sshconnect.c revision 181111
1/* $OpenBSD: sshconnect.c,v 1.211 2008/07/01 07:24:22 dtucker Exp $ */ 2/* $FreeBSD: head/crypto/openssh/sshconnect.c 181111 2008-08-01 02:48:36Z des $ */ 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 <netdb.h> 33#ifdef HAVE_PATHS_H 34#include <paths.h> 35#endif 36#include <pwd.h> 37#include <stdarg.h> 38#include <stdio.h> 39#include <stdlib.h> 40#include <string.h> 41#include <unistd.h> 42 43#include "xmalloc.h" 44#include "key.h" 45#include "hostfile.h" 46#include "ssh.h" 47#include "rsa.h" 48#include "buffer.h" 49#include "packet.h" 50#include "uidswap.h" 51#include "compat.h" 52#include "key.h" 53#include "sshconnect.h" 54#include "hostfile.h" 55#include "log.h" 56#include "readconf.h" 57#include "atomicio.h" 58#include "misc.h" 59#include "dns.h" 60#include "version.h" 61 62char *client_version_string = NULL; 63char *server_version_string = NULL; 64 65static int matching_host_key_dns = 0; 66 67/* import */ 68extern Options options; 69extern char *__progname; 70extern uid_t original_real_uid; 71extern uid_t original_effective_uid; 72extern pid_t proxy_command_pid; 73 74#ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ 75#define INET6_ADDRSTRLEN 46 76#endif 77 78static int show_other_keys(const char *, Key *); 79static void warn_changed_key(Key *); 80 81/* 82 * Connect to the given ssh server using a proxy command. 83 */ 84static int 85ssh_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) 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, 107 "p", strport, (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 execv(argv[0], argv); 147 perror(argv[0]); 148 exit(1); 149 } 150 /* Parent. */ 151 if (pid < 0) 152 fatal("fork failed: %.100s", strerror(errno)); 153 else 154 proxy_command_pid = pid; /* save pid to clean up later */ 155 156 /* Close child side of the descriptors. */ 157 close(pin[0]); 158 close(pout[1]); 159 160 /* Free the command name. */ 161 xfree(command_string); 162 163 /* Set the connection file descriptors. */ 164 packet_set_connection(pout[0], pin[1]); 165 packet_set_timeout(options.server_alive_interval, 166 options.server_alive_count_max); 167 168 /* Indicate OK return */ 169 return 0; 170} 171 172/* 173 * Creates a (possibly privileged) socket for use as the ssh connection. 174 */ 175static int 176ssh_create_socket(int privileged, struct addrinfo *ai) 177{ 178 int sock, gaierr; 179 struct addrinfo hints, *res; 180 181 /* 182 * If we are running as root and want to connect to a privileged 183 * port, bind our own socket to a privileged port. 184 */ 185 if (privileged) { 186 int p = IPPORT_RESERVED - 1; 187 PRIV_START; 188 sock = rresvport_af(&p, ai->ai_family); 189 PRIV_END; 190 if (sock < 0) 191 error("rresvport: af=%d %.100s", ai->ai_family, 192 strerror(errno)); 193 else 194 debug("Allocated local port %d.", p); 195 return sock; 196 } 197 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 198 if (sock < 0) 199 error("socket: %.100s", strerror(errno)); 200 201 /* Bind the socket to an alternative local IP address */ 202 if (options.bind_address == NULL) 203 return sock; 204 205 memset(&hints, 0, sizeof(hints)); 206 hints.ai_family = ai->ai_family; 207 hints.ai_socktype = ai->ai_socktype; 208 hints.ai_protocol = ai->ai_protocol; 209 hints.ai_flags = AI_PASSIVE; 210 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 211 if (gaierr) { 212 error("getaddrinfo: %s: %s", options.bind_address, 213 ssh_gai_strerror(gaierr)); 214 close(sock); 215 return -1; 216 } 217 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 218 error("bind: %s: %s", options.bind_address, strerror(errno)); 219 close(sock); 220 freeaddrinfo(res); 221 return -1; 222 } 223 freeaddrinfo(res); 224 return sock; 225} 226 227static int 228timeout_connect(int sockfd, const struct sockaddr *serv_addr, 229 socklen_t addrlen, int *timeoutp) 230{ 231 fd_set *fdset; 232 struct timeval tv, t_start; 233 socklen_t optlen; 234 int optval, rc, result = -1; 235 236 gettimeofday(&t_start, NULL); 237 238 if (*timeoutp <= 0) { 239 result = connect(sockfd, serv_addr, addrlen); 240 goto done; 241 } 242 243 