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3c0ef626 | 1 | /* |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Code to connect to a remote host, and to perform the client side of the | |
6 | * login (authentication) dialog. | |
7 | * | |
8 | * As far as I am concerned, the code I have written for this software | |
9 | * can be used freely for any purpose. Any derived versions of this | |
10 | * software must be clearly marked as such, and if the derived work is | |
11 | * incompatible with the protocol description in the RFC file, it must be | |
12 | * called by a name other than "ssh" or "Secure Shell". | |
13 | */ | |
14 | ||
15 | #include "includes.h" | |
70791e56 | 16 | RCSID("$OpenBSD: sshconnect1.c,v 1.56 2003/08/28 12:54:34 markus Exp $"); |
3c0ef626 | 17 | |
18 | #include <openssl/bn.h> | |
1e608e42 | 19 | #include <openssl/md5.h> |
3c0ef626 | 20 | |
3c0ef626 | 21 | #include "ssh.h" |
22 | #include "ssh1.h" | |
23 | #include "xmalloc.h" | |
24 | #include "rsa.h" | |
25 | #include "buffer.h" | |
26 | #include "packet.h" | |
27 | #include "mpaux.h" | |
28 | #include "uidswap.h" | |
29 | #include "log.h" | |
30 | #include "readconf.h" | |
31 | #include "key.h" | |
32 | #include "authfd.h" | |
33 | #include "sshconnect.h" | |
34 | #include "authfile.h" | |
35 | #include "readpass.h" | |
36 | #include "cipher.h" | |
37 | #include "canohost.h" | |
38 | #include "auth.h" | |
39 | ||
40 | /* Session id for the current session. */ | |
41 | u_char session_id[16]; | |
42 | u_int supported_authentications = 0; | |
43 | ||
44 | extern Options options; | |
45 | extern char *__progname; | |
46 | ||
47 | /* | |
48 | * Checks if the user has an authentication agent, and if so, tries to | |
49 | * authenticate using the agent. | |
50 | */ | |
51 | static int | |
52 | try_agent_authentication(void) | |
53 | { | |
54 | int type; | |
55 | char *comment; | |
56 | AuthenticationConnection *auth; | |
57 | u_char response[16]; | |
58 | u_int i; | |
3c0ef626 | 59 | Key *key; |
60 | BIGNUM *challenge; | |
61 | ||
62 | /* Get connection to the agent. */ | |
63 | auth = ssh_get_authentication_connection(); | |
64 | if (!auth) | |
65 | return 0; | |
66 | ||
1e608e42 | 67 | if ((challenge = BN_new()) == NULL) |
68 | fatal("try_agent_authentication: BN_new failed"); | |
3c0ef626 | 69 | /* Loop through identities served by the agent. */ |
70 | for (key = ssh_get_first_identity(auth, &comment, 1); | |
1e608e42 | 71 | key != NULL; |
72 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
3c0ef626 | 73 | |
74 | /* Try this identity. */ | |
75 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
76 | xfree(comment); | |
77 | ||
78 | /* Tell the server that we are willing to authenticate using this key. */ | |
79 | packet_start(SSH_CMSG_AUTH_RSA); | |
80 | packet_put_bignum(key->rsa->n); | |
81 | packet_send(); | |
82 | packet_write_wait(); | |
83 | ||
84 | /* Wait for server's response. */ | |
1e608e42 | 85 | type = packet_read(); |
3c0ef626 | 86 | |
87 | /* The server sends failure if it doesn\'t like our key or | |
88 | does not support RSA authentication. */ | |
89 | if (type == SSH_SMSG_FAILURE) { | |
90 | debug("Server refused our key."); | |
91 | key_free(key); | |
92 | continue; | |
93 | } | |
94 | /* Otherwise it should have sent a challenge. */ | |
95 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
96 | packet_disconnect("Protocol error during RSA authentication: %d", | |
97 | type); | |
98 | ||
1e608e42 | 99 | packet_get_bignum(challenge); |
100 | packet_check_eom(); | |
3c0ef626 | 101 | |
102 | debug("Received RSA challenge from server."); | |
103 | ||
104 | /* Ask the agent to decrypt the challenge. */ | |
105 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { | |
106 | /* | |
107 | * The agent failed to authenticate this identifier | |
108 | * although it advertised it supports this. Just | |
109 | * return a wrong value. | |
110 | */ | |
70791e56 | 111 | logit("Authentication agent failed to decrypt challenge."); |
