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 #include <rpc/rpc.h> 31 32 #include <ctype.h> 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <netdb.h> 36 #ifdef HAVE_PATHS_H 37 #include <paths.h> 38 #endif 39 #include <pwd.h> 40 #ifdef HAVE_POLL_H 41 #include <poll.h> 42 #endif 43 #include <signal.h> 44 #include <stdarg.h> 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include <unistd.h> 49 #ifdef HAVE_IFADDRS_H 50 # include <ifaddrs.h> 51 #endif 52 53 #include "xmalloc.h" 54 #include "hostfile.h" 55 #include "ssh.h" 56 #include "sshbuf.h" 57 #include "packet.h" 58 #include "compat.h" 59 #include "sshkey.h" 60 #include "sshconnect.h" 61 #include "hostfile.h" 62 #include "log.h" 63 #include "misc.h" 64 #include "readconf.h" 65 #include "atomicio.h" 66 #include "dns.h" 67 #include "monitor_fdpass.h" 68 #include "ssh2.h" 69 #include "version.h" 70 #include "authfile.h" 71 #include "ssherr.h" 72 #include "authfd.h" 73 74 char *client_version_string = NULL; 75 char *server_version_string = NULL; 76 struct sshkey *previous_host_key = NULL; 77 78 static int matching_host_key_dns = 0; 79 80 static pid_t proxy_command_pid = 0; 81 82 /* import */ 83 extern Options options; 84 extern char *__progname; 85 86 static int show_other_keys(struct hostkeys *, struct sshkey *); 87 static void warn_changed_key(struct sshkey *); 88 89 /* Expand a proxy command */ 90 static char * 91 expand_proxy_command(const char *proxy_command, const char *user, 92 const char *host, int port) 93 { 94 char *tmp, *ret, strport[NI_MAXSERV]; 95 96 snprintf(strport, sizeof strport, "%d", port); 97 xasprintf(&tmp, "exec %s", proxy_command); 98 ret = percent_expand(tmp, "h", host, "p", strport, 99 "r", options.user, (char *)NULL); 100 free(tmp); 101 return ret; 102 } 103 104 /* 105 * Connect to the given ssh server using a proxy command that passes a 106 * a connected fd back to us. 107 */ 108 static int 109 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port, 110 const char *proxy_command) 111 { 112 char *command_string; 113 int sp[2], sock; 114 pid_t pid; 115 char *shell; 116 117 if ((shell = getenv("SHELL")) == NULL) 118 shell = _PATH_BSHELL; 119 120 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) 121 fatal("Could not create socketpair to communicate with " 122 "proxy dialer: %.100s", strerror(errno)); 123 124 command_string = expand_proxy_command(proxy_command, options.user, 125 host, port); 126 debug("Executing proxy dialer command: %.500s", command_string); 127 128 /* Fork and execute the proxy command. */ 129 if ((pid = fork()) == 0) { 130 char *argv[10]; 131 132 close(sp[1]); 133 /* Redirect stdin and stdout. */ 134 if (sp[0] != 0) { 135 if (dup2(sp[0], 0) < 0) 136 perror("dup2 stdin"); 137 } 138 if (sp[0] != 1) { 139 if (dup2(sp[0], 1) < 0) 140 perror("dup2 stdout"); 141 } 142 if (sp[0] >= 2) 143 close(sp[0]); 144 145 /* 146 * Stderr is left as it is so that error messages get 147 * printed on the user's terminal. 148 */ 149 argv[0] = shell; 150 argv[1] = "-c"; 151 argv[2] = command_string; 152 argv[3] = NULL; 153 154 /* 155 * Execute the proxy command. 156 * Note that we gave up any extra privileges above. 157 */ 158 execv(argv[0], argv); 159 perror(argv[0]); 160 exit(1); 161 } 162 /* Parent. */ 163 if (pid < 0) 164 fatal("fork failed: %.100s", strerror(errno)); 165 close(sp[0]); 166 free(command_string); 167 168 if ((sock = mm_receive_fd(sp[1])) == -1) 169 fatal("proxy dialer did not pass back a connection"); 170 close(sp[1]); 171 172 while (waitpid(pid, NULL, 0) == -1) 173 if (errno != EINTR) 174 fatal("Couldn't wait for child: %s", strerror(errno)); 175 176 /* Set the connection file descriptors. */ 177 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 178 return -1; /* ssh_packet_set_connection logs error */ 179 180 return 0; 181 } 182 183 /* 184 * Connect to the given ssh server using a proxy command. 185 */ 186 static int 187 ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port, 188 const char *proxy_command) 189 { 190 char *command_string; 191 int pin[2], pout[2]; 192 pid_t pid; 193 char *shell; 194 195 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 196 shell = _PATH_BSHELL; 197 198 /* Create pipes for communicating with the proxy. */ 199 if (pipe(pin) < 0 || pipe(pout) < 0) 200 fatal("Could not create pipes to communicate with the proxy: %.100s", 201 strerror(errno)); 202 203 command_string = expand_proxy_command(proxy_command, options.user, 204 host, port); 205 debug("Executing proxy command: %.500s", command_string); 206 207 /* Fork and execute the proxy command. */ 208 if ((pid = fork()) == 0) { 209 char *argv[10]; 210 211 /* Redirect stdin and stdout. */ 212 close(pin[1]); 213 if (pin[0] != 0) { 214 if (dup2(pin[0], 0) < 0) 215 perror("dup2 stdin"); 216 close(pin[0]); 217 } 218 close(pout[0]); 219 if (dup2(pout[1], 1) < 0) 220 perror("dup2 stdout"); 221 /* Cannot be 1 because pin allocated two descriptors. */ 222 close(pout[1]); 223 224 /* Stderr is left as it is so that error messages get 225 printed on the user's terminal. */ 226 argv[0] = shell; 227 argv[1] = "-c"; 228 argv[2] = command_string; 229 argv[3] = NULL; 230 231 /* Execute the proxy command. Note that we gave up any 232 extra privileges above. */ 233 signal(SIGPIPE, SIG_DFL); 234 execv(argv[0], argv); 235 perror(argv[0]); 236 exit(1); 237 } 238 /* Parent. */ 239 if (pid < 0) 240 fatal("fork failed: %.100s", strerror(errno)); 241 else 242 proxy_command_pid = pid; /* save pid to clean up later */ 243 244 /* Close child side of the descriptors. */ 245 close(pin[0]); 246 close(pout[1]); 247 248 /* Free the command name. */ 249 free(command_string); 250 251 /* Set the connection file descriptors. */ 252 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 253 return -1; /* ssh_packet_set_connection logs error */ 254 255 return 0; 256 } 257 258 void 259 ssh_kill_proxy_command(void) 260 { 261 /* 262 * Send SIGHUP to proxy command if used. We don't wait() in 263 * case it hangs and instead rely on init to reap the child 264 */ 265 if (proxy_command_pid > 1) 266 kill(proxy_command_pid, SIGHUP); 267 } 268 269 #ifdef HAVE_IFADDRS_H 270 /* 271 * Search a interface address list (returned from getifaddrs(3)) for an 272 * address that matches the desired address family on the specified interface. 