 484 host, ntop, strport); 485 486 /* Create a socket for connecting. */ 487 sock = ssh_create_socket(needpriv, ai); 488 if (sock < 0) 489 /* Any error is already output */ 490 continue; 491 492 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 493 timeout_ms) >= 0) { 494 /* Successful connection. */ 495 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 496 break; 497 } else { 498 debug("connect to address %s port %s: %s", 499 ntop, strport, strerror(errno)); 500 close(sock); 501 sock = -1; 502 } 503 } 504 if (sock != -1) 505 break; /* Successful connection. */ 506 } 507 508 /* Return failure if we didn't get a successful connection. */ 509 if (sock == -1) { 510 error("ssh: connect to host %s port %s: %s", 511 host, strport, strerror(errno)); 512 return (-1); 513 } 514 515 debug("Connection established."); 516 517 /* Set SO_KEEPALIVE if requested. */ 518 if (want_keepalive && 519 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 520 sizeof(on)) < 0) 521 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 522 523 /* Set the connection. */ 524 packet_set_connection(sock, sock); 525 526 return 0; 527 } 528 529 int 530 ssh_connect(const char *host, struct addrinfo *addrs, 531 struct sockaddr_storage *hostaddr, u_short port, int family, 532 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 533 { 534 if (options.proxy_command == NULL) { 535 return ssh_connect_direct(host, addrs, hostaddr, port, family, 536 connection_attempts, timeout_ms, want_keepalive, needpriv); 537 } else if (strcmp(options.proxy_command, "-") == 0) { 538 packet_set_connection(STDIN_FILENO, STDOUT_FILENO); 539 return 0; /* Always succeeds */ 540 } else if (options.proxy_use_fdpass) { 541 return ssh_proxy_fdpass_connect(host, port, 542 options.proxy_command); 543 } 544 return ssh_proxy_connect(host, port, options.proxy_command); 545 } 546 547 static void 548 send_client_banner(int connection_out, int minor1) 549 { 550 /* Send our own protocol version identification. */ 551 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s%s%s", 552 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 553 compat20 ? PROTOCOL_MINOR_2 : minor1, 554 SSH_RELEASE, options.hpn_disabled ? "" : SSH_VERSION_HPN, 555 *options.version_addendum == '\0' ? "" : " ", 556 options.version_addendum, compat20 ? "\r\n" : "\n"); 557 if (roaming_atomicio(vwrite, connection_out, client_version_string, 558 strlen(client_version_string)) != strlen(client_version_string)) 559 fatal("write: %.100s", strerror(errno)); 560 chop(client_version_string); 561 debug("Local version string %.100s", client_version_string); 562 } 563 564 /* 565 * Waits for the server identification string, and sends our own 566 * identification string. 567 */ 568 void 569 ssh_exchange_identification(int timeout_ms) 570 { 571 char buf[256], remote_version[256]; /* must be same size! */ 572 int remote_major, remote_minor, mismatch; 573 int connection_in = packet_get_connection_in(); 574 int connection_out = packet_get_connection_out(); 575 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0; 576 u_int i, n; 577 size_t len; 578 int fdsetsz, remaining, rc; 579 struct timeval t_start, t_remaining; 580 fd_set *fdset; 581 582 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 583 fdset = xcalloc(1, fdsetsz); 584 585 /* 586 * If we are SSH2-only then we can send the banner immediately and 587 * save a round-trip. 588 */ 589 if (options.protocol == SSH_PROTO_2) { 590 enable_compat20(); 591 send_client_banner(connection_out, 0); 592 client_banner_sent = 1; 593 } 594 595 /* Read other side's version identification. */ 596 remaining = timeout_ms; 597 for (n = 0;;) { 598 for (i = 0; i < sizeof(buf) - 1; i++) { 599 if (timeout_ms > 0) { 600 gettimeofday(&t_start, NULL); 601 ms_to_timeval(&t_remaining, remaining); 602 