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1 | /* $OpenBSD: sshconnect.c,v 1.201 2007/08/23 03:23:26 djm 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 | #include <arpa/inet.h> | |
28 | ||
29 | #include <ctype.h> | |
30 | #include <errno.h> | |
31 | #include <netdb.h> | |
32 | #ifdef HAVE_PATHS_H | |
33 | #include <paths.h> | |
34 | #endif | |
35 | #include <pwd.h> | |
36 | #include <stdarg.h> | |
37 | #include <stdio.h> | |
38 | #include <stdlib.h> | |
39 | #include <string.h> | |
40 | #include <unistd.h> | |
41 | ||
42 | #include "xmalloc.h" | |
43 | #include "key.h" | |
44 | #include "hostfile.h" | |
45 | #include "ssh.h" | |
46 | #include "rsa.h" | |
47 | #include "buffer.h" | |
48 | #include "packet.h" | |
49 | #include "uidswap.h" | |
50 | #include "compat.h" | |
51 | #include "key.h" | |
52 | #include "sshconnect.h" | |
53 | #include "hostfile.h" | |
54 | #include "log.h" | |
55 | #include "readconf.h" | |
56 | #include "atomicio.h" | |
57 | #include "misc.h" | |
58 | #include "dns.h" | |
59 | #include "version.h" | |
60 | ||
61 | char *client_version_string = NULL; | |
62 | char *server_version_string = NULL; | |
63 | ||
64 | static int matching_host_key_dns = 0; | |
65 | ||
66 | /* import */ | |
67 | extern Options options; | |
68 | extern char *__progname; | |
69 | extern uid_t original_real_uid; | |
70 | extern uid_t original_effective_uid; | |
71 | extern pid_t proxy_command_pid; | |
72 | ||
73 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
74 | #define INET6_ADDRSTRLEN 46 | |
75 | #endif | |
76 | ||
77 | static int show_other_keys(const char *, Key *); | |
78 | static void warn_changed_key(Key *); | |
79 | ||
80 | /* | |
81 | * Connect to the given ssh server using a proxy command. | |
82 | */ | |
83 | static int | |
84 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) | |
85 | { | |
86 | char *command_string, *tmp; | |
87 | int pin[2], pout[2]; | |
88 | pid_t pid; | |
89 | char *shell, strport[NI_MAXSERV]; | |
90 | ||
91 | if ((shell = getenv("SHELL")) == NULL) | |
92 | shell = _PATH_BSHELL; | |
93 | ||
94 | /* Convert the port number into a string. */ | |
95 | snprintf(strport, sizeof strport, "%hu", port); | |
96 | ||
97 | /* | |
98 | * Build the final command string in the buffer by making the | |
99 | * appropriate substitutions to the given proxy command. | |
100 | * | |
101 | * Use "exec" to avoid "sh -c" processes on some platforms | |
102 | * (e.g. Solaris) | |
103 | */ | |
104 | xasprintf(&tmp, "exec %s", proxy_command); | |
105 | command_string = percent_expand(tmp, "h", host, | |
106 | "p", strport, (char *)NULL); | |
107 | xfree(tmp); | |
108 | ||
109 | /* Create pipes for communicating with the proxy. */ | |
110 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
111 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
112 | strerror(errno)); | |
113 | ||
114 | debug("Executing proxy command: %.500s", command_string); | |
115 | ||
116 | /* Fork and execute the proxy command. */ | |
117 | if ((pid = fork()) == 0) { | |
118 | char *argv[10]; | |
119 | ||
120 | /* Child. Permanently give up superuser privileges. */ | |
121 | permanently_drop_suid(original_real_uid); | |
122 | ||
123 | /* Redirect stdin and stdout. */ | |
124 | close(pin[1]); | |
125 | if (pin[0] != 0) { | |
126 | if (dup2(pin[0], 0) < 0) | |
127 | perror("dup2 stdin"); | |
128 | close(pin[0]); | |
129 | } | |
130 | close(pout[0]); | |
131 | if (dup2(pout[1], 1) < 0) | |
132 | perror("dup2 stdout"); | |
133 | /* Cannot be 1 because pin allocated two descriptors. */ | |
134 | close(pout[1]); | |
135 | ||
136 | /* Stderr is left as it is so that error messages get | |
137 | printed on the user's terminal. */ | |
138 | argv[0] = shell; | |
139 | argv[1] = "-c"; | |
140 | argv[2] = command_string; | |
141 | argv[3] = NULL; | |
142 | ||
143 | /* Execute the proxy command. Note that we gave up any | |
144 | extra privileges above. */ | |
145 | execv(argv[0], argv); | |
146 | perror(argv[0]); | |
147 | exit(1); | |
148 | } | |
149 | /* Parent. */ | |
150 | if (pid < 0) | |
151 | fatal("fork failed: %.100s", strerror(errno)); | |
152 | else | |
153 | proxy_command_pid = pid; /* save pid to clean up later */ | |
154 | ||
155 | /* Close child side of the descriptors. */ | |
156 | close(pin[0]); | |
157 | close(pout[1]); | |
158 | ||
159 | /* Free the command name. */ | |
160 | xfree(command_string); | |
161 | ||
162 | /* Set the connection file descriptors. */ | |
163 | packet_set_connection(pout[0], pin[1]); | |
164 | ||
165 | /* Indicate OK return */ | |
166 | return 0; | |
167 | } | |
168 | ||
169 | /* | |
170 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
171 | */ | |
