A parser for Basic Encoding Rules (BER [[X.690]]) and Distinguished Encoding Rules(DER [[X.690]]), implemented with the nom parser combinator framework.
It is written in pure Rust, fast, and makes extensive use of zero-copy. A lot of care is taken to ensure security and safety of this crate, including design (recursion limit, defensive programming), tests, and fuzzing. It also aims to be panic-free.
The code is available on Github and is part of the Rusticata project.
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.
It is useful when decoding an arbitrary DER object.
However, it cannot fully parse all objects, especially those containing IMPLICIT, OPTIONAL, or
DEFINED BY items.
```rust use derparser::parseder;
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:
```rust use derparser::ber::*; use derparser::error::BerResult;
fn localparseseq(i:&[u8]) -> BerResult { parsedersequencedefined!(i, parseberinteger >> parseberinteger ) }
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.
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.
```rust use derparser::ber::*; use derparser::error::BerResult;
let data = &[0x02, 0x03, 0x01, 0x00, 0x01];
let (, object) = parseberinteger(data).expect("parsing failed"); asserteq!(object.as_u64(), Ok(65537)); ```
Access to the raw value is possible using the as_slice method.
parse_der.BerObject and DerObject are the same objects (type alias). The only difference is the
verification of constraints during parsing.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
[[X.690]] ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER).
Specification of basic notation." Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER)."
See CHANGELOG.md, and UPGRADING.md for instructions for upgrading major versions.
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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.