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 */
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 if (key->user->user_ns != cred->user->user_ns)
39 goto use_other_perms;
40
41 /* use the second 8-bits of permissions for keys the caller owns */
42 if (key->uid == cred->fsuid) {
43 kperm = key->perm >> 16;
44 goto use_these_perms;
45 }
46
47 /* use the third 8-bits of permissions for keys the caller has a group
48 * membership in common with */
49 if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
50 if (key->gid == cred->fsgid) {
51 kperm = key->perm >> 8;
52 goto use_these_perms;
53 }
54
55 ret = groups_search(cred->group_info, key->gid);
56 if (ret) {
57 kperm = key->perm >> 8;
58 goto use_these_perms;
59 }
60 }
61
62 use_other_perms:
63
64 /* otherwise use the least-significant 8-bits */
65 kperm = key->perm;
66
67 use_these_perms:
68
69 /* use the top 8-bits of permissions for keys the caller possesses
70 * - possessor permissions are additive with other permissions
71 */
72 if (is_key_possessed(key_ref))
73 kperm |= key->perm >> 24;
74
75 kperm = kperm & perm & KEY_ALL;
76
77 if (kperm != perm)
78 return -EACCES;
79
80 /* let LSM be the final arbiter */
81 return security_key_permission(key_ref, cred, perm);
82
83 } /* end key_task_permission() */
84
85 EXPORT_SYMBOL(key_task_permission);
86
87 /*****************************************************************************/
88 /*
89 * validate a key
90 */
91 int key_validate(struct key *key)
92 {
93 struct timespec now;
94 int ret = 0;
95
96 if (key) {
97 /* check it's still accessible */
98 ret = -EKEYREVOKED;
99 if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
100 test_bit(KEY_FLAG_DEAD, &key->flags))
101 goto error;
102
103 /* check it hasn't expired */
104 ret = 0;
105 if (key->expiry) {
106 now = current_kernel_time();
107 if (now.tv_sec >= key->expiry)
108 ret = -EKEYEXPIRED;
109 }
110 }
111
112 error:
113 return ret;
114
115 } /* end key_validate() */
116
117 EXPORT_SYMBOL(key_validate);
118
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