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 * key_task_permission - Check a key can be used
19 * @key_ref: The key to check
20 * @cred: The credentials to use
21 * @perm: The permissions to check for
22 *
23 * Check to see whether permission is granted to use a key in the desired way,
24 * but permit the security modules to override.
25 *
26 * The caller must hold either a ref on cred or must hold the RCU readlock or a
27 * spinlock.
28 */
key_task_permission(const key_ref_t key_ref,const struct cred * cred,key_perm_t perm)29 int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
30 key_perm_t perm)
31 {
32 struct key *key;
33 key_perm_t kperm;
34 int ret;
35
36 key = key_ref_to_ptr(key_ref);
37
38 /* use the second 8-bits of permissions for keys the caller owns */
39 if (key->uid == cred->fsuid) {
40 kperm = key->perm >> 16;
41 goto use_these_perms;
42 }
43
44 /* use the third 8-bits of permissions for keys the caller has a group
45 * membership in common with */
46 if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
47 if (key->gid == cred->fsgid) {
48 kperm = key->perm >> 8;
49 goto use_these_perms;
50 }
51
52 ret = groups_search(cred->group_info, key->gid);
53 if (ret) {
54 kperm = key->perm >> 8;
55 goto use_these_perms;
56 }
57 }
58
59 /* otherwise use the least-significant 8-bits */
60 kperm = key->perm;
61
62 use_these_perms:
63
64 /* use the top 8-bits of permissions for keys the caller possesses
65 * - possessor permissions are additive with other permissions
66 */
67 if (is_key_possessed(key_ref))
68 kperm |= key->perm >> 24;
69
70 kperm = kperm & perm & KEY_ALL;
71
72 if (kperm != perm)
73 return -EACCES;
74
75 /* let LSM be the final arbiter */
76 return security_key_permission(key_ref, cred, perm);
77
78 } /* end key_task_permission() */
79
80 EXPORT_SYMBOL(key_task_permission);
81
82 /*****************************************************************************/
83 /*
84 * validate a key
85 */
key_validate(struct key * key)86 int key_validate(struct key *key)
87 {
88 struct timespec now;
89 int ret = 0;
90
91 if (key) {
92 /* check it's still accessible */
93 ret = -EKEYREVOKED;
94 if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
95 test_bit(KEY_FLAG_DEAD, &key->flags))
96 goto error;
97
98 /* check it hasn't expired */
99 ret = 0;
100 if (key->expiry) {
101 now = current_kernel_time();
102 if (now.tv_sec >= key->expiry)
103 ret = -EKEYEXPIRED;
104 }
105 }
106
107 error:
108 return ret;
109
110 } /* end key_validate() */
111
112 EXPORT_SYMBOL(key_validate);
113