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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 | |
5 | * Created: Sat Mar 18 22:15:47 1995 ylo | |
6 | * Code to connect to a remote host, and to perform the client side of the | |
7 | * login (authentication) dialog. | |
8 | * | |
9 | */ | |
10 | ||
11 | #include "includes.h" | |
2e73a022 | 12 | RCSID("$OpenBSD: sshconnect1.c,v 1.5 2000/08/19 21:34:44 markus Exp $"); |
a306f2dd | 13 | |
14 | #include <openssl/bn.h> | |
15 | #include <openssl/dsa.h> | |
16 | #include <openssl/rsa.h> | |
17 | #include <openssl/evp.h> | |
18 | ||
19 | #include "xmalloc.h" | |
20 | #include "rsa.h" | |
21 | #include "ssh.h" | |
22 | #include "buffer.h" | |
23 | #include "packet.h" | |
a306f2dd | 24 | #include "cipher.h" |
25 | #include "mpaux.h" | |
26 | #include "uidswap.h" | |
27 | #include "readconf.h" | |
28 | #include "key.h" | |
4c8722d9 | 29 | #include "authfd.h" |
a306f2dd | 30 | #include "sshconnect.h" |
31 | #include "authfile.h" | |
32 | ||
33 | /* Session id for the current session. */ | |
34 | unsigned char session_id[16]; | |
35 | unsigned int supported_authentications = 0; | |
36 | ||
37 | extern Options options; | |
38 | extern char *__progname; | |
39 | ||
40 | /* | |
41 | * Checks if the user has an authentication agent, and if so, tries to | |
42 | * authenticate using the agent. | |
43 | */ | |
44 | int | |
45 | try_agent_authentication() | |
46 | { | |
2e73a022 | 47 | int type; |
a306f2dd | 48 | char *comment; |
49 | AuthenticationConnection *auth; | |
50 | unsigned char response[16]; | |
51 | unsigned int i; | |
2e73a022 | 52 | int plen, clen; |
53 | Key *key; | |
54 | BIGNUM *challenge; | |
a306f2dd | 55 | |
56 | /* Get connection to the agent. */ | |
57 | auth = ssh_get_authentication_connection(); | |
58 | if (!auth) | |
59 | return 0; | |
60 | ||
a306f2dd | 61 | challenge = BN_new(); |
2e73a022 | 62 | key = key_new(KEY_RSA); |
a306f2dd | 63 | |
64 | /* Loop through identities served by the agent. */ | |
2e73a022 | 65 | for (key = ssh_get_first_identity(auth, &comment, 1); |
66 | key != NULL; | |
67 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 68 | |
69 | /* Try this identity. */ | |
70 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
71 | xfree(comment); | |
72 | ||
73 | /* Tell the server that we are willing to authenticate using this key. */ | |
74 | packet_start(SSH_CMSG_AUTH_RSA); | |
2e73a022 | 75 | packet_put_bignum(key->rsa->n); |
a306f2dd | 76 | packet_send(); |
77 | packet_write_wait(); | |
78 | ||
79 | /* Wait for server's response. */ | |
80 | type = packet_read(&plen); | |
81 | ||
82 | /* The server sends failure if it doesn\'t like our key or | |
83 | does not support RSA authentication. */ | |
84 | if (type == SSH_SMSG_FAILURE) { | |
85 | debug("Server refused our key."); | |
2e73a022 | 86 | key_free(key); |
a306f2dd | 87 | continue; |
88 | } | |
89 | /* Otherwise it should have sent a challenge. */ | |
90 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
91 | packet_disconnect("Protocol error during RSA authentication: %d", | |
92 | type); | |
93 | ||
94 | packet_get_bignum(challenge, &clen); | |
95 | ||
96 | packet_integrity_check(plen, clen, type); | |
97 | ||
98 | debug("Received RSA challenge from server."); | |
99 | ||
100 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 101 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { |
102 | /* | |
103 | * The agent failed to authenticate this identifier | |
104 | * although it advertised it supports this. Just | |
105 | * return a wrong value. | |
106 | */ | |
a306f2dd | 107 | log("Authentication agent failed to decrypt challenge."); |
108 | memset(response, 0, sizeof(response)); | |
109 | } | |
2e73a022 | 110 | key_free(key); |
a306f2dd | 111 | debug("Sending response to RSA challenge."); |
112 | ||
113 | /* Send the decrypted challenge back to the server. */ | |
114 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
115 | for (i = 0; i < 16; i++) | |
116 | packet_put_char(response[i]); | |
117 | packet_send(); | |
118 | packet_write_wait(); | |
119 | ||
120 | /* Wait for response from the server. */ | |
121 | type = packet_read(&plen); | |
122 | ||
123 | /* The server returns success if it accepted the authentication. */ | |
124 | if (type == SSH_SMSG_SUCCESS) { | |
a306f2dd | 125 | BN_clear_free(challenge); |
2e73a022 | 126 | debug("RSA authentication accepted by server."); |
a306f2dd | 127 | return 1; |
128 | } | |
129 | /* Otherwise it should return failure. */ | |
130 | if (type != SSH_SMSG_FAILURE) | |
131 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
132 | type); | |
133 | } | |
