1 /* $OpenBSD: sshconnect.c,v 1.232 2011/01/16 11:50:36 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Code to connect to a remote host, and to perform the client side of the 7 * login (authentication) dialog. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16 #include "includes.h" 17 18 #include <sys/types.h> 19 #include <sys/wait.h> 20 #include <sys/stat.h> 21 #include <sys/socket.h> 22 #ifdef HAVE_SYS_TIME_H 23 # include <sys/time.h> 24 #endif 25 26 #include <netinet/in.h> 27 #include <arpa/inet.h> 28 29 #include <ctype.h> 30 #include <errno.h> 31 #include <fcntl.h> 32 #include <netdb.h> 33 #ifdef HAVE_PATHS_H 34 #include <paths.h> 35 #endif 36 #include <pwd.h> 37 #include <signal.h> 38 #include <stdarg.h> 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include <unistd.h> 43 44 #include "xmalloc.h" 45 #include "key.h" 46 #include "hostfile.h" 47 #include "ssh.h" 48 #include "rsa.h" 49 #include "buffer.h" 50 #include "packet.h" 51 #include "uidswap.h" 52 #include "compat.h" 53 #include "key.h" 54 #include "sshconnect.h" 55 #include "hostfile.h" 56 #include "log.h" 57 #include "readconf.h" 58 #include "atomicio.h" 59 #include "misc.h" 60 #include "dns.h" 61 #include "roaming.h" 62 #include "ssh2.h" 63 #include "version.h" 64 65 char *client_version_string = NULL; 66 char *server_version_string = NULL; 67 68 static int matching_host_key_dns = 0; 69 70 static pid_t proxy_command_pid = 0; 71 72 /* import */ 73 extern Options options; 74 extern char *__progname; 75 extern uid_t original_real_uid; 76 extern uid_t original_effective_uid; 77 78 static int show_other_keys(struct hostkeys *, Key *); 79 static void warn_changed_key(Key *); 80 81 /* 82 * Connect to the given ssh server using a proxy command. 83 */ 84 static int 85 ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) 86 { 87 char *command_string, *tmp; 88 int pin[2], pout[2]; 89 pid_t pid; 90 char *shell, strport[NI_MAXSERV]; 91 92 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 93 shell = _PATH_BSHELL; 94 95 /* Convert the port number into a string. */ 96 snprintf(strport, sizeof strport, "%hu", port); 97 98 /* 99 * Build the final command string in the buffer by making the 100 * appropriate substitutions to the given proxy command. 101 * 102 * Use "exec" to avoid "sh -c" processes on some platforms 103 * (e.g. Solaris) 104 */ 105 xasprintf(&tmp, "exec %s", proxy_command); 106 command_string = percent_expand(tmp, "h", host, "p", strport, 107 "r", options.user, (char *)NULL); 108 xfree(tmp); 109 110 /* Create pipes for communicating with the proxy. */ 111 if (pipe(pin) < 0 || pipe(pout) < 0) 112 fatal("Could not create pipes to communicate with the proxy: %.100s", 113 strerror(errno)); 114 115 debug("Executing proxy command: %.500s", command_string); 116 117 /* Fork and execute the proxy command. */ 118 if ((pid = fork()) == 0) { 119 char *argv[10]; 120 121 /* Child. Permanently give up superuser privileges. */ 122 permanently_drop_suid(original_real_uid); 123 124 /* Redirect stdin and stdout. */ 125 close(pin[1]); 126 if (pin[0] != 0) { 127 if (dup2(pin[0], 0) < 0) 128 perror("dup2 stdin"); 129 close(pin[0]); 130 } 131 close(pout[0]); 132 if (dup2(pout[1], 1) < 0) 133 perror("dup2 stdout"); 134 /* Cannot be 1 because pin allocated two descriptors. */ 135 close(pout[1]); 136 137 /* Stderr is left as it is so that error messages get 138 printed on the user's terminal. */ 139 argv[0] = shell; 140 argv[1] = "-c"; 141 argv[2] = command_string; 142 argv[3] = NULL; 143 144 /* Execute the proxy command. Note that we gave up any 145 extra privileges above. */ 146 signal(SIGPIPE, SIG_DFL); 147 execv(argv[0], argv); 148 perror(argv[0]); 149 exit(1); 150 } 151 /* Parent. */ 152 if (pid < 0) 153 fatal("fork failed: %.100s", strerror(errno)); 154 else 155 proxy_command_pid = pid; /* save pid to clean up later */ 156 157 /* Close child side of the descriptors. */ 158 close(pin[0]); 159 close(pout[1]); 160 161 /* Free the command name. */ 162 xfree(command_string); 163 164 /* Set the connection file descriptors. */ 165 packet_set_connection(pout[0], pin[1]); 166 packet_set_timeout(options.server_alive_interval, 167 options.server_alive_count_max); 168 169 /* Indicate OK return */ 170 return 0; 171 } 172 173 void 174 ssh_kill_proxy_command(void) 175 { 176 /* 177 * Send SIGHUP to proxy command if used. We don't wait() in 178 * case it hangs and instead rely on init to reap the child 179 */ 180 if (proxy_command_pid > 1) 181 kill(proxy_command_pid, SIGHUP); 182 } 183 184 /* 185 * Set TCP receive buffer if requested. 