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//! ASN.1 Object Identifiers. //! //! This module contains the [`Oid`] type that implements object identifiers, //! a construct used by ANS.1 to uniquely identify all sorts of things. The //! type is also re-exported at the top-level. //! //! [`Oid`]: struct.Oid.html use std::{fmt, hash, io}; use bytes::Bytes; use super::{decode, encode}; use super::decode::Source; use super::mode::Mode; use super::tag::Tag; //------------ Oid ----------------------------------------------------------- /// An object identifer. /// /// Object identifiers are globally unique, hierarchical values that are used /// to identify objects or their type. When written, they are presented as a /// sequence of integers separated by dots such as ‘1.3.6.1.5.5.7.1’ or with /// the integers separated by white space and enclosed in curly braces such /// as ‘{ 1 3 6 1 5 5 7 1 }’. Individual integers or sequences of integers /// can also be given names which then are used instead of the integers. /// /// Values of this type keep a single object identifer in its BER encoding, /// i.e., in some form of byte sequence. Because different representations /// may be useful, the type is actually generic over something that can /// become a reference to a bytes slice. Parsing is only defined for `Bytes` /// values, though. /// /// The only use for object identifiers currently is to compare them to /// predefined values. For this purpose, you typically define your known /// object identifiers in a `oid` submodule as contants of /// `Oid<&'static [u8]>` – or its type alias `ConstOid`. This is also the /// reason why the wrapped value is `pub` for now. This will change once /// `const fn` is stable. /// /// Unfortunately, there is currently no proc macro to generate the object /// identifier constants in the code. Instead, the crate ships with a /// `mkoid` binary which accepts object identifiers in ‘dot integer’ notation /// and produces the `u8` array for their encoded value. You can install /// this binary via `cargo install ber`. #[derive(Clone, Debug)] pub struct Oid<T: AsRef<[u8]>=Bytes>(pub T); /// A type alias for `Oid<&'static [u8]>. /// /// This is useful when defining object identifier constants. pub type ConstOid = Oid<&'static [u8]>; /// # Decoding and Encoding /// impl Oid<Bytes> { /// Skips over an object identifier value. /// /// If the source has reached its end, if the next value does not have /// the `Tag::OID`, or if it is not a primitive value, returns a malformed /// error. pub fn skip_in<S: decode::Source>( cons: &mut decode::Constructed<S> ) -> Result<(), S::Err> { cons.take_primitive_if(Tag::OID, |prim| prim.skip_all()) } /// Skips over an optional object identifier value. /// /// If the source has reached its end of if the next value does not have /// the `Tag::OID`, returns `Ok(None)`. If the next value has the right /// tag but is not a primitive value, returns a malformed error. pub fn skip_opt_in<S: decode::Source>( cons: &mut decode::Constructed<S> ) -> Result<Option<()>, S::Err> { cons.take_opt_primitive_if(Tag::OID, |prim| prim.skip_all()) } /// Takes an object identifier value from the source. /// /// If the source has reached its end, if the next value does not have /// the `Tag::OID`, or if it is not a primitive value, returns a malformed /// error. pub fn take_from<S: decode::Source>( constructed: &mut decode::Constructed<S> ) -> Result<Self, S::Err> { constructed.take_primitive_if(Tag::OID, |content| { content.take_all().map(Oid) }) } /// Takes an optional object identifier value from the source. /// /// If the source has reached its end of if the next value does not have /// the `Tag::OID`, returns `Ok(None)`. If the next value has the right /// tag but is not a primitive value, returns a malformed error. pub fn take_opt_from<S: decode::Source>( constructed: &mut decode::Constructed<S> ) -> Result<Option<Self>, S::Err> { constructed.take_opt_primitive_if(Tag::OID, |content| { content.take_all().map(Oid) }) } } impl<T: AsRef<[u8]>> Oid<T> { /// Skip over an object identifier if it matches `self`. pub fn skip_if<S: decode::Source>( &self, constructed: &mut decode::Constructed<S> ) -> Result<(), S::Err> { constructed.take_primitive_if(Tag::OID, |content| { let len = content.remaining(); content.request(len)?; if &content.slice()[..len] == self.0.as_ref() { content.skip_all()?; Ok(()) } else { xerr!(Err(decode::Error::Malformed.into())) } }) } } /// # Access to Sub-identifiers /// impl<T: AsRef<[u8]>> Oid<T> { /// Returns an iterator to the components of this object identifiers. /// /// # Panics /// /// The returned identifier will eventually panic if `self` does not /// contain a correctly encoded object identifier. pub fn iter(&self) -> Iter { Iter::new(self.0.as_ref()) } } //--- AsRef impl<T: AsRef<[u8]>> AsRef<[u8]> for Oid<T> { fn as_ref(&self) -> &[u8] { self.0.as_ref() } } //--- PartialEq and Eq impl<T: AsRef<[u8]>, U: AsRef<[u8]>> PartialEq<Oid<U>> for Oid<T> { fn eq(&self, other: &Oid<U>) -> bool { self.0.as_ref() == other.0.as_ref() } } impl<T: AsRef<[u8]>> Eq for Oid<T> { } //--- Hash impl<T: AsRef<[u8]>> hash::Hash for Oid<T> { fn hash<H: hash::Hasher>(&self, state: &mut H) { self.0.as_ref().hash(state) } } //--- Display impl<T: AsRef<[u8]>> fmt::Display for Oid<T> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { // XXX This can’t deal correctly with overly large components. // Since this is a really rare (if not non-existant) case, // I can’t be bothered to figure out how to convert a seven // bit integer into decimal. let mut components = self.iter(); // There’s at least one and it is always an valid u32. write!