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3c0ef626 | 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" | |
c9f39d2c | 16 | RCSID("$OpenBSD: sshconnect.c,v 1.158 2004/06/21 17:36:31 avsm Exp $"); |
3c0ef626 | 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 | ||
0fff78ff | 35 | #include "dns.h" |
0fff78ff | 36 | |
3c0ef626 | 37 | char *client_version_string = NULL; |
38 | char *server_version_string = NULL; | |
39 | ||
cdd66111 | 40 | int matching_host_key_dns = 0; |
0fff78ff | 41 | |
f5799ae1 | 42 | /* import */ |
3c0ef626 | 43 | extern Options options; |
44 | extern char *__progname; | |
f5799ae1 | 45 | extern uid_t original_real_uid; |
46 | extern uid_t original_effective_uid; | |
41b2f314 | 47 | extern pid_t proxy_command_pid; |
3c0ef626 | 48 | |
49 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
50 | #define INET6_ADDRSTRLEN 46 | |
51 | #endif | |
52 | ||
41b2f314 | 53 | static int show_other_keys(const char *, Key *); |
cdd66111 | 54 | static void warn_changed_key(Key *); |
3c0ef626 | 55 | |
56 | /* | |
57 | * Connect to the given ssh server using a proxy command. | |
58 | */ | |
59 | static int | |
f5799ae1 | 60 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) |
3c0ef626 | 61 | { |
62 | Buffer command; | |
63 | const char *cp; | |
64 | char *command_string; | |
65 | int pin[2], pout[2]; | |
66 | pid_t pid; | |
67 | char strport[NI_MAXSERV]; | |
68 | ||
69 | /* Convert the port number into a string. */ | |
70 | snprintf(strport, sizeof strport, "%hu", port); | |
71 | ||
41b2f314 | 72 | /* |
73 | * Build the final command string in the buffer by making the | |
74 | * appropriate substitutions to the given proxy command. | |
75 | * | |
cdd66111 | 76 | * Use "exec" to avoid "sh -c" processes on some platforms |
41b2f314 | 77 | * (e.g. Solaris) |
78 | */ | |
3c0ef626 | 79 | buffer_init(&command); |
41b2f314 | 80 | buffer_append(&command, "exec ", 5); |
81 | ||
3c0ef626 | 82 | for (cp = proxy_command; *cp; cp++) { |
83 | if (cp[0] == '%' && cp[1] == '%') { | |
84 | buffer_append(&command, "%", 1); | |
85 | cp++; | |
86 | continue; | |
87 | } | |
88 | if (cp[0] == '%' && cp[1] == 'h') { | |
89 | buffer_append(&command, host, strlen(host)); | |
90 | cp++; | |
91 | continue; | |
92 | } | |
93 | if (cp[0] == '%' && cp[1] == 'p') { | |
94 | buffer_append(&command, strport, strlen(strport)); | |
95 | cp++; | |
96 | continue; | |
97 | } | |
98 | buffer_append(&command, cp, 1); | |
99 | } | |
100 | buffer_append(&command, "\0", 1); | |
101 | ||
102 | /* Get the final command string. */ | |
103 | command_string = buffer_ptr(&command); | |
104 | ||
105 | /* Create pipes for communicating with the proxy. */ | |
106 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
107 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
e9a17296 | 108 | strerror(errno)); |
3c0ef626 | 109 | |
110 | debug("Executing proxy command: %.500s", command_string); | |
111 | ||
112 | /* Fork and execute the proxy command. */ | |
113 | if ((pid = fork()) == 0) { | |
114 | char *argv[10]; | |
115 | ||
116 | /* Child. Permanently give up superuser privileges. */ | |
f5799ae1 | 117 | seteuid(original_real_uid); |
118 | setuid(original_real_uid); | |
3c0ef626 | 119 | |
120 | /* Redirect stdin and stdout. */ | |
121 | close(pin[1]); | |
122 | if (pin[0] != 0) { | |
123 | if (dup2(pin[0], 0) < 0) | |
124 | perror("dup2 stdin"); | |
125 | close(pin[0]); | |
126 | } | |
127 | close(pout[0]); | |
128 | if (dup2(pout[1], 1) < 0) | |
129 | perror("dup2 stdout"); | |
130 | /* Cannot be 1 because pin allocated two descriptors. */ | |
131 | close(pout[1]); | |
132 | ||
133 | /* Stderr is left as it is so that error messages get | |
134 | printed on the user's terminal. */ | |
135 | argv[0] = _PATH_BSHELL; | |
