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1 | /* $OpenBSD: sshconnect.c,v 1.200 2006/10/10 10:12:45 markus Exp $ */ | |
2 | /* | |
3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | * All rights reserved | |
6 | * Code to connect to a remote host, and to perform the client side of the | |
7 | * login (authentication) dialog. | |
8 | * | |
9 | * As far as I am concerned, the code I have written for this software | |
10 | * can be used freely for any purpose. Any derived versions of this | |
11 | * software must be clearly marked as such, and if the derived work is | |
12 | * incompatible with the protocol description in the RFC file, it must be | |
13 | * called by a name other than "ssh" or "Secure Shell". | |
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | ||
18 | #include <sys/types.h> | |
19 | #include <sys/wait.h> | |
20 | #include <sys/stat.h> | |
21 | #include <sys/socket.h> | |
22 | #ifdef HAVE_SYS_TIME_H | |
23 | # include <sys/time.h> | |
24 | #endif | |
25 | ||
26 | #include <netinet/in.h> | |
27 | #include <arpa/inet.h> | |
28 | ||
29 | #include <ctype.h> | |
30 | #include <errno.h> | |
31 | #include <netdb.h> | |
32 | #ifdef HAVE_PATHS_H | |
33 | #include <paths.h> | |
34 | #endif | |
35 | #include <pwd.h> | |
36 | #include <stdarg.h> | |
37 | #include <stdio.h> | |
38 | #include <stdlib.h> | |
39 | #include <string.h> | |
40 | #include <unistd.h> | |
41 | ||
42 | #include "xmalloc.h" | |
43 | #include "key.h" | |
44 | #include "hostfile.h" | |
45 | #include "ssh.h" | |
46 | #include "rsa.h" | |
47 | #include "buffer.h" | |
48 | #include "packet.h" | |
49 | #include "uidswap.h" | |
50 | #include "compat.h" | |
51 | #include "key.h" | |
52 | #include "sshconnect.h" | |
53 | #include "hostfile.h" | |
54 | #include "log.h" | |
55 | #include "readconf.h" | |
56 | #include "atomicio.h" | |
57 | #include "misc.h" | |
58 | #include "dns.h" | |
59 | #include "version.h" | |
60 | ||
61 | char *client_version_string = NULL; | |
62 | char *server_version_string = NULL; | |
63 | ||
64 | static int matching_host_key_dns = 0; | |
65 | ||
66 | /* import */ | |
67 | extern Options options; | |
68 | extern char *__progname; | |
69 | extern uid_t original_real_uid; | |
70 | extern uid_t original_effective_uid; | |
71 | extern pid_t proxy_command_pid; | |
72 | ||
73 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
74 | #define INET6_ADDRSTRLEN 46 | |
75 | #endif | |
76 | ||
77 | static int show_other_keys(const char *, Key *); | |
78 | static void warn_changed_key(Key *); | |
79 | ||
80 | /* | |
81 | * Connect to the given ssh server using a proxy command. | |
82 | */ | |
83 | static int | |
84 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
85 | { | |
86 | char *command_string, *tmp; | |
87 | int pin[2], pout[2]; | |
88 | pid_t pid; | |
89 | char strport[NI_MAXSERV]; | |
90 | ||
91 | /* Convert the port number into a string. */ | |
92 | snprintf(strport, sizeof strport, "%hu", port); | |
93 | ||
94 | /* | |
95 | * Build the final command string in the buffer by making the | |
96 | * appropriate substitutions to the given proxy command. | |
97 | * | |
98 | * Use "exec" to avoid "sh -c" processes on some platforms | |
99 | * (e.g. Solaris) | |
100 | */ | |
101 | xasprintf(&tmp, "exec %s", proxy_command); | |
102 | command_string = percent_expand(tmp, "h", host, | |
103 | "p", strport, (char *)NULL); | |
104 | xfree(tmp); | |
105 | ||
106 | /* Create pipes for communicating with the proxy. */ | |
107 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
108 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
109 | strerror(errno)); | |
110 | ||
111 | debug("Executing proxy command: %.500s", command_string); | |
112 | ||
113 | /* Fork and execute the proxy command. */ | |
114 | if ((pid = fork()) == 0) { | |
115 | char *argv[10]; | |
116 | ||
117 | /* Child. Permanently give up superuser privileges. */ | |
118 | permanently_drop_suid(original_real_uid); | |
119 | ||
120 | /* Redirect stdin and stdout. */ | |
121 | close(pin[1]); | |
122 | if (pin[0] != 0) { | |
123 | if (dup2(pin[0], 0) < 0) | |
124 | perror("dup2 stdin"); | |
125 | close(pin[0]); | |
126 | } | |
127 | close(pout[0]); | |
128 | if (dup2(pout[1], 1) < 0) | |
129 | perror("dup2 stdout"); | |
130 | /* Cannot be 1 because pin allocated two descriptors. */ | |
131 | close(pout[1]); | |
132 | ||
133 | /* Stderr is left as it is so that error messages get | |
134 | printed on the user's terminal. */ | |
135 | argv[0] = _PATH_BSHELL; | |
136 | argv[1] = "-c"; | |
137 | argv[2] = command_string; | |
138 | argv[3] = NULL; | |
139 | ||
140 | /* Execute the proxy command. Note that we gave up any | |
141 | extra privileges above. */ | |
142 | execv(argv[0], argv); | |
143 | perror(argv[0]); | |
144 | exit(1); | |
145 | } | |
146 | /* Parent. */ | |
147 | if (pid < 0) | |
148 | fatal("fork failed: %.100s", strerror(errno)); | |
149 | else | |
150 | proxy_command_pid = pid; /* save pid to clean up later */ | |
