Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.305
1.305 ! djm 1: /* $OpenBSD: sshconnect.c,v 1.304 2018/07/27 05:34:42 dtucker 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;
1.91 markus 70:
1.279 markus 71: static int show_other_keys(struct hostkeys *, struct sshkey *);
72: static void warn_changed_key(struct sshkey *);
1.132 markus 73:
1.239 djm 74: /* Expand a proxy command */
75: static char *
76: expand_proxy_command(const char *proxy_command, const char *user,
77: const char *host, int port)
78: {
79: char *tmp, *ret, strport[NI_MAXSERV];
80:
1.241 djm 81: snprintf(strport, sizeof strport, "%d", port);
1.239 djm 82: xasprintf(&tmp, "exec %s", proxy_command);
83: ret = percent_expand(tmp, "h", host, "p", strport,
84: "r", options.user, (char *)NULL);
85: free(tmp);
86: return ret;
87: }
88:
89: /*
90: * Connect to the given ssh server using a proxy command that passes a
91: * a connected fd back to us.
92: */
93: static int
1.286 djm 94: ssh_proxy_fdpass_connect(struct ssh *ssh, const char *host, u_short port,
1.239 djm 95: const char *proxy_command)
96: {
97: char *command_string;
98: int sp[2], sock;
99: pid_t pid;
100: char *shell;
101:
102: if ((shell = getenv("SHELL")) == NULL)
103: shell = _PATH_BSHELL;
104:
105: if (socketpair(AF_UNIX, SOCK_STREAM, 0, sp) < 0)
106: fatal("Could not create socketpair to communicate with "
107: "proxy dialer: %.100s", strerror(errno));
108:
109: command_string = expand_proxy_command(proxy_command, options.user,
110: host, port);
111: debug("Executing proxy dialer command: %.500s", command_string);
112:
113: /* Fork and execute the proxy command. */
114: if ((pid = fork()) == 0) {
115: char *argv[10];
116:
117: close(sp[1]);
118: /* Redirect stdin and stdout. */
119: if (sp[0] != 0) {
120: if (dup2(sp[0], 0) < 0)
121: perror("dup2 stdin");
122: }
123: if (sp[0] != 1) {
124: if (dup2(sp[0], 1) < 0)
125: perror("dup2 stdout");
126: }
127: if (sp[0] >= 2)
128: close(sp[0]);
129:
130: /*
131: * Stderr is left as it is so that error messages get
132: * printed on the user's terminal.
133: */
134: argv[0] = shell;
135: argv[1] = "-c";
136: argv[2] = command_string;
137: argv[3] = NULL;
138:
139: /*
140: * Execute the proxy command.
141: * Note that we gave up any extra privileges above.
142: */
143: execv(argv[0], argv);
144: perror(argv[0]);
145: exit(1);
146: }
147: /* Parent. */
148: if (pid < 0)
149: fatal("fork failed: %.100s", strerror(errno));
150: close(sp[0]);
151: free(command_string);
152:
153: if ((sock = mm_receive_fd(sp[1])) == -1)
154: fatal("proxy dialer did not pass back a connection");
1.271 markus 155: close(sp[1]);
1.239 djm 156:
157: while (waitpid(pid, NULL, 0) == -1)
158: if (errno != EINTR)
159: fatal("Couldn't wait for child: %s", strerror(errno));
160:
161: /* Set the connection file descriptors. */
1.286 djm 162: if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
163: return -1; /* ssh_packet_set_connection logs error */
1.239 djm 164:
165: return 0;
166: }
167:
1.39 deraadt 168: /*
169: * Connect to the given ssh server using a proxy command.
170: */
1.109 itojun 171: static int
1.286 djm 172: ssh_proxy_connect(struct ssh *ssh, const char *host, u_short port,
173: const char *proxy_command)
1.1 deraadt 174: {
1.239 djm 175: char *command_string;
1.38 markus 176: int pin[2], pout[2];
1.69 deraadt 177: pid_t pid;
1.239 djm 178: char *shell;
1.237 markus 179:
1.226 djm 180: if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1.201 djm 181: shell = _PATH_BSHELL;
1.38 markus 182:
183: /* Create pipes for communicating with the proxy. */
184: if (pipe(pin) < 0 || pipe(pout) < 0)
185: fatal("Could not create pipes to communicate with the proxy: %.100s",
1.118 deraadt 186: strerror(errno));
1.38 markus 187:
1.239 djm 188: command_string = expand_proxy_command(proxy_command, options.user,
189: host, port);
1.38 markus 190: debug("Executing proxy command: %.500s", command_string);
191:
192: /* Fork and execute the proxy command. */
193: if ((pid = fork()) == 0) {
194: char *argv[10];
195:
196: /* Redirect stdin and stdout. */
197: close(pin[1]);
198: if (pin[0] != 0) {
199: if (dup2(pin[0], 0) < 0)
200: perror("dup2 stdin");
201: close(pin[0]);
202: }
203: close(pout[0]);
204: if (dup2(pout[1], 1) < 0)
205: perror("dup2 stdout");
206: /* Cannot be 1 because pin allocated two descriptors. */
207: close(pout[1]);
208:
209: /* Stderr is left as it is so that error messages get
210: printed on the user's terminal. */
1.201 djm 211: argv[0] = shell;
1.38 markus 212: argv[1] = "-c";
213: argv[2] = command_string;
214: argv[3] = NULL;
215:
216: /* Execute the proxy command. Note that we gave up any
217: extra privileges above. */
1.232 djm 218: signal(SIGPIPE, SIG_DFL);
1.89 markus 219: execv(argv[0], argv);
220: perror(argv[0]);
1.38 markus 221: exit(1);
222: }
223: /* Parent. */
224: if (pid < 0)
225: fatal("fork failed: %.100s", strerror(errno));
1.135 djm 226: else
227: proxy_command_pid = pid; /* save pid to clean up later */
1.38 markus 228:
229: /* Close child side of the descriptors. */
230: close(pin[0]);
231: close(pout[1]);
232:
233: /* Free the command name. */
1.238 djm 234: free(command_string);
1.38 markus 235:
236: /* Set the connection file descriptors. */
1.286 djm 237: if (ssh_packet_set_connection(ssh, pout[0], pin[1]) == NULL)
238: return -1; /* ssh_packet_set_connection logs error */
1.1 deraadt 239:
1.110 markus 240: return 0;
1.227 djm 241: }
242:
243: void
244: ssh_kill_proxy_command(void)
245: {
246: /*
247: * Send SIGHUP to proxy command if used. We don't wait() in
248: * case it hangs and instead rely on init to reap the child
249: */
250: if (proxy_command_pid > 1)
1.228 djm 251: kill(proxy_command_pid, SIGHUP);
1.1 deraadt 252: }
253:
1.39 deraadt 254: /*
1.295 djm 255: * Search a interface address list (returned from getifaddrs(3)) for an
1.298 djm 256: * address that matches the desired address family on the specified interface.
1.295 djm 257: * Returns 0 and fills in *resultp and *rlenp on success. Returns -1 on failure.
258: */
259: static int
260: check_ifaddrs(const char *ifname, int af, const struct ifaddrs *ifaddrs,
261: struct sockaddr_storage *resultp, socklen_t *rlenp)
262: {
263: struct sockaddr_in6 *sa6;
264: struct sockaddr_in *sa;
265: struct in6_addr *v6addr;
266: const struct ifaddrs *ifa;
267: int allow_local;
268:
269: /*
270: * Prefer addresses that are not loopback or linklocal, but use them
271: * if nothing else matches.