set_nonblock(sockfd); 244 rc = connect(sockfd, serv_addr, addrlen); 245 if (rc == 0) { 246 unset_nonblock(sockfd); 247 result = 0; 248 goto done; 249 } 250 if (errno != EINPROGRESS) { 251 result = -1; 252 goto done; 253 } 254 255 fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), 256 sizeof(fd_mask)); 257 FD_SET(sockfd, fdset); 258 ms_to_timeval(&tv, *timeoutp); 259 260 for (;;) { 261 rc = select(sockfd + 1, NULL, fdset, NULL, &tv); 262 if (rc != -1 || errno != EINTR) 263 break; 264 } 265 266 switch (rc) { 267 case 0: 268 /* Timed out */ 269 errno = ETIMEDOUT; 270 break; 271 case -1: 272 /* Select error */ 273 debug("select: %s", strerror(errno)); 274 break; 275 case 1: 276 /* Completed or failed */ 277 optval = 0; 278 optlen = sizeof(optval); 279 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, 280 &optlen) == -1) { 281 debug("getsockopt: %s", strerror(errno)); 282 break; 283 } 284 if (optval != 0) { 285 errno = optval; 286 break; 287 } 288 result = 0; 289 unset_nonblock(sockfd); 290 break; 291 default: 292 /* Should not occur */ 293 fatal("Bogus return (%d) from select()", rc); 294 } 295 296 xfree(fdset); 297 298 done: 299 if (result == 0 && *timeoutp > 0) { 300 ms_subtract_diff(&t_start, timeoutp); 301 if (*timeoutp <= 0) { 302 errno = ETIMEDOUT; 303 result = -1; 304 } 305 } 306 307 return (result); 308} 309 310/* 311 * Opens a TCP/IP connection to the remote server on the given host. 312 * The address of the remote host will be returned in hostaddr. 313 * If port is 0, the default port will be used. If needpriv is true, 314 * a privileged port will be allocated to make the connection. 315 * This requires super-user privileges if needpriv is true. 316 * Connection_attempts specifies the maximum number of tries (one per 317 * second). If proxy_command is non-NULL, it specifies the command (with %h 318 * and %p substituted for host and port, respectively) to use to contact 319 * the daemon. 320 */ 321int 322ssh_connect(const char *host, struct sockaddr_storage * hostaddr, 323 u_short port, int family, int connection_attempts, int *timeout_ms, 324 int want_keepalive, int needpriv, const char *proxy_command) 325{ 326 int gaierr; 327 int on = 1; 328 int sock = -1, attempt; 329 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 330 struct addrinfo hints, *ai, *aitop; 331 332 debug2("ssh_connect: needpriv %d", needpriv); 333 334 /* If a proxy command is given, connect using it. */ 335 if (proxy_command != NULL) 336 return ssh_proxy_connect(host, port, proxy_command); 337 338 /* No proxy command. */ 339 340 memset(&hints, 0, sizeof(hints)); 341 hints.ai_family = family; 342 hints.ai_socktype = SOCK_STREAM; 343 snprintf(strport, sizeof strport, "%u", port); 344 if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) 345 fatal("%s: Could not resolve hostname %.100s: %s", __progname, 346 host, ssh_gai_strerror(gaierr)); 347 348 for (attempt = 0; attempt < connection_attempts; attempt++) { 349 if (attempt > 0) { 350 /* Sleep a moment before retrying. */ 351 sleep(1); 352 debug("Trying again..."); 353 } 354 /* 355 * Loop through addresses for this host, and try each one in 356 * sequence until the connection succeeds. 357 */ 358 for (ai = aitop; ai; ai = ai->ai_next) { 359 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 360 continue; 361 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 362 ntop, sizeof(ntop), strport, sizeof(strport), 363 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 364 error("ssh_connect: getnameinfo failed"); 365 continue; 366 } 367 debug("Connecting to %.200s [%.100s] port %s.", 368 host, ntop, strport); 369 370 /* Create a socket for connecting. */ 371 sock = ssh_create_socket(needpriv, ai); 372 if (sock < 0) 373 /* Any error is already output */ 374 continue; 375 376 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 377 timeout_ms) >= 0) { 378 /* Successful connection. */ 379 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 380 break; 381 } else { 382 debug("connect to address %s port %s: %s", 383 ntop, strport, strerror(errno)); 384 close(sock); 385 sock = -1; 386 } 387 } 388 if (sock != -1) 389 break; /* Successful connection. */ 390 } 391 392 freeaddrinfo(aitop); 393 394 /* Return failure if we didn't get a successful connection. */ 395 if (sock == -1) { 396 error("ssh: connect to host %s port %s: %s", 397 host, strport, strerror(errno)); 398 return (-1); 399 } 400 401 debug("Connection established."); 402 403 /* Set SO_KEEPALIVE if requested. */ 404 if (want_keepalive && 405 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 406 sizeof(on)) < 0) 407 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 408 409 /* Set the connection. */ 410 packet_set_connection(sock, sock); 411 packet_set_timeout(options.server_alive_interval, 412 options.server_alive_count_max); 413 414 return 0; 415} 416 417/* 418 * Waits for the server identification string, and sends our own 419 * identification string. 420 */ 421static void 422ssh_exchange_identification(int timeout_ms) 423{ 424 char buf[256], remote_version[256]; /* must be same size! */ 425 int remote_major, remote_minor, mismatch; 426 int connection_in = packet_get_connection_in(); 427 int connection_out = packet_get_connection_out(); 428 int minor1 = PROTOCOL_MINOR_1; 429 u_int i, n; 430 size_t len; 431 int fdsetsz, remaining, rc; 432 struct timeval t_start, t_remaining; 433 fd_set *fdset; 434 435 fdsetsz = howmany(connection_in + 1, NFDBITS) * sizeof(fd_mask); 436 fdset = xcalloc(1, fdsetsz); 437 438 /* Read other side's version identification. */ 439 remaining = timeout_ms; 440 for (n = 0;;) { 441 for (i = 0; i < sizeof(buf) - 1; i++) { 442 if (timeout_ms > 0) { 443 gettimeofday(&t_start, NULL); 444 ms_to_timeval(&t_remaining, remaining); 445 FD_SET(connection_in, fdset); 446 rc = select(connection_in + 1, fdset, NULL, 447 fdset, &t_remaining); 448 ms_subtract_diff(&t_start, &remaining); 449 if (rc == 0 || remaining <= 0) 450 fatal("Connection timed out during " 451 "banner exchange"); 452 if (rc == -1) { 453 if (errno == EINTR) 454 continue; 455 fatal("ssh_exchange_identification: " 456 "select: %s", strerror(errno)); 457 } 458 } 459 460 len = atomicio(read, connection_in, &buf[i], 1); 461 462 if (len != 1 && errno == EPIPE) 463 fatal("ssh_exchange_identification: " 464 "Connection closed by remote host"); 465 else if (len != 1) 466 fatal("ssh_exchange_identification: " 467 "read: %.100s", strerror(errno)); 468 if (buf[i] == '\r') { 469 buf[i] = '\n'; 470 buf[i + 1] = 0; 471 continue; /**XXX wait for \n */ 472 } 473 if (buf[i] == '\n') { 474 buf[i + 1] = 0; 475 break; 476 } 477 if (++n > 65536) 478 fatal("ssh_exchange_identification: " 479 "No banner received"); 480 } 481 buf[sizeof(buf) - 1] = 0; 482 if (strncmp(buf, "SSH-", 4) == 0) 483 break; 484 debug("ssh_exchange_identification: %s", buf); 485 } 486 server_version_string = xstrdup(buf); 487 xfree(fdset); 488 489 /* 490 * Check that the versions match. In future this might accept 491 * several versions and set appropriate flags to handle them. 492 */ 493 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 494 &remote_major, &remote_minor, remote_version) != 3) 495 fatal("Bad remote protocol version identification: '%.100s'", buf); 496 debug("Remote protocol version %d.%d, remote software version %.100s", 497 remote_major, remote_minor, remote_version); 498 499 compat_datafellows(remote_version); 500 mismatch = 0; 501 502 switch (remote_major) { 503 case 1: 504 if (remote_minor == 99 && 505 (options.protocol & SSH_PROTO_2) && 506 !(options.protocol & SSH_PROTO_1_PREFERRED)) { 507 enable_compat20(); 508 break; 509 } 510 if (!