/* 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.
 */

/*
 * http_alias.c: Stuff for dealing with directory aliases
 *
 * Original by Rob McCool, rewritten in succession by David Robinson
 * and rst.
 *
 */

#include "apr_strings.h"
#include "apr_lib.h"

#define APR_WANT_STRFUNC
#include "apr_want.h"

#include "ap_config.h"
#include "httpd.h"
#include "http_core.h"
#include "http_config.h"
#include "http_request.h"
#include "http_log.h"
#include "ap_expr.h"


#define ALIAS_FLAG_DEFAULT -1
#define ALIAS_FLAG_OFF 0
#define ALIAS_FLAG_ON  1

typedef struct {
    const char *real;
    const char *fake;
    char *handler;
    ap_regex_t *regexp;
    int redir_status;                /* 301, 302, 303, 410, etc */
} alias_entry;

typedef struct {
    apr_array_header_t *aliases;
    apr_array_header_t *redirects;
} alias_server_conf;

typedef struct {
    unsigned int alias_set:1;
    unsigned int redirect_set:1;
    apr_array_header_t *redirects;
    const ap_expr_info_t *alias;
    char *handler;
    const ap_expr_info_t *redirect;
    int redirect_status;                /* 301, 302, 303, 410, etc */
    int allow_relative;                 /* skip ap_construct_url() */
} alias_dir_conf;

module AP_MODULE_DECLARE_DATA alias_module;

static char magic_error_value;
#define PREGSUB_ERROR      (&magic_error_value)

static void *create_alias_config(apr_pool_t *p, server_rec *s)
{
    alias_server_conf *a =
    (alias_server_conf *) apr_pcalloc(p, sizeof(alias_server_conf));

    a->aliases = apr_array_make(p, 20, sizeof(alias_entry));
    a->redirects = apr_array_make(p, 20, sizeof(alias_entry));
    return a;
}

static void *create_alias_dir_config(apr_pool_t *p, char *d)
{
    alias_dir_conf *a =
    (alias_dir_conf *) apr_pcalloc(p, sizeof(alias_dir_conf));
    a->redirects = apr_array_make(p, 2, sizeof(alias_entry));
    a->allow_relative = ALIAS_FLAG_DEFAULT;
    return a;
}

static void *merge_alias_config(apr_pool_t *p, void *basev, void *overridesv)
{
    alias_server_conf *a =
    (alias_server_conf *) apr_pcalloc(p, sizeof(alias_server_conf));
    alias_server_conf *base = (alias_server_conf *) basev;
    alias_server_conf *overrides = (alias_server_conf *) overridesv;

    a->aliases = apr_array_append(p, overrides->aliases, base->aliases);
    a->redirects = apr_array_append(p, overrides->redirects, base->redirects);
    return a;
}

static void *merge_alias_dir_config(apr_pool_t *p, void *basev, void *overridesv)
{
    alias_dir_conf *a =
    (alias_dir_conf *) apr_pcalloc(p, sizeof(alias_dir_conf));
    alias_dir_conf *base = (alias_dir_conf *) basev;
    alias_dir_conf *overrides = (alias_dir_conf *) overridesv;

    a->redirects = apr_array_append(p, overrides->redirects, base->redirects);

    a->alias = (overrides->alias_set == 0) ? base->alias : overrides->alias;
    a->handler = (overrides->alias_set == 0) ? base->handler : overrides->handler;
    a->alias_set = overrides->alias_set || base->alias_set;

    a->redirect = (overrides->redirect_set == 0) ? base->redirect : overrides->redirect;
    a->redirect_status = (overrides->redirect_set == 0) ? base->redirect_status : overrides->redirect_status;
    a->redirect_set = overrides->redirect_set || base->redirect_set;
    a->allow_relative = (overrides->allow_relative != ALIAS_FLAG_DEFAULT)
                                  ? overrides->allow_relative 
                                  : base->allow_relative;
    return a;
}

