pub trait FromDer<'a> {
    fn from_der(bytes: &'a [u8]) -> Result<(&'a [u8], Self), Err<Error>>;
Available on crate feature mtls only.
Expand description

Base trait for DER object parsers

Library authors should usually not directly implement this trait, but should prefer implementing the TryFrom<Any> + CheckDerConstraint traits, which offers greater flexibility and provides an equivalent FromDer implementation for free (in fact, it provides both FromBer and FromDer).

Note: if you already implemented TryFrom<Any> to get the FromBer implementation, then you only have to add a CheckDerConstraint implementation.


use asn1_rs::{Any, CheckDerConstraints, Result, Tag};
use std::convert::TryFrom;

// The type to be decoded
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct MyType(pub u32);

impl<'a> TryFrom<Any<'a>> for MyType {
    type Error = asn1_rs::Error;

    fn try_from(any: Any<'a>) -> Result<MyType> {
        // for this fictive example, the type contains the number of characters
        let n = any.data.len() as u32;

impl CheckDerConstraints for MyType {
    fn check_constraints(any: &Any) -> Result<()> {

// The above code provides a `FromDer` implementation for free.

// Example of parsing code:
use asn1_rs::FromDer;

let input = &[2, 1, 2];
// Objects can be parsed using `from_der`, which returns the remaining bytes
// and the parsed object:
let (rem, my_type) = MyType::from_der(input).expect("parsing failed");

Required Methods

Attempt to parse input bytes into a DER object (enforcing constraints)