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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" | |
473db5ab | 16 | RCSID("$OpenBSD: sshconnect.c,v 1.168 2005/07/17 07:17:55 djm 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 | ||
473db5ab | 35 | #include "dns.h" |
36 | ||
3c0ef626 | 37 | char *client_version_string = NULL; |
38 | char *server_version_string = NULL; | |
39 | ||
473db5ab | 40 | int matching_host_key_dns = 0; |
41 | ||
42 | /* import */ | |
3c0ef626 | 43 | extern Options options; |
44 | extern char *__progname; | |
473db5ab | 45 | extern uid_t original_real_uid; |
46 | extern uid_t original_effective_uid; | |
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 | ||
473db5ab | 53 | static int show_other_keys(const char *, Key *); |
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 | |
473db5ab | 60 | ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) |
3c0ef626 | 61 | { |
473db5ab | 62 | char *command_string, *tmp; |
3c0ef626 | 63 | int pin[2], pout[2]; |
64 | pid_t pid; | |
65 | char strport[NI_MAXSERV]; | |
473db5ab | 66 | size_t len; |
3c0ef626 | 67 | |
68 | /* Convert the port number into a string. */ | |
69 | snprintf(strport, sizeof strport, "%hu", port); | |
70 | ||
473db5ab | 71 | /* |
72 | * Build the final command string in the buffer by making the | |
73 | * appropriate substitutions to the given proxy command. | |
74 | * | |
75 | * Use "exec" to avoid "sh -c" processes on some platforms | |
76 | * (e.g. Solaris) | |
77 | */ | |
78 | len = strlen(proxy_command) + 6; | |
79 | tmp = xmalloc(len); | |
80 | strlcpy(tmp, "exec ", len); | |
81 | strlcat(tmp, proxy_command, len); | |
82 | command_string = percent_expand(tmp, "h", host, | |
83 | "p", strport, (char *)NULL); | |
84 | xfree(tmp); | |
3c0ef626 | 85 | |
86 | /* Create pipes for communicating with the proxy. */ | |
87 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
88 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
473db5ab | 89 | strerror(errno)); |
3c0ef626 | 90 | |
91 | debug("Executing proxy command: %.500s", command_string); | |
92 | ||
93 | /* Fork and execute the proxy command. */ | |
94 | if ((pid = fork()) == 0) { | |
95 | char *argv[10]; | |
96 | ||
97 | /* Child. Permanently give up superuser privileges. */ | |
473db5ab | 98 | seteuid(original_real_uid); |
99 | setuid(original_real_uid); | |
3c0ef626 | 100 | |
101 | /* Redirect stdin and stdout. */ | |
102 | close(pin[1]); | |
103 | if (pin[0] != 0) { | |
104 | if (dup2(pin[0], 0) < 0) | |
105 | perror("dup2 stdin"); | |
106 | close(pin[0]); | |
107 | } | |
108 | close(pout[0]); | |
109 | if (dup2(pout[1], 1) < 0) | |
110 | perror("dup2 stdout"); | |
111 | /* Cannot be 1 because pin allocated two descriptors. */ | |
112 | close(pout[1]); | |
113 | ||
114 | /* Stderr is left as it is so that error messages get | |
115 | printed on the user's terminal. */ | |
116 | argv[0] = _PATH_BSHELL; | |
117 | argv[1] = "-c"; | |
118 | argv[2] = command_string; | |
119 | argv[3] = NULL; | |
120 | ||
121 | /* Execute the proxy command. Note that we gave up any | |
122 | extra privileges above. */ | |
123 | execv(argv[0], argv); | |
124 | perror(argv[0]); | |
125 | exit(1); | |
126 | } | |
127 | /* Parent. */ | |
128 | if (pid < 0) | |
129 | fatal("fork failed: %.100s", strerror(errno)); | |
473db5ab | 130 | else |
131 | proxy_command_pid = pid; /* save pid to clean up later */ | |
3c0ef626 | 132 | |
133 | /* Close child side of the descriptors. */ | |
134 | close(pin[0]); | |
135 | close(pout[1]); | |
136 | ||
137 | /* Free the command name. */ | |
473db5ab | 138 | xfree(command_string); |
3c0ef626 | 139 | |
140 | /* Set the connection file descriptors. */ | |
141 | packet_set_connection(pout[0], pin[1]); | |
142 | ||
143 | /* Indicate OK return */ | |
144 | return 0; | |
145 | } | |
146 | ||
147 | /* | |
148 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
149 | */ | |
150 | static int | |
473db5ab | 151 | ssh_create_socket(int privileged, struct addrinfo *ai) |
3c0ef626 | 152 | { |
153 | int sock, gaierr; | |
154 | struct addrinfo hints, *res; | |
155 | ||
156 | /* | |
157 | * If we are running as root and want to connect to a privileged | |
158 | * port, bind our own socket to a privileged port. | |
159 | */ | |
160 | if (privileged) { | |
161 | int p = IPPORT_RESERVED - 1; | |
473db5ab | 162 | PRIV_START; |
163 | sock = rresvport_af(&p, ai->ai_family); | |
164 | PRIV_END; | |
3c0ef626 | 165 | if (sock < 0) |
473db5ab | 166 | error("rresvport: af=%d %.100s", ai->ai_family, |
167 | strerror(errno)); | |
3c0ef626 | 168 | else |
169 | debug("Allocated local port %d.", p); | |
473db5ab | 170 | |
171 | ||
172 | /* tuning needs to happen after the socket is */ | |
173 | /* created but before the connection happens */ | |
174 | /* so winscale is negotiated properly -cjr */ | |
