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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" | |
e3a70753 | 16 | RCSID("$OpenBSD: sshconnect1.c,v 1.12 2000/12/10 17:01:53 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. */ | |
37 | unsigned char session_id[16]; | |
38 | unsigned int supported_authentications = 0; | |
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; | |
53 | unsigned char response[16]; | |
54 | unsigned 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(); |
fa08c86b | 65 | key = key_new(KEY_RSA1); |
a306f2dd | 66 | |
67 | /* Loop through identities served by the agent. */ | |
2e73a022 | 68 | for (key = ssh_get_first_identity(auth, &comment, 1); |
69 | key != NULL; | |
70 | key = ssh_get_next_identity(auth, &comment, 1)) { | |
a306f2dd | 71 | |
72 | /* Try this identity. */ | |
73 | debug("Trying RSA authentication via agent with '%.100s'", comment); | |
74 | xfree(comment); | |
75 | ||
76 | /* Tell the server that we are willing to authenticate using this key. */ | |
77 | packet_start(SSH_CMSG_AUTH_RSA); | |
2e73a022 | 78 | packet_put_bignum(key->rsa->n); |
a306f2dd | 79 | packet_send(); |
80 | packet_write_wait(); | |
81 | ||
82 | /* Wait for server's response. */ | |
83 | type = packet_read(&plen); | |
84 | ||
85 | /* The server sends failure if it doesn\'t like our key or | |
86 | does not support RSA authentication. */ | |
87 | if (type == SSH_SMSG_FAILURE) { | |
88 | debug("Server refused our key."); | |
2e73a022 | 89 | key_free(key); |
a306f2dd | 90 | continue; |
91 | } | |
92 | /* Otherwise it should have sent a challenge. */ | |
93 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
94 | packet_disconnect("Protocol error during RSA authentication: %d", | |
95 | type); | |
96 | ||
97 | packet_get_bignum(challenge, &clen); | |
98 | ||
99 | packet_integrity_check(plen, clen, type); | |
100 | ||
101 | debug("Received RSA challenge from server."); | |
102 | ||
103 | /* Ask the agent to decrypt the challenge. */ | |
2e73a022 | 104 | if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) { |
105 | /* | |
106 | * The agent failed to authenticate this identifier | |
107 | * although it advertised it supports this. Just | |
108 | * return a wrong value. | |
109 | */ | |
a306f2dd | 110 | log("Authentication agent failed to decrypt challenge."); |
111 | memset(response, 0, sizeof(response)); | |
112 | } | |
2e73a022 | 113 | key_free(key); |
a306f2dd | 114 | debug("Sending response to RSA challenge."); |
115 | ||
116 | /* Send the decrypted challenge back to the server. */ | |
117 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
118 | for (i = 0; i < 16; i++) | |
119 | packet_put_char(response[i]); | |
120 | packet_send(); | |
121 | packet_write_wait(); | |
122 | ||
123 | /* Wait for response from the server. */ | |
124 | type = packet_read(&plen); | |
125 | ||
126 | /* The server returns success if it accepted the authentication. */ | |
127 | if (type == SSH_SMSG_SUCCESS) { | |
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 | } | |
a306f2dd | 137 | BN_clear_free(challenge); |
a306f2dd | 138 | debug("RSA authentication using agent refused."); |
139 | return 0; | |
140 | } | |
141 | ||
142 | /* | |
143 | * Computes the proper response to a RSA challenge, and sends the response to | |
144 | * the server. | |
145 | */ | |
146 | void | |
147 | respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv) | |
148 | { | |
149 | unsigned char buf[32], response[16]; | |
150 | MD5_CTX md; | |
151 | int i, len; | |
152 | ||
153 | /* Decrypt the challenge using the private key. */ | |
154 | rsa_private_decrypt(challenge, challenge, prv); | |
155 | ||
156 | /* Compute the response. */ | |
157 | /* The response is MD5 of decrypted challenge plus session id. */ | |
