/*
 * Copyright (c) 2016 MariaDB Corporation Ab
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
 *
 * Change Date: 2019-07-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2 or later of the General
 * Public License.
 */

/**
 * @file mysql_auth.c
 *
 * MySQL Authentication module for handling the checking of clients credentials
 * in the MySQL protocol.
 *
 * @verbatim
 * Revision History
 * Date         Who                     Description
 * 02/02/2016   Martin Brampton         Initial version
 *
 * @endverbatim
 */

#include "mysql_auth.h"

#include <maxscale/protocol/mysql.h>
#include <maxscale/authenticator.h>
#include <maxscale/alloc.h>
#include <maxscale/poll.h>
#include <maxscale/paths.h>
#include <maxscale/secrets.h>
#include <maxscale/utils.h>

static void* mysql_auth_init(char **options);
static int mysql_auth_set_protocol_data(DCB *dcb, GWBUF *buf);
static bool mysql_auth_is_client_ssl_capable(DCB *dcb);
static int mysql_auth_authenticate(DCB *dcb);
static void mysql_auth_free_client_data(DCB *dcb);
static int mysql_auth_load_users(SERV_LISTENER *port);
static void *mysql_auth_create(void *instance);
static void mysql_auth_destroy(void *data);

static int combined_auth_check(
    DCB             *dcb,
    uint8_t         *auth_token,
    size_t          auth_token_len,
    MySQLProtocol   *protocol,
    char            *username,
    uint8_t         *stage1_hash,
    char            *database
);
static int mysql_auth_set_client_data(
    MYSQL_session *client_data,
    MySQLProtocol *protocol,
    GWBUF         *buffer);

void mysql_auth_diagnostic(DCB *dcb, SERV_LISTENER *port);

int mysql_auth_reauthenticate(DCB *dcb, const char *user,
                              uint8_t *token, size_t token_len,
                              uint8_t *scramble, size_t scramble_len,
                              uint8_t *output_token, size_t output_token_len);
/**
 * The module entry point routine. It is this routine that
 * must populate the structure that is referred to as the
 * "module object", this is a structure with the set of
 * external entry points for this module.
 *
 * @return The module object
 */
MXS_MODULE* MXS_CREATE_MODULE()
{
    static MXS_AUTHENTICATOR MyObject =
    {
        mysql_auth_init,                  /* Initialize the authenticator */
        mysql_auth_create,                /* Create entry point */
        mysql_auth_set_protocol_data,     /* Extract data into structure   */
        mysql_auth_is_client_ssl_capable, /* Check if client supports SSL  */
        mysql_auth_authenticate,          /* Authenticate user credentials */
        mysql_auth_free_client_data,      /* Free the client data held in DCB */
        mysql_auth_destroy,               /* Destroy entry point */
        mysql_auth_load_users,            /* Load users from backend databases */
        mysql_auth_diagnostic,
        mysql_auth_reauthenticate         /* Handle COM_CHANGE_USER */
    };

    static MXS_MODULE info =
    {
        MXS_MODULE_API_AUTHENTICATOR,
        MXS_MODULE_GA,
        MXS_AUTHENTICATOR_VERSION,
        "The MySQL client to MaxScale authenticator implementation",
        "V1.1.0",
        &MyObject,
        NULL, /* Process init. */
        NULL, /* Process finish. */
        NULL, /* Thread init. */
        NULL, /* Thread finish. */
        { { MXS_END_MODULE_PARAMS} }
    };

    return &info;
}

static void get_database_path(SERV_LISTENER *port, char *dest)
{
    MYSQL_AUTH *instance = port->auth_instance;
    SERVICE *service = port->service;

    if (instance->cache_dir)
    {
        snprintf(dest, sizeof(dest) - sizeof(DBUSERS_FILE) - 1, "%s/", instance->cache_dir);
    }
    else
    {
        sprintf(dest, "%s/%s/%s/%s/", get_cachedir(), service->name, port->name, DBUSERS_DIR);
    }

    if (mxs_mkdir_all(dest, S_IRWXU))
    {
        strcat(dest, DBUSERS_FILE);
    }
}

static bool open_instance_database(const char *path, sqlite3 **handle)
{
    if (sqlite3_open_v2(path, handle, db_flags, NULL) != SQLITE_OK)
    {
        MXS_ERROR("Failed to open SQLite3 handle.");
        return false;
    }