(options.protocol & SSH_PROTO_1)) { 511 mismatch = 1; 512 break; 513 } 514 if (remote_minor < 3) { 515 fatal("Remote machine has too old SSH software version."); 516 } else if (remote_minor == 3 || remote_minor == 4) { 517 /* We speak 1.3, too. */ 518 enable_compat13(); 519 minor1 = 3; 520 if (options.forward_agent) { 521 logit("Agent forwarding disabled for protocol 1.3"); 522 options.forward_agent = 0; 523 } 524 } 525 break; 526 case 2: 527 if (options.protocol & SSH_PROTO_2) { 528 enable_compat20(); 529 break; 530 } 531 /* FALLTHROUGH */ 532 default: 533 mismatch = 1; 534 break; 535 } 536 if (mismatch) 537 fatal("Protocol major versions differ: %d vs. %d", 538 (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 539 remote_major); 540 /* Send our own protocol version identification. */ 541 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", 542 compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, 543 compat20 ? PROTOCOL_MINOR_2 : minor1, 544 SSH_VERSION, compat20 ? "\r\n" : "\n"); 545 if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) 546 fatal("write: %.100s", strerror(errno)); 547 client_version_string = xstrdup(buf); 548 chop(client_version_string); 549 chop(server_version_string); 550 debug("Local version string %.100s", client_version_string); 551} 552 553/* defaults to 'no' */ 554static int 555confirm(const char *prompt) 556{ 557 const char *msg, *again = "Please type 'yes' or 'no': "; 558 char *p; 559 int ret = -1; 560 561 if (options.batch_mode) 562 return 0; 563 for (msg = prompt;;msg = again) { 564 p = read_passphrase(msg, RP_ECHO); 565 if (p == NULL || 566 (p[0] == '\0') || (p[0] == '\n') || 567 strncasecmp(p, "no", 2) == 0) 568 ret = 0; 569 if (p && strncasecmp(p, "yes", 3) == 0) 570 ret = 1; 571 if (p) 572 xfree(p); 573 if (ret != -1) 574 return ret; 575 } 576} 577 578/* 579 * check whether the supplied host key is valid, return -1 if the key 580 * is not valid. the user_hostfile will not be updated if 'readonly' is true. 581 */ 582#define RDRW 0 583#define RDONLY 1 584#define ROQUIET 2 585static int 586check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 587 Key *host_key, int readonly, const char *user_hostfile, 588 const char *system_hostfile) 589{ 590 Key *file_key; 591 const char *type = key_type(host_key); 592 char *ip = NULL, *host = NULL; 593 char hostline[1000], *hostp, *fp, *ra; 594 HostStatus host_status; 595 HostStatus ip_status; 596 int r, local = 0, host_ip_differ = 0; 597 int salen; 598 char ntop[NI_MAXHOST]; 599 char msg[1024]; 600 int len, host_line, ip_line, cancelled_forwarding = 0; 601 const char *host_file = NULL, *ip_file = NULL; 602 603 /* 604 * Force accepting of the host key for loopback/localhost. The 605 * problem is that if the home directory is NFS-mounted to multiple 606 * machines, localhost will refer to a different machine in each of 607 * them, and the user will get bogus HOST_CHANGED warnings. This 608 * essentially disables host authentication for localhost; however, 609 * this is probably not a real problem. 610 */ 611 /** hostaddr == 0! */ 612 switch (hostaddr->sa_family) { 613 case AF_INET: 614 local = (ntohl(((struct sockaddr_in *)hostaddr)-> 615 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 616 salen = sizeof(struct sockaddr_in); 617 break; 618 case AF_INET6: 619 local = IN6_IS_ADDR_LOOPBACK( 620 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 621 salen = sizeof(struct sockaddr_in6); 622 break; 623 default: 624 local = 0; 625 salen = sizeof(struct sockaddr_storage); 626 break; 627 } 628 if (options.no_host_authentication_for_localhost == 1 && local && 629 options.host_key_alias == NULL) { 630 debug("Forcing accepting of host key for " 631 "loopback/localhost."); 632 return 0; 633 } 634 635 /* 636 * We don't have the remote ip-address for connections 637 * using a proxy command 638 */ 639 if (options.proxy_command == NULL) { 640 if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), 641 NULL, 0, NI_NUMERICHOST) != 0) 642 fatal("check_host_key: getnameinfo failed"); 643 ip = put_host_port(ntop, port); 644 } else { 645 ip = xstrdup("<no hostip for proxy command>"); 646 } 647 648 /* 649 * Turn off check_host_ip if the connection is to localhost, via proxy 650 * command or if we don't have a hostname to compare with 651 */ 652 if (options.check_host_ip && (local || 653 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 654 options.check_host_ip = 0; 655 656 /* 657 * Allow the user to record the key under a different name or 658 * differentiate a non-standard port. This is useful for ssh 659 * tunneling over forwarded connections or if you run multiple 660 * sshd's on different ports on the same machine. 