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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" | |
4c8722d9 | 12 | RCSID("$OpenBSD: sshconnect1.c,v 1.4 2000/07/16 08:27:22 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 | { | |
47 | int status, type; | |
48 | char *comment; | |
49 | AuthenticationConnection *auth; | |
50 | unsigned char response[16]; | |
51 | unsigned int i; | |
52 | BIGNUM *e, *n, *challenge; | |
53 | ||
54 | /* Get connection to the agent. */ | |
55 | auth = ssh_get_authentication_connection(); | |
56 | if (!auth) | |
57 | return 0; | |
58 | ||
59 | e = BN_new(); | |
60 | n = BN_new(); | |
61 | challenge = BN_new(); | |
62 | ||
63 | /* Loop through identities served by the agent. */ | |
64 | for (status = ssh_get_first_identity(auth, e, n, &comment); | |
65 | status; | |
66 | status = ssh_get_next_identity(auth, e, n, &comment)) { | |
67 | int plen, clen; | |
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); | |
75 | packet_put_bignum(n); | |
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."); | |
86 | continue; | |
87 | } | |
88 | /* Otherwise it should have sent a challenge. */ | |
89 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
90 | packet_disconnect("Protocol error during RSA authentication: %d", | |
91 | type); | |
92 | ||
93 | packet_get_bignum(challenge, &clen); | |
94 | ||
95 | packet_integrity_check(plen, clen, type); | |
96 | ||
97 | debug("Received RSA challenge from server."); | |
98 | ||
99 | /* Ask the agent to decrypt the challenge. */ | |
100 | if (!ssh_decrypt_challenge(auth, e, n, challenge, | |
101 | session_id, 1, response)) { | |
102 | /* The agent failed to authenticate this identifier although it | |
103 | advertised it supports this. Just return a wrong value. */ | |
104 | log("Authentication agent failed to decrypt challenge."); | |
105 | memset(response, 0, sizeof(response)); | |
106 | } | |
107 | debug("Sending response to RSA challenge."); | |
108 | ||
109 | /* Send the decrypted challenge back to the server. */ | |
110 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
111 | for (i = 0; i < 16; i++) | |
112 | packet_put_char(response[i]); | |
113 | packet_send(); | |
114 | packet_write_wait(); | |
115 | ||
116 | /* Wait for response from the server. */ | |
117 | type = packet_read(&plen); | |
118 | ||
119 | /* The server returns success if it accepted the authentication. */ | |
120 | if (type == SSH_SMSG_SUCCESS) { | |
121 | debug("RSA authentication accepted by server."); | |
122 | BN_clear_free(e); | |
123 | BN_clear_free(n); | |
124 | BN_clear_free(challenge); | |
125 | return 1; | |
126 | } | |
127 | /* Otherwise it should return failure. */ | |
128 | if (type != SSH_SMSG_FAILURE) | |
129 | packet_disconnect("Protocol error waiting RSA auth response: %d", | |
130 | type); | |
131 | } | |
132 | ||
133 | BN_clear_free(e); | |
134 | BN_clear_free(n); | |
135 | BN_clear_free(challenge); | |
136 | ||
137 | debug("RSA authentication using agent refused."); | |
138 | return 0; | |
139 | } | |
140 | ||
141 | /* | |
142 | * Computes the proper response to a RSA challenge, and sends the response to | |
143 | * the server. | |
144 | */ | |
145 | void | |
146 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
147 | { | |
148 | unsigned char buf[32], response[16]; | |
149 | MD5_CTX md; | |
150 | int i, len; | |
151 | ||
152 | /* Decrypt the challenge using the private key. */ | |
153 | rsa_private_decrypt(challenge, challenge, prv); | |
154 | ||
155 | /* Compute the response. */ | |
156 | /* The response is MD5 of decrypted challenge plus session id. */ | |
157 | len = BN_num_bytes(challenge); | |
158 | if (len <= 0 || len > sizeof(buf)) | |
159 | packet_disconnect("respond_to_rsa_challenge: bad challenge length %d", | |
160 | len); | |
161 | ||
162 | memset(buf, 0, sizeof(buf)); | |
163 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
164 | MD5_Init(&md); | |
165 | MD5_Update(&md, buf, 32); | |
166 | MD5_Update(&md, session_id, 16); | |
167 | MD5_Final(response, &md); | |
168 | ||
169 | debug("Sending response to host key RSA challenge."); | |
170 | ||
171 | /* Send the response back to the server. */ | |
172 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
173 | for (i = 0; i < 16; i++) | |
174 | packet_put_char(response[i]); | |
175 | packet_send(); | |
176 | packet_write_wait(); | |
177 | ||
178 | memset(buf, 0, sizeof(buf)); | |
179 | memset(response, 0, sizeof(response)); | |
