modules/filters/mod_reflector.c

/* 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 "apr_strings.h"
#include "apr_tables.h"

#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#include "http_log.h"
#include "http_protocol.h"
#include "http_request.h"
#include "mod_core.h"

module AP_MODULE_DECLARE_DATA reflector_module;

typedef struct {
    apr_table_t *headers;
} reflector_cfg;

static int header_do(void *dummy, const char *key, const char *value)
{
    request_rec *r = (request_rec *) dummy;
    const char *payload;

    payload = apr_table_get(r->headers_in, key);
    if (payload) {
        apr_table_setn(r->headers_out, value, payload);
    }

    return 1;
}

static int reflector_handler(request_rec * r)
{
    apr_bucket_brigade *bbin, *bbout;
    reflector_cfg *conf;
    apr_status_t status;

    if (strcmp(r->handler, "reflector")) {
        return DECLINED;
    }

    conf = (reflector_cfg *) ap_get_module_config(r->per_dir_config,
                                                  &reflector_module);

    ap_allow_methods(r, 1, "POST", "OPTIONS", NULL);

    if (r->method_number == M_OPTIONS) {
        return ap_send_http_options(r);
    }

    else if (r->method_number == M_POST) {
        const char *content_length, *content_type;
        int seen_eos;

        /*
         * Sometimes we'll get in a state where the input handling has
         * detected an error where we want to drop the connection, so if
         * that's the case, don't read the data as that is what we're trying
         * to avoid.
         *
         * This function is also a no-op on a subrequest.
         */
        if (r->main || r->connection->keepalive == AP_CONN_CLOSE ||
            ap_status_drops_connection(r->status)) {
            return OK;
        }

        /* copy headers from in to out if configured */
        apr_table_do(header_do, r, conf->headers, NULL);

        /* last modified defaults to now, unless otherwise set on the way in */
        if (!apr_table_get(r->headers_out, "Last-Modified")) {
            ap_update_mtime(r, apr_time_now());
            ap_set_last_modified(r);
        }
        ap_set_accept_ranges(r);

        /* reflect the content length, if present */
        if ((content_length = apr_table_get(r->headers_in, "Content-Length"))) {
            apr_off_t offset;

            apr_strtoff(&offset, content_length, NULL, 10);
            ap_set_content_length(r, offset);

        }

        /* reflect the content type, if present */
        if ((content_type = apr_table_get(r->headers_in, "Content-Type"))) {

            ap_set_content_type(r, content_type);

        }

        bbin = apr_brigade_create(r->pool, r->connection->bucket_alloc);
        bbout = apr_brigade_create(r->pool, r->connection->bucket_alloc);

        seen_eos = 0;
        do {
            apr_bucket *bucket;

            status = ap_get_brigade(r->input_filters, bbin, AP_MODE_READBYTES,
                                    APR_BLOCK_READ, HUGE_STRING_LEN);

            if (status != APR_SUCCESS) {
                apr_brigade_destroy(bbin);
                return ap_map_http_request_error(status, HTTP_BAD_REQUEST);
            }

            for (bucket = APR_BRIGADE_FIRST(bbin);
                 bucket != APR_BRIGADE_SENTINEL(bbin);
                 bucket = APR_BUCKET_NEXT(bucket)) {
                const char *data;
                apr_size_t len;

                if (APR_BUCKET_IS_EOS(bucket)) {
                    seen_eos = 1;
                    break;
                }

                /* These are metadata buckets. */
                if (bucket->length == 0) {
                    continue;
                }

                /*
                 * We MUST read because in case we have an unknown-length
                 * bucket or one that morphs, we want to exhaust it.
                 */
                status = apr_bucket_read(bucket, &data, &len, APR_BLOCK_READ);
                if (status != APR_SUCCESS) {
                    apr_brigade_destroy(bbin);
                    return HTTP_BAD_REQUEST;
                }

                apr_brigade_write(bbout, NULL, NULL, data, len);

                status = ap_pass_brigade(r->output_filters, bbout);
                if (status != APR_SUCCESS) {
                    /* no way to know what type of error occurred */
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, status, r, APLOGNO(01410)
                             "reflector_handler: ap_pass_brigade returned %i",
                                  status);
                    return AP_FILTER_ERROR;
                }

            }

            apr_brigade_cleanup(bbin);

        } while (!seen_eos);

        return OK;

    }

    else {
        return HTTP_METHOD_NOT_ALLOWED;
    }

}

static void *create_reflector_dir_config(apr_pool_t * p, char *d)
{
    reflector_cfg *conf = apr_pcalloc(p, sizeof(reflector_cfg));

    conf->headers = apr_table_make(p, 8);

    return conf;
}

static void *merge_reflector_dir_config(apr_pool_t * p, void *basev, void *addv)
{
    reflector_cfg *new = (reflector_cfg *) apr_pcalloc(p,
            sizeof(reflector_cfg));
    reflector_cfg *add = (reflector_cfg *) addv;
    reflector_cfg *base = (reflector_cfg *) basev;

    new->headers = apr_table_overlay(p, add->headers, base->headers);

    return new;
}

static const char *reflector_header(cmd_parms * cmd, void *dummy, const char *in,
        const char *out)
{
    reflector_cfg *cfg = (reflector_cfg *) dummy;

    apr_table_addn(cfg->headers, in, out ? out : in);

    return NULL;
}

static void reflector_hooks(apr_pool_t * p)
{
    ap_hook_handler(reflector_handler, NULL, NULL, APR_HOOK_MIDDLE);
}

static const command_rec reflector_cmds[] = {
    AP_INIT_TAKE12("ReflectorHeader", reflector_header, NULL, OR_OPTIONS,
      "Header to reflect back in the response, with an optional new name."),
    {NULL}
};

AP_DECLARE_MODULE(reflector) = {
    STANDARD20_MODULE_STUFF,
    create_reflector_dir_config,
    merge_reflector_dir_config,
    NULL,
    NULL,
    reflector_cmds,
    reflector_hooks
};