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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 1.96 2001/02/08 22:35:30 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 | /* AF_UNSPEC or AF_INET or AF_INET6 */ | |
42 | extern int IPv4or6; | |
43 | ||
44 | /* | |
45 | * Connect to the given ssh server using a proxy command. | |
46 | */ | |
47 | int | |
48 | ssh_proxy_connect(const char *host, u_short port, uid_t original_real_uid, | |
49 | const char *proxy_command) | |
50 | { | |
51 | Buffer command; | |
52 | const char *cp; | |
53 | char *command_string; | |
54 | int pin[2], pout[2]; | |
55 | pid_t pid; | |
56 | char strport[NI_MAXSERV]; | |
57 | ||
58 | /* Convert the port number into a string. */ | |
59 | snprintf(strport, sizeof strport, "%hu", port); | |
60 | ||
61 | /* Build the final command string in the buffer by making the | |
62 | appropriate substitutions to the given proxy command. */ | |
63 | buffer_init(&command); | |
64 | for (cp = proxy_command; *cp; cp++) { | |
65 | if (cp[0] == '%' && cp[1] == '%') { | |
66 | buffer_append(&command, "%", 1); | |
67 | cp++; | |
68 | continue; | |
69 | } | |
70 | if (cp[0] == '%' && cp[1] == 'h') { | |
71 | buffer_append(&command, host, strlen(host)); | |
72 | cp++; | |
73 | continue; | |
74 | } | |
75 | if (cp[0] == '%' && cp[1] == 'p') { | |
76 | buffer_append(&command, strport, strlen(strport)); | |
77 | cp++; | |
78 | continue; | |
79 | } | |
80 | buffer_append(&command, cp, 1); | |
81 | } | |
82 | buffer_append(&command, "\0", 1); | |
83 | ||
84 | /* Get the final command string. */ | |
85 | command_string = buffer_ptr(&command); | |
86 | ||
87 | /* Create pipes for communicating with the proxy. */ | |
88 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
89 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
90 | strerror(errno)); | |
91 | ||
92 | debug("Executing proxy command: %.500s", command_string); | |
93 | ||
94 | /* Fork and execute the proxy command. */ | |
95 | if ((pid = fork()) == 0) { | |
96 | char *argv[10]; | |
97 | ||
98 | /* Child. Permanently give up superuser privileges. */ | |
99 | permanently_set_uid(original_real_uid); | |
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)); | |
130 | ||
131 | /* Close child side of the descriptors. */ | |
132 | close(pin[0]); | |
133 | close(pout[1]); | |
134 | ||
135 | /* Free the command name. */ | |
136 | buffer_free(&command); | |
137 | ||
138 | /* Set the connection file descriptors. */ | |
139 | packet_set_connection(pout[0], pin[1]); | |
140 | ||
141 | return 1; | |
142 | } | |
143 | ||
144 | /* | |
145 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
146 | */ | |
147 | int | |
148 | ssh_create_socket(uid_t original_real_uid, int privileged, int family) | |
149 | { | |
150 | int sock; | |
151 | ||
152 | /* | |
153 | * If we are running as root and want to connect to a privileged | |
154 | * port, bind our own socket to a privileged port. | |
155 | */ | |
156 | if (privileged) { | |
157 | int p = IPPORT_RESERVED - 1; | |
158 | sock = rresvport_af(&p, family); | |
159 | if (sock < 0) | |
160 | error("rresvport: af=%d %.100s", family, strerror(errno)); | |
161 | else | |
162 | debug("Allocated local port %d.", p); | |
163 | } else { | |
164 | /* | |
165 | * Just create an ordinary socket on arbitrary port. We use | |
166 | * the user's uid to create the socket. | |
167 | */ | |
168 | temporarily_use_uid(original_real_uid); | |
169 | sock = socket(family, SOCK_STREAM, 0); | |
170 | if (sock < 0) | |
171 | error("socket: %.100s", strerror(errno)); | |
172 | restore_uid(); | |
173 | } | |
174 | return sock; | |
175 | } | |
176 | ||
177 | /* | |
178 | * Opens a TCP/IP connection to the remote server on the given host. | |
179 | * The address of the remote host will be returned in hostaddr. | |