3c0ef626 | 112 | memset(response, 0, sizeof(response)); |
113 | } | |
114 | key_free(key); | |
115 | debug("Sending response to RSA challenge."); | |
116 | ||
117 | /* Send the decrypted challenge back to the server. */ | |
118 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
119 | for (i = 0; i < 16; i++) | |
120 | packet_put_char(response[i]); | |
121 | packet_send(); | |
122 | packet_write_wait(); | |
123 | ||
124 | /* Wait for response from the server. */ | |
1e608e42 | 125 | type = packet_read(); |
3c0ef626 | 126 | |
127 | /* The server returns success if it accepted the authentication. */ | |
128 | if (type == SSH_SMSG_SUCCESS) { | |
129 | ssh_close_authentication_connection(auth); | |
130 | BN_clear_free(challenge); | |
131 | debug("RSA authentication accepted by server."); | |
132 | return 1; | |
133 | } | |
134 | /* Otherwise it should return failure. */ | |
135 | if (type != SSH_SMSG_FAILURE) | |
136 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
137 | type); | |
138 | } | |
139 | ssh_close_authentication_connection(auth); | |
140 | BN_clear_free(challenge); | |
141 | debug("RSA authentication using agent refused."); | |
142 | return 0; | |
143 | } | |
144 | ||
145 | /* | |
146 | * Computes the proper response to a RSA challenge, and sends the response to | |
147 | * the server. | |
148 | */ | |
149 | static void | |
150 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
151 | { | |
152 | u_char buf[32], response[16]; | |
153 | MD5_CTX md; | |
154 | int i, len; | |
155 | ||
156 | /* Decrypt the challenge using the private key. */ | |
157 | /* XXX think about Bleichenbacher, too */ | |
158 | if (rsa_private_decrypt(challenge, challenge, prv) <= 0) | |
159 | packet_disconnect( | |
160 | "respond_to_rsa_challenge: rsa_private_decrypt failed"); | |
161 | ||
162 | /* Compute the response. */ | |
163 | /* The response is MD5 of decrypted challenge plus session id. */ | |
164 | len = BN_num_bytes(challenge); | |
165 | if (len <= 0 || len > sizeof(buf)) | |
166 | packet_disconnect( | |
167 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
168 | ||
169 | memset(buf, 0, sizeof(buf)); | |
170 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
171 | MD5_Init(&md); | |
172 | MD5_Update(&md, buf, 32); | |
173 | MD5_Update(&md, session_id, 16); | |
174 | MD5_Final(response, &md); | |
175 | ||
176 | debug("Sending response to host key RSA challenge."); | |
177 | ||
178 | /* Send the response back to the server. */ | |
179 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
180 | for (i = 0; i < 16; i++) | |
181 | packet_put_char(response[i]); | |
182 | packet_send(); | |
183 | packet_write_wait(); | |
184 | ||
185 | memset(buf, 0, sizeof(buf)); | |
186 | memset(response, 0, sizeof(response)); | |
187 | memset(&md, 0, sizeof(md)); | |
188 | } | |
189 | ||
190 | /* | |
191 | * Checks if the user has authentication file, and if so, tries to authenticate | |
192 | * the user using it. | |
193 | */ | |
194 | static int | |
195 | try_rsa_authentication(int idx) | |
196 | { | |
197 | BIGNUM *challenge; | |
198 | Key *public, *private; | |
199 | char buf[300], *passphrase, *comment, *authfile; | |
1e608e42 | 200 | int i, type, quit; |
3c0ef626 | 201 | |
202 | public = options.identity_keys[idx]; | |
203 | authfile = options.identity_files[idx]; | |
204 | comment = xstrdup(authfile); | |
205 | ||
206 | debug("Trying RSA authentication with key '%.100s'", comment); | |
207 | ||
208 | /* Tell the server that we are willing to authenticate using this key. */ | |
209 | packet_start(SSH_CMSG_AUTH_RSA); | |
210 | packet_put_bignum(public->rsa->n); | |
211 | packet_send(); | |
212 | packet_write_wait(); | |
213 | ||
214 | /* Wait for server's response. */ | |
1e608e42 | 215 | type = packet_read(); |
3c0ef626 | 216 | |
217 | /* | |
218 | * The server responds with failure if it doesn\'t like our key or | |
219 | * doesn\'t support RSA authentication. | |
220 | */ | |