272: */
273: for (allow_local = 0; allow_local < 2; allow_local++) {
274: for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
275: if (ifa->ifa_addr == NULL || ifa->ifa_name == NULL ||
276: (ifa->ifa_flags & IFF_UP) == 0 ||
277: ifa->ifa_addr->sa_family != af ||
278: strcmp(ifa->ifa_name, options.bind_interface) != 0)
279: continue;
280: switch (ifa->ifa_addr->sa_family) {
281: case AF_INET:
282: sa = (struct sockaddr_in *)ifa->ifa_addr;
283: if (!allow_local && sa->sin_addr.s_addr ==
284: htonl(INADDR_LOOPBACK))
285: continue;
286: if (*rlenp < sizeof(struct sockaddr_in)) {
287: error("%s: v4 addr doesn't fit",
288: __func__);
289: return -1;
290: }
291: *rlenp = sizeof(struct sockaddr_in);
292: memcpy(resultp, sa, *rlenp);
293: return 0;
294: case AF_INET6:
295: sa6 = (struct sockaddr_in6 *)ifa->ifa_addr;
296: v6addr = &sa6->sin6_addr;
297: if (!allow_local &&
298: (IN6_IS_ADDR_LINKLOCAL(v6addr) ||
299: IN6_IS_ADDR_LOOPBACK(v6addr)))
300: continue;
301: if (*rlenp < sizeof(struct sockaddr_in6)) {
302: error("%s: v6 addr doesn't fit",
303: __func__);
304: return -1;
305: }
306: *rlenp = sizeof(struct sockaddr_in6);
307: memcpy(resultp, sa6, *rlenp);
308: return 0;
309: }
310: }
311: }
312: return -1;
313: }
314:
315: /*
1.303 dtucker 316: * Creates a socket for use as the ssh connection.
1.39 deraadt 317: */
1.109 itojun 318: static int
1.302 dtucker 319: ssh_create_socket(struct addrinfo *ai)
1.1 deraadt 320: {
1.301 dtucker 321: int sock, r;
1.295 djm 322: struct sockaddr_storage bindaddr;
323: socklen_t bindaddrlen = 0;
1.246 djm 324: struct addrinfo hints, *res = NULL;
1.295 djm 325: struct ifaddrs *ifaddrs = NULL;
326: char ntop[NI_MAXHOST];
1.1 deraadt 327:
1.217 dtucker 328: sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
1.216 dtucker 329: if (sock < 0) {
1.240 djm 330: error("socket: %s", strerror(errno));
1.216 dtucker 331: return -1;
332: }
333: fcntl(sock, F_SETFD, FD_CLOEXEC);
1.105 markus 334:
335: /* Bind the socket to an alternative local IP address */
1.302 dtucker 336: if (options.bind_address == NULL && options.bind_interface == NULL)
1.105 markus 337: return sock;
338:
1.295 djm 339: if (options.bind_address != NULL) {
1.246 djm 340: memset(&hints, 0, sizeof(hints));
341: hints.ai_family = ai->ai_family;
342: hints.ai_socktype = ai->ai_socktype;
343: hints.ai_protocol = ai->ai_protocol;
344: hints.ai_flags = AI_PASSIVE;
1.295 djm 345: if ((r = getaddrinfo(options.bind_address, NULL,
346: &hints, &res)) != 0) {
1.246 djm 347: error("getaddrinfo: %s: %s", options.bind_address,
1.295 djm 348: ssh_gai_strerror(r));
349: goto fail;
350: }
1.296 dtucker 351: if (res == NULL) {
1.295 djm 352: error("getaddrinfo: no addrs");
353: goto fail;
1.296 dtucker 354: }
1.295 djm 355: if (res->ai_addrlen > sizeof(bindaddr)) {
356: error("%s: addr doesn't fit", __func__);
357: goto fail;
358: }
359: memcpy(&bindaddr, res->ai_addr, res->ai_addrlen);
360: bindaddrlen = res->ai_addrlen;
361: } else if (options.bind_interface != NULL) {
362: if ((r = getifaddrs(&ifaddrs)) != 0) {
363: error("getifaddrs: %s: %s", options.bind_interface,
364: strerror(errno));
365: goto fail;
366: }
367: bindaddrlen = sizeof(bindaddr);
368: if (check_ifaddrs(options.bind_interface, ai->ai_family,
369: ifaddrs, &bindaddr, &bindaddrlen) != 0) {
370: logit("getifaddrs: %s: no suitable addresses",
371: options.bind_interface);
372: goto fail;
1.246 djm 373: }
1.105 markus 374: }
1.295 djm 375: if ((r = getnameinfo((struct sockaddr *)&bindaddr, bindaddrlen,
376: ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST)) != 0) {
377: error("%s: getnameinfo failed: %s", __func__,
378: ssh_gai_strerror(r));
379: goto fail;
380: }
1.301 dtucker 381: if (bind(sock, (struct sockaddr *)&bindaddr, bindaddrlen) != 0) {
1.295 djm 382: error("bind %s: %s", ntop, strerror(errno));
383: goto fail;
1.38 markus 384: }
1.295 djm 385: debug("%s: bound to %s", __func__, ntop);
386: /* success */
387: goto out;
388: fail:
389: close(sock);
390: sock = -1;
391: out:
1.246 djm 392: if (res != NULL)
393: freeaddrinfo(res);
1.295 djm 394: if (ifaddrs != NULL)
395: freeifaddrs(ifaddrs);
1.38 markus 396: return sock;
1.1 deraadt 397: }
398:
1.282 djm 399: /*
400: * Wait up to *timeoutp milliseconds for fd to be readable. Updates
401: * *timeoutp with time remaining.
402: * Returns 0 if fd ready or -1 on timeout or error (see errno).
403: */
404: static int
405: waitrfd(int fd, int *timeoutp)
406: {
407: struct pollfd pfd;
408: struct timeval t_start;
409: int oerrno, r;
410:
1.288 dtucker 411: monotime_tv(&t_start);
1.282 djm 412: pfd.fd = fd;
413: pfd.events = POLLIN;
414: for (; *timeoutp >= 0;) {
415: r = poll(&pfd, 1, *timeoutp);
416: oerrno = errno;
417: ms_subtract_diff(&t_start, timeoutp);
418: errno = oerrno;
419: if (r > 0)
420: return 0;
421: else if (r == -1 && errno != EAGAIN)
422: return -1;
423: else if (r == 0)
424: break;
425: }
426: /* timeout */
427: errno = ETIMEDOUT;
428: return -1;
429: }
430:
1.141 djm 431: static int
432: timeout_connect(int sockfd, const struct sockaddr *serv_addr,
1.202 djm 433: socklen_t addrlen, int *timeoutp)
1.141 djm 434: {
1.282 djm 435: int optval = 0;
436: socklen_t optlen = sizeof(optval);
1.141 djm 437:
1.282 djm 438: /* No timeout: just do a blocking connect() */
439: if (*timeoutp <= 0)
440: return connect(sockfd, serv_addr, addrlen);
1.141 djm 441:
1.156 djm 442: set_nonblock(sockfd);
1.282 djm 443: if (connect(sockfd, serv_addr, addrlen) == 0) {
444: /* Succeeded already? */
1.156 djm 445: unset_nonblock(sockfd);
1.282 djm 446: return 0;
447: } else if (errno != EINPROGRESS)
448: return -1;
449:
450: if (waitrfd(sockfd, timeoutp) == -1)
451: return -1;
1.141 djm 452:
1.282 djm 453: /* Completed or failed */
454: if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, &optlen) == -1) {
455: debug("getsockopt: %s", strerror(errno));
456: return -1;
1.141 djm 457: }
1.282 djm 458: if (optval != 0) {
459: errno = optval;
460: return -1;
1.202 djm 461: }
1.282 djm 462: unset_nonblock(sockfd);
463: return 0;
1.141 djm 464: }
465:
1.39 deraadt 466: /*
1.49 markus 467: * Opens a TCP/IP connection to the remote server on the given host.
