1 /* $NetBSD: sshconnect.c,v 1.31 2021/09/02 11:26:18 christos Exp $ */ 2 /* $OpenBSD: sshconnect.c,v 1.355 2021/07/02 05:11:21 dtucker Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo@cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * Code to connect to a remote host, and to perform the client side of the 9 * login (authentication) dialog. 10 * 11 * As far as I am concerned, the code I have written for this software 12 * can be used freely for any purpose. Any derived versions of this 13 * software must be clearly marked as such, and if the derived work is 14 * incompatible with the protocol description in the RFC file, it must be 15 * called by a name other than "ssh" or "Secure Shell". 16 */ 17 18 #include "includes.h" 19 __RCSID("$NetBSD: sshconnect.c,v 1.31 2021/09/02 11:26:18 christos Exp $"); 20 21 #include <sys/param.h> /* roundup */ 22 #include <sys/types.h> 23 #include <sys/param.h> 24 #include <sys/wait.h> 25 #include <sys/stat.h> 26 #include <sys/socket.h> 27 #include <sys/time.h> 28 29 #include <net/if.h> 30 #include <netinet/in.h> 31 #include <rpc/rpc.h> 32 33 #include <ctype.h> 34 #include <errno.h> 35 #include <fcntl.h> 36 #include <netdb.h> 37 #include <limits.h> 38 #include <paths.h> 39 #include <signal.h> 40 #include <pwd.h> 41 #include <stdio.h> 42 #include <stdlib.h> 43 #include <stdarg.h> 44 #include <string.h> 45 #include <unistd.h> 46 #include <ifaddrs.h> 47 48 #include "xmalloc.h" 49 #include "ssh.h" 50 #include "sshbuf.h" 51 #include "packet.h" 52 #include "compat.h" 53 #include "sshkey.h" 54 #include "sshconnect.h" 55 #include "hostfile.h" 56 #include "log.h" 57 #include "misc.h" 58 #include "readconf.h" 59 #include "atomicio.h" 60 #include "dns.h" 61 #include "monitor_fdpass.h" 62 #include "ssh2.h" 63 #include "version.h" 64 #include "authfile.h" 65 #include "ssherr.h" 66 #include "authfd.h" 67 #include "kex.h" 68 69 struct sshkey *previous_host_key = NULL; 70 71 static int matching_host_key_dns = 0; 72 73 static pid_t proxy_command_pid = 0; 74 75 /* import */ 76 extern int debug_flag; 77 extern Options options; 78 extern char *__progname; 79 80 static int show_other_keys(struct hostkeys *, struct sshkey *); 81 static void warn_changed_key(struct sshkey *); 82 83 /* Expand a proxy command */ 84 static char * 85 expand_proxy_command(const char *proxy_command, const char *user, 86 const char *host, const char *host_arg, int port) 87 { 88 char *tmp, *ret, strport[NI_MAXSERV]; 89 const char *keyalias = options.host_key_alias ? 90 options.host_key_alias : host_arg; 91 92 snprintf(strport, sizeof strport, "%d", port); 93 xasprintf(&tmp, "exec %s", proxy_command); 94 ret = percent_expand(tmp, 95 "h", host, 96 "k", keyalias, 97 "n", host_arg, 98 "p", strport, 99 "r", options.user, 100 (char *)NULL); 101 free(tmp); 102 return ret; 103 } 104 105 /* 106 * Connect to the given ssh server using a proxy command that passes a 107 * a connected fd back to us. 108 */ 109 static int 110 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, 111 const char *host_arg, u_short port, const char *proxy_command) 112 { 113 char *command_string; 114 int sp[2], sock; 115 pid_t pid; 116 const char *shell; 117 118 if ((shell = getenv("SHELL")) == NULL) 119 shell = _PATH_BSHELL; 120 121 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) == -1) 122 fatal("Could not create socketpair to communicate with " 123 "proxy dialer: %.100s", strerror(errno)); 124 close(sp[1]); 125 126 command_string = expand_proxy_command(proxy_command, options.user, 127 host, host_arg, port); 128 debug("Executing proxy dialer command: %.500s", command_string); 129 130 /* Fork and execute the proxy command. */ 131 if ((pid = fork()) == 0) { 132 char *argv[10]; 133 134 close(sp[1]); 135 /* Redirect stdin and stdout. */ 136 if (sp[0] != 0) { 137 if (dup2(sp[0], 0) == -1) 138 perror("dup2 stdin"); 139 } 140 if (sp[0] != 1) { 141 if (dup2(sp[0], 1) == -1) 142 perror("dup2 stdout"); 143 } 144 if (sp[0] >= 2) 145 close(sp[0]); 146 147 /* 148 * Stderr is left for non-ControlPersist connections is so 149 * error messages may be printed on the user's terminal. 150 */ 151 if (!debug_flag && options.control_path != NULL && 152 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 153 error_f("stdfd_devnull failed"); 154 155 argv[0] = __UNCONST(shell); 156 argv[1] = __UNCONST("-c"); 157 argv[2] = command_string; 158 argv[3] = NULL; 159 160 /* 161 * Execute the proxy command. 162 * Note that we gave up any extra privileges above. 163 */ 164 execv(argv[0], argv); 165 perror(argv[0]); 166 exit(1); 167 } 168 /* Parent. */ 169 if (pid == -1) 170 fatal("fork failed: %.100s", strerror(errno)); 171 close(sp[0]); 172 free(command_string); 173 174 if ((sock = mm_receive_fd(sp[1])) == -1) 175 fatal("proxy dialer did not pass back a connection"); 176 close(sp[1]); 177 178 while (waitpid(pid, NULL, 0) == -1) 179 if (errno != EINTR) 180 fatal("Couldn't wait for child: %s", strerror(errno)); 181 182 /* Set the connection file descriptors. */ 183 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 184 return -1; /* ssh_packet_set_connection logs error */ 185 186 return 0; 187 } 188 189 /* 190 * Connect to the given ssh server using a proxy command. 191 */ 192 static int 193 ssh_proxy_connect(struct ssh *ssh, const char *host, const char *host_arg, 194 u_short port, const char *proxy_command) 195 { 196 char *command_string; 197 int pin[2], pout[2]; 198 pid_t pid; 199 char *shell; 200 201 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 202 shell = __UNCONST(_PATH_BSHELL); 203 204 /* Create pipes for communicating with the proxy. */ 205 if (pipe(pin) == -1 || pipe(pout) == -1) 206 fatal("Could not create pipes to communicate with the proxy: %.100s", 207 strerror(errno)); 208 209 command_string = expand_proxy_command(proxy_command, options.user, 210 host, host_arg, port); 211 debug("Executing proxy command: %.500s", command_string); 212 213 /* Fork and execute the proxy command. */ 214 if ((pid = fork()) == 0) { 215 char *argv[10]; 216 217 /* Redirect stdin and stdout. */ 218 close(pin[1]); 219 if (pin[0] != 0) { 220 if (dup2(pin[0], 0) == -1) 221 perror("dup2 stdin"); 222 close(pin[0]); 223 } 224 close(pout[0]); 225 if (dup2(pout[1], 1) == -1) 226 perror("dup2 stdout"); 227 /* Cannot be 1 because pin allocated two descriptors. */ 228 close(pout[1]); 229 230 /* 231 * Stderr is left for non-ControlPersist connections is so 232 * error messages may be printed on the user's terminal. 