175 | ||
176 | /* Set tcp receive buffer if requested */ | |
177 | if (options.tcp_rcv_buf) | |
178 | { | |
179 | if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, | |
180 | (void *)&options.tcp_rcv_buf, | |
181 | sizeof(options.tcp_rcv_buf)) >= 0) | |
182 | { | |
183 | debug("setsockopt SO_RCVBUF: %.100s", strerror(errno)); | |
184 | } | |
185 | else | |
186 | { | |
187 | /* coudln't set the socket size to use spec. */ | |
188 | /* should default to system param and continue */ | |
189 | /* warn the user though - cjr */ | |
190 | error("Couldn't set socket receive buffer as requested. Continuing anyway."); | |
191 | } | |
192 | } | |
3c0ef626 | 193 | return sock; |
194 | } | |
473db5ab | 195 | sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); |
3c0ef626 | 196 | if (sock < 0) |
197 | error("socket: %.100s", strerror(errno)); | |
473db5ab | 198 | |
199 | /* tuning needs to happen after the socket is */ | |
200 | /* created but before the connection happens */ | |
201 | /* so winscale is negotiated properly -cjr */ | |
202 | ||
203 | /* Set tcp receive buffer if requested */ | |
204 | if (options.tcp_rcv_buf) | |
205 | { | |
206 | if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, | |
207 | (void *)&options.tcp_rcv_buf, | |
208 | sizeof(options.tcp_rcv_buf)) >= 0) | |
209 | { | |
210 | debug("setsockopt SO_RCVBUF: %.100s", strerror(errno)); | |
211 | } | |
212 | else | |
213 | { | |
214 | /* coudln't set the socket size to use spec. */ | |
215 | /* should default to system param and continue */ | |
216 | /* warn the user though - cjr */ | |
217 | error("Couldn't set socket receive buffer as requested. Continuing anyway."); | |
218 | } | |
219 | } | |
220 | ||
221 | /* Bind the socket to an alternative local IP address */ | |
3c0ef626 | 222 | if (options.bind_address == NULL) |
223 | return sock; | |
224 | ||
225 | memset(&hints, 0, sizeof(hints)); | |
473db5ab | 226 | hints.ai_family = ai->ai_family; |
227 | hints.ai_socktype = ai->ai_socktype; | |
228 | hints.ai_protocol = ai->ai_protocol; | |
3c0ef626 | 229 | hints.ai_flags = AI_PASSIVE; |
230 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
231 | if (gaierr) { | |
232 | error("getaddrinfo: %s: %s", options.bind_address, | |
233 | gai_strerror(gaierr)); | |
234 | close(sock); | |
235 | return -1; | |
236 | } | |
237 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
238 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
239 | close(sock); | |
240 | freeaddrinfo(res); | |
241 | return -1; | |
242 | } | |
243 | freeaddrinfo(res); | |
244 | return sock; | |
245 | } | |
246 | ||
473db5ab | 247 | static int |
248 | timeout_connect(int sockfd, const struct sockaddr *serv_addr, | |
249 | socklen_t addrlen, int timeout) | |
250 | { | |
251 | fd_set *fdset; | |
252 | struct timeval tv; | |
253 | socklen_t optlen; | |
254 | int fdsetsz, optval, rc, result = -1; | |
255 | ||
256 | if (timeout <= 0) | |
257 | return (connect(sockfd, serv_addr, addrlen)); | |
258 | ||
259 | set_nonblock(sockfd); | |
260 | rc = connect(sockfd, serv_addr, addrlen); | |
261 | if (rc == 0) { | |
262 | unset_nonblock(sockfd); | |
263 | return (0); | |
264 | } | |
265 | if (errno != EINPROGRESS) | |
266 | return (-1); | |
267 | ||
268 | fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); | |
269 | fdset = (fd_set *)xmalloc(fdsetsz); | |
270 | ||
271 | memset(fdset, 0, fdsetsz); | |
272 | FD_SET(sockfd, fdset); | |
273 | tv.tv_sec = timeout; | |
274 | tv.tv_usec = 0; | |
275 | ||
276 | for (;;) { | |
277 | rc = select(sockfd + 1, NULL, fdset, NULL, &tv); | |
278 | if (rc != -1 || errno != EINTR) | |
279 | break; | |
280 | } | |
281 | ||
282 | switch (rc) { | |
283 | case 0: | |
284 | /* Timed out */ | |
285 | errno = ETIMEDOUT; | |
286 | break; | |
287 | case -1: | |
288 | /* Select error */ | |
289 | debug("select: %s", strerror(errno)); | |
290 | break; | |
291 | case 1: | |
292 | /* Completed or failed */ | |
293 | optval = 0; | |
294 | optlen = sizeof(optval); | |
295 | if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, | |
296 | &optlen) == -1) { | |
297 | debug("getsockopt: %s", strerror(errno)); | |
298 | break; | |
299 | } | |
300 | if (optval != 0) { | |
301 | errno = optval; | |
302 | break; | |
303 | } | |
304 | result = 0; | |
305 | unset_nonblock(sockfd); | |
306 | break; | |
307 | default: | |
308 | /* Should not occur */ | |
309 | fatal("Bogus return (%d) from select()", rc); | |
310 | } | |
311 | ||
312 | xfree(fdset); | |
313 | return (result); | |
314 | } | |
315 | ||
3c0ef626 | 316 | /* |
317 | * Opens a TCP/IP connection to the remote server on the given host. | |
318 | * The address of the remote host will be returned in hostaddr. | |
473db5ab | 319 | * If port is 0, the default port will be used. If needpriv is true, |
