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 */
47 extern ServerOptions options;
48
49 static int auth2_challenge_start(Authctxt *);
50 static int send_userauth_info_request(Authctxt *);
51 static void input_userauth_info_response(int, u_int32_t, void *);
52
53 #ifdef BSD_AUTH
54 extern KbdintDevice bsdauth_device;
55 #else
56 #ifdef USE_PAM
57 extern KbdintDevice sshpam_device;
58 #endif
59 #ifdef SKEY
60 extern KbdintDevice skey_device;
61 #endif
62 #endif
63
64 KbdintDevice *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
78 typedef struct KbdintAuthctxt KbdintAuthctxt;
79 struct KbdintAuthctxt
80 {
81 char *devices;
82 void *ctxt;
83 KbdintDevice *device;
84 u_int nreq;
85 };
86
87 #ifdef USE_PAM
88 void
remove_kbdint_device(const char * devname)89 remove_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
102 static KbdintAuthctxt *
kbdint_alloc(const char * devs)103 kbdint_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 }
136 static void
kbdint_reset_device(KbdintAuthctxt * kbdintctxt)137 kbdint_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 }
145 static void
kbdint_free(KbdintAuthctxt * kbdintctxt)146 kbdint_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 */
155 static int
kbdint_next_device(Authctxt * authctxt,KbdintAuthctxt * kbdintctxt)156 kbdint_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 */
191 int
auth2_challenge(Authctxt * authctxt,char * devs)192 auth2_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 */
206 void
auth2_challenge_stop(Authctxt * authctxt)207 auth2_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*/
218 static int
auth2_challenge_start(Authctxt * authctxt)219 auth2_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
248 static int
send_userauth_info_request(Authctxt * authctxt)249 send_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
281 static void
input_userauth_info_response(int type,u_int32_t seq,void * ctxt)282 input_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
348 void
privsep_challenge_enable(void)349 privsep_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