1 /* $NetBSD: sshconnect.c,v 1.32 2022/02/23 19:07:20 christos Exp $ */ 2 /* $OpenBSD: sshconnect.c,v 1.356 2021/12/19 22:10:24 djm Exp $ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Code to connect to a remote host, and to perform the client side of the 8 * login (authentication) dialog. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 */ 16 17 #include "includes.h" 18 __RCSID("$NetBSD: sshconnect.c,v 1.32 2022/02/23 19:07:20 christos Exp $"); 19 20 #include <sys/param.h> /* roundup */ 21 #include <sys/types.h> 22 #include <sys/param.h> 23 #include <sys/wait.h> 24 #include <sys/stat.h> 25 #include <sys/socket.h> 26 #include <sys/time.h> 27 28 #include <net/if.h> 29 #include <netinet/in.h> 30 #include <rpc/rpc.h> 31 32 #include <ctype.h> 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <netdb.h> 36 #include <limits.h> 37 #include <paths.h> 38 #include <signal.h> 39 #include <pwd.h> 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <stdarg.h> 43 #include <string.h> 44 #include <unistd.h> 45 #include <ifaddrs.h> 46 47 #include "xmalloc.h" 48 #include "ssh.h" 49 #include "sshbuf.h" 50 #include "packet.h" 51 #include "compat.h" 52 #include "sshkey.h" 53 #include "sshconnect.h" 54 #include "hostfile.h" 55 #include "log.h" 56 #include "misc.h" 57 #include "readconf.h" 58 #include "atomicio.h" 59 #include "dns.h" 60 #include "monitor_fdpass.h" 61 #include "ssh2.h" 62 #include "version.h" 63 #include "authfile.h" 64 #include "ssherr.h" 65 #include "authfd.h" 66 #include "kex.h" 67 68 struct sshkey *previous_host_key = NULL; 69 70 static int matching_host_key_dns = 0; 71 72 static pid_t proxy_command_pid = 0; 73 74 /* import */ 75 extern int debug_flag; 76 extern Options options; 77 extern char *__progname; 78 79 static int show_other_keys(struct hostkeys *, struct sshkey *); 80 static void warn_changed_key(struct sshkey *); 81 82 /* Expand a proxy command */ 83 static char * 84 expand_proxy_command(const char *proxy_command, const char *user, 85 const char *host, const char *host_arg, int port) 86 { 87 char *tmp, *ret, strport[NI_MAXSERV]; 88 const char *keyalias = options.host_key_alias ? 89 options.host_key_alias : host_arg; 90 91 snprintf(strport, sizeof strport, "%d", port); 92 xasprintf(&tmp, "exec %s", proxy_command); 93 ret = percent_expand(tmp, 94 "h", host, 95 "k", keyalias, 96 "n", host_arg, 97 "p", strport, 98 "r", options.user, 99 (char *)NULL); 100 free(tmp); 101 return ret; 102 } 103 104 /* 105 * Connect to the given ssh server using a proxy command that passes a 106 * a connected fd back to us. 107 */ 108 static int 109 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, 110 const char *host_arg, u_short port, const char *proxy_command) 111 { 112 char *command_string; 113 int sp[2], sock; 114 pid_t pid; 115 const char *shell; 116 117 if ((shell = getenv("SHELL")) == NULL) 118 shell = _PATH_BSHELL; 119 120 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) == -1) 121 fatal("Could not create socketpair to communicate with " 122 "proxy dialer: %.100s", strerror(errno)); 123 close(sp[1]); 124 125 command_string = expand_proxy_command(proxy_command, options.user, 126 host, host_arg, port); 127 debug("Executing proxy dialer command: %.500s", command_string); 128 129 /* Fork and execute the proxy command. */ 130 if ((pid = fork()) == 0) { 131 char *argv[10]; 132 133 close(sp[1]); 134 /* Redirect stdin and stdout. */ 135 if (sp[0] != 0) { 136 if (dup2(sp[0], 0) == -1) 137 perror("dup2 stdin"); 138 } 139 if (sp[0] != 1) { 140 if (dup2(sp[0], 1) == -1) 141 perror("dup2 stdout"); 142 } 143 if (sp[0] >= 2) 144 close(sp[0]); 145 146 /* 147 * Stderr is left for non-ControlPersist connections is so 148 * error messages may be printed on the user's terminal. 149 */ 150 if (!debug_flag && options.control_path != NULL && 151 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 152 error_f("stdfd_devnull failed"); 153 154 argv[0] = __UNCONST(shell); 155 argv[1] = __UNCONST("-c"); 156 argv[2] = command_string; 157 argv[3] = NULL; 158 159 /* 160 * Execute the proxy command. 161 * Note that we gave up any extra privileges above. 162 */ 163 execv(argv[0], argv); 164 perror(argv[0]); 165 exit(1); 166 } 167 /* Parent. */ 168 if (pid == -1) 169 fatal("fork failed: %.100s", strerror(errno)); 170 close(sp[0]); 171 free(command_string); 172 173 if ((sock = mm_receive_fd(sp[1])) == -1) 174 fatal("proxy dialer did not pass back a connection"); 175 close(sp[1]); 176 177 while (waitpid(pid, NULL, 0) == -1) 178 if (errno != EINTR) 179 fatal("Couldn't wait for child: %s", strerror(errno)); 180 181 /* Set the connection file descriptors. */ 182 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 183 return -1; /* ssh_packet_set_connection logs error */ 184 185 return 0; 186 } 187 188 /* 189 * Connect to the given ssh server using a proxy command. 190 */ 191 static int 192 ssh_proxy_connect(struct ssh *ssh, const char *host, const char *host_arg, 193 u_short port, const char *proxy_command) 194 { 195 char *command_string; 196 int pin[2], pout[2]; 197 pid_t pid; 198 char *shell; 199 200 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 201 shell = __UNCONST(_PATH_BSHELL); 202 203 /* Create pipes for communicating with the proxy. */ 204 if (pipe(pin) == -1 || pipe(pout) == -1) 205 fatal("Could not create pipes to communicate with the proxy: %.100s", 206 strerror(errno)); 207 208 command_string = expand_proxy_command(proxy_command, options.user, 209 host, host_arg, port); 210 debug("Executing proxy command: %.500s", command_string); 211 212 /* Fork and execute the proxy command. */ 213 if ((pid = fork()) == 0) { 214 char *argv[10]; 215 216 /* Redirect stdin and stdout. */ 217 close(pin[1]); 218 if (pin[0] != 0) { 219 if (dup2(pin[0], 0) == -1) 220 perror("dup2 stdin"); 221 close(pin[0]); 222 } 223 close(pout[0]); 224 if (dup2(pout[1], 1) == -1) 225 perror("dup2 stdout"); 226 /* Cannot be 1 because pin allocated two descriptors. */ 227 close(pout[1]); 228 229 /* 230 * Stderr is left for non-ControlPersist connections is so 231 * error messages may be printed on the user's terminal. 232 */ 233 if (!debug_flag && options.control_path != NULL && 234 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 235 error_f("stdfd_devnull failed"); 236 237 argv[0] = shell; 238 argv[1] = __UNCONST("-c"); 239 argv[2] = command_string; 240 argv[3] = NULL; 241 242 /* 243 * Execute the proxy command. Note that we gave up any 244 * extra privileges above. 