auth2-chall.c revision 285979 
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	u_int devices_done;
86};
87
88#ifdef USE_PAM
89void
90remove_kbdint_device(const char *devname)
91{
92	int i, j;
93
94	for (i = 0; devices[i] != NULL; i++)
95		if (strcmp(devices[i]->name, devname) == 0) {
96			for (j = i; devices[j] != NULL; j++)
97				devices[j] = devices[j+1];
98			i--;
99		}
100}
101#endif
102
103static KbdintAuthctxt *
104kbdint_alloc(const char *devs)
105{
106	KbdintAuthctxt *kbdintctxt;
107	Buffer b;
108	int i;
109
110#ifdef USE_PAM
111	if (!options.use_pam)
112		remove_kbdint_device("pam");
113#endif
114
115	kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
116	if (strcmp(devs, "") == 0) {
117		buffer_init(&b);
118		for (i = 0; devices[i]; i++) {
119			if (buffer_len(&b) > 0)
120				buffer_append(&b, ",", 1);
121			buffer_append(&b, devices[i]->name,
122			    strlen(devices[i]->name));
123		}
124		buffer_append(&b, "\0", 1);
125		kbdintctxt->devices = xstrdup(buffer_ptr(&b));
126		buffer_free(&b);
127	} else {
128		kbdintctxt->devices = xstrdup(devs);
129	}
130	debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
131	kbdintctxt->ctxt = NULL;
132	kbdintctxt->device = NULL;
133	kbdintctxt->nreq = 0;
134
135	return kbdintctxt;
136}
137static void
138kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
139{
140	if (kbdintctxt->ctxt) {
141		kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
142		kbdintctxt->ctxt = NULL;
143	}
144	kbdintctxt->device = NULL;
145}
146static void
147kbdint_free(KbdintAuthctxt *kbdintctxt)
148{
149	if (kbdintctxt->device)
150		kbdint_reset_device(kbdintctxt);
151	free(kbdintctxt->devices);
152	explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
153	free(kbdintctxt);
154}
155/* get next device */
156static int
157kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
158{
159	size_t len;
160	char *t;
161	int i;
162
163	if (kbdintctxt->device)
164		kbdint_reset_device(kbdintctxt);
165	do {
166		len = kbdintctxt->devices ?
167		    strcspn(kbdintctxt->devices, ",") : 0;
168
169		if (len == 0)
170			break;
171		for (i = 0; devices[i]; i++) {
172			if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
173			    !auth2_method_allowed(authctxt,
174			    "keyboard-interactive", devices[i]->name))
175				continue;
176			if (strncmp(kbdintctxt->devices, devices[i]->name,
177			    len) == 0) {
178				kbdintctxt->device = devices[i];
179				kbdintctxt->devices_done |= 1 << i;
180			}
181		}
182		t = kbdintctxt->devices;
183		kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
184		free(t);
185		debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
186		    kbdintctxt->devices : "<empty>");
187	} while (kbdintctxt->devices && !kbdintctxt->device);
188
189	return kbdintctxt->device ? 1 : 0;
190}
191
192/*
193 * try challenge-response, set authctxt->postponed if we have to
194 * wait for the response.
