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cf851879 | 1 | /* $OpenBSD: sshconnect1.c,v 1.68 2006/08/01 23:22:47 stevesk 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 | |
cf851879 | 21 | #include <stdio.h> |
ffa517a8 | 22 | #include <stdlib.h> |
00146caa | 23 | #include <string.h> |
24 | ||
42f11eb2 | 25 | #include "ssh.h" |
26 | #include "ssh1.h" | |
a306f2dd | 27 | #include "xmalloc.h" |
28 | #include "rsa.h" | |
a306f2dd | 29 | #include "buffer.h" |
30 | #include "packet.h" | |
8bbf1fa6 | 31 | #include "kex.h" |
a306f2dd | 32 | #include "uidswap.h" |
42f11eb2 | 33 | #include "log.h" |
a306f2dd | 34 | #include "readconf.h" |
35 | #include "key.h" | |
4c8722d9 | 36 | #include "authfd.h" |
a306f2dd | 37 | #include "sshconnect.h" |
38 | #include "authfile.h" | |
58ae9cb8 | 39 | #include "misc.h" |
42f11eb2 | 40 | #include "cipher.h" |
41 | #include "canohost.h" | |
ced49be2 | 42 | #include "auth.h" |
a306f2dd | 43 | |
44 | /* Session id for the current session. */ | |
1e3b8b07 | 45 | u_char session_id[16]; |
46 | u_int supported_authentications = 0; | |
a306f2dd | 47 | |
48 | extern Options options; | |
49 | extern char *__progname; | |
50 | ||
51 | /* | |
52 | * Checks if the user has an authentication agent, and if so, tries to | |
53 | * authenticate using the agent. | |
54 | */ | |
396c147e | 55 | static int |
5ca51e19 | 56 | try_agent_authentication(void) |
a306f2dd | 57 | { |
2e73a022 | 58 | int type; |
a306f2dd | 59 | char *comment; |
60 | AuthenticationConnection *auth; | |
1e3b8b07 | 61 | u_char response[16]; |
62 | u_int i; | |
2e73a022 | 63 | Key *key; |
64 | BIGNUM *challenge; | |
a306f2dd | 65 | |
66 | /* Get connection to the agent. */ | |
67 | auth = ssh_get_authentication_connection(); | |
68 | if (!auth) | |
69 | return 0; | |
70 | ||
b775c6f2 | 71 | if ((challenge = BN_new()) == NULL) |
72 | fatal("try_agent_authentication: BN_new failed"); | |
a306f2dd | 73 | /* Loop through identities served by the agent. */ |
2e73a022 | 74 | for (key = ssh_get_first_identity(auth, &comment, 1); |
184eed6a | 75 | key != NULL; |
76 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 77 | |
78 | /* Try this identity. */ | |
79 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
80 | xfree(comment); | |
81 | ||
82 | /* Tell the server that we are willing to authenticate using this key. */ | |
83 | packet_start(SSH_CMSG_AUTH_RSA); | |
2e73a022 | 84 | packet_put_bignum(key->rsa->n); |
a306f2dd | 85 | packet_send(); |
86 | packet_write_wait(); | |
87 | ||
88 | /* Wait for server's response. */ | |
54a5250f | 89 | type = packet_read(); |
a306f2dd | 90 | |
7b9b0103 | 91 | /* The server sends failure if it doesn't like our key or |
a306f2dd | 92 | does not support RSA authentication. */ |
93 | if (type == SSH_SMSG_FAILURE) { | |
94 | debug("Server refused our key."); | |
2e73a022 | 95 | key_free(key); |
a306f2dd | 96 | continue; |
97 | } | |
98 | /* Otherwise it should have sent a challenge. */ | |
99 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
100 | packet_disconnect("Protocol error during RSA authentication: %d", | |
101 | type); | |
102 | ||
20b279e6 | 103 | packet_get_bignum(challenge); |
95500969 | 104 | packet_check_eom(); |
a306f2dd | 105 | |
106 | debug("Received RSA challenge from server."); | |
107 | ||
108 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 109 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { |
110 | /* | |
111 | * The agent failed to authenticate this identifier | |
112 | * although it advertised it supports this. Just | |
113 | * return a wrong value. | |
114 | */ | |
