Annotation of src/usr.bin/ssh/sshconnect.c, Revision 1.304
1.304 ! dtucker 1: /* $OpenBSD: sshconnect.c,v 1.303 2018/07/19 23:03:16 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
1.279 markus 714: check_host_cert(const char *host, const struct sshkey *host_key)
1.219 djm 715: {
716: const char *reason;
717:
1.300 markus 718: if (sshkey_cert_check_authority(host_key, 1, 0, host, &reason) != 0) {
1.219 djm 719: error("%s", reason);
720: return 0;
721: }
1.299 markus 722: if (sshbuf_len(host_key->cert->critical) != 0) {
1.223 djm 723: error("Certificate for %s contains unsupported "
724: "critical options(s)", host);
1.219 djm 725: return 0;
726: }
727: return 1;
728: }
729:
1.229 djm 730: static int
731: sockaddr_is_local(struct sockaddr *hostaddr)
732: {
733: switch (hostaddr->sa_family) {
734: case AF_INET:
735: return (ntohl(((struct sockaddr_in *)hostaddr)->
736: sin_addr.s_addr) >> 24) == IN_LOOPBACKNET;
737: case AF_INET6:
738: return IN6_IS_ADDR_LOOPBACK(
739: &(((struct sockaddr_in6 *)hostaddr)->sin6_addr));
740: default:
741: return 0;
742: }
743: }
744:
745: /*
746: * Prepare the hostname and ip address strings that are used to lookup
747: * host keys in known_hosts files. These may have a port number appended.
748: */
749: void
750: get_hostfile_hostname_ipaddr(char *hostname, struct sockaddr *hostaddr,
751: u_short port, char **hostfile_hostname, char **hostfile_ipaddr)
752: {
753: char ntop[NI_MAXHOST];
754:
755: /*
756: * We don't have the remote ip-address for connections
757: * using a proxy command
758: */
759: if (hostfile_ipaddr != NULL) {
760: if (options.proxy_command == NULL) {
761: if (getnameinfo(hostaddr, hostaddr->sa_len,
762: ntop, sizeof(ntop), NULL, 0, NI_NUMERICHOST) != 0)
1.259 djm 763: fatal("%s: getnameinfo failed", __func__);
1.229 djm 764: *hostfile_ipaddr = put_host_port(ntop, port);
765: } else {
766: *hostfile_ipaddr = xstrdup("<no hostip for proxy "
767: "command>");
768: }
769: }
770:
771: /*
772: * Allow the user to record the key under a different name or
773: * differentiate a non-standard port. This is useful for ssh
774: * tunneling over forwarded connections or if you run multiple
775: * sshd's on different ports on the same machine.
776: */
777: if (hostfile_hostname != NULL) {
778: if (options.host_key_alias != NULL) {
779: *hostfile_hostname = xstrdup(options.host_key_alias);
780: debug("using hostkeyalias: %s", *hostfile_hostname);
781: } else {
782: *hostfile_hostname = put_host_port(hostname, port);
783: }
784: }
785: }
786:
1.39 deraadt 787: /*
1.108 markus 788: * check whether the supplied host key is valid, return -1 if the key
1.234 djm 789: * is not valid. user_hostfile[0] will not be updated if 'readonly' is true.
1.39 deraadt 790: */
1.197 dtucker 791: #define RDRW 0
792: #define RDONLY 1
793: #define ROQUIET 2
1.109 itojun 794: static int
1.197 dtucker 795: check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port,
1.279 markus 796: struct sshkey *host_key, int readonly,
1.234 djm 797: char **user_hostfiles, u_int num_user_hostfiles,
798: char **system_hostfiles, u_int num_system_hostfiles)
1.1 deraadt 799: {
1.234 djm 800: HostStatus host_status;
801: HostStatus ip_status;
1.279 markus 802: struct sshkey *raw_key = NULL;
1.189 dtucker 803: char *ip = NULL, *host = NULL;
1.204 grunk 804: char hostline[1000], *hostp, *fp, *ra;
1.119 markus 805: char msg[1024];
1.234 djm 806: const char *type;
807: const struct hostkey_entry *host_found, *ip_found;
1.229 djm 808: int len, cancelled_forwarding = 0;
1.234 djm 809: int local = sockaddr_is_local(hostaddr);
1.280 markus 810: int r, want_cert = sshkey_is_cert(host_key), host_ip_differ = 0;
1.257 djm 811: int hostkey_trusted = 0; /* Known or explicitly accepted by user */
1.229 djm 812: struct hostkeys *host_hostkeys, *ip_hostkeys;
1.234 djm 813: u_int i;
1.49 markus 814:
815: /*
816: * Force accepting of the host key for loopback/localhost. The
817: * problem is that if the home directory is NFS-mounted to multiple
818: * machines, localhost will refer to a different machine in each of
819: * them, and the user will get bogus HOST_CHANGED warnings. This
820: * essentially disables host authentication for localhost; however,
821: * this is probably not a real problem.
