1 /* $OpenBSD: sshconnect.c,v 1.234 2011/05/24 07:15:47 djm Exp $ */ 2 /* $FreeBSD$ */ 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 ((shell = getenv("SHELL")) == NULL || *shell == '\0') 94 shell = _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 xfree(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] = "-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 xfree(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 created but before the 188 * connection happens so winscale is negotiated properly. 189 */ 190 static void 191 ssh_set_socket_recvbuf(int sock) 192 { 193 void *buf = (void *)&options.tcp_rcv_buf; 194 int socksize, sz = sizeof(options.tcp_rcv_buf); 195 socklen_t len = sizeof(int); 196 197 debug("setsockopt attempting to set SO_RCVBUF to %d", 198 options.tcp_rcv_buf); 199 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 200 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len); 201 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), 202 socksize); 203 } else 204 error("Couldn't set socket receive buffer to %d: %.100s", 205 options.tcp_rcv_buf, strerror(errno)); 206 } 207 208 /* 209 * Creates a (possibly privileged) socket for use as the ssh connection. 210 */ 211 static int 212 ssh_create_socket(int privileged, struct addrinfo *ai) 213 { 214 int sock, gaierr; 215 struct addrinfo hints, *res; 216 217 /* 218 * If we are running as root and want to connect to a privileged 219 * port, bind our own socket to a privileged port. 220 */ 221 if (privileged) { 222 int p = IPPORT_RESERVED - 1; 223 PRIV_START; 224 sock = rresvport_af(&p, ai->ai_family); 225 PRIV_END; 226 if (sock < 0) 227 error("rresvport: af=%d %.100s", ai->ai_family, 228 strerror(errno)); 229 else 230 debug("Allocated local port %d.", p); 231 if (options.tcp_rcv_buf > 0) 232 ssh_set_socket_recvbuf(sock); 233 return sock; 234 } 235 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 236 if (sock < 0) { 237 error("socket: %.100s", strerror(errno)); 238 return -1; 239 } 240 fcntl(sock, F_SETFD, FD_CLOEXEC); 241 242 if (options.tcp_rcv_buf > 0) 243 ssh_set_socket_recvbuf(sock); 244 245 /* Bind the socket to an alternative local IP address */ 246 if (options.bind_address == NULL) 247 return sock; 248 249 memset(&hints, 0, sizeof(hints)); 250 hints.ai_family = ai->ai_family; 251 hints.ai_socktype = ai->ai_socktype; 252 hints.ai_protocol = ai->ai_protocol; 253 hints.ai_flags = AI_PASSIVE; 254 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 255 if (gaierr) { 256 error("getaddrinfo: %s: %s", options.bind_address, 257 ssh_gai_strerror(gaierr)); 258 close(sock); 259 return -1; 260 } 261 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 262 error("bind: %s: %s", options.bind_address, strerror(errno)); 263 close(sock); 264 freeaddrinfo(res); 265 return -1; 266 } 267 freeaddrinfo(res); 268 return sock; 269 } 270 271 static int 272 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 273 socklen_t addrlen, int *timeoutp) 274 { 275 fd_set *fdset; 276 struct timeval tv, t_start; 277 socklen_t optlen; 278 int optval, rc, result = -1; 279 280 gettimeofday(&t_start, NULL); 281 282 if (*timeoutp <= 0) { 283 result = connect(sockfd, serv_addr, addrlen); 284 goto done; 285 } 286 287 set_nonblock(sockfd); 288 rc = connect(sockfd, serv_addr, addrlen); 289 if (rc == 0) { 290 unset_nonblock(sockfd); 291 result = 0; 292 goto done; 293 } 294 if (errno != EINPROGRESS) { 295 result = -1; 296 goto done; 297 } 298 299 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 300 sizeof(fd_mask)); 301 FD_SET(sockfd, fdset); 302 ms_to_timeval(&tv, *timeoutp); 303 304 for (;;) { 305 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 306 if (rc != -1 || errno != EINTR) 307 break; 308 } 309 310 switch (rc) { 311 case 0: 312 /* Timed out */ 313 errno = ETIMEDOUT; 314 break; 315 case -1: 316 /* Select error */ 317 debug("select: %s", strerror(errno)); 318 break; 319 case 1: 320 /* Completed or failed */ 321 optval = 0; 322 optlen = sizeof(optval); 323 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 324 &optlen) == -1) { 325 debug("getsockopt: %s", strerror(errno)); 326 break; 327 } 328 if (optval != 0) { 329 errno = optval; 330 break; 331 } 332 result = 0; 333 unset_nonblock(sockfd); 334 break; 335 default: 336 /* Should not occur */ 337 fatal("Bogus return (%d) from select()", rc); 338 } 339 340 xfree(fdset); 341 342 done: 343 if (result == 0 && *timeoutp > 0) { 344 ms_subtract_diff(&t_start, timeoutp); 345 if (*timeoutp <= 0) { 346 errno = ETIMEDOUT; 347 result = -1; 348 } 349 } 350 351 return (result); 352 } 353 354 /* 355 * Opens a TCP/IP connection to the remote server on the given host. 356 * The address of the remote host will be returned in hostaddr. 