1 /* $OpenBSD: sshconnect.c,v 1.287 2017/09/14 04:32:21 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Code to connect to a remote host, and to perform the client side of the 7 * login (authentication) dialog. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 */ 15 16 #include "includes.h" 17 18 #include <sys/types.h> 19 #include <sys/wait.h> 20 #include <sys/stat.h> 21 #include <sys/socket.h> 22 #ifdef HAVE_SYS_TIME_H 23 # include <sys/time.h> 24 #endif 25 26 #include <netinet/in.h> 27 #include <arpa/inet.h> 28 #include <rpc/rpc.h> 29 30 #include <ctype.h> 31 #include <errno.h> 32 #include <fcntl.h> 33 #include <netdb.h> 34 #ifdef HAVE_PATHS_H 35 #include <paths.h> 36 #endif 37 #include <pwd.h> 38 #ifdef HAVE_POLL_H 39 #include <poll.h> 40 #endif 41 #include <signal.h> 42 #include <stdarg.h> 43 #include <stdio.h> 44 #include <stdlib.h> 45 #include <string.h> 46 #include <unistd.h> 47 48 #include "xmalloc.h" 49 #include "key.h" 50 #include "hostfile.h" 51 #include "ssh.h" 52 #include "buffer.h" 53 #include "packet.h" 54 #include "uidswap.h" 55 #include "compat.h" 56 #include "key.h" 57 #include "sshconnect.h" 58 #include "hostfile.h" 59 #include "log.h" 60 #include "misc.h" 61 #include "readconf.h" 62 #include "atomicio.h" 63 #include "dns.h" 64 #include "monitor_fdpass.h" 65 #include "ssh2.h" 66 #include "version.h" 67 #include "authfile.h" 68 #include "ssherr.h" 69 #include "authfd.h" 70 71 char *client_version_string = NULL; 72 char *server_version_string = NULL; 73 struct sshkey *previous_host_key = NULL; 74 75 static int matching_host_key_dns = 0; 76 77 static pid_t proxy_command_pid = 0; 78 79 /* import */ 80 extern Options options; 81 extern char *__progname; 82 extern uid_t original_real_uid; 83 extern uid_t original_effective_uid; 84 85 static int show_other_keys(struct hostkeys *, struct sshkey *); 86 static void warn_changed_key(struct sshkey *); 87 88 /* Expand a proxy command */ 89 static char * 90 expand_proxy_command(const char *proxy_command, const char *user, 91 const char *host, int port) 92 { 93 char *tmp, *ret, strport[NI_MAXSERV]; 94 95 snprintf(strport, sizeof strport, "%d", port); 96 xasprintf(&tmp, "exec %s", proxy_command); 97 ret = percent_expand(tmp, "h", host, "p", strport, 98 "r", options.user, (char *)NULL); 99 free(tmp); 100 return ret; 101 } 102 103 /* 104 * Connect to the given ssh server using a proxy command that passes a 105 * a connected fd back to us. 106 */ 107 static int 108 ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port, 109 const char *proxy_command) 110 { 111 char *command_string; 112 int sp[2], sock; 113 pid_t pid; 114 char *shell; 115 116 if ((shell = getenv("SHELL")) == NULL) 117 shell = _PATH_BSHELL; 118 119 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0) 120 fatal("Could not create socketpair to communicate with " 121 "proxy dialer: %.100s", strerror(errno)); 122 123 command_string = expand_proxy_command(proxy_command, options.user, 124 host, port); 125 debug("Executing proxy dialer command: %.500s", command_string); 126 127 /* Fork and execute the proxy command. */ 128 if ((pid = fork()) == 0) { 129 char *argv[10]; 130 131 /* Child. Permanently give up superuser privileges. */ 132 permanently_drop_suid(original_real_uid); 133 134 close(sp[1]); 135 /* Redirect stdin and stdout. */ 136 if (sp[0] != 0) { 137 if (dup2(sp[0], 0) < 0) 138 perror("dup2 stdin"); 139 } 140 if (sp[0] != 1) { 141 if (dup2(sp[0], 1) < 0) 142 perror("dup2 stdout"); 143 } 144 if (sp[0] >= 2) 145 close(sp[0]); 146 147 /* 148 * Stderr is left as it is so that error messages get 149 * printed on the user's terminal. 150 */ 151 argv[0] = shell; 152 argv[1] = "-c"; 153 argv[2] = command_string; 154 argv[3] = NULL; 155 156 /* 157 * Execute the proxy command. 158 * Note that we gave up any extra privileges above. 159 */ 160 execv(argv[0], argv); 161 perror(argv[0]); 162 exit(1); 163 } 164 /* Parent. */ 165 if (pid < 0) 166 fatal("fork failed: %.100s", strerror(errno)); 167 close(sp[0]); 168 free(command_string); 169 170 if ((sock = mm_receive_fd(sp[1])) == -1) 171 fatal("proxy dialer did not pass back a connection"); 172 close(sp[1]); 173 174 while (waitpid(pid, NULL, 0) == -1) 175 if (errno != EINTR) 176 fatal("Couldn't wait for child: %s", strerror(errno)); 177 178 /* Set the connection file descriptors. */ 179 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 180 return -1; /* ssh_packet_set_connection logs error */ 181 182 return 0; 183 } 184 185 /* 186 * Connect to the given ssh server using a proxy command. 187 */ 188 static int 189 ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port, 190 const char *proxy_command) 191 { 192 char *command_string; 193 int pin[2], pout[2]; 194 pid_t pid; 195 char *shell; 196 197 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 198 shell = _PATH_BSHELL; 199 200 /* Create pipes for communicating with the proxy. */ 201 if (pipe(pin) < 0 || pipe(pout) < 0) 202 fatal("Could not create pipes to communicate with the proxy: %.100s", 203 strerror(errno)); 204 205 command_string = expand_proxy_command(proxy_command, options.user, 206 host, port); 207 debug("Executing proxy command: %.500s", command_string); 208 209 /* Fork and execute the proxy command. */ 210 if ((pid = fork()) == 0) { 211 char *argv[10]; 212 213 /* Child. Permanently give up superuser privileges. */ 214 permanently_drop_suid(original_real_uid); 215 216 /* Redirect stdin and stdout. */ 217 close(pin[1]); 218 if (pin[0] != 0) { 219 if (dup2(pin[0], 0) < 0) 220 perror("dup2 stdin"); 221 close(pin[0]); 222 } 223 close(pout[0]); 224 if (dup2(pout[1], 1) < 0) 225 perror("dup2 stdout"); 226 /* Cannot be 1 because pin allocated two descriptors. */ 227 close(pout[1]); 228 229 /* Stderr is left as it is so that error messages get 230 printed on the user's terminal. */ 231 argv[0] = shell; 232 argv[1] = "-c"; 233 argv[2] = command_string; 234 argv[3] = NULL; 235 236 /* Execute the proxy command. Note that we gave up any 237 extra privileges above. */ 238 signal(SIGPIPE, SIG_DFL); 239 execv(argv[0], argv); 240 perror(argv[0]); 241 exit(1); 242 } 243 /* Parent. */ 244 if (pid < 0) 245 fatal("fork failed: %.100s", strerror(errno)); 246 else 247 proxy_command_pid = pid; /* save pid to clean up later */ 248 249 /* Close child side of the descriptors. */ 250 close(pin[0]); 251 close(pout[1]); 252 253 /* Free the command name. */ 254 free(command_string); 255 256 /* Set the connection file descriptors. */ 257 if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL) 258 return -1; /* ssh_packet_set_connection logs error */ 259 260 return 0; 261 } 262 263 void 264 ssh_kill_proxy_command(void) 265 { 266 /* 267 * Send SIGHUP to proxy command if used. We don't wait() in 268 * case it hangs and instead rely on init to reap the child 269 */ 270 if (proxy_command_pid > 1) 271 kill(proxy_command_pid, SIGHUP); 272 } 273 274 /* 275 * Creates a (possibly privileged) socket for use as the ssh connection. 276 */ 277 static int 278 ssh_create_socket(int privileged, struct addrinfo *ai) 279 { 280 int sock, r, gaierr; 281 struct addrinfo hints, *res = NULL; 282 283 sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); 284 if (sock < 0) { 285 error("socket: %s", strerror(errno)); 286 return -1; 287 } 288 fcntl(sock, F_SETFD, FD_CLOEXEC); 289 290 /* Bind the socket to an alternative local IP address */ 291 if (options.bind_address == NULL && !privileged) 292 return sock; 293 294 if (options.bind_address) { 295 memset(&hints, 0, sizeof(hints)); 296 hints.ai_family = ai->ai_family; 297 hints.ai_socktype = ai->ai_socktype; 298 hints.ai_protocol = ai->ai_protocol; 299 hints.ai_flags = AI_PASSIVE; 300 gaierr = getaddrinfo(options.bind_address, NULL, &hints, &res); 301 if (gaierr) { 302 error("getaddrinfo: %s: %s", options.bind_address, 303 ssh_gai_strerror(gaierr)); 304 close(sock); 305 return -1; 306 } 307 } 308 /* 309 * If we are running as root and want to connect to a privileged 310 * port, bind our own socket to a privileged port. 311 */ 312 if (privileged) { 313 PRIV_START; 314 r = bindresvport_sa(sock, res ? res->ai_addr : NULL); 315 PRIV_END; 316 if (r < 0) { 317 error("bindresvport_sa: af=%d %s", ai->ai_family, 318 strerror(errno)); 319 goto fail; 320 } 321 } else { 322 if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { 323 error("bind: %s: %s", options.bind_address, 324 strerror(errno)); 325 fail: 326 close(sock); 327 freeaddrinfo(res); 328 return -1; 329 } 330 } 331 if (res != NULL) 332 freeaddrinfo(res); 333 return sock; 334 } 335 336 /* 337 * Wait up to *timeoutp milliseconds for fd to be readable. Updates 338 * *timeoutp with time remaining. 339 * Returns 0 if fd ready or -1 on timeout or error (see errno). 340 */ 341 static int 342 waitrfd(int fd, int *timeoutp) 343 { 344 struct pollfd pfd; 345 struct timeval t_start; 346 int oerrno, r; 347 348 gettimeofday(&t_start, NULL); 349 pfd.fd = fd; 350 pfd.events = POLLIN; 351 for (; *timeoutp >= 0;) { 352 r = poll(&pfd, 1, *timeoutp); 353 oerrno = errno; 354 ms_subtract_diff(&t_start, timeoutp); 355 errno = oerrno; 356 if (r > 0) 357 return 0; 358 else if (r == -1 && errno != EAGAIN) 359 return -1; 360 else if (r == 0) 361 break; 362 } 363 /* timeout */ 364 errno = ETIMEDOUT; 365 return -1; 366 } 367 368 static int 369 timeout_connect(int sockfd, const struct sockaddr *serv_addr, 370 socklen_t addrlen, int *timeoutp) 371 { 372 int optval = 0; 373 socklen_t optlen = sizeof(optval); 374 375 /* No timeout: just do a blocking connect() */ 376 if (*timeoutp <= 0) 377 return connect(sockfd, serv_addr, addrlen); 378 379 set_nonblock(sockfd); 380 if (connect(sockfd, serv_addr, addrlen) == 0) { 381 /* Succeeded already? */ 382 unset_nonblock(sockfd); 383 return 0; 384 } else if (errno != EINPROGRESS) 385 return -1; 386 387 if (waitrfd(sockfd, timeoutp) == -1) 388 return -1; 389 390 /* Completed or failed */ 391 if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) { 392 debug("getsockopt: %s", strerror(errno)); 393 return -1; 394 } 395 if (optval != 0) { 396 errno = optval; 397 return -1; 398 } 399 unset_nonblock(sockfd); 400 return 0; 401 } 402 403 /* 404 * Opens a TCP/IP connection to the remote server on the given host. 405 * The address of the remote host will be returned in hostaddr. 406 * If port is 0, the default port will be used. If needpriv is true, 407 * a privileged port will be allocated to make the connection. 408 * This requires super-user privileges if needpriv is true. 409 * Connection_attempts specifies the maximum number of tries (one per 410 * second). If proxy_command is non-NULL, it specifies the command (with %h 411 * and %p substituted for host and port, respectively) to use to contact 412 * the daemon. 413 */ 414 static int 415 ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop, 416 struct sockaddr_storage *hostaddr, u_short port, int family, 417 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 418 { 419 int on = 1; 420 int sock = -1, attempt; 421 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 422 struct addrinfo *ai; 423 424 debug2("%s: needpriv %d", __func__, needpriv); 425 memset(ntop, 0, sizeof(ntop)); 426 memset(strport, 0, sizeof(strport)); 427 428 for (attempt = 0; attempt < connection_attempts; attempt++) { 429 if (attempt > 0) { 430 /* Sleep a moment before retrying. */ 431 sleep(1); 432 debug("Trying again..."); 433 } 434 /* 435 * Loop through addresses for this host, and try each one in 436 * sequence until the connection succeeds. 