822: */
1.111 markus 823: if (options.no_host_authentication_for_localhost == 1 && local &&
824: options.host_key_alias == NULL) {
1.88 markus 825: debug("Forcing accepting of host key for "
826: "loopback/localhost.");
1.108 markus 827: return 0;
1.49 markus 828: }
1.42 markus 829:
830: /*
1.229 djm 831: * Prepare the hostname and address strings used for hostkey lookup.
832: * In some cases, these will have a port number appended.
1.42 markus 833: */
1.229 djm 834: get_hostfile_hostname_ipaddr(hostname, hostaddr, port, &host, &ip);
1.206 grunk 835:
836: /*
1.88 markus 837: * Turn off check_host_ip if the connection is to localhost, via proxy
838: * command or if we don't have a hostname to compare with
839: */
1.189 dtucker 840: if (options.check_host_ip && (local ||
841: strcmp(hostname, ip) == 0 || options.proxy_command != NULL))
1.88 markus 842: options.check_host_ip = 0;
1.86 markus 843:
1.229 djm 844: host_hostkeys = init_hostkeys();
1.234 djm 845: for (i = 0; i < num_user_hostfiles; i++)
846: load_hostkeys(host_hostkeys, host, user_hostfiles[i]);
847: for (i = 0; i < num_system_hostfiles; i++)
848: load_hostkeys(host_hostkeys, host, system_hostfiles[i]);
1.229 djm 849:
850: ip_hostkeys = NULL;
851: if (!want_cert && options.check_host_ip) {
852: ip_hostkeys = init_hostkeys();
1.234 djm 853: for (i = 0; i < num_user_hostfiles; i++)
854: load_hostkeys(ip_hostkeys, ip, user_hostfiles[i]);
855: for (i = 0; i < num_system_hostfiles; i++)
856: load_hostkeys(ip_hostkeys, ip, system_hostfiles[i]);
1.84 markus 857: }
1.38 markus 858:
1.219 djm 859: retry:
1.229 djm 860: /* Reload these as they may have changed on cert->key downgrade */
1.280 markus 861: want_cert = sshkey_is_cert(host_key);
862: type = sshkey_type(host_key);
1.219 djm 863:
1.46 markus 864: /*
1.170 djm 865: * Check if the host key is present in the user's list of known
1.40 markus 866: * hosts or in the systemwide list.
867: */
1.229 djm 868: host_status = check_key_in_hostkeys(host_hostkeys, host_key,
869: &host_found);
870:
1.40 markus 871: /*
872: * Also perform check for the ip address, skip the check if we are
1.219 djm 873: * localhost, looking for a certificate, or the hostname was an ip
874: * address to begin with.
1.40 markus 875: */
1.229 djm 876: if (!want_cert && ip_hostkeys != NULL) {
877: ip_status = check_key_in_hostkeys(ip_hostkeys, host_key,
878: &ip_found);
1.38 markus 879: if (host_status == HOST_CHANGED &&
1.229 djm 880: (ip_status != HOST_CHANGED ||
881: (ip_found != NULL &&
1.280 markus 882: !sshkey_equal(ip_found->key, host_found->key))))
1.38 markus 883: host_ip_differ = 1;
884: } else
885: ip_status = host_status;
886:
887: switch (host_status) {
888: case HOST_OK:
889: /* The host is known and the key matches. */
1.219 djm 890: debug("Host '%.200s' is known and matches the %s host %s.",
891: host, type, want_cert ? "certificate" : "key");
1.229 djm 892: debug("Found %s in %s:%lu", want_cert ? "CA key" : "key",
893: host_found->file, host_found->line);
1.281 djm 894: if (want_cert &&
895: !check_host_cert(options.host_key_alias == NULL ?