151 | ||
152 | /* Close child side of the descriptors. */ | |
153 | close(pin[0]); | |
154 | close(pout[1]); | |
155 | ||
156 | /* Free the command name. */ | |
157 | xfree(command_string); | |
158 | ||
159 | /* Set the connection file descriptors. */ | |
160 | packet_set_connection(pout[0], pin[1]); | |
161 | ||
162 | /* Indicate OK return */ | |
163 | return 0; | |
164 | } | |
165 | ||
166 | /* | |
167 | * Set TCP receive buffer if requested. | |
168 | * Note: tuning needs to happen after the socket is | |
169 | * created but before the connection happens | |
170 | * so winscale is negotiated properly -cjr | |
171 | */ | |
172 | static void | |
173 | ssh_set_socket_recvbuf(int sock) | |
174 | { | |
175 | void *buf = (void *)&options.tcp_rcv_buf; | |
176 | int sz = sizeof(options.tcp_rcv_buf); | |
177 | int socksize; | |
178 | int socksizelen = sizeof(int); | |
179 | ||
180 | debug("setsockopt Attempting to set SO_RCVBUF to %d", options.tcp_rcv_buf); | |
181 | if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, buf, sz) >= 0) { | |
182 | getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &socksize, &socksizelen); | |
183 | debug("setsockopt SO_RCVBUF: %.100s %d", strerror(errno), socksize); | |
184 | } | |
185 | else | |
186 | error("Couldn't set socket receive buffer to %d: %.100s", | |
187 | options.tcp_rcv_buf, strerror(errno)); | |
188 | } | |
189 | ||
190 | ||
191 | /* | |
192 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
193 | */ | |
194 | static int | |
195 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
196 | { | |
197 | int sock, gaierr; | |
198 | struct addrinfo hints, *res; | |
199 | ||
200 | /* | |
201 | * If we are running as root and want to connect to a privileged | |
202 | * port, bind our own socket to a privileged port. | |
203 | */ | |
204 | if (privileged) { | |
205 | int p = IPPORT_RESERVED - 1; | |
206 | PRIV_START; | |
207 | sock = rresvport_af(&p, ai->ai_family); | |
208 | PRIV_END; | |
209 | if (sock < 0) | |
210 | error("rresvport: af=%d %.100s", ai->ai_family, | |
211 | strerror(errno)); | |
212 | else | |
213 | debug("Allocated local port %d.", p); | |
214 | ||
215 | if (options.tcp_rcv_buf > 0) | |
216 | ssh_set_socket_recvbuf(sock); | |
217 | return sock; | |
218 | } | |
219 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
220 | if (sock < 0) | |
221 | error("socket: %.100s", strerror(errno)); | |
222 | ||
223 | ||
224 | if (options.tcp_rcv_buf > 0) | |
225 | ssh_set_socket_recvbuf(sock); | |
226 | ||
227 | /* Bind the socket to an alternative local IP address */ | |
228 | if (options.bind_address == NULL) | |
229 | return sock; | |
230 | ||
231 | memset(&hints, 0, sizeof(hints)); | |
232 | hints.ai_family = ai->ai_family; | |
233 | hints.ai_socktype = ai->ai_socktype; | |
234 | hints.ai_protocol = ai->ai_protocol; | |
235 | hints.ai_flags = AI_PASSIVE; | |
236 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
237 | if (gaierr) { | |
238 | error("getaddrinfo: %s: %s", options.bind_address, | |
239 | gai_strerror(gaierr)); | |
240 | close(sock); | |
241 | return -1; | |
242 | } | |
243 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
244 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
245 | close(sock); | |
246 | freeaddrinfo(res); | |
247 | return -1; | |
248 | } | |
249 | freeaddrinfo(res); | |
250 | return sock; | |
251 | } | |
252 | ||
253 | static int | |
254 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
255 | socklen_t addrlen, int timeout) | |
256 | { | |
257 | fd_set *fdset; | |
258 | struct timeval tv; | |
259 | socklen_t optlen; | |
260 | int optval, rc, result = -1; | |
261 | ||
262 | if (timeout <= 0) | |
263 | return (connect(sockfd, serv_addr, addrlen)); | |
264 | ||
265 | set_nonblock(sockfd); | |
266 | rc = connect(sockfd, serv_addr, addrlen); | |
267 | if (rc == 0) { | |
268 | unset_nonblock(sockfd); | |
269 | return (0); | |
270 | } | |
271 | if (errno != EINPROGRESS) | |
272 | return (-1); | |
273 | ||
274 | fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), | |
275 | sizeof(fd_mask)); | |
276 | FD_SET(sockfd, fdset); | |
277 | tv.tv_sec = timeout; | |
278 | tv.tv_usec = 0; | |
279 | ||
280 | for (;;) { | |
281 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
282 | if (rc != -1 || errno != EINTR) | |
283 | break; | |
284 | } | |
285 | ||
286 | switch (rc) { | |
287 | case 0: | |
288 | /* Timed out */ | |
289 | errno = ETIMEDOUT; | |
290 | break; | |
291 | case -1: | |
292 | /* Select error */ | |
293 | debug("select: %s", strerror(errno)); | |
294 | break; | |
295 | case 1: | |
296 | /* Completed or failed */ | |
297 | optval = 0; | |
298 | optlen = sizeof(optval); | |
299 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
300 | &optlen) == -1) { | |
301 | debug("getsockopt: %s", strerror(errno)); | |
302 | break; | |
303 | } | |
304 | if (optval != 0) { | |
305 | errno = optval; | |
306 | break; | |
307 | } | |
308 | result = 0; | |
309 | unset_nonblock(sockfd); | |