/* need prototype for overlap check */
static int alias_matches(const char *uri, const char *alias_fakename);

static const char *add_alias_internal(cmd_parms *cmd, void *dummy,
                                      const char *fake, const char *real,
                                      int use_regex)
{
    server_rec *s = cmd->server;
    alias_server_conf *conf = ap_get_module_config(s->module_config,
                                                   &alias_module);
    alias_entry *new = apr_array_push(conf->aliases);
    alias_entry *entries = (alias_entry *)conf->aliases->elts;
    int i;

    /* XXX: real can NOT be relative to DocumentRoot here... compat bug. */

    const char *err = ap_check_cmd_context(cmd, NOT_IN_DIR_CONTEXT);

    if (err != NULL) {
        return err;
    }

    if (use_regex) {
        new->regexp = ap_pregcomp(cmd->pool, fake, AP_REG_EXTENDED);
        if (new->regexp == NULL)
            return "Regular expression could not be compiled.";
        new->real = real;
    }
    else {
        /* XXX This may be optimized, but we must know that new->real
         * exists.  If so, we can dir merge later, trusing new->real
         * and just canonicalizing the remainder.  Not till I finish
         * cleaning out the old ap_canonical stuff first.
         */
        new->real = real;
    }
    new->fake = fake;
    new->handler = cmd->info;

    /* check for overlapping (Script)Alias directives
     * and throw a warning if found one
     */
    if (!use_regex) {
        for (i = 0; i < conf->aliases->nelts - 1; ++i) {
            alias_entry *alias = &entries[i];

            if (  (!alias->regexp &&  alias_matches(fake, alias->fake) > 0)
                || (alias->regexp && !ap_regexec(alias->regexp, fake, 0, NULL, 0))) {
                ap_log_error(APLOG_MARK, APLOG_WARNING, 0, cmd->server, APLOGNO(00671)
                             "The %s directive in %s at line %d will probably "
                             "never match because it overlaps an earlier "
                             "%sAlias%s.",
                             cmd->cmd->name, cmd->directive->filename,
                             cmd->directive->line_num,
                             alias->handler ? "Script" : "",
                             alias->regexp ? "Match" : "");

                break; /* one warning per alias should be sufficient */
            }
        }
    }

    return NULL;
}

static const char *add_alias(cmd_parms *cmd, void *dummy, const char *fake,
        const char *real)
{
    if (real) {

        return add_alias_internal(cmd, dummy, fake, real, 0);

    }
    else {
        alias_dir_conf *dirconf = (alias_dir_conf *) dummy;

        const char *err = ap_check_cmd_context(cmd, NOT_IN_DIRECTORY|NOT_IN_FILES);

        if (err != NULL) {
            return err;
        }

        if (!cmd->path) {
            return "Alias must have two arguments when used globally";
        }

        dirconf->alias =
                ap_expr_parse_cmd(cmd, fake, AP_EXPR_FLAG_STRING_RESULT,
                        &err, NULL);
        if (err) {
            return apr_pstrcat(cmd->temp_pool,
                    "Cannot parse alias expression '", fake, "': ", err,
                    NULL);
        }

        dirconf->handler = cmd->info;
        dirconf->alias_set = 1;

        return NULL;

    }
}

static const char *add_alias_regex(cmd_parms *cmd, void *dummy,
                                   const char *fake, const char *real)
{
    return add_alias_internal(cmd, dummy, fake, real, 1);
}

static const char *add_redirect_internal(cmd_parms *cmd,
                                         alias_dir_conf *dirconf,
                                         const char *arg1, const char *arg2,
                                         const char *arg3, int use_regex)
{
    alias_entry *new;
    server_rec *s = cmd->server;
    alias_server_conf *serverconf = ap_get_module_config(s->module_config,
                                                         &alias_module);
    int status = (int) (long) cmd->info;
    int grokarg1 = 1;
    ap_regex_t *regex = NULL;
    const char *fake = arg2;
    const char *url = arg3;

