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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" | |
16 | RCSID("$OpenBSD: sshconnect.c,v 1.115 2001/10/08 19:05:05 markus Exp $"); | |
17 | ||
18 | #include <openssl/bn.h> | |
19 | ||
20 | #include "ssh.h" | |
21 | #include "xmalloc.h" | |
22 | #include "rsa.h" | |
23 | #include "buffer.h" | |
24 | #include "packet.h" | |
25 | #include "uidswap.h" | |
26 | #include "compat.h" | |
27 | #include "key.h" | |
28 | #include "sshconnect.h" | |
29 | #include "hostfile.h" | |
30 | #include "log.h" | |
31 | #include "readconf.h" | |
32 | #include "atomicio.h" | |
33 | #include "misc.h" | |
34 | ||
35 | char *client_version_string = NULL; | |
36 | char *server_version_string = NULL; | |
37 | ||
38 | extern Options options; | |
39 | extern char *__progname; | |
40 | ||
41 | #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ | |
42 | #define INET6_ADDRSTRLEN 46 | |
43 | #endif | |
44 | ||
45 | static const char * | |
46 | sockaddr_ntop(struct sockaddr *sa) | |
47 | { | |
48 | void *addr; | |
49 | static char addrbuf[INET6_ADDRSTRLEN]; | |
50 | ||
51 | switch (sa->sa_family) { | |
52 | case AF_INET: | |
53 | addr = &((struct sockaddr_in *)sa)->sin_addr; | |
54 | break; | |
55 | case AF_INET6: | |
56 | addr = &((struct sockaddr_in6 *)sa)->sin6_addr; | |
57 | break; | |
58 | default: | |
59 | /* This case should be protected against elsewhere */ | |
60 | abort(); | |
61 | } | |
62 | inet_ntop(sa->sa_family, addr, addrbuf, sizeof(addrbuf)); | |
63 | return addrbuf; | |
64 | } | |
65 | ||
66 | /* | |
67 | * Connect to the given ssh server using a proxy command. | |
68 | */ | |
69 | static int | |
70 | ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, | |
71 | const char *proxy_command) | |
72 | { | |
73 | Buffer command; | |
74 | const char *cp; | |
75 | char *command_string; | |
76 | int pin[2], pout[2]; | |
77 | pid_t pid; | |
78 | char strport[NI_MAXSERV]; | |
79 | ||
80 | /* Convert the port number into a string. */ | |
81 | snprintf(strport, sizeof strport, "%hu", port); | |
82 | ||
83 | /* Build the final command string in the buffer by making the | |
84 | appropriate substitutions to the given proxy command. */ | |
85 | buffer_init(&command); | |
86 | for (cp = proxy_command; *cp; cp++) { | |
87 | if (cp[0] == '%' && cp[1] == '%') { | |
88 | buffer_append(&command, "%", 1); | |
89 | cp++; | |
90 | continue; | |
91 | } | |
92 | if (cp[0] == '%' && cp[1] == 'h') { | |
93 | buffer_append(&command, host, strlen(host)); | |
94 | cp++; | |
95 | continue; | |
96 | } | |
97 | if (cp[0] == '%' && cp[1] == 'p') { | |
98 | buffer_append(&command, strport, strlen(strport)); | |
99 | cp++; | |
100 | continue; | |
101 | } | |
102 | buffer_append(&command, cp, 1); | |
103 | } | |
104 | buffer_append(&command, "\0", 1); | |
105 | ||
106 | /* Get the final command string. */ | |
107 | command_string = buffer_ptr(&command); | |
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_set_uid(pw); | |
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] = _PATH_BSHELL; | |
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 | ||
153 | /* Close child side of the descriptors. */ | |
154 | close(pin[0]); | |
155 | close(pout[1]); | |
156 | ||
157 | /* Free the command name. */ | |
158 | buffer_free(&command); | |
159 | ||
160 | /* Set the connection file descriptors. */ | |
161 | packet_set_connection(pout[0], pin[1]); | |
162 | ||
163 | /* Indicate OK return */ | |
164 | return 0; | |
165 | } | |
166 | ||
167 | /* | |
168 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
169 | */ | |
170 | static int | |
171 | ssh_create_socket(struct passwd *pw, int privileged, int family) | |
172 | { | |
173 | int sock, gaierr; | |
174 | struct addrinfo hints, *res; | |
