mod_proxy.c

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    if (r->proxyreq) {
        /* someone has already set up the proxy, it was possibly ourselves
         * in proxy_detect
         */
        return OK;
    }

#ifndef FIX_15207
    /* XXX: since r->uri has been manipulated already we're not really
     * compliant with RFC1945 at this point.  But this probably isn't
     * an issue because this is a hybrid proxy/origin server.
     */

    for (i = 0; i < conf->aliases->nelts; i++) {
        len = alias_match(r->uri, ent[i].fake);

       if (len > 0) {
           if ((ent[i].real[0] == '!') && (ent[i].real[1] == 0)) {
               return DECLINED;
           }

           r->filename = apr_pstrcat(r->pool, "proxy:", ent[i].real,
                                     r->uri + len, NULL);
           r->handler = "proxy-server";
           r->proxyreq = PROXYREQ_REVERSE;
           return OK;
       }
    }
#endif
    return DECLINED;
}

static int proxy_walk(request_rec *r)
{
    proxy_server_conf *sconf = ap_get_module_config(r->server->module_config,
                                                    &proxy_module);
    ap_conf_vector_t *per_dir_defaults = r->server->lookup_defaults;
    ap_conf_vector_t **sec_proxy = (ap_conf_vector_t **) sconf->sec_proxy->elts;
    ap_conf_vector_t *entry_config;
    proxy_dir_conf *entry_proxy;
    int num_sec = sconf->sec_proxy->nelts;
    /* XXX: shouldn't we use URI here?  Canonicalize it first?
     * Pass over "proxy:" prefix 
     */
    const char *proxyname = r->filename + 6;
    int j;

    for (j = 0; j < num_sec; ++j) 
    {
        entry_config = sec_proxy[j];
        entry_proxy = ap_get_module_config(entry_config, &proxy_module);

        /* XXX: What about case insensitive matching ???
         * Compare regex, fnmatch or string as appropriate
         * If the entry doesn't relate, then continue 
         */
        if (entry_proxy->r 
              ? ap_regexec(entry_proxy->r, proxyname, 0, NULL, 0)
              : (entry_proxy->p_is_fnmatch
                   ? apr_fnmatch(entry_proxy->p, proxyname, 0)
                   : strncmp(proxyname, entry_proxy->p, 
                                        strlen(entry_proxy->p)))) {
            continue;
        }
        per_dir_defaults = ap_merge_per_dir_configs(r->pool, per_dir_defaults,
                                                             entry_config);
    }

    r->per_dir_config = per_dir_defaults;

    return OK;
}

static int proxy_map_location(request_rec *r)
{
    int access_status;

    if (!r->proxyreq || !r->filename || strncmp(r->filename, "proxy:", 6) != 0)
        return DECLINED;

    /* Don't let the core or mod_http map_to_storage hooks handle this,
     * We don't need directory/file_walk, and we want to TRACE on our own.
     */
    if ((access_status = proxy_walk(r))) {
        ap_die(access_status, r);
        return access_status;
    }

    return OK;
}
#ifndef FIX_15207
/* -------------------------------------------------------------- */
/* Fixup the filename */

/*
 * Canonicalise the URL
 */
static int proxy_fixup(request_rec *r)
{
    char *url, *p;
    int access_status;

    if (!r->proxyreq || !r->filename || strncmp(r->filename, "proxy:", 6) != 0)
        return DECLINED;

#ifdef FIX_15207
/* We definitely shouldn't canonicalize a proxy_pass.
 * But should we really canonicalize a STD_PROXY??? -- Fahree
 */
    if (r->proxyreq == PROXYREQ_REVERSE) {
        return OK;
    }
#endif

    /* XXX: Shouldn't we try this before we run the proxy_walk? */
    url = &r->filename[6];

    /* canonicalise each specific scheme */
    if ((access_status = proxy_run_canon_handler(r, url))) {
        return access_status;
    }

    p = strchr(url, ':');
    if (p == NULL || p == url)
        return HTTP_BAD_REQUEST;

    return OK;		/* otherwise; we've done the best we can */
}
#endif
/* Send a redirection if the request contains a hostname which is not */
/* fully qualified, i.e. doesn't have a domain name appended. Some proxy */
/* servers like Netscape's allow this and access hosts from the local */
/* domain in this case. I think it is better to redirect to a FQDN, since */
/* these will later be found in the bookmarks files. */
/* The "ProxyDomain" directive determines what domain will be appended */
static int proxy_needsdomain(request_rec *r, const char *url, const char *domain)
{
    char *nuri;
    const char *ref;

