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1 | /* $OpenBSD: sshconnect1.c,v 1.66 2006/07/22 20:48:23 stevesk Exp $ */ | |
2 | /* | |
3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | * All rights reserved | |
6 | * Code to connect to a remote host, and to perform the client side of the | |
7 | * login (authentication) dialog. | |
8 | * | |
9 | * As far as I am concerned, the code I have written for this software | |
10 | * can be used freely for any purpose. Any derived versions of this | |
11 | * software must be clearly marked as such, and if the derived work is | |
12 | * incompatible with the protocol description in the RFC file, it must be | |
13 | * called by a name other than "ssh" or "Secure Shell". | |
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | ||
18 | #include <openssl/bn.h> | |
19 | #include <openssl/md5.h> | |
20 | ||
21 | #include <string.h> | |
22 | ||
23 | #include "ssh.h" | |
24 | #include "ssh1.h" | |
25 | #include "xmalloc.h" | |
26 | #include "rsa.h" | |
27 | #include "buffer.h" | |
28 | #include "packet.h" | |
29 | #include "kex.h" | |
30 | #include "uidswap.h" | |
31 | #include "log.h" | |
32 | #include "readconf.h" | |
33 | #include "key.h" | |
34 | #include "authfd.h" | |
35 | #include "sshconnect.h" | |
36 | #include "authfile.h" | |
37 | #include "misc.h" | |
38 | #include "cipher.h" | |
39 | #include "canohost.h" | |
40 | #include "auth.h" | |
41 | ||
42 | /* Session id for the current session. */ | |
43 | u_char session_id[16]; | |
44 | u_int supported_authentications = 0; | |
45 | ||
46 | extern Options options; | |
47 | extern char *__progname; | |
48 | ||
49 | /* | |
50 | * Checks if the user has an authentication agent, and if so, tries to | |
51 | * authenticate using the agent. | |
52 | */ | |
53 | static int | |
54 | try_agent_authentication(void) | |
55 | { | |
56 | int type; | |
57 | char *comment; | |
58 | AuthenticationConnection *auth; | |
59 | u_char response[16]; | |
60 | u_int i; | |
61 | Key *key; | |
62 | BIGNUM *challenge; | |
63 | ||
64 | /* Get connection to the agent. */ | |
65 | auth = ssh_get_authentication_connection(); | |
66 | if (!auth) | |
67 | return 0; | |
68 | ||
69 | if ((challenge = BN_new()) == NULL) | |
70 | fatal("try_agent_authentication: BN_new failed"); | |
71 | /* Loop through identities served by the agent. */ | |
72 | for (key = ssh_get_first_identity(auth, &comment, 1); | |
73 | key != NULL; | |
74 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
75 | ||
76 | /* Try this identity. */ | |
77 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
78 | xfree(comment); | |
79 | ||
80 | /* Tell the server that we are willing to authenticate using this key. */ | |
81 | packet_start(SSH_CMSG_AUTH_RSA); | |
82 | packet_put_bignum(key->rsa->n); | |
83 | packet_send(); | |
84 | packet_write_wait(); | |
85 | ||
86 | /* Wait for server's response. */ | |
87 | type = packet_read(); | |
88 | ||
89 | /* The server sends failure if it doesn't like our key or | |
90 | does not support RSA authentication. */ | |
91 | if (type == SSH_SMSG_FAILURE) { | |
92 | debug("Server refused our key."); | |
93 | key_free(key); | |
94 | continue; | |
95 | } | |
96 | /* Otherwise it should have sent a challenge. */ | |
97 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
98 | packet_disconnect("Protocol error during RSA authentication: %d", | |
99 | type); | |
100 | ||
101 | packet_get_bignum(challenge); | |
102 | packet_check_eom(); | |
103 | ||
104 | debug("Received RSA challenge from server."); | |
105 | ||
106 | /* Ask the agent to decrypt the challenge. */ | |
107 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { | |
108 | /* | |
109 | * The agent failed to authenticate this identifier | |
110 | * although it advertised it supports this. Just | |
111 | * return a wrong value. | |
112 | */ | |
