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test_malicious_html.rb
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/
test_malicious_html.rb
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# encoding: utf-8
require_relative 'common'
# Miscellaneous attempts to sneak maliciously crafted HTML past Sanitize. Many
# of these are courtesy of (or inspired by) the OWASP XSS Filter Evasion Cheat
# Sheet.
#
# https://www.owasp.org/index.php/XSS_Filter_Evasion_Cheat_Sheet
describe 'Malicious HTML' do
make_my_diffs_pretty!
parallelize_me!
before do
@s = Sanitize.new(Sanitize::Config::RELAXED)
end
describe 'comments' do
it 'should not allow script injection via conditional comments' do
@s.fragment(%[<!--[if gte IE 4]>\n<script>alert('XSS');</script>\n<![endif]-->]).
must_equal ''
end
end
describe 'interpolation (ERB, PHP, etc.)' do
it 'should escape ERB-style tags' do
@s.fragment('<% naughty_ruby_code %>').
must_equal '<% naughty_ruby_code %>'
@s.fragment('<%= naughty_ruby_code %>').
must_equal '<%= naughty_ruby_code %>'
end
it 'should remove PHP-style tags' do
@s.fragment('<? naughtyPHPCode(); ?>').
must_equal ''
@s.fragment('<?= naughtyPHPCode(); ?>').
must_equal ''
end
end
describe '<body>' do
it 'should not be possible to inject JS via a malformed event attribute' do
@s.document('<html><head></head><body onload!#$%&()*~+-_.,:;?@[/|\\]^`=alert("XSS")></body></html>').
must_equal "<html><head></head><body></body></html>"
end
end
describe '<iframe>' do
it 'should not be possible to inject an iframe using an improperly closed tag' do
@s.fragment(%[<iframe src=http://ha.ckers.org/scriptlet.html <]).
must_equal ''
end
end
describe '<img>' do
it 'should not be possible to inject JS via an unquoted <img> src attribute' do
@s.fragment("<img src=javascript:alert('XSS')>").must_equal '<img>'
end
it 'should not be possible to inject JS using grave accents as <img> src delimiters' do
@s.fragment("<img src=`javascript:alert('XSS')`>").must_equal '<img>'
end
it 'should not be possible to inject <script> via a malformed <img> tag' do
@s.fragment('<img """><script>alert("XSS")</script>">').
must_equal '<img>">'
end
it 'should not be possible to inject protocol-based JS' do
@s.fragment('<img src=javascript:alert('XSS')>').
must_equal '<img>'
@s.fragment('<img src=javascript:alert('XSS')>').
must_equal '<img>'
@s.fragment('<img src=javascript:alert('XSS')>').
must_equal '<img>'
# Encoded tab character.
@s.fragment(%[<img src="jav	ascript:alert('XSS');">]).
must_equal '<img>'
# Encoded newline.
@s.fragment(%[<img src="jav
ascript:alert('XSS');">]).
must_equal '<img>'
# Encoded carriage return.
@s.fragment(%[<img src="jav
ascript:alert('XSS');">]).
must_equal '<img>'
# Null byte.
@s.fragment(%[<img src=java\0script:alert("XSS")>]).
must_equal '<img>'
# Spaces plus meta char.
@s.fragment(%[<img src="  javascript:alert('XSS');">]).
must_equal '<img>'
# Mixed spaces and tabs.
@s.fragment(%[<img src="j\na v\tascript://alert('XSS');">]).
must_equal '<img>'
end
it 'should not be possible to inject protocol-based JS via whitespace' do
@s.fragment(%[<img src="jav\tascript:alert('XSS');">]).
must_equal '<img>'
end
it 'should not be possible to inject JS using a half-open <img> tag' do
@s.fragment(%[<img src="javascript:alert('XSS')"]).
must_equal ''
end
end
describe '<script>' do
it 'should not be possible to inject <script> using a malformed non-alphanumeric tag name' do
@s.fragment(%[<script/xss src="http://ha.ckers.org/xss.js">alert(1)</script>]).
