Chapter 14. Creating ASN.1 Dissectors

Table of Contents

14.1. About ASN.1
14.2. ASN.1 Dissector Requirements
14.2.1. Building An ASN.1-Based Plugin
14.3. Understanding Error Messages
14.4. Hand-Massaging The ASN.1 File
14.5. Command Line Syntax
14.6. Generated Files
14.7. Step By Step Instructions
14.8. Hints For Using Asn2wrs
14.8.1. ANY And Parameterized Types
14.8.2. Tagged Assignments
14.8.3. Untagged CHOICEs
14.8.4. Imported Module Name Conflicts
14.9. Simple ASN.1-Based Dissector
14.10. Conformance (.cnf) Files
14.10.1. Example .cnf File
14.10.2. Example packet-protocol-template.h File
14.10.3. Example packet-protocol-template.c File
14.11. Conformance File Directive Reference
14.11.1. #.END
14.11.2. #.EXPORTS
14.11.3. #.FN_BODY
14.11.5. #.MODULE_IMPORT
14.11.6. #.INCLUDE
14.11.7. #.NO_EMIT And #.USER_DEFINED
14.11.8. #.PDU and #.PDU_NEW
14.11.9. #.REGISTER and #.REGISTER_NEW

The asn2wrs compiler can be used to create a dissector from an ASN.1 specification of a protocol. It is a work in progress but has been used to create a number of dissectors.

It supports:

It has inbuilt support for:

14.1. About ASN.1

The most useful first step in writing an ASN.1-based dissector is to learn about ASN.1. There are a number of free resources available to help with this. One collection of such resources is maintained on the ASN.1 Consortium’s web site.