1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Key permission checking
3 *
4 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8 #include <linux/export.h>
9 #include <linux/security.h>
10 #include "internal.h"
11
12 /**
13 * key_task_permission - Check a key can be used
14 * @key_ref: The key to check.
15 * @cred: The credentials to use.
16 * @perm: The permissions to check for.
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 * The caller must hold either a ref on cred or must hold the RCU readlock.
22 *
23 * Returns 0 if successful, -EACCES if access is denied based on the
24 * permissions bits or the LSM check.
25 */
key_task_permission(const key_ref_t key_ref,const struct cred * cred,unsigned perm)26 int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
27 unsigned perm)
28 {
29 struct key *key;
30 key_perm_t kperm;
31 int ret;
32
33 key = key_ref_to_ptr(key_ref);
34
35 /* use the second 8-bits of permissions for keys the caller owns */
36 if (uid_eq(key->uid, cred->fsuid)) {
37 kperm = key->perm >> 16;
38 goto use_these_perms;
39 }
40
41 /* use the third 8-bits of permissions for keys the caller has a group
42 * membership in common with */
43 if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) {
44 if (gid_eq(key->gid, cred->fsgid)) {
45 kperm = key->perm >> 8;
46 goto use_these_perms;
47 }
48
49 ret = groups_search(cred->group_info, key->gid);
50 if (ret) {
51 kperm = key->perm >> 8;
52 goto use_these_perms;
53 }
54 }
55
56 /* otherwise use the least-significant 8-bits */
57 kperm = key->perm;
58
59 use_these_perms:
60
61 /* use the top 8-bits of permissions for keys the caller possesses
62 * - possessor permissions are additive with other permissions
63 */
64 if (is_key_possessed(key_ref))
65 kperm |= key->perm >> 24;
66
67 kperm = kperm & perm & KEY_NEED_ALL;
68
69 if (kperm != perm)
70 return -EACCES;
71
72 /* let LSM be the final arbiter */
73 return security_key_permission(key_ref, cred, perm);
74 }
75 EXPORT_SYMBOL(key_task_permission);
76
77 /**
78 * key_validate - Validate a key.
79 * @key: The key to be validated.
80 *
81 * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the
82 * key is invalidated, -EKEYREVOKED if the key's type has been removed or if
83 * the key has been revoked or -EKEYEXPIRED if the key has expired.
84 */
key_validate(const struct key * key)85 int key_validate(const struct key *key)
86 {
87 unsigned long flags = READ_ONCE(key->flags);
88 time64_t expiry = READ_ONCE(key->expiry);
89
90 if (flags & (1 << KEY_FLAG_INVALIDATED))
91 return -ENOKEY;
92
93 /* check it's still accessible */
94 if (flags & ((1 << KEY_FLAG_REVOKED) |
95 (1 << KEY_FLAG_DEAD)))
96 return -EKEYREVOKED;
97
98 /* check it hasn't expired */
99 if (expiry) {
100 if (ktime_get_real_seconds() >= expiry)
101 return -EKEYEXPIRED;
102 }
103
104 return 0;
105 }
106 EXPORT_SYMBOL(key_validate);
107