Linux-2.6.12-rc2
[linux-3.10.git] / security / keys / request_key.c
1 /* request_key.c: request a key from userspace
2  *
3  * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells (dhowells@redhat.com)
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/kmod.h>
15 #include <linux/err.h>
16 #include "internal.h"
17
18 struct key_construction {
19         struct list_head        link;   /* link in construction queue */
20         struct key              *key;   /* key being constructed */
21 };
22
23 /* when waiting for someone else's keys, you get added to this */
24 DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
25
26 /*****************************************************************************/
27 /*
28  * request userspace finish the construction of a key
29  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring> <info>"
30  * - if callout_info is an empty string, it'll be rendered as a "-" instead
31  */
32 static int call_request_key(struct key *key,
33                             const char *op,
34                             const char *callout_info)
35 {
36         struct task_struct *tsk = current;
37         unsigned long flags;
38         key_serial_t prkey, sskey;
39         char *argv[10], *envp[3], uid_str[12], gid_str[12];
40         char key_str[12], keyring_str[3][12];
41         int i;
42
43         /* record the UID and GID */
44         sprintf(uid_str, "%d", current->fsuid);
45         sprintf(gid_str, "%d", current->fsgid);
46
47         /* we say which key is under construction */
48         sprintf(key_str, "%d", key->serial);
49
50         /* we specify the process's default keyrings */
51         sprintf(keyring_str[0], "%d",
52                 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
53
54         prkey = 0;
55         if (tsk->signal->process_keyring)
56                 prkey = tsk->signal->process_keyring->serial;
57
58         sskey = 0;
59         spin_lock_irqsave(&tsk->sighand->siglock, flags);
60         if (tsk->signal->session_keyring)
61                 sskey = tsk->signal->session_keyring->serial;
62         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
63
64
65         if (!sskey)
66                 sskey = tsk->user->session_keyring->serial;
67
68         sprintf(keyring_str[1], "%d", prkey);
69         sprintf(keyring_str[2], "%d", sskey);
70
71         /* set up a minimal environment */
72         i = 0;
73         envp[i++] = "HOME=/";
74         envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
75         envp[i] = NULL;
76
77         /* set up the argument list */
78         i = 0;
79         argv[i++] = "/sbin/request-key";
80         argv[i++] = (char *) op;
81         argv[i++] = key_str;
82         argv[i++] = uid_str;
83         argv[i++] = gid_str;
84         argv[i++] = keyring_str[0];
85         argv[i++] = keyring_str[1];
86         argv[i++] = keyring_str[2];
87         argv[i++] = callout_info[0] ? (char *) callout_info : "-";
88         argv[i] = NULL;
89
90         /* do it */
91         return call_usermodehelper(argv[0], argv, envp, 1);
92
93 } /* end call_request_key() */
94
95 /*****************************************************************************/
96 /*
97  * call out to userspace for the key
98  * - called with the construction sem held, but the sem is dropped here
99  * - we ignore program failure and go on key status instead
100  */
101 static struct key *__request_key_construction(struct key_type *type,
102                                               const char *description,
103                                               const char *callout_info)
104 {
105         struct key_construction cons;
106         struct timespec now;
107         struct key *key;
108         int ret, negative;
109
110         /* create a key and add it to the queue */
111         key = key_alloc(type, description,
112                         current->fsuid, current->fsgid, KEY_USR_ALL, 0);
113         if (IS_ERR(key))
114                 goto alloc_failed;
115
116         write_lock(&key->lock);
117         key->flags |= KEY_FLAG_USER_CONSTRUCT;
118         write_unlock(&key->lock);
119
120         cons.key = key;
121         list_add_tail(&cons.link, &key->user->consq);
122
123         /* we drop the construction sem here on behalf of the caller */
124         up_write(&key_construction_sem);
125
126         /* make the call */
127         ret = call_request_key(key, "create", callout_info);
128         if (ret < 0)
129                 goto request_failed;
130
131         /* if the key wasn't instantiated, then we want to give an error */
132         ret = -ENOKEY;
133         if (!(key->flags & KEY_FLAG_INSTANTIATED))
134                 goto request_failed;
135
136         down_write(&key_construction_sem);
137         list_del(&cons.link);
138         up_write(&key_construction_sem);
139
140         /* also give an error if the key was negatively instantiated */
141  check_not_negative:
142         if (key->flags & KEY_FLAG_NEGATIVE) {
143                 key_put(key);
144                 key = ERR_PTR(-ENOKEY);
145         }
146
147  out:
148         return key;
149
150  request_failed:
151         /* it wasn't instantiated
152          * - remove from construction queue
153          * - mark the key as dead
154          */
155         negative = 0;
156         down_write(&key_construction_sem);
157
158         list_del(&cons.link);
159
160         write_lock(&key->lock);
161         key->flags &= ~KEY_FLAG_USER_CONSTRUCT;
162
163         /* check it didn't get instantiated between the check and the down */
164         if (!(key->flags & KEY_FLAG_INSTANTIATED)) {
165                 key->flags |= KEY_FLAG_INSTANTIATED | KEY_FLAG_NEGATIVE;
166                 negative = 1;
167         }
168
169         write_unlock(&key->lock);
170         up_write(&key_construction_sem);
171
172         if (!negative)
173                 goto check_not_negative; /* surprisingly, the key got
174                                           * instantiated */
175
176         /* set the timeout and store in the session keyring if we can */
177         now = current_kernel_time();
178         key->expiry = now.tv_sec + key_negative_timeout;
179
180         if (current->signal->session_keyring) {
181                 unsigned long flags;
182                 struct key *keyring;
