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8efc0c15 | 1 | /* |
2 | ||
3 | sshconnect.c | |
4 | ||
5 | Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | ||
7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | All rights reserved | |
9 | ||
10 | Created: Sat Mar 18 22:15:47 1995 ylo | |
11 | ||
12 | Code to connect to a remote host, and to perform the client side of the | |
13 | login (authentication) dialog. | |
14 | ||
15 | */ | |
16 | ||
5881cd60 | 17 | #include "config.h" |
8efc0c15 | 18 | #include "includes.h" |
19 | RCSID("$Id$"); | |
20 | ||
5881cd60 | 21 | #ifdef HAVE_OPENSSL |
8efc0c15 | 22 | #include <openssl/bn.h> |
5881cd60 | 23 | #include <openssl/md5.h> |
24 | #endif | |
25 | #ifdef HAVE_SSL | |
26 | #include <ssl/bn.h> | |
27 | #include <ssl/md5.h> | |
28 | #endif | |
29 | ||
8efc0c15 | 30 | #include "xmalloc.h" |
31 | #include "rsa.h" | |
32 | #include "ssh.h" | |
33 | #include "packet.h" | |
34 | #include "authfd.h" | |
35 | #include "cipher.h" | |
36 | #include "mpaux.h" | |
37 | #include "uidswap.h" | |
38 | #include "compat.h" | |
39 | ||
8efc0c15 | 40 | |
41 | /* Session id for the current session. */ | |
42 | unsigned char session_id[16]; | |
43 | ||
44 | /* Connect to the given ssh server using a proxy command. */ | |
45 | ||
46 | int | |
47 | ssh_proxy_connect(const char *host, int port, uid_t original_real_uid, | |
48 | const char *proxy_command) | |
49 | { | |
50 | Buffer command; | |
51 | const char *cp; | |
52 | char *command_string; | |
53 | int pin[2], pout[2]; | |
54 | int pid; | |
55 | char portstring[100]; | |
56 | ||
57 | /* Convert the port number into a string. */ | |
58 | snprintf(portstring, sizeof portstring, "%d", port); | |
59 | ||
60 | /* Build the final command string in the buffer by making the appropriate | |
61 | substitutions to the given proxy command. */ | |
62 | buffer_init(&command); | |
63 | for (cp = proxy_command; *cp; cp++) | |
64 | { | |
65 | if (cp[0] == '%' && cp[1] == '%') | |
66 | { | |
67 | buffer_append(&command, "%", 1); | |
68 | cp++; | |
69 | continue; | |
70 | } | |
71 | if (cp[0] == '%' && cp[1] == 'h') | |
72 | { | |
73 | buffer_append(&command, host, strlen(host)); | |
74 | cp++; | |
75 | continue; | |
76 | } | |
77 | if (cp[0] == '%' && cp[1] == 'p') | |
78 | { | |
79 | buffer_append(&command, portstring, strlen(portstring)); | |
80 | cp++; | |
81 | continue; | |
82 | } | |
83 | buffer_append(&command, cp, 1); | |
84 | } | |
85 | buffer_append(&command, "\0", 1); | |
86 | ||
87 | /* Get the final command string. */ | |
88 | command_string = buffer_ptr(&command); | |
89 | ||
90 | /* Create pipes for communicating with the proxy. */ | |
91 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
92 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
93 | strerror(errno)); | |
94 | ||
95 | debug("Executing proxy command: %.500s", command_string); | |
96 | ||
97 | /* Fork and execute the proxy command. */ | |
98 | if ((pid = fork()) == 0) | |
99 | { | |
100 | char *argv[10]; | |
101 | ||
102 | /* Child. Permanently give up superuser privileges. */ | |
103 | permanently_set_uid(original_real_uid); | |
104 | ||
105 | /* Redirect stdin and stdout. */ | |
106 | close(pin[1]); | |
107 | if (pin[0] != 0) | |
108 | { | |
109 | if (dup2(pin[0], 0) < 0) | |
110 | perror("dup2 stdin"); | |
111 | close(pin[0]); | |
112 | } | |
113 | close(pout[0]); | |
114 | if (dup2(pout[1], 1) < 0) | |
115 | perror("dup2 stdout"); | |
116 | close(pout[1]); /* Cannot be 1 because pin allocated two descriptors. */ | |
117 | ||
118 | /* Stderr is left as it is so that error messages get printed on | |
119 | the user's terminal. */ | |
120 | argv[0] = "/bin/sh"; | |
121 | argv[1] = "-c"; | |
122 | argv[2] = command_string; | |
123 | argv[3] = NULL; | |
124 | ||
125 | /* Execute the proxy command. Note that we gave up any extra | |
126 | privileges above. */ | |
127 | execv("/bin/sh", argv); | |
128 | perror("/bin/sh"); | |
129 | exit(1); | |
130 | } | |
131 | /* Parent. */ | |
132 | if (pid < 0) | |
133 | fatal("fork failed: %.100s", strerror(errno)); | |
134 | ||
135 | /* Close child side of the descriptors. */ | |
136 | close(pin[0]); | |
137 | close(pout[1]); | |
138 | ||
139 | /* Free the command name. */ | |
140 | buffer_free(&command); | |
141 | ||
142 | /* Set the connection file descriptors. */ | |
143 | packet_set_connection(pout[0], pin[1]); | |
144 | ||
145 | return 1; | |
146 | } | |
147 | ||
148 | /* Creates a (possibly privileged) socket for use as the ssh connection. */ | |
149 | ||
150 | int ssh_create_socket(uid_t original_real_uid, int privileged) | |
151 | { | |
152 | int sock; | |
153 | ||
154 | /* If we are running as root and want to connect to a privileged port, | |
155 | bind our own socket to a privileged port. */ | |
156 | if (privileged) | |
157 | { | |
158 | int p = IPPORT_RESERVED - 1; | |
159 | ||
160 | sock = rresvport(&p); | |
161 | if (sock < 0) | |
162 | fatal("rresvport: %.100s", strerror(errno)); | |
163 | debug("Allocated local port %d.", p); | |
164 | } | |
165 | else | |
166 | { | |
167 | /* Just create an ordinary socket on arbitrary port. We use the | |
168 | user's uid to create the socket. */ | |
169 | temporarily_use_uid(original_real_uid); | |
170 | sock = socket(AF_INET, SOCK_STREAM, 0); | |
171 | if (sock < 0) | |
172 | fatal("socket: %.100s", strerror(errno)); | |
173 | restore_uid(); | |
174 | } | |
175 | return sock; | |
176 | } | |
177 | ||
178 | /* Opens a TCP/IP connection to the remote server on the given host. If | |
179 | port is 0, the default port will be used. If anonymous is zero, | |
180 | a privileged port will be allocated to make the connection. | |
181 | This requires super-user privileges if anonymous is false. | |
182 | Connection_attempts specifies the maximum number of tries (one per | |
183 | second). If proxy_command is non-NULL, it specifies the command (with %h | |
184 | and %p substituted for host and port, respectively) to use to contact | |
185 | the daemon. */ | |
186 | ||
187 | int ssh_connect(const char *host, struct sockaddr_in *hostaddr, | |
188 | int port, int connection_attempts, | |
189 | int anonymous, uid_t original_real_uid, | |
190 | const char *proxy_command) | |
191 | { | |
192 | int sock = -1, attempt, i; | |
193 | int on = 1; | |
194 | struct servent *sp; | |
195 | struct hostent *hp; | |
196 | struct linger linger; | |
197 | ||
198 | debug("ssh_connect: getuid %d geteuid %d anon %d", | |
199 | (int)getuid(), (int)geteuid(), anonymous); | |
200 | ||
201 | /* Get default port if port has not been set. */ | |
202 | if (port == 0) | |
203 | { | |
204 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
205 | if (sp) | |
206 | port = ntohs(sp->s_port); | |
207 | else | |
208 | port = SSH_DEFAULT_PORT; | |
209 | } | |
210 | ||
211 | /* If a proxy command is given, connect using it. */ | |
212 | if (proxy_command != NULL) | |
213 | return ssh_proxy_connect(host, port, original_real_uid, proxy_command); | |
214 | ||
215 | /* No proxy command. */ | |
216 | ||
217 | /* No host lookup made yet. */ | |
218 | hp = NULL; | |
219 | ||
220 | /* Try to connect several times. On some machines, the first time will | |
