Branch data Line data Source code
1 : : /* Key permission checking
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 : : * key_task_permission - Check a key can be used
18 : : * @key_ref: The key to check.
19 : : * @cred: The credentials to use.
20 : : * @perm: The permissions to check for.
21 : : *
22 : : * Check to see whether permission is granted to use a key in the desired way,
23 : : * but permit the security modules to override.
24 : : *
25 : : * The caller must hold either a ref on cred or must hold the RCU readlock.
26 : : *
27 : : * Returns 0 if successful, -EACCES if access is denied based on the
28 : : * permissions bits or the LSM check.
29 : : */
30 : 0 : int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
31 : : key_perm_t perm)
32 : : {
33 : : struct key *key;
34 : : key_perm_t kperm;
35 : : int ret;
36 : :
37 : : key = key_ref_to_ptr(key_ref);
38 : :
39 : : /* use the second 8-bits of permissions for keys the caller owns */
40 [ + - ]: 4 : if (uid_eq(key->uid, cred->fsuid)) {
41 : 4 : kperm = key->perm >> 16;
42 : 4 : goto use_these_perms;
43 : : }
44 : :
45 : : /* use the third 8-bits of permissions for keys the caller has a group
46 : : * membership in common with */
47 [ # # ][ # # ]: 0 : if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) {
48 [ # # ]: 0 : if (gid_eq(key->gid, cred->fsgid)) {
49 : 0 : kperm = key->perm >> 8;
50 : 0 : goto use_these_perms;
51 : : }
52 : :
53 : 0 : ret = groups_search(cred->group_info, key->gid);
54 [ # # ]: 0 : if (ret) {
55 : 0 : kperm = key->perm >> 8;
56 : 0 : goto use_these_perms;
57 : : }
58 : : }
59 : :
60 : : /* otherwise use the least-significant 8-bits */
61 : 0 : kperm = key->perm;
62 : :
63 : : use_these_perms:
64 : :
65 : : /* use the top 8-bits of permissions for keys the caller possesses
66 : : * - possessor permissions are additive with other permissions
67 : : */
68 [ + - ]: 4 : if (is_key_possessed(key_ref))
69 : 4 : kperm |= key->perm >> 24;
70 : :
71 : 4 : kperm = kperm & perm & KEY_ALL;
72 : :
73 [ + - ]: 4 : if (kperm != perm)
74 : : return -EACCES;
75 : :
76 : : /* let LSM be the final arbiter */
77 : 4 : return security_key_permission(key_ref, cred, perm);
78 : : }
79 : : EXPORT_SYMBOL(key_task_permission);
80 : :
81 : : /**
82 : : * key_validate - Validate a key.
83 : : * @key: The key to be validated.
84 : : *
85 : : * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the
86 : : * key is invalidated, -EKEYREVOKED if the key's type has been removed or if
87 : : * the key has been revoked or -EKEYEXPIRED if the key has expired.
88 : : */
89 : 0 : int key_validate(const struct key *key)
90 : : {
91 : 2 : unsigned long flags = key->flags;
92 : :
93 [ + - ]: 2 : if (flags & (1 << KEY_FLAG_INVALIDATED))
94 : : return -ENOKEY;
95 : :
96 : : /* check it's still accessible */
97 [ + - ]: 2 : if (flags & ((1 << KEY_FLAG_REVOKED) |
98 : : (1 << KEY_FLAG_DEAD)))
99 : : return -EKEYREVOKED;
100 : :
101 : : /* check it hasn't expired */
102 [ - + ]: 2 : if (key->expiry) {
103 : 0 : struct timespec now = current_kernel_time();
104 [ # # ]: 2 : if (now.tv_sec >= key->expiry)
105 : 0 : return -EKEYEXPIRED;
106 : : }
107 : :
108 : : return 0;
109 : : }
110 : : EXPORT_SYMBOL(key_validate);
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