245 */ 246 ssh_signal(SIGPIPE, SIG_DFL); 247 execv(argv[0], argv); 248 perror(argv[0]); 249 exit(1); 250 } 251 /* Parent. */ 252 if (pid == -1) 253 fatal("fork failed: %.100s", strerror(errno)); 254 else 255 proxy_command_pid = pid; /* save pid to clean up later */ 256 257 /* Close child side of the descriptors. */ 258 close(pin[0]); 259 close(pout[1]); 260 261 /* Free the command name. */ 262 free(command_string); 263 264 /* Set the connection file descriptors. */ 265 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 266 return -1; /* ssh_packet_set_connection logs error */ 267 268 return 0; 269 } 270 271 void 272 ssh_kill_proxy_command(void) 273 { 274 /* 275 * Send SIGHUP to proxy command if used. We don't wait() in 276 * case it hangs and instead rely on init to reap the child 277 */ 278 if (proxy_command_pid > 1) 279 kill(proxy_command_pid, SIGHUP); 280 } 281 282 /* 283 * Set TCP receive buffer if requested. 284 * Note: tuning needs to happen after the socket is 285 * created but before the connection happens 286 * so winscale is negotiated properly -cjr 287 */ 288 static void 289 ssh_set_socket_recvbuf(int sock) 290 { 291 void *buf = (void *)&options.tcp_rcv_buf; 292 int sz = sizeof(options.tcp_rcv_buf); 293 int socksize; 294 socklen_t socksizelen = sizeof(int); 295 296 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 297 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 298 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 299 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 300 } 301 else 302 error("Couldn't set socket receive buffer to %d: %.100s", 303 options.tcp_rcv_buf, strerror(errno)); 304 } 305 306 /* 307 * Search a interface address list (returned from getifaddrs(3)) for an 308 * address that matches the desired address family on the specified interface. 309 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 310 */ 311 static int 312 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 313 struct sockaddr_storage *resultp, socklen_t *rlenp) 314 { 315 struct sockaddr_in6 *sa6; 316 struct sockaddr_in *sa; 317 struct in6_addr *v6addr; 318 const struct ifaddrs *ifa; 319 int allow_local; 320 321 /* 322 * Prefer addresses that are not loopback or linklocal, but use them 323 * if nothing else matches. 324 */ 325 for (allow_local = 0; allow_local < 2; allow_local++) { 326 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 327 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 328 (ifa->ifa_flags & IFF_UP) == 0 || 329 ifa->ifa_addr->sa_family != af || 330 strcmp(ifa->ifa_name, options.bind_interface) != 0) 331 continue; 332 switch (ifa->ifa_addr->sa_family) { 333 case AF_INET: 334 sa = (struct sockaddr_in *)ifa->ifa_addr; 335 if (!allow_local && sa->sin_addr.s_addr == 336 htonl(INADDR_LOOPBACK)) 337 continue; 338 if (*rlenp < sizeof(struct sockaddr_in)) { 339 error_f("v4 addr doesn't fit"); 340 return -1; 341 } 342 *rlenp = sizeof(struct sockaddr_in); 343 memcpy(resultp, sa, *rlenp); 344 return 0; 345 case AF_INET6: 346 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 347 v6addr = &sa6->sin6_addr; 348 if (!allow_local && 349 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 350 IN6_IS_ADDR_LOOPBACK(v6addr))) 351 continue; 352 if (*rlenp < sizeof(struct sockaddr_in6)) { 353 error_f("v6 addr doesn't fit"); 354 return -1; 355 } 356 *rlenp = sizeof(struct sockaddr_in6); 357 memcpy(resultp, sa6, *rlenp); 358 return 0; 359 } 360 } 361 } 362 return -1; 363 } 364 365 /* 366 * Creates a socket for use as the ssh connection. 367 */ 368 static int 369 ssh_create_socket(struct addrinfo *ai) 370 { 371 int sock, r; 372 struct sockaddr_storage bindaddr; 373 socklen_t bindaddrlen = 0; 374 struct addrinfo hints, *res = NULL; 375 struct ifaddrs *ifaddrs = NULL; 376 char ntop[NI_MAXHOST]; 377 378 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 379 if (sock == -1) { 380 error("socket: %s", strerror(errno)); 381 return -1; 382 } 383 fcntl(sock, F_SETFD, FD_CLOEXEC); 384 385 if (options.tcp_rcv_buf > 0) 386 ssh_set_socket_recvbuf(sock); 387 388 /* Use interactive QOS (if specified) until authentication completed */ 389 if (options.ip_qos_interactive != INT_MAX) 390 set_sock_tos(sock, options.ip_qos_interactive); 391 392 /* Bind the socket to an alternative local IP address */ 393 if (options.bind_address == NULL && options.bind_interface == NULL) 394 return sock; 395 396 if (options.bind_address != NULL) { 397 memset(&hints, 0, sizeof(hints)); 398 hints.ai_family = ai->ai_family; 399 hints.ai_socktype = ai->ai_socktype; 400 hints.ai_protocol = ai->ai_protocol; 401 hints.ai_flags = AI_PASSIVE; 402 if ((r = getaddrinfo(options.bind_address, NULL, 403 &hints, &res)) != 0) { 404 error("getaddrinfo: %s: %s", options.bind_address, 405 ssh_gai_strerror(r)); 406 goto fail; 407 } 408 if (res == NULL) { 409 error("getaddrinfo: no addrs"); 410 goto fail; 411 } 412 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 413 bindaddrlen = res->ai_addrlen; 414 } else if (options.bind_interface != NULL) { 415 if ((r = getifaddrs(&ifaddrs)) != 0) { 416 error("getifaddrs: %s: %s", options.bind_interface, 417 strerror(errno)); 418 goto fail; 419 } 420 bindaddrlen = sizeof(bindaddr); 421 if (check_ifaddrs(options.bind_interface, ai->ai_family, 422 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 423 logit("getifaddrs: %s: no suitable addresses", 424 options.bind_interface); 425 goto fail; 426 } 427 } 428 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 429 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 430 error_f("getnameinfo failed: %s", ssh_gai_strerror(r)); 431 goto fail; 432 } 433 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 434 error("bind %s: %s", ntop, strerror(errno)); 435 goto fail; 436 } 437 debug_f("bound to %s", ntop); 438 /* success */ 439 goto out; 440 fail: 441 close(sock); 442 sock = -1; 443 out: 444 if (res != NULL) 445 freeaddrinfo(res); 446 if (ifaddrs != NULL) 447 freeifaddrs(ifaddrs); 448 return sock; 449 } 450 451 /* 452 * Opens a TCP/IP connection to the remote server on the given host. 453 * The address of the remote host will be returned in hostaddr. 454 * If port is 0, the default port will be used. 455 * Connection_attempts specifies the maximum number of tries (one per 456 * second). If proxy_command is non-NULL, it specifies the command (with %h 457 * and %p substituted for host and port, respectively) to use to contact 458 * the daemon. 