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2e437378 | 1 | /* $OpenBSD: sshconnect1.c,v 1.70 2006/11/06 21:25:28 markus Exp $ */ |
3c0ef626 | 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" | |
2e437378 | 17 | |
18 | #include <sys/types.h> | |
19 | #include <sys/socket.h> | |
3c0ef626 | 20 | |
21 | #include <openssl/bn.h> | |
1e608e42 | 22 | #include <openssl/md5.h> |
3c0ef626 | 23 | |
2e437378 | 24 | #include <stdarg.h> |
25 | #include <stdio.h> | |
26 | #include <stdlib.h> | |
27 | #include <string.h> | |
28 | #include <signal.h> | |
29 | #include <pwd.h> | |
30 | ||
31 | #include "xmalloc.h" | |
3c0ef626 | 32 | #include "ssh.h" |
33 | #include "ssh1.h" | |
3c0ef626 | 34 | #include "rsa.h" |
35 | #include "buffer.h" | |
36 | #include "packet.h" | |
2e437378 | 37 | #include "key.h" |
38 | #include "cipher.h" | |
1b56ff3d | 39 | #include "kex.h" |
3c0ef626 | 40 | #include "uidswap.h" |
41 | #include "log.h" | |
42 | #include "readconf.h" | |
3c0ef626 | 43 | #include "authfd.h" |
44 | #include "sshconnect.h" | |
45 | #include "authfile.h" | |
1b56ff3d | 46 | #include "misc.h" |
3c0ef626 | 47 | #include "canohost.h" |
2e437378 | 48 | #include "hostfile.h" |
3c0ef626 | 49 | #include "auth.h" |
50 | ||
51 | /* Session id for the current session. */ | |
52 | u_char session_id[16]; | |
53 | u_int supported_authentications = 0; | |
54 | ||
55 | extern Options options; | |
56 | extern char *__progname; | |
57 | ||
58 | /* | |
59 | * Checks if the user has an authentication agent, and if so, tries to | |
60 | * authenticate using the agent. | |
61 | */ | |
62 | static int | |
63 | try_agent_authentication(void) | |
64 | { | |
65 | int type; | |
66 | char *comment; | |
67 | AuthenticationConnection *auth; | |
68 | u_char response[16]; | |
69 | u_int i; | |
3c0ef626 | 70 | Key *key; |
71 | BIGNUM *challenge; | |
72 | ||
73 | /* Get connection to the agent. */ | |
74 | auth = ssh_get_authentication_connection(); | |
75 | if (!auth) | |
76 | return 0; | |
77 | ||
1e608e42 | 78 | if ((challenge = BN_new()) == NULL) |
79 | fatal("try_agent_authentication: BN_new failed"); | |
3c0ef626 | 80 | /* Loop through identities served by the agent. */ |
81 | for (key = ssh_get_first_identity(auth, &comment, 1); | |
1e608e42 | 82 | key != NULL; |
83 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
3c0ef626 | 84 | |
85 | /* Try this identity. */ | |
86 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
87 | xfree(comment); | |
88 | ||
89 | /* Tell the server that we are willing to authenticate using this key. */ | |
90 | packet_start(SSH_CMSG_AUTH_RSA); | |
91 | packet_put_bignum(key->rsa->n); | |
92 | packet_send(); | |
93 | packet_write_wait(); | |
94 | ||
95 | /* Wait for server's response. */ | |
1e608e42 | 96 | type = packet_read(); |
3c0ef626 | 97 | |
e00da40d | 98 | /* The server sends failure if it doesn't like our key or |
3c0ef626 | 99 | does not support RSA authentication. */ |
100 | if (type == SSH_SMSG_FAILURE) { | |
101 | debug("Server refused our key."); | |
102 | key_free(key); | |
103 | continue; | |
104 | } | |
105 | /* Otherwise it should have sent a challenge. */ | |
106 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
107 | packet_disconnect("Protocol error during RSA authentication: %d", | |
108 | type); | |
109 | ||
1e608e42 | 110 | packet_get_bignum(challenge); |
111 | packet_check_eom(); | |
3c0ef626 | 112 | |
113 | debug("Received RSA challenge from server."); | |
114 | ||
115 | /* Ask the agent to decrypt the challenge. */ | |
116 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { | |
117 | /* | |
118 | * The agent failed to authenticate this identifier | |
119 | * although it advertised it supports this. Just | |
120 | * return a wrong value. | |
121 | */ | |
70791e56 | 122 | logit("Authentication agent failed to decrypt challenge."); |
3c0ef626 | 123 | memset(response, 0, sizeof(response)); |
124 | } | |
125 | key_free(key); | |
126 | debug("Sending response to RSA challenge."); | |
127 | ||
