wifidog 源码初分析(二)

上一篇分析了接入设备的首次浏览器访问请求如何通过 防火墙过滤规则 重定向到 wifidog 的 HTTP 服务中,本篇主要分析了 wifidog 在接收到 接入设备的 HTTP 访问请求后,如何将此 HTTP 请求重定向到 认证服务器(auth-server) 上。

通过上面的防火墙规则,会将通过上面的防火墙规则,会将HTTP请求的外部IP地址和端口通过NAT方式重定向至本地wifidog内嵌HTTP服务器的地址和端口上,并由内嵌HTTP服务器进行服务,而内嵌HTTP服务器的路径和回调处理如下:

if ((webserver = httpdCreate(config->gw_address, config->gw_port)) == NULL) {  
    debug(LOG_ERR, "Could not create web server: %s", strerror(errno));  
    exit(1);  
}  
debug(LOG_DEBUG, "Assigning callbacks to web server");  
httpdAddCContent(webserver, "/", "wifidog", 0, NULL, http_callback_wifidog);  
httpdAddCContent(webserver, "/wifidog", "", 0, NULL, http_callback_wifidog);  
httpdAddCContent(webserver, "/wifidog", "about", 0, NULL, http_callback_about);  
httpdAddCContent(webserver, "/wifidog", "status", 0, NULL, http_callback_status);  
httpdAddCContent(webserver, "/wifidog", "auth", 0, NULL, http_callback_auth);  
httpdAddC404Content(webserver, http_callback_404);

客户端首次访问时回调客户端首次访问时回调http_callback_404函数,在该函数中根据获取的客户端信息来配置重定向的URL fragment,如下:

/** The 404 handler is also responsible for redirecting to the auth server */
void http_callback_404(httpd *webserver, request *r)
{
    char        tmp_url[MAX_BUF],
        *url;
    s_config    *config = config_get_config();
    t_auth_serv *auth_server = get_auth_server();

    memset(tmp_url, 0, sizeof(tmp_url));
    /* 
     * XXX Note the code below assumes that the client's request is a plain
     * http request to a standard port. At any rate, this handler is called only
     * if the internet/auth server is down so it's not a huge loss, but still.
     */
    snprintf(tmp_url, (sizeof(tmp_url) - 1), "http://%s%s%s%s",
                    r->request.host,
                    r->request.path,
                    r->request.query[0] ? "?" : "",
                    r->request.query);
    url = httpdUrlEncode(tmp_url);

    if (!is_online()) {
        /* The internet connection is down at the moment  - apologize and do not redirect anywhere */
        char * buf;
        safe_asprintf(&buf, 
            "<p>We apologize, but it seems that the internet connection that powers this hotspot is temporarily unavailable.</p>"
            "<p>If at all possible, please notify the owners of this hotspot that the internet connection is out of service.</p>"
            "<p>The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.</p>"
            "<p>In a while please <a href='%s'>click here</a> to try your request again.</p>", tmp_url);

        send_http_page(r, "Uh oh! Internet access unavailable!", buf);
        free(buf);
        debug(LOG_INFO, "Sent %s an apology since I am not online - no point sending them to auth server", r->clientAddr);
    }
    else if (!is_auth_online()) {
        /* The auth server is down at the moment - apologize and do not redirect anywhere */
        char * buf;
        safe_asprintf(&buf, 
            "<p>We apologize, but it seems that we are currently unable to re-direct you to the login screen.</p>"
            "<p>The maintainers of this network are aware of this disruption.  We hope that this situation will be resolved soon.</p>"
        "<p>In a couple of minutes please <a href='%s'>click here</a> to try your request again.</p>", tmp_url);

        send_http_page(r, "Uh oh! Login screen unavailable!", buf);
        free(buf);
        debug(LOG_INFO, "Sent %s an apology since auth server not online - no point sending them to auth server", r->clientAddr);
    }
    else {
        /* Re-direct them to auth server */
        char *urlFragment;
        safe_asprintf(&urlFragment, "%sgw_address=%s&gw_port=%d&gw_id=%s&url=%s",
            auth_server->authserv_login_script_path_fragment,
            config->gw_address,
            config->gw_port, 
            config->gw_id,
            url);
        debug(LOG_INFO, "Captured %s requesting [%s] and re-directing them to login page", r->clientAddr, url);
        http_send_redirect_to_auth(r, urlFragment, "Redirect to login page");
        free(urlFragment);
    }
    free(url);
}

