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Hongyu Gao Clint Sbisa. Automated Parser Generation for High-Speed NIDS. Motivation. Processing speed is crucial concern for NIDS/NIPS Limited by rate of parsing packets Inefficient parsing leads to slow speeds and bottlenecks. Current Solutions. Binpac Declarative language and compiler

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Hongyu gao clint sbisa

Hongyu Gao

Clint Sbisa

Automated Parser Generation for High-Speed NIDS


Motivation
Motivation

  • Processing speed is crucial concern for NIDS/NIPS

  • Limited by rate of parsing packets

  • Inefficient parsing leads to slow speeds and bottlenecks


Current solutions
Current Solutions

  • Binpac

    • Declarative language and compiler

    • Designed to simplify task of constructing complex protocol parsers

    • Constructs a full parsing tree


Current solutions1
Current Solutions

  • Netshield

    • Integrate high-speed protocol parser to provide fast parsing speed

    • Parsers are manually written, which is tedious work and error-prone


Proposed solution
Proposed Solution

  • A protocol parser generator

  • Read the protocol specification

  • Output the parser for the specific protocol

  • The parser is aware of matching

  • The parser focuses on the fields needed by matching and skip unnecessary fields



Design principles
Design Principles

  • The parsing process should avoid recursive calls

    • Parse trees are not used in parsing phase

  • Skip unneeded information

    • After parsing one field, the parser should be able to quickly jump to the next necessary field


Detailed design
Detailed design

  • The parser consists of three parts

  • A pair of buffer pointers

  • A field table ( key data structure)

  • A table pointer




Implementation
Implementation

  • Basic approach:

    • Fixed driver

    • Fixed data structure

    • Protocol-specific table content



How to realize the system
How to realize the system

  • Determine the size of field table

    • Start with one root node in protocol parse tree

    • Iteratively substitute complex field with multiple simpler fields

  • Determine the FieldLength function

    • Retrieve the information from Type class

    • Type::attr_length_expr_,

    • Type::attr_oneline_,

    • etc.


How to realize the system1
How to realize the system

Determine the GarbageLength function

Before compression, GarbageLength returns “0” for every field

Compress the table

Look forward for consequent fields

Merge the length of unused fields into garbage fields of the field that precedes them







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