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31652869 | 1 | /* $OpenBSD: sshconnect1.c,v 1.69 2006/08/03 03:34:42 deraadt Exp $ */ |
a306f2dd | 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 | |
a306f2dd | 6 | * Code to connect to a remote host, and to perform the client side of the |
7 | * login (authentication) dialog. | |
8 | * | |
bcbf86ec | 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". | |
a306f2dd | 14 | */ |
15 | ||
16 | #include "includes.h" | |
a306f2dd | 17 | |
31652869 | 18 | #include <sys/types.h> |
19 | #include <sys/socket.h> | |
20 | ||
a306f2dd | 21 | #include <openssl/bn.h> |
6b4b5e49 | 22 | #include <openssl/md5.h> |
a306f2dd | 23 | |
cf851879 | 24 | #include <stdio.h> |
ffa517a8 | 25 | #include <stdlib.h> |
00146caa | 26 | #include <string.h> |
31652869 | 27 | #include <signal.h> |
28 | #include <pwd.h> | |
00146caa | 29 | |
31652869 | 30 | #include "xmalloc.h" |
42f11eb2 | 31 | #include "ssh.h" |
32 | #include "ssh1.h" | |
a306f2dd | 33 | #include "rsa.h" |
a306f2dd | 34 | #include "buffer.h" |
35 | #include "packet.h" | |
31652869 | 36 | #include "key.h" |
37 | #include "cipher.h" | |
8bbf1fa6 | 38 | #include "kex.h" |
a306f2dd | 39 | #include "uidswap.h" |
42f11eb2 | 40 | #include "log.h" |
a306f2dd | 41 | #include "readconf.h" |
4c8722d9 | 42 | #include "authfd.h" |
a306f2dd | 43 | #include "sshconnect.h" |
44 | #include "authfile.h" | |
58ae9cb8 | 45 | #include "misc.h" |
42f11eb2 | 46 | #include "canohost.h" |
31652869 | 47 | #include "hostfile.h" |
ced49be2 | 48 | #include "auth.h" |
a306f2dd | 49 | |
50 | /* Session id for the current session. */ | |
1e3b8b07 | 51 | u_char session_id[16]; |
52 | u_int supported_authentications = 0; | |
a306f2dd | 53 | |
54 | extern Options options; | |
55 | extern char *__progname; | |
56 | ||
57 | /* | |
58 | * Checks if the user has an authentication agent, and if so, tries to | |
59 | * authenticate using the agent. | |
60 | */ | |
396c147e | 61 | static int |
5ca51e19 | 62 | try_agent_authentication(void) |
a306f2dd | 63 | { |
2e73a022 | 64 | int type; |
a306f2dd | 65 | char *comment; |
66 | AuthenticationConnection *auth; | |
1e3b8b07 | 67 | u_char response[16]; |
68 | u_int i; | |
2e73a022 | 69 | Key *key; |
70 | BIGNUM *challenge; | |
a306f2dd | 71 | |
72 | /* Get connection to the agent. */ | |
73 | auth = ssh_get_authentication_connection(); | |
74 | if (!auth) | |
75 | return 0; | |
76 | ||
b775c6f2 | 77 | if ((challenge = BN_new()) == NULL) |
78 | fatal("try_agent_authentication: BN_new failed"); | |
a306f2dd | 79 | /* Loop through identities served by the agent. */ |
2e73a022 | 80 | for (key = ssh_get_first_identity(auth, &comment, 1); |
184eed6a | 81 | key != NULL; |
82 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 83 | |
84 | /* Try this identity. */ | |
85 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
86 | xfree(comment); | |
87 | ||
88 | /* Tell the server that we are willing to authenticate using this key. */ | |
89 | packet_start(SSH_CMSG_AUTH_RSA); | |
2e73a022 | 90 | packet_put_bignum(key->rsa->n); |
a306f2dd | 91 | packet_send(); |
92 | packet_write_wait(); | |
93 | ||
94 | /* Wait for server's response. */ | |
54a5250f | 95 | type = packet_read(); |
a306f2dd | 96 | |
7b9b0103 | 97 | /* The server sends failure if it doesn't like our key or |
a306f2dd | 98 | does not support RSA authentication. */ |
99 | if (type == SSH_SMSG_FAILURE) { | |
100 | debug("Server refused our key."); | |
2e73a022 | 101 | key_free(key); |
a306f2dd | 102 | continue; |
103 | } | |
104 | /* Otherwise it should have sent a challenge. */ | |
105 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