273 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 274 */ 275 static int 276 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 277 struct sockaddr_storage *resultp, socklen_t *rlenp) 278 { 279 struct sockaddr_in6 *sa6; 280 struct sockaddr_in *sa; 281 struct in6_addr *v6addr; 282 const struct ifaddrs *ifa; 283 int allow_local; 284 285 /* 286 * Prefer addresses that are not loopback or linklocal, but use them 287 * if nothing else matches. 288 */ 289 for (allow_local = 0; allow_local < 2; allow_local++) { 290 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 291 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 292 (ifa->ifa_flags & IFF_UP) == 0 || 293 ifa->ifa_addr->sa_family != af || 294 strcmp(ifa->ifa_name, options.bind_interface) != 0) 295 continue; 296 switch (ifa->ifa_addr->sa_family) { 297 case AF_INET: 298 sa = (struct sockaddr_in *)ifa->ifa_addr; 299 if (!allow_local && sa->sin_addr.s_addr == 300 htonl(INADDR_LOOPBACK)) 301 continue; 302 if (*rlenp < sizeof(struct sockaddr_in)) { 303 error("%s: v4 addr doesn't fit", 304 __func__); 305 return -1; 306 } 307 *rlenp = sizeof(struct sockaddr_in); 308 memcpy(resultp, sa, *rlenp); 309 return 0; 310 case AF_INET6: 311 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 312 v6addr = &sa6->sin6_addr; 313 if (!allow_local && 314 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 315 IN6_IS_ADDR_LOOPBACK(v6addr))) 316 continue; 317 if (*rlenp < sizeof(struct sockaddr_in6)) { 318 error("%s: v6 addr doesn't fit", 319 __func__); 320 return -1; 321 } 322 *rlenp = sizeof(struct sockaddr_in6); 323 memcpy(resultp, sa6, *rlenp); 324 return 0; 325 } 326 } 327 } 328 return -1; 329 } 330 #endif 331 332 /* 333 * Creates a socket for use as the ssh connection. 334 */ 335 static int 336 ssh_create_socket(struct addrinfo *ai) 337 { 338 int sock, r; 339 struct sockaddr_storage bindaddr; 340 socklen_t bindaddrlen = 0; 341 struct addrinfo hints, *res = NULL; 342 #ifdef HAVE_IFADDRS_H 343 struct ifaddrs *ifaddrs = NULL; 344 #endif 345 char ntop[NI_MAXHOST]; 346 347 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 348 if (sock < 0) { 349 error("socket: %s", strerror(errno)); 350 return -1; 351 } 352 fcntl(sock, F_SETFD, FD_CLOEXEC); 353 354 /* Bind the socket to an alternative local IP address */ 355 if (options.bind_address == NULL && options.bind_interface == NULL) 356 return sock; 357 358 if (options.bind_address != NULL) { 359 memset(&hints, 0, sizeof(hints)); 360 hints.ai_family = ai->ai_family; 361 hints.ai_socktype = ai->ai_socktype; 362 hints.ai_protocol = ai->ai_protocol; 363 hints.ai_flags = AI_PASSIVE; 364 if ((r = getaddrinfo(options.bind_address, NULL, 365 &hints, &res)) != 0) { 366 error("getaddrinfo: %s: %s", options.bind_address, 367 ssh_gai_strerror(r)); 368 goto fail; 369 } 370 if (res == NULL) { 371 error("getaddrinfo: no addrs"); 372 goto fail; 373 } 374 if (res->ai_addrlen > sizeof(bindaddr)) { 375 error("%s: addr doesn't fit", __func__); 376 goto fail; 377 } 378 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 379 bindaddrlen = res->ai_addrlen; 380 } else if (options.bind_interface != NULL) { 381 #ifdef HAVE_IFADDRS_H 382 if ((r = getifaddrs(&ifaddrs)) != 0) { 383 error("getifaddrs: %s: %s", options.bind_interface, 384 strerror(errno)); 385 goto fail; 386 } 387 bindaddrlen = sizeof(bindaddr); 388 if (check_ifaddrs(options.bind_interface, ai->ai_family, 389 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 390 logit("getifaddrs: %s: no suitable addresses", 391 options.bind_interface); 392 goto fail; 393 } 394 #else 395 error("BindInterface not supported on this platform."); 396 #endif 397 } 398 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 399 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 400 error("%s: getnameinfo failed: %s", __func__, 401 ssh_gai_strerror(r)); 402 goto fail; 403 } 404 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 405 error("bind %s: %s", ntop, strerror(errno)); 406 goto fail; 407 } 408 debug("%s: bound to %s", __func__, ntop); 409 /* success */ 410 goto out; 411 fail: 412 close(sock); 413 sock = -1; 414 out: 415 if (res != NULL) 416 freeaddrinfo(res); 417 #ifdef HAVE_IFADDRS_H 418 if (ifaddrs != NULL) 419 freeifaddrs(ifaddrs); 420 #endif 421 return sock; 422 } 423 424 /* 425 * Wait up to *timeoutp milliseconds for fd to be readable. Updates 426 * *timeoutp with time remaining. 427 * Returns 0 if fd ready or -1 on timeout or error (see errno). 428 */ 429 static int 430 waitrfd(int fd, int *timeoutp) 431 { 432 struct pollfd pfd; 433 struct timeval t_start; 434 int oerrno, r; 435 436 monotime_tv(&t_start); 437 pfd.fd = fd; 438 pfd.events = POLLIN; 439 for (; *timeoutp >= 0;) { 440 r = poll(&pfd, 1, *timeoutp); 441 oerrno = errno; 442 ms_subtract_diff(&t_start, timeoutp); 443 errno = oerrno; 444 if (r > 0) 445 return 0; 446 else if (r == -1 && errno != EAGAIN) 447 return -1; 448 else if (r == 0) 449 break; 450 } 451 /* timeout */ 452 errno = ETIMEDOUT; 453 return -1; 454 } 455 456 static int 457 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 458 socklen_t addrlen, int *timeoutp) 459 { 460 int optval = 0; 461 socklen_t optlen = sizeof(optval); 462 463 /* No timeout: just do a blocking connect() */ 464 if (*timeoutp <= 0) 465 return connect(sockfd, serv_addr, addrlen); 466 467 set_nonblock(sockfd); 468 if (connect(sockfd, serv_addr, addrlen) == 0) { 469 /* Succeeded already? */ 470 unset_nonblock(sockfd); 471 return 0; 472 } else if (errno != EINPROGRESS) 473 return -1; 474 475 if (waitrfd(sockfd, timeoutp) == -1) 476 return -1; 477 478 /* Completed or failed */ 479 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) { 480 debug("getsockopt: %s", strerror(errno)); 481 return -1; 482 } 483 if (optval != 0) { 484 errno = optval; 485 return -1; 486 } 487 unset_nonblock(sockfd); 488 return 0; 489 } 490 491 /* 492 * Opens a TCP/IP connection to the remote server on the given host. 493 * The address of the remote host will be returned in hostaddr. 