blob: 2bb4d5387d10426a1159531fa32a4554e4475f10 [file] [log] [blame]
Damien Millereba71ba2000-04-29 23:57:08 +10001/*
2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4 * All rights reserved
Damien Millereba71ba2000-04-29 23:57:08 +10005 * Code to connect to a remote host, and to perform the client side of the
6 * login (authentication) dialog.
7 *
Damien Millere4340be2000-09-16 13:29:08 +11008 * 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".
Damien Millereba71ba2000-04-29 23:57:08 +100013 */
14
15#include "includes.h"
Damien Millere4340be2000-09-16 13:29:08 +110016RCSID("$OpenBSD: sshconnect1.c,v 1.6 2000/09/07 20:27:54 deraadt Exp $");
Damien Millereba71ba2000-04-29 23:57:08 +100017
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"
Damien Millereba71ba2000-04-29 23:57:08 +100028#include "cipher.h"
29#include "mpaux.h"
30#include "uidswap.h"
31#include "readconf.h"
32#include "key.h"
Damien Miller994cf142000-07-21 10:19:44 +100033#include "authfd.h"
Damien Millereba71ba2000-04-29 23:57:08 +100034#include "sshconnect.h"
35#include "authfile.h"
36
37/* Session id for the current session. */
38unsigned char session_id[16];
39unsigned int supported_authentications = 0;
40
41extern Options options;
42extern char *__progname;
43
44/*
45 * Checks if the user has an authentication agent, and if so, tries to
46 * authenticate using the agent.
47 */
48int
49try_agent_authentication()
50{
Damien Millerad833b32000-08-23 10:46:23 +100051 int type;
Damien Millereba71ba2000-04-29 23:57:08 +100052 char *comment;
53 AuthenticationConnection *auth;
54 unsigned char response[16];
55 unsigned int i;
Damien Millerad833b32000-08-23 10:46:23 +100056 int plen, clen;
57 Key *key;
58 BIGNUM *challenge;
Damien Millereba71ba2000-04-29 23:57:08 +100059
60 /* Get connection to the agent. */
61 auth = ssh_get_authentication_connection();
62 if (!auth)
63 return 0;
64
Damien Millereba71ba2000-04-29 23:57:08 +100065 challenge = BN_new();
Damien Millerad833b32000-08-23 10:46:23 +100066 key = key_new(KEY_RSA);
Damien Millereba71ba2000-04-29 23:57:08 +100067
68 /* Loop through identities served by the agent. */
Damien Millerad833b32000-08-23 10:46:23 +100069 for (key = ssh_get_first_identity(auth, &comment, 1);
70 key != NULL;
71 key = ssh_get_next_identity(auth, &comment, 1)) {
Damien Millereba71ba2000-04-29 23:57:08 +100072
73 /* Try this identity. */
74 debug("Trying RSA authentication via agent with '%.100s'", comment);
75 xfree(comment);
76
77 /* Tell the server that we are willing to authenticate using this key. */
78 packet_start(SSH_CMSG_AUTH_RSA);
Damien Millerad833b32000-08-23 10:46:23 +100079 packet_put_bignum(key->rsa->n);
Damien Millereba71ba2000-04-29 23:57:08 +100080 packet_send();
81 packet_write_wait();
82
83 /* Wait for server's response. */
84 type = packet_read(&plen);
85
86 /* The server sends failure if it doesn\'t like our key or
87 does not support RSA authentication. */
88 if (type == SSH_SMSG_FAILURE) {
89 debug("Server refused our key.");
Damien Millerad833b32000-08-23 10:46:23 +100090 key_free(key);
Damien Millereba71ba2000-04-29 23:57:08 +100091 continue;
92 }
93 /* Otherwise it should have sent a challenge. */
94 if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
95 packet_disconnect("Protocol error during RSA authentication: %d",
96 type);
97
98 packet_get_bignum(challenge, &clen);
99
100 packet_integrity_check(plen, clen, type);
101
102 debug("Received RSA challenge from server.");
103
104 /* Ask the agent to decrypt the challenge. */
Damien Millerad833b32000-08-23 10:46:23 +1000105 if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) {
106 /*
107 * The agent failed to authenticate this identifier
108 * although it advertised it supports this. Just
109 * return a wrong value.
