ASN.1 TypeScript Library

• Author: Jonathan M. Wilbur <jonathan@wilbur.space>
• Copyright Year: 2018
• License: MIT License
• Version: See version file or git tags.

This library was based off of my D ASN.1 Library.

What is ASN.1?

ASN.1 stands for Abstract Syntax Notation. ASN.1 was first specified in X.680 - Abstract Syntax Notation One (ASN.1), by the International Telecommunications Union. ASN.1 messages can be encoded in one of several encoding/decoding standards. It provides a system of types that are extensible, and can presumably describe every protocol. You can think of it as a protocol for describing other protocols as well as a family of standards for encoding and decoding said protocols. It is similar to Google's Protocol Buffers, or Sun Microsystems' External Data Representation (XDR).

For more information on what ASN.1 is, see documentation/asn1.md.

Why ASN.1?

ASN.1 is used in, or required by, multiple technologies, including:

• X.509 Certificates, used in SSL/TLS
• Lightweight Directory Access Protocol (LDAP)
• X.400, the messaging system used by the U.S. Military
• X.500
• The magnetic stripes on credit cards and debit cards
• Microsoft's Remote Desktop Protocol (RDP)
• Simple Network Management Protocol (SNMP)
• Common Management Information Protocol (CMIP)
• Signalling System Number 7 (SS7), used to make most phone calls on the Public Switched Telephone Network (PSTN).
• Kerberos 5
• H.323 Video conferencing
• Biometrics Protocols:
  • BioAPI Interworking Protocol (BIP)
  • Common Biometric Exchange Formats Framework (CBEFF)
  • Authentication Contexts for Biometrics (ACBio)
• Computer Supported Telecommunications Applications (CSTA)
• Dedicated Short Range Communications (SAE J2735)
• Cellular telephony:
  • Global System for Mobile Communications (GSM)
  • Global Packet Radio Service (GPRS) / Enhanced Data Rates for Global Evolution (EDGE)
  • Universal Mobile Telecommunications System (UTMS)
  • Long-Term Evolution (LTE)

If you look in the asn1 directory of WireShark's source code, you'll see all of the protocols that use ASN.1.

This list can also be found in documentation/asn1.d.

Building

This library requires NodeJS v10.3.0 or higher, mostly to support Regular Expression Named Capture Groups. See this page for NodeJS ES2018 support.

You can build this library by running:

• npm run-script build
• make -f build/Makefile

The outputs will all be in dist.

• dist/web/asn1.js is the entire ASN.1 library for the web browser, which is not minified.
• dist/web contains other smaller libraries that only contain specific codecs, and which are minified.
• dist/node/asn1.js is the entire NodeJS library.
• dist/types contains all of the type declarations.

Library Usage

For each codec in the library, usage entails instantiating the class, then using that class' properties to get and set the encoded value. For all classes, the empty constructor creates an END OF CONTENT element. The remaining constructors will be codec-specific.

Here is a TypeScript example of encoding with Basic Encoding Rules, using the BERElement class.

let el : BERElement = new BERElement();
el.typeTag = ASN1UniversalType.integer;
el.integer = 1433; // Now the data is encoded.
console.log(el.integer); // Logs '1433'

... and here is how you would decode that same element:

let encodedData : Uint8Array = el.toBytes();
let el2 : BERElement = new BERElement();
el2.fromBytes(encodedData);
console.log(el2.integer); // Logs '1433'

See Also

• X.680 - Abstract Syntax Notation One (ASN.1), published by the International Telecommunications Union.
• X.690 - ASN.1 encoding rules, published by the International Telecommunications Union.
• ASN.1: Communication Between Heterogeneous Systems by Olivier Dubuisson

Contact Me

If you would like to suggest fixes or improvements on this library, please just leave an issue on this GitHub page. If you would like to contact me for other reasons, please email me at jonathan@wilbur.space (My GPG Key) (My TLS Certificate). 🐗