request.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.
 */

/*
 * @file  request.c
 * @brief functions to get and process requests
 *
 * @author Rob McCool 3/21/93
 *
 * Thoroughly revamped by rst for Apache.  NB this file reads
 * best from the bottom up.
 *
 */

#include "apr_strings.h"
#include "apr_file_io.h"
#include "apr_fnmatch.h"

#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "ap_config.h"
#include "ap_provider.h"
#include "httpd.h"
#include "http_config.h"
#include "http_request.h"
#include "http_core.h"
#include "http_protocol.h"
#include "http_log.h"
#include "http_main.h"
#include "util_filter.h"
#include "util_charset.h"
#include "util_script.h"
#include "ap_expr.h"
#include "mod_request.h"

#include "mod_core.h"
#include "mod_auth.h"

#if APR_HAVE_STDARG_H
#include <stdarg.h>
#endif

/* we know core's module_index is 0 */
#undef APLOG_MODULE_INDEX
#define APLOG_MODULE_INDEX AP_CORE_MODULE_INDEX

APR_HOOK_STRUCT(
    APR_HOOK_LINK(translate_name)
    APR_HOOK_LINK(map_to_storage)
    APR_HOOK_LINK(check_user_id)
    APR_HOOK_LINK(fixups)
    APR_HOOK_LINK(type_checker)
    APR_HOOK_LINK(access_checker)
    APR_HOOK_LINK(access_checker_ex)
    APR_HOOK_LINK(auth_checker)
    APR_HOOK_LINK(insert_filter)
    APR_HOOK_LINK(create_request)
    APR_HOOK_LINK(post_perdir_config)
    APR_HOOK_LINK(dirwalk_stat)
    APR_HOOK_LINK(force_authn)
)

AP_IMPLEMENT_HOOK_RUN_FIRST(int,translate_name,
                            (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,map_to_storage,
                            (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,check_user_id,
                            (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_RUN_ALL(int,fixups,
                          (request_rec *r), (r), OK, DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,type_checker,
                            (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_RUN_ALL(int,access_checker,
                          (request_rec *r), (r), OK, DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,access_checker_ex,
                          (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,auth_checker,
                            (request_rec *r), (r), DECLINED)
AP_IMPLEMENT_HOOK_VOID(insert_filter, (request_rec *r), (r))
AP_IMPLEMENT_HOOK_RUN_ALL(int, create_request,
                          (request_rec *r), (r), OK, DECLINED)
AP_IMPLEMENT_HOOK_RUN_ALL(int, post_perdir_config,
                          (request_rec *r), (r), OK, DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(apr_status_t,dirwalk_stat,
                            (apr_finfo_t *finfo, request_rec *r, apr_int32_t wanted),
                            (finfo, r, wanted), AP_DECLINED)
AP_IMPLEMENT_HOOK_RUN_FIRST(int,force_authn,
                          (request_rec *r), (r), DECLINED)

static int auth_internal_per_conf = 0;
static int auth_internal_per_conf_hooks = 0;
static int auth_internal_per_conf_providers = 0;


static int decl_die(int status, const char *phase, request_rec *r)
{
    if (status == DECLINED) {
        ap_log_rerror(APLOG_MARK, APLOG_CRIT, 0, r, APLOGNO(00025)
                      "configuration error:  couldn't %s: %s", phase, r->uri);
        return HTTP_INTERNAL_SERVER_ERROR;
    }
    else {
        ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r,
                      "auth phase '%s' gave status %d: %s", phase,
                      status, r->uri);
        return status;
    }
}

AP_DECLARE(int) ap_some_authn_required(request_rec *r)
{
    int access_status;
    char *olduser = r->user;
    int rv = FALSE;

    switch (ap_satisfies(r)) {
    case SATISFY_ALL:
    case SATISFY_NOSPEC:
        if ((access_status = ap_run_access_checker(r)) != OK) {
            break;
        }

        access_status = ap_run_access_checker_ex(r);
        if (access_status == DECLINED) {
            rv = TRUE;
        }

        break;
    case SATISFY_ANY:
        if ((access_status = ap_run_access_checker(r)) == OK) {
            break;
        }

        access_status = ap_run_access_checker_ex(r);
        if (access_status == DECLINED) {
            rv = TRUE;
        }

        break;
    }

    r->user = olduser;
    return rv;
}

/* This is the master logic for processing requests.  Do NOT duplicate
 * this logic elsewhere, or the security model will be broken by future
 * API changes.  Each phase must be individually optimized to pick up
 * redundant/duplicate calls by subrequests, and redirects.
 */
AP_DECLARE(int) ap_process_request_internal(request_rec *r)
{
    int file_req = (r->main && r->filename);
    int access_status;
    core_dir_config *d;

