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/*
 * mod_cern_meta.c
 * version 0.1.0
 * status beta
 * 
 * Andrew Wilson <Andrew.Wilson@cm.cf.ac.uk> 25.Jan.96
 *
 * *** IMPORTANT ***
 * This version of mod_cern_meta.c controls Meta File behaviour on a
 * per-directory basis.  Previous versions of the module defined behaviour
 * on a per-server basis.  The upshot is that you'll need to revisit your 
 * configuration files in order to make use of the new module.
 * ***
 *
 * Emulate the CERN HTTPD Meta file semantics.  Meta files are HTTP
 * headers that can be output in addition to the normal range of
 * headers for each file accessed.  They appear rather like the Apache
 * .asis files, and are able to provide a crude way of influencing
 * the Expires: header, as well as providing other curiosities.
 * There are many ways to manage meta information, this one was
 * chosen because there is already a large number of CERN users
 * who can exploit this module.  It should be noted that there are probably
 * more sensitive ways of managing the Expires: header specifically.
 *
 * The module obeys the following directives, which can appear 
 * in the server's .conf files and in .htaccess files.
 *
 *  MetaFiles <on|off> 
 *
 *    turns on|off meta file processing for any directory.  
 *    Default value is off
 *
 *        # turn on MetaFiles in this directory
 *        MetaFiles on
 *
 *  MetaDir <directory name>
 *      
 *    specifies the name of the directory in which Apache can find
 *    meta information files.  The directory is usually a 'hidden'
 *    subdirectory of the directory that contains the file being
 *    accessed.  eg:
 *
 *        # .meta files are in the *same* directory as the 
 *        # file being accessed
 *        MetaDir .
 *
 *    the default is to look in a '.web' subdirectory. This is the
 *    same as for CERN 3.+ webservers and behaviour is the same as 
 *    for the directive:
 *
 *        MetaDir .web
 *
 *  MetaSuffix <meta file suffix>
 *
 *    specifies the file name suffix for the file containing the
 *    meta information.  eg:
 *
 *       # our meta files are suffixed with '.cern_meta'
 *       MetaSuffix .cern_meta
 *
 *    the default is to look for files with the suffix '.meta'.  This
 *    behaviour is the same as for the directive:
 *
 *       MetaSuffix .meta
 *
 * When accessing the file
 *
 *   DOCUMENT_ROOT/somedir/index.html
 *
 * this module will look for the file
 *
 *   DOCUMENT_ROOT/somedir/.web/index.html.meta
 *
 * and will use its contents to generate additional MIME header 
 * information.
 *
 * For more information on the CERN Meta file semantics see:
 *
 *   http://www.w3.org/hypertext/WWW/Daemon/User/Config/General.html#MetaDir
 *
 * Change-log:
 * 29.Jan.96 pfopen/pfclose instead of fopen/fclose
 *           DECLINE when real file not found, we may be checking each
 *           of the index.html/index.shtml/index.htm variants and don't
 *           need to report missing ones as spurious errors. 
 * 31.Jan.96 log_error reports about a malformed .meta file, rather
 *           than a script error.
 * 20.Jun.96 MetaFiles <on|off> default off, added, so that module
 *           can be configured per-directory.  Prior to this the module
 *           was running for each request anywhere on the server, naughty..
 * 29.Jun.96 All directives made per-directory.
 */
#include "httpd.h"
#include "http_config.h"
#ifndef NETWARE
#include <sys/types.h>
#endif
#include <sys/stat.h>
#include "util_script.h"
#include "http_log.h"
#include "http_request.h"
#define DIR_CMD_PERMS OR_INDEXES
#define DEFAULT_METADIR         ".web"
#define DEFAULT_METASUFFIX      ".meta"
#define DEFAULT_METAFILES       0
module MODULE_VAR_EXPORT cern_meta_module;
typedef struct {
    char *metadir;
    char *metasuffix;
    int metafiles;
} cern_meta_dir_config;
static void *create_cern_meta_dir_config(pool *p, char *dummy)
{
    cern_meta_dir_config *new =
    (cern_meta_dir_config *) ap_palloc(p, sizeof(cern_meta_dir_config));
    new->metadir = NULL;
    new->metasuffix = NULL;
    new->metafiles = DEFAULT_METAFILES;
    return new;
}
static void *merge_cern_meta_dir_configs(pool *p, void *basev, void *addv)
{
    cern_meta_dir_config *base = (cern_meta_dir_config *) basev;
    cern_meta_dir_config *add = (cern_meta_dir_config *) addv;
    cern_meta_dir_config *new =
    (cern_meta_dir_config *) ap_palloc(p, sizeof(cern_meta_dir_config));
    new->metadir = add->metadir ? add->metadir : base->metadir;
    new->metasuffix = add->metasuffix ? add->metasuffix : base->metasuffix;
    new->metafiles = add->metafiles;
    return new;
}
static const char *set_metadir(cmd_parms *parms, cern_meta_dir_config * dconf, char *arg)
{
    dconf->metadir = arg;
    return NULL;
}
static const char *set_metasuffix(cmd_parms *parms, cern_meta_dir_config * dconf, char *arg)
{
    dconf->metasuffix = arg;
    return NULL;
}
static const char *set_metafiles(cmd_parms *parms, cern_meta_dir_config * dconf, int arg)
{
    dconf->metafiles = arg;
    return NULL;
}
static const command_rec cern_meta_cmds[] =
{
    {"MetaFiles", set_metafiles, NULL, DIR_CMD_PERMS, FLAG,
    "Limited to 'on' or 'off'"},
    {"MetaDir", set_metadir, NULL, DIR_CMD_PERMS, TAKE1,
     "the name of the directory containing meta files"},
    {"MetaSuffix", set_metasuffix, NULL, DIR_CMD_PERMS, TAKE1,
     "the filename suffix for meta files"},
    {NULL}
};
/* XXX: this is very similar to ap_scan_script_header_err_core...
