DevSecCon London 2017: zap scripting workshop by Simon Bennetts

Join the conversation
#DevSecCon
By Simon Bennetts
Scripting OWASP ZAP

●
Session 1 : 2pm
– Introduction
– Standard Scripts (JavaScript, Python, Ruby)
– Proxy and Http Sender Scripts
– Passive and Active Scan rule Scripts
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Session 2 : 3pm
– Zest Scripts
– Standalone and Targeted Scripts
The Plan

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Session 3 : 4pm
– How to use scripts in automation
– How to add scripting support in add-ons (overview)
– Authentication Scripts
– More chance to write any or all of the above types
●
Session 4 : 5pm
– Optional – keep writing scripts, ask more questions...
The Plan

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We want more script examples
● Submit PRs to https://github.com/zaproxy/community-scripts
●
Can be anything useful – eg copies of existing scripts in different
languages :)
●
Anything useful will earn a ZAP Contributor sticker (max one per
person)
●
Lots of useful scripts will earn a ZAP T-shirt!
●
Only valid for this workshop
Competition Time!

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Advantages:
– Quick to write and test
– Full access to ZAP classes and data structures
– No need for separate development environment
●
Disadvantages
– Documentation could be (much) better
– No auto complete
– No sandbox – only run scripts you trust!
Introduction – why do we need scripts?

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JavaScript – built in
●
Python – optional add-on
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Ruby – optional add-on
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Zest – built in, macro language on steroids
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JSR 223 languages relatively easy to add
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Beanshell – optional, no longer really maintained
Introduction – What languages are supported?

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Stand Alone
– Run manually
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Targeted
– Run manually against a specified requests
●
Proxy
– Change proxied browser requests on the fly
●
HTTP Sender
– Change any request on the fly (proxy, spider, active scanner ...)
Script types (built in)

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Passive Scan Rule
– Detect potential issues just by looking
●
Active Scan Rule
– Detect potential issues by attacking
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Authentication
– Automatically login to sites
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Script Input Vector
– Define exactly what ZAP will attack
Script types (built in)

●
Fuzzer HTTP Processor
– Called before and after HTTP messages are fuzzed
●
Fuzzer Websocket Processor
– Called before and after Websocket messages are fuzzed
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Payload Generator
– Generate attacks to be used in the fuzzer
●
Payload Processor
– Change fuzzer payloads before they are used
●
Sequence
– Define sequences of requests to be attacked (alpha)
Script types (add-ons)

●
All roughly equivalent
●
All have good Java integration
●
JavaScript (ECMAScript)
– Java 7 – Rhino
– Java 8 – Nashhorn
– Can write to local filestore via Java classes
– Use load("nashorn:mozilla_compat.js"); for Rhino scripts in Nashorn
●
JavaScript Nashhorn – supports loading scripts from files
– https://wiki.openjdk.java.net/display/Nashorn/Nashorn+extensions
●
Python – supports modules path
‘Standard’ Script languages

● Scripts group: https://groups.google.com/group/zaproxy-scripts
● Dev group: https://groups.google.com/group/zaproxy-develop
● Community Scripts: https://github.com/zaproxy/community-scripts
● JavaDocs: https://javadoc.io/doc/org.zaproxy/zap/2.6.0
Useful links

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Fire up ZAP
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Check for Updates (Help / Check for Updates...)
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Update everything
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Install Community Scripts
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Optionally install Python / Ruby Scripting
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Demo: “Hello world”
Getting started

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Scripts tab
– Shows all of the scripts an templates
– Allows you to select, add, remove, duplicate, enable, disable and save scripts
– Icons show state – enabled / disabled, error and not saved
●
Script Console tab
– Top pane – edit scripts
– Bottom pane – output and error messages
– Run and Stop buttons – enabled when appropriate
– Output pane buttons – control that pane
– Right click for lots more options!
The tabs

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Proxy Scripts
– Only affect requests and responses proxied via a browser
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HTTP Sender Scripts
– Affect all requests and responses (proxy active scan, spider …)
– Initiator param gives the component that initiated the request
– Provides helper to make new requests
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Both
– Must enable scripts before they will take effect
– Will be disabled on error
Proxy and HTTP Sender scripts

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Key ZAP class: org/parosproxy/paros/network/HttpMessage.html
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Provides methods like
– getRequestBody()
– getRequestHeader()
– getResponseBody()
– getResponseHeader()
● See JavaDocs: https://javadoc.io/doc/org.zaproxy/zap/2.6.0
● Or the code: https://github.com/zaproxy/zaproxy
Script parameter: HttpMessage - msg

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Proxy Scripts
– Replace in request or response body.js
– Drop requests not in scope.js
– Return fake response.js
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HTTP Sender Scripts
– Alert in HTTP Response Code Errors.js
– Alert on Unexpected Content Types.js
– Capture and Replace Anti CSRF Token.js
Proxy and HTTP Sender scripts - examples

Suggestions:
●
Replace headers
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Auto redirect from one page to another
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Do different things based on content, eg:
– Replace different content
– Redirect to different pages
Exercise – write Proxy &/ HTTP Sender scripts

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Passive Rule Scripts
– Can only view requests and responses (should not change anything)
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Active Rule Scripts
– Attack nodes or specific parameters
– Can do pretty much anything you like :)
– Must Enable Script Input Vectors
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Both
– Can raise alerts
– Must enable scripts before they will take effect
– Will be disabled on error
Passive and Active Rule scripts

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Passive Rule Scripts
– Server Header Disclosure.js
– Find emails.js
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Active Rule Scripts
– User defined attacks.js
– gof_lite.js
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Demo: testing passive and active rule scripts
Passive and Active Rule scripts - examples