bbe88b6d | 115 | logit("Authentication agent failed to decrypt challenge."); |
a306f2dd | 116 | memset(response, 0, sizeof(response)); |
117 | } | |
2e73a022 | 118 | key_free(key); |
a306f2dd | 119 | debug("Sending response to RSA challenge."); |
120 | ||
121 | /* Send the decrypted challenge back to the server. */ | |
122 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
123 | for (i = 0; i < 16; i++) | |
124 | packet_put_char(response[i]); | |
125 | packet_send(); | |
126 | packet_write_wait(); | |
127 | ||
128 | /* Wait for response from the server. */ | |
54a5250f | 129 | type = packet_read(); |
a306f2dd | 130 | |
131 | /* The server returns success if it accepted the authentication. */ | |
132 | if (type == SSH_SMSG_SUCCESS) { | |
eea39c02 | 133 | ssh_close_authentication_connection(auth); |
a306f2dd | 134 | BN_clear_free(challenge); |
2e73a022 | 135 | debug("RSA authentication accepted by server."); |
a306f2dd | 136 | return 1; |
137 | } | |
138 | /* Otherwise it should return failure. */ | |
139 | if (type != SSH_SMSG_FAILURE) | |
140 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
141 | type); | |
142 | } | |
eea39c02 | 143 | ssh_close_authentication_connection(auth); |
a306f2dd | 144 | BN_clear_free(challenge); |
a306f2dd | 145 | debug("RSA authentication using agent refused."); |
146 | return 0; | |
147 | } | |
148 | ||
149 | /* | |
150 | * Computes the proper response to a RSA challenge, and sends the response to | |
151 | * the server. | |
152 | */ | |
396c147e | 153 | static void |
a306f2dd | 154 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) |
155 | { | |
1e3b8b07 | 156 | u_char buf[32], response[16]; |
a306f2dd | 157 | MD5_CTX md; |
158 | int i, len; | |
159 | ||
160 | /* Decrypt the challenge using the private key. */ | |
46aa2d1f | 161 | /* XXX think about Bleichenbacher, too */ |
162 | if (rsa_private_decrypt(challenge, challenge, prv) <= 0) | |
163 | packet_disconnect( | |
164 | "respond_to_rsa_challenge: rsa_private_decrypt failed"); | |
a306f2dd | 165 | |
166 | /* Compute the response. */ | |
167 | /* The response is MD5 of decrypted challenge plus session id. */ | |
168 | len = BN_num_bytes(challenge); | |
2ceb8101 | 169 | if (len <= 0 || (u_int)len > sizeof(buf)) |
46aa2d1f | 170 | packet_disconnect( |
171 | "respond_to_rsa_challenge: bad challenge length %d", len); | |
a306f2dd | 172 | |
173 | memset(buf, 0, sizeof(buf)); | |
174 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
175 | MD5_Init(&md); | |
176 | MD5_Update(&md, buf, 32); | |
177 | MD5_Update(&md, session_id, 16); | |
178 | MD5_Final(response, &md); | |
179 | ||
180 | debug("Sending response to host key RSA challenge."); | |
181 | ||
182 | /* Send the response back to the server. */ | |
183 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
184 | for (i = 0; i < 16; i++) | |
185 | packet_put_char(response[i]); | |
186 | packet_send(); | |
187 | packet_write_wait(); | |
188 | ||
189 | memset(buf, 0, sizeof(buf)); | |
190 | memset(response, 0, sizeof(response)); | |
191 | memset(&md, 0, sizeof(md)); | |
192 | } | |
193 | ||
194 | /* | |
195 | * Checks if the user has authentication file, and if so, tries to authenticate | |
196 | * the user using it. | |
197 | */ | |
396c147e | 198 | static int |
383546c4 | 199 | try_rsa_authentication(int idx) |
a306f2dd | 200 | { |
201 | BIGNUM *challenge; | |
ce404659 | 202 | Key *public, *private; |
383546c4 | 203 | char buf[300], *passphrase, *comment, *authfile; |
fc231518 | 204 | int i, perm_ok = 1, type, quit; |
a306f2dd | 205 | |
383546c4 | 206 | public = options.identity_keys[idx]; |
207 | authfile = options.identity_files[idx]; | |
