92 lines
2.6 KiB
Ruby
92 lines
2.6 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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# An untrusted regular expression is any regexp containing patterns sourced
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# from user input.
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#
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# Ruby's built-in regular expression library allows patterns which complete in
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# exponential time, permitting denial-of-service attacks.
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#
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# Not all regular expression features are available in untrusted regexes, and
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# there is a strict limit on total execution time. See the RE2 documentation
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# at https://github.com/google/re2/wiki/Syntax for more details.
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class UntrustedRegexp
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require_dependency 're2'
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delegate :===, :source, to: :regexp
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def initialize(pattern, multiline: false)
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if multiline
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pattern = "(?m)#{pattern}"
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end
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@regexp = RE2::Regexp.new(pattern, log_errors: false)
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raise RegexpError.new(regexp.error) unless regexp.ok?
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end
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def replace_all(text, rewrite)
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RE2.GlobalReplace(text, regexp, rewrite)
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end
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def scan(text)
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matches = scan_regexp.scan(text).to_a
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matches.map!(&:first) if regexp.number_of_capturing_groups.zero?
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matches
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end
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def replace(text, rewrite)
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RE2.Replace(text, regexp, rewrite)
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end
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def ==(other)
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self.source == other.source
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end
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# Handles regular expressions with the preferred RE2 library where possible
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# via UntustedRegex. Falls back to Ruby's built-in regular expression library
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# when the syntax would be invalid in RE2.
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#
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# One difference between these is `(?m)` multi-line mode. Ruby regex enables
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# this by default, but also handles `^` and `$` differently.
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# See: https://www.regular-expressions.info/modifiers.html
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def self.with_fallback(pattern, multiline: false)
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UntrustedRegexp.new(pattern, multiline: multiline)
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rescue RegexpError
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Regexp.new(pattern)
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end
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def self.valid?(pattern)
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!!self.fabricate(pattern)
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rescue RegexpError
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false
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end
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def self.fabricate(pattern)
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matches = pattern.match(%r{^/(?<regexp>.+)/(?<flags>[ismU]*)$})
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raise RegexpError, 'Invalid regular expression!' if matches.nil?
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expression = matches[:regexp]
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flags = matches[:flags]
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expression.prepend("(?#{flags})") if flags.present?
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self.new(expression, multiline: false)
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end
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private
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attr_reader :regexp
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# RE2 scan operates differently to Ruby scan when there are no capture
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# groups, so work around it
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def scan_regexp
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@scan_regexp ||=
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if regexp.number_of_capturing_groups.zero?
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RE2::Regexp.new('(' + regexp.source + ')')
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else
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regexp
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end
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end
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end
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end
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