1 /* $OpenBSD: sshconnect.c,v 1.346 2020/12/20 23:36:51 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 <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 <limits.h> 30 #include <paths.h> 31 #include <signal.h> 32 #include <pwd.h> 33 #include <stdio.h> 34 #include <stdlib.h> 35 #include <stdarg.h> 36 #include <string.h> 37 #include <unistd.h> 38 #include <ifaddrs.h> 39 40 #include "xmalloc.h" 41 #include "ssh.h" 42 #include "sshbuf.h" 43 #include "packet.h" 44 #include "compat.h" 45 #include "sshkey.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 #include "kex.h" 60 61 struct sshkey *previous_host_key = NULL; 62 63 static int matching_host_key_dns = 0; 64 65 static pid_t proxy_command_pid = 0; 66 67 /* import */ 68 extern int debug_flag; 69 extern Options options; 70 extern char *__progname; 71 72 static int show_other_keys(struct hostkeys *, struct sshkey *); 73 static void warn_changed_key(struct sshkey *); 74 75 /* Expand a proxy command */ 76 static char * 77 expand_proxy_command(const char *proxy_command, const char *user, 78 const char *host, const char *host_arg, int port) 79 { 80 char *tmp, *ret, strport[NI_MAXSERV]; 81 const char *keyalias = options.host_key_alias ? 82 options.host_key_alias : host_arg; 83 84 snprintf(strport, sizeof strport, "%d", port); 85 xasprintf(&tmp, "exec %s", proxy_command); 86 ret = percent_expand(tmp, 87 "h", host, 88 "k", keyalias, 89 "n", host_arg, 90 "p", strport, 91 "r", options.user, 92 (char *)NULL); 93 free(tmp); 94 return ret; 95 } 96 97 /* 98 * Connect to the given ssh server using a proxy command that passes a 99 * a connected fd back to us. 100 */ 101 static int 102 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, 103 const char *host_arg, u_short port, const char *proxy_command) 104 { 105 char *command_string; 106 int sp[2], sock; 107 pid_t pid; 108 char *shell; 109 110 if ((shell = getenv("SHELL")) == NULL) 111 shell = _PATH_BSHELL; 112 113 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) == -1) 114 fatal("Could not create socketpair to communicate with " 115 "proxy dialer: %.100s", strerror(errno)); 116 117 command_string = expand_proxy_command(proxy_command, options.user, 118 host, host_arg, port); 119 debug("Executing proxy dialer command: %.500s", command_string); 120 121 /* Fork and execute the proxy command. */ 122 if ((pid = fork()) == 0) { 123 char *argv[10]; 124 125 close(sp[1]); 126 /* Redirect stdin and stdout. */ 127 if (sp[0] != 0) { 128 if (dup2(sp[0], 0) == -1) 129 perror("dup2 stdin"); 130 } 131 if (sp[0] != 1) { 132 if (dup2(sp[0], 1) == -1) 133 perror("dup2 stdout"); 134 } 135 if (sp[0] >= 2) 136 close(sp[0]); 137 138 /* 139 * Stderr is left for non-ControlPersist connections is so 140 * error messages may be printed on the user's terminal. 141 */ 142 if (!debug_flag && options.control_path != NULL && 143 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 144 error_f("stdfd_devnull failed"); 145 146 argv[0] = shell; 147 argv[1] = "-c"; 148 argv[2] = command_string; 149 argv[3] = NULL; 150 151 /* 152 * Execute the proxy command. 153 * Note that we gave up any extra privileges above. 154 */ 155 execv(argv[0], argv); 156 perror(argv[0]); 157 exit(1); 158 } 159 /* Parent. */ 160 if (pid == -1) 161 fatal("fork failed: %.100s", strerror(errno)); 162 close(sp[0]); 163 free(command_string); 164 165 if ((sock = mm_receive_fd(sp[1])) == -1) 166 fatal("proxy dialer did not pass back a connection"); 167 close(sp[1]); 168 169 while (waitpid(pid, NULL, 0) == -1) 170 if (errno != EINTR) 171 fatal("Couldn't wait for child: %s", strerror(errno)); 172 173 /* Set the connection file descriptors. */ 174 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 175 return -1; /* ssh_packet_set_connection logs error */ 176 177 return 0; 178 } 179 180 /* 181 * Connect to the given ssh server using a proxy command. 182 */ 183 static int 184 ssh_proxy_connect(struct ssh *ssh, const char *host, const char *host_arg, 185 u_short port, const char *proxy_command) 186 { 187 char *command_string; 188 int pin[2], pout[2]; 189 pid_t pid; 190 char *shell; 191 192 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 193 shell = _PATH_BSHELL; 194 195 /* Create pipes for communicating with the proxy. */ 196 if (pipe(pin) == -1 || pipe(pout) == -1) 197 fatal("Could not create pipes to communicate with the proxy: %.100s", 198 strerror(errno)); 199 200 command_string = expand_proxy_command(proxy_command, options.user, 201 host, host_arg, port); 202 debug("Executing proxy command: %.500s", command_string); 203 204 /* Fork and execute the proxy command. */ 205 if ((pid = fork()) == 0) { 206 char *argv[10]; 207 208 /* Redirect stdin and stdout. */ 209 close(pin[1]); 210 if (pin[0] != 0) { 211 if (dup2(pin[0], 0) == -1) 212 perror("dup2 stdin"); 213 close(pin[0]); 214 } 215 close(pout[0]); 216 if (dup2(pout[1], 1) == -1) 217 perror("dup2 stdout"); 218 /* Cannot be 1 because pin allocated two descriptors. */ 219 close(pout[1]); 220 221 /* 222 * Stderr is left for non-ControlPersist connections is so 223 * error messages may be printed on the user's terminal. 224 */ 225 if (!debug_flag && options.control_path != NULL && 226 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 227 error_f("stdfd_devnull failed"); 228 229 argv[0] = shell; 230 argv[1] = "-c"; 231 argv[2] = command_string; 232 argv[3] = NULL; 233 234 /* Execute the proxy command. Note that we gave up any 235 extra privileges above. */ 236 ssh_signal(SIGPIPE, SIG_DFL); 237 execv(argv[0], argv); 238 perror(argv[0]); 239 exit(1); 240 } 241 /* Parent. */ 242 if (pid == -1) 243 fatal("fork failed: %.100s", strerror(errno)); 244 else 245 proxy_command_pid = pid; /* save pid to clean up later */ 246 247 /* Close child side of the descriptors. */ 248 close(pin[0]); 249 close(pout[1]); 250 251 /* Free the command name. */ 252 free(command_string); 253 254 /* Set the connection file descriptors. */ 255 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 256 return -1; /* ssh_packet_set_connection logs error */ 257 258 return 0; 259 } 260 261 void 262 ssh_kill_proxy_command(void) 263 { 264 /* 265 * Send SIGHUP to proxy command if used. We don't wait() in 266 * case it hangs and instead rely on init to reap the child 267 */ 268 if (proxy_command_pid > 1) 269 kill(proxy_command_pid, SIGHUP); 270 } 271 272 /* 273 * Search a interface address list (returned from getifaddrs(3)) for an 274 * address that matches the desired address family on the specified interface. 