494 * If port is 0, the default port will be used. 495 * Connection_attempts specifies the maximum number of tries (one per 496 * second). If proxy_command is non-NULL, it specifies the command (with %h 497 * and %p substituted for host and port, respectively) to use to contact 498 * the daemon. 499 */ 500 static int 501 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 502 struct sockaddr_storage *hostaddr, u_short port, int family, 503 int connection_attempts, int *timeout_ms, int want_keepalive) 504 { 505 int on = 1; 506 int oerrno, sock = -1, attempt; 507 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 508 struct addrinfo *ai; 509 510 debug2("%s", __func__); 511 memset(ntop, 0, sizeof(ntop)); 512 memset(strport, 0, sizeof(strport)); 513 514 for (attempt = 0; attempt < connection_attempts; attempt++) { 515 if (attempt > 0) { 516 /* Sleep a moment before retrying. */ 517 sleep(1); 518 debug("Trying again..."); 519 } 520 /* 521 * Loop through addresses for this host, and try each one in 522 * sequence until the connection succeeds. 523 */ 524 for (ai = aitop; ai; ai = ai->ai_next) { 525 if (ai->ai_family != AF_INET && 526 ai->ai_family != AF_INET6) { 527 errno = EAFNOSUPPORT; 528 continue; 529 } 530 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 531 ntop, sizeof(ntop), strport, sizeof(strport), 532 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 533 oerrno = errno; 534 error("%s: getnameinfo failed", __func__); 535 errno = oerrno; 536 continue; 537 } 538 debug("Connecting to %.200s [%.100s] port %s.", 539 host, ntop, strport); 540 541 /* Create a socket for connecting. */ 542 sock = ssh_create_socket(ai); 543 if (sock < 0) { 544 /* Any error is already output */ 545 errno = 0; 546 continue; 547 } 548 549 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 550 timeout_ms) >= 0) { 551 /* Successful connection. */ 552 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 553 break; 554 } else { 555 oerrno = errno; 556 debug("connect to address %s port %s: %s", 557 ntop, strport, strerror(errno)); 558 close(sock); 559 sock = -1; 560 errno = oerrno; 561 } 562 } 563 if (sock != -1) 564 break; /* Successful connection. */ 565 } 566 567 /* Return failure if we didn't get a successful connection. */ 568 if (sock == -1) { 569 error("ssh: connect to host %s port %s: %s", 570 host, strport, errno == 0 ? "failure" : strerror(errno)); 571 return -1; 572 } 573 574 debug("Connection established."); 575 576 /* Set SO_KEEPALIVE if requested. */ 577 if (want_keepalive && 578 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 579 sizeof(on)) < 0) 580 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 581 582 /* Set the connection. */ 583 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 584 return -1; /* ssh_packet_set_connection logs error */ 585 586 return 0; 587 } 588 589 int 590 ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs, 591 struct sockaddr_storage *hostaddr, u_short port, int family, 592 int connection_attempts, int *timeout_ms, int want_keepalive) 593 { 594 if (options.proxy_command == NULL) { 595 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 596 family, connection_attempts, timeout_ms, want_keepalive); 597 } else if (strcmp(options.proxy_command, "-") == 0) { 598 if ((ssh_packet_set_connection(ssh, 599 STDIN_FILENO, STDOUT_FILENO)) == NULL) 600 return -1; /* ssh_packet_set_connection logs error */ 601 return 0; 602 } else if (options.proxy_use_fdpass) { 603 return ssh_proxy_fdpass_connect(ssh, host, port, 604 options.proxy_command); 605 } 606 return ssh_proxy_connect(ssh, host, port, options.proxy_command); 607 } 608 609 static void 610 send_client_banner(int connection_out, int minor1) 611 { 612 /* Send our own protocol version identification. */ 613 xasprintf(&client_version_string, "SSH-%d.%d-%.100s%s%s\n", 614 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION, 615 *options.version_addendum == '\0' ? "" : " ", 616 options.version_addendum); 617 if (atomicio(vwrite, connection_out, client_version_string, 618 strlen(client_version_string)) != strlen(client_version_string)) 619 fatal("write: %.100s", strerror(errno)); 620 chop(client_version_string); 621 debug("Local version string %.100s", client_version_string); 622 } 623 624 /* 625 * Waits for the server identification string, and sends our own 626 * identification string. 627 */ 628 void 629 ssh_exchange_identification(int timeout_ms) 630 { 631 char buf[256], remote_version[256]; /* must be same size! */ 632 int remote_major, remote_minor, mismatch; 633 int connection_in = packet_get_connection_in(); 634 int connection_out = packet_get_connection_out(); 635 u_int i, n; 636 size_t len; 637 int rc; 638 639 send_client_banner(connection_out, 0); 640 641 /* Read other side's version identification. */ 642 for (n = 0;;) { 643 for (i = 0; i < sizeof(buf) - 1; i++) { 644 if (timeout_ms > 0) { 645 rc = waitrfd(connection_in, &timeout_ms); 646 if (rc == -1 && errno == ETIMEDOUT) { 647 fatal("Connection timed out during " 648 "banner exchange"); 649 } else if (rc == -1) { 650 fatal("%s: %s", 651 __func__, strerror(errno)); 652 } 653 } 654 655 len = atomicio(read, connection_in, &buf[i], 1); 656 if (len != 1 && errno == EPIPE) 657 