Crate der_derive[−][src]
Expand description
RustCrypto: DER Custom Derive Support
Custom derive support for the der crate’s Choice and Sequence traits.
Minimum Supported Rust Version
This crate requires Rust 1.56 at a minimum.
We may change the MSRV in the future, but it will be accompanied by a minor version bump.
License
Licensed under either of:
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
About
Custom derive support for the der crate.
This crate contains custom derive macros intended to be used in the following way:
Choice: map ASN.1CHOICEto a Rust enum.Enumerated: map ASN.1ENUMERATEDto a C-like Rust enum.Sequence: map ASN.1SEQUENCEto a Rust struct.ValueOrd: determine DER ordering for ASN.1SET OF.
Note that this crate shouldn’t be used directly, but instead accessed
by using the derive feature of the der crate, which re-exports the
above macros from the toplevel.
Why not serde?
The der crate is designed to be easily usable in embedded environments,
including ones where code size comes at a premium.
This crate (i.e. der_derive) is able to generate code which is
significantly smaller than serde_derive. This is because the der
crate has been designed with high-level abstractions which reduce
code size, including trait object-based encoders which allow encoding
logic which is duplicated in serde serializers to be implemented in
a single place in the der crate.
This is a deliberate tradeoff in terms of performance, flexibility, and
code size. At least for now, the der crate is optimizing for leveraging
as many abstractions as it can to minimize code size.
Toplevel attributes
The following attributes can be added to an enum or struct when
deriving either Choice or Sequence respectively:
#[asn1(tag_mode = "...")] attribute: EXPLICIT vs IMPLICIT
This attribute can be used to declare the tagging mode used by a particular ASN.1 module.
It’s used when parsing CONTEXT-SENSITIVE fields.
The default is EXPLICIT, so the attribute only needs to be added when
a particular module is declared IMPLICIT.
Field-level attributes
The following attributes can be added to either the fields of a particular
struct or the variants of a particular enum:
#[asn1(context_specific = "...")] attribute: CONTEXT-SPECIFIC support
This attribute can be added to associate a particular CONTEXT-SPECIFIC
tag number with a given enum variant or struct field.
The value must be quoted and contain a number, e.g. #[asn1(context_specific = "42"].
#[asn1(default = "...")] attribute: DEFAULT support
This behaves like serde_derive’s default attribute, allowing you to
specify the path to a function which returns a default value.
#[asn1(extensible = "true")] attribute: support for ... extensibility operator
This attribute can be applied to the fields of struct types, and will
skip over unrecognized lower-numbered CONTEXT-SPECIFIC fields when
looking for a particular field of a struct.
#[asn1(optional = "true")] attribute: support for OPTIONAL fields
This attribute explicitly annotates a field as OPTIONAL.
#[asn1(type = "...")] attribute: ASN.1 type declaration
This attribute can be used to specify the ASN.1 type for a particular
enum variant or struct field.
It’s presently mandatory for all enum variants, even when using one of
the ASN.1 types defined by this crate.
For structs, placing this attribute on a field makes it possible to
decode/encode types which don’t directly implement the Decode/Encode
traits but do impl From and TryInto and From for one of the ASN.1 types
listed below (use the ASN.1 type keywords as the type):
BIT STRING: performs an intermediate conversion toder::asn1::BitStringIA5String: performs an intermediate conversion toder::asn1::IA5StringGeneralizedTime: performs an intermediate conversion toder::asn1::GeneralizedTimeOCTET STRING: performs an intermediate conversion toder::asn1::OctetStringPrintableString: performs an intermediate conversion toder::asn1::PrintableStringUTCTime: performs an intermediate conversion toder::asn1::UtcTimeUTF8String: performs an intermediate conversion toder::asn1::Utf8String
Note: please open a GitHub Issue if you would like to request support for additional ASN.1 types.
Derive Macros
Derive decoders and encoders for ASN.1 Enumerated types on a
C-like enum type.