221 | sometimes fail. In general socket code appears to behave quite | |
222 | magically on many machines. */ | |
223 | for (attempt = 0; attempt < connection_attempts; attempt++) | |
224 | { | |
225 | if (attempt > 0) | |
226 | debug("Trying again..."); | |
227 | ||
228 | /* Try to parse the host name as a numeric inet address. */ | |
229 | memset(hostaddr, 0, sizeof(hostaddr)); | |
230 | hostaddr->sin_family = AF_INET; | |
231 | hostaddr->sin_port = htons(port); | |
232 | hostaddr->sin_addr.s_addr = inet_addr(host); | |
233 | if ((hostaddr->sin_addr.s_addr & 0xffffffff) != 0xffffffff) | |
234 | { | |
235 | /* Valid numeric IP address */ | |
236 | debug("Connecting to %.100s port %d.", | |
237 | inet_ntoa(hostaddr->sin_addr), port); | |
238 | ||
239 | /* Create a socket. */ | |
240 | sock = ssh_create_socket(original_real_uid, | |
241 | !anonymous && geteuid() == 0 && | |
242 | port < IPPORT_RESERVED); | |
243 | ||
244 | /* Connect to the host. We use the user's uid in the hope that | |
245 | it will help with the problems of tcp_wrappers showing the | |
246 | remote uid as root. */ | |
247 | temporarily_use_uid(original_real_uid); | |
248 | if (connect(sock, (struct sockaddr *)hostaddr, sizeof(*hostaddr)) | |
249 | >= 0) | |
250 | { | |
251 | /* Successful connect. */ | |
252 | restore_uid(); | |
253 | break; | |
254 | } | |
255 | debug("connect: %.100s", strerror(errno)); | |
256 | restore_uid(); | |
257 | ||
258 | /* Destroy the failed socket. */ | |
259 | shutdown(sock, SHUT_RDWR); | |
260 | close(sock); | |
261 | } | |
262 | else | |
263 | { | |
264 | /* Not a valid numeric inet address. */ | |
265 | /* Map host name to an address. */ | |
266 | if (!hp) | |
267 | hp = gethostbyname(host); | |
268 | if (!hp) | |
269 | fatal("Bad host name: %.100s", host); | |
270 | if (!hp->h_addr_list[0]) | |
271 | fatal("Host does not have an IP address: %.100s", host); | |
272 | ||
273 | /* Loop through addresses for this host, and try each one in | |
274 | sequence until the connection succeeds. */ | |
275 | for (i = 0; hp->h_addr_list[i]; i++) | |
276 | { | |
277 | /* Set the address to connect to. */ | |
278 | hostaddr->sin_family = hp->h_addrtype; | |
279 | memcpy(&hostaddr->sin_addr, hp->h_addr_list[i], | |
280 | sizeof(hostaddr->sin_addr)); | |
281 | ||
282 | debug("Connecting to %.200s [%.100s] port %d.", | |
283 | host, inet_ntoa(hostaddr->sin_addr), port); | |
284 | ||
285 | /* Create a socket for connecting. */ | |
286 | sock = ssh_create_socket(original_real_uid, | |
287 | !anonymous && geteuid() == 0 && | |
288 | port < IPPORT_RESERVED); | |
289 | ||
290 | /* Connect to the host. We use the user's uid in the hope that | |
291 | it will help with tcp_wrappers showing the remote uid as | |
292 | root. */ | |
293 | temporarily_use_uid(original_real_uid); | |
294 | if (connect(sock, (struct sockaddr *)hostaddr, | |
295 | sizeof(*hostaddr)) >= 0) | |
296 | { | |
297 | /* Successful connection. */ | |
298 | restore_uid(); | |
299 | break; | |
300 | } | |
301 | debug("connect: %.100s", strerror(errno)); | |
302 | restore_uid(); | |
303 | ||
304 | /* Close the failed socket; there appear to be some problems | |
305 | when reusing a socket for which connect() has already | |
306 | returned an error. */ | |
307 | shutdown(sock, SHUT_RDWR); | |
308 | close(sock); | |
309 | } | |
310 | if (hp->h_addr_list[i]) | |
311 | break; /* Successful connection. */ | |
312 | } | |
313 | ||
314 | /* Sleep a moment before retrying. */ | |
315 | sleep(1); | |
316 | } | |
317 | /* Return failure if we didn't get a successful connection. */ | |
318 | if (attempt >= connection_attempts) | |
319 | return 0; | |
320 | ||
321 | debug("Connection established."); | |
322 | ||
323 | /* Set socket options. We would like the socket to disappear as soon as | |
324 | it has been closed for whatever reason. */ | |
325 | /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
326 | setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void *)&on, sizeof(on)); | |
327 | linger.l_onoff = 1; | |
328 | linger.l_linger = 5; | |
329 | setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger)); | |
330 | ||
331 | /* Set the connection. */ | |
332 | packet_set_connection(sock, sock); | |
333 | ||
334 | return 1; | |
335 | } | |
336 | ||
337 | /* Checks if the user has an authentication agent, and if so, tries to | |
338 | authenticate using the agent. */ | |
339 | ||
340 | int | |
341 | try_agent_authentication() | |
342 | { | |
343 | int status, type, bits; | |
344 | char *comment; | |
345 | AuthenticationConnection *auth; | |
346 | unsigned char response[16]; | |
347 | unsigned int i; | |
348 | BIGNUM *e, *n, *challenge; | |
349 | ||
350 | /* Get connection to the agent. */ | |
351 | auth = ssh_get_authentication_connection(); | |
352 | if (!auth) | |
353 | return 0; | |
354 | ||
355 | e = BN_new(); | |
356 | n = BN_new(); | |
357 | challenge = BN_new(); | |
358 | ||
359 | /* Loop through identities served by the agent. */ | |
360 | for (status = ssh_get_first_identity(auth, &bits, e, n, &comment); | |
361 | status; | |
362 | status = ssh_get_next_identity(auth, &bits, e, n, &comment)) | |
363 | { | |
364 | int plen, clen; | |
365 | ||
366 | /* Try this identity. */ | |
367 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
368 | xfree(comment); | |
369 | ||
370 | /* Tell the server that we are willing to authenticate using this key. */ | |
371 | packet_start(SSH_CMSG_AUTH_RSA); | |
372 | packet_put_bignum(n); | |
373 | packet_send(); | |
374 | packet_write_wait(); | |
375 | ||
376 | /* Wait for server's response. */ | |
377 | type = packet_read(&plen); | |
378 | ||
379 | /* The server sends failure if it doesn\'t like our key or does not | |
380 | support RSA authentication. */ | |
381 | if (type == SSH_SMSG_FAILURE) | |
382 | { | |
383 | debug("Server refused our key."); | |
384 | continue; | |
385 | } | |
386 | ||
387 | /* Otherwise it should have sent a challenge. */ | |
388 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
389 | packet_disconnect("Protocol error during RSA authentication: %d", | |
390 | type); | |
391 | ||
392 | packet_get_bignum(challenge, &clen); | |
393 | ||
394 | packet_integrity_check(plen, clen, type); | |
395 | ||
396 | debug("Received RSA challenge from server."); | |
397 | ||
398 | /* Ask the agent to decrypt the challenge. */ | |
399 | if (!ssh_decrypt_challenge(auth, bits, e, n, challenge, | |
400 | session_id, 1, response)) | |
401 | { | |
402 | /* The agent failed to authenticate this identifier although it | |
403 | advertised it supports this. Just return a wrong value. */ | |
404 | log("Authentication agent failed to decrypt challenge."); | |
405 | memset(response, 0, sizeof(response)); | |
406 | } | |
407 | ||
408 | debug("Sending response to RSA challenge."); | |
409 | ||
410 | /* Send the decrypted challenge back to the server. */ | |
411 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
412 | for (i = 0; i < 16; i++) | |
413 | packet_put_char(response[i]); | |
414 | packet_send(); | |
415 | packet_write_wait(); | |
416 | ||
417 | /* Wait for response from the server. */ | |
418 | type = packet_read(&plen); | |
