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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 1.164 2005/06/06 11:20:36 djm 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 | ||
35 | #include "dns.h" | |
36 | ||
37 | char *client_version_string = NULL; | |
38 | char *server_version_string = NULL; | |
39 | ||
40 | int matching_host_key_dns = 0; | |
41 | ||
42 | /* import */ | |
43 | extern Options options; | |
44 | extern char *__progname; | |
45 | extern uid_t original_real_uid; | |
46 | extern uid_t original_effective_uid; | |
47 | extern pid_t proxy_command_pid; | |
48 | ||
49 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
50 | #define INET6_ADDRSTRLEN 46 | |
51 | #endif | |
52 | ||
53 | static int show_other_keys(const char *, Key *); | |
54 | static void warn_changed_key(Key *); | |
55 | ||
56 | /* | |
57 | * Connect to the given ssh server using a proxy command. | |
58 | */ | |
59 | static int | |
60 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
61 | { | |
62 | char *command_string, *tmp; | |
63 | int pin[2], pout[2]; | |
64 | pid_t pid; | |
65 | char strport[NI_MAXSERV]; | |
66 | size_t len; | |
67 | ||
68 | /* Convert the port number into a string. */ | |
69 | snprintf(strport, sizeof strport, "%hu", port); | |
70 | ||
71 | /* | |
72 | * Build the final command string in the buffer by making the | |
73 | * appropriate substitutions to the given proxy command. | |
74 | * | |
75 | * Use "exec" to avoid "sh -c" processes on some platforms | |
76 | * (e.g. Solaris) | |
77 | */ | |
78 | len = strlen(proxy_command) + 6; | |
79 | tmp = xmalloc(len); | |
80 | strlcpy(tmp, "exec ", len); | |
81 | strlcat(tmp, proxy_command, len); | |
82 | command_string = percent_expand(tmp, "h", host, | |
83 | "p", strport, (char *)NULL); | |
84 | xfree(tmp); | |
85 | ||
86 | /* Create pipes for communicating with the proxy. */ | |
87 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
88 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
89 | strerror(errno)); | |
90 | ||
91 | debug("Executing proxy command: %.500s", command_string); | |
92 | ||
93 | /* Fork and execute the proxy command. */ | |
94 | if ((pid = fork()) == 0) { | |
95 | char *argv[10]; | |
96 | ||
97 | /* Child. Permanently give up superuser privileges. */ | |
98 | seteuid(original_real_uid); | |
99 | setuid(original_real_uid); | |
100 | ||
101 | /* Redirect stdin and stdout. */ | |
102 | close(pin[1]); | |
103 | if (pin[0] != 0) { | |
104 | if (dup2(pin[0], 0) < 0) | |
105 | perror("dup2 stdin"); | |
106 | close(pin[0]); | |
107 | } | |
108 | close(pout[0]); | |
109 | if (dup2(pout[1], 1) < 0) | |
110 | perror("dup2 stdout"); | |
111 | /* Cannot be 1 because pin allocated two descriptors. */ | |
112 | close(pout[1]); | |
113 | ||
114 | /* Stderr is left as it is so that error messages get | |
115 | printed on the user's terminal. */ | |
116 | argv[0] = _PATH_BSHELL; | |
117 | argv[1] = "-c"; | |
118 | argv[2] = command_string; | |
119 | argv[3] = NULL; | |
120 | ||
121 | /* Execute the proxy command. Note that we gave up any | |
122 | extra privileges above. */ | |
123 | execv(argv[0], argv); | |
124 | perror(argv[0]); | |
125 | exit(1); | |
126 | } | |
127 | /* Parent. */ | |
128 | if (pid < 0) | |
129 | fatal("fork failed: %.100s", strerror(errno)); | |
130 | else | |
131 | proxy_command_pid = pid; /* save pid to clean up later */ | |
132 | ||
133 | /* Close child side of the descriptors. */ | |
134 | close(pin[0]); | |
135 | close(pout[1]); | |
136 | ||
137 | /* Free the command name. */ | |
138 | xfree(command_string); | |
139 | ||
140 | /* Set the connection file descriptors. */ | |
141 | packet_set_connection(pout[0], pin[1]); | |
142 | ||
143 | /* Indicate OK return */ | |
144 | return 0; | |
145 | } | |
146 | ||
147 | /* | |
148 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
149 | */ | |
150 | static int | |
151 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
152 | { | |
153 | int sock, gaierr; | |
154 | struct addrinfo hints, *res; | |
155 | ||
156 | /* | |
157 | * If we are running as root and want to connect to a privileged | |
158 | * port, bind our own socket to a privileged port. | |
159 | */ | |
160 | if (privileged) { | |
161 | int p = IPPORT_RESERVED - 1; | |
162 | PRIV_START; | |
163 | sock = rresvport_af(&p, ai->ai_family); | |
164 | PRIV_END; | |
165 | if (sock < 0) | |
166 | error("rresvport: af=%d %.100s", ai->ai_family, | |
