x509-parser 0.8.2

Parser for the X.509 v3 format (RFC 5280 certificates)

License: MIT Apache License 2.0 docs.rs crates.io Download numbers Travis CI Github CI

X.509 Parser

A X.509 v3 (RFC5280) parser, 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.

The main parsing method is parse_x509_der, which takes a DER-encoded certificate as input, and builds a X509Certificate object.

For PEM-encoded certificates, use the pem module.


Parsing a certificate in DER format:

use x509_parser::parse_x509_der;

static IGCA_DER: &'static [u8] = include_bytes!("../assets/IGC_A.der");

let res = parse_x509_der(IGCA_DER);
match res {
    Ok((rem, cert)) => {
        assert_eq!(cert.tbs_certificate.version, 2);
    _ => panic!("x509 parsing failed: {:?}", res),

See also examples/print-cert.rs.


  • The verify feature adds support for (cryptographic) signature verification, based on ring. It adds the verify_signature to X509Certificate.
/// Cryptographic signature verification: returns true if certificate was signed by issuer
#[cfg(feature = "verify")]
pub fn check_signature(cert: &X509Certificate<'_>, issuer: &X509Certificate<'_>) -> bool {
    let issuer_public_key = &issuer.tbs_certificate.subject_pki;

Compatibility with older rust versions


There is a build error in arrayvec with rust 1.34: error[E0658]: use of unstable library feature 'maybe_uninit'

To fix it, force the version of lexical-core down:

cargo update -p lexical-core --precise 0.6.7

The verify feature is not compatible with rustc 1.34.




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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.