    /* Ignore embedded %2F's in path for proxy requests */
    if (!r->proxyreq && r->parsed_uri.path) {
        d = ap_get_core_module_config(r->per_dir_config);
        if (d->allow_encoded_slashes) {
            access_status = ap_unescape_url_keep2f(r->parsed_uri.path, d->decode_encoded_slashes);
        }
        else {
            access_status = ap_unescape_url(r->parsed_uri.path);
        }
        if (access_status) {
            if (access_status == HTTP_NOT_FOUND) {
                if (! d->allow_encoded_slashes) {
                    ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(00026)
                                  "found %%2f (encoded '/') in URI "
                                  "(decoded='%s'), returning 404",
                                  r->parsed_uri.path);
                }
            }
            return access_status;
        }
    }

    ap_getparents(r->uri);     /* OK --- shrinking transformations... */

    /* All file subrequests are a huge pain... they cannot bubble through the
     * next several steps.  Only file subrequests are allowed an empty uri,
     * otherwise let translate_name kill the request.
     */
    if (!file_req) {
        if ((access_status = ap_location_walk(r))) {
            return access_status;
        }
        if ((access_status = ap_if_walk(r))) {
            return access_status;
        }

        d = ap_get_core_module_config(r->per_dir_config);
        if (d->log) {
            r->log = d->log;
        }

        if ((access_status = ap_run_translate_name(r))) {
            return decl_die(access_status, "translate", r);
        }
    }

    /* Reset to the server default config prior to running map_to_storage
     */
    r->per_dir_config = r->server->lookup_defaults;

    if ((access_status = ap_run_map_to_storage(r))) {
        /* This request wasn't in storage (e.g. TRACE) */
        return access_status;
    }

    /* Rerun the location walk, which overrides any map_to_storage config.
     */
    if ((access_status = ap_location_walk(r))) {
        return access_status;
    }
    if ((access_status = ap_if_walk(r))) {
        return access_status;
    }

    d = ap_get_core_module_config(r->per_dir_config);
    if (d->log) {
        r->log = d->log;
    }

    if ((access_status = ap_run_post_perdir_config(r))) {
        return access_status;
    }

    /* Only on the main request! */
    if (r->main == NULL) {
        if ((access_status = ap_run_header_parser(r))) {
            return access_status;
        }
    }

    /* Skip authn/authz if the parent or prior request passed the authn/authz,
     * and that configuration didn't change (this requires optimized _walk()
     * functions in map_to_storage that use the same merge results given
     * identical input.)  If the config changes, we must re-auth.
     */
    if (r->prev && (r->prev->per_dir_config == r->per_dir_config)) {
        r->user = r->prev->user;
        r->ap_auth_type = r->prev->ap_auth_type;
    }
    else if (r->main && (r->main->per_dir_config == r->per_dir_config)) {
        r->user = r->main->user;
        r->ap_auth_type = r->main->ap_auth_type;
    }
    else {
        /* A module using a confusing API (ap_get_basic_auth_pw) caused
        ** r->user to be filled out prior to check_authn hook. We treat
        ** it is inadvertent.
        */
        if (r->user && apr_table_get(r->notes, AP_GET_BASIC_AUTH_PW_NOTE)) { 
            r->user = NULL;
        }

        switch (ap_satisfies(r)) {
        case SATISFY_ALL:
        case SATISFY_NOSPEC:
            if ((access_status = ap_run_access_checker(r)) != OK) {
                return decl_die(access_status,
                                "check access (with Satisfy All)", r);
            }

