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 * check to see whether permission is granted to use a key in the desired way,
19 * but permit the security modules to override
20 */
21int key_task_permission(const key_ref_t key_ref,
22			struct task_struct *context,
23			key_perm_t perm)
24{
25	struct key *key;
26	key_perm_t kperm;
27	int ret;
28
29	key = key_ref_to_ptr(key_ref);
30
31	/* use the second 8-bits of permissions for keys the caller owns */
32	if (key->uid == context->fsuid) {
33		kperm = key->perm >> 16;
34		goto use_these_perms;
35	}
36
37	/* use the third 8-bits of permissions for keys the caller has a group
38	 * membership in common with */
39	if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
40		if (key->gid == context->fsgid) {
41			kperm = key->perm >> 8;
42			goto use_these_perms;
43		}
44
45		task_lock(context);
46		ret = groups_search(context->group_info, key->gid);
47		task_unlock(context);
48
49		if (ret) {
50			kperm = key->perm >> 8;
51			goto use_these_perms;
52		}
53	}
54
55	/* otherwise use the least-significant 8-bits */
56	kperm = key->perm;
57
58use_these_perms:
59	/* use the top 8-bits of permissions for keys the caller possesses
60	 * - possessor permissions are additive with other permissions
61	 */
62	if (is_key_possessed(key_ref))
63		kperm |= key->perm >> 24;
64
65	kperm = kperm & perm & KEY_ALL;
66
67	if (kperm != perm)
68		return -EACCES;
69
70	/* let LSM be the final arbiter */
71	return security_key_permission(key_ref, context, perm);
72
73} /* end key_task_permission() */
74
75EXPORT_SYMBOL(key_task_permission);
76
77/*****************************************************************************/
78/*
79 * validate a key
80 */
81int key_validate(struct key *key)
82{
83	struct timespec now;
84	int ret = 0;
85
86	if (key) {
87		/* check it's still accessible */
88		ret = -EKEYREVOKED;
89		if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
90		    test_bit(KEY_FLAG_DEAD, &key->flags))
91			goto error;
92
93		/* check it hasn't expired */
94		ret = 0;
95		if (key->expiry) {
96			now = current_kernel_time();
97			if (now.tv_sec >= key->expiry)
98				ret = -EKEYEXPIRED;
99		}
100	}
101
102 error:
103	return ret;
104
105} /* end key_validate() */
106
107EXPORT_SYMBOL(key_validate);
108