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fc231518 | 1 | /* $OpenBSD: sshconnect1.c,v 1.65 2006/04/25 08:02:27 dtucker 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 | |
18 | #include <openssl/bn.h> | |
6b4b5e49 | 19 | #include <openssl/md5.h> |
a306f2dd | 20 | |
42f11eb2 | 21 | #include "ssh.h" |
22 | #include "ssh1.h" | |
a306f2dd | 23 | #include "xmalloc.h" |
24 | #include "rsa.h" | |
a306f2dd | 25 | #include "buffer.h" |
26 | #include "packet.h" | |
8bbf1fa6 | 27 | #include "kex.h" |
a306f2dd | 28 | #include "uidswap.h" |
42f11eb2 | 29 | #include "log.h" |
a306f2dd | 30 | #include "readconf.h" |
31 | #include "key.h" | |
4c8722d9 | 32 | #include "authfd.h" |
a306f2dd | 33 | #include "sshconnect.h" |
34 | #include "authfile.h" | |
58ae9cb8 | 35 | #include "misc.h" |
42f11eb2 | 36 | #include "cipher.h" |
37 | #include "canohost.h" | |
ced49be2 | 38 | #include "auth.h" |
a306f2dd | 39 | |
40 | /* Session id for the current session. */ | |
1e3b8b07 | 41 | u_char session_id[16]; |
42 | u_int supported_authentications = 0; | |
a306f2dd | 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 | */ | |
396c147e | 51 | static int |
5ca51e19 | 52 | try_agent_authentication(void) |
a306f2dd | 53 | { |
2e73a022 | 54 | int type; |
a306f2dd | 55 | char *comment; |
56 | AuthenticationConnection *auth; | |
1e3b8b07 | 57 | u_char response[16]; |
58 | u_int i; | |
2e73a022 | 59 | Key *key; |
60 | BIGNUM *challenge; | |
a306f2dd | 61 | |
62 | /* Get connection to the agent. */ | |
63 | auth = ssh_get_authentication_connection(); | |
64 | if (!auth) | |
65 | return 0; | |
66 | ||
b775c6f2 | 67 | if ((challenge = BN_new()) == NULL) |
68 | fatal("try_agent_authentication: BN_new failed"); | |
a306f2dd | 69 | /* Loop through identities served by the agent. */ |
2e73a022 | 70 | for (key = ssh_get_first_identity(auth, &comment, 1); |
184eed6a | 71 | key != NULL; |
72 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 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); | |
2e73a022 | 80 | packet_put_bignum(key->rsa->n); |
a306f2dd | 81 | packet_send(); |
82 | packet_write_wait(); | |
83 | ||
84 | /* Wait for server's response. */ | |
54a5250f | 85 | type = packet_read(); |
a306f2dd | 86 | |
7b9b0103 | 87 | /* The server sends failure if it doesn't like our key or |
a306f2dd | 88 | does not support RSA authentication. */ |
89 | if (type == SSH_SMSG_FAILURE) { | |
90 | debug("Server refused our key."); | |
2e73a022 | 91 | key_free(key); |
a306f2dd | 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 | ||
20b279e6 | 99 | packet_get_bignum(challenge); |
95500969 | 100 | packet_check_eom(); |
a306f2dd | 101 | |
102 | debug("Received RSA challenge from server."); | |
103 | ||
104 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 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 | */ | |
bbe88b6d | 111 | logit("Authentication agent failed to decrypt challenge."); |
a306f2dd | 112 | memset(response, 0, sizeof(response)); |
113 | } | |
2e73a022 | 114 | key_free(key); |
a306f2dd | 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. */ | |
54a5250f | 125 | type = packet_read(); |
a306f2dd | 126 | |
127 | /* The server returns success if it accepted the authentication. */ | |
128 | if (type == SSH_SMSG_SUCCESS) { | |
eea39c02 | 129 | ssh_close_authentication_connection(auth); |
a306f2dd | 130 | BN_clear_free(challenge); |
2e73a022 | 131 | debug("RSA authentication accepted by server."); |
a306f2dd | 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 | } | |
eea39c02 | 139 | ssh_close_authentication_connection(auth); |
a306f2dd | 140 | BN_clear_free(challenge); |
a306f2dd | 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 | */ | |
