1 /* $OpenBSD: sshconnect.c,v 1.360 2022/11/03 21:59:20 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 /* 235 * Execute the proxy command. Note that we gave up any 236 * extra privileges above. 237 */ 238 ssh_signal(SIGPIPE, SIG_DFL); 239 execv(argv[0], argv); 240 perror(argv[0]); 241 exit(1); 242 } 243 /* Parent. */ 244 if (pid == -1) 245 fatal("fork failed: %.100s", strerror(errno)); 246 else 247 proxy_command_pid = pid; /* save pid to clean up later */ 248 249 /* Close child side of the descriptors. */ 250 close(pin[0]); 251 close(pout[1]); 252 253 /* Free the command name. */ 254 free(command_string); 255 256 /* Set the connection file descriptors. */ 257 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 258 return -1; /* ssh_packet_set_connection logs error */ 259 260 return 0; 261 } 262 263 void 264 ssh_kill_proxy_command(void) 265 { 266 /* 267 * Send SIGHUP to proxy command if used. We don't wait() in 268 * case it hangs and instead rely on init to reap the child 269 */ 270 if (proxy_command_pid > 1) 271 kill(proxy_command_pid, SIGHUP); 272 } 273 274 /* 275 * Search a interface address list (returned from getifaddrs(3)) for an 276 * address that matches the desired address family on the specified interface. 277 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 278 */ 279 static int 280 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 281 struct sockaddr_storage *resultp, socklen_t *rlenp) 282 { 283 struct sockaddr_in6 *sa6; 284 struct sockaddr_in *sa; 285 struct in6_addr *v6addr; 286 const struct ifaddrs *ifa; 287 int allow_local; 288 289 /* 290 * Prefer addresses that are not loopback or linklocal, but use them 291 * if nothing else matches. 292 */ 293 for (allow_local = 0; allow_local < 2; allow_local++) { 294 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 295 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 296 (ifa->ifa_flags & IFF_UP) == 0 || 297 ifa->ifa_addr->sa_family != af || 298 strcmp(ifa->ifa_name, options.bind_interface) != 0) 299 continue; 300 switch (ifa->ifa_addr->sa_family) { 301 case AF_INET: 302 sa = (struct sockaddr_in *)ifa->ifa_addr; 303 if (!allow_local && sa->sin_addr.s_addr == 304 htonl(INADDR_LOOPBACK)) 305 continue; 306 if (*rlenp < sizeof(struct sockaddr_in)) { 307 error_f("v4 addr doesn't fit"); 308 return -1; 309 } 310 *rlenp = sizeof(struct sockaddr_in); 311 memcpy(resultp, sa, *rlenp); 312 return 0; 313 case AF_INET6: 314 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 315 v6addr = &sa6->sin6_addr; 316 if (!allow_local && 317 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 318 IN6_IS_ADDR_LOOPBACK(v6addr))) 319 continue; 320 if (*rlenp < sizeof(struct sockaddr_in6)) { 321 error_f("v6 addr doesn't fit"); 322 return -1; 323 } 324 *rlenp = sizeof(struct sockaddr_in6); 325 memcpy(resultp, sa6, *rlenp); 326 return 0; 327 } 328 } 329 } 330 return -1; 331 } 332 333 /* 334 * Creates a socket for use as the ssh connection. 335 */ 336 static int 337 ssh_create_socket(struct addrinfo *ai) 338 { 339 int sock, r; 340 struct sockaddr_storage bindaddr; 341 socklen_t bindaddrlen = 0; 342 struct addrinfo hints, *res = NULL; 343 struct ifaddrs *ifaddrs = NULL; 344 char ntop[NI_MAXHOST]; 345 346 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 347 if (sock == -1) { 348 error("socket: %s", strerror(errno)); 349 return -1; 350 } 351 fcntl(sock, F_SETFD, FD_CLOEXEC); 352 353 /* Use interactive QOS (if specified) until authentication completed */ 354 if (options.ip_qos_interactive != INT_MAX) 355 set_sock_tos(sock, options.ip_qos_interactive); 356 357 /* Bind the socket to an alternative local IP address */ 358 if (options.bind_address == NULL && options.bind_interface == NULL) 359 return sock; 360 361 if (options.bind_address != NULL) { 362 memset(&hints, 0, sizeof(hints)); 363 hints.ai_family = ai->ai_family; 364 hints.ai_socktype = ai->ai_socktype; 365 hints.ai_protocol = ai->ai_protocol; 366 hints.ai_flags = AI_PASSIVE; 367 if ((r = getaddrinfo(options.bind_address, NULL, 368 &hints, &res)) != 0) { 369 error("getaddrinfo: %s: %s", options.bind_address, 370 ssh_gai_strerror(r)); 371 goto fail; 372 } 373 if (res == NULL) { 374 error("getaddrinfo: no addrs"); 375 goto fail; 376 } 377 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 378 bindaddrlen = res->ai_addrlen; 379 } else if (options.bind_interface != NULL) { 380 if ((r = getifaddrs(&ifaddrs)) != 0) { 381 error("getifaddrs: %s: %s", options.bind_interface, 382 strerror(errno)); 383 goto fail; 384 } 385 bindaddrlen = sizeof(bindaddr); 386 if (check_ifaddrs(options.bind_interface, ai->ai_family, 387 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 388 logit("getifaddrs: %s: no suitable addresses", 389 options.bind_interface); 390 goto fail; 391 } 392 } 393 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 394 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 395 error_f("getnameinfo failed: %s", ssh_gai_strerror(r)); 396 goto fail; 397 } 398 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 399 error("bind %s: %s", ntop, strerror(errno)); 400 goto fail; 401 } 402 debug_f("bound to %s", ntop); 403 /* success */ 404 goto out; 405 fail: 406 close(sock); 407 sock = -1; 408 out: 409 if (res != NULL) 410 freeaddrinfo(res); 411 if (ifaddrs != NULL) 412 freeifaddrs(ifaddrs); 413 return sock; 414 } 415 416 /* 417 * Opens a TCP/IP connection to the remote server on the given host. 418 * The address of the remote host will be returned in hostaddr. 419 * If port is 0, the default port will be used. 420 * Connection_attempts specifies the maximum number of tries (one per 421 * second). If proxy_command is non-NULL, it specifies the command (with %h 422 * and %p substituted for host and port, respectively) to use to contact 423 * the daemon. 