DER Parser
A DER (X.690) parser, 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_der
method.
However, it cannot fully parse all objects, especially those containing IMPLICIT, OPTIONAL, or
DEFINED BY items.
# extern crate der_parser;
use 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:
# extern crate nom;
# extern crate rusticata_macros;
# extern crate der_parser;
use *;
use ;
#
All functions return an IResult
object from nom
: the parsed
DerObject
, an Incomplete
value, or an error.
Notes
- The DER constraints are not enforced or verified. Because of that, this parser is mostly compatible with BER.
- 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
DerObject::as_u32
(knowning that this method will return an error if the integer is too large), or use thebigint
feature of this crate and useDerObject::as_bigint
.