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a306f2dd | 1 | /* |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
a306f2dd | 5 | * Code to connect to a remote host, and to perform the client side of the |
6 | * login (authentication) dialog. | |
7 | * | |
bcbf86ec | 8 | * As far as I am concerned, the code I have written for this software |
9 | * can be used freely for any purpose. Any derived versions of this | |
10 | * software must be clearly marked as such, and if the derived work is | |
11 | * incompatible with the protocol description in the RFC file, it must be | |
12 | * called by a name other than "ssh" or "Secure Shell". | |
a306f2dd | 13 | */ |
14 | ||
15 | #include "includes.h" | |
59c97189 | 16 | RCSID("$OpenBSD: sshconnect1.c,v 1.16 2001/01/18 17:00:00 markus Exp $"); |
a306f2dd | 17 | |
18 | #include <openssl/bn.h> | |
19 | #include <openssl/dsa.h> | |
20 | #include <openssl/rsa.h> | |
21 | #include <openssl/evp.h> | |
22 | ||
23 | #include "xmalloc.h" | |
24 | #include "rsa.h" | |
25 | #include "ssh.h" | |
26 | #include "buffer.h" | |
27 | #include "packet.h" | |
a306f2dd | 28 | #include "mpaux.h" |
29 | #include "uidswap.h" | |
30 | #include "readconf.h" | |
31 | #include "key.h" | |
4c8722d9 | 32 | #include "authfd.h" |
a306f2dd | 33 | #include "sshconnect.h" |
34 | #include "authfile.h" | |
35 | ||
36 | /* Session id for the current session. */ | |
1e3b8b07 | 37 | u_char session_id[16]; |
38 | u_int supported_authentications = 0; | |
a306f2dd | 39 | |
40 | extern Options options; | |
41 | extern char *__progname; | |
42 | ||
43 | /* | |
44 | * Checks if the user has an authentication agent, and if so, tries to | |
45 | * authenticate using the agent. | |
46 | */ | |
47 | int | |
48 | try_agent_authentication() | |
49 | { | |
2e73a022 | 50 | int type; |
a306f2dd | 51 | char *comment; |
52 | AuthenticationConnection *auth; | |
1e3b8b07 | 53 | u_char response[16]; |
54 | u_int i; | |
2e73a022 | 55 | int plen, clen; |
56 | Key *key; | |
57 | BIGNUM *challenge; | |
a306f2dd | 58 | |
59 | /* Get connection to the agent. */ | |
60 | auth = ssh_get_authentication_connection(); | |
61 | if (!auth) | |
62 | return 0; | |
63 | ||
a306f2dd | 64 | challenge = BN_new(); |
65 | ||
66 | /* Loop through identities served by the agent. */ | |
2e73a022 | 67 | for (key = ssh_get_first_identity(auth, &comment, 1); |
68 | key != NULL; | |
69 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 70 | |
71 | /* Try this identity. */ | |
72 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
73 | xfree(comment); | |
74 | ||
75 | /* Tell the server that we are willing to authenticate using this key. */ | |
76 | packet_start(SSH_CMSG_AUTH_RSA); | |
2e73a022 | 77 | packet_put_bignum(key->rsa->n); |
a306f2dd | 78 | packet_send(); |
79 | packet_write_wait(); | |
80 | ||
81 | /* Wait for server's response. */ | |
82 | type = packet_read(&plen); | |
83 | ||
84 | /* The server sends failure if it doesn\'t like our key or | |
85 | does not support RSA authentication. */ | |
86 | if (type == SSH_SMSG_FAILURE) { | |
87 | debug("Server refused our key."); | |
2e73a022 | 88 | key_free(key); |
a306f2dd | 89 | continue; |
90 | } | |
91 | /* Otherwise it should have sent a challenge. */ | |
92 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
93 | packet_disconnect("Protocol error during RSA authentication: %d", | |
94 | type); | |
95 | ||
96 | packet_get_bignum(challenge, &clen); | |
97 | ||
98 | packet_integrity_check(plen, clen, type); | |
99 | ||
100 | debug("Received RSA challenge from server."); | |
101 | ||
102 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 103 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { |
104 | /* | |
105 | * The agent failed to authenticate this identifier | |
106 | * although it advertised it supports this. Just | |
107 | * return a wrong value. | |
108 | */ | |
a306f2dd | 109 | log("Authentication agent failed to decrypt challenge."); |
110 | memset(response, 0, sizeof(response)); | |
111 | } | |
2e73a022 | 112 | key_free(key); |
a306f2dd | 113 | debug("Sending response to RSA challenge."); |
114 | ||
115 | /* Send the decrypted challenge back to the server. */ | |
116 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
117 | for (i = 0; i < 16; i++) | |
118 | packet_put_char(response[i]); | |
119 | packet_send(); | |
120 | packet_write_wait(); | |
121 | ||
122 | /* Wait for response from the server. */ | |
123 | type = packet_read(&plen); | |
124 | ||
125 | /* The server returns success if it accepted the authentication. */ | |
126 | if (type == SSH_SMSG_SUCCESS) { | |
eea39c02 | 127 | ssh_close_authentication_connection(auth); |
a306f2dd | 128 | BN_clear_free(challenge); |
2e73a022 | 129 | debug("RSA authentication accepted by server."); |
