1 /* $OpenBSD: sshconnect.c,v 1.297 2018/02/23 15:58:38 markus 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 <sys/types.h> 17 #include <sys/wait.h> 18 #include <sys/stat.h> 19 #include <sys/socket.h> 20 #include <sys/time.h> 21 22 #include <net/if.h> 23 #include <netinet/in.h> 24 25 #include <ctype.h> 26 #include <errno.h> 27 #include <fcntl.h> 28 #include <netdb.h> 29 #include <paths.h> 30 #include <poll.h> 31 #include <signal.h> 32 #include <pwd.h> 33 #include <stdio.h> 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 #include <ifaddrs.h> 38 39 #include "xmalloc.h" 40 #include "ssh.h" 41 #include "buffer.h" 42 #include "packet.h" 43 #include "uidswap.h" 44 #include "compat.h" 45 #include "key.h" 46 #include "sshconnect.h" 47 #include "hostfile.h" 48 #include "log.h" 49 #include "misc.h" 50 #include "readconf.h" 51 #include "atomicio.h" 52 #include "dns.h" 53 #include "monitor_fdpass.h" 54 #include "ssh2.h" 55 #include "version.h" 56 #include "authfile.h" 57 #include "ssherr.h" 58 #include "authfd.h" 59 60 char *client_version_string = NULL; 61 char *server_version_string = NULL; 62 struct sshkey *previous_host_key = NULL; 63 64 static int matching_host_key_dns = 0; 65 66 static pid_t proxy_command_pid = 0; 67 68 /* import */ 69 extern Options options; 70 extern char *__progname; 71 extern uid_t original_real_uid; 72 extern uid_t original_effective_uid; 73 74 static int show_other_keys(struct hostkeys *, struct sshkey *); 75 static void warn_changed_key(struct sshkey *); 76 77 /* Expand a proxy command */ 78 static char * 79 expand_proxy_command(const char *proxy_command, const char *user, 80 const char *host, int port) 81 { 82 char *tmp, *ret, strport[NI_MAXSERV]; 83 84 snprintf(strport, sizeof strport, "%d", port); 85 xasprintf(&tmp, "exec %s", proxy_command); 86 ret = percent_expand(tmp, "h", host, "p", strport, 87 "r", options.user, (char *)NULL); 88 free(tmp); 89 return ret; 90 } 91 92 /* 93 * Connect to the given ssh server using a proxy command that passes a 94 * a connected fd back to us. 95 */ 96 static int 97 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port, 98 const char *proxy_command) 99 { 100 char *command_string; 101 int sp[2], sock; 102 pid_t pid; 103 char *shell; 104 105 if ((shell = getenv("SHELL")) == NULL) 106 shell = _PATH_BSHELL; 107 108 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) 109 fatal("Could not create socketpair to communicate with " 110 "proxy dialer: %.100s", strerror(errno)); 111 112 command_string = expand_proxy_command(proxy_command, options.user, 113 host, port); 114 debug("Executing proxy dialer command: %.500s", command_string); 115 116 /* Fork and execute the proxy command. */ 117 if ((pid = fork()) == 0) { 118 char *argv[10]; 119 120 /* Child. Permanently give up superuser privileges. */ 121 permanently_drop_suid(original_real_uid); 122 123 close(sp[1]); 124 /* Redirect stdin and stdout. */ 125 if (sp[0] != 0) { 126 if (dup2(sp[0], 0) < 0) 127 perror("dup2 stdin"); 128 } 129 if (sp[0] != 1) { 130 if (dup2(sp[0], 1) < 0) 131 perror("dup2 stdout"); 132 } 133 if (sp[0] >= 2) 134 close(sp[0]); 135 136 /* 137 * Stderr is left as it is so that error messages get 138 * printed on the user's terminal. 139 */ 140 argv[0] = shell; 141 argv[1] = "-c"; 142 argv[2] = command_string; 143 argv[3] = NULL; 144 145 /* 146 * Execute the proxy command. 147 * Note that we gave up any extra privileges above. 148 */ 149 execv(argv[0], argv); 150 perror(argv[0]); 151 exit(1); 152 } 153 /* Parent. */ 154 if (pid < 0) 155 fatal("fork failed: %.100s", strerror(errno)); 156 close(sp[0]); 157 free(command_string); 158 159 if ((sock = mm_receive_fd(sp[1])) == -1) 160 fatal("proxy dialer did not pass back a connection"); 161 close(sp[1]); 162 163 while (waitpid(pid, NULL, 0) == -1) 164 if (errno != EINTR) 165 fatal("Couldn't wait for child: %s", strerror(errno)); 166 167 /* Set the connection file descriptors. */ 168 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 169 return -1; /* ssh_packet_set_connection logs error */ 170 171 return 0; 172 } 173 174 /* 175 * Connect to the given ssh server using a proxy command. 176 */ 177 static int 178 ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port, 179 const char *proxy_command) 180 { 181 char *command_string; 182 int pin[2], pout[2]; 183 pid_t pid; 184 char *shell; 185 186 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 187 shell = _PATH_BSHELL; 188 189 /* Create pipes for communicating with the proxy. */ 190 if (pipe(pin) < 0 || pipe(pout) < 0) 191 fatal("Could not create pipes to communicate with the proxy: %.100s", 192 strerror(errno)); 193 194 command_string = expand_proxy_command(proxy_command, options.user, 195 host, port); 196 debug("Executing proxy command: %.500s", command_string); 197 198 /* Fork and execute the proxy command. */ 199 if ((pid = fork()) == 0) { 200 char *argv[10]; 201 202 /* Child. Permanently give up superuser privileges. */ 203 permanently_drop_suid(original_real_uid); 204 205 /* Redirect stdin and stdout. */ 206 close(pin[1]); 207 if (pin[0] != 0) { 208 if (dup2(pin[0], 0) < 0) 209 perror("dup2 stdin"); 210 close(pin[0]); 211 } 212 close(pout[0]); 213 if (dup2(pout[1], 1) < 0) 214 perror("dup2 stdout"); 215 /* Cannot be 1 because pin allocated two descriptors. */ 216 close(pout[1]); 217 218 /* Stderr is left as it is so that error messages get 219 printed on the user's terminal. */ 220 argv[0] = shell; 221 argv[1] = "-c"; 222 argv[2] = command_string; 223 argv[3] = NULL; 224 225 /* Execute the proxy command. Note that we gave up any 226 extra privileges above. */ 227 