113 | logit("Authentication agent failed to decrypt challenge."); | |
114 | memset(response, 0, sizeof(response)); | |
115 | } | |
116 | key_free(key); | |
117 | debug("Sending response to RSA challenge."); | |
118 | ||
119 | /* Send the decrypted challenge back to the server. */ | |
120 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
121 | for (i = 0; i < 16; i++) | |
122 | packet_put_char(response[i]); | |
123 | packet_send(); | |
124 | packet_write_wait(); | |
125 | ||
126 | /* Wait for response from the server. */ | |
127 | type = packet_read(); | |
128 | ||
129 | /* The server returns success if it accepted the authentication. */ | |
130 | if (type == SSH_SMSG_SUCCESS) { | |
131 | ssh_close_authentication_connection(auth); | |
132 | BN_clear_free(challenge); | |
133 | debug("RSA authentication accepted by server."); | |
134 | return 1; | |
135 | } | |
136 | /* Otherwise it should return failure. */ | |
137 | if (type != SSH_SMSG_FAILURE) | |
138 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
139 | type); | |
140 | } | |
141 | ssh_close_authentication_connection(auth); | |
142 | BN_clear_free(challenge); | |
143 | debug("RSA authentication using agent refused."); | |
144 | return 0; | |
145 | } | |
146 | ||
147 | /* | |
148 | * Computes the proper response to a RSA challenge, and sends the response to | |
149 | * the server. | |
150 | */ | |
151 | static void | |
152 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
153 | { | |
154 | u_char buf[32], response[16]; | |
155 | MD5_CTX md; | |
156 | int i, len; | |
157 | ||
158 | /* Decrypt the challenge using the private key. */ | |
159 | /* XXX think about Bleichenbacher, too */ | |
160 | if (rsa_private_decrypt(challenge, challenge, prv) <= 0) | |
161 | packet_disconnect( | |
162 | "respond_to_rsa_challenge: rsa_private_decrypt failed"); | |
163 | ||
164 | /* Compute the response. */ | |
165 | /* The response is MD5 of decrypted challenge plus session id. */ | |
166 | len = BN_num_bytes(challenge); | |
167 | if (len <= 0 || (u_int)len > sizeof(buf)) | |
168 | packet_disconnect( | |
169 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
170 | ||
171 | memset(buf, 0, sizeof(buf)); | |
172 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
173 | MD5_Init(&md); | |
174 | MD5_Update(&md, buf, 32); | |
175 | MD5_Update(&md, session_id, 16); | |
176 | MD5_Final(response, &md); | |
177 | ||
178 | debug("Sending response to host key RSA challenge."); | |
179 | ||
180 | /* Send the response back to the server. */ | |
181 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
182 | for (i = 0; i < 16; i++) | |
183 | packet_put_char(response[i]); | |
184 | packet_send(); | |
185 | packet_write_wait(); | |
186 | ||
187 | memset(buf, 0, sizeof(buf)); | |
188 | memset(response, 0, sizeof(response)); | |
189 | memset(&md, 0, sizeof(md)); | |
190 | } | |
191 | ||
192 | /* | |
193 | * Checks if the user has authentication file, and if so, tries to authenticate | |
194 | * the user using it. | |
195 | */ | |
196 | static int | |
197 | try_rsa_authentication(int idx) | |
198 | { | |
199 | BIGNUM *challenge; | |
200 | Key *public, *private; | |
201 | char buf[300], *passphrase, *comment, *authfile; | |
202 | int i, perm_ok = 1, type, quit; | |
203 | ||
204 | public = options.identity_keys[idx]; | |
205 | authfile = options.identity_files[idx]; | |
206 | comment = xstrdup(authfile); | |
207 | ||
208 | debug("Trying RSA authentication with key '%.100s'", comment); | |
209 | ||
210 | /* Tell the server that we are willing to authenticate using this key. */ | |
211 | packet_start(SSH_CMSG_AUTH_RSA); | |
212 | packet_put_bignum(public->rsa->n); | |
213 | packet_send(); | |
214 | packet_write_wait(); | |
215 | ||
216 | /* Wait for server's response. */ | |
217 | type = packet_read(); | |
218 | ||
219 | /* | |
