blob: 03db073ba45c526ef82979babcc4abff47ea8438 [file] [log] [blame]
David Howells468ed2b2005-10-07 15:07:38 +01001/* 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 */
20int 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
David Howells468ed2b2005-10-07 15:07:38 +010030 /* 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
57use_these_perms:
David Howells7ab501d2005-10-07 16:41:24 +010058 /* 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
David Howells468ed2b2005-10-07 15:07:38 +010064 kperm = kperm & perm & KEY_ALL;
65
66 return kperm == perm;
67
68} /* end key_task_permission() */
69
70EXPORT_SYMBOL(key_task_permission);