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import base64
import gzip
import io
import unittest
import warnings
import lxml.html
from lxml_html_clean import AmbiguousURLWarning, Cleaner, clean_html, LXMLHTMLCleanWarning
from .utils import peak_memory_usage
class CleanerTest(unittest.TestCase):
def test_allow_tags(self):
html = """
<html>
<head>
</head>
<body>
<p>some text</p>
<table>
<tr>
<td>hello</td><td>world</td>
</tr>
<tr>
<td>hello</td><td>world</td>
</tr>
</table>
<img>
</body>
</html>
"""
html_root = lxml.html.document_fromstring(html)
cleaner = Cleaner(
remove_unknown_tags = False,
allow_tags = ['table', 'tr', 'td'])
result = cleaner.clean_html(html_root)
self.assertEqual(12-5+1, len(list(result.iter())))
def test_allow_and_remove(self):
with self.assertRaises(ValueError):
Cleaner(allow_tags=['a'], remove_unknown_tags=True)
def test_remove_unknown_tags(self):
html = """<div><bun>lettuce, tomato, veggie patty</bun></div>"""
clean_html = """<div>lettuce, tomato, veggie patty</div>"""
cleaner = Cleaner(remove_unknown_tags=True)
result = cleaner.clean_html(html)
self.assertEqual(
result,
clean_html,
msg="Unknown tags not removed. Got: %s" % result,
)
def test_safe_attrs_included(self):
html = """<p><span style="color: #00ffff;">Cyan</span></p>"""
safe_attrs=set(lxml.html.defs.safe_attrs)
safe_attrs.add('style')
cleaner = Cleaner(
safe_attrs_only=True,
safe_attrs=safe_attrs)
result = cleaner.clean_html(html)
self.assertEqual(html, result)
def test_safe_attrs_excluded(self):
html = """<p><span style="color: #00ffff;">Cyan</span></p>"""
expected = """<p><span>Cyan</span></p>"""
safe_attrs=set()
cleaner = Cleaner(
safe_attrs_only=True,
safe_attrs=safe_attrs)
result = cleaner.clean_html(html)
self.assertEqual(expected, result)
def test_clean_invalid_root_tag(self):
# only testing that cleaning with invalid root tags works at all
s = lxml.html.fromstring('parent <invalid tag>child</another>')
self.assertEqual('parent child', clean_html(s).text_content())
s = lxml.html.fromstring('<invalid tag>child</another>')
self.assertEqual('child', clean_html(s).text_content())
def test_clean_with_comments(self):
html = """<p><span style="color: #00ffff;">Cy<!-- xx -->an</span><!-- XXX --></p>"""
s = lxml.html.fragment_fromstring(html)
self.assertEqual(
b'<p><span>Cyan</span></p>',
lxml.html.tostring(clean_html(s)))
self.assertEqual(
'<p><span>Cyan</span></p>',
clean_html(html))
cleaner = Cleaner(comments=False)
result = cleaner.clean_html(s)
self.assertEqual(
b'<p><span>Cy<!-- xx -->an</span><!-- XXX --></p>',
lxml.html.tostring(result))
self.assertEqual(
'<p><span>Cy<!-- xx -->an</span><!-- XXX --></p>',
cleaner.clean_html(html))
def test_sneaky_noscript_in_style(self):
# This gets parsed as <noscript> -> <style>"...</noscript>..."</style>
# thus passing the </noscript> through into the output.
html = '<noscript><style><a title="</noscript><img src=x onerror=alert(1)>">'
s = lxml.html.fragment_fromstring(html)
self.assertEqual(
b'<noscript><style>/* deleted */</style></noscript>',
lxml.html.tostring(clean_html(s)))
def test_sneaky_js_in_math_style(self):
# This gets parsed as <math> -> <style>"..."</style>
# thus passing any tag/script/whatever content through into the output.
html = '<math><style><img src=x onerror=alert(1)></style></math>'
s = lxml.html.fragment_fromstring(html)
self.assertEqual(
b'<math><style>/* deleted */</style></math>',
lxml.html.tostring(clean_html(s)))
def test_sneaky_js_in_style_comment_math_svg(self):
for tag in "svg", "math":
html = f'<{tag}><style>p {{color: red;}}/*<img src onerror=alert(origin)>*/h2 {{color: blue;}}</style></{tag}>'
s = lxml.html.fragment_fromstring(html)
expected = f'<{tag}><style>p {{color: red;}}/* deleted */h2 {{color: blue;}}</style></{tag}>'.encode()
self.assertEqual(
expected,
lxml.html.tostring(clean_html(s)))
def test_sneaky_js_in_style_comment_noscript(self):
html = '<noscript><style>p {{color: red;}}/*</noscript><img src onerror=alert(origin)>*/h2 {{color: blue;}}</style></noscript>'
s = lxml.html.fragment_fromstring(html)
self.assertEqual(
b'<noscript><style>p {{color: red;}}/* deleted */h2 {{color: blue;}}</style></noscript>',
lxml.html.tostring(clean_html(s)))
def test_sneaky_import_in_style(self):