180 | * If port is 0, the default port will be used. If anonymous is zero, | |
181 | * a privileged port will be allocated to make the connection. | |
182 | * This requires super-user privileges if anonymous is false. | |
183 | * Connection_attempts specifies the maximum number of tries (one per | |
184 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
185 | * and %p substituted for host and port, respectively) to use to contact | |
186 | * the daemon. | |
187 | */ | |
188 | int | |
189 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
190 | u_short port, int connection_attempts, | |
191 | int anonymous, uid_t original_real_uid, | |
192 | const char *proxy_command) | |
193 | { | |
194 | int gaierr; | |
195 | int on = 1; | |
196 | int sock = -1, attempt; | |
197 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
198 | struct addrinfo hints, *ai, *aitop; | |
199 | struct linger linger; | |
200 | struct servent *sp; | |
201 | ||
202 | debug("ssh_connect: getuid %u geteuid %u anon %d", | |
203 | (u_int) getuid(), (u_int) geteuid(), anonymous); | |
204 | ||
205 | /* Get default port if port has not been set. */ | |
206 | if (port == 0) { | |
207 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
208 | if (sp) | |
209 | port = ntohs(sp->s_port); | |
210 | else | |
211 | port = SSH_DEFAULT_PORT; | |
212 | } | |
213 | /* If a proxy command is given, connect using it. */ | |
214 | if (proxy_command != NULL) | |
215 | return ssh_proxy_connect(host, port, original_real_uid, proxy_command); | |
216 | ||
217 | /* No proxy command. */ | |
218 | ||
219 | memset(&hints, 0, sizeof(hints)); | |
220 | hints.ai_family = IPv4or6; | |
221 | hints.ai_socktype = SOCK_STREAM; | |
222 | snprintf(strport, sizeof strport, "%d", port); | |
223 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
224 | fatal("%s: %.100s: %s", __progname, host, | |
225 | gai_strerror(gaierr)); | |
226 | ||
227 | /* | |
228 | * Try to connect several times. On some machines, the first time | |
229 | * will sometimes fail. In general socket code appears to behave | |
230 | * quite magically on many machines. | |
231 | */ | |
232 | for (attempt = 0; attempt < connection_attempts; attempt++) { | |
233 | if (attempt > 0) | |
234 | debug("Trying again..."); | |
235 | ||
236 | /* Loop through addresses for this host, and try each one in | |
237 | sequence until the connection succeeds. */ | |
238 | for (ai = aitop; ai; ai = ai->ai_next) { | |
239 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
240 | continue; | |
241 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
242 | ntop, sizeof(ntop), strport, sizeof(strport), | |
243 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
244 | error("ssh_connect: getnameinfo failed"); | |
245 | continue; | |
246 | } | |
247 | debug("Connecting to %.200s [%.100s] port %s.", | |
248 | host, ntop, strport); | |
249 | ||
250 | /* Create a socket for connecting. */ | |
251 | sock = ssh_create_socket(original_real_uid, | |
252 | #ifdef HAVE_CYGWIN | |
253 | !anonymous, | |
254 | #else | |
255 | !anonymous && geteuid() == 0, | |
256 | #endif | |
257 | ai->ai_family); | |
258 | if (sock < 0) | |
259 | continue; | |
260 | ||
261 | /* Connect to the host. We use the user's uid in the | |
262 | * hope that it will help with tcp_wrappers showing | |
263 | * the remote uid as root. | |
264 | */ | |
265 | temporarily_use_uid(original_real_uid); | |
266 | if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) { | |
267 | /* Successful connection. */ | |
268 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
269 | restore_uid(); | |
270 | break; | |
271 | } else { | |
272 | debug("connect: %.100s", strerror(errno)); | |
273 | restore_uid(); | |
274 | /* | |
275 | * Close the failed socket; there appear to | |
