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Allow boolean and empty attributes for certain node types #278

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Allow boolean and empty attributes for certain node types #278

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148 changes: 148 additions & 0 deletions lib/loofah/html5/safelist.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -229,6 +229,154 @@ module SafeList
"use",
])

ACCEPTABLE_EMPTY_ATTRIBUTES = {
"*" => Set.new([
"title",
]),
"area" => Set.new([
"alt",
]),
"audio" => Set.new([
"src",
]),
"base" => Set.new([
"href",
]),
"img" => Set.new([
"alt",
]),
"input" => Set.new([
"value",
"placeholder",
]),
"li" => Set.new([
"value",
]),
"link" => Set.new([
"href",
]),
"meter" => Set.new([
"value",
]),
"option" => Set.new([
"value",
]),
"progress" => Set.new([
"value",
]),
"source" => Set.new([
"src",
]),
"textarea" => Set.new([
"placeholder",
]),
"track" => Set.new([
"default",
]),
}

ACCEPTABLE_BOOLEAN_ATTRIBUTES = {
"*" => Set.new([
"hidden",
"contenteditable",
"draggable",
"spellcheck",
"translate",
]),
"a" => Set.new([
"download",
]),
"area" => Set.new([
"download",
]),
"audio" => Set.new([
"autoplay",
"controls",
"loop",
"muted",
]),
"button" => Set.new([
"autofocus",
"disabled",
"formnovalidate",
]),
"details" => Set.new([
"open",
]),
"fieldset" => Set.new([
"disabled",
]),
"form" => Set.new([
"novalidate",
]),
"iframe" => Set.new([
"allowfullscreen",
"seamless",
]),
"img" => Set.new([
"alt",
"ismap",
]),
"input" => Set.new([
"autofocus",
"checked",
"disabled",
"multiple",
"readonly",
"required",
"formnovalidate",
]),
"ol" => Set.new([
"reversed",
]),
"optgroup" => Set.new([
"disabled",
]),
"option" => Set.new([
"disabled",
"selected",
]),
"select" => Set.new([
"autofocus",
"disabled",
"multiple",
"required",
]),
"style" => Set.new([
"scoped",
]),
"table" => Set.new([
"sortable",
]),
"td" => Set.new([
"nowrap",
]),
"th" => Set.new([
"nowrap",
]),
"textarea" => Set.new([
"autofocus",
"disabled",
"readonly",
"required",
]),
"track" => Set.new([
"default",
]),
"video" => Set.new([
"autoplay",
"controls",
"loop",
"muted",
"playsinline",
]),
}

ACCEPTABLE_BOOLEAN_OR_EMPTY_ATTRIBUTES =
ACCEPTABLE_BOOLEAN_ATTRIBUTES.merge(ACCEPTABLE_EMPTY_ATTRIBUTES) do |_, a, b|
a + b
end

ACCEPTABLE_ATTRIBUTES = Set.new([
"abbr",
"accept",
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12 changes: 8 additions & 4 deletions lib/loofah/html5/scrub.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,9 @@ def scrub_attributes(node)
next
end

unless SafeList::ALLOWED_ATTRIBUTES.include?(attr_name)
unless SafeList::ALLOWED_ATTRIBUTES.include?(attr_name) ||
SafeList::ACCEPTABLE_BOOLEAN_OR_EMPTY_ATTRIBUTES[node.name]&.include?(attr_node.name) ||
SafeList::ACCEPTABLE_BOOLEAN_OR_EMPTY_ATTRIBUTES["*"].include?(attr_node.name)
attr_node.remove
next
end
Expand All @@ -56,9 +58,11 @@ def scrub_attributes(node)
scrub_css_attribute(node)

node.attribute_nodes.each do |attr_node|
if attr_node.value !~ /[^[:space:]]/ && attr_node.name !~ DATA_ATTRIBUTE_NAME
node.remove_attribute(attr_node.name)
end
next if attr_node.value =~ /[^[:space:]]/ || attr_node.name =~ DATA_ATTRIBUTE_NAME ||
SafeList::ACCEPTABLE_BOOLEAN_OR_EMPTY_ATTRIBUTES[node.name]&.include?(attr_node.name) ||
SafeList::ACCEPTABLE_BOOLEAN_OR_EMPTY_ATTRIBUTES["*"].include?(attr_node.name)

node.remove_attribute(attr_node.name)
end

force_correct_attribute_escaping!(node)
Expand Down
18 changes: 18 additions & 0 deletions test/assets/testdata_sanitizer_tests1.dat
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Original file line number Diff line number Diff line change
Expand Up @@ -526,5 +526,23 @@
"name": "attributes_with_embedded_quotes_II",
"input": "<img src=notthere.jpg\"\"onerror=\"alert(2) />",
"libxml": "<img src='notthere.jpg%22%22onerror=%22alert(2)'>"
},

{
"name": "empty_attributes_1",
"input": "<option value=\"\">Empty Value<script>alert(1)</script></option>",
"libxml": "<option value=''>Empty Value&lt;script&gt;alert(1)&lt;/script&gt;</option>"
},

{
"name": "empty_attributes_2",
"input": "<option value=\"\">Empty Value</script></option>",
"libxml": "<option value=''>Empty Value</option>"
},

{
"name": "empty_attributes_3",
"input": "<option value=\"\" download=\"foo-bar\">Empty Value</option>",
"libxml": "<option value=''>Empty Value</option>"
}
]
8 changes: 8 additions & 0 deletions test/html5/test_sanitizer.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,14 @@ def test_should_allow_contenteditable
check_sanitization(input, output)
end

def test_boolean_attributes
input = "<video controls download></video>"
expected_html5 = "<video controls=''></video>"
output_html5 = sanitize_html5(input).tr('"', "'")

assert_equal(expected_html5, output_html5)
end

##
## libxml2 downcases attributes, so this is moot.
##
Expand Down