110 */
Damien Millereba71ba2000-04-29 23:57:08 +1000111 log("Authentication agent failed to decrypt challenge.");
112 memset(response, 0, sizeof(response));
113 }
Damien Millerad833b32000-08-23 10:46:23 +1000114 key_free(key);
Damien Millereba71ba2000-04-29 23:57:08 +1000115 debug("Sending response to RSA challenge.");
116
117 /* Send the decrypted challenge back to the server. */
118 packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
119 for (i = 0; i < 16; i++)
120 packet_put_char(response[i]);
121 packet_send();
122 packet_write_wait();
123
124 /* Wait for response from the server. */
125 type = packet_read(&plen);
126
127 /* The server returns success if it accepted the authentication. */
128 if (type == SSH_SMSG_SUCCESS) {
Damien Millereba71ba2000-04-29 23:57:08 +1000129 BN_clear_free(challenge);
Damien Millerad833b32000-08-23 10:46:23 +1000130 debug("RSA authentication accepted by server.");
Damien Millereba71ba2000-04-29 23:57:08 +1000131 return 1;
132 }
133 /* Otherwise it should return failure. */
134 if (type != SSH_SMSG_FAILURE)
135 packet_disconnect("Protocol error waiting RSA auth response: %d",
136 type);
137 }
Damien Millereba71ba2000-04-29 23:57:08 +1000138 BN_clear_free(challenge);
Damien Millereba71ba2000-04-29 23:57:08 +1000139 debug("RSA authentication using agent refused.");
140 return 0;
141}
142
143/*
144 * Computes the proper response to a RSA challenge, and sends the response to
145 * the server.
146 */
147void
148respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
149{
150 unsigned char buf[32], response[16];
151 MD5_CTX md;
152 int i, len;
153
154 /* Decrypt the challenge using the private key. */
155 rsa_private_decrypt(challenge, challenge, prv);
156
157 /* Compute the response. */
158 /* The response is MD5 of decrypted challenge plus session id. */
159 len = BN_num_bytes(challenge);
160 if (len <= 0 || len > sizeof(buf))
161 packet_disconnect("respond_to_rsa_challenge: bad challenge length %d",
162 len);
163
164 memset(buf, 0, sizeof(buf));
165 BN_bn2bin(challenge, buf + sizeof(buf) - len);
166 MD5_Init(&md);
167 MD5_Update(&md, buf, 32);
168 MD5_Update(&md, session_id, 16);
169 MD5_Final(response, &md);
170
171 debug("Sending response to host key RSA challenge.");
172
173 /* Send the response back to the server. */
174 packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
175 for (i = 0; i < 16; i++)
176 packet_put_char(response[i]);
177 packet_send();
178 packet_write_wait();
179
180 memset(buf, 0, sizeof(buf));
181 memset(response, 0, sizeof(response));
182 memset(&md, 0, sizeof(md));
183}
184
185/*
186 * Checks if the user has authentication file, and if so, tries to authenticate
187 * the user using it.
188 */
189int
190try_rsa_authentication(const char *authfile)
191{
192 BIGNUM *challenge;
193 Key *public;
194 Key *private;
195 char *passphrase, *comment;
196 int type, i;
197 int plen, clen;
198
199 /* Try to load identification for the authentication key. */
200 public = key_new(KEY_RSA);
201 if (!load_public_key(authfile, public, &comment)) {
202 key_free(public);
203 /* Could not load it. Fail. */
204 return 0;
205 }
206 debug("Trying RSA authentication with key '%.100s'", comment);
207
208 /* Tell the server that we are willing to authenticate using this key. */
209 packet_start(SSH_CMSG_AUTH_RSA);
210 packet_put_bignum(public->rsa->n);
211 packet_send();
212 packet_write_wait();
213
214 /* We no longer need the public key. */
215 key_free(public);
216
217 /* Wait for server's response. */
218 type = packet_read(&plen);
219
220 /*
221 * The server responds with failure if it doesn\'t like our key or
222 * doesn\'t support RSA authentication.
223 */
224 if (type == SSH_SMSG_FAILURE) {
225 debug("Server refused our key.");
226 xfree(comment);
227 return 0;
228 }
229 /* Otherwise, the server should respond with a challenge. */
230 if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
231 packet_disconnect("Protocol error during RSA authentication: %d", type);
232
233 /* Get the challenge from the packet. */
234 challenge = BN_new();
235 packet_get_bignum(challenge, &clen);
236
237 packet_integrity_check(plen, clen, type);
238
239 debug("Received RSA challenge from server.");
240
241 private = key_new(KEY_RSA);
242 /*
243 * Load the private key. Try first with empty passphrase; if it
244 * fails, ask for a passphrase.