上面代码基本不用解释,具体重定向至auth server的消息在下面的 http_send_redirect_to_auth 函数中实现:

void http_send_redirect_to_auth(request *r, char *urlFragment, char *text)
{
    char *protocol = NULL;
    int port = 80;
    t_auth_serv *auth_server = get_auth_server();

    if (auth_server->authserv_use_ssl) {
        protocol = "https";
        port = auth_server->authserv_ssl_port;
    } else {
        protocol = "http";
        port = auth_server->authserv_http_port;
    }

    char *url = NULL;
    safe_asprintf(&url, "%s://%s:%d%s%s",
        protocol,
        auth_server->authserv_hostname,
        port,
        auth_server->authserv_path,
        urlFragment
    );
    http_send_redirect(r, url, text);
    free(url);  
}

具体的重定向URL给个实例:
POST /login/?gw_address=192.168.1.1&gw_port=2060&gw_id=default&mac=44:94:fc:ef:28:40&url=http%3A//www.baidu.com/ HTTP/1.1
gw_address,路由器的LAN地址

gw_port:为wifidog的监听端口

gw_id:路由器的标识名

mac:客户端设备的MAC地址

url:为客户端访问的原URL(以便于重定向)

本文章由 http://www.wifidog.pro/2014/12/08/wifidog%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90-1.html 整理编辑,转载请注明出处

wifidog 源码初分析(一)

wifidog 的核心还是依赖于 iptables 防火墙过滤规则来实现的,所以建议对 iptables 有了了解后再去阅读 wifidog 的源码。
在路由器上启动 wifidog 之后,wifidog 在启动时会初始化一堆的防火墙规则,如下:

/** Initialize the firewall rules
*/
int iptables_fw_init(void)
{
    const s_config *config;
    char * ext_interface = NULL;
    int gw_port = 0;
    t_trusted_mac *p;

    fw_quiet = 0;

    LOCK_CONFIG();
    config = config_get_config();
    gw_port = config->gw_port;
    if (config->external_interface) {
            ext_interface = safe_strdup(config->external_interface);
    } else {
            ext_interface = get_ext_iface();
    }

    if (ext_interface == NULL) {
            UNLOCK_CONFIG();
            debug(LOG_ERR, "FATAL: no external interface");
            return 0;
    }
    /*
     *
     * Everything in the MANGLE table
     *
     */

    /* Create new chains */
    iptables_do_command("-t mangle -N " TABLE_WIFIDOG_TRUSTED);
    iptables_do_command("-t mangle -N " TABLE_WIFIDOG_OUTGOING);
    iptables_do_command("-t mangle -N " TABLE_WIFIDOG_INCOMING);

    /* Assign links and rules to these new chains */
    iptables_do_command("-t mangle -I PREROUTING 1 -i %s -j " TABLE_WIFIDOG_OUTGOING, config->gw_interface);
    iptables_do_command("-t mangle -I PREROUTING 1 -i %s -j " TABLE_WIFIDOG_TRUSTED, config->gw_interface);//this rule will be inserted before the prior one
    iptables_do_command("-t mangle -I POSTROUTING 1 -o %s -j " TABLE_WIFIDOG_INCOMING, config->gw_interface);

    for (p = config->trustedmaclist; p != NULL; p = p->next)
            iptables_do_command("-t mangle -A " TABLE_WIFIDOG_TRUSTED " -m mac --mac-source %s -j MARK --set-mark %d", p->mac, FW_MARK_KNOWN);

    /*
     *
     * Everything in the NAT table
     *
     */

    /* Create new chains */
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_OUTGOING);
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_WIFI_TO_ROUTER);
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_WIFI_TO_INTERNET);
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_GLOBAL);
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_UNKNOWN);
    iptables_do_command("-t nat -N " TABLE_WIFIDOG_AUTHSERVERS);

    /* Assign links and rules to these new chains */
    iptables_do_command("-t nat -A PREROUTING -i %s -j " TABLE_WIFIDOG_OUTGOING, config->gw_interface);

    iptables_do_command("-t nat -A " TABLE_WIFIDOG_OUTGOING " -d %s -j " TABLE_WIFIDOG_WIFI_TO_ROUTER, config->gw_address);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_ROUTER " -j ACCEPT");

    iptables_do_command("-t nat -A " TABLE_WIFIDOG_OUTGOING " -j " TABLE_WIFIDOG_WIFI_TO_INTERNET);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j ACCEPT", FW_MARK_KNOWN);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j ACCEPT", FW_MARK_PROBATION);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_UNKNOWN);

    iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -j " TABLE_WIFIDOG_AUTHSERVERS);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -j " TABLE_WIFIDOG_GLOBAL);
    iptables_do_command("-t nat -A " TABLE_WIFIDOG_UNKNOWN " -p tcp --dport 80 -j REDIRECT --to-ports %d", gw_port);