661 */ 662 if (options.host_key_alias != NULL) { 663 host = xstrdup(options.host_key_alias); 664 debug("using hostkeyalias: %s", host); 665 } else { 666 host = put_host_port(hostname, port); 667 } 668 669 /* 670 * Store the host key from the known host file in here so that we can 671 * compare it with the key for the IP address. 672 */ 673 file_key = key_new(host_key->type); 674 675 /* 676 * Check if the host key is present in the user's list of known 677 * hosts or in the systemwide list. 678 */ 679 host_file = user_hostfile; 680 host_status = check_host_in_hostfile(host_file, host, host_key, 681 file_key, &host_line); 682 if (host_status == HOST_NEW) { 683 host_file = system_hostfile; 684 host_status = check_host_in_hostfile(host_file, host, host_key, 685 file_key, &host_line); 686 } 687 /* 688 * Also perform check for the ip address, skip the check if we are 689 * localhost or the hostname was an ip address to begin with 690 */ 691 if (options.check_host_ip) { 692 Key *ip_key = key_new(host_key->type); 693 694 ip_file = user_hostfile; 695 ip_status = check_host_in_hostfile(ip_file, ip, host_key, 696 ip_key, &ip_line); 697 if (ip_status == HOST_NEW) { 698 ip_file = system_hostfile; 699 ip_status = check_host_in_hostfile(ip_file, ip, 700 host_key, ip_key, &ip_line); 701 } 702 if (host_status == HOST_CHANGED && 703 (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) 704 host_ip_differ = 1; 705 706 key_free(ip_key); 707 } else 708 ip_status = host_status; 709 710 key_free(file_key); 711 712 switch (host_status) { 713 case HOST_OK: 714 /* The host is known and the key matches. */ 715 debug("Host '%.200s' is known and matches the %s host key.", 716 host, type); 717 debug("Found key in %s:%d", host_file, host_line); 718 if (options.check_host_ip && ip_status == HOST_NEW) { 719 if (readonly) 720 logit("%s host key for IP address " 721 "'%.128s' not in list of known hosts.", 722 type, ip); 723 else if (!add_host_to_hostfile(user_hostfile, ip, 724 host_key, options.hash_known_hosts)) 725 logit("Failed to add the %s host key for IP " 726 "address '%.128s' to the list of known " 727 "hosts (%.30s).", type, ip, user_hostfile); 728 else 729 logit("Warning: Permanently added the %s host " 730 "key for IP address '%.128s' to the list " 731 "of known hosts.", type, ip); 732 } else if (options.visual_host_key) { 733 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 734 ra = key_fingerprint(host_key, SSH_FP_MD5, 735 SSH_FP_RANDOMART); 736 logit("Host key fingerprint is %s\n%s\n", fp, ra); 737 xfree(ra); 738 xfree(fp); 739 } 740 break; 741 case HOST_NEW: 742 if (options.host_key_alias == NULL && port != 0 && 743 port != SSH_DEFAULT_PORT) { 744 debug("checking without port identifier"); 745 if (check_host_key(hostname, hostaddr, 0, host_key, 2, 746 user_hostfile, system_hostfile) == 0) { 747 debug("found matching key w/out port"); 748 break; 749 } 750 } 751 if (readonly) 752 goto fail; 753 /* The host is new. */ 754 if (options.strict_host_key_checking == 1) { 755 /* 756 * User has requested strict host key checking. We 757 * will not add the host key automatically. The only 758 * alternative left is to abort. 759 */ 760 error("No %s host key is known for %.200s and you " 761 "have requested strict checking.", type, host); 762 goto fail; 763 } else if (options.strict_host_key_checking == 2) { 764 char msg1[1024], msg2[1024]; 765 766 if (show_other_keys(host, host_key)) 767 snprintf(msg1, sizeof(msg1), 768 "\nbut keys of different type are already" 769 " known for this host."); 770 else 771 snprintf(msg1, sizeof(msg1), "."); 772 /* The default */ 773 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 774 ra = key_fingerprint(host_key, SSH_FP_MD5, 775 SSH_FP_RANDOMART); 776 msg2[0] = '\0'; 777 if (options.verify_host_key_dns) { 778 if (matching_host_key_dns) 779 snprintf(msg2, sizeof(msg2), 780 "Matching host key fingerprint" 781 " found in DNS.\n"); 782 else 783 snprintf(msg2, sizeof(msg2), 784 "No matching host key fingerprint" 785 " found in DNS.\n"); 786 } 787 snprintf(msg, sizeof(msg), 788 "The authenticity of host '%.200s (%s)' can't be " 789 "established%s\n" 790 "%s key fingerprint is %s.