175 | ||
176 | /* | |
177 | * If we are running as root and want to connect to a privileged | |
178 | * port, bind our own socket to a privileged port. | |
179 | */ | |
180 | if (privileged) { | |
181 | int p = IPPORT_RESERVED - 1; | |
182 | sock = rresvport_af(&p, family); | |
183 | if (sock < 0) | |
184 | error("rresvport: af=%d %.100s", family, strerror(errno)); | |
185 | else | |
186 | debug("Allocated local port %d.", p); | |
187 | return sock; | |
188 | } | |
189 | /* | |
190 | * Just create an ordinary socket on arbitrary port. We use | |
191 | * the user's uid to create the socket. | |
192 | */ | |
193 | temporarily_use_uid(pw); | |
194 | sock = socket(family, SOCK_STREAM, 0); | |
195 | if (sock < 0) | |
196 | error("socket: %.100s", strerror(errno)); | |
197 | restore_uid(); | |
198 | ||
199 | /* Bind the socket to an alternative local IP address */ | |
200 | if (options.bind_address == NULL) | |
201 | return sock; | |
202 | ||
203 | memset(&hints, 0, sizeof(hints)); | |
204 | hints.ai_family = family; | |
205 | hints.ai_socktype = SOCK_STREAM; | |
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 | /* | |
225 | * Opens a TCP/IP connection to the remote server on the given host. | |
226 | * The address of the remote host will be returned in hostaddr. | |
227 | * If port is 0, the default port will be used. If anonymous is zero, | |
228 | * a privileged port will be allocated to make the connection. | |
229 | * This requires super-user privileges if anonymous is false. | |
230 | * Connection_attempts specifies the maximum number of tries (one per | |
231 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
232 | * and %p substituted for host and port, respectively) to use to contact | |
233 | * the daemon. | |
234 | * Return values: | |
235 | * 0 for OK | |
236 | * ECONNREFUSED if we got a "Connection Refused" by the peer on any address | |
237 | * ECONNABORTED if we failed without a "Connection refused" | |
238 | * Suitable error messages for the connection failure will already have been | |
239 | * printed. | |
240 | */ | |
241 | int | |
242 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
243 | u_short port, int family, int connection_attempts, | |
244 | int anonymous, struct passwd *pw, const char *proxy_command) | |
245 | { | |
246 | int gaierr; | |
247 | int on = 1; | |
248 | int sock = -1, attempt; | |
249 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
250 | struct addrinfo hints, *ai, *aitop; | |
251 | struct linger linger; | |
252 | struct servent *sp; | |
253 | /* | |
254 | * Did we get only other errors than "Connection refused" (which | |
255 | * should block fallback to rsh and similar), or did we get at least | |
256 | * one "Connection refused"? | |
257 | */ | |
258 | int full_failure = 1; | |
259 | ||
260 | debug("ssh_connect: getuid %u geteuid %u anon %d", | |
261 | (u_int) getuid(), (u_int) geteuid(), anonymous); | |
262 | ||
263 | /* Get default port if port has not been set. */ | |
264 | if (port == 0) { | |
265 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
266 | if (sp) | |
267 | port = ntohs(sp->s_port); | |
268 | else | |
269 | port = SSH_DEFAULT_PORT; | |
270 | } | |
271 | /* If a proxy command is given, connect using it. */ | |
272 | if (proxy_command != NULL) | |
273 | return ssh_proxy_connect(host, port, pw, proxy_command); | |
274 | ||
275 | /* No proxy command. */ | |
276 | ||
277 | memset(&hints, 0, sizeof(hints)); | |
278 | hints.ai_family = family; | |
279 | hints.ai_socktype = SOCK_STREAM; | |
280 | snprintf(strport, sizeof strport, "%d", port); | |
281 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
282 | fatal("%s: %.100s: %s", __progname, host, | |
283 | gai_strerror(gaierr)); | |
284 | ||
285 | /* | |
