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1 | /* $OpenBSD: sshconnect.c,v 1.199 2006/08/03 03:34:42 deraadt Exp $ */ | |
2 | /* | |
3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | * All rights reserved | |
6 | * Code to connect to a remote host, and to perform the client side of the | |
7 | * login (authentication) dialog. | |
8 | * | |
9 | * As far as I am concerned, the code I have written for this software | |
10 | * can be used freely for any purpose. Any derived versions of this | |
11 | * software must be clearly marked as such, and if the derived work is | |
12 | * incompatible with the protocol description in the RFC file, it must be | |
13 | * called by a name other than "ssh" or "Secure Shell". | |
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | ||
18 | #include <sys/types.h> | |
19 | #include <sys/wait.h> | |
20 | #include <sys/stat.h> | |
21 | #include <sys/socket.h> | |
22 | #ifdef HAVE_SYS_TIME_H | |
23 | # include <sys/time.h> | |
24 | #endif | |
25 | ||
26 | #include <netinet/in.h> | |
27 | ||
28 | #include <ctype.h> | |
29 | #include <errno.h> | |
30 | #include <netdb.h> | |
31 | #ifdef HAVE_PATHS_H | |
32 | #include <paths.h> | |
33 | #endif | |
34 | #include <pwd.h> | |
35 | #include <stdio.h> | |
36 | #include <stdlib.h> | |
37 | #include <string.h> | |
38 | #include <unistd.h> | |
39 | ||
40 | #include "xmalloc.h" | |
41 | #include "key.h" | |
42 | #include "hostfile.h" | |
43 | #include "ssh.h" | |
44 | #include "rsa.h" | |
45 | #include "buffer.h" | |
46 | #include "packet.h" | |
47 | #include "uidswap.h" | |
48 | #include "compat.h" | |
49 | #include "key.h" | |
50 | #include "sshconnect.h" | |
51 | #include "hostfile.h" | |
52 | #include "log.h" | |
53 | #include "readconf.h" | |
54 | #include "atomicio.h" | |
55 | #include "misc.h" | |
56 | #include "dns.h" | |
57 | #include "version.h" | |
58 | ||
59 | char *client_version_string = NULL; | |
60 | char *server_version_string = NULL; | |
61 | ||
62 | static int matching_host_key_dns = 0; | |
63 | ||
64 | /* import */ | |
65 | extern Options options; | |
66 | extern char *__progname; | |
67 | extern uid_t original_real_uid; | |
68 | extern uid_t original_effective_uid; | |
69 | extern pid_t proxy_command_pid; | |
70 | ||
71 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
72 | #define INET6_ADDRSTRLEN 46 | |
73 | #endif | |
74 | ||
75 | static int show_other_keys(const char *, Key *); | |
76 | static void warn_changed_key(Key *); | |
77 | ||
78 | /* | |
79 | * Connect to the given ssh server using a proxy command. | |
80 | */ | |
81 | static int | |
82 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
83 | { | |
84 | char *command_string, *tmp; | |
85 | int pin[2], pout[2]; | |
86 | pid_t pid; | |
87 | char strport[NI_MAXSERV]; | |
88 | ||
89 | /* Convert the port number into a string. */ | |
90 | snprintf(strport, sizeof strport, "%hu", port); | |
91 | ||
92 | /* | |
93 | * Build the final command string in the buffer by making the | |
94 | * appropriate substitutions to the given proxy command. | |
95 | * | |
96 | * Use "exec" to avoid "sh -c" processes on some platforms | |
97 | * (e.g. Solaris) | |
98 | */ | |
99 | xasprintf(&tmp, "exec %s", proxy_command); | |
100 | command_string = percent_expand(tmp, "h", host, | |
101 | "p", strport, (char *)NULL); | |
102 | xfree(tmp); | |
103 | ||
104 | /* Create pipes for communicating with the proxy. */ | |
105 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
106 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
107 | strerror(errno)); | |
108 | ||
109 | debug("Executing proxy command: %.500s", command_string); | |
110 | ||
111 | /* Fork and execute the proxy command. */ | |
112 | if ((pid = fork()) == 0) { | |
113 | char *argv[10]; | |
114 | ||
115 | /* Child. Permanently give up superuser privileges. */ | |
116 | permanently_drop_suid(original_real_uid); | |
117 | ||
118 | /* Redirect stdin and stdout. */ | |
119 | close(pin[1]); | |
120 | if (pin[0] != 0) { | |
121 | if (dup2(pin[0], 0) < 0) | |
122 | perror("dup2 stdin"); | |
123 | close(pin[0]); | |
124 | } | |
125 | close(pout[0]); | |
126 | if (dup2(pout[1], 1) < 0) | |
127 | perror("dup2 stdout"); | |
128 | /* Cannot be 1 because pin allocated two descriptors. */ | |
129 | close(pout[1]); | |
130 | ||
131 | /* Stderr is left as it is so that error messages get | |
132 | printed on the user's terminal. */ | |
133 | argv[0] = _PATH_BSHELL; | |
134 | argv[1] = "-c"; | |
135 | argv[2] = command_string; | |
136 | argv[3] = NULL; | |
137 | ||
138 | /* Execute the proxy command. Note that we gave up any | |
139 | extra privileges above. */ | |
140 | execv(argv[0], argv); | |
141 | perror(argv[0]); | |
142 | exit(1); | |
143 | } | |
144 | /* Parent. */ | |
145 | if (pid < 0) | |
146 | fatal("fork failed: %.100s", strerror(errno)); | |