896: hostname : options.host_key_alias, host_key))
1.219 djm 897: goto fail;
1.88 markus 898: if (options.check_host_ip && ip_status == HOST_NEW) {
1.219 djm 899: if (readonly || want_cert)
1.138 itojun 900: logit("%s host key for IP address "
1.108 markus 901: "'%.128s' not in list of known hosts.",
902: type, ip);
1.234 djm 903: else if (!add_host_to_hostfile(user_hostfiles[0], ip,
1.160 djm 904: host_key, options.hash_known_hosts))
1.138 itojun 905: logit("Failed to add the %s host key for IP "
1.108 markus 906: "address '%.128s' to the list of known "
1.262 dtucker 907: "hosts (%.500s).", type, ip,
1.234 djm 908: user_hostfiles[0]);
1.88 markus 909: else
1.138 itojun 910: logit("Warning: Permanently added the %s host "
1.108 markus 911: "key for IP address '%.128s' to the list "
912: "of known hosts.", type, ip);
1.209 grunk 913: } else if (options.visual_host_key) {
1.259 djm 914: fp = sshkey_fingerprint(host_key,
1.254 djm 915: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 916: ra = sshkey_fingerprint(host_key,
1.254 djm 917: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 918: if (fp == NULL || ra == NULL)
919: fatal("%s: sshkey_fingerprint fail", __func__);
1.264 djm 920: logit("Host key fingerprint is %s\n%s", fp, ra);
1.238 djm 921: free(ra);
922: free(fp);
1.38 markus 923: }
1.257 djm 924: hostkey_trusted = 1;
1.38 markus 925: break;
926: case HOST_NEW:
1.197 dtucker 927: if (options.host_key_alias == NULL && port != 0 &&
928: port != SSH_DEFAULT_PORT) {
929: debug("checking without port identifier");
1.212 stevesk 930: if (check_host_key(hostname, hostaddr, 0, host_key,
1.234 djm 931: ROQUIET, user_hostfiles, num_user_hostfiles,
932: system_hostfiles, num_system_hostfiles) == 0) {
1.197 dtucker 933: debug("found matching key w/out port");
934: break;
935: }
936: }
1.219 djm 937: if (readonly || want_cert)
1.108 markus 938: goto fail;
1.38 markus 939: /* The host is new. */
1.285 djm 940: if (options.strict_host_key_checking ==
941: SSH_STRICT_HOSTKEY_YES) {
1.108 markus 942: /*
943: * User has requested strict host key checking. We
944: * will not add the host key automatically. The only
945: * alternative left is to abort.
946: */
947: error("No %s host key is known for %.200s and you "
948: "have requested strict checking.", type, host);
949: goto fail;
1.285 djm 950: } else if (options.strict_host_key_checking ==
951: SSH_STRICT_HOSTKEY_ASK) {
1.145 jakob 952: char msg1[1024], msg2[1024];
953:
1.229 djm 954: if (show_other_keys(host_hostkeys, host_key))
1.145 jakob 955: snprintf(msg1, sizeof(msg1),
1.168 djm 956: "\nbut keys of different type are already"
957: " known for this host.");
1.145 jakob 958: else
959: snprintf(msg1, sizeof(msg1), ".");
1.38 markus 960: /* The default */
1.259 djm 961: fp = sshkey_fingerprint(host_key,
1.254 djm 962: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 963: ra = sshkey_fingerprint(host_key,
1.254 djm 964: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 965: if (fp == NULL || ra == NULL)
966: fatal("%s: sshkey_fingerprint fail", __func__);
1.145 jakob 967: msg2[0] = '\0';
968: if (options.verify_host_key_dns) {
1.153 jakob 969: if (matching_host_key_dns)
1.145 jakob 970: snprintf(msg2, sizeof(msg2),
971: "Matching host key fingerprint"
972: " found in DNS.\n");
973: else
974: snprintf(msg2, sizeof(msg2),
975: "No matching host key fingerprint"
976: " found in DNS.\n");
977: }
1.119 markus 978: snprintf(msg, sizeof(msg),
1.108 markus 979: "The authenticity of host '%.200s (%s)' can't be "
1.132 markus 980: "established%s\n"
1.209 grunk 981: "%s key fingerprint is %s.%s%s\n%s"
1.108 markus 982: "Are you sure you want to continue connecting "
1.132 markus 983: "(yes/no)? ",
1.209 grunk 984: host, ip, msg1, type, fp,
985: options.visual_host_key ? "\n" : "",
986: options.visual_host_key ? ra : "",
987: msg2);
1.238 djm 988: free(ra);
989: free(fp);
1.119 markus 990: if (!confirm(msg))
1.108 markus 991: goto fail;
1.257 djm 992: hostkey_trusted = 1; /* user explicitly confirmed */
1.38 markus 993: }
1.161 djm 994: /*
1.285 djm 995: * If in "new" or "off" strict mode, add the key automatically
996: * to the local known_hosts file.