128 | /* Send the decrypted challenge back to the server. */ | |
129 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
130 | for (i = 0; i < 16; i++) | |
131 | packet_put_char(response[i]); | |
132 | packet_send(); | |
133 | packet_write_wait(); | |
134 | ||
135 | /* Wait for response from the server. */ | |
1e608e42 | 136 | type = packet_read(); |
3c0ef626 | 137 | |
138 | /* The server returns success if it accepted the authentication. */ | |
139 | if (type == SSH_SMSG_SUCCESS) { | |
140 | ssh_close_authentication_connection(auth); | |
141 | BN_clear_free(challenge); | |
142 | debug("RSA authentication accepted by server."); | |
143 | return 1; | |
144 | } | |
145 | /* Otherwise it should return failure. */ | |
146 | if (type != SSH_SMSG_FAILURE) | |
147 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
148 | type); | |
149 | } | |
150 | ssh_close_authentication_connection(auth); | |
151 | BN_clear_free(challenge); | |
152 | debug("RSA authentication using agent refused."); | |
153 | return 0; | |
154 | } | |
155 | ||
156 | /* | |
157 | * Computes the proper response to a RSA challenge, and sends the response to | |
158 | * the server. | |
159 | */ | |
160 | static void | |
161 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
162 | { | |
163 | u_char buf[32], response[16]; | |
164 | MD5_CTX md; | |
165 | int i, len; | |
166 | ||
167 | /* Decrypt the challenge using the private key. */ | |
168 | /* XXX think about Bleichenbacher, too */ | |
169 | if (rsa_private_decrypt(challenge, challenge, prv) <= 0) | |
170 | packet_disconnect( | |
171 | "respond_to_rsa_challenge: rsa_private_decrypt failed"); | |
172 | ||
173 | /* Compute the response. */ | |
174 | /* The response is MD5 of decrypted challenge plus session id. */ | |
175 | len = BN_num_bytes(challenge); | |
34fee935 | 176 | if (len <= 0 || (u_int)len > sizeof(buf)) |
3c0ef626 | 177 | packet_disconnect( |
178 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
179 | ||
180 | memset(buf, 0, sizeof(buf)); | |
181 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
182 | MD5_Init(&md); | |
183 | MD5_Update(&md, buf, 32); | |
184 | MD5_Update(&md, session_id, 16); | |
185 | MD5_Final(response, &md); | |
186 | ||
187 | debug("Sending response to host key RSA challenge."); | |
188 | ||
189 | /* Send the response back to the server. */ | |
190 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
191 | for (i = 0; i < 16; i++) | |
192 | packet_put_char(response[i]); | |
193 | packet_send(); | |
194 | packet_write_wait(); | |
195 | ||
196 | memset(buf, 0, sizeof(buf)); | |
197 | memset(response, 0, sizeof(response)); | |
198 | memset(&md, 0, sizeof(md)); | |
199 | } | |
200 | ||
201 | /* | |
202 | * Checks if the user has authentication file, and if so, tries to authenticate | |
203 | * the user using it. | |
204 | */ | |
205 | static int | |
206 | try_rsa_authentication(int idx) | |
207 | { | |
208 | BIGNUM *challenge; | |
209 | Key *public, *private; | |
210 | char buf[300], *passphrase, *comment, *authfile; | |
2e437378 | 211 | int i, perm_ok = 1, type, quit; |
3c0ef626 | 212 | |
213 | public = options.identity_keys[idx]; | |
214 | authfile = options.identity_files[idx]; | |
215 | comment = xstrdup(authfile); | |
216 | ||
217 | debug("Trying RSA authentication with key '%.100s'", comment); | |
218 | ||
219 | /* Tell the server that we are willing to authenticate using this key. */ | |
220 | packet_start(SSH_CMSG_AUTH_RSA); | |
221 | packet_put_bignum(public->rsa->n); | |
222 | packet_send(); | |
223 | packet_write_wait(); | |
224 | ||
225 | /* Wait for server's response. */ | |
1e608e42 | 226 | type = packet_read(); |
3c0ef626 | 227 | |
228 | /* | |
e00da40d | 229 | * The server responds with failure if it doesn't like our key or |
230 | * doesn't support RSA authentication. | |
3c0ef626 | 231 | */ |
232 | if (type == SSH_SMSG_FAILURE) { | |
233 | debug("Server refused our key."); | |
234 | xfree(comment); | |
235 | return 0; | |
236 | } | |