220 | * The server responds with failure if it doesn't like our key or | |
221 | * doesn't support RSA authentication. | |
222 | */ | |
223 | if (type == SSH_SMSG_FAILURE) { | |
224 | debug("Server refused our key."); | |
225 | xfree(comment); | |
226 | return 0; | |
227 | } | |
228 | /* Otherwise, the server should respond with a challenge. */ | |
229 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
230 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
231 | ||
232 | /* Get the challenge from the packet. */ | |
233 | if ((challenge = BN_new()) == NULL) | |
234 | fatal("try_rsa_authentication: BN_new failed"); | |
235 | packet_get_bignum(challenge); | |
236 | packet_check_eom(); | |
237 | ||
238 | debug("Received RSA challenge from server."); | |
239 | ||
240 | /* | |
241 | * If the key is not stored in external hardware, we have to | |
242 | * load the private key. Try first with empty passphrase; if it | |
243 | * fails, ask for a passphrase. | |
244 | */ | |
245 | if (public->flags & KEY_FLAG_EXT) | |
246 | private = public; | |
247 | else | |
248 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL, | |
249 | &perm_ok); | |
250 | if (private == NULL && !options.batch_mode && perm_ok) { | |
251 | snprintf(buf, sizeof(buf), | |
252 | "Enter passphrase for RSA key '%.100s': ", comment); | |
253 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
254 | passphrase = read_passphrase(buf, 0); | |
255 | if (strcmp(passphrase, "") != 0) { | |
256 | private = key_load_private_type(KEY_RSA1, | |
257 | authfile, passphrase, NULL, NULL); | |
258 | quit = 0; | |
259 | } else { | |
260 | debug2("no passphrase given, try next key"); | |
261 | quit = 1; | |
262 | } | |
263 | memset(passphrase, 0, strlen(passphrase)); | |
264 | xfree(passphrase); | |
265 | if (private != NULL || quit) | |
266 | break; | |
267 | debug2("bad passphrase given, try again..."); | |
268 | } | |
269 | } | |
270 | /* We no longer need the comment. */ | |
271 | xfree(comment); | |
272 | ||
273 | if (private == NULL) { | |
274 | if (!options.batch_mode && perm_ok) | |
275 | error("Bad passphrase."); | |
276 | ||
277 | /* Send a dummy response packet to avoid protocol error. */ | |
278 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
279 | for (i = 0; i < 16; i++) | |
280 | packet_put_char(0); | |
281 | packet_send(); | |
282 | packet_write_wait(); | |
283 | ||
284 | /* Expect the server to reject it... */ | |
285 | packet_read_expect(SSH_SMSG_FAILURE); | |
286 | BN_clear_free(challenge); | |
287 | return 0; | |
288 | } | |
289 | ||
290 | /* Compute and send a response to the challenge. */ | |
291 | respond_to_rsa_challenge(challenge, private->rsa); | |
292 | ||
293 | /* Destroy the private key unless it in external hardware. */ | |
294 | if (!(private->flags & KEY_FLAG_EXT)) | |
295 | key_free(private); | |
296 | ||
297 | /* We no longer need the challenge. */ | |
298 | BN_clear_free(challenge); | |
299 | ||
300 | /* Wait for response from the server. */ | |
301 | type = packet_read(); | |
302 | if (type == SSH_SMSG_SUCCESS) { | |
303 | debug("RSA authentication accepted by server."); | |
304 | return 1; | |
305 | } | |
306 | if (type != SSH_SMSG_FAILURE) | |
307 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
308 | debug("RSA authentication refused."); | |
309 | return 0; | |
310 | } | |
311 | ||
312 | /* | |
313 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
314 | * authentication and RSA host authentication. | |
315 | */ | |
316 | static int | |
317 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) | |
318 | { | |
319 | int type; | |
320 | BIGNUM *challenge; | |
321 | ||
322 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
323 | ||
324 | /* Tell the server that we are willing to authenticate using this key. */ | |
325 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