    /*
     * Logic flow:
     *   Go ahead and try to grok the 1st arg, in case it is a
     *   Redirect status. Now if we have 3 args, we expect that
     *   we were able to understand that 1st argument (it's something
     *   we expected, so if not, then we bail
     */
    if (!strcasecmp(arg1, "permanent"))
        status = HTTP_MOVED_PERMANENTLY;
    else if (!strcasecmp(arg1, "temp"))
        status = HTTP_MOVED_TEMPORARILY;
    else if (!strcasecmp(arg1, "seeother"))
        status = HTTP_SEE_OTHER;
    else if (!strcasecmp(arg1, "gone")) {
        status = HTTP_GONE;
        grokarg1 = -1;
    }
    else if (apr_isdigit(*arg1)) {
        status = atoi(arg1);
        if (!ap_is_HTTP_REDIRECT(status)) {
            grokarg1 = -1;
        }
    }
    else {
        grokarg1 = 0;
    }

    if (arg3 && !grokarg1)
        return "Redirect: invalid first argument (of three)";

    /*
     * if we have the 2nd arg and we understand the 1st one as a redirect
     * status (3xx, but not things like 404 /robots.txt), or if we have the
     * 1st arg but don't understand it, we use the expression syntax assuming
     * a path from the location.
     *
     * if we understand the first arg but have no second arg, we are dealing
     * with a status like "GONE" or a non-redirect status (e.g. 404, 503).
     */
    if (!cmd->path) {
        /* <Location> context only for now */
        ;
    }
    else if ((grokarg1 > 0 && arg2 && !arg3) || (!grokarg1 && !arg2)) {
        const char *expr_err = NULL;

        url = grokarg1 ? arg2 : arg1;
        dirconf->redirect =
                ap_expr_parse_cmd(cmd, url, AP_EXPR_FLAG_STRING_RESULT,
                        &expr_err, NULL);
        if (expr_err) {
            return apr_pstrcat(cmd->temp_pool,
                    "Cannot parse redirect expression '", url, "': ", expr_err,
                    NULL);
        }

        dirconf->redirect_status = status;
        dirconf->redirect_set = 1;

        return NULL;

    }
    else if (grokarg1 < 0 && !arg2) {

        dirconf->redirect_status = status;
        dirconf->redirect_set = 1;

        return NULL;

    }

    /*
     * if we don't have the 3rd arg and we didn't understand the 1st
     * one, then assume URL-path URL. This also handles case, eg, GONE
     * we even though we don't have a 3rd arg, we did understand the 1st
     * one, so we don't want to re-arrange
     */
    if (!arg3 && !grokarg1) {
        fake = arg1;
        url = arg2;
    }

    if (use_regex) {
        regex = ap_pregcomp(cmd->pool, fake, AP_REG_EXTENDED);
        if (regex == NULL)
            return "Regular expression could not be compiled.";
    }

    if (ap_is_HTTP_REDIRECT(status)) {
        if (!url)
            return "URL to redirect to is missing";
        /* PR#35314: we can allow path components here;
         * they get correctly resolved to full URLs.
         */
        if (!use_regex && !ap_is_url(url) && (url[0] != '/'))
            return "Redirect to non-URL";
    }
    else {
        if (url)
            return "Redirect URL not valid for this status";
    }

    if (cmd->path)
        new = apr_array_push(dirconf->redirects);
    else
        new = apr_array_push(serverconf->redirects);

    new->fake = fake;
    new->real = url;
    new->regexp = regex;
    new->redir_status = status;
    return NULL;
}

static const char *add_redirect(cmd_parms *cmd, void *dirconf,
                                const char *arg1, const char *arg2,
                                const char *arg3)
{
    return add_redirect_internal(cmd, dirconf, arg1, arg2, arg3, 0);
}

static const char *add_redirect2(cmd_parms *cmd, void *dirconf,
                                 const char *arg1, const char *arg2)
{
    return add_redirect_internal(cmd, dirconf, arg1, arg2, NULL, 0);
}

static const char *add_redirect_regex(cmd_parms *cmd, void *dirconf,
                                      const char *arg1, const char *arg2,
                                      const char *arg3)
{
    return add_redirect_internal(cmd, dirconf, arg1, arg2, arg3, 1);
}

static int alias_matches(const char *uri, const char *alias_fakename)
{
    const char *aliasp = alias_fakename, *urip = uri;

    while (*aliasp) {
        if (*aliasp == '/') {
            /* any number of '/' in the alias matches any number in
             * the supplied URI, but there must be at least one...
             */
            if (*urip != '/')
                return 0;

            do {
                ++aliasp;
            } while (*aliasp == '/');
            do {
                ++urip;
            } while (*urip == '/');
        }
        else {
            /* Other characters are compared literally */
            if (*urip++ != *aliasp++)
                return 0;
        }
    }