396c147e | 149 | static void |
a306f2dd | 150 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) |
151 | { | |
1e3b8b07 | 152 | u_char buf[32], response[16]; |
a306f2dd | 153 | MD5_CTX md; |
154 | int i, len; | |
155 | ||
156 | /* Decrypt the challenge using the private key. */ | |
46aa2d1f | 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"); | |
a306f2dd | 161 | |
162 | /* Compute the response. */ | |
163 | /* The response is MD5 of decrypted challenge plus session id. */ | |
164 | len = BN_num_bytes(challenge); | |
2ceb8101 | 165 | if (len <= 0 || (u_int)len > sizeof(buf)) |
46aa2d1f | 166 | packet_disconnect( |
167 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
a306f2dd | 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 | */ | |
396c147e | 194 | static int |
383546c4 | 195 | try_rsa_authentication(int idx) |
a306f2dd | 196 | { |
197 | BIGNUM *challenge; | |
ce404659 | 198 | Key *public, *private; |
383546c4 | 199 | char buf[300], *passphrase, *comment, *authfile; |
fc231518 | 200 | int i, perm_ok = 1, type, quit; |
a306f2dd | 201 | |
383546c4 | 202 | public = options.identity_keys[idx]; |
203 | authfile = options.identity_files[idx]; | |
204 | comment = xstrdup(authfile); | |
205 | ||
a306f2dd | 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 | ||
a306f2dd | 214 | /* Wait for server's response. */ |
54a5250f | 215 | type = packet_read(); |
a306f2dd | 216 | |
217 | /* | |
7b9b0103 | 218 | * The server responds with failure if it doesn't like our key or |
219 | * doesn't support RSA authentication. | |
a306f2dd | 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. */ | |
b775c6f2 | 231 | if ((challenge = BN_new()) == NULL) |
232 | fatal("try_rsa_authentication: BN_new failed"); | |
20b279e6 | 233 | packet_get_bignum(challenge); |
95500969 | 234 | packet_check_eom(); |
a306f2dd | 235 | |
236 | debug("Received RSA challenge from server."); | |
237 | ||
a306f2dd | 238 | /* |
383546c4 | 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 | |
a306f2dd | 241 | * fails, ask for a passphrase. |
242 | */ | |
75cf7563 | 243 | if (public->flags & KEY_FLAG_EXT) |
383546c4 | 244 | private = public; |
245 | else | |
fc231518 | 246 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL, |
247 | &perm_ok); | |
248 | if (private == NULL && !options.batch_mode && perm_ok) { | |
ce404659 | 249 | snprintf(buf, sizeof(buf), |
250 | "Enter passphrase for RSA key '%.100s': ", comment); | |
251 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
a306f2dd | 252 | passphrase = read_passphrase(buf, 0); |
ce404659 | 253 | if (strcmp(passphrase, "") != 0) { |
254 | private = key_load_private_type(KEY_RSA1, | |
fc231518 | 255 | authfile, passphrase, NULL, NULL); |
ce404659 | 256 | quit = 0; |
257 | } else { | |
258 | debug2("no passphrase given, try next key"); | |
259 | quit = 1; | |
260 | } | |
a306f2dd | 261 | memset(passphrase, 0, strlen(passphrase)); |
262 | xfree(passphrase); | |
ce404659 | 263 | if (private != NULL || quit) |
264 | break; | |
265 | debug2("bad passphrase given, try again..."); | |
a306f2dd | 266 | } |
a306f2dd | 267 | } |
268 | /* We no longer need the comment. */ | |
269 | xfree(comment); | |
270 | ||
ce404659 | 271 | if (private == NULL) { |
fc231518 | 272 | if (!options.batch_mode && perm_ok) |
ce404659 | 273 | error("Bad passphrase."); |
274 | ||
275 | /* Send a dummy response packet to avoid protocol error. */ | |
276 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
277 | for (i = 0; i < 16; i++) | |
278 | packet_put_char(0); | |
279 | packet_send(); | |
280 | packet_write_wait(); | |
281 | ||
282 | /* Expect the server to reject it... */ | |
