[−][src]Crate der_parser

BER/DER Parser

A parser for Basic Encoding Rules (BER [X.690]) and Distinguished Encoding Rules(DER [X.690]), implemented with the nom parser combinator framework.

The code is available on Github and is part of the Rusticata project.

DER parser design

There are two different approaches for parsing DER objects: reading the objects recursively as long as the tags are known, or specifying a description of the expected objects (generally from the ASN.1 description).

The first parsing method can be done using the parse_ber and parse_der methods. However, it cannot fully parse all objects, especially those containing IMPLICIT, OPTIONAL, or DEFINED BY items.

use der_parser::parse_der;

let bytes = [ 0x30, 0x0a,
              0x02, 0x03, 0x01, 0x00, 0x01,
              0x02, 0x03, 0x01, 0x00, 0x00,
];

let parsed = parse_der(&bytes);

The second (and preferred) parsing method is to specify the expected objects recursively. The following macros can be used: parse_der_sequence_defined and similar functions, parse_der_struct, etc.

For example, to read a sequence containing two integers:

use der_parser::ber::*;
use der_parser::error::BerResult;

fn localparse_seq(i:&[u8]) -> BerResult {
    parse_der_sequence_defined!(i,
        parse_ber_integer >>
        parse_ber_integer
    )
}

let bytes = [ 0x30, 0x0a,
              0x02, 0x03, 0x01, 0x00, 0x01,
              0x02, 0x03, 0x01, 0x00, 0x00,
];
let parsed = localparse_seq(&bytes);

All functions return a BerResult object: the parsed BerObject, an Incomplete value, or an error.

Note that this type is also a Result, so usual functions (map, unwrap etc.) are available.

Notes

  • The DER constraints are verified if using parse_der.
  • BerObject and DerObject are the same objects (type alias). The only difference is the verification of constraints during parsing.
  • DER integers can be of any size, so it is not possible to store them as simple integers (they are stored as raw bytes). To get a simple value, use BerObject::as_u32 (knowning that this method will return an error if the integer is too large), BerObject::as_u64, or use the bigint feature of this crate and use BerObject::as_bigint.

References

  • [X.680] Abstract Syntax Notation One (ASN.1): Specification of basic notation.
  • [X.690] ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER).

Modules

ber

Basic Encoding Rules (BER) objects and parser

der

Basic Encoding Rules (BER) objects and parser

error

Error type for BER/DER parsers

oid

Object ID (OID) representation

Macros

parse_der_application

Parse an application DER element

parse_der_optional

Parse an optional DER element

parse_der_sequence_defined

Parse a defined sequence of DER elements

parse_der_sequence_defined_mDeprecated

Parse a defined sequence of DER elements (macro version)

parse_der_sequence_of

Parse a sequence of identical DER elements

parse_der_set_defined

Parse a defined set of DER elements

parse_der_set_defined_mDeprecated

Parse a defined set of DER elements

parse_der_set_of

Parse a set of identical DER elements

parse_der_struct

Parse a constructed DER element

parse_der_tagged

Parse a tagged DER element

Functions

parse_ber

Parse BER object

parse_der

Parse DER object