158 | len = BN_num_bytes(challenge); | |
159 | if (len <= 0 || len > sizeof(buf)) | |
160 | packet_disconnect("respond_to_rsa_challenge: bad challenge length %d", | |
161 | len); | |
162 | ||
163 | memset(buf, 0, sizeof(buf)); | |
164 | BN_bn2bin(challenge, buf + sizeof(buf) - len); | |
165 | MD5_Init(&md); | |
166 | MD5_Update(&md, buf, 32); | |
167 | MD5_Update(&md, session_id, 16); | |
168 | MD5_Final(response, &md); | |
169 | ||
170 | debug("Sending response to host key RSA challenge."); | |
171 | ||
172 | /* Send the response back to the server. */ | |
173 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
174 | for (i = 0; i < 16; i++) | |
175 | packet_put_char(response[i]); | |
176 | packet_send(); | |
177 | packet_write_wait(); | |
178 | ||
179 | memset(buf, 0, sizeof(buf)); | |
180 | memset(response, 0, sizeof(response)); | |
181 | memset(&md, 0, sizeof(md)); | |
182 | } | |
183 | ||
184 | /* | |
185 | * Checks if the user has authentication file, and if so, tries to authenticate | |
186 | * the user using it. | |
187 | */ | |
188 | int | |
189 | try_rsa_authentication(const char *authfile) | |
190 | { | |
191 | BIGNUM *challenge; | |
192 | Key *public; | |
193 | Key *private; | |
194 | char *passphrase, *comment; | |
195 | int type, i; | |
196 | int plen, clen; | |
197 | ||
198 | /* Try to load identification for the authentication key. */ | |
fa08c86b | 199 | public = key_new(KEY_RSA1); |
a306f2dd | 200 | if (!load_public_key(authfile, public, &comment)) { |
201 | key_free(public); | |
202 | /* Could not load it. Fail. */ | |
203 | return 0; | |
204 | } | |
205 | debug("Trying RSA authentication with key '%.100s'", comment); | |
206 | ||
207 | /* Tell the server that we are willing to authenticate using this key. */ | |
208 | packet_start(SSH_CMSG_AUTH_RSA); | |
209 | packet_put_bignum(public->rsa->n); | |
210 | packet_send(); | |
211 | packet_write_wait(); | |
212 | ||
213 | /* We no longer need the public key. */ | |
214 | key_free(public); | |
215 | ||
216 | /* Wait for server's response. */ | |
217 | type = packet_read(&plen); | |
218 | ||
219 | /* | |
220 | * The server responds with failure if it doesn\'t like our key or | |
221 | * doesn\'t support RSA authentication. | |
222 | */ | |
223 | if (type == SSH_SMSG_FAILURE) { | |
224 | debug("Server refused our key."); | |
225 | xfree(comment); | |
226 | return 0; | |
227 | } | |
228 | /* Otherwise, the server should respond with a challenge. */ | |
229 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
230 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
231 | ||
232 | /* Get the challenge from the packet. */ | |
233 | challenge = BN_new(); | |
234 | packet_get_bignum(challenge, &clen); | |
235 | ||
236 | packet_integrity_check(plen, clen, type); | |
237 | ||
238 | debug("Received RSA challenge from server."); | |
239 | ||
fa08c86b | 240 | private = key_new(KEY_RSA1); |
a306f2dd | 241 | /* |
242 | * Load the private key. Try first with empty passphrase; if it | |
243 | * fails, ask for a passphrase. | |
244 | */ | |
245 | if (!load_private_key(authfile, "", private, NULL)) { | |
246 | char buf[300]; | |
247 | snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ", | |
248 | comment); | |
249 | if (!options.batch_mode) | |
250 | passphrase = read_passphrase(buf, 0); | |
251 | else { | |
252 | debug("Will not query passphrase for %.100s in batch mode.", | |
253 | comment); | |
254 | passphrase = xstrdup(""); | |
255 | } | |
256 | ||
257 | /* Load the authentication file using the pasphrase. */ | |
258 | if (!load_private_key(authfile, passphrase, private, NULL)) { | |
259 | memset(passphrase, 0, strlen(passphrase)); | |
260 | xfree(passphrase); | |
261 | error("Bad passphrase."); | |
262 | ||
263 | /* Send a dummy response packet to avoid protocol error. */ | |
