xref: /freebsd/crypto/openssh/auth2.c (revision 195ebc7e9e4b129de810833791a19dfb4349d6a9)
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 __RCSID("$FreeBSD$");
28 
29 #include <sys/types.h>
30 #include <sys/stat.h>
31 #include <sys/uio.h>
32 
33 #include <fcntl.h>
34 #include <pwd.h>
35 #include <stdarg.h>
36 #include <string.h>
37 #include <unistd.h>
38 
39 #include "xmalloc.h"
40 #include "atomicio.h"
41 #include "ssh2.h"
42 #include "packet.h"
43 #include "log.h"
44 #include "buffer.h"
45 #include "servconf.h"
46 #include "compat.h"
47 #include "key.h"
48 #include "hostfile.h"
49 #include "auth.h"
50 #include "dispatch.h"
51 #include "pathnames.h"
52 #include "buffer.h"
53 #include "canohost.h"
54 
55 #ifdef GSSAPI
56 #include "ssh-gss.h"
57 #endif
58 #include "monitor_wrap.h"
59 
60 /* import */
61 extern ServerOptions options;
62 extern u_char *session_id2;
63 extern u_int session_id2_len;
64 extern Buffer loginmsg;
65 
66 /* methods */
67 
68 extern Authmethod method_none;
69 extern Authmethod method_pubkey;
70 extern Authmethod method_passwd;
71 extern Authmethod method_kbdint;
72 extern Authmethod method_hostbased;
73 #ifdef GSSAPI
74 extern Authmethod method_gssapi;
75 #endif
76 #ifdef JPAKE
77 extern Authmethod method_jpake;
78 #endif
79 
80 Authmethod *authmethods[] = {
81 	&method_none,
82 	&method_pubkey,
83 #ifdef GSSAPI
84 	&method_gssapi,
85 #endif
86 #ifdef JPAKE
87 	&method_jpake,
88 #endif
89 	&method_passwd,
90 	&method_kbdint,
91 	&method_hostbased,
92 	NULL
93 };
94 
95 /* protocol */
96 
97 static void input_service_request(int, u_int32_t, void *);
98 static void input_userauth_request(int, u_int32_t, void *);
99 
100 /* helper */
101 static Authmethod *authmethod_lookup(const char *);
102 static char *authmethods_get(void);
103 
104 char *
105 auth2_read_banner(void)
106 {
107 	struct stat st;
108 	char *banner = NULL;
109 	size_t len, n;
110 	int fd;
111 
112 	if ((fd = open(options.banner, O_RDONLY)) == -1)
113 		return (NULL);
114 	if (fstat(fd, &st) == -1) {
115 		close(fd);
116 		return (NULL);
117 	}
118 	if (st.st_size > 1*1024*1024) {
119 		close(fd);
120 		return (NULL);
121 	}
122 
123 	len = (size_t)st.st_size;		/* truncate */
124 	banner = xmalloc(len + 1);
125 	n = atomicio(read, fd, banner, len);
126 	close(fd);
127 
128 	if (n != len) {
129 		xfree(banner);
130 		return (NULL);
131 	}
132 	banner[n] = '\0';
133 
134 	return (banner);
135 }
136 
137 void
138 userauth_send_banner(const char *msg)
139 {
140 	if (datafellows & SSH_BUG_BANNER)
141 		return;
142 
143 	packet_start(SSH2_MSG_USERAUTH_BANNER);
144 	packet_put_cstring(msg);
145 	packet_put_cstring("");		/* language, unused */
146 	packet_send();
147 	debug("%s: sent", __func__);
148 }
149 
150 static void
151 userauth_banner(void)
152 {
153 	char *banner = NULL;
154 
155 	if (options.banner == NULL ||
156 	    strcasecmp(options.banner, "none") == 0 ||
157 	    (datafellows & SSH_BUG_BANNER) != 0)
158 		return;
159 
160 	if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
161 		goto done;
162 	userauth_send_banner(banner);
163 
164 done:
165 	if (banner)
166 		xfree(banner);
167 }
168 
169 /*
170  * loop until authctxt->success == TRUE
171  */
172 void
173 do_authentication2(Authctxt *authctxt)
174 {
175 	dispatch_init(&dispatch_protocol_error);
176 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
177 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
178 }
179 
180 /*ARGSUSED*/
181 static void
182 input_service_request(int type, u_int32_t seq, void *ctxt)
183 {
184 	Authctxt *authctxt = ctxt;
185 	u_int len;
186 	int acceptit = 0;
187 	char *service = packet_get_string(&len);
188 	packet_check_eom();
189 
190 	if (authctxt == NULL)
191 		fatal("input_service_request: no authctxt");
192 
193 	if (strcmp(service, "ssh-userauth") == 0) {
194 		if (!authctxt->success) {
195 			acceptit = 1;