a306f2dd | 130 | return 1; |
131 | } | |
132 | /* Otherwise it should return failure. */ | |
133 | if (type != SSH_SMSG_FAILURE) | |
134 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
135 | type); | |
136 | } | |
eea39c02 | 137 | ssh_close_authentication_connection(auth); |
a306f2dd | 138 | BN_clear_free(challenge); |
a306f2dd | 139 | debug("RSA authentication using agent refused."); |
140 | return 0; | |
141 | } | |
142 | ||
143 | /* | |
144 | * Computes the proper response to a RSA challenge, and sends the response to | |
145 | * the server. | |
146 | */ | |
147 | void | |
148 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
149 | { | |
1e3b8b07 | 150 | u_char buf[32], response[16]; |
a306f2dd | 151 | MD5_CTX md; |
152 | int i, len; | |
153 | ||
154 | /* Decrypt the challenge using the private key. */ | |
155 | rsa_private_decrypt(challenge, challenge, prv); | |
156 | ||
157 | /* Compute the response. */ | |
158 | /* The response is MD5 of decrypted challenge plus session id. */ | |
159 | len = BN_num_bytes(challenge); | |
160 | if (len <= 0 || len > sizeof(buf)) | |
161 | packet_disconnect("respond_to_rsa_challenge: bad challenge length %d", | |
162 | len); | |
163 | ||
164 | memset(buf, 0, sizeof(buf)); | |
165 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
166 | MD5_Init(&md); | |
167 | MD5_Update(&md, buf, 32); | |
168 | MD5_Update(&md, session_id, 16); | |
169 | MD5_Final(response, &md); | |
170 | ||
171 | debug("Sending response to host key RSA challenge."); | |
172 | ||
173 | /* Send the response back to the server. */ | |
174 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
175 | for (i = 0; i < 16; i++) | |
176 | packet_put_char(response[i]); | |
177 | packet_send(); | |
178 | packet_write_wait(); | |
179 | ||
180 | memset(buf, 0, sizeof(buf)); | |
181 | memset(response, 0, sizeof(response)); | |
182 | memset(&md, 0, sizeof(md)); | |
183 | } | |
184 | ||
185 | /* | |
186 | * Checks if the user has authentication file, and if so, tries to authenticate | |
187 | * the user using it. | |
188 | */ | |
189 | int | |
190 | try_rsa_authentication(const char *authfile) | |
191 | { | |
192 | BIGNUM *challenge; | |
193 | Key *public; | |
194 | Key *private; | |
195 | char *passphrase, *comment; | |
196 | int type, i; | |
197 | int plen, clen; | |
198 | ||
199 | /* Try to load identification for the authentication key. */ | |
fa08c86b | 200 | public = key_new(KEY_RSA1); |
a306f2dd | 201 | if (!load_public_key(authfile, public, &comment)) { |
202 | key_free(public); | |
203 | /* Could not load it. Fail. */ | |
204 | return 0; | |
205 | } | |
206 | debug("Trying RSA authentication with key '%.100s'", comment); | |
207 | ||
208 | /* Tell the server that we are willing to authenticate using this key. */ | |
209 | packet_start(SSH_CMSG_AUTH_RSA); | |
210 | packet_put_bignum(public->rsa->n); | |
211 | packet_send(); | |
212 | packet_write_wait(); | |
213 | ||
214 | /* We no longer need the public key. */ | |
215 | key_free(public); | |
216 | ||
217 | /* Wait for server's response. */ | |
218 | type = packet_read(&plen); | |
219 | ||
220 | /* | |
221 | * The server responds with failure if it doesn\'t like our key or | |
222 | * doesn\'t support RSA authentication. | |
223 | */ | |
224 | if (type == SSH_SMSG_FAILURE) { | |
225 | debug("Server refused our key."); | |
226 | xfree(comment); | |
227 | return 0; | |
228 | } | |
229 | /* Otherwise, the server should respond with a challenge. */ | |
230 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
231 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
232 | ||
233 | /* Get the challenge from the packet. */ | |
234 | challenge = BN_new(); | |
235 | packet_get_bignum(challenge, &clen); | |
236 | ||
237 | packet_integrity_check(plen, clen, type); | |
238 | ||
239 | debug("Received RSA challenge from server."); | |
240 | ||
fa08c86b | 241 | private = key_new(KEY_RSA1); |
a306f2dd | 242 | /* |
243 | * Load the private key. Try first with empty passphrase; if it | |
244 | * fails, ask for a passphrase. | |
245 | */ | |
246 | if (!load_private_key(authfile, "", private, NULL)) { | |
247 | char buf[300]; | |
248 | snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ", | |
249 | comment); | |
250 | if (!options.batch_mode) | |
251 | passphrase = read_passphrase(buf, 0); | |
252 | else { | |
253 | debug("Will not query passphrase for %.100s in batch mode.", | |
254 | comment); | |
255 | passphrase = xstrdup(""); | |
256 | } | |
257 | ||
258 | /* Load the authentication file using the pasphrase. */ | |
259 | if (!load_private_key(authfile, passphrase, private, NULL)) { | |
260 | memset(passphrase, 0, strlen(passphrase)); | |
261 | xfree(passphrase); | |
262 | error("Bad passphrase."); | |