208 | comment = xstrdup(authfile); | |
209 | ||
a306f2dd | 210 | debug("Trying RSA authentication with key '%.100s'", comment); |
211 | ||
212 | /* Tell the server that we are willing to authenticate using this key. */ | |
213 | packet_start(SSH_CMSG_AUTH_RSA); | |
214 | packet_put_bignum(public->rsa->n); | |
215 | packet_send(); | |
216 | packet_write_wait(); | |
217 | ||
a306f2dd | 218 | /* Wait for server's response. */ |
54a5250f | 219 | type = packet_read(); |
a306f2dd | 220 | |
221 | /* | |
7b9b0103 | 222 | * The server responds with failure if it doesn't like our key or |
223 | * doesn't support RSA authentication. | |
a306f2dd | 224 | */ |
225 | if (type == SSH_SMSG_FAILURE) { | |
226 | debug("Server refused our key."); | |
227 | xfree(comment); | |
228 | return 0; | |
229 | } | |
230 | /* Otherwise, the server should respond with a challenge. */ | |
231 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
232 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
233 | ||
234 | /* Get the challenge from the packet. */ | |
b775c6f2 | 235 | if ((challenge = BN_new()) == NULL) |
236 | fatal("try_rsa_authentication: BN_new failed"); | |
20b279e6 | 237 | packet_get_bignum(challenge); |
95500969 | 238 | packet_check_eom(); |
a306f2dd | 239 | |
240 | debug("Received RSA challenge from server."); | |
241 | ||
a306f2dd | 242 | /* |
383546c4 | 243 | * If the key is not stored in external hardware, we have to |
244 | * load the private key. Try first with empty passphrase; if it | |
a306f2dd | 245 | * fails, ask for a passphrase. |
246 | */ | |
75cf7563 | 247 | if (public->flags & KEY_FLAG_EXT) |
383546c4 | 248 | private = public; |
249 | else | |
fc231518 | 250 | private = key_load_private_type(KEY_RSA1, authfile, "", NULL, |
251 | &perm_ok); | |
252 | if (private == NULL && !options.batch_mode && perm_ok) { | |
ce404659 | 253 | snprintf(buf, sizeof(buf), |
254 | "Enter passphrase for RSA key '%.100s': ", comment); | |
255 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
a306f2dd | 256 | passphrase = read_passphrase(buf, 0); |
ce404659 | 257 | if (strcmp(passphrase, "") != 0) { |
258 | private = key_load_private_type(KEY_RSA1, | |
fc231518 | 259 | authfile, passphrase, NULL, NULL); |
ce404659 | 260 | quit = 0; |
261 | } else { | |
262 | debug2("no passphrase given, try next key"); | |
263 | quit = 1; | |
264 | } | |
a306f2dd | 265 | memset(passphrase, 0, strlen(passphrase)); |
266 | xfree(passphrase); | |
ce404659 | 267 | if (private != NULL || quit) |
268 | break; | |
269 | debug2("bad passphrase given, try again..."); | |
a306f2dd | 270 | } |
a306f2dd | 271 | } |
272 | /* We no longer need the comment. */ | |
273 | xfree(comment); | |
274 | ||
ce404659 | 275 | if (private == NULL) { |
fc231518 | 276 | if (!options.batch_mode && perm_ok) |
ce404659 | 277 | error("Bad passphrase."); |
278 | ||
279 | /* Send a dummy response packet to avoid protocol error. */ | |
280 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
281 | for (i = 0; i < 16; i++) | |
282 | packet_put_char(0); | |
283 | packet_send(); | |
284 | packet_write_wait(); | |
285 | ||
286 | /* Expect the server to reject it... */ | |
54a5250f | 287 | packet_read_expect(SSH_SMSG_FAILURE); |
ce404659 | 288 | BN_clear_free(challenge); |
289 | return 0; | |
290 | } | |
291 | ||
a306f2dd | 292 | /* Compute and send a response to the challenge. */ |
293 | respond_to_rsa_challenge(challenge, private->rsa); | |
294 | ||
383546c4 | 295 | /* Destroy the private key unless it in external hardware. */ |
296 | if (!(private->flags & KEY_FLAG_EXT)) | |
297 | key_free(private); | |