357 * If port is 0, the default port will be used. If needpriv is true, 358 * a privileged port will be allocated to make the connection. 359 * This requires super-user privileges if needpriv is true. 360 * Connection_attempts specifies the maximum number of tries (one per 361 * second). If proxy_command is non-NULL, it specifies the command (with %h 362 * and %p substituted for host and port, respectively) to use to contact 363 * the daemon. 364 */ 365 int 366 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 367 u_short port, int family, int connection_attempts, int *timeout_ms, 368 int want_keepalive, int needpriv, const char *proxy_command) 369 { 370 int gaierr; 371 int on = 1; 372 int sock = -1, attempt; 373 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 374 struct addrinfo hints, *ai, *aitop; 375 376 debug2("ssh_connect: needpriv %d", needpriv); 377 378 /* If a proxy command is given, connect using it. */ 379 if (proxy_command != NULL) 380 return ssh_proxy_connect(host, port, proxy_command); 381 382 /* No proxy command. */ 383 384 memset(&hints, 0, sizeof(hints)); 385 hints.ai_family = family; 386 hints.ai_socktype = SOCK_STREAM; 387 snprintf(strport, sizeof strport, "%u", port); 388 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 389 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 390 host, ssh_gai_strerror(gaierr)); 391 392 for (attempt = 0; attempt < connection_attempts; attempt++) { 393 if (attempt > 0) { 394 /* Sleep a moment before retrying. */ 395 sleep(1); 396 debug("Trying again..."); 397 } 398 /* 399 * Loop through addresses for this host, and try each one in 400 * sequence until the connection succeeds. 401 */ 402 for (ai = aitop; ai; ai = ai->ai_next) { 403 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 404 continue; 405 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 406 ntop, sizeof(ntop), strport, sizeof(strport), 407 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 408 error("ssh_connect: getnameinfo failed"); 409 continue; 410 } 411 debug("Connecting to %.200s [%.100s] port %s.", 412 host, ntop, strport); 413 414 /* Create a socket for connecting. */ 415 sock = ssh_create_socket(needpriv, ai); 416 if (sock < 0) 417 /* Any error is already output */ 418 continue; 419 420 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 421 timeout_ms) >= 0) { 422 /* Successful connection. */ 423 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 424 break; 425 } else { 426 debug("connect to address %s port %s: %s", 427 ntop, strport, strerror(errno)); 428 close(sock); 429 sock = -1; 430 } 431 } 432 if (sock != -1) 433 break; /* Successful connection. */ 434 } 435 436 freeaddrinfo(aitop); 437 438 /* Return failure if we didn't get a successful connection. */ 439 if (sock == -1) { 440 error("ssh: connect to host %s port %s: %s", 441 host, strport, strerror(errno)); 442 return (-1); 443 } 444 445 debug("Connection established."); 446 447 /* Set SO_KEEPALIVE if requested. */ 448 if (want_keepalive && 449 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 450 sizeof(on)) < 0) 451 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 452 453 /* Set the connection. */ 454 packet_set_connection(sock, sock); 455 packet_set_timeout(options.server_alive_interval, 456 options.server_alive_count_max); 457 458 return 0; 459 } 460 461 /* 462 * Waits for the server identification string, and sends our own 463 * identification string. 