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1 | /* | |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Code to connect to a remote host, and to perform the client side of the | |
6 | * login (authentication) dialog. | |
7 | * | |
8 | * As far as I am concerned, the code I have written for this software | |
9 | * can be used freely for any purpose. Any derived versions of this | |
10 | * software must be clearly marked as such, and if the derived work is | |
11 | * incompatible with the protocol description in the RFC file, it must be | |
12 | * called by a name other than "ssh" or "Secure Shell". | |
13 | */ | |
14 | ||
15 | #include "includes.h" | |
16 | RCSID("$OpenBSD: sshconnect.c,v 1.151 2003/11/03 09:37:32 jakob Exp $"); | |
17 | ||
18 | #include <openssl/bn.h> | |
19 | ||
20 | #include "ssh.h" | |
21 | #include "xmalloc.h" | |
22 | #include "rsa.h" | |
23 | #include "buffer.h" | |
24 | #include "packet.h" | |
25 | #include "uidswap.h" | |
26 | #include "compat.h" | |
27 | #include "key.h" | |
28 | #include "sshconnect.h" | |
29 | #include "hostfile.h" | |
30 | #include "log.h" | |
31 | #include "readconf.h" | |
32 | #include "atomicio.h" | |
33 | #include "misc.h" | |
34 | #include "readpass.h" | |
35 | ||
36 | #include "dns.h" | |
37 | ||
38 | char *client_version_string = NULL; | |
39 | char *server_version_string = NULL; | |
40 | ||
41 | int verified_host_key_dns = 0; | |
42 | ||
43 | /* import */ | |
44 | extern Options options; | |
45 | extern char *__progname; | |
46 | extern uid_t original_real_uid; | |
47 | extern uid_t original_effective_uid; | |
48 | extern pid_t proxy_command_pid; | |
49 | ||
50 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
51 | #define INET6_ADDRSTRLEN 46 | |
52 | #endif | |
53 | ||
54 | static int show_other_keys(const char *, Key *); | |
55 | static void warn_changed_key(Key *); | |
56 | ||
57 | /* | |
58 | * Connect to the given ssh server using a proxy command. | |
59 | */ | |
60 | static int | |
61 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
62 | { | |
63 | Buffer command; | |
64 | const char *cp; | |
65 | char *command_string; | |
66 | int pin[2], pout[2]; | |
67 | pid_t pid; | |
68 | char strport[NI_MAXSERV]; | |
69 | ||
70 | /* Convert the port number into a string. */ | |
71 | snprintf(strport, sizeof strport, "%hu", port); | |
72 | ||
73 | /* | |
74 | * Build the final command string in the buffer by making the | |
75 | * appropriate substitutions to the given proxy command. | |
76 | * | |
77 | * Use "exec" to avoid "sh -c" processes on some platforms | |
78 | * (e.g. Solaris) | |
79 | */ | |
80 | buffer_init(&command); | |
81 | buffer_append(&command, "exec ", 5); | |
82 | ||
83 | for (cp = proxy_command; *cp; cp++) { | |
84 | if (cp[0] == '%' && cp[1] == '%') { | |
85 | buffer_append(&command, "%", 1); | |
86 | cp++; | |
87 | continue; | |
88 | } | |
89 | if (cp[0] == '%' && cp[1] == 'h') { | |
90 | buffer_append(&command, host, strlen(host)); | |
91 | cp++; | |
92 | continue; | |
93 | } | |
94 | if (cp[0] == '%' && cp[1] == 'p') { | |
95 | buffer_append(&command, strport, strlen(strport)); | |
96 | cp++; | |
97 | continue; | |
98 | } | |
99 | buffer_append(&command, cp, 1); | |
100 | } | |
101 | buffer_append(&command, "\0", 1); | |
102 | ||
103 | /* Get the final command string. */ | |
104 | command_string = buffer_ptr(&command); | |
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 | seteuid(original_real_uid); | |
119 | setuid(original_real_uid); | |
120 | ||
121 | /* Redirect stdin and stdout. */ | |
122 | close(pin[1]); | |
123 | if (pin[0] != 0) { | |
124 | if (dup2(pin[0], 0) < 0) | |
125 | perror("dup2 stdin"); | |
126 | close(pin[0]); | |
127 | } | |
128 | close(pout[0]); | |
129 | if (dup2(pout[1], 1) < 0) | |
130 | perror("dup2 stdout"); | |
131 | /* Cannot be 1 because pin allocated two descriptors. */ | |
132 | close(pout[1]); | |
133 | ||
134 | /* Stderr is left as it is so that error messages get | |
135 | printed on the user's terminal. */ | |
136 | argv[0] = _PATH_BSHELL; | |
137 | argv[1] = "-c"; | |
138 | argv[2] = command_string; | |
139 | argv[3] = NULL; | |
140 | ||
141 | /* Execute the proxy command. Note that we gave up any | |
142 | extra privileges above. */ | |
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 | else | |
151 | proxy_command_pid = pid; /* save pid to clean up later */ | |
152 | ||
153 | /* Close child side of the descriptors. */ | |
154 | close(pin[0]); | |
155 | close(pout[1]); | |
156 | ||
157 | /* Free the command name. */ | |