237 | /* Otherwise, the server should respond with a challenge. */ | |
238 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
239 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
240 | ||
241 | /* Get the challenge from the packet. */ | |
1e608e42 | 242 | if ((challenge = BN_new()) == NULL) |
243 | fatal("try_rsa_authentication: BN_new failed"); | |
244 | packet_get_bignum(challenge); | |
245 | packet_check_eom(); | |
3c0ef626 | 246 | |
247 | debug("Received RSA challenge from server."); | |
248 | ||
249 | /* | |
250 | * If the key is not stored in external hardware, we have to | |
251 | * load the private key. Try first with empty passphrase; if it | |
252 | * fails, ask for a passphrase. | |
253 | */ | |
e54b3d7c | 254 | if (public->flags & KEY_FLAG_EXT) |
3c0ef626 | 255 | private = public; |
256 | else | |
2e437378 | 257 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL, |
258 | &perm_ok); | |
259 | if (private == NULL && !options.batch_mode && perm_ok) { | |
3c0ef626 | 260 | snprintf(buf, sizeof(buf), |
261 | "Enter passphrase for RSA key '%.100s': ", comment); | |
262 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
263 | passphrase = read_passphrase(buf, 0); | |
264 | if (strcmp(passphrase, "") != 0) { | |
265 | private = key_load_private_type(KEY_RSA1, | |
2e437378 | 266 | authfile, passphrase, NULL, NULL); |
3c0ef626 | 267 | quit = 0; |
268 | } else { | |
269 | debug2("no passphrase given, try next key"); | |
270 | quit = 1; | |
271 | } | |
272 | memset(passphrase, 0, strlen(passphrase)); | |
273 | xfree(passphrase); | |
274 | if (private != NULL || quit) | |
275 | break; | |
276 | debug2("bad passphrase given, try again..."); | |
277 | } | |
278 | } | |
279 | /* We no longer need the comment. */ | |
280 | xfree(comment); | |
281 | ||
282 | if (private == NULL) { | |
2e437378 | 283 | if (!options.batch_mode && perm_ok) |
3c0ef626 | 284 | error("Bad passphrase."); |
285 | ||
286 | /* Send a dummy response packet to avoid protocol error. */ | |
287 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
288 | for (i = 0; i < 16; i++) | |
289 | packet_put_char(0); | |
290 | packet_send(); | |
291 | packet_write_wait(); | |
292 | ||
293 | /* Expect the server to reject it... */ | |
1e608e42 | 294 | packet_read_expect(SSH_SMSG_FAILURE); |
3c0ef626 | 295 | BN_clear_free(challenge); |
296 | return 0; | |
297 | } | |
298 | ||
299 | /* Compute and send a response to the challenge. */ | |
300 | respond_to_rsa_challenge(challenge, private->rsa); | |
301 | ||
302 | /* Destroy the private key unless it in external hardware. */ | |
303 | if (!(private->flags & KEY_FLAG_EXT)) | |
304 | key_free(private); | |
305 | ||
306 | /* We no longer need the challenge. */ | |
307 | BN_clear_free(challenge); | |
308 | ||
309 | /* Wait for response from the server. */ | |
1e608e42 | 310 | type = packet_read(); |
3c0ef626 | 311 | if (type == SSH_SMSG_SUCCESS) { |
312 | debug("RSA authentication accepted by server."); | |
313 | return 1; | |
314 | } | |
315 | if (type != SSH_SMSG_FAILURE) | |
316 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
317 | debug("RSA authentication refused."); | |
318 | return 0; | |
319 | } | |
320 | ||
321 | /* | |
322 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
323 | * authentication and RSA host authentication. | |
324 | */ | |
325 | static int | |
326 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) | |
327 | { | |
328 | int type; | |
329 | BIGNUM *challenge; | |
3c0ef626 | 330 | |
331 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
332 | ||
333 | /* Tell the server that we are willing to authenticate using this key. */ | |
334 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
335 | packet_put_cstring(local_user); | |
336 | packet_put_int(BN_num_bits(host_key->rsa->n)); | |
337 | packet_put_bignum(host_key->rsa->e); | |
338 | packet_put_bignum(host_key->rsa->n); | |
339 | packet_send(); | |
340 | packet_write_wait(); | |
341 | ||
342 | /* Wait for server's response. */ | |
1e608e42 | 343 | type = packet_read(); |