    char *err;

    if (sqlite3_exec(*handle, users_create_sql, NULL, NULL, &err) != SQLITE_OK ||
        sqlite3_exec(*handle, databases_create_sql, NULL, NULL, &err) != SQLITE_OK ||
        sqlite3_exec(*handle, pragma_sql, NULL, NULL, &err) != SQLITE_OK)
    {
        MXS_ERROR("Failed to create database: %s", err);
        sqlite3_free(err);
        sqlite3_close_v2(*handle);
        return false;
    }

    return true;
}

static bool open_client_database(const char *path, sqlite3 **handle)
{
    bool rval = false;

    if (sqlite3_open_v2(path, handle, db_flags, NULL) == SQLITE_OK)
    {
        sqlite3_busy_timeout(*handle, MXS_SQLITE_BUSY_TIMEOUT);
        rval = true;
    }
    else
    {
        MXS_ERROR("Failed to open SQLite3 handle.");
    }

    return rval;
}

/**
 * @brief Initialize the authenticator instance
 *
 * @param options Authenticator options
 * @return New MYSQL_AUTH instance or NULL on error
 */
static void* mysql_auth_init(char **options)
{
    MYSQL_AUTH *instance = MXS_MALLOC(sizeof(*instance));

    if (instance)
    {
        bool error = false;
        instance->cache_dir = NULL;
        instance->inject_service_user = true;
        instance->skip_auth = false;
        instance->handle = NULL;

        for (int i = 0; options[i]; i++)
        {
            char *value = strchr(options[i], '=');

            if (value)
            {
                *value++ = '\0';

                if (strcmp(options[i], "cache_dir") == 0)
                {
                    if ((instance->cache_dir = MXS_STRDUP(value)) == NULL ||
                        !clean_up_pathname(instance->cache_dir))
                    {
                        error = true;
                    }
                }
                else if (strcmp(options[i], "inject_service_user") == 0)
                {
                    instance->inject_service_user = config_truth_value(value);
                }
                else if (strcmp(options[i], "skip_authentication") == 0)
                {
                    instance->skip_auth = config_truth_value(value);
                }
                else
                {
                    MXS_ERROR("Unknown authenticator option: %s", options[i]);
                    error = true;
                }
            }
            else
            {
                MXS_ERROR("Unknown authenticator option: %s", options[i]);
                error = true;
            }
        }

        if (error)
        {
            MXS_FREE(instance->cache_dir);
            MXS_FREE(instance);
            instance = NULL;
        }
    }

    return instance;
}

static void* mysql_auth_create(void *instance)
{
    mysql_auth_t *rval = MXS_MALLOC(sizeof(*rval));

    if (rval)
    {
        rval->handle = NULL;
    }

    return rval;
}

static void mysql_auth_destroy(void *data)
{
    mysql_auth_t *auth = (mysql_auth_t*)data;
    if (auth)
    {
        sqlite3_close_v2(auth->handle);
        MXS_FREE(auth);
    }
}

/**
 * @brief Authenticates a MySQL user who is a client to MaxScale.
 *
 * First call the SSL authentication function, passing the DCB and a boolean
 * indicating whether the client is SSL capable. If SSL authentication is
 * successful, check whether connection is complete. Fail if we do not have a
 * user name.  Call other functions to validate the user, reloading the user
 * data if the first attempt fails.
 *
 * @param dcb Request handler DCB connected to the client
 * @return Authentication status
 * @note Authentication status codes are defined in maxscale/protocol/mysql.h
 */
static int
mysql_auth_authenticate(DCB *dcb)
{
    MySQLProtocol *protocol = DCB_PROTOCOL(dcb, MySQLProtocol);
    MYSQL_session *client_data = (MYSQL_session *)dcb->data;
    int auth_ret = MXS_AUTH_FAILED;