            access_status = ap_run_access_checker_ex(r);
            if (access_status == DECLINED
                || (access_status == OK && ap_run_force_authn(r) == OK)) {
                if ((access_status = ap_run_check_user_id(r)) != OK) {
                    return decl_die(access_status, "check user", r);
                }
                if (r->user == NULL) {
                    /* don't let buggy authn module crash us in authz */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00027)
                                  "No authentication done but request not "
                                  "allowed without authentication for %s. "
                                  "Authentication not configured?",
                                  r->uri);
                    access_status = HTTP_INTERNAL_SERVER_ERROR;
                    return decl_die(access_status, "check user", r);
                }
                if ((access_status = ap_run_auth_checker(r)) != OK) {
                    return decl_die(access_status, "check authorization", r);
                }
            }
            else if (access_status == OK) {
                ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r,
                              "request authorized without authentication by "
                              "access_checker_ex hook: %s", r->uri);
            }
            else {
                return decl_die(access_status, "check access", r);
            }
            break;
        case SATISFY_ANY:
            if ((access_status = ap_run_access_checker(r)) == OK) {
                ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r,
                              "request authorized without authentication by "
                              "access_checker hook and 'Satisfy any': %s",
                              r->uri);
                break;
            }

            access_status = ap_run_access_checker_ex(r);
            if (access_status == DECLINED
                || (access_status == OK && ap_run_force_authn(r) == OK)) {
                if ((access_status = ap_run_check_user_id(r)) != OK) {
                    return decl_die(access_status, "check user", r);
                }
                if (r->user == NULL) {
                    /* don't let buggy authn module crash us in authz */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00028)
                                  "No authentication done but request not "
                                  "allowed without authentication for %s. "
                                  "Authentication not configured?",
                                  r->uri);
                    access_status = HTTP_INTERNAL_SERVER_ERROR;
                    return decl_die(access_status, "check user", r);
                }
                if ((access_status = ap_run_auth_checker(r)) != OK) {
                    return decl_die(access_status, "check authorization", r);
                }
            }
            else if (access_status == OK) {
                ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r,
                              "request authorized without authentication by "
                              "access_checker_ex hook: %s", r->uri);
            }
            else {
                return decl_die(access_status, "check access", r);
            }
            break;
        }
    }
    /* XXX Must make certain the ap_run_type_checker short circuits mime
     * in mod-proxy for r->proxyreq && r->parsed_uri.scheme
     *                              && !strcmp(r->parsed_uri.scheme, "http")
     */
    if ((access_status = ap_run_type_checker(r)) != OK) {
        return decl_die(access_status, "find types", r);
    }

    if ((access_status = ap_run_fixups(r)) != OK) {
        ap_log_rerror(APLOG_MARK, APLOG_TRACE3, 0, r, "fixups hook gave %d: %s",
                      access_status, r->uri);
        return access_status;
    }

    return OK;
}


/* Useful caching structures to repeat _walk/merge sequences as required
 * when a subrequest or redirect reuses substantially the same config.
 *
 * Directive order in the httpd.conf file and its Includes significantly
 * impact this optimization.  Grouping common blocks at the front of the
 * config that are less likely to change between a request and
 * its subrequests, or between a request and its redirects reduced
 * the work of these functions significantly.
 */

typedef struct walk_walked_t {
    ap_conf_vector_t *matched; /* A dir_conf sections we matched */
    ap_conf_vector_t *merged;  /* The dir_conf merged result */
} walk_walked_t;

typedef struct walk_cache_t {
    const char         *cached;          /* The identifier we matched */
    ap_conf_vector_t  **dir_conf_tested; /* The sections we matched against */
    ap_conf_vector_t   *dir_conf_merged; /* Base per_dir_config */
    ap_conf_vector_t   *per_dir_result;  /* per_dir_config += walked result */
    apr_array_header_t *walked;          /* The list of walk_walked_t results */
    struct walk_cache_t *prev; /* Prev cache of same call in this (sub)req */
    int count; /* Number of prev invocations of same call in this (sub)req */
} walk_cache_t;

static walk_cache_t *prep_walk_cache(apr_size_t t, request_rec *r)
{
    void **note, **inherit_note;
    walk_cache_t *cache, *prev_cache, *copy_cache;
    int count;