FD_SET(connection_in, fdset); 603 rc = select(connection_in + 1, fdset, NULL, 604 fdset, &t_remaining); 605 ms_subtract_diff(&t_start, &remaining); 606 if (rc == 0 || remaining <= 0) 607 fatal("Connection timed out during " 608 "banner exchange"); 609 if (rc == -1) { 610 if (errno == EINTR) 611 continue; 612 fatal("ssh_exchange_identification: " 613 "select: %s", strerror(errno)); 614 } 615 } 616 617 len = roaming_atomicio(read, connection_in, &buf[i], 1); 618 619 if (len != 1 && errno == EPIPE) 620 fatal("ssh_exchange_identification: " 621 "Connection closed by remote host"); 622 else if (len != 1) 623 fatal("ssh_exchange_identification: " 624 "read: %.100s", strerror(errno)); 625 if (buf[i] == '\r') { 626 buf[i] = '\n'; 627 buf[i + 1] = 0; 628 continue; /**XXX wait for \n */ 629 } 630 if (buf[i] == '\n') { 631 buf[i + 1] = 0; 632 break; 633 } 634 if (++n > 65536) 635 fatal("ssh_exchange_identification: " 636 "No banner received"); 637 } 638 buf[sizeof(buf) - 1] = 0; 639 if (strncmp(buf, "SSH-", 4) == 0) 640 break; 641 debug("ssh_exchange_identification: %s", buf); 642 } 643 server_version_string = xstrdup(buf); 644 free(fdset); 645 646 /* 647 * Check that the versions match. In future this might accept 648 * several versions and set appropriate flags to handle them. 649 */ 650 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 651 &remote_major, &remote_minor, remote_version) != 3) 652 fatal("Bad remote protocol version identification: '%.100s'", buf); 653 debug("Remote protocol version %d.%d, remote software version %.100s", 654 remote_major, remote_minor, remote_version); 655 656 compat_datafellows(remote_version); 657 mismatch = 0; 658 659 switch (remote_major) { 660 case 1: 661 if (remote_minor == 99 && 662 (options.protocol & SSH_PROTO_2) && 663 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 664 enable_compat20(); 665 break; 666 } 667 if (!(options.protocol & SSH_PROTO_1)) { 668 mismatch = 1; 669 break; 670 } 671 if (remote_minor < 3) { 672 fatal("Remote machine has too old SSH software version."); 673 } else if (remote_minor == 3 || remote_minor == 4) { 674 /* We speak 1.3, too. */ 675 enable_compat13(); 676 minor1 = 3; 677 if (options.forward_agent) { 678 logit("Agent forwarding disabled for protocol 1.3"); 679 options.forward_agent = 0; 680 } 681 } 682 break; 683 case 2: 684 if (options.protocol & SSH_PROTO_2) { 685 enable_compat20(); 686 break; 687 } 688 /* FALLTHROUGH */ 689 default: 690 mismatch = 1; 691 break; 692 } 693 if (mismatch) 694 fatal("Protocol major versions differ: %d vs. %d", 695 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 696 remote_major); 697 if ((datafellows & SSH_BUG_DERIVEKEY) != 0) 698 fatal("Server version \"%.100s\" uses unsafe key agreement; " 699 "refusing connection", remote_version); 700 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) 701 logit("Server version \"%.100s\" uses unsafe RSA signature " 702 "scheme; disabling use of RSA keys", remote_version); 703 if (!client_banner_sent) 704 send_client_banner(connection_out, minor1); 705 chop(server_version_string); 706 } 707 708 /* defaults to 'no' */ 709 static int 710 confirm(const char *prompt) 711 { 712 const char *msg, *again = "Please type 'yes' or 'no': "; 713 char *p; 714 int ret = -1; 715 716 if (options.batch_mode) 717 return 0; 718 for (msg = prompt;;msg = again) { 719 p = read_passphrase(msg, RP_ECHO); 720 if (p == NULL || 721 (p[0] == '\0') || (p[0] == '\n') || 722 strncasecmp(p, "no", 2) == 0) 723 ret = 0; 724 if (p && strncasecmp(p, "yes", 3) == 0) 725 ret = 1; 726 free(p); 727 if (ret != -1) 728 return ret; 729 } 730 } 731 732 static int 733 check_host_cert(const char *host, const Key *host_key) 734 { 735 const char *reason; 736 737 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 738 error("%s", reason); 739 return 