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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 1.171 2005/12/06 22:38:27 reyk 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 "dns.h" | |
35 | ||
36 | char *client_version_string = NULL; | |
37 | char *server_version_string = NULL; | |
38 | ||
39 | static int matching_host_key_dns = 0; | |
40 | ||
41 | /* import */ | |
42 | extern Options options; | |
43 | extern char *__progname; | |
44 | extern uid_t original_real_uid; | |
45 | extern uid_t original_effective_uid; | |
46 | extern pid_t proxy_command_pid; | |
47 | ||
48 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
49 | #define INET6_ADDRSTRLEN 46 | |
50 | #endif | |
51 | ||
52 | static int show_other_keys(const char *, Key *); | |
53 | static void warn_changed_key(Key *); | |
54 | ||
55 | /* | |
56 | * Connect to the given ssh server using a proxy command. | |
57 | */ | |
58 | static int | |
59 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
60 | { | |
61 | char *command_string, *tmp; | |
62 | int pin[2], pout[2]; | |
63 | pid_t pid; | |
64 | char strport[NI_MAXSERV]; | |
65 | size_t len; | |
66 | ||
67 | /* Convert the port number into a string. */ | |
68 | snprintf(strport, sizeof strport, "%hu", port); | |
69 | ||
70 | /* | |
71 | * Build the final command string in the buffer by making the | |
72 | * appropriate substitutions to the given proxy command. | |
73 | * | |
74 | * Use "exec" to avoid "sh -c" processes on some platforms | |
75 | * (e.g. Solaris) | |
76 | */ | |
77 | len = strlen(proxy_command) + 6; | |
78 | tmp = xmalloc(len); | |
79 | strlcpy(tmp, "exec ", len); | |
80 | strlcat(tmp, proxy_command, len); | |
81 | command_string = percent_expand(tmp, "h", host, | |
82 | "p", strport, (char *)NULL); | |
83 | xfree(tmp); | |
84 | ||
85 | /* Create pipes for communicating with the proxy. */ | |
86 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
87 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
88 | strerror(errno)); | |
89 | ||
90 | debug("Executing proxy command: %.500s", command_string); | |
91 | ||
92 | /* Fork and execute the proxy command. */ | |
93 | if ((pid = fork()) == 0) { | |
94 | char *argv[10]; | |
95 | ||
96 | /* Child. Permanently give up superuser privileges. */ | |
97 | seteuid(original_real_uid); | |
98 | setuid(original_real_uid); | |
99 | ||
100 | /* Redirect stdin and stdout. */ | |
101 | close(pin[1]); | |
102 | if (pin[0] != 0) { | |
103 | if (dup2(pin[0], 0) < 0) | |
104 | perror("dup2 stdin"); | |
105 | close(pin[0]); | |
106 | } | |
107 | close(pout[0]); | |
108 | if (dup2(pout[1], 1) < 0) | |
109 | perror("dup2 stdout"); | |
110 | /* Cannot be 1 because pin allocated two descriptors. */ | |
111 | close(pout[1]); | |
112 | ||
113 | /* Stderr is left as it is so that error messages get | |
114 | printed on the user's terminal. */ | |
115 | argv[0] = _PATH_BSHELL; | |
116 | argv[1] = "-c"; | |
117 | argv[2] = command_string; | |
118 | argv[3] = NULL; | |
119 | ||
120 | /* Execute the proxy command. Note that we gave up any | |
121 | extra privileges above. */ | |
122 | execv(argv[0], argv); | |
123 | perror(argv[0]); | |
124 | exit(1); | |
125 | } | |
126 | /* Parent. */ | |
127 | if (pid < 0) | |
128 | fatal("fork failed: %.100s", strerror(errno)); | |
129 | else | |
130 | proxy_command_pid = pid; /* save pid to clean up later */ | |
131 | ||
132 | /* Close child side of the descriptors. */ | |
133 | close(pin[0]); | |
134 | close(pout[1]); | |
135 | ||
136 | /* Free the command name. */ | |
137 | xfree(command_string); | |
138 | ||
139 | /* Set the connection file descriptors. */ | |
140 | packet_set_connection(pout[0], pin[1]); | |
141 | ||
142 | /* Indicate OK return */ | |
143 | return 0; | |
144 | } | |
145 | ||
146 | /* | |
147 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
148 | */ | |
149 | static int | |
150 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
151 | { | |
152 | int sock, gaierr; | |
153 | struct addrinfo hints, *res; | |
154 | ||
155 | /* | |
156 | * If we are running as root and want to connect to a privileged | |
157 | * port, bind our own socket to a privileged port. | |
158 | */ | |
159 | if (privileged) { | |
160 | int p = IPPORT_RESERVED - 1; | |
161 | PRIV_START; | |
162 | sock = rresvport_af(&p, ai->ai_family); | |
163 | PRIV_END; | |
164 | if (sock < 0) | |
165 | error("rresvport: af=%d %.100s", ai->ai_family, | |
166 | strerror(errno)); | |
167 | else | |
168 | debug("Allocated local port %d.", p); | |
169 | return sock; | |
170 | } | |
