/*
 * Greybus Component Authentication Protocol (CAP) Driver.
 *
 * Copyright 2016 Google Inc.
 * Copyright 2016 Linaro Ltd.
 *
 * Released under the GPLv2 only.
 */

#include "greybus.h"

#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/ioctl.h>
#include <linux/uaccess.h>

#include "greybus_authentication.h"
#include "firmware.h"

#define CAP_TIMEOUT_MS          1000

/*
 * Number of minor devices this driver supports.
 * There will be exactly one required per Interface.
 */
#define NUM_MINORS              U8_MAX

struct gb_cap {
        struct device           *parent;
        struct gb_connection    *connection;
        struct kref             kref;
        struct list_head        node;
        bool                    disabled; /* connection getting disabled */

        struct mutex            mutex;
        struct cdev             cdev;
        struct device           *class_device;
        dev_t                   dev_num;
};

static struct class *cap_class;
static dev_t cap_dev_num;
static DEFINE_IDA(cap_minors_map);
static LIST_HEAD(cap_list);
static DEFINE_MUTEX(list_mutex);

static void cap_kref_release(struct kref *kref)
{
        struct gb_cap *cap = container_of(kref, struct gb_cap, kref);

        kfree(cap);
}

/*
 * All users of cap take a reference (from within list_mutex lock), before
 * they get a pointer to play with. And the structure will be freed only after
 * the last user has put the reference to it.
 */
static void put_cap(struct gb_cap *cap)
{
        kref_put(&cap->kref, cap_kref_release);
}

/* Caller must call put_cap() after using struct gb_cap */
static struct gb_cap *get_cap(struct cdev *cdev)
{
        struct gb_cap *cap;

        mutex_lock(&list_mutex);

        list_for_each_entry(cap, &cap_list, node) {
                if (&cap->cdev == cdev) {
                        kref_get(&cap->kref);
                        goto unlock;
                }
        }

        cap = NULL;

unlock:
        mutex_unlock(&list_mutex);

        return cap;
}

static int cap_get_endpoint_uid(struct gb_cap *cap, u8 *euid)
{
        struct gb_connection *connection = cap->connection;
        struct gb_cap_get_endpoint_uid_response response;
        int ret;

        ret = gb_operation_sync(connection, GB_CAP_TYPE_GET_ENDPOINT_UID, NULL,
                                0, &response, sizeof(response));
        if (ret) {
                dev_err(cap->parent, "failed to get endpoint uid (%d)\n", ret);
                return ret;
        }

        memcpy(euid, response.uid, sizeof(response.uid));

        return 0;
}

static int cap_get_ims_certificate(struct gb_cap *cap, u32 class, u32 id,
                                   u8 *certificate, u32 *size, u8 *result)
{
        struct gb_connection *connection = cap->connection;
        struct gb_cap_get_ims_certificate_request *request;
        struct gb_cap_get_ims_certificate_response *response;
        size_t max_size = gb_operation_get_payload_size_max(connection);
        struct gb_operation *op;
        int ret;

        op = gb_operation_create_flags(connection,
                                       GB_CAP_TYPE_GET_IMS_CERTIFICATE,
                                       sizeof(*request), max_size,
                                       GB_OPERATION_FLAG_SHORT_RESPONSE,
                                       GFP_KERNEL);
        if (!op)
                return -ENOMEM;

        request = op->request->payload;
        request->certificate_class = cpu_to_le32(class);
        request->certificate_id = cpu_to_le32(id);

        ret = gb_operation_request_send_sync(op);
        if (ret) {
                dev_err(cap->parent, "failed to get certificate (%d)\n", ret);
                goto done;
        }

        response = op->response->payload;
        *result = response->result_code;
        *size = op->response->payload_size - sizeof(*response);
        memcpy(certificate, response->certificate, *size);

done:
        gb_operation_put(op);
        return ret;
}

static int cap_authenticate(struct gb_cap *cap, u32 auth_type, u8 *uid,
                            u8 *challenge, u8 *result, u8 *auth_response,
                            u32 *signature_size, u8 *signature)
{
        struct gb_connection *connection = cap->connection;
        struct gb_cap_authenticate_request *request;
        struct gb_cap_authenticate_response *response;
        size_t max_size = gb_operation_get_payload_size_max(connection);
        struct gb_operation *op;
        int ret;