172 | static int | |
173 | ssh_create_socket(int privileged, struct addrinfo *ai) | |
174 | { | |
175 | int sock, gaierr; | |
176 | struct addrinfo hints, *res; | |
177 | ||
178 | /* | |
179 | * If we are running as root and want to connect to a privileged | |
180 | * port, bind our own socket to a privileged port. | |
181 | */ | |
182 | if (privileged) { | |
183 | int p = IPPORT_RESERVED - 1; | |
184 | PRIV_START; | |
185 | sock = rresvport_af(&p, ai->ai_family); | |
186 | PRIV_END; | |
187 | if (sock < 0) | |
188 | error("rresvport: af=%d %.100s", ai->ai_family, | |
189 | strerror(errno)); | |
190 | else | |
191 | debug("Allocated local port %d.", p); | |
192 | return sock; | |
193 | } | |
194 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); | |
195 | if (sock < 0) | |
196 | error("socket: %.100s", strerror(errno)); | |
197 | ||
198 | /* Bind the socket to an alternative local IP address */ | |
199 | if (options.bind_address == NULL) | |
200 | return sock; | |
201 | ||
202 | memset(&hints, 0, sizeof(hints)); | |
203 | hints.ai_family = ai->ai_family; | |
204 | hints.ai_socktype = ai->ai_socktype; | |
205 | hints.ai_protocol = ai->ai_protocol; | |
206 | hints.ai_flags = AI_PASSIVE; | |
207 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
208 | if (gaierr) { | |
209 | error("getaddrinfo: %s: %s", options.bind_address, | |
210 | gai_strerror(gaierr)); | |
211 | close(sock); | |
212 | return -1; | |
213 | } | |
214 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
215 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
216 | close(sock); | |
217 | freeaddrinfo(res); | |
218 | return -1; | |
219 | } | |
220 | freeaddrinfo(res); | |
221 | return sock; | |
222 | } | |
223 | ||
224 | static int | |
225 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
226 | socklen_t addrlen, int timeout) | |
227 | { | |
228 | fd_set *fdset; | |
229 | struct timeval tv; | |
230 | socklen_t optlen; | |
231 | int optval, rc, result = -1; | |
232 | ||
233 | if (timeout <= 0) | |
234 | return (connect(sockfd, serv_addr, addrlen)); | |
235 | ||
236 | set_nonblock(sockfd); | |
237 | rc = connect(sockfd, serv_addr, addrlen); | |
238 | if (rc == 0) { | |
239 | unset_nonblock(sockfd); | |
240 | return (0); | |
241 | } | |
242 | if (errno != EINPROGRESS) | |
243 | return (-1); | |
244 | ||
245 | fdset = (fd_set *)xcalloc(howmany(sockfd + 1, NFDBITS), | |
246 | sizeof(fd_mask)); | |
247 | FD_SET(sockfd, fdset); | |
248 | tv.tv_sec = timeout; | |
249 | tv.tv_usec = 0; | |
250 | ||
251 | for (;;) { | |
252 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
253 | if (rc != -1 || errno != EINTR) | |
254 | break; | |
255 | } | |
256 | ||
257 | switch (rc) { | |
258 | case 0: | |
259 | /* Timed out */ | |
260 | errno = ETIMEDOUT; | |
261 | break; | |
262 | case -1: | |
263 | /* Select error */ | |
264 | debug("select: %s", strerror(errno)); | |
265 | break; | |
266 | case 1: | |
267 | /* Completed or failed */ | |
268 | optval = 0; | |
269 | optlen = sizeof(optval); | |
270 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
271 | &optlen) == -1) { | |
272 | debug("getsockopt: %s", strerror(errno)); | |
273 | break; | |
274 | } | |
275 | if (optval != 0) { | |
276 | errno = optval; | |
277 | break; | |
278 | } | |
279 | result = 0; | |
280 | unset_nonblock(sockfd); | |
281 | break; | |
282 | default: | |
283 | /* Should not occur */ | |
284 | fatal("Bogus return (%d) from select()", rc); | |
285 | } | |
286 | ||
287 | xfree(fdset); | |
288 | return (result); | |
289 | } | |
290 | ||
291 | /* | |
292 | * Opens a TCP/IP connection to the remote server on the given host. | |
293 | * The address of the remote host will be returned in hostaddr. | |
294 | * If port is 0, the default port will be used. If needpriv is true, | |
295 | * a privileged port will be allocated to make the connection. | |
296 | * This requires super-user privileges if needpriv is true. | |
297 | * Connection_attempts specifies the maximum number of tries (one per | |
298 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
299 | * and %p substituted for host and port, respectively) to use to contact | |
300 | * the daemon. | |
301 | */ | |
302 | int | |
303 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
304 | u_short port, int family, int connection_attempts, | |
305 | int needpriv, const char *proxy_command) | |
306 | { | |
307 | int gaierr; | |
308 | int on = 1; | |
309 | int sock = -1, attempt; | |
310 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
311 | struct addrinfo hints, *ai, *aitop; | |
312 | ||
313 | debug2("ssh_connect: needpriv %d", needpriv); | |
314 | ||
315 | /* If a proxy command is given, connect using it. */ | |