263 | ||
264 | /* Send a dummy response packet to avoid protocol error. */ | |
265 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
266 | for (i = 0; i < 16; i++) | |
267 | packet_put_char(0); | |
268 | packet_send(); | |
269 | packet_write_wait(); | |
270 | ||
271 | /* Expect the server to reject it... */ | |
272 | packet_read_expect(&plen, SSH_SMSG_FAILURE); | |
273 | xfree(comment); | |
eea39c02 | 274 | key_free(private); |
275 | BN_clear_free(challenge); | |
a306f2dd | 276 | return 0; |
277 | } | |
278 | /* Destroy the passphrase. */ | |
279 | memset(passphrase, 0, strlen(passphrase)); | |
280 | xfree(passphrase); | |
281 | } | |
282 | /* We no longer need the comment. */ | |
283 | xfree(comment); | |
284 | ||
285 | /* Compute and send a response to the challenge. */ | |
286 | respond_to_rsa_challenge(challenge, private->rsa); | |
287 | ||
288 | /* Destroy the private key. */ | |
289 | key_free(private); | |
290 | ||
291 | /* We no longer need the challenge. */ | |
292 | BN_clear_free(challenge); | |
293 | ||
294 | /* Wait for response from the server. */ | |
295 | type = packet_read(&plen); | |
296 | if (type == SSH_SMSG_SUCCESS) { | |
297 | debug("RSA authentication accepted by server."); | |
298 | return 1; | |
299 | } | |
300 | if (type != SSH_SMSG_FAILURE) | |
301 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
302 | debug("RSA authentication refused."); | |
303 | return 0; | |
304 | } | |
305 | ||
306 | /* | |
307 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
308 | * authentication and RSA host authentication. | |
309 | */ | |
310 | int | |
311 | try_rhosts_rsa_authentication(const char *local_user, RSA * host_key) | |
312 | { | |
313 | int type; | |
314 | BIGNUM *challenge; | |
315 | int plen, clen; | |
316 | ||
317 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
318 | ||
319 | /* Tell the server that we are willing to authenticate using this key. */ | |
320 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
321 | packet_put_string(local_user, strlen(local_user)); | |
322 | packet_put_int(BN_num_bits(host_key->n)); | |
323 | packet_put_bignum(host_key->e); | |
324 | packet_put_bignum(host_key->n); | |
325 | packet_send(); | |
326 | packet_write_wait(); | |
327 | ||
328 | /* Wait for server's response. */ | |
329 | type = packet_read(&plen); | |
330 | ||
331 | /* The server responds with failure if it doesn't admit our | |
332 | .rhosts authentication or doesn't know our host key. */ | |
333 | if (type == SSH_SMSG_FAILURE) { | |
334 | debug("Server refused our rhosts authentication or host key."); | |
335 | return 0; | |
336 | } | |
337 | /* Otherwise, the server should respond with a challenge. */ | |
338 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
339 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
340 | ||
341 | /* Get the challenge from the packet. */ | |
342 | challenge = BN_new(); | |
343 | packet_get_bignum(challenge, &clen); | |
344 | ||
345 | packet_integrity_check(plen, clen, type); | |
346 | ||
347 | debug("Received RSA challenge for host key from server."); | |
348 | ||
349 | /* Compute a response to the challenge. */ | |
350 | respond_to_rsa_challenge(challenge, host_key); | |
351 | ||
352 | /* We no longer need the challenge. */ | |
353 | BN_clear_free(challenge); | |
354 | ||
355 | /* Wait for response from the server. */ | |
356 | type = packet_read(&plen); | |
357 | if (type == SSH_SMSG_SUCCESS) { | |
358 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
359 | return 1; | |
360 | } | |
361 | if (type != SSH_SMSG_FAILURE) | |
362 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
363 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
364 | return 0; | |
365 | } | |
366 | ||
367 | #ifdef KRB4 | |
368 | int | |
369 | try_kerberos_authentication() | |
370 | { | |
371 | KTEXT_ST auth; /* Kerberos data */ | |
372 | char *reply; | |
373 | char inst[INST_SZ]; | |
374 | char *realm; | |
375 | CREDENTIALS cred; | |
376 | int r, type, plen; | |
377 | socklen_t slen; | |
378 | Key_schedule schedule; | |
379 | u_long checksum, cksum; | |
380 | MSG_DAT msg_data; | |
381 | struct sockaddr_in local, foreign; | |
382 | struct stat st; | |
383 | ||
384 | /* Don't do anything if we don't have any tickets. */ | |
385 | if (stat(tkt_string(), &st) < 0) | |
386 | return 0; | |
387 | ||
388 | strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ); | |
389 | ||
390 | realm = (char *) krb_realmofhost(get_canonical_hostname()); | |
391 | if (!realm) { | |
392 | debug("Kerberos V4: no realm for %s", get_canonical_hostname()); | |
393 | return 0; | |
394 | } | |
395 | /* This can really be anything. */ | |
396 | checksum = (u_long) getpid(); | |
397 | ||
398 | r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); | |