286 | * Try to connect several times. On some machines, the first time | |
287 | * will sometimes fail. In general socket code appears to behave | |
288 | * quite magically on many machines. | |
289 | */ | |
290 | for (attempt = 0; ;) { | |
291 | if (attempt > 0) | |
292 | debug("Trying again..."); | |
293 | ||
294 | /* Loop through addresses for this host, and try each one in | |
295 | sequence until the connection succeeds. */ | |
296 | for (ai = aitop; ai; ai = ai->ai_next) { | |
297 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
298 | continue; | |
299 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
300 | ntop, sizeof(ntop), strport, sizeof(strport), | |
301 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
302 | error("ssh_connect: getnameinfo failed"); | |
303 | continue; | |
304 | } | |
305 | debug("Connecting to %.200s [%.100s] port %s.", | |
306 | host, ntop, strport); | |
307 | ||
308 | /* Create a socket for connecting. */ | |
309 | sock = ssh_create_socket(pw, | |
310 | #ifdef HAVE_CYGWIN | |
311 | !anonymous, | |
312 | #else | |
313 | !anonymous && geteuid() == 0, | |
314 | #endif | |
315 | ai->ai_family); | |
316 | if (sock < 0) | |
317 | /* Any error is already output */ | |
318 | continue; | |
319 | ||
320 | /* Connect to the host. We use the user's uid in the | |
321 | * hope that it will help with tcp_wrappers showing | |
322 | * the remote uid as root. | |
323 | */ | |
324 | temporarily_use_uid(pw); | |
325 | if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) { | |
326 | /* Successful connection. */ | |
327 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
328 | restore_uid(); | |
329 | break; | |
330 | } else { | |
331 | if (errno == ECONNREFUSED) | |
332 | full_failure = 0; | |
333 | log("ssh: connect to address %s port %s: %s", | |
334 | sockaddr_ntop(ai->ai_addr), strport, | |
335 | strerror(errno)); | |
336 | restore_uid(); | |
337 | /* | |
338 | * Close the failed socket; there appear to | |
339 | * be some problems when reusing a socket for | |
340 | * which connect() has already returned an | |
341 | * error. | |
342 | */ | |
343 | shutdown(sock, SHUT_RDWR); | |
344 | close(sock); | |
345 | } | |
346 | } | |
347 | if (ai) | |
348 | break; /* Successful connection. */ | |
349 | ||
350 | attempt++; | |
351 | if (attempt >= connection_attempts) | |
352 | break; | |
353 | /* Sleep a moment before retrying. */ | |
354 | sleep(1); | |
355 | } | |
356 | ||
357 | freeaddrinfo(aitop); | |
358 | ||
359 | /* Return failure if we didn't get a successful connection. */ | |
360 | if (attempt >= connection_attempts) | |
361 | return full_failure ? ECONNABORTED : ECONNREFUSED; | |
362 | ||
363 | debug("Connection established."); | |
364 | ||
365 | /* | |
366 | * Set socket options. We would like the socket to disappear as soon | |
367 | * as it has been closed for whatever reason. | |
368 | */ | |
369 | /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
370 | linger.l_onoff = 1; | |
371 | linger.l_linger = 5; | |
372 | setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger)); | |
373 | ||
374 | /* Set keepalives if requested. */ | |
375 | if (options.keepalives && | |
376 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
377 | sizeof(on)) < 0) | |
378 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
379 | ||
380 | /* Set the connection. */ | |
381 | packet_set_connection(sock, sock); | |
382 | ||
383 | return 0; | |
384 | } | |
385 | ||
386 | /* | |
387 | * Waits for the server identification string, and sends our own | |
388 | * identification string. | |
389 | */ | |
390 | static void | |
391 | ssh_exchange_identification(void) | |
392 | { | |
393 | char buf[256], remote_version[256]; /* must be same size! */ | |
394 | int remote_major, remote_minor, i, mismatch; | |