275 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 276 */ 277 static int 278 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 279 struct sockaddr_storage *resultp, socklen_t *rlenp) 280 { 281 struct sockaddr_in6 *sa6; 282 struct sockaddr_in *sa; 283 struct in6_addr *v6addr; 284 const struct ifaddrs *ifa; 285 int allow_local; 286 287 /* 288 * Prefer addresses that are not loopback or linklocal, but use them 289 * if nothing else matches. 290 */ 291 for (allow_local = 0; allow_local < 2; allow_local++) { 292 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 293 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 294 (ifa->ifa_flags & IFF_UP) == 0 || 295 ifa->ifa_addr->sa_family != af || 296 strcmp(ifa->ifa_name, options.bind_interface) != 0) 297 continue; 298 switch (ifa->ifa_addr->sa_family) { 299 case AF_INET: 300 sa = (struct sockaddr_in *)ifa->ifa_addr; 301 if (!allow_local && sa->sin_addr.s_addr == 302 htonl(INADDR_LOOPBACK)) 303 continue; 304 if (*rlenp < sizeof(struct sockaddr_in)) { 305 error_f("v4 addr doesn't fit"); 306 return -1; 307 } 308 *rlenp = sizeof(struct sockaddr_in); 309 memcpy(resultp, sa, *rlenp); 310 return 0; 311 case AF_INET6: 312 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 313 v6addr = &sa6->sin6_addr; 314 if (!allow_local && 315 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 316 IN6_IS_ADDR_LOOPBACK(v6addr))) 317 continue; 318 if (*rlenp < sizeof(struct sockaddr_in6)) { 319 error_f("v6 addr doesn't fit"); 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 } 330 331 /* 332 * Creates a socket for use as the ssh connection. 333 */ 334 static int 335 ssh_create_socket(struct addrinfo *ai) 336 { 337 int sock, r; 338 struct sockaddr_storage bindaddr; 339 socklen_t bindaddrlen = 0; 340 struct addrinfo hints, *res = NULL; 341 struct ifaddrs *ifaddrs = NULL; 342 char ntop[NI_MAXHOST]; 343 344 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 345 if (sock == -1) { 346 error("socket: %s", strerror(errno)); 347 return -1; 348 } 349 fcntl(sock, F_SETFD, FD_CLOEXEC); 350 351 /* Use interactive QOS (if specified) until authentication completed */ 352 if (options.ip_qos_interactive != INT_MAX) 353 set_sock_tos(sock, options.ip_qos_interactive); 354 355 /* Bind the socket to an alternative local IP address */ 356 if (options.bind_address == NULL && options.bind_interface == NULL) 357 return sock; 358 359 if (options.bind_address != NULL) { 360 memset(&hints, 0, sizeof(hints)); 361 hints.ai_family = ai->ai_family; 362 hints.ai_socktype = ai->ai_socktype; 363 hints.ai_protocol = ai->ai_protocol; 364 hints.ai_flags = AI_PASSIVE; 365 if ((r = getaddrinfo(options.bind_address, NULL, 366 &hints, &res)) != 0) { 367 error("getaddrinfo: %s: %s", options.bind_address, 368 ssh_gai_strerror(r)); 369 goto fail; 370 } 371 if (res == NULL) { 372 error("getaddrinfo: no addrs"); 373 goto fail; 374 } 375 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 376 bindaddrlen = res->ai_addrlen; 377 } else if (options.bind_interface != NULL) { 378 if ((r = getifaddrs(&ifaddrs)) != 0) { 379 error("getifaddrs: %s: %s", options.bind_interface, 380 strerror(errno)); 381 goto fail; 382 } 383 bindaddrlen = sizeof(bindaddr); 384 if (check_ifaddrs(options.bind_interface, ai->ai_family, 385 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 386 logit("getifaddrs: %s: no suitable addresses", 387 options.bind_interface); 388 goto fail; 389 } 390 } 391 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 392 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 393 error_f("getnameinfo failed: %s", ssh_gai_strerror(r)); 394 goto fail; 395 } 396 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 397 error("bind %s: %s", ntop, strerror(errno)); 398 goto fail; 399 } 400 debug_f("bound to %s", ntop); 401 /* success */ 402 goto out; 403 fail: 404 close(sock); 405 sock = -1; 406 out: 407 if (res != NULL) 408 freeaddrinfo(res); 409 if (ifaddrs != NULL) 410 freeifaddrs(ifaddrs); 411 return sock; 412 } 413 414 /* 415 * Opens a TCP/IP connection to the remote server on the given host. 416 * The address of the remote host will be returned in hostaddr. 417 * If port is 0, the default port will be used. 418 * Connection_attempts specifies the maximum number of tries (one per 419 * second). If proxy_command is non-NULL, it specifies the command (with %h 420 * and %p substituted for host and port, respectively) to use to contact 421 * the daemon. 422 */ 423 static int 424 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 425 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts, 426 int *timeout_ms, int want_keepalive) 427 { 428 int on = 1, saved_timeout_ms = *timeout_ms; 429 int oerrno, sock = -1, attempt; 430 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 431 struct addrinfo *ai; 432 433 debug3_f("entering"); 434 memset(ntop, 0, sizeof(ntop)); 435 memset(strport, 0, sizeof(strport)); 436 437 for (attempt = 0; attempt < connection_attempts; attempt++) { 438 if (attempt > 0) { 439 /* Sleep a moment before retrying. */ 440 sleep(1); 441 debug("Trying again..."); 442 } 443 /* 444 * Loop through addresses for this host, and try each one in 445 * sequence until the connection succeeds. 