1.161 djm 997: */
1.88 markus 998: if (options.check_host_ip && ip_status == HOST_NEW) {
1.229 djm 999: snprintf(hostline, sizeof(hostline), "%s,%s", host, ip);
1.38 markus 1000: hostp = hostline;
1.161 djm 1001: if (options.hash_known_hosts) {
1002: /* Add hash of host and IP separately */
1.234 djm 1003: r = add_host_to_hostfile(user_hostfiles[0],
1004: host, host_key, options.hash_known_hosts) &&
1005: add_host_to_hostfile(user_hostfiles[0], ip,
1.161 djm 1006: host_key, options.hash_known_hosts);
1007: } else {
1008: /* Add unhashed "host,ip" */
1.234 djm 1009: r = add_host_to_hostfile(user_hostfiles[0],
1.161 djm 1010: hostline, host_key,
1011: options.hash_known_hosts);
1012: }
1013: } else {
1.234 djm 1014: r = add_host_to_hostfile(user_hostfiles[0], host,
1015: host_key, options.hash_known_hosts);
1.38 markus 1016: hostp = host;
1.161 djm 1017: }
1.38 markus 1018:
1.161 djm 1019: if (!r)
1.138 itojun 1020: logit("Failed to add the host to the list of known "
1.234 djm 1021: "hosts (%.500s).", user_hostfiles[0]);
1.38 markus 1022: else
1.138 itojun 1023: logit("Warning: Permanently added '%.200s' (%s) to the "
1.108 markus 1024: "list of known hosts.", hostp, type);
1.38 markus 1025: break;
1.220 djm 1026: case HOST_REVOKED:
1027: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1028: error("@ WARNING: REVOKED HOST KEY DETECTED! @");
1029: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1030: error("The %s host key for %s is marked as revoked.", type, host);
1031: error("This could mean that a stolen key is being used to");
1032: error("impersonate this host.");
1033:
1034: /*
1035: * If strict host key checking is in use, the user will have
1036: * to edit the key manually and we can only abort.
1037: */
1.285 djm 1038: if (options.strict_host_key_checking !=
1039: SSH_STRICT_HOSTKEY_OFF) {
1.220 djm 1040: error("%s host key for %.200s was revoked and you have "
1041: "requested strict checking.", type, host);
1042: goto fail;
1043: }
1044: goto continue_unsafe;
1045:
1.38 markus 1046: case HOST_CHANGED:
1.219 djm 1047: if (want_cert) {
1048: /*
1049: * This is only a debug() since it is valid to have
1050: * CAs with wildcard DNS matches that don't match
1051: * all hosts that one might visit.
1052: */
1053: debug("Host certificate authority does not "
1.229 djm 1054: "match %s in %s:%lu", CA_MARKER,
1055: host_found->file, host_found->line);
1.219 djm 1056: goto fail;
1057: }
1.197 dtucker 1058: if (readonly == ROQUIET)
1059: goto fail;
1.38 markus 1060: if (options.check_host_ip && host_ip_differ) {
1.158 avsm 1061: char *key_msg;
1.38 markus 1062: if (ip_status == HOST_NEW)
1.158 avsm 1063: key_msg = "is unknown";
1.38 markus 1064: else if (ip_status == HOST_OK)
1.158 avsm 1065: key_msg = "is unchanged";
1.38 markus 1066: else
1.158 avsm 1067: key_msg = "has a different value";
1.38 markus 1068: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1069: error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @");
1070: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1.72 markus 1071: error("The %s host key for %s has changed,", type, host);
1.208 ian 1072: error("and the key for the corresponding IP address %s", ip);
1.158 avsm 1073: error("%s. This could either mean that", key_msg);
1.38 markus 1074: error("DNS SPOOFING is happening or the IP address for the host");
1.85 markus 1075: error("and its host key have changed at the same time.");
1.88 markus 1076: if (ip_status != HOST_NEW)
1.229 djm 1077: error("Offending key for IP in %s:%lu",
1078: ip_found->file, ip_found->line);
1.38 markus 1079: }
1080: /* The host key has changed. */
1.150 jakob 1081: warn_changed_key(host_key);
1.38 markus 1082: error("Add correct host key in %.100s to get rid of this message.",
1.234 djm 1083: user_hostfiles[0]);
1.280 markus 1084: error("Offending %s key in %s:%lu",
1085: sshkey_type(host_found->key),
1.229 djm 1086: host_found->file, host_found->line);
1.38 markus 1087:
1.40 markus 1088: /*
1089: * If strict host key checking is in use, the user will have
1090: * to edit the key manually and we can only abort.
1091: */
1.285 djm 1092: if (options.strict_host_key_checking !=
1093: SSH_STRICT_HOSTKEY_OFF) {
1.108 markus 1094: error("%s host key for %.200s has changed and you have "
1095: "requested strict checking.", type, host);
1096: goto fail;
1097: }
1.38 markus 1098:
1.220 djm 1099: continue_unsafe:
1.40 markus 1100: /*
1101: * If strict host key checking has not been requested, allow
1.144 djm 1102: * the connection but without MITM-able authentication or
1.194 stevesk 1103: * forwarding.