395 | int connection_in = packet_get_connection_in(); | |
396 | int connection_out = packet_get_connection_out(); | |
397 | int minor1 = PROTOCOL_MINOR_1; | |
398 | ||
399 | /* Read other side\'s version identification. */ | |
400 | for (;;) { | |
401 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
402 | int len = atomicio(read, connection_in, &buf[i], 1); | |
403 | if (len < 0) | |
404 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
405 | if (len != 1) | |
406 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
407 | if (buf[i] == '\r') { | |
408 | buf[i] = '\n'; | |
409 | buf[i + 1] = 0; | |
410 | continue; /**XXX wait for \n */ | |
411 | } | |
412 | if (buf[i] == '\n') { | |
413 | buf[i + 1] = 0; | |
414 | break; | |
415 | } | |
416 | } | |
417 | buf[sizeof(buf) - 1] = 0; | |
418 | if (strncmp(buf, "SSH-", 4) == 0) | |
419 | break; | |
420 | debug("ssh_exchange_identification: %s", buf); | |
421 | } | |
422 | server_version_string = xstrdup(buf); | |
423 | ||
424 | /* | |
425 | * Check that the versions match. In future this might accept | |
426 | * several versions and set appropriate flags to handle them. | |
427 | */ | |
428 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
429 | &remote_major, &remote_minor, remote_version) != 3) | |
430 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
431 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
432 | remote_major, remote_minor, remote_version); | |
433 | ||
434 | compat_datafellows(remote_version); | |
435 | mismatch = 0; | |
436 | ||
437 | switch(remote_major) { | |
438 | case 1: | |
439 | if (remote_minor == 99 && | |
440 | (options.protocol & SSH_PROTO_2) && | |
441 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
442 | enable_compat20(); | |
443 | break; | |
444 | } | |
445 | if (!(options.protocol & SSH_PROTO_1)) { | |
446 | mismatch = 1; | |
447 | break; | |
448 | } | |
449 | if (remote_minor < 3) { | |
450 | fatal("Remote machine has too old SSH software version."); | |
451 | } else if (remote_minor == 3 || remote_minor == 4) { | |
452 | /* We speak 1.3, too. */ | |
453 | enable_compat13(); | |
454 | minor1 = 3; | |
455 | if (options.forward_agent) { | |
456 | log("Agent forwarding disabled for protocol 1.3"); | |
457 | options.forward_agent = 0; | |
458 | } | |
459 | } | |
460 | break; | |
461 | case 2: | |
462 | if (options.protocol & SSH_PROTO_2) { | |
463 | enable_compat20(); | |
464 | break; | |
465 | } | |
466 | /* FALLTHROUGH */ | |
467 | default: | |
468 | mismatch = 1; | |
469 | break; | |
470 | } | |
471 | if (mismatch) | |
472 | fatal("Protocol major versions differ: %d vs. %d", | |
473 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
474 | remote_major); | |
475 | /* Send our own protocol version identification. */ | |
476 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
477 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
478 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
479 | SSH_VERSION); | |
480 | if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf)) | |
481 | fatal("write: %.100s", strerror(errno)); | |
482 | client_version_string = xstrdup(buf); | |
483 | chop(client_version_string); | |
484 | chop(server_version_string); | |
485 | debug("Local version string %.100s", client_version_string); | |
486 | } | |
487 | ||
488 | /* defaults to 'no' */ | |
489 | static int | |
490 | confirm(const char *prompt) | |
491 | { | |
492 | char buf[1024]; | |
493 | FILE *f; | |
494 | int retval = -1; | |
495 | ||
496 | if (options.batch_mode) | |
497 | return 0; | |
498 | if (isatty(STDIN_FILENO)) | |
499 | f = stdin; | |
500 | else | |
501 | f = fopen(_PATH_TTY, "rw"); | |
502 | if (f == NULL) | |
503 | return 0; | |
504 | fflush(stdout); | |