183
184                 spin_lock_irqsave(&current->sighand->siglock, flags);
185                 keyring = current->signal->session_keyring;
186                 atomic_inc(&keyring->usage);
187                 spin_unlock_irqrestore(&current->sighand->siglock, flags);
188
189                 key_link(keyring, key);
190                 key_put(keyring);
191         }
192
193         key_put(key);
194
195         /* notify anyone who was waiting */
196         wake_up_all(&request_key_conswq);
197
198         key = ERR_PTR(ret);
199         goto out;
200
201  alloc_failed:
202         up_write(&key_construction_sem);
203         goto out;
204
205 } /* end __request_key_construction() */
206
207 /*****************************************************************************/
208 /*
209  * call out to userspace to request the key
210  * - we check the construction queue first to see if an appropriate key is
211  *   already being constructed by userspace
212  */
213 static struct key *request_key_construction(struct key_type *type,
214                                             const char *description,
215                                             struct key_user *user,
216                                             const char *callout_info)
217 {
218         struct key_construction *pcons;
219         struct key *key, *ckey;
220
221         DECLARE_WAITQUEUE(myself, current);
222
223         /* see if there's such a key under construction already */
224         down_write(&key_construction_sem);
225
226         list_for_each_entry(pcons, &user->consq, link) {
227                 ckey = pcons->key;
228
229                 if (ckey->type != type)
230                         continue;
231
232                 if (type->match(ckey, description))
233                         goto found_key_under_construction;
234         }
235
236         /* see about getting userspace to construct the key */
237         key = __request_key_construction(type, description, callout_info);
238  error:
239         return key;
240
241         /* someone else has the same key under construction
242          * - we want to keep an eye on their key
243          */
244  found_key_under_construction:
245         atomic_inc(&ckey->usage);
246         up_write(&key_construction_sem);
247
248         /* wait for the key to be completed one way or another */
249         add_wait_queue(&request_key_conswq, &myself);
250
251         for (;;) {
252                 set_current_state(TASK_UNINTERRUPTIBLE);
253                 if (!(ckey->flags & KEY_FLAG_USER_CONSTRUCT))
254                         break;
255                 schedule();
256         }
257
258         set_current_state(TASK_RUNNING);
259         remove_wait_queue(&request_key_conswq, &myself);
260
261         /* we'll need to search this process's keyrings to see if the key is
262          * now there since we can't automatically assume it's also available
263          * there */
264         key_put(ckey);
265         ckey = NULL;
266
267         key = NULL; /* request a retry */
268         goto error;
269
270 } /* end request_key_construction() */
271
272 /*****************************************************************************/
273 /*
274  * request a key
275  * - search the process's keyrings
276  * - check the list of keys being created or updated
277  * - call out to userspace for a key if requested (supplementary info can be
278  *   passed)
279  */
280 struct key *request_key(struct key_type *type,
281                         const char *description,
282                         const char *callout_info)
283 {
284         struct key_user *user;
285         struct key *key;
286
287         /* search all the process keyrings for a key */
288         key = search_process_keyrings_aux(type, description, type->match);
289
290         if (PTR_ERR(key) == -EAGAIN) {
291                 /* the search failed, but the keyrings were searchable, so we
292                  * should consult userspace if we can */
293                 key = ERR_PTR(-ENOKEY);
294                 if (!callout_info)
295                         goto error;
296
297                 /* - get hold of the user's construction queue */
298                 user = key_user_lookup(current->fsuid);
299                 if (!user) {
300                         key = ERR_PTR(-ENOMEM);
301                         goto error;
302                 }
303
304                 for (;;) {
305                         /* ask userspace (returns NULL if it waited on a key
306                          * being constructed) */
307                         key = request_key_construction(type, description,
308                                                        user, callout_info);
309                         if (key)
310                                 break;
311
312                         /* someone else made the key we want, so we need to
313                          * search again as it might now be available to us */
314                         key = search_process_keyrings_aux(type, description,
315                                                           type->match);
316                         if (PTR_ERR(key) != -EAGAIN)
317                                 break;
318                 }
319
320                 key_user_put(user);
321         }
322
323  error:
324         return key;
325
326 } /* end request_key() */
327
328 EXPORT_SYMBOL(request_key);
329
330 /*****************************************************************************/
331 /*
332  * validate a key
333  */
334 int key_validate(struct key *key)
335 {
336         struct timespec now;
337         int ret = 0;
338
339         if (key) {
340                 /* check it's still accessible */
341                 ret = -EKEYREVOKED;
342                 if (key->flags & (KEY_FLAG_REVOKED | KEY_FLAG_DEAD))
343                         goto error;
344
345                 /* check it hasn't expired */
346                 ret = 0;
347                 if (key->expiry) {
348                         now = current_kernel_time();
349                         if (now.tv_sec >= key->expiry)
350                                 ret = -EKEYEXPIRED;
351                 }
352         }
353
354  error:
355         return ret;
356
357 } /* end key_validate() */
358
359 EXPORT_SYMBOL(key_validate);