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1 | /* $OpenBSD: auth2.c,v 1.120 2008/11/04 08:22:12 djm Exp $ */ | |
2 | /* | |
3 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
8 | * 1. Redistributions of source code must retain the above copyright | |
9 | * notice, this list of conditions and the following disclaimer. | |
10 | * 2. Redistributions in binary form must reproduce the above copyright | |
11 | * notice, this list of conditions and the following disclaimer in the | |
12 | * documentation and/or other materials provided with the distribution. | |
13 | * | |
14 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
15 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
16 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
17 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
18 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
19 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
20 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
21 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
22 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
23 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
24 | */ | |
25 | ||
26 | #include "includes.h" | |
27 | ||
28 | #include <sys/types.h> | |
29 | #include <sys/stat.h> | |
30 | #include <sys/uio.h> | |
31 | ||
32 | #include <fcntl.h> | |
33 | #include <pwd.h> | |
34 | #include <stdarg.h> | |
35 | #include <string.h> | |
36 | #include <unistd.h> | |
37 | ||
38 | #include "xmalloc.h" | |
39 | #include "atomicio.h" | |
40 | #include "ssh2.h" | |
41 | #include "packet.h" | |
42 | #include "log.h" | |
43 | #include "buffer.h" | |
44 | #include "servconf.h" | |
45 | #include "compat.h" | |
46 | #include "key.h" | |
47 | #include "hostfile.h" | |
48 | #include "auth.h" | |
49 | #include "dispatch.h" | |
50 | #include "pathnames.h" | |
51 | #include "buffer.h" | |
52 | #include "canohost.h" | |
53 | ||
54 | #ifdef GSSAPI | |
55 | #include "ssh-gss.h" | |
56 | #endif | |
57 | #include "monitor_wrap.h" | |
58 | ||
59 | /* import */ | |
60 | extern ServerOptions options; | |
61 | extern u_char *session_id2; | |
62 | extern u_int session_id2_len; | |
63 | extern Buffer loginmsg; | |
64 | ||
65 | /* methods */ | |
66 | ||
67 | extern Authmethod method_none; | |
68 | extern Authmethod method_pubkey; | |
69 | extern Authmethod method_passwd; | |
70 | extern Authmethod method_kbdint; | |
71 | extern Authmethod method_hostbased; | |
72 | #ifdef GSSAPI | |
73 | extern Authmethod method_external; | |
74 | extern Authmethod method_gsskeyex; | |
75 | extern Authmethod method_gssapi; | |
76 | extern Authmethod method_gssapi_compat; | |
77 | #endif | |
78 | #ifdef JPAKE | |
79 | extern Authmethod method_jpake; | |
80 | #endif | |
81 | ||
82 | static int log_flag = 0; | |
83 | ||
84 | ||
85 | Authmethod *authmethods[] = { | |
86 | &method_none, | |
87 | &method_pubkey, | |
88 | #ifdef GSSAPI | |
89 | &method_gsskeyex, | |
90 | &method_external, | |
91 | &method_gssapi, | |
92 | &method_gssapi_compat, | |
93 | #endif | |
94 | #ifdef JPAKE | |
95 | &method_jpake, | |
96 | #endif | |
97 | &method_passwd, | |
98 | &method_kbdint, | |
99 | &method_hostbased, | |
100 | NULL | |
101 | }; | |
102 | ||
103 | /* protocol */ | |
104 | ||
105 | static void input_service_request(int, u_int32_t, void *); | |
106 | static void input_userauth_request(int, u_int32_t, void *); | |
107 | ||
108 | /* helper */ | |
109 | static Authmethod *authmethod_lookup(const char *); | |
110 | static char *authmethods_get(void); | |
111 | ||
112 | char * | |
113 | auth2_read_banner(void) | |
114 | { | |
115 | struct stat st; | |
116 | char *banner = NULL; | |
117 | size_t len, n; | |
118 | int fd; | |
119 | ||
120 | if ((fd = open(options.banner, O_RDONLY)) == -1) | |
121 | return (NULL); | |
122 | if (fstat(fd, &st) == -1) { | |
123 | close(fd); | |
124 | return (NULL); | |
