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164 lines
5.6 KiB
164 lines
5.6 KiB
# Copyright (c) 2017, 2020 Pieter Wuille
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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# THE SOFTWARE.
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"""Reference implementation for Bech32/Bech32m and segwit addresses."""
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from micropython import const
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from trezorcrypto import bech32
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from typing import TYPE_CHECKING
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bech32_decode = bech32.decode # reexported
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if TYPE_CHECKING:
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from enum import IntEnum
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from typing import Sequence, TypeVar
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A = TypeVar("A")
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B = TypeVar("B")
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C = TypeVar("C")
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# usage: OptionalTuple[int, list[int]] is either (None, None) or (someint, somelist)
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# but not (None, somelist)
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OptionalTuple2 = tuple[None, None] | tuple[A, B]
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else:
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IntEnum = object
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class Encoding(IntEnum):
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"""Enumeration type to list the various supported encodings."""
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BECH32 = const(1)
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BECH32M = const(2)
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CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
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_BECH32M_CONST = const(0x2BC830A3)
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def bech32_polymod(values: list[int]) -> int:
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"""Internal function that computes the Bech32 checksum."""
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generator = [0x3B6A_57B2, 0x2650_8E6D, 0x1EA1_19FA, 0x3D42_33DD, 0x2A14_62B3]
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chk = 1
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for value in values:
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top = chk >> 25
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chk = (chk & 0x1FF_FFFF) << 5 ^ value
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for i in range(5):
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chk ^= generator[i] if ((top >> i) & 1) else 0
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return chk
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def bech32_hrp_expand(hrp: str) -> list[int]:
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"""Expand the HRP into values for checksum computation."""
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return [ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp]
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def _bech32_create_checksum(hrp: str, data: list[int], spec: Encoding) -> list[int]:
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"""Compute the checksum values given HRP and data."""
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values = bech32_hrp_expand(hrp) + data
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const = _BECH32M_CONST if spec == Encoding.BECH32M else 1
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polymod = bech32_polymod(values + [0, 0, 0, 0, 0, 0]) ^ const
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return [(polymod >> 5 * (5 - i)) & 31 for i in range(6)]
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def bech32_encode(hrp: str, data: list[int], spec: Encoding) -> str:
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"""Compute a Bech32 string given HRP and data values."""
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combined = data + _bech32_create_checksum(hrp, data, spec)
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return hrp + "1" + "".join([CHARSET[d] for d in combined])
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def convertbits(
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data: Sequence[int], frombits: int, tobits: int, arbitrary_input: bool = True
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) -> list[int]:
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"""General power-of-2 base conversion.
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The `arbitrary_input` parameter specifies what happens when the total length
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of input bits is not a multiple of `tobits`.
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If True (default), the overflowing bits are zero-padded to the right.
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If False, the input must must be a valid output of `convertbits()` in the opposite
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direction.
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Namely:
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(a) the overflow must only be the zero padding
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(b) length of the overflow is less than `frombits`, meaning that there is no
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additional all-zero `frombits`-sized group at the end.
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If both conditions hold, the all-zero overflow is discarded.
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Otherwise a ValueError is raised.
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"""
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acc = 0
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bits = 0
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ret = []
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maxv = (1 << tobits) - 1
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max_acc = (1 << (frombits + tobits - 1)) - 1
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for value in data:
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if value < 0 or (value >> frombits):
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raise ValueError # input value does not match `frombits` size
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acc = ((acc << frombits) | value) & max_acc
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bits += frombits
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while bits >= tobits:
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bits -= tobits
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ret.append((acc >> bits) & maxv)
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if arbitrary_input:
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if bits:
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# append remaining bits, zero-padded from right
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ret.append((acc << (tobits - bits)) & maxv)
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elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
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# (1) either there is a superfluous group at end of input, and/or
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# (2) the remainder is nonzero
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raise ValueError
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return ret
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def decode(hrp: str, addr: str) -> OptionalTuple2[int, bytes]:
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"""Decode a segwit address."""
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from trezorcrypto import bech32
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try:
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hrpgot, data, spec = bech32.decode(addr)
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decoded = bytes(convertbits(data[1:], 5, 8, False))
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except ValueError:
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return (None, None)
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if hrpgot != hrp:
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return (None, None)
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if not 2 <= len(decoded) <= 40:
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return (None, None)
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if data[0] > 16:
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return (None, None)
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if data[0] == 0 and len(decoded) not in (20, 32):
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return (None, None)
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if (
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data[0] == 0
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and spec != Encoding.BECH32
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or data[0] != 0
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and spec != Encoding.BECH32M
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):
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return (None, None)
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return (data[0], decoded)
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def encode(hrp: str, witver: int, witprog: bytes) -> str | None:
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"""Encode a segwit address."""
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data = convertbits(witprog, 8, 5)
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spec = Encoding.BECH32 if witver == 0 else Encoding.BECH32M
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ret = bech32_encode(hrp, [witver] + data, spec)
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if decode(hrp, ret) == (None, None):
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return None
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return ret
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