我有一个包含文字和HTML的字符串。我想删除或禁用某些HTML标记，例如<script>，同时允许其他标记，以便我可以安全地在网页上呈现它。我有一个允许的标签列表，如何处理字符串以删除任何其他标签？
答案 0 :(得分：54)
使用lxml.html.clean！这很简单！
from lxml.html.clean import clean_html
print clean_html(html)
假设以下html：
html = '''\
<html>
<head>
<script type="text/javascript" src="evil-site"></script>
<link rel="alternate" type="text/rss" src="evil-rss">
<style>
body {background-image: url(javascript:do_evil)};
div {color: expression(evil)};
</style>
</head>
<body onload="evil_function()">
<!-- I am interpreted for EVIL! -->
<a href="javascript:evil_function()">a link</a>
<a href="#" onclick="evil_function()">another link</a>
<p onclick="evil_function()">a paragraph</p>
<div style="display: none">secret EVIL!</div>
<object> of EVIL! </object>
<iframe src="evil-site"></iframe>
<form action="evil-site">
Password: <input type="password" name="password">
</form>
<blink>annoying EVIL!</blink>
<a href="evil-site">spam spam SPAM!</a>
<image src="evil!">
</body>
</html>'''
结果......
<html>
<body>
<div>
<style>/* deleted */</style>
<a href="">a link</a>
<a href="#">another link</a>
<p>a paragraph</p>
<div>secret EVIL!</div>
of EVIL!
Password:
annoying EVIL!
<a href="evil-site">spam spam SPAM!</a>
<img src="evil!">
</div>
</body>
</html>
您可以自定义要清理的元素等等。
答案 1 :(得分：41)
以下是使用BeautifulSoup的简单解决方案：
from bs4 import BeautifulSoup
VALID_TAGS = ['strong', 'em', 'p', 'ul', 'li', 'br']
def sanitize_html(value):
soup = BeautifulSoup(value)
for tag in soup.findAll(True):
if tag.name not in VALID_TAGS:
tag.hidden = True
return soup.renderContents()
如果您想删除无效标记的内容，请将tag.extract()替换为tag.hidden。
答案 2 :(得分：37)
通过Beautiful Soup的上述解决方案将无效。你可能能够使用Beautiful Soup来破解它们之外的东西，因为Beautiful Soup可以访问解析树。有一段时间，我想我会尽力解决问题，但这是一个为期一周的项目，我很快就没有一个免费的一周。
只是具体而言，Beautiful Soup不仅会抛出上述代码无法捕获的一些解析错误的异常;但是，还有很多非常真实的XSS漏洞没有被发现，例如：
<<script>script> alert("Haha, I hacked your page."); </</script>script>
您可以做的最好的事情是将<元素删除为<，禁止所有 HTML，然后使用像Markdown这样的受限子集正确呈现格式。特别是，您还可以使用正则表达式返回并重新引入HTML的常见位。这是流程的样子，粗略地说：
_lt_ = re.compile('<')
_tc_ = '~(lt)~' # or whatever, so long as markdown doesn't mangle it.
_ok_ = re.compile(_tc_ + '(/?(?:u|b|i|em|strong|sup|sub|p|br|q|blockquote|code))>', re.I)
_sqrt_ = re.compile(_tc_ + 'sqrt>', re.I) #just to give an example of extending
_endsqrt_ = re.compile(_tc_ + '/sqrt>', re.I) #html syntax with your own elements.
_tcre_ = re.compile(_tc_)
def sanitize(text):
text = _lt_.sub(_tc_, text)
text = markdown(text)
text = _ok_.sub(r'<\1>', text)
text = _sqrt_.sub(r'√<span style="text-decoration:overline;">', text)
text = _endsqrt_.sub(r'</span>', text)
return _tcre_.sub('<', text)
我尚未测试该代码，因此可能存在错误。但是你看到了一般的想法：你必须将所有HTML列入黑名单，然后才将白名单列入白名单。
答案 3 :(得分：25)
这是我在自己的项目中使用的内容。 acceptable_elements / attributes来自feedparser，BeautifulSoup可以完成工作。
from BeautifulSoup import BeautifulSoup
acceptable_elements = ['a', 'abbr', 'acronym', 'address', 'area', 'b', 'big',
'blockquote', 'br', 'button', 'caption', 'center', 'cite', 'code', 'col',
'colgroup', 'dd', 'del', 'dfn', 'dir', 'div', 'dl', 'dt', 'em',
'font', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'hr', 'i', 'img',
'ins', 'kbd', 'label', 'legend', 'li', 'map', 'menu', 'ol',
'p', 'pre', 'q', 's', 'samp', 'small', 'span', 'strike',
'strong', 'sub', 'sup', 'table', 'tbody', 'td', 'tfoot', 'th',
'thead', 'tr', 'tt', 'u', 'ul', 'var']
acceptable_attributes = ['abbr', 'accept', 'accept-charset', 'accesskey',
'action', 'align', 'alt', 'axis', 'border', 'cellpadding', 'cellspacing',
'char', 'charoff', 'charset', 'checked', 'cite', 'clear', 'cols',
'colspan', 'color', 'compact', 'coords', 'datetime', 'dir',
'enctype', 'for', 'headers', 'height', 'href', 'hreflang', 'hspace',
'id', 'ismap', 'label', 'lang', 'longdesc', 'maxlength', 'method',
'multiple', 'name', 'nohref', 'noshade', 'nowrap', 'prompt',
'rel', 'rev', 'rows', 'rowspan', 'rules', 'scope', 'shape', 'size',
'span', 'src', 'start', 'summary', 'tabindex', 'target', 'title', 'type',
'usemap', 'valign', 'value', 'vspace', 'width']
def clean_html( fragment ):
while True:
soup = BeautifulSoup( fragment )
removed = False
for tag in soup.findAll(True): # find all tags
if tag.name not in acceptable_elements:
tag.extract() # remove the bad ones
removed = True
else: # it might have bad attributes
# a better way to get all attributes?
for attr in tag._getAttrMap().keys():
if attr not in acceptable_attributes:
del tag[attr]
# turn it back to html
fragment = unicode(soup)
if removed:
# we removed tags and tricky can could exploit that!
# we need to reparse the html until it stops changing
continue # next round
return fragment
一些小测试，以确保其行为正确：
tests = [ #text should work
('<p>this is text</p>but this too', '<p>this is text</p>but this too'),
# make sure we cant exploit removal of tags
('<<script></script>script> alert("Haha, I hacked your page."); <<script></script>/script>', ''),
# try the same trick with attributes, gives an Exception
('<div on<script></script>load="alert("Haha, I hacked your page.");">1</div>', Exception),
# no tags should be skipped
('<script>bad</script><script>bad</script><script>bad</script>', ''),
# leave valid tags but remove bad attributes
('<a href="good" onload="bad" onclick="bad" alt="good">1</div>', '<a href="good" alt="good">1</a>'),
]
for text, out in tests:
try:
res = clean_html(text)
assert res == out, "%s => %s != %s" % (text, res, out)
except out, e:
assert isinstance(e, out), "Wrong exception %r" % e
答案 4 :(得分：22)
Bleach会做得更好。它建立在html5lib上，可以投入生产。查看bleack.clean功能的文档。它的默认配置会转义不安全的代码，例如<script>，同时允许有用的代码，例如<a>。
import bleach
bleach.clean("<script>evil</script> <a href='http://example.com'>example</a>")
# '<script>evil</script> <a href="http://example.com">example</a>'
答案 5 :(得分：10)
我修改了Bryan的solution with BeautifulSoup以解决problem raised by Chris Drost问题。有点粗糙，但做的工作：
from BeautifulSoup import BeautifulSoup, Comment
VALID_TAGS = {'strong': [],
'em': [],
'p': [],
'ol': [],
'ul': [],
'li': [],
'br': [],
'a': ['href', 'title']
}
def sanitize_html(value, valid_tags=VALID_TAGS):
soup = BeautifulSoup(value)
comments = soup.findAll(text=lambda text:isinstance(text, Comment))
[comment.extract() for comment in comments]
# Some markup can be crafted to slip through BeautifulSoup's parser, so
# we run this repeatedly until it generates the same output twice.
newoutput = soup.renderContents()
while 1:
oldoutput = newoutput
soup = BeautifulSoup(newoutput)
for tag in soup.findAll(True):
if tag.name not in valid_tags:
tag.hidden = True
else:
tag.attrs = [(attr, value) for attr, value in tag.attrs if attr in valid_tags[tag.name]]
newoutput = soup.renderContents()
if oldoutput == newoutput:
break
return newoutput
修改：已更新，以支持有效的属性。
答案 6 :(得分：3)
我使用FilterHTML。它很简单，允许您定义一个控制良好的白名单，擦除URL，甚至匹配正则表达式的属性值或每个属性具有自定义过滤功能。如果小心使用它可能是一个安全的解决方案。以下是自述文件的简化示例：
import FilterHTML # only allow: # <a> tags with valid href URLs # <img> tags with valid src URLs and measurements whitelist = { 'a': { 'href': 'url', 'target': [ '_blank', '_self' ], 'class': [ 'button' ] }, 'img': { 'src': 'url', 'width': 'measurement', 'height': 'measurement' }, } filtered_html = FilterHTML.filter_html(unfiltered_html, whitelist)
答案 7 :(得分：2)
您可以使用html5lib，它使用白名单进行清理。
一个例子：
import html5lib
from html5lib import sanitizer, treebuilders, treewalkers, serializer
def clean_html(buf):
"""Cleans HTML of dangerous tags and content."""
buf = buf.strip()
if not buf:
return buf
p = html5lib.HTMLParser(tree=treebuilders.getTreeBuilder("dom"),
tokenizer=sanitizer.HTMLSanitizer)
dom_tree = p.parseFragment(buf)
walker = treewalkers.getTreeWalker("dom")
stream = walker(dom_tree)
s = serializer.htmlserializer.HTMLSerializer(
omit_optional_tags=False,
quote_attr_values=True)
return s.render(stream)
答案 8 :(得分：1)
我更喜欢lxml.html.clean解决方案，例如nosklo points out。这里也删除一些空标记：
from lxml import etree
from lxml.html import clean, fromstring, tostring
remove_attrs = ['class']
remove_tags = ['table', 'tr', 'td']
nonempty_tags = ['a', 'p', 'span', 'div']
cleaner = clean.Cleaner(remove_tags=remove_tags)
def squeaky_clean(html):
clean_html = cleaner.clean_html(html)
# now remove the useless empty tags
root = fromstring(clean_html)
context = etree.iterwalk(root) # just the end tag event
for action, elem in context:
clean_text = elem.text and elem.text.strip(' \t\r\n')
if elem.tag in nonempty_tags and \
not (len(elem) or clean_text): # no children nor text
elem.getparent().remove(elem)
continue
elem.text = clean_text # if you want
# and if you also wanna remove some attrs:
for badattr in remove_attrs:
if elem.attrib.has_key(badattr):
del elem.attrib[badattr]
return tostring(root)