459 */ 460 static int 461 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 462 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts, 463 int *timeout_ms, int want_keepalive) 464 { 465 int on = 1, saved_timeout_ms = *timeout_ms; 466 int oerrno, sock = -1, attempt; 467 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 468 struct addrinfo *ai; 469 470 debug3_f("entering"); 471 memset(ntop, 0, sizeof(ntop)); 472 memset(strport, 0, sizeof(strport)); 473 474 for (attempt = 0; attempt < connection_attempts; attempt++) { 475 if (attempt > 0) { 476 /* Sleep a moment before retrying. */ 477 sleep(1); 478 debug("Trying again..."); 479 } 480 /* 481 * Loop through addresses for this host, and try each one in 482 * sequence until the connection succeeds. 483 */ 484 for (ai = aitop; ai; ai = ai->ai_next) { 485 if (ai->ai_family != AF_INET && 486 ai->ai_family != AF_INET6) { 487 errno = EAFNOSUPPORT; 488 continue; 489 } 490 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 491 ntop, sizeof(ntop), strport, sizeof(strport), 492 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 493 oerrno = errno; 494 error_f("getnameinfo failed"); 495 errno = oerrno; 496 continue; 497 } 498 debug("Connecting to %.200s [%.100s] port %s.", 499 host, ntop, strport); 500 501 /* Create a socket for connecting. */ 502 sock = ssh_create_socket(ai); 503 if (sock < 0) { 504 /* Any error is already output */ 505 errno = 0; 506 continue; 507 } 508 509 *timeout_ms = saved_timeout_ms; 510 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 511 timeout_ms) >= 0) { 512 /* Successful connection. */ 513 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 514 break; 515 } else { 516 oerrno = errno; 517 debug("connect to address %s port %s: %s", 518 ntop, strport, strerror(errno)); 519 close(sock); 520 sock = -1; 521 errno = oerrno; 522 } 523 } 524 if (sock != -1) 525 break; /* Successful connection. */ 526 } 527 528 /* Return failure if we didn't get a successful connection. */ 529 if (sock == -1) { 530 error("ssh: connect to host %s port %s: %s", 531 host, strport, errno == 0 ? "failure" : strerror(errno)); 532 return -1; 533 } 534 535 debug("Connection established."); 536 537 /* Set SO_KEEPALIVE if requested. */ 538 if (want_keepalive && 539 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 540 sizeof(on)) == -1) 541 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 542 543 /* Set the connection. */ 544 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 545 return -1; /* ssh_packet_set_connection logs error */ 546 547 return 0; 548 } 549 550 int 551 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg, 552 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port, 553 int connection_attempts, int *timeout_ms, int want_keepalive) 554 { 555 int in, out; 556 557 if (options.proxy_command == NULL) { 558 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 559 connection_attempts, timeout_ms, want_keepalive); 560 } else if (strcmp(options.proxy_command, "-") == 0) { 561 if ((in = dup(STDIN_FILENO)) == -1 || 562 (out = dup(STDOUT_FILENO)) == -1) { 563 if (in >= 0) 564 close(in); 565 error_f("dup() in/out failed"); 566 return -1; /* ssh_packet_set_connection logs error */ 567 } 568 if ((ssh_packet_set_connection(ssh, in, out)) == NULL) 569 return -1; /* ssh_packet_set_connection logs error */ 570 return 0; 571 } else if (options.proxy_use_fdpass) { 572 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port, 573 options.proxy_command); 574 } 575 return ssh_proxy_connect(ssh, host, host_arg, port, 576 options.proxy_command); 577 } 578 579 /* defaults to 'no' */ 580 static int 581 confirm(const char *prompt, const char *fingerprint) 582 { 583 const char *msg, *again = "Please type 'yes' or 'no': "; 584 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: "; 585 char *p, *cp; 586 int ret = -1; 587 588 if (options.batch_mode) 589 return 0; 590 for (msg = prompt;;msg = fingerprint ? again_fp : again) { 591 cp = p = read_passphrase(msg, RP_ECHO); 592 if (p == NULL) 593 return 0; 594 p += strspn(p, " \t"); /* skip leading whitespace */ 595 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */ 596 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 597 ret = 0; 598 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL && 599 strcmp(p, fingerprint) == 0)) 600 ret = 1; 601 free(cp); 602 if (ret != -1) 603 return ret; 604 } 605 } 606 607 static int 608 sockaddr_is_local(struct sockaddr *hostaddr) 609 { 610 switch (hostaddr->sa_family) { 611 case AF_INET: 612 return (ntohl(((struct sockaddr_in *)hostaddr)-> 613 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 614 case AF_INET6: 615 return IN6_IS_ADDR_LOOPBACK( 616 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 617 default: 618 return 0; 619 } 620 } 621 622 /* 623 * Prepare the hostname and ip address strings that are used to lookup 624 * host keys in known_hosts files. These may have a port number appended. 625 */ 626 void 627 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 628 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 629 { 630 char ntop[NI_MAXHOST]; 631 632 /* 633 * We don't have the remote ip-address for connections 634 * using a proxy command 635 */ 636 if (hostfile_ipaddr != NULL) { 637 if (options.proxy_command == NULL) { 638 if (getnameinfo(hostaddr, hostaddr->sa_len, 639 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 640 fatal_f("getnameinfo failed"); 641 *hostfile_ipaddr = put_host_port(ntop, port); 642 } else { 643 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 644 "command>"); 645 } 646 } 647 648 /* 649 * Allow the user to record the key under a different name or 650 * differentiate a non-standard port. This is useful for ssh 651 * tunneling over forwarded connections or if you run multiple 652 * sshd's on different ports on the same machine. 653 */ 654 if (hostfile_hostname != NULL) { 655 if (options.host_key_alias != NULL) { 656 *hostfile_hostname = xstrdup(options.host_key_alias); 657 debug("using hostkeyalias: %s", *hostfile_hostname); 658 } else { 659 *hostfile_hostname = put_host_port(hostname, port); 660 } 661 } 662 } 663 664 /* returns non-zero if path appears in hostfiles, or 0 if not. */ 665 static int 666 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles) 667 { 668 u_int i; 669 670 for (i = 0; i < num_hostfiles; i++) { 671 if (strcmp(path, hostfiles[i]) == 0) 672 return 1; 673 } 674 return 0; 675 } 676 677 struct find_by_key_ctx { 678 const char *host, *ip; 679 const struct sshkey *key; 680 char **names; 681 u_int nnames; 682 }; 683 684 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */ 685 static char * 686 try_tilde_unexpand(const char *path) 687 { 688 char *home, *ret = NULL; 689 size_t l; 690 691 if (*path != '/') 692 return xstrdup(path); 693 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0) 694 return xstrdup(path); 695 if (strncmp(path, home, l) != 0) 696 return xstrdup(path); 697 /* 698 * ensure we have matched on a path boundary: either the $HOME that 699 * we just compared ends with a '/' or the next character of the path 700 * must be a '/'. 