316 | if (proxy_command != NULL) | |
317 | return ssh_proxy_connect(host, port, proxy_command); | |
318 | ||
319 | /* No proxy command. */ | |
320 | ||
321 | memset(&hints, 0, sizeof(hints)); | |
322 | hints.ai_family = family; | |
323 | hints.ai_socktype = SOCK_STREAM; | |
324 | snprintf(strport, sizeof strport, "%u", port); | |
325 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
326 | fatal("%s: %.100s: %s", __progname, host, | |
327 | gai_strerror(gaierr)); | |
328 | ||
329 | for (attempt = 0; attempt < connection_attempts; attempt++) { | |
330 | if (attempt > 0) { | |
331 | /* Sleep a moment before retrying. */ | |
332 | sleep(1); | |
333 | debug("Trying again..."); | |
334 | } | |
335 | /* | |
336 | * Loop through addresses for this host, and try each one in | |
337 | * sequence until the connection succeeds. | |
338 | */ | |
339 | for (ai = aitop; ai; ai = ai->ai_next) { | |
340 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
341 | continue; | |
342 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
343 | ntop, sizeof(ntop), strport, sizeof(strport), | |
344 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
345 | error("ssh_connect: getnameinfo failed"); | |
346 | continue; | |
347 | } | |
348 | debug("Connecting to %.200s [%.100s] port %s.", | |
349 | host, ntop, strport); | |
350 | ||
351 | /* Create a socket for connecting. */ | |
352 | sock = ssh_create_socket(needpriv, ai); | |
353 | if (sock < 0) | |
354 | /* Any error is already output */ | |
355 | continue; | |
356 | ||
357 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, | |
358 | options.connection_timeout) >= 0) { | |
359 | /* Successful connection. */ | |
360 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
361 | break; | |
362 | } else { | |
363 | debug("connect to address %s port %s: %s", | |
364 | ntop, strport, strerror(errno)); | |
365 | close(sock); | |
366 | sock = -1; | |
367 | } | |
368 | } | |
369 | if (sock != -1) | |
370 | break; /* Successful connection. */ | |
371 | } | |
372 | ||
373 | freeaddrinfo(aitop); | |
374 | ||
375 | /* Return failure if we didn't get a successful connection. */ | |
376 | if (sock == -1) { | |
377 | error("ssh: connect to host %s port %s: %s", | |
378 | host, strport, strerror(errno)); | |
379 | return (-1); | |
380 | } | |
381 | ||
382 | debug("Connection established."); | |
383 | ||
384 | /* Set SO_KEEPALIVE if requested. */ | |
385 | if (options.tcp_keep_alive && | |
386 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
387 | sizeof(on)) < 0) | |
388 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
389 | ||
390 | /* Set the connection. */ | |
391 | packet_set_connection(sock, sock); | |
392 | ||
393 | return 0; | |
394 | } | |
395 | ||
396 | /* | |
397 | * Waits for the server identification string, and sends our own | |
398 | * identification string. | |
399 | */ | |
400 | static void | |
401 | ssh_exchange_identification(void) | |
402 | { | |
403 | char buf[256], remote_version[256]; /* must be same size! */ | |
404 | int remote_major, remote_minor, mismatch; | |
405 | int connection_in = packet_get_connection_in(); | |
406 | int connection_out = packet_get_connection_out(); | |
407 | int minor1 = PROTOCOL_MINOR_1; | |
408 | u_int i, n; | |
409 | ||
410 | /* Read other side's version identification. */ | |
411 | for (n = 0;;) { | |
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 | if (++n > 65536) | |
429 | fatal("ssh_exchange_identification: No banner received"); | |
430 | } | |
431 | buf[sizeof(buf) - 1] = 0; | |
432 | if (strncmp(buf, "SSH-", 4) == 0) | |
433 | break; | |
434 | debug("ssh_exchange_identification: %s", buf); | |
435 | } | |
436 | server_version_string = xstrdup(buf); | |
437 | ||
438 | /* | |
439 | * Check that the versions match. In future this might accept | |
440 | * several versions and set appropriate flags to handle them. | |
441 | */ | |
442 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
443 | &remote_major, &remote_minor, remote_version) != 3) | |
444 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
445 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
446 | remote_major, remote_minor, remote_version); | |
447 | ||
448 | compat_datafellows(remote_version); | |
449 | mismatch = 0; | |
450 | ||
451 | switch (remote_major) { | |
452 | case 1: | |
453 | if (remote_minor == 99 && | |
454 | (options.protocol & SSH_PROTO_2) && | |
455 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
456 | enable_compat20(); | |
457 | break; | |
458 | } | |
459 | if (!(options.protocol & SSH_PROTO_1)) { | |
460 | mismatch = 1; | |
461 | break; | |
462 | } | |
463 | if (remote_minor < 3) { | |
