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Handle data URLs better #134

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Handle data URLs better #134

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ff9364e
add failing test
goromlagche Jun 8, 2022
97e67bc
handle data mediatypes better
goromlagche Jun 8, 2022
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7 changes: 7 additions & 0 deletions lib/rails/html/scrubbers.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,13 @@ def scrub_attribute(node, attr_node)
val_unescaped = CGI.unescapeHTML(attr_node.value).gsub(Loofah::HTML5::Scrub::CONTROL_CHARACTERS,'').downcase
if val_unescaped =~ /^[a-z0-9][-+.a-z0-9]*:/ && ! Loofah::HTML5::SafeList::ALLOWED_PROTOCOLS.include?(val_unescaped.split(Loofah::HTML5::SafeList::PROTOCOL_SEPARATOR)[0])
attr_node.remove
elsif val_unescaped.split(Loofah::HTML5::SafeList::PROTOCOL_SEPARATOR)[0] == "data"
# permit only allowed data mediatypes
mediatype = val_unescaped.split(Loofah::HTML5::SafeList::PROTOCOL_SEPARATOR)[1]
mediatype, _ = mediatype.split(";")[0..1] if mediatype
if mediatype && !Loofah::HTML5::SafeList::ALLOWED_URI_DATA_MEDIATYPES.include?(mediatype)
attr_node.remove
end
end
end
if Loofah::HTML5::SafeList::SVG_ATTR_VAL_ALLOWS_REF.include?(attr_name)
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10 changes: 10 additions & 0 deletions test/sanitizer_test.rb
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Expand Up @@ -515,6 +515,16 @@ def test_allow_data_attribute_if_requested
assert_equal %(<a data-foo="foo">foo</a>), safe_list_sanitize(text, attributes: ['data-foo'])
end

def test_sanitize_data_protocol
text = "- XSS\"><iframe src=\"data:text/html;base64,PHNjcmlwdD5hbGVydCgnWFNTJyk8L3NjcmlwdD4=\">- XSS\"><iframe src=\"data:application/vnd.wap.xhtml+xml;base64,PHg6c2NyaXB0IHhtbG5zOng9Imh0dHA6Ly93d3cudzMub3JnLzE5OTkveGh0bWwiPmFsZXJ0KGRvY3VtZW50LmRvbWFpbik8L3g6c2NyaXB0Pg==\">"

scope_allowed_tags %w(iframe) do
scope_allowed_attributes %w(src) do
assert_equal %(- XSS\"&gt;<iframe>- XSS\"&gt;<iframe></iframe></iframe>), safe_list_sanitize(text)
end
end
end

def test_uri_escaping_of_href_attr_in_a_tag_in_safe_list_sanitizer
skip if RUBY_VERSION < "2.3"

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