446 */ 447 for (ai = aitop; ai; ai = ai->ai_next) { 448 if (ai->ai_family != AF_INET && 449 ai->ai_family != AF_INET6) { 450 errno = EAFNOSUPPORT; 451 continue; 452 } 453 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 454 ntop, sizeof(ntop), strport, sizeof(strport), 455 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 456 oerrno = errno; 457 error_f("getnameinfo failed"); 458 errno = oerrno; 459 continue; 460 } 461 debug("Connecting to %.200s [%.100s] port %s.", 462 host, ntop, strport); 463 464 /* Create a socket for connecting. */ 465 sock = ssh_create_socket(ai); 466 if (sock < 0) { 467 /* Any error is already output */ 468 errno = 0; 469 continue; 470 } 471 472 *timeout_ms = saved_timeout_ms; 473 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 474 timeout_ms) >= 0) { 475 /* Successful connection. */ 476 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 477 break; 478 } else { 479 oerrno = errno; 480 debug("connect to address %s port %s: %s", 481 ntop, strport, strerror(errno)); 482 close(sock); 483 sock = -1; 484 errno = oerrno; 485 } 486 } 487 if (sock != -1) 488 break; /* Successful connection. */ 489 } 490 491 /* Return failure if we didn't get a successful connection. */ 492 if (sock == -1) { 493 error("ssh: connect to host %s port %s: %s", 494 host, strport, errno == 0 ? "failure" : strerror(errno)); 495 return -1; 496 } 497 498 debug("Connection established."); 499 500 /* Set SO_KEEPALIVE if requested. */ 501 if (want_keepalive && 502 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 503 sizeof(on)) == -1) 504 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 505 506 /* Set the connection. */ 507 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 508 return -1; /* ssh_packet_set_connection logs error */ 509 510 return 0; 511 } 512 513 int 514 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg, 515 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port, 516 int connection_attempts, int *timeout_ms, int want_keepalive) 517 { 518 int in, out; 519 520 if (options.proxy_command == NULL) { 521 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 522 connection_attempts, timeout_ms, want_keepalive); 523 } else if (strcmp(options.proxy_command, "-") == 0) { 524 if ((in = dup(STDIN_FILENO)) == -1 || 525 (out = dup(STDOUT_FILENO)) == -1) { 526 if (in >= 0) 527 close(in); 528 error_f("dup() in/out failed"); 529 return -1; /* ssh_packet_set_connection logs error */ 530 } 531 if ((ssh_packet_set_connection(ssh, in, out)) == NULL) 532 return -1; /* ssh_packet_set_connection logs error */ 533 return 0; 534 } else if (options.proxy_use_fdpass) { 535 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port, 536 options.proxy_command); 537 } 538 return ssh_proxy_connect(ssh, host, host_arg, port, 539 options.proxy_command); 540 } 541 542 /* defaults to 'no' */ 543 static int 544 confirm(const char *prompt, const char *fingerprint) 545 { 546 const char *msg, *again = "Please type 'yes' or 'no': "; 547 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: "; 548 char *p, *cp; 549 int ret = -1; 550 551 if (options.batch_mode) 552 return 0; 553 for (msg = prompt;;msg = fingerprint ? again_fp : again) { 554 cp = p = read_passphrase(msg, RP_ECHO); 555 if (p == NULL) 556 return 0; 557 p += strspn(p, " \t"); /* skip leading whitespace */ 558 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */ 559 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 560 ret = 0; 561 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL && 562 strcmp(p, fingerprint) == 0)) 563 ret = 1; 564 free(cp); 565 if (ret != -1) 566 return ret; 567 } 568 } 569 570 static int 571 check_host_cert(const char *host, const struct sshkey *key) 572 { 573 const char *reason; 574 int r; 575 576 if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) { 577 error("%s", reason); 578 return 0; 579 } 580 if (sshbuf_len(key->cert->critical) != 0) { 581 error("Certificate for %s contains unsupported " 582 "critical options(s)", host); 583 return 0; 584 } 585 if ((r = sshkey_check_cert_sigtype(key, 586 options.ca_sign_algorithms)) != 0) { 587 logit_fr(r, "certificate signature algorithm %s", 588 (key->cert == NULL || key->cert->signature_type == NULL) ? 589 "(null)" : key->cert->signature_type); 590 return 0; 591 } 592 /* Do not attempt hostkey update if a certificate was successful */ 593 if (options.update_hostkeys != 0) { 594 options.update_hostkeys = 0; 595 debug3_f("certificate host key in use; disabling UpdateHostkeys"); 596 } 597 return 1; 598 } 599 600 static int 601 sockaddr_is_local(struct sockaddr *hostaddr) 602 { 603 switch (hostaddr->sa_family) { 604 case AF_INET: 605 return (ntohl(((struct sockaddr_in *)hostaddr)-> 606 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 607 case AF_INET6: 608 return IN6_IS_ADDR_LOOPBACK( 609 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 610 default: 611 return 0; 612 } 613 } 614 615 /* 616 * Prepare the hostname and ip address strings that are used to lookup 617 * host keys in known_hosts files. These may have a port number appended. 618 */ 619 void 620 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 621 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 622 { 623 char ntop[NI_MAXHOST]; 624 625 /* 626 * We don't have the remote ip-address for connections 627 * using a proxy command 628 */ 629 if (hostfile_ipaddr != NULL) { 630 if (options.proxy_command == NULL) { 631 if (getnameinfo(hostaddr, hostaddr->sa_len, 632 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 633 fatal_f("getnameinfo failed"); 634 *hostfile_ipaddr = put_host_port(ntop, port); 635 } else { 636 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 637 "command>"); 638 } 639 } 640 641 /* 642 * Allow the user to record the key under a different name or 643 * differentiate a non-standard port. This is useful for ssh 644 * tunneling over forwarded connections or if you run multiple 645 * sshd's on different ports on the same machine. 