424 */ 425 static int 426 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 427 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts, 428 int *timeout_ms, int want_keepalive) 429 { 430 int on = 1, saved_timeout_ms = *timeout_ms; 431 int oerrno, sock = -1, attempt; 432 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 433 struct addrinfo *ai; 434 435 debug3_f("entering"); 436 memset(ntop, 0, sizeof(ntop)); 437 memset(strport, 0, sizeof(strport)); 438 439 for (attempt = 0; attempt < connection_attempts; attempt++) { 440 if (attempt > 0) { 441 /* Sleep a moment before retrying. */ 442 sleep(1); 443 debug("Trying again..."); 444 } 445 /* 446 * Loop through addresses for this host, and try each one in 447 * sequence until the connection succeeds. 448 */ 449 for (ai = aitop; ai; ai = ai->ai_next) { 450 if (ai->ai_family != AF_INET && 451 ai->ai_family != AF_INET6) { 452 errno = EAFNOSUPPORT; 453 continue; 454 } 455 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 456 ntop, sizeof(ntop), strport, sizeof(strport), 457 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 458 oerrno = errno; 459 error_f("getnameinfo failed"); 460 errno = oerrno; 461 continue; 462 } 463 debug("Connecting to %.200s [%.100s] port %s.", 464 host, ntop, strport); 465 466 /* Create a socket for connecting. */ 467 sock = ssh_create_socket(ai); 468 if (sock < 0) { 469 /* Any error is already output */ 470 errno = 0; 471 continue; 472 } 473 474 *timeout_ms = saved_timeout_ms; 475 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 476 timeout_ms) >= 0) { 477 /* Successful connection. */ 478 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 479 break; 480 } else { 481 oerrno = errno; 482 debug("connect to address %s port %s: %s", 483 ntop, strport, strerror(errno)); 484 close(sock); 485 sock = -1; 486 errno = oerrno; 487 } 488 } 489 if (sock != -1) 490 break; /* Successful connection. */ 491 } 492 493 /* Return failure if we didn't get a successful connection. */ 494 if (sock == -1) { 495 error("ssh: connect to host %s port %s: %s", 496 host, strport, errno == 0 ? "failure" : strerror(errno)); 497 return -1; 498 } 499 500 debug("Connection established."); 501 502 /* Set SO_KEEPALIVE if requested. */ 503 if (want_keepalive && 504 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 505 sizeof(on)) == -1) 506 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 507 508 /* Set the connection. */ 509 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 510 return -1; /* ssh_packet_set_connection logs error */ 511 512 return 0; 513 } 514 515 int 516 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg, 517 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port, 518 int connection_attempts, int *timeout_ms, int want_keepalive) 519 { 520 int in, out; 521 522 if (options.proxy_command == NULL) { 523 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 524 connection_attempts, timeout_ms, want_keepalive); 525 } else if (strcmp(options.proxy_command, "-") == 0) { 526 if ((in = dup(STDIN_FILENO)) == -1 || 527 (out = dup(STDOUT_FILENO)) == -1) { 528 if (in >= 0) 529 close(in); 530 error_f("dup() in/out failed"); 531 return -1; /* ssh_packet_set_connection logs error */ 532 } 533 if ((ssh_packet_set_connection(ssh, in, out)) == NULL) 534 return -1; /* ssh_packet_set_connection logs error */ 535 return 0; 536 } else if (options.proxy_use_fdpass) { 537 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port, 538 options.proxy_command); 539 } 540 return ssh_proxy_connect(ssh, host, host_arg, port, 541 options.proxy_command); 542 } 543 544 /* defaults to 'no' */ 545 static int 546 confirm(const char *prompt, const char *fingerprint) 547 { 548 const char *msg, *again = "Please type 'yes' or 'no': "; 549 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: "; 550 char *p, *cp; 551 int ret = -1; 552 553 if (options.batch_mode) 554 return 0; 555 for (msg = prompt;;msg = fingerprint ? again_fp : again) { 556 cp = p = read_passphrase(msg, RP_ECHO); 557 if (p == NULL) 558 return 0; 559 p += strspn(p, " \t"); /* skip leading whitespace */ 560 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */ 561 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 562 ret = 0; 563 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL && 564 strcmp(p, fingerprint) == 0)) 565 ret = 1; 566 free(cp); 567 if (ret != -1) 568 return ret; 569 } 570 } 571 572 static int 573 sockaddr_is_local(struct sockaddr *hostaddr) 574 { 575 switch (hostaddr->sa_family) { 576 case AF_INET: 577 return (ntohl(((struct sockaddr_in *)hostaddr)-> 578 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 579 case AF_INET6: 580 return IN6_IS_ADDR_LOOPBACK( 581 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 582 default: 583 return 0; 584 } 585 } 586 587 /* 588 * Prepare the hostname and ip address strings that are used to lookup 589 * host keys in known_hosts files. These may have a port number appended. 590 */ 591 void 592 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 593 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 594 { 595 char ntop[NI_MAXHOST]; 596 597 /* 598 * We don't have the remote ip-address for connections 599 * using a proxy command 600 */ 601 if (hostfile_ipaddr != NULL) { 602 if (options.proxy_command == NULL) { 603 if (getnameinfo(hostaddr, hostaddr->sa_len, 604 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 605 fatal_f("getnameinfo failed"); 606 *hostfile_ipaddr = put_host_port(ntop, port); 607 } else { 608 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 609 "command>"); 610 } 611 } 612 613 /* 614 * Allow the user to record the key under a different name or 615 * differentiate a non-standard port. This is useful for ssh 616 * tunneling over forwarded connections or if you run multiple 617 * sshd's on different ports on the same machine. 