auth2-chall.c revision 264377 
1/* $OpenBSD: auth2-chall.c,v 1.41 2014/02/02 03:44:31 djm Exp $ */
2/*
3 * Copyright (c) 2001 Markus Friedl.  All rights reserved.
4 * Copyright (c) 2001 Per Allansson.  All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include "includes.h"
28
29#include <sys/types.h>
30
31#include <stdarg.h>
32#include <stdio.h>
33#include <string.h>
34
35#include "xmalloc.h"
36#include "ssh2.h"
37#include "key.h"
38#include "hostfile.h"
39#include "auth.h"
40#include "buffer.h"
41#include "packet.h"
42#include "dispatch.h"
43#include "log.h"
44#include "servconf.h"
45
46/* import */
47extern ServerOptions options;
48
49static int auth2_challenge_start(Authctxt *);
50static int send_userauth_info_request(Authctxt *);
51static void input_userauth_info_response(int, u_int32_t, void *);
52
53#ifdef BSD_AUTH
54extern KbdintDevice bsdauth_device;
55#else
56#ifdef USE_PAM
57extern KbdintDevice sshpam_device;
58#endif
59#ifdef SKEY
60extern KbdintDevice skey_device;
61#endif
62#endif
63
64KbdintDevice *devices[] = {
65#ifdef BSD_AUTH
66	&bsdauth_device,
67#else
68#ifdef USE_PAM
69	&sshpam_device,
70#endif
71#ifdef SKEY
72	&skey_device,
73#endif
74#endif
75	NULL
76};
77
78typedef struct KbdintAuthctxt KbdintAuthctxt;
79struct KbdintAuthctxt
80{
81	char *devices;
82	void *ctxt;
83	KbdintDevice *device;
84	u_int nreq;
85};
86
87#ifdef USE_PAM
88void
89remove_kbdint_device(const char *devname)
90{
91	int i, j;
92
93	for (i = 0; devices[i] != NULL; i++)
94		if (strcmp(devices[i]->name, devname) == 0) {
95			for (j = i; devices[j] != NULL; j++)
96				devices[j] = devices[j+1];
97			i--;
98		}
99}
100#endif
101
102static KbdintAuthctxt *
103kbdint_alloc(const char *devs)
104{
105	KbdintAuthctxt *kbdintctxt;
106	Buffer b;
107	int i;
108
109#ifdef USE_PAM
110	if (!options.use_pam)
111		remove_kbdint_device("pam");
112#endif
113
114	kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
115	if (strcmp(devs, "") == 0) {
116		buffer_init(&b);
117		for (i = 0; devices[i]; i++) {
118			if (buffer_len(&b) > 0)
119				buffer_append(&b, ",", 1);
120			buffer_append(&b, devices[i]->name,
121			    strlen(devices[i]->name));
122		}
123		buffer_append(&b, "\0", 1);
124		kbdintctxt->devices = xstrdup(buffer_ptr(&b));
125		buffer_free(&b);
126	} else {
127		kbdintctxt->devices = xstrdup(devs);
128	}
129	debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
130	kbdintctxt->ctxt = NULL;
131	kbdintctxt->device = NULL;
132	kbdintctxt->nreq = 0;
133
134	return kbdintctxt;
135}
136static void
137kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
138{
139	if (kbdintctxt->ctxt) {
140		kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
141		kbdintctxt->ctxt = NULL;
142	}
143	kbdintctxt->device = NULL;
144}
145static void
146kbdint_free(KbdintAuthctxt *kbdintctxt)
147{
148	if (kbdintctxt->device)
149		kbdint_reset_device(kbdintctxt);
150	free(kbdintctxt->devices);
151	explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
152	free(kbdintctxt);
153}
154/* get next device */
155static int
156kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
157{
158	size_t len;
159	char *t;
160	int i;
161
162	if (kbdintctxt->device)
163		kbdint_reset_device(kbdintctxt);
164	do {
165		len = kbdintctxt->devices ?
166		    strcspn(kbdintctxt->devices, ",") : 0;
167
168		if (len == 0)
169			break;
170		for (i = 0; devices[i]; i++) {
171			if (!auth2_method_allowed(authctxt,
172			    "keyboard-interactive", devices[i]->name))
173				continue;
174			if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
175				kbdintctxt->device = devices[i];
176		}
177		t = kbdintctxt->devices;
178		kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
179		free(t);
180		debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
181		    kbdintctxt->devices : "<empty>");
182	} while (kbdintctxt->devices && !kbdintctxt->device);
183
184	return kbdintctxt->device ? 1 : 0;
185}
186
187/*
188 * try challenge-response, set authctxt->postponed if we have to
189 * wait for the response.