245 */
246 if (!load_private_key(authfile, "", private, NULL)) {
247 char buf[300];
248 snprintf(buf, sizeof buf, "Enter passphrase for RSA key '%.100s': ",
249 comment);
250 if (!options.batch_mode)
251 passphrase = read_passphrase(buf, 0);
252 else {
253 debug("Will not query passphrase for %.100s in batch mode.",
254 comment);
255 passphrase = xstrdup("");
256 }
257
258 /* Load the authentication file using the pasphrase. */
259 if (!load_private_key(authfile, passphrase, private, NULL)) {
260 memset(passphrase, 0, strlen(passphrase));
261 xfree(passphrase);
262 error("Bad passphrase.");
263
264 /* Send a dummy response packet to avoid protocol error. */
265 packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
266 for (i = 0; i < 16; i++)
267 packet_put_char(0);
268 packet_send();
269 packet_write_wait();
270
271 /* Expect the server to reject it... */
272 packet_read_expect(&plen, SSH_SMSG_FAILURE);
273 xfree(comment);
274 return 0;
275 }
276 /* Destroy the passphrase. */
277 memset(passphrase, 0, strlen(passphrase));
278 xfree(passphrase);
279 }
280 /* We no longer need the comment. */
281 xfree(comment);
282
283 /* Compute and send a response to the challenge. */
284 respond_to_rsa_challenge(challenge, private->rsa);
285
286 /* Destroy the private key. */
287 key_free(private);
288
289 /* We no longer need the challenge. */
290 BN_clear_free(challenge);
291
292 /* Wait for response from the server. */
293 type = packet_read(&plen);
294 if (type == SSH_SMSG_SUCCESS) {
295 debug("RSA authentication accepted by server.");
296 return 1;
297 }
298 if (type != SSH_SMSG_FAILURE)
299 packet_disconnect("Protocol error waiting RSA auth response: %d", type);
300 debug("RSA authentication refused.");
301 return 0;
302}
303
304/*
305 * Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
306 * authentication and RSA host authentication.
307 */
308int
309try_rhosts_rsa_authentication(const char *local_user, RSA * host_key)
310{
311 int type;
312 BIGNUM *challenge;
313 int plen, clen;
314
315 debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
316
317 /* Tell the server that we are willing to authenticate using this key. */
318 packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
319 packet_put_string(local_user, strlen(local_user));
320 packet_put_int(BN_num_bits(host_key->n));
321 packet_put_bignum(host_key->e);
322 packet_put_bignum(host_key->n);
323 packet_send();
324 packet_write_wait();
325
326 /* Wait for server's response. */
327 type = packet_read(&plen);
328
329 /* The server responds with failure if it doesn't admit our
330 .rhosts authentication or doesn't know our host key. */
331 if (type == SSH_SMSG_FAILURE) {
332 debug("Server refused our rhosts authentication or host key.");
333 return 0;
334 }
335 /* Otherwise, the server should respond with a challenge. */
336 if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
337 packet_disconnect("Protocol error during RSA authentication: %d", type);
338
339 /* Get the challenge from the packet. */
340 challenge = BN_new();
341 packet_get_bignum(challenge, &clen);
342
343 packet_integrity_check(plen, clen, type);
344
345 debug("Received RSA challenge for host key from server.");
346
347 /* Compute a response to the challenge. */
348 respond_to_rsa_challenge(challenge, host_key);
349
350 /* We no longer need the challenge. */
351 BN_clear_free(challenge);
352
353 /* Wait for response from the server. */
354 type = packet_read(&plen);
355 if (type == SSH_SMSG_SUCCESS) {
356 debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
357 return 1;
358 }
359 if (type != SSH_SMSG_FAILURE)
360 packet_disconnect("Protocol error waiting RSA auth response: %d", type);
361 debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
362 return 0;
363}
364
365#ifdef KRB4
366int
367try_kerberos_authentication()
368{
369 KTEXT_ST auth; /* Kerberos data */
370 char *reply;
371 char inst[INST_SZ];
372 char *realm;
373 CREDENTIALS cred;
374 int r, type, plen;
375 socklen_t slen;
376 Key_schedule schedule;
377 u_long checksum, cksum;
378 MSG_DAT msg_data;
379 struct sockaddr_in local, foreign;
380 struct stat st;
381
382 /* Don't do anything if we don't have any tickets. */
383 if (stat(tkt_string(), &st) < 0)
384 return 0;
385
386 strncpy(inst, (char *) krb_get_phost(get_canonical_hostname()), INST_SZ);