399 | if (r != KSUCCESS) { | |
400 | debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]); | |
401 | return 0; | |
402 | } | |
403 | /* Get session key to decrypt the server's reply with. */ | |
404 | r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); | |
405 | if (r != KSUCCESS) { | |
406 | debug("get_cred failed: %s", krb_err_txt[r]); | |
407 | return 0; | |
408 | } | |
409 | des_key_sched((des_cblock *) cred.session, schedule); | |
410 | ||
411 | /* Send authentication info to server. */ | |
412 | packet_start(SSH_CMSG_AUTH_KERBEROS); | |
413 | packet_put_string((char *) auth.dat, auth.length); | |
414 | packet_send(); | |
415 | packet_write_wait(); | |
416 | ||
417 | /* Zero the buffer. */ | |
418 | (void) memset(auth.dat, 0, MAX_KTXT_LEN); | |
419 | ||
420 | slen = sizeof(local); | |
421 | memset(&local, 0, sizeof(local)); | |
422 | if (getsockname(packet_get_connection_in(), | |
423 | (struct sockaddr *) & local, &slen) < 0) | |
424 | debug("getsockname failed: %s", strerror(errno)); | |
425 | ||
426 | slen = sizeof(foreign); | |
427 | memset(&foreign, 0, sizeof(foreign)); | |
428 | if (getpeername(packet_get_connection_in(), | |
429 | (struct sockaddr *) & foreign, &slen) < 0) { | |
430 | debug("getpeername failed: %s", strerror(errno)); | |
431 | fatal_cleanup(); | |
432 | } | |
433 | /* Get server reply. */ | |
434 | type = packet_read(&plen); | |
435 | switch (type) { | |
436 | case SSH_SMSG_FAILURE: | |
437 | /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ | |
438 | debug("Kerberos V4 authentication failed."); | |
439 | return 0; | |
440 | break; | |
441 | ||
442 | case SSH_SMSG_AUTH_KERBEROS_RESPONSE: | |
443 | /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ | |
444 | debug("Kerberos V4 authentication accepted."); | |
445 | ||
446 | /* Get server's response. */ | |
1e3b8b07 | 447 | reply = packet_get_string((u_int *) &auth.length); |
a306f2dd | 448 | memcpy(auth.dat, reply, auth.length); |
449 | xfree(reply); | |
450 | ||
451 | packet_integrity_check(plen, 4 + auth.length, type); | |
452 | ||
453 | /* | |
454 | * If his response isn't properly encrypted with the session | |
455 | * key, and the decrypted checksum fails to match, he's | |
456 | * bogus. Bail out. | |
457 | */ | |
458 | r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, | |
459 | &foreign, &local, &msg_data); | |
460 | if (r != KSUCCESS) { | |
461 | debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]); | |
462 | packet_disconnect("Kerberos V4 challenge failed!"); | |
463 | } | |
464 | /* Fetch the (incremented) checksum that we supplied in the request. */ | |
465 | (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum)); | |
466 | cksum = ntohl(cksum); | |
467 | ||
468 | /* If it matches, we're golden. */ | |
469 | if (cksum == checksum + 1) { | |
470 | debug("Kerberos V4 challenge successful."); | |
471 | return 1; | |
472 | } else | |
473 | packet_disconnect("Kerberos V4 challenge failed!"); | |
474 | break; | |
475 | ||
476 | default: | |
477 | packet_disconnect("Protocol error on Kerberos V4 response: %d", type); | |
478 | } | |
479 | return 0; | |
480 | } | |
481 | ||
482 | #endif /* KRB4 */ | |
483 | ||
484 | #ifdef AFS | |
485 | int | |
486 | send_kerberos_tgt() | |
487 | { | |
488 | CREDENTIALS *creds; | |
489 | char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; | |
490 | int r, type, plen; | |
491 | char buffer[8192]; | |
492 | struct stat st; | |
493 | ||
494 | /* Don't do anything if we don't have any tickets. */ | |
495 | if (stat(tkt_string(), &st) < 0) | |
496 | return 0; | |
497 | ||
498 | creds = xmalloc(sizeof(*creds)); | |
499 | ||
500 | if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) { | |
501 | debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]); | |
502 | return 0; | |
503 | } | |
504 | if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) { | |
505 | debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]); | |
506 | return 0; | |
507 | } | |
508 | if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { | |
509 | debug("Kerberos V4 ticket expired: %s", TKT_FILE); | |
510 | return 0; | |
511 | } | |
1e3b8b07 | 512 | creds_to_radix(creds, (u_char *)buffer, sizeof buffer); |
a306f2dd | 513 | xfree(creds); |
514 | ||
515 | packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); | |
516 | packet_put_string(buffer, strlen(buffer)); | |
517 | packet_send(); | |
518 | packet_write_wait(); | |
519 | ||
520 | type = packet_read(&plen); | |
521 | ||
522 | if (type == SSH_SMSG_FAILURE) | |
523 | debug("Kerberos TGT for realm %s rejected.", prealm); | |
524 | else if (type != SSH_SMSG_SUCCESS) | |
525 | packet_disconnect("Protocol error on Kerberos TGT response: %d", type); | |