186 * Note: tuning needs to happen after the socket is 187 * created but before the connection happens 188 * so winscale is negotiated properly -cjr 189 */ 190 static void 191 ssh_set_socket_recvbuf(int sock) 192 { 193 void *buf = (void *)&options.tcp_rcv_buf; 194 int sz = sizeof(options.tcp_rcv_buf); 195 int socksize; 196 int socksizelen = sizeof(int); 197 198 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 199 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 200 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 201 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 202 } 203 else 204 error("Couldn't set socket receive buffer to %d: %.100s", 205 options.tcp_rcv_buf, strerror(errno)); 206 } 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 error("socket: %.100s", strerror(errno)); 240 return -1; 241 } 242 fcntl(sock, F_SETFD, FD_CLOEXEC); 243 244 if (options.tcp_rcv_buf > 0) 245 ssh_set_socket_recvbuf(sock); 246 247 /* Bind the socket to an alternative local IP address */ 248 if (options.bind_address == NULL) 249 return sock; 250 251 memset(&hints, 0, sizeof(hints)); 252 hints.ai_family = ai->ai_family; 253 hints.ai_socktype = ai->ai_socktype; 254 hints.ai_protocol = ai->ai_protocol; 255 hints.ai_flags = AI_PASSIVE; 256 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 257 if (gaierr) { 258 error("getaddrinfo: %s: %s", options.bind_address, 259 ssh_gai_strerror(gaierr)); 260 close(sock); 261 return -1; 262 } 263 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 264 error("bind: %s: %s", options.bind_address, strerror(errno)); 265 close(sock); 266 freeaddrinfo(res); 267 return -1; 268 } 269 freeaddrinfo(res); 270 return sock; 271 } 272 273 static int 274 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 275 socklen_t addrlen, int *timeoutp) 276 { 277 fd_set *fdset; 278 struct timeval tv, t_start; 279 socklen_t optlen; 280 int optval, rc, result = -1; 281 282 gettimeofday(&t_start, NULL); 283 284 if (*timeoutp <= 0) { 285 result = connect(sockfd, serv_addr, addrlen); 286 goto done; 287 } 288 289 set_nonblock(sockfd); 290 rc = connect(sockfd, serv_addr, addrlen); 291 if (rc == 0) { 292 unset_nonblock(sockfd); 293 result = 0; 294 goto done; 295 } 296 if (errno != EINPROGRESS) { 297 result = -1; 298 goto done; 299 } 300 301 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 302 sizeof(fd_mask)); 303 FD_SET(sockfd, fdset); 304 ms_to_timeval(&tv, *timeoutp); 305 306 for (;;) { 307 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 308 if (rc != -1 || errno != EINTR) 309 break; 310 } 311 312 switch (rc) { 313 case 0: 314 /* Timed out */ 315 errno = ETIMEDOUT; 316 break; 317 case -1: 318 /* Select error */ 319 debug("select: %s", strerror(errno)); 320 break; 321 case 1: 322 /* Completed or failed */ 323 optval = 0; 324 optlen = sizeof(optval); 325 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 326 &optlen) == -1) { 327 debug("getsockopt: %s", strerror(errno)); 328 break; 329 } 330 if (optval != 0) { 331 errno = optval; 332 break; 333 } 334 result = 0; 335 unset_nonblock(sockfd); 336 break; 337 default: 338 /* Should not occur */ 339 fatal("Bogus return (%d) from select()", rc); 340 } 341 342 xfree(fdset); 343 344 done: 345 if (result == 0 && *timeoutp > 0) { 346 ms_subtract_diff(&t_start, timeoutp); 347 if (*timeoutp <= 0) { 348 errno = ETIMEDOUT; 349 result = -1; 350 } 351 } 352 353 return (result); 354 } 355 356 /* 357 * Opens a TCP/IP connection to the remote server on the given host. 358 * The address of the remote host will be returned in hostaddr. 359 * If port is 0, the default port will be used. If needpriv is true, 360 * a privileged port will be allocated to make the connection. 361 * This requires super-user privileges if needpriv is true. 362 * Connection_attempts specifies the maximum number of tries (one per 363 * second). If proxy_command is non-NULL, it specifies the command (with %h 364 * and %p substituted for host and port, respectively) to use to contact 365 * the daemon. 366 */ 367 int 368 ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 369 u_short port, int family, int connection_attempts, int *timeout_ms, 370 int want_keepalive, int needpriv, const char *proxy_command) 371 { 372 int gaierr; 373 int on = 1; 374 int sock = -1, attempt; 375 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 376 struct addrinfo hints, *ai, *aitop; 377 378 debug2("ssh_connect: needpriv %d", needpriv); 379 380 /* If a proxy command is given, connect using it. */ 381 if (proxy_command != NULL) 382 return ssh_proxy_connect(host, port, proxy_command); 383 384 /* No proxy command. */ 385 386 memset(&hints, 0, sizeof(hints)); 387 hints.ai_family = family; 388 hints.ai_socktype = SOCK_STREAM; 389 snprintf(strport, sizeof strport, "%u", port); 390 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 391 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 392 host, ssh_gai_strerror(gaierr)); 393 394 for (attempt = 0; attempt < connection_attempts; attempt++) { 395 if (attempt > 0) { 396 /* Sleep a moment before retrying. */ 397 sleep(1); 398 debug("Trying again..."); 399 } 400 /* 401 * Loop through addresses for this host, and try each one in 402 * sequence until the connection succeeds. 