264 | packet_start(SSH_CMSG_AUTH_RSA_RESPONSE); | |
265 | for (i = 0; i < 16; i++) | |
266 | packet_put_char(0); | |
267 | packet_send(); | |
268 | packet_write_wait(); | |
269 | ||
270 | /* Expect the server to reject it... */ | |
271 | packet_read_expect(&plen, SSH_SMSG_FAILURE); | |
272 | xfree(comment); | |
273 | return 0; | |
274 | } | |
275 | /* Destroy the passphrase. */ | |
276 | memset(passphrase, 0, strlen(passphrase)); | |
277 | xfree(passphrase); | |
278 | } | |
279 | /* We no longer need the comment. */ | |
280 | xfree(comment); | |
281 | ||
282 | /* Compute and send a response to the challenge. */ | |
283 | respond_to_rsa_challenge(challenge, private->rsa); | |
284 | ||
285 | /* Destroy the private key. */ | |
286 | key_free(private); | |
287 | ||
288 | /* We no longer need the challenge. */ | |
289 | BN_clear_free(challenge); | |
290 | ||
291 | /* Wait for response from the server. */ | |
292 | type = packet_read(&plen); | |
293 | if (type == SSH_SMSG_SUCCESS) { | |
294 | debug("RSA authentication accepted by server."); | |
295 | return 1; | |
296 | } | |
297 | if (type != SSH_SMSG_FAILURE) | |
298 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
299 | debug("RSA authentication refused."); | |
300 | return 0; | |
301 | } | |
302 | ||
303 | /* | |
304 | * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv | |
305 | * authentication and RSA host authentication. | |
306 | */ | |
307 | int | |
308 | try_rhosts_rsa_authentication(const char *local_user, RSA * host_key) | |
309 | { | |
310 | int type; | |
311 | BIGNUM *challenge; | |
312 | int plen, clen; | |
313 | ||
314 | debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication."); | |
315 | ||
316 | /* Tell the server that we are willing to authenticate using this key. */ | |
317 | packet_start(SSH_CMSG_AUTH_RHOSTS_RSA); | |
318 | packet_put_string(local_user, strlen(local_user)); | |
319 | packet_put_int(BN_num_bits(host_key->n)); | |
320 | packet_put_bignum(host_key->e); | |
321 | packet_put_bignum(host_key->n); | |
322 | packet_send(); | |
323 | packet_write_wait(); | |
324 | ||
325 | /* Wait for server's response. */ | |
326 | type = packet_read(&plen); | |
327 | ||
328 | /* The server responds with failure if it doesn't admit our | |
329 | .rhosts authentication or doesn't know our host key. */ | |
330 | if (type == SSH_SMSG_FAILURE) { | |
331 | debug("Server refused our rhosts authentication or host key."); | |
332 | return 0; | |
333 | } | |
334 | /* Otherwise, the server should respond with a challenge. */ | |
335 | if (type != SSH_SMSG_AUTH_RSA_CHALLENGE) | |
336 | packet_disconnect("Protocol error during RSA authentication: %d", type); | |
337 | ||
338 | /* Get the challenge from the packet. */ | |
339 | challenge = BN_new(); | |
340 | packet_get_bignum(challenge, &clen); | |
341 | ||
342 | packet_integrity_check(plen, clen, type); | |
343 | ||
344 | debug("Received RSA challenge for host key from server."); | |
345 | ||
346 | /* Compute a response to the challenge. */ | |
347 | respond_to_rsa_challenge(challenge, host_key); | |
348 | ||
349 | /* We no longer need the challenge. */ | |
350 | BN_clear_free(challenge); | |
351 | ||
352 | /* Wait for response from the server. */ | |
353 | type = packet_read(&plen); | |
354 | if (type == SSH_SMSG_SUCCESS) { | |
355 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server."); | |
356 | return 1; | |
357 | } | |
358 | if (type != SSH_SMSG_FAILURE) | |
359 | packet_disconnect("Protocol error waiting RSA auth response: %d", type); | |
360 | debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused."); | |
361 | return 0; | |
362 | } | |
363 | ||
364 | #ifdef KRB4 | |
365 | int | |
366 | try_kerberos_authentication() | |
367 | { | |
368 | KTEXT_ST auth; /* Kerberos data */ | |