    /**
     * We record the SSL status before and after the authentication. This allows
     * us to detect if the SSL handshake is immediately completed which means more
     * data needs to be read from the socket.
     */

    bool health_before = ssl_is_connection_healthy(dcb);
    int ssl_ret = ssl_authenticate_client(dcb, dcb->authfunc.connectssl(dcb));
    bool health_after = ssl_is_connection_healthy(dcb);

    if (0 != ssl_ret)
    {
        auth_ret = (SSL_ERROR_CLIENT_NOT_SSL == ssl_ret) ? MXS_AUTH_FAILED_SSL : MXS_AUTH_FAILED;
    }
    else if (!health_after)
    {
        auth_ret = MXS_AUTH_SSL_INCOMPLETE;
    }
    else if (!health_before && health_after)
    {
        auth_ret = MXS_AUTH_SSL_INCOMPLETE;
        poll_add_epollin_event_to_dcb(dcb, NULL);
    }
    else if (*client_data->user)
    {
        MXS_DEBUG("Receiving connection from '%s' to database '%s'.",
                  client_data->user, client_data->db);

        MYSQL_AUTH *instance = (MYSQL_AUTH*)dcb->listener->auth_instance;

        auth_ret = validate_mysql_user(instance->handle, dcb, client_data,
                                       protocol->scramble, sizeof(protocol->scramble));

        if (auth_ret != MXS_AUTH_SUCCEEDED &&
            !instance->skip_auth &&
            service_refresh_users(dcb->service) == 0)
        {
            auth_ret = validate_mysql_user(instance->handle, dcb, client_data,
                                           protocol->scramble, sizeof(protocol->scramble));
        }

        /* on successful authentication, set user into dcb field */
        if (auth_ret == MXS_AUTH_SUCCEEDED || instance->skip_auth)
        {
            auth_ret = MXS_AUTH_SUCCEEDED;
            dcb->user = MXS_STRDUP_A(client_data->user);
            /** Send an OK packet to the client */
        }
        else if (dcb->service->log_auth_warnings)
        {
            MXS_WARNING("%s: login attempt for user '%s'@%s:%d, authentication failed.",
                        dcb->service->name, client_data->user, dcb->remote, dcb_get_port(dcb));
        }

        /* let's free the auth_token now */
        if (client_data->auth_token)
        {
            MXS_FREE(client_data->auth_token);
            client_data->auth_token = NULL;
        }
    }

    return auth_ret;
}

/**
 * @brief Transfer data from the authentication request to the DCB.
 *
 * The request handler DCB has a field called data that contains protocol
 * specific information. This function examines a buffer containing MySQL
 * authentication data and puts it into a structure that is referred to
 * by the DCB. If the information in the buffer is invalid, then a failure
 * code is returned. A call to mysql_auth_set_client_data does the
 * detailed work.
 *
 * @param dcb Request handler DCB connected to the client
 * @param buffer Pointer to pointer to buffer containing data from client
 * @return Authentication status
 * @note Authentication status codes are defined in maxscale/protocol/mysql.h
 * @see https://dev.mysql.com/doc/internals/en/client-server-protocol.html
 */
static int
mysql_auth_set_protocol_data(DCB *dcb, GWBUF *buf)
{
    MySQLProtocol *protocol = NULL;
    MYSQL_session *client_data = NULL;
    int client_auth_packet_size = 0;
    mysql_auth_t *auth_ses = (mysql_auth_t*)dcb->authenticator_data;

    if (auth_ses->handle == NULL)
    {
        char path[PATH_MAX];
        get_database_path(dcb->listener, path);

        if (!open_client_database(path, &auth_ses->handle))
        {
            return MXS_AUTH_FAILED;
        }
    }

    protocol = DCB_PROTOCOL(dcb, MySQLProtocol);
    CHK_PROTOCOL(protocol);

    client_data = (MYSQL_session *)dcb->data;

    client_auth_packet_size = gwbuf_length(buf);

    /* For clients supporting CLIENT_PROTOCOL_41
     * the Handshake Response Packet is:
     *
     * 4            bytes mysql protocol heade
     * 4            bytes capability flags
     * 4            max-packet size
     * 1            byte character set
     * string[23]   reserved (all [0])
     * ...
     * ...
     * Note that the fixed elements add up to 36
     */

