Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.301
1.301 ! dtucker 1: /* $OpenBSD: sshconnect.c,v 1.300 2018/07/11 18:53:29 markus Exp $ */
1.1 deraadt 2: /*
1.39 deraadt 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.
1.78 deraadt 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".
1.39 deraadt 14: */
1.1 deraadt 15:
1.174 stevesk 16: #include <sys/types.h>
17: #include <sys/wait.h>
1.175 stevesk 18: #include <sys/stat.h>
1.187 stevesk 19: #include <sys/socket.h>
1.195 stevesk 20: #include <sys/time.h>
1.187 stevesk 21:
1.295 djm 22: #include <net/if.h>
1.187 stevesk 23: #include <netinet/in.h>
1.172 stevesk 24:
1.176 stevesk 25: #include <ctype.h>
1.190 stevesk 26: #include <errno.h>
1.216 dtucker 27: #include <fcntl.h>
1.191 stevesk 28: #include <netdb.h>
1.172 stevesk 29: #include <paths.h>
1.282 djm 30: #include <poll.h>
1.199 deraadt 31: #include <signal.h>
1.188 stevesk 32: #include <pwd.h>
1.198 stevesk 33: #include <stdio.h>
1.196 stevesk 34: #include <stdlib.h>
1.193 stevesk 35: #include <string.h>
1.192 stevesk 36: #include <unistd.h>
1.295 djm 37: #include <ifaddrs.h>
1.71 markus 38:
1.199 deraadt 39: #include "xmalloc.h"
1.91 markus 40: #include "ssh.h"
1.299 markus 41: #include "sshbuf.h"
1.1 deraadt 42: #include "packet.h"
1.21 markus 43: #include "compat.h"
1.300 markus 44: #include "sshkey.h"
1.71 markus 45: #include "sshconnect.h"
1.58 markus 46: #include "hostfile.h"
1.91 markus 47: #include "log.h"
1.251 millert 48: #include "misc.h"
1.91 markus 49: #include "readconf.h"
50: #include "atomicio.h"
1.140 jakob 51: #include "dns.h"
1.239 djm 52: #include "monitor_fdpass.h"
1.219 djm 53: #include "ssh2.h"
1.186 stevesk 54: #include "version.h"
1.252 djm 55: #include "authfile.h"
56: #include "ssherr.h"
1.266 jcs 57: #include "authfd.h"
1.140 jakob 58:
1.70 markus 59: char *client_version_string = NULL;
60: char *server_version_string = NULL;
1.279 markus 61: struct sshkey *previous_host_key = NULL;
1.59 markus 62:
1.169 stevesk 63: static int matching_host_key_dns = 0;
1.145 jakob 64:
1.227 djm 65: static pid_t proxy_command_pid = 0;
66:
1.124 markus 67: /* import */
1.43 markus 68: extern Options options;
1.50 markus 69: extern char *__progname;
1.124 markus 70: extern uid_t original_real_uid;
71: extern uid_t original_effective_uid;
1.91 markus 72:
1.279 markus 73: static int show_other_keys(struct hostkeys *, struct sshkey *);
74: static void warn_changed_key(struct sshkey *);
1.132 markus 75:
1.239 djm 76: /* Expand a proxy command */
77: static char *
78: expand_proxy_command(const char *proxy_command, const char *user,
79: const char *host, int port)
80: {
81: char *tmp, *ret, strport[NI_MAXSERV];
82:
1.241 djm 83: snprintf(strport, sizeof strport, "%d", port);
1.239 djm 84: xasprintf(&tmp, "exec %s", proxy_command);
85: ret = percent_expand(tmp, "h", host, "p", strport,
86: "r", options.user, (char *)NULL);
87: free(tmp);
88: return ret;
89: }
90:
91: /*
92: * Connect to the given ssh server using a proxy command that passes a
93: * a connected fd back to us.
94: */
95: static int
1.286 djm 96: ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port,
1.239 djm 97: const char *proxy_command)
98: {
99: char *command_string;
100: int sp[2], sock;
101: pid_t pid;
102: char *shell;
103:
104: if ((shell = getenv("SHELL")) == NULL)
105: shell = _PATH_BSHELL;
106:
107: if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
108: fatal("Could not create socketpair to communicate with "
109: "proxy dialer: %.100s", strerror(errno));
110:
111: command_string = expand_proxy_command(proxy_command, options.user,
112: host, port);
113: debug("Executing proxy dialer command: %.500s", command_string);
114:
115: /* Fork and execute the proxy command. */
116: if ((pid = fork()) == 0) {
117: char *argv[10];
118:
119: close(sp[1]);
120: /* Redirect stdin and stdout. */
121: if (sp[0] != 0) {
122: if (dup2(sp[0], 0) < 0)
123: perror("dup2 stdin");
124: }
125: if (sp[0] != 1) {
126: if (dup2(sp[0], 1) < 0)
127: perror("dup2 stdout");
128: }
129: if (sp[0] >= 2)
130: close(sp[0]);
131:
132: /*
133: * Stderr is left as it is so that error messages get
134: * printed on the user's terminal.
135: */
136: argv[0] = shell;
137: argv[1] = "-c";
138: argv[2] = command_string;
139: argv[3] = NULL;
140:
141: /*
142: * Execute the proxy command.
143: * Note that we gave up any extra privileges above.
144: */
145: execv(argv[0], argv);
146: perror(argv[0]);
147: exit(1);
148: }
149: /* Parent. */
150: if (pid < 0)
151: fatal("fork failed: %.100s", strerror(errno));
152: close(sp[0]);
153: free(command_string);
154:
155: if ((sock = mm_receive_fd(sp[1])) == -1)
156: fatal("proxy dialer did not pass back a connection");
1.271 markus 157: close(sp[1]);
1.239 djm 158:
159: while (waitpid(pid, NULL, 0) == -1)
160: if (errno != EINTR)
161: fatal("Couldn't wait for child: %s", strerror(errno));
162:
163: /* Set the connection file descriptors. */
1.286 djm 164: if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
165: return -1; /* ssh_packet_set_connection logs error */
1.239 djm 166:
167: return 0;
168: }
169:
1.39 deraadt 170: /*
171: * Connect to the given ssh server using a proxy command.
172: */
1.109 itojun 173: static int
1.286 djm 174: ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port,
175: const char *proxy_command)
1.1 deraadt 176: {
1.239 djm 177: char *command_string;
1.38 markus 178: int pin[2], pout[2];
1.69 deraadt 179: pid_t pid;
1.239 djm 180: char *shell;
1.237 markus 181:
1.226 djm 182: if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1.201 djm 183: shell = _PATH_BSHELL;
1.38 markus 184:
185: /* Create pipes for communicating with the proxy. */
186: if (pipe(pin) < 0 || pipe(pout) < 0)
187: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 188: strerror(errno));
1.38 markus 189:
1.239 djm 190: command_string = expand_proxy_command(proxy_command, options.user,
191: host, port);
1.38 markus 192: debug("Executing proxy command: %.500s", command_string);
193:
194: /* Fork and execute the proxy command. */
195: if ((pid = fork()) == 0) {
196: char *argv[10];
197:
198: /* Redirect stdin and stdout. */
199: close(pin[1]);
200: if (pin[0] != 0) {
201: if (dup2(pin[0], 0) < 0)
202: perror("dup2 stdin");
203: close(pin[0]);
204: }
205: close(pout[0]);
206: if (dup2(pout[1], 1) < 0)
207: perror("dup2 stdout");
208: /* Cannot be 1 because pin allocated two descriptors. */
209: close(pout[1]);
210:
211: /* Stderr is left as it is so that error messages get
212: printed on the user's terminal. */
1.201 djm 213: argv[0] = shell;
1.38 markus 214: argv[1] = "-c";
215: argv[2] = command_string;
216: argv[3] = NULL;
217:
218: /* Execute the proxy command. Note that we gave up any
219: extra privileges above. */
1.232 djm 220: signal(SIGPIPE, SIG_DFL);
1.89 markus 221: execv(argv[0], argv);
222: perror(argv[0]);
1.38 markus 223: exit(1);
224: }
225: /* Parent. */
226: if (pid < 0)
227: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 228: else
229: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 230:
231: /* Close child side of the descriptors. */
232: close(pin[0]);
233: close(pout[1]);
234:
235: /* Free the command name. */
1.238 djm 236: free(command_string);
1.38 markus 237:
238: /* Set the connection file descriptors. */
1.286 djm 239: if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
240: return -1; /* ssh_packet_set_connection logs error */
1.1 deraadt 241:
1.110 markus 242: return 0;
1.227 djm 243: }
244:
245: void
246: ssh_kill_proxy_command(void)
247: {
248: /*
249: * Send SIGHUP to proxy command if used. We don't wait() in
250: * case it hangs and instead rely on init to reap the child
251: */
252: if (proxy_command_pid > 1)
1.228 djm 253: kill(proxy_command_pid, SIGHUP);
1.1 deraadt 254: }
255:
1.39 deraadt 256: /*
1.295 djm 257: * Search a interface address list (returned from getifaddrs(3)) for an
1.298 djm 258: * address that matches the desired address family on the specified interface.
