/*

* ModSecurity for Apache 2.x, http://www.modsecurity.org/

* Copyright (c) 2004-2013 Trustwave Holdings, Inc. (http://www.trustwave.com/)

*

* 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

*

* If any of the files related to licensing are missing or if you have any

* other questions related to licensing please contact Trustwave Holdings, Inc.

* directly using the email address security@modsecurity.org.

*/

#include "httpd.h"

#include "http_core.h"

#include "http_config.h"

#include "http_log.h"

#include "http_protocol.h"

#include "ap_config.h"

#include "apr_optional.h"

#include "modsecurity.h"

/**

 * This function will be invoked by

 * ModSecurity to transform input.

 */

static int reverse(apr_pool_t *mptmp, unsigned char *input,

    long int input_len, char **rval, long int *rval_len)

{

    /* Transformation functions can choose to do their

     * thing in-place, overwriting the existing content. This

     * is normally possible only if the transformed content

     * is of equal length or shorter.

     *

     * If you need to expand the content use the temporary

     * memory pool mptmp to allocate the space.

     */

    /* Reverse the string in place, but only if it's long enough. */

    if (input_len > 1) {

        long int i = 0;

        long int j = input_len - 1;

        while(i < j) {

            char c = input[i];

            input[i] = input[j];

            input[j] = c;

            i++;

            j--;

        }

    }

    /* Tell ModSecurity about the content

     * we have generated. In this case we

     * merely point back to the input buffer.

     */

    *rval = (char *)input;

    *rval_len = input_len;

    /* Must return 1 if the content was

     * changed, or 0 otherwise.

     */

    return 1; 

}

static int hook_pre_config(apr_pool_t *mp, apr_pool_t *mp_log, apr_pool_t *mp_temp) {

    void (*fn)(const char *name, void *fn);

    /* Look for the registration function

     * exported by ModSecurity.

     */

    fn = APR_RETRIEVE_OPTIONAL_FN(modsec_register_tfn);

    if (fn) {

        /* Use it to register our new

         * transformation function under the

         * name "reverse".

         */

        fn("reverse", (void *)reverse);

    } else {

        ap_log_error(APLOG_MARK, APLOG_ERR | APLOG_NOERRNO, 0, NULL,

            "mod_tfn_reverse: Unable to find modsec_register_tfn.");

    }

    return OK;

}

static void register_hooks(apr_pool_t *p) {

    ap_hook_pre_config(hook_pre_config, NULL, NULL, APR_HOOK_LAST);

}

/* Dispatch list for API hooks */

module AP_MODULE_DECLARE_DATA tfn_reverse_module = {

    STANDARD20_MODULE_STUFF, 

    NULL,                  /* create per-dir    config structures */

    NULL,                  /* merge  per-dir    config structures */

    NULL,                  /* create per-server config structures */

    NULL,                  /* merge  per-server config structures */

    NULL,                  /* table of config file commands       */

    register_hooks         /* register hooks                      */

};