xref: /freebsd/crypto/openssh/auth2.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
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 __RCSID("$FreeBSD$");
28 
29 #include <sys/types.h>
30 
31 #include <pwd.h>
32 #include <stdarg.h>
33 #include <string.h>
34 
35 #include "xmalloc.h"
36 #include "ssh2.h"
37 #include "packet.h"
38 #include "log.h"
39 #include "buffer.h"
40 #include "servconf.h"
41 #include "compat.h"
42 #include "key.h"
43 #include "hostfile.h"
44 #include "auth.h"
45 #include "dispatch.h"
46 #include "pathnames.h"
47 #include "buffer.h"
48 #include "canohost.h"
49 
50 #ifdef GSSAPI
51 #include "ssh-gss.h"
52 #endif
53 #include "monitor_wrap.h"
54 
55 /* import */
56 extern ServerOptions options;
57 extern u_char *session_id2;
58 extern u_int session_id2_len;
59 extern Buffer loginmsg;
60 
61 /* methods */
62 
63 extern Authmethod method_none;
64 extern Authmethod method_pubkey;
65 extern Authmethod method_passwd;
66 extern Authmethod method_kbdint;
67 extern Authmethod method_hostbased;
68 #ifdef GSSAPI
69 extern Authmethod method_gssapi;
70 #endif
71 
72 Authmethod *authmethods[] = {
73 	&method_none,
74 	&method_pubkey,
75 #ifdef GSSAPI
76 	&method_gssapi,
77 #endif
78 	&method_passwd,
79 	&method_kbdint,
80 	&method_hostbased,
81 	NULL
82 };
83 
84 /* protocol */
85 
86 static void input_service_request(int, u_int32_t, void *);
87 static void input_userauth_request(int, u_int32_t, void *);
88 
89 /* helper */
90 static Authmethod *authmethod_lookup(const char *);
91 static char *authmethods_get(void);
92 int user_key_allowed(struct passwd *, Key *);
93 
94 /*
95  * loop until authctxt->success == TRUE
96  */
97 
98 void
99 do_authentication2(Authctxt *authctxt)
100 {
101 	/* challenge-response is implemented via keyboard interactive */
102 	if (options.challenge_response_authentication)
103 		options.kbd_interactive_authentication = 1;
104 
105 	dispatch_init(&dispatch_protocol_error);
106 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
107 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
108 }
109 
110 /*ARGSUSED*/
111 static void
112 input_service_request(int type, u_int32_t seq, void *ctxt)
113 {
114 	Authctxt *authctxt = ctxt;
115 	u_int len;
116 	int acceptit = 0;
117 	char *service = packet_get_string(&len);
118 	packet_check_eom();
119 
120 	if (authctxt == NULL)
121 		fatal("input_service_request: no authctxt");
122 
123 	if (strcmp(service, "ssh-userauth") == 0) {
124 		if (!authctxt->success) {
125 			acceptit = 1;
126 			/* now we can handle user-auth requests */
127 			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
128 		}
129 	}
130 	/* XXX all other service requests are denied */
131 
132 	if (acceptit) {
133 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
134 		packet_put_cstring(service);
135 		packet_send();
136 		packet_write_wait();
137 	} else {
138 		debug("bad service request %s", service);
139 		packet_disconnect("bad service request %s", service);
140 	}
141 	xfree(service);
142 }
143 
144 /*ARGSUSED*/
145 static void
146 input_userauth_request(int type, u_int32_t seq, void *ctxt)
147 {
148 	Authctxt *authctxt = ctxt;
149 	Authmethod *m = NULL;
150 	char *user, *service, *method, *style = NULL;
151 	int authenticated = 0;
152 #ifdef HAVE_LOGIN_CAP
153 	login_cap_t *lc;
154 	const char *from_host, *from_ip;
155 
156         from_host = get_canonical_hostname(options.use_dns);
157         from_ip = get_remote_ipaddr();
158 #endif
159 
160 	if (authctxt == NULL)
161 		fatal("input_userauth_request: no authctxt");
162 
163 	user = packet_get_string(NULL);
164 	service = packet_get_string(NULL);
165 	method = packet_get_string(NULL);
166 	debug("userauth-request for user %s service %s method %s", user, service, method);
167 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
168 
169 	if ((style = strchr(user, ':')) != NULL)
170 		*style++ = 0;
171 
172 	if (authctxt->attempt++ == 0) {
173 		/* setup auth context */
174 		authctxt->pw = PRIVSEP(getpwnamallow(user));
175 		authctxt->user = xstrdup(user);
176 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
177 			authctxt->valid = 1;
178 			debug2("input_userauth_request: setting up authctxt for %s", user);
179 		} else {
180 			logit("input_userauth_request: invalid user %s", user);
181 			authctxt->pw = fakepw();
182 #ifdef SSH_AUDIT_EVENTS
183 			PRIVSEP(audit_event(SSH_INVALID_USER));
184 #endif
185 		}
186 #ifdef USE_PAM
187 		if (options.use_pam)
188 			PRIVSEP(start_pam(authctxt));
189 #endif
190 		setproctitle("%s%s", authctxt->valid ? user : "unknown",
191 		    use_privsep ? " [net]" : "");
192 		authctxt->service = xstrdup(service);
193 		authctxt->style = style ? xstrdup(style) : NULL;
194 		if (use_privsep)
195 			mm_inform_authserv(service, style);
196 	} else if (strcmp(user, authctxt->user) != 0 ||
197 	    strcmp(service, authctxt->service) != 0) {
198 		packet_disconnect("Change of username or service not allowed: "
