1 /* $OpenBSD: auth2-chall.c,v 1.42 2015/01/19 20:07:45 markus 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 "misc.h"
45 #include "servconf.h"
46
47 /* import */
48 extern ServerOptions options;
49
50 static int auth2_challenge_start(Authctxt *);
51 static int send_userauth_info_request(Authctxt *);
52 static int input_userauth_info_response(int, u_int32_t, void *);
53
54 #ifdef BSD_AUTH
55 extern KbdintDevice bsdauth_device;
56 #else
57 #ifdef USE_PAM
58 extern KbdintDevice sshpam_device;
59 #endif
60 #ifdef SKEY
61 extern KbdintDevice skey_device;
62 #endif
63 #endif
64
65 KbdintDevice *devices[] = {
66 #ifdef BSD_AUTH
67 &bsdauth_device,
68 #else
69 #ifdef USE_PAM
70 &sshpam_device,
71 #endif
72 #ifdef SKEY
73 &skey_device,
74 #endif
75 #endif
76 NULL
77 };
78
79 typedef struct KbdintAuthctxt KbdintAuthctxt;
80 struct KbdintAuthctxt
81 {
82 char *devices;
83 void *ctxt;
84 KbdintDevice *device;
85 u_int nreq;
86 };
87
88 #ifdef USE_PAM
89 void
remove_kbdint_device(const char * devname)90 remove_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
103 static KbdintAuthctxt *
kbdint_alloc(const char * devs)104 kbdint_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 }
137 static void
kbdint_reset_device(KbdintAuthctxt * kbdintctxt)138 kbdint_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 }
146 static void
kbdint_free(KbdintAuthctxt * kbdintctxt)147 kbdint_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 */
156 static int
kbdint_next_device(Authctxt * authctxt,KbdintAuthctxt * kbdintctxt)157 kbdint_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 (!auth2_method_allowed(authctxt,
173 "keyboard-interactive", devices[i]->name))
174 continue;
175 if (strncmp(kbdintctxt->devices, devices[i]->name, len) == 0)
176 kbdintctxt->device = devices[i];
177 }
178 t = kbdintctxt->devices;
179 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
180 free(t);
181 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
182 kbdintctxt->devices : "<empty>");
183 } while (kbdintctxt->devices && !kbdintctxt->device);
184
185 return kbdintctxt->device ? 1 : 0;
186 }
187
188 /*
189 * try challenge-response, set authctxt->postponed if we have to
190 * wait for the response.
191 */
192 int
auth2_challenge(Authctxt * authctxt,char * devs)193 auth2_challenge(Authctxt *authctxt, char *devs)
194 {
195 debug("auth2_challenge: user=%s devs=%s",
196 authctxt->user ? authctxt->user : "<nouser>",
197 devs ? devs : "<no devs>");
198
199 if (authctxt->user == NULL || !devs)
200 return 0;
201 if (authctxt->kbdintctxt == NULL)
202 authctxt->kbdintctxt = kbdint_alloc(devs);
203 return auth2_challenge_start(authctxt);
204 }
205
206 /* unregister kbd-int callbacks and context */
207 void
auth2_challenge_stop(Authctxt * authctxt)208 auth2_challenge_stop(Authctxt *authctxt)
209 {
210 /* unregister callback */
211 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
212 if (authctxt->kbdintctxt != NULL) {
213 kbdint_free(authctxt->kbdintctxt);
214 authctxt->kbdintctxt = NULL;
215 }
216 }
217
218 /* side effect: sets authctxt->postponed if a reply was sent*/
219 static int
auth2_challenge_start(Authctxt * authctxt)220 auth2_challenge_start(Authctxt *authctxt)
221 {
222 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
223
224 debug2("auth2_challenge_start: devices %s",
225 kbdintctxt->devices ? kbdintctxt->devices : "<empty>");
226
227 if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
228 auth2_challenge_stop(authctxt);
229 return 0;
230 }
231 debug("auth2_challenge_start: trying authentication method '%s'",
232 kbdintctxt->device->name);
233
234 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
235 auth2_challenge_stop(authctxt);
236 return 0;
237 }