468: * The address of the remote host will be returned in hostaddr.
1.302 dtucker 469: * If port is 0, the default port will be used.
1.39 deraadt 470: * Connection_attempts specifies the maximum number of tries (one per
471: * second). If proxy_command is non-NULL, it specifies the command (with %h
472: * and %p substituted for host and port, respectively) to use to contact
473: * the daemon.
474: */
1.241 djm 475: static int
1.286 djm 476: ssh_connect_direct(struct ssh *ssh, const char *host, struct addrinfo *aitop,
1.241 djm 477: struct sockaddr_storage *hostaddr, u_short port, int family,
1.302 dtucker 478: int connection_attempts, int *timeout_ms, int want_keepalive)
1.1 deraadt 479: {
1.90 markus 480: int on = 1;
1.290 djm 481: int oerrno, sock = -1, attempt;
1.90 markus 482: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1.241 djm 483: struct addrinfo *ai;
1.38 markus 484:
1.302 dtucker 485: debug2("%s", __func__);
1.268 djm 486: memset(ntop, 0, sizeof(ntop));
487: memset(strport, 0, sizeof(strport));
1.38 markus 488:
1.181 markus 489: for (attempt = 0; attempt < connection_attempts; attempt++) {
1.200 markus 490: if (attempt > 0) {
491: /* Sleep a moment before retrying. */
492: sleep(1);
1.38 markus 493: debug("Trying again...");
1.200 markus 494: }
1.181 markus 495: /*
496: * Loop through addresses for this host, and try each one in
497: * sequence until the connection succeeds.
498: */
1.49 markus 499: for (ai = aitop; ai; ai = ai->ai_next) {
1.241 djm 500: if (ai->ai_family != AF_INET &&
1.290 djm 501: ai->ai_family != AF_INET6) {
502: errno = EAFNOSUPPORT;
1.49 markus 503: continue;
1.290 djm 504: }
1.49 markus 505: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
506: ntop, sizeof(ntop), strport, sizeof(strport),
507: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1.290 djm 508: oerrno = errno;
1.265 djm 509: error("%s: getnameinfo failed", __func__);
1.290 djm 510: errno = oerrno;
1.49 markus 511: continue;
512: }
513: debug("Connecting to %.200s [%.100s] port %s.",
514: host, ntop, strport);
515:
516: /* Create a socket for connecting. */
1.302 dtucker 517: sock = ssh_create_socket(ai);
1.292 stsp 518: if (sock < 0) {
1.110 markus 519: /* Any error is already output */
1.290 djm 520: errno = 0;
1.49 markus 521: continue;
1.292 stsp 522: }
1.49 markus 523:
1.141 djm 524: if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen,
1.202 djm 525: timeout_ms) >= 0) {
1.49 markus 526: /* Successful connection. */
1.102 markus 527: memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen);
1.38 markus 528: break;
1.49 markus 529: } else {
1.290 djm 530: oerrno = errno;
1.131 itojun 531: debug("connect to address %s port %s: %s",
532: ntop, strport, strerror(errno));
1.38 markus 533: close(sock);
1.181 markus 534: sock = -1;
1.290 djm 535: errno = oerrno;
1.38 markus 536: }
537: }
1.181 markus 538: if (sock != -1)
1.49 markus 539: break; /* Successful connection. */
1.38 markus 540: }
1.49 markus 541:
1.38 markus 542: /* Return failure if we didn't get a successful connection. */
1.181 markus 543: if (sock == -1) {
1.159 markus 544: error("ssh: connect to host %s port %s: %s",
1.290 djm 545: host, strport, errno == 0 ? "failure" : strerror(errno));
546: return -1;
1.130 itojun 547: }
1.38 markus 548:
549: debug("Connection established.");
1.90 markus 550:
1.155 markus 551: /* Set SO_KEEPALIVE if requested. */
1.202 djm 552: if (want_keepalive &&
1.90 markus 553: setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
554: sizeof(on)) < 0)
555: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.38 markus 556:
557: /* Set the connection. */
1.286 djm 558: if (ssh_packet_set_connection(ssh, sock, sock) == NULL)
559: return -1; /* ssh_packet_set_connection logs error */
1.1 deraadt 560:
1.286 djm 561: return 0;
1.59 markus 562: }
563:
1.241 djm 564: int
1.286 djm 565: ssh_connect(struct ssh *ssh, const char *host, struct addrinfo *addrs,
1.241 djm 566: struct sockaddr_storage *hostaddr, u_short port, int family,
1.302 dtucker 567: int connection_attempts, int *timeout_ms, int want_keepalive)
1.241 djm 568: {
569: if (options.proxy_command == NULL) {
1.286 djm 570: return ssh_connect_direct(ssh, host, addrs, hostaddr, port,
1.302 dtucker 571: family, connection_attempts, timeout_ms, want_keepalive);
1.241 djm 572: } else if (strcmp(options.proxy_command, "-") == 0) {
1.286 djm 573: if ((ssh_packet_set_connection(ssh,
574: STDIN_FILENO, STDOUT_FILENO)) == NULL)
575: return -1; /* ssh_packet_set_connection logs error */
576: return 0;
1.241 djm 577: } else if (options.proxy_use_fdpass) {
1.286 djm 578: return ssh_proxy_fdpass_connect(ssh, host, port,
1.241 djm 579: options.proxy_command);
580: }
1.286 djm 581: return ssh_proxy_connect(ssh, host, port, options.proxy_command);
1.241 djm 582: }
583:
1.235 djm 584: static void
585: send_client_banner(int connection_out, int minor1)
586: {
587: /* Send our own protocol version identification. */
1.276 djm 588: xasprintf(&client_version_string, "SSH-%d.%d-%.100s\r\n",
589: PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION);
1.270 markus 590: if (atomicio(vwrite, connection_out, client_version_string,
1.235 djm 591: strlen(client_version_string)) != strlen(client_version_string))
592: fatal("write: %.100s", strerror(errno));
593: chop(client_version_string);
594: debug("Local version string %.100s", client_version_string);
595: }
596:
1.43 markus 597: /*
1.39 deraadt 598: * Waits for the server identification string, and sends our own
599: * identification string.
600: */
1.213 andreas 601: void
1.202 djm 602: ssh_exchange_identification(int timeout_ms)
1.1 deraadt 603: {
1.38 markus 604: char buf[256], remote_version[256]; /* must be same size! */
1.165 djm 605: int remote_major, remote_minor, mismatch;
1.38 markus 606: int connection_in = packet_get_connection_in();
607: int connection_out = packet_get_connection_out();
1.185 djm 608: u_int i, n;
1.202 djm 609: size_t len;
1.282 djm 610: int rc;
1.38 markus 611:
1.275 djm 612: send_client_banner(connection_out, 0);
1.235 djm 613:
1.163 avsm 614: /* Read other side's version identification. */
1.185 djm 615: for (n = 0;;) {
1.75 markus 616: for (i = 0; i < sizeof(buf) - 1; i++) {
1.202 djm 617: if (timeout_ms > 0) {
1.282 djm 618: rc = waitrfd(connection_in, &timeout_ms);
619: if (rc == -1 && errno == ETIMEDOUT) {
1.202 djm 620: fatal("Connection timed out during "
621: "banner exchange");
1.282 djm 622: } else if (rc == -1) {
623: fatal("%s: %s",
624: __func__, strerror(errno));
1.202 djm 625: }
626: }
627:
1.270 markus 628: len = atomicio(read, connection_in, &buf[i], 1);
1.167 djm 629: if (len != 1 && errno == EPIPE)
1.202 djm 630: fatal("ssh_exchange_identification: "
631: "Connection closed by remote host");
1.163 avsm 632: else if (len != 1)
1.202 djm 633: fatal("ssh_exchange_identification: "
634: "read: %.100s", strerror(errno));
1.75 markus 635: if (buf[i] == '\r') {
636: buf[i] = '\n';
637: buf[i + 1] = 0;
638: continue; /**XXX wait for \n */
639: }
640: if (buf[i] == '\n') {
641: buf[i + 1] = 0;
642: break;
643: }
1.185 djm 644: if (++n > 65536)
1.202 djm 645: fatal("ssh_exchange_identification: "
646: "No banner received");
1.38 markus 647: }
1.75 markus 648: buf[sizeof(buf) - 1] = 0;
1.76 markus 649: if (strncmp(buf, "SSH-", 4) == 0)
1.38 markus 650: break;
1.75 markus 651: debug("ssh_exchange_identification: %s", buf);
1.38 markus 652: }
1.59 markus 653: server_version_string = xstrdup(buf);
1.38 markus 654:
1.40 markus 655: /*
656: * Check that the versions match. In future this might accept
657: * several versions and set appropriate flags to handle them.