419 | ||
420 | /* The server returns success if it accepted the authentication. */ | |
421 | if (type == SSH_SMSG_SUCCESS) | |
422 | { | |
423 | debug("RSA authentication accepted by server."); | |
424 | BN_clear_free(e); | |
425 | BN_clear_free(n); | |
426 | BN_clear_free(challenge); | |
427 | return 1; | |
428 | } | |
429 | ||
430 | /* Otherwise it should return failure. */ | |
431 | if (type != SSH_SMSG_FAILURE) | |
432 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
433 | type); | |
434 | } | |
435 | ||
436 | BN_clear_free(e); | |
437 | BN_clear_free(n); | |
438 | BN_clear_free(challenge); | |
439 | ||
440 | debug("RSA authentication using agent refused."); | |
441 | return 0; | |
442 | } | |
443 | ||
444 | /* Computes the proper response to a RSA challenge, and sends the response to | |
445 | the server. */ | |
446 | ||
447 | void | |
448 | respond_to_rsa_challenge(BIGNUM *challenge, RSA *prv) | |
449 | { | |
450 | unsigned char buf[32], response[16]; | |
451 | MD5_CTX md; | |
452 | int i, len; | |
453 | ||
454 | /* Decrypt the challenge using the private key. */ | |
455 | rsa_private_decrypt(challenge, challenge, prv); | |
456 | ||
457 | /* Compute the response. */ | |
458 | /* The response is MD5 of decrypted challenge plus session id. */ | |
459 | len = BN_num_bytes(challenge); | |
5bae4ab8 | 460 | if (len <= 0 || len > sizeof(buf)) |
461 | packet_disconnect("respond_to_rsa_challenge: bad challenge length %d", | |
462 | len); | |
463 | ||
8efc0c15 | 464 | memset(buf, 0, sizeof(buf)); |
465 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
466 | MD5_Init(&md); | |
467 | MD5_Update(&md, buf, 32); | |
468 | MD5_Update(&md, session_id, 16); | |
469 | MD5_Final(response, &md); | |
470 | ||
471 | debug("Sending response to host key RSA challenge."); | |
472 | ||
473 | /* Send the response back to the server. */ | |
474 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
475 | for (i = 0; i < 16; i++) | |
476 | packet_put_char(response[i]); | |
477 | packet_send(); | |
478 | packet_write_wait(); | |
479 | ||
480 | memset(buf, 0, sizeof(buf)); | |
481 | memset(response, 0, sizeof(response)); | |
482 | memset(&md, 0, sizeof(md)); | |
483 | } | |
484 | ||
485 | /* Checks if the user has authentication file, and if so, tries to authenticate | |
486 | the user using it. */ | |
487 | ||
488 | int | |
489 | try_rsa_authentication(struct passwd *pw, const char *authfile, | |
490 | int may_ask_passphrase) | |
491 | { | |
492 | BIGNUM *challenge; | |
493 | RSA *private_key; | |
494 | RSA *public_key; | |
495 | char *passphrase, *comment; | |
496 | int type, i; | |
497 | int plen, clen; | |
498 | ||
499 | /* Try to load identification for the authentication key. */ | |
500 | public_key = RSA_new(); | |
501 | if (!load_public_key(authfile, public_key, &comment)) { | |
502 | RSA_free(public_key); | |
503 | return 0; /* Could not load it. Fail. */ | |
504 | } | |
505 | ||
506 | debug("Trying RSA authentication with key '%.100s'", comment); | |
507 | ||
508 | /* Tell the server that we are willing to authenticate using this key. */ | |
509 | packet_start(SSH_CMSG_AUTH_RSA); | |
510 | packet_put_bignum(public_key->n); | |
511 | packet_send(); | |
512 | packet_write_wait(); | |
513 | ||
514 | /* We no longer need the public key. */ | |
515 | RSA_free(public_key); | |
516 | ||
517 | /* Wait for server's response. */ | |
518 | type = packet_read(&plen); | |
519 | ||
520 | /* The server responds with failure if it doesn\'t like our key or doesn\'t | |
521 | support RSA authentication. */ | |
522 | if (type == SSH_SMSG_FAILURE) | |
523 | { | |
524 | debug("Server refused our key."); | |
525 | xfree(comment); | |
526 | return 0; /* Server refuses to authenticate with this key. */ | |
527 | } | |
528 | ||
529 | /* Otherwise, the server should respond with a challenge. */ | |
530 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
531 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
532 | ||
533 | /* Get the challenge from the packet. */ | |
534 | challenge = BN_new(); | |
535 | packet_get_bignum(challenge, &clen); | |
536 | ||
537 | packet_integrity_check(plen, clen, type); | |
538 | ||
539 | debug("Received RSA challenge from server."); | |
540 | ||
541 | private_key = RSA_new(); | |
542 | /* Load the private key. Try first with empty passphrase; if it fails, | |
543 | ask for a passphrase. */ | |
544 | if (!load_private_key(authfile, "", private_key, NULL)) | |
545 | { | |
546 | char buf[300]; | |
547 | /* Request passphrase from the user. We read from /dev/tty to make | |
548 | this work even if stdin has been redirected. If running in | |
549 | batch mode, we just use the empty passphrase, which will fail and | |
550 | return. */ | |
551 | snprintf(buf, sizeof buf, | |
552 | "Enter passphrase for RSA key '%.100s': ", comment); | |
553 | if (may_ask_passphrase) | |
554 | passphrase = read_passphrase(buf, 0); | |
555 | else | |
556 | { | |
557 | debug("Will not query passphrase for %.100s in batch mode.", | |
558 | comment); | |
559 | passphrase = xstrdup(""); | |
560 | } | |
561 | ||
562 | /* Load the authentication file using the pasphrase. */ | |
563 | if (!load_private_key(authfile, passphrase, private_key, NULL)) | |
564 | { | |
565 | memset(passphrase, 0, strlen(passphrase)); | |
566 | xfree(passphrase); | |
567 | error("Bad passphrase."); | |
568 | ||
569 | /* Send a dummy response packet to avoid protocol error. */ | |
570 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
571 | for (i = 0; i < 16; i++) | |
572 | packet_put_char(0); | |
573 | packet_send(); | |
574 | packet_write_wait(); | |
575 | ||
576 | /* Expect the server to reject it... */ | |
577 | packet_read_expect(&plen, SSH_SMSG_FAILURE); | |
578 | xfree(comment); | |
579 | return 0; | |
580 | } | |
581 | ||
582 | /* Destroy the passphrase. */ | |
583 | memset(passphrase, 0, strlen(passphrase)); | |
584 | xfree(passphrase); | |
585 | } | |
586 | ||
587 | /* We no longer need the comment. */ | |
588 | xfree(comment); | |
589 | ||
590 | /* Compute and send a response to the challenge. */ | |
591 | respond_to_rsa_challenge(challenge, private_key); | |
592 | ||
593 | /* Destroy the private key. */ | |
594 | RSA_free(private_key); | |
595 | ||
596 | /* We no longer need the challenge. */ | |
597 | BN_clear_free(challenge); | |
598 | ||
599 | /* Wait for response from the server. */ | |
600 | type = packet_read(&plen); | |
601 | if (type == SSH_SMSG_SUCCESS) | |
602 | { | |
603 | debug("RSA authentication accepted by server."); | |
604 | return 1; | |
605 | } | |
606 | if (type != SSH_SMSG_FAILURE) | |
607 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
608 | debug("RSA authentication refused."); | |
609 | return 0; | |
610 | } | |
611 | ||
612 | /* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
613 | authentication and RSA host authentication. */ | |
614 | ||
615 | int | |
616 | try_rhosts_rsa_authentication(const char *local_user, RSA *host_key) | |
617 | { | |
618 | int type; | |
619 | BIGNUM *challenge; | |
620 | int plen, clen; | |
621 | ||
622 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
623 | ||