238 if (send_userauth_info_request(authctxt) == 0) {
239 auth2_challenge_stop(authctxt);
240 return 0;
241 }
242 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
243 &input_userauth_info_response);
244
245 authctxt->postponed = 1;
246 return 0;
247 }
248
249 static int
send_userauth_info_request(Authctxt * authctxt)250 send_userauth_info_request(Authctxt *authctxt)
251 {
252 KbdintAuthctxt *kbdintctxt;
253 char *name, *instr, **prompts;
254 u_int i, *echo_on;
255
256 kbdintctxt = authctxt->kbdintctxt;
257 if (kbdintctxt->device->query(kbdintctxt->ctxt,
258 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
259 return 0;
260
261 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
262 packet_put_cstring(name);
263 packet_put_cstring(instr);
264 packet_put_cstring(""); /* language not used */
265 packet_put_int(kbdintctxt->nreq);
266 for (i = 0; i < kbdintctxt->nreq; i++) {
267 packet_put_cstring(prompts[i]);
268 packet_put_char(echo_on[i]);
269 }
270 packet_send();
271 packet_write_wait();
272
273 for (i = 0; i < kbdintctxt->nreq; i++)
274 free(prompts[i]);
275 free(prompts);
276 free(echo_on);
277 free(name);
278 free(instr);
279 return 1;
280 }
281
282 static int
input_userauth_info_response(int type,u_int32_t seq,void * ctxt)283 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
284 {
285 Authctxt *authctxt = ctxt;
286 KbdintAuthctxt *kbdintctxt;
287 int authenticated = 0, res;
288 u_int i, nresp;
289 const char *devicename = NULL;
290 char **response = NULL;
291
292 if (authctxt == NULL)
293 fatal("input_userauth_info_response: no authctxt");
294 kbdintctxt = authctxt->kbdintctxt;
295 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
296 fatal("input_userauth_info_response: no kbdintctxt");
297 if (kbdintctxt->device == NULL)
298 fatal("input_userauth_info_response: no device");
299
300 authctxt->postponed = 0; /* reset */
301 nresp = packet_get_int();
302 if (nresp != kbdintctxt->nreq)
303 fatal("input_userauth_info_response: wrong number of replies");
304 if (nresp > 100)
305 fatal("input_userauth_info_response: too many replies");
306 if (nresp > 0) {
307 response = xcalloc(nresp, sizeof(char *));
308 for (i = 0; i < nresp; i++)
309 response[i] = packet_get_string(NULL);
310 }
311 packet_check_eom();
312
313 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
314
315 for (i = 0; i < nresp; i++) {
316 explicit_bzero(response[i], strlen(response[i]));
317 free(response[i]);
318 }
319 free(response);
320
321 switch (res) {
322 case 0:
323 /* Success! */
324 authenticated = authctxt->valid ? 1 : 0;
325 break;
326 case 1:
327 /* Authentication needs further interaction */
328 if (send_userauth_info_request(authctxt) == 1)
329 authctxt->postponed = 1;
330 break;
331 default:
332 /* Failure! */
333 break;
334 }
335 devicename = kbdintctxt->device->name;
336 if (!authctxt->postponed) {
337 if (authenticated) {
338 auth2_challenge_stop(authctxt);
339 } else {
340 /* start next device */
341 /* may set authctxt->postponed */
342 auth2_challenge_start(authctxt);
343 }
344 }
345 userauth_finish(authctxt, authenticated, "keyboard-interactive",
346 devicename);
347 return 0;
348 }
349
350 void
privsep_challenge_enable(void)351 privsep_challenge_enable(void)
352 {
353 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
354 int n = 0;
355 #endif
356 #ifdef BSD_AUTH
357 extern KbdintDevice mm_bsdauth_device;
358 #endif
359 #ifdef USE_PAM
360 extern KbdintDevice mm_sshpam_device;
361 #endif
362 #ifdef SKEY
363 extern KbdintDevice mm_skey_device;
364 #endif
365
366 #ifdef BSD_AUTH
367 devices[n++] = &mm_bsdauth_device;
368 #else
369 #ifdef USE_PAM
370 devices[n++] = &mm_sshpam_device;
371 #endif
372 #ifdef SKEY
373 devices[n++] = &mm_skey_device;
374 #endif
375 #endif
376 }
377