147 | else | |
148 | proxy_command_pid = pid; /* save pid to clean up later */ | |
149 | ||
150 | /* Close child side of the descriptors. */ | |
151 | close(pin[0]); | |
152 | close(pout[1]); | |
153 | ||
154 | /* Free the command name. */ | |
155 | xfree(command_string); | |
156 | ||
157 | /* Set the connection file descriptors. */ | |
158 | packet_set_connection(pout[0], pin[1]); | |
159 | ||
160 | /* Indicate OK return */ | |
161 | return 0; | |
162 | } | |
163 | ||
164 | /* | |
165 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
166 | */ | |
167 | static int | |
168 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
169 | { | |
170 | int sock, gaierr; | |
171 | struct addrinfo hints, *res; | |
172 | ||
173 | /* | |
174 | * If we are running as root and want to connect to a privileged | |
175 | * port, bind our own socket to a privileged port. | |
176 | */ | |
177 | if (privileged) { | |
178 | int p = IPPORT_RESERVED - 1; | |
179 | PRIV_START; | |
180 | sock = rresvport_af(&p, ai->ai_family); | |
181 | PRIV_END; | |
182 | if (sock < 0) | |
183 | error("rresvport: af=%d %.100s", ai->ai_family, | |
184 | strerror(errno)); | |
185 | else | |
186 | debug("Allocated local port %d.", p); | |
187 | return sock; | |
188 | } | |
189 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
190 | if (sock < 0) | |
191 | error("socket: %.100s", strerror(errno)); | |
192 | ||
193 | /* Bind the socket to an alternative local IP address */ | |
194 | if (options.bind_address == NULL) | |
195 | return sock; | |
196 | ||
197 | memset(&hints, 0, sizeof(hints)); | |
198 | hints.ai_family = ai->ai_family; | |
199 | hints.ai_socktype = ai->ai_socktype; | |
200 | hints.ai_protocol = ai->ai_protocol; | |
201 | hints.ai_flags = AI_PASSIVE; | |
202 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
203 | if (gaierr) { | |
204 | error("getaddrinfo: %s: %s", options.bind_address, | |
205 | gai_strerror(gaierr)); | |
206 | close(sock); | |
207 | return -1; | |
208 | } | |
209 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
210 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
211 | close(sock); | |
212 | freeaddrinfo(res); | |
213 | return -1; | |
214 | } | |
215 | freeaddrinfo(res); | |
216 | return sock; | |
217 | } | |
218 | ||
219 | static int | |
220 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
221 | socklen_t addrlen, int timeout) | |
222 | { | |
223 | fd_set *fdset; | |
224 | struct timeval tv; | |
225 | socklen_t optlen; | |
226 | int optval, rc, result = -1; | |
227 | ||
228 | if (timeout <= 0) | |
229 | return (connect(sockfd, serv_addr, addrlen)); | |
230 | ||
231 | set_nonblock(sockfd); | |
232 | rc = connect(sockfd, serv_addr, addrlen); | |
233 | if (rc == 0) { | |
234 | unset_nonblock(sockfd); | |
235 | return (0); | |
236 | } | |
237 | if (errno != EINPROGRESS) | |
238 | return (-1); | |
239 | ||
240 | fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), | |
241 | sizeof(fd_mask)); | |
242 | FD_SET(sockfd, fdset); | |
243 | tv.tv_sec = timeout; | |
244 | tv.tv_usec = 0; | |
245 | ||
246 | for (;;) { | |
247 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
248 | if (rc != -1 || errno != EINTR) | |
249 | break; | |
250 | } | |
251 | ||
252 | switch (rc) { | |
253 | case 0: | |
254 | /* Timed out */ | |
255 | errno = ETIMEDOUT; | |
256 | break; | |
257 | case -1: | |
258 | /* Select error */ | |
259 | debug("select: %s", strerror(errno)); | |
260 | break; | |
261 | case 1: | |
262 | /* Completed or failed */ | |
263 | optval = 0; | |
264 | optlen = sizeof(optval); | |
265 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
266 | &optlen) == -1) { | |
267 | debug("getsockopt: %s", strerror(errno)); | |
268 | break; | |
269 | } | |
270 | if (optval != 0) { | |
271 | errno = optval; | |
272 | break; | |
273 | } | |
274 | result = 0; | |
275 | unset_nonblock(sockfd); | |
276 | break; | |
277 | default: | |
278 | /* Should not occur */ | |
279 | fatal("Bogus return (%d) from select()", rc); | |
280 | } | |
281 | ||
282 | xfree(fdset); | |
283 | return (result); | |
284 | } | |
285 | ||
286 | /* | |
287 | * Opens a TCP/IP connection to the remote server on the given host. | |
288 | * The address of the remote host will be returned in hostaddr. | |
289 | * If port is 0, the default port will be used. If needpriv is true, | |
290 | * a privileged port will be allocated to make the connection. | |
291 | * This requires super-user privileges if needpriv is true. | |
292 | * Connection_attempts specifies the maximum number of tries (one per | |
293 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
294 | * and %p substituted for host and port, respectively) to use to contact | |
295 | * the daemon. | |
296 | */ | |
297 | int | |
298 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