158 | buffer_free(&command); | |
159 | ||
160 | /* Set the connection file descriptors. */ | |
161 | packet_set_connection(pout[0], pin[1]); | |
162 | ||
163 | /* Indicate OK return */ | |
164 | return 0; | |
165 | } | |
166 | ||
167 | /* | |
168 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
169 | */ | |
170 | static int | |
171 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
172 | { | |
173 | int sock, gaierr; | |
174 | struct addrinfo hints, *res; | |
175 | ||
176 | /* | |
177 | * If we are running as root and want to connect to a privileged | |
178 | * port, bind our own socket to a privileged port. | |
179 | */ | |
180 | if (privileged) { | |
181 | int p = IPPORT_RESERVED - 1; | |
182 | PRIV_START; | |
183 | sock = rresvport_af(&p, ai->ai_family); | |
184 | PRIV_END; | |
185 | if (sock < 0) | |
186 | error("rresvport: af=%d %.100s", ai->ai_family, | |
187 | strerror(errno)); | |
188 | else | |
189 | debug("Allocated local port %d.", p); | |
190 | return sock; | |
191 | } | |
192 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
193 | if (sock < 0) | |
194 | error("socket: %.100s", strerror(errno)); | |
195 | ||
196 | /* Bind the socket to an alternative local IP address */ | |
197 | if (options.bind_address == NULL) | |
198 | return sock; | |
199 | ||
200 | memset(&hints, 0, sizeof(hints)); | |
201 | hints.ai_family = ai->ai_family; | |
202 | hints.ai_socktype = ai->ai_socktype; | |
203 | hints.ai_protocol = ai->ai_protocol; | |
204 | hints.ai_flags = AI_PASSIVE; | |
205 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
206 | if (gaierr) { | |
207 | error("getaddrinfo: %s: %s", options.bind_address, | |
208 | gai_strerror(gaierr)); | |
209 | close(sock); | |
210 | return -1; | |
211 | } | |
212 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
213 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
214 | close(sock); | |
215 | freeaddrinfo(res); | |
216 | return -1; | |
217 | } | |
218 | freeaddrinfo(res); | |
219 | return sock; | |
220 | } | |
221 | ||
222 | static int | |
223 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
224 | socklen_t addrlen, int timeout) | |
225 | { | |
226 | fd_set *fdset; | |
227 | struct timeval tv; | |
228 | socklen_t optlen; | |
229 | int fdsetsz, optval, rc, result = -1; | |
230 | ||
231 | if (timeout <= 0) | |
232 | return (connect(sockfd, serv_addr, addrlen)); | |
233 | ||
234 | if (fcntl(sockfd, F_SETFL, O_NONBLOCK) < 0) | |
235 | return (-1); | |
236 | ||
237 | rc = connect(sockfd, serv_addr, addrlen); | |
238 | if (rc == 0) | |
239 | return (0); | |
240 | if (errno != EINPROGRESS) | |
241 | return (-1); | |
242 | ||
243 | fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); | |
244 | fdset = (fd_set *)xmalloc(fdsetsz); | |
245 | ||
246 | memset(fdset, 0, fdsetsz); | |
247 | FD_SET(sockfd, fdset); | |
248 | tv.tv_sec = timeout; | |
249 | tv.tv_usec = 0; | |
250 | ||
251 | for(;;) { | |
252 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
253 | if (rc != -1 || errno != EINTR) | |
254 | break; | |
255 | } | |
256 | ||
257 | switch(rc) { | |
258 | case 0: | |
259 | /* Timed out */ | |
260 | errno = ETIMEDOUT; | |
261 | break; | |
262 | case -1: | |
263 | /* Select error */ | |
264 | debug("select: %s", strerror(errno)); | |
265 | break; | |
266 | case 1: | |
267 | /* Completed or failed */ | |
268 | optval = 0; | |
269 | optlen = sizeof(optval); | |
270 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
271 | &optlen) == -1) { | |
272 | debug("getsockopt: %s", strerror(errno)); | |
273 | break; | |
274 | } | |
275 | if (optval != 0) { | |
276 | errno = optval; | |
277 | break; | |
278 | } | |
279 | result = 0; | |
280 | break; | |
281 | default: | |
282 | /* Should not occur */ | |
283 | fatal("Bogus return (%d) from select()", rc); | |
284 | } | |
285 | ||
286 | xfree(fdset); | |
287 | return (result); | |
288 | } | |
289 | ||
290 | /* | |
291 | * Opens a TCP/IP connection to the remote server on the given host. | |
292 | * The address of the remote host will be returned in hostaddr. | |
293 | * If port is 0, the default port will be used. If needpriv is true, | |
294 | * a privileged port will be allocated to make the connection. | |
295 | * This requires super-user privileges if needpriv is true. | |
296 | * Connection_attempts specifies the maximum number of tries (one per | |
297 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
298 | * and %p substituted for host and port, respectively) to use to contact | |
299 | * the daemon. | |
300 | * Return values: | |
301 | * 0 for OK | |