    /* Find the most relevant, recent walk cache to work from and provide
     * a copy the caller is allowed to munge.  In the case of a sub-request
     * or internal redirect, this is the cache corresponding to the equivalent
     * invocation of the same function call in the "parent" request, if such
     * a cache exists.  Otherwise it is the walk cache of the previous
     * invocation of the same function call in the current request, if
     * that exists; if not, then create a new walk cache.
     */
    note = ap_get_request_note(r, t);
    AP_DEBUG_ASSERT(note != NULL);

    copy_cache = prev_cache = *note;
    count = prev_cache ? (prev_cache->count + 1) : 0;

    if ((r->prev
         && (inherit_note = ap_get_request_note(r->prev, t))
         && *inherit_note)
        || (r->main
            && (inherit_note = ap_get_request_note(r->main, t))
            && *inherit_note)) {
        walk_cache_t *inherit_cache = *inherit_note;

        while (inherit_cache->count > count) {
            inherit_cache = inherit_cache->prev;
        }
        if (inherit_cache->count == count) {
            copy_cache = inherit_cache;
        }
    }

    if (copy_cache) {
        cache = apr_pmemdup(r->pool, copy_cache, sizeof(*cache));
        cache->walked = apr_array_copy(r->pool, cache->walked);
        cache->prev = prev_cache;
        cache->count = count;
    }
    else {
        cache = apr_pcalloc(r->pool, sizeof(*cache));
        cache->walked = apr_array_make(r->pool, 4, sizeof(walk_walked_t));
    }

    *note = cache;

    return cache;
}

/*****************************************************************
 *
 * Getting and checking directory configuration.  Also checks the
 * FollowSymlinks and FollowSymOwner stuff, since this is really the
 * only place that can happen (barring a new mid_dir_walk callout).
 *
 * We can't do it as an access_checker module function which gets
 * called with the final per_dir_config, since we could have a directory
 * with FollowSymLinks disabled, which contains a symlink to another
 * with a .htaccess file which turns FollowSymLinks back on --- and
 * access in such a case must be denied.  So, whatever it is that
 * checks FollowSymLinks needs to know the state of the options as
 * they change, all the way down.
 */


/*
 * resolve_symlink must _always_ be called on an APR_LNK file type!
 * It will resolve the actual target file type, modification date, etc,
 * and provide any processing required for symlink evaluation.
 * Path must already be cleaned, no trailing slash, no multi-slashes,
 * and don't call this on the root!
 *
 * Simply, the number of times we deref a symlink are minimal compared
 * to the number of times we had an extra lstat() since we 'weren't sure'.
 *
 * To optimize, we stat() anything when given (opts & OPT_SYM_LINKS), otherwise
 * we start off with an lstat().  Every lstat() must be dereferenced in case
 * it points at a 'nasty' - we must always rerun check_safe_file (or similar.)
 */
static int resolve_symlink(char *d, apr_finfo_t *lfi, int opts, apr_pool_t *p)
{
    apr_finfo_t fi;
    const char *savename;

    if (!(opts & (OPT_SYM_OWNER | OPT_SYM_LINKS))) {
        return HTTP_FORBIDDEN;
    }

    /* Save the name from the valid bits. */
    savename = (lfi->valid & APR_FINFO_NAME) ? lfi->name : NULL;

    /* if OPT_SYM_OWNER is unset, we only need to check target accessible */
    if (!(opts & OPT_SYM_OWNER)) {
        if (apr_stat(&fi, d, lfi->valid & ~(APR_FINFO_NAME | APR_FINFO_LINK), p)
            != APR_SUCCESS)
        {
            return HTTP_FORBIDDEN;
        }

        /* Give back the target */
        memcpy(lfi, &fi, sizeof(fi));
        if (savename) {
            lfi->name = savename;
            lfi->valid |= APR_FINFO_NAME;
        }

        return OK;
    }

    /* OPT_SYM_OWNER only works if we can get the owner of
     * both the file and symlink.  First fill in a missing
     * owner of the symlink, then get the info of the target.
     */
    if (!(lfi->valid & APR_FINFO_OWNER)) {
        if (apr_stat(lfi, d, lfi->valid | APR_FINFO_LINK | APR_FINFO_OWNER, p)
            != APR_SUCCESS)
        {
            return HTTP_FORBIDDEN;
        }
    }

    if (apr_stat(&fi, d, lfi->valid & ~(APR_FINFO_NAME), p) != APR_SUCCESS) {
        return HTTP_FORBIDDEN;
    }

    if (apr_uid_compare(fi.user, lfi->user) != APR_SUCCESS) {
        return HTTP_FORBIDDEN;
    }

