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/* permission.c: key permission determination
*
* 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"
/*****************************************************************************/
/*
* check to see whether permission is granted to use a key in the desired way,
* but permit the security modules to override
*/
int key_task_permission(const key_ref_t key_ref,
struct task_struct *context,
key_perm_t perm)
{
struct key *key;
key_perm_t kperm;
int ret;
key = key_ref_to_ptr(key_ref);
/* use the second 8-bits of permissions for keys the caller owns */
if (key->uid == context->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 == context->fsgid) {
kperm = key->perm >> 8;
goto use_these_perms;
}
task_lock(context);
ret = groups_search(context->group_info, key->gid);
task_unlock(context);
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;
kperm = kperm & perm & KEY_ALL;
if (kperm != perm)
return -EACCES;
/* let LSM be the final arbiter */
return security_key_permission(key_ref, context, perm);
} /* end key_task_permission() */
EXPORT_SYMBOL(key_task_permission);
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