326 | packet_put_cstring(local_user); | |
327 | packet_put_int(BN_num_bits(host_key->rsa->n)); | |
328 | packet_put_bignum(host_key->rsa->e); | |
329 | packet_put_bignum(host_key->rsa->n); | |
330 | packet_send(); | |
331 | packet_write_wait(); | |
332 | ||
333 | /* Wait for server's response. */ | |
334 | type = packet_read(); | |
335 | ||
336 | /* The server responds with failure if it doesn't admit our | |
337 | .rhosts authentication or doesn't know our host key. */ | |
338 | if (type == SSH_SMSG_FAILURE) { | |
339 | debug("Server refused our rhosts authentication or host key."); | |
340 | return 0; | |
341 | } | |
342 | /* Otherwise, the server should respond with a challenge. */ | |
343 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
344 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
345 | ||
346 | /* Get the challenge from the packet. */ | |
347 | if ((challenge = BN_new()) == NULL) | |
348 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
349 | packet_get_bignum(challenge); | |
350 | packet_check_eom(); | |
351 | ||
352 | debug("Received RSA challenge for host key from server."); | |
353 | ||
354 | /* Compute a response to the challenge. */ | |
355 | respond_to_rsa_challenge(challenge, host_key->rsa); | |
356 | ||
357 | /* We no longer need the challenge. */ | |
358 | BN_clear_free(challenge); | |
359 | ||
360 | /* Wait for response from the server. */ | |
361 | type = packet_read(); | |
362 | if (type == SSH_SMSG_SUCCESS) { | |
363 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
364 | return 1; | |
365 | } | |
366 | if (type != SSH_SMSG_FAILURE) | |
367 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
368 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
369 | return 0; | |
370 | } | |
371 | ||
372 | /* | |
373 | * Tries to authenticate with any string-based challenge/response system. | |
374 | * Note that the client code is not tied to s/key or TIS. | |
375 | */ | |
376 | static int | |
377 | try_challenge_response_authentication(void) | |
378 | { | |
379 | int type, i; | |
380 | u_int clen; | |
381 | char prompt[1024]; | |
382 | char *challenge, *response; | |
383 | ||
384 | debug("Doing challenge response authentication."); | |
385 | ||
386 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
387 | /* request a challenge */ | |
388 | packet_start(SSH_CMSG_AUTH_TIS); | |
389 | packet_send(); | |
390 | packet_write_wait(); | |
391 | ||
392 | type = packet_read(); | |
393 | if (type != SSH_SMSG_FAILURE && | |
394 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
395 | packet_disconnect("Protocol error: got %d in response " | |
396 | "to SSH_CMSG_AUTH_TIS", type); | |
397 | } | |
398 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
399 | debug("No challenge."); | |
400 | return 0; | |
401 | } | |
402 | challenge = packet_get_string(&clen); | |
403 | packet_check_eom(); | |
404 | snprintf(prompt, sizeof prompt, "%s%s", challenge, | |
405 | strchr(challenge, '\n') ? "" : "\nResponse: "); | |
406 | xfree(challenge); | |
407 | if (i != 0) | |
408 | error("Permission denied, please try again."); | |
409 | if (options.cipher == SSH_CIPHER_NONE) | |
410 | logit("WARNING: Encryption is disabled! " | |
411 | "Response will be transmitted in clear text."); | |
412 | response = read_passphrase(prompt, 0); | |
413 | if (strcmp(response, "") == 0) { | |
414 | xfree(response); | |
415 | break; | |
416 | } | |
417 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); | |
418 | ssh_put_password(response); | |
419 | memset(response, 0, strlen(response)); | |
420 | xfree(response); | |
421 | packet_send(); | |
422 | packet_write_wait(); | |
423 | type = packet_read(); | |
424 | if (type == SSH_SMSG_SUCCESS) | |
425 | return 1; | |
426 | if (type != SSH_SMSG_FAILURE) | |
427 | packet_disconnect("Protocol error: got %d in response " | |