    /* Give back the target */
    memcpy(lfi, &fi, sizeof(fi));
    if (savename) {
        lfi->name = savename;
        lfi->valid |= APR_FINFO_NAME;
    }

    return OK;
}


/*
 * As we walk the directory configuration, the merged config won't
 * be 'rooted' to a specific vhost until the very end of the merge.
 *
 * We need a very fast mini-merge to a real, vhost-rooted merge
 * of core.opts and core.override, the only options tested within
 * directory_walk itself.
 *
 * See core.c::merge_core_dir_configs() for explanation.
 */

typedef struct core_opts_t {
        allow_options_t opts;
        allow_options_t add;
        allow_options_t remove;
        overrides_t override;
        overrides_t override_opts;
        apr_table_t *override_list;
} core_opts_t;

static void core_opts_merge(const ap_conf_vector_t *sec, core_opts_t *opts)
{
    core_dir_config *this_dir = ap_get_core_module_config(sec);

    if (!this_dir) {
        return;
    }

    if (this_dir->opts & OPT_UNSET) {
        opts->add = (opts->add & ~this_dir->opts_remove)
                   | this_dir->opts_add;
        opts->remove = (opts->remove & ~this_dir->opts_add)
                      | this_dir->opts_remove;
        opts->opts = (opts->opts & ~opts->remove) | opts->add;
    }
    else {
        opts->opts = this_dir->opts;
        opts->add = this_dir->opts_add;
        opts->remove = this_dir->opts_remove;
    }

    if (!(this_dir->override & OR_UNSET)) {
        opts->override = this_dir->override;
        opts->override_opts = this_dir->override_opts;
    }

    if (this_dir->override_list != NULL) {
        opts->override_list = this_dir->override_list;
    }
}


/*****************************************************************
 *
 * Getting and checking directory configuration.  Also checks the
 * FollowSymlinks and FollowSymOwner stuff, since this is really the
 * only place that can happen (barring a new mid_dir_walk callout).
 *
 * We can't do it as an access_checker module function which gets
 * called with the final per_dir_config, since we could have a directory
 * with FollowSymLinks disabled, which contains a symlink to another
 * with a .htaccess file which turns FollowSymLinks back on --- and
 * access in such a case must be denied.  So, whatever it is that
 * checks FollowSymLinks needs to know the state of the options as
 * they change, all the way down.
 */

AP_DECLARE(int) ap_directory_walk(request_rec *r)
{
    ap_conf_vector_t *now_merged = NULL;
    core_server_config *sconf =
        ap_get_core_module_config(r->server->module_config);
    ap_conf_vector_t **sec_ent = (ap_conf_vector_t **) sconf->sec_dir->elts;
    int num_sec = sconf->sec_dir->nelts;
    walk_cache_t *cache;
    char *entry_dir;
    apr_status_t rv;
    int cached;

    /* XXX: Better (faster) tests needed!!!
     *
     * "OK" as a response to a real problem is not _OK_, but to allow broken
     * modules to proceed, we will permit the not-a-path filename to pass the
     * following two tests.  This behavior may be revoked in future versions
     * of Apache.  We still must catch it later if it's heading for the core
     * handler.  Leave INFO notes here for module debugging.
     */
    if (r->filename == NULL) {
        ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(00029)
                      "Module bug?  Request filename is missing for URI %s",
                      r->uri);
        return OK;
    }

    /* Canonicalize the file path without resolving filename case or aliases
     * so we can begin by checking the cache for a recent directory walk.
     * This call will ensure we have an absolute path in the same pass.
     */
    if ((rv = apr_filepath_merge(&entry_dir, NULL, r->filename,
                                 APR_FILEPATH_NOTRELATIVE, r->pool))
                  != APR_SUCCESS) {
        ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r, APLOGNO(00030)
                      "Module bug?  Request filename path %s is invalid or "
                      "or not absolute for uri %s",
                      r->filename, r->uri);
        return OK;
    }