a306f2dd | 134 | BN_clear_free(challenge); |
a306f2dd | 135 | debug("RSA authentication using agent refused."); |
136 | return 0; | |
137 | } | |
138 | ||
139 | /* | |
140 | * Computes the proper response to a RSA challenge, and sends the response to | |
141 | * the server. | |
142 | */ | |
143 | void | |
144 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
145 | { | |
146 | unsigned char buf[32], response[16]; | |
147 | MD5_CTX md; | |
148 | int i, len; | |
149 | ||
150 | /* Decrypt the challenge using the private key. */ | |
151 | rsa_private_decrypt(challenge, challenge, prv); | |
152 | ||
153 | /* Compute the response. */ | |
154 | /* The response is MD5 of decrypted challenge plus session id. */ | |
155 | len = BN_num_bytes(challenge); | |
156 | if (len <= 0 || len > sizeof(buf)) | |
157 | packet_disconnect("respond_to_rsa_challenge: bad challenge length %d", | |
158 | len); | |
159 | ||
160 | memset(buf, 0, sizeof(buf)); | |
161 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
162 | MD5_Init(&md); | |
163 | MD5_Update(&md, buf, 32); | |
164 | MD5_Update(&md, session_id, 16); | |
165 | MD5_Final(response, &md); | |
166 | ||
167 | debug("Sending response to host key RSA challenge."); | |
168 | ||
169 | /* Send the response back to the server. */ | |
170 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
171 | for (i = 0; i < 16; i++) | |
172 | packet_put_char(response[i]); | |
173 | packet_send(); | |
174 | packet_write_wait(); | |
175 | ||
176 | memset(buf, 0, sizeof(buf)); | |
177 | memset(response, 0, sizeof(response)); | |
178 | memset(&md, 0, sizeof(md)); | |
179 | } | |
180 | ||
181 | /* | |
182 | * Checks if the user has authentication file, and if so, tries to authenticate | |
183 | * the user using it. | |
184 | */ | |
185 | int | |
186 | try_rsa_authentication(const char *authfile) | |
187 | { | |
188 | BIGNUM *challenge; | |
189 | Key *public; | |
190 | Key *private; | |
191 | char *passphrase, *comment; | |
192 | int type, i; | |
193 | int plen, clen; | |
194 | ||
195 | /* Try to load identification for the authentication key. */ | |
196 | public = key_new(KEY_RSA); | |
197 | if (!load_public_key(authfile, public, &comment)) { | |
198 | key_free(public); | |
199 | /* Could not load it. Fail. */ | |
200 | return 0; | |
201 | } | |
202 | debug("Trying RSA authentication with key '%.100s'", comment); | |
203 | ||
204 | /* Tell the server that we are willing to authenticate using this key. */ | |
205 | packet_start(SSH_CMSG_AUTH_RSA); | |
206 | packet_put_bignum(public->rsa->n); | |
207 | packet_send(); | |
208 | packet_write_wait(); | |
209 | ||
210 | /* We no longer need the public key. */ | |
211 | key_free(public); | |
212 | ||
213 | /* Wait for server's response. */ | |
214 | type = packet_read(&plen); | |
215 | ||
216 | /* | |
217 | * The server responds with failure if it doesn\'t like our key or | |
218 | * doesn\'t support RSA authentication. | |
219 | */ | |
220 | if (type == SSH_SMSG_FAILURE) { | |
221 | debug("Server refused our key."); | |
222 | xfree(comment); | |
223 | return 0; | |
224 | } | |
225 | /* Otherwise, the server should respond with a challenge. */ | |
226 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
227 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
228 | ||
229 | /* Get the challenge from the packet. */ | |
230 | challenge = BN_new(); | |
231 | packet_get_bignum(challenge, &clen); | |
232 | ||
233 | packet_integrity_check(plen, clen, type); | |
234 | ||
235 | debug("Received RSA challenge from server."); | |
236 | ||
237 | private = key_new(KEY_RSA); | |
238 | /* | |
239 | * Load the private key. Try first with empty passphrase; if it | |
240 | * fails, ask for a passphrase. | |
241 | */ | |
242 | if (!load_private_key(authfile, "", private, NULL)) { | |
243 | char buf[300]; | |
244 | snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ", | |
245 | comment); | |
246 | if (!options.batch_mode) | |
247 | passphrase = read_passphrase(buf, 0); | |
248 | else { | |
249 | debug("Will not query passphrase for %.100s in batch mode.", | |
250 | comment); | |
251 | passphrase = xstrdup(""); | |
252 | } | |
253 | ||
254 | /* Load the authentication file using the pasphrase. */ | |
255 | if (!load_private_key(authfile, passphrase, private, NULL)) { | |
256 | memset(passphrase, 0, strlen(passphrase)); | |
257 | xfree(passphrase); | |
258 | error("Bad passphrase."); | |
259 | ||
260 | /* Send a dummy response packet to avoid protocol error. */ | |
261 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
262 | for (i = 0; i < 16; i++) | |
263 | packet_put_char(0); | |
264 | packet_send(); | |
265 | packet_write_wait(); | |