428 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); | |
429 | } | |
430 | /* failure */ | |
431 | return 0; | |
432 | } | |
433 | ||
434 | /* | |
435 | * Tries to authenticate with plain passwd authentication. | |
436 | */ | |
437 | static int | |
438 | try_password_authentication(char *prompt) | |
439 | { | |
440 | int type, i; | |
441 | char *password; | |
442 | ||
443 | debug("Doing password authentication."); | |
444 | if (options.cipher == SSH_CIPHER_NONE) | |
445 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
446 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
447 | if (i != 0) | |
448 | error("Permission denied, please try again."); | |
449 | password = read_passphrase(prompt, 0); | |
450 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
451 | ssh_put_password(password); | |
452 | memset(password, 0, strlen(password)); | |
453 | xfree(password); | |
454 | packet_send(); | |
455 | packet_write_wait(); | |
456 | ||
457 | type = packet_read(); | |
458 | if (type == SSH_SMSG_SUCCESS) | |
459 | return 1; | |
460 | if (type != SSH_SMSG_FAILURE) | |
461 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
462 | } | |
463 | /* failure */ | |
464 | return 0; | |
465 | } | |
466 | ||
467 | /* | |
468 | * SSH1 key exchange | |
469 | */ | |
470 | void | |
471 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
472 | { | |
473 | int i; | |
474 | BIGNUM *key; | |
475 | Key *host_key, *server_key; | |
476 | int bits, rbits; | |
477 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
478 | u_char session_key[SSH_SESSION_KEY_LENGTH]; | |
479 | u_char cookie[8]; | |
480 | u_int supported_ciphers; | |
481 | u_int server_flags, client_flags; | |
482 | u_int32_t rnd = 0; | |
483 | ||
484 | debug("Waiting for server public key."); | |
485 | ||
486 | /* Wait for a public key packet from the server. */ | |
487 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); | |
488 | ||
489 | /* Get cookie from the packet. */ | |
490 | for (i = 0; i < 8; i++) | |
491 | cookie[i] = packet_get_char(); | |
492 | ||
493 | /* Get the public key. */ | |
494 | server_key = key_new(KEY_RSA1); | |
495 | bits = packet_get_int(); | |
496 | packet_get_bignum(server_key->rsa->e); | |
497 | packet_get_bignum(server_key->rsa->n); | |
498 | ||
499 | rbits = BN_num_bits(server_key->rsa->n); | |
500 | if (bits != rbits) { | |
501 | logit("Warning: Server lies about size of server public key: " | |
502 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
503 | logit("Warning: This may be due to an old implementation of ssh."); | |
504 | } | |
505 | /* Get the host key. */ | |
506 | host_key = key_new(KEY_RSA1); | |
507 | bits = packet_get_int(); | |
508 | packet_get_bignum(host_key->rsa->e); | |
509 | packet_get_bignum(host_key->rsa->n); | |
510 | ||
511 | rbits = BN_num_bits(host_key->rsa->n); | |
512 | if (bits != rbits) { | |
513 | logit("Warning: Server lies about size of server host key: " | |
514 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
515 | logit("Warning: This may be due to an old implementation of ssh."); | |
516 | } | |
517 | ||
518 | /* Get protocol flags. */ | |
519 | server_flags = packet_get_int(); | |
520 | packet_set_protocol_flags(server_flags); | |
521 | ||
522 | supported_ciphers = packet_get_int(); | |
523 | supported_authentications = packet_get_int(); | |
524 | packet_check_eom(); | |
525 | ||
526 | debug("Received server public key (%d bits) and host key (%d bits).", | |
527 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); | |
528 | ||
529 | if (verify_host_key(host, hostaddr, host_key) == -1) | |
530 | fatal("Host key verification failed."); | |
531 | ||
532 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
533 | ||
534 | derive_ssh1_session_id(host_key->rsa->n, server_key->rsa->n, cookie, session_id); | |
535 | ||
536 | /* Generate a session key. */ | |