310 | break; | |
311 | default: | |
312 | /* Should not occur */ | |
313 | fatal("Bogus return (%d) from select()", rc); | |
314 | } | |
315 | ||
316 | xfree(fdset); | |
317 | return (result); | |
318 | } | |
319 | ||
320 | /* | |
321 | * Opens a TCP/IP connection to the remote server on the given host. | |
322 | * The address of the remote host will be returned in hostaddr. | |
323 | * If port is 0, the default port will be used. If needpriv is true, | |
324 | * a privileged port will be allocated to make the connection. | |
325 | * This requires super-user privileges if needpriv is true. | |
326 | * Connection_attempts specifies the maximum number of tries (one per | |
327 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
328 | * and %p substituted for host and port, respectively) to use to contact | |
329 | * the daemon. | |
330 | */ | |
331 | int | |
332 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
333 | u_short port, int family, int connection_attempts, | |
334 | int needpriv, const char *proxy_command) | |
335 | { | |
336 | int gaierr; | |
337 | int on = 1; | |
338 | int sock = -1, attempt; | |
339 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
340 | struct addrinfo hints, *ai, *aitop; | |
341 | ||
342 | debug2("ssh_connect: needpriv %d", needpriv); | |
343 | ||
344 | /* If a proxy command is given, connect using it. */ | |
345 | if (proxy_command != NULL) | |
346 | return ssh_proxy_connect(host, port, proxy_command); | |
347 | ||
348 | /* No proxy command. */ | |
349 | ||
350 | memset(&hints, 0, sizeof(hints)); | |
351 | hints.ai_family = family; | |
352 | hints.ai_socktype = SOCK_STREAM; | |
353 | snprintf(strport, sizeof strport, "%u", port); | |
354 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
355 | fatal("%s: %.100s: %s", __progname, host, | |
356 | gai_strerror(gaierr)); | |
357 | ||
358 | for (attempt = 0; attempt < connection_attempts; attempt++) { | |
359 | if (attempt > 0) { | |
360 | /* Sleep a moment before retrying. */ | |
361 | sleep(1); | |
362 | debug("Trying again..."); | |
363 | } | |
364 | /* | |
365 | * Loop through addresses for this host, and try each one in | |
366 | * sequence until the connection succeeds. | |
367 | */ | |
368 | for (ai = aitop; ai; ai = ai->ai_next) { | |
369 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
370 | continue; | |
371 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
372 | ntop, sizeof(ntop), strport, sizeof(strport), | |
373 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
374 | error("ssh_connect: getnameinfo failed"); | |
375 | continue; | |
376 | } | |
377 | debug("Connecting to %.200s [%.100s] port %s.", | |
378 | host, ntop, strport); | |
379 | ||
380 | /* Create a socket for connecting. */ | |
381 | sock = ssh_create_socket(needpriv, ai); | |
382 | if (sock < 0) | |
383 | /* Any error is already output */ | |
384 | continue; | |
385 | ||
386 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
387 | options.connection_timeout) >= 0) { | |
388 | /* Successful connection. */ | |
389 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
390 | break; | |
391 | } else { | |
392 | debug("connect to address %s port %s: %s", | |
393 | ntop, strport, strerror(errno)); | |
394 | close(sock); | |
395 | sock = -1; | |
396 | } | |
397 | } | |
398 | if (sock != -1) | |
399 | break; /* Successful connection. */ | |
400 | } | |
401 | ||
402 | freeaddrinfo(aitop); | |
403 | ||
404 | /* Return failure if we didn't get a successful connection. */ | |
405 | if (sock == -1) { | |
406 | error("ssh: connect to host %s port %s: %s", | |
407 | host, strport, strerror(errno)); | |
408 | return (-1); | |
409 | } | |
410 | ||
411 | debug("Connection established."); | |
412 | ||
413 | /* Set SO_KEEPALIVE if requested. */ | |
414 | if (options.tcp_keep_alive && | |
415 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
416 | sizeof(on)) < 0) | |
417 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
418 | ||
419 | /* Set the connection. */ | |
420 | packet_set_connection(sock, sock); | |
421 | ||
422 | return 0; | |
423 | } | |
424 | ||
425 | /* | |
426 | * Waits for the server identification string, and sends our own | |
427 | * identification string. | |
428 | */ | |
429 | static void | |
430 | ssh_exchange_identification(void) | |
431 | { | |
432 | char buf[256], remote_version[256]; /* must be same size! */ | |
433 | int remote_major, remote_minor, mismatch; | |
434 | int connection_in = packet_get_connection_in(); | |
435 | int connection_out = packet_get_connection_out(); | |
436 | int minor1 = PROTOCOL_MINOR_1; | |
437 | u_int i, n; | |
438 | ||
439 | /* Read other side's version identification. */ | |
440 | for (n = 0;;) { | |
441 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
442 | size_t len = atomicio(read, connection_in, &buf[i], 1); | |
443 | ||
444 | if (len != 1 && errno == EPIPE) | |
445 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
446 | else if (len != 1) | |
