1 /*
2 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3 * All rights reserved
4 *
5 * As far as I am concerned, the code I have written for this software
6 * can be used freely for any purpose. Any derived versions of this
7 * software must be clearly marked as such, and if the derived work is
8 * incompatible with the protocol description in the RFC file, it must be
9 * called by a name other than "ssh" or "Secure Shell".
10 */
11 /*
12 * Copyright 2008 Sun Microsystems, Inc. All rights reserved.
13 * Use is subject to license terms.
14 */
15
16 #include "includes.h"
17 RCSID("$OpenBSD: auth1.c,v 1.44 2002/09/26 11:38:43 markus Exp $");
18
19 #include "xmalloc.h"
20 #include "rsa.h"
21 #include "ssh1.h"
22 #include "packet.h"
23 #include "buffer.h"
24 #include "mpaux.h"
25 #include "log.h"
26 #include "servconf.h"
27 #include "compat.h"
28 #include "auth.h"
29 #include "channels.h"
30 #include "session.h"
31 #include "uidswap.h"
32
33 #ifdef HAVE_BSM
34 #include "bsmaudit.h"
35 extern adt_session_data_t *ah;
36 #endif /* HAVE_BSM */
37
38 /* import */
39 extern ServerOptions options;
40
41 /*
42 * convert ssh auth msg type into description
43 */
44 static char *
45 get_authname(int type)
46 {
47 static char buf[1024];
48 switch (type) {
49 case SSH_CMSG_AUTH_PASSWORD:
50 return "password";
51 case SSH_CMSG_AUTH_RSA:
52 return "rsa";
53 case SSH_CMSG_AUTH_RHOSTS_RSA:
54 return "rhosts-rsa";
55 case SSH_CMSG_AUTH_RHOSTS:
56 return "rhosts";
57 case SSH_CMSG_AUTH_TIS:
58 case SSH_CMSG_AUTH_TIS_RESPONSE:
59 return "challenge-response";
60 #if defined(KRB4) || defined(KRB5)
61 case SSH_CMSG_AUTH_KERBEROS:
62 return "kerberos";
63 #endif
64 }
65 snprintf(buf, sizeof buf, "bad-auth-msg-%d", type);
66 return buf;
67 }
68
69 /*
70 * read packets, try to authenticate the user and
71 * return only if authentication is successful
72 */
73 static void
74 do_authloop(Authctxt *authctxt)
75 {
76 int authenticated = 0;
77 u_int bits;
78 Key *client_host_key;
79 BIGNUM *n;
80 char *client_user, *password;
81 char info[1024];
82 u_int dlen;
83 u_int ulen;
84 int type = 0;
85 struct passwd *pw = authctxt->pw;
86
87 debug("Attempting authentication for %s%.100s.",
88 authctxt->valid ? "" : "illegal user ", authctxt->user);
89
90 /* If the user has no password, accept authentication immediately. */
91 if (options.password_authentication &&
92 #if defined(KRB4) || defined(KRB5)
93 (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
94 #endif
95 auth_password(authctxt, "")) {
96 auth_log(authctxt, 1, "without authentication", "");
97 return;
98 }
99
100 /* Indicate that authentication is needed. */
101 packet_start(SSH_SMSG_FAILURE);
102 packet_send();
103 packet_write_wait();
104
105 client_user = NULL;
106
107 for ( ;; ) {
108 /* default to fail */
109 authenticated = 0;
110
111 info[0] = '\0';
112
113 /* Get a packet from the client. */
114 authctxt->v1_auth_type = type = packet_read();
115 authctxt->v1_auth_name = get_authname(type);
116
117 authctxt->attempt++;
118
119 /* Process the packet. */
120 switch (type) {
121
122 #if defined(KRB4) || defined(KRB5)
123 case SSH_CMSG_AUTH_KERBEROS:
124 if (!options.kerberos_authentication) {
125 verbose("Kerberos authentication disabled.");
126 } else {
127 char *kdata = packet_get_string(&dlen);
128 packet_check_eom();
129
130 if (kdata[0] == 4) { /* KRB_PROT_VERSION */
131 #ifdef KRB4
132 KTEXT_ST tkt, reply;
133 tkt.length = dlen;
134 if (tkt.length < MAX_KTXT_LEN)
135 memcpy(tkt.dat, kdata, tkt.length);
136
137 if (auth_krb4(authctxt, &tkt,
138 &client_user, &reply)) {
139 authenticated = 1;
140 snprintf(info, sizeof(info),
141 " tktuser %.100s",
142 client_user);
143
144 packet_start(
145 SSH_SMSG_AUTH_KERBEROS_RESPONSE);
146 packet_put_string((char *)
147 reply.dat, reply.length);
148 packet_send();
149 packet_write_wait();
150 }
151 #endif /* KRB4 */
152 } else {
153 #ifdef KRB5
154 krb5_data tkt, reply;
155 tkt.length = dlen;
156 tkt.data = kdata;
157
158 if (auth_krb5(authctxt, &tkt,
159 &client_user, &reply)) {
160 authenticated = 1;
161 snprintf(info, sizeof(info),
162 " tktuser %.100s",
163 client_user);
164
165 /* Send response to client */
166 packet_start(
167 SSH_SMSG_AUTH_KERBEROS_RESPONSE);
168 packet_put_string((char *)
169 reply.data, reply.length);
170 packet_send();
171 packet_write_wait();
172
173 if (reply.length)
174 xfree(reply.data);
175 }
176 #endif /* KRB5 */
177 }
178 xfree(kdata);
179 }
180 break;
181 #endif /* KRB4 || KRB5 */
182
183 #if defined(AFS) || defined(KRB5)
184 /* XXX - punt on backward compatibility here. */
185 case SSH_CMSG_HAVE_KERBEROS_TGT:
186 packet_send_debug("Kerberos TGT passing disabled before authentication.");
187 break;
188 #ifdef AFS
189 case SSH_CMSG_HAVE_AFS_TOKEN:
190 packet_send_debug("AFS token passing disabled before authentication.");
191 break;
192 #endif /* AFS */
193 #endif /* AFS || KRB5 */
194
195 case SSH_CMSG_AUTH_RHOSTS:
196 if (!options.rhosts_authentication) {
197 verbose("Rhosts authentication disabled.");
198 break;
199 }
200 /*
201 * Get client user name. Note that we just have to
202 * trust the client; this is one reason why rhosts
203 * authentication is insecure. (Another is
204 * IP-spoofing on a local network.)
