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1 | /* $OpenBSD: auth2.c,v 1.113 2006/08/03 03:34:41 deraadt 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 | ||
30 | #include <pwd.h> | |
31 | #include <stdarg.h> | |
32 | #include <string.h> | |
33 | ||
34 | #include "xmalloc.h" | |
35 | #include "ssh2.h" | |
36 | #include "packet.h" | |
37 | #include "log.h" | |
38 | #include "buffer.h" | |
39 | #include "servconf.h" | |
40 | #include "compat.h" | |
41 | #include "key.h" | |
42 | #include "hostfile.h" | |
43 | #include "auth.h" | |
44 | #include "dispatch.h" | |
45 | #include "pathnames.h" | |
46 | #include "buffer.h" | |
47 | ||
48 | #ifdef GSSAPI | |
49 | #include "ssh-gss.h" | |
50 | #endif | |
51 | #include "monitor_wrap.h" | |
52 | ||
53 | /* import */ | |
54 | extern ServerOptions options; | |
55 | extern u_char *session_id2; | |
56 | extern u_int session_id2_len; | |
57 | extern Buffer loginmsg; | |
58 | ||
59 | /* methods */ | |
60 | ||
61 | extern Authmethod method_none; | |
62 | extern Authmethod method_pubkey; | |
63 | extern Authmethod method_passwd; | |
64 | extern Authmethod method_kbdint; | |
65 | extern Authmethod method_hostbased; | |
66 | #ifdef GSSAPI | |
67 | extern Authmethod method_external; | |
68 | extern Authmethod method_gsskeyex; | |
69 | extern Authmethod method_gssapi; | |
70 | extern Authmethod method_gssapi_compat; | |
71 | #endif | |
72 | ||
73 | Authmethod *authmethods[] = { | |
74 | &method_none, | |
75 | &method_pubkey, | |
76 | #ifdef GSSAPI | |
77 | &method_gsskeyex, | |
78 | &method_external, | |
79 | &method_gssapi, | |
80 | &method_gssapi_compat, | |
81 | #endif | |
82 | &method_passwd, | |
83 | &method_kbdint, | |
84 | &method_hostbased, | |
85 | NULL | |
86 | }; | |
87 | ||
88 | /* protocol */ | |
89 | ||
90 | static void input_service_request(int, u_int32_t, void *); | |
91 | static void input_userauth_request(int, u_int32_t, void *); | |
92 | ||
93 | /* helper */ | |
94 | static Authmethod *authmethod_lookup(const char *); | |
95 | static char *authmethods_get(void); | |
96 | int user_key_allowed(struct passwd *, Key *); | |
97 | ||
98 | /* | |
99 | * loop until authctxt->success == TRUE | |
100 | */ | |
101 | ||
102 | void | |
103 | do_authentication2(Authctxt *authctxt) | |
104 | { | |
105 | /* challenge-response is implemented via keyboard interactive */ | |
106 | if (options.challenge_response_authentication) | |
107 | options.kbd_interactive_authentication = 1; | |
108 | ||
109 | dispatch_init(&dispatch_protocol_error); | |
110 | dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); | |
111 | dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); | |
112 | } | |
113 | ||
114 | /*ARGSUSED*/ | |
115 | static void | |
116 | input_service_request(int type, u_int32_t seq, void *ctxt) | |
117 | { | |
118 | Authctxt *authctxt = ctxt; | |
119 | u_int len; | |
120 | int acceptit = 0; | |
121 | char *service = packet_get_string(&len); | |
122 | packet_check_eom(); | |
123 | ||
124 | if (authctxt == NULL) | |
125 | fatal("input_service_request: no authctxt"); | |
126 | ||
127 | if (strcmp(service, "ssh-userauth") == 0) { | |
128 | if (!authctxt->success) { | |
129 | acceptit = 1; | |
130 | /* now we can handle user-auth requests */ | |
131 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); | |
132 | } | |
133 | } | |
134 | /* XXX all other service requests are denied */ | |
135 | ||
136 | if (acceptit) { | |
137 | packet_start(SSH2_MSG_SERVICE_ACCEPT); | |
138 | packet_put_cstring(service); | |
139 | packet_send(); | |
140 | packet_write_wait(); | |
141 | } else { | |
142 | debug("bad service request %s", service); | |
143 | packet_disconnect("bad service request %s", service); | |
144 | } | |
145 | xfree(service); | |
146 | } | |
147 | ||
148 | /*ARGSUSED*/ | |
149 | static void | |
150 | input_userauth_request(int type, u_int32_t seq, void *ctxt) | |
151 | { | |
152 | Authctxt *authctxt = ctxt; | |
153 | Authmethod *m = NULL; | |
154 | char *user, *service, *method, *style = NULL; | |
155 | int authenticated = 0; | |