1.295 djm 259: * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
260: */
261: static int
262: check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
263: struct sockaddr_storage *resultp, socklen_t *rlenp)
264: {
265: struct sockaddr_in6 *sa6;
266: struct sockaddr_in *sa;
267: struct in6_addr *v6addr;
268: const struct ifaddrs *ifa;
269: int allow_local;
270:
271: /*
272: * Prefer addresses that are not loopback or linklocal, but use them
273: * if nothing else matches.
274: */
275: for (allow_local = 0; allow_local < 2; allow_local++) {
276: for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
277: if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
278: (ifa->ifa_flags & IFF_UP) == 0 ||
279: ifa->ifa_addr->sa_family != af ||
280: strcmp(ifa->ifa_name, options.bind_interface) != 0)
281: continue;
282: switch (ifa->ifa_addr->sa_family) {
283: case AF_INET:
284: sa = (struct sockaddr_in *)ifa->ifa_addr;
285: if (!allow_local && sa->sin_addr.s_addr ==
286: htonl(INADDR_LOOPBACK))
287: continue;
288: if (*rlenp < sizeof(struct sockaddr_in)) {
289: error("%s: v4 addr doesn't fit",
290: __func__);
291: return -1;
292: }
293: *rlenp = sizeof(struct sockaddr_in);
294: memcpy(resultp, sa, *rlenp);
295: return 0;
296: case AF_INET6:
297: sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
298: v6addr = &sa6->sin6_addr;
299: if (!allow_local &&
300: (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
301: IN6_IS_ADDR_LOOPBACK(v6addr)))
302: continue;
303: if (*rlenp < sizeof(struct sockaddr_in6)) {
304: error("%s: v6 addr doesn't fit",
305: __func__);
306: return -1;
307: }
308: *rlenp = sizeof(struct sockaddr_in6);
309: memcpy(resultp, sa6, *rlenp);
310: return 0;
311: }
312: }
313: }
314: return -1;
315: }
316:
317: /*
1.39 deraadt 318: * Creates a (possibly privileged) socket for use as the ssh connection.
319: */
1.109 itojun 320: static int
1.139 markus 321: ssh_create_socket(int privileged, struct addrinfo *ai)
1.1 deraadt 322: {
1.301 ! dtucker 323: int sock, r;
1.295 djm 324: struct sockaddr_storage bindaddr;
325: socklen_t bindaddrlen = 0;
1.246 djm 326: struct addrinfo hints, *res = NULL;
1.295 djm 327: struct ifaddrs *ifaddrs = NULL;
328: char ntop[NI_MAXHOST];
1.1 deraadt 329:
1.217 dtucker 330: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.216 dtucker 331: if (sock < 0) {
1.240 djm 332: error("socket: %s", strerror(errno));
1.216 dtucker 333: return -1;
334: }
335: fcntl(sock, F_SETFD, FD_CLOEXEC);
1.105 markus 336:
337: /* Bind the socket to an alternative local IP address */
1.295 djm 338: if (options.bind_address == NULL && options.bind_interface == NULL &&
339: !privileged)
1.105 markus 340: return sock;
341:
1.295 djm 342: if (options.bind_address != NULL) {
1.246 djm 343: memset(&hints, 0, sizeof(hints));
344: hints.ai_family = ai->ai_family;
345: hints.ai_socktype = ai->ai_socktype;
346: hints.ai_protocol = ai->ai_protocol;
347: hints.ai_flags = AI_PASSIVE;
1.295 djm 348: if ((r = getaddrinfo(options.bind_address, NULL,
349: &hints, &res)) != 0) {
1.246 djm 350: error("getaddrinfo: %s: %s", options.bind_address,
1.295 djm 351: ssh_gai_strerror(r));
352: goto fail;
353: }
1.296 dtucker 354: if (res == NULL) {
1.295 djm 355: error("getaddrinfo: no addrs");
356: goto fail;
1.296 dtucker 357: }
1.295 djm 358: if (res->ai_addrlen > sizeof(bindaddr)) {
359: error("%s: addr doesn't fit", __func__);
360: goto fail;
361: }
362: memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
363: bindaddrlen = res->ai_addrlen;
364: } else if (options.bind_interface != NULL) {
365: if ((r = getifaddrs(&ifaddrs)) != 0) {
366: error("getifaddrs: %s: %s", options.bind_interface,
367: strerror(errno));
368: goto fail;
369: }
370: bindaddrlen = sizeof(bindaddr);
371: if (check_ifaddrs(options.bind_interface, ai->ai_family,
372: ifaddrs, &bindaddr, &bindaddrlen) != 0) {
373: logit("getifaddrs: %s: no suitable addresses",
374: options.bind_interface);
375: goto fail;
1.246 djm 376: }
1.105 markus 377: }
1.295 djm 378: if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
379: ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
380: error("%s: getnameinfo failed: %s", __func__,
381: ssh_gai_strerror(r));
382: goto fail;
383: }
1.301 ! dtucker 384: if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
1.295 djm 385: error("bind %s: %s", ntop, strerror(errno));
386: goto fail;
1.38 markus 387: }
1.295 djm 388: debug("%s: bound to %s", __func__, ntop);
389: /* success */
390: goto out;
391: fail:
392: close(sock);
393: sock = -1;
394: out:
1.246 djm 395: if (res != NULL)
396: freeaddrinfo(res);
1.295 djm 397: if (ifaddrs != NULL)
398: freeifaddrs(ifaddrs);
1.38 markus 399: return sock;
1.1 deraadt 400: }
401:
1.282 djm 402: /*
403: * Wait up to *timeoutp milliseconds for fd to be readable. Updates
404: * *timeoutp with time remaining.
405: * Returns 0 if fd ready or -1 on timeout or error (see errno).