signal(SIGPIPE, SIG_DFL); 228 execv(argv[0], argv); 229 perror(argv[0]); 230 exit(1); 231 } 232 /* Parent. */ 233 if (pid < 0) 234 fatal("fork failed: %.100s", strerror(errno)); 235 else 236 proxy_command_pid = pid; /* save pid to clean up later */ 237 238 /* Close child side of the descriptors. */ 239 close(pin[0]); 240 close(pout[1]); 241 242 /* Free the command name. */ 243 free(command_string); 244 245 /* Set the connection file descriptors. */ 246 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 247 return -1; /* ssh_packet_set_connection logs error */ 248 249 return 0; 250 } 251 252 void 253 ssh_kill_proxy_command(void) 254 { 255 /* 256 * Send SIGHUP to proxy command if used. We don't wait() in 257 * case it hangs and instead rely on init to reap the child 258 */ 259 if (proxy_command_pid > 1) 260 kill(proxy_command_pid, SIGHUP); 261 } 262 263 /* 264 * Search a interface address list (returned from getifaddrs(3)) for an 265 * address that matches the desired address family on the specifed interface. 266 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 267 */ 268 static int 269 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 270 struct sockaddr_storage *resultp, socklen_t *rlenp) 271 { 272 struct sockaddr_in6 *sa6; 273 struct sockaddr_in *sa; 274 struct in6_addr *v6addr; 275 const struct ifaddrs *ifa; 276 int allow_local; 277 278 /* 279 * Prefer addresses that are not loopback or linklocal, but use them 280 * if nothing else matches. 281 */ 282 for (allow_local = 0; allow_local < 2; allow_local++) { 283 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 284 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 285 (ifa->ifa_flags & IFF_UP) == 0 || 286 ifa->ifa_addr->sa_family != af || 287 strcmp(ifa->ifa_name, options.bind_interface) != 0) 288 continue; 289 switch (ifa->ifa_addr->sa_family) { 290 case AF_INET: 291 sa = (struct sockaddr_in *)ifa->ifa_addr; 292 if (!allow_local && sa->sin_addr.s_addr == 293 htonl(INADDR_LOOPBACK)) 294 continue; 295 if (*rlenp < sizeof(struct sockaddr_in)) { 296 error("%s: v4 addr doesn't fit", 297 __func__); 298 return -1; 299 } 300 *rlenp = sizeof(struct sockaddr_in); 301 memcpy(resultp, sa, *rlenp); 302 return 0; 303 case AF_INET6: 304 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 305 v6addr = &sa6->sin6_addr; 306 if (!allow_local && 307 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 308 IN6_IS_ADDR_LOOPBACK(v6addr))) 309 continue; 310 if (*rlenp < sizeof(struct sockaddr_in6)) { 311 error("%s: v6 addr doesn't fit", 312 __func__); 313 return -1; 314 } 315 *rlenp = sizeof(struct sockaddr_in6); 316 memcpy(resultp, sa6, *rlenp); 317 return 0; 318 } 319 } 320 } 321 return -1; 322 } 323 324 /* 325 * Creates a (possibly privileged) socket for use as the ssh connection. 326 */ 327 static int 328 ssh_create_socket(int privileged, struct addrinfo *ai) 329 { 330 int sock, r, oerrno; 331 struct sockaddr_storage bindaddr; 332 socklen_t bindaddrlen = 0; 333 struct addrinfo hints, *res = NULL; 334 struct ifaddrs *ifaddrs = NULL; 335 char ntop[NI_MAXHOST]; 336 337 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 338 if (sock < 0) { 339 error("socket: %s", strerror(errno)); 340 return -1; 341 } 342 fcntl(sock, F_SETFD, FD_CLOEXEC); 343 344 /* Bind the socket to an alternative local IP address */ 345 if (options.bind_address == NULL && options.bind_interface == NULL && 346 !privileged) 347 return sock; 348 349 if (options.bind_address != NULL) { 350 memset(&hints, 0, sizeof(hints)); 351 hints.ai_family = ai->ai_family; 352 hints.ai_socktype = ai->ai_socktype; 353 hints.ai_protocol = ai->ai_protocol; 354 hints.ai_flags = AI_PASSIVE; 355 if ((r = getaddrinfo(options.bind_address, NULL, 356 &hints, &res)) != 0) { 357 error("getaddrinfo: %s: %s", options.bind_address, 358 ssh_gai_strerror(r)); 359 goto fail; 360 } 361 if (res == NULL) { 362 error("getaddrinfo: no addrs"); 363 goto fail; 364 } 365 if (res->ai_addrlen > sizeof(bindaddr)) { 366 error("%s: addr doesn't fit", __func__); 367 goto fail; 368 } 369 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 370 bindaddrlen = res->ai_addrlen; 371 } else if (options.bind_interface != NULL) { 372 if ((r = getifaddrs(&ifaddrs)) != 0) { 373 error("getifaddrs: %s: %s", options.bind_interface, 374 strerror(errno)); 375 goto fail; 376 } 377 bindaddrlen = sizeof(bindaddr); 378 if (check_ifaddrs(options.bind_interface, ai->ai_family, 379 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 380 logit("getifaddrs: %s: no suitable addresses", 381 options.bind_interface); 382 goto fail; 383 } 384 } 385 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 386 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 387 error("%s: getnameinfo failed: %s", __func__, 388 ssh_gai_strerror(r)); 389 goto fail; 390 } 391 /* 392 * If we are running as root and want to connect to a privileged 393 * port, bind our own socket to a privileged port. 394 */ 395 if (privileged) { 396 PRIV_START; 397 r = bindresvport_sa(sock, 398 bindaddrlen == 0 ? NULL : (struct sockaddr *)&bindaddr); 399 oerrno = errno; 400 PRIV_END; 401 if (r < 0) { 402 error("bindresvport_sa %s: %s", ntop, 403 strerror(oerrno)); 404 goto fail; 405 } 406 } else if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 407 error("bind %s: %s", ntop, strerror(errno)); 408 goto fail; 409 } 410 debug("%s: bound to %s", __func__, ntop); 411 /* success */ 412 goto out; 413 fail: 414 close(sock); 415 sock = -1; 416 out: 417 if (res != NULL) 418 freeaddrinfo(res); 419 if (ifaddrs != NULL) 420 freeifaddrs(ifaddrs); 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. If needpriv is true, 495 * a privileged port will be allocated to make the connection. 