3c0ef626 | 344 | |
345 | /* The server responds with failure if it doesn't admit our | |
346 | .rhosts authentication or doesn't know our host key. */ | |
347 | if (type == SSH_SMSG_FAILURE) { | |
348 | debug("Server refused our rhosts authentication or host key."); | |
349 | return 0; | |
350 | } | |
351 | /* Otherwise, the server should respond with a challenge. */ | |
352 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
353 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
354 | ||
355 | /* Get the challenge from the packet. */ | |
1e608e42 | 356 | if ((challenge = BN_new()) == NULL) |
357 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
358 | packet_get_bignum(challenge); | |
359 | packet_check_eom(); | |
3c0ef626 | 360 | |
361 | debug("Received RSA challenge for host key from server."); | |
362 | ||
363 | /* Compute a response to the challenge. */ | |
364 | respond_to_rsa_challenge(challenge, host_key->rsa); | |
365 | ||
366 | /* We no longer need the challenge. */ | |
367 | BN_clear_free(challenge); | |
368 | ||
369 | /* Wait for response from the server. */ | |
1e608e42 | 370 | type = packet_read(); |
3c0ef626 | 371 | if (type == SSH_SMSG_SUCCESS) { |
372 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
373 | return 1; | |
374 | } | |
375 | if (type != SSH_SMSG_FAILURE) | |
376 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
377 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
378 | return 0; | |
379 | } | |
380 | ||
3c0ef626 | 381 | /* |
382 | * Tries to authenticate with any string-based challenge/response system. | |
383 | * Note that the client code is not tied to s/key or TIS. | |
384 | */ | |
385 | static int | |
386 | try_challenge_response_authentication(void) | |
387 | { | |
388 | int type, i; | |
3c0ef626 | 389 | u_int clen; |
390 | char prompt[1024]; | |
391 | char *challenge, *response; | |
392 | ||
393 | debug("Doing challenge response authentication."); | |
394 | ||
395 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
396 | /* request a challenge */ | |
397 | packet_start(SSH_CMSG_AUTH_TIS); | |
398 | packet_send(); | |
399 | packet_write_wait(); | |
400 | ||
1e608e42 | 401 | type = packet_read(); |
3c0ef626 | 402 | if (type != SSH_SMSG_FAILURE && |
403 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
404 | packet_disconnect("Protocol error: got %d in response " | |
405 | "to SSH_CMSG_AUTH_TIS", type); | |
406 | } | |
407 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
408 | debug("No challenge."); | |
409 | return 0; | |
410 | } | |
411 | challenge = packet_get_string(&clen); | |
1e608e42 | 412 | packet_check_eom(); |
3c0ef626 | 413 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
1e608e42 | 414 | strchr(challenge, '\n') ? "" : "\nResponse: "); |
3c0ef626 | 415 | xfree(challenge); |
416 | if (i != 0) | |
417 | error("Permission denied, please try again."); | |
418 | if (options.cipher == SSH_CIPHER_NONE) | |
70791e56 | 419 | logit("WARNING: Encryption is disabled! " |
2980ea68 | 420 | "Response will be transmitted in clear text."); |
3c0ef626 | 421 | response = read_passphrase(prompt, 0); |
422 | if (strcmp(response, "") == 0) { | |
423 | xfree(response); | |
424 | break; | |
425 | } | |
426 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); | |
427 | ssh_put_password(response); | |
428 | memset(response, 0, strlen(response)); | |
429 | xfree(response); | |
430 | packet_send(); | |
431 | packet_write_wait(); | |
1e608e42 | 432 | type = packet_read(); |
3c0ef626 | 433 | if (type == SSH_SMSG_SUCCESS) |
434 | return 1; | |
435 | if (type != SSH_SMSG_FAILURE) | |
436 | packet_disconnect("Protocol error: got %d in response " | |
437 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); | |
438 | } | |
439 | /* failure */ | |
440 | return 0; | |
441 | } | |
442 | ||
443 | /* | |
444 | * Tries to authenticate with plain passwd authentication. | |
445 | */ | |
446 | static int | |
447 | try_password_authentication(char *prompt) | |
448 | { | |