276 | * be some problems when reusing a socket for | |
277 | * which connect() has already returned an | |
278 | * error. | |
279 | */ | |
280 | shutdown(sock, SHUT_RDWR); | |
281 | close(sock); | |
282 | } | |
283 | } | |
284 | if (ai) | |
285 | break; /* Successful connection. */ | |
286 | ||
287 | /* Sleep a moment before retrying. */ | |
288 | sleep(1); | |
289 | } | |
290 | ||
291 | freeaddrinfo(aitop); | |
292 | ||
293 | /* Return failure if we didn't get a successful connection. */ | |
294 | if (attempt >= connection_attempts) | |
295 | return 0; | |
296 | ||
297 | debug("Connection established."); | |
298 | ||
299 | /* | |
300 | * Set socket options. We would like the socket to disappear as soon | |
301 | * as it has been closed for whatever reason. | |
302 | */ | |
303 | /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
304 | linger.l_onoff = 1; | |
305 | linger.l_linger = 5; | |
306 | setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger)); | |
307 | ||
308 | /* Set keepalives if requested. */ | |
309 | if (options.keepalives && | |
310 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
311 | sizeof(on)) < 0) | |
312 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
313 | ||
314 | /* Set the connection. */ | |
315 | packet_set_connection(sock, sock); | |
316 | ||
317 | return 1; | |
318 | } | |
319 | ||
320 | /* | |
321 | * Waits for the server identification string, and sends our own | |
322 | * identification string. | |
323 | */ | |
324 | void | |
325 | ssh_exchange_identification(void) | |
326 | { | |
327 | char buf[256], remote_version[256]; /* must be same size! */ | |
328 | int remote_major, remote_minor, i, mismatch; | |
329 | int connection_in = packet_get_connection_in(); | |
330 | int connection_out = packet_get_connection_out(); | |
331 | int minor1 = PROTOCOL_MINOR_1; | |
332 | ||
333 | /* Read other side\'s version identification. */ | |
334 | for (;;) { | |
335 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
336 | int len = atomicio(read, connection_in, &buf[i], 1); | |
337 | if (len < 0) | |
338 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
339 | if (len != 1) | |
340 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
341 | if (buf[i] == '\r') { | |
342 | buf[i] = '\n'; | |
343 | buf[i + 1] = 0; | |
344 | continue; /**XXX wait for \n */ | |
345 | } | |
346 | if (buf[i] == '\n') { | |
347 | buf[i + 1] = 0; | |
348 | break; | |
349 | } | |
350 | } | |
351 | buf[sizeof(buf) - 1] = 0; | |
352 | if (strncmp(buf, "SSH-", 4) == 0) | |
353 | break; | |
354 | debug("ssh_exchange_identification: %s", buf); | |
355 | } | |
356 | server_version_string = xstrdup(buf); | |
357 | ||
358 | /* | |
359 | * Check that the versions match. In future this might accept | |
360 | * several versions and set appropriate flags to handle them. | |
361 | */ | |
362 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
363 | &remote_major, &remote_minor, remote_version) != 3) | |
364 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
365 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
366 | remote_major, remote_minor, remote_version); | |
367 | ||
368 | compat_datafellows(remote_version); | |
369 | mismatch = 0; | |
370 | ||
371 | switch(remote_major) { | |
372 | case 1: | |
373 | if (remote_minor == 99 && | |
374 | (options.protocol & SSH_PROTO_2) && | |
375 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
376 | enable_compat20(); | |
377 | break; | |
378 | } | |
379 | if (!(options.protocol & SSH_PROTO_1)) { | |
380 | mismatch = 1; | |
381 | break; | |
382 | } | |
383 | if (remote_minor < 3) { | |
384 | fatal("Remote machine has too old SSH software version."); | |
385 | } else if (remote_minor == 3 || remote_minor == 4) { | |
386 | /* We speak 1.3, too. */ | |
387 | enable_compat13(); | |