167 | strerror(errno)); | |
168 | else | |
169 | debug("Allocated local port %d.", p); | |
170 | return sock; | |
171 | } | |
172 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
173 | if (sock < 0) | |
174 | error("socket: %.100s", strerror(errno)); | |
175 | ||
176 | /* Bind the socket to an alternative local IP address */ | |
177 | if (options.bind_address == NULL) | |
178 | return sock; | |
179 | ||
180 | memset(&hints, 0, sizeof(hints)); | |
181 | hints.ai_family = ai->ai_family; | |
182 | hints.ai_socktype = ai->ai_socktype; | |
183 | hints.ai_protocol = ai->ai_protocol; | |
184 | hints.ai_flags = AI_PASSIVE; | |
185 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
186 | if (gaierr) { | |
187 | error("getaddrinfo: %s: %s", options.bind_address, | |
188 | gai_strerror(gaierr)); | |
189 | close(sock); | |
190 | return -1; | |
191 | } | |
192 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
193 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
194 | close(sock); | |
195 | freeaddrinfo(res); | |
196 | return -1; | |
197 | } | |
198 | freeaddrinfo(res); | |
199 | return sock; | |
200 | } | |
201 | ||
202 | static int | |
203 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
204 | socklen_t addrlen, int timeout) | |
205 | { | |
206 | fd_set *fdset; | |
207 | struct timeval tv; | |
208 | socklen_t optlen; | |
209 | int fdsetsz, optval, rc, result = -1; | |
210 | ||
211 | if (timeout <= 0) | |
212 | return (connect(sockfd, serv_addr, addrlen)); | |
213 | ||
214 | set_nonblock(sockfd); | |
215 | rc = connect(sockfd, serv_addr, addrlen); | |
216 | if (rc == 0) { | |
217 | unset_nonblock(sockfd); | |
218 | return (0); | |
219 | } | |
220 | if (errno != EINPROGRESS) | |
221 | return (-1); | |
222 | ||
223 | fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); | |
224 | fdset = (fd_set *)xmalloc(fdsetsz); | |
225 | ||
226 | memset(fdset, 0, fdsetsz); | |
227 | FD_SET(sockfd, fdset); | |
228 | tv.tv_sec = timeout; | |
229 | tv.tv_usec = 0; | |
230 | ||
231 | for (;;) { | |
232 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
233 | if (rc != -1 || errno != EINTR) | |
234 | break; | |
235 | } | |
236 | ||
237 | switch (rc) { | |
238 | case 0: | |
239 | /* Timed out */ | |
240 | errno = ETIMEDOUT; | |
241 | break; | |
242 | case -1: | |
243 | /* Select error */ | |
244 | debug("select: %s", strerror(errno)); | |
245 | break; | |
246 | case 1: | |
247 | /* Completed or failed */ | |
248 | optval = 0; | |
249 | optlen = sizeof(optval); | |
250 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
251 | &optlen) == -1) { | |
252 | debug("getsockopt: %s", strerror(errno)); | |
253 | break; | |
254 | } | |
255 | if (optval != 0) { | |
256 | errno = optval; | |
257 | break; | |
258 | } | |
259 | result = 0; | |
260 | unset_nonblock(sockfd); | |
261 | break; | |
262 | default: | |
263 | /* Should not occur */ | |
264 | fatal("Bogus return (%d) from select()", rc); | |
265 | } | |
266 | ||
267 | xfree(fdset); | |
268 | return (result); | |
269 | } | |
270 | ||
271 | /* | |
272 | * Opens a TCP/IP connection to the remote server on the given host. | |
273 | * The address of the remote host will be returned in hostaddr. | |
274 | * If port is 0, the default port will be used. If needpriv is true, | |
275 | * a privileged port will be allocated to make the connection. | |
276 | * This requires super-user privileges if needpriv is true. | |
277 | * Connection_attempts specifies the maximum number of tries (one per | |
278 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
279 | * and %p substituted for host and port, respectively) to use to contact | |
280 | * the daemon. | |
281 | */ | |
282 | int | |
283 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
284 | u_short port, int family, int connection_attempts, | |
285 | int needpriv, const char *proxy_command) | |
286 | { | |
287 | int gaierr; | |
288 | int on = 1; | |
289 | int sock = -1, attempt; | |
290 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
291 | struct addrinfo hints, *ai, *aitop; | |
292 | struct servent *sp; | |
293 | ||
294 | debug2("ssh_connect: needpriv %d", needpriv); | |
295 | ||
296 | /* Get default port if port has not been set. */ | |
297 | if (port == 0) { | |
298 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
299 | if (sp) | |
300 | port = ntohs(sp->s_port); | |
301 | else | |
302 | port = SSH_DEFAULT_PORT; | |
303 | } | |
304 | /* If a proxy command is given, connect using it. */ | |