302 | * ECONNREFUSED if we got a "Connection Refused" by the peer on any address | |
303 | * ECONNABORTED if we failed without a "Connection refused" | |
304 | * Suitable error messages for the connection failure will already have been | |
305 | * printed. | |
306 | */ | |
307 | int | |
308 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
309 | u_short port, int family, int connection_attempts, | |
310 | int needpriv, const char *proxy_command) | |
311 | { | |
312 | int gaierr; | |
313 | int on = 1; | |
314 | int sock = -1, attempt; | |
315 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
316 | struct addrinfo hints, *ai, *aitop; | |
317 | struct servent *sp; | |
318 | /* | |
319 | * Did we get only other errors than "Connection refused" (which | |
320 | * should block fallback to rsh and similar), or did we get at least | |
321 | * one "Connection refused"? | |
322 | */ | |
323 | int full_failure = 1; | |
324 | ||
325 | debug2("ssh_connect: needpriv %d", needpriv); | |
326 | ||
327 | /* Get default port if port has not been set. */ | |
328 | if (port == 0) { | |
329 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
330 | if (sp) | |
331 | port = ntohs(sp->s_port); | |
332 | else | |
333 | port = SSH_DEFAULT_PORT; | |
334 | } | |
335 | /* If a proxy command is given, connect using it. */ | |
336 | if (proxy_command != NULL) | |
337 | return ssh_proxy_connect(host, port, proxy_command); | |
338 | ||
339 | /* No proxy command. */ | |
340 | ||
341 | memset(&hints, 0, sizeof(hints)); | |
342 | hints.ai_family = family; | |
343 | hints.ai_socktype = SOCK_STREAM; | |
344 | snprintf(strport, sizeof strport, "%u", port); | |
345 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
346 | fatal("%s: %.100s: %s", __progname, host, | |
347 | gai_strerror(gaierr)); | |
348 | ||
349 | /* | |
350 | * Try to connect several times. On some machines, the first time | |
351 | * will sometimes fail. In general socket code appears to behave | |
352 | * quite magically on many machines. | |
353 | */ | |
354 | for (attempt = 0; ;) { | |
355 | if (attempt > 0) | |
356 | debug("Trying again..."); | |
357 | ||
358 | /* Loop through addresses for this host, and try each one in | |
359 | sequence until the connection succeeds. */ | |
360 | for (ai = aitop; ai; ai = ai->ai_next) { | |
361 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
362 | continue; | |
363 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
364 | ntop, sizeof(ntop), strport, sizeof(strport), | |
365 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
366 | error("ssh_connect: getnameinfo failed"); | |
367 | continue; | |
368 | } | |
369 | debug("Connecting to %.200s [%.100s] port %s.", | |
370 | host, ntop, strport); | |
371 | ||
372 | /* Create a socket for connecting. */ | |
373 | sock = ssh_create_socket(needpriv, ai); | |
374 | if (sock < 0) | |
375 | /* Any error is already output */ | |
376 | continue; | |
377 | ||
378 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
379 | options.connection_timeout) >= 0) { | |
380 | /* Successful connection. */ | |
381 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
382 | break; | |
383 | } else { | |
384 | if (errno == ECONNREFUSED) | |
385 | full_failure = 0; | |
386 | debug("connect to address %s port %s: %s", | |
387 | ntop, strport, strerror(errno)); | |
388 | /* | |
389 | * Close the failed socket; there appear to | |
390 | * be some problems when reusing a socket for | |
391 | * which connect() has already returned an | |
392 | * error. | |
393 | */ | |
394 | close(sock); | |
395 | } | |
396 | } | |
397 | if (ai) | |
398 | break; /* Successful connection. */ | |
399 | ||
400 | attempt++; | |
401 | if (attempt >= connection_attempts) | |
402 | break; | |
403 | /* Sleep a moment before retrying. */ | |
404 | sleep(1); | |
405 | } | |
406 | ||
407 | freeaddrinfo(aitop); | |
408 | ||
409 | /* Return failure if we didn't get a successful connection. */ | |
410 | if (attempt >= connection_attempts) { | |
411 | logit("ssh: connect to host %s port %s: %s", | |
412 | host, strport, strerror(errno)); | |
413 | return full_failure ? ECONNABORTED : ECONNREFUSED; | |
414 | } | |
415 | ||
416 | debug("Connection established."); | |
417 | ||
418 | /* Set keepalives if requested. */ | |
419 | if (options.keepalives && | |
420 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
421 | sizeof(on)) < 0) | |
422 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
423 | ||
424 | /* Set the connection. */ | |
425 | packet_set_connection(sock, sock); | |
426 | ||
