mod_usertrack.c

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/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/* User Tracking Module (Was mod_cookies.c)
 *
 * *** IMPORTANT NOTE: This module is not designed to generate 
 * *** cryptographically secure cookies.  This means you should not 
 * *** use cookies generated by this module for authentication purposes
 *
 * This Apache module is designed to track users paths through a site.
 * It uses the client-side state ("Cookie") protocol developed by Netscape.
 * It is known to work on most browsers.
 *
 * Each time a page is requested we look to see if the browser is sending
 * us a Cookie: header that we previously generated.
 *
 * If we don't find one then the user hasn't been to this site since
 * starting their browser or their browser doesn't support cookies.  So
 * we generate a unique Cookie for the transaction and send it back to
 * the browser (via a "Set-Cookie" header)
 * Future requests from the same browser should keep the same Cookie line.
 *
 * By matching up all the requests with the same cookie you can
 * work out exactly what path a user took through your site.  To log
 * the cookie use the " %{Cookie}n " directive in a custom access log;
 *
 * Example 1 : If you currently use the standard Log file format (CLF)
 * and use the command "TransferLog somefilename", add the line
 *       LogFormat "%h %l %u %t \"%r\" %s %b %{Cookie}n"
 * to your config file.
 *
 * Example 2 : If you used to use the old "CookieLog" directive, you
 * can emulate it by adding the following command to your config file
 *       CustomLog filename "%{Cookie}n \"%r\" %t"
 *
 * Mark Cox, [e-mail], 6 July 95
 *
 * This file replaces mod_cookies.c
 */

#include "httpd.h"
#include "http_config.h"
#include "http_core.h"
#if !defined(WIN32) && !defined(MPE) && !defined(TPF41)
#include <sys/time.h>
#endif

module MODULE_VAR_EXPORT usertrack_module;

typedef struct {
    int always;
    time_t expires;
} cookie_log_state;

typedef enum {
    CT_UNSET,
    CT_NETSCAPE,
    CT_COOKIE,
    CT_COOKIE2
} cookie_type_e;

typedef enum {
    CF_NORMAL,
    CF_COMPACT
} cookie_format_e;

typedef struct {
    int enabled;
    cookie_type_e style;
    cookie_format_e format;
    char *cookie_name;
    char *cookie_domain;
    char *prefix_string;
    char *regexp_string;  /* used to compile regexp; save for debugging */
    regex_t *regexp;  /* used to find usertrack cookie in cookie header */
} cookie_dir_rec;

/* Define this to allow post-2000 cookies. Cookies use two-digit dates,
 * so it might be dicey. (Netscape does it correctly, but others may not)
 */
#define MILLENIAL_COOKIES

/* Default name of the cookie
 */
#define COOKIE_NAME "Apache"


/* Make cookie id: Try to make something unique based on 
 * pid, time, and hostid, plus the user-configurable prefix.
 *
 */
static char * make_cookie_id(char * buffer, int bufsize, request_rec *r,
                             cookie_format_e cformat)
{
#if defined(NO_GETTIMEOFDAY) && !defined(NO_TIMES)
    clock_t mpe_times;
    struct tms mpe_tms;
#elif !defined(WIN32)
    struct timeval tv;
#ifdef NETWARE
    time_t tz = 0;
#else
    struct timezone tz = {0, 0};
#endif /* defined(NETWARE) */
#endif

    cookie_dir_rec *dcfg;

    long reqtime = (long) r->request_time;
    long clocktime;

    unsigned long ipaddr = ntohl(r->connection->remote_addr.sin_addr.s_addr);
    const char *rname = ap_get_remote_host(r->connection, r->per_dir_config,
					   REMOTE_NAME);
    dcfg = ap_get_module_config(r->per_dir_config, &usertrack_module);

#if defined(NO_GETTIMEOFDAY) && !defined(NO_TIMES)
/* We lack gettimeofday(), so we must use time() to obtain the epoch
   seconds, and then times() to obtain CPU clock ticks (milliseconds).
   Combine this together to obtain a hopefully unique cookie ID. */

    mpe_times = times(&mpe_tms);
    clocktime = (long) mpe_tms.tms_utime;
    
#elif defined(NETWARE)
    clocktime = (long) clock();

#elif defined(WIN32)
    /*
     * We lack gettimeofday() and we lack times(). So we'll use
     * GetTickCount(), which returns milliseconds since Windows
     * was started. It should be relatively unique.
     */

    clocktime = (long) GetTickCount();

