114 lines
3.4 KiB
Rust
114 lines
3.4 KiB
Rust
// Bitcoin Dev Kit
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// Written in 2020 by Alekos Filini <alekos.filini@gmail.com>
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//
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// Copyright (c) 2020-2021 Bitcoin Dev Kit Developers
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//
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// This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
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// or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
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// You may not use this file except in accordance with one or both of these
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// licenses.
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//! Descriptor checksum
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//!
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//! This module contains a re-implementation of the function used by Bitcoin Core to calculate the
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//! checksum of a descriptor
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use std::iter::FromIterator;
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use crate::descriptor::DescriptorError;
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const INPUT_CHARSET: &str = "0123456789()[],'/*abcdefgh@:$%{}IJKLMNOPQRSTUVWXYZ&+-.;<=>?!^_|~ijklmnopqrstuvwxyzABCDEFGH`#\"\\ ";
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const CHECKSUM_CHARSET: &str = "qpzry9x8gf2tvdw0s3jn54khce6mua7l";
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fn poly_mod(mut c: u64, val: u64) -> u64 {
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let c0 = c >> 35;
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c = ((c & 0x7ffffffff) << 5) ^ val;
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if c0 & 1 > 0 {
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c ^= 0xf5dee51989
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};
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if c0 & 2 > 0 {
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c ^= 0xa9fdca3312
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};
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if c0 & 4 > 0 {
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c ^= 0x1bab10e32d
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};
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if c0 & 8 > 0 {
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c ^= 0x3706b1677a
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};
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if c0 & 16 > 0 {
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c ^= 0x644d626ffd
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};
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c
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}
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/// Compute the checksum of a descriptor
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pub fn get_checksum(desc: &str) -> Result<String, DescriptorError> {
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let mut c = 1;
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let mut cls = 0;
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let mut clscount = 0;
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for ch in desc.chars() {
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let pos = INPUT_CHARSET
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.find(ch)
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.ok_or(DescriptorError::InvalidDescriptorCharacter(ch))? as u64;
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c = poly_mod(c, pos & 31);
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cls = cls * 3 + (pos >> 5);
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clscount += 1;
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if clscount == 3 {
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c = poly_mod(c, cls);
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cls = 0;
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clscount = 0;
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}
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}
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if clscount > 0 {
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c = poly_mod(c, cls);
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}
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(0..8).for_each(|_| c = poly_mod(c, 0));
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c ^= 1;
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let mut chars = Vec::with_capacity(8);
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for j in 0..8 {
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chars.push(
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CHECKSUM_CHARSET
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.chars()
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.nth(((c >> (5 * (7 - j))) & 31) as usize)
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.unwrap(),
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);
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}
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Ok(String::from_iter(chars))
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}
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#[cfg(test)]
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mod test {
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use super::*;
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use crate::descriptor::get_checksum;
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// test get_checksum() function; it should return the same value as Bitcoin Core
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#[test]
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fn test_get_checksum() {
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let desc = "wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcLNfjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)";
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assert_eq!(get_checksum(desc).unwrap(), "tqz0nc62");
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let desc = "pkh(tpubD6NzVbkrYhZ4XHndKkuB8FifXm8r5FQHwrN6oZuWCz13qb93rtgKvD4PQsqC4HP4yhV3tA2fqr2RbY5mNXfM7RxXUoeABoDtsFUq2zJq6YK/44'/1'/0'/0/*)";
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assert_eq!(get_checksum(desc).unwrap(), "lasegmfs");
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}
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#[test]
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fn test_get_checksum_invalid_character() {
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let sparkle_heart = vec![240, 159, 146, 150];
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let sparkle_heart = std::str::from_utf8(&sparkle_heart)
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.unwrap()
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.chars()
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.next()
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.unwrap();
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let invalid_desc = format!("wpkh(tprv8ZgxMBicQKsPdpkqS7Eair4YxjcuuvDPNYmKX3sCniCf16tHEVrjjiSXEkFRnUH77yXc6ZcwHHcL{}fjdi5qUvw3VDfgYiH5mNsj5izuiu2N/1/2/*)", sparkle_heart);
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assert!(matches!(
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get_checksum(&invalid_desc).err(),
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Some(DescriptorError::InvalidDescriptorCharacter(invalid_char)) if invalid_char == sparkle_heart
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));
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}
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}
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