537 | arc4random_stir(); | |
538 | ||
539 | /* | |
540 | * Generate an encryption key for the session. The key is a 256 bit | |
541 | * random number, interpreted as a 32-byte key, with the least | |
542 | * significant 8 bits being the first byte of the key. | |
543 | */ | |
544 | for (i = 0; i < 32; i++) { | |
545 | if (i % 4 == 0) | |
546 | rnd = arc4random(); | |
547 | session_key[i] = rnd & 0xff; | |
548 | rnd >>= 8; | |
549 | } | |
550 | ||
551 | /* | |
552 | * According to the protocol spec, the first byte of the session key | |
553 | * is the highest byte of the integer. The session key is xored with | |
554 | * the first 16 bytes of the session id. | |
555 | */ | |
556 | if ((key = BN_new()) == NULL) | |
557 | fatal("respond_to_rsa_challenge: BN_new failed"); | |
558 | BN_set_word(key, 0); | |
559 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
560 | BN_lshift(key, key, 8); | |
561 | if (i < 16) | |
562 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
563 | else | |
564 | BN_add_word(key, session_key[i]); | |
565 | } | |
566 | ||
567 | /* | |
568 | * Encrypt the integer using the public key and host key of the | |
569 | * server (key with smaller modulus first). | |
570 | */ | |
571 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { | |
572 | /* Public key has smaller modulus. */ | |
573 | if (BN_num_bits(host_key->rsa->n) < | |
574 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
575 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
576 | "SSH_KEY_BITS_RESERVED %d", | |
577 | BN_num_bits(host_key->rsa->n), | |
578 | BN_num_bits(server_key->rsa->n), | |
579 | SSH_KEY_BITS_RESERVED); | |
580 | } | |
581 | rsa_public_encrypt(key, key, server_key->rsa); | |
582 | rsa_public_encrypt(key, key, host_key->rsa); | |
583 | } else { | |
584 | /* Host key has smaller modulus (or they are equal). */ | |
585 | if (BN_num_bits(server_key->rsa->n) < | |
586 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
587 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
588 | "SSH_KEY_BITS_RESERVED %d", | |
589 | BN_num_bits(server_key->rsa->n), | |
590 | BN_num_bits(host_key->rsa->n), | |
591 | SSH_KEY_BITS_RESERVED); | |
592 | } | |
593 | rsa_public_encrypt(key, key, host_key->rsa); | |
594 | rsa_public_encrypt(key, key, server_key->rsa); | |
595 | } | |
596 | ||
597 | /* Destroy the public keys since we no longer need them. */ | |
598 | key_free(server_key); | |
599 | key_free(host_key); | |
600 | ||
601 | if (options.cipher == SSH_CIPHER_NOT_SET) { | |
602 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
603 | options.cipher = ssh_cipher_default; | |
604 | } else if (options.cipher == SSH_CIPHER_INVALID || | |
605 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { | |
606 | logit("No valid SSH1 cipher, using %.100s instead.", | |
607 | cipher_name(ssh_cipher_default)); | |
608 | options.cipher = ssh_cipher_default; | |
609 | } | |
610 | /* Check that the selected cipher is supported. */ | |
611 | if (!(supported_ciphers & (1 << options.cipher))) | |
612 | fatal("Selected cipher type %.100s not supported by server.", | |
613 | cipher_name(options.cipher)); | |
614 | ||
615 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
616 | ||
617 | /* Send the encrypted session key to the server. */ | |
618 | packet_start(SSH_CMSG_SESSION_KEY); | |
619 | packet_put_char(options.cipher); | |
620 | ||
621 | /* Send the cookie back to the server. */ | |
622 | for (i = 0; i < 8; i++) | |
623 | packet_put_char(cookie[i]); | |
624 | ||
625 | /* Send and destroy the encrypted encryption key integer. */ | |
626 | packet_put_bignum(key); | |
627 | BN_clear_free(key); | |
628 | ||
629 | /* Send protocol flags. */ | |
630 | packet_put_int(client_flags); | |
631 | ||
632 | /* Send the packet now. */ | |
633 | packet_send(); | |
634 | packet_write_wait(); | |
635 | ||