233 */ 234 if (!debug_flag && options.control_path != NULL && 235 options.control_persist && stdfd_devnull(0, 0, 1) == -1) 236 error_f("stdfd_devnull failed"); 237 238 argv[0] = shell; 239 argv[1] = __UNCONST("-c"); 240 argv[2] = command_string; 241 argv[3] = NULL; 242 243 /* 244 * Execute the proxy command. Note that we gave up any 245 * extra privileges above. 246 */ 247 ssh_signal(SIGPIPE, SIG_DFL); 248 execv(argv[0], argv); 249 perror(argv[0]); 250 exit(1); 251 } 252 /* Parent. */ 253 if (pid == -1) 254 fatal("fork failed: %.100s", strerror(errno)); 255 else 256 proxy_command_pid = pid; /* save pid to clean up later */ 257 258 /* Close child side of the descriptors. */ 259 close(pin[0]); 260 close(pout[1]); 261 262 /* Free the command name. */ 263 free(command_string); 264 265 /* Set the connection file descriptors. */ 266 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 267 return -1; /* ssh_packet_set_connection logs error */ 268 269 return 0; 270 } 271 272 void 273 ssh_kill_proxy_command(void) 274 { 275 /* 276 * Send SIGHUP to proxy command if used. We don't wait() in 277 * case it hangs and instead rely on init to reap the child 278 */ 279 if (proxy_command_pid > 1) 280 kill(proxy_command_pid, SIGHUP); 281 } 282 283 /* 284 * Set TCP receive buffer if requested. 285 * Note: tuning needs to happen after the socket is 286 * created but before the connection happens 287 * so winscale is negotiated properly -cjr 288 */ 289 static void 290 ssh_set_socket_recvbuf(int sock) 291 { 292 void *buf = (void *)&options.tcp_rcv_buf; 293 int sz = sizeof(options.tcp_rcv_buf); 294 int socksize; 295 socklen_t socksizelen = sizeof(int); 296 297 debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); 298 if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { 299 getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); 300 debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); 301 } 302 else 303 error("Couldn't set socket receive buffer to %d: %.100s", 304 options.tcp_rcv_buf, strerror(errno)); 305 } 306 307 /* 308 * Search a interface address list (returned from getifaddrs(3)) for an 309 * address that matches the desired address family on the specified interface. 310 * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure. 311 */ 312 static int 313 check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs, 314 struct sockaddr_storage *resultp, socklen_t *rlenp) 315 { 316 struct sockaddr_in6 *sa6; 317 struct sockaddr_in *sa; 318 struct in6_addr *v6addr; 319 const struct ifaddrs *ifa; 320 int allow_local; 321 322 /* 323 * Prefer addresses that are not loopback or linklocal, but use them 324 * if nothing else matches. 325 */ 326 for (allow_local = 0; allow_local < 2; allow_local++) { 327 for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) { 328 if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL || 329 (ifa->ifa_flags & IFF_UP) == 0 || 330 ifa->ifa_addr->sa_family != af || 331 strcmp(ifa->ifa_name, options.bind_interface) != 0) 332 continue; 333 switch (ifa->ifa_addr->sa_family) { 334 case AF_INET: 335 sa = (struct sockaddr_in *)ifa->ifa_addr; 336 if (!allow_local && sa->sin_addr.s_addr == 337 htonl(INADDR_LOOPBACK)) 338 continue; 339 if (*rlenp < sizeof(struct sockaddr_in)) { 340 error_f("v4 addr doesn't fit"); 341 return -1; 342 } 343 *rlenp = sizeof(struct sockaddr_in); 344 memcpy(resultp, sa, *rlenp); 345 return 0; 346 case AF_INET6: 347 sa6 = (struct sockaddr_in6 *)ifa->ifa_addr; 348 v6addr = &sa6->sin6_addr; 349 if (!allow_local && 350 (IN6_IS_ADDR_LINKLOCAL(v6addr) || 351 IN6_IS_ADDR_LOOPBACK(v6addr))) 352 continue; 353 if (*rlenp < sizeof(struct sockaddr_in6)) { 354 error_f("v6 addr doesn't fit"); 355 return -1; 356 } 357 *rlenp = sizeof(struct sockaddr_in6); 358 memcpy(resultp, sa6, *rlenp); 359 return 0; 360 } 361 } 362 } 363 return -1; 364 } 365 366 /* 367 * Creates a socket for use as the ssh connection. 368 */ 369 static int 370 ssh_create_socket(struct addrinfo *ai) 371 { 372 int sock, r; 373 struct sockaddr_storage bindaddr; 374 socklen_t bindaddrlen = 0; 375 struct addrinfo hints, *res = NULL; 376 struct ifaddrs *ifaddrs = NULL; 377 char ntop[NI_MAXHOST]; 378 379 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 380 if (sock == -1) { 381 error("socket: %s", strerror(errno)); 382 return -1; 383 } 384 fcntl(sock, F_SETFD, FD_CLOEXEC); 385 386 if (options.tcp_rcv_buf > 0) 387 ssh_set_socket_recvbuf(sock); 388 389 /* Use interactive QOS (if specified) until authentication completed */ 390 if (options.ip_qos_interactive != INT_MAX) 391 set_sock_tos(sock, options.ip_qos_interactive); 392 393 /* Bind the socket to an alternative local IP address */ 394 if (options.bind_address == NULL && options.bind_interface == NULL) 395 return sock; 396 397 if (options.bind_address != NULL) { 398 memset(&hints, 0, sizeof(hints)); 399 hints.ai_family = ai->ai_family; 400 hints.ai_socktype = ai->ai_socktype; 401 hints.ai_protocol = ai->ai_protocol; 402 hints.ai_flags = AI_PASSIVE; 403 if ((r = getaddrinfo(options.bind_address, NULL, 404 &hints, &res)) != 0) { 405 error("getaddrinfo: %s: %s", options.bind_address, 406 ssh_gai_strerror(r)); 407 goto fail; 408 } 409 if (res == NULL) { 410 error("getaddrinfo: no addrs"); 411 goto fail; 412 } 413 memcpy(&bindaddr, res->ai_addr, res->ai_addrlen); 414 bindaddrlen = res->ai_addrlen; 415 } else if (options.bind_interface != NULL) { 416 if ((r = getifaddrs(&ifaddrs)) != 0) { 417 error("getifaddrs: %s: %s", options.bind_interface, 418 strerror(errno)); 419 goto fail; 420 } 421 bindaddrlen = sizeof(bindaddr); 422 if (check_ifaddrs(options.bind_interface, ai->ai_family, 423 ifaddrs, &bindaddr, &bindaddrlen) != 0) { 424 logit("getifaddrs: %s: no suitable addresses", 425 options.bind_interface); 426 goto fail; 427 } 428 } 429 if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen, 430 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) { 431 error_f("getnameinfo failed: %s", ssh_gai_strerror(r)); 432 goto fail; 433 } 434 if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) { 435 error("bind %s: %s", ntop, strerror(errno)); 436 goto fail; 437 } 438 debug_f("bound to %s", ntop); 439 /* success */ 440 goto out; 441 fail: 442 close(sock); 443 sock = -1; 444 out: 445 if (res != NULL) 446 freeaddrinfo(res); 447 if (ifaddrs != NULL) 448 freeifaddrs(ifaddrs); 449 return sock; 450 } 451 452 /* 453 * Opens a TCP/IP connection to the remote server on the given host. 454 * The address of the remote host will be returned in hostaddr. 455 * If port is 0, the default port will be used. 456 * Connection_attempts specifies the maximum number of tries (one per 457 * second). If proxy_command is non-NULL, it specifies the command (with %h 458 * and %p substituted for host and port, respectively) to use to contact 459 * the daemon. 