299 | u_short port, int family, int connection_attempts, | |
300 | int needpriv, const char *proxy_command) | |
301 | { | |
302 | int gaierr; | |
303 | int on = 1; | |
304 | int sock = -1, attempt; | |
305 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
306 | struct addrinfo hints, *ai, *aitop; | |
307 | ||
308 | debug2("ssh_connect: needpriv %d", needpriv); | |
309 | ||
310 | /* If a proxy command is given, connect using it. */ | |
311 | if (proxy_command != NULL) | |
312 | return ssh_proxy_connect(host, port, proxy_command); | |
313 | ||
314 | /* No proxy command. */ | |
315 | ||
316 | memset(&hints, 0, sizeof(hints)); | |
317 | hints.ai_family = family; | |
318 | hints.ai_socktype = SOCK_STREAM; | |
319 | snprintf(strport, sizeof strport, "%u", port); | |
320 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
321 | fatal("%s: %.100s: %s", __progname, host, | |
322 | gai_strerror(gaierr)); | |
323 | ||
324 | for (attempt = 0; attempt < connection_attempts; attempt++) { | |
325 | if (attempt > 0) | |
326 | debug("Trying again..."); | |
327 | ||
328 | /* | |
329 | * Loop through addresses for this host, and try each one in | |
330 | * sequence until the connection succeeds. | |
331 | */ | |
332 | for (ai = aitop; ai; ai = ai->ai_next) { | |
333 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
334 | continue; | |
335 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
336 | ntop, sizeof(ntop), strport, sizeof(strport), | |
337 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
338 | error("ssh_connect: getnameinfo failed"); | |
339 | continue; | |
340 | } | |
341 | debug("Connecting to %.200s [%.100s] port %s.", | |
342 | host, ntop, strport); | |
343 | ||
344 | /* Create a socket for connecting. */ | |
345 | sock = ssh_create_socket(needpriv, ai); | |
346 | if (sock < 0) | |
347 | /* Any error is already output */ | |
348 | continue; | |
349 | ||
350 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
351 | options.connection_timeout) >= 0) { | |
352 | /* Successful connection. */ | |
353 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
354 | break; | |
355 | } else { | |
356 | debug("connect to address %s port %s: %s", | |
357 | ntop, strport, strerror(errno)); | |
358 | close(sock); | |
359 | sock = -1; | |
360 | } | |
361 | } | |
362 | if (sock != -1) | |
363 | break; /* Successful connection. */ | |
364 | ||
365 | /* Sleep a moment before retrying. */ | |
366 | sleep(1); | |
367 | } | |
368 | ||
369 | freeaddrinfo(aitop); | |
370 | ||
371 | /* Return failure if we didn't get a successful connection. */ | |
372 | if (sock == -1) { | |
373 | error("ssh: connect to host %s port %s: %s", | |
374 | host, strport, strerror(errno)); | |
375 | return (-1); | |
376 | } | |
377 | ||
378 | debug("Connection established."); | |
379 | ||
380 | /* Set SO_KEEPALIVE if requested. */ | |
381 | if (options.tcp_keep_alive && | |
382 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
383 | sizeof(on)) < 0) | |
384 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
385 | ||
386 | /* Set the connection. */ | |
387 | packet_set_connection(sock, sock); | |
388 | ||
389 | return 0; | |
390 | } | |
391 | ||
392 | /* | |
393 | * Waits for the server identification string, and sends our own | |
394 | * identification string. | |
395 | */ | |
396 | static void | |
397 | ssh_exchange_identification(void) | |
398 | { | |
399 | char buf[256], remote_version[256]; /* must be same size! */ | |
400 | int remote_major, remote_minor, mismatch; | |
401 | int connection_in = packet_get_connection_in(); | |
402 | int connection_out = packet_get_connection_out(); | |
403 | int minor1 = PROTOCOL_MINOR_1; | |
404 | u_int i, n; | |
405 | ||
406 | /* Read other side's version identification. */ | |
407 | for (n = 0;;) { | |
408 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
409 | size_t len = atomicio(read, connection_in, &buf[i], 1); | |
410 | ||
411 | if (len != 1 && errno == EPIPE) | |
412 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
413 | else if (len != 1) | |
414 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
415 | if (buf[i] == '\r') { | |
416 | buf[i] = '\n'; | |
417 | buf[i + 1] = 0; | |
418 | continue; /**XXX wait for \n */ | |
419 | } | |
420 | if (buf[i] == '\n') { | |
421 | buf[i + 1] = 0; | |
422 | break; | |
423 | } | |
424 | if (++n > 65536) | |
425 | fatal("ssh_exchange_identification: No banner received"); | |
426 | } | |
427 | buf[sizeof(buf) - 1] = 0; | |
428 | if (strncmp(buf, "SSH-", 4) == 0) | |
429 | break; | |
430 | debug("ssh_exchange_identification: %s", buf); | |
431 | } | |
432 | server_version_string = xstrdup(buf); | |
433 | ||
434 | /* | |
435 | * Check that the versions match. In future this might accept | |
436 | * several versions and set appropriate flags to handle them. | |