136 | argv[1] = "-c"; | |
137 | argv[2] = command_string; | |
138 | argv[3] = NULL; | |
139 | ||
140 | /* Execute the proxy command. Note that we gave up any | |
141 | extra privileges above. */ | |
142 | execv(argv[0], argv); | |
143 | perror(argv[0]); | |
144 | exit(1); | |
145 | } | |
146 | /* Parent. */ | |
147 | if (pid < 0) | |
148 | fatal("fork failed: %.100s", strerror(errno)); | |
41b2f314 | 149 | else |
150 | proxy_command_pid = pid; /* save pid to clean up later */ | |
3c0ef626 | 151 | |
152 | /* Close child side of the descriptors. */ | |
153 | close(pin[0]); | |
154 | close(pout[1]); | |
155 | ||
156 | /* Free the command name. */ | |
157 | buffer_free(&command); | |
158 | ||
159 | /* Set the connection file descriptors. */ | |
160 | packet_set_connection(pout[0], pin[1]); | |
161 | ||
162 | /* Indicate OK return */ | |
163 | return 0; | |
164 | } | |
165 | ||
166 | /* | |
167 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
168 | */ | |
169 | static int | |
0fff78ff | 170 | ssh_create_socket(int privileged, struct addrinfo *ai) |
3c0ef626 | 171 | { |
172 | int sock, gaierr; | |
173 | struct addrinfo hints, *res; | |
174 | ||
175 | /* | |
176 | * If we are running as root and want to connect to a privileged | |
177 | * port, bind our own socket to a privileged port. | |
178 | */ | |
179 | if (privileged) { | |
180 | int p = IPPORT_RESERVED - 1; | |
f5799ae1 | 181 | PRIV_START; |
0fff78ff | 182 | sock = rresvport_af(&p, ai->ai_family); |
f5799ae1 | 183 | PRIV_END; |
3c0ef626 | 184 | if (sock < 0) |
0fff78ff | 185 | error("rresvport: af=%d %.100s", ai->ai_family, |
186 | strerror(errno)); | |
3c0ef626 | 187 | else |
188 | debug("Allocated local port %d.", p); | |
189 | return sock; | |
190 | } | |
0fff78ff | 191 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); |
3c0ef626 | 192 | if (sock < 0) |
193 | error("socket: %.100s", strerror(errno)); | |
3c0ef626 | 194 | |
195 | /* Bind the socket to an alternative local IP address */ | |
196 | if (options.bind_address == NULL) | |
197 | return sock; | |
198 | ||
199 | memset(&hints, 0, sizeof(hints)); | |
0fff78ff | 200 | hints.ai_family = ai->ai_family; |
201 | hints.ai_socktype = ai->ai_socktype; | |
202 | hints.ai_protocol = ai->ai_protocol; | |
3c0ef626 | 203 | hints.ai_flags = AI_PASSIVE; |
204 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
205 | if (gaierr) { | |
206 | error("getaddrinfo: %s: %s", options.bind_address, | |
207 | gai_strerror(gaierr)); | |
208 | close(sock); | |
209 | return -1; | |
210 | } | |
211 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
212 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
213 | close(sock); | |
214 | freeaddrinfo(res); | |
215 | return -1; | |
216 | } | |
217 | freeaddrinfo(res); | |
218 | return sock; | |
219 | } | |
220 | ||
0fff78ff | 221 | static int |
222 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
223 | socklen_t addrlen, int timeout) | |
224 | { | |
225 | fd_set *fdset; | |
226 | struct timeval tv; | |
227 | socklen_t optlen; | |
228 | int fdsetsz, optval, rc, result = -1; | |
229 | ||
230 | if (timeout <= 0) | |
231 | return (connect(sockfd, serv_addr, addrlen)); | |
232 | ||
cdd66111 | 233 | set_nonblock(sockfd); |
0fff78ff | 234 | rc = connect(sockfd, serv_addr, addrlen); |
cdd66111 | 235 | if (rc == 0) { |
236 | unset_nonblock(sockfd); | |
0fff78ff | 237 | return (0); |
cdd66111 | 238 | } |
0fff78ff | 239 | if (errno != EINPROGRESS) |
240 | return (-1); | |
241 | ||
242 | fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); | |
243 | fdset = (fd_set *)xmalloc(fdsetsz); | |
244 | ||
245 | memset(fdset, 0, fdsetsz); | |
246 | FD_SET(sockfd, fdset); | |
247 | tv.tv_sec = timeout; | |
248 | tv.tv_usec = 0; | |
249 | ||
250 | for(;;) { | |
