1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
|
require "helper"
module Nokogiri
module HTML
class TestAttr < Nokogiri::TestCase
unless Nokogiri::VersionInfo.instance.libxml2? && Nokogiri::VersionInfo.instance.libxml2_using_system?
#
# libxml2 >= 2.9.2 fails to escape comments within some attributes. It
# wants to ensure these comments can be treated as "server-side includes",
# but as a result fails to ensure that serialization is well-formed,
# resulting in an opportunity for XSS injection of code into a final
# re-parsed document (presumably in a browser).
#
# the offending commit is:
#
# https://github.com/GNOME/libxml2/commit/960f0e2
#
# we'll test this by parsing the HTML, serializing it, then
# re-parsing it to ensure there isn't any ambiguity in the output
# that might allow code injection into a browser consuming
# "sanitized" output.
#
# complaints have been made upstream about this behavior, notably at
#
# https://bugzilla.gnome.org/show_bug.cgi?id=769760
#
# and multiple CVEs have been declared and fixed in downstream
# libraries as a result, a list is being kept up to date here:
#
# https://github.com/flavorjones/loofah/issues/144
#
[
#
# these tags and attributes are determined by the code at:
#
# https://git.gnome.org/browse/libxml2/tree/HTMLtree.c?h=v2.9.2#n714
#
{tag: "a", attr: "href"},
{tag: "div", attr: "href"},
{tag: "a", attr: "action"},
{tag: "div", attr: "action"},
{tag: "a", attr: "src"},
{tag: "div", attr: "src"},
{tag: "a", attr: "name"},
#
# note that div+name is _not_ affected by the libxml2 issue.
# but we test it anyway to ensure our logic isn't modifying
# attributes that don't need modifying.
#
{tag: "div", attr: "name", unescaped: true},
].each do |config|
define_method "test_uri_escaping_of_#{config[:attr]}_attr_in_#{config[:tag]}_tag" do
html = %{<#{config[:tag]} #{config[:attr]}='examp<!--" unsafeattr=unsafevalue()>-->le.com'>test</#{config[:tag]}>}
reparsed = HTML.fragment(HTML.fragment(html).to_html)
attributes = reparsed.at_css(config[:tag]).attribute_nodes
assert_equal [config[:attr]], attributes.collect(&:name)
if Nokogiri::VersionInfo.instance.libxml2?
if config[:unescaped]
#
# this attribute was emitted wrapped in single-quotes, so a double quote is A-OK.
# assert that this attribute's serialization is unaffected.
#
assert_equal %{examp<!--" unsafeattr=unsafevalue()>-->le.com}, attributes.first.value
else
#
# let's match the behavior in libxml < 2.9.2.
# test that this attribute's serialization is well-formed and sanitized.
#
assert_equal %{examp<!--%22%20unsafeattr=unsafevalue()>-->le.com}, attributes.first.value
end
else
#
# yay for consistency in javaland. move along, nothing to see here.
#
assert_equal %{examp<!--%22 unsafeattr=unsafevalue()>-->le.com}, attributes.first.value
end
end
end
end
end
end
end
|