3c0ef626 | 320 | * a privileged port will be allocated to make the connection. |
473db5ab | 321 | * This requires super-user privileges if needpriv is true. |
3c0ef626 | 322 | * Connection_attempts specifies the maximum number of tries (one per |
323 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
324 | * and %p substituted for host and port, respectively) to use to contact | |
325 | * the daemon. | |
3c0ef626 | 326 | */ |
327 | int | |
328 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
329 | u_short port, int family, int connection_attempts, | |
473db5ab | 330 | int needpriv, const char *proxy_command) |
3c0ef626 | 331 | { |
332 | int gaierr; | |
333 | int on = 1; | |
334 | int sock = -1, attempt; | |
335 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
336 | struct addrinfo hints, *ai, *aitop; | |
3c0ef626 | 337 | |
473db5ab | 338 | debug2("ssh_connect: needpriv %d", needpriv); |
3c0ef626 | 339 | |
3c0ef626 | 340 | /* If a proxy command is given, connect using it. */ |
341 | if (proxy_command != NULL) | |
473db5ab | 342 | return ssh_proxy_connect(host, port, proxy_command); |
3c0ef626 | 343 | |
344 | /* No proxy command. */ | |
345 | ||
346 | memset(&hints, 0, sizeof(hints)); | |
347 | hints.ai_family = family; | |
348 | hints.ai_socktype = SOCK_STREAM; | |
473db5ab | 349 | snprintf(strport, sizeof strport, "%u", port); |
3c0ef626 | 350 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) |
351 | fatal("%s: %.100s: %s", __progname, host, | |
352 | gai_strerror(gaierr)); | |
353 | ||
354 | /* | |
355 | * Try to connect several times. On some machines, the first time | |
356 | * will sometimes fail. In general socket code appears to behave | |
357 | * quite magically on many machines. | |
358 | */ | |
359 | for (attempt = 0; ;) { | |
360 | if (attempt > 0) | |
361 | debug("Trying again..."); | |
362 | ||
363 | /* Loop through addresses for this host, and try each one in | |
364 | sequence until the connection succeeds. */ | |
365 | for (ai = aitop; ai; ai = ai->ai_next) { | |
366 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
367 | continue; | |
368 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
369 | ntop, sizeof(ntop), strport, sizeof(strport), | |
370 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
371 | error("ssh_connect: getnameinfo failed"); | |
372 | continue; | |
373 | } | |
374 | debug("Connecting to %.200s [%.100s] port %s.", | |
375 | host, ntop, strport); | |
376 | ||
377 | /* Create a socket for connecting. */ | |
473db5ab | 378 | sock = ssh_create_socket(needpriv, ai); |
3c0ef626 | 379 | if (sock < 0) |
380 | /* Any error is already output */ | |
381 | continue; | |
382 | ||
473db5ab | 383 | if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, |
384 | options.connection_timeout) >= 0) { | |
3c0ef626 | 385 | /* Successful connection. */ |
386 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
3c0ef626 | 387 | break; |
388 | } else { | |
473db5ab | 389 | debug("connect to address %s port %s: %s", |
390 | ntop, strport, strerror(errno)); | |
3c0ef626 | 391 | /* |
392 | * Close the failed socket; there appear to | |
393 | * be some problems when reusing a socket for | |
394 | * which connect() has already returned an | |
395 | * error. | |
396 | */ | |
3c0ef626 | 397 | close(sock); |
398 | } | |
399 | } | |
400 | if (ai) | |
401 | break; /* Successful connection. */ | |
402 | ||
403 | attempt++; | |
404 | if (attempt >= connection_attempts) | |
405 | break; | |
406 | /* Sleep a moment before retrying. */ | |
407 | sleep(1); | |
408 | } | |
409 | ||
410 | freeaddrinfo(aitop); | |
411 | ||
412 | /* Return failure if we didn't get a successful connection. */ | |
473db5ab | 413 | if (attempt >= connection_attempts) { |
414 | error("ssh: connect to host %s port %s: %s", | |
415 | host, strport, strerror(errno)); | |
416 | return (-1); | |
417 | } | |
3c0ef626 | 418 | |
419 | debug("Connection established."); | |
420 | ||
473db5ab | 421 | /* Set SO_KEEPALIVE if requested. */ |
422 | if (options.tcp_keep_alive && | |
3c0ef626 | 423 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, |
424 | sizeof(on)) < 0) | |
425 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
426 | ||
427 | /* Set the connection. */ | |
428 | packet_set_connection(sock, sock); | |
429 | ||
430 | return 0; | |
431 | } | |
432 | ||
433 | /* | |
434 | * Waits for the server identification string, and sends our own | |
435 | * identification string. | |
436 | */ | |
437 | static void | |
438 | ssh_exchange_identification(void) | |
439 | { | |
440 | char buf[256], remote_version[256]; /* must be same size! */ | |
473db5ab | 441 | int remote_major, remote_minor, mismatch; |
3c0ef626 | 442 | int connection_in = packet_get_connection_in(); |
443 | int connection_out = packet_get_connection_out(); | |