464 | fatal("Remote machine has too old SSH software version."); | |
465 | } else if (remote_minor == 3 || remote_minor == 4) { | |
466 | /* We speak 1.3, too. */ | |
467 | enable_compat13(); | |
468 | minor1 = 3; | |
469 | if (options.forward_agent) { | |
470 | logit("Agent forwarding disabled for protocol 1.3"); | |
471 | options.forward_agent = 0; | |
472 | } | |
473 | } | |
474 | break; | |
475 | case 2: | |
476 | if (options.protocol & SSH_PROTO_2) { | |
477 | enable_compat20(); | |
478 | break; | |
479 | } | |
480 | /* FALLTHROUGH */ | |
481 | default: | |
482 | mismatch = 1; | |
483 | break; | |
484 | } | |
485 | if (mismatch) | |
486 | fatal("Protocol major versions differ: %d vs. %d", | |
487 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
488 | remote_major); | |
489 | /* Send our own protocol version identification. */ | |
490 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
491 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
492 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
493 | SSH_VERSION); | |
494 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
495 | fatal("write: %.100s", strerror(errno)); | |
496 | client_version_string = xstrdup(buf); | |
497 | chop(client_version_string); | |
498 | chop(server_version_string); | |
499 | debug("Local version string %.100s", client_version_string); | |
500 | } | |
501 | ||
502 | /* defaults to 'no' */ | |
503 | static int | |
504 | confirm(const char *prompt) | |
505 | { | |
506 | const char *msg, *again = "Please type 'yes' or 'no': "; | |
507 | char *p; | |
508 | int ret = -1; | |
509 | ||
510 | if (options.batch_mode) | |
511 | return 0; | |
512 | for (msg = prompt;;msg = again) { | |
513 | p = read_passphrase(msg, RP_ECHO); | |
514 | if (p == NULL || | |
515 | (p[0] == '\0') || (p[0] == '\n') || | |
516 | strncasecmp(p, "no", 2) == 0) | |
517 | ret = 0; | |
518 | if (p && strncasecmp(p, "yes", 3) == 0) | |
519 | ret = 1; | |
520 | if (p) | |
521 | xfree(p); | |
522 | if (ret != -1) | |
523 | return ret; | |
524 | } | |
525 | } | |
526 | ||
527 | /* | |
528 | * check whether the supplied host key is valid, return -1 if the key | |
529 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
530 | */ | |
531 | #define RDRW 0 | |
532 | #define RDONLY 1 | |
533 | #define ROQUIET 2 | |
534 | static int | |
535 | check_host_key(char *hostname, struct sockaddr *hostaddr, u_short port, | |
536 | Key *host_key, int readonly, const char *user_hostfile, | |
537 | const char *system_hostfile) | |
538 | { | |
539 | Key *file_key; | |
540 | const char *type = key_type(host_key); | |
541 | char *ip = NULL, *host = NULL; | |
542 | char hostline[1000], *hostp, *fp; | |
543 | HostStatus host_status; | |
544 | HostStatus ip_status; | |
545 | int r, local = 0, host_ip_differ = 0; | |
546 | int salen; | |
547 | char ntop[NI_MAXHOST]; | |
548 | char msg[1024]; | |
549 | int len, host_line, ip_line; | |
550 | const char *host_file = NULL, *ip_file = NULL; | |
551 | ||
552 | /* | |
553 | * Force accepting of the host key for loopback/localhost. The | |
554 | * problem is that if the home directory is NFS-mounted to multiple | |
555 | * machines, localhost will refer to a different machine in each of | |
556 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
557 | * essentially disables host authentication for localhost; however, | |
558 | * this is probably not a real problem. | |
559 | */ | |
560 | /** hostaddr == 0! */ | |
561 | switch (hostaddr->sa_family) { | |
562 | case AF_INET: | |
563 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
564 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
565 | salen = sizeof(struct sockaddr_in); | |
566 | break; | |
567 | case AF_INET6: | |
568 | local = IN6_IS_ADDR_LOOPBACK( | |
569 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
570 | salen = sizeof(struct sockaddr_in6); | |
571 | break; | |
572 | default: | |
573 | local = 0; | |
574 | salen = sizeof(struct sockaddr_storage); | |
575 | break; | |
576 | } | |
577 | if (options.no_host_authentication_for_localhost == 1 && local && | |
578 | options.host_key_alias == NULL) { | |
579 | debug("Forcing accepting of host key for " | |
580 | "loopback/localhost."); | |
581 | return 0; | |
582 | } | |
583 | ||
584 | /* | |
585 | * We don't have the remote ip-address for connections | |
586 | * using a proxy command | |
587 | */ | |
588 | if (options.proxy_command == NULL) { | |
589 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
590 | NULL, 0, NI_NUMERICHOST) != 0) | |
591 | fatal("check_host_key: getnameinfo failed"); | |
592 | ip = put_host_port(ntop, port); | |
593 | } else { | |