624 | /* Tell the server that we are willing to authenticate using this key. */ | |
625 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
626 | packet_put_string(local_user, strlen(local_user)); | |
627 | packet_put_int(BN_num_bits(host_key->n)); | |
628 | packet_put_bignum(host_key->e); | |
629 | packet_put_bignum(host_key->n); | |
630 | packet_send(); | |
631 | packet_write_wait(); | |
632 | ||
633 | /* Wait for server's response. */ | |
634 | type = packet_read(&plen); | |
635 | ||
636 | /* The server responds with failure if it doesn't admit our .rhosts | |
637 | authentication or doesn't know our host key. */ | |
638 | if (type == SSH_SMSG_FAILURE) | |
639 | { | |
640 | debug("Server refused our rhosts authentication or host key."); | |
641 | return 0; /* Server refuses to authenticate us with this method. */ | |
642 | } | |
643 | ||
644 | /* Otherwise, the server should respond with a challenge. */ | |
645 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
646 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
647 | ||
648 | /* Get the challenge from the packet. */ | |
649 | challenge = BN_new(); | |
650 | packet_get_bignum(challenge, &clen); | |
651 | ||
652 | packet_integrity_check(plen, clen, type); | |
653 | ||
654 | debug("Received RSA challenge for host key from server."); | |
655 | ||
656 | /* Compute a response to the challenge. */ | |
657 | respond_to_rsa_challenge(challenge, host_key); | |
658 | ||
659 | /* We no longer need the challenge. */ | |
660 | BN_clear_free(challenge); | |
661 | ||
662 | /* Wait for response from the server. */ | |
663 | type = packet_read(&plen); | |
664 | if (type == SSH_SMSG_SUCCESS) | |
665 | { | |
666 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
667 | return 1; | |
668 | } | |
669 | if (type != SSH_SMSG_FAILURE) | |
670 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
671 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
672 | return 0; | |
673 | } | |
674 | ||
675 | #ifdef KRB4 | |
676 | int try_kerberos_authentication() | |
677 | { | |
678 | KTEXT_ST auth; /* Kerberos data */ | |
679 | char *reply; | |
680 | char inst[INST_SZ]; | |
681 | char *realm; | |
682 | CREDENTIALS cred; | |
683 | int r, type, plen; | |
684 | Key_schedule schedule; | |
685 | u_long checksum, cksum; | |
686 | MSG_DAT msg_data; | |
687 | struct sockaddr_in local, foreign; | |
688 | struct stat st; | |
689 | ||
690 | /* Don't do anything if we don't have any tickets. */ | |
691 | if (stat(tkt_string(), &st) < 0) return 0; | |
692 | ||
693 | strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ); | |
694 | ||
695 | realm = (char *)krb_realmofhost(get_canonical_hostname()); | |
696 | if (!realm) { | |
697 | debug("Kerberos V4: no realm for %s", get_canonical_hostname()); | |
698 | return 0; | |
699 | } | |
700 | /* This can really be anything. */ | |
701 | checksum = (u_long) getpid(); | |
702 | ||
703 | r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); | |
704 | if (r != KSUCCESS) { | |
705 | debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]); | |
706 | return 0; | |
707 | } | |
708 | /* Get session key to decrypt the server's reply with. */ | |
709 | r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); | |
710 | if (r != KSUCCESS) { | |
711 | debug("get_cred failed: %s", krb_err_txt[r]); | |
712 | return 0; | |
713 | } | |
714 | des_key_sched((des_cblock *)cred.session, schedule); | |
715 | ||
716 | /* Send authentication info to server. */ | |
717 | packet_start(SSH_CMSG_AUTH_KERBEROS); | |
718 | packet_put_string((char *)auth.dat, auth.length); | |
719 | packet_send(); | |
720 | packet_write_wait(); | |
721 | ||
722 | /* Zero the buffer. */ | |
723 | (void) memset(auth.dat, 0, MAX_KTXT_LEN); | |
724 | ||
725 | r = sizeof(local); | |
726 | memset(&local, 0, sizeof(local)); | |
727 | if (getsockname(packet_get_connection_in(), | |
728 | (struct sockaddr *) &local, &r) < 0) | |
729 | debug("getsockname failed: %s", strerror(errno)); | |
730 | ||
731 | r = sizeof(foreign); | |
732 | memset(&foreign, 0, sizeof(foreign)); | |
733 | if (getpeername(packet_get_connection_in(), | |
734 | (struct sockaddr *)&foreign, &r) < 0) | |
735 | debug("getpeername failed: %s", strerror(errno)); | |
736 | ||
737 | /* Get server reply. */ | |
738 | type = packet_read(&plen); | |
739 | switch(type) { | |
740 | ||
741 | case SSH_SMSG_FAILURE: /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ | |
742 | debug("Kerberos V4 authentication failed."); | |
743 | return 0; | |
744 | break; | |
745 | ||
746 | case SSH_SMSG_AUTH_KERBEROS_RESPONSE: /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ | |
747 | debug("Kerberos V4 authentication accepted."); | |
748 | ||
749 | /* Get server's response. */ | |
750 | reply = packet_get_string((unsigned int *)&auth.length); | |
751 | memcpy(auth.dat, reply, auth.length); | |
752 | xfree(reply); | |
753 | ||
754 | packet_integrity_check(plen, 4 + auth.length, type); | |
755 | ||
756 | /* If his response isn't properly encrypted with the session key, | |
757 | and the decrypted checksum fails to match, he's bogus. Bail out. */ | |
758 | r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, | |
759 | &foreign, &local, &msg_data); | |
760 | if (r != KSUCCESS) { | |
761 | debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]); | |
762 | packet_disconnect("Kerberos V4 challenge failed!"); | |
763 | } | |
764 | /* Fetch the (incremented) checksum that we supplied in the request. */ | |
765 | (void)memcpy((char *)&cksum, (char *)msg_data.app_data, sizeof(cksum)); | |
766 | cksum = ntohl(cksum); | |
767 | ||
768 | /* If it matches, we're golden. */ | |
769 | if (cksum == checksum + 1) { | |
770 | debug("Kerberos V4 challenge successful."); | |
771 | return 1; | |
772 | } | |
773 | else | |
774 | packet_disconnect("Kerberos V4 challenge failed!"); | |
775 | break; | |
776 | ||
777 | default: | |
778 | packet_disconnect("Protocol error on Kerberos V4 response: %d", type); | |
779 | } | |
780 | return 0; | |
781 | } | |
782 | #endif /* KRB4 */ | |
783 | ||
784 | #ifdef AFS | |
785 | int send_kerberos_tgt() | |
786 | { | |
787 | CREDENTIALS *creds; | |
788 | char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; | |
789 | int r, type, plen; | |
790 | unsigned char buffer[8192]; | |
791 | struct stat st; | |
792 | ||
793 | /* Don't do anything if we don't have any tickets. */ | |
794 | if (stat(tkt_string(), &st) < 0) return 0; | |
795 | ||
796 | creds = xmalloc(sizeof(*creds)); | |
797 | ||
798 | if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) { | |
799 | debug("Kerberos V4 tf_fullname failed: %s",krb_err_txt[r]); | |
800 | return 0; | |
801 | } | |
802 | if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) { | |
803 | debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]); | |
804 | return 0; | |
805 | } | |
806 | if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { | |
807 | debug("Kerberos V4 ticket expired: %s", TKT_FILE); | |
808 | return 0; | |
809 | } | |
810 | ||
811 | creds_to_radix(creds, buffer); | |
812 | xfree(creds); | |
813 | ||
814 | packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); | |
815 | packet_put_string((char *)buffer, strlen(buffer)); | |