171 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
172 | if (sock < 0) | |
173 | error("socket: %.100s", strerror(errno)); | |
174 | ||
175 | /* Bind the socket to an alternative local IP address */ | |
176 | if (options.bind_address == NULL) | |
177 | return sock; | |
178 | ||
179 | memset(&hints, 0, sizeof(hints)); | |
180 | hints.ai_family = ai->ai_family; | |
181 | hints.ai_socktype = ai->ai_socktype; | |
182 | hints.ai_protocol = ai->ai_protocol; | |
183 | hints.ai_flags = AI_PASSIVE; | |
184 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
185 | if (gaierr) { | |
186 | error("getaddrinfo: %s: %s", options.bind_address, | |
187 | gai_strerror(gaierr)); | |
188 | close(sock); | |
189 | return -1; | |
190 | } | |
191 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
192 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
193 | close(sock); | |
194 | freeaddrinfo(res); | |
195 | return -1; | |
196 | } | |
197 | freeaddrinfo(res); | |
198 | return sock; | |
199 | } | |
200 | ||
201 | static int | |
202 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
203 | socklen_t addrlen, int timeout) | |
204 | { | |
205 | fd_set *fdset; | |
206 | struct timeval tv; | |
207 | socklen_t optlen; | |
208 | int fdsetsz, optval, rc, result = -1; | |
209 | ||
210 | if (timeout <= 0) | |
211 | return (connect(sockfd, serv_addr, addrlen)); | |
212 | ||
213 | set_nonblock(sockfd); | |
214 | rc = connect(sockfd, serv_addr, addrlen); | |
215 | if (rc == 0) { | |
216 | unset_nonblock(sockfd); | |
217 | return (0); | |
218 | } | |
219 | if (errno != EINPROGRESS) | |
220 | return (-1); | |
221 | ||
222 | fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); | |
223 | fdset = (fd_set *)xmalloc(fdsetsz); | |
224 | ||
225 | memset(fdset, 0, fdsetsz); | |
226 | FD_SET(sockfd, fdset); | |
227 | tv.tv_sec = timeout; | |
228 | tv.tv_usec = 0; | |
229 | ||
230 | for (;;) { | |
231 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
232 | if (rc != -1 || errno != EINTR) | |
233 | break; | |
234 | } | |
235 | ||
236 | switch (rc) { | |
237 | case 0: | |
238 | /* Timed out */ | |
239 | errno = ETIMEDOUT; | |
240 | break; | |
241 | case -1: | |
242 | /* Select error */ | |
243 | debug("select: %s", strerror(errno)); | |
244 | break; | |
245 | case 1: | |
246 | /* Completed or failed */ | |
247 | optval = 0; | |
248 | optlen = sizeof(optval); | |
249 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
250 | &optlen) == -1) { | |
251 | debug("getsockopt: %s", strerror(errno)); | |
252 | break; | |
253 | } | |
254 | if (optval != 0) { | |
255 | errno = optval; | |
256 | break; | |
257 | } | |
258 | result = 0; | |
259 | unset_nonblock(sockfd); | |
260 | break; | |
261 | default: | |
262 | /* Should not occur */ | |
263 | fatal("Bogus return (%d) from select()", rc); | |
264 | } | |
265 | ||
266 | xfree(fdset); | |
267 | return (result); | |
268 | } | |
269 | ||
270 | /* | |
271 | * Opens a TCP/IP connection to the remote server on the given host. | |
272 | * The address of the remote host will be returned in hostaddr. | |
273 | * If port is 0, the default port will be used. If needpriv is true, | |
274 | * a privileged port will be allocated to make the connection. | |
275 | * This requires super-user privileges if needpriv is true. | |
276 | * Connection_attempts specifies the maximum number of tries (one per | |
277 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
278 | * and %p substituted for host and port, respectively) to use to contact | |
279 | * the daemon. | |
280 | */ | |
281 | int | |
282 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
283 | u_short port, int family, int connection_attempts, | |
284 | int needpriv, const char *proxy_command) | |
285 | { | |
286 | int gaierr; | |
287 | int on = 1; | |
288 | int sock = -1, attempt; | |
289 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
290 | struct addrinfo hints, *ai, *aitop; | |
291 | ||
292 | debug2("ssh_connect: needpriv %d", needpriv); | |
293 | ||
294 | /* If a proxy command is given, connect using it. */ | |
295 | if (proxy_command != NULL) | |
296 | return ssh_proxy_connect(host, port, proxy_command); | |
297 | ||
298 | /* No proxy command. */ | |
299 | ||
300 | memset(&hints, 0, sizeof(hints)); | |
301 | hints.ai_family = family; | |
302 | hints.ai_socktype = SOCK_STREAM; | |
303 | snprintf(strport, sizeof strport, "%u", port); | |
304 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
305 | fatal("%s: %.100s: %s", __progname, host, | |
306 | gai_strerror(gaierr)); | |
307 | ||
