/* 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.

 */

/*

 * mod_expires.c

 * version 0.0.11

 * status beta

 *

 * Andrew Wilson <Andrew.Wilson@cm.cf.ac.uk> 26.Jan.96

 *

 * This module allows you to control the form of the Expires: header

 * that Apache issues for each access.  Directives can appear in

 * configuration files or in .htaccess files so expiry semantics can

 * be defined on a per-directory basis.

 *

 * DIRECTIVE SYNTAX

 *

 * Valid directives are:

 *

 *     ExpiresActive on | off

 *     ExpiresDefault <seconds>

 *     ExpiresByType type/encoding <seconds>

 *

 * Valid values for  are:

 *

 *     'M'      expires header shows file modification date + <seconds>

 *     'A'      expires header shows access time + <seconds>

 *

 *              [I'm not sure which of these is best under different

 *              circumstances, I guess it's for other people to explore.

 *              The effects may be indistinguishable for a number of cases]

 *

 * <seconds> should be an integer value [acceptable to atoi()]

 *

 * There is NO space between the  and <seconds>.

 *

 * For example, a directory which contains information which changes

 * frequently might contain:

 *

 *     # reports generated by cron every hour.  don't let caches

 *     # hold onto stale information

 *     ExpiresDefault M3600

 *

 * Another example, our html pages can change all the time, the gifs

 * tend not to change often:

 *

 *     # pages are hot (1 week), images are cold (1 month)

 *     ExpiresByType text/html A604800

 *     ExpiresByType image/gif A2592000

 *

 * Expires can be turned on for all URLs on the server by placing the

 * following directive in a conf file:

 *

 *     ExpiresActive on

 *

 * ExpiresActive can also appear in .htaccess files, enabling the

 * behaviour to be turned on or off for each chosen directory.

 *

 *     # turn off Expires behaviour in this directory

 *     # and subdirectories

 *     ExpiresActive off

 *

 * Directives defined for a directory are valid in subdirectories

 * unless explicitly overridden by new directives in the subdirectory

 * .htaccess files.

 *

 * ALTERNATIVE DIRECTIVE SYNTAX

 *

 * Directives can also be defined in a more readable syntax of the form:

 *

 *     ExpiresDefault "<base> [plus] {<num> <type>}*"

 *     ExpiresByType type/encoding "<base> [plus] {<num> <type>}*"

 *

 * where <base> is one of:

 *      access

 *      now             equivalent to 'access'

 *      modification

 *

 * where the 'plus' keyword is optional

 *

 * where <num> should be an integer value [acceptable to atoi()]

 *

 * where <type> is one of:

 *      years

 *      months

 *      weeks

 *      days

 *      hours

 *      minutes

 *      seconds

 *

 * For example, any of the following directives can be used to make

 * documents expire 1 month after being accessed, by default:

 *

 *      ExpiresDefault "access plus 1 month"

 *      ExpiresDefault "access plus 4 weeks"

 *      ExpiresDefault "access plus 30 days"

 *

 * The expiry time can be fine-tuned by adding several '<num> <type>'

 * clauses:

 *

 *      ExpiresByType text/html "access plus 1 month 15 days 2 hours"

 *      ExpiresByType image/gif "modification plus 5 hours 3 minutes"

 *

 * ---

 *

 * Change-log:

 * 29.Jan.96    Hardened the add_* functions.  Server will now bail out

 *              if bad directives are given in the conf files.

 * 02.Feb.96    Returns DECLINED if not 'ExpiresActive on', giving other

 *              expires-aware modules a chance to play with the same

 *              directives. [Michael Rutman]

 * 03.Feb.96    Call tzset() before localtime().  Trying to get the module

 *              to work properly in non GMT timezones.

 * 12.Feb.96    Modified directive syntax to allow more readable commands:

 *                ExpiresDefault "now plus 10 days 20 seconds"

 *                ExpiresDefault "access plus 30 days"

 *                ExpiresDefault "modification plus 1 year 10 months 30 days"

 * 13.Feb.96    Fix call to table_get() with NULL 2nd parameter [Rob Hartill]

 * 19.Feb.96    Call gm_timestr_822() to get time formatted correctly, can't

 *              rely on presence of HTTP_TIME_FORMAT in Apache 1.1+.

 * 21.Feb.96    This version (0.0.9) reverses assumptions made in 0.0.8

 *              about star/star handlers.  Reverting to 0.0.7 behaviour.