221 | if (type == SSH_SMSG_FAILURE) { | |
222 | debug("Server refused our key."); | |
223 | xfree(comment); | |
224 | return 0; | |
225 | } | |
226 | /* Otherwise, the server should respond with a challenge. */ | |
227 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
228 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
229 | ||
230 | /* Get the challenge from the packet. */ | |
1e608e42 | 231 | if ((challenge = BN_new()) == NULL) |
232 | fatal("try_rsa_authentication: BN_new failed"); | |
233 | packet_get_bignum(challenge); | |
234 | packet_check_eom(); | |
3c0ef626 | 235 | |
236 | debug("Received RSA challenge from server."); | |
237 | ||
238 | /* | |
239 | * If the key is not stored in external hardware, we have to | |
240 | * load the private key. Try first with empty passphrase; if it | |
241 | * fails, ask for a passphrase. | |
242 | */ | |
e54b3d7c | 243 | if (public->flags & KEY_FLAG_EXT) |
3c0ef626 | 244 | private = public; |
245 | else | |
246 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL); | |
247 | if (private == NULL && !options.batch_mode) { | |
248 | snprintf(buf, sizeof(buf), | |
249 | "Enter passphrase for RSA key '%.100s': ", comment); | |
250 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
251 | passphrase = read_passphrase(buf, 0); | |
252 | if (strcmp(passphrase, "") != 0) { | |
253 | private = key_load_private_type(KEY_RSA1, | |
254 | authfile, passphrase, NULL); | |
255 | quit = 0; | |
256 | } else { | |
257 | debug2("no passphrase given, try next key"); | |
258 | quit = 1; | |
259 | } | |
260 | memset(passphrase, 0, strlen(passphrase)); | |
261 | xfree(passphrase); | |
262 | if (private != NULL || quit) | |
263 | break; | |
264 | debug2("bad passphrase given, try again..."); | |
265 | } | |
266 | } | |
267 | /* We no longer need the comment. */ | |
268 | xfree(comment); | |
269 | ||
270 | if (private == NULL) { | |
271 | if (!options.batch_mode) | |
272 | error("Bad passphrase."); | |
273 | ||
274 | /* Send a dummy response packet to avoid protocol error. */ | |
275 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
276 | for (i = 0; i < 16; i++) | |
277 | packet_put_char(0); | |
278 | packet_send(); | |
279 | packet_write_wait(); | |
280 | ||
281 | /* Expect the server to reject it... */ | |
1e608e42 | 282 | packet_read_expect(SSH_SMSG_FAILURE); |
3c0ef626 | 283 | BN_clear_free(challenge); |
284 | return 0; | |
285 | } | |
286 | ||
287 | /* Compute and send a response to the challenge. */ | |
288 | respond_to_rsa_challenge(challenge, private->rsa); | |
289 | ||
290 | /* Destroy the private key unless it in external hardware. */ | |
291 | if (!(private->flags & KEY_FLAG_EXT)) | |
292 | key_free(private); | |
293 | ||
294 | /* We no longer need the challenge. */ | |
295 | BN_clear_free(challenge); | |
296 | ||
297 | /* Wait for response from the server. */ | |
1e608e42 | 298 | type = packet_read(); |
3c0ef626 | 299 | if (type == SSH_SMSG_SUCCESS) { |
300 | debug("RSA authentication accepted by server."); | |
301 | return 1; | |
302 | } | |
303 | if (type != SSH_SMSG_FAILURE) | |
304 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
305 | debug("RSA authentication refused."); | |
306 | return 0; | |
307 | } | |
308 | ||
309 | /* | |
310 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
311 | * authentication and RSA host authentication. | |
312 | */ | |
313 | static int | |
314 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) | |
315 | { | |
316 | int type; | |
317 | BIGNUM *challenge; | |
3c0ef626 | 318 | |
319 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
320 | ||
321 | /* Tell the server that we are willing to authenticate using this key. */ | |
322 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
323 | packet_put_cstring(local_user); | |
324 | packet_put_int(BN_num_bits(host_key->rsa->n)); | |
325 | packet_put_bignum(host_key->rsa->e); | |
326 | packet_put_bignum(host_key->rsa->n); | |
327 | packet_send(); | |
328 | packet_write_wait(); | |
329 | ||