594 | ip = xstrdup("<no hostip for proxy command>"); | |
595 | } | |
596 | /* | |
597 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
598 | * command or if we don't have a hostname to compare with | |
599 | */ | |
600 | if (options.check_host_ip && (local || | |
601 | strcmp(hostname, ip) == 0 || options.proxy_command != NULL)) | |
602 | options.check_host_ip = 0; | |
603 | ||
604 | /* | |
605 | * Allow the user to record the key under a different name or | |
606 | * differentiate a non-standard port. This is useful for ssh | |
607 | * tunneling over forwarded connections or if you run multiple | |
608 | * sshd's on different ports on the same machine. | |
609 | */ | |
610 | if (options.host_key_alias != NULL) { | |
611 | host = xstrdup(options.host_key_alias); | |
612 | debug("using hostkeyalias: %s", host); | |
613 | } else { | |
614 | host = put_host_port(hostname, port); | |
615 | } | |
616 | ||
617 | /* | |
618 | * Store the host key from the known host file in here so that we can | |
619 | * compare it with the key for the IP address. | |
620 | */ | |
621 | file_key = key_new(host_key->type); | |
622 | ||
623 | /* | |
624 | * Check if the host key is present in the user's list of known | |
625 | * hosts or in the systemwide list. | |
626 | */ | |
627 | host_file = user_hostfile; | |
628 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
629 | file_key, &host_line); | |
630 | if (host_status == HOST_NEW) { | |
631 | host_file = system_hostfile; | |
632 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
633 | file_key, &host_line); | |
634 | } | |
635 | /* | |
636 | * Also perform check for the ip address, skip the check if we are | |
637 | * localhost or the hostname was an ip address to begin with | |
638 | */ | |
639 | if (options.check_host_ip) { | |
640 | Key *ip_key = key_new(host_key->type); | |
641 | ||
642 | ip_file = user_hostfile; | |
643 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
644 | ip_key, &ip_line); | |
645 | if (ip_status == HOST_NEW) { | |
646 | ip_file = system_hostfile; | |
647 | ip_status = check_host_in_hostfile(ip_file, ip, | |
648 | host_key, ip_key, &ip_line); | |
649 | } | |
650 | if (host_status == HOST_CHANGED && | |
651 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
652 | host_ip_differ = 1; | |
653 | ||
654 | key_free(ip_key); | |
655 | } else | |
656 | ip_status = host_status; | |
657 | ||
658 | key_free(file_key); | |
659 | ||
660 | switch (host_status) { | |
661 | case HOST_OK: | |
662 | /* The host is known and the key matches. */ | |
663 | debug("Host '%.200s' is known and matches the %s host key.", | |
664 | host, type); | |
665 | debug("Found key in %s:%d", host_file, host_line); | |
666 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
667 | if (readonly) | |
668 | logit("%s host key for IP address " | |
669 | "'%.128s' not in list of known hosts.", | |
670 | type, ip); | |
671 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
672 | host_key, options.hash_known_hosts)) | |
673 | logit("Failed to add the %s host key for IP " | |
674 | "address '%.128s' to the list of known " | |
675 | "hosts (%.30s).", type, ip, user_hostfile); | |
676 | else | |
677 | logit("Warning: Permanently added the %s host " | |
678 | "key for IP address '%.128s' to the list " | |
679 | "of known hosts.", type, ip); | |
680 | } | |
681 | break; | |
682 | case HOST_NEW: | |
683 | if (options.host_key_alias == NULL && port != 0 && | |
684 | port != SSH_DEFAULT_PORT) { | |
685 | debug("checking without port identifier"); | |
686 | if (check_host_key(hostname, hostaddr, 0, host_key, 2, | |
687 | user_hostfile, system_hostfile) == 0) { | |
688 | debug("found matching key w/out port"); | |
689 | break; | |
690 | } | |
691 | } | |
692 | if (readonly) | |
693 | goto fail; | |
694 | /* The host is new. */ | |
695 | if (options.strict_host_key_checking == 1) { | |
696 | /* | |
697 | * User has requested strict host key checking. We | |
698 | * will not add the host key automatically. The only | |
699 | * alternative left is to abort. | |
700 | */ | |
701 | error("No %s host key is known for %.200s and you " | |
702 | "have requested strict checking.", type, host); | |
703 | goto fail; | |
704 | } else if (options.strict_host_key_checking == 2) { | |
705 | char msg1[1024], msg2[1024]; | |
706 | ||
707 | if (show_other_keys(host, host_key)) | |
708 | snprintf(msg1, sizeof(msg1), | |
709 | "\nbut keys of different type are already" | |
710 | " known for this host."); | |
711 | else | |
712 | snprintf(msg1, sizeof(msg1), "."); | |
713 | /* The default */ | |
714 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
715 | msg2[0] = '\0'; | |
716 | if (options.verify_host_key_dns) { | |
