连上Wi-Fi 热点自动弹窗的实现方法

小程序：扫一扫查出行
【扫一扫了解最新限行尾号】
复制小程序

当我们连上某个热点，会自动弹出登录窗口的专业名称叫做： Captive portal

原理，实现方式有三种

1 ： dns 跳转，在热点上面实现配置，把所有dns请求返回都配置为： 服务器地址 ；服务器有404跳转或者DNS url跳转，跳转到的界面即为自动弹出登录界面；

2 : http跳转，对所有的http请求返回302或者301或者404跳转，跳转到的界面即为自动弹出登录界面；

3 : ip跳转，既把所有的ip包里的目标地址改为认证服务器，然后在认证服务器上做404跳转

第三种实现起来比较麻烦，我们要实现第一种和第二种 Captive portal；

配置本地服务器

使用NodeJS搭建一个本地WEB服务器，服务器端口为默认的80，无论访问服务器的任意地址都有正常200返回，app.use函数是精华..，然后使用node app.js启动服务器：

var express = require('express');

var path = require('path');

var favicon = require('serve-favicon');

var logger = require('morgan');

var cookieParser = require('cookie-parser');

var bodyParser = require('body-parser');

var http = require("http");

var index = require('./routes/index');

var app = express();

app.set('views', path.join(__dirname, 'views'));

app.use(bodyParser.json());

app.use(bodyParser.urlencoded({ extended: false }));

app.use('/', index);

app.use(cookieParser());

app.use(express.static(path.join(__dirname, 'public')));

//该函数是关键 ， 如论用户访问任何页面 ， 都会重定向到本地index.html文件

app.use(function(req, res, next) {

  res.status = ;

  res.redirect('/index.html');

});

http.createServer(app).listen();

使用HTTP跳转

本机环境是kali系统，外加一个usb网卡，使用以下代码实现热点：

#!/bin/bash

## quick and dirty AP with hostapd and dnsmasq

## exit properly with ctrl-c

echo "Exit this script with Ctrl-C and it will attempt to clean up properly."

if [ -z $ ]; then

   echo -n "SSID: "

   read ssid

else

   ssid=$

fi

# get wep key

function get_wep_key() {

    echo -n "WEP Key [must be exactly 5 or 13 ascii characters]: "

    read wep_key

    if [[  $wep_key =~ ^[a-zA-Z0-]{}$ ]] ; then

       echo "Key accepted"

   elif [[  $wep_key =~ ^[a-zA-Z0-]{}$ ]] ; then

        echo "Key accepted"

    else

        echo "WEP key must be exactly 5 or 13 characters"

        get_wep_key

    fi

}

# get mac

function get_mac() {

    echo -n "Enter MAC address in the following format AB:CD:EF:12:34:56: "

    read new_mac

    if [[  $new_mac =~ ^[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}$ ]] ; then

        macchanger --mac=$new_mac wlan0

   else

        echo "MAC Address format not correct."

        get_mac

    fi

}

# ask for WEP

echo -n "Do you want WEP enabled? [y/n]: "

read wep

case $wep in

    y*)

        get_wep_key

    ;;

    *)

    ;;

esac

# ask for MAC change

echo -n "Do you want to change your MAC? [y/n]: "

read changemac

case $changemac in

    y*)

        echo -n "Custom MAC? [y/n]: "

      read random_mac

        case $random_mac in

            y*)

                get_mac

            ;;

            n*)

                macchanger -r wlan0

            ;;

            *)

                echo "Invalid choice, keeping current MAC address."

            ;;

        esac

    ;;

   n*)

    ;;

esac

# install packages if need be

if [ $(dpkg-query -W -f='${Status}' dnsmasq >/dev/null | grep -c "ok installed") -eq  ];

then

  apt-get install dnsmasq

fi

if [ $(dpkg-query -W -f='${Status}' hostapd >/dev/null | grep -c "ok installed") -eq  ];

then

  apt-get install hostapd

fi

# trap control c

trap ctrl_c INT

function ctrl_c() {

   echo "wlan0 managed mode"

   iwconfig wlan0 mode managed

   echo "downing wlan0"

   ifconfig wlan0 down

   echo "flushing firewall"

   iptables -F

   iptables -F -t nat

   echo "resetting wlan0 mac"

   macchanger -p wlan0

   kill - `cat /tmp/dnsmasq.run`

}

## script begins

# stop and disable services

service hostapd stop

service dnsmasq stop

pkill - dnsmasq

pkill - hostapd

# bring up wlan0

nmcli radio wifi off

rfkill unblock wlan

iwconfig wlan0 mode monitor

ifconfig wlan0 10.0.0.1/ up

# forwarding and nat

sysctl -w net.ipv4.conf.all.route_localnet=

iptables -t nat -I PREROUTING -p tcp --dport  -j DNAT --to 10.0.0.1:

# dns masq conf

cat > /tmp/dnsmasq.conf <<!

bind-interfaces

interface=wlan0

dhcp-range=10.0.0.2,10.0.0.254

!

# hostapd conf

cat > /tmp/hostapd.conf<<!

interface=wlan0

driver=nl80211

ssid=${ssid}

hw_mode=g

channel=

!