388 | minor1 = 3; | |
389 | if (options.forward_agent) { | |
390 | log("Agent forwarding disabled for protocol 1.3"); | |
391 | options.forward_agent = 0; | |
392 | } | |
393 | } | |
394 | break; | |
395 | case 2: | |
396 | if (options.protocol & SSH_PROTO_2) { | |
397 | enable_compat20(); | |
398 | break; | |
399 | } | |
400 | /* FALLTHROUGH */ | |
401 | default: | |
402 | mismatch = 1; | |
403 | break; | |
404 | } | |
405 | if (mismatch) | |
406 | fatal("Protocol major versions differ: %d vs. %d", | |
407 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
408 | remote_major); | |
409 | if (compat20) | |
410 | packet_set_ssh2_format(); | |
411 | /* Send our own protocol version identification. */ | |
412 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
413 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
414 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
415 | SSH_VERSION); | |
416 | if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf)) | |
417 | fatal("write: %.100s", strerror(errno)); | |
418 | client_version_string = xstrdup(buf); | |
419 | chop(client_version_string); | |
420 | chop(server_version_string); | |
421 | debug("Local version string %.100s", client_version_string); | |
422 | } | |
423 | ||
424 | /* defaults to 'no' */ | |
425 | int | |
426 | read_yes_or_no(const char *prompt, int defval) | |
427 | { | |
428 | char buf[1024]; | |
429 | FILE *f; | |
430 | int retval = -1; | |
431 | ||
432 | if (options.batch_mode) | |
433 | return 0; | |
434 | ||
435 | if (isatty(STDIN_FILENO)) | |
436 | f = stdin; | |
437 | else | |
438 | f = fopen(_PATH_TTY, "rw"); | |
439 | ||
440 | if (f == NULL) | |
441 | return 0; | |
442 | ||
443 | fflush(stdout); | |
444 | ||
445 | while (1) { | |
446 | fprintf(stderr, "%s", prompt); | |
447 | if (fgets(buf, sizeof(buf), f) == NULL) { | |
448 | /* Print a newline (the prompt probably didn\'t have one). */ | |
449 | fprintf(stderr, "\n"); | |
450 | strlcpy(buf, "no", sizeof buf); | |
451 | } | |
452 | /* Remove newline from response. */ | |
453 | if (strchr(buf, '\n')) | |
454 | *strchr(buf, '\n') = 0; | |
455 | ||
456 | if (buf[0] == 0) | |
457 | retval = defval; | |
458 | if (strcmp(buf, "yes") == 0) | |
459 | retval = 1; | |
460 | else if (strcmp(buf, "no") == 0) | |
461 | retval = 0; | |
462 | else | |
463 | fprintf(stderr, "Please type 'yes' or 'no'.\n"); | |
464 | ||
465 | if (retval != -1) { | |
466 | if (f != stdin) | |
467 | fclose(f); | |
468 | return retval; | |
469 | } | |
470 | } | |
471 | } | |
472 | ||
473 | /* | |
474 | * check whether the supplied host key is valid, return only if ok. | |
475 | */ | |
476 | ||
477 | void | |
478 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
479 | const char *user_hostfile, const char *system_hostfile) | |
480 | { | |
481 | Key *file_key; | |
482 | char *type = key_type(host_key); | |
483 | char *ip = NULL; | |
484 | char hostline[1000], *hostp; | |
485 | HostStatus host_status; | |
486 | HostStatus ip_status; | |
487 | int local = 0, host_ip_differ = 0; | |
488 | int salen; | |
489 | char ntop[NI_MAXHOST]; | |
490 | int host_line, ip_line; | |
491 | const char *host_file = NULL, *ip_file = NULL; | |
492 | ||
493 | /* | |
494 | * Force accepting of the host key for loopback/localhost. The | |
495 | * problem is that if the home directory is NFS-mounted to multiple | |
496 | * machines, localhost will refer to a different machine in each of | |
497 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
498 | * essentially disables host authentication for localhost; however, | |
499 | * this is probably not a real problem. | |
500 | */ | |
501 | /** hostaddr == 0! */ | |
502 | switch (hostaddr->sa_family) { | |
503 | case AF_INET: | |
504 | local = (ntohl(((struct sockaddr_in *)hostaddr)->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