717 | if (matching_host_key_dns) | |
718 | snprintf(msg2, sizeof(msg2), | |
719 | "Matching host key fingerprint" | |
720 | " found in DNS.\n"); | |
721 | else | |
722 | snprintf(msg2, sizeof(msg2), | |
723 | "No matching host key fingerprint" | |
724 | " found in DNS.\n"); | |
725 | } | |
726 | snprintf(msg, sizeof(msg), | |
727 | "The authenticity of host '%.200s (%s)' can't be " | |
728 | "established%s\n" | |
729 | "%s key fingerprint is %s.\n%s" | |
730 | "Are you sure you want to continue connecting " | |
731 | "(yes/no)? ", | |
732 | host, ip, msg1, type, fp, msg2); | |
733 | xfree(fp); | |
734 | if (!confirm(msg)) | |
735 | goto fail; | |
736 | } | |
737 | /* | |
738 | * If not in strict mode, add the key automatically to the | |
739 | * local known_hosts file. | |
740 | */ | |
741 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
742 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
743 | host, ip); | |
744 | hostp = hostline; | |
745 | if (options.hash_known_hosts) { | |
746 | /* Add hash of host and IP separately */ | |
747 | r = add_host_to_hostfile(user_hostfile, host, | |
748 | host_key, options.hash_known_hosts) && | |
749 | add_host_to_hostfile(user_hostfile, ip, | |
750 | host_key, options.hash_known_hosts); | |
751 | } else { | |
752 | /* Add unhashed "host,ip" */ | |
753 | r = add_host_to_hostfile(user_hostfile, | |
754 | hostline, host_key, | |
755 | options.hash_known_hosts); | |
756 | } | |
757 | } else { | |
758 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
759 | options.hash_known_hosts); | |
760 | hostp = host; | |
761 | } | |
762 | ||
763 | if (!r) | |
764 | logit("Failed to add the host to the list of known " | |
765 | "hosts (%.500s).", user_hostfile); | |
766 | else | |
767 | logit("Warning: Permanently added '%.200s' (%s) to the " | |
768 | "list of known hosts.", hostp, type); | |
769 | break; | |
770 | case HOST_CHANGED: | |
771 | if (readonly == ROQUIET) | |
772 | goto fail; | |
773 | if (options.check_host_ip && host_ip_differ) { | |
774 | char *key_msg; | |
775 | if (ip_status == HOST_NEW) | |
776 | key_msg = "is unknown"; | |
777 | else if (ip_status == HOST_OK) | |
778 | key_msg = "is unchanged"; | |
779 | else | |
780 | key_msg = "has a different value"; | |
781 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
782 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
783 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
784 | error("The %s host key for %s has changed,", type, host); | |
785 | error("and the key for the according IP address %s", ip); | |
786 | error("%s. This could either mean that", key_msg); | |
787 | error("DNS SPOOFING is happening or the IP address for the host"); | |
788 | error("and its host key have changed at the same time."); | |
789 | if (ip_status != HOST_NEW) | |
790 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
791 | } | |
792 | /* The host key has changed. */ | |
793 | warn_changed_key(host_key); | |
794 | error("Add correct host key in %.100s to get rid of this message.", | |
795 | user_hostfile); | |
796 | error("Offending key in %s:%d", host_file, host_line); | |
797 | ||
798 | /* | |
799 | * If strict host key checking is in use, the user will have | |
800 | * to edit the key manually and we can only abort. | |
801 | */ | |
802 | if (options.strict_host_key_checking) { | |
803 | error("%s host key for %.200s has changed and you have " | |
804 | "requested strict checking.", type, host); | |
805 | goto fail; | |
806 | } | |
807 | ||
808 | /* | |
809 | * If strict host key checking has not been requested, allow | |
810 | * the connection but without MITM-able authentication or | |
811 | * forwarding. | |
812 | */ | |
813 | if (options.password_authentication) { | |
814 | error("Password authentication is disabled to avoid " | |
815 | "man-in-the-middle attacks."); | |
816 | options.password_authentication = 0; | |
817 | } | |
818 | if (options.kbd_interactive_authentication) { | |
819 | error("Keyboard-interactive authentication is disabled" | |
820 | " to avoid man-in-the-middle attacks."); | |
821 | options.kbd_interactive_authentication = 0; | |
822 | options.challenge_response_authentication = 0; | |
823 | } | |
824 | if (options.challenge_response_authentication) { | |
825 | error("Challenge/response authentication is disabled" | |
826 | " to avoid man-in-the-middle attacks."); | |
827 | options.challenge_response_authentication = 0; | |
828 | } | |
829 | if (options.forward_agent) { | |
830 | error("Agent forwarding is disabled to avoid " | |
831 | "man-in-the-middle attacks."); | |
832 | options.forward_agent = 0; | |
833 | } | |
834 | if (options.forward_x11) { | |