403 */ 404 for (ai = aitop; ai; ai = ai->ai_next) { 405 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 406 continue; 407 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 408 ntop, sizeof(ntop), strport, sizeof(strport), 409 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 410 error("ssh_connect: getnameinfo failed"); 411 continue; 412 } 413 debug("Connecting to %.200s [%.100s] port %s.", 414 host, ntop, strport); 415 416 /* Create a socket for connecting. */ 417 sock = ssh_create_socket(needpriv, ai); 418 if (sock < 0) 419 /* Any error is already output */ 420 continue; 421 422 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 423 timeout_ms) >= 0) { 424 /* Successful connection. */ 425 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 426 break; 427 } else { 428 debug("connect to address %s port %s: %s", 429 ntop, strport, strerror(errno)); 430 close(sock); 431 sock = -1; 432 } 433 } 434 if (sock != -1) 435 break; /* Successful connection. */ 436 } 437 438 freeaddrinfo(aitop); 439 440 /* Return failure if we didn't get a successful connection. */ 441 if (sock == -1) { 442 error("ssh: connect to host %s port %s: %s", 443 host, strport, strerror(errno)); 444 return (-1); 445 } 446 447 debug("Connection established."); 448 449 /* Set SO_KEEPALIVE if requested. */ 450 if (want_keepalive && 451 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 452 sizeof(on)) < 0) 453 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 454 455 /* Set the connection. */ 456 packet_set_connection(sock, sock); 457 packet_set_timeout(options.server_alive_interval, 458 options.server_alive_count_max); 459 460 return 0; 461 } 462 463 /* 464 * Waits for the server identification string, and sends our own 465 * identification string. 466 */ 467 void 468 ssh_exchange_identification(int timeout_ms) 469 { 470 char buf[256], remote_version[256]; /* must be same size! */ 471 int remote_major, remote_minor, mismatch; 472 int connection_in = packet_get_connection_in(); 473 int connection_out = packet_get_connection_out(); 474 int minor1 = PROTOCOL_MINOR_1; 475 u_int i, n; 476 size_t len; 477 int fdsetsz, remaining, rc; 478 struct timeval t_start, t_remaining; 479 fd_set *fdset; 480 481 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 482 fdset = xcalloc(1, fdsetsz); 483 484 /* Read other side's version identification. */ 485 remaining = timeout_ms; 486 for (n = 0;;) { 487 for (i = 0; i < sizeof(buf) - 1; i++) { 488 if (timeout_ms > 0) { 489 gettimeofday(&t_start, NULL); 490 ms_to_timeval(&t_remaining, remaining); 491 FD_SET(connection_in, fdset); 492 rc = select(connection_in + 1, fdset, NULL, 493 fdset, &t_remaining); 494 ms_subtract_diff(&t_start, &remaining); 495 if (rc == 0 || remaining <= 0) 496 fatal("Connection timed out during " 497 "banner exchange"); 498 if (rc == -1) { 499 if (errno == EINTR) 500 continue; 501 fatal("ssh_exchange_identification: " 502 "select: %s", strerror(errno)); 503 } 504 } 505 506 len = roaming_atomicio(read, connection_in, &buf[i], 1); 507 508 if (len != 1 && errno == EPIPE) 509 fatal("ssh_exchange_identification: " 510 "Connection closed by remote host"); 511 else if (len != 1) 512 fatal("ssh_exchange_identification: " 513 "read: %.100s", strerror(errno)); 514 if (buf[i] == '\r') { 515 buf[i] = '\n'; 516 buf[i + 1] = 0; 517 continue; /**XXX wait for \n */ 518 } 519 if (buf[i] == '\n') { 520 buf[i + 1] = 0; 521 break; 522 } 523 if (++n > 65536) 524 fatal("ssh_exchange_identification: " 525 "No banner received"); 526 } 527 buf[sizeof(buf) - 1] = 0; 528 if (strncmp(buf, "SSH-", 4) == 0) 529 break; 530 debug("ssh_exchange_identification: %s", buf); 531 } 532 server_version_string = xstrdup(buf); 533 xfree(fdset); 534 535 /* 536 * Check that the versions match. In future this might accept 537 * several versions and set appropriate flags to handle them. 538 */ 539 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 540 &remote_major, &remote_minor, remote_version) != 3) 541 fatal("Bad remote protocol version identification: '%.100s'", buf); 542 debug("Remote protocol version %d.