444 | int minor1 = PROTOCOL_MINOR_1; | |
473db5ab | 445 | u_int i; |
3c0ef626 | 446 | |
473db5ab | 447 | /* Read other side's version identification. */ |
3c0ef626 | 448 | for (;;) { |
449 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
473db5ab | 450 | size_t len = atomicio(read, connection_in, &buf[i], 1); |
451 | ||
452 | if (len != 1 && errno == EPIPE) | |
3c0ef626 | 453 | fatal("ssh_exchange_identification: Connection closed by remote host"); |
473db5ab | 454 | else if (len != 1) |
455 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
3c0ef626 | 456 | if (buf[i] == '\r') { |
457 | buf[i] = '\n'; | |
458 | buf[i + 1] = 0; | |
459 | continue; /**XXX wait for \n */ | |
460 | } | |
461 | if (buf[i] == '\n') { | |
462 | buf[i + 1] = 0; | |
463 | break; | |
464 | } | |
465 | } | |
466 | buf[sizeof(buf) - 1] = 0; | |
467 | if (strncmp(buf, "SSH-", 4) == 0) | |
468 | break; | |
469 | debug("ssh_exchange_identification: %s", buf); | |
470 | } | |
471 | server_version_string = xstrdup(buf); | |
472 | ||
473 | /* | |
474 | * Check that the versions match. In future this might accept | |
475 | * several versions and set appropriate flags to handle them. | |
476 | */ | |
477 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
478 | &remote_major, &remote_minor, remote_version) != 3) | |
479 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
480 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
473db5ab | 481 | remote_major, remote_minor, remote_version); |
3c0ef626 | 482 | |
483 | compat_datafellows(remote_version); | |
484 | mismatch = 0; | |
485 | ||
473db5ab | 486 | switch (remote_major) { |
3c0ef626 | 487 | case 1: |
488 | if (remote_minor == 99 && | |
489 | (options.protocol & SSH_PROTO_2) && | |
490 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
491 | enable_compat20(); | |
492 | break; | |
493 | } | |
494 | if (!(options.protocol & SSH_PROTO_1)) { | |
495 | mismatch = 1; | |
496 | break; | |
497 | } | |
498 | if (remote_minor < 3) { | |
499 | fatal("Remote machine has too old SSH software version."); | |
500 | } else if (remote_minor == 3 || remote_minor == 4) { | |
501 | /* We speak 1.3, too. */ | |
502 | enable_compat13(); | |
503 | minor1 = 3; | |
504 | if (options.forward_agent) { | |
473db5ab | 505 | logit("Agent forwarding disabled for protocol 1.3"); |
3c0ef626 | 506 | options.forward_agent = 0; |
507 | } | |
508 | } | |
509 | break; | |
510 | case 2: | |
511 | if (options.protocol & SSH_PROTO_2) { | |
512 | enable_compat20(); | |
513 | break; | |
514 | } | |
515 | /* FALLTHROUGH */ | |
516 | default: | |
517 | mismatch = 1; | |
518 | break; | |
519 | } | |
520 | if (mismatch) | |
521 | fatal("Protocol major versions differ: %d vs. %d", | |
522 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
523 | remote_major); | |
524 | /* Send our own protocol version identification. */ | |
525 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
526 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
527 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
473db5ab | 528 | SSH_RELEASE); |
529 | if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) | |
3c0ef626 | 530 | fatal("write: %.100s", strerror(errno)); |
531 | client_version_string = xstrdup(buf); | |
532 | chop(client_version_string); | |
533 | chop(server_version_string); | |
534 | debug("Local version string %.100s", client_version_string); | |
535 | } | |
536 | ||
537 | /* defaults to 'no' */ | |
538 | static int | |
539 | confirm(const char *prompt) | |
540 | { | |
473db5ab | 541 | const char *msg, *again = "Please type 'yes' or 'no': "; |
542 | char *p; | |
543 | int ret = -1; | |
3c0ef626 | 544 | |
545 | if (options.batch_mode) | |
546 | return 0; | |
473db5ab | 547 | for (msg = prompt;;msg = again) { |
548 | p = read_passphrase(msg, RP_ECHO); | |
549 | if (p == NULL || | |
550 | (p[0] == '\0') || (p[0] == '\n') || | |
551 | strncasecmp(p, "no", 2) == 0) | |
552 | ret = 0; | |
553 | if (p && strncasecmp(p, "yes", 3) == 0) | |
554 | ret = 1; | |
555 | if (p) | |
556 | xfree(p); | |
557 | if (ret != -1) | |
558 | return ret; | |
3c0ef626 | 559 | } |
560 | } | |
561 | ||
562 | /* | |
563 | * check whether the supplied host key is valid, return -1 if the key | |
564 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
565 | */ | |
3c0ef626 | 566 | static int |
567 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
568 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
569 | { | |
570 | Key *file_key; | |
473db5ab | 571 | const char *type = key_type(host_key); |
3c0ef626 | 572 | char *ip = NULL; |
573 | char hostline[1000], *hostp, *fp; | |
574 | HostStatus host_status; | |
575 | HostStatus ip_status; | |
473db5ab | 576 | int r, local = 0, host_ip_differ = 0; |
3c0ef626 | 577 | int salen; |
578 | char ntop[NI_MAXHOST]; | |
473db5ab | 579 | char msg[1024]; |