437 */ 438 for (ai = aitop; ai; ai = ai->ai_next) { 439 if (ai->ai_family != AF_INET && 440 ai->ai_family != AF_INET6) 441 continue; 442 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 443 ntop, sizeof(ntop), strport, sizeof(strport), 444 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 445 error("%s: getnameinfo failed", __func__); 446 continue; 447 } 448 debug("Connecting to %.200s [%.100s] port %s.", 449 host, ntop, strport); 450 451 /* Create a socket for connecting. */ 452 sock = ssh_create_socket(needpriv, ai); 453 if (sock < 0) 454 /* Any error is already output */ 455 continue; 456 457 if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, 458 timeout_ms) >= 0) { 459 /* Successful connection. */ 460 memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); 461 break; 462 } else { 463 debug("connect to address %s port %s: %s", 464 ntop, strport, strerror(errno)); 465 close(sock); 466 sock = -1; 467 } 468 } 469 if (sock != -1) 470 break; /* Successful connection. */ 471 } 472 473 /* Return failure if we didn't get a successful connection. */ 474 if (sock == -1) { 475 error("ssh: connect to host %s port %s: %s", 476 host, strport, strerror(errno)); 477 return (-1); 478 } 479 480 debug("Connection established."); 481 482 /* Set SO_KEEPALIVE if requested. */ 483 if (want_keepalive && 484 setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, 485 sizeof(on)) < 0) 486 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 487 488 /* Set the connection. */ 489 if (ssh_packet_set_connection(ssh, sock, sock) == NULL) 490 return -1; /* ssh_packet_set_connection logs error */ 491 492 return 0; 493 } 494 495 int 496 ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs, 497 struct sockaddr_storage *hostaddr, u_short port, int family, 498 int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv) 499 { 500 if (options.proxy_command == NULL) { 501 return ssh_connect_direct(ssh, host, addrs, hostaddr, port, 502 family, connection_attempts, timeout_ms, want_keepalive, 503 needpriv); 504 } else if (strcmp(options.proxy_command, "-") == 0) { 505 if ((ssh_packet_set_connection(ssh, 506 STDIN_FILENO, STDOUT_FILENO)) == NULL) 507 return -1; /* ssh_packet_set_connection logs error */ 508 return 0; 509 } else if (options.proxy_use_fdpass) { 510 return ssh_proxy_fdpass_connect(ssh, host, port, 511 options.proxy_command); 512 } 513 return ssh_proxy_connect(ssh, host, port, options.proxy_command); 514 } 515 516 static void 517 send_client_banner(int connection_out, int minor1) 518 { 519 /* Send our own protocol version identification. */ 520 xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n", 521 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION); 522 if (atomicio(vwrite, connection_out, client_version_string, 523 strlen(client_version_string)) != strlen(client_version_string)) 524 fatal("write: %.100s", strerror(errno)); 525 chop(client_version_string); 526 debug("Local version string %.100s", client_version_string); 527 } 528 529 /* 530 * Waits for the server identification string, and sends our own 531 * identification string. 532 */ 533 void 534 ssh_exchange_identification(int timeout_ms) 535 { 536 char buf[256], remote_version[256]; /* must be same size! */ 537 int remote_major, remote_minor, mismatch; 538 int connection_in = packet_get_connection_in(); 539 int connection_out = packet_get_connection_out(); 540 u_int i, n; 541 size_t len; 542 int rc; 543 544 send_client_banner(connection_out, 0); 545 546 /* Read other side's version identification. */ 547 for (n = 0;;) { 548 for (i = 0; i < sizeof(buf) - 1; i++) { 549 if (timeout_ms > 0) { 550 rc = waitrfd(connection_in, &timeout_ms); 551 if (rc == -1 && errno == ETIMEDOUT) { 552 fatal("Connection timed out during " 553 "banner exchange"); 554 } else if (rc == -1) { 555 fatal("%s: %s", 556 __func__, strerror(errno)); 557 } 558 } 559 560 len = atomicio(read, connection_in, &buf[i], 1); 561 if (len != 1 && errno == EPIPE) 562 fatal("ssh_exchange_identification: " 563 "Connection closed by remote host"); 564 else if (len != 1) 565 fatal("ssh_exchange_identification: " 566 "read: %.100s", strerror(errno)); 567 if (buf[i] == '\r') { 568 buf[i] = '\n'; 569 buf[i + 1] = 0; 570 continue; /**XXX wait for \n */ 571 } 572 if (buf[i] == '\n') { 573 buf[i + 1] = 0; 574 break; 575 } 576 if (++n > 65536) 577 fatal("ssh_exchange_identification: " 578 "No banner received"); 579 } 580 buf[sizeof(buf) - 1] = 0; 581 if (strncmp(buf, "SSH-", 4) == 0) 582 break; 583 debug("ssh_exchange_identification: %s", buf); 584 } 585 server_version_string = xstrdup(buf); 586 587 /* 588 * Check that the versions match. In future this might accept 589 * several versions and set appropriate flags to handle them. 590 */ 591 if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", 592 &remote_major, &remote_minor, remote_version) != 3) 593 fatal("Bad remote protocol version identification: '%.100s'", buf); 594 debug("Remote protocol version %d.