    /* We only want to worry about GETs */
    if (!r->proxyreq || r->method_number != M_GET || !r->parsed_uri.hostname)
        return DECLINED;

    /* If host does contain a dot already, or it is "localhost", decline */
    if (strchr(r->parsed_uri.hostname, '.') != NULL
     || strcasecmp(r->parsed_uri.hostname, "localhost") == 0)
        return DECLINED;	/* host name has a dot already */

    ref = apr_table_get(r->headers_in, "Referer");

    /* Reassemble the request, but insert the domain after the host name */
    /* Note that the domain name always starts with a dot */
    r->parsed_uri.hostname = apr_pstrcat(r->pool, r->parsed_uri.hostname,
                                         domain, NULL);
    nuri = apr_uri_unparse(r->pool,
                           &r->parsed_uri,
                           APR_URI_UNP_REVEALPASSWORD);

    apr_table_set(r->headers_out, "Location", nuri);
    ap_log_rerror(APLOG_MARK, APLOG_INFO, 0, r,
                  "Domain missing: %s sent to %s%s%s", r->uri,
                  apr_uri_unparse(r->pool, &r->parsed_uri,
                                  APR_URI_UNP_OMITUSERINFO),
                  ref ? " from " : "", ref ? ref : "");

    return HTTP_MOVED_PERMANENTLY;
}

/* -------------------------------------------------------------- */
/* Invoke handler */

static int proxy_handler(request_rec *r)
{
    char *url, *scheme, *p;
    const char *p2;
    void *sconf = r->server->module_config;
    proxy_server_conf *conf = (proxy_server_conf *)
        ap_get_module_config(sconf, &proxy_module);
    apr_array_header_t *proxies = conf->proxies;
    struct proxy_remote *ents = (struct proxy_remote *) proxies->elts;
    int i, rc, access_status;
    int direct_connect = 0;
    const char *str;
    long maxfwd;
    proxy_balancer *balancer = NULL;
    proxy_worker *worker = NULL;

    /* is this for us? */
    if (!r->proxyreq || !r->filename || strncmp(r->filename, "proxy:", 6) != 0)
        return DECLINED;

    /* handle max-forwards / OPTIONS / TRACE */
    if ((str = apr_table_get(r->headers_in, "Max-Forwards"))) {
        maxfwd = strtol(str, NULL, 10);
        if (maxfwd < 1) {
            switch (r->method_number) {
            case M_TRACE: {
                int access_status;
                r->proxyreq = PROXYREQ_NONE;
                if ((access_status = ap_send_http_trace(r)))
                    ap_die(access_status, r);
                else
                    ap_finalize_request_protocol(r);
                return OK;
            }
            case M_OPTIONS: {
                int access_status;
                r->proxyreq = PROXYREQ_NONE;
                if ((access_status = ap_send_http_options(r)))
                    ap_die(access_status, r);
                else
                    ap_finalize_request_protocol(r);
                return OK;
            }
            default: {
                return ap_proxyerror(r, HTTP_BAD_GATEWAY,
                                     "Max-Forwards has reached zero - proxy loop?");
            }
            }
        }
        maxfwd = (maxfwd > 0) ? maxfwd - 1 : 0;
    }
    else {
        /* set configured max-forwards */
        maxfwd = conf->maxfwd;
    }
    apr_table_set(r->headers_in, "Max-Forwards", 
                  apr_psprintf(r->pool, "%ld", (maxfwd > 0) ? maxfwd : 0));

    url = r->filename + 6;
    p = strchr(url, ':');
    if (p == NULL) {
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                      "proxy_handler no URL in %s", r->filename);
        return HTTP_BAD_REQUEST;
    }

    /* If the host doesn't have a domain name, add one and redirect. */
    if (conf->domain != NULL) {
        rc = proxy_needsdomain(r, url, conf->domain);
        if (ap_is_HTTP_REDIRECT(rc))
            return HTTP_MOVED_PERMANENTLY;
    }

    *p = '\0';
    scheme = apr_pstrdup(r->pool, url);
    *p = ':';