464 */ 465 void 466 ssh_exchange_identification(int timeout_ms) 467 { 468 char buf[256], remote_version[256]; /* must be same size! */ 469 int remote_major, remote_minor, mismatch; 470 int connection_in = packet_get_connection_in(); 471 int connection_out = packet_get_connection_out(); 472 int minor1 = PROTOCOL_MINOR_1; 473 u_int i, n; 474 size_t len; 475 int fdsetsz, remaining, rc; 476 struct timeval t_start, t_remaining; 477 fd_set *fdset; 478 479 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 480 fdset = xcalloc(1, fdsetsz); 481 482 /* Read other side's version identification. */ 483 remaining = timeout_ms; 484 for (n = 0;;) { 485 for (i = 0; i < sizeof(buf) - 1; i++) { 486 if (timeout_ms > 0) { 487 gettimeofday(&t_start, NULL); 488 ms_to_timeval(&t_remaining, remaining); 489 FD_SET(connection_in, fdset); 490 rc = select(connection_in + 1, fdset, NULL, 491 fdset, &t_remaining); 492 ms_subtract_diff(&t_start, &remaining); 493 if (rc == 0 || remaining <= 0) 494 fatal("Connection timed out during " 495 "banner exchange"); 496 if (rc == -1) { 497 if (errno == EINTR) 498 continue; 499 fatal("ssh_exchange_identification: " 500 "select: %s", strerror(errno)); 501 } 502 } 503 504 len = roaming_atomicio(read, connection_in, &buf[i], 1); 505 506 if (len != 1 && errno == EPIPE) 507 fatal("ssh_exchange_identification: " 508 "Connection closed by remote host"); 509 else if (len != 1) 510 fatal("ssh_exchange_identification: " 511 "read: %.100s", strerror(errno)); 512 if (buf[i] == '\r') { 513 buf[i] = '\n'; 514 buf[i + 1] = 0; 515 continue; /**XXX wait for \n */ 516 } 517 if (buf[i] == '\n') { 518 buf[i + 1] = 0; 519 break; 520 } 521 if (++n > 65536) 522 fatal("ssh_exchange_identification: " 523 "No banner received"); 524 } 525 buf[sizeof(buf) - 1] = 0; 526 if (strncmp(buf, "SSH-", 4) == 0) 527 break; 528 debug("ssh_exchange_identification: %s", buf); 529 } 530 server_version_string = xstrdup(buf); 531 xfree(fdset); 532 533 /* 534 * Check that the versions match. In future this might accept 535 * several versions and set appropriate flags to handle them. 536 */ 537 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 538 &remote_major, &remote_minor, remote_version) != 3) 539 fatal("Bad remote protocol version identification: '%.100s'", buf); 540 debug("Remote protocol version %d.%d, remote software version %.100s", 541 remote_major, remote_minor, remote_version); 542 543 compat_datafellows(remote_version); 544 mismatch = 0; 545 546 switch (remote_major) { 547 case 1: 548 if (remote_minor == 99 && 549 (options.protocol & SSH_PROTO_2) && 550 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 551 enable_compat20(); 552 break; 553 } 554 if (!(options.protocol & SSH_PROTO_1)) { 555 mismatch = 1; 556 break; 557 } 558 if (remote_minor < 3) { 559 fatal("Remote machine has too old SSH software version."); 560 } else if (remote_minor == 3 || remote_minor == 4) { 561 /* We speak 1.3, too. */ 562 enable_compat13(); 563 minor1 = 3; 564 if (options.forward_agent) { 565 logit("Agent forwarding disabled for protocol 1.3"); 566 options.forward_agent = 0; 567 } 568 } 569 break; 570 case 2: 571 if (options.protocol & SSH_PROTO_2) { 572 enable_compat20(); 573 break; 574 } 575 /* FALLTHROUGH */ 576 default: 577 mismatch = 1; 578 break; 579 } 580 if (mismatch) 581 fatal("Protocol major versions differ: %d vs. %d", 582 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 583 remote_major); 584 /* Send our own protocol version identification. */ 585 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 586 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 587 compat20 ? PROTOCOL_MINOR_2 : minor1, 588 ssh_version_get(options.hpn_disabled), compat20 ? "\r\n" : "\n"); 589 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 590 != strlen(buf)) 591 fatal("write: %.100s", strerror(errno)); 592 client_version_string = xstrdup(buf); 593 chop(client_version_string); 594 chop(server_version_string); 595 debug("Local version string %.100s", client_version_string); 596 } 597 598 /* defaults to 'no' */ 599 static int 600 confirm(const char *prompt) 601 { 602 const char *msg, *again = "Please type 'yes' or 'no': "; 603 char *p; 604 int ret = -1; 605 606 if (options.batch_mode) 607 return 0; 608 for (msg = prompt;;msg = again) { 609 p = read_passphrase(msg, RP_ECHO); 610 if (p == NULL || 611 (p[0] == '\0') || (p[0] == '\n') || 612 strncasecmp(p, "no", 2) == 0) 613 ret = 0; 614 if (p && strncasecmp(p, "yes", 3) == 0) 615 ret = 1; 616 if (p) 617 xfree(p); 618 if (ret != -1) 619 return ret; 620 } 621 } 622 623 static int 624 check_host_cert(const char *host, const Key *host_key) 625 { 626 const char *reason; 627 628 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 629 error("%s", reason); 630 return 0; 631 } 632 if (buffer_len(&host_key->cert->critical) != 0) { 633 error("Certificate for %s contains unsupported " 634 "critical options(s)", host); 635 return 0; 636 } 637 return 1; 638 } 639 640 static int 641 sockaddr_is_local(struct sockaddr *hostaddr) 642 { 643 switch (hostaddr->sa_family) { 644 case AF_INET: 645 return (ntohl(((struct sockaddr_in *)hostaddr)-> 646 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 647 case AF_INET6: 648 return IN6_IS_ADDR_LOOPBACK( 649 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 650 default: 651 return 0; 652 } 653 } 654 655 /* 656 * Prepare the hostname and ip address strings that are used to lookup 657 * host keys in known_hosts files. These may have a port number appended. 