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// SPDX-License-Identifier: GPL-2.0-or-later
/* Key permission checking
*
* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/export.h>
#include <linux/security.h>
#include "internal.h"
/**
* key_task_permission - Check a key can be used
* @key_ref: The key to check.
* @cred: The credentials to use.
* @need_perm: The permission required.
*
* Check to see whether permission is granted to use a key in the desired way,
* but permit the security modules to override.
*
* The caller must hold either a ref on cred or must hold the RCU readlock.
*
* Returns 0 if successful, -EACCES if access is denied based on the
* permissions bits or the LSM check.
*/
int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
enum key_need_perm need_perm)
{
struct key *key;
key_perm_t kperm, mask;
int ret;
switch (need_perm) {
default:
WARN_ON(1);
return -EACCES;
case KEY_NEED_UNLINK:
case KEY_SYSADMIN_OVERRIDE:
case KEY_AUTHTOKEN_OVERRIDE:
case KEY_DEFER_PERM_CHECK:
goto lsm;
case KEY_NEED_VIEW: mask = KEY_OTH_VIEW; break;
case KEY_NEED_READ: mask = KEY_OTH_READ; break;
case KEY_NEED_WRITE: mask = KEY_OTH_WRITE; break;
case KEY_NEED_SEARCH: mask = KEY_OTH_SEARCH; break;
case KEY_NEED_LINK: mask = KEY_OTH_LINK; break;
case KEY_NEED_SETATTR: mask = KEY_OTH_SETATTR; break;
}
key = key_ref_to_ptr(key_ref);
/* use the second 8-bits of permissions for keys the caller owns */
if (uid_eq(key->uid, cred->fsuid)) {
kperm = key->perm >> 16;
goto use_these_perms;
}
/* use the third 8-bits of permissions for keys the caller has a group
* membership in common with */
if (gid_valid(key->gid) && key->perm & KEY_GRP_ALL) {
if (gid_eq(key->gid, cred->fsgid)) {
kperm = key->perm >> 8;
goto use_these_perms;
}
ret = groups_search(cred->group_info, key->gid);
if (ret) {
kperm = key->perm >> 8;
goto use_these_perms;
}
}
/* otherwise use the least-significant 8-bits */
kperm = key->perm;
use_these_perms:
/* use the top 8-bits of permissions for keys the caller possesses
* - possessor permissions are additive with other permissions
*/
if (is_key_possessed(key_ref))
kperm |= key->perm >> 24;
if ((kperm & mask) != mask)
return -EACCES;
/* let LSM be the final arbiter */
lsm:
return security_key_permission(key_ref, cred, need_perm);
}
EXPORT_SYMBOL(key_task_permission);
/**
* key_validate - Validate a key.
* @key: The key to be validated.
*
* Check that a key is valid, returning 0 if the key is okay, -ENOKEY if the
* key is invalidated, -EKEYREVOKED if the key's type has been removed or if
* the key has been revoked or -EKEYEXPIRED if the key has expired.
*/
int key_validate(const struct key *key)
{
unsigned long flags = READ_ONCE(key->flags);
time64_t expiry = READ_ONCE(key->expiry);
if (flags & (1 << KEY_FLAG_INVALIDATED))
return -ENOKEY;
/* check it's still accessible */
if (flags & ((1 << KEY_FLAG_REVOKED) |
(1 << KEY_FLAG_DEAD)))
return -EKEYREVOKED;
/* check it hasn't expired */
if (expiry) {
if (ktime_get_real_seconds() >= expiry)
return -EKEYEXPIRED;
}
return 0;
}
EXPORT_SYMBOL(key_validate);
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