106 | packet_disconnect("Protocol error during RSA authentication: %d", | |
107 | type); | |
108 | ||
20b279e6 | 109 | packet_get_bignum(challenge); |
95500969 | 110 | packet_check_eom(); |
a306f2dd | 111 | |
112 | debug("Received RSA challenge from server."); | |
113 | ||
114 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 115 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { |
116 | /* | |
117 | * The agent failed to authenticate this identifier | |
118 | * although it advertised it supports this. Just | |
119 | * return a wrong value. | |
120 | */ | |
bbe88b6d | 121 | logit("Authentication agent failed to decrypt challenge."); |
a306f2dd | 122 | memset(response, 0, sizeof(response)); |
123 | } | |
2e73a022 | 124 | key_free(key); |
a306f2dd | 125 | debug("Sending response to RSA challenge."); |
126 | ||
127 | /* Send the decrypted challenge back to the server. */ | |
128 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
129 | for (i = 0; i < 16; i++) | |
130 | packet_put_char(response[i]); | |
131 | packet_send(); | |
132 | packet_write_wait(); | |
133 | ||
134 | /* Wait for response from the server. */ | |
54a5250f | 135 | type = packet_read(); |
a306f2dd | 136 | |
137 | /* The server returns success if it accepted the authentication. */ | |
138 | if (type == SSH_SMSG_SUCCESS) { | |
eea39c02 | 139 | ssh_close_authentication_connection(auth); |
a306f2dd | 140 | BN_clear_free(challenge); |
2e73a022 | 141 | debug("RSA authentication accepted by server."); |
a306f2dd | 142 | return 1; |
143 | } | |
144 | /* Otherwise it should return failure. */ | |
145 | if (type != SSH_SMSG_FAILURE) | |
146 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
147 | type); | |
148 | } | |
eea39c02 | 149 | ssh_close_authentication_connection(auth); |
a306f2dd | 150 | BN_clear_free(challenge); |
a306f2dd | 151 | debug("RSA authentication using agent refused."); |
152 | return 0; | |
153 | } | |
154 | ||
155 | /* | |
156 | * Computes the proper response to a RSA challenge, and sends the response to | |
157 | * the server. | |
158 | */ | |
396c147e | 159 | static void |
a306f2dd | 160 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) |
161 | { | |
1e3b8b07 | 162 | u_char buf[32], response[16]; |
a306f2dd | 163 | MD5_CTX md; |
164 | int i, len; | |
165 | ||
166 | /* Decrypt the challenge using the private key. */ | |
46aa2d1f | 167 | /* XXX think about Bleichenbacher, too */ |
168 | if (rsa_private_decrypt(challenge, challenge, prv) <= 0) | |
169 | packet_disconnect( | |
170 | "respond_to_rsa_challenge: rsa_private_decrypt failed"); | |
a306f2dd | 171 | |
172 | /* Compute the response. */ | |
173 | /* The response is MD5 of decrypted challenge plus session id. */ | |
174 | len = BN_num_bytes(challenge); | |
2ceb8101 | 175 | if (len <= 0 || (u_int)len > sizeof(buf)) |
46aa2d1f | 176 | packet_disconnect( |
177 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
a306f2dd | 178 | |
179 | memset(buf, 0, sizeof(buf)); | |
180 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
181 | MD5_Init(&md); | |
182 | MD5_Update(&md, buf, 32); | |
183 | MD5_Update(&md, session_id, 16); | |
184 | MD5_Final(response, &md); | |
185 | ||
186 | debug("Sending response to host key RSA challenge."); | |
187 | ||
188 | /* Send the response back to the server. */ | |
189 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
190 | for (i = 0; i < 16; i++) | |
191 | packet_put_char(response[i]); | |
192 | packet_send(); | |
193 | packet_write_wait(); | |
194 | ||
195 | memset(buf, 0, sizeof(buf)); | |
196 | memset(response, 0, sizeof(response)); | |
197 | memset(&md, 0, sizeof(md)); | |
198 | } | |
199 | ||
200 | /* | |