816 | packet_send(); | |
817 | packet_write_wait(); | |
818 | ||
819 | type = packet_read(&plen); | |
820 | ||
821 | if (type == SSH_SMSG_FAILURE) | |
822 | debug("Kerberos TGT for realm %s rejected.", prealm); | |
823 | else if (type != SSH_SMSG_SUCCESS) | |
824 | packet_disconnect("Protocol error on Kerberos TGT response: %d", type); | |
825 | ||
826 | return 1; | |
827 | } | |
828 | ||
829 | void send_afs_tokens(void) | |
830 | { | |
831 | CREDENTIALS creds; | |
832 | struct ViceIoctl parms; | |
833 | struct ClearToken ct; | |
834 | int i, type, len, plen; | |
835 | char buf[2048], *p, *server_cell; | |
836 | unsigned char buffer[8192]; | |
837 | ||
838 | /* Move over ktc_GetToken, here's something leaner. */ | |
839 | for (i = 0; i < 100; i++) { /* just in case */ | |
840 | parms.in = (char *)&i; | |
841 | parms.in_size = sizeof(i); | |
842 | parms.out = buf; | |
843 | parms.out_size = sizeof(buf); | |
844 | if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) break; | |
845 | p = buf; | |
846 | ||
847 | /* Get secret token. */ | |
848 | memcpy(&creds.ticket_st.length, p, sizeof(unsigned int)); | |
849 | if (creds.ticket_st.length > MAX_KTXT_LEN) break; | |
850 | p += sizeof(unsigned int); | |
851 | memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); | |
852 | p += creds.ticket_st.length; | |
853 | ||
854 | /* Get clear token. */ | |
855 | memcpy(&len, p, sizeof(len)); | |
856 | if (len != sizeof(struct ClearToken)) break; | |
857 | p += sizeof(len); | |
858 | memcpy(&ct, p, len); | |
859 | p += len; | |
860 | p += sizeof(len); /* primary flag */ | |
861 | server_cell = p; | |
862 | ||
863 | /* Flesh out our credentials. */ | |
864 | strlcpy(creds.service, "afs", sizeof creds.service); | |
865 | creds.instance[0] = '\0'; | |
866 | strlcpy(creds.realm, server_cell, REALM_SZ); | |
867 | memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); | |
868 | creds.issue_date = ct.BeginTimestamp; | |
869 | creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp); | |
870 | creds.kvno = ct.AuthHandle; | |
871 | snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); | |
872 | creds.pinst[0] = '\0'; | |
873 | ||
874 | /* Encode token, ship it off. */ | |
875 | if (!creds_to_radix(&creds, buffer)) break; | |
876 | packet_start(SSH_CMSG_HAVE_AFS_TOKEN); | |
877 | packet_put_string((char *)buffer, strlen(buffer)); | |
878 | packet_send(); | |
879 | packet_write_wait(); | |
880 | ||
881 | /* Roger, Roger. Clearance, Clarence. What's your vector, Victor? */ | |
882 | type = packet_read(&plen); | |
883 | ||
884 | if (type == SSH_SMSG_FAILURE) | |
885 | debug("AFS token for cell %s rejected.", server_cell); | |
886 | else if (type != SSH_SMSG_SUCCESS) | |
887 | packet_disconnect("Protocol error on AFS token response: %d", type); | |
888 | } | |
889 | } | |
890 | #endif /* AFS */ | |
891 | ||
892 | /* Waits for the server identification string, and sends our own identification | |
893 | string. */ | |
894 | ||
895 | void ssh_exchange_identification() | |
896 | { | |
897 | char buf[256], remote_version[256]; /* must be same size! */ | |
898 | int remote_major, remote_minor, i; | |
899 | int connection_in = packet_get_connection_in(); | |
900 | int connection_out = packet_get_connection_out(); | |
901 | extern Options options; | |
902 | ||
903 | /* Read other side\'s version identification. */ | |
904 | for (i = 0; i < sizeof(buf) - 1; i++) | |
905 | { | |
906 | if (read(connection_in, &buf[i], 1) != 1) | |
907 | fatal("read: %.100s", strerror(errno)); | |
908 | if (buf[i] == '\r') | |
909 | { | |
910 | buf[i] = '\n'; | |
911 | buf[i + 1] = 0; | |
912 | break; | |
913 | } | |
914 | if (buf[i] == '\n') | |
915 | { | |
916 | buf[i + 1] = 0; | |
917 | break; | |
918 | } | |
919 | } | |
920 | buf[sizeof(buf) - 1] = 0; | |
921 | ||
922 | /* Check that the versions match. In future this might accept several | |
923 | versions and set appropriate flags to handle them. */ | |
924 | if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor, | |
925 | remote_version) != 3) | |
926 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
927 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
928 | remote_major, remote_minor, remote_version); | |
929 | ||
930 | /* Check if the remote protocol version is too old. */ | |
931 | if (remote_major == 1 && remote_minor < 3) | |
932 | fatal("Remote machine has too old SSH software version."); | |
933 | ||
934 | /* We speak 1.3, too. */ | |
935 | if (remote_major == 1 && remote_minor == 3) { | |
936 | enable_compat13(); | |
937 | if (options.forward_agent && strcmp(remote_version, SSH_VERSION) != 0) { | |
938 | log("Agent forwarding disabled, remote version '%s' is not compatible.", | |
939 | remote_version); | |
940 | options.forward_agent = 0; | |
941 | } | |
942 | } | |
943 | #if 0 | |
944 | /* Removed for now, to permit compatibility with latter versions. The server | |
945 | will reject our version and disconnect if it doesn't support it. */ | |
946 | if (remote_major != PROTOCOL_MAJOR) | |
947 | fatal("Protocol major versions differ: %d vs. %d", | |
948 | PROTOCOL_MAJOR, remote_major); | |
949 | #endif | |
950 | ||
951 | /* Send our own protocol version identification. */ | |
952 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
953 | PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION); | |
954 | if (write(connection_out, buf, strlen(buf)) != strlen(buf)) | |
955 | fatal("write: %.100s", strerror(errno)); | |
956 | } | |
957 | ||
958 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
959 | ||
960 | int read_yes_or_no(const char *prompt, int defval) | |
961 | { | |
962 | char buf[1024]; | |
963 | FILE *f; | |
964 | int retval = -1; | |
965 | ||
966 | if (isatty(0)) | |
967 | f = stdin; | |
968 | else | |
969 | f = fopen("/dev/tty", "rw"); | |
970 | ||
971 | if (f == NULL) | |
972 | return 0; | |
973 | ||
974 | fflush(stdout); | |
975 | ||
976 | while (1) | |
977 | { | |
978 | fprintf(stderr, "%s", prompt); | |
979 | if (fgets(buf, sizeof(buf), f) == NULL) | |
980 | { | |
981 | /* Print a newline (the prompt probably didn\'t have one). */ | |
982 | fprintf(stderr, "\n"); | |
983 | strlcpy(buf, "no", sizeof buf); | |
984 | } | |
985 | /* Remove newline from response. */ | |
986 | if (strchr(buf, '\n')) | |
987 | *strchr(buf, '\n') = 0; | |
988 | ||
989 | if (buf[0] == 0) | |
990 | retval = defval; | |
991 | if (strcmp(buf, "yes") == 0) | |
992 | retval = 1; | |
993 | if (strcmp(buf, "no") == 0) | |
994 | retval = 0; | |
995 | ||
996 | if (retval != -1) | |
997 | { | |
998 | if (f != stdin) | |
999 | fclose(f); | |
1000 | return retval; | |
1001 | } | |
1002 | } | |
1003 | } | |
1004 | ||
1005 | /* Starts a dialog with the server, and authenticates the current user on the | |
1006 | server. This does not need any extra privileges. The basic connection | |
1007 | to the server must already have been established before this is called. | |
1008 | User is the remote user; if it is NULL, the current local user name will | |
1009 | be used. Anonymous indicates that no rhosts authentication will be used. | |
1010 | If login fails, this function prints an error and never returns. | |