618 */ 619 if (hostfile_hostname != NULL) { 620 if (options.host_key_alias != NULL) { 621 *hostfile_hostname = xstrdup(options.host_key_alias); 622 debug("using hostkeyalias: %s", *hostfile_hostname); 623 } else { 624 *hostfile_hostname = put_host_port(hostname, port); 625 } 626 } 627 } 628 629 /* returns non-zero if path appears in hostfiles, or 0 if not. */ 630 static int 631 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles) 632 { 633 u_int i; 634 635 for (i = 0; i < num_hostfiles; i++) { 636 if (strcmp(path, hostfiles[i]) == 0) 637 return 1; 638 } 639 return 0; 640 } 641 642 struct find_by_key_ctx { 643 const char *host, *ip; 644 const struct sshkey *key; 645 char **names; 646 u_int nnames; 647 }; 648 649 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */ 650 static char * 651 try_tilde_unexpand(const char *path) 652 { 653 char *home, *ret = NULL; 654 size_t l; 655 656 if (*path != '/') 657 return xstrdup(path); 658 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0) 659 return xstrdup(path); 660 if (strncmp(path, home, l) != 0) 661 return xstrdup(path); 662 /* 663 * ensure we have matched on a path boundary: either the $HOME that 664 * we just compared ends with a '/' or the next character of the path 665 * must be a '/'. 666 */ 667 if (home[l - 1] != '/' && path[l] != '/') 668 return xstrdup(path); 669 if (path[l] == '/') 670 l++; 671 xasprintf(&ret, "~/%s", path + l); 672 return ret; 673 } 674 675 static int 676 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx) 677 { 678 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx; 679 char *path; 680 681 /* we are looking for keys with names that *do not* match */ 682 if ((l->match & HKF_MATCH_HOST) != 0) 683 return 0; 684 /* not interested in marker lines */ 685 if (l->marker != MRK_NONE) 686 return 0; 687 /* we are only interested in exact key matches */ 688 if (l->key == NULL || !sshkey_equal(ctx->key, l->key)) 689 return 0; 690 path = try_tilde_unexpand(l->path); 691 debug_f("found matching key in %s:%lu", path, l->linenum); 692 ctx->names = xrecallocarray(ctx->names, 693 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names)); 694 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum, 695 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ? 696 "[hashed name]" : l->hosts); 697 ctx->nnames++; 698 free(path); 699 return 0; 700 } 701 702 static int 703 hostkeys_find_by_key_hostfile(const char *file, const char *which, 704 struct find_by_key_ctx *ctx) 705 { 706 int r; 707 708 debug3_f("trying %s hostfile \"%s\"", which, file); 709 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx, 710 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) { 711 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) { 712 debug_f("hostkeys file %s does not exist", file); 713 return 0; 714 } 715 error_fr(r, "hostkeys_foreach failed for %s", file); 716 return r; 717 } 718 return 0; 719 } 720 721 /* 722 * Find 'key' in known hosts file(s) that do not match host/ip. 723 * Used to display also-known-as information for previously-unseen hostkeys. 724 */ 725 static void 726 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key, 727 char **user_hostfiles, u_int num_user_hostfiles, 728 char **system_hostfiles, u_int num_system_hostfiles, 729 char ***names, u_int *nnames) 730 { 731 struct find_by_key_ctx ctx = {0, 0, 0, 0, 0}; 732 u_int i; 733 734 *names = NULL; 735 *nnames = 0; 736 737 if (key == NULL || sshkey_is_cert(key)) 738 return; 739 740 ctx.host = host; 741 ctx.ip = ip; 742 ctx.key = key; 743 744 for (i = 0; i < num_user_hostfiles; i++) { 745 if (hostkeys_find_by_key_hostfile(user_hostfiles[i], 746 "user", &ctx) != 0) 747 goto fail; 748 } 749 for (i = 0; i < num_system_hostfiles; i++) { 750 if (hostkeys_find_by_key_hostfile(system_hostfiles[i], 751 "system", &ctx) != 0) 752 goto fail; 753 } 754 /* success */ 755 *names = ctx.names; 756 *nnames = ctx.nnames; 757 ctx.names = NULL; 758 ctx.nnames = 0; 759 return; 760 fail: 761 for (i = 0; i < ctx.nnames; i++) 762 free(ctx.names[i]); 763 free(ctx.names); 764 } 765 766 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */ 767 static char * 768 other_hostkeys_message(const char *host, const char *ip, 769 const struct sshkey *key, 770 char **user_hostfiles, u_int num_user_hostfiles, 771 char **system_hostfiles, u_int num_system_hostfiles) 772 { 773 char *ret = NULL, **othernames = NULL; 774 u_int i, n, num_othernames = 0; 775 776 hostkeys_find_by_key(host, ip, key, 777 user_hostfiles, num_user_hostfiles, 778 system_hostfiles, num_system_hostfiles, 779 &othernames, &num_othernames); 780 if (num_othernames == 0) 781 return xstrdup("This key is not known by any other names."); 782 783 xasprintf(&ret, "This host key is known by the following other " 784 "names/addresses:"); 785 786 n = num_othernames; 787 if (n > MAX_OTHER_NAMES) 788 n = MAX_OTHER_NAMES; 789 for (i = 0; i < n; i++) { 790 xextendf(&ret, "\n", " %s", othernames[i]); 791 } 792 if (n < num_othernames) { 793 xextendf(&ret, "\n", " (%d additional names omitted)", 794 num_othernames - n); 795 } 796 for (i = 0; i < num_othernames; i++) 797 free(othernames[i]); 798 free(othernames); 799 return ret; 800 } 801 802 void 803 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template, 804 const char *invocation, const struct ssh_conn_info *cinfo, 805 const struct sshkey *host_key, const char *hostfile_hostname) 806 { 807 int r, i, ac = 0; 808 char *key_fp = NULL, *keytext = NULL, *tmp; 809 char *command = NULL, *tag = NULL, **av = NULL; 810 FILE *f = NULL; 811 pid_t pid; 812 void (*osigchld)(int); 813 814 xasprintf(&tag, "KnownHostsCommand-%s", invocation); 815 816 if (host_key != NULL) { 817 if ((key_fp = sshkey_fingerprint(host_key, 818 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 819 fatal_f("sshkey_fingerprint failed"); 820 if ((r = sshkey_to_base64(host_key, &keytext)) != 0) 821 fatal_fr(r, "sshkey_to_base64 failed"); 822 } 823 /* 824 * NB. all returns later this function should go via "out" to 825 * ensure the original SIGCHLD handler is restored properly. 