330 | /* Wait for server's response. */ | |
1e608e42 | 331 | type = packet_read(); |
3c0ef626 | 332 | |
333 | /* The server responds with failure if it doesn't admit our | |
334 | .rhosts authentication or doesn't know our host key. */ | |
335 | if (type == SSH_SMSG_FAILURE) { | |
336 | debug("Server refused our rhosts authentication or host key."); | |
337 | return 0; | |
338 | } | |
339 | /* Otherwise, the server should respond with a challenge. */ | |
340 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
341 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
342 | ||
343 | /* Get the challenge from the packet. */ | |
1e608e42 | 344 | if ((challenge = BN_new()) == NULL) |
345 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
346 | packet_get_bignum(challenge); | |
347 | packet_check_eom(); | |
3c0ef626 | 348 | |
349 | debug("Received RSA challenge for host key from server."); | |
350 | ||
351 | /* Compute a response to the challenge. */ | |
352 | respond_to_rsa_challenge(challenge, host_key->rsa); | |
353 | ||
354 | /* We no longer need the challenge. */ | |
355 | BN_clear_free(challenge); | |
356 | ||
357 | /* Wait for response from the server. */ | |
1e608e42 | 358 | type = packet_read(); |
3c0ef626 | 359 | if (type == SSH_SMSG_SUCCESS) { |
360 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
361 | return 1; | |
362 | } | |
363 | if (type != SSH_SMSG_FAILURE) | |
364 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
365 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
366 | return 0; | |
367 | } | |
368 | ||
3c0ef626 | 369 | /* |
370 | * Tries to authenticate with any string-based challenge/response system. | |
371 | * Note that the client code is not tied to s/key or TIS. | |
372 | */ | |
373 | static int | |
374 | try_challenge_response_authentication(void) | |
375 | { | |
376 | int type, i; | |
3c0ef626 | 377 | u_int clen; |
378 | char prompt[1024]; | |
379 | char *challenge, *response; | |
380 | ||
381 | debug("Doing challenge response authentication."); | |
382 | ||
383 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
384 | /* request a challenge */ | |
385 | packet_start(SSH_CMSG_AUTH_TIS); | |
386 | packet_send(); | |
387 | packet_write_wait(); | |
388 | ||
1e608e42 | 389 | type = packet_read(); |
3c0ef626 | 390 | if (type != SSH_SMSG_FAILURE && |
391 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
392 | packet_disconnect("Protocol error: got %d in response " | |
393 | "to SSH_CMSG_AUTH_TIS", type); | |
394 | } | |
395 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
396 | debug("No challenge."); | |
397 | return 0; | |
398 | } | |
399 | challenge = packet_get_string(&clen); | |
1e608e42 | 400 | packet_check_eom(); |
3c0ef626 | 401 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
1e608e42 | 402 | strchr(challenge, '\n') ? "" : "\nResponse: "); |
3c0ef626 | 403 | xfree(challenge); |
404 | if (i != 0) | |
405 | error("Permission denied, please try again."); | |
406 | if (options.cipher == SSH_CIPHER_NONE) | |
70791e56 | 407 | logit("WARNING: Encryption is disabled! " |
2980ea68 | 408 | "Response will be transmitted in clear text."); |
3c0ef626 | 409 | response = read_passphrase(prompt, 0); |
410 | if (strcmp(response, "") == 0) { | |
411 | xfree(response); | |
412 | break; | |
413 | } | |
414 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); | |
415 | ssh_put_password(response); | |
416 | memset(response, 0, strlen(response)); | |
417 | xfree(response); | |
418 | packet_send(); | |
419 | packet_write_wait(); | |
1e608e42 | 420 | type = packet_read(); |
3c0ef626 | 421 | if (type == SSH_SMSG_SUCCESS) |
422 | return 1; | |
423 | if (type != SSH_SMSG_FAILURE) | |
424 | packet_disconnect("Protocol error: got %d in response " | |
425 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); | |
426 | } | |
427 | /* failure */ | |
428 | return 0; | |
429 | } | |
430 | ||
431 | /* | |
432 | * Tries to authenticate with plain passwd authentication. | |
