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//! Variable length octet sequences. //! //! This module provides the basic traits that allow defining types that are //! generic over a variable length sequence of octets. It implements these //! traits for most comonly used types of such sequences and provides a few //! additional types for use in a no-std environment. In addition, it provides //! a few types and traits that make it easier to access data contained in //! such sequences. //! //! //! # Traits for Octet Sequences //! //! There are two fundamental types of octet sequences. If a sequence is of a //! given size, we call it simply ‘octets.’ If the sequence is actually a //! buffer into which octets can be placed, it is called an `octets builder.` //! //! //! ## Octets and Octets References //! //! There is no special trait for octets, we simply use `AsRef<[u8]>` for //! imutable octets or `AsMut<[u8]>` if the octets of the sequence can be //! manipulated (but the length is still fixed). This way, any type //! implementing these traits can be used already. The trait [`OctetsExt`] //! has been defined to collect additional methods that aren’t available via //! plain `AsRef<[u8]>`. //! //! A reference to an octets type implements [`OctetsRef`]. The main purpose //! of this trait is to allow cheaply taking a sub-sequence, called a ‘range’, //! out of the octets. For most types, ranges will be octet slices `&[u8]` but //! some shareable types (most notably `bytes::Bytes`) allow ranges to be //! owned values, thus avoiding the lifetime limitations a slice would //! bring. //! //! One type is special in that it is its own octets reference: `&[u8]`, //! referred to as an octets slice in the documentation. This means that you //! always use an octets slice irregardless whether a type is generic over //! an octets sequence or an octets reference. Because an octets slice is //! also a useful basis when only looking at some value without planning on //! keeping any ranges from it, most generic types provide a method //! `for_slice` that converts the value from whatever octets type it is //! currently generic over into an identical value atop a octets slice of //! that sequence. //! //! The trait is separate because of limitations of lifetimes in traits. It //! has an associated type `OctetsRef::Range` that defines the type of a //! range. When using the trait as a trait bound for a generic type, you will //! typically bound a reference to this type. For instance, a generic function //! taking part out of some octets and returning a reference to it could be //! defined like so: //! //! ``` //! # use domain::base::octets::OctetsRef; //! //! fn take_part<'a, Octets>( //! src: &'a Octets //! ) -> <&'a Octets as OctetsRef>::Range //! where &'a Octets: OctetsRef { //! unimplemented!() //! } //! ``` //! //! The where clause demands that whatever octets type is being used, a //! reference to it must be an octets ref. The return value refers to the //! range type defined for this octets ref. The lifetime argument is //! necessary to tie all these references together. //! //! //! ## Octets Builders //! //! Octets builders and their [`OctetsBuilder`] trait are comparatively //! straightforward. They represent a buffer to which octets can be appended. //! Whether the buffer can grow to accommodate appended data depends on the //! underlying type. Because it may not, all such operations may fail with a //! [`ShortBuf`] error. //! //! The [`EmptyBuilder`] trait marks a type as being able to create a new, //! empty builder. //! //! //! ## Conversion Traits //! //! A series of special traits allows converting octets into octets builder //! and vice versa. They pair octets with their natural builders via //! associated types. These conversions are always cyclic, i.e., if an //! octets value is converted into a builder and then that builder is //! converted back into an octets value, the initial and final octets value //! have the same type. //! //! //! ## Using Trait Bounds //! //! When using these traits as bounds for generic types, always limit yourself //! to the most loose bounds you can get away with. Not all types holding //! octet sequences can actually implement all these traits, so by being to //! eager you may paint yourself into a corner. //! //! In many cases you can get away with a simple `AsRef<[u8]>` bound. Only use //! an explicit `OctetsRef` bound when you need to return a range that may be //! kept around. //! //! //! # Composing and Parsing //! //! Octet sequences are often used to encode data, such as with the DNS wire //! format. We call the process of converting data into its octet sequence //! encoding ‘composing’ and the reverse process of reading data out of its //! encoded form ‘parsing.’ In order to make implementing these functions //! easier, the module contains a traits for types that can be composed or //! parsed as well as helper types for parsing. //! //! ## Composing //! //! Composing encoded data always happens directly into an octets builder. //! Any type that can be encoded as DNS wire data implements the [`Compose`] //! trait through which its values can be appened to the builder. //! //! ## Parsing //! //! Parsing is a little more complicated since encoded data may very well be //! broken or ambiguously encoded. The helper type [`Parser`] wraps an octets //! ref and allows to parse values from the octets. The trait [`Parse`] is //! implemented by types that can decode values from octets. //! //! //! # Octet Sequences for `no_std` Use //! //! When using the crate without an allocator, creating octets sequences can //! be difficult. However, since DNS data is often limited in size, you can in //! many cases get away with using a octets array as the basis for an octets //! sequence. The crate provides a macro [`octets_array!