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