526 | ||
527 | return 1; | |
528 | } | |
529 | ||
530 | void | |
531 | send_afs_tokens(void) | |
532 | { | |
533 | CREDENTIALS creds; | |
534 | struct ViceIoctl parms; | |
535 | struct ClearToken ct; | |
536 | int i, type, len, plen; | |
537 | char buf[2048], *p, *server_cell; | |
538 | char buffer[8192]; | |
539 | ||
540 | /* Move over ktc_GetToken, here's something leaner. */ | |
541 | for (i = 0; i < 100; i++) { /* just in case */ | |
542 | parms.in = (char *) &i; | |
543 | parms.in_size = sizeof(i); | |
544 | parms.out = buf; | |
545 | parms.out_size = sizeof(buf); | |
546 | if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) | |
547 | break; | |
548 | p = buf; | |
549 | ||
550 | /* Get secret token. */ | |
1e3b8b07 | 551 | memcpy(&creds.ticket_st.length, p, sizeof(u_int)); |
a306f2dd | 552 | if (creds.ticket_st.length > MAX_KTXT_LEN) |
553 | break; | |
1e3b8b07 | 554 | p += sizeof(u_int); |
a306f2dd | 555 | memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); |
556 | p += creds.ticket_st.length; | |
557 | ||
558 | /* Get clear token. */ | |
559 | memcpy(&len, p, sizeof(len)); | |
560 | if (len != sizeof(struct ClearToken)) | |
561 | break; | |
562 | p += sizeof(len); | |
563 | memcpy(&ct, p, len); | |
564 | p += len; | |
565 | p += sizeof(len); /* primary flag */ | |
566 | server_cell = p; | |
567 | ||
568 | /* Flesh out our credentials. */ | |
569 | strlcpy(creds.service, "afs", sizeof creds.service); | |
570 | creds.instance[0] = '\0'; | |
571 | strlcpy(creds.realm, server_cell, REALM_SZ); | |
572 | memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); | |
573 | creds.issue_date = ct.BeginTimestamp; | |
574 | creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp); | |
575 | creds.kvno = ct.AuthHandle; | |
576 | snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); | |
577 | creds.pinst[0] = '\0'; | |
578 | ||
579 | /* Encode token, ship it off. */ | |
b5c334cc | 580 | if (creds_to_radix(&creds, (u_char *) buffer, sizeof buffer) <= 0) |
a306f2dd | 581 | break; |
582 | packet_start(SSH_CMSG_HAVE_AFS_TOKEN); | |
583 | packet_put_string(buffer, strlen(buffer)); | |
584 | packet_send(); | |
585 | packet_write_wait(); | |
586 | ||
587 | /* Roger, Roger. Clearance, Clarence. What's your vector, | |
588 | Victor? */ | |
589 | type = packet_read(&plen); | |
590 | ||
591 | if (type == SSH_SMSG_FAILURE) | |
592 | debug("AFS token for cell %s rejected.", server_cell); | |
593 | else if (type != SSH_SMSG_SUCCESS) | |
594 | packet_disconnect("Protocol error on AFS token response: %d", type); | |
595 | } | |
596 | } | |
597 | ||
598 | #endif /* AFS */ | |
599 | ||
600 | /* | |
601 | * Tries to authenticate with any string-based challenge/response system. | |
602 | * Note that the client code is not tied to s/key or TIS. | |
603 | */ | |
604 | int | |
605 | try_skey_authentication() | |
606 | { | |
607 | int type, i; | |
608 | int payload_len; | |
1e3b8b07 | 609 | u_int clen; |
e3a70753 | 610 | char prompt[1024]; |
a306f2dd | 611 | char *challenge, *response; |
612 | ||
613 | debug("Doing skey authentication."); | |
614 | ||
a306f2dd | 615 | for (i = 0; i < options.number_of_password_prompts; i++) { |
e3a70753 | 616 | /* request a challenge */ |
617 | packet_start(SSH_CMSG_AUTH_TIS); | |
618 | packet_send(); | |
619 | packet_write_wait(); | |
620 | ||
621 | type = packet_read(&payload_len); | |
622 | if (type != SSH_SMSG_FAILURE && | |
623 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
624 | packet_disconnect("Protocol error: got %d in response " | |
625 | "to skey-auth", type); | |
626 | } | |
627 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
628 | debug("No challenge for skey authentication."); | |
629 | return 0; | |
630 | } | |
631 | challenge = packet_get_string(&clen); | |
632 | packet_integrity_check(payload_len, (4 + clen), type); | |
59c97189 | 633 | snprintf(prompt, sizeof prompt, "%s%s", challenge, |
634 | strchr(challenge, '\n') ? "" : "\nResponse: "); | |
e3a70753 | 635 | xfree(challenge); |
a306f2dd | 636 | if (i != 0) |
637 | error("Permission denied, please try again."); | |
e3a70753 | 638 | if (options.cipher == SSH_CIPHER_NONE) |
639 | log("WARNING: Encryption is disabled! " | |
640 | "Reponse will be transmitted in clear text."); | |
641 | response = read_passphrase(prompt, 0); | |
642 | if (strcmp(response, "") == 0) { | |
643 | xfree(response); | |
644 | break; | |
645 | } | |
a306f2dd | 646 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); |
647 | packet_put_string(response, strlen(response)); | |
648 | memset(response, 0, strlen(response)); | |
649 | xfree(response); | |
650 | packet_send(); | |
651 | packet_write_wait(); | |
652 | type = packet_read(&payload_len); | |
653 | if (type == SSH_SMSG_SUCCESS) | |