 * 08.Jun.96    allows ExpiresDefault to be used with responses that use

 *              the DefaultType by not DECLINING, but instead skipping

 *              the table_get check and then looking for an ExpiresDefault.

 *              [Rob Hartill]

 * 04.Nov.96    'const' definitions added.

 *

 * TODO

 * add support for Cache-Control: max-age=20 from the HTTP/1.1

 * proposal (in this case, a ttl of 20 seconds) [ask roy]

 * add per-file expiry and explicit expiry times - duplicates some

 * of the mod_cern_meta.c functionality.  eg:

 *              ExpiresExplicit index.html "modification plus 30 days"

 *

 * BUGS

 * Hi, welcome to the internet.

 */

#include "apr.h"

#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_config.h"

#include "http_log.h"

#include "http_request.h"

#include "http_protocol.h"

typedef struct {

    int active;

    int wildcards;

    char *expiresdefault;

    apr_table_t *expiresbytype;

} expires_dir_config;

/* from mod_dir, why is this alias used?

 */

#define DIR_CMD_PERMS OR_INDEXES

#define ACTIVE_ON       1

#define ACTIVE_OFF      0

#define ACTIVE_DONTCARE 2

module AP_MODULE_DECLARE_DATA expires_module;

static void *create_dir_expires_config(apr_pool_t *p, char *dummy)

{

    expires_dir_config *new =

    (expires_dir_config *) apr_pcalloc(p, sizeof(expires_dir_config));

    new->active = ACTIVE_DONTCARE;

    new->wildcards = 0;

    new->expiresdefault = NULL;

    new->expiresbytype = apr_table_make(p, 4);

    return (void *) new;

}

static const char *set_expiresactive(cmd_parms *cmd, void *in_dir_config, int arg)

{

    expires_dir_config *dir_config = in_dir_config;

    /* if we're here at all it's because someone explicitly

     * set the active flag

     */

    dir_config->active = ACTIVE_ON;

    if (arg == 0) {

        dir_config->active = ACTIVE_OFF;

    }

    return NULL;

}

/* check_code() parse 'code' and return NULL or an error response

 * string.  If we return NULL then real_code contains code converted

 * to the cnnnn format.

 */

static char *check_code(apr_pool_t *p, const char *code, char **real_code)

{

    char *word;

    char base = 'X';

    int modifier = 0;

    int num = 0;

    int factor;

    /* 0.0.4 compatibility?

     */

    if ((code[0] == 'A') || (code[0] == 'M')) {

        *real_code = (char *)code;

        return NULL;

    }

    /* <base> [plus] {<num> <type>}*

     */

    /* <base>

     */

    word = ap_getword_conf(p, &code);

    if (!strncasecmp(word, "now", 1) ||

        !strncasecmp(word, "access", 1)) {

        base = 'A';

    }

    else if (!strncasecmp(word, "modification", 1)) {

        base = 'M';

    }

    else {

        return apr_pstrcat(p, "bad expires code, unrecognised <base> '",

                       word, "'", NULL);

    }

    /* [plus]

     */

    word = ap_getword_conf(p, &code);

    if (!strncasecmp(word, "plus", 1)) {

        word = ap_getword_conf(p, &code);

    }

    /* {<num> <type>}*

     */

    while (word[0]) {

        /* <num>

         */

        if (apr_isdigit(word[0])) {

            num = atoi(word);

        }

        else {

            return apr_pstrcat(p, "bad expires code, numeric value expected <num> '",

                           word, "'", NULL);

        }

        /* <type>

         */

        word = ap_getword_conf(p, &code);

        if (word[0] == '\0') {

            return apr_pstrcat(p, "bad expires code, missing <type>", NULL);

        }

        if (!strncasecmp(word, "years", 1)) {

            factor = 60 * 60 * 24 * 365;

        }

        else if (!strncasecmp(word, "months", 2)) {

            factor = 60 * 60 * 24 * 30;

        }

        else if (!strncasecmp(word, "weeks", 1)) {

            factor = 60 * 60 * 24 * 7;

        }

        else if (!strncasecmp(word, "days", 1)) {

            factor = 60 * 60 * 24;

        }

        else if (!strncasecmp(word, "hours", 1)) {

            factor = 60 * 60;

        }

        else if (!strncasecmp(word, "minutes", 2)) {

            factor = 60;

        }

        else if (!strncasecmp(word, "seconds", 1)) {

            factor = 1;