406: */
407: static int
408: waitrfd(int fd, int *timeoutp)
409: {
410: struct pollfd pfd;
411: struct timeval t_start;
412: int oerrno, r;
413:
1.288 dtucker 414: monotime_tv(&t_start);
1.282 djm 415: pfd.fd = fd;
416: pfd.events = POLLIN;
417: for (; *timeoutp >= 0;) {
418: r = poll(&pfd, 1, *timeoutp);
419: oerrno = errno;
420: ms_subtract_diff(&t_start, timeoutp);
421: errno = oerrno;
422: if (r > 0)
423: return 0;
424: else if (r == -1 && errno != EAGAIN)
425: return -1;
426: else if (r == 0)
427: break;
428: }
429: /* timeout */
430: errno = ETIMEDOUT;
431: return -1;
432: }
433:
1.141 djm 434: static int
435: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
1.202 djm 436: socklen_t addrlen, int *timeoutp)
1.141 djm 437: {
1.282 djm 438: int optval = 0;
439: socklen_t optlen = sizeof(optval);
1.141 djm 440:
1.282 djm 441: /* No timeout: just do a blocking connect() */
442: if (*timeoutp <= 0)
443: return connect(sockfd, serv_addr, addrlen);
1.141 djm 444:
1.156 djm 445: set_nonblock(sockfd);
1.282 djm 446: if (connect(sockfd, serv_addr, addrlen) == 0) {
447: /* Succeeded already? */
1.156 djm 448: unset_nonblock(sockfd);
1.282 djm 449: return 0;
450: } else if (errno != EINPROGRESS)
451: return -1;
452:
453: if (waitrfd(sockfd, timeoutp) == -1)
454: return -1;
1.141 djm 455:
1.282 djm 456: /* Completed or failed */
457: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) {
458: debug("getsockopt: %s", strerror(errno));
459: return -1;
1.141 djm 460: }
1.282 djm 461: if (optval != 0) {
462: errno = optval;
463: return -1;
1.202 djm 464: }
1.282 djm 465: unset_nonblock(sockfd);
466: return 0;
1.141 djm 467: }
468:
1.39 deraadt 469: /*
1.49 markus 470: * Opens a TCP/IP connection to the remote server on the given host.
471: * The address of the remote host will be returned in hostaddr.
1.124 markus 472: * If port is 0, the default port will be used. If needpriv is true,
1.39 deraadt 473: * a privileged port will be allocated to make the connection.
1.124 markus 474: * This requires super-user privileges if needpriv is true.
1.39 deraadt 475: * Connection_attempts specifies the maximum number of tries (one per
476: * second). If proxy_command is non-NULL, it specifies the command (with %h
477: * and %p substituted for host and port, respectively) to use to contact
478: * the daemon.
479: */
1.241 djm 480: static int
1.286 djm 481: ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
1.241 djm 482: struct sockaddr_storage *hostaddr, u_short port, int family,
483: int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
1.1 deraadt 484: {
1.90 markus 485: int on = 1;
1.290 djm 486: int oerrno, sock = -1, attempt;
1.90 markus 487: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.241 djm 488: struct addrinfo *ai;
1.38 markus 489:
1.265 djm 490: debug2("%s: needpriv %d", __func__, needpriv);
1.268 djm 491: memset(ntop, 0, sizeof(ntop));
492: memset(strport, 0, sizeof(strport));
1.38 markus 493:
1.181 markus 494: for (attempt = 0; attempt < connection_attempts; attempt++) {
1.200 markus 495: if (attempt > 0) {
496: /* Sleep a moment before retrying. */
497: sleep(1);
1.38 markus 498: debug("Trying again...");
1.200 markus 499: }
1.181 markus 500: /*
501: * Loop through addresses for this host, and try each one in
502: * sequence until the connection succeeds.
503: */
1.49 markus 504: for (ai = aitop; ai; ai = ai->ai_next) {
1.241 djm 505: if (ai->ai_family != AF_INET &&
1.290 djm 506: ai->ai_family != AF_INET6) {
507: errno = EAFNOSUPPORT;
1.49 markus 508: continue;
1.290 djm 509: }
1.49 markus 510: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
511: ntop, sizeof(ntop), strport, sizeof(strport),
512: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1.290 djm 513: oerrno = errno;
1.265 djm 514: error("%s: getnameinfo failed", __func__);
1.290 djm 515: errno = oerrno;
1.49 markus 516: continue;
517: }
518: debug("Connecting to %.200s [%.100s] port %s.",
519: host, ntop, strport);
520:
521: /* Create a socket for connecting. */
1.139 markus 522: sock = ssh_create_socket(needpriv, ai);
1.292 stsp 523: if (sock < 0) {
1.110 markus 524: /* Any error is already output */
1.290 djm 525: errno = 0;
1.49 markus 526: continue;
1.292 stsp 527: }
1.49 markus 528:
1.141 djm 529: if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
1.202 djm 530: timeout_ms) >= 0) {
1.49 markus 531: /* Successful connection. */
1.102 markus 532: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 533: break;
1.49 markus 534: } else {
1.290 djm 535: oerrno = errno;
1.131 itojun 536: debug("connect to address %s port %s: %s",
537: ntop, strport, strerror(errno));
1.38 markus 538: close(sock);
1.181 markus 539: sock = -1;
1.290 djm 540: errno = oerrno;
1.38 markus 541: }
542: }
1.181 markus 543: if (sock != -1)
1.49 markus 544: break; /* Successful connection. */
1.38 markus 545: }
1.49 markus 546:
1.38 markus 547: /* Return failure if we didn't get a successful connection. */
1.181 markus 548: if (sock == -1) {
1.159 markus 549: error("ssh: connect to host %s port %s: %s",
1.290 djm 550: host, strport, errno == 0 ? "failure" : strerror(errno));
551: return -1;
1.130 itojun 552: }
1.38 markus 553:
554: debug("Connection established.");
1.90 markus 555:
1.155 markus 556: /* Set SO_KEEPALIVE if requested. */
1.202 djm 557: if (want_keepalive &&
1.90 markus 558: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
559: sizeof(on)) < 0)
560: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 561:
562: /* Set the connection. */
1.286 djm 563: if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
564: return -1; /* ssh_packet_set_connection logs error */
1.1 deraadt 565:
1.286 djm 566: return 0;
1.59 markus 567: }
568:
1.241 djm 569: int
1.286 djm 570: ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs,
1.241 djm 571: struct sockaddr_storage *hostaddr, u_short port, int family,
572: int connection_attempts, int *timeout_ms, int want_keepalive, int needpriv)
573: {
574: if (options.proxy_command == NULL) {
1.286 djm 575: return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
576: family, connection_attempts, timeout_ms, want_keepalive,
577: needpriv);
1.241 djm 578: } else if (strcmp(options.proxy_command, "-") == 0) {
1.286 djm 579: if ((ssh_packet_set_connection(ssh,
580: STDIN_FILENO, STDOUT_FILENO)) == NULL)
581: return -1; /* ssh_packet_set_connection logs error */
582: return 0;
1.241 djm 583: } else if (options.proxy_use_fdpass) {
1.286 djm 584: return ssh_proxy_fdpass_connect(ssh, host, port,
1.241 djm 585: options.proxy_command);
586: }
1.286 djm 587: return ssh_proxy_connect(ssh, host, port, options.proxy_command);
1.241 djm 588: }
589:
1.235 djm 590: static void
591: send_client_banner(int connection_out, int minor1)
592: {
593: /* Send our own protocol version identification. */
1.276 djm 594: xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
595: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
1.270 markus 596: if (atomicio(vwrite, connection_out, client_version_string,
1.235 djm 597: strlen(client_version_string)) != strlen(client_version_string))
598: fatal("write: %.100s", strerror(errno));
599: chop(client_version_string);
600: debug("Local version string %.100s", client_version_string);
601: }
602:
1.43 markus 603: /*
1.39 deraadt 604: * Waits for the server identification string, and sends our own
605: * identification string.