654 | return 1; | |
655 | if (type != SSH_SMSG_FAILURE) | |
656 | packet_disconnect("Protocol error: got %d in response " | |
e3a70753 | 657 | "to skey-auth-reponse", type); |
a306f2dd | 658 | } |
659 | /* failure */ | |
660 | return 0; | |
661 | } | |
662 | ||
663 | /* | |
664 | * Tries to authenticate with plain passwd authentication. | |
665 | */ | |
666 | int | |
667 | try_password_authentication(char *prompt) | |
668 | { | |
669 | int type, i, payload_len; | |
670 | char *password; | |
671 | ||
672 | debug("Doing password authentication."); | |
673 | if (options.cipher == SSH_CIPHER_NONE) | |
674 | log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
675 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
676 | if (i != 0) | |
677 | error("Permission denied, please try again."); | |
678 | password = read_passphrase(prompt, 0); | |
679 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
680 | packet_put_string(password, strlen(password)); | |
681 | memset(password, 0, strlen(password)); | |
682 | xfree(password); | |
683 | packet_send(); | |
684 | packet_write_wait(); | |
685 | ||
686 | type = packet_read(&payload_len); | |
687 | if (type == SSH_SMSG_SUCCESS) | |
688 | return 1; | |
689 | if (type != SSH_SMSG_FAILURE) | |
690 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
691 | } | |
692 | /* failure */ | |
693 | return 0; | |
694 | } | |
695 | ||
696 | /* | |
697 | * SSH1 key exchange | |
698 | */ | |
699 | void | |
700 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
701 | { | |
702 | int i; | |
703 | BIGNUM *key; | |
704 | RSA *host_key; | |
705 | RSA *public_key; | |
706 | Key k; | |
707 | int bits, rbits; | |
708 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
1e3b8b07 | 709 | u_char session_key[SSH_SESSION_KEY_LENGTH]; |
710 | u_char cookie[8]; | |
711 | u_int supported_ciphers; | |
712 | u_int server_flags, client_flags; | |
a306f2dd | 713 | int payload_len, clen, sum_len = 0; |
714 | u_int32_t rand = 0; | |
715 | ||
716 | debug("Waiting for server public key."); | |
717 | ||
718 | /* Wait for a public key packet from the server. */ | |
719 | packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY); | |
720 | ||
721 | /* Get cookie from the packet. */ | |
722 | for (i = 0; i < 8; i++) | |
723 | cookie[i] = packet_get_char(); | |
724 | ||
725 | /* Get the public key. */ | |
726 | public_key = RSA_new(); | |
727 | bits = packet_get_int();/* bits */ | |
728 | public_key->e = BN_new(); | |
729 | packet_get_bignum(public_key->e, &clen); | |
730 | sum_len += clen; | |
731 | public_key->n = BN_new(); | |
732 | packet_get_bignum(public_key->n, &clen); | |
733 | sum_len += clen; | |
734 | ||
735 | rbits = BN_num_bits(public_key->n); | |
736 | if (bits != rbits) { | |
737 | log("Warning: Server lies about size of server public key: " | |
738 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
739 | log("Warning: This may be due to an old implementation of ssh."); | |
740 | } | |
741 | /* Get the host key. */ | |
742 | host_key = RSA_new(); | |
743 | bits = packet_get_int();/* bits */ | |
744 | host_key->e = BN_new(); | |
745 | packet_get_bignum(host_key->e, &clen); | |
746 | sum_len += clen; | |
747 | host_key->n = BN_new(); | |
748 | packet_get_bignum(host_key->n, &clen); | |
749 | sum_len += clen; | |
750 | ||
751 | rbits = BN_num_bits(host_key->n); | |
752 | if (bits != rbits) { | |
753 | log("Warning: Server lies about size of server host key: " | |
754 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
755 | log("Warning: This may be due to an old implementation of ssh."); | |
756 | } | |
757 | ||
758 | /* Get protocol flags. */ | |
759 | server_flags = packet_get_int(); | |
760 | packet_set_protocol_flags(server_flags); | |
761 | ||
762 | supported_ciphers = packet_get_int(); | |
763 | supported_authentications = packet_get_int(); | |
764 | ||
765 | debug("Received server public key (%d bits) and host key (%d bits).", | |
766 | BN_num_bits(public_key->n), BN_num_bits(host_key->n)); | |
767 | ||
768 | packet_integrity_check(payload_len, | |
769 | 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, | |
770 | SSH_SMSG_PUBLIC_KEY); | |
fa08c86b | 771 | k.type = KEY_RSA1; |
a306f2dd | 772 | k.rsa = host_key; |
773 | check_host_key(host, hostaddr, &k, | |
774 | options.user_hostfile, options.system_hostfile); | |
775 | ||
776 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
777 | ||
778 | compute_session_id(session_id, cookie, host_key->n, public_key->n); | |
779 | ||
780 | /* Generate a session key. */ | |
781 | arc4random_stir(); | |
782 | ||
783 | /* | |
784 | * Generate an encryption key for the session. The key is a 256 bit | |
785 | * random number, interpreted as a 32-byte key, with the least | |
