RustCrypto: ASN.1 DER

Pure Rust embedded-friendly implementation of the Distinguished Encoding Rules (DER) for Abstract Syntax Notation One (ASN.1) as described in ITU X.690.

Documentation

About

This crate provides a no_std-friendly implementation of a subset of ASN.1 DER necessary for decoding/encoding the following cryptography-related formats implemented as crates maintained by the RustCrypto project:

• cms: Cryptographic Message Syntax
• pkcs1: RSA Cryptography Specifications
• pkcs5: Password-Based Cryptography Specification
• pkcs8: Private-Key Information Syntax Specification
• pkcs12: Personal Information Exchange Syntax
• sec1: Elliptic Curve Cryptography
• spki: X.509 Subject Public Key Info
• x509-cert: Public Key Infrastructure Certificate
• x509-ocsp: Online Certificate Status Protocol

The core implementation avoids any heap usage (with convenience methods that allocate gated under the off-by-default alloc feature).

The DER decoder in this crate performs checks to ensure that the input document is in canonical form, and will return errors if non-canonical productions are encountered. There is currently no way to disable these checks.

Features

• Rich support for ASN.1 types used by PKCS/PKIX documents
• Performs DER canonicalization checks at decoding time
• no_std friendly: supports "heapless" usage
• Optionally supports alloc and std if desired
• No hard dependencies! Self-contained implementation with optional integrations with the following crates, all of which are no_std friendly:
  • const-oid: const-friendly OID implementation
  • pem-rfc7468: PKCS/PKIX-flavored PEM library with constant-time decoder/encoders
  • time crate: date/time library

Minimum Supported Rust Version (MSRV) Policy

MSRV increases are not considered breaking changes and can happen in patch releases.

The crate MSRV accounts for all supported targets and crate feature combinations, excluding explicitly unstable features.

License

Licensed under either of:

• Apache License, Version 2.0
• MIT license

at your option.

Contribution

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.