308 | /* | |
309 | * Try to connect several times. On some machines, the first time | |
310 | * will sometimes fail. In general socket code appears to behave | |
311 | * quite magically on many machines. | |
312 | */ | |
313 | for (attempt = 0; ;) { | |
314 | if (attempt > 0) | |
315 | debug("Trying again..."); | |
316 | ||
317 | /* Loop through addresses for this host, and try each one in | |
318 | sequence until the connection succeeds. */ | |
319 | for (ai = aitop; ai; ai = ai->ai_next) { | |
320 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
321 | continue; | |
322 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
323 | ntop, sizeof(ntop), strport, sizeof(strport), | |
324 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
325 | error("ssh_connect: getnameinfo failed"); | |
326 | continue; | |
327 | } | |
328 | debug("Connecting to %.200s [%.100s] port %s.", | |
329 | host, ntop, strport); | |
330 | ||
331 | /* Create a socket for connecting. */ | |
332 | sock = ssh_create_socket(needpriv, ai); | |
333 | if (sock < 0) | |
334 | /* Any error is already output */ | |
335 | continue; | |
336 | ||
337 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
338 | options.connection_timeout) >= 0) { | |
339 | /* Successful connection. */ | |
340 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
341 | break; | |
342 | } else { | |
343 | debug("connect to address %s port %s: %s", | |
344 | ntop, strport, strerror(errno)); | |
345 | /* | |
346 | * Close the failed socket; there appear to | |
347 | * be some problems when reusing a socket for | |
348 | * which connect() has already returned an | |
349 | * error. | |
350 | */ | |
351 | close(sock); | |
352 | } | |
353 | } | |
354 | if (ai) | |
355 | break; /* Successful connection. */ | |
356 | ||
357 | attempt++; | |
358 | if (attempt >= connection_attempts) | |
359 | break; | |
360 | /* Sleep a moment before retrying. */ | |
361 | sleep(1); | |
362 | } | |
363 | ||
364 | freeaddrinfo(aitop); | |
365 | ||
366 | /* Return failure if we didn't get a successful connection. */ | |
367 | if (attempt >= connection_attempts) { | |
368 | error("ssh: connect to host %s port %s: %s", | |
369 | host, strport, strerror(errno)); | |
370 | return (-1); | |
371 | } | |
372 | ||
373 | debug("Connection established."); | |
374 | ||
375 | /* Set SO_KEEPALIVE if requested. */ | |
376 | if (options.tcp_keep_alive && | |
377 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
378 | sizeof(on)) < 0) | |
379 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
380 | ||
381 | /* Set the connection. */ | |
382 | packet_set_connection(sock, sock); | |
383 | ||
384 | return 0; | |
385 | } | |
386 | ||
387 | /* | |
388 | * Waits for the server identification string, and sends our own | |
389 | * identification string. | |
390 | */ | |
391 | static void | |
392 | ssh_exchange_identification(void) | |
393 | { | |
394 | char buf[256], remote_version[256]; /* must be same size! */ | |
395 | int remote_major, remote_minor, mismatch; | |
396 | int connection_in = packet_get_connection_in(); | |
397 | int connection_out = packet_get_connection_out(); | |
398 | int minor1 = PROTOCOL_MINOR_1; | |
399 | u_int i; | |
400 | ||
401 | /* Read other side's version identification. */ | |
402 | for (;;) { | |
403 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
404 | size_t len = atomicio(read, connection_in, &buf[i], 1); | |
405 | ||
406 | if (len != 1 && errno == EPIPE) | |
407 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
408 | else if (len != 1) | |
409 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
410 | if (buf[i] == '\r') { | |
411 | buf[i] = '\n'; | |
412 | buf[i + 1] = 0; | |
413 | continue; /**XXX wait for \n */ | |
414 | } | |
415 | if (buf[i] == '\n') { | |
416 | buf[i + 1] = 0; | |
417 | break; | |
418 | } | |
419 | } | |
420 | buf[sizeof(buf) - 1] = 0; | |
421 | if (strncmp(buf, "SSH-", 4) == 0) | |
422 | break; | |
423 | debug("ssh_exchange_identification: %s", buf); | |
424 | } | |
425 | server_version_string = xstrdup(buf); | |
426 | ||
427 | /* | |
428 | * Check that the versions match. In future this might accept | |
429 | * several versions and set appropriate flags to handle them. | |
430 | */ | |
431 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
432 | &remote_major, &remote_minor, remote_version) != 3) | |
433 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
434 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
435 | remote_major, remote_minor, remote_version); | |
436 | ||