636 | debug("Sent encrypted session key."); | |
637 | ||
638 | /* Set the encryption key. */ | |
639 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
640 | ||
641 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
642 | memset(session_key, 0, sizeof(session_key)); | |
643 | ||
644 | /* | |
645 | * Expect a success message from the server. Note that this message | |
646 | * will be received in encrypted form. | |
647 | */ | |
648 | packet_read_expect(SSH_SMSG_SUCCESS); | |
649 | ||
650 | debug("Received encrypted confirmation."); | |
651 | } | |
652 | ||
653 | /* | |
654 | * Authenticate user | |
655 | */ | |
656 | void | |
657 | ssh_userauth1(const char *local_user, const char *server_user, char *host, | |
658 | Sensitive *sensitive) | |
659 | { | |
660 | int i, type; | |
661 | ||
662 | if (supported_authentications == 0) | |
663 | fatal("ssh_userauth1: server supports no auth methods"); | |
664 | ||
665 | /* Send the name of the user to log in as on the server. */ | |
666 | packet_start(SSH_CMSG_USER); | |
667 | packet_put_cstring(server_user); | |
668 | packet_send(); | |
669 | packet_write_wait(); | |
670 | ||
671 | /* | |
672 | * The server should respond with success if no authentication is | |
673 | * needed (the user has no password). Otherwise the server responds | |
674 | * with failure. | |
675 | */ | |
676 | type = packet_read(); | |
677 | ||
678 | /* check whether the connection was accepted without authentication. */ | |
679 | if (type == SSH_SMSG_SUCCESS) | |
680 | goto success; | |
681 | if (type != SSH_SMSG_FAILURE) | |
682 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); | |
683 | ||
684 | /* | |
685 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
686 | * authentication. | |
687 | */ | |
688 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
689 | options.rhosts_rsa_authentication) { | |
690 | for (i = 0; i < sensitive->nkeys; i++) { | |
691 | if (sensitive->keys[i] != NULL && | |
692 | sensitive->keys[i]->type == KEY_RSA1 && | |
693 | try_rhosts_rsa_authentication(local_user, | |
694 | sensitive->keys[i])) | |
695 | goto success; | |
696 | } | |
697 | } | |
698 | /* Try RSA authentication if the server supports it. */ | |
699 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
700 | options.rsa_authentication) { | |
701 | /* | |
702 | * Try RSA authentication using the authentication agent. The | |
703 | * agent is tried first because no passphrase is needed for | |
704 | * it, whereas identity files may require passphrases. | |
705 | */ | |
706 | if (try_agent_authentication()) | |
707 | goto success; | |
708 | ||
709 | /* Try RSA authentication for each identity. */ | |
710 | for (i = 0; i < options.num_identity_files; i++) | |
711 | if (options.identity_keys[i] != NULL && | |
712 | options.identity_keys[i]->type == KEY_RSA1 && | |
713 | try_rsa_authentication(i)) | |
714 | goto success; | |
715 | } | |
716 | /* Try challenge response authentication if the server supports it. */ | |
717 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
718 | options.challenge_response_authentication && !options.batch_mode) { | |
719 | if (try_challenge_response_authentication()) | |
720 | goto success; | |
721 | } | |
722 | /* Try password authentication if the server supports it. */ | |
723 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
724 | options.password_authentication && !options.batch_mode) { | |
725 | char prompt[80]; | |
726 | ||
727 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", | |
728 | server_user, host); | |
729 | if (try_password_authentication(prompt)) | |
730 | goto success; | |
731 | } | |
732 | /* All authentication methods have failed. Exit with an error message. */ | |
733 | fatal("Permission denied."); | |
734 | /* NOTREACHED */ | |
735 | ||
736 | success: | |
737 | return; /* need statement after label */ | |
738 | } |