%d, remote software version %.100s", 595 remote_major, remote_minor, remote_version); 596 597 active_state->compat = compat_datafellows(remote_version); 598 mismatch = 0; 599 600 switch (remote_major) { 601 case 2: 602 break; 603 case 1: 604 if (remote_minor != 99) 605 mismatch = 1; 606 break; 607 default: 608 mismatch = 1; 609 break; 610 } 611 if (mismatch) 612 fatal("Protocol major versions differ: %d vs. %d", 613 PROTOCOL_MAJOR_2, remote_major); 614 if ((datafellows & SSH_BUG_DERIVEKEY) != 0) 615 fatal("Server version \"%.100s\" uses unsafe key agreement; " 616 "refusing connection", remote_version); 617 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) 618 logit("Server version \"%.100s\" uses unsafe RSA signature " 619 "scheme; disabling use of RSA keys", remote_version); 620 chop(server_version_string); 621 } 622 623 /* defaults to 'no' */ 624 static int 625 confirm(const char *prompt) 626 { 627 const char *msg, *again = "Please type 'yes' or 'no': "; 628 char *p; 629 int ret = -1; 630 631 if (options.batch_mode) 632 return 0; 633 for (msg = prompt;;msg = again) { 634 p = read_passphrase(msg, RP_ECHO); 635 if (p == NULL || 636 (p[0] == '\0') || (p[0] == '\n') || 637 strncasecmp(p, "no", 2) == 0) 638 ret = 0; 639 if (p && strncasecmp(p, "yes", 3) == 0) 640 ret = 1; 641 free(p); 642 if (ret != -1) 643 return ret; 644 } 645 } 646 647 static int 648 check_host_cert(const char *host, const struct sshkey *host_key) 649 { 650 const char *reason; 651 652 if (key_cert_check_authority(host_key, 1, 0, host, &reason) != 0) { 653 error("%s", reason); 654 return 0; 655 } 656 if (buffer_len(host_key->cert->critical) != 0) { 657 error("Certificate for %s contains unsupported " 658 "critical options(s)", host); 659 return 0; 660 } 661 return 1; 662 } 663 664 static int 665 sockaddr_is_local(struct sockaddr *hostaddr) 666 { 667 switch (hostaddr->sa_family) { 668 case AF_INET: 669 return (ntohl(((struct sockaddr_in *)hostaddr)-> 670 sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; 671 case AF_INET6: 672 return IN6_IS_ADDR_LOOPBACK( 673 &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); 674 default: 675 return 0; 676 } 677 } 678 679 /* 680 * Prepare the hostname and ip address strings that are used to lookup 681 * host keys in known_hosts files. These may have a port number appended. 682 */ 683 void 684 get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr, 685 u_short port, char **hostfile_hostname, char **hostfile_ipaddr) 686 { 687 char ntop[NI_MAXHOST]; 688 socklen_t addrlen; 689 690 switch (hostaddr == NULL ? -1 : hostaddr->sa_family) { 691 case -1: 692 addrlen = 0; 693 break; 694 case AF_INET: 695 addrlen = sizeof(struct sockaddr_in); 696 break; 697 case AF_INET6: 698 addrlen = sizeof(struct sockaddr_in6); 699 break; 700 default: 701 addrlen = sizeof(struct sockaddr); 702 break; 703 } 704 705 /* 706 * We don't have the remote ip-address for connections 707 * using a proxy command 708 */ 709 if (hostfile_ipaddr != NULL) { 710 if (options.proxy_command == NULL) { 711 if (getnameinfo(hostaddr, addrlen, 712 ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0) 713 fatal("%s: getnameinfo failed", __func__); 714 *hostfile_ipaddr = put_host_port(ntop, port); 715 } else { 716 *hostfile_ipaddr = xstrdup("<no hostip for proxy " 717 "command>"); 718 } 719 } 720 721 /* 722 * Allow the user to record the key under a different name or 723 * differentiate a non-standard port. This is useful for ssh 724 * tunneling over forwarded connections or if you run multiple 725 * sshd's on different ports on the same machine. 726 */ 727 if (hostfile_hostname != NULL) { 728 if (options.host_key_alias != NULL) { 729 *hostfile_hostname = xstrdup(options.host_key_alias); 730 debug("using hostkeyalias: %s", *hostfile_hostname); 731 } else { 732 *hostfile_hostname = put_host_port(hostname, port); 733 } 734 } 735 } 736 737 /* 738 * check whether the supplied host key is valid, return -1 if the key 739 * is not valid. user_hostfile[0] will not be updated if 'readonly' is true. 740 */ 741 #define RDRW 0 742 #define RDONLY 1 743 #define ROQUIET 2 744 static int 745 check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, 746 struct sshkey *host_key, int readonly, 747 char **user_hostfiles, u_int num_user_hostfiles, 748 char **system_hostfiles, u_int num_system_hostfiles) 749 { 750 HostStatus host_status; 751 HostStatus ip_status; 752 struct sshkey *raw_key = NULL; 753 char *ip = NULL, *host = NULL; 754 char hostline[1000], *hostp, *fp, *ra; 755 char msg[1024]; 756 const char *type; 757 const struct hostkey_entry *host_found, *ip_found; 758 int len, cancelled_forwarding = 0; 759 int local = sockaddr_is_local(hostaddr); 760 int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0; 761 int hostkey_trusted = 0; /* Known or explicitly accepted by user */ 762 struct hostkeys *host_hostkeys, *ip_hostkeys; 763 u_int i; 764 765 /* 766 * Force accepting of the host key for loopback/localhost. The 767 * problem is that if the home directory is NFS-mounted to multiple 768 * machines, localhost will refer to a different machine in each of 769 * them, and the user will get bogus HOST_CHANGED warnings. This 770 * essentially disables host authentication for localhost; however, 771 * this is probably not a real problem. 772 */ 773 if (options.no_host_authentication_for_localhost == 1 && local && 774 options.host_key_alias == NULL) { 775 debug("Forcing accepting of host key for " 776 "loopback/localhost."); 777 return 0; 778 } 779 780 /* 781 * Prepare the hostname and address strings used for hostkey lookup. 782 * In some cases, these will have a port number appended. 