xref: /freebsd/crypto/openssh/auth2.c (revision c98323078dede7579020518ec84cdcb478e5c142)
1 /*
2  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  * 1. Redistributions of source code must retain the above copyright
8  *    notice, this list of conditions and the following disclaimer.
9  * 2. Redistributions in binary form must reproduce the above copyright
10  *    notice, this list of conditions and the following disclaimer in the
11  *    documentation and/or other materials provided with the distribution.
12  *
13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23  */
24 
25 #include "includes.h"
26 RCSID("$OpenBSD: auth2.c,v 1.104 2003/11/04 08:54:09 djm Exp $");
27 RCSID("$FreeBSD$");
28 
29 #include "canohost.h"
30 #include "ssh2.h"
31 #include "xmalloc.h"
32 #include "packet.h"
33 #include "log.h"
34 #include "servconf.h"
35 #include "compat.h"
36 #include "auth.h"
37 #include "dispatch.h"
38 #include "pathnames.h"
39 #include "monitor_wrap.h"
40 
41 #ifdef GSSAPI
42 #include "ssh-gss.h"
43 #endif
44 
45 /* import */
46 extern ServerOptions options;
47 extern u_char *session_id2;
48 extern u_int session_id2_len;
49 
50 /* methods */
51 
52 extern Authmethod method_none;
53 extern Authmethod method_pubkey;
54 extern Authmethod method_passwd;
55 extern Authmethod method_kbdint;
56 extern Authmethod method_hostbased;
57 #ifdef GSSAPI
58 extern Authmethod method_gssapi;
59 #endif
60 
61 Authmethod *authmethods[] = {
62 	&method_none,
63 	&method_pubkey,
64 #ifdef GSSAPI
65 	&method_gssapi,
66 #endif
67 	&method_passwd,
68 	&method_kbdint,
69 	&method_hostbased,
70 	NULL
71 };
72 
73 /* protocol */
74 
75 static void input_service_request(int, u_int32_t, void *);
76 static void input_userauth_request(int, u_int32_t, void *);
77 
78 /* helper */
79 static Authmethod *authmethod_lookup(const char *);
80 static char *authmethods_get(void);
81 int user_key_allowed(struct passwd *, Key *);
82 
83 /*
84  * loop until authctxt->success == TRUE
85  */
86 
87 void
88 do_authentication2(Authctxt *authctxt)
89 {
90 	/* challenge-response is implemented via keyboard interactive */
91 	if (options.challenge_response_authentication)
92 		options.kbd_interactive_authentication = 1;
93 
94 	dispatch_init(&dispatch_protocol_error);
95 	dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
96 	dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
97 }
98 
99 static void
100 input_service_request(int type, u_int32_t seq, void *ctxt)
101 {
102 	Authctxt *authctxt = ctxt;
103 	u_int len;
104 	int acceptit = 0;
105 	char *service = packet_get_string(&len);
106 	packet_check_eom();
107 
108 	if (authctxt == NULL)
109 		fatal("input_service_request: no authctxt");
110 
111 	if (strcmp(service, "ssh-userauth") == 0) {
112 		if (!authctxt->success) {
113 			acceptit = 1;
114 			/* now we can handle user-auth requests */
115 			dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
116 		}
117 	}
118 	/* XXX all other service requests are denied */
119 
120 	if (acceptit) {
121 		packet_start(SSH2_MSG_SERVICE_ACCEPT);
122 		packet_put_cstring(service);
123 		packet_send();
124 		packet_write_wait();
125 	} else {
126 		debug("bad service request %s", service);
127 		packet_disconnect("bad service request %s", service);
128 	}
129 	xfree(service);
130 }
131 
132 static void
133 input_userauth_request(int type, u_int32_t seq, void *ctxt)
134 {
135 	Authctxt *authctxt = ctxt;
136 	Authmethod *m = NULL;
137 	char *user, *service, *method, *style = NULL;
138 	int authenticated = 0;
139 #ifdef HAVE_LOGIN_CAP
140 	login_cap_t *lc;
141 	const char *from_host, *from_ip;
142 
143         from_host = get_canonical_hostname(options.use_dns);
144         from_ip = get_remote_ipaddr();
145 #endif
146 
147 	if (authctxt == NULL)
148 		fatal("input_userauth_request: no authctxt");
149 
150 	user = packet_get_string(NULL);
151 	service = packet_get_string(NULL);
152 	method = packet_get_string(NULL);
153 	debug("userauth-request for user %s service %s method %s", user, service, method);
154 	debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
155 
156 	if ((style = strchr(user, ':')) != NULL)
157 		*style++ = 0;
158 
159 	if (authctxt->attempt++ == 0) {
160 		/* setup auth context */
161 		authctxt->pw = PRIVSEP(getpwnamallow(user));
162 		authctxt->user = xstrdup(user);
163 		if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
164 			authctxt->valid = 1;
165 			debug2("input_userauth_request: setting up authctxt for %s", user);
166 #ifdef USE_PAM
167 			if (options.use_pam)
168 				PRIVSEP(start_pam(authctxt));
169 #endif
170 		} else {
171 			logit("input_userauth_request: illegal user %s", user);
172 			authctxt->pw = fakepw();
173 #ifdef USE_PAM
174 			if (options.use_pam)
175 				PRIVSEP(start_pam(authctxt));
176 #endif
177 		}