369 | char *reply; | |
370 | char inst[INST_SZ]; | |
371 | char *realm; | |
372 | CREDENTIALS cred; | |
373 | int r, type, plen; | |
374 | socklen_t slen; | |
375 | Key_schedule schedule; | |
376 | u_long checksum, cksum; | |
377 | MSG_DAT msg_data; | |
378 | struct sockaddr_in local, foreign; | |
379 | struct stat st; | |
380 | ||
381 | /* Don't do anything if we don't have any tickets. */ | |
382 | if (stat(tkt_string(), &st) < 0) | |
383 | return 0; | |
384 | ||
385 | strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ); | |
386 | ||
387 | realm = (char *) krb_realmofhost(get_canonical_hostname()); | |
388 | if (!realm) { | |
389 | debug("Kerberos V4: no realm for %s", get_canonical_hostname()); | |
390 | return 0; | |
391 | } | |
392 | /* This can really be anything. */ | |
393 | checksum = (u_long) getpid(); | |
394 | ||
395 | r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum); | |
396 | if (r != KSUCCESS) { | |
397 | debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]); | |
398 | return 0; | |
399 | } | |
400 | /* Get session key to decrypt the server's reply with. */ | |
401 | r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred); | |
402 | if (r != KSUCCESS) { | |
403 | debug("get_cred failed: %s", krb_err_txt[r]); | |
404 | return 0; | |
405 | } | |
406 | des_key_sched((des_cblock *) cred.session, schedule); | |
407 | ||
408 | /* Send authentication info to server. */ | |
409 | packet_start(SSH_CMSG_AUTH_KERBEROS); | |
410 | packet_put_string((char *) auth.dat, auth.length); | |
411 | packet_send(); | |
412 | packet_write_wait(); | |
413 | ||
414 | /* Zero the buffer. */ | |
415 | (void) memset(auth.dat, 0, MAX_KTXT_LEN); | |
416 | ||
417 | slen = sizeof(local); | |
418 | memset(&local, 0, sizeof(local)); | |
419 | if (getsockname(packet_get_connection_in(), | |
420 | (struct sockaddr *) & local, &slen) < 0) | |
421 | debug("getsockname failed: %s", strerror(errno)); | |
422 | ||
423 | slen = sizeof(foreign); | |
424 | memset(&foreign, 0, sizeof(foreign)); | |
425 | if (getpeername(packet_get_connection_in(), | |
426 | (struct sockaddr *) & foreign, &slen) < 0) { | |
427 | debug("getpeername failed: %s", strerror(errno)); | |
428 | fatal_cleanup(); | |
429 | } | |
430 | /* Get server reply. */ | |
431 | type = packet_read(&plen); | |
432 | switch (type) { | |
433 | case SSH_SMSG_FAILURE: | |
434 | /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */ | |
435 | debug("Kerberos V4 authentication failed."); | |
436 | return 0; | |
437 | break; | |
438 | ||
439 | case SSH_SMSG_AUTH_KERBEROS_RESPONSE: | |
440 | /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */ | |
441 | debug("Kerberos V4 authentication accepted."); | |
442 | ||
443 | /* Get server's response. */ | |
444 | reply = packet_get_string((unsigned int *) &auth.length); | |
445 | memcpy(auth.dat, reply, auth.length); | |
446 | xfree(reply); | |
447 | ||
448 | packet_integrity_check(plen, 4 + auth.length, type); | |
449 | ||
450 | /* | |
451 | * If his response isn't properly encrypted with the session | |
452 | * key, and the decrypted checksum fails to match, he's | |
453 | * bogus. Bail out. | |
454 | */ | |
455 | r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session, | |
456 | &foreign, &local, &msg_data); | |
457 | if (r != KSUCCESS) { | |
458 | debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]); | |
459 | packet_disconnect("Kerberos V4 challenge failed!"); | |
460 | } | |
461 | /* Fetch the (incremented) checksum that we supplied in the request. */ | |
462 | (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum)); | |
463 | cksum = ntohl(cksum); | |
464 | ||
465 | /* If it matches, we're golden. */ | |
466 | if (cksum == checksum + 1) { | |
467 | debug("Kerberos V4 challenge successful."); | |