205 */
206 client_user = packet_get_string(&ulen);
207 packet_check_eom();
208
209 /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
210 authenticated = auth_rhosts(pw, client_user);
211
212 snprintf(info, sizeof info, " ruser %.100s", client_user);
213 break;
214
215 case SSH_CMSG_AUTH_RHOSTS_RSA:
216 if (!options.rhosts_rsa_authentication) {
217 verbose("Rhosts with RSA authentication disabled.");
218 break;
219 }
220 /*
221 * Get client user name. Note that we just have to
222 * trust the client; root on the client machine can
223 * claim to be any user.
224 */
225 client_user = packet_get_string(&ulen);
226
227 /* Get the client host key. */
228 client_host_key = key_new(KEY_RSA1);
229 bits = packet_get_int();
230 packet_get_bignum(client_host_key->rsa->e);
231 packet_get_bignum(client_host_key->rsa->n);
232
233 if (bits != BN_num_bits(client_host_key->rsa->n))
234 verbose("Warning: keysize mismatch for client_host_key: "
235 "actual %d, announced %d",
236 BN_num_bits(client_host_key->rsa->n), bits);
237 packet_check_eom();
238
239 authenticated = auth_rhosts_rsa(pw, client_user,
240 client_host_key);
241 key_free(client_host_key);
242
243 snprintf(info, sizeof info, " ruser %.100s", client_user);
244 break;
245
246 case SSH_CMSG_AUTH_RSA:
247 if (!options.rsa_authentication) {
248 verbose("RSA authentication disabled.");
249 break;
250 }
251 /* RSA authentication requested. */
252 if ((n = BN_new()) == NULL)
253 fatal("do_authloop: BN_new failed");
254 packet_get_bignum(n);
255 packet_check_eom();
256 authenticated = auth_rsa(pw, n);
257 BN_clear_free(n);
258 break;
259
260 case SSH_CMSG_AUTH_PASSWORD:
261 authctxt->init_attempt++;
262
263 if (!options.password_authentication) {
264 verbose("Password authentication disabled.");
265 break;
266 }
267 /*
268 * Read user password. It is in plain text, but was
269 * transmitted over the encrypted channel so it is
270 * not visible to an outside observer.
271 */
272 password = packet_get_string(&dlen);
273 packet_check_eom();
274
275 /* Try authentication with the password. */
276 if (authctxt->init_failures <
277 options.max_init_auth_tries)
278 authenticated =
279 auth_password(authctxt, password);
280
281 memset(password, 0, strlen(password));
282 xfree(password);
283 break;
284
285 case SSH_CMSG_AUTH_TIS:
286 debug("rcvd SSH_CMSG_AUTH_TIS");
287 if (options.challenge_response_authentication == 1) {
288 char *challenge = get_challenge(authctxt);
289 if (challenge != NULL) {
290 debug("sending challenge '%s'", challenge);
291 packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
292 packet_put_cstring(challenge);
293 xfree(challenge);
294 packet_send();
295 packet_write_wait();
296 continue;
297 }
298 }
299 break;
300 case SSH_CMSG_AUTH_TIS_RESPONSE:
301 debug("rcvd SSH_CMSG_AUTH_TIS_RESPONSE");
302 if (options.challenge_response_authentication == 1) {
303 char *response = packet_get_string(&dlen);
304 debug("got response '%s'", response);
305 packet_check_eom();
306 authenticated = verify_response(authctxt, response);
307 memset(response, 'r', dlen);
308 xfree(response);
309 }
310 break;
311
312 default:
313 /*
314 * Any unknown messages will be ignored (and failure
315 * returned) during authentication.