0; 740 } 741 if (buffer_len(host_key->cert->critical) != 0) { 742 error("Certificate for %s contains unsupported " 743 "critical options(s)", host); 744 return 0; 745 } 746 return 1; 747 } 748 749 static int 750 sockaddr_is_local(struct sockaddr *hostaddr) 751 { 752 switch (hostaddr->sa_family) { 753 case AF_INET: 754 return (ntohl(((struct sockaddr_in *)hostaddr)-> 755 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 756 case AF_INET6: 757 return IN6_IS_ADDR_LOOPBACK( 758 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 759 default: 760 return 0; 761 } 762 } 763 764 /* 765 * Prepare the hostname and ip address strings that are used to lookup 766 * host keys in known_hosts files. These may have a port number appended. 767 */ 768 void 769 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 770 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 771 { 772 char ntop[NI_MAXHOST]; 773 socklen_t addrlen; 774 775 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 776 case -1: 777 addrlen = 0; 778 break; 779 case AF_INET: 780 addrlen = sizeof(struct sockaddr_in); 781 break; 782 case AF_INET6: 783 addrlen = sizeof(struct sockaddr_in6); 784 break; 785 default: 786 addrlen = sizeof(struct sockaddr); 787 break; 788 } 789 790 /* 791 * We don't have the remote ip-address for connections 792 * using a proxy command 793 */ 794 if (hostfile_ipaddr != NULL) { 795 if (options.proxy_command == NULL) { 796 if (getnameinfo(hostaddr, addrlen, 797 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 798 fatal("check_host_key: getnameinfo failed"); 799 *hostfile_ipaddr = put_host_port(ntop, port); 800 } else { 801 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 802 "command>"); 803 } 804 } 805 806 /* 807 * Allow the user to record the key under a different name or 808 * differentiate a non-standard port. This is useful for ssh 809 * tunneling over forwarded connections or if you run multiple 810 * sshd's on different ports on the same machine. 811 */ 812 if (hostfile_hostname != NULL) { 813 if (options.host_key_alias != NULL) { 814 *hostfile_hostname = xstrdup(options.host_key_alias); 815 debug("using hostkeyalias: %s", *hostfile_hostname); 816 } else { 817 *hostfile_hostname = put_host_port(hostname, port); 818 } 819 } 820 } 821 822 /* 823 * check whether the supplied host key is valid, return -1 if the key 824 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 825 */ 826 #define RDRW 0 827 #define RDONLY 1 828 #define ROQUIET 2 829 static int 830 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 831 Key *host_key, int readonly, 832 char **user_hostfiles, u_int num_user_hostfiles, 833 char **system_hostfiles, u_int num_system_hostfiles) 834 { 835 HostStatus host_status; 836 HostStatus ip_status; 837 Key *raw_key = NULL; 838 char *ip = NULL, *host = NULL; 839 char hostline[1000], *hostp, *fp, *ra; 840 char msg[1024]; 841 const char *type; 842 const struct hostkey_entry *host_found, *ip_found; 843 int len, cancelled_forwarding = 0; 844 int local = sockaddr_is_local(hostaddr); 845 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 846 struct hostkeys *host_hostkeys, *ip_hostkeys; 847 u_int i; 848 849 /* 850 * Force accepting of the host key for loopback/localhost. The 851 * problem is that if the home directory is NFS-mounted to multiple 852 * machines, localhost will refer to a different machine in each of 853 * them, and the user will get bogus HOST_CHANGED warnings. This 854 * essentially disables host authentication for localhost; however, 855 * this is probably not a real problem. 856 */ 857 if (options.no_host_authentication_for_localhost == 1 && local && 858 options.host_key_alias == NULL) { 859 debug("Forcing accepting of host key for " 860 "loopback/localhost."); 861 return 0; 862 } 863 864 /* 865 * Prepare the hostname and address strings used for hostkey lookup. 