%d, remote software version %.100s", 543 remote_major, remote_minor, remote_version); 544 545 compat_datafellows(remote_version); 546 mismatch = 0; 547 548 switch (remote_major) { 549 case 1: 550 if (remote_minor == 99 && 551 (options.protocol & SSH_PROTO_2) && 552 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 553 enable_compat20(); 554 break; 555 } 556 if (!(options.protocol & SSH_PROTO_1)) { 557 mismatch = 1; 558 break; 559 } 560 if (remote_minor < 3) { 561 fatal("Remote machine has too old SSH software version."); 562 } else if (remote_minor == 3 || remote_minor == 4) { 563 /* We speak 1.3, too. */ 564 enable_compat13(); 565 minor1 = 3; 566 if (options.forward_agent) { 567 logit("Agent forwarding disabled for protocol 1.3"); 568 options.forward_agent = 0; 569 } 570 } 571 break; 572 case 2: 573 if (options.protocol & SSH_PROTO_2) { 574 enable_compat20(); 575 break; 576 } 577 /* FALLTHROUGH */ 578 default: 579 mismatch = 1; 580 break; 581 } 582 if (mismatch) 583 fatal("Protocol major versions differ: %d vs. %d", 584 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 585 remote_major); 586 /* Send our own protocol version identification. */ 587 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 588 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 589 compat20 ? PROTOCOL_MINOR_2 : minor1, 590 SSH_RELEASE, compat20 ? "\r\n" : "\n"); 591 if (roaming_atomicio(vwrite, connection_out, buf, strlen(buf)) 592 != strlen(buf)) 593 fatal("write: %.100s", strerror(errno)); 594 client_version_string = xstrdup(buf); 595 chop(client_version_string); 596 chop(server_version_string); 597 debug("Local version string %.100s", client_version_string); 598 } 599 600 /* defaults to 'no' */ 601 static int 602 confirm(const char *prompt) 603 { 604 const char *msg, *again = "Please type 'yes' or 'no': "; 605 char *p; 606 int ret = -1; 607 608 if (options.batch_mode) 609 return 0; 610 for (msg = prompt;;msg = again) { 611 p = read_passphrase(msg, RP_ECHO); 612 if (p == NULL || 613 (p[0] == '\0') || (p[0] == '\n') || 614 strncasecmp(p, "no", 2) == 0) 615 ret = 0; 616 if (p && strncasecmp(p, "yes", 3) == 0) 617 ret = 1; 618 if (p) 619 xfree(p); 620 if (ret != -1) 621 return ret; 622 } 623 } 624 625 static int 626 check_host_cert(const char *host, const Key *host_key) 627 { 628 const char *reason; 629 630 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 631 error("%s", reason); 632 return 0; 633 } 634 if (buffer_len(&host_key->cert->critical) != 0) { 635 error("Certificate for %s contains unsupported " 636 "critical options(s)", host); 637 return 0; 638 } 639 return 1; 640 } 641 642 static int 643 sockaddr_is_local(struct sockaddr *hostaddr) 644 { 645 switch (hostaddr->sa_family) { 646 case AF_INET: 647 return (ntohl(((struct sockaddr_in *)hostaddr)-> 648 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 649 case AF_INET6: 650 return IN6_IS_ADDR_LOOPBACK( 651 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 652 default: 653 return 0; 654 } 655 } 656 657 /* 658 * Prepare the hostname and ip address strings that are used to lookup 659 * host keys in known_hosts files. These may have a port number appended. 660 */ 661 void 662 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 663 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 664 { 665 char ntop[NI_MAXHOST]; 666 socklen_t addrlen; 667 668 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 669 case -1: 670 addrlen = 0; 671 break; 672 case AF_INET: 673 addrlen = sizeof(struct sockaddr_in); 674 break; 675 case AF_INET6: 676 addrlen = sizeof(struct sockaddr_in6); 677 break; 678 default: 679 addrlen = sizeof(struct sockaddr); 680 break; 681 } 682 683 /* 684 * We don't have the remote ip-address for connections 685 * using a proxy command 686 */ 687 if (hostfile_ipaddr != NULL) { 688 if (options.proxy_command == NULL) { 689 if (getnameinfo(hostaddr, addrlen, 690 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 691 fatal("check_host_key: getnameinfo failed"); 692 *hostfile_ipaddr = put_host_port(ntop, port); 693 } else { 694 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 695 "command>"); 696 } 697 } 698 699 /* 700 * Allow the user to record the key under a different name or 701 * differentiate a non-standard port. This is useful for ssh 702 * tunneling over forwarded connections or if you run multiple 703 * sshd's on different ports on the same machine. 