580 | int len, host_line, ip_line; | |
3c0ef626 | 581 | const char *host_file = NULL, *ip_file = NULL; |
582 | ||
583 | /* | |
584 | * Force accepting of the host key for loopback/localhost. The | |
585 | * problem is that if the home directory is NFS-mounted to multiple | |
586 | * machines, localhost will refer to a different machine in each of | |
587 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
588 | * essentially disables host authentication for localhost; however, | |
589 | * this is probably not a real problem. | |
590 | */ | |
591 | /** hostaddr == 0! */ | |
592 | switch (hostaddr->sa_family) { | |
593 | case AF_INET: | |
594 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
595 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
596 | salen = sizeof(struct sockaddr_in); | |
597 | break; | |
598 | case AF_INET6: | |
599 | local = IN6_IS_ADDR_LOOPBACK( | |
600 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
601 | salen = sizeof(struct sockaddr_in6); | |
602 | break; | |
603 | default: | |
604 | local = 0; | |
605 | salen = sizeof(struct sockaddr_storage); | |
606 | break; | |
607 | } | |
608 | if (options.no_host_authentication_for_localhost == 1 && local && | |
609 | options.host_key_alias == NULL) { | |
610 | debug("Forcing accepting of host key for " | |
611 | "loopback/localhost."); | |
612 | return 0; | |
613 | } | |
614 | ||
615 | /* | |
616 | * We don't have the remote ip-address for connections | |
617 | * using a proxy command | |
618 | */ | |
619 | if (options.proxy_command == NULL) { | |
620 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
621 | NULL, 0, NI_NUMERICHOST) != 0) | |
622 | fatal("check_host_key: getnameinfo failed"); | |
623 | ip = xstrdup(ntop); | |
624 | } else { | |
625 | ip = xstrdup("<no hostip for proxy command>"); | |
626 | } | |
627 | /* | |
628 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
629 | * command or if we don't have a hostname to compare with | |
630 | */ | |
631 | if (options.check_host_ip && | |
632 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
633 | options.check_host_ip = 0; | |
634 | ||
635 | /* | |
636 | * Allow the user to record the key under a different name. This is | |
637 | * useful for ssh tunneling over forwarded connections or if you run | |
638 | * multiple sshd's on different ports on the same machine. | |
639 | */ | |
640 | if (options.host_key_alias != NULL) { | |
641 | host = options.host_key_alias; | |
642 | debug("using hostkeyalias: %s", host); | |
643 | } | |
644 | ||
645 | /* | |
646 | * Store the host key from the known host file in here so that we can | |
647 | * compare it with the key for the IP address. | |
648 | */ | |
649 | file_key = key_new(host_key->type); | |
650 | ||
651 | /* | |
652 | * Check if the host key is present in the user\'s list of known | |
653 | * hosts or in the systemwide list. | |
654 | */ | |
655 | host_file = user_hostfile; | |
656 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
473db5ab | 657 | file_key, &host_line); |
3c0ef626 | 658 | if (host_status == HOST_NEW) { |
659 | host_file = system_hostfile; | |
660 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
661 | file_key, &host_line); | |
662 | } | |
663 | /* | |
664 | * Also perform check for the ip address, skip the check if we are | |
665 | * localhost or the hostname was an ip address to begin with | |
666 | */ | |
667 | if (options.check_host_ip) { | |
668 | Key *ip_key = key_new(host_key->type); | |
669 | ||
670 | ip_file = user_hostfile; | |
671 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
672 | ip_key, &ip_line); | |
673 | if (ip_status == HOST_NEW) { | |
674 | ip_file = system_hostfile; | |
675 | ip_status = check_host_in_hostfile(ip_file, ip, | |
676 | host_key, ip_key, &ip_line); | |
677 | } | |
678 | if (host_status == HOST_CHANGED && | |
679 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
680 | host_ip_differ = 1; | |
681 | ||
682 | key_free(ip_key); | |
683 | } else | |
684 | ip_status = host_status; | |
685 | ||
686 | key_free(file_key); | |
687 | ||
688 | switch (host_status) { | |
689 | case HOST_OK: | |
690 | /* The host is known and the key matches. */ | |
691 | debug("Host '%.200s' is known and matches the %s host key.", | |
692 | host, type); | |
693 | debug("Found key in %s:%d", host_file, host_line); | |
694 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
695 | if (readonly) | |
473db5ab | 696 | logit("%s host key for IP address " |
3c0ef626 | 697 | "'%.128s' not in list of known hosts.", |
698 | type, ip); | |
699 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
473db5ab | 700 | host_key, options.hash_known_hosts)) |
701 | logit("Failed to add the %s host key for IP " | |
3c0ef626 | 702 | "address '%.128s' to the list of known " |