437 | */ | |
438 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
439 | &remote_major, &remote_minor, remote_version) != 3) | |
440 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
441 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
442 | remote_major, remote_minor, remote_version); | |
443 | ||
444 | compat_datafellows(remote_version); | |
445 | mismatch = 0; | |
446 | ||
447 | switch (remote_major) { | |
448 | case 1: | |
449 | if (remote_minor == 99 && | |
450 | (options.protocol & SSH_PROTO_2) && | |
451 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
452 | enable_compat20(); | |
453 | break; | |
454 | } | |
455 | if (!(options.protocol & SSH_PROTO_1)) { | |
456 | mismatch = 1; | |
457 | break; | |
458 | } | |
459 | if (remote_minor < 3) { | |
460 | fatal("Remote machine has too old SSH software version."); | |
461 | } else if (remote_minor == 3 || remote_minor == 4) { | |
462 | /* We speak 1.3, too. */ | |
463 | enable_compat13(); | |
464 | minor1 = 3; | |
465 | if (options.forward_agent) { | |
466 | logit("Agent forwarding disabled for protocol 1.3"); | |
467 | options.forward_agent = 0; | |
468 | } | |
469 | } | |
470 | break; | |
471 | case 2: | |
472 | if (options.protocol & SSH_PROTO_2) { | |
473 | enable_compat20(); | |
474 | break; | |
475 | } | |
476 | /* FALLTHROUGH */ | |
477 | default: | |
478 | mismatch = 1; | |
479 | break; | |
480 | } | |
481 | if (mismatch) | |
482 | fatal("Protocol major versions differ: %d vs. %d", | |
483 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
484 | remote_major); | |
485 | /* Send our own protocol version identification. */ | |
486 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
487 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
488 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
489 | SSH_VERSION); | |
490 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
491 | fatal("write: %.100s", strerror(errno)); | |
492 | client_version_string = xstrdup(buf); | |
493 | chop(client_version_string); | |
494 | chop(server_version_string); | |
495 | debug("Local version string %.100s", client_version_string); | |
496 | } | |
497 | ||
498 | /* defaults to 'no' */ | |
499 | static int | |
500 | confirm(const char *prompt) | |
501 | { | |
502 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
503 | char *p; | |
504 | int ret = -1; | |
505 | ||
506 | if (options.batch_mode) | |
507 | return 0; | |
508 | for (msg = prompt;;msg = again) { | |
509 | p = read_passphrase(msg, RP_ECHO); | |
510 | if (p == NULL || | |
511 | (p[0] == '\0') || (p[0] == '\n') || | |
512 | strncasecmp(p, "no", 2) == 0) | |
513 | ret = 0; | |
514 | if (p && strncasecmp(p, "yes", 3) == 0) | |
515 | ret = 1; | |
516 | if (p) | |
517 | xfree(p); | |
518 | if (ret != -1) | |
519 | return ret; | |
520 | } | |
521 | } | |
522 | ||
523 | /* | |
524 | * check whether the supplied host key is valid, return -1 if the key | |
525 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
526 | */ | |
527 | #define RDRW 0 | |
528 | #define RDONLY 1 | |
529 | #define ROQUIET 2 | |
530 | static int | |
531 | check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, | |
532 | Key *host_key, int readonly, const char *user_hostfile, | |
533 | const char *system_hostfile) | |
534 | { | |
535 | Key *file_key; | |
536 | const char *type = key_type(host_key); | |
537 | char *ip = NULL, *host = NULL; | |
538 | char hostline[1000], *hostp, *fp; | |
539 | HostStatus host_status; | |
540 | HostStatus ip_status; | |
541 | int r, local = 0, host_ip_differ = 0; | |
542 | int salen; | |
543 | char ntop[NI_MAXHOST]; | |
544 | char msg[1024]; | |
545 | int len, host_line, ip_line; | |
546 | const char *host_file = NULL, *ip_file = NULL; | |
547 | ||
548 | /* | |
549 | * Force accepting of the host key for loopback/localhost. The | |
550 | * problem is that if the home directory is NFS-mounted to multiple | |
551 | * machines, localhost will refer to a different machine in each of | |
552 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
553 | * essentially disables host authentication for localhost; however, | |
554 | * this is probably not a real problem. | |
555 | */ | |
556 | /** hostaddr == 0! */ | |
557 | switch (hostaddr->sa_family) { | |
558 | case AF_INET: | |
559 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
560 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
561 | salen = sizeof(struct sockaddr_in); | |
562 | break; | |
563 | case AF_INET6: | |
564 | local = IN6_IS_ADDR_LOOPBACK( | |
565 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
566 | salen = sizeof(struct sockaddr_in6); | |
567 | break; | |
568 | default: | |
569 | local = 0; | |
570 | salen = sizeof(struct sockaddr_storage); | |
571 | break; | |
572 | } | |
573 | if (options.no_host_authentication_for_localhost == 1 && local && | |