1e608e42 | 449 | int type, i; |
3c0ef626 | 450 | char *password; |
451 | ||
452 | debug("Doing password authentication."); | |
453 | if (options.cipher == SSH_CIPHER_NONE) | |
70791e56 | 454 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); |
3c0ef626 | 455 | for (i = 0; i < options.number_of_password_prompts; i++) { |
456 | if (i != 0) | |
457 | error("Permission denied, please try again."); | |
458 | password = read_passphrase(prompt, 0); | |
459 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
460 | ssh_put_password(password); | |
461 | memset(password, 0, strlen(password)); | |
462 | xfree(password); | |
463 | packet_send(); | |
464 | packet_write_wait(); | |
465 | ||
1e608e42 | 466 | type = packet_read(); |
3c0ef626 | 467 | if (type == SSH_SMSG_SUCCESS) |
468 | return 1; | |
469 | if (type != SSH_SMSG_FAILURE) | |
470 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
471 | } | |
472 | /* failure */ | |
473 | return 0; | |
474 | } | |
475 | ||
476 | /* | |
477 | * SSH1 key exchange | |
478 | */ | |
479 | void | |
480 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
481 | { | |
482 | int i; | |
483 | BIGNUM *key; | |
1e608e42 | 484 | Key *host_key, *server_key; |
3c0ef626 | 485 | int bits, rbits; |
486 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
487 | u_char session_key[SSH_SESSION_KEY_LENGTH]; | |
488 | u_char cookie[8]; | |
489 | u_int supported_ciphers; | |
490 | u_int server_flags, client_flags; | |
1b56ff3d | 491 | u_int32_t rnd = 0; |
3c0ef626 | 492 | |
493 | debug("Waiting for server public key."); | |
494 | ||
495 | /* Wait for a public key packet from the server. */ | |
1e608e42 | 496 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); |
3c0ef626 | 497 | |
498 | /* Get cookie from the packet. */ | |
499 | for (i = 0; i < 8; i++) | |
500 | cookie[i] = packet_get_char(); | |
501 | ||
502 | /* Get the public key. */ | |
1e608e42 | 503 | server_key = key_new(KEY_RSA1); |
504 | bits = packet_get_int(); | |
505 | packet_get_bignum(server_key->rsa->e); | |
506 | packet_get_bignum(server_key->rsa->n); | |
507 | ||
508 | rbits = BN_num_bits(server_key->rsa->n); | |
3c0ef626 | 509 | if (bits != rbits) { |
70791e56 | 510 | logit("Warning: Server lies about size of server public 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 | /* Get the host key. */ | |
1e608e42 | 515 | host_key = key_new(KEY_RSA1); |
516 | bits = packet_get_int(); | |
517 | packet_get_bignum(host_key->rsa->e); | |
518 | packet_get_bignum(host_key->rsa->n); | |
519 | ||
520 | rbits = BN_num_bits(host_key->rsa->n); | |
3c0ef626 | 521 | if (bits != rbits) { |
70791e56 | 522 | logit("Warning: Server lies about size of server host key: " |
3c0ef626 | 523 | "actual size is %d bits vs. announced %d.", rbits, bits); |
70791e56 | 524 | logit("Warning: This may be due to an old implementation of ssh."); |
3c0ef626 | 525 | } |
526 | ||
527 | /* Get protocol flags. */ | |
528 | server_flags = packet_get_int(); | |
529 | packet_set_protocol_flags(server_flags); | |
530 | ||
531 | supported_ciphers = packet_get_int(); | |
532 | supported_authentications = packet_get_int(); | |
1e608e42 | 533 | packet_check_eom(); |
3c0ef626 | 534 | |
535 | debug("Received server public key (%d bits) and host key (%d bits).", | |
1e608e42 | 536 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); |
537 | ||
538 | if (verify_host_key(host, hostaddr, host_key) == -1) | |
3c0ef626 | 539 | fatal("Host key verification failed."); |
540 | ||
541 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
542 | ||
1b56ff3d | 543 | derive_ssh1_session_id(host_key->rsa->n, server_key->rsa->n, cookie, session_id); |
3c0ef626 | 544 | |
545 | /* Generate a session key. */ | |
546 | arc4random_stir(); | |
547 | ||
548 | /* | |
549 | * Generate an encryption key for the session. The key is a 256 bit | |
550 | * random number, interpreted as a 32-byte key, with the least | |
551 | * significant 8 bits being the first byte of the key. | |
552 | */ | |
553 | for (i = 0; i < 32; i++) { | |
