1 /* $OpenBSD: auth2.c,v 1.123 2011/03/10 02:52:57 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 "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 *
auth2_read_banner(void)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
userauth_send_banner(const char * msg)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
userauth_banner(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
do_authentication2(Authctxt * authctxt)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
input_service_request(int type,u_int32_t seq,void * ctxt)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_cstring(&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
input_userauth_request(int type,u_int32_t seq,void * ctxt)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_cstring(NULL);
225 service = packet_get_cstring(NULL);
226 method = packet_get_cstring(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 authctxt->server_caused_failure = 0;
278
279 /* try to authenticate user */
280 m = authmethod_lookup(method);
281 if (m != NULL && authctxt->failures < options.max_authtries) {
282 debug2("input_userauth_request: try method %s", method);
283 authenticated = m->userauth(authctxt);
284 }
285 userauth_finish(authctxt, authenticated, method);
286
287 xfree(service);
288 xfree(user);
289 xfree(method);
290 }
291
292 void
userauth_finish(Authctxt * authctxt,int authenticated,char * method)293 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
294 {
295 char *methods;
296
297 if (!authctxt->valid && authenticated)
298 fatal("INTERNAL ERROR: authenticated invalid user %s",
299 authctxt->user);
300
301 /* Special handling for root */
302 if (authenticated && authctxt->pw->pw_uid == 0 &&
303 !auth_root_allowed(method)) {
304 authenticated = 0;
305 #ifdef SSH_AUDIT_EVENTS
306 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
307 #endif
308 }
309
310 #ifdef USE_PAM
311 if (options.use_pam && authenticated) {
312 if (!PRIVSEP(do_pam_account())) {
313 /* if PAM returned a message, send it to the user */
314 if (buffer_len(&loginmsg) > 0) {
315 buffer_append(&loginmsg, "\0", 1);
316 userauth_send_banner(buffer_ptr(&loginmsg));
317 packet_write_wait();
318 }
319 fatal("Access denied for user %s by PAM account "
320 "configuration", authctxt->user);
321 }
322 }
323 #endif
324
325 #ifdef _UNICOS
326 if (authenticated && cray_access_denied(authctxt->user)) {
327 authenticated = 0;
328 fatal("Access denied for user %s.",authctxt->user);
329 }
330 #endif /* _UNICOS */
331
332 /* Log before sending the reply */
333 auth_log(authctxt, authenticated, method, " ssh2");
334
335 if (authctxt->postponed)
336 return;
337
338 /* XXX todo: check if multiple auth methods are needed */
339 if (authenticated == 1) {
340 /* turn off userauth */
341 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
342 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
343 packet_send();
344 packet_write_wait();
345 /* now we can break out */
346 authctxt->success = 1;
347 } else {
348
349 /* Allow initial try of "none" auth without failure penalty */
350 if (!authctxt->server_caused_failure &&
351 (authctxt->attempt > 1 || strcmp(method, "none") != 0))
352 authctxt->failures++;
353 if (authctxt->failures >= options.max_authtries) {
354 #ifdef SSH_AUDIT_EVENTS
355 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
356 #endif
357 packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
358 }
359 methods = authmethods_get();
360 packet_start(SSH2_MSG_USERAUTH_FAILURE);
361 packet_put_cstring(methods);
362 packet_put_char(0); /* XXX partial success, unused */
363 packet_send();
364 packet_write_wait();
365 xfree(methods);
366 }
367 }
368
369 static char *
authmethods_get(void)370 authmethods_get(void)
371 {
372 Buffer b;
373 char *list;
374 int i;
375
376 buffer_init(&b);
377 for (i = 0; authmethods[i] != NULL; i++) {
378 if (strcmp(authmethods[i]->name, "none") == 0)
379 continue;
380 if (authmethods[i]->enabled != NULL &&
381 *(authmethods[i]->enabled) != 0) {
382 if (buffer_len(&b) > 0)
383 buffer_append(&b, ",", 1);
384 buffer_append(&b, authmethods[i]->name,
385 strlen(authmethods[i]->name));
386 }
387 }
388 buffer_append(&b, "\0", 1);
389 list = xstrdup(buffer_ptr(&b));
390 buffer_free(&b);
391 return list;
392 }
393
394 static Authmethod *
authmethod_lookup(const char * name)395 authmethod_lookup(const char *name)
396 {
397 int i;
398
399 if (name != NULL)
400 for (i = 0; authmethods[i] != NULL; i++)
401 if (authmethods[i]->enabled != NULL &&
402 *(authmethods[i]->enabled) != 0 &&
403 strcmp(name, authmethods[i]->name) == 0)
404 return authmethods[i];
405 debug2("Unrecognized authentication method name: %s",
406 name ? name : "NULL");
407 return NULL;
408 }
409
410