125 | } | |
126 | if (st.st_size > 1*1024*1024) { | |
127 | close(fd); | |
128 | return (NULL); | |
129 | } | |
130 | ||
131 | len = (size_t)st.st_size; /* truncate */ | |
132 | banner = xmalloc(len + 1); | |
133 | n = atomicio(read, fd, banner, len); | |
134 | close(fd); | |
135 | ||
136 | if (n != len) { | |
137 | xfree(banner); | |
138 | return (NULL); | |
139 | } | |
140 | banner[n] = '\0'; | |
141 | ||
142 | return (banner); | |
143 | } | |
144 | ||
145 | void | |
146 | userauth_send_banner(const char *msg) | |
147 | { | |
148 | if (datafellows & SSH_BUG_BANNER) | |
149 | return; | |
150 | ||
151 | packet_start(SSH2_MSG_USERAUTH_BANNER); | |
152 | packet_put_cstring(msg); | |
153 | packet_put_cstring(""); /* language, unused */ | |
154 | packet_send(); | |
155 | debug("%s: sent", __func__); | |
156 | } | |
157 | ||
158 | static void | |
159 | userauth_banner(void) | |
160 | { | |
161 | char *banner = NULL; | |
162 | ||
163 | if (options.banner == NULL || | |
164 | strcasecmp(options.banner, "none") == 0 || | |
165 | (datafellows & SSH_BUG_BANNER) != 0) | |
166 | return; | |
167 | ||
168 | if ((banner = PRIVSEP(auth2_read_banner())) == NULL) | |
169 | goto done; | |
170 | userauth_send_banner(banner); | |
171 | ||
172 | done: | |
173 | if (banner) | |
174 | xfree(banner); | |
175 | } | |
176 | ||
177 | /* | |
178 | * loop until authctxt->success == TRUE | |
179 | */ | |
180 | void | |
181 | do_authentication2(Authctxt *authctxt) | |
182 | { | |
183 | dispatch_init(&dispatch_protocol_error); | |
184 | dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); | |
185 | dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); | |
186 | } | |
187 | ||
188 | /*ARGSUSED*/ | |
189 | static void | |
190 | input_service_request(int type, u_int32_t seq, void *ctxt) | |
191 | { | |
192 | Authctxt *authctxt = ctxt; | |
193 | u_int len; | |
194 | int acceptit = 0; | |
195 | char *service = packet_get_string(&len); | |
196 | packet_check_eom(); | |
197 | ||
198 | if (authctxt == NULL) | |
199 | fatal("input_service_request: no authctxt"); | |
200 | ||
201 | if (strcmp(service, "ssh-userauth") == 0) { | |
202 | if (!authctxt->success) { | |
203 | acceptit = 1; | |
204 | /* now we can handle user-auth requests */ | |
205 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); | |
206 | } | |
207 | } | |
208 | /* XXX all other service requests are denied */ | |
209 | ||
210 | if (acceptit) { | |
211 | packet_start(SSH2_MSG_SERVICE_ACCEPT); | |
212 | packet_put_cstring(service); | |
213 | packet_send(); | |
214 | packet_write_wait(); | |
215 | } else { | |
216 | debug("bad service request %s", service); | |
217 | packet_disconnect("bad service request %s", service); | |
218 | } | |
219 | xfree(service); | |
220 | } | |
221 | ||
222 | /*ARGSUSED*/ | |
223 | static void | |
224 | input_userauth_request(int type, u_int32_t seq, void *ctxt) | |
225 | { | |
226 | Authctxt *authctxt = ctxt; | |
227 | Authmethod *m = NULL; | |
228 | char *user, *service, *method, *style = NULL; | |
229 | int authenticated = 0; | |
230 | ||
231 | if (authctxt == NULL) | |
232 | fatal("input_userauth_request: no authctxt"); | |
233 | ||
234 | user = packet_get_string(NULL); | |
235 | service = packet_get_string(NULL); | |
236 | method = packet_get_string(NULL); | |
237 | ||
238 | #ifdef GSSAPI | |
239 | if (user[0] == '\0') { | |
240 | debug("received empty username for %s", method); | |
241 | if (strcmp(method, "external-keyx") == 0 || | |
242 | strcmp(method, "gssapi-keyex") == 0) { | |
243 | char *lname = NULL; | |
244 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
245 | if (lname && lname[0] != '\0') { | |
246 | xfree(user); | |
247 | user = lname; | |
248 | debug("set username to %s from gssapi context", user); | |
249 | } else { | |
250 | debug("failed to set username from gssapi context"); | |