    /* XXX Notice that this forces path_info to be canonical.  That might
     * not be desired by all apps.  However, some of those same apps likely
     * have significant security holes.
     */
    r->filename = entry_dir;

    cache = prep_walk_cache(AP_NOTE_DIRECTORY_WALK, r);
    cached = (cache->cached != NULL);

    /* If this is not a dirent subrequest with a preconstructed
     * r->finfo value, then we can simply stat the filename to
     * save burning mega-cycles with unneeded stats - if this is
     * an exact file match.  We don't care about failure... we
     * will stat by component failing this meager attempt.
     *
     * It would be nice to distinguish APR_ENOENT from other
     * types of failure, such as APR_ENOTDIR.  We can do something
     * with APR_ENOENT, knowing that the path is good.
     */
    if (r->finfo.filetype == APR_NOFILE || r->finfo.filetype == APR_LNK) {
        rv = ap_run_dirwalk_stat(&r->finfo, r, APR_FINFO_MIN);

        /* some OSs will return APR_SUCCESS/APR_REG if we stat
         * a regular file but we have '/' at the end of the name;
         *
         * other OSs will return APR_ENOTDIR for that situation;
         *
         * handle it the same everywhere by simulating a failure
         * if it looks like a directory but really isn't
         *
         * Also reset if the stat failed, just for safety.
         */
        if ((rv != APR_SUCCESS) ||
            (r->finfo.filetype != APR_NOFILE &&
             (r->finfo.filetype != APR_DIR) &&
             (r->filename[strlen(r->filename) - 1] == '/'))) {
             r->finfo.filetype = APR_NOFILE; /* forget what we learned */
        }
    }

    if (r->finfo.filetype == APR_REG) {
        entry_dir = ap_make_dirstr_parent(r->pool, entry_dir);
    }
    else if (r->filename[strlen(r->filename) - 1] != '/') {
        entry_dir = apr_pstrcat(r->pool, r->filename, "/", NULL);
    }

    /* If we have a file already matches the path of r->filename,
     * and the vhost's list of directory sections hasn't changed,
     * we can skip rewalking the directory_walk entries.
     */
    if (cached
        && ((r->finfo.filetype == APR_REG)
            || ((r->finfo.filetype == APR_DIR)
                && (!r->path_info || !*r->path_info)))
        && (cache->dir_conf_tested == sec_ent)
        && (strcmp(entry_dir, cache->cached) == 0)) {
        int familiar = 0;

        /* Well this looks really familiar!  If our end-result (per_dir_result)
         * didn't change, we have absolutely nothing to do :)
         * Otherwise (as is the case with most dir_merged/file_merged requests)
         * we must merge our dir_conf_merged onto this new r->per_dir_config.
         */
        if (r->per_dir_config == cache->per_dir_result) {
            familiar = 1;
        }

        if (r->per_dir_config == cache->dir_conf_merged) {
            r->per_dir_config = cache->per_dir_result;
            familiar = 1;
        }

        if (familiar) {
            apr_finfo_t thisinfo;
            int res;
            allow_options_t opts;
            core_dir_config *this_dir;

            this_dir = ap_get_core_module_config(r->per_dir_config);
            opts = this_dir->opts;
            /*
             * If Symlinks are allowed in general we do not need the following
             * check.
             */
            if (!(opts & OPT_SYM_LINKS)) {
                rv = ap_run_dirwalk_stat(&thisinfo, r,
                                         APR_FINFO_MIN | APR_FINFO_NAME | APR_FINFO_LINK);
                /*
                 * APR_INCOMPLETE is as fine as result as APR_SUCCESS as we
                 * have added APR_FINFO_NAME to the wanted parameter of
                 * apr_stat above. On Unix platforms this means that apr_stat
                 * is always going to return APR_INCOMPLETE in the case that
                 * the call to the native stat / lstat did not fail.
                 */
                if ((rv != APR_INCOMPLETE) && (rv != APR_SUCCESS)) {
                    /*
                     * This should never happen, because we did a stat on the
                     * same file, resolving a possible symlink several lines
                     * above. Therefore do not make a detailed analysis of rv
                     * in this case for the reason of the failure, just bail out
                     * with a HTTP_FORBIDDEN in case we hit a race condition
                     * here.
                     */
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(00031)
                                  "access to %s failed; stat of '%s' failed.",
                                  r->uri, r->filename);
                    return r->status = HTTP_FORBIDDEN;
                }
                if (thisinfo.filetype == APR_LNK) {
                    /* Is this a possibly acceptable symlink? */
                    if ((res = resolve_symlink(r->filename, &thisinfo,
                                               opts, r->pool)) != OK) {
                        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00032)
                                      "Symbolic link not allowed "
                                      "or link target not accessible: %s",
                                      r->filename);
                        return r->status = res;
                    }
                }
            }
            return OK;
        }