505 | salen = sizeof(struct sockaddr_in); | |
506 | break; | |
507 | case AF_INET6: | |
508 | local = IN6_IS_ADDR_LOOPBACK(&(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
509 | salen = sizeof(struct sockaddr_in6); | |
510 | break; | |
511 | default: | |
512 | local = 0; | |
513 | salen = sizeof(struct sockaddr_storage); | |
514 | break; | |
515 | } | |
516 | if (local && options.host_key_alias == NULL) { | |
517 | debug("Forcing accepting of host key for " | |
518 | "loopback/localhost."); | |
519 | return; | |
520 | } | |
521 | ||
522 | /* | |
523 | * We don't have the remote ip-address for connections | |
524 | * using a proxy command | |
525 | */ | |
526 | if (options.proxy_command == NULL) { | |
527 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
528 | NULL, 0, NI_NUMERICHOST) != 0) | |
529 | fatal("check_host_key: getnameinfo failed"); | |
530 | ip = xstrdup(ntop); | |
531 | } else { | |
532 | ip = xstrdup("<no hostip for proxy command>"); | |
533 | } | |
534 | /* | |
535 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
536 | * command or if we don't have a hostname to compare with | |
537 | */ | |
538 | if (options.check_host_ip && | |
539 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
540 | options.check_host_ip = 0; | |
541 | ||
542 | /* | |
543 | * Allow the user to record the key under a different name. This is | |
544 | * useful for ssh tunneling over forwarded connections or if you run | |
545 | * multiple sshd's on different ports on the same machine. | |
546 | */ | |
547 | if (options.host_key_alias != NULL) { | |
548 | host = options.host_key_alias; | |
549 | debug("using hostkeyalias: %s", host); | |
550 | } | |
551 | ||
552 | /* | |
553 | * Store the host key from the known host file in here so that we can | |
554 | * compare it with the key for the IP address. | |
555 | */ | |
556 | file_key = key_new(host_key->type); | |
557 | ||
558 | /* | |
559 | * Check if the host key is present in the user\'s list of known | |
560 | * hosts or in the systemwide list. | |
561 | */ | |
562 | host_file = user_hostfile; | |
563 | host_status = check_host_in_hostfile(host_file, host, host_key, file_key, &host_line); | |
564 | if (host_status == HOST_NEW) { | |
565 | host_file = system_hostfile; | |
566 | host_status = check_host_in_hostfile(host_file, host, host_key, file_key, &host_line); | |
567 | } | |
568 | /* | |
569 | * Also perform check for the ip address, skip the check if we are | |
570 | * localhost or the hostname was an ip address to begin with | |
571 | */ | |
572 | if (options.check_host_ip) { | |
573 | Key *ip_key = key_new(host_key->type); | |
574 | ||
575 | ip_file = user_hostfile; | |
576 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line); | |
577 | if (ip_status == HOST_NEW) { | |
578 | ip_file = system_hostfile; | |
579 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, ip_key, &ip_line); | |
580 | } | |
581 | if (host_status == HOST_CHANGED && | |
582 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
583 | host_ip_differ = 1; | |
584 | ||
585 | key_free(ip_key); | |
586 | } else | |
587 | ip_status = host_status; | |
588 | ||
589 | key_free(file_key); | |
590 | ||
591 | switch (host_status) { | |
592 | case HOST_OK: | |
593 | /* The host is known and the key matches. */ | |
594 | debug("Host '%.200s' is known and matches the %s host key.", | |
595 | host, type); | |
596 | debug("Found key in %s:%d", host_file, host_line); | |
597 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
598 | if (!add_host_to_hostfile(user_hostfile, ip, host_key)) | |
599 | log("Failed to add the %s host key for IP address '%.128s' to the list of known hosts (%.30s).", | |
600 | type, ip, user_hostfile); | |
601 | else | |
