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bpo-40480 "fnmatch" exponential execution time (GH-19908)

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bpo-40480:  create different regexps in the presence of multiple `*`
patterns to prevent fnmatch() from taking exponential time.
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Tim Peters 2020-05-05 21:28:24 -05:00 • committed by GitHub
parent 96074de573
commit b9c46a2c2d
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3 changed files with 71 additions and 7 deletions
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17
Lib/test/test_fnmatch.py
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@ -45,6 +45,13 @@ class FnmatchTestCase(unittest.TestCase):
check('\nfoo', 'foo*', False)
check('\n', '*')
def test_slow_fnmatch(self):
check = self.check_match
check('a' * 50, '*a*a*a*a*a*a*a*a*a*a')
# The next "takes forever" if the regexp translation is
# straightforward. See bpo-40480.
check('a' * 50 + 'b', '*a*a*a*a*a*a*a*a*a*a', False)
def test_mix_bytes_str(self):
self.assertRaises(TypeError, fnmatch, 'test', b'*')
self.assertRaises(TypeError, fnmatch, b'test', '*')
@ -107,6 +114,16 @@ class TranslateTestCase(unittest.TestCase):
self.assertEqual(translate('[!x]'), r'(?s:[^x])\Z')
self.assertEqual(translate('[^x]'), r'(?s:[\^x])\Z')
self.assertEqual(translate('[x'), r'(?s:\[x)\Z')
# from the docs
self.assertEqual(translate('*.txt'), r'(?s:.*\.txt)\Z')
# squash consecutive stars
self.assertEqual(translate('*********'), r'(?s:.*)\Z')
self.assertEqual(translate('A*********'), r'(?s:A.*)\Z')
self.assertEqual(translate('*********A'), r'(?s:.*A)\Z')
self.assertEqual(translate('A*********?[?]?'), r'(?s:A.*.[?].)\Z')
# fancy translation to prevent exponential-time match failure
self.assertEqual(translate('**a*a****a'),
r'(?s:(?=(?P<g1>.*?a))(?P=g1)(?=(?P<g2>.*?a))(?P=g2).*a)\Z')
class FilterTestCase(unittest.TestCase):