1 /* $NetBSD: sshconnect.c,v 1.9 2013/11/08 19:18:25 christos Exp $ */ 2 /* $OpenBSD: sshconnect.c,v 1.238 2013/05/17 00:13:14 djm 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 __RCSID("$NetBSD: sshconnect.c,v 1.9 2013/11/08 19:18:25 christos Exp $"); 19 #include <sys/types.h> 20 #include <sys/param.h> 21 #include <sys/wait.h> 22 #include <sys/stat.h> 23 #include <sys/socket.h> 24 #include <sys/time.h> 25 26 #include <netinet/in.h> 27 28 #include <ctype.h> 29 #include <errno.h> 30 #include <fcntl.h> 31 #include <netdb.h> 32 #include <paths.h> 33 #include <signal.h> 34 #include <pwd.h> 35 #include <stdio.h> 36 #include <stdlib.h> 37 #include <string.h> 38 #include <unistd.h> 39 40 #include "xmalloc.h" 41 #include "ssh.h" 42 #include "rsa.h" 43 #include "buffer.h" 44 #include "packet.h" 45 #include "uidswap.h" 46 #include "compat.h" 47 #include "key.h" 48 #include "sshconnect.h" 49 #include "hostfile.h" 50 #include "log.h" 51 #include "readconf.h" 52 #include "atomicio.h" 53 #include "misc.h" 54 #include "dns.h" 55 #include "roaming.h" 56 #include "ssh2.h" 57 #include "version.h" 58 59 char *client_version_string = NULL; 60 char *server_version_string = NULL; 61 62 static int matching_host_key_dns = 0; 63 64 static pid_t proxy_command_pid = 0; 65 66 /* import */ 67 extern Options options; 68 extern char *__progname; 69 extern uid_t original_real_uid; 70 extern uid_t original_effective_uid; 71 72 static int show_other_keys(struct hostkeys *, Key *); 73 static void warn_changed_key(Key *); 74 75 /* 76 * Connect to the given ssh server using a proxy command. 77 */ 78 static int 79 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 80 { 81 char *command_string, *tmp; 82 int pin[2], pout[2]; 83 pid_t pid; 84 char *shell, strport[NI_MAXSERV]; 85 86 if (!strcmp(proxy_command, "-")) { 87 packet_set_connection(STDIN_FILENO, STDOUT_FILENO); 88 packet_set_timeout(options.server_alive_interval, 89 options.server_alive_count_max); 90 return 0; 91 } 92 93 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 94 shell = __UNCONST(_PATH_BSHELL); 95 96 /* Convert the port number into a string. */ 97 snprintf(strport, sizeof strport, "%hu", port); 98 99 /* 100 * Build the final command string in the buffer by making the 101 * appropriate substitutions to the given proxy command. 102 * 103 * Use "exec" to avoid "sh -c" processes on some platforms 104 * (e.g. Solaris) 105 */ 106 xasprintf(&tmp, "exec %s", proxy_command); 107 command_string = percent_expand(tmp, "h", host, "p", strport, 108 "r", options.user, (char *)NULL); 109 free(tmp); 110 111 /* Create pipes for communicating with the proxy. */ 112 if (pipe(pin) < 0 || pipe(pout) < 0) 113 fatal("Could not create pipes to communicate with the proxy: %.100s", 114 strerror(errno)); 115 116 debug("Executing proxy command: %.500s", command_string); 117 118 /* Fork and execute the proxy command. */ 119 if ((pid = fork()) == 0) { 120 char *argv[10]; 121 122 /* Child. Permanently give up superuser privileges. */ 123 permanently_drop_suid(original_real_uid); 124 125 /* Redirect stdin and stdout. */ 126 close(pin[1]); 127 if (pin[0] != 0) { 128 if (dup2(pin[0], 0) < 0) 129 perror("dup2 stdin"); 130 close(pin[0]); 131 } 132 close(pout[0]); 133 if (dup2(pout[1], 1) < 0) 134 perror("dup2 stdout"); 135 /* Cannot be 1 because pin allocated two descriptors. */ 136 close(pout[1]); 137 138 /* Stderr is left as it is so that error messages get 139 printed on the user's terminal. */ 140 argv[0] = shell; 141 argv[1] = __UNCONST("-c"); 142 argv[2] = command_string; 143 argv[3] = NULL; 144 145 /* Execute the proxy command. Note that we gave up any 146 extra privileges above. */ 147 signal(SIGPIPE, SIG_DFL); 148 execv(argv[0], argv); 149 perror(argv[0]); 150 exit(1); 151 } 152 /* Parent. */ 153 if (pid < 0) 154 fatal("fork failed: %.100s", strerror(errno)); 155 else 156 proxy_command_pid = pid; /* save pid to clean up later */ 157 158 /* Close child side of the descriptors. */ 159 close(pin[0]); 160 close(pout[1]); 161 162 /* Free the command name. */ 163 free(command_string); 164 165 /* Set the connection file descriptors. */ 166 packet_set_connection(pout[0], pin[1]); 167 packet_set_timeout(options.server_alive_interval, 168 options.server_alive_count_max); 169 170 /* Indicate OK return */ 171 return 0; 172 } 173 174 void 175 ssh_kill_proxy_command(void) 176 { 177 /* 178 * Send SIGHUP to proxy command if used. We don't wait() in 179 * case it hangs and instead rely on init to reap the child 180 */ 181 if (proxy_command_pid > 1) 182 kill(proxy_command_pid, SIGHUP); 183 } 184 185 /* 186 * Set TCP receive buffer if requested. 