// SPDX-License-Identifier: GPL-2.0-or-later
/* user_defined.c: user defined key type
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/export.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <keys/user-type.h>
#include <linux/uaccess.h>
#include "internal.h"

static int logon_vet_description(const char *desc);

/*
 * user defined keys take an arbitrary string as the description and an
 * arbitrary blob of data as the payload
 */
struct key_type key_type_user = {
        .name                   = "user",
        .preparse               = user_preparse,
        .free_preparse          = user_free_preparse,
        .instantiate            = generic_key_instantiate,
        .update                 = user_update,
        .revoke                 = user_revoke,
        .destroy                = user_destroy,
        .describe               = user_describe,
        .read                   = user_read,
};

EXPORT_SYMBOL_GPL(key_type_user);

/*
 * This key type is essentially the same as key_type_user, but it does
 * not define a .read op. This is suitable for storing username and
 * password pairs in the keyring that you do not want to be readable
 * from userspace.
 */
struct key_type key_type_logon = {
        .name                   = "logon",
        .preparse               = user_preparse,
        .free_preparse          = user_free_preparse,
        .instantiate            = generic_key_instantiate,
        .update                 = user_update,
        .revoke                 = user_revoke,
        .destroy                = user_destroy,
        .describe               = user_describe,
        .vet_description        = logon_vet_description,
};
EXPORT_SYMBOL_GPL(key_type_logon);

/*
 * Preparse a user defined key payload
 */
int user_preparse(struct key_preparsed_payload *prep)
{
        struct user_key_payload *upayload;
        size_t datalen = prep->datalen;

        if (datalen <= 0 || datalen > 32767 || !prep->data)
                return -EINVAL;

        upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
        if (!upayload)
                return -ENOMEM;

        /* attach the data */
        prep->quotalen = datalen;
        prep->payload.data[0] = upayload;
        upayload->datalen = datalen;
        memcpy(upayload->data, prep->data, datalen);
        return 0;
}
EXPORT_SYMBOL_GPL(user_preparse);

/*
 * Free a preparse of a user defined key payload
 */
void user_free_preparse(struct key_preparsed_payload *prep)
{
        kzfree(prep->payload.data[0]);
}
EXPORT_SYMBOL_GPL(user_free_preparse);

static void user_free_payload_rcu(struct rcu_head *head)
{
        struct user_key_payload *payload;

        payload = container_of(head, struct user_key_payload, rcu);
        kzfree(payload);
}

/*
 * update a user defined key
 * - the key's semaphore is write-locked
 */
int user_update(struct key *key, struct key_preparsed_payload *prep)
{
        struct user_key_payload *zap = NULL;
        int ret;

        /* check the quota and attach the new data */
        ret = key_payload_reserve(key, prep->datalen);
        if (ret < 0)
                return ret;

        /* attach the new data, displacing the old */
        key->expiry = prep->expiry;
        if (key_is_positive(key))
                zap = dereference_key_locked(key);
        rcu_assign_keypointer(key, prep->payload.data[0]);
        prep->payload.data[0] = NULL;

        if (zap)
                call_rcu(&zap->rcu, user_free_payload_rcu);
        return ret;
}
EXPORT_SYMBOL_GPL(user_update);

/*
 * dispose of the links from a revoked keyring
 * - called with the key sem write-locked
 */
void user_revoke(struct key *key)
{
        struct user_key_payload *upayload = user_key_payload_locked(key);

        /* clear the quota */
        key_payload_reserve(key, 0);

        if (upayload) {
                rcu_assign_keypointer(key, NULL);
                call_rcu(&upayload->rcu, user_free_payload_rcu);
        }
}

EXPORT_SYMBOL(user_revoke);

/*
 * dispose of the data dangling from the corpse of a user key
 */
void user_destroy(struct key *key)
{
        struct user_key_payload *upayload = key->payload.data[0];

        kzfree(upayload);
}

EXPORT_SYMBOL_GPL(user_destroy);

/*
 * describe the user key
 */
void user_describe(const struct key *key, struct seq_file *m)
{
        seq_puts(m, key->description);
        if (key_is_positive(key))
                seq_printf(m, ": %u", key->datalen);
}

EXPORT_SYMBOL_GPL(user_describe);

/*
 * read the key data
 * - the key's semaphore is read-locked
 */
long user_read(const struct key *key, char __user *buffer, size_t buflen)
{
        const struct user_key_payload *upayload;
        long ret;

        upayload = user_key_payload_locked(key);
        ret = upayload->datalen;

        /* we can return the data as is */
        if (buffer && buflen > 0) {
                if (buflen > upayload->datalen)
                        buflen = upayload->datalen;

                if (copy_to_user(buffer, upayload->data, buflen) != 0)
                        ret = -EFAULT;
        }

        return ret;
}

EXPORT_SYMBOL_GPL(user_read);

/* Vet the description for a "logon" key */
static int logon_vet_description(const char *desc)
{
        char *p;

        /* require a "qualified" description string */
        p = strchr(desc, ':');
        if (!p)
                return -EINVAL;

        /* also reject description with ':' as first char */
        if (p == desc)
                return -EINVAL;

        return 0;
}