835 | error("X11 forwarding is disabled to avoid " | |
836 | "man-in-the-middle attacks."); | |
837 | options.forward_x11 = 0; | |
838 | } | |
839 | if (options.num_local_forwards > 0 || | |
840 | options.num_remote_forwards > 0) { | |
841 | error("Port forwarding is disabled to avoid " | |
842 | "man-in-the-middle attacks."); | |
843 | options.num_local_forwards = | |
844 | options.num_remote_forwards = 0; | |
845 | } | |
846 | if (options.tun_open != SSH_TUNMODE_NO) { | |
847 | error("Tunnel forwarding is disabled to avoid " | |
848 | "man-in-the-middle attacks."); | |
849 | options.tun_open = SSH_TUNMODE_NO; | |
850 | } | |
851 | /* | |
852 | * XXX Should permit the user to change to use the new id. | |
853 | * This could be done by converting the host key to an | |
854 | * identifying sentence, tell that the host identifies itself | |
855 | * by that sentence, and ask the user if he/she whishes to | |
856 | * accept the authentication. | |
857 | */ | |
858 | break; | |
859 | case HOST_FOUND: | |
860 | fatal("internal error"); | |
861 | break; | |
862 | } | |
863 | ||
864 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
865 | ip_status == HOST_CHANGED) { | |
866 | snprintf(msg, sizeof(msg), | |
867 | "Warning: the %s host key for '%.200s' " | |
868 | "differs from the key for the IP address '%.128s'" | |
869 | "\nOffending key for IP in %s:%d", | |
870 | type, host, ip, ip_file, ip_line); | |
871 | if (host_status == HOST_OK) { | |
872 | len = strlen(msg); | |
873 | snprintf(msg + len, sizeof(msg) - len, | |
874 | "\nMatching host key in %s:%d", | |
875 | host_file, host_line); | |
876 | } | |
877 | if (options.strict_host_key_checking == 1) { | |
878 | logit("%s", msg); | |
879 | error("Exiting, you have requested strict checking."); | |
880 | goto fail; | |
881 | } else if (options.strict_host_key_checking == 2) { | |
882 | strlcat(msg, "\nAre you sure you want " | |
883 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
884 | if (!confirm(msg)) | |
885 | goto fail; | |
886 | } else { | |
887 | logit("%s", msg); | |
888 | } | |
889 | } | |
890 | ||
891 | xfree(ip); | |
892 | xfree(host); | |
893 | return 0; | |
894 | ||
895 | fail: | |
896 | xfree(ip); | |
897 | xfree(host); | |
898 | return -1; | |
899 | } | |
900 | ||
901 | /* returns 0 if key verifies or -1 if key does NOT verify */ | |
902 | int | |
903 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
904 | { | |
905 | struct stat st; | |
906 | int flags = 0; | |
907 | ||
908 | if (options.verify_host_key_dns && | |
909 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
910 | ||
911 | if (flags & DNS_VERIFY_FOUND) { | |
912 | ||
913 | if (options.verify_host_key_dns == 1 && | |
914 | flags & DNS_VERIFY_MATCH && | |
915 | flags & DNS_VERIFY_SECURE) | |
916 | return 0; | |
917 | ||
918 | if (flags & DNS_VERIFY_MATCH) { | |
919 | matching_host_key_dns = 1; | |
920 | } else { | |
921 | warn_changed_key(host_key); | |
922 | error("Update the SSHFP RR in DNS with the new " | |
923 | "host key to get rid of this message."); | |
924 | } | |
925 | } | |
926 | } | |
927 | ||
928 | /* return ok if the key can be found in an old keyfile */ | |
929 | if (stat(options.system_hostfile2, &st) == 0 || | |
930 | stat(options.user_hostfile2, &st) == 0) { | |
931 | if (check_host_key(host, hostaddr, options.port, host_key, | |
932 | RDONLY, options.user_hostfile2, | |
933 | options.system_hostfile2) == 0) | |
934 | return 0; | |
935 | } | |
936 | return check_host_key(host, hostaddr, options.port, host_key, | |
937 | RDRW, options.user_hostfile, options.system_hostfile); | |
938 | } | |
939 | ||
940 | /* | |
941 | * Starts a dialog with the server, and authenticates the current user on the | |
942 | * server. This does not need any extra privileges. The basic connection | |
943 | * to the server must already have been established before this is called. | |
944 | * If login fails, this function prints an error and never returns. | |
945 | * This function does not require super-user privileges. | |
946 | */ | |
947 | void | |
948 | ssh_login(Sensitive *sensitive, const char *orighost, | |
949 | struct sockaddr *hostaddr, struct passwd *pw) | |
950 | { | |
951 | char *host, *cp; | |
952 | char *server_user, *local_user; | |
953 | ||
954 | local_user = xstrdup(pw->pw_name); | |
955 | server_user = options.user ? options.user : local_user; | |
956 | ||
957 | /* Convert the user-supplied hostname into all lowercase. */ | |
958 | host = xstrdup(orighost); | |
959 | for (cp = host; *cp; cp++) | |
960 | if (isupper(*cp)) | |
961 | *cp = (char)tolower(*cp); | |
962 | ||
963 | /* Exchange protocol version identification strings with the server. */ | |