1.40 markus 1104: */
1.38 markus 1105: if (options.password_authentication) {
1.108 markus 1106: error("Password authentication is disabled to avoid "
1107: "man-in-the-middle attacks.");
1.38 markus 1108: options.password_authentication = 0;
1.210 dtucker 1109: cancelled_forwarding = 1;
1.144 djm 1110: }
1111: if (options.kbd_interactive_authentication) {
1112: error("Keyboard-interactive authentication is disabled"
1113: " to avoid man-in-the-middle attacks.");
1114: options.kbd_interactive_authentication = 0;
1115: options.challenge_response_authentication = 0;
1.210 dtucker 1116: cancelled_forwarding = 1;
1.144 djm 1117: }
1118: if (options.challenge_response_authentication) {
1119: error("Challenge/response authentication is disabled"
1120: " to avoid man-in-the-middle attacks.");
1121: options.challenge_response_authentication = 0;
1.210 dtucker 1122: cancelled_forwarding = 1;
1.38 markus 1123: }
1124: if (options.forward_agent) {
1.108 markus 1125: error("Agent forwarding is disabled to avoid "
1126: "man-in-the-middle attacks.");
1.38 markus 1127: options.forward_agent = 0;
1.210 dtucker 1128: cancelled_forwarding = 1;
1.83 markus 1129: }
1130: if (options.forward_x11) {
1.108 markus 1131: error("X11 forwarding is disabled to avoid "
1132: "man-in-the-middle attacks.");
1.83 markus 1133: options.forward_x11 = 0;
1.210 dtucker 1134: cancelled_forwarding = 1;
1.83 markus 1135: }
1.108 markus 1136: if (options.num_local_forwards > 0 ||
1137: options.num_remote_forwards > 0) {
1138: error("Port forwarding is disabled to avoid "
1139: "man-in-the-middle attacks.");
1140: options.num_local_forwards =
1.118 deraadt 1141: options.num_remote_forwards = 0;
1.210 dtucker 1142: cancelled_forwarding = 1;
1.194 stevesk 1143: }
1144: if (options.tun_open != SSH_TUNMODE_NO) {
1145: error("Tunnel forwarding is disabled to avoid "
1146: "man-in-the-middle attacks.");
1147: options.tun_open = SSH_TUNMODE_NO;
1.210 dtucker 1148: cancelled_forwarding = 1;
1.38 markus 1149: }
1.210 dtucker 1150: if (options.exit_on_forward_failure && cancelled_forwarding)
1151: fatal("Error: forwarding disabled due to host key "
1152: "check failure");
1153:
1.40 markus 1154: /*
1155: * XXX Should permit the user to change to use the new id.
1156: * This could be done by converting the host key to an
1157: * identifying sentence, tell that the host identifies itself
1.218 dtucker 1158: * by that sentence, and ask the user if he/she wishes to
1.40 markus 1159: * accept the authentication.
1160: */
1.38 markus 1161: break;
1.132 markus 1162: case HOST_FOUND:
1163: fatal("internal error");
1164: break;
1.88 markus 1165: }
1166:
1167: if (options.check_host_ip && host_status != HOST_CHANGED &&
1168: ip_status == HOST_CHANGED) {
1.119 markus 1169: snprintf(msg, sizeof(msg),
1170: "Warning: the %s host key for '%.200s' "
1171: "differs from the key for the IP address '%.128s'"
1.229 djm 1172: "\nOffending key for IP in %s:%lu",
1173: type, host, ip, ip_found->file, ip_found->line);
1.119 markus 1174: if (host_status == HOST_OK) {
1175: len = strlen(msg);
1176: snprintf(msg + len, sizeof(msg) - len,
1.229 djm 1177: "\nMatching host key in %s:%lu",
1178: host_found->file, host_found->line);
1.119 markus 1179: }
1.285 djm 1180: if (options.strict_host_key_checking ==
1181: SSH_STRICT_HOSTKEY_ASK) {
1.119 markus 1182: strlcat(msg, "\nAre you sure you want "
1183: "to continue connecting (yes/no)? ", sizeof(msg));
1184: if (!confirm(msg))
1.108 markus 1185: goto fail;
1.285 djm 1186: } else if (options.strict_host_key_checking !=
1187: SSH_STRICT_HOSTKEY_OFF) {
1188: logit("%s", msg);
1189: error("Exiting, you have requested strict checking.");
1190: goto fail;
1.119 markus 1191: } else {
1.143 djm 1192: logit("%s", msg);
1.88 markus 1193: }
1.257 djm 1194: }
1195:
1196: if (!hostkey_trusted && options.update_hostkeys) {
1197: debug("%s: hostkey not known or explicitly trusted: "
1198: "disabling UpdateHostkeys", __func__);
1199: options.update_hostkeys = 0;
1.38 markus 1200: }
1.82 provos 1201:
1.238 djm 1202: free(ip);
1203: free(host);
1.229 djm 1204: if (host_hostkeys != NULL)
1205: free_hostkeys(host_hostkeys);
1206: if (ip_hostkeys != NULL)
1207: free_hostkeys(ip_hostkeys);
1.108 markus 1208: return 0;
1209:
1210: fail:
1.220 djm 1211: if (want_cert && host_status != HOST_REVOKED) {
1.219 djm 1212: /*
1213: * No matching certificate. Downgrade cert to raw key and
1214: * search normally.