658: */
1.59 markus 659: if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n",
660: &remote_major, &remote_minor, remote_version) != 3)
1.38 markus 661: fatal("Bad remote protocol version identification: '%.100s'", buf);
662: debug("Remote protocol version %d.%d, remote software version %.100s",
1.118 deraadt 663: remote_major, remote_minor, remote_version);
1.38 markus 664:
1.255 markus 665: active_state->compat = compat_datafellows(remote_version);
1.64 markus 666: mismatch = 0;
1.59 markus 667:
1.116 deraadt 668: switch (remote_major) {
1.276 djm 669: case 2:
670: break;
1.64 markus 671: case 1:
1.276 djm 672: if (remote_minor != 99)
1.64 markus 673: mismatch = 1;
674: break;
1.68 markus 675: default:
1.64 markus 676: mismatch = 1;
677: break;
1.38 markus 678: }
1.64 markus 679: if (mismatch)
1.38 markus 680: fatal("Protocol major versions differ: %d vs. %d",
1.275 djm 681: PROTOCOL_MAJOR_2, remote_major);
1.243 djm 682: if ((datafellows & SSH_BUG_RSASIGMD5) != 0)
683: logit("Server version \"%.100s\" uses unsafe RSA signature "
684: "scheme; disabling use of RSA keys", remote_version);
1.59 markus 685: chop(server_version_string);
1.1 deraadt 686: }
687:
1.96 markus 688: /* defaults to 'no' */
1.109 itojun 689: static int
1.112 markus 690: confirm(const char *prompt)
1.1 deraadt 691: {
1.119 markus 692: const char *msg, *again = "Please type 'yes' or 'no': ";
693: char *p;
694: int ret = -1;
1.96 markus 695:
696: if (options.batch_mode)
697: return 0;
1.119 markus 698: for (msg = prompt;;msg = again) {
699: p = read_passphrase(msg, RP_ECHO);
1.289 djm 700: if (p == NULL)
701: return 0;
702: p[strcspn(p, "\n")] = '\0';
703: if (p[0] == '\0' || strcasecmp(p, "no") == 0)
1.119 markus 704: ret = 0;
1.289 djm 705: else if (strcasecmp(p, "yes") == 0)
1.119 markus 706: ret = 1;
1.238 djm 707: free(p);
1.119 markus 708: if (ret != -1)
709: return ret;
1.1 deraadt 710: }
711: }
712:
1.219 djm 713: static int
1.305 ! djm 714: check_host_cert(const char *host, const struct sshkey *key)
1.219 djm 715: {
716: const char *reason;
1.305 ! djm 717: int r;
1.219 djm 718:
1.305 ! djm 719: if (sshkey_cert_check_authority(key, 1, 0, host, &reason) != 0) {
1.219 djm 720: error("%s", reason);
721: return 0;
722: }
1.305 ! djm 723: if (sshbuf_len(key->cert->critical) != 0) {
1.223 djm 724: error("Certificate for %s contains unsupported "
725: "critical options(s)", host);
1.219 djm 726: return 0;
727: }
1.305 ! djm 728: if ((r = sshkey_check_cert_sigtype(key,
! 729: options.ca_sign_algorithms)) != 0) {
! 730: logit("%s: certificate signature algorithm %s: %s", __func__,
! 731: (key->cert == NULL || key->cert->signature_type == NULL) ?
! 732: "(null)" : key->cert->signature_type, ssh_err(r));
! 733: return 0;
! 734: }
! 735:
1.219 djm 736: return 1;
737: }
738:
1.229 djm 739: static int
740: sockaddr_is_local(struct sockaddr *hostaddr)
741: {
742: switch (hostaddr->sa_family) {
743: case AF_INET:
744: return (ntohl(((struct sockaddr_in *)hostaddr)->
745: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
746: case AF_INET6:
747: return IN6_IS_ADDR_LOOPBACK(
748: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
749: default:
750: return 0;
751: }
752: }
753:
754: /*
755: * Prepare the hostname and ip address strings that are used to lookup
756: * host keys in known_hosts files. These may have a port number appended.
757: */
758: void
759: get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
760: u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
761: {
762: char ntop[NI_MAXHOST];
763:
764: /*
765: * We don't have the remote ip-address for connections
766: * using a proxy command
767: */
768: if (hostfile_ipaddr != NULL) {
769: if (options.proxy_command == NULL) {
770: if (getnameinfo(hostaddr, hostaddr->sa_len,
771: ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
1.259 djm 772: fatal("%s: getnameinfo failed", __func__);
1.229 djm 773: *hostfile_ipaddr = put_host_port(ntop, port);
774: } else {
775: *hostfile_ipaddr = xstrdup("<no hostip for proxy "
776: "command>");
777: }
778: }
779:
780: /*
781: * Allow the user to record the key under a different name or
782: * differentiate a non-standard port. This is useful for ssh
783: * tunneling over forwarded connections or if you run multiple
784: * sshd's on different ports on the same machine.
785: */
786: if (hostfile_hostname != NULL) {
787: if (options.host_key_alias != NULL) {
788: *hostfile_hostname = xstrdup(options.host_key_alias);
789: debug("using hostkeyalias: %s", *hostfile_hostname);
790: } else {
791: *hostfile_hostname = put_host_port(hostname, port);
792: }
793: }
794: }
795:
1.39 deraadt 796: /*
1.108 markus 797: * check whether the supplied host key is valid, return -1 if the key
1.234 djm 798: * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
1.39 deraadt 799: */
1.197 dtucker 800: #define RDRW 0
801: #define RDONLY 1
802: #define ROQUIET 2
1.109 itojun 803: static int
1.197 dtucker 804: check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
1.279 markus 805: struct sshkey *host_key, int readonly,
1.234 djm 806: char **user_hostfiles, u_int num_user_hostfiles,
807: char **system_hostfiles, u_int num_system_hostfiles)
1.1 deraadt 808: {
1.234 djm 809: HostStatus host_status;
810: HostStatus ip_status;
1.279 markus 811: struct sshkey *raw_key = NULL;
1.189 dtucker 812: char *ip = NULL, *host = NULL;
1.204 grunk 813: char hostline[1000], *hostp, *fp, *ra;
1.119 markus 814: char msg[1024];
1.234 djm 815: const char *type;
816: const struct hostkey_entry *host_found, *ip_found;
1.229 djm 817: int len, cancelled_forwarding = 0;
1.234 djm 818: int local = sockaddr_is_local(hostaddr);
1.280 markus 819: int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
1.257 djm 820: int hostkey_trusted = 0; /* Known or explicitly accepted by user */
1.229 djm 821: struct hostkeys *host_hostkeys, *ip_hostkeys;
1.234 djm 822: u_int i;
1.49 markus 823:
824: /*
825: * Force accepting of the host key for loopback/localhost. The
826: * problem is that if the home directory is NFS-mounted to multiple
827: * machines, localhost will refer to a different machine in each of
828: * them, and the user will get bogus HOST_CHANGED warnings. This
829: * essentially disables host authentication for localhost; however,
830: * this is probably not a real problem.
