1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0-or-later
2*4882a593Smuzhiyun /* Key permission checking
3*4882a593Smuzhiyun *
4*4882a593Smuzhiyun * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
5*4882a593Smuzhiyun * Written by David Howells (dhowells@redhat.com)
6*4882a593Smuzhiyun */
7*4882a593Smuzhiyun
8*4882a593Smuzhiyun #include <linux/export.h>
9*4882a593Smuzhiyun #include <linux/security.h>
10*4882a593Smuzhiyun #include "internal.h"
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun /**
13*4882a593Smuzhiyun * key_task_permission - Check a key can be used
14*4882a593Smuzhiyun * @key_ref: The key to check.
15*4882a593Smuzhiyun * @cred: The credentials to use.
16*4882a593Smuzhiyun * @need_perm: The permission required.
17*4882a593Smuzhiyun *
18*4882a593Smuzhiyun * Check to see whether permission is granted to use a key in the desired way,
19*4882a593Smuzhiyun * but permit the security modules to override.
20*4882a593Smuzhiyun *
21*4882a593Smuzhiyun * The caller must hold either a ref on cred or must hold the RCU readlock.
22*4882a593Smuzhiyun *
23*4882a593Smuzhiyun * Returns 0 if successful, -EACCES if access is denied based on the
24*4882a593Smuzhiyun * permissions bits or the LSM check.
25*4882a593Smuzhiyun */
key_task_permission(const key_ref_t key_ref,const struct cred * cred,enum key_need_perm need_perm)26*4882a593Smuzhiyun int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
27*4882a593Smuzhiyun enum key_need_perm need_perm)
28*4882a593Smuzhiyun {
29*4882a593Smuzhiyun struct key *key;
30*4882a593Smuzhiyun key_perm_t kperm, mask;
31*4882a593Smuzhiyun int ret;
32*4882a593Smuzhiyun
33*4882a593Smuzhiyun switch (need_perm) {
34*4882a593Smuzhiyun default:
35*4882a593Smuzhiyun WARN_ON(1);
36*4882a593Smuzhiyun return -EACCES;
37*4882a593Smuzhiyun case KEY_NEED_UNLINK:
38*4882a593Smuzhiyun case KEY_SYSADMIN_OVERRIDE:
39*4882a593Smuzhiyun case KEY_AUTHTOKEN_OVERRIDE:
40*4882a593Smuzhiyun case KEY_DEFER_PERM_CHECK:
41*4882a593Smuzhiyun goto lsm;
42*4882a593Smuzhiyun
43*4882a593Smuzhiyun case KEY_NEED_VIEW: mask = KEY_OTH_VIEW; break;
44*4882a593Smuzhiyun case KEY_NEED_READ: mask = KEY_OTH_READ; break;
45*4882a593Smuzhiyun case KEY_NEED_WRITE: mask = KEY_OTH_WRITE; break;
46*4882a593Smuzhiyun case KEY_NEED_SEARCH: mask = KEY_OTH_SEARCH; break;
47*4882a593Smuzhiyun case KEY_NEED_LINK: mask = KEY_OTH_LINK; break;
48*4882a593Smuzhiyun case KEY_NEED_SETATTR: mask = KEY_OTH_SETATTR; break;
49*4882a593Smuzhiyun }
50*4882a593Smuzhiyun
51*4882a593Smuzhiyun key = key_ref_to_ptr(key_ref);
52*4882a593Smuzhiyun
53*4882a593Smuzhiyun /* use the second 8-bits of permissions for keys the caller owns */
54*4882a593Smuzhiyun if (uid_eq(key->uid, cred->fsuid)) {
55*4882a593Smuzhiyun kperm = key->perm >> 16;
56*4882a593Smuzhiyun goto use_these_perms;
57*4882a593Smuzhiyun }
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun /* use the third 8-bits of permissions for keys the caller has a group
60*4882a593Smuzhiyun * membership in common with */
61*4882a593Smuzhiyun if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) {
62*4882a593Smuzhiyun if (gid_eq(key->gid, cred->fsgid)) {
63*4882a593Smuzhiyun kperm = key->perm >> 8;
64*4882a593Smuzhiyun goto use_these_perms;
65*4882a593Smuzhiyun }
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun ret = groups_search(cred->group_info, key->gid);
68*4882a593Smuzhiyun if (ret) {
69*4882a593Smuzhiyun kperm = key->perm >> 8;
70*4882a593Smuzhiyun goto use_these_perms;
71*4882a593Smuzhiyun }
72*4882a593Smuzhiyun }
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun /* otherwise use the least-significant 8-bits */
75*4882a593Smuzhiyun kperm = key->perm;
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun use_these_perms:
78*4882a593Smuzhiyun
79*4882a593Smuzhiyun /* use the top 8-bits of permissions for keys the caller possesses
80*4882a593Smuzhiyun * - possessor permissions are additive with other permissions
81*4882a593Smuzhiyun */
82*4882a593Smuzhiyun if (is_key_possessed(key_ref))
83*4882a593Smuzhiyun kperm |= key->perm >> 24;
84*4882a593Smuzhiyun
85*4882a593Smuzhiyun if ((kperm & mask) != mask)
86*4882a593Smuzhiyun return -EACCES;
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun /* let LSM be the final arbiter */
89*4882a593Smuzhiyun lsm:
90*4882a593Smuzhiyun return security_key_permission(key_ref, cred, need_perm);
91*4882a593Smuzhiyun }
92*4882a593Smuzhiyun EXPORT_SYMBOL(key_task_permission);
93*4882a593Smuzhiyun
94*4882a593Smuzhiyun /**
95*4882a593Smuzhiyun * key_validate - Validate a key.
96*4882a593Smuzhiyun * @key: The key to be validated.
97*4882a593Smuzhiyun *
98*4882a593Smuzhiyun * Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the
99*4882a593Smuzhiyun * key is invalidated, -EKEYREVOKED if the key's type has been removed or if
100*4882a593Smuzhiyun * the key has been revoked or -EKEYEXPIRED if the key has expired.
101*4882a593Smuzhiyun */
key_validate(const struct key * key)102*4882a593Smuzhiyun int key_validate(const struct key *key)
103*4882a593Smuzhiyun {
104*4882a593Smuzhiyun unsigned long flags = READ_ONCE(key->flags);
105*4882a593Smuzhiyun time64_t expiry = READ_ONCE(key->expiry);
106*4882a593Smuzhiyun
107*4882a593Smuzhiyun if (flags & (1 << KEY_FLAG_INVALIDATED))
108*4882a593Smuzhiyun return -ENOKEY;
109*4882a593Smuzhiyun
110*4882a593Smuzhiyun /* check it's still accessible */
111*4882a593Smuzhiyun if (flags & ((1 << KEY_FLAG_REVOKED) |
112*4882a593Smuzhiyun (1 << KEY_FLAG_DEAD)))
113*4882a593Smuzhiyun return -EKEYREVOKED;
114*4882a593Smuzhiyun
115*4882a593Smuzhiyun /* check it hasn't expired */
116*4882a593Smuzhiyun if (expiry) {
117*4882a593Smuzhiyun if (ktime_get_real_seconds() >= expiry)
118*4882a593Smuzhiyun return -EKEYEXPIRED;
119*4882a593Smuzhiyun }
120*4882a593Smuzhiyun
121*4882a593Smuzhiyun return 0;
122*4882a593Smuzhiyun }
123*4882a593Smuzhiyun EXPORT_SYMBOL(key_validate);
124