703 | "hosts (%.30s).", type, ip, user_hostfile); | |
704 | else | |
473db5ab | 705 | logit("Warning: Permanently added the %s host " |
3c0ef626 | 706 | "key for IP address '%.128s' to the list " |
707 | "of known hosts.", type, ip); | |
708 | } | |
709 | break; | |
710 | case HOST_NEW: | |
711 | if (readonly) | |
712 | goto fail; | |
713 | /* The host is new. */ | |
714 | if (options.strict_host_key_checking == 1) { | |
715 | /* | |
716 | * User has requested strict host key checking. We | |
717 | * will not add the host key automatically. The only | |
718 | * alternative left is to abort. | |
719 | */ | |
720 | error("No %s host key is known for %.200s and you " | |
721 | "have requested strict checking.", type, host); | |
722 | goto fail; | |
723 | } else if (options.strict_host_key_checking == 2) { | |
473db5ab | 724 | char msg1[1024], msg2[1024]; |
725 | ||
726 | if (show_other_keys(host, host_key)) | |
727 | snprintf(msg1, sizeof(msg1), | |
728 | "\nbut keys of different type are already" | |
729 | " known for this host."); | |
730 | else | |
731 | snprintf(msg1, sizeof(msg1), "."); | |
3c0ef626 | 732 | /* The default */ |
3c0ef626 | 733 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); |
473db5ab | 734 | msg2[0] = '\0'; |
735 | if (options.verify_host_key_dns) { | |
736 | if (matching_host_key_dns) | |
737 | snprintf(msg2, sizeof(msg2), | |
738 | "Matching host key fingerprint" | |
739 | " found in DNS.\n"); | |
740 | else | |
741 | snprintf(msg2, sizeof(msg2), | |
742 | "No matching host key fingerprint" | |
743 | " found in DNS.\n"); | |
744 | } | |
745 | snprintf(msg, sizeof(msg), | |
3c0ef626 | 746 | "The authenticity of host '%.200s (%s)' can't be " |
473db5ab | 747 | "established%s\n" |
748 | "%s key fingerprint is %s.\n%s" | |
3c0ef626 | 749 | "Are you sure you want to continue connecting " |
473db5ab | 750 | "(yes/no)? ", |
751 | host, ip, msg1, type, fp, msg2); | |
3c0ef626 | 752 | xfree(fp); |
473db5ab | 753 | if (!confirm(msg)) |
3c0ef626 | 754 | goto fail; |
3c0ef626 | 755 | } |
3c0ef626 | 756 | /* |
757 | * If not in strict mode, add the key automatically to the | |
758 | * local known_hosts file. | |
759 | */ | |
473db5ab | 760 | if (options.check_host_ip && ip_status == HOST_NEW) { |
761 | snprintf(hostline, sizeof(hostline), "%s,%s", | |
762 | host, ip); | |
763 | hostp = hostline; | |
764 | if (options.hash_known_hosts) { | |
765 | /* Add hash of host and IP separately */ | |
766 | r = add_host_to_hostfile(user_hostfile, host, | |
767 | host_key, options.hash_known_hosts) && | |
768 | add_host_to_hostfile(user_hostfile, ip, | |
769 | host_key, options.hash_known_hosts); | |
770 | } else { | |
771 | /* Add unhashed "host,ip" */ | |
772 | r = add_host_to_hostfile(user_hostfile, | |
773 | hostline, host_key, | |
774 | options.hash_known_hosts); | |
775 | } | |
776 | } else { | |
777 | r = add_host_to_hostfile(user_hostfile, host, host_key, | |
778 | options.hash_known_hosts); | |
779 | hostp = host; | |
780 | } | |
781 | ||
782 | if (!r) | |
783 | logit("Failed to add the host to the list of known " | |
3c0ef626 | 784 | "hosts (%.500s).", user_hostfile); |
785 | else | |
473db5ab | 786 | logit("Warning: Permanently added '%.200s' (%s) to the " |
3c0ef626 | 787 | "list of known hosts.", hostp, type); |
788 | break; | |
789 | case HOST_CHANGED: | |
790 | if (options.check_host_ip && host_ip_differ) { | |
473db5ab | 791 | char *key_msg; |
3c0ef626 | 792 | if (ip_status == HOST_NEW) |
473db5ab | 793 | key_msg = "is unknown"; |
3c0ef626 | 794 | else if (ip_status == HOST_OK) |
473db5ab | 795 | key_msg = "is unchanged"; |
3c0ef626 | 796 | else |
473db5ab | 797 | key_msg = "has a different value"; |
3c0ef626 | 798 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); |
799 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
800 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
801 | error("The %s host key for %s has changed,", type, host); | |
802 | error("and the key for the according IP address %s", ip); | |
473db5ab | 803 | error("%s. This could either mean that", key_msg); |
3c0ef626 | 804 | error("DNS SPOOFING is happening or the IP address for the host"); |
805 | error("and its host key have changed at the same time."); | |
806 | if (ip_status != HOST_NEW) | |
807 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
808 | } | |
809 | /* The host key has changed. */ | |
473db5ab | 810 | warn_changed_key(host_key); |
3c0ef626 | 811 | error("Add correct host key in %.100s to get rid of this message.", |
812 | user_hostfile); | |
813 | error("Offending key in %s:%d", host_file, host_line); | |
3c0ef626 | 814 | |
815 | /* | |
816 | * If strict host key checking is in use, the user will have | |
817 | * to edit the key manually and we can only abort. | |
818 | */ | |
819 | if (options.strict_host_key_checking) { | |