831: */
1.111 markus 832: if (options.no_host_authentication_for_localhost == 1 && local &&
833: options.host_key_alias == NULL) {
1.88 markus 834: debug("Forcing accepting of host key for "
835: "loopback/localhost.");
1.108 markus 836: return 0;
1.49 markus 837: }
1.42 markus 838:
839: /*
1.229 djm 840: * Prepare the hostname and address strings used for hostkey lookup.
841: * In some cases, these will have a port number appended.
1.42 markus 842: */
1.229 djm 843: get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
1.206 grunk 844:
845: /*
1.88 markus 846: * Turn off check_host_ip if the connection is to localhost, via proxy
847: * command or if we don't have a hostname to compare with
848: */
1.189 dtucker 849: if (options.check_host_ip && (local ||
850: strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1.88 markus 851: options.check_host_ip = 0;
1.86 markus 852:
1.229 djm 853: host_hostkeys = init_hostkeys();
1.234 djm 854: for (i = 0; i < num_user_hostfiles; i++)
855: load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
856: for (i = 0; i < num_system_hostfiles; i++)
857: load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
1.229 djm 858:
859: ip_hostkeys = NULL;
860: if (!want_cert && options.check_host_ip) {
861: ip_hostkeys = init_hostkeys();
1.234 djm 862: for (i = 0; i < num_user_hostfiles; i++)
863: load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
864: for (i = 0; i < num_system_hostfiles; i++)
865: load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
1.84 markus 866: }
1.38 markus 867:
1.219 djm 868: retry:
1.229 djm 869: /* Reload these as they may have changed on cert->key downgrade */
1.280 markus 870: want_cert = sshkey_is_cert(host_key);
871: type = sshkey_type(host_key);
1.219 djm 872:
1.46 markus 873: /*
1.170 djm 874: * Check if the host key is present in the user's list of known
1.40 markus 875: * hosts or in the systemwide list.
876: */
1.229 djm 877: host_status = check_key_in_hostkeys(host_hostkeys, host_key,
878: &host_found);
879:
1.40 markus 880: /*
881: * Also perform check for the ip address, skip the check if we are
1.219 djm 882: * localhost, looking for a certificate, or the hostname was an ip
883: * address to begin with.
1.40 markus 884: */
1.229 djm 885: if (!want_cert && ip_hostkeys != NULL) {
886: ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
887: &ip_found);
1.38 markus 888: if (host_status == HOST_CHANGED &&
1.229 djm 889: (ip_status != HOST_CHANGED ||
890: (ip_found != NULL &&
1.280 markus 891: !sshkey_equal(ip_found->key, host_found->key))))
1.38 markus 892: host_ip_differ = 1;
893: } else
894: ip_status = host_status;
895:
896: switch (host_status) {
897: case HOST_OK:
898: /* The host is known and the key matches. */
1.219 djm 899: debug("Host '%.200s' is known and matches the %s host %s.",
900: host, type, want_cert ? "certificate" : "key");
1.229 djm 901: debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
902: host_found->file, host_found->line);
1.281 djm 903: if (want_cert &&
904: !check_host_cert(options.host_key_alias == NULL ?
905: hostname : options.host_key_alias, host_key))
1.219 djm 906: goto fail;
1.88 markus 907: if (options.check_host_ip && ip_status == HOST_NEW) {
1.219 djm 908: if (readonly || want_cert)
1.138 itojun 909: logit("%s host key for IP address "
1.108 markus 910: "'%.128s' not in list of known hosts.",
911: type, ip);
1.234 djm 912: else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1.160 djm 913: host_key, options.hash_known_hosts))
1.138 itojun 914: logit("Failed to add the %s host key for IP "
1.108 markus 915: "address '%.128s' to the list of known "
1.262 dtucker 916: "hosts (%.500s).", type, ip,
1.234 djm 917: user_hostfiles[0]);
1.88 markus 918: else
1.138 itojun 919: logit("Warning: Permanently added the %s host "
1.108 markus 920: "key for IP address '%.128s' to the list "
921: "of known hosts.", type, ip);
1.209 grunk 922: } else if (options.visual_host_key) {
1.259 djm 923: fp = sshkey_fingerprint(host_key,
1.254 djm 924: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 925: ra = sshkey_fingerprint(host_key,
1.254 djm 926: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 927: if (fp == NULL || ra == NULL)
928: fatal("%s: sshkey_fingerprint fail", __func__);
1.264 djm 929: logit("Host key fingerprint is %s\n%s", fp, ra);
1.238 djm 930: free(ra);
931: free(fp);
1.38 markus 932: }
1.257 djm 933: hostkey_trusted = 1;
1.38 markus 934: break;
935: case HOST_NEW:
1.197 dtucker 936: if (options.host_key_alias == NULL && port != 0 &&
937: port != SSH_DEFAULT_PORT) {
938: debug("checking without port identifier");
1.212 stevesk 939: if (check_host_key(hostname, hostaddr, 0, host_key,
1.234 djm 940: ROQUIET, user_hostfiles, num_user_hostfiles,
941: system_hostfiles, num_system_hostfiles) == 0) {
1.197 dtucker 942: debug("found matching key w/out port");
943: break;
944: }
945: }
1.219 djm 946: if (readonly || want_cert)
1.108 markus 947: goto fail;
1.38 markus 948: /* The host is new. */
1.285 djm 949: if (options.strict_host_key_checking ==
950: SSH_STRICT_HOSTKEY_YES) {
1.108 markus 951: /*
952: * User has requested strict host key checking. We
953: * will not add the host key automatically. The only
954: * alternative left is to abort.
955: */
956: error("No %s host key is known for %.200s and you "
957: "have requested strict checking.", type, host);
958: goto fail;
1.285 djm 959: } else if (options.strict_host_key_checking ==
960: SSH_STRICT_HOSTKEY_ASK) {
1.145 jakob 961: char msg1[1024], msg2[1024];
962:
1.229 djm 963: if (show_other_keys(host_hostkeys, host_key))
1.145 jakob 964: snprintf(msg1, sizeof(msg1),
1.168 djm 965: "\nbut keys of different type are already"
966: " known for this host.");
1.145 jakob 967: else
968: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 969: /* The default */
1.259 djm 970: fp = sshkey_fingerprint(host_key,
1.254 djm 971: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 972: ra = sshkey_fingerprint(host_key,
1.254 djm 973: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 974: if (fp == NULL || ra == NULL)
975: fatal("%s: sshkey_fingerprint fail", __func__);
1.145 jakob 976: msg2[0] = '\0';
977: if (options.verify_host_key_dns) {
1.153 jakob 978: if (matching_host_key_dns)
1.145 jakob 979: snprintf(msg2, sizeof(msg2),
980: "Matching host key fingerprint"
981: " found in DNS.\n");
982: else
983: snprintf(msg2, sizeof(msg2),
984: "No matching host key fingerprint"
985: " found in DNS.\n");
986: }
1.119 markus 987: snprintf(msg, sizeof(msg),
1.108 markus 988: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 989: "established%s\n"
1.209 grunk 990: "%s key fingerprint is %s.%s%s\n%s"
1.108 markus 991: "Are you sure you want to continue connecting "
1.132 markus 992: "(yes/no)? ",
1.209 grunk 993: host, ip, msg1, type, fp,
994: options.visual_host_key ? "\n" : "",
995: options.visual_host_key ? ra : "",
996: msg2);
1.238 djm 997: free(ra);
998: free(fp);
1.119 markus 999: if (!confirm(msg))
1.108 markus 1000: goto fail;
1.257 djm 1001: hostkey_trusted = 1; /* user explicitly confirmed */
1.38 markus 1002: }
1.161 djm 1003: /*
1.285 djm 1004: * If in "new" or "off" strict mode, add the key automatically
1005: * to the local known_hosts file.