574 | options.host_key_alias == NULL) { | |
575 | debug("Forcing accepting of host key for " | |
576 | "loopback/localhost."); | |
577 | return 0; | |
578 | } | |
579 | ||
580 | /* | |
581 | * We don't have the remote ip-address for connections | |
582 | * using a proxy command | |
583 | */ | |
584 | if (options.proxy_command == NULL) { | |
585 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
586 | NULL, 0, NI_NUMERICHOST) != 0) | |
587 | fatal("check_host_key: getnameinfo failed"); | |
588 | ip = put_host_port(ntop, port); | |
589 | } else { | |
590 | ip = xstrdup("<no hostip for proxy command>"); | |
591 | } | |
592 | /* | |
593 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
594 | * command or if we don't have a hostname to compare with | |
595 | */ | |
596 | if (options.check_host_ip && (local || | |
597 | strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) | |
598 | options.check_host_ip = 0; | |
599 | ||
600 | /* | |
601 | * Allow the user to record the key under a different name or | |
602 | * differentiate a non-standard port. This is useful for ssh | |
603 | * tunneling over forwarded connections or if you run multiple | |
604 | * sshd's on different ports on the same machine. | |
605 | */ | |
606 | if (options.host_key_alias != NULL) { | |
607 | host = xstrdup(options.host_key_alias); | |
608 | debug("using hostkeyalias: %s", host); | |
609 | } else { | |
610 | host = put_host_port(hostname, port); | |
611 | } | |
612 | ||
613 | /* | |
614 | * Store the host key from the known host file in here so that we can | |
615 | * compare it with the key for the IP address. | |
616 | */ | |
617 | file_key = key_new(host_key->type); | |
618 | ||
619 | /* | |
620 | * Check if the host key is present in the user's list of known | |
621 | * hosts or in the systemwide list. | |
622 | */ | |
623 | host_file = user_hostfile; | |
624 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
625 | file_key, &host_line); | |
626 | if (host_status == HOST_NEW) { | |
627 | host_file = system_hostfile; | |
628 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
629 | file_key, &host_line); | |
630 | } | |
631 | /* | |
632 | * Also perform check for the ip address, skip the check if we are | |
633 | * localhost or the hostname was an ip address to begin with | |
634 | */ | |
635 | if (options.check_host_ip) { | |
636 | Key *ip_key = key_new(host_key->type); | |
637 | ||
638 | ip_file = user_hostfile; | |
639 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
640 | ip_key, &ip_line); | |
641 | if (ip_status == HOST_NEW) { | |
642 | ip_file = system_hostfile; | |
643 | ip_status = check_host_in_hostfile(ip_file, ip, | |
644 | host_key, ip_key, &ip_line); | |
645 | } | |
646 | if (host_status == HOST_CHANGED && | |
647 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
648 | host_ip_differ = 1; | |
649 | ||
650 | key_free(ip_key); | |
651 | } else | |
652 | ip_status = host_status; | |
653 | ||
654 | key_free(file_key); | |
655 | ||
656 | switch (host_status) { | |
657 | case HOST_OK: | |
658 | /* The host is known and the key matches. */ | |
659 | debug("Host '%.200s' is known and matches the %s host key.", | |
660 | host, type); | |
661 | debug("Found key in %s:%d", host_file, host_line); | |
662 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
663 | if (readonly) | |
664 | logit("%s host key for IP address " | |
665 | "'%.128s' not in list of known hosts.", | |
666 | type, ip); | |
667 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
668 | host_key, options.hash_known_hosts)) | |
669 | logit("Failed to add the %s host key for IP " | |
670 | "address '%.128s' to the list of known " | |
671 | "hosts (%.30s).", type, ip, user_hostfile); | |
672 | else | |
673 | logit("Warning: Permanently added the %s host " | |
674 | "key for IP address '%.128s' to the list " | |
675 | "of known hosts.", type, ip); | |
676 | } | |
677 | break; | |
678 | case HOST_NEW: | |
679 | if (options.host_key_alias == NULL && port != 0 && | |
680 | port != SSH_DEFAULT_PORT) { | |
681 | debug("checking without port identifier"); | |
682 | if (check_host_key(hostname, hostaddr, 0, host_key, 2, | |
683 | user_hostfile, system_hostfile) == 0) { | |
684 | debug("found matching key w/out port"); | |
685 | break; | |
686 | } | |
687 | } | |
688 | if (readonly) | |
689 | goto fail; | |
690 | /* The host is new. */ | |
691 | if (options.strict_host_key_checking == 1) { | |
692 | /* | |
693 | * User has requested strict host key checking. We | |
694 | * will not add the host key automatically. The only | |
695 | * alternative left is to abort. | |
696 | */ | |
697 | error("No %s host key is known for %.200s and you " | |
698 | "have requested strict checking.", type, host); | |
699 | goto fail; | |
