/* Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include "httpd.h"

#include "http_core.h"

#include "http_config.h"

#include "http_protocol.h"

#include "http_request.h"

#include "http_log.h"

#include "apr_strings.h"

/**

 * This module makes it easy to restrict what HTTP methods can be ran against

 * a server.

 *

 * It provides one command:

 *    AllowMethods

 * This command takes a list of HTTP methods to allow.

 *

 *  The most common configuration should be like this:

 *   <Directory />

 *    AllowMethods GET HEAD OPTIONS

 *   </Directory>

 *   <Directory /special/cgi-bin>

 *      AllowMethods GET HEAD OPTIONS POST

 *   </Directory>

 *  Non-matching methods will be returned a status 405 (method not allowed)

 *

 *  To allow all methods, and effectively turn off mod_allowmethods, use:

 *    AllowMethods reset

 */

typedef struct am_conf_t {

    int allowed_set;

    apr_int64_t allowed;

} am_conf_t;

module AP_MODULE_DECLARE_DATA allowmethods_module;

static int am_check_access(request_rec *r)

{

    int method = r->method_number;

    am_conf_t *conf;

    conf = (am_conf_t *) ap_get_module_config(r->per_dir_config,

                                              &allowmethods_module);

    if (!conf || conf->allowed == 0) {

        return DECLINED;

    }

    r->allowed = conf->allowed;

    if (conf->allowed & (AP_METHOD_BIT << method)) {

        return DECLINED;

    }

    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01623)

                  "client method denied by server configuration: '%s' to %s%s",

                  r->method,

                  r->filename ? "" : "uri ",

                  r->filename ? r->filename : r->uri);

    return HTTP_METHOD_NOT_ALLOWED;

}

static void *am_create_conf(apr_pool_t *p, char *dummy)

{

    am_conf_t *conf = apr_pcalloc(p, sizeof(am_conf_t));

    conf->allowed = 0;

    conf->allowed_set = 0;

    return conf;

}

static void *am_merge_conf(apr_pool_t *pool, void *a, void *b)

{

    am_conf_t *base = (am_conf_t *)a;

    am_conf_t *add = (am_conf_t *)b;

    am_conf_t *conf = apr_palloc(pool, sizeof(am_conf_t));

    if (add->allowed_set) {

        conf->allowed = add->allowed;

        conf->allowed_set = add->allowed_set;

    }

    else {

        conf->allowed = base->allowed;

        conf->allowed_set = base->allowed_set;

    }

    return conf;

}

static const char *am_allowmethods(cmd_parms *cmd, void *d, int argc,

                                   char *const argv[])

{

    int i;

    am_conf_t *conf = (am_conf_t *)d;

    if (argc == 0) {

        return "AllowMethods: No method or 'reset' keyword given";

    }

    if (argc == 1) {

        if (strcasecmp("reset", argv[0]) == 0) {

            conf->allowed = 0;

            conf->allowed_set = 1;

            return NULL;

        }

    }

    for (i = 0; i < argc; i++) {

        int m;

        m = ap_method_number_of(argv[i]);

        if (m == M_INVALID) {

            return apr_pstrcat(cmd->pool, "AllowMethods: Invalid Method '",

                               argv[i], "'", NULL);

        }

        conf->allowed |= (AP_METHOD_BIT << m);

    }

    conf->allowed_set = 1;

    return NULL;

}

static void am_register_hooks(apr_pool_t * p)

{

    ap_hook_access_checker(am_check_access, NULL, NULL, APR_HOOK_REALLY_FIRST);

}

static const command_rec am_cmds[] = {

    AP_INIT_TAKE_ARGV("AllowMethods", am_allowmethods, NULL,

                      ACCESS_CONF,

                      "only allow specific methods"),

    {NULL}

};

AP_DECLARE_MODULE(allowmethods) = {

    STANDARD20_MODULE_STUFF,

    am_create_conf,

    am_merge_conf,

    NULL,

    NULL,

    am_cmds,

    am_register_hooks,

};