505 | fprintf(stderr, "%s", prompt); | |
506 | while (1) { | |
507 | if (fgets(buf, sizeof(buf), f) == NULL) { | |
508 | fprintf(stderr, "\n"); | |
509 | strlcpy(buf, "no", sizeof buf); | |
510 | } | |
511 | /* Remove newline from response. */ | |
512 | if (strchr(buf, '\n')) | |
513 | *strchr(buf, '\n') = 0; | |
514 | if (strcmp(buf, "yes") == 0) | |
515 | retval = 1; | |
516 | else if (strcmp(buf, "no") == 0) | |
517 | retval = 0; | |
518 | else | |
519 | fprintf(stderr, "Please type 'yes' or 'no': "); | |
520 | ||
521 | if (retval != -1) { | |
522 | if (f != stdin) | |
523 | fclose(f); | |
524 | return retval; | |
525 | } | |
526 | } | |
527 | } | |
528 | ||
529 | /* | |
530 | * check whether the supplied host key is valid, return -1 if the key | |
531 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
532 | */ | |
533 | ||
534 | static int | |
535 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
536 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
537 | { | |
538 | Key *file_key; | |
539 | char *type = key_type(host_key); | |
540 | char *ip = NULL; | |
541 | char hostline[1000], *hostp, *fp; | |
542 | HostStatus host_status; | |
543 | HostStatus ip_status; | |
544 | int local = 0, host_ip_differ = 0; | |
545 | int salen; | |
546 | char ntop[NI_MAXHOST]; | |
547 | int host_line, ip_line; | |
548 | const char *host_file = NULL, *ip_file = NULL; | |
549 | ||
550 | /* | |
551 | * Force accepting of the host key for loopback/localhost. The | |
552 | * problem is that if the home directory is NFS-mounted to multiple | |
553 | * machines, localhost will refer to a different machine in each of | |
554 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
555 | * essentially disables host authentication for localhost; however, | |
556 | * this is probably not a real problem. | |
557 | */ | |
558 | /** hostaddr == 0! */ | |
559 | switch (hostaddr->sa_family) { | |
560 | case AF_INET: | |
561 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
562 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
563 | salen = sizeof(struct sockaddr_in); | |
564 | break; | |
565 | case AF_INET6: | |
566 | local = IN6_IS_ADDR_LOOPBACK( | |
567 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
568 | salen = sizeof(struct sockaddr_in6); | |
569 | break; | |
570 | default: | |
571 | local = 0; | |
572 | salen = sizeof(struct sockaddr_storage); | |
573 | break; | |
574 | } | |
575 | if (options.no_host_authentication_for_localhost == 1 && local && | |
576 | options.host_key_alias == NULL) { | |
577 | debug("Forcing accepting of host key for " | |
578 | "loopback/localhost."); | |
579 | return 0; | |
580 | } | |
581 | ||
582 | /* | |
583 | * We don't have the remote ip-address for connections | |
584 | * using a proxy command | |
585 | */ | |
586 | if (options.proxy_command == NULL) { | |
587 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
588 | NULL, 0, NI_NUMERICHOST) != 0) | |
589 | fatal("check_host_key: getnameinfo failed"); | |
590 | ip = xstrdup(ntop); | |
591 | } else { | |
592 | ip = xstrdup("<no hostip for proxy command>"); | |
593 | } | |
594 | /* | |
595 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
596 | * command or if we don't have a hostname to compare with | |
597 | */ | |
598 | if (options.check_host_ip && | |
599 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
600 | options.check_host_ip = 0; | |
601 | ||
602 | /* | |
603 | * Allow the user to record the key under a different name. This is | |
604 | * useful for ssh tunneling over forwarded connections or if you run | |
605 | * multiple sshd's on different ports on the same machine. | |
606 | */ | |
607 | if (options.host_key_alias != NULL) { | |
608 | host = options.host_key_alias; | |
609 | debug("using hostkeyalias: %s", host); | |