606: */
1.213 andreas 607: void
1.202 djm 608: ssh_exchange_identification(int timeout_ms)
1.1 deraadt 609: {
1.38 markus 610: char buf[256], remote_version[256]; /* must be same size! */
1.165 djm 611: int remote_major, remote_minor, mismatch;
1.38 markus 612: int connection_in = packet_get_connection_in();
613: int connection_out = packet_get_connection_out();
1.185 djm 614: u_int i, n;
1.202 djm 615: size_t len;
1.282 djm 616: int rc;
1.38 markus 617:
1.275 djm 618: send_client_banner(connection_out, 0);
1.235 djm 619:
1.163 avsm 620: /* Read other side's version identification. */
1.185 djm 621: for (n = 0;;) {
1.75 markus 622: for (i = 0; i < sizeof(buf) - 1; i++) {
1.202 djm 623: if (timeout_ms > 0) {
1.282 djm 624: rc = waitrfd(connection_in, &timeout_ms);
625: if (rc == -1 && errno == ETIMEDOUT) {
1.202 djm 626: fatal("Connection timed out during "
627: "banner exchange");
1.282 djm 628: } else if (rc == -1) {
629: fatal("%s: %s",
630: __func__, strerror(errno));
1.202 djm 631: }
632: }
633:
1.270 markus 634: len = atomicio(read, connection_in, &buf[i], 1);
1.167 djm 635: if (len != 1 && errno == EPIPE)
1.202 djm 636: fatal("ssh_exchange_identification: "
637: "Connection closed by remote host");
1.163 avsm 638: else if (len != 1)
1.202 djm 639: fatal("ssh_exchange_identification: "
640: "read: %.100s", strerror(errno));
1.75 markus 641: if (buf[i] == '\r') {
642: buf[i] = '\n';
643: buf[i + 1] = 0;
644: continue; /**XXX wait for \n */
645: }
646: if (buf[i] == '\n') {
647: buf[i + 1] = 0;
648: break;
649: }
1.185 djm 650: if (++n > 65536)
1.202 djm 651: fatal("ssh_exchange_identification: "
652: "No banner received");
1.38 markus 653: }
1.75 markus 654: buf[sizeof(buf) - 1] = 0;
1.76 markus 655: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 656: break;
1.75 markus 657: debug("ssh_exchange_identification: %s", buf);
1.38 markus 658: }
1.59 markus 659: server_version_string = xstrdup(buf);
1.38 markus 660:
1.40 markus 661: /*
662: * Check that the versions match. In future this might accept
663: * several versions and set appropriate flags to handle them.
664: */
1.59 markus 665: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
666: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 667: fatal("Bad remote protocol version identification: '%.100s'", buf);
668: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 669: remote_major, remote_minor, remote_version);
1.38 markus 670:
1.255 markus 671: active_state->compat = compat_datafellows(remote_version);
1.64 markus 672: mismatch = 0;
1.59 markus 673:
1.116 deraadt 674: switch (remote_major) {
1.276 djm 675: case 2:
676: break;
1.64 markus 677: case 1:
1.276 djm 678: if (remote_minor != 99)
1.64 markus 679: mismatch = 1;
680: break;
1.68 markus 681: default:
1.64 markus 682: mismatch = 1;
683: break;
1.38 markus 684: }
1.64 markus 685: if (mismatch)
1.38 markus 686: fatal("Protocol major versions differ: %d vs. %d",
1.275 djm 687: PROTOCOL_MAJOR_2, remote_major);
1.243 djm 688: if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
689: logit("Server version \"%.100s\" uses unsafe RSA signature "
690: "scheme; disabling use of RSA keys", remote_version);
1.59 markus 691: chop(server_version_string);
1.1 deraadt 692: }
693:
1.96 markus 694: /* defaults to 'no' */
1.109 itojun 695: static int
1.112 markus 696: confirm(const char *prompt)
1.1 deraadt 697: {
1.119 markus 698: const char *msg, *again = "Please type 'yes' or 'no': ";
699: char *p;
700: int ret = -1;
1.96 markus 701:
702: if (options.batch_mode)
703: return 0;
1.119 markus 704: for (msg = prompt;;msg = again) {
705: p = read_passphrase(msg, RP_ECHO);
1.289 djm 706: if (p == NULL)
707: return 0;
708: p[strcspn(p, "\n")] = '\0';
709: if (p[0] == '\0' || strcasecmp(p, "no") == 0)
1.119 markus 710: ret = 0;
1.289 djm 711: else if (strcasecmp(p, "yes") == 0)
1.119 markus 712: ret = 1;
1.238 djm 713: free(p);
1.119 markus 714: if (ret != -1)
715: return ret;
1.1 deraadt 716: }
717: }
718:
1.219 djm 719: static int
1.279 markus 720: check_host_cert(const char *host, const struct sshkey *host_key)
1.219 djm 721: {
722: const char *reason;
723:
1.300 markus 724: if (sshkey_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
1.219 djm 725: error("%s", reason);
726: return 0;
727: }
1.299 markus 728: if (sshbuf_len(host_key->cert->critical) != 0) {
1.223 djm 729: error("Certificate for %s contains unsupported "
730: "critical options(s)", host);
1.219 djm 731: return 0;
732: }
733: return 1;
734: }
735:
1.229 djm 736: static int
737: sockaddr_is_local(struct sockaddr *hostaddr)
738: {
739: switch (hostaddr->sa_family) {
740: case AF_INET:
741: return (ntohl(((struct sockaddr_in *)hostaddr)->
742: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
743: case AF_INET6:
744: return IN6_IS_ADDR_LOOPBACK(
745: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
746: default:
747: return 0;
748: }
749: }
750:
751: /*
752: * Prepare the hostname and ip address strings that are used to lookup
753: * host keys in known_hosts files. These may have a port number appended.
754: */
755: void
756: get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
757: u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
758: {
759: char ntop[NI_MAXHOST];
760:
761: /*
762: * We don't have the remote ip-address for connections
763: * using a proxy command
764: */
765: if (hostfile_ipaddr != NULL) {
766: if (options.proxy_command == NULL) {
767: if (getnameinfo(hostaddr, hostaddr->sa_len,
768: ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
1.259 djm 769: fatal("%s: getnameinfo failed", __func__);
1.229 djm 770: *hostfile_ipaddr = put_host_port(ntop, port);
771: } else {
772: *hostfile_ipaddr = xstrdup("<no hostip for proxy "
773: "command>");
774: }
775: }
776:
777: /*
778: * Allow the user to record the key under a different name or
779: * differentiate a non-standard port. This is useful for ssh
780: * tunneling over forwarded connections or if you run multiple
781: * sshd's on different ports on the same machine.
782: */
783: if (hostfile_hostname != NULL) {
784: if (options.host_key_alias != NULL) {
785: *hostfile_hostname = xstrdup(options.host_key_alias);
786: debug("using hostkeyalias: %s", *hostfile_hostname);
787: } else {
788: *hostfile_hostname = put_host_port(hostname, port);
789: }
790: }
791: }
792:
1.39 deraadt 793: /*
1.108 markus 794: * check whether the supplied host key is valid, return -1 if the key
1.234 djm 795: * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
1.39 deraadt 796: */
1.197 dtucker 797: #define RDRW 0
798: #define RDONLY 1
799: #define ROQUIET 2
1.109 itojun 800: static int
1.197 dtucker 801: check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
1.279 markus 802: struct sshkey *host_key, int readonly,
1.234 djm 803: char **user_hostfiles, u_int num_user_hostfiles,
804: char **system_hostfiles, u_int num_system_hostfiles)
1.1 deraadt 805: {
1.234 djm 806: HostStatus host_status;
807: HostStatus ip_status;
1.279 markus 808: struct sshkey *raw_key = NULL;
1.189 dtucker 809: char *ip = NULL, *host = NULL;
1.204 grunk 810: char hostline[1000], *hostp, *fp, *ra;
1.119 markus 811: char msg[1024];
1.234 djm 812: const char *type;
813: const struct hostkey_entry *host_found, *ip_found;
1.229 djm 814: int len, cancelled_forwarding = 0;
1.234 djm 815: int local = sockaddr_is_local(hostaddr);
1.280 markus 816: int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
1.257 djm 817: int hostkey_trusted = 0; /* Known or explicitly accepted by user */
1.229 djm 818: struct hostkeys *host_hostkeys, *ip_hostkeys;
1.234 djm 819: u_int i;
1.49 markus 820:
821: /*
822: * Force accepting of the host key for loopback/localhost. The
823: * problem is that if the home directory is NFS-mounted to multiple
824: * machines, localhost will refer to a different machine in each of
825: * them, and the user will get bogus HOST_CHANGED warnings. This
826: * essentially disables host authentication for localhost; however,
827: * this is probably not a real problem.