826 */ 827 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 828 829 /* Turn the command into an argument vector */ 830 if (argv_split(command_template, &ac, &av, 0) != 0) { 831 error("%s \"%s\" contains invalid quotes", tag, 832 command_template); 833 goto out; 834 } 835 if (ac == 0) { 836 error("%s \"%s\" yielded no arguments", tag, 837 command_template); 838 goto out; 839 } 840 for (i = 1; i < ac; i++) { 841 tmp = percent_dollar_expand(av[i], 842 DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo), 843 "H", hostfile_hostname, 844 "I", invocation, 845 "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key), 846 "f", key_fp == NULL ? "NONE" : key_fp, 847 "K", keytext == NULL ? "NONE" : keytext, 848 (char *)NULL); 849 if (tmp == NULL) 850 fatal_f("percent_expand failed"); 851 free(av[i]); 852 av[i] = tmp; 853 } 854 /* Prepare a printable command for logs, etc. */ 855 command = argv_assemble(ac, av); 856 857 if ((pid = subprocess(tag, command, ac, av, &f, 858 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH| 859 SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0) 860 goto out; 861 862 load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1); 863 864 if (exited_cleanly(pid, tag, command, 0) != 0) 865 fatal("KnownHostsCommand failed"); 866 867 out: 868 if (f != NULL) 869 fclose(f); 870 ssh_signal(SIGCHLD, osigchld); 871 for (i = 0; i < ac; i++) 872 free(av[i]); 873 free(av); 874 free(tag); 875 free(command); 876 free(key_fp); 877 free(keytext); 878 } 879 880 /* 881 * check whether the supplied host key is valid, return -1 if the key 882 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 883 */ 884 #define RDRW 0 885 #define RDONLY 1 886 #define ROQUIET 2 887 static int 888 check_host_key(char *hostname, const struct ssh_conn_info *cinfo, 889 struct sockaddr *hostaddr, u_short port, 890 struct sshkey *host_key, int readonly, int clobber_port, 891 char **user_hostfiles, u_int num_user_hostfiles, 892 char **system_hostfiles, u_int num_system_hostfiles, 893 const char *hostfile_command) 894 { 895 HostStatus host_status = -1, ip_status = -1; 896 struct sshkey *raw_key = NULL; 897 char *ip = NULL, *host = NULL; 898 char hostline[1000], *hostp, *fp, *ra; 899 char msg[1024]; 900 const char *type, *fail_reason = NULL; 901 const struct hostkey_entry *host_found = NULL, *ip_found = NULL; 902 int len, cancelled_forwarding = 0, confirmed; 903 int local = sockaddr_is_local(hostaddr); 904 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 905 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 906 struct hostkeys *host_hostkeys, *ip_hostkeys; 907 u_int i; 908 909 /* 910 * Force accepting of the host key for loopback/localhost. The 911 * problem is that if the home directory is NFS-mounted to multiple 912 * machines, localhost will refer to a different machine in each of 913 * them, and the user will get bogus HOST_CHANGED warnings. This 914 * essentially disables host authentication for localhost; however, 915 * this is probably not a real problem. 916 */ 917 if (options.no_host_authentication_for_localhost == 1 && local && 918 options.host_key_alias == NULL) { 919 debug("Forcing accepting of host key for " 920 "loopback/localhost."); 921 options.update_hostkeys = 0; 922 return 0; 923 } 924 925 /* 926 * Don't ever try to write an invalid name to a known hosts file. 927 * Note: do this before get_hostfile_hostname_ipaddr() to catch 928 * '[' or ']' in the name before they are added. 929 */ 930 if (strcspn(hostname, "@?*#[]|'\'\"\\") != strlen(hostname)) { 931 debug_f("invalid hostname \"%s\"; will not record: %s", 932 hostname, fail_reason); 933 readonly = RDONLY; 934 } 935 936 /* 937 * Prepare the hostname and address strings used for hostkey lookup. 938 * In some cases, these will have a port number appended. 939 */ 940 get_hostfile_hostname_ipaddr(hostname, hostaddr, 941 clobber_port ? 0 : port, &host, &ip); 942 943 /* 944 * Turn off check_host_ip if the connection is to localhost, via proxy 945 * command or if we don't have a hostname to compare with 946 */ 947 if (options.check_host_ip && (local || 948 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 949 options.check_host_ip = 0; 950 951 host_hostkeys = init_hostkeys(); 952 for (i = 0; i < num_user_hostfiles; i++) 953 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0); 954 for (i = 0; i < num_system_hostfiles; i++) 955 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0); 956 if (hostfile_command != NULL && !clobber_port) { 957 load_hostkeys_command(host_hostkeys, hostfile_command, 958 "HOSTNAME", cinfo, host_key, host); 959 } 960 961 ip_hostkeys = NULL; 962 if (!want_cert && options.check_host_ip) { 963 ip_hostkeys = init_hostkeys(); 964 for (i = 0; i < num_user_hostfiles; i++) 965 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0); 966 for (i = 0; i < num_system_hostfiles; i++) 967 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0); 968 if (hostfile_command != NULL && !clobber_port) { 969 load_hostkeys_command(ip_hostkeys, hostfile_command, 970 "ADDRESS", cinfo, host_key, ip); 971 } 972 } 973 974 retry: 975 /* Reload these as they may have changed on cert->key downgrade */ 976 want_cert = sshkey_is_cert(host_key); 977 type = sshkey_type(host_key); 978 979 /* 980 * Check if the host key is present in the user's list of known 981 * hosts or in the systemwide list. 982 */ 983 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 984 &host_found); 985 986 /* 987 * If there are no hostfiles, or if the hostkey was found via 988 * KnownHostsCommand, then don't try to touch the disk. 989 */ 990 if (!readonly && (num_user_hostfiles == 0 || 991 (host_found != NULL && host_found->note != 0))) 992 readonly = RDONLY; 993 994 /* 995 * Also perform check for the ip address, skip the check if we are 996 * localhost, looking for a certificate, or the hostname was an ip 997 * address to begin with. 998 */ 999 if (!want_cert && ip_hostkeys != NULL) { 1000 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 1001 &ip_found); 1002 if (host_status == HOST_CHANGED && 1003 (ip_status != HOST_CHANGED || 1004 (ip_found != NULL && 1005 !sshkey_equal(ip_found->key, host_found->key)))) 1006 host_ip_differ = 1; 1007 } else 1008 ip_status = host_status; 1009 1010 switch (host_status) { 1011 case HOST_OK: 1012 /* The host is known and the key matches. */ 1013 debug("Host '%.200s' is known and matches the %s host %s.", 1014 host, type, want_cert ? "certificate" : "key"); 1015 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 1016 host_found->file, host_found->line); 1017 if (want_cert) { 1018 if (sshkey_cert_check_host(host_key, 1019 options.host_key_alias == NULL ? 1020 hostname : options.host_key_alias, 0, 1021 options.ca_sign_algorithms, &fail_reason) != 0) { 1022 error("%s", fail_reason); 1023 goto fail; 1024 } 1025 /* 1026 * Do not attempt hostkey update if a certificate was 1027 * successfully matched. 1028 */ 1029 if (options.update_hostkeys != 0) { 1030 options.update_hostkeys = 0; 1031 debug3_f("certificate host key in use; " 1032 "disabling UpdateHostkeys"); 1033 } 1034 } 1035 /* Turn off UpdateHostkeys if key was in system known_hosts */ 1036 if (options.update_hostkeys != 0 && 1037 (path_in_hostfiles(host_found->file, 1038 system_hostfiles, num_system_hostfiles) || 1039 (ip_status == HOST_OK && ip_found != NULL && 1040 path_in_hostfiles(ip_found->file, 1041 system_hostfiles, num_system_hostfiles)))) { 1042 options.update_hostkeys = 0; 1043 debug3_f("host key found in GlobalKnownHostsFile; " 1044 "disabling UpdateHostkeys"); 1045 } 1046 if (options.update_hostkeys != 0 && host_found->note) { 1047 options.update_hostkeys = 0; 1048 debug3_f("host key found via KnownHostsCommand; " 1049 "disabling UpdateHostkeys"); 1050 } 1051 if (options.check_host_ip && ip_status == HOST_NEW) { 1052 if (readonly || want_cert) 1053 logit("%s host key for IP address " 1054 "'%.128s' not in list of known hosts.", 1055 type, ip); 1056 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 1057 host_key, options.hash_known_hosts)) 1058 logit("Failed to add the %s host key for IP " 1059 "address '%.128s' to the list of known " 1060 "hosts (%.500s).", type, ip, 1061 user_hostfiles[0]); 1062 else 1063 logit("Warning: Permanently added the %s host " 1064 "key for IP address '%.128s' to the list " 1065 "of known hosts.", type, ip); 1066 } else if (options.visual_host_key) { 1067 fp = sshkey_fingerprint(host_key, 1068 options.fingerprint_hash, SSH_FP_DEFAULT); 1069 ra = sshkey_fingerprint(host_key, 1070 options.fingerprint_hash, SSH_FP_RANDOMART); 1071 if (fp == NULL || ra == NULL) 1072 fatal_f("sshkey_fingerprint failed"); 1073 logit("Host key fingerprint is %s\n%s", fp, ra); 1074 free(ra); 1075 free(fp); 1076 } 1077 hostkey_trusted = 1; 1078 break; 1079 case HOST_NEW: 1080 if (options.host_key_alias == NULL && port != 0 && 1081 port != SSH_DEFAULT_PORT && !clobber_port) { 1082 debug("checking without port identifier"); 1083 if (check_host_key(hostname, cinfo, hostaddr, 0, 1084 host_key, ROQUIET, 1, 1085 user_hostfiles, num_user_hostfiles, 1086 system_hostfiles, num_system_hostfiles, 1087 hostfile_command) == 0) { 1088 debug("found matching key w/out port"); 1089 break; 1090 } 1091 } 1092 if (readonly || want_cert) 1093 goto fail; 1094 /* The host is new. */ 1095 if (options.strict_host_key_checking == 1096 SSH_STRICT_HOSTKEY_YES) { 1097 /* 1098 * User has requested strict host key checking. We 1099 * will not add the host key automatically. The only 1100 * alternative left is to abort. 1101 */ 1102 error("No %s host key is known for %.200s and you " 1103 "have requested strict checking.", type, host); 1104 goto fail; 1105 } else if (options.strict_host_key_checking == 1106 SSH_STRICT_HOSTKEY_ASK) { 1107 char *msg1 = NULL, *msg2 = NULL; 1108 1109 xasprintf(&msg1, "The authenticity of host " 1110 "'%.200s (%s)' can't be established", host, ip); 1111 1112 if (show_other_keys(host_hostkeys, host_key)) { 1113 xextendf(&msg1, "\n", "but keys of different " 1114 "type are already known for this host."); 1115 } else 1116 xextendf(&msg1, "", "."); 1117 1118 fp = sshkey_fingerprint(host_key, 1119 options.fingerprint_hash, SSH_FP_DEFAULT); 1120 ra = sshkey_fingerprint(host_key, 1121 options.fingerprint_hash, SSH_FP_RANDOMART); 1122 if (fp == NULL || ra == NULL) 1123 fatal_f("sshkey_fingerprint failed"); 1124 xextendf(&msg1, "\n", "%s key fingerprint is %s.", 1125 type, fp); 1126 if (options.visual_host_key) 1127 xextendf(&msg1, "\n", "%s", ra); 1128 if (options.verify_host_key_dns) { 1129 xextendf(&msg1, "\n", 1130 "%s host key fingerprint found in DNS.", 1131 matching_host_key_dns ? 