387
388 realm = (char *) krb_realmofhost(get_canonical_hostname());
389 if (!realm) {
390 debug("Kerberos V4: no realm for %s", get_canonical_hostname());
391 return 0;
392 }
393 /* This can really be anything. */
394 checksum = (u_long) getpid();
395
396 r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
397 if (r != KSUCCESS) {
398 debug("Kerberos V4 krb_mk_req failed: %s", krb_err_txt[r]);
399 return 0;
400 }
401 /* Get session key to decrypt the server's reply with. */
402 r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
403 if (r != KSUCCESS) {
404 debug("get_cred failed: %s", krb_err_txt[r]);
405 return 0;
406 }
407 des_key_sched((des_cblock *) cred.session, schedule);
408
409 /* Send authentication info to server. */
410 packet_start(SSH_CMSG_AUTH_KERBEROS);
411 packet_put_string((char *) auth.dat, auth.length);
412 packet_send();
413 packet_write_wait();
414
415 /* Zero the buffer. */
416 (void) memset(auth.dat, 0, MAX_KTXT_LEN);
417
418 slen = sizeof(local);
419 memset(&local, 0, sizeof(local));
420 if (getsockname(packet_get_connection_in(),
421 (struct sockaddr *) & local, &slen) < 0)
422 debug("getsockname failed: %s", strerror(errno));
423
424 slen = sizeof(foreign);
425 memset(&foreign, 0, sizeof(foreign));
426 if (getpeername(packet_get_connection_in(),
427 (struct sockaddr *) & foreign, &slen) < 0) {
428 debug("getpeername failed: %s", strerror(errno));
429 fatal_cleanup();
430 }
431 /* Get server reply. */
432 type = packet_read(&plen);
433 switch (type) {
434 case SSH_SMSG_FAILURE:
435 /* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
436 debug("Kerberos V4 authentication failed.");
437 return 0;
438 break;
439
440 case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
441 /* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
442 debug("Kerberos V4 authentication accepted.");
443
444 /* Get server's response. */
445 reply = packet_get_string((unsigned int *) &auth.length);
446 memcpy(auth.dat, reply, auth.length);
447 xfree(reply);
448
449 packet_integrity_check(plen, 4 + auth.length, type);
450
451 /*
452 * If his response isn't properly encrypted with the session
453 * key, and the decrypted checksum fails to match, he's
454 * bogus. Bail out.
455 */
456 r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
457 &foreign, &local, &msg_data);
458 if (r != KSUCCESS) {
459 debug("Kerberos V4 krb_rd_priv failed: %s", krb_err_txt[r]);
460 packet_disconnect("Kerberos V4 challenge failed!");
461 }
462 /* Fetch the (incremented) checksum that we supplied in the request. */
463 (void) memcpy((char *) &cksum, (char *) msg_data.app_data, sizeof(cksum));
464 cksum = ntohl(cksum);
465
466 /* If it matches, we're golden. */
467 if (cksum == checksum + 1) {
468 debug("Kerberos V4 challenge successful.");
469 return 1;
470 } else
471 packet_disconnect("Kerberos V4 challenge failed!");
472 break;
473
474 default:
475 packet_disconnect("Protocol error on Kerberos V4 response: %d", type);
476 }
477 return 0;
478}
479
480#endif /* KRB4 */
481
482#ifdef AFS
483int
484send_kerberos_tgt()
485{
486 CREDENTIALS *creds;
487 char pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
488 int r, type, plen;
489 char buffer[8192];
490 struct stat st;
491
492 /* Don't do anything if we don't have any tickets. */
493 if (stat(tkt_string(), &st) < 0)
494 return 0;
495
496 creds = xmalloc(sizeof(*creds));
497
498 if ((r = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm)) != KSUCCESS) {
499 debug("Kerberos V4 tf_fullname failed: %s", krb_err_txt[r]);
500 return 0;
501 }
502 if ((r = krb_get_cred("krbtgt", prealm, prealm, creds)) != GC_OK) {
503 debug("Kerberos V4 get_cred failed: %s", krb_err_txt[r]);
504 return 0;
505 }
506 if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
507 debug("Kerberos V4 ticket expired: %s", TKT_FILE);
508 return 0;
509 }
Damien Millere247cc42000-05-07 12:03:14 +1000510 creds_to_radix(creds, (unsigned char *)buffer, sizeof buffer);
Damien Millereba71ba2000-04-29 23:57:08 +1000511 xfree(creds);
512
513 packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
514 packet_put_string(buffer, strlen(buffer));
515 packet_send();
516 packet_write_wait();
517
518 type = packet_read(&plen);
519
520 if (type == SSH_SMSG_FAILURE)