427 | return 0; | |
428 | } | |
429 | ||
430 | /* | |
431 | * Waits for the server identification string, and sends our own | |
432 | * identification string. | |
433 | */ | |
434 | static void | |
435 | ssh_exchange_identification(void) | |
436 | { | |
437 | char buf[256], remote_version[256]; /* must be same size! */ | |
438 | int remote_major, remote_minor, i, mismatch; | |
439 | int connection_in = packet_get_connection_in(); | |
440 | int connection_out = packet_get_connection_out(); | |
441 | int minor1 = PROTOCOL_MINOR_1; | |
442 | ||
443 | /* Read other side\'s version identification. */ | |
444 | for (;;) { | |
445 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
446 | int len = atomicio(read, connection_in, &buf[i], 1); | |
447 | if (len < 0) | |
448 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
449 | if (len != 1) | |
450 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
451 | if (buf[i] == '\r') { | |
452 | buf[i] = '\n'; | |
453 | buf[i + 1] = 0; | |
454 | continue; /**XXX wait for \n */ | |
455 | } | |
456 | if (buf[i] == '\n') { | |
457 | buf[i + 1] = 0; | |
458 | break; | |
459 | } | |
460 | } | |
461 | buf[sizeof(buf) - 1] = 0; | |
462 | if (strncmp(buf, "SSH-", 4) == 0) | |
463 | break; | |
464 | debug("ssh_exchange_identification: %s", buf); | |
465 | } | |
466 | server_version_string = xstrdup(buf); | |
467 | ||
468 | /* | |
469 | * Check that the versions match. In future this might accept | |
470 | * several versions and set appropriate flags to handle them. | |
471 | */ | |
472 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
473 | &remote_major, &remote_minor, remote_version) != 3) | |
474 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
475 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
476 | remote_major, remote_minor, remote_version); | |
477 | ||
478 | compat_datafellows(remote_version); | |
479 | mismatch = 0; | |
480 | ||
481 | switch (remote_major) { | |
482 | case 1: | |
483 | if (remote_minor == 99 && | |
484 | (options.protocol & SSH_PROTO_2) && | |
485 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
486 | enable_compat20(); | |
487 | break; | |
488 | } | |
489 | if (!(options.protocol & SSH_PROTO_1)) { | |
490 | mismatch = 1; | |
491 | break; | |
492 | } | |
493 | if (remote_minor < 3) { | |
494 | fatal("Remote machine has too old SSH software version."); | |
495 | } else if (remote_minor == 3 || remote_minor == 4) { | |
496 | /* We speak 1.3, too. */ | |
497 | enable_compat13(); | |
498 | minor1 = 3; | |
499 | if (options.forward_agent) { | |
500 | logit("Agent forwarding disabled for protocol 1.3"); | |
501 | options.forward_agent = 0; | |
502 | } | |
503 | } | |
504 | break; | |
505 | case 2: | |
506 | if (options.protocol & SSH_PROTO_2) { | |
507 | enable_compat20(); | |
508 | break; | |
509 | } | |
510 | /* FALLTHROUGH */ | |
511 | default: | |
512 | mismatch = 1; | |
513 | break; | |
514 | } | |
515 | if (mismatch) | |
516 | fatal("Protocol major versions differ: %d vs. %d", | |
517 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
518 | remote_major); | |
519 | /* Send our own protocol version identification. */ | |
520 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
521 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
522 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
523 | SSH_VERSION); | |
524 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
525 | fatal("write: %.100s", strerror(errno)); | |
526 | client_version_string = xstrdup(buf); | |
527 | chop(client_version_string); | |
528 | chop(server_version_string); | |
529 | debug("Local version string %.100s", client_version_string); | |
530 | } | |
531 | ||
532 | /* defaults to 'no' */ | |
533 | static int | |
534 | confirm(const char *prompt) | |
535 | { | |
536 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
537 | char *p; | |
538 | int ret = -1; | |
539 | ||
540 | if (options.batch_mode) | |
541 | return 0; | |
542 | for (msg = prompt;;msg = again) { | |
543 | p = read_passphrase(msg, RP_ECHO); | |
544 | if (p == NULL || | |
545 | (p[0] == '\0') || (p[0] == '\n') || | |
546 | strncasecmp(p, "no", 2) == 0) | |
547 | ret = 0; | |
548 | if (p && strncasecmp(p, "yes", 3) == 0) | |
549 | ret = 1; | |
550 | if (p) | |
551 | xfree(p); | |
552 | if (ret != -1) | |
553 | return ret; | |
554 | } | |
555 | } | |
556 | ||
557 | /* | |
558 | * check whether the supplied host key is valid, return -1 if the key | |
559 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
560 | */ | |
561 | static int | |