658 */ 659 void 660 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 661 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 662 { 663 char ntop[NI_MAXHOST]; 664 socklen_t addrlen; 665 666 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 667 case -1: 668 addrlen = 0; 669 break; 670 case AF_INET: 671 addrlen = sizeof(struct sockaddr_in); 672 break; 673 case AF_INET6: 674 addrlen = sizeof(struct sockaddr_in6); 675 break; 676 default: 677 addrlen = sizeof(struct sockaddr); 678 break; 679 } 680 681 /* 682 * We don't have the remote ip-address for connections 683 * using a proxy command 684 */ 685 if (hostfile_ipaddr != NULL) { 686 if (options.proxy_command == NULL) { 687 if (getnameinfo(hostaddr, addrlen, 688 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 689 fatal("check_host_key: getnameinfo failed"); 690 *hostfile_ipaddr = put_host_port(ntop, port); 691 } else { 692 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 693 "command>"); 694 } 695 } 696 697 /* 698 * Allow the user to record the key under a different name or 699 * differentiate a non-standard port. This is useful for ssh 700 * tunneling over forwarded connections or if you run multiple 701 * sshd's on different ports on the same machine. 702 */ 703 if (hostfile_hostname != NULL) { 704 if (options.host_key_alias != NULL) { 705 *hostfile_hostname = xstrdup(options.host_key_alias); 706 debug("using hostkeyalias: %s", *hostfile_hostname); 707 } else { 708 *hostfile_hostname = put_host_port(hostname, port); 709 } 710 } 711 } 712 713 /* 714 * check whether the supplied host key is valid, return -1 if the key 715 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 716 */ 717 #define RDRW 0 718 #define RDONLY 1 719 #define ROQUIET 2 720 static int 721 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 722 Key *host_key, int readonly, 723 char **user_hostfiles, u_int num_user_hostfiles, 724 char **system_hostfiles, u_int num_system_hostfiles) 725 { 726 HostStatus host_status; 727 HostStatus ip_status; 728 Key *raw_key = NULL; 729 char *ip = NULL, *host = NULL; 730 char hostline[1000], *hostp, *fp, *ra; 731 char msg[1024]; 732 const char *type; 733 const struct hostkey_entry *host_found, *ip_found; 734 int len, cancelled_forwarding = 0; 735 int local = sockaddr_is_local(hostaddr); 736 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 737 struct hostkeys *host_hostkeys, *ip_hostkeys; 738 u_int i; 739 740 /* 741 * Force accepting of the host key for loopback/localhost. The 742 * problem is that if the home directory is NFS-mounted to multiple 743 * machines, localhost will refer to a different machine in each of 744 * them, and the user will get bogus HOST_CHANGED warnings. This 745 * essentially disables host authentication for localhost; however, 746 * this is probably not a real problem. 747 */ 748 if (options.no_host_authentication_for_localhost == 1 && local && 749 options.host_key_alias == NULL) { 750 debug("Forcing accepting of host key for " 751 "loopback/localhost."); 752 return 0; 753 } 754 755 /* 756 * Prepare the hostname and address strings used for hostkey lookup. 757 * In some cases, these will have a port number appended. 758 */ 759 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 760 761 /* 762 * Turn off check_host_ip if the connection is to localhost, via proxy 763 * command or if we don't have a hostname to compare with 764 */ 765 if (options.check_host_ip && (local || 766 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 767 options.check_host_ip = 0; 768 769 host_hostkeys = init_hostkeys(); 770 for (i = 0; i < num_user_hostfiles; i++) 771 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 772 for (i = 0; i < num_system_hostfiles; i++) 773 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 774 775 ip_hostkeys = NULL; 776 if (!want_cert && options.check_host_ip) { 777 ip_hostkeys = init_hostkeys(); 