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 */
30int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
31			unsigned 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	if (uid_eq(key->uid, cred->fsuid)) {
41		kperm = key->perm >> 16;
42		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	if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) {
48		if (gid_eq(key->gid, cred->fsgid)) {
49			kperm = key->perm >> 8;
50			goto use_these_perms;
51		}
52
53		ret = groups_search(cred->group_info, key->gid);
54		if (ret) {
55			kperm = key->perm >> 8;
56			goto use_these_perms;
57		}
58	}
59
60	/* otherwise use the least-significant 8-bits */
61	kperm = key->perm;
62
63use_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	if (is_key_possessed(key_ref))
69		kperm |= key->perm >> 24;
70
71	kperm = kperm & perm & KEY_NEED_ALL;
72
73	if (kperm != perm)
74		return -EACCES;
75
76	/* let LSM be the final arbiter */
77	return security_key_permission(key_ref, cred, perm);
78}
79EXPORT_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 */
89int key_validate(const struct key *key)
90{
91	unsigned long flags = key->flags;
92
93	if (flags & (1 << KEY_FLAG_INVALIDATED))
94		return -ENOKEY;
95
96	/* check it's still accessible */
97	if (flags & ((1 << KEY_FLAG_REVOKED) |
98		     (1 << KEY_FLAG_DEAD)))
99		return -EKEYREVOKED;
100
101	/* check it hasn't expired */
102	if (key->expiry) {
103		struct timespec now = current_kernel_time();
104		if (now.tv_sec >= key->expiry)
105			return -EKEYEXPIRED;
106	}
107
108	return 0;
109}
110EXPORT_SYMBOL(key_validate);
111