domain/utils/base32.rs
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//! Decoding and encoding of base 32.
//!
//! The base 32 encoding is defined in [RFC 4648]. It is essentially a
//! case-insensitive version of [base64][super::base64] which is necessary
//! when encoding binary data in domain names. The RFC defines two separate
//! encodings, called *base32* and *base32hex*. The DNS uses the latter
//! version, particularly in [NSEC3], for encoding binary data in domain
//! names, because it has the property that the encoding maintains the order
//! of the original data.
//!
//! This module currently only implements *base32hex* but is prepared for
//! adding the other option by using the prefix `_hex` wherever distinction
//! is necessary.
//!
//! The module defines the type [`Decoder`] which keeps the state necessary
//! for decoding. The various functions offered use such a decoder to decode
//! and encode octets in various forms.
//!
//! [RFC 4648]: https://tools.ietf.org/html/rfc4648
//! [NSEC3]: ../../rdata/rfc5155/index.html
use crate::base::scan::{ConvertSymbols, EntrySymbol, ScannerError};
use core::fmt;
use octseq::builder::{
EmptyBuilder, FreezeBuilder, FromBuilder, OctetsBuilder,
};
#[cfg(feature = "std")]
use std::string::String;
//------------ Re-exports ----------------------------------------------------
pub use super::base64::DecodeError;
//------------ Convenience Functions -----------------------------------------
/// Decodes a string with *base32hex* encoded data.
///
/// The function attempts to decode the entire string and returns the result
/// as an `Octets` value.
pub fn decode_hex<Octets>(s: &str) -> Result<Octets, DecodeError>
where
Octets: FromBuilder,
<Octets as FromBuilder>::Builder: OctetsBuilder + EmptyBuilder,
{
let mut decoder = Decoder::<<Octets as FromBuilder>::Builder>::new_hex();
for ch in s.chars() {
decoder.push(ch)?;
}
decoder.finalize()
}
/// Encodes binary data in *base32hex* and writes it into a format stream.
///
/// This function is intended to be used in implementations of formatting
/// traits:
///
/// ```
/// use core::fmt;
/// use domain::utils::base32;
///
/// struct Foo<'a>(&'a [u8]);
///
/// impl<'a> fmt::Display for Foo<'a> {
/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
/// base32::display_hex(&self.0, f)
/// }
/// }
/// ```
pub fn display_hex<B, W>(bytes: &B, f: &mut W) -> fmt::Result
where
B: AsRef<[u8]> + ?Sized,
W: fmt::Write,
{
fn ch(i: u8) -> char {
ENCODE_HEX_ALPHABET[i as usize]
}
for chunk in bytes.as_ref().chunks(5) {
f.write_char(ch(chunk[0] >> 3))?; // 0
if chunk.len() == 1 {
f.write_char(ch((chunk[0] & 0x07) << 2))?; // 1
break;
}
f.write_char(ch((chunk[0] & 0x07) << 2 | chunk[1] >> 6))?; // 1
f.write_char(ch((chunk[1] & 0x3F) >> 1))?; // 2
if chunk.len() == 2 {
f.write_char(ch((chunk[1] & 0x01) << 4))?; // 3
break;
}
f.write_char(ch((chunk[1] & 0x01) << 4 | chunk[2] >> 4))?; // 3
if chunk.len() == 3 {
f.write_char(ch((chunk[2] & 0x0F) << 1))?; // 4
break;
}
f.write_char(ch((chunk[2] & 0x0F) << 1 | chunk[3] >> 7))?; // 4
f.write_char(ch((chunk[3] & 0x7F) >> 2))?; // 5
if chunk.len() == 4 {
f.write_char(ch((chunk[3] & 0x03) << 3))?; // 6
break;
}
f.write_char(ch((chunk[3] & 0x03) << 3 | chunk[4] >> 5))?; // 6
f.write_char(ch(chunk[4] & 0x1F))?; // 7
}
Ok(())
}
/// Encodes binary data in *base32hex* and returns the encoded data as a string.
#[cfg(feature = "std")]
pub fn encode_string_hex<B: AsRef<[u8]> + ?Sized>(bytes: &B) -> String {
let mut res = String::with_capacity((bytes.as_ref().len() / 5 + 1) * 8);
display_hex(bytes, &mut res).unwrap();
res
}
/// Returns a placeholder value that implements `Display` for encoded data.
pub fn encode_display_hex<Octets: AsRef<[u8]>>(
octets: &Octets,
) -> impl fmt::Display + '_ {
struct Display<'a>(&'a [u8]);
impl<'a> fmt::Display for Display<'a> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
display_hex(self.0, f)
}
}
Display(octets.as_ref())
}
/// Serialize and deserialize octets Base64 encoded or binary.
