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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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