778 for (i = 0; i < num_user_hostfiles; i++) 779 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 780 for (i = 0; i < num_system_hostfiles; i++) 781 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 782 } 783 784 retry: 785 /* Reload these as they may have changed on cert->key downgrade */ 786 want_cert = key_is_cert(host_key); 787 type = key_type(host_key); 788 789 /* 790 * Check if the host key is present in the user's list of known 791 * hosts or in the systemwide list. 792 */ 793 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 794 &host_found); 795 796 /* 797 * Also perform check for the ip address, skip the check if we are 798 * localhost, looking for a certificate, or the hostname was an ip 799 * address to begin with. 800 */ 801 if (!want_cert && ip_hostkeys != NULL) { 802 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 803 &ip_found); 804 if (host_status == HOST_CHANGED && 805 (ip_status != HOST_CHANGED || 806 (ip_found != NULL && 807 !key_equal(ip_found->key, host_found->key)))) 808 host_ip_differ = 1; 809 } else 810 ip_status = host_status; 811 812 switch (host_status) { 813 case HOST_OK: 814 /* The host is known and the key matches. */ 815 debug("Host '%.200s' is known and matches the %s host %s.", 816 host, type, want_cert ? "certificate" : "key"); 817 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 818 host_found->file, host_found->line); 819 if (want_cert && !check_host_cert(hostname, host_key)) 820 goto fail; 821 if (options.check_host_ip && ip_status == HOST_NEW) { 822 if (readonly || want_cert) 823 logit("%s host key for IP address " 824 "'%.128s' not in list of known hosts.", 825 type, ip); 826 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 827 host_key, options.hash_known_hosts)) 828 logit("Failed to add the %s host key for IP " 829 "address '%.128s' to the list of known " 830 "hosts (%.30s).", type, ip, 831 user_hostfiles[0]); 832 else 833 logit("Warning: Permanently added the %s host " 834 "key for IP address '%.128s' to the list " 835 "of known hosts.", type, ip); 836 } else if (options.visual_host_key) { 837 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 838 ra = key_fingerprint(host_key, SSH_FP_MD5, 839 SSH_FP_RANDOMART); 840 logit("Host key fingerprint is %s\n%s\n", fp, ra); 841 xfree(ra); 842 xfree(fp); 843 } 844 break; 845 case HOST_NEW: 846 if (options.host_key_alias == NULL && port != 0 && 847 port != SSH_DEFAULT_PORT) { 848 debug("checking without port identifier"); 849 if (check_host_key(hostname, hostaddr, 0, host_key, 850 ROQUIET, user_hostfiles, num_user_hostfiles, 851 system_hostfiles, num_system_hostfiles) == 0) { 852 debug("found matching key w/out port"); 853 break; 854 } 855 } 856 if (readonly || want_cert) 857 goto fail; 858 /* The host is new. */ 859 if (options.strict_host_key_checking == 1) { 860 /* 861 * User has requested strict host key checking. We 862 * will not add the host key automatically. The only 863 * alternative left is to abort. 864 */ 865 error("No %s host key is known for %.200s and you " 866 "have requested strict checking.", type, host); 867 goto fail; 868 } else if (options.strict_host_key_checking == 2) { 869 char msg1[1024], msg2[1024]; 870 871 if (show_other_keys(host_hostkeys, host_key)) 872 snprintf(msg1, sizeof(msg1), 873 "\nbut keys of different type are already" 874 " known for this host."); 875 else 876 snprintf(msg1, sizeof(msg1), "."); 877 /* The default */ 878 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 879 ra = key_fingerprint(host_key, SSH_FP_MD5, 880 SSH_FP_RANDOMART); 881 msg2[0] = '\0'; 882 if (options.verify_host_key_dns) { 883 if (matching_host_key_dns) 884 snprintf(msg2, sizeof(msg2), 885 "Matching host key fingerprint" 886 " found in DNS.\n"); 887 else 888 snprintf(msg2, sizeof(msg2), 889 "No matching host key fingerprint" 890 " found in DNS.\n"); 891 } 892 snprintf(msg, sizeof(msg), 893 "The authenticity of host '%.200s (%s)' can't be " 894 "established%s\n" 895 "%s key fingerprint is %s.