180 | memset(&md, 0, sizeof(md)); | |
181 | } | |
182 | ||
183 | /* | |
184 | * Checks if the user has authentication file, and if so, tries to authenticate | |
185 | * the user using it. | |
186 | */ | |
187 | int | |
188 | try_rsa_authentication(const char *authfile) | |
189 | { | |
190 | BIGNUM *challenge; | |
191 | Key *public; | |
192 | Key *private; | |
193 | char *passphrase, *comment; | |
194 | int type, i; | |
195 | int plen, clen; | |
196 | ||
197 | /* Try to load identification for the authentication key. */ | |
198 | public = key_new(KEY_RSA); | |
199 | if (!load_public_key(authfile, public, &comment)) { | |
200 | key_free(public); | |
201 | /* Could not load it. Fail. */ | |
202 | return 0; | |
203 | } | |
204 | debug("Trying RSA authentication with key '%.100s'", comment); | |
205 | ||
206 | /* Tell the server that we are willing to authenticate using this key. */ | |
207 | packet_start(SSH_CMSG_AUTH_RSA); | |
208 | packet_put_bignum(public->rsa->n); | |
209 | packet_send(); | |
210 | packet_write_wait(); | |
211 | ||
212 | /* We no longer need the public key. */ | |
213 | key_free(public); | |
214 | ||
215 | /* Wait for server's response. */ | |
216 | type = packet_read(&plen); | |
217 | ||
218 | /* | |
219 | * The server responds with failure if it doesn\'t like our key or | |
220 | * doesn\'t support RSA authentication. | |
221 | */ | |
222 | if (type == SSH_SMSG_FAILURE) { | |
223 | debug("Server refused our key."); | |
224 | xfree(comment); | |
225 | return 0; | |
226 | } | |
227 | /* Otherwise, the server should respond with a challenge. */ | |
228 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
229 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
230 | ||
231 | /* Get the challenge from the packet. */ | |
232 | challenge = BN_new(); | |
233 | packet_get_bignum(challenge, &clen); | |
234 | ||
235 | packet_integrity_check(plen, clen, type); | |
236 | ||
237 | debug("Received RSA challenge from server."); | |
238 | ||
239 | private = key_new(KEY_RSA); | |
240 | /* | |
241 | * Load the private key. Try first with empty passphrase; if it | |
242 | * fails, ask for a passphrase. | |
243 | */ | |
244 | if (!load_private_key(authfile, "", private, NULL)) { | |
245 | char buf[300]; | |
246 | snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ", | |
247 | comment); | |
248 | if (!options.batch_mode) | |
249 | passphrase = read_passphrase(buf, 0); | |
250 | else { | |
251 | debug("Will not query passphrase for %.100s in batch mode.", | |
252 | comment); | |
253 | passphrase = xstrdup(""); | |
254 | } | |
255 | ||
256 | /* Load the authentication file using the pasphrase. */ | |
257 | if (!load_private_key(authfile, passphrase, private, NULL)) { | |
258 | memset(passphrase, 0, strlen(passphrase)); | |
259 | xfree(passphrase); | |
260 | error("Bad passphrase."); | |
261 | ||
262 | /* Send a dummy response packet to avoid protocol error. */ | |
263 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
264 | for (i = 0; i < 16; i++) | |
265 | packet_put_char(0); | |
266 | packet_send(); | |
267 | packet_write_wait(); | |
268 | ||
269 | /* Expect the server to reject it... */ | |
270 | packet_read_expect(&plen, SSH_SMSG_FAILURE); | |
271 | xfree(comment); | |
272 | return 0; | |
273 | } | |
274 | /* Destroy the passphrase. */ | |
275 | memset(passphrase, 0, strlen(passphrase)); | |
276 | xfree(passphrase); | |
277 | } | |
278 | /* We no longer need the comment. */ | |
279 | xfree(comment); | |
280 | ||
281 | /* Compute and send a response to the challenge. */ | |
282 | respond_to_rsa_challenge(challenge, private->rsa); | |
283 | ||
284 | /* Destroy the private key. */ | |
285 | key_free(private); | |
286 | ||
287 | /* We no longer need the challenge. */ | |
288 | BN_clear_free(challenge); | |
289 | ||
290 | /* Wait for response from the server. */ | |
291 | type = packet_read(&plen); | |
292 | if (type == SSH_SMSG_SUCCESS) { | |
293 | debug("RSA authentication accepted by server."); | |
294 | return 1; | |
295 | } | |
296 | if (type != SSH_SMSG_FAILURE) | |
297 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
298 | debug("RSA authentication refused."); | |
299 | return 0; | |
300 | } | |
301 | ||
302 | /* | |
303 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
304 | * authentication and RSA host authentication. | |
305 | */ | |
306 | int | |
307 | try_rhosts_rsa_authentication(const char *local_user, RSA * host_key) | |