562 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
563 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
564 | { | |
565 | Key *file_key; | |
566 | char *type = key_type(host_key); | |
567 | char *ip = NULL; | |
568 | char hostline[1000], *hostp, *fp; | |
569 | HostStatus host_status; | |
570 | HostStatus ip_status; | |
571 | int local = 0, host_ip_differ = 0; | |
572 | int salen; | |
573 | char ntop[NI_MAXHOST]; | |
574 | char msg[1024]; | |
575 | int len, host_line, ip_line; | |
576 | const char *host_file = NULL, *ip_file = NULL; | |
577 | ||
578 | /* | |
579 | * Force accepting of the host key for loopback/localhost. The | |
580 | * problem is that if the home directory is NFS-mounted to multiple | |
581 | * machines, localhost will refer to a different machine in each of | |
582 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
583 | * essentially disables host authentication for localhost; however, | |
584 | * this is probably not a real problem. | |
585 | */ | |
586 | /** hostaddr == 0! */ | |
587 | switch (hostaddr->sa_family) { | |
588 | case AF_INET: | |
589 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
590 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
591 | salen = sizeof(struct sockaddr_in); | |
592 | break; | |
593 | case AF_INET6: | |
594 | local = IN6_IS_ADDR_LOOPBACK( | |
595 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
596 | salen = sizeof(struct sockaddr_in6); | |
597 | break; | |
598 | default: | |
599 | local = 0; | |
600 | salen = sizeof(struct sockaddr_storage); | |
601 | break; | |
602 | } | |
603 | if (options.no_host_authentication_for_localhost == 1 && local && | |
604 | options.host_key_alias == NULL) { | |
605 | debug("Forcing accepting of host key for " | |
606 | "loopback/localhost."); | |
607 | return 0; | |
608 | } | |
609 | ||
610 | /* | |
611 | * We don't have the remote ip-address for connections | |
612 | * using a proxy command | |
613 | */ | |
614 | if (options.proxy_command == NULL) { | |
615 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
616 | NULL, 0, NI_NUMERICHOST) != 0) | |
617 | fatal("check_host_key: getnameinfo failed"); | |
618 | ip = xstrdup(ntop); | |
619 | } else { | |
620 | ip = xstrdup("<no hostip for proxy command>"); | |
621 | } | |
622 | /* | |
623 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
624 | * command or if we don't have a hostname to compare with | |
625 | */ | |
626 | if (options.check_host_ip && | |
627 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
628 | options.check_host_ip = 0; | |
629 | ||
630 | /* | |
631 | * Allow the user to record the key under a different name. This is | |
632 | * useful for ssh tunneling over forwarded connections or if you run | |
633 | * multiple sshd's on different ports on the same machine. | |
634 | */ | |
635 | if (options.host_key_alias != NULL) { | |
636 | host = options.host_key_alias; | |
637 | debug("using hostkeyalias: %s", host); | |
638 | } | |
639 | ||
640 | /* | |
641 | * Store the host key from the known host file in here so that we can | |
642 | * compare it with the key for the IP address. | |
643 | */ | |
644 | file_key = key_new(host_key->type); | |
645 | ||
646 | /* | |
647 | * Check if the host key is present in the user\'s list of known | |
648 | * hosts or in the systemwide list. | |
649 | */ | |
650 | host_file = user_hostfile; | |
651 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
652 | file_key, &host_line); | |
653 | if (host_status == HOST_NEW) { | |
654 | host_file = system_hostfile; | |
655 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
656 | file_key, &host_line); | |
657 | } | |
658 | /* | |
659 | * Also perform check for the ip address, skip the check if we are | |
660 | * localhost or the hostname was an ip address to begin with | |
661 | */ | |
662 | if (options.check_host_ip) { | |
663 | Key *ip_key = key_new(host_key->type); | |
664 | ||
665 | ip_file = user_hostfile; | |
666 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
667 | ip_key, &ip_line); | |
668 | if (ip_status == HOST_NEW) { | |
669 | ip_file = system_hostfile; | |
670 | ip_status = check_host_in_hostfile(ip_file, ip, | |
671 | host_key, ip_key, &ip_line); | |
672 | } | |
673 | if (host_status == HOST_CHANGED && | |
674 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
675 | host_ip_differ = 1; | |
676 | ||
677 | key_free(ip_key); | |
678 | } else | |
679 | ip_status = host_status; | |
680 | ||
681 | key_free(file_key); | |
682 | ||
683 | switch (host_status) { | |
684 | case HOST_OK: | |