    /*
     *
     * Everything in the FILTER table
     *
     */

    /* Create new chains */
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_WIFI_TO_INTERNET);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_AUTHSERVERS);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_LOCKED);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_GLOBAL);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_VALIDATE);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_KNOWN);
    iptables_do_command("-t filter -N " TABLE_WIFIDOG_UNKNOWN);

    /* Assign links and rules to these new chains */

    /* Insert at the beginning */
    iptables_do_command("-t filter -I FORWARD -i %s -j " TABLE_WIFIDOG_WIFI_TO_INTERNET, config->gw_interface);


    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m state --state INVALID -j DROP");

    /* XXX: Why this? it means that connections setup after authentication
       stay open even after the connection is done... 
       iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m state --state RELATED,ESTABLISHED -j ACCEPT");*/

    //Won't this rule NEVER match anyway?!?!? benoitg, 2007-06-23
    //iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -i %s -m state --state NEW -j DROP", ext_interface);

    /* TCPMSS rule for PPPoE */
    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -o %s -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu", ext_interface);

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_AUTHSERVERS);
    iptables_fw_set_authservers();

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_LOCKED, FW_MARK_LOCKED);
    iptables_load_ruleset("filter", "locked-users", TABLE_WIFIDOG_LOCKED);

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_GLOBAL);
    iptables_load_ruleset("filter", "global", TABLE_WIFIDOG_GLOBAL);
    iptables_load_ruleset("nat", "global", TABLE_WIFIDOG_GLOBAL);

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_VALIDATE, FW_MARK_PROBATION);
    iptables_load_ruleset("filter", "validating-users", TABLE_WIFIDOG_VALIDATE);

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -m mark --mark 0x%u -j " TABLE_WIFIDOG_KNOWN, FW_MARK_KNOWN);
    iptables_load_ruleset("filter", "known-users", TABLE_WIFIDOG_KNOWN);

    iptables_do_command("-t filter -A " TABLE_WIFIDOG_WIFI_TO_INTERNET " -j " TABLE_WIFIDOG_UNKNOWN);
    iptables_load_ruleset("filter", "unknown-users", TABLE_WIFIDOG_UNKNOWN);
    iptables_do_command("-t filter -A " TABLE_WIFIDOG_UNKNOWN " -j REJECT --reject-with icmp-port-unreachable");

    UNLOCK_CONFIG();
    return 1;
}

在该 防火墙规则的初始化过程中,会首先清除掉已有的防火墙规则,重新创建新的过滤链,另外,除了通过iptables_do_command("-t nat -A "TABLE_WIFIDOG_UNKNOWN " -p tcp --dport 80 -j REDIRECT --to-ports %d",gw_port); 这个命令将 接入设备的 80 端口(HTTP)的访问重定向至网关自身的 HTTP 的端口之外,还通过iptables_fw_set_authservers(); 函数设置了 鉴权服务器(auth-server) 的防火墙规则:

void iptables_fw_set_authservers(void)
{
    const s_config *config;
    t_auth_serv *auth_server;

    config = config_get_config();

    for (auth_server = config->auth_servers; auth_server != NULL; auth_server = auth_server->next) {
        if (auth_server->last_ip && strcmp(auth_server->last_ip, "0.0.0.0") != 0) {
            iptables_do_command("-t filter -A " TABLE_WIFIDOG_AUTHSERVERS " -d %s -j ACCEPT", auth_server->last_ip);
            iptables_do_command("-t nat -A " TABLE_WIFIDOG_AUTHSERVERS " -d %s -j ACCEPT", auth_server->last_ip);
        }
    }
}

首先从上面的代码可以看出 wifidog 支持多个鉴权服务器,并且针对每一个鉴权服务器设置了如下两条规则:
1)在filter表中追加一条[任何访问鉴权服务器都被接受]的WiFiDog_$ID$AuthServers过滤链:iptables -t filter -A WiFiDog$ID$AuthServers -d auth-server地址 -j ACCEPT
2)在nat表中追加一条[任何访问鉴权服务器都被接受]的WiFiDog
$ID$AuthServers过滤链:iptables -t nat -A WiFiDog$ID$_AuthServers -d auth-server地址 -j ACCEPT
这样确保可以访问鉴权服务器,而不是拒绝所有的出口访问。