447 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
448 | if (buf[i] == '\r') { | |
449 | buf[i] = '\n'; | |
450 | buf[i + 1] = 0; | |
451 | continue; /**XXX wait for \n */ | |
452 | } | |
453 | if (buf[i] == '\n') { | |
454 | buf[i + 1] = 0; | |
455 | break; | |
456 | } | |
457 | if (++n > 65536) | |
458 | fatal("ssh_exchange_identification: No banner received"); | |
459 | } | |
460 | buf[sizeof(buf) - 1] = 0; | |
461 | if (strncmp(buf, "SSH-", 4) == 0) | |
462 | break; | |
463 | debug("ssh_exchange_identification: %s", buf); | |
464 | } | |
465 | server_version_string = xstrdup(buf); | |
466 | ||
467 | /* | |
468 | * Check that the versions match. In future this might accept | |
469 | * several versions and set appropriate flags to handle them. | |
470 | */ | |
471 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
472 | &remote_major, &remote_minor, remote_version) != 3) | |
473 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
474 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
475 | remote_major, remote_minor, remote_version); | |
476 | ||
477 | compat_datafellows(remote_version); | |
478 | mismatch = 0; | |
479 | ||
480 | switch (remote_major) { | |
481 | case 1: | |
482 | if (remote_minor == 99 && | |
483 | (options.protocol & SSH_PROTO_2) && | |
484 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
485 | enable_compat20(); | |
486 | break; | |
487 | } | |
488 | if (!(options.protocol & SSH_PROTO_1)) { | |
489 | mismatch = 1; | |
490 | break; | |
491 | } | |
492 | if (remote_minor < 3) { | |
493 | fatal("Remote machine has too old SSH software version."); | |
494 | } else if (remote_minor == 3 || remote_minor == 4) { | |
495 | /* We speak 1.3, too. */ | |
496 | enable_compat13(); | |
497 | minor1 = 3; | |
498 | if (options.forward_agent) { | |
499 | logit("Agent forwarding disabled for protocol 1.3"); | |
500 | options.forward_agent = 0; | |
501 | } | |
502 | } | |
503 | break; | |
504 | case 2: | |
505 | if (options.protocol & SSH_PROTO_2) { | |
506 | enable_compat20(); | |
507 | break; | |
508 | } | |
509 | /* FALLTHROUGH */ | |
510 | default: | |
511 | mismatch = 1; | |
512 | break; | |
513 | } | |
514 | if (mismatch) | |
515 | fatal("Protocol major versions differ: %d vs. %d", | |
516 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
517 | remote_major); | |
518 | /* Send our own protocol version identification. */ | |
519 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
520 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
521 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
522 | SSH_RELEASE); | |
523 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
524 | fatal("write: %.100s", strerror(errno)); | |
525 | client_version_string = xstrdup(buf); | |
526 | chop(client_version_string); | |
527 | chop(server_version_string); | |
528 | debug("Local version string %.100s", client_version_string); | |
529 | } | |
530 | ||
531 | /* defaults to 'no' */ | |
532 | static int | |
533 | confirm(const char *prompt) | |
534 | { | |
535 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
536 | char *p; | |
537 | int ret = -1; | |
538 | ||
539 | if (options.batch_mode) | |
540 | return 0; | |
541 | for (msg = prompt;;msg = again) { | |
542 | p = read_passphrase(msg, RP_ECHO); | |
543 | if (p == NULL || | |
544 | (p[0] == '\0') || (p[0] == '\n') || | |
545 | strncasecmp(p, "no", 2) == 0) | |
546 | ret = 0; | |
547 | if (p && strncasecmp(p, "yes", 3) == 0) | |
548 | ret = 1; | |
549 | if (p) | |
550 | xfree(p); | |
551 | if (ret != -1) | |
552 | return ret; | |
553 | } | |
554 | } | |
555 | ||
556 | /* | |
557 | * check whether the supplied host key is valid, return -1 if the key | |
558 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
559 | */ | |
560 | #define RDRW 0 | |
561 | #define RDONLY 1 | |
562 | #define ROQUIET 2 | |
563 | static int | |
564 | check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, | |
565 | Key *host_key, int readonly, const char *user_hostfile, | |
566 | const char *system_hostfile) | |
567 | { | |
568 | Key *file_key; | |
569 | const char *type = key_type(host_key); | |
570 | char *ip = NULL, *host = NULL; | |
571 | char hostline[1000], *hostp, *fp; | |
572 | HostStatus host_status; | |
573 | HostStatus ip_status; | |
574 | int r, local = 0, host_ip_differ = 0; | |
575 | int salen; | |
576 | char ntop[NI_MAXHOST]; | |
577 | char msg[1024]; | |
578 | int len, host_line, ip_line; | |
579 | const char *host_file = NULL, *ip_file = NULL; | |
580 | ||
581 | /* | |
582 | * Force accepting of the host key for loopback/localhost. The | |
583 | * problem is that if the home directory is NFS-mounted to multiple | |
584 | * machines, localhost will refer to a different machine in each of | |
585 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
586 | * essentially disables host authentication for localhost; however, | |
587 | * this is probably not a real problem. | |
588 | */ | |
589 | /** hostaddr == 0! */ | |