820 | error("%s host key for %.200s has changed and you have " | |
821 | "requested strict checking.", type, host); | |
822 | goto fail; | |
823 | } | |
824 | ||
825 | /* | |
826 | * If strict host key checking has not been requested, allow | |
473db5ab | 827 | * the connection but without MITM-able authentication or |
3c0ef626 | 828 | * agent forwarding. |
829 | */ | |
830 | if (options.password_authentication) { | |
831 | error("Password authentication is disabled to avoid " | |
832 | "man-in-the-middle attacks."); | |
833 | options.password_authentication = 0; | |
834 | } | |
473db5ab | 835 | if (options.kbd_interactive_authentication) { |
836 | error("Keyboard-interactive authentication is disabled" | |
837 | " to avoid man-in-the-middle attacks."); | |
838 | options.kbd_interactive_authentication = 0; | |
839 | options.challenge_response_authentication = 0; | |
840 | } | |
841 | if (options.challenge_response_authentication) { | |
842 | error("Challenge/response authentication is disabled" | |
843 | " to avoid man-in-the-middle attacks."); | |
844 | options.challenge_response_authentication = 0; | |
845 | } | |
3c0ef626 | 846 | if (options.forward_agent) { |
847 | error("Agent forwarding is disabled to avoid " | |
848 | "man-in-the-middle attacks."); | |
849 | options.forward_agent = 0; | |
850 | } | |
851 | if (options.forward_x11) { | |
852 | error("X11 forwarding is disabled to avoid " | |
853 | "man-in-the-middle attacks."); | |
854 | options.forward_x11 = 0; | |
855 | } | |
856 | if (options.num_local_forwards > 0 || | |
857 | options.num_remote_forwards > 0) { | |
858 | error("Port forwarding is disabled to avoid " | |
859 | "man-in-the-middle attacks."); | |
860 | options.num_local_forwards = | |
473db5ab | 861 | options.num_remote_forwards = 0; |
3c0ef626 | 862 | } |
863 | /* | |
864 | * XXX Should permit the user to change to use the new id. | |
865 | * This could be done by converting the host key to an | |
866 | * identifying sentence, tell that the host identifies itself | |
867 | * by that sentence, and ask the user if he/she whishes to | |
868 | * accept the authentication. | |
869 | */ | |
870 | break; | |
473db5ab | 871 | case HOST_FOUND: |
872 | fatal("internal error"); | |
873 | break; | |
3c0ef626 | 874 | } |
875 | ||
876 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
877 | ip_status == HOST_CHANGED) { | |
473db5ab | 878 | snprintf(msg, sizeof(msg), |
879 | "Warning: the %s host key for '%.200s' " | |
880 | "differs from the key for the IP address '%.128s'" | |
881 | "\nOffending key for IP in %s:%d", | |
882 | type, host, ip, ip_file, ip_line); | |
883 | if (host_status == HOST_OK) { | |
884 | len = strlen(msg); | |
885 | snprintf(msg + len, sizeof(msg) - len, | |
886 | "\nMatching host key in %s:%d", | |
887 | host_file, host_line); | |
888 | } | |
3c0ef626 | 889 | if (options.strict_host_key_checking == 1) { |
473db5ab | 890 | logit("%s", msg); |
3c0ef626 | 891 | error("Exiting, you have requested strict checking."); |
892 | goto fail; | |
893 | } else if (options.strict_host_key_checking == 2) { | |
473db5ab | 894 | strlcat(msg, "\nAre you sure you want " |
895 | "to continue connecting (yes/no)? ", sizeof(msg)); | |
896 | if (!confirm(msg)) | |
3c0ef626 | 897 | goto fail; |
473db5ab | 898 | } else { |
899 | logit("%s", msg); | |
3c0ef626 | 900 | } |
901 | } | |
902 | ||
903 | xfree(ip); | |
904 | return 0; | |
905 | ||
906 | fail: | |
907 | xfree(ip); | |
908 | return -1; | |
909 | } | |
910 | ||
473db5ab | 911 | /* returns 0 if key verifies or -1 if key does NOT verify */ |
3c0ef626 | 912 | int |
913 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
914 | { | |
915 | struct stat st; | |
473db5ab | 916 | int flags = 0; |
917 | ||
918 | if (options.verify_host_key_dns && | |
919 | verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { | |
920 | ||
921 | if (flags & DNS_VERIFY_FOUND) { | |
922 | ||
923 | if (options.verify_host_key_dns == 1 && | |
924 | flags & DNS_VERIFY_MATCH && | |
925 | flags & DNS_VERIFY_SECURE) | |
926 | return 0; | |
927 | ||
928 | if (flags & DNS_VERIFY_MATCH) { | |
929 | matching_host_key_dns = 1; | |
930 | } else { | |
931 | warn_changed_key(host_key); | |
932 | error("Update the SSHFP RR in DNS with the new " | |
933 | "host key to get rid of this message."); | |
934 | } | |
935 | } | |
936 | } | |
3c0ef626 | 937 | |
938 | /* return ok if the key can be found in an old keyfile */ | |
939 | if (stat(options.system_hostfile2, &st) == 0 || | |
940 | stat(options.user_hostfile2, &st) == 0) { | |
941 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
942 | options.user_hostfile2, options.system_hostfile2) == 0) | |
943 | return 0; | |
944 | } | |
945 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
946 | options.user_hostfile, options.system_hostfile); | |
