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 parse_der;
let bytes = ;
let parsed = parse_der;
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 *;
use BerResult;
let bytes = ;
let parsed = localparse_seq;
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
andDerObject
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 thebigint
feature of this crate and useBerObject::as_bigint
.
Serialization
Support for encoding BER/DER objects is currently being tested and can be used by activating the serialize
feature.
Note that current status is experimental.
See the ber_encode_*
functions in the ber
module, and BerObject::to_vec
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).
Changes
See CHANGELOG.md
, and UPGRADING.md
for instructions for upgrading major versions.
License
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
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.