866 * In some cases, these will have a port number appended. 867 */ 868 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 869 870 /* 871 * Turn off check_host_ip if the connection is to localhost, via proxy 872 * command or if we don't have a hostname to compare with 873 */ 874 if (options.check_host_ip && (local || 875 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 876 options.check_host_ip = 0; 877 878 host_hostkeys = init_hostkeys(); 879 for (i = 0; i < num_user_hostfiles; i++) 880 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 881 for (i = 0; i < num_system_hostfiles; i++) 882 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 883 884 ip_hostkeys = NULL; 885 if (!want_cert && options.check_host_ip) { 886 ip_hostkeys = init_hostkeys(); 887 for (i = 0; i < num_user_hostfiles; i++) 888 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 889 for (i = 0; i < num_system_hostfiles; i++) 890 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 891 } 892 893 retry: 894 /* Reload these as they may have changed on cert->key downgrade */ 895 want_cert = key_is_cert(host_key); 896 type = key_type(host_key); 897 898 /* 899 * Check if the host key is present in the user's list of known 900 * hosts or in the systemwide list. 901 */ 902 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 903 &host_found); 904 905 /* 906 * Also perform check for the ip address, skip the check if we are 907 * localhost, looking for a certificate, or the hostname was an ip 908 * address to begin with. 909 */ 910 if (!want_cert && ip_hostkeys != NULL) { 911 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 912 &ip_found); 913 if (host_status == HOST_CHANGED && 914 (ip_status != HOST_CHANGED || 915 (ip_found != NULL && 916 !key_equal(ip_found->key, host_found->key)))) 917 host_ip_differ = 1; 918 } else 919 ip_status = host_status; 920 921 switch (host_status) { 922 case HOST_OK: 923 /* The host is known and the key matches. */ 924 debug("Host '%.200s' is known and matches the %s host %s.", 925 host, type, want_cert ? "certificate" : "key"); 926 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 927 host_found->file, host_found->line); 928 if (want_cert && !check_host_cert(hostname, host_key)) 929 goto fail; 930 if (options.check_host_ip && ip_status == HOST_NEW) { 931 if (readonly || want_cert) 932 logit("%s host key for IP address " 933 "'%.128s' not in list of known hosts.", 934 type, ip); 935 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 936 host_key, options.hash_known_hosts)) 937 logit("Failed to add the %s host key for IP " 938 "address '%.128s' to the list of known " 939 "hosts (%.30s).", type, ip, 940 user_hostfiles[0]); 941 else 942 logit("Warning: Permanently added the %s host " 943 "key for IP address '%.128s' to the list " 944 "of known hosts.", type, ip); 945 } else if (options.visual_host_key) { 946 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 947 ra = key_fingerprint(host_key, SSH_FP_MD5, 948 SSH_FP_RANDOMART); 949 logit("Host key fingerprint is %s\n%s\n", fp, ra); 950 free(ra); 951 free(fp); 952 } 953 break; 954 case HOST_NEW: 955 if (options.host_key_alias == NULL && port != 0 && 956 port != SSH_DEFAULT_PORT) { 957 debug("checking without port identifier"); 958 if (check_host_key(hostname, hostaddr, 0, host_key, 959 ROQUIET, user_hostfiles, num_user_hostfiles, 960 system_hostfiles, num_system_hostfiles) == 0) { 961 debug("found matching key w/out port"); 962 break; 963 } 964 } 965 if (readonly || want_cert) 966 goto fail; 967 /* The host is new. */ 968 if (options.strict_host_key_checking == 1) { 969 /* 970 * User has requested strict host key checking. We 971 * will not add the host key automatically. The only 972 * alternative left is to abort. 