700 | } else if (options.strict_host_key_checking == 2) { | |
701 | char msg1[1024], msg2[1024]; | |
702 | ||
703 | if (show_other_keys(host, host_key)) | |
704 | snprintf(msg1, sizeof(msg1), | |
705 | "\nbut keys of different type are already" | |
706 | " known for this host."); | |
707 | else | |
708 | snprintf(msg1, sizeof(msg1), "."); | |
709 | /* The default */ | |
710 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
711 | msg2[0] = '\0'; | |
712 | if (options.verify_host_key_dns) { | |
713 | if (matching_host_key_dns) | |
714 | snprintf(msg2, sizeof(msg2), | |
715 | "Matching host key fingerprint" | |
716 | " found in DNS.\n"); | |
717 | else | |
718 | snprintf(msg2, sizeof(msg2), | |
719 | "No matching host key fingerprint" | |
720 | " found in DNS.\n"); | |
721 | } | |
722 | snprintf(msg, sizeof(msg), | |
723 | "The authenticity of host '%.200s (%s)' can't be " | |
724 | "established%s\n" | |
725 | "%s key fingerprint is %s.\n%s" | |
726 | "Are you sure you want to continue connecting " | |
727 | "(yes/no)? ", | |
728 | host, ip, msg1, type, fp, msg2); | |
729 | xfree(fp); | |
730 | if (!confirm(msg)) | |
731 | goto fail; | |
732 | } | |
733 | /* | |
734 | * If not in strict mode, add the key automatically to the | |
735 | * local known_hosts file. | |
736 | */ | |
737 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
738 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
739 | host, ip); | |
740 | hostp = hostline; | |
741 | if (options.hash_known_hosts) { | |
742 | /* Add hash of host and IP separately */ | |
743 | r = add_host_to_hostfile(user_hostfile, host, | |
744 | host_key, options.hash_known_hosts) && | |
745 | add_host_to_hostfile(user_hostfile, ip, | |
746 | host_key, options.hash_known_hosts); | |
747 | } else { | |
748 | /* Add unhashed "host,ip" */ | |
749 | r = add_host_to_hostfile(user_hostfile, | |
750 | hostline, host_key, | |
751 | options.hash_known_hosts); | |
752 | } | |
753 | } else { | |
754 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
755 | options.hash_known_hosts); | |
756 | hostp = host; | |
757 | } | |
758 | ||
759 | if (!r) | |
760 | logit("Failed to add the host to the list of known " | |
761 | "hosts (%.500s).", user_hostfile); | |
762 | else | |
763 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
764 | "list of known hosts.", hostp, type); | |
765 | break; | |
766 | case HOST_CHANGED: | |
767 | if (readonly == ROQUIET) | |
768 | goto fail; | |
769 | if (options.check_host_ip && host_ip_differ) { | |
770 | char *key_msg; | |
771 | if (ip_status == HOST_NEW) | |
772 | key_msg = "is unknown"; | |
773 | else if (ip_status == HOST_OK) | |
774 | key_msg = "is unchanged"; | |
775 | else | |
776 | key_msg = "has a different value"; | |
777 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
778 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
779 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
780 | error("The %s host key for %s has changed,", type, host); | |
781 | error("and the key for the according IP address %s", ip); | |
782 | error("%s. This could either mean that", key_msg); | |
783 | error("DNS SPOOFING is happening or the IP address for the host"); | |
784 | error("and its host key have changed at the same time."); | |
785 | if (ip_status != HOST_NEW) | |
786 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
787 | } | |
788 | /* The host key has changed. */ | |
789 | warn_changed_key(host_key); | |
790 | error("Add correct host key in %.100s to get rid of this message.", | |
791 | user_hostfile); | |
792 | error("Offending key in %s:%d", host_file, host_line); | |
793 | ||
794 | /* | |
795 | * If strict host key checking is in use, the user will have | |
796 | * to edit the key manually and we can only abort. | |
797 | */ | |
798 | if (options.strict_host_key_checking) { | |
799 | error("%s host key for %.200s has changed and you have " | |
800 | "requested strict checking.", type, host); | |
801 | goto fail; | |
802 | } | |
803 | ||
804 | /* | |
805 | * If strict host key checking has not been requested, allow | |
806 | * the connection but without MITM-able authentication or | |
807 | * forwarding. | |
808 | */ | |
809 | if (options.password_authentication) { | |
810 | error("Password authentication is disabled to avoid " | |
811 | "man-in-the-middle attacks."); | |
812 | options.password_authentication = 0; | |
813 | } | |
814 | if (options.kbd_interactive_authentication) { | |
815 | error("Keyboard-interactive authentication is disabled" | |
816 | " to avoid man-in-the-middle attacks."); | |
817 | options.kbd_interactive_authentication = 0; | |
818 | options.challenge_response_authentication = 0; | |
819 | } | |
820 | if (options.challenge_response_authentication) { | |
821 | error("Challenge/response authentication is disabled" | |
822 | " to avoid man-in-the-middle attacks."); | |