        }

        else {

            return apr_pstrcat(p, "bad expires code, unrecognised <type>",

                           "'", word, "'", NULL);

        }

        modifier = modifier + factor * num;

        /* next <num>

         */

        word = ap_getword_conf(p, &code);

    }

    *real_code = apr_psprintf(p, "%c%d", base, modifier);

    return NULL;

}

static const char *set_expiresbytype(cmd_parms *cmd, void *in_dir_config,

                                     const char *mime, const char *code)

{

    expires_dir_config *dir_config = in_dir_config;

    char *response, *real_code;

    const char *check;

    check = ap_strrchr_c(mime, '/');

    if (check == NULL) {

        return "Invalid mimetype: should contain a slash";

    }

    if ((strlen(++check) == 1) && (*check == '*')) {

        dir_config->wildcards = 1;

    }

    if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {

        apr_table_setn(dir_config->expiresbytype, mime, real_code);

        return NULL;

    }

    return apr_pstrcat(cmd->pool,

                 "'ExpiresByType ", mime, " ", code, "': ", response, NULL);

}

static const char *set_expiresdefault(cmd_parms *cmd, void *in_dir_config,

                                      const char *code)

{

    expires_dir_config * dir_config = in_dir_config;

    char *response, *real_code;

    if ((response = check_code(cmd->pool, code, &real_code)) == NULL) {

        dir_config->expiresdefault = real_code;

        return NULL;

    }

    return apr_pstrcat(cmd->pool,

                   "'ExpiresDefault ", code, "': ", response, NULL);

}

static const command_rec expires_cmds[] =

{

    AP_INIT_FLAG("ExpiresActive", set_expiresactive, NULL, DIR_CMD_PERMS,

                 "Limited to 'on' or 'off'"),

    AP_INIT_TAKE2("ExpiresByType", set_expiresbytype, NULL, DIR_CMD_PERMS,

                  "a MIME type followed by an expiry date code"),

    AP_INIT_TAKE1("ExpiresDefault", set_expiresdefault, NULL, DIR_CMD_PERMS,

                  "an expiry date code"),

    {NULL}

};

static void *merge_expires_dir_configs(apr_pool_t *p, void *basev, void *addv)

{

    expires_dir_config *new = (expires_dir_config *) apr_pcalloc(p, sizeof(expires_dir_config));

    expires_dir_config *base = (expires_dir_config *) basev;

    expires_dir_config *add = (expires_dir_config *) addv;

    if (add->active == ACTIVE_DONTCARE) {

        new->active = base->active;

    }

    else {

        new->active = add->active;

    }

    if (add->expiresdefault != NULL) {

        new->expiresdefault = add->expiresdefault;

    }

    else {

        new->expiresdefault = base->expiresdefault;

    }

    new->wildcards = add->wildcards;

    new->expiresbytype = apr_table_overlay(p, add->expiresbytype,

                                        base->expiresbytype);

    return new;

}

/*

 * Handle the setting of the expiration response header fields according

 * to our criteria.

 */

static int set_expiration_fields(request_rec *r, const char *code,

                                 apr_table_t *t)

{

    apr_time_t base;

    apr_time_t additional;

    apr_time_t expires;

    int additional_sec;

    char *timestr;

    switch (code[0]) {

    case 'M':

        if (r->finfo.filetype == APR_NOFILE) {

            /* file doesn't exist on disk, so we can't do anything based on

             * modification time.  Note that this does _not_ log an error.

             */

            return DECLINED;

        }

        base = r->finfo.mtime;

        additional_sec = atoi(&code[1]);

        additional = apr_time_from_sec(additional_sec);

        break;

    case 'A':

        /* there's been some discussion and it's possible that

         * 'access time' will be stored in request structure

         */

        base = r->request_time;

        additional_sec = atoi(&code[1]);

        additional = apr_time_from_sec(additional_sec);

        break;

    default:

        /* expecting the add_* routines to be case-hardened this

         * is just a reminder that module is beta

         */

        ap_log_rerror(APLOG_MARK, APLOG_ERR, 0, r, APLOGNO(01500)

                    "internal error: bad expires code: %s", r->filename);

        return HTTP_INTERNAL_SERVER_ERROR;

    }

    expires = base + additional;

    if (expires < r->request_time) {

        expires = r->request_time;

    }

    apr_table_mergen(t, "Cache-Control",

                     apr_psprintf(r->pool, "max-age=%" APR_TIME_T_FMT,

                                  apr_time_sec(expires - r->request_time)));

    timestr = apr_palloc(r->pool, APR_RFC822_DATE_LEN);

    apr_rfc822_date(timestr, expires);

    apr_table_setn(t, "Expires", timestr);

    return OK;

}

/*

 * Output filter to set the Expires response header field

 * according to the content-type of the response -- if it hasn't

 * already been set.