308 | { | |
309 | int type; | |
310 | BIGNUM *challenge; | |
311 | int plen, clen; | |
312 | ||
313 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
314 | ||
315 | /* Tell the server that we are willing to authenticate using this key. */ | |
316 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
317 | packet_put_string(local_user, strlen(local_user)); | |
318 | packet_put_int(BN_num_bits(host_key->n)); | |
319 | packet_put_bignum(host_key->e); | |
320 | packet_put_bignum(host_key->n); | |
321 | packet_send(); | |
322 | packet_write_wait(); | |
323 | ||
324 | /* Wait for server's response. */ | |
325 | type = packet_read(&plen); | |
326 | ||
327 | /* The server responds with failure if it doesn't admit our | |
328 | .rhosts authentication or doesn't know our host key. */ | |
329 | if (type == SSH_SMSG_FAILURE) { | |
330 | debug("Server refused our rhosts authentication or host key."); | |
331 | return 0; | |
332 | } | |
333 | /* Otherwise, the server should respond with a challenge. */ | |
334 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
335 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
336 | ||
337 | /* Get the challenge from the packet. */ | |
338 | challenge = BN_new(); | |
339 | packet_get_bignum(challenge, &clen); | |
340 | ||
341 | packet_integrity_check(plen, clen, type); | |
342 | ||
343 | debug("Received RSA challenge for host key from server."); | |
344 | ||
345 | /* Compute a response to the challenge. */ | |
346 | respond_to_rsa_challenge(challenge, host_key); | |
347 | ||
348 | /* We no longer need the challenge. */ | |
349 | BN_clear_free(challenge); | |
350 | ||
351 | /* Wait for response from the server. */ | |
352 | type = packet_read(&plen); | |
353 | if (type == SSH_SMSG_SUCCESS) { | |
354 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
355 | return 1; | |
356 | } | |
357 | if (type != SSH_SMSG_FAILURE) | |
358 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
359 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
360 | return 0; | |
361 | } | |
362 | ||
363 | #ifdef KRB4 | |
364 | int | |
365 | try_kerberos_authentication() | |
366 | { | |
367 | KTEXT_ST auth; /* Kerberos data */ | |
368 | char *reply; | |
369 | char inst[INST_SZ]; | |
370 | char *realm; | |
371 | CREDENTIALS cred; | |
372 | int r, type, plen; | |
373 | socklen_t slen; | |
374 | Key_schedule schedule; | |
375 | u_long checksum, cksum; | |
376 | MSG_DAT msg_data; | |
377 | struct sockaddr_in local, foreign; | |
378 | struct stat st; | |
379 | ||
380 | /* Don't do anything if we don't have any tickets. */ | |
381 | if (stat(tkt_string(), &st) < 0) | |
382 | return 0; | |
383 | ||
384 | strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ); | |
385 | ||
386 | realm = (char *) krb_realmofhost(get_canonical_hostname()); | |
387 | if (!realm) { | |
388 | debug("Kerberos V4: no realm for %s", get_canonical_hostname()); | |
389 | return 0; | |
390 | } | |
391 | /* This can really be anything. */ | |
392 | checksum = (u_long) getpid(); | |
393 | ||
394 | r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); | |
395 | if (r != KSUCCESS) { | |
396 | debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]); | |
397 | return 0; | |
398 | } | |
399 | /* Get session key to decrypt the server's reply with. */ | |
400 | r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); | |
401 | if (r != KSUCCESS) { | |
402 | debug("get_cred failed: %s", krb_err_txt[r]); | |
403 | return 0; | |
404 | } | |
405 | des_key_sched((des_cblock *) cred.session, schedule); | |
406 | ||
407 | /* Send authentication info to server. */ | |
408 | packet_start(SSH_CMSG_AUTH_KERBEROS); | |
409 | packet_put_string((char *) auth.dat, auth.length); | |
410 | packet_send(); | |
411 | packet_write_wait(); | |
412 | ||
413 | /* Zero the buffer. */ | |
414 | (void) memset(auth.dat, 0, MAX_KTXT_LEN); | |
415 | ||
416 | slen = sizeof(local); | |
417 | memset(&local, 0, sizeof(local)); | |
418 | if (getsockname(packet_get_connection_in(), | |
419 | (struct sockaddr *) & local, &slen) < 0) | |
420 | debug("getsockname failed: %s", strerror(errno)); | |
421 | ||
422 | slen = sizeof(foreign); | |
423 | memset(&foreign, 0, sizeof(foreign)); | |
424 | if (getpeername(packet_get_connection_in(), | |
425 | (struct sockaddr *) & foreign, &slen) < 0) { | |
426 | debug("getpeername failed: %s", strerror(errno)); | |
427 | fatal_cleanup(); | |
428 | } | |
429 | /* Get server reply. */ | |