554 | if (i % 4 == 0) | |
1b56ff3d | 555 | rnd = arc4random(); |
556 | session_key[i] = rnd & 0xff; | |
557 | rnd >>= 8; | |
3c0ef626 | 558 | } |
559 | ||
560 | /* | |
561 | * According to the protocol spec, the first byte of the session key | |
562 | * is the highest byte of the integer. The session key is xored with | |
563 | * the first 16 bytes of the session id. | |
564 | */ | |
1e608e42 | 565 | if ((key = BN_new()) == NULL) |
2e437378 | 566 | fatal("ssh_kex: BN_new failed"); |
567 | if (BN_set_word(key, 0) == 0) | |
568 | fatal("ssh_kex: BN_set_word failed"); | |
3c0ef626 | 569 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { |
2e437378 | 570 | if (BN_lshift(key, key, 8) == 0) |
571 | fatal("ssh_kex: BN_lshift failed"); | |
572 | if (i < 16) { | |
573 | if (BN_add_word(key, session_key[i] ^ session_id[i]) | |
574 | == 0) | |
575 | fatal("ssh_kex: BN_add_word failed"); | |
576 | } else { | |
577 | if (BN_add_word(key, session_key[i]) == 0) | |
578 | fatal("ssh_kex: BN_add_word failed"); | |
579 | } | |
3c0ef626 | 580 | } |
581 | ||
582 | /* | |
583 | * Encrypt the integer using the public key and host key of the | |
584 | * server (key with smaller modulus first). | |
585 | */ | |
1e608e42 | 586 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { |
3c0ef626 | 587 | /* Public key has smaller modulus. */ |
1e608e42 | 588 | if (BN_num_bits(host_key->rsa->n) < |
589 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
590 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
591 | "SSH_KEY_BITS_RESERVED %d", | |
592 | BN_num_bits(host_key->rsa->n), | |
593 | BN_num_bits(server_key->rsa->n), | |
594 | SSH_KEY_BITS_RESERVED); | |
3c0ef626 | 595 | } |
1e608e42 | 596 | rsa_public_encrypt(key, key, server_key->rsa); |
597 | rsa_public_encrypt(key, key, host_key->rsa); | |
3c0ef626 | 598 | } else { |
599 | /* Host key has smaller modulus (or they are equal). */ | |
1e608e42 | 600 | if (BN_num_bits(server_key->rsa->n) < |
601 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
602 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
603 | "SSH_KEY_BITS_RESERVED %d", | |
604 | BN_num_bits(server_key->rsa->n), | |
605 | BN_num_bits(host_key->rsa->n), | |
606 | SSH_KEY_BITS_RESERVED); | |
3c0ef626 | 607 | } |
1e608e42 | 608 | rsa_public_encrypt(key, key, host_key->rsa); |
609 | rsa_public_encrypt(key, key, server_key->rsa); | |
3c0ef626 | 610 | } |
611 | ||
612 | /* Destroy the public keys since we no longer need them. */ | |
1e608e42 | 613 | key_free(server_key); |
614 | key_free(host_key); | |
3c0ef626 | 615 | |
616 | if (options.cipher == SSH_CIPHER_NOT_SET) { | |
617 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
618 | options.cipher = ssh_cipher_default; | |
1b56ff3d | 619 | } else if (options.cipher == SSH_CIPHER_INVALID || |
3c0ef626 | 620 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { |
70791e56 | 621 | logit("No valid SSH1 cipher, using %.100s instead.", |
3c0ef626 | 622 | cipher_name(ssh_cipher_default)); |
623 | options.cipher = ssh_cipher_default; | |
624 | } | |
625 | /* Check that the selected cipher is supported. */ | |
626 | if (!(supported_ciphers & (1 << options.cipher))) | |
627 | fatal("Selected cipher type %.100s not supported by server.", | |
1e608e42 | 628 | cipher_name(options.cipher)); |
3c0ef626 | 629 | |
630 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
631 | ||
632 | /* Send the encrypted session key to the server. */ | |
633 | packet_start(SSH_CMSG_SESSION_KEY); | |
634 | packet_put_char(options.cipher); | |
635 | ||
636 | /* Send the cookie back to the server. */ | |
637 | for (i = 0; i < 8; i++) | |
638 | packet_put_char(cookie[i]); | |
639 | ||
640 | /* Send and destroy the encrypted encryption key integer. */ | |
641 | packet_put_bignum(key); | |
642 | BN_clear_free(key); | |
643 | ||
644 | /* Send protocol flags. */ | |
645 | packet_put_int(client_flags); | |
646 | ||
647 | /* Send the packet now. */ | |
648 | packet_send(); | |
649 | packet_write_wait(); | |
