69 lines
1.6 KiB
Python
69 lines
1.6 KiB
Python
# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
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# Licensed to PSF under a Contributor Agreement.
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"""Safely evaluate Python string literals without using eval()."""
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import re
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from typing import Dict, Match, Text
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simple_escapes: Dict[Text, Text] = {
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"a": "\a",
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"b": "\b",
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"f": "\f",
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"n": "\n",
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"r": "\r",
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"t": "\t",
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"v": "\v",
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"'": "'",
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'"': '"',
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"\\": "\\",
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}
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def escape(m: Match[Text]) -> Text:
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all, tail = m.group(0, 1)
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assert all.startswith("\\")
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esc = simple_escapes.get(tail)
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if esc is not None:
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return esc
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if tail.startswith("x"):
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hexes = tail[1:]
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if len(hexes) < 2:
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raise ValueError("invalid hex string escape ('\\%s')" % tail)
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try:
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i = int(hexes, 16)
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except ValueError:
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raise ValueError("invalid hex string escape ('\\%s')" % tail) from None
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else:
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try:
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i = int(tail, 8)
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except ValueError:
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raise ValueError("invalid octal string escape ('\\%s')" % tail) from None
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return chr(i)
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def evalString(s: Text) -> Text:
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assert s.startswith("'") or s.startswith('"'), repr(s[:1])
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q = s[0]
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if s[:3] == q * 3:
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q = q * 3
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assert s.endswith(q), repr(s[-len(q) :])
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assert len(s) >= 2 * len(q)
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s = s[len(q) : -len(q)]
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return re.sub(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3})", escape, s)
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def test() -> None:
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for i in range(256):
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c = chr(i)
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s = repr(c)
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e = evalString(s)
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if e != c:
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print(i, c, s, e)
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if __name__ == "__main__":
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test()
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