701 */ 702 if (home[l - 1] != '/' && path[l] != '/') 703 return xstrdup(path); 704 if (path[l] == '/') 705 l++; 706 xasprintf(&ret, "~/%s", path + l); 707 return ret; 708 } 709 710 static int 711 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx) 712 { 713 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx; 714 char *path; 715 716 /* we are looking for keys with names that *do not* match */ 717 if ((l->match & HKF_MATCH_HOST) != 0) 718 return 0; 719 /* not interested in marker lines */ 720 if (l->marker != MRK_NONE) 721 return 0; 722 /* we are only interested in exact key matches */ 723 if (l->key == NULL || !sshkey_equal(ctx->key, l->key)) 724 return 0; 725 path = try_tilde_unexpand(l->path); 726 debug_f("found matching key in %s:%lu", path, l->linenum); 727 ctx->names = xrecallocarray(ctx->names, 728 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names)); 729 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum, 730 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ? 731 "[hashed name]" : l->hosts); 732 ctx->nnames++; 733 free(path); 734 return 0; 735 } 736 737 static int 738 hostkeys_find_by_key_hostfile(const char *file, const char *which, 739 struct find_by_key_ctx *ctx) 740 { 741 int r; 742 743 debug3_f("trying %s hostfile \"%s\"", which, file); 744 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx, 745 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) { 746 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) { 747 debug_f("hostkeys file %s does not exist", file); 748 return 0; 749 } 750 error_fr(r, "hostkeys_foreach failed for %s", file); 751 return r; 752 } 753 return 0; 754 } 755 756 /* 757 * Find 'key' in known hosts file(s) that do not match host/ip. 758 * Used to display also-known-as information for previously-unseen hostkeys. 759 */ 760 static void 761 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key, 762 char **user_hostfiles, u_int num_user_hostfiles, 763 char **system_hostfiles, u_int num_system_hostfiles, 764 char ***names, u_int *nnames) 765 { 766 struct find_by_key_ctx ctx = {0, 0, 0, 0, 0}; 767 u_int i; 768 769 *names = NULL; 770 *nnames = 0; 771 772 if (key == NULL || sshkey_is_cert(key)) 773 return; 774 775 ctx.host = host; 776 ctx.ip = ip; 777 ctx.key = key; 778 779 for (i = 0; i < num_user_hostfiles; i++) { 780 if (hostkeys_find_by_key_hostfile(user_hostfiles[i], 781 "user", &ctx) != 0) 782 goto fail; 783 } 784 for (i = 0; i < num_system_hostfiles; i++) { 785 if (hostkeys_find_by_key_hostfile(system_hostfiles[i], 786 "system", &ctx) != 0) 787 goto fail; 788 } 789 /* success */ 790 *names = ctx.names; 791 *nnames = ctx.nnames; 792 ctx.names = NULL; 793 ctx.nnames = 0; 794 return; 795 fail: 796 for (i = 0; i < ctx.nnames; i++) 797 free(ctx.names[i]); 798 free(ctx.names); 799 } 800 801 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */ 802 static char * 803 other_hostkeys_message(const char *host, const char *ip, 804 const struct sshkey *key, 805 char **user_hostfiles, u_int num_user_hostfiles, 806 char **system_hostfiles, u_int num_system_hostfiles) 807 { 808 char *ret = NULL, **othernames = NULL; 809 u_int i, n, num_othernames = 0; 810 811 hostkeys_find_by_key(host, ip, key, 812 user_hostfiles, num_user_hostfiles, 813 system_hostfiles, num_system_hostfiles, 814 &othernames, &num_othernames); 815 if (num_othernames == 0) 816 return xstrdup("This key is not known by any other names"); 817 818 xasprintf(&ret, "This host key is known by the following other " 819 "names/addresses:"); 820 821 n = num_othernames; 822 if (n > MAX_OTHER_NAMES) 823 n = MAX_OTHER_NAMES; 824 for (i = 0; i < n; i++) { 825 xextendf(&ret, "\n", " %s", othernames[i]); 826 } 827 if (n < num_othernames) { 828 xextendf(&ret, "\n", " (%d additional names omitted)", 829 num_othernames - n); 830 } 831 for (i = 0; i < num_othernames; i++) 832 free(othernames[i]); 833 free(othernames); 834 return ret; 835 } 836 837 void 838 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template, 839 const char *invocation, const struct ssh_conn_info *cinfo, 840 const struct sshkey *host_key, const char *hostfile_hostname) 841 { 842 int r, i, ac = 0; 843 char *key_fp = NULL, *keytext = NULL, *tmp; 844 char *command = NULL, *tag = NULL, **av = NULL; 845 FILE *f = NULL; 846 pid_t pid; 847 void (*osigchld)(int); 848 849 xasprintf(&tag, "KnownHostsCommand-%s", invocation); 850 851 if (host_key != NULL) { 852 if ((key_fp = sshkey_fingerprint(host_key, 853 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 854 fatal_f("sshkey_fingerprint failed"); 855 if ((r = sshkey_to_base64(host_key, &keytext)) != 0) 856 fatal_fr(r, "sshkey_to_base64 failed"); 857 } 858 /* 859 * NB. all returns later this function should go via "out" to 860 * ensure the original SIGCHLD handler is restored properly. 861 */ 862 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 863 864 /* Turn the command into an argument vector */ 865 if (argv_split(command_template, &ac, &av, 0) != 0) { 866 error("%s \"%s\" contains invalid quotes", tag, 867 command_template); 868 goto out; 869 } 870 if (ac == 0) { 871 error("%s \"%s\" yielded no arguments", tag, 872 command_template); 873 goto out; 874 } 875 for (i = 1; i < ac; i++) { 876 tmp = percent_dollar_expand(av[i], 877 DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo), 878 "H", hostfile_hostname, 879 "I", invocation, 880 "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key), 881 "f", key_fp == NULL ? "NONE" : key_fp, 882 "K", keytext == NULL ? "NONE" : keytext, 883 (char *)NULL); 884 if (tmp == NULL) 885 fatal_f("percent_expand failed"); 886 free(av[i]); 887 av[i] = tmp; 888 } 889 /* Prepare a printable command for logs, etc. */ 890 command = argv_assemble(ac, av); 891 892 if ((pid = subprocess(tag, command, ac, av, &f, 893 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH| 894 SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0) 895 goto out; 896 897 load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1); 898 899 if (exited_cleanly(pid, tag, command, 0) != 0) 900 fatal("KnownHostsCommand failed"); 901 902 out: 903 if (f != NULL) 904 fclose(f); 905 ssh_signal(SIGCHLD, osigchld); 906 for (i = 0; i < ac; i++) 907 free(av[i]); 908 free(av); 909 free(tag); 910 free(command); 911 