201 | * Checks if the user has authentication file, and if so, tries to authenticate | |
202 | * the user using it. | |
203 | */ | |
396c147e | 204 | static int |
383546c4 | 205 | try_rsa_authentication(int idx) |
a306f2dd | 206 | { |
207 | BIGNUM *challenge; | |
ce404659 | 208 | Key *public, *private; |
383546c4 | 209 | char buf[300], *passphrase, *comment, *authfile; |
fc231518 | 210 | int i, perm_ok = 1, type, quit; |
a306f2dd | 211 | |
383546c4 | 212 | public = options.identity_keys[idx]; |
213 | authfile = options.identity_files[idx]; | |
214 | comment = xstrdup(authfile); | |
215 | ||
a306f2dd | 216 | debug("Trying RSA authentication with key '%.100s'", comment); |
217 | ||
218 | /* Tell the server that we are willing to authenticate using this key. */ | |
219 | packet_start(SSH_CMSG_AUTH_RSA); | |
220 | packet_put_bignum(public->rsa->n); | |
221 | packet_send(); | |
222 | packet_write_wait(); | |
223 | ||
a306f2dd | 224 | /* Wait for server's response. */ |
54a5250f | 225 | type = packet_read(); |
a306f2dd | 226 | |
227 | /* | |
7b9b0103 | 228 | * The server responds with failure if it doesn't like our key or |
229 | * doesn't support RSA authentication. | |
a306f2dd | 230 | */ |
231 | if (type == SSH_SMSG_FAILURE) { | |
232 | debug("Server refused our key."); | |
233 | xfree(comment); | |
234 | return 0; | |
235 | } | |
236 | /* Otherwise, the server should respond with a challenge. */ | |
237 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
238 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
239 | ||
240 | /* Get the challenge from the packet. */ | |
b775c6f2 | 241 | if ((challenge = BN_new()) == NULL) |
242 | fatal("try_rsa_authentication: BN_new failed"); | |
20b279e6 | 243 | packet_get_bignum(challenge); |
95500969 | 244 | packet_check_eom(); |
a306f2dd | 245 | |
246 | debug("Received RSA challenge from server."); | |
247 | ||
a306f2dd | 248 | /* |
383546c4 | 249 | * If the key is not stored in external hardware, we have to |
250 | * load the private key. Try first with empty passphrase; if it | |
a306f2dd | 251 | * fails, ask for a passphrase. |
252 | */ | |
75cf7563 | 253 | if (public->flags & KEY_FLAG_EXT) |
383546c4 | 254 | private = public; |
255 | else | |
fc231518 | 256 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL, |
257 | &perm_ok); | |
258 | if (private == NULL && !options.batch_mode && perm_ok) { | |
ce404659 | 259 | snprintf(buf, sizeof(buf), |
260 | "Enter passphrase for RSA key '%.100s': ", comment); | |
261 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
a306f2dd | 262 | passphrase = read_passphrase(buf, 0); |
ce404659 | 263 | if (strcmp(passphrase, "") != 0) { |
264 | private = key_load_private_type(KEY_RSA1, | |
fc231518 | 265 | authfile, passphrase, NULL, NULL); |
ce404659 | 266 | quit = 0; |
267 | } else { | |
268 | debug2("no passphrase given, try next key"); | |
269 | quit = 1; | |
270 | } | |
a306f2dd | 271 | memset(passphrase, 0, strlen(passphrase)); |
272 | xfree(passphrase); | |
ce404659 | 273 | if (private != NULL || quit) |
274 | break; | |
275 | debug2("bad passphrase given, try again..."); | |
a306f2dd | 276 | } |
a306f2dd | 277 | } |
278 | /* We no longer need the comment. */ | |
279 | xfree(comment); | |
280 | ||
ce404659 | 281 | if (private == NULL) { |
fc231518 | 282 | if (!options.batch_mode && perm_ok) |
ce404659 | 283 | error("Bad passphrase."); |
284 | ||
285 | /* Send a dummy response packet to avoid protocol error. */ | |
286 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
287 | for (i = 0; i < 16; i++) | |
288 | packet_put_char(0); | |
289 | packet_send(); | |
290 | packet_write_wait(); | |
291 | ||
292 | /* Expect the server to reject it... */ | |