fatal("ssh_exchange_identification: " 658 "Connection closed by remote host"); 659 else if (len != 1) 660 fatal("ssh_exchange_identification: " 661 "read: %.100s", strerror(errno)); 662 if (buf[i] == '\r') { 663 buf[i] = '\n'; 664 buf[i + 1] = 0; 665 continue; /**XXX wait for \n */ 666 } 667 if (buf[i] == '\n') { 668 buf[i + 1] = 0; 669 break; 670 } 671 if (++n > 65536) 672 fatal("ssh_exchange_identification: " 673 "No banner received"); 674 } 675 buf[sizeof(buf) - 1] = 0; 676 if (strncmp(buf, "SSH-", 4) == 0) 677 break; 678 debug("ssh_exchange_identification: %s", buf); 679 } 680 server_version_string = xstrdup(buf); 681 682 /* 683 * Check that the versions match. In future this might accept 684 * several versions and set appropriate flags to handle them. 685 */ 686 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 687 &remote_major, &remote_minor, remote_version) != 3) 688 fatal("Bad remote protocol version identification: '%.100s'", buf); 689 debug("Remote protocol version %d.%d, remote software version %.100s", 690 remote_major, remote_minor, remote_version); 691 692 active_state->compat = compat_datafellows(remote_version); 693 mismatch = 0; 694 695 switch (remote_major) { 696 case 2: 697 break; 698 case 1: 699 if (remote_minor != 99) 700 mismatch = 1; 701 break; 702 default: 703 mismatch = 1; 704 break; 705 } 706 if (mismatch) 707 fatal("Protocol major versions differ: %d vs. %d", 708 PROTOCOL_MAJOR_2, remote_major); 709 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) 710 logit("Server version \"%.100s\" uses unsafe RSA signature " 711 "scheme; disabling use of RSA keys", remote_version); 712 chop(server_version_string); 713 } 714 715 /* defaults to 'no' */ 716 static int 717 confirm(const char *prompt) 718 { 719 const char *msg, *again = "Please type 'yes' or 'no': "; 720 char *p; 721 int ret = -1; 722 723 if (options.batch_mode) 724 return 0; 725 for (msg = prompt;;msg = again) { 726 p = read_passphrase(msg, RP_ECHO); 727 if (p == NULL) 728 return 0; 729 p[strcspn(p, "\n")] = '\0'; 730 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 731 ret = 0; 732 else if (strcasecmp(p, "yes") == 0) 733 ret = 1; 734 free(p); 735 if (ret != -1) 736 return ret; 737 } 738 } 739 740 static int 741 check_host_cert(const char *host, const struct sshkey *key) 742 { 743 const char *reason; 744 int r; 745 746 if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) { 747 error("%s", reason); 748 return 0; 749 } 750 if (sshbuf_len(key->cert->critical) != 0) { 751 error("Certificate for %s contains unsupported " 752 "critical options(s)", host); 753 return 0; 754 } 755 if ((r = sshkey_check_cert_sigtype(key, 756 options.ca_sign_algorithms)) != 0) { 757 logit("%s: certificate signature algorithm %s: %s", __func__, 758 (key->cert == NULL || key->cert->signature_type == NULL) ? 759 "(null)" : key->cert->signature_type, ssh_err(r)); 760 return 0; 761 } 762 763 return 1; 764 } 765 766 static int 767 sockaddr_is_local(struct sockaddr *hostaddr) 768 { 769 switch (hostaddr->sa_family) { 770 case AF_INET: 771 return (ntohl(((struct sockaddr_in *)hostaddr)-> 772 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 773 case AF_INET6: 774 return IN6_IS_ADDR_LOOPBACK( 775 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 776 default: 777 return 0; 778 } 779 } 780 781 /* 782 * Prepare the hostname and ip address strings that are used to lookup 783 * host keys in known_hosts files. These may have a port number appended. 784 */ 785 void 786 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 787 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 788 { 789 char ntop[NI_MAXHOST]; 790 socklen_t addrlen; 791 792 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 793 case -1: 794 addrlen = 0; 795 break; 796 case AF_INET: 797 addrlen = sizeof(struct sockaddr_in); 798 break; 799 case AF_INET6: 800 addrlen = sizeof(struct sockaddr_in6); 801 break; 802 default: 803 addrlen = sizeof(struct sockaddr); 804 break; 805 } 806 807 /* 808 * We don't have the remote ip-address for connections 809 * using a proxy command 810 */ 811 if (hostfile_ipaddr != NULL) { 812 if (options.proxy_command == NULL) { 813 if (getnameinfo(hostaddr, addrlen, 814 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 815 fatal("%s: getnameinfo failed", __func__); 816 *hostfile_ipaddr = put_host_port(ntop, port); 817 } else { 818 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 819 "command>"); 820 } 821 } 822 823 /* 824 * Allow the user to record the key under a different name or 825 * differentiate a non-standard port. This is useful for ssh 826 * tunneling over forwarded connections or if you run multiple 827 * sshd's on different ports on the same machine. 828 */ 829 if (hostfile_hostname != NULL) { 830 if (options.host_key_alias != NULL) { 831 *hostfile_hostname = xstrdup(options.host_key_alias); 832 debug("using hostkeyalias: %s", *hostfile_hostname); 833 } else { 834 *hostfile_hostname = put_host_port(hostname, port); 835 } 836 } 837 } 838 839 /* 840 * check whether the supplied host key is valid, return -1 if the key 841 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 842 */ 843 #define RDRW 0 844 #define RDONLY 1 845 #define ROQUIET 2 846 static int 847 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 848 struct sshkey *host_key, int readonly, 849 char **user_hostfiles, u_int num_user_hostfiles, 850 char **system_hostfiles, u_int num_system_hostfiles) 851 { 852 HostStatus host_status; 853 HostStatus ip_status; 854 struct sshkey *raw_key = NULL; 855 char *ip = NULL, *host = NULL; 856 char hostline[1000], *hostp, *fp, *ra; 857 char msg[1024]; 858 const char *type; 859 const struct hostkey_entry *host_found, *ip_found; 860 int len, cancelled_forwarding = 0; 861 int local = sockaddr_is_local(hostaddr); 862 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 863 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 864 struct hostkeys *host_hostkeys, *ip_hostkeys; 865 u_int i; 866 867 /* 868 * Force accepting of the host key for loopback/localhost. The 869 * problem is that if the home directory is NFS-mounted to multiple 870 * machines, localhost will refer to a different machine in each of 871 * them, and the user will get bogus HOST_CHANGED warnings. This 872 * essentially disables host authentication for localhost; however, 873 * this is probably not a real problem. 