wip

Author: Fraccaman

scripts/utils.py

@@ -0,0 +1,157 @@
+# License for original (reference) implementation:
+#
+# Copyright (c) 2017, 2020 Pieter Wuille
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+"""Reference implementation for Bech32/Bech32m and segwit addresses."""
+"""This implementation removes the constrain of maximum 90 characters."""
+
+
+from collections.abc import ByteString
+from enum import Enum
+from typing import NamedTuple
+
+
+class Encoding(Enum):
+    """Enumeration type to list the various supported encodings."""
+
+    BECH32 = 1
+    BECH32M = 2
+
+
+CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+BECH32M_CONST = 0x2BC830A3
+
+
+class DecodeError(ValueError):
+    pass
+
+
+class HrpDoesNotMatch(DecodeError):
+    pass
+
+
+class DecodedAddress(NamedTuple):
+    witver: int
+    witprog: bytes
+
+
+def bech32_polymod(values: ByteString) -> int:
+    """Internal function that computes the Bech32 checksum."""
+    generator = [0x3B6A57B2, 0x26508E6D, 0x1EA119FA, 0x3D4233DD, 0x2A1462B3]
+    chk = 1
+    for value in values:
+        top = chk >> 25
+        chk = (chk & 0x1FFFFFF) << 5 ^ value
+        for i in range(5):
+            chk ^= generator[i] if ((top >> i) & 1) else 0
+    return chk
+
+
+def bech32_hrp_expand(hrp: str) -> bytes:
+    """Expand the HRP into values for checksum computation."""
+    return bytes([ord(x) >> 5 for x in hrp] + [0] + [ord(x) & 31 for x in hrp])
+
+
+def bech32_verify_checksum(hrp: str, data: bytes) -> Encoding:
+    """Verify a checksum given HRP and converted data characters."""
+    const = bech32_polymod(bech32_hrp_expand(hrp) + data)
+    if const == 1:
+        return Encoding.BECH32
+    if const == BECH32M_CONST:
+        return Encoding.BECH32M
+    # Invalid checksum
+    raise DecodeError()
+
+
+def bech32_decode(bech: str) -> tuple[str, memoryview, Encoding]:
+    """Validate a Bech32/Bech32m string, and determine HRP and data."""
+    if (any(ord(x) < 33 or ord(x) > 126 for x in bech)) or (
+        bech.lower() != bech and bech.upper() != bech
+    ):
+        # HRP character out of range
+        raise DecodeError()
+    bech = bech.lower()
+    pos = bech.rfind("1")
+    if pos < 1 or pos + 7 > len(bech):
+        # No separator character / Empty HRP / overall max length exceeded
+        raise DecodeError()
+    if not all(x in CHARSET for x in bech[pos + 1 :]):
+        # Invalid data character
+        raise DecodeError()
+    hrp = bech[:pos]
+    data = memoryview(bytes(CHARSET.find(x) for x in bech[pos + 1 :]))
+    spec = bech32_verify_checksum(hrp, data)
+    return (hrp, data[:-6], spec)
+
+
+def convertbits(data: ByteString, frombits: int, tobits: int, pad: bool = True) -> bytearray:
+    """General power-of-2 base conversion."""
+    acc = 0
+    bits = 0
+    ret = bytearray()
+    maxv = (1 << tobits) - 1
+    max_acc = (1 << (frombits + tobits - 1)) - 1
+    for value in data:
+        if value < 0 or (value >> frombits):
+            # XXX Not covered by tests
+            raise DecodeError()
+        acc = ((acc << frombits) | value) & max_acc
+        bits += frombits
+        while bits >= tobits:
+            bits -= tobits
+            ret.append((acc >> bits) & maxv)
+    if pad:
+        if bits:
+            ret.append((acc << (tobits - bits)) & maxv)
+    elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
+        # More than 4 padding bits / Non-zero padding in 8-to-5 conversion
+        raise DecodeError()
+    return ret
+
+
+def decode(hrp: str, addr: str) -> DecodedAddress:
+    """Decode a segwit address."""
+    hrpgot, data, spec = bech32_decode(addr)
+    if hrpgot != hrp:
+        raise HrpDoesNotMatch()
+    witprog = convertbits(data[1:], 5, 8, False)
+    if len(witprog) < 2 or len(witprog) > 40:
+        # Invalid program length
+        raise DecodeError()
+    witver = data[0]
+    if witver > 16:
+        # Invalid witness version
+        raise DecodeError()
+    if witver == 0 and len(witprog) != 20 and len(witprog) != 32:
+        # Invalid program length for witness version 0 (per BIP141)
+        raise DecodeError()
+    if witver == 0 and spec != Encoding.BECH32 or witver != 0 and spec != Encoding.BECH32M:
+        # Invalid checksum algorithm
+        raise DecodeError()
+    return DecodedAddress(witver, witprog)
+
+
+def is_valid_bech32m(data, hrp):
+    try:
+        this_hrp, _, _ = bech32_decode(data)
+        return this_hrp == hrp
+    except Exception:
+        return False