a306f2dd | 298 | |
299 | /* We no longer need the challenge. */ | |
300 | BN_clear_free(challenge); | |
301 | ||
302 | /* Wait for response from the server. */ | |
54a5250f | 303 | type = packet_read(); |
a306f2dd | 304 | if (type == SSH_SMSG_SUCCESS) { |
305 | debug("RSA authentication accepted by server."); | |
306 | return 1; | |
307 | } | |
308 | if (type != SSH_SMSG_FAILURE) | |
309 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
310 | debug("RSA authentication refused."); | |
311 | return 0; | |
312 | } | |
313 | ||
314 | /* | |
315 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
316 | * authentication and RSA host authentication. | |
317 | */ | |
396c147e | 318 | static int |
aeaa3d9e | 319 | try_rhosts_rsa_authentication(const char *local_user, Key * host_key) |
a306f2dd | 320 | { |
321 | int type; | |
322 | BIGNUM *challenge; | |
a306f2dd | 323 | |
324 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
325 | ||
326 | /* Tell the server that we are willing to authenticate using this key. */ | |
327 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
449c5ba5 | 328 | packet_put_cstring(local_user); |
aeaa3d9e | 329 | packet_put_int(BN_num_bits(host_key->rsa->n)); |
330 | packet_put_bignum(host_key->rsa->e); | |
331 | packet_put_bignum(host_key->rsa->n); | |
a306f2dd | 332 | packet_send(); |
333 | packet_write_wait(); | |
334 | ||
335 | /* Wait for server's response. */ | |
54a5250f | 336 | type = packet_read(); |
a306f2dd | 337 | |
338 | /* The server responds with failure if it doesn't admit our | |
339 | .rhosts authentication or doesn't know our host key. */ | |
340 | if (type == SSH_SMSG_FAILURE) { | |
341 | debug("Server refused our rhosts authentication or host key."); | |
342 | return 0; | |
343 | } | |
344 | /* Otherwise, the server should respond with a challenge. */ | |
345 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
346 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
347 | ||
348 | /* Get the challenge from the packet. */ | |
b775c6f2 | 349 | if ((challenge = BN_new()) == NULL) |
350 | fatal("try_rhosts_rsa_authentication: BN_new failed"); | |
20b279e6 | 351 | packet_get_bignum(challenge); |
95500969 | 352 | packet_check_eom(); |
a306f2dd | 353 | |
354 | debug("Received RSA challenge for host key from server."); | |
355 | ||
356 | /* Compute a response to the challenge. */ | |
aeaa3d9e | 357 | respond_to_rsa_challenge(challenge, host_key->rsa); |
a306f2dd | 358 | |
359 | /* We no longer need the challenge. */ | |
360 | BN_clear_free(challenge); | |
361 | ||
362 | /* Wait for response from the server. */ | |
54a5250f | 363 | type = packet_read(); |
a306f2dd | 364 | if (type == SSH_SMSG_SUCCESS) { |
365 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
366 | return 1; | |
367 | } | |
368 | if (type != SSH_SMSG_FAILURE) | |
369 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
370 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
371 | return 0; | |
372 | } | |
373 | ||
a306f2dd | 374 | /* |
375 | * Tries to authenticate with any string-based challenge/response system. | |
376 | * Note that the client code is not tied to s/key or TIS. | |
377 | */ | |
396c147e | 378 | static int |
5ba55ada | 379 | try_challenge_response_authentication(void) |
a306f2dd | 380 | { |
381 | int type, i; | |
1e3b8b07 | 382 | u_int clen; |
e3a70753 | 383 | char prompt[1024]; |
a306f2dd | 384 | char *challenge, *response; |
aa8003d6 | 385 | |
386 | debug("Doing challenge response authentication."); | |
387 | ||
a306f2dd | 388 | for (i = 0; i < options.number_of_password_prompts; i++) { |