187 * Note: tuning needs to happen after the socket is 188 * created but before the connection happens 189 * so winscale is negotiated properly -cjr 190 */ 191 static void 192 ssh_set_socket_recvbuf(int sock) 193 { 194 void *buf = (void *)&options.tcp_rcv_buf; 195 int sz = sizeof(options.tcp_rcv_buf); 196 int socksize; 197 socklen_t socksizelen = sizeof(int); 198 199 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 200 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 201 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 202 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 203 } 204 else 205 error("Couldn't set socket receive buffer to %d: %.100s", 206 options.tcp_rcv_buf, strerror(errno)); 207 } 208 209 /* 210 * Creates a (possibly privileged) socket for use as the ssh connection. 211 */ 212 static int 213 ssh_create_socket(int privileged, struct addrinfo *ai) 214 { 215 int sock, gaierr; 216 struct addrinfo hints, *res; 217 218 /* 219 * If we are running as root and want to connect to a privileged 220 * port, bind our own socket to a privileged port. 221 */ 222 if (privileged) { 223 int p = IPPORT_RESERVED - 1; 224 PRIV_START; 225 sock = rresvport_af(&p, ai->ai_family); 226 PRIV_END; 227 if (sock < 0) 228 error("rresvport: af=%d %.100s", ai->ai_family, 229 strerror(errno)); 230 else 231 debug("Allocated local port %d.", p); 232 233 if (options.tcp_rcv_buf > 0) 234 ssh_set_socket_recvbuf(sock); 235 return sock; 236 } 237 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 238 if (sock < 0) { 239 switch (errno) { 240 case EAFNOSUPPORT: 241 debug("socket: %.100s", strerror(errno)); 242 break; 243 default: 244 error("socket: %.100s", strerror(errno)); 245 } 246 return -1; 247 } 248 fcntl(sock, F_SETFD, FD_CLOEXEC); 249 250 if (options.tcp_rcv_buf > 0) 251 ssh_set_socket_recvbuf(sock); 252 253 /* Bind the socket to an alternative local IP address */ 254 if (options.bind_address == NULL) 255 return sock; 256 257 memset(&hints, 0, sizeof(hints)); 258 hints.ai_family = ai->ai_family; 259 hints.ai_socktype = ai->ai_socktype; 260 hints.ai_protocol = ai->ai_protocol; 261 hints.ai_flags = AI_PASSIVE; 262 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 263 if (gaierr) { 264 error("getaddrinfo: %s: %s", options.bind_address, 265 ssh_gai_strerror(gaierr)); 266 close(sock); 267 return -1; 268 } 269 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 270 error("bind: %s: %s", options.bind_address, strerror(errno)); 271 close(sock); 272 freeaddrinfo(res); 273 return -1; 274 } 275 freeaddrinfo(res); 276 return sock; 277 } 278 279 static int 280 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 281 socklen_t addrlen, int *timeoutp) 282 { 283 fd_set *fdset; 284 struct timeval tv, t_start; 285 socklen_t optlen; 286 int optval, rc, result = -1; 287 288 gettimeofday(&t_start, NULL); 289 290 if (*timeoutp <= 0) { 291 result = connect(sockfd, serv_addr, addrlen); 292 goto done; 293 } 294 295 set_nonblock(sockfd); 296 rc = connect(sockfd, serv_addr, addrlen); 297 if (rc == 0) { 298 unset_nonblock(sockfd); 299 result = 0; 300 goto done; 301 } 302 if (errno != EINPROGRESS) { 303 result = -1; 304 goto done; 305 } 306 307 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 308 sizeof(fd_mask)); 309 FD_SET(sockfd, fdset); 310 ms_to_timeval(&tv, *timeoutp); 311 312 for (;;) { 313 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 314 if (rc != -1 || errno != EINTR) 315 break; 316 } 317 318 switch (rc) { 319 case 0: 320 /* Timed out */ 321 errno = ETIMEDOUT; 322 break; 323 case -1: 324 /* Select error */ 325 debug("select: %s", strerror(errno)); 326 break; 327 case 1: 328 /* Completed or failed */ 329 optval = 0; 330 optlen = sizeof(optval); 331 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 332 &optlen) == -1) { 333 debug("getsockopt: %s", strerror(errno)); 334 break; 335 } 336 if (optval != 0) { 337 errno = optval; 338 break; 339 } 340 result = 0; 341 unset_nonblock(sockfd); 342 break; 343 default: 344 /* Should not occur */ 345 fatal("Bogus return (%d) from select()", rc); 346 } 347 348 free(fdset); 349 350 done: 351 if (result == 0 && *timeoutp > 0) { 352 ms_subtract_diff(&t_start, timeoutp); 353 if (*timeoutp <= 0) { 354 errno = ETIMEDOUT; 355 result = -1; 356 } 357 } 358 359 return (result); 360 } 361 362 /* 363 * Opens a TCP/IP connection to the remote server on the given host. 364 * The address of the remote host will be returned in hostaddr. 365 * If port is 0, the default port will be used. If needpriv is true, 366 * a privileged port will be allocated to make the connection. 367 * This requires super-user privileges if needpriv is true. 368 * Connection_attempts specifies the maximum number of tries (one per 369 * second). If proxy_command is non-NULL, it specifies the command (with %h 370 * and %p substituted for host and port, respectively) to use to contact 371 * the daemon. 