646 */ 647 if (hostfile_hostname != NULL) { 648 if (options.host_key_alias != NULL) { 649 *hostfile_hostname = xstrdup(options.host_key_alias); 650 debug("using hostkeyalias: %s", *hostfile_hostname); 651 } else { 652 *hostfile_hostname = put_host_port(hostname, port); 653 } 654 } 655 } 656 657 /* returns non-zero if path appears in hostfiles, or 0 if not. */ 658 static int 659 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles) 660 { 661 u_int i; 662 663 for (i = 0; i < num_hostfiles; i++) { 664 if (strcmp(path, hostfiles[i]) == 0) 665 return 1; 666 } 667 return 0; 668 } 669 670 struct find_by_key_ctx { 671 const char *host, *ip; 672 const struct sshkey *key; 673 char **names; 674 u_int nnames; 675 }; 676 677 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */ 678 static char * 679 try_tilde_unexpand(const char *path) 680 { 681 char *home, *ret = NULL; 682 size_t l; 683 684 if (*path != '/') 685 return xstrdup(path); 686 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0) 687 return xstrdup(path); 688 if (strncmp(path, home, l) != 0) 689 return xstrdup(path); 690 /* 691 * ensure we have matched on a path boundary: either the $HOME that 692 * we just compared ends with a '/' or the next character of the path 693 * must be a '/'. 694 */ 695 if (home[l - 1] != '/' && path[l] != '/') 696 return xstrdup(path); 697 if (path[l] == '/') 698 l++; 699 xasprintf(&ret, "~/%s", path + l); 700 return ret; 701 } 702 703 static int 704 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx) 705 { 706 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx; 707 char *path; 708 709 /* we are looking for keys with names that *do not* match */ 710 if ((l->match & HKF_MATCH_HOST) != 0) 711 return 0; 712 /* not interested in marker lines */ 713 if (l->marker != MRK_NONE) 714 return 0; 715 /* we are only interested in exact key matches */ 716 if (l->key == NULL || !sshkey_equal(ctx->key, l->key)) 717 return 0; 718 path = try_tilde_unexpand(l->path); 719 debug_f("found matching key in %s:%lu", path, l->linenum); 720 ctx->names = xrecallocarray(ctx->names, 721 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names)); 722 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum, 723 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ? 724 "[hashed name]" : l->hosts); 725 ctx->nnames++; 726 free(path); 727 return 0; 728 } 729 730 static int 731 hostkeys_find_by_key_hostfile(const char *file, const char *which, 732 struct find_by_key_ctx *ctx) 733 { 734 int r; 735 736 debug3_f("trying %s hostfile \"%s\"", which, file); 737 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx, 738 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) { 739 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) { 740 debug_f("hostkeys file %s does not exist", file); 741 return 0; 742 } 743 error_fr(r, "hostkeys_foreach failed for %s", file); 744 return r; 745 } 746 return 0; 747 } 748 749 /* 750 * Find 'key' in known hosts file(s) that do not match host/ip. 751 * Used to display also-known-as information for previously-unseen hostkeys. 752 */ 753 static void 754 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key, 755 char **user_hostfiles, u_int num_user_hostfiles, 756 char **system_hostfiles, u_int num_system_hostfiles, 757 char ***names, u_int *nnames) 758 { 759 struct find_by_key_ctx ctx = {0, 0, 0, 0, 0}; 760 u_int i; 761 762 *names = NULL; 763 *nnames = 0; 764 765 if (key == NULL || sshkey_is_cert(key)) 766 return; 767 768 ctx.host = host; 769 ctx.ip = ip; 770 ctx.key = key; 771 772 for (i = 0; i < num_user_hostfiles; i++) { 773 if (hostkeys_find_by_key_hostfile(user_hostfiles[i], 774 "user", &ctx) != 0) 775 goto fail; 776 } 777 for (i = 0; i < num_system_hostfiles; i++) { 778 if (hostkeys_find_by_key_hostfile(system_hostfiles[i], 779 "system", &ctx) != 0) 780 goto fail; 781 } 782 /* success */ 783 *names = ctx.names; 784 *nnames = ctx.nnames; 785 ctx.names = NULL; 786 ctx.nnames = 0; 787 return; 788 fail: 789 for (i = 0; i < ctx.nnames; i++) 790 free(ctx.names[i]); 791 free(ctx.names); 792 } 793 794 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */ 795 static char * 796 other_hostkeys_message(const char *host, const char *ip, 797 const struct sshkey *key, 798 char **user_hostfiles, u_int num_user_hostfiles, 799 char **system_hostfiles, u_int num_system_hostfiles) 800 { 801 char *ret = NULL, **othernames = NULL; 802 u_int i, n, num_othernames = 0; 803 804 hostkeys_find_by_key(host, ip, key, 805 user_hostfiles, num_user_hostfiles, 806 system_hostfiles, num_system_hostfiles, 807 &othernames, &num_othernames); 808 if (num_othernames == 0) 809 return xstrdup("This key is not known by any other names"); 810 811 xasprintf(&ret, "This host key is known by the following other " 812 "names/addresses:"); 813 814 n = num_othernames; 815 if (n > MAX_OTHER_NAMES) 816 n = MAX_OTHER_NAMES; 817 for (i = 0; i < n; i++) { 818 xextendf(&ret, "\n", " %s", othernames[i]); 819 } 820 if (n < num_othernames) { 821 xextendf(&ret, "\n", " (%d additional names ommitted)", 822 num_othernames - n); 823 } 824 for (i = 0; i < num_othernames; i++) 825 free(othernames[i]); 826 free(othernames); 827 return ret; 828 } 829 830 /* 831 * check whether the supplied host key is valid, return -1 if the key 832 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 833 */ 834 #define RDRW 0 835 #define RDONLY 1 836 #define ROQUIET 2 837 static int 838 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 839 struct sshkey *host_key, int readonly, 840 char **user_hostfiles, u_int num_user_hostfiles, 841 char **system_hostfiles, u_int num_system_hostfiles) 842 { 843 HostStatus host_status = -1, ip_status = -1; 844 struct sshkey *raw_key = NULL; 845 char *ip = NULL, *host = NULL; 846 char hostline[1000], *hostp, *fp, *ra; 847 char msg[1024]; 848 const char *type; 849 const struct hostkey_entry *host_found = NULL, *ip_found = NULL; 850 int len, cancelled_forwarding = 0, confirmed; 851 int local = sockaddr_is_local(hostaddr); 852 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 853 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 854 struct hostkeys *host_hostkeys, *ip_hostkeys; 855 u_int i; 856 857 /* 858 * Force accepting of the host key for loopback/localhost. The 859 * problem is that if the home directory is NFS-mounted to multiple 860 * machines, localhost will refer to a different machine in each of 861 * them, and the user will get bogus HOST_CHANGED warnings. This 862 * essentially disables host authentication for localhost; however, 863 * this is probably not a real problem. 