437 | compat_datafellows(remote_version); | |
438 | mismatch = 0; | |
439 | ||
440 | switch (remote_major) { | |
441 | case 1: | |
442 | if (remote_minor == 99 && | |
443 | (options.protocol & SSH_PROTO_2) && | |
444 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
445 | enable_compat20(); | |
446 | break; | |
447 | } | |
448 | if (!(options.protocol & SSH_PROTO_1)) { | |
449 | mismatch = 1; | |
450 | break; | |
451 | } | |
452 | if (remote_minor < 3) { | |
453 | fatal("Remote machine has too old SSH software version."); | |
454 | } else if (remote_minor == 3 || remote_minor == 4) { | |
455 | /* We speak 1.3, too. */ | |
456 | enable_compat13(); | |
457 | minor1 = 3; | |
458 | if (options.forward_agent) { | |
459 | logit("Agent forwarding disabled for protocol 1.3"); | |
460 | options.forward_agent = 0; | |
461 | } | |
462 | } | |
463 | break; | |
464 | case 2: | |
465 | if (options.protocol & SSH_PROTO_2) { | |
466 | enable_compat20(); | |
467 | break; | |
468 | } | |
469 | /* FALLTHROUGH */ | |
470 | default: | |
471 | mismatch = 1; | |
472 | break; | |
473 | } | |
474 | if (mismatch) | |
475 | fatal("Protocol major versions differ: %d vs. %d", | |
476 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
477 | remote_major); | |
478 | /* Send our own protocol version identification. */ | |
479 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
480 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
481 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
482 | SSH_VERSION); | |
483 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
484 | fatal("write: %.100s", strerror(errno)); | |
485 | client_version_string = xstrdup(buf); | |
486 | chop(client_version_string); | |
487 | chop(server_version_string); | |
488 | debug("Local version string %.100s", client_version_string); | |
489 | } | |
490 | ||
491 | /* defaults to 'no' */ | |
492 | static int | |
493 | confirm(const char *prompt) | |
494 | { | |
495 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
496 | char *p; | |
497 | int ret = -1; | |
498 | ||
499 | if (options.batch_mode) | |
500 | return 0; | |
501 | for (msg = prompt;;msg = again) { | |
502 | p = read_passphrase(msg, RP_ECHO); | |
503 | if (p == NULL || | |
504 | (p[0] == '\0') || (p[0] == '\n') || | |
505 | strncasecmp(p, "no", 2) == 0) | |
506 | ret = 0; | |
507 | if (p && strncasecmp(p, "yes", 3) == 0) | |
508 | ret = 1; | |
509 | if (p) | |
510 | xfree(p); | |
511 | if (ret != -1) | |
512 | return ret; | |
513 | } | |
514 | } | |
515 | ||
516 | /* | |
517 | * check whether the supplied host key is valid, return -1 if the key | |
518 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
519 | */ | |
520 | static int | |
521 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
522 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
523 | { | |
524 | Key *file_key; | |
525 | const char *type = key_type(host_key); | |
526 | char *ip = NULL; | |
527 | char hostline[1000], *hostp, *fp; | |
528 | HostStatus host_status; | |
529 | HostStatus ip_status; | |
530 | int r, local = 0, host_ip_differ = 0; | |
531 | int salen; | |
532 | char ntop[NI_MAXHOST]; | |
533 | char msg[1024]; | |
534 | int len, host_line, ip_line; | |
535 | const char *host_file = NULL, *ip_file = NULL; | |
536 | ||
537 | /* | |
538 | * Force accepting of the host key for loopback/localhost. The | |
539 | * problem is that if the home directory is NFS-mounted to multiple | |
540 | * machines, localhost will refer to a different machine in each of | |
541 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
542 | * essentially disables host authentication for localhost; however, | |
543 | * this is probably not a real problem. | |
544 | */ | |
545 | /** hostaddr == 0! */ | |
546 | switch (hostaddr->sa_family) { | |
547 | case AF_INET: | |
548 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
549 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
550 | salen = sizeof(struct sockaddr_in); | |
551 | break; | |
552 | case AF_INET6: | |
553 | local = IN6_IS_ADDR_LOOPBACK( | |
554 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
555 | salen = sizeof(struct sockaddr_in6); | |
556 | break; | |
557 | default: | |
558 | local = 0; | |
559 | salen = sizeof(struct sockaddr_storage); | |
560 | break; | |
561 | } | |
562 | if (options.no_host_authentication_for_localhost == 1 && local && | |
563 | options.host_key_alias == NULL) { | |
564 | debug("Forcing accepting of host key for " | |
565 | "loopback/localhost."); | |
566 | return 0; | |
567 | } | |
568 | ||