874 */ 875 if (options.no_host_authentication_for_localhost == 1 && local && 876 options.host_key_alias == NULL) { 877 debug("Forcing accepting of host key for " 878 "loopback/localhost."); 879 return 0; 880 } 881 882 /* 883 * Prepare the hostname and address strings used for hostkey lookup. 884 * In some cases, these will have a port number appended. 885 */ 886 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 887 888 /* 889 * Turn off check_host_ip if the connection is to localhost, via proxy 890 * command or if we don't have a hostname to compare with 891 */ 892 if (options.check_host_ip && (local || 893 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 894 options.check_host_ip = 0; 895 896 host_hostkeys = init_hostkeys(); 897 for (i = 0; i < num_user_hostfiles; i++) 898 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 899 for (i = 0; i < num_system_hostfiles; i++) 900 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 901 902 ip_hostkeys = NULL; 903 if (!want_cert && options.check_host_ip) { 904 ip_hostkeys = init_hostkeys(); 905 for (i = 0; i < num_user_hostfiles; i++) 906 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 907 for (i = 0; i < num_system_hostfiles; i++) 908 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 909 } 910 911 retry: 912 /* Reload these as they may have changed on cert->key downgrade */ 913 want_cert = sshkey_is_cert(host_key); 914 type = sshkey_type(host_key); 915 916 /* 917 * Check if the host key is present in the user's list of known 918 * hosts or in the systemwide list. 919 */ 920 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 921 &host_found); 922 923 /* 924 * Also perform check for the ip address, skip the check if we are 925 * localhost, looking for a certificate, or the hostname was an ip 926 * address to begin with. 927 */ 928 if (!want_cert && ip_hostkeys != NULL) { 929 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 930 &ip_found); 931 if (host_status == HOST_CHANGED && 932 (ip_status != HOST_CHANGED || 933 (ip_found != NULL && 934 !sshkey_equal(ip_found->key, host_found->key)))) 935 host_ip_differ = 1; 936 } else 937 ip_status = host_status; 938 939 switch (host_status) { 940 case HOST_OK: 941 /* The host is known and the key matches. */ 942 debug("Host '%.200s' is known and matches the %s host %s.", 943 host, type, want_cert ? "certificate" : "key"); 944 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 945 host_found->file, host_found->line); 946 if (want_cert && 947 !check_host_cert(options.host_key_alias == NULL ? 948 hostname : options.host_key_alias, host_key)) 949 goto fail; 950 if (options.check_host_ip && ip_status == HOST_NEW) { 951 if (readonly || want_cert) 952 logit("%s host key for IP address " 953 "'%.128s' not in list of known hosts.", 954 type, ip); 955 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 956 host_key, options.hash_known_hosts)) 957 logit("Failed to add the %s host key for IP " 958 "address '%.128s' to the list of known " 959 "hosts (%.500s).", type, ip, 960 user_hostfiles[0]); 961 else 962 logit("Warning: Permanently added the %s host " 963 "key for IP address '%.128s' to the list " 964 "of known hosts.", type, ip); 965 } else if (options.visual_host_key) { 966 fp = sshkey_fingerprint(host_key, 967 options.fingerprint_hash, SSH_FP_DEFAULT); 968 ra = sshkey_fingerprint(host_key, 969 options.fingerprint_hash, SSH_FP_RANDOMART); 970 if (fp == NULL || ra == NULL) 971 fatal("%s: sshkey_fingerprint fail", __func__); 972 logit("Host key fingerprint is %s\n%s", fp, ra); 973 free(ra); 974 free(fp); 975 } 976 hostkey_trusted = 1; 977 break; 978 case HOST_NEW: 979 if (options.host_key_alias == NULL && port != 0 && 980 port != SSH_DEFAULT_PORT) { 981 debug("checking without port identifier"); 982 if (check_host_key(hostname, hostaddr, 0, host_key, 983 ROQUIET, user_hostfiles, num_user_hostfiles, 984 system_hostfiles, num_system_hostfiles) == 0) { 985 debug("found matching key w/out port"); 986 break; 987 } 988 } 989 if (readonly || want_cert) 990 goto fail; 991 /* The host is new. */ 992 if (options.strict_host_key_checking == 993 SSH_STRICT_HOSTKEY_YES) { 994 /* 995 * User has requested strict host key checking. We 996 * will not add the host key automatically. The only 997 * alternative left is to abort. 998 */ 999 error("No %s host key is known for %.200s and you " 1000 "have requested strict checking.", type, host); 1001 goto fail; 1002 } else if (options.strict_host_key_checking == 1003 SSH_STRICT_HOSTKEY_ASK) { 1004 char msg1[1024], msg2[1024]; 1005 1006 if (show_other_keys(host_hostkeys, host_key)) 1007 snprintf(msg1, sizeof(msg1), 1008 "\nbut keys of different type are already" 1009 " known for this host."); 1010 else 1011 snprintf(msg1, sizeof(msg1), "."); 1012 /* The default */ 1013 fp = sshkey_fingerprint(host_key, 1014 options.fingerprint_hash, SSH_FP_DEFAULT); 1015 ra = sshkey_fingerprint(host_key, 1016 options.fingerprint_hash, SSH_FP_RANDOMART); 1017 if (fp == NULL || ra == NULL) 1018 fatal("%s: sshkey_fingerprint fail", __func__); 1019 msg2[0] = '\0'; 1020 if (options.verify_host_key_dns) { 1021 if (matching_host_key_dns) 1022 snprintf(msg2, sizeof(msg2), 1023 "Matching host key fingerprint" 1024 " found in DNS.\n"); 1025 else 1026 snprintf(msg2, sizeof(msg2), 1027 "No matching host key fingerprint" 1028 " found in DNS.