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1 | /* $OpenBSD: auth2.c,v 1.121 2009/06/22 05:39:28 dtucker 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 "atomicio.h" | |
39 | #include "xmalloc.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 | ||
53 | #ifdef GSSAPI | |
54 | #include "ssh-gss.h" | |
55 | #endif | |
56 | #include "monitor_wrap.h" | |
57 | ||
58 | /* import */ | |
59 | extern ServerOptions options; | |
60 | extern u_char *session_id2; | |
61 | extern u_int session_id2_len; | |
62 | extern Buffer loginmsg; | |
63 | ||
64 | /* methods */ | |
65 | ||
66 | extern Authmethod method_none; | |
67 | extern Authmethod method_pubkey; | |
68 | extern Authmethod method_passwd; | |
69 | extern Authmethod method_kbdint; | |
70 | extern Authmethod method_hostbased; | |
71 | #ifdef GSSAPI | |
72 | extern Authmethod method_gssapi; | |
73 | #endif | |
74 | #ifdef JPAKE | |
75 | extern Authmethod method_jpake; | |
76 | #endif | |
77 | ||
78 | Authmethod *authmethods[] = { | |
79 | &method_none, | |
80 | &method_pubkey, | |
81 | #ifdef GSSAPI | |
82 | &method_gssapi, | |
83 | #endif | |
84 | #ifdef JPAKE | |
85 | &method_jpake, | |
86 | #endif | |
87 | &method_passwd, | |
88 | &method_kbdint, | |
89 | &method_hostbased, | |
90 | NULL | |
91 | }; | |
92 | ||
93 | /* protocol */ | |
94 | ||
95 | static void input_service_request(int, u_int32_t, void *); | |
96 | static void input_userauth_request(int, u_int32_t, void *); | |
97 | ||
98 | /* helper */ | |
99 | static Authmethod *authmethod_lookup(const char *); | |
100 | static char *authmethods_get(void); | |
101 | ||
102 | char * | |
103 | auth2_read_banner(void) | |
104 | { | |
105 | struct stat st; | |
106 | char *banner = NULL; | |
107 | size_t len, n; | |
108 | int fd; | |
109 | ||
110 | if ((fd = open(options.banner, O_RDONLY)) == -1) | |
111 | return (NULL); | |
112 | if (fstat(fd, &st) == -1) { | |
113 | close(fd); | |
114 | return (NULL); | |
115 | } | |
116 | if (st.st_size > 1*1024*1024) { | |
117 | close(fd); | |
118 | return (NULL); | |
119 | } | |
120 | ||
121 | len = (size_t)st.st_size; /* truncate */ | |
122 | banner = xmalloc(len + 1); | |
123 | n = atomicio(read, fd, banner, len); | |
124 | close(fd); | |
125 | ||
126 | if (n != len) { | |
127 | xfree(banner); | |
128 | return (NULL); | |
129 | } | |
130 | banner[n] = '\0'; | |
131 | ||
132 | return (banner); | |
133 | } | |
134 | ||
135 | void | |
136 | userauth_send_banner(const char *msg) | |
137 | { | |
138 | if (datafellows & SSH_BUG_BANNER) | |
139 | return; | |
140 | ||
141 | packet_start(SSH2_MSG_USERAUTH_BANNER); | |
142 | packet_put_cstring(msg); | |
143 | packet_put_cstring(""); /* language, unused */ | |
144 | packet_send(); | |
145 | debug("%s: sent", __func__); | |
146 | } | |
147 | ||
148 | static void | |
149 | userauth_banner(void) | |
150 | { | |
151 | char *banner = NULL; | |
152 | ||
153 | if (options.banner == NULL || | |
154 | strcasecmp(options.banner, "none") == 0 || | |
155 | (datafellows & SSH_BUG_BANNER) != 0) | |
156 | return; | |
157 | ||
158 | if ((banner = PRIVSEP(auth2_read_banner())) == NULL) | |
159 | goto done; | |
160 | userauth_send_banner(banner); | |
161 | ||
162 | done: | |
163 | if (banner) | |
164 | xfree(banner); | |
165 | } | |
166 | ||
167 | /* | |
168 | * loop until authctxt->success == TRUE | |
169 | */ | |
170 | void | |
171 | do_authentication2(Authctxt *authctxt) | |
172 | { | |
173 | dispatch_init(&dispatch_protocol_error); | |
174 | dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); | |
175 | dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); | |
176 | } | |
177 | ||
178 | /*ARGSUSED*/ | |
179 | static void | |
180 | input_service_request(int type, u_int32_t seq, void *ctxt) | |
181 | { | |
182 | Authctxt *authctxt = ctxt; | |
183 | u_int len; | |
184 | int acceptit = 0; | |