372 */ 373 int 374 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 375 u_short port, int family, int connection_attempts, int *timeout_ms, 376 int want_keepalive, int needpriv, const char *proxy_command) 377 { 378 int gaierr; 379 int on = 1; 380 int sock = -1, attempt; 381 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 382 struct addrinfo hints, *ai, *aitop; 383 384 debug2("ssh_connect: needpriv %d", needpriv); 385 386 /* If a proxy command is given, connect using it. */ 387 if (proxy_command != NULL) 388 return ssh_proxy_connect(host, port, proxy_command); 389 390 /* No proxy command. */ 391 392 memset(&hints, 0, sizeof(hints)); 393 hints.ai_family = family; 394 hints.ai_socktype = SOCK_STREAM; 395 snprintf(strport, sizeof strport, "%u", port); 396 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 397 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 398 host, ssh_gai_strerror(gaierr)); 399 400 for (attempt = 0; attempt < connection_attempts; attempt++) { 401 if (attempt > 0) { 402 /* Sleep a moment before retrying. */ 403 sleep(1); 404 debug("Trying again..."); 405 } 406 /* 407 * Loop through addresses for this host, and try each one in 408 * sequence until the connection succeeds. 409 */ 410 for (ai = aitop; ai; ai = ai->ai_next) { 411 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 412 continue; 413 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 414 ntop, sizeof(ntop), strport, sizeof(strport), 415 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 416 error("ssh_connect: getnameinfo failed"); 417 continue; 418 } 419 debug("Connecting to %.200s [%.100s] port %s.", 420 host, ntop, strport); 421 422 /* Create a socket for connecting. */ 423 sock = ssh_create_socket(needpriv, ai); 424 if (sock < 0) 425 /* 426 * Any serious error is already output, 427 * at least in the debug case. 428 */ 429 continue; 430 431 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 432 timeout_ms) >= 0) { 433 /* Successful connection. */ 434 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 435 break; 436 } else { 437 debug("connect to address %s port %s: %s", 438 ntop, strport, strerror(errno)); 439 close(sock); 440 sock = -1; 441 } 442 } 443 if (sock != -1) 444 break; /* Successful connection. */ 445 } 446 447 freeaddrinfo(aitop); 448 449 /* Return failure if we didn't get a successful connection. */ 450 if (sock == -1) { 451 error("ssh: connect to host %s port %s: %s", 452 host, strport, strerror(errno)); 453 return (-1); 454 } 455 456 debug("Connection established."); 457 458 /* Set SO_KEEPALIVE if requested. */ 459 if (want_keepalive && 460 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 461 sizeof(on)) < 0) 462 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 463 464 /* Set the connection. */ 465 packet_set_connection(sock, sock); 466 packet_set_timeout(options.server_alive_interval, 467 options.server_alive_count_max); 468 469 return 0; 470 } 471 472 static void 473 send_client_banner(int connection_out, int minor1) 474 { 475 /* Send our own protocol version identification. */ 476 if (compat20) { 477 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n", 478 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION); 479 } else { 480 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\n", 481 PROTOCOL_MAJOR_1, minor1, SSH_VERSION); 482 } 483 if (roaming_atomicio(vwrite, connection_out, client_version_string, 484 strlen(client_version_string)) != strlen(client_version_string)) 485 fatal("write: %.100s", strerror(errno)); 486 chop(client_version_string); 487 debug("Local version string %.100s", client_version_string); 488 } 489 490 /* 491 * Waits for the server identification string, and sends our own 492 * identification string. 493 */ 494 void 495 ssh_exchange_identification(int timeout_ms) 496 { 497 char buf[256], remote_version[256]; /* must be same size! */ 498 int remote_major, remote_minor, mismatch; 499 int connection_in = packet_get_connection_in(); 500 int connection_out = packet_get_connection_out(); 501 int minor1 = PROTOCOL_MINOR_1, client_banner_sent = 0; 502 u_int i, n; 503 size_t len; 504 int fdsetsz, remaining, rc; 505 struct timeval t_start, t_remaining; 506 fd_set *fdset; 507 508 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 509 fdset = xcalloc(1, fdsetsz); 510 511 /* 512 * If we are SSH2-only then we can send the banner immediately and 513 * save a round-trip. 514 */ 515 if (options.protocol == SSH_PROTO_2) { 516 enable_compat20(); 517 send_client_banner(connection_out, 0); 518 client_banner_sent = 1; 519 } 520 521 /* Read other side's version identification. */ 522 remaining = timeout_ms; 523 for (n = 0;;) { 524 for (i = 0; i < sizeof(buf) - 1; i++) { 525 if (timeout_ms > 0) { 526 gettimeofday(&t_start, NULL); 527 ms_to_timeval(&t_remaining, remaining); 528 FD_SET(connection_in, fdset); 529 rc = select(connection_in + 1, fdset, NULL, 530 fdset, &t_remaining); 531 ms_subtract_diff(&t_start, &remaining); 532 if (rc == 0 || remaining <= 0) 533 fatal("Connection timed out during " 534 "banner exchange"); 535 if (rc == -1) { 536 if (errno == EINTR) 537 continue; 538 fatal("ssh_exchange_identification: " 539 "select: %s", strerror(errno)); 540 } 541 } 542 543 len = roaming_atomicio(read, connection_in, &buf[i], 1); 544 545 if (len != 1 && errno == EPIPE) 546 fatal("ssh_exchange_identification: " 547 "Connection closed by remote host"); 548 else if (len != 1) 549 fatal("ssh_exchange_identification: " 550 "read: %.100s", strerror(errno)); 551 if (buf[i] == '\r') { 552 buf[i] = '\n'; 553 buf[i + 1] = 0; 554 continue; /**XXX wait for \n */ 555 } 556 if (buf[i] == '\n') { 557 buf[i + 1] = 0; 558 break; 559 } 560 if (++n > 65536) 561 fatal("ssh_exchange_identification: " 562 "No banner received"); 563 } 564 buf[sizeof(buf) - 1] = 0; 565 if (strncmp(buf, "SSH-", 4) == 0) 566 break; 567 debug("ssh_exchange_identification: %s", buf); 568 } 569 server_version_string = xstrdup(buf); 570 free(fdset); 571 572 /* 573 * Check that the versions match. In future this might accept 574 * several versions and set appropriate flags to handle them. 575 */ 576 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 577 &remote_major, &remote_minor, remote_version) != 3) 578 fatal("Bad remote protocol version identification: '%.100s'", buf); 579 debug("Remote protocol version %d.%d, remote software version %.100s", 580 remote_major, remote_minor, remote_version); 581 582 compat_datafellows(remote_version); 583 mismatch = 0; 584 585 switch (remote_major) { 586 case 1: 587 if (remote_minor == 99 && 588 (options.protocol & SSH_PROTO_2) && 589 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 590 enable_compat20(); 591 break; 592 } 593 if (!(options.protocol & SSH_PROTO_1)) { 594 mismatch = 1; 595 break; 596 } 597 if (remote_minor < 3) { 598 fatal("Remote machine has too old SSH software version."); 599 } else if (remote_minor == 3 || remote_minor == 4) { 600 /* We speak 1.3, too. */ 601 enable_compat13(); 602 minor1 = 3; 603 if (options.forward_agent) { 604 logit("Agent forwarding disabled for protocol 1.3"); 605 options.forward_agent = 0; 606 } 607 } 608 break; 609 case 2: 610 if (options.protocol & SSH_PROTO_2) { 611 enable_compat20(); 612 break; 613 } 614 /* FALLTHROUGH */ 615 default: 616 mismatch = 1; 617 break; 618 } 619 if (mismatch) 620 fatal("Protocol major versions differ: %d vs. %d", 621 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 622 remote_major); 623 if (!client_banner_sent) 624 send_client_banner(connection_out, minor1); 625 chop(server_version_string); 626 } 627 628 /* defaults to 'no' */ 629 static int 630 confirm(const char *prompt) 631 { 632 const char *msg, *again = "Please type 'yes' or 'no': "; 633 char *p; 634 int ret = -1; 635 636 if (options.batch_mode) 637 return 0; 638 for (msg = prompt;;msg = again) { 639 p = read_passphrase(msg, RP_ECHO); 640 if (p == NULL || 641 (p[0] == '\0') || (p[0] == '\n') || 642 strncasecmp(p, "no", 2) == 0) 643 ret = 0; 644 if (p && strncasecmp(p, "yes", 3) == 0) 645 ret = 1; 646 free(p); 647 if (ret != -1) 648 return ret; 649 } 650 } 651 652 static int 653 check_host_cert(const char *host, const Key *host_key) 654 { 655 const char *reason; 656 657 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 658 error("%s", reason); 659 return 0; 660 } 661 if (buffer_len(&host_key->cert->critical) != 0) { 662 error("Certificate for %s contains unsupported " 663 "critical options(s)", host); 664 return 0; 665 } 666 return 1; 667 } 668 669 static int 670 sockaddr_is_local(struct sockaddr *hostaddr) 671 { 672 switch (hostaddr->sa_family) { 673 case AF_INET: 674 return (ntohl(((struct sockaddr_in *)hostaddr)-> 675 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 676 case AF_INET6: 677 return IN6_IS_ADDR_LOOPBACK( 678 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 679 default: 680 return 0; 681 } 682 } 683 684 /* 685 * Prepare the hostname and ip address strings that are used to lookup 686 * host keys in known_hosts files. These may have a port number appended. 687 */ 688 void 689 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 690 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 691 { 692 char ntop[NI_MAXHOST]; 693 694 /* 695 * We don't have the remote ip-address for connections 696 * using a proxy command 697 */ 698 if (hostfile_ipaddr != NULL) { 699 if (options.proxy_command == NULL) { 700 if (getnameinfo(hostaddr, hostaddr->sa_len, 701 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 702 fatal("check_host_key: getnameinfo failed"); 703 *hostfile_ipaddr = put_host_port(ntop, port); 704 } else { 705 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 706 "command>"); 707 } 708 } 709 710 /* 711 * Allow the user to record the key under a different name or 712 * differentiate a non-standard port. This is useful for ssh 713 * tunneling over forwarded connections or if you run multiple 714 * sshd's on different ports on the same machine. 