e3a70753 | 389 | /* request a challenge */ |
390 | packet_start(SSH_CMSG_AUTH_TIS); | |
391 | packet_send(); | |
392 | packet_write_wait(); | |
393 | ||
54a5250f | 394 | type = packet_read(); |
e3a70753 | 395 | if (type != SSH_SMSG_FAILURE && |
396 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
397 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 398 | "to SSH_CMSG_AUTH_TIS", type); |
e3a70753 | 399 | } |
400 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
d464095c | 401 | debug("No challenge."); |
e3a70753 | 402 | return 0; |
403 | } | |
404 | challenge = packet_get_string(&clen); | |
95500969 | 405 | packet_check_eom(); |
59c97189 | 406 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
184eed6a | 407 | strchr(challenge, '\n') ? "" : "\nResponse: "); |
e3a70753 | 408 | xfree(challenge); |
a306f2dd | 409 | if (i != 0) |
410 | error("Permission denied, please try again."); | |
e3a70753 | 411 | if (options.cipher == SSH_CIPHER_NONE) |
bbe88b6d | 412 | logit("WARNING: Encryption is disabled! " |
134c552b | 413 | "Response will be transmitted in clear text."); |
e3a70753 | 414 | response = read_passphrase(prompt, 0); |
415 | if (strcmp(response, "") == 0) { | |
416 | xfree(response); | |
417 | break; | |
418 | } | |
a306f2dd | 419 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); |
0ae4fe1d | 420 | ssh_put_password(response); |
a306f2dd | 421 | memset(response, 0, strlen(response)); |
422 | xfree(response); | |
423 | packet_send(); | |
424 | packet_write_wait(); | |
54a5250f | 425 | type = packet_read(); |
a306f2dd | 426 | if (type == SSH_SMSG_SUCCESS) |
427 | return 1; | |
428 | if (type != SSH_SMSG_FAILURE) | |
429 | packet_disconnect("Protocol error: got %d in response " | |
d464095c | 430 | "to SSH_CMSG_AUTH_TIS_RESPONSE", type); |
a306f2dd | 431 | } |
432 | /* failure */ | |
433 | return 0; | |
434 | } | |
435 | ||
436 | /* | |
437 | * Tries to authenticate with plain passwd authentication. | |
438 | */ | |
396c147e | 439 | static int |
a306f2dd | 440 | try_password_authentication(char *prompt) |
441 | { | |
54a5250f | 442 | int type, i; |
a306f2dd | 443 | char *password; |
444 | ||
445 | debug("Doing password authentication."); | |
446 | if (options.cipher == SSH_CIPHER_NONE) | |
bbe88b6d | 447 | logit("WARNING: Encryption is disabled! Password will be transmitted in clear text."); |
a306f2dd | 448 | for (i = 0; i < options.number_of_password_prompts; i++) { |
449 | if (i != 0) | |
450 | error("Permission denied, please try again."); | |
451 | password = read_passphrase(prompt, 0); | |
452 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
0ae4fe1d | 453 | ssh_put_password(password); |
a306f2dd | 454 | memset(password, 0, strlen(password)); |
455 | xfree(password); | |
456 | packet_send(); | |
457 | packet_write_wait(); | |
458 | ||
54a5250f | 459 | type = packet_read(); |
a306f2dd | 460 | if (type == SSH_SMSG_SUCCESS) |
461 | return 1; | |
462 | if (type != SSH_SMSG_FAILURE) | |
463 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
464 | } | |
465 | /* failure */ | |
466 | return 0; | |
467 | } | |
468 | ||
469 | /* | |
470 | * SSH1 key exchange | |
471 | */ | |
472 | void | |
473 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
474 | { | |
475 | int i; | |
476 | BIGNUM *key; | |
b775c6f2 | 477 | Key *host_key, *server_key; |
a306f2dd | 478 | int bits, rbits; |
479 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
1e3b8b07 | 480 | u_char session_key[SSH_SESSION_KEY_LENGTH]; |
481 | u_char cookie[8]; | |
482 | u_int supported_ciphers; | |
483 | u_int server_flags, client_flags; | |
ca75d7de | 484 | u_int32_t rnd = 0; |