460 */ 461 static int 462 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 463 struct sockaddr_storage *hostaddr, u_short port, int connection_attempts, 464 int *timeout_ms, int want_keepalive) 465 { 466 int on = 1, saved_timeout_ms = *timeout_ms; 467 int oerrno, sock = -1, attempt; 468 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 469 struct addrinfo *ai; 470 471 debug3_f("entering"); 472 memset(ntop, 0, sizeof(ntop)); 473 memset(strport, 0, sizeof(strport)); 474 475 for (attempt = 0; attempt < connection_attempts; attempt++) { 476 if (attempt > 0) { 477 /* Sleep a moment before retrying. */ 478 sleep(1); 479 debug("Trying again..."); 480 } 481 /* 482 * Loop through addresses for this host, and try each one in 483 * sequence until the connection succeeds. 484 */ 485 for (ai = aitop; ai; ai = ai->ai_next) { 486 if (ai->ai_family != AF_INET && 487 ai->ai_family != AF_INET6) { 488 errno = EAFNOSUPPORT; 489 continue; 490 } 491 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 492 ntop, sizeof(ntop), strport, sizeof(strport), 493 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 494 oerrno = errno; 495 error_f("getnameinfo failed"); 496 errno = oerrno; 497 continue; 498 } 499 debug("Connecting to %.200s [%.100s] port %s.", 500 host, ntop, strport); 501 502 /* Create a socket for connecting. */ 503 sock = ssh_create_socket(ai); 504 if (sock < 0) { 505 /* Any error is already output */ 506 errno = 0; 507 continue; 508 } 509 510 *timeout_ms = saved_timeout_ms; 511 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 512 timeout_ms) >= 0) { 513 /* Successful connection. */ 514 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 515 break; 516 } else { 517 oerrno = errno; 518 debug("connect to address %s port %s: %s", 519 ntop, strport, strerror(errno)); 520 close(sock); 521 sock = -1; 522 errno = oerrno; 523 } 524 } 525 if (sock != -1) 526 break; /* Successful connection. */ 527 } 528 529 /* Return failure if we didn't get a successful connection. */ 530 if (sock == -1) { 531 error("ssh: connect to host %s port %s: %s", 532 host, strport, errno == 0 ? "failure" : strerror(errno)); 533 return -1; 534 } 535 536 debug("Connection established."); 537 538 /* Set SO_KEEPALIVE if requested. */ 539 if (want_keepalive && 540 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 541 sizeof(on)) == -1) 542 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 543 544 /* Set the connection. */ 545 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 546 return -1; /* ssh_packet_set_connection logs error */ 547 548 return 0; 549 } 550 551 int 552 ssh_connect(struct ssh *ssh, const char *host, const char *host_arg, 553 struct addrinfo *addrs, struct sockaddr_storage *hostaddr, u_short port, 554 int connection_attempts, int *timeout_ms, int want_keepalive) 555 { 556 int in, out; 557 558 if (options.proxy_command == NULL) { 559 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 560 connection_attempts, timeout_ms, want_keepalive); 561 } else if (strcmp(options.proxy_command, "-") == 0) { 562 if ((in = dup(STDIN_FILENO)) == -1 || 563 (out = dup(STDOUT_FILENO)) == -1) { 564 if (in >= 0) 565 close(in); 566 error_f("dup() in/out failed"); 567 return -1; /* ssh_packet_set_connection logs error */ 568 } 569 if ((ssh_packet_set_connection(ssh, in, out)) == NULL) 570 return -1; /* ssh_packet_set_connection logs error */ 571 return 0; 572 } else if (options.proxy_use_fdpass) { 573 return ssh_proxy_fdpass_connect(ssh, host, host_arg, port, 574 options.proxy_command); 575 } 576 return ssh_proxy_connect(ssh, host, host_arg, port, 577 options.proxy_command); 578 } 579 580 /* defaults to 'no' */ 581 static int 582 confirm(const char *prompt, const char *fingerprint) 583 { 584 const char *msg, *again = "Please type 'yes' or 'no': "; 585 const char *again_fp = "Please type 'yes', 'no' or the fingerprint: "; 586 char *p, *cp; 587 int ret = -1; 588 589 if (options.batch_mode) 590 return 0; 591 for (msg = prompt;;msg = fingerprint ? again_fp : again) { 592 cp = p = read_passphrase(msg, RP_ECHO); 593 if (p == NULL) 594 return 0; 595 p += strspn(p, " \t"); /* skip leading whitespace */ 596 p[strcspn(p, " \t\n")] = '\0'; /* remove trailing whitespace */ 597 if (p[0] == '\0' || strcasecmp(p, "no") == 0) 598 ret = 0; 599 else if (strcasecmp(p, "yes") == 0 || (fingerprint != NULL && 600 strcmp(p, fingerprint) == 0)) 601 ret = 1; 602 free(cp); 603 if (ret != -1) 604 return ret; 605 } 606 } 607 608 static int 609 sockaddr_is_local(struct sockaddr *hostaddr) 610 { 611 switch (hostaddr->sa_family) { 612 case AF_INET: 613 return (ntohl(((struct sockaddr_in *)hostaddr)-> 614 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 615 case AF_INET6: 616 return IN6_IS_ADDR_LOOPBACK( 617 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 618 default: 619 return 0; 620 } 621 } 622 623 /* 624 * Prepare the hostname and ip address strings that are used to lookup 625 * host keys in known_hosts files. These may have a port number appended. 626 */ 627 void 628 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 629 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 630 { 631 char ntop[NI_MAXHOST]; 632 633 /* 634 * We don't have the remote ip-address for connections 635 * using a proxy command 636 */ 637 if (hostfile_ipaddr != NULL) { 638 if (options.proxy_command == NULL) { 639 if (getnameinfo(hostaddr, hostaddr->sa_len, 640 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 641 fatal_f("getnameinfo failed"); 642 *hostfile_ipaddr = put_host_port(ntop, port); 643 } else { 644 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 645 "command>"); 646 } 647 } 648 649 /* 650 * Allow the user to record the key under a different name or 651 * differentiate a non-standard port. This is useful for ssh 652 * tunneling over forwarded connections or if you run multiple 653 * sshd's on different ports on the same machine. 654 */ 655 if (hostfile_hostname != NULL) { 656 if (options.host_key_alias != NULL) { 657 *hostfile_hostname = xstrdup(options.host_key_alias); 658 debug("using hostkeyalias: %s", *hostfile_hostname); 659 } else { 660 *hostfile_hostname = put_host_port(hostname, port); 661 } 662 } 663 } 664 665 /* returns non-zero if path appears in hostfiles, or 0 if not. */ 666 static int 667 path_in_hostfiles(const char *path, char **hostfiles, u_int num_hostfiles) 668 { 669 u_int i; 670 671 for (i = 0; i < num_hostfiles; i++) { 672 if (strcmp(path, hostfiles[i]) == 0) 673 return 1; 674 } 675 return 0; 676 } 677 678 struct find_by_key_ctx { 679 const char *host, *ip; 680 const struct sshkey *key; 681 char **names; 682 u_int nnames; 683 }; 684 685 /* Try to replace home directory prefix (per $HOME) with a ~/ sequence */ 686 static char * 687 try_tilde_unexpand(const char *path) 688 { 689 char *home, *ret = NULL; 690 size_t l; 691 692 if (*path != '/') 693 return xstrdup(path); 694 if ((home = getenv("HOME")) == NULL || (l = strlen(home)) == 0) 695 return xstrdup(path); 696 if (strncmp(path, home, l) != 0) 697 return xstrdup(path); 698 /* 699 * ensure we have matched on a path boundary: either the $HOME that 700 * we just compared ends with a '/' or the next character of the path 701 * must be a '/'. 