domain/base/name/builder.rs
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//! Building a domain name.
//!
//! This is a private module for tidiness. `NameBuilder` and `PushError`
//! are re-exported by the parent module.
use super::super::scan::{BadSymbol, Symbol, SymbolCharsError, Symbols};
use super::absolute::Name;
use super::relative::{RelativeName, RelativeNameError};
use super::traits::{ToName, ToRelativeName};
use super::Label;
#[cfg(feature = "bytes")]
use bytes::BytesMut;
use core::fmt;
use octseq::builder::{EmptyBuilder, FreezeBuilder, OctetsBuilder, ShortBuf};
#[cfg(feature = "std")]
use std::vec::Vec;
//------------ NameBuilder --------------------------------------------------
/// Builds a domain name step by step by appending data.
///
/// The domain name builder is the most fundamental way to construct a new
/// domain name. It wraps an octets builder that assembles the name step by
/// step.
///
/// The methods [`push`][Self::push] and [`append_slice`][Self::append_slice]
/// to add the octets of a label to end of the builder. Once a label is
/// complete, [`end_label`][Self::end_label] finishes the current label and
/// starts a new one.
///
/// The method [`append_label`][Self::append_label] combines this process
/// and appends the given octets as a label.
///
/// The name builder currently is not aware of internationalized domain
/// names. The octets passed to it are used as is and are not converted.
#[derive(Clone)]
pub struct NameBuilder<Builder> {
/// The buffer to build the name in.
builder: Builder,
/// The position in `octets` where the current label started.
///
/// If this is `None` we currently do not have a label.
head: Option<usize>,
}
impl<Builder> NameBuilder<Builder> {
/// Creates a new domain name builder from an octets builder.
///
/// Whatever is in the buffer already is considered to be a relative
/// domain name. Since that may not be the case, this function is
/// unsafe.
pub(super) unsafe fn from_builder_unchecked(builder: Builder) -> Self {
NameBuilder {
builder,
head: None,
}
}
/// Creates a new, empty name builder.
#[must_use]
pub fn new() -> Self
where
Builder: EmptyBuilder,
{
unsafe { NameBuilder::from_builder_unchecked(Builder::empty()) }
}
/// Creates a new, empty builder with a given capacity.
#[must_use]
pub fn with_capacity(capacity: usize) -> Self
where
Builder: EmptyBuilder,
{
unsafe {
NameBuilder::from_builder_unchecked(Builder::with_capacity(
capacity,
))
}
}
/// Creates a new domain name builder atop an existing octets builder.
///
/// The function checks that whatever is in the builder already
/// consititutes a correctly encoded relative domain name.
pub fn from_builder(builder: Builder) -> Result<Self, RelativeNameError>
where
Builder: OctetsBuilder + AsRef<[u8]>,
{
RelativeName::check_slice(builder.as_ref())?;
Ok(unsafe { NameBuilder::from_builder_unchecked(builder) })
}
}
#[cfg(feature = "std")]
impl NameBuilder<Vec<u8>> {
/// Creates an empty domain name builder atop a `Vec<u8>`.
#[must_use]
pub fn new_vec() -> Self {
Self::new()
}
/// Creates an empty builder atop a `Vec<u8>` with given capacity.
///
/// Names are limited to a length of 255 octets, but you can provide any
/// capacity you like here.
#[must_use]
pub fn vec_with_capacity(capacity: usize) -> Self {
Self::with_capacity(capacity)
}
}
#[cfg(feature = "bytes")]
impl NameBuilder<BytesMut> {
/// Creates an empty domain name bulider atop a bytes value.
pub fn new_bytes() -> Self {
Self::new()
}
/// Creates an empty bulider atop a bytes value with given capacity.