54a5250f | 283 | packet_read_expect(SSH_SMSG_FAILURE); |
ce404659 | 284 | BN_clear_free(challenge); |
285 | return 0; | |
286 | } | |
287 | ||
a306f2dd | 288 | /* Compute and send a response to the challenge. */ |
289 | respond_to_rsa_challenge(challenge, private->rsa); | |
290 | ||
383546c4 | 291 | /* Destroy the private key unless it in external hardware. */ |
292 | if (!(private->flags & KEY_FLAG_EXT)) | |
293 | key_free(private); | |
a306f2dd | 294 | |
295 | /* We no longer need the challenge. */ | |
296 | BN_clear_free(challenge); | |
297 | ||
298 | /* Wait for response from the server. */ | |
54a5250f | 299 | type = packet_read(); |
a306f2dd | 300 | if (type == SSH_SMSG_SUCCESS) { |
301 | debug("RSA authentication accepted by server."); | |
302 | return 1; | |
303 | } | |
304 | if (type != SSH_SMSG_FAILURE) | |
305 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
306 | debug("RSA authentication refused."); | |
307 | return 0; | |
308 | } | |
309 | ||
310 | /* | |
311 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
312 | * authentication and RSA host authentication. | |
313 | */ | |
396c147e | 314 | static int |
aeaa3d9e | 315 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) |
a306f2dd | 316 | { |
317 | int type; | |
318 | BIGNUM *challenge; | |
a306f2dd | 319 | |
320 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
321 | ||
322 | /* Tell the server that we are willing to authenticate using this key. */ | |
323 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
449c5ba5 | 324 | packet_put_cstring(local_user); |
aeaa3d9e | 325 | packet_put_int(BN_num_bits(host_key->rsa->n)); |
326 | packet_put_bignum(host_key->rsa->e); | |
327 | packet_put_bignum(host_key->rsa->n); | |
a306f2dd | 328 | packet_send(); |
329 | packet_write_wait(); | |
330 | ||
331 | /* Wait for server's response. */ | |
54a5250f | 332 | type = packet_read(); |
a306f2dd | 333 | |
334 | /* The server responds with failure if it doesn't admit our | |
335 | .rhosts authentication or doesn't know our host key. */ | |
336 | if (type == SSH_SMSG_FAILURE) { | |
337 | debug("Server refused our rhosts authentication or host key."); | |
338 | return 0; | |
339 | } | |
340 | /* Otherwise, the server should respond with a challenge. */ | |
341 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
342 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
343 | ||
344 | /* Get the challenge from the packet. */ | |
b775c6f2 | 345 | if ((challenge = BN_new()) == NULL) |
346 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
20b279e6 | 347 | packet_get_bignum(challenge); |
95500969 | 348 | packet_check_eom(); |
a306f2dd | 349 | |
350 | debug("Received RSA challenge for host key from server."); | |
351 | ||
352 | /* Compute a response to the challenge. */ | |
aeaa3d9e | 353 | respond_to_rsa_challenge(challenge, host_key->rsa); |
a306f2dd | 354 | |
355 | /* We no longer need the challenge. */ | |
356 | BN_clear_free(challenge); | |
357 | ||
358 | /* Wait for response from the server. */ | |
54a5250f | 359 | type = packet_read(); |
a306f2dd | 360 | if (type == SSH_SMSG_SUCCESS) { |
361 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
362 | return 1; | |
363 | } | |
364 | if (type != SSH_SMSG_FAILURE) | |
365 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
366 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
367 | return 0; | |
368 | } | |
369 | ||
a306f2dd | 370 | /* |
371 | * Tries to authenticate with any string-based challenge/response system. | |
372 | * Note that the client code is not tied to s/key or TIS. | |
373 | */ | |
396c147e | 374 | static int |
5ba55ada | 375 | try_challenge_response_authentication(void) |