free(key_fp); 912 free(keytext); 913 } 914 915 /* 916 * check whether the supplied host key is valid, return -1 if the key 917 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 918 */ 919 #define RDRW 0 920 #define RDONLY 1 921 #define ROQUIET 2 922 static int 923 check_host_key(char *hostname, const struct ssh_conn_info *cinfo, 924 struct sockaddr *hostaddr, u_short port, 925 struct sshkey *host_key, int readonly, int clobber_port, 926 char **user_hostfiles, u_int num_user_hostfiles, 927 char **system_hostfiles, u_int num_system_hostfiles, 928 const char *hostfile_command) 929 { 930 HostStatus host_status = -1, ip_status = -1; 931 struct sshkey *raw_key = NULL; 932 char *ip = NULL, *host = NULL; 933 char hostline[1000], *hostp, *fp, *ra; 934 char msg[1024]; 935 const char *type, *fail_reason; 936 const struct hostkey_entry *host_found = NULL, *ip_found = NULL; 937 int len, cancelled_forwarding = 0, confirmed; 938 int local = sockaddr_is_local(hostaddr); 939 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 940 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 941 struct hostkeys *host_hostkeys, *ip_hostkeys; 942 u_int i; 943 944 /* 945 * Force accepting of the host key for loopback/localhost. The 946 * problem is that if the home directory is NFS-mounted to multiple 947 * machines, localhost will refer to a different machine in each of 948 * them, and the user will get bogus HOST_CHANGED warnings. This 949 * essentially disables host authentication for localhost; however, 950 * this is probably not a real problem. 951 */ 952 if (options.no_host_authentication_for_localhost == 1 && local && 953 options.host_key_alias == NULL) { 954 debug("Forcing accepting of host key for " 955 "loopback/localhost."); 956 options.update_hostkeys = 0; 957 return 0; 958 } 959 960 /* 961 * Prepare the hostname and address strings used for hostkey lookup. 962 * In some cases, these will have a port number appended. 963 */ 964 get_hostfile_hostname_ipaddr(hostname, hostaddr, 965 clobber_port ? 0 : port, &host, &ip); 966 967 /* 968 * Turn off check_host_ip if the connection is to localhost, via proxy 969 * command or if we don't have a hostname to compare with 970 */ 971 if (options.check_host_ip && (local || 972 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 973 options.check_host_ip = 0; 974 975 host_hostkeys = init_hostkeys(); 976 for (i = 0; i < num_user_hostfiles; i++) 977 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0); 978 for (i = 0; i < num_system_hostfiles; i++) 979 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0); 980 if (hostfile_command != NULL && !clobber_port) { 981 load_hostkeys_command(host_hostkeys, hostfile_command, 982 "HOSTNAME", cinfo, host_key, host); 983 } 984 985 ip_hostkeys = NULL; 986 if (!want_cert && options.check_host_ip) { 987 ip_hostkeys = init_hostkeys(); 988 for (i = 0; i < num_user_hostfiles; i++) 989 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0); 990 for (i = 0; i < num_system_hostfiles; i++) 991 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0); 992 if (hostfile_command != NULL && !clobber_port) { 993 load_hostkeys_command(ip_hostkeys, hostfile_command, 994 "ADDRESS", cinfo, host_key, ip); 995 } 996 } 997 998 retry: 999 /* Reload these as they may have changed on cert->key downgrade */ 1000 want_cert = sshkey_is_cert(host_key); 1001 type = sshkey_type(host_key); 1002 1003 /* 1004 * Check if the host key is present in the user's list of known 1005 * hosts or in the systemwide list. 1006 */ 1007 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 1008 &host_found); 1009 1010 /* 1011 * If there are no hostfiles, or if the hostkey was found via 1012 * KnownHostsCommand, then don't try to touch the disk. 1013 */ 1014 if (!readonly && (num_user_hostfiles == 0 || 1015 (host_found != NULL && host_found->note != 0))) 1016 readonly = RDONLY; 1017 1018 /* 1019 * Also perform check for the ip address, skip the check if we are 1020 * localhost, looking for a certificate, or the hostname was an ip 1021 * address to begin with. 1022 */ 1023 if (!want_cert && ip_hostkeys != NULL) { 1024 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 1025 &ip_found); 1026 if (host_status == HOST_CHANGED && 1027 (ip_status != HOST_CHANGED || 1028 (ip_found != NULL && 1029 !sshkey_equal(ip_found->key, host_found->key)))) 1030 host_ip_differ = 1; 1031 } else 1032 ip_status = host_status; 1033 1034 switch (host_status) { 1035 case HOST_OK: 1036 /* The host is known and the key matches. */ 1037 debug("Host '%.200s' is known and matches the %s host %s.", 1038 host, type, want_cert ? "certificate" : "key"); 1039 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 1040 host_found->file, host_found->line); 1041 if (want_cert) { 1042 if (sshkey_cert_check_host(host_key, 1043 options.host_key_alias == NULL ? 1044 hostname : options.host_key_alias, 0, 1045 options.ca_sign_algorithms, &fail_reason) != 0) { 1046 error("%s", fail_reason); 1047 goto fail; 1048 } 1049 /* 1050 * Do not attempt hostkey update if a certificate was 1051 * successfully matched. 1052 */ 1053 if (options.update_hostkeys != 0) { 1054 options.update_hostkeys = 0; 1055 debug3_f("certificate host key in use; " 1056 "disabling UpdateHostkeys"); 1057 } 1058 } 1059 /* Turn off UpdateHostkeys if key was in system known_hosts */ 1060 if (options.update_hostkeys != 0 && 1061 (path_in_hostfiles(host_found->file, 1062 system_hostfiles, num_system_hostfiles) || 1063 (ip_status == HOST_OK && ip_found != NULL && 1064 path_in_hostfiles(ip_found->file, 1065 system_hostfiles, num_system_hostfiles)))) { 1066 options.update_hostkeys = 0; 1067 debug3_f("host key found in GlobalKnownHostsFile; " 1068 "disabling UpdateHostkeys"); 1069 } 1070 if (options.update_hostkeys != 0 && host_found->note) { 1071 options.update_hostkeys = 0; 1072 debug3_f("host key found via KnownHostsCommand; " 1073 "disabling UpdateHostkeys"); 1074 } 1075 if (options.check_host_ip && ip_status == HOST_NEW) { 1076 if (readonly || want_cert) 1077 logit("%s host key for IP address " 1078 "'%.128s' not in list of known hosts.", 1079 type, ip); 1080 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 1081 host_key, options.hash_known_hosts)) 1082 logit("Failed to add the %s host key for IP " 1083 "address '%.128s' to the list of known " 1084 "hosts (%.500s).", type, ip, 1085 user_hostfiles[0]); 1086 else 1087 logit("Warning: Permanently added the %s host " 1088 "key for IP address '%.128s' to the list " 1089 "of known hosts.", type, ip); 1090 } else if (options.visual_host_key) { 1091 