823 | options.challenge_response_authentication = 0; | |
824 | } | |
825 | if (options.forward_agent) { | |
826 | error("Agent forwarding is disabled to avoid " | |
827 | "man-in-the-middle attacks."); | |
828 | options.forward_agent = 0; | |
829 | } | |
830 | if (options.forward_x11) { | |
831 | error("X11 forwarding is disabled to avoid " | |
832 | "man-in-the-middle attacks."); | |
833 | options.forward_x11 = 0; | |
834 | } | |
835 | if (options.num_local_forwards > 0 || | |
836 | options.num_remote_forwards > 0) { | |
837 | error("Port forwarding is disabled to avoid " | |
838 | "man-in-the-middle attacks."); | |
839 | options.num_local_forwards = | |
840 | options.num_remote_forwards = 0; | |
841 | } | |
842 | if (options.tun_open != SSH_TUNMODE_NO) { | |
843 | error("Tunnel forwarding is disabled to avoid " | |
844 | "man-in-the-middle attacks."); | |
845 | options.tun_open = SSH_TUNMODE_NO; | |
846 | } | |
847 | /* | |
848 | * XXX Should permit the user to change to use the new id. | |
849 | * This could be done by converting the host key to an | |
850 | * identifying sentence, tell that the host identifies itself | |
851 | * by that sentence, and ask the user if he/she whishes to | |
852 | * accept the authentication. | |
853 | */ | |
854 | break; | |
855 | case HOST_FOUND: | |
856 | fatal("internal error"); | |
857 | break; | |
858 | } | |
859 | ||
860 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
861 | ip_status == HOST_CHANGED) { | |
862 | snprintf(msg, sizeof(msg), | |
863 | "Warning: the %s host key for '%.200s' " | |
864 | "differs from the key for the IP address '%.128s'" | |
865 | "\nOffending key for IP in %s:%d", | |
866 | type, host, ip, ip_file, ip_line); | |
867 | if (host_status == HOST_OK) { | |
868 | len = strlen(msg); | |
869 | snprintf(msg + len, sizeof(msg) - len, | |
870 | "\nMatching host key in %s:%d", | |
871 | host_file, host_line); | |
872 | } | |
873 | if (options.strict_host_key_checking == 1) { | |
874 | logit("%s", msg); | |
875 | error("Exiting, you have requested strict checking."); | |
876 | goto fail; | |
877 | } else if (options.strict_host_key_checking == 2) { | |
878 | strlcat(msg, "\nAre you sure you want " | |
879 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
880 | if (!confirm(msg)) | |
881 | goto fail; | |
882 | } else { | |
883 | logit("%s", msg); | |
884 | } | |
885 | } | |
886 | ||
887 | xfree(ip); | |
888 | xfree(host); | |
889 | return 0; | |
890 | ||
891 | fail: | |
892 | xfree(ip); | |
893 | xfree(host); | |
894 | return -1; | |
895 | } | |
896 | ||
897 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
898 | int | |
899 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
900 | { | |
901 | struct stat st; | |
902 | int flags = 0; | |
903 | ||
904 | if (options.verify_host_key_dns && | |
905 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
906 | ||
907 | if (flags & DNS_VERIFY_FOUND) { | |
908 | ||
909 | if (options.verify_host_key_dns == 1 && | |
910 | flags & DNS_VERIFY_MATCH && | |
911 | flags & DNS_VERIFY_SECURE) | |
912 | return 0; | |
913 | ||
914 | if (flags & DNS_VERIFY_MATCH) { | |
915 | matching_host_key_dns = 1; | |
916 | } else { | |
917 | warn_changed_key(host_key); | |
918 | error("Update the SSHFP RR in DNS with the new " | |
919 | "host key to get rid of this message."); | |
920 | } | |
921 | } | |
922 | } | |
923 | ||
924 | /* return ok if the key can be found in an old keyfile */ | |
925 | if (stat(options.system_hostfile2, &st) == 0 || | |
926 | stat(options.user_hostfile2, &st) == 0) { | |
927 | if (check_host_key(host, hostaddr, options.port, host_key, | |
928 | RDONLY, options.user_hostfile2, | |
929 | options.system_hostfile2) == 0) | |
930 | return 0; | |
931 | } | |
932 | return check_host_key(host, hostaddr, options.port, host_key, | |
933 | RDRW, options.user_hostfile, options.system_hostfile); | |
934 | } | |
935 | ||
936 | /* | |
937 | * Starts a dialog with the server, and authenticates the current user on the | |
938 | * server. This does not need any extra privileges. The basic connection | |
939 | * to the server must already have been established before this is called. | |
940 | * If login fails, this function prints an error and never returns. | |
941 | * This function does not require super-user privileges. | |
942 | */ | |
943 | void | |
944 | ssh_login(Sensitive *sensitive, const char *orighost, | |
945 | struct sockaddr *hostaddr, struct passwd *pw) | |
946 | { | |
947 | char *host, *cp; | |
948 | char *server_user, *local_user; | |
949 | ||
950 | local_user = xstrdup(pw->pw_name); | |
951 | server_user = options.user ? options.user : local_user; | |
952 | ||
953 | /* Convert the user-supplied hostname into all lowercase. */ | |
954 | host = xstrdup(orighost); | |
955 | for (cp = host; *cp; cp++) | |