    /* Check URI's destination host against NoProxy hosts */
    /* Bypass ProxyRemote server lookup if configured as NoProxy */
    /* we only know how to handle communication to a proxy via http */
    /*if (strcasecmp(scheme, "http") == 0) */
    {
        int ii;
        struct dirconn_entry *list = (struct dirconn_entry *) conf->dirconn->elts;

        for (direct_connect = ii = 0; ii < conf->dirconn->nelts && !direct_connect; ii++) {
            direct_connect = list[ii].matcher(&list[ii], r);
        }
#if DEBUGGING
        ap_log_rerror(APLOG_MARK, APLOG_DEBUG, 0, r,
                      (direct_connect) ? "NoProxy for %s" : "UseProxy for %s",
                      r->uri);
#endif
    }
    
    /* Try to obtain the most suitable worker */
    access_status = ap_proxy_pre_request(&worker, &balancer, r, conf, &url);
    if (access_status != OK)
        return access_status;
    
    /* firstly, try a proxy, unless a NoProxy directive is active */
    if (!direct_connect) {
        for (i = 0; i < proxies->nelts; i++) {
            p2 = ap_strchr_c(ents[i].scheme, ':');  /* is it a partial URL? */
            if (strcmp(ents[i].scheme, "*") == 0 ||
                (ents[i].use_regex && ap_regexec(ents[i].regexp, url, 0,NULL, 0)) ||
                (p2 == NULL && strcasecmp(scheme, ents[i].scheme) == 0) ||
                (p2 != NULL &&
                 strncasecmp(url, ents[i].scheme, strlen(ents[i].scheme)) == 0)) {

                /* handle the scheme */
                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                             "Trying to run scheme_handler against proxy");
                access_status = proxy_run_scheme_handler(r, worker, conf, url, ents[i].hostname, ents[i].port);

                /* an error or success */
                if (access_status != DECLINED && access_status != HTTP_BAD_GATEWAY) {
                    goto cleanup;
                }
                /* we failed to talk to the upstream proxy */
            }
        }
    }

    /* otherwise, try it direct */
    /* N.B. what if we're behind a firewall, where we must use a proxy or
     * give up??
     */

    /* handle the scheme */
    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, r->server,
                 "Trying to run scheme_handler");
    access_status = proxy_run_scheme_handler(r, worker, conf, url, NULL, 0);
    if (DECLINED == access_status) {
        ap_log_error(APLOG_MARK, APLOG_WARNING, 0, r->server,
                    "proxy: No protocol handler was valid for the URL %s. "
                    "If you are using a DSO version of mod_proxy, make sure "
                    "the proxy submodules are included in the configuration "
                    "using LoadModule.", r->uri);
        access_status = HTTP_FORBIDDEN;
        goto cleanup;
    }

cleanup:
    if (balancer) {
        int post_status = proxy_run_post_request(worker, balancer, r, conf);
        if (post_status == DECLINED) {
            post_status = OK; /* no post_request handler available */
            /* TODO: reclycle direct worker */
        }
    }
    return access_status;
}

/* -------------------------------------------------------------- */
/* Setup configurable data */

static void * create_proxy_config(apr_pool_t *p, server_rec *s)
{
    proxy_server_conf *ps = apr_pcalloc(p, sizeof(proxy_server_conf));

    ps->sec_proxy = apr_array_make(p, 10, sizeof(ap_conf_vector_t *));
    ps->proxies = apr_array_make(p, 10, sizeof(struct proxy_remote));
    ps->aliases = apr_array_make(p, 10, sizeof(struct proxy_alias));
    ps->raliases = apr_array_make(p, 10, sizeof(struct proxy_alias));
    ps->cookie_paths = apr_array_make(p, 10, sizeof(struct proxy_alias));
    ps->cookie_domains = apr_array_make(p, 10, sizeof(struct proxy_alias));
    ps->cookie_path_str = apr_strmatch_precompile(p, "path=", 0);
    ps->cookie_domain_str = apr_strmatch_precompile(p, "domain=", 0);
    ps->noproxies = apr_array_make(p, 10, sizeof(struct noproxy_entry));
    ps->dirconn = apr_array_make(p, 10, sizeof(struct dirconn_entry));
    ps->allowed_connect_ports = apr_array_make(p, 10, sizeof(int));