786 | * significant 8 bits being the first byte of the key. | |
787 | */ | |
788 | for (i = 0; i < 32; i++) { | |
789 | if (i % 4 == 0) | |
790 | rand = arc4random(); | |
791 | session_key[i] = rand & 0xff; | |
792 | rand >>= 8; | |
793 | } | |
794 | ||
795 | /* | |
796 | * According to the protocol spec, the first byte of the session key | |
797 | * is the highest byte of the integer. The session key is xored with | |
798 | * the first 16 bytes of the session id. | |
799 | */ | |
800 | key = BN_new(); | |
801 | BN_set_word(key, 0); | |
802 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
803 | BN_lshift(key, key, 8); | |
804 | if (i < 16) | |
805 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
806 | else | |
807 | BN_add_word(key, session_key[i]); | |
808 | } | |
809 | ||
810 | /* | |
811 | * Encrypt the integer using the public key and host key of the | |
812 | * server (key with smaller modulus first). | |
813 | */ | |
814 | if (BN_cmp(public_key->n, host_key->n) < 0) { | |
815 | /* Public key has smaller modulus. */ | |
816 | if (BN_num_bits(host_key->n) < | |
817 | BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) { | |
818 | fatal("respond_to_rsa_challenge: host_key %d < public_key %d + " | |
819 | "SSH_KEY_BITS_RESERVED %d", | |
820 | BN_num_bits(host_key->n), | |
821 | BN_num_bits(public_key->n), | |
822 | SSH_KEY_BITS_RESERVED); | |
823 | } | |
824 | rsa_public_encrypt(key, key, public_key); | |
825 | rsa_public_encrypt(key, key, host_key); | |
826 | } else { | |
827 | /* Host key has smaller modulus (or they are equal). */ | |
828 | if (BN_num_bits(public_key->n) < | |
829 | BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) { | |
830 | fatal("respond_to_rsa_challenge: public_key %d < host_key %d + " | |
831 | "SSH_KEY_BITS_RESERVED %d", | |
832 | BN_num_bits(public_key->n), | |
833 | BN_num_bits(host_key->n), | |
834 | SSH_KEY_BITS_RESERVED); | |
835 | } | |
836 | rsa_public_encrypt(key, key, host_key); | |
837 | rsa_public_encrypt(key, key, public_key); | |
838 | } | |
839 | ||
840 | /* Destroy the public keys since we no longer need them. */ | |
841 | RSA_free(public_key); | |
842 | RSA_free(host_key); | |
843 | ||
c523303b | 844 | if (options.cipher == SSH_CIPHER_NOT_SET) { |
845 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
846 | options.cipher = ssh_cipher_default; | |
847 | } else if (options.cipher == SSH_CIPHER_ILLEGAL || | |
848 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { | |
d0c832f3 | 849 | log("No valid SSH1 cipher, using %.100s instead.", |
94ec8c6b | 850 | cipher_name(ssh_cipher_default)); |
851 | options.cipher = ssh_cipher_default; | |
a306f2dd | 852 | } |
853 | /* Check that the selected cipher is supported. */ | |
854 | if (!(supported_ciphers & (1 << options.cipher))) | |
855 | fatal("Selected cipher type %.100s not supported by server.", | |
856 | cipher_name(options.cipher)); | |
857 | ||
858 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
859 | ||
860 | /* Send the encrypted session key to the server. */ | |
861 | packet_start(SSH_CMSG_SESSION_KEY); | |
862 | packet_put_char(options.cipher); | |
863 | ||
864 | /* Send the cookie back to the server. */ | |
865 | for (i = 0; i < 8; i++) | |
866 | packet_put_char(cookie[i]); | |
867 | ||
868 | /* Send and destroy the encrypted encryption key integer. */ | |
869 | packet_put_bignum(key); | |
870 | BN_clear_free(key); | |
871 | ||
872 | /* Send protocol flags. */ | |
873 | packet_put_int(client_flags); | |
874 | ||
875 | /* Send the packet now. */ | |
876 | packet_send(); | |
877 | packet_write_wait(); | |
878 | ||
879 | debug("Sent encrypted session key."); | |
880 | ||
881 | /* Set the encryption key. */ | |
882 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
883 | ||
884 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
885 | memset(session_key, 0, sizeof(session_key)); | |
886 | ||
887 | /* | |
888 | * Expect a success message from the server. Note that this message | |
889 | * will be received in encrypted form. | |
890 | */ | |
891 | packet_read_expect(&payload_len, SSH_SMSG_SUCCESS); | |
892 | ||
893 | debug("Received encrypted confirmation."); | |
894 | } | |
895 | ||
896 | /* | |
897 | * Authenticate user | |
898 | */ | |
899 | void | |
900 | ssh_userauth( | |
b5c334cc | 901 | const char *local_user, |
902 | const char *server_user, | |
a306f2dd | 903 | char *host, |
904 | int host_key_valid, RSA *own_host_key) | |
905 | { | |
906 | int i, type; | |
907 | int payload_len; | |
908 | ||
909 | if (supported_authentications == 0) | |
910 | fatal("ssh_userauth: server supports no auth methods"); | |
911 | ||
912 | /* Send the name of the user to log in as on the server. */ | |
913 | packet_start(SSH_CMSG_USER); | |
