Crate simple_asn1

A small ASN.1 parsing library for Rust. In particular, this library is used to translate the binary DER encoding of an ASN.1-formatted document into the core primitives of ASN.1. It is assumed that you can do what you need to from there.

The critical items for this document are the traits ToASN1 and FromASN1. The first takes your data type and encodes it into a Vec of simple ASN.1 structures (ASN1Blocks). The latter inverts the process.

Items that implement ToASN1 can be used with the function der_encode to provide single-step encoding of a data type to binary DER encoding. Similarly, items that are FromASN can be single-step decoded using the helper function der_decode.

You can implement one or both traits, depending on your needs. If you do implement both, the obvious encode/decode quickcheck property is strongly advised.

For decoding schemes that require the actual bytes associated with the binary representation, we also provide FromASN1WithBody. This can be used with the offset information in the primitive ASN1Blocks to, for example, validate signatures in X509 documents.

Finally, this library supports ASN.1 class information. I’m still not sure why it’s useful, but there it is.

Please send any bug reports, patches, and curses to the GitHub repository at https://github.com/acw/simple_asn1.

Macros

• oid
  A handy macro for generating OIDs from a sequence of u64s.

Structs

• BigInt
  A big signed integer type.
• BigUint
  A big unsigned integer type.
• OID
  An ASN.1 OID.

Enums

• ASN1Block
  A primitive block from ASN.1.
• ASN1Class
  An ASN.1 block class.
• ASN1DecodeErr
  An error that can arise decoding ASN.1 primitive blocks.
• ASN1EncodeErr
  An error that can arise encoding ASN.1 primitive blocks.

Traits

• FromASN1
  A trait defining types that can be decoded from an ASN1Block stream. Any member of this trait is also automatically a member of FromASN1WithBody, as it can obviously just ignore the body.
• FromASN1WithBody
  A trait defining types that can be decoded from an ASN1Block stream, assuming they also have access to the underlying bytes making up the stream.
• ToASN1
  The set of types that can automatically converted into a sequence of ASN1Blocks. You should probably use to_asn1() but implement to_asn1_class(). The former has a default implementation that passes ASN1Class::Universal as the tag to use, which should be good for most people.

Functions

• der_decode
  Automatically decode a type via DER encoding, assuming that the type is a member of FromASN1 or FromASN1WithBody.
• der_encode
  Automatically encode a type into binary via DER encoding, assuming that the type is a member of ToASN1.
• from_der
  Translate a binary blob into a series of ASN1Blocks, or provide an error if it didn’t work.
• to_der
  Given an ASN1Block, covert it to its DER encoding, or return an error if something broke along the way.