602 | log("Warning: Permanently added the %s host key for IP address '%.128s' to the list of known hosts.", | |
603 | type, ip); | |
604 | } | |
605 | break; | |
606 | case HOST_NEW: | |
607 | /* The host is new. */ | |
608 | if (options.strict_host_key_checking == 1) { | |
609 | /* User has requested strict host key checking. We will not add the host key | |
610 | automatically. The only alternative left is to abort. */ | |
611 | fatal("No %s host key is known for %.200s and you have requested strict checking.", type, host); | |
612 | } else if (options.strict_host_key_checking == 2) { | |
613 | /* The default */ | |
614 | char prompt[1024]; | |
615 | snprintf(prompt, sizeof(prompt), | |
616 | "The authenticity of host '%.200s (%s)' can't be established.\n" | |
617 | "%s key fingerprint is %s.\n" | |
618 | "Are you sure you want to continue connecting (yes/no)? ", | |
619 | host, ip, type, key_fingerprint(host_key)); | |
620 | if (!read_yes_or_no(prompt, -1)) | |
621 | fatal("Aborted by user!\n"); | |
622 | } | |
623 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
624 | snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); | |
625 | hostp = hostline; | |
626 | } else | |
627 | hostp = host; | |
628 | ||
629 | /* If not in strict mode, add the key automatically to the local known_hosts file. */ | |
630 | if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) | |
631 | log("Failed to add the host to the list of known hosts (%.500s).", | |
632 | user_hostfile); | |
633 | else | |
634 | log("Warning: Permanently added '%.200s' (%s) to the list of known hosts.", | |
635 | hostp, type); | |
636 | break; | |
637 | case HOST_CHANGED: | |
638 | if (options.check_host_ip && host_ip_differ) { | |
639 | char *msg; | |
640 | if (ip_status == HOST_NEW) | |
641 | msg = "is unknown"; | |
642 | else if (ip_status == HOST_OK) | |
643 | msg = "is unchanged"; | |
644 | else | |
645 | msg = "has a different value"; | |
646 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
647 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
648 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
649 | error("The %s host key for %s has changed,", type, host); | |
650 | error("and the key for the according IP address %s", ip); | |
651 | error("%s. This could either mean that", msg); | |
652 | error("DNS SPOOFING is happening or the IP address for the host"); | |
653 | error("and its host key have changed at the same time."); | |
654 | if (ip_status != HOST_NEW) | |
655 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
656 | } | |
657 | /* The host key has changed. */ | |
658 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
659 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
660 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
661 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
662 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
663 | error("It is also possible that the %s host key has just been changed.", type); | |
664 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
665 | type, key_fingerprint(host_key)); | |
666 | error("Please contact your system administrator."); | |
667 | error("Add correct host key in %.100s to get rid of this message.", | |
668 | user_hostfile); | |
669 | error("Offending key in %s:%d", host_file, host_line); | |
670 | ||
671 | /* | |
672 | * If strict host key checking is in use, the user will have | |
673 | * to edit the key manually and we can only abort. | |
674 | */ | |
675 | if (options.strict_host_key_checking) | |
676 | fatal("%s host key for %.200s has changed and you have requested strict checking.", type, host); | |
677 | ||
678 | /* | |
679 | * If strict host key checking has not been requested, allow | |
680 | * the connection but without password authentication or | |