715 */ 716 if (hostfile_hostname != NULL) { 717 if (options.host_key_alias != NULL) { 718 *hostfile_hostname = xstrdup(options.host_key_alias); 719 debug("using hostkeyalias: %s", *hostfile_hostname); 720 } else { 721 *hostfile_hostname = put_host_port(hostname, port); 722 } 723 } 724 } 725 726 /* 727 * check whether the supplied host key is valid, return -1 if the key 728 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 729 */ 730 #define RDRW 0 731 #define RDONLY 1 732 #define ROQUIET 2 733 static int 734 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 735 Key *host_key, int readonly, 736 char **user_hostfiles, u_int num_user_hostfiles, 737 char **system_hostfiles, u_int num_system_hostfiles) 738 { 739 HostStatus host_status; 740 HostStatus ip_status; 741 Key *raw_key = NULL; 742 char *ip = NULL, *host = NULL; 743 char hostline[1000], *hostp, *fp, *ra; 744 char msg[1024]; 745 const char *type; 746 const struct hostkey_entry *host_found, *ip_found; 747 int len, cancelled_forwarding = 0; 748 int local = sockaddr_is_local(hostaddr); 749 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 750 struct hostkeys *host_hostkeys, *ip_hostkeys; 751 u_int i; 752 753 /* 754 * Force accepting of the host key for loopback/localhost. The 755 * problem is that if the home directory is NFS-mounted to multiple 756 * machines, localhost will refer to a different machine in each of 757 * them, and the user will get bogus HOST_CHANGED warnings. This 758 * essentially disables host authentication for localhost; however, 759 * this is probably not a real problem. 760 */ 761 if (options.no_host_authentication_for_localhost == 1 && local && 762 options.host_key_alias == NULL) { 763 debug("Forcing accepting of host key for " 764 "loopback/localhost."); 765 return 0; 766 } 767 768 /* 769 * Prepare the hostname and address strings used for hostkey lookup. 770 * In some cases, these will have a port number appended. 771 */ 772 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 773 774 /* 775 * Turn off check_host_ip if the connection is to localhost, via proxy 776 * command or if we don't have a hostname to compare with 777 */ 778 if (options.check_host_ip && (local || 779 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 780 options.check_host_ip = 0; 781 782 host_hostkeys = init_hostkeys(); 783 for (i = 0; i < num_user_hostfiles; i++) 784 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 785 for (i = 0; i < num_system_hostfiles; i++) 786 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 787 788 ip_hostkeys = NULL; 789 if (!want_cert && options.check_host_ip) { 790 ip_hostkeys = init_hostkeys(); 791 for (i = 0; i < num_user_hostfiles; i++) 792 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 793 for (i = 0; i < num_system_hostfiles; i++) 794 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 795 } 796 797 retry: 798 /* Reload these as they may have changed on cert->key downgrade */ 799 want_cert = key_is_cert(host_key); 800 type = key_type(host_key); 801 802 /* 803 * Check if the host key is present in the user's list of known 804 * hosts or in the systemwide list. 805 */ 806 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 807 &host_found); 808 809 /* 810 * Also perform check for the ip address, skip the check if we are 811 * localhost, looking for a certificate, or the hostname was an ip 812 * address to begin with. 813 */ 814 if (!want_cert && ip_hostkeys != NULL) { 815 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 816 &ip_found); 817 if (host_status == HOST_CHANGED && 818 (ip_status != HOST_CHANGED || 819 (ip_found != NULL && 820 !key_equal(ip_found->key, host_found->key)))) 821 host_ip_differ = 1; 822 } else 823 ip_status = host_status; 824 825 switch (host_status) { 826 case HOST_OK: 827 /* The host is known and the key matches. */ 828 debug("Host '%.200s' is known and matches the %s host %s.", 829 host, type, want_cert ? "certificate" : "key"); 830 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 831 host_found->file, host_found->line); 832 if (want_cert && !check_host_cert(hostname, host_key)) 833 goto fail; 834 if (options.check_host_ip && ip_status == HOST_NEW) { 835 if (readonly || want_cert) 836 logit("%s host key for IP address " 837 "'%.128s' not in list of known hosts.", 838 type, ip); 839 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 840 host_key, options.hash_known_hosts)) 841 logit("Failed to add the %s host key for IP " 842 "address '%.128s' to the list of known " 843 "hosts (%.30s).", type, ip, 844 user_hostfiles[0]); 845 else 846 logit("Warning: Permanently added the %s host " 847 "key for IP address '%.128s' to the list " 848 "of known hosts.", type, ip); 849 } else if (options.visual_host_key) { 850 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 851 ra = key_fingerprint(host_key, SSH_FP_MD5, 852 SSH_FP_RANDOMART); 853 logit("Host key fingerprint is %s\n%s\n", fp, ra); 854 free(ra); 855 free(fp); 856 } 857 break; 858 case HOST_NEW: 859 if (options.host_key_alias == NULL && port != 0 && 860 port != SSH_DEFAULT_PORT) { 861 debug("checking without port identifier"); 862 if (check_host_key(hostname, hostaddr, 0, host_key, 863 ROQUIET, user_hostfiles, num_user_hostfiles, 864 system_hostfiles, num_system_hostfiles) == 0) { 865 debug("found matching key w/out port"); 866 break; 867 } 868 } 869 if (readonly || want_cert) 870 goto fail; 871 /* The host is new. */ 872 if (options.strict_host_key_checking == 1) { 873 /* 874 * User has requested strict host key checking. We 875 * will not add the host key automatically. The only 876 * alternative left is to abort. 