196 			/* now we can handle user-auth requests */
197 			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
198 		}
199 	}
200 	/* XXX all other service requests are denied */
201 
202 	if (acceptit) {
203 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
204 		packet_put_cstring(service);
205 		packet_send();
206 		packet_write_wait();
207 	} else {
208 		debug("bad service request %s", service);
209 		packet_disconnect("bad service request %s", service);
210 	}
211 	xfree(service);
212 }
213 
214 /*ARGSUSED*/
215 static void
216 input_userauth_request(int type, u_int32_t seq, void *ctxt)
217 {
218 	Authctxt *authctxt = ctxt;
219 	Authmethod *m = NULL;
220 	char *user, *service, *method, *style = NULL;
221 	int authenticated = 0;
222 #ifdef HAVE_LOGIN_CAP
223 	login_cap_t *lc;
224 	const char *from_host, *from_ip;
225 
226         from_host = get_canonical_hostname(options.use_dns);
227         from_ip = get_remote_ipaddr();
228 #endif
229 
230 	if (authctxt == NULL)
231 		fatal("input_userauth_request: no authctxt");
232 
233 	user = packet_get_string(NULL);
234 	service = packet_get_string(NULL);
235 	method = packet_get_string(NULL);
236 	debug("userauth-request for user %s service %s method %s", user, service, method);
237 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
238 
239 	if ((style = strchr(user, ':')) != NULL)
240 		*style++ = 0;
241 
242 	if (authctxt->attempt++ == 0) {
243 		/* setup auth context */
244 		authctxt->pw = PRIVSEP(getpwnamallow(user));
245 		authctxt->user = xstrdup(user);
246 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
247 			authctxt->valid = 1;
248 			debug2("input_userauth_request: setting up authctxt for %s", user);
249 		} else {
250 			logit("input_userauth_request: invalid user %s", user);
251 			authctxt->pw = fakepw();
252 #ifdef SSH_AUDIT_EVENTS
253 			PRIVSEP(audit_event(SSH_INVALID_USER));
254 #endif
255 		}
256 #ifdef USE_PAM
257 		if (options.use_pam)
258 			PRIVSEP(start_pam(authctxt));
259 #endif
260 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
261 		    use_privsep ? " [net]" : "");
262 		authctxt->service = xstrdup(service);
263 		authctxt->style = style ? xstrdup(style) : NULL;
264 		if (use_privsep)
265 			mm_inform_authserv(service, style);
266 		userauth_banner();
267 	} else if (strcmp(user, authctxt->user) != 0 ||
268 	    strcmp(service, authctxt->service) != 0) {
269 		packet_disconnect("Change of username or service not allowed: "
270 		    "(%s,%s) -> (%s,%s)",
271 		    authctxt->user, authctxt->service, user, service);
272 	}
273 
274 #ifdef HAVE_LOGIN_CAP
275         if (authctxt->pw != NULL) {
276                 lc = login_getpwclass(authctxt->pw);
277                 if (lc == NULL)
278                         lc = login_getclassbyname(NULL, authctxt->pw);
279                 if (!auth_hostok(lc, from_host, from_ip)) {
280                         logit("Denied connection for %.200s from %.200s [%.200s].",
281                             authctxt->pw->pw_name, from_host, from_ip);
282                         packet_disconnect("Sorry, you are not allowed to connect.");
283                 }
284                 if (!auth_timeok(lc, time(NULL))) {
285                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
286                             authctxt->pw->pw_name, from_host);
287                         packet_disconnect("Logins not available right now.");
288                 }
289                 login_close(lc);
290                 lc = NULL;
291         }
292 #endif  /* HAVE_LOGIN_CAP */
293 
294 	/* reset state */
295 	auth2_challenge_stop(authctxt);
296 #ifdef JPAKE
297 	auth2_jpake_stop(authctxt);
298 #endif
299 
300 #ifdef GSSAPI
301 	/* XXX move to auth2_gssapi_stop() */
302 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
303 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