1132 "Matching" : "No matching"); 1133 } 1134 /* msg2 informs for other names matching this key */ 1135 if ((msg2 = other_hostkeys_message(host, ip, host_key, 1136 user_hostfiles, num_user_hostfiles, 1137 system_hostfiles, num_system_hostfiles)) != NULL) 1138 xextendf(&msg1, "\n", "%s", msg2); 1139 1140 xextendf(&msg1, "\n", 1141 "Are you sure you want to continue connecting " 1142 "(yes/no/[fingerprint])? "); 1143 1144 confirmed = confirm(msg1, fp); 1145 free(ra); 1146 free(fp); 1147 free(msg1); 1148 free(msg2); 1149 if (!confirmed) 1150 goto fail; 1151 hostkey_trusted = 1; /* user explicitly confirmed */ 1152 } 1153 /* 1154 * If in "new" or "off" strict mode, add the key automatically 1155 * to the local known_hosts file. 1156 */ 1157 if (options.check_host_ip && ip_status == HOST_NEW) { 1158 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1159 hostp = hostline; 1160 if (options.hash_known_hosts) { 1161 /* Add hash of host and IP separately */ 1162 r = add_host_to_hostfile(user_hostfiles[0], 1163 host, host_key, options.hash_known_hosts) && 1164 add_host_to_hostfile(user_hostfiles[0], ip, 1165 host_key, options.hash_known_hosts); 1166 } else { 1167 /* Add unhashed "host,ip" */ 1168 r = add_host_to_hostfile(user_hostfiles[0], 1169 hostline, host_key, 1170 options.hash_known_hosts); 1171 } 1172 } else { 1173 r = add_host_to_hostfile(user_hostfiles[0], host, 1174 host_key, options.hash_known_hosts); 1175 hostp = host; 1176 } 1177 1178 if (!r) 1179 logit("Failed to add the host to the list of known " 1180 "hosts (%.500s).", user_hostfiles[0]); 1181 else 1182 logit("Warning: Permanently added '%.200s' (%s) to the " 1183 "list of known hosts.", hostp, type); 1184 break; 1185 case HOST_REVOKED: 1186 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1187 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1188 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1189 error("The %s host key for %s is marked as revoked.", type, host); 1190 error("This could mean that a stolen key is being used to"); 1191 error("impersonate this host."); 1192 1193 /* 1194 * If strict host key checking is in use, the user will have 1195 * to edit the key manually and we can only abort. 1196 */ 1197 if (options.strict_host_key_checking != 1198 SSH_STRICT_HOSTKEY_OFF) { 1199 error("%s host key for %.200s was revoked and you have " 1200 "requested strict checking.", type, host); 1201 goto fail; 1202 } 1203 goto continue_unsafe; 1204 1205 case HOST_CHANGED: 1206 if (want_cert) { 1207 /* 1208 * This is only a debug() since it is valid to have 1209 * CAs with wildcard DNS matches that don't match 1210 * all hosts that one might visit. 1211 */ 1212 debug("Host certificate authority does not " 1213 "match %s in %s:%lu", CA_MARKER, 1214 host_found->file, host_found->line); 1215 goto fail; 1216 } 1217 if (readonly == ROQUIET) 1218 goto fail; 1219 if (options.check_host_ip && host_ip_differ) { 1220 char *key_msg; 1221 if (ip_status == HOST_NEW) 1222 key_msg = "is unknown"; 1223 else if (ip_status == HOST_OK) 1224 key_msg = "is unchanged"; 1225 else 1226 key_msg = "has a different value"; 1227 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1228 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1229 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1230 error("The %s host key for %s has changed,", type, host); 1231 error("and the key for the corresponding IP address %s", ip); 1232 error("%s. This could either mean that", key_msg); 1233 error("DNS SPOOFING is happening or the IP address for the host"); 1234 error("and its host key have changed at the same time."); 1235 if (ip_status != HOST_NEW) 1236 error("Offending key for IP in %s:%lu", 1237 ip_found->file, ip_found->line); 1238 } 1239 /* The host key has changed. */ 1240 warn_changed_key(host_key); 1241 error("Add correct host key in %.100s to get rid of this message.", 1242 user_hostfiles[0]); 1243 error("Offending %s key in %s:%lu", 1244 sshkey_type(host_found->key), 1245 host_found->file, host_found->line); 1246 1247 /* 1248 * If strict host key checking is in use, the user will have 1249 * to edit the key manually and we can only abort. 1250 */ 1251 if (options.strict_host_key_checking != 1252 SSH_STRICT_HOSTKEY_OFF) { 1253 error("Host key for %.200s has changed and you have " 1254 "requested strict checking.", host); 1255 goto fail; 1256 } 1257 1258 continue_unsafe: 1259 /* 1260 * If strict host key checking has not been requested, allow 1261 * the connection but without MITM-able authentication or 1262 * forwarding. 1263 */ 1264 if (options.password_authentication) { 1265 error("Password authentication is disabled to avoid " 1266 "man-in-the-middle attacks."); 1267 options.password_authentication = 0; 1268 cancelled_forwarding = 1; 1269 } 1270 if (options.kbd_interactive_authentication) { 1271 error("Keyboard-interactive authentication is disabled" 1272 " to avoid man-in-the-middle attacks."); 1273 options.kbd_interactive_authentication = 0; 1274 cancelled_forwarding = 1; 1275 } 1276 if (options.forward_agent) { 1277 error("Agent forwarding is disabled to avoid " 1278 "man-in-the-middle attacks."); 1279 options.forward_agent = 0; 1280 cancelled_forwarding = 1; 1281 } 1282 if (options.forward_x11) { 1283 error("X11 forwarding is disabled to avoid " 1284 "man-in-the-middle attacks."); 1285 options.forward_x11 = 0; 1286 cancelled_forwarding = 1; 1287 } 1288 if (options.num_local_forwards > 0 || 1289 options.num_remote_forwards > 0) { 1290 error("Port forwarding is disabled to avoid " 1291 "man-in-the-middle attacks."); 1292 options.num_local_forwards = 1293 options.num_remote_forwards = 0; 1294 cancelled_forwarding = 1; 1295 } 1296 if (options.tun_open != SSH_TUNMODE_NO) { 1297 error("Tunnel forwarding is disabled to avoid " 1298 "man-in-the-middle attacks."); 1299 options.tun_open = SSH_TUNMODE_NO; 1300 cancelled_forwarding = 1; 1301 } 1302 if (options.update_hostkeys != 0) { 1303 error("UpdateHostkeys is disabled because the host " 1304 "key is not trusted."); 1305 options.update_hostkeys = 0; 1306 } 1307 if (options.exit_on_forward_failure && cancelled_forwarding) 1308 fatal("Error: forwarding disabled due to host key " 1309 "check failure"); 1310 1311 /* 1312 * XXX Should permit the user to change to use the new id. 1313 * This could be done by converting the host key to an 1314 * identifying sentence, tell that the host identifies itself 1315 * by that sentence, and ask the user if they wish to 1316 * accept the authentication. 