828: */
1.111 markus 829: if (options.no_host_authentication_for_localhost == 1 && local &&
830: options.host_key_alias == NULL) {
1.88 markus 831: debug("Forcing accepting of host key for "
832: "loopback/localhost.");
1.108 markus 833: return 0;
1.49 markus 834: }
1.42 markus 835:
836: /*
1.229 djm 837: * Prepare the hostname and address strings used for hostkey lookup.
838: * In some cases, these will have a port number appended.
1.42 markus 839: */
1.229 djm 840: get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
1.206 grunk 841:
842: /*
1.88 markus 843: * Turn off check_host_ip if the connection is to localhost, via proxy
844: * command or if we don't have a hostname to compare with
845: */
1.189 dtucker 846: if (options.check_host_ip && (local ||
847: strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1.88 markus 848: options.check_host_ip = 0;
1.86 markus 849:
1.229 djm 850: host_hostkeys = init_hostkeys();
1.234 djm 851: for (i = 0; i < num_user_hostfiles; i++)
852: load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
853: for (i = 0; i < num_system_hostfiles; i++)
854: load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
1.229 djm 855:
856: ip_hostkeys = NULL;
857: if (!want_cert && options.check_host_ip) {
858: ip_hostkeys = init_hostkeys();
1.234 djm 859: for (i = 0; i < num_user_hostfiles; i++)
860: load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
861: for (i = 0; i < num_system_hostfiles; i++)
862: load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
1.84 markus 863: }
1.38 markus 864:
1.219 djm 865: retry:
1.229 djm 866: /* Reload these as they may have changed on cert->key downgrade */
1.280 markus 867: want_cert = sshkey_is_cert(host_key);
868: type = sshkey_type(host_key);
1.219 djm 869:
1.46 markus 870: /*
1.170 djm 871: * Check if the host key is present in the user's list of known
1.40 markus 872: * hosts or in the systemwide list.
873: */
1.229 djm 874: host_status = check_key_in_hostkeys(host_hostkeys, host_key,
875: &host_found);
876:
1.40 markus 877: /*
878: * Also perform check for the ip address, skip the check if we are
1.219 djm 879: * localhost, looking for a certificate, or the hostname was an ip
880: * address to begin with.
1.40 markus 881: */
1.229 djm 882: if (!want_cert && ip_hostkeys != NULL) {
883: ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
884: &ip_found);
1.38 markus 885: if (host_status == HOST_CHANGED &&
1.229 djm 886: (ip_status != HOST_CHANGED ||
887: (ip_found != NULL &&
1.280 markus 888: !sshkey_equal(ip_found->key, host_found->key))))
1.38 markus 889: host_ip_differ = 1;
890: } else
891: ip_status = host_status;
892:
893: switch (host_status) {
894: case HOST_OK:
895: /* The host is known and the key matches. */
1.219 djm 896: debug("Host '%.200s' is known and matches the %s host %s.",
897: host, type, want_cert ? "certificate" : "key");
1.229 djm 898: debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
899: host_found->file, host_found->line);
1.281 djm 900: if (want_cert &&
901: !check_host_cert(options.host_key_alias == NULL ?
902: hostname : options.host_key_alias, host_key))
1.219 djm 903: goto fail;
1.88 markus 904: if (options.check_host_ip && ip_status == HOST_NEW) {
1.219 djm 905: if (readonly || want_cert)
1.138 itojun 906: logit("%s host key for IP address "
1.108 markus 907: "'%.128s' not in list of known hosts.",
908: type, ip);
1.234 djm 909: else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1.160 djm 910: host_key, options.hash_known_hosts))
1.138 itojun 911: logit("Failed to add the %s host key for IP "
1.108 markus 912: "address '%.128s' to the list of known "
1.262 dtucker 913: "hosts (%.500s).", type, ip,
1.234 djm 914: user_hostfiles[0]);
1.88 markus 915: else
1.138 itojun 916: logit("Warning: Permanently added the %s host "
1.108 markus 917: "key for IP address '%.128s' to the list "
918: "of known hosts.", type, ip);
1.209 grunk 919: } else if (options.visual_host_key) {
1.259 djm 920: fp = sshkey_fingerprint(host_key,
1.254 djm 921: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 922: ra = sshkey_fingerprint(host_key,
1.254 djm 923: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 924: if (fp == NULL || ra == NULL)
925: fatal("%s: sshkey_fingerprint fail", __func__);
1.264 djm 926: logit("Host key fingerprint is %s\n%s", fp, ra);
1.238 djm 927: free(ra);
928: free(fp);
1.38 markus 929: }
1.257 djm 930: hostkey_trusted = 1;
1.38 markus 931: break;
932: case HOST_NEW:
1.197 dtucker 933: if (options.host_key_alias == NULL && port != 0 &&
934: port != SSH_DEFAULT_PORT) {
935: debug("checking without port identifier");
1.212 stevesk 936: if (check_host_key(hostname, hostaddr, 0, host_key,
1.234 djm 937: ROQUIET, user_hostfiles, num_user_hostfiles,
938: system_hostfiles, num_system_hostfiles) == 0) {
1.197 dtucker 939: debug("found matching key w/out port");
940: break;
941: }
942: }
1.219 djm 943: if (readonly || want_cert)
1.108 markus 944: goto fail;
1.38 markus 945: /* The host is new. */
1.285 djm 946: if (options.strict_host_key_checking ==
947: SSH_STRICT_HOSTKEY_YES) {
1.108 markus 948: /*
949: * User has requested strict host key checking. We
950: * will not add the host key automatically. The only
951: * alternative left is to abort.
952: */
953: error("No %s host key is known for %.200s and you "
954: "have requested strict checking.", type, host);
955: goto fail;
1.285 djm 956: } else if (options.strict_host_key_checking ==
957: SSH_STRICT_HOSTKEY_ASK) {
1.145 jakob 958: char msg1[1024], msg2[1024];
959:
1.229 djm 960: if (show_other_keys(host_hostkeys, host_key))
1.145 jakob 961: snprintf(msg1, sizeof(msg1),
1.168 djm 962: "\nbut keys of different type are already"
963: " known for this host.");
1.145 jakob 964: else
965: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 966: /* The default */
1.259 djm 967: fp = sshkey_fingerprint(host_key,
1.254 djm 968: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 969: ra = sshkey_fingerprint(host_key,
1.254 djm 970: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 971: if (fp == NULL || ra == NULL)
972: fatal("%s: sshkey_fingerprint fail", __func__);
1.145 jakob 973: msg2[0] = '\0';
974: if (options.verify_host_key_dns) {
1.153 jakob 975: if (matching_host_key_dns)
1.145 jakob 976: snprintf(msg2, sizeof(msg2),
977: "Matching host key fingerprint"
978: " found in DNS.\n");
979: else
980: snprintf(msg2, sizeof(msg2),
981: "No matching host key fingerprint"
982: " found in DNS.\n");
983: }
1.119 markus 984: snprintf(msg, sizeof(msg),
1.108 markus 985: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 986: "established%s\n"
1.209 grunk 987: "%s key fingerprint is %s.%s%s\n%s"
1.108 markus 988: "Are you sure you want to continue connecting "
1.132 markus 989: "(yes/no)? ",
1.209 grunk 990: host, ip, msg1, type, fp,
991: options.visual_host_key ? "\n" : "",
992: options.visual_host_key ? ra : "",
993: msg2);
1.238 djm 994: free(ra);
995: free(fp);
1.119 markus 996: if (!confirm(msg))
1.108 markus 997: goto fail;
1.257 djm 998: hostkey_trusted = 1; /* user explicitly confirmed */
1.38 markus 999: }
1.161 djm 1000: /*
1.285 djm 1001: * If in "new" or "off" strict mode, add the key automatically
1002: * to the local known_hosts file.