a306f2dd | 485 | |
486 | debug("Waiting for server public key."); | |
487 | ||
488 | /* Wait for a public key packet from the server. */ | |
54a5250f | 489 | packet_read_expect(SSH_SMSG_PUBLIC_KEY); |
a306f2dd | 490 | |
491 | /* Get cookie from the packet. */ | |
492 | for (i = 0; i < 8; i++) | |
493 | cookie[i] = packet_get_char(); | |
494 | ||
495 | /* Get the public key. */ | |
b775c6f2 | 496 | server_key = key_new(KEY_RSA1); |
497 | bits = packet_get_int(); | |
20b279e6 | 498 | packet_get_bignum(server_key->rsa->e); |
499 | packet_get_bignum(server_key->rsa->n); | |
a306f2dd | 500 | |
b775c6f2 | 501 | rbits = BN_num_bits(server_key->rsa->n); |
a306f2dd | 502 | if (bits != rbits) { |
bbe88b6d | 503 | logit("Warning: Server lies about size of server public key: " |
a306f2dd | 504 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 505 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 506 | } |
507 | /* Get the host key. */ | |
b775c6f2 | 508 | host_key = key_new(KEY_RSA1); |
509 | bits = packet_get_int(); | |
20b279e6 | 510 | packet_get_bignum(host_key->rsa->e); |
511 | packet_get_bignum(host_key->rsa->n); | |
a306f2dd | 512 | |
b775c6f2 | 513 | rbits = BN_num_bits(host_key->rsa->n); |
a306f2dd | 514 | if (bits != rbits) { |
bbe88b6d | 515 | logit("Warning: Server lies about size of server host key: " |
a306f2dd | 516 | "actual size is %d bits vs. announced %d.", rbits, bits); |
bbe88b6d | 517 | logit("Warning: This may be due to an old implementation of ssh."); |
a306f2dd | 518 | } |
519 | ||
520 | /* Get protocol flags. */ | |
521 | server_flags = packet_get_int(); | |
522 | packet_set_protocol_flags(server_flags); | |
523 | ||
524 | supported_ciphers = packet_get_int(); | |
525 | supported_authentications = packet_get_int(); | |
95500969 | 526 | packet_check_eom(); |
a306f2dd | 527 | |
528 | debug("Received server public key (%d bits) and host key (%d bits).", | |
b775c6f2 | 529 | BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n)); |
a306f2dd | 530 | |
b775c6f2 | 531 | if (verify_host_key(host, hostaddr, host_key) == -1) |
01e9ef57 | 532 | fatal("Host key verification failed."); |
a306f2dd | 533 | |
534 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
535 | ||
8bbf1fa6 | 536 | derive_ssh1_session_id(host_key->rsa->n, server_key->rsa->n, cookie, session_id); |
a306f2dd | 537 | |
538 | /* Generate a session key. */ | |
539 | arc4random_stir(); | |
540 | ||
541 | /* | |
542 | * Generate an encryption key for the session. The key is a 256 bit | |
543 | * random number, interpreted as a 32-byte key, with the least | |
544 | * significant 8 bits being the first byte of the key. | |
545 | */ | |
546 | for (i = 0; i < 32; i++) { | |
547 | if (i % 4 == 0) | |
ca75d7de | 548 | rnd = arc4random(); |
549 | session_key[i] = rnd & 0xff; | |
550 | rnd >>= 8; | |
a306f2dd | 551 | } |
552 | ||
553 | /* | |
554 | * According to the protocol spec, the first byte of the session key | |
555 | * is the highest byte of the integer. The session key is xored with | |
556 | * the first 16 bytes of the session id. | |
557 | */ | |
b775c6f2 | 558 | if ((key = BN_new()) == NULL) |
559 | fatal("respond_to_rsa_challenge: BN_new failed"); | |
a306f2dd | 560 | BN_set_word(key, 0); |
561 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
562 | BN_lshift(key, key, 8); | |
563 | if (i < 16) | |
564 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
565 | else | |
566 | BN_add_word(key, session_key[i]); | |
567 | } | |
568 | ||
569 | /* | |
570 | * Encrypt the integer using the public key and host key of the | |
571 | * server (key with smaller modulus first). | |