973 */ 974 error("No %s host key is known for %.200s and you " 975 "have requested strict checking.", type, host); 976 goto fail; 977 } else if (options.strict_host_key_checking == 2) { 978 char msg1[1024], msg2[1024]; 979 980 if (show_other_keys(host_hostkeys, host_key)) 981 snprintf(msg1, sizeof(msg1), 982 "\nbut keys of different type are already" 983 " known for this host."); 984 else 985 snprintf(msg1, sizeof(msg1), "."); 986 /* The default */ 987 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 988 ra = key_fingerprint(host_key, SSH_FP_MD5, 989 SSH_FP_RANDOMART); 990 msg2[0] = '\0'; 991 if (options.verify_host_key_dns) { 992 if (matching_host_key_dns) 993 snprintf(msg2, sizeof(msg2), 994 "Matching host key fingerprint" 995 " found in DNS.\n"); 996 else 997 snprintf(msg2, sizeof(msg2), 998 "No matching host key fingerprint" 999 " found in DNS.\n"); 1000 } 1001 snprintf(msg, sizeof(msg), 1002 "The authenticity of host '%.200s (%s)' can't be " 1003 "established%s\n" 1004 "%s key fingerprint is %s.%s%s\n%s" 1005 "Are you sure you want to continue connecting " 1006 "(yes/no)? ", 1007 host, ip, msg1, type, fp, 1008 options.visual_host_key ? "\n" : "", 1009 options.visual_host_key ? ra : "", 1010 msg2); 1011 free(ra); 1012 free(fp); 1013 if (!confirm(msg)) 1014 goto fail; 1015 } 1016 /* 1017 * If not in strict mode, add the key automatically to the 1018 * local known_hosts file. 1019 */ 1020 if (options.check_host_ip && ip_status == HOST_NEW) { 1021 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1022 hostp = hostline; 1023 if (options.hash_known_hosts) { 1024 /* Add hash of host and IP separately */ 1025 r = add_host_to_hostfile(user_hostfiles[0], 1026 host, host_key, options.hash_known_hosts) && 1027 add_host_to_hostfile(user_hostfiles[0], ip, 1028 host_key, options.hash_known_hosts); 1029 } else { 1030 /* Add unhashed "host,ip" */ 1031 r = add_host_to_hostfile(user_hostfiles[0], 1032 hostline, host_key, 1033 options.hash_known_hosts); 1034 } 1035 } else { 1036 r = add_host_to_hostfile(user_hostfiles[0], host, 1037 host_key, options.hash_known_hosts); 1038 hostp = host; 1039 } 1040 1041 if (!r) 1042 logit("Failed to add the host to the list of known " 1043 "hosts (%.500s).", user_hostfiles[0]); 1044 else 1045 logit("Warning: Permanently added '%.200s' (%s) to the " 1046 "list of known hosts.", hostp, type); 1047 break; 1048 case HOST_REVOKED: 1049 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1050 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1051 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1052 error("The %s host key for %s is marked as revoked.", type, host); 1053 error("This could mean that a stolen key is being used to"); 1054 error("impersonate this host."); 1055 1056 /* 1057 * If strict host key checking is in use, the user will have 1058 * to edit the key manually and we can only abort. 1059 */ 1060 if (options.strict_host_key_checking) { 1061 error("%s host key for %.200s was revoked and you have " 1062 "requested strict checking.", type, host); 1063 goto fail; 1064 } 1065 goto continue_unsafe; 1066 1067 case HOST_CHANGED: 1068 if (want_cert) { 1069 /* 1070 * This is only a debug() since it is valid to have 1071 * CAs with wildcard DNS matches that don't match 1072 * all hosts that one might visit. 