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1 | /* $OpenBSD: auth2.c,v 1.119 2008/07/04 23:30:16 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 | ||
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 | ||
75 | Authmethod *authmethods[] = { | |
76 | &method_none, | |
77 | &method_pubkey, | |
78 | #ifdef GSSAPI | |
79 | &method_gssapi, | |
80 | #endif | |
81 | &method_passwd, | |
82 | &method_kbdint, | |
83 | &method_hostbased, | |
84 | NULL | |
85 | }; | |
86 | ||
87 | /* protocol */ | |
88 | ||
89 | static void input_service_request(int, u_int32_t, void *); | |
90 | static void input_userauth_request(int, u_int32_t, void *); | |
91 | ||
92 | /* helper */ | |
93 | static Authmethod *authmethod_lookup(const char *); | |
94 | static char *authmethods_get(void); | |
95 | ||
96 | char * | |
97 | auth2_read_banner(void) | |
98 | { | |
99 | struct stat st; | |
100 | char *banner = NULL; | |
101 | size_t len, n; | |
102 | int fd; | |
103 | ||
104 | if ((fd = open(options.banner, O_RDONLY)) == -1) | |
105 | return (NULL); | |
106 | if (fstat(fd, &st) == -1) { | |
107 | close(fd); | |
108 | return (NULL); | |
109 | } | |
110 | if (st.st_size > 1*1024*1024) { | |
111 | close(fd); | |
112 | return (NULL); | |
113 | } | |
114 | ||
115 | len = (size_t)st.st_size; /* truncate */ | |
116 | banner = xmalloc(len + 1); | |
117 | n = atomicio(read, fd, banner, len); | |
118 | close(fd); | |
119 | ||
120 | if (n != len) { | |
121 | xfree(banner); | |
122 | return (NULL); | |
123 | } | |
124 | banner[n] = '\0'; | |
125 | ||
126 | return (banner); | |
127 | } | |
128 | ||
129 | void | |
130 | userauth_send_banner(const char *msg) | |
131 | { | |
132 | if (datafellows & SSH_BUG_BANNER) | |
133 | return; | |
134 | ||
135 | packet_start(SSH2_MSG_USERAUTH_BANNER); | |
136 | packet_put_cstring(msg); | |
137 | packet_put_cstring(""); /* language, unused */ | |
138 | packet_send(); | |
139 | debug("%s: sent", __func__); | |
140 | } | |
141 | ||
142 | static void | |
143 | userauth_banner(void) | |
144 | { | |
145 | char *banner = NULL; | |
146 | ||
147 | if (options.banner == NULL || | |
148 | strcasecmp(options.banner, "none") == 0 || | |
149 | (datafellows & SSH_BUG_BANNER) != 0) | |
150 | return; | |
151 | ||
152 | if ((banner = PRIVSEP(auth2_read_banner())) == NULL) | |
153 | goto done; | |
154 | userauth_send_banner(banner); | |
155 | ||
156 | done: | |
157 | if (banner) | |
158 | xfree(banner); | |
159 | } | |
160 | ||
161 | /* | |
162 | * loop until authctxt->success == TRUE | |
163 | */ | |
164 | void | |
165 | do_authentication2(Authctxt *authctxt) | |
166 | { | |
167 | dispatch_init(&dispatch_protocol_error); | |
168 | dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); | |
169 | dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); | |
170 | } | |
171 | ||
172 | /*ARGSUSED*/ | |
173 | static void | |
174 | input_service_request(int type, u_int32_t seq, void *ctxt) | |
175 | { | |
176 | Authctxt *authctxt = ctxt; | |
177 | u_int len; | |
178 | int acceptit = 0; | |
179 | char *service = packet_get_string(&len); | |
180 | packet_check_eom(); | |
181 | ||
182 | if (authctxt == NULL) | |
183 | fatal("input_service_request: no authctxt"); | |
184 | ||
185 | if (strcmp(service, "ssh-userauth") == 0) { | |
186 | if (!authctxt->success) { | |
187 | acceptit = 1; | |
188 | /* now we can handle user-auth requests */ | |
189 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); | |
190 | } | |
191 | } | |
192 | /* XXX all other service requests are denied */ | |
193 | ||