195 */
196int
197auth2_challenge(Authctxt *authctxt, char *devs)
198{
199	debug("auth2_challenge: user=%s devs=%s",
200	    authctxt->user ? authctxt->user : "<nouser>",
201	    devs ? devs : "<no devs>");
202
203	if (authctxt->user == NULL || !devs)
204		return 0;
205	if (authctxt->kbdintctxt == NULL)
206		authctxt->kbdintctxt = kbdint_alloc(devs);
207	return auth2_challenge_start(authctxt);
208}
209
210/* unregister kbd-int callbacks and context */
211void
212auth2_challenge_stop(Authctxt *authctxt)
213{
214	/* unregister callback */
215	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
216	if (authctxt->kbdintctxt != NULL) {
217		kbdint_free(authctxt->kbdintctxt);
218		authctxt->kbdintctxt = NULL;
219	}
220}
221
222/* side effect: sets authctxt->postponed if a reply was sent*/
223static int
224auth2_challenge_start(Authctxt *authctxt)
225{
226	KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
227
228	debug2("auth2_challenge_start: devices %s",
229	    kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
230
231	if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
232		auth2_challenge_stop(authctxt);
233		return 0;
234	}
235	debug("auth2_challenge_start: trying authentication method '%s'",
236	    kbdintctxt->device->name);
237
238	if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
239		auth2_challenge_stop(authctxt);
240		return 0;
241	}
242	if (send_userauth_info_request(authctxt) == 0) {
243		auth2_challenge_stop(authctxt);
244		return 0;
245	}
246	dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
247	    &input_userauth_info_response);
248
249	authctxt->postponed = 1;
250	return 0;
251}
252
253static int
254send_userauth_info_request(Authctxt *authctxt)
255{
256	KbdintAuthctxt *kbdintctxt;
257	char *name, *instr, **prompts;
258	u_int i, *echo_on;
259
260	kbdintctxt = authctxt->kbdintctxt;
261	if (kbdintctxt->device->query(kbdintctxt->ctxt,
262	    &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
263		return 0;
264
265	packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
266	packet_put_cstring(name);
267	packet_put_cstring(instr);
268	packet_put_cstring("");		/* language not used */
269	packet_put_int(kbdintctxt->nreq);
270	for (i = 0; i < kbdintctxt->nreq; i++) {
271		packet_put_cstring(prompts[i]);
272		packet_put_char(echo_on[i]);
273	}
274	packet_send();
275	packet_write_wait();
276
277	for (i = 0; i < kbdintctxt->nreq; i++)
278		free(prompts[i]);
279	free(prompts);
280	free(echo_on);
281	free(name);
282	free(instr);
283	return 1;
284}
285
286static void
287input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
288{
289	Authctxt *authctxt = ctxt;
290	KbdintAuthctxt *kbdintctxt;
291	int authenticated = 0, res;
292	u_int i, nresp;
293	const char *devicename = NULL;
294	char **response = NULL;
295
296	if (authctxt == NULL)
297		fatal("input_userauth_info_response: no authctxt");
298	kbdintctxt = authctxt->kbdintctxt;
299	if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
300		fatal("input_userauth_info_response: no kbdintctxt");
301	if (kbdintctxt->device == NULL)
302		fatal("input_userauth_info_response: no device");
303
304	authctxt->postponed = 0;	/* reset */
305	nresp = packet_get_int();
306	if (nresp != kbdintctxt->nreq)
307		fatal("input_userauth_info_response: wrong number of replies");
308	if (nresp > 100)
309		fatal("input_userauth_info_response: too many replies");
310	if (nresp > 0) {
311		response = xcalloc(nresp, sizeof(char *));
312		for (i = 0; i < nresp; i++)
313			response[i] = packet_get_string(NULL);
314	}
315	packet_check_eom();
316
317	res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
318
319	for (i = 0; i < nresp; i++) {
320		explicit_bzero(response[i], strlen(response[i]));
321		free(response[i]);
322	}
323	free(response);
324
325	switch (res) {
326	case 0:
327		/* Success! */
328		authenticated = authctxt->valid ? 1 : 0;
329		break;
330	case 1:
331		/* Authentication needs further interaction */
332		if (send_userauth_info_request(authctxt) == 1)
333			authctxt->postponed = 1;
334		break;
335	default:
336		/* Failure! */
337		break;
338	}
339	devicename = kbdintctxt->device->name;
340	if (!authctxt->postponed) {
341		if (authenticated) {
342			auth2_challenge_stop(authctxt);
343		} else {
344			/* start next device */
345			/* may set authctxt->postponed */
346			auth2_challenge_start(authctxt);
347		}
348	}
349	userauth_finish(authctxt, authenticated, "keyboard-interactive",
350	    devicename);
351}
352
353void
354privsep_challenge_enable(void)
355{
356#if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
357	int n = 0;
358#endif
359#ifdef BSD_AUTH
360	extern KbdintDevice mm_bsdauth_device;
361#endif
362#ifdef USE_PAM
363	extern KbdintDevice mm_sshpam_device;
364#endif
365#ifdef SKEY
366	extern KbdintDevice mm_skey_device;
367#endif
368
369#ifdef BSD_AUTH
370	devices[n++] = &mm_bsdauth_device;
371#else
372#ifdef USE_PAM
373	devices[n++] = &mm_sshpam_device;
374#endif
375#ifdef SKEY
376	devices[n++] = &mm_skey_device;
377#endif
378#endif
379}
380