mod_rewrite.c

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**
**  [used for redirect support]
**
*/

static int handler_redirect(request_rec *r)
{
    /* just make sure that we are really meant! */
    if (strncmp(r->filename, "redirect:", 9) != 0) {
        return DECLINED;
    }

    if (is_redirect_limit_exceeded(r)) {
        ap_log_rerror(APLOG_MARK, APLOG_ERR|APLOG_NOERRNO, r,
                      "mod_rewrite: maximum number of internal redirects "
                      "reached. Assuming configuration error. Use "
                      "'RewriteOptions MaxRedirects' to increase the limit "
                      "if neccessary.");
        return HTTP_INTERNAL_SERVER_ERROR;
    }

    /* now do the internal redirect */
    ap_internal_redirect(ap_pstrcat(r->pool, r->filename+9,
                                    r->args ? "?" : NULL, r->args, NULL), r);

    /* and return gracefully */
    return OK;
}

/*
 * check whether redirect limit is reached
 */
static int is_redirect_limit_exceeded(request_rec *r)
{
    request_rec *top = r;
    rewrite_request_conf *reqc;
    rewrite_perdir_conf *dconf;

    /* we store it in the top request */
    while (top->main) {
        top = top->main;
    }
    while (top->prev) {
        top = top->prev;
    }

    /* fetch our config */
    reqc = (rewrite_request_conf *) ap_get_module_config(top->request_config,
                                                         &rewrite_module);

    /* no config there? create one. */
    if (!reqc) {
        rewrite_server_conf *sconf;

        reqc = ap_palloc(top->pool, sizeof(rewrite_request_conf));
        sconf = ap_get_module_config(r->server->module_config, &rewrite_module);

        reqc->redirects = 0;
        reqc->redirect_limit = sconf->redirect_limit
                                 ? sconf->redirect_limit
                                 : REWRITE_REDIRECT_LIMIT;

        /* associate it with this request */
        ap_set_module_config(top->request_config, &rewrite_module, reqc);
    }

    /* allow to change the limit during redirects. */
    dconf = (rewrite_perdir_conf *)ap_get_module_config(r->per_dir_config,
                                                        &rewrite_module);

    /* 0 == unset; take server conf ... */
    if (dconf->redirect_limit) {
        reqc->redirect_limit = dconf->redirect_limit;
    }

    ap_log_rerror(APLOG_MARK, APLOG_DEBUG|APLOG_NOERRNO, r,
                  "mod_rewrite's internal redirect status: %d/%d.",
                  reqc->redirects, reqc->redirect_limit);

    /* and now give the caller a hint */
    return (reqc->redirects++ >= reqc->redirect_limit);
}


/*
** +-------------------------------------------------------+
** |                                                       |
** |                  the rewriting engine
** |                                                       |
** +-------------------------------------------------------+
*/

/*
 *  Apply a complete rule set,
 *  i.e. a list of rewrite rules
 */
static int apply_rewrite_list(request_rec *r, array_header *rewriterules,
                              char *perdir)
{
    rewriterule_entry *entries;
    rewriterule_entry *p;
    int i;
    int changed;
    int rc;
    int s;

    /*
     *  Iterate over all existing rules
     */
    entries = (rewriterule_entry *)rewriterules->elts;
    changed = 0;
    loop:
    for (i = 0; i < rewriterules->nelts; i++) {
        p = &entries[i];

        /*
         *  Ignore this rule on subrequests if we are explicitly
         *  asked to do so or this is a proxy-throughput or a
         *  forced redirect rule.
         */
        if (r->main != NULL &&
            (p->flags & RULEFLAG_IGNOREONSUBREQ ||
             p->flags & RULEFLAG_PROXY          ||
             p->flags & RULEFLAG_FORCEREDIRECT    )) {
            continue;
        }

        /*
         *  Apply the current rule.
         */
        rc = apply_rewrite_rule(r, p, perdir);
        if (rc) {
            /*
             *  Indicate a change if this was not a match-only rule.
             */
            if (rc != 2) {
                changed = ((p->flags & RULEFLAG_NOESCAPE)
                           ? ACTION_NOESCAPE : ACTION_NORMAL);
            }