 * are the differences deliberate, or just a result of bit rot?
 */
static int scan_meta_file(request_rec *r, FILE *f)
{
    char w[MAX_STRING_LEN];
    char *l;
    int p;
    table *tmp_headers;
    tmp_headers = ap_make_table(r->pool, 5);
    while (fgets(w, MAX_STRING_LEN - 1, f) != NULL) {
        /* Delete terminal (CR?)LF */
        p = strlen(w);
        if (p > 0 && w[p - 1] == '\n') {
            if (p > 1 && w[p - 2] == '\015')
                w[p - 2] = '\0';
            else
                w[p - 1] = '\0';
        }
        if (w[0] == '\0') {
            return OK;
        }
        /* if we see a bogus header don't ignore it. Shout and scream */
        if (!(l = strchr(w, ':'))) {
            ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                        "malformed header in meta file: %s", r->filename);
            return SERVER_ERROR;
        }
        *l++ = '\0';
        while (*l && ap_isspace(*l))
            ++l;
        if (!strcasecmp(w, "Content-type")) {
            char *tmp;
            /* Nuke trailing whitespace */
            char *endp = l + strlen(l) - 1;
            while (endp > l && ap_isspace(*endp))
                *endp-- = '\0';
            tmp = ap_pstrdup(r->pool, l);
            ap_content_type_tolower(tmp);
            r->content_type = tmp;
        }
        else if (!strcasecmp(w, "Status")) {
            sscanf(l, "%d", &r->status);
            r->status_line = ap_pstrdup(r->pool, l);
        }
        else {
            ap_table_set(tmp_headers, w, l);
        }
    }
    ap_overlap_tables(r->headers_out, tmp_headers, AP_OVERLAP_TABLES_SET);
    return OK;
}
static int add_cern_meta_data(request_rec *r)
{
    char *metafilename;
    char *last_slash;
    char *real_file;
    char *scrap_book;
    FILE *f;
    cern_meta_dir_config *dconf;
    int rv;
    request_rec *rr;
    dconf = ap_get_module_config(r->per_dir_config, &cern_meta_module);
    if (!dconf->metafiles) {
        return DECLINED;
    };
    /* if ./.web/$1.meta exists then output 'asis' */
    if (r->finfo.st_mode == 0) {
        return DECLINED;
    };
    /* is this a directory? */
    if (S_ISDIR(r->finfo.st_mode) || r->uri[strlen(r->uri) - 1] == '/') {
        return DECLINED;
    };
    /* what directory is this file in? */
    scrap_book = ap_pstrdup(r->pool, r->filename);
    /* skip leading slash, recovered in later processing */
    scrap_book++;
    last_slash = strrchr(scrap_book, '/');
    if (last_slash != NULL) {
        /* skip over last slash */
        real_file = last_slash;
        real_file++;
        *last_slash = '\0';
    }
    else {
        /* no last slash, buh?! */
        ap_log_rerror(APLOG_MARK, APLOG_NOERRNO|APLOG_ERR, r,
                    "internal error in mod_cern_meta: %s", r->filename);
        /* should really barf, but hey, let's be friends... */
        return DECLINED;
    };
    metafilename = ap_pstrcat(r->pool, "/", scrap_book, "/",
                           dconf->metadir ? dconf->metadir : DEFAULT_METADIR,
                           "/", real_file,
                 dconf->metasuffix ? dconf->metasuffix : DEFAULT_METASUFFIX,
                           NULL);
    /* XXX: it sucks to require this subrequest to complete, because this
     * means people must leave their meta files accessible to the world.
     * A better solution might be a "safe open" feature of pfopen to avoid
     * pipes, symlinks, and crap like that.
     */
    rr = ap_sub_req_lookup_file(metafilename, r);
    if (rr->status != HTTP_OK) {
        ap_destroy_sub_req(rr);
        return DECLINED;
    }
    ap_destroy_sub_req(rr);
    f = ap_pfopen(r->pool, metafilename, "r");
    if (f == NULL) {
        if (errno == ENOENT) {
            return DECLINED;
        }
        ap_log_rerror(APLOG_MARK, APLOG_ERR, r,
              "meta file permissions deny server access: %s", metafilename);
        return FORBIDDEN;
    };
    /* read the headers in */
    rv = scan_meta_file(r, f);
    ap_pfclose(r->pool, f);
    return rv;
}
module MODULE_VAR_EXPORT cern_meta_module =
{
    STANDARD_MODULE_STUFF,
    NULL,                       /* initializer */
    create_cern_meta_dir_config,        /* dir config creater */
    merge_cern_meta_dir_configs,        /* dir merger --- default is to override */
    NULL,                       /* server config */
    NULL,                       /* merge server configs */
    cern_meta_cmds,             /* command table */
    NULL,                       /* handlers */
    NULL,                       /* filename translation */
    NULL,                       /* check_user_id */
    NULL,                       /* check auth */
    NULL,                       /* check access */
    NULL,                       /* type_checker */
    add_cern_meta_data,         /* fixups */
    NULL,                       /* logger */
    NULL,                       /* header parser */
    NULL,                       /* child_init */
    NULL,                       /* child_exit */
    NULL                        /* post read-request */
};