433 | */ | |
434 | static int | |
435 | try_password_authentication(char *prompt) | |
436 | { | |
1e608e42 | 437 | int type, i; |
3c0ef626 | 438 | char *password; |
439 | ||
440 | debug("Doing password authentication."); | |
441 | if (options.cipher == SSH_CIPHER_NONE) | |
70791e56 | 442 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); |
3c0ef626 | 443 | for (i = 0; i < options.number_of_password_prompts; i++) { |
444 | if (i != 0) | |
445 | error("Permission denied, please try again."); | |
446 | password = read_passphrase(prompt, 0); | |
447 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
448 | ssh_put_password(password); | |
449 | memset(password, 0, strlen(password)); | |
450 | xfree(password); | |
451 | packet_send(); | |
452 | packet_write_wait(); | |
453 | ||
1e608e42 | 454 | type = packet_read(); |
3c0ef626 | 455 | if (type == SSH_SMSG_SUCCESS) |
456 | return 1; | |
457 | if (type != SSH_SMSG_FAILURE) | |
458 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
459 | } | |
460 | /* failure */ | |
461 | return 0; | |
462 | } | |
463 | ||
464 | /* | |
465 | * SSH1 key exchange | |
466 | */ | |
467 | void | |
468 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
469 | { | |
470 | int i; | |
471 | BIGNUM *key; | |
1e608e42 | 472 | Key *host_key, *server_key; |
3c0ef626 | 473 | int bits, rbits; |
474 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
475 | u_char session_key[SSH_SESSION_KEY_LENGTH]; | |
476 | u_char cookie[8]; | |
477 | u_int supported_ciphers; | |
478 | u_int server_flags, client_flags; | |
3c0ef626 | 479 | u_int32_t rand = 0; |
480 | ||
481 | debug("Waiting for server public key."); | |
482 | ||
483 | /* Wait for a public key packet from the server. */ | |
1e608e42 | 484 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); |
3c0ef626 | 485 | |
486 | /* Get cookie from the packet. */ | |
487 | for (i = 0; i < 8; i++) | |
488 | cookie[i] = packet_get_char(); | |
489 | ||
490 | /* Get the public key. */ | |
1e608e42 | 491 | server_key = key_new(KEY_RSA1); |
492 | bits = packet_get_int(); | |
493 | packet_get_bignum(server_key->rsa->e); | |
494 | packet_get_bignum(server_key->rsa->n); | |
495 | ||
496 | rbits = BN_num_bits(server_key->rsa->n); | |
3c0ef626 | 497 | if (bits != rbits) { |
70791e56 | 498 | logit("Warning: Server lies about size of server public key: " |
3c0ef626 | 499 | "actual size is %d bits vs. announced %d.", rbits, bits); |
70791e56 | 500 | logit("Warning: This may be due to an old implementation of ssh."); |
3c0ef626 | 501 | } |
502 | /* Get the host key. */ | |
1e608e42 | 503 | host_key = key_new(KEY_RSA1); |
504 | bits = packet_get_int(); | |
505 | packet_get_bignum(host_key->rsa->e); | |
506 | packet_get_bignum(host_key->rsa->n); | |
507 | ||
508 | rbits = BN_num_bits(host_key->rsa->n); | |
3c0ef626 | 509 | if (bits != rbits) { |
70791e56 | 510 | logit("Warning: Server lies about size of server host key: " |
3c0ef626 | 511 | "actual size is %d bits vs. announced %d.", rbits, bits); |
70791e56 | 512 | logit("Warning: This may be due to an old implementation of ssh."); |
3c0ef626 | 513 | } |
514 | ||
515 | /* Get protocol flags. */ | |
516 | server_flags = packet_get_int(); | |
517 | packet_set_protocol_flags(server_flags); | |
518 | ||
519 | supported_ciphers = packet_get_int(); | |
520 | supported_authentications = packet_get_int(); | |
1e608e42 | 521 | packet_check_eom(); |
3c0ef626 | 522 | |
523 | debug("Received server public key (%d bits) and host key (%d bits).", | |
1e608e42 | 524 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); |
525 | ||
526 | if (verify_host_key(host, hostaddr, host_key) == -1) | |
3c0ef626 | 527 | fatal("Host key verification failed."); |
528 | ||
529 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
530 | ||
1e608e42 | 531 | compute_session_id(session_id, cookie, host_key->rsa->n, server_key->rsa->n); |
3c0ef626 | 532 | |
533 | /* Generate a session key. */ | |
534 | arc4random_stir(); | |
535 | ||