266 | ||
267 | /* Expect the server to reject it... */ | |
268 | packet_read_expect(&plen, SSH_SMSG_FAILURE); | |
269 | xfree(comment); | |
270 | return 0; | |
271 | } | |
272 | /* Destroy the passphrase. */ | |
273 | memset(passphrase, 0, strlen(passphrase)); | |
274 | xfree(passphrase); | |
275 | } | |
276 | /* We no longer need the comment. */ | |
277 | xfree(comment); | |
278 | ||
279 | /* Compute and send a response to the challenge. */ | |
280 | respond_to_rsa_challenge(challenge, private->rsa); | |
281 | ||
282 | /* Destroy the private key. */ | |
283 | key_free(private); | |
284 | ||
285 | /* We no longer need the challenge. */ | |
286 | BN_clear_free(challenge); | |
287 | ||
288 | /* Wait for response from the server. */ | |
289 | type = packet_read(&plen); | |
290 | if (type == SSH_SMSG_SUCCESS) { | |
291 | debug("RSA authentication accepted by server."); | |
292 | return 1; | |
293 | } | |
294 | if (type != SSH_SMSG_FAILURE) | |
295 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
296 | debug("RSA authentication refused."); | |
297 | return 0; | |
298 | } | |
299 | ||
300 | /* | |
301 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
302 | * authentication and RSA host authentication. | |
303 | */ | |
304 | int | |
305 | try_rhosts_rsa_authentication(const char *local_user, RSA * host_key) | |
306 | { | |
307 | int type; | |
308 | BIGNUM *challenge; | |
309 | int plen, clen; | |
310 | ||
311 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
312 | ||
313 | /* Tell the server that we are willing to authenticate using this key. */ | |
314 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
315 | packet_put_string(local_user, strlen(local_user)); | |
316 | packet_put_int(BN_num_bits(host_key->n)); | |
317 | packet_put_bignum(host_key->e); | |
318 | packet_put_bignum(host_key->n); | |
319 | packet_send(); | |
320 | packet_write_wait(); | |
321 | ||
322 | /* Wait for server's response. */ | |
323 | type = packet_read(&plen); | |
324 | ||
325 | /* The server responds with failure if it doesn't admit our | |
326 | .rhosts authentication or doesn't know our host key. */ | |
327 | if (type == SSH_SMSG_FAILURE) { | |
328 | debug("Server refused our rhosts authentication or host key."); | |
329 | return 0; | |
330 | } | |
331 | /* Otherwise, the server should respond with a challenge. */ | |
332 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
333 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
334 | ||
335 | /* Get the challenge from the packet. */ | |
336 | challenge = BN_new(); | |
337 | packet_get_bignum(challenge, &clen); | |
338 | ||
339 | packet_integrity_check(plen, clen, type); | |
340 | ||
341 | debug("Received RSA challenge for host key from server."); | |
342 | ||
343 | /* Compute a response to the challenge. */ | |
344 | respond_to_rsa_challenge(challenge, host_key); | |
345 | ||
346 | /* We no longer need the challenge. */ | |
347 | BN_clear_free(challenge); | |
348 | ||
349 | /* Wait for response from the server. */ | |
350 | type = packet_read(&plen); | |
351 | if (type == SSH_SMSG_SUCCESS) { | |
352 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
353 | return 1; | |
354 | } | |
355 | if (type != SSH_SMSG_FAILURE) | |
356 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
357 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
358 | return 0; | |
359 | } | |
360 | ||
361 | #ifdef KRB4 | |
362 | int | |
363 | try_kerberos_authentication() | |
364 | { | |
365 | KTEXT_ST auth; /* Kerberos data */ | |
366 | char *reply; | |
367 | char inst[INST_SZ]; | |
368 | char *realm; | |
369 | CREDENTIALS cred; | |
370 | int r, type, plen; | |
371 | socklen_t slen; | |
372 | Key_schedule schedule; | |
373 | u_long checksum, cksum; | |
374 | MSG_DAT msg_data; | |
375 | struct sockaddr_in local, foreign; | |
376 | struct stat st; | |
377 | ||
378 | /* Don't do anything if we don't have any tickets. */ | |
379 | if (stat(tkt_string(), &st) < 0) | |
380 | return 0; | |
381 | ||
382 | strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ); | |
383 | ||
384 | realm = (char *) krb_realmofhost(get_canonical_hostname()); | |
385 | if (!realm) { | |
386 | debug("Kerberos V4: no realm for %s", get_canonical_hostname()); | |
387 | return 0; | |
388 | } | |
389 | /* This can really be anything. */ | |
390 | checksum = (u_long) getpid(); | |
391 | ||
392 | r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); | |
393 | if (r != KSUCCESS) { | |
394 | debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]); | |
395 | return 0; | |
396 | } | |
397 | /* Get session key to decrypt the server's reply with. */ | |
