This extension registers an IHttpListener configured to execute a custom script editable via the Script tab added to Burp. The script is executed in the context with the following global and local variables (extender, callbacks, helpers, toolFlag, messageIsRequest, messageInfo).

burpscript.py

from java.awt import Font
from javax.swing import JScrollPane, JTextPane
from javax.swing.text import SimpleAttributeSet

from burp import IBurpExtender, IExtensionStateListener, IHttpListener, ITab

import base64
import traceback


class BurpExtender(IBurpExtender, IExtensionStateListener, IHttpListener, ITab):
    def registerExtenderCallbacks(self, callbacks):
        self.callbacks = callbacks
        self.helpers = callbacks.helpers

        self.scriptpane = JTextPane()
        self.scriptpane.setFont(Font('Monospaced', Font.PLAIN, 11))

        self.scrollpane = JScrollPane()
        self.scrollpane.setViewportView(self.scriptpane)

        self._code = compile('', '<string>', 'exec')
        self._script = ''

        script = callbacks.loadExtensionSetting('script')

        if script:
            script = base64.b64decode(script)

            self.scriptpane.document.insertString(
                    self.scriptpane.document.length,
                    script,
                    SimpleAttributeSet())

            self._script = script
            self._code = compile(script, '<string>', 'exec')

        callbacks.registerExtensionStateListener(self)
        callbacks.registerHttpListener(self)
        callbacks.customizeUiComponent(self.getUiComponent())
        callbacks.addSuiteTab(self)

        self.scriptpane.requestFocus()

    def extensionUnloaded(self):
        try:
            self.callbacks.saveExtensionSetting(
                    'script', base64.b64encode(self._script))
        except Exception:
            traceback.print_exc(file=self.callbacks.getStderr())
        return

    def processHttpMessage(self, toolFlag, messageIsRequest, messageInfo):
        try:
            globals_ = {}
            locals_  = {'extender': self,
                        'callbacks': self.callbacks,
                        'helpers': self.helpers,
                        'toolFlag': toolFlag,
                        'messageIsRequest': messageIsRequest,
                        'messageInfo': messageInfo
                        }
            exec(self.script, globals_, locals_)
        except Exception:
            traceback.print_exc(file=self.callbacks.getStderr())
        return

    def getTabCaption(self):
        return 'Script'

    def getUiComponent(self):
        return self.scrollpane

    @property
    def script(self):
        end = self.scriptpane.document.length
        _script = self.scriptpane.document.getText(0, end)

        if _script == self._script:
            return self._code

        self._script = _script
        self._code = compile(_script, '<string>', 'exec')
        return self._code

Changed scope of extender, callbacks, and helpers variables to the local variable scope. Result should be a slight increase in performance as we avoid searching the global namespace for a variable.

Is there any way to import more burp modules such as IParameter?

Great work. This has been published in BApp Store: https://portswigger.net/bappstore/eb563ada801346e6bdb7a7d7c5c52583.

Sample code:

if (messageIsRequest):
	# Crude state:
	fname="c:/BURP/mystate5.txt"
	
	with open(fname,"r+") as myfile:
		myvalue=myfile.read()
		myvalue=int(myvalue)
		myvalue+=1
		print(myvalue)
		myfile.seek(0)
		myfile.write(str(myvalue))
		myfile.truncate()

	reqbytes=messageInfo.getRequest()
	req=helpers.analyzeRequest(reqbytes)
	headers=req.getHeaders()
	mydate="date: Wed, 22 Feb 2019 14:40:"+str(myvalue)+" GMT"
	headers.add(mydate)
	print(mydate)
	msgbody=reqbytes[(req.getBodyOffset()):]
	newreq=helpers.buildHttpMessage(headers,msgbody)
	messageInfo.setRequest(newreq)

👋 Hello there, i wanted to try this tool, but i am not sure how to use it, do you have documentation somewhere ?
Even better if you could show steps what needs to be done, what and where should you need to look for the result/output ..
Thanks

Is there any example? It's very hard understand how to use it without example

Is there any example? It's very hard understand how to use it without example

Simply adding header. The code is based on python. Consult python docs if you have issue.

Learn about returned object type from burp
If it's list, python list applies.

headers.add(mydate)
headers.append(mydate)

If it's object, you can call its method

messageInfo.getRequest()

Example codes : https://portswigger.net/burp/extender