702 */ 703 if (home[l - 1] != '/' && path[l] != '/') 704 return xstrdup(path); 705 if (path[l] == '/') 706 l++; 707 xasprintf(&ret, "~/%s", path + l); 708 return ret; 709 } 710 711 static int 712 hostkeys_find_by_key_cb(struct hostkey_foreach_line *l, void *_ctx) 713 { 714 struct find_by_key_ctx *ctx = (struct find_by_key_ctx *)_ctx; 715 char *path; 716 717 /* we are looking for keys with names that *do not* match */ 718 if ((l->match & HKF_MATCH_HOST) != 0) 719 return 0; 720 /* not interested in marker lines */ 721 if (l->marker != MRK_NONE) 722 return 0; 723 /* we are only interested in exact key matches */ 724 if (l->key == NULL || !sshkey_equal(ctx->key, l->key)) 725 return 0; 726 path = try_tilde_unexpand(l->path); 727 debug_f("found matching key in %s:%lu", path, l->linenum); 728 ctx->names = xrecallocarray(ctx->names, 729 ctx->nnames, ctx->nnames + 1, sizeof(*ctx->names)); 730 xasprintf(&ctx->names[ctx->nnames], "%s:%lu: %s", path, l->linenum, 731 strncmp(l->hosts, HASH_MAGIC, strlen(HASH_MAGIC)) == 0 ? 732 "[hashed name]" : l->hosts); 733 ctx->nnames++; 734 free(path); 735 return 0; 736 } 737 738 static int 739 hostkeys_find_by_key_hostfile(const char *file, const char *which, 740 struct find_by_key_ctx *ctx) 741 { 742 int r; 743 744 debug3_f("trying %s hostfile \"%s\"", which, file); 745 if ((r = hostkeys_foreach(file, hostkeys_find_by_key_cb, ctx, 746 ctx->host, ctx->ip, HKF_WANT_PARSE_KEY, 0)) != 0) { 747 if (r == SSH_ERR_SYSTEM_ERROR && errno == ENOENT) { 748 debug_f("hostkeys file %s does not exist", file); 749 return 0; 750 } 751 error_fr(r, "hostkeys_foreach failed for %s", file); 752 return r; 753 } 754 return 0; 755 } 756 757 /* 758 * Find 'key' in known hosts file(s) that do not match host/ip. 759 * Used to display also-known-as information for previously-unseen hostkeys. 760 */ 761 static void 762 hostkeys_find_by_key(const char *host, const char *ip, const struct sshkey *key, 763 char **user_hostfiles, u_int num_user_hostfiles, 764 char **system_hostfiles, u_int num_system_hostfiles, 765 char ***names, u_int *nnames) 766 { 767 struct find_by_key_ctx ctx = {0, 0, 0, 0, 0}; 768 u_int i; 769 770 *names = NULL; 771 *nnames = 0; 772 773 if (key == NULL || sshkey_is_cert(key)) 774 return; 775 776 ctx.host = host; 777 ctx.ip = ip; 778 ctx.key = key; 779 780 for (i = 0; i < num_user_hostfiles; i++) { 781 if (hostkeys_find_by_key_hostfile(user_hostfiles[i], 782 "user", &ctx) != 0) 783 goto fail; 784 } 785 for (i = 0; i < num_system_hostfiles; i++) { 786 if (hostkeys_find_by_key_hostfile(system_hostfiles[i], 787 "system", &ctx) != 0) 788 goto fail; 789 } 790 /* success */ 791 *names = ctx.names; 792 *nnames = ctx.nnames; 793 ctx.names = NULL; 794 ctx.nnames = 0; 795 return; 796 fail: 797 for (i = 0; i < ctx.nnames; i++) 798 free(ctx.names[i]); 799 free(ctx.names); 800 } 801 802 #define MAX_OTHER_NAMES 8 /* Maximum number of names to list */ 803 static char * 804 other_hostkeys_message(const char *host, const char *ip, 805 const struct sshkey *key, 806 char **user_hostfiles, u_int num_user_hostfiles, 807 char **system_hostfiles, u_int num_system_hostfiles) 808 { 809 char *ret = NULL, **othernames = NULL; 810 u_int i, n, num_othernames = 0; 811 812 hostkeys_find_by_key(host, ip, key, 813 user_hostfiles, num_user_hostfiles, 814 system_hostfiles, num_system_hostfiles, 815 &othernames, &num_othernames); 816 if (num_othernames == 0) 817 return xstrdup("This key is not known by any other names"); 818 819 xasprintf(&ret, "This host key is known by the following other " 820 "names/addresses:"); 821 822 n = num_othernames; 823 if (n > MAX_OTHER_NAMES) 824 n = MAX_OTHER_NAMES; 825 for (i = 0; i < n; i++) { 826 xextendf(&ret, "\n", " %s", othernames[i]); 827 } 828 if (n < num_othernames) { 829 xextendf(&ret, "\n", " (%d additional names omitted)", 830 num_othernames - n); 831 } 832 for (i = 0; i < num_othernames; i++) 833 free(othernames[i]); 834 free(othernames); 835 return ret; 836 } 837 838 void 839 load_hostkeys_command(struct hostkeys *hostkeys, const char *command_template, 840 const char *invocation, const struct ssh_conn_info *cinfo, 841 const struct sshkey *host_key, const char *hostfile_hostname) 842 { 843 int r, i, ac = 0; 844 char *key_fp = NULL, *keytext = NULL, *tmp; 845 char *command = NULL, *tag = NULL, **av = NULL; 846 FILE *f = NULL; 847 pid_t pid; 848 void (*osigchld)(int); 849 850 xasprintf(&tag, "KnownHostsCommand-%s", invocation); 851 852 if (host_key != NULL) { 853 if ((key_fp = sshkey_fingerprint(host_key, 854 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 855 fatal_f("sshkey_fingerprint failed"); 856 if ((r = sshkey_to_base64(host_key, &keytext)) != 0) 857 fatal_fr(r, "sshkey_to_base64 failed"); 858 } 859 /* 860 * NB. all returns later this function should go via "out" to 861 * ensure the original SIGCHLD handler is restored properly. 862 */ 863 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 864 865 /* Turn the command into an argument vector */ 866 if (argv_split(command_template, &ac, &av, 0) != 0) { 867 error("%s \"%s\" contains invalid quotes", tag, 868 command_template); 869 goto out; 870 } 871 if (ac == 0) { 872 error("%s \"%s\" yielded no arguments", tag, 873 command_template); 874 goto out; 875 } 876 for (i = 1; i < ac; i++) { 877 tmp = percent_dollar_expand(av[i], 878 DEFAULT_CLIENT_PERCENT_EXPAND_ARGS(cinfo), 879 "H", hostfile_hostname, 880 "I", invocation, 881 "t", host_key == NULL ? "NONE" : sshkey_ssh_name(host_key), 882 "f", key_fp == NULL ? "NONE" : key_fp, 883 "K", keytext == NULL ? "NONE" : keytext, 884 (char *)NULL); 885 if (tmp == NULL) 886 fatal_f("percent_expand failed"); 887 free(av[i]); 888 av[i] = tmp; 889 } 890 /* Prepare a printable command for logs, etc. */ 891 command = argv_assemble(ac, av); 892 893 if ((pid = subprocess(tag, command, ac, av, &f, 894 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_UNSAFE_PATH| 895 SSH_SUBPROCESS_PRESERVE_ENV, NULL, NULL, NULL)) == 0) 896 goto out; 897 898 load_hostkeys_file(hostkeys, hostfile_hostname, tag, f, 1); 899 900 if (exited_cleanly(pid, tag, command, 0) != 0) 901 fatal("KnownHostsCommand failed"); 902 903 out: 904 if (f != NULL) 905 fclose(f); 906 ssh_signal(SIGCHLD, osigchld); 907 for (i = 0; i < ac; i++) 908 free(av[i]); 909 free(av); 910 free(tag); 911 free(command); 912 free(key_fp); 913 free(keytext); 914 } 915 916 /* 917 * check whether the supplied host key is valid, return -1 if the key 918 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 919 */ 920 #define RDRW 0 921 #define RDONLY 1 922 #define ROQUIET 2 923 static int 924 check_host_key(char *hostname, const struct ssh_conn_info *cinfo, 925 struct sockaddr *hostaddr, u_short port, 926 struct sshkey *host_key, int readonly, int clobber_port, 927 char **user_hostfiles, u_int num_user_hostfiles, 928 char **system_hostfiles, u_int num_system_hostfiles, 929 const char *hostfile_command) 930 { 931 HostStatus host_status = -1, ip_status = -1; 932 struct sshkey *raw_key = NULL; 933 char *ip = NULL, *host = NULL; 934 char hostline[1000], *hostp, *fp, *ra; 935 char msg[1024]; 936 const char *type, *fail_reason; 937 const struct hostkey_entry *host_found = NULL, *ip_found = NULL; 938 int len, cancelled_forwarding = 0, confirmed; 939 int local = sockaddr_is_local(hostaddr); 940 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 941 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 942 struct hostkeys *host_hostkeys, *ip_hostkeys; 943 u_int i; 944 945 /* 946 * Force accepting of the host key for loopback/localhost. The 947 * problem is that if the home directory is NFS-mounted to multiple 948 * machines, localhost will refer to a different machine in each of 949 * them, and the user will get bogus HOST_CHANGED warnings. This 950 * essentially disables host authentication for localhost; however, 951 * this is probably not a real problem. 952 */ 953 if (options.no_host_authentication_for_localhost == 1 && local && 954 options.host_key_alias == NULL) { 955 debug("Forcing accepting of host key for " 956 "loopback/localhost."); 957 options.update_hostkeys = 0; 958 return 0; 959 } 960 961 /* 962 * Prepare the hostname and address strings used for hostkey lookup. 963 * In some cases, these will have a port number appended. 964 */ 965 get_hostfile_hostname_ipaddr(hostname, hostaddr, 966 clobber_port ? 0 : port, &host, &ip); 967 968 /* 969 * Turn off check_host_ip if the connection is to localhost, via proxy 970 * command or if we don't have a hostname to compare with 971 */ 972 if (options.check_host_ip && (local || 973 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 974 options.check_host_ip = 0; 975 976 host_hostkeys = init_hostkeys(); 977 for (i = 0; i < num_user_hostfiles; i++) 978 load_hostkeys(host_hostkeys, host, user_hostfiles[i], 0); 979 for (i = 0; i < num_system_hostfiles; i++) 980 load_hostkeys(host_hostkeys, host, system_hostfiles[i], 0); 981 if (hostfile_command != NULL && !clobber_port) { 982 load_hostkeys_command(host_hostkeys, hostfile_command, 983 "HOSTNAME", cinfo, host_key, host); 984 } 985 986 ip_hostkeys = NULL; 987 if (!want_cert && options.check_host_ip) { 988 ip_hostkeys = init_hostkeys(); 989 for (i = 0; i < num_user_hostfiles; i++) 990 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i], 0); 991 for (i = 0; i < num_system_hostfiles; i++) 992 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i], 0); 993 if (hostfile_command != NULL && !clobber_port) { 994 load_hostkeys_command(ip_hostkeys, hostfile_command, 995 "ADDRESS", cinfo, host_key, ip); 996 } 997 } 998 999 retry: 1000 /* Reload these as they may have changed on cert->key downgrade */ 1001 want_cert = sshkey_is_cert(host_key); 1002 type = sshkey_type(host_key); 1003 1004 /* 1005 * Check if the host key is present in the user's list of known 1006 * hosts or in the systemwide list. 1007 */ 1008 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 1009 &host_found); 1010 1011 /* 1012 * If there are no hostfiles, or if the hostkey was found via 1013 * KnownHostsCommand, then don't try to touch the disk. 1014 */ 1015 if (!readonly && (num_user_hostfiles == 0 || 1016 (host_found != NULL && host_found->note != 0))) 1017 readonly = RDONLY; 1018 1019 /* 1020 * Also perform check for the ip address, skip the check if we are 1021 * localhost, looking for a certificate, or the hostname was an ip 1022 * address to begin with. 1023 */ 1024 if (!want_cert && ip_hostkeys != NULL) { 1025 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 1026 &ip_found); 1027 if (host_status == HOST_CHANGED && 1028 (ip_status != HOST_CHANGED || 1029 (ip_found != NULL && 1030 !sshkey_equal(ip_found->key, host_found->key)))) 1031 host_ip_differ = 1; 1032 } else 1033 ip_status = host_status; 1034 1035 switch (host_status) { 1036 case HOST_OK: 1037 /* The host is known and the key matches. */ 1038 debug("Host '%.200s' is known and matches the %s host %s.", 1039 host, type, want_cert ? "certificate" : "key"); 1040 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 1041 host_found->file, host_found->line); 1042 if (want_cert) { 1043 if (sshkey_cert_check_host(host_key, 1044 options.host_key_alias == NULL ? 1045 hostname : options.host_key_alias, 0, 1046 options.ca_sign_algorithms, &fail_reason) != 0) { 1047 error("%s", fail_reason); 1048 goto fail; 1049 } 1050 /* 1051 * Do not attempt hostkey update if a certificate was 1052 * successfully matched. 1053 */ 1054 if (options.update_hostkeys != 0) { 1055 options.update_hostkeys = 0; 1056 debug3_f("certificate host key in use; " 1057 "disabling UpdateHostkeys"); 1058 } 1059 } 1060 /* Turn off UpdateHostkeys if key was in system known_hosts */ 1061 if (options.update_hostkeys != 0 && 1062 (path_in_hostfiles(host_found->file, 1063 system_hostfiles, num_system_hostfiles) || 1064 (ip_status == HOST_OK && ip_found != NULL && 1065 path_in_hostfiles(ip_found->file, 1066 system_hostfiles, num_system_hostfiles)))) { 1067 options.update_hostkeys = 0; 1068 debug3_f("host key found in GlobalKnownHostsFile; " 1069 "disabling UpdateHostkeys"); 1070 } 1071 if (options.update_hostkeys != 0 && host_found->note) { 1072 options.update_hostkeys = 0; 1073 debug3_f("host key found via KnownHostsCommand; " 1074 "disabling UpdateHostkeys"); 1075 } 1076 if (options.check_host_ip && ip_status == HOST_NEW) { 1077 if (readonly || want_cert) 1078 logit("%s host key for IP address " 1079 "'%.128s' not in list of known hosts.", 1080 type, ip); 1081 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 1082 host_key, options.hash_known_hosts)) 1083 logit("Failed to add the %s host key for IP " 1084 "address '%.128s' to the list of known " 1085 "hosts (%.500s).", type, ip, 1086 user_hostfiles[0]); 