305 | if (proxy_command != NULL) | |
306 | return ssh_proxy_connect(host, port, proxy_command); | |
307 | ||
308 | /* No proxy command. */ | |
309 | ||
310 | memset(&hints, 0, sizeof(hints)); | |
311 | hints.ai_family = family; | |
312 | hints.ai_socktype = SOCK_STREAM; | |
313 | snprintf(strport, sizeof strport, "%u", port); | |
314 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
315 | fatal("%s: %.100s: %s", __progname, host, | |
316 | gai_strerror(gaierr)); | |
317 | ||
318 | /* | |
319 | * Try to connect several times. On some machines, the first time | |
320 | * will sometimes fail. In general socket code appears to behave | |
321 | * quite magically on many machines. | |
322 | */ | |
323 | for (attempt = 0; ;) { | |
324 | if (attempt > 0) | |
325 | debug("Trying again..."); | |
326 | ||
327 | /* Loop through addresses for this host, and try each one in | |
328 | sequence until the connection succeeds. */ | |
329 | for (ai = aitop; ai; ai = ai->ai_next) { | |
330 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
331 | continue; | |
332 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
333 | ntop, sizeof(ntop), strport, sizeof(strport), | |
334 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
335 | error("ssh_connect: getnameinfo failed"); | |
336 | continue; | |
337 | } | |
338 | debug("Connecting to %.200s [%.100s] port %s.", | |
339 | host, ntop, strport); | |
340 | ||
341 | /* Create a socket for connecting. */ | |
342 | sock = ssh_create_socket(needpriv, ai); | |
343 | if (sock < 0) | |
344 | /* Any error is already output */ | |
345 | continue; | |
346 | ||
347 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
348 | options.connection_timeout) >= 0) { | |
349 | /* Successful connection. */ | |
350 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
351 | break; | |
352 | } else { | |
353 | debug("connect to address %s port %s: %s", | |
354 | ntop, strport, strerror(errno)); | |
355 | /* | |
356 | * Close the failed socket; there appear to | |
357 | * be some problems when reusing a socket for | |
358 | * which connect() has already returned an | |
359 | * error. | |
360 | */ | |
361 | close(sock); | |
362 | } | |
363 | } | |
364 | if (ai) | |
365 | break; /* Successful connection. */ | |
366 | ||
367 | attempt++; | |
368 | if (attempt >= connection_attempts) | |
369 | break; | |
370 | /* Sleep a moment before retrying. */ | |
371 | sleep(1); | |
372 | } | |
373 | ||
374 | freeaddrinfo(aitop); | |
375 | ||
376 | /* Return failure if we didn't get a successful connection. */ | |
377 | if (attempt >= connection_attempts) { | |
378 | error("ssh: connect to host %s port %s: %s", | |
379 | host, strport, strerror(errno)); | |
380 | return (-1); | |
381 | } | |
382 | ||
383 | debug("Connection established."); | |
384 | ||
385 | /* Set SO_KEEPALIVE if requested. */ | |
386 | if (options.tcp_keep_alive && | |
387 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
388 | sizeof(on)) < 0) | |
389 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
390 | ||
391 | /* Set the connection. */ | |
392 | packet_set_connection(sock, sock); | |
393 | ||
394 | return 0; | |
395 | } | |
396 | ||
397 | /* | |
398 | * Waits for the server identification string, and sends our own | |
399 | * identification string. | |
400 | */ | |
401 | static void | |
402 | ssh_exchange_identification(void) | |
403 | { | |
404 | char buf[256], remote_version[256]; /* must be same size! */ | |
405 | int remote_major, remote_minor, i, mismatch; | |
406 | int connection_in = packet_get_connection_in(); | |
407 | int connection_out = packet_get_connection_out(); | |
408 | int minor1 = PROTOCOL_MINOR_1; | |
409 | ||
410 | /* Read other side's version identification. */ | |
411 | for (;;) { | |
412 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
413 | size_t len = atomicio(read, connection_in, &buf[i], 1); | |
414 | ||
415 | if (len != 1 && errno == EPIPE) | |
416 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
417 | else if (len != 1) | |
418 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
419 | if (buf[i] == '\r') { | |
420 | buf[i] = '\n'; | |
421 | buf[i + 1] = 0; | |
422 | continue; /**XXX wait for \n */ | |
423 | } | |
424 | if (buf[i] == '\n') { | |
425 | buf[i + 1] = 0; | |
426 | break; | |
427 | } | |
428 | } | |
429 | buf[sizeof(buf) - 1] = 0; | |
430 | if (strncmp(buf, "SSH-", 4) == 0) | |
431 | break; | |