398 | r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); | |
399 | if (r != KSUCCESS) { | |
400 | debug("get_cred failed: %s", krb_err_txt[r]); | |
401 | return 0; | |
402 | } | |
403 | des_key_sched((des_cblock *) cred.session, schedule); | |
404 | ||
405 | /* Send authentication info to server. */ | |
406 | packet_start(SSH_CMSG_AUTH_KERBEROS); | |
407 | packet_put_string((char *) auth.dat, auth.length); | |
408 | packet_send(); | |
409 | packet_write_wait(); | |
410 | ||
411 | /* Zero the buffer. */ | |
412 | (void) memset(auth.dat, 0, MAX_KTXT_LEN); | |
413 | ||
414 | slen = sizeof(local); | |
415 | memset(&local, 0, sizeof(local)); | |
416 | if (getsockname(packet_get_connection_in(), | |
417 | (struct sockaddr *) & local, &slen) < 0) | |
418 | debug("getsockname failed: %s", strerror(errno)); | |
419 | ||
420 | slen = sizeof(foreign); | |
421 | memset(&foreign, 0, sizeof(foreign)); | |
422 | if (getpeername(packet_get_connection_in(), | |
423 | (struct sockaddr *) & foreign, &slen) < 0) { | |
424 | debug("getpeername failed: %s", strerror(errno)); | |
425 | fatal_cleanup(); | |
426 | } | |
427 | /* Get server reply. */ | |
428 | type = packet_read(&plen); | |
429 | switch (type) { | |
430 | case SSH_SMSG_FAILURE: | |
431 | /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ | |
432 | debug("Kerberos V4 authentication failed."); | |
433 | return 0; | |
434 | break; | |
435 | ||
436 | case SSH_SMSG_AUTH_KERBEROS_RESPONSE: | |
437 | /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ | |
438 | debug("Kerberos V4 authentication accepted."); | |
439 | ||
440 | /* Get server's response. */ | |
441 | reply = packet_get_string((unsigned int *) &auth.length); | |
442 | memcpy(auth.dat, reply, auth.length); | |
443 | xfree(reply); | |
444 | ||
445 | packet_integrity_check(plen, 4 + auth.length, type); | |
446 | ||
447 | /* | |
448 | * If his response isn't properly encrypted with the session | |
449 | * key, and the decrypted checksum fails to match, he's | |
450 | * bogus. Bail out. | |
451 | */ | |
452 | r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, | |
453 | &foreign, &local, &msg_data); | |
454 | if (r != KSUCCESS) { | |
455 | debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]); | |
456 | packet_disconnect("Kerberos V4 challenge failed!"); | |
457 | } | |
458 | /* Fetch the (incremented) checksum that we supplied in the request. */ | |
459 | (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum)); | |
460 | cksum = ntohl(cksum); | |
461 | ||
462 | /* If it matches, we're golden. */ | |
463 | if (cksum == checksum + 1) { | |
464 | debug("Kerberos V4 challenge successful."); | |
465 | return 1; | |
466 | } else | |
467 | packet_disconnect("Kerberos V4 challenge failed!"); | |
468 | break; | |
469 | ||
470 | default: | |
471 | packet_disconnect("Protocol error on Kerberos V4 response: %d", type); | |
472 | } | |
473 | return 0; | |
474 | } | |
475 | ||
476 | #endif /* KRB4 */ | |
477 | ||
478 | #ifdef AFS | |
479 | int | |
480 | send_kerberos_tgt() | |
481 | { | |
482 | CREDENTIALS *creds; | |
483 | char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; | |
484 | int r, type, plen; | |
485 | char buffer[8192]; | |
486 | struct stat st; | |
487 | ||
488 | /* Don't do anything if we don't have any tickets. */ | |
489 | if (stat(tkt_string(), &st) < 0) | |
490 | return 0; | |
491 | ||
492 | creds = xmalloc(sizeof(*creds)); | |
493 | ||
494 | if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) { | |
495 | debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]); | |
496 | return 0; | |
497 | } | |
498 | if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) { | |
499 | debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]); | |
500 | return 0; | |
501 | } | |
502 | if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { | |
503 | debug("Kerberos V4 ticket expired: %s", TKT_FILE); | |
504 | return 0; | |
505 | } | |
1d1ffb87 | 506 | creds_to_radix(creds, (unsigned char *)buffer, sizeof buffer); |
a306f2dd | 507 | xfree(creds); |
508 | ||
509 | packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); | |
510 | packet_put_string(buffer, strlen(buffer)); | |
511 | packet_send(); | |
512 | packet_write_wait(); | |
513 | ||
514 | type = packet_read(&plen); | |
515 | ||
516 | if (type == SSH_SMSG_FAILURE) | |
517 | debug("Kerberos TGT for realm %s rejected.", prealm); | |
518 | else if (type != SSH_SMSG_SUCCESS) | |
519 | packet_disconnect("Protocol error on Kerberos TGT response: %d", type); | |
520 | ||
521 | return 1; | |
522 | } | |
523 | ||
524 | void | |
525 | send_afs_tokens(void) | |
526 | { | |
527 | CREDENTIALS creds; | |
528 | struct ViceIoctl parms; | |
