1/* $OpenBSD: sshconnect.c,v 1.305 2018/09/20 03:30:44 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__RCSID("$FreeBSD$"); 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 <net/if.h> 28#include <netinet/in.h> 29#include <arpa/inet.h> 30 31#include <ctype.h> 32#include <errno.h> 33#include <fcntl.h> 34#include <netdb.h> 35#ifdef HAVE_PATHS_H 36#include <paths.h> 37#endif 38#include <pwd.h> 39#ifdef HAVE_POLL_H 40#include <poll.h> 41#endif 42#include <signal.h> 43#include <stdarg.h> 44#include <stdio.h> 45#include <stdlib.h> 46#include <string.h> 47#include <unistd.h> 48#ifdef HAVE_IFADDRS_H 49# include <ifaddrs.h> 50#endif 51 52#include "xmalloc.h" 53#include "hostfile.h" 54#include "ssh.h" 55#include "sshbuf.h" 56#include "packet.h" 57#include "compat.h" 58#include "sshkey.h" 59#include "sshconnect.h" 60#include "hostfile.h" 61#include "log.h" 62#include "misc.h" 63#include "readconf.h" 64#include "atomicio.h" 65#include "dns.h" 66#include "monitor_fdpass.h" 67#include "ssh2.h" 68#include "version.h" 69#include "authfile.h" 70#include "ssherr.h" 71#include "authfd.h" 72 73char *client_version_string = NULL; 74char *server_version_string = NULL; 75struct sshkey *previous_host_key = NULL; 76 77static int matching_host_key_dns = 0; 78 79static pid_t proxy_command_pid = 0; 80 81/* import */ 82extern Options options; 83extern char *__progname; 84 85static int show_other_keys(struct hostkeys *, struct sshkey *); 86static void warn_changed_key(struct sshkey *); 87 88/* Expand a proxy command */ 89static char * 90expand_proxy_command(const char *proxy_command, const char *user, 91 const char *host, int port) 92{ 93 char *tmp, *ret, strport[NI_MAXSERV]; 94 95 snprintf(strport, sizeof strport, "%d", port); 96 xasprintf(&tmp, "exec %s", proxy_command); 97 ret = percent_expand(tmp, "h", host, "p", strport, 98 "r", options.user, (char *)NULL); 99 free(tmp); 100 return ret; 101} 102 103/* 104 * Connect to the given ssh server using a proxy command that passes a 105 * a connected fd back to us. 106 */ 107static int 108ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port, 109 const char *proxy_command) 110{ 111 char *command_string; 112 int sp[2], sock; 113 pid_t pid; 114 char *shell; 115 116 if ((shell = getenv("SHELL")) == NULL) 117 shell = _PATH_BSHELL; 118 119 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) 120 fatal("Could not create socketpair to communicate with " 121 "proxy dialer: %.100s", strerror(errno)); 122 123 command_string = expand_proxy_command(proxy_command, options.user, 124 host, port); 125 debug("Executing proxy dialer command: %.500s", command_string); 126 127 /* Fork and execute the proxy command. */ 128 if ((pid = fork()) == 0) { 129 char *argv[10]; 130 131 close(sp[1]); 132 /* Redirect stdin and stdout. */ 133 if (sp[0] != 0) { 134 if (dup2(sp[0], 0) < 0) 135 perror("dup2 stdin"); 136 } 137 if (sp[0] != 1) { 138 if (dup2(sp[0], 1) < 0) 139 perror("dup2 stdout"); 140 } 141 if (sp[0] >= 2) 142 close(sp[0]); 143 144 /* 145 * Stderr is left as it is so that error messages get 146 * printed on the user's terminal. 147 */ 148 argv[0] = shell; 149 argv[1] = "-c"; 150 argv[2] = command_string; 151 argv[3] = NULL; 152 153 /* 154 * Execute the proxy command. 155 * Note that we gave up any extra privileges above. 156 */ 157 execv(argv[0], argv); 158 perror(argv[0]); 159 exit(1); 160 } 161 /* Parent. */ 162 if (pid < 0) 163 fatal("fork failed: %.100s", strerror(errno)); 164 close(sp[0]); 165 free(command_string); 166 167 if ((sock = mm_receive_fd(sp[1])) == -1) 168 fatal("proxy dialer did not pass back a connection"); 169 close(sp[1]); 170 171 while (waitpid(pid, NULL, 0) == -1) 172 if (errno != EINTR) 173 fatal("Couldn't wait for child: %s", strerror(errno)); 174 175 /* Set the connection file descriptors. */ 176 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 177 return -1; /* ssh_packet_set_connection logs error */ 178 179 return 0; 180} 181 182/* 183 * Connect to the given ssh server using a proxy command. 184 */ 185static int 186ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port, 187 const char *proxy_command) 188{ 189 char *command_string; 190 int pin[2], pout[2]; 191 pid_t pid; 192 char *shell; 193 194 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 195 shell = _PATH_BSHELL; 196 197 /* Create pipes for communicating with the proxy. */ 198 if (pipe(pin) < 0 || pipe(pout) < 0) 199 fatal("Could not create pipes to communicate with the proxy: %.100s", 200 strerror(errno)); 201 202 command_string = expand_proxy_command(proxy_command, options.user, 203 host, port); 204 debug("Executing proxy command: %.500s", command_string); 205 206 /* Fork and execute the proxy command. */ 207 if ((pid = fork()) == 0) { 208 char *argv[10]; 209 210 /* Redirect stdin and stdout. */ 211 close(pin[1]); 212 if (pin[0] != 0) { 213 if (dup2(pin[0], 0) < 0) 214 perror("dup2 stdin"); 215 close(pin[0]); 216 } 217 close(pout[0]); 218 if (dup2(pout[1], 1) < 0) 219 perror("dup2 stdout"); 220 /* Cannot be 1 because pin allocated two descriptors. */ 221 close(pout[1]); 222 223 /* Stderr is left as it is so that error messages get 224 printed on the user's terminal. */ 225 argv[0] = shell; 226 argv[1] = "-c"; 227 argv[2] = command_string; 228 argv[3] = NULL; 229 230 /* Execute the proxy command. Note that we gave up any 231 extra privileges above. */ 232 signal(SIGPIPE, SIG_DFL); 233 execv(argv[0], argv); 234 perror(argv[0]); 235 exit(1); 236 } 237 /* Parent. */ 238 if (pid < 0) 239 fatal("fork failed: %.100s", strerror(errno)); 240 else 241 proxy_command_pid = pid; /* save pid to clean up later */ 242 243 /* Close child side of the descriptors. */ 244 close(pin[0]); 245 close(pout[1]); 246 247 /* Free the command name. */ 248 free(command_string); 249 250 /* Set the connection file descriptors. */ 251 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 252 return -1; /* ssh_packet_set_connection logs error */ 253 254 return 0; 255} 256 257void 258ssh_kill_proxy_command(void) 259{ 260 /* 261 * Send SIGHUP to proxy command if used. We don't wait() in 262 * case it hangs and instead rely on init to reap the child 263 */ 264 if (proxy_command_pid > 1) 265 kill(proxy_command_pid, SIGHUP); 266} 267 268#ifdef HAVE_IFADDRS_H 269/* 270 * Search a interface address list (returned from getifaddrs(3)) for an 271 * address that matches the desired address family on the specified interface. 