569 | /* | |
570 | * We don't have the remote ip-address for connections | |
571 | * using a proxy command | |
572 | */ | |
573 | if (options.proxy_command == NULL) { | |
574 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
575 | NULL, 0, NI_NUMERICHOST) != 0) | |
576 | fatal("check_host_key: getnameinfo failed"); | |
577 | ip = xstrdup(ntop); | |
578 | } else { | |
579 | ip = xstrdup("<no hostip for proxy command>"); | |
580 | } | |
581 | /* | |
582 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
583 | * command or if we don't have a hostname to compare with | |
584 | */ | |
585 | if (options.check_host_ip && | |
586 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
587 | options.check_host_ip = 0; | |
588 | ||
589 | /* | |
590 | * Allow the user to record the key under a different name. This is | |
591 | * useful for ssh tunneling over forwarded connections or if you run | |
592 | * multiple sshd's on different ports on the same machine. | |
593 | */ | |
594 | if (options.host_key_alias != NULL) { | |
595 | host = options.host_key_alias; | |
596 | debug("using hostkeyalias: %s", host); | |
597 | } | |
598 | ||
599 | /* | |
600 | * Store the host key from the known host file in here so that we can | |
601 | * compare it with the key for the IP address. | |
602 | */ | |
603 | file_key = key_new(host_key->type); | |
604 | ||
605 | /* | |
606 | * Check if the host key is present in the user's list of known | |
607 | * hosts or in the systemwide list. | |
608 | */ | |
609 | host_file = user_hostfile; | |
610 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
611 | file_key, &host_line); | |
612 | if (host_status == HOST_NEW) { | |
613 | host_file = system_hostfile; | |
614 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
615 | file_key, &host_line); | |
616 | } | |
617 | /* | |
618 | * Also perform check for the ip address, skip the check if we are | |
619 | * localhost or the hostname was an ip address to begin with | |
620 | */ | |
621 | if (options.check_host_ip) { | |
622 | Key *ip_key = key_new(host_key->type); | |
623 | ||
624 | ip_file = user_hostfile; | |
625 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
626 | ip_key, &ip_line); | |
627 | if (ip_status == HOST_NEW) { | |
628 | ip_file = system_hostfile; | |
629 | ip_status = check_host_in_hostfile(ip_file, ip, | |
630 | host_key, ip_key, &ip_line); | |
631 | } | |
632 | if (host_status == HOST_CHANGED && | |
633 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
634 | host_ip_differ = 1; | |
635 | ||
636 | key_free(ip_key); | |
637 | } else | |
638 | ip_status = host_status; | |
639 | ||
640 | key_free(file_key); | |
641 | ||
642 | switch (host_status) { | |
643 | case HOST_OK: | |
644 | /* The host is known and the key matches. */ | |
645 | debug("Host '%.200s' is known and matches the %s host key.", | |
646 | host, type); | |
647 | debug("Found key in %s:%d", host_file, host_line); | |
648 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
649 | if (readonly) | |
650 | logit("%s host key for IP address " | |
651 | "'%.128s' not in list of known hosts.", | |
652 | type, ip); | |
653 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
654 | host_key, options.hash_known_hosts)) | |
655 | logit("Failed to add the %s host key for IP " | |
656 | "address '%.128s' to the list of known " | |
657 | "hosts (%.30s).", type, ip, user_hostfile); | |
658 | else | |
659 | logit("Warning: Permanently added the %s host " | |
660 | "key for IP address '%.128s' to the list " | |
661 | "of known hosts.", type, ip); | |
662 | } | |
663 | break; | |
664 | case HOST_NEW: | |
665 | if (readonly) | |
666 | goto fail; | |
667 | /* The host is new. */ | |
668 | if (options.strict_host_key_checking == 1) { | |
669 | /* | |
670 | * User has requested strict host key checking. We | |
671 | * will not add the host key automatically. The only | |
672 | * alternative left is to abort. | |
673 | */ | |
674 | error("No %s host key is known for %.200s and you " | |
675 | "have requested strict checking.", type, host); | |
676 | goto fail; | |
677 | } else if (options.strict_host_key_checking == 2) { | |
678 | char msg1[1024], msg2[1024]; | |
679 | ||
680 | if (show_other_keys(host, host_key)) | |
681 | snprintf(msg1, sizeof(msg1), | |
682 | "\nbut keys of different type are already" | |
683 | " known for this host."); | |
684 | else | |
685 | snprintf(msg1, sizeof(msg1), "."); | |
686 | /* The default */ | |
687 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
688 | msg2[0] = '\0'; | |