    /* Detect now if there are enough bytes to continue */
    if (client_auth_packet_size < (4 + 4 + 4 + 1 + 23))
    {
        /* Packet is not big enough */
        return MXS_AUTH_FAILED;
    }

    return mysql_auth_set_client_data(client_data, protocol, buf);
}

/**
 * @brief Transfer detailed data from the authentication request to the DCB.
 *
 * The caller has created the data structure pointed to by the DCB, and this
 * function fills in the details. If problems are found with the data, the
 * return code indicates failure.
 *
 * @param client_data The data structure for the DCB
 * @param protocol The protocol structure for this connection
 * @param client_auth_packet The data from the buffer received from client
 * @param client_auth_packet size An integer giving the size of the data
 * @return Authentication status
 * @note Authentication status codes are defined in maxscale/protocol/mysql.h
 * @see https://dev.mysql.com/doc/internals/en/client-server-protocol.html
 */
static int
mysql_auth_set_client_data(
    MYSQL_session *client_data,
    MySQLProtocol *protocol,
    GWBUF         *buffer)
{
    size_t client_auth_packet_size = gwbuf_length(buffer);
    uint8_t client_auth_packet[client_auth_packet_size];
    gwbuf_copy_data(buffer, 0, client_auth_packet_size, client_auth_packet);

    int packet_length_used = 0;

    /* Make authentication token length 0 and token null in case none is provided */
    client_data->auth_token_len = 0;
    client_data->auth_token = NULL;

    if (client_auth_packet_size > MYSQL_AUTH_PACKET_BASE_SIZE)
    {
        /* Should have a username */
        char *first_letter_of_username = (char *)(client_auth_packet + MYSQL_AUTH_PACKET_BASE_SIZE);
        int user_length = strlen(first_letter_of_username);

        ss_dassert(client_auth_packet_size > (MYSQL_AUTH_PACKET_BASE_SIZE + user_length)
                   && user_length <= MYSQL_USER_MAXLEN);

        if (client_auth_packet_size > (MYSQL_AUTH_PACKET_BASE_SIZE + user_length + 1))
        {
            /* Extra 1 is for the terminating null after user name */
            packet_length_used = MYSQL_AUTH_PACKET_BASE_SIZE + user_length + 1;
            /* We should find an authentication token next */
            /* One byte of packet is the length of authentication token */
            memcpy(&client_data->auth_token_len,
                   client_auth_packet + packet_length_used, 1);

            if (client_auth_packet_size >
                (packet_length_used + client_data->auth_token_len))
            {
                /* Packet is large enough for authentication token */
                if (NULL != (client_data->auth_token = (uint8_t *)MXS_MALLOC(client_data->auth_token_len)))
                {
                    /* The extra 1 is for the token length byte, just extracted*/
                    memcpy(client_data->auth_token,
                           client_auth_packet + MYSQL_AUTH_PACKET_BASE_SIZE + user_length + 1 + 1,
                           client_data->auth_token_len);
                }
                else
                {
                    /* Failed to allocate space for authentication token string */
                    return MXS_AUTH_FAILED;
                }
            }
            else
            {
                /* Packet was too small to contain authentication token */
                return MXS_AUTH_FAILED;
            }
        }
    }
    return MXS_AUTH_SUCCEEDED;
}

/**
 * @brief Determine whether the client is SSL capable
 *
 * The authentication request from the client will indicate whether the client
 * is expecting to make an SSL connection. The information has been extracted
 * in the previous functions.
 *
 * @param dcb Request handler DCB connected to the client
 * @return Boolean indicating whether client is SSL capable
 */
static bool
mysql_auth_is_client_ssl_capable(DCB *dcb)
{
    MySQLProtocol *protocol;

    protocol = DCB_PROTOCOL(dcb, MySQLProtocol);
    return (protocol->client_capabilities & (int)GW_MYSQL_CAPABILITIES_SSL) ? true : false;
}

/**
 * @brief Free the client data pointed to by the passed DCB.
 *
 * Currently all that is required is to free the storage pointed to by
 * dcb->data.  But this is intended to be implemented as part of the
 * authentication API at which time this code will be moved into the
 * MySQL authenticator.  If the data structure were to become more complex
 * the mechanism would still work and be the responsibility of the authenticator.
 * The DCB should not know authenticator implementation details.
 *
 * @param dcb Request handler DCB connected to the client
 */
static void
mysql_auth_free_client_data(DCB *dcb)
{
    MXS_FREE(dcb->data);
}