54a5250f | 293 | packet_read_expect(SSH_SMSG_FAILURE); |
ce404659 | 294 | BN_clear_free(challenge); |
295 | return 0; | |
296 | } | |
297 | ||
a306f2dd | 298 | /* Compute and send a response to the challenge. */ |
299 | respond_to_rsa_challenge(challenge, private->rsa); | |
300 | ||
383546c4 | 301 | /* Destroy the private key unless it in external hardware. */ |
302 | if (!(private->flags & KEY_FLAG_EXT)) | |
303 | key_free(private); | |
a306f2dd | 304 | |
305 | /* We no longer need the challenge. */ | |
306 | BN_clear_free(challenge); | |
307 | ||
308 | /* Wait for response from the server. */ | |
54a5250f | 309 | type = packet_read(); |
a306f2dd | 310 | if (type == SSH_SMSG_SUCCESS) { |
311 | debug("RSA authentication accepted by server."); | |
312 | return 1; | |
313 | } | |
314 | if (type != SSH_SMSG_FAILURE) | |
315 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
316 | debug("RSA authentication refused."); | |
317 | return 0; | |
318 | } | |
319 | ||
320 | /* | |
321 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
322 | * authentication and RSA host authentication. | |
323 | */ | |
396c147e | 324 | static int |
aeaa3d9e | 325 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) |
a306f2dd | 326 | { |
327 | int type; | |
328 | BIGNUM *challenge; | |
a306f2dd | 329 | |
330 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
331 | ||
332 | /* Tell the server that we are willing to authenticate using this key. */ | |
333 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
449c5ba5 | 334 | packet_put_cstring(local_user); |
aeaa3d9e | 335 | packet_put_int(BN_num_bits(host_key->rsa->n)); |
336 | packet_put_bignum(host_key->rsa->e); | |
337 | packet_put_bignum(host_key->rsa->n); | |
a306f2dd | 338 | packet_send(); |
339 | packet_write_wait(); | |
340 | ||
341 | /* Wait for server's response. */ | |
54a5250f | 342 | type = packet_read(); |
a306f2dd | 343 | |
344 | /* The server responds with failure if it doesn't admit our | |
345 | .rhosts authentication or doesn't know our host key. */ | |
346 | if (type == SSH_SMSG_FAILURE) { | |
347 | debug("Server refused our rhosts authentication or host key."); | |
348 | return 0; | |
349 | } | |
350 | /* Otherwise, the server should respond with a challenge. */ | |
351 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
352 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
353 | ||
354 | /* Get the challenge from the packet. */ | |
b775c6f2 | 355 | if ((challenge = BN_new()) == NULL) |
356 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
20b279e6 | 357 | packet_get_bignum(challenge); |
95500969 | 358 | packet_check_eom(); |
a306f2dd | 359 | |
360 | debug("Received RSA challenge for host key from server."); | |
361 | ||
362 | /* Compute a response to the challenge. */ | |
aeaa3d9e | 363 | respond_to_rsa_challenge(challenge, host_key->rsa); |
a306f2dd | 364 | |
365 | /* We no longer need the challenge. */ | |
366 | BN_clear_free(challenge); | |
367 | ||
368 | /* Wait for response from the server. */ | |
54a5250f | 369 | type = packet_read(); |
a306f2dd | 370 | if (type == SSH_SMSG_SUCCESS) { |
371 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
372 | return 1; | |
373 | } | |
374 | if (type != SSH_SMSG_FAILURE) | |
375 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
376 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
377 | return 0; | |
378 | } | |
379 | ||
a306f2dd | 380 | /* |
381 | * Tries to authenticate with any string-based challenge/response system. | |
382 | * Note that the client code is not tied to s/key or TIS. | |
383 | */ | |
396c147e | 384 | static int |
5ba55ada | 385 | try_challenge_response_authentication(void) |
