/* General persistent per-UID keyrings register
 *
 * Copyright (C) 2013 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 Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#include <linux/user_namespace.h>
#include <linux/cred.h>

#include "internal.h"

unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */

/*
 * Create the persistent keyring register for the current user namespace.
 *
 * Called with the namespace's sem locked for writing.
 */
static int key_create_persistent_register(struct user_namespace *ns)
{
        struct key *reg = keyring_alloc(".persistent_register",
                                        KUIDT_INIT(0), KGIDT_INIT(0),
                                        current_cred(),
                                        ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
                                         KEY_USR_VIEW | KEY_USR_READ),
                                        KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
        if (IS_ERR(reg))
                return PTR_ERR(reg);

        ns->persistent_keyring_register = reg;
        return 0;
}

/*
 * Create the persistent keyring for the specified user.
 *
 * Called with the namespace's sem locked for writing.
 */
static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
                                       struct keyring_index_key *index_key)
{
        struct key *persistent;
        key_ref_t reg_ref, persistent_ref;

        if (!ns->persistent_keyring_register) {
                long err = key_create_persistent_register(ns);
                if (err < 0)
                        return ERR_PTR(err);
        } else {
                reg_ref = make_key_ref(ns->persistent_keyring_register, true);
                persistent_ref = find_key_to_update(reg_ref, index_key);
                if (persistent_ref)
                        return persistent_ref;
        }

        persistent = keyring_alloc(index_key->description,
                                   uid, INVALID_GID, current_cred(),
                                   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
                                    KEY_USR_VIEW | KEY_USR_READ),
                                   KEY_ALLOC_NOT_IN_QUOTA, NULL,
                                   ns->persistent_keyring_register);
        if (IS_ERR(persistent))
                return ERR_CAST(persistent);

        return make_key_ref(persistent, true);
}

/*
 * Get the persistent keyring for a specific UID and link it to the nominated
 * keyring.
 */
static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
                               key_ref_t dest_ref)
{
        struct keyring_index_key index_key;
        struct key *persistent;
        key_ref_t reg_ref, persistent_ref;
        char buf[32];
        long ret;

        /* Look in the register if it exists */
        index_key.type = &key_type_keyring;
        index_key.description = buf;
        index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));

        if (ns->persistent_keyring_register) {
                reg_ref = make_key_ref(ns->persistent_keyring_register, true);
                down_read(&ns->persistent_keyring_register_sem);
                persistent_ref = find_key_to_update(reg_ref, &index_key);
                up_read(&ns->persistent_keyring_register_sem);

                if (persistent_ref)
                        goto found;
        }

        /* It wasn't in the register, so we'll need to create it.  We might
         * also need to create the register.
         */
        down_write(&ns->persistent_keyring_register_sem);
        persistent_ref = key_create_persistent(ns, uid, &index_key);
        up_write(&ns->persistent_keyring_register_sem);
        if (!IS_ERR(persistent_ref))
                goto found;

        return PTR_ERR(persistent_ref);

found:
        ret = key_task_permission(persistent_ref, current_cred(), KEY_NEED_LINK);
        if (ret == 0) {
                persistent = key_ref_to_ptr(persistent_ref);
                ret = key_link(key_ref_to_ptr(dest_ref), persistent);
                if (ret == 0) {
                        key_set_timeout(persistent, persistent_keyring_expiry);
                        ret = persistent->serial;
                }
        }

        key_ref_put(persistent_ref);
        return ret;
}

/*
 * Get the persistent keyring for a specific UID and link it to the nominated
 * keyring.
 */
long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
{
        struct user_namespace *ns = current_user_ns();
        key_ref_t dest_ref;
        kuid_t uid;
        long ret;

        /* -1 indicates the current user */
        if (_uid == (uid_t)-1) {
                uid = current_uid();
        } else {
                uid = make_kuid(ns, _uid);
                if (!uid_valid(uid))
                        return -EINVAL;

                /* You can only see your own persistent cache if you're not
                 * sufficiently privileged.
                 */
                if (!uid_eq(uid, current_uid()) &&
                    !uid_eq(uid, current_euid()) &&
                    !ns_capable(ns, CAP_SETUID))
                        return -EPERM;
        }

        /* There must be a destination keyring */
        dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
        if (IS_ERR(dest_ref))
                return PTR_ERR(dest_ref);
        if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
                ret = -ENOTDIR;
                goto out_put_dest;
        }

        ret = key_get_persistent(ns, uid, dest_ref);

out_put_dest:
        key_ref_put(dest_ref);
        return ret;
}