[](./LICENSE-MIT) [](./LICENSE-APACHE) [](https://docs.rs/x509-parser) [](https://crates.io/crates/x509-parser) [](https://crates.io/crates/x509-parser) [](https://github.com/rusticata/x509-parser/actions) [](#rust-version-requirements) # X.509 Parser A X.509 v3 ([RFC5280]) parser, implemented with the [nom](https://github.com/Geal/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](https://github.com/rusticata/x509-parser) and is part of the [Rusticata](https://github.com/rusticata) project. Certificates are usually encoded in two main formats: PEM (usually the most common format) or DER. A PEM-encoded certificate is a container, storing a DER object. See the [`pem`](https://docs.rs/x509-parser/latest/x509_parser/pem/index.html) module for more documentation. To decode a DER-encoded certificate, the main parsing method is `X509Certificate::from_der` ( part of the [`FromDer`](https://docs.rs/x509-parser/latest/x509_parser/prelude/trait.FromDer.html) trait ), which builds a [`X509Certificate`](https://docs.rs/x509-parser/latest/x509_parser/certificate/struct.X509Certificate.html) object. An alternative method is to use [`X509CertificateParser`](https://docs.rs/x509-parser/latest/x509_parser/certificate/struct.X509CertificateParser.html), which allows specifying parsing options (for example, not automatically parsing option contents). The returned objects for parsers follow the definitions of the RFC. This means that accessing fields is done by accessing struct members recursively. Some helper functions are provided, for example [`X509Certificate::issuer()`](https://docs.rs/x509-parser/latest/x509_parser/certificate/struct.X509Certificate.html#method.issuer) returns the same as accessing `