1215: */
1216: debug("No matching CA found. Retry with plain key");
1.280 markus 1217: if ((r = sshkey_from_private(host_key, &raw_key)) != 0)
1218: fatal("%s: sshkey_from_private: %s",
1219: __func__, ssh_err(r));
1220: if ((r = sshkey_drop_cert(raw_key)) != 0)
1221: fatal("Couldn't drop certificate: %s", ssh_err(r));
1.219 djm 1222: host_key = raw_key;
1223: goto retry;
1224: }
1.293 dtucker 1225: sshkey_free(raw_key);
1.238 djm 1226: free(ip);
1227: free(host);
1.229 djm 1228: if (host_hostkeys != NULL)
1229: free_hostkeys(host_hostkeys);
1230: if (ip_hostkeys != NULL)
1231: free_hostkeys(ip_hostkeys);
1.108 markus 1232: return -1;
1233: }
1234:
1.140 jakob 1235: /* returns 0 if key verifies or -1 if key does NOT verify */
1.108 markus 1236: int
1.279 markus 1237: verify_host_key(char *host, struct sockaddr *hostaddr, struct sshkey *host_key)
1.108 markus 1238: {
1.267 djm 1239: u_int i;
1.250 djm 1240: int r = -1, flags = 0;
1.267 djm 1241: char valid[64], *fp = NULL, *cafp = NULL;
1.252 djm 1242: struct sshkey *plain = NULL;
1.229 djm 1243:
1.252 djm 1244: if ((fp = sshkey_fingerprint(host_key,
1.254 djm 1245: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1.252 djm 1246: error("%s: fingerprint host key: %s", __func__, ssh_err(r));
1247: r = -1;
1248: goto out;
1249: }
1250:
1.267 djm 1251: if (sshkey_is_cert(host_key)) {
1252: if ((cafp = sshkey_fingerprint(host_key->cert->signature_key,
1253: options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) {
1254: error("%s: fingerprint CA key: %s",
1255: __func__, ssh_err(r));
1256: r = -1;
1257: goto out;
1258: }
1259: sshkey_format_cert_validity(host_key->cert,
1260: valid, sizeof(valid));
1261: debug("Server host certificate: %s %s, serial %llu "
1262: "ID \"%s\" CA %s %s valid %s",
1263: sshkey_ssh_name(host_key), fp,
1.269 djm 1264: (unsigned long long)host_key->cert->serial,
1265: host_key->cert->key_id,
1.267 djm 1266: sshkey_ssh_name(host_key->cert->signature_key), cafp,
1267: valid);
1268: for (i = 0; i < host_key->cert->nprincipals; i++) {
1269: debug2("Server host certificate hostname: %s",
1270: host_key->cert->principals[i]);
1271: }
1272: } else {
1.276 djm 1273: debug("Server host key: %s %s", sshkey_ssh_name(host_key), fp);
1.267 djm 1274: }
1.252 djm 1275:
1276: if (sshkey_equal(previous_host_key, host_key)) {
1277: debug2("%s: server host key %s %s matches cached key",
1278: __func__, sshkey_type(host_key), fp);
1279: r = 0;
1280: goto out;
1281: }
1282:
1283: /* Check in RevokedHostKeys file if specified */
1284: if (options.revoked_host_keys != NULL) {
1285: r = sshkey_check_revoked(host_key, options.revoked_host_keys);
1286: switch (r) {
1287: case 0:
1288: break; /* not revoked */
1289: case SSH_ERR_KEY_REVOKED:
1290: error("Host key %s %s revoked by file %s",
1291: sshkey_type(host_key), fp,
1292: options.revoked_host_keys);
1293: r = -1;
1294: goto out;
1295: default:
1296: error("Error checking host key %s %s in "
1297: "revoked keys file %s: %s", sshkey_type(host_key),
1298: fp, options.revoked_host_keys, ssh_err(r));
1299: r = -1;
1300: goto out;
1301: }
1.250 djm 1302: }
1303:
1.247 djm 1304: if (options.verify_host_key_dns) {
1305: /*
1306: * XXX certs are not yet supported for DNS, so downgrade
1307: * them and try the plain key.