///
/// This module can be used with Serde’s `with` attribute. It will serialize
/// an octets sequence as a Base64 encoded string with human readable
/// serializers or as a raw octets sequence for compact serializers.
#[cfg(feature = "serde")]
pub mod serde {
use core::fmt;
use octseq::builder::{EmptyBuilder, FromBuilder, OctetsBuilder};
use octseq::serde::{DeserializeOctets, SerializeOctets};
pub fn serialize<Octets, S>(
octets: &Octets,
serializer: S,
) -> Result<S::Ok, S::Error>
where
Octets: AsRef<[u8]> + SerializeOctets,
S: serde::Serializer,
{
if serializer.is_human_readable() {
serializer.collect_str(&super::encode_display_hex(octets))
} else {
octets.serialize_octets(serializer)
}
}
pub fn deserialize<'de, Octets, D: serde::Deserializer<'de>>(
deserializer: D,
) -> Result<Octets, D::Error>
where
Octets: FromBuilder + DeserializeOctets<'de>,
<Octets as FromBuilder>::Builder: EmptyBuilder,
{
struct Visitor<'de, Octets: DeserializeOctets<'de>>(Octets::Visitor);
impl<'de, Octets> serde::de::Visitor<'de> for Visitor<'de, Octets>
where
Octets: FromBuilder + DeserializeOctets<'de>,
<Octets as FromBuilder>::Builder: OctetsBuilder + EmptyBuilder,
{
type Value = Octets;
fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.write_str("an Base32-encoded string")
}
fn visit_str<E: serde::de::Error>(
self,
v: &str,
) -> Result<Self::Value, E> {
super::decode_hex(v).map_err(E::custom)
}
fn visit_borrowed_bytes<E: serde::de::Error>(
self,
value: &'de [u8],
) -> Result<Self::Value, E> {
self.0.visit_borrowed_bytes(value)
}
#[cfg(feature = "std")]
fn visit_byte_buf<E: serde::de::Error>(
self,
value: std::vec::Vec<u8>,
) -> Result<Self::Value, E> {
self.0.visit_byte_buf(value)
}
}
if deserializer.is_human_readable() {
deserializer.deserialize_str(Visitor(Octets::visitor()))
} else {
Octets::deserialize_with_visitor(
deserializer,
Visitor(Octets::visitor()),
)
}
}
}
//------------ Decoder -------------------------------------------------------
/// A base 32 decoder.
///
/// This type keeps all the state for decoding a sequence of characters
/// representing data encoded in base 32. Upon success, the decoder returns
/// the decoded data.
///
/// # Limitations
///
/// The decoder does not support padding.
pub struct Decoder<Builder> {
/// The alphabet we are using.
alphabet: &'static [u8; 128],
/// A buffer for up to eight characters.
///
/// We only keep `u8`s here because only ASCII characters are used by
/// Base32.
buf: [u8; 8],
/// The index in `buf` where we place the next character.
next: usize,
/// The target or an error if something went wrong.
target: Result<Builder, DecodeError>,
}
impl<Builder: EmptyBuilder> Decoder<Builder> {
/// Creates a new, empty decoder using the *base32hex* variant.
#[must_use]
pub fn new_hex() -> Self {
Decoder {
alphabet: &DECODE_HEX_ALPHABET,
buf: [0; 8],
next: 0,
target: Ok(Builder::empty()),
}
}
}
impl<Builder: OctetsBuilder> Decoder<Builder> {
/// Finalizes decoding and returns the decoded data.
#[allow(clippy::question_mark)] // false positive
pub fn finalize(mut self) -> Result<Builder::Octets, DecodeError>
where
Builder: FreezeBuilder,
{
if let Err(err) = self.target {
return Err(err);
}
match self.next {
0 => {}
1 | 3 | 6 => return Err(DecodeError::ShortInput),
2 => {
self.octet_0();
}
4 => {
self.octet_0();
self.octet_1();
}
5 => {
self.octet_0();
self.octet_1();
self.octet_2();
}
7 => {
self.octet_0();
self.octet_1();
self.octet_2();
self.octet_3();
}
_ => unreachable!(),
}
self.target.map(FreezeBuilder::freeze)
}
/// Decodes one more character of data.