877 */ 878 error("No %s host key is known for %.200s and you " 879 "have requested strict checking.", type, host); 880 goto fail; 881 } else if (options.strict_host_key_checking == 2) { 882 char msg1[1024], msg2[1024]; 883 884 if (show_other_keys(host_hostkeys, host_key)) 885 snprintf(msg1, sizeof(msg1), 886 "\nbut keys of different type are already" 887 " known for this host."); 888 else 889 snprintf(msg1, sizeof(msg1), "."); 890 /* The default */ 891 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 892 ra = key_fingerprint(host_key, SSH_FP_MD5, 893 SSH_FP_RANDOMART); 894 msg2[0] = '\0'; 895 if (options.verify_host_key_dns) { 896 if (matching_host_key_dns) 897 snprintf(msg2, sizeof(msg2), 898 "Matching host key fingerprint" 899 " found in DNS.\n"); 900 else 901 snprintf(msg2, sizeof(msg2), 902 "No matching host key fingerprint" 903 " found in DNS.\n"); 904 } 905 snprintf(msg, sizeof(msg), 906 "The authenticity of host '%.200s (%s)' can't be " 907 "established%s\n" 908 "%s key fingerprint is %s.%s%s\n%s" 909 "Are you sure you want to continue connecting " 910 "(yes/no)? ", 911 host, ip, msg1, type, fp, 912 options.visual_host_key ? "\n" : "", 913 options.visual_host_key ? ra : "", 914 msg2); 915 free(ra); 916 free(fp); 917 if (!confirm(msg)) 918 goto fail; 919 } 920 /* 921 * If not in strict mode, add the key automatically to the 922 * local known_hosts file. 923 */ 924 if (options.check_host_ip && ip_status == HOST_NEW) { 925 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 926 hostp = hostline; 927 if (options.hash_known_hosts) { 928 /* Add hash of host and IP separately */ 929 r = add_host_to_hostfile(user_hostfiles[0], 930 host, host_key, options.hash_known_hosts) && 931 add_host_to_hostfile(user_hostfiles[0], ip, 932 host_key, options.hash_known_hosts); 933 } else { 934 /* Add unhashed "host,ip" */ 935 r = add_host_to_hostfile(user_hostfiles[0], 936 hostline, host_key, 937 options.hash_known_hosts); 938 } 939 } else { 940 r = add_host_to_hostfile(user_hostfiles[0], host, 941 host_key, options.hash_known_hosts); 942 hostp = host; 943 } 944 945 if (!r) 946 logit("Failed to add the host to the list of known " 947 "hosts (%.500s).", user_hostfiles[0]); 948 else 949 logit("Warning: Permanently added '%.200s' (%s) to the " 950 "list of known hosts.", hostp, type); 951 break; 952 case HOST_REVOKED: 953 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 954 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 955 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 956 error("The %s host key for %s is marked as revoked.", type, host); 957 error("This could mean that a stolen key is being used to"); 958 error("impersonate this host."); 959 960 /* 961 * If strict host key checking is in use, the user will have 962 * to edit the key manually and we can only abort. 963 */ 964 if (options.strict_host_key_checking) { 965 error("%s host key for %.200s was revoked and you have " 966 "requested strict checking.", type, host); 967 goto fail; 968 } 969 goto continue_unsafe; 970 971 case HOST_CHANGED: 972 if (want_cert) { 973 /* 974 * This is only a debug() since it is valid to have 975 * CAs with wildcard DNS matches that don't match 976 * all hosts that one might visit. 977 */ 978 debug("Host certificate authority does not " 979 "match %s in %s:%lu", CA_MARKER, 980 host_found->file, host_found->line); 981 goto fail; 982 } 983 if (readonly == ROQUIET) 984 goto fail; 985 if (options.check_host_ip && host_ip_differ) { 986 const char *key_msg; 987 if (ip_status == HOST_NEW) 988 key_msg = "is unknown"; 989 else if (ip_status == HOST_OK) 990 key_msg = "is unchanged"; 991 else 992 key_msg = "has a different value"; 993 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 994 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 995 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 996 error("The %s host key for %s has changed,", type, host); 997 error("and the key for the corresponding IP address %s", ip); 998 error("%s. This could either mean that", key_msg); 999 error("DNS SPOOFING is happening or the IP address for the host"); 1000 error("and its host key have changed at the same time."); 1001 if (ip_status != HOST_NEW) 1002 error("Offending key for IP in %s:%lu", 1003 ip_found->file, ip_found->line); 1004 } 1005 /* The host key has changed. */ 1006 warn_changed_key(host_key); 1007 error("Add correct host key in %.100s to get rid of this message.", 1008 user_hostfiles[0]); 1009 error("Offending %s key in %s:%lu", key_type(host_found->key), 1010 host_found->file, host_found->line); 1011 1012 /* 1013 * If strict host key checking is in use, the user will have 1014 * to edit the key manually and we can only abort. 