            /*
             *  Pass-Through Feature (`RewriteRule .. .. [PT]'):
             *  Because the Apache 1.x API is very limited we
             *  need this hack to pass the rewritten URL to other
             *  modules like mod_alias, mod_userdir, etc.
             */
            if (p->flags & RULEFLAG_PASSTHROUGH) {
                rewritelog(r, 2, "forcing '%s' to get passed through "
                           "to next API URI-to-filename handler", r->filename);
                r->filename = ap_pstrcat(r->pool, "passthrough:",
                                         r->filename, NULL);
                changed = ACTION_NORMAL;
                break;
            }

            /*
             *  Rule has the "forbidden" flag set which means that
             *  we stop processing and indicate this to the caller.
             */
            if (p->flags & RULEFLAG_FORBIDDEN) {
                rewritelog(r, 2, "forcing '%s' to be forbidden", r->filename);
                r->filename = ap_pstrcat(r->pool, "forbidden:",
                                         r->filename, NULL);
                changed = ACTION_NORMAL;
                break;
            }

            /*
             *  Rule has the "gone" flag set which means that
             *  we stop processing and indicate this to the caller.
             */
            if (p->flags & RULEFLAG_GONE) {
                rewritelog(r, 2, "forcing '%s' to be gone", r->filename);
                r->filename = ap_pstrcat(r->pool, "gone:", r->filename, NULL);
                changed = ACTION_NORMAL;
                break;
            }

            /*
             *  Stop processing also on proxy pass-through and
             *  last-rule and new-round flags.
             */
            if (p->flags & RULEFLAG_PROXY) {
                break;
            }
            if (p->flags & RULEFLAG_LASTRULE) {
                break;
            }

            /*
             *  On "new-round" flag we just start from the top of
             *  the rewriting ruleset again.
             */
            if (p->flags & RULEFLAG_NEWROUND) {
                goto loop;
            }

            /*
             *  If we are forced to skip N next rules, do it now.
             */
            if (p->skip > 0) {
                s = p->skip;
                while (   i < rewriterules->nelts
                       && s > 0) {
                    i++;
                    p = &entries[i];
                    s--;
                }
            }
        }
        else {
            /*
             *  If current rule is chained with next rule(s),
             *  skip all this next rule(s)
             */
            while (   i < rewriterules->nelts
                   && p->flags & RULEFLAG_CHAIN) {
                i++;
                p = &entries[i];
            }
        }
    }
    return changed;
}

/*
 *  Apply a single(!) rewrite rule
 */
static int apply_rewrite_rule(request_rec *r, rewriterule_entry *p,
                              char *perdir)
{
    char *uri;
    char *output;
    const char *vary;
    char newuri[MAX_STRING_LEN];
    regex_t *regexp;
    regmatch_t regmatch[AP_MAX_REG_MATCH];
    backrefinfo *briRR = NULL;
    backrefinfo *briRC = NULL;
    int prefixstrip;
    int failed;
    array_header *rewriteconds;
    rewritecond_entry *conds;
    rewritecond_entry *c;
    int i;
    int rc;

    /*
     *  Initialisation
     */
    uri     = r->filename;
    regexp  = p->regexp;
    output  = p->output;

    /*
     *  Add (perhaps splitted away) PATH_INFO postfix to URL to
     *  make sure we really match against the complete URL.
     */
    if (perdir != NULL && r->path_info != NULL && r->path_info[0] != '\0') {
        rewritelog(r, 3, "[per-dir %s] add path-info postfix: %s -> %s%s",
                   perdir, uri, uri, r->path_info);
        uri = ap_pstrcat(r->pool, uri, r->path_info, NULL);
    }

    /*
     *  On per-directory context (.htaccess) strip the location
     *  prefix from the URL to make sure patterns apply only to
     *  the local part.  Additionally indicate this special
     *  threatment in the logfile.
     */
    prefixstrip = 0;
    if (perdir != NULL) {
        if (   strlen(uri) >= strlen(perdir)
            && strncmp(uri, perdir, strlen(perdir)) == 0) {
            rewritelog(r, 3, "[per-dir %s] strip per-dir prefix: %s -> %s",
                       perdir, uri, uri+strlen(perdir));
            uri = uri+strlen(perdir);
            prefixstrip = 1;
        }
    }