a306f2dd | 376 | { |
377 | int type, i; | |
1e3b8b07 | 378 | u_int clen; |
e3a70753 | 379 | char prompt[1024]; |
a306f2dd | 380 | char *challenge, *response; |
aa8003d6 | 381 | |
382 | debug("Doing challenge response authentication."); | |
383 | ||
a306f2dd | 384 | for (i = 0; i < options.number_of_password_prompts; i++) { |
e3a70753 | 385 | /* request a challenge */ |
386 | packet_start(SSH_CMSG_AUTH_TIS); | |
387 | packet_send(); | |
388 | packet_write_wait(); | |
389 | ||
54a5250f | 390 | type = packet_read(); |
e3a70753 | 391 | if (type != SSH_SMSG_FAILURE && |
392 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
393 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 394 | "to SSH_CMSG_AUTH_TIS", type); |
e3a70753 | 395 | } |
396 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
d464095c | 397 | debug("No challenge."); |
e3a70753 | 398 | return 0; |
399 | } | |
400 | challenge = packet_get_string(&clen); | |
95500969 | 401 | packet_check_eom(); |
59c97189 | 402 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
184eed6a | 403 | strchr(challenge, '\n') ? "" : "\nResponse: "); |
e3a70753 | 404 | xfree(challenge); |
a306f2dd | 405 | if (i != 0) |
406 | error("Permission denied, please try again."); | |
e3a70753 | 407 | if (options.cipher == SSH_CIPHER_NONE) |
bbe88b6d | 408 | logit("WARNING: Encryption is disabled! " |
134c552b | 409 | "Response will be transmitted in clear text."); |
e3a70753 | 410 | response = read_passphrase(prompt, 0); |
411 | if (strcmp(response, "") == 0) { | |
412 | xfree(response); | |
413 | break; | |
414 | } | |
a306f2dd | 415 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); |
0ae4fe1d | 416 | ssh_put_password(response); |
a306f2dd | 417 | memset(response, 0, strlen(response)); |
418 | xfree(response); | |
419 | packet_send(); | |
420 | packet_write_wait(); | |
54a5250f | 421 | type = packet_read(); |
a306f2dd | 422 | if (type == SSH_SMSG_SUCCESS) |
423 | return 1; | |
424 | if (type != SSH_SMSG_FAILURE) | |
425 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 426 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); |
a306f2dd | 427 | } |
428 | /* failure */ | |
429 | return 0; | |
430 | } | |
431 | ||
432 | /* | |
433 | * Tries to authenticate with plain passwd authentication. | |
434 | */ | |
396c147e | 435 | static int |
a306f2dd | 436 | try_password_authentication(char *prompt) |
437 | { | |
54a5250f | 438 | int type, i; |
a306f2dd | 439 | char *password; |
440 | ||
441 | debug("Doing password authentication."); | |
442 | if (options.cipher == SSH_CIPHER_NONE) | |
bbe88b6d | 443 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); |
a306f2dd | 444 | for (i = 0; i < options.number_of_password_prompts; i++) { |
445 | if (i != 0) | |
446 | error("Permission denied, please try again."); | |
447 | password = read_passphrase(prompt, 0); | |
448 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
0ae4fe1d | 449 | ssh_put_password(password); |
a306f2dd | 450 | memset(password, 0, strlen(password)); |
451 | xfree(password); | |
452 | packet_send(); | |
453 | packet_write_wait(); | |
454 | ||
54a5250f | 455 | type = packet_read(); |
a306f2dd | 456 | if (type == SSH_SMSG_SUCCESS) |
457 | return 1; | |
458 | if (type != SSH_SMSG_FAILURE) | |
459 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
460 | } | |
461 | /* failure */ | |
462 | return 0; | |
463 | } | |
464 | ||
465 | /* | |
466 | * SSH1 key exchange | |
467 | */ | |
468 | void | |
469 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
470 | { | |
471 | int i; | |
472 | BIGNUM *key; | |
b775c6f2 | 473 | Key *host_key, *server_key; |
a306f2dd | 474 | int bits, rbits; |