`] to define such a //! type for specific array length. The octets module also contains a number //! of types defined via that module for typical array sizes. //! //! //! [`Compose`]: trait.Compose.html //! [`EmptyBuilder`]: trait.EmptyBuilder.html //! [`Octets`]: trait.Octets.html //! [`OctetsExt`]: trait.OctetsExt.html //! [`OctetsBuilder`]: trait.OctetsBuilder.html //! [`OctetsRef`]: trait.OctetsRef.html //! [`Parse`]: trait.Parse.html //! [`Parser`]: struct.Parser.html //! [`ShortBuf`]: struct.ShortBuf.html use super::name::ToDname; use super::net::{Ipv4Addr, Ipv6Addr}; #[cfg(feature = "bytes")] use bytes::{Bytes, BytesMut}; use core::cmp::Ordering; use core::convert::TryFrom; use core::{borrow, fmt, hash}; #[cfg(feature = "smallvec")] use smallvec::{Array, SmallVec}; #[cfg(feature = "std")] use std::borrow::Cow; #[cfg(feature = "std")] use std::vec::Vec; //============ Octets and Octet Builders ===================================== //------------ OctetsExt ----------------------------------------------------- /// An extension trait for octet sequences. /// /// This trait collects some additional functionality that is not available /// via the more general `AsRef<[u8]>`. Currently, that is only truncating /// the sequence to a given length. pub trait OctetsExt: AsRef<[u8]> { /// Truncate the sequence to `len` octets. /// /// If `len` is larger than the length of the sequence, nothing happens. fn truncate(&mut self, len: usize); } impl<'a> OctetsExt for &'a [u8] { fn truncate(&mut self, len: usize) { if len < self.len() { *self = &self[..len] } } } #[cfg(feature = "std")] impl<'a> OctetsExt for Cow<'a, [u8]> { fn truncate(&mut self, len: usize) { match *self { Cow::Borrowed(ref mut slice) => *slice = &slice[..len], Cow::Owned(ref mut vec) => vec.truncate(len), } } } #[cfg(feature = "std")] impl OctetsExt for Vec<u8> { fn truncate(&mut self, len: usize) { self.truncate(len) } } #[cfg(feature = "bytes")] impl OctetsExt for Bytes { fn truncate(&mut self, len: usize) { self.truncate(len) } } #[cfg(feature = "smallvec")] impl<A: Array<Item = u8>> OctetsExt for SmallVec<A> { fn truncate(&mut self, len: usize) { self.truncate(len) } } //------------ OctetsRef ----------------------------------------------------- /// A reference to an octets sequence. /// /// This trait is to be implemented for a (imutable) reference to a type of /// an octets sequence. I.e., it `T` is an octets sequence, `OctetsRef` needs /// to be implemented for `&T`. /// /// The primary purpose of the trait is to allow access to a sub-sequence, /// called a ‘range.’ The type of this range is given via the `Range` /// associated type. For most types it will be a `&[u8]` with a lifetime equal /// to that of the reference itself. Only if an owned range can be created /// cheaply, it should be that type. /// /// There is two basic ways of using the trait for a trait bound. You can /// either limit the octets sequence type itself by bounding references to it /// via a where clause. I.e., for an octets sequence type argument `Octets` /// you can specify `where &'a Octets: OctetsRef` or, if you don’t have a /// lifetime argument available `where for<'a> &'a Octets: OctetsRef`. For /// this option, you’d typically refer to values as references to the /// octets type, i.e., `&Octets`. /// /// Alternatively, you can refer to the reference itself as a owned value. /// This works out fine since all octets references are required to be /// `Copy`. For instance, a function can take a value of generic type `Oref` /// and that type can then be directly bounded via `Oref: OctetsRef`. pub trait OctetsRef: AsRef<[u8]> + Copy + Sized { /// The type of a range of the sequence. type Range: AsRef<[u8]>; /// Returns a sub-sequence or ‘range’ of the sequence. fn range(self, start: usize, end: usize) -> Self::Range; /// Returns a range starting at index `start` and going to the end. fn range_from(self, start: usize) -> Self::Range { self.range(start, self.as_ref().len()) } /// Returns a range from the start to before index `end`. fn range_to(self, end: usize) -> Self::Range { self.range(0, end) } /// Returns a range that covers the entire sequence. fn range_all(self) -> Self::Range { self.range(0, self.as_ref().len()) } } impl<'a, T: OctetsRef> OctetsRef for &'a T { type Range = T::Range; fn range(self, start: usize, end: usize) -> Self::Range { (*self).range(start, end) } } impl<'a> OctetsRef for &'a [u8] { type Range = &'a [u8]; fn range(self, start: usize, end: usize) -> Self::Range { &self[start..end] } } #[cfg(feature = "std")] impl<'a, 's> OctetsRef for &'a Cow<'s, [u8]> { type Range = &'a [u8]; fn range(self, start: usize, end: usize) -> Self::Range { &self.as_ref()[start..end] } } #[cfg(feature = "std")] impl<'a> OctetsRef for &'a Vec<u8> { type Range = &'a [u8]; fn range(self, start: usize, end: usize) -> Self::Range { &self[start..end] } } #[cfg(feature = "bytes")] impl<'a> OctetsRef for &'a Bytes { type Range = Bytes; fn range(self, start: usize, end: usize) -> Self::Range { self.slice(start..end) } } #[cfg(feature = "smallvec")] impl<'a, A: Array<Item = u8>> OctetsRef for &'a SmallVec<A> { type Range = &'a [u8]; fn range(self, start: usize, end: usize) -> Self::Range { &self.as_slice()[start..end] } } //------------ OctetsFrom ---------------------------------------------------- /// Convert a type from one octets type to another. /// /// This trait allows creating a value of a type that is generic over an /// octets sequence from an identical value using a different type of octets /// sequence. /// /// This is different from just `From` in that the conversion may fail if the /// source sequence is longer than the space available for the target type. pub trait OctetsFrom<Source>: Sized { /// Performs the conversion. fn octets_from(source: Source) -> Result<Self, ShortBuf>; } impl<'a, Source: AsRef<[u8]> + 'a> OctetsFrom<&'a Source> for &'a [u8] { fn octets_from(source: &'a Source) -> Result<Self, ShortBuf> { Ok(source.as_ref()) } } #[cfg(feature = "std")] impl<Source> OctetsFrom<Source> for Vec<u8> where Self: From<Source>, { fn octets_from(source: Source) -> Result<Self, ShortBuf> { Ok(From::from(source)) } } #[cfg(feature = "bytes")] impl<Source> OctetsFrom<Source> for Bytes where Self: From<Source>, { fn octets_from(source: Source) -> Result<Self, ShortBuf> { Ok(From::from(source)) } } #[cfg(feature = "bytes")] impl<Source> OctetsFrom<Source> for BytesMut where Self: From<Source>, { fn octets_from(source: Source) -> Result<Self, ShortBuf> { Ok(From::from(source)) } } #[cfg(features = "smallvec")] impl<Source, A> OctetsFrom<Source> for SmallVec<A> where Source: AsRef<u8>, A: Array<Item = u8>, { fn octets_from(source: Source) -> Result<Self, ShortBuf> { Ok(smallvec::ToSmallVec::to_smallvec(source.as_ref())) } } //------------ OctetsInto ---------------------------------------------------- /// Convert a type from one octets type to another. /// /// This trait allows trading in a value of a type that is generic over an /// octets sequence for an identical value using a different type of octets /// sequence. /// /// This is different from just `Into` in that the conversion may fail if the /// source sequence is longer than the space available for the target type. /// /// This trait has a blanket implementation for all pairs of types where /// `OctetsFrom` has been implemented. pub trait OctetsInto<Target> { /// Performs the conversion. fn octets_into(self) -> Result<Target, ShortBuf>; } impl<Source, Target: OctetsFrom<Source>> OctetsInto<Target> for Source { fn octets_into(self) -> Result<Target, ShortBuf> { Target::octets_from(self) } } //------------ OctetsBuilder ------------------------------------------------- /// A buffer to construct an octet sequence. /// /// Octet builders represent a buffer of space available for building an /// octets sequence by appending the contents of octet slices. The buffers /// may consist of a predefined amount of space or grow as needed. /// /// Octet builders provide access to the already assembled data through /// octet slices via their implementations of `AsRef<[u8]>` and /// `AsMut<[u8]>`. pub trait OctetsBuilder: AsRef<[u8]> + AsMut<[u8]> + Sized { /// The type of the octets the builder can be converted into. /// /// If `Octets` implements [`IntoBuilder`], the `Builder` associated /// type of that trait must be `Self`. /// /// [`IntoBuilder`]: trait.IntoBuilder.html type Octets: AsRef<[u8]>; /// Appends the content of a slice to the builder. /// /// If there isn’t enough space available for appending the slice, /// returns an error and leaves the builder alone. fn append_slice(&mut self, slice: &[u8]) -> Result<(), ShortBuf>; /// Truncates the builder back to a length of `len` octets. fn truncate(&mut self, len: usize); /// Converts the builder into immutable octets. fn freeze(self) -> Self::Octets; /// Returns the length of the already assembled data. /// /// This is a convenience method and identical to `self.as_ref().len()`. fn len(&self) -> usize { self.as_ref().len() } /// Returns whether the builder is currently empty. /// /// This is a convenience method and identical to /// `self.as_ref().is_empty()`. fn is_empty(&self) -> bool { self.as_ref().is_empty() } /// Appends all data or nothing. /// /// The method executes the provided closure that presumably will try to /// append data to the builder and propagates an error from the builder. /// If the closure returns with an error, the builder is truncated back /// to the length from before the closure was executed. /// /// Note that upon an error the builder is _only_ truncated. If the /// closure modified any already present data via `AsMut<[u8]>`, these /// modification will survive. fn append_all<F>(&mut self, op: F) -> Result<(), ShortBuf> where F: FnOnce(&mut Self) -> Result<(), ShortBuf>, { let pos = self.len(); match op(self) { Ok(_) => Ok(()), Err(_) => { self.truncate(pos); Err(ShortBuf) } } } /// Appends a domain name using name compression if supported. /// /// Domain name compression attempts to lower the size of a DNS message /// by avoiding to include repeated domain name suffixes. Instead of /// adding the full suffix, a pointer to the location of the previous /// occurence is added. Since that occurence may itself contain a /// compressed suffix, doing name compression isn’t cheap and therefore /// optional. However, in order to be able to opt in, we need to know /// if we are dealing with a domain name that ought to be compressed. /// /// The trait provides a default implementation which simply appends the /// name uncompressed. fn append_compressed_dname<N: ToDname>( &mut self, name: &N, ) -> Result<(), ShortBuf> { if let Some(slice) = name.as_flat_slice() { self.append_slice(slice) } else { self.append_all(|target| { for label in name.iter_labels() { label.build(target)?; } Ok(()) }) } } /// Prepends some appended data with its length as a `u16`. /// /// The method will append the data being added via the closure `op` to /// the builder prepended with a 16 bit unsigned value of its length. /// /// The implementation will prepend a `0u16` before executing the closure /// and update it to the number of octets added afterwards. If the /// closure adds more than 65535 octets or if any appending fails, the /// builder will be truncated to its previous length. fn u16_len_prefixed<F>(&mut self, op: F) -> Result<(), ShortBuf> where F: FnOnce(&mut Self) -> Result<(), ShortBuf>, { let pos = self.len(); self.append_slice(&[0; 2])?; match op(self) { Ok(_) => { let len = self.len() - pos - 2; if len > usize::from(u16::max_value()) { self.truncate(pos); Err(ShortBuf) } else { self.as_mut()[pos..pos + 2] .copy_from_slice(&(len as