fp = sshkey_fingerprint(host_key, 1092 options.fingerprint_hash, SSH_FP_DEFAULT); 1093 ra = sshkey_fingerprint(host_key, 1094 options.fingerprint_hash, SSH_FP_RANDOMART); 1095 if (fp == NULL || ra == NULL) 1096 fatal_f("sshkey_fingerprint failed"); 1097 logit("Host key fingerprint is %s\n%s", fp, ra); 1098 free(ra); 1099 free(fp); 1100 } 1101 hostkey_trusted = 1; 1102 break; 1103 case HOST_NEW: 1104 if (options.host_key_alias == NULL && port != 0 && 1105 port != SSH_DEFAULT_PORT && !clobber_port) { 1106 debug("checking without port identifier"); 1107 if (check_host_key(hostname, cinfo, hostaddr, 0, 1108 host_key, ROQUIET, 1, 1109 user_hostfiles, num_user_hostfiles, 1110 system_hostfiles, num_system_hostfiles, 1111 hostfile_command) == 0) { 1112 debug("found matching key w/out port"); 1113 break; 1114 } 1115 } 1116 if (readonly || want_cert) 1117 goto fail; 1118 /* The host is new. */ 1119 if (options.strict_host_key_checking == 1120 SSH_STRICT_HOSTKEY_YES) { 1121 /* 1122 * User has requested strict host key checking. We 1123 * will not add the host key automatically. The only 1124 * alternative left is to abort. 1125 */ 1126 error("No %s host key is known for %.200s and you " 1127 "have requested strict checking.", type, host); 1128 goto fail; 1129 } else if (options.strict_host_key_checking == 1130 SSH_STRICT_HOSTKEY_ASK) { 1131 char *msg1 = NULL, *msg2 = NULL; 1132 1133 xasprintf(&msg1, "The authenticity of host " 1134 "'%.200s (%s)' can't be established", host, ip); 1135 1136 if (show_other_keys(host_hostkeys, host_key)) { 1137 xextendf(&msg1, "\n", "but keys of different " 1138 "type are already known for this host."); 1139 } else 1140 xextendf(&msg1, "", "."); 1141 1142 fp = sshkey_fingerprint(host_key, 1143 options.fingerprint_hash, SSH_FP_DEFAULT); 1144 ra = sshkey_fingerprint(host_key, 1145 options.fingerprint_hash, SSH_FP_RANDOMART); 1146 if (fp == NULL || ra == NULL) 1147 fatal_f("sshkey_fingerprint failed"); 1148 xextendf(&msg1, "\n", "%s key fingerprint is %s.", 1149 type, fp); 1150 if (options.visual_host_key) 1151 xextendf(&msg1, "\n", "%s", ra); 1152 if (options.verify_host_key_dns) { 1153 xextendf(&msg1, "\n", 1154 "%s host key fingerprint found in DNS.", 1155 matching_host_key_dns ? 1156 "Matching" : "No matching"); 1157 } 1158 /* msg2 informs for other names matching this key */ 1159 if ((msg2 = other_hostkeys_message(host, ip, host_key, 1160 user_hostfiles, num_user_hostfiles, 1161 system_hostfiles, num_system_hostfiles)) != NULL) 1162 xextendf(&msg1, "\n", "%s", msg2); 1163 1164 xextendf(&msg1, "\n", 1165 "Are you sure you want to continue connecting " 1166 "(yes/no/[fingerprint])? "); 1167 1168 confirmed = confirm(msg1, fp); 1169 free(ra); 1170 free(fp); 1171 free(msg1); 1172 free(msg2); 1173 if (!confirmed) 1174 goto fail; 1175 hostkey_trusted = 1; /* user explicitly confirmed */ 1176 } 1177 /* 1178 * If in "new" or "off" strict mode, add the key automatically 1179 * to the local known_hosts file. 1180 */ 1181 if (options.check_host_ip && ip_status == HOST_NEW) { 1182 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1183 hostp = hostline; 1184 if (options.hash_known_hosts) { 1185 /* Add hash of host and IP separately */ 1186 r = add_host_to_hostfile(user_hostfiles[0], 1187 host, host_key, options.hash_known_hosts) && 1188 add_host_to_hostfile(user_hostfiles[0], ip, 1189 host_key, options.hash_known_hosts); 1190 } else { 1191 /* Add unhashed "host,ip" */ 1192 r = add_host_to_hostfile(user_hostfiles[0], 1193 hostline, host_key, 1194 options.hash_known_hosts); 1195 } 1196 } else { 1197 r = add_host_to_hostfile(user_hostfiles[0], host, 1198 host_key, options.hash_known_hosts); 1199 hostp = host; 1200 } 1201 1202 if (!r) 1203 logit("Failed to add the host to the list of known " 1204 "hosts (%.500s).", user_hostfiles[0]); 1205 else 1206 logit("Warning: Permanently added '%.200s' (%s) to the " 1207 "list of known hosts.", hostp, type); 1208 break; 1209 case HOST_REVOKED: 1210 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1211 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1212 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1213 error("The %s host key for %s is marked as revoked.", type, host); 1214 error("This could mean that a stolen key is being used to"); 1215 error("impersonate this host."); 1216 1217 /* 1218 * If strict host key checking is in use, the user will have 1219 * to edit the key manually and we can only abort. 1220 */ 1221 if (options.strict_host_key_checking != 1222 SSH_STRICT_HOSTKEY_OFF) { 1223 error("%s host key for %.200s was revoked and you have " 1224 "requested strict checking.", type, host); 1225 goto fail; 1226 } 1227 goto continue_unsafe; 1228 1229 case HOST_CHANGED: 1230 if (want_cert) { 1231 /* 1232 * This is only a debug() since it is valid to have 1233 * CAs with wildcard DNS matches that don't match 1234 * all hosts that one might visit. 1235 */ 1236 debug("Host certificate authority does not " 1237 "match %s in %s:%lu", CA_MARKER, 1238 host_found->file, host_found->line); 1239 goto fail; 1240 } 1241 if (readonly == ROQUIET) 1242 goto fail; 1243 if (options.check_host_ip && host_ip_differ) { 1244 const char *key_msg; 1245 if (ip_status == HOST_NEW) 1246 key_msg = "is unknown"; 1247 else if (ip_status == HOST_OK) 1248 key_msg = "is unchanged"; 1249 else 1250 key_msg = "has a different value"; 1251 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1252 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1253 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1254 error("The %s host key for %s has changed,", type, host); 1255 error("and the key for the corresponding IP address %s", ip); 1256 error("%s. This could either mean that", key_msg); 1257 error("DNS SPOOFING is happening or the IP address for the host"); 1258 error("and its host key have changed at the same time."); 1259 if (ip_status != HOST_NEW) 1260 error("Offending key for IP in %s:%lu", 1261 ip_found->file, ip_found->line); 1262 } 1263 /* The host key has changed. */ 1264 warn_changed_key(host_key); 1265 error("Add correct host key in %.100s to get rid of this message.", 1266 user_hostfiles[0]); 1267 error("Offending %s key in %s:%lu", 1268 sshkey_type(host_found->key), 1269 host_found->file, host_found->line); 1270 1271 /* 1272 * If strict host key checking is in use, the user will have 1273 * to edit the key manually and we can only abort. 