1011 | This function does not require super-user privileges. */ | |
1012 | ||
1013 | void ssh_login(int host_key_valid, | |
1014 | RSA *own_host_key, | |
1015 | const char *orighost, | |
1016 | struct sockaddr_in *hostaddr, | |
1017 | Options *options, uid_t original_real_uid) | |
1018 | { | |
1019 | int i, type; | |
1020 | char *password; | |
1021 | struct passwd *pw; | |
1022 | BIGNUM *key; | |
1023 | RSA *host_key, *file_key; | |
1024 | RSA *public_key; | |
1025 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
1026 | const char *server_user, *local_user; | |
1027 | char *cp, *host, *ip = NULL; | |
1028 | unsigned char check_bytes[8]; | |
1029 | unsigned int supported_ciphers, supported_authentications, protocol_flags; | |
1030 | HostStatus host_status; | |
1031 | HostStatus ip_status; | |
1032 | int host_ip_differ = 0; | |
1033 | int local = (ntohl(hostaddr->sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
1034 | int payload_len, clen, sum_len = 0; | |
1035 | u_int32_t rand = 0; | |
1036 | ||
1037 | if (options->check_host_ip) | |
1038 | ip = xstrdup(inet_ntoa(hostaddr->sin_addr)); | |
1039 | ||
1040 | /* Convert the user-supplied hostname into all lowercase. */ | |
1041 | host = xstrdup(orighost); | |
1042 | for (cp = host; *cp; cp++) | |
1043 | if (isupper(*cp)) | |
1044 | *cp = tolower(*cp); | |
1045 | ||
1046 | /* Exchange protocol version identification strings with the server. */ | |
1047 | ssh_exchange_identification(); | |
1048 | ||
1049 | /* Put the connection into non-blocking mode. */ | |
1050 | packet_set_nonblocking(); | |
1051 | ||
1052 | /* Get local user name. Use it as server user if no user name | |
1053 | was given. */ | |
1054 | pw = getpwuid(original_real_uid); | |
1055 | if (!pw) | |
1056 | fatal("User id %d not found from user database.", original_real_uid); | |
1057 | local_user = xstrdup(pw->pw_name); | |
1058 | server_user = options->user ? options->user : local_user; | |
1059 | ||
1060 | debug("Waiting for server public key."); | |
1061 | ||
1062 | /* Wait for a public key packet from the server. */ | |
1063 | packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY); | |
1064 | ||
1065 | /* Get check bytes from the packet. */ | |
1066 | for (i = 0; i < 8; i++) | |
1067 | check_bytes[i] = packet_get_char(); | |
1068 | ||
1069 | /* Get the public key. */ | |
1070 | public_key = RSA_new(); | |
1071 | packet_get_int(); /* bits */ | |
1072 | public_key->e = BN_new(); | |
1073 | packet_get_bignum(public_key->e, &clen); | |
1074 | sum_len += clen; | |
1075 | public_key->n = BN_new(); | |
1076 | packet_get_bignum(public_key->n, &clen); | |
1077 | sum_len += clen; | |
1078 | ||
1079 | /* Get the host key. */ | |
1080 | host_key = RSA_new(); | |
1081 | packet_get_int(); /* bits */ | |
1082 | host_key->e = BN_new(); | |
1083 | packet_get_bignum(host_key->e, &clen); | |
1084 | sum_len += clen; | |
1085 | host_key->n = BN_new(); | |
1086 | packet_get_bignum(host_key->n, &clen); | |
1087 | sum_len += clen; | |
1088 | ||
1089 | /* Store the host key from the known host file in here | |
1090 | * so that we can compare it with the key for the IP | |
1091 | * address. */ | |
1092 | file_key = RSA_new(); | |
1093 | file_key->n = BN_new(); | |
1094 | file_key->e = BN_new(); | |
1095 | ||
1096 | /* Get protocol flags. */ | |
1097 | protocol_flags = packet_get_int(); | |
1098 | packet_set_protocol_flags(protocol_flags); | |
1099 | ||
1100 | /* Get supported cipher types. */ | |
1101 | supported_ciphers = packet_get_int(); | |
1102 | ||
1103 | /* Get supported authentication types. */ | |
1104 | supported_authentications = packet_get_int(); | |
1105 | ||
1106 | debug("Received server public key (%d bits) and host key (%d bits).", | |
1107 | BN_num_bits(public_key->n), BN_num_bits(host_key->n)); | |
1108 | ||
1109 | packet_integrity_check(payload_len, | |
1110 | 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, | |
1111 | SSH_SMSG_PUBLIC_KEY); | |
1112 | ||
1113 | /* Compute the session id. */ | |
1114 | compute_session_id(session_id, check_bytes, | |
1115 | BN_num_bits(host_key->n), host_key->n, | |
1116 | BN_num_bits(public_key->n), public_key->n); | |
1117 | ||
1118 | /* Check if the host key is present in the user\'s list of known hosts | |
1119 | or in the systemwide list. */ | |
1120 | host_status = check_host_in_hostfile(options->user_hostfile, | |
1121 | host, BN_num_bits(host_key->n), | |
1122 | host_key->e, host_key->n, | |
1123 | file_key->e, file_key->n); | |
1124 | if (host_status == HOST_NEW) | |
1125 | host_status = check_host_in_hostfile(options->system_hostfile, host, | |
1126 | BN_num_bits(host_key->n), | |
1127 | host_key->e, host_key->n, | |
1128 | file_key->e, file_key->n); | |
1129 | /* Force accepting of the host key for localhost and 127.0.0.1. | |
1130 | The problem is that if the home directory is NFS-mounted to multiple | |
1131 | machines, localhost will refer to a different machine in each of them, | |
1132 | and the user will get bogus HOST_CHANGED warnings. This essentially | |
1133 | disables host authentication for localhost; however, this is probably | |
1134 | not a real problem. */ | |
1135 | if (local) { | |
1136 | debug("Forcing accepting of host key for localhost."); | |
1137 | host_status = HOST_OK; | |
1138 | } | |
1139 | ||
1140 | /* Also perform check for the ip address, skip the check if we are | |
1141 | localhost or the hostname was an ip address to begin with */ | |
1142 | if (options->check_host_ip && !local && strcmp(host, ip)) { | |
1143 | RSA *ip_key = RSA_new(); | |
1144 | ip_key->n = BN_new(); | |
1145 | ip_key->e = BN_new(); | |
1146 | ip_status = check_host_in_hostfile(options->user_hostfile, ip, | |
1147 | BN_num_bits(host_key->n), | |
1148 | host_key->e, host_key->n, | |
1149 | ip_key->e, ip_key->n); | |
1150 | ||
1151 | if (ip_status == HOST_NEW) | |
1152 | ip_status = check_host_in_hostfile(options->system_hostfile, ip, | |
1153 | BN_num_bits(host_key->n), | |
1154 | host_key->e, host_key->n, | |
1155 | ip_key->e, ip_key->n); | |
1156 | if (host_status == HOST_CHANGED && | |
1157 | (ip_status != HOST_CHANGED || | |
1158 | (BN_cmp(ip_key->e, file_key->e) || BN_cmp(ip_key->n, file_key->n)))) | |
1159 | host_ip_differ = 1; | |
1160 | ||
1161 | RSA_free(ip_key); | |
1162 | } else | |
1163 | ip_status = host_status; | |
1164 | ||
1165 | RSA_free(file_key); | |
1166 | ||
1167 | switch (host_status) { | |
1168 | case HOST_OK: | |
1169 | /* The host is known and the key matches. */ | |
1170 | debug("Host '%.200s' is known and matches the host key.", host); | |
1171 | if (options->check_host_ip) { | |
1172 | if (ip_status == HOST_NEW) { | |
1173 | if (!add_host_to_hostfile(options->user_hostfile, ip, | |
1174 | BN_num_bits(host_key->n), | |
1175 | host_key->e, host_key->n)) | |
1176 | log("Failed to add the host ip to the list of known hosts (%.30s).", | |
1177 | options->user_hostfile); | |
1178 | else | |
1179 | log("Warning: Permanently added host ip '%.30s' to the list of known hosts.", ip); | |
1180 | } else if (ip_status != HOST_OK) | |
1181 | log("Warning: the host key differ from the key of the ip address '%.30s' differs", ip); | |
1182 | } | |