1308: */
1.252 djm 1309: if ((r = sshkey_from_private(host_key, &plain)) != 0)
1310: goto out;
1311: if (sshkey_is_cert(plain))
1312: sshkey_drop_cert(plain);
1.247 djm 1313: if (verify_host_key_dns(host, hostaddr, plain, &flags) == 0) {
1314: if (flags & DNS_VERIFY_FOUND) {
1315: if (options.verify_host_key_dns == 1 &&
1316: flags & DNS_VERIFY_MATCH &&
1317: flags & DNS_VERIFY_SECURE) {
1.250 djm 1318: r = 0;
1.252 djm 1319: goto out;
1.247 djm 1320: }
1321: if (flags & DNS_VERIFY_MATCH) {
1322: matching_host_key_dns = 1;
1323: } else {
1.287 djm 1324: warn_changed_key(plain);
1325: error("Update the SSHFP RR in DNS "
1326: "with the new host key to get rid "
1327: "of this message.");
1.247 djm 1328: }
1.153 jakob 1329: }
1.140 jakob 1330: }
1331: }
1.250 djm 1332: r = check_host_key(host, hostaddr, options.port, host_key, RDRW,
1.234 djm 1333: options.user_hostfiles, options.num_user_hostfiles,
1334: options.system_hostfiles, options.num_system_hostfiles);
1.250 djm 1335:
1.252 djm 1336: out:
1337: sshkey_free(plain);
1338: free(fp);
1.267 djm 1339: free(cafp);
1.250 djm 1340: if (r == 0 && host_key != NULL) {
1.280 markus 1341: sshkey_free(previous_host_key);
1342: r = sshkey_from_private(host_key, &previous_host_key);
1.250 djm 1343: }
1344:
1345: return r;
1.51 markus 1346: }
1.70 markus 1347:
1.51 markus 1348: /*
1349: * Starts a dialog with the server, and authenticates the current user on the
1350: * server. This does not need any extra privileges. The basic connection
1351: * to the server must already have been established before this is called.
1352: * If login fails, this function prints an error and never returns.
1353: * This function does not require super-user privileges.
1354: */
1355: void
1.120 markus 1356: ssh_login(Sensitive *sensitive, const char *orighost,
1.229 djm 1357: struct sockaddr *hostaddr, u_short port, struct passwd *pw, int timeout_ms)
1.51 markus 1358: {
1.241 djm 1359: char *host;
1.70 markus 1360: char *server_user, *local_user;
1361:
1362: local_user = xstrdup(pw->pw_name);
1363: server_user = options.user ? options.user : local_user;
1.51 markus 1364:
1365: /* Convert the user-supplied hostname into all lowercase. */
1366: host = xstrdup(orighost);
1.241 djm 1367: lowercase(host);
1.51 markus 1368:
1369: /* Exchange protocol version identification strings with the server. */
1.202 djm 1370: ssh_exchange_identification(timeout_ms);
1.51 markus 1371:
1372: /* Put the connection into non-blocking mode. */
1373: packet_set_nonblocking();
1374:
1375: /* key exchange */
1376: /* authenticate user */
1.261 dtucker 1377: debug("Authenticating to %s:%d as '%s'", host, port, server_user);
1.276 djm 1378: ssh_kex2(host, hostaddr, port);
1379: ssh_userauth2(local_user, server_user, host, sensitive);
1.238 djm 1380: free(local_user);
1.97 markus 1381: }
1382:
1383: void
1384: ssh_put_password(char *password)
1385: {
1386: int size;
1387: char *padded;
1388:
1.99 deraadt 1389: if (datafellows & SSH_BUG_PASSWORDPAD) {
1.107 markus 1390: packet_put_cstring(password);
1.99 deraadt 1391: return;
1392: }
1.272 deraadt 1393: size = ROUNDUP(strlen(password) + 1, 32);
1.179 djm 1394: padded = xcalloc(1, size);
1.97 markus 1395: strlcpy(padded, password, size);
1396: packet_put_string(padded, size);
1.245 djm 1397: explicit_bzero(padded, size);
1.238 djm 1398: free(padded);
1.132 markus 1399: }
1400:
1401: /* print all known host keys for a given host, but skip keys of given type */
1402: static int
1.279 markus 1403: show_other_keys(struct hostkeys *hostkeys, struct sshkey *key)
1.132 markus 1404: {
1.242 djm 1405: int type[] = {
1406: KEY_RSA,
1407: KEY_DSA,
1408: KEY_ECDSA,
1409: KEY_ED25519,
1.297 markus 1410: KEY_XMSS,
1.242 djm 1411: -1
1412: };
1.229 djm 1413: int i, ret = 0;
1414: char *fp, *ra;
1415: const struct hostkey_entry *found;
1.132 markus 1416:
1417: for (i = 0; type[i] != -1; i++) {
1418: if (type[i] == key->type)
1419: continue;
1.229 djm 1420: if (!lookup_key_in_hostkeys_by_type(hostkeys, type[i], &found))
1.132 markus 1421: continue;