        op = gb_operation_create_flags(connection, GB_CAP_TYPE_AUTHENTICATE,
                                       sizeof(*request), max_size,
                                       GB_OPERATION_FLAG_SHORT_RESPONSE,
                                       GFP_KERNEL);
        if (!op)
                return -ENOMEM;

        request = op->request->payload;
        request->auth_type = cpu_to_le32(auth_type);
        memcpy(request->uid, uid, sizeof(request->uid));
        memcpy(request->challenge, challenge, sizeof(request->challenge));

        ret = gb_operation_request_send_sync(op);
        if (ret) {
                dev_err(cap->parent, "failed to authenticate (%d)\n", ret);
                goto done;
        }

        response = op->response->payload;
        *result = response->result_code;
        *signature_size = op->response->payload_size - sizeof(*response);
        memcpy(auth_response, response->response, sizeof(response->response));
        memcpy(signature, response->signature, *signature_size);

done:
        gb_operation_put(op);
        return ret;
}

/* Char device fops */

static int cap_open(struct inode *inode, struct file *file)
{
        struct gb_cap *cap = get_cap(inode->i_cdev);

        /* cap structure can't get freed until file descriptor is closed */
        if (cap) {
                file->private_data = cap;
                return 0;
        }

        return -ENODEV;
}

static int cap_release(struct inode *inode, struct file *file)
{
        struct gb_cap *cap = file->private_data;

        put_cap(cap);
        return 0;
}

static int cap_ioctl(struct gb_cap *cap, unsigned int cmd,
                         void __user *buf)
{
        struct cap_ioc_get_endpoint_uid endpoint_uid;
        struct cap_ioc_get_ims_certificate *ims_cert;
        struct cap_ioc_authenticate *authenticate;
        size_t size;
        int ret;

        switch (cmd) {
        case CAP_IOC_GET_ENDPOINT_UID:
                ret = cap_get_endpoint_uid(cap, endpoint_uid.uid);
                if (ret)
                        return ret;

                if (copy_to_user(buf, &endpoint_uid, sizeof(endpoint_uid)))
                        return -EFAULT;

                return 0;
        case CAP_IOC_GET_IMS_CERTIFICATE:
                size = sizeof(*ims_cert);
                ims_cert = memdup_user(buf, size);
                if (IS_ERR(ims_cert))
                        return PTR_ERR(ims_cert);

                ret = cap_get_ims_certificate(cap, ims_cert->certificate_class,
                                              ims_cert->certificate_id,
                                              ims_cert->certificate,
                                              &ims_cert->cert_size,
                                              &ims_cert->result_code);
                if (!ret && copy_to_user(buf, ims_cert, size))
                        ret = -EFAULT;
                kfree(ims_cert);

                return ret;
        case CAP_IOC_AUTHENTICATE:
                size = sizeof(*authenticate);
                authenticate = memdup_user(buf, size);
                if (IS_ERR(authenticate))
                        return PTR_ERR(authenticate);

                ret = cap_authenticate(cap, authenticate->auth_type,
                                       authenticate->uid,
                                       authenticate->challenge,
                                       &authenticate->result_code,
                                       authenticate->response,
                                       &authenticate->signature_size,
                                       authenticate->signature);
                if (!ret && copy_to_user(buf, authenticate, size))
                        ret = -EFAULT;
                kfree(authenticate);

                return ret;
        default:
                return -ENOTTY;
        }
}

static long cap_ioctl_unlocked(struct file *file, unsigned int cmd,
                               unsigned long arg)
{
        struct gb_cap *cap = file->private_data;
        struct gb_bundle *bundle = cap->connection->bundle;
        int ret = -ENODEV;