536 | /* | |
537 | * Generate an encryption key for the session. The key is a 256 bit | |
538 | * random number, interpreted as a 32-byte key, with the least | |
539 | * significant 8 bits being the first byte of the key. | |
540 | */ | |
541 | for (i = 0; i < 32; i++) { | |
542 | if (i % 4 == 0) | |
543 | rand = arc4random(); | |
544 | session_key[i] = rand & 0xff; | |
545 | rand >>= 8; | |
546 | } | |
547 | ||
548 | /* | |
549 | * According to the protocol spec, the first byte of the session key | |
550 | * is the highest byte of the integer. The session key is xored with | |
551 | * the first 16 bytes of the session id. | |
552 | */ | |
1e608e42 | 553 | if ((key = BN_new()) == NULL) |
554 | fatal("respond_to_rsa_challenge: BN_new failed"); | |
3c0ef626 | 555 | BN_set_word(key, 0); |
556 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
557 | BN_lshift(key, key, 8); | |
558 | if (i < 16) | |
559 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
560 | else | |
561 | BN_add_word(key, session_key[i]); | |
562 | } | |
563 | ||
564 | /* | |
565 | * Encrypt the integer using the public key and host key of the | |
566 | * server (key with smaller modulus first). | |
567 | */ | |
1e608e42 | 568 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { |
3c0ef626 | 569 | /* Public key has smaller modulus. */ |
1e608e42 | 570 | if (BN_num_bits(host_key->rsa->n) < |
571 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
572 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
573 | "SSH_KEY_BITS_RESERVED %d", | |
574 | BN_num_bits(host_key->rsa->n), | |
575 | BN_num_bits(server_key->rsa->n), | |
576 | SSH_KEY_BITS_RESERVED); | |
3c0ef626 | 577 | } |
1e608e42 | 578 | rsa_public_encrypt(key, key, server_key->rsa); |
579 | rsa_public_encrypt(key, key, host_key->rsa); | |
3c0ef626 | 580 | } else { |
581 | /* Host key has smaller modulus (or they are equal). */ | |
1e608e42 | 582 | if (BN_num_bits(server_key->rsa->n) < |
583 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
584 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
585 | "SSH_KEY_BITS_RESERVED %d", | |
586 | BN_num_bits(server_key->rsa->n), | |
587 | BN_num_bits(host_key->rsa->n), | |
588 | SSH_KEY_BITS_RESERVED); | |
3c0ef626 | 589 | } |
1e608e42 | 590 | rsa_public_encrypt(key, key, host_key->rsa); |
591 | rsa_public_encrypt(key, key, server_key->rsa); | |
3c0ef626 | 592 | } |
593 | ||
594 | /* Destroy the public keys since we no longer need them. */ | |
1e608e42 | 595 | key_free(server_key); |
596 | key_free(host_key); | |
3c0ef626 | 597 | |
598 | if (options.cipher == SSH_CIPHER_NOT_SET) { | |
599 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
600 | options.cipher = ssh_cipher_default; | |
601 | } else if (options.cipher == SSH_CIPHER_ILLEGAL || | |
602 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { | |
70791e56 | 603 | logit("No valid SSH1 cipher, using %.100s instead.", |
3c0ef626 | 604 | cipher_name(ssh_cipher_default)); |
605 | options.cipher = ssh_cipher_default; | |
606 | } | |
607 | /* Check that the selected cipher is supported. */ | |
608 | if (!(supported_ciphers & (1 << options.cipher))) | |
609 | fatal("Selected cipher type %.100s not supported by server.", | |
1e608e42 | 610 | cipher_name(options.cipher)); |
3c0ef626 | 611 | |
612 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
613 | ||
614 | /* Send the encrypted session key to the server. */ | |
615 | packet_start(SSH_CMSG_SESSION_KEY); | |
616 | packet_put_char(options.cipher); | |
617 | ||
618 | /* Send the cookie back to the server. */ | |
619 | for (i = 0; i < 8; i++) | |
620 | packet_put_char(cookie[i]); | |
621 | ||
622 | /* Send and destroy the encrypted encryption key integer. */ | |
623 | packet_put_bignum(key); | |
624 | BN_clear_free(key); | |
625 | ||
626 | /* Send protocol flags. */ | |
627 | packet_put_int(client_flags); | |
628 | ||
629 | /* Send the packet now. */ | |
630 | packet_send(); | |
631 | packet_write_wait(); | |
632 | ||
