// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2019 Microsoft Corporation
 *
 * Author: Lakshmi Ramasubramanian (nramas@linux.microsoft.com)
 *
 * File: ima_queue_keys.c
 *       Enables deferred processing of keys
 */

#include <linux/user_namespace.h>
#include <linux/workqueue.h>
#include <keys/asymmetric-type.h>
#include "ima.h"

/*
 * Flag to indicate whether a key can be processed
 * right away or should be queued for processing later.
 */
static bool ima_process_keys;

/*
 * To synchronize access to the list of keys that need to be measured
 */
static DEFINE_MUTEX(ima_keys_lock);
static LIST_HEAD(ima_keys);

/*
 * If custom IMA policy is not loaded then keys queued up
 * for measurement should be freed. This worker is used
 * for handling this scenario.
 */
static long ima_key_queue_timeout = 300000; /* 5 Minutes */
static void ima_keys_handler(struct work_struct *work);
static DECLARE_DELAYED_WORK(ima_keys_delayed_work, ima_keys_handler);
static bool timer_expired;

/*
 * This worker function frees keys that may still be
 * queued up in case custom IMA policy was not loaded.
 */
static void ima_keys_handler(struct work_struct *work)
{
        timer_expired = true;
        ima_process_queued_keys();
}

/*
 * This function sets up a worker to free queued keys in case
 * custom IMA policy was never loaded.
 */
void ima_init_key_queue(void)
{
        schedule_delayed_work(&ima_keys_delayed_work,
                              msecs_to_jiffies(ima_key_queue_timeout));
}

static void ima_free_key_entry(struct ima_key_entry *entry)
{
        if (entry) {
                kfree(entry->payload);
                kfree(entry->keyring_name);
                kfree(entry);
        }
}

static struct ima_key_entry *ima_alloc_key_entry(struct key *keyring,
                                                 const void *payload,
                                                 size_t payload_len)
{
        int rc = 0;
        const char *audit_cause = "ENOMEM";
        struct ima_key_entry *entry;

        entry = kzalloc_obj(*entry);
        if (entry) {
                entry->payload = kmemdup(payload, payload_len, GFP_KERNEL);
                entry->keyring_name = kstrdup(keyring->description,
                                              GFP_KERNEL);
                entry->payload_len = payload_len;
        }

        if ((entry == NULL) || (entry->payload == NULL) ||
            (entry->keyring_name == NULL)) {
                rc = -ENOMEM;
                goto out;
        }

        INIT_LIST_HEAD(&entry->list);

out:
        if (rc) {
                integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL,
                                        keyring->description,
                                        func_measure_str(KEY_CHECK),
                                        audit_cause, rc, 0, rc);
                ima_free_key_entry(entry);
                entry = NULL;
        }

        return entry;
}

bool ima_queue_key(struct key *keyring, const void *payload,
                   size_t payload_len)
{
        bool queued = false;
        struct ima_key_entry *entry;

        entry = ima_alloc_key_entry(keyring, payload, payload_len);
        if (!entry)
                return false;

        mutex_lock(&ima_keys_lock);
        if (!ima_process_keys) {
                list_add_tail(&entry->list, &ima_keys);
                queued = true;
        }
        mutex_unlock(&ima_keys_lock);

        if (!queued)
                ima_free_key_entry(entry);

        return queued;
}

/*
 * ima_process_queued_keys() - process keys queued for measurement
 *
 * This function sets ima_process_keys to true and processes queued keys.
 * From here on keys will be processed right away (not queued).
 */
void ima_process_queued_keys(void)
{
        struct ima_key_entry *entry, *tmp;
        bool process = false;

        if (ima_process_keys)
                return;

        /*
         * Since ima_process_keys is set to true, any new key will be
         * processed immediately and not be queued to ima_keys list.
         * First one setting the ima_process_keys flag to true will
         * process the queued keys.
         */
        mutex_lock(&ima_keys_lock);
        if (!ima_process_keys) {
                ima_process_keys = true;
                process = true;
        }
        mutex_unlock(&ima_keys_lock);

        if (!process)
                return;

        if (!timer_expired)
                cancel_delayed_work_sync(&ima_keys_delayed_work);

        list_for_each_entry_safe(entry, tmp, &ima_keys, list) {
                if (!timer_expired)
                        process_buffer_measurement(&nop_mnt_idmap, NULL,
                                                   entry->payload,
                                                   entry->payload_len,
                                                   entry->keyring_name,
                                                   KEY_CHECK, 0,
                                                   entry->keyring_name,
                                                   false, NULL, 0);
                list_del(&entry->list);
                ima_free_key_entry(entry);
        }
}

inline bool ima_should_queue_key(void)
{
        return !ima_process_keys;
}