272 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 273 */ 274static int 275check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 276 struct sockaddr_storage *resultp, socklen_t *rlenp) 277{ 278 struct sockaddr_in6 *sa6; 279 struct sockaddr_in *sa; 280 struct in6_addr *v6addr; 281 const struct ifaddrs *ifa; 282 int allow_local; 283 284 /* 285 * Prefer addresses that are not loopback or linklocal, but use them 286 * if nothing else matches. 287 */ 288 for (allow_local = 0; allow_local < 2; allow_local++) { 289 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 290 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 291 (ifa->ifa_flags & IFF_UP) == 0 || 292 ifa->ifa_addr->sa_family != af || 293 strcmp(ifa->ifa_name, options.bind_interface) != 0) 294 continue; 295 switch (ifa->ifa_addr->sa_family) { 296 case AF_INET: 297 sa = (struct sockaddr_in *)ifa->ifa_addr; 298 if (!allow_local && sa->sin_addr.s_addr == 299 htonl(INADDR_LOOPBACK)) 300 continue; 301 if (*rlenp < sizeof(struct sockaddr_in)) { 302 error("%s: v4 addr doesn't fit", 303 __func__); 304 return -1; 305 } 306 *rlenp = sizeof(struct sockaddr_in); 307 memcpy(resultp, sa, *rlenp); 308 return 0; 309 case AF_INET6: 310 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 311 v6addr = &sa6->sin6_addr; 312 if (!allow_local && 313 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 314 IN6_IS_ADDR_LOOPBACK(v6addr))) 315 continue; 316 if (*rlenp < sizeof(struct sockaddr_in6)) { 317 error("%s: v6 addr doesn't fit", 318 __func__); 319 return -1; 320 } 321 *rlenp = sizeof(struct sockaddr_in6); 322 memcpy(resultp, sa6, *rlenp); 323 return 0; 324 } 325 } 326 } 327 return -1; 328} 329#endif 330 331/* 332 * Creates a socket for use as the ssh connection. 333 */ 334static int 335ssh_create_socket(struct addrinfo *ai) 336{ 337 int sock, r; 338 struct sockaddr_storage bindaddr; 339 socklen_t bindaddrlen = 0; 340 struct addrinfo hints, *res = NULL; 341#ifdef HAVE_IFADDRS_H 342 struct ifaddrs *ifaddrs = NULL; 343#endif 344 char ntop[NI_MAXHOST]; 345 346 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 347 if (sock < 0) { 348 error("socket: %s", strerror(errno)); 349 return -1; 350 } 351 fcntl(sock, F_SETFD, FD_CLOEXEC); 352 353 /* Bind the socket to an alternative local IP address */ 354 if (options.bind_address == NULL && options.bind_interface == NULL) 355 return sock; 356 357 if (options.bind_address != NULL) { 358 memset(&hints, 0, sizeof(hints)); 359 hints.ai_family = ai->ai_family; 360 hints.ai_socktype = ai->ai_socktype; 361 hints.ai_protocol = ai->ai_protocol; 362 hints.ai_flags = AI_PASSIVE; 363 if ((r = getaddrinfo(options.bind_address, NULL, 364 &hints, &res)) != 0) { 365 error("getaddrinfo: %s: %s", options.bind_address, 366 ssh_gai_strerror(r)); 367 goto fail; 368 } 369 if (res == NULL) { 370 error("getaddrinfo: no addrs"); 371 goto fail; 372 } 373 if (res->ai_addrlen > sizeof(bindaddr)) { 374 error("%s: addr doesn't fit", __func__); 375 goto fail; 376 } 377 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 378 bindaddrlen = res->ai_addrlen; 379 } else if (options.bind_interface != NULL) { 380#ifdef HAVE_IFADDRS_H 381 if ((r = getifaddrs(&ifaddrs)) != 0) { 382 error("getifaddrs: %s: %s", options.bind_interface, 383 strerror(errno)); 384 goto fail; 385 } 386 bindaddrlen = sizeof(bindaddr); 387 if (check_ifaddrs(options.bind_interface, ai->ai_family, 388 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 389 logit("getifaddrs: %s: no suitable addresses", 390 options.bind_interface); 391 goto fail; 392 } 393#else 394 error("BindInterface not supported on this platform."); 395#endif 396 } 397 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 398 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 399 error("%s: getnameinfo failed: %s", __func__, 400 ssh_gai_strerror(r)); 401 goto fail; 402 } 403 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 404 error("bind %s: %s", ntop, strerror(errno)); 405 goto fail; 406 } 407 debug("%s: bound to %s", __func__, ntop); 408 /* success */ 409 goto out; 410fail: 411 close(sock); 412 sock = -1; 413 out: 414 if (res != NULL) 415 freeaddrinfo(res); 416#ifdef HAVE_IFADDRS_H 417 if (ifaddrs != NULL) 418 freeifaddrs(ifaddrs); 419#endif 420 return sock; 421} 422 423/* 424 * Wait up to *timeoutp milliseconds for fd to be readable. Updates 425 * *timeoutp with time remaining. 426 * Returns 0 if fd ready or -1 on timeout or error (see errno). 427 */ 428static int 429waitrfd(int fd, int *timeoutp) 430{ 431 struct pollfd pfd; 432 struct timeval t_start; 433 int oerrno, r; 434 435 monotime_tv(&t_start); 436 pfd.fd = fd; 437 pfd.events = POLLIN; 438 for (; *timeoutp >= 0;) { 439 r = poll(&pfd, 1, *timeoutp); 440 oerrno = errno; 441 ms_subtract_diff(&t_start, timeoutp); 442 errno = oerrno; 443 if (r > 0) 444 return 0; 445 else if (r == -1 && errno != EAGAIN) 446 return -1; 447 else if (r == 0) 448 break; 449 } 450 /* timeout */ 451 errno = ETIMEDOUT; 452 return -1; 453} 454 455static int 456timeout_connect(int sockfd, const struct sockaddr *serv_addr, 457 socklen_t addrlen, int *timeoutp) 458{ 459 int optval = 0; 460 socklen_t optlen = sizeof(optval); 461 462 /* No timeout: just do a blocking connect() */ 463 if (*timeoutp <= 0) 464 return connect(sockfd, serv_addr, addrlen); 465 466 set_nonblock(sockfd); 467 if (connect(sockfd, serv_addr, addrlen) == 0) { 468 /* Succeeded already? */ 469 unset_nonblock(sockfd); 470 return 0; 471 } else if (errno != EINPROGRESS) 472 return -1; 473 474 if (waitrfd(sockfd, timeoutp) == -1) 475 return -1; 476 477 /* Completed or failed */ 478 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) { 479 debug("getsockopt: %s", strerror(errno)); 480 return -1; 481 } 482 if (optval != 0) { 483 errno = optval; 484 return -1; 485 } 486 unset_nonblock(sockfd); 487 return 0; 488} 489 490/* 491 * Opens a TCP/IP connection to the remote server on the given host. 492 * The address of the remote host will be returned in hostaddr. 