251 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
252 | if (rc != -1 || errno != EINTR) | |
253 | break; | |
254 | } | |
255 | ||
256 | switch(rc) { | |
257 | case 0: | |
258 | /* Timed out */ | |
259 | errno = ETIMEDOUT; | |
260 | break; | |
261 | case -1: | |
262 | /* Select error */ | |
cdd66111 | 263 | debug("select: %s", strerror(errno)); |
0fff78ff | 264 | break; |
265 | case 1: | |
266 | /* Completed or failed */ | |
267 | optval = 0; | |
268 | optlen = sizeof(optval); | |
cdd66111 | 269 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, |
acc3d05e | 270 | &optlen) == -1) { |
cdd66111 | 271 | debug("getsockopt: %s", strerror(errno)); |
0fff78ff | 272 | break; |
acc3d05e | 273 | } |
0fff78ff | 274 | if (optval != 0) { |
275 | errno = optval; | |
276 | break; | |
277 | } | |
278 | result = 0; | |
cdd66111 | 279 | unset_nonblock(sockfd); |
0fff78ff | 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 | ||
3c0ef626 | 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. | |
f5799ae1 | 293 | * If port is 0, the default port will be used. If needpriv is true, |
3c0ef626 | 294 | * a privileged port will be allocated to make the connection. |
f5799ae1 | 295 | * This requires super-user privileges if needpriv is true. |
3c0ef626 | 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, | |
f5799ae1 | 310 | int needpriv, const char *proxy_command) |
3c0ef626 | 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; | |
3c0ef626 | 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 | ||
6a9b3198 | 325 | debug2("ssh_connect: needpriv %d", needpriv); |
3c0ef626 | 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) | |
f5799ae1 | 337 | return ssh_proxy_connect(host, port, proxy_command); |
3c0ef626 | 338 | |
339 | /* No proxy command. */ | |
340 | ||
341 | memset(&hints, 0, sizeof(hints)); | |
342 | hints.ai_family = family; | |
343 | hints.ai_socktype = SOCK_STREAM; | |
680cee3b | 344 | snprintf(strport, sizeof strport, "%u", port); |
3c0ef626 | 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. */ | |
0fff78ff | 373 | sock = ssh_create_socket(needpriv, ai); |
3c0ef626 | 374 | if (sock < 0) |
375 | /* Any error is already output */ | |
376 | continue; | |
377 | ||
0fff78ff | 378 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, |
379 | options.connection_timeout) >= 0) { | |
3c0ef626 | 380 | /* Successful connection. */ |
381 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
3c0ef626 | 382 | break; |
383 | } else { | |
384 | if (errno == ECONNREFUSED) | |
385 | full_failure = 0; | |
41b2f314 | 386 | debug("connect to address %s port %s: %s", |
387 | ntop, strport, strerror(errno)); | |
3c0ef626 | 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 | */ | |
3c0ef626 | 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. */ | |
41b2f314 | 410 | if (attempt >= connection_attempts) { |
0fff78ff | 411 | logit("ssh: connect to host %s port %s: %s", |
41b2f314 | 412 | host, strport, strerror(errno)); |
3c0ef626 | 413 | return full_failure ? ECONNABORTED : ECONNREFUSED; |
41b2f314 | 414 | } |
3c0ef626 | 415 | |
416 | debug("Connection established."); | |
417 | ||
cdd66111 | 418 | /* Set SO_KEEPALIVE if requested. */ |
419 | if (options.tcp_keep_alive && | |
3c0ef626 | 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", | |
e9a17296 | 476 | remote_major, remote_minor, remote_version); |
3c0ef626 | 477 | |
478 | compat_datafellows(remote_version); | |
479 | mismatch = 0; | |
480 | ||
e9a17296 | 481 | switch (remote_major) { |
3c0ef626 | 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) { | |
0fff78ff | 500 | logit("Agent forwarding disabled for protocol 1.3"); |
3c0ef626 | 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); | |