    /* Check last alias path component matched all the way */

    if (aliasp[-1] != '/' && *urip != '\0' && *urip != '/')
        return 0;

    /* Return number of characters from URI which matched (may be
     * greater than length of alias, since we may have matched
     * doubled slashes)
     */

    return urip - uri;
}

static char *try_alias(request_rec *r)
{
    alias_dir_conf *dirconf =
            (alias_dir_conf *) ap_get_module_config(r->per_dir_config, &alias_module);

    if (dirconf->alias) {
        const char *err = NULL;

        char *found = apr_pstrdup(r->pool,
                ap_expr_str_exec(r, dirconf->alias, &err));
        if (err) {
            ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(02825)
                          "Can't evaluate alias expression: %s", err);
            return PREGSUB_ERROR;
        }

        if (dirconf->handler) { /* Set handler, and leave a note for mod_cgi */
            r->handler = dirconf->handler;
            apr_table_setn(r->notes, "alias-forced-type", r->handler);
        }
        /* XXX This is as SLOW as can be, next step, we optimize
         * and merge to whatever part of the found path was already
         * canonicalized.  After I finish eliminating os canonical.
         * Better fail test for ap_server_root_relative needed here.
         */
        found = ap_server_root_relative(r->pool, found);
        return found;

    }

    return NULL;
}

static char *try_redirect(request_rec *r, int *status)
{
    alias_dir_conf *dirconf =
            (alias_dir_conf *) ap_get_module_config(r->per_dir_config, &alias_module);

    if (dirconf->redirect_set) {
        apr_uri_t uri;
        const char *err = NULL;
        char *found = "";

        if (dirconf->redirect) {

            found = apr_pstrdup(r->pool,
                    ap_expr_str_exec(r, dirconf->redirect, &err));
            if (err) {
                ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(02826)
                              "Can't evaluate redirect expression: %s", err);
                return PREGSUB_ERROR;
            }

            apr_uri_parse(r->pool, found, &uri);
            /* Do not escape the query string or fragment. */
            found = apr_uri_unparse(r->pool, &uri, APR_URI_UNP_OMITQUERY);
            found = ap_escape_uri(r->pool, found);
            if (uri.query) {
                found = apr_pstrcat(r->pool, found, "?", uri.query, NULL);
            }
            if (uri.fragment) {
                found = apr_pstrcat(r->pool, found, "#", uri.fragment, NULL);
            }

        }

        *status = dirconf->redirect_status;
        return found;

    }

    return NULL;
}

static char *try_alias_list(request_rec *r, apr_array_header_t *aliases,
                            int is_redir, int *status)
{
    alias_entry *entries = (alias_entry *) aliases->elts;
    ap_regmatch_t regm[AP_MAX_REG_MATCH];
    char *found = NULL;
    int i;

    for (i = 0; i < aliases->nelts; ++i) {
        alias_entry *alias = &entries[i];
        int l;