/**
 * @brief Inject the service user into the cache
 *
 * @param port Service listener
 * @return True on success, false on error
 */
static bool add_service_user(SERV_LISTENER *port)
{
    char *user = NULL;
    char *pw = NULL;
    bool rval = false;

    if (serviceGetUser(port->service, &user, &pw))
    {
        pw = decrypt_password(pw);

        if (pw)
        {
            char *newpw = create_hex_sha1_sha1_passwd(pw);

            if (newpw)
            {
                MYSQL_AUTH *inst = (MYSQL_AUTH*)port->auth_instance;
                add_mysql_user(inst->handle, user, "%", "", "Y", newpw);
                add_mysql_user(inst->handle, user, "localhost", "", "Y", newpw);
                MXS_FREE(newpw);
                rval = true;
            }
            MXS_FREE(pw);
        }
        else
        {
            MXS_ERROR("[%s] Failed to decrypt service user password.", port->service->name);
        }
    }
    else
    {
        MXS_ERROR("[%s] Failed to retrieve service credentials.", port->service->name);
    }

    return rval;
}

/**
 * @brief Load MySQL authentication users
 *
 * This function loads MySQL users from the backend database.
 *
 * @param port Listener definition
 * @return MXS_AUTH_LOADUSERS_OK on success, MXS_AUTH_LOADUSERS_ERROR and
 * MXS_AUTH_LOADUSERS_FATAL on fatal error
 */
static int mysql_auth_load_users(SERV_LISTENER *port)
{
    int rc = MXS_AUTH_LOADUSERS_OK;
    SERVICE *service = port->listener->service;
    MYSQL_AUTH *instance = (MYSQL_AUTH*)port->auth_instance;

    if (port->users == NULL && !check_service_permissions(port->service))
    {
        return MXS_AUTH_LOADUSERS_FATAL;
    }

    if (instance->handle == NULL)
    {
        char path[PATH_MAX];
        get_database_path(port, path);
        if (!open_instance_database(path, &instance->handle))
        {
            return MXS_AUTH_LOADUSERS_FATAL;
        }
    }

    int loaded = replace_mysql_users(port);

    if (loaded < 0)
    {
        MXS_ERROR("[%s] Unable to load users for listener %s listening at %s:%d.", service->name,
                  port->name, port->address ? port->address : "0.0.0.0", port->port);

        if (instance->inject_service_user)
        {
            /** Inject the service user as a 'backup' user that's available
             * if loading of the users fails */
            if (!add_service_user(port))
            {
                MXS_ERROR("[%s] Failed to inject service user.", port->service->name);
            }
        }
    }

    if (loaded == 0)
    {
        MXS_WARNING("[%s]: failed to load any user information. Authentication"
                    " will probably fail as a result.", service->name);
    }
    else if (loaded > 0)
    {
        MXS_NOTICE("[%s] Loaded %d MySQL users for listener %s.", service->name, loaded, port->name);
    }

    return rc;
}

int mysql_auth_reauthenticate(DCB *dcb, const char *user,
                              uint8_t *token, size_t token_len,
                              uint8_t *scramble, size_t scramble_len,
                              uint8_t *output_token, size_t output_token_len)
{
    MYSQL_session *client_data = (MYSQL_session *)dcb->data;
    MYSQL_session temp;
    int rval = 1;

    memcpy(&temp, client_data, sizeof(*client_data));
    strcpy(temp.user, user);
    temp.auth_token = token;
    temp.auth_token_len = token_len;

    MYSQL_AUTH *instance = (MYSQL_AUTH*)dcb->listener->auth_instance;
    int rc = validate_mysql_user(instance->handle, dcb, &temp, scramble, scramble_len);

    if (rc == MXS_AUTH_SUCCEEDED)
    {
        memcpy(output_token, temp.client_sha1, output_token_len);
        rval = 0;
    }

    return rval;

}

int diag_cb(void *data, int columns, char **row, char **field_names)
{
    DCB *dcb = (DCB*)data;
    dcb_printf(dcb, "%s@%s ", row[0], row[1]);
    return 0;
}

void mysql_auth_diagnostic(DCB *dcb, SERV_LISTENER *port)
{
    dcb_printf(dcb, "User names: ");

    MYSQL_AUTH *instance = (MYSQL_AUTH*)port->auth_instance;
    char *err;

    if (sqlite3_exec(instance->handle, "SELECT user, host FROM " MYSQLAUTH_USERS_TABLE_NAME,
                     diag_cb, dcb, &err) != SQLITE_OK)
    {
        dcb_printf(dcb, "Failed to print users: %s\n", err);
        MXS_ERROR("Failed to print users: %s", err);
        sqlite3_free(err);
    }
    dcb_printf(dcb, "\n");
}