783 */ 784 get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip); 785 786 /* 787 * Turn off check_host_ip if the connection is to localhost, via proxy 788 * command or if we don't have a hostname to compare with 789 */ 790 if (options.check_host_ip && (local || 791 strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) 792 options.check_host_ip = 0; 793 794 host_hostkeys = init_hostkeys(); 795 for (i = 0; i < num_user_hostfiles; i++) 796 load_hostkeys(host_hostkeys, host, user_hostfiles[i]); 797 for (i = 0; i < num_system_hostfiles; i++) 798 load_hostkeys(host_hostkeys, host, system_hostfiles[i]); 799 800 ip_hostkeys = NULL; 801 if (!want_cert && options.check_host_ip) { 802 ip_hostkeys = init_hostkeys(); 803 for (i = 0; i < num_user_hostfiles; i++) 804 load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]); 805 for (i = 0; i < num_system_hostfiles; i++) 806 load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]); 807 } 808 809 retry: 810 /* Reload these as they may have changed on cert->key downgrade */ 811 want_cert = sshkey_is_cert(host_key); 812 type = sshkey_type(host_key); 813 814 /* 815 * Check if the host key is present in the user's list of known 816 * hosts or in the systemwide list. 817 */ 818 host_status = check_key_in_hostkeys(host_hostkeys, host_key, 819 &host_found); 820 821 /* 822 * Also perform check for the ip address, skip the check if we are 823 * localhost, looking for a certificate, or the hostname was an ip 824 * address to begin with. 825 */ 826 if (!want_cert && ip_hostkeys != NULL) { 827 ip_status = check_key_in_hostkeys(ip_hostkeys, host_key, 828 &ip_found); 829 if (host_status == HOST_CHANGED && 830 (ip_status != HOST_CHANGED || 831 (ip_found != NULL && 832 !sshkey_equal(ip_found->key, host_found->key)))) 833 host_ip_differ = 1; 834 } else 835 ip_status = host_status; 836 837 switch (host_status) { 838 case HOST_OK: 839 /* The host is known and the key matches. */ 840 debug("Host '%.200s' is known and matches the %s host %s.", 841 host, type, want_cert ? "certificate" : "key"); 842 debug("Found %s in %s:%lu", want_cert ? "CA key" : "key", 843 host_found->file, host_found->line); 844 if (want_cert && 845 !check_host_cert(options.host_key_alias == NULL ? 846 hostname : options.host_key_alias, host_key)) 847 goto fail; 848 if (options.check_host_ip && ip_status == HOST_NEW) { 849 if (readonly || want_cert) 850 logit("%s host key for IP address " 851 "'%.128s' not in list of known hosts.", 852 type, ip); 853 else if (!add_host_to_hostfile(user_hostfiles[0], ip, 854 host_key, options.hash_known_hosts)) 855 logit("Failed to add the %s host key for IP " 856 "address '%.128s' to the list of known " 857 "hosts (%.500s).", type, ip, 858 user_hostfiles[0]); 859 else 860 logit("Warning: Permanently added the %s host " 861 "key for IP address '%.128s' to the list " 862 "of known hosts.", type, ip); 863 } else if (options.visual_host_key) { 864 fp = sshkey_fingerprint(host_key, 865 options.fingerprint_hash, SSH_FP_DEFAULT); 866 ra = sshkey_fingerprint(host_key, 867 options.fingerprint_hash, SSH_FP_RANDOMART); 868 if (fp == NULL || ra == NULL) 869 fatal("%s: sshkey_fingerprint fail", __func__); 870 logit("Host key fingerprint is %s\n%s", fp, ra); 871 free(ra); 872 free(fp); 873 } 874 hostkey_trusted = 1; 875 break; 876 case HOST_NEW: 877 if (options.host_key_alias == NULL && port != 0 && 878 port != SSH_DEFAULT_PORT) { 879 debug("checking without port identifier"); 880 if (check_host_key(hostname, hostaddr, 0, host_key, 881 ROQUIET, user_hostfiles, num_user_hostfiles, 882 system_hostfiles, num_system_hostfiles) == 0) { 883 debug("found matching key w/out port"); 884 break; 885 } 886 } 887 if (readonly || want_cert) 888 goto fail; 889 /* The host is new. */ 890 if (options.strict_host_key_checking == 891 SSH_STRICT_HOSTKEY_YES) { 892 /* 893 * User has requested strict host key checking. We 894 * will not add the host key automatically. The only 895 * alternative left is to abort. 896 */ 897 error("No %s host key is known for %.200s and you " 898 "have requested strict checking.", type, host); 899 goto fail; 900 } else if (options.strict_host_key_checking == 901 SSH_STRICT_HOSTKEY_ASK) { 902 char msg1[1024], msg2[1024]; 903 904 if (show_other_keys(host_hostkeys, host_key)) 905 snprintf(msg1, sizeof(msg1), 906 "\nbut keys of different type are already" 907 " known for this host."); 908 else 909 snprintf(msg1, sizeof(msg1), "."); 910 /* The default */ 911 fp = sshkey_fingerprint(host_key, 912 options.fingerprint_hash, SSH_FP_DEFAULT); 913 ra = sshkey_fingerprint(host_key, 914 options.fingerprint_hash, SSH_FP_RANDOMART); 915 if (fp == NULL || ra == NULL) 916 fatal("%s: sshkey_fingerprint fail", __func__); 917 msg2[0] = '\0'; 918 if (options.verify_host_key_dns) { 919 if (matching_host_key_dns) 920 snprintf(msg2, sizeof(msg2), 921 "Matching host key fingerprint" 922 " found in DNS.\n"); 923 else 924 snprintf(msg2, sizeof(msg2), 925 "No matching host key fingerprint" 926 " found in DNS.\n"); 927 } 928 snprintf(msg, sizeof(msg), 929 "The authenticity of host '%.200s (%s)' can't be " 930 "established%s\n" 931 "%s key fingerprint is %s.