Commit 06a99cf7 authored by Robert Speicher's avatar Robert Speicher

Merge branch 'bug/svg_sanitizer' into 'master'

Improve SVG sanitizer to handle namespaced attributes

* Small refactor in the SVG sanitizer
* Enable already whitelisted namespaced attributes to be allowed
* Disable `xlink:href`to reference any external resource

Fixes #18100 

See merge request !4427
parents 8d243f9b 7c87dac5
Pipeline #3504514 passed with stages
in 2176 minutes and 7 seconds
......@@ -13,6 +13,7 @@ v 8.9.0 (unreleased)
- Fix issue todo not remove when leave project !4150 (Long Nguyen)
- Allow customisable text on the 'nearly there' page after a user signs up
- Bump recaptcha gem to 3.0.0 to remove deprecated stoken support
- Fix SVG sanitizer to allow more elements
- Allow forking projects with restricted visibility level
- Added descriptions to notification settings dropdown
- Improve note validation to prevent errors when creating invalid note via API
......
......@@ -12,23 +12,45 @@ module Gitlab
def scrub(node)
unless Whitelist::ALLOWED_ELEMENTS.include?(node.name)
node.unlink
else
node.attributes.each do |attr_name, attr|
valid_attributes = Whitelist::ALLOWED_ATTRIBUTES[node.name]
unless valid_attributes && valid_attributes.include?(attr_name)
if Whitelist::ALLOWED_DATA_ATTRIBUTES_IN_ELEMENTS.include?(node.name) &&
attr_name.start_with?('data-')
# Arbitrary data attributes are allowed. Verify that the attribute
# is a valid data attribute.
attr.unlink unless attr_name =~ DATA_ATTR_PATTERN
else
attr.unlink
end
return
end
valid_attributes = Whitelist::ALLOWED_ATTRIBUTES[node.name]
return unless valid_attributes
node.attribute_nodes.each do |attr|
attr_name = attribute_name_with_namespace(attr)
if valid_attributes.include?(attr_name)
attr.unlink if unsafe_href?(attr)
else
# Arbitrary data attributes are allowed.
unless allows_data_attribute?(node) && data_attribute?(attr)
attr.unlink
end
end
end
end
def attribute_name_with_namespace(attr)
if attr.namespace
"#{attr.namespace.prefix}:#{attr.name}"
else
attr.name
end
end
def allows_data_attribute?(node)
Whitelist::ALLOWED_DATA_ATTRIBUTES_IN_ELEMENTS.include?(node.name)
end
def unsafe_href?(attr)
attribute_name_with_namespace(attr) == 'xlink:href' && !attr.value.start_with?('#')
end
def data_attribute?(attr)
attr.name.start_with?('data-') && attr.name =~ DATA_ATTR_PATTERN && attr.namespace.nil?
end
end
end
end
......
require 'spec_helper'
describe Gitlab::Sanitizers::SVG do
let(:scrubber) { Gitlab::Sanitizers::SVG::Scrubber.new }
let(:namespace) { double(Nokogiri::XML::Namespace, prefix: 'xlink', href: 'http://www.w3.org/1999/xlink') }
let(:namespaced_attr) { double(Nokogiri::XML::Attr, name: 'href', namespace: namespace, value: '#awesome_id') }
describe '.clean' do
let(:input_svg_path) { File.join(Rails.root, 'spec', 'fixtures', 'unsanitized.svg') }
let(:data) { open(input_svg_path).read }
let(:sanitized_svg_path) { File.join(Rails.root, 'spec', 'fixtures', 'sanitized.svg') }
let(:sanitized) { open(sanitized_svg_path).read }
it 'delegates sanitization to scrubber' do
expect_any_instance_of(Gitlab::Sanitizers::SVG::Scrubber).to receive(:scrub).at_least(:once)
described_class.clean(data)
end
it 'returns sanitized data' do
expect(described_class.clean(data)).to eq(sanitized)
end
end
context 'scrubber' do
describe '#scrub' do
let(:invalid_element) { double(Nokogiri::XML::Node, name: 'invalid', value: 'invalid') }
let(:invalid_attribute) { double(Nokogiri::XML::Attr, name: 'invalid', namespace: nil) }
let(:valid_element) { double(Nokogiri::XML::Node, name: 'use') }
it 'removes an invalid element' do
expect(invalid_element).to receive(:unlink)
scrubber.scrub(invalid_element)
end
it 'removes an invalid attribute' do
allow(valid_element).to receive(:attribute_nodes) { [invalid_attribute] }
expect(invalid_attribute).to receive(:unlink)
scrubber.scrub(valid_element)
end
it 'accepts valid element' do
allow(valid_element).to receive(:attribute_nodes) { [namespaced_attr] }
expect(valid_element).not_to receive(:unlink)
scrubber.scrub(valid_element)
end
it 'accepts valid namespaced attributes' do
allow(valid_element).to receive(:attribute_nodes) { [namespaced_attr] }
expect(namespaced_attr).not_to receive(:unlink)
scrubber.scrub(valid_element)
end
end
describe '#attribute_name_with_namespace' do
it 'returns name with prefix when attribute is namespaced' do
expect(scrubber.attribute_name_with_namespace(namespaced_attr)).to eq('xlink:href')
end
end
describe '#unsafe_href?' do
let(:unsafe_attr) { double(Nokogiri::XML::Attr, name: 'href', namespace: namespace, value: 'http://evilsite.example.com/random.svg') }
it 'returns true if href attribute is an external url' do
expect(scrubber.unsafe_href?(unsafe_attr)).to be_truthy
end
it 'returns false if href atttribute is an internal reference' do
expect(scrubber.unsafe_href?(namespaced_attr)).to be_falsey
end
end
describe '#data_attribute?' do
let(:data_attr) { double(Nokogiri::XML::Attr, name: 'data-gitlab', namespace: nil, value: 'gitlab is awesome') }
let(:namespaced_attr) { double(Nokogiri::XML::Attr, name: 'data-gitlab', namespace: namespace, value: 'gitlab is awesome') }
let(:other_attr) { double(Nokogiri::XML::Attr, name: 'something', namespace: nil, value: 'content') }
it 'returns true if is a valid data attribute' do
expect(scrubber.data_attribute?(data_attr)).to be_truthy
end
it 'returns false if attribute is namespaced' do
expect(scrubber.data_attribute?(namespaced_attr)).to be_falsey
end
it 'returns false if not a data attribute' do
expect(scrubber.data_attribute?(other_attr)).to be_falsey
end
end
end
end
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