u16).to_be_bytes()); Ok(()) } } Err(_) => { self.truncate(pos); Err(ShortBuf) } } } } #[cfg(feature = "std")] impl OctetsBuilder for Vec<u8> { type Octets = Self; fn append_slice(&mut self, slice: &[u8]) -> Result<(), ShortBuf> { self.extend_from_slice(slice); Ok(()) } fn truncate(&mut self, len: usize) { Vec::truncate(self, len) } fn freeze(self) -> Self::Octets { self } } #[cfg(feature = "bytes")] impl OctetsBuilder for BytesMut { type Octets = Bytes; fn append_slice(&mut self, slice: &[u8]) -> Result<(), ShortBuf> { self.extend_from_slice(slice); Ok(()) } fn truncate(&mut self, len: usize) { BytesMut::truncate(self, len) } fn freeze(self) -> Self::Octets { self.freeze() } } #[cfg(feature = "smallvec")] impl<A: Array<Item = u8>> OctetsBuilder for SmallVec<A> { type Octets = Self; fn append_slice(&mut self, slice: &[u8]) -> Result<(), ShortBuf> { self.extend_from_slice(slice); Ok(()) } fn truncate(&mut self, len: usize) { SmallVec::truncate(self, len) } fn freeze(self) -> Self::Octets { self } } //------------ EmptyBuilder -------------------------------------------------- /// An octets builder that can be newly created empty. pub trait EmptyBuilder { /// Creates a new empty octets builder with a default size. fn empty() -> Self; /// Creates a new empty octets builder with a suggested initial size. /// /// The builder may or may not use the size provided by `capacity` as the /// initial size of the buffer. It may very well be possibly that the /// builder is never able to grow to this capacity at all. Therefore, /// even if you create a builder for your data size via this function, /// appending may still fail. fn with_capacity(capacity: usize) -> Self; } #[cfg(feature = "std")] impl EmptyBuilder for Vec<u8> { fn empty() -> Self { Vec::new() } fn with_capacity(capacity: usize) -> Self { Vec::with_capacity(capacity) } } #[cfg(feature = "bytes")] impl EmptyBuilder for BytesMut { fn empty() -> Self { BytesMut::new() } fn with_capacity(capacity: usize) -> Self { BytesMut::with_capacity(capacity) } } #[cfg(feature = "smallvec")] impl<A: Array<Item = u8>> EmptyBuilder for SmallVec<A> { fn empty() -> Self { SmallVec::new() } fn with_capacity(capacity: usize) -> Self { SmallVec::with_capacity(capacity) } } //------------ IntoBuilder --------------------------------------------------- /// An octets type that can be converted into an octets builder. pub trait IntoBuilder { /// The type of octets builder this octets type can be converted into. type Builder: OctetsBuilder; /// Converts an octets value into an octets builder. fn into_builder(self) -> Self::Builder; } #[cfg(feature = "std")] impl IntoBuilder for Vec<u8> { type Builder = Self; fn into_builder(self) -> Self::Builder { self } } #[cfg(feature = "std")] impl<'a> IntoBuilder for &'a [u8] { type Builder = Vec<u8>; fn into_builder(self) -> Self::Builder { self.into() } } #[cfg(feature = "std")] impl<'a> IntoBuilder for Cow<'a, [u8]> { type Builder = Vec<u8>; fn into_builder(self) -> Self::Builder { self.into_owned() } } #[cfg(feature = "bytes")] impl IntoBuilder for Bytes { type Builder = BytesMut; fn into_builder(self) -> Self::Builder { // XXX Currently, we need to copy to do this. If bytes gains a way // to convert from Bytes to BytesMut for non-shared data without // copying, we should change this. BytesMut::from(self.as_ref()) } } #[cfg(feature = "smallvec")] impl<A: Array<Item = u8>> IntoBuilder for SmallVec<A> { type Builder = Self; fn into_builder(self) -> Self::Builder { self } } //------------ FromBuilder --------------------------------------------------- /// An octets type that can be created from an octets builder. pub trait FromBuilder: AsRef<[u8]> + Sized { /// The type of builder this octets type can be created from. type Builder: OctetsBuilder<Octets = Self>; /// Creates an octets value from an octets builder. fn from_builder(builder: Self::Builder) -> Self; } #[cfg(feature = "std")] impl FromBuilder for Vec<u8> { type Builder = Self; fn from_builder(builder: Self) -> Self { builder } } #[cfg(feature = "bytes")] impl FromBuilder for Bytes { type Builder = BytesMut; fn from_builder(builder: Self::Builder) -> Self { builder.freeze() } } #[cfg(feature = "smallvec")] impl<A: Array<Item = u8>> FromBuilder for SmallVec<A> { type Builder = Self; fn from_builder(builder: Self) -> Self { builder } } //============ Parsing ======================================================= //------------ Parser -------------------------------------------------------- /// A parser for sequentially extracting data from an octets sequence. /// /// The parser wraps an [octets reference] and remembers the read position on /// the referenced sequence. Methods allow reading out data and progressing /// the position beyond processed data. /// /// [octets reference]: trait.OctetsRef.html #[derive(Clone, Copy, Debug)] pub struct Parser<Ref> { /// The underlying octets reference. octets: Ref, /// The current position of the parser from the beginning of `octets`. pos: usize, /// The length of the octets sequence. /// /// This starts out as the length of the underlying sequence and is kept /// here to be able to temporarily limit the allowed length for /// `parse_blocks`. len: usize, } impl<Ref> Parser<Ref> { /// Creates a new parser atop a reference to an octet sequence. pub fn from_ref(octets: Ref) -> Self where Ref: AsRef<[u8]>, { Parser { pos: 0, len: octets.as_ref().len(), octets, } } /// Returns the wrapped reference to the underlying octets sequence. pub fn octets_ref(&self) -> Ref where Ref: Copy, { self.octets } /// Returns the current parse position as an index into the octets. pub fn pos(&self) -> usize { self.pos } /// Returns the length of the underlying octet sequence. /// /// This is _not_ the number of octets left for parsing. Use /// [`remaining`] for that. /// /// [`remaining`]: #method.remaining pub fn