0fff78ff | 524 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) |
3c0ef626 | 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 | { | |
e9a17296 | 536 | const char *msg, *again = "Please type 'yes' or 'no': "; |
537 | char *p; | |
538 | int ret = -1; | |
3c0ef626 | 539 | |
540 | if (options.batch_mode) | |
541 | return 0; | |
e9a17296 | 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; | |
41b2f314 | 548 | if (p && strncasecmp(p, "yes", 3) == 0) |
e9a17296 | 549 | ret = 1; |
550 | if (p) | |
551 | xfree(p); | |
552 | if (ret != -1) | |
553 | return ret; | |
3c0ef626 | 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 | */ | |
3c0ef626 | 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; | |
cdd66111 | 566 | const char *type = key_type(host_key); |
3c0ef626 | 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]; | |
e9a17296 | 574 | char msg[1024]; |
0fff78ff | 575 | int len, host_line, ip_line; |
3c0ef626 | 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)-> | |
e9a17296 | 590 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; |
3c0ef626 | 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, | |
e9a17296 | 652 | file_key, &host_line); |
3c0ef626 | 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) | |
0fff78ff | 691 | logit("%s host key for IP address " |
3c0ef626 | 692 | "'%.128s' not in list of known hosts.", |
693 | type, ip); | |
694 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
e9a17296 | 695 | host_key)) |
0fff78ff | 696 | logit("Failed to add the %s host key for IP " |
3c0ef626 | 697 | "address '%.128s' to the list of known " |
698 | "hosts (%.30s).", type, ip, user_hostfile); | |
699 | else | |
0fff78ff | 700 | logit("Warning: Permanently added the %s host " |
3c0ef626 | 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) { | |
0fff78ff | 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), "."); | |
3c0ef626 | 727 | /* The default */ |
3c0ef626 | 728 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); |
0fff78ff | 729 | msg2[0] = '\0'; |
0fff78ff | 730 | if (options.verify_host_key_dns) { |
cdd66111 | 731 | if (matching_host_key_dns) |
0fff78ff | 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 | } | |
e9a17296 | 740 | snprintf(msg, sizeof(msg), |
3c0ef626 | 741 | "The authenticity of host '%.200s (%s)' can't be " |
41b2f314 | 742 | "established%s\n" |
0fff78ff | 743 | "%s key fingerprint is %s.\n%s" |
3c0ef626 | 744 | "Are you sure you want to continue connecting " |
41b2f314 | 745 | "(yes/no)? ", |
0fff78ff | 746 | host, ip, msg1, type, fp, msg2); |
3c0ef626 | 747 | xfree(fp); |
e9a17296 | 748 | if (!confirm(msg)) |
3c0ef626 | 749 | goto fail; |
3c0ef626 | 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)) | |
0fff78ff | 762 | logit("Failed to add the host to the list of known " |
3c0ef626 | 763 | "hosts (%.500s).", user_hostfile); |
764 | else | |
0fff78ff | 765 | logit("Warning: Permanently added '%.200s' (%s) to the " |
3c0ef626 | 766 | "list of known hosts.", hostp, type); |
767 | break; | |
768 | case HOST_CHANGED: | |
769 | if (options.check_host_ip && host_ip_differ) { | |
c9f39d2c | 770 | char *key_msg; |
3c0ef626 | 771 | if (ip_status == HOST_NEW) |
c9f39d2c | 772 | key_msg = "is unknown"; |
3c0ef626 | 773 | else if (ip_status == HOST_OK) |
c9f39d2c | 774 | key_msg = "is unchanged"; |
3c0ef626 | 775 | else |
c9f39d2c | 776 | key_msg = "has a different value"; |
3c0ef626 | 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); | |
c9f39d2c | 782 | error("%s. This could either mean that", key_msg); |
3c0ef626 | 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. */ | |
cdd66111 | 789 | warn_changed_key(host_key); |
3c0ef626 | 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); | |
3c0ef626 | 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 | |