590 | switch (hostaddr->sa_family) { | |
591 | case AF_INET: | |
592 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
593 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
594 | salen = sizeof(struct sockaddr_in); | |
595 | break; | |
596 | case AF_INET6: | |
597 | local = IN6_IS_ADDR_LOOPBACK( | |
598 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
599 | salen = sizeof(struct sockaddr_in6); | |
600 | break; | |
601 | default: | |
602 | local = 0; | |
603 | salen = sizeof(struct sockaddr_storage); | |
604 | break; | |
605 | } | |
606 | if (options.no_host_authentication_for_localhost == 1 && local && | |
607 | options.host_key_alias == NULL) { | |
608 | debug("Forcing accepting of host key for " | |
609 | "loopback/localhost."); | |
610 | return 0; | |
611 | } | |
612 | ||
613 | /* | |
614 | * We don't have the remote ip-address for connections | |
615 | * using a proxy command | |
616 | */ | |
617 | if (options.proxy_command == NULL) { | |
618 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
619 | NULL, 0, NI_NUMERICHOST) != 0) | |
620 | fatal("check_host_key: getnameinfo failed"); | |
621 | ip = put_host_port(ntop, port); | |
622 | } else { | |
623 | ip = xstrdup("<no hostip for proxy command>"); | |
624 | } | |
625 | /* | |
626 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
627 | * command or if we don't have a hostname to compare with | |
628 | */ | |
629 | if (options.check_host_ip && (local || | |
630 | strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) | |
631 | options.check_host_ip = 0; | |
632 | ||
633 | /* | |
634 | * Allow the user to record the key under a different name or | |
635 | * differentiate a non-standard port. This is useful for ssh | |
636 | * tunneling over forwarded connections or if you run multiple | |
637 | * sshd's on different ports on the same machine. | |
638 | */ | |
639 | if (options.host_key_alias != NULL) { | |
640 | host = xstrdup(options.host_key_alias); | |
641 | debug("using hostkeyalias: %s", host); | |
642 | } else { | |
643 | host = put_host_port(hostname, port); | |
644 | } | |
645 | ||
646 | /* | |
647 | * Store the host key from the known host file in here so that we can | |
648 | * compare it with the key for the IP address. | |
649 | */ | |
650 | file_key = key_new(host_key->type); | |
651 | ||
652 | /* | |
653 | * Check if the host key is present in the user's list of known | |
654 | * hosts or in the systemwide list. | |
655 | */ | |
656 | host_file = user_hostfile; | |
657 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
658 | file_key, &host_line); | |
659 | if (host_status == HOST_NEW) { | |
660 | host_file = system_hostfile; | |
661 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
662 | file_key, &host_line); | |
663 | } | |
664 | /* | |
665 | * Also perform check for the ip address, skip the check if we are | |
666 | * localhost or the hostname was an ip address to begin with | |
667 | */ | |
668 | if (options.check_host_ip) { | |
669 | Key *ip_key = key_new(host_key->type); | |
670 | ||
671 | ip_file = user_hostfile; | |
672 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
673 | ip_key, &ip_line); | |
674 | if (ip_status == HOST_NEW) { | |
675 | ip_file = system_hostfile; | |
676 | ip_status = check_host_in_hostfile(ip_file, ip, | |
677 | host_key, ip_key, &ip_line); | |
678 | } | |
679 | if (host_status == HOST_CHANGED && | |
680 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
681 | host_ip_differ = 1; | |
682 | ||
683 | key_free(ip_key); | |
684 | } else | |
685 | ip_status = host_status; | |
686 | ||
687 | key_free(file_key); | |
688 | ||
689 | switch (host_status) { | |
690 | case HOST_OK: | |
691 | /* The host is known and the key matches. */ | |
692 | debug("Host '%.200s' is known and matches the %s host key.", | |
693 | host, type); | |
694 | debug("Found key in %s:%d", host_file, host_line); | |
695 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
696 | if (readonly) | |
697 | logit("%s host key for IP address " | |
698 | "'%.128s' not in list of known hosts.", | |
699 | type, ip); | |
700 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
701 | host_key, options.hash_known_hosts)) | |
702 | logit("Failed to add the %s host key for IP " | |
703 | "address '%.128s' to the list of known " | |
704 | "hosts (%.30s).", type, ip, user_hostfile); | |
705 | else | |
706 | logit("Warning: Permanently added the %s host " | |
707 | "key for IP address '%.128s' to the list " | |
708 | "of known hosts.", type, ip); | |
709 | } | |
710 | break; | |
711 | case HOST_NEW: | |
712 | if (options.host_key_alias == NULL && port != 0 && | |
713 | port != SSH_DEFAULT_PORT) { | |
714 | debug("checking without port identifier"); | |
715 | if (check_host_key(hostname, hostaddr, 0, host_key, 2, | |
716 | user_hostfile, system_hostfile) == 0) { | |
717 | debug("found matching key w/out port"); | |
718 | break; | |
719 | } | |
720 | } | |
721 | if (readonly) | |
722 | goto fail; | |