1317 */ 1318 break; 1319 case HOST_FOUND: 1320 fatal("internal error"); 1321 break; 1322 } 1323 1324 if (options.check_host_ip && host_status != HOST_CHANGED && 1325 ip_status == HOST_CHANGED) { 1326 snprintf(msg, sizeof(msg), 1327 "Warning: the %s host key for '%.200s' " 1328 "differs from the key for the IP address '%.128s'" 1329 "\nOffending key for IP in %s:%lu", 1330 type, host, ip, ip_found->file, ip_found->line); 1331 if (host_status == HOST_OK) { 1332 len = strlen(msg); 1333 snprintf(msg + len, sizeof(msg) - len, 1334 "\nMatching host key in %s:%lu", 1335 host_found->file, host_found->line); 1336 } 1337 if (options.strict_host_key_checking == 1338 SSH_STRICT_HOSTKEY_ASK) { 1339 strlcat(msg, "\nAre you sure you want " 1340 "to continue connecting (yes/no)? ", sizeof(msg)); 1341 if (!confirm(msg, NULL)) 1342 goto fail; 1343 } else if (options.strict_host_key_checking != 1344 SSH_STRICT_HOSTKEY_OFF) { 1345 logit("%s", msg); 1346 error("Exiting, you have requested strict checking."); 1347 goto fail; 1348 } else { 1349 logit("%s", msg); 1350 } 1351 } 1352 1353 if (!hostkey_trusted && options.update_hostkeys) { 1354 debug_f("hostkey not known or explicitly trusted: " 1355 "disabling UpdateHostkeys"); 1356 options.update_hostkeys = 0; 1357 } 1358 1359 free(ip); 1360 free(host); 1361 if (host_hostkeys != NULL) 1362 free_hostkeys(host_hostkeys); 1363 if (ip_hostkeys != NULL) 1364 free_hostkeys(ip_hostkeys); 1365 return 0; 1366 1367 fail: 1368 if (want_cert && host_status != HOST_REVOKED) { 1369 /* 1370 * No matching certificate. Downgrade cert to raw key and 1371 * search normally. 1372 */ 1373 debug("No matching CA found. Retry with plain key"); 1374 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1375 fatal_fr(r, "decode key"); 1376 if ((r = sshkey_drop_cert(raw_key)) != 0) 1377 fatal_r(r, "Couldn't drop certificate"); 1378 host_key = raw_key; 1379 goto retry; 1380 } 1381 sshkey_free(raw_key); 1382 free(ip); 1383 free(host); 1384 if (host_hostkeys != NULL) 1385 free_hostkeys(host_hostkeys); 1386 if (ip_hostkeys != NULL) 1387 free_hostkeys(ip_hostkeys); 1388 return -1; 1389 } 1390 1391 /* returns 0 if key verifies or -1 if key does NOT verify */ 1392 int 1393 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key, 1394 const struct ssh_conn_info *cinfo) 1395 { 1396 u_int i; 1397 int r = -1, flags = 0; 1398 char valid[64], *fp = NULL, *cafp = NULL; 1399 struct sshkey *plain = NULL; 1400 1401 if ((fp = sshkey_fingerprint(host_key, 1402 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1403 error_fr(r, "fingerprint host key"); 1404 r = -1; 1405 goto out; 1406 } 1407 1408 if (sshkey_is_cert(host_key)) { 1409 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1410 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1411 error_fr(r, "fingerprint CA key"); 1412 r = -1; 1413 goto out; 1414 } 1415 sshkey_format_cert_validity(host_key->cert, 1416 valid, sizeof(valid)); 1417 debug("Server host certificate: %s %s, serial %llu " 1418 "ID \"%s\" CA %s %s valid %s", 1419 sshkey_ssh_name(host_key), fp, 1420 (unsigned long long)host_key->cert->serial, 1421 host_key->cert->key_id, 1422 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1423 valid); 1424 for (i = 0; i < host_key->cert->nprincipals; i++) { 1425 debug2("Server host certificate hostname: %s", 1426 host_key->cert->principals[i]); 1427 } 1428 } else { 1429 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1430 } 1431 1432 if (sshkey_equal(previous_host_key, host_key)) { 1433 debug2_f("server host key %s %s matches cached key", 1434 sshkey_type(host_key), fp); 1435 r = 0; 1436 goto out; 1437 } 1438 1439 /* Check in RevokedHostKeys file if specified */ 1440 if (options.revoked_host_keys != NULL) { 1441 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1442 switch (r) { 1443 case 0: 1444 break; /* not revoked */ 1445 case SSH_ERR_KEY_REVOKED: 1446 error("Host key %s %s revoked by file %s", 1447 sshkey_type(host_key), fp, 1448 options.revoked_host_keys); 1449 r = -1; 1450 goto out; 1451 default: 1452 error_r(r, "Error checking host key %s %s in " 1453 "revoked keys file %s", sshkey_type(host_key), 1454 fp, options.revoked_host_keys); 1455 r = -1; 1456 goto out; 1457 } 1458 } 1459 1460 if (options.verify_host_key_dns) { 1461 /* 1462 * XXX certs are not yet supported for DNS, so downgrade 1463 * them and try the plain key. 1464 */ 1465 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1466 goto out; 1467 if (sshkey_is_cert(plain)) 1468 sshkey_drop_cert(plain); 1469 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1470 if (flags & DNS_VERIFY_FOUND) { 1471 if (options.verify_host_key_dns == 1 && 1472 flags & DNS_VERIFY_MATCH && 1473 flags & DNS_VERIFY_SECURE) { 1474 r = 0; 1475 goto out; 1476 } 1477 if (flags & DNS_VERIFY_MATCH) { 1478 matching_host_key_dns = 1; 1479 } else { 1480 warn_changed_key(plain); 1481 error("Update the SSHFP RR in DNS " 1482 "with the new host key to get rid " 1483 "of this message."); 1484 } 1485 } 1486 } 1487 } 1488 r = check_host_key(host, cinfo, hostaddr, options.port, host_key, 1489 RDRW, 0, options.user_hostfiles, options.num_user_hostfiles, 1490 options.system_hostfiles, options.num_system_hostfiles, 1491 options.known_hosts_command); 1492 1493 out: 1494 sshkey_free(plain); 1495 free(fp); 1496 free(cafp); 1497 if (r == 0 && host_key != NULL) { 1498 sshkey_free(previous_host_key); 1499 r = sshkey_from_private(host_key, &previous_host_key); 1500 } 1501 1502 return r; 1503 } 1504 1505 /* 1506 * Starts a dialog with the server, and authenticates the current user on the 1507 * server. This does not need any extra privileges. The basic connection 1508 * to the server must already have been established before this is called. 