1.161 djm 1003: */
1.88 markus 1004: if (options.check_host_ip && ip_status == HOST_NEW) {
1.229 djm 1005: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1.38 markus 1006: hostp = hostline;
1.161 djm 1007: if (options.hash_known_hosts) {
1008: /* Add hash of host and IP separately */
1.234 djm 1009: r = add_host_to_hostfile(user_hostfiles[0],
1010: host, host_key, options.hash_known_hosts) &&
1011: add_host_to_hostfile(user_hostfiles[0], ip,
1.161 djm 1012: host_key, options.hash_known_hosts);
1013: } else {
1014: /* Add unhashed "host,ip" */
1.234 djm 1015: r = add_host_to_hostfile(user_hostfiles[0],
1.161 djm 1016: hostline, host_key,
1017: options.hash_known_hosts);
1018: }
1019: } else {
1.234 djm 1020: r = add_host_to_hostfile(user_hostfiles[0], host,
1021: host_key, options.hash_known_hosts);
1.38 markus 1022: hostp = host;
1.161 djm 1023: }
1.38 markus 1024:
1.161 djm 1025: if (!r)
1.138 itojun 1026: logit("Failed to add the host to the list of known "
1.234 djm 1027: "hosts (%.500s).", user_hostfiles[0]);
1.38 markus 1028: else
1.138 itojun 1029: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 1030: "list of known hosts.", hostp, type);
1.38 markus 1031: break;
1.220 djm 1032: case HOST_REVOKED:
1033: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1034: error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1035: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1036: error("The %s host key for %s is marked as revoked.", type, host);
1037: error("This could mean that a stolen key is being used to");
1038: error("impersonate this host.");
1039:
1040: /*
1041: * If strict host key checking is in use, the user will have
1042: * to edit the key manually and we can only abort.
1043: */
1.285 djm 1044: if (options.strict_host_key_checking !=
1045: SSH_STRICT_HOSTKEY_OFF) {
1.220 djm 1046: error("%s host key for %.200s was revoked and you have "
1047: "requested strict checking.", type, host);
1048: goto fail;
1049: }
1050: goto continue_unsafe;
1051:
1.38 markus 1052: case HOST_CHANGED:
1.219 djm 1053: if (want_cert) {
1054: /*
1055: * This is only a debug() since it is valid to have
1056: * CAs with wildcard DNS matches that don't match
1057: * all hosts that one might visit.
1058: */
1059: debug("Host certificate authority does not "
1.229 djm 1060: "match %s in %s:%lu", CA_MARKER,
1061: host_found->file, host_found->line);
1.219 djm 1062: goto fail;
1063: }
1.197 dtucker 1064: if (readonly == ROQUIET)
1065: goto fail;
1.38 markus 1066: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 1067: char *key_msg;
1.38 markus 1068: if (ip_status == HOST_NEW)
1.158 avsm 1069: key_msg = "is unknown";
1.38 markus 1070: else if (ip_status == HOST_OK)
1.158 avsm 1071: key_msg = "is unchanged";
1.38 markus 1072: else
1.158 avsm 1073: key_msg = "has a different value";
1.38 markus 1074: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1075: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1076: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 1077: error("The %s host key for %s has changed,", type, host);
1.208 ian 1078: error("and the key for the corresponding IP address %s", ip);
1.158 avsm 1079: error("%s. This could either mean that", key_msg);
1.38 markus 1080: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 1081: error("and its host key have changed at the same time.");
1.88 markus 1082: if (ip_status != HOST_NEW)
1.229 djm 1083: error("Offending key for IP in %s:%lu",
1084: ip_found->file, ip_found->line);
1.38 markus 1085: }
1086: /* The host key has changed. */
1.150 jakob 1087: warn_changed_key(host_key);
1.38 markus 1088: error("Add correct host key in %.100s to get rid of this message.",
1.234 djm 1089: user_hostfiles[0]);
1.280 markus 1090: error("Offending %s key in %s:%lu",
1091: sshkey_type(host_found->key),
1.229 djm 1092: host_found->file, host_found->line);
1.38 markus 1093:
1.40 markus 1094: /*
1095: * If strict host key checking is in use, the user will have
1096: * to edit the key manually and we can only abort.
1097: */
1.285 djm 1098: if (options.strict_host_key_checking !=
1099: SSH_STRICT_HOSTKEY_OFF) {
1.108 markus 1100: error("%s host key for %.200s has changed and you have "
1101: "requested strict checking.", type, host);
1102: goto fail;
1103: }
1.38 markus 1104:
1.220 djm 1105: continue_unsafe:
1.40 markus 1106: /*
1107: * If strict host key checking has not been requested, allow
1.144 djm 1108: * the connection but without MITM-able authentication or
1.194 stevesk 1109: * forwarding.
1.40 markus 1110: */
1.38 markus 1111: if (options.password_authentication) {
1.108 markus 1112: error("Password authentication is disabled to avoid "
1113: "man-in-the-middle attacks.");
1.38 markus 1114: options.password_authentication = 0;
1.210 dtucker 1115: cancelled_forwarding = 1;
1.144 djm 1116: }
1117: if (options.kbd_interactive_authentication) {
1118: error("Keyboard-interactive authentication is disabled"
1119: " to avoid man-in-the-middle attacks.");
1120: options.kbd_interactive_authentication = 0;
1121: options.challenge_response_authentication = 0;
1.210 dtucker 1122: cancelled_forwarding = 1;
1.144 djm 1123: }
1124: if (options.challenge_response_authentication) {
1125: error("Challenge/response authentication is disabled"
1126: " to avoid man-in-the-middle attacks.");
1127: options.challenge_response_authentication = 0;
1.210 dtucker 1128: cancelled_forwarding = 1;
1.38 markus 1129: }
1130: if (options.forward_agent) {
1.108 markus 1131: error("Agent forwarding is disabled to avoid "
1132: "man-in-the-middle attacks.");
1.38 markus 1133: options.forward_agent = 0;
1.210 dtucker 1134: cancelled_forwarding = 1;
1.83 markus 1135: }
1136: if (options.forward_x11) {
1.108 markus 1137: error("X11 forwarding is disabled to avoid "
1138: "man-in-the-middle attacks.");
1.83 markus 1139: options.forward_x11 = 0;
1.210 dtucker 1140: cancelled_forwarding = 1;
1.83 markus 1141: }
1.108 markus 1142: if (options.num_local_forwards > 0 ||
1143: options.num_remote_forwards > 0) {
1144: error("Port forwarding is disabled to avoid "
1145: "man-in-the-middle attacks.");
1146: options.num_local_forwards =
1.118 deraadt 1147: options.num_remote_forwards = 0;
1.210 dtucker 1148: cancelled_forwarding = 1;
1.194 stevesk 1149: }
1150: if (options.tun_open != SSH_TUNMODE_NO) {
1151: error("Tunnel forwarding is disabled to avoid "
1152: "man-in-the-middle attacks.");
1153: options.tun_open = SSH_TUNMODE_NO;
1.210 dtucker 1154: cancelled_forwarding = 1;
1.38 markus 1155: }
1.210 dtucker 1156: if (options.exit_on_forward_failure && cancelled_forwarding)
1157: fatal("Error: forwarding disabled due to host key "
1158: "check failure");
1159:
1.40 markus 1160: /*
1161: * XXX Should permit the user to change to use the new id.