723 | /* The host is new. */ | |
724 | if (options.strict_host_key_checking == 1) { | |
725 | /* | |
726 | * User has requested strict host key checking. We | |
727 | * will not add the host key automatically. The only | |
728 | * alternative left is to abort. | |
729 | */ | |
730 | error("No %s host key is known for %.200s and you " | |
731 | "have requested strict checking.", type, host); | |
732 | goto fail; | |
733 | } else if (options.strict_host_key_checking == 2) { | |
734 | char msg1[1024], msg2[1024]; | |
735 | ||
736 | if (show_other_keys(host, host_key)) | |
737 | snprintf(msg1, sizeof(msg1), | |
738 | "\nbut keys of different type are already" | |
739 | " known for this host."); | |
740 | else | |
741 | snprintf(msg1, sizeof(msg1), "."); | |
742 | /* The default */ | |
743 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
744 | msg2[0] = '\0'; | |
745 | if (options.verify_host_key_dns) { | |
746 | if (matching_host_key_dns) | |
747 | snprintf(msg2, sizeof(msg2), | |
748 | "Matching host key fingerprint" | |
749 | " found in DNS.\n"); | |
750 | else | |
751 | snprintf(msg2, sizeof(msg2), | |
752 | "No matching host key fingerprint" | |
753 | " found in DNS.\n"); | |
754 | } | |
755 | snprintf(msg, sizeof(msg), | |
756 | "The authenticity of host '%.200s (%s)' can't be " | |
757 | "established%s\n" | |
758 | "%s key fingerprint is %s.\n%s" | |
759 | "Are you sure you want to continue connecting " | |
760 | "(yes/no)? ", | |
761 | host, ip, msg1, type, fp, msg2); | |
762 | xfree(fp); | |
763 | if (!confirm(msg)) | |
764 | goto fail; | |
765 | } | |
766 | /* | |
767 | * If not in strict mode, add the key automatically to the | |
768 | * local known_hosts file. | |
769 | */ | |
770 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
771 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
772 | host, ip); | |
773 | hostp = hostline; | |
774 | if (options.hash_known_hosts) { | |
775 | /* Add hash of host and IP separately */ | |
776 | r = add_host_to_hostfile(user_hostfile, host, | |
777 | host_key, options.hash_known_hosts) && | |
778 | add_host_to_hostfile(user_hostfile, ip, | |
779 | host_key, options.hash_known_hosts); | |
780 | } else { | |
781 | /* Add unhashed "host,ip" */ | |
782 | r = add_host_to_hostfile(user_hostfile, | |
783 | hostline, host_key, | |
784 | options.hash_known_hosts); | |
785 | } | |
786 | } else { | |
787 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
788 | options.hash_known_hosts); | |
789 | hostp = host; | |
790 | } | |
791 | ||
792 | if (!r) | |
793 | logit("Failed to add the host to the list of known " | |
794 | "hosts (%.500s).", user_hostfile); | |
795 | else | |
796 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
797 | "list of known hosts.", hostp, type); | |
798 | break; | |
799 | case HOST_CHANGED: | |
800 | if (readonly == ROQUIET) | |
801 | goto fail; | |
802 | if (options.check_host_ip && host_ip_differ) { | |
803 | char *key_msg; | |
804 | if (ip_status == HOST_NEW) | |
805 | key_msg = "is unknown"; | |
806 | else if (ip_status == HOST_OK) | |
807 | key_msg = "is unchanged"; | |
808 | else | |
809 | key_msg = "has a different value"; | |
810 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
811 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
812 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
813 | error("The %s host key for %s has changed,", type, host); | |
814 | error("and the key for the according IP address %s", ip); | |
815 | error("%s. This could either mean that", key_msg); | |
816 | error("DNS SPOOFING is happening or the IP address for the host"); | |
817 | error("and its host key have changed at the same time."); | |
818 | if (ip_status != HOST_NEW) | |
819 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
820 | } | |
821 | /* The host key has changed. */ | |
822 | warn_changed_key(host_key); | |
823 | error("Add correct host key in %.100s to get rid of this message.", | |
824 | user_hostfile); | |
825 | error("Offending key in %s:%d", host_file, host_line); | |
826 | ||
827 | /* | |
828 | * If strict host key checking is in use, the user will have | |
829 | * to edit the key manually and we can only abort. | |
830 | */ | |
831 | if (options.strict_host_key_checking) { | |
832 | error("%s host key for %.200s has changed and you have " | |
833 | "requested strict checking.", type, host); | |
834 | goto fail; | |
835 | } | |
836 | ||
837 | /* | |
838 | * If strict host key checking has not been requested, allow | |
839 | * the connection but without MITM-able authentication or | |
840 | * forwarding. | |
841 | */ | |
842 | if (options.password_authentication) { | |
843 | error("Password authentication is disabled to avoid " | |
844 | "man-in-the-middle attacks."); | |
845 | options.password_authentication = 0; | |
846 | } | |
847 | if (options.kbd_interactive_authentication) { | |
848 | error("Keyboard-interactive authentication is disabled" | |
849 | " to avoid man-in-the-middle attacks."); | |