a306f2dd | 386 | { |
387 | int type, i; | |
1e3b8b07 | 388 | u_int clen; |
e3a70753 | 389 | char prompt[1024]; |
a306f2dd | 390 | char *challenge, *response; |
aa8003d6 | 391 | |
392 | debug("Doing challenge response authentication."); | |
393 | ||
a306f2dd | 394 | for (i = 0; i < options.number_of_password_prompts; i++) { |
e3a70753 | 395 | /* request a challenge */ |
396 | packet_start(SSH_CMSG_AUTH_TIS); | |
397 | packet_send(); | |
398 | packet_write_wait(); | |
399 | ||
54a5250f | 400 | type = packet_read(); |
e3a70753 | 401 | if (type != SSH_SMSG_FAILURE && |
402 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
403 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 404 | "to SSH_CMSG_AUTH_TIS", type); |
e3a70753 | 405 | } |
406 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
d464095c | 407 | debug("No challenge."); |
e3a70753 | 408 | return 0; |
409 | } | |
410 | challenge = packet_get_string(&clen); | |
95500969 | 411 | packet_check_eom(); |
59c97189 | 412 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
184eed6a | 413 | strchr(challenge, '\n') ? "" : "\nResponse: "); |
e3a70753 | 414 | xfree(challenge); |
a306f2dd | 415 | if (i != 0) |
416 | error("Permission denied, please try again."); | |
e3a70753 | 417 | if (options.cipher == SSH_CIPHER_NONE) |
bbe88b6d | 418 | logit("WARNING: Encryption is disabled! " |
134c552b | 419 | "Response will be transmitted in clear text."); |
e3a70753 | 420 | response = read_passphrase(prompt, 0); |
421 | if (strcmp(response, "") == 0) { | |
422 | xfree(response); | |
423 | break; | |
424 | } | |
a306f2dd | 425 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); |
0ae4fe1d | 426 | ssh_put_password(response); |
a306f2dd | 427 | memset(response, 0, strlen(response)); |
428 | xfree(response); | |
429 | packet_send(); | |
430 | packet_write_wait(); | |
54a5250f | 431 | type = packet_read(); |
a306f2dd | 432 | if (type == SSH_SMSG_SUCCESS) |
433 | return 1; | |
434 | if (type != SSH_SMSG_FAILURE) | |
435 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 436 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); |
a306f2dd | 437 | } |
438 | /* failure */ | |
439 | return 0; | |
440 | } | |
441 | ||
442 | /* | |
443 | * Tries to authenticate with plain passwd authentication. | |
444 | */ | |
396c147e | 445 | static int |
a306f2dd | 446 | try_password_authentication(char *prompt) |
447 | { | |
54a5250f | 448 | int type, i; |
a306f2dd | 449 | char *password; |
450 | ||
451 | debug("Doing password authentication."); | |
452 | if (options.cipher == SSH_CIPHER_NONE) | |
bbe88b6d | 453 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); |
a306f2dd | 454 | for (i = 0; i < options.number_of_password_prompts; i++) { |
455 | if (i != 0) | |
456 | error("Permission denied, please try again."); | |
457 | password = read_passphrase(prompt, 0); | |
458 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
0ae4fe1d | 459 | ssh_put_password(password); |
a306f2dd | 460 | memset(password, 0, strlen(password)); |
461 | xfree(password); | |
462 | packet_send(); | |
463 | packet_write_wait(); | |
464 | ||
54a5250f | 465 | type = packet_read(); |
a306f2dd | 466 | if (type == SSH_SMSG_SUCCESS) |
467 | return 1; | |
468 | if (type != SSH_SMSG_FAILURE) | |
469 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
470 | } | |
471 | /* failure */ | |
472 | return 0; | |
473 | } | |
474 | ||
475 | /* | |
476 | * SSH1 key exchange | |
477 | */ | |
478 | void | |
479 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
480 | { | |
481 | int i; | |
482 | BIGNUM *key; | |
b775c6f2 | 483 | Key *host_key, *server_key; |
a306f2dd | 484 | int bits, rbits; |