496 * This requires super-user privileges if needpriv is true. 497 * Connection_attempts specifies the maximum number of tries (one per 498 * second). If proxy_command is non-NULL, it specifies the command (with %h 499 * and %p substituted for host and port, respectively) to use to contact 500 * the daemon. 501 */ 502 static int 503 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 504 struct sockaddr_storage *hostaddr, u_short port, int family, 505 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 506 { 507 int on = 1; 508 int oerrno, sock = -1, attempt; 509 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 510 struct addrinfo *ai; 511 512 debug2("%s: needpriv %d", __func__, needpriv); 513 memset(ntop, 0, sizeof(ntop)); 514 memset(strport, 0, sizeof(strport)); 515 516 for (attempt = 0; attempt < connection_attempts; attempt++) { 517 if (attempt > 0) { 518 /* Sleep a moment before retrying. */ 519 sleep(1); 520 debug("Trying again..."); 521 } 522 /* 523 * Loop through addresses for this host, and try each one in 524 * sequence until the connection succeeds. 525 */ 526 for (ai = aitop; ai; ai = ai->ai_next) { 527 if (ai->ai_family != AF_INET && 528 ai->ai_family != AF_INET6) { 529 errno = EAFNOSUPPORT; 530 continue; 531 } 532 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 533 ntop, sizeof(ntop), strport, sizeof(strport), 534 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 535 oerrno = errno; 536 error("%s: getnameinfo failed", __func__); 537 errno = oerrno; 538 continue; 539 } 540 debug("Connecting to %.200s [%.100s] port %s.", 541 host, ntop, strport); 542 543 /* Create a socket for connecting. */ 544 sock = ssh_create_socket(needpriv, ai); 545 if (sock < 0) { 546 /* Any error is already output */ 547 errno = 0; 548 continue; 549 } 550 551 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 552 timeout_ms) >= 0) { 553 /* Successful connection. */ 554 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 555 break; 556 } else { 557 oerrno = errno; 558 debug("connect to address %s port %s: %s", 559 ntop, strport, strerror(errno)); 560 close(sock); 561 sock = -1; 562 errno = oerrno; 563 } 564 } 565 if (sock != -1) 566 break; /* Successful connection. */ 567 } 568 569 /* Return failure if we didn't get a successful connection. */ 570 if (sock == -1) { 571 error("ssh: connect to host %s port %s: %s", 572 host, strport, errno == 0 ? "failure" : strerror(errno)); 573 return -1; 574 } 575 576 debug("Connection established."); 577 578 /* Set SO_KEEPALIVE if requested. */ 579 if (want_keepalive && 580 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 581 sizeof(on)) < 0) 582 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 583 584 /* Set the connection. */ 585 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 586 return -1; /* ssh_packet_set_connection logs error */ 587 588 return 0; 589 } 590 591 int 592 ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs, 593 struct sockaddr_storage *hostaddr, u_short port, int family, 594 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 595 { 596 if (options.proxy_command == NULL) { 597 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 598 family, connection_attempts, timeout_ms, want_keepalive, 599 needpriv); 600 } else if (strcmp(options.proxy_command, "-") == 0) { 601 if ((ssh_packet_set_connection(ssh, 602 STDIN_FILENO, STDOUT_FILENO)) == NULL) 603 return -1; /* ssh_packet_set_connection logs error */ 604 return 0; 605 } else if (options.proxy_use_fdpass) { 606 return ssh_proxy_fdpass_connect(ssh, host, port, 607 options.proxy_command); 608 } 609 return ssh_proxy_connect(ssh, host, port, options.proxy_command); 610 } 611 612 static void 613 send_client_banner(int connection_out, int minor1) 614 { 615 /* Send our own protocol version identification. */ 616 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n", 617 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION); 618 if (atomicio(vwrite, connection_out, client_version_string, 619 strlen(client_version_string)) != strlen(client_version_string)) 620 fatal("write: %.100s", strerror(errno)); 621 chop(client_version_string); 622 debug("Local version string %.100s", client_version_string); 623 } 624 625 /* 626 * Waits for the server identification string, and sends our own 627 * identification string. 628 */ 629 void 630 ssh_exchange_identification(int timeout_ms) 631 { 632 char buf[256], remote_version[256]; /* must be same size! */ 633 int remote_major, remote_minor, mismatch; 634 int connection_in = packet_get_connection_in(); 635 int connection_out = packet_get_connection_out(); 636 u_int i, n; 637 size_t len; 638 int rc; 639 640 send_client_banner(connection_out, 0); 641 642 /* Read other side's version identification. */ 643 for (n = 0;;) { 644 for (i = 0; i < sizeof(buf) - 1; i++) { 645 if (timeout_ms > 0) { 646 rc = waitrfd(connection_in, &timeout_ms); 647 if (rc == -1 && errno == ETIMEDOUT) { 648 fatal("Connection timed out during " 649 "banner exchange"); 650 } else if (rc == -1) { 651 fatal("%s: %s", 652 __func__, strerror(errno)); 653 } 654 } 655 656 len = atomicio(read, connection_in, &buf[i], 1); 657 if (len != 1 && errno == EPIPE) 658 fatal("ssh_exchange_identification: " 659 "Connection closed by remote host"); 660 else if (len != 1) 661 fatal("ssh_exchange_identification: " 662 "read: %.100s", strerror(errno)); 663 if (buf[i] == '\r') { 664 buf[i] = '\n'; 665 buf[i + 1] = 0; 666 continue; /**XXX wait for \n */ 667 } 668 if (buf[i] == '\n') { 669 buf[i + 1] = 0; 670 break; 671 } 672 if (++n > 65536) 673 fatal("ssh_exchange_identification: " 674 "No banner received"); 675 } 676 buf[sizeof(buf) - 1] = 0; 677 if (strncmp(buf, "SSH-", 4) == 0) 678 break; 679 debug("ssh_exchange_identification: %s", buf); 680 } 681 server_version_string = xstrdup(buf); 682 683 /* 684 * Check that the versions match. In future this might accept 685 * several versions and set appropriate flags to handle them. 686 */ 687 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 688 &remote_major, &remote_minor, remote_version) != 3) 689 fatal("Bad remote protocol version identification: '%.100s'", buf); 690 debug("Remote protocol version %d.