190 */
191int
192auth2_challenge(Authctxt *authctxt, char *devs)
193{
194	debug("auth2_challenge: user=%s devs=%s",
195	    authctxt->user ? authctxt->user : "<nouser>",
196	    devs ? devs : "<no devs>");
197
198	if (authctxt->user == NULL || !devs)
199		return 0;
200	if (authctxt->kbdintctxt == NULL)
201		authctxt->kbdintctxt = kbdint_alloc(devs);
202	return auth2_challenge_start(authctxt);
203}
204
205/* unregister kbd-int callbacks and context */
206void
207auth2_challenge_stop(Authctxt *authctxt)
208{
209	/* unregister callback */
210	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
211	if (authctxt->kbdintctxt != NULL) {
212		kbdint_free(authctxt->kbdintctxt);
213		authctxt->kbdintctxt = NULL;
214	}
215}
216
217/* side effect: sets authctxt->postponed if a reply was sent*/
218static int
219auth2_challenge_start(Authctxt *authctxt)
220{
221	KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
222
223	debug2("auth2_challenge_start: devices %s",
224	    kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
225
226	if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
227		auth2_challenge_stop(authctxt);
228		return 0;
229	}
230	debug("auth2_challenge_start: trying authentication method '%s'",
231	    kbdintctxt->device->name);
232
233	if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
234		auth2_challenge_stop(authctxt);
235		return 0;
236	}
237	if (send_userauth_info_request(authctxt) == 0) {
238		auth2_challenge_stop(authctxt);
239		return 0;
240	}
241	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
242	    &input_userauth_info_response);
243
244	authctxt->postponed = 1;
245	return 0;
246}
247
248static int
249send_userauth_info_request(Authctxt *authctxt)
250{
251	KbdintAuthctxt *kbdintctxt;
252	char *name, *instr, **prompts;
253	u_int i, *echo_on;
254
255	kbdintctxt = authctxt->kbdintctxt;
256	if (kbdintctxt->device->query(kbdintctxt->ctxt,
257	    &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
258		return 0;
259
260	packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
261	packet_put_cstring(name);
262	packet_put_cstring(instr);
263	packet_put_cstring("");		/* language not used */
264	packet_put_int(kbdintctxt->nreq);
265	for (i = 0; i < kbdintctxt->nreq; i++) {
266		packet_put_cstring(prompts[i]);
267		packet_put_char(echo_on[i]);
268	}
269	packet_send();
270	packet_write_wait();
271
272	for (i = 0; i < kbdintctxt->nreq; i++)
273		free(prompts[i]);
274	free(prompts);
275	free(echo_on);
276	free(name);
277	free(instr);
278	return 1;
279}
280
281static void
282input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
283{
284	Authctxt *authctxt = ctxt;
285	KbdintAuthctxt *kbdintctxt;
286	int authenticated = 0, res;
287	u_int i, nresp;
288	const char *devicename = NULL;
289	char **response = NULL;
290
291	if (authctxt == NULL)
292		fatal("input_userauth_info_response: no authctxt");
293	kbdintctxt = authctxt->kbdintctxt;
294	if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
295		fatal("input_userauth_info_response: no kbdintctxt");
296	if (kbdintctxt->device == NULL)
297		fatal("input_userauth_info_response: no device");
298
299	authctxt->postponed = 0;	/* reset */
300	nresp = packet_get_int();
301	if (nresp != kbdintctxt->nreq)
302		fatal("input_userauth_info_response: wrong number of replies");
303	if (nresp > 100)
304		fatal("input_userauth_info_response: too many replies");
305	if (nresp > 0) {
306		response = xcalloc(nresp, sizeof(char *));
307		for (i = 0; i < nresp; i++)
308			response[i] = packet_get_string(NULL);
309	}
310	packet_check_eom();
311
312	res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
313
314	for (i = 0; i < nresp; i++) {
315		explicit_bzero(response[i], strlen(response[i]));
316		free(response[i]);
317	}
318	free(response);
319
320	switch (res) {
321	case 0:
322		/* Success! */
323		authenticated = authctxt->valid ? 1 : 0;
324		break;
325	case 1:
326		/* Authentication needs further interaction */
327		if (send_userauth_info_request(authctxt) == 1)
328			authctxt->postponed = 1;
329		break;
330	default:
331		/* Failure! */
332		break;
333	}
334	devicename = kbdintctxt->device->name;
335	if (!authctxt->postponed) {
336		if (authenticated) {
337			auth2_challenge_stop(authctxt);
338		} else {
339			/* start next device */
340			/* may set authctxt->postponed */
341			auth2_challenge_start(authctxt);
342		}
343	}
344	userauth_finish(authctxt, authenticated, "keyboard-interactive",
345	    devicename);
346}
347
348void
349privsep_challenge_enable(void)
350{
351#if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
352	int n = 0;
353#endif
354#ifdef BSD_AUTH
355	extern KbdintDevice mm_bsdauth_device;
356#endif
357#ifdef USE_PAM
358	extern KbdintDevice mm_sshpam_device;
359#endif
360#ifdef SKEY
361	extern KbdintDevice mm_skey_device;
362#endif
363
364#ifdef BSD_AUTH
365	devices[n++] = &mm_bsdauth_device;
366#else
367#ifdef USE_PAM
368	devices[n++] = &mm_sshpam_device;
369#endif
370#ifdef SKEY
371	devices[n++] = &mm_skey_device;
372#endif
373#endif
374}
375