Installation

Git

Installing the source from Git is done as follows:

git clone git://github.com/tenable/nasl.git

Gem

Installing the package from RubyGems is done as follows:

gem install nasl

Usage

Standalone

To avoid conflicting with the NASL interpreter, the NASL gem's binary is installed as nasl-parse. As an application, it has very few actions that it can perform.

• Benchmark: This benchmarks the time taken to parse the input path(s) over a number of iterations. The number of iterations can be adjusted by the -i switch.

  % nasl-parse -i 10 benchmark /opt/nessus/lib/nessus/plugins/ssl_certificate_chain.nasl
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  Rehearsal --------------------------------------------
  Tokenize   1.687500   0.000000   1.687500 (  1.688397)
  Parse      1.835938   0.015625   1.851562 (  1.857094)
  ----------------------------------- total: 3.539062sec
  
                 user     system      total        real
  Tokenize   1.304688   0.015625   1.320312 (  1.319951)
  Parse      1.046875   0.000000   1.046875 (  1.046957)
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  

• Parse: This parses the input path(s) and indicates whether the parse was successful.

  % nasl-parse parse /opt/nessus/lib/nessus/plugins/ssl_certificate_chain.nasl
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  Successfully parsed the contents of the file.
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  

• Test: This runs unit tests distributed with the application. Specific unit tests can be specified on the command line, otherwise all tests will be run.

  % nasl-parse test
  Run options:
  
  # Running tests:
  
  .............................................................................
  
  Finished tests in 11.773983s, 6.5398 tests/s, 33493.8487 assertions/s.
  
  77 tests, 394356 assertions, 0 failures, 0 errors, 0 skips
  

• Tokenize: This tokenizes the input path(s) and prints the token/byte-range pairs to stdout.

  % nasl-parse tokenize /opt/nessus/lib/nessus/plugins/ssl_certificate_chain.nasl
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  [COMMENT,              0...1076]
  [IF,                1076...1079]
  [LPAREN,            1079...1080]
  [IDENT,             1080...1091]
  [CMP_LT,            1091...1093]
  ...
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  

• XML: This parses the input path(s), and then prints an XML representation of the parse tree to stdout.

  % nasl-parse xml /opt/nessus/lib/nessus/plugins/ssl_certificate_chain.nasl
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  <tree>
    <if>
      <expression>
        <op>&lt;</op>
        <lvalue>
  ...
  -------------------------[ ssl_certificate_chain.nasl ]-------------------------
  

Library

The primary users of this gem are Pedant and Nasldoc. Other uses are encouraged, of course! The Parser class is the most useful part, obviously, and can be used as follows:

require 'nasl'

tree = Nasl::Parser.new.parse(file_contents, path_to_file)

That's all there is to it. If there are any errors, it'll throw an instance of ParseException that will include as much context about the error as possible.