1162: * This could be done by converting the host key to an
1163: * identifying sentence, tell that the host identifies itself
1.218 dtucker 1164: * by that sentence, and ask the user if he/she wishes to
1.40 markus 1165: * accept the authentication.
1166: */
1.38 markus 1167: break;
1.132 markus 1168: case HOST_FOUND:
1169: fatal("internal error");
1170: break;
1.88 markus 1171: }
1172:
1173: if (options.check_host_ip && host_status != HOST_CHANGED &&
1174: ip_status == HOST_CHANGED) {
1.119 markus 1175: snprintf(msg, sizeof(msg),
1176: "Warning: the %s host key for '%.200s' "
1177: "differs from the key for the IP address '%.128s'"
1.229 djm 1178: "\nOffending key for IP in %s:%lu",
1179: type, host, ip, ip_found->file, ip_found->line);
1.119 markus 1180: if (host_status == HOST_OK) {
1181: len = strlen(msg);
1182: snprintf(msg + len, sizeof(msg) - len,
1.229 djm 1183: "\nMatching host key in %s:%lu",
1184: host_found->file, host_found->line);
1.119 markus 1185: }
1.285 djm 1186: if (options.strict_host_key_checking ==
1187: SSH_STRICT_HOSTKEY_ASK) {
1.119 markus 1188: strlcat(msg, "\nAre you sure you want "
1189: "to continue connecting (yes/no)? ", sizeof(msg));
1190: if (!confirm(msg))
1.108 markus 1191: goto fail;
1.285 djm 1192: } else if (options.strict_host_key_checking !=
1193: SSH_STRICT_HOSTKEY_OFF) {
1194: logit("%s", msg);
1195: error("Exiting, you have requested strict checking.");
1196: goto fail;
1.119 markus 1197: } else {
1.143 djm 1198: logit("%s", msg);
1.88 markus 1199: }
1.257 djm 1200: }
1201:
1202: if (!hostkey_trusted && options.update_hostkeys) {
1203: debug("%s: hostkey not known or explicitly trusted: "
1204: "disabling UpdateHostkeys", __func__);
1205: options.update_hostkeys = 0;
1.38 markus 1206: }
1.82 provos 1207:
1.238 djm 1208: free(ip);
1209: free(host);
1.229 djm 1210: if (host_hostkeys != NULL)
1211: free_hostkeys(host_hostkeys);
1212: if (ip_hostkeys != NULL)
1213: free_hostkeys(ip_hostkeys);
1.108 markus 1214: return 0;
1215:
1216: fail:
1.220 djm 1217: if (want_cert && host_status != HOST_REVOKED) {
1.219 djm 1218: /*
1219: * No matching certificate. Downgrade cert to raw key and
1220: * search normally.
1221: */
1222: debug("No matching CA found. Retry with plain key");
1.280 markus 1223: if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1224: fatal("%s: sshkey_from_private: %s",
1225: __func__, ssh_err(r));
1226: if ((r = sshkey_drop_cert(raw_key)) != 0)
1227: fatal("Couldn't drop certificate: %s", ssh_err(r));
1.219 djm 1228: host_key = raw_key;
1229: goto retry;
1230: }
1.293 dtucker 1231: sshkey_free(raw_key);
1.238 djm 1232: free(ip);
1233: free(host);
1.229 djm 1234: if (host_hostkeys != NULL)
1235: free_hostkeys(host_hostkeys);
1236: if (ip_hostkeys != NULL)
1237: free_hostkeys(ip_hostkeys);
1.108 markus 1238: return -1;
1239: }
1240:
1.140 jakob 1241: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 1242: int
1.279 markus 1243: verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
1.108 markus 1244: {
1.267 djm 1245: u_int i;
1.250 djm 1246: int r = -1, flags = 0;
1.267 djm 1247: char valid[64], *fp = NULL, *cafp = NULL;
1.252 djm 1248: struct sshkey *plain = NULL;
1.229 djm 1249:
1.252 djm 1250: if ((fp = sshkey_fingerprint(host_key,
1.254 djm 1251: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.252 djm 1252: error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1253: r = -1;
1254: goto out;
1255: }
1256:
1.267 djm 1257: if (sshkey_is_cert(host_key)) {
1258: if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1259: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1260: error("%s: fingerprint CA key: %s",
1261: __func__, ssh_err(r));
1262: r = -1;
1263: goto out;
1264: }
1265: sshkey_format_cert_validity(host_key->cert,
1266: valid, sizeof(valid));
1267: debug("Server host certificate: %s %s, serial %llu "
1268: "ID \"%s\" CA %s %s valid %s",
1269: sshkey_ssh_name(host_key), fp,
1.269 djm 1270: (unsigned long long)host_key->cert->serial,
1271: host_key->cert->key_id,
1.267 djm 1272: sshkey_ssh_name(host_key->cert->signature_key), cafp,
1273: valid);
1274: for (i = 0; i < host_key->cert->nprincipals; i++) {
1275: debug2("Server host certificate hostname: %s",
1276: host_key->cert->principals[i]);
1277: }
1278: } else {
1.276 djm 1279: debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1.267 djm 1280: }
1.252 djm 1281:
1282: if (sshkey_equal(previous_host_key, host_key)) {
1283: debug2("%s: server host key %s %s matches cached key",
1284: __func__, sshkey_type(host_key), fp);
1285: r = 0;
1286: goto out;
1287: }
1288:
1289: /* Check in RevokedHostKeys file if specified */
1290: if (options.revoked_host_keys != NULL) {
1291: r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1292: switch (r) {
1293: case 0:
1294: break; /* not revoked */
1295: case SSH_ERR_KEY_REVOKED:
1296: error("Host key %s %s revoked by file %s",
1297: sshkey_type(host_key), fp,
1298: options.revoked_host_keys);
1299: r = -1;
1300: goto out;
1301: default:
1302: error("Error checking host key %s %s in "
1303: "revoked keys file %s: %s", sshkey_type(host_key),
1304: fp, options.revoked_host_keys, ssh_err(r));
1305: r = -1;
1306: goto out;
1307: }
1.250 djm 1308: }
1309:
1.247 djm 1310: if (options.verify_host_key_dns) {
1311: /*
1312: * XXX certs are not yet supported for DNS, so downgrade
1313: * them and try the plain key.
1314: */
1.252 djm 1315: if ((r = sshkey_from_private(host_key, &plain)) != 0)
1316: goto out;
1317: if (sshkey_is_cert(plain))
1318: sshkey_drop_cert(plain);
1.247 djm 1319: if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1320: if (flags & DNS_VERIFY_FOUND) {
1321: if (options.verify_host_key_dns == 1 &&
1322: flags & DNS_VERIFY_MATCH &&
1323: flags & DNS_VERIFY_SECURE) {
1.250 djm 1324: r = 0;
1.252 djm 1325: goto out;
1.247 djm 1326: }
1327: if (flags & DNS_VERIFY_MATCH) {
1328: matching_host_key_dns = 1;
1329: } else {
1.287 djm 1330: warn_changed_key(plain);
1331: error("Update the SSHFP RR in DNS "
1332: "with the new host key to get rid "
1333: "of this message.");
1.247 djm 1334: }
1.153 jakob 1335: }
1.140 jakob 1336: }
1337: }
1.250 djm 1338: r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1.234 djm 1339: options.user_hostfiles, options.num_user_hostfiles,
1340: options.system_hostfiles, options.num_system_hostfiles);
1.250 djm 1341:
1.252 djm 1342: out:
1343: sshkey_free(plain);
1344: free(fp);
1.267 djm 1345: free(cafp);
1.250 djm 1346: if (r == 0 && host_key != NULL) {
1.280 markus 1347: sshkey_free(previous_host_key);
1348: r = sshkey_from_private(host_key, &previous_host_key);
1.250 djm 1349: }
1350:
1351: return r;
1.51 markus 1352: }
1.70 markus 1353:
1.51 markus 1354: /*
1355: * Starts a dialog with the server, and authenticates the current user on the
1356: * server. This does not need any extra privileges. The basic connection
1357: * to the server must already have been established before this is called.