304 #endif
305 
306 	authctxt->postponed = 0;
307 
308 	/* try to authenticate user */
309 	m = authmethod_lookup(method);
310 	if (m != NULL && authctxt->failures < options.max_authtries) {
311 		debug2("input_userauth_request: try method %s", method);
312 		authenticated =	m->userauth(authctxt);
313 	}
314 	userauth_finish(authctxt, authenticated, method);
315 
316 	xfree(service);
317 	xfree(user);
318 	xfree(method);
319 }
320 
321 void
322 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
323 {
324 	char *methods;
325 
326 	if (!authctxt->valid && authenticated)
327 		fatal("INTERNAL ERROR: authenticated invalid user %s",
328 		    authctxt->user);
329 
330 	/* Special handling for root */
331 	if (authenticated && authctxt->pw->pw_uid == 0 &&
332 	    !auth_root_allowed(method)) {
333 		authenticated = 0;
334 #ifdef SSH_AUDIT_EVENTS
335 		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
336 #endif
337 	}
338 
339 #ifdef USE_PAM
340 	if (options.use_pam && authenticated) {
341 		if (!PRIVSEP(do_pam_account())) {
342 			/* if PAM returned a message, send it to the user */
343 			if (buffer_len(&loginmsg) > 0) {
344 				buffer_append(&loginmsg, "\0", 1);
345 				userauth_send_banner(buffer_ptr(&loginmsg));
346 				packet_write_wait();
347 			}
348 			fatal("Access denied for user %s by PAM account "
349 			    "configuration", authctxt->user);
350 		}
351 	}
352 #endif
353 
354 #ifdef _UNICOS
355 	if (authenticated && cray_access_denied(authctxt->user)) {
356 		authenticated = 0;
357 		fatal("Access denied for user %s.",authctxt->user);
358 	}
359 #endif /* _UNICOS */
360 
361 	/* Log before sending the reply */
362 	auth_log(authctxt, authenticated, method, " ssh2");
363 
364 	if (authctxt->postponed)
365 		return;
366 
367 	/* XXX todo: check if multiple auth methods are needed */
368 	if (authenticated == 1) {
369 		/* turn off userauth */
370 		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
371 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
372 		packet_send();
373 		packet_write_wait();
374 		/* now we can break out */
375 		authctxt->success = 1;
376 	} else {
377 
378 		/* Allow initial try of "none" auth without failure penalty */
379 		if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
380 			authctxt->failures++;
381 		if (authctxt->failures >= options.max_authtries) {
382 #ifdef SSH_AUDIT_EVENTS
383 			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
384 #endif
385 			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
386 		}
387 		methods = authmethods_get();
388 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
389 		packet_put_cstring(methods);
390 		packet_put_char(0);	/* XXX partial success, unused */
391 		packet_send();
392 		packet_write_wait();
393 		xfree(methods);
394 	}
395 }
396 
397 static char *
398 authmethods_get(void)
399 {
400 	Buffer b;
401 	char *list;
402 	int i;
403 
404 	buffer_init(&b);
405 	for (i = 0; authmethods[i] != NULL; i++) {
406 		if (strcmp(authmethods[i]->name, "none") == 0)
407 			continue;
408 		if (authmethods[i]->enabled != NULL &&
409 		    *(authmethods[i]->enabled) != 0) {
410 			if (buffer_len(&b) > 0)
411 				buffer_append(&b, ",", 1);
412 			buffer_append(&b, authmethods[i]->name,
413 			    strlen(authmethods[i]->name));
414 		}
415 	}
416 	buffer_append(&b, "\0", 1);
417 	list = xstrdup(buffer_ptr(&b));
418 	buffer_free(&b);
419 	return list;
420 }
421 
422 static Authmethod *
423 authmethod_lookup(const char *name)
424 {
425 	int i;
426 
427 	if (name != NULL)
428 		for (i = 0; authmethods[i] != NULL; i++)
429 			if (authmethods[i]->enabled != NULL &&
430 			    *(authmethods[i]->enabled) != 0 &&
431 			    strcmp(name, authmethods[i]->name) == 0)
432 				return authmethods[i];
433 	debug2("Unrecognized authentication method name: %s",
434 	    name ? name : "NULL");
435 	return NULL;
436 }
437 
438