199 		    "(%s,%s) -> (%s,%s)",
200 		    authctxt->user, authctxt->service, user, service);
201 	}
202 
203 #ifdef HAVE_LOGIN_CAP
204         if (authctxt->pw != NULL) {
205                 lc = login_getpwclass(authctxt->pw);
206                 if (lc == NULL)
207                         lc = login_getclassbyname(NULL, authctxt->pw);
208                 if (!auth_hostok(lc, from_host, from_ip)) {
209                         logit("Denied connection for %.200s from %.200s [%.200s].",
210                             authctxt->pw->pw_name, from_host, from_ip);
211                         packet_disconnect("Sorry, you are not allowed to connect.");
212                 }
213                 if (!auth_timeok(lc, time(NULL))) {
214                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
215                             authctxt->pw->pw_name, from_host);
216                         packet_disconnect("Logins not available right now.");
217                 }
218                 login_close(lc);
219                 lc = NULL;
220         }
221 #endif  /* HAVE_LOGIN_CAP */
222 
223 	/* reset state */
224 	auth2_challenge_stop(authctxt);
225 
226 #ifdef GSSAPI
227 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
228 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
229 #endif
230 
231 	authctxt->postponed = 0;
232 
233 	/* try to authenticate user */
234 	m = authmethod_lookup(method);
235 	if (m != NULL) {
236 		debug2("input_userauth_request: try method %s", method);
237 		authenticated =	m->userauth(authctxt);
238 	}
239 	userauth_finish(authctxt, authenticated, method);
240 
241 	xfree(service);
242 	xfree(user);
243 	xfree(method);
244 }
245 
246 void
247 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
248 {
249 	char *methods;
250 
251 	if (!authctxt->valid && authenticated)
252 		fatal("INTERNAL ERROR: authenticated invalid user %s",
253 		    authctxt->user);
254 
255 	/* Special handling for root */
256 	if (authenticated && authctxt->pw->pw_uid == 0 &&
257 	    !auth_root_allowed(method)) {
258 		authenticated = 0;
259 #ifdef SSH_AUDIT_EVENTS
260 		PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
261 #endif
262 	}
263 
264 #ifdef USE_PAM
265 	if (options.use_pam && authenticated) {
266 		if (!PRIVSEP(do_pam_account())) {
267 			/* if PAM returned a message, send it to the user */
268 			if (buffer_len(&loginmsg) > 0) {
269 				buffer_append(&loginmsg, "\0", 1);
270 				userauth_send_banner(buffer_ptr(&loginmsg));
271 				packet_write_wait();
272 			}
273 			fatal("Access denied for user %s by PAM account "
274 			    "configuration", authctxt->user);
275 		}
276 	}
277 #endif
278 
279 #ifdef _UNICOS
280 	if (authenticated && cray_access_denied(authctxt->user)) {
281 		authenticated = 0;
282 		fatal("Access denied for user %s.",authctxt->user);
283 	}
284 #endif /* _UNICOS */
285 
286 	/* Log before sending the reply */
287 	auth_log(authctxt, authenticated, method, " ssh2");
288 
289 	if (authctxt->postponed)
290 		return;
291 
292 	/* XXX todo: check if multiple auth methods are needed */
293 	if (authenticated == 1) {
294 		/* turn off userauth */
295 		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
296 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
297 		packet_send();
298 		packet_write_wait();
299 		/* now we can break out */
300 		authctxt->success = 1;
301 	} else {
302 		if (authctxt->failures++ > options.max_authtries) {
303 #ifdef SSH_AUDIT_EVENTS
304 			PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
305 #endif
306 			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
307 		}
308 		methods = authmethods_get();
309 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
310 		packet_put_cstring(methods);
311 		packet_put_char(0);	/* XXX partial success, unused */
312 		packet_send();
313 		packet_write_wait();
314 		xfree(methods);
315 	}
316 }
317 
318 #define	DELIM	","
319 
320 static char *
321 authmethods_get(void)
322 {
323 	Buffer b;
324 	char *list;
325 	int i;
326 
327 	buffer_init(&b);
328 	for (i = 0; authmethods[i] != NULL; i++) {
329 		if (strcmp(authmethods[i]->name, "none") == 0)
330 			continue;
331 		if (authmethods[i]->enabled != NULL &&
332 		    *(authmethods[i]->enabled) != 0) {
333 			if (buffer_len(&b) > 0)
334 				buffer_append(&b, ",", 1);
335 			buffer_append(&b, authmethods[i]->name,
336 			    strlen(authmethods[i]->name));
337 		}
338 	}
339 	buffer_append(&b, "\0", 1);
340 	list = xstrdup(buffer_ptr(&b));
341 	buffer_free(&b);
342 	return list;
343 }
344 
345 static Authmethod *
346 authmethod_lookup(const char *name)
347 {
348 	int i;
349 
350 	if (name != NULL)
351 		for (i = 0; authmethods[i] != NULL; i++)
352 			if (authmethods[i]->enabled != NULL &&
353 			    *(authmethods[i]->enabled) != 0 &&
354 			    strcmp(name, authmethods[i]->name) == 0)
355 				return authmethods[i];
356 	debug2("Unrecognized authentication method name: %s",
357 	    name ? name : "NULL");
358 	return NULL;
359 }
360