430 | type = packet_read(&plen); | |
431 | switch (type) { | |
432 | case SSH_SMSG_FAILURE: | |
433 | /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ | |
434 | debug("Kerberos V4 authentication failed."); | |
435 | return 0; | |
436 | break; | |
437 | ||
438 | case SSH_SMSG_AUTH_KERBEROS_RESPONSE: | |
439 | /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ | |
440 | debug("Kerberos V4 authentication accepted."); | |
441 | ||
442 | /* Get server's response. */ | |
443 | reply = packet_get_string((unsigned int *) &auth.length); | |
444 | memcpy(auth.dat, reply, auth.length); | |
445 | xfree(reply); | |
446 | ||
447 | packet_integrity_check(plen, 4 + auth.length, type); | |
448 | ||
449 | /* | |
450 | * If his response isn't properly encrypted with the session | |
451 | * key, and the decrypted checksum fails to match, he's | |
452 | * bogus. Bail out. | |
453 | */ | |
454 | r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, | |
455 | &foreign, &local, &msg_data); | |
456 | if (r != KSUCCESS) { | |
457 | debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]); | |
458 | packet_disconnect("Kerberos V4 challenge failed!"); | |
459 | } | |
460 | /* Fetch the (incremented) checksum that we supplied in the request. */ | |
461 | (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum)); | |
462 | cksum = ntohl(cksum); | |
463 | ||
464 | /* If it matches, we're golden. */ | |
465 | if (cksum == checksum + 1) { | |
466 | debug("Kerberos V4 challenge successful."); | |
467 | return 1; | |
468 | } else | |
469 | packet_disconnect("Kerberos V4 challenge failed!"); | |
470 | break; | |
471 | ||
472 | default: | |
473 | packet_disconnect("Protocol error on Kerberos V4 response: %d", type); | |
474 | } | |
475 | return 0; | |
476 | } | |
477 | ||
478 | #endif /* KRB4 */ | |
479 | ||
480 | #ifdef AFS | |
481 | int | |
482 | send_kerberos_tgt() | |
483 | { | |
484 | CREDENTIALS *creds; | |
485 | char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; | |
486 | int r, type, plen; | |
487 | char buffer[8192]; | |
488 | struct stat st; | |
489 | ||
490 | /* Don't do anything if we don't have any tickets. */ | |
491 | if (stat(tkt_string(), &st) < 0) | |
492 | return 0; | |
493 | ||
494 | creds = xmalloc(sizeof(*creds)); | |
495 | ||
496 | if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) { | |
497 | debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]); | |
498 | return 0; | |
499 | } | |
500 | if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) { | |
501 | debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]); | |
502 | return 0; | |
503 | } | |
504 | if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { | |
505 | debug("Kerberos V4 ticket expired: %s", TKT_FILE); | |
506 | return 0; | |
507 | } | |
1d1ffb87 | 508 | creds_to_radix(creds, (unsigned char *)buffer, sizeof buffer); |
a306f2dd | 509 | xfree(creds); |
510 | ||
511 | packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); | |
512 | packet_put_string(buffer, strlen(buffer)); | |
513 | packet_send(); | |
514 | packet_write_wait(); | |
515 | ||
516 | type = packet_read(&plen); | |
517 | ||
518 | if (type == SSH_SMSG_FAILURE) | |
519 | debug("Kerberos TGT for realm %s rejected.", prealm); | |
520 | else if (type != SSH_SMSG_SUCCESS) | |
521 | packet_disconnect("Protocol error on Kerberos TGT response: %d", type); | |
522 | ||
523 | return 1; | |
524 | } | |
525 | ||
526 | void | |
527 | send_afs_tokens(void) | |
528 | { | |
529 | CREDENTIALS creds; | |
530 | struct ViceIoctl parms; | |
531 | struct ClearToken ct; | |
532 | int i, type, len, plen; | |
533 | char buf[2048], *p, *server_cell; | |
534 | char buffer[8192]; | |
535 | ||
536 | /* Move over ktc_GetToken, here's something leaner. */ | |
537 | for (i = 0; i < 100; i++) { /* just in case */ | |
538 | parms.in = (char *) &i; | |
539 | parms.in_size = sizeof(i); | |
540 | parms.out = buf; | |
541 | parms.out_size = sizeof(buf); | |
542 | if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) | |
543 | break; | |
544 | p = buf; | |
545 | ||
546 | /* Get secret token. */ | |
547 | memcpy(&creds.ticket_st.length, p, sizeof(unsigned int)); | |
548 | if (creds.ticket_st.length > MAX_KTXT_LEN) | |
549 | break; | |
550 | p += sizeof(unsigned int); | |
551 | memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); | |
552 | p += creds.ticket_st.length; | |
553 | ||
554 | /* Get clear token. */ | |
555 | memcpy(&len, p, sizeof(len)); | |