1073 */ 1074 debug("Host certificate authority does not " 1075 "match %s in %s:%lu", CA_MARKER, 1076 host_found->file, host_found->line); 1077 goto fail; 1078 } 1079 if (readonly == ROQUIET) 1080 goto fail; 1081 if (options.check_host_ip && host_ip_differ) { 1082 char *key_msg; 1083 if (ip_status == HOST_NEW) 1084 key_msg = "is unknown"; 1085 else if (ip_status == HOST_OK) 1086 key_msg = "is unchanged"; 1087 else 1088 key_msg = "has a different value"; 1089 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1090 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1091 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1092 error("The %s host key for %s has changed,", type, host); 1093 error("and the key for the corresponding IP address %s", ip); 1094 error("%s. This could either mean that", key_msg); 1095 error("DNS SPOOFING is happening or the IP address for the host"); 1096 error("and its host key have changed at the same time."); 1097 if (ip_status != HOST_NEW) 1098 error("Offending key for IP in %s:%lu", 1099 ip_found->file, ip_found->line); 1100 } 1101 /* The host key has changed. */ 1102 warn_changed_key(host_key); 1103 error("Add correct host key in %.100s to get rid of this message.", 1104 user_hostfiles[0]); 1105 error("Offending %s key in %s:%lu", key_type(host_found->key), 1106 host_found->file, host_found->line); 1107 1108 /* 1109 * If strict host key checking is in use, the user will have 1110 * to edit the key manually and we can only abort. 1111 */ 1112 if (options.strict_host_key_checking) { 1113 error("%s host key for %.200s has changed and you have " 1114 "requested strict checking.", type, host); 1115 goto fail; 1116 } 1117 1118 continue_unsafe: 1119 /* 1120 * If strict host key checking has not been requested, allow 1121 * the connection but without MITM-able authentication or 1122 * forwarding. 1123 */ 1124 if (options.password_authentication) { 1125 error("Password authentication is disabled to avoid " 1126 "man-in-the-middle attacks."); 1127 options.password_authentication = 0; 1128 cancelled_forwarding = 1; 1129 } 1130 if (options.kbd_interactive_authentication) { 1131 error("Keyboard-interactive authentication is disabled" 1132 " to avoid man-in-the-middle attacks."); 1133 options.kbd_interactive_authentication = 0; 1134 options.challenge_response_authentication = 0; 1135 cancelled_forwarding = 1; 1136 } 1137 if (options.challenge_response_authentication) { 1138 error("Challenge/response authentication is disabled" 1139 " to avoid man-in-the-middle attacks."); 1140 options.challenge_response_authentication = 0; 1141 cancelled_forwarding = 1; 1142 } 1143 if (options.forward_agent) { 1144 error("Agent forwarding is disabled to avoid " 1145 "man-in-the-middle attacks."); 1146 options.forward_agent = 0; 1147 cancelled_forwarding = 1; 1148 } 1149 if (options.forward_x11) { 1150 error("X11 forwarding is disabled to avoid " 1151 "man-in-the-middle attacks."); 1152 options.forward_x11 = 0; 1153 cancelled_forwarding = 1; 1154 } 1155 if (options.num_local_forwards > 0 || 1156 options.num_remote_forwards > 0) { 1157 error("Port forwarding is disabled to avoid " 1158 "man-in-the-middle attacks."); 1159 options.num_local_forwards = 1160 options.num_remote_forwards = 0; 1161 cancelled_forwarding = 1; 1162 } 1163 if (options.tun_open != SSH_TUNMODE_NO) { 1164 error("Tunnel forwarding is disabled to avoid " 1165 "man-in-the-middle attacks."); 1166 options.tun_open = SSH_TUNMODE_NO; 1167 cancelled_forwarding = 1; 1168 } 1169 if (options.exit_on_forward_failure && cancelled_forwarding) 1170 fatal("Error: forwarding disabled due to host key " 1171 "check failure"); 1172 1173 /* 1174 * XXX Should permit the user to change to use the new id. 1175 * This could be done by converting the host key to an 1176 * identifying sentence, tell that the host identifies itself 1177 * by that sentence, and ask the user if he/she wishes to 1178 * accept the authentication. 