len(&self) -> usize { self.len } /// Returns whether the underlying octets sequence is empty. /// /// This does _not_ return whether there are no more octets left to parse. pub fn is_empty(&self) -> bool { self.len == 0 } } impl Parser<&'static [u8]> { /// Creates a new parser atop a static byte slice. /// /// This function is most useful for testing. pub fn from_static(slice: &'static [u8]) -> Self { Self::from_ref(slice) } } impl<Ref: AsRef<[u8]>> Parser<Ref> { /// Returns an octets slice of the underlying sequence. /// /// The slice covers the entire sequence, not just the remaining data. You /// can use [`peek`] for that. /// /// [`peek`]: #method.peek pub fn as_slice(&self) -> &[u8] { &self.octets.as_ref()[..self.len] } /// Returns a mutable octets slice of the underlying sequence. /// /// The slice covers the entire sequence, not just the remaining data. pub fn as_slice_mut(&mut self) -> &mut [u8] where Ref: AsMut<[u8]>, { &mut self.octets.as_mut()[..self.len] } /// Returns the number of remaining octets to parse. pub fn remaining(&self) -> usize { self.len - self.pos } /// Returns a slice for the next `len` octets. /// /// If less than `len` octets are left, returns an error. pub fn peek(&self, len: usize) -> Result<&[u8], ParseError> { self.check_len(len)?; Ok(&self.peek_all()[..len]) } /// Returns a slice of the data left to parse. pub fn peek_all(&self) -> &[u8] { &self.octets.as_ref()[self.pos..] } /// Repositions the parser to the given index. /// /// It is okay to reposition anywhere within the sequence. However, /// if `pos` is larger than the length of the sequence, an error is /// returned. pub fn seek(&mut self, pos: usize) -> Result<(), ParseError> { if pos > self.len { Err(ParseError::ShortInput) } else { self.pos = pos; Ok(()) } } /// Advances the parser‘s position by `len` octets. /// /// If this would take the parser beyond its end, an error is returned. pub fn advance(&mut self, len: usize) -> Result<(), ParseError> { if len > self.remaining() { Err(ParseError::ShortInput) } else { self.pos += len; Ok(()) } } /// Advances to the end of the parser. pub fn advance_to_end(&mut self) { self.pos = self.len } /// Checks that there are `len` octets left to parse. /// /// If there aren’t, returns an error. pub fn check_len(&self, len: usize) -> Result<(), ParseError> { if self.remaining() < len { Err(ParseError::ShortInput) } else { Ok(()) } } } impl<Ref: AsRef<[u8]>> Parser<Ref> { /// Takes and returns the next `len` octets. /// /// Advances the parser by `len` octets. If there aren’t enough octats /// left, leaves the parser untouched and returns an error instead. pub fn parse_octets( &mut self, len: usize, ) -> Result<Ref::Range, ParseError> where Ref: OctetsRef, { let end = self.pos + len; if end > self.len { return Err(ParseError::ShortInput); } let res = self.octets.range(self.pos, end); self.pos = end; Ok(res) } /// Fills the provided buffer by taking octets from the parser. /// /// Copies as many octets as the buffer is long from the parser into the /// buffer and advances the parser by that many octets. /// /// If there aren’t enough octets left in the parser to fill the buffer /// completely, returns an error and leaves the parser untouched. pub fn parse_buf(&mut self, buf: &mut [u8]) -> Result<(), ParseError> { let pos = self.pos; self.advance(buf.len())?; buf.copy_from_slice(&self.octets.as_ref()[pos..self.pos]); Ok(()) } /// Takes an `i8` from the beginning of the parser. /// /// Advances the parser by one octet. If there aren’t enough octets left, /// leaves the parser untouched and returns an error instead. pub fn parse_i8(&mut self) -> Result<i8, ParseError> { let res = self.peek(1)?[0] as i8; self.pos += 1; Ok(res) } /// Takes a `u8` from the beginning of the parser. /// /// Advances the parser by one octet. If there aren’t enough octets left, /// leaves the parser untouched and returns an error instead. pub fn parse_u8(&mut self) -> Result<u8, ParseError> { let res = self.peek(1)?[0]; self.pos += 1; Ok(res) } /// Takes an `i16` from the beginning of the parser. /// /// The value is converted from network byte order into the system’s own /// byte order if necessary. The parser is advanced by two octets. If /// there aren’t enough octets left, leaves the parser untouched and /// returns an error instead. pub fn parse_i16(&mut self) -> Result<i16, ParseError> { let mut res = [0; 2]; self.parse_buf(&mut res)?; Ok(i16::from_be_bytes(res)) } /// Takes a `u16` from the beginning of the parser. /// /// The value is converted from network byte order into the system’s own /// byte order if necessary. The parser is advanced by two ocetets. If /// there aren’t enough octets left, leaves the parser untouched and /// returns an error instead. pub fn parse_u16(&mut self) -> Result<u16, ParseError> { let mut res = [0; 2]; self.parse_buf(&mut res)?; Ok(u16::from_be_bytes(res)) } /// Takes an `i32` from the beginning of the parser. /// /// The value is converted from network byte order into the system’s own /// byte order if necessary. The parser is advanced by four octets. If /// there aren’t enough octets left, leaves the parser untouched and /// returns an error instead. pub fn parse_i32(&mut self) -> Result<i32, ParseError> { let mut res = [0; 4]; self.parse_buf(&mut res)?; Ok(i32::from_be_bytes(res)) } /// Takes a `u32` from the beginning of the parser. /// /// The value is converted from network byte order into the system’s own /// byte order if necessary. The parser is advanced by four octets. If /// there aren’t enough octets left, leaves the parser untouched and /// returns an error instead. pub fn parse_u32(&mut self) -> Result<u32, ParseError> { let mut res = [0; 4]; self.parse_buf(&mut res)?; Ok(u32::from_be_bytes(res)) } /// Parses a given amount of octets through a closure. /// /// Parses a block of `limit` octets and