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273 lines
8.5 KiB
Rust
273 lines
8.5 KiB
Rust
// This is a modification of base32 encoding to support the zbase32 alphabet.
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// The original piece of software can be found at https://crates.io/crates/base32(v0.4.0)
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// The original portions of this software are Copyright (c) 2015 The base32 Developers
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// This file is licensed under either of
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// Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0) or
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// MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT) at your option.
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use crate::prelude::*;
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/// RFC4648 encoding table
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const RFC4648_ALPHABET: &'static [u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
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/// Zbase encoding alphabet
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const ZBASE_ALPHABET: &'static [u8] = b"ybndrfg8ejkmcpqxot1uwisza345h769";
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/// RFC4648 decoding table
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const RFC4648_INV_ALPHABET: [i8; 43] = [
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-1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
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];
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/// Zbase decoding table
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const ZBASE_INV_ALPHABET: [i8; 43] = [
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-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,
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21, 9, 10, -1, 11, 2, 16, 13, 14, 4, 22, 17, 19, -1, 20, 15, 0, 23,
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];
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/// Alphabet used for encoding and decoding.
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#[derive(Copy, Clone)]
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pub enum Alphabet {
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/// RFC4648 encoding.
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RFC4648 {
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/// Whether to use padding.
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padding: bool
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},
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/// Zbase32 encoding.
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ZBase32
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}
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impl Alphabet {
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/// Encode bytes into a base32 string.
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pub fn encode(&self, data: &[u8]) -> String {
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// output_length is calculated as follows:
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// / 5 divides the data length by the number of bits per chunk (5),
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// * 8 multiplies the result by the number of characters per chunk (8).
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// + 4 rounds up to the nearest character.
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let output_length = (data.len() * 8 + 4) / 5;
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let mut ret = match self {
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Self::RFC4648 { padding } => {
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let mut ret = Self::encode_data(data, RFC4648_ALPHABET);
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if *padding {
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let len = ret.len();
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for i in output_length..len {
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ret[i] = b'=';
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}
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return String::from_utf8(ret).expect("Invalid UTF-8");
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}
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ret
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},
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Self::ZBase32 => {
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Self::encode_data(data, ZBASE_ALPHABET)
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},
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};
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ret.truncate(output_length);
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#[cfg(fuzzing)]
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assert_eq!(ret.capacity(), (data.len() + 4) / 5 * 8);
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String::from_utf8(ret).expect("Invalid UTF-8")
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}
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/// Decode a base32 string into a byte vector.
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pub fn decode(&self, data: &str) -> Result<Vec<u8>, ()> {
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let data = data.as_bytes();
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let (data, alphabet) = match self {
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Self::RFC4648 { padding } => {
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let mut unpadded_data_length = data.len();
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if *padding {
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if data.len() % 8 != 0 { return Err(()); }
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data.iter().rev().take(6).for_each(|&c| {
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if c == b'=' {
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unpadded_data_length -= 1;
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}
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});
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}
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(&data[..unpadded_data_length], RFC4648_INV_ALPHABET)
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},
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Self::ZBase32 => {
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(data, ZBASE_INV_ALPHABET)
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}
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};
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// If the string has more characters than are required to alphabet_encode the number of bytes
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// decodable, treat the string as invalid.
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match data.len() % 8 { 1|3|6 => return Err(()), _ => {} }
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Ok(Self::decode_data(data, alphabet)?)
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}
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/// Encode a byte slice into a base32 string.
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fn encode_data(data: &[u8], alphabet: &'static [u8]) -> Vec<u8> {
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// cap is calculated as follows:
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// / 5 divides the data length by the number of bits per chunk (5),
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// * 8 multiplies the result by the number of characters per chunk (8).
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// + 4 rounds up to the nearest character.
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let cap = (data.len() + 4) / 5 * 8;
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let mut ret = Vec::with_capacity(cap);
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for chunk in data.chunks(5) {
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let mut buf = [0u8; 5];
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for (i, &b) in chunk.iter().enumerate() {
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buf[i] = b;
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}
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ret.push(alphabet[((buf[0] & 0xF8) >> 3) as usize]);
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ret.push(alphabet[(((buf[0] & 0x07) << 2) | ((buf[1] & 0xC0) >> 6)) as usize]);
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ret.push(alphabet[((buf[1] & 0x3E) >> 1) as usize]);
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ret.push(alphabet[(((buf[1] & 0x01) << 4) | ((buf[2] & 0xF0) >> 4)) as usize]);
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ret.push(alphabet[(((buf[2] & 0x0F) << 1) | (buf[3] >> 7)) as usize]);
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ret.push(alphabet[((buf[3] & 0x7C) >> 2) as usize]);
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ret.push(alphabet[(((buf[3] & 0x03) << 3) | ((buf[4] & 0xE0) >> 5)) as usize]);
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ret.push(alphabet[(buf[4] & 0x1F) as usize]);
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}
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#[cfg(fuzzing)]
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assert_eq!(ret.capacity(), cap);
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ret
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}
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fn decode_data(data: &[u8], alphabet: [i8; 43]) -> Result<Vec<u8>, ()> {
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// cap is calculated as follows:
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// / 8 divides the data length by the number of characters per chunk (8),
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// * 5 multiplies the result by the number of bits per chunk (5),
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// + 7 rounds up to the nearest byte.