1509 * If login fails, this function prints an error and never returns. 1510 * This function does not require super-user privileges. 1511 */ 1512 void 1513 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost, 1514 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms, 1515 const struct ssh_conn_info *cinfo) 1516 { 1517 char *host; 1518 char *server_user, *local_user; 1519 int r; 1520 1521 local_user = xstrdup(pw->pw_name); 1522 server_user = options.user ? options.user : local_user; 1523 1524 /* Convert the user-supplied hostname into all lowercase. */ 1525 host = xstrdup(orighost); 1526 lowercase(host); 1527 1528 /* Exchange protocol version identification strings with the server. */ 1529 if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0) 1530 sshpkt_fatal(ssh, r, "banner exchange"); 1531 1532 /* Put the connection into non-blocking mode. */ 1533 ssh_packet_set_nonblocking(ssh); 1534 1535 /* key exchange */ 1536 /* authenticate user */ 1537 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1538 ssh_kex2(ssh, host, hostaddr, port, cinfo); 1539 ssh_userauth2(ssh, local_user, server_user, host, sensitive); 1540 free(local_user); 1541 free(host); 1542 } 1543 1544 /* print all known host keys for a given host, but skip keys of given type */ 1545 static int 1546 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1547 { 1548 int type[] = { 1549 KEY_RSA, 1550 KEY_DSA, 1551 KEY_ECDSA, 1552 KEY_ED25519, 1553 KEY_XMSS, 1554 -1 1555 }; 1556 int i, ret = 0; 1557 char *fp, *ra; 1558 const struct hostkey_entry *found; 1559 1560 for (i = 0; type[i] != -1; i++) { 1561 if (type[i] == key->type) 1562 continue; 1563 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], 1564 -1, &found)) 1565 continue; 1566 fp = sshkey_fingerprint(found->key, 1567 options.fingerprint_hash, SSH_FP_DEFAULT); 1568 ra = sshkey_fingerprint(found->key, 1569 options.fingerprint_hash, SSH_FP_RANDOMART); 1570 if (fp == NULL || ra == NULL) 1571 fatal_f("sshkey_fingerprint fail"); 1572 logit("WARNING: %s key found for host %s\n" 1573 "in %s:%lu\n" 1574 "%s key fingerprint %s.", 1575 sshkey_type(found->key), 1576 found->host, found->file, found->line, 1577 sshkey_type(found->key), fp); 1578 if (options.visual_host_key) 1579 logit("%s", ra); 1580 free(ra); 1581 free(fp); 1582 ret = 1; 1583 } 1584 return ret; 1585 } 1586 1587 static void 1588 warn_changed_key(struct sshkey *host_key) 1589 { 1590 char *fp; 1591 1592 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1593 SSH_FP_DEFAULT); 1594 if (fp == NULL) 1595 fatal_f("sshkey_fingerprint fail"); 1596 1597 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1598 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1599 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1600 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1601 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1602 error("It is also possible that a host key has just been changed."); 1603 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1604 sshkey_type(host_key), fp); 1605 error("Please contact your system administrator."); 1606 1607 free(fp); 1608 } 1609 1610 /* 1611 * Execute a local command 1612 */ 1613 int 1614 ssh_local_cmd(const char *args) 1615 { 1616 char *shell; 1617 pid_t pid; 1618 int status; 1619 void (*osighand)(int); 1620 1621 if (!options.permit_local_command || 1622 args == NULL || !*args) 1623 return (1); 1624 1625 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1626 shell = _PATH_BSHELL; 1627 1628 osighand = ssh_signal(SIGCHLD, SIG_DFL); 1629 pid = fork(); 1630 if (pid == 0) { 1631 ssh_signal(SIGPIPE, SIG_DFL); 1632 debug3("Executing %s -c \"%s\"", shell, args); 1633 execl(shell, shell, "-c", args, (char *)NULL); 1634 error("Couldn't execute %s -c \"%s\": %s", 1635 shell, args, strerror(errno)); 1636 _exit(1); 1637 } else if (pid == -1) 1638 fatal("fork failed: %.100s", strerror(errno)); 1639 while (waitpid(pid, &status, 0) == -1) 1640 if (errno != EINTR) 1641 fatal("Couldn't wait for child: %s", strerror(errno)); 1642 ssh_signal(SIGCHLD, osighand); 1643 1644 if (!WIFEXITED(status)) 1645 return (1); 1646 1647 return (WEXITSTATUS(status)); 1648 } 1649 1650 void 1651 maybe_add_key_to_agent(const char *authfile, struct sshkey *private, 1652 const char *comment, const char *passphrase) 1653 { 1654 int auth_sock = -1, r; 1655 const char *skprovider = NULL; 1656 1657 if (options.add_keys_to_agent == 0) 1658 return; 1659 1660 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1661 debug3("no authentication agent, not adding key"); 1662 return; 1663 } 1664 1665 if (options.add_keys_to_agent == 2 && 1666 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1667 debug3("user denied adding this key"); 1668 close(auth_sock); 1669 return; 1670 } 1671 if (sshkey_is_sk(private)) 1672 skprovider = options.sk_provider; 1673 if ((r = ssh_add_identity_constrained(auth_sock, private, 1674 comment == NULL ? authfile : comment, 1675 options.add_keys_to_agent_lifespan, 1676 (options.add_keys_to_agent == 3), 0, skprovider, NULL, 0)) == 0) 1677 debug("identity added to agent: %s", authfile); 1678 else 1679 debug("could not add identity to agent: %s (%d)", authfile, r); 1680 close(auth_sock); 1681 } 1682