493 * If port is 0, the default port will be used. 494 * Connection_attempts specifies the maximum number of tries (one per 495 * second). If proxy_command is non-NULL, it specifies the command (with %h 496 * and %p substituted for host and port, respectively) to use to contact 497 * the daemon. 498 */ 499static int 500ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 501 struct sockaddr_storage *hostaddr, u_short port, int family, 502 int connection_attempts, int *timeout_ms, int want_keepalive) 503{ 504 int on = 1; 505 int oerrno, sock = -1, attempt; 506 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 507 struct addrinfo *ai; 508 509 debug2("%s", __func__); 510 memset(ntop, 0, sizeof(ntop)); 511 memset(strport, 0, sizeof(strport)); 512 513 for (attempt = 0; attempt < connection_attempts; attempt++) { 514 if (attempt > 0) { 515 /* Sleep a moment before retrying. */ 516 sleep(1); 517 debug("Trying again..."); 518 } 519 /* 520 * Loop through addresses for this host, and try each one in 521 * sequence until the connection succeeds. 522 */ 523 for (ai = aitop; ai; ai = ai->ai_next) { 524 if (ai->ai_family != AF_INET && 525 ai->ai_family != AF_INET6) { 526 errno = EAFNOSUPPORT; 527 continue; 528 } 529 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 530 ntop, sizeof(ntop), strport, sizeof(strport), 531 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 532 oerrno = errno; 533 error("%s: getnameinfo failed", __func__); 534 errno = oerrno; 535 continue; 536 } 537 debug("Connecting to %.200s [%.100s] port %s.", 538 host, ntop, strport); 539 540 /* Create a socket for connecting. */ 541 sock = ssh_create_socket(ai); 542 if (sock < 0) { 543 /* Any error is already output */ 544 errno = 0; 545 continue; 546 } 547 548 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 549 timeout_ms) >= 0) { 550 /* Successful connection. */ 551 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 552 break; 553 } else { 554 oerrno = errno; 555 debug("connect to address %s port %s: %s", 556 ntop, strport, strerror(errno)); 557 close(sock); 558 sock = -1; 559 errno = oerrno; 560 } 561 } 562 if (sock != -1) 563 break; /* Successful connection. */ 564 } 565 566 /* Return failure if we didn't get a successful connection. */ 567 if (sock == -1) { 568 error("ssh: connect to host %s port %s: %s", 569 host, strport, errno == 0 ? "failure" : strerror(errno)); 570 return -1; 571 } 572 573 debug("Connection established."); 574 575 /* Set SO_KEEPALIVE if requested. */ 576 if (want_keepalive && 577 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 578 sizeof(on)) < 0) 579 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 580 581 /* Set the connection. */ 582 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 583 return -1; /* ssh_packet_set_connection logs error */ 584 585 return 0; 586} 587 588int 589ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs, 590 struct sockaddr_storage *hostaddr, u_short port, int family, 591 int connection_attempts, int *timeout_ms, int want_keepalive) 592{ 593 if (options.proxy_command == NULL) { 594 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 595 family, connection_attempts, timeout_ms, want_keepalive); 596 } else if (strcmp(options.proxy_command, "-") == 0) { 597 if ((ssh_packet_set_connection(ssh, 598 STDIN_FILENO, STDOUT_FILENO)) == NULL) 599 return -1; /* ssh_packet_set_connection logs error */ 600 return 0; 601 } else if (options.proxy_use_fdpass) { 602 return ssh_proxy_fdpass_connect(ssh, host, port, 603 options.proxy_command); 604 } 605 return ssh_proxy_connect(ssh, host, port, options.proxy_command); 606} 607 608static void 609send_client_banner(int connection_out, int minor1) 610{ 611 /* Send our own protocol version identification. */ 612 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s\n", 613 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION, 614 *options.version_addendum == '\0' ? "" : " ", 615 options.version_addendum); 616 if (atomicio(vwrite, connection_out, client_version_string, 617 strlen(client_version_string)) != strlen(client_version_string)) 618 fatal("write: %.100s", strerror(errno)); 619 chop(client_version_string); 620 debug("Local version string %.100s", client_version_string); 621} 622 623/* 624 * Waits for the server identification string, and sends our own 625 * identification string. 