\n"); 1029 } 1030 snprintf(msg, sizeof(msg), 1031 "The authenticity of host '%.200s (%s)' can't be " 1032 "established%s\n" 1033 "%s key fingerprint is %s.%s%s\n%s" 1034 "Are you sure you want to continue connecting " 1035 "(yes/no)? ", 1036 host, ip, msg1, type, fp, 1037 options.visual_host_key ? "\n" : "", 1038 options.visual_host_key ? ra : "", 1039 msg2); 1040 free(ra); 1041 free(fp); 1042 if (!confirm(msg)) 1043 goto fail; 1044 hostkey_trusted = 1; /* user explicitly confirmed */ 1045 } 1046 /* 1047 * If in "new" or "off" strict mode, add the key automatically 1048 * to the local known_hosts file. 1049 */ 1050 if (options.check_host_ip && ip_status == HOST_NEW) { 1051 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1052 hostp = hostline; 1053 if (options.hash_known_hosts) { 1054 /* Add hash of host and IP separately */ 1055 r = add_host_to_hostfile(user_hostfiles[0], 1056 host, host_key, options.hash_known_hosts) && 1057 add_host_to_hostfile(user_hostfiles[0], ip, 1058 host_key, options.hash_known_hosts); 1059 } else { 1060 /* Add unhashed "host,ip" */ 1061 r = add_host_to_hostfile(user_hostfiles[0], 1062 hostline, host_key, 1063 options.hash_known_hosts); 1064 } 1065 } else { 1066 r = add_host_to_hostfile(user_hostfiles[0], host, 1067 host_key, options.hash_known_hosts); 1068 hostp = host; 1069 } 1070 1071 if (!r) 1072 logit("Failed to add the host to the list of known " 1073 "hosts (%.500s).", user_hostfiles[0]); 1074 else 1075 logit("Warning: Permanently added '%.200s' (%s) to the " 1076 "list of known hosts.", hostp, type); 1077 break; 1078 case HOST_REVOKED: 1079 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1080 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1081 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1082 error("The %s host key for %s is marked as revoked.", type, host); 1083 error("This could mean that a stolen key is being used to"); 1084 error("impersonate this host."); 1085 1086 /* 1087 * If strict host key checking is in use, the user will have 1088 * to edit the key manually and we can only abort. 1089 */ 1090 if (options.strict_host_key_checking != 1091 SSH_STRICT_HOSTKEY_OFF) { 1092 error("%s host key for %.200s was revoked and you have " 1093 "requested strict checking.", type, host); 1094 goto fail; 1095 } 1096 goto continue_unsafe; 1097 1098 case HOST_CHANGED: 1099 if (want_cert) { 1100 /* 1101 * This is only a debug() since it is valid to have 1102 * CAs with wildcard DNS matches that don't match 1103 * all hosts that one might visit. 1104 */ 1105 debug("Host certificate authority does not " 1106 "match %s in %s:%lu", CA_MARKER, 1107 host_found->file, host_found->line); 1108 goto fail; 1109 } 1110 if (readonly == ROQUIET) 1111 goto fail; 1112 if (options.check_host_ip && host_ip_differ) { 1113 char *key_msg; 1114 if (ip_status == HOST_NEW) 1115 key_msg = "is unknown"; 1116 else if (ip_status == HOST_OK) 1117 key_msg = "is unchanged"; 1118 else 1119 key_msg = "has a different value"; 1120 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1121 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1122 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1123 error("The %s host key for %s has changed,", type, host); 1124 error("and the key for the corresponding IP address %s", ip); 1125 error("%s. This could either mean that", key_msg); 1126 error("DNS SPOOFING is happening or the IP address for the host"); 1127 error("and its host key have changed at the same time."); 1128 if (ip_status != HOST_NEW) 1129 error("Offending key for IP in %s:%lu", 1130 ip_found->file, ip_found->line); 1131 } 1132 /* The host key has changed. */ 1133 warn_changed_key(host_key); 1134 error("Add correct host key in %.100s to get rid of this message.", 1135 user_hostfiles[0]); 1136 error("Offending %s key in %s:%lu", 1137 sshkey_type(host_found->key), 1138 host_found->file, host_found->line); 1139 1140 /* 1141 * If strict host key checking is in use, the user will have 1142 * to edit the key manually and we can only abort. 1143 */ 1144 if (options.strict_host_key_checking != 1145 SSH_STRICT_HOSTKEY_OFF) { 1146 error("%s host key for %.200s has changed and you have " 1147 "requested strict checking.", type, host); 1148 goto fail; 1149 } 1150 1151 continue_unsafe: 1152 /* 1153 * If strict host key checking has not been requested, allow 1154 * the connection but without MITM-able authentication or 1155 * forwarding. 1156 */ 1157 if (options.password_authentication) { 1158 error("Password authentication is disabled to avoid " 1159 "man-in-the-middle attacks."); 1160 options.password_authentication = 0; 1161 cancelled_forwarding = 1; 1162 } 1163 if (options.kbd_interactive_authentication) { 1164 error("Keyboard-interactive authentication is disabled" 1165 " to avoid man-in-the-middle attacks."); 1166 options.kbd_interactive_authentication = 0; 1167 options.challenge_response_authentication = 0; 1168 cancelled_forwarding = 1; 1169 } 1170 if (options.challenge_response_authentication) { 1171 error("Challenge/response authentication is disabled" 1172 " to avoid man-in-the-middle attacks."); 1173 options.challenge_response_authentication = 0; 1174 cancelled_forwarding = 1; 1175 } 1176 if (options.forward_agent) { 1177 error("Agent forwarding is disabled to avoid " 1178 "man-in-the-middle attacks."); 1179 options.forward_agent = 0; 1180 cancelled_forwarding = 1; 1181 } 1182 if (options.forward_x11) { 1183 error("X11 forwarding is disabled to avoid " 1184 "man-in-the-middle attacks."); 1185 options.forward_x11 = 0; 1186 cancelled_forwarding = 1; 1187 } 1188 if (options.num_local_forwards > 0 || 1189 options.num_remote_forwards > 0) { 1190 error("Port forwarding is disabled to avoid " 1191 "man-in-the-middle attacks."); 1192 options.num_local_forwards = 1193 options.num_remote_forwards = 0; 1194 cancelled_forwarding = 1; 1195 } 1196 if (options.tun_open != SSH_TUNMODE_NO) { 1197 error("Tunnel forwarding is disabled to avoid " 1198 "man-in-the-middle attacks."); 1199 options.tun_open = SSH_TUNMODE_NO; 1200 cancelled_forwarding = 1; 1201 } 1202 if (options.exit_on_forward_failure && cancelled_forwarding) 1203 fatal("Error: forwarding disabled due to host key " 1204 "check failure"); 1205 1206 /* 1207 * XXX Should permit the user to change to use the new id. 1208 * This could be done by converting the host key to an 1209 * identifying sentence, tell that the host identifies itself 1210 * by that sentence, and ask the user if he/she wishes to 1211 * accept the authentication. 