///
/// Names are limited to a length of 255 octets, but you can provide any
/// capacity you like here.
pub fn bytes_with_capacity(capacity: usize) -> Self {
Self::with_capacity(capacity)
}
}
impl<Builder: AsRef<[u8]>> NameBuilder<Builder> {
/// Returns the already assembled domain name as an octets slice.
pub fn as_slice(&self) -> &[u8] {
self.builder.as_ref()
}
/// Returns the length of the already assembled domain name.
pub fn len(&self) -> usize {
self.builder.as_ref().len()
}
/// Returns whether the name is still empty.
pub fn is_empty(&self) -> bool {
self.builder.as_ref().is_empty()
}
}
impl<Builder> NameBuilder<Builder>
where
Builder: OctetsBuilder + AsRef<[u8]> + AsMut<[u8]>,
{
/// Returns whether there currently is a label under construction.
///
/// This returns `false` if the name is still empty or if the last thing
/// that happend was a call to [`end_label`].
///
/// [`end_label`]: NameBuilder::end_label
pub fn in_label(&self) -> bool {
self.head.is_some()
}
/// Attempts to append a slice to the underlying builder.
///
/// This method doesn’t perform any checks but only does the necessary
/// error conversion.
fn _append_slice(&mut self, slice: &[u8]) -> Result<(), PushError> {
self.builder
.append_slice(slice)
.map_err(|_| PushError::ShortBuf)
}
/// Pushes an octet to the end of the domain name.
///
/// Starts a new label if necessary. Returns an error if pushing the
/// octet would exceed the size limits for labels or domain names.
pub fn push(&mut self, ch: u8) -> Result<(), PushError> {
let len = self.len();
if len >= 254 {
return Err(PushError::LongName);
}
if let Some(head) = self.head {
if len - head > Label::MAX_LEN {
return Err(PushError::LongLabel);
}
self._append_slice(&[ch])?;
} else {
self.head = Some(len);
self._append_slice(&[0, ch])?;
}
Ok(())
}
/// Pushes a symbol to the end of the domain name.
///
/// The symbol is iterpreted as part of the presentation format of a
/// domain name, i.e., an unescaped dot is considered a label separator.
pub fn push_symbol(&mut self, sym: Symbol) -> Result<(), FromStrError> {
if matches!(sym, Symbol::Char('.')) {
if !self.in_label() {
return Err(PresentationErrorEnum::EmptyLabel.into());
}
self.end_label();
Ok(())
} else if matches!(sym, Symbol::SimpleEscape(b'['))
&& !self.in_label()
{
Err(LabelFromStrErrorEnum::BinaryLabel.into())
} else {
self.push(sym.into_octet()?).map_err(Into::into)
}
}
/// Appends the content of an octets slice to the end of the domain name.
///
/// Starts a new label if necessary. Returns an error if pushing
/// would exceed the size limits for labels or domain names.
///
/// If `slice` is empty, does absolutely nothing.
pub fn append_slice(&mut self, slice: &[u8]) -> Result<(), PushError> {
if slice.is_empty() {
return Ok(());
}
if let Some(head) = self.head {
if slice.len() > Label::MAX_LEN - (self.len() - head) {
return Err(PushError::LongLabel);
}
} else {
if slice.len() > Label::MAX_LEN {
return Err(PushError::LongLabel);
}
if self.len() + slice.len() > 254 {
return Err(PushError::LongName);
}
self.head = Some(self.len());
self._append_slice(&[0])?;
}
self._append_slice(slice)?;
Ok(())
}
/// Ends the current label.
///
/// If there isn’t a current label, does nothing.
pub fn end_label(&mut self) {
if let Some(head) = self.head {
let len = self.len() - head - 1;
self.builder.as_mut()[head] = len as u8;
self.head = None;
}
}
/// Appends an octets slice as a complete label.
///
/// If there currently is a label under construction, it will be ended
/// before appending `label`.
///
/// Returns an error if `label` exceeds the label size limit of 63 bytes
/// or appending the label would exceed the domain name size limit of
/// 255 bytes.
pub fn append_label(&mut self, label: &[u8]) -> Result<(), PushError> {
let head = self.head;
self.end_label();
if let Err(err) = self.append_slice(label) {
self.head = head;
return Err(err);
}
self.end_label();
Ok(())
}
/// Appends a label with the decimal representation of `u8`.