864 */ 865 if (options.no_host_authentication_for_localhost == 1 && local && 866 options.host_key_alias == NULL) { 867 debug("Forcing accepting of host key for " 868 "loopback/localhost."); 869 options.update_hostkeys = 0; 870 return 0; 871 } 872 873 /* 874 * Prepare the hostname and address strings used for hostkey lookup. 875 * In some cases, these will have a port number appended. 876 */ 877 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 878 879 /* 880 * Turn off check_host_ip if the connection is to localhost, via proxy 881 * command or if we don't have a hostname to compare with 882 */ 883 if (options.check_host_ip && (local || 884 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 885 options.check_host_ip = 0; 886 887 host_hostkeys = init_hostkeys(); 888 for (i = 0; i < num_user_hostfiles; i++) 889 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0); 890 for (i = 0; i < num_system_hostfiles; i++) 891 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0); 892 893 ip_hostkeys = NULL; 894 if (!want_cert && options.check_host_ip) { 895 ip_hostkeys = init_hostkeys(); 896 for (i = 0; i < num_user_hostfiles; i++) 897 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0); 898 for (i = 0; i < num_system_hostfiles; i++) 899 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0); 900 } 901 902 retry: 903 /* Reload these as they may have changed on cert->key downgrade */ 904 want_cert = sshkey_is_cert(host_key); 905 type = sshkey_type(host_key); 906 907 /* 908 * Check if the host key is present in the user's list of known 909 * hosts or in the systemwide list. 910 */ 911 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 912 &host_found); 913 914 /* 915 * Also perform check for the ip address, skip the check if we are 916 * localhost, looking for a certificate, or the hostname was an ip 917 * address to begin with. 918 */ 919 if (!want_cert && ip_hostkeys != NULL) { 920 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 921 &ip_found); 922 if (host_status == HOST_CHANGED && 923 (ip_status != HOST_CHANGED || 924 (ip_found != NULL && 925 !sshkey_equal(ip_found->key, host_found->key)))) 926 host_ip_differ = 1; 927 } else 928 ip_status = host_status; 929 930 switch (host_status) { 931 case HOST_OK: 932 /* The host is known and the key matches. */ 933 debug("Host '%.200s' is known and matches the %s host %s.", 934 host, type, want_cert ? "certificate" : "key"); 935 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 936 host_found->file, host_found->line); 937 if (want_cert && 938 !check_host_cert(options.host_key_alias == NULL ? 939 hostname : options.host_key_alias, host_key)) 940 goto fail; 941 /* Turn off UpdateHostkeys if key was in system known_hosts */ 942 if (options.update_hostkeys != 0 && 943 (path_in_hostfiles(host_found->file, 944 system_hostfiles, num_system_hostfiles) || 945 (ip_status == HOST_OK && ip_found != NULL && 946 path_in_hostfiles(ip_found->file, 947 system_hostfiles, num_system_hostfiles)))) { 948 options.update_hostkeys = 0; 949 debug3_f("host key found in GlobalKnownHostsFile; " 950 "disabling UpdateHostkeys"); 951 } 952 if (options.check_host_ip && ip_status == HOST_NEW) { 953 if (readonly || want_cert) 954 logit("%s host key for IP address " 955 "'%.128s' not in list of known hosts.", 956 type, ip); 957 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 958 host_key, options.hash_known_hosts)) 959 logit("Failed to add the %s host key for IP " 960 "address '%.128s' to the list of known " 961 "hosts (%.500s).", type, ip, 962 user_hostfiles[0]); 963 else 964 logit("Warning: Permanently added the %s host " 965 "key for IP address '%.128s' to the list " 966 "of known hosts.", type, ip); 967 } else if (options.visual_host_key) { 968 fp = sshkey_fingerprint(host_key, 969 options.fingerprint_hash, SSH_FP_DEFAULT); 970 ra = sshkey_fingerprint(host_key, 971 options.fingerprint_hash, SSH_FP_RANDOMART); 972 if (fp == NULL || ra == NULL) 973 fatal_f("sshkey_fingerprint failed"); 974 logit("Host key fingerprint is %s\n%s", fp, ra); 975 free(ra); 976 free(fp); 977 } 978 hostkey_trusted = 1; 979 break; 980 case HOST_NEW: 981 if (options.host_key_alias == NULL && port != 0 && 982 port != SSH_DEFAULT_PORT) { 983 debug("checking without port identifier"); 984 if (check_host_key(hostname, hostaddr, 0, host_key, 985 ROQUIET, user_hostfiles, num_user_hostfiles, 986 system_hostfiles, num_system_hostfiles) == 0) { 987 debug("found matching key w/out port"); 988 break; 989 } 990 } 991 if (readonly || want_cert) 992 goto fail; 993 /* The host is new. */ 994 if (options.strict_host_key_checking == 995 SSH_STRICT_HOSTKEY_YES) { 996 /* 997 * User has requested strict host key checking. We 998 * will not add the host key automatically. The only 999 * alternative left is to abort. 1000 */ 1001 error("No %s host key is known for %.200s and you " 1002 "have requested strict checking.", type, host); 1003 goto fail; 1004 } else if (options.strict_host_key_checking == 1005 SSH_STRICT_HOSTKEY_ASK) { 1006 char *msg1 = NULL, *msg2 = NULL; 1007 1008 xasprintf(&msg1, "The authenticity of host " 1009 "'%.200s (%s)' can't be established", host, ip); 1010 1011 if (show_other_keys(host_hostkeys, host_key)) { 1012 xextendf(&msg1, "\n", "but keys of different " 1013 "type are already known for this host."); 1014 } else 1015 xextendf(&msg1, "", "."); 1016 1017 fp = sshkey_fingerprint(host_key, 1018 options.fingerprint_hash, SSH_FP_DEFAULT); 1019 ra = sshkey_fingerprint(host_key, 1020 options.fingerprint_hash, SSH_FP_RANDOMART); 1021 if (fp == NULL || ra == NULL) 1022 fatal_f("sshkey_fingerprint failed"); 1023 xextendf(&msg1, "\n", "%s key fingerprint is %s.", 1024 type, fp); 1025 if (options.visual_host_key) 1026 xextendf(&msg1, "\n", "%s", ra); 1027 if (options.verify_host_key_dns) { 1028 xextendf(&msg1, "\n", 1029 "%s host key fingerprint found in DNS.", 1030 matching_host_key_dns ? 