@peculiar/asn1-schema

What is @peculiar/asn1-schema?

@peculiar/asn1-schema is a JavaScript library for working with ASN.1 (Abstract Syntax Notation One) schemas. It provides tools for defining, encoding, and decoding ASN.1 data structures, which are commonly used in cryptographic protocols and data interchange formats.

What are @peculiar/asn1-schema's main functionalities?

Defining ASN.1 Schemas

This feature allows you to define ASN.1 schemas using decorators. The code sample demonstrates how to define a simple ASN.1 schema with an integer and a UTF-8 string.

const { AsnProp, AsnPropTypes, AsnType, AsnTypeTypes } = require('@peculiar/asn1-schema');

@AsnType({ type: AsnTypeTypes.Sequence })
class MySchema {
  @AsnProp({ type: AsnPropTypes.Integer })
  public id = 0;

  @AsnProp({ type: AsnPropTypes.Utf8String })
  public name = '';
}

const schema = new MySchema();
schema.id = 1;
schema.name = 'Example';

Encoding ASN.1 Data

This feature allows you to encode data according to the defined ASN.1 schema. The code sample shows how to serialize an instance of the schema into an ASN.1 encoded format.

const { AsnConvert } = require('@peculiar/asn1-schema');

const schema = new MySchema();
schema.id = 1;
schema.name = 'Example';

const encoded = AsnConvert.serialize(schema);
console.log(encoded);

Decoding ASN.1 Data

This feature allows you to decode ASN.1 encoded data back into the defined schema. The code sample demonstrates how to parse an ASN.1 encoded byte array into an instance of the schema.

const { AsnConvert } = require('@peculiar/asn1-schema');

const encoded = new Uint8Array([48, 10, 2, 1, 1, 12, 5, 69, 120, 97, 109, 112, 108, 101]);
const decoded = AsnConvert.parse(encoded, MySchema);
console.log(decoded);

Other packages similar to @peculiar/asn1-schema

asn1js

asn1js is a JavaScript library for encoding and decoding ASN.1 data structures. It provides a low-level API for working with ASN.1, making it more flexible but also more complex compared to @peculiar/asn1-schema, which offers a higher-level, decorator-based approach.

asn1

asn1 is a library for encoding and decoding ASN.1 data structures in JavaScript. It is similar to node-asn1 but provides a more comprehensive set of features for working with ASN.1, though it lacks the decorator-based schema definition found in @peculiar/asn1-schema.

README

@peculiar/asn1-schema

This package uses ES2015 decorators to simplify working with ASN.1 creation and parsing.

Introduction

Abstract Syntax Notation One (ASN.1) is a standard interface description language for defining data structures that can be serialized and deserialized in a cross-platform way. Working with ASN.1 can be complicated as there are many ways to represent the same data and many solutions handcraft, incorrectly, the ASN.1 representation of the data.

asn1-schema addresses this by using decorators to make both serialization and parsing of ASN.1 possible via a simple class that handles these problems for you.

This is important because validating input data before its use is important to do because all input data is evil.

Installation

Installation is handled via npm:

$ npm install @peculiar/asn1-schema

TypeScript examples

Node.js:

ASN.1 schema

Extension  ::=  SEQUENCE  {
  extnID      OBJECT IDENTIFIER,
  critical    BOOLEAN DEFAULT FALSE,
  extnValue   OCTET STRING
              -- contains the DER encoding of an ASN.1 value
              -- corresponding to the extension type identified
              -- by extnID
}

id-ce-basicConstraints OBJECT IDENTIFIER ::=  { id-ce 19 }

BasicConstraints ::= SEQUENCE {
  cA                      BOOLEAN DEFAULT FALSE,
  pathLenConstraint       INTEGER (0..MAX) OPTIONAL 
}

ASN.1 schema declaration in TypeScript project

import { Asn1Prop, Asn1PropTypes, Asn1Serializer } from "@peculiar/asn1-schema";

class Extension {

  public static CRITICAL = false;

  @AsnProp({ type: Asn1PropTypes.ObjectIdentifier })
  public extnID: string = "";

  @AsnProp({
    type: Asn1PropTypes.Boolean,
    defaultValue: Extension.CRITICAL,
  })
  public critical = Extension.CRITICAL;

  @AsnProp({ type: Asn1PropTypes.OctetString })
  public extnValue: ArrayBuffer = new ArrayBuffer(0);

}

class BasicConstraints {
  @AsnProp({ type: Asn1PropTypes.Boolean, defaultValue: false })
  public ca = false;

  @AsnProp({ type: Asn1PropTypes.Integer, optional: true })
  public pathLenConstraint?: number;
}

Encoding ASN.1 data

const basicConstraints = new BasicConstraints();
basicConstraints.ca = true;
basicConstraints.pathLenConstraint = 1;

const extension = new Extension();
extension.critical = true;
extension.extnID = "2.5.29.19";
extension.extnValue = AsnSerializer.serialize(basicConstraints);

console.log(Buffer.from(AsnSerializer.serialize(extension)).toString("hex")); // 30120603551d130101ff040830060101ff020101

ASN.1 encoded data

Decoding ASN.1 data

const extension = AsnParser.parse(Buffer.from("30120603551d130101ff040830060101ff020101", "hex"), Extension);
console.log("Extension ID:", extension.extnID); // Extension ID: 2.5.29.19
console.log("Critical:", extension.critical); // Critical: true

const basicConstraints = AsnParser.parse(extension.extnValue, BasicConstraints);
console.log("CA:", basicConstraints.ca); // CA: true
console.log("Path length:", basicConstraints.pathLenConstraint); // Path length: 1