must_equal ''
end
it 'should not be possible to inject <script> via extraneous open brackets' do
@s.fragment(%[<<script>alert("XSS");//<</script>]).
must_equal '<'
end
end
# libxml2 >= 2.9.2 doesn't escape comments within some attributes, in an
# attempt to preserve server-side includes. This can result in XSS since an
# unescaped double quote can allow an attacker to inject a non-whitelisted
# attribute. Sanitize works around this by implementing its own escaping for
# affected attributes.
#
# The relevant libxml2 code is here:
# <https://github.com/GNOME/libxml2/commit/960f0e275616cadc29671a218d7fb9b69eb35588>
describe 'unsafe libxml2 server-side includes in attributes' do
using_unpatched_libxml2 = (Nokogiri::VERSION_INFO["libxml"]["source"] == "system")
tag_configs = [
{
tag_name: 'a',
escaped_attrs: %w[ action href src name ],
unescaped_attrs: []
},
{
tag_name: 'div',
escaped_attrs: %w[ action href src ],
unescaped_attrs: %w[ name ]
}
]
before do
@s = Sanitize.new({
elements: %w[ a div ],
attributes: {
all: %w[ action href src name ]
}
})
end
tag_configs.each do |tag_config|
tag_name = tag_config[:tag_name]
tag_config[:escaped_attrs].each do |attr_name|
input = %[<#{tag_name} #{attr_name}='examp<!--" onmouseover=alert(1)>-->le.com'>foo</#{tag_name}>]
it 'should escape unsafe characters in attributes' do
skip "behavior should only exist in nokogiri's patched libxml" if using_unpatched_libxml2
# This uses Nokogumbo's HTML-compliant serializer rather than
# libxml2's.
@s.fragment(input).
must_equal(%[<#{tag_name} #{attr_name}="examp<!--%22%20onmouseover=alert(1)>-->le.com">foo</#{tag_name}>])
# This uses the not-quite-standards-compliant libxml2 serializer via
# Nokogiri, so the output may be a little different as of Nokogiri
# 1.10.2 when using Nokogiri's vendored libxml2 due to this patch:
# https://github.com/sparklemotion/nokogiri/commit/4852e43cb6039e26d8c51af78621e539cbf46c5d
fragment = Nokogiri::HTML.fragment(input)
@s.node!(fragment)
fragment.to_html.
must_equal(%[<#{tag_name} #{attr_name}="examp<!--%22%20onmouseover=alert(1)>-->le.com">foo</#{tag_name}>])
end
it 'should round-trip to the same output' do
output = @s.fragment(input)
@s.fragment(output).must_equal(output)
end
end
tag_config[:unescaped_attrs].each do |attr_name|
input = %[<#{tag_name} #{attr_name}='examp<!--" onmouseover=alert(1)>-->le.com'>foo</#{tag_name}>]
it 'should not escape characters unnecessarily' do
skip "behavior should only exist in nokogiri's patched libxml" if using_unpatched_libxml2
# This uses Nokogumbo's HTML-compliant serializer rather than
# libxml2's.
@s.fragment(input).
must_equal(%[<#{tag_name} #{attr_name}="examp<!--" onmouseover=alert(1)>-->le.com">foo</#{tag_name}>])
# This uses the not-quite-standards-compliant libxml2 serializer via
# Nokogiri, so the output may be a little different as of Nokogiri
# 1.10.2 when using Nokogiri's vendored libxml2 due to this patch:
# https://github.com/sparklemotion/nokogiri/commit/4852e43cb6039e26d8c51af78621e539cbf46c5d
fragment = Nokogiri::HTML.fragment(input)
@s.node!(fragment)
fragment.to_html.
must_equal(%[<#{tag_name} #{attr_name}='examp<!--" onmouseover=alert(1)>-->le.com'>foo</#{tag_name}>])
end
it 'should round-trip to the same output' do
output = @s.fragment(input)
@s.fragment(output).must_equal(output)
end
end
end
end
end