529 | struct ClearToken ct; | |
530 | int i, type, len, plen; | |
531 | char buf[2048], *p, *server_cell; | |
532 | char buffer[8192]; | |
533 | ||
534 | /* Move over ktc_GetToken, here's something leaner. */ | |
535 | for (i = 0; i < 100; i++) { /* just in case */ | |
536 | parms.in = (char *) &i; | |
537 | parms.in_size = sizeof(i); | |
538 | parms.out = buf; | |
539 | parms.out_size = sizeof(buf); | |
540 | if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) | |
541 | break; | |
542 | p = buf; | |
543 | ||
544 | /* Get secret token. */ | |
545 | memcpy(&creds.ticket_st.length, p, sizeof(unsigned int)); | |
546 | if (creds.ticket_st.length > MAX_KTXT_LEN) | |
547 | break; | |
548 | p += sizeof(unsigned int); | |
549 | memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); | |
550 | p += creds.ticket_st.length; | |
551 | ||
552 | /* Get clear token. */ | |
553 | memcpy(&len, p, sizeof(len)); | |
554 | if (len != sizeof(struct ClearToken)) | |
555 | break; | |
556 | p += sizeof(len); | |
557 | memcpy(&ct, p, len); | |
558 | p += len; | |
559 | p += sizeof(len); /* primary flag */ | |
560 | server_cell = p; | |
561 | ||
562 | /* Flesh out our credentials. */ | |
563 | strlcpy(creds.service, "afs", sizeof creds.service); | |
564 | creds.instance[0] = '\0'; | |
565 | strlcpy(creds.realm, server_cell, REALM_SZ); | |
566 | memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); | |
567 | creds.issue_date = ct.BeginTimestamp; | |
568 | creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp); | |
569 | creds.kvno = ct.AuthHandle; | |
570 | snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); | |
571 | creds.pinst[0] = '\0'; | |
572 | ||
573 | /* Encode token, ship it off. */ | |
1d1ffb87 | 574 | if (creds_to_radix(&creds, (unsigned char*) buffer, sizeof buffer) <= 0) |
a306f2dd | 575 | break; |
576 | packet_start(SSH_CMSG_HAVE_AFS_TOKEN); | |
577 | packet_put_string(buffer, strlen(buffer)); | |
578 | packet_send(); | |
579 | packet_write_wait(); | |
580 | ||
581 | /* Roger, Roger. Clearance, Clarence. What's your vector, | |
582 | Victor? */ | |
583 | type = packet_read(&plen); | |
584 | ||
585 | if (type == SSH_SMSG_FAILURE) | |
586 | debug("AFS token for cell %s rejected.", server_cell); | |
587 | else if (type != SSH_SMSG_SUCCESS) | |
588 | packet_disconnect("Protocol error on AFS token response: %d", type); | |
589 | } | |
590 | } | |
591 | ||
592 | #endif /* AFS */ | |
593 | ||
594 | /* | |
595 | * Tries to authenticate with any string-based challenge/response system. | |
596 | * Note that the client code is not tied to s/key or TIS. | |
597 | */ | |
598 | int | |
599 | try_skey_authentication() | |
600 | { | |
601 | int type, i; | |
602 | int payload_len; | |
603 | unsigned int clen; | |
604 | char *challenge, *response; | |
605 | ||
606 | debug("Doing skey authentication."); | |
607 | ||
608 | /* request a challenge */ | |
609 | packet_start(SSH_CMSG_AUTH_TIS); | |
610 | packet_send(); | |
611 | packet_write_wait(); | |
612 | ||
613 | type = packet_read(&payload_len); | |
614 | if (type != SSH_SMSG_FAILURE && | |
615 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
616 | packet_disconnect("Protocol error: got %d in response " | |
617 | "to skey-auth", type); | |
618 | } | |
619 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
620 | debug("No challenge for skey authentication."); | |
621 | return 0; | |
622 | } | |
623 | challenge = packet_get_string(&clen); | |
624 | packet_integrity_check(payload_len, (4 + clen), type); | |
625 | if (options.cipher == SSH_CIPHER_NONE) | |
626 | log("WARNING: Encryption is disabled! " | |
627 | "Reponse will be transmitted in clear text."); | |
628 | fprintf(stderr, "%s\n", challenge); | |
629 | xfree(challenge); | |
630 | fflush(stderr); | |
631 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
632 | if (i != 0) | |
633 | error("Permission denied, please try again."); | |
634 | response = read_passphrase("Response: ", 0); | |
635 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); | |
636 | packet_put_string(response, strlen(response)); | |
637 | memset(response, 0, strlen(response)); | |
638 | xfree(response); | |
639 | packet_send(); | |
640 | packet_write_wait(); | |
641 | type = packet_read(&payload_len); | |
642 | if (type == SSH_SMSG_SUCCESS) | |
643 | return 1; | |
644 | if (type != SSH_SMSG_FAILURE) | |
645 | packet_disconnect("Protocol error: got %d in response " | |
646 | "to skey-auth-reponse", type); | |
647 | } | |
648 | /* failure */ | |
649 | return 0; | |
650 | } | |
651 | ||
652 | /* | |
653 | * Tries to authenticate with plain passwd authentication. | |
654 | */ | |