485 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
1e3b8b07 | 486 | u_char session_key[SSH_SESSION_KEY_LENGTH]; |
487 | u_char cookie[8]; | |
488 | u_int supported_ciphers; | |
489 | u_int server_flags, client_flags; | |
ca75d7de | 490 | u_int32_t rnd = 0; |
a306f2dd | 491 | |
492 | debug("Waiting for server public key."); | |
493 | ||
494 | /* Wait for a public key packet from the server. */ | |
54a5250f | 495 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); |
a306f2dd | 496 | |
497 | /* Get cookie from the packet. */ | |
498 | for (i = 0; i < 8; i++) | |
499 | cookie[i] = packet_get_char(); | |
500 | ||
501 | /* Get the public key. */ | |
b775c6f2 | 502 | server_key = key_new(KEY_RSA1); |
503 | bits = packet_get_int(); | |
20b279e6 | 504 | packet_get_bignum(server_key->rsa->e); |
505 | packet_get_bignum(server_key->rsa->n); | |
a306f2dd | 506 | |
b775c6f2 | 507 | rbits = BN_num_bits(server_key->rsa->n); |
a306f2dd | 508 | if (bits != rbits) { |
bbe88b6d | 509 | logit("Warning: Server lies about size of server public key: " |
a306f2dd | 510 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 511 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 512 | } |
513 | /* Get the host key. */ | |
b775c6f2 | 514 | host_key = key_new(KEY_RSA1); |
515 | bits = packet_get_int(); | |
20b279e6 | 516 | packet_get_bignum(host_key->rsa->e); |
517 | packet_get_bignum(host_key->rsa->n); | |
a306f2dd | 518 | |
b775c6f2 | 519 | rbits = BN_num_bits(host_key->rsa->n); |
a306f2dd | 520 | if (bits != rbits) { |
bbe88b6d | 521 | logit("Warning: Server lies about size of server host key: " |
a306f2dd | 522 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 523 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 524 | } |
525 | ||
526 | /* Get protocol flags. */ | |
527 | server_flags = packet_get_int(); | |
528 | packet_set_protocol_flags(server_flags); | |
529 | ||
530 | supported_ciphers = packet_get_int(); | |
531 | supported_authentications = packet_get_int(); | |
95500969 | 532 | packet_check_eom(); |
a306f2dd | 533 | |
534 | debug("Received server public key (%d bits) and host key (%d bits).", | |
b775c6f2 | 535 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); |
a306f2dd | 536 | |
b775c6f2 | 537 | if (verify_host_key(host, hostaddr, host_key) == -1) |
01e9ef57 | 538 | fatal("Host key verification failed."); |
a306f2dd | 539 | |
540 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
541 | ||
8bbf1fa6 | 542 | derive_ssh1_session_id(host_key->rsa->n, server_key->rsa->n, cookie, session_id); |
a306f2dd | 543 | |
544 | /* Generate a session key. */ | |
545 | arc4random_stir(); | |
546 | ||
547 | /* | |
548 | * Generate an encryption key for the session. The key is a 256 bit | |
549 | * random number, interpreted as a 32-byte key, with the least | |
550 | * significant 8 bits being the first byte of the key. | |
551 | */ | |
552 | for (i = 0; i < 32; i++) { | |
553 | if (i % 4 == 0) | |
ca75d7de | 554 | rnd = arc4random(); |
555 | session_key[i] = rnd & 0xff; | |
556 | rnd >>= 8; | |
a306f2dd | 557 | } |
558 | ||
559 | /* | |
560 | * According to the protocol spec, the first byte of the session key | |
561 | * is the highest byte of the integer. The session key is xored with | |
562 | * the first 16 bytes of the session id. | |
563 | */ | |
b775c6f2 | 564 | if ((key = BN_new()) == NULL) |
565 | fatal("respond_to_rsa_challenge: BN_new failed"); | |
a306f2dd | 566 | BN_set_word(key, 0); |
567 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
568 | BN_lshift(key, key, 8); | |
569 | if (i < 16) | |
570 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
571 | else | |
572 | BN_add_word(key, session_key[i]); | |