689 | if (options.verify_host_key_dns) { | |
690 | if (matching_host_key_dns) | |
691 | snprintf(msg2, sizeof(msg2), | |
692 | "Matching host key fingerprint" | |
693 | " found in DNS.\n"); | |
694 | else | |
695 | snprintf(msg2, sizeof(msg2), | |
696 | "No matching host key fingerprint" | |
697 | " found in DNS.\n"); | |
698 | } | |
699 | snprintf(msg, sizeof(msg), | |
700 | "The authenticity of host '%.200s (%s)' can't be " | |
701 | "established%s\n" | |
702 | "%s key fingerprint is %s.\n%s" | |
703 | "Are you sure you want to continue connecting " | |
704 | "(yes/no)? ", | |
705 | host, ip, msg1, type, fp, msg2); | |
706 | xfree(fp); | |
707 | if (!confirm(msg)) | |
708 | goto fail; | |
709 | } | |
710 | /* | |
711 | * If not in strict mode, add the key automatically to the | |
712 | * local known_hosts file. | |
713 | */ | |
714 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
715 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
716 | host, ip); | |
717 | hostp = hostline; | |
718 | if (options.hash_known_hosts) { | |
719 | /* Add hash of host and IP separately */ | |
720 | r = add_host_to_hostfile(user_hostfile, host, | |
721 | host_key, options.hash_known_hosts) && | |
722 | add_host_to_hostfile(user_hostfile, ip, | |
723 | host_key, options.hash_known_hosts); | |
724 | } else { | |
725 | /* Add unhashed "host,ip" */ | |
726 | r = add_host_to_hostfile(user_hostfile, | |
727 | hostline, host_key, | |
728 | options.hash_known_hosts); | |
729 | } | |
730 | } else { | |
731 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
732 | options.hash_known_hosts); | |
733 | hostp = host; | |
734 | } | |
735 | ||
736 | if (!r) | |
737 | logit("Failed to add the host to the list of known " | |
738 | "hosts (%.500s).", user_hostfile); | |
739 | else | |
740 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
741 | "list of known hosts.", hostp, type); | |
742 | break; | |
743 | case HOST_CHANGED: | |
744 | if (options.check_host_ip && host_ip_differ) { | |
745 | char *key_msg; | |
746 | if (ip_status == HOST_NEW) | |
747 | key_msg = "is unknown"; | |
748 | else if (ip_status == HOST_OK) | |
749 | key_msg = "is unchanged"; | |
750 | else | |
751 | key_msg = "has a different value"; | |
752 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
753 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
754 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
755 | error("The %s host key for %s has changed,", type, host); | |
756 | error("and the key for the according IP address %s", ip); | |
757 | error("%s. This could either mean that", key_msg); | |
758 | error("DNS SPOOFING is happening or the IP address for the host"); | |
759 | error("and its host key have changed at the same time."); | |
760 | if (ip_status != HOST_NEW) | |
761 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
762 | } | |
763 | /* The host key has changed. */ | |
764 | warn_changed_key(host_key); | |
765 | error("Add correct host key in %.100s to get rid of this message.", | |
766 | user_hostfile); | |
767 | error("Offending key in %s:%d", host_file, host_line); | |
768 | ||
769 | /* | |
770 | * If strict host key checking is in use, the user will have | |
771 | * to edit the key manually and we can only abort. | |
772 | */ | |
773 | if (options.strict_host_key_checking) { | |
774 | error("%s host key for %.200s has changed and you have " | |
775 | "requested strict checking.", type, host); | |
776 | goto fail; | |
777 | } | |
778 | ||
779 | /* | |
780 | * If strict host key checking has not been requested, allow | |
781 | * the connection but without MITM-able authentication or | |
782 | * agent forwarding. | |
783 | */ | |
784 | if (options.password_authentication) { | |
785 | error("Password authentication is disabled to avoid " | |
786 | "man-in-the-middle attacks."); | |
787 | options.password_authentication = 0; | |
788 | } | |
789 | if (options.kbd_interactive_authentication) { | |
790 | error("Keyboard-interactive authentication is disabled" | |
791 | " to avoid man-in-the-middle attacks."); | |
792 | options.kbd_interactive_authentication = 0; | |
793 | options.challenge_response_authentication = 0; | |
794 | } | |
795 | if (options.challenge_response_authentication) { | |
796 | error("Challenge/response authentication is disabled" | |
797 | " to avoid man-in-the-middle attacks."); | |
798 | options.challenge_response_authentication = 0; | |
799 | } | |
800 | if (options.forward_agent) { | |
801 | error("Agent forwarding is disabled to avoid " | |
802 | "man-in-the-middle attacks."); | |