655 | int | |
656 | try_password_authentication(char *prompt) | |
657 | { | |
658 | int type, i, payload_len; | |
659 | char *password; | |
660 | ||
661 | debug("Doing password authentication."); | |
662 | if (options.cipher == SSH_CIPHER_NONE) | |
663 | log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
664 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
665 | if (i != 0) | |
666 | error("Permission denied, please try again."); | |
667 | password = read_passphrase(prompt, 0); | |
668 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
669 | packet_put_string(password, strlen(password)); | |
670 | memset(password, 0, strlen(password)); | |
671 | xfree(password); | |
672 | packet_send(); | |
673 | packet_write_wait(); | |
674 | ||
675 | type = packet_read(&payload_len); | |
676 | if (type == SSH_SMSG_SUCCESS) | |
677 | return 1; | |
678 | if (type != SSH_SMSG_FAILURE) | |
679 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
680 | } | |
681 | /* failure */ | |
682 | return 0; | |
683 | } | |
684 | ||
685 | /* | |
686 | * SSH1 key exchange | |
687 | */ | |
688 | void | |
689 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
690 | { | |
691 | int i; | |
692 | BIGNUM *key; | |
693 | RSA *host_key; | |
694 | RSA *public_key; | |
695 | Key k; | |
696 | int bits, rbits; | |
697 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
698 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
699 | unsigned char cookie[8]; | |
700 | unsigned int supported_ciphers; | |
701 | unsigned int server_flags, client_flags; | |
702 | int payload_len, clen, sum_len = 0; | |
703 | u_int32_t rand = 0; | |
704 | ||
705 | debug("Waiting for server public key."); | |
706 | ||
707 | /* Wait for a public key packet from the server. */ | |
708 | packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY); | |
709 | ||
710 | /* Get cookie from the packet. */ | |
711 | for (i = 0; i < 8; i++) | |
712 | cookie[i] = packet_get_char(); | |
713 | ||
714 | /* Get the public key. */ | |
715 | public_key = RSA_new(); | |
716 | bits = packet_get_int();/* bits */ | |
717 | public_key->e = BN_new(); | |
718 | packet_get_bignum(public_key->e, &clen); | |
719 | sum_len += clen; | |
720 | public_key->n = BN_new(); | |
721 | packet_get_bignum(public_key->n, &clen); | |
722 | sum_len += clen; | |
723 | ||
724 | rbits = BN_num_bits(public_key->n); | |
725 | if (bits != rbits) { | |
726 | log("Warning: Server lies about size of server public key: " | |
727 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
728 | log("Warning: This may be due to an old implementation of ssh."); | |
729 | } | |
730 | /* Get the host key. */ | |
731 | host_key = RSA_new(); | |
732 | bits = packet_get_int();/* bits */ | |
733 | host_key->e = BN_new(); | |
734 | packet_get_bignum(host_key->e, &clen); | |
735 | sum_len += clen; | |
736 | host_key->n = BN_new(); | |
737 | packet_get_bignum(host_key->n, &clen); | |
738 | sum_len += clen; | |
739 | ||
740 | rbits = BN_num_bits(host_key->n); | |
741 | if (bits != rbits) { | |
742 | log("Warning: Server lies about size of server host key: " | |
743 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
744 | log("Warning: This may be due to an old implementation of ssh."); | |
745 | } | |
746 | ||
747 | /* Get protocol flags. */ | |
748 | server_flags = packet_get_int(); | |
749 | packet_set_protocol_flags(server_flags); | |
750 | ||
751 | supported_ciphers = packet_get_int(); | |
752 | supported_authentications = packet_get_int(); | |
753 | ||
754 | debug("Received server public key (%d bits) and host key (%d bits).", | |
755 | BN_num_bits(public_key->n), BN_num_bits(host_key->n)); | |
756 | ||
757 | packet_integrity_check(payload_len, | |
758 | 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, | |
759 | SSH_SMSG_PUBLIC_KEY); | |
760 | k.type = KEY_RSA; | |
761 | k.rsa = host_key; | |
762 | check_host_key(host, hostaddr, &k, | |
763 | options.user_hostfile, options.system_hostfile); | |
764 | ||
765 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
766 | ||
767 | compute_session_id(session_id, cookie, host_key->n, public_key->n); | |
768 | ||
769 | /* Generate a session key. */ | |
770 | arc4random_stir(); | |
771 | ||
772 | /* | |
773 | * Generate an encryption key for the session. The key is a 256 bit | |
774 | * random number, interpreted as a 32-byte key, with the least | |
775 | * significant 8 bits being the first byte of the key. | |
776 | */ | |
777 | for (i = 0; i < 32; i++) { | |
778 | if (i % 4 == 0) | |
779 | rand = arc4random(); | |
780 | session_key[i] = rand & 0xff; | |
781 | rand >>= 8; | |
782 | } | |
783 | ||
784 | /* | |