1087 else 1088 logit("Warning: Permanently added the %s host " 1089 "key for IP address '%.128s' to the list " 1090 "of known hosts.", type, ip); 1091 } else if (options.visual_host_key) { 1092 fp = sshkey_fingerprint(host_key, 1093 options.fingerprint_hash, SSH_FP_DEFAULT); 1094 ra = sshkey_fingerprint(host_key, 1095 options.fingerprint_hash, SSH_FP_RANDOMART); 1096 if (fp == NULL || ra == NULL) 1097 fatal_f("sshkey_fingerprint failed"); 1098 logit("Host key fingerprint is %s\n%s", fp, ra); 1099 free(ra); 1100 free(fp); 1101 } 1102 hostkey_trusted = 1; 1103 break; 1104 case HOST_NEW: 1105 if (options.host_key_alias == NULL && port != 0 && 1106 port != SSH_DEFAULT_PORT && !clobber_port) { 1107 debug("checking without port identifier"); 1108 if (check_host_key(hostname, cinfo, hostaddr, 0, 1109 host_key, ROQUIET, 1, 1110 user_hostfiles, num_user_hostfiles, 1111 system_hostfiles, num_system_hostfiles, 1112 hostfile_command) == 0) { 1113 debug("found matching key w/out port"); 1114 break; 1115 } 1116 } 1117 if (readonly || want_cert) 1118 goto fail; 1119 /* The host is new. */ 1120 if (options.strict_host_key_checking == 1121 SSH_STRICT_HOSTKEY_YES) { 1122 /* 1123 * User has requested strict host key checking. We 1124 * will not add the host key automatically. The only 1125 * alternative left is to abort. 1126 */ 1127 error("No %s host key is known for %.200s and you " 1128 "have requested strict checking.", type, host); 1129 goto fail; 1130 } else if (options.strict_host_key_checking == 1131 SSH_STRICT_HOSTKEY_ASK) { 1132 char *msg1 = NULL, *msg2 = NULL; 1133 1134 xasprintf(&msg1, "The authenticity of host " 1135 "'%.200s (%s)' can't be established", host, ip); 1136 1137 if (show_other_keys(host_hostkeys, host_key)) { 1138 xextendf(&msg1, "\n", "but keys of different " 1139 "type are already known for this host."); 1140 } else 1141 xextendf(&msg1, "", "."); 1142 1143 fp = sshkey_fingerprint(host_key, 1144 options.fingerprint_hash, SSH_FP_DEFAULT); 1145 ra = sshkey_fingerprint(host_key, 1146 options.fingerprint_hash, SSH_FP_RANDOMART); 1147 if (fp == NULL || ra == NULL) 1148 fatal_f("sshkey_fingerprint failed"); 1149 xextendf(&msg1, "\n", "%s key fingerprint is %s.", 1150 type, fp); 1151 if (options.visual_host_key) 1152 xextendf(&msg1, "\n", "%s", ra); 1153 if (options.verify_host_key_dns) { 1154 xextendf(&msg1, "\n", 1155 "%s host key fingerprint found in DNS.", 1156 matching_host_key_dns ? 1157 "Matching" : "No matching"); 1158 } 1159 /* msg2 informs for other names matching this key */ 1160 if ((msg2 = other_hostkeys_message(host, ip, host_key, 1161 user_hostfiles, num_user_hostfiles, 1162 system_hostfiles, num_system_hostfiles)) != NULL) 1163 xextendf(&msg1, "\n", "%s", msg2); 1164 1165 xextendf(&msg1, "\n", 1166 "Are you sure you want to continue connecting " 1167 "(yes/no/[fingerprint])? "); 1168 1169 confirmed = confirm(msg1, fp); 1170 free(ra); 1171 free(fp); 1172 free(msg1); 1173 free(msg2); 1174 if (!confirmed) 1175 goto fail; 1176 hostkey_trusted = 1; /* user explicitly confirmed */ 1177 } 1178 /* 1179 * If in "new" or "off" strict mode, add the key automatically 1180 * to the local known_hosts file. 1181 */ 1182 if (options.check_host_ip && ip_status == HOST_NEW) { 1183 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 1184 hostp = hostline; 1185 if (options.hash_known_hosts) { 1186 /* Add hash of host and IP separately */ 1187 r = add_host_to_hostfile(user_hostfiles[0], 1188 host, host_key, options.hash_known_hosts) && 1189 add_host_to_hostfile(user_hostfiles[0], ip, 1190 host_key, options.hash_known_hosts); 1191 } else { 1192 /* Add unhashed "host,ip" */ 1193 r = add_host_to_hostfile(user_hostfiles[0], 1194 hostline, host_key, 1195 options.hash_known_hosts); 1196 } 1197 } else { 1198 r = add_host_to_hostfile(user_hostfiles[0], host, 1199 host_key, options.hash_known_hosts); 1200 hostp = host; 1201 } 1202 1203 if (!r) 1204 logit("Failed to add the host to the list of known " 1205 "hosts (%.500s).", user_hostfiles[0]); 1206 else 1207 logit("Warning: Permanently added '%.200s' (%s) to the " 1208 "list of known hosts.", hostp, type); 1209 break; 1210 case HOST_REVOKED: 1211 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1212 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 1213 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1214 error("The %s host key for %s is marked as revoked.", type, host); 1215 error("This could mean that a stolen key is being used to"); 1216 error("impersonate this host."); 1217 1218 /* 1219 * If strict host key checking is in use, the user will have 1220 * to edit the key manually and we can only abort. 1221 */ 1222 if (options.strict_host_key_checking != 1223 SSH_STRICT_HOSTKEY_OFF) { 1224 error("%s host key for %.200s was revoked and you have " 1225 "requested strict checking.", type, host); 1226 goto fail; 1227 } 1228 goto continue_unsafe; 1229 1230 case HOST_CHANGED: 1231 if (want_cert) { 1232 /* 1233 * This is only a debug() since it is valid to have 1234 * CAs with wildcard DNS matches that don't match 1235 * all hosts that one might visit. 1236 */ 1237 debug("Host certificate authority does not " 1238 "match %s in %s:%lu", CA_MARKER, 1239 host_found->file, host_found->line); 1240 goto fail; 1241 } 1242 if (readonly == ROQUIET) 1243 goto fail; 1244 if (options.check_host_ip && host_ip_differ) { 1245 const char *key_msg; 1246 if (ip_status == HOST_NEW) 1247 key_msg = "is unknown"; 1248 else if (ip_status == HOST_OK) 1249 key_msg = "is unchanged"; 1250 else 1251 key_msg = "has a different value"; 1252 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1253 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1254 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1255 error("The %s host key for %s has changed,", type, host); 1256 error("and the key for the corresponding IP address %s", ip); 1257 error("%s. This could either mean that", key_msg); 1258 error("DNS SPOOFING is happening or the IP address for the host"); 1259 error("and its host key have changed at the same time."); 1260 if (ip_status != HOST_NEW) 1261 error("Offending key for IP in %s:%lu", 1262 ip_found->file, ip_found->line); 1263 } 1264 /* The host key has changed. */ 1265 warn_changed_key(host_key); 1266 error("Add correct host key in %.100s to get rid of this message.", 1267 user_hostfiles[0]); 1268 error("Offending %s key in %s:%lu", 1269 sshkey_type(host_found->key), 1270 host_found->file, host_found->line); 1271 1272 /* 1273 * If strict host key checking is in use, the user will have 1274 * to edit the key manually and we can only abort. 