1 /* $OpenBSD: auth2-chall.c,v 1.44 2016/05/02 08:49:03 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 "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 u_int devices_done;
87 };
88
89 #ifdef USE_PAM
90 void
remove_kbdint_device(const char * devname)91 remove_kbdint_device(const char *devname)
92 {
93 int i, j;
94
95 for (i = 0; devices[i] != NULL; i++)
96 if (strcmp(devices[i]->name, devname) == 0) {
97 for (j = i; devices[j] != NULL; j++)
98 devices[j] = devices[j+1];
99 i--;
100 }
101 }
102 #endif
103
104 static KbdintAuthctxt *
kbdint_alloc(const char * devs)105 kbdint_alloc(const char *devs)
106 {
107 KbdintAuthctxt *kbdintctxt;
108 Buffer b;
109 int i;
110
111 #ifdef USE_PAM
112 if (!options.use_pam)
113 remove_kbdint_device("pam");
114 #endif
115
116 kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
117 if (strcmp(devs, "") == 0) {
118 buffer_init(&b);
119 for (i = 0; devices[i]; i++) {
120 if (buffer_len(&b) > 0)
121 buffer_append(&b, ",", 1);
122 buffer_append(&b, devices[i]->name,
123 strlen(devices[i]->name));
124 }
125 if ((kbdintctxt->devices = sshbuf_dup_string(&b)) == NULL)
126 fatal("%s: sshbuf_dup_string failed", __func__);
127 buffer_free(&b);
128 } else {
129 kbdintctxt->devices = xstrdup(devs);
130 }
131 debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
132 kbdintctxt->ctxt = NULL;
133 kbdintctxt->device = NULL;
134 kbdintctxt->nreq = 0;
135
136 return kbdintctxt;
137 }
138 static void
kbdint_reset_device(KbdintAuthctxt * kbdintctxt)139 kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
140 {
141 if (kbdintctxt->ctxt) {
142 kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
143 kbdintctxt->ctxt = NULL;
144 }
145 kbdintctxt->device = NULL;
146 }
147 static void
kbdint_free(KbdintAuthctxt * kbdintctxt)148 kbdint_free(KbdintAuthctxt *kbdintctxt)
149 {
150 if (kbdintctxt->device)
151 kbdint_reset_device(kbdintctxt);
152 free(kbdintctxt->devices);
153 explicit_bzero(kbdintctxt, sizeof(*kbdintctxt));
154 free(kbdintctxt);
155 }
156 /* get next device */
157 static int
kbdint_next_device(Authctxt * authctxt,KbdintAuthctxt * kbdintctxt)158 kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
159 {
160 size_t len;
161 char *t;
162 int i;
163
164 if (kbdintctxt->device)
165 kbdint_reset_device(kbdintctxt);
166 do {
167 len = kbdintctxt->devices ?
168 strcspn(kbdintctxt->devices, ",") : 0;
169
170 if (len == 0)
171 break;
172 for (i = 0; devices[i]; i++) {
173 if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
174 !auth2_method_allowed(authctxt,
175 "keyboard-interactive", devices[i]->name))
176 continue;
177 if (strncmp(kbdintctxt->devices, devices[i]->name,
178 len) == 0) {
179 kbdintctxt->device = devices[i];
180 kbdintctxt->devices_done |= 1 << i;
181 }
182 }
183 t = kbdintctxt->devices;
184 kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
185 free(t);
186 debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
187 kbdintctxt->devices : "<empty>");
188 } while (kbdintctxt->devices && !kbdintctxt->device);
189
190 return kbdintctxt->device ? 1 : 0;
191 }
192
193 /*
194 * try challenge-response, set authctxt->postponed if we have to
195 * wait for the response.