432 | debug("ssh_exchange_identification: %s", buf); | |
433 | } | |
434 | server_version_string = xstrdup(buf); | |
435 | ||
436 | /* | |
437 | * Check that the versions match. In future this might accept | |
438 | * several versions and set appropriate flags to handle them. | |
439 | */ | |
440 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
441 | &remote_major, &remote_minor, remote_version) != 3) | |
442 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
443 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
444 | remote_major, remote_minor, remote_version); | |
445 | ||
446 | compat_datafellows(remote_version); | |
447 | mismatch = 0; | |
448 | ||
449 | switch (remote_major) { | |
450 | case 1: | |
451 | if (remote_minor == 99 && | |
452 | (options.protocol & SSH_PROTO_2) && | |
453 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
454 | enable_compat20(); | |
455 | break; | |
456 | } | |
457 | if (!(options.protocol & SSH_PROTO_1)) { | |
458 | mismatch = 1; | |
459 | break; | |
460 | } | |
461 | if (remote_minor < 3) { | |
462 | fatal("Remote machine has too old SSH software version."); | |
463 | } else if (remote_minor == 3 || remote_minor == 4) { | |
464 | /* We speak 1.3, too. */ | |
465 | enable_compat13(); | |
466 | minor1 = 3; | |
467 | if (options.forward_agent) { | |
468 | logit("Agent forwarding disabled for protocol 1.3"); | |
469 | options.forward_agent = 0; | |
470 | } | |
471 | } | |
472 | break; | |
473 | case 2: | |
474 | if (options.protocol & SSH_PROTO_2) { | |
475 | enable_compat20(); | |
476 | break; | |
477 | } | |
478 | /* FALLTHROUGH */ | |
479 | default: | |
480 | mismatch = 1; | |
481 | break; | |
482 | } | |
483 | if (mismatch) | |
484 | fatal("Protocol major versions differ: %d vs. %d", | |
485 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
486 | remote_major); | |
487 | /* Send our own protocol version identification. */ | |
488 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
489 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
490 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
491 | SSH_VERSION); | |
492 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
493 | fatal("write: %.100s", strerror(errno)); | |
494 | client_version_string = xstrdup(buf); | |
495 | chop(client_version_string); | |
496 | chop(server_version_string); | |
497 | debug("Local version string %.100s", client_version_string); | |
498 | } | |
499 | ||
500 | /* defaults to 'no' */ | |
501 | static int | |
502 | confirm(const char *prompt) | |
503 | { | |
504 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
505 | char *p; | |
506 | int ret = -1; | |
507 | ||
508 | if (options.batch_mode) | |
509 | return 0; | |
510 | for (msg = prompt;;msg = again) { | |
511 | p = read_passphrase(msg, RP_ECHO); | |
512 | if (p == NULL || | |
513 | (p[0] == '\0') || (p[0] == '\n') || | |
514 | strncasecmp(p, "no", 2) == 0) | |
515 | ret = 0; | |
516 | if (p && strncasecmp(p, "yes", 3) == 0) | |
517 | ret = 1; | |
518 | if (p) | |
519 | xfree(p); | |
520 | if (ret != -1) | |
521 | return ret; | |
522 | } | |
523 | } | |
524 | ||
525 | /* | |
526 | * check whether the supplied host key is valid, return -1 if the key | |
527 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
528 | */ | |
529 | static int | |
530 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
531 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
532 | { | |
533 | Key *file_key; | |
534 | const char *type = key_type(host_key); | |
535 | char *ip = NULL; | |
536 | char hostline[1000], *hostp, *fp; | |
537 | HostStatus host_status; | |
538 | HostStatus ip_status; | |
539 | int r, local = 0, host_ip_differ = 0; | |
540 | int salen; | |
541 | char ntop[NI_MAXHOST]; | |
542 | char msg[1024]; | |
543 | int len, host_line, ip_line; | |
544 | const char *host_file = NULL, *ip_file = NULL; | |
545 | ||
546 | /* | |
547 | * Force accepting of the host key for loopback/localhost. The | |
548 | * problem is that if the home directory is NFS-mounted to multiple | |
549 | * machines, localhost will refer to a different machine in each of | |
550 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
551 | * essentially disables host authentication for localhost; however, | |
552 | * this is probably not a real problem. | |
553 | */ | |
554 | /** hostaddr == 0! */ | |
555 | switch (hostaddr->sa_family) { | |
556 | case AF_INET: | |
557 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