1275 */ 1276 if (options.strict_host_key_checking != 1277 SSH_STRICT_HOSTKEY_OFF) { 1278 error("Host key for %.200s has changed and you have " 1279 "requested strict checking.", host); 1280 goto fail; 1281 } 1282 1283 continue_unsafe: 1284 /* 1285 * If strict host key checking has not been requested, allow 1286 * the connection but without MITM-able authentication or 1287 * forwarding. 1288 */ 1289 if (options.password_authentication) { 1290 error("Password authentication is disabled to avoid " 1291 "man-in-the-middle attacks."); 1292 options.password_authentication = 0; 1293 cancelled_forwarding = 1; 1294 } 1295 if (options.kbd_interactive_authentication) { 1296 error("Keyboard-interactive authentication is disabled" 1297 " to avoid man-in-the-middle attacks."); 1298 options.kbd_interactive_authentication = 0; 1299 cancelled_forwarding = 1; 1300 } 1301 if (options.forward_agent) { 1302 error("Agent forwarding is disabled to avoid " 1303 "man-in-the-middle attacks."); 1304 options.forward_agent = 0; 1305 cancelled_forwarding = 1; 1306 } 1307 if (options.forward_x11) { 1308 error("X11 forwarding is disabled to avoid " 1309 "man-in-the-middle attacks."); 1310 options.forward_x11 = 0; 1311 cancelled_forwarding = 1; 1312 } 1313 if (options.num_local_forwards > 0 || 1314 options.num_remote_forwards > 0) { 1315 error("Port forwarding is disabled to avoid " 1316 "man-in-the-middle attacks."); 1317 options.num_local_forwards = 1318 options.num_remote_forwards = 0; 1319 cancelled_forwarding = 1; 1320 } 1321 if (options.tun_open != SSH_TUNMODE_NO) { 1322 error("Tunnel forwarding is disabled to avoid " 1323 "man-in-the-middle attacks."); 1324 options.tun_open = SSH_TUNMODE_NO; 1325 cancelled_forwarding = 1; 1326 } 1327 if (options.update_hostkeys != 0) { 1328 error("UpdateHostkeys is disabled because the host " 1329 "key is not trusted."); 1330 options.update_hostkeys = 0; 1331 } 1332 if (options.exit_on_forward_failure && cancelled_forwarding) 1333 fatal("Error: forwarding disabled due to host key " 1334 "check failure"); 1335 1336 /* 1337 * XXX Should permit the user to change to use the new id. 1338 * This could be done by converting the host key to an 1339 * identifying sentence, tell that the host identifies itself 1340 * by that sentence, and ask the user if they wish to 1341 * accept the authentication. 1342 */ 1343 break; 1344 case HOST_FOUND: 1345 fatal("internal error"); 1346 break; 1347 } 1348 1349 if (options.check_host_ip && host_status != HOST_CHANGED && 1350 ip_status == HOST_CHANGED) { 1351 snprintf(msg, sizeof(msg), 1352 "Warning: the %s host key for '%.200s' " 1353 "differs from the key for the IP address '%.128s'" 1354 "\nOffending key for IP in %s:%lu", 1355 type, host, ip, ip_found->file, ip_found->line); 1356 if (host_status == HOST_OK) { 1357 len = strlen(msg); 1358 snprintf(msg + len, sizeof(msg) - len, 1359 "\nMatching host key in %s:%lu", 1360 host_found->file, host_found->line); 1361 } 1362 if (options.strict_host_key_checking == 1363 SSH_STRICT_HOSTKEY_ASK) { 1364 strlcat(msg, "\nAre you sure you want " 1365 "to continue connecting (yes/no)? ", sizeof(msg)); 1366 if (!confirm(msg, NULL)) 1367 goto fail; 1368 } else if (options.strict_host_key_checking != 1369 SSH_STRICT_HOSTKEY_OFF) { 1370 logit("%s", msg); 1371 error("Exiting, you have requested strict checking."); 1372 goto fail; 1373 } else { 1374 logit("%s", msg); 1375 } 1376 } 1377 1378 if (!hostkey_trusted && options.update_hostkeys) { 1379 debug_f("hostkey not known or explicitly trusted: " 1380 "disabling UpdateHostkeys"); 1381 options.update_hostkeys = 0; 1382 } 1383 1384 free(ip); 1385 free(host); 1386 if (host_hostkeys != NULL) 1387 free_hostkeys(host_hostkeys); 1388 if (ip_hostkeys != NULL) 1389 free_hostkeys(ip_hostkeys); 1390 return 0; 1391 1392 fail: 1393 if (want_cert && host_status != HOST_REVOKED) { 1394 /* 1395 * No matching certificate. Downgrade cert to raw key and 1396 * search normally. 1397 */ 1398 debug("No matching CA found. Retry with plain key"); 1399 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1400 fatal_fr(r, "decode key"); 1401 if ((r = sshkey_drop_cert(raw_key)) != 0) 1402 fatal_r(r, "Couldn't drop certificate"); 1403 host_key = raw_key; 1404 goto retry; 1405 } 1406 sshkey_free(raw_key); 1407 free(ip); 1408 free(host); 1409 if (host_hostkeys != NULL) 1410 free_hostkeys(host_hostkeys); 1411 if (ip_hostkeys != NULL) 1412 free_hostkeys(ip_hostkeys); 1413 return -1; 1414 } 1415 1416 /* returns 0 if key verifies or -1 if key does NOT verify */ 1417 int 1418 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key, 1419 const struct ssh_conn_info *cinfo) 1420 { 1421 u_int i; 1422 int r = -1, flags = 0; 1423 char valid[64], *fp = NULL, *cafp = NULL; 1424 struct sshkey *plain = NULL; 1425 1426 if ((fp = sshkey_fingerprint(host_key, 1427 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1428 error_fr(r, "fingerprint host key"); 1429 r = -1; 1430 goto out; 1431 } 1432 1433 if (sshkey_is_cert(host_key)) { 1434 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1435 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1436 error_fr(r, "fingerprint CA key"); 1437 r = -1; 1438 goto out; 1439 } 1440 sshkey_format_cert_validity(host_key->cert, 1441 valid, sizeof(valid)); 1442 debug("Server host certificate: %s %s, serial %llu " 1443 "ID \"%s\" CA %s %s valid %s", 1444 sshkey_ssh_name(host_key), fp, 1445 (unsigned long long)host_key->cert->serial, 1446 host_key->cert->key_id, 1447 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1448 valid); 1449 for (i = 0; i < host_key->cert->nprincipals; i++) { 1450 debug2("Server host certificate hostname: %s", 1451 host_key->cert->principals[i]); 1452 } 1453 } else { 1454 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1455 } 1456 1457 if (sshkey_equal(previous_host_key, host_key)) { 1458 debug2_f("server host key %s %s matches cached key", 1459 sshkey_type(host_key), fp); 1460 r = 0; 1461 goto out; 1462 } 1463 1464 /* Check in RevokedHostKeys file if specified */ 1465 if (options.revoked_host_keys != NULL) { 1466 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1467 switch (r) { 1468 case 0: 1469 break; /* not revoked */ 1470 case SSH_ERR_KEY_REVOKED: 1471 error("Host key %s %s revoked by file %s", 1472 sshkey_type(host_key), fp, 1473 options.revoked_host_keys); 1474 r = -1; 1475 goto out; 1476 default: 1477 error_r(r, "Error checking host key %s %s in " 1478 "revoked keys file %s", sshkey_type(host_key), 1479 fp, options.revoked_host_keys); 1480 r = -1; 1481 goto out; 1482 } 1483 } 1484 1485 if (options.verify_host_key_dns) { 1486 /* 1487 * XXX certs are not yet supported for DNS, so