84 lines
2.2 KiB
Ruby
84 lines
2.2 KiB
Ruby
module Banzai
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module Filter
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# Sanitize HTML
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#
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# Extends HTML::Pipeline::SanitizationFilter with a custom whitelist.
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class SanitizationFilter < HTML::Pipeline::SanitizationFilter
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UNSAFE_PROTOCOLS = %w(data javascript vbscript).freeze
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def whitelist
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whitelist = super
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customize_whitelist(whitelist)
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whitelist
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end
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private
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def customized?(transformers)
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transformers.last.source_location[0] == __FILE__
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end
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def customize_whitelist(whitelist)
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# Only push these customizations once
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return if customized?(whitelist[:transformers])
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# Allow table alignment
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whitelist[:attributes]['th'] = %w(style)
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whitelist[:attributes]['td'] = %w(style)
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# Allow span elements
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whitelist[:elements].push('span')
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# Allow html5 details/summary elements
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whitelist[:elements].push('details')
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whitelist[:elements].push('summary')
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# Allow abbr elements with title attribute
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whitelist[:elements].push('abbr')
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whitelist[:attributes]['abbr'] = %w(title)
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# Allow any protocol in `a` elements...
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whitelist[:protocols].delete('a')
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# ...but then remove links with unsafe protocols
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whitelist[:transformers].push(self.class.remove_unsafe_links)
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# Remove `rel` attribute from `a` elements
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whitelist[:transformers].push(self.class.remove_rel)
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whitelist
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end
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class << self
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def remove_unsafe_links
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lambda do |env|
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node = env[:node]
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return unless node.name == 'a'
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return unless node.has_attribute?('href')
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begin
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uri = Addressable::URI.parse(node['href'])
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uri.scheme = uri.scheme.strip.downcase if uri.scheme
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node.remove_attribute('href') if UNSAFE_PROTOCOLS.include?(uri.scheme)
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rescue Addressable::URI::InvalidURIError
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node.remove_attribute('href')
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end
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end
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end
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def remove_rel
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lambda do |env|
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if env[:node_name] == 'a'
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env[:node].remove_attribute('rel')
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end
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end
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end
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end
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end
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end
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end
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