1015 */ 1016 if (options.strict_host_key_checking) { 1017 error("%s host key for %.200s has changed and you have " 1018 "requested strict checking.", type, host); 1019 goto fail; 1020 } 1021 1022 continue_unsafe: 1023 /* 1024 * If strict host key checking has not been requested, allow 1025 * the connection but without MITM-able authentication or 1026 * forwarding. 1027 */ 1028 if (options.password_authentication) { 1029 error("Password authentication is disabled to avoid " 1030 "man-in-the-middle attacks."); 1031 options.password_authentication = 0; 1032 cancelled_forwarding = 1; 1033 } 1034 if (options.kbd_interactive_authentication) { 1035 error("Keyboard-interactive authentication is disabled" 1036 " to avoid man-in-the-middle attacks."); 1037 options.kbd_interactive_authentication = 0; 1038 options.challenge_response_authentication = 0; 1039 cancelled_forwarding = 1; 1040 } 1041 if (options.challenge_response_authentication) { 1042 error("Challenge/response authentication is disabled" 1043 " to avoid man-in-the-middle attacks."); 1044 options.challenge_response_authentication = 0; 1045 cancelled_forwarding = 1; 1046 } 1047 if (options.forward_agent) { 1048 error("Agent forwarding is disabled to avoid " 1049 "man-in-the-middle attacks."); 1050 options.forward_agent = 0; 1051 cancelled_forwarding = 1; 1052 } 1053 if (options.forward_x11) { 1054 error("X11 forwarding is disabled to avoid " 1055 "man-in-the-middle attacks."); 1056 options.forward_x11 = 0; 1057 cancelled_forwarding = 1; 1058 } 1059 if (options.num_local_forwards > 0 || 1060 options.num_remote_forwards > 0) { 1061 error("Port forwarding is disabled to avoid " 1062 "man-in-the-middle attacks."); 1063 options.num_local_forwards = 1064 options.num_remote_forwards = 0; 1065 cancelled_forwarding = 1; 1066 } 1067 if (options.tun_open != SSH_TUNMODE_NO) { 1068 error("Tunnel forwarding is disabled to avoid " 1069 "man-in-the-middle attacks."); 1070 options.tun_open = SSH_TUNMODE_NO; 1071 cancelled_forwarding = 1; 1072 } 1073 if (options.exit_on_forward_failure && cancelled_forwarding) 1074 fatal("Error: forwarding disabled due to host key " 1075 "check failure"); 1076 1077 /* 1078 * XXX Should permit the user to change to use the new id. 1079 * This could be done by converting the host key to an 1080 * identifying sentence, tell that the host identifies itself 1081 * by that sentence, and ask the user if he/she wishes to 1082 * accept the authentication. 1083 */ 1084 break; 1085 case HOST_FOUND: 1086 fatal("internal error"); 1087 break; 1088 } 1089 1090 if (options.check_host_ip && host_status != HOST_CHANGED && 1091 ip_status == HOST_CHANGED) { 1092 snprintf(msg, sizeof(msg), 1093 "Warning: the %s host key for '%.200s' " 1094 "differs from the key for the IP address '%.128s'" 1095 "\nOffending key for IP in %s:%lu", 1096 type, host, ip, ip_found->file, ip_found->line); 1097 if (host_status == HOST_OK) { 1098 len = strlen(msg); 1099 snprintf(msg + len, sizeof(msg) - len, 1100 "\nMatching host key in %s:%lu", 1101 host_found->file, host_found->line); 1102 } 1103 if (options.strict_host_key_checking == 1) { 1104 logit("%s", msg); 1105 error("Exiting, you have requested strict checking."); 1106 goto fail; 1107 } else if (options.strict_host_key_checking == 2) { 1108 strlcat(msg, "\nAre you sure you want " 1109 "to continue connecting (yes/no)? ", sizeof(msg)); 1110 if (!confirm(msg)) 1111 goto fail; 1112 } else { 1113 logit("%s", msg); 1114 } 1115 } 1116 1117 free(ip); 1118 free(host); 1119 if (host_hostkeys != NULL) 1120 free_hostkeys(host_hostkeys); 1121 if (ip_hostkeys != NULL) 1122 free_hostkeys(ip_hostkeys); 1123 return 0; 1124 1125 fail: 1126 if (want_cert && host_status != HOST_REVOKED) { 1127 /* 1128 * No matching certificate. Downgrade cert to raw key and 1129 * search normally. 1130 */ 1131 debug("No matching CA found. Retry with plain key"); 1132 raw_key = key_from_private(host_key); 1133 if (key_drop_cert(raw_key) != 0) 1134 fatal("Couldn't drop certificate"); 1135 host_key = raw_key; 1136 goto retry; 1137 } 1138 if (raw_key != NULL) 1139 key_free(raw_key); 1140 free(ip); 1141 free(host); 1142 if (host_hostkeys != NULL) 1143 free_hostkeys(host_hostkeys); 1144 if (ip_hostkeys != NULL) 1145 free_hostkeys(ip_hostkeys); 1146 return -1; 1147 } 1148 1149 /* returns 0 if key verifies or -1 if key does NOT verify */ 1150 int 1151 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1152 { 1153 int flags = 0; 1154 char *fp; 1155 1156 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1157 debug("Server host key: %s %s", key_type(host_key), fp); 1158 free(fp); 1159 1160 /* XXX certs are not yet supported for DNS */ 1161 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1162 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1163 if (flags & DNS_VERIFY_FOUND) { 1164 1165 if (options.verify_host_key_dns == 1 && 1166 flags & DNS_VERIFY_MATCH && 1167 flags & DNS_VERIFY_SECURE) 1168 return 0; 1169 1170 if (flags & DNS_VERIFY_MATCH) { 1171 matching_host_key_dns = 1; 1172 } else { 1173 warn_changed_key(host_key); 1174 error("Update the SSHFP RR in DNS with the new " 1175 "host key to get rid of this message."); 1176 } 1177 } 1178 } 1179 1180 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1181 options.user_hostfiles, options.num_user_hostfiles, 1182 options.system_hostfiles, options.num_system_hostfiles); 1183 } 1184 1185 /* 1186 * Starts a dialog with the server, and authenticates the current user on the 1187 * server. This does not need any extra privileges. The basic connection 1188 * to the server must already have been established before this is called. 