%s%s\n%s" 896 "Are you sure you want to continue connecting " 897 "(yes/no)? ", 898 host, ip, msg1, type, fp, 899 options.visual_host_key ? "\n" : "", 900 options.visual_host_key ? ra : "", 901 msg2); 902 xfree(ra); 903 xfree(fp); 904 if (!confirm(msg)) 905 goto fail; 906 } 907 /* 908 * If not in strict mode, add the key automatically to the 909 * local known_hosts file. 910 */ 911 if (options.check_host_ip && ip_status == HOST_NEW) { 912 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 913 hostp = hostline; 914 if (options.hash_known_hosts) { 915 /* Add hash of host and IP separately */ 916 r = add_host_to_hostfile(user_hostfiles[0], 917 host, host_key, options.hash_known_hosts) && 918 add_host_to_hostfile(user_hostfiles[0], ip, 919 host_key, options.hash_known_hosts); 920 } else { 921 /* Add unhashed "host,ip" */ 922 r = add_host_to_hostfile(user_hostfiles[0], 923 hostline, host_key, 924 options.hash_known_hosts); 925 } 926 } else { 927 r = add_host_to_hostfile(user_hostfiles[0], host, 928 host_key, options.hash_known_hosts); 929 hostp = host; 930 } 931 932 if (!r) 933 logit("Failed to add the host to the list of known " 934 "hosts (%.500s).", user_hostfiles[0]); 935 else 936 logit("Warning: Permanently added '%.200s' (%s) to the " 937 "list of known hosts.", hostp, type); 938 break; 939 case HOST_REVOKED: 940 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 941 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 942 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 943 error("The %s host key for %s is marked as revoked.", type, host); 944 error("This could mean that a stolen key is being used to"); 945 error("impersonate this host."); 946 947 /* 948 * If strict host key checking is in use, the user will have 949 * to edit the key manually and we can only abort. 950 */ 951 if (options.strict_host_key_checking) { 952 error("%s host key for %.200s was revoked and you have " 953 "requested strict checking.", type, host); 954 goto fail; 955 } 956 goto continue_unsafe; 957 958 case HOST_CHANGED: 959 if (want_cert) { 960 /* 961 * This is only a debug() since it is valid to have 962 * CAs with wildcard DNS matches that don't match 963 * all hosts that one might visit. 964 */ 965 debug("Host certificate authority does not " 966 "match %s in %s:%lu", CA_MARKER, 967 host_found->file, host_found->line); 968 goto fail; 969 } 970 if (readonly == ROQUIET) 971 goto fail; 972 if (options.check_host_ip && host_ip_differ) { 973 char *key_msg; 974 if (ip_status == HOST_NEW) 975 key_msg = "is unknown"; 976 else if (ip_status == HOST_OK) 977 key_msg = "is unchanged"; 978 else 979 key_msg = "has a different value"; 980 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 981 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 982 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 983 error("The %s host key for %s has changed,", type, host); 984 error("and the key for the corresponding IP address %s", ip); 985 error("%s. This could either mean that", key_msg); 986 error("DNS SPOOFING is happening or the IP address for the host"); 987 error("and its host key have changed at the same time."); 988 if (ip_status != HOST_NEW) 989 error("Offending key for IP in %s:%lu", 990 ip_found->file, ip_found->line); 991 } 992 /* The host key has changed. */ 993 warn_changed_key(host_key); 994 error("Add correct host key in %.100s to get rid of this message.", 995 user_hostfiles[0]); 996 error("Offending %s key in %s:%lu", key_type(host_found->key), 997 host_found->file, host_found->line); 998 999 /* 1000 * If strict host key checking is in use, the user will have 1001 * to edit the key manually and we can only abort. 1002 */ 1003 if (options.strict_host_key_checking) { 1004 error("%s host key for %.200s has changed and you have " 1005 "requested strict checking.", type, host); 1006 goto fail; 1007 } 1008 1009 continue_unsafe: 1010 /* 1011 * If strict host key checking has not been requested, allow 1012 * the connection but without MITM-able authentication or 1013 * forwarding. 1014 */ 1015 if (options.password_authentication) { 1016 error("Password authentication is disabled to avoid " 1017 "man-in-the-middle attacks."); 1018 options.password_authentication = 0; 1019 cancelled_forwarding = 1; 1020 } 1021 if (options.kbd_interactive_authentication) { 1022 error("Keyboard-interactive authentication is disabled" 1023 " to avoid man-in-the-middle attacks."); 1024 options.kbd_interactive_authentication = 0; 1025 options.challenge_response_authentication = 0; 1026 cancelled_forwarding = 1; 1027 } 1028 if (options.challenge_response_authentication) { 1029 error("Challenge/response authentication is disabled" 1030 " to avoid man-in-the-middle attacks."); 1031 options.challenge_response_authentication = 0; 1032 cancelled_forwarding = 1; 1033 } 1034 if (options.forward_agent) { 1035 error("Agent forwarding is disabled to avoid " 1036 "man-in-the-middle attacks."); 1037 options.forward_agent = 0; 1038 cancelled_forwarding = 1; 1039 } 1040 if (options.forward_x11) { 1041 error("X11 forwarding is disabled to avoid " 1042 "man-in-the-middle attacks."); 1043 options.forward_x11 = 0; 1044 cancelled_forwarding = 1; 1045 } 1046 if (options.num_local_forwards > 0 || 1047 options.num_remote_forwards > 0) { 1048 error("Port forwarding is disabled to avoid " 1049 "man-in-the-middle attacks."); 1050 options.num_local_forwards = 1051 options.num_remote_forwards = 0; 1052 cancelled_forwarding = 1; 1053 } 1054 if (options.tun_open != SSH_TUNMODE_NO) { 1055 error("Tunnel forwarding is disabled to avoid " 1056 "man-in-the-middle attacks."); 1057 options.tun_open = SSH_TUNMODE_NO; 1058 cancelled_forwarding = 1; 1059 } 1060 if (options.exit_on_forward_failure && cancelled_forwarding) 1061 fatal("Error: forwarding disabled due to host key " 1062 "check failure"); 1063 1064 /* 1065 * XXX Should permit the user to change to use the new id. 1066 * This could be done by converting the host key to an 1067 * identifying sentence, tell that the host identifies itself 1068 * by that sentence, and ask the user if he/she wishes to 1069 * accept the authentication. 1070 */ 1071 break; 1072 case HOST_FOUND: 1073 fatal("internal error"); 1074 break; 1075 } 1076 1077 if (options.check_host_ip && host_status != HOST_CHANGED && 1078 ip_status == HOST_CHANGED) { 1079 snprintf(msg, sizeof(msg), 1080 "Warning: the %s host key for '%.200s' " 1081 "differs from the key for the IP address '%.128s'" 1082 "\nOffending key for IP in %s:%lu", 1083 type, host, ip, ip_found->file, ip_found->line); 1084 if (host_status == HOST_OK) { 1085 len = strlen(msg); 1086 snprintf(msg + len, sizeof(msg) - len, 1087 "\nMatching host key in %s:%lu", 1088 host_found->file, host_found->line); 1089 } 1090 if (options.strict_host_key_checking == 1) { 1091 logit("%s", msg); 1092 error("Exiting, you have requested strict checking."); 1093 goto fail; 1094 } else if (options.strict_host_key_checking == 2) { 1095 strlcat(msg, "\nAre you sure you want " 1096 "to continue connecting (yes/no)? ", sizeof(msg)); 1097 if (!confirm(msg)) 1098 goto fail; 1099 } else { 1100 logit("%s", msg); 1101 } 1102 } 1103 1104 xfree(ip); 1105 xfree(host); 1106 if (host_hostkeys != NULL) 1107 free_hostkeys(host_hostkeys); 1108 if (ip_hostkeys != NULL) 1109 free_hostkeys(ip_hostkeys); 1110 return 0; 1111 1112 fail: 1113 if (want_cert && host_status != HOST_REVOKED) { 1114 /* 1115 * No matching certificate. Downgrade cert to raw key and 1116 * search normally. 1117 */ 1118 debug("No matching CA found. Retry with plain key"); 1119 raw_key = key_from_private(host_key); 1120 if (key_drop_cert(raw_key) != 0) 1121 fatal("Couldn't drop certificate"); 1122 host_key = raw_key; 1123 goto retry; 1124 } 1125 if (raw_key != NULL) 1126 key_free(raw_key); 1127 xfree(ip); 1128 xfree(host); 1129 if (host_hostkeys != NULL) 1130 free_hostkeys(host_hostkeys); 1131 if (ip_hostkeys != NULL) 1132 free_hostkeys(ip_hostkeys); 1133 return -1; 1134 } 1135 1136 /* returns 0 if key verifies or -1 if key does NOT verify */ 1137 int 1138 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1139 { 1140 int flags = 0; 1141 char *fp; 1142 1143 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1144 debug("Server host key: %s %s", key_type(host_key), fp); 1145 xfree(fp); 1146 1147 /* XXX certs are not yet supported for DNS */ 1148 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1149 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1150 if (flags & DNS_VERIFY_FOUND) { 1151 1152 if (options.verify_host_key_dns == 1 && 1153 flags & DNS_VERIFY_MATCH && 1154 flags & DNS_VERIFY_SECURE) 1155 return 0; 1156 1157 if (flags & DNS_VERIFY_MATCH) { 1158 matching_host_key_dns = 1; 1159 } else { 1160 warn_changed_key(host_key); 1161 error("Update the SSHFP RR in DNS with the new " 1162 "host key to get rid of this message."); 1163 } 1164 } 1165 } 1166 1167 return check_host_key(host, hostaddr, options.port, host_key, RDRW, 1168 options.user_hostfiles, options.num_user_hostfiles, 1169 options.system_hostfiles, options.num_system_hostfiles); 1170 } 1171 1172 /* 1173 * Starts a dialog with the server, and authenticates the current user on the 1174 * server. This does not need any extra privileges. The basic connection 1175 * to the server must already have been established before this is called. 