626 */ 627void 628ssh_exchange_identification(int timeout_ms) 629{ 630 char buf[256], remote_version[256]; /* must be same size! */ 631 int remote_major, remote_minor, mismatch; 632 int connection_in = packet_get_connection_in(); 633 int connection_out = packet_get_connection_out(); 634 u_int i, n; 635 size_t len; 636 int rc; 637 638 send_client_banner(connection_out, 0); 639 640 /* Read other side's version identification. */ 641 for (n = 0;;) { 642 for (i = 0; i < sizeof(buf) - 1; i++) { 643 if (timeout_ms > 0) { 644 rc = waitrfd(connection_in, &timeout_ms); 645 if (rc == -1 && errno == ETIMEDOUT) { 646 fatal("Connection timed out during " 647 "banner exchange"); 648 } else if (rc == -1) { 649 fatal("%s: %s", 650 __func__, strerror(errno)); 651 } 652 } 653 654 len = atomicio(read, connection_in, &buf[i], 1); 655 if (len != 1 && errno == EPIPE) 656 fatal("ssh_exchange_identification: " 657 "Connection closed by remote host"); 658 else if (len != 1) 659 fatal("ssh_exchange_identification: " 660 "read: %.100s", strerror(errno)); 661 if (buf[i] == '\r') { 662 buf[i] = '\n'; 663 buf[i + 1] = 0; 664 continue; /**XXX wait for \n */ 665 } 666 if (buf[i] == '\n') { 667 buf[i + 1] = 0; 668 break; 669 } 670 if (++n > 65536) 671 fatal("ssh_exchange_identification: " 672 "No banner received"); 673 } 674 buf[sizeof(buf) - 1] = 0; 675 if (strncmp(buf, "SSH-", 4) == 0) 676 break; 677 debug("ssh_exchange_identification: %s", buf); 678 } 679 server_version_string = xstrdup(buf); 680 681 /* 682 * Check that the versions match. In future this might accept 683 * several versions and set appropriate flags to handle them. 684 */ 685 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 686 &remote_major, &remote_minor, remote_version) != 3) 687 fatal("Bad remote protocol version identification: '%.100s'", buf); 688 debug("Remote protocol version %d.%d, remote software version %.100s", 689 remote_major, remote_minor, remote_version); 690 691 active_state->compat = compat_datafellows(remote_version); 692 mismatch = 0; 693 694 switch (remote_major) { 695 case 2: 696 break; 697 case 1: 698 if (remote_minor != 99) 699 mismatch = 1; 700 break; 701 default: 702 mismatch = 1; 703 break; 704 } 705 if (mismatch) 706 fatal("Protocol major versions differ: %d vs. %d", 707 PROTOCOL_MAJOR_2, remote_major); 708 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) 709 logit("Server version \"%.100s\" uses unsafe RSA signature " 710 "scheme; disabling use of RSA keys", remote_version); 711 chop(server_version_string); 712} 713 714/* defaults to 'no' */ 715static int 716confirm(const char *prompt) 717{ 718 const char *msg, *again = "Please type 'yes' or 'no': "; 719 char *p; 720 int ret = -1; 721 722 if (options.batch_mode) 723 return 0; 724 for (msg = prompt;;msg = again) { 725 p = read_passphrase(msg, RP_ECHO); 726 if (p == NULL) 727 return 0; 728 p[strcspn(p, "\n")] = '\0'; 729 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 730 ret = 0; 731 else if (strcasecmp(p, "yes") == 0) 732 ret = 1; 733 free(p); 734 if (ret != -1) 735 return ret; 736 } 737} 738 739static int 740check_host_cert(const char *host, const struct sshkey *key) 741{ 742 const char *reason; 743 int r; 744 745 if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) { 746 error("%s", reason); 747 return 0; 748 } 749 if (sshbuf_len(key->cert->critical) != 0) { 750 error("Certificate for %s contains unsupported " 751 "critical options(s)", host); 752 return 0; 753 } 754 if ((r = sshkey_check_cert_sigtype(key, 755 options.ca_sign_algorithms)) != 0) { 756 logit("%s: certificate signature algorithm %s: %s", __func__, 757 (key->cert == NULL || key->cert->signature_type == NULL) ? 758 "(null)" : key->cert->signature_type, ssh_err(r)); 759 return 0; 760 } 761 762 return 1; 763} 764 765static int 766sockaddr_is_local(struct sockaddr *hostaddr) 767{ 768 switch (hostaddr->sa_family) { 769 case AF_INET: 770 return (ntohl(((struct sockaddr_in *)hostaddr)-> 771 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 772 case AF_INET6: 773 return IN6_IS_ADDR_LOOPBACK( 774 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 775 default: 776 return 0; 777 } 778} 779 780/* 781 * Prepare the hostname and ip address strings that are used to lookup 782 * host keys in known_hosts files. These may have a port number appended. 783 */ 784void 785get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 786 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 787{ 788 char ntop[NI_MAXHOST]; 789 socklen_t addrlen; 790 791 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 792 case -1: 793 addrlen = 0; 794 break; 795 case AF_INET: 796 addrlen = sizeof(struct sockaddr_in); 797 break; 798 case AF_INET6: 799 addrlen = sizeof(struct sockaddr_in6); 800 break; 801 default: 802 addrlen = sizeof(struct sockaddr); 803 break; 804 } 805 806 /* 807 * We don't have the remote ip-address for connections 808 * using a proxy command 809 */ 810 if (hostfile_ipaddr != NULL) { 811 if (options.proxy_command == NULL) { 812 if (getnameinfo(hostaddr, addrlen, 813 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 814 fatal("%s: getnameinfo failed", __func__); 815 *hostfile_ipaddr = put_host_port(ntop, port); 816 } else { 817 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 818 "command>"); 819 } 820 } 821 822 /* 823 * Allow the user to record the key under a different name or 824 * differentiate a non-standard port. This is useful for ssh 825 * tunneling over forwarded connections or if you run multiple 826 * sshd's on different ports on the same machine. 827 */ 828 if (hostfile_hostname != NULL) { 829 if (options.host_key_alias != NULL) { 830 *hostfile_hostname = xstrdup(options.host_key_alias); 831 debug("using hostkeyalias: %s", *hostfile_hostname); 832 } else { 833 *hostfile_hostname = put_host_port(hostname, port); 834 } 835 } 836} 837 838/* 839 * check whether the supplied host key is valid, return -1 if the key 840 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 841 */ 842#define RDRW 0 843#define RDONLY 1 844#define ROQUIET 2 845static int 846check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 847 struct sshkey *host_key, int readonly, 848 char **user_hostfiles, u_int num_user_hostfiles, 849 char **system_hostfiles, u_int num_system_hostfiles) 850{ 851 HostStatus host_status; 852 HostStatus ip_status; 853 struct sshkey *raw_key = NULL; 854 char *ip = NULL, *host = NULL; 855 char hostline[1000], *hostp, *fp, *ra; 856 char msg[1024]; 857 const char *type; 858 const struct hostkey_entry *host_found, *ip_found; 859 int len, cancelled_forwarding = 0; 860 int local = sockaddr_is_local(hostaddr); 861 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 862 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 863 struct hostkeys *host_hostkeys, *ip_hostkeys; 864 u_int i; 865 866 /* 867 * Force accepting of the host key for loopback/localhost. The 868 * problem is that if the home directory is NFS-mounted to multiple 869 * machines, localhost will refer to a different machine in each of 870 * them, and the user will get bogus HOST_CHANGED warnings. This 871 * essentially disables host authentication for localhost; however, 872 * this is probably not a real problem. 