///
/// If there currently is a label under construction, it will be ended
/// before appending `label`.
///
/// Returns an error if appending would result in a name longer than 254
/// bytes.
pub fn append_dec_u8_label(
&mut self,
value: u8,
) -> Result<(), PushError> {
self.end_label();
let hecto = value / 100;
if hecto > 0 {
self.push(hecto + b'0')?;
}
let deka = (value / 10) % 10;
if hecto > 0 || deka > 0 {
self.push(deka + b'0')?;
}
self.push(value % 10 + b'0')?;
self.end_label();
Ok(())
}
/// Appends a label with the hex digit.
///
/// If there currently is a label under construction, it will be ended
/// before appending `label`.
///
/// Returns an error if appending would result in a name longer than 254
/// bytes.
pub fn append_hex_digit_label(
&mut self,
nibble: u8,
) -> Result<(), PushError> {
fn hex_digit(nibble: u8) -> u8 {
match nibble & 0x0F {
0 => b'0',
1 => b'1',
2 => b'2',
3 => b'3',
4 => b'4',
5 => b'5',
6 => b'6',
7 => b'7',
8 => b'8',
9 => b'9',
10 => b'A',
11 => b'B',
12 => b'C',
13 => b'D',
14 => b'E',
15 => b'F',
_ => unreachable!(),
}
}
self.end_label();
self.push(hex_digit(nibble))?;
self.end_label();
Ok(())
}
/// Appends a relative domain name.
///
/// If there currently is a label under construction, it will be ended
/// before appending `name`.
///
/// Returns an error if appending would result in a name longer than 254
/// bytes.
//
// XXX NEEDS TESTS
pub fn append_name<N: ToRelativeName>(
&mut self,
name: &N,
) -> Result<(), PushNameError> {
let head = self.head.take();
self.end_label();
if self.len() + usize::from(name.compose_len()) > 254 {
self.head = head;
return Err(PushNameError::LongName);
}
for label in name.iter_labels() {
label
.compose(&mut self.builder)
.map_err(|_| PushNameError::ShortBuf)?;
}
Ok(())
}
/// Appends a name from a sequence of symbols.
///
/// If there currently is a label under construction, it will be ended
/// before appending `chars`.
///
/// The character sequence must result in a domain name in representation
/// format. That is, its labels should be separated by dots,
/// actual dots, white space, backslashes and byte values that are not
/// printable ASCII characters should be escaped.
///
/// The last label will only be ended if the last character was a dot.
/// Thus, you can determine if that was the case via
/// [`in_label`][Self::in_label].
pub fn append_symbols<Sym: IntoIterator<Item = Symbol>>(
&mut self,
symbols: Sym,
) -> Result<(), FromStrError> {
symbols
.into_iter()
.try_for_each(|symbol| self.push_symbol(symbol))
}
/// Appends a name from a sequence of characters.
///
/// If there currently is a label under construction, it will be ended
/// before appending `chars`.
///
/// The character sequence must result in a domain name in representation
/// format. That is, its labels should be separated by dots,
/// actual dots, white space and backslashes should be escaped by a
/// preceeding backslash, and any byte value that is not a printable
/// ASCII character should be encoded by a backslash followed by its
/// three digit decimal value.
///
/// The last label will only be ended if the last character was a dot.
/// Thus, you can determine if that was the case via
/// [`in_label`][Self::in_label].
pub fn append_chars<C: IntoIterator<Item = char>>(
&mut self,
chars: C,
) -> Result<(), FromStrError> {
Symbols::with(chars.into_iter(), |symbols| {
self.append_symbols(symbols)
})
}
/// Finishes building the name and returns the resulting relative name.
///
/// If there currently is a label being built, ends the label first
/// before returning the name. I.e., you don’t have to call [`end_label`]
/// explicitely.