1031 "Matching" : "No matching"); 1032 } 1033 /* msg2 informs for other names matching this key */ 1034 if ((msg2 = other_hostkeys_message(host, ip, host_key, 1035 user_hostfiles, num_user_hostfiles, 1036 system_hostfiles, num_system_hostfiles)) != NULL) 1037 xextendf(&msg1, "\n", "%s", msg2); 1038 1039 xextendf(&msg1, "\n", 1040 "Are you sure you want to continue connecting " 1041 "(yes/no/[fingerprint])? "); 1042 1043 confirmed = confirm(msg1, fp); 1044 free(ra); 1045 free(fp); 1046 free(msg1); 1047 free(msg2); 1048 if (!confirmed) 1049 goto fail; 1050 hostkey_trusted = 1; /* user explicitly confirmed */ 1051 } 1052 /* 1053 * If in "new" or "off" strict mode, add the key automatically 1054 * to the local known_hosts file. 1055 */ 1056 if (options.check_host_ip && ip_status == HOST_NEW) { 1057 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1058 hostp = hostline; 1059 if (options.hash_known_hosts) { 1060 /* Add hash of host and IP separately */ 1061 r = add_host_to_hostfile(user_hostfiles[0], 1062 host, host_key, options.hash_known_hosts) && 1063 add_host_to_hostfile(user_hostfiles[0], ip, 1064 host_key, options.hash_known_hosts); 1065 } else { 1066 /* Add unhashed "host,ip" */ 1067 r = add_host_to_hostfile(user_hostfiles[0], 1068 hostline, host_key, 1069 options.hash_known_hosts); 1070 } 1071 } else { 1072 r = add_host_to_hostfile(user_hostfiles[0], host, 1073 host_key, options.hash_known_hosts); 1074 hostp = host; 1075 } 1076 1077 if (!r) 1078 logit("Failed to add the host to the list of known " 1079 "hosts (%.500s).", user_hostfiles[0]); 1080 else 1081 logit("Warning: Permanently added '%.200s' (%s) to the " 1082 "list of known hosts.", hostp, type); 1083 break; 1084 case HOST_REVOKED: 1085 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1086 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1087 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1088 error("The %s host key for %s is marked as revoked.", type, host); 1089 error("This could mean that a stolen key is being used to"); 1090 error("impersonate this host."); 1091 1092 /* 1093 * If strict host key checking is in use, the user will have 1094 * to edit the key manually and we can only abort. 1095 */ 1096 if (options.strict_host_key_checking != 1097 SSH_STRICT_HOSTKEY_OFF) { 1098 error("%s host key for %.200s was revoked and you have " 1099 "requested strict checking.", type, host); 1100 goto fail; 1101 } 1102 goto continue_unsafe; 1103 1104 case HOST_CHANGED: 1105 if (want_cert) { 1106 /* 1107 * This is only a debug() since it is valid to have 1108 * CAs with wildcard DNS matches that don't match 1109 * all hosts that one might visit. 1110 */ 1111 debug("Host certificate authority does not " 1112 "match %s in %s:%lu", CA_MARKER, 1113 host_found->file, host_found->line); 1114 goto fail; 1115 } 1116 if (readonly == ROQUIET) 1117 goto fail; 1118 if (options.check_host_ip && host_ip_differ) { 1119 char *key_msg; 1120 if (ip_status == HOST_NEW) 1121 key_msg = "is unknown"; 1122 else if (ip_status == HOST_OK) 1123 key_msg = "is unchanged"; 1124 else 1125 key_msg = "has a different value"; 1126 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1127 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1128 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1129 error("The %s host key for %s has changed,", type, host); 1130 error("and the key for the corresponding IP address %s", ip); 1131 error("%s. This could either mean that", key_msg); 1132 error("DNS SPOOFING is happening or the IP address for the host"); 1133 error("and its host key have changed at the same time."); 1134 if (ip_status != HOST_NEW) 1135 error("Offending key for IP in %s:%lu", 1136 ip_found->file, ip_found->line); 1137 } 1138 /* The host key has changed. */ 1139 warn_changed_key(host_key); 1140 error("Add correct host key in %.100s to get rid of this message.", 1141 user_hostfiles[0]); 1142 error("Offending %s key in %s:%lu", 1143 sshkey_type(host_found->key), 1144 host_found->file, host_found->line); 1145 1146 /* 1147 * If strict host key checking is in use, the user will have 1148 * to edit the key manually and we can only abort. 1149 */ 1150 if (options.strict_host_key_checking != 1151 SSH_STRICT_HOSTKEY_OFF) { 1152 error("Host key for %.200s has changed and you have " 1153 "requested strict checking.", host); 1154 goto fail; 1155 } 1156 1157 continue_unsafe: 1158 /* 1159 * If strict host key checking has not been requested, allow 1160 * the connection but without MITM-able authentication or 1161 * forwarding. 1162 */ 1163 if (options.password_authentication) { 1164 error("Password authentication is disabled to avoid " 1165 "man-in-the-middle attacks."); 1166 options.password_authentication = 0; 1167 cancelled_forwarding = 1; 1168 } 1169 if (options.kbd_interactive_authentication) { 1170 error("Keyboard-interactive authentication is disabled" 1171 " to avoid man-in-the-middle attacks."); 1172 options.kbd_interactive_authentication = 0; 1173 options.challenge_response_authentication = 0; 1174 cancelled_forwarding = 1; 1175 } 1176 if (options.challenge_response_authentication) { 1177 error("Challenge/response authentication is disabled" 1178 " to avoid man-in-the-middle attacks."); 1179 options.challenge_response_authentication = 0; 1180 cancelled_forwarding = 1; 1181 } 1182 if (options.forward_agent) { 1183 error("Agent forwarding is disabled to avoid " 1184 "man-in-the-middle attacks."); 1185 options.forward_agent = 0; 1186 cancelled_forwarding = 1; 1187 } 1188 if (options.forward_x11) { 1189 error("X11 forwarding is disabled to avoid " 1190 "man-in-the-middle attacks."); 1191 options.forward_x11 = 0; 1192 cancelled_forwarding = 1; 1193 } 1194 if (options.num_local_forwards > 0 || 1195 options.num_remote_forwards > 0) { 1196 error("Port forwarding is disabled to avoid " 1197 "man-in-the-middle attacks."); 1198 options.num_local_forwards = 1199 options.num_remote_forwards = 0; 1200 cancelled_forwarding = 1; 1201 } 1202 if (options.tun_open != SSH_TUNMODE_NO) { 1203 error("Tunnel forwarding is disabled to avoid " 1204 "man-in-the-middle attacks."); 1205 options.tun_open = SSH_TUNMODE_NO; 1206 cancelled_forwarding = 1; 1207 } 1208 if (options.update_hostkeys != 0) { 1209 error("UpdateHostkeys is disabled because the host " 1210 "key is not trusted."); 1211 options.update_hostkeys = 0; 1212 } 1213 if (options.exit_on_forward_failure && cancelled_forwarding) 1214 fatal("Error: forwarding disabled due to host key " 1215 "check failure"); 1216 1217 /* 1218 * XXX Should permit the user to change to use the new id. 1219 * This could be done by converting the host key to an 1220 * identifying sentence, tell that the host identifies itself 1221 * by that sentence, and ask the user if he/she wishes to 1222 * accept the authentication. 1223 */ 1224 break; 1225 case HOST_FOUND: 1226 fatal("internal error"); 1227 break; 1228 } 1229 1230 if (options.check_host_ip && host_status != HOST_CHANGED && 1231 ip_status == HOST_CHANGED) { 1232 snprintf(msg, sizeof(msg), 1233 "Warning: the %s host key for '%.200s' " 1234 "differs from the key for the IP address '%.128s'" 1235 "\nOffending key for IP in %s:%lu", 1236 type, host, ip, ip_found->file, ip_found->line); 1237 if (host_status == HOST_OK) { 1238 len = strlen(msg); 1239 snprintf(msg + len, sizeof(msg) - len, 1240 "\nMatching host key in %s:%lu", 1241 host_found->file, host_found->line); 1242 } 1243 if (options.strict_host_key_checking == 1244 SSH_STRICT_HOSTKEY_ASK) { 1245 strlcat(msg, "\nAre you sure you want " 1246 "to continue connecting (yes/no)? ", sizeof(msg)); 1247 if (!confirm(msg, NULL)) 1248 goto fail; 1249 } else if (options.strict_host_key_checking != 1250 SSH_STRICT_HOSTKEY_OFF) { 1251 logit("%s", msg); 1252 error("Exiting, you have requested strict checking."); 1253 goto fail; 1254 } else { 1255 logit("%s", msg); 1256 } 1257 } 1258 1259 if (!hostkey_trusted && options.update_hostkeys) { 1260 debug_f("hostkey not known or explicitly trusted: " 1261 "disabling UpdateHostkeys"); 1262 options.update_hostkeys = 0; 1263 } 1264 1265 free(ip); 1266 free(host); 1267 if (host_hostkeys != NULL) 1268 free_hostkeys(host_hostkeys); 1269 if (ip_hostkeys != NULL) 1270 free_hostkeys(ip_hostkeys); 1271 return 0; 1272 1273 fail: 1274 if (want_cert && host_status != HOST_REVOKED) { 1275 /* 1276 * No matching certificate. Downgrade cert to raw key and 1277 * search normally. 1278 */ 1279 debug("No matching CA found. Retry with plain key"); 1280 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1281 fatal_fr(r, "decode key"); 1282 if ((r = sshkey_drop_cert(raw_key)) != 0) 1283 fatal_r(r, "Couldn't drop certificate"); 1284 host_key = raw_key; 1285 goto retry; 1286 } 1287 sshkey_free(raw_key); 1288 free(ip); 1289 free(host); 1290 if (host_hostkeys != NULL) 1291 free_hostkeys(host_hostkeys); 1292 if (ip_hostkeys != NULL) 1293 free_hostkeys(ip_hostkeys); 1294 return -1; 1295 } 1296 1297 /* returns 0 if key verifies or -1 if key does NOT verify */ 1298 int 1299 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key) 1300 { 1301 u_int i; 1302 int r = -1, flags = 0; 1303 char valid[64], *fp = NULL, *cafp = NULL; 1304 struct sshkey *plain = NULL; 1305 1306 if ((fp = sshkey_fingerprint(host_key, 1307 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1308 error_fr(r, "fingerprint host key"); 1309 r = -1; 1310 goto out; 1311 } 1312 1313 if (sshkey_is_cert(host_key)) { 1314 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1315 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1316 error_fr(r, "fingerprint CA key"); 1317 r = -1; 1318 goto out; 1319 } 1320 sshkey_format_cert_validity(host_key->cert, 1321 valid, sizeof(valid)); 1322 debug("Server host certificate: %s %s, serial %llu " 1323 "ID \"%s\" CA %s %s valid %s", 1324 sshkey_ssh_name(host_key), fp, 1325 (unsigned long long)host_key->cert->serial, 1326 host_key->cert->key_id, 1327 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1328 valid); 1329 for (i = 0; i < host_key->cert->nprincipals; i++) { 1330 debug2("Server host certificate hostname: %s", 1331 host_key->cert->principals[i]); 1332 } 1333 } else { 1334 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1335 } 1336 1337 if (sshkey_equal(previous_host_key, host_key)) { 1338 debug2_f("server host key %s %s matches cached key", 1339 sshkey_type(host_key), fp); 1340 r = 0; 1341 goto out; 1342 } 1343 1344 /* Check in RevokedHostKeys file if specified */ 1345 if (options.revoked_host_keys != NULL) { 1346 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1347 switch (r) { 1348 case 0: 1349 break; /* not revoked */ 1350 case SSH_ERR_KEY_REVOKED: 1351 error("Host key %s %s revoked by file %s", 1352 sshkey_type(host_key), fp, 1353 options.revoked_host_keys); 1354 r = -1; 1355 goto out; 1356 default: 1357 error_r(r, "Error checking host key %s %s in " 1358 "revoked keys file %s", sshkey_type(host_key), 1359 fp, options.revoked_host_keys); 1360 r = -1; 1361 goto out; 1362 } 1363 } 1364 1365 if (options.verify_host_key_dns) { 1366 /* 1367 * XXX certs are not yet supported for DNS, so downgrade 1368 * them and try the plain key. 1369 */ 1370 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1371 goto out; 1372 if (sshkey_is_cert(plain)) 1373 sshkey_drop_cert(plain); 1374 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1375 if (flags & DNS_VERIFY_FOUND) { 1376 if (options.verify_host_key_dns == 1 && 1377 flags & DNS_VERIFY_MATCH && 1378 flags & DNS_VERIFY_SECURE) { 1379 r = 0; 1380 goto out; 1381 } 1382 if (flags & DNS_VERIFY_MATCH) { 1383 matching_host_key_dns = 1; 1384 } else { 1385 warn_changed_key(plain); 1386 error("Update the SSHFP RR in DNS " 1387 "with the new host key to get rid " 1388 "of this message."); 1389 } 1390 } 1391 } 1392 } 1393 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1394 options.user_hostfiles, options.num_user_hostfiles, 1395 options.system_hostfiles, options.num_system_hostfiles); 1396 1397 out: 1398 sshkey_free(plain); 1399 free(fp); 1400 free(cafp); 1401 if (r == 0 && host_key != NULL) { 1402 sshkey_free(previous_host_key); 1403 r = sshkey_from_private(host_key, &previous_host_key); 1404 } 1405 1406 return r; 1407 } 1408 1409 /* 1410 * Starts a dialog with the server, and authenticates the current user on the 1411 * server. This does not need any extra privileges. The basic connection 1412 * to the server must already have been established before this is called. 