65 lines
2.2 KiB
Python
65 lines
2.2 KiB
Python
#!/usr/bin/env python3
|
|
# Copyright (c) 2019 Pieter Wuille
|
|
# Distributed under the MIT software license, see the accompanying
|
|
# file COPYING or http://www.opensource.org/licenses/mit-license.php.
|
|
"""Utility functions related to output descriptors"""
|
|
|
|
import re
|
|
|
|
INPUT_CHARSET = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ "
|
|
CHECKSUM_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
|
|
GENERATOR = [0xf5dee51989, 0xa9fdca3312, 0x1bab10e32d, 0x3706b1677a, 0x644d626ffd]
|
|
|
|
def descsum_polymod(symbols):
|
|
"""Internal function that computes the descriptor checksum."""
|
|
chk = 1
|
|
for value in symbols:
|
|
top = chk >> 35
|
|
chk = (chk & 0x7ffffffff) << 5 ^ value
|
|
for i in range(5):
|
|
chk ^= GENERATOR[i] if ((top >> i) & 1) else 0
|
|
return chk
|
|
|
|
def descsum_expand(s):
|
|
"""Internal function that does the character to symbol expansion"""
|
|
groups = []
|
|
symbols = []
|
|
for c in s:
|
|
if not c in INPUT_CHARSET:
|
|
return None
|
|
v = INPUT_CHARSET.find(c)
|
|
symbols.append(v & 31)
|
|
groups.append(v >> 5)
|
|
if len(groups) == 3:
|
|
symbols.append(groups[0] * 9 + groups[1] * 3 + groups[2])
|
|
groups = []
|
|
if len(groups) == 1:
|
|
symbols.append(groups[0])
|
|
elif len(groups) == 2:
|
|
symbols.append(groups[0] * 3 + groups[1])
|
|
return symbols
|
|
|
|
def descsum_create(s):
|
|
"""Add a checksum to a descriptor without"""
|
|
symbols = descsum_expand(s) + [0, 0, 0, 0, 0, 0, 0, 0]
|
|
checksum = descsum_polymod(symbols) ^ 1
|
|
return s + '#' + ''.join(CHECKSUM_CHARSET[(checksum >> (5 * (7 - i))) & 31] for i in range(8))
|
|
|
|
def descsum_check(s, require=True):
|
|
"""Verify that the checksum is correct in a descriptor"""
|
|
if not '#' in s:
|
|
return not require
|
|
if s[-9] != '#':
|
|
return False
|
|
if not all(x in CHECKSUM_CHARSET for x in s[-8:]):
|
|
return False
|
|
symbols = descsum_expand(s[:-9]) + [CHECKSUM_CHARSET.find(x) for x in s[-8:]]
|
|
return descsum_polymod(symbols) == 1
|
|
|
|
def drop_origins(s):
|
|
'''Drop the key origins from a descriptor'''
|
|
desc = re.sub(r'\[.+?\]', '', s)
|
|
if '#' in s:
|
|
desc = desc[:desc.index('#')]
|
|
return descsum_create(desc)
|