521 debug("Kerberos TGT for realm %s rejected.", prealm);
522 else if (type != SSH_SMSG_SUCCESS)
523 packet_disconnect("Protocol error on Kerberos TGT response: %d", type);
524
525 return 1;
526}
527
528void
529send_afs_tokens(void)
530{
531 CREDENTIALS creds;
532 struct ViceIoctl parms;
533 struct ClearToken ct;
534 int i, type, len, plen;
535 char buf[2048], *p, *server_cell;
536 char buffer[8192];
537
538 /* Move over ktc_GetToken, here's something leaner. */
539 for (i = 0; i < 100; i++) { /* just in case */
540 parms.in = (char *) &i;
541 parms.in_size = sizeof(i);
542 parms.out = buf;
543 parms.out_size = sizeof(buf);
544 if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
545 break;
546 p = buf;
547
548 /* Get secret token. */
549 memcpy(&creds.ticket_st.length, p, sizeof(unsigned int));
550 if (creds.ticket_st.length > MAX_KTXT_LEN)
551 break;
552 p += sizeof(unsigned int);
553 memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
554 p += creds.ticket_st.length;
555
556 /* Get clear token. */
557 memcpy(&len, p, sizeof(len));
558 if (len != sizeof(struct ClearToken))
559 break;
560 p += sizeof(len);
561 memcpy(&ct, p, len);
562 p += len;
563 p += sizeof(len); /* primary flag */
564 server_cell = p;
565
566 /* Flesh out our credentials. */
567 strlcpy(creds.service, "afs", sizeof creds.service);
568 creds.instance[0] = '\0';
569 strlcpy(creds.realm, server_cell, REALM_SZ);
570 memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
571 creds.issue_date = ct.BeginTimestamp;
572 creds.lifetime = krb_time_to_life(creds.issue_date, ct.EndTimestamp);
573 creds.kvno = ct.AuthHandle;
574 snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
575 creds.pinst[0] = '\0';
576
577 /* Encode token, ship it off. */
Damien Millere247cc42000-05-07 12:03:14 +1000578 if (creds_to_radix(&creds, (unsigned char*) buffer, sizeof buffer) <= 0)
Damien Millereba71ba2000-04-29 23:57:08 +1000579 break;
580 packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
581 packet_put_string(buffer, strlen(buffer));
582 packet_send();
583 packet_write_wait();
584
585 /* Roger, Roger. Clearance, Clarence. What's your vector,
586 Victor? */
587 type = packet_read(&plen);
588
589 if (type == SSH_SMSG_FAILURE)
590 debug("AFS token for cell %s rejected.", server_cell);
591 else if (type != SSH_SMSG_SUCCESS)
592 packet_disconnect("Protocol error on AFS token response: %d", type);
593 }
594}
595
596#endif /* AFS */
597
598/*
599 * Tries to authenticate with any string-based challenge/response system.
600 * Note that the client code is not tied to s/key or TIS.
601 */
602int
603try_skey_authentication()
604{
605 int type, i;
606 int payload_len;
607 unsigned int clen;
608 char *challenge, *response;
609
610 debug("Doing skey authentication.");
611
612 /* request a challenge */
613 packet_start(SSH_CMSG_AUTH_TIS);
614 packet_send();
615 packet_write_wait();
616
617 type = packet_read(&payload_len);
618 if (type != SSH_SMSG_FAILURE &&
619 type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
620 packet_disconnect("Protocol error: got %d in response "
621 "to skey-auth", type);
622 }
623 if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
624 debug("No challenge for skey authentication.");
625 return 0;
626 }
627 challenge = packet_get_string(&clen);
628 packet_integrity_check(payload_len, (4 + clen), type);
629 if (options.cipher == SSH_CIPHER_NONE)
630 log("WARNING: Encryption is disabled! "
631 "Reponse will be transmitted in clear text.");
632 fprintf(stderr, "%s\n", challenge);
633 xfree(challenge);
634 fflush(stderr);
635 for (i = 0; i < options.number_of_password_prompts; i++) {
636 if (i != 0)
637 error("Permission denied, please try again.");
638 response = read_passphrase("Response: ", 0);
639 packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
640 packet_put_string(response, strlen(response));
641 memset(response, 0, strlen(response));
642 xfree(response);
643 packet_send();
644 packet_write_wait();
645 type = packet_read(&payload_len);
646 if (type == SSH_SMSG_SUCCESS)
647 return 1;
648 if (type != SSH_SMSG_FAILURE)
649 packet_disconnect("Protocol error: got %d in response "
650 "to skey-auth-reponse", type);
651 }
652 /* failure */
653 return 0;
654}
655
656/*
657 * Tries to authenticate with plain passwd authentication.