%s%s\n%s" 932 "Are you sure you want to continue connecting " 933 "(yes/no)? ", 934 host, ip, msg1, type, fp, 935 options.visual_host_key ? "\n" : "", 936 options.visual_host_key ? ra : "", 937 msg2); 938 free(ra); 939 free(fp); 940 if (!confirm(msg)) 941 goto fail; 942 hostkey_trusted = 1; /* user explicitly confirmed */ 943 } 944 /* 945 * If in "new" or "off" strict mode, add the key automatically 946 * to the local known_hosts file. 947 */ 948 if (options.check_host_ip && ip_status == HOST_NEW) { 949 snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); 950 hostp = hostline; 951 if (options.hash_known_hosts) { 952 /* Add hash of host and IP separately */ 953 r = add_host_to_hostfile(user_hostfiles[0], 954 host, host_key, options.hash_known_hosts) && 955 add_host_to_hostfile(user_hostfiles[0], ip, 956 host_key, options.hash_known_hosts); 957 } else { 958 /* Add unhashed "host,ip" */ 959 r = add_host_to_hostfile(user_hostfiles[0], 960 hostline, host_key, 961 options.hash_known_hosts); 962 } 963 } else { 964 r = add_host_to_hostfile(user_hostfiles[0], host, 965 host_key, options.hash_known_hosts); 966 hostp = host; 967 } 968 969 if (!r) 970 logit("Failed to add the host to the list of known " 971 "hosts (%.500s).", user_hostfiles[0]); 972 else 973 logit("Warning: Permanently added '%.200s' (%s) to the " 974 "list of known hosts.", hostp, type); 975 break; 976 case HOST_REVOKED: 977 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 978 error("@ WARNING: REVOKED HOST KEY DETECTED! @"); 979 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 980 error("The %s host key for %s is marked as revoked.", type, host); 981 error("This could mean that a stolen key is being used to"); 982 error("impersonate this host."); 983 984 /* 985 * If strict host key checking is in use, the user will have 986 * to edit the key manually and we can only abort. 987 */ 988 if (options.strict_host_key_checking != 989 SSH_STRICT_HOSTKEY_OFF) { 990 error("%s host key for %.200s was revoked and you have " 991 "requested strict checking.", type, host); 992 goto fail; 993 } 994 goto continue_unsafe; 995 996 case HOST_CHANGED: 997 if (want_cert) { 998 /* 999 * This is only a debug() since it is valid to have 1000 * CAs with wildcard DNS matches that don't match 1001 * all hosts that one might visit. 1002 */ 1003 debug("Host certificate authority does not " 1004 "match %s in %s:%lu", CA_MARKER, 1005 host_found->file, host_found->line); 1006 goto fail; 1007 } 1008 if (readonly == ROQUIET) 1009 goto fail; 1010 if (options.check_host_ip && host_ip_differ) { 1011 char *key_msg; 1012 if (ip_status == HOST_NEW) 1013 key_msg = "is unknown"; 1014 else if (ip_status == HOST_OK) 1015 key_msg = "is unchanged"; 1016 else 1017 key_msg = "has a different value"; 1018 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1019 error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); 1020 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1021 error("The %s host key for %s has changed,", type, host); 1022 error("and the key for the corresponding IP address %s", ip); 1023 error("%s. This could either mean that", key_msg); 1024 error("DNS SPOOFING is happening or the IP address for the host"); 1025 error("and its host key have changed at the same time."); 1026 if (ip_status != HOST_NEW) 1027 error("Offending key for IP in %s:%lu", 1028 ip_found->file, ip_found->line); 1029 } 1030 /* The host key has changed. */ 1031 warn_changed_key(host_key); 1032 error("Add correct host key in %.100s to get rid of this message.", 1033 user_hostfiles[0]); 1034 error("Offending %s key in %s:%lu", 1035 sshkey_type(host_found->key), 1036 host_found->file, host_found->line); 1037 1038 /* 1039 * If strict host key checking is in use, the user will have 1040 * to edit the key manually and we can only abort. 1041 */ 1042 if (options.strict_host_key_checking != 1043 SSH_STRICT_HOSTKEY_OFF) { 1044 error("%s host key for %.200s has changed and you have " 1045 "requested strict checking.", type, host); 1046 goto fail; 1047 } 1048 1049 continue_unsafe: 1050 /* 1051 * If strict host key checking has not been requested, allow 1052 * the connection but without MITM-able authentication or 1053 * forwarding. 1054 */ 1055 if (options.password_authentication) { 1056 error("Password authentication is disabled to avoid " 1057 "man-in-the-middle attacks."); 1058 options.password_authentication = 0; 1059 cancelled_forwarding = 1; 1060 } 1061 if (options.kbd_interactive_authentication) { 1062 error("Keyboard-interactive authentication is disabled" 1063 " to avoid man-in-the-middle attacks."); 1064 options.kbd_interactive_authentication = 0; 1065 options.challenge_response_authentication = 0; 1066 cancelled_forwarding = 1; 1067 } 1068 if (options.challenge_response_authentication) { 1069 error("Challenge/response authentication is disabled" 1070 " to avoid man-in-the-middle attacks."); 1071 options.challenge_response_authentication = 0; 1072 cancelled_forwarding = 1; 1073 } 1074 if (options.forward_agent) { 1075 error("Agent forwarding is disabled to avoid " 1076 "man-in-the-middle attacks."); 1077 options.forward_agent = 0; 1078 cancelled_forwarding = 1; 1079 } 1080 if (options.forward_x11) { 1081 error("X11 forwarding is disabled to avoid " 1082 "man-in-the-middle attacks."); 1083 options.forward_x11 = 0; 1084 cancelled_forwarding = 1; 1085 } 1086 if (options.num_local_forwards > 0 || 1087 options.num_remote_forwards > 0) { 1088 error("Port forwarding is disabled to avoid " 1089 "man-in-the-middle attacks."); 1090 options.num_local_forwards = 1091 options.num_remote_forwards = 0; 1092 cancelled_forwarding = 1; 1093 } 1094 if (options.tun_open != SSH_TUNMODE_NO) { 1095 error("Tunnel forwarding is disabled to avoid " 1096 "man-in-the-middle attacks."); 1097 options.tun_open = SSH_TUNMODE_NO; 1098 cancelled_forwarding = 1; 1099 } 1100 if (options.exit_on_forward_failure && cancelled_forwarding) 1101 fatal("Error: forwarding disabled due to host key " 1102 "check failure"); 1103 1104 /* 1105 * XXX Should permit the user to change to use the new id. 1106 * This could be done by converting the host key to an 1107 * identifying sentence, tell that the host identifies itself 1108 * by that sentence, and ask the user if he/she wishes to 1109 * accept the authentication. 