785 | * According to the protocol spec, the first byte of the session key | |
786 | * is the highest byte of the integer. The session key is xored with | |
787 | * the first 16 bytes of the session id. | |
788 | */ | |
789 | key = BN_new(); | |
790 | BN_set_word(key, 0); | |
791 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
792 | BN_lshift(key, key, 8); | |
793 | if (i < 16) | |
794 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
795 | else | |
796 | BN_add_word(key, session_key[i]); | |
797 | } | |
798 | ||
799 | /* | |
800 | * Encrypt the integer using the public key and host key of the | |
801 | * server (key with smaller modulus first). | |
802 | */ | |
803 | if (BN_cmp(public_key->n, host_key->n) < 0) { | |
804 | /* Public key has smaller modulus. */ | |
805 | if (BN_num_bits(host_key->n) < | |
806 | BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) { | |
807 | fatal("respond_to_rsa_challenge: host_key %d < public_key %d + " | |
808 | "SSH_KEY_BITS_RESERVED %d", | |
809 | BN_num_bits(host_key->n), | |
810 | BN_num_bits(public_key->n), | |
811 | SSH_KEY_BITS_RESERVED); | |
812 | } | |
813 | rsa_public_encrypt(key, key, public_key); | |
814 | rsa_public_encrypt(key, key, host_key); | |
815 | } else { | |
816 | /* Host key has smaller modulus (or they are equal). */ | |
817 | if (BN_num_bits(public_key->n) < | |
818 | BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) { | |
819 | fatal("respond_to_rsa_challenge: public_key %d < host_key %d + " | |
820 | "SSH_KEY_BITS_RESERVED %d", | |
821 | BN_num_bits(public_key->n), | |
822 | BN_num_bits(host_key->n), | |
823 | SSH_KEY_BITS_RESERVED); | |
824 | } | |
825 | rsa_public_encrypt(key, key, host_key); | |
826 | rsa_public_encrypt(key, key, public_key); | |
827 | } | |
828 | ||
829 | /* Destroy the public keys since we no longer need them. */ | |
830 | RSA_free(public_key); | |
831 | RSA_free(host_key); | |
832 | ||
d0c832f3 | 833 | if (options.cipher == SSH_CIPHER_ILLEGAL) { |
834 | log("No valid SSH1 cipher, using %.100s instead.", | |
835 | cipher_name(SSH_FALLBACK_CIPHER)); | |
836 | options.cipher = SSH_FALLBACK_CIPHER; | |
837 | } else if (options.cipher == SSH_CIPHER_NOT_SET) { | |
a306f2dd | 838 | if (cipher_mask1() & supported_ciphers & (1 << ssh_cipher_default)) |
839 | options.cipher = ssh_cipher_default; | |
840 | else { | |
841 | debug("Cipher %s not supported, using %.100s instead.", | |
d0c832f3 | 842 | cipher_name(ssh_cipher_default), |
843 | cipher_name(SSH_FALLBACK_CIPHER)); | |
a306f2dd | 844 | options.cipher = SSH_FALLBACK_CIPHER; |
845 | } | |
846 | } | |
847 | /* Check that the selected cipher is supported. */ | |
848 | if (!(supported_ciphers & (1 << options.cipher))) | |
849 | fatal("Selected cipher type %.100s not supported by server.", | |
850 | cipher_name(options.cipher)); | |
851 | ||
852 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
853 | ||
854 | /* Send the encrypted session key to the server. */ | |
855 | packet_start(SSH_CMSG_SESSION_KEY); | |
856 | packet_put_char(options.cipher); | |
857 | ||
858 | /* Send the cookie back to the server. */ | |
859 | for (i = 0; i < 8; i++) | |
860 | packet_put_char(cookie[i]); | |
861 | ||
862 | /* Send and destroy the encrypted encryption key integer. */ | |
863 | packet_put_bignum(key); | |
864 | BN_clear_free(key); | |
865 | ||
866 | /* Send protocol flags. */ | |
867 | packet_put_int(client_flags); | |
868 | ||
869 | /* Send the packet now. */ | |
870 | packet_send(); | |
871 | packet_write_wait(); | |
872 | ||
873 | debug("Sent encrypted session key."); | |
874 | ||
875 | /* Set the encryption key. */ | |
876 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
877 | ||
878 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
879 | memset(session_key, 0, sizeof(session_key)); | |
880 | ||
881 | /* | |
882 | * Expect a success message from the server. Note that this message | |
883 | * will be received in encrypted form. | |
884 | */ | |
885 | packet_read_expect(&payload_len, SSH_SMSG_SUCCESS); | |
886 | ||
887 | debug("Received encrypted confirmation."); | |
888 | } | |
889 | ||
890 | /* | |
891 | * Authenticate user | |
892 | */ | |
893 | void | |
894 | ssh_userauth( | |
895 | const char* local_user, | |
896 | const char* server_user, | |
897 | char *host, | |
898 | int host_key_valid, RSA *own_host_key) | |
899 | { | |
900 | int i, type; | |
901 | int payload_len; | |
902 | ||
903 | if (supported_authentications == 0) | |
904 | fatal("ssh_userauth: server supports no auth methods"); | |
905 | ||
906 | /* Send the name of the user to log in as on the server. */ | |
907 | packet_start(SSH_CMSG_USER); | |