    /*
     *  Try to match the URI against the RewriteRule pattern
     *  and exit immeddiately if it didn't apply.
     */
    if (perdir == NULL) {
        rewritelog(r, 3, "applying pattern '%s' to uri '%s'",
                   p->pattern, uri);
    }
    else {
        rewritelog(r, 3, "[per-dir %s] applying pattern '%s' to uri '%s'",
                   perdir, p->pattern, uri);
    }
    rc = (ap_regexec(regexp, uri, AP_MAX_REG_MATCH, regmatch, 0) == 0);
    if (! (( rc && !(p->flags & RULEFLAG_NOTMATCH)) ||
           (!rc &&  (p->flags & RULEFLAG_NOTMATCH))   ) ) {
        return 0;
    }

    /*
     *  Else create the RewriteRule `regsubinfo' structure which
     *  holds the substitution information.
     */
    briRR = (backrefinfo *)ap_palloc(r->pool, sizeof(backrefinfo));
    if (!rc && (p->flags & RULEFLAG_NOTMATCH)) {
        /*  empty info on negative patterns  */
        briRR->source = "";
        briRR->nsub   = 0;
    }
    else {
        briRR->source = ap_pstrdup(r->pool, uri);
        briRR->nsub   = regexp->re_nsub;
        memcpy((void *)(briRR->regmatch), (void *)(regmatch),
               sizeof(regmatch));
    }

    /*
     *  Initiallally create the RewriteCond backrefinfo with
     *  empty backrefinfo, i.e. not subst parts
     *  (this one is adjusted inside apply_rewrite_cond() later!!)
     */
    briRC = (backrefinfo *)ap_pcalloc(r->pool, sizeof(backrefinfo));
    briRC->source = "";
    briRC->nsub   = 0;

    /*
     *  Ok, we already know the pattern has matched, but we now
     *  additionally have to check for all existing preconditions
     *  (RewriteCond) which have to be also true. We do this at
     *  this very late stage to avoid unnessesary checks which
     *  would slow down the rewriting engine!!
     */
    rewriteconds = p->rewriteconds;
    conds = (rewritecond_entry *)rewriteconds->elts;
    failed = 0;
    for (i = 0; i < rewriteconds->nelts; i++) {
        c = &conds[i];
        rc = apply_rewrite_cond(r, c, perdir, briRR, briRC);
        if (c->flags & CONDFLAG_ORNEXT) {
            /*
             *  The "OR" case
             */
            if (rc == 0) {
                /*  One condition is false, but another can be
                 *  still true, so we have to continue...
                 */
                ap_table_unset(r->notes, VARY_KEY_THIS);
                continue;
            }
            else {
                /*  One true condition is enough in "or" case, so
                 *  skip the other conditions which are "ornext"
                 *  chained
                 */
                while (   i < rewriteconds->nelts
                       && c->flags & CONDFLAG_ORNEXT) {
                    i++;
                    c = &conds[i];
                }
                continue;
            }
        }
        else {
            /*
             *  The "AND" case, i.e. no "or" flag,
             *  so a single failure means total failure.
             */
            if (rc == 0) {
                failed = 1;
                break;
            }
        }
        vary = ap_table_get(r->notes, VARY_KEY_THIS);
        if (vary != NULL) {
            ap_table_merge(r->notes, VARY_KEY, vary);
            ap_table_unset(r->notes, VARY_KEY_THIS);
        }
    }
    /*  if any condition fails the complete rule fails  */
    if (failed) {
        ap_table_unset(r->notes, VARY_KEY);
        ap_table_unset(r->notes, VARY_KEY_THIS);
        return 0;
    }

    /*
     * Regardless of what we do next, we've found a match.  Check to see
     * if any of the request header fields were involved, and add them
     * to the Vary field of the response.
     */
    if ((vary = ap_table_get(r->notes, VA