127 lines
3.4 KiB
Ruby
127 lines
3.4 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module WikiPages
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class FrontMatterParser
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FEATURE_FLAG = :wiki_front_matter
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# We limit the maximum length of text we are prepared to parse as YAML, to
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# avoid exploitations and attempts to consume memory and CPU. We allow for:
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# - a title line
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# - a "slugs:" line
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# - and up to 50 slugs
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#
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# This limit does not take comments into account.
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MAX_SLUGS = 50
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SLUG_LINE_LENGTH = (4 + Gitlab::WikiPages::MAX_DIRECTORY_BYTES + 1 + Gitlab::WikiPages::MAX_TITLE_BYTES)
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MAX_FRONT_MATTER_LENGTH = (8 + Gitlab::WikiPages::MAX_TITLE_BYTES) + 7 + (SLUG_LINE_LENGTH * MAX_SLUGS)
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ParseError = Class.new(StandardError)
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class Result
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attr_reader :front_matter, :content, :reason, :error
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def initialize(content:, front_matter: {}, reason: nil, error: nil)
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@content = content
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@front_matter = front_matter.freeze
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@reason = reason
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@error = error
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end
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end
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# @param [String] wiki_content
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# @param [FeatureGate] feature_gate The scope for feature availability
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def initialize(wiki_content, feature_gate)
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@wiki_content = wiki_content
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@feature_gate = feature_gate
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end
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def self.enabled?(gate = nil)
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Feature.enabled?(FEATURE_FLAG, gate)
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end
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def parse
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return empty_result unless enabled? && wiki_content.present?
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return empty_result(block.error) unless block.valid?
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Result.new(front_matter: block.data, content: strip_front_matter_block)
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rescue ParseError => error
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empty_result(:parse_error, error)
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end
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class Block
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include Gitlab::Utils::StrongMemoize
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def initialize(delim = nil, lang = '', text = nil)
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@lang = lang&.downcase.presence || Gitlab::FrontMatter::DELIM_LANG[delim]
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@text = text&.strip!
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end
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def data
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@data ||= YAML.safe_load(text, symbolize_names: true)
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rescue Psych::DisallowedClass, Psych::SyntaxError => error
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raise ParseError, error.message
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end
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def valid?
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error.nil?
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end
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def error
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strong_memoize(:error) { no_match? || too_long? || not_yaml? || not_mapping? }
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end
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private
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attr_reader :lang, :text
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def no_match?
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:no_match if text.nil?
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end
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def not_yaml?
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:not_yaml if lang != 'yaml'
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end
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def too_long?
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:too_long if text.size > MAX_FRONT_MATTER_LENGTH
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end
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def not_mapping?
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:not_mapping unless data.is_a?(Hash)
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end
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end
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private
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attr_reader :wiki_content, :feature_gate
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def empty_result(reason = nil, error = nil)
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Result.new(content: wiki_content, reason: reason, error: error)
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end
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def enabled?
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self.class.enabled?(feature_gate)
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end
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def block
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@block ||= parse_front_matter_block
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end
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def parse_front_matter_block
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if match = Gitlab::FrontMatter::PATTERN_UNTRUSTED_REGEX.match(wiki_content)
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Block.new(match[:delim], match[:lang], match[:front_matter])
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else
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Block.new
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end
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end
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def strip_front_matter_block
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Gitlab::FrontMatter::PATTERN_UNTRUSTED_REGEX.replace_gsub(wiki_content) do
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''
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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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