803 | options.forward_agent = 0; | |
804 | } | |
805 | if (options.forward_x11) { | |
806 | error("X11 forwarding is disabled to avoid " | |
807 | "man-in-the-middle attacks."); | |
808 | options.forward_x11 = 0; | |
809 | } | |
810 | if (options.num_local_forwards > 0 || | |
811 | options.num_remote_forwards > 0) { | |
812 | error("Port forwarding is disabled to avoid " | |
813 | "man-in-the-middle attacks."); | |
814 | options.num_local_forwards = | |
815 | options.num_remote_forwards = 0; | |
816 | } | |
817 | /* | |
818 | * XXX Should permit the user to change to use the new id. | |
819 | * This could be done by converting the host key to an | |
820 | * identifying sentence, tell that the host identifies itself | |
821 | * by that sentence, and ask the user if he/she whishes to | |
822 | * accept the authentication. | |
823 | */ | |
824 | break; | |
825 | case HOST_FOUND: | |
826 | fatal("internal error"); | |
827 | break; | |
828 | } | |
829 | ||
830 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
831 | ip_status == HOST_CHANGED) { | |
832 | snprintf(msg, sizeof(msg), | |
833 | "Warning: the %s host key for '%.200s' " | |
834 | "differs from the key for the IP address '%.128s'" | |
835 | "\nOffending key for IP in %s:%d", | |
836 | type, host, ip, ip_file, ip_line); | |
837 | if (host_status == HOST_OK) { | |
838 | len = strlen(msg); | |
839 | snprintf(msg + len, sizeof(msg) - len, | |
840 | "\nMatching host key in %s:%d", | |
841 | host_file, host_line); | |
842 | } | |
843 | if (options.strict_host_key_checking == 1) { | |
844 | logit("%s", msg); | |
845 | error("Exiting, you have requested strict checking."); | |
846 | goto fail; | |
847 | } else if (options.strict_host_key_checking == 2) { | |
848 | strlcat(msg, "\nAre you sure you want " | |
849 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
850 | if (!confirm(msg)) | |
851 | goto fail; | |
852 | } else { | |
853 | logit("%s", msg); | |
854 | } | |
855 | } | |
856 | ||
857 | xfree(ip); | |
858 | return 0; | |
859 | ||
860 | fail: | |
861 | xfree(ip); | |
862 | return -1; | |
863 | } | |
864 | ||
865 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
866 | int | |
867 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
868 | { | |
869 | struct stat st; | |
870 | int flags = 0; | |
871 | ||
872 | if (options.verify_host_key_dns && | |
873 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
874 | ||
875 | if (flags & DNS_VERIFY_FOUND) { | |
876 | ||
877 | if (options.verify_host_key_dns == 1 && | |
878 | flags & DNS_VERIFY_MATCH && | |
879 | flags & DNS_VERIFY_SECURE) | |
880 | return 0; | |
881 | ||
882 | if (flags & DNS_VERIFY_MATCH) { | |
883 | matching_host_key_dns = 1; | |
884 | } else { | |
885 | warn_changed_key(host_key); | |
886 | error("Update the SSHFP RR in DNS with the new " | |
887 | "host key to get rid of this message."); | |
888 | } | |
889 | } | |
890 | } | |
891 | ||
892 | /* return ok if the key can be found in an old keyfile */ | |
893 | if (stat(options.system_hostfile2, &st) == 0 || | |
894 | stat(options.user_hostfile2, &st) == 0) { | |
895 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
896 | options.user_hostfile2, options.system_hostfile2) == 0) | |
897 | return 0; | |
898 | } | |
899 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
900 | options.user_hostfile, options.system_hostfile); | |
901 | } | |
902 | ||
903 | /* | |
904 | * Starts a dialog with the server, and authenticates the current user on the | |
905 | * server. This does not need any extra privileges. The basic connection | |
906 | * to the server must already have been established before this is called. | |
907 | * If login fails, this function prints an error and never returns. | |
908 | * This function does not require super-user privileges. | |
909 | */ | |
910 | void | |
911 | ssh_login(Sensitive *sensitive, const char *orighost, | |
912 | struct sockaddr *hostaddr, struct passwd *pw) | |
913 | { | |
914 | char *host, *cp; | |
915 | char *server_user, *local_user; | |
916 | ||
917 | local_user = xstrdup(pw->pw_name); | |
918 | server_user = options.user ? options.user : local_user; | |
919 | ||
920 | /* Convert the user-supplied hostname into all lowercase. */ | |
921 | host = xstrdup(orighost); | |
922 | for (cp = host; *cp; cp++) | |
923 | if (isupper(*cp)) | |
924 | *cp = tolower(*cp); | |
925 | ||
926 | /* Exchange protocol version identification strings with the server. */ | |
927 | ssh_exchange_identification(); | |
928 | ||
