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468ed2b0 DH |
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 "internal.h" | |
14 | ||
15 | /*****************************************************************************/ | |
16 | /* | |
17 | * check to see whether permission is granted to use a key in the desired way, | |
18 | * but permit the security modules to override | |
19 | */ | |
20 | int key_task_permission(const key_ref_t key_ref, | |
21 | struct task_struct *context, | |
22 | key_perm_t perm) | |
23 | { | |
24 | struct key *key; | |
25 | key_perm_t kperm; | |
26 | int ret; | |
27 | ||
28 | key = key_ref_to_ptr(key_ref); | |
29 | ||
468ed2b0 DH |
30 | /* use the second 8-bits of permissions for keys the caller owns */ |
31 | if (key->uid == context->fsuid) { | |
32 | kperm = key->perm >> 16; | |
33 | goto use_these_perms; | |
34 | } | |
35 | ||
36 | /* use the third 8-bits of permissions for keys the caller has a group | |
37 | * membership in common with */ | |
38 | if (key->gid != -1 && key->perm & KEY_GRP_ALL) { | |
39 | if (key->gid == context->fsgid) { | |
40 | kperm = key->perm >> 8; | |
41 | goto use_these_perms; | |
42 | } | |
43 | ||
44 | task_lock(context); | |
45 | ret = groups_search(context->group_info, key->gid); | |
46 | task_unlock(context); | |
47 | ||
48 | if (ret) { | |
49 | kperm = key->perm >> 8; | |
50 | goto use_these_perms; | |
51 | } | |
52 | } | |
53 | ||
54 | /* otherwise use the least-significant 8-bits */ | |
55 | kperm = key->perm; | |
56 | ||
57 | use_these_perms: | |
7ab501db DH |
58 | /* use the top 8-bits of permissions for keys the caller possesses |
59 | * - possessor permissions are additive with other permissions | |
60 | */ | |
61 | if (is_key_possessed(key_ref)) | |
62 | kperm |= key->perm >> 24; | |
63 | ||
468ed2b0 DH |
64 | kperm = kperm & perm & KEY_ALL; |
65 | ||
66 | return kperm == perm; | |
67 | ||
68 | } /* end key_task_permission() */ | |
69 | ||
70 | EXPORT_SYMBOL(key_task_permission); |