 */

static apr_status_t expires_filter(ap_filter_t *f,

                                   apr_bucket_brigade *b)

{

    request_rec *r;

    expires_dir_config *conf;

    const char *expiry;

    apr_table_t *t;

    /* Don't add Expires headers to errors */

    if (ap_is_HTTP_ERROR(f->r->status)) {

        ap_remove_output_filter(f);

        return ap_pass_brigade(f->next, b);

    }

    r = f->r;

    conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,

                                                       &expires_module);

    /*

     * Check to see which output header table we should use;

     * mod_cgi loads script fields into r->err_headers_out,

     * for instance.

     */

    expiry = apr_table_get(r->err_headers_out, "Expires");

    if (expiry != NULL) {

        t = r->err_headers_out;

    }

    else {

        expiry = apr_table_get(r->headers_out, "Expires");

        t = r->headers_out;

    }

    if (expiry == NULL) {

        /*

         * No expiration has been set, so we can apply any managed by

         * this module.  First, check to see if there is an applicable

         * ExpiresByType directive.

         */

        expiry = apr_table_get(conf->expiresbytype,

                               ap_field_noparam(r->pool, r->content_type));

        if (expiry == NULL) {

            int usedefault = 1;

            /*

             * See if we have a wildcard entry for the major type.

             */

            if (conf->wildcards) {

                char *checkmime;

                char *spos;

                checkmime = apr_pstrdup(r->pool, r->content_type);

                spos = checkmime ? ap_strchr(checkmime, '/') : NULL;

                if (spos != NULL) {

                    /*

                     * Without a '/' character, nothing we have will match.

                     * However, we have one.

                     */

                    if (strlen(++spos) > 0) {

                        *spos++ = '*';

                        *spos = '\0';

                    }

                    else {

                        checkmime = apr_pstrcat(r->pool, checkmime, "*", NULL);

                    }

                    expiry = apr_table_get(conf->expiresbytype, checkmime);

                    usedefault = (expiry == NULL);

                }

            }

            if (usedefault) {

                /*

                 * Use the ExpiresDefault directive

                 */

                expiry = conf->expiresdefault;

            }

        }

        if (expiry != NULL) {

            set_expiration_fields(r, expiry, t);

        }

    }

    ap_remove_output_filter(f);

    return ap_pass_brigade(f->next, b);

}

static void expires_insert_filter(request_rec *r)

{

    expires_dir_config *conf;

    /* Don't add Expires headers to errors */

    if (ap_is_HTTP_ERROR(r->status)) {

        return;

    }

    /* Say no to subrequests */

    if (r->main != NULL) {

        return;

    }

    conf = (expires_dir_config *) ap_get_module_config(r->per_dir_config,

                                                       &expires_module);

    /* Check to see if the filter is enabled and if there are any applicable

     * config directives for this directory scope

     */

    if (conf->active != ACTIVE_ON ||

        (apr_is_empty_table(conf->expiresbytype) && !conf->expiresdefault)) {

        return;

    }

    ap_add_output_filter("MOD_EXPIRES", NULL, r, r->connection);

}

static void register_hooks(apr_pool_t *p)

{

    /* mod_expires needs to run *before* the cache save filter which is

     * AP_FTYPE_CONTENT_SET-1.  Otherwise, our expires won't be honored.

     */

    ap_register_output_filter("MOD_EXPIRES", expires_filter, NULL,

                              AP_FTYPE_CONTENT_SET-2);

    ap_hook_insert_error_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);

    ap_hook_insert_filter(expires_insert_filter, NULL, NULL, APR_HOOK_MIDDLE);

}

AP_DECLARE_MODULE(expires) =

{

    STANDARD20_MODULE_STUFF,

    create_dir_expires_config,  /* dir config creater */

    merge_expires_dir_configs,  /* dir merger --- default is to override */

    NULL,                       /* server config */

    NULL,                       /* merge server configs */

    expires_cmds,               /* command apr_table_t */

    register_hooks              /* register hooks */

};