rust-lightning/lightning/src/util/zbase32.rs

// This is a modification of base32 encoding to support the zbase32 alphabet.
// The original piece of software can be found at https://github.com/andreasots/base32
// The original portions of this software are Copyright (c) 2015 The base32 Developers

/* This file is licensed under either of
 *  Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) or
 *  MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
 * at your option.
*/

use prelude::*;

const ALPHABET: &'static [u8] = b"ybndrfg8ejkmcpqxot1uwisza345h769";

/// Encodes some bytes as a zbase32 string
pub fn encode(data: &[u8]) -> String {
	let mut ret = Vec::with_capacity((data.len() + 4) / 5 * 8);

	for chunk in data.chunks(5) {
		let buf = {
			let mut buf = [0u8; 5];
			for (i, &b) in chunk.iter().enumerate() {
				buf[i] = b;
			}
			buf
		};

		ret.push(ALPHABET[((buf[0] & 0xF8) >> 3) as usize]);
		ret.push(ALPHABET[(((buf[0] & 0x07) << 2) | ((buf[1] & 0xC0) >> 6)) as usize]);
		ret.push(ALPHABET[((buf[1] & 0x3E) >> 1) as usize]);
		ret.push(ALPHABET[(((buf[1] & 0x01) << 4) | ((buf[2] & 0xF0) >> 4)) as usize]);
		ret.push(ALPHABET[(((buf[2] & 0x0F) << 1) | (buf[3] >> 7)) as usize]);
		ret.push(ALPHABET[((buf[3] & 0x7C) >> 2) as usize]);
		ret.push(ALPHABET[(((buf[3] & 0x03) << 3) | ((buf[4] & 0xE0) >> 5)) as usize]);
		ret.push(ALPHABET[(buf[4] & 0x1F) as usize]);
	}

	ret.truncate((data.len() * 8 + 4) / 5);

	// Check that our capacity calculation doesn't under-shoot in fuzzing
	#[cfg(fuzzing)]
	assert_eq!(ret.capacity(), (data.len() + 4) / 5 * 8);

	String::from_utf8(ret).unwrap()
}

// ASCII 0-Z
const INV_ALPHABET: [i8; 43] = [
	-1, 18, -1, 25, 26, 27, 30, 29, 7, 31, -1, -1, -1, -1, -1, -1, -1,  24, 1, 12, 3, 8, 5, 6, 28,
	21, 9, 10, -1, 11, 2, 16, 13, 14, 4, 22, 17, 19, -1, 20, 15, 0, 23,
];

/// Decodes a zbase32 string to the original bytes, failing if the string was not encoded by a
/// proper zbase32 encoder.
pub fn decode(data: &str) -> Result<Vec<u8>, ()> {
	if !data.is_ascii() {
		return Err(());
	}

	let data = data.as_bytes();
	let output_length = data.len() * 5 / 8;
	if data.len() > (output_length * 8 + 4) / 5 {
		// If the string has more charachters than are required to encode the number of bytes
		// decodable, treat the string as invalid.
		return Err(());
	}

	let mut ret = Vec::with_capacity((data.len() + 7) / 8 * 5);

	for chunk in data.chunks(8) {
		let buf = {
			let mut buf = [0u8; 8];
			for (i, &c) in chunk.iter().enumerate() {
				match INV_ALPHABET.get(c.to_ascii_uppercase().wrapping_sub(b'0') as usize) {
					Some(&-1) | None => return Err(()),
					Some(&value) => buf[i] = value as u8,
				};
			}
			buf
		};
		ret.push((buf[0] << 3) | (buf[1] >> 2));
		ret.push((buf[1] << 6) | (buf[2] << 1) | (buf[3] >> 4));
		ret.push((buf[3] << 4) | (buf[4] >> 1));
		ret.push((buf[4] << 7) | (buf[5] << 2) | (buf[6] >> 3));
		ret.push((buf[6] << 5) | buf[7]);
	}
	for c in ret.drain(output_length..) {
		if c != 0 {
			// If the original string had any bits set at positions outside of the encoded data,
			// treat the string as invalid.
			return Err(());
		}
	}

	// Check that our capacity calculation doesn't under-shoot in fuzzing
	#[cfg(fuzzing)]
	assert_eq!(ret.capacity(), (data.len() + 7) / 8 * 5);

	Ok(ret)
}

#[cfg(test)]
mod tests {
	use super::*;

	const TEST_DATA: &[(&str, &[u8])] = &[
		("",	   &[]),
		("yy",	 &[0x00]),
		("oy",	 &[0x80]),
		("tqrey",   &[0x8b, 0x88, 0x80]),
		("6n9hq",  &[0xf0, 0xbf, 0xc7]),
		("4t7ye",  &[0xd4, 0x7a, 0x04]),
		("6im5sdy", &[0xf5, 0x57, 0xbb, 0x0c]),
		("ybndrfg8ejkmcpqxot1uwisza345h769", &[0x00, 0x44, 0x32, 0x14, 0xc7, 0x42, 0x54, 0xb6,
													0x35, 0xcf, 0x84, 0x65, 0x3a, 0x56, 0xd7, 0xc6,
													0x75, 0xbe, 0x77, 0xdf])
	];

	#[test]
	fn test_encode() {
		for &(zbase32, data) in TEST_DATA {
			assert_eq!(encode(data), zbase32);
		}
	}

	#[test]
	fn test_decode() {
		for &(zbase32, data) in TEST_DATA {
			assert_eq!(decode(zbase32).unwrap(), data);
		}
	}

	#[test]
	fn test_decode_wrong() {
		const WRONG_DATA: &[&str] = &["00", "l1", "?", "="];

		for &data in WRONG_DATA {
			match decode(data) {
				Ok(_) => assert!(false, "Data shouldn't be decodable"),
				Err(_) => assert!(true),
			}
		}
	}
}