685 | /* The host is known and the key matches. */ | |
686 | debug("Host '%.200s' is known and matches the %s host key.", | |
687 | host, type); | |
688 | debug("Found key in %s:%d", host_file, host_line); | |
689 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
690 | if (readonly) | |
691 | logit("%s host key for IP address " | |
692 | "'%.128s' not in list of known hosts.", | |
693 | type, ip); | |
694 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
695 | host_key)) | |
696 | logit("Failed to add the %s host key for IP " | |
697 | "address '%.128s' to the list of known " | |
698 | "hosts (%.30s).", type, ip, user_hostfile); | |
699 | else | |
700 | logit("Warning: Permanently added the %s host " | |
701 | "key for IP address '%.128s' to the list " | |
702 | "of known hosts.", type, ip); | |
703 | } | |
704 | break; | |
705 | case HOST_NEW: | |
706 | if (readonly) | |
707 | goto fail; | |
708 | /* The host is new. */ | |
709 | if (options.strict_host_key_checking == 1) { | |
710 | /* | |
711 | * User has requested strict host key checking. We | |
712 | * will not add the host key automatically. The only | |
713 | * alternative left is to abort. | |
714 | */ | |
715 | error("No %s host key is known for %.200s and you " | |
716 | "have requested strict checking.", type, host); | |
717 | goto fail; | |
718 | } else if (options.strict_host_key_checking == 2) { | |
719 | char msg1[1024], msg2[1024]; | |
720 | ||
721 | if (show_other_keys(host, host_key)) | |
722 | snprintf(msg1, sizeof(msg1), | |
723 | "\nbut keys of different type are already" | |
724 | " known for this host."); | |
725 | else | |
726 | snprintf(msg1, sizeof(msg1), "."); | |
727 | /* The default */ | |
728 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
729 | msg2[0] = '\0'; | |
730 | if (options.verify_host_key_dns) { | |
731 | if (verified_host_key_dns) | |
732 | snprintf(msg2, sizeof(msg2), | |
733 | "Matching host key fingerprint" | |
734 | " found in DNS.\n"); | |
735 | else | |
736 | snprintf(msg2, sizeof(msg2), | |
737 | "No matching host key fingerprint" | |
738 | " found in DNS.\n"); | |
739 | } | |
740 | snprintf(msg, sizeof(msg), | |
741 | "The authenticity of host '%.200s (%s)' can't be " | |
742 | "established%s\n" | |
743 | "%s key fingerprint is %s.\n%s" | |
744 | "Are you sure you want to continue connecting " | |
745 | "(yes/no)? ", | |
746 | host, ip, msg1, type, fp, msg2); | |
747 | xfree(fp); | |
748 | if (!confirm(msg)) | |
749 | goto fail; | |
750 | } | |
751 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
752 | snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); | |
753 | hostp = hostline; | |
754 | } else | |
755 | hostp = host; | |
756 | ||
757 | /* | |
758 | * If not in strict mode, add the key automatically to the | |
759 | * local known_hosts file. | |
760 | */ | |
761 | if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) | |
762 | logit("Failed to add the host to the list of known " | |
763 | "hosts (%.500s).", user_hostfile); | |
764 | else | |
765 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
766 | "list of known hosts.", hostp, type); | |
767 | break; | |
768 | case HOST_CHANGED: | |
769 | if (options.check_host_ip && host_ip_differ) { | |
770 | char *msg; | |
771 | if (ip_status == HOST_NEW) | |
772 | msg = "is unknown"; | |
773 | else if (ip_status == HOST_OK) | |
774 | msg = "is unchanged"; | |
775 | else | |
776 | msg = "has a different value"; | |
777 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
778 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
779 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
780 | error("The %s host key for %s has changed,", type, host); | |
781 | error("and the key for the according IP address %s", ip); | |
782 | error("%s. This could either mean that", msg); | |
783 | error("DNS SPOOFING is happening or the IP address for the host"); | |
784 | error("and its host key have changed at the same time."); | |
785 | if (ip_status != HOST_NEW) | |
786 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
787 | } | |
788 | /* The host key has changed. */ | |
789 | warn_changed_key(host_key); | |
790 | error("Add correct host key in %.100s to get rid of this message.", | |
791 | user_hostfile); | |
792 | error("Offending key in %s:%d", host_file, host_line); | |
793 | ||
794 | /* | |
795 | * If strict host key checking is in use, the user will have | |
796 | * to edit the key manually and we can only abort. | |
797 | */ | |
798 | if (options.strict_host_key_checking) { | |