873 */ 874 if (options.no_host_authentication_for_localhost == 1 && local && 875 options.host_key_alias == NULL) { 876 debug("Forcing accepting of host key for " 877 "loopback/localhost."); 878 return 0; 879 } 880 881 /* 882 * Prepare the hostname and address strings used for hostkey lookup. 883 * In some cases, these will have a port number appended. 884 */ 885 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 886 887 /* 888 * Turn off check_host_ip if the connection is to localhost, via proxy 889 * command or if we don't have a hostname to compare with 890 */ 891 if (options.check_host_ip && (local || 892 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 893 options.check_host_ip = 0; 894 895 host_hostkeys = init_hostkeys(); 896 for (i = 0; i < num_user_hostfiles; i++) 897 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 898 for (i = 0; i < num_system_hostfiles; i++) 899 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 900 901 ip_hostkeys = NULL; 902 if (!want_cert && options.check_host_ip) { 903 ip_hostkeys = init_hostkeys(); 904 for (i = 0; i < num_user_hostfiles; i++) 905 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 906 for (i = 0; i < num_system_hostfiles; i++) 907 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 908 } 909 910 retry: 911 /* Reload these as they may have changed on cert->key downgrade */ 912 want_cert = sshkey_is_cert(host_key); 913 type = sshkey_type(host_key); 914 915 /* 916 * Check if the host key is present in the user's list of known 917 * hosts or in the systemwide list. 918 */ 919 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 920 &host_found); 921 922 /* 923 * Also perform check for the ip address, skip the check if we are 924 * localhost, looking for a certificate, or the hostname was an ip 925 * address to begin with. 926 */ 927 if (!want_cert && ip_hostkeys != NULL) { 928 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 929 &ip_found); 930 if (host_status == HOST_CHANGED && 931 (ip_status != HOST_CHANGED || 932 (ip_found != NULL && 933 !sshkey_equal(ip_found->key, host_found->key)))) 934 host_ip_differ = 1; 935 } else 936 ip_status = host_status; 937 938 switch (host_status) { 939 case HOST_OK: 940 /* The host is known and the key matches. */ 941 debug("Host '%.200s' is known and matches the %s host %s.", 942 host, type, want_cert ? "certificate" : "key"); 943 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 944 host_found->file, host_found->line); 945 if (want_cert && 946 !check_host_cert(options.host_key_alias == NULL ? 947 hostname : options.host_key_alias, host_key)) 948 goto fail; 949 if (options.check_host_ip && ip_status == HOST_NEW) { 950 if (readonly || want_cert) 951 logit("%s host key for IP address " 952 "'%.128s' not in list of known hosts.", 953 type, ip); 954 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 955 host_key, options.hash_known_hosts)) 956 logit("Failed to add the %s host key for IP " 957 "address '%.128s' to the list of known " 958 "hosts (%.500s).", type, ip, 959 user_hostfiles[0]); 960 else 961 logit("Warning: Permanently added the %s host " 962 "key for IP address '%.128s' to the list " 963 "of known hosts.", type, ip); 964 } else if (options.visual_host_key) { 965 fp = sshkey_fingerprint(host_key, 966 options.fingerprint_hash, SSH_FP_DEFAULT); 967 ra = sshkey_fingerprint(host_key, 968 options.fingerprint_hash, SSH_FP_RANDOMART); 969 if (fp == NULL || ra == NULL) 970 fatal("%s: sshkey_fingerprint fail", __func__); 971 logit("Host key fingerprint is %s\n%s", fp, ra); 972 free(ra); 973 free(fp); 974 } 975 hostkey_trusted = 1; 976 break; 977 case HOST_NEW: 978 if (options.host_key_alias == NULL && port != 0 && 979 port != SSH_DEFAULT_PORT) { 980 debug("checking without port identifier"); 981 if (check_host_key(hostname, hostaddr, 0, host_key, 982 ROQUIET, user_hostfiles, num_user_hostfiles, 983 system_hostfiles, num_system_hostfiles) == 0) { 984 debug("found matching key w/out port"); 985 break; 986 } 987 } 988 if (readonly || want_cert) 989 goto fail; 990 /* The host is new. */ 991 if (options.strict_host_key_checking == 992 SSH_STRICT_HOSTKEY_YES) { 993 /* 994 * User has requested strict host key checking. We 995 * will not add the host key automatically. The only 996 * alternative left is to abort. 997 */ 998 error("No %s host key is known for %.200s and you " 999 "have requested strict checking.", type, host); 1000 goto fail; 1001 } else if (options.strict_host_key_checking == 1002 SSH_STRICT_HOSTKEY_ASK) { 1003 char msg1[1024], msg2[1024]; 1004 1005 if (show_other_keys(host_hostkeys, host_key)) 1006 snprintf(msg1, sizeof(msg1), 1007 "\nbut keys of different type are already" 1008 " known for this host."); 1009 else 1010 snprintf(msg1, sizeof(msg1), "."); 1011 /* The default */ 1012 fp = sshkey_fingerprint(host_key, 1013 options.fingerprint_hash, SSH_FP_DEFAULT); 1014 ra = sshkey_fingerprint(host_key, 1015 options.fingerprint_hash, SSH_FP_RANDOMART); 1016 if (fp == NULL || ra == NULL) 1017 fatal("%s: sshkey_fingerprint fail", __func__); 1018 msg2[0] = '\0'; 1019 if (options.verify_host_key_dns) { 1020 if (matching_host_key_dns) 1021 snprintf(msg2, sizeof(msg2), 1022 "Matching host key fingerprint" 1023 " found in DNS.