1110 */ 1111 break; 1112 case HOST_FOUND: 1113 fatal("internal error"); 1114 break; 1115 } 1116 1117 if (options.check_host_ip && host_status != HOST_CHANGED && 1118 ip_status == HOST_CHANGED) { 1119 snprintf(msg, sizeof(msg), 1120 "Warning: the %s host key for '%.200s' " 1121 "differs from the key for the IP address '%.128s'" 1122 "\nOffending key for IP in %s:%lu", 1123 type, host, ip, ip_found->file, ip_found->line); 1124 if (host_status == HOST_OK) { 1125 len = strlen(msg); 1126 snprintf(msg + len, sizeof(msg) - len, 1127 "\nMatching host key in %s:%lu", 1128 host_found->file, host_found->line); 1129 } 1130 if (options.strict_host_key_checking == 1131 SSH_STRICT_HOSTKEY_ASK) { 1132 strlcat(msg, "\nAre you sure you want " 1133 "to continue connecting (yes/no)? ", sizeof(msg)); 1134 if (!confirm(msg)) 1135 goto fail; 1136 } else if (options.strict_host_key_checking != 1137 SSH_STRICT_HOSTKEY_OFF) { 1138 logit("%s", msg); 1139 error("Exiting, you have requested strict checking."); 1140 goto fail; 1141 } else { 1142 logit("%s", msg); 1143 } 1144 } 1145 1146 if (!hostkey_trusted && options.update_hostkeys) { 1147 debug("%s: hostkey not known or explicitly trusted: " 1148 "disabling UpdateHostkeys", __func__); 1149 options.update_hostkeys = 0; 1150 } 1151 1152 free(ip); 1153 free(host); 1154 if (host_hostkeys != NULL) 1155 free_hostkeys(host_hostkeys); 1156 if (ip_hostkeys != NULL) 1157 free_hostkeys(ip_hostkeys); 1158 return 0; 1159 1160 fail: 1161 if (want_cert && host_status != HOST_REVOKED) { 1162 /* 1163 * No matching certificate. Downgrade cert to raw key and 1164 * search normally. 1165 */ 1166 debug("No matching CA found. Retry with plain key"); 1167 if ((r = sshkey_from_private(host_key, &raw_key)) != 0) 1168 fatal("%s: sshkey_from_private: %s", 1169 __func__, ssh_err(r)); 1170 if ((r = sshkey_drop_cert(raw_key)) != 0) 1171 fatal("Couldn't drop certificate: %s", ssh_err(r)); 1172 host_key = raw_key; 1173 goto retry; 1174 } 1175 if (raw_key != NULL) 1176 sshkey_free(raw_key); 1177 free(ip); 1178 free(host); 1179 if (host_hostkeys != NULL) 1180 free_hostkeys(host_hostkeys); 1181 if (ip_hostkeys != NULL) 1182 free_hostkeys(ip_hostkeys); 1183 return -1; 1184 } 1185 1186 /* returns 0 if key verifies or -1 if key does NOT verify */ 1187 int 1188 verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key) 1189 { 1190 u_int i; 1191 int r = -1, flags = 0; 1192 char valid[64], *fp = NULL, *cafp = NULL; 1193 struct sshkey *plain = NULL; 1194 1195 if ((fp = sshkey_fingerprint(host_key, 1196 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1197 error("%s: fingerprint host key: %s", __func__, ssh_err(r)); 1198 r = -1; 1199 goto out; 1200 } 1201 1202 if (sshkey_is_cert(host_key)) { 1203 if ((cafp = sshkey_fingerprint(host_key->cert->signature_key, 1204 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 1205 error("%s: fingerprint CA key: %s", 1206 __func__, ssh_err(r)); 1207 r = -1; 1208 goto out; 1209 } 1210 sshkey_format_cert_validity(host_key->cert, 1211 valid, sizeof(valid)); 1212 debug("Server host certificate: %s %s, serial %llu " 1213 "ID \"%s\" CA %s %s valid %s", 1214 sshkey_ssh_name(host_key), fp, 1215 (unsigned long long)host_key->cert->serial, 1216 host_key->cert->key_id, 1217 sshkey_ssh_name(host_key->cert->signature_key), cafp, 1218 valid); 1219 for (i = 0; i < host_key->cert->nprincipals; i++) { 1220 debug2("Server host certificate hostname: %s", 1221 host_key->cert->principals[i]); 1222 } 1223 } else { 1224 debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp); 1225 } 1226 1227 if (sshkey_equal(previous_host_key, host_key)) { 1228 debug2("%s: server host key %s %s matches cached key", 1229 __func__, sshkey_type(host_key), fp); 1230 r = 0; 1231 goto out; 1232 } 1233 1234 /* Check in RevokedHostKeys file if specified */ 1235 if (options.revoked_host_keys != NULL) { 1236 r = sshkey_check_revoked(host_key, options.revoked_host_keys); 1237 switch (r) { 1238 case 0: 1239 break; /* not revoked */ 1240 case SSH_ERR_KEY_REVOKED: 1241 error("Host key %s %s revoked by file %s", 1242 sshkey_type(host_key), fp, 1243 options.revoked_host_keys); 1244 r = -1; 1245 goto out; 1246 default: 1247 error("Error checking host key %s %s in " 1248 "revoked keys file %s: %s", sshkey_type(host_key), 1249 fp, options.revoked_host_keys, ssh_err(r)); 1250 r = -1; 1251 goto out; 1252 } 1253 } 1254 1255 if (options.verify_host_key_dns) { 1256 /* 1257 * XXX certs are not yet supported for DNS, so downgrade 1258 * them and try the plain key. 1259 */ 1260 if ((r = sshkey_from_private(host_key, &plain)) != 0) 1261 goto out; 1262 if (sshkey_is_cert(plain)) 1263 sshkey_drop_cert(plain); 1264 if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) { 1265 if (flags & DNS_VERIFY_FOUND) { 1266 if (options.verify_host_key_dns == 1 && 1267 flags & DNS_VERIFY_MATCH && 1268 flags & DNS_VERIFY_SECURE) { 1269 r = 0; 1270 goto out; 1271 } 1272 if (flags & DNS_VERIFY_MATCH) { 1273 matching_host_key_dns = 1; 1274 } else { 1275 warn_changed_key(plain); 1276 error("Update the SSHFP RR in DNS " 1277 "with the new host key to get rid " 1278 "of this message."); 1279 } 1280 } 1281 } 1282 } 1283 r = check_host_key(host, hostaddr, options.port, host_key, RDRW, 1284 options.user_hostfiles, options.num_user_hostfiles, 1285 options.system_hostfiles, options.num_system_hostfiles); 1286 1287 out: 1288 sshkey_free(plain); 1289 free(fp); 1290 free(cafp); 1291 if (r == 0 && host_key != NULL) { 1292 sshkey_free(previous_host_key); 1293 r = sshkey_from_private(host_key, &previous_host_key); 1294 } 1295 1296 return r; 1297 } 1298 1299 /* 1300 * Starts a dialog with the server, and authenticates the current user on the 1301 * server. This does not need any extra privileges. The basic connection 1302 * to the server must already have been established before this is called. 