650 | ||
651 | debug("Sent encrypted session key."); | |
652 | ||
653 | /* Set the encryption key. */ | |
654 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
655 | ||
656 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
657 | memset(session_key, 0, sizeof(session_key)); | |
658 | ||
659 | /* | |
660 | * Expect a success message from the server. Note that this message | |
661 | * will be received in encrypted form. | |
662 | */ | |
1e608e42 | 663 | packet_read_expect(SSH_SMSG_SUCCESS); |
3c0ef626 | 664 | |
665 | debug("Received encrypted confirmation."); | |
666 | } | |
667 | ||
668 | /* | |
669 | * Authenticate user | |
670 | */ | |
671 | void | |
672 | ssh_userauth1(const char *local_user, const char *server_user, char *host, | |
ff2d7a98 | 673 | Sensitive *sensitive) |
3c0ef626 | 674 | { |
3c0ef626 | 675 | int i, type; |
1e608e42 | 676 | |
3c0ef626 | 677 | if (supported_authentications == 0) |
678 | fatal("ssh_userauth1: server supports no auth methods"); | |
679 | ||
680 | /* Send the name of the user to log in as on the server. */ | |
681 | packet_start(SSH_CMSG_USER); | |
682 | packet_put_cstring(server_user); | |
683 | packet_send(); | |
684 | packet_write_wait(); | |
685 | ||
686 | /* | |
687 | * The server should respond with success if no authentication is | |
688 | * needed (the user has no password). Otherwise the server responds | |
689 | * with failure. | |
690 | */ | |
1e608e42 | 691 | type = packet_read(); |
3c0ef626 | 692 | |
693 | /* check whether the connection was accepted without authentication. */ | |
694 | if (type == SSH_SMSG_SUCCESS) | |
695 | goto success; | |
696 | if (type != SSH_SMSG_FAILURE) | |
697 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); | |
0b582e46 | 698 | |
3c0ef626 | 699 | /* |
700 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
701 | * authentication. | |
702 | */ | |
703 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
704 | options.rhosts_rsa_authentication) { | |
ff2d7a98 | 705 | for (i = 0; i < sensitive->nkeys; i++) { |
706 | if (sensitive->keys[i] != NULL && | |
707 | sensitive->keys[i]->type == KEY_RSA1 && | |
708 | try_rhosts_rsa_authentication(local_user, | |
709 | sensitive->keys[i])) | |
3c0ef626 | 710 | goto success; |
711 | } | |
712 | } | |
713 | /* Try RSA authentication if the server supports it. */ | |
714 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
715 | options.rsa_authentication) { | |
716 | /* | |
717 | * Try RSA authentication using the authentication agent. The | |
718 | * agent is tried first because no passphrase is needed for | |
719 | * it, whereas identity files may require passphrases. | |
720 | */ | |
721 | if (try_agent_authentication()) | |
722 | goto success; | |
723 | ||
724 | /* Try RSA authentication for each identity. */ | |
725 | for (i = 0; i < options.num_identity_files; i++) | |
726 | if (options.identity_keys[i] != NULL && | |
727 | options.identity_keys[i]->type == KEY_RSA1 && | |
728 | try_rsa_authentication(i)) | |
729 | goto success; | |
730 | } | |
731 | /* Try challenge response authentication if the server supports it. */ | |
732 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
733 | options.challenge_response_authentication && !options.batch_mode) { | |
734 | if (try_challenge_response_authentication()) | |
735 | goto success; | |
736 | } | |
737 | /* Try password authentication if the server supports it. */ | |
738 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
739 | options.password_authentication && !options.batch_mode) { | |
740 | char prompt[80]; | |
741 | ||
742 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", | |
743 | server_user, host); | |
744 | if (try_password_authentication(prompt)) | |
745 | goto success; | |
746 | } | |
747 | /* All authentication methods have failed. Exit with an error message. */ | |
748 | fatal("Permission denied."); | |
749 | /* NOTREACHED */ | |
750 | ||
751 | success: | |
3c0ef626 | 752 | return; /* need statement after label */ |
753 | } |