196 */
197 int
auth2_challenge(Authctxt * authctxt,char * devs)198 auth2_challenge(Authctxt *authctxt, char *devs)
199 {
200 debug("auth2_challenge: user=%s devs=%s",
201 authctxt->user ? authctxt->user : "<nouser>",
202 devs ? devs : "<no devs>");
203
204 if (authctxt->user == NULL || !devs)
205 return 0;
206 if (authctxt->kbdintctxt == NULL)
207 authctxt->kbdintctxt = kbdint_alloc(devs);
208 return auth2_challenge_start(authctxt);
209 }
210
211 /* unregister kbd-int callbacks and context */
212 void
auth2_challenge_stop(Authctxt * authctxt)213 auth2_challenge_stop(Authctxt *authctxt)
214 {
215 /* unregister callback */
216 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
217 if (authctxt->kbdintctxt != NULL) {
218 kbdint_free(authctxt->kbdintctxt);
219 authctxt->kbdintctxt = NULL;
220 }
221 }
222
223 /* side effect: sets authctxt->postponed if a reply was sent*/
224 static int
auth2_challenge_start(Authctxt * authctxt)225 auth2_challenge_start(Authctxt *authctxt)
226 {
227 KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
228
229 debug2("auth2_challenge_start: devices %s",
230 kbdintctxt->devices ? kbdintctxt->devices : "<empty>");
231
232 if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
233 auth2_challenge_stop(authctxt);
234 return 0;
235 }
236 debug("auth2_challenge_start: trying authentication method '%s'",
237 kbdintctxt->device->name);
238
239 if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
240 auth2_challenge_stop(authctxt);
241 return 0;
242 }
243 if (send_userauth_info_request(authctxt) == 0) {
244 auth2_challenge_stop(authctxt);
245 return 0;
246 }
247 dispatch_set(SSH2_MSG_USERAUTH_INFO_RESPONSE,
248 &input_userauth_info_response);
249
250 authctxt->postponed = 1;
251 return 0;
252 }
253
254 static int
send_userauth_info_request(Authctxt * authctxt)255 send_userauth_info_request(Authctxt *authctxt)
256 {
257 KbdintAuthctxt *kbdintctxt;
258 char *name, *instr, **prompts;
259 u_int i, *echo_on;
260
261 kbdintctxt = authctxt->kbdintctxt;
262 if (kbdintctxt->device->query(kbdintctxt->ctxt,
263 &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
264 return 0;
265
266 packet_start(SSH2_MSG_USERAUTH_INFO_REQUEST);
267 packet_put_cstring(name);
268 packet_put_cstring(instr);
269 packet_put_cstring(""); /* language not used */
270 packet_put_int(kbdintctxt->nreq);
271 for (i = 0; i < kbdintctxt->nreq; i++) {
272 packet_put_cstring(prompts[i]);
273 packet_put_char(echo_on[i]);
274 }
275 packet_send();
276 packet_write_wait();
277
278 for (i = 0; i < kbdintctxt->nreq; i++)
279 free(prompts[i]);
280 free(prompts);
281 free(echo_on);
282 free(name);
283 free(instr);
284 return 1;
285 }
286
287 static int
input_userauth_info_response(int type,u_int32_t seq,void * ctxt)288 input_userauth_info_response(int type, u_int32_t seq, void *ctxt)
289 {
290 Authctxt *authctxt = ctxt;
291 KbdintAuthctxt *kbdintctxt;
292 int authenticated = 0, res;
293 u_int i, nresp;
294 const char *devicename = NULL;
295 char **response = NULL;
296
297 if (authctxt == NULL)
298 fatal("input_userauth_info_response: no authctxt");
299 kbdintctxt = authctxt->kbdintctxt;
300 if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
301 fatal("input_userauth_info_response: no kbdintctxt");
302 if (kbdintctxt->device == NULL)
303 fatal("input_userauth_info_response: no device");
304
305 authctxt->postponed = 0; /* reset */
306 nresp = packet_get_int();
307 if (nresp != kbdintctxt->nreq)
308 fatal("input_userauth_info_response: wrong number of replies");
309 if (nresp > 100)
310 fatal("input_userauth_info_response: too many replies");
311 if (nresp > 0) {
312 response = xcalloc(nresp, sizeof(char *));
313 for (i = 0; i < nresp; i++)
314 response[i] = packet_get_string(NULL);
315 }
316 packet_check_eom();
317
318 res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
319
320 for (i = 0; i < nresp; i++) {
321 explicit_bzero(response[i], strlen(response[i]));
322 free(response[i]);
323 }
324 free(response);
325
326 switch (res) {
327 case 0:
328 /* Success! */
329 authenticated = authctxt->valid ? 1 : 0;
330 break;
331 case 1:
332 /* Authentication needs further interaction */
333 if (send_userauth_info_request(authctxt) == 1)
334 authctxt->postponed = 1;
335 break;
336 default:
337 /* Failure! */
338 break;
339 }
340 devicename = kbdintctxt->device->name;
341 if (!authctxt->postponed) {
342 if (authenticated) {
343 auth2_challenge_stop(authctxt);
344 } else {
345 /* start next device */
346 /* may set authctxt->postponed */
347 auth2_challenge_start(authctxt);
348 }
349 }
350 userauth_finish(authctxt, authenticated, "keyboard-interactive",
351 devicename);
352 return 0;
353 }
354
355 void
privsep_challenge_enable(void)356 privsep_challenge_enable(void)
357 {
358 #if defined(BSD_AUTH) || defined(USE_PAM) || defined(SKEY)
359 int n = 0;
360 #endif
361 #ifdef BSD_AUTH
362 extern KbdintDevice mm_bsdauth_device;
363 #endif
364 #ifdef USE_PAM
365 extern KbdintDevice mm_sshpam_device;
366 #endif
367 #ifdef SKEY
368 extern KbdintDevice mm_skey_device;
369 #endif
370
371 #ifdef BSD_AUTH
372 devices[n++] = &mm_bsdauth_device;
373 #else
374 #ifdef USE_PAM
375 devices[n++] = &mm_sshpam_device;
376 #endif
377 #ifdef SKEY
378 devices[n++] = &mm_skey_device;
379 #endif
380 #endif
381 }
382