799 | error("%s host key for %.200s has changed and you have " | |
800 | "requested strict checking.", type, host); | |
801 | goto fail; | |
802 | } | |
803 | ||
804 | /* | |
805 | * If strict host key checking has not been requested, allow | |
806 | * the connection but without MITM-able authentication or | |
807 | * agent forwarding. | |
808 | */ | |
809 | if (options.password_authentication) { | |
810 | error("Password authentication is disabled to avoid " | |
811 | "man-in-the-middle attacks."); | |
812 | options.password_authentication = 0; | |
813 | } | |
814 | if (options.kbd_interactive_authentication) { | |
815 | error("Keyboard-interactive authentication is disabled" | |
816 | " to avoid man-in-the-middle attacks."); | |
817 | options.kbd_interactive_authentication = 0; | |
818 | options.challenge_response_authentication = 0; | |
819 | } | |
820 | if (options.challenge_response_authentication) { | |
821 | error("Challenge/response authentication is disabled" | |
822 | " to avoid man-in-the-middle attacks."); | |
823 | options.challenge_response_authentication = 0; | |
824 | } | |
825 | if (options.forward_agent) { | |
826 | error("Agent forwarding is disabled to avoid " | |
827 | "man-in-the-middle attacks."); | |
828 | options.forward_agent = 0; | |
829 | } | |
830 | if (options.forward_x11) { | |
831 | error("X11 forwarding is disabled to avoid " | |
832 | "man-in-the-middle attacks."); | |
833 | options.forward_x11 = 0; | |
834 | } | |
835 | if (options.num_local_forwards > 0 || | |
836 | options.num_remote_forwards > 0) { | |
837 | error("Port forwarding is disabled to avoid " | |
838 | "man-in-the-middle attacks."); | |
839 | options.num_local_forwards = | |
840 | options.num_remote_forwards = 0; | |
841 | } | |
842 | /* | |
843 | * XXX Should permit the user to change to use the new id. | |
844 | * This could be done by converting the host key to an | |
845 | * identifying sentence, tell that the host identifies itself | |
846 | * by that sentence, and ask the user if he/she whishes to | |
847 | * accept the authentication. | |
848 | */ | |
849 | break; | |
850 | case HOST_FOUND: | |
851 | fatal("internal error"); | |
852 | break; | |
853 | } | |
854 | ||
855 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
856 | ip_status == HOST_CHANGED) { | |
857 | snprintf(msg, sizeof(msg), | |
858 | "Warning: the %s host key for '%.200s' " | |
859 | "differs from the key for the IP address '%.128s'" | |
860 | "\nOffending key for IP in %s:%d", | |
861 | type, host, ip, ip_file, ip_line); | |
862 | if (host_status == HOST_OK) { | |
863 | len = strlen(msg); | |
864 | snprintf(msg + len, sizeof(msg) - len, | |
865 | "\nMatching host key in %s:%d", | |
866 | host_file, host_line); | |
867 | } | |
868 | if (options.strict_host_key_checking == 1) { | |
869 | logit("%s", msg); | |
870 | error("Exiting, you have requested strict checking."); | |
871 | goto fail; | |
872 | } else if (options.strict_host_key_checking == 2) { | |
873 | strlcat(msg, "\nAre you sure you want " | |
874 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
875 | if (!confirm(msg)) | |
876 | goto fail; | |
877 | } else { | |
878 | logit("%s", msg); | |
879 | } | |
880 | } | |
881 | ||
882 | xfree(ip); | |
883 | return 0; | |
884 | ||
885 | fail: | |
886 | xfree(ip); | |
887 | return -1; | |
888 | } | |
889 | ||
890 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
891 | int | |
892 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
893 | { | |
894 | struct stat st; | |
895 | ||
896 | if (options.verify_host_key_dns) { | |
897 | switch(verify_host_key_dns(host, hostaddr, host_key)) { | |
898 | case DNS_VERIFY_OK: | |
899 | #ifdef DNSSEC | |
900 | return 0; | |
901 | #else | |
902 | verified_host_key_dns = 1; | |
903 | break; | |
904 | #endif | |
905 | case DNS_VERIFY_FAILED: | |
906 | return -1; | |
907 | case DNS_VERIFY_ERROR: | |
908 | break; | |
909 | default: | |
910 | debug3("bad return value from verify_host_key_dns"); | |
911 | break; | |
912 | } | |
913 | } | |
914 | ||
915 | /* return ok if the key can be found in an old keyfile */ | |
916 | if (stat(options.system_hostfile2, &st) == 0 || | |
917 | stat(options.user_hostfile2, &st) == 0) { | |
918 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
919 | options.user_hostfile2, options.system_hostfile2) == 0) | |
920 | return 0; | |
921 | } | |
922 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
923 | options.user_hostfile, options.system_hostfile); | |
924 | } | |
925 | ||
926 | /* | |
927 | * Starts a dialog with the server, and authenticates the current user on the | |
