mod_rewrite.c

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/* 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.
 */


/*                       _                            _ _
**   _ __ ___   ___   __| |    _ __ _____      ___ __(_) |_ ___
**  | '_ ` _ \ / _ \ / _` |   | '__/ _ \ \ /\ / / '__| | __/ _ \
**  | | | | | | (_) | (_| |   | | |  __/\ V  V /| |  | | ||  __/
**  |_| |_| |_|\___/ \__,_|___|_|  \___| \_/\_/ |_|  |_|\__\___|
**                       |_____|
**
**  URL Rewriting Module
**
**  This module uses a rule-based rewriting engine (based on a
**  regular-expression parser) to rewrite requested URLs on the fly.
**
**  It supports an unlimited number of additional rule conditions (which can
**  operate on a lot of variables, even on HTTP headers) for granular
**  matching and even external database lookups (either via plain text
**  tables, DBM hash files or even external processes) for advanced URL
**  substitution.
**
**  It operates on the full URLs (including the PATH_INFO part) both in
**  per-server context (httpd.conf) and per-dir context (.htaccess) and even
**  can generate QUERY_STRING parts on result.   The rewriting result finally
**  can lead to internal subprocessing, external request redirection or even
**  to internal proxy throughput.
**
**  This module was originally written in April 1996 and
**  gifted exclusively to the The Apache Group in July 1997 by
**
**      Ralf S. Engelschall
**      [e-mail]
**      www.engelschall.com
*/


#include "mod_rewrite.h"

#ifndef NO_WRITEV
#ifndef NETWARE
#include <sys/types.h>
#endif
#include <sys/uio.h>
#endif

#ifdef NETWARE
#include <nwsemaph.h>
static LONG locking_sem = 0;
#endif

/*
** +-------------------------------------------------------+
** |                                                       |
** |             static module configuration
** |                                                       |
** +-------------------------------------------------------+
*/


/*
**  Our interface to the Apache server kernel:
**
**  o  Runtime logic of a request is as following:
**       while(request or subrequest)
**           foreach(stage #0...#9)
**               foreach(module) (**)
**                   try to run hook
**
**  o  the order of modules at (**) is the inverted order as
**     given in the "Configuration" file, i.e. the last module
**     specified is the first one called for each hook!
**     The core module is always the last!
**
**  o  there are two different types of result checking and
**     continue processing:
**     for hook #0,#1,#4,#5,#6,#8:
**         hook run loop stops on first modules which gives
**         back a result != DECLINED, i.e. it usually returns OK
**         which says "OK, module has handled this _stage_" and for #1
**         this have not to mean "Ok, the filename is now valid".
**     for hook #2,#3,#7,#9:
**         all hooks are run, independend of result
**
**  o  at the last stage, the core module always
**       - says "BAD_REQUEST" if r->filename does not begin with "/"
**       - prefix URL with document_root or replaced server_root
**         with document_root and sets r->filename
**       - always return a "OK" independed if the file really exists
**         or not!
*/

    /* The section for the Configure script:
     * MODULE-DEFINITION-START
     * Name: rewrite_module
     * ConfigStart
    . ./helpers/find-dbm-lib
    if [ "x$found_dbm" = "x1" ]; then
        echo "      enabling DBM support for mod_rewrite"
    else
        echo "      disabling DBM support for mod_rewrite"
        echo "      (perhaps you need to add -ldbm, -lndbm or -lgdbm to EXTRA_LIBS)"
        CFLAGS="$CFLAGS -DNO_DBM_REWRITEMAP"
    fi
     * ConfigEnd
     * MODULE-DEFINITION-END
     */

    /* the table of commands we provide */
static const command_rec command_table[] = {
    { "RewriteEngine",   cmd_rewriteengine,   NULL, OR_FILEINFO, FLAG,
      "On or Off to enable or disable (default) the whole rewriting engine" },
    { "RewriteOptions",  cmd_rewriteoptions,  NULL, OR_FILEINFO, ITERATE,
      "List of option strings to set" },
    { "RewriteBase",     cmd_rewritebase,     NULL, OR_FILEINFO, TAKE1,
      "the base URL of the per-directory context" },
    { "RewriteCond",     cmd_rewritecond,     NULL, OR_FILEINFO, RAW_ARGS,
      "an input string and a to be applied regexp-pattern" },
    { "RewriteRule",     cmd_rewriterule,     NULL, OR_FILEINFO, RAW_ARGS,
      "an URL-applied regexp-pattern and a substitution URL" },
    { "RewriteMap",      cmd_rewritemap,      NULL, RSRC_CONF,   TAKE2,
      "a mapname and a filename" },
    { "RewriteLock",     cmd_rewritelock,     NULL, RSRC_CONF,   TAKE1,
      "the filename of a lockfile used for inter-process synchronization"},
    { "RewriteLog",      cmd_rewritelog,      NULL, RSRC_CONF,   TAKE1,
      "the filename of the rewriting logfile" },
    { "RewriteLogLevel", cmd_rewriteloglevel, NULL, RSRC_CONF,   TAKE1,
      "the level of the rewriting logfile verbosity "
      "(0=none, 1=std, .., 9=max)" },
    { NULL }
};