本文章由 http://www.wifidog.pro/2014/12/08/wifidog%E6%BA%90%E7%A0%81%E5%88%86%E6%9E%90.html整理编辑,转载请注明出处

linux 系统安装wifidog

  1. 下载源码:
    1) 从svn checkout https://dev.wifidog.org/svn/trunk/wifidog-auth下载最新的wifidog 网关源码
    2) 从http://sourceforge.net/projects/wifidog/files/wifidog-gateway/下载wifidog 网关源码
    我使用第二种下载方法下载wifidog-20090925.tar.gz 版本,这是目前最新的wifidog。

  2. 解压: tar -zxvf wifidog-20090925.tar.gz

  3. cd wifidog-20090925; ./configure; make; make install, /usr/local/bin/目录下会多一个wifidog

  4. 到这里我们需要配置下源码根目录下的wifidog.conf,并再修改后将文件拷贝至 /usr/local/etc/,

    GatewayID default #网关的ID,如果不设置默认是网关interface 的 mac地址

    GatewayInterface br0  #网关使用的LAN Interface,必须设置
    
    GatewayAddress 192.168.1.1  #网关LAN 的IP地址,不设置默认从interface拿IP
    
    AuthServer   #必须设置
    {
        Hostname                 (Mandatory; Default: NONE)  #认证server 的主机名
        SSLAvailable             (Optional; Default: no; Possible values: yes, no) #认证server是否使用ssl协议
        SSLPort                  (Optional; Default: 443)  #认证server ssl协议端口
        HTTPPort                 (Optional; Default: 80)   #http协议端口
        Path                     (Optional; Default: /wifidog/ Note:  The path must be both prefixed and suffixed by /.  Use a single / for server root.) 
        LoginScriptPathFragment  (Optional; Default: login/? Note:  This is the script the user will be sent to for login.) 
        PortalScriptPathFragment (Optional; Default: portal/? Note:  This is the script the user will be sent to after a successfull login.)
        MsgScriptPathFragment    (Optional; Default: gw_message.php? Note:  This is the script the user will be sent to upon error to read a readable message.)
        PingScriptPathFragment    (Optional; Default: ping/? Note:  This is the script the user will be sent to upon error to read a readable message.)
        AuthScriptPathFragment    (Optional; Default: auth/? Note:  This is the script the user will be sent to upon error to read a readable message.)
    }
    
    GatewayPort 2060  #wifidog监听的端口
    
    CheckInterval 60   #检查连接网关客户端的流量,主要是用于流量更新、超时重新认证
    ClientTimeout 5  #checkinterval的间隔数,这里要注意,实际流量更新遗迹超时、检查使用的时间是CheckInterval * ClientTimeout
    
    TrustedMACList 00:00:DE:AD:BE:AF,00:00:C0:1D:F0:0D #MAC地址白名单
    

    后面还有一些关于网段、port 的黑白名单规则,以及其他一些设置,这里就不一一列举了。

  5. 启动wifidog -c /usr/local/etc/wifidog.conf 就可以和auth server交互了,auth server可以参考http://www.authpuppy.org 安装authpuppy,这里就不详细解释了

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wifidog 认证流程

一. 用户上线

  1. 用户访问网络,通过iptables将未认证的用户dnat到wifidog进程,wifidog通过307报文将用户重定向到认证服务器
  2. 用户打开认证服务器登录页面,输入用户名密码,发送认证请求
  3. 认证成功的话服务器会发送302报文,携带token信息重定向到wifidog页面。认证失败的话会返回失败页面
  4. 用户携带token信息向wifidog发起认证请求,wifidog再向认证服务器发起请求,认证成功后授权,并将用户重定向到成功页面

1.jpg

二. 保活和下线

  1. wifidog会定时向认证服务器发送保活消息
  2. 当用户主动请求下线后,wifidog此时并没有下线
  3. 当wifidog再次发起保活请求时,认证服务器会告诉它用户已下线,此时wifidog会将用户下线

2.png

本文章由 http://www.wifidog.pro/2014/12/08/wifidog-%E8%AE%A4%E8%AF%81%E6%B5%81%E7%A8%8B.html整理编辑,转载请注明出处