%d, remote software version %.100s", 691 remote_major, remote_minor, remote_version); 692 693 active_state->compat = compat_datafellows(remote_version); 694 mismatch = 0; 695 696 switch (remote_major) { 697 case 2: 698 break; 699 case 1: 700 if (remote_minor != 99) 701 mismatch = 1; 702 break; 703 default: 704 mismatch = 1; 705 break; 706 } 707 if (mismatch) 708 fatal("Protocol major versions differ: %d vs. %d", 709 PROTOCOL_MAJOR_2, remote_major); 710 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) 711 logit("Server version \"%.100s\" uses unsafe RSA signature " 712 "scheme; disabling use of RSA keys", remote_version); 713 chop(server_version_string); 714 } 715 716 /* defaults to 'no' */ 717 static int 718 confirm(const char *prompt) 719 { 720 const char *msg, *again = "Please type 'yes' or 'no': "; 721 char *p; 722 int ret = -1; 723 724 if (options.batch_mode) 725 return 0; 726 for (msg = prompt;;msg = again) { 727 p = read_passphrase(msg, RP_ECHO); 728 if (p == NULL) 729 return 0; 730 p[strcspn(p, "\n")] = '\0'; 731 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 732 ret = 0; 733 else if (strcasecmp(p, "yes") == 0) 734 ret = 1; 735 free(p); 736 if (ret != -1) 737 return ret; 738 } 739 } 740 741 static int 742 check_host_cert(const char *host, const struct sshkey *host_key) 743 { 744 const char *reason; 745 746 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 747 error("%s", reason); 748 return 0; 749 } 750 if (buffer_len(host_key->cert->critical) != 0) { 751 error("Certificate for %s contains unsupported " 752 "critical options(s)", host); 753 return 0; 754 } 755 return 1; 756 } 757 758 static int 759 sockaddr_is_local(struct sockaddr *hostaddr) 760 { 761 switch (hostaddr->sa_family) { 762 case AF_INET: 763 return (ntohl(((struct sockaddr_in *)hostaddr)-> 764 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 765 case AF_INET6: 766 return IN6_IS_ADDR_LOOPBACK( 767 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 768 default: 769 return 0; 770 } 771 } 772 773 /* 774 * Prepare the hostname and ip address strings that are used to lookup 775 * host keys in known_hosts files. These may have a port number appended. 776 */ 777 void 778 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 779 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 780 { 781 char ntop[NI_MAXHOST]; 782 783 /* 784 * We don't have the remote ip-address for connections 785 * using a proxy command 786 */ 787 if (hostfile_ipaddr != NULL) { 788 if (options.proxy_command == NULL) { 789 if (getnameinfo(hostaddr, hostaddr->sa_len, 790 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 791 fatal("%s: getnameinfo failed", __func__); 792 *hostfile_ipaddr = put_host_port(ntop, port); 793 } else { 794 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 795 "command>"); 796 } 797 } 798 799 /* 800 * Allow the user to record the key under a different name or 801 * differentiate a non-standard port. This is useful for ssh 802 * tunneling over forwarded connections or if you run multiple 803 * sshd's on different ports on the same machine. 804 */ 805 if (hostfile_hostname != NULL) { 806 if (options.host_key_alias != NULL) { 807 *hostfile_hostname = xstrdup(options.host_key_alias); 808 debug("using hostkeyalias: %s", *hostfile_hostname); 809 } else { 810 *hostfile_hostname = put_host_port(hostname, port); 811 } 812 } 813 } 814 815 /* 816 * check whether the supplied host key is valid, return -1 if the key 817 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 818 */ 819 #define RDRW 0 820 #define RDONLY 1 821 #define ROQUIET 2 822 static int 823 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 824 struct sshkey *host_key, int readonly, 825 char **user_hostfiles, u_int num_user_hostfiles, 826 char **system_hostfiles, u_int num_system_hostfiles) 827 { 828 HostStatus host_status; 829 HostStatus ip_status; 830 struct sshkey *raw_key = NULL; 831 char *ip = NULL, *host = NULL; 832 char hostline[1000], *hostp, *fp, *ra; 833 char msg[1024]; 834 const char *type; 835 const struct hostkey_entry *host_found, *ip_found; 836 int len, cancelled_forwarding = 0; 837 int local = sockaddr_is_local(hostaddr); 838 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 839 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 840 struct hostkeys *host_hostkeys, *ip_hostkeys; 841 u_int i; 842 843 /* 844 * Force accepting of the host key for loopback/localhost. The 845 * problem is that if the home directory is NFS-mounted to multiple 846 * machines, localhost will refer to a different machine in each of 847 * them, and the user will get bogus HOST_CHANGED warnings. This 848 * essentially disables host authentication for localhost; however, 849 * this is probably not a real problem. 850 */ 851 if (options.no_host_authentication_for_localhost == 1 && local && 852 options.host_key_alias == NULL) { 853 debug("Forcing accepting of host key for " 854 "loopback/localhost."); 855 return 0; 856 } 857 858 /* 859 * Prepare the hostname and address strings used for hostkey lookup. 