468 | return 1; | |
469 | } else | |
470 | packet_disconnect("Kerberos V4 challenge failed!"); | |
471 | break; | |
472 | ||
473 | default: | |
474 | packet_disconnect("Protocol error on Kerberos V4 response: %d", type); | |
475 | } | |
476 | return 0; | |
477 | } | |
478 | ||
479 | #endif /* KRB4 */ | |
480 | ||
481 | #ifdef AFS | |
482 | int | |
483 | send_kerberos_tgt() | |
484 | { | |
485 | CREDENTIALS *creds; | |
486 | char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ]; | |
487 | int r, type, plen; | |
488 | char buffer[8192]; | |
489 | struct stat st; | |
490 | ||
491 | /* Don't do anything if we don't have any tickets. */ | |
492 | if (stat(tkt_string(), &st) < 0) | |
493 | return 0; | |
494 | ||
495 | creds = xmalloc(sizeof(*creds)); | |
496 | ||
497 | if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) { | |
498 | debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]); | |
499 | return 0; | |
500 | } | |
501 | if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) { | |
502 | debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]); | |
503 | return 0; | |
504 | } | |
505 | if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) { | |
506 | debug("Kerberos V4 ticket expired: %s", TKT_FILE); | |
507 | return 0; | |
508 | } | |
1d1ffb87 | 509 | creds_to_radix(creds, (unsigned char *)buffer, sizeof buffer); |
a306f2dd | 510 | xfree(creds); |
511 | ||
512 | packet_start(SSH_CMSG_HAVE_KERBEROS_TGT); | |
513 | packet_put_string(buffer, strlen(buffer)); | |
514 | packet_send(); | |
515 | packet_write_wait(); | |
516 | ||
517 | type = packet_read(&plen); | |
518 | ||
519 | if (type == SSH_SMSG_FAILURE) | |
520 | debug("Kerberos TGT for realm %s rejected.", prealm); | |
521 | else if (type != SSH_SMSG_SUCCESS) | |
522 | packet_disconnect("Protocol error on Kerberos TGT response: %d", type); | |
523 | ||
524 | return 1; | |
525 | } | |
526 | ||
527 | void | |
528 | send_afs_tokens(void) | |
529 | { | |
530 | CREDENTIALS creds; | |
531 | struct ViceIoctl parms; | |
532 | struct ClearToken ct; | |
533 | int i, type, len, plen; | |
534 | char buf[2048], *p, *server_cell; | |
535 | char buffer[8192]; | |
536 | ||
537 | /* Move over ktc_GetToken, here's something leaner. */ | |
538 | for (i = 0; i < 100; i++) { /* just in case */ | |
539 | parms.in = (char *) &i; | |
540 | parms.in_size = sizeof(i); | |
541 | parms.out = buf; | |
542 | parms.out_size = sizeof(buf); | |
543 | if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0) | |
544 | break; | |
545 | p = buf; | |
546 | ||
547 | /* Get secret token. */ | |
548 | memcpy(&creds.ticket_st.length, p, sizeof(unsigned int)); | |
549 | if (creds.ticket_st.length > MAX_KTXT_LEN) | |
550 | break; | |
551 | p += sizeof(unsigned int); | |
552 | memcpy(creds.ticket_st.dat, p, creds.ticket_st.length); | |
553 | p += creds.ticket_st.length; | |
554 | ||
555 | /* Get clear token. */ | |
556 | memcpy(&len, p, sizeof(len)); | |
557 | if (len != sizeof(struct ClearToken)) | |
558 | break; | |
559 | p += sizeof(len); | |
560 | memcpy(&ct, p, len); | |
561 | p += len; | |
562 | p += sizeof(len); /* primary flag */ | |
563 | server_cell = p; | |
564 | ||
565 | /* Flesh out our credentials. */ | |
566 | strlcpy(creds.service, "afs", sizeof creds.service); | |
567 | creds.instance[0] = '\0'; | |
568 | strlcpy(creds.realm, server_cell, REALM_SZ); | |
569 | memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ); | |
570 | creds.issue_date = ct.BeginTimestamp; | |
571 | creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp); | |
572 | creds.kvno = ct.AuthHandle; | |
573 | snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId); | |
574 | creds.pinst[0] = '\0'; | |
575 | ||
576 | /* Encode token, ship it off. */ | |
