MuSL Builder

Handcrafting customMu Scenarios

MuSL in the Mu Scenario Editor

MuSL Builder Overview

• MuSL_Builder is a Ruby project that creates scenarios in the Mu Scenario Language (MuSL)

• Each MuSL_Builder component class creates a single protocol message from a text template

• Classes are chained together to create a complete scenario

High Level: The Builder UI

Builder UI

• The Builder UI puts together properties from the parameters and scenario steps dynamically created by the user

• The Builder UI then builds the MuSL file using the MuslBuilder class

The Power of MuSL_Builder

• From a few message classes, it is easy to create a wide variety of scenarios

• For example, to create a simple ‘ping’ flood, one would only need to use a single ICMP message class and a one-line statement in a MuSL_Builder properties file: messages=ICMPPing(100)

A SIP Example

• Given the sample SIP message templates, you could easily create a wacky scenario from properties files entries such as:

sequence=wacky:SIPInvite(17),SIPPrack(3),SIPBye,SIPRegister(2),SIPAck,SIPBye,SIPTrying(12)

messages=wacky(114)

• A scenario created from this definition would contain 4,218 messages

MuSL Builder Source Code

• The project is located in mu-labs:– http://code.google.com/p/mu-labs/source/brows

e/trunk/analyzer/automation/MuSL_Builder

• The project contains sample code for a variety of protocols, including SIP, IMAP, FTP, BGP and ICMP

MuSL Builder Pieces

• A complete set of MuSL Builder components includes:– The MuslBuilder class• the executable run from the command-line

– A Base class• defines custom headers, options and variables

– A Properties File• defines the scenario

– Protocol Message Classes• composes the scenario steps

Base Classes

• Each component implements its own Base class in order to customize the header with:– transports– options– variables

• Base classes derive from a common base class which shares global fields among messages of the same component

FTPBase with transport and options

Message Classes

• There are two types of messages:– Client messages are sent to a Server– Server messages are sent to a Client

• Each message class creates a complete protocol message in MuSL

• Message classes are always enclosed in module MuslMessage

A Sample Message

• Each message class consists of:– a constructor (def initialize)– a configure() method, which produces a protocol

message in text from a template object, and increments a step counter

• Templates often contain some embedded ruby code, which is replaced at runtime by option or variable values

A Sample Message Class

Sample Message: Counter

• The counter is a unique identifier for each message pair, and is tracked globally

• In the example template, the following line in the template:– SIP_Client_Send_<%= @base.counter %> =

• Is transformed at runtime, replacing <%= @base.counter %> with the value of the base class’s ‘counter’ field.

• The resulting line might look like this:– SIP_Client_Send_2 =

Sample Message: Transport

• Each message class has a default transport in its constructor

• The default transport can be overridden by specification in the properties file:– messages=FTPMkdir[ALT_FTP_TRANSPORT]

<%= @transport %>.client_send

becomes ALT_FTP_TRANSPORT.client_send

The MuslBuilder Class

• muslbuilder.rb is the executable class– reads in a properties file or array– output a complete scenario in the Mu Scenario

Language• The builder class creates a Hash (called

‘params’) from the properties which is passed into the Component base class constructor

Properties

• Properties can be in a text file or passed in to muslbuilder as an array, containing– options– sequences – messages– components– scenario_name

• The properties are read by the muslbuilder (executable) and contain the blueprint for constructing the scenario

• Properties files can have any name

Properties: Parameters

• Parameters are passed along to base class constructors, and typically contain global Scenario option or variable names and default values:– domain=mydomain.com– sender=joe_sender– recipient=joanna-recipient

• The only required properties are “messages” and “components”, which defines the name of the protocol(s) to be used– components=FTP,HTTP

Properties Files: Sequences

• Sequences– Sequences are comma-separated lists of component

message class names, in the format– sequence=sequence_name:Class1,Class2,Class3…

• sequence=bye:SIPBye,SIPOk• A properties file can contain any number of user defined

sequences– Sequences also provide a repeat syntax, which causes

the specified message to be repeated as many times in a row as indicated• sequence=flood:SIPInvite(1000),SIPBye(12),SIPOk

Properties Files: Messages

• Messages are a comma-separated list containing any combination of message class and/or sequence names

• There can be only one messages line per properties file messages=bye,SIPAck(12),flood,SIPRinging,SIPAck(2)

• Using messages and sequences, all sorts of message patterns can be arbitrarily constructed

Building a Scenario

• From the command-line in the root directory, invoke ruby specifying and a properties file name. ruby muslbuilder.rb properties/sip.properties

• The resulting text is a complete scenario in the Mu Scenario Language

Load the scenario into the MuSL Editor

• Open the Mu Scenario Editor in pcapr.net• Copy and Paste your MuSL Builder scenario

into the left pane• Any syntax errors will be caught and indicated

by the editor• The right pane will show the actual hex or text

output of the scenario

Importing into Studio

• In order to import your scenario into Studio from the Mu Scenario Editor, you must have first opened pcapr from the Mu

• Click the ‘studio’ link above the right pane• The scenario will be imported into the Mu and

opened in a new browser window

Executing the Scenario

• In Mu Studio, set your testbed appropriately and run the scenario as usual– Scenario -> Verify

Customizing the Scenario

• Assertions are placed in Component Server classes

• Global options and variables are placed in Component Base classes

• Captured variables are placed in Component Server classes

Sample Assertions and Variables

SIP_Client_Receive=SIP_Server_Send.client_receive{ assertions { /SIP\\/2.0 (\\d+)/:1 == "200" } variables { @to_tag = /To:.*?tag=(\\w+)/:1 } }

Sample Global Options

template = 'scenario(name: "SIP") { options { $domain="<%= @domain %>” $sender="<%= @sender %>" $recipient="<%= @recipient %>" } steps { SIP = udp(src_port: 5060, dst_port: 5060) }}'

Sample Global Variables

template ='scenario(name: "ICMP") { variables { @data = random_bytes(56) @id = random_integer(4096) } steps { ICMP = ip(protocol: 1) }}'

MuslParser: From Pcap To MuslBuilder

• MuslBuilder message classes can be built readily from existing pcaps– 1. import pcap into the MuSL Editor– 2. save the left-pane as a text file (e.g. “a.msl”)– 3. ruby musl_parser.rb a.msl output_

• MuslParser splits the .msl file into individual message step text files– Use these as the template strings in your message class files

• ** You will still need to edit the strings to• a) create unique message and struct names with <%= @base.counter

%>• b) insert your global options and variables