///
/// Returns an error as soon as the encoded data is determined to be
/// illegal. It is okay to push more data after the first error. The
/// method will just keep returning errors.
pub fn push(&mut self, ch: char) -> Result<(), DecodeError> {
if ch > (127 as char) {
self.target = Err(DecodeError::IllegalChar(ch));
return Err(DecodeError::IllegalChar(ch));
}
let val = self.alphabet[ch as usize];
if val == 0xFF {
self.target = Err(DecodeError::IllegalChar(ch));
return Err(DecodeError::IllegalChar(ch));
}
self.buf[self.next] = val;
self.next += 1;
if self.next == 8 {
self.octet_0();
self.octet_1();
self.octet_2();
self.octet_3();
self.octet_4();
self.next = 0;
}
match self.target {
Ok(_) => Ok(()),
Err(err) => Err(err),
}
}
/// Decodes the zeroth octet in a base 32 sequence.
fn octet_0(&mut self) {
let ch = self.buf[0] << 3 | self.buf[1] >> 2;
self.append(ch)
}
/// Decodes the first octet in a base 32 sequence.
fn octet_1(&mut self) {
let ch = self.buf[1] << 6 | self.buf[2] << 1 | self.buf[3] >> 4;
self.append(ch)
}
/// Decodes the second octet in a base 32 sequence.
fn octet_2(&mut self) {
let ch = self.buf[3] << 4 | self.buf[4] >> 1;
self.append(ch)
}
/// Decodes the third octet in a base 32 sequence.
fn octet_3(&mut self) {
let ch = self.buf[4] << 7 | self.buf[5] << 2 | self.buf[6] >> 3;
self.append(ch)
}
/// Decodes the forth octet in a base 32 sequence.
fn octet_4(&mut self) {
let ch = self.buf[6] << 5 | self.buf[7];
self.append(ch)
}
/// Appends a decoded octet to the target.
fn append(&mut self, value: u8) {
let target = match self.target.as_mut() {
Ok(target) => target,
Err(_) => return,
};
if let Err(err) = target.append_slice(&[value]) {
self.target = Err(err.into().into());
}
}
}
//------------ SymbolConverter -----------------------------------------------
/// A Base 32 decoder that can be used as a converter with a scanner.
#[derive(Clone, Debug)]
pub struct SymbolConverter {
/// The alphabet we are using.
alphabet: &'static [u8; 128],
/// A buffer for up to eight input characters.
///
/// We only keep `u8`s here because only ASCII characters are used by
/// Base64.
input: [u8; 8],
/// The index in `input` where we place the next character.
///
/// We also abuse this to mark when we are done (because there was
/// padding, in which case we set it to 0xF0).
next: usize,
/// A buffer to return a slice for the output.
output: [u8; 5],
}
impl Default for SymbolConverter {
fn default() -> Self {
SymbolConverter {
alphabet: &DECODE_HEX_ALPHABET,
input: [0; 8],
next: 0,
output: Default::default(),
}
}
}
impl SymbolConverter {
/// Creates a new symbol converter.
#[must_use]
pub fn new() -> Self {
Default::default()
}
fn process_char<Error: ScannerError>(
&mut self,
ch: char,
) -> Result<Option<&[u8]>, Error> {
if ch > (127 as char) {
return Err(Error::custom("illegal Base 32 data"));
}
let val = self.alphabet[ch as usize];
if val == 0xFF {
return Err(Error::custom("illegal Base 32 data"));
}
self.input[self.next] = val;
self.next += 1;
if self.next == 8 {
self.output = [
self.input[0] << 3 | self.input[1] >> 2,
self.input[1] << 6 | self.input[2] << 1 | self.input[3] >> 4,
self.input[3] << 4 | self.input[4] >> 1,
self.input[4] << 7 | self.input[5] << 2 | self.input[6] >> 3,
self.input[6] << 5 | self.input[7],
];
self.next = 0;
Ok(Some(&self.output))
} else {
Ok(None)
}
}
}
impl<Sym, Error> ConvertSymbols<Sym, Error> for SymbolConverter
where
Sym: Into<EntrySymbol>,
Error: ScannerError,
{
fn process_symbol(
&mut self,
symbol: Sym,
) -> Result<Option<&[u8]>, Error> {
match symbol.into() {
EntrySymbol::Symbol(symbol) => self.process_char(
symbol
.into_char()
.map_err(|_| Error::custom("illegal Base 32 data"))?,
),
EntrySymbol::EndOfToken => Ok(None),
}
}
/// Process the end of token.
