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/* Key permission checking
*
* Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/module.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.
* @perm: The permissions to check for.
*
* 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,
key_perm_t perm)
{
struct key *key;
key_perm_t kperm;
int ret;
key = key_ref_to_ptr(key_ref);
if (key->user->user_ns != cred->user_ns)
goto use_other_perms;
/* use the second 8-bits of permissions for keys the caller owns */
if (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 (key->gid != -1 && key->perm & KEY_GRP_ALL) {
if (key->gid == cred->fsgid) {
kperm = key->perm >> 8;
goto use_these_perms;
}
ret = groups_search(cred->group_info,
make_kgid(current_user_ns(), key->gid));
if (ret) {
kperm = key->perm >> 8;
goto use_these_perms;
}
}
use_other_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;
kperm = kperm & perm & KEY_ALL;
if (kperm != perm)
return -EACCES;
/* let LSM be the final arbiter */
return security_key_permission(key_ref, cred, 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, -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* the key's type has been removed or if the key has been revoked or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(struct key *key)
{
struct timespec now;
int ret = 0;
if (key) {
/* check it's still accessible */
ret = -EKEYREVOKED;
if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
test_bit(KEY_FLAG_DEAD, &key->flags))
goto error;
/* check it hasn't expired */
ret = 0;
if (key->expiry) {
now = current_kernel_time();
if (now.tv_sec >= key->expiry)
ret = -EKEYEXPIRED;
}
}
error:
return ret;
}
EXPORT_SYMBOL(key_validate);
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