1274 */ 1275 if (options.strict_host_key_checking != 1276 SSH_STRICT_HOSTKEY_OFF) { 1277 error("Host key for %.200s has changed and you have " 1278 "requested strict checking.", host); 1279 goto fail; 1280 } 1281 1282 continue_unsafe: 1283 /* 1284 * If strict host key checking has not been requested, allow 1285 * the connection but without MITM-able authentication or 1286 * forwarding. 1287 */ 1288 if (options.password_authentication) { 1289 error("Password authentication is disabled to avoid " 1290 "man-in-the-middle attacks."); 1291 options.password_authentication = 0; 1292 cancelled_forwarding = 1; 1293 } 1294 if (options.kbd_interactive_authentication) { 1295 error("Keyboard-interactive authentication is disabled" 1296 " to avoid man-in-the-middle attacks."); 1297 options.kbd_interactive_authentication = 0; 1298 cancelled_forwarding = 1; 1299 } 1300 if (options.forward_agent) { 1301 error("Agent forwarding is disabled to avoid " 1302 "man-in-the-middle attacks."); 1303 options.forward_agent = 0; 1304 cancelled_forwarding = 1; 1305 } 1306 if (options.forward_x11) { 1307 error("X11 forwarding is disabled to avoid " 1308 "man-in-the-middle attacks."); 1309 options.forward_x11 = 0; 1310 cancelled_forwarding = 1; 1311 } 1312 if (options.num_local_forwards > 0 || 1313 options.num_remote_forwards > 0) { 1314 error("Port forwarding is disabled to avoid " 1315 "man-in-the-middle attacks."); 1316 options.num_local_forwards = 1317 options.num_remote_forwards = 0; 1318 cancelled_forwarding = 1; 1319 } 1320 if (options.tun_open != SSH_TUNMODE_NO) { 1321 error("Tunnel forwarding is disabled to avoid " 1322 "man-in-the-middle attacks."); 1323 options.tun_open = SSH_TUNMODE_NO; 1324 cancelled_forwarding = 1; 1325 } 1326 if (options.update_hostkeys != 0) { 1327 error("UpdateHostkeys is disabled because the host " 1328 "key is not trusted."); 1329 options.update_hostkeys = 0; 1330 } 1331 if (options.exit_on_forward_failure && cancelled_forwarding) 1332 fatal("Error: forwarding disabled due to host key " 1333 "check failure"); 1334 1335 /* 1336 * XXX Should permit the user to change to use the new id. 1337 * This could be done by converting the host key to an 1338 * identifying sentence, tell that the host identifies itself 1339 * by that sentence, and ask the user if they wish to 1340 * accept the authentication. 1341 */ 1342 break; 1343 case HOST_FOUND: 1344 fatal("internal error"); 1345 break; 1346 } 1347 1348 if (options.check_host_ip && host_status != HOST_CHANGED && 1349 ip_status == HOST_CHANGED) { 1350 snprintf(msg, sizeof(msg), 1351 "Warning: the %s host key for '%.200s' " 1352 "differs from the key for the IP address '%.128s'" 1353 "\nOffending key for IP in %s:%lu", 1354 type, host, ip, ip_found->file, ip_found->line); 1355 if (host_status == HOST_OK) { 1356 len = strlen(msg); 1357 snprintf(msg + len, sizeof(msg) - len, 1358 "\nMatching host key in %s:%lu", 1359 host_found->file, host_found->line); 1360 } 1361 if (options.strict_host_key_checking == 1362 SSH_STRICT_HOSTKEY_ASK) { 1363 strlcat(msg, "\nAre you sure you want " 1364 "to continue connecting (yes/no)? ", sizeof(msg)); 1365 if (!confirm(msg, NULL)) 1366 goto fail; 1367 } else if (options.strict_host_key_checking != 1368 SSH_STRICT_HOSTKEY_OFF) { 1369 logit("%s", msg); 1370 error("Exiting, you have requested strict checking."); 1371 goto fail; 1372 } else { 1373 logit("%s", msg); 1374 } 1375 } 1376 1377 if (!hostkey_trusted && options.update_hostkeys) { 1378 debug_f("hostkey not known or explicitly trusted: " 1379 "disabling UpdateHostkeys"); 1380 options.update_hostkeys = 0; 1381 } 1382 1383 free(ip); 1384 free(host); 1385 if (host_hostkeys != NULL) 1386 free_hostkeys(host_hostkeys); 1387 if (ip_hostkeys != NULL) 1388 free_hostkeys(ip_hostkeys); 1389 return 0; 1390 1391 fail: 1392 if (want_cert && host_status != HOST_REVOKED) { 1393 /* 1394 * No matching certificate. Downgrade cert to raw key and 1395 * search normally. 1396 */ 1397 debug("No matching CA found. Retry with plain key"); 1398 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1399 fatal_fr(r, "decode key"); 1400 if ((r = sshkey_drop_cert(raw_key)) != 0) 1401 fatal_r(r, "Couldn't drop certificate"); 1402 host_key = raw_key; 1403 goto retry; 1404 } 1405 sshkey_free(raw_key); 1406 free(ip); 1407 free(host); 1408 if (host_hostkeys != NULL) 1409 free_hostkeys(host_hostkeys); 1410 if (ip_hostkeys != NULL) 1411 free_hostkeys(ip_hostkeys); 1412 return -1; 1413 } 1414 1415 /* returns 0 if key verifies or -1 if key does NOT verify */ 1416 int 1417 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key, 1418 const struct ssh_conn_info *cinfo) 1419 { 1420 u_int i; 1421 int r = -1, flags = 0; 1422 char valid[64], *fp = NULL, *cafp = NULL; 1423 struct sshkey *plain = NULL; 1424 1425 if ((fp = sshkey_fingerprint(host_key, 1426 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1427 error_fr(r, "fingerprint host key"); 1428 r = -1; 1429 goto out; 1430 } 1431 1432 if (sshkey_is_cert(host_key)) { 1433 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1434 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1435 error_fr(r, "fingerprint CA key"); 1436 r = -1; 1437 goto out; 1438 } 1439 sshkey_format_cert_validity(host_key->cert, 1440 valid, sizeof(valid)); 1441 debug("Server host certificate: %s %s, serial %llu " 1442 "ID \"%s\" CA %s %s valid %s", 1443 sshkey_ssh_name(host_key), fp, 1444 (unsigned long long)host_key->cert->serial, 1445 host_key->cert->key_id, 1446 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1447 valid); 1448 for (i = 0; i < host_key->cert->nprincipals; i++) { 1449 debug2("Server host certificate hostname: %s", 1450 host_key->cert->principals[i]); 1451 } 1452 } else { 1453 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1454 } 1455 1456 if (sshkey_equal(previous_host_key, host_key)) { 1457 debug2_f("server host key %s %s matches cached key", 1458 sshkey_type(host_key), fp); 1459 r = 0; 1460 goto out; 1461 } 1462 1463 /* Check in RevokedHostKeys file if specified */ 1464 if (options.revoked_host_keys != NULL) { 1465 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1466 switch (r) { 1467 case 0: 1468 break; /* not revoked */ 1469 case SSH_ERR_KEY_REVOKED: 1470 error("Host key %s %s revoked by file %s", 1471 sshkey_type(host_key), fp, 1472 options.revoked_host_keys); 1473 r = -1; 1474 goto out; 1475 default: 1476 error_r(r, "Error checking host key %s %s in " 1477 "revoked keys file %s", sshkey_type(host_key), 1478 fp, options.revoked_host_keys); 1479 r = -1; 1480 goto out; 1481 } 1482 } 1483 1484 if (options.verify_host_key_dns) { 1485 /* 1486 * XXX certs are not yet supported for DNS, so downgrade 1487 * them and try the plain key. 1488 */ 1489 