704 */ 705 if (hostfile_hostname != NULL) { 706 if (options.host_key_alias != NULL) { 707 *hostfile_hostname = xstrdup(options.host_key_alias); 708 debug("using hostkeyalias: %s", *hostfile_hostname); 709 } else { 710 *hostfile_hostname = put_host_port(hostname, port); 711 } 712 } 713 } 714 715 /* 716 * check whether the supplied host key is valid, return -1 if the key 717 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 718 */ 719 #define RDRW 0 720 #define RDONLY 1 721 #define ROQUIET 2 722 static int 723 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 724 Key *host_key, int readonly, char *user_hostfile, 725 char *system_hostfile) 726 { 727 Key *raw_key = NULL; 728 const char *type; 729 char *ip = NULL, *host = NULL; 730 char hostline[1000], *hostp, *fp, *ra; 731 HostStatus host_status; 732 HostStatus ip_status; 733 int r, want_cert = key_is_cert(host_key), host_ip_differ = 0; 734 int local = sockaddr_is_local(hostaddr); 735 char msg[1024]; 736 int len, cancelled_forwarding = 0; 737 struct hostkeys *host_hostkeys, *ip_hostkeys; 738 const struct hostkey_entry *host_found, *ip_found; 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 load_hostkeys(host_hostkeys, host, user_hostfile); 771 load_hostkeys(host_hostkeys, host, system_hostfile); 772 773 ip_hostkeys = NULL; 774 if (!want_cert && options.check_host_ip) { 775 ip_hostkeys = init_hostkeys(); 776 load_hostkeys(ip_hostkeys, ip, user_hostfile); 777 load_hostkeys(ip_hostkeys, ip, system_hostfile); 778 } 779 780 retry: 781 /* Reload these as they may have changed on cert->key downgrade */ 782 want_cert = key_is_cert(host_key); 783 type = key_type(host_key); 784 785 /* 786 * Check if the host key is present in the user's list of known 787 * hosts or in the systemwide list. 788 */ 789 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 790 &host_found); 791 792 /* 793 * Also perform check for the ip address, skip the check if we are 794 * localhost, looking for a certificate, or the hostname was an ip 795 * address to begin with. 796 */ 797 if (!want_cert && ip_hostkeys != NULL) { 798 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 799 &ip_found); 800 if (host_status == HOST_CHANGED && 801 (ip_status != HOST_CHANGED || 802 (ip_found != NULL && 803 !key_equal(ip_found->key, host_found->key)))) 804 host_ip_differ = 1; 805 } else 806 ip_status = host_status; 807 808 switch (host_status) { 809 case HOST_OK: 810 /* The host is known and the key matches. */ 811 debug("Host '%.200s' is known and matches the %s host %s.", 812 host, type, want_cert ? "certificate" : "key"); 813 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 814 host_found->file, host_found->line); 815 if (want_cert && !check_host_cert(hostname, host_key)) 816 goto fail; 817 if (options.check_host_ip && ip_status == HOST_NEW) { 818 if (readonly || want_cert) 819 logit("%s host key for IP address " 820 "'%.128s' not in list of known hosts.", 821 type, ip); 822 else if (!add_host_to_hostfile(user_hostfile, ip, 823 host_key, options.hash_known_hosts)) 824 logit("Failed to add the %s host key for IP " 825 "address '%.128s' to the list of known " 826 "hosts (%.30s).", type, ip, user_hostfile); 827 else 828 logit("Warning: Permanently added the %s host " 829 "key for IP address '%.128s' to the list " 830 "of known hosts.", type, ip); 831 } else if (options.visual_host_key) { 832 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 833 ra = key_fingerprint(host_key, SSH_FP_MD5, 834 SSH_FP_RANDOMART); 835 logit("Host key fingerprint is %s\n%s\n", fp, ra); 836 xfree(ra); 837 xfree(fp); 838 } 839 break; 840 case HOST_NEW: 841 if (options.host_key_alias == NULL && port != 0 && 842 port != SSH_DEFAULT_PORT) { 843 debug("checking without port identifier"); 844 if (check_host_key(hostname, hostaddr, 0, host_key, 845 ROQUIET, user_hostfile, system_hostfile) == 0) { 846 debug("found matching key w/out port"); 847 break; 848 } 849 } 850 if (readonly || want_cert) 851 goto fail; 852 /* The host is new. */ 853 if (options.strict_host_key_checking == 1) { 854 /* 855 * User has requested strict host key checking. We 856 * will not add the host key automatically. The only 857 * alternative left is to abort. 858 */ 859 error("No %s host key is known for %.200s and you " 860 "have requested strict checking.", type, host); 861 goto fail; 862 } else if (options.strict_host_key_checking == 2) { 863 char msg1[1024], msg2[1024]; 864 865 if (show_other_keys(host_hostkeys, host_key)) 866 snprintf(msg1, sizeof(msg1), 867 "\nbut keys of different type are already" 868 " known for this host."); 869 else 870 snprintf(msg1, sizeof(msg1), "."); 871 /* The default */ 872 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 873 ra = key_fingerprint(host_key, SSH_FP_MD5, 874 SSH_FP_RANDOMART); 875 msg2[0] = '\0'; 876 if (options.verify_host_key_dns) { 877 if (matching_host_key_dns) 878 snprintf(msg2, sizeof(msg2), 879 "Matching host key fingerprint" 880 " found in DNS.\n"); 881 else 882 snprintf(msg2, sizeof(msg2), 883 "No matching host key fingerprint" 884 " found in DNS.