        /*
         * Serialize ioctls.
         *
         * We don't want the user to do multiple authentication operations in
         * parallel.
         *
         * This is also used to protect ->disabled, which is used to check if
         * the connection is getting disconnected, so that we don't start any
         * new operations.
         */
        mutex_lock(&cap->mutex);
        if (!cap->disabled) {
                ret = gb_pm_runtime_get_sync(bundle);
                if (!ret) {
                        ret = cap_ioctl(cap, cmd, (void __user *)arg);
                        gb_pm_runtime_put_autosuspend(bundle);
                }
        }
        mutex_unlock(&cap->mutex);

        return ret;
}

static const struct file_operations cap_fops = {
        .owner          = THIS_MODULE,
        .open           = cap_open,
        .release        = cap_release,
        .unlocked_ioctl = cap_ioctl_unlocked,
};

int gb_cap_connection_init(struct gb_connection *connection)
{
        struct gb_cap *cap;
        int ret, minor;

        if (!connection)
                return 0;

        cap = kzalloc(sizeof(*cap), GFP_KERNEL);
        if (!cap)
                return -ENOMEM;

        cap->parent = &connection->bundle->dev;
        cap->connection = connection;
        mutex_init(&cap->mutex);
        gb_connection_set_data(connection, cap);
        kref_init(&cap->kref);

        mutex_lock(&list_mutex);
        list_add(&cap->node, &cap_list);
        mutex_unlock(&list_mutex);

        ret = gb_connection_enable(connection);
        if (ret)
                goto err_list_del;

        minor = ida_simple_get(&cap_minors_map, 0, NUM_MINORS, GFP_KERNEL);
        if (minor < 0) {
                ret = minor;
                goto err_connection_disable;
        }

        /* Add a char device to allow userspace to interact with cap */
        cap->dev_num = MKDEV(MAJOR(cap_dev_num), minor);
        cdev_init(&cap->cdev, &cap_fops);

        ret = cdev_add(&cap->cdev, cap->dev_num, 1);
        if (ret)
                goto err_remove_ida;

        /* Add a soft link to the previously added char-dev within the bundle */
        cap->class_device = device_create(cap_class, cap->parent, cap->dev_num,
                                          NULL, "gb-authenticate-%d", minor);
        if (IS_ERR(cap->class_device)) {
                ret = PTR_ERR(cap->class_device);
                goto err_del_cdev;
        }

        return 0;

err_del_cdev:
        cdev_del(&cap->cdev);
err_remove_ida:
        ida_simple_remove(&cap_minors_map, minor);
err_connection_disable:
        gb_connection_disable(connection);
err_list_del:
        mutex_lock(&list_mutex);
        list_del(&cap->node);
        mutex_unlock(&list_mutex);

        put_cap(cap);

        return ret;
}

void gb_cap_connection_exit(struct gb_connection *connection)
{
        struct gb_cap *cap;

        if (!connection)
                return;

        cap = gb_connection_get_data(connection);

        device_destroy(cap_class, cap->dev_num);
        cdev_del(&cap->cdev);
        ida_simple_remove(&cap_minors_map, MINOR(cap->dev_num));

        /*
         * Disallow any new ioctl operations on the char device and wait for
         * existing ones to finish.
         */
        mutex_lock(&cap->mutex);
        cap->disabled = true;
        mutex_unlock(&cap->mutex);

        /* All pending greybus operations should have finished by now */
        gb_connection_disable(cap->connection);

        /* Disallow new users to get access to the cap structure */
        mutex_lock(&list_mutex);
        list_del(&cap->node);
        mutex_unlock(&list_mutex);

        /*
         * All current users of cap would have taken a reference to it by
         * now, we can drop our reference and wait the last user will get
         * cap freed.
         */
        put_cap(cap);
}

int cap_init(void)
{
        int ret;

        cap_class = class_create(THIS_MODULE, "gb_authenticate");
        if (IS_ERR(cap_class))
                return PTR_ERR(cap_class);

        ret = alloc_chrdev_region(&cap_dev_num, 0, NUM_MINORS,
                                  "gb_authenticate");
        if (ret)
                goto err_remove_class;

        return 0;

err_remove_class:
        class_destroy(cap_class);
        return ret;
}

void cap_exit(void)
{
        unregister_chrdev_region(cap_dev_num, NUM_MINORS);
        class_destroy(cap_class);
        ida_destroy(&cap_minors_map);
}