556 | if (len != sizeof(struct ClearToken)) | |
557 | break; | |
558 | p += sizeof(len); | |
559 | memcpy(&ct, p, len); | |
560 | p += len; | |
561 | p += sizeof(len); /* primary flag */ | |
562 | server_cell = p; | |
563 | ||
564 | /* Flesh out our credentials. */ | |
565 | strlcpy(creds.service, "afs", sizeof creds.service); | |
566 | creds.instance[0] = '\0'; | |
567 | strlcpy(creds.realm, server_cell, REALM_SZ); | |
568 | memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); | |
569 | creds.issue_date = ct.BeginTimestamp; | |
570 | creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp); | |
571 | creds.kvno = ct.AuthHandle; | |
572 | snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); | |
573 | creds.pinst[0] = '\0'; | |
574 | ||
575 | /* Encode token, ship it off. */ | |
1d1ffb87 | 576 | if (creds_to_radix(&creds, (unsigned char*) buffer, sizeof buffer) <= 0) |
a306f2dd | 577 | break; |
578 | packet_start(SSH_CMSG_HAVE_AFS_TOKEN); | |
579 | packet_put_string(buffer, strlen(buffer)); | |
580 | packet_send(); | |
581 | packet_write_wait(); | |
582 | ||
583 | /* Roger, Roger. Clearance, Clarence. What's your vector, | |
584 | Victor? */ | |
585 | type = packet_read(&plen); | |
586 | ||
587 | if (type == SSH_SMSG_FAILURE) | |
588 | debug("AFS token for cell %s rejected.", server_cell); | |
589 | else if (type != SSH_SMSG_SUCCESS) | |
590 | packet_disconnect("Protocol error on AFS token response: %d", type); | |
591 | } | |
592 | } | |
593 | ||
594 | #endif /* AFS */ | |
595 | ||
596 | /* | |
597 | * Tries to authenticate with any string-based challenge/response system. | |
598 | * Note that the client code is not tied to s/key or TIS. | |
599 | */ | |
600 | int | |
601 | try_skey_authentication() | |
602 | { | |
603 | int type, i; | |
604 | int payload_len; | |
605 | unsigned int clen; | |
606 | char *challenge, *response; | |
607 | ||
608 | debug("Doing skey authentication."); | |
609 | ||
610 | /* request a challenge */ | |
611 | packet_start(SSH_CMSG_AUTH_TIS); | |
612 | packet_send(); | |
613 | packet_write_wait(); | |
614 | ||
615 | type = packet_read(&payload_len); | |
616 | if (type != SSH_SMSG_FAILURE && | |
617 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
618 | packet_disconnect("Protocol error: got %d in response " | |
619 | "to skey-auth", type); | |
620 | } | |
621 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
622 | debug("No challenge for skey authentication."); | |
623 | return 0; | |
624 | } | |
625 | challenge = packet_get_string(&clen); | |
626 | packet_integrity_check(payload_len, (4 + clen), type); | |
627 | if (options.cipher == SSH_CIPHER_NONE) | |
628 | log("WARNING: Encryption is disabled! " | |
629 | "Reponse will be transmitted in clear text."); | |
630 | fprintf(stderr, "%s\n", challenge); | |
631 | xfree(challenge); | |
632 | fflush(stderr); | |
633 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
634 | if (i != 0) | |
635 | error("Permission denied, please try again."); | |
636 | response = read_passphrase("Response: ", 0); | |
637 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); | |
638 | packet_put_string(response, strlen(response)); | |
639 | memset(response, 0, strlen(response)); | |
640 | xfree(response); | |
641 | packet_send(); | |
642 | packet_write_wait(); | |
643 | type = packet_read(&payload_len); | |
644 | if (type == SSH_SMSG_SUCCESS) | |
645 | return 1; | |
646 | if (type != SSH_SMSG_FAILURE) | |
647 | packet_disconnect("Protocol error: got %d in response " | |
648 | "to skey-auth-reponse", type); | |
649 | } | |
650 | /* failure */ | |
651 | return 0; | |
652 | } | |
653 | ||
654 | /* | |
655 | * Tries to authenticate with plain passwd authentication. | |
656 | */ | |
657 | int | |
658 | try_password_authentication(char *prompt) | |
659 | { | |
660 | int type, i, payload_len; | |
661 | char *password; | |
662 | ||
663 | debug("Doing password authentication."); | |
664 | if (options.cipher == SSH_CIPHER_NONE) | |
665 | log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
666 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
667 | if (i != 0) | |
668 | error("Permission denied, please try again."); | |
669 | password = read_passphrase(prompt, 0); | |
670 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
671 | packet_put_string(password, strlen(password)); | |
672 | memset(password, 0, strlen(password)); | |
673 | xfree(password); | |
674 | packet_send(); | |