1189 * If login fails, this function prints an error and never returns. 1190 * This function does not require super-user privileges. 1191 */ 1192 void 1193 ssh_login(Sensitive *sensitive, const char *orighost, 1194 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1195 { 1196 char *host, *cp; 1197 char *server_user, *local_user; 1198 1199 local_user = xstrdup(pw->pw_name); 1200 server_user = options.user ? options.user : local_user; 1201 1202 /* Convert the user-supplied hostname into all lowercase. */ 1203 host = xstrdup(orighost); 1204 for (cp = host; *cp; cp++) 1205 if (isupper((unsigned char)*cp)) 1206 *cp = (char)tolower((unsigned char)*cp); 1207 1208 /* Exchange protocol version identification strings with the server. */ 1209 ssh_exchange_identification(timeout_ms); 1210 1211 /* Put the connection into non-blocking mode. */ 1212 packet_set_nonblocking(); 1213 1214 /* key exchange */ 1215 /* authenticate user */ 1216 if (compat20) { 1217 ssh_kex2(host, hostaddr, port); 1218 ssh_userauth2(local_user, server_user, host, sensitive); 1219 } else { 1220 ssh_kex(host, hostaddr); 1221 ssh_userauth1(local_user, server_user, host, sensitive); 1222 } 1223 free(local_user); 1224 } 1225 1226 void 1227 ssh_put_password(char *password) 1228 { 1229 int size; 1230 char *padded; 1231 1232 if (datafellows & SSH_BUG_PASSWORDPAD) { 1233 packet_put_cstring(password); 1234 return; 1235 } 1236 size = roundup(strlen(password) + 1, 32); 1237 padded = xcalloc(1, size); 1238 strlcpy(padded, password, size); 1239 packet_put_string(padded, size); 1240 memset(padded, 0, size); 1241 free(padded); 1242 } 1243 1244 /* print all known host keys for a given host, but skip keys of given type */ 1245 static int 1246 show_other_keys(struct hostkeys *hostkeys, Key *key) 1247 { 1248 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1249 int i, ret = 0; 1250 char *fp, *ra; 1251 const struct hostkey_entry *found; 1252 1253 for (i = 0; type[i] != -1; i++) { 1254 if (type[i] == key->type) 1255 continue; 1256 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1257 continue; 1258 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1259 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1260 logit("WARNING: %s key found for host %s\n" 1261 "in %s:%lu\n" 1262 "%s key fingerprint %s.", 1263 key_type(found->key), 1264 found->host, found->file, found->line, 1265 key_type(found->key), fp); 1266 if (options.visual_host_key) 1267 logit("%s", ra); 1268 free(ra); 1269 free(fp); 1270 ret = 1; 1271 } 1272 return ret; 1273 } 1274 1275 static void 1276 warn_changed_key(Key *host_key) 1277 { 1278 char *fp; 1279 1280 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1281 1282 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1283 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1284 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1285 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1286 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1287 error("It is also possible that a host key has just been changed."); 1288 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1289 key_type(host_key), fp); 1290 error("Please contact your system administrator."); 1291 1292 free(fp); 1293 } 1294 1295 /* 1296 * Execute a local command 1297 */ 1298 int 1299 ssh_local_cmd(const char *args) 1300 { 1301 const char *shell; 1302 pid_t pid; 1303 int status; 1304 void (*osighand)(int); 1305 1306 if (!options.permit_local_command || 1307 args == NULL || !*args) 1308 return (1); 1309 1310 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1311 shell = _PATH_BSHELL; 1312 1313 osighand = signal(SIGCHLD, SIG_DFL); 1314 pid = fork(); 1315 if (pid == 0) { 1316 signal(SIGPIPE, SIG_DFL); 1317 debug3("Executing %s -c \"%s\"", shell, args); 1318 execl(shell, shell, "-c", args, (char *)NULL); 1319 error("Couldn't execute %s -c \"%s\": %s", 1320 shell, args, strerror(errno)); 1321 _exit(1); 1322 } else if (pid == -1) 1323 fatal("fork failed: %.100s", strerror(errno)); 1324 while (waitpid(pid, &status, 0) == -1) 1325 if (errno != EINTR) 1326 fatal("Couldn't wait for child: %s", strerror(errno)); 1327 signal(SIGCHLD, osighand); 1328 1329 if (!WIFEXITED(status)) 1330 return (1); 1331 1332 return (WEXITSTATUS(status)); 1333 } 1334