1.161 djm 1006: */
1.88 markus 1007: if (options.check_host_ip && ip_status == HOST_NEW) {
1.229 djm 1008: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1.38 markus 1009: hostp = hostline;
1.161 djm 1010: if (options.hash_known_hosts) {
1011: /* Add hash of host and IP separately */
1.234 djm 1012: r = add_host_to_hostfile(user_hostfiles[0],
1013: host, host_key, options.hash_known_hosts) &&
1014: add_host_to_hostfile(user_hostfiles[0], ip,
1.161 djm 1015: host_key, options.hash_known_hosts);
1016: } else {
1017: /* Add unhashed "host,ip" */
1.234 djm 1018: r = add_host_to_hostfile(user_hostfiles[0],
1.161 djm 1019: hostline, host_key,
1020: options.hash_known_hosts);
1021: }
1022: } else {
1.234 djm 1023: r = add_host_to_hostfile(user_hostfiles[0], host,
1024: host_key, options.hash_known_hosts);
1.38 markus 1025: hostp = host;
1.161 djm 1026: }
1.38 markus 1027:
1.161 djm 1028: if (!r)
1.138 itojun 1029: logit("Failed to add the host to the list of known "
1.234 djm 1030: "hosts (%.500s).", user_hostfiles[0]);
1.38 markus 1031: else
1.138 itojun 1032: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 1033: "list of known hosts.", hostp, type);
1.38 markus 1034: break;
1.220 djm 1035: case HOST_REVOKED:
1036: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1037: error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1038: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1039: error("The %s host key for %s is marked as revoked.", type, host);
1040: error("This could mean that a stolen key is being used to");
1041: error("impersonate this host.");
1042:
1043: /*
1044: * If strict host key checking is in use, the user will have
1045: * to edit the key manually and we can only abort.
1046: */
1.285 djm 1047: if (options.strict_host_key_checking !=
1048: SSH_STRICT_HOSTKEY_OFF) {
1.220 djm 1049: error("%s host key for %.200s was revoked and you have "
1050: "requested strict checking.", type, host);
1051: goto fail;
1052: }
1053: goto continue_unsafe;
1054:
1.38 markus 1055: case HOST_CHANGED:
1.219 djm 1056: if (want_cert) {
1057: /*
1058: * This is only a debug() since it is valid to have
1059: * CAs with wildcard DNS matches that don't match
1060: * all hosts that one might visit.
1061: */
1062: debug("Host certificate authority does not "
1.229 djm 1063: "match %s in %s:%lu", CA_MARKER,
1064: host_found->file, host_found->line);
1.219 djm 1065: goto fail;
1066: }
1.197 dtucker 1067: if (readonly == ROQUIET)
1068: goto fail;
1.38 markus 1069: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 1070: char *key_msg;
1.38 markus 1071: if (ip_status == HOST_NEW)
1.158 avsm 1072: key_msg = "is unknown";
1.38 markus 1073: else if (ip_status == HOST_OK)
1.158 avsm 1074: key_msg = "is unchanged";
1.38 markus 1075: else
1.158 avsm 1076: key_msg = "has a different value";
1.38 markus 1077: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1078: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1079: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 1080: error("The %s host key for %s has changed,", type, host);
1.208 ian 1081: error("and the key for the corresponding IP address %s", ip);
1.158 avsm 1082: error("%s. This could either mean that", key_msg);
1.38 markus 1083: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 1084: error("and its host key have changed at the same time.");
1.88 markus 1085: if (ip_status != HOST_NEW)
1.229 djm 1086: error("Offending key for IP in %s:%lu",
1087: ip_found->file, ip_found->line);
1.38 markus 1088: }
1089: /* The host key has changed. */
1.150 jakob 1090: warn_changed_key(host_key);
1.38 markus 1091: error("Add correct host key in %.100s to get rid of this message.",
1.234 djm 1092: user_hostfiles[0]);
1.280 markus 1093: error("Offending %s key in %s:%lu",
1094: sshkey_type(host_found->key),
1.229 djm 1095: host_found->file, host_found->line);
1.38 markus 1096:
1.40 markus 1097: /*
1098: * If strict host key checking is in use, the user will have
1099: * to edit the key manually and we can only abort.
1100: */
1.285 djm 1101: if (options.strict_host_key_checking !=
1102: SSH_STRICT_HOSTKEY_OFF) {
1.108 markus 1103: error("%s host key for %.200s has changed and you have "
1104: "requested strict checking.", type, host);
1105: goto fail;
1106: }
1.38 markus 1107:
1.220 djm 1108: continue_unsafe:
1.40 markus 1109: /*
1110: * If strict host key checking has not been requested, allow
1.144 djm 1111: * the connection but without MITM-able authentication or
1.194 stevesk 1112: * forwarding.
1.40 markus 1113: */
1.38 markus 1114: if (options.password_authentication) {
1.108 markus 1115: error("Password authentication is disabled to avoid "
1116: "man-in-the-middle attacks.");
1.38 markus 1117: options.password_authentication = 0;
1.210 dtucker 1118: cancelled_forwarding = 1;
1.144 djm 1119: }
1120: if (options.kbd_interactive_authentication) {
1121: error("Keyboard-interactive authentication is disabled"
1122: " to avoid man-in-the-middle attacks.");
1123: options.kbd_interactive_authentication = 0;
1124: options.challenge_response_authentication = 0;
1.210 dtucker 1125: cancelled_forwarding = 1;
1.144 djm 1126: }
1127: if (options.challenge_response_authentication) {
1128: error("Challenge/response authentication is disabled"
1129: " to avoid man-in-the-middle attacks.");
1130: options.challenge_response_authentication = 0;
1.210 dtucker 1131: cancelled_forwarding = 1;
1.38 markus 1132: }
1133: if (options.forward_agent) {
1.108 markus 1134: error("Agent forwarding is disabled to avoid "
1135: "man-in-the-middle attacks.");
1.38 markus 1136: options.forward_agent = 0;
1.210 dtucker 1137: cancelled_forwarding = 1;
1.83 markus 1138: }
1139: if (options.forward_x11) {
1.108 markus 1140: error("X11 forwarding is disabled to avoid "
1141: "man-in-the-middle attacks.");
1.83 markus 1142: options.forward_x11 = 0;
1.210 dtucker 1143: cancelled_forwarding = 1;
1.83 markus 1144: }
1.108 markus 1145: if (options.num_local_forwards > 0 ||
1146: options.num_remote_forwards > 0) {
1147: error("Port forwarding is disabled to avoid "
1148: "man-in-the-middle attacks.");
1149: options.num_local_forwards =
1.118 deraadt 1150: options.num_remote_forwards = 0;
1.210 dtucker 1151: cancelled_forwarding = 1;
1.194 stevesk 1152: }
1153: if (options.tun_open != SSH_TUNMODE_NO) {
1154: error("Tunnel forwarding is disabled to avoid "
1155: "man-in-the-middle attacks.");
1156: options.tun_open = SSH_TUNMODE_NO;
1.210 dtucker 1157: cancelled_forwarding = 1;
1.38 markus 1158: }
1.210 dtucker 1159: if (options.exit_on_forward_failure && cancelled_forwarding)
1160: fatal("Error: forwarding disabled due to host key "
1161: "check failure");
1162:
1.40 markus 1163: /*
1164: * XXX Should permit the user to change to use the new id.