475 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
1e3b8b07 | 476 | u_char session_key[SSH_SESSION_KEY_LENGTH]; |
477 | u_char cookie[8]; | |
478 | u_int supported_ciphers; | |
479 | u_int server_flags, client_flags; | |
ca75d7de | 480 | u_int32_t rnd = 0; |
a306f2dd | 481 | |
482 | debug("Waiting for server public key."); | |
483 | ||
484 | /* Wait for a public key packet from the server. */ | |
54a5250f | 485 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); |
a306f2dd | 486 | |
487 | /* Get cookie from the packet. */ | |
488 | for (i = 0; i < 8; i++) | |
489 | cookie[i] = packet_get_char(); | |
490 | ||
491 | /* Get the public key. */ | |
b775c6f2 | 492 | server_key = key_new(KEY_RSA1); |
493 | bits = packet_get_int(); | |
20b279e6 | 494 | packet_get_bignum(server_key->rsa->e); |
495 | packet_get_bignum(server_key->rsa->n); | |
a306f2dd | 496 | |
b775c6f2 | 497 | rbits = BN_num_bits(server_key->rsa->n); |
a306f2dd | 498 | if (bits != rbits) { |
bbe88b6d | 499 | logit("Warning: Server lies about size of server public key: " |
a306f2dd | 500 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 501 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 502 | } |
503 | /* Get the host key. */ | |
b775c6f2 | 504 | host_key = key_new(KEY_RSA1); |
505 | bits = packet_get_int(); | |
20b279e6 | 506 | packet_get_bignum(host_key->rsa->e); |
507 | packet_get_bignum(host_key->rsa->n); | |
a306f2dd | 508 | |
b775c6f2 | 509 | rbits = BN_num_bits(host_key->rsa->n); |
a306f2dd | 510 | if (bits != rbits) { |
bbe88b6d | 511 | logit("Warning: Server lies about size of server host key: " |
a306f2dd | 512 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 513 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 514 | } |
515 | ||
516 | /* Get protocol flags. */ | |
517 | server_flags = packet_get_int(); | |
518 | packet_set_protocol_flags(server_flags); | |
519 | ||
520 | supported_ciphers = packet_get_int(); | |
521 | supported_authentications = packet_get_int(); | |
95500969 | 522 | packet_check_eom(); |
a306f2dd | 523 | |
524 | debug("Received server public key (%d bits) and host key (%d bits).", | |
b775c6f2 | 525 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); |
a306f2dd | 526 | |
b775c6f2 | 527 | if (verify_host_key(host, hostaddr, host_key) == -1) |
01e9ef57 | 528 | fatal("Host key verification failed."); |
a306f2dd | 529 | |
530 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
531 | ||
8bbf1fa6 | 532 | derive_ssh1_session_id(host_key->rsa->n, server_key->rsa->n, cookie, session_id); |
a306f2dd | 533 | |
534 | /* Generate a session key. */ | |
535 | arc4random_stir(); | |
536 | ||
537 | /* | |
538 | * Generate an encryption key for the session. The key is a 256 bit | |
539 | * random number, interpreted as a 32-byte key, with the least | |
540 | * significant 8 bits being the first byte of the key. | |
541 | */ | |
542 | for (i = 0; i < 32; i++) { | |
543 | if (i % 4 == 0) | |
ca75d7de | 544 | rnd = arc4random(); |
545 | session_key[i] = rnd & 0xff; | |
546 | rnd >>= 8; | |
a306f2dd | 547 | } |
548 | ||
549 | /* | |
550 | * According to the protocol spec, the first byte of the session key | |
551 | * is the highest byte of the integer. The session key is xored with | |
552 | * the first 16 bytes of the session id. | |
553 | */ | |
b775c6f2 | 554 | if ((key = BN_new()) == NULL) |
555 | fatal("respond_to_rsa_challenge: BN_new failed"); | |
a306f2dd | 556 | BN_set_word(key, 0); |
557 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
558 | BN_lshift(key, key, 8); | |
559 | if (i < 16) | |
560 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
561 | else | |
562 | BN_add_word(key, session_key[i]); | |