# Prevent "@@importimport" -> "@import" replacement etc.
style_codes = [
"@@importimport(extstyle.css)",
"@ @ import import(extstyle.css)",
"@ @ importimport(extstyle.css)",
"@@ import import(extstyle.css)",
"@ @import import(extstyle.css)",
"@@importimport()",
"@@importimport() ()",
"@/* ... */import()",
"@im/* ... */port()",
"@ @import/* ... */import()",
"@ /* ... */ import()",
]
for style_code in style_codes:
html = '<style>%s</style>' % style_code
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
b'<style>/* deleted */</style>',
cleaned,
"%s -> %s" % (style_code, cleaned))
def test_sneaky_schemes_in_style(self):
style_codes = [
"javasjavascript:cript:",
"javascriptjavascript::",
"javascriptjavascript:: :",
"vbjavascript:cript:",
]
for style_code in style_codes:
html = '<style>%s</style>' % style_code
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
b'<style>/* deleted */</style>',
cleaned,
"%s -> %s" % (style_code, cleaned))
def test_sneaky_urls_in_style(self):
style_codes = [
"url(data:image/svg+xml;base64,...)",
"url(javasjavascript:cript:)",
"url(javasjavascript:cript: ::)",
"url(vbjavascript:cript:)",
"url(vbjavascript:cript: :)",
]
for style_code in style_codes:
html = '<style>%s</style>' % style_code
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
b'<style>url()</style>',
cleaned,
"%s -> %s" % (style_code, cleaned))
def test_svg_data_links(self):
# Remove SVG images with potentially insecure content.
svg = b'<svg onload="alert(123)" />'
gzout = io.BytesIO()
f = gzip.GzipFile(fileobj=gzout, mode='wb')
f.write(svg)
f.close()
svgz = gzout.getvalue()
svg_b64 = base64.b64encode(svg).decode('ASCII')
svgz_b64 = base64.b64encode(svgz).decode('ASCII')
urls = [
"data:image/svg+xml;base64," + svg_b64,
"data:image/svg+xml-compressed;base64," + svgz_b64,
]
for url in urls:
html = '<img src="%s">' % url
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
b'<img src="">',
cleaned,
"%s -> %s" % (url, cleaned))
def test_image_data_links(self):
data = b'123'
data_b64 = base64.b64encode(data).decode('ASCII')
urls = [
"data:image/jpeg;base64," + data_b64,
"data:image/apng;base64," + data_b64,
"data:image/png;base64," + data_b64,
"data:image/gif;base64," + data_b64,
"data:image/webp;base64," + data_b64,
"data:image/bmp;base64," + data_b64,
"data:image/tiff;base64," + data_b64,
"data:image/x-icon;base64," + data_b64,
]
for url in urls:
html = '<img src="%s">' % url
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
html.encode("UTF-8"),
cleaned,
"%s -> %s" % (url, cleaned))
def test_image_data_links_in_style(self):
data = b'123'
data_b64 = base64.b64encode(data).decode('ASCII')
urls = [
"data:image/jpeg;base64," + data_b64,
"data:image/apng;base64," + data_b64,
"data:image/png;base64," + data_b64,
"data:image/gif;base64," + data_b64,
"data:image/webp;base64," + data_b64,
"data:image/bmp;base64," + data_b64,
"data:image/tiff;base64," + data_b64,
"data:image/x-icon;base64," + data_b64,
]
for url in urls:
html = '<style> url(%s) </style>' % url
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(clean_html(s))
self.assertEqual(
html.encode("UTF-8"),
cleaned,
"%s -> %s" % (url, cleaned))
def test_image_data_links_in_inline_style(self):
safe_attrs = set(lxml.html.defs.safe_attrs)
safe_attrs.add('style')
cleaner = Cleaner(
safe_attrs_only=True,
safe_attrs=safe_attrs)
data = b'123'
data_b64 = base64.b64encode(data).decode('ASCII')
url = "url(data:image/jpeg;base64,%s)" % data_b64
styles = [
"background: %s" % url,
"background: %s; background-image: %s" % (url, url),
]
for style in styles:
html = '<div style="%s"></div>' % style
s = lxml.html.fragment_fromstring(html)
cleaned = lxml.html.tostring(cleaner.clean_html(s))
self.assertEqual(
html.encode("UTF-8"),
cleaned,
"%s -> %s" % (style, cleaned))
def test_formaction_attribute_in_button_input(self):
# The formaction attribute overrides the form's action and should be
# treated as a malicious link attribute
html = ('<form id="test"><input type="submit" formaction="javascript:alert(1)"></form>'
'<button form="test" formaction="javascript:alert(1)">X</button>')
expected = ('<div><form id="test"><input type="submit" formaction=""></form>'
'<button form="test" formaction="">X</button></div>')
cleaner = Cleaner(
forms=False,
safe_attrs_only=False,
)
self.assertEqual(
expected,
cleaner.clean_html(html))
def test_host_whitelist_slash_type_confusion(self):