675 | packet_write_wait(); | |
676 | ||
677 | type = packet_read(&payload_len); | |
678 | if (type == SSH_SMSG_SUCCESS) | |
679 | return 1; | |
680 | if (type != SSH_SMSG_FAILURE) | |
681 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
682 | } | |
683 | /* failure */ | |
684 | return 0; | |
685 | } | |
686 | ||
687 | /* | |
688 | * SSH1 key exchange | |
689 | */ | |
690 | void | |
691 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
692 | { | |
693 | int i; | |
694 | BIGNUM *key; | |
695 | RSA *host_key; | |
696 | RSA *public_key; | |
697 | Key k; | |
698 | int bits, rbits; | |
699 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
700 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
701 | unsigned char cookie[8]; | |
702 | unsigned int supported_ciphers; | |
703 | unsigned int server_flags, client_flags; | |
704 | int payload_len, clen, sum_len = 0; | |
705 | u_int32_t rand = 0; | |
706 | ||
707 | debug("Waiting for server public key."); | |
708 | ||
709 | /* Wait for a public key packet from the server. */ | |
710 | packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY); | |
711 | ||
712 | /* Get cookie from the packet. */ | |
713 | for (i = 0; i < 8; i++) | |
714 | cookie[i] = packet_get_char(); | |
715 | ||
716 | /* Get the public key. */ | |
717 | public_key = RSA_new(); | |
718 | bits = packet_get_int();/* bits */ | |
719 | public_key->e = BN_new(); | |
720 | packet_get_bignum(public_key->e, &clen); | |
721 | sum_len += clen; | |
722 | public_key->n = BN_new(); | |
723 | packet_get_bignum(public_key->n, &clen); | |
724 | sum_len += clen; | |
725 | ||
726 | rbits = BN_num_bits(public_key->n); | |
727 | if (bits != rbits) { | |
728 | log("Warning: Server lies about size of server public key: " | |
729 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
730 | log("Warning: This may be due to an old implementation of ssh."); | |
731 | } | |
732 | /* Get the host key. */ | |
733 | host_key = RSA_new(); | |
734 | bits = packet_get_int();/* bits */ | |
735 | host_key->e = BN_new(); | |
736 | packet_get_bignum(host_key->e, &clen); | |
737 | sum_len += clen; | |
738 | host_key->n = BN_new(); | |
739 | packet_get_bignum(host_key->n, &clen); | |
740 | sum_len += clen; | |
741 | ||
742 | rbits = BN_num_bits(host_key->n); | |
743 | if (bits != rbits) { | |
744 | log("Warning: Server lies about size of server host key: " | |
745 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
746 | log("Warning: This may be due to an old implementation of ssh."); | |
747 | } | |
748 | ||
749 | /* Get protocol flags. */ | |
750 | server_flags = packet_get_int(); | |
751 | packet_set_protocol_flags(server_flags); | |
752 | ||
753 | supported_ciphers = packet_get_int(); | |
754 | supported_authentications = packet_get_int(); | |
755 | ||
756 | debug("Received server public key (%d bits) and host key (%d bits).", | |
757 | BN_num_bits(public_key->n), BN_num_bits(host_key->n)); | |
758 | ||
759 | packet_integrity_check(payload_len, | |
760 | 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, | |
761 | SSH_SMSG_PUBLIC_KEY); | |
762 | k.type = KEY_RSA; | |
763 | k.rsa = host_key; | |
764 | check_host_key(host, hostaddr, &k, | |
765 | options.user_hostfile, options.system_hostfile); | |
766 | ||
767 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
768 | ||
769 | compute_session_id(session_id, cookie, host_key->n, public_key->n); | |
770 | ||
771 | /* Generate a session key. */ | |
772 | arc4random_stir(); | |
773 | ||
774 | /* | |
775 | * Generate an encryption key for the session. The key is a 256 bit | |
776 | * random number, interpreted as a 32-byte key, with the least | |
777 | * significant 8 bits being the first byte of the key. | |
778 | */ | |
779 | for (i = 0; i < 32; i++) { | |
780 | if (i % 4 == 0) | |
781 | rand = arc4random(); | |
782 | session_key[i] = rand & 0xff; | |
783 | rand >>= 8; | |
784 | } | |
785 | ||
786 | /* | |
787 | * According to the protocol spec, the first byte of the session key | |
788 | * is the highest byte of the integer. The session key is xored with | |
789 | * the first 16 bytes of the session id. | |
790 | */ | |
791 | key = BN_new(); | |
792 | BN_set_word(key, 0); | |
793 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
794 | BN_lshift(key, key, 8); | |
795 | if (i < 16) | |
796 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
797 | else | |
798 | BN_add_word(key, session_key[i]); | |
799 | } | |
800 | ||
801 | /* | |