610 | } | |
611 | ||
612 | /* | |
613 | * Store the host key from the known host file in here so that we can | |
614 | * compare it with the key for the IP address. | |
615 | */ | |
616 | file_key = key_new(host_key->type); | |
617 | ||
618 | /* | |
619 | * Check if the host key is present in the user\'s list of known | |
620 | * hosts or in the systemwide list. | |
621 | */ | |
622 | host_file = user_hostfile; | |
623 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
624 | file_key, &host_line); | |
625 | if (host_status == HOST_NEW) { | |
626 | host_file = system_hostfile; | |
627 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
628 | file_key, &host_line); | |
629 | } | |
630 | /* | |
631 | * Also perform check for the ip address, skip the check if we are | |
632 | * localhost or the hostname was an ip address to begin with | |
633 | */ | |
634 | if (options.check_host_ip) { | |
635 | Key *ip_key = key_new(host_key->type); | |
636 | ||
637 | ip_file = user_hostfile; | |
638 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
639 | ip_key, &ip_line); | |
640 | if (ip_status == HOST_NEW) { | |
641 | ip_file = system_hostfile; | |
642 | ip_status = check_host_in_hostfile(ip_file, ip, | |
643 | host_key, ip_key, &ip_line); | |
644 | } | |
645 | if (host_status == HOST_CHANGED && | |
646 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
647 | host_ip_differ = 1; | |
648 | ||
649 | key_free(ip_key); | |
650 | } else | |
651 | ip_status = host_status; | |
652 | ||
653 | key_free(file_key); | |
654 | ||
655 | switch (host_status) { | |
656 | case HOST_OK: | |
657 | /* The host is known and the key matches. */ | |
658 | debug("Host '%.200s' is known and matches the %s host key.", | |
659 | host, type); | |
660 | debug("Found key in %s:%d", host_file, host_line); | |
661 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
662 | if (readonly) | |
663 | log("%s host key for IP address " | |
664 | "'%.128s' not in list of known hosts.", | |
665 | type, ip); | |
666 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
667 | host_key)) | |
668 | log("Failed to add the %s host key for IP " | |
669 | "address '%.128s' to the list of known " | |
670 | "hosts (%.30s).", type, ip, user_hostfile); | |
671 | else | |
672 | log("Warning: Permanently added the %s host " | |
673 | "key for IP address '%.128s' to the list " | |
674 | "of known hosts.", type, ip); | |
675 | } | |
676 | break; | |
677 | case HOST_NEW: | |
678 | if (readonly) | |
679 | goto fail; | |
680 | /* The host is new. */ | |
681 | if (options.strict_host_key_checking == 1) { | |
682 | /* | |
683 | * User has requested strict host key checking. We | |
684 | * will not add the host key automatically. The only | |
685 | * alternative left is to abort. | |
686 | */ | |
687 | error("No %s host key is known for %.200s and you " | |
688 | "have requested strict checking.", type, host); | |
689 | goto fail; | |
690 | } else if (options.strict_host_key_checking == 2) { | |
691 | /* The default */ | |
692 | char prompt[1024]; | |
693 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
694 | snprintf(prompt, sizeof(prompt), | |
695 | "The authenticity of host '%.200s (%s)' can't be " | |
696 | "established.\n" | |
697 | "%s key fingerprint is %s.\n" | |
698 | "Are you sure you want to continue connecting " | |
699 | "(yes/no)? ", host, ip, type, fp); | |
700 | xfree(fp); | |
701 | if (!confirm(prompt)) { | |
702 | goto fail; | |
703 | } | |
704 | } | |
705 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
706 | snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); | |
707 | hostp = hostline; | |
708 | } else | |
709 | hostp = host; | |
710 | ||
711 | /* | |
712 | * If not in strict mode, add the key automatically to the | |