#else
    gettimeofday(&tv, &tz);

    reqtime = (long) tv.tv_sec;
    if (cformat == CF_COMPACT)
	clocktime = (long) (tv.tv_usec % 65535);
    else
	clocktime = (long) (tv.tv_usec / 1000);
#endif

    if (cformat == CF_COMPACT)
	ap_snprintf(buffer, bufsize, "%s%lx%x%lx%lx", 
		    dcfg->prefix_string, ipaddr, (int) getpid(),
                    reqtime, clocktime);
    else
	ap_snprintf(buffer, bufsize, "%s%s.%d%ld%ld", 
		    dcfg->prefix_string, rname, (int) getpid(),
                    reqtime, clocktime);

    return buffer;
}



static void make_cookie(request_rec *r)
{
    cookie_log_state *cls = ap_get_module_config(r->server->module_config,
						 &usertrack_module);

    /* 1024 == hardcoded constant */
    char cookiebuf[1024];
    char *new_cookie;
    cookie_dir_rec *dcfg;

    dcfg = ap_get_module_config(r->per_dir_config, &usertrack_module);

    make_cookie_id(cookiebuf, sizeof(cookiebuf), r, dcfg->format);

    if (cls->expires) {
        struct tm *tms;
        time_t when;

        when = cls->expires;
        if ((dcfg->style == CT_UNSET) || (dcfg->style == CT_NETSCAPE)) {
            when += r->request_time;

#ifndef MILLENIAL_COOKIES
        /*
         * Only two-digit date string, so we can't trust "00" or more.
         * Therefore, we knock it all back to just before midnight on
         * 1/1/2000 (which is 946684799)
         */

        if (when > 946684799)
            when = 946684799;
#endif
        }
        tms = gmtime(&when);

        /* Cookie with date; as strftime '%a, %d-%h-%y %H:%M:%S GMT' */
        new_cookie = ap_psprintf(r->pool, "%s=%s; path=/",
                                 dcfg->cookie_name, cookiebuf);
        if ((dcfg->style == CT_UNSET) || (dcfg->style == CT_NETSCAPE)) {
            new_cookie = ap_psprintf(r->pool, "%s; "
                                     "expires=%s, %.2d-%s-%.2d "
                                     "%.2d:%.2d:%.2d GMT",
                                     new_cookie,
                                     ap_day_snames[tms->tm_wday],
                                     tms->tm_mday,
                                     ap_month_snames[tms->tm_mon],
                                     tms->tm_year % 100,
                                     tms->tm_hour, tms->tm_min, tms->tm_sec);
        }
        else {
            new_cookie = ap_psprintf(r->pool, "%s; max-age=%d",
                                     new_cookie, (int) when);
        }
    }
    else {
	new_cookie = ap_psprintf(r->pool, "%s=%s; path=/",
				 dcfg->cookie_name, cookiebuf);
    }
    if (dcfg->cookie_domain != NULL) {
        new_cookie = ap_psprintf(r->pool, "%s; domain=%s",
                                 new_cookie, dcfg->cookie_domain);
    }
    if (dcfg->style == CT_COOKIE2) {
        new_cookie = ap_pstrcat(r->pool, new_cookie, "; version=1", NULL);
    }

    ap_table_addn(r->headers_out,
                  (dcfg->style == CT_COOKIE2 ? "Set-Cookie2" : "Set-Cookie"),
                  new_cookie);
    ap_table_setn(r->notes, "cookie", ap_pstrdup(r->pool, cookiebuf));   /* log first time */
    return;
}

/*
 * dcfg->regexp is "^cookie_name=([^;]+)|;[ \t]+cookie_name=([^;]+)",
 * which has three subexpressions, $0..$2
 */
#define NUM_SUBS 3

static void set_and_comp_regexp(cookie_dir_rec *dcfg, 
                                pool *p,
                                const char *cookie_name) 
{
    int danger_chars = 0;
    const char *sp = cookie_name;

    /*
     * The goal is to end up with this regexp, 
     * ^cookie_name=([^;]+)|;[\t]+cookie_name=([^;]+) 
     * with cookie_name obviously substituted either
     * with the real cookie name set by the user in httpd.conf,
     * or with the default COOKIE_NAME.
     */

    /* Anyway, we need to escape the cookie_name before pasting it
     * into the regex
     */
    while (*sp) {
        if (!ap_isalnum(*sp)) {
            ++danger_chars;
        }
        ++sp;
    }

    if (danger_chars) {
        char *cp;
        cp = ap_palloc(p, sp - cookie_name + danger_chars + 1); /* 1 == \0 */
        sp = cookie_name;
        cookie_name = cp;
        while (*sp) {
            if (!ap_isalnum(*sp)) {
                *cp++ = '\\';
            }
            *cp++ = *sp++;
        }
        *cp = '\0';
    }

    dcfg->regexp_string = ap_pstrcat(p, "^", cookie_name,
                                     "=([^;]+)|;[ \t]+", cookie_name,
                                     "=([^;]+)", NULL);
    dcfg->regexp = ap_pregcomp(p, dcfg->regexp_string, REG_EXTENDED);
    ap_assert(dcfg->regexp != NULL);