316 */
317 log("Unknown message during authentication: type %d", type);
318 break;
319 }
320 #ifdef BSD_AUTH
321 if (authctxt->as) {
322 auth_close(authctxt->as);
323 authctxt->as = NULL;
324 }
325 #endif
326 if (!authctxt->valid && authenticated) {
327 authenticated = 0;
328 log("Ignoring authenticated invalid user %s",
329 authctxt->user);
330 }
331
332 #ifdef _UNICOS
333 if (type == SSH_CMSG_AUTH_PASSWORD && !authenticated)
334 cray_login_failure(authctxt->user, IA_UDBERR);
335 if (authenticated && cray_access_denied(authctxt->user)) {
336 authenticated = 0;
337 fatal("Access denied for user %s.",authctxt->user);
338 }
339 #endif /* _UNICOS */
340
341 #ifdef HAVE_CYGWIN
342 if (authenticated &&
343 !check_nt_auth(type == SSH_CMSG_AUTH_PASSWORD, pw)) {
344 packet_disconnect("Authentication rejected for uid %d.",
345 pw == NULL ? -1 : pw->pw_uid);
346 authenticated = 0;
347 }
348 #else
349 /* Special handling for root */
350 if (authenticated && authctxt->pw->pw_uid == 0 &&
351 !auth_root_allowed(get_authname(type)))
352 authenticated = 0;
353 #endif
354 #ifdef USE_PAM
355 if (authenticated && type != SSH_CMSG_AUTH_PASSWORD)
356 authenticated = do_pam_non_initial_userauth(authctxt);
357 else if (authenticated && !AUTHPAM_DONE(authctxt))
358 authenticated = 0;
359
360 if (!authenticated)
361 authctxt->pam_retval = AUTHPAM_ERROR(authctxt,
362 PAM_PERM_DENIED);
363 #endif /* USE_PAM */
364
365 /* Log before sending the reply */
366 auth_log(authctxt, authenticated, get_authname(type), info);
367
368 if (client_user != NULL) {
369 xfree(client_user);
370 client_user = NULL;
371 }
372
373 if (authenticated)
374 return;
375
376 if (type == SSH_CMSG_AUTH_PASSWORD)
377 authctxt->init_failures++;
378
379 if (authctxt->failures++ > options.max_auth_tries) {
380 #ifdef HAVE_BSM
381 fatal_remove_cleanup(audit_failed_login_cleanup,
382 authctxt);
383 audit_sshd_login_failure(&ah, PAM_MAXTRIES,
384 authctxt->user);
385 #endif /* HAVE_BSM */
386 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
387 }
388
389 packet_start(SSH_SMSG_FAILURE);
390 packet_send();
391 packet_write_wait();
392 }
393 }
394
395 /*
396 * Performs authentication of an incoming connection. Session key has already
397 * been exchanged and encryption is enabled.
398 */
399 Authctxt *
400 do_authentication(void)
401 {
402 Authctxt *authctxt;
403 u_int ulen;
404 char *user, *style = NULL;
405
406 /* Get the name of the user that we wish to log in as. */
407 packet_read_expect(SSH_CMSG_USER);
408
409 /* Get the user name. */
410 user = packet_get_string(&ulen);
411 packet_check_eom();
412
413 if ((style = strchr(user, ':')) != NULL)
414 *style++ = '\0';
415
416 #ifdef KRB5
417 /* XXX - SSH.com Kerberos v5 braindeath. */
418 if ((datafellows & SSH_BUG_K5USER) &&
419 options.kerberos_authentication) {
420 char *p;
421 if ((p = strchr(user, '@')) != NULL)
422 *p = '\0';
423 }
424 #endif
425
426 authctxt = authctxt_new();
427 authctxt->user = user;
428 authctxt->style = style;
429
430 #ifdef HAVE_BSM
431 fatal_add_cleanup(audit_failed_login_cleanup, authctxt);
432 #endif /* HAVE_BSM */
433
434 /* Verify that the user is a valid user. */
435 if ((authctxt->pw = getpwnamallow(user)) != NULL) {
436 authctxt->valid = 1;
437 } else {
438 authctxt->valid = 0;
439 debug("do_authentication: illegal user %s", user);
440 }
441
442 setproctitle("%s", authctxt->pw ? user : "unknown");
443
444 /*
445 * If we are not running as root, the user must have the same uid as
446 * the server. (Unless you are running Windows)
447 */
448 #ifndef HAVE_CYGWIN
449 if (getuid() != 0 && authctxt->pw &&
450 authctxt->pw->pw_uid != getuid())
451 packet_disconnect("Cannot change user when server not running as root.");
452 #endif
453
454 /*
455 * Loop until the user has been authenticated or the connection is
456 * closed, do_authloop() returns only if authentication is successful
457 */
458 do_authloop(authctxt);
459
460 /* The user has been authenticated and accepted. */
461 packet_start(SSH_SMSG_SUCCESS);
462 packet_send();
463 packet_write_wait();
464
465 return (authctxt);
466 }