    /* the table of content handlers we provide */
static const handler_rec handler_table[] = {
    { "redirect-handler", handler_redirect },
    { NULL }
};

    /* the main config structure */
module MODULE_VAR_EXPORT rewrite_module = {
   STANDARD_MODULE_STUFF,
   init_module,                 /* module initializer                  */
   config_perdir_create,        /* create per-dir    config structures */
   config_perdir_merge,         /* merge  per-dir    config structures */
   config_server_create,        /* create per-server config structures */
   config_server_merge,         /* merge  per-server config structures */
   command_table,               /* table of config file commands       */
   handler_table,               /* [#8] MIME-typed-dispatched handlers */
   hook_uri2file,               /* [#1] URI to filename translation    */
   NULL,                        /* [#4] validate user id from request  */
   NULL,                        /* [#5] check if the user is ok _here_ */
   NULL,                        /* [#3] check access by host address   */
   hook_mimetype,               /* [#6] determine MIME type            */
   hook_fixup,                  /* [#7] pre-run fixups                 */
   NULL,                        /* [#9] log a transaction              */
   NULL,                        /* [#2] header parser                  */
   init_child,                  /* child_init                          */
   NULL,                        /* child_exit                          */
   NULL                         /* [#0] post read-request              */
};

    /* the cache */
static cache *cachep;

    /* whether proxy module is available or not */
static int proxy_available;

static char *lockname;
static int lockfd = -1;

/*
** +-------------------------------------------------------+
** |                                                       |
** |           configuration directive handling
** |                                                       |
** +-------------------------------------------------------+
*/

/*
**
**  per-server configuration structure handling
**
*/

static void *config_server_create(pool *p, server_rec *s)
{
    rewrite_server_conf *a;

    a = (rewrite_server_conf *)ap_pcalloc(p, sizeof(rewrite_server_conf));

    a->state           = ENGINE_DISABLED;
    a->options         = OPTION_NONE;
    a->rewritelogfile  = NULL;
    a->rewritelogfp    = -1;
    a->rewriteloglevel = 0;
    a->rewritemaps     = ap_make_array(p, 2, sizeof(rewritemap_entry));
    a->rewriteconds    = ap_make_array(p, 2, sizeof(rewritecond_entry));
    a->rewriterules    = ap_make_array(p, 2, sizeof(rewriterule_entry));
    a->server          = s;
    a->redirect_limit  = 0; /* unset (use default) */

    return (void *)a;
}

static void *config_server_merge(pool *p, void *basev, void *overridesv)
{
    rewrite_server_conf *a, *base, *overrides;

    a         = (rewrite_server_conf *)ap_pcalloc(p, sizeof(rewrite_server_conf));
    base      = (rewrite_server_conf *)basev;
    overrides = (rewrite_server_conf *)overridesv;

    a->state   = overrides->state;
    a->options = overrides->options;
    a->server  = overrides->server;
    a->redirect_limit = overrides->redirect_limit
                          ? overrides->redirect_limit
                          : base->redirect_limit;