\n"); 1024 else 1025 snprintf(msg2, sizeof(msg2), 1026 "No matching host key fingerprint" 1027 " found in DNS.\n"); 1028 } 1029 snprintf(msg, sizeof(msg), 1030 "The authenticity of host '%.200s (%s)' can't be " 1031 "established%s\n" 1032 "%s key fingerprint is %s.%s%s\n%s" 1033 "Are you sure you want to continue connecting " 1034 "(yes/no)? ", 1035 host, ip, msg1, type, fp, 1036 options.visual_host_key ? "\n" : "", 1037 options.visual_host_key ? ra : "", 1038 msg2); 1039 free(ra); 1040 free(fp); 1041 if (!confirm(msg)) 1042 goto fail; 1043 hostkey_trusted = 1; /* user explicitly confirmed */ 1044 } 1045 /* 1046 * If in "new" or "off" strict mode, add the key automatically 1047 * to the local known_hosts file. 1048 */ 1049 if (options.check_host_ip && ip_status == HOST_NEW) { 1050 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1051 hostp = hostline; 1052 if (options.hash_known_hosts) { 1053 /* Add hash of host and IP separately */ 1054 r = add_host_to_hostfile(user_hostfiles[0], 1055 host, host_key, options.hash_known_hosts) && 1056 add_host_to_hostfile(user_hostfiles[0], ip, 1057 host_key, options.hash_known_hosts); 1058 } else { 1059 /* Add unhashed "host,ip" */ 1060 r = add_host_to_hostfile(user_hostfiles[0], 1061 hostline, host_key, 1062 options.hash_known_hosts); 1063 } 1064 } else { 1065 r = add_host_to_hostfile(user_hostfiles[0], host, 1066 host_key, options.hash_known_hosts); 1067 hostp = host; 1068 } 1069 1070 if (!r) 1071 logit("Failed to add the host to the list of known " 1072 "hosts (%.500s).", user_hostfiles[0]); 1073 else 1074 logit("Warning: Permanently added '%.200s' (%s) to the " 1075 "list of known hosts.", hostp, type); 1076 break; 1077 case HOST_REVOKED: 1078 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1079 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1080 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1081 error("The %s host key for %s is marked as revoked.", type, host); 1082 error("This could mean that a stolen key is being used to"); 1083 error("impersonate this host."); 1084 1085 /* 1086 * If strict host key checking is in use, the user will have 1087 * to edit the key manually and we can only abort. 1088 */ 1089 if (options.strict_host_key_checking != 1090 SSH_STRICT_HOSTKEY_OFF) { 1091 error("%s host key for %.200s was revoked and you have " 1092 "requested strict checking.", type, host); 1093 goto fail; 1094 } 1095 goto continue_unsafe; 1096 1097 case HOST_CHANGED: 1098 if (want_cert) { 1099 /* 1100 * This is only a debug() since it is valid to have 1101 * CAs with wildcard DNS matches that don't match 1102 * all hosts that one might visit. 1103 */ 1104 debug("Host certificate authority does not " 1105 "match %s in %s:%lu", CA_MARKER, 1106 host_found->file, host_found->line); 1107 goto fail; 1108 } 1109 if (readonly == ROQUIET) 1110 goto fail; 1111 if (options.check_host_ip && host_ip_differ) { 1112 char *key_msg; 1113 if (ip_status == HOST_NEW) 1114 key_msg = "is unknown"; 1115 else if (ip_status == HOST_OK) 1116 key_msg = "is unchanged"; 1117 else 1118 key_msg = "has a different value"; 1119 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1120 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1121 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1122 error("The %s host key for %s has changed,", type, host); 1123 error("and the key for the corresponding IP address %s", ip); 1124 error("%s. This could either mean that", key_msg); 1125 error("DNS SPOOFING is happening or the IP address for the host"); 1126 error("and its host key have changed at the same time."); 1127 if (ip_status != HOST_NEW) 1128 error("Offending key for IP in %s:%lu", 1129 ip_found->file, ip_found->line); 1130 } 1131 /* The host key has changed. */ 1132 warn_changed_key(host_key); 1133 error("Add correct host key in %.100s to get rid of this message.", 1134 user_hostfiles[0]); 1135 error("Offending %s key in %s:%lu", 1136 sshkey_type(host_found->key), 1137 host_found->file, host_found->line); 1138 1139 /* 1140 * If strict host key checking is in use, the user will have 1141 * to edit the key manually and we can only abort. 1142 */ 1143 if (options.strict_host_key_checking != 1144 SSH_STRICT_HOSTKEY_OFF) { 1145 error("%s host key for %.200s has changed and you have " 1146 "requested strict checking.", type, host); 1147 goto fail; 1148 } 1149 1150 continue_unsafe: 1151 /* 1152 * If strict host key checking has not been requested, allow 1153 * the connection but without MITM-able authentication or 1154 * forwarding. 1155 */ 1156 if (options.password_authentication) { 1157 error("Password authentication is disabled to avoid " 1158 "man-in-the-middle attacks."); 1159 options.password_authentication = 0; 1160 cancelled_forwarding = 1; 1161 } 1162 if (options.kbd_interactive_authentication) { 1163 error("Keyboard-interactive authentication is disabled" 1164 " to avoid man-in-the-middle attacks."); 1165 options.kbd_interactive_authentication = 0; 1166 options.challenge_response_authentication = 0; 1167 cancelled_forwarding = 1; 1168 } 1169 if (options.challenge_response_authentication) { 1170 error("Challenge/response authentication is disabled" 1171 " to avoid man-in-the-middle attacks."); 1172 options.challenge_response_authentication = 0; 1173 cancelled_forwarding = 1; 1174 } 1175 if (options.forward_agent) { 1176 error("Agent forwarding is disabled to avoid " 1177 "man-in-the-middle attacks."); 1178 options.forward_agent = 0; 1179 cancelled_forwarding = 1; 1180 } 1181 if (options.forward_x11) { 1182 error("X11 forwarding is disabled to avoid " 1183 "man-in-the-middle attacks."); 1184 options.forward_x11 = 0; 1185 cancelled_forwarding = 1; 1186 } 1187 if (options.num_local_forwards > 0 || 1188 options.num_remote_forwards > 0) { 1189 error("Port forwarding is disabled to avoid " 1190 "man-in-the-middle attacks."); 1191 options.num_local_forwards = 1192 options.num_remote_forwards = 0; 1193 cancelled_forwarding = 1; 1194 } 1195 if (options.tun_open != SSH_TUNMODE_NO) { 1196 error("Tunnel forwarding is disabled to avoid " 1197 "man-in-the-middle attacks."); 1198 options.tun_open = SSH_TUNMODE_NO; 1199 cancelled_forwarding = 1; 1200 } 1201 if (options.exit_on_forward_failure && cancelled_forwarding) 1202 fatal("Error: forwarding disabled due to host key " 1203 "check failure"); 1204 1205 /* 1206 * XXX Should permit the user to change to use the new id. 1207 * This could be done by converting the host key to an 1208 * identifying sentence, tell that the host identifies itself 1209 * by that sentence, and ask the user if he/she wishes to 1210 * accept the authentication. 