251 | packet_send_debug("failed to set username from gssapi context"); | |
252 | } | |
253 | } | |
254 | } | |
255 | #endif | |
256 | ||
257 | debug("userauth-request for user %s service %s method %s", | |
258 | user[0] ? user : "<implicit>", service, method); | |
259 | if (!log_flag) { | |
260 | logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s", | |
261 | get_remote_ipaddr(), get_remote_port(), | |
262 | user[0] ? user : "<implicit>"); | |
263 | log_flag = 1; | |
264 | } | |
265 | debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); | |
266 | ||
267 | if ((style = strchr(user, ':')) != NULL) | |
268 | *style++ = 0; | |
269 | ||
270 | /* If first time or username changed or empty username, | |
271 | setup/reset authentication context. */ | |
272 | if ((authctxt->attempt++ == 0) || | |
273 | (strcmp(user, authctxt->user) != 0) || | |
274 | (strcmp(user, "") == 0)) { | |
275 | if (authctxt->user) { | |
276 | xfree(authctxt->user); | |
277 | authctxt->user = NULL; | |
278 | } | |
279 | authctxt->valid = 0; | |
280 | authctxt->user = xstrdup(user); | |
281 | if (strcmp(service, "ssh-connection") != 0) { | |
282 | packet_disconnect("Unsupported service %s", service); | |
283 | } | |
284 | #ifdef GSSAPI | |
285 | /* If we're going to set the username based on the | |
286 | GSSAPI context later, then wait until then to | |
287 | verify it. Just put in placeholders for now. */ | |
288 | if ((strcmp(user, "") == 0) && | |
289 | ((strcmp(method, "gssapi") == 0) || | |
290 | (strcmp(method, "gssapi-with-mic") == 0))) { | |
291 | authctxt->pw = fakepw(); | |
292 | } else { | |
293 | #endif | |
294 | authctxt->pw = PRIVSEP(getpwnamallow(user)); | |
295 | if (authctxt->pw) { | |
296 | authctxt->valid = 1; | |
297 | debug2("input_userauth_request: setting up authctxt for %s", user); | |
298 | } else { | |
299 | logit("input_userauth_request: invalid user %s", user); | |
300 | authctxt->pw = fakepw(); | |
301 | #ifdef SSH_AUDIT_EVENTS | |
302 | PRIVSEP(audit_event(SSH_INVALID_USER)); | |
303 | #endif | |
304 | } | |
305 | #ifdef GSSAPI | |
306 | } /* endif for setting username based on GSSAPI context */ | |
307 | #endif | |
308 | #ifdef USE_PAM | |
309 | if (options.use_pam) | |
310 | PRIVSEP(start_pam(authctxt)); | |
311 | #endif | |
312 | setproctitle("%s%s", authctxt->valid ? user : "unknown", | |
313 | use_privsep ? " [net]" : ""); | |
314 | if (authctxt->attempt == 1) { | |
315 | authctxt->service = xstrdup(service); | |
316 | authctxt->style = style ? xstrdup(style) : NULL; | |
317 | if (use_privsep) | |
318 | mm_inform_authserv(service, style); | |
319 | userauth_banner(); | |
320 | } | |
321 | } | |
322 | if (strcmp(service, authctxt->service) != 0) { | |
323 | packet_disconnect("Change of service not allowed: " | |
324 | "(%s,%s) -> (%s,%s)", | |
325 | authctxt->user, authctxt->service, user, service); | |
326 | } | |
327 | /* reset state */ | |
328 | auth2_challenge_stop(authctxt); | |
329 | #ifdef JPAKE | |
330 | auth2_jpake_stop(authctxt); | |
331 | #endif | |
332 | ||
333 | #ifdef GSSAPI | |
334 | /* XXX move to auth2_gssapi_stop() */ | |
335 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
336 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
337 | #endif | |
338 | ||
339 | authctxt->postponed = 0; | |
340 | authctxt->server_caused_failure = 0; | |
341 | ||
342 | /* try to authenticate user */ | |
343 | m = authmethod_lookup(method); | |
344 | if (m != NULL && authctxt->failures < options.max_authtries) { | |
345 | debug2("input_userauth_request: try method %s", method); | |
346 | authenticated = m->userauth(authctxt); | |
347 | } | |
348 | userauth_finish(authctxt, authenticated, method); | |
349 | ||
350 | xfree(service); | |
351 | xfree(user); | |
352 | xfree(method); | |
353 | } | |
354 | ||
355 | void | |
356 | userauth_finish(Authctxt *authctxt, int authenticated, char *method) | |
357 | { | |