194 | if (acceptit) { | |
195 | packet_start(SSH2_MSG_SERVICE_ACCEPT); | |
196 | packet_put_cstring(service); | |
197 | packet_send(); | |
198 | packet_write_wait(); | |
199 | } else { | |
200 | debug("bad service request %s", service); | |
201 | packet_disconnect("bad service request %s", service); | |
202 | } | |
203 | xfree(service); | |
204 | } | |
205 | ||
206 | /*ARGSUSED*/ | |
207 | static void | |
208 | input_userauth_request(int type, u_int32_t seq, void *ctxt) | |
209 | { | |
210 | Authctxt *authctxt = ctxt; | |
211 | Authmethod *m = NULL; | |
212 | char *user, *service, *method, *style = NULL; | |
213 | int authenticated = 0; | |
214 | ||
215 | if (authctxt == NULL) | |
216 | fatal("input_userauth_request: no authctxt"); | |
217 | ||
218 | user = packet_get_string(NULL); | |
219 | service = packet_get_string(NULL); | |
220 | method = packet_get_string(NULL); | |
221 | debug("userauth-request for user %s service %s method %s", user, service, method); | |
222 | debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); | |
223 | ||
224 | if ((style = strchr(user, ':')) != NULL) | |
225 | *style++ = 0; | |
226 | ||
227 | if (authctxt->attempt++ == 0) { | |
228 | /* setup auth context */ | |
229 | authctxt->pw = PRIVSEP(getpwnamallow(user)); | |
230 | authctxt->user = xstrdup(user); | |
231 | if (authctxt->pw && strcmp(service, "ssh-connection")==0) { | |
232 | authctxt->valid = 1; | |
233 | debug2("input_userauth_request: setting up authctxt for %s", user); | |
234 | } else { | |
235 | logit("input_userauth_request: invalid user %s", user); | |
236 | authctxt->pw = fakepw(); | |
237 | #ifdef SSH_AUDIT_EVENTS | |
238 | PRIVSEP(audit_event(SSH_INVALID_USER)); | |
239 | #endif | |
240 | } | |
241 | #ifdef USE_PAM | |
242 | if (options.use_pam) | |
243 | PRIVSEP(start_pam(authctxt)); | |
244 | #endif | |
245 | setproctitle("%s%s", authctxt->valid ? user : "unknown", | |
246 | use_privsep ? " [net]" : ""); | |
247 | authctxt->service = xstrdup(service); | |
248 | authctxt->style = style ? xstrdup(style) : NULL; | |
249 | if (use_privsep) | |
250 | mm_inform_authserv(service, style); | |
251 | userauth_banner(); | |
252 | } else if (strcmp(user, authctxt->user) != 0 || | |
253 | strcmp(service, authctxt->service) != 0) { | |
254 | packet_disconnect("Change of username or service not allowed: " | |
255 | "(%s,%s) -> (%s,%s)", | |
256 | authctxt->user, authctxt->service, user, service); | |
257 | } | |
258 | /* reset state */ | |
259 | auth2_challenge_stop(authctxt); | |
260 | ||
261 | #ifdef GSSAPI | |
262 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); | |
263 | dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); | |
264 | #endif | |
265 | ||
266 | authctxt->postponed = 0; | |
267 | ||
268 | /* try to authenticate user */ | |
269 | m = authmethod_lookup(method); | |
270 | if (m != NULL && authctxt->failures < options.max_authtries) { | |
271 | debug2("input_userauth_request: try method %s", method); | |
272 | authenticated = m->userauth(authctxt); | |
273 | } | |
274 | userauth_finish(authctxt, authenticated, method); | |
275 | ||
276 | xfree(service); | |
277 | xfree(user); | |
278 | xfree(method); | |
279 | } | |
280 | ||
281 | void | |
282 | userauth_finish(Authctxt *authctxt, int authenticated, char *method) | |
283 | { | |
284 | char *methods; | |
285 | ||
286 | if (!authctxt->valid && authenticated) | |
287 | fatal("INTERNAL ERROR: authenticated invalid user %s", | |
288 | authctxt->user); | |
289 | ||
290 | /* Special handling for root */ | |
291 | if (authenticated && authctxt->pw->pw_uid == 0 && | |