downgrade 1488 * them and try the plain key. 1489 */ 1490 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1491 goto out; 1492 if (sshkey_is_cert(plain)) 1493 sshkey_drop_cert(plain); 1494 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1495 if (flags & DNS_VERIFY_FOUND) { 1496 if (options.verify_host_key_dns == 1 && 1497 flags & DNS_VERIFY_MATCH && 1498 flags & DNS_VERIFY_SECURE) { 1499 r = 0; 1500 goto out; 1501 } 1502 if (flags & DNS_VERIFY_MATCH) { 1503 matching_host_key_dns = 1; 1504 } else { 1505 warn_changed_key(plain); 1506 error("Update the SSHFP RR in DNS " 1507 "with the new host key to get rid " 1508 "of this message."); 1509 } 1510 } 1511 } 1512 } 1513 r = check_host_key(host, cinfo, hostaddr, options.port, host_key, 1514 RDRW, 0, options.user_hostfiles, options.num_user_hostfiles, 1515 options.system_hostfiles, options.num_system_hostfiles, 1516 options.known_hosts_command); 1517 1518 out: 1519 sshkey_free(plain); 1520 free(fp); 1521 free(cafp); 1522 if (r == 0 && host_key != NULL) { 1523 sshkey_free(previous_host_key); 1524 r = sshkey_from_private(host_key, &previous_host_key); 1525 } 1526 1527 return r; 1528 } 1529 1530 /* 1531 * Starts a dialog with the server, and authenticates the current user on the 1532 * server. This does not need any extra privileges. The basic connection 1533 * to the server must already have been established before this is called. 1534 * If login fails, this function prints an error and never returns. 1535 * This function does not require super-user privileges. 1536 */ 1537 void 1538 ssh_login(struct ssh *ssh, Sensitive *sensitive, const char *orighost, 1539 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms, 1540 const struct ssh_conn_info *cinfo) 1541 { 1542 char *host; 1543 char *server_user, *local_user; 1544 int r; 1545 1546 local_user = xstrdup(pw->pw_name); 1547 server_user = options.user ? options.user : local_user; 1548 1549 /* Convert the user-supplied hostname into all lowercase. */ 1550 host = xstrdup(orighost); 1551 lowercase(host); 1552 1553 /* Exchange protocol version identification strings with the server. */ 1554 if ((r = kex_exchange_identification(ssh, timeout_ms, NULL)) != 0) 1555 sshpkt_fatal(ssh, r, "banner exchange"); 1556 1557 /* Put the connection into non-blocking mode. */ 1558 ssh_packet_set_nonblocking(ssh); 1559 1560 /* key exchange */ 1561 /* authenticate user */ 1562 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1563 ssh_kex2(ssh, host, hostaddr, port, cinfo); 1564 ssh_userauth2(ssh, local_user, server_user, host, sensitive); 1565 free(local_user); 1566 free(host); 1567 } 1568 1569 /* print all known host keys for a given host, but skip keys of given type */ 1570 static int 1571 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1572 { 1573 int type[] = { 1574 KEY_RSA, 1575 KEY_DSA, 1576 KEY_ECDSA, 1577 KEY_ED25519, 1578 KEY_XMSS, 1579 -1 1580 }; 1581 int i, ret = 0; 1582 char *fp, *ra; 1583 const struct hostkey_entry *found; 1584 1585 for (i = 0; type[i] != -1; i++) { 1586 if (type[i] == key->type) 1587 continue; 1588 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], 1589 -1, &found)) 1590 continue; 1591 fp = sshkey_fingerprint(found->key, 1592 options.fingerprint_hash, SSH_FP_DEFAULT); 1593 ra = sshkey_fingerprint(found->key, 1594 options.fingerprint_hash, SSH_FP_RANDOMART); 1595 if (fp == NULL || ra == NULL) 1596 fatal_f("sshkey_fingerprint fail"); 1597 logit("WARNING: %s key found for host %s\n" 1598 "in %s:%lu\n" 1599 "%s key fingerprint %s.", 1600 sshkey_type(found->key), 1601 found->host, found->file, found->line, 1602 sshkey_type(found->key), fp); 1603 if (options.visual_host_key) 1604 logit("%s", ra); 1605 free(ra); 1606 free(fp); 1607 ret = 1; 1608 } 1609 return ret; 1610 } 1611 1612 static void 1613 warn_changed_key(struct sshkey *host_key) 1614 { 1615 char *fp; 1616 1617 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1618 SSH_FP_DEFAULT); 1619 if (fp == NULL) 1620 fatal_f("sshkey_fingerprint fail"); 1621 1622 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1623 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1624 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1625 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1626 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1627 error("It is also possible that a host key has just been changed."); 1628 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1629 sshkey_type(host_key), fp); 1630 error("Please contact your system administrator."); 1631 1632 free(fp); 1633 } 1634 1635 /* 1636 * Execute a local command 1637 */ 1638 int 1639 ssh_local_cmd(const char *args) 1640 { 1641 const char *shell; 1642 pid_t pid; 1643 int status; 1644 void (*osighand)(int); 1645 1646 if (!options.permit_local_command || 1647 args == NULL || !*args) 1648 return (1); 1649 1650 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1651 shell = _PATH_BSHELL; 1652 1653 osighand = ssh_signal(SIGCHLD, SIG_DFL); 1654 pid = fork(); 1655 if (pid == 0) { 1656 ssh_signal(SIGPIPE, SIG_DFL); 1657 debug3("Executing %s -c \"%s\"", shell, args); 1658 execl(shell, shell, "-c", args, (char *)NULL); 1659 error("Couldn't execute %s -c \"%s\": %s", 1660 shell, args, strerror(errno)); 1661 _exit(1); 1662 } else if (pid == -1) 1663 fatal("fork failed: %.100s", strerror(errno)); 1664 while (waitpid(pid, &status, 0) == -1) 1665 if (errno != EINTR) 1666 fatal("Couldn't wait for child: %s", strerror(errno)); 1667 ssh_signal(SIGCHLD, osighand); 1668 1669 if (!WIFEXITED(status)) 1670 return (1); 1671 1672 return (WEXITSTATUS(status)); 1673 } 1674 1675 void 1676 maybe_add_key_to_agent(const char *authfile, struct sshkey *private, 1677 const char *comment, const char *passphrase) 1678 { 1679 int auth_sock = -1, r; 1680 const char *skprovider = NULL; 1681 1682 if (options.add_keys_to_agent == 0) 1683 return; 1684 1685 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1686 debug3("no authentication agent, not adding key"); 1687 return; 1688 } 1689 1690 if (options.add_keys_to_agent == 2 && 1691 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1692 debug3("user denied adding this key"); 1693 close(auth_sock); 1694 return; 1695 } 1696 if (sshkey_is_sk(private)) 1697 skprovider = options.sk_provider; 1698 if ((r = ssh_add_identity_constrained(auth_sock, private, 1699 comment == NULL ? authfile : comment, 1700 options.add_keys_to_agent_lifespan, 1701 (options.add_keys_to_agent == 3), 0, skprovider)) == 0) 1702 debug("identity added to agent: %s", authfile); 1703 else 1704 debug("could not add identity to agent: %s (%d)", authfile, r); 1705 close(auth_sock); 1706 } 1707