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Hacking ZAP Blog posts
– https://zaproxy.blogspot.com/2014/04/hacking-zap-3-passive-scan-rules.html
– https://zaproxy.blogspot.com/2014/04/hacking-zap-4-active-scan-rules.html
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Java code
– https://github.com/zaproxy/zap-extensions
– master branch – org/zaproxy/zap/extension/ascanrules and pscanrules
– beta branch – org/zaproxy/zap/extension/ascanrulesBeta and pscanrulesBeta
– alpha branch – org/zaproxy/zap/extension/ascanrulesAlpha and pscanrulesAlpha
Passive and Active Rule links

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Global Variables
– Variables can be shared between all scripts
org.zaproxy.zap.extension.script.ScriptVars.setGlobalVar("var.name","value")
org.zaproxy.zap.extension.script.ScriptVars.getGlobalVar("var.name")
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Script Variables
– Variables can be shared between separate invocations of the same script
org.zaproxy.zap.extension.script.ScriptVars.setScriptVar(
this.context, "var.name","value")
org.zaproxy.zap.extension.script.ScriptVars.getScriptVar(
this.context, "var.name")
Variables (all script types)

Suggestions:
●
Rewrite existing java rules (see previous links)
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Alert on anything that ZAP doesn’t currently find :)
Exercise – write Passive &/ Active Rule scripts

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Domain Specific Language (DSL)
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Its domain is security and automation
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Closer to a macro language .. on steroids :)
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Format – JSON :O
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Intended to be ‘written’ graphically
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Its tool independent (no access to ZAP internals)
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Demo: “Hello world”
Zest Scripts

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Creating from templates
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Duplicating existing script
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Recording
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Selecting and adding requests
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Manually
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Demo: playing with BodgeIt
Zest Scripts - creating

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Double click to edit nodes
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Right click:
– Add and delete nodes
– Delete nodes
– Surround with loops, conditionals
– Cut, copy and paste
– Comment
– Move up / down
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Drag and drop
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Selecting and adding requests
Zest Scripts - editing

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Request – make requests (and make assertions)
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Action – scan, script, print, fail, sleep
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Assignment – assign things to variables
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Client – launch and control browsers
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Conditions – and, or, equals, length, etc ...
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Loop – though strings, files, integers, regexes, client elements
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Comment – comment :)
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Controls – return, break, next
Zest Scripts – statement types

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Paste Zest variables (right click in Zest text boxes)
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Parameterize strings (right click in requests)
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Redact strings (right click in requests)
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Drag and drop
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Change prefix – applies to all requests
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Anti CSRF tokens – automatically handled
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Generate Zest script from alert
Zest Scripts – hidden extras

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You have to start by launching a browser in Zest
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No record option at the moment :(
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Browser - View source / Inspect is your friend
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Demo: Persona video …
Zest Scripts – client side

DevSecCon London 2017: zap scripting workshop by Simon Bennetts

Suggestions:
●
Passive script – alert on the presence of 2 strings
●
Rewrite a script you’ve just written in another language
●
Rewrite one of the existing a/pscan rules
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Record a script and start changing it
Exercise – write Zest scripts

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Both run ‘on-demand’ only
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Standalone – run from the console
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Targeted – right click on requests
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Standard scripts (not Zest) – can access ZAP internals, eg:
– Sites tree
– History
– Other extensions
Standalone and Targeted scripts

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Standalone Scripts
– loop through history table.js
– traverse sites tree.js
– domainFinder.js
– window_creation_template.js
●
Targeted Scripts
– Resend as a GET request.zst
– Find HTML comments.js
Standalone and Targeted scripts - examples

Suggestions:
●
Count number of static vs dynamic pages
●
Detect authentication, registration and password changing?
(1 2 and 3 password fields)
Exercise – Standalone and Targeted scripts

-config script.scripts(0).name="Remove STS"
-config script.scripts(0).engine="Mozilla Zest"
-config script.scripts(0).type=proxy
-config script.scripts(0).enabled=true
-config script.scripts(0).file="/scripts/Remove STS.zst"
-config script.scripts(1).name="Another one..."
Scripts in Automation – set via cmd line

zap.script.load("Remove STS", “proxy”, "Mozilla Zest",
"/scripts/Remove STS.zst")
zap.script.enable("Remove STS")
●
Pro Tip: Configure in the UI, look at whats set in config.xml ;)
Scripts in Automation – set via API

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Implement a script interface
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Implement one or more templates / examples which implement
the interface
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Register a new script type:
ExtensionScript extensionScript = Control.getSingleton().
getExtensionLoader().getExtension(ExtensionScript.class);
extensionScript.registerScriptType(new ScriptType(
"newname", "i18nKey", icon, true, true));
Adding script support in add-ons

●
Use the enabled scripts:
ExtensionScript extensionScript = Control.getSingleton().
getExtensionLoader().getExtension(ExtensionScript.class);
List<ScriptWrapper> scripts = extension.getScripts("newname");
for (ScriptWrapper script : scripts) {
try {
if (script.isEnabled()) {
MyScript s = extension.getInterface(
script, MyScript.class);
// Do something with it...
}
Adding script support in add-ons

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For when simple form based auth isnt enough
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Need to configure context
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Demo: BodgeIt authentication
● https://github.com/zaproxy/zaproxy/wiki/FAQformauth - auth FAQ
Authentication Scripts

Suggestions:
●
Authenticate against any vulnerable app you have installed
Exercise – Authentication scripts

Join the conversation
#DevSecCon
Many thanks
PRs always appreciated ;)

DevSecCon London 2017: zap scripting workshop by Simon Bennetts

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