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fix: reject underscores in BIP32 path indexes #860

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fix: reject underscores in BIP32 path indexes #860

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0191bdd
fix: reject underscores in BIP32 path indexes
SashaMIT Sep 25, 2026
cee9680
fix: reject non-ASCII digits and out-of-range BIP32 indexes
SashaMIT Oct 9, 2026
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20 changes: 15 additions & 5 deletions hwilib/key.py
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Original file line number Diff line number Diff line change
Expand Up @@ -335,11 +335,21 @@ def _parse_path(nstr: str, allow_multipath: bool) -> List[List[int]]:

def str_to_harden(x: str) -> int:
if x.startswith("-"):
return H_(abs(int(x)))
elif x.endswith(("h", "'")):
return H_(int(x[:-1]))
else:
return int(x)
body = x[1:]
if not (body.isascii() and body.isdigit()):
raise ValueError(f"Invalid BIP32 path component: {x}")
index = int(body)
if index >= HARDENED_FLAG:
raise ValueError(f"Invalid BIP32 path component: {x}")
return H_(abs(index))
harden = x.endswith(("h", "'"))
body = x[:-1] if harden else x
if not (body.isascii() and body.isdigit()):
raise ValueError(f"Invalid BIP32 path component: {x}")
index = int(body)
if index >= HARDENED_FLAG:
raise ValueError(f"Invalid BIP32 path component: {x}")
return H_(index) if harden else index

def parse_index(x: str, seen_multipath: bool) -> Tuple[List[int], bool]:
if x.startswith("<"):
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14 changes: 14 additions & 0 deletions test/test_bip32.py
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Expand Up @@ -122,6 +122,20 @@ def test_deriv_path(self):
xprv_der = par_xprv.derive_pub_path(path)
self.assertEqual(xprv_der.to_string(), child_xpub)

def test_parse_path_rejects_underscore(self):
with self.assertRaises(ValueError):
parse_path("m/1_0")
self.assertEqual(parse_path("m/10"), [10])
self.assertEqual(parse_path("m/1h"), [0x80000001])

def test_parse_path_rejects_non_ascii_digits_and_out_of_range(self):
for path in ("m/١", "m/１h", "m/2147483648", "m/2147483648h", "m/4294967296"):
with self.subTest(path=path):
with self.assertRaises(ValueError):
parse_path(path)
self.assertEqual(parse_path("m/2147483647"), [2147483647])
self.assertEqual(parse_path("m/2147483647h"), [2147483647 | 0x80000000])


if __name__ == "__main__":
unittest.main()