1179 */ 1180 break; 1181 case HOST_FOUND: 1182 fatal("internal error"); 1183 break; 1184 } 1185 1186 if (options.check_host_ip && host_status != HOST_CHANGED && 1187 ip_status == HOST_CHANGED) { 1188 snprintf(msg, sizeof(msg), 1189 "Warning: the %s host key for '%.200s' " 1190 "differs from the key for the IP address '%.128s'" 1191 "\nOffending key for IP in %s:%lu", 1192 type, host, ip, ip_found->file, ip_found->line); 1193 if (host_status == HOST_OK) { 1194 len = strlen(msg); 1195 snprintf(msg + len, sizeof(msg) - len, 1196 "\nMatching host key in %s:%lu", 1197 host_found->file, host_found->line); 1198 } 1199 if (options.strict_host_key_checking == 1) { 1200 logit("%s", msg); 1201 error("Exiting, you have requested strict checking."); 1202 goto fail; 1203 } else if (options.strict_host_key_checking == 2) { 1204 strlcat(msg, "\nAre you sure you want " 1205 "to continue connecting (yes/no)? ", sizeof(msg)); 1206 if (!confirm(msg)) 1207 goto fail; 1208 } else { 1209 logit("%s", msg); 1210 } 1211 } 1212 1213 free(ip); 1214 free(host); 1215 if (host_hostkeys != NULL) 1216 free_hostkeys(host_hostkeys); 1217 if (ip_hostkeys != NULL) 1218 free_hostkeys(ip_hostkeys); 1219 return 0; 1220 1221 fail: 1222 if (want_cert && host_status != HOST_REVOKED) { 1223 /* 1224 * No matching certificate. Downgrade cert to raw key and 1225 * search normally. 1226 */ 1227 debug("No matching CA found. Retry with plain key"); 1228 raw_key = key_from_private(host_key); 1229 if (key_drop_cert(raw_key) != 0) 1230 fatal("Couldn't drop certificate"); 1231 host_key = raw_key; 1232 goto retry; 1233 } 1234 if (raw_key != NULL) 1235 key_free(raw_key); 1236 free(ip); 1237 free(host); 1238 if (host_hostkeys != NULL) 1239 free_hostkeys(host_hostkeys); 1240 if (ip_hostkeys != NULL) 1241 free_hostkeys(ip_hostkeys); 1242 return -1; 1243 } 1244 1245 /* returns 0 if key verifies or -1 if key does NOT verify */ 1246 int 1247 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1248 { 1249 int r = -1, flags = 0; 1250 char *fp; 1251 Key *plain = NULL; 1252 1253 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1254 debug("Server host key: %s %s", key_type(host_key), fp); 1255 free(fp); 1256 1257 if (key_equal(previous_host_key, host_key)) { 1258 debug("%s: server host key matches cached key", __func__); 1259 return 0; 1260 } 1261 1262 if (options.verify_host_key_dns) { 1263 /* 1264 * XXX certs are not yet supported for DNS, so downgrade 1265 * them and try the plain key. 1266 */ 1267 plain = key_from_private(host_key); 1268 if (key_is_cert(plain)) 1269 key_drop_cert(plain); 1270 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1271 if (flags & DNS_VERIFY_FOUND) { 1272 if (options.verify_host_key_dns == 1 && 1273 flags & DNS_VERIFY_MATCH && 1274 flags & DNS_VERIFY_SECURE) { 1275 key_free(plain); 1276 r = 0; 1277 goto done; 1278 } 1279 if (flags & DNS_VERIFY_MATCH) { 1280 matching_host_key_dns = 1; 1281 } else { 1282 warn_changed_key(plain); 1283 error("Update the SSHFP RR in DNS " 1284 "with the new host key to get rid " 1285 "of this message."); 1286 } 1287 } 1288 } 1289 key_free(plain); 1290 } 1291 1292 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1293 options.user_hostfiles, options.num_user_hostfiles, 1294 options.system_hostfiles, options.num_system_hostfiles); 1295 1296 done: 1297 if (r == 0 && host_key != NULL) { 1298 key_free(previous_host_key); 1299 previous_host_key = key_from_private(host_key); 1300 } 1301 1302 return r; 1303 } 1304 1305 /* 1306 * Starts a dialog with the server, and authenticates the current user on the 1307 * server. This does not need any extra privileges. The basic connection 1308 * to the server must already have been established before this is called. 1309 * If login fails, this function prints an error and never returns. 1310 * This function does not require super-user privileges. 