#!/usr/bin/env python

# -*- coding:utf-8 -*-

from bs4 import BeautifulSoup

class XSSFilter(object):

    __instance = None

    def __init__(self):

        # XSS白名单

        self.valid_tags = {

            "font": ['color', 'size', 'face', 'style'],

            'b': [],

            'div': [],

            "span": [],

            "table": [

                'border', 'cellspacing', 'cellpadding'

            ],

            'th': [

                'colspan', 'rowspan'

            ],

            'td': [

                'colspan', 'rowspan'

            ],

            "a": ['href', 'target', 'name'],

            "img": ['src', 'alt', 'title'],

            'p': [

                'align'

            ],

            "pre": ['class'],

            "hr": ['class'],

            'strong': []

        }

    def __new__(cls, *args, **kwargs):

        """

        单例模式

        :param cls:

        :param args:

        :param kwargs:

        :return:

        """

        if not cls.__instance:

            obj = object.__new__(cls, *args, **kwargs)

            cls.__instance = obj

        return cls.__instance

    def process(self, content):

        soup = BeautifulSoup(content, 'html.parser')

        # 遍历所有HTML标签

        for tag in soup.find_all(recursive=True):

            # 判断标签名是否在白名单中

            if tag.name not in self.valid_tags:

                tag.hidden = True

                if tag.name not in ['html', 'body']:

                    tag.hidden = True

                    tag.clear()

                continue

            # 当前标签的所有属性白名单

            attr_rules = self.valid_tags[tag.name]

            keys = list(tag.attrs.keys())

            for key in keys:

                if key not in attr_rules:

                    del tag[key]

        return soup.decode()

if __name__ == '__main__':

    html = """<p class="title">

                        <b>The Dormouse's story</b>

                    </p>

                    <p class="story">

                        <div name='root'>

                            Once upon a time there were three little sisters; and their names were

                            <a href="http://example.com/elsie" class="sister c1" style='color:red;background-color:green;' id="link1"><!-- Elsie --></a>

                            <a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and

                            <a href="http://example.com/tillie" class="sister" id="link3">Tilffffffffffffflie</a>;

                            and they lived at the bottom of a well.

                            <script>alert(123)</script>

                        </div>

                    </p>

                    <p class="story">...</p>"""

    obj = XSSFilter()

    v = obj.process(html)

    print(v)