///
/// The method may return data to be added to the output octets sequence.
fn process_tail(&mut self) -> Result<Option<&[u8]>, Error> {
match self.next {
0 => return Ok(None),
1 | 3 | 6 => return Err(Error::custom("short Base 32 input")),
_ => {}
}
self.output[0] = self.input[0] << 3 | self.input[1] >> 2;
if self.next == 2 {
return Ok(Some(&self.output[0..1]));
}
self.output[1] =
self.input[1] << 6 | self.input[2] << 1 | self.input[3] >> 4;
if self.next == 4 {
return Ok(Some(&self.output[0..2]));
}
self.output[2] = self.input[3] << 4 | self.input[4] >> 1;
if self.next == 5 {
return Ok(Some(&self.output[0..3]));
}
self.output[3] =
self.input[4] << 7 | self.input[5] << 2 | self.input[6] >> 3;
Ok(Some(&self.output[0..4]))
}
}
//------------ Constants -----------------------------------------------------
/// The alphabet used for decoding *base32hex.*
///
/// This maps encoding characters into their values. A value of 0xFF stands in
/// for illegal characters. We only provide the first 128 characters since the
/// alphabet will only use ASCII characters.
const DECODE_HEX_ALPHABET: [u8; 128] = [
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x00 .. 0x07
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x08 .. 0x0F
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x10 .. 0x17
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x18 .. 0x1F
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x20 .. 0x27
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x28 .. 0x2F
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, // 0x30 .. 0x37
0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x38 .. 0x3F
0xFF, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, // 0x40 .. 0x47
0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, // 0x48 .. 0x4F
0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0xFF, // 0x50 .. 0x57
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x58 .. 0x5F
0xFF, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, // 0x60 .. 0x67
0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, // 0x68 .. 0x6F
0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0xFF, // 0x70 .. 0x77
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, // 0x78 .. 0x7F
];
/// The alphabet used for encoding *base32hex.*
const ENCODE_HEX_ALPHABET: [char; 32] = [
'0', '1', '2', '3', '4', '5', '6', '7', // 0x00 .. 0x07
'8', '9', 'A', 'B', 'C', 'D', 'E', 'F', // 0x08 .. 0x0F
'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', // 0x10 .. 0x17
'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', // 0x18 .. 0x1F
];
//============ Test ==========================================================
#[cfg(test)]
#[cfg(feature = "std")]
mod test {
use super::*;
#[test]
#[cfg(feature = "bytes")]
fn decode_str_hex() {
use super::DecodeError;
fn decode_hex(s: &str) -> Result<std::vec::Vec<u8>, DecodeError> {
super::decode_hex(s)
}
assert_eq!(&decode_hex("").unwrap(), b"");
assert_eq!(&decode_hex("CO").unwrap(), b"f");
assert_eq!(&decode_hex("CPNG").unwrap(), b"fo");
assert_eq!(&decode_hex("CPNMU").unwrap(), b"foo");
assert_eq!(&decode_hex("CPNMUOG").unwrap(), b"foob");
assert_eq!(&decode_hex("CPNMUOJ1").unwrap(), b"fooba");
assert_eq!(&decode_hex("CPNMUOJ1E8").unwrap(), b"foobar");
assert_eq!(&decode_hex("co").unwrap(), b"f");
assert_eq!(&decode_hex("cpng").unwrap(), b"fo");
assert_eq!(&decode_hex("cpnmu").unwrap(), b"foo");
assert_eq!(&decode_hex("cpnmuog").unwrap(), b"foob");
assert_eq!(&decode_hex("cpnmuoj1").unwrap(), b"fooba");
assert_eq!(&decode_hex("cpnmuoj1e8").unwrap(), b"foobar");
}
#[test]
fn test_display_hex() {
fn fmt(s: &[u8]) -> String {
let mut out = String::new();
display_hex(s, &mut out).unwrap();
out
}
assert_eq!(fmt(b""), "");
assert_eq!(fmt(b"f"), "CO");
assert_eq!(fmt(b"fo"), "CPNG");
assert_eq!(fmt(b"foo"), "CPNMU");
assert_eq!(fmt(b"foob"), "CPNMUOG");
assert_eq!(fmt(b"fooba"), "CPNMUOJ1");
assert_eq!(fmt(b"foobar"), "CPNMUOJ1E8");
}
}