33 lines
1.0 KiB
Python
33 lines
1.0 KiB
Python
import re
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class UnsafePatternError(Exception):
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pass
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cached_patterns = {}
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def isSafePattern(pattern):
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if len(pattern) > 255:
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raise UnsafePatternError("Pattern too long: %s characters in %s" % (len(pattern), pattern))
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unsafe_pattern_match = re.search(r"[^\.][\*\{\+]", pattern) # Always should be "." before "*{+" characters to avoid ReDoS
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if unsafe_pattern_match:
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raise UnsafePatternError("Potentially unsafe part of the pattern: %s in %s" % (unsafe_pattern_match.group(0), pattern))
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repetitions = re.findall(r"\.[\*\{\+]", pattern)
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if len(repetitions) >= 10:
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raise UnsafePatternError("More than 10 repetitions of %s in %s" % (repetitions[0], pattern))
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return True
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def match(pattern, *args, **kwargs):
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cached_pattern = cached_patterns.get(pattern)
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if cached_pattern:
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return cached_pattern.match(*args, **kwargs)
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else:
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if isSafePattern(pattern):
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cached_patterns[pattern] = re.compile(pattern)
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return cached_patterns[pattern].match(*args, **kwargs)
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