802 | * Encrypt the integer using the public key and host key of the | |
803 | * server (key with smaller modulus first). | |
804 | */ | |
805 | if (BN_cmp(public_key->n, host_key->n) < 0) { | |
806 | /* Public key has smaller modulus. */ | |
807 | if (BN_num_bits(host_key->n) < | |
808 | BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) { | |
809 | fatal("respond_to_rsa_challenge: host_key %d < public_key %d + " | |
810 | "SSH_KEY_BITS_RESERVED %d", | |
811 | BN_num_bits(host_key->n), | |
812 | BN_num_bits(public_key->n), | |
813 | SSH_KEY_BITS_RESERVED); | |
814 | } | |
815 | rsa_public_encrypt(key, key, public_key); | |
816 | rsa_public_encrypt(key, key, host_key); | |
817 | } else { | |
818 | /* Host key has smaller modulus (or they are equal). */ | |
819 | if (BN_num_bits(public_key->n) < | |
820 | BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) { | |
821 | fatal("respond_to_rsa_challenge: public_key %d < host_key %d + " | |
822 | "SSH_KEY_BITS_RESERVED %d", | |
823 | BN_num_bits(public_key->n), | |
824 | BN_num_bits(host_key->n), | |
825 | SSH_KEY_BITS_RESERVED); | |
826 | } | |
827 | rsa_public_encrypt(key, key, host_key); | |
828 | rsa_public_encrypt(key, key, public_key); | |
829 | } | |
830 | ||
831 | /* Destroy the public keys since we no longer need them. */ | |
832 | RSA_free(public_key); | |
833 | RSA_free(host_key); | |
834 | ||
d0c832f3 | 835 | if (options.cipher == SSH_CIPHER_ILLEGAL) { |
836 | log("No valid SSH1 cipher, using %.100s instead.", | |
837 | cipher_name(SSH_FALLBACK_CIPHER)); | |
838 | options.cipher = SSH_FALLBACK_CIPHER; | |
839 | } else if (options.cipher == SSH_CIPHER_NOT_SET) { | |
a306f2dd | 840 | if (cipher_mask1() & supported_ciphers & (1 << ssh_cipher_default)) |
841 | options.cipher = ssh_cipher_default; | |
842 | else { | |
843 | debug("Cipher %s not supported, using %.100s instead.", | |
d0c832f3 | 844 | cipher_name(ssh_cipher_default), |
845 | cipher_name(SSH_FALLBACK_CIPHER)); | |
a306f2dd | 846 | options.cipher = SSH_FALLBACK_CIPHER; |
847 | } | |
848 | } | |
849 | /* Check that the selected cipher is supported. */ | |
850 | if (!(supported_ciphers & (1 << options.cipher))) | |
851 | fatal("Selected cipher type %.100s not supported by server.", | |
852 | cipher_name(options.cipher)); | |
853 | ||
854 | debug("Encryption type: %.100s", cipher_name(options.cipher)); | |
855 | ||
856 | /* Send the encrypted session key to the server. */ | |
857 | packet_start(SSH_CMSG_SESSION_KEY); | |
858 | packet_put_char(options.cipher); | |
859 | ||
860 | /* Send the cookie back to the server. */ | |
861 | for (i = 0; i < 8; i++) | |
862 | packet_put_char(cookie[i]); | |
863 | ||
864 | /* Send and destroy the encrypted encryption key integer. */ | |
865 | packet_put_bignum(key); | |
866 | BN_clear_free(key); | |
867 | ||
868 | /* Send protocol flags. */ | |
869 | packet_put_int(client_flags); | |
870 | ||
871 | /* Send the packet now. */ | |
872 | packet_send(); | |
873 | packet_write_wait(); | |
874 | ||
875 | debug("Sent encrypted session key."); | |
876 | ||
877 | /* Set the encryption key. */ | |
878 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher); | |
879 | ||
880 | /* We will no longer need the session key here. Destroy any extra copies. */ | |
881 | memset(session_key, 0, sizeof(session_key)); | |
882 | ||
883 | /* | |
884 | * Expect a success message from the server. Note that this message | |
885 | * will be received in encrypted form. | |
886 | */ | |
887 | packet_read_expect(&payload_len, SSH_SMSG_SUCCESS); | |
888 | ||
889 | debug("Received encrypted confirmation."); | |
890 | } | |
891 | ||
892 | /* | |
893 | * Authenticate user | |
894 | */ | |
895 | void | |
896 | ssh_userauth( | |
897 | const char* local_user, | |
898 | const char* server_user, | |
899 | char *host, | |
900 | int host_key_valid, RSA *own_host_key) | |
901 | { | |
902 | int i, type; | |
903 | int payload_len; | |
904 | ||
905 | if (supported_authentications == 0) | |
906 | fatal("ssh_userauth: server supports no auth methods"); | |
907 | ||
908 | /* Send the name of the user to log in as on the server. */ | |
909 | packet_start(SSH_CMSG_USER); | |
910 | packet_put_string(server_user, strlen(server_user)); | |
911 | packet_send(); | |
912 | packet_write_wait(); | |
913 | ||
914 | /* | |
915 | * The server should respond with success if no authentication is | |
916 | * needed (the user has no password). Otherwise the server responds | |