358 | char *methods; | |
359 | ||
360 | if (!authctxt->valid && authenticated) | |
361 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
362 | authctxt->user); | |
363 | ||
364 | /* Special handling for root */ | |
365 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
366 | !auth_root_allowed(method)) { | |
367 | authenticated = 0; | |
368 | #ifdef SSH_AUDIT_EVENTS | |
369 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
370 | #endif | |
371 | } | |
372 | ||
373 | #ifdef USE_PAM | |
374 | if (options.use_pam && authenticated) { | |
375 | if (!PRIVSEP(do_pam_account())) { | |
376 | /* if PAM returned a message, send it to the user */ | |
377 | if (buffer_len(&loginmsg) > 0) { | |
378 | buffer_append(&loginmsg, "\0", 1); | |
379 | userauth_send_banner(buffer_ptr(&loginmsg)); | |
380 | packet_write_wait(); | |
381 | } | |
382 | fatal("Access denied for user %s by PAM account " | |
383 | "configuration", authctxt->user); | |
384 | } | |
385 | } | |
386 | #endif | |
387 | ||
388 | #ifdef _UNICOS | |
389 | if (authenticated && cray_access_denied(authctxt->user)) { | |
390 | authenticated = 0; | |
391 | fatal("Access denied for user %s.",authctxt->user); | |
392 | } | |
393 | #endif /* _UNICOS */ | |
394 | ||
395 | /* Log before sending the reply */ | |
396 | auth_log(authctxt, authenticated, method, " ssh2"); | |
397 | ||
398 | if (authctxt->postponed) | |
399 | return; | |
400 | ||
401 | /* XXX todo: check if multiple auth methods are needed */ | |
402 | if (authenticated == 1) { | |
403 | /* turn off userauth */ | |
404 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); | |
405 | packet_start(SSH2_MSG_USERAUTH_SUCCESS); | |
406 | packet_send(); | |
407 | packet_write_wait(); | |
408 | /* now we can break out */ | |
409 | authctxt->success = 1; | |
410 | } else { | |
411 | /* Dont count server configuration issues against the client */ | |
412 | /* Allow initial try of "none" auth without failure penalty */ | |
413 | if (!authctxt->server_caused_failure && | |
414 | (authctxt->attempt > 1 || strcmp(method, "none") != 0)) | |
415 | authctxt->failures++; | |
416 | if (authctxt->failures >= options.max_authtries) { | |
417 | #ifdef SSH_AUDIT_EVENTS | |
418 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
419 | #endif | |
420 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
421 | } | |
422 | methods = authmethods_get(); | |
423 | packet_start(SSH2_MSG_USERAUTH_FAILURE); | |
424 | packet_put_cstring(methods); | |
425 | packet_put_char(0); /* XXX partial success, unused */ | |
426 | packet_send(); | |
427 | packet_write_wait(); | |
428 | xfree(methods); | |
429 | } | |
430 | } | |
431 | ||
432 | static char * | |
433 | authmethods_get(void) | |
434 | { | |
435 | Buffer b; | |
436 | char *list; | |
437 | int i; | |
438 | ||
439 | buffer_init(&b); | |
440 | for (i = 0; authmethods[i] != NULL; i++) { | |
441 | if (strcmp(authmethods[i]->name, "none") == 0) | |
442 | continue; | |
443 | if (authmethods[i]->enabled != NULL && | |
444 | *(authmethods[i]->enabled) != 0) { | |
445 | if (buffer_len(&b) > 0) | |
446 | buffer_append(&b, ",", 1); | |
447 | buffer_append(&b, authmethods[i]->name, | |
448 | strlen(authmethods[i]->name)); | |
449 | } | |
450 | } | |
451 | buffer_append(&b, "\0", 1); | |
452 | list = xstrdup(buffer_ptr(&b)); | |
453 | buffer_free(&b); | |
454 | return list; | |
455 | } | |
456 | ||
457 | static Authmethod * | |
458 | authmethod_lookup(const char *name) | |
459 | { | |
460 | int i; | |
461 | ||
462 | if (name != NULL) | |
463 | for (i = 0; authmethods[i] != NULL; i++) | |
464 | if (authmethods[i]->enabled != NULL && | |
465 | *(authmethods[i]->enabled) != 0 && | |
466 | strcmp(name, authmethods[i]->name) == 0) | |
467 | return authmethods[i]; | |
468 | debug2("Unrecognized authentication method name: %s", | |
469 | name ? name : "NULL"); | |
470 | return NULL; | |
471 | } | |
472 |