658 */
659int
660try_password_authentication(char *prompt)
661{
662 int type, i, payload_len;
663 char *password;
664
665 debug("Doing password authentication.");
666 if (options.cipher == SSH_CIPHER_NONE)
667 log("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
668 for (i = 0; i < options.number_of_password_prompts; i++) {
669 if (i != 0)
670 error("Permission denied, please try again.");
671 password = read_passphrase(prompt, 0);
672 packet_start(SSH_CMSG_AUTH_PASSWORD);
673 packet_put_string(password, strlen(password));
674 memset(password, 0, strlen(password));
675 xfree(password);
676 packet_send();
677 packet_write_wait();
678
679 type = packet_read(&payload_len);
680 if (type == SSH_SMSG_SUCCESS)
681 return 1;
682 if (type != SSH_SMSG_FAILURE)
683 packet_disconnect("Protocol error: got %d in response to passwd auth", type);
684 }
685 /* failure */
686 return 0;
687}
688
689/*
690 * SSH1 key exchange
691 */
692void
693ssh_kex(char *host, struct sockaddr *hostaddr)
694{
695 int i;
696 BIGNUM *key;
697 RSA *host_key;
698 RSA *public_key;
699 Key k;
700 int bits, rbits;
701 int ssh_cipher_default = SSH_CIPHER_3DES;
702 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
703 unsigned char cookie[8];
704 unsigned int supported_ciphers;
705 unsigned int server_flags, client_flags;
706 int payload_len, clen, sum_len = 0;
707 u_int32_t rand = 0;
708
709 debug("Waiting for server public key.");
710
711 /* Wait for a public key packet from the server. */
712 packet_read_expect(&payload_len, SSH_SMSG_PUBLIC_KEY);
713
714 /* Get cookie from the packet. */
715 for (i = 0; i < 8; i++)
716 cookie[i] = packet_get_char();
717
718 /* Get the public key. */
719 public_key = RSA_new();
720 bits = packet_get_int();/* bits */
721 public_key->e = BN_new();
722 packet_get_bignum(public_key->e, &clen);
723 sum_len += clen;
724 public_key->n = BN_new();
725 packet_get_bignum(public_key->n, &clen);
726 sum_len += clen;
727
728 rbits = BN_num_bits(public_key->n);
729 if (bits != rbits) {
730 log("Warning: Server lies about size of server public key: "
731 "actual size is %d bits vs. announced %d.", rbits, bits);
732 log("Warning: This may be due to an old implementation of ssh.");
733 }
734 /* Get the host key. */
735 host_key = RSA_new();
736 bits = packet_get_int();/* bits */
737 host_key->e = BN_new();
738 packet_get_bignum(host_key->e, &clen);
739 sum_len += clen;
740 host_key->n = BN_new();
741 packet_get_bignum(host_key->n, &clen);
742 sum_len += clen;
743
744 rbits = BN_num_bits(host_key->n);
745 if (bits != rbits) {
746 log("Warning: Server lies about size of server host key: "
747 "actual size is %d bits vs. announced %d.", rbits, bits);
748 log("Warning: This may be due to an old implementation of ssh.");
749 }
750
751 /* Get protocol flags. */
752 server_flags = packet_get_int();
753 packet_set_protocol_flags(server_flags);
754
755 supported_ciphers = packet_get_int();
756 supported_authentications = packet_get_int();
757
758 debug("Received server public key (%d bits) and host key (%d bits).",
759 BN_num_bits(public_key->n), BN_num_bits(host_key->n));
760
761 packet_integrity_check(payload_len,
762 8 + 4 + sum_len + 0 + 4 + 0 + 0 + 4 + 4 + 4,
763 SSH_SMSG_PUBLIC_KEY);
764 k.type = KEY_RSA;
765 k.rsa = host_key;
766 check_host_key(host, hostaddr, &k,
767 options.user_hostfile, options.system_hostfile);
768
769 client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
770
771 compute_session_id(session_id, cookie, host_key->n, public_key->n);
772
773 /* Generate a session key. */
774 arc4random_stir();
775
776 /*
777 * Generate an encryption key for the session. The key is a 256 bit
778 * random number, interpreted as a 32-byte key, with the least
779 * significant 8 bits being the first byte of the key.