860 * In some cases, these will have a port number appended. 861 */ 862 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 863 864 /* 865 * Turn off check_host_ip if the connection is to localhost, via proxy 866 * command or if we don't have a hostname to compare with 867 */ 868 if (options.check_host_ip && (local || 869 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 870 options.check_host_ip = 0; 871 872 host_hostkeys = init_hostkeys(); 873 for (i = 0; i < num_user_hostfiles; i++) 874 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 875 for (i = 0; i < num_system_hostfiles; i++) 876 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 877 878 ip_hostkeys = NULL; 879 if (!want_cert && options.check_host_ip) { 880 ip_hostkeys = init_hostkeys(); 881 for (i = 0; i < num_user_hostfiles; i++) 882 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 883 for (i = 0; i < num_system_hostfiles; i++) 884 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 885 } 886 887 retry: 888 /* Reload these as they may have changed on cert->key downgrade */ 889 want_cert = sshkey_is_cert(host_key); 890 type = sshkey_type(host_key); 891 892 /* 893 * Check if the host key is present in the user's list of known 894 * hosts or in the systemwide list. 895 */ 896 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 897 &host_found); 898 899 /* 900 * Also perform check for the ip address, skip the check if we are 901 * localhost, looking for a certificate, or the hostname was an ip 902 * address to begin with. 903 */ 904 if (!want_cert && ip_hostkeys != NULL) { 905 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 906 &ip_found); 907 if (host_status == HOST_CHANGED && 908 (ip_status != HOST_CHANGED || 909 (ip_found != NULL && 910 !sshkey_equal(ip_found->key, host_found->key)))) 911 host_ip_differ = 1; 912 } else 913 ip_status = host_status; 914 915 switch (host_status) { 916 case HOST_OK: 917 /* The host is known and the key matches. */ 918 debug("Host '%.200s' is known and matches the %s host %s.", 919 host, type, want_cert ? "certificate" : "key"); 920 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 921 host_found->file, host_found->line); 922 if (want_cert && 923 !check_host_cert(options.host_key_alias == NULL ? 924 hostname : options.host_key_alias, host_key)) 925 goto fail; 926 if (options.check_host_ip && ip_status == HOST_NEW) { 927 if (readonly || want_cert) 928 logit("%s host key for IP address " 929 "'%.128s' not in list of known hosts.", 930 type, ip); 931 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 932 host_key, options.hash_known_hosts)) 933 logit("Failed to add the %s host key for IP " 934 "address '%.128s' to the list of known " 935 "hosts (%.500s).", type, ip, 936 user_hostfiles[0]); 937 else 938 logit("Warning: Permanently added the %s host " 939 "key for IP address '%.128s' to the list " 940 "of known hosts.", type, ip); 941 } else if (options.visual_host_key) { 942 fp = sshkey_fingerprint(host_key, 943 options.fingerprint_hash, SSH_FP_DEFAULT); 944 ra = sshkey_fingerprint(host_key, 945 options.fingerprint_hash, SSH_FP_RANDOMART); 946 if (fp == NULL || ra == NULL) 947 fatal("%s: sshkey_fingerprint fail", __func__); 948 logit("Host key fingerprint is %s\n%s", fp, ra); 949 free(ra); 950 free(fp); 951 } 952 hostkey_trusted = 1; 953 break; 954 case HOST_NEW: 955 if (options.host_key_alias == NULL && port != 0 && 956 port != SSH_DEFAULT_PORT) { 957 debug("checking without port identifier"); 958 if (check_host_key(hostname, hostaddr, 0, host_key, 959 ROQUIET, user_hostfiles, num_user_hostfiles, 960 system_hostfiles, num_system_hostfiles) == 0) { 961 debug("found matching key w/out port"); 962 break; 963 } 964 } 965 if (readonly || want_cert) 966 goto fail; 967 /* The host is new. */ 968 if (options.strict_host_key_checking == 969 SSH_STRICT_HOSTKEY_YES) { 970 /* 971 * User has requested strict host key checking. We 972 * will not add the host key automatically. The only 973 * alternative left is to abort. 974 */ 975 error("No %s host key is known for %.200s and you " 976 "have requested strict checking.", type, host); 977 goto fail; 978 } else if (options.strict_host_key_checking == 979 SSH_STRICT_HOSTKEY_ASK) { 980 char msg1[1024], msg2[1024]; 981 982 if (show_other_keys(host_hostkeys, host_key)) 983 snprintf(msg1, sizeof(msg1), 984 "\nbut keys of different type are already" 985 " known for this host."); 986 else 987 snprintf(msg1, sizeof(msg1), "."); 988 /* The default */ 989 fp = sshkey_fingerprint(host_key, 990 options.fingerprint_hash, SSH_FP_DEFAULT); 991 ra = sshkey_fingerprint(host_key, 992 options.fingerprint_hash, SSH_FP_RANDOMART); 993 if (fp == NULL || ra == NULL) 994 fatal("%s: sshkey_fingerprint fail", __func__); 995 msg2[0] = '\0'; 996 if (options.verify_host_key_dns) { 997 if (matching_host_key_dns) 998 snprintf(msg2, sizeof(msg2), 999 "Matching host key fingerprint" 1000 " found in DNS.\n"); 1001 else 1002 snprintf(msg2, sizeof(msg2), 1003 "No matching host key fingerprint" 1004 " found in DNS.\n"); 1005 } 1006 snprintf(msg, sizeof(msg), 1007 "The authenticity of host '%.200s (%s)' can't be " 1008 "established%s\n" 1009 "%s key fingerprint is %s.