713 | * local known_hosts file. | |
714 | */ | |
715 | if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) | |
716 | log("Failed to add the host to the list of known " | |
717 | "hosts (%.500s).", user_hostfile); | |
718 | else | |
719 | log("Warning: Permanently added '%.200s' (%s) to the " | |
720 | "list of known hosts.", hostp, type); | |
721 | break; | |
722 | case HOST_CHANGED: | |
723 | if (options.check_host_ip && host_ip_differ) { | |
724 | char *msg; | |
725 | if (ip_status == HOST_NEW) | |
726 | msg = "is unknown"; | |
727 | else if (ip_status == HOST_OK) | |
728 | msg = "is unchanged"; | |
729 | else | |
730 | msg = "has a different value"; | |
731 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
732 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
733 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
734 | error("The %s host key for %s has changed,", type, host); | |
735 | error("and the key for the according IP address %s", ip); | |
736 | error("%s. This could either mean that", msg); | |
737 | error("DNS SPOOFING is happening or the IP address for the host"); | |
738 | error("and its host key have changed at the same time."); | |
739 | if (ip_status != HOST_NEW) | |
740 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
741 | } | |
742 | /* The host key has changed. */ | |
743 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
744 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
745 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
746 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
747 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
748 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
749 | error("It is also possible that the %s host key has just been changed.", type); | |
750 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
751 | type, fp); | |
752 | error("Please contact your system administrator."); | |
753 | error("Add correct host key in %.100s to get rid of this message.", | |
754 | user_hostfile); | |
755 | error("Offending key in %s:%d", host_file, host_line); | |
756 | xfree(fp); | |
757 | ||
758 | /* | |
759 | * If strict host key checking is in use, the user will have | |
760 | * to edit the key manually and we can only abort. | |
761 | */ | |
762 | if (options.strict_host_key_checking) { | |
763 | error("%s host key for %.200s has changed and you have " | |
764 | "requested strict checking.", type, host); | |
765 | goto fail; | |
766 | } | |
767 | ||
768 | /* | |
769 | * If strict host key checking has not been requested, allow | |
770 | * the connection but without password authentication or | |
771 | * agent forwarding. | |
772 | */ | |
773 | if (options.password_authentication) { | |
774 | error("Password authentication is disabled to avoid " | |
775 | "man-in-the-middle attacks."); | |
776 | options.password_authentication = 0; | |
777 | } | |
778 | if (options.forward_agent) { | |
779 | error("Agent forwarding is disabled to avoid " | |
780 | "man-in-the-middle attacks."); | |
781 | options.forward_agent = 0; | |
782 | } | |
783 | if (options.forward_x11) { | |
784 | error("X11 forwarding is disabled to avoid " | |
785 | "man-in-the-middle attacks."); | |
786 | options.forward_x11 = 0; | |
787 | } | |
788 | if (options.num_local_forwards > 0 || | |
789 | options.num_remote_forwards > 0) { | |
790 | error("Port forwarding is disabled to avoid " | |
791 | "man-in-the-middle attacks."); | |
792 | options.num_local_forwards = | |
793 | options.num_remote_forwards = 0; | |
794 | } | |
795 | /* | |
796 | * XXX Should permit the user to change to use the new id. | |
797 | * This could be done by converting the host key to an | |
798 | * identifying sentence, tell that the host identifies itself | |