%s%s\n%s" 791 "Are you sure you want to continue connecting " 792 "(yes/no)? ", 793 host, ip, msg1, type, fp, 794 options.visual_host_key ? "\n" : "", 795 options.visual_host_key ? ra : "", 796 msg2); 797 xfree(ra); 798 xfree(fp); 799 if (!confirm(msg)) 800 goto fail; 801 } 802 /* 803 * If not in strict mode, add the key automatically to the 804 * local known_hosts file. 805 */ 806 if (options.check_host_ip && ip_status == HOST_NEW) { 807 snprintf(hostline, sizeof(hostline), "%s,%s", 808 host, ip); 809 hostp = hostline; 810 if (options.hash_known_hosts) { 811 /* Add hash of host and IP separately */ 812 r = add_host_to_hostfile(user_hostfile, host, 813 host_key, options.hash_known_hosts) && 814 add_host_to_hostfile(user_hostfile, ip, 815 host_key, options.hash_known_hosts); 816 } else { 817 /* Add unhashed "host,ip" */ 818 r = add_host_to_hostfile(user_hostfile, 819 hostline, host_key, 820 options.hash_known_hosts); 821 } 822 } else { 823 r = add_host_to_hostfile(user_hostfile, host, host_key, 824 options.hash_known_hosts); 825 hostp = host; 826 } 827 828 if (!r) 829 logit("Failed to add the host to the list of known " 830 "hosts (%.500s).", user_hostfile); 831 else 832 logit("Warning: Permanently added '%.200s' (%s) to the " 833 "list of known hosts.", hostp, type); 834 break; 835 case HOST_CHANGED: 836 if (readonly == ROQUIET) 837 goto fail; 838 if (options.check_host_ip && host_ip_differ) { 839 char *key_msg; 840 if (ip_status == HOST_NEW) 841 key_msg = "is unknown"; 842 else if (ip_status == HOST_OK) 843 key_msg = "is unchanged"; 844 else 845 key_msg = "has a different value"; 846 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 847 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 848 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 849 error("The %s host key for %s has changed,", type, host); 850 error("and the key for the corresponding IP address %s", ip); 851 error("%s. This could either mean that", key_msg); 852 error("DNS SPOOFING is happening or the IP address for the host"); 853 error("and its host key have changed at the same time."); 854 if (ip_status != HOST_NEW) 855 error("Offending key for IP in %s:%d", ip_file, ip_line); 856 } 857 /* The host key has changed. */ 858 warn_changed_key(host_key); 859 error("Add correct host key in %.100s to get rid of this message.", 860 user_hostfile); 861 error("Offending key in %s:%d", host_file, host_line); 862 863 /* 864 * If strict host key checking is in use, the user will have 865 * to edit the key manually and we can only abort. 866 */ 867 if (options.strict_host_key_checking) { 868 error("%s host key for %.200s has changed and you have " 869 "requested strict checking.", type, host); 870 goto fail; 871 } 872 873 /* 874 * If strict host key checking has not been requested, allow 875 * the connection but without MITM-able authentication or 876 * forwarding. 877 */ 878 if (options.password_authentication) { 879 error("Password authentication is disabled to avoid " 880 "man-in-the-middle attacks."); 881 options.password_authentication = 0; 882 cancelled_forwarding = 1; 883 } 884 if (options.kbd_interactive_authentication) { 885 error("Keyboard-interactive authentication is disabled" 886 " to avoid man-in-the-middle attacks."); 887 options.kbd_interactive_authentication = 0; 888 options.challenge_response_authentication = 0; 889 cancelled_forwarding = 1; 890 } 891 if (options.challenge_response_authentication) { 892 error("Challenge/response authentication is disabled" 893 " to avoid man-in-the-middle attacks."); 894 options.challenge_response_authentication = 0; 895 cancelled_forwarding = 1; 896 } 897 if (options.forward_agent) { 898 error("Agent forwarding is disabled to avoid " 899 "man-in-the-middle attacks."); 900 options.forward_agent = 0; 901 cancelled_forwarding = 1; 902 } 903 if (options.forward_x11) { 904 error("X11 forwarding is disabled to avoid " 905 "man-in-the-middle attacks."); 906 options.forward_x11 = 0; 907 cancelled_forwarding = 1; 908 } 909 if (options.num_local_forwards > 0 || 910 options.num_remote_forwards > 0) { 911 error("Port forwarding is disabled to avoid " 912 "man-in-the-middle attacks."); 913 options.num_local_forwards = 914 options.num_remote_forwards = 0; 915 cancelled_forwarding = 1; 916 } 917 if (options.tun_open != SSH_TUNMODE_NO) { 918 error("Tunnel forwarding is disabled to avoid " 919 "man-in-the-middle attacks."); 920 options.tun_open = SSH_TUNMODE_NO; 921 cancelled_forwarding = 1; 922 } 923 if (options.exit_on_forward_failure && cancelled_forwarding) 924 fatal("Error: forwarding disabled due to host key " 925 "check failure"); 926 927 /* 928 * XXX Should permit the user to change to use the new id. 929 * This could be done by converting the host key to an 930 * identifying sentence, tell that the host identifies itself 931 * by that sentence, and ask the user if he/she whishes to 932 * accept the authentication. 933 */ 934 break; 935 case HOST_FOUND: 936 fatal("internal error"); 937 break; 938 } 939 940 if (options.check_host_ip && host_status != HOST_CHANGED && 941 ip_status == HOST_CHANGED) { 942 snprintf(msg, sizeof(msg), 943 "Warning: the %s host key for '%.200s' " 944 "differs from the key for the IP address '%.128s'" 945 "\nOffending key for IP in %s:%d", 946 type, host, ip, ip_file, ip_line); 947 if (host_status == HOST_OK) { 948 len = strlen(msg); 949 snprintf(msg + len, sizeof(msg) - len, 950 "\nMatching host key in %s:%d", 951 host_file, host_line); 952 } 953 if (options.strict_host_key_checking == 1) { 954 logit("%s", msg); 955 error("Exiting, you have requested strict checking."); 956 goto fail; 957 } else if (options.strict_host_key_checking == 2) { 958 strlcat(msg, "\nAre you sure you want " 959 "to continue connecting (yes/no)? ", sizeof(msg)); 960 if (!confirm(msg)) 961 goto fail; 962 } else { 963 logit("%s", msg); 964 } 965 } 966 967 xfree(ip); 968 xfree(host); 969 return 0; 970 971fail: 972 xfree(ip); 973 xfree(host); 974 return -1; 975} 976 977/* returns 0 if key verifies or -1 if key does NOT verify */ 978int 979verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) 980{ 981 struct stat st; 982 int flags = 0; 983 984 if (options.verify_host_key_dns && 985 verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { 986 987 if (flags & DNS_VERIFY_FOUND) { 988 989 if (options.verify_host_key_dns == 1 && 990 flags & DNS_VERIFY_MATCH && 991 flags & DNS_VERIFY_SECURE) 992 return 0; 993 994 if (flags & DNS_VERIFY_MATCH) { 995 matching_host_key_dns = 1; 996 } else { 997 warn_changed_key(host_key); 998 error("Update the SSHFP RR in DNS with the new " 999 "host key to get rid of this message."); 1000 } 1001 } 1002 } 1003 1004 /* return ok if the key can be found in an old keyfile */ 1005 if (stat(options.system_hostfile2, &st) == 0 || 1006 stat(options.user_hostfile2, &st) == 0) { 1007 if (check_host_key(host, hostaddr, options.port, host_key, 1008 RDONLY, options.user_hostfile2, 1009 options.system_hostfile2) == 0) 1010 return 0; 1011 } 1012 return check_host_key(host, hostaddr, options.port, host_key, 1013 RDRW, options.user_hostfile, options.system_hostfile); 1014} 1015 1016/* 1017 * Starts a dialog with the server, and authenticates the current user on the 1018 * server. This does not need any extra privileges. The basic connection 1019 * to the server must already have been established before this is called. 1020 * If login fails, this function prints an error and never returns. 1021 * This function does not require super-user privileges. 1022 */ 1023void 1024ssh_login(Sensitive *sensitive, const char *orighost, 1025 struct sockaddr *hostaddr, struct passwd *pw, int timeout_ms) 1026{ 1027 char *host, *cp; 1028 char *server_user, *local_user; 1029 1030 local_user = xstrdup(pw->pw_name); 1031 server_user = options.user ? options.user : local_user; 1032 1033 /* Convert the user-supplied hostname into all lowercase. */ 1034 host = xstrdup(orighost); 1035 for (cp = host; *cp; cp++) 1036 if (isupper(*cp)) 1037 *cp = (char)tolower(*cp); 1038 1039 /* Exchange protocol version identification strings with the server. */ 1040 ssh_exchange_identification(timeout_ms); 1041 1042 /* Put the connection into