        if (alias->regexp) {
            if (!ap_regexec(alias->regexp, r->uri, AP_MAX_REG_MATCH, regm, 0)) {
                if (alias->real) {
                    found = ap_pregsub(r->pool, alias->real, r->uri,
                                       AP_MAX_REG_MATCH, regm);
                    if (found) {
                       if (is_redir) {
                            apr_uri_t uri;
                            apr_uri_parse(r->pool, found, &uri);
                            /* Do not escape the query string or fragment. */
                            found = apr_uri_unparse(r->pool, &uri,
                                                    APR_URI_UNP_OMITQUERY);
                            found = ap_escape_uri(r->pool, found);
                            if (uri.query) {
                                found = apr_pstrcat(r->pool, found, "?",
                                                    uri.query, NULL);
                            }
                            if (uri.fragment) {
                                found = apr_pstrcat(r->pool, found, "#",
                                                    uri.fragment, NULL);
                            }
                       }
                    }
                    else {
                        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00672)
                                      "Regex substitution in '%s' failed. "
                                      "Replacement too long?", alias->real);
                        return PREGSUB_ERROR;
                    }
                }
                else {
                    /* need something non-null */
                    found = "";
                }
            }
        }
        else {
            l = alias_matches(r->uri, alias->fake);

            if (l > 0) {
                ap_set_context_info(r, alias->fake, alias->real);
                if (is_redir) {
                    char *escurl;
                    escurl = ap_os_escape_path(r->pool, r->uri + l, 1);

                    found = apr_pstrcat(r->pool, alias->real, escurl, NULL);
                }
                else
                    found = apr_pstrcat(r->pool, alias->real, r->uri + l, NULL);
            }
        }

        if (found) {
            if (alias->handler) {    /* Set handler, and leave a note for mod_cgi */
                r->handler = alias->handler;
                apr_table_setn(r->notes, "alias-forced-type", r->handler);
            }
            /* XXX This is as SLOW as can be, next step, we optimize
             * and merge to whatever part of the found path was already
             * canonicalized.  After I finish eliminating os canonical.
             * Better fail test for ap_server_root_relative needed here.
             */
            if (!is_redir) {
                found = ap_server_root_relative(r->pool, found);
            }
            if (found) {
                *status = alias->redir_status;
            }
            return found;
        }

    }

    return NULL;
}

static int translate_alias_redir(request_rec *r)
{
    ap_conf_vector_t *sconf = r->server->module_config;
    alias_server_conf *serverconf = ap_get_module_config(sconf, &alias_module);
    char *ret;
    int status;

    if (r->uri[0] != '/' && r->uri[0] != '\0') {
        return DECLINED;
    }

    if ((ret = try_redirect(r, &status)) != NULL
            || (ret = try_alias_list(r, serverconf->redirects, 1, &status))
                    != NULL) {
        if (ret == PREGSUB_ERROR)
            return HTTP_INTERNAL_SERVER_ERROR;
        if (ap_is_HTTP_REDIRECT(status)) {
            alias_dir_conf *dirconf = (alias_dir_conf *) 
                ap_get_module_config(r->per_dir_config, &alias_module);
            if (dirconf->allow_relative != ALIAS_FLAG_ON || ret[0] != '/') {
                if (ret[0] == '/') {
                    char *orig_target = ret;

                    ret = ap_construct_url(r->pool, ret, r);
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(00673)
                                  "incomplete redirection target of '%s' for "
                                  "URI '%s' modified to '%s'",
                                  orig_target, r->uri, ret);
                }
                if (!ap_is_url(ret)) {
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00674)
                                  "cannot redirect '%s' to '%s'; "
                                  "target is not a valid absoluteURI or abs_path",
                                  r->uri, ret);
                    return HTTP_INTERNAL_SERVER_ERROR;
                }
            }
            /* append requested query only, if the config didn't
             * supply its own.
             */
            if (r->args && !ap_strchr(ret, '?')) {
                ret = apr_pstrcat(r->pool, ret, "?", r->args, NULL);
            }
            apr_table_setn(r->headers_out, "Location", ret);
        }
        return status;
    }

    if ((ret = try_alias(r)) != NULL
            || (ret = try_alias_list(r, serverconf->aliases, 0, &status))
                    != NULL) {
        r->filename = ret;
        return OK;
    }

    return DECLINED;
}

static int fixup_redir(request_rec *r)
{
    void *dconf = r->per_dir_config;
    alias_dir_conf *dirconf =
    (alias_dir_conf *) ap_get_module_config(dconf, &alias_module);
    char *ret;
    int status;