929 | /* Put the connection into non-blocking mode. */ | |
930 | packet_set_nonblocking(); | |
931 | ||
932 | /* key exchange */ | |
933 | /* authenticate user */ | |
934 | if (compat20) { | |
935 | ssh_kex2(host, hostaddr); | |
936 | ssh_userauth2(local_user, server_user, host, sensitive); | |
937 | } else { | |
938 | ssh_kex(host, hostaddr); | |
939 | ssh_userauth1(local_user, server_user, host, sensitive); | |
940 | } | |
941 | } | |
942 | ||
943 | void | |
944 | ssh_put_password(char *password) | |
945 | { | |
946 | int size; | |
947 | char *padded; | |
948 | ||
949 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
950 | packet_put_cstring(password); | |
951 | return; | |
952 | } | |
953 | size = roundup(strlen(password) + 1, 32); | |
954 | padded = xmalloc(size); | |
955 | memset(padded, 0, size); | |
956 | strlcpy(padded, password, size); | |
957 | packet_put_string(padded, size); | |
958 | memset(padded, 0, size); | |
959 | xfree(padded); | |
960 | } | |
961 | ||
962 | static int | |
963 | show_key_from_file(const char *file, const char *host, int keytype) | |
964 | { | |
965 | Key *found; | |
966 | char *fp; | |
967 | int line, ret; | |
968 | ||
969 | found = key_new(keytype); | |
970 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
971 | keytype, found, &line))) { | |
972 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
973 | logit("WARNING: %s key found for host %s\n" | |
974 | "in %s:%d\n" | |
975 | "%s key fingerprint %s.", | |
976 | key_type(found), host, file, line, | |
977 | key_type(found), fp); | |
978 | xfree(fp); | |
979 | } | |
980 | key_free(found); | |
981 | return (ret); | |
982 | } | |
983 | ||
984 | /* print all known host keys for a given host, but skip keys of given type */ | |
985 | static int | |
986 | show_other_keys(const char *host, Key *key) | |
987 | { | |
988 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
989 | int i, found = 0; | |
990 | ||
991 | for (i = 0; type[i] != -1; i++) { | |
992 | if (type[i] == key->type) | |
993 | continue; | |
994 | if (type[i] != KEY_RSA1 && | |
995 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
996 | found = 1; | |
997 | continue; | |
998 | } | |
999 | if (type[i] != KEY_RSA1 && | |
1000 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1001 | found = 1; | |
1002 | continue; | |
1003 | } | |
1004 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1005 | found = 1; | |
1006 | continue; | |
1007 | } | |
1008 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1009 | found = 1; | |
1010 | continue; | |
1011 | } | |
1012 | debug2("no key of type %d for host %s", type[i], host); | |
1013 | } | |
1014 | return (found); | |
1015 | } | |
1016 | ||
1017 | static void | |
1018 | warn_changed_key(Key *host_key) | |
1019 | { | |
1020 | char *fp; | |
1021 | const char *type = key_type(host_key); | |
1022 | ||
1023 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1024 | ||
1025 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1026 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1027 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1028 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1029 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1030 | error("It is also possible that the %s host key has just been changed.", type); | |
1031 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1032 | type, fp); | |
1033 | error("Please contact your system administrator."); | |
1034 | ||
1035 | xfree(fp); | |
1036 | } | |
1037 | ||
1038 | /* | |
1039 | * Execute a local command | |
1040 | */ | |
1041 | int | |
1042 | ssh_local_cmd(const char *args) | |
1043 | { | |
1044 | char *shell; | |
1045 | pid_t pid; | |
1046 | int status; | |
1047 | ||
1048 | if (!options.permit_local_command || | |
1049 | args == NULL || !*args) | |
1050 | return (1); | |
1051 | ||
1052 | if ((shell = getenv("SHELL")) == NULL) | |
1053 | shell = _PATH_BSHELL; | |
1054 | ||
1055 | pid = fork(); | |
1056 | if (pid == 0) { | |
1057 | debug3("Executing %s -c \"%s\"", shell, args); | |
1058 | execl(shell, shell, "-c", args, (char *)NULL); | |
1059 | error("Couldn't execute %s -c \"%s\": %s", | |
1060 | shell, args, strerror(errno)); | |
1061 | _exit(1); | |
1062 | } else if (pid == -1) | |
1063 | fatal("fork failed: %.100s", strerror(errno)); | |
1064 | while (waitpid(pid, &status, 0) == -1) | |
1065 | if (errno != EINTR) | |
1066 | fatal("Couldn't wait for child: %s", strerror(errno)); | |
1067 | ||
1068 | if (!WIFEXITED(status)) | |
1069 | return (1); | |
1070 | ||
1071 | return (WEXITSTATUS(status)); | |
1072 | } |