        if (cache->walked->nelts) {
            now_merged = ((walk_walked_t*)cache->walked->elts)
                [cache->walked->nelts - 1].merged;
        }
    }
    else {
        /* We start now_merged from NULL since we want to build
         * a locations list that can be merged to any vhost.
         */
        int sec_idx;
        int matches = cache->walked->nelts;
        int cached_matches = matches;
        walk_walked_t *last_walk = (walk_walked_t*)cache->walked->elts;
        core_dir_config *this_dir;
        core_opts_t opts;
        apr_finfo_t thisinfo;
        char *save_path_info;
        apr_size_t buflen;
        char *buf;
        unsigned int seg, startseg;
        apr_pool_t *rxpool = NULL;

        /* Invariant: from the first time filename_len is set until
         * it goes out of scope, filename_len==strlen(r->filename)
         */
        apr_size_t filename_len;
#ifdef CASE_BLIND_FILESYSTEM
        apr_size_t canonical_len;
#endif

        cached &= auth_internal_per_conf;

        /*
         * We must play our own mini-merge game here, for the few
         * running dir_config values we care about within dir_walk.
         * We didn't start the merge from r->per_dir_config, so we
         * accumulate opts and override as we merge, from the globals.
         */
        this_dir = ap_get_core_module_config(r->per_dir_config);
        opts.opts = this_dir->opts;
        opts.add = this_dir->opts_add;
        opts.remove = this_dir->opts_remove;
        opts.override = this_dir->override;
        opts.override_opts = this_dir->override_opts;
        opts.override_list = this_dir->override_list;

        /* Set aside path_info to merge back onto path_info later.
         * If r->filename is a directory, we must remerge the path_info,
         * before we continue!  [Directories cannot, by definition, have
         * path info.  Either the next segment is not-found, or a file.]
         *
         * r->path_info tracks the unconsumed source path.
         * r->filename  tracks the path as we process it
         */
        if ((r->finfo.filetype == APR_DIR) && r->path_info && *r->path_info)
        {
            if ((rv = apr_filepath_merge(&r->path_info, r->filename,
                                         r->path_info,
                                         APR_FILEPATH_NOTABOVEROOT, r->pool))
                != APR_SUCCESS) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(00033)
                              "dir_walk error, path_info %s is not relative "
                              "to the filename path %s for uri %s",
                              r->path_info, r->filename, r->uri);
                return HTTP_INTERNAL_SERVER_ERROR;
            }

            save_path_info = NULL;
        }
        else {
            save_path_info = r->path_info;
            r->path_info = r->filename;
        }

#ifdef CASE_BLIND_FILESYSTEM

        canonical_len = 0;
        while (r->canonical_filename && r->canonical_filename[canonical_len]
               && (r->canonical_filename[canonical_len]
                   == r->path_info[canonical_len])) {
             ++canonical_len;
        }

        while (canonical_len
               && ((r->canonical_filename[canonical_len - 1] != '/'
                   && r->canonical_filename[canonical_len - 1])
                   || (r->path_info[canonical_len - 1] != '/'
                       && r->path_info[canonical_len - 1]))) {
            --canonical_len;
        }

        /*
         * Now build r->filename component by component, starting
         * with the root (on Unix, simply "/").  We will make a huge
         * assumption here for efficiency, that any canonical path
         * already given included a canonical root.
         */
        rv = apr_filepath_root((const char **)&r->filename,
                               (const char **)&r->path_info,
                               canonical_len ? 0 : APR_FILEPATH_TRUENAME,
                               r->pool);
        filename_len = strlen(r->filename);