# Regression test: Accidentally passing a string when a 1-tuple was intended
# creates a host_whitelist of the empty string; a malformed triple-slash
# URL has an "empty host" according to urlsplit, and `"" in ""` passes.
# So, don't allow user to accidentally pass a string for host_whitelist.
html = '<div><iframe src="https:///evil.com/page"></div>'
with self.assertRaises(TypeError) as exc:
# If this were the intended `("example.com",)` the expected
# output would be '<div></div>'
Cleaner(frames=False, host_whitelist=("example.com")).clean_html(html)
self.assertEqual(("Expected a collection, got str: host_whitelist='example.com'",), exc.exception.args)
def test_host_whitelist_valid(self):
# Frame with valid hostname in src is allowed.
html = '<div><iframe src="https://example.com/page"></iframe></div>'
expected = '<div><iframe src="https://example.com/page"></iframe></div>'
cleaner = Cleaner(frames=False, host_whitelist=["example.com"])
self.assertEqual(expected, cleaner.clean_html(html))
def test_host_whitelist_invalid(self):
html = '<div><iframe src="https://evil.com/page"></iframe></div>'
expected = '<div></div>'
cleaner = Cleaner(frames=False, host_whitelist=["example.com"])
self.assertEqual(expected, cleaner.clean_html(html))
def test_host_whitelist_sneaky_userinfo(self):
# Regression test: Don't be fooled by hostname and colon in userinfo.
html = '<div><iframe src="https://example.com:@evil.com/page"></iframe></div>'
expected = '<div></div>'
cleaner = Cleaner(frames=False, host_whitelist=["example.com"])
self.assertEqual(expected, cleaner.clean_html(html))
def test_ascii_control_chars_removed(self):
html = """<a href="java\x1bscript:alert()">Link</a>"""
expected = """<a href="">Link</a>"""
cleaner = Cleaner()
self.assertEqual(expected, cleaner.clean_html(html))
def test_ascii_control_chars_removed_from_bytes(self):
html = b"""<a href="java\x1bscript:alert()">Link</a>"""
expected = b"""<a href="">Link</a>"""
cleaner = Cleaner()
self.assertEqual(expected, cleaner.clean_html(html))
def test_memory_usage_many_elements_with_long_tails(self):
comment = "<!-- foo bar baz -->\n"
empty_line = "\t" * 10 + "\n"
element = comment + empty_line * 10
content = element * 5_000
html = f"<html>{content}</html>"
cleaner = Cleaner()
mem = peak_memory_usage(cleaner.clean_html, html)
self.assertTrue(mem < 10, f"Used {mem} MiB memory, expected at most 10 MiB")
def test_possibly_invalid_url_with_whitelist(self):
cleaner = Cleaner(host_whitelist=['google.com'])
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always")
result = cleaner.clean_html(r"<p><iframe src='http://example.com:\@google.com'> </iframe></p>")
self.assertGreaterEqual(len(w), 1)
self.assertIs(w[-1].category, AmbiguousURLWarning)
self.assertTrue(issubclass(w[-1].category, LXMLHTMLCleanWarning))
self.assertIn("impossible to parse the hostname", str(w[-1].message))
self.assertNotIn("google.com", result)
self.assertNotIn("example.com", result)
def test_possibly_invalid_url_without_whitelist(self):
cleaner = Cleaner()
with warnings.catch_warnings(record=True) as w:
warnings.simplefilter("always")
result = cleaner.clean_html(r"<p><iframe src='http://example.com:\@google.com'> </iframe></p>")
self.assertEqual(len(w), 0)
self.assertNotIn("google.com", result)
self.assertNotIn("example.com", result)
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