    if (a->options & OPTION_INHERIT) {
        /*
         *  local directives override
         *  and anything else is inherited
         */
        a->rewriteloglevel = overrides->rewriteloglevel != 0 
                             ? overrides->rewriteloglevel
                             : base->rewriteloglevel;
        a->rewritelogfile  = overrides->rewritelogfile != NULL 
                             ? overrides->rewritelogfile
                             : base->rewritelogfile;
        a->rewritelogfp    = overrides->rewritelogfp != -1 
                             ? overrides->rewritelogfp 
                             : base->rewritelogfp;
        a->rewritemaps     = ap_append_arrays(p, overrides->rewritemaps,
                                              base->rewritemaps);
        a->rewriteconds    = ap_append_arrays(p, overrides->rewriteconds,
                                              base->rewriteconds);
        a->rewriterules    = ap_append_arrays(p, overrides->rewriterules,
                                              base->rewriterules);
    }
    else {
        /*
         *  local directives override
         *  and anything else gets defaults
         */
        a->rewriteloglevel = overrides->rewriteloglevel;
        a->rewritelogfile  = overrides->rewritelogfile;
        a->rewritelogfp    = overrides->rewritelogfp;
        a->rewritemaps     = overrides->rewritemaps;
        a->rewriteconds    = overrides->rewriteconds;
        a->rewriterules    = overrides->rewriterules;
    }

    return (void *)a;
}


/*
**
**  per-directory configuration structure handling
**
*/

static void *config_perdir_create(pool *p, char *path)
{
    rewrite_perdir_conf *a;

    a = (rewrite_perdir_conf *)ap_pcalloc(p, sizeof(rewrite_perdir_conf));

    a->state           = ENGINE_DISABLED;
    a->options         = OPTION_NONE;
    a->baseurl         = NULL;
    a->rewriteconds    = ap_make_array(p, 2, sizeof(rewritecond_entry));
    a->rewriterules    = ap_make_array(p, 2, sizeof(rewriterule_entry));
    a->redirect_limit  = 0; /* unset (use server config) */

    if (path == NULL) {
        a->directory = NULL;
    }
    else {
        /* make sure it has a trailing slash */
        if (path[strlen(path)-1] == '/') {
            a->directory = ap_pstrdup(p, path);
        }
        else {
            a->directory = ap_pstrcat(p, path, "/", NULL);
        }
    }

    return (void *)a;
}

static void *config_perdir_merge(pool *p, void *basev, void *overridesv)
{
    rewrite_perdir_conf *a, *base, *overrides;

    a         = (rewrite_perdir_conf *)ap_pcalloc(p,
                                                  sizeof(rewrite_perdir_conf));
    base      = (rewrite_perdir_conf *)basev;
    overrides = (rewrite_perdir_conf *)overridesv;

    a->state     = overrides->state;
    a->options   = overrides->options;
    a->directory = overrides->directory;
    a->baseurl   = overrides->baseurl;
    a->redirect_limit = overrides->redirect_limit
                          ? overrides->redirect_limit
                          : base->redirect_limit;

    if (a->options & OPTION_INHERIT) {
        a->rewriteconds = ap_append_arrays(p, overrides->rewriteconds,
                                           base->rewriteconds);
        a->rewriterules = ap_append_arrays(p, overrides->rewriterules,
                                           base->rewriterules);
    }
    else {
        a->rewriteconds = overrides->rewriteconds;
        a->rewriterules = overrides->rewriterules;
    }

    return (void *)a;
}


/*
**
**  the configuration commands
**
*/

static const char *cmd_rewriteengine(cmd_parms *cmd,
                                     rewrite_perdir_conf *dconf, int flag)
{
    rewrite_server_conf *sconf;

    sconf = 
        (rewrite_server_conf *)ap_get_module_config(cmd->server->module_config,
                                                    &rewrite_module);

    if (cmd->path == NULL) { /* is server command */
        sconf->state = (flag ? ENGINE_ENABLED : ENGINE_DISABLED);
    }
    else                   /* is per-directory command */ {
        dconf->state = (flag ? ENGINE_ENABLED : ENGINE_DISABLED);
    }

    return NULL;
}

static const char *cmd_rewriteoptions(cmd_parms *cmd,
                                      void *in_dconf, const char *option)
{
    int options = 0, limit = 0;
    char *w;

    while (*option) {
        w = ap_getword_conf(cmd->pool, &option);

        if (!strcasecmp(w, "inherit")) {
            options |= OPTION_INHERIT;
        }
        else if (!strncasecmp(w, "MaxRedirects=", 13)) {
            limit = atoi(&w[13]);
            if (limit <= 0) {
                return "RewriteOptions: MaxRedirects takes a number greater "
                       "than zero.";
            }
        }
        else if (!strcasecmp(w, "MaxRedirects")) { /* be nice */
            return "RewriteOptions: MaxRedirects has the format MaxRedirects"
                   "=n.";
        }
        else {
            return ap_pstrcat(cmd->pool, "RewriteOptions: unknown option '",
                              w, "'", NULL);
        }
    }

    /* put it into the appropriate config */