1176 * If login fails, this function prints an error and never returns. 1177 * This function does not require super-user privileges. 1178 */ 1179 void 1180 ssh_login(Sensitive *sensitive, const char *orighost, 1181 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1182 { 1183 char *host, *cp; 1184 char *server_user, *local_user; 1185 1186 local_user = xstrdup(pw->pw_name); 1187 server_user = options.user ? options.user : local_user; 1188 1189 /* Convert the user-supplied hostname into all lowercase. */ 1190 host = xstrdup(orighost); 1191 for (cp = host; *cp; cp++) 1192 if (isupper(*cp)) 1193 *cp = (char)tolower(*cp); 1194 1195 /* Exchange protocol version identification strings with the server. */ 1196 ssh_exchange_identification(timeout_ms); 1197 1198 /* Put the connection into non-blocking mode. */ 1199 packet_set_nonblocking(); 1200 1201 /* key exchange */ 1202 /* authenticate user */ 1203 if (compat20) { 1204 ssh_kex2(host, hostaddr, port); 1205 ssh_userauth2(local_user, server_user, host, sensitive); 1206 } else { 1207 ssh_kex(host, hostaddr); 1208 ssh_userauth1(local_user, server_user, host, sensitive); 1209 } 1210 xfree(local_user); 1211 } 1212 1213 void 1214 ssh_put_password(char *password) 1215 { 1216 int size; 1217 char *padded; 1218 1219 if (datafellows & SSH_BUG_PASSWORDPAD) { 1220 packet_put_cstring(password); 1221 return; 1222 } 1223 size = roundup(strlen(password) + 1, 32); 1224 padded = xcalloc(1, size); 1225 strlcpy(padded, password, size); 1226 packet_put_string(padded, size); 1227 memset(padded, 0, size); 1228 xfree(padded); 1229 } 1230 1231 /* print all known host keys for a given host, but skip keys of given type */ 1232 static int 1233 show_other_keys(struct hostkeys *hostkeys, Key *key) 1234 { 1235 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1236 int i, ret = 0; 1237 char *fp, *ra; 1238 const struct hostkey_entry *found; 1239 1240 for (i = 0; type[i] != -1; i++) { 1241 if (type[i] == key->type) 1242 continue; 1243 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1244 continue; 1245 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1246 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1247 logit("WARNING: %s key found for host %s\n" 1248 "in %s:%lu\n" 1249 "%s key fingerprint %s.", 1250 key_type(found->key), 1251 found->host, found->file, found->line, 1252 key_type(found->key), fp); 1253 if (options.visual_host_key) 1254 logit("%s", ra); 1255 xfree(ra); 1256 xfree(fp); 1257 ret = 1; 1258 } 1259 return ret; 1260 } 1261 1262 static void 1263 warn_changed_key(Key *host_key) 1264 { 1265 char *fp; 1266 1267 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1268 1269 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1270 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1271 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1272 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1273 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1274 error("It is also possible that a host key has just been changed."); 1275 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1276 key_type(host_key), fp); 1277 error("Please contact your system administrator."); 1278 1279 xfree(fp); 1280 } 1281 1282 /* 1283 * Execute a local command 1284 */ 1285 int 1286 ssh_local_cmd(const char *args) 1287 { 1288 char *shell; 1289 pid_t pid; 1290 int status; 1291 void (*osighand)(int); 1292 1293 if (!options.permit_local_command || 1294 args == NULL || !*args) 1295 return (1); 1296 1297 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1298 shell = _PATH_BSHELL; 1299 1300 osighand = signal(SIGCHLD, SIG_DFL); 1301 pid = fork(); 1302 if (pid == 0) { 1303 signal(SIGPIPE, SIG_DFL); 1304 debug3("Executing %s -c \"%s\"", shell, args); 1305 execl(shell, shell, "-c", args, (char *)NULL); 1306 error("Couldn't execute %s -c \"%s\": %s", 1307 shell, args, strerror(errno)); 1308 _exit(1); 1309 } else if (pid == -1) 1310 fatal("fork failed: %.100s", strerror(errno)); 1311 while (waitpid(pid, &status, 0) == -1) 1312 if (errno != EINTR) 1313 fatal("Couldn't wait for child: %s", strerror(errno)); 1314 signal(SIGCHLD, osighand); 1315 1316 if (!WIFEXITED(status)) 1317 return (1); 1318 1319 return (WEXITSTATUS(status)); 1320 } 1321