1211 */ 1212 break; 1213 case HOST_FOUND: 1214 fatal("internal error"); 1215 break; 1216 } 1217 1218 if (options.check_host_ip && host_status != HOST_CHANGED && 1219 ip_status == HOST_CHANGED) { 1220 snprintf(msg, sizeof(msg), 1221 "Warning: the %s host key for '%.200s' " 1222 "differs from the key for the IP address '%.128s'" 1223 "\nOffending key for IP in %s:%lu", 1224 type, host, ip, ip_found->file, ip_found->line); 1225 if (host_status == HOST_OK) { 1226 len = strlen(msg); 1227 snprintf(msg + len, sizeof(msg) - len, 1228 "\nMatching host key in %s:%lu", 1229 host_found->file, host_found->line); 1230 } 1231 if (options.strict_host_key_checking == 1232 SSH_STRICT_HOSTKEY_ASK) { 1233 strlcat(msg, "\nAre you sure you want " 1234 "to continue connecting (yes/no)? ", sizeof(msg)); 1235 if (!confirm(msg)) 1236 goto fail; 1237 } else if (options.strict_host_key_checking != 1238 SSH_STRICT_HOSTKEY_OFF) { 1239 logit("%s", msg); 1240 error("Exiting, you have requested strict checking."); 1241 goto fail; 1242 } else { 1243 logit("%s", msg); 1244 } 1245 } 1246 1247 if (!hostkey_trusted && options.update_hostkeys) { 1248 debug("%s: hostkey not known or explicitly trusted: " 1249 "disabling UpdateHostkeys", __func__); 1250 options.update_hostkeys = 0; 1251 } 1252 1253 free(ip); 1254 free(host); 1255 if (host_hostkeys != NULL) 1256 free_hostkeys(host_hostkeys); 1257 if (ip_hostkeys != NULL) 1258 free_hostkeys(ip_hostkeys); 1259 return 0; 1260 1261fail: 1262 if (want_cert && host_status != HOST_REVOKED) { 1263 /* 1264 * No matching certificate. Downgrade cert to raw key and 1265 * search normally. 1266 */ 1267 debug("No matching CA found. Retry with plain key"); 1268 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1269 fatal("%s: sshkey_from_private: %s", 1270 __func__, ssh_err(r)); 1271 if ((r = sshkey_drop_cert(raw_key)) != 0) 1272 fatal("Couldn't drop certificate: %s", ssh_err(r)); 1273 host_key = raw_key; 1274 goto retry; 1275 } 1276 sshkey_free(raw_key); 1277 free(ip); 1278 free(host); 1279 if (host_hostkeys != NULL) 1280 free_hostkeys(host_hostkeys); 1281 if (ip_hostkeys != NULL) 1282 free_hostkeys(ip_hostkeys); 1283 return -1; 1284} 1285 1286/* returns 0 if key verifies or -1 if key does NOT verify */ 1287int 1288verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key) 1289{ 1290 u_int i; 1291 int r = -1, flags = 0; 1292 char valid[64], *fp = NULL, *cafp = NULL; 1293 struct sshkey *plain = NULL; 1294 1295 if ((fp = sshkey_fingerprint(host_key, 1296 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1297 error("%s: fingerprint host key: %s", __func__, ssh_err(r)); 1298 r = -1; 1299 goto out; 1300 } 1301 1302 if (sshkey_is_cert(host_key)) { 1303 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1304 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1305 error("%s: fingerprint CA key: %s", 1306 __func__, ssh_err(r)); 1307 r = -1; 1308 goto out; 1309 } 1310 sshkey_format_cert_validity(host_key->cert, 1311 valid, sizeof(valid)); 1312 debug("Server host certificate: %s %s, serial %llu " 1313 "ID \"%s\" CA %s %s valid %s", 1314 sshkey_ssh_name(host_key), fp, 1315 (unsigned long long)host_key->cert->serial, 1316 host_key->cert->key_id, 1317 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1318 valid); 1319 for (i = 0; i < host_key->cert->nprincipals; i++) { 1320 debug2("Server host certificate hostname: %s", 1321 host_key->cert->principals[i]); 1322 } 1323 } else { 1324 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1325 } 1326 1327 if (sshkey_equal(previous_host_key, host_key)) { 1328 debug2("%s: server host key %s %s matches cached key", 1329 __func__, sshkey_type(host_key), fp); 1330 r = 0; 1331 goto out; 1332 } 1333 1334 /* Check in RevokedHostKeys file if specified */ 1335 if (options.revoked_host_keys != NULL) { 1336 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1337 switch (r) { 1338 case 0: 1339 break; /* not revoked */ 1340 case SSH_ERR_KEY_REVOKED: 1341 error("Host key %s %s revoked by file %s", 1342 sshkey_type(host_key), fp, 1343 options.revoked_host_keys); 1344 r = -1; 1345 goto out; 1346 default: 1347 error("Error checking host key %s %s in " 1348 "revoked keys file %s: %s", sshkey_type(host_key), 1349 fp, options.revoked_host_keys, ssh_err(r)); 1350 r = -1; 1351 goto out; 1352 } 1353 } 1354 1355 if (options.verify_host_key_dns) { 1356 /* 1357 * XXX certs are not yet supported for DNS, so downgrade 1358 * them and try the plain key. 1359 */ 1360 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1361 goto out; 1362 if (sshkey_is_cert(plain)) 1363 sshkey_drop_cert(plain); 1364 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1365 if (flags & DNS_VERIFY_FOUND) { 1366 if (options.verify_host_key_dns == 1 && 1367 flags & DNS_VERIFY_MATCH && 1368 flags & DNS_VERIFY_SECURE) { 1369 r = 0; 1370 goto out; 1371 } 1372 if (flags & DNS_VERIFY_MATCH) { 1373 matching_host_key_dns = 1; 1374 } else { 1375 warn_changed_key(plain); 1376 error("Update the SSHFP RR in DNS " 1377 "with the new host key to get rid " 1378 "of this message."); 1379 } 1380 } 1381 } 1382 } 1383 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1384 options.user_hostfiles, options.num_user_hostfiles, 1385 options.system_hostfiles, options.num_system_hostfiles); 1386 1387out: 1388 sshkey_free(plain); 1389 free(fp); 1390 free(cafp); 1391 if (r == 0 && host_key != NULL) { 1392 sshkey_free(previous_host_key); 1393 r = sshkey_from_private(host_key, &previous_host_key); 1394 } 1395 1396 return r; 1397} 1398 1399/* 1400 * Starts a dialog with the server, and authenticates the current user on the 1401 * server. This does not need any extra privileges. The basic connection 1402 * to the server must already have been established before this is called. 