1183 | ||
1184 | break; | |
1185 | case HOST_NEW: | |
1186 | { | |
1187 | char hostline[1000], *hostp = hostline; | |
1188 | /* The host is new. */ | |
1189 | if (options->strict_host_key_checking == 1) { | |
1190 | /* User has requested strict host key checking. We will not | |
1191 | add the host key automatically. The only alternative left | |
1192 | is to abort. */ | |
1193 | fatal("No host key is known for %.200s and you have requested strict checking.", host); | |
1194 | } else if (options->strict_host_key_checking == 2) { /* The default */ | |
1195 | char prompt[1024]; | |
1196 | snprintf(prompt, sizeof(prompt), | |
1197 | "The authenticity of host '%.200s' can't be established.\n" | |
1198 | "Are you sure you want to continue connecting (yes/no)? ", | |
1199 | host); | |
1200 | if (!read_yes_or_no(prompt, -1)) | |
1201 | fatal("Aborted by user!\n"); | |
1202 | } | |
1203 | ||
1204 | if (options->check_host_ip && ip_status == HOST_NEW && strcmp(host, ip)) | |
1205 | snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); | |
1206 | else | |
1207 | hostp = host; | |
1208 | ||
1209 | /* If not in strict mode, add the key automatically to the local | |
1210 | known_hosts file. */ | |
1211 | if (!add_host_to_hostfile(options->user_hostfile, hostp, | |
1212 | BN_num_bits(host_key->n), | |
1213 | host_key->e, host_key->n)) | |
1214 | log("Failed to add the host to the list of known hosts (%.500s).", | |
1215 | options->user_hostfile); | |
1216 | else | |
1217 | log("Warning: Permanently added '%.200s' to the list of known hosts.", | |
1218 | hostp); | |
1219 | break; | |
1220 | } | |
1221 | case HOST_CHANGED: | |
1222 | if (options->check_host_ip) { | |
1223 | if (host_ip_differ) { | |
1224 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1225 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
1226 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1227 | error("The host key for %s has changed,", host); | |
1228 | error("but the key for the according IP address %s has", ip); | |
1229 | error("a different status. This could either mean that DNS"); | |
1230 | error("SPOOFING is happening or the IP address for the host"); | |
1231 | error("and its host key have changed at the same time"); | |
1232 | } | |
1233 | } | |
1234 | ||
1235 | /* The host key has changed. */ | |
1236 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1237 | error("@ WARNING: HOST IDENTIFICATION HAS CHANGED! @"); | |
1238 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
1239 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
1240 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
1241 | error("It is also possible that the host key has just been changed."); | |
1242 | error("Please contact your system administrator."); | |
1243 | error("Add correct host key in %.100s to get rid of this message.", | |
1244 | options->user_hostfile); | |
1245 | ||
1246 | /* If strict host key checking is in use, the user will have to edit | |
1247 | the key manually and we can only abort. */ | |
1248 | if (options->strict_host_key_checking) | |
1249 | fatal("Host key for %.200s has changed and you have requested strict checking.", host); | |
1250 | ||
1251 | /* If strict host key checking has not been requested, allow the | |
1252 | connection but without password authentication or | |
1253 | agent forwarding. */ | |
1254 | if (options->password_authentication) { | |
1255 | error("Password authentication is disabled to avoid trojan horses."); | |
1256 | options->password_authentication = 0; | |
1257 | } | |
1258 | if (options->forward_agent) { | |
1259 | error("Agent forwarding is disabled to avoid trojan horses."); | |
1260 | options->forward_agent = 0; | |
1261 | } | |
1262 | /* XXX Should permit the user to change to use the new id. This could | |
1263 | be done by converting the host key to an identifying sentence, tell | |
1264 | that the host identifies itself by that sentence, and ask the user | |
1265 | if he/she whishes to accept the authentication. */ | |
1266 | break; | |
1267 | } | |
1268 | ||
1269 | if (options->check_host_ip) | |
1270 | xfree(ip); | |
1271 | ||
1272 | /* Generate a session key. */ | |
1273 | arc4random_stir(); | |
1274 | ||
1275 | /* Generate an encryption key for the session. The key is a 256 bit | |
1276 | random number, interpreted as a 32-byte key, with the least significant | |
1277 | 8 bits being the first byte of the key. */ | |
1278 | for (i = 0; i < 32; i++) { | |
1279 | if (i % 4 == 0) | |
1280 | rand = arc4random(); | |
1281 | session_key[i] = rand & 0xff; | |
1282 | rand >>= 8; | |
1283 | } | |
1284 | ||
1285 | /* According to the protocol spec, the first byte of the session key is | |
1286 | the highest byte of the integer. The session key is xored with the | |
1287 | first 16 bytes of the session id. */ | |
1288 | key = BN_new(); | |
1289 | BN_set_word(key, 0); | |
1290 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) | |
1291 | { | |
1292 | BN_lshift(key, key, 8); | |
1293 | if (i < 16) | |
1294 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
1295 | else | |
1296 | BN_add_word(key, session_key[i]); | |
1297 | } | |
1298 | ||
1299 | /* Encrypt the integer using the public key and host key of the server | |
1300 | (key with smaller modulus first). */ | |
1301 | if (BN_cmp(public_key->n, host_key->n) < 0) | |
1302 | { | |
1303 | /* Public key has smaller modulus. */ | |
5bae4ab8 | 1304 | if (BN_num_bits(host_key->n) < |
1305 | BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) { | |
1306 | fatal("respond_to_rsa_challenge: host_key %d < public_key %d + " | |
1307 | "SSH_KEY_BITS_RESERVED %d", | |
1308 | BN_num_bits(host_key->n), | |
1309 | BN_num_bits(public_key->n), | |
1310 | SSH_KEY_BITS_RESERVED); | |
1311 | } | |
8efc0c15 | 1312 | |
1313 | rsa_public_encrypt(key, key, public_key); | |
1314 | rsa_public_encrypt(key, key, host_key); | |
1315 | } | |
1316 | else | |
1317 | { | |
1318 | /* Host key has smaller modulus (or they are equal). */ | |
5bae4ab8 | 1319 | if (BN_num_bits(public_key->n) < |
1320 | BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) { | |
1321 | fatal("respond_to_rsa_challenge: public_key %d < host_key %d + " | |
1322 | "SSH_KEY_BITS_RESERVED %d", | |
1323 | BN_num_bits(public_key->n), | |
1324 | BN_num_bits(host_key->n), | |
1325 | SSH_KEY_BITS_RESERVED); | |
1326 | } | |
8efc0c15 | 1327 | |
1328 | rsa_public_encrypt(key, key, host_key); | |
1329 | rsa_public_encrypt(key, key, public_key); | |
1330 | } | |
1331 | ||
1332 | if (options->cipher == SSH_CIPHER_NOT_SET) { | |
1333 | if (cipher_mask() & supported_ciphers & (1 << ssh_cipher_default)) | |
1334 | options->cipher = ssh_cipher_default; | |
1335 | else { | |
1336 | debug("Cipher %d not supported, using %.100s instead.", | |
1337 | cipher_name(ssh_cipher_default), | |
1338 | cipher_name(SSH_FALLBACK_CIPHER)); | |
1339 | options->cipher = SSH_FALLBACK_CIPHER; | |
1340 | } | |
1341 | } | |
1342 | ||
1343 | /* Check that the selected cipher is supported. */ | |
1344 | if (!(supported_ciphers & (1 << options->cipher))) | |
1345 | fatal("Selected cipher type %.100s not supported by server.", | |