572 | */ | |
b775c6f2 | 573 | if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) { |
a306f2dd | 574 | /* Public key has smaller modulus. */ |
b775c6f2 | 575 | if (BN_num_bits(host_key->rsa->n) < |
576 | BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
577 | fatal("respond_to_rsa_challenge: host_key %d < server_key %d + " | |
184eed6a | 578 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 579 | BN_num_bits(host_key->rsa->n), |
580 | BN_num_bits(server_key->rsa->n), | |
184eed6a | 581 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 582 | } |
b775c6f2 | 583 | rsa_public_encrypt(key, key, server_key->rsa); |
584 | rsa_public_encrypt(key, key, host_key->rsa); | |
a306f2dd | 585 | } else { |
586 | /* Host key has smaller modulus (or they are equal). */ | |
b775c6f2 | 587 | if (BN_num_bits(server_key->rsa->n) < |
588 | BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
589 | fatal("respond_to_rsa_challenge: server_key %d < host_key %d + " | |
184eed6a | 590 | "SSH_KEY_BITS_RESERVED %d", |
b775c6f2 | 591 | BN_num_bits(server_key->rsa->n), |
592 | BN_num_bits(host_key->rsa->n), | |
184eed6a | 593 | SSH_KEY_BITS_RESERVED); |
a306f2dd | 594 | } |
b775c6f2 | 595 | rsa_public_encrypt(key, key, host_key->rsa); |
596 | rsa_public_encrypt(key, key, server_key->rsa); | |
a306f2dd | 597 | } |
598 | ||
599 | /* Destroy the public keys since we no longer need them. */ | |
b775c6f2 | 600 | key_free(server_key); |
601 | key_free(host_key); | |
a306f2dd | 602 | |
c523303b | 603 | if (options.cipher == SSH_CIPHER_NOT_SET) { |
604 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
605 | options.cipher = ssh_cipher_default; | |
d77347cc | 606 | } else if (options.cipher == SSH_CIPHER_INVALID || |
c523303b | 607 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { |
bbe88b6d | 608 | logit("No valid SSH1 cipher, using %.100s instead.", |
94ec8c6b | 609 | cipher_name(ssh_cipher_default)); |
610 | options.cipher = ssh_cipher_default; | |
a306f2dd | 611 | } |
612 | /* Check that the selected cipher is supported. */ | |
613 | if (!(supported_ciphers & (1 << options.cipher))) | |
614 | fatal("Selected cipher type %.100s not supported by server.", | |
184eed6a | 615 | cipher_name(options.cipher)); |
a306f2dd | 616 | |
617 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
618 | ||
619 | /* Send the encrypted session key to the server. */ | |
620 | packet_start(SSH_CMSG_SESSION_KEY); | |
621 | packet_put_char(options.cipher); | |
622 | ||
623 | /* Send the cookie back to the server. */ | |
624 | for (i = 0; i < 8; i++) | |
625 | packet_put_char(cookie[i]); | |
626 | ||
627 | /* Send and destroy the encrypted encryption key integer. */ | |
628 | packet_put_bignum(key); | |
629 | BN_clear_free(key); | |
630 | ||
631 | /* Send protocol flags. */ | |
632 | packet_put_int(client_flags); | |
633 | ||
634 | /* Send the packet now. */ | |
635 | packet_send(); | |
636 | packet_write_wait(); | |
637 | ||
638 | debug("Sent encrypted session key."); | |
639 | ||
640 | /* Set the encryption key. */ | |
641 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
642 | ||
643 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
644 | memset(session_key, 0, sizeof(session_key)); | |
645 | ||
646 | /* | |
647 | * Expect a success message from the server. Note that this message | |
648 | * will be received in encrypted form. | |
649 | */ | |
54a5250f | 650 | packet_read_expect(SSH_SMSG_SUCCESS); |
a306f2dd | 651 | |
652 | debug("Received encrypted confirmation."); | |
653 | } | |
654 | ||
655 | /* | |
656 | * Authenticate user | |
657 | */ | |