1d1ffb87 | 577 | if (creds_to_radix(&creds, (unsigned char*) buffer, sizeof buffer) <= 0) |
a306f2dd | 578 | break; |
579 | packet_start(SSH_CMSG_HAVE_AFS_TOKEN); | |
580 | packet_put_string(buffer, strlen(buffer)); | |
581 | packet_send(); | |
582 | packet_write_wait(); | |
583 | ||
584 | /* Roger, Roger. Clearance, Clarence. What's your vector, | |
585 | Victor? */ | |
586 | type = packet_read(&plen); | |
587 | ||
588 | if (type == SSH_SMSG_FAILURE) | |
589 | debug("AFS token for cell %s rejected.", server_cell); | |
590 | else if (type != SSH_SMSG_SUCCESS) | |
591 | packet_disconnect("Protocol error on AFS token response: %d", type); | |
592 | } | |
593 | } | |
594 | ||
595 | #endif /* AFS */ | |
596 | ||
597 | /* | |
598 | * Tries to authenticate with any string-based challenge/response system. | |
599 | * Note that the client code is not tied to s/key or TIS. | |
600 | */ | |
601 | int | |
602 | try_skey_authentication() | |
603 | { | |
604 | int type, i; | |
605 | int payload_len; | |
606 | unsigned int clen; | |
e3a70753 | 607 | char prompt[1024]; |
a306f2dd | 608 | char *challenge, *response; |
609 | ||
610 | debug("Doing skey authentication."); | |
611 | ||
a306f2dd | 612 | for (i = 0; i < options.number_of_password_prompts; i++) { |
e3a70753 | 613 | /* request a challenge */ |
614 | packet_start(SSH_CMSG_AUTH_TIS); | |
615 | packet_send(); | |
616 | packet_write_wait(); | |
617 | ||
618 | type = packet_read(&payload_len); | |
619 | if (type != SSH_SMSG_FAILURE && | |
620 | type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
621 | packet_disconnect("Protocol error: got %d in response " | |
622 | "to skey-auth", type); | |
623 | } | |
624 | if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) { | |
625 | debug("No challenge for skey authentication."); | |
626 | return 0; | |
627 | } | |
628 | challenge = packet_get_string(&clen); | |
629 | packet_integrity_check(payload_len, (4 + clen), type); | |
630 | snprintf(prompt, sizeof prompt, "%s\nResponse: ", challenge); | |
631 | xfree(challenge); | |
a306f2dd | 632 | if (i != 0) |
633 | error("Permission denied, please try again."); | |
e3a70753 | 634 | if (options.cipher == SSH_CIPHER_NONE) |
635 | log("WARNING: Encryption is disabled! " | |
636 | "Reponse will be transmitted in clear text."); | |
637 | response = read_passphrase(prompt, 0); | |
638 | if (strcmp(response, "") == 0) { | |
639 | xfree(response); | |
640 | break; | |
641 | } | |
a306f2dd | 642 | packet_start(SSH_CMSG_AUTH_TIS_RESPONSE); |
643 | packet_put_string(response, strlen(response)); | |
644 | memset(response, 0, strlen(response)); | |
645 | xfree(response); | |
646 | packet_send(); | |
647 | packet_write_wait(); | |
648 | type = packet_read(&payload_len); | |
649 | if (type == SSH_SMSG_SUCCESS) | |
650 | return 1; | |
651 | if (type != SSH_SMSG_FAILURE) | |
652 | packet_disconnect("Protocol error: got %d in response " | |
e3a70753 | 653 | "to skey-auth-reponse", type); |
a306f2dd | 654 | } |
655 | /* failure */ | |
656 | return 0; | |
657 | } | |
658 | ||
659 | /* | |
660 | * Tries to authenticate with plain passwd authentication. | |
661 | */ | |
662 | int | |
663 | try_password_authentication(char *prompt) | |
664 | { | |
665 | int type, i, payload_len; | |
666 | char *password; | |
667 | ||
668 | debug("Doing password authentication."); | |
669 | if (options.cipher == SSH_CIPHER_NONE) | |
670 | log("WARNING: Encryption is disabled! Password will be transmitted in clear text."); | |
671 | for (i = 0; i < options.number_of_password_prompts; i++) { | |
672 | if (i != 0) | |
673 | error("Permission denied, please try again."); | |
674 | password = read_passphrase(prompt, 0); | |
675 | packet_start(SSH_CMSG_AUTH_PASSWORD); | |
676 | packet_put_string(password, strlen(password)); | |
677 | memset(password, 0, strlen(password)); | |