%s%s\n%s" 1010 "Are you sure you want to continue connecting " 1011 "(yes/no)? ", 1012 host, ip, msg1, type, fp, 1013 options.visual_host_key ? "\n" : "", 1014 options.visual_host_key ? ra : "", 1015 msg2); 1016 free(ra); 1017 free(fp); 1018 if (!confirm(msg)) 1019 goto fail; 1020 hostkey_trusted = 1; /* user explicitly confirmed */ 1021 } 1022 /* 1023 * If in "new" or "off" strict mode, add the key automatically 1024 * to the local known_hosts file. 1025 */ 1026 if (options.check_host_ip && ip_status == HOST_NEW) { 1027 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1028 hostp = hostline; 1029 if (options.hash_known_hosts) { 1030 /* Add hash of host and IP separately */ 1031 r = add_host_to_hostfile(user_hostfiles[0], 1032 host, host_key, options.hash_known_hosts) && 1033 add_host_to_hostfile(user_hostfiles[0], ip, 1034 host_key, options.hash_known_hosts); 1035 } else { 1036 /* Add unhashed "host,ip" */ 1037 r = add_host_to_hostfile(user_hostfiles[0], 1038 hostline, host_key, 1039 options.hash_known_hosts); 1040 } 1041 } else { 1042 r = add_host_to_hostfile(user_hostfiles[0], host, 1043 host_key, options.hash_known_hosts); 1044 hostp = host; 1045 } 1046 1047 if (!r) 1048 logit("Failed to add the host to the list of known " 1049 "hosts (%.500s).", user_hostfiles[0]); 1050 else 1051 logit("Warning: Permanently added '%.200s' (%s) to the " 1052 "list of known hosts.", hostp, type); 1053 break; 1054 case HOST_REVOKED: 1055 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1056 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1057 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1058 error("The %s host key for %s is marked as revoked.", type, host); 1059 error("This could mean that a stolen key is being used to"); 1060 error("impersonate this host."); 1061 1062 /* 1063 * If strict host key checking is in use, the user will have 1064 * to edit the key manually and we can only abort. 1065 */ 1066 if (options.strict_host_key_checking != 1067 SSH_STRICT_HOSTKEY_OFF) { 1068 error("%s host key for %.200s was revoked and you have " 1069 "requested strict checking.", type, host); 1070 goto fail; 1071 } 1072 goto continue_unsafe; 1073 1074 case HOST_CHANGED: 1075 if (want_cert) { 1076 /* 1077 * This is only a debug() since it is valid to have 1078 * CAs with wildcard DNS matches that don't match 1079 * all hosts that one might visit. 1080 */ 1081 debug("Host certificate authority does not " 1082 "match %s in %s:%lu", CA_MARKER, 1083 host_found->file, host_found->line); 1084 goto fail; 1085 } 1086 if (readonly == ROQUIET) 1087 goto fail; 1088 if (options.check_host_ip && host_ip_differ) { 1089 char *key_msg; 1090 if (ip_status == HOST_NEW) 1091 key_msg = "is unknown"; 1092 else if (ip_status == HOST_OK) 1093 key_msg = "is unchanged"; 1094 else 1095 key_msg = "has a different value"; 1096 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1097 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1098 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1099 error("The %s host key for %s has changed,", type, host); 1100 error("and the key for the corresponding IP address %s", ip); 1101 error("%s. This could either mean that", key_msg); 1102 error("DNS SPOOFING is happening or the IP address for the host"); 1103 error("and its host key have changed at the same time."); 1104 if (ip_status != HOST_NEW) 1105 error("Offending key for IP in %s:%lu", 1106 ip_found->file, ip_found->line); 1107 } 1108 /* The host key has changed. */ 1109 warn_changed_key(host_key); 1110 error("Add correct host key in %.100s to get rid of this message.", 1111 user_hostfiles[0]); 1112 error("Offending %s key in %s:%lu", 1113 sshkey_type(host_found->key), 1114 host_found->file, host_found->line); 1115 1116 /* 1117 * If strict host key checking is in use, the user will have 1118 * to edit the key manually and we can only abort. 1119 */ 1120 if (options.strict_host_key_checking != 1121 SSH_STRICT_HOSTKEY_OFF) { 1122 error("%s host key for %.200s has changed and you have " 1123 "requested strict checking.", type, host); 1124 goto fail; 1125 } 1126 1127 continue_unsafe: 1128 /* 1129 * If strict host key checking has not been requested, allow 1130 * the connection but without MITM-able authentication or 1131 * forwarding. 1132 */ 1133 if (options.password_authentication) { 1134 error("Password authentication is disabled to avoid " 1135 "man-in-the-middle attacks."); 1136 options.password_authentication = 0; 1137 cancelled_forwarding = 1; 1138 } 1139 if (options.kbd_interactive_authentication) { 1140 error("Keyboard-interactive authentication is disabled" 1141 " to avoid man-in-the-middle attacks."); 1142 options.kbd_interactive_authentication = 0; 1143 options.challenge_response_authentication = 0; 1144 cancelled_forwarding = 1; 1145 } 1146 if (options.challenge_response_authentication) { 1147 error("Challenge/response authentication is disabled" 1148 " to avoid man-in-the-middle attacks."); 1149 options.challenge_response_authentication = 0; 1150 cancelled_forwarding = 1; 1151 } 1152 if (options.forward_agent) { 1153 error("Agent forwarding is disabled to avoid " 1154 "man-in-the-middle attacks."); 1155 options.forward_agent = 0; 1156 cancelled_forwarding = 1; 1157 } 1158 if (options.forward_x11) { 1159 error("X11 forwarding is disabled to avoid " 1160 "man-in-the-middle attacks."); 1161 options.forward_x11 = 0; 1162 cancelled_forwarding = 1; 1163 } 1164 if (options.num_local_forwards > 0 || 1165 options.num_remote_forwards > 0) { 1166 error("Port forwarding is disabled to avoid " 1167 "man-in-the-middle attacks."); 1168 options.num_local_forwards = 1169 options.num_remote_forwards = 0; 1170 cancelled_forwarding = 1; 1171 } 1172 if (options.tun_open != SSH_TUNMODE_NO) { 1173 error("Tunnel forwarding is disabled to avoid " 1174 "man-in-the-middle attacks."); 1175 options.tun_open = SSH_TUNMODE_NO; 1176 cancelled_forwarding = 1; 1177 } 1178 if (options.exit_on_forward_failure && cancelled_forwarding) 1179 fatal("Error: forwarding disabled due to host key " 1180 "check failure"); 1181 1182 /* 1183 * XXX Should permit the user to change to use the new id. 1184 * This could be done by converting the host key to an 1185 * identifying sentence, tell that the host identifies itself 1186 * by that sentence, and ask the user if he/she wishes to 1187 * accept the authentication. 