1403 * If login fails, this function prints an error and never returns. 1404 * This function does not require super-user privileges. 1405 */ 1406void 1407ssh_login(Sensitive *sensitive, const char *orighost, 1408 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1409{ 1410 char *host; 1411 char *server_user, *local_user; 1412 1413 local_user = xstrdup(pw->pw_name); 1414 server_user = options.user ? options.user : local_user; 1415 1416 /* Convert the user-supplied hostname into all lowercase. */ 1417 host = xstrdup(orighost); 1418 lowercase(host); 1419 1420 /* Exchange protocol version identification strings with the server. */ 1421 ssh_exchange_identification(timeout_ms); 1422 1423 /* Put the connection into non-blocking mode. */ 1424 packet_set_nonblocking(); 1425 1426 /* key exchange */ 1427 /* authenticate user */ 1428 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1429 ssh_kex2(host, hostaddr, port); 1430 ssh_userauth2(local_user, server_user, host, sensitive); 1431 free(local_user); 1432} 1433 1434void 1435ssh_put_password(char *password) 1436{ 1437 int size; 1438 char *padded; 1439 1440 if (datafellows & SSH_BUG_PASSWORDPAD) { 1441 packet_put_cstring(password); 1442 return; 1443 } 1444 size = ROUNDUP(strlen(password) + 1, 32); 1445 padded = xcalloc(1, size); 1446 strlcpy(padded, password, size); 1447 packet_put_string(padded, size); 1448 explicit_bzero(padded, size); 1449 free(padded); 1450} 1451 1452/* print all known host keys for a given host, but skip keys of given type */ 1453static int 1454show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1455{ 1456 int type[] = { 1457 KEY_RSA, 1458 KEY_DSA, 1459 KEY_ECDSA, 1460 KEY_ED25519, 1461 KEY_XMSS, 1462 -1 1463 }; 1464 int i, ret = 0; 1465 char *fp, *ra; 1466 const struct hostkey_entry *found; 1467 1468 for (i = 0; type[i] != -1; i++) { 1469 if (type[i] == key->type) 1470 continue; 1471 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1472 continue; 1473 fp = sshkey_fingerprint(found->key, 1474 options.fingerprint_hash, SSH_FP_DEFAULT); 1475 ra = sshkey_fingerprint(found->key, 1476 options.fingerprint_hash, SSH_FP_RANDOMART); 1477 if (fp == NULL || ra == NULL) 1478 fatal("%s: sshkey_fingerprint fail", __func__); 1479 logit("WARNING: %s key found for host %s\n" 1480 "in %s:%lu\n" 1481 "%s key fingerprint %s.", 1482 sshkey_type(found->key), 1483 found->host, found->file, found->line, 1484 sshkey_type(found->key), fp); 1485 if (options.visual_host_key) 1486 logit("%s", ra); 1487 free(ra); 1488 free(fp); 1489 ret = 1; 1490 } 1491 return ret; 1492} 1493 1494static void 1495warn_changed_key(struct sshkey *host_key) 1496{ 1497 char *fp; 1498 1499 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1500 SSH_FP_DEFAULT); 1501 if (fp == NULL) 1502 fatal("%s: sshkey_fingerprint fail", __func__); 1503 1504 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1505 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1506 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1507 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1508 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1509 error("It is also possible that a host key has just been changed."); 1510 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1511 sshkey_type(host_key), fp); 1512 error("Please contact your system administrator."); 1513 1514 free(fp); 1515} 1516 1517/* 1518 * Execute a local command 1519 */ 1520int 1521ssh_local_cmd(const char *args) 1522{ 1523 char *shell; 1524 pid_t pid; 1525 int status; 1526 void (*osighand)(int); 1527 1528 if (!options.permit_local_command || 1529 args == NULL || !*args) 1530 return (1); 1531 1532 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1533 shell = _PATH_BSHELL; 1534 1535 osighand = signal(SIGCHLD, SIG_DFL); 1536 pid = fork(); 1537 if (pid == 0) { 1538 signal(SIGPIPE, SIG_DFL); 1539 debug3("Executing %s -c \"%s\"", shell, args); 1540 execl(shell, shell, "-c", args, (char *)NULL); 1541 error("Couldn't execute %s -c \"%s\": %s", 1542 shell, args, strerror(errno)); 1543 _exit(1); 1544 } else if (pid == -1) 1545 fatal("fork failed: %.100s", strerror(errno)); 1546 while (waitpid(pid, &status, 0) == -1) 1547 if (errno != EINTR) 1548 fatal("Couldn't wait for child: %s", strerror(errno)); 1549 signal(SIGCHLD, osighand); 1550 1551 if (!WIFEXITED(status)) 1552 return (1); 1553 1554 return (WEXITSTATUS(status)); 1555} 1556 1557void 1558maybe_add_key_to_agent(char *authfile, const struct sshkey *private, 1559 char *comment, char *passphrase) 1560{ 1561 int auth_sock = -1, r; 1562 1563 if (options.add_keys_to_agent == 0) 1564 return; 1565 1566 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1567 debug3("no authentication agent, not adding key"); 1568 return; 1569 } 1570 1571 if (options.add_keys_to_agent == 2 && 1572 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1573 debug3("user denied adding this key"); 1574 close(auth_sock); 1575 return; 1576 } 1577 1578 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0, 1579 (options.add_keys_to_agent == 3), 0)) == 0) 1580 debug("identity added to agent: %s", authfile); 1581 else 1582 debug("could not add identity to agent: %s (%d)", authfile, r); 1583 close(auth_sock); 1584} 1585