573 | } | |
574 | ||
575 | /* | |
576 | * Encrypt the integer using the public key and host key of the | |
577 | * server (key with smaller modulus first). | |
578 | */ | |
b775c6f2 | 579 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { |
a306f2dd | 580 | /* Public key has smaller modulus. */ |
b775c6f2 | 581 | if (BN_num_bits(host_key->rsa->n) < |
582 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
583 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
184eed6a | 584 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 585 | BN_num_bits(host_key->rsa->n), |
586 | BN_num_bits(server_key->rsa->n), | |
184eed6a | 587 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 588 | } |
b775c6f2 | 589 | rsa_public_encrypt(key, key, server_key->rsa); |
590 | rsa_public_encrypt(key, key, host_key->rsa); | |
a306f2dd | 591 | } else { |
592 | /* Host key has smaller modulus (or they are equal). */ | |
b775c6f2 | 593 | if (BN_num_bits(server_key->rsa->n) < |
594 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
595 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
184eed6a | 596 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 597 | BN_num_bits(server_key->rsa->n), |
598 | BN_num_bits(host_key->rsa->n), | |
184eed6a | 599 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 600 | } |
b775c6f2 | 601 | rsa_public_encrypt(key, key, host_key->rsa); |
602 | rsa_public_encrypt(key, key, server_key->rsa); | |
a306f2dd | 603 | } |
604 | ||
605 | /* Destroy the public keys since we no longer need them. */ | |
b775c6f2 | 606 | key_free(server_key); |
607 | key_free(host_key); | |
a306f2dd | 608 | |
c523303b | 609 | if (options.cipher == SSH_CIPHER_NOT_SET) { |
610 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
611 | options.cipher = ssh_cipher_default; | |
d77347cc | 612 | } else if (options.cipher == SSH_CIPHER_INVALID || |
c523303b | 613 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { |
bbe88b6d | 614 | logit("No valid SSH1 cipher, using %.100s instead.", |
94ec8c6b | 615 | cipher_name(ssh_cipher_default)); |
616 | options.cipher = ssh_cipher_default; | |
a306f2dd | 617 | } |
618 | /* Check that the selected cipher is supported. */ | |
619 | if (!(supported_ciphers & (1 << options.cipher))) | |
620 | fatal("Selected cipher type %.100s not supported by server.", | |
184eed6a | 621 | cipher_name(options.cipher)); |
a306f2dd | 622 | |
623 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
624 | ||
625 | /* Send the encrypted session key to the server. */ | |
626 | packet_start(SSH_CMSG_SESSION_KEY); | |
627 | packet_put_char(options.cipher); | |
628 | ||
629 | /* Send the cookie back to the server. */ | |
630 | for (i = 0; i < 8; i++) | |
631 | packet_put_char(cookie[i]); | |
632 | ||
633 | /* Send and destroy the encrypted encryption key integer. */ | |
634 | packet_put_bignum(key); | |
635 | BN_clear_free(key); | |
636 | ||
637 | /* Send protocol flags. */ | |
638 | packet_put_int(client_flags); | |
639 | ||
640 | /* Send the packet now. */ | |
641 | packet_send(); | |
642 | packet_write_wait(); | |
643 | ||
644 | debug("Sent encrypted session key."); | |
645 | ||
646 | /* Set the encryption key. */ | |
647 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
648 | ||
649 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
650 | memset(session_key, 0, sizeof(session_key)); | |
651 | ||
652 | /* | |
653 | * Expect a success message from the server. Note that this message | |
654 | * will be received in encrypted form. | |
655 | */ | |
54a5250f | 656 | packet_read_expect(SSH_SMSG_SUCCESS); |
a306f2dd | 657 | |
658 | debug("Received encrypted confirmation."); | |
659 | } | |
