Root/security/keys/permission.c

Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 9 years 5 months ago.
By Lars-Peter Clausen, jz4740: Fix compile error
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            key_perm_t 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    if (key->user->user_ns != cred->user->user_ns)
40        goto use_other_perms;
41
42    /* use the second 8-bits of permissions for keys the caller owns */
43    if (key->uid == cred->fsuid) {
44        kperm = key->perm >> 16;
45        goto use_these_perms;
46    }
47
48    /* use the third 8-bits of permissions for keys the caller has a group
49     * membership in common with */
50    if (key->gid != -1 && key->perm & KEY_GRP_ALL) {
51        if (key->gid == cred->fsgid) {
52            kperm = key->perm >> 8;
53            goto use_these_perms;
54        }
55
56        ret = groups_search(cred->group_info, key->gid);
57        if (ret) {
58            kperm = key->perm >> 8;
59            goto use_these_perms;
60        }
61    }
62
63use_other_perms:
64
65    /* otherwise use the least-significant 8-bits */
66    kperm = key->perm;
67
68use_these_perms:
69
70    /* use the top 8-bits of permissions for keys the caller possesses
71     * - possessor permissions are additive with other permissions
72     */
73    if (is_key_possessed(key_ref))
74        kperm |= key->perm >> 24;
75
76    kperm = kperm & perm & KEY_ALL;
77
78    if (kperm != perm)
79        return -EACCES;
80
81    /* let LSM be the final arbiter */
82    return security_key_permission(key_ref, cred, perm);
83}
84EXPORT_SYMBOL(key_task_permission);
85
86/**
87 * key_validate - Validate a key.
88 * @key: The key to be validated.
89 *
90 * Check that a key is valid, returning 0 if the key is okay, -EKEYREVOKED if
91 * the key's type has been removed or if the key has been revoked or
92 * -EKEYEXPIRED if the key has expired.
93 */
94int key_validate(struct key *key)
95{
96    struct timespec now;
97    int ret = 0;
98
99    if (key) {
100        /* check it's still accessible */
101        ret = -EKEYREVOKED;
102        if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
103            test_bit(KEY_FLAG_DEAD, &key->flags))
104            goto error;
105
106        /* check it hasn't expired */
107        ret = 0;
108        if (key->expiry) {
109            now = current_kernel_time();
110            if (now.tv_sec >= key->expiry)
111                ret = -EKEYEXPIRED;
112        }
113    }
114
115error:
116    return ret;
117}
118EXPORT_SYMBOL(key_validate);
119

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