1358: * If login fails, this function prints an error and never returns.
1359: * This function does not require super-user privileges.
1360: */
1361: void
1.120 markus 1362: ssh_login(Sensitive *sensitive, const char *orighost,
1.229 djm 1363: struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1.51 markus 1364: {
1.241 djm 1365: char *host;
1.70 markus 1366: char *server_user, *local_user;
1367:
1368: local_user = xstrdup(pw->pw_name);
1369: server_user = options.user ? options.user : local_user;
1.51 markus 1370:
1371: /* Convert the user-supplied hostname into all lowercase. */
1372: host = xstrdup(orighost);
1.241 djm 1373: lowercase(host);
1.51 markus 1374:
1375: /* Exchange protocol version identification strings with the server. */
1.202 djm 1376: ssh_exchange_identification(timeout_ms);
1.51 markus 1377:
1378: /* Put the connection into non-blocking mode. */
1379: packet_set_nonblocking();
1380:
1381: /* key exchange */
1382: /* authenticate user */
1.261 dtucker 1383: debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1.276 djm 1384: ssh_kex2(host, hostaddr, port);
1385: ssh_userauth2(local_user, server_user, host, sensitive);
1.238 djm 1386: free(local_user);
1.97 markus 1387: }
1388:
1389: void
1390: ssh_put_password(char *password)
1391: {
1392: int size;
1393: char *padded;
1394:
1.99 deraadt 1395: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 1396: packet_put_cstring(password);
1.99 deraadt 1397: return;
1398: }
1.272 deraadt 1399: size = ROUNDUP(strlen(password) + 1, 32);
1.179 djm 1400: padded = xcalloc(1, size);
1.97 markus 1401: strlcpy(padded, password, size);
1402: packet_put_string(padded, size);
1.245 djm 1403: explicit_bzero(padded, size);
1.238 djm 1404: free(padded);
1.132 markus 1405: }
1406:
1407: /* print all known host keys for a given host, but skip keys of given type */
1408: static int
1.279 markus 1409: show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1.132 markus 1410: {
1.242 djm 1411: int type[] = {
1412: KEY_RSA,
1413: KEY_DSA,
1414: KEY_ECDSA,
1415: KEY_ED25519,
1.297 markus 1416: KEY_XMSS,
1.242 djm 1417: -1
1418: };
1.229 djm 1419: int i, ret = 0;
1420: char *fp, *ra;
1421: const struct hostkey_entry *found;
1.132 markus 1422:
1423: for (i = 0; type[i] != -1; i++) {
1424: if (type[i] == key->type)
1425: continue;
1.229 djm 1426: if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1.132 markus 1427: continue;
1.259 djm 1428: fp = sshkey_fingerprint(found->key,
1.254 djm 1429: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 1430: ra = sshkey_fingerprint(found->key,
1.254 djm 1431: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 1432: if (fp == NULL || ra == NULL)
1433: fatal("%s: sshkey_fingerprint fail", __func__);
1.229 djm 1434: logit("WARNING: %s key found for host %s\n"
1435: "in %s:%lu\n"
1436: "%s key fingerprint %s.",
1.300 markus 1437: sshkey_type(found->key),
1.229 djm 1438: found->host, found->file, found->line,
1.300 markus 1439: sshkey_type(found->key), fp);
1.229 djm 1440: if (options.visual_host_key)
1441: logit("%s", ra);
1.238 djm 1442: free(ra);
1443: free(fp);
1.229 djm 1444: ret = 1;
1.132 markus 1445: }
1.229 djm 1446: return ret;
1.150 jakob 1447: }
1448:
1449: static void
1.279 markus 1450: warn_changed_key(struct sshkey *host_key)
1.150 jakob 1451: {
1452: char *fp;
1453:
1.259 djm 1454: fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1.254 djm 1455: SSH_FP_DEFAULT);
1.259 djm 1456: if (fp == NULL)
1457: fatal("%s: sshkey_fingerprint fail", __func__);
1.150 jakob 1458:
1459: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1460: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1461: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1462: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1463: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.230 markus 1464: error("It is also possible that a host key has just been changed.");
1.150 jakob 1465: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1.300 markus 1466: sshkey_type(host_key), fp);
1.150 jakob 1467: error("Please contact your system administrator.");
1468:
1.238 djm 1469: free(fp);
1.171 reyk 1470: }
1471:
1472: /*
1473: * Execute a local command
1474: */
1475: int
1476: ssh_local_cmd(const char *args)
1477: {
1478: char *shell;
1479: pid_t pid;
1480: int status;
1.231 djm 1481: void (*osighand)(int);
1.171 reyk 1482:
1483: if (!options.permit_local_command ||
1484: args == NULL || !*args)
1485: return (1);
1486:
1.226 djm 1487: if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1.171 reyk 1488: shell = _PATH_BSHELL;
1489:
1.231 djm 1490: osighand = signal(SIGCHLD, SIG_DFL);
1.171 reyk 1491: pid = fork();
1492: if (pid == 0) {
1.232 djm 1493: signal(SIGPIPE, SIG_DFL);
1.171 reyk 1494: debug3("Executing %s -c \"%s\"", shell, args);
1495: execl(shell, shell, "-c", args, (char *)NULL);
1496: error("Couldn't execute %s -c \"%s\": %s",
1497: shell, args, strerror(errno));
1498: _exit(1);
1499: } else if (pid == -1)
1500: fatal("fork failed: %.100s", strerror(errno));
1501: while (waitpid(pid, &status, 0) == -1)
1502: if (errno != EINTR)
1503: fatal("Couldn't wait for child: %s", strerror(errno));
1.231 djm 1504: signal(SIGCHLD, osighand);
1.171 reyk 1505:
1506: if (!WIFEXITED(status))
1507: return (1);
1508:
1509: return (WEXITSTATUS(status));
1.266 jcs 1510: }
1511:
1512: void
1.294 djm 1513: maybe_add_key_to_agent(char *authfile, const struct sshkey *private,
1514: char *comment, char *passphrase)
1.266 jcs 1515: {
1516: int auth_sock = -1, r;
1517:
1518: if (options.add_keys_to_agent == 0)
1519: return;
1520:
1521: if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1522: debug3("no authentication agent, not adding key");
1523: return;
1524: }
1525:
1526: if (options.add_keys_to_agent == 2 &&
1527: !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1528: debug3("user denied adding this key");
1.273 dtucker 1529: close(auth_sock);
1.266 jcs 1530: return;
1531: }
1532:
1533: if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1.297 markus 1534: (options.add_keys_to_agent == 3), 0)) == 0)
1.266 jcs 1535: debug("identity added to agent: %s", authfile);
1536: else
1537: debug("could not add identity to agent: %s (%d)", authfile, r);
1.273 dtucker 1538: close(auth_sock);
1.1 deraadt 1539: }
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