660 | ||
661 | /* | |
662 | * Authenticate user | |
663 | */ | |
664 | void | |
8002af61 | 665 | ssh_userauth1(const char *local_user, const char *server_user, char *host, |
39c00dc2 | 666 | Sensitive *sensitive) |
a306f2dd | 667 | { |
668 | int i, type; | |
184eed6a | 669 | |
a306f2dd | 670 | if (supported_authentications == 0) |
8002af61 | 671 | fatal("ssh_userauth1: server supports no auth methods"); |
a306f2dd | 672 | |
673 | /* Send the name of the user to log in as on the server. */ | |
674 | packet_start(SSH_CMSG_USER); | |
449c5ba5 | 675 | packet_put_cstring(server_user); |
a306f2dd | 676 | packet_send(); |
677 | packet_write_wait(); | |
678 | ||
679 | /* | |
680 | * The server should respond with success if no authentication is | |
681 | * needed (the user has no password). Otherwise the server responds | |
682 | * with failure. | |
683 | */ | |
54a5250f | 684 | type = packet_read(); |
a306f2dd | 685 | |
686 | /* check whether the connection was accepted without authentication. */ | |
687 | if (type == SSH_SMSG_SUCCESS) | |
ced49be2 | 688 | goto success; |
a306f2dd | 689 | if (type != SSH_SMSG_FAILURE) |
ced49be2 | 690 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); |
184eed6a | 691 | |
a306f2dd | 692 | /* |
693 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
694 | * authentication. | |
695 | */ | |
696 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
8002af61 | 697 | options.rhosts_rsa_authentication) { |
39c00dc2 | 698 | for (i = 0; i < sensitive->nkeys; i++) { |
699 | if (sensitive->keys[i] != NULL && | |
700 | sensitive->keys[i]->type == KEY_RSA1 && | |
701 | try_rhosts_rsa_authentication(local_user, | |
702 | sensitive->keys[i])) | |
ced49be2 | 703 | goto success; |
8002af61 | 704 | } |
a306f2dd | 705 | } |
706 | /* Try RSA authentication if the server supports it. */ | |
707 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
708 | options.rsa_authentication) { | |
709 | /* | |
710 | * Try RSA authentication using the authentication agent. The | |
711 | * agent is tried first because no passphrase is needed for | |
712 | * it, whereas identity files may require passphrases. | |
713 | */ | |
714 | if (try_agent_authentication()) | |
ced49be2 | 715 | goto success; |
a306f2dd | 716 | |
717 | /* Try RSA authentication for each identity. */ | |
718 | for (i = 0; i < options.num_identity_files; i++) | |
fee56204 | 719 | if (options.identity_keys[i] != NULL && |
720 | options.identity_keys[i]->type == KEY_RSA1 && | |
383546c4 | 721 | try_rsa_authentication(i)) |
ced49be2 | 722 | goto success; |
a306f2dd | 723 | } |
d464095c | 724 | /* Try challenge response authentication if the server supports it. */ |
a306f2dd | 725 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && |
5ba55ada | 726 | options.challenge_response_authentication && !options.batch_mode) { |
727 | if (try_challenge_response_authentication()) | |
ced49be2 | 728 | goto success; |
a306f2dd | 729 | } |
730 | /* Try password authentication if the server supports it. */ | |
731 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
732 | options.password_authentication && !options.batch_mode) { | |
733 | char prompt[80]; | |
734 | ||
b3b9ad8e | 735 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", |
a306f2dd | 736 | server_user, host); |
737 | if (try_password_authentication(prompt)) | |
ced49be2 | 738 | goto success; |
a306f2dd | 739 | } |
740 | /* All authentication methods have failed. Exit with an error message. */ | |
741 | fatal("Permission denied."); | |
742 | /* NOTREACHED */ | |
ced49be2 | 743 | |
744 | success: | |
62bb2c8f | 745 | return; /* need statement after label */ |
a306f2dd | 746 | } |