\n"); 885 } 886 snprintf(msg, sizeof(msg), 887 "The authenticity of host '%.200s (%s)' can't be " 888 "established%s\n" 889 "%s key fingerprint is %s.%s%s\n%s" 890 "Are you sure you want to continue connecting " 891 "(yes/no)? ", 892 host, ip, msg1, type, fp, 893 options.visual_host_key ? "\n" : "", 894 options.visual_host_key ? ra : "", 895 msg2); 896 xfree(ra); 897 xfree(fp); 898 if (!confirm(msg)) 899 goto fail; 900 } 901 /* 902 * If not in strict mode, add the key automatically to the 903 * local known_hosts file. 904 */ 905 if (options.check_host_ip && ip_status == HOST_NEW) { 906 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 907 hostp = hostline; 908 if (options.hash_known_hosts) { 909 /* Add hash of host and IP separately */ 910 r = add_host_to_hostfile(user_hostfile, host, 911 host_key, options.hash_known_hosts) && 912 add_host_to_hostfile(user_hostfile, ip, 913 host_key, options.hash_known_hosts); 914 } else { 915 /* Add unhashed "host,ip" */ 916 r = add_host_to_hostfile(user_hostfile, 917 hostline, host_key, 918 options.hash_known_hosts); 919 } 920 } else { 921 r = add_host_to_hostfile(user_hostfile, host, host_key, 922 options.hash_known_hosts); 923 hostp = host; 924 } 925 926 if (!r) 927 logit("Failed to add the host to the list of known " 928 "hosts (%.500s).", user_hostfile); 929 else 930 logit("Warning: Permanently added '%.200s' (%s) to the " 931 "list of known hosts.", hostp, type); 932 break; 933 case HOST_REVOKED: 934 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 935 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 936 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 937 error("The %s host key for %s is marked as revoked.", type, host); 938 error("This could mean that a stolen key is being used to"); 939 error("impersonate this host."); 940 941 /* 942 * If strict host key checking is in use, the user will have 943 * to edit the key manually and we can only abort. 944 */ 945 if (options.strict_host_key_checking) { 946 error("%s host key for %.200s was revoked and you have " 947 "requested strict checking.", type, host); 948 goto fail; 949 } 950 goto continue_unsafe; 951 952 case HOST_CHANGED: 953 if (want_cert) { 954 /* 955 * This is only a debug() since it is valid to have 956 * CAs with wildcard DNS matches that don't match 957 * all hosts that one might visit. 958 */ 959 debug("Host certificate authority does not " 960 "match %s in %s:%lu", CA_MARKER, 961 host_found->file, host_found->line); 962 goto fail; 963 } 964 if (readonly == ROQUIET) 965 goto fail; 966 if (options.check_host_ip && host_ip_differ) { 967 char *key_msg; 968 if (ip_status == HOST_NEW) 969 key_msg = "is unknown"; 970 else if (ip_status == HOST_OK) 971 key_msg = "is unchanged"; 972 else 973 key_msg = "has a different value"; 974 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 975 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 976 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 977 error("The %s host key for %s has changed,", type, host); 978 error("and the key for the corresponding IP address %s", ip); 979 error("%s. This could either mean that", key_msg); 980 error("DNS SPOOFING is happening or the IP address for the host"); 981 error("and its host key have changed at the same time."); 982 if (ip_status != HOST_NEW) 983 error("Offending key for IP in %s:%lu", 984 ip_found->file, ip_found->line); 985 } 986 /* The host key has changed. */ 987 warn_changed_key(host_key); 988 error("Add correct host key in %.100s to get rid of this message.", 989 user_hostfile); 990 error("Offending %s key in %s:%lu", key_type(host_found->key), 991 host_found->file, host_found->line); 992 993 /* 994 * If strict host key checking is in use, the user will have 995 * to edit the key manually and we can only abort. 996 */ 997 if (options.strict_host_key_checking) { 998 error("%s host key for %.200s has changed and you have " 999 "requested strict checking.", type, host); 1000 goto fail; 1001 } 1002 1003 continue_unsafe: 1004 /* 1005 * If strict host key checking has not been requested, allow 1006 * the connection but without MITM-able authentication or 1007 * forwarding. 