non-blocking mode. */ 1043 packet_set_nonblocking(); 1044 1045 /* key exchange */ 1046 /* authenticate user */ 1047 if (compat20) { 1048 ssh_kex2(host, hostaddr); 1049 ssh_userauth2(local_user, server_user, host, sensitive); 1050 } else { 1051 ssh_kex(host, hostaddr); 1052 ssh_userauth1(local_user, server_user, host, sensitive); 1053 } 1054 xfree(local_user); 1055} 1056 1057void 1058ssh_put_password(char *password) 1059{ 1060 int size; 1061 char *padded; 1062 1063 if (datafellows & SSH_BUG_PASSWORDPAD) { 1064 packet_put_cstring(password); 1065 return; 1066 } 1067 size = roundup(strlen(password) + 1, 32); 1068 padded = xcalloc(1, size); 1069 strlcpy(padded, password, size); 1070 packet_put_string(padded, size); 1071 memset(padded, 0, size); 1072 xfree(padded); 1073} 1074 1075static int 1076show_key_from_file(const char *file, const char *host, int keytype) 1077{ 1078 Key *found; 1079 char *fp, *ra; 1080 int line, ret; 1081 1082 found = key_new(keytype); 1083 if ((ret = lookup_key_in_hostfile_by_type(file, host, 1084 keytype, found, &line))) { 1085 fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); 1086 if (options.visual_host_key) 1087 ra = key_fingerprint(found, SSH_FP_MD5, SSH_FP_RANDOMART); 1088 logit("WARNING: %s key found for host %s\n" 1089 "in %s:%d\n" 1090 "%s key fingerprint %s.%s%s\n", 1091 key_type(found), host, file, line, 1092 key_type(found), fp, 1093 options.visual_host_key ? "\n" : "", 1094 options.visual_host_key ? ra : ""); 1095 if (options.visual_host_key) 1096 xfree(ra); 1097 xfree(fp); 1098 } 1099 key_free(found); 1100 return (ret); 1101} 1102 1103/* print all known host keys for a given host, but skip keys of given type */ 1104static int 1105show_other_keys(const char *host, Key *key) 1106{ 1107 int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; 1108 int i, found = 0; 1109 1110 for (i = 0; type[i] != -1; i++) { 1111 if (type[i] == key->type) 1112 continue; 1113 if (type[i] != KEY_RSA1 && 1114 show_key_from_file(options.user_hostfile2, host, type[i])) { 1115 found = 1; 1116 continue; 1117 } 1118 if (type[i] != KEY_RSA1 && 1119 show_key_from_file(options.system_hostfile2, host, type[i])) { 1120 found = 1; 1121 continue; 1122 } 1123 if (show_key_from_file(options.user_hostfile, host, type[i])) { 1124 found = 1; 1125 continue; 1126 } 1127 if (show_key_from_file(options.system_hostfile, host, type[i])) { 1128 found = 1; 1129 continue; 1130 } 1131 debug2("no key of type %d for host %s", type[i], host); 1132 } 1133 return (found); 1134} 1135 1136static void 1137warn_changed_key(Key *host_key) 1138{ 1139 char *fp; 1140 const char *type = key_type(host_key); 1141 1142 fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); 1143 1144 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1145 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1146 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1147 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1148 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1149 error("It is also possible that the %s host key has just been changed.", type); 1150 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1151 type, fp); 1152 error("Please contact your system administrator."); 1153 1154 xfree(fp); 1155} 1156 1157/* 1158 * Execute a local command 1159 */ 1160int 1161ssh_local_cmd(const char *args) 1162{ 1163 char *shell; 1164 pid_t pid; 1165 int status; 1166 1167 if (!options.permit_local_command || 1168 args == NULL || !*args) 1169 return (1); 1170 1171 if ((shell = getenv("SHELL")) == NULL) 1172 shell = _PATH_BSHELL; 1173 1174 pid = fork(); 1175 if (pid == 0) { 1176 debug3("Executing %s -c \"%s\"", shell, args); 1177 execl(shell, shell, "-c", args, (char *)NULL); 1178 error("Couldn't execute %s -c \"%s\": %s", 1179 shell, args, strerror(errno)); 1180 _exit(1); 1181 } else if (pid == -1) 1182 fatal("fork failed: %.100s", strerror(errno)); 1183 while (waitpid(pid, &status, 0) == -1) 1184 if (errno != EINTR) 1185 fatal("Couldn't wait for child: %s", strerror(errno)); 1186 1187 if (!WIFEXITED(status)) 1188 return (1); 1189 1190 return (WEXITSTATUS(status)); 1191} 1192