558 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
559 | salen = sizeof(struct sockaddr_in); | |
560 | break; | |
561 | case AF_INET6: | |
562 | local = IN6_IS_ADDR_LOOPBACK( | |
563 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
564 | salen = sizeof(struct sockaddr_in6); | |
565 | break; | |
566 | default: | |
567 | local = 0; | |
568 | salen = sizeof(struct sockaddr_storage); | |
569 | break; | |
570 | } | |
571 | if (options.no_host_authentication_for_localhost == 1 && local && | |
572 | options.host_key_alias == NULL) { | |
573 | debug("Forcing accepting of host key for " | |
574 | "loopback/localhost."); | |
575 | return 0; | |
576 | } | |
577 | ||
578 | /* | |
579 | * We don't have the remote ip-address for connections | |
580 | * using a proxy command | |
581 | */ | |
582 | if (options.proxy_command == NULL) { | |
583 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
584 | NULL, 0, NI_NUMERICHOST) != 0) | |
585 | fatal("check_host_key: getnameinfo failed"); | |
586 | ip = xstrdup(ntop); | |
587 | } else { | |
588 | ip = xstrdup("<no hostip for proxy command>"); | |
589 | } | |
590 | /* | |
591 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
592 | * command or if we don't have a hostname to compare with | |
593 | */ | |
594 | if (options.check_host_ip && | |
595 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
596 | options.check_host_ip = 0; | |
597 | ||
598 | /* | |
599 | * Allow the user to record the key under a different name. This is | |
600 | * useful for ssh tunneling over forwarded connections or if you run | |
601 | * multiple sshd's on different ports on the same machine. | |
602 | */ | |
603 | if (options.host_key_alias != NULL) { | |
604 | host = options.host_key_alias; | |
605 | debug("using hostkeyalias: %s", host); | |
606 | } | |
607 | ||
608 | /* | |
609 | * Store the host key from the known host file in here so that we can | |
610 | * compare it with the key for the IP address. | |
611 | */ | |
612 | file_key = key_new(host_key->type); | |
613 | ||
614 | /* | |
615 | * Check if the host key is present in the user\'s list of known | |
616 | * hosts or in the systemwide list. | |
617 | */ | |
618 | host_file = user_hostfile; | |
619 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
620 | file_key, &host_line); | |
621 | if (host_status == HOST_NEW) { | |
622 | host_file = system_hostfile; | |
623 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
624 | file_key, &host_line); | |
625 | } | |
626 | /* | |
627 | * Also perform check for the ip address, skip the check if we are | |
628 | * localhost or the hostname was an ip address to begin with | |
629 | */ | |
630 | if (options.check_host_ip) { | |
631 | Key *ip_key = key_new(host_key->type); | |
632 | ||
633 | ip_file = user_hostfile; | |
634 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
635 | ip_key, &ip_line); | |
636 | if (ip_status == HOST_NEW) { | |
637 | ip_file = system_hostfile; | |
638 | ip_status = check_host_in_hostfile(ip_file, ip, | |
639 | host_key, ip_key, &ip_line); | |
640 | } | |
641 | if (host_status == HOST_CHANGED && | |
642 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
643 | host_ip_differ = 1; | |
644 | ||
645 | key_free(ip_key); | |
646 | } else | |
647 | ip_status = host_status; | |
648 | ||
649 | key_free(file_key); | |
650 | ||
651 | switch (host_status) { | |
652 | case HOST_OK: | |
653 | /* The host is known and the key matches. */ | |
654 | debug("Host '%.200s' is known and matches the %s host key.", | |
655 | host, type); | |
656 | debug("Found key in %s:%d", host_file, host_line); | |
657 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
658 | if (readonly) | |
659 | logit("%s host key for IP address " | |
660 | "'%.128s' not in list of known hosts.", | |
661 | type, ip); | |
662 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
663 | host_key, options.hash_known_hosts)) | |
664 | logit("Failed to add the %s host key for IP " | |
665 | "address '%.128s' to the list of known " | |
666 | "hosts (%.30s).", type, ip, user_hostfile); | |
667 | else | |
668 | logit("Warning: Permanently added the %s host " | |
669 | "key for IP address '%.128s' to the list " | |
670 | "of known hosts.", type, ip); | |
671 | } | |
672 | break; | |
673 | case HOST_NEW: | |
674 | if (readonly) | |
675 | goto fail; | |
676 | /* The host is new. */ | |
677 | if (options.strict_host_key_checking == 1) { | |
678 | /* | |