156 | ||
157 | if (authctxt == NULL) | |
158 | fatal("input_userauth_request: no authctxt"); | |
159 | ||
160 | user = packet_get_string(NULL); | |
161 | service = packet_get_string(NULL); | |
162 | method = packet_get_string(NULL); | |
163 | ||
164 | #ifdef GSSAPI | |
165 | if (user[0] == '\0') { | |
166 | debug("received empty username for %s", method); | |
167 | if (strcmp(method, "external-keyx") == 0 || | |
168 | strcmp(method, "gssapi-keyex") == 0) { | |
169 | char *lname = NULL; | |
170 | PRIVSEP(ssh_gssapi_localname(&lname)); | |
171 | if (lname && lname[0] != '\0') { | |
172 | xfree(user); | |
173 | user = lname; | |
174 | debug("set username to %s from gssapi context", user); | |
175 | } else { | |
176 | debug("failed to set username from gssapi context"); | |
177 | packet_send_debug("failed to set username from gssapi context"); | |
178 | } | |
179 | } | |
180 | } | |
181 | #endif | |
182 | ||
183 | debug("userauth-request for user %s service %s method %s", | |
184 | user[0] ? user : "<implicit>", service, method); | |
185 | debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); | |
186 | ||
187 | if ((style = strchr(user, ':')) != NULL) | |
188 | *style++ = 0; | |
189 | ||
190 | /* If first time or username changed or implicit username, | |
191 | setup/reset authentication context. */ | |
192 | if ((authctxt->attempt++ == 0) || | |
193 | (strcmp(user, authctxt->user) != 0) || | |
194 | (strcmp(user, "") == 0)) { | |
195 | if (authctxt->user) { | |
196 | xfree(authctxt->user); | |
197 | authctxt->user = NULL; | |
198 | } | |
199 | authctxt->valid = 0; | |
200 | #ifdef GSSAPI | |
201 | /* If we're going to set the username based on the | |
202 | GSSAPI context later, then wait until then to | |
203 | verify it. Just put in placeholders for now. */ | |
204 | if ((strcmp(user, "") == 0) && | |
205 | ((strcmp(method, "gssapi") == 0) || | |
206 | (strcmp(method, "gssapi-with-mic") == 0))) { | |
207 | authctxt->pw = fakepw(); | |
208 | authctxt->user = xstrdup(user); | |
209 | } else { | |
210 | #endif | |
211 | authctxt->pw = PRIVSEP(getpwnamallow(user)); | |
212 | authctxt->user = xstrdup(user); | |
213 | if (authctxt->pw && strcmp(service, "ssh-connection")==0) { | |
214 | authctxt->valid = 1; | |
215 | debug2("input_userauth_request: setting up authctxt for %s", user); | |
216 | } else { | |
217 | logit("input_userauth_request: invalid user %s", user); | |
218 | authctxt->pw = fakepw(); | |
219 | #ifdef SSH_AUDIT_EVENTS | |
220 | PRIVSEP(audit_event(SSH_INVALID_USER)); | |
221 | #endif | |
222 | } | |
223 | #ifdef GSSAPI | |
224 | } /* endif for setting username based on GSSAPI context */ | |
225 | #endif | |
226 | #ifdef USE_PAM | |
227 | if (options.use_pam) | |
228 | PRIVSEP(start_pam(authctxt)); | |
229 | #endif | |
230 | setproctitle("%s%s", authctxt->valid ? user : "unknown", | |
231 | use_privsep ? " [net]" : ""); | |
232 | #ifdef GSSAPI | |
233 | if (authctxt->attempt == 1) { | |
234 | #endif | |
235 | authctxt->service = xstrdup(service); | |
236 | authctxt->style = style ? xstrdup(style) : NULL; | |
237 | if (use_privsep) | |
238 | mm_inform_authserv(service, style); | |
239 | #ifdef GSSAPI | |
240 | } /* if (authctxt->attempt == 1) */ | |
241 | #endif | |
242 | } | |
243 | if (strcmp(service, authctxt->service) != 0) { | |
244 | packet_disconnect("Change of service not allowed: " | |
245 | "(%s,%s) -> (%s,%s)", | |
246 | authctxt->user, authctxt->service, user, service); | |
247 | } | |
248 | /* reset state */ | |
249 | auth2_challenge_stop(authctxt); | |
250 | ||
251 | #ifdef GSSAPI | |
252 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
253 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
254 | #endif | |
255 | ||
256 | authctxt->postponed = 0; | |
257 | authctxt->server_caused_failure = 0; | |
258 | ||
259 | /* try to authenticate user */ | |
260 | m = authmethod_lookup(method); | |
261 | if (m != NULL) { | |
262 | debug2("input_userauth_request: try method %s", method); | |
263 | authenticated = m->userauth(authctxt); | |
