WiFiDog 与 AuthServer

背景

在一些公共场所（比如公交车、地跌、机场等）连接当地的 WiFi 时会弹出一个验证表单，输入验证信息（比如短信验证码）后就能够通过该 WiFi 联网。

本文将介绍通过 OpenWrt WiFiDog 来实现这个认证过程，认证服务器（WiFiDog Captive Portal/AuthServer）由 Java 编写。

WiFiDog

WiFiDog 是一套开源的无线热点认证管理工具，它主要提供如下功能：

位置相关的内容递送（比如不同的接入点可以投递不同的广告）
用户认证和授权（认证方式可以通过短信，或者是基础第三方开放平台，比如 QQ、微信等，授权可通过流控实现）
集中式网络监控（在认证服务器上可以获得各个 WiFi 热点上用户的流量使用情况）

WiFiDog 在架构上分为两个部分：

Gateway：即安装在路由器上的 WiFiDog 软件
Captive Portal：即认证服务器（AuthServer），是 Web HTTP 服务，独立部署在公网上

为了启用认证功能，我们需要对 WiFiDog 进行一点配置，修改配置文件 /etc/wifidog.conf，找到 AuthServer，并取消其中的几行注释：

AuthServer {
    Hostname 192.168.1.109
# SSLAvailable
# SSLPort
    HTTPPort 8910
# Path
# LoginScriptPathFragment
# PortalScriptPathFragment
# MsgScriptPathFragment
# PingScriptPathFragment
# AuthScriptPathFragment
}

为了简便，其他的配置项我们都用默认的。修改后重启 WiFiDog：/etc/init.d/wifidog restart

认证协议

WiFiDog v1 协议是目前（2016）使用最广泛的，协议流程如下（红色部分即认证服务需要实现的接口）：

GW（Gateway）会定时调用 AS（AuthServer）的 ping 接口来检查 AS 是否在线

1.1. AS 在响应 body 里写入 “Pong”
用户连上 GW 后，通过浏览器发出对某站点的请求

2.1. GW 收到请求后发现用户没有认证过，则重定向用户到 AS 的 /login
浏览器请求 AS 的 /login

3.1. AS 返回验证表单 HTML
用户填写验证表单后提交 AS

4.1. AS 验证通过后生成 token 并重定向用户到 GW
浏览器带 token 请求 GW 的验证接口

5.1. GW 获取用户 token 后再请求 AS /auth 接口

5.2. AS 验证 token 有效性，成功则返回 “Auth: 1”（注意空格），验证通过后 GW 会定时请求 AS 的 /auth 接口来检查 token 有效性，期间会带上用户的流量数据

5.3. GW 重定向用户到 AS /portal
浏览器请求 GW 的 /portal 接口

6.1 AS 重定向用户到 2 中指定的某站点（也可以按需进行广告投放）

报文详解

基于 WiFiDog 1.2.1 整理，192.168.1.1 是路由 IP，192.168.1.109 同时是客户端和 AuthServer 的 IP。

ping

request [
  URI=/wifidog/ping/
  method=GET
  remoteAddr=192.168.1.1
  queryStr=gw_id=100D7F6F25F5&sys_uptime=7265&sys_memfree=95256&sys_load=0.03&wifidog_uptime=61
  headers=[
    user-agent=WiFiDog 1.2.1
    host=192.168.1.109
  ]
]

GW 将系路由标识、负载情况传给 AuthSer，可以基于这些数据做监控。

login

request [
  URI=/wifidog/login/
  method=GET
  remoteAddr=192.168.1.109
  queryStr=gw_address=192.168.1.1&gw_port=2060&gw_id=100D7F6F25F5&ip=192.168.1.109&mac=64:00:6a:5d:0a:23&url=http%3A%2F%2Ffangstar.net%2F
  headers=[
    host=192.168.1.109:8910
    connection=keep-alive
    upgrade-insecure-requests=1
    user-agent=Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36
    accept=text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    accept-encoding=gzip, deflate, sdch
    accept-language=zh-CN,zh;q=0.8,da;q=0.6,en;q=0.4,id;q=0.2,ja;q=0.2,sq;q=0.2,zh-TW;q=0.2,en-US;q=0.2
    cookie=JSESSIONID=3AE20A3B0636E2F7DB7247AD055491FE
  ]
]

查询参数中的 url 是用户要访问的目标站点。

auth

request [
  URI=/wifidog/auth/
  method=GET
  remoteAddr=192.168.1.1
  queryStr=stage=login&ip=192.168.1.109&mac=64:00:6a:5d:0a:23&token=22&incoming=0&outgoing=0&gw_id=100D7F6F25F5
  headers=[
    user-agent=WiFiDog 1.2.1
    host=192.168.1.109
  ]
]

stage：第一次认证是 login，后续定时轮询是 counters
incoming/outgoing：用户流量

portal

request [
  URI=/wifidog/portal/
  method=GET
  remoteAddr=192.168.1.109
  queryStr=gw_id=100D7F6F25F5
  headers=[
    host=192.168.1.109:8910
    connection=keep-alive
    cache-control=max-age=0
    upgrade-insecure-requests=1
    user-agent=Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/52.0.2743.82 Safari/537.36
    accept=text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
    referer=http://192.168.1.109:8910/wifidog/login/?gw_address=192.168.1.1&gw_port=2060&gw_id=100D7F6F25F5&ip=192.168.1.109&mac=64:00:6a:5d:0a:23&url=http%3A%2F%2Ffangstar.net%2F
    accept-encoding=gzip, deflate, sdch
    accept-language=zh-CN,zh;q=0.8,da;q=0.6,en;q=0.4,id;q=0.2,ja;q=0.2,sq;q=0.2,zh-TW;q=0.2,en-US;q=0.2
    cookie=JSESSIONID=3AE20A3B0636E2F7DB7247AD055491FE
  ]
]