        /*
         * Bad assumption above?  If the root's length is longer
         * than the canonical length, then it cannot be trusted as
         * a truename.  So try again, this time more seriously.
         */
        if ((rv == APR_SUCCESS) && canonical_len
            && (filename_len > canonical_len)) {
            rv = apr_filepath_root((const char **)&r->filename,
                                   (const char **)&r->path_info,
                                   APR_FILEPATH_TRUENAME, r->pool);
            filename_len = strlen(r->filename);
            canonical_len = 0;
        }

#else /* ndef CASE_BLIND_FILESYSTEM, really this simple for Unix today; */

        rv = apr_filepath_root((const char **)&r->filename,
                               (const char **)&r->path_info,
                               0, r->pool);
        filename_len = strlen(r->filename);

#endif

        if (rv != APR_SUCCESS) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, APLOGNO(00034)
                          "dir_walk error, could not determine the root "
                          "path of filename %s%s for uri %s",
                          r->filename, r->path_info, r->uri);
            return HTTP_INTERNAL_SERVER_ERROR;
        }

        /* Working space for terminating null and an extra / is required.
         */
        buflen = filename_len + strlen(r->path_info) + 2;
        buf = apr_palloc(r->pool, buflen);
        memcpy(buf, r->filename, filename_len + 1);
        r->filename = buf;
        thisinfo.valid = APR_FINFO_TYPE;
        thisinfo.filetype = APR_DIR; /* It's the root, of course it's a dir */

        /*
         * seg keeps track of which segment we've copied.
         * sec_idx keeps track of which section we're on, since sections are
         *     ordered by number of segments. See core_reorder_directories
         * startseg tells us how many segments describe the root path
         *     e.g. the complete path "//host/foo/" to a UNC share (4)
         */
        startseg = seg = ap_count_dirs(r->filename);
        sec_idx = 0;

        /*
         * Go down the directory hierarchy.  Where we have to check for
         * symlinks, do so.  Where a .htaccess file has permission to
         * override anything, try to find one.
         */
        do {
            int res;
            char *seg_name;
            char *delim;
            int temp_slash=0;

            /* We have no trailing slash, but we sure would appreciate one.
             * However, we don't want to append a / our first time through.
             */
            if ((seg > startseg) && r->filename[filename_len-1] != '/') {
                r->filename[filename_len++] = '/';
                r->filename[filename_len] = 0;
                temp_slash=1;
            }

            /* Begin *this* level by looking for matching <Directory> sections
             * from the server config.
             */
            for (; sec_idx < num_sec; ++sec_idx) {

                ap_conf_vector_t *entry_config = sec_ent[sec_idx];
                core_dir_config *entry_core;
                entry_core = ap_get_core_module_config(entry_config);

                /* No more possible matches for this many segments?
                 * We are done when we find relative/regex/longer components.
                 */
                if (entry_core->r || entry_core->d_components > seg) {
                    break;
                }

                /* We will never skip '0' element components, e.g. plain old
                 * <Directory >, and <Directory "/"> are classified as zero
                 * so that Win32/Netware/OS2 etc all pick them up.
                 * Otherwise, skip over the mismatches.
                 */
                if (entry_core->d_components
                    && ((entry_core->d_components < seg)
                     || (entry_core->d_is_fnmatch
                         ? (apr_fnmatch(entry_core->d, r->filename,
                                        APR_FNM_PATHNAME) != APR_SUCCESS)
                         : (strcmp(r->filename, entry_core->d) != 0)))) {
                    continue;
                }

                /* If we haven't continue'd above, we have a match.
                 *
                 * Calculate our full-context core opts & override.
                 */
                core_opts_merge(sec_ent[sec_idx], &opts);

                /* If we merged this same section last time, reuse it
                 */
                if (matches) {
                    if (last_walk->matched == sec_ent[sec_idx]) {
                        now_merged = last_walk->merged;
                        ++last_walk;
                        --matches;
                        continue;
                    }

                    /* We fell out of sync.  This is our own copy of walked,
                     * so truncate the remaining matches and reset remaining.
                     */
                    cache->walked->nelts -= matches;
                    matches = 0;
                    cached = 0;
                }

                if (now_merged) {
                    now_merged = ap_merge_per_dir_configs(r->pool,
                                                          now_merged,
                                                          sec_ent[sec_idx]);
                }
                else {