292 | !auth_root_allowed(method)) { | |
293 | authenticated = 0; | |
294 | #ifdef SSH_AUDIT_EVENTS | |
295 | PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); | |
296 | #endif | |
297 | } | |
298 | ||
299 | #ifdef USE_PAM | |
300 | if (options.use_pam && authenticated) { | |
301 | if (!PRIVSEP(do_pam_account())) { | |
302 | /* if PAM returned a message, send it to the user */ | |
303 | if (buffer_len(&loginmsg) > 0) { | |
304 | buffer_append(&loginmsg, "\0", 1); | |
305 | userauth_send_banner(buffer_ptr(&loginmsg)); | |
306 | packet_write_wait(); | |
307 | } | |
308 | fatal("Access denied for user %s by PAM account " | |
309 | "configuration", authctxt->user); | |
310 | } | |
311 | } | |
312 | #endif | |
313 | ||
314 | #ifdef _UNICOS | |
315 | if (authenticated && cray_access_denied(authctxt->user)) { | |
316 | authenticated = 0; | |
317 | fatal("Access denied for user %s.",authctxt->user); | |
318 | } | |
319 | #endif /* _UNICOS */ | |
320 | ||
321 | /* Log before sending the reply */ | |
322 | auth_log(authctxt, authenticated, method, " ssh2"); | |
323 | ||
324 | if (authctxt->postponed) | |
325 | return; | |
326 | ||
327 | /* XXX todo: check if multiple auth methods are needed */ | |
328 | if (authenticated == 1) { | |
329 | /* turn off userauth */ | |
330 | dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); | |
331 | packet_start(SSH2_MSG_USERAUTH_SUCCESS); | |
332 | packet_send(); | |
333 | packet_write_wait(); | |
334 | /* now we can break out */ | |
335 | authctxt->success = 1; | |
336 | } else { | |
337 | ||
338 | /* Allow initial try of "none" auth without failure penalty */ | |
339 | if (authctxt->attempt > 1 || strcmp(method, "none") != 0) | |
340 | authctxt->failures++; | |
341 | if (authctxt->failures >= options.max_authtries) { | |
342 | #ifdef SSH_AUDIT_EVENTS | |
343 | PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); | |
344 | #endif | |
345 | packet_disconnect(AUTH_FAIL_MSG, authctxt->user); | |
346 | } | |
347 | methods = authmethods_get(); | |
348 | packet_start(SSH2_MSG_USERAUTH_FAILURE); | |
349 | packet_put_cstring(methods); | |
350 | packet_put_char(0); /* XXX partial success, unused */ | |
351 | packet_send(); | |
352 | packet_write_wait(); | |
353 | xfree(methods); | |
354 | } | |
355 | } | |
356 | ||
357 | static char * | |
358 | authmethods_get(void) | |
359 | { | |
360 | Buffer b; | |
361 | char *list; | |
362 | int i; | |
363 | ||
364 | buffer_init(&b); | |
365 | for (i = 0; authmethods[i] != NULL; i++) { | |
366 | if (strcmp(authmethods[i]->name, "none") == 0) | |
367 | continue; | |
368 | if (authmethods[i]->enabled != NULL && | |
369 | *(authmethods[i]->enabled) != 0) { | |
370 | if (buffer_len(&b) > 0) | |
371 | buffer_append(&b, ",", 1); | |
372 | buffer_append(&b, authmethods[i]->name, | |
373 | strlen(authmethods[i]->name)); | |
374 | } | |
375 | } | |
376 | buffer_append(&b, "\0", 1); | |
377 | list = xstrdup(buffer_ptr(&b)); | |
378 | buffer_free(&b); | |
379 | return list; | |
380 | } | |
381 | ||
382 | static Authmethod * | |
383 | authmethod_lookup(const char *name) | |
384 | { | |
385 | int i; | |
386 | ||
387 | if (name != NULL) | |
388 | for (i = 0; authmethods[i] != NULL; i++) | |
389 | if (authmethods[i]->enabled != NULL && | |
390 | *(authmethods[i]->enabled) != 0 && | |
391 | strcmp(name, authmethods[i]->name) == 0) | |
392 | return authmethods[i]; | |
393 | debug2("Unrecognized authentication method name: %s", | |
394 | name ? name : "NULL"); | |
395 | return NULL; | |
396 | } | |
397 |