moves the parser to the end of /// that block or, if less than `limit` octets are still available, to /// the end of the parser. /// /// The closure `op` will be allowed to parse up to `limit` octets. If it /// does so successfully or returns with a form error, the method returns /// its return value. If it returns with a short buffer error, the method /// returns a form error. If it returns successfully with less than /// `limit` octets parsed, returns a form error indicating trailing data. /// If the limit is larger than the remaining number of octets, returns a /// `ParseError::ShortInput`. /// // XXX NEEDS TESTS!!! pub fn parse_block<F, U>( &mut self, limit: usize, op: F, ) -> Result<U, ParseError> where F: FnOnce(&mut Self) -> Result<U, ParseError>, { let end = self.pos + limit; if end > self.len { self.advance_to_end(); return Err(ParseError::ShortInput); } let len = self.len; self.len = end; let res = op(self); self.len = len; let res = if self.pos != end { Err(ParseError::Form(FormError::new("trailing data in field"))) } else if let Err(ParseError::ShortInput) = res { Err(ParseError::Form(FormError::new("short field"))) } else { res }; self.pos = end; res } } //------------ Parse ------------------------------------------------------ /// A type that can extract a value from a parser. /// /// The trait is a companion to [`Parser<Ref>`]: it allows a type to use a /// parser to create a value of itself. Because types may be generic over /// octets types, the trait is generic over the octets reference of the /// parser in question. Implementations should use minimal trait bounds /// matching the parser methods they use. /// /// For types that are generic over an octets sequence, the reference type /// should be tied to the type’s own type argument. This will avoid having /// to provide type annotations when simply calling `Parse::parse` for the /// type. Typically this will happen via `OctetsRef::Range`. For instance, /// a type `Foo<Octets>` should provide: /// /// ```ignore /// impl<Ref: OctetsRef> Parse<Ref> for Foo<Ref::Range> { /// // etc. /// } /// ``` /// /// [`Parser<Ref>`]: struct.Parser.html pub trait Parse<Ref>: Sized { /// Extracts a value from the beginning of `parser`. /// /// If parsing fails and an error is returned, the parser’s position /// should be considered to be undefined. If it is supposed to be reused /// in this case, you should store the position before attempting to parse /// and seek to that position again before continuing. fn parse(parser: &mut Parser<Ref>) -> Result<Self, ParseError>; /// Skips over a value of this type at the beginning of `parser`. /// /// This function is the same as `parse` but doesn’t return the result. /// It can be used to check if the content of `parser` is correct or to /// skip over unneeded parts of the parser. fn skip(parser: &mut Parser<Ref>) -> Result<(), ParseError>; } impl<T: AsRef<[u8]>> Parse<T> for i8 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_i8().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(1).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for u8 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_u8().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(1).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for i16 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_i16().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(2).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for u16 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_u16().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(2).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for i32 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_i32().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(4).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for u32 { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { parser.parse_u32().map_err(Into::into) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(4).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for Ipv4Addr { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { Ok(Self::new( u8::parse(parser)?, u8::parse(parser)?, u8::parse(parser)?, u8::parse(parser)?, )) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(4).map_err(Into::into) } } impl<T: AsRef<[u8]>> Parse<T> for Ipv6Addr { fn parse(parser: &mut Parser<T>) -> Result<Self, ParseError> { let mut buf = [0u8; 16]; parser.parse_buf(&mut buf)?; Ok(buf.into()) } fn skip(parser: &mut Parser<T>) -> Result<(), ParseError> { parser.advance(16).map_err(Into::into) } } //============ Composing ===================================================== //------------ Compose ------------------------------------------------------- /// A type that knows how to compose itself into an octets builder. /// /// The term ‘composing’ refers to the process of creating a DNS wire-format /// representation of a value’s data by appending this representation to the /// end of an [octets builder]. /// /// The trait supports two different representations: a concrete and a /// canonical representation. The former represents the actual data of the /// value. For instance, it reflects the capitalisation of strings. The /// canonical representation is used when calculating digests or ordering /// values. Typically, it ignores capitalization and never compresses domain /// names. See the documentation of [`CanonicalOrd`] for more details on /// canonical representation. /// /// [octets builder]: trait.OctetsBuilder.html /// [`CanonicalOrd`]: ../cmp/trait.CanonicalOrd.html pub trait Compose { /// Appends the concrete representation of the value to the target. /// /// If the representation doesn’t fit into the builder, returns an error. /// In this case the target is considered undefined. If it is supposed to /// be reused, it needs to be reset