1188 */ 1189 break; 1190 case HOST_FOUND: 1191 fatal("internal error"); 1192 break; 1193 } 1194 1195 if (options.check_host_ip && host_status != HOST_CHANGED && 1196 ip_status == HOST_CHANGED) { 1197 snprintf(msg, sizeof(msg), 1198 "Warning: the %s host key for '%.200s' " 1199 "differs from the key for the IP address '%.128s'" 1200 "\nOffending key for IP in %s:%lu", 1201 type, host, ip, ip_found->file, ip_found->line); 1202 if (host_status == HOST_OK) { 1203 len = strlen(msg); 1204 snprintf(msg + len, sizeof(msg) - len, 1205 "\nMatching host key in %s:%lu", 1206 host_found->file, host_found->line); 1207 } 1208 if (options.strict_host_key_checking == 1209 SSH_STRICT_HOSTKEY_ASK) { 1210 strlcat(msg, "\nAre you sure you want " 1211 "to continue connecting (yes/no)? ", sizeof(msg)); 1212 if (!confirm(msg)) 1213 goto fail; 1214 } else if (options.strict_host_key_checking != 1215 SSH_STRICT_HOSTKEY_OFF) { 1216 logit("%s", msg); 1217 error("Exiting, you have requested strict checking."); 1218 goto fail; 1219 } else { 1220 logit("%s", msg); 1221 } 1222 } 1223 1224 if (!hostkey_trusted && options.update_hostkeys) { 1225 debug("%s: hostkey not known or explicitly trusted: " 1226 "disabling UpdateHostkeys", __func__); 1227 options.update_hostkeys = 0; 1228 } 1229 1230 free(ip); 1231 free(host); 1232 if (host_hostkeys != NULL) 1233 free_hostkeys(host_hostkeys); 1234 if (ip_hostkeys != NULL) 1235 free_hostkeys(ip_hostkeys); 1236 return 0; 1237 1238 fail: 1239 if (want_cert && host_status != HOST_REVOKED) { 1240 /* 1241 * No matching certificate. Downgrade cert to raw key and 1242 * search normally. 1243 */ 1244 debug("No matching CA found. Retry with plain key"); 1245 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1246 fatal("%s: sshkey_from_private: %s", 1247 __func__, ssh_err(r)); 1248 if ((r = sshkey_drop_cert(raw_key)) != 0) 1249 fatal("Couldn't drop certificate: %s", ssh_err(r)); 1250 host_key = raw_key; 1251 goto retry; 1252 } 1253 sshkey_free(raw_key); 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 -1; 1261 } 1262 1263 /* returns 0 if key verifies or -1 if key does NOT verify */ 1264 int 1265 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key) 1266 { 1267 u_int i; 1268 int r = -1, flags = 0; 1269 char valid[64], *fp = NULL, *cafp = NULL; 1270 struct sshkey *plain = NULL; 1271 1272 if ((fp = sshkey_fingerprint(host_key, 1273 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1274 error("%s: fingerprint host key: %s", __func__, ssh_err(r)); 1275 r = -1; 1276 goto out; 1277 } 1278 1279 if (sshkey_is_cert(host_key)) { 1280 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1281 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1282 error("%s: fingerprint CA key: %s", 1283 __func__, ssh_err(r)); 1284 r = -1; 1285 goto out; 1286 } 1287 sshkey_format_cert_validity(host_key->cert, 1288 valid, sizeof(valid)); 1289 debug("Server host certificate: %s %s, serial %llu " 1290 "ID \"%s\" CA %s %s valid %s", 1291 sshkey_ssh_name(host_key), fp, 1292 (unsigned long long)host_key->cert->serial, 1293 host_key->cert->key_id, 1294 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1295 valid); 1296 for (i = 0; i < host_key->cert->nprincipals; i++) { 1297 debug2("Server host certificate hostname: %s", 1298 host_key->cert->principals[i]); 1299 } 1300 } else { 1301 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1302 } 1303 1304 if (sshkey_equal(previous_host_key, host_key)) { 1305 debug2("%s: server host key %s %s matches cached key", 1306 __func__, sshkey_type(host_key), fp); 1307 r = 0; 1308 goto out; 1309 } 1310 1311 /* Check in RevokedHostKeys file if specified */ 1312 if (options.revoked_host_keys != NULL) { 1313 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1314 switch (r) { 1315 case 0: 1316 break; /* not revoked */ 1317 case SSH_ERR_KEY_REVOKED: 1318 error("Host key %s %s revoked by file %s", 1319 sshkey_type(host_key), fp, 1320 options.revoked_host_keys); 1321 r = -1; 1322 goto out; 1323 default: 1324 error("Error checking host key %s %s in " 1325 "revoked keys file %s: %s", sshkey_type(host_key), 1326 fp, options.revoked_host_keys, ssh_err(r)); 1327 r = -1; 1328 goto out; 1329 } 1330 } 1331 1332 if (options.verify_host_key_dns) { 1333 /* 1334 * XXX certs are not yet supported for DNS, so downgrade 1335 * them and try the plain key. 1336 */ 1337 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1338 goto out; 1339 if (sshkey_is_cert(plain)) 1340 sshkey_drop_cert(plain); 1341 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1342 if (flags & DNS_VERIFY_FOUND) { 1343 if (options.verify_host_key_dns == 1 && 1344 flags & DNS_VERIFY_MATCH && 1345 flags & DNS_VERIFY_SECURE) { 1346 r = 0; 1347 goto out; 1348 } 1349 if (flags & DNS_VERIFY_MATCH) { 1350 matching_host_key_dns = 1; 1351 } else { 1352 warn_changed_key(plain); 1353 error("Update the SSHFP RR in DNS " 1354 "with the new host key to get rid " 1355 "of this message."); 1356 } 1357 } 1358 } 1359 } 1360 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1361 options.user_hostfiles, options.num_user_hostfiles, 1362 options.system_hostfiles, options.num_system_hostfiles); 1363 1364 out: 1365 sshkey_free(plain); 1366 free(fp); 1367 free(cafp); 1368 if (r == 0 && host_key != NULL) { 1369 sshkey_free(previous_host_key); 1370 r = sshkey_from_private(host_key, &previous_host_key); 1371 } 1372 1373 return r; 1374 } 1375 1376 /* 1377 * Starts a dialog with the server, and authenticates the current user on the 1378 * server. This does not need any extra privileges. The basic connection 1379 * to the server must already have been established before this is called. 