1212 */ 1213 break; 1214 case HOST_FOUND: 1215 fatal("internal error"); 1216 break; 1217 } 1218 1219 if (options.check_host_ip && host_status != HOST_CHANGED && 1220 ip_status == HOST_CHANGED) { 1221 snprintf(msg, sizeof(msg), 1222 "Warning: the %s host key for '%.200s' " 1223 "differs from the key for the IP address '%.128s'" 1224 "\nOffending key for IP in %s:%lu", 1225 type, host, ip, ip_found->file, ip_found->line); 1226 if (host_status == HOST_OK) { 1227 len = strlen(msg); 1228 snprintf(msg + len, sizeof(msg) - len, 1229 "\nMatching host key in %s:%lu", 1230 host_found->file, host_found->line); 1231 } 1232 if (options.strict_host_key_checking == 1233 SSH_STRICT_HOSTKEY_ASK) { 1234 strlcat(msg, "\nAre you sure you want " 1235 "to continue connecting (yes/no)? ", sizeof(msg)); 1236 if (!confirm(msg)) 1237 goto fail; 1238 } else if (options.strict_host_key_checking != 1239 SSH_STRICT_HOSTKEY_OFF) { 1240 logit("%s", msg); 1241 error("Exiting, you have requested strict checking."); 1242 goto fail; 1243 } else { 1244 logit("%s", msg); 1245 } 1246 } 1247 1248 if (!hostkey_trusted && options.update_hostkeys) { 1249 debug("%s: hostkey not known or explicitly trusted: " 1250 "disabling UpdateHostkeys", __func__); 1251 options.update_hostkeys = 0; 1252 } 1253 1254 free(ip); 1255 free(host); 1256 if (host_hostkeys != NULL) 1257 free_hostkeys(host_hostkeys); 1258 if (ip_hostkeys != NULL) 1259 free_hostkeys(ip_hostkeys); 1260 return 0; 1261 1262 fail: 1263 if (want_cert && host_status != HOST_REVOKED) { 1264 /* 1265 * No matching certificate. Downgrade cert to raw key and 1266 * search normally. 1267 */ 1268 debug("No matching CA found. Retry with plain key"); 1269 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1270 fatal("%s: sshkey_from_private: %s", 1271 __func__, ssh_err(r)); 1272 if ((r = sshkey_drop_cert(raw_key)) != 0) 1273 fatal("Couldn't drop certificate: %s", ssh_err(r)); 1274 host_key = raw_key; 1275 goto retry; 1276 } 1277 sshkey_free(raw_key); 1278 free(ip); 1279 free(host); 1280 if (host_hostkeys != NULL) 1281 free_hostkeys(host_hostkeys); 1282 if (ip_hostkeys != NULL) 1283 free_hostkeys(ip_hostkeys); 1284 return -1; 1285 } 1286 1287 /* returns 0 if key verifies or -1 if key does NOT verify */ 1288 int 1289 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key) 1290 { 1291 u_int i; 1292 int r = -1, flags = 0; 1293 char valid[64], *fp = NULL, *cafp = NULL; 1294 struct sshkey *plain = NULL; 1295 1296 if ((fp = sshkey_fingerprint(host_key, 1297 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1298 error("%s: fingerprint host key: %s", __func__, ssh_err(r)); 1299 r = -1; 1300 goto out; 1301 } 1302 1303 if (sshkey_is_cert(host_key)) { 1304 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1305 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1306 error("%s: fingerprint CA key: %s", 1307 __func__, ssh_err(r)); 1308 r = -1; 1309 goto out; 1310 } 1311 sshkey_format_cert_validity(host_key->cert, 1312 valid, sizeof(valid)); 1313 debug("Server host certificate: %s %s, serial %llu " 1314 "ID \"%s\" CA %s %s valid %s", 1315 sshkey_ssh_name(host_key), fp, 1316 (unsigned long long)host_key->cert->serial, 1317 host_key->cert->key_id, 1318 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1319 valid); 1320 for (i = 0; i < host_key->cert->nprincipals; i++) { 1321 debug2("Server host certificate hostname: %s", 1322 host_key->cert->principals[i]); 1323 } 1324 } else { 1325 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1326 } 1327 1328 if (sshkey_equal(previous_host_key, host_key)) { 1329 debug2("%s: server host key %s %s matches cached key", 1330 __func__, sshkey_type(host_key), fp); 1331 r = 0; 1332 goto out; 1333 } 1334 1335 /* Check in RevokedHostKeys file if specified */ 1336 if (options.revoked_host_keys != NULL) { 1337 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1338 switch (r) { 1339 case 0: 1340 break; /* not revoked */ 1341 case SSH_ERR_KEY_REVOKED: 1342 error("Host key %s %s revoked by file %s", 1343 sshkey_type(host_key), fp, 1344 options.revoked_host_keys); 1345 r = -1; 1346 goto out; 1347 default: 1348 error("Error checking host key %s %s in " 1349 "revoked keys file %s: %s", sshkey_type(host_key), 1350 fp, options.revoked_host_keys, ssh_err(r)); 1351 r = -1; 1352 goto out; 1353 } 1354 } 1355 1356 if (options.verify_host_key_dns) { 1357 /* 1358 * XXX certs are not yet supported for DNS, so downgrade 1359 * them and try the plain key. 1360 */ 1361 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1362 goto out; 1363 if (sshkey_is_cert(plain)) 1364 sshkey_drop_cert(plain); 1365 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1366 if (flags & DNS_VERIFY_FOUND) { 1367 if (options.verify_host_key_dns == 1 && 1368 flags & DNS_VERIFY_MATCH && 1369 flags & DNS_VERIFY_SECURE) { 1370 r = 0; 1371 goto out; 1372 } 1373 if (flags & DNS_VERIFY_MATCH) { 1374 matching_host_key_dns = 1; 1375 } else { 1376 warn_changed_key(plain); 1377 error("Update the SSHFP RR in DNS " 1378 "with the new host key to get rid " 1379 "of this message."); 1380 } 1381 } 1382 } 1383 } 1384 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1385 options.user_hostfiles, options.num_user_hostfiles, 1386 options.system_hostfiles, options.num_system_hostfiles); 1387 1388 out: 1389 sshkey_free(plain); 1390 free(fp); 1391 free(cafp); 1392 if (r == 0 && host_key != NULL) { 1393 sshkey_free(previous_host_key); 1394 r = sshkey_from_private(host_key, &previous_host_key); 1395 } 1396 1397 return r; 1398 } 1399 1400 /* 1401 * Starts a dialog with the server, and authenticates the current user on the 1402 * server. This does not need any extra privileges. The basic connection 1403 * to the server must already have been established before this is called. 