681 | * agent forwarding. | |
682 | */ | |
683 | if (options.password_authentication) { | |
684 | error("Password authentication is disabled to avoid trojan horses."); | |
685 | options.password_authentication = 0; | |
686 | } | |
687 | if (options.forward_agent) { | |
688 | error("Agent forwarding is disabled to avoid trojan horses."); | |
689 | options.forward_agent = 0; | |
690 | } | |
691 | if (options.forward_x11) { | |
692 | error("X11 forwarding is disabled to avoid trojan horses."); | |
693 | options.forward_x11 = 0; | |
694 | } | |
695 | if (options.num_local_forwards > 0 || options.num_remote_forwards > 0) { | |
696 | error("Port forwarding is disabled to avoid trojan horses."); | |
697 | options.num_local_forwards = options.num_remote_forwards = 0; | |
698 | } | |
699 | /* | |
700 | * XXX Should permit the user to change to use the new id. | |
701 | * This could be done by converting the host key to an | |
702 | * identifying sentence, tell that the host identifies itself | |
703 | * by that sentence, and ask the user if he/she whishes to | |
704 | * accept the authentication. | |
705 | */ | |
706 | break; | |
707 | } | |
708 | ||
709 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
710 | ip_status == HOST_CHANGED) { | |
711 | log("Warning: the %s host key for '%.200s' " | |
712 | "differs from the key for the IP address '%.128s'", | |
713 | type, host, ip); | |
714 | if (host_status == HOST_OK) | |
715 | log("Matching host key in %s:%d", host_file, host_line); | |
716 | log("Offending key for IP in %s:%d", ip_file, ip_line); | |
717 | if (options.strict_host_key_checking == 1) { | |
718 | fatal("Exiting, you have requested strict checking."); | |
719 | } else if (options.strict_host_key_checking == 2) { | |
720 | if (!read_yes_or_no("Are you sure you want " \ | |
721 | "to continue connecting (yes/no)? ", -1)) | |
722 | fatal("Aborted by user!\n"); | |
723 | } | |
724 | } | |
725 | ||
726 | xfree(ip); | |
727 | } | |
728 | ||
729 | /* | |
730 | * Starts a dialog with the server, and authenticates the current user on the | |
731 | * server. This does not need any extra privileges. The basic connection | |
732 | * to the server must already have been established before this is called. | |
733 | * If login fails, this function prints an error and never returns. | |
734 | * This function does not require super-user privileges. | |
735 | */ | |
736 | void | |
737 | ssh_login(int host_key_valid, RSA *own_host_key, const char *orighost, | |
738 | struct sockaddr *hostaddr, uid_t original_real_uid) | |
739 | { | |
740 | struct passwd *pw; | |
741 | char *host, *cp; | |
742 | char *server_user, *local_user; | |
743 | ||
744 | /* Get local user name. Use it as server user if no user name was given. */ | |
745 | pw = getpwuid(original_real_uid); | |
746 | if (!pw) | |
747 | fatal("User id %u not found from user database.", original_real_uid); | |
748 | local_user = xstrdup(pw->pw_name); | |
749 | server_user = options.user ? options.user : local_user; | |
750 | ||
751 | /* Convert the user-supplied hostname into all lowercase. */ | |
752 | host = xstrdup(orighost); | |
753 | for (cp = host; *cp; cp++) | |
754 | if (isupper(*cp)) | |
755 | *cp = tolower(*cp); | |
756 | ||
757 | /* Exchange protocol version identification strings with the server. */ | |
758 | ssh_exchange_identification(); | |
759 | ||
760 | /* Put the connection into non-blocking mode. */ | |
761 | packet_set_nonblocking(); | |
762 | ||
763 | /* key exchange */ | |
764 | /* authenticate user */ | |
765 | if (compat20) { | |
766 | ssh_kex2(host, hostaddr); | |
767 | ssh_userauth2(server_user, host); | |
768 | } else { | |
769 | ssh_kex(host, hostaddr); | |
770 | ssh_userauth(local_user, server_user, host, host_key_valid, own_host_key); | |
771 | } | |
772 | } |