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let cap = (data.len() + 7) / 8 * 5;
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let mut ret = Vec::with_capacity(cap);
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for chunk in data.chunks(8) {
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let mut buf = [0u8; 8];
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for (i, &c) in chunk.iter().enumerate() {
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match alphabet.get(c.to_ascii_uppercase().wrapping_sub(b'0') as usize) {
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Some(&-1) | None => return Err(()),
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Some(&value) => buf[i] = value as u8,
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};
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}
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ret.push((buf[0] << 3) | (buf[1] >> 2));
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ret.push((buf[1] << 6) | (buf[2] << 1) | (buf[3] >> 4));
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ret.push((buf[3] << 4) | (buf[4] >> 1));
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ret.push((buf[4] << 7) | (buf[5] << 2) | (buf[6] >> 3));
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ret.push((buf[6] << 5) | buf[7]);
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}
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let output_length = data.len() * 5 / 8;
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for c in ret.drain(output_length..) {
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if c != 0 {
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// If the original string had any bits set at positions outside of the encoded data,
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// treat the string as invalid.
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return Err(());
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}
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}
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// Check that our capacity calculation doesn't under-shoot in fuzzing
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#[cfg(fuzzing)]
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assert_eq!(ret.capacity(), cap);
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Ok(ret)
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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const ZBASE32_TEST_DATA: &[(&str, &[u8])] = &[
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("", &[]),
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("yy", &[0x00]),
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("oy", &[0x80]),
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("tqrey", &[0x8b, 0x88, 0x80]),
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("6n9hq", &[0xf0, 0xbf, 0xc7]),
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("4t7ye", &[0xd4, 0x7a, 0x04]),
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("6im5sdy", &[0xf5, 0x57, 0xbb, 0x0c]),
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("ybndrfg8ejkmcpqxot1uwisza345h769", &[0x00, 0x44, 0x32, 0x14, 0xc7, 0x42, 0x54, 0xb6,
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0x35, 0xcf, 0x84, 0x65, 0x3a, 0x56, 0xd7, 0xc6,
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0x75, 0xbe, 0x77, 0xdf])
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];
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#[test]
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fn test_zbase32_encode() {
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for &(zbase32, data) in ZBASE32_TEST_DATA {
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assert_eq!(Alphabet::ZBase32.encode(data), zbase32);
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}
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}
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#[test]
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fn test_zbase32_decode() {
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for &(zbase32, data) in ZBASE32_TEST_DATA {
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assert_eq!(Alphabet::ZBase32.decode(zbase32).unwrap(), data);
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}
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}
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#[test]
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fn test_decode_wrong() {
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const WRONG_DATA: &[&str] = &["00", "l1", "?", "="];
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for &data in WRONG_DATA {
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match Alphabet::ZBase32.decode(data) {
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Ok(_) => assert!(false, "Data shouldn't be decodable"),
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Err(_) => assert!(true),
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}
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}
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}
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const RFC4648_NON_PADDED_TEST_VECTORS: &[(&[u8], &[u8])] = &[
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(&[0xF8, 0x3E, 0x7F, 0x83, 0xE7], b"7A7H7A7H"),
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(&[0x77, 0xC1, 0xF7, 0x7C, 0x1F], b"O7A7O7A7"),
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(&[0xF8, 0x3E, 0x7F, 0x83, 0xE7], b"7A7H7A7H"),
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(&[0x77, 0xC1, 0xF7, 0x7C, 0x1F], b"O7A7O7A7"),
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];
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const RFC4648_TEST_VECTORS: &[(&[u8], &str)] = &[
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(b"", ""),
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(b"f", "MY======"),
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(b"fo", "MZXQ===="),
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(b"foo", "MZXW6==="),
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(b"foob", "MZXW6YQ="),
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(b"fooba", "MZXW6YTB"),
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(b"foobar", "MZXW6YTBOI======"),
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(&[0xF8, 0x3E, 0x7F, 0x83], "7A7H7AY="),
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];
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#[test]
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fn test_rfc4648_encode() {
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for (input, encoded) in RFC4648_TEST_VECTORS {
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assert_eq!(&Alphabet::RFC4648 { padding: true }.encode(input), encoded);
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}
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for (input, encoded) in RFC4648_NON_PADDED_TEST_VECTORS {
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assert_eq!(&Alphabet::RFC4648 { padding: false }.encode(input).as_bytes(), encoded);
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}
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}
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#[test]
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fn test_rfc4648_decode() {
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for (input, encoded) in RFC4648_TEST_VECTORS {
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let res = &Alphabet::RFC4648 { padding: true }.decode(encoded).unwrap();
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assert_eq!(&res[..], &input[..]);
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}
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for (input, encoded) in RFC4648_NON_PADDED_TEST_VECTORS {
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let res = &Alphabet::RFC4648 { padding: false }.decode(std::str::from_utf8(encoded).unwrap()).unwrap();
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assert_eq!(&res[..], &input[..]);
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}
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}
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#[test]
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fn padding() {
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let num_padding = [0, 6, 4, 3, 1];
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for i in 1..6 {
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let encoded = Alphabet::RFC4648 { padding: true }.encode(
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(0..(i as u8)).collect::<Vec<u8>>().as_ref()
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);
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assert_eq!(encoded.len(), 8);
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for j in 0..(num_padding[i % 5]) {
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assert_eq!(encoded.as_bytes()[encoded.len() - j - 1], b'=');
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}
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for j in 0..(8 - num_padding[i % 5]) {
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assert!(encoded.as_bytes()[j] != b'=');
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}
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}
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}
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#[test]
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fn test_decode_rfc4648_errors() {
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assert!(Alphabet::RFC4648 { padding: false }.decode("abc2def===").is_err()); // Invalid char because padding is disabled
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assert!(Alphabet::RFC4648 { padding: true }.decode("abc2def===").is_err()); // Invalid length
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assert!(Alphabet::RFC4648 { padding: true }.decode("MZX=6YTB").is_err()); // Invalid char
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}
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}
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