633 | debug("Sent encrypted session key."); | |
634 | ||
635 | /* Set the encryption key. */ | |
636 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
637 | ||
638 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
639 | memset(session_key, 0, sizeof(session_key)); | |
640 | ||
641 | /* | |
642 | * Expect a success message from the server. Note that this message | |
643 | * will be received in encrypted form. | |
644 | */ | |
1e608e42 | 645 | packet_read_expect(SSH_SMSG_SUCCESS); |
3c0ef626 | 646 | |
647 | debug("Received encrypted confirmation."); | |
648 | } | |
649 | ||
650 | /* | |
651 | * Authenticate user | |
652 | */ | |
653 | void | |
654 | ssh_userauth1(const char *local_user, const char *server_user, char *host, | |
ff2d7a98 | 655 | Sensitive *sensitive) |
3c0ef626 | 656 | { |
3c0ef626 | 657 | int i, type; |
1e608e42 | 658 | |
3c0ef626 | 659 | if (supported_authentications == 0) |
660 | fatal("ssh_userauth1: server supports no auth methods"); | |
661 | ||
662 | /* Send the name of the user to log in as on the server. */ | |
663 | packet_start(SSH_CMSG_USER); | |
664 | packet_put_cstring(server_user); | |
665 | packet_send(); | |
666 | packet_write_wait(); | |
667 | ||
668 | /* | |
669 | * The server should respond with success if no authentication is | |
670 | * needed (the user has no password). Otherwise the server responds | |
671 | * with failure. | |
672 | */ | |
1e608e42 | 673 | type = packet_read(); |
3c0ef626 | 674 | |
675 | /* check whether the connection was accepted without authentication. */ | |
676 | if (type == SSH_SMSG_SUCCESS) | |
677 | goto success; | |
678 | if (type != SSH_SMSG_FAILURE) | |
679 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); | |
0b582e46 | 680 | |
3c0ef626 | 681 | /* |
682 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
683 | * authentication. | |
684 | */ | |
685 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
686 | options.rhosts_rsa_authentication) { | |
ff2d7a98 | 687 | for (i = 0; i < sensitive->nkeys; i++) { |
688 | if (sensitive->keys[i] != NULL && | |
689 | sensitive->keys[i]->type == KEY_RSA1 && | |
690 | try_rhosts_rsa_authentication(local_user, | |
691 | sensitive->keys[i])) | |
3c0ef626 | 692 | goto success; |
693 | } | |
694 | } | |
695 | /* Try RSA authentication if the server supports it. */ | |
696 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
697 | options.rsa_authentication) { | |
698 | /* | |
699 | * Try RSA authentication using the authentication agent. The | |
700 | * agent is tried first because no passphrase is needed for | |
701 | * it, whereas identity files may require passphrases. | |
702 | */ | |
703 | if (try_agent_authentication()) | |
704 | goto success; | |
705 | ||
706 | /* Try RSA authentication for each identity. */ | |
707 | for (i = 0; i < options.num_identity_files; i++) | |
708 | if (options.identity_keys[i] != NULL && | |
709 | options.identity_keys[i]->type == KEY_RSA1 && | |
710 | try_rsa_authentication(i)) | |
711 | goto success; | |
712 | } | |
713 | /* Try challenge response authentication if the server supports it. */ | |
714 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
715 | options.challenge_response_authentication && !options.batch_mode) { | |
716 | if (try_challenge_response_authentication()) | |
717 | goto success; | |
718 | } | |
719 | /* Try password authentication if the server supports it. */ | |
720 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
721 | options.password_authentication && !options.batch_mode) { | |
722 | char prompt[80]; | |
723 | ||
724 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", | |
725 | server_user, host); | |
726 | if (try_password_authentication(prompt)) | |
727 | goto success; | |
728 | } | |
729 | /* All authentication methods have failed. Exit with an error message. */ | |
730 | fatal("Permission denied."); | |
731 | /* NOTREACHED */ | |
732 | ||
733 | success: | |
3c0ef626 | 734 | return; /* need statement after label */ |
735 | } |