Java 实现

项目基于 Spring Boot 进行实现，用 maven 构建，主要代码如下：

/*
 * Copyright (c) 2016, fangstar.com
 *
 * All rights reserved.
 */
package net.fangstar.wifi.portal.controller;

import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import net.fangstar.wifi.portal.Server;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

/**
 * WiFiPortal 控制器.
 *
 * @author <a href="http://88250.b3log.org">Liang Ding</a>
 * @version 1.0.0.0, Aug 1, 2016
 * @since 1.0.0
 */
@Controller
@RequestMapping("/wifidog")
public class WiFiPortalController {

    /**
     * Logger.
     */
    private static final Logger LOGGER = LoggerFactory.getLogger(WiFiPortalController.class);

    /**
     * WiFiDog 网关地址.
     */
    private static final String GATEWAY_ADDR = Server.CONF.getString("gateway.addr");

    /**
     * Test token.
     */
    private static final String TOKEN = "22";

    @RequestMapping(value = "/login", method = RequestMethod.GET)
    public void showLogin(final HttpServletRequest request, final HttpServletResponse response) {
        logReq(request);

        try (final PrintWriter writer = response.getWriter()) {
            final HttpSession session = request.getSession();
            String visitURL = (String) session.getAttribute("url");
            if (StringUtils.isBlank(visitURL)) {
                visitURL = request.getParameter("url");
            }
            session.setAttribute("url", visitURL);

            writer.write("<html>    \n"
                    + "    <head>\n"
                    + "        <meta charset=\"UTF-8\">\n"
                    + "        <title>登录 - Portal</title>\n"
                    + "    </head>\n"
                    + "    <body>\n"
                    + "        <form action=\"http://192.168.1.109:8910/wifidog/login\" method=\"POST\">\n"
                    + "            <input type=\"text\" id=\"username\" name=\"username\" "
                    + "                   placeholder=\"Username\">\n"
                    + "            <input type=\"password\" id=\"password\" name=\"password\" "
                    + "                   placeholder=\"Password\">\n"
                    + "            <button type=\"submit\">登录</button>\n"
                    + "        </form>\n"
                    + "    </body>\n"
                    + "</html>");

            writer.flush();
        } catch (final Exception e) {
            LOGGER.error("Write response failed", e);
        }
    }

    @RequestMapping(value = "/login", method = RequestMethod.POST)
    public void login(final HttpServletRequest request, final HttpServletResponse response) {
        logReq(request);

        try {
            response.sendRedirect(GATEWAY_ADDR + "/wifidog/auth?token=" + TOKEN);
        } catch (final Exception e) {
            LOGGER.error("Write response failed", e);
        }
    }

    @RequestMapping(value = "/auth", method = {RequestMethod.POST, RequestMethod.GET})
    public void auth(final HttpServletRequest request, final HttpServletResponse response) {
        logReq(request);

        try (final PrintWriter writer = response.getWriter()) {
            final String token = request.getParameter("token");
            if (TOKEN.equals(token)) {
                writer.write("Auth: 1");
            } else {
                writer.write("Auth: 0");
            }

            writer.flush();
        } catch (final Exception e) {
            LOGGER.error("Write response failed", e);
        }
    }

    @RequestMapping(value = "portal", method = {RequestMethod.POST, RequestMethod.GET})
    public void portal(final HttpServletRequest request, final HttpServletResponse response) {
        logReq(request);

        try {
            final String visitURL = (String) request.getSession().getAttribute("url");

            response.sendRedirect(visitURL);
        } catch (final Exception e) {
            LOGGER.error("Write response failed", e);
        }
    }

    @RequestMapping(value = "ping", method = {RequestMethod.POST, RequestMethod.GET})
    public void ping(final HttpServletRequest request, final HttpServletResponse response) {
        logReq(request);

        try (final PrintWriter writer = response.getWriter()) {
            writer.write("Pong");
            writer.flush();
        } catch (final Exception e) {
            LOGGER.error("Write response failed", e);
        }
    }

    private void logReq(final HttpServletRequest request) {
        final StringBuilder reqBuilder = new StringBuilder("\nrequest [\n  URI=")
                .append(request.getRequestURI())
                .append("\n  method=").append(request.getMethod())
                .append("\n  remoteAddr=").append(request.getRemoteAddr());

        final String queryStr = request.getQueryString();
        if (StringUtils.isNotBlank(queryStr)) {
            reqBuilder.append("\n  queryStr=").append(queryStr);
        }

        final StringBuilder headerBuilder = new StringBuilder();
        final Enumeration<String> headerNames = request.getHeaderNames();
        while (headerNames.hasMoreElements()) {
            final String headerName = headerNames.nextElement();
            final String headerValue = request.getHeader(headerName);

            headerBuilder.append("    ").append(headerName).append("=").append(headerValue).append("\n");
        }
        headerBuilder.append("  ]");
        reqBuilder.append("\n  headers=[\n").append(headerBuilder.toString()).append("\n]");

        LOGGER.debug(reqBuilder.toString());
    }
}

完整项目代码已经在 GitHub 上开源，欢迎大家关注 wifidog-java-portal。

PS：欢迎加入开源技术 Q 群 13139268，让学习和分享成为一种习惯！