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 */
59extern ServerOptions options;
60extern u_char *session_id2;
61extern u_int session_id2_len;
62extern Buffer loginmsg;
63
64/* methods */
65
66extern Authmethod method_none;
67extern Authmethod method_pubkey;
68extern Authmethod method_passwd;
69extern Authmethod method_kbdint;
70extern Authmethod method_hostbased;
71#ifdef GSSAPI
72extern Authmethod method_gssapi;
73#endif
74#ifdef JPAKE
75extern Authmethod method_jpake;
76#endif
77
78Authmethod *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
95static void input_service_request(int, u_int32_t, void *);
96static void input_userauth_request(int, u_int32_t, void *);
97
98/* helper */
99static Authmethod *authmethod_lookup(const char *);
100static char *authmethods_get(void);
101
102char *
103auth2_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
135void
136userauth_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
148static void
149userauth_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
162done:
163	if (banner)
164		xfree(banner);
165}
166
167/*
168 * loop until authctxt->success == TRUE
169 */
170void
171do_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*/
179static void
180input_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*/
213static void
214input_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
292void
293userauth_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
369static char *
370authmethods_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
394static Authmethod *
395authmethod_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