563 | } | |
564 | ||
565 | /* | |
566 | * Encrypt the integer using the public key and host key of the | |
567 | * server (key with smaller modulus first). | |
568 | */ | |
b775c6f2 | 569 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { |
a306f2dd | 570 | /* Public key has smaller modulus. */ |
b775c6f2 | 571 | if (BN_num_bits(host_key->rsa->n) < |
572 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
573 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
184eed6a | 574 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 575 | BN_num_bits(host_key->rsa->n), |
576 | BN_num_bits(server_key->rsa->n), | |
184eed6a | 577 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 578 | } |
b775c6f2 | 579 | rsa_public_encrypt(key, key, server_key->rsa); |
580 | rsa_public_encrypt(key, key, host_key->rsa); | |
a306f2dd | 581 | } else { |
582 | /* Host key has smaller modulus (or they are equal). */ | |
b775c6f2 | 583 | if (BN_num_bits(server_key->rsa->n) < |
584 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
585 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
184eed6a | 586 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 587 | BN_num_bits(server_key->rsa->n), |
588 | BN_num_bits(host_key->rsa->n), | |
184eed6a | 589 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 590 | } |
b775c6f2 | 591 | rsa_public_encrypt(key, key, host_key->rsa); |
592 | rsa_public_encrypt(key, key, server_key->rsa); | |
a306f2dd | 593 | } |
594 | ||
595 | /* Destroy the public keys since we no longer need them. */ | |
b775c6f2 | 596 | key_free(server_key); |
597 | key_free(host_key); | |
a306f2dd | 598 | |
c523303b | 599 | if (options.cipher == SSH_CIPHER_NOT_SET) { |
600 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
601 | options.cipher = ssh_cipher_default; | |
d77347cc | 602 | } else if (options.cipher == SSH_CIPHER_INVALID || |
c523303b | 603 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { |
bbe88b6d | 604 | logit("No valid SSH1 cipher, using %.100s instead.", |
94ec8c6b | 605 | cipher_name(ssh_cipher_default)); |
606 | options.cipher = ssh_cipher_default; | |
a306f2dd | 607 | } |
608 | /* Check that the selected cipher is supported. */ | |
609 | if (!(supported_ciphers & (1 << options.cipher))) | |
610 | fatal("Selected cipher type %.100s not supported by server.", | |
184eed6a | 611 | cipher_name(options.cipher)); |
a306f2dd | 612 | |
613 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
614 | ||
615 | /* Send the encrypted session key to the server. */ | |
616 | packet_start(SSH_CMSG_SESSION_KEY); | |
617 | packet_put_char(options.cipher); | |
618 | ||
619 | /* Send the cookie back to the server. */ | |
620 | for (i = 0; i < 8; i++) | |
621 | packet_put_char(cookie[i]); | |
622 | ||
623 | /* Send and destroy the encrypted encryption key integer. */ | |
624 | packet_put_bignum(key); | |
625 | BN_clear_free(key); | |
626 | ||
627 | /* Send protocol flags. */ | |
628 | packet_put_int(client_flags); | |
629 | ||
630 | /* Send the packet now. */ | |
631 | packet_send(); | |
632 | packet_write_wait(); | |
633 | ||
634 | debug("Sent encrypted session key."); | |
635 | ||
636 | /* Set the encryption key. */ | |
637 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
638 | ||
639 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
640 | memset(session_key, 0, sizeof(session_key)); | |
641 | ||
642 | /* | |
643 | * Expect a success message from the server. Note that this message | |
644 | * will be received in encrypted form. | |
645 | */ | |
54a5250f | 646 | packet_read_expect(SSH_SMSG_SUCCESS); |
a306f2dd | 647 | |
648 | debug("Received encrypted confirmation."); | |