264 | } | |
265 | userauth_finish(authctxt, authenticated, method); | |
266 | ||
267 | xfree(service); | |
268 | xfree(user); | |
269 | xfree(method); | |
270 | } | |
271 | ||
272 | void | |
273 | userauth_finish(Authctxt *authctxt, int authenticated, char *method) | |
274 | { | |
275 | char *methods; | |
276 | ||
277 | if (!authctxt->valid && authenticated) | |
278 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
279 | authctxt->user); | |
280 | ||
281 | /* Special handling for root */ | |
282 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
283 | !auth_root_allowed(method)) { | |
284 | authenticated = 0; | |
285 | #ifdef SSH_AUDIT_EVENTS | |
286 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
287 | #endif | |
288 | } | |
289 | ||
290 | #ifdef USE_PAM | |
291 | if (options.use_pam && authenticated) { | |
292 | if (!PRIVSEP(do_pam_account())) { | |
293 | /* if PAM returned a message, send it to the user */ | |
294 | if (buffer_len(&loginmsg) > 0) { | |
295 | buffer_append(&loginmsg, "\0", 1); | |
296 | userauth_send_banner(buffer_ptr(&loginmsg)); | |
297 | packet_write_wait(); | |
298 | } | |
299 | fatal("Access denied for user %s by PAM account " | |
300 | "configuration", authctxt->user); | |
301 | } | |
302 | } | |
303 | #endif | |
304 | ||
305 | #ifdef _UNICOS | |
306 | if (authenticated && cray_access_denied(authctxt->user)) { | |
307 | authenticated = 0; | |
308 | fatal("Access denied for user %s.",authctxt->user); | |
309 | } | |
310 | #endif /* _UNICOS */ | |
311 | ||
312 | /* Log before sending the reply */ | |
313 | auth_log(authctxt, authenticated, method, " ssh2"); | |
314 | ||
315 | if (authctxt->postponed) | |
316 | return; | |
317 | ||
318 | /* XXX todo: check if multiple auth methods are needed */ | |
319 | if (authenticated == 1) { | |
320 | /* turn off userauth */ | |
321 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); | |
322 | packet_start(SSH2_MSG_USERAUTH_SUCCESS); | |
323 | packet_send(); | |
324 | packet_write_wait(); | |
325 | /* now we can break out */ | |
326 | authctxt->success = 1; | |
327 | } else { | |
328 | /* Dont count server configuration issues against the client */ | |
329 | if (!authctxt->server_caused_failure && | |
330 | authctxt->failures++ > options.max_authtries) { | |
331 | #ifdef SSH_AUDIT_EVENTS | |
332 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
333 | #endif | |
334 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
335 | } | |
336 | methods = authmethods_get(); | |
337 | packet_start(SSH2_MSG_USERAUTH_FAILURE); | |
338 | packet_put_cstring(methods); | |
339 | packet_put_char(0); /* XXX partial success, unused */ | |
340 | packet_send(); | |
341 | packet_write_wait(); | |
342 | xfree(methods); | |
343 | } | |
344 | } | |
345 | ||
346 | #define DELIM "," | |
347 | ||
348 | static char * | |
349 | authmethods_get(void) | |
350 | { | |
351 | Buffer b; | |
352 | char *list; | |
353 | int i; | |
354 | ||
355 | buffer_init(&b); | |
356 | for (i = 0; authmethods[i] != NULL; i++) { | |
357 | if (strcmp(authmethods[i]->name, "none") == 0) | |
358 | continue; | |
359 | if (authmethods[i]->enabled != NULL && | |
360 | *(authmethods[i]->enabled) != 0) { | |
361 | if (buffer_len(&b) > 0) | |
362 | buffer_append(&b, ",", 1); | |
363 | buffer_append(&b, authmethods[i]->name, | |
364 | strlen(authmethods[i]->name)); | |
365 | } | |
366 | } | |
367 | buffer_append(&b, "\0", 1); | |
368 | list = xstrdup(buffer_ptr(&b)); | |
369 | buffer_free(&b); | |
370 | return list; | |
371 | } | |
372 | ||
373 | static Authmethod * | |
374 | authmethod_lookup(const char *name) | |
375 | { | |
376 | int i; | |
377 | ||
378 | if (name != NULL) | |
379 | for (i = 0; authmethods[i] != NULL; i++) | |
380 | if (authmethods[i]->enabled != NULL && | |
381 | *(authmethods[i]->enabled) != 0 && | |
382 | strcmp(name, authmethods[i]->name) == 0) | |
383 | return authmethods[i]; | |
384 | debug2("Unrecognized authentication method name: %s", | |
385 | name ? name : "NULL"); | |
386 | return NULL; | |
387 | } |