658 | void | |
8002af61 | 659 | ssh_userauth1(const char *local_user, const char *server_user, char *host, |
39c00dc2 | 660 | Sensitive *sensitive) |
a306f2dd | 661 | { |
662 | int i, type; | |
184eed6a | 663 | |
a306f2dd | 664 | if (supported_authentications == 0) |
8002af61 | 665 | fatal("ssh_userauth1: server supports no auth methods"); |
a306f2dd | 666 | |
667 | /* Send the name of the user to log in as on the server. */ | |
668 | packet_start(SSH_CMSG_USER); | |
449c5ba5 | 669 | packet_put_cstring(server_user); |
a306f2dd | 670 | packet_send(); |
671 | packet_write_wait(); | |
672 | ||
673 | /* | |
674 | * The server should respond with success if no authentication is | |
675 | * needed (the user has no password). Otherwise the server responds | |
676 | * with failure. | |
677 | */ | |
54a5250f | 678 | type = packet_read(); |
a306f2dd | 679 | |
680 | /* check whether the connection was accepted without authentication. */ | |
681 | if (type == SSH_SMSG_SUCCESS) | |
ced49be2 | 682 | goto success; |
a306f2dd | 683 | if (type != SSH_SMSG_FAILURE) |
ced49be2 | 684 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type); |
184eed6a | 685 | |
a306f2dd | 686 | /* |
687 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
688 | * authentication. | |
689 | */ | |
690 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
8002af61 | 691 | options.rhosts_rsa_authentication) { |
39c00dc2 | 692 | for (i = 0; i < sensitive->nkeys; i++) { |
693 | if (sensitive->keys[i] != NULL && | |
694 | sensitive->keys[i]->type == KEY_RSA1 && | |
695 | try_rhosts_rsa_authentication(local_user, | |
696 | sensitive->keys[i])) | |
ced49be2 | 697 | goto success; |
8002af61 | 698 | } |
a306f2dd | 699 | } |
700 | /* Try RSA authentication if the server supports it. */ | |
701 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
702 | options.rsa_authentication) { | |
703 | /* | |
704 | * Try RSA authentication using the authentication agent. The | |
705 | * agent is tried first because no passphrase is needed for | |
706 | * it, whereas identity files may require passphrases. | |
707 | */ | |
708 | if (try_agent_authentication()) | |
ced49be2 | 709 | goto success; |
a306f2dd | 710 | |
711 | /* Try RSA authentication for each identity. */ | |
712 | for (i = 0; i < options.num_identity_files; i++) | |
fee56204 | 713 | if (options.identity_keys[i] != NULL && |
714 | options.identity_keys[i]->type == KEY_RSA1 && | |
383546c4 | 715 | try_rsa_authentication(i)) |
ced49be2 | 716 | goto success; |
a306f2dd | 717 | } |
d464095c | 718 | /* Try challenge response authentication if the server supports it. */ |
a306f2dd | 719 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && |
5ba55ada | 720 | options.challenge_response_authentication && !options.batch_mode) { |
721 | if (try_challenge_response_authentication()) | |
ced49be2 | 722 | goto success; |
a306f2dd | 723 | } |
724 | /* Try password authentication if the server supports it. */ | |
725 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
726 | options.password_authentication && !options.batch_mode) { | |
727 | char prompt[80]; | |
728 | ||
b3b9ad8e | 729 | snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ", |
a306f2dd | 730 | server_user, host); |
731 | if (try_password_authentication(prompt)) | |
ced49be2 | 732 | goto success; |
a306f2dd | 733 | } |
734 | /* All authentication methods have failed. Exit with an error message. */ | |
735 | fatal("Permission denied."); | |
736 | /* NOTREACHED */ | |
ced49be2 | 737 | |
738 | success: | |
62bb2c8f | 739 | return; /* need statement after label */ |
a306f2dd | 740 | } |