850 | options.kbd_interactive_authentication = 0; | |
851 | options.challenge_response_authentication = 0; | |
852 | } | |
853 | if (options.challenge_response_authentication) { | |
854 | error("Challenge/response authentication is disabled" | |
855 | " to avoid man-in-the-middle attacks."); | |
856 | options.challenge_response_authentication = 0; | |
857 | } | |
858 | if (options.forward_agent) { | |
859 | error("Agent forwarding is disabled to avoid " | |
860 | "man-in-the-middle attacks."); | |
861 | options.forward_agent = 0; | |
862 | } | |
863 | if (options.forward_x11) { | |
864 | error("X11 forwarding is disabled to avoid " | |
865 | "man-in-the-middle attacks."); | |
866 | options.forward_x11 = 0; | |
867 | } | |
868 | if (options.num_local_forwards > 0 || | |
869 | options.num_remote_forwards > 0) { | |
870 | error("Port forwarding is disabled to avoid " | |
871 | "man-in-the-middle attacks."); | |
872 | options.num_local_forwards = | |
873 | options.num_remote_forwards = 0; | |
874 | } | |
875 | if (options.tun_open != SSH_TUNMODE_NO) { | |
876 | error("Tunnel forwarding is disabled to avoid " | |
877 | "man-in-the-middle attacks."); | |
878 | options.tun_open = SSH_TUNMODE_NO; | |
879 | } | |
880 | /* | |
881 | * XXX Should permit the user to change to use the new id. | |
882 | * This could be done by converting the host key to an | |
883 | * identifying sentence, tell that the host identifies itself | |
884 | * by that sentence, and ask the user if he/she whishes to | |
885 | * accept the authentication. | |
886 | */ | |
887 | break; | |
888 | case HOST_FOUND: | |
889 | fatal("internal error"); | |
890 | break; | |
891 | } | |
892 | ||
893 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
894 | ip_status == HOST_CHANGED) { | |
895 | snprintf(msg, sizeof(msg), | |
896 | "Warning: the %s host key for '%.200s' " | |
897 | "differs from the key for the IP address '%.128s'" | |
898 | "\nOffending key for IP in %s:%d", | |
899 | type, host, ip, ip_file, ip_line); | |
900 | if (host_status == HOST_OK) { | |
901 | len = strlen(msg); | |
902 | snprintf(msg + len, sizeof(msg) - len, | |
903 | "\nMatching host key in %s:%d", | |
904 | host_file, host_line); | |
905 | } | |
906 | if (options.strict_host_key_checking == 1) { | |
907 | logit("%s", msg); | |
908 | error("Exiting, you have requested strict checking."); | |
909 | goto fail; | |
910 | } else if (options.strict_host_key_checking == 2) { | |
911 | strlcat(msg, "\nAre you sure you want " | |
912 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
913 | if (!confirm(msg)) | |
914 | goto fail; | |
915 | } else { | |
916 | logit("%s", msg); | |
917 | } | |
918 | } | |
919 | ||
920 | xfree(ip); | |
921 | xfree(host); | |
922 | return 0; | |
923 | ||
924 | fail: | |
925 | xfree(ip); | |
926 | xfree(host); | |
927 | return -1; | |
928 | } | |
929 | ||
930 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
931 | int | |
932 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
933 | { | |
934 | struct stat st; | |
935 | int flags = 0; | |
936 | ||
937 | if (options.verify_host_key_dns && | |
938 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
939 | ||
940 | if (flags & DNS_VERIFY_FOUND) { | |
941 | ||
942 | if (options.verify_host_key_dns == 1 && | |
943 | flags & DNS_VERIFY_MATCH && | |
944 | flags & DNS_VERIFY_SECURE) | |
945 | return 0; | |
946 | ||
947 | if (flags & DNS_VERIFY_MATCH) { | |
948 | matching_host_key_dns = 1; | |
949 | } else { | |
950 | warn_changed_key(host_key); | |
951 | error("Update the SSHFP RR in DNS with the new " | |
952 | "host key to get rid of this message."); | |
953 | } | |
954 | } | |
955 | } | |
956 | ||
957 | /* return ok if the key can be found in an old keyfile */ | |
958 | if (stat(options.system_hostfile2, &st) == 0 || | |
959 | stat(options.user_hostfile2, &st) == 0) { | |
960 | if (check_host_key(host, hostaddr, options.port, host_key, | |
961 | RDONLY, options.user_hostfile2, | |
962 | options.system_hostfile2) == 0) | |
963 | return 0; | |
964 | } | |
965 | return check_host_key(host, hostaddr, options.port, host_key, | |
966 | RDRW, options.user_hostfile, options.system_hostfile); | |
967 | } | |
968 | ||
969 | /* | |
970 | * Starts a dialog with the server, and authenticates the current user on the | |
971 | * server. This does not need any extra privileges. The basic connection | |
972 | * to the server must already have been established before this is called. | |
973 | * If login fails, this function prints an error and never returns. | |
974 | * This function does not require super-user privileges. | |
975 | */ | |
976 | void | |
977 | ssh_login(Sensitive *sensitive, const char *orighost, | |
978 | struct sockaddr *hostaddr, struct passwd *pw) | |
979 | { | |
980 | char *host, *cp; | |
981 | char *server_user, *local_user; | |
982 | ||
983 | local_user = xstrdup(pw->pw_name); | |
984 | server_user = options.user ? options.user : local_user; | |
985 | ||