185 | char *service = packet_get_string(&len); | |
186 | packet_check_eom(); | |
187 | ||
188 | if (authctxt == NULL) | |
189 | fatal("input_service_request: no authctxt"); | |
190 | ||
191 | if (strcmp(service, "ssh-userauth") == 0) { | |
192 | if (!authctxt->success) { | |
193 | acceptit = 1; | |
194 | /* now we can handle user-auth requests */ | |
195 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); | |
196 | } | |
197 | } | |
198 | /* XXX all other service requests are denied */ | |
199 | ||
200 | if (acceptit) { | |
201 | packet_start(SSH2_MSG_SERVICE_ACCEPT); | |
202 | packet_put_cstring(service); | |
203 | packet_send(); | |
204 | packet_write_wait(); | |
205 | } else { | |
206 | debug("bad service request %s", service); | |
207 | packet_disconnect("bad service request %s", service); | |
208 | } | |
209 | xfree(service); | |
210 | } | |
211 | ||
212 | /*ARGSUSED*/ | |
213 | static void | |
214 | input_userauth_request(int type, u_int32_t seq, void *ctxt) | |
215 | { | |
216 | Authctxt *authctxt = ctxt; | |
217 | Authmethod *m = NULL; | |
218 | char *user, *service, *method, *style = NULL; | |
219 | int authenticated = 0; | |
220 | ||
221 | if (authctxt == NULL) | |
222 | fatal("input_userauth_request: no authctxt"); | |
223 | ||
224 | user = packet_get_string(NULL); | |
225 | service = packet_get_string(NULL); | |
226 | method = packet_get_string(NULL); | |
227 | debug("userauth-request for user %s service %s method %s", user, service, method); | |
228 | debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); | |
229 | ||
230 | if ((style = strchr(user, ':')) != NULL) | |
231 | *style++ = 0; | |
232 | ||
233 | if (authctxt->attempt++ == 0) { | |
234 | /* setup auth context */ | |
235 | authctxt->pw = PRIVSEP(getpwnamallow(user)); | |
236 | authctxt->user = xstrdup(user); | |
237 | if (authctxt->pw && strcmp(service, "ssh-connection")==0) { | |
238 | authctxt->valid = 1; | |
239 | debug2("input_userauth_request: setting up authctxt for %s", user); | |
240 | } else { | |
241 | logit("input_userauth_request: invalid user %s", user); | |
242 | authctxt->pw = fakepw(); | |
243 | #ifdef SSH_AUDIT_EVENTS | |
244 | PRIVSEP(audit_event(SSH_INVALID_USER)); | |
245 | #endif | |
246 | } | |
247 | #ifdef USE_PAM | |
248 | if (options.use_pam) | |
249 | PRIVSEP(start_pam(authctxt)); | |
250 | #endif | |
251 | setproctitle("%s%s", authctxt->valid ? user : "unknown", | |
252 | use_privsep ? " [net]" : ""); | |
253 | authctxt->service = xstrdup(service); | |
254 | authctxt->style = style ? xstrdup(style) : NULL; | |
255 | if (use_privsep) | |
256 | mm_inform_authserv(service, style); | |
257 | userauth_banner(); | |
258 | } else if (strcmp(user, authctxt->user) != 0 || | |
259 | strcmp(service, authctxt->service) != 0) { | |
260 | packet_disconnect("Change of username or service not allowed: " | |
261 | "(%s,%s) -> (%s,%s)", | |
262 | authctxt->user, authctxt->service, user, service); | |
263 | } | |
264 | /* reset state */ | |
265 | auth2_challenge_stop(authctxt); | |
266 | #ifdef JPAKE | |
267 | auth2_jpake_stop(authctxt); | |
268 | #endif | |
269 | ||
270 | #ifdef GSSAPI | |
271 | /* XXX move to auth2_gssapi_stop() */ | |
272 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
273 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
274 | #endif | |
275 | ||
276 | authctxt->postponed = 0; | |
277 | ||
278 | /* try to authenticate user */ | |
279 | m = authmethod_lookup(method); | |
280 | if (m != NULL && authctxt->failures < options.max_authtries) { | |
281 | debug2("input_userauth_request: try method %s", method); | |
282 | authenticated = m->userauth(authctxt); | |
283 | } | |
284 | userauth_finish(authctxt, authenticated, method); | |
285 | ||
286 | xfree(service); | |
287 | xfree(user); | |
288 | xfree(method); | |
289 | } | |
290 | ||
291 | void | |