780 */
781 for (i = 0; i < 32; i++) {
782 if (i % 4 == 0)
783 rand = arc4random();
784 session_key[i] = rand & 0xff;
785 rand >>= 8;
786 }
787
788 /*
789 * According to the protocol spec, the first byte of the session key
790 * is the highest byte of the integer. The session key is xored with
791 * the first 16 bytes of the session id.
792 */
793 key = BN_new();
794 BN_set_word(key, 0);
795 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
796 BN_lshift(key, key, 8);
797 if (i < 16)
798 BN_add_word(key, session_key[i] ^ session_id[i]);
799 else
800 BN_add_word(key, session_key[i]);
801 }
802
803 /*
804 * Encrypt the integer using the public key and host key of the
805 * server (key with smaller modulus first).
806 */
807 if (BN_cmp(public_key->n, host_key->n) < 0) {
808 /* Public key has smaller modulus. */
809 if (BN_num_bits(host_key->n) <
810 BN_num_bits(public_key->n) + SSH_KEY_BITS_RESERVED) {
811 fatal("respond_to_rsa_challenge: host_key %d < public_key %d + "
812 "SSH_KEY_BITS_RESERVED %d",
813 BN_num_bits(host_key->n),
814 BN_num_bits(public_key->n),
815 SSH_KEY_BITS_RESERVED);
816 }
817 rsa_public_encrypt(key, key, public_key);
818 rsa_public_encrypt(key, key, host_key);
819 } else {
820 /* Host key has smaller modulus (or they are equal). */
821 if (BN_num_bits(public_key->n) <
822 BN_num_bits(host_key->n) + SSH_KEY_BITS_RESERVED) {
823 fatal("respond_to_rsa_challenge: public_key %d < host_key %d + "
824 "SSH_KEY_BITS_RESERVED %d",
825 BN_num_bits(public_key->n),
826 BN_num_bits(host_key->n),
827 SSH_KEY_BITS_RESERVED);
828 }
829 rsa_public_encrypt(key, key, host_key);
830 rsa_public_encrypt(key, key, public_key);
831 }
832
833 /* Destroy the public keys since we no longer need them. */
834 RSA_free(public_key);
835 RSA_free(host_key);
836
Damien Miller30c3d422000-05-09 11:02:59 +1000837 if (options.cipher == SSH_CIPHER_ILLEGAL) {
838 log("No valid SSH1 cipher, using %.100s instead.",
839 cipher_name(SSH_FALLBACK_CIPHER));
840 options.cipher = SSH_FALLBACK_CIPHER;
841 } else if (options.cipher == SSH_CIPHER_NOT_SET) {
Damien Millereba71ba2000-04-29 23:57:08 +1000842 if (cipher_mask1() & supported_ciphers & (1 << ssh_cipher_default))
843 options.cipher = ssh_cipher_default;
844 else {
845 debug("Cipher %s not supported, using %.100s instead.",
Damien Miller30c3d422000-05-09 11:02:59 +1000846 cipher_name(ssh_cipher_default),
847 cipher_name(SSH_FALLBACK_CIPHER));
Damien Millereba71ba2000-04-29 23:57:08 +1000848 options.cipher = SSH_FALLBACK_CIPHER;
849 }
850 }
851 /* Check that the selected cipher is supported. */
852 if (!(supported_ciphers & (1 << options.cipher)))
853 fatal("Selected cipher type %.100s not supported by server.",
854 cipher_name(options.cipher));
855
856 debug("Encryption type: %.100s", cipher_name(options.cipher));
857
858 /* Send the encrypted session key to the server. */
859 packet_start(SSH_CMSG_SESSION_KEY);
860 packet_put_char(options.cipher);
861
862 /* Send the cookie back to the server. */
863 for (i = 0; i < 8; i++)
864 packet_put_char(cookie[i]);
865
866 /* Send and destroy the encrypted encryption key integer. */
867 packet_put_bignum(key);
868 BN_clear_free(key);
869
870 /* Send protocol flags. */
871 packet_put_int(client_flags);
872
873 /* Send the packet now. */
874 packet_send();
875 packet_write_wait();
876
877 debug("Sent encrypted session key.");
878
879 /* Set the encryption key. */
880 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
881
882 /* We will no longer need the session key here. Destroy any extra copies. */
883 memset(session_key, 0, sizeof(session_key));
884
885 /*
886 * Expect a success message from the server. Note that this message
887 * will be received in encrypted form.
