root/security/keys/permission.c

DEFINITIONS

1. key_task_permission
2. key_validate

/* 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);

/*****************************************************************************/
/*
 * validate a key
 */
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;

} /* end key_validate() */

EXPORT_SYMBOL(key_validate);