964 | ssh_exchange_identification(); | |
965 | ||
966 | /* Put the connection into non-blocking mode. */ | |
967 | packet_set_nonblocking(); | |
968 | ||
969 | /* key exchange */ | |
970 | /* authenticate user */ | |
971 | if (compat20) { | |
972 | ssh_kex2(host, hostaddr); | |
973 | ssh_userauth2(local_user, server_user, host, sensitive); | |
974 | } else { | |
975 | ssh_kex(host, hostaddr); | |
976 | ssh_userauth1(local_user, server_user, host, sensitive); | |
977 | } | |
978 | xfree(local_user); | |
979 | } | |
980 | ||
981 | void | |
982 | ssh_put_password(char *password) | |
983 | { | |
984 | int size; | |
985 | char *padded; | |
986 | ||
987 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
988 | packet_put_cstring(password); | |
989 | return; | |
990 | } | |
991 | size = roundup(strlen(password) + 1, 32); | |
992 | padded = xcalloc(1, size); | |
993 | strlcpy(padded, password, size); | |
994 | packet_put_string(padded, size); | |
995 | memset(padded, 0, size); | |
996 | xfree(padded); | |
997 | } | |
998 | ||
999 | static int | |
1000 | show_key_from_file(const char *file, const char *host, int keytype) | |
1001 | { | |
1002 | Key *found; | |
1003 | char *fp; | |
1004 | int line, ret; | |
1005 | ||
1006 | found = key_new(keytype); | |
1007 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
1008 | keytype, found, &line))) { | |
1009 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
1010 | logit("WARNING: %s key found for host %s\n" | |
1011 | "in %s:%d\n" | |
1012 | "%s key fingerprint %s.", | |
1013 | key_type(found), host, file, line, | |
1014 | key_type(found), fp); | |
1015 | xfree(fp); | |
1016 | } | |
1017 | key_free(found); | |
1018 | return (ret); | |
1019 | } | |
1020 | ||
1021 | /* print all known host keys for a given host, but skip keys of given type */ | |
1022 | static int | |
1023 | show_other_keys(const char *host, Key *key) | |
1024 | { | |
1025 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1026 | int i, found = 0; | |
1027 | ||
1028 | for (i = 0; type[i] != -1; i++) { | |
1029 | if (type[i] == key->type) | |
1030 | continue; | |
1031 | if (type[i] != KEY_RSA1 && | |
1032 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1033 | found = 1; | |
1034 | continue; | |
1035 | } | |
1036 | if (type[i] != KEY_RSA1 && | |
1037 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1038 | found = 1; | |
1039 | continue; | |
1040 | } | |
1041 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1042 | found = 1; | |
1043 | continue; | |
1044 | } | |
1045 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1046 | found = 1; | |
1047 | continue; | |
1048 | } | |
1049 | debug2("no key of type %d for host %s", type[i], host); | |
1050 | } | |
1051 | return (found); | |
1052 | } | |
1053 | ||
1054 | static void | |
1055 | warn_changed_key(Key *host_key) | |
1056 | { | |
1057 | char *fp; | |
1058 | const char *type = key_type(host_key); | |
1059 | ||
1060 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1061 | ||
1062 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1063 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1064 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1065 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1066 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1067 | error("It is also possible that the %s host key has just been changed.", type); | |
1068 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1069 | type, fp); | |
1070 | error("Please contact your system administrator."); | |
1071 | ||
1072 | xfree(fp); | |
1073 | } | |
1074 | ||
1075 | /* | |
1076 | * Execute a local command | |
1077 | */ | |
1078 | int | |
1079 | ssh_local_cmd(const char *args) | |
1080 | { | |
1081 | char *shell; | |
1082 | pid_t pid; | |
1083 | int status; | |
1084 | ||
1085 | if (!options.permit_local_command || | |
1086 | args == NULL || !*args) | |
1087 | return (1); | |
1088 | ||
1089 | if ((shell = getenv("SHELL")) == NULL) | |
1090 | shell = _PATH_BSHELL; | |
1091 | ||
1092 | pid = fork(); | |
1093 | if (pid == 0) { | |
1094 | debug3("Executing %s -c \"%s\"", shell, args); | |
1095 | execl(shell, shell, "-c", args, (char *)NULL); | |
1096 | error("Couldn't execute %s -c \"%s\": %s", | |
1097 | shell, args, strerror(errno)); | |
1098 | _exit(1); | |
1099 | } else if (pid == -1) | |
1100 | fatal("fork failed: %.100s", strerror(errno)); | |
1101 | while (waitpid(pid, &status, 0) == -1) | |
1102 | if (errno != EINTR) | |
1103 | fatal("Couldn't wait for child: %s", strerror(errno)); | |
1104 | ||
1105 | if (!WIFEXITED(status)) | |
1106 | return (1); | |
1107 | ||
1108 | return (WEXITSTATUS(status)); | |
1109 | } |