679 | * User has requested strict host key checking. We | |
680 | * will not add the host key automatically. The only | |
681 | * alternative left is to abort. | |
682 | */ | |
683 | error("No %s host key is known for %.200s and you " | |
684 | "have requested strict checking.", type, host); | |
685 | goto fail; | |
686 | } else if (options.strict_host_key_checking == 2) { | |
687 | char msg1[1024], msg2[1024]; | |
688 | ||
689 | if (show_other_keys(host, host_key)) | |
690 | snprintf(msg1, sizeof(msg1), | |
691 | "\nbut keys of different type are already" | |
692 | " known for this host."); | |
693 | else | |
694 | snprintf(msg1, sizeof(msg1), "."); | |
695 | /* The default */ | |
696 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
697 | msg2[0] = '\0'; | |
698 | if (options.verify_host_key_dns) { | |
699 | if (matching_host_key_dns) | |
700 | snprintf(msg2, sizeof(msg2), | |
701 | "Matching host key fingerprint" | |
702 | " found in DNS.\n"); | |
703 | else | |
704 | snprintf(msg2, sizeof(msg2), | |
705 | "No matching host key fingerprint" | |
706 | " found in DNS.\n"); | |
707 | } | |
708 | snprintf(msg, sizeof(msg), | |
709 | "The authenticity of host '%.200s (%s)' can't be " | |
710 | "established%s\n" | |
711 | "%s key fingerprint is %s.\n%s" | |
712 | "Are you sure you want to continue connecting " | |
713 | "(yes/no)? ", | |
714 | host, ip, msg1, type, fp, msg2); | |
715 | xfree(fp); | |
716 | if (!confirm(msg)) | |
717 | goto fail; | |
718 | } | |
719 | /* | |
720 | * If not in strict mode, add the key automatically to the | |
721 | * local known_hosts file. | |
722 | */ | |
723 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
724 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
725 | host, ip); | |
726 | hostp = hostline; | |
727 | if (options.hash_known_hosts) { | |
728 | /* Add hash of host and IP separately */ | |
729 | r = add_host_to_hostfile(user_hostfile, host, | |
730 | host_key, options.hash_known_hosts) && | |
731 | add_host_to_hostfile(user_hostfile, ip, | |
732 | host_key, options.hash_known_hosts); | |
733 | } else { | |
734 | /* Add unhashed "host,ip" */ | |
735 | r = add_host_to_hostfile(user_hostfile, | |
736 | hostline, host_key, | |
737 | options.hash_known_hosts); | |
738 | } | |
739 | } else { | |
740 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
741 | options.hash_known_hosts); | |
742 | hostp = host; | |
743 | } | |
744 | ||
745 | if (!r) | |
746 | logit("Failed to add the host to the list of known " | |
747 | "hosts (%.500s).", user_hostfile); | |
748 | else | |
749 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
750 | "list of known hosts.", hostp, type); | |
751 | break; | |
752 | case HOST_CHANGED: | |
753 | if (options.check_host_ip && host_ip_differ) { | |
754 | char *key_msg; | |
755 | if (ip_status == HOST_NEW) | |
756 | key_msg = "is unknown"; | |
757 | else if (ip_status == HOST_OK) | |
758 | key_msg = "is unchanged"; | |
759 | else | |
760 | key_msg = "has a different value"; | |
761 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
762 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
763 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
764 | error("The %s host key for %s has changed,", type, host); | |
765 | error("and the key for the according IP address %s", ip); | |
766 | error("%s. This could either mean that", key_msg); | |
767 | error("DNS SPOOFING is happening or the IP address for the host"); | |
768 | error("and its host key have changed at the same time."); | |
769 | if (ip_status != HOST_NEW) | |
770 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
771 | } | |
772 | /* The host key has changed. */ | |
773 | warn_changed_key(host_key); | |
774 | error("Add correct host key in %.100s to get rid of this message.", | |
775 | user_hostfile); | |
776 | error("Offending key in %s:%d", host_file, host_line); | |
777 | ||
778 | /* | |
779 | * If strict host key checking is in use, the user will have | |
780 | * to edit the key manually and we can only abort. | |
781 | */ | |
782 | if (options.strict_host_key_checking) { | |
783 | error("%s host key for %.200s has changed and you have " | |
784 | "requested strict checking.", type, host); | |
785 | goto fail; | |
786 | } | |
787 | ||
788 | /* | |
789 | * If strict host key checking has not been requested, allow | |
790 | * the connection but without MITM-able authentication or | |
791 | * agent forwarding. | |