678 | xfree(password); | |
679 | packet_send(); | |
680 | packet_write_wait(); | |
681 | ||
682 | type = packet_read(&payload_len); | |
683 | if (type == SSH_SMSG_SUCCESS) | |
684 | return 1; | |
685 | if (type != SSH_SMSG_FAILURE) | |
686 | packet_disconnect("Protocol error: got %d in response to passwd auth", type); | |
687 | } | |
688 | /* failure */ | |
689 | return 0; | |
690 | } | |
691 | ||
692 | /* | |
693 | * SSH1 key exchange | |
694 | */ | |
695 | void | |
696 | ssh_kex(char *host, struct sockaddr *hostaddr) | |
697 | { | |
698 | int i; | |
699 | BIGNUM *key; | |
700 | RSA *host_key; | |
701 | RSA *public_key; | |
702 | Key k; | |
703 | int bits, rbits; | |
704 | int ssh_cipher_default = SSH_CIPHER_3DES; | |
705 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
706 | unsigned char cookie[8]; | |
707 | unsigned int supported_ciphers; | |
708 | unsigned int server_flags, client_flags; | |
709 | int payload_len, clen, sum_len = 0; | |
710 | u_int32_t rand = 0; | |
711 | ||
712 | debug("Waiting for server public key."); | |
713 | ||
714 | /* Wait for a public key packet from the server. */ | |
715 | packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY); | |
716 | ||
717 | /* Get cookie from the packet. */ | |
718 | for (i = 0; i < 8; i++) | |
719 | cookie[i] = packet_get_char(); | |
720 | ||
721 | /* Get the public key. */ | |
722 | public_key = RSA_new(); | |
723 | bits = packet_get_int();/* bits */ | |
724 | public_key->e = BN_new(); | |
725 | packet_get_bignum(public_key->e, &clen); | |
726 | sum_len += clen; | |
727 | public_key->n = BN_new(); | |
728 | packet_get_bignum(public_key->n, &clen); | |
729 | sum_len += clen; | |
730 | ||
731 | rbits = BN_num_bits(public_key->n); | |
732 | if (bits != rbits) { | |
733 | log("Warning: Server lies about size of server public key: " | |
734 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
735 | log("Warning: This may be due to an old implementation of ssh."); | |
736 | } | |
737 | /* Get the host key. */ | |
738 | host_key = RSA_new(); | |
739 | bits = packet_get_int();/* bits */ | |
740 | host_key->e = BN_new(); | |
741 | packet_get_bignum(host_key->e, &clen); | |
742 | sum_len += clen; | |
743 | host_key->n = BN_new(); | |
744 | packet_get_bignum(host_key->n, &clen); | |
745 | sum_len += clen; | |
746 | ||
747 | rbits = BN_num_bits(host_key->n); | |
748 | if (bits != rbits) { | |
749 | log("Warning: Server lies about size of server host key: " | |
750 | "actual size is %d bits vs. announced %d.", rbits, bits); | |
751 | log("Warning: This may be due to an old implementation of ssh."); | |
752 | } | |
753 | ||
754 | /* Get protocol flags. */ | |
755 | server_flags = packet_get_int(); | |
756 | packet_set_protocol_flags(server_flags); | |
757 | ||
758 | supported_ciphers = packet_get_int(); | |
759 | supported_authentications = packet_get_int(); | |
760 | ||
761 | debug("Received server public key (%d bits) and host key (%d bits).", | |
762 | BN_num_bits(public_key->n), BN_num_bits(host_key->n)); | |
763 | ||
764 | packet_integrity_check(payload_len, | |
765 | 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4, | |
766 | SSH_SMSG_PUBLIC_KEY); | |
fa08c86b | 767 | k.type = KEY_RSA1; |
a306f2dd | 768 | k.rsa = host_key; |
769 | check_host_key(host, hostaddr, &k, | |
770 | options.user_hostfile, options.system_hostfile); | |
771 | ||
772 | client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN; | |
773 | ||
774 | compute_session_id(session_id, cookie, host_key->n, public_key->n); | |
775 | ||
776 | /* Generate a session key. */ | |
777 | arc4random_stir(); | |
778 | ||
779 | /* | |
780 | * Generate an encryption key for the session. The key is a 256 bit | |
781 | * random number, interpreted as a 32-byte key, with the least | |