1165: * This could be done by converting the host key to an
1166: * identifying sentence, tell that the host identifies itself
1.218 dtucker 1167: * by that sentence, and ask the user if he/she wishes to
1.40 markus 1168: * accept the authentication.
1169: */
1.38 markus 1170: break;
1.132 markus 1171: case HOST_FOUND:
1172: fatal("internal error");
1173: break;
1.88 markus 1174: }
1175:
1176: if (options.check_host_ip && host_status != HOST_CHANGED &&
1177: ip_status == HOST_CHANGED) {
1.119 markus 1178: snprintf(msg, sizeof(msg),
1179: "Warning: the %s host key for '%.200s' "
1180: "differs from the key for the IP address '%.128s'"
1.229 djm 1181: "\nOffending key for IP in %s:%lu",
1182: type, host, ip, ip_found->file, ip_found->line);
1.119 markus 1183: if (host_status == HOST_OK) {
1184: len = strlen(msg);
1185: snprintf(msg + len, sizeof(msg) - len,
1.229 djm 1186: "\nMatching host key in %s:%lu",
1187: host_found->file, host_found->line);
1.119 markus 1188: }
1.285 djm 1189: if (options.strict_host_key_checking ==
1190: SSH_STRICT_HOSTKEY_ASK) {
1.119 markus 1191: strlcat(msg, "\nAre you sure you want "
1192: "to continue connecting (yes/no)? ", sizeof(msg));
1193: if (!confirm(msg))
1.108 markus 1194: goto fail;
1.285 djm 1195: } else if (options.strict_host_key_checking !=
1196: SSH_STRICT_HOSTKEY_OFF) {
1197: logit("%s", msg);
1198: error("Exiting, you have requested strict checking.");
1199: goto fail;
1.119 markus 1200: } else {
1.143 djm 1201: logit("%s", msg);
1.88 markus 1202: }
1.257 djm 1203: }
1204:
1205: if (!hostkey_trusted && options.update_hostkeys) {
1206: debug("%s: hostkey not known or explicitly trusted: "
1207: "disabling UpdateHostkeys", __func__);
1208: options.update_hostkeys = 0;
1.38 markus 1209: }
1.82 provos 1210:
1.238 djm 1211: free(ip);
1212: free(host);
1.229 djm 1213: if (host_hostkeys != NULL)
1214: free_hostkeys(host_hostkeys);
1215: if (ip_hostkeys != NULL)
1216: free_hostkeys(ip_hostkeys);
1.108 markus 1217: return 0;
1218:
1219: fail:
1.220 djm 1220: if (want_cert && host_status != HOST_REVOKED) {
1.219 djm 1221: /*
1222: * No matching certificate. Downgrade cert to raw key and
1223: * search normally.
1224: */
1225: debug("No matching CA found. Retry with plain key");
1.280 markus 1226: if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1227: fatal("%s: sshkey_from_private: %s",
1228: __func__, ssh_err(r));
1229: if ((r = sshkey_drop_cert(raw_key)) != 0)
1230: fatal("Couldn't drop certificate: %s", ssh_err(r));
1.219 djm 1231: host_key = raw_key;
1232: goto retry;
1233: }
1.293 dtucker 1234: sshkey_free(raw_key);
1.238 djm 1235: free(ip);
1236: free(host);
1.229 djm 1237: if (host_hostkeys != NULL)
1238: free_hostkeys(host_hostkeys);
1239: if (ip_hostkeys != NULL)
1240: free_hostkeys(ip_hostkeys);
1.108 markus 1241: return -1;
1242: }
1243:
1.140 jakob 1244: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 1245: int
1.279 markus 1246: verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
1.108 markus 1247: {
1.267 djm 1248: u_int i;
1.250 djm 1249: int r = -1, flags = 0;
1.267 djm 1250: char valid[64], *fp = NULL, *cafp = NULL;
1.252 djm 1251: struct sshkey *plain = NULL;
1.229 djm 1252:
1.252 djm 1253: if ((fp = sshkey_fingerprint(host_key,
1.254 djm 1254: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.252 djm 1255: error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1256: r = -1;
1257: goto out;
1258: }
1259:
1.267 djm 1260: if (sshkey_is_cert(host_key)) {
1261: if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1262: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1263: error("%s: fingerprint CA key: %s",
1264: __func__, ssh_err(r));
1265: r = -1;
1266: goto out;
1267: }
1268: sshkey_format_cert_validity(host_key->cert,
1269: valid, sizeof(valid));
1270: debug("Server host certificate: %s %s, serial %llu "
1271: "ID \"%s\" CA %s %s valid %s",
1272: sshkey_ssh_name(host_key), fp,
1.269 djm 1273: (unsigned long long)host_key->cert->serial,
1274: host_key->cert->key_id,
1.267 djm 1275: sshkey_ssh_name(host_key->cert->signature_key), cafp,
1276: valid);
1277: for (i = 0; i < host_key->cert->nprincipals; i++) {
1278: debug2("Server host certificate hostname: %s",
1279: host_key->cert->principals[i]);
1280: }
1281: } else {
1.276 djm 1282: debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1.267 djm 1283: }
1.252 djm 1284:
1285: if (sshkey_equal(previous_host_key, host_key)) {
1286: debug2("%s: server host key %s %s matches cached key",
1287: __func__, sshkey_type(host_key), fp);
1288: r = 0;
1289: goto out;
1290: }
1291:
1292: /* Check in RevokedHostKeys file if specified */
1293: if (options.revoked_host_keys != NULL) {
1294: r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1295: switch (r) {
1296: case 0:
1297: break; /* not revoked */
1298: case SSH_ERR_KEY_REVOKED:
1299: error("Host key %s %s revoked by file %s",
1300: sshkey_type(host_key), fp,
1301: options.revoked_host_keys);
1302: r = -1;
1303: goto out;
1304: default:
1305: error("Error checking host key %s %s in "
1306: "revoked keys file %s: %s", sshkey_type(host_key),
1307: fp, options.revoked_host_keys, ssh_err(r));
1308: r = -1;
1309: goto out;
1310: }
1.250 djm 1311: }
1312:
1.247 djm 1313: if (options.verify_host_key_dns) {
1314: /*
1315: * XXX certs are not yet supported for DNS, so downgrade
1316: * them and try the plain key.
1317: */
1.252 djm 1318: if ((r = sshkey_from_private(host_key, &plain)) != 0)
1319: goto out;
1320: if (sshkey_is_cert(plain))
1321: sshkey_drop_cert(plain);
1.247 djm 1322: if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1323: if (flags & DNS_VERIFY_FOUND) {
1324: if (options.verify_host_key_dns == 1 &&
1325: flags & DNS_VERIFY_MATCH &&
1326: flags & DNS_VERIFY_SECURE) {
1.250 djm 1327: r = 0;
1.252 djm 1328: goto out;
1.247 djm 1329: }
1330: if (flags & DNS_VERIFY_MATCH) {
1331: matching_host_key_dns = 1;
1332: } else {
1.287 djm 1333: warn_changed_key(plain);
1334: error("Update the SSHFP RR in DNS "
1335: "with the new host key to get rid "
1336: "of this message.");
1.247 djm 1337: }
1.153 jakob 1338: }
1.140 jakob 1339: }
1340: }
1.250 djm 1341: r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1.234 djm 1342: options.user_hostfiles, options.num_user_hostfiles,
1343: options.system_hostfiles, options.num_system_hostfiles);
1.250 djm 1344:
1.252 djm 1345: out:
1346: sshkey_free(plain);
1347: free(fp);
1.267 djm 1348: free(cafp);
1.250 djm 1349: if (r == 0 && host_key != NULL) {
1.280 markus 1350: sshkey_free(previous_host_key);
1351: r = sshkey_from_private(host_key, &previous_host_key);
1.250 djm 1352: }
1353:
1354: return r;
1.51 markus 1355: }
1.70 markus 1356:
1.51 markus 1357: /*
1358: * Starts a dialog with the server, and authenticates the current user on the
1359: * server. This does not need any extra privileges. The basic connection
1360: * to the server must already have been established before this is called.