1008 */ 1009 if (options.password_authentication) { 1010 error("Password authentication is disabled to avoid " 1011 "man-in-the-middle attacks."); 1012 options.password_authentication = 0; 1013 cancelled_forwarding = 1; 1014 } 1015 if (options.kbd_interactive_authentication) { 1016 error("Keyboard-interactive authentication is disabled" 1017 " to avoid man-in-the-middle attacks."); 1018 options.kbd_interactive_authentication = 0; 1019 options.challenge_response_authentication = 0; 1020 cancelled_forwarding = 1; 1021 } 1022 if (options.challenge_response_authentication) { 1023 error("Challenge/response authentication is disabled" 1024 " to avoid man-in-the-middle attacks."); 1025 options.challenge_response_authentication = 0; 1026 cancelled_forwarding = 1; 1027 } 1028 if (options.forward_agent) { 1029 error("Agent forwarding is disabled to avoid " 1030 "man-in-the-middle attacks."); 1031 options.forward_agent = 0; 1032 cancelled_forwarding = 1; 1033 } 1034 if (options.forward_x11) { 1035 error("X11 forwarding is disabled to avoid " 1036 "man-in-the-middle attacks."); 1037 options.forward_x11 = 0; 1038 cancelled_forwarding = 1; 1039 } 1040 if (options.num_local_forwards > 0 || 1041 options.num_remote_forwards > 0) { 1042 error("Port forwarding is disabled to avoid " 1043 "man-in-the-middle attacks."); 1044 options.num_local_forwards = 1045 options.num_remote_forwards = 0; 1046 cancelled_forwarding = 1; 1047 } 1048 if (options.tun_open != SSH_TUNMODE_NO) { 1049 error("Tunnel forwarding is disabled to avoid " 1050 "man-in-the-middle attacks."); 1051 options.tun_open = SSH_TUNMODE_NO; 1052 cancelled_forwarding = 1; 1053 } 1054 if (options.exit_on_forward_failure && cancelled_forwarding) 1055 fatal("Error: forwarding disabled due to host key " 1056 "check failure"); 1057 1058 /* 1059 * XXX Should permit the user to change to use the new id. 1060 * This could be done by converting the host key to an 1061 * identifying sentence, tell that the host identifies itself 1062 * by that sentence, and ask the user if he/she wishes to 1063 * accept the authentication. 1064 */ 1065 break; 1066 case HOST_FOUND: 1067 fatal("internal error"); 1068 break; 1069 } 1070 1071 if (options.check_host_ip && host_status != HOST_CHANGED && 1072 ip_status == HOST_CHANGED) { 1073 snprintf(msg, sizeof(msg), 1074 "Warning: the %s host key for '%.200s' " 1075 "differs from the key for the IP address '%.128s'" 1076 "\nOffending key for IP in %s:%lu", 1077 type, host, ip, ip_found->file, ip_found->line); 1078 if (host_status == HOST_OK) { 1079 len = strlen(msg); 1080 snprintf(msg + len, sizeof(msg) - len, 1081 "\nMatching host key in %s:%lu", 1082 host_found->file, host_found->line); 1083 } 1084 if (options.strict_host_key_checking == 1) { 1085 logit("%s", msg); 1086 error("Exiting, you have requested strict checking."); 1087 goto fail; 1088 } else if (options.strict_host_key_checking == 2) { 1089 strlcat(msg, "\nAre you sure you want " 1090 "to continue connecting (yes/no)? ", sizeof(msg)); 1091 if (!confirm(msg)) 1092 goto fail; 1093 } else { 1094 logit("%s", msg); 1095 } 1096 } 1097 1098 xfree(ip); 1099 xfree(host); 1100 if (host_hostkeys != NULL) 1101 free_hostkeys(host_hostkeys); 1102 if (ip_hostkeys != NULL) 1103 free_hostkeys(ip_hostkeys); 1104 return 0; 1105 1106 fail: 1107 if (want_cert && host_status != HOST_REVOKED) { 1108 /* 1109 * No matching certificate. Downgrade cert to raw key and 1110 * search normally. 1111 */ 1112 debug("No matching CA found. Retry with plain key"); 1113 raw_key = key_from_private(host_key); 1114 if (key_drop_cert(raw_key) != 0) 1115 fatal("Couldn't drop certificate"); 1116 host_key = raw_key; 1117 goto retry; 1118 } 1119 if (raw_key != NULL) 1120 key_free(raw_key); 1121 xfree(ip); 1122 xfree(host); 1123 if (host_hostkeys != NULL) 1124 free_hostkeys(host_hostkeys); 1125 if (ip_hostkeys != NULL) 1126 free_hostkeys(ip_hostkeys); 1127 return -1; 1128 } 1129 1130 /* returns 0 if key verifies or -1 if key does NOT verify */ 1131 int 1132 verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 1133 { 1134 struct stat st; 1135 int flags = 0; 1136 char *fp; 1137 1138 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1139 debug("Server host key: %s %s", key_type(host_key), fp); 1140 xfree(fp); 1141 1142 /* XXX certs are not yet supported for DNS */ 1143 if (!key_is_cert(host_key) && options.verify_host_key_dns && 1144 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 1145 1146 if (flags & DNS_VERIFY_FOUND) { 1147 1148 if (options.verify_host_key_dns == 1 && 1149 flags & DNS_VERIFY_MATCH && 1150 flags & DNS_VERIFY_SECURE) 1151 return 0; 1152 1153 if (flags & DNS_VERIFY_MATCH) { 1154 matching_host_key_dns = 1; 1155 } else { 1156 warn_changed_key(host_key); 1157 error("Update the SSHFP RR in DNS with the new " 1158 "host key to get rid of this message."); 1159 } 1160 } 1161 } 1162 1163 /* return ok if the key can be found in an old keyfile */ 1164 if (stat(options.system_hostfile2, &st) == 0 || 1165 stat(options.user_hostfile2, &st) == 0) { 1166 if (check_host_key(host, hostaddr, options.port, host_key, 1167 RDONLY, options.user_hostfile2, 1168 options.system_hostfile2) == 0) 1169 return 0; 1170 } 1171 return check_host_key(host, hostaddr, options.port, host_key, 1172 RDRW, options.user_hostfile, options.system_hostfile); 1173 } 1174 1175 /* 1176 * Starts a dialog with the server, and authenticates the current user on the 1177 * server. This does not need any extra privileges. The basic connection 1178 * to the server must already have been established before this is called. 