799 | * by that sentence, and ask the user if he/she whishes to | |
800 | * accept the authentication. | |
801 | */ | |
802 | break; | |
803 | } | |
804 | ||
805 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
806 | ip_status == HOST_CHANGED) { | |
807 | log("Warning: the %s host key for '%.200s' " | |
808 | "differs from the key for the IP address '%.128s'", | |
809 | type, host, ip); | |
810 | if (host_status == HOST_OK) | |
811 | log("Matching host key in %s:%d", host_file, host_line); | |
812 | log("Offending key for IP in %s:%d", ip_file, ip_line); | |
813 | if (options.strict_host_key_checking == 1) { | |
814 | error("Exiting, you have requested strict checking."); | |
815 | goto fail; | |
816 | } else if (options.strict_host_key_checking == 2) { | |
817 | if (!confirm("Are you sure you want " | |
818 | "to continue connecting (yes/no)? ")) { | |
819 | goto fail; | |
820 | } | |
821 | } | |
822 | } | |
823 | ||
824 | xfree(ip); | |
825 | return 0; | |
826 | ||
827 | fail: | |
828 | xfree(ip); | |
829 | return -1; | |
830 | } | |
831 | ||
832 | int | |
833 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
834 | { | |
835 | struct stat st; | |
836 | ||
837 | /* return ok if the key can be found in an old keyfile */ | |
838 | if (stat(options.system_hostfile2, &st) == 0 || | |
839 | stat(options.user_hostfile2, &st) == 0) { | |
840 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
841 | options.user_hostfile2, options.system_hostfile2) == 0) | |
842 | return 0; | |
843 | } | |
844 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
845 | options.user_hostfile, options.system_hostfile); | |
846 | } | |
847 | ||
848 | /* | |
849 | * Starts a dialog with the server, and authenticates the current user on the | |
850 | * server. This does not need any extra privileges. The basic connection | |
851 | * to the server must already have been established before this is called. | |
852 | * If login fails, this function prints an error and never returns. | |
853 | * This function does not require super-user privileges. | |
854 | */ | |
855 | void | |
856 | ssh_login(Key **keys, int nkeys, const char *orighost, | |
857 | struct sockaddr *hostaddr, struct passwd *pw) | |
858 | { | |
859 | char *host, *cp; | |
860 | char *server_user, *local_user; | |
861 | ||
862 | local_user = xstrdup(pw->pw_name); | |
863 | server_user = options.user ? options.user : local_user; | |
864 | ||
865 | /* Convert the user-supplied hostname into all lowercase. */ | |
866 | host = xstrdup(orighost); | |
867 | for (cp = host; *cp; cp++) | |
868 | if (isupper(*cp)) | |
869 | *cp = tolower(*cp); | |
870 | ||
871 | /* Exchange protocol version identification strings with the server. */ | |
872 | ssh_exchange_identification(); | |
873 | ||
874 | /* Put the connection into non-blocking mode. */ | |
875 | packet_set_nonblocking(); | |
876 | ||
877 | /* key exchange */ | |
878 | /* authenticate user */ | |
879 | if (compat20) { | |
880 | ssh_kex2(host, hostaddr); | |
881 | ssh_userauth2(local_user, server_user, host, keys, nkeys); | |
882 | } else { | |
883 | ssh_kex(host, hostaddr); | |
884 | ssh_userauth1(local_user, server_user, host, keys, nkeys); | |
885 | } | |
886 | } | |
887 | ||
888 | void | |
889 | ssh_put_password(char *password) | |
890 | { | |
891 | int size; | |
892 | char *padded; | |
893 | ||
894 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
895 | packet_put_cstring(password); | |
896 | return; | |
897 | } | |
898 | size = roundup(strlen(password) + 1, 32); | |
899 | padded = xmalloc(size); | |
900 | memset(padded, 0, size); | |
901 | strlcpy(padded, password, size); | |
902 | packet_put_string(padded, size); | |
903 | memset(padded, 0, size); | |
904 | xfree(padded); | |
905 | } |