1361: * If login fails, this function prints an error and never returns.
1362: * This function does not require super-user privileges.
1363: */
1364: void
1.120 markus 1365: ssh_login(Sensitive *sensitive, const char *orighost,
1.229 djm 1366: struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1.51 markus 1367: {
1.241 djm 1368: char *host;
1.70 markus 1369: char *server_user, *local_user;
1370:
1371: local_user = xstrdup(pw->pw_name);
1372: server_user = options.user ? options.user : local_user;
1.51 markus 1373:
1374: /* Convert the user-supplied hostname into all lowercase. */
1375: host = xstrdup(orighost);
1.241 djm 1376: lowercase(host);
1.51 markus 1377:
1378: /* Exchange protocol version identification strings with the server. */
1.202 djm 1379: ssh_exchange_identification(timeout_ms);
1.51 markus 1380:
1381: /* Put the connection into non-blocking mode. */
1382: packet_set_nonblocking();
1383:
1384: /* key exchange */
1385: /* authenticate user */
1.261 dtucker 1386: debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1.276 djm 1387: ssh_kex2(host, hostaddr, port);
1388: ssh_userauth2(local_user, server_user, host, sensitive);
1.238 djm 1389: free(local_user);
1.97 markus 1390: }
1391:
1392: void
1393: ssh_put_password(char *password)
1394: {
1395: int size;
1396: char *padded;
1397:
1.99 deraadt 1398: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 1399: packet_put_cstring(password);
1.99 deraadt 1400: return;
1401: }
1.272 deraadt 1402: size = ROUNDUP(strlen(password) + 1, 32);
1.179 djm 1403: padded = xcalloc(1, size);
1.97 markus 1404: strlcpy(padded, password, size);
1405: packet_put_string(padded, size);
1.245 djm 1406: explicit_bzero(padded, size);
1.238 djm 1407: free(padded);
1.132 markus 1408: }
1409:
1410: /* print all known host keys for a given host, but skip keys of given type */
1411: static int
1.279 markus 1412: show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1.132 markus 1413: {
1.242 djm 1414: int type[] = {
1415: KEY_RSA,
1416: KEY_DSA,
1417: KEY_ECDSA,
1418: KEY_ED25519,
1.297 markus 1419: KEY_XMSS,
1.242 djm 1420: -1
1421: };
1.229 djm 1422: int i, ret = 0;
1423: char *fp, *ra;
1424: const struct hostkey_entry *found;
1.132 markus 1425:
1426: for (i = 0; type[i] != -1; i++) {
1427: if (type[i] == key->type)
1428: continue;
1.229 djm 1429: if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1.132 markus 1430: continue;
1.259 djm 1431: fp = sshkey_fingerprint(found->key,
1.254 djm 1432: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 1433: ra = sshkey_fingerprint(found->key,
1.254 djm 1434: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 1435: if (fp == NULL || ra == NULL)
1436: fatal("%s: sshkey_fingerprint fail", __func__);
1.229 djm 1437: logit("WARNING: %s key found for host %s\n"
1438: "in %s:%lu\n"
1439: "%s key fingerprint %s.",
1.300 markus 1440: sshkey_type(found->key),
1.229 djm 1441: found->host, found->file, found->line,
1.300 markus 1442: sshkey_type(found->key), fp);
1.229 djm 1443: if (options.visual_host_key)
1444: logit("%s", ra);
1.238 djm 1445: free(ra);
1446: free(fp);
1.229 djm 1447: ret = 1;
1.132 markus 1448: }
1.229 djm 1449: return ret;
1.150 jakob 1450: }
1451:
1452: static void
1.279 markus 1453: warn_changed_key(struct sshkey *host_key)
1.150 jakob 1454: {
1455: char *fp;
1456:
1.259 djm 1457: fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1.254 djm 1458: SSH_FP_DEFAULT);
1.259 djm 1459: if (fp == NULL)
1460: fatal("%s: sshkey_fingerprint fail", __func__);
1.150 jakob 1461:
1462: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1463: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1464: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1465: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1466: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.230 markus 1467: error("It is also possible that a host key has just been changed.");
1.150 jakob 1468: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1.300 markus 1469: sshkey_type(host_key), fp);
1.150 jakob 1470: error("Please contact your system administrator.");
1471:
1.238 djm 1472: free(fp);
1.171 reyk 1473: }
1474:
1475: /*
1476: * Execute a local command
1477: */
1478: int
1479: ssh_local_cmd(const char *args)
1480: {
1481: char *shell;
1482: pid_t pid;
1483: int status;
1.231 djm 1484: void (*osighand)(int);
1.171 reyk 1485:
1486: if (!options.permit_local_command ||
1487: args == NULL || !*args)
1488: return (1);
1489:
1.226 djm 1490: if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1.171 reyk 1491: shell = _PATH_BSHELL;
1492:
1.231 djm 1493: osighand = signal(SIGCHLD, SIG_DFL);
1.171 reyk 1494: pid = fork();
1495: if (pid == 0) {
1.232 djm 1496: signal(SIGPIPE, SIG_DFL);
1.171 reyk 1497: debug3("Executing %s -c \"%s\"", shell, args);
1498: execl(shell, shell, "-c", args, (char *)NULL);
1499: error("Couldn't execute %s -c \"%s\": %s",
1500: shell, args, strerror(errno));
1501: _exit(1);
1502: } else if (pid == -1)
1503: fatal("fork failed: %.100s", strerror(errno));
1504: while (waitpid(pid, &status, 0) == -1)
1505: if (errno != EINTR)
1506: fatal("Couldn't wait for child: %s", strerror(errno));
1.231 djm 1507: signal(SIGCHLD, osighand);
1.171 reyk 1508:
1509: if (!WIFEXITED(status))
1510: return (1);
1511:
1512: return (WEXITSTATUS(status));
1.266 jcs 1513: }
1514:
1515: void
1.294 djm 1516: maybe_add_key_to_agent(char *authfile, const struct sshkey *private,
1517: char *comment, char *passphrase)
1.266 jcs 1518: {
1519: int auth_sock = -1, r;
1520:
1521: if (options.add_keys_to_agent == 0)
1522: return;
1523:
1524: if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1525: debug3("no authentication agent, not adding key");
1526: return;
1527: }
1528:
1529: if (options.add_keys_to_agent == 2 &&
1530: !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1531: debug3("user denied adding this key");
1.273 dtucker 1532: close(auth_sock);
1.266 jcs 1533: return;
1534: }
1535:
1536: if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1.297 markus 1537: (options.add_keys_to_agent == 3), 0)) == 0)
1.266 jcs 1538: debug("identity added to agent: %s", authfile);
1539: else
1540: debug("could not add identity to agent: %s (%d)", authfile, r);
1.273 dtucker 1541: close(auth_sock);
1.1 deraadt 1542: }
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