914 | packet_put_string(server_user, strlen(server_user)); | |
915 | packet_send(); | |
916 | packet_write_wait(); | |
917 | ||
918 | /* | |
919 | * The server should respond with success if no authentication is | |
920 | * needed (the user has no password). Otherwise the server responds | |
921 | * with failure. | |
922 | */ | |
923 | type = packet_read(&payload_len); | |
924 | ||
925 | /* check whether the connection was accepted without authentication. */ | |
926 | if (type == SSH_SMSG_SUCCESS) | |
927 | return; | |
928 | if (type != SSH_SMSG_FAILURE) | |
929 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", | |
930 | type); | |
931 | ||
932 | #ifdef AFS | |
933 | /* Try Kerberos tgt passing if the server supports it. */ | |
934 | if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && | |
935 | options.kerberos_tgt_passing) { | |
936 | if (options.cipher == SSH_CIPHER_NONE) | |
937 | log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); | |
938 | (void) send_kerberos_tgt(); | |
939 | } | |
940 | /* Try AFS token passing if the server supports it. */ | |
941 | if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) && | |
942 | options.afs_token_passing && k_hasafs()) { | |
943 | if (options.cipher == SSH_CIPHER_NONE) | |
944 | log("WARNING: Encryption is disabled! Token will be transmitted in the clear!"); | |
945 | send_afs_tokens(); | |
946 | } | |
947 | #endif /* AFS */ | |
948 | ||
949 | #ifdef KRB4 | |
950 | if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && | |
951 | options.kerberos_authentication) { | |
952 | debug("Trying Kerberos authentication."); | |
953 | if (try_kerberos_authentication()) { | |
954 | /* The server should respond with success or failure. */ | |
955 | type = packet_read(&payload_len); | |
956 | if (type == SSH_SMSG_SUCCESS) | |
957 | return; | |
958 | if (type != SSH_SMSG_FAILURE) | |
959 | packet_disconnect("Protocol error: got %d in response to Kerberos auth", type); | |
960 | } | |
961 | } | |
962 | #endif /* KRB4 */ | |
963 | ||
964 | /* | |
965 | * Use rhosts authentication if running in privileged socket and we | |
966 | * do not wish to remain anonymous. | |
967 | */ | |
968 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) && | |
969 | options.rhosts_authentication) { | |
970 | debug("Trying rhosts authentication."); | |
971 | packet_start(SSH_CMSG_AUTH_RHOSTS); | |
972 | packet_put_string(local_user, strlen(local_user)); | |
973 | packet_send(); | |
974 | packet_write_wait(); | |
975 | ||
976 | /* The server should respond with success or failure. */ | |
977 | type = packet_read(&payload_len); | |
978 | if (type == SSH_SMSG_SUCCESS) | |
979 | return; | |
980 | if (type != SSH_SMSG_FAILURE) | |
981 | packet_disconnect("Protocol error: got %d in response to rhosts auth", | |
982 | type); | |
983 | } | |
984 | /* | |
985 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
986 | * authentication. | |
987 | */ | |
988 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
989 | options.rhosts_rsa_authentication && host_key_valid) { | |
990 | if (try_rhosts_rsa_authentication(local_user, own_host_key)) | |
991 | return; | |
992 | } | |
993 | /* Try RSA authentication if the server supports it. */ | |
994 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
995 | options.rsa_authentication) { | |
996 | /* | |
997 | * Try RSA authentication using the authentication agent. The | |
998 | * agent is tried first because no passphrase is needed for | |
999 | * it, whereas identity files may require passphrases. | |
1000 | */ | |
1001 | if (try_agent_authentication()) | |
1002 | return; | |
1003 | ||
1004 | /* Try RSA authentication for each identity. */ | |
1005 | for (i = 0; i < options.num_identity_files; i++) | |
fa08c86b | 1006 | if (options.identity_files_type[i] == KEY_RSA1 && |
1007 | try_rsa_authentication(options.identity_files[i])) | |
a306f2dd | 1008 | return; |
1009 | } | |
1010 | /* Try skey authentication if the server supports it. */ | |
1011 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
1012 | options.skey_authentication && !options.batch_mode) { | |
1013 | if (try_skey_authentication()) | |
1014 | return; | |
1015 | } | |
1016 | /* Try password authentication if the server supports it. */ | |
1017 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
1018 | options.password_authentication && !options.batch_mode) { | |
1019 | char prompt[80]; | |
1020 | ||
1021 | snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", | |
1022 | server_user, host); | |
1023 | if (try_password_authentication(prompt)) | |
1024 | return; | |
1025 | } | |
1026 | /* All authentication methods have failed. Exit with an error message. */ | |
1027 | fatal("Permission denied."); | |
1028 | /* NOTREACHED */ | |
1029 | } |