///
/// This method converts the builder into a relative name. If you would
/// like to turn it into an absolute name, use [`into_name`] which
/// appends the root label before finishing.
///
/// [`end_label`]: NameBuilder::end_label
/// [`into_name`]: NameBuilder::into_name
pub fn finish(mut self) -> RelativeName<Builder::Octets>
where
Builder: FreezeBuilder,
{
self.end_label();
unsafe { RelativeName::from_octets_unchecked(self.builder.freeze()) }
}
/// Appends the root label to the name and returns it as a [`Name`].
///
/// If there currently is a label under construction, ends the label.
/// Then adds the empty root label and transforms the name into a
/// [`Name`].
pub fn into_name(mut self) -> Result<Name<Builder::Octets>, PushError>
where
Builder: FreezeBuilder,
{
self.end_label();
self._append_slice(&[0])?;
Ok(unsafe { Name::from_octets_unchecked(self.builder.freeze()) })
}
/// Appends an origin and returns the resulting [`Name`].
///
/// If there currently is a label under construction, ends the label.
/// Then adds the `origin` and transforms the name into a
/// [`Name`].
//
// XXX NEEDS TESTS
pub fn append_origin<N: ToName>(
mut self,
origin: &N,
) -> Result<Name<Builder::Octets>, PushNameError>
where
Builder: FreezeBuilder,
{
self.end_label();
if self.len() + usize::from(origin.compose_len()) > Name::MAX_LEN {
return Err(PushNameError::LongName);
}
for label in origin.iter_labels() {
label
.compose(&mut self.builder)
.map_err(|_| PushNameError::ShortBuf)?;
}
Ok(unsafe { Name::from_octets_unchecked(self.builder.freeze()) })
}
}
//--- Default
impl<Builder: EmptyBuilder> Default for NameBuilder<Builder> {
fn default() -> Self {
Self::new()
}
}
//--- AsRef
impl<Builder: AsRef<[u8]>> AsRef<[u8]> for NameBuilder<Builder> {
fn as_ref(&self) -> &[u8] {
self.builder.as_ref()
}
}
//------------ Santa’s Little Helpers ----------------------------------------
/// Parses the contents of an escape sequence from `chars`.
///
/// The backslash should already have been taken out of `chars`.
pub(super) fn parse_escape<C>(
chars: &mut C,
in_label: bool,
) -> Result<u8, LabelFromStrError>
where
C: Iterator<Item = char>,
{
let ch = chars.next().ok_or(SymbolCharsError::short_input())?;
if ch.is_ascii_digit() {
let v = ch.to_digit(10).unwrap() * 100
+ chars
.next()
.ok_or(SymbolCharsError::short_input())
.and_then(|c| {
c.to_digit(10).ok_or(SymbolCharsError::bad_escape())
})?
* 10
+ chars
.next()
.ok_or(SymbolCharsError::short_input())
.and_then(|c| {
c.to_digit(10).ok_or(SymbolCharsError::bad_escape())
})?;
if v > 255 {
return Err(SymbolCharsError::bad_escape().into());
}
Ok(v as u8)
} else if ch == '[' {
// `\[` at the start of a label marks a binary label which we don’t
// support. Within a label, the sequence is fine.
if in_label {
Ok(b'[')
} else {
Err(LabelFromStrErrorEnum::BinaryLabel.into())
}
} else {
Ok(ch as u8)
}
}
//============ Error Types ===================================================
//------------ PushError -----------------------------------------------------
/// An error happened while trying to push data to a domain name builder.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum PushError {
/// The current label would exceed the limit of 63 bytes.
LongLabel,
/// The name would exceed the limit of 255 bytes.
LongName,
/// The buffer is too short to contain the name.
ShortBuf,
}
//--- From
impl From<ShortBuf> for PushError {
fn from(_: ShortBuf) -> PushError {
PushError::ShortBuf
}
}
//--- Display and Error
impl fmt::Display for PushError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
PushError::LongLabel => f.write_str("long label"),
PushError::LongName => f.write_str("long domain name"),
PushError::ShortBuf => ShortBuf.fmt(f),
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for PushError {}
//------------ PushNameError -------------------------------------------------
/// An error happened while trying to push a name to a domain name builder.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum PushNameError {
/// The name would exceed the limit of 255 bytes.