649 | } | |
650 | ||
651 | /* | |
652 | * Authenticate user | |
653 | */ | |
654 | void | |
8002af61 | 655 | ssh_userauth1(const char *local_user, const char *server_user, char *host, |
39c00dc2 | 656 | Sensitive *sensitive) |
a306f2dd | 657 | { |
658 | int i, type; | |
184eed6a | 659 | |
a306f2dd | 660 | if (supported_authentications == 0) |
8002af61 | 661 | fatal("ssh_userauth1: server supports no auth methods"); |
a306f2dd | 662 | |
663 | /* Send the name of the user to log in as on the server. */ | |
664 | packet_start(SSH_CMSG_USER); | |
449c5ba5 | 665 | packet_put_cstring(server_user); |
a306f2dd | 666 | packet_send(); |
667 | packet_write_wait(); | |
668 | ||
669 | /* | |
670 | * The server should respond with success if no authentication is | |
671 | * needed (the user has no password). Otherwise the server responds | |
672 | * with failure. | |
673 | */ | |
54a5250f | 674 | type = packet_read(); |
a306f2dd | 675 | |
676 | /* check whether the connection was accepted without authentication. */ | |
677 | if (type == SSH_SMSG_SUCCESS) | |
ced49be2 | 678 | goto success; |
a306f2dd | 679 | if (type != SSH_SMSG_FAILURE) |
ced49be2 | 680 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); |
184eed6a | 681 | |
a306f2dd | 682 | /* |
683 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
684 | * authentication. | |
685 | */ | |
686 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
8002af61 | 687 | options.rhosts_rsa_authentication) { |
39c00dc2 | 688 | for (i = 0; i < sensitive->nkeys; i++) { |
689 | if (sensitive->keys[i] != NULL && | |
690 | sensitive->keys[i]->type == KEY_RSA1 && | |
691 | try_rhosts_rsa_authentication(local_user, | |
692 | sensitive->keys[i])) | |
ced49be2 | 693 | goto success; |
8002af61 | 694 | } |
a306f2dd | 695 | } |
696 | /* Try RSA authentication if the server supports it. */ | |
697 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
698 | options.rsa_authentication) { | |
699 | /* | |
700 | * Try RSA authentication using the authentication agent. The | |
701 | * agent is tried first because no passphrase is needed for | |
702 | * it, whereas identity files may require passphrases. | |
703 | */ | |
704 | if (try_agent_authentication()) | |
ced49be2 | 705 | goto success; |
a306f2dd | 706 | |
707 | /* Try RSA authentication for each identity. */ | |
708 | for (i = 0; i < options.num_identity_files; i++) | |
fee56204 | 709 | if (options.identity_keys[i] != NULL && |
710 | options.identity_keys[i]->type == KEY_RSA1 && | |
383546c4 | 711 | try_rsa_authentication(i)) |
ced49be2 | 712 | goto success; |
a306f2dd | 713 | } |
d464095c | 714 | /* Try challenge response authentication if the server supports it. */ |
a306f2dd | 715 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && |
5ba55ada | 716 | options.challenge_response_authentication && !options.batch_mode) { |
717 | if (try_challenge_response_authentication()) | |
ced49be2 | 718 | goto success; |
a306f2dd | 719 | } |
720 | /* Try password authentication if the server supports it. */ | |
721 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
722 | options.password_authentication && !options.batch_mode) { | |
723 | char prompt[80]; | |
724 | ||
b3b9ad8e | 725 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", |
a306f2dd | 726 | server_user, host); |
727 | if (try_password_authentication(prompt)) | |
ced49be2 | 728 | goto success; |
a306f2dd | 729 | } |
730 | /* All authentication methods have failed. Exit with an error message. */ | |
731 | fatal("Permission denied."); | |
732 | /* NOTREACHED */ | |
ced49be2 | 733 | |
734 | success: | |
62bb2c8f | 735 | return; /* need statement after label */ |
a306f2dd | 736 | } |