1 /* permission.c: key permission determination
2 *
3 * Copyright (C) 2005 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/security.h>
14 #include "internal.h"
15
16 /*****************************************************************************/
17 /*
18 * check to see whether permission is granted to use a key in the desired way,
19 * but permit the security modules to override
20 */
21 int key_task_permission(const key_ref_t key_ref,
22 struct task_struct *context,
23 key_perm_t perm)
24 {
25 struct key *key;
26 key_perm_t kperm;
27 int ret;
28
29 key = key_ref_to_ptr(key_ref);
30
31 /* use the second 8-bits of permissions for keys the caller owns */
32 if (key->uid == context->fsuid) {
33 kperm = key->perm >> 16;
34 goto use_these_perms;
35 }
36
37 /* use the third 8-bits of permissions for keys the caller has a group
38 * membership in common with */
39 if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
40 if (key->gid == context->fsgid) {
41 kperm = key->perm >> 8;
42 goto use_these_perms;
43 }
44
45 task_lock(context);
46 ret = groups_search(context->group_info, key->gid);
47 task_unlock(context);
48
49 if (ret) {
50 kperm = key->perm >> 8;
51 goto use_these_perms;
52 }
53 }
54
55 /* otherwise use the least-significant 8-bits */
56 kperm = key->perm;
57
58 use_these_perms:
59 /* use the top 8-bits of permissions for keys the caller possesses
60 * - possessor permissions are additive with other permissions
61 */
62 if (is_key_possessed(key_ref))
63 kperm |= key->perm >> 24;
64
65 kperm = kperm & perm & KEY_ALL;
66
67 if (kperm != perm)
68 return -EACCES;
69
70 /* let LSM be the final arbiter */
71 return security_key_permission(key_ref, context, perm);
72
73 } /* end key_task_permission() */
74
75 EXPORT_SYMBOL(key_task_permission);
76
77 /*****************************************************************************/
78 /*
79 * validate a key
80 */
81 int key_validate(struct key *key)
82 {
83 struct timespec now;
84 int ret = 0;
85
86 if (key) {
87 /* check it's still accessible */
88 ret = -EKEYREVOKED;
89 if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
90 test_bit(KEY_FLAG_DEAD, &key->flags))
91 goto error;
92
93 /* check it hasn't expired */
94 ret = 0;
95 if (key->expiry) {
96 now = current_kernel_time();
97 if (now.tv_sec >= key->expiry)
98 ret = -EKEYEXPIRED;
99 }
100 }
101
102 error:
103 return ret;
104
105 } /* end key_validate() */
106
107 EXPORT_SYMBOL(key_validate);
108
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