LongName,
/// The buffer is too short to contain the name.
ShortBuf,
}
//--- From
impl From<ShortBuf> for PushNameError {
fn from(_: ShortBuf) -> Self {
PushNameError::ShortBuf
}
}
//--- Display and Error
impl fmt::Display for PushNameError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
PushNameError::LongName => f.write_str("long domain name"),
PushNameError::ShortBuf => ShortBuf.fmt(f),
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for PushNameError {}
//------------ LabelFromStrError ---------------------------------------------
/// An error occured while reading a label from a string.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct LabelFromStrError(LabelFromStrErrorEnum);
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub(super) enum LabelFromStrErrorEnum {
SymbolChars(SymbolCharsError),
BadSymbol(BadSymbol),
/// A binary label was encountered.
BinaryLabel,
/// The label would exceed the limit of 63 bytes.
LongLabel,
}
//--- From
impl From<LabelFromStrErrorEnum> for LabelFromStrError {
fn from(inner: LabelFromStrErrorEnum) -> Self {
Self(inner)
}
}
impl From<SymbolCharsError> for LabelFromStrError {
fn from(err: SymbolCharsError) -> Self {
Self(LabelFromStrErrorEnum::SymbolChars(err))
}
}
impl From<BadSymbol> for LabelFromStrError {
fn from(err: BadSymbol) -> Self {
Self(LabelFromStrErrorEnum::BadSymbol(err))
}
}
//--- Display and Error
impl fmt::Display for LabelFromStrError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.0 {
LabelFromStrErrorEnum::SymbolChars(err) => err.fmt(f),
LabelFromStrErrorEnum::BadSymbol(err) => err.fmt(f),
LabelFromStrErrorEnum::BinaryLabel => {
f.write_str("a binary label was encountered")
}
LabelFromStrErrorEnum::LongLabel => {
f.write_str("label length limit exceeded")
}
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for LabelFromStrError {}
//------------ FromStrError --------------------------------------------------
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum FromStrError {
/// The string content was wrongly formatted.
Presentation(PresentationError),
/// The buffer is too short to contain the name.
ShortBuf,
}
impl FromStrError {
pub(super) fn empty_label() -> Self {
Self::Presentation(PresentationErrorEnum::EmptyLabel.into())
}
}
//--- From
impl From<PushError> for FromStrError {
fn from(err: PushError) -> FromStrError {
match err {
PushError::LongLabel => LabelFromStrErrorEnum::LongLabel.into(),
PushError::LongName => PresentationErrorEnum::LongName.into(),
PushError::ShortBuf => FromStrError::ShortBuf,
}
}
}
impl From<PushNameError> for FromStrError {
fn from(err: PushNameError) -> FromStrError {
match err {
PushNameError::LongName => PresentationErrorEnum::LongName.into(),
PushNameError::ShortBuf => FromStrError::ShortBuf,
}
}
}
impl<T: Into<PresentationError>> From<T> for FromStrError {
fn from(err: T) -> Self {
Self::Presentation(err.into())
}
}
//--- Display and Error
impl fmt::Display for FromStrError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
FromStrError::Presentation(err) => err.fmt(f),
FromStrError::ShortBuf => ShortBuf.fmt(f),
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for FromStrError {}
//------------ PresentationError ---------------------------------------------
/// An illegal presentation format was encountered.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct PresentationError(PresentationErrorEnum);
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
enum PresentationErrorEnum {
BadLabel(LabelFromStrError),
/// An empty label was encountered.
EmptyLabel,
/// The name has more than 255 characters.