792 | */ | |
793 | if (options.password_authentication) { | |
794 | error("Password authentication is disabled to avoid " | |
795 | "man-in-the-middle attacks."); | |
796 | options.password_authentication = 0; | |
797 | } | |
798 | if (options.kbd_interactive_authentication) { | |
799 | error("Keyboard-interactive authentication is disabled" | |
800 | " to avoid man-in-the-middle attacks."); | |
801 | options.kbd_interactive_authentication = 0; | |
802 | options.challenge_response_authentication = 0; | |
803 | } | |
804 | if (options.challenge_response_authentication) { | |
805 | error("Challenge/response authentication is disabled" | |
806 | " to avoid man-in-the-middle attacks."); | |
807 | options.challenge_response_authentication = 0; | |
808 | } | |
809 | if (options.forward_agent) { | |
810 | error("Agent forwarding is disabled to avoid " | |
811 | "man-in-the-middle attacks."); | |
812 | options.forward_agent = 0; | |
813 | } | |
814 | if (options.forward_x11) { | |
815 | error("X11 forwarding is disabled to avoid " | |
816 | "man-in-the-middle attacks."); | |
817 | options.forward_x11 = 0; | |
818 | } | |
819 | if (options.num_local_forwards > 0 || | |
820 | options.num_remote_forwards > 0) { | |
821 | error("Port forwarding is disabled to avoid " | |
822 | "man-in-the-middle attacks."); | |
823 | options.num_local_forwards = | |
824 | options.num_remote_forwards = 0; | |
825 | } | |
826 | /* | |
827 | * XXX Should permit the user to change to use the new id. | |
828 | * This could be done by converting the host key to an | |
829 | * identifying sentence, tell that the host identifies itself | |
830 | * by that sentence, and ask the user if he/she whishes to | |
831 | * accept the authentication. | |
832 | */ | |
833 | break; | |
834 | case HOST_FOUND: | |
835 | fatal("internal error"); | |
836 | break; | |
837 | } | |
838 | ||
839 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
840 | ip_status == HOST_CHANGED) { | |
841 | snprintf(msg, sizeof(msg), | |
842 | "Warning: the %s host key for '%.200s' " | |
843 | "differs from the key for the IP address '%.128s'" | |
844 | "\nOffending key for IP in %s:%d", | |
845 | type, host, ip, ip_file, ip_line); | |
846 | if (host_status == HOST_OK) { | |
847 | len = strlen(msg); | |
848 | snprintf(msg + len, sizeof(msg) - len, | |
849 | "\nMatching host key in %s:%d", | |
850 | host_file, host_line); | |
851 | } | |
852 | if (options.strict_host_key_checking == 1) { | |
853 | logit("%s", msg); | |
854 | error("Exiting, you have requested strict checking."); | |
855 | goto fail; | |
856 | } else if (options.strict_host_key_checking == 2) { | |
857 | strlcat(msg, "\nAre you sure you want " | |
858 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
859 | if (!confirm(msg)) | |
860 | goto fail; | |
861 | } else { | |
862 | logit("%s", msg); | |
863 | } | |
864 | } | |
865 | ||
866 | xfree(ip); | |
867 | return 0; | |
868 | ||
869 | fail: | |
870 | xfree(ip); | |
871 | return -1; | |
872 | } | |
873 | ||
874 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
875 | int | |
876 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
877 | { | |
878 | struct stat st; | |
879 | int flags = 0; | |
880 | ||
881 | if (options.verify_host_key_dns && | |
882 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
883 | ||
884 | if (flags & DNS_VERIFY_FOUND) { | |
885 | ||
886 | if (options.verify_host_key_dns == 1 && | |
887 | flags & DNS_VERIFY_MATCH && | |
888 | flags & DNS_VERIFY_SECURE) | |
889 | return 0; | |
890 | ||
891 | if (flags & DNS_VERIFY_MATCH) { | |
892 | matching_host_key_dns = 1; | |
893 | } else { | |
894 | warn_changed_key(host_key); | |
895 | error("Update the SSHFP RR in DNS with the new " | |
896 | "host key to get rid of this message."); | |
897 | } | |
898 | } | |
899 | } | |
900 | ||
901 | /* return ok if the key can be found in an old keyfile */ | |
902 | if (stat(options.system_hostfile2, &st) == 0 || | |
903 | stat(options.user_hostfile2, &st) == 0) { | |
904 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
905 | options.user_hostfile2, options.system_hostfile2) == 0) | |
906 | return 0; | |
907 | } | |
908 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
909 | options.user_hostfile, options.system_hostfile); | |
910 | } | |
911 | ||
912 | /* | |
913 | * Starts a dialog with the server, and authenticates the current user on the | |
914 | * server. This does not need any extra privileges. The basic connection | |