908 | packet_put_string(server_user, strlen(server_user)); | |
909 | packet_send(); | |
910 | packet_write_wait(); | |
911 | ||
912 | /* | |
913 | * The server should respond with success if no authentication is | |
914 | * needed (the user has no password). Otherwise the server responds | |
915 | * with failure. | |
916 | */ | |
917 | type = packet_read(&payload_len); | |
918 | ||
919 | /* check whether the connection was accepted without authentication. */ | |
920 | if (type == SSH_SMSG_SUCCESS) | |
921 | return; | |
922 | if (type != SSH_SMSG_FAILURE) | |
923 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", | |
924 | type); | |
925 | ||
926 | #ifdef AFS | |
927 | /* Try Kerberos tgt passing if the server supports it. */ | |
928 | if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && | |
929 | options.kerberos_tgt_passing) { | |
930 | if (options.cipher == SSH_CIPHER_NONE) | |
931 | log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); | |
932 | (void) send_kerberos_tgt(); | |
933 | } | |
934 | /* Try AFS token passing if the server supports it. */ | |
935 | if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) && | |
936 | options.afs_token_passing && k_hasafs()) { | |
937 | if (options.cipher == SSH_CIPHER_NONE) | |
938 | log("WARNING: Encryption is disabled! Token will be transmitted in the clear!"); | |
939 | send_afs_tokens(); | |
940 | } | |
941 | #endif /* AFS */ | |
942 | ||
943 | #ifdef KRB4 | |
944 | if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && | |
945 | options.kerberos_authentication) { | |
946 | debug("Trying Kerberos authentication."); | |
947 | if (try_kerberos_authentication()) { | |
948 | /* The server should respond with success or failure. */ | |
949 | type = packet_read(&payload_len); | |
950 | if (type == SSH_SMSG_SUCCESS) | |
951 | return; | |
952 | if (type != SSH_SMSG_FAILURE) | |
953 | packet_disconnect("Protocol error: got %d in response to Kerberos auth", type); | |
954 | } | |
955 | } | |
956 | #endif /* KRB4 */ | |
957 | ||
958 | /* | |
959 | * Use rhosts authentication if running in privileged socket and we | |
960 | * do not wish to remain anonymous. | |
961 | */ | |
962 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) && | |
963 | options.rhosts_authentication) { | |
964 | debug("Trying rhosts authentication."); | |
965 | packet_start(SSH_CMSG_AUTH_RHOSTS); | |
966 | packet_put_string(local_user, strlen(local_user)); | |
967 | packet_send(); | |
968 | packet_write_wait(); | |
969 | ||
970 | /* The server should respond with success or failure. */ | |
971 | type = packet_read(&payload_len); | |
972 | if (type == SSH_SMSG_SUCCESS) | |
973 | return; | |
974 | if (type != SSH_SMSG_FAILURE) | |
975 | packet_disconnect("Protocol error: got %d in response to rhosts auth", | |
976 | type); | |
977 | } | |
978 | /* | |
979 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
980 | * authentication. | |
981 | */ | |
982 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
983 | options.rhosts_rsa_authentication && host_key_valid) { | |
984 | if (try_rhosts_rsa_authentication(local_user, own_host_key)) | |
985 | return; | |
986 | } | |
987 | /* Try RSA authentication if the server supports it. */ | |
988 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
989 | options.rsa_authentication) { | |
990 | /* | |
991 | * Try RSA authentication using the authentication agent. The | |
992 | * agent is tried first because no passphrase is needed for | |
993 | * it, whereas identity files may require passphrases. | |
994 | */ | |
995 | if (try_agent_authentication()) | |
996 | return; | |
997 | ||
998 | /* Try RSA authentication for each identity. */ | |
999 | for (i = 0; i < options.num_identity_files; i++) | |
1000 | if (try_rsa_authentication(options.identity_files[i])) | |
1001 | return; | |
1002 | } | |
1003 | /* Try skey authentication if the server supports it. */ | |
1004 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
1005 | options.skey_authentication && !options.batch_mode) { | |
1006 | if (try_skey_authentication()) | |
1007 | return; | |
1008 | } | |
1009 | /* Try password authentication if the server supports it. */ | |
1010 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
1011 | options.password_authentication && !options.batch_mode) { | |
1012 | char prompt[80]; | |
1013 | ||
1014 | snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", | |
1015 | server_user, host); | |
1016 | if (try_password_authentication(prompt)) | |
1017 | return; | |
1018 | } | |
1019 | /* All authentication methods have failed. Exit with an error message. */ | |
1020 | fatal("Permission denied."); | |
1021 | /* NOTREACHED */ | |
1022 | } |