1413 * If login fails, this function prints an error and never returns. 1414 * This function does not require super-user privileges. 1415 */ 1416 void 1417 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost, 1418 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1419 { 1420 char *host; 1421 char *server_user, *local_user; 1422 int r; 1423 1424 local_user = xstrdup(pw->pw_name); 1425 server_user = options.user ? options.user : local_user; 1426 1427 /* Convert the user-supplied hostname into all lowercase. */ 1428 host = xstrdup(orighost); 1429 lowercase(host); 1430 1431 /* Exchange protocol version identification strings with the server. */ 1432 if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0) 1433 sshpkt_fatal(ssh, r, "banner exchange"); 1434 1435 /* Put the connection into non-blocking mode. */ 1436 ssh_packet_set_nonblocking(ssh); 1437 1438 /* key exchange */ 1439 /* authenticate user */ 1440 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1441 ssh_kex2(ssh, host, hostaddr, port); 1442 ssh_userauth2(ssh, local_user, server_user, host, sensitive); 1443 free(local_user); 1444 free(host); 1445 } 1446 1447 /* print all known host keys for a given host, but skip keys of given type */ 1448 static int 1449 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1450 { 1451 int type[] = { 1452 KEY_RSA, 1453 KEY_DSA, 1454 KEY_ECDSA, 1455 KEY_ED25519, 1456 KEY_XMSS, 1457 -1 1458 }; 1459 int i, ret = 0; 1460 char *fp, *ra; 1461 const struct hostkey_entry *found; 1462 1463 for (i = 0; type[i] != -1; i++) { 1464 if (type[i] == key->type) 1465 continue; 1466 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], 1467 -1, &found)) 1468 continue; 1469 fp = sshkey_fingerprint(found->key, 1470 options.fingerprint_hash, SSH_FP_DEFAULT); 1471 ra = sshkey_fingerprint(found->key, 1472 options.fingerprint_hash, SSH_FP_RANDOMART); 1473 if (fp == NULL || ra == NULL) 1474 fatal_f("sshkey_fingerprint fail"); 1475 logit("WARNING: %s key found for host %s\n" 1476 "in %s:%lu\n" 1477 "%s key fingerprint %s.", 1478 sshkey_type(found->key), 1479 found->host, found->file, found->line, 1480 sshkey_type(found->key), fp); 1481 if (options.visual_host_key) 1482 logit("%s", ra); 1483 free(ra); 1484 free(fp); 1485 ret = 1; 1486 } 1487 return ret; 1488 } 1489 1490 static void 1491 warn_changed_key(struct sshkey *host_key) 1492 { 1493 char *fp; 1494 1495 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1496 SSH_FP_DEFAULT); 1497 if (fp == NULL) 1498 fatal_f("sshkey_fingerprint fail"); 1499 1500 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1501 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1502 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1503 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1504 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1505 error("It is also possible that a host key has just been changed."); 1506 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1507 sshkey_type(host_key), fp); 1508 error("Please contact your system administrator."); 1509 1510 free(fp); 1511 } 1512 1513 /* 1514 * Execute a local command 1515 */ 1516 int 1517 ssh_local_cmd(const char *args) 1518 { 1519 char *shell; 1520 pid_t pid; 1521 int status; 1522 void (*osighand)(int); 1523 1524 if (!options.permit_local_command || 1525 args == NULL || !*args) 1526 return (1); 1527 1528 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1529 shell = _PATH_BSHELL; 1530 1531 osighand = ssh_signal(SIGCHLD, SIG_DFL); 1532 pid = fork(); 1533 if (pid == 0) { 1534 ssh_signal(SIGPIPE, SIG_DFL); 1535 debug3("Executing %s -c \"%s\"", shell, args); 1536 execl(shell, shell, "-c", args, (char *)NULL); 1537 error("Couldn't execute %s -c \"%s\": %s", 1538 shell, args, strerror(errno)); 1539 _exit(1); 1540 } else if (pid == -1) 1541 fatal("fork failed: %.100s", strerror(errno)); 1542 while (waitpid(pid, &status, 0) == -1) 1543 if (errno != EINTR) 1544 fatal("Couldn't wait for child: %s", strerror(errno)); 1545 ssh_signal(SIGCHLD, osighand); 1546 1547 if (!WIFEXITED(status)) 1548 return (1); 1549 1550 return (WEXITSTATUS(status)); 1551 } 1552 1553 void 1554 maybe_add_key_to_agent(const char *authfile, struct sshkey *private, 1555 const char *comment, const char *passphrase) 1556 { 1557 int auth_sock = -1, r; 1558 const char *skprovider = NULL; 1559 1560 if (options.add_keys_to_agent == 0) 1561 return; 1562 1563 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1564 debug3("no authentication agent, not adding key"); 1565 return; 1566 } 1567 1568 if (options.add_keys_to_agent == 2 && 1569 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1570 debug3("user denied adding this key"); 1571 close(auth_sock); 1572 return; 1573 } 1574 if (sshkey_is_sk(private)) 1575 skprovider = options.sk_provider; 1576 if ((r = ssh_add_identity_constrained(auth_sock, private, 1577 comment == NULL ? authfile : comment, 1578 options.add_keys_to_agent_lifespan, 1579 (options.add_keys_to_agent == 3), 0, skprovider)) == 0) 1580 debug("identity added to agent: %s", authfile); 1581 else 1582 debug("could not add identity to agent: %s (%d)", authfile, r); 1583 close(auth_sock); 1584 } 1585