782 | * significant 8 bits being the first byte of the key. | |
783 | */ | |
784 | for (i = 0; i < 32; i++) { | |
785 | if (i % 4 == 0) | |
786 | rand = arc4random(); | |
787 | session_key[i] = rand & 0xff; | |
788 | rand >>= 8; | |
789 | } | |
790 | ||
791 | /* | |
792 | * According to the protocol spec, the first byte of the session key | |
793 | * is the highest byte of the integer. The session key is xored with | |
794 | * the first 16 bytes of the session id. | |
795 | */ | |
796 | key = BN_new(); | |
797 | BN_set_word(key, 0); | |
798 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
799 | BN_lshift(key, key, 8); | |
800 | if (i < 16) | |
801 | BN_add_word(key, session_key[i] ^ session_id[i]); | |
802 | else | |
803 | BN_add_word(key, session_key[i]); | |
804 | } | |
805 | ||
806 | /* | |
807 | * Encrypt the integer using the public key and host key of the | |
808 | * server (key with smaller modulus first). | |
809 | */ | |
810 | if (BN_cmp(public_key->n, host_key->n) < 0) { | |
811 | /* Public key has smaller modulus. */ | |
812 | if (BN_num_bits(host_key->n) < | |
813 | BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) { | |
814 | fatal("respond_to_rsa_challenge: host_key %d < public_key %d + " | |
815 | "SSH_KEY_BITS_RESERVED %d", | |
816 | BN_num_bits(host_key->n), | |
817 | BN_num_bits(public_key->n), | |
818 | SSH_KEY_BITS_RESERVED); | |
819 | } | |
820 | rsa_public_encrypt(key, key, public_key); | |
821 | rsa_public_encrypt(key, key, host_key); | |
822 | } else { | |
823 | /* Host key has smaller modulus (or they are equal). */ | |
824 | if (BN_num_bits(public_key->n) < | |
825 | BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) { | |
826 | fatal("respond_to_rsa_challenge: public_key %d < host_key %d + " | |
827 | "SSH_KEY_BITS_RESERVED %d", | |
828 | BN_num_bits(public_key->n), | |
829 | BN_num_bits(host_key->n), | |
830 | SSH_KEY_BITS_RESERVED); | |
831 | } | |
832 | rsa_public_encrypt(key, key, host_key); | |
833 | rsa_public_encrypt(key, key, public_key); | |
834 | } | |
835 | ||
836 | /* Destroy the public keys since we no longer need them. */ | |
837 | RSA_free(public_key); | |
838 | RSA_free(host_key); | |
839 | ||
c523303b | 840 | if (options.cipher == SSH_CIPHER_NOT_SET) { |
841 | if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default)) | |
842 | options.cipher = ssh_cipher_default; | |
843 | } else if (options.cipher == SSH_CIPHER_ILLEGAL || | |
844 | !(cipher_mask_ssh1(1) & (1 << options.cipher))) { | |
d0c832f3 | 845 | log("No valid SSH1 cipher, using %.100s instead.", |
94ec8c6b | 846 | cipher_name(ssh_cipher_default)); |
847 | options.cipher = ssh_cipher_default; | |
a306f2dd | 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++) | |
fa08c86b | 1002 | if (options.identity_files_type[i] == KEY_RSA1 && |
1003 | try_rsa_authentication(options.identity_files[i])) | |
a306f2dd | 1004 | return; |
1005 | } | |
1006 | /* Try skey authentication if the server supports it. */ | |
1007 | if ((supported_authentications & (1 << SSH_AUTH_TIS)) && | |
1008 | options.skey_authentication && !options.batch_mode) { | |
1009 | if (try_skey_authentication()) | |
1010 | return; | |
1011 | } | |
1012 | /* Try password authentication if the server supports it. */ | |
1013 | if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) && | |
1014 | options.password_authentication && !options.batch_mode) { | |
1015 | char prompt[80]; | |
1016 | ||
1017 | snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ", | |
1018 | server_user, host); | |
1019 | if (try_password_authentication(prompt)) | |
1020 | return; | |
1021 | } | |
1022 | /* All authentication methods have failed. Exit with an error message. */ | |
1023 | fatal("Permission denied."); | |
1024 | /* NOTREACHED */ | |
1025 | } |