mod_proxy.c

Apache HTTP Server 是一个功能强大的灵活的与HTTP/1.1相兼容的web服务器.这里给出的是Apache HTTP服务器的源码。

/* Copyright 1999-2005 The Apache Software Foundation or its licensors, as
 * applicable.
 *
 * Licensed 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.
 */

#define CORE_PRIVATE

#include "mod_proxy.h"
#include "mod_core.h"

#include "apr_optional.h"

#ifndef MAX
#define MAX(x,y) ((x) >= (y) ? (x) : (y))
#endif

/*
 * A Web proxy module. Stages:
 *
 *  translate_name: set filename to proxy:<URL>
 *  map_to_storage: run proxy_walk (rather than directory_walk/file_walk)
 *                  can't trust directory_walk/file_walk since these are
 *                  not in our filesystem.  Prevents mod_http from serving
 *                  the TRACE request we will set aside to handle later.
 *  type_checker:   set type to PROXY_MAGIC_TYPE if filename begins proxy:
 *  fix_ups:        convert the URL stored in the filename to the
 *                  canonical form.
 *  handler:        handle proxy requests
 */

/* -------------------------------------------------------------- */
/* Translate the URL into a 'filename' */

static int alias_match(const char *uri, const char *alias_fakename)
{
    const char *end_fakename = alias_fakename + strlen(alias_fakename);
    const char *aliasp = alias_fakename, *urip = uri;

    while (aliasp < end_fakename) {
        if (*aliasp == '/') {
            /* any number of '/' in the alias matches any number in
             * the supplied URI, but there must be at least one...
             */
            if (*urip != '/')
                return 0;

            while (*aliasp == '/')
                ++aliasp;
            while (*urip == '/')
                ++urip;
        }
        else {
            /* Other characters are compared literally */
            if (*urip++ != *aliasp++)
                return 0;
        }
    }

    /* Check last alias path component matched all the way */

    if (aliasp[-1] != '/' && *urip != '\0' && *urip != '/')
        return 0;

    /* Return number of characters from URI which matched (may be
     * greater than length of alias, since we may have matched
     * doubled slashes)
     */

    return urip - uri;
}

/* Detect if an absoluteURI should be proxied or not.  Note that we
 * have to do this during this phase because later phases are
 * "short-circuiting"... i.e. translate_names will end when the first
 * module returns OK.  So for example, if the request is something like:
 *
 * GET http://othervhost/cgi-bin/printenv HTTP/1.0
 *
 * mod_alias will notice the /cgi-bin part and ScriptAlias it and
 * short-circuit the proxy... just because of the ordering in the
 * configuration file.
 */
static int proxy_detect(request_rec *r)
{
    void *sconf = r->server->module_config;
    proxy_server_conf *conf;

    conf = (proxy_server_conf *) ap_get_module_config(sconf, &proxy_module);

    /* Ick... msvc (perhaps others) promotes ternary short results to int */

    if (conf->req && r->parsed_uri.scheme) {
        /* but it might be something vhosted */
        if (!(r->parsed_uri.hostname
              && !strcasecmp(r->parsed_uri.scheme, ap_http_method(r))
              && ap_matches_request_vhost(r, r->parsed_uri.hostname,
                                          (apr_port_t)(r->parsed_uri.port_str ? r->parsed_uri.port 
                                                       : ap_default_port(r))))) {
            r->proxyreq = PROXYREQ_PROXY;
            r->uri = r->unparsed_uri;
            r->filename = apr_pstrcat(r->pool, "proxy:", r->uri, NULL);
            r->handler = "proxy-server";
        }
    }
    /* We need special treatment for CONNECT proxying: it has no scheme part */
    else if (conf->req && r->method_number == M_CONNECT
             && r->parsed_uri.hostname
             && r->parsed_uri.port_str) {
        r->proxyreq = PROXYREQ_PROXY;
        r->uri = r->unparsed_uri;
        r->filename = apr_pstrcat(r->pool, "proxy:", r->uri, NULL);
        r->handler = "proxy-server";
    }
    return DECLINED;
}

static int proxy_trans(request_rec *r)
{
    void *sconf = r->server->module_config;
    proxy_server_conf *conf =
    (proxy_server_conf *) ap_get_module_config(sconf, &proxy_module);
    int i, len;
    struct proxy_alias *ent = (struct proxy_alias *) conf->aliases->elts;

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

    /* 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;
       }
    }
    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;
}

/* -------------------------------------------------------------- */
/* 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;

    /* 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 */
}

/* 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;

    /* 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)
        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;