292 | userauth_finish(Authctxt *authctxt, int authenticated, char *method) | |
293 | { | |
294 | char *methods; | |
295 | ||
296 | if (!authctxt->valid && authenticated) | |
297 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
298 | authctxt->user); | |
299 | ||
300 | /* Special handling for root */ | |
301 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
302 | !auth_root_allowed(method)) { | |
303 | authenticated = 0; | |
304 | #ifdef SSH_AUDIT_EVENTS | |
305 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
306 | #endif | |
307 | } | |
308 | ||
309 | #ifdef USE_PAM | |
310 | if (options.use_pam && authenticated) { | |
311 | if (!PRIVSEP(do_pam_account())) { | |
312 | /* if PAM returned a message, send it to the user */ | |
313 | if (buffer_len(&loginmsg) > 0) { | |
314 | buffer_append(&loginmsg, "\0", 1); | |
315 | userauth_send_banner(buffer_ptr(&loginmsg)); | |
316 | packet_write_wait(); | |
317 | } | |
318 | fatal("Access denied for user %s by PAM account " | |
319 | "configuration", authctxt->user); | |
320 | } | |
321 | } | |
322 | #endif | |
323 | ||
324 | #ifdef _UNICOS | |
325 | if (authenticated && cray_access_denied(authctxt->user)) { | |
326 | authenticated = 0; | |
327 | fatal("Access denied for user %s.",authctxt->user); | |
328 | } | |
329 | #endif /* _UNICOS */ | |
330 | ||
331 | /* Log before sending the reply */ | |
332 | auth_log(authctxt, authenticated, method, " ssh2"); | |
333 | ||
334 | if (authctxt->postponed) | |
335 | return; | |
336 | ||
337 | /* XXX todo: check if multiple auth methods are needed */ | |
338 | if (authenticated == 1) { | |
339 | /* turn off userauth */ | |
340 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); | |
341 | packet_start(SSH2_MSG_USERAUTH_SUCCESS); | |
342 | packet_send(); | |
343 | packet_write_wait(); | |
344 | /* now we can break out */ | |
345 | authctxt->success = 1; | |
346 | } else { | |
347 | ||
348 | /* Allow initial try of "none" auth without failure penalty */ | |
349 | if (authctxt->attempt > 1 || strcmp(method, "none") != 0) | |
350 | authctxt->failures++; | |
351 | if (authctxt->failures >= options.max_authtries) { | |
352 | #ifdef SSH_AUDIT_EVENTS | |
353 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
354 | #endif | |
355 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
356 | } | |
357 | methods = authmethods_get(); | |
358 | packet_start(SSH2_MSG_USERAUTH_FAILURE); | |
359 | packet_put_cstring(methods); | |
360 | packet_put_char(0); /* XXX partial success, unused */ | |
361 | packet_send(); | |
362 | packet_write_wait(); | |
363 | xfree(methods); | |
364 | } | |
365 | } | |
366 | ||
367 | static char * | |
368 | authmethods_get(void) | |
369 | { | |
370 | Buffer b; | |
371 | char *list; | |
372 | int i; | |
373 | ||
374 | buffer_init(&b); | |
375 | for (i = 0; authmethods[i] != NULL; i++) { | |
376 | if (strcmp(authmethods[i]->name, "none") == 0) | |
377 | continue; | |
378 | if (authmethods[i]->enabled != NULL && | |
379 | *(authmethods[i]->enabled) != 0) { | |
380 | if (buffer_len(&b) > 0) | |
381 | buffer_append(&b, ",", 1); | |
382 | buffer_append(&b, authmethods[i]->name, | |
383 | strlen(authmethods[i]->name)); | |
384 | } | |
385 | } | |
386 | buffer_append(&b, "\0", 1); | |
387 | list = xstrdup(buffer_ptr(&b)); | |
388 | buffer_free(&b); | |
389 | return list; | |
390 | } | |
391 | ||
392 | static Authmethod * | |
393 | authmethod_lookup(const char *name) | |
394 | { | |
395 | int i; | |
396 | ||
397 | if (name != NULL) | |
398 | for (i = 0; authmethods[i] != NULL; i++) | |
399 | if (authmethods[i]->enabled != NULL && | |
400 | *(authmethods[i]->enabled) != 0 && | |
401 | strcmp(name, authmethods[i]->name) == 0) | |
402 | return authmethods[i]; | |
403 | debug2("Unrecognized authentication method name: %s", | |
404 | name ? name : "NULL"); | |
405 | return NULL; | |
406 | } | |
407 |