1.259 djm 1422: fp = sshkey_fingerprint(found->key,
1.254 djm 1423: options.fingerprint_hash, SSH_FP_DEFAULT);
1.259 djm 1424: ra = sshkey_fingerprint(found->key,
1.254 djm 1425: options.fingerprint_hash, SSH_FP_RANDOMART);
1.259 djm 1426: if (fp == NULL || ra == NULL)
1427: fatal("%s: sshkey_fingerprint fail", __func__);
1.229 djm 1428: logit("WARNING: %s key found for host %s\n"
1429: "in %s:%lu\n"
1430: "%s key fingerprint %s.",
1.300 markus 1431: sshkey_type(found->key),
1.229 djm 1432: found->host, found->file, found->line,
1.300 markus 1433: sshkey_type(found->key), fp);
1.229 djm 1434: if (options.visual_host_key)
1435: logit("%s", ra);
1.238 djm 1436: free(ra);
1437: free(fp);
1.229 djm 1438: ret = 1;
1.132 markus 1439: }
1.229 djm 1440: return ret;
1.150 jakob 1441: }
1442:
1443: static void
1.279 markus 1444: warn_changed_key(struct sshkey *host_key)
1.150 jakob 1445: {
1446: char *fp;
1447:
1.259 djm 1448: fp = sshkey_fingerprint(host_key, options.fingerprint_hash,
1.254 djm 1449: SSH_FP_DEFAULT);
1.259 djm 1450: if (fp == NULL)
1451: fatal("%s: sshkey_fingerprint fail", __func__);
1.150 jakob 1452:
1453: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1454: error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @");
1455: error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
1456: error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!");
1457: error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!");
1.230 markus 1458: error("It is also possible that a host key has just been changed.");
1.150 jakob 1459: error("The fingerprint for the %s key sent by the remote host is\n%s.",
1.300 markus 1460: sshkey_type(host_key), fp);
1.150 jakob 1461: error("Please contact your system administrator.");
1462:
1.238 djm 1463: free(fp);
1.171 reyk 1464: }
1465:
1466: /*
1467: * Execute a local command
1468: */
1469: int
1470: ssh_local_cmd(const char *args)
1471: {
1472: char *shell;
1473: pid_t pid;
1474: int status;
1.231 djm 1475: void (*osighand)(int);
1.171 reyk 1476:
1477: if (!options.permit_local_command ||
1478: args == NULL || !*args)
1479: return (1);
1480:
1.226 djm 1481: if ((shell = getenv("SHELL")) == NULL || *shell == '\0')
1.171 reyk 1482: shell = _PATH_BSHELL;
1483:
1.231 djm 1484: osighand = signal(SIGCHLD, SIG_DFL);
1.171 reyk 1485: pid = fork();
1486: if (pid == 0) {
1.232 djm 1487: signal(SIGPIPE, SIG_DFL);
1.171 reyk 1488: debug3("Executing %s -c \"%s\"", shell, args);
1489: execl(shell, shell, "-c", args, (char *)NULL);
1490: error("Couldn't execute %s -c \"%s\": %s",
1491: shell, args, strerror(errno));
1492: _exit(1);
1493: } else if (pid == -1)
1494: fatal("fork failed: %.100s", strerror(errno));
1495: while (waitpid(pid, &status, 0) == -1)
1496: if (errno != EINTR)
1497: fatal("Couldn't wait for child: %s", strerror(errno));
1.231 djm 1498: signal(SIGCHLD, osighand);
1.171 reyk 1499:
1500: if (!WIFEXITED(status))
1501: return (1);
1502:
1503: return (WEXITSTATUS(status));
1.266 jcs 1504: }
1505:
1506: void
1.294 djm 1507: maybe_add_key_to_agent(char *authfile, const struct sshkey *private,
1508: char *comment, char *passphrase)
1.266 jcs 1509: {
1510: int auth_sock = -1, r;
1511:
1512: if (options.add_keys_to_agent == 0)
1513: return;
1514:
1515: if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
1516: debug3("no authentication agent, not adding key");
1517: return;
1518: }
1519:
1520: if (options.add_keys_to_agent == 2 &&
1521: !ask_permission("Add key %s (%s) to agent?", authfile, comment)) {
1522: debug3("user denied adding this key");
1.273 dtucker 1523: close(auth_sock);
1.266 jcs 1524: return;
1525: }
1526:
1527: if ((r = ssh_add_identity_constrained(auth_sock, private, comment, 0,
1.297 markus 1528: (options.add_keys_to_agent == 3), 0)) == 0)
1.266 jcs 1529: debug("identity added to agent: %s", authfile);
1530: else
1531: debug("could not add identity to agent: %s (%d)", authfile, r);
1.273 dtucker 1532: close(auth_sock);
1.1 deraadt 1533: }
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