986 | /* Convert the user-supplied hostname into all lowercase. */ | |
987 | host = xstrdup(orighost); | |
988 | for (cp = host; *cp; cp++) | |
989 | if (isupper(*cp)) | |
990 | *cp = (char)tolower(*cp); | |
991 | ||
992 | /* Exchange protocol version identification strings with the server. */ | |
993 | ssh_exchange_identification(); | |
994 | ||
995 | /* Put the connection into non-blocking mode. */ | |
996 | packet_set_nonblocking(); | |
997 | ||
998 | /* key exchange */ | |
999 | /* authenticate user */ | |
1000 | if (compat20) { | |
1001 | ssh_kex2(host, hostaddr); | |
1002 | ssh_userauth2(local_user, server_user, host, sensitive); | |
1003 | } else { | |
1004 | ssh_kex(host, hostaddr); | |
1005 | ssh_userauth1(local_user, server_user, host, sensitive); | |
1006 | } | |
1007 | xfree(local_user); | |
1008 | } | |
1009 | ||
1010 | void | |
1011 | ssh_put_password(char *password) | |
1012 | { | |
1013 | int size; | |
1014 | char *padded; | |
1015 | ||
1016 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
1017 | packet_put_cstring(password); | |
1018 | return; | |
1019 | } | |
1020 | size = roundup(strlen(password) + 1, 32); | |
1021 | padded = xcalloc(1, size); | |
1022 | strlcpy(padded, password, size); | |
1023 | packet_put_string(padded, size); | |
1024 | memset(padded, 0, size); | |
1025 | xfree(padded); | |
1026 | } | |
1027 | ||
1028 | static int | |
1029 | show_key_from_file(const char *file, const char *host, int keytype) | |
1030 | { | |
1031 | Key *found; | |
1032 | char *fp; | |
1033 | int line, ret; | |
1034 | ||
1035 | found = key_new(keytype); | |
1036 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
1037 | keytype, found, &line))) { | |
1038 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
1039 | logit("WARNING: %s key found for host %s\n" | |
1040 | "in %s:%d\n" | |
1041 | "%s key fingerprint %s.", | |
1042 | key_type(found), host, file, line, | |
1043 | key_type(found), fp); | |
1044 | xfree(fp); | |
1045 | } | |
1046 | key_free(found); | |
1047 | return (ret); | |
1048 | } | |
1049 | ||
1050 | /* print all known host keys for a given host, but skip keys of given type */ | |
1051 | static int | |
1052 | show_other_keys(const char *host, Key *key) | |
1053 | { | |
1054 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1055 | int i, found = 0; | |
1056 | ||
1057 | for (i = 0; type[i] != -1; i++) { | |
1058 | if (type[i] == key->type) | |
1059 | continue; | |
1060 | if (type[i] != KEY_RSA1 && | |
1061 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1062 | found = 1; | |
1063 | continue; | |
1064 | } | |
1065 | if (type[i] != KEY_RSA1 && | |
1066 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1067 | found = 1; | |
1068 | continue; | |
1069 | } | |
1070 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1071 | found = 1; | |
1072 | continue; | |
1073 | } | |
1074 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1075 | found = 1; | |
1076 | continue; | |
1077 | } | |
1078 | debug2("no key of type %d for host %s", type[i], host); | |
1079 | } | |
1080 | return (found); | |
1081 | } | |
1082 | ||
1083 | static void | |
1084 | warn_changed_key(Key *host_key) | |
1085 | { | |
1086 | char *fp; | |
1087 | const char *type = key_type(host_key); | |
1088 | ||
1089 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1090 | ||
1091 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1092 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1093 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1094 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1095 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1096 | error("It is also possible that the %s host key has just been changed.", type); | |
1097 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1098 | type, fp); | |
1099 | error("Please contact your system administrator."); | |
1100 | ||
1101 | xfree(fp); | |
1102 | } | |
1103 | ||
1104 | /* | |
1105 | * Execute a local command | |
1106 | */ | |
1107 | int | |
1108 | ssh_local_cmd(const char *args) | |
1109 | { | |
1110 | char *shell; | |
1111 | pid_t pid; | |
1112 | int status; | |
1113 | ||
1114 | if (!options.permit_local_command || | |
1115 | args == NULL || !*args) | |
1116 | return (1); | |
1117 | ||
1118 | if ((shell = getenv("SHELL")) == NULL) | |
1119 | shell = _PATH_BSHELL; | |
1120 | ||
1121 | pid = fork(); | |
1122 | if (pid == 0) { | |
1123 | debug3("Executing %s -c \"%s\"", shell, args); | |
1124 | execl(shell, shell, "-c", args, (char *)NULL); | |
1125 | error("Couldn't execute %s -c \"%s\": %s", | |
1126 | shell, args, strerror(errno)); | |
1127 | _exit(1); | |
1128 | } else if (pid == -1) | |
1129 | fatal("fork failed: %.100s", strerror(errno)); | |
1130 | while (waitpid(pid, &status, 0) == -1) | |
1131 | if (errno != EINTR) | |
1132 | fatal("Couldn't wait for child: %s", strerror(errno)); | |
1133 | ||
1134 | if (!WIFEXITED(status)) | |
1135 | return (1); | |
1136 | ||
1137 | return (WEXITSTATUS(status)); | |
1138 | } |