1179 * If login fails, this function prints an error and never returns. 1180 * This function does not require super-user privileges. 1181 */ 1182 void 1183 ssh_login(Sensitive *sensitive, const char *orighost, 1184 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1185 { 1186 char *host, *cp; 1187 char *server_user, *local_user; 1188 1189 local_user = xstrdup(pw->pw_name); 1190 server_user = options.user ? options.user : local_user; 1191 1192 /* Convert the user-supplied hostname into all lowercase. */ 1193 host = xstrdup(orighost); 1194 for (cp = host; *cp; cp++) 1195 if (isupper(*cp)) 1196 *cp = (char)tolower(*cp); 1197 1198 /* Exchange protocol version identification strings with the server. */ 1199 ssh_exchange_identification(timeout_ms); 1200 1201 /* Put the connection into non-blocking mode. */ 1202 packet_set_nonblocking(); 1203 1204 /* key exchange */ 1205 /* authenticate user */ 1206 if (compat20) { 1207 ssh_kex2(host, hostaddr, port); 1208 ssh_userauth2(local_user, server_user, host, sensitive); 1209 } else { 1210 ssh_kex(host, hostaddr); 1211 ssh_userauth1(local_user, server_user, host, sensitive); 1212 } 1213 xfree(local_user); 1214 } 1215 1216 void 1217 ssh_put_password(char *password) 1218 { 1219 int size; 1220 char *padded; 1221 1222 if (datafellows & SSH_BUG_PASSWORDPAD) { 1223 packet_put_cstring(password); 1224 return; 1225 } 1226 size = roundup(strlen(password) + 1, 32); 1227 padded = xcalloc(1, size); 1228 strlcpy(padded, password, size); 1229 packet_put_string(padded, size); 1230 memset(padded, 0, size); 1231 xfree(padded); 1232 } 1233 1234 /* print all known host keys for a given host, but skip keys of given type */ 1235 static int 1236 show_other_keys(struct hostkeys *hostkeys, Key *key) 1237 { 1238 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, KEY_ECDSA, -1}; 1239 int i, ret = 0; 1240 char *fp, *ra; 1241 const struct hostkey_entry *found; 1242 1243 for (i = 0; type[i] != -1; i++) { 1244 if (type[i] == key->type) 1245 continue; 1246 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1247 continue; 1248 fp = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_HEX); 1249 ra = key_fingerprint(found->key, SSH_FP_MD5, SSH_FP_RANDOMART); 1250 logit("WARNING: %s key found for host %s\n" 1251 "in %s:%lu\n" 1252 "%s key fingerprint %s.", 1253 key_type(found->key), 1254 found->host, found->file, found->line, 1255 key_type(found->key), fp); 1256 if (options.visual_host_key) 1257 logit("%s", ra); 1258 xfree(ra); 1259 xfree(fp); 1260 ret = 1; 1261 } 1262 return ret; 1263 } 1264 1265 static void 1266 warn_changed_key(Key *host_key) 1267 { 1268 char *fp; 1269 1270 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1271 1272 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1273 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1274 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1275 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1276 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1277 error("It is also possible that a host key has just been changed."); 1278 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1279 key_type(host_key), fp); 1280 error("Please contact your system administrator."); 1281 1282 xfree(fp); 1283 } 1284 1285 /* 1286 * Execute a local command 1287 */ 1288 int 1289 ssh_local_cmd(const char *args) 1290 { 1291 char *shell; 1292 pid_t pid; 1293 int status; 1294 void (*osighand)(int); 1295 1296 if (!options.permit_local_command || 1297 args == NULL || !*args) 1298 return (1); 1299 1300 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1301 shell = _PATH_BSHELL; 1302 1303 osighand = signal(SIGCHLD, SIG_DFL); 1304 pid = fork(); 1305 if (pid == 0) { 1306 signal(SIGPIPE, SIG_DFL); 1307 debug3("Executing %s -c \"%s\"", shell, args); 1308 execl(shell, shell, "-c", args, (char *)NULL); 1309 error("Couldn't execute %s -c \"%s\": %s", 1310 shell, args, strerror(errno)); 1311 _exit(1); 1312 } else if (pid == -1) 1313 fatal("fork failed: %.100s", strerror(errno)); 1314 while (waitpid(pid, &status, 0) == -1) 1315 if (errno != EINTR) 1316 fatal("Couldn't wait for child: %s", strerror(errno)); 1317 signal(SIGCHLD, osighand); 1318 1319 if (!WIFEXITED(status)) 1320 return (1); 1321 1322 return (WEXITSTATUS(status)); 1323 } 1324