888 */
889 packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
890
891 debug("Received encrypted confirmation.");
892}
893
894/*
895 * Authenticate user
896 */
897void
898ssh_userauth(
899 const char* local_user,
900 const char* server_user,
901 char *host,
902 int host_key_valid, RSA *own_host_key)
903{
904 int i, type;
905 int payload_len;
906
907 if (supported_authentications == 0)
908 fatal("ssh_userauth: server supports no auth methods");
909
910 /* Send the name of the user to log in as on the server. */
911 packet_start(SSH_CMSG_USER);
912 packet_put_string(server_user, strlen(server_user));
913 packet_send();
914 packet_write_wait();
915
916 /*
917 * The server should respond with success if no authentication is
918 * needed (the user has no password). Otherwise the server responds
919 * with failure.
920 */
921 type = packet_read(&payload_len);
922
923 /* check whether the connection was accepted without authentication. */
924 if (type == SSH_SMSG_SUCCESS)
925 return;
926 if (type != SSH_SMSG_FAILURE)
927 packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER",
928 type);
929
930#ifdef AFS
931 /* Try Kerberos tgt passing if the server supports it. */
932 if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
933 options.kerberos_tgt_passing) {
934 if (options.cipher == SSH_CIPHER_NONE)
935 log("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
936 (void) send_kerberos_tgt();
937 }
938 /* Try AFS token passing if the server supports it. */
939 if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
940 options.afs_token_passing && k_hasafs()) {
941 if (options.cipher == SSH_CIPHER_NONE)
942 log("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
943 send_afs_tokens();
944 }
945#endif /* AFS */
946
947#ifdef KRB4
948 if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
949 options.kerberos_authentication) {
950 debug("Trying Kerberos authentication.");
951 if (try_kerberos_authentication()) {
952 /* The server should respond with success or failure. */
953 type = packet_read(&payload_len);
954 if (type == SSH_SMSG_SUCCESS)
955 return;
956 if (type != SSH_SMSG_FAILURE)
957 packet_disconnect("Protocol error: got %d in response to Kerberos auth", type);
958 }
959 }
960#endif /* KRB4 */
961
962 /*
963 * Use rhosts authentication if running in privileged socket and we
964 * do not wish to remain anonymous.
965 */
966 if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
967 options.rhosts_authentication) {
968 debug("Trying rhosts authentication.");
969 packet_start(SSH_CMSG_AUTH_RHOSTS);
970 packet_put_string(local_user, strlen(local_user));
971 packet_send();
972 packet_write_wait();
973
974 /* The server should respond with success or failure. */
975 type = packet_read(&payload_len);
976 if (type == SSH_SMSG_SUCCESS)
977 return;
978 if (type != SSH_SMSG_FAILURE)
979 packet_disconnect("Protocol error: got %d in response to rhosts auth",
980 type);
981 }
982 /*
983 * Try .rhosts or /etc/hosts.equiv authentication with RSA host
984 * authentication.
985 */
986 if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
987 options.rhosts_rsa_authentication && host_key_valid) {
988 if (try_rhosts_rsa_authentication(local_user, own_host_key))
989 return;
990 }
991 /* Try RSA authentication if the server supports it. */
992 if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
993 options.rsa_authentication) {
994 /*
995 * Try RSA authentication using the authentication agent. The
996 * agent is tried first because no passphrase is needed for
997 * it, whereas identity files may require passphrases.
998 */
999 if (try_agent_authentication())
1000 return;
1001
1002 /* Try RSA authentication for each identity. */
1003 for (i = 0; i < options.num_identity_files; i++)
1004 if (try_rsa_authentication(options.identity_files[i]))
1005 return;
1006 }
1007 /* Try skey authentication if the server supports it. */
1008 if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
1009 options.skey_authentication && !options.batch_mode) {
1010 if (try_skey_authentication())
1011 return;
1012 }
1013 /* Try password authentication if the server supports it. */
1014 if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
1015 options.password_authentication && !options.batch_mode) {
1016 char prompt[80];
1017
1018 snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
1019 server_user, host);
1020 if (try_password_authentication(prompt))
1021 return;
1022 }
1023 /* All authentication methods have failed. Exit with an error message. */
1024 fatal("Permission denied.");
1025 /* NOTREACHED */
1026}