1 /* request_key.c: request a key from userspace
3 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
12 #include <linux/module.h>
13 #include <linux/sched.h>
14 #include <linux/kmod.h>
15 #include <linux/err.h>
18 struct key_construction {
19 struct list_head link; /* link in construction queue */
20 struct key *key; /* key being constructed */
23 /* when waiting for someone else's keys, you get added to this */
24 DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
26 /*****************************************************************************/
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
32 static int call_request_key(struct key *key,
34 const char *callout_info)
36 struct task_struct *tsk = current;
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];
43 /* record the UID and GID */
44 sprintf(uid_str, "%d", current->fsuid);
45 sprintf(gid_str, "%d", current->fsgid);
47 /* we say which key is under construction */
48 sprintf(key_str, "%d", key->serial);
50 /* we specify the process's default keyrings */
51 sprintf(keyring_str[0], "%d",
52 tsk->thread_keyring ? tsk->thread_keyring->serial : 0);
55 if (tsk->signal->process_keyring)
56 prkey = tsk->signal->process_keyring->serial;
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);
66 sskey = tsk->user->session_keyring->serial;
68 sprintf(keyring_str[1], "%d", prkey);
69 sprintf(keyring_str[2], "%d", sskey);
71 /* set up a minimal environment */
74 envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
77 /* set up the argument list */
79 argv[i++] = "/sbin/request-key";
80 argv[i++] = (char *) op;
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 : "-";
91 return call_usermodehelper(argv[0], argv, envp, 1);
93 } /* end call_request_key() */
95 /*****************************************************************************/
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
101 static struct key *__request_key_construction(struct key_type *type,
102 const char *description,
103 const char *callout_info)
105 struct key_construction cons;
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);
116 set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
119 list_add_tail(&cons.link, &key->user->consq);
121 /* we drop the construction sem here on behalf of the caller */
122 up_write(&key_construction_sem);
125 ret = call_request_key(key, "create", callout_info);
129 /* if the key wasn't instantiated, then we want to give an error */
131 if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
134 down_write(&key_construction_sem);
135 list_del(&cons.link);
136 up_write(&key_construction_sem);
138 /* also give an error if the key was negatively instantiated */
140 if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
142 key = ERR_PTR(-ENOKEY);
149 /* it wasn't instantiated
150 * - remove from construction queue
151 * - mark the key as dead
154 down_write(&key_construction_sem);
156 list_del(&cons.link);
158 /* check it didn't get instantiated between the check and the down */
159 if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
160 set_bit(KEY_FLAG_NEGATIVE, &key->flags);
161 set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
165 clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
167 up_write(&key_construction_sem);
170 goto check_not_negative; /* surprisingly, the key got
173 /* set the timeout and store in the session keyring if we can */
174 now = current_kernel_time();
175 key->expiry = now.tv_sec + key_negative_timeout;
177 if (current->signal->session_keyring) {
181 spin_lock_irqsave(¤t->sighand->siglock, flags);
182 keyring = current->signal->session_keyring;
183 atomic_inc(&keyring->usage);
184 spin_unlock_irqrestore(¤t->sighand->siglock, flags);
186 key_link(keyring, key);
192 /* notify anyone who was waiting */
193 wake_up_all(&request_key_conswq);
199 up_write(&key_construction_sem);
202 } /* end __request_key_construction() */
204 /*****************************************************************************/
206 * call out to userspace to request the key
207 * - we check the construction queue first to see if an appropriate key is
208 * already being constructed by userspace
210 static struct key *request_key_construction(struct key_type *type,
211 const char *description,
212 struct key_user *user,
213 const char *callout_info)
215 struct key_construction *pcons;
216 struct key *key, *ckey;
218 DECLARE_WAITQUEUE(myself, current);
220 /* see if there's such a key under construction already */
221 down_write(&key_construction_sem);
223 list_for_each_entry(pcons, &user->consq, link) {
226 if (ckey->type != type)
229 if (type->match(ckey, description))
230 goto found_key_under_construction;
233 /* see about getting userspace to construct the key */
234 key = __request_key_construction(type, description, callout_info);
238 /* someone else has the same key under construction
239 * - we want to keep an eye on their key
241 found_key_under_construction:
242 atomic_inc(&ckey->usage);
243 up_write(&key_construction_sem);
245 /* wait for the key to be completed one way or another */
246 add_wait_queue(&request_key_conswq, &myself);
249 set_current_state(TASK_UNINTERRUPTIBLE);
250 if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
255 set_current_state(TASK_RUNNING);
256 remove_wait_queue(&request_key_conswq, &myself);
258 /* we'll need to search this process's keyrings to see if the key is
259 * now there since we can't automatically assume it's also available
264 key = NULL; /* request a retry */
267 } /* end request_key_construction() */
269 /*****************************************************************************/
272 * - search the process's keyrings
273 * - check the list of keys being created or updated
274 * - call out to userspace for a key if requested (supplementary info can be
277 struct key *request_key(struct key_type *type,
278 const char *description,
279 const char *callout_info)
281 struct key_user *user;
284 /* search all the process keyrings for a key */
285 key = search_process_keyrings_aux(type, description, type->match);
287 if (PTR_ERR(key) == -EAGAIN) {
288 /* the search failed, but the keyrings were searchable, so we
289 * should consult userspace if we can */
290 key = ERR_PTR(-ENOKEY);
294 /* - get hold of the user's construction queue */
295 user = key_user_lookup(current->fsuid);
297 key = ERR_PTR(-ENOMEM);
302 /* ask userspace (returns NULL if it waited on a key
303 * being constructed) */
304 key = request_key_construction(type, description,
309 /* someone else made the key we want, so we need to
310 * search again as it might now be available to us */
311 key = search_process_keyrings_aux(type, description,
313 if (PTR_ERR(key) != -EAGAIN)
323 } /* end request_key() */
325 EXPORT_SYMBOL(request_key);
327 /*****************************************************************************/
331 int key_validate(struct key *key)
337 /* check it's still accessible */
339 if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
340 test_bit(KEY_FLAG_DEAD, &key->flags))
343 /* check it hasn't expired */
346 now = current_kernel_time();
347 if (now.tv_sec >= key->expiry)
355 } /* end key_validate() */
357 EXPORT_SYMBOL(key_validate);