1380 * If login fails, this function prints an error and never returns. 1381 * This function does not require super-user privileges. 1382 */ 1383 void 1384 ssh_login(Sensitive *sensitive, const char *orighost, 1385 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1386 { 1387 char *host; 1388 char *server_user, *local_user; 1389 1390 local_user = xstrdup(pw->pw_name); 1391 server_user = options.user ? options.user : local_user; 1392 1393 /* Convert the user-supplied hostname into all lowercase. */ 1394 host = xstrdup(orighost); 1395 lowercase(host); 1396 1397 /* Exchange protocol version identification strings with the server. */ 1398 ssh_exchange_identification(timeout_ms); 1399 1400 /* Put the connection into non-blocking mode. */ 1401 packet_set_nonblocking(); 1402 1403 /* key exchange */ 1404 /* authenticate user */ 1405 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1406 ssh_kex2(host, hostaddr, port); 1407 ssh_userauth2(local_user, server_user, host, sensitive); 1408 free(local_user); 1409 } 1410 1411 void 1412 ssh_put_password(char *password) 1413 { 1414 int size; 1415 char *padded; 1416 1417 if (datafellows & SSH_BUG_PASSWORDPAD) { 1418 packet_put_cstring(password); 1419 return; 1420 } 1421 size = ROUNDUP(strlen(password) + 1, 32); 1422 padded = xcalloc(1, size); 1423 strlcpy(padded, password, size); 1424 packet_put_string(padded, size); 1425 explicit_bzero(padded, size); 1426 free(padded); 1427 } 1428 1429 /* print all known host keys for a given host, but skip keys of given type */ 1430 static int 1431 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1432 { 1433 int type[] = { 1434 KEY_RSA, 1435 KEY_DSA, 1436 KEY_ECDSA, 1437 KEY_ED25519, 1438 KEY_XMSS, 1439 -1 1440 }; 1441 int i, ret = 0; 1442 char *fp, *ra; 1443 const struct hostkey_entry *found; 1444 1445 for (i = 0; type[i] != -1; i++) { 1446 if (type[i] == key->type) 1447 continue; 1448 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1449 continue; 1450 fp = sshkey_fingerprint(found->key, 1451 options.fingerprint_hash, SSH_FP_DEFAULT); 1452 ra = sshkey_fingerprint(found->key, 1453 options.fingerprint_hash, SSH_FP_RANDOMART); 1454 if (fp == NULL || ra == NULL) 1455 fatal("%s: sshkey_fingerprint fail", __func__); 1456 logit("WARNING: %s key found for host %s\n" 1457 "in %s:%lu\n" 1458 "%s key fingerprint %s.", 1459 key_type(found->key), 1460 found->host, found->file, found->line, 1461 key_type(found->key), fp); 1462 if (options.visual_host_key) 1463 logit("%s", ra); 1464 free(ra); 1465 free(fp); 1466 ret = 1; 1467 } 1468 return ret; 1469 } 1470 1471 static void 1472 warn_changed_key(struct sshkey *host_key) 1473 { 1474 char *fp; 1475 1476 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1477 SSH_FP_DEFAULT); 1478 if (fp == NULL) 1479 fatal("%s: sshkey_fingerprint fail", __func__); 1480 1481 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1482 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1483 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1484 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1485 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1486 error("It is also possible that a host key has just been changed."); 1487 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1488 key_type(host_key), fp); 1489 error("Please contact your system administrator."); 1490 1491 free(fp); 1492 } 1493 1494 /* 1495 * Execute a local command 1496 */ 1497 int 1498 ssh_local_cmd(const char *args) 1499 { 1500 char *shell; 1501 pid_t pid; 1502 int status; 1503 void (*osighand)(int); 1504 1505 if (!options.permit_local_command || 1506 args == NULL || !*args) 1507 return (1); 1508 1509 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1510 shell = _PATH_BSHELL; 1511 1512 osighand = signal(SIGCHLD, SIG_DFL); 1513 pid = fork(); 1514 if (pid == 0) { 1515 signal(SIGPIPE, SIG_DFL); 1516 debug3("Executing %s -c \"%s\"", shell, args); 1517 execl(shell, shell, "-c", args, (char *)NULL); 1518 error("Couldn't execute %s -c \"%s\": %s", 1519 shell, args, strerror(errno)); 1520 _exit(1); 1521 } else if (pid == -1) 1522 fatal("fork failed: %.100s", strerror(errno)); 1523 while (waitpid(pid, &status, 0) == -1) 1524 if (errno != EINTR) 1525 fatal("Couldn't wait for child: %s", strerror(errno)); 1526 signal(SIGCHLD, osighand); 1527 1528 if (!WIFEXITED(status)) 1529 return (1); 1530 1531 return (WEXITSTATUS(status)); 1532 } 1533 1534 void 1535 maybe_add_key_to_agent(char *authfile, const struct sshkey *private, 1536 char *comment, char *passphrase) 1537 { 1538 int auth_sock = -1, r; 1539 1540 if (options.add_keys_to_agent == 0) 1541 return; 1542 1543 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1544 debug3("no authentication agent, not adding key"); 1545 return; 1546 } 1547 1548 if (options.add_keys_to_agent == 2 && 1549 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1550 debug3("user denied adding this key"); 1551 close(auth_sock); 1552 return; 1553 } 1554 1555 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0, 1556 (options.add_keys_to_agent == 3), 0)) == 0) 1557 debug("identity added to agent: %s", authfile); 1558 else 1559 debug("could not add identity to agent: %s (%d)", authfile, r); 1560 close(auth_sock); 1561 } 1562