947 | } | |
948 | ||
949 | /* | |
950 | * Starts a dialog with the server, and authenticates the current user on the | |
951 | * server. This does not need any extra privileges. The basic connection | |
952 | * to the server must already have been established before this is called. | |
953 | * If login fails, this function prints an error and never returns. | |
954 | * This function does not require super-user privileges. | |
955 | */ | |
956 | void | |
473db5ab | 957 | ssh_login(Sensitive *sensitive, const char *orighost, |
3c0ef626 | 958 | struct sockaddr *hostaddr, struct passwd *pw) |
959 | { | |
960 | char *host, *cp; | |
961 | char *server_user, *local_user; | |
962 | ||
963 | local_user = xstrdup(pw->pw_name); | |
964 | server_user = options.user ? options.user : local_user; | |
965 | ||
966 | /* Convert the user-supplied hostname into all lowercase. */ | |
967 | host = xstrdup(orighost); | |
968 | for (cp = host; *cp; cp++) | |
969 | if (isupper(*cp)) | |
970 | *cp = tolower(*cp); | |
971 | ||
972 | /* Exchange protocol version identification strings with the server. */ | |
973 | ssh_exchange_identification(); | |
974 | ||
975 | /* Put the connection into non-blocking mode. */ | |
976 | packet_set_nonblocking(); | |
977 | ||
978 | /* key exchange */ | |
979 | /* authenticate user */ | |
980 | if (compat20) { | |
981 | ssh_kex2(host, hostaddr); | |
473db5ab | 982 | ssh_userauth2(local_user, server_user, host, sensitive); |
3c0ef626 | 983 | } else { |
984 | ssh_kex(host, hostaddr); | |
473db5ab | 985 | ssh_userauth1(local_user, server_user, host, sensitive); |
3c0ef626 | 986 | } |
987 | } | |
988 | ||
989 | void | |
990 | ssh_put_password(char *password) | |
991 | { | |
992 | int size; | |
993 | char *padded; | |
994 | ||
995 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
996 | packet_put_cstring(password); | |
997 | return; | |
998 | } | |
999 | size = roundup(strlen(password) + 1, 32); | |
1000 | padded = xmalloc(size); | |
1001 | memset(padded, 0, size); | |
1002 | strlcpy(padded, password, size); | |
1003 | packet_put_string(padded, size); | |
1004 | memset(padded, 0, size); | |
1005 | xfree(padded); | |
1006 | } | |
473db5ab | 1007 | |
1008 | static int | |
1009 | show_key_from_file(const char *file, const char *host, int keytype) | |
1010 | { | |
1011 | Key *found; | |
1012 | char *fp; | |
1013 | int line, ret; | |
1014 | ||
1015 | found = key_new(keytype); | |
1016 | if ((ret = lookup_key_in_hostfile_by_type(file, host, | |
1017 | keytype, found, &line))) { | |
1018 | fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); | |
1019 | logit("WARNING: %s key found for host %s\n" | |
1020 | "in %s:%d\n" | |
1021 | "%s key fingerprint %s.", | |
1022 | key_type(found), host, file, line, | |
1023 | key_type(found), fp); | |
1024 | xfree(fp); | |
1025 | } | |
1026 | key_free(found); | |
1027 | return (ret); | |
1028 | } | |
1029 | ||
1030 | /* print all known host keys for a given host, but skip keys of given type */ | |
1031 | static int | |
1032 | show_other_keys(const char *host, Key *key) | |
1033 | { | |
1034 | int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; | |
1035 | int i, found = 0; | |
1036 | ||
1037 | for (i = 0; type[i] != -1; i++) { | |
1038 | if (type[i] == key->type) | |
1039 | continue; | |
1040 | if (type[i] != KEY_RSA1 && | |
1041 | show_key_from_file(options.user_hostfile2, host, type[i])) { | |
1042 | found = 1; | |
1043 | continue; | |
1044 | } | |
1045 | if (type[i] != KEY_RSA1 && | |
1046 | show_key_from_file(options.system_hostfile2, host, type[i])) { | |
1047 | found = 1; | |
1048 | continue; | |
1049 | } | |
1050 | if (show_key_from_file(options.user_hostfile, host, type[i])) { | |
1051 | found = 1; | |
1052 | continue; | |
1053 | } | |
1054 | if (show_key_from_file(options.system_hostfile, host, type[i])) { | |
1055 | found = 1; | |
1056 | continue; | |
1057 | } | |
1058 | debug2("no key of type %d for host %s", type[i], host); | |
1059 | } | |
1060 | return (found); | |
1061 | } | |
1062 | ||
1063 | static void | |
1064 | warn_changed_key(Key *host_key) | |
1065 | { | |
1066 | char *fp; | |
1067 | const char *type = key_type(host_key); | |
1068 | ||
1069 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
1070 | ||
1071 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1072 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
1073 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1074 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1075 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1076 | error("It is also possible that the %s host key has just been changed.", type); | |
1077 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
1078 | type, fp); | |
1079 | error("Please contact your system administrator."); | |
1080 | ||
1081 | xfree(fp); | |
1082 | } |