1346 | cipher_name(options->cipher)); | |
1347 | ||
1348 | debug("Encryption type: %.100s", cipher_name(options->cipher)); | |
1349 | ||
1350 | /* Send the encrypted session key to the server. */ | |
1351 | packet_start(SSH_CMSG_SESSION_KEY); | |
1352 | packet_put_char(options->cipher); | |
1353 | ||
1354 | /* Send the check bytes back to the server. */ | |
1355 | for (i = 0; i < 8; i++) | |
1356 | packet_put_char(check_bytes[i]); | |
1357 | ||
1358 | /* Send the encrypted encryption key. */ | |
1359 | packet_put_bignum(key); | |
1360 | ||
1361 | /* Send protocol flags. */ | |
1362 | packet_put_int(SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN); | |
1363 | ||
1364 | /* Send the packet now. */ | |
1365 | packet_send(); | |
1366 | packet_write_wait(); | |
1367 | ||
1368 | /* Destroy the session key integer and the public keys since we no longer | |
1369 | need them. */ | |
1370 | BN_clear_free(key); | |
1371 | RSA_free(public_key); | |
1372 | RSA_free(host_key); | |
1373 | ||
1374 | debug("Sent encrypted session key."); | |
1375 | ||
1376 | /* Set the encryption key. */ | |
1377 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, | |
1378 | options->cipher, 1); | |
1379 | ||
1380 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
1381 | memset(session_key, 0, sizeof(session_key)); | |
1382 | ||
1383 | /* Expect a success message from the server. Note that this message will | |
1384 | be received in encrypted form. */ | |
1385 | packet_read_expect(&payload_len, SSH_SMSG_SUCCESS); | |
1386 | ||
1387 | debug("Received encrypted confirmation."); | |
1388 | ||
1389 | /* Send the name of the user to log in as on the server. */ | |
1390 | packet_start(SSH_CMSG_USER); | |
1391 | packet_put_string(server_user, strlen(server_user)); | |
1392 | packet_send(); | |
1393 | packet_write_wait(); | |
1394 | ||
1395 | /* The server should respond with success if no authentication is needed | |
1396 | (the user has no password). Otherwise the server responds with | |
1397 | failure. */ | |
1398 | type = packet_read(&payload_len); | |
1399 | if (type == SSH_SMSG_SUCCESS) | |
1400 | return; /* Connection was accepted without authentication. */ | |
1401 | if (type != SSH_SMSG_FAILURE) | |
1402 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", | |
1403 | type); | |
1404 | ||
1405 | #ifdef AFS | |
1406 | /* Try Kerberos tgt passing if the server supports it. */ | |
1407 | if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && | |
1408 | options->kerberos_tgt_passing) | |
1409 | { | |
1410 | if (options->cipher == SSH_CIPHER_NONE) | |
1411 | log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); | |
1412 | (void)send_kerberos_tgt(); | |
1413 | } | |
1414 | ||
1415 | /* Try AFS token passing if the server supports it. */ | |
1416 | if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) && | |
1417 | options->afs_token_passing && k_hasafs()) { | |
1418 | if (options->cipher == SSH_CIPHER_NONE) | |
1419 | log("WARNING: Encryption is disabled! Token will be transmitted in the clear!"); | |
1420 | send_afs_tokens(); | |
1421 | } | |
1422 | #endif /* AFS */ | |
1423 | ||
1424 | #ifdef KRB4 | |
1425 | if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && | |
1426 | options->kerberos_authentication) | |
1427 | { | |
1428 | debug("Trying Kerberos authentication."); | |
1429 | if (try_kerberos_authentication()) { | |
1430 | /* The server should respond with success or failure. */ | |
1431 | type = packet_read(&payload_len); | |
1432 | if (type == SSH_SMSG_SUCCESS) | |
1433 | return; /* Successful connection. */ | |
1434 | if (type != SSH_SMSG_FAILURE) | |
1435 | packet_disconnect("Protocol error: got %d in response to Kerberos auth", type); | |
1436 | } | |
1437 | } | |
1438 | #endif /* KRB4 */ | |
1439 | ||
1440 | /* Use rhosts authentication if running in privileged socket and we do not | |
1441 | wish to remain anonymous. */ | |
1442 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) && | |
1443 | options->rhosts_authentication) | |
1444 | { | |
1445 | debug("Trying rhosts authentication."); | |
1446 | packet_start(SSH_CMSG_AUTH_RHOSTS); | |
1447 | packet_put_string(local_user, strlen(local_user)); | |
1448 | packet_send(); | |
1449 | packet_write_wait(); | |
1450 | ||
1451 | /* The server should respond with success or failure. */ | |
1452 | type = packet_read(&payload_len); | |
1453 | if (type == SSH_SMSG_SUCCESS) | |
1454 | return; /* Successful connection. */ | |
1455 | if (type != SSH_SMSG_FAILURE) | |
1456 | packet_disconnect("Protocol error: got %d in response to rhosts auth", | |
1457 | type); | |
1458 | } | |
1459 | ||
1460 | /* Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
1461 | authentication. */ | |
1462 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
1463 | options->rhosts_rsa_authentication && host_key_valid) | |
1464 | { | |
1465 | if (try_rhosts_rsa_authentication(local_user, own_host_key)) | |
1466 | return; /* Successful authentication. */ | |
1467 | } | |
1468 | ||
1469 | /* Try RSA authentication if the server supports it. */ | |
1470 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
1471 | options->rsa_authentication) | |
1472 | { | |
1473 | /* Try RSA authentication using the authentication agent. The agent | |
1474 | is tried first because no passphrase is needed for it, whereas | |
1475 | identity files may require passphrases. */ | |
1476 | if (try_agent_authentication()) | |
1477 | return; /* Successful connection. */ | |
1478 | ||
1479 | /* Try RSA authentication for each identity. */ | |
1480 | for (i = 0; i < options->num_identity_files; i++) | |
1481 | if (try_rsa_authentication(pw, options->identity_files[i], | |
1482 | !options->batch_mode)) | |
1483 | return; /* Successful connection. */ | |
1484 | } | |
1485 | ||
1486 | /* Try password authentication if the server supports it. */ | |
1487 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
1488 | options->password_authentication && !options->batch_mode) | |
1489 | { | |
1490 | char prompt[80]; | |
1491 | snprintf(prompt, sizeof(prompt), "%.30s@%.30s's password: ", | |
1492 | server_user, host); | |
1493 | debug("Doing password authentication."); | |
1494 | if (options->cipher == SSH_CIPHER_NONE) | |
1495 | log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
1496 | for (i = 0; i < options->number_of_password_prompts; i++) { | |
1497 | if (i != 0) | |
1498 | error("Permission denied, please try again."); | |
1499 | password = read_passphrase(prompt, 0); | |
1500 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
1501 | packet_put_string(password, strlen(password)); | |
1502 | memset(password, 0, strlen(password)); | |
1503 | xfree(password); | |
1504 | packet_send(); | |
1505 | packet_write_wait(); | |
1506 | ||
1507 | type = packet_read(&payload_len); | |
1508 | if (type == SSH_SMSG_SUCCESS) | |
1509 | return; /* Successful connection. */ | |
1510 | if (type != SSH_SMSG_FAILURE) | |
1511 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
1512 | } | |
1513 | } | |
1514 | ||
1515 | /* All authentication methods have failed. Exit with an error message. */ | |
1516 | fatal("Permission denied."); | |
1517 | /*NOTREACHED*/ | |
1518 | } |