    /* It may have changed since last time, so try again */

    if ((ret = try_redirect(r, &status)) != NULL
            || (ret = try_alias_list(r, dirconf->redirects, 1, &status))
                    != NULL) {
        if (ret == PREGSUB_ERROR)
            return HTTP_INTERNAL_SERVER_ERROR;
        if (ap_is_HTTP_REDIRECT(status)) {
            if (dirconf->allow_relative != ALIAS_FLAG_ON || ret[0] != '/') {
                if (ret[0] == '/') {
                    char *orig_target = ret;

                    ret = ap_construct_url(r->pool, ret, r);
                    ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r, APLOGNO(00675)
                                  "incomplete redirection target of '%s' for "
                                  "URI '%s' modified to '%s'",
                                  orig_target, r->uri, ret);
                }
                if (!ap_is_url(ret)) {
                    ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(00676)
                                  "cannot redirect '%s' to '%s'; "
                                  "target is not a valid absoluteURI or abs_path",
                                  r->uri, ret);
                    return HTTP_INTERNAL_SERVER_ERROR;
                }
            }
            /* append requested query only, if the config didn't
             * supply its own.
             */
            if (r->args && !ap_strchr(ret, '?')) {
                ret = apr_pstrcat(r->pool, ret, "?", r->args, NULL);
            }
            apr_table_setn(r->headers_out, "Location", ret);
        }
        return status;
    }

    return DECLINED;
}

static const command_rec alias_cmds[] =
{
    AP_INIT_TAKE12("Alias", add_alias, NULL, RSRC_CONF | ACCESS_CONF,
                  "a fakename and a realname, or a realname in a Location"),
    AP_INIT_TAKE12("ScriptAlias", add_alias, "cgi-script", RSRC_CONF | ACCESS_CONF,
                  "a fakename and a realname, or a realname in a Location"),
    AP_INIT_TAKE123("Redirect", add_redirect, (void *) HTTP_MOVED_TEMPORARILY,
                   OR_FILEINFO,
                   "an optional status, then document to be redirected and "
                   "destination URL"),
    AP_INIT_TAKE2("AliasMatch", add_alias_regex, NULL, RSRC_CONF,
                  "a regular expression and a filename"),
    AP_INIT_TAKE2("ScriptAliasMatch", add_alias_regex, "cgi-script", RSRC_CONF,
                  "a regular expression and a filename"),
    AP_INIT_TAKE23("RedirectMatch", add_redirect_regex,
                   (void *) HTTP_MOVED_TEMPORARILY, OR_FILEINFO,
                   "an optional status, then a regular expression and "
                   "destination URL"),
    AP_INIT_TAKE2("RedirectTemp", add_redirect2,
                  (void *) HTTP_MOVED_TEMPORARILY, OR_FILEINFO,
                  "a document to be redirected, then the destination URL"),
    AP_INIT_TAKE2("RedirectPermanent", add_redirect2,
                  (void *) HTTP_MOVED_PERMANENTLY, OR_FILEINFO,
                  "a document to be redirected, then the destination URL"),
    AP_INIT_FLAG("RedirectRelative", ap_set_flag_slot,
                  (void*)APR_OFFSETOF(alias_dir_conf, allow_relative), OR_FILEINFO,
                  "Set to ON to allow relative redirect targets to be issued as-is"),

    {NULL}
};


static void register_hooks(apr_pool_t *p)
{
    static const char * const aszSucc[]={ "mod_userdir.c",
                                          "mod_vhost_alias.c",NULL };

    ap_hook_translate_name(translate_alias_redir,NULL,aszSucc,APR_HOOK_MIDDLE);
    ap_hook_fixups(fixup_redir,NULL,NULL,APR_HOOK_MIDDLE);
}

AP_DECLARE_MODULE(alias) =
{
    STANDARD20_MODULE_STUFF,
    create_alias_dir_config,       /* dir config creater */
    merge_alias_dir_config,        /* dir merger --- default is to override */
    create_alias_config,           /* server config */
    merge_alias_config,            /* merge server configs */
    alias_cmds,                    /* command apr_table_t */
    register_hooks                 /* register hooks */
};