917 | * with failure. | |
918 | */ | |
919 | type = packet_read(&payload_len); | |
920 | ||
921 | /* check whether the connection was accepted without authentication. */ | |
922 | if (type == SSH_SMSG_SUCCESS) | |
923 | return; | |
924 | if (type != SSH_SMSG_FAILURE) | |
925 | packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", | |
926 | type); | |
927 | ||
928 | #ifdef AFS | |
929 | /* Try Kerberos tgt passing if the server supports it. */ | |
930 | if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) && | |
931 | options.kerberos_tgt_passing) { | |
932 | if (options.cipher == SSH_CIPHER_NONE) | |
933 | log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!"); | |
934 | (void) send_kerberos_tgt(); | |
935 | } | |
936 | /* Try AFS token passing if the server supports it. */ | |
937 | if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) && | |
938 | options.afs_token_passing && k_hasafs()) { | |
939 | if (options.cipher == SSH_CIPHER_NONE) | |
940 | log("WARNING: Encryption is disabled! Token will be transmitted in the clear!"); | |
941 | send_afs_tokens(); | |
942 | } | |
943 | #endif /* AFS */ | |
944 | ||
945 | #ifdef KRB4 | |
946 | if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) && | |
947 | options.kerberos_authentication) { | |
948 | debug("Trying Kerberos authentication."); | |
949 | if (try_kerberos_authentication()) { | |
950 | /* The server should respond with success or failure. */ | |
951 | type = packet_read(&payload_len); | |
952 | if (type == SSH_SMSG_SUCCESS) | |
953 | return; | |
954 | if (type != SSH_SMSG_FAILURE) | |
955 | packet_disconnect("Protocol error: got %d in response to Kerberos auth", type); | |
956 | } | |
957 | } | |
958 | #endif /* KRB4 */ | |
959 | ||
960 | /* | |
961 | * Use rhosts authentication if running in privileged socket and we | |
962 | * do not wish to remain anonymous. | |
963 | */ | |
964 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) && | |
965 | options.rhosts_authentication) { | |
966 | debug("Trying rhosts authentication."); | |
967 | packet_start(SSH_CMSG_AUTH_RHOSTS); | |
968 | packet_put_string(local_user, strlen(local_user)); | |
969 | packet_send(); | |
970 | packet_write_wait(); | |
971 | ||
972 | /* The server should respond with success or failure. */ | |
973 | type = packet_read(&payload_len); | |
974 | if (type == SSH_SMSG_SUCCESS) | |
975 | return; | |
976 | if (type != SSH_SMSG_FAILURE) | |
977 | packet_disconnect("Protocol error: got %d in response to rhosts auth", | |
978 | type); | |
979 | } | |
980 | /* | |
981 | * Try .rhosts or /etc/hosts.equiv authentication with RSA host | |
982 | * authentication. | |
983 | */ | |
984 | if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) && | |
985 | options.rhosts_rsa_authentication && host_key_valid) { | |
986 | if (try_rhosts_rsa_authentication(local_user, own_host_key)) | |
987 | return; | |
988 | } | |
989 | /* Try RSA authentication if the server supports it. */ | |
990 | if ((supported_authentications & (1 << SSH_AUTH_RSA)) && | |
991 | options.rsa_authentication) { | |
992 | /* | |
993 | * Try RSA authentication using the authentication agent. The | |
994 | * agent is tried first because no passphrase is needed for | |
995 | * it, whereas identity files may require passphrases. | |
996 | */ | |
997 | if (try_agent_authentication()) | |
998 | return; | |
999 | ||
1000 | /* Try RSA authentication for each identity. */ | |
1001 | for (i = 0; i < options.num_identity_files; i++) | |
1002 | if (try_rsa_authentication(options.identity_files[i])) | |
1003 | return; | |
1004 | } | |
1005 | /* Try skey authentication if the server supports it. */ | |
1006 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
1007 | options.skey_authentication && !options.batch_mode) { | |
1008 | if (try_skey_authentication()) | |
1009 | return; | |
1010 | } | |
1011 | /* Try password authentication if the server supports it. */ | |
1012 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
1013 | options.password_authentication && !options.batch_mode) { | |
1014 | char prompt[80]; | |
1015 | ||
1016 | snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", | |
1017 | server_user, host); | |
1018 | if (try_password_authentication(prompt)) | |
1019 | return; | |
1020 | } | |
1021 | /* All authentication methods have failed. Exit with an error message. */ | |
1022 | fatal("Permission denied."); | |
1023 | /* NOTREACHED */ | |
1024 | } |