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1490 goto out; 1491 if (sshkey_is_cert(plain)) 1492 sshkey_drop_cert(plain); 1493 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1494 if (flags & DNS_VERIFY_FOUND) { 1495 if (options.verify_host_key_dns == 1 && 1496 flags & DNS_VERIFY_MATCH && 1497 flags & DNS_VERIFY_SECURE) { 1498 r = 0; 1499 goto out; 1500 } 1501 if (flags & DNS_VERIFY_MATCH) { 1502 matching_host_key_dns = 1; 1503 } else { 1504 warn_changed_key(plain); 1505 error("Update the SSHFP RR in DNS " 1506 "with the new host key to get rid " 1507 "of this message."); 1508 } 1509 } 1510 } 1511 } 1512 r = check_host_key(host, cinfo, hostaddr, options.port, host_key, 1513 RDRW, 0, options.user_hostfiles, options.num_user_hostfiles, 1514 options.system_hostfiles, options.num_system_hostfiles, 1515 options.known_hosts_command); 1516 1517 out: 1518 sshkey_free(plain); 1519 free(fp); 1520 free(cafp); 1521 if (r == 0 && host_key != NULL) { 1522 sshkey_free(previous_host_key); 1523 r = sshkey_from_private(host_key, &previous_host_key); 1524 } 1525 1526 return r; 1527 } 1528 1529 /* 1530 * Starts a dialog with the server, and authenticates the current user on the 1531 * server. This does not need any extra privileges. The basic connection 1532 * to the server must already have been established before this is called. 1533 * If login fails, this function prints an error and never returns. 1534 * This function does not require super-user privileges. 1535 */ 1536 void 1537 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost, 1538 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms, 1539 const struct ssh_conn_info *cinfo) 1540 { 1541 char *host; 1542 char *server_user, *local_user; 1543 int r; 1544 1545 local_user = xstrdup(pw->pw_name); 1546 server_user = options.user ? options.user : local_user; 1547 1548 /* Convert the user-supplied hostname into all lowercase. */ 1549 host = xstrdup(orighost); 1550 lowercase(host); 1551 1552 /* Exchange protocol version identification strings with the server. */ 1553 if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0) 1554 sshpkt_fatal(ssh, r, "banner exchange"); 1555 1556 /* Put the connection into non-blocking mode. */ 1557 ssh_packet_set_nonblocking(ssh); 1558 1559 /* key exchange */ 1560 /* authenticate user */ 1561 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1562 ssh_kex2(ssh, host, hostaddr, port, cinfo); 1563 ssh_userauth2(ssh, local_user, server_user, host, sensitive); 1564 free(local_user); 1565 free(host); 1566 } 1567 1568 /* print all known host keys for a given host, but skip keys of given type */ 1569 static int 1570 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1571 { 1572 int type[] = { 1573 KEY_RSA, 1574 KEY_DSA, 1575 KEY_ECDSA, 1576 KEY_ED25519, 1577 KEY_XMSS, 1578 -1 1579 }; 1580 int i, ret = 0; 1581 char *fp, *ra; 1582 const struct hostkey_entry *found; 1583 1584 for (i = 0; type[i] != -1; i++) { 1585 if (type[i] == key->type) 1586 continue; 1587 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], 1588 -1, &found)) 1589 continue; 1590 fp = sshkey_fingerprint(found->key, 1591 options.fingerprint_hash, SSH_FP_DEFAULT); 1592 ra = sshkey_fingerprint(found->key, 1593 options.fingerprint_hash, SSH_FP_RANDOMART); 1594 if (fp == NULL || ra == NULL) 1595 fatal_f("sshkey_fingerprint fail"); 1596 logit("WARNING: %s key found for host %s\n" 1597 "in %s:%lu\n" 1598 "%s key fingerprint %s.", 1599 sshkey_type(found->key), 1600 found->host, found->file, found->line, 1601 sshkey_type(found->key), fp); 1602 if (options.visual_host_key) 1603 logit("%s", ra); 1604 free(ra); 1605 free(fp); 1606 ret = 1; 1607 } 1608 return ret; 1609 } 1610 1611 static void 1612 warn_changed_key(struct sshkey *host_key) 1613 { 1614 char *fp; 1615 1616 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1617 SSH_FP_DEFAULT); 1618 if (fp == NULL) 1619 fatal_f("sshkey_fingerprint fail"); 1620 1621 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1622 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1623 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1624 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1625 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1626 error("It is also possible that a host key has just been changed."); 1627 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1628 sshkey_type(host_key), fp); 1629 error("Please contact your system administrator."); 1630 1631 free(fp); 1632 } 1633 1634 /* 1635 * Execute a local command 1636 */ 1637 int 1638 ssh_local_cmd(const char *args) 1639 { 1640 const char *shell; 1641 pid_t pid; 1642 int status; 1643 void (*osighand)(int); 1644 1645 if (!options.permit_local_command || 1646 args == NULL || !*args) 1647 return (1); 1648 1649 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1650 shell = _PATH_BSHELL; 1651 1652 osighand = ssh_signal(SIGCHLD, SIG_DFL); 1653 pid = fork(); 1654 if (pid == 0) { 1655 ssh_signal(SIGPIPE, SIG_DFL); 1656 debug3("Executing %s -c \"%s\"", shell, args); 1657 execl(shell, shell, "-c", args, (char *)NULL); 1658 error("Couldn't execute %s -c \"%s\": %s", 1659 shell, args, strerror(errno)); 1660 _exit(1); 1661 } else if (pid == -1) 1662 fatal("fork failed: %.100s", strerror(errno)); 1663 while (waitpid(pid, &status, 0) == -1) 1664 if (errno != EINTR) 1665 fatal("Couldn't wait for child: %s", strerror(errno)); 1666 ssh_signal(SIGCHLD, osighand); 1667 1668 if (!WIFEXITED(status)) 1669 return (1); 1670 1671 return (WEXITSTATUS(status)); 1672 } 1673 1674 void 1675 maybe_add_key_to_agent(const char *authfile, struct sshkey *private, 1676 const char *comment, const char *passphrase) 1677 { 1678 int auth_sock = -1, r; 1679 const char *skprovider = NULL; 1680 1681 if (options.add_keys_to_agent == 0) 1682 return; 1683 1684 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1685 debug3("no authentication agent, not adding key"); 1686 return; 1687 } 1688 1689 if (options.add_keys_to_agent == 2 && 1690 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1691 debug3("user denied adding this key"); 1692 close(auth_sock); 1693 return; 1694 } 1695 if (sshkey_is_sk(private)) 1696 skprovider = options.sk_provider; 1697 if ((r = ssh_add_identity_constrained(auth_sock, private, 1698 comment == NULL ? authfile : comment, 1699 options.add_keys_to_agent_lifespan, 1700 (options.add_keys_to_agent == 3), 0, skprovider, NULL, 0)) == 0) 1701 debug("identity added to agent: %s", authfile); 1702 else 1703 debug("could not add identity to agent: %s (%d)", authfile, r); 1704 close(auth_sock); 1705 } 1706