0fff78ff | 806 | * the connection but without MITM-able authentication or |
3c0ef626 | 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 | } | |
0fff78ff | 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 | } | |
3c0ef626 | 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 = | |
e9a17296 | 840 | options.num_remote_forwards = 0; |
3c0ef626 | 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; | |
41b2f314 | 850 | case HOST_FOUND: |
851 | fatal("internal error"); | |
852 | break; | |
3c0ef626 | 853 | } |
854 | ||
855 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
856 | ip_status == HOST_CHANGED) { | |
e9a17296 | 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", | |
f5799ae1 | 866 | host_file, host_line); |
e9a17296 | 867 | } |
3c0ef626 | 868 | if (options.strict_host_key_checking == 1) { |
0fff78ff | 869 | logit("%s", msg); |
3c0ef626 | 870 | error("Exiting, you have requested strict checking."); |
871 | goto fail; | |
872 | } else if (options.strict_host_key_checking == 2) { | |
e9a17296 | 873 | strlcat(msg, "\nAre you sure you want " |
874 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
875 | if (!confirm(msg)) | |
3c0ef626 | 876 | goto fail; |
e9a17296 | 877 | } else { |
0fff78ff | 878 | logit("%s", msg); |
3c0ef626 | 879 | } |
880 | } | |
881 | ||
882 | xfree(ip); | |
883 | return 0; | |
884 | ||
885 | fail: | |
886 | xfree(ip); | |
887 | return -1; | |
888 | } | |
889 | ||
0fff78ff | 890 | /* returns 0 if key verifies or -1 if key does NOT verify */ |
3c0ef626 | 891 | int |
892 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
893 | { | |
894 | struct stat st; | |
cdd66111 | 895 | int flags = 0; |
12408a1b | 896 | |
cdd66111 | 897 | if (options.verify_host_key_dns && |
898 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
899 | ||
900 | if (flags & DNS_VERIFY_FOUND) { | |
901 | ||
902 | if (options.verify_host_key_dns == 1 && | |
903 | flags & DNS_VERIFY_MATCH && | |
904 | flags & DNS_VERIFY_SECURE) | |
905 | return 0; | |
906 | ||
907 | if (flags & DNS_VERIFY_MATCH) { | |
908 | matching_host_key_dns = 1; | |
909 | } else { | |
910 | warn_changed_key(host_key); | |
911 | error("Update the SSHFP RR in DNS with the new " | |
912 | "host key to get rid of this message."); | |
913 | } | |
0fff78ff | 914 | } |
915 | } | |
0fff78ff | 916 | |
3c0ef626 | 917 | /* return ok if the key can be found in an old keyfile */ |
918 | if (stat(options.system_hostfile2, &st) == 0 || | |
919 | stat(options.user_hostfile2, &st) == 0) { | |
920 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
921 | options.user_hostfile2, options.system_hostfile2) == 0) | |
922 | return 0; | |
923 | } | |
924 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
925 | options.user_hostfile, options.system_hostfile); | |
926 | } | |
927 | ||
928 | /* | |
929 | * Starts a dialog with the server, and authenticates the current user on the | |
930 | * server. This does not need any extra privileges. The basic connection | |
931 | * to the server must already have been established before this is called. | |
932 | * If login fails, this function prints an error and never returns. | |
933 | * This function does not require super-user privileges. | |
934 | */ | |
935 | void | |
f5799ae1 | 936 | ssh_login(Sensitive *sensitive, const char *orighost, |
3c0ef626 | 937 | struct sockaddr *hostaddr, struct passwd *pw) |
938 | { | |
939 | char *host, *cp; | |
940 | char *server_user, *local_user; | |
941 | ||
942 | local_user = xstrdup(pw->pw_name); | |
943 | server_user = options.user ? options.user : local_user; | |
944 | ||
945 | /* Convert the user-supplied hostname into all lowercase. */ | |
946 | host = xstrdup(orighost); | |
947 | for (cp = host; *cp; cp++) | |
948 | if (isupper(*cp)) | |