1404 * If login fails, this function prints an error and never returns. 1405 * This function does not require super-user privileges. 1406 */ 1407 void 1408 ssh_login(Sensitive *sensitive, const char *orighost, 1409 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1410 { 1411 char *host; 1412 char *server_user, *local_user; 1413 1414 local_user = xstrdup(pw->pw_name); 1415 server_user = options.user ? options.user : local_user; 1416 1417 /* Convert the user-supplied hostname into all lowercase. */ 1418 host = xstrdup(orighost); 1419 lowercase(host); 1420 1421 /* Exchange protocol version identification strings with the server. */ 1422 ssh_exchange_identification(timeout_ms); 1423 1424 /* Put the connection into non-blocking mode. */ 1425 packet_set_nonblocking(); 1426 1427 /* key exchange */ 1428 /* authenticate user */ 1429 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1430 ssh_kex2(host, hostaddr, port); 1431 ssh_userauth2(local_user, server_user, host, sensitive); 1432 free(local_user); 1433 } 1434 1435 void 1436 ssh_put_password(char *password) 1437 { 1438 int size; 1439 char *padded; 1440 1441 if (datafellows & SSH_BUG_PASSWORDPAD) { 1442 packet_put_cstring(password); 1443 return; 1444 } 1445 size = ROUNDUP(strlen(password) + 1, 32); 1446 padded = xcalloc(1, size); 1447 strlcpy(padded, password, size); 1448 packet_put_string(padded, size); 1449 explicit_bzero(padded, size); 1450 free(padded); 1451 } 1452 1453 /* print all known host keys for a given host, but skip keys of given type */ 1454 static int 1455 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1456 { 1457 int type[] = { 1458 KEY_RSA, 1459 KEY_DSA, 1460 KEY_ECDSA, 1461 KEY_ED25519, 1462 KEY_XMSS, 1463 -1 1464 }; 1465 int i, ret = 0; 1466 char *fp, *ra; 1467 const struct hostkey_entry *found; 1468 1469 for (i = 0; type[i] != -1; i++) { 1470 if (type[i] == key->type) 1471 continue; 1472 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1473 continue; 1474 fp = sshkey_fingerprint(found->key, 1475 options.fingerprint_hash, SSH_FP_DEFAULT); 1476 ra = sshkey_fingerprint(found->key, 1477 options.fingerprint_hash, SSH_FP_RANDOMART); 1478 if (fp == NULL || ra == NULL) 1479 fatal("%s: sshkey_fingerprint fail", __func__); 1480 logit("WARNING: %s key found for host %s\n" 1481 "in %s:%lu\n" 1482 "%s key fingerprint %s.", 1483 sshkey_type(found->key), 1484 found->host, found->file, found->line, 1485 sshkey_type(found->key), fp); 1486 if (options.visual_host_key) 1487 logit("%s", ra); 1488 free(ra); 1489 free(fp); 1490 ret = 1; 1491 } 1492 return ret; 1493 } 1494 1495 static void 1496 warn_changed_key(struct sshkey *host_key) 1497 { 1498 char *fp; 1499 1500 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1501 SSH_FP_DEFAULT); 1502 if (fp == NULL) 1503 fatal("%s: sshkey_fingerprint fail", __func__); 1504 1505 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1506 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1507 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1508 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1509 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1510 error("It is also possible that a host key has just been changed."); 1511 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1512 sshkey_type(host_key), fp); 1513 error("Please contact your system administrator."); 1514 1515 free(fp); 1516 } 1517 1518 /* 1519 * Execute a local command 1520 */ 1521 int 1522 ssh_local_cmd(const char *args) 1523 { 1524 char *shell; 1525 pid_t pid; 1526 int status; 1527 void (*osighand)(int); 1528 1529 if (!options.permit_local_command || 1530 args == NULL || !*args) 1531 return (1); 1532 1533 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1534 shell = _PATH_BSHELL; 1535 1536 osighand = signal(SIGCHLD, SIG_DFL); 1537 pid = fork(); 1538 if (pid == 0) { 1539 signal(SIGPIPE, SIG_DFL); 1540 debug3("Executing %s -c \"%s\"", shell, args); 1541 execl(shell, shell, "-c", args, (char *)NULL); 1542 error("Couldn't execute %s -c \"%s\": %s", 1543 shell, args, strerror(errno)); 1544 _exit(1); 1545 } else if (pid == -1) 1546 fatal("fork failed: %.100s", strerror(errno)); 1547 while (waitpid(pid, &status, 0) == -1) 1548 if (errno != EINTR) 1549 fatal("Couldn't wait for child: %s", strerror(errno)); 1550 signal(SIGCHLD, osighand); 1551 1552 if (!WIFEXITED(status)) 1553 return (1); 1554 1555 return (WEXITSTATUS(status)); 1556 } 1557 1558 void 1559 maybe_add_key_to_agent(char *authfile, const struct sshkey *private, 1560 char *comment, char *passphrase) 1561 { 1562 int auth_sock = -1, r; 1563 1564 if (options.add_keys_to_agent == 0) 1565 return; 1566 1567 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1568 debug3("no authentication agent, not adding key"); 1569 return; 1570 } 1571 1572 if (options.add_keys_to_agent == 2 && 1573 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1574 debug3("user denied adding this key"); 1575 close(auth_sock); 1576 return; 1577 } 1578 1579 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0, 1580 (options.add_keys_to_agent == 3), 0)) == 0) 1581 debug("identity added to agent: %s", authfile); 1582 else 1583 debug("could not add identity to agent: %s (%d)", authfile, r); 1584 close(auth_sock); 1585 } 1586