178 		setproctitle("%s%s", authctxt->pw ? user : "unknown",
179 		    use_privsep ? " [net]" : "");
180 		authctxt->service = xstrdup(service);
181 		authctxt->style = style ? xstrdup(style) : NULL;
182 		if (use_privsep)
183 			mm_inform_authserv(service, style);
184 	} else if (strcmp(user, authctxt->user) != 0 ||
185 	    strcmp(service, authctxt->service) != 0) {
186 		packet_disconnect("Change of username or service not allowed: "
187 		    "(%s,%s) -> (%s,%s)",
188 		    authctxt->user, authctxt->service, user, service);
189 	}
190 
191 #ifdef HAVE_LOGIN_CAP
192         if (authctxt->pw != NULL) {
193                 lc = login_getpwclass(authctxt->pw);
194                 if (lc == NULL)
195                         lc = login_getclassbyname(NULL, authctxt->pw);
196                 if (!auth_hostok(lc, from_host, from_ip)) {
197                         logit("Denied connection for %.200s from %.200s [%.200s].",
198                             authctxt->pw->pw_name, from_host, from_ip);
199                         packet_disconnect("Sorry, you are not allowed to connect.");
200                 }
201                 if (!auth_timeok(lc, time(NULL))) {
202                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
203                             authctxt->pw->pw_name, from_host);
204                         packet_disconnect("Logins not available right now.");
205                 }
206                 login_close(lc);
207                 lc = NULL;
208         }
209 #endif  /* HAVE_LOGIN_CAP */
210 
211 	/* reset state */
212 	auth2_challenge_stop(authctxt);
213 
214 #ifdef GSSAPI
215 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
216 	dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
217 #endif
218 
219 	authctxt->postponed = 0;
220 
221 	/* try to authenticate user */
222 	m = authmethod_lookup(method);
223 	if (m != NULL) {
224 		debug2("input_userauth_request: try method %s", method);
225 		authenticated =	m->userauth(authctxt);
226 	}
227 	userauth_finish(authctxt, authenticated, method);
228 
229 	xfree(service);
230 	xfree(user);
231 	xfree(method);
232 }
233 
234 void
235 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
236 {
237 	char *methods;
238 
239 	if (!authctxt->valid && authenticated)
240 		fatal("INTERNAL ERROR: authenticated invalid user %s",
241 		    authctxt->user);
242 
243 	/* Special handling for root */
244 	if (authenticated && authctxt->pw->pw_uid == 0 &&
245 	    !auth_root_allowed(method))
246 		authenticated = 0;
247 
248 #ifdef USE_PAM
249 	if (options.use_pam && authenticated && !PRIVSEP(do_pam_account()))
250 		authenticated = 0;
251 #endif
252 
253 #ifdef _UNICOS
254 	if (authenticated && cray_access_denied(authctxt->user)) {
255 		authenticated = 0;
256 		fatal("Access denied for user %s.",authctxt->user);
257 	}
258 #endif /* _UNICOS */
259 
260 	/* Log before sending the reply */
261 	auth_log(authctxt, authenticated, method, " ssh2");
262 
263 	if (authctxt->postponed)
264 		return;
265 
266 	/* XXX todo: check if multiple auth methods are needed */
267 	if (authenticated == 1) {
268 		/* turn off userauth */
269 		dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
270 		packet_start(SSH2_MSG_USERAUTH_SUCCESS);
271 		packet_send();
272 		packet_write_wait();
273 		/* now we can break out */
274 		authctxt->success = 1;
275 	} else {
276 		if (authctxt->failures++ > AUTH_FAIL_MAX)
277 			packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
278 		methods = authmethods_get();
279 		packet_start(SSH2_MSG_USERAUTH_FAILURE);
280 		packet_put_cstring(methods);
281 		packet_put_char(0);	/* XXX partial success, unused */
282 		packet_send();
283 		packet_write_wait();
284 		xfree(methods);
285 	}
286 }
287 
288 #define	DELIM	","
289 
290 static char *
291 authmethods_get(void)
292 {
293 	Buffer b;
294 	char *list;
295 	int i;
296 
297 	buffer_init(&b);
298 	for (i = 0; authmethods[i] != NULL; i++) {
299 		if (strcmp(authmethods[i]->name, "none") == 0)
300 			continue;
301 		if (authmethods[i]->enabled != NULL &&
302 		    *(authmethods[i]->enabled) != 0) {
303 			if (buffer_len(&b) > 0)
304 				buffer_append(&b, ",", 1);
305 			buffer_append(&b, authmethods[i]->name,
306 			    strlen(authmethods[i]->name));
307 		}
308 	}
309 	buffer_append(&b, "\0", 1);
310 	list = xstrdup(buffer_ptr(&b));
311 	buffer_free(&b);
312 	return list;
313 }
314 
315 static Authmethod *
316 authmethod_lookup(const char *name)
317 {
318 	int i;
319 
320 	if (name != NULL)
321 		for (i = 0; authmethods[i] != NULL; i++)
322 			if (authmethods[i]->enabled != NULL &&
323 			    *(authmethods[i]->enabled) != 0 &&
324 			    strcmp(name, authmethods[i]->name) == 0)
325 				return authmethods[i];
326 	debug2("Unrecognized authentication method name: %s",
327 	    name ? name : "NULL");
328 	return NULL;
329 }
330