LongName,
}
//--- From
impl From<PresentationErrorEnum> for PresentationError {
fn from(err: PresentationErrorEnum) -> Self {
Self(err)
}
}
impl<T: Into<LabelFromStrError>> From<T> for PresentationError {
fn from(err: T) -> Self {
Self(PresentationErrorEnum::BadLabel(err.into()))
}
}
//--- Display and Error
impl fmt::Display for PresentationError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self.0 {
PresentationErrorEnum::BadLabel(ref err) => err.fmt(f),
PresentationErrorEnum::EmptyLabel => f.write_str("empty label"),
PresentationErrorEnum::LongName => {
f.write_str("long domain name")
}
}
}
}
#[cfg(feature = "std")]
impl std::error::Error for PresentationError {}
//============ Testing =======================================================
#[cfg(test)]
#[cfg(feature = "std")]
mod test {
use super::*;
#[test]
fn compose() {
let mut builder = NameBuilder::new_vec();
builder.push(b'w').unwrap();
builder.append_slice(b"ww").unwrap();
builder.end_label();
builder.append_slice(b"exa").unwrap();
builder.push(b'm').unwrap();
builder.push(b'p').unwrap();
builder.append_slice(b"le").unwrap();
builder.end_label();
builder.append_slice(b"com").unwrap();
assert_eq!(builder.finish().as_slice(), b"\x03www\x07example\x03com");
}
#[test]
fn build_by_label() {
let mut builder = NameBuilder::new_vec();
builder.append_label(b"www").unwrap();
builder.append_label(b"example").unwrap();
builder.append_label(b"com").unwrap();
assert_eq!(builder.finish().as_slice(), b"\x03www\x07example\x03com");
}
#[test]
fn build_mixed() {
let mut builder = NameBuilder::new_vec();
builder.push(b'w').unwrap();
builder.append_slice(b"ww").unwrap();
builder.append_label(b"example").unwrap();
builder.append_slice(b"com").unwrap();
assert_eq!(builder.finish().as_slice(), b"\x03www\x07example\x03com");
}
#[test]
fn name_limit() {
let mut builder = NameBuilder::new_vec();
for _ in 0..25 {
// 9 bytes label is 10 bytes in total
builder.append_label(b"123456789").unwrap();
}
assert_eq!(builder.append_label(b"12345"), Err(PushError::LongName));
assert_eq!(builder.clone().append_label(b"1234"), Ok(()));
assert_eq!(builder.append_slice(b"12345"), Err(PushError::LongName));
assert_eq!(builder.clone().append_slice(b"1234"), Ok(()));
assert_eq!(builder.append_slice(b"12"), Ok(()));
assert_eq!(builder.push(b'3'), Ok(()));
assert_eq!(builder.push(b'4'), Err(PushError::LongName))
}
#[test]
fn label_limit() {
let mut builder = NameBuilder::new_vec();
builder.append_label(&[0u8; 63][..]).unwrap();
assert_eq!(
builder.append_label(&[0u8; 64][..]),
Err(PushError::LongLabel)
);
assert_eq!(
builder.append_label(&[0u8; 164][..]),
Err(PushError::LongLabel)
);
builder.append_slice(&[0u8; 60][..]).unwrap();
builder.clone().append_label(b"123").unwrap();
assert_eq!(builder.append_slice(b"1234"), Err(PushError::LongLabel));
builder.append_slice(b"12").unwrap();
builder.push(b'3').unwrap();
assert_eq!(builder.push(b'4'), Err(PushError::LongLabel));
}
#[test]
fn finish() {
let mut builder = NameBuilder::new_vec();
builder.append_label(b"www").unwrap();
builder.append_label(b"example").unwrap();
builder.append_slice(b"com").unwrap();
assert_eq!(builder.finish().as_slice(), b"\x03www\x07example\x03com");
}
#[test]
fn into_name() {
let mut builder = NameBuilder::new_vec();
builder.append_label(b"www").unwrap();
builder.append_label(b"example").unwrap();
builder.append_slice(b"com").unwrap();
assert_eq!(
builder.into_name().unwrap().as_slice(),
b"\x03www\x07example\x03com\x00"
);
}
}