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fix: polynomial regex on uncontrolled input #3196

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Merged
stefannibrasil merged 2 commits into from
Jan 29, 2026
+8 −7
Merged

fix: polynomial regex on uncontrolled input #3196

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dee8b33
fix: add possessive quantifier to regex match for formatted strings
thdaraujo Jan 29, 2026
066f63a
fix: add possessive quantifier to regex match for regexify
thdaraujo Jan 29, 2026
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15 changes: 8 additions & 7 deletions lib/faker.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -95,12 +95,12 @@ def regexify(reg)
reg
.gsub(%r{^/?\^?}, '').gsub(%r{\$?/?$}, '') # Ditch the anchors
.gsub(/\{(\d+)\}/, '{\1,\1}').gsub('?', '{0,1}') # All {2} become {2,2} and ? become {0,1}
.gsub(/(\[[^\]]+\])\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # [12]{1,2} becomes [12] or [12][12]
.gsub(/(\([^)]+\))\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # (12|34){1,2} becomes (12|34) or (12|34)(12|34)
.gsub(/(\\?.)\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # A{1,2} becomes A or AA or \d{3} becomes \d\d\d
.gsub(/\((.*?)\)/) { |match| sample(match.gsub(/[()]/, '').split('|')) } # (this|that) becomes 'this' or 'that'
.gsub(/\[([^\]]+)\]/) { |match| match.gsub(/(\w-\w)/) { |range| sample(Array(Range.new(*range.split('-')))) } } # All A-Z inside of [] become C (or X, or whatever)
.gsub(/\[([^\]]+)\]/) { |_match| sample(Regexp.last_match(1).chars) } # All [ABC] become B (or A or C)
.gsub(/(\[[^\]]++\])\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # [12]{1,2} becomes [12] or [12][12]
.gsub(/(\([^)]++\))\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # (12|34){1,2} becomes (12|34) or (12|34)(12|34)
.gsub(/(\\?.)\{(\d+),(\d+)\}/) { |_match| Regexp.last_match(1) * sample(Array(Range.new(Regexp.last_match(2).to_i, Regexp.last_match(3).to_i))) } # A{1,2} becomes A or AA or \d{3} becomes \d\d\d
.gsub(/\((.*?)\)/) { |match| sample(match.gsub(/[()]/, '').split('|')) } # (this|that) becomes 'this' or 'that'
.gsub(/\[([^\]]++)\]/) { |match| match.gsub(/(\w-\w)/) { |range| sample(Array(Range.new(*range.split('-')))) } } # All A-Z inside of [] become C (or X, or whatever)
.gsub(/\[([^\]]++)\]/) { |_match| sample(Regexp.last_match(1).chars) } # All [ABC] become B (or A or C)
.gsub('\d') { |_match| sample(Numbers) }
.gsub('\w') { |_match| sample(Letters) }
end
Expand Down Expand Up @@ -133,7 +133,8 @@ def fetch_all(key)
# formatted translation: e.g., "#{first_name} #{last_name}".
def parse(key)
fetched = fetch(key)
parts = fetched.scan(/(\(?)#\{([A-Za-z]+\.)?([^}]+)\}([^#]+)?/).map do |prefix, kls, meth, etc|

parts = fetched.scan(/(\(?)#\{([A-Za-z]+\.)?([^}]+)\}([^#]++)?/).map do |prefix, kls, meth, etc|
# If the token had a class Prefix (e.g., Name.first_name)
# grab the constant, otherwise use self
cls = kls ? Faker.const_get(kls.chop) : self
Expand Down