1303 * If login fails, this function prints an error and never returns. 1304 * This function does not require super-user privileges. 1305 */ 1306 void 1307 ssh_login(Sensitive *sensitive, const char *orighost, 1308 struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms) 1309 { 1310 char *host; 1311 char *server_user, *local_user; 1312 1313 local_user = xstrdup(pw->pw_name); 1314 server_user = options.user ? options.user : local_user; 1315 1316 /* Convert the user-supplied hostname into all lowercase. */ 1317 host = xstrdup(orighost); 1318 lowercase(host); 1319 1320 /* Exchange protocol version identification strings with the server. */ 1321 ssh_exchange_identification(timeout_ms); 1322 1323 /* Put the connection into non-blocking mode. */ 1324 packet_set_nonblocking(); 1325 1326 /* key exchange */ 1327 /* authenticate user */ 1328 debug("Authenticating to %s:%d as '%s'", host, port, server_user); 1329 ssh_kex2(host, hostaddr, port); 1330 ssh_userauth2(local_user, server_user, host, sensitive); 1331 free(local_user); 1332 } 1333 1334 void 1335 ssh_put_password(char *password) 1336 { 1337 int size; 1338 char *padded; 1339 1340 if (datafellows & SSH_BUG_PASSWORDPAD) { 1341 packet_put_cstring(password); 1342 return; 1343 } 1344 size = ROUNDUP(strlen(password) + 1, 32); 1345 padded = xcalloc(1, size); 1346 strlcpy(padded, password, size); 1347 packet_put_string(padded, size); 1348 explicit_bzero(padded, size); 1349 free(padded); 1350 } 1351 1352 /* print all known host keys for a given host, but skip keys of given type */ 1353 static int 1354 show_other_keys(struct hostkeys *hostkeys, struct sshkey *key) 1355 { 1356 int type[] = { 1357 KEY_RSA, 1358 KEY_DSA, 1359 KEY_ECDSA, 1360 KEY_ED25519, 1361 -1 1362 }; 1363 int i, ret = 0; 1364 char *fp, *ra; 1365 const struct hostkey_entry *found; 1366 1367 for (i = 0; type[i] != -1; i++) { 1368 if (type[i] == key->type) 1369 continue; 1370 if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found)) 1371 continue; 1372 fp = sshkey_fingerprint(found->key, 1373 options.fingerprint_hash, SSH_FP_DEFAULT); 1374 ra = sshkey_fingerprint(found->key, 1375 options.fingerprint_hash, SSH_FP_RANDOMART); 1376 if (fp == NULL || ra == NULL) 1377 fatal("%s: sshkey_fingerprint fail", __func__); 1378 logit("WARNING: %s key found for host %s\n" 1379 "in %s:%lu\n" 1380 "%s key fingerprint %s.", 1381 key_type(found->key), 1382 found->host, found->file, found->line, 1383 key_type(found->key), fp); 1384 if (options.visual_host_key) 1385 logit("%s", ra); 1386 free(ra); 1387 free(fp); 1388 ret = 1; 1389 } 1390 return ret; 1391 } 1392 1393 static void 1394 warn_changed_key(struct sshkey *host_key) 1395 { 1396 char *fp; 1397 1398 fp = sshkey_fingerprint(host_key, options.fingerprint_hash, 1399 SSH_FP_DEFAULT); 1400 if (fp == NULL) 1401 fatal("%s: sshkey_fingerprint fail", __func__); 1402 1403 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1404 error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); 1405 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 1406 error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); 1407 error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); 1408 error("It is also possible that a host key has just been changed."); 1409 error("The fingerprint for the %s key sent by the remote host is\n%s.", 1410 key_type(host_key), fp); 1411 error("Please contact your system administrator."); 1412 1413 free(fp); 1414 } 1415 1416 /* 1417 * Execute a local command 1418 */ 1419 int 1420 ssh_local_cmd(const char *args) 1421 { 1422 char *shell; 1423 pid_t pid; 1424 int status; 1425 void (*osighand)(int); 1426 1427 if (!options.permit_local_command || 1428 args == NULL || !*args) 1429 return (1); 1430 1431 if ((shell = getenv("SHELL")) == NULL || *shell == '\0') 1432 shell = _PATH_BSHELL; 1433 1434 osighand = signal(SIGCHLD, SIG_DFL); 1435 pid = fork(); 1436 if (pid == 0) { 1437 signal(SIGPIPE, SIG_DFL); 1438 debug3("Executing %s -c \"%s\"", shell, args); 1439 execl(shell, shell, "-c", args, (char *)NULL); 1440 error("Couldn't execute %s -c \"%s\": %s", 1441 shell, args, strerror(errno)); 1442 _exit(1); 1443 } else if (pid == -1) 1444 fatal("fork failed: %.100s", strerror(errno)); 1445 while (waitpid(pid, &status, 0) == -1) 1446 if (errno != EINTR) 1447 fatal("Couldn't wait for child: %s", strerror(errno)); 1448 signal(SIGCHLD, osighand); 1449 1450 if (!WIFEXITED(status)) 1451 return (1); 1452 1453 return (WEXITSTATUS(status)); 1454 } 1455 1456 void 1457 maybe_add_key_to_agent(char *authfile, struct sshkey *private, char *comment, 1458 char *passphrase) 1459 { 1460 int auth_sock = -1, r; 1461 1462 if (options.add_keys_to_agent == 0) 1463 return; 1464 1465 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 1466 debug3("no authentication agent, not adding key"); 1467 return; 1468 } 1469 1470 if (options.add_keys_to_agent == 2 && 1471 !ask_permission("Add key %s (%s) to agent?", authfile, comment)) { 1472 debug3("user denied adding this key"); 1473 close(auth_sock); 1474 return; 1475 } 1476 1477 if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0, 1478 (options.add_keys_to_agent == 3))) == 0) 1479 debug("identity added to agent: %s", authfile); 1480 else 1481 debug("could not add identity to agent: %s (%d)", authfile, r); 1482 close(auth_sock); 1483 } 1484