specifically. fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf>; /// Appends the canonical representation of the value to the target. /// /// If the representation doesn’t fit into the builder, returns an error. /// In this case the target is considered undefined. If it is supposed to /// be reused, it needs to be reset specifically. fn compose_canonical<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { self.compose(target) } } impl<'a, C: Compose + ?Sized> Compose for &'a C { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { (*self).compose(target) } fn compose_canonical<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { (*self).compose_canonical(target) } } impl Compose for i8 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&[*self as u8]) } } impl Compose for u8 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&[*self]) } } impl Compose for i16 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.to_be_bytes()) } } impl Compose for u16 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.to_be_bytes()) } } impl Compose for i32 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.to_be_bytes()) } } impl Compose for u32 { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.to_be_bytes()) } } impl Compose for Ipv4Addr { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.octets()) } } impl Compose for Ipv6Addr { fn compose<T: OctetsBuilder>( &self, target: &mut T, ) -> Result<(), ShortBuf> { target.append_slice(&self.octets()) } } //------------ octets_array -------------------------------------------------- #[macro_export] macro_rules! octets_array { ( $vis:vis $name:ident => $len:expr) => { /// A fixed length octet buffer. /// /// The type functions both as an octets sequence and an octets /// builder atop a fixed size bytes array. #[derive(Clone)] $vis struct $name { octets: [u8; $len], len: usize } impl $name { /// Creates a new empty value. pub fn new() -> Self { Default::default() } /// Returns the contents as an octet slice. pub fn as_slice(&self) -> &[u8] { &self.octets[..self.len] } /// Returns the contents as a mutable octet slice. pub fn as_slice_mut(&mut self) -> &mut [u8] { &mut self.octets[..self.len] } } impl Default for $name { fn default() -> Self { $name { octets: [0; $len], len: 0 } } } impl<'a> TryFrom<&'a [u8]> for $name { type Error = ShortBuf; fn try_from(src: &'a [u8]) -> Result<Self, ShortBuf> { let len = src.len(); if len > $len { Err(ShortBuf) } else { let mut res = Self::default(); res.octets[..len].copy_from_slice(src); res.len = len; Ok(res) } } } impl core::ops::Deref for $name { type Target = [u8]; fn deref(&self) -> &[u8] { self.as_slice() } } impl core::ops::DerefMut for $name { fn deref_mut(&mut self) -> &mut [u8] { self.as_slice_mut() } } impl AsRef<[u8]> for $name { fn as_ref(&self) -> &[u8] { self.as_slice() } } impl AsMut<[u8]> for $name { fn as_mut(&mut self) -> &mut [u8] { self.as_slice_mut() } } impl borrow::Borrow<[u8]> for $name { fn borrow(&self) -> &[u8] { self.as_slice() } } impl borrow::BorrowMut<[u8]> for $name { fn borrow_mut(&mut self) -> &mut [u8] { self.as_slice_mut() } } impl $crate::base::octets::OctetsBuilder for $name { type Octets = Self; fn append_slice(&mut self, slice: &[u8]) -> Result<(), ShortBuf> { if slice.len() > $len - self.len { Err(ShortBuf) } else { let end = self.len + slice.len(); self.octets[self.len..end].copy_from_slice(slice); self.len = end; Ok(()) } } fn truncate(&mut self, len: usize) { if len < self.len { self.len = len } } fn freeze(self) -> Self::Octets { self } } impl $crate::base::octets::EmptyBuilder for $name { fn empty() -> Self { $name { octets: [0; $len], len: 0 } } fn with_capacity(_capacity: usize) -> Self { Self::empty() } } impl $crate::base::octets::IntoBuilder for $name { type Builder = Self; fn into_builder(self) -> Self::Builder { self } } impl $crate::base::octets::FromBuilder for $name { type Builder = Self; fn from_builder(builder: Self::Builder) -> Self { builder } } impl<T: AsRef<[u8]>> PartialEq<T> for $name { fn eq(&self, other: &T) -> bool { self.as_slice().eq(other.as_ref()) } } impl Eq for $name { } impl<T: AsRef<[u8]>> PartialOrd<T> for $name { fn partial_cmp(&self, other: &T) -> Option<Ordering> { self.as_slice().partial_cmp(other.as_ref()) } } impl Ord for $name { fn cmp(&self, other: &Self) -> Ordering { self.as_slice().cmp(other.as_slice()) } } impl hash::Hash for $name { fn hash<H: hash::Hasher>(&self, state: &mut H) { self.as_slice().hash(state) } } impl fmt::Debug for $name { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.debug_tuple(stringify!($name)) .field(&self.as_slice()) .finish() } } } } octets_array!(pub Octets32 => 32); octets_array!(pub Octets64 => 64); octets_array!(pub Octets128 => 128); octets_array!(pub Octets256 => 256); octets_array!(pub Octets512 => 512); octets_array!(pub Octets1024 => 1024); octets_array!(pub Octets2048 => 2048); octets_array!(pub Octets4096 => 4096); //------------ OctetsVec ----------------------------------------------------- /// A octets vector that doesn’t allocate for small sizes. #[cfg(feature = "smallvec")] pub type OctetsVec = SmallVec<[u8; 24]>; //============ Error Types =================================================== //------------ ShortBuf ------------------------------------------------------ /// An attempt was made to write beyond the end of a buffer. /// /// This type is returned as an error by all functions and methods that append /// data to an [octets builder] when the buffer size of the builder is not /// sufficient to append the data. /// /// [octets builder]: trait.OctetsBuilder.html #[derive(Clone, Debug, Eq, PartialEq)] pub struct ShortBuf; //--- Display and Error impl fmt::Display for ShortBuf { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str("buffer size exceeded") } } #[cfg(feature = "std")] impl std::error::Error for ShortBuf {} //--------- ParseError ------------------------------------------------------- /// An error happened while parsing data. #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub enum ParseError { /// An attempt was made to go beyond the end of the parser. ShortInput, /// A formatting error occurred. Form(FormError), } impl ParseError { /// Creates a new parse error as a form error with the given message. pub fn form_error(msg: &'static str) -> Self { FormError::new(msg).into() } } //--- From impl From<FormError> for ParseError { fn from(err: FormError) -> Self { ParseError::Form(err) } } //--- Display and Error impl fmt::Display for ParseError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { match *self { ParseError::ShortInput => f.write_str("unexpected end of input"), ParseError::Form(ref err) => err.fmt(f), } } } #[cfg(feature = "std")] impl std::error::Error for ParseError {} //------------ FormError ----------------------------------------------------- /// A formatting error occured. /// /// This is a generic error for all kinds of error cases that result in data /// not being accepted. For diagnostics, the error is being given a static /// string describing the error. #[derive(Clone, Copy, Debug, Eq, PartialEq)] pub struct FormError(&'static str); impl FormError { /// Creates a new form error value with the given diagnostics string. pub fn new(msg: &'static str) -> Self { FormError(msg) } } //--- Display and Error impl fmt::Display for FormError { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { f.write_str(self.0) } } #[cfg(feature = "std")] impl std::error::Error for FormError {} //============ Testing ======================================================= #[cfg(test)] mod test { use super::*; #[test] fn pos_seek_remaining() { let mut parser = Parser::from_static(b"0123456789"); assert_eq!(parser.peek(1).unwrap(), b"0"); assert_eq!(parser.pos(), 0); assert_eq!(parser.remaining(), 10); assert_eq!(parser.seek(2), Ok(())); assert_eq!(parser.pos(), 2); assert_eq!(parser.remaining(), 8); assert_eq!(parser.peek(1).unwrap(), b"2"); assert_eq!(parser.seek(10), Ok(())); assert_eq!(parser.pos(), 10); assert_eq!(parser.remaining(), 0); assert_eq!(parser.peek_all(), b""); assert_eq!(parser.seek(11), Err(ParseError::ShortInput)); assert_eq!(parser.pos(), 10); assert_eq!(parser.remaining(), 0); } #[test] fn peek_check_len() { let mut parser = Parser::from_static(b"0123456789"); assert_eq!(parser.peek(2), Ok(b"01".as_ref())); assert_eq!(parser.check_len(2), Ok(())); assert_eq!(parser.peek(10), Ok(b"0123456789".as_ref())); assert_eq!(parser.check_len(10), Ok(())); assert_eq!(parser.peek(11), Err(ParseError::ShortInput)); assert_eq!(parser.check_len(11), Err(ParseError::ShortInput)); parser.advance(2).unwrap(); assert_eq!(parser.peek(2), Ok(b"23".as_ref())); assert_eq!(parser.check_len(2), Ok(())); assert_eq!(parser.peek(8), Ok(b"23456789".as_ref())); assert_eq!(parser.check_len(8), Ok(())); assert_eq!(parser.peek(9), Err(ParseError::ShortInput)); assert_eq!(parser.check_len(9), Err(ParseError::ShortInput)); } #[test] fn peek_all() { let mut parser = Parser::from_static(b"0123456789"); assert_eq!(parser.peek_all(), b"0123456789"); parser.advance(2).unwrap(); assert_eq!(parser.peek_all(), b"23456789"); } #[test] fn advance() { let mut parser = Parser::from_static(b"0123456789"); assert_eq!(parser.pos(), 0); assert_eq!(parser.peek(1).unwrap(), b"0"); assert_eq!(parser.advance(2), Ok(())); assert_eq!(parser.pos(), 2); assert_eq!(parser.peek(1).unwrap(), b"2"); assert_eq!(parser.advance(9), Err(ParseError::ShortInput)); assert_eq!(parser.advance(8), Ok(())); assert_eq!(parser.pos(), 10); assert_eq!(parser.peek_all(), b""); } #[test] fn parse_octets() { let mut parser = Parser::from_static(b"0123456789"); assert_eq!(parser.parse_octets(2).unwrap(), b"01"); assert_eq!(parser.parse_octets(2).unwrap(), b"23"); assert_eq!(parser.parse_octets(7), Err(ParseError::ShortInput)); assert_eq!(parser.parse_octets(6).unwrap(), b"456789"); } #[test] fn parse_buf() { let mut parser = Parser::from_static(b"0123456789"); let mut buf = [0u8; 2]; assert_eq!(parser.parse_buf(&mut buf), Ok(())); assert_eq!(&buf, b"01"); assert_eq!(parser.parse_buf(&mut buf), Ok(())); assert_eq!(&buf, b"23"); let mut buf = [0u8; 7]; assert_eq!(parser.parse_buf(&mut buf), Err(ParseError::ShortInput)); let mut buf = [0u8; 6]; assert_eq!(parser.parse_buf(&mut buf), Ok(())); assert_eq!(&buf, b"456789"); } #[test] fn parse_i8() { let mut parser = Parser::from_static(b"\x12\xd6"); assert_eq!(parser.parse_i8(), Ok(0x12)); assert_eq!(parser.parse_i8(), Ok(-42)); assert_eq!(parser.parse_i8(), Err(ParseError::ShortInput)); } #[test] fn parse_u8() { let mut parser = Parser::from_static(b"\x12\xd6"); assert_eq!(parser.parse_u8(), Ok(0x12)); assert_eq!(parser.parse_u8(), Ok(0xd6)); assert_eq!(parser.parse_u8(), Err(ParseError::ShortInput)); } #[test] fn parse_i16() { let mut parser = Parser::from_static(b"\x12\x34\xef\x6e\0"); assert_eq!(parser.parse_i16(), Ok(0x1234)); assert_eq!(parser.parse_i16(), Ok(-4242)); assert_eq!(parser.parse_i16(), Err(ParseError::ShortInput)); } #[test] fn parse_u16() { let mut parser = Parser::from_static(b"\x12\x34\xef\x6e\0"); assert_eq!(parser.parse_u16(), Ok(0x1234)); assert_eq!(parser.parse_u16(), Ok(0xef6e)); assert_eq!(parser.parse_u16(), Err(ParseError::ShortInput)); } #[test] fn parse_i32() { let mut parser = Parser::from_static(b"\x12\x34\x56\x78\xfd\x78\xa8\x4e\0\0\0"); assert_eq!(parser.parse_i32(), Ok(0x12345678)); assert_eq!(parser.parse_i32(), Ok(-42424242)); assert_eq!(parser.parse_i32(), Err(ParseError::ShortInput)); } #[test] fn parse_u32() { let mut parser = Parser::from_static(b"\x12\x34\x56\x78\xfd\x78\xa8\x4e\0\0\0"); assert_eq!(parser.parse_u32(), Ok(0x12345678)); assert_eq!(parser.parse_u32(), Ok(0xfd78a84e)); assert_eq!(parser.parse_u32(), Err(ParseError::ShortInput)); } }