956 | if (isupper(*cp)) | |
957 | *cp = (char)tolower(*cp); | |
958 | ||
959 | /* Exchange protocol version identification strings with the server. */ | |
960 | ssh_exchange_identification(); | |
961 | ||
962 | /* Put the connection into non-blocking mode. */ | |
963 | packet_set_nonblocking(); | |
964 | ||
965 | /* key exchange */ | |
966 | /* authenticate user */ | |
967 | if (compat20) { | |
968 | ssh_kex2(host, hostaddr); | |
969 | ssh_userauth2(local_user, server_user, host, sensitive); | |
970 | } else { | |
971 | ssh_kex(host, hostaddr); | |
972 | ssh_userauth1(local_user, server_user, host, sensitive); | |
973 | } | |
974 | xfree(local_user); | |
975 | } | |
976 | ||
977 | void | |
978 | ssh_put_password(char *password) | |
979 | { | |
980 | int size; | |
981 | char *padded; | |
982 | ||
983 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
984 | packet_put_cstring(password); | |
985 | return; | |
986 | } | |
987 | size = roundup(strlen(password) + 1, 32); | |
988 | padded = xcalloc(1, size); | |
989 | strlcpy(padded, password, size); | |
990 | packet_put_string(padded, size); | |
991 | memset(padded, 0, size); | |
992 | xfree(padded); | |
993 | } | |
994 | ||
995 | static int | |
996 | show_key_from_file(const char *file, const char *host, int keytype) | |
997 | { | |
998 | Key *found; | |
999 | char *fp; | |
1000 | int line, ret; | |
1001 | ||
1002 | found = key_new(keytype); | |
1003 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
1004 | keytype, found, &line))) { | |
1005 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
1006 | logit("WARNING: %s key found for host %s\n" | |
1007 | "in %s:%d\n" | |
1008 | "%s key fingerprint %s.", | |
1009 | key_type(found), host, file, line, | |
1010 | key_type(found), fp); | |
1011 | xfree(fp); | |
1012 | } | |
1013 | key_free(found); | |
1014 | return (ret); | |
1015 | } | |
1016 | ||
1017 | /* print all known host keys for a given host, but skip keys of given type */ | |
1018 | static int | |
1019 | show_other_keys(const char *host, Key *key) | |
1020 | { | |
1021 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1022 | int i, found = 0; | |
1023 | ||
1024 | for (i = 0; type[i] != -1; i++) { | |
1025 | if (type[i] == key->type) | |
1026 | continue; | |
1027 | if (type[i] != KEY_RSA1 && | |
1028 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1029 | found = 1; | |
1030 | continue; | |
1031 | } | |
1032 | if (type[i] != KEY_RSA1 && | |
1033 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1034 | found = 1; | |
1035 | continue; | |
1036 | } | |
1037 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1038 | found = 1; | |
1039 | continue; | |
1040 | } | |
1041 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1042 | found = 1; | |
1043 | continue; | |
1044 | } | |
1045 | debug2("no key of type %d for host %s", type[i], host); | |
1046 | } | |
1047 | return (found); | |
1048 | } | |
1049 | ||
1050 | static void | |
1051 | warn_changed_key(Key *host_key) | |
1052 | { | |
1053 | char *fp; | |
1054 | const char *type = key_type(host_key); | |
1055 | ||
1056 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1057 | ||
1058 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1059 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1060 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1061 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1062 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1063 | error("It is also possible that the %s host key has just been changed.", type); | |
1064 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1065 | type, fp); | |
1066 | error("Please contact your system administrator."); | |
1067 | ||
1068 | xfree(fp); | |
1069 | } | |
1070 | ||
1071 | /* | |
1072 | * Execute a local command | |
1073 | */ | |
1074 | int | |
1075 | ssh_local_cmd(const char *args) | |
1076 | { | |
1077 | char *shell; | |
1078 | pid_t pid; | |
1079 | int status; | |
1080 | ||
1081 | if (!options.permit_local_command || | |
1082 | args == NULL || !*args) | |
1083 | return (1); | |
1084 | ||
1085 | if ((shell = getenv("SHELL")) == NULL) | |
1086 | shell = _PATH_BSHELL; | |
1087 | ||
1088 | pid = fork(); | |
1089 | if (pid == 0) { | |
1090 | debug3("Executing %s -c \"%s\"", shell, args); | |
1091 | execl(shell, shell, "-c", args, (char *)NULL); | |
1092 | error("Couldn't execute %s -c \"%s\": %s", | |
1093 | shell, args, strerror(errno)); | |
1094 | _exit(1); | |
1095 | } else if (pid == -1) | |
1096 | fatal("fork failed: %.100s", strerror(errno)); | |
1097 | while (waitpid(pid, &status, 0) == -1) | |
1098 | if (errno != EINTR) | |
1099 | fatal("Couldn't wait for child: %s", strerror(errno)); | |
1100 | ||
1101 | if (!WIFEXITED(status)) | |
1102 | return (1); | |
1103 | ||
1104 | return (WEXITSTATUS(status)); | |
1105 | } |