(f, "{}", components.next().unwrap().to_u32().unwrap())?; for component in components { if let Some(val) = component.to_u32() { write!(f, ".{}", val)?; } else { write!(f, ".(not implemented)")?; } } Ok(()) } } //--- encode::PrimitiveContent impl<T: AsRef<[u8]>> encode::PrimitiveContent for Oid<T> { const TAG: Tag = Tag::OID; fn encoded_len(&self, _: Mode) -> usize { self.0.as_ref().len() } fn write_encoded<W: io::Write>( &self, _: Mode, target: &mut W ) -> Result<(), io::Error> { target.write_all(self.0.as_ref()) } } //------------ Component ----------------------------------------------------- /// A component of an object identifier. /// /// Although these components are integers, they are encoded in a slightly /// inconvenient way. Because of this we don’t convert them to native integers /// but rather keep them as references to the underlying octets. /// /// This type allows comparison and formatting, which hopefully is all you’ll /// need. If you insist, the method `to_u32` allows you to try to convert a /// component to a native integer. #[derive(Clone, Copy, Debug)] pub struct Component<'a> { /// The position of the component in the object identifer. position: Position, /// The octets of the subidentifer. /// /// These octets translate to an integer value. The most significant bit /// of each octet indicates whether there are more octets to follow (and /// can thus be ignored in this context), the lower seven bits are then /// shifted accordingly to make up an unsigned integer in big endian /// notation. Since this isn’t bounded in any way, we can’t just simply /// turn these into, say, `u32`s although, realistically, it is unlikely /// there is anything bigger than that. slice: &'a [u8], } /// The position of the component in the object identifier. /// /// As the first two components of the object identifer are encoded in the /// first subidentifier of the encoded value, we have three different cases. #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)] enum Position { /// This is the first component of the identifier. /// /// This is 0 if the integer value of the subidentifer is 0..39, /// 1 for 40..79, and 2 for anything else. First, /// This is the second component of the identifier. /// /// This is the integer value of the subidentifer module 40 if the value /// is below 80 and otherwise the value minus 80. Second, /// This is any later component of the identifier. /// /// This is identical to the integer value of the subidentifier. Other, } impl<'a> Component<'a> { /// Creates a new component. fn new(slice: &'a [u8], position: Position) -> Self { Component { slice, position } } /// Attempts to convert the component to `u32`. /// /// Since the component’s value can be larger than the maximum value of /// a `u32`, this may fail in which case the method will return `None`. pub fn to_u32(self) -> Option<u32> { // This can be at most five octets with at most four bits in the // topmost octet. if self.slice.len() > 5 || (self.slice.len() == 4 && self.slice[0] & 0x70 != 0) { return None } let mut res = 0; for &ch in self.slice { res = res << 7 | u32::from(ch & 0x7F); } match self.position { Position::First => { if res < 40 { Some(0) } else if res < 80{ Some(1) } else { Some(2) } } Position::Second => { if res < 80 { Some(res % 40) } else { Some(res - 80) } } Position::Other => Some(res) } } } //--- PartialEq and Eq impl<'a> PartialEq for Component<'a> { fn eq(&self, other: &Self) -> bool { self.position == other.position && self.slice == other.slice } } impl<'a> Eq for Component<'a> { } //------------ Iter ---------------------------------------------------------- /// An iterator over the sub-identifiers in an object identifier. pub struct Iter<'a> { /// The remainder of the object identifier’s encoded octets. slice: &'a [u8], /// The position of the next component. position: Position, } impl<'a> Iter<'a> { /// Creates a new iterator. fn new(slice: &'a [u8]) -> Self { Iter { slice, position: Position::First } } fn advance_position(&mut self) -> Position { let res = self.position; self.position = match res { Position::First => Position::Second, _ => Position::Other }; res } } impl<'a> Iterator for Iter<'a> { type Item = Component<'a>; fn next(&mut self) -> Option<Self::Item> { if self.slice.is_empty() { return None } for i in 0..self.slice.len() { if self.slice[i] & 0x80 == 0 { let (res, tail) = self.slice.split_at(i); self.slice = tail; return Some(Component::new(res, self.advance_position())); } } panic!("illegal object identifier (last octet has bit 8 set)"); } }