949 | *cp = tolower(*cp); | |
950 | ||
951 | /* Exchange protocol version identification strings with the server. */ | |
952 | ssh_exchange_identification(); | |
953 | ||
954 | /* Put the connection into non-blocking mode. */ | |
955 | packet_set_nonblocking(); | |
956 | ||
957 | /* key exchange */ | |
958 | /* authenticate user */ | |
959 | if (compat20) { | |
960 | ssh_kex2(host, hostaddr); | |
f5799ae1 | 961 | ssh_userauth2(local_user, server_user, host, sensitive); |
3c0ef626 | 962 | } else { |
963 | ssh_kex(host, hostaddr); | |
f5799ae1 | 964 | ssh_userauth1(local_user, server_user, host, sensitive); |
3c0ef626 | 965 | } |
966 | } | |
967 | ||
968 | void | |
969 | ssh_put_password(char *password) | |
970 | { | |
971 | int size; | |
972 | char *padded; | |
973 | ||
974 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
975 | packet_put_cstring(password); | |
976 | return; | |
977 | } | |
978 | size = roundup(strlen(password) + 1, 32); | |
979 | padded = xmalloc(size); | |
980 | memset(padded, 0, size); | |
981 | strlcpy(padded, password, size); | |
982 | packet_put_string(padded, size); | |
983 | memset(padded, 0, size); | |
984 | xfree(padded); | |
985 | } | |
41b2f314 | 986 | |
987 | static int | |
988 | show_key_from_file(const char *file, const char *host, int keytype) | |
989 | { | |
990 | Key *found; | |
991 | char *fp; | |
992 | int line, ret; | |
993 | ||
994 | found = key_new(keytype); | |
995 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
996 | keytype, found, &line))) { | |
997 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
0fff78ff | 998 | logit("WARNING: %s key found for host %s\n" |
41b2f314 | 999 | "in %s:%d\n" |
1000 | "%s key fingerprint %s.", | |
1001 | key_type(found), host, file, line, | |
1002 | key_type(found), fp); | |
1003 | xfree(fp); | |
1004 | } | |
1005 | key_free(found); | |
1006 | return (ret); | |
1007 | } | |
1008 | ||
1009 | /* print all known host keys for a given host, but skip keys of given type */ | |
1010 | static int | |
1011 | show_other_keys(const char *host, Key *key) | |
1012 | { | |
1013 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1014 | int i, found = 0; | |
1015 | ||
1016 | for (i = 0; type[i] != -1; i++) { | |
1017 | if (type[i] == key->type) | |
1018 | continue; | |
1019 | if (type[i] != KEY_RSA1 && | |
1020 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1021 | found = 1; | |
1022 | continue; | |
1023 | } | |
1024 | if (type[i] != KEY_RSA1 && | |
1025 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1026 | found = 1; | |
1027 | continue; | |
1028 | } | |
1029 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1030 | found = 1; | |
1031 | continue; | |
1032 | } | |
1033 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1034 | found = 1; | |
1035 | continue; | |
1036 | } | |
1037 | debug2("no key of type %d for host %s", type[i], host); | |
1038 | } | |
1039 | return (found); | |
1040 | } | |
cdd66111 | 1041 | |
1042 | static void | |
1043 | warn_changed_key(Key *host_key) | |
1044 | { | |
1045 | char *fp; | |
1046 | const char *type = key_type(host_key); | |
1047 | ||
1048 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1049 | ||
1050 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1051 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1052 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1053 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1054 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1055 | error("It is also possible that the %s host key has just been changed.", type); | |
1056 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1057 | type, fp); | |
1058 | error("Please contact your system administrator."); | |
1059 | ||
1060 | xfree(fp); | |
1061 | } |