915 | * to the server must already have been established before this is called. | |
916 | * If login fails, this function prints an error and never returns. | |
917 | * This function does not require super-user privileges. | |
918 | */ | |
919 | void | |
920 | ssh_login(Sensitive *sensitive, const char *orighost, | |
921 | struct sockaddr *hostaddr, struct passwd *pw) | |
922 | { | |
923 | char *host, *cp; | |
924 | char *server_user, *local_user; | |
925 | ||
926 | local_user = xstrdup(pw->pw_name); | |
927 | server_user = options.user ? options.user : local_user; | |
928 | ||
929 | /* Convert the user-supplied hostname into all lowercase. */ | |
930 | host = xstrdup(orighost); | |
931 | for (cp = host; *cp; cp++) | |
932 | if (isupper(*cp)) | |
933 | *cp = tolower(*cp); | |
934 | ||
935 | /* Exchange protocol version identification strings with the server. */ | |
936 | ssh_exchange_identification(); | |
937 | ||
938 | /* Put the connection into non-blocking mode. */ | |
939 | packet_set_nonblocking(); | |
940 | ||
941 | /* key exchange */ | |
942 | /* authenticate user */ | |
943 | if (compat20) { | |
944 | ssh_kex2(host, hostaddr); | |
945 | ssh_userauth2(local_user, server_user, host, sensitive); | |
946 | } else { | |
947 | ssh_kex(host, hostaddr); | |
948 | ssh_userauth1(local_user, server_user, host, sensitive); | |
949 | } | |
950 | } | |
951 | ||
952 | void | |
953 | ssh_put_password(char *password) | |
954 | { | |
955 | int size; | |
956 | char *padded; | |
957 | ||
958 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
959 | packet_put_cstring(password); | |
960 | return; | |
961 | } | |
962 | size = roundup(strlen(password) + 1, 32); | |
963 | padded = xmalloc(size); | |
964 | memset(padded, 0, size); | |
965 | strlcpy(padded, password, size); | |
966 | packet_put_string(padded, size); | |
967 | memset(padded, 0, size); | |
968 | xfree(padded); | |
969 | } | |
970 | ||
971 | static int | |
972 | show_key_from_file(const char *file, const char *host, int keytype) | |
973 | { | |
974 | Key *found; | |
975 | char *fp; | |
976 | int line, ret; | |
977 | ||
978 | found = key_new(keytype); | |
979 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
980 | keytype, found, &line))) { | |
981 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
982 | logit("WARNING: %s key found for host %s\n" | |
983 | "in %s:%d\n" | |
984 | "%s key fingerprint %s.", | |
985 | key_type(found), host, file, line, | |
986 | key_type(found), fp); | |
987 | xfree(fp); | |
988 | } | |
989 | key_free(found); | |
990 | return (ret); | |
991 | } | |
992 | ||
993 | /* print all known host keys for a given host, but skip keys of given type */ | |
994 | static int | |
995 | show_other_keys(const char *host, Key *key) | |
996 | { | |
997 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
998 | int i, found = 0; | |
999 | ||
1000 | for (i = 0; type[i] != -1; i++) { | |
1001 | if (type[i] == key->type) | |
1002 | continue; | |
1003 | if (type[i] != KEY_RSA1 && | |
1004 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1005 | found = 1; | |
1006 | continue; | |
1007 | } | |
1008 | if (type[i] != KEY_RSA1 && | |
1009 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1010 | found = 1; | |
1011 | continue; | |
1012 | } | |
1013 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1014 | found = 1; | |
1015 | continue; | |
1016 | } | |
1017 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1018 | found = 1; | |
1019 | continue; | |
1020 | } | |
1021 | debug2("no key of type %d for host %s", type[i], host); | |
1022 | } | |
1023 | return (found); | |
1024 | } | |
1025 | ||
1026 | static void | |
1027 | warn_changed_key(Key *host_key) | |
1028 | { | |
1029 | char *fp; | |
1030 | const char *type = key_type(host_key); | |
1031 | ||
1032 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1033 | ||
1034 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1035 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1036 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1037 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1038 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1039 | error("It is also possible that the %s host key has just been changed.", type); | |
1040 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1041 | type, fp); | |
1042 | error("Please contact your system administrator."); | |
1043 | ||
1044 | xfree(fp); | |
1045 | } |