1311 */ 1312 void 1313 ssh_login(Sensitive *sensitive, const char *orighost, 1314 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1315 { 1316 char *host; 1317 char *server_user, *local_user; 1318 1319 local_user = xstrdup(pw->pw_name); 1320 server_user = options.user ? options.user : local_user; 1321 1322 /* Convert the user-supplied hostname into all lowercase. */ 1323 host = xstrdup(orighost); 1324 lowercase(host); 1325 1326 /* Exchange protocol version identification strings with the server. */ 1327 ssh_exchange_identification(timeout_ms); 1328 1329 /* Put the connection into non-blocking mode. */ 1330 packet_set_nonblocking(); 1331 1332 /* key exchange */ 1333 /* authenticate user */ 1334 if (compat20) { 1335 ssh_kex2(host, hostaddr, port); 1336 ssh_userauth2(local_user, server_user, host, sensitive); 1337 } else { 1338 #ifdef WITH_SSH1 1339 ssh_kex(host, hostaddr); 1340 ssh_userauth1(local_user, server_user, host, sensitive); 1341 #else 1342 fatal("ssh1 is not unsupported"); 1343 #endif 1344 } 1345 free(local_user); 1346 } 1347 1348 void 1349 ssh_put_password(char *password) 1350 { 1351 int size; 1352 char *padded; 1353 1354 if (datafellows & SSH_BUG_PASSWORDPAD) { 1355 packet_put_cstring(password); 1356 return; 1357 } 1358 size = roundup(strlen(password) + 1, 32); 1359 padded = xcalloc(1, size); 1360 strlcpy(padded, password, size); 1361 packet_put_string(padded, size); 1362 explicit_bzero(padded, size); 1363 free(padded); 1364 } 1365 1366 /* print all known host keys for a given host, but skip keys of given type */ 1367 static int 1368 show_other_keys(struct hostkeys *hostkeys, Key *key) 1369 { 1370 int type[] = { 1371 KEY_RSA1, 1372 KEY_RSA, 1373 KEY_DSA, 1374 KEY_ECDSA, 1375 KEY_ED25519, 1376 -1 1377 }; 1378 int i, ret = 0; 1379 char *fp, *ra; 1380 const struct hostkey_entry *found; 1381 1382 for (i = 0; type[i] != -1; i++) { 1383 if (type[i] == key->type) 1384 continue; 1385 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1386 continue; 1387 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1388 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1389 logit("WARNING: %s key found for host %s\n" 1390 "in %s:%lu\n" 1391 "%s key fingerprint %s.", 1392 key_type(found->key), 1393 found->host, found->file, found->line, 1394 key_type(found->key), fp); 1395 if (options.visual_host_key) 1396 logit("%s", ra); 1397 free(ra); 1398 free(fp); 1399 ret = 1; 1400 } 1401 return ret; 1402 } 1403 1404 static void 1405 warn_changed_key(Key *host_key) 1406 { 1407 char *fp; 1408 1409 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1410 1411 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1412 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1413 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1414 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1415 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1416 error("It is also possible that a host key has just been changed."); 1417 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1418 key_type(host_key), fp); 1419 error("Please contact your system administrator."); 1420 1421 free(fp); 1422 } 1423 1424 /* 1425 * Execute a local command 1426 */ 1427 int 1428 ssh_local_cmd(const char *args) 1429 { 1430 char *shell; 1431 pid_t pid; 1432 int status; 1433 void (*osighand)(int); 1434 1435 if (!options.permit_local_command || 1436 args == NULL || !*args) 1437 return (1); 1438 1439 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1440 shell = _PATH_BSHELL; 1441 1442 osighand = signal(SIGCHLD, SIG_DFL); 1443 pid = fork(); 1444 if (pid == 0) { 1445 signal(SIGPIPE, SIG_DFL); 1446 debug3("Executing %s -c \"%s\"", shell, args); 1447 execl(shell, shell, "-c", args, (char *)NULL); 1448 error("Couldn't execute %s -c \"%s\": %s", 1449 shell, args, strerror(errno)); 1450 _exit(1); 1451 } else if (pid == -1) 1452 fatal("fork failed: %.100s", strerror(errno)); 1453 while (waitpid(pid, &status, 0) == -1) 1454 if (errno != EINTR) 1455 fatal("Couldn't wait for child: %s", strerror(errno)); 1456 signal(SIGCHLD, osighand); 1457 1458 if (!WIFEXITED(status)) 1459 return (1); 1460 1461 return (WEXITSTATUS(status)); 1462 } 1463