928 | * server. This does not need any extra privileges. The basic connection | |
929 | * to the server must already have been established before this is called. | |
930 | * If login fails, this function prints an error and never returns. | |
931 | * This function does not require super-user privileges. | |
932 | */ | |
933 | void | |
934 | ssh_login(Sensitive *sensitive, const char *orighost, | |
935 | struct sockaddr *hostaddr, struct passwd *pw) | |
936 | { | |
937 | char *host, *cp; | |
938 | char *server_user, *local_user; | |
939 | ||
940 | local_user = xstrdup(pw->pw_name); | |
941 | server_user = options.user ? options.user : local_user; | |
942 | ||
943 | /* Convert the user-supplied hostname into all lowercase. */ | |
944 | host = xstrdup(orighost); | |
945 | for (cp = host; *cp; cp++) | |
946 | if (isupper(*cp)) | |
947 | *cp = tolower(*cp); | |
948 | ||
949 | /* Exchange protocol version identification strings with the server. */ | |
950 | ssh_exchange_identification(); | |
951 | ||
952 | /* Put the connection into non-blocking mode. */ | |
953 | packet_set_nonblocking(); | |
954 | ||
955 | /* key exchange */ | |
956 | /* authenticate user */ | |
957 | if (compat20) { | |
958 | ssh_kex2(host, hostaddr); | |
959 | ssh_userauth2(local_user, server_user, host, sensitive); | |
960 | } else { | |
961 | ssh_kex(host, hostaddr); | |
962 | ssh_userauth1(local_user, server_user, host, sensitive); | |
963 | } | |
964 | } | |
965 | ||
966 | void | |
967 | ssh_put_password(char *password) | |
968 | { | |
969 | int size; | |
970 | char *padded; | |
971 | ||
972 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
973 | packet_put_cstring(password); | |
974 | return; | |
975 | } | |
976 | size = roundup(strlen(password) + 1, 32); | |
977 | padded = xmalloc(size); | |
978 | memset(padded, 0, size); | |
979 | strlcpy(padded, password, size); | |
980 | packet_put_string(padded, size); | |
981 | memset(padded, 0, size); | |
982 | xfree(padded); | |
983 | } | |
984 | ||
985 | static int | |
986 | show_key_from_file(const char *file, const char *host, int keytype) | |
987 | { | |
988 | Key *found; | |
989 | char *fp; | |
990 | int line, ret; | |
991 | ||
992 | found = key_new(keytype); | |
993 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
994 | keytype, found, &line))) { | |
995 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
996 | logit("WARNING: %s key found for host %s\n" | |
997 | "in %s:%d\n" | |
998 | "%s key fingerprint %s.", | |
999 | key_type(found), host, file, line, | |
1000 | key_type(found), fp); | |
1001 | xfree(fp); | |
1002 | } | |
1003 | key_free(found); | |
1004 | return (ret); | |
1005 | } | |
1006 | ||
1007 | /* print all known host keys for a given host, but skip keys of given type */ | |
1008 | static int | |
1009 | show_other_keys(const char *host, Key *key) | |
1010 | { | |
1011 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1012 | int i, found = 0; | |
1013 | ||
1014 | for (i = 0; type[i] != -1; i++) { | |
1015 | if (type[i] == key->type) | |
1016 | continue; | |
1017 | if (type[i] != KEY_RSA1 && | |
1018 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1019 | found = 1; | |
1020 | continue; | |
1021 | } | |
1022 | if (type[i] != KEY_RSA1 && | |
1023 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1024 | found = 1; | |
1025 | continue; | |
1026 | } | |
1027 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1028 | found = 1; | |
1029 | continue; | |
1030 | } | |
1031 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1032 | found = 1; | |
1033 | continue; | |
1034 | } | |
1035 | debug2("no key of type %d for host %s", type[i], host); | |
1036 | } | |
1037 | return (found); | |
1038 | } | |
1039 | ||
1040 | static void | |
1041 | warn_changed_key(Key *host_key) | |
1042 | { | |
1043 | char *fp; | |
1044 | const char *type = key_type(host_key); | |
1045 | ||
1046 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1047 | ||
1048 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1049 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1050 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1051 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1052 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1053 | error("It is also possible that the %s host key has just been changed.", type); | |
1054 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1055 | type, fp); | |
1056 | error("Please contact your system administrator."); | |
1057 | ||
1058 | xfree(fp); | |
1059 | } |