# if WEP key, add to hostapd conf

if [[ -n $wep_key ]]; then echo -e "wep_default_key=0\nwep_key0=\"${wep_key}\"" >> /tmp/hostapd.conf; fi

# run dnsmasq and hostapd

dnsmasq --pid-file=/tmp/dnsmasq.run -C /tmp/dnsmasq.conf

hostapd /tmp/hostapd.conf

以上代码中：

sysctl -w net.ipv4.conf.all.route_localnet=1
iptables -t nat -I PREROUTING -p tcp --dport 80 -j DNAT --to 10.0.0.1:80

是本例子的精华所在，第一句的意思是指所有的ipv4请求全部重定向到本地，第二句的意思为所有准备访问本地80端口的机器，全部指向到10.0.0.1的80端口，而我们本地的80端口为我们部署的服务器，这样即可实现 Captive portal

使用DNS跳转

在本地网关搭建DNS服务器，局域网内部的所有DNS请求全部返回10.0.0.1

sh文件代码如下：

#!/bin/bash

## quick and dirty AP with hostapd and dnsmasq

## exit properly with ctrl-c

echo "Exit this script with Ctrl-C and it will attempt to clean up properly."

if [ -z $ ]; then

   echo -n "SSID: "

   read ssid

else

   ssid=$

fi

# get wep key

function get_wep_key() {

    echo -n "WEP Key [must be exactly 5 or 13 ascii characters]: "

    read wep_key

    if [[  $wep_key =~ ^[a-zA-Z0-]{}$ ]] ; then

       echo "Key accepted"

   elif [[  $wep_key =~ ^[a-zA-Z0-]{}$ ]] ; then

        echo "Key accepted"

    else

        echo "WEP key must be exactly 5 or 13 characters"

        get_wep_key

    fi

}

# get mac

function get_mac() {

    echo -n "Enter MAC address in the following format AB:CD:EF:12:34:56: "

    read new_mac

    if [[  $new_mac =~ ^[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}:[a-fA-F0-]{}$ ]] ; then

        macchanger --mac=$new_mac wlan0

   else

        echo "MAC Address format not correct."

        get_mac

    fi

}

# ask for WEP

echo -n "Do you want WEP enabled? [y/n]: "

read wep

case $wep in

    y*)

        get_wep_key

    ;;

    *)

    ;;

esac

# ask for MAC change

echo -n "Do you want to change your MAC? [y/n]: "

read changemac

case $changemac in

    y*)

        echo -n "Custom MAC? [y/n]: "

      read random_mac

        case $random_mac in

            y*)

                get_mac

            ;;

            n*)

                macchanger -r wlan0

            ;;

            *)

                echo "Invalid choice, keeping current MAC address."

            ;;

        esac

    ;;

   n*)

    ;;

esac

# install packages if need be

if [ $(dpkg-query -W -f='${Status}' dnsmasq >/dev/null | grep -c "ok installed") -eq  ];

then

  apt-get install dnsmasq

fi

if [ $(dpkg-query -W -f='${Status}' hostapd >/dev/null | grep -c "ok installed") -eq  ];

then

  apt-get install hostapd

fi

# trap control c

trap ctrl_c INT

function ctrl_c() {

   echo "wlan0 managed mode"

   iwconfig wlan0 mode managed

   echo "downing wlan0"

   ifconfig wlan0 down

   echo "flushing firewall"

   iptables -F

   iptables -F -t nat

   echo "resetting wlan0 mac"

   macchanger -p wlan0

   kill - `cat /tmp/dnsmasq.run`

}

## script begins

# stop and disable services

service hostapd stop

service dnsmasq stop

pkill - dnsmasq

pkill - hostapd

# bring up wlan0

nmcli radio wifi off

rfkill unblock wlan

iwconfig wlan0 mode monitor

ifconfig wlan0 10.0.0.1/ up

#dhcp

iptables --policy INPUT ACCEPT

iptables --policy FORWARD ACCEPT

iptables --policy OUTPUT ACCEPT

iptables -F

iptables -t nat -F

iptables -t nat -A PREROUTING -i wlan0 -p udp --dport  -j DNAT --to 10.0.0.1

# dns masq conf

cat > /tmp/dnsmasq.conf <<!

bind-interfaces

interface=wlan0

address=/#/10.0.0.1

dhcp-range=10.0.0.2,10.0.0.254

dhcp-option=,10.0.0.1 #DNS

dhcp-option=,10.0.0.1 #Gateway

dhcp-option=,"http://wpad.example.com/wpad.dat\n" #WPAD

dhcp-authoritative

!

# hostapd conf

cat > /tmp/hostapd.conf<<!

interface=wlan0

driver=nl80211

ssid=${ssid}

hw_mode=g

channel=

!

# if WEP key, add to hostapd conf

if [[ -n $wep_key ]]; then echo -e "wep_default_key=0\nwep_key0=\"${wep_key}\"" >> /tmp/hostapd.conf; fi

# run dnsmasq and hostapd

dnsmasq --pid-file=/tmp/dnsmasq.run -C /tmp/dnsmasq.conf

hostapd /tmp/hostapd.conf

其中以下代码尤为重要：

bind-interfaces
interface=wlan0
address=/#/10.0.0.1 《＝＝这个配置说明为所有dns请求